Mitochondrial dysfunction and insulin resistance from the outside in: extracellular matrix, the cytoskeleton, and mitochondria

A Systematic Review of Proteomics in Obesity: Unpacking the Molecular Puzzle

PURPOSE OF REVIEW

The present study aims to review the existing literature to identify pathophysiological proteins in obesity by conducting a systematic review of proteomics studies. Proteomics may reveal the mechanisms of obesity development and clarify the links between obesity and related diseases, improving our comprehension of obesity and its clinical implications.

RECENT FINDINGS

Most of the molecular events implicated in obesity development remain incomplete. Proteomics stands as a powerful tool for elucidating the intricate interactions among proteins in the context of obesity. This methodology has the potential to identify proteins involved in pathological processes and to evaluate changes in protein abundance during obesity development, contributing to the identification of early disease predisposition, monitoring the effectiveness of interventions and improving disease management overall. Despite many non-targeted proteomic studies exploring obesity, a comprehensive and up-to-date systematic review of the molecular events implicated in obesity development is lacking. The lack of such a review presents a significant challenge for researchers trying to interpret the existing literature. This systematic review was conducted following the PRISMA guidelines and included sixteen human proteomic studies, each of which delineated proteins exhibiting significant alterations in obesity. A total of 41 proteins were reported to be altered in obesity by at least two or more studies. These proteins were involved in metabolic pathways, oxidative stress responses, inflammatory processes, protein folding, coagulation, as well as structure/cytoskeleton. Many of the identified proteomic biomarkers of obesity have also been reported to be dysregulated in obesity-related disease. Among them, seven proteins, which belong to metabolic pathways (aldehyde dehydrogenase and apolipoprotein A1), the chaperone family (albumin, heat shock protein beta 1, protein disulfide-isomerase A3) and oxidative stress and inflammation proteins (catalase and complement C3), could potentially serve as biomarkers for the progression of obesity and the development of comorbidities, contributing to personalized medicine in the field of obesity. Our systematic review in proteomics represents a substantial step forward in unravelling the complexities of protein alterations associated with obesity. It provides valuable insights into the pathophysiological mechanisms underlying obesity, thereby opening avenues for the discovery of potential biomarkers and the development of personalized medicine in obesity.

Link between insulin resistance and skeletal muscle extracellular matrix remodeling

Skeletal muscle is the main metabolic tissue responsible for glucose homeostasis in the body. It is surrounded by the extracellular matrix (ECM) consisting of three layers: epimysium, perimysium, and endomysium. ECM plays an important role in the muscle, as it provides integrity and scaffolding cells. The observed disturbances in this structure are related to the abnormal remodeling of the ECM (through an increase in the concentration of its components). ECM rearrangement may impair insulin action by increasing the physical barrier to insulin transport and reducing insulin transport into muscle cells as well as by directly inhibiting insulin action through integrin signaling. Thus, improper ECM remodeling may contribute to the development of insulin resistance (IR) and related comorbidities. In turn, IR-associated conditions may further aggravate disturbances of ECM in skeletal muscle. This review describes the major components of the ECM that are necessary for its proper function. Particular attention was also paid to receptors (integrins) involved in the signaling of metabolic pathways. Finally, changes in ECM components in the context of clinical and animal studies are discussed. This article will help the reader to systematize knowledge related to the ECM and to better understand the relationship between ECM remodeling and IR, and its role in the pathogenesis of T2DM. The information in this article presents the concept of the role of ECM and its remodeling in the pathogenesis of IR, which may contribute to developing new therapeutic solutions.

Linking Mitochondrial Function to Insulin Resistance: Focusing on Comparing the Old and the Young

Long-term intake of high-energy diet can lead to decreased insulin sensitivity and even insulin resistance, eventually leading to diabetes. Diabetes often occurs in middle-aged and elderly people. However, there is growing evidence that the incidence rate of young body is increasing over the years. This means that insulin resistance can be caused by excessive energy intake in both young and old people. In this study, high-fat diet (HFD) and normal diet were fed to rats of elderly experimental group (EE), elderly control group (EC), young experimental group (YE), and young control group (YC), respectively, for 8 weeks, by which insulin resistance model was obtained. Insulin sensitivity was measured, histopathology changes in liver and skeletal muscle tissues were observed, and mitochondrial fusion and division and cell senescence were detected in four groups of rats. The results showed that both young and elderly rats developed significant insulin resistance, fat deposition, decline of mitochondrial function and mitochondrial biosynthesis in liver and skeletal muscle, and cell aging after HFD feeding. In addition, the degree of mitochondrial dysfunction and aging in young rats was similar to that of aged rats fed a normal diet after HFD. This experiment provides a reference for an in-depth study of the regulatory mechanisms of cellular energy metabolism in this state.

Extreme Variations in Muscle Fiber Composition Enable Detection of Insulin Resistance and Excessive Insulin Secretion

CONTEXT

Muscle fiber composition is associated with peripheral insulin action.

OBJECTIVE

We investigated whether extreme differences in muscle fiber composition are associated with alterations in peripheral insulin action and secretion in young, healthy subjects who exhibit normal fasting glycemia and insulinemia.

METHODS

Relaxation time following a tetanic contraction was used to identify subjects with a high or low expression of type I muscle fibers: group 1 (n = 11), area occupied by type I muscle fibers = 61.0 ± 11.8%, and group 2 (n = 8), type I area = 36.0 ± 4.9% (P < 0.001). Biopsies were obtained from the vastus lateralis muscle and analyzed for mitochondrial respiration on permeabilized fibers, muscle fiber composition, and capillary density. An intravenous glucose tolerance test was performed and indices of glucose tolerance, insulin sensitivity, and secretion were determined.

RESULTS

Glucose tolerance was similar between groups, whereas whole-body insulin sensitivity was decreased by ~50% in group 2 vs group 1 (P = 0.019). First-phase insulin release (area under the insulin curve during 10 minutes after glucose infusion) was increased by almost 4-fold in group 2 vs group 1 (P = 0.01). Whole-body insulin sensitivity was correlated with percentage area occupied by type I fibers (r = 0.54; P = 0.018) and capillary density in muscle (r = 0.61; P = 0.005) but not with mitochondrial respiration. Insulin release was strongly related to percentage area occupied by type II fibers (r = 0.93; P < 0.001).

CONCLUSIONS

Assessment of muscle contractile function in young healthy subjects may prove useful in identifying individuals with insulin resistance and enhanced glucose-stimulated insulin secretion prior to onset of clinical manifestations.

Incretin-induced changes in the transcriptome of skeletal muscles of fa/fa Zucker rat (ZFR) with obesity, without diabetes

INTRODUCTION

Glucagon-like peptide-1 receptor agonists (GLP-1ra) are increasingly used in treating type 2 diabetes and obesity. Exendin-4 (Ex-4), a long acting GLP-1ra, was previously reported to decrease oxidative stress in hepatocytes, adipocytes and skeletal muscle cells in obese nondiabetic fa/fa Zucker rats (ZFR), thereby improving insulin resistance.

AIM

We aimed first to identify Ex-4-induced changes in the transcriptome of skeletal muscle cells in ZFR.

RESULTS

Ontology analysis of differentially expressed genes (DEGs) in ZFR versus lean animals (LR) showed that the extracellular matrix (ECM) is the first most affected cellular compartment, followed by myofibrils and endoplasmic reticulum (ER). Interestingly, among 15 genes regulated in ZFR versus LR, 14 of them were inversely regulated by Ex-4, as further confirmed by RT-qPCR. Picro-Sirius red histological staining showed that decreased ECM fiber area in ZFR is partially restored by Ex-4. Ontology analysis of the myofibril compartment revealed that decreased muscle contractile function in ZFR is partially restored by Ex-4, as confirmed by Phalloidin histological staining that showed a partial restoration by Ex-4 of altered contractile apparatus in ZFR. Ontology analysis of ER DEGs in ZFR versus LR showed that some of them are related to the AMP-activated protein kinase (AMPK) signaling pathway. Phosphorylated AMPK levels were strongly increased in Ex-4-treated ZFR.

CONCLUSION

Altogether, our results suggest that GLP-1ra strongly restructure ECM and reinforce contractile capabilities in ZFR, while optimizing the cellular metabolism through AMPK.

