Lipid accumulation in non-adipose tissue and lipotoxicity

The Flexibility of Ectopic Lipids

In addition to the subcutaneous and the visceral fat tissue, lipids can also be stored in non-adipose tissue such as in hepatocytes (intrahepatocellular lipids; IHCL), skeletal (intramyocellular lipids; IMCL) or cardiac muscle cells (intracardiomyocellular lipids; ICCL). Ectopic lipids are flexible fuel stores that can be depleted by physical exercise and repleted by diet. They are related to obesity and insulin resistance. Quantification of IMCL was initially performed invasively, using muscle biopsies with biochemical and/or histological analysis. ¹H-magnetic resonance spectroscopy (¹H-MRS) is now a validated method that allows for not only quantifying IMCL non-invasively and repeatedly, but also assessing IHCL and ICCL. This review summarizes the current available knowledge on the flexibility of ectopic lipids. The available evidence suggests a complex interplay between quantitative and qualitative diet, fat availability (fat mass), insulin action, and physical exercise, all important factors that influence the flexibility of ectopic lipids. Furthermore, the time frame of the intervention on these parameters (short-term vs. long-term) appears to be critical. Consequently, standardization of physical activity and diet are critical when assessing ectopic lipids in predefined clinical situations.

LXR activation causes G1/S arrest through inhibiting SKP2 expression in MIN6 pancreatic beta cells

Liver X receptors (LXRs) are nuclear hormone receptors with central roles in lipid homeostasis. We previously showed that LXR activation induced aberrant lipid metabolism and G1 cell cycle arrest in pancreatic beta cells. In this study, we aimed to identify the molecular target of LXR causing G1 arrest. LXR activation was induced by its agonist, T0901317. A series of luciferase reporters of truncated Skp2 promoter were analyzed in MIN6 cells. mRNA and protein levels of SKP2 and P27 were detected. Flow cytometry assay was used to determine the cell cycle distribution. MTT assay was used to evaluate cell viability. LXR activation increased cell distribution in G1 phase and lipid accumulation. Since dominant-negative Srebp1c could clear the deposited lipid rather than recover the G1 arrest, we identified S-phase kinase-associated protein 2 (Skp2) as a potential target gene of LXR. In deed, LXR activation significantly inhibited Skp2 gene expression and protein amount. We also observed that the luciferase activity of Skp2 promoter was suppressed by T0901317 and the potential LXR regulatory site was narrowed down to a region of nt -289 to -38. Silencing Lxrα and Lxrβ rescued SKP2 protein level and recovered the cellular growth repressed by LXR activation. Moreover, SKP2 overabundance reduced P27 protein level by promoting its degradation, consequently overcame the G1 arrest caused by T0901317. Our findings demonstrate that transrepressing Skp2 expression by LXR activation resulted in defective SKP2-mediated P27 degradation and inhibitory cell growth in beta cells.

Drosophila as a Model for Diabetes and Diseases of Insulin Resistance

Despite the importance of insulin signaling pathways in human disease, initial concerns that insect physiology and sugar metabolism differ enough from humans that flies would not model human disease hampered research in this area. However, during the past 10-15 years, evidence has accumulated that flies can indeed model various aspects of diabetes and related human disorders. This cluster of diseases impact insulin and insulin signaling pathways, fields which have been discussed in many excellent review articles in recent years. In this chapter, we restrict our focus to specific examples of diabetes-related disease models in Drosophila, discussing the advantages and limitations of these models in light of physiological similarities and differences between insects and mammals. We discuss features of metabolism and sugar regulation that are shared between flies and mammals, and specific Drosophila models for Type 1 and Type 2 diabetes, Metabolic syndrome, and related abnormalities including insulin resistance and heart disease. We conclude that fly models for diabetes and related disorders enhance our ability to identify genes and discern functional interactions that can be exploited for disease intervention.

Appraisal of clinical practice guidelines for management of paediatric type 2 diabetes mellitus using the AGREE II instrument: a systematic review protocol

BACKGROUND

The prevalence of type 2 diabetes mellitus (T2DM) in children and adolescents is increasing. This has spurred the development and publication of clinical practice guidelines (CPGs) for the management of paediatric T2DM. Given the long-term complications of T2DM, optimal management is important to prevent or delay these complications. However, the quality of published CPGs has not yet been empirically evaluated. Our objective is to systematically appraise all published CPGs for the management of T2DM in children and adolescents.

METHODS

We will identify all published CPGs that address T2DM in children and adolescents through MEDLINE, Embase, CINAHL, Trip, and the National Guideline Clearinghouse and will screen diabetes and paediatric societies and associations' websites. Search records will be screened in duplicate for inclusion. Grey literature will be covered by systematically searching publications of all relevant diabetes societies and associations and other health organizations for CPGs that meet our inclusion criteria. CPGs deemed eligible for inclusion will be retrieved. Quality assessment will be conducted using the Appraisal of Guidelines for Research and Evaluation II (AGREE II) tool by a team of four appraisers. Scaled scores of the AGREE II will be used to gauge the overall quality of CPGs.

DISCUSSION

The results of this review will be disseminated through presentations at local, national, and international conferences and publication in a peer-reviewed journal. The results of this review can help improve the reporting of future guidelines, inform decisions of policy-makers to endorse CPGs, and affect the choice of guideline use in clinical practice.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42016034187.

Optical Coherence Tomography for Brain Imaging and Developmental Biology

Optical coherence tomography (OCT) is a promising research tool for brain imaging and developmental biology. Serving as a three-dimensional optical biopsy technique, OCT provides volumetric reconstruction of brain tissues and embryonic structures with micrometer resolution and video rate imaging speed. Functional OCT enables label-free monitoring of hemodynamic and metabolic changes in the brain in vitro and in vivo in animal models. Due to its non-invasiveness nature, OCT enables longitudinal imaging of developing specimens in vivo without potential damage from surgical operation, tissue fixation and processing, and staining with exogenous contrast agents. In this paper, various OCT applications in brain imaging and developmental biology are reviewed, with a particular focus on imaging heart development. In addition, we report findings on the effects of a circadian gene (Clock) and high-fat-diet on heart development in Drosophila melanogaster. These findings contribute to our understanding of the fundamental mechanisms connecting circadian genes and obesity to heart development and cardiac diseases.

Biochemical, Transcriptional, and Bioinformatic Analysis of Lipid Droplets from Seeds of Date Palm (Phoenix dactylifera L.) and Their Use as Potent Sequestration Agents against the Toxic Pollutant, 2,3,7,8-Tetrachlorinated Dibenzo-p-Dioxin

Contamination of aquatic environments with dioxins, the most toxic group of persistent organic pollutants (POPs), is a major ecological issue. Dioxins are highly lipophilic and bioaccumulate in fatty tissues of marine organisms used for seafood where they constitute a potential risk for human health. Lipid droplets (LDs) purified from date palm, Phoenix dactylifera, seeds were characterized and their capacity to extract dioxins from aquatic systems was assessed. The bioaffinity of date palm LDs toward 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), the most toxic congener of dioxins was determined. Fractioned LDs were spheroidal with mean diameters of 2.5 µm, enclosing an oil-rich core of 392.5 mg mL(-1). Isolated LDs did not aggregate and/or coalesce unless placed in acidic media and were strongly associated with three major groups of polypeptides of relative mass 32-37, 20-24, and 16-18 kDa. These masses correspond to the LD-associated proteins, oleosins, caleosins, and steroleosins, respectively. Efficient partitioning of TCDD into LDs occurred with a coefficient of log K LB/w,TCDD = 7.528 ± 0.024; it was optimal at neutral pH and was dependent on the presence of the oil-rich core, but was independent of the presence of LD-associated proteins. Bioinformatic analysis of the date palm genome revealed nine oleosin-like, five caleosin-like, and five steroleosin-like sequences, with predicted structures having putative lipid-binding domains that match their LD stabilizing roles and use as bio-based encapsulation systems. Transcriptomic analysis of date palm seedlings exposed to TCDD showed strong up-regulation of several caleosin and steroleosin genes, consistent with increased LD formation. The results suggest that the plant LDs could be used in ecological remediation strategies to remove POPs from aquatic environments. Recent reports suggest that several fungal and algal species also use LDs to sequester both external and internally derived hydrophobic toxins, which indicates that our approach could be used as a broader biomimetic strategy for toxin removal.

