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Logesh R, Hari B, Chidambaram K, Das N. Molecular effects of Vitamin-D and PUFAs metabolism in skeletal muscle combating Type-II diabetes mellitus. Gene 2024; 904:148216. [PMID: 38307219 DOI: 10.1016/j.gene.2024.148216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2023] [Revised: 01/10/2024] [Accepted: 01/25/2024] [Indexed: 02/04/2024]
Abstract
Multiple post-receptor intracellular alterations such as impaired glucose transfer, glucose phosphorylation, decreased glucose oxidation, and glycogen production contribute to insulin resistance (IR) in skeletal muscle, manifested by diminished insulin-stimulated glucose uptake. Type-2 diabetes mellites (T2DM) has caused by IR, which is also seen in obese patients and those with metabolic syndrome. The Vitamin-D receptor (VDR) and poly unsaturated fatty acids (PUFAs) roles in skeletal muscle growth, shapes, and function for combating type-2 diabetes have been clarified throughout this research. VDR and PUFAs appears to show a variety of effects on skeletal muscle, in addition it shows a promising role on bone and mineral homeostasis. Individuals having T2DM are reported to suffer from severe muscular weakness and alterations in shape of the muscle. Several studies have investigated the effect on VDR on muscular strength and mass, which leads to Vitamin-D deficiency (VDD) in individuals, in which most commonly seen in elderly. VDR has been shown to affect skeletal cellular proliferation, intracellular calcium handling, as well as genomic activity in a variety of different ways such as muscle metabolism, insulin sensitivity, which is the major characteristic pathogenesis for IR in combating T2DM. The identified VDR gene polymorphisms are ApaI, TaqI, FokI, and BsmI that are associated with T2DM. This review collates informations on the mechanisms by which VDR activation takes place in skeletal muscles. Despite the significant breakthroughs made in recent decades, various studies show that IR affects VDR and PUFAs metabolism in skeletal muscle. Therefore, this review collates the data to show the role of VDR and PUFAs in the skeletal muscles to combat T2DM.
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Affiliation(s)
- Rajan Logesh
- Department of Pharmacognosy, JSS College of Pharmacy, Mysuru, JSS Academy of Higher Education & Research, Karnataka, India.
| | - Balaji Hari
- TIFAC CORE in Herbal Drugs, Department of Pharmacognosy, JSS Academy of Higher Education & Research, JSS College of Pharmacy, The Nilgiris, Ooty 643001, Tamil Nadu, India
| | - Kumarappan Chidambaram
- Department of Pharmacology, College of Pharmacy, King Khalid University, Al-Qara, Asir Province, Saudi Arabia
| | - Niranjan Das
- Department of Chemistry, Iswar Chandra Vidyasagar College, Belonia 799155, Tripura, India
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2
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Pathak R, Sachan N, Chandra P. Mechanistic approach towards diabetic neuropathy screening techniques and future challenges: A review. Biomed Pharmacother 2022; 150:113025. [PMID: 35658222 DOI: 10.1016/j.biopha.2022.113025] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 04/16/2022] [Accepted: 04/20/2022] [Indexed: 11/24/2022] Open
Abstract
Diabetic neuropathy, also called peripheral diabetic neuropathy (PDN), is among the most significant diabetes health consequences, alongside diabetic nephropathy, diabetic cardiomyopathy and diabetic retinopathy. Diabetic neuropathy is the existence of signs and indications of peripheral nerve damage in patients with diabetes after other causes have been governed out. Diabetic neuropathy is a painful and severe complication of diabetes that affects roughly 20% of people. The development of diabetic neuropathy is regulated by blood arteries that nourish the peripheral nerves and metabolic problems such as increased stimulation of polyol pathway, loss of myo-inositol and enhanced non-enzymatic glycation. It's divided into four types based on where neurons are most affected: autonomic, peripheral, proximal, and focal, with each kind presenting different symptoms like numbing, gastrointestinal disorders, and heart concerns. Pharmacotherapy for neuropathic pain is complex and for many patients, effective treatment is lacking; as a result, scientific proof recommendations are crucial. As a result, the current demand is to give the most vital medications or combinations of drugs that work directly on the nerves to help diabetic neuropathy patients feel less pain without causing any adverse effects. In diabetic neuropathy research, animal models are ubiquitous, with rats and mice being the most typically chosen for various reasons. This review covers the epidemiology, clinical features, pathology, clinical symptom, mechanism of diabetic neuropathy development, diagnosis, screening models of animals, diabetic neuropathy pharmacotherapy.
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Affiliation(s)
- Rashmi Pathak
- School of Pharmaceutical Sciences, IFTM University, Lodhipur Rajput Delhi Road (NH-24), Moradabad, UP 244102, India
| | - Neetu Sachan
- School of Pharmaceutical Sciences, IFTM University, Lodhipur Rajput Delhi Road (NH-24), Moradabad, UP 244102, India
| | - Phool Chandra
- School of Pharmaceutical Sciences, IFTM University, Lodhipur Rajput Delhi Road (NH-24), Moradabad, UP 244102, India.
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3
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Luna R, Talanki Manjunatha R, Bollu B, Jhaveri S, Avanthika C, Reddy N, Saha T, Gandhi F. A Comprehensive Review of Neuronal Changes in Diabetics. Cureus 2021; 13:e19142. [PMID: 34868777 PMCID: PMC8628358 DOI: 10.7759/cureus.19142] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/30/2021] [Indexed: 12/11/2022] Open
Abstract
There has been an exponential rise in diabetes mellitus (DM) cases on a global scale. Diabetes affects almost every system of the body, and the nervous system is no exception. Although the brain is dependent on glucose, providing it with the energy required for optimal functionality, glucose also plays a key role in the regulation of oxidative stress, cell death, among others, which furthermore contribute to the pathophysiology of neurological disorders. The variety of biochemical processes engaged in this process is only matched by the multitude of clinical consequences resulting from it. The wide-ranging effects on the central and peripheral nervous system include, but are not limited to axonopathies, neurodegenerative diseases, neurovascular diseases, and general cognitive impairment. All language search was conducted on MEDLINE, COCHRANE, EMBASE, and GOOGLE SCHOLAR till September 2021. The following search strings and Medical Subject Headings (MeSH terms) were used: "Diabetes Mellitus," "CNS," "Diabetic Neuropathy," and "Insulin." We explored the literature on diabetic neuropathy, covering its epidemiology, pathophysiology with the respective molecular pathways, clinical consequences with a special focus on the central nervous system and finally, measures to prevent and treat neuronal changes. Diabetes is slowly becoming an epidemic, rapidly increasing the clinical burden on account of its wide-ranging complications. This review focuses on the neuronal changes occurring in diabetes such as the impact of hyperglycemia on brain function and structure, its association with various neurological disorders, and a few diabetes-induced peripheral neuropathic changes. It is an attempt to summarize the relevant literature about neuronal consequences of DM as treatment options available today are mostly focused on achieving better glycemic control; further research on novel treatment options to prevent or delay the progression of neuronal changes is still needed.
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Affiliation(s)
- Rudy Luna
- Neurofisiología, Instituto Nacional de Neurologia y Neurocirugia, CDMX, MEX
| | | | | | | | - Chaithanya Avanthika
- Medicine and Surgery; Pediatrics, Karnataka Institute of Medical Sciences, Hubli, IND
| | - Nikhil Reddy
- Internal Medicine, Kamineni Academy of Medical Science and Research Centre, Hyderabad, IND
| | - Tias Saha
- Internal Medicine, Diabetic Association Medical College, Faridpur, BGD
| | - Fenil Gandhi
- Medicine, Shree Krishna Hospital, Anand, IND
- Research Project Associate, Memorial Sloan Kettering Cancer Center, New York, USA
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4
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O'Reilly CL, Uranga S, Fluckey JD. Culprits or consequences: Understanding the metabolic dysregulation of muscle in diabetes. World J Biol Chem 2021; 12:70-86. [PMID: 34630911 PMCID: PMC8473417 DOI: 10.4331/wjbc.v12.i5.70] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 06/21/2021] [Accepted: 08/03/2021] [Indexed: 02/06/2023] Open
Abstract
The prevalence of type 2 diabetes (T2D) continues to rise despite the amount of research dedicated to finding the culprits of this debilitating disease. Skeletal muscle is arguably the most important contributor to glucose disposal making it a clear target in insulin resistance and T2D research. Within skeletal muscle there is a clear link to metabolic dysregulation during the progression of T2D but the determination of culprits vs consequences of the disease has been elusive. Emerging evidence in skeletal muscle implicates influential cross talk between a key anabolic regulatory protein, the mammalian target of rapamycin (mTOR) and its associated complexes (mTORC1 and mTORC2), and the well-described canonical signaling for insulin-stimulated glucose uptake. This new understanding of cellular signaling crosstalk has blurred the lines of what is a culprit and what is a consequence with regard to insulin resistance. Here, we briefly review the most recent understanding of insulin signaling in skeletal muscle, and how anabolic responses favoring anabolism directly impact cellular glucose disposal. This review highlights key cross-over interactions between protein and glucose regulatory pathways and the implications this may have for the design of new therapeutic targets for the control of glucoregulatory function in skeletal muscle.
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Affiliation(s)
| | - Selina Uranga
- Health and Kinesiology, Texas A&M University, TX 77843, United States
| | - James D Fluckey
- Health and Kinesiology, Texas A&M University, TX 77843, United States
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5
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Kale MB, Bajaj K, Umare M, Wankhede NL, Taksande BG, Umekar MJ, Upaganlawar A. Exercise and Nutraceuticals: Eminent approach for Diabetic Neuropathy. Curr Mol Pharmacol 2021; 15:108-128. [PMID: 34191703 DOI: 10.2174/1874467214666210629123010] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 02/28/2021] [Accepted: 03/05/2021] [Indexed: 11/22/2022]
Abstract
Diabetic neuropathy is an incapacitating chronic pathological condition that encompasses a large group of diseases and manifestations of nerve damage. It affects approximately 50% of patients with diabetes mellitus. Autonomic, sensory, and motor neurons are affected. Disabilities are severe, along with poor recovery and diverse pathophysiology. Physical exercise and herbal-based therapies have the potential to decrease the disabilities associated with diabetic neuropathy. Aerobic exercises like walking, weight lifting, the use of nutraceuticals and herbal extracts are found to be effective. Literature from the public domain was studied emphasizing various beneficial effects of different exercises, use of herbal and nutraceuticals for their therapeutic action in diabetic neuropathy. Routine exercises and administration of herbal and nutraceuticals, either the extract of plant material containing the active phytoconstituent or isolated phytoconstituent at safe concentration, have been shown to have promising positive action in the treatment of diabetic neuropathy. Exercise has shown promising effects on vascular and neuronal health and has proven to be well effective in the treatment as well as prevention of diabetic neuropathy by various novel mechanisms, including herbal and nutraceuticals therapy is also beneficial for the condition. They primarily show the anti-oxidant effect, secretagogue, anti-inflammatory, analgesic, and neuroprotective action. Severe adverse events are rare with these therapies. The current review investigates the benefits of exercise and nutraceutical therapies in the treatment of diabetic neuropathy.