Potential evidence for epigenetic biomarkers of metabolic syndrome in human whole blood in Latinos

Metabolic syndrome (MetS) is highly prevalent worldwide. In the United States, estimates show that more than 30% of the adult population has MetS. MetS consists of multiple phenotypes, including obesity, dyslipidemia, and impaired glucose tolerance. Therefore, identifying the molecular mechanisms to explain this complex disease is critical for diagnosing and treating MetS. We previously showed 70 increased genes and 20 decreased genes in whole blood in MetS participants. The present study aimed to identify blood-based DNA methylation biomarkers in non-MetS versus MetS participants. The present study analyzed whole blood DNA samples from 184 adult participants of Latino descent from the Arizona Insulin Resistance (AIR) registry. We used the National Cholesterol Education Program Adult Treatment Panel III (NCEP: ATP III) criteria to identify non-MetS (n = 110) and MetS (n = 74) participants. We performed whole blood methylation analysis on select genes: ATP Synthase, H+ Transporting mitochondrial F1 Complex, Epsilon Subunit (ATP5E), Cytochrome C Oxidase Subunit VIc (COX6C), and Ribosomal Protein L9 (RPL9). The pyrosequencing analysis was a targeted approach focusing on the promoter region of each gene that specifically captured CpG methylation sites. In MetS participants, we showed decreased methylation in two CpG sites in COX6C and three CpG sites in RPL9, all p < 0.05 using the Mann-Whitney U test. There were no ATP5E CpG sites differently methylated in the MetS participants. Furthermore, while adjusting for age, gender, and smoking status, logistic regression analysis reaffirmed the associations between MetS and mean methylation within COX6C and RPL9 (both p < 0.05). In addition, Spearman's correlation revealed a significant inverse relationship between the previously published gene expression data and methylation data for RPL9 (p < 0.05). In summary, these results highlight potential blood DNA methylation biomarkers for the MetS phenotype. However, future validation studies are warranted to strengthen our findings.

A nexus of miR-1271, PAX4 and ALK/RYK influences the cytoskeletal architectures in Alzheimer's Disease and Type 2 Diabetes

Alzheimer's Disease (AD) and Type 2 Diabetes (T2D) share a common hallmark of insulin resistance. Reportedly, two non-canonical Receptor Tyrosine Kinases (RTKs), ALK and RYK, both targets of the same micro RNA miR-1271, exhibit significant and consistent functional down-regulation in post-mortem AD and T2D tissues. Incidentally, both have Grb2 as a common downstream adapter and NOX4 as a common ROS producing factor. Here we show that Grb2 and NOX4 play critical roles in reducing the severity of both the diseases. The study demonstrates that the abundance of Grb2 in degenerative conditions, in conjunction with NOX4, reverse cytoskeletal degradation by counterbalancing the network of small GTPases. PAX4, a transcription factor for both Grb2 and NOX4, emerges as the key link between the common pathways of AD and T2D. Down-regulation of both ALK and RYK through miR-1271, elevates the PAX4 level by reducing its suppressor ARX via Wnt/β-Catenin signaling. For the first time, this study brings together RTKs beyond Insulin Receptor (IR) family, transcription factor PAX4 and both AD and T2D pathologies on a common regulatory platform.

Inflammation Parameters Associated with Metabolic Disorders: Relationship Between Diet and Microbiota

The metabolic syndrome (MetS) includes numerous interrelated clinical, anthropometric, biochemical, and metabolic components and has become a public health problem due to its impact on morbimortality. Inflammation is a central mechanism underlying the etiology and clinical manifestations of MetS, contributing to its related pathological outcomes. Dietary patterns have been associated with the promotion of the diversity of microbiota in the digestive tract. Recently, research has focused on the importance of microbiota changes associated with MetS and inflammation. Other studies have been performed to understand the impact of prebiotics, probiotics, and synbiotics as allies on diet, inflammation, and MetS parameters. This review analyses the correlation between metabolic disorders, inflammation parameters, gut microbiota, and how diet has been involved as treatment of MetS and the modulation of inflammation and microbiota.

Weight loss after Roux-En-Y gastric bypass surgery reveals skeletal muscle DNA methylation changes

BACKGROUND

The mechanisms of weight loss and metabolic improvements following bariatric surgery in skeletal muscle are not well known; however, epigenetic modifications are likely to contribute. The aim of our study was to investigate skeletal muscle DNA methylation after weight loss induced by Roux-en-Y gastric bypass (RYGB) surgery. Muscle biopsies were obtained basally from seven insulin-resistant obese (BMI > 40 kg/m²) female subjects (45.1 ± 3.6 years) pre- and 3-month post-surgery with euglycemic hyperinsulinemic clamps to assess insulin sensitivity. Four lean (BMI < 25 kg/m²) females (38.5 ± 5.8 years) served as controls. We performed reduced representation bisulfite sequencing next generation methylation on DNA isolated from the vastus lateralis muscle biopsies.

RESULTS

Global methylation was significantly higher in the pre- (32.97 ± 0.02%) and post-surgery (33.31 ± 0.02%) compared to the lean (30.46 ± 0.02%), P < 0.05. MethylSig analysis identified 117 differentially methylated cytosines (DMCs) that were significantly altered in the post- versus pre-surgery (Benjamini-Hochberg q < 0.05). In addition, 2978 DMCs were significantly altered in the pre-surgery obese versus the lean controls (Benjamini-Hochberg q < 0.05). For the post-surgery obese versus the lean controls, 2885 DMCs were altered (Benjamini-Hochberg q < 0.05). Seven post-surgery obese DMCs were normalized to levels similar to those observed in lean controls. Of these, 5 were within intergenic regions (chr11.68,968,018, chr16.73,100,688, chr5.174,115,531, chr5.1,831,958 and chr9.98,547,011) and the remaining two DMCs chr17.45,330,989 and chr14.105,353,824 were within in the integrin beta 3 (ITGB3) promoter and KIAA0284 exon, respectively. ITGB3 methylation was significantly decreased in the post-surgery (0.5 ± 0.5%) and lean controls (0 ± 0%) versus pre-surgery (13.6 ± 2.7%, P < 0.05). This decreased methylation post-surgery was associated with an increase in ITGB3 gene expression (fold change + 1.52, P = 0.0087). In addition, we showed that ITGB3 promoter methylation in vitro significantly suppressed transcriptional activity (P < 0.05). Transcription factor binding analysis for ITGB3 chr17.45,330,989 identified three putative transcription factor binding motifs; PAX-5, p53 and AP-2alphaA.

CONCLUSIONS

These results demonstrate that weight loss after RYGB alters the epigenome through DNA methylation. In particular, this study highlights ITGB3 as a novel gene that may contribute to the metabolic improvements observed post-surgery. Future additional studies are warranted to address the exact mechanism of ITGB3 in skeletal muscle.

Propolis in Metabolic Syndrome and Its Associated Chronic Diseases: A Narrative Review

Propolis is a resinous product collected by bees from plants to protect and maintain the homeostasis of their hives. Propolis has been used therapeutically by humans for centuries. This review article attempts to analyze the potential use of propolis in metabolic syndrome (MetS) and its associated chronic diseases. MetS and its chronic diseases were shown to be involved in at least seven out of the top 10 causes of death in 2019. Patients with MetS are also at a heightened risk of severe morbidity and mortality in the present COVID-19 pandemic. Propolis with its antioxidant and anti-inflammatory properties is potentially useful in ameliorating the symptoms of MetS and its associated chronic diseases. The aim of this article is to provide a comprehensive review on propolis and its therapeutic benefit in MetS and its chronic diseases, with an emphasis on in vitro and in vivo studies, as well as human clinical trials. Moreover, the molecular and biochemical mechanisms of action of propolis are also discussed. Propolis inhibits the development and manifestation of MetS and its chronic diseases by inhibiting of the expression and interaction of advanced glycation end products (AGEs) and their receptors (RAGEs), inhibiting pro-inflammatory signaling cascades, and promoting the cellular antioxidant systems.

Genetic reduction of the extracellular matrix protein versican attenuates inflammatory cell infiltration and improves contractile function in dystrophic mdx diaphragm muscles

There is a persistent, aberrant accumulation of V0/V1 versican in skeletal muscles from patients with Duchenne muscular dystrophy and in diaphragm muscles from mdx mice. Versican is a provisional matrix protein implicated in fibrosis and inflammation in various disease states, yet its role in the pathogenesis of muscular dystrophy is not known. Here, female mdx and male hdf mice (haploinsufficient for the versican allele) were bred. In the resulting F1 mdx-hdf male pups, V0/V1 versican expression in diaphragm muscles was decreased by 50% compared to mdx littermates at 20-26 weeks of age. In mdx-hdf mice, spontaneous physical activity increased by 17% and there was a concomitant decrease in total energy expenditure and whole-body glucose oxidation. Versican reduction improved the ex vivo strength and endurance of diaphragm muscle strips. These changes in diaphragm contractile properties in mdx-hdf mice were associated with decreased monocyte and macrophage infiltration and a reduction in the proportion of fibres expressing the slow type I myosin heavy chain isoform. Given the high metabolic cost of inflammation in dystrophy, an attenuated inflammatory response may contribute to the effects of versican reduction on whole-body metabolism. Altogether, versican reduction ameliorates the dystrophic pathology of mdx-hdf mice as evidenced by improved diaphragm contractile function and increased physical activity.

