Role of mitochondrial dysfunction in insulin resistance

Metabolic Dysregulation and Neurovascular Dysfunction in Diabetic Retinopathy

Diabetic retinopathy is a major cause of ocular complications in patients with type 1 and type 2 diabetes in developed countries. Due to the continued increase in the number of people with obesity and diabetes in the United States of America and globally, the incidence of diabetic retinopathy is expected to increase significantly in the coming years. Diabetic retinopathy is widely accepted as a combination of neurodegenerative and microvascular changes; however, which change occurs first is not yet understood. Although the pathogenesis of diabetic retinopathy is very complex, regulated by numerous signaling pathways and cellular processes, maintaining glucose homeostasis is still an essential component for normal physiological functioning of retinal cells. The maintenance of glucose homeostasis is finely regulated by coordinated interplay between glycolysis, Krebs cycle, and oxidative phosphorylation. Glycolysis is the most conserved metabolic pathway in biology and is tightly regulated to maintain a steady-state concentration of glycolytic intermediates; this regulation is called scheduled or regulated glycolysis. However, an abnormal increase in glycolytic flux generates large amounts of intermediate metabolites that can be shunted into different damaging pathways including the polyol pathway, hexosamine pathway, diacylglycerol-dependent activation of the protein kinase C pathway, and Amadori/advanced glycation end products (AGEs) pathway. In addition, disrupting the balance between glycolysis and oxidative phosphorylation leads to other biochemical and molecular changes observed in diabetic retinopathy including endoplasmic reticulum-mitochondria miscommunication and mitophagy dysregulation. This review will focus on how dysregulation of glycolysis contributes to diabetic retinopathy.

Role of AMP-activated protein kinase on cardio-metabolic abnormalities in the development of diabetic cardiomyopathy: A molecular landscape

Cardiovascular complications associated with diabetes mellitus remains a leading cause of morbidity and mortality across the world. Diabetic cardiomyopathy is a descriptive pathology that in absence of co-morbidities such as hypertension, dyslipidemia initially characterized by cardiac stiffness, myocardial fibrosis, ventricular hypertrophy, and remodeling. These abnormalities further contribute to diastolic dysfunctions followed by systolic dysfunctions and eventually results in clinical heart failure (HF). The clinical outcomes associated with HF are considerably worse in patients with diabetes. The complexity of the pathogenesis and clinical features of diabetic cardiomyopathy raises serious questions in developing a therapeutic strategy to manage cardio-metabolic abnormalities. Despite extensive research in the past decade the compelling approaches to manage and treat diabetic cardiomyopathy are limited. AMP-Activated Protein Kinase (AMPK), a serine-threonine kinase, often referred to as cellular "metabolic master switch". During the development and progression of diabetic cardiomyopathy, a plethora of evidence demonstrate the beneficial role of AMPK on cardio-metabolic abnormalities including altered substrate utilization, impaired cardiac insulin metabolic signaling, mitochondrial dysfunction and oxidative stress, myocardial inflammation, increased accumulation of advanced glycation end-products, impaired cardiac calcium handling, maladaptive activation of the renin-angiotensin-aldosterone system, endoplasmic reticulum stress, myocardial fibrosis, ventricular hypertrophy, cardiac apoptosis, and impaired autophagy. Therefore, in this review, we have summarized the findings from pre-clinical and clinical studies and provided a collective overview of the pathophysiological mechanism and the regulatory role of AMPK on cardio-metabolic abnormalities during the development of diabetic cardiomyopathy.

Neuroprotective Effect of Syringic Acid by Modulation of Oxidative Stress and Mitochondrial Mass in Diabetic Rats

Diabetes is a metabolic complaint associated with oxidative stress and dysfunction of mitochondria. One of the most common complications of diabetes mellitus is neuropathy. This study evaluated the possible neuroprotective effects of syringic acid (SYR), a natural polyphenolic derivative of benzoic acid, on oxidative damage and mitochondria in the brain, spinal cord, and sciatic nerve of streptozotocin-induced diabetic rats. Different groups of rats including normal control, diabetics (induced by streptozotocin), diabetic groups treated with 25, 50, and 100 mg/kg of SYR, and non-diabetic group treated with only 100 mg/kg of SYR were treated for 6 weeks. Learning and memory function, physical coordination, and acetylcholinesterase (AChE) and antioxidant indexes, as well as mRNA expression of mitochondrial biogenesis, were measured in the brain, spinal cord, and sciatic nerves. Diabetic rats treated with 100 mg/kg SYR exhibited significantly improved learning, memory, and movement deficiency (p < 0.05). SYR 100 mg/kg also significantly upregulated the brain mRNA expression of PGC-1α and NRF-1, the key regulators of energy metabolism, oxidative phosphorylation, and mitochondrial biogenesis. In addition, SYR 100 mg/kg and SYR 50 mg/kg increased the mtDNA/nDNA ratio in the brain and the spinal cord of diabetic rats, respectively (p < 0.05). SYR attenuated the lipid peroxidation in all the tissues, but not significant effects were observed on GSH, AChE, catalase, and superoxide dismutase activity. In all the tests, nonsignificant differences were observed between the control and SYR 100 mg/kg groups. Moreover, SYR reduced inflammation and demyelination in sciatic nerves. This is the first study to reveal the regulation of mitochondrial biogenesis and energy metabolism by SYR, beyond its antioxidant role in the diabetic rats' brain and spinal tissues.

Methionine sulfoxide reductase B3 deficiency inhibits the development of diet-induced insulin resistance in mice

Oxidative and endoplasmic reticulum (ER) stress are involved in mediating high-fat diet (HFD)-induced insulin resistance. As the ER-localized methionine sulfoxide reductase B3 (MsrB3) protects cells against oxidative and ER stress, we hypothesized that MsrB3 might be associated with HFD-induced insulin resistance. To test this hypothesis, we examined the effect of MsrB3 deficiency on HFD-induced insulin resistance using MsrB3 knockout (KO) mice. Mice were fed a control diet or HFD for 12 weeks and insulin sensitivity was measured using a hyperinsulinemic-euglycemic clamp. HFD consumption increased the body weight of both wild-type and MsrB3 KO mice, and no significant difference was observed between the genotypes. The HFD increased oxidative stress and induced insulin resistance in the skeletal muscle of wild-type mice, but did not affect either in MsrB3 KO mice. The unfolded protein response (UPR) was increased in MsrB3 KO mice upon consumption of HFD, but not in wild-type mice. Mitochondrial oxidative phosphorylation proteins and the levels of superoxide dismutase 2 and glutathione peroxidase 1 were increased in MsrB3 KO mice upon HFD consumption. The respiratory control ratio was reduced in wild-type mice consuming HFD but not in MsrB3 KO mice. The levels of calcium/calmodulin-dependent protein kinase kinase β, phosphorylated AMP-activated protein kinase, and peroxisome proliferator-activated receptor gamma coactivator 1α were increased in MsrB3 KO mice following HFD consumption. These results suggest that MsrB3 deficiency inhibits HFD-induced insulin resistance, and the increased mitochondrial biogenesis and antioxidant induction might be the mechanisms underlying this phenomenon.

