Targeted disruption of inducible nitric oxide synthase protects against aging, S-nitrosation, and insulin resistance in muscle of male mice

Insulin Sensitivity Initially Worsens but Later Improves With Aging in Male C57BL/6N Mice

Aging is believed to induce insulin resistance in humans. However, when and how insulin sensitivity changes with aging remains unclear in both humans and mice. In this study, groups of male C57BL/6N mice at 9-19 weeks (young), 34-67 weeks (mature adult), 84-85 weeks (presenile), and 107-121 weeks of age underwent hyperinsulinemic-euglycemic clamp studies with somatostatin infusion under awake and nonrestrained conditions. The glucose infusion rates for maintaining euglycemia were 18.4 ± 2.9, 5.9 ± 1.3, 20.3 ± 7.2, and 25.3 ± 4.4 mg/kg/min in young, mature adult, presenile, and aged mice, respectively. Thus, compared with young mice, mature adult mice exhibited the expected insulin resistance. In contrast, presenile and aged mice showed significantly higher insulin sensitivity than mature adult mice. These age-related changes were mainly observed in glucose uptake into adipose tissue and skeletal muscle (rates of glucose disappearance were 24.3 ± 2.0, 17.1 ± 1.0, 25.5 ± 5.2, and 31.8 ± 2.9 mg/kg/min in young, mature adult, presenile, and aged mice, respectively). Epididymal fat weight and hepatic triglyceride levels were higher in mature adult mice than those in young and aged mice. Our observations indicate that, in male C57BL/6N mice, insulin resistance appears at the mature adult stage of life but subsequently improves markedly. These alterations in insulin sensitivity are attributable to changes in visceral fat accumulations and age-related factors.

Cysteine residues in signal transduction and its relevance in pancreatic beta cells

Cysteine is one of the least abundant but most conserved amino acid residues in proteins, playing a role in their structure, metal binding, catalysis, and redox chemistry. Thiols present in cysteines can be modified by post-translational modifications like sulfenylation, acylation, or glutathionylation, regulating protein activity and function and serving as signals. Their modification depends on their position in the structure, surrounding amino acids, solvent accessibility, pH, etc. The most studied modifications are the redox modifications by reactive oxygen, nitrogen, and sulfur species, leading to reversible changes that serve as cell signals or irreversible changes indicating oxidative stress and cell damage. Selected antioxidants undergoing reversible oxidative modifications like peroxiredoxin-thioredoxin system are involved in a redox-relay signaling that can propagate to target proteins. Cysteine thiols can also be modified by acyl moieties' addition (derived from lipid metabolism), resulting in protein functional modification or changes in protein anchoring in the membrane. In this review, we update the current knowledge on cysteine modifications and their consequences in pancreatic β-cells. Because β-cells exhibit well-balanced redox homeostasis, the redox modifications of cysteines here serve primarily for signaling purposes. Similarly, lipid metabolism provides regulatory intermediates that have been shown to be necessary in addition to redox modifications for proper β-cell function and, in particular, for efficient insulin secretion. On the contrary, the excess of reactive oxygen, nitrogen, and sulfur species and the imbalance of lipids under pathological conditions cause irreversible changes and contribute to oxidative stress leading to cell failure and the development of type 2 diabetes.

Aging Affects Insulin Resistance, Insulin Secretion, and Glucose Effectiveness in Subjects with Normal Blood Glucose and Body Weight

AIM

Several studies have demonstrated that factors including diabetes, including insulin resistance (IR), glucose effectiveness (GE), and the first and second phase of insulin secretion (FPIS, SPIS) could easily be calculated using basic characteristics and biochemistry profiles. Aging is accompanied by deteriorations of insulin resistance (IR) and insulin secretion. However, little is known about the roles of aging in the different phases of insulin secretion (ISEC), i.e., the first and second phase of insulin secretion (FPIS, SPIS), and glucose effectiveness (GE).

METHODS

In total, 169 individuals (43 men and 126 women) recruited from the data bank of the Meei-Jaw (MJ) Health Screening Center and Cardinal Tien Hospital Data Access Center between 1999 and 2008, with a similar fasting plasma glucose (FPG: 90 mg/dL) and BMI (men: 23 kg/m², women 22 kg/m²) were enrolled. The IR, FPIS, SPIS, and GE were estimated using our previously developed equations shown below. Pearson correlation analysis was conducted to assess the correlations between age and four diabetes factors (DFs: IR, FPIS, SPIS, and GE). The equations that are used to calculate the DF in the present study were built and published by our group.

RESULTS

The age of the participants ranged from 18 to 78 years. Men had higher FPIS but lower HDL-C levels than women (2.067 ± 0.159, 1.950 ± 0.186 μU/min and 1.130 ± 0.306, 1.348 ± 0.357 mmol/dl, accordingly). The results of the Pearson correlation revealed that age was negatively related to the IR and GE in both genders (IR: r = -0.39, p < 0.001 for men, r = -0.24, p < 0.003 for women; GE: r = 0.66, p < 0.001 for men, r = 0.78, p < 0.001 for women). At the same time, the FPIS was also only found to be negatively correlated with age in females (r = -0.238, p = 0.003), but there was no difference in the SPIS and age among both genders.

CONCLUSIONS

We have found that in Chinese subjects with a normal FPG level (90 mg/dL) and body mass index (men: 23 kg/m², women: 22: kg/m²), age is negatively related to the IR and GE among both genders. Only the FPIS was found to be negatively related to age in women. The tightness of their relationships, from the highest to the lowest, are GE, FPIS, and IR. These results should be interpreted with caution because of the small sample size.

Shift work and insulin resistance (HOMA-IR) among professional drivers

BACKGROUND: Shift work may be associated with insulin resistance. OBJECTIVE: This study aimed to investigate the potential association between shift work and the homeostatic model assessment of insulin resistance (HOMA-IR) index in professional drivers. METHOD: A total of four hundred fifty-three professional drivers were invited to participate in the study within a periodic medical examination in the occupational setting. One hundred seventy-seven daytime workers were compared with 175 night shifts and 101 early morning shift drivers. Demographic, occupational, and medical examination including blood pressure, anthropometric data was assessed. Measurement of serum insulin, fasting blood glucose and lipid profile were done for all drivers. RESULTS: Compared with day workers, night shift and early morning shift drivers displayed higher levels of HOMA-IR. Metabolic syndrome was found to be significantly increased in night workers. In linear regression analysis, insulin resistance was correlated with shift work independently of demographic and occupational characteristics. CONCLUSION: The study revealed that shift work could be a risk factor in developing the risk of metabolic syndrome and insulin resistance. Suggestively, health strategies such as structured lifestyle counseling in occupational health settings are warranted to improve and modify cardiometabolic risk factors.

The manifold roles of protein S-nitrosylation in the life of insulin

Insulin, which is released by pancreatic islet β-cells in response to elevated levels of glucose in the blood, is a critical regulator of metabolism. Insulin triggers the uptake of glucose and fatty acids into the liver, adipose tissue and muscle, and promotes the storage of these nutrients in the form of glycogen and lipids. Dysregulation of insulin synthesis, secretion, transport, degradation or signal transduction all cause failure to take up and store nutrients, resulting in type 1 diabetes mellitus, type 2 diabetes mellitus and metabolic dysfunction. In this Review, we make the case that insulin signalling is intimately coupled to protein S-nitrosylation, in which nitric oxide groups are conjugated to cysteine thiols to form S-nitrosothiols, within effectors of insulin action. We discuss the role of S-nitrosylation in the life cycle of insulin, from its synthesis and secretion in pancreatic β-cells, to its signalling and degradation in target tissues. Finally, we consider how aberrant S-nitrosylation contributes to metabolic diseases, including the roles of human genetic mutations and cellular events that alter S-nitrosylation of insulin-regulating proteins. Given the growing influence of S-nitrosylation in cellular metabolism, the field of metabolic signalling could benefit from renewed focus on S-nitrosylation in type 2 diabetes mellitus and insulin-related disorders.