Gypenosides improve diabetic cardiomyopathy by inhibiting ROS-mediated NLRP3 inflammasome activation

NLRP3 inflammasome activation plays an important role in diabetic cardiomyopathy (DCM), which may relate to excessive production of reactive oxygen species (ROS). Gypenosides (Gps), the major ingredients of Gynostemma pentaphylla (Thunb.) Makino, have exerted the properties of anti-hyperglycaemia and anti-inflammation, but whether Gps improve myocardial damage and the mechanism remains unclear. Here, we found that high glucose (HG) induced myocardial damage by activating the NLRP3 inflammasome and then promoting IL-1β and IL-18 secretion in H9C2 cells and NRVMs. Meanwhile, HG elevated the production of ROS, which was vital to NLRP3 inflammasome activation. Moreover, the ROS activated the NLRP3 inflammasome mainly by cytochrome c influx into the cytoplasm and binding to NLRP3. Inhibition of ROS and cytochrome c dramatically down-regulated NLRP3 inflammasome activation and improved the cardiomyocyte damage induced by HG, which was also detected in cells treated by Gps. Furthermore, Gps also reduced the levels of the C-reactive proteins (CRPs), IL-1β and IL-18, inhibited NLRP3 inflammasome activation and consequently improved myocardial damage in vivo. These findings provide a mechanism that ROS induced by HG activates the NLRP3 inflammasome by cytochrome c binding to NLRP3 and that Gps may be potential and effective drugs for DCM via the inhibition of ROS-mediated NLRP3 inflammasome activation.

The Vasculature in Prediabetes

The frequency of prediabetes is increasing as the prevalence of obesity rises worldwide. In prediabetes, hyperglycemia, insulin resistance, and inflammation and metabolic derangements associated with concomitant obesity cause endothelial vasodilator and fibrinolytic dysfunction, leading to increased risk of cardiovascular and renal disease. Importantly, the microvasculature affects insulin sensitivity by affecting the delivery of insulin and glucose to skeletal muscle; thus, endothelial dysfunction and extracellular matrix remodeling promote the progression from prediabetes to diabetes mellitus. Weight loss is the mainstay of treatment in prediabetes, but therapies that improved endothelial function and vasodilation may not only prevent cardiovascular disease but also slow progression to diabetes mellitus.

3,5-Diiodo-L-Thyronine Affects Structural and Metabolic Features of Skeletal Muscle Mitochondria in High-Fat-Diet Fed Rats Producing a Co-adaptation to the Glycolytic Fiber Phenotype

Hyperlipidemic state-associated perturbations in the network of factors controlling mitochondrial functions, i. e., morphogenesis machinery and metabolic sensor proteins, produce metabolic inflexibility, insulin resistance and reduced oxidative capacity in skeletal muscle. Moreover, intramyocellular lipid (IMCL) accumulation leads to tissue damage and inflammation. The administration of the naturally occurring metabolite 3,5-diiodo-L-thyronine (T2) with thyromimetic actions to high fat diet (HFD)-fed rats exerts a systemic hypolipidemic effect, which produces a lack of IMCL accumulation, a shift toward glycolytic fibers and amelioration of insulin sensitivity in gastrocnemius muscle. In this study, an integrated approach combining large-scale expression profile and functional analyses was used to characterize the response of skeletal muscle mitochondria to T2 during a HFD regimen. Long-term T2 administration to HDF rats induced a glycolytic phenotype of gastrocnemius muscle as well as an adaptation of mitochondria to the fiber type, with a decreased representation of enzymes involved in mitochondrial oxidative metabolism. At the same time, T2 stimulated the activity of individual respiratory complex I, IV, and V. Moreover, T2 prevented the HFD-associated increase in the expression of peroxisome proliferative activated receptor γ coactivator-1α and dynamin-1-like protein as well as mitochondrial morphological aberrations, favoring the appearance of tubular and tethered organelles in the intermyofibrillar regions. Remarkably, T2 reverted the HDF-associated expression pattern of proinflammatory factors, such as p65 subunit of NF-kB, and increased the fiber-specific immunoreactivity of adipose differentiation–related protein in lipid droplets. All together, these results further support a role of T2 in counteracting in vivo some of the HFD-induced impairment in structural/metabolic features of skeletal muscle by impacting the mitochondrial phenotype.

Skeletal Muscle as an Endocrine Organ: The Role of Myokines in Exercise Adaptations

Exercise stimulates the release of proteins with autocrine, paracrine, or endocrine functions produced in skeletal muscle, termed myokines. Based on the current state of knowledge, the major physiological function of myokines is to protect the functionality and to enhance the exercise capacity of skeletal muscle. Myokines control adaptive processes in skeletal muscle by acting as paracrine regulators of fuel oxidation, hypertrophy, angiogenesis, inflammatory processes, and regulation of the extracellular matrix. Endocrine functions attributed to myokines are involved in body weight regulation, low-grade inflammation, insulin sensitivity, suppression of tumor growth, and improvement of cognitive function. Muscle-derived regulatory RNAs and metabolites, as well as the design of modified myokines, are promising novel directions for treatment of chronic diseases.

Alterations of sorbin and SH3 domain containing 3 (SORBS3) in human skeletal muscle following Roux-en-Y gastric bypass surgery

Background

Obesity is a disease that is caused by genetic and environmental factors. However, epigenetic mechanisms of obesity are less well known. DNA methylation provides a mechanism whereby environmental factors can influence gene transcription. The aim of our study was to investigate skeletal muscle DNA methylation of sorbin and SH3 domain containing 3 (SORBS3) with weight loss induced by Roux-en-Y gastric bypass (RYGB).

Results

Previously, we had shown increased methylation (5.0 to 24.4%) and decreased gene expression (fold change − 1.9) of SORBS3 with obesity (BMI > 30 kg/m²) compared to lean controls. In the present study, basal muscle biopsies were obtained from seven morbidly obese (BMI > 40 kg/m²) female subjects pre- and 3 months post-RYGB surgery, in combination with euglycemic-hyperinsulinemic clamps to assess insulin sensitivity. We identified 30 significantly altered promoter and untranslated region methylation sites in SORBS3 using reduced representation bisulfite sequencing (RRBS). Twenty-nine of these sites were decreased (− 5.6 to − 24.2%) post-RYGB compared to pre-RYGB. We confirmed the methylation in 2 (Chr.8:22,423,690 and Chr.8:22,423,702) of the 29 decreased SORBS3 sites using pyrosequencing. This decreased methylation was associated with an increase in SORBS3 gene expression (fold change + 1.7) post-surgery. In addition, we demonstrated that SORBS3 promoter methylation in vitro significantly alters reporter gene expression (P < 0.0001). Two of the SORBS3 methylation sites (Chr.8:22,423,111 and Chr.8:22,423,205) were strongly correlated with fasting plasma glucose levels (r = 0.9, P = 0.00009 and r = 0.8, P = 0.0010). Changes in SORBS3 gene expression post-surgery were correlated with obesity measures and fasting insulin levels (r = 0.5 to 0.8; P < 0.05).

Conclusions

These results demonstrate that SORBS3 methylation and gene expression are altered in obesity and restored to normal levels through weight loss induced by RYGB surgery.