Current perspectives of oleic acid: Regulation of molecular pathways in mitochondrial and endothelial functioning against insulin resistance and diabetes

Insulin resistance (IR) and type 2 diabetes mellitus (T2DM) is a leading cause of deaths due to metabolic disorders in recent years. Molecular mechanisms involved in the initiation and development of IR and T2DM are multiples. The major factors include mitochondrial dysfunction which may cause incomplete fatty acid oxidation (FAO). Oleic acid upregulates the expression of genes causing FAO by deacetylation of PGC1α by PKA-dependent activation of SIRT1-PGC1α complex. Another potent factor for the development of IR and T2DM is endothelial dysfunction as damaged endothelium causes increased release of inflammatory mediators such as TNF-α, IL-6, IL-1β, sVCAM, sICAM, E-selectin and other proinflammatory cytokines. While, on the other hand, oleic acid has the ability to regulate E-selectin, and sICAM expression. Rest of the risk factors may include inflammation, β-cell dysfunction, oxidative stress, hormonal imbalance, apoptosis, and enzyme dysregulation. Here, we have highlighted how oleic acid regulates underlying causatives factors and hence, keeps surpassing effect in prevention and treatment of IR and T2DM. However, the percentage contribution of these factors in combating IR and ultimately averting T2DM is still debatable. Thus, because of its exceptional protective effect, it can be considered as an improved therapeutic agent in prophylaxis and/or treatment of IR and T2DM.

New Amphiphilic Squalene Derivative Improves Metabolism of Adipocytes Differentiated From Diabetic Adipose-Derived Stem Cells and Prevents Excessive Lipogenesis

Squalene (Sq) is a natural compound, found in various plant oils, algae, and larger quantity in deep-sea shark liver. It is also known as an intermediate of cholesterol synthesis in plants and animals including humans. Although evidences demonstrated its antioxidant, anticancer, hypolipidemic, and hepatoprotective and cardioprotective effects, its biological effects in cellular function might have been underestimated because of the water-insoluble property. To overcome this hydrophobicity, we synthesized new amphiphilic Sq derivative (HH-Sq). On the other hand, adipose-derived stem cells (ASCs) are a valuable source in regenerative medicine for its ease of accessibility and multilineage differentiation potential. Nevertheless, impaired cellular functions of ASCs derived from diabetic donor have still been debated controversially. In this study, we explored the effect of the HH-Sq in comparison to Sq on the adipocyte differentiation of ASCs obtained from subjects with type 2 diabetes. Gene expression profile by microarray analysis at 14 days of adipogenic differentiation revealed that HH-Sq induced more genes involved in intracellular signaling processes, whereas Sq activated more transmembrane receptor pathway-related genes. In addition, more important number of down-regulated and up-regulated genes by Sq and HH-Sq were not overlapped, suggesting the compounds might not only have difference in their chemical property but also potentially exert different biological effects. Both Sq and HH-Sq improved metabolism of adipocytes by enhancing genes associated with energy homeostasis and insulin sensitivity, SIRT1, PRKAA2, and IRS1. Interestingly, Sq increased significantly early adipogenic markers and lipogenic gene expression such as PPARG, SREBF1, and CEBPA, but not HH-Sq. As a consequence, smaller and fewer lipid droplet formation was observed in HH-Sq-treated adipocytes. Based on our findings, we report that both Sq and HH-Sq improved adipocyte metabolism, but only HH-Sq prevented excessive lipogenesis without abrogating adipocyte differentiation. The beneficial effect of HH-Sq provides an importance of synthesized derivatives from a natural compound with therapeutic potentials in the application of cell therapies.

Mechanisms of muscle insulin resistance and the cross-talk with liver and adipose tissue

Insulin resistance is a metabolic disorder affecting multiple tissues and is a precursor event to type 2 diabetes (T2D). As T2D affects over 425 million people globally, there is an imperative need for research into insulin resistance to better understand the underlying mechanisms. The proposed mechanisms involved in insulin resistance include both whole body aspects, such as inflammation and metabolic inflexibility; as well as cellular phenomena, such as lipotoxicity, ER stress, and mitochondrial dysfunction. Despite numerous studies emphasizing the role of lipotoxicity in the pathogenesis of insulin resistance, an understanding of the interplay between tissues and these proposed mechanisms is still emerging. Furthermore, the tissue-specific and unique responses each of the three major insulin target tissues and how each interconnect to regulate the whole body insulin response has become a new priority in metabolic research. With an emphasis on skeletal muscle, this mini-review highlights key similarities and differences in insulin signaling and resistance between different target-tissues, and presents the latest findings related to how these tissues communicate to control whole body metabolism.

Molecular mechanisms of right ventricular dysfunction in pulmonary arterial hypertension: focus on the coronary vasculature, sex hormones, and glucose/lipid metabolism

Pulmonary arterial hypertension (PAH) is a rare, life-threatening condition characterized by dysregulated metabolism, pulmonary vascular remodeling, and loss of pulmonary vascular cross-sectional area due to a variety of etiologies. Right ventricular (RV) dysfunction in PAH is a critical mediator of both long-term morbidity and mortality. While combinatory oral pharmacotherapy and/or intravenous prostacyclin aimed at decreasing pulmonary vascular resistance (PVR) have improved clinical outcomes, there are currently no treatments that directly address RV failure in PAH. This is, in part, due to the incomplete understanding of the pathogenesis of RV dysfunction in PAH. The purpose of this review is to discuss the current understanding of key molecular mechanisms that cause, contribute and/or sustain RV dysfunction, with a special focus on pathways that either have led to or have the potential to lead to clinical therapeutic intervention. Specifically, this review discusses the mechanisms by which vessel loss and dysfunctional angiogenesis, sex hormones, and metabolic derangements in PAH directly contribute to RV dysfunction. Finally, this review discusses limitations and future areas of investigation that may lead to novel understanding and therapeutic interventions for RV dysfunction in PAH.

Mechanisms of insulin resistance, mitochondrial dysfunction and the action of the ketogenic diet in bipolar disorder. Focus on the PI3K/AKT/HIF1-a pathway

Over the past decade evidence from multiple research trajectories have converged to provide evidence that impaired glucose metabolism and mitochondrial dysfunction in the brain are the critical issues laying at the root of Bipolar Disorder (BD). These developments have been paralleled by increasing recognition of the systemic metabolic dysfunction accompanying mood disorders. Significant insulin resistance (IR) occurs in BD patients and this has been demonstrated to be related to illness severity independent of medication status. Preliminary evidence for a therapeutic effect of a Ketogenic Diet (KD) in BD and other neuropsychiatric conditions has recently refocused interest in the role of IR in BD pathogenesis. In this paper we review evidence of hyperinsulinemia in BD as the primary cause of mitochondrial dysfunction mediated by impairment of the PI3K/AKT/HIF1-a insulin signaling pathway. This cascade of dysfunction directly suppresses the Pyruvate Dehydrogenase Complex through HIF1-a mediated activation of Pyruvate dehydrogenase kinase 1 (PDK1) leading to the Warburg effect and mitochondrial dysfunction. We review evidence that the KD acts directly on each of these mechanisms and propose that a trial of KD in BD with a mechanistic component is needed to further investigate the role of IR in BD.