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Affiliation(s)
- Mayur Bhimrao Kale
- Shrimati Kishoritai Bhoyar College of Pharmacy, New Kamptee, Nagpur 441002, Maharashtra, India
| | - Komal Bajaj
- Shrimati Kishoritai Bhoyar College of Pharmacy, New Kamptee, Nagpur 441002, Maharashtra, India
| | - Mohit Umare
- Shrimati Kishoritai Bhoyar College of Pharmacy, New Kamptee, Nagpur 441002, Maharashtra, India
| | - Nitu L Wankhede
- Shrimati Kishoritai Bhoyar College of Pharmacy, New Kamptee, Nagpur 441002, Maharashtra, India
| | | | - Milind Janrao Umekar
- Shrimati Kishoritai Bhoyar College of Pharmacy, New Kamptee, Nagpur 441002, Maharashtra, India
| | - Aman Upaganlawar
- SNJB's Shriman Sureshdada Jain College of Pharmacy, Neminagar, Chandwad-42310, Nasik, Maharashtra, India
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The Influence of Physical Activity on the Bioactive Lipids Metabolism in Obesity-Induced Muscle Insulin Resistance. Biomolecules 2020; 10:biom10121665. [PMID: 33322719 PMCID: PMC7764345 DOI: 10.3390/biom10121665] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Revised: 12/08/2020] [Accepted: 12/11/2020] [Indexed: 12/14/2022] Open
Abstract
High-fat diet consumption and lack of physical activity are important risk factors for metabolic disorders such as insulin resistance and cardiovascular diseases. Insulin resistance is a state of a weakened response of tissues such as skeletal muscle, adipose tissue, and liver to insulin, which causes an increase in blood glucose levels. This condition is the result of inhibition of the intracellular insulin signaling pathway. Skeletal muscle is an important insulin-sensitive tissue that accounts for about 80% of insulin-dependent glucose uptake. Although the exact mechanism by which insulin resistance is induced has not been thoroughly understood, it is known that insulin resistance is most commonly associated with obesity. Therefore, it is believed that lipids may play an important role in inducing insulin resistance. Among lipids, researchers’ attention is mainly focused on biologically active lipids: diacylglycerols (DAG) and ceramides. These lipids are able to regulate the activity of intracellular enzymes, including those involved in insulin signaling. Available data indicate that physical activity affects lipid metabolism and has a positive effect on insulin sensitivity in skeletal muscles. In this review, we have presented the current state of knowledge about the impact of physical activity on insulin resistance and metabolism of biologically active lipids.
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Obesity, Bioactive Lipids, and Adipose Tissue Inflammation in Insulin Resistance. Nutrients 2020; 12:nu12051305. [PMID: 32375231 PMCID: PMC7284998 DOI: 10.3390/nu12051305] [Citation(s) in RCA: 175] [Impact Index Per Article: 43.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2020] [Revised: 04/29/2020] [Accepted: 04/30/2020] [Indexed: 12/11/2022] Open
Abstract
Obesity is a major risk factor for the development of insulin resistance and type 2 diabetes. The exact mechanism by which adipose tissue induces insulin resistance is still unclear. It has been demonstrated that obesity is associated with the adipocyte dysfunction, macrophage infiltration, and low-grade inflammation, which probably contributes to the induction of insulin resistance. Adipose tissue synthesizes and secretes numerous bioactive molecules, namely adipokines and cytokines, which affect the metabolism of both lipids and glucose. Disorders in the synthesis of adipokines and cytokines that occur in obesity lead to changes in lipid and carbohydrates metabolism and, as a consequence, may lead to insulin resistance and type 2 diabetes. Obesity is also associated with the accumulation of lipids. A special group of lipids that are able to regulate the activity of intracellular enzymes are biologically active lipids: long-chain acyl-CoAs, ceramides, and diacylglycerols. According to the latest data, the accumulation of these lipids in adipocytes is probably related to the development of insulin resistance. Recent studies indicate that the accumulation of biologically active lipids in adipose tissue may regulate the synthesis/secretion of adipokines and proinflammatory cytokines. Although studies have revealed that inflammation caused by excessive fat accumulation and abnormalities in lipid metabolism can contribute to the development of obesity-related insulin resistance, further research is needed to determine the exact mechanism by which obesity-related insulin resistance is induced.
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8
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Ding C, Leow MKS, Magkos F. Oxytocin in metabolic homeostasis: implications for obesity and diabetes management. Obes Rev 2019; 20:22-40. [PMID: 30253045 PMCID: PMC7888317 DOI: 10.1111/obr.12757] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/28/2018] [Revised: 07/25/2018] [Accepted: 07/25/2018] [Indexed: 12/20/2022]
Abstract
Oxytocin was once understood solely as a neuropeptide with a central role in social bonding, reproduction, parturition, lactation and appetite regulation. Recent evidence indicates that oxytocin enhances glucose uptake and lipid utilization in adipose tissue and skeletal muscle, suggesting that dysfunction of the oxytocin system could underlie the pathogenesis of insulin resistance and dyslipidaemia. Murine studies revealed that deficiencies in oxytocin signalling and oxytocin receptor expression lead to obesity despite normal food intake, motor activity and increased leptin levels. In addition, plasma oxytocin concentration is notably lower in obese individuals with diabetes, which may suggest an involvement of the oxytocin system in the pathogenesis of cardiometabolic disease. More recently, small scale studies demonstrated that intranasal administration of oxytocin was associated with significant weight loss as well as improvements in insulin sensitivity and pancreatic β-cell responsivity in human subjects. The multi-pronged effects of oxytocin signalling on improving peripheral insulin sensitivity, pancreatic function and lipid homeostasis strongly suggest a role for this system as a therapeutic target in obesity and diabetes management. The complexity of obesity aetiology and the pathogenesis of obesity-related metabolic complications underscore the need for a systems approach to better understand the role of oxytocin in metabolic function.
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Affiliation(s)
- C Ding
- Clinical Nutrition Research Centre (CNRC), Singapore Institute for Clinical Sciences (SICS), Agency for Science, Technology and Research (A*STAR) and National University Health System, Singapore
| | - M K-S Leow
- Clinical Nutrition Research Centre (CNRC), Singapore Institute for Clinical Sciences (SICS), Agency for Science, Technology and Research (A*STAR) and National University Health System, Singapore.,Department of Endocrinology, Tan Tock Seng Hospital, Singapore.,Cardiovascular and Metabolic Disorders Program, Duke-NUS Medical School, Singapore.,Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore
| | - F Magkos
- Clinical Nutrition Research Centre (CNRC), Singapore Institute for Clinical Sciences (SICS), Agency for Science, Technology and Research (A*STAR) and National University Health System, Singapore.,Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore (NUS), Singapore
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9
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Dewanjee S, Das S, Das AK, Bhattacharjee N, Dihingia A, Dua TK, Kalita J, Manna P. Molecular mechanism of diabetic neuropathy and its pharmacotherapeutic targets. Eur J Pharmacol 2018; 833:472-523. [DOI: 10.1016/j.ejphar.2018.06.034] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2017] [Revised: 06/15/2018] [Accepted: 06/26/2018] [Indexed: 02/07/2023]
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10
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Royal jelly supplementation reduces skeletal muscle lipotoxicity and insulin resistance in aged obese rats. ACTA ACUST UNITED AC 2018; 25:307-315. [PMID: 29960833 DOI: 10.1016/j.pathophys.2018.05.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 04/28/2018] [Accepted: 05/03/2018] [Indexed: 02/08/2023]
Abstract
BACKGROUND Consumption of a high-fat diet (HFD) in aged rats is associated with several metabolic disorders. The mechanism of skeletal muscle lipotoxicity and insulin resistance (IR) is multi-factorial, but the exact mechanism of how aging affects these processes unknown. Royal jelly (RJ) is a dietary supplement with many physiological and pharmacological properties. No previous studies have demonstrated the protective effects and mechanism of RJ in aged obese rats. OBJECTIVES The study was carried to investigate the effects of aging and HFD on skeletal muscles, and adipose tissue metabolism and inflammation, in aged rats, and whether RJ could combat such adverse effects. METHODOLOGY A total of 40 male rats were divided into5 groups; young rats fed a standard diet, aged rats fed a standard diet, aged rats fed RJ, aged rats fed a HFD, and aged rats fed both a HFD and RJ for 8 weeks. We investigated changes in body weights (BW), abdominal fat weights, total cholesterol, triglycerides (TG), low density lipoprotein-cholesterol (LDL-c), high density lipoprotein-cholesterol (HDL-c), muscle TG, and IR levels. Also, concentrations of TNF-α receptor 1(TNFR1) were estimated in the serum and adipose tissues. RESULTS Aged, obese rats showed increased BW, adipose weights, IR, and disturbed serum and muscle lipids. Also, TNFR1 was increased. Rats fed RJ showed decreased adiposity, improved lipids' profiles, improved IR, and decreased TNFR1. CONCLUSION Aging and HFD were associated with disturbed metabolism, and muscle lipotoxicity and inflammation, while RJ could counteract muscle lipotoxicity in rats and reduce IR, most likely due to an anti-inflammatory effect.
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Bidwell AJ. Chronic Fructose Ingestion as a Major Health Concern: Is a Sedentary Lifestyle Making It Worse? A Review. Nutrients 2017; 9:nu9060549. [PMID: 28555043 PMCID: PMC5490528 DOI: 10.3390/nu9060549] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 05/17/2017] [Accepted: 05/25/2017] [Indexed: 12/13/2022] Open
Abstract
Obesity contributes to metabolic abnormalities such as insulin resistance, dyslipidemia, hypertension, and glucose intolerance, all of which are risk factors associated with metabolic syndrome. The growing prevelance of metabolic syndrome seems to be an end result of our current lifestyle which promotes high caloric, high-fat foods and minimal physical activity, resulting in a state of positive energy balance. Increased adiposity and physical inactivity may represent the beginning of the appearance of these risk factors. Understanding the metabolic and cardiovascular disturbances associated with diet and exercise habits is a crucial step towards reducing the risk factors for metabolic syndrome. Although considerable research has been conducted linking chronic fructose ingestion to the increased prevalence of obesity and metabolic syndrome risk factors, these studies have mainly been performed on animals, and/or in a post-absorptive state. Further, the magnitude of the effect of fructose may depend on other aspects of the diet, including the total amount of carbohydrates and fats in the diet and the overall consumption of meals. Therefore, the overall aim of this review paper is to examine the effects of a diet high in fructose on postprandial lipidemia, inflammatory markers and glucose tolerance, all risk factors for diabetes and cardiovascular disease. Moreover, an objective is to investigate whether increased physical activity can alter such effects.
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Affiliation(s)
- Amy J Bidwell
- Department of Health Promotion and Wellness, State University of New York at Oswego, 105G Park Hall, Oswego, NY 13027, USA.
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12
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Abstract
The heart utilizes large amounts of fatty acids as energy providing substrates. The physiological balance of lipid uptake and oxidation prevents accumulation of excess lipids. Several processes that affect cardiac function, including ischemia, obesity, diabetes mellitus, sepsis, and most forms of heart failure lead to altered fatty acid oxidation and often also to the accumulation of lipids. There is now mounting evidence associating certain species of these lipids with cardiac lipotoxicity and subsequent myocardial dysfunction. Experimental and clinical data are discussed and paths to reduction of toxic lipids as a means to improve cardiac function are suggested.
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Affiliation(s)
- P Christian Schulze
- From the Divisions of Cardiology, Friedrich-Schiller-University Jena, Germany, and Columbia University, New York, NY (P.C.S.); Metabolic Biology Laboratory, Center for Translational Medicine, Lewis Katz School of Medicine at Temple University, Philadelphia, PA (K.D.); and Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, New York University School of Medicine, New York, NY (I.J.G.).
| | - Konstantinos Drosatos
- From the Divisions of Cardiology, Friedrich-Schiller-University Jena, Germany, and Columbia University, New York, NY (P.C.S.); Metabolic Biology Laboratory, Center for Translational Medicine, Lewis Katz School of Medicine at Temple University, Philadelphia, PA (K.D.); and Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, New York University School of Medicine, New York, NY (I.J.G.)
| | - Ira J Goldberg
- From the Divisions of Cardiology, Friedrich-Schiller-University Jena, Germany, and Columbia University, New York, NY (P.C.S.); Metabolic Biology Laboratory, Center for Translational Medicine, Lewis Katz School of Medicine at Temple University, Philadelphia, PA (K.D.); and Department of Medicine, Division of Endocrinology, Diabetes and Metabolism, New York University School of Medicine, New York, NY (I.J.G.)