Shared genetic regulatory networks for cardiovascular disease and type 2 diabetes in multiple populations of diverse ethnicities in the United States

Cardiovascular diseases (CVD) and type 2 diabetes (T2D) are closely interrelated complex diseases likely sharing overlapping pathogenesis driven by aberrant activities in gene networks. However, the molecular circuitries underlying the pathogenic commonalities remain poorly understood. We sought to identify the shared gene networks and their key intervening drivers for both CVD and T2D by conducting a comprehensive integrative analysis driven by five multi-ethnic genome-wide association studies (GWAS) for CVD and T2D, expression quantitative trait loci (eQTLs), ENCODE, and tissue-specific gene network models (both co-expression and graphical models) from CVD and T2D relevant tissues. We identified pathways regulating the metabolism of lipids, glucose, and branched-chain amino acids, along with those governing oxidation, extracellular matrix, immune response, and neuronal system as shared pathogenic processes for both diseases. Further, we uncovered 15 key drivers including HMGCR, CAV1, IGF1 and PCOLCE, whose network neighbors collectively account for approximately 35% of known GWAS hits for CVD and 22% for T2D. Finally, we cross-validated the regulatory role of the top key drivers using in vitro siRNA knockdown, in vivo gene knockout, and two Hybrid Mouse Diversity Panels each comprised of >100 strains. Findings from this in-depth assessment of genetic and functional data from multiple human cohorts provide strong support that common sets of tissue-specific molecular networks drive the pathogenesis of both CVD and T2D across ethnicities and help prioritize new therapeutic avenues for both CVD and T2D.

The emerging role of skeletal muscle extracellular matrix remodelling in obesity and exercise

Skeletal muscle extracellular matrix remodelling has been proposed as a new feature associated with obesity and metabolic dysfunction. Exercise training improves muscle function in obesity, which may be mediated by regulatory effects on the muscle extracellular matrix. This review examined available literature on skeletal muscle extracellular matrix remodelling during obesity and the effects of exercise. A non-systematic literature review was performed on PubMed of publications from 1970 to 2015. A total of 37 studies from humans and animals were retained. Studies reported overall increases in gene and protein expression of different types of collagen, growth factors and enzymatic regulators of the skeletal muscle extracellular matrix in obesity. Only two studies investigated the effects of exercise on skeletal muscle extracellular matrix during obesity, with both suggesting a regulatory effect of exercise. The effects of exercise on muscle extracellular matrix seem to be influenced by the duration and type of exercise training with variable effects from a single session compared with a longer duration of exercise. More studies are needed to elucidate the mechanisms behind skeletal muscle extracellular matrix remodelling during obesity and the effects of exercise.

Melatonin protects against lipid-induced mitochondrial dysfunction in hepatocytes and inhibits stellate cell activation during hepatic fibrosis in mice

Lipid generates reactive oxygen species (ROS) in consequence to mitochondrial fission followed by inflammation in propagating hepatic fibrosis. The interaction of SIRT1/Mitofusin2 is critical for maintaining mitochondrial integrity and functioning, which is disrupted upon excess lipid infiltration during the progression of steatohepatitis. The complex interplay between hepatic stellate cells and steatotic hepatocytes is critically regulated by extracellular factors including increased circulating free fatty acids during fibrogenesis. Melatonin, a potent antioxidant, protects against lipid-mediated mitochondrial ROS generation. Lipotoxicity induces disruption of SIRT1 and Mitofusin2 interaction leading to mitochondrial morphological disintegration in hepatocytes. Further, fragmented mitochondria leads to mitochondrial permeability transition pore opening, cell cycle arrest and apoptosis and melatonin protects against all these lipotoxicity-mediated dysfunctions. These impaired mitochondrial dynamics also enhances the cellular glycolytic flux and reduces mitochondrial oxygen consumption rate that potentiates ROS production. High glycolytic flux generates metabolically unfavorable milieu in hepatocytes leading to inflammation, which is abrogated by melatonin. The melatonin-mediated protection against mitochondrial dysfunction was also observed in high-fat diet (HFD)-fed mice through restoration of enzymatic activities associated with respiratory chain and TCA cycle. Subsequently, melatonin reduces hepatic fat deposition and inflammation in HFD-fed mice. Thus, melatonin disrupts the interaction between steatotic hepatocyte and stellate cells, leading to the activation of the latter to abrogate collagen deposition. Altogether, the results of the current study document that the pharmacological intervention with low dose of melatonin could abrogate lipotoxicity-mediated hepatic stellate cell activation and prevent the fibrosis progression.

The association among skeletal muscle phosphocreatine recovery, adiposity, and insulin resistance in children

BACKGROUND

Obesity is associated with cardiometabolic disturbances, which may have significant implications for musculoskeletal health and exercise tolerance.

OBJECTIVE

We sought to determine the association between muscle structure, function, and metabolism in adolescents across the weight spectrum.

METHODS

This cross-sectional case-control study included overweight and obese participants (n = 24) 8-18 years of age with a body mass index (BMI) ≥ 85th percentile for age and gender, and non-obese participants (n = 24) with a BMI < 85^th percentile. Body composition, physical activity, peak aerobic capacity, cardiometabolic blood markers and insulin resistance (measured by the homeostatic model assessment of insulin resistance, HOMA-IR), skeletal muscle mitochondrial oxidative capacity (via ³¹ Phosphorous-Magnetic Resonance Spectroscopy, ³¹ P-MRS, to assess phosphocreatine (PCr) recovery after exercise), and extramyocellular and intramyocellular lipid (IMCL) levels (via ¹ Hydrogen-MRS) were assessed. Stepwise regression was performed to examine the factors associated with oxidative capacity.

RESULTS

bese and overweight patients had similar age, height, and physical activity to non-obese controls, but obese and overweight participants exhibited higher insulin resistance. Obese and overweight participants had longer PCr recovery than non-obese controls following 5x30s of moderate-intensity exercise (51.2 ± 20.1 s vs. 23.9 ± 7.5 s, p = 0.004). In univariate correlation analysis, impaired PCr recovery was associated with a higher BMI z-score (r_s  = 0.51, p < 0.001), circulating triglycerides (r_s  = 0.41, p = 0.005), and HOMA-IR (r_s  = 0.46, p = 0.001). In stepwise multivariate regression analysis, impaired PCr recovery was associated with a higher BMI z-score (β = 0.47, p = 0.002), but not insulin resistance (β = 0.07, p = 0.07) or circulating triglycerides (β = 0.16 p = 0.33).

CONCLUSION

A slower phosphocreatine recovery following aerobic exercise is strongly associated with increasing adiposity. A slower metabolic recovery following aerobic exercise stress suggests that endurance exercise training in obese adolescents may be an optimal strategy to target exercise intolerance in this cohort.

Potential epigenetic biomarkers of obesity-related insulin resistance in human whole-blood

Obesity can increase the risk of complex metabolic diseases, including insulin resistance. Moreover, obesity can be caused by environmental and genetic factors. However, the epigenetic mechanisms of obesity are not well defined. Therefore, the identification of novel epigenetic biomarkers of obesity allows for a more complete understanding of the disease and its underlying insulin resistance. The aim of our study was to identify DNA methylation changes in whole-blood that were strongly associated with obesity and insulin resistance. Whole-blood was obtained from lean (n = 10; BMI = 23.6 ± 0.7 kg/m²) and obese (n = 10; BMI = 34.4 ± 1.3 kg/m²) participants in combination with euglycemic hyperinsulinemic clamps to assess insulin sensitivity. We performed reduced representation bisulfite sequencing on genomic DNA isolated from the blood. We identified 49 differentially methylated cytosines (DMCs; q < 0.05) that were altered in obese compared with lean participants. We identified 2 sites (Chr.21:46,957,981 and Chr.21:46,957,915) in the 5' untranslated region of solute carrier family 19 member 1 (SLC19A1) with decreased methylation in obese participants (lean 0.73 ± 0.11 vs. obese 0.09 ± 0.05; lean 0.68 ± 0.10 vs. obese 0.09 ± 0.05, respectively). These 2 DMCs identified by obesity were also significantly predicted by insulin sensitivity (r = 0.68, P = 0.003; r = 0.66; P = 0.004). In addition, we performed a differentially methylated region (DMR) analysis and demonstrated a decrease in methylation of Chr.21:46,957,915-46,958,001 in SLC19A1 of -34.9% (70.4% lean vs. 35.5% obese). The decrease in whole-blood SLC19A1 methylation in our obese participants was similar to the change observed in skeletal muscle (Chr.21:46,957,981, lean 0.70 ± 0.09 vs. obese 0.31 ± 0.11 and Chr.21:46,957,915, lean 0.72 ± 0.11 vs. obese 0.31 ± 0.13). Pyrosequencing analysis further demonstrated a decrease in methylation at Chr.21:46,957,915 in both whole-blood (lean 0.71 ± 0.10 vs. obese 0.18 ± 0.06) and skeletal muscle (lean 0.71 ± 0.10 vs. obese 0.30 ± 0.11). Our findings demonstrate a new potential epigenetic biomarker, SLC19A1, for obesity and its underlying insulin resistance.