Oral treatment with a zinc complex of acetylsalicylic acid prevents diabetic cardiomyopathy in a rat model of type-2 diabetes: activation of the Akt pathway

BACKGROUND

Type-2 diabetics have an increased risk of cardiomyopathy, and heart failure is a major cause of death among these patients. Growing evidence indicates that proinflammatory cytokines may induce the development of insulin resistance, and that anti-inflammatory medications may reverse this process. We investigated the effects of the oral administration of zinc and acetylsalicylic acid, in the form of bis(aspirinato)zinc(II)-complex Zn(ASA)2, on different aspects of cardiac damage in Zucker diabetic fatty (ZDF) rats, an experimental model of type-2 diabetic cardiomyopathy.

METHODS

Nondiabetic control (ZL) and ZDF rats were treated orally with vehicle or Zn(ASA)2 for 24 days. At the age of 29-30 weeks, the electrical activities, left-ventricular functional parameters and left-ventricular wall thicknesses were assessed. Nitrotyrosine immunohistochemistry, TUNEL-assay, and hematoxylin-eosin staining were performed. The protein expression of the insulin-receptor and PI3K/AKT pathway were quantified by Western blot.

RESULTS

Zn(ASA)2-treatment significantly decreased plasma glucose concentration in ZDF rats (39.0 ± 3.6 vs 49.4 ± 2.8 mM, P < 0.05) while serum insulin-levels were similar among the groups. Data from cardiac catheterization showed that Zn(ASA)2 normalized the increased left-ventricular diastolic stiffness (end-diastolic pressure-volume relationship: 0.064 ± 0.008 vs 0.084 ± 0.014 mmHg/µl; end-diastolic pressure: 6.5 ± 0.6 vs 7.9 ± 0.7 mmHg, P < 0.05). Furthermore, ECG-recordings revealed a restoration of prolonged QT-intervals (63 ± 3 vs 83 ± 4 ms, P < 0.05) with Zn(ASA)2. Left-ventricular wall thickness, assessed by echocardiography, did not differ among the groups. However histological examination revealed an increase in the cardiomyocytes' transverse cross-section area in ZDF compared to the ZL rats, which was significantly decreased after Zn(ASA)2-treatment. Additionally, a significant fibrotic remodeling was observed in the diabetic rats compared to ZL rats, and Zn(ASA)2-administered ZDF rats showed a similar collagen content as ZL animals. In diabetic hearts Zn(ASA)2 significantly decreased DNA-fragmentation, and nitro-oxidative stress, and up-regulated myocardial phosphorylated-AKT/AKT protein expression. Zn(ASA)2 reduced cardiomyocyte death in a cellular model of oxidative stress. Zn(ASA)2 had no effects on altered myocardial CD36, GLUT-4, and PI3K protein expression.

CONCLUSIONS

We demonstrated that treatment of type-2 diabetic rats with Zn(ASA)2 reduced plasma glucose-levels and prevented diabetic cardiomyopathy. The increased myocardial AKT activation could, in part, help to explain the cardioprotective effects of Zn(ASA)2. The oral administration of Zn(ASA)2 may have therapeutic potential, aiming to prevent/treat cardiac complications in type-2 diabetic patients.

Metabolic Inflammation-Differential Modulation by Dietary Constituents

Obesity arises from a sustained positive energy balance which triggers a pro-inflammatory response, a key contributor to metabolic diseases such as T2D. Recent studies, focused on the emerging area of metabolic-inflammation, highlight that specific metabolites can modulate the functional nature and inflammatory phenotype of immune cells. In obesity, expanding adipose tissue attracts immune cells, creating an inflammatory environment within this fatty acid storage organ. Resident immune cells undergo both a pro-inflammatory and metabolic switch in their function. Inflammatory mediators, such as TNF-α and IL-1β, are induced by saturated fatty acids and disrupt insulin signaling. Conversely, monounsaturated and polyunsaturated fatty acids do not interrupt metabolism and inflammation to the same extent. AMPK links inflammation, metabolism and T2D, with roles to play in all and is influenced negatively by obesity. Lipid spillover results in hepatic lipotoxicity and steatosis. Also in skeletal muscle, excessive FFA can impede insulin's action and promote inflammation. Ectopic fat can also affect pancreatic β-cell function, thereby contributing to insulin resistance. Therapeutics, lifestyle changes, supplements and dietary manipulation are all possible avenues to combat metabolic inflammation and the subsequent insulin resistant state which will be explored in the current review.

A long-term high-fat, high-sucrose diet in Bama minipigs promotes lipid deposition and amyotrophy by up-regulating the myostatin pathway

Skeletal muscle is as an important regulator of blood glucose and glycolipid metabolism and is closely related to motor ability. The underlying mechanisms by which dietary ectopic lipids in skeletal muscle prevents muscle growth remain elusive. We utilized miniature Bama swine as a model to mimic human obesity using prolonged dietary induction. After 23 months on a high-fat, high-sucrose diet, metabolic disorders were induced in the animals, which exhibited increased body weight, extensive lipid deposition in the skeletal muscle and amyotrophy. Microarray profiles demonstrated the up-regulation of genes related to fat deposition and muscle growth inhibition. We outline a clear potential pathway that in combination with increased 11β-hydroxysteroid dehydrogenase type 1, promotes expression of a major inhibitor, myostatin, by converting corticosterone to cortisol, which leads to the growth inhibition of skeletal muscle. This research provides new insights into the treatment of muscle diseases induced by obesity.

The correlation between pancreatic steatosis and metabolic syndrome in a Chinese population

BACKGROUND

Type 2 diabetes mellitus, obesity and hepatic steatosis showed a strong correlation with metabolic syndrome. However, data on the influence of pancreatic steatosis on metabolic syndrome are lacking.

OBJECTIVE

Our aim is to perform the prevalence of pancreatic steatosis in adults and its association with metabolic syndrome in a Chinese population.

METHODS

This was a cross-sectional study, randomly selected. A total of 1190 health examination subjects were recruited. Pancreatic steatosis or hepatic steatosis was diagnosed via trans-abdominal sonography. The clinical and metabolic parameters were compared between the two groups, and their associations with pancreatic steatosis were examined.

RESULTS

The prevalence of pancreatic steatosis was 30.7%. The presence of pancreatic steatosis was significantly increased by age, gender, central obesity, hepatic steatosis, hypertriglyceridemia and hyperglycemia. In the logistic regression analysis, age (P < 0.05), central obesity (P < 0.01), diabetes (P < 0.05), hypertriglyceridemia (P < 0.05) and hepatic steatosis (P < 0.01) were independently associated with pancreatic steatosis. The number of the parameters of the metabolic syndrome in pancreatic steatosis group was more than that in non-pancreatic steatosis group [(2.5 ± 1.1) vs (1.4 ± 1.2)] (P < 0.01).

CONCLUSION

The pancreatic steatosis is strongly associated with the parameters of metabolic syndrome, such as central obesity, diabetes, and hepatic steatosis.