Gut microbial DNA and immune checkpoint gene Vsig4/CRIg are key antagonistic players in healthy aging and age-associated development of hypertension and diabetes

AIMS

Aging is associated with the development of insulin resistance and hypertension which may stem from inflammation induced by accumulation of toxic bacterial DNA crossing the gut barrier. The aim of this study was to identify factors counter-regulating these processes. Taking advantage of the Chromogranin A (CgA) knockout (CgA-KO) mouse as a model for healthy aging, we have identified Vsig4 (V-set and immunoglobulin domain containing 4) as the critical checkpoint gene in offsetting age-associated hypertension and diabetes.

METHODS AND RESULTS

The CgA-KO mice display two opposite aging phenotypes: hypertension but heightened insulin sensitivity at young age, whereas the blood pressure normalizes at older age and insulin sensitivity further improves. In comparison, aging WT mice gradually lost glucose tolerance and insulin sensitivity and developed hypertension. The gut barrier, compromised in aging WT mice, was preserved in CgA KO mice leading to major 35-fold protection against bacterial DNA-induced inflammation. Similarly, RNA sequencing showed increased expression of the Vsig4 gene (which removes bacterial DNA) in the liver of 2-yr-old CgA-KO mice, which may account for the very low accumulation of microbial DNA in the heart. The reversal of hypertension in aging CgA-KO mice likely stems from (i) low accumulation of microbial DNA, (ii) decreased spillover of norepinephrine in the heart and kidneys, and (iii) reduced inflammation.

CONCLUSION

We conclude that healthy aging relies on protection from bacterial DNA and the consequent low inflammation afforded by CgA-KO. Vsig4 also plays a crucial role in "healthy aging" by counteracting age-associated insulin resistance and hypertension.

Astaxanthin as a Novel Mitochondrial Regulator: A New Aspect of Carotenoids, beyond Antioxidants

Astaxanthin is a member of the carotenoid family that is found abundantly in marine organisms, and has been gaining attention in recent years due to its varied biological/physiological activities. It has been reported that astaxanthin functions both as a pigment, and as an antioxidant with superior free radical quenching capacity. We recently reported that astaxanthin modulated mitochondrial functions by a novel mechanism independent of its antioxidant function. In this paper, we review astaxanthin’s well-known antioxidant activity, and expand on astaxanthin’s lesser-known molecular targets, and its role in mitochondrial energy metabolism.

Genes controlling skeletal muscle glucose uptake and their regulation by endurance and resistance exercise

Exercise improves the insulin sensitivity of glucose uptake in skeletal muscle. Due to that, exercise has become a cornerstone treatment for type 2 diabetes mellitus (T2DM). The mechanisms by which exercise improves skeletal muscle insulin sensitivity are, however, incompletely understood. We conducted a systematic review to identify all genes whose gain or loss of function alters skeletal muscle glucose uptake. We subsequently cross-referenced these genes with recently generated data sets on exercise-induced gene expression and signaling. Our search revealed 176 muscle glucose-uptake genes, meaning that their genetic manipulation altered glucose uptake in skeletal muscle. Notably, exercise regulates the expression or phosphorylation of more than 50% of the glucose-uptake genes or their protein products. This included many genes that previously have not been associated with exercise-induced insulin sensitivity. Interestingly, endurance and resistance exercise triggered some common but mostly unique changes in expression and phosphorylation of glucose-uptake genes or their protein products. Collectively, our work provides a resource of potentially new molecular effectors that play a role in the incompletely understood regulation of muscle insulin sensitivity by exercise.

The Molecular Mechanisms of Hypoglycemic Properties and Safety Profiles of Swietenia Macrophylla Seeds Extract: A Review

BACKGROUND: Insulin resistance (IR) is known as the root cause of type 2 diabetes; hence, it is a substantial therapeutic target. Nowadays, studies have shifted the focus to natural ingredients that have been utilized as a traditional diabetes treatment, including Swietenia macrophylla. Accumulating evidence supports the hypoglycemic activities of S. macrophylla seeds extract, although its molecular mechanisms have yet to be well-established. AIM: This review focuses on the hypoglycemic molecular mechanisms of S. macrophylla seeds extract and its safety profiles. METHODS: An extensive search of the latest literature was conducted from four main databases (PubMed, Scopus, Science Direct, and Google Scholar) using several keywords: “swietenia macrophylla, seeds, and diabetes;” “swietenia macrophylla, seeds, and oxidative stress;” “swietenia macrophylla, seeds, and inflammation;” “swietenia macrophylla, seeds, and GLUT4;” and “swietenia macrophylla, seeds, and toxicities.” RESULTS: The hypoglycemic activities occur through modulating several pathways associated with IR and T2D pathogenesis. The seeds extract of S. macrophylla modulates oxidative stress by decreasing malondialdehyde (MDA), oxidized low-density lipoprotein, and thiobarbituric acid-reactive substances while increasing antioxidant enzymes (superoxide dismutase, glutathione peroxidase, and catalase). Another propose mechanism is the modulating of the inflammatory pathway by attenuating nuclear factor kappa β, tumor necrosis factor α, inducible nitric oxide synthase, and cyclooxygenase 2. Some studies have shown that the extract can also control phosphatidylinositol-3-kinase/ Akt (PI3K/Akt) pathway by inducing glucose transporter 4, while suppressing phosphoenolpyruvate carboxykinase. Moreover, in vitro cytotoxicity and in vivo toxicity studies supported the safety profile of S. macrophylla seeds extract with the LD50 higher than 2000 mg/kg. CONCLUSION: The potential of S. macrophylla seeds as antidiabetic candidate is supported by many studies that have documented their non-toxic and hypoglycemic effects, which involve several molecular pathways.

An Overview of NO Signaling Pathways in Aging

Nitric Oxide (NO) is a potent signaling molecule involved in the regulation of various cellular mechanisms and pathways under normal and pathological conditions. NO production, its effects, and its efficacy, are extremely sensitive to aging-related changes in the cells. Herein, we review the mechanisms of NO signaling in the cardiovascular system, central nervous system (CNS), reproduction system, as well as its effects on skin, kidneys, thyroid, muscles, and on the immune system during aging. The aging-related decline in NO levels and bioavailability is also discussed in this review. The decreased NO production by endothelial nitric oxide synthase (eNOS) was revealed in the aged cardiovascular system. In the CNS, the decline of the neuronal (n)NOS production of NO was related to the impairment of memory, sleep, and cognition. NO played an important role in the aging of oocytes and aged-induced erectile dysfunction. Aging downregulated NO signaling pathways in endothelial cells resulting in skin, kidney, thyroid, and muscle disorders. Putative therapeutic agents (natural/synthetic) affecting NO signaling mechanisms in the aging process are discussed in the present study. In summary, all of the studies reviewed demonstrate that NO plays a crucial role in the cellular aging processes.

Exercise Counterbalances Rho/ROCK2 Signaling Impairment in the Skeletal Muscle and Ameliorates Insulin Sensitivity in Obese Mice

Physical exercise is considered a fundamental strategy in improving insulin sensitivity and glucose uptake in skeletal muscle. However, the molecular mechanisms underlying this regulation, primarily on skeletal muscle glucose uptake, are not fully understood. Recent evidence has shown that Rho-kinase (ROCK) isoforms play a pivotal role in regulating skeletal muscle glucose uptake and systemic glucose homeostasis. The current study evaluated the effect of physical exercise on ROCK2 signaling in skeletal muscle of insulin-resistant obese animals. Physiological (ITT) and molecular analysis (immunoblotting, and RT-qPCR) were performed. The contents of RhoA and ROCK2 protein were decreased in skeletal muscle of obese mice compared to control mice but were restored to normal levels in response to physical exercise. The exercised animals also showed higher phosphorylation of insulin receptor substrate 1 (IRS1 Serine 632/635) and protein kinase B (Akt) in the skeletal muscle. However, phosphatase and tensin homolog (PTEN) and protein-tyrosine phosphatase-1B (PTP-1B), both inhibitory regulators for insulin action, were increased in obesity but decreased after exercise. The impact of ROCK2 action on muscle insulin signaling is further underscored by the fact that impaired IRS1 and Akt phosphorylation caused by palmitate in C2C12 myotubes was entirely restored by ROCK2 overexpression. These results suggest that the exercise-induced upregulation of RhoA-ROCK2 signaling in skeletal muscle is associated with increased systemic insulin sensitivity in obese mice and further implicate that muscle ROCK2 could be a potential target for treating obesity-linked metabolic disorders.