Identification of Novel Changes in Human Skeletal Muscle Proteome After Roux-en-Y Gastric Bypass Surgery

The mechanisms of metabolic improvements after Roux-en-Y gastric bypass (RYGB) surgery are not entirely clear. Therefore, the aim of our study was to investigate the role of obesity and RYGB on the human skeletal muscle proteome. Basal muscle biopsies were obtained from seven obese (BMI >40 kg/m(2)) female subjects (45.1 ± 3.6 years) pre- and 3 months post-RYGB, and euglycemic-hyperinsulinemic clamps were used to assess insulin sensitivity. Four age-matched (48.5 ± 4.7 years) lean (BMI <25 kg/m(2)) females served as control subjects. We performed quantitative mass spectrometry and microarray analyses on protein and RNA isolated from the muscle biopsies. Significant improvements in fasting plasma glucose (104.2 ± 7.8 vs. 86.7 ± 3.1 mg/dL) and BMI (42.1 ± 2.2 vs. 35.3 ± 1.8 kg/m(2)) were demonstrated in the pre- versus post-RYGB, both P < 0.05. Proteomic analysis identified 2,877 quantifiable proteins. Of these, 395 proteins were significantly altered in obesity before surgery, and 280 proteins differed significantly post-RYGB. Post-RYGB, 49 proteins were returned to normal levels after surgery. KEGG pathway analysis revealed a decreased abundance in ribosomal and oxidative phosphorylation proteins in obesity, and a normalization of ribosomal proteins post-RYGB. The transcriptomic data confirmed the normalization of the ribosomal proteins. Our results provide evidence that obesity and RYGB have a dynamic effect on the skeletal muscle proteome.

Changes in Pre- and Post-Exercise Gene Expression among Patients with Chronic Kidney Disease and Kidney Transplant Recipients

Introduction

Decreased insulin sensitivity blunts the normal increase in gene expression from skeletal muscle after exercise. In addition, chronic inflammation decreases insulin sensitivity. Chronic kidney disease (CKD) is an inflammatory state. How CKD and, subsequently, kidney transplantation affects skeletal muscle gene expression after exercise are unknown.

Methods

Study cohort: non-diabetic male/female 4/1, age 52±2 years, with end-stage CKD who underwent successful kidney transplantation. The following were measured both pre-transplant and post-transplant and compared to normals: Inflammatory markers, euglycemic insulin clamp studies determine insulin sensitivity, and skeletal muscle biopsies performed before and within 30 minutes after an acute exercise protocol. Microarray analyses were performed on the skeletal muscle using the 4x44K Whole Human Genome Microarrays. Since nuclear factor of activated T cells (NFAT) plays an important role in T cell activation and calcineurin inhibitors are mainstay immunosuppression, calcineurin/NFAT pathway gene expression was compared at rest and after exercise. Log transformation was performed to prevent skewing of data and regression analyses comparing measures pre- and post-transplant performed.

Result

Markers of inflammation significantly improved post-transplantation. Insulin infusion raised glucose disposal slightly lower post-transplant compared to pre-transplant, but not significantly, thus concluding differences in insulin sensitivity were similar. The overall pattern of gene expression in response to exercise was reduced both pre-and post-transplant compared to healthy volunteers. Although significant changes were observed among NFAT/Calcineurin gene at rest and after exercise in normal cohort, there were no significant differences comparing NFAT/calcineurin pathway gene expression pre- and post-transplant.

Conclusions

Despite an improvement in serum inflammatory markers, no significant differences in glucose disposal were observed post-transplant. The reduced skeletal muscle gene expression, including NFAT/calcineurin gene expression, in response to a single bout of exercise was not improved post-transplant. This study suggests that the improvements in inflammatory mediators post-transplant are unrelated to changes of NFAT/calcineurin gene expression.

Next-generation sequencing methylation profiling of subjects with obesity identifies novel gene changes

Background

Obesity is a metabolic disease caused by environmental and genetic factors. However, the epigenetic mechanisms of obesity are incompletely understood. The aim of our study was to investigate the role of skeletal muscle DNA methylation in combination with transcriptomic changes in obesity.

Results

Muscle biopsies were obtained basally from lean (n = 12; BMI = 23.4 ± 0.7 kg/m²) and obese (n = 10; BMI = 32.9 ± 0.7 kg/m²) participants in combination with euglycemic-hyperinsulinemic clamps to assess insulin sensitivity. We performed reduced representation bisulfite sequencing (RRBS) next-generation methylation and microarray analyses on DNA and RNA isolated from vastus lateralis muscle biopsies. There were 13,130 differentially methylated cytosines (DMC; uncorrected P < 0.05) that were altered in the promoter and untranslated (5' and 3'UTR) regions in the obese versus lean analysis. Microarray analysis revealed 99 probes that were significantly (corrected P < 0.05) altered. Of these, 12 genes (encompassing 22 methylation sites) demonstrated a negative relationship between gene expression and DNA methylation. Specifically, sorbin and SH3 domain containing 3 (SORBS3) which codes for the adapter protein vinexin was significantly decreased in gene expression (fold change −1.9) and had nine DMCs that were significantly increased in methylation in obesity (methylation differences ranged from 5.0 to 24.4 %). Moreover, differentially methylated region (DMR) analysis identified a region in the 5'UTR (Chr.8:22,423,530–22,423,569) of SORBS3 that was increased in methylation by 11.2 % in the obese group. The negative relationship observed between DNA methylation and gene expression for SORBS3 was validated by a site-specific sequencing approach, pyrosequencing, and qRT-PCR. Additionally, we performed transcription factor binding analysis and identified a number of transcription factors whose binding to the differentially methylated sites or region may contribute to obesity.

Conclusions

These results demonstrate that obesity alters the epigenome through DNA methylation and highlights novel transcriptomic changes in SORBS3 in skeletal muscle.

Electronic supplementary material

The online version of this article (doi:10.1186/s13148-016-0246-x) contains supplementary material, which is available to authorized users.

A nontargeted study of muscle proteome in severely obese women with androgen excess compared with severely obese men and nonhyperandrogenic women

OBJECTIVE

Androgen excess in women is frequently associated with muscle insulin resistance, especially in obese women with polycystic ovary syndrome. However, whether this is a primary event or the result of indirect mechanisms is currently debated.

DESIGN

This is an observational study.

METHODS

We obtained skeletal muscle biopsies during bariatric surgery from severely obese men (n=6) and women with (n=5) or without (n=5) androgen excess. We used two-dimensional differential gel electrophoresis and matrix-assisted laser desorption/ionization-time-of-flight/time-of-flight mass spectrometry to identify muscle proteins showing differences in abundance between the groups of obese subjects.

RESULTS

Women with hyperandrogenism presented the lowest abundances of glycogen phosphorylase, pyruvate kinase, β-enolase, glycerol-3-phosphate dehydrogenase, creatine kinase M-type, and desmin, whereas the abundances of these molecules were similar in control women and men.

CONCLUSION

According to our nontargeted proteomic approach, women with hyperandrogenism show a specific alteration of the skeletal muscle proteome that could contribute to their insulin resistance. Because men do not show similar results, this alteration does not appear to be the direct effect on muscle of androgen excess, but rather the consequence of indirect mechanisms that merit further studies.

Differential Mitochondrial Adaptation in Primary Vascular Smooth Muscle Cells from a Diabetic Rat Model

Diabetes affects more than 330 million people worldwide and causes elevated cardiovascular disease risk. Mitochondria are critical for vascular function, generate cellular reactive oxygen species (ROS), and are perturbed by diabetes, representing a novel target for therapeutics. We hypothesized that adaptive mitochondrial plasticity in response to nutrient stress would be impaired in diabetes cellular physiology via a nitric oxide synthase- (NOS-) mediated decrease in mitochondrial function. Primary smooth muscle cells (SMCs) from aorta of the nonobese, insulin resistant rat diabetes model Goto-Kakizaki (GK) and the Wistar control rat were exposed to high glucose (25 mM). At baseline, significantly greater nitric oxide evolution, ROS production, and respiratory control ratio (RCR) were observed in GK SMCs. Upon exposure to high glucose, expression of phosphorylated eNOS, uncoupled respiration, and expression of mitochondrial complexes I, II, III, and V were significantly decreased in GK SMCs (p < 0.05). Mitochondrial superoxide increased with high glucose in Wistar SMCs (p < 0.05) with no change in the GK beyond elevated baseline concentrations. Baseline comparisons show persistent metabolic perturbations in a diabetes phenotype. Overall, nutrient stress in GK SMCs caused a persistent decline in eNOS and mitochondrial function and disrupted mitochondrial plasticity, illustrating eNOS and mitochondria as potential therapeutic targets.