Not all fats are created equal: adipose vs. ectopic fat, implication in cardiometabolic diseases

Adipose tissue is a recognized endocrine organ that acts not only as a fuel storage but also is able to secrete adipokines that can modulate inflammation. Most of the fat is composed of white adipocytes (WAT), although also brown/beige adipocytes (BAT/BeAT) have been found in humans. BAT is located close to the neck but also among WAT in the epicardial fat and perivascular fat. Adipocyte hypertrophy and infiltration of macrophages impair adipose tissue metabolism determining "adiposopathy" (i.e., sick fat) and increasing the risk to develop metabolic and cardiovascular diseases. The purpose of this review was to search and discuss the available literature on the impact of different types of fat and fat distribution on cardiometabolic risk. Visceral fat, but also ectopic fat, either in liver, muscle and heart, can increase the risk to develop insulin resistance, type 2 diabetes and cardiovascular diseases. Results recently published showed that BAT could have an impact on cardiometabolic risk, not only because it is implicated in energy metabolism but also because it can modulate glucose and lipid metabolism. Therapeutical interventions that can increase energy expenditure, successfully change fat distribution and reduce ectopic fat, also through BAT activation, were discussed.

A mitochondrial-targeted ubiquinone modulates muscle lipid profile and improves mitochondrial respiration in obesogenic diet-fed rats

The prevalence of the metabolic syndrome components including abdominal obesity, dyslipidaemia and insulin resistance is increasing in both developed and developing countries. It is generally accepted that the development of these features is preceded by, or accompanied with, impaired mitochondrial function. The present study was designed to analyse the effects of a mitochondrial-targeted lipophilic ubiquinone (MitoQ) on muscle lipid profile modulation and mitochondrial function in obesogenic diet-fed rats. For this purpose, twenty-four young male Sprague-Dawley rats were divided into three groups and fed one of the following diets: (1) control, (2) high fat (HF) and (3) HF+MitoQ. After 8 weeks, mitochondrial function markers and lipid metabolism/profile modifications in skeletal muscle were measured. The HF diet was effective at inducing the major features of the metabolic syndrome--namely, obesity, hepatic enlargement and glucose intolerance. MitoQ intake prevented the increase in rat body weight, attenuated the increase in adipose tissue and liver weights and partially reversed glucose intolerance. At the muscle level, the HF diet induced moderate TAG accumulation associated with important modifications in the muscle phospholipid classes and in the fatty acid composition of total muscle lipid. These lipid modifications were accompanied with decrease in mitochondrial respiration. MitoQ intake corrected the lipid alterations and restored mitochondrial respiration. These results indicate that MitoQ protected obesogenic diet-fed rats from some features of the metabolic syndrome through its effects on muscle lipid metabolism and mitochondrial activity. These findings suggest that MitoQ is a promising candidate for future human trials in the metabolic syndrome prevention.

Obesity in MENX Rats Is Accompanied by High Circulating Levels of Ghrelin and Improved Insulin Sensitivity

Ghrelin, the natural ligand of the growth hormone secretagogue receptor type 1a (GHS-R1a), is mainly secreted from the stomach and regulates food intake and energy homeostasis. p27 regulates cell cycle progression in many cell types. Here, we report that rats affected by the multiple endocrine neoplasia syndrome MENX, caused by a p27 mutation, develop pancreatic islet hyperplasia containing elevated numbers of ghrelin-producing ε-cells. The metabolic phenotype of MENX-affected rats featured high endogenous acylated and unacylated plasma ghrelin levels. Supporting increased ghrelin action, MENX rats show increased food intake, enhanced body fat mass, and elevated plasma levels of triglycerides and cholesterol. Ghrelin effect on food intake was confirmed by treating MENX rats with a GHS-R1a antagonist. At 7.5 months, MENX-affected rats show decreased mRNA levels of hypothalamic GHS-R1a, neuropeptide Y (NPY), and agouti-related protein (AgRP), suggesting that prolonged hyperghrelinemia may lead to decreased ghrelin efficacy. In line with ghrelin's proposed role in glucose metabolism, we find decreased glucose-stimulated insulin secretion in MENX rats, while insulin sensitivity is improved. In summary, we provide a novel nontransgenic rat model with high endogenous ghrelin plasma levels and, interestingly, improved glucose tolerance. This model might aid in identifying new therapeutic approaches for obesity and obesity-related diseases, including type 2 diabetes.

Chlorogenic acid from honeysuckle improves hepatic lipid dysregulation and modulates hepatic fatty acid composition in rats with chronic endotoxin infusion

Chlorogenic acid as a natural hydroxycinnamic acid has protective effect for liver. Endotoxin induced metabolic disorder, such as lipid dysregulation and hyperlipidemia. In this study, we investigated the effect of chlorogenic acid in rats with chronic endotoxin infusion. The Sprague-Dawley rats with lipid metabolic disorder (LD group) were intraperitoneally injected endotoxin. And the rats of chlorogenic acid-LD group were daily received chlorogenic acid by intragastric administration. In chlorogenic acid-LD group, the area of visceral adipocyte was decreased and liver injury was ameliorated, as compared to LD group. In chlorogenic acid-LD group, serum triglycerides, free fatty acids, hepatic triglycerides and cholesterol were decreased, the proportion of C20:1, C24:1 and C18:3n-6, Δ9-18 and Δ6-desaturase activity index in the liver were decreased, and the proportion of C18:3n-3 acid was increased, compared to the LD group. Moreover, levels of phosphorylated AMP-activated protein kinase, carnitine palmitoyltransferase-I, and fatty acid β-oxidation were increased in chlorogenic acid-LD group compared to LD rats, whereas levels of fatty acid synthase and acetyl-CoA carboxylase were decreased. These findings demonstrate that chlorogenic acid effectively improves hepatic lipid dysregulation in rats by regulating fatty acid metabolism enzymes, stimulating AMP-activated protein kinase activation, and modulating levels of hepatic fatty acids.

Damaging effects of hyperglycemia on cardiovascular function: spotlight on glucose metabolic pathways

The incidence of cardiovascular complications associated with hyperglycemia is a growing global health problem. This review discusses the link between hyperglycemia and cardiovascular diseases onset, focusing on the role of recently emerging downstream mediators, namely, oxidative stress and glucose metabolic pathway perturbations. The role of hyperglycemia-mediated activation of nonoxidative glucose pathways (NOGPs) [i.e., the polyol pathway, hexosamine biosynthetic pathway, advanced glycation end products (AGEs), and protein kinase C] in this process is extensively reviewed. The proposal is made that there is a unique interplay between NOGPs and a downstream convergence of detrimental effects that especially affect cardiac endothelial cells, thereby contributing to contractile dysfunction. In this process the AGE pathway emerges as a crucial mediator of hyperglycemia-mediated detrimental effects. In addition, a vicious metabolic cycle is established whereby hyperglycemia-induced NOGPs further fuel their own activation by generating even more oxidative stress, thereby exacerbating damaging effects on cardiac function. Thus NOGP inhibition, and particularly that of the AGE pathway, emerges as a novel therapeutic intervention for the treatment of cardiovascular complications such as acute myocardial infarction in the presence hyperglycemia.