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13
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Capel F, Cheraiti N, Acquaviva C, Hénique C, Bertrand-Michel J, Vianey-Saban C, Prip-Buus C, Morio B. Oleate dose-dependently regulates palmitate metabolism and insulin signaling in C2C12 myotubes. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:2000-2010. [PMID: 27725263 DOI: 10.1016/j.bbalip.2016.10.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 09/10/2016] [Accepted: 10/05/2016] [Indexed: 01/22/2023]
Abstract
Because the protective effect of oleate against palmitate-induced insulin resistance may be lessened in skeletal muscle once cell metabolism is overloaded by fatty acids (FAs), we examined the impact of varying amounts of oleate on palmitate metabolic channeling and insulin signaling in C2C12 myotubes. Cells were exposed to 0.5mM of palmitate and to increasing doses of oleate (0.05, 0.25 and 0.5mM). Impacts of FA treatments on radio-labelled FA fluxes, on cellular content in diacylglycerols (DAG), triacylglycerols (TAG), ceramides, acylcarnitines, on PKCθ, MAPKs (ERK1/2, p38) and NF-ΚB activation, and on insulin-dependent Akt phosphorylation were examined. Low dose of oleate (0.05mM) was sufficient to improve palmitate complete oxidation to CO2 (+29%, P<0.05) and to alter the cellular acylcarnitine profile. Insulin-induced Akt phosphorylation was 48% higher in that condition vs. palmitate alone (p<0.01). Although DAG and ceramide contents were significantly decreased with 0.05mM of oleate vs. palmitate alone (-47 and -28%, respectively, p<0.01), 0.25mM of oleate was required to decrease p38 MAPK and PKCθ phosphorylation, thus further improving the insulin signaling (+32%, p<0.05). By contrast, increasing oleate concentration from 0.25 to 0.5mM, thus increasing total amount of FA from 0.75 to 1mM, deteriorated the insulin signaling pathway (-30%, p<0.01). This was observed despite low contents in DAG and ceramides, and enhanced palmitate incorporation into TAG (+27%, p<0.05). This was associated with increased incomplete FA β-oxidation and impairment of acylcarnitine profile. In conclusion, these combined data place mitochondrial β-oxidation at the center of the regulation of muscle insulin sensitivity, besides p38 MAPK and PKCθ.
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Affiliation(s)
- Frédéric Capel
- INRA UMR1019 Nutrition Humaine, Laboratoire de Nutrition Humaine, Université d'Auvergne, CRNH, 58 rue Montalembert BP321, 63009 Clermont Ferrand CEDEX 1, France.
| | - Naoufel Cheraiti
- INRA UMR1019 Nutrition Humaine, Laboratoire de Nutrition Humaine, Université d'Auvergne, CRNH, 58 rue Montalembert BP321, 63009 Clermont Ferrand CEDEX 1, France.
| | - Cécile Acquaviva
- Service Maladies Héréditaires du Métabolisme, Centre de Biologie et Pathologie Est, CHU de Lyon, France.
| | - Carole Hénique
- Institut Cochin, Département d'Endocrinologie, Métabolisme and Diabète, INSERM U1016/CNRS UMR8104/UMR-S8104, Bâtiment Faculté, 24 rue du faubourg Saint Jacques, 75014 Paris, France.
| | - Justine Bertrand-Michel
- MetaToul-Lipidomic, MetaboHUB, INSERM UMR 1048, Institute of Metabolic and Cardiovascular Diseases, Toulouse, France University of Toulouse, UMR1048, Paul Sabatier University, France.
| | - Christine Vianey-Saban
- Service Maladies Héréditaires du Métabolisme, Centre de Biologie et Pathologie Est, CHU de Lyon, France.
| | - Carina Prip-Buus
- Institut Cochin, Département d'Endocrinologie, Métabolisme and Diabète, INSERM U1016/CNRS UMR8104/UMR-S8104, Bâtiment Faculté, 24 rue du faubourg Saint Jacques, 75014 Paris, France.
| | - Béatrice Morio
- INRA UMR1019 Nutrition Humaine, Laboratoire de Nutrition Humaine, Université d'Auvergne, CRNH, 58 rue Montalembert BP321, 63009 Clermont Ferrand CEDEX 1, France; INRA UMR1397, Laboratoire CarMeN, Inserm UMR1060, Université Lyon 1, INSA de Lyon, Faculté de Médecine Lyon Sud, BP 12, 165 Chemin du Grand Revoyet, 69921 Oullins Cedex, France.
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Al-Bayati A, Lukka D, Brown AE, Walker M. Effects of thrombin on insulin signalling and glucose uptake in cultured human myotubes. J Diabetes Complications 2016; 30:1209-16. [PMID: 27396242 DOI: 10.1016/j.jdiacomp.2016.06.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Revised: 05/19/2016] [Accepted: 06/14/2016] [Indexed: 01/22/2023]
Abstract
BACKGROUND Hyper-coagulability (elevated thrombin) is a feature of type 2 diabetes and contributes to an increased risk of thrombotic and vascular events. Skeletal muscle is the key peripheral tissue site of insulin resistance in type 2 diabetes. Cultured human skeletal muscle cells were used to explore the effects of thrombin on insulin signalling and glucose uptake. We hypothesized that thrombin affects insulin activity in human skeletal muscle cells which could link the hypercoagulability and insulin resistance in type 2 diabetes. METHODS Human skeletal muscle cell cultures (myotubes) were treated with +/-5 units/ml thrombin for 6h. Insulin signalling pathway components and AMPK were examined by Western blotting. Real time PCR and glucose uptake assays were performed. RESULTS There was a significant decrease (p<0.01) in insulin mediated IRS-1 and Akt phosphorylation in response to thrombin in cultured myotubes. Diminished Akt phosphorylation was alleviated by treatment with a PKC inhibitor. Thrombin directly increased basal glucose uptake (p<0.05) that involved AMPK phosphorylation (p<0.01) and this was partly repressed by compound C (AMPK inhibitor). Thrombin also significantly increased the gene expression level of both GLUT1 and GLUT4 in cultured human skeletal muscle cells. CONCLUSION Thrombin decreased insulin signalling in skeletal muscle cells through a PKC mediated mechanism, but did not affect the net action of insulin on glucose uptake. The direct stimulatory effect of thrombin on glucose uptake was mediated, at least in part, via an AMPK dependent mechanism. We conclude that thrombin activation results in multiple metabolic effects beyond increased thrombogenicity but does not include a decrease in insulin sensitivity (glucose uptake) in cultured human skeletal muscle cells.
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Affiliation(s)
- Ali Al-Bayati
- Diabetes Research Group, Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom.
| | - Dhanisha Lukka
- Diabetes Research Group, Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Audrey E Brown
- Diabetes Research Group, Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Mark Walker
- Diabetes Research Group, Institute of Cellular Medicine, Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
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Wolf P, Winhofer Y, Anderwald CH, Krššák M, Krebs M. Intracellular lipid accumulation and shift during diabetes progression. Wien Med Wochenschr 2014; 164:320-9. [DOI: 10.1007/s10354-014-0292-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Accepted: 06/23/2014] [Indexed: 02/08/2023]
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Abstract
The prevalence of Type 2 diabetes mellitus is predicted to increase dramatically over the coming years and the clinical implications and healthcare costs from this disease are overwhelming. In many cases, this pathological condition is linked to a cluster of metabolic disorders, such as obesity, systemic hypertension and dyslipidaemia, defined as the metabolic syndrome. Insulin resistance has been proposed as the key mediator of all of these features and contributes to the associated high cardiovascular morbidity and mortality. Although the molecular mechanisms behind insulin resistance are not completely understood, a negative cross-talk between AngII (angiotensin II) and the insulin signalling pathway has been the focus of great interest in the last decade. Indeed, substantial evidence has shown that anti-hypertensive drugs that block the RAS (renin-angiotensin system) may also act to prevent diabetes. Despite its long history, new components within the RAS continue to be discovered. Among them, Ang-(1-7) [angiotensin-(1-7)] has gained special attention as a counter-regulatory hormone opposing many of the AngII-related deleterious effects. Specifically, we and others have demonstrated that Ang-(1-7) improves the action of insulin and opposes the negative effect that AngII exerts at this level. In the present review, we provide evidence showing that insulin and Ang-(1-7) share a common intracellular signalling pathway. We also address the molecular mechanisms behind the beneficial effects of Ang-(1-7) on AngII-mediated insulin resistance. Finally, we discuss potential therapeutic approaches leading to modulation of the ACE2 (angiotensin-converting enzyme 2)/Ang-(1-7)/Mas receptor axis as a very attractive strategy in the therapy of the metabolic syndrome and diabetes-associated diseases.
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Abstract
Diabetes and obesity are both associated with lipotoxic cardiomyopathy exclusive of coronary artery disease and hypertension. Lipotoxicities have become a public health concern and are responsible for a significant portion of clinical cardiac disease. These abnormalities may be the result of a toxic metabolic shift to more fatty acid and less glucose oxidation with concomitant accumulation of toxic lipids. Lipids can directly alter cellular structures and activate downstream pathways leading to toxicity. Recent data have implicated fatty acids and fatty acyl coenzyme A, diacylglycerol, and ceramide in cellular lipotoxicity, which may be caused by apoptosis, defective insulin signaling, endoplasmic reticulum stress, activation of protein kinase C, MAPK activation, or modulation of PPARs.
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Rector RS, Morris EM, Ridenhour S, Meers GM, Hsu FF, Turk J, Ibdah JA. Selective hepatic insulin resistance in a murine model heterozygous for a mitochondrial trifunctional protein defect. Hepatology 2013; 57:2213-23. [PMID: 23359250 PMCID: PMC3660447 DOI: 10.1002/hep.26285] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2012] [Accepted: 01/04/2013] [Indexed: 12/20/2022]
Abstract
UNLABELLED Earlier reports suggest a link between mitochondrial dysfunction and development of hepatic insulin resistance. Here we used a murine model heterozygous (HET) for a mitochondrial trifunctional protein (MTP) gene defect to determine if a primary defect in mitochondrial long-chain fatty acid oxidation disrupts hepatic insulin action. Hyperinsulinemic-euglycemic clamps and signaling studies were performed for assessment of whole-body and hepatic insulin resistance/signaling. In addition, hepatic fatty acid oxidation and hepatic insulin action were assessed in vitro using primary hepatocytes isolated from HET and wildtype (WT) mice. In both hepatic mitochondria and isolated primary hepatocytes, heterozygosity of MTP caused an ∼50% reduction in mitochondrial fatty acid oxidation, a significantly impaired glucose disposal during the insulin clamp, and a markedly lower insulin-stimulated suppression of hepatic glucose production. HET mice also exhibited impaired insulin signaling, with increased hepatic phosphorylation of IRS2 (ser731) and reduced Akt phosphorylation (ser473) in both hepatic tissue and isolated primary hepatocytes. Assessment of insulin-stimulated FOXO1/phospho-FOXO1 protein content and PEPCK/G6Pase messenger RNA (mRNA) expression did not reveal differences between HET and WT mice. However, insulin-induced phosphorylation of GSK3β was significantly blunted in HET mice. Hepatic insulin resistance was associated with an increased methylation status of the catalytic subunit of protein phosphatase 2A (PP2A-C), but was not associated with differences in hepatic diacylglycerol content, activated protein kinase C-ϵ (PKC-ϵ), inhibitor κB kinase β (IKK-β), c-Jun N-terminal kinase (JNK), or phospho-JNK protein contents. Surprisingly, hepatic ceramides were significantly lower in the HET mice compared with WT. CONCLUSION A primary defect in mitochondrial fatty acid β-oxidation causes hepatic insulin resistance selective to hepatic glycogen metabolism that is associated with elevated methylated PP2A-C, but independent of other mechanisms commonly considered responsible for insulin resistance. (HEPATOLOGY 2013;).