Diabetic Retinopathy: The Role of Mitochondria in the Neural Retina and Microvascular Disease

Diabetic retinopathy (DR), a common chronic complication of diabetes mellitus and the leading cause of vision loss in the working-age population, is clinically defined as a microvascular disease that involves damage of the retinal capillaries with secondary visual impairment. While its clinical diagnosis is based on vascular pathology, DR is associated with early abnormalities in the electroretinogram, indicating alterations of the neural retina and impaired visual signaling. The pathogenesis of DR is complex and likely involves the simultaneous dysregulation of multiple metabolic and signaling pathways through the retinal neurovascular unit. There is evidence that microvascular disease in DR is caused in part by altered energetic metabolism in the neural retina and specifically from signals originating in the photoreceptors. In this review, we discuss the main pathogenic mechanisms that link alterations in neural retina bioenergetics with vascular regression in DR. We focus specifically on the recent developments related to alterations in mitochondrial metabolism including energetic substrate selection, mitochondrial function, oxidation-reduction (redox) imbalance, and oxidative stress, and critically discuss the mechanisms of these changes and their consequences on retinal function. We also acknowledge implications for emerging therapeutic approaches and future research directions to find novel mitochondria-targeted therapeutic strategies to correct bioenergetics in diabetes. We conclude that retinal bioenergetics is affected in the early stages of diabetes with consequences beyond changes in ATP content, and that maintaining mitochondrial integrity may alleviate retinal disease.

Nutrition, Bioenergetics, and Metabolic Syndrome

According to the World Health Organization (WHO), the global nutrition report shows that whilst part of the world's population starves, the other part suffers from obesity and associated complications. A balanced diet counterparts these extreme conditions with the proper proportion, composition, quantity, and presence of macronutrients, micronutrients, and bioactive compounds. However, little is known on the way these components exert any influence on our health. These nutrients aiming to feed our bodies, our tissues, and our cells, first need to reach mitochondria, where they are decomposed into CO2 and H2O to obtain energy. Mitochondria are the powerhouse of the cell and mainly responsible for nutrients metabolism, but they are also the main source of oxidative stress and cell death by apoptosis. Unappropriated nutrients may support mitochondrial to become the Trojan horse in the cell. This review aims to provide an approach to the role that some nutrients exert on mitochondria as a major contributor to high prevalent Western conditions including metabolic syndrome (MetS), a constellation of pathologic conditions which promotes type II diabetes and cardiovascular risk. Clinical and experimental data extracted from in vitro animal and cell models further demonstrated in patients, support the idea that a balanced diet, in a healthy lifestyle context, promotes proper bioenergetic and mitochondrial function, becoming the best medicine to prevent the onset and progression of MetS. Any advance in the prevention and management of these prevalent complications help to face these challenging global health problems, by ameliorating the quality of life of patients and reducing the associated sociosanitary burden.

Pathophysiology of Type 2 Diabetes Mellitus

Type 2 Diabetes Mellitus (T2DM), one of the most common metabolic disorders, is caused by a combination of two primary factors: defective insulin secretion by pancreatic β-cells and the inability of insulin-sensitive tissues to respond appropriately to insulin. Because insulin release and activity are essential processes for glucose homeostasis, the molecular mechanisms involved in the synthesis and release of insulin, as well as in its detection are tightly regulated. Defects in any of the mechanisms involved in these processes can lead to a metabolic imbalance responsible for the development of the disease. This review analyzes the key aspects of T2DM, as well as the molecular mechanisms and pathways implicated in insulin metabolism leading to T2DM and insulin resistance. For that purpose, we summarize the data gathered up until now, focusing especially on insulin synthesis, insulin release, insulin sensing and on the downstream effects on individual insulin-sensitive organs. The review also covers the pathological conditions perpetuating T2DM such as nutritional factors, physical activity, gut dysbiosis and metabolic memory. Additionally, because T2DM is associated with accelerated atherosclerosis development, we review here some of the molecular mechanisms that link T2DM and insulin resistance (IR) as well as cardiovascular risk as one of the most important complications in T2DM.

A novel oral glucagon-like peptide 1 receptor agonist protects against diabetic cardiomyopathy via alleviating cardiac lipotoxicity induced mitochondria dysfunction

Diabetic cardiomyopathy is one of the major cardiovascular complications of diabetes mellitus associated with left ventricular diastolic dysfunction. There are still no specific therapeutic guidelines for the disease. In recent years, glucagon-like peptide 1 receptor agonists were proved to exert cardioprotective effects in comprehensive studies. Therefore, we examined whether a novel oral availably glucagon-like peptide 1 receptor agonist, oral hypoglycemic peptide 2 (OHP2), could protect against diabetic cardiomyopathy in high-fat diets and continuous streptozocin injection induced rat models. After treatment for eight weeks, heart function was evaluated by echocardiography. As expected, OHP2 improved cardiac structure and function beyond glycemic control. Both hyperlipidemia and myocardium lipid accumulation were decreased by OHP2 treatment. In addition, OHP2 reversed oxidative stress and mitochondrial dysfunction in diabetic hearts. In vitro study suggested that OHP2 prevented palmitic acid-induced oxidative stress and mitochondrial dysfunction via suppressing intercellular lipid accumulation. Hence, our present findings pointed out that OHP2 is a promising oral glucagon-like peptide 1 receptor agonist for preventing diabetic cardiomyopathy.

Adipose Tissue Inflammation Is Directly Linked to Obesity-Induced Insulin Resistance, while Gut Dysbiosis and Mitochondrial Dysfunction Are Not Required

Obesity is associated with adipose tissue hypertrophy, systemic inflammation, mitochondrial dysfunction, and intestinal dysbiosis. Rodent models of high-fat diet (HFD)-feeding or genetic deletion of multifunctional proteins involved in immunity and metabolism are often used to probe the etiology of obesity; however, these models make it difficult to divorce the effects of obesity, diet composition, or immunity on endocrine regulation of blood glucose. We, therefore, investigated the importance of adipose inflammation, mitochondrial dysfunction, and gut dysbiosis for obesity-induced insulin resistance using a spontaneously obese mouse model. We examined metabolic changes in skeletal muscle, adipose tissue, liver, the intestinal microbiome, and whole-body glucose control in spontaneously hyperphagic C57Bl/6J mice compared to lean littermates. A separate subset of lean and obese mice was subject to 8 weeks of obesogenic HFD feeding, or to pair feeding of a standard rodent diet. Hyperphagia, obesity, adipose inflammation, and insulin resistance were present in obese mice despite consuming a standard rodent diet, and these effects were blunted with caloric restriction. However, hyperphagic obese mice had normal mitochondrial respiratory function in all tissues tested and no discernable intestinal dysbiosis relative to lean littermates. In contrast, feeding mice an obesogenic HFD altered the composition of the gut microbiome, impaired skeletal muscle mitochondrial bioenergetics, and promoted poor glucose control. These data show that adipose inflammation and redox stress occurred in all models of obesity, but gut dysbiosis and mitochondrial respiratory dysfunction are not always required for obesity-induced insulin resistance. Rather, changes in the intestinal microbiome and mitochondrial bioenergetics may reflect physiological consequences of HFD feeding.