Ameliorative potential of gingerol: Promising modulation of inflammatory factors and lipid marker enzymes expressions in HFD induced obesity in rats

Obesity, generally linked to hyperlipidemia, has been occurring of late with distressing alarm and has now become a global phenomenon casting a huge economic burden on the health care system of countries around the world. The present study investigated the effects of gingerol over 30 days on the changes in HFD-induced obese rats in marker enzymes of lipid metabolism such as fatty-acid synthase (FAS), Acetyl CoA Carboxylase (ACC), Carnitine Palmitoyl Transferase-1(CPT-1), HMG co-A Reductase (HMGR), Lecithin Choline Acyl Transferase (LCAT) and Lipoprotein Lipase (LPL) and inflammatory markers (TNF-α and IL-6). The rats were treated orally with gingerol (75 mg kg(-1)) once daily for 30 days with a lorcaserin-treated group (10 mg kg(-1)) included for comparison. Changes in body weight, glucose, insulin resistance and expressions of lipid marker enzymes and inflammatory markers in tissues were observed in experimental rats. The administration of gingerol resulted in a significant reduction in body weight gain, glucose and insulin levels, and insulin resistance, which altered the activity, expressions of lipid marker enzymes and inflammatory markers. It showed that gingerol had significantly altered these parameters when compared with HFD control rats. This study confirms that gingerol prevents HFD-induced hyperlipidemia by modulating the expression of enzymes important to cholesterol metabolism.

Hdac3 Deficiency Increases Marrow Adiposity and Induces Lipid Storage and Glucocorticoid Metabolism in Osteochondroprogenitor Cells

Bone loss and increased marrow adiposity are hallmarks of aging skeletons. Conditional deletion of histone deacetylase 3 (Hdac3) in murine osteochondroprogenitor cells causes osteopenia and increases marrow adiposity, even in young animals, but the origins of the increased adiposity are unclear. To explore this, bone marrow stromal cells (BMSCs) from Hdac3-depleted and control mice were cultured in osteogenic medium. Hdac3-deficient cultures accumulated lipid droplets in greater abundance than control cultures and expressed high levels of genes related to lipid storage (Fsp27/Cidec, Plin1) and glucocorticoid metabolism (Hsd11b1) despite normal levels of Pparγ2. Approximately 5% of the lipid containing cells in the wild-type cultures expressed the master osteoblast transcription factor Runx2, but this population was threefold greater in the Hdac3-depleted cultures. Adenoviral expression of Hdac3 restored normal gene expression, indicating that Hdac3 controls glucocorticoid activation and lipid storage within osteoblast lineage cells. HDAC3 expression was reduced in bone cells from postmenopausal as compared to young women, and in osteoblasts from aged as compared to younger mice. Moreover, phosphorylation of S424 in Hdac3, a posttranslational mark necessary for deacetylase activity, was suppressed in osseous cells from old mice. Thus, concurrent declines in transcription and phosphorylation combine to suppress Hdac3 activity in aging bone, and reduced Hdac3 activity in osteochondroprogenitor cells contributes to increased marrow adiposity associated with aging. © 2015 American Society for Bone and Mineral Research.

Distinct Hepatic Macrophage Populations in Lean and Obese Mice

Obesity is a complex metabolic disorder associated with the development of non-communicable diseases such as cirrhosis, non-alcoholic fatty liver disease, and type 2 diabetes. In humans and rodents, obesity promotes hepatic steatosis and inflammation, which leads to increased production of pro-inflammatory cytokines and acute-phase proteins. Liver macrophages (resident as well as recruited) play a significant role in hepatic inflammation and insulin resistance (IR). Interestingly, depletion of hepatic macrophages protects against the development of high-fat-induced steatosis, inflammation, and IR. Kupffer cells (KCs), liver-resident macrophages, are the first-line defense against invading pathogens, clear toxic or immunogenic molecules, and help to maintain the liver in a tolerogenic immune environment. During high fat diet feeding and steatosis, there is an increased number of recruited hepatic macrophages (RHMs) in the liver and activation of KCs to a more inflammatory or M1 state. In this review, we will focus on the role of liver macrophages (KCs and RHMs) during obesity.

Effects of low-stearate palm oil and high-stearate lard high-fat diets on rat liver lipid metabolism and glucose tolerance

Background

Excess consumption of energy-dense, high-fat Western diets contributes to the development of obesity and obesity-related disorders, such as fatty liver disease. However, not only the quantity but also the composition of dietary fat may play a role in the development of liver steatosis. The aim of this study was to determine the effects of low-stearate palm oil and high-stearate lard high-fat diets on in vivo liver lipid metabolism.

Methods

Wistar rats were fed with either normal chow (CON), a high-fat diet based on palm oil (HFP), or a high-fat diet based on lard (HFL). After 10 weeks of diet, magnetic resonance spectroscopy was applied for the in vivo determination of intrahepatocellular lipid content and the uptake and turnover of dietary fat after oral administration of ¹³C-labeled lipids. Derangements in liver lipid metabolism were further assessed by measuring hepatic very-low density lipoprotein (VLDL) secretion and ex vivo respiratory capacity of liver mitochondria using fat-derived substrates. In addition, whole-body and hepatic glucose tolerance were determined with an intraperitoneal glucose tolerance test.

Results

Both high-fat diets induced liver lipid accumulation (p < 0.001), which was accompanied by a delayed uptake and/or slower turnover of dietary fat in the liver (p < 0.01), but without any change in VLDL secretion rates. Surprisingly, liver lipid content was higher in HFP than in HFL (p < 0.05), despite the increased fatty acid oxidative capacity in isolated liver mitochondria of HFP animals (p < 0.05). In contrast, while both high-fat diets induced whole-body glucose intolerance, only HFL impaired hepatic glucose tolerance.

Conclusion

High-fat diets based on palm oil and lard similarly impair the handling of dietary lipids in the liver, but only the high-fat lard diet induces hepatic glucose intolerance.

Skeletal muscle as a therapeutic target for delaying type 1 diabetic complications

Type 1 diabetes mellitus (T1DM) is a chronic autoimmune disease targeting the pancreatic beta-cells and rendering the person hypoinsulinemic and hyperglycemic. Despite exogenous insulin therapy, individuals with T1DM will invariably develop long-term complications such as blindness, kidney failure and cardiovascular disease. Though often overlooked, skeletal muscle is also adversely affected in T1DM, with both physical and metabolic derangements reported. As the largest metabolic organ in the body, impairments to skeletal muscle health in T1DM would impact insulin sensitivity, glucose/lipid disposal and basal metabolic rate and thus affect the ability of persons with T1DM to manage their disease. In this review, we discuss the impact of T1DM on skeletal muscle health with a particular focus on the proposed mechanisms involved. We then identify and discuss established and potential adjuvant therapies which, in association with insulin therapy, would improve the health of skeletal muscle in those with T1DM and thereby improve disease management- ultimately delaying the onset and severity of other long-term diabetic complications.

Dietary fiber prevents obesity-related liver lipotoxicity by modulating sterol-regulatory element binding protein pathway in C57BL/6J mice fed a high-fat/cholesterol diet

Adequate intake of dietary fibers has proven metabolic and cardiovascular benefits, molecular mechanisms remain still limited. This study was aimed to investigate the effects of cereal dietary fiber on obesity-related liver lipotoxicity in C57BL/6J mice fed a high-fat/cholesterol (HFC) diet and underlying mechanism. Forty-eight adult male C57BL/6J mice were randomly given a reference chow diet, or a high fat/cholesterol (HFC) diet supplemented with or without oat fiber or wheat bran fiber for 24 weeks. Our results showed mice fed oat or wheat bran fiber exhibited lower weight gain, lipid profiles and insulin resistance, compared with HFC diet. The two cereal dietary fibers potently decreased protein expressions of sterol regulatory element binding protein-1 and key factors involved in lipogenesis, including fatty acid synthase and acetyl-CoA carboxylase in target tissues. At molecular level, the two cereal dietary fibers augmented protein expressions of peroxisome proliferator-activated receptor alpha and gamma, liver X receptor alpha, and ATP-binding cassette transporter A1 in target tissues. Our findings indicated that cereal dietary fiber supplementation abrogated obesity-related liver lipotoxicity and dyslipidemia in C57BL/6J mice fed a HFC diet. In addition, the efficacy of oat fiber is greater than wheat bran fiber in normalizing these metabolic disorders and pathological profiles.