Mitochondrial DNA in placenta: associations with fetal growth and superoxide dismutase activity

BACKGROUND

Prenatal growth restraint is associated with increased oxidative stress--as judged by mitochondrial dysfunction--in pregnancies complicated by preeclampsia or diabetes, but it is uncertain whether this is also the case in uncomplicated pregnancies. We assessed the link between fetal growth restraint and placental mitochondrial dysfunction, as reflected by changes in mitochondrial DNA (mtDNA) content and superoxide dismutase (SOD) activity.

METHODS

After uncomplicated pregnancies, placentas (n = 48) were collected at term delivery of singleton infants who were appropriate for gestational age (AGA) or small for gestational age (SGA) (n = 24 in each subgroup). Placental mtDNA content was assessed by real-time PCR, placental SOD activity by colorimetry, and citrate synthase activity--to determine mitochondrial mass--by the spectrophotometric method.

RESULTS

Placentas of SGA infants had a lower mtDNA content (p = 0.015) and a higher SOD activity (p = 0.001) than those of AGA controls. These differences were maintained after normalization of the mtDNA content by citrate synthase activity. In placentas of SGA infants, there was a negative association between mtDNA content and SOD activity (r = -0.58, p = 0.008).

CONCLUSIONS

Fetal growth restraint is accompanied by adaptive changes in the mitochondrial function of the placenta, also in uncomplicated pregnancies.

Mitochondrial dysfunction as a central event for mechanisms underlying insulin resistance: the roles of long chain fatty acids

Insulin resistance is characterized by hyperglycaemia, dyslipidaemia and oxidative stress prior to the development of type 2 diabetes mellitus. To date, a number of mechanisms have been proposed to link these syndromes together, but it remains unclear what the unifying condition that triggered these events in the progression of this metabolic disease. There have been a steady accumulation of data in numerous experimental studies showing the strong correlations between mitochondrial dysfunction, oxidative stress and insulin resistance. In addition, a growing number of studies suggest that the raised plasma free fatty acid level induced insulin resistance with the significant alteration of oxidative metabolism in various target tissues such as skeletal muscle, liver and adipose tissue. In this review, we herein propose the idea of long chain fatty acid-induced mitochondrial dysfunctions as one of the key events in the pathophysiological development of insulin resistance and type 2 diabetes. The accumulation of reactive oxygen species, lipotoxicity, inflammation-induced endoplasmic reticulum stress and alterations of mitochondrial gene subset expressions are the most detrimental that lead to the developments of aberrant intracellular insulin signalling activity in a number of peripheral tissues, thereby leading to insulin resistance and type 2 diabetes.

Gene and MicroRNA Expression Responses to Exercise; Relationship with Insulin Sensitivity

Background

Healthy individuals on the lower end of the insulin sensitivity spectrum also have a reduced gene expression response to exercise for specific genes. The goal of this study was to determine the relationship between insulin sensitivity and exercise-induced gene expression in an unbiased, global manner.

Methods and Findings

Euglycemic clamps were used to measure insulin sensitivity and muscle biopsies were done at rest and 30 minutes after a single acute exercise bout in 14 healthy participants. Changes in mRNA expression were assessed using microarrays, and miRNA analysis was performed in a subset of 6 of the participants using sequencing techniques. Following exercise, 215 mRNAs were changed at the probe level (Bonferroni-corrected P<0.00000115). Pathway and Gene Ontology analysis showed enrichment in MAP kinase signaling, transcriptional regulation and DNA binding. Changes in several transcription factor mRNAs were correlated with insulin sensitivity, including MYC, r=0.71; SNF1LK, r=0.69; and ATF3, r= 0.61 (5 corrected for false discovery rate). Enrichment in the 5’-UTRs of exercise-responsive genes suggested regulation by common transcription factors, especially EGR1. miRNA species of interest that changed after exercise included miR-378, which is located in an intron of the PPARGC1B gene.

Conclusions

These results indicate that transcription factor gene expression responses to exercise depend highly on insulin sensitivity in healthy people. The overall pattern suggests a coordinated cycle by which exercise and insulin sensitivity regulate gene expression in muscle.

Effects of vildagliptin versus sitagliptin, on cardiac function, heart rate variability and mitochondrial function in obese insulin-resistant rats

BACKGROUND AND PURPOSE

Long-term high-fat diet (HFD) consumption has been shown to cause insulin resistance, which is characterized by hyperinsulinaemia with metabolic inflexibility. Insulin resistance is associated with cardiac sympathovagal imbalance, cardiac dysfunction and cardiac mitochondrial dysfunction. Dipeptidyl peptidase-4 (DPP-4) inhibitors, vildagliptin and sitagliptin, are oral anti-diabetic drugs often prescribed in patients with cardiovascular disease. Therefore, in this study, we sought to determine the effects of vildagliptin and sitagliptin in a murine model of insulin resistance.

EXPERIMENTAL APPROACH

Male Wistar rats weighing 180-200 g, were fed either a normal diet (20% energy from fat) or a HFD (59% energy from fat) for 12 weeks. These rats were then divided into three subgroups to receive vildagliptin (3 mg·kg(-1)·day(-1)), sitagliptin (30 mg·kg(-1)·day(-1)) or vehicle for another 21 days. Metabolic parameters, oxidative stress, heart rate variability (HRV), cardiac function and cardiac mitochondrial function were determined.

KEY RESULTS

Rats that received HFD developed insulin resistance characterized by increased body weight, plasma insulin, total cholesterol and oxidative stress levels along with a decreased high-density lipoprotein (HDL) level. Moreover, cardiac dysfunction, depressed HRV, cardiac mitochondrial dysfunction and cardiac mitochondrial morphology changes were observed in HFD rats. Both vildagliptin and sitagliptin decreased plasma insulin, total cholesterol and oxidative stress as well as increased HDL level. Furthermore, vildagliptin and sitagliptin attenuated cardiac dysfunction, prevented cardiac mitochondrial dysfunction and completely restored HRV.

CONCLUSIONS AND IMPLICATIONS

Both vildagliptin and sitagliptin share similar efficacy in cardioprotection in obese insulin-resistant rats.

Failure of hyperglycemia and hyperinsulinemia to compensate for impaired metabolic response to an oral glucose load

OBJECTIVE

To evaluate whether the augmented insulin and glucose response to a glucose challenge is sufficient to compensate for defects in glucose utilization in obesity and type 2 diabetes, using a breath test measurement of integrated glucose metabolism.

METHODS

Non-obese, obese normoglycemic and obese type 2 diabetic subjects were studied on 2 consecutive days. A 75g oral glucose load spiked with ¹³C-glucose was administered, measuring exhaled breath ¹³CO₂ as an integrated measure of glucose metabolism and oxidation. A hyperinsulinemic euglycemic clamp was performed, measuring whole body glucose disposal rate. Body composition was measured by DEXA. Multivariable analyses were performed to evaluate the determinants of the breath ¹³CO₂.

RESULTS

Breath ¹³CO₂ was reduced in obese and type 2 diabetic subjects despite hyperglycemia and hyperinsulinemia. The primary determinants of breath response were lean mass, fat mass, fasting FFA concentrations, and OGTT glucose excursion. Multiple approaches to analysis showed that hyperglycemia and hyperinsulinemia were not sufficient to compensate for the defect in glucose metabolism in obesity and diabetes.

CONCLUSIONS

Augmented insulin and glucose responses during an OGTT are not sufficient to overcome the underlying defects in glucose metabolism in obesity and diabetes.

The impact of host diet on Wolbachia titer in Drosophila

While a number of studies have identified host factors that influence endosymbiont titer, little is known concerning environmental influences on titer. Here we examined nutrient impact on maternally transmitted Wolbachia endosymbionts in Drosophila. We demonstrate that Drosophila reared on sucrose- and yeast-enriched diets exhibit increased and reduced Wolbachia titers in oogenesis, respectively. The yeast-induced Wolbachia depletion is mediated in large part by the somatic TOR and insulin signaling pathways. Disrupting TORC1 with the small molecule rapamycin dramatically increases oocyte Wolbachia titer, whereas hyper-activating somatic TORC1 suppresses oocyte titer. Furthermore, genetic ablation of insulin-producing cells located in the Drosophila brain abolished the yeast impact on oocyte titer. Exposure to yeast-enriched diets altered Wolbachia nucleoid morphology in oogenesis. Furthermore, dietary yeast increased somatic Wolbachia titer overall, though not in the central nervous system. These findings highlight the interactions between Wolbachia and germline cells as strongly nutrient-sensitive, and implicate conserved host signaling pathways by which nutrients influence Wolbachia titer.