HWL-088, a new and highly effective FFA1/PPARδ dual agonist, attenuates nonalcoholic steatohepatitis by regulating lipid metabolism, inflammation and fibrosis

OBJECTIVES

Nonalcoholic fatty liver (NAFLD), a chronic progressive liver disease, is highly correlated with pathoglycemia, dyslipidemia and oxidative stress. The free fatty acid receptor 1 (FFA1) agonists have been reported to improve liver steatosis and fibrosis, and the peroxisome proliferator-activated receptor δ (PPARδ) plays a synergistic role with FFA1 in energy metabolism and fibrosis. HWL-088, a PPARδ/FFA1 dual agonist, exerts better glucose-lowering effects than the representative FFA1 agonist TAK-875. However, the ability of HWL-088 to protect NAFLD was unknown. This study aimed to discover a new strategy for the treatment of NAFLD.

METHODS

The methionine- and choline-deficient diet (MCD)-induced Nonalcoholic steatohepatitis (NASH) model was constructed to evaluate the effects of HWL-088.

KEY FINDINGS

Administration of HWL-088 exerted multiple benefits on glucose control, lipid metabolism and fatty liver. Further mechanism research indicated that HWL-088 promotes lipid metabolism by decreasing lipogenesis and increasing lipolysis. Moreover, HWL-088 attenuates NASH by regulating the expression levels of genes related to inflammation, fibrosis and oxidative stress.

CONCLUSIONS

These positive results indicated that PPARδ/FFA1 dual agonist HWL-088 might be a potential candidate to improve multiple pathogenesis of NASH.

Ganoderic acid A attenuates high-fat-diet-induced liver injury in rats by regulating the lipid oxidation and liver inflammation

Ganoderic Acid A (GA) has many pharmacological effects such as anti-tumor, antibacterial, anti-inflammatory, and immunosuppressive effects. However, the protective effect of GA on liver injury has not been reported. This study aimed to investigate the action of GA on insufficient methionine and choline combined with high-fat diet (HFD)-induced non-alcoholic fatty liver disease (NAFLD) in rats. NAFLD model was established by insufficient methionine and choline combined with high fat feeding to rats. The levels of Acetyl-CoA carboxylase, fatty acid synthase, sterol regulatory element binding protein, liver X receptors, AMP-activated protein kinase, peroxisome proliferator-activated receptor α, PPARg coactivator 1α and NF-κB pathway in the liver were detected by western blot. The results of this study demonstrated that the expression of GA can not only significantly decrease the live weight and liver weight per body weight of HFD mice, but also restore the alanine aminotransferase, aspartate aminotransferase, total bilirubin levels, triglyceride and cholesterol in serum. In addition, the expression of GA increased the levels of high-density lipoprotein cholesterol in serum, ameliorated pathological changes and decreased NAS score of mice's liver. In conclusion, the treatment with GA could improve NAFLD in rats by regulating the levels of signaling events involved in free fatty acid production, lipid oxidation and liver inflammation.

Role of exercise and rapamycin on the expression of energy metabolism genes in liver tissues of rats fed a high‑fat diet

The mTOR pathway serves an important role in the development of insulin resistance induced by obesity. Exercise improves obesity-associated insulin resistance and hepatic energy metabolism; however, the precise mechanism of this process remains unknown. Therefore, the present study investigated the role of rapamycin, an inhibitor of mTOR, on exercise-induced expression of hepatic energy metabolism genes in rats fed a high-fat diet (HFD). A total of 30 male rats were divided into the following groups: Normal group (n=6) fed chow diets and HFD group (n=24) fed an HFD for 6 weeks. The HFD rats performed exercise adaptation for 1 week and were randomly divided into the four following groups (each containing six rats): i) Group of HFD rats with sedentary (H group); ii) group of HFD rats with exercise (HE group); iii) group of HFD rats with rapamycin (HR group); and iv) group of HFD rats with exercise and rapamycin (HER group). Both HE and HER rats were placed on incremental treadmill training for 4 weeks (from week 8–11). Both HR and HER rats were injected with rapamycin intraperitoneally at the dose of 2 mg/kg once a day for 2 weeks (from week 10–11). All rats were sacrificed following a 12–16 h fasting period at the end of week 11. The levels of mitochondrial and oxidative enzyme activities, as well as of the expression of genes involved in energy metabolism were assessed in liver tissues. Biochemical assays and oil red staining were used to assess the content of hepatic triglycerides (TGs). The results indicated that exercise, but not rapamycin, reduced TG content in the liver of HFD rats. Further analysis indicated that rapamycin reduced the activity of cytochrome c oxidase, but not the activities of succinate dehydrogenase and β-hydroxyacyl-CoA dehydrogenase in the liver of HFD rats. Exercise significantly upregulated the mRNA expression of peroxisome proliferator-activated receptor γ coactivator 1 β, while rapamycin exhibited no effect on the mRNA expression levels of hepatic transcription factors associated with energy metabolism enzymes in the liver of HFD rats. Collectively, the results indicated that exercise reduced TG content and upregulated mitochondrial metabolic gene expression in the liver of HFD rats. Moreover, this mechanism may not involve the mTOR pathway.

Ancient wheats: beneficial effects on insulin resistance

Non-alcoholic fatty liver disease and type 2 diabetes mellitus are two conditions that commonly exist together in the context of the metabolic syndrome. Several scientific advances in understanding this association have identified insulin resistance as the key point in the pathogenesis of both diseases. The first line treatment suggested in the management of these diseases is represented by lifestyle changes and in particular the modification of alimentary regimen, with the transition to a healthy diet. In this context, several studies have focused their attention on the identification of food products with beneficial actions, like ancient wheat (AW). AW are defined as the early cereals that were domesticated in their places of origin in the "Fertile Crescent" of the Middle East, and played a central role as a main source of food for the early civilizations in that region. The present narrative review aims to provide a systematic overview of the state of the art on the effects of AW on insulin resistance.

Effect of Non-Surgical Periodontal Treatment on Oxidative Stress Markers in Leukocytes and Their Interaction with the Endothelium in Obese Subjects with Periodontitis: A Pilot Study

Aim: The primary objective of this pilot study was to evaluate the effect of non-surgical periodontal treatment. The secondary aim was to evaluate the effect of dietary therapy on both parameters of oxidative stress in leukocytes and leukocyte-endothelial cell interactions in an obese population. Methods: This was a pilot study with a before-and-after design. Forty-nine obese subjects with periodontitis were randomized by means of the minimization method and assigned to one of two groups, one of which underwent dietary therapy while the other did not. All the subjects underwent non-surgical periodontal treatment. We determined periodontal, inflammatory and oxidative stress parameters—total reactive oxygen species (ROS), superoxide production, intracellular Ca²⁺, mitochondrial membrane potential and superoxide dismutase (SOD) activity. We also evaluated interactions between leukocytes and endothelium cells—velocity, rolling flux and adhesion—at baseline and 12 weeks after intervention. Results: Periodontal treatment improved the periodontal health of all the patients, with a reduction in serum retinol-binding protein 4 (RBP4), total superoxide production and cytosolic Ca²⁺ in leukocytes. In the patients undergoing dietary therapy, there were less leukocyte adhesion to the endothelium, an effect that was accompanied by a decrease in TNFα, P-selectin and total ROS and an increase in SOD activity. Conclusions: Whereas non-surgical periodontal treatment induces an improvement in leukocyte homeostasis, dietary therapy as an adjuvant reduces systemic inflammation and increases antioxidant status which, in turn, modulates leukocyte-endothelium dynamics.

Can adipokine visfatin be a novel marker of pregnancy-related disorders in women with obesity?