Inflammatory stress induces lipid accumulation in multi-organs of db/db mice

Dyslipidemia and chronic inflammation play crucial roles in the progression of diabetes. This study aimed to investigate the effects of inflammatory stress on lipid accumulation in multi-organs in diabetes. Eight-week-old male db/db mice were randomly assigned to inflamed group with alternating day subcutaneous injection of 10% casein or control group with daily injection of distilled water. The lipid profile and plasma levels of inflammatory cytokines were determined using a clinical biochemical assay and enzyme-linked immunosorbent assay. The effects of inflammation on lipid accumulation in target organs were evaluated by hematoxylin-eosin staining, Oil Red O staining, Filipin staining, and a quantitative intracellular cholesterol assay. The protein expressions of low-density lipoprotein receptor (LDLr), sterol regulatory element binding protein-2 (SREBP-2), and SREBP-cleavage-activating protein (SCAP) in tissues were assessed by immunohistochemical staining and western blotting. Results showed that the serum levels of inflammatory cytokines were significantly elevated in casein-injected mice, suggesting that an inflamed diabetic model was established. Furthermore, the protein expressions of inflammatory cytokines in aortas, livers, kidneys, and intestines were significantly increased in inflamed group compared with control. Whereas the serum levels of lipid moieties in inflamed mice were not different compared with the control, inflammatory stress significantly increased lipid accumulation in aortas, livers, kidneys, and intestines, which coincided with increased protein expressions of LDLr, SREBP-2, and SCAP in these organs of inflamed mice. In conclusion, inflammation induces lipid accumulation in multi-organs of db/db mice from the circulation to peripheral tissues, potentially due to lipid redistribution mediated by the disruption of LDLr feedback regulation.

Antitumour effects of tetrazanbigen against human hepatocellular carcinoma QGY-7701 through inducing lipid accumulation in vitro and in vivo

Objectives

Tetrazanbigen (TNBG) is a newly synthesized compound with an isoquinoline moiety, and its antitumour effects were evaluated in in-vitro and in-vivo models.

Methods

3-[4, 5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay was used to measure the antiproliferative activity of TNBG on cancer cell lines. Antitumour activity of TNGB in vivo was also assessed in a xenograft model of human hepatocellular carcinoma QGY-7701 cell line. Cell cycle and cell apoptosis analysis was performed.

Key findings

TNBG exhibited strong antitumour efficacy against six human cancer cell lines with IC50 range of 2.13–8.01 μg/ml. The IC50 of TNBG on normal hepatic cells was 11.25 μg/ml. Lots of lipid droplets were observed in cytoplasm of human hepatocellular carcinoma QGY-7701 cells after treatment of TNBG. S phase arrest and apoptosis induction by TNBG were also found on QGY-7701 cells. Intraperitoneal injection of TNBG (1.5 mg/kg/day) resulted in significant decreases in tumour volume and tumour weight on nude mice bearing QGY-7701 cells xenografts. Results from pathological analysis in nude mice demonstrated that TNBG could induce lipid accumulation specifically in cancer tissue rather than in other normal organs, tissues and blood.

Conclusions

These results suggested that TNBG might exert potent antitumour activity through inducing lipid accumulation in cancer cell.

The role of metabolic syndrome in heart failure

Metabolic syndrome (MS) is a highly prevalent condition in patients affected by heart failure (HF); however, it is still unclear whether, in the setting of cardiac dysfunction, it represents an adverse risk factor for the occurrence of cardiac events. The epidemiologic implications of MS in HF have been studied intensely, as many of its components contribute to the incidence and severity of HF. In particular, insulin resistance, diabetes mellitus, and lipid abnormalities represent the main components that negatively influence disease progression and evolution. Yet, other components of the MS, i.e. overweight/obesity and high blood pressure, are favourably associated with outcome in HF patients. The aim of this review was to report epidemiology and prognostic role of MS in HF and to investigate current clinical implications and future research needs.

Oncostatin M is a potential agent for the treatment of obesity and related metabolic disorders: a study in mice

AIMS/HYPOTHESIS

Obesity and insulin resistance are closely associated with adipose tissue dysfunction caused by the abnormal recruitment of inflammatory cells, including macrophages. Oncostatin M (OSM), a member of the IL-6 family of cytokines, plays important roles in a variety of biological functions including the regulation of inflammatory responses. In previous reports, we have demonstrated that mice deficient in the OSM receptor β subunit show obesity, adipose tissue inflammation, insulin resistance and hepatic steatosis, all of which are exacerbated by feeding the mice a high-fat diet. These results prompted us to test the therapeutic effects of OSM on obesity-induced metabolic disorders using mouse models of obesity.

METHODS

In diet-induced obese and ob/ob mice, metabolic variables were assessed physiologically, histologically and biochemically after the intraperitoneal injection of recombinant mouse OSM twice a day for 1 week.

RESULTS

Treatment with OSM improved obesity, adipose tissue inflammation, insulin resistance and hepatic steatosis in both mouse models. Although OSM reduced food intake, such therapeutic effects of OSM were observed even under pair-feeding conditions. Functionally, OSM directly changed the phenotype of adipose tissue macrophages from M1 type (inflammatory) to M2 type (anti-inflammatory). In the liver, OSM suppressed the expression of genes related to fatty acid synthesis and increased the expression of genes related to fatty acid oxidation. Furthermore, OSM decreased lipid absorption and increased the expression of active glucagon-like peptide-1 in the intestine.

CONCLUSIONS/INTERPRETATION

We showed that OSM is a novel candidate to act as a powerful therapeutic agent for the treatment of obesity-induced metabolic disorders.

Liver disease in menopause

There are numerous physiologic and biochemical changes in menopause that can affect the function of the liver and mediate the development of liver disease. Menopause represents a state of growing estrogen deficiency, and this loss of estrogen in the setting of physiologic aging increases the likelihood of mitochondrial dysfunction, cellular senescence, declining immune responses to injury, and disarray in the balance between antioxidant formation and oxidative stress. The sum effect of these changes can contribute to increased susceptibility to development of significant liver pathology, particularly nonalcoholic fatty liver disease and hepatocellular carcinoma, as well as accelerated progression of fibrosis in liver diseases, as has been particularly demonstrated in hepatitis C virus liver disease. Recognition of the unique nature of these mediating factors should raise suspicion for liver disease in perimenopausal and menopausal women and offer an opportunity for implementation of aggressive treatment measures so as to avoid progression of liver disease to cirrhosis, liver cancer and liver failure.