Impact of hepatogenous diabetes on clinical features of patients with HBV related chronic liver failure

AIM: To investigate the impact of hepatogenous diabetes (HD) on the clinical features of patients with hepatitis B virus (HBV) related chronic liver failure (CLF).

METHODS: One hundred and eighty-seven patients with HBV related CLF were divided into either an HD group (n = 65) or a control group (n = 122). The liver and kidney function, HBV DNA level, coagulation function, glycosylated hemoglobin Alc (HbAlc) level, Child-Pugh score, model for end-stage liver disease (MELD) score, complications and mortality at 24 wk were analyzed. The correlations between HbAlc level and Child-Pugh score and MELD score were analyzed by linear correlation analysis. Unconditional binary response logistic regression model was used to determine the correlations between HbAlc level and the incidence of complications and mortality at 24 wk.

RESULTS: The incidence of HD in patients with HBV related CLF was 34.76%. The level of total bilirubin (TBIL), international normalized ratio (INR), creatinine (CRE), HbAlc, Child-Pugh score and MELD score were significantly higher in the HD group (P < 0.05). The incidence rates of spontaneous peritonitis and hepatorenal syndrome and mortality at 24 wk were also significantly higher in the HD group (P < 0.05). There were positive correlations between the HbAlc level and Child-Pugh score (r² = 0.17, F = 14.74, P = 0.021) and MELD score (r² = 0.19, F = 16.61, P = 0.014) in patients with CLF. Logistic regression analysis identified that high HbAlc level was related to the high incidence of spontaneous peritonitis (P = 0.019, OR = 2.27) and hepatorenal syndrome (P = 0.023, OR = 1.02) and high mortality at 24 wk (P = 0.032, OR = 0.85).

CONCLUSION: The clinical features of patients with HBV related CLF complicated with HD are more serious. High HbAlc level is a risk factor for spontaneous peritonitis, hepatorenal syndrome and worse prognosis in patients with HBV related CLF.

Multi-omic integrated networks connect DNA methylation and miRNA with skeletal muscle plasticity to chronic exercise in Type 2 diabetic obesity

Epigenomic regulation of the transcriptome by DNA methylation and posttranscriptional gene silencing by miRNAs are potential environmental modulators of skeletal muscle plasticity to chronic exercise in healthy and diseased populations. We utilized transcriptome networks to connect exercise-induced differential methylation and miRNA with functional skeletal muscle plasticity. Biopsies of the vastus lateralis were collected from middle-aged Polynesian men and women with morbid obesity (44 kg/m(2) ± 10) and Type 2 diabetes before and following 16 wk of resistance (n = 9) or endurance training (n = 8). Longitudinal transcriptome, methylome, and microRNA (miRNA) responses were obtained via microarray, filtered by novel effect-size based false discovery rate probe selection preceding bioinformatic interrogation. Metabolic and microvascular transcriptome topology dominated the network landscape following endurance exercise. Lipid and glucose metabolism modules were connected to: microRNA (miR)-29a; promoter region hypomethylation of nuclear receptor factor (NRF1) and fatty acid transporter (SLC27A4), and hypermethylation of fatty acid synthase, and to exon hypomethylation of 6-phosphofructo-2-kinase and Ser/Thr protein kinase. Directional change in the endurance networks was validated by lower intramyocellular lipid, increased capillarity, GLUT4, hexokinase, and mitochondrial enzyme activity and proteome. Resistance training also lowered lipid and increased enzyme activity and caused GLUT4 promoter hypomethylation; however, training was inconsequential to GLUT4, capillarity, and metabolic transcriptome. miR-195 connected to negative regulation of vascular development. To conclude, integrated molecular network modelling revealed differential DNA methylation and miRNA expression changes occur in skeletal muscle in response to chronic exercise training that are most pronounced with endurance training and topographically associated with functional metabolic and microvascular plasticity relevant to diabetes rehabilitation.

Exercise-induced regulation of matrix metalloproteinases in the skeletal muscle of subjects with type 2 diabetes

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMP) play a critical role during vascular remodelling, in both health and disease. Impaired MMP regulation is associated with many diabetes-related complications. This study examined whether exercise-induced regulation of MMPs is maintained in the skeletal muscle of patients with uncomplicated type 2 diabetes (T2DM). Subjects [12 T2DM, 9 healthy control subjects (CON)] underwent 8 weeks of physical training. Messenger RNA (mRNA) was measured at baseline, during and after 8 weeks of training. Protein was measured pre- and post-training. At baseline, there were no effects of diabetes on MMP or TIMP mRNA or protein. mRNA and protein response to training was similar in both groups, except active MMP-2 protein was elevated post training in T2DM only. Our results indicate that exercise-induced stimulation of MMPs is preserved in skeletal muscle of patients with T2DM. This early stage of diabetes may provide an opportunity for intervention and prevention of complications.

Obesity and lifespan health--importance of the fetal environment

A marked increase in the frequency of obesity at the population level has resulted in an increasing number of obese women entering pregnancy. The increasing realization of the importance of the fetal environment in relation to chronic disease across the lifespan has focused attention on the role of maternal obesity in fetal development. Previous studies have demonstrated that obesity during adolescence and adulthood can be traced back to fetal and early childhood exposures. This review focuses on factors that contribute to early developmental events, such as epigenetic modifications, the potential for an increase in inflammatory burden, early developmental programming changes such as the variable development of white versus brown adipose tissue, and alterations in organ ontogeny. We hypothesize that these mechanisms promote an unfavorable fetal environment and can have a long-standing impact, with early manifestations of chronic disease that can result in an increased demand for future health care. In order to identify appropriate preventive measures, attention needs to be placed both on reducing maternal obesity as well as understanding the molecular, cellular, and epigenetic mechanisms that may be responsible for the prenatal onset of chronic disease.

Insight into the impact of dietary saturated fat on tissue-specific cellular processes underlying obesity-related diseases

This study investigated the influence of three high-fat diets (HFDs), differing in the percentage of total calories from saturated fat (SF) (6%, 12%, 24%) but identical in total fat (40%), for a 16-week period in mice on a variety of tissue-specific cellular processes believed to be at the root of obesity-related diseases. Specifically, we examined ectopic lipid accumulation, oxidative capacity [peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) mRNA and protein; mtDNA; Cox IV and cytochrome C protein; citrate synthase activity; and gene expression of fission 1, mitofusin (Mfn) 1 and Mfn2], oxidative stress (4-hydroxy-2-nonenal), endoplasmic reticulum (ER) stress (binding immunoglobulin protein, activating transcription factor 6-p50, p-eukaryotic initiation factor 2 alpha and x-box binding protein 1 spliced protein), inflammatory [p-c-Jun N-terminal kinase (JNK), p-nuclear factor kappa-B, p-p38 mitogen-activated protein kinase) and insulin signaling (p-Akt), and inflammation [tumor necrosis factor-alpha, monocyte chemotactic protein-1, interleukin-6, F4/80, toll-like receptor (TLR)2 and TLR4 gene expression] in various tissues, including the adipose tissue, liver, skeletal muscle and heart. In general, adipose and hepatic tissues were the only tissues which displayed evidence of dysfunction. All HFDs down-regulated adipose, cardiac and hepatic PGC-1α mRNA and hepatic citrate synthase activity, and induced adipose tissue oxidative stress, whereas only the 6%-SF and 12%-SF diet produced hepatic steatosis. However, compared to the 6%-SF and 24%-SF diets, consumption of the 12%-SF diet resulted in the greatest degree of dysregulation (hepatic ER and oxidative stress, JNK activation, increased F4/80 gene expression and down-regulation of adipose tissue Akt signaling). These findings suggest that the saturated fatty acid composition of an HFD can greatly influence the processes responsible for obesity-related diseases - nonalcoholic fatty liver disease, in particular - as well as provide further evidence that the mechanisms at the root of these diseases are diet and tissue sensitive.

Effect of exercise on the skeletal muscle proteome in patients with type 2 diabetes

PURPOSE

Exercise training alters protein abundance in the muscle of healthy individuals, but the effect of exercise on these proteins in patients with type 2 diabetes (T2D) is unknown. The aim of this study was to determine how exercise training alters the skeletal muscle proteome in patients with T2D.