Knockout of NOS2 Promotes Adipogenic Differentiation of Rat MSCs by Enhancing Activation of JAK/STAT3 Signaling

Mesenchymal stromal cells (MSCs) are a heterogeneous population of cells that possess multilineage differentiation potential and extensive immunomodulatory properties. In mice and rats, MSCs produce nitric oxide (NO), as immunomodulatory effector molecule that exerts an antiproliferative effect on T cells, while the role of NO in differentiation was less clear. Here, we investigated the role of NO synthase 2 (NOS2) on adipogenic and osteogenic differentiation of rat MSCs. MSCs isolated from NOS2-null (NOS2^–/–) and wild type (WT) Sprague–Dawley (SD) rats exhibited homogenous fibroblast-like morphology and characteristic phenotypes. However, after induction, adipogenic differentiation was found significantly promoted in NOS2^–/– MSCs compared to WT MSCs, but not in osteogenic differentiation. Accordingly, qRT-PCR revealed that the adipogenesis-related genes PPAR-γ, C/EBP-α, LPL and FABP4 were markedly upregulated in NOS2^–/– MSCs, but not for osteogenic transcription factors or marker genes. Further investigations revealed that the significant enhancement of adipogenic differentiation in NOS2^–/– MSCs was due to overactivation of the STAT3 signaling pathway. Both AG490 and S3I-201, small molecule inhibitors that selectively inhibit STAT3 activation, reversed this adipogenic effect. Furthermore, after high-fat diet (HFD) feeding, knockout of NOS2 in rat MSCs resulted in significant obesity. In summary, NOS2 is involved in the regulation of rat MSC adipogenic differentiation via the STAT3 signaling pathway.

Insulin and aging

Aging is characterized by a progressive loss of physiological function leading to increase in the vulnerability to death. This deterioration process occurs in all living organisms and is the primary risk factor for pathological conditions including obesity, type 2 diabetes mellitus, Alzheimer's disease and cardiovascular diseases. Most of the age-related diseases have been associated with impairment of action of an important hormone, namely insulin. It is well-known that this hormone is a critical mediator of metabolism, growth, proliferation and differentiation. Insulin action depends on two processes that determine its circulating levels, insulin secretion and clearance, and insulin sensitivity in its target tissues. Aging has deleterious effects on these three mechanisms, impairing insulin action, thereby increasing the risk for diseases and death. Thus, improving insulin action may be an important strategy to have a healthier and longer life.

β-blockade prevents coronary macro- and microvascular dysfunction induced by a high salt diet and insulin resistance in the Goto-Kakizaki rat

A high salt intake exacerbates insulin resistance, evoking hypertension due to systemic perivascular inflammation, oxidative-nitrosative stress and endothelial dysfunction. Angiotensin-converting enzyme inhibitor (ACEi) and angiotensin receptor blockers (ARBs) have been shown to abolish inflammation and redox stress but only partially restore endothelial function in mesenteric vessels. We investigated whether sympatho-adrenal overactivation evokes coronary vascular dysfunction when a high salt intake is combined with insulin resistance in male Goto-Kakizaki (GK) and Wistar rats treated with two different classes of β-blocker or vehicle, utilising synchrotron-based microangiography in vivo. Further, we examined if chronic carvedilol (CAR) treatment preserves nitric oxide (NO)-mediated coronary dilation more than metoprolol (MET). A high salt diet (6% NaCl w/w) exacerbated coronary microvessel endothelial dysfunction and NO-resistance in vehicle-treated GK rats while Wistar rats showed modest impairment. Microvascular dysfunction was associated with elevated expression of myocardial endothelin, inducible NO synthase (NOS) protein and 3-nitrotyrosine (3-NT). Both CAR and MET reduced basal coronary perfusion but restored microvessel endothelium-dependent and -independent dilation indicating a role for sympatho-adrenal overactivation in vehicle-treated rats. While MET treatment reduced myocardial nitrates, only MET treatment completely restored microvessel dilation to dobutamine (DOB) stimulation in the absence of NO and prostanoids (combined inhibition), indicating that MET restored the coronary flow reserve attributable to endothelium-derived hyperpolarisation (EDH). In conclusion, sympatho-adrenal overactivation caused by high salt intake and insulin resistance evoked coronary microvessel endothelial dysfunction and diminished NO sensitivity, which were restored by MET and CAR treatment in spite of ongoing inflammation and oxidative-nitrosative stress presumably caused by uninhibited renin-angiotensin-aldosterone system (RAAS) overactivation.

Role of Gut Microbiome and Microbial Metabolites in Alleviating Insulin Resistance After Bariatric Surgery

Insulin resistance (IR) is the most common pathophysiological change in patients with type 2 diabetes mellitus (T2DM). Several recent studies have suggested that the gut microbiome and microbial metabolites are involved in the pathogenesis of IR. Bariatric surgery, as an effective treatment for T2DM, can markedly alleviate IR through mechanisms that have not been elucidated. In this review, we summarize the current evidence on the changes in the gut microbiome and microbial metabolites (including lipopolysaccharide, short-chain fatty acids, branched-chain amino acids, aromatic amino acids, bile acids, methylamines, and indole derivatives) after bariatric surgery. Additionally, we discuss the mechanisms that correlate the changes in microbial metabolites with the postoperative alleviation of IR. Furthermore, we discuss the prospect of bariatric surgery as a treatment for T2DM.

Metabolic inflammation in heart failure with preserved ejection fraction

One in 10 persons in the world aged 40 years and older will develop the syndrome of HFpEF (heart failure with preserved ejection fraction), the most common form of chronic cardiovascular disease for which no effective therapies are currently available. Metabolic disturbance and inflammatory burden contribute importantly to HFpEF pathogenesis. The interplay within these two biological processes is complex; indeed, it is now becoming clear that the notion of metabolic inflammation-metainflammation-must be considered central to HFpEF pathophysiology. Inflammation and metabolism interact over the course of syndrome progression, and likely impact HFpEF treatment and prevention. Here, we discuss evidence in support of a causal, mechanistic role of metainflammation in shaping HFpEF, proposing a framework in which metabolic comorbidities profoundly impact cardiac metabolism and inflammatory pathways in the syndrome.

Body Mass Dynamics Is Determined by the Metabolic Ohm's Law and Adipocyte-Autonomous Fat Mass Homeostasis

An ODE model integrating metabolic mechanisms with clinical data reveals an Ohm's law governing lifetime body mass dynamics, where fat and lean tissues are analogous to a parallel nonlinear capacitor and resistor, respectively. The law unexpectedly decouples weight stability (a cell-autonomous property of adipocytes) and weight change (a parabolic trajectory governed by Ohm's law). In middle age, insulin resistance causes fat accumulation to avoid excessive body shrinkage in old age. Moderate middle-age spread is thus natural, not an anomaly caused by hypothalamic defects, as proposed by lipostatic theory. These discoveries provide valuable insights into health care practices such as weight control and health assessment, explain certain observed phenomena, make testable predictions, and may help to resolve major conundrums in the field. The ODE model, which is more comprehensive than Ohm's law, is useful to study metabolism at the detailed microscopic levels.

iNOS as a metabolic enzyme under stress conditions

Nitric oxide (NO) is a free radical acting as a cellular signaling molecule in many different biochemical processes. NO is synthesized from l-arginine through the action of the nitric oxide synthase (NOS) family of enzymes, which includes three isoforms: endothelial NOS (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS). iNOS-derived NO has been associated with the pathogenesis and progression of several diseases, including liver diseases, insulin resistance, obesity and diseases of the cardiovascular system. However, transient NO production can modulate metabolism to survive and cope with stress conditions. Accumulating evidence strongly imply that iNOS-derived NO plays a central role in the regulation of several biochemical pathways and energy metabolism including glucose and lipid metabolism during inflammatory conditions. This review summarizes current evidence for the regulation of glucose and lipid metabolism by iNOS during inflammation, and argues for the role of iNOS as a metabolic enzyme in immune and non-immune cells.