Magnolia bioactive constituent 4-O-methylhonokiol prevents the impairment of cardiac insulin signaling and the cardiac pathogenesis in high-fat diet-induced obese mice

In obesity, cardiac insulin resistance is a putative cause of cardiac hypertrophy and dysfunction. In our previous study, we observed that Magnolia extract BL153 attenuated high-fat-diet (HFD)-induced cardiac pathogenic changes. In this study, we further investigated the protective effects of the BL153 bioactive constituent, 4-O-methylhonokiol (MH), against HFD-induced cardiac pathogenesis and its possible mechanisms. C57BL/6J mice were fed a normal diet or a HFD with gavage administration of vehicle, BL153, or MH (low or high dose) daily for 24 weeks. Treatment with MH attenuated HFD-induced obesity, as evidenced by body weight gain, and cardiac pathogenesis, as assessed by the heart weight and echocardiography. Mechanistically, MH treatment significantly reduced HFD-induced impairment of cardiac insulin signaling by preferentially augmenting Akt2 signaling. MH also inhibited cardiac expression of the inflammatory factors tumor necrosis factor-α and plasminogen activator inhibitor-1 and increased the phosphorylation of nuclear factor erythroid-derived 2-like 2 (Nrf2) as well as the expression of a Nrf2 downstream target gene heme oxygenase-1. The increased Nrf2 signaling was associated with decreased oxidative stress and damage, as reflected by lowered malondialdehyde and 3-nitrotyrosine levels. Furthermore, MH reduced HFD-induced cardiac lipid accumulation along with lowering expression of cardiac fatty acid translocase/CD36 protein. These results suggest that MH, a bioactive constituent of Magnolia, prevents HFD-induced cardiac pathogenesis by attenuating the impairment of cardiac insulin signaling, perhaps via activation of Nrf2 and Akt2 signaling to attenuate CD36-mediated lipid accumulation and lipotoxicity.

Gender-specific differences in the development of sarcopenia in the rodent model of the ageing high-fat rat

BACKGROUND

Sarcopenia is linked to functional impairments, loss of independence, and mortality. In the past few years, obesity has been established as being a risk factor for a decline in muscle mass and function. There are several molecular pathological mechanisms, which have been under discussion that might explain this relationship. However, most studies were conducted using male animals and for a short period of time.

METHODS

In this study, the gender-specific effect of long-term, high-fat content feeding in Sprague-Dawley rats was examined. Development of the quadriceps muscle of the animals was monitored in vivo using magnetic resonance. The results of these measurements and of the biochemical analysis of the aged muscle were compared.

RESULTS

Surprisingly, only male but not female rats showed a decline in muscle cross-sectional area at 16 months of age as a result of a chronic oversupply of dietary fats. This loss of muscle mass could not be explained by either de-regulation of the anabolic Akt pathway or by up-regulation of the main ubiquitin ligases of muscle, MAFbx and MuRF-1. However, fusion of satellite cells to myotubes was induced by the high-fat diet in male rats, possibly as a result of an increased need for compensatory regeneration processes. Caspase-3-dependent apoptosis induction, irrespective of diet, seems to be the major determinant of muscle decline during ageing in male but not female rats.

CONCLUSION

Taken together, activation of the apoptosis-inducing Caspase-3 seems to be the most important trigger for the age-related muscle loss. Male rats were more prone to the decline of muscle during ageing than female animals, which was further enforced by a long-term, high fat diet.

Lipid profiles of adipose and muscle tissues in mouse models of juvenile onset of obesity without high fat diet induction: a Fourier transform infrared (FT-IR) spectroscopic study

The current study aims to determine lipid profiles in terms of the content and structure of skeletal muscle and adipose tissues to better understand the characteristics of juvenile-onset spontaneous obesity without high fat diet induction. For the purposes of this study, muscle (longissimus, quadriceps) and adipose (inguinal, gonadal) tissues of 10-week-old male DBA/2J and Berlin fat mouse inbred (BFMI) lines (BFMI856, BFMI860, BFMI861) fed with a standard breeding diet were used. Biomolecular structure and composition was determined using attenuated total reflection Fourier transform (ATR FT-IR) spectroscopy, and muscle triglyceride content was further quantified using high-performance liquid chromatography (HPLC) coupled with an evaporative light scattering detector (ELSD). The results revealed a loss of unsaturation in BFMI860 and BFMI861 lines in both muscles and inguinal adipose tissue, together with a decrease in the hydrocarbon chain length of lipids, especially in the BFMI860 line in muscles, suggesting an increased lipid peroxidation. There was an increase in saturated lipid and triglyceride content in all tissues of BFMI lines, more profoundly in longissimus muscle, where the increased triglyceride content was quantitatively confirmed by HPLC-ELSD. Moreover, an increase in the metabolic turnover of carbohydrates in muscles of the BFMI860 line was observed. The results demonstrated that subcutaneous (inguinal) fat also displayed considerable obesity-induced alterations. Taken together, the results revealed differences in lipid structure and content of BFMI lines, which may originate from different insulin sensitivity levels of the lines, making them promising animal models for spontaneous obesity. The results will contribute to the understanding of the generation of insulin resistance in obesity without high fat diet induction.

Follicular fluid concentrations of lipids and their metabolites are associated with intraovarian gonadotropin-stimulated androgen production in women undergoing in vitro fertilization

CONTEXT

Although growing evidence points toward a role of lipotoxicity in the development of hyperandrogenesis, the main feature of polycystic ovary syndrome, few studies directly assessed this association in vivo in humans, and none targeted the ovarian milieu.

OBJECTIVE

The main objective of this study was to correlate follicular fluid (FF) T levels with lipids, lipid metabolites, and inflammation markers.

DESIGN

This was a cross-sectional study.

SETTING

Recruitment was performed in two fertility clinics at one private and one academic center.

PARTICIPANTS

Eighty women requiring in vitro fertilization were recruited during one of their scheduled visit at the fertility clinic. All women aged between 18 and 40 years with a body mass index between 18 and 40 kg/m(2) were invited to participate.

INTERVENTION(S)

There were no interventions.

MAIN OUTCOME MEASURE(S)

At the time of oocyte aspiration, FF was collected and analyzed for total T, lipids [nonesterified fatty acids (NEFAs) plus triglycerides], NEFA metabolites (acylcarnitines; markers of ineffective NEFAs β-oxidation), and inflammatory marker composition. The hypothesis being tested was formulated before the data collection.

RESULTS

FF T levels were significantly correlated with FF levels of lipids (r = 0.381, P = .001; independently of IL-6), acylcarnitines (r ≥ 0.255, all P = .008; not independently of lipids), and IL-6 (r = 0.300, P = .009, independently of lipids). Additionally, FF lipid levels were significantly and strongly correlated with acylcarnitines (r ≥ 0.594; all P < .001).

CONCLUSIONS

These results suggest that ovarian androgen production is related to intraovarian exposure to lipids, independently of inflammation and mainly through ineffective NEFA β-oxidation (as shown by higher acylcarnitine levels). Inflammation is also associated with intraovarian androgenesis, independently of lipids.

Macrophage-derived upd3 cytokine causes impaired glucose homeostasis and reduced lifespan in Drosophila fed a lipid-rich diet

Long-term consumption of fatty foods is associated with obesity, macrophage activation and inflammation, metabolic imbalance, and a reduced lifespan. We took advantage of Drosophila genetics to investigate the role of macrophages and the pathway(s) that govern their response to dietary stress. Flies fed a lipid-rich diet presented with increased fat storage, systemic activation of JAK-STAT signaling, reduced insulin sensitivity, hyperglycemia, and a shorter lifespan. Drosophila macrophages produced the JAK-STAT-activating cytokine upd3, in a scavenger-receptor (crq) and JNK-dependent manner. Genetic depletion of macrophages or macrophage-specific silencing of upd3 decreased JAK-STAT activation and rescued insulin sensitivity and the lifespan of Drosophila, but did not decrease fat storage. NF-κB signaling made no contribution to the phenotype observed. These results identify an evolutionarily conserved “scavenger receptor-JNK-type 1 cytokine” cassette in macrophages, which controls glucose metabolism and reduces lifespan in Drosophila maintained on a lipid-rich diet via activation of the JAK-STAT pathway.