Overweight and obesity have become a dangerous disease requiring multiple interventions, treatment and preventions. In women of reproductive age, obesity is one of the most common medical conditions. Among others, obese state is characterized by low-grade systemic inflammation and enhanced oxidative stress. Increased maternal body mass index might amplify inflammation and reactive oxygen species production, which is associated with unfavourable clinical outcomes that affect both mother and child. Intrauterine growth retardation, preeclampsia, or gestational diabetes mellitus are examples of the hampered maternal and foetoplacental unit interactions. Visfatin is the obesity-related adipokine produced mainly by the visceral adipose tissue. Visfatin affects glucose homeostasis, as well as the regulation of genes related to oxidative stress and inflammatory response. Here, we review visfatin interactions in pregnancy-related disorders linked to obesity. We highlight the possible predictive and prognostic value of visfatin in diagnostic strategies on gravidas with obesity.

The Impact of Sugar-Sweetened Beverage Consumption on the Liver: A Proteomics-based Analysis

Cardiometabolic complications such as the metabolic syndrome and Type 2 Diabetes Mellitus (T2DM) are major causes of global morbidity and mortality. As sugar-sweetened beverages (SSBs) are implicated in this process, this study aimed to obtain greater mechanistic insights. Male Wistar rats (~200 g) were gavaged with a local SSB every day for a period of six months while the control group was gavaged with an iso-volumetric amount of water. Experimental dosages were calculated according to the surface area-to-volume ratio and were equivalent to 125 mL/day (in human terms). A proteomic analysis was performed on isolated liver samples and thereafter, markers of endoplasmic reticulum (ER) stress, antioxidant/oxidant capacity, calcium regulation, and mitochondrial functionality were assessed. These data show that SSB consumption resulted in (a) the induction of mild hepatic ER stress; (b) altered hepatic mitochondrial dynamics; and (c) perturbed calcium handling across mitochondria-associated ER membranes. Despite significant changes in markers of ER stress, the antioxidant response and calcium handling (proteomics data), the liver is able to initiate adaptive responses to counteract such stressors. However, the mitochondrial data showed increased fission and decreased fusion that may put the organism at risk for developing insulin resistance and T2DM in the longer term.

ZLY032, the first-in-class dual FFA1/PPARδ agonist, improves glucolipid metabolism and alleviates hepatic fibrosis

The free fatty acid receptor 1 (FFA1) and peroxisome proliferator-activated receptor δ (PPARδ) are considered as anti-diabetic targets based on their role in improving insulin secretion and resistance. Based on their synergetic mechanisms, we have previously identified the first-in-class dual FFA1/PPARδ agonist ZLY032. After long-term treatment, ZLY032 significantly improved glucolipid metabolism and alleviated fatty liver in ob/ob mice and methionine choline-deficient diet-fed db/db mice, mainly by regulating triglyceride metabolism, fatty acid β-oxidation, lipid synthesis, inflammation, oxidative stress and mitochondrial function. Notably, ZLY032 exhibited greater advantages on lipid metabolism, insulin sensitivity and pancreatic β-cell function than TAK-875, the most advanced candidate of FFA1 agonists. Moreover, ZLY032 prevented CCl₄-induced liver fibrosis by reducing the expressions of genes involved in inflammation and fibrosis development. These results suggest that the dual FFA1/PPARδ agonists such as ZLY032 may be useful for the treatment of metabolic disorders.

Molecular mechanisms of hepatic insulin resistance in nonalcoholic fatty liver disease and potential treatment strategies

The prevalence of nonalcoholic fatty liver disease (NAFLD) in the general population is estimated at 25 %, and there is currently no effective treatment of NAFLD. Although insulin resistance (IR) is not the only factor causing the pathogenesis of NAFLD, hepatic IR has a cause-effective relationship with NAFLD. Improving hepatic IR is a potential therapeutic strategy to treat NAFLD. This review highlights the molecular mechanisms of hepatic IR in the development of NAFLD. Available data on potential drugs including glucagon-like peptide 1 receptor (GLP-1) agonists, peroxisome proliferator-activated receptor (PPAR-γ/α/δ) agonists, farnesoid X receptor (FXR) agonists, etc. are carefully discussed.

Mitochondrial Dysfunctions: A Red Thread across Neurodegenerative Diseases

Mitochondria play a central role in a plethora of processes related to the maintenance of cellular homeostasis and genomic integrity. They contribute to preserving the optimal functioning of cells and protecting them from potential DNA damage which could result in mutations and disease. However, perturbations of the system due to senescence or environmental factors induce alterations of the physiological balance and lead to the impairment of mitochondrial functions. After the description of the crucial roles of mitochondria for cell survival and activity, the core of this review focuses on the "mitochondrial switch" which occurs at the onset of neuronal degeneration. We dissect the pathways related to mitochondrial dysfunctions which are shared among the most frequent or disabling neurodegenerative diseases such as Alzheimer's, Parkinson's, and Huntington's, Amyotrophic Lateral Sclerosis, and Spinal Muscular Atrophy. Can mitochondrial dysfunctions (affecting their morphology and activities) represent the early event eliciting the shift towards pathological neurobiological processes? Can mitochondria represent a common target against neurodegeneration? We also review here the drugs that target mitochondria in neurodegenerative diseases.

Activation of Systemic Inflammation and Oxidative Stress in Adolescent Girls with Polycystic Ovary Syndrome in Combination with Metabolic Disorders and Excessive Body Weight

Relevance: Mitochondrial dysfunction and systemic inflammation are believed to play pivotal role in the pathogenesis of polycystic ovary syndrome (PCOS) and related complications of metabolic disorders in adult patients. Though such researches are limited or almost absent in adolescents. The aim of the study is to evaluate the impact of mitochondrial dysfunction and systemic inflammation on PCOS pathogenesis during adolescence with regard to body mass index and insulin resistance. Design: a case-control study. Methods: The study included 95 adolescent girls (15 to 17 years old inclusive) diagnosed with PCOS based on the Rotterdam criteria. The control group consisted of 30 healthy girls of the same age with a regular menstrual cycle. All participants were subjected to a full clinical and instrumental examination, as well as an assessment of the levels of leptin, C-reactive protein (CRP), and malondialdehyde (MDA) as oxidative stress marker. Serum levels of IL-6, IL-10, IL-18, TNF-α, and plasma concentrations of macrophage migration inhibitory factor (MIF), sFas, and sFasL were determined. Patients with PCOS were divided into groups according to the presence of metabolic disorders (MD) (impaired glucose tolerance and/or over insulin resistance) and normal weight or excessive weight (NW or OW). Results: Patients with PCOS of NW in the absence of metabolic disorders (MD−/NW) had a lower concentration of MDA and a higher level of IL-10 compared to healthy girls (p < 0.05). The group (MD−/NW) was characterized with lower levels of CRP, leptin, MDA, and higher levels of sFasL, when compared to OW patients with PCOS in the absence of metabolic disorders (MD−/OW) (p < 0.05). Overweight adolescent girls with PCOS and metabolic disorders (MD+/OW) showed higher CRP, leptin, and a two-fold increase in IL-6 and IL-18 concentrations compared to the control group of healthy girls (p < 0.05 for all parameters). The group (MD+/OW) was also characterized with higher levels of CRP, leptin, MDA, IL-18, MIF (p < 0.05), when compared to overweight patients with PCOS in the absence of metabolic disorders (MD−/NW). In comparison with the MD−/OW group, the obese insulin resistant girls with PCOS (MD+/OW) had a highera level of IL-18 (p < 0.05). Moreover, the MD+/OW girls demonstrated a significant increase in CRP, MDA and IL-18 levels when compared to the MD+/NW group (p < 0.05). OW girls with PCOS without MD (MD−/OW) had lower concentrations of sFasL compared to healthy girls (p < 0.05), and higher levels of MDA compared to MD+/NW (p < 0.05). Adolescent girls of NW with PCOS and with MD (MD+/NW) had lower levels of MDA compared to the control group of healthy girls (p < 0.05). These data are confirmed by a correlation analysis and two-factor ANOVA test. Conclusions: Lean girls with PCOS demonstrate the protective mechanism of decrease in oxidative stress mediated by the activation of antioxidant defense, reduction of lipid peroxidation and systemic inflammation. Excessive weight and metabolic disorders in adolescents with PCOS are the most significant factors in reducing the capacity of antioxidant systems, activation of oxidative stress, mitochondrial dysfunction, and systemic inflammation.