Vascular Dysfunction and Insulin Resistance in Aging

:

Insulin was discovered in 1922 by Banting and Best. Since that time, extensive research on the mechanisms of insulin activity and action has continued. Currently, it is known that the role of insulin is much greater than simply regulating carbohydrate metabolism. Insulin in physiological concentration is also necessary to maintain normal vascular function.

:

Insulin resistance is defined as a pathological condition characterized by reduced sensitivity of skeletal muscles, liver, and adipose tissue, to insulin and its downstream metabolic effects under normal serum glucose concentrations. There are also selective forms of insulin resistance with unique features, including vascular insulin resistance. Insulin resistance, both classical and vascular, contributes to vascular impairment resulting in increased risk of cardiovascular disease. Furthermore, in the elderly population, additional factors including redistribution of fat concentrations, low-grade inflammation, and decreased self-repair capacity [or cell senescence] amplify the vascular abnormalities related to insulin resistance.

Palmitic acid causes insulin resistance in granulosa cells via activation of JNK

Obesity is a worldwide health problem with rising incidence and results in reproductive difficulties. Elevated saturated free fatty acids (FFAs) in obesity can cause insulin resistance (IR) in peripheral tissues. The high intra-follicular saturated FFAs may also account for IR in ovarian granulosa cells (GCs). In the present study, we investigated the relationship between saturated FFAs and IR in GCs by the use of palmitic acid (PA). We demonstrated that the glucose uptake in cultured GCs and lactate accumulation in the culture medium were stimulated by insulin, but the effects of insulin were attenuated by PA treatment. Besides, insulin-induced phosphorylation of Akt was reduced by PA in a dose- and time-dependent manner. Furthermore, PA increased phosphorylation of JNK and JNK blockage rescued the phosphorylation of Akt which was downregulated by PA. These findings highlighted the negative effect of PA on GCs metabolism and may partially account for the obesity-related reproductive disorders.

Adiposity-Independent Effects of Aging on Insulin Sensitivity and Clearance in Mice and Humans

OBJECTIVE

Aging is associated with impaired insulin sensitivity and increased prevalence of type 2 diabetes. However, it remains unclear whether aging-associated insulin resistance is due to increased adiposity or other age-related factors. To address this question, the impact of aging on insulin sensitivity was investigated independently of changes in body composition.

METHODS

Cohorts of mice aged 4 to 8 months ("young") and 18 to 27 months ("aged") exhibiting similar body composition were characterized for glucose metabolism on chow and high-fat diets. Insulin sensitivity was assessed by hyperinsulinemic-euglycemic clamp analyses. The relationship between aging and insulin resistance in humans was investigated in 1,250 nondiabetic Mexican Americans who underwent hyperinsulinemic-euglycemic clamps.

RESULTS

In mice with similar body composition, age had no detrimental effect on plasma glucose and insulin levels. While aging did not diminish glucose tolerance, hyperinsulinemic-euglycemic clamps demonstrated impaired insulin sensitivity and reduced insulin clearance in aged mice on chow and high-fat diets. Consistent with results in the mouse, age remained an independent determinant of insulin resistance after adjustment for body composition in Mexican American males.

CONCLUSIONS

This study demonstrates that in addition to altered body composition, adiposity-independent mechanisms also contribute to aging-associated insulin resistance in mice and humans.

Effects of three flavonoids from an ancient traditional Chinese medicine Radix puerariae on geriatric diseases

As the worldwide population ages, the morbidity of neurodegenerative, cardiovascular, cerebrovascular, and endocrine diseases, such as diabetes and osteoporosis, continues to increase. The etiology of geriatric diseases is complex, involving the interaction of genes and the environment, which makes effective treatment challenging. Traditional Chinese medicine, unlike Western medicine, uses diverse bioactive ingredients to target multiple signaling pathways in geriatric diseases. Radix puerariae is one of the most widely used ancient traditional Chinese medicines and is also consumed as food. This review summarizes the evidence from in vivo and in vitro studies of the pharmacological effects of the main active components of the tuber of Radix puerariae on geriatric diseases.

Microbiota, Obesity and NAFLD

Non-alcoholic fatty liver disease (NAFLD) is an increasingly important cause of chronic liver disease globally. Similar to metabolic syndrome and obesity, NAFLD is associated with alternations in the gut microbiota and its related biological pathways. While the exact pathophysiology of NAFLD remains largely unknown, changes in intestinal inflammation, gut permeability, energy harvest, anaerobic fermentation and insulin resistance have been described. In this chapter, we review the relationship between the gut microbiota, obesity and NAFLD, and highlight potential ways to modify the gut microbiota to help managing NAFLD patients.

Endothelium-specific CYP2J2 overexpression attenuates age-related insulin resistance

Ample evidences demonstrate that cytochrome P450 epoxygenase‐derived epoxyeicosatrienoic acids (EETs) exert diverse biological activities, which include potent vasodilatory, anti‐inflammatory, and cardiovascular protective effects. In this study, we investigated the effects of endothelium‐specific CYP2J2 overexpression on age‐related insulin resistance and metabolic dysfunction. Endothelium‐specific targeting of the human CYP epoxygenase, CYP2J2, transgenic mice (Tie2‐CYP2J2‐Tr mice) was utilized. The effects of endothelium‐specific CYP2J2 overexpression on aging‐associated obesity, inflammation, and peripheral insulin resistance were evaluated by assessing metabolic parameters in young (3 months old) and aged (16 months old) adult male Tie2‐CYP2J2‐Tr mice. Decreased insulin sensitivity and attenuated insulin signaling in aged skeletal muscle, adipose tissue, and liver were observed in aged adult male mice, and moreover, these effects were partly inhibited in 16‐month‐old CYP2J2‐Tr mice. In addition, CYP2J2 overexpression‐mediated insulin sensitization in aged mice was associated with the amelioration of inflammatory state. Notably, the aging‐associated increases in fat mass and adipocyte size were only observed in 16‐month‐old wild‐type mice, and CYP2J2 overexpression markedly prevented the increase in fat mass and adipocyte size in aged Tie2‐CYP2J2‐Tr mice, which was associated with increased energy expenditure and decreased lipogenic genes expression. Furthermore, these antiaging phenotypes of Tie2‐CYP2J2‐Tr mice were also associated with increased muscle blood flow, enhanced active‐phase locomotor activity, and improved mitochondrial dysfunction in skeletal muscle. Collectively, our findings indicated that endothelium‐specific CYP2J2 overexpression alleviated age‐related insulin resistance and metabolic dysfunction, which highlighted CYP epoxygenase‐EET system as a potential target for combating aging‐related metabolic disorders.

iNOS promotes hypothalamic insulin resistance associated with deregulation of energy balance and obesity in rodents

Inducible nitric oxide (iNOS)-mediated S-nitrosation of the metabolic signaling pathway has emerged as a post-translational modification that triggers insulin resistance in obesity and aging. However, the effects of S-nitrosation in controlling energy homeostasis are unknown. Thus, in the present study we aimed to evaluate the effects of S-nitrosation in insulin signaling pathway in the hypothalamus of rodents. Herein, we demonstrated that the intracerebroventricular infusion of the nitric oxide (NO) donor S-nitrosoglutathione (GSNO) promoted hypothalamic insulin signaling resistance and replicated the food intake pattern of obese individuals. Indeed, obesity induced S-nitrosation of hypothalamic IR and Akt, whereas inhibition of iNOS or S-nitrosation of insulin signaling pathway protected against hypothalamic insulin resistance and normalized energy homeostasis. Overall, these findings indicated that S-nitrosation of insulin signaling pathway is required to sustain hypothalamic insulin resistance in obesity.