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Affiliation(s)
- R. Scott Rector
- Harry S Truman Memorial Veterans Medical Center, Columbia, Missouri 65212, USA,Department of Internal Medicine-Division of Gastroenterology and Hepatology, University of Missouri,Department of Nutrition and Exercise Physiology, University of Missouri
| | - E. Matthew Morris
- Harry S Truman Memorial Veterans Medical Center, Columbia, Missouri 65212, USA,Department of Internal Medicine-Division of Gastroenterology and Hepatology, University of Missouri
| | - Suzanne Ridenhour
- Harry S Truman Memorial Veterans Medical Center, Columbia, Missouri 65212, USA,Department of Internal Medicine-Division of Gastroenterology and Hepatology, University of Missouri
| | - Grace M. Meers
- Harry S Truman Memorial Veterans Medical Center, Columbia, Missouri 65212, USA,Department of Internal Medicine-Division of Gastroenterology and Hepatology, University of Missouri
| | - Fong-Fu Hsu
- Department of Internal Medicine, Mass Spectrometry Resource, Division of Endocrinology, Diabetes, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - John Turk
- Department of Internal Medicine, Mass Spectrometry Resource, Division of Endocrinology, Diabetes, Metabolism, and Lipid Research, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Jamal A. Ibdah
- Harry S Truman Memorial Veterans Medical Center, Columbia, Missouri 65212, USA,Department of Internal Medicine-Division of Gastroenterology and Hepatology, University of Missouri,Department of Nutrition and Exercise Physiology, University of Missouri,Department of Medical Pharmacology and Physiology, University of Missouri
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Abstract
Severe obesity is increasing at a disproportionate rate compared with milder grade obesity. Our research group has obtained evidence indicative of an "obesity metabolic program" in skeletal muscles of severely obese individuals, which may be determined genetically or epigenetically. We believe that this represents a paradigm shift in thinking about metabolic regulation in obesity.
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Abstract
Obesity is associated with skeletal muscle insulin resistance, which is a crucial step in the development of type 2 diabetes. Among the mechanisms by which obesity may lead to insulin resistance, lipotoxicity is one of the hypotheses being explored; others include inflammation or the oxidative stress hypotheses. This review focuses on the role of diacylglycerols (DAG), a family of lipid metabolites implicated in the pathogenesis of lipotoxicity and insulin resistance. While recent studies report contradictory results in humans with regard to the importance of DAG-induced insulin resistance in skeletal muscle, other current literature highlight a potential role for DAG as signalling molecules. This review will discuss possible hypotheses explaining these contradictory results and the need to explore further the role of DAG in human metabolism.
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Affiliation(s)
- F Amati
- Department of Physiology, University of Lausanne, 7 Bugnon, Lausanne, Switzerland.
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21
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Sobhia ME, Grewal BK, Bhat J, Rohit S, Punia V. Protein kinase C βII in diabetic complications: survey of structural, biological and computational studies. Expert Opin Ther Targets 2012; 16:325-44. [PMID: 22404224 DOI: 10.1517/14728222.2012.667804] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION PKC-βII is a conventional isoform of PKC. It is overexpressed in hyperglycemic conditions and is known to trigger various diabetic complications, mainly cardiovascular complications and to a certain extent nephropathy, neuropathy, retinopathy etc. Selective inhibition of this enzyme will be one of the favorable approaches to treat diabetes-mellitus-related complications. Due to high sequence similarities among PKC isoforms, selective inhibition of PKC-βII is difficult and yet to be achieved successfully. AREAS COVERED This review discusses the studies carried out in various aspects of PKC-βII. The biological aspects, crystal structure data, structure–activity relationship study (SAR) and in silico studies related to PKC-βII such as homology modeling, molecular docking, molecular dynamics, quantitative structure–activity relationship (QSAR) studies and pharmacophore modeling etc. are summarized. EXPERT OPINION PKC-βII is a potential target for treating diabetes-related complications. Selective inhibitors of this enzyme are under clinical trials but to date, success has not been achieved. Thus, extensive research is essential in this direction; the contribution of in silico tools in designing and optimizing selective inhibitors of PKC-βII is valuable.
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Affiliation(s)
- M Elizabeth Sobhia
- National Institute of Pharmaceutical Education and Research, Department of Pharmacoinformatics, Punjab, India.
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22
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Verspohl EJ. Novel Pharmacological Approaches to the Treatment of Type 2 Diabetes. Pharmacol Rev 2012; 64:188-237. [DOI: 10.1124/pr.110.003319] [Citation(s) in RCA: 71] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
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23
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Salvadó L, Serrano-Marco L, Barroso E, Palomer X, Vázquez-Carrera M. Targeting PPARβ/δ for the treatment of type 2 diabetes mellitus. Expert Opin Ther Targets 2012; 16:209-23. [DOI: 10.1517/14728222.2012.658370] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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Lipina C, Hundal HS. Sphingolipids: agents provocateurs in the pathogenesis of insulin resistance. Diabetologia 2011; 54:1596-607. [PMID: 21468641 DOI: 10.1007/s00125-011-2127-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/29/2010] [Accepted: 02/18/2011] [Indexed: 12/16/2022]
Abstract
Obesity is a major risk factor for a variety of chronic diseases, including diabetes mellitus, and comorbidities such as cardiovascular disorders. Despite recommended alterations in lifestyle, including physical activity and energy restriction, being the foundation of any anti-obesity therapy, this approach has so far proved to be of little success in tackling this major public health concern. Because of this, alternative means of tackling this problem are currently being investigated, including pharmacotherapeutic intervention. Consequently, much attention has been directed towards elucidating the molecular mechanisms underlying the development of insulin resistance. This review discusses some of these potential mechanisms, with particular focus on the involvement of the sphingolipid ceramide. Various factors associated with obesity, such as saturated fatty acids and inflammatory cytokines, promote the synthesis of ceramide and other intermediates. Furthermore, studies performed in cultured cells and in vivo associate these sphingolipids with impaired insulin action. In light of this, we provide an account of the research investigating how pharmacological inhibition or genetic manipulation of enzymes involved in regulating sphingolipid synthesis can attenuate the insulin-desensitising effects of these obesity-related factors. By doing so, we outline potential therapeutic targets that may prove useful in the treatment of metabolic disorders.
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Affiliation(s)
- C Lipina
- Division of Cell Signalling and Immunology, Sir James Black Centre, College of Life Sciences, University of Dundee, Dundee, DD1 5EH, Scotland, UK
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Houmard JA, Pories WJ, Dohm GL. Is there a metabolic program in the skeletal muscle of obese individuals? J Obes 2011; 2011:250496. [PMID: 21603262 PMCID: PMC3092539 DOI: 10.1155/2011/250496] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Accepted: 02/24/2011] [Indexed: 01/22/2023] Open
Abstract
Severe obesity (BMI ≥ 40 kg/m(2)) is associated with multiple defects in skeletal muscle which contribute to insulin resistance and a reduction in fatty acid oxidation (FAO) in this tissue. These metabolic derangements are retained in human skeletal muscle cells raised in culture. Together, these findings are indicative of a dysfunctional global metabolic program with severe obesity which is of an epigenetic or genetic origin. Weight loss via gastric bypass surgery can "turn off" and/or correct components of this metabolic program as insulin sensitivity is restored; however, the impairment in FAO in skeletal muscle remains evident. Physical activity can improve FAO and insulin action, indicating that this patient population is not exercise resistant and that exercise offers a pathway to circumvent the abnormal program. Findings presented in this review will hopefully increase the understanding of and aid in preventing and/or treating the severely obese condition.
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Affiliation(s)
- Joseph A. Houmard
- Department of Exercise and Sport Science, College of Health and Human Performance, East Carolina University, Greenville, NC 27834, USA
- Human Performance Laboratory, College of Health and Human Performance, East Carolina University, Greenville, NC 27858, USA
- East Carolina Diabetes and Obesity Center, East Carolina University, Greenville, NC 27858, USA
- *Joseph A. Houmard:
| | - Walter J. Pories
- East Carolina Diabetes and Obesity Center, East Carolina University, Greenville, NC 27858, USA
- Department of Surgery, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
| | - G. Lynis Dohm
- East Carolina Diabetes and Obesity Center, East Carolina University, Greenville, NC 27858, USA
- Department of Physiology, Brody School of Medicine, East Carolina University, Greenville, NC 27834, USA
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Free fatty acids induce endothelial dysfunction and activate protein kinase C and nuclear factor-κB pathway in rat aorta. Int J Cardiol 2010; 152:218-24. [PMID: 20692055 DOI: 10.1016/j.ijcard.2010.07.019] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2010] [Revised: 06/06/2010] [Accepted: 07/04/2010] [Indexed: 02/05/2023]
Abstract
BACKGROUND Insulin resistance is associated with an inappropriate elevation of plasma free fatty acids (FFAs) and endothelial dysfunction. In this study, we asked if elevated circulating FFA levels led to impaired insulin signaling and endothelial dysfunction in-vivo via activation of PKC-mediated inflammatory pathways. METHODS Sprague-Dawley (S-D) rats were infused with 1) 20% intralipid+heparin (FFA group) or 2) saline alone (Control group) for 6h. The intact aorta thoracica and aorta abdominalis were then removed. Aortic rings were isolated and evaluated for endothelial-dependent and non-dependent relaxation in an organ bath. The activities of eNOS and PKC were measured in endothelial homogenates prepared from endothelial cells harvested from the aorta. The expression levels of insulin signaling molecules IRS-1, Akt, eNOS, ERK1/ERK2, PKC-α, NFκB-p65 subunit and IκB-α in rat aortic endothelium were determined by immunohistochemistry and Western blot. RESULTS Elevation of FFAs resulted in a 35.9% reduction in the response to acetylcholine (p < 0.01), a 26% decline in plasma NOx levels (p < 0.05), a 53% decrease in eNOS activity and a 34 ± 9% inhibition in IRS-1 tyrosine phosphorylation (p < 0.05). We also found a 46% decrease in Akt phosphorylation and a 36% decrease in eNOS phosphorylation. FFA-induced endothelial insulin resistance was associated with 82% increase in total membrane-associated PKC activity, a 1.7-fold increase in total PKC-α protein, 1.29-fold decrease in IκB-α expression levels and 1.47-fold increase in NF-κB p65 subunit expression in rat aortic endothelium. CONCLUSION The molecular mechanisms underlying FFA-induced endothelial insulin resistance and eNOS inhibition may provide an important link implicating the PKC and IκB-α/NF-κB pathways in FFA-mediated inhibition of vascular insulin signaling.
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The Role of Peroxisome Proliferator-Activated Receptor beta/delta on the Inflammatory Basis of Metabolic Disease. PPAR Res 2010; 2010. [PMID: 20706688 PMCID: PMC2913795 DOI: 10.1155/2010/368467] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2010] [Accepted: 06/28/2010] [Indexed: 01/04/2023] Open
Abstract
The pathophysiology underlying several metabolic diseases, such as obesity, type 2 diabetes mellitus, and atherosclerosis, involves a state of chronic low-level inflammation. Evidence is now emerging that the nuclear receptor Peroxisome Proliferator-Activated Receptor (PPAR)β/δ ameliorates these pathologies partly through its anti-inflammatory effects. PPARβ/δ activation prevents the production of inflammatory cytokines by adipocytes, and it is involved in the acquisition of the anti-inflammatory phenotype of macrophages infiltrated in adipose tissue. Furthermore, PPARβ/δ ligands prevent fatty acid-induced inflammation in skeletal muscle cells, avoid the development of cardiac hypertrophy, and suppress macrophage-derived inflammation in atherosclerosis. These data are promising and suggest that PPARβ/δ ligands may become a therapeutic option for preventing the inflammatory basis of metabolic diseases.
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28
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Bell JA, Reed MA, Consitt LA, Martin OJ, Haynie KR, Hulver MW, Muoio DM, Dohm GL. Lipid partitioning, incomplete fatty acid oxidation, and insulin signal transduction in primary human muscle cells: effects of severe obesity, fatty acid incubation, and fatty acid translocase/CD36 overexpression. J Clin Endocrinol Metab 2010; 95:3400-10. [PMID: 20427507 PMCID: PMC2928911 DOI: 10.1210/jc.2009-1596] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
CONTEXT Intracellular lipid partitioning toward storage and the incomplete oxidation of fatty acids (FA) have been linked to insulin resistance. OBJECTIVE To gain insight into how intracellular lipid metabolism is related to insulin signal transduction, we examined the effects of severe obesity, excess FA, and overexpression of the FA transporter, FA translocase (FAT)/CD36, in primary human skeletal myocytes. DESIGN, SETTING, AND PATIENTS Insulin signal transduction, FA oxidation, and metabolism were measured in skeletal muscle cells harvested from lean and severely obese women. To emulate the obesity phenotype in our cell culture system, we incubated cells from lean individuals with excess FA or overexpressed FAT/CD36 using recombinant adenoviral technology. RESULTS Complete oxidation of FA was significantly reduced, whereas total lipid accumulation, FA esterification into lipid intermediates, and incomplete oxidation were up-regulated in the muscle cells of severely obese subjects. Insulin signal transduction was reduced in the muscle cells from severely obese subjects compared to lean controls. Incubation of muscle cells from lean subjects with lipids reduced insulin signal transduction and increased lipid storage and incomplete FA oxidation. CD36 overexpression increased FA transport capacity, but did not impair complete FA oxidation and insulin signal transduction in muscle cells from lean subjects. CONCLUSIONS Cultured myocytes from severely obese women express perturbations in FA metabolism and insulin signaling reminiscent of those observed in vivo. The obesity phenotype can be recapitulated in muscle cells from lean subjects via exposure to excess lipid, but not by overexpressing the FAT/CD36 FA transporter.
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Affiliation(s)
- Jill A Bell
- East Carolina University, Brody Medical School, Department of Physiology, 600 Moye Boulevard, Greenville, NC 27834, USA
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Frisard MI, McMillan RP, Marchand J, Wahlberg KA, Wu Y, Voelker KA, Heilbronn L, Haynie K, Muoio B, Li L, Hulver MW. Toll-like receptor 4 modulates skeletal muscle substrate metabolism. Am J Physiol Endocrinol Metab 2010; 298:E988-98. [PMID: 20179247 PMCID: PMC2867377 DOI: 10.1152/ajpendo.00307.2009] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
Toll-like receptor 4 (TLR4), a protein integral to innate immunity, is elevated in skeletal muscle of obese and type 2 diabetic humans and has been implicated in the development of lipid-induced insulin resistance. The purpose of this study was to examine the role of TLR4 as a modulator of basal (non-insulin-stimulated) substrate metabolism in skeletal muscle with the hypothesis that its activation would result in reduced fatty acid oxidation and increased partitioning of fatty acids toward neutral lipid storage. Human skeletal muscle, rodent skeletal muscle, and skeletal muscle cell cultures were employed to study the functional consequences of TLR4 activation on glucose and fatty acid metabolism. Herein, we demonstrate that activation of TLR4 with low (metabolic endotoxemia) and high (septic conditions) doses of LPS results in increased glucose utilization and reduced fatty acid oxidation in skeletal muscle and that these changes in metabolism in vivo occur in concert with increased circulating triglycerides. Moreover, animals with a loss of TLR4 function possess increased oxidative capacity in skeletal muscle and present with lower fasting levels of triglycerides and nonesterified free fatty acids. Evidence is also presented to suggest that these changes in substrate metabolism under metabolic endotoxemic conditions are independent of skeletal muscle-derived proinflammatory cytokine production. This report illustrates that skeletal muscle is a target for circulating endotoxin and may provide critical insight into the link between a proinflammatory state and dysregulated metabolism as observed with obesity, type 2 diabetes, and metabolic syndrome.
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Affiliation(s)
- Madlyn I Frisard
- Virginia Polytechnic Institute and State University, Department of Human Nutrition, Foods, and Exercise, Blacksburg, VA 24061, USA
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Coll T, Alvarez-Guardia D, Barroso E, Gómez-Foix AM, Palomer X, Laguna JC, Vázquez-Carrera M. Activation of peroxisome proliferator-activated receptor-{delta} by GW501516 prevents fatty acid-induced nuclear factor-{kappa}B activation and insulin resistance in skeletal muscle cells. Endocrinology 2010; 151:1560-9. [PMID: 20185762 DOI: 10.1210/en.2009-1211] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Elevated plasma free fatty acids cause insulin resistance in skeletal muscle through the activation of a chronic inflammatory process. This process involves nuclear factor (NF)-kappaB activation as a result of diacylglycerol (DAG) accumulation and subsequent protein kinase Ctheta (PKCtheta) phosphorylation. At present, it is unknown whether peroxisome proliferator-activated receptor-delta (PPARdelta) activation prevents fatty acid-induced inflammation and insulin resistance in skeletal muscle cells. In C2C12 skeletal muscle cells, the PPARdelta agonist GW501516 prevented phosphorylation of insulin receptor substrate-1 at Ser(307) and the inhibition of insulin-stimulated Akt phosphorylation caused by exposure to the saturated fatty acid palmitate. This latter effect was reversed by the PPARdelta antagonist GSK0660. Treatment with the PPARdelta agonist enhanced the expression of two well known PPARdelta target genes involved in fatty acid oxidation, carnitine palmitoyltransferase-1 and pyruvate dehydrogenase kinase 4 and increased the phosphorylation of AMP-activated protein kinase, preventing the reduction in fatty acid oxidation caused by palmitate exposure. In agreement with these changes, GW501516 treatment reversed the increase in DAG and PKCtheta activation caused by palmitate. These effects were abolished in the presence of the carnitine palmitoyltransferase-1 inhibitor etomoxir, thereby indicating that increased fatty acid oxidation was involved in the changes observed. Consistent with these findings, PPARdelta activation by GW501516 blocked palmitate-induced NF-kappaB DNA-binding activity. Likewise, drug treatment inhibited the increase in IL-6 expression caused by palmitate in C2C12 and human skeletal muscle cells as well as the protein secretion of this cytokine. These findings indicate that PPARdelta attenuates fatty acid-induced NF-kappaB activation and the subsequent development of insulin resistance in skeletal muscle cells by reducing DAG accumulation. Our results point to PPARdelta activation as a pharmacological target to prevent insulin resistance.
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Affiliation(s)
- Teresa Coll
- Unitat de Farmacologia. Facultat de Farmàcia, Diagonal 643, E-08028 Barcelona, Spain
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31
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Venables MC, Jeukendrup AE. Physical inactivity and obesity: links with insulin resistance and type 2 diabetes mellitus. Diabetes Metab Res Rev 2009; 25 Suppl 1:S18-23. [PMID: 19662619 DOI: 10.1002/dmrr.983] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Data from the health survey for England 2006, showed that the prevalence of type 2 diabetes mellitus (T2DM) has more than doubled in men and women since 1991. In the USA certain States have a prevalence of T2DM of greater than 10%. Globally it has been reported that this increase is by no means slowing down and that the number of individuals with the disease is expected to rise from 171 million cases reported in 2000 to 366 million by the year 2030. Physical inactivity and obesity are two major risk factors for the development of T2DM. In this review we will discuss evidence of an association between physical inactivity, obesity and T2DM from prospective cohort studies and clinical trials. We will also discuss some of the potential mechanisms that are thought to link obesity and physical inactivity with the major pathophysiological precursor of T2DM, insulin resistance.
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Affiliation(s)
- Michelle C Venables
- Exercise Metabolism Research Group, Human Performance Laboratory, School of Sport and Exercise Sciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
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Benoit SC, Kemp CJ, Elias CF, Abplanalp W, Herman JP, Migrenne S, Lefevre AL, Cruciani-Guglielmacci C, Magnan C, Yu F, Niswender K, Irani BG, Holland WL, Clegg DJ. Palmitic acid mediates hypothalamic insulin resistance by altering PKC-theta subcellular localization in rodents. J Clin Invest 2009; 119:2577-89. [PMID: 19726875 DOI: 10.1172/jci36714] [Citation(s) in RCA: 234] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Accepted: 05/20/2009] [Indexed: 01/06/2023] Open
Abstract
Insulin signaling can be modulated by several isoforms of PKC in peripheral tissues. Here, we assessed whether one specific isoform, PKC-theta, was expressed in critical CNS regions that regulate energy balance and whether it mediated the deleterious effects of diets high in fat, specifically palmitic acid, on hypothalamic insulin activity in rats and mice. Using a combination of in situ hybridization and immunohistochemistry, we found that PKC-theta was expressed in discrete neuronal populations of the arcuate nucleus, specifically the neuropeptide Y/agouti-related protein neurons and the dorsal medial nucleus in the hypothalamus. CNS exposure to palmitic acid via direct infusion or by oral gavage increased the localization of PKC-theta to cell membranes in the hypothalamus, which was associated with impaired hypothalamic insulin and leptin signaling. This finding was specific for palmitic acid, as the monounsaturated fatty acid, oleic acid, neither increased membrane localization of PKC-theta nor induced insulin resistance. Finally, arcuate-specific knockdown of PKC-theta attenuated diet-induced obesity and improved insulin signaling. These results suggest that many of the deleterious effects of high-fat diets, specifically those enriched with palmitic acid, are CNS mediated via PKC-theta activation, resulting in reduced insulin activity.
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Affiliation(s)
- Stephen C Benoit
- Department of Psychiatry, University of Cincinnati, Cincinnati, Ohio, USA
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Dyck DJ. Adipokines as regulators of muscle metabolism and insulin sensitivity. Appl Physiol Nutr Metab 2009; 34:396-402. [PMID: 19448705 DOI: 10.1139/h09-037] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Skeletal muscle is the largest tissue responsible for the insulin-stimulated disposal of glucose. However, identifying the link between excess body fat and impaired insulin sensitivity in skeletal muscle has been difficult. Several adipose-derived cytokines (adipokines) have been implicated in the impairment of insulin sensitivity, while adipokines such as leptin and adiponectin exert an insulin-sensitizing effect. Leptin and adiponectin have each been shown to increase fatty acid (FA) oxidation and decrease triglyceride storage in muscle, which may explain, in part, the insulin-sensitizing effect of these cytokines. Recent evidence strongly implicates an increased localization of the FA transporters to the plasma membrane (PM) as an important factor in the accumulation of intramuscular lipids with high-fat diets and obesity. Perhaps surprisingly, relatively little attention has been paid to the ability of insulin-sensitizing compounds, such as leptin and adiponectin, to decrease the abundance of FA transporters in the PM, thereby decreasing lipid accumulation. In the case of both adipokines, there is also evidence that a resistance to their ability to stimulate FA oxidation in skeletal muscle develops during obesity. One of our recent studies indicates that this development can be very rapid (i.e., within days), and precedes the increase in lipid uptake and accumulation that leads to insulin resistance. It is noteworthy that leptin resistance can be modulated by both diet and training in rodents. Further studies examining the underlying mechanisms of the development of leptin and adiponectin resistance are warranted.
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Affiliation(s)
- David J Dyck
- Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada.
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Chappell DS, Patel NA, Jiang K, Li P, Watson JE, Byers DM, Cooper DR. Functional involvement of protein kinase C-betaII and its substrate, myristoylated alanine-rich C-kinase substrate (MARCKS), in insulin-stimulated glucose transport in L6 rat skeletal muscle cells. Diabetologia 2009; 52:901-11. [PMID: 19252893 PMCID: PMC2677811 DOI: 10.1007/s00125-009-1298-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2008] [Accepted: 01/19/2009] [Indexed: 12/17/2022]
Abstract
AIMS/HYPOTHESIS Insulin stimulates phosphorylation cascades, including phosphatidylinositol-3-kinase (PI3K), phosphatidylinositol-dependent kinase (PDK1), Akt, and protein kinase C (PKC). Myristoylated alanine-rich C-kinase substrate (MARCKS), a PKCbetaII substrate, could link the effects of insulin to insulin-stimulated glucose transport (ISGT) via phosphorylation of its effector domain since MARCKS has a role in cytoskeletal rearrangements. METHODS We examined phosphoPKCbetaII after insulin treatment of L6 myocytes, and cytosolic and membrane phosphoMARCKS, MARCKS and phospholipase D1 in cells pretreated with LY294002 (PI3K inhibitor), CG53353 (PKCbetaII inhibitor) or W13 (calmodulin inhibitor), PI3K, PKCbetaII and calmodulin inhibitors, respectively, before insulin treatment, using western blots. ISGT was examined after cells had been treated with inhibitors, small inhibitory RNA (siRNA) for MARCKS, or transfection with MARCKS mutated at a PKC site. MARCKS, PKCbetaII, GLUT4 and insulin receptor were immunoblotted in subcellular fractions with F-actin antibody immunoprecipitates to demonstrate changes following insulin treatment. GLUT4 membrane insertion was followed after insulin with or without CG53353. RESULTS Insulin increased phosphoPKCbetaII(Ser660 and Thr641); LY294002 blocked this, indicating its activation by PI3K. Insulin treatment increased cytosolic phosphoMARCKS, decreased membrane MARCKS and increased membrane phospholipase D1 (PLD1), a protein regulating glucose transporter vesicle fusion resulted. PhosphoMARCKS was attenuated by CG53353 or MARCKS siRNA. MARCKS siRNA blocked ISGT. Association of PKCbetaII and GLUT4 with membrane F-actin was enhanced by insulin, as was that of cytosolic and membrane MARCKS. ISGT was attenuated in myocytes transfected with mutated MARCKS (Ser152Ala), whereas overproduction of wild-type MARCKS enhanced ISGT. CG53353 blocked insertion of GLUT4 into membranes of insulin treated cells. CONCLUSIONS/INTERPRETATION The results suggest that PKCbetaII is involved in mediating downstream steps of ISGT through MARCKS phosphorylation and cytoskeletal remodelling.
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Affiliation(s)
- D. S. Chappell
- Department of Molecular Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, Tampa, FL 33612, USA
| | - N. A. Patel
- Department of Molecular Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, Tampa, FL 33612, USA
- The Research Service, James A. Haley Veterans Hospital, Tampa, FL, USA
| | - K. Jiang
- Department of Molecular Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, Tampa, FL 33612, USA
| | - P. Li
- Department of Molecular Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, Tampa, FL 33612, USA
| | - J. E. Watson
- The Research Service, James A. Haley Veterans Hospital, Tampa, FL, USA
| | - D. M. Byers
- Atlantic Research Centre, Departments of Pediatrics and Biochemistry and Molecular Biology, Dalhousie University, Halifax, NS, Canada
| | - D. R. Cooper
- Department of Molecular Medicine, University of South Florida, 12901 Bruce B. Downs Blvd, Tampa, FL 33612, USA, e-mail:
- The Research Service, James A. Haley Veterans Hospital, Tampa, FL, USA
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Jiang K, Patel NA, Watson JE, Apostolatos H, Kleiman E, Hanson O, Hagiwara M, Cooper DR. Akt2 regulation of Cdc2-like kinases (Clk/Sty), serine/arginine-rich (SR) protein phosphorylation, and insulin-induced alternative splicing of PKCbetaII messenger ribonucleic acid. Endocrinology 2009; 150:2087-97. [PMID: 19116344 PMCID: PMC2671910 DOI: 10.1210/en.2008-0818] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Serine/arginine-rich (SR) proteins play essential roles in the constitutive and regulated splicing of precursor mRNAs. Phosphorylation of the arginine/serine dipeptide-rich (RS) domain by SR protein kinases such as Cdc2-like kinases (Clk/Sty) modulates their subcellular localization and activation. However, it remains unclear how these kinases and their target SR proteins are regulated by extracellular signals. Regulation of protein kinase C betaII (PKCbetaII) pre-mRNA alternative splicing via exon inclusion by Akt2, a central kinase in insulin action, involves phosphorylation of SR proteins. Here we showed that Akt2, in response to insulin, resulted in phosphorylation of Clk/Sty, which then altered SR protein phosphorylation in concert with Akt2. Insulin-stimulated PKCbetaII pre-mRNA splicing was blocked by Clk/Sty and phosphatidylinositol-3-kinase inhibitors, and diabetic Akt2-null mouse tissues had impaired phospho-Clk/Sty, SR protein phosphorylation, and PKCbetaII expression. Furthermore, we observed that Akt2 phosphorylated several SR proteins distinct from Clk/Sty in response to insulin. Akt2-catalyzed phosphorylation of Clk/Sty and SR proteins revealed a role for both kinases in splicing regulation indicating dual functions for Akt2 in response to insulin in this pathway.
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Affiliation(s)
- Kun Jiang
- Department of Molecular Medicine, University of South Florida College of Medicine, Tampa, Florida 33612, USA
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Consitt LA, Bell JA, Houmard JA. Intramuscular lipid metabolism, insulin action, and obesity. IUBMB Life 2009; 61:47-55. [PMID: 18839419 DOI: 10.1002/iub.142] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
With the increasing prevalence of obesity, research has focused on the molecular mechanism(s) linking obesity and skeletal muscle insulin resistance. Metabolic alterations within muscle, such as changes in the cellular location of fatty acid transporter proteins, decreased mitochondrial enzyme activity, and defects in mitochondrial morphology, likely contribute to obesity and insulin resistance. These defects are thought to play a role in the reduced skeletal muscle fatty acid oxidation and increased intramuscular lipid (IMCL) accumulation that is apparent with obesity and other insulin-resistant states such as type 2 diabetes. Intramuscular triacylglycerol does not appear to be a ubiquitous marker of insulin resistance, although specific IMCL intermediates such as long-chain fatty acyl-CoAs, ceramide, and diacylglycerol may inhibit insulin signal transduction. In this review, we will briefly summarize the defects in skeletal muscle lipid metabolism associated with obesity, and discuss the proposed mechanisms by which these defects may contribute to insulin resistance.
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Affiliation(s)
- Leslie A Consitt
- Department of Exercise and Sport Science and Human Performance Laboratory, East Carolina University, Greenville, NC 27858, USA.
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Abstract
Diabetic neuropathy is the most common complication of diabetes, affecting 50% of diabetic patients. Currently, the only treatment for diabetic neuropathy is glucose control and careful foot care. In this review, we discuss the idea that excess glucose overloads the electron transport chain, leading to the production of superoxides and subsequent mitochondrial and cytosolic oxidative stress. Defects in metabolic and vascular pathways intersect with oxidative stress to produce the onset and progression of nerve injury present in diabetic neuropathy. These pathways include the production of advanced glycation end products, alterations in the sorbitol, hexosamine and protein kinase C pathways and activation of poly-ADP ribose polymerase. New bioinformatics approaches can augment current research and lead to new discoveries to understand the pathogenesis of diabetic neuropathy and to identify more effective molecular therapeutic targets.
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Affiliation(s)
- Claudia Figueroa-Romero
- Department of Neurology, University of Michigan, 5017 BSRB, 109 Zina Pitcher Place, Ann Arbor, MI, 48109-2200, USA
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Edwards JL, Vincent A, Cheng T, Feldman EL. Diabetic neuropathy: mechanisms to management. Pharmacol Ther 2008; 120:1-34. [PMID: 18616962 PMCID: PMC4007052 DOI: 10.1016/j.pharmthera.2008.05.005] [Citation(s) in RCA: 461] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2008] [Accepted: 05/15/2008] [Indexed: 02/07/2023]
Abstract
Neuropathy is the most common and debilitating complication of diabetes and results in pain, decreased motility, and amputation. Diabetic neuropathy encompasses a variety of forms whose impact ranges from discomfort to death. Hyperglycemia induces oxidative stress in diabetic neurons and results in activation of multiple biochemical pathways. These activated pathways are a major source of damage and are potential therapeutic targets in diabetic neuropathy. Though therapies are available to alleviate the symptoms of diabetic neuropathy, few options are available to eliminate the root causes. The immense physical, psychological, and economic cost of diabetic neuropathy underscore the need for causally targeted therapies. This review covers the pathology, epidemiology, biochemical pathways, and prevention of diabetic neuropathy, as well as discusses current symptomatic and causal therapies and novel approaches to identify therapeutic targets.
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Affiliation(s)
- James L. Edwards
- The University of Michigan, Department of Neurology, Ann Arbor, Michigan 48109
| | - Andrea Vincent
- The University of Michigan, Department of Neurology, Ann Arbor, Michigan 48109
| | - Thomas Cheng
- The University of Michigan, Department of Neurology, Ann Arbor, Michigan 48109
| | - Eva L. Feldman
- The University of Michigan, Department of Neurology, Ann Arbor, Michigan 48109
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Coll T, Eyre E, Rodríguez-Calvo R, Palomer X, Sánchez RM, Merlos M, Laguna JC, Vázquez-Carrera M. Oleate Reverses Palmitate-induced Insulin Resistance and Inflammation in Skeletal Muscle Cells. J Biol Chem 2008; 283:11107-16. [DOI: 10.1074/jbc.m708700200] [Citation(s) in RCA: 247] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
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Goldfine ID, Maddux BA, Youngren JF, Reaven G, Accili D, Trischitta V, Vigneri R, Frittitta L. The role of membrane glycoprotein plasma cell antigen 1/ectonucleotide pyrophosphatase phosphodiesterase 1 in the pathogenesis of insulin resistance and related abnormalities. Endocr Rev 2008; 29:62-75. [PMID: 18199690 PMCID: PMC2244935 DOI: 10.1210/er.2007-0004] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Insulin resistance is a major feature of most patients with type 2 diabetes mellitus (T2D). A number of laboratories have observed that PC-1 (membrane [corrected] glycoprotein plasma cell antigen 1; also termed [corrected] ectonucleotide pyrophosphatase phosphodiesterase 1 or ENPP1) [corrected] is either overexpressed or overactive in muscle, adipose tissue, fibroblasts, and other tissues of insulin-resistant individuals, both nondiabetic and diabetic. Moreover, PC-1 (ENPP1) overexpression [corrected] in cultured cells in vitro and in transgenic mice in vivo, [corrected] impairs insulin stimulation of insulin receptor (IR) activation and downstream signaling. PC-1 binds to the connecting domain of the IR alpha-subunit that is located in residues 485-599. The connecting domain transmits insulin binding in the alpha-subunit to activation of tyrosine kinase activation in the beta-subunit. When PC-1 is overexpressed, it inhibits insulin [corrected]induced IR beta-subunit tyrosine kinase activity. In addition, a polymorphism of PC-1 (K121Q) in various ethnic populations is closely associated with insulin resistance, T2D, and cardio [corrected] and nephrovascular diseases. The product of this polymorphism has a 2- to 3-fold increased binding affinity for the IR and is more potent than the wild-type PC-1 protein (K121K) in inhibiting the IR. These data suggest therefore that PC-1 is a candidate protein that may play a role in human insulin resistance and T2D by its overexpression, its overactivity, or both.
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Affiliation(s)
- Ira D Goldfine
- Department of Medicine and Diabetes Center, University of California San Francisco, San Francisco, California 94143, USA.
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Osterhoff MA, Heuer S, Pfeiffer M, Tasic J, Kaiser S, Isken F, Spranger J, Weickert MO, Möhlig M, Pfeiffer AFH. Identification of a functional protein kinase Cbeta promoter polymorphism in humans related to insulin resistance. Mol Genet Metab 2008; 93:210-5. [PMID: 17950644 DOI: 10.1016/j.ymgme.2007.09.004] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2007] [Revised: 09/11/2007] [Accepted: 09/11/2007] [Indexed: 12/22/2022]
Abstract
Protein kinase Cbeta (PKCbeta) is known to inhibit insulin production in beta-cells and to support insulin action in skeletal muscle. We therefore searched for functional polymorphisms among already known genetic variants in the PKCbeta promoter and investigated their relation to glucose metabolism in humans. We found that the gene variant in the PKCbeta promoter at position -546 significantly reduced promoter activity in functional assays (P<0.05). Human subjects carrying this variant had a 3.5-fold decrease in PKCbeta2-protein expression in their thrombocytes (P=0.006). Additionally, we tested whether this variant affects parameters of glucose metabolism using 1012 humans included into the MeSyBePo study (Metabolic Syndrome Berlin Potsdam). The -546 variant was highly significant associated with increased homeostasis model assessment for insulin resistance (HOMA-IR, P=0.009) in the cohort. This association was accompanied by significantly increased fasting insulin concentrations in carriers of the homozygous polymorphism (P=0.021). Our results suggest that the -546 polymorphism in the PKCbeta promoter reduces promoter activity, which leads to a decreased expression of PKCbeta2 and subsequently is associated with decreased peripheral insulin-dependent glucose uptake.
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Affiliation(s)
- Martin A Osterhoff
- German Institute of Human Nutrition, Potsdam-Rehbruecke (DIfE), Department of Clinical Nutrition (KLE), Arthur-Scheunert-Allee 155, D-14558 Nuthetal, Germany.
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Xi L, Qian Z, Xu G, Zhou C, Sun S. Crocetin attenuates palmitate-induced insulin insensitivity and disordered tumor necrosis factor-alpha and adiponectin expression in rat adipocytes. Br J Pharmacol 2007; 151:610-7. [PMID: 17471172 PMCID: PMC2013994 DOI: 10.1038/sj.bjp.0707276] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND AND PURPOSE A number of studies have implicated adipocyte-derived factors in the development of insulin resistance. Intracellular redox status has been reported to play a significant role in the modulation of insulin action. This study was designed to investigate the potential of crocetin, a potent antioxidant, to protect adipocytes against the induction of insulin insensitivity and disordered expression of tumor necrosis factor (TNF)-alpha and adiponectin in vitro. EXPERIMENTAL APPROACH We used palmitate to induce insulin resistance in freshly isolated rat adipocytes, and observed the effect of crocetin, N-acetylcysteine, diphenyleneiodonium, rotenone and oxypurinol. Insulin sensitivity was measured using 2-deoxy-D-[1-(3)H]-glucose uptake assay. Levels of glucose transporter 4, TNF-alpha and adiponectin were evaluated by immunoblot analysis, and levels of mRNA for TNF-alpha and adiponectin by reverse transcription-polymerase chain reaction analysis. Intracellular production of reactive oxygen species (ROS) was determined spectrofluorometrically using 2',7'-dichlorofluorescin diacetate. KEY RESULTS Palmitate induced a 45% decrease in insulin-stimulated glucose uptake in adipocytes. The mRNA and protein expression of TNF-alpha were enhanced by 64% and 59% respectively whereas the mRNA and protein expression of adiponectin were reduced by 43% and 36% respectively by palmitate treatment. These changes were accompanied by a 54% increase in intracellular ROS levels. Crocetin, N-acetylcysteine and diphenyleneiodonium were found to attenuate these abnormalities. CONCLUSIONS AND IMPLICATIONS Crocetin blocked the impaired insulin-stimulated glucose uptake and disordered TNF-alpha and adiponectin expression induced by palmitate in rat adipocytes. Inactivation of NADPH oxidase may account for these observations.
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Affiliation(s)
- L Xi
- Department of Pharmacology, China Pharmaceutical University Nanjing, PR China
| | - Z Qian
- Department of Pharmacology, China Pharmaceutical University Nanjing, PR China
- Author for correspondence:
| | - G Xu
- Center for New Drug Research and Development, College of Life Science, Nanjing Normal University Nanjing, PR China
| | - C Zhou
- Department of Pharmacology, China Pharmaceutical University Nanjing, PR China
| | - S Sun
- Department of Pharmacology, China Pharmaceutical University Nanjing, PR China
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Ghosh N, Patel N, Jiang K, Watson JE, Cheng J, Chalfant CE, Cooper DR. Ceramide-activated protein phosphatase involvement in insulin resistance via Akt, serine/arginine-rich protein 40, and ribonucleic acid splicing in L6 skeletal muscle cells. Endocrinology 2007; 148:1359-66. [PMID: 17158207 PMCID: PMC2664306 DOI: 10.1210/en.2006-0750] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Elevated TNFalpha levels are associated with insulin resistance, but the molecular mechanisms linking cytokine signaling to impaired insulin function remain elusive. We previously demonstrated a role for Akt in insulin regulation of protein kinase CbetaII alternative splicing through phosphorylation of serine/arginine-rich protein 40, a required mechanism for insulin-stimulated glucose uptake. We hypothesized that TNFalpha attenuated insulin signaling by dephosphorylating Akt and its targets via ceramide-activated protein phosphatase. Western blot analysis of L6 cell lysates demonstrated impaired insulin-stimulated phosphorylation of Akt, serine/arginine-rich protein 40, and glycogen synthase kinase 3beta in response to TNFalpha and the short chain C6 ceramide analog. TNFalpha increased serine/threonine phosphatase activity of protein phosphatase 1 (PP1) in response to C6, but not insulin, suggesting a ceramide-specific effect. Myriocin, an inhibitor of de novo ceramide synthesis, blocked stimulation of the PP1 activity. Ceramide species measurement by liquid chromatography-mass spectrometry showed consistent increases in C24:1 and C16 ceramides. Effects of TNFalpha and C6 on insulin-stimulated phosphorylation of glycogen synthase kinase 3beta were prevented by myriocin and tautomycin, a PP1 inhibitor, further implicating a de novo ceramide-PP1 pathway. Alternative splicing assays demonstrated that TNFalpha abolished insulin-mediated inclusion of the protein kinase CbetaII exon. Collectively, our work demonstrates a role for PP1-like ceramide-activated protein phosphatase in mediating TNFalpha effects blocking insulin phosphorylation cascades involved in glycogen metabolism and alternative splicing.
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Affiliation(s)
- Nilanjan Ghosh
- Department of Molecular Medicine, College of Medicine, University of South Florida, Tampa, FL 33612
| | - Niketa Patel
- Department of Molecular Medicine, College of Medicine, University of South Florida, Tampa, FL 33612
| | - Kun Jiang
- Department of Molecular Medicine, College of Medicine, University of South Florida, Tampa, FL 33612
| | - James E. Watson
- The Research Service, James A. Haley Veterans Hospital, Tampa, FL 33612
| | - Jin Cheng
- Moffitt Cancer Center, Tampa, FL 33612
| | - Charles E. Chalfant
- Department of Biochemistry, Virginia Commonwealth University, Richmond Virginia 23298
| | - Denise R. Cooper
- Department of Molecular Medicine, College of Medicine, University of South Florida, Tampa, FL 33612
- The Research Service, James A. Haley Veterans Hospital, Tampa, FL 33612
- Corresponding author: Denise R. Cooper, Ph.D., J.A. Haley Veterans Hospital VAR 151, 13000 Bruce B. Downs Blvd, Tampa, FL 33612, E-mail: , Telephone: 813-972-2000 ext 7017, Fax: 813-972-7623
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Muñoz MC, Argentino DP, Dominici FP, Turyn D, Toblli JE. Irbesartan restores the in-vivo insulin signaling pathway leading to Akt activation in obese Zucker rats. J Hypertens 2006; 24:1607-17. [PMID: 16877964 DOI: 10.1097/01.hjh.0000239297.63377.3f] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Angiotensin II (AII) has been shown to contribute to the pathogenesis of hypertension and insulin resistance. In addition, the administration of selective AII type 1 receptor blockers has been shown to improve insulin sensitivity. However, only a few studies have addressed the molecular mechanisms involved in this association. Furthermore, in a previous study we illustrated that obese Zucker rats (OZR) present increased serine 994 (Ser994) phosphorylation of hepatic insulin receptor, and this event seems to be implicated in the regulation of the intrinsic IRK in this model of insulin resistance. OBJECTIVE AND DESIGN We examined the effects of chronic treatment with irbesartan (50 mg/kg a day for 6 months) on the hepatic insulin signaling system of OZR. METHODS The extent of phosphorylation of several components of the insulin signaling system was assessed by immunoprecipitation, followed by immunoblotting with phosphospecific antibodies. In addition, liver AII levels and fat deposits were determined by immunohistochemistry and Oil red O, respectively. RESULTS OZR displayed a marked attenuation in the in-vivo phosphorylation of several components of the insulin signaling pathways in the liver, together with significantly higher hepatic AII levels and hepatic steatosis when compared with lean Zucker rats. We found that in the livers of OZR long-term administration of irbesartan is associated with: (i) increased insulin-stimulated insulin receptor tyrosine phosphorylation; (ii) decreased insulin receptor Ser994 phosphorylation; (iii) augmented insulin receptor substrate (IRS) 1 and 2 abundance and tyrosine phosphorylation; (iv) augmented association between IRS and the p85 regulatory subunit of phosphatidylinositol 3-kinase; (v) increased insulin-induced Akt phosphorylation; and (vi) decreased hepatic steatosis. CONCLUSION The present study provides substantial information that demonstrates that long-term selective AII blockade by irbesartan improves insulin signaling and is associated with decreased insulin receptor Ser994 phosphorylation in the liver of a representative animal model of the human metabolic syndrome.
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Affiliation(s)
- Marina C Muñoz
- Instituto de Química y Fisicoquímica Biológicas (UBA-CONICET), Facultad de Farmacia y Bioquímica, Buenos Aires, Argentina
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van Ginneken MME, de Graaf-Roelfsema E, Keizer HA, van Dam KG, Wijnberg ID, van der Kolk JH, van Breda E. Effect of exercise on activation of the p38 mitogen-activated protein kinase pathway, c-Jun NH2 terminal kinase, and heat shock protein 27 in equine skeletal muscle. Am J Vet Res 2006; 67:837-44. [PMID: 16649919 DOI: 10.2460/ajvr.67.5.837] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To investigate the effects of exercise on activation of mitogen-activated protein kinase (MAPK) signaling proteins in horses. ANIMALS 6 young trained Standardbred geldings. PROCEDURE Horses performed a 20-minute bout of exercise on a treadmill at 80% of maximal heart rate. Muscle biopsy specimens were obtained from the vastus lateralis and pectoralis descendens muscles before and after exercise. Amount of expression and intracellular location of phosphospecific MAPK pathway intermediates were determined by use of western blotting and immunofluorescence staining. RESULTS Exercise resulted in a significant increase in phosphorylation of p38 pathway intermediates, c-Jun NH2 terminal kinase (JNK), and heat shock protein 27 (HSP27) in the vastus lateralis muscle, whereas no significant changes were found in phosphorylation of extracellular regulated kinase. In the pectoralis descendens muscle, phosphorylation of p38 and HSP27 was significantly increased after exercise. Immunohistochemical analysis revealed fiber-type- specific locations of phosphorylated JNK in type 2a/b intermediate and 2b fibers and phosphorylated p38 in type 1 fibers. Phosphorylated HSP27 was strongly increased after exercise in type 1 and 2a fibers. CONCLUSIONS AND CLINICAL RELEVANCE The p38 pathway and JNK are activated in the vastus lateralis muscle after a single 20-minute bout of submaximal exercise in trained horses. Phosphorylation of HSP27 as detected in the study reported here is most likely induced through the p38 signaling pathway.
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Affiliation(s)
- Mireille M E van Ginneken
- Department of Equine Sciences, Medicine Section, Faculty of Veterinary Medicine, Utrecht University, PO Box 80153, NL3508 TD Utrecht, The Netherlands
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Cortright RN, Sandhoff KM, Basilio JL, Berggren JR, Hickner RC, Hulver MW, Dohm GL, Houmard JA. Skeletal muscle fat oxidation is increased in African-American and white women after 10 days of endurance exercise training. Obesity (Silver Spring) 2006; 14:1201-10. [PMID: 16899801 DOI: 10.1038/oby.2006.137] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
OBJECTIVE Obesity is associated with lower rates of skeletal muscle fatty acid oxidation (FAO), which is linked to insulin resistance. FAO is reduced further in obese African-American (AAW) vs. white women (CW) and may also be lower in lean AAW vs. CW. In lean CW, endurance exercise training (EET) elevates the oxidative capacity of skeletal muscle. Therefore, we determined whether EET would elevate skeletal muscle FAO similarly in AAW and CW with a lower lipid oxidative capacity. RESEARCH METHODS AND PROCEDURES In vitro rates of FAO were assessed in rectus abdominus muscle strips using [1- 14C] palmitate (Pal) from lean AAW [BMI = 24.2 +/- 0.9 (standard error) kg/m2] and CW (23.6 +/- 0.8 kg/m2) undergoing voluntary abdominal surgery. Lean AAW (22 +/- 0.9 kg/m(2)) and CW (24 +/- 0.8 kg/m2) and obese AAW (36 +/- 1.2 kg/m2) and CW (40 +/- 1.3 kg/m2) underwent 10 consecutive days of EET on a cycle ergometer (60 min/d, 75% peak oxygen uptake). FAO was measured in vastus lateralis homogenates as captured 14CO2 using [1- 14C] Pal, palmitoyl-CoA (Pal-CoA), and palmityl-carnitine (Pal-Car). RESULTS Muscle strip experiments showed suppressed rates of FAO (p = 0.03) in lean AAW vs. CW. EET increased the rates of skeletal muscle Pal oxidation (p = 0.05) in both lean AAW and CW. In obese subjects, Pre-EET Pal (but not Pal-CoA or Pal-Car) oxidation was lower (p = 0.05) in AAW vs. CW. EET increased Pal oxidation 100% in obese AAW (p < 0.05) and 59% (p < 0.05) in obese CW. Similar increases (p < 0.05) in post-EET FAO were observed for Pal-CoA and Pal-Car in both groups. DISCUSSION Both lean and obese AAW possess a lower capacity for skeletal muscle FAO, but EET increases FAO similarly in both AAW and CW. These data suggest the use of EET for treatment against obesity and diabetes for both AAW and CW.
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Affiliation(s)
- Ronald N Cortright
- The Human Performance Laboratory, Department of Excercise and Sport Science, College of Health and Human Performance, The Brody School of Medicine, East Carolina University, Greenville, NC 27858, USA.
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Haasch D, Berg C, Clampit JE, Pederson T, Frost L, Kroeger P, Rondinone CM. PKCtheta is a key player in the development of insulin resistance. Biochem Biophys Res Commun 2006; 343:361-8. [PMID: 16545776 DOI: 10.1016/j.bbrc.2006.02.177] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2006] [Accepted: 02/28/2006] [Indexed: 11/30/2022]
Abstract
Activation of PKCtheta is associated with lipid-induced insulin resistance and PKCtheta knockout mice are protected from the lipid-induced defects. However, the exact mechanism by which PKCtheta contributes to insulin resistance is not known. To investigate whether an increase in PKCtheta expression leads to insulin resistance, C2C12 skeletal muscle cells were transfected with PKCtheta DNA and treated with different concentrations of insulin for 10 min. PKCtheta overexpression induced reduction of IRS-1 protein levels with a decrease in insulin-induced p85 binding to IRS-1, phosphorylation of PKB and its substrates, p70 and GSK3. Pretreatment of these cells with GF-109203X (a non-specific PKC inhibitor, IC50 for PKCtheta = 10 nM) recovered insulin signaling. PKCtheta was found to be expressed in liver and treatment of human hepatoma cells (HepG2) with high insulin and glucose resulted in an increase in PKCtheta expression that correlated with a decrease in IRS-1 protein levels and the development of insulin resistance. Reduction of PKCtheta expression using RNAi technology significantly inhibited the degradation of IRS-1 and enhanced insulin-induced IRS-1 tyrosine phosphorylation, p85 association to IRS-1 and PKB phosphorylation. In conclusion, by overexpressing PKCtheta or using RNAi technology to downregulate PKCtheta, we have demonstrated that PKCtheta has a key role in the development of insulin resistance. These findings suggest that PKCtheta mediates not only insulin resistance in muscle but also in liver, which may contribute to the development of whole body insulin resistance and diabetes.
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Affiliation(s)
- Deanna Haasch
- Metabolic Diseases Research, Global Pharmaceutical Research and Development, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064, USA
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Jové M, Planavila A, Sánchez RM, Merlos M, Laguna JC, Vázquez-Carrera M. Palmitate induces tumor necrosis factor-alpha expression in C2C12 skeletal muscle cells by a mechanism involving protein kinase C and nuclear factor-kappaB activation. Endocrinology 2006; 147:552-61. [PMID: 16223857 DOI: 10.1210/en.2005-0440] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The mechanisms responsible for increased expression of TNF-alpha in skeletal muscle cells in diabetic states are not well understood. We examined the effects of the saturated acid palmitate on TNF-alpha expression. Exposure of C2C12 skeletal muscle cells to 0.75 mm palmitate enhanced mRNA (25-fold induction, P < 0.001) and protein (2.5-fold induction) expression of the proinflammatory cytokine TNF-alpha. This induction was inversely correlated with a fall in GLUT4 mRNA levels (57% reduction, P < 0.001) and glucose uptake (34% reduction, P < 0.001). PD98059 and U0126, inhibitors of the ERK-MAPK cascade, partially prevented the palmitate-induced TNF-alpha expression. Palmitate increased nuclear factor (NF)-kappaB activation and incubation of the cells with the NF-kappaB inhibitors pyrrolidine dithiocarbamate and parthenolide partially prevented TNF-alpha expression. Incubation of palmitate-treated cells with calphostin C, a strong and specific inhibitor of protein kinase C (PKC), abolished palmitate-induced TNF-alpha expression, and restored GLUT4 mRNA levels. Palmitate treatment enhanced the expression of phospho-PKCtheta, suggesting that this PKC isoform was involved in the changes reported, and coincubation of palmitate-treated cells with the PKC inhibitor chelerythrine prevented the palmitate-induced reduction in the expression of IkappaBalpha and insulin-stimulated Akt activation. These findings suggest that enhanced TNF-alpha expression and GLUT4 down-regulation caused by palmitate are mediated through the PKC activation, confirming that this enzyme may be a target for either the prevention or the treatment of fatty acid-induced insulin resistance.
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Affiliation(s)
- Mireia Jové
- Pharmacology Unit, Department of Pharmacology and Therapeutic Chemistry, Faculty of Pharmacy, University of Barcelona, E-08028 Barcelona, Spain
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Hulver MW, Berggren JR, Carper MJ, Miyazaki M, Ntambi JM, Hoffman EP, Thyfault JP, Stevens R, Dohm GL, Houmard JA, Muoio DM. Elevated stearoyl-CoA desaturase-1 expression in skeletal muscle contributes to abnormal fatty acid partitioning in obese humans. Cell Metab 2005; 2:251-61. [PMID: 16213227 PMCID: PMC4285571 DOI: 10.1016/j.cmet.2005.09.002] [Citation(s) in RCA: 302] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2004] [Revised: 07/21/2005] [Accepted: 09/15/2005] [Indexed: 11/30/2022]
Abstract
Obesity and type 2 diabetes are strongly associated with abnormal lipid metabolism and accumulation of intramyocellular triacylglycerol, but the underlying cause of these perturbations are yet unknown. Herein, we show that the lipogenic gene, stearoyl-CoA desaturase 1 (SCD1), is robustly up-regulated in skeletal muscle from extremely obese humans. High expression and activity of SCD1, an enzyme that catalyzes the synthesis of monounsaturated fatty acids, corresponded with low rates of fatty acid oxidation, increased triacylglycerol synthesis and increased monounsaturation of muscle lipids. Elevated SCD1 expression and abnormal lipid partitioning were retained in primary skeletal myocytes derived from obese compared to lean donors, implying that these traits might be driven by epigenetic and/or heritable mechanisms. Overexpression of human SCD1 in myotubes from lean subjects was sufficient to mimic the obese phenotype. These results suggest that elevated expression of SCD1 in skeletal muscle contributes to abnormal lipid metabolism and progression of obesity.
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Affiliation(s)
- Matthew W. Hulver
- Pennington Biomedical Research, Louisiana State University System, Baton Rouge, Louisiana 70808
| | - Jason R. Berggren
- Human Performance Laboratory and Department of Exercise and Sport Science, East Carolina University, Greenville, North Carolina 27835
| | - Michael J. Carper
- Pennington Biomedical Research, Louisiana State University System, Baton Rouge, Louisiana 70808
| | - Makoto Miyazaki
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - James M. Ntambi
- Department of Biochemistry, University of Wisconsin, Madison, Wisconsin 53706
| | - Eric P. Hoffman
- Research Center For Genetic Medicine, Children’s National Medical Center, Washington, DC 20010
| | - John P. Thyfault
- Department of Physiology, East Carolina University, Greenville, North Carolina 27835
| | - Robert Stevens
- Sarah W. Stedman Nutrition and Metabolism Center and Departments of Medicine and Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27704
| | - G. Lynis Dohm
- Department of Physiology, East Carolina University, Greenville, North Carolina 27835
| | - Joseph A. Houmard
- Human Performance Laboratory and Department of Exercise and Sport Science, East Carolina University, Greenville, North Carolina 27835
| | - Deborah M. Muoio
- Sarah W. Stedman Nutrition and Metabolism Center and Departments of Medicine and Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27704
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Jové M, Planavila A, Laguna JC, Vázquez-Carrera M. Palmitate-induced interleukin 6 production is mediated by protein kinase C and nuclear-factor kappaB activation and leads to glucose transporter 4 down-regulation in skeletal muscle cells. Endocrinology 2005; 146:3087-95. [PMID: 15802498 DOI: 10.1210/en.2004-1560] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The mechanisms by which elevated levels of free fatty acids cause insulin resistance are not well understood. In addition, accumulating evidence suggests a link between inflammation and type 2 diabetes. Here, we report that exposure of C2C12 skeletal muscle cells to 0.5 mm palmitate results in increased mRNA levels (3.5-fold induction; P < 0.05) and secretion (control 375 +/- 57 vs. palmitate 1129 +/- 177 pg/ml; P < 0.001) of the proinflammatory cytokine IL-6. Palmitate increased nuclear factor-kappaB activation and coincubation of the cells with palmitate and the nuclear factor-kappaB inhibitor pyrrolidine dithiocarbamate prevented both IL-6 expression and secretion. Furthermore, incubation of palmitate-treated cells with calphostin C, a strong and specific inhibitor of protein kinase C, and phorbol myristate acetate, that down-regulates protein kinase C in long-term incubations, abolished induction of IL-6 production. Finally, exposure of skeletal muscle cells to palmitate caused a fall in the mRNA levels of glucose transporter 4 and insulin-stimulated glucose uptake, whereas in the presence of anti-IL-6 antibody, which neutralizes the biological activity of mouse IL-6 in cell culture, these reductions were prevented. These findings suggest that IL-6 may mediate several of the prodiabetic effects of palmitate.
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Affiliation(s)
- Mireia Jové
- Pharmacology Unit, Department of Pharmacology and Therapeutic Chemistry, University of Barcelona, E-08028 Barcelona, Spain
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