HWL-088, a new potent free fatty acid receptor 1 (FFAR1) agonist, improves glucolipid metabolism and acts additively with metformin in ob/ob diabetic mice

BACKGROUND AND PURPOSE

The free fatty acid receptor 1 (FFAR1) plays an important role in glucose-stimulated insulin secretion making it an attractive anti-diabetic target. This study characterizes the pharmacological profile of HWL-088 (2-(2-fluoro-4-((2'-methyl-[1,1'- biphenyl]-3-yl)methoxy)phenoxy)acetic acid), a novel highly potent FFAR1 agonist in vitro and in vivo. Moreover, we investigated the long-term effects of HWL-088 alone and in combination with metformin in diabetic mice.

EXPERIMENTAL APPROACH

In vitro effects of HWL-088 on FFAR1 and PPARα/γ/δ were studied in cell-based assays. Glucose-dependent insulinotropic effects were evaluated in MIN6 cell line and in rats. Long-term effects on glucose and lipid metabolism were investigated in ob/ob mice.

KEY RESULTS

HWL-088 is a highly potent FFAR1 agonist (EC50 = 18.9 nM) with moderate PPARδ activity (EC50 = 570.9 nM) and promotes glucose-dependent insulin secretion in vitro and in vivo. Long-term administration of HWL-088 exhibited better glucose control and plasma lipid profiles than those of another FFAR1 agonist, TAK-875, and synergistic improvements were observed when combined with metformin. Moreover, HWL-088 and combination therapy improved β-cell function by up-regulation of pancreas duodenum homeobox-1, reduced fat accumulation in adipose tissue and alleviated fatty liver in ob/ob mice. The effect of HWL-088 involves a reduction in hepatic lipogenesis and oxidative stress, increased lipoprotein lipolysis, glucose uptake, mitochondrial function and fatty acid β-oxidation.

CONCLUSION AND IMPLICATIONS

These data indicate that long-term treatment with HWL-088, a highly potent FFAR1 agonist, improves glucose and lipid metabolism and may be useful for the treatment of diabetes mellitus by mono-therapy or combination with metformin.

Recurrent Hyperkalemia During General Anesthesia in a Dog

Objective: To describe the development of recurrent hyperkalemia in a dog that underwent general anesthesia at two different hospitals within a month. The definitive underlying cause of the hyperkalemia remains unknown. Case summary: A 11 year-old male neutered Rottweiler underwent general anesthesia on two separate occasions at two different hospitals for ophthalmic surgery within a month and developed marked hyperkalemia on each occasion. The patient received similar drug protocols in both instances, including propofol, midazolam, non-depolarizing neuromuscular blocking agents, and isoflurane inhalant anesthetic. The patient showed ECG changes consistent with hyperkalemia during the first anesthetic event, but not the second. No underlying cause of hyperkalemia was definitively identified. The patient responded to standard therapy for hyperkalemia on both occasions and serum potassium levels returned to normal. The patient was discharged from the hospital without further complications and post-operative rechecks showed persistently normal serum potassium levels. New or unique information provided: Considering that there is a relationship between the development of severe hyperkalemia and propofol administration in human patients, it is possible that such a relationship exists in veterinary patients. However, numerous other diseases and medications can also lead to peri-operative hyperkalemia. Veterinary professionals should be aware that hyperkalemia can develop intra-operatively and remains be an important differential diagnosis in bradycardic patients under anesthesia that are not responding to traditional therapies.

The EDCMET Project: Metabolic Effects of Endocrine Disruptors

Endocrine disruptors (EDs) are defined as chemicals that mimic, block, or interfere with hormones in the body's endocrine systems and have been associated with a diverse array of health issues. The concept of endocrine disruption has recently been extended to metabolic alterations that may result in diseases, such as obesity, diabetes, and fatty liver disease, and constitute an increasing health concern worldwide. However, while epidemiological and experimental data on the close association of EDs and adverse metabolic effects are mounting, predictive methods and models to evaluate the detailed mechanisms and pathways behind these observed effects are lacking, thus restricting the regulatory risk assessment of EDs. The EDCMET (Metabolic effects of Endocrine Disrupting Chemicals: novel testing METhods and adverse outcome pathways) project brings together systems toxicologists; experimental biologists with a thorough understanding of the molecular mechanisms of metabolic disease and comprehensive in vitro and in vivo methodological skills; and, ultimately, epidemiologists linking environmental exposure to adverse metabolic outcomes. During its 5-year journey, EDCMET aims to identify novel ED mechanisms of action, to generate (pre)validated test methods to assess the metabolic effects of Eds, and to predict emergent adverse biological phenotypes by following the adverse outcome pathway (AOP) paradigm.

Primrose syndrome: Characterization of the phenotype in 42 patients

Primrose syndrome (PS; MIM# 259050) is characterized by intellectual disability (ID), macrocephaly, unusual facial features (frontal bossing, deeply set eyes, down‐slanting palpebral fissures), calcified external ears, sparse body hair and distal muscle wasting. The syndrome is caused by de novo heterozygous missense variants in ZBTB20. Most of the 29 published patients are adults as characteristics appear more recognizable with age. We present 13 hitherto unpublished individuals and summarize the clinical and molecular findings in all 42 patients. Several signs and symptoms of PS develop during childhood, but the cardinal features, such as calcification of the external ears, cystic bone lesions, muscle wasting, and contractures typically develop between 10 and 16 years of age. Biochemically, anemia and increased alpha‐fetoprotein levels are often present. Two adult males with PS developed a testicular tumor. Although PS should be regarded as a progressive entity, there are no indications that cognition becomes more impaired with age. No obvious genotype‐phenotype correlation is present. A subgroup of patients with ZBTB20 variants may be associated with mild, nonspecific ID. Metabolic investigations suggest a disturbed mitochondrial fatty acid oxidation. We suggest a regular surveillance in all adult males with PS until it is clear whether or not there is a truly elevated risk of testicular cancer.