Doxorubicin-induced nitrosative stress is mitigated by vitamin C via the modulation of nitric oxide synthases

An increase in oxidative stress is suggested to be the main cause in Doxorubicin (Dox)–induced cardiotoxicity. However, there is now evidence that activation of inducible nitric oxide synthase (iNOS) and nitrosative stress are also involved. The role of vitamin C (Vit C) in the regulation of nitric oxide synthase (NOS) and reduction of nitrosative stress in Dox-induced cardiotoxicity is unknown. The present study investigated the effects of Vit C in the mitigation of Dox-induced changes in the levels of nitric oxide (NO), NOS activity, protein expression of NOS isoforms, and nitrosative stress as well as cytokines TNF-α and IL-10 in isolated cardiomyocytes. Cardiomyocytes isolated from adult Sprague-Dawley rats were segregated into four groups: 1) control, 2) Vit C (25 µM), 3) Dox (10 µM), and 4) Vit C + Dox. Dox caused a significant increase in the generation of superoxide radical (O2·−), peroxynitrite, and NO, and these effects of Dox were blunted by Vit C. Dox increased the expression of iNOS and altered protein expression as well as activation of endothelial NOS (eNOS). These changes were prevented by Vit C. Dox induced an increase in the ratio of monomeric/dimeric eNOS, promoting the production of O2·−, which was prevented by Vit C by increasing the stability of the dimeric form of eNOS. Vit C protected against the Dox-induced increase in TNFα as well as a reduction in IL-10. These results suggest that Vit C provides cardioprotection by reducing oxidative/nitrosative stress and inflammation via a modulation of Dox-induced increase in the NO levels and NOS activity.

High Dietary Fructose: Direct or Indirect Dangerous Factors Disturbing Tissue and Organ Functions

High dietary fructose is a major contributor to insulin resistance and metabolic syndrome, disturbing tissue and organ functions. Fructose is mainly absorbed into systemic circulation by glucose transporter 2 (GLUT2) and GLUT5, and metabolized in liver to produce glucose, lactate, triglyceride (TG), free fatty acid (FFA), uric acid (UA) and methylglyoxal (MG). Its extrahepatic absorption and metabolism also take place. High levels of these metabolites are the direct dangerous factors. During fructose metabolism, ATP depletion occurs and induces oxidative stress and inflammatory response, disturbing functions of local tissues and organs to overproduce inflammatory cytokine, adiponectin, leptin and endotoxin, which act as indirect dangerous factors. Fructose and its metabolites directly and/or indirectly cause oxidative stress, chronic inflammation, endothelial dysfunction, autophagy and increased intestinal permeability, and then further aggravate the metabolic syndrome with tissue and organ dysfunctions. Therefore, this review addresses fructose-induced metabolic syndrome, and the disturbance effects of direct and/or indirect dangerous factors on the functions of liver, adipose, pancreas islet, skeletal muscle, kidney, heart, brain and small intestine. It is important to find the potential correlations between direct and/or indirect risk factors and healthy problems under excess dietary fructose consumption.

Linking Gut Microbiota and Inflammation to Obesity and Insulin Resistance

Obesity and insulin resistance are the major predisposing factors to comorbidities, such as Type 2 diabetes, nonalcoholic fatty liver disease, cardiovascular and neurodegenerative diseases, and several types of cancer. The prevalence of obesity is still increasing worldwide and now affects a large number of individuals. Here, we review the role of the gut microbiota in the pathophysiology of insulin resistance/obesity. The human intestine is colonized by ∼100 trillion bacteria, which constitute the gut microbiota. Studies have shown that lean and overweight rodents and humans may present differences in the composition of their intestinal flora. Over the past 10 years, data from different sources have established a causal link between the intestinal microbiota and obesity/insulin resistance. It is important to emphasize that diet-induced obesity promotes insulin resistance by mechanisms independent and dependent on gut microbiota. In this review, we present several mechanisms that contribute to explaining the link between intestinal flora and insulin resistance/obesity. The LPS from intestinal flora bacteria can induce a chronic subclinical inflammatory process and obesity, leading to insulin resistance through activation of TLR4. The reduction in circulating SCFA may also have an essential role in the installation of reduced insulin sensitivity and obesity. Other mechanisms include effects of bile acids, branched-chain amino acids (BCAA), and some other lesser-known factors. In the near future, this area should open new therapeutic avenues for obesity/insulin resistance and its comorbidities.

Altered glucose and lipid homeostasis in liver and adipose tissue pre-dispose inducible NOS knockout mice to insulin resistance

On the basis of diet induced obesity and KO mice models, nitric oxide is implied to play an important role in the initiation of dyslipidemia induced insulin resistance. However, outcomes using iNOS KO mice have so far remained inconclusive. The present study aimed to assess IR in iNOS KO mice after 5 weeks of LFD feeding by monitoring body composition, energy homeostasis, insulin sensitivity/signaling, nitrite content and gene expressions changes in the tissues. We found that body weight and fat content in KO mice were significantly higher while the respiratory exchange ratio (RER), volume of carbon dioxide (VCO₂), and heat production were lower as compared to WT mice. Furthermore, altered systemic glucose tolerance, tissue insulin signaling, hepatic gluconeogenesis, augmented hepatic lipids, adiposity, as well as gene expression regulating lipid synthesis, catabolism and efflux were evident in iNOS KO mice. Significant reduction in eNOS and nNOS gene expression, hepatic and adipose tissue nitrite content, circulatory nitrite was also observed. Oxygen consumption rate of mitochondrial respiration has remained unaltered in KO mice as measured using extracellular flux analyzer. Our findings establish a link between the NO status with systemic and tissue specific IR in iNOS KO mice at 5 weeks.

Excessive training impairs the insulin signal transduction in mice skeletal muscles

The main aim of this investigation was to verify the effects of overtraining (OT) on the insulin and inflammatory signaling pathways in mice skeletal muscles. Rodents were divided into control (CT), overtrained by downhill running (OTR/down), overtrained by uphill running (OTR/up), and overtrained by running without inclination (OTR) groups. Rotarod, incremental load, exhaustive, and grip force tests were used to evaluate performance. Thirty-six hours after the grip force test, the extensor digitorum longus (EDL) and soleus were extracted for subsequent protein analyses. The three OT protocols led to similar responses of all performance evaluation tests. The phosphorylation of insulin receptor beta (pIRβ; Tyr), protein kinase B (pAkt; Ser473), and the protein levels of plasma membrane glucose transporter-4 (GLUT4) were lower in the EDL and soleus after the OTR/down protocol and in the soleus after the OTR/up and OTR protocols. While the pIRβ was lower after the OTR/up and OTR protocols, the pAkt was higher after the OTR/up in the EDL. The phosphorylation of IκB kinase alpha and beta (pIKKα/β; Ser180/181), stress-activated protein kinases/Jun amino-terminal kinases (pSAPK-JNK; Thr183/Tyr185), factor nuclear kappa B (pNFκB p65; Ser536), and insulin receptor substrate 1 (pIRS1; Ser307) were higher after the OTR/down protocol, but were not altered after the two other OT protocols. In summary, these data suggest that OT may lead to skeletal muscle insulin signaling pathway impairment, regardless of the predominance of eccentric contractions, although the insulin signal pathway impairment induced in OTR/up and OTR appeared to be muscle fiber-type specific.

Interplay between the kinin B1 receptor and inducible nitric oxide synthase in insulin resistance

BACKGROUND AND PURPOSE

Kinins are vasoactive and pro-inflammatory peptides whose biological effects are mediated by two GPCRs, named B1 and B2 receptors. While the B2 receptor plays a protective role in the cardiovascular system via the activation of endothelial NOS, the B1 receptor is associated with vascular inflammation, insulin resistance and diabetic complications. Because the B1 receptor is a potent activator of the inducible form of NOS (iNOS), this study has addressed the role of iNOS in the deleterious effects of B1 receptors in insulin resistance.

EXPERIMENTAL APPROACH

Male Sprague-Dawley rats (50-75 g) had free access to a drinking solution containing 10% d-glucose or tap water (control) for 9 weeks. During the last week, a selective iNOS inhibitor (1400W, 1 mg·kg(-1) twice daily) or its vehicle was administered s.c.