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Chronic lipid-rich diet results in JAK-STAT activation in Drosophila

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Chronic JAK-STAT activation reduces lifespan and insulin sensitivity

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Lipid-rich diet induces JNK pathway-dependent production of upd3 by macrophages

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Macrophage upd3 controls JAK-STAT activation, survival, and insulin sensitivity

Lkb1 deletion promotes ectopic lipid accumulation in muscle progenitor cells and mature muscles

Excessive intramyocellular triglycerides (muscle lipids) are associated with reduced contractile function, insulin resistance, and Type 2 diabetes, but what governs lipid accumulation in muscle is unclear. Here we report a role of Lkb1 in regulating lipid metabolism in muscle stem cells and their descendent mature muscles. We used Myod(Cre) and Lkb1(flox/flox) mice to specifically delete Lkb1 in myogenic cells including stem and differentiated cells, and examined the lipid accumulation and gene expression of myoblasts cultured from muscle stem cells (satellite cells). Genetic deletion of Lkb1 in myogenic progenitors led to elevated expression of lipogenic genes and ectopic lipid accumulation in proliferating myoblasts. Interestingly, the Lkb1-deficient myoblasts differentiated into adipocyte-like cells upon adipogenic induction. However, these adipocyte-like cells maintained myogenic gene expression with reduced ability to form myotubes efficiently. Activation of AMPK by AICAR prevented ectopic lipid formation in the Lkb1-null myoblasts. Notably, Lkb1-deficient muscles accumulated excessive lipids in vivo in response to high-fat diet feeding. These results demonstrate that Lkb1 acts through AMPK to limit lipid deposition in muscle stem cells and their derivative mature muscles, and point to the possibility of controlling muscle lipid content using AMPK activating drugs.

Effects of Piper nigrum extracts: Restorative perspectives of high-fat diet-induced changes on lipid profile, body composition, and hormones in Sprague-Dawley rats

CONTEXT

Piper nigrum Linn (Piperaceae) (PnL) is used in traditional medicine to treat gastric ailments, dyslipidemia, diabetes, and hypertension.

OBJECTIVE

The present study explores the possible protective effects of P. nigrum extracts on high-fat diet-induced obesity in rats.

MATERIALS AND METHODS

High-fat diet-induced obese rats were treated orally with 200 mg/kg bw of different extracts (hexane, ethylacetate, ethanol, and aqueous extracts) of PnL for 42 d. The effects of PnL extracts on body composition, insulin resistance, biochemical parameters, leptin, adiponectin, lipid profile, liver marker enzymes, and antioxidants were studied.

RESULTS AND DISCUSSION

The HFD control group rats showed a substantial raise in body weight (472.8 ± 9.3 g), fat% (20.8 ± 0.6%), and fat-free mass (165.9 ± 2.4 g) when compared with normal control rats whose body weight, fat%, and fat-free mass were 314.3 ± 4.4 g, 6.4 ± 1.4%, and 133.8 ± 2.2 g, respectively. Oral administration of ethyl acetate or aqueous extracts of PnL markedly reduced the body weight, fat%, and fat-free mass of HFD-fed rats. In contrast to the normal control group, a profound increase in plasma glucose, insulin resistance, lipid profile, leptin, thiobarbituric acid reactive substance (TBARS), and the activities of lipase and liver marker enzymes, and a decrease in adiponectin and antioxidant enzymes were noted in HFD control rats. Administration of PnL extracts to HFD-induced obese rats significantly (p < 0.05) restored the above profiles.

CONCLUSION

PnL extracts significantly reduced the body weight, fat%, and ameliorated HFD-induced hyperlipidemia and its constituents.

Rapid depot-specific activation of adipocyte precursor cells at the onset of obesity

Excessive accumulation of white adipose tissue (WAT) is the defining characteristic of obesity. WAT mass is composed primarily of mature adipocytes, which are generated through the proliferation and differentiation of adipocyte precursors (APs). Although the production of new adipocytes contributes to WAT growth in obesity, little is known about the cellular and molecular mechanisms underlying adipogenesis in vivo. Here, we show that high-fat diet feeding in mice rapidly and transiently induces proliferation of APs within WAT to produce new adipocytes. Importantly, the activation of adipogenesis is specific to the perigonadal visceral depot in male mice, consistent with the patterns of obesogenic WAT growth observed in humans. Furthermore, we find that in multiple models of obesity, the activation of APs is dependent on the phosphoinositide 3-kinase (PI3K)-AKT2 pathway; however, the development of WAT does not require AKT2. These data indicate that developmental and obesogenic adipogenesis are regulated through distinct molecular mechanisms.

Maternal use of flaxseed oil during pregnancy and lactation prevents morphological alterations in pancreas of female offspring from rat dams with experimental diabetes

Nutritional recommendations have promoted the increased need to consume n-3 polyunsaturated fatty acids. Flaxseed is the richest dietary source of n-3 fatty acids among plant sources and is widely used for its edible oil. This study aimed to investigate whether maternal use of flaxseed oil has effects on pancreas morphology in the female offspring of diabetic mothers. Female Wistar rats (n = 12) were induced into diabetes by a high-fat diet and low dose of streptozotocin. After confirmation of the diabetes, rats were mated, and once pregnancy was confirmed, they were allocated into three groups (n = 6): high-fat group (HG); flaxseed oil group (FOG); and control group (CG) (non-diabetic rats). At weaning, female offspring (n = 6/group) received standard chow diet. The animals were euthanized at 180 days. Pancreas was collected for histomorphometric and immunohistochemistry analysis. HG showed hypertrophy of pancreatic islets (P < 0.0001), whereas FOG offspring had islets with smaller diameters compared to HG (P < 0.0001). HG offspring showed higher percentage of larger (P = 0.0061) and lower percentage of smaller islets (P = 0.0036). HG showed lower islet insulin immunodensity at 180 days (P < 0.0001), whereas FOG was similar to CG (P < 0.0001). Flaxseed oil reduced the damage caused by maternal hyperglycaemia, promoting normal pancreas histomorphometry and β-cell mass in female offspring.

PEDF and PEDF-derived peptide 44mer stimulate cardiac triglyceride degradation via ATGL

BACKGROUND

Pigment epithelium-derived factor (PEDF) is a 50-kDa secreted glycoprotein that is highly expressed in cardiomyocytes. A variety of peptides derived from PEDF exerts diverse physiological activities including anti-angiogenesis, antivasopermeability, and neurotrophic activities. Recent studies demonstrated that segmental functional peptides of PEDF, 44mer peptide (Val78-Thr121), show similar neurotrophic and cytoprotective effect to that of the holoprotein. We found that PEDF can reduce infarct size and protect cardiac function after acute myocardial infarction (AMI). However, the effects of PEDF on cardiac triglyceride (TG) accumulation after AMI remain unknown. The present study was performed to demonstrate the influence of PEDF and its functional peptides 44mer on TG degradation in AMI.

METHODS

The left ascending coronary artery (LAD) was ligated to induce AMI. PEDF-small interfering RNA (siRNA)-lentivirus (PEDF-RNAi-LV) or PEDF-LV was delivered to the ischemic myocardium in order to knock down or overexpress PEDF, respectively. Oil Red O staining and a TG assay kit were used to analyze the TG content in cardiomyocytes and infarcted areas.

RESULTS

The TG content significantly decreased in the PEDF-overexpressing heart compared to the sham group (P < 0.05). Both rPEDF and 44mer administration stimulate the TG degradation in cultured cardiomyocytes (P < 0.05). Adipose triglyceride lipase (ATGL)-specific inhibitor, atglistatin, attenuated the PEDF or 44mer-induced TG lipolysis activation of cardiomyocytes at 10 μmol/L. The effects of PEDF and 44mer on myocardial TG degradation were also abolished when ATGL was downregulated.

CONCLUSIONS

We conclude that PEDF and 44mer promote TG degradation in cardiomyocytes after AMI via ATGL. The substitution of PEDF and 44mer may be a novel therapeutic strategy for cardiac TG accumulation after AMI.

Increasing fatty acid oxidation remodels the hypothalamic neurometabolome to mitigate stress and inflammation

Modification of hypothalamic fatty acid (FA) metabolism can improve energy homeostasis and prevent hyperphagia and excessive weight gain in diet-induced obesity (DIO) from a diet high in saturated fatty acids. We have shown previously that C75, a stimulator of carnitine palmitoyl transferase-1 (CPT-1) and fatty acid oxidation (FAOx), exerts at least some of its hypophagic effects via neuronal mechanisms in the hypothalamus. In the present work, we characterized the effects of C75 and another anorexigenic compound, the glycerol-3-phosphate acyltransferase (GPAT) inhibitor FSG67, on FA metabolism, metabolomics profiles, and metabolic stress responses in cultured hypothalamic neurons and hypothalamic neuronal cell lines during lipid excess with palmitate. Both compounds enhanced palmitate oxidation, increased ATP, and inactivated AMP-activated protein kinase (AMPK) in hypothalamic neurons in vitro. Lipidomics and untargeted metabolomics revealed that enhanced catabolism of FA decreased palmitate availability and prevented the production of fatty acylglycerols, ceramides, and cholesterol esters, lipids that are associated with lipotoxicity-provoked metabolic stress. This improved metabolic signature was accompanied by increased levels of reactive oxygen species (ROS), and yet favorable changes in oxidative stress, overt ER stress, and inflammation. We propose that enhancing FAOx in hypothalamic neurons exposed to excess lipids promotes metabolic remodeling that reduces local inflammatory and cell stress responses. This shift would restore mitochondrial function such that increased FAOx can produce hypothalamic neuronal ATP and lead to decreased food intake and body weight to improve systemic metabolism.

A model of metabolic syndrome and related diseases with intestinal endotoxemia in rats fed a high fat and high sucrose diet

AIM

We sought develop and characterize a diet-induced model of metabolic syndrome and its related diseases.

METHODS

The experimental animals (Spague-Dawley rats) were randomly divided into two groups, and each group was fed a different feed for 48 weeks as follows: 1) standard control diet (SC), and 2) a high sucrose and high fat diet (HSHF). The blood, small intestine, liver, pancreas, and adipose tissues were sampled for analysis and characterization.

RESULTS

Typical metabolic syndrome (MS), non-alcoholic fatty liver disease (NAFLD), and type II diabetes (T2DM) were common in the HSHF group after a 48 week feeding period. The rats fed HSHF exhibited signs of obesity, dyslipidemia, hyperglycaemia, glucose intolerance, and insulin resistance (IR). At the same time, these animals had significantly increased levels of circulating LPS, TNFα, and IL-6 and increased ALP in their intestinal tissue homogenates. These animals also showed a significant reduction in the expression of occluding protein. The HSHF rats showed fatty degeneration, inflammation, fibrosis, cirrhosis, and lipid accumulation when their liver pathologies were examined. The HSHF rats also displayed increased islet diameters from 12 to 24 weeks, while reduced islet diameters occurred from 36 to 48 weeks with inflammatory cell infiltration and islet fat deposition. The morphometry of adipocytes in HSHF rats showed hypertrophy and inflammatory cell infiltration. HSHF CD68 analysis showed macrophage infiltration and significant increases in fat and pancreas size. HSHF Tunel analysis showed significant increases in liver and pancreas cell apoptosis.

CONCLUSIONS

This work demonstrated the following: 1) a characteristic rat model of metabolic syndrome (MS) can be induced by a high sucrose and high fat diet, 2) this model can be used to research metabolic syndrome and its related diseases, such as NAFLD and T2DM, and 3) intestinal endotoxemia (IETM) may play an important role in the pathogenesis of MS and related diseases, such as NAFLD and T2DM.

Effects of berberine and cinnamic acid on palmitic acid-induced intracellular triglyceride accumulation in NIT-1 pancreatic β cells

OBJECTIVE

To investigate the effects of berberine (BBR) and cinnamic acid (CA), the main active components in Jiaotai Pill (, JTP), on palmitic acid (PA)-induced intracellular triglyceride (TG) accumulation in NIT-1 pancreatic β cells.

METHODS

Cells were incubated in culture medium containing PA (0.25 mmol/L) for 24 h. Then treatments with BBR (10 μmol/L), CA (100 μmol/L) and the combination of BBR and CA (BBR+CA) were performed respectively. Intracellular lipid accumulation was assessed by Oil Red O staining and TG content was measured by colorimetric assay. The expression of adenosine monophosphate-activated protein kinase (AMPK) protein and its downstream lipogenic and fatty acid oxidation genes, including fatty acid synthase (FAS), acetyl-coA carboxylase (ACC), phosphorylation acetyl-coA carboxylase (pACC), carnitine acyl transferase 1 (CPT-1) and sterol regulating element binding protein 1c (SREBP-1c) were determined by Western blot or real time polymerase chain reaction.

RESULTS

PA induced an obvious lipid accumulation and a significant increase in intracellular TG content in NIT-1 cells. PA also induced a remarkable decrease in AMPK protein expression and its downstream targets such as pACC and CPT-1. Meanwhile, AMPK downstream lipogenic genes including SREBP-1c mRNA, FAS and ACC protein expressions were increased. Treatments with BBR and BBR+CA, superior to CA, significantly reversed the above genes changes in NIT-1 pancreatic β cells. However, the synergistic effect of BBR and CA on intracellular TG content was not observed in the present study.

CONCLUSION

It can be concluded that in vitro, BBR and BBR+CA could inhibit PA-induced lipid accumulation by decreasing lipogenesis and increasing lipid oxidation in NIT-1 pancreatic β cells.

Effect of maternal use of flaxseed oil during pregnancy and lactation on glucose metabolism and pancreas histomorphometry of male offspring from diabetic rats

AIM

Investigate if the maternal use of flaxseed oil prevents pancreatic alterations in the offspring of diabetic mothers.

METHODS

Diabetes was induced in female wistar rats (n=12) by a high-fat diet and low-dose of streptozotocin. After the confirmation of the diabetes (glucose >300 mg/dL), rats were mated and once pregnancy was confirmed, they were allocated into three groups (n=6): high-fat group (HFG); flaxseed oil group (FOG); and control group (CG) (nondiabetic rats). At weaning, male offspring (n=12/group) received a standard chow diet. The animals were euthanized in two phases: at 100 and at 180 days, (n=6/group). The pancreas was collected for histomorphometric and immunohistochemistry analysis.

RESULTS

HFG showed hypertrophy of pancreatic islets at 100 and at 180 days (p<0.0001), while the FOG offspring had islets with smaller diameters compared to HFG at both phases of sacrifice (p<0.0001). HFG had a lower percentage of small islets when compared to CG and FOG, which had a higher percentage when compared to HFG (p=0.0053) at 100 days. At 180 days HFG showed higher percentage of larger islets (p=0.00137) and lower percentage of smaller islets (p=0.00112), when compared to FOG. HFG showed lower islet insulin immunodensity at 100 days (p<0.0001) and 180 days (p<0.0001), whereas FOG was similar to CG (p<0.0001) at 100 days and higher at 180 days (p<0.0001).

CONCLUSIONS

Flaxseed oil reduced the damage caused by maternal hyperglycemia, promoting normal pancreas histomorphometry and β cell mass.