Ticagrelor reverses the mitochondrial dysfunction through preventing accumulated autophagosomes-dependent apoptosis and ER stress in insulin-resistant H9c2 myocytes

Ticagrelor, a P₂Y₁₂-receptor inhibitor, and a non-thienopyridine agent are used to treat diabetic patients via its effects on off-target mechanisms. However, the exact sub-cellular mechanisms by which ticagrelor exerts those effects remains to be elucidated. Accordingly, the present study aimed to examine whether ticagrelor influences directly the cardiomyocytes function under insulin resistance through affecting mitochondria-sarco(endo)plasmic reticulum (SER) cross-talk. Therefore, we analyzed the function and ultrastructure of mitochondria and SER in insulin resistance-mimicked (50-μM palmitic acid for 24-h) H9c2 cardiomyocytes in the presence or absence of ticagrelor (1-µM for 24-h). We found that ticagrelor treatment significantly prevented depolarization of mitochondrial membrane potential and increases in reactive oxygen species with a marked increase in the ATP level in insulin-resistant H9c2 cells. Ticagrelor treatment also reversed the increases in the resting level of free Ca²⁺ and mRNA level of P₂Y₁₂ receptors as well as preserved ER stress and apoptosis in insulin-resistant H9c2 cells. Furthermore, we determined marked repression with ticagrelor treatment in the increased number of autophagosomes and degeneration of mitochondrion, including swelling and loss of crista besides recoveries in enlargement and irregularity seen in SER in insulin-resistant H9c2 cells. Moreover, ticagrelor treatment could prevent the altered mRNA levels of Becklin-1 and type 1 equilibrative nucleoside transporter (ENT1), which are parallel to the preservation of ultrastructural ones. Our overall data demonstrated that ticagrelor can directly affect cardiomyocytes and provide marked protection against ER stress and dramatic induction of autophagosomes, and therefore, can alleviate the ER stress-induced oxidative stress increase and cell apoptosis during insulin resistance.

Subpopulation-specific differences in skeletal muscle mitochondria in humans with obesity: insights from studies employing acute nutritional and exercise stimuli

Mitochondria from skeletal muscle of humans with obesity often display alterations with respect to their morphology, proteome, biogenesis, and function. These changes in muscle mitochondria are considered to contribute to metabolic abnormalities observed in humans with obesity. Most of the evidence describing alterations in muscle mitochondria in humans with obesity, however, lacks reference to a specific subcellular location. This is despite data over the years showing differences in the morphology and function of subsarcolemmal (found near the plasma membrane) and intermyofibrillar (nested between the myofibrils) mitochondria in skeletal muscle. Recent studies reveal that impairments in mitochondrial function in obesity with respect to the subcellular location of the mitochondria in muscle are more readily evident following exposure of the skeletal muscle to physiological stimuli. In this review, we highlight the need to understand skeletal muscle mitochondria metabolism in obesity in a subpopulation-specific manner and in the presence of physiological stimuli that modify mitochondrial function in vivo. Experimental approaches employed under these conditions will allow for more precise characterization of impairments in skeletal muscle mitochondria and their implications in inducing metabolic dysfunction in human obesity.

Reduction of oxidative stress improves insulin signaling in cardiac tissue of obese mice

Objective

To evaluate the effects of oxidative stress on insulin signaling in cardiac tissue of obese mice.

Methods

Thirty Swiss mice were equally divided (n=10) into three groups: Control Group, Obese Group, and Obese Group Treated with N-acetylcysteine. After obesity and insulin resistance were established, the obese mice were treated with N-acetylcysteine at a dose of 50mg/kg daily for 15 days via oral gavage.

Results

Higher blood glucose levels and nitrite and carbonyl contents, and lower protein levels of glutathione peroxidase and phosphorylated protein kinase B were observed in the obese group when compared with their respective control. On the other hand, treatment with N-acetylcysteine was effective in reducing blood glucose levels and nitrite and carbonyl contents, and significantly increased protein levels of glutathione peroxidase and phosphorylated protein kinase B compared to the Obese Group.

Conclusion

Obesity and/or a high-lipid diet may result in oxidative stress and insulin resistance in the heart tissue of obese mice, and the use of N-acetylcysteine as a methodological and therapeutic strategy suggested there is a relation between them.

Proanthocyanidins Ameliorated Deficits of Lipid Metabolism in Type 2 Diabetes Mellitus Via Inhibiting Adipogenesis and Improving Mitochondrial Function

Proanthocyanidins are the major active compounds extracted from Iris lactea Pall. var. Chinensis (Fisch.) Koidz (I. lactea). Proanthocyanidins exhibit a variety of pharmacological activities such as anti-oxidation, anti-inflammation, anti-tumor, and lowering blood lipids. However, the underlying mechanism of its regulating effect on lipid metabolism in diabetic conditions remains unclear. The present study investigated the effects of I. lactea-derived proanthocyanidins on lipid metabolism in mice of type 2 diabetes mellitus (T2DM). Results demonstrated a beneficial effect of total proanthocyanidins on dysregulated lipid metabolism and hepatic steatosis in high-fat-diet/streptozocin (STZ)-induced T2DM. To identify the mechanisms, six flavan-3-ols were isolated from proanthocyanidins of I. lacteal and their effects on adipogenesis and dexamethasone (Dex)-induced mitochondrial dysfunctions in 3T3-L1 adipocytes were determined. In vitro studies showed flavan-3-ols inhibited adipogenesis and restored mitochondrial function after Dex-induced insulin resistance, being suggested by increased mitochondrial membrane potential, intracellular ATP contents, mitochondrial mass and mitochondrial biogenesis, and reduced reactive oxygen species. Among the six flavan-3-ols, procyanidin B3 and procyanidin B1 exhibited the strongest effects. Our study suggests potential of proanthocyanidins as therapeutic target for diabetes.

Mitophagy Is Essential for Maintaining Cardiac Function During High Fat Diet-Induced Diabetic Cardiomyopathy

RATIONALE

Diabetic patients develop cardiomyopathy characterized by hypertrophy, diastolic dysfunction, and intracellular lipid accumulation, termed lipotoxicity. Diabetic hearts utilize fatty acids as a major energy source, which produces high levels of oxidative stress, thereby inducing mitochondrial dysfunction.

OBJECTIVE

To elucidate how mitochondrial function is regulated in diabetic cardiomyopathy.

METHODS AND RESULTS

Mice were fed either a normal diet or high-fat diet (HFD, 60 kcal % fat). Although autophagic flux was activated by HFD consumption, peaking at 6 weeks ( P<0.05), it was attenuated thereafter. Mitophagy, evaluated with Mito-Keima, was increased after 3 weeks of HFD feeding (mitophagy area: 8.3% per cell with normal diet and 12.4% with HFD) and continued to increase even after 2 months ( P<0.05). By isolating adult cardiomyocytes from GFP-LC3 mice fed HFD, we confirmed that mitochondria were sequestrated by LC3-positive autophagosomes during mitophagy. In wild-type mice, cardiac hypertrophy, diastolic dysfunction (end diastolic pressure-volume relationship =0.051±0.009 in normal diet and 0.11±0.004 in HFD) and lipid accumulation occurred within 2 months of HFD feeding ( P<0.05). Deletion of atg7 impaired mitophagy, increased lipid accumulation, exacerbated diastolic dysfunction (end diastolic pressure-volume relationship =0.11±0.004 in wild type and 0.152±0.019 in atg7 cKO; P<0.05) and induced systolic dysfunction (end systolic pressure-volume relationship =24.86±2.46 in wild type and 15.93±1.76 in atg7 cKO; P<0.05) during HFD feeding. Deletion of Parkin partially inhibited mitophagy, increased lipid accumulation and exacerbated diastolic dysfunction (end diastolic pressure-volume relationship =0.124±0.005 in wild type and 0.176±0.018 in Parkin KO, P<0.05) in response to HFD feeding. Injection of TB1 (Tat-Beclin1) activated mitophagy, attenuated mitochondrial dysfunction, decreased lipid accumulation, and protected against cardiac diastolic dysfunction (end diastolic pressure-volume relationship =0.110±0.009 in Control peptide and 0.078±0.015 in TB1, P<0.05) during HFD feeding.