KEY RESULTS

Prolonged glucose treatment caused insulin resistance and several hallmarks of type 2 diabetes. Whereas the treatment with 1400W had no impact on the elevated systolic blood pressure and leptin levels in glucose-fed rats, it significantly reversed or attenuated hyperglycaemia, hyperinsulinaemia, insulin resistance (HOMA index), body weight gain, peroxynitrite formation (nitrotyrosine expression) and the up-regulation of biomarkers of inflammation (B1 receptor, carboxypeptidase M, iNOS and IL-1β) in renal cortex and aorta and to some extent in the liver.

CONCLUSIONS AND IMPLICATIONS

Pharmacological blockade of iNOS prevents the formation of peroxynitrite, which amplifies the pro-inflammatory effects of B1 receptors through a positive feedback mechanism. Hence, targeting iNOS can prevent the deleterious effects of B1 receptors in insulin resistance and peripheral inflammation.

Obesity and brain inflammation: a focus on multiple sclerosis

The increase in prevalence of obesity in industrialized societies is an indisputable fact. However, the apparent passive role played by adipocytes, in pathophysiological terms, has been gradually substituted by a metabolically active performance, relevant to many biochemical mechanisms that may contribute to a chronic low-grade inflammatory status, which increasingly imposes itself as a key feature of obesity. This chronic inflammatory status will have to be integrated into the complex equation of many diseases in which inflammation plays a crucial role. Multiple sclerosis (MS) is a chronic inflammatory condition typically confined to the central nervous system, and many work has been produced to find possible points of contact between the biology of this immune-mediated disease and obesity. So far, clinical data are not conclusive, but many biochemical features have been recently disclosed. Brain inflammation has been implicated in some of the mechanisms that lead to obesity, which has also been recognized as an important player in inducing some degree of immune dysfunction. In this review, we collected evidence that allows establishing bridges between obesity and MS. After considering epidemiological controversies, we will focus on possible shared mechanisms, as well as on the potential contributions that disease-modifying drugs may have on this apparent relationship of mutual interference.

Effects of long-term resveratrol-induced SIRT1 activation on insulin and apoptotic signalling in aged skeletal muscle

AIMS

Activation of Foxo1 is known to promote apoptosis and disturbances to insulin signalling. However, their modulating roles in aged skeletal muscle are not clear. The present study tested the hypothesis that long-term (i.e. 8 month) resveratrol supplementation would improve physical traits including exercise capacity and basal voluntary activity of aged mice and modulate insulin/apoptotic signalling in aged skeletal muscle. This study also examined whether these resveratrol-associated alterations would involve orchestration of the SIRT1-Foxo1 signalling axis.

METHODS

Two-month-old SAMP8 mice were randomly assigned to young, aged and aged with resveratrol treatment (AR) groups. The AR mice were supplemented with 4.9 mg(-1) kg(-1) day(-1) resveratrol for 8 months. All animals were subject to endurance capacity test and voluntary motor behaviour assessment. The lateral gastrocnemius muscle tissues were harvested for further analyses.

RESULTS

Long-term resveratrol treatment significantly alleviated the age-associated reductions in exercise capacity and voluntary motor behaviour. The protein content, but not the deacetylase activity of SIRT1 was increased with concomitant elevations of p300 acetylase and acetylation of Foxo1 in aged muscle. The aged muscle also manifested signs of impaired insulin signalling including attenuated phosphorylation of Akt, activity of pyruvate dehydrogenase and membrane trafficking of GLUT4 and elevated levels of phosphorylated IRS1 and iNOS and apoptotic activation measured as Bim, p53 and apoptotic DNA fragmentation. Intriguingly, all these age-related adverse changes were mitigated with the activation of SIRT1 deacetylase activity after long-term resveratrol treatment.

CONCLUSIONS

These data suggest that modulation of the SIRT1-Foxo1 axis by long-term resveratrol treatment enhances physical traits and alleviates the unfavourable changes in insulin and apoptotic signalling in aged muscle.

Sex differences with aging in nutritive skeletal muscle blood flow: impact of exercise training, nitric oxide, and α-adrenergic-mediated mechanisms

The incidence of cardiovascular disease increases progressively with age, but aging may affect men and women differently. Age-associated changes in vascular structure and function may manifest in impaired nutritive blood flow, although the regulation of nutritive blood flow in healthy aging is not well understood. The purpose of this study was to determine if nitric oxide (NO)-mediated or α-adrenergic-mediated regulation of nutritive skeletal muscle blood flow is impaired with advanced age, and if exercise training improves age-related deficiencies. Nutritive blood flow was monitored in the vastus lateralis of healthy young and aged men and women via the microdialysis-ethanol technique prior to and following seven consecutive days of exercise training. NO-mediated and α-adrenergic-mediated regulation of nutritive blood flow was assessed by microdialysis perfusion of acetylcholine, sodium nitroprusside, N(G)-monomethyl-L-arginine, norepinephrine, or phentolamine. Pretraining nutritive blood flow was attenuated in aged compared with young women (7.39 ± 1.5 vs. 15.5 ± 1.9 ml·100 g(−1)·min(−1), P = 0.018), but not aged men (aged 13.5 ± 3.7 vs. young 9.4 ± 1.3 ml·100 g(−1)·min(−1), P = 0.747). There were no age-associated differences in NO-mediated or α-adrenergic-mediated nutritive blood flow. Exercise training increased resting nutritive blood flow only in young men (9.4 ± 1.3 vs. 19.7 ml·100 g(−1)·min(−1), P = 0.005). The vasodilatory effect of phentolamine was significantly reduced following exercise training only in young men (12.3 ± 6.14 vs. −3.68 ± 3.26 ml·100 g(−1)·min(−1), P = 0.048). In conclusion, the age-associated attenuation of resting nutritive skeletal muscle blood flow was specific to women, while the exercise-induced alleviation of α-adrenergic mediated vasoconstriction that was specific to young men suggests an age-associated modulation of the sympathetic response to exercise training.

Eccentric exercise leads to performance decrease and insulin signaling impairment

PURPOSE

This study aimed to evaluate the effects of an overtraining (OT) protocol based on eccentric exercise (EE) sessions on the insulin and inflammatory signaling pathways in the skeletal muscles of Swiss mice.

METHODS

Rodents were divided into control (C; sedentary mice), trained (TR; performed the aerobic training protocol), and overtrained (OTR; performed the OT protocol). The incremental load test and exhaustive test were used to measure performances before and after exercise protocols. Twenty-four hours after the exhaustive test performed at the end of week 8, the extensor digitorum longus (EDL) and soleus muscles were removed for subsequent protein analysis by immunoblotting.

RESULTS

The phosphorylation of insulin receptor beta (pIRbeta; Tyr1146) diminished for EDL and soleus muscles in OTR compared with C. The phosphorylation of insulin receptor substrate 1 (pIRS-1; Ser307) increased for EDL and soleus muscles in OTR compared with C and TR. The phosphorylation of protein kinase B (pAkt; Ser473) diminished for EDL and soleus muscles in OTR compared with C and TR. The phosphorylation of IκB kinase alpha and beta (pIKKalpha/beta; Ser176/180), stress-activated protein kinases/Jun amino-terminal kinases (pSAPK/JNK; Thr183/Tyr185), and the protein levels of suppressor of cytokine signaling 3 (SOCS3) increased for EDL and soleus muscles in OTR compared with C and TR.

CONCLUSION

In summary, the current used OT protocol based on eccentric exercise sessions impaired the insulin signaling pathway with concomitant increases of IKK, SAPK/JNK, and SOCS3 protein levels.