METHODS

Biopsies of the vastus lateralis were obtained before and after 4 wk of exercise training in six patients with T2D (54 ± 4 yr; body mass index (BMI), 29 ± 2) and six age- and BMI-matched control subjects (48 ± 2; BMI, 28 ± 3) studied at the baseline. The proteins were identified and quantified using normalized spectral abundance factors by multidimensional high-resolution mass spectrometry.

RESULTS

Of the 1329 proteins assigned at the baseline, 438 were present in at least half of all the muscle samples; of these, 15 proteins differed significantly between the patients with T2D and control subjects (P < 0.05). In the diabetic patients, the exercise training altered the abundance of 17 proteins (P < 0.05). Key training adaptations included an increase in proteins of the malate-aspartate shuttle and citric acid cycle, reduced the abundance of glycolytic proteins, and altered the abundance of cytoskeleton proteins.

CONCLUSION

The data from this study support the ability of exercise training to alter the abundance of proteins that regulate metabolism and cytoskeletal structure in patients with T2D. These findings open new avenues for future research.

Role of estrogen on skeletal muscle mitochondrial function in ovariectomized rats: a time course study in different fiber types

Postmenopausal women are prone to develop obesity and insulin resistance, which might be related to skeletal muscle mitochondrial dysfunction. In a rat model of ovariectomy (OVX), skeletal muscle mitochondrial function was examined at short- and long-term periods after castration. Mitochondrial parameters in the soleus and white gastrocnemius muscle fibers were analyzed. Three weeks after surgery, there were no differences in coupled mitochondrial respiration (ATP synthesis) with pyruvate, malate, and succinate; proton leak respiration; or mitochondrial reactive oxygen species production. However, after 3 wk of OVX, the soleus and white gastrocnemius muscles of the OVX animals showed a lower use of palmitoyl-carnitine and glycerol-phosphate substrates, respectively, and decreased peroxisome proliferator-activated receptor-γ coactivator-1α expression. Estrogen replacement reverted all of these phenotypes. Eight weeks after OVX, ATP synthesis was lower in the soleus and white gastrocnemius muscles of the OVX animals than in the sham-operated and estrogen-treated animals; however, when normalized by citrate synthase activity, these differences disappeared, indicating a lower muscle mitochondria content. No differences were observed in the proton leak parameter. Mitochondrial alterations did not impair the treadmill exercise capacity of the OVX animals. However, blood lactate levels in the OVX animals were higher after the physical test, indicating a compensatory extramitochondrial ATP synthesis system, but this phenotype was reverted by estrogen replacement. These results suggest early mitochondrial dysfunction related to lipid substrate use, which could be associated with the development of the overweight phenotype of ovariectomized animals.

Whole blood gene expression profiles in insulin resistant Latinos with the metabolic syndrome

Although insulin resistance in skeletal muscle is well-characterized, the role of circulating whole blood in the metabolic syndrome phenotype is not well understood. We set out to test the hypothesis that genes involved in inflammation, insulin signaling and mitochondrial function would be altered in expression in the whole blood of individuals with metabolic syndrome. We further wanted to examine whether similar relationships that we have found previously in skeletal muscle exist in peripheral whole blood cells. All subjects (n=184) were Latino descent from the Arizona Insulin Resistance registry. Subjects were classified based on the metabolic syndrome phenotype according to the National Cholesterol Education Program’s Adult Treatment Panel III. Of the 184 Latino subjects in the study, 74 were classified with the metabolic syndrome and 110 were without. Whole blood gene expression profiling was performed using the Agilent 4x44K Whole Human Genome Microarray. Whole blood microarray analysis identified 1,432 probes that were altered in expression ≥1.2 fold and P<0.05 after Benjamini-Hochberg in the metabolic syndrome subjects. KEGG pathway analysis revealed significant enrichment for pathways including ribosome, oxidative phosphorylation and MAPK signaling (all Benjamini-Hochberg P<0.05). Whole blood mRNA expression changes observed in the microarray data were confirmed by quantitative RT-PCR. Transcription factor binding motif enrichment analysis revealed E2F1, ELK1, NF-kappaB, STAT1 and STAT3 significantly enriched after Bonferroni correction (all P<0.05). The results of the present study demonstrate that whole blood is a useful tissue for studying the metabolic syndrome and its underlying insulin resistance although the relationship between blood and skeletal muscle differs.

Urethral striated muscle and extracellular matrix morphological characteristics among mildly diabetic pregnant rats: translational approach

INTRODUCTION AND HYPOTHESIS

Diabetes mellitus (DM) during pregnancy is associated with high levels of urinary incontinence (UI) and pelvic floor muscle dysfunction. Mild DM can lead to changes in urethral striated muscle and extracellular matrix (ECM) in pregnant rats considering both structures as an entire system responsible for urinary continence.

METHODS

Ninety-two female Wistar rats were distributed in four experimental groups: virgin, pregnant, diabetic, and diabetic pregnant. In adult life, parental nondiabetic female rats were mated with nondiabetic male rats to obtain newborns. At the first day of birth, newborns received citrate buffer (nondiabetic group) or streptozotocin 100 mg/kg body weight, subcutaneous route (mild DM group). At day 21 of the pregnancy, the rats were lethally anesthetized and the urethra and vagina were extracted as a unit. Urethral and vaginal sections were cut and analyzed by: (a) cytochemical staining for ECM and muscle structural components, (b) immunohistochemistry to identify fast- and slow-muscle fibers, and (c) transmission electron microscopy for ultrastructural analysis of urethral striated muscle.

RESULTS

In comparison with the three control groups, variations in the urethral striated muscle and ECM from diabetic pregnant rats were observed including thinning, atrophy, fibrosis, increased area of blood vessels, mitochondria accumulation, increased lipid droplets, glycogen granules associated with colocalization of fast and slow fibers, and a steady decrease in the proportion of fast to slow fibers.

CONCLUSIONS

Mild DM and pregnancy can lead to a time-dependent disorder and tissue remodeling in which the urethral striated muscle and ECM has a fundamental function.

Metabolic crosstalk between choline/1-carbon metabolism and energy homeostasis

There are multiple identified mechanisms involved in energy metabolism, insulin resistance and adiposity, but there are here-to-fore unsuspected metabolic factors that also influence these processes. Studies in animal models suggest important links between choline/1-carbon metabolism and energy homeostasis. Rodents fed choline deficient diets become hypermetabolic. Mice with deletions in one of several different genes of choline metabolism have phenotypes that include increased metabolic rate, decreased body fat/lean mass ratio, increased insulin sensitivity, decreased ATP production by mitochondria, or decreased weight gain on a high fat diet. In addition, farmers have recognized that the addition of a metabolite of choline (betaine) to cattle and swine feed reduces body fat/lean mass ratio. Choline dietary intake in humans varies over a > three-fold range, and genetic variation exists that modifies individual requirements for this nutrient. Although there are some epidemiologic studies in humans suggesting a link between choline/1-carbon metabolism and energy metabolism, there have been no controlled studies in humans that were specifically designed to examine this relationship.

A matter of life, death and diseases: mitochondria from a proteomic perspective

Mitochondria are highly ordered, integrated organelles that energize cellular activities and contribute to programmed death by initiating disciplined apoptotic cascades. This review seeks to clarify our understanding of mitochondrial structural-functional integrity beyond the resolved nuclear genome by unraveling the dynamic mitochondrial proteome and elucidating proteome/genome interplay. The roles of mechanochemical coupling between mitoskeleton and cytoskeleton and crosstalk with other organelles in orchestrating cellular outcomes are explained. The authors also review the modulation of mitochondrial-related oxidative stress on apoptosis and cancer development and the context is applied to interpret pathogenetic events in neurodegenerative disorders and cardiovascular diseases. The accumulated proteomics evidence is used to describe the integral role that mitochondria play and how they influence other intracellular organelles. Possible mitochondrial-targeted therapeutic interventions are also discussed.

Mitochondria: sensors and mediators of innate immune receptor signaling

By integrating stress signals with inputs from other cellular organelles, eukaryotic mitochondria are dynamic sensing systems that can confer substantial impact on innate immune signaling in both health and disease. This review highlights recently discovered elements of innate immune receptor signaling (TLR, RLR, NLR, and CLR) associated with mitochondrial function and discusses the role of mitochondria in the initiation and/or manifestation of inflammatory diseases and disorders. We also highlight the role of mitochondria as therapeutic targets for inflammatory disease.