CONCLUSIONS

Mitophagy serves as an essential quality control mechanism for mitochondria in the heart during HFD consumption. Impairment of mitophagy induces mitochondrial dysfunction and lipid accumulation, thereby exacerbating diabetic cardiomyopathy. Conversely, activation of mitophagy protects against HFD-induced diabetic cardiomyopathy.

Detecting metabolic differences in fetal and adult sheep adipose and skeletal muscle tissues

The primary metabolic pathway required to produce ATP differs as a result of tissue type, developmental stage and substrate availability. We utilized molecular and histological techniques to define the metabolic status in foetal and adult, adipose and skeletal muscle tissues. Redox ratios of these tissues were also determined optically by two-photon microscopy. Adult perirenal adipose tissue had a higher optical redox ratio than fetal perirenal adipose tissue, which aligned with glycolysis being used for ATP production; whereas adult skeletal muscle had a lower optical redox ratio than fetal skeletal muscle, which aligned with oxygen demanding oxidative phosphorylation activity being utilized for ATP production. We have compared traditional molecular and microscopy techniques of metabolic tissue characterization with optical redox ratios to provide a more comprehensive report on the dynamics of tissue metabolism.

Metformin upregulates mitophagy in patients with T2DM: A randomized placebo-controlled study

Impaired mitochondrial autophagy (mitophagy) and NLRP3 inflammasome activation have been incriminated in the pathogenesis of T2DM. Metformin besides being an insulin sensitizer also induces autophagy; however, its effect on mitophagy and NLRP3 activation in patients with T2DM still remains elusive. Forty-five drug-naïve T2DM patients with HbA_1C 7%-9% (53-75 mmol/mol) were randomly assigned to receive either metformin, voglibose, or placebo for 3 months, and were also recommended for lifestyle intervention programme (n = 15 each). Mitochondrial oxidative stress (MOS) parameters, qPCR and immunoblotting of mitophagy-related markers (PINK1, PARKIN, MFN2, NIX, LC3-II, LAMP2), p-AMPKα (T172), and NLRP3 proteins, as well as transmission electron microscopy (TEM) for assessing mitochondrial morphology were performed in the mononuclear cells of study patients. Both metformin and voglibose showed a similar efficacy towards the reduction in HbA_1c and MOS indices. However, multivariate ANCOVA divulged that mRNA and protein expression of mitophagy markers, NLRP3 and p-AMPKα (T172), were significantly increased only with metformin therapy. Moreover, PINK1 expression displayed a significant positive association with HOMA-β indices, and TEM studies further confirmed reduced distortions in mitochondrial morphology in the metformin group only. Our observations underscore that metformin upregulates mitophagy and subsequently ameliorates the altered mitochondrial morphology and function, independent of its glucose-lowering effect. Further, restoration of normal mitochondrial phenotype may improve cellular function, including β-cells, which may prevent further worsening of hyperglycaemia in patients with T2DM.

Neuroprotective effect of Annona muricata-derived polysaccharides in neuronal HT22 cell damage induced by hydrogen peroxide

Crude extracts and phytochemical compounds derived from Annona muricata leaves have been demonstrated to exert neuroprotective effects. However, the neuroprotective effects of Annona muricata leaves-derived polysaccharide extracts (ALPs) have not been investigated. ALP treatment was shown to induce concentration-dependent antioxidant activity in HT22 cells, and to increase cell viability in H₂O₂-treated HT22 cells. These effects were correlated with a decrease in major components of oxidation, including: Ca²⁺, ROS, and malondialdehyde (MDA). Mediators of the intracellular response to oxidation, including Bax, cytochrome c, and cleaved caspases-3, -8, -9, MAPKs, and NF-κB, were positively influenced by ALP treatment under conditions of H₂O₂-mediated oxidative stress. In addition, ALP restored the expression of superoxide dismutase (SOD) and associated signaling pathways (PARP, PI3K/AKT and Nrf2-mediated HO-1/NQO-1) following H₂O₂ treatment. These results provide new pharmacological evidence that ALP facilitates neuroprotection via prevention of neuronal oxidative stress and promotion of cell survival signaling pathways.Abbreviations: ABTS: 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonicacid); AD: Alzheimer's disease; ALP: polysaccharide extracts isolated from Annona muricata leaves; ARE: antioxidant response element; DPPH: 1,1-diphenyl-picrylhydrazyl; DCFH-DA: 2',7'-dichlorofluorescin diacetate; ECL: electrochemiluminescence; ERK: extracellular regulated kinase; FBS: Fetal bovine serum; FITC: fluorescein isothiocyanate; FRAP: ferric reducing antioxidant power; HO-1: Heme oxygenase-1; JNK: c-jun N-terminal kinase; MAPKs: mitogen-activated protein kinases; MDA: malondialdehyde; MMP: mitochondrial membrane potential; MTT: 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide; NQO1: NAD(P)H:quinine oxidoreductase 1, Nrf2: nuclear factor-E2-related factor 2; PD: parkinson's disease; PI3K: phosphatidylinositol-3kinase; PVDF: polyvinylidene difluoride; ROS: reactive oxygen species; SOD: Superoxidedismutase; TPTZ: tripydyltriazine.

Grape seed proanthocyanidins prevent H2 O2 -induced mitochondrial dysfunction and apoptosis via SIRT 1 activation in embryonic kidney cells

Grape proanthocyanidins are compounds widely ingested in the diet. This study evaluated their effects on mitochondrial function, apoptosis, and sirtuin 1 and 3 expressions in HEK-293 cells exposed to H₂ O₂ . High-resolution mass spectrometry and high-performance liquid chromatography characterized the proanthocyanidins extract and the presence of procyanidins B and C was detected. The extract prevented H₂ O₂ -induced oxidative damage to proteins and lipids and depletion in superoxide dismutase activity. Moreover, it was able to regulate the expression of NADH: Ubiquinone oxidoreductase core subunit S7 and prevent mitochondrial electron transport chain dysfunction, ATP depletion, and apoptosis induced by H₂ O₂ . Finally, the extract was able to regulate sirtuin 1 and 3 expressions, thus maintaining cell viability. These data show that the grape seed proanthocyanidins can target mitochondrial proteins, which may represent an important approach for the management of numerous chronic illnesses associated with mitochondrial dysfunction. PRACTICAL APPLICATIONS: Proanthocyanidins are phenolic compounds abundant in regular diet, commonly found in grapes and derivatives, pomegranates, apples, and red fruits, all foods known for their beneficial effects on health. The current study highlights the role of proanthocyanidins as mitochondrial modulators that may explain the biological activity attributed to these compounds. This study brings evidence that proanthocyanidins might be considered as a value