Muscle microvascular blood flow responses in insulin resistance and ageing

Insulin resistance plays a key role in the development of type 2 diabetes. Skeletal muscle is the major storage site for glucose following a meal and as such has a key role in maintenance of blood glucose concentrations. Insulin resistance is characterised by impaired insulin-mediated glucose disposal in skeletal muscle. Multiple mechanisms can contribute to development of muscle insulin resistance and our research has demonstrated an important role for loss of microvascular function within skeletal muscle. We have shown that insulin can enhance blood flow to the microvasculature in muscle thus improving the access of glucose and insulin to the myocytes to augment glucose disposal. Obesity, insulin resistance and ageing are all associated with impaired microvascular responses to insulin in skeletal muscle. Impairments in insulin-mediated microvascular perfusion in muscle can directly cause insulin resistance, and this event can occur early in the aetiology of this condition. Understanding the mechanisms involved in the loss of microvascular function in muscle has the potential to identify novel treatment strategies to prevent or delay progression of insulin resistance and type 2 diabetes.

Nitric oxide availability is increased in contracting skeletal muscle from aged mice, but does not differentially decrease muscle superoxide

Reactive oxygen and nitrogen species have been implicated in the loss of skeletal muscle mass and function that occurs during aging. Nitric oxide (NO) and superoxide are generated by skeletal muscle and where these are generated in proximity their chemical reaction to form peroxynitrite can compete with the superoxide dismutation to hydrogen peroxide. Changes in NO availability may therefore theoretically modify superoxide and peroxynitrite activities in tissues, but published data are contradictory regarding aging effects on muscle NO availability. We hypothesised that an age-related increase in NO generation might increase peroxynitrite generation in muscles from old mice, leading to an increased nitration of muscle proteins and decreased superoxide availability. This was examined using fluorescent probes and an isolated fiber preparation to examine NO content and superoxide in the cytosol and mitochondria of muscle fibers from adult and old mice both at rest and following contractile activity. We also examined the 3-nitrotyrosine (3-NT) and peroxiredoxin 5 (Prx5) content of muscles from mice as markers of peroxynitrite activity. Data indicate that a substantial age-related increase in NO levels occurred in muscle fibers during contractile activity and this was associated with an increase in muscle eNOS. Muscle proteins from old mice also showed an increased 3-NT content. Inhibition of NOS indicated that NO decreased superoxide bioavailability in muscle mitochondria, although this effect was not age related. Thus increased NO in muscles of old mice was associated with an increased 3-NT content that may potentially contribute to age-related degenerative changes in skeletal muscle.

Effects of different intensities of physical exercise on insulin sensitivity and protein kinase B/Akt activity in skeletal muscle of obese mice

Objective:

To investigate the effects of different intensities of acute exercise on insulin sensitivity and protein kinase B/Akt activity in skeletal muscle of obese mice.

Methods:

Swiss mice were randomly divided into four groups, and fed either a standard diet (control group) or high fat diet (obese sedentary group and obese exercise group 1 and 2) for 12 weeks. Two different exercise protocols were used: swimming for 1 hour with or without an overload of 5% body weight. The insulin tolerance test was performed to estimate whole-body sensitivity. Western blot technique was used to determine protein levels of protein kinase B/Akt and phosphorylation by protein Kinase B/Akt in mice skeletal muscle.

Results:

A single bout of exercise inhibited the high fat diet-induced insulin resistance. There was increase in phosphorylation by protein kinase B/Akt serine, improve in insulin signaling and reduce of fasting glucose in mice that swam for 1 hour without overload and mice that swan for 1 hour with overload of 5%. However, no significant differences were seen between exercised groups.

Conclusion:

Regardless of intensity, aerobic exercise was able to improve insulin sensitivity and phosphorylation by protein kinase B/Ak, and proved to be a good form of treatment and prevention of type 2 diabetes.

Nitric oxide synthase inhibitors: a review of patents from 2011 to the present

INTRODUCTION

Nitric oxide synthases (NOSs) are a family of enzymes that play an essential role in synthesizing nitric oxide (NO) by oxidizing l-arginine. As previously reported, NO is a significant mediator in cellular signaling pathways. It serves as a crucial regulator in insulin secretion, vascular tone, peristalsis, angiogenesis, neural development and inflammation. Due to its important role, the inhibition of these vital enzymes provides, as tools, the opportunity to gain an insight into potential therapeutic applications targeting NOSs.

AREAS COVERED

This paper reviews the patent literature between 2011 and mid-2014 that specified inhibitors of NOS family members as the significant targets. Google and Baidu search engines were used to find relevant patents and clinical information using NOSs or NOS inhibitor as search terms.

EXPERT OPINION

Considerable recent progress has been made in the development of NOS inhibitors with pharmacodynamic and pharmacokinetic properties, and such development is likely to continue. The patented compounds attenuated mostly embodying evidence from in vitro and in vivo trials that demonstrate good potential for future clinical human trials and industrial applications. Furthermore, new techniques such as X-ray ligand crystallographic study and structure-activity relationship were popularly utilized, which give new insights for developing novel, safe, efficient and selective NOS inhibitors.

Hypothalamic inflammation and the central nervous system control of energy homeostasis

The control of energy homeostasis relies on robust neuronal circuits that regulate food intake and energy expenditure. Although the physiology of these circuits is well understood, the molecular and cellular response of this program to chronic diseases is still largely unclear. Hypothalamic inflammation has emerged as a major driver of energy homeostasis dysfunction in both obesity and anorexia. Importantly, this inflammation disrupts the action of metabolic signals promoting anabolism or supporting catabolism. In this review, we address the evidence that favors hypothalamic inflammation as a factor that resets energy homeostasis in pathological states.

Selective anticancer agents suppress aging in Drosophila

Mutations of the PI3K, TOR, iNOS, and NF-κB genes increase lifespan of model organisms and reduce the risk of some aging-associated diseases. We studied the effects of inhibitors of PI3K (wortmannin), TOR (rapamycin), iNOS (1400W), NF-κB (pyrrolidin dithiocarbamate and QNZ), and the combined effects of inhibitors: PI3K (wortmannin) and TOR (rapamycin), NF-κB (pyrrolidin dithiocarbamates) and PI3K (wortmannin), NF-κB (pyrrolidine dithiocarbamates) and TOR (rapamycin) on Drosophila melanogaster lifespan and quality of life (locomotor activity and fertility). Our data demonstrate that pharmacological inhibition of PI3K, TOR, NF-κB, and iNOS increases lifespan of Drosophila without decreasing quality of life. The greatest lifespan expanding effect was achieved by a combination of rapamycin (5 μM) and wortmannin (5 μM) (by 23.4%). The bioinformatic analysis (KEGG, REACTOME.PATH, DOLite, and GO.BP) showed the greatest aging-suppressor activity of rapamycin, consistent with experimental data.

Chronic treatment with qiliqiangxin ameliorates aortic endothelial cell dysfunction in diabetic rats

Qiliqiangxin (QL), a traditional Chinese medicine, has been shown to be beneficial for chronic heart failure. However, whether QL can also improve endothelial cell function in diabetic rats remains unknown. Here, we investigated the effect of QL treatment on endothelial dysfunction by comparing the effect of QL to that of benazepril (Ben) in diabetic Sprague-Dawley rats for 8 weeks. Cardiac function was evaluated by echocardiography and catheterization. Assays for acetylcholine-induced, endothelium-dependent relaxation (EDR), sodium nitroprusside-induced endothelium-independent relaxation, serum nitric oxide (NO), and nitric oxide synthase (NOS) as well as histological analyses were performed to assess endothelial function. Diabetic rats showed significantly inhibited cardiac function and EDR, decreased expression of serum NO and phosphorylation at Ser(1177) on endothelial NOS (eNOS), and impaired endothelial integrity after 8 weeks. Chronic treatment for 8 weeks with either QL or Ben prevented the inhibition of cardiac function and EDR and the decrease in serum NO and eNOS phosphorylation caused by diabetes. Moreover, either QL or Ben suppressed inducible NOS (iNOS) protein levels as well as endothelial necrosis compared with the diabetic rats. Additionally, QL prevented the increase in angiotensin-converting enzyme 1 and angiotensin II receptor type 1 in diabetes. Thus, chronic administration of QL improved serum NO production, EDR, and endothelial integrity in diabetic rat aortas, possibly through balancing eNOS and iNOS activity and decreasing renin-angiotensin system expression.

Ethyl Acetate Extract of Artemisia anomala S. Moore Displays Potent Anti-Inflammatory Effect

Artemisia anomala S. Moore has been widely used in China to treat inflammatory diseases for hundreds of years. However, mechanisms associated with its anti-inflammatory effect are not clear. In this study, we prepared ethyl acetate, petroleum ether, n-BuOH, and aqueous extracts from ethanol extract of Artemisia anomala S. Moore. Comparing anti-inflammatory effects of these extracts, we found that ethyl acetate extract of this herb (EAFA) exhibited the strongest inhibitory effect on nitric oxide (NO) production in LPS/IFNγ-stimulated RAW264.7 cells. EAFA suppressed the production of NO in a time- and dose-dependent manner without eliciting cytotoxicity to RAW264.7 cells. To understand the molecular mechanism underlying EAFA's anti-inflammatory effect, we showed that EAFA increased total cellular anti-oxidant capacity while reducing the amount of inducible nitric oxide synthase (iNOS) in stimulated RAW264.7 cells. EAFA also suppressed the expression of IL-1β and IL-6, whereas it elevates the level of heme oxygenase-1. These EAFA-induced events were apparently associated with NF-κB and MAPK signaling pathways because the DNA binding activity of p50/p65 was impaired and the activities of both ERK and JNK were decreased in EFEA-treated cells comparing to untreated cells. Our findings suggest that EAFA exerts its anti-inflammatory effect by inhibiting the expression of iNOS.

High sugar intake and development of skeletal muscle insulin resistance and inflammation in mice: a protective role for PPAR- δ agonism

Peroxisome Proliferator Activated Receptor (PPAR)-δ agonists may serve for treating metabolic diseases. However, the effects of PPAR-δ agonism within the skeletal muscle, which plays a key role in whole-body glucose metabolism, remain unclear. This study aimed to investigate the signaling pathways activated in the gastrocnemius muscle by chronic administration of the selective PPAR-δ agonist, GW0742 (1 mg/kg/day for 16 weeks), in male C57Bl6/J mice treated for 30 weeks with high-fructose corn syrup (HFCS), the major sweetener in foods and soft-drinks (15% wt/vol in drinking water). Mice fed with the HFCS diet exhibited hyperlipidemia, hyperinsulinemia, hyperleptinemia, and hypoadiponectinemia. In the gastrocnemius muscle, HFCS impaired insulin and AMP-activated protein kinase signaling pathways and reduced GLUT-4 and GLUT-5 expression and membrane translocation. GW0742 administration induced PPAR-δ upregulation and improvement in glucose and lipid metabolism. Diet-induced activation of nuclear factor-κB and expression of inducible-nitric-oxide-synthase and intercellular-adhesion-molecule-1 were attenuated by drug treatment. These effects were accompanied by reduction in the serum concentration of interleukin-6 and increase in muscular expression of fibroblast growth factor-21. Overall, here we show that PPAR-δ activation protects the skeletal muscle against the metabolic abnormalities caused by chronic HFCS exposure by affecting multiple levels of the insulin and inflammatory cascades.

Influence of gut microbiota on subclinical inflammation and insulin resistance. Mediators Inflamm. 2013;2013:986734. [PMID: 23840101 PMCID: PMC3694527 DOI: 10.1155/2013/986734]

Obesity is the main condition that is correlated with the appearance of insulin resistance, which is the major link among its comorbidities, such as type 2 diabetes, nonalcoholic fatty liver disease, cardiovascular and neurodegenerative diseases, and several types of cancer. Obesity affects a large number of individuals worldwide; it degrades human health and quality of life. Here, we review the role of the gut microbiota in the pathophysiology of obesity and type 2 diabetes, which is promoted by a bacterial diversity shift mediated by overnutrition. Whole bacteria, their products, and metabolites undergo increased translocation through the gut epithelium to the circulation due to degraded tight junctions and the consequent increase in intestinal permeability that culminates in inflammation and insulin resistance. Several strategies focusing on modulation of the gut microbiota (antibiotics, probiotics, and prebiotics) are being experimentally employed in metabolic derangement in order to reduce intestinal permeability, increase the production of short chain fatty acids and anorectic gut hormones, and promote insulin sensitivity to counteract the inflammatory status and insulin resistance found in obese individuals.

Early cardiac changes in a rat model of prediabetes: brain natriuretic peptide overexpression seems to be the best marker

Background

Diabetic cardiomyopathy (DCM) is defined as structural and functional changes in the myocardium due to metabolic and cellular abnormalities induced by diabetes mellitus (DM). The impact of prediabetic conditions on the cardiac tissue remains to be elucidated. The goal of this study was to elucidate whether cardiac dysfunction is already present in a state of prediabetes, in the presence of insulin resistance, and to unravel the underlying mechanisms, in a rat model without obesity and hypertension as confounding factors.

Methods

Two groups of 16-week-old Wistar rats were tested during a 9 week protocol: high sucrose (HSu) diet group (n = 7) – rats receiving 35% of sucrose in drinking water vs the vehicle control group (n = 7). The animal model was characterized in terms of body weight (BW) and the glycemic, insulinemic and lipidic profiles. The following parameters were assessed to evaluate possible early cardiac alterations and underlying mechanisms: blood pressure, heart rate, heart and left ventricle (LV) trophism indexes, as well as the serum and tissue protein and/or the mRNA expression of markers for fibrosis, hypertrophy, proliferation, apoptosis, angiogenesis, endothelial function, inflammation and oxidative stress.

Results

The HSu-treated rats presented normal fasting plasma glucose (FPG) but impaired glucose tolerance (IGT), accompanied by hyperinsulinemia and insulin resistance (P < 0.01), confirming this rat model as prediabetic. Furthermore, although hypertriglyceridemia (P < 0.05) was observed, obesity and hypertension were absent. Regarding the impact of the HSu diet on the cardiac tissue, our results indicated that 9 weeks of treatment might be associated with initial cardiac changes, as suggested by the increased LV weight/BW ratio (P < 0.01) and a remarkable brain natriuretic peptide (BNP) mRNA overexpression (P < 0.01), together with a marked trend for an upregulation of other important mediators of fibrosis, hypertrophy, angiogenesis and endothelial lesions, as well as oxidative stress. The inflammatory and apoptotic markers measured were unchanged.

Conclusions

This animal model of prediabetes/insulin resistance could be an important tool to evaluate the early cardiac impact of dysmetabolism (hyperinsulinemia and impaired glucose tolerance with fasting normoglycemia), without confounding factors such as obesity and hypertension. Left ventricle hypertrophy is already present and brain natriuretic peptide seems to be the best early marker for this condition.

Acute exercise decreases PTP-1B protein level and improves insulin signaling in the liver of old rats

It is now commonly accepted that chronic inflammation associated with obesity during aging induces insulin resistance in the liver. In the present study, we investigated whether the improvement in insulin sensitivity and insulin signaling, mediated by acute exercise, could be associated with modulation of protein-tyrosine phosphatase 1B (PTP-1B) in the liver of old rats. Aging rats were subjected to swimming for two 1.5-h long bouts, separated by a 45 min rest period. Sixteen hours after the exercise, the rats were sacrificed and proteins from the insulin signaling pathway were analyzed by immunoblotting. Our results show that the fat mass was increased in old rats. The reduction in glucose disappearance rate (Kitt) observed in aged rats was restored 16 h after exercise. Aging increased the content of PTP-1B and attenuated insulin signaling in the liver of rats, a phenomenon that was reversed by exercise. Aging rats also increased the IRβ/PTP-1B and IRS-1/PTP-1B association in the liver when compared with young rats. Conversely, in the liver of exercised old rats, IRβ/PTP-1B and IRS-1/PTP-1B association was markedly decreased. Moreover, in the hepatic tissue of old rats, the insulin signalling was decreased and PEPCK and G6Pase levels were increased when compared with young rats. Interestingly, 16 h after acute exercise, the PEPCK and G6Pase protein level were decreased in the old exercised group. These results provide new insights into the mechanisms by which exercise restores insulin signalling in liver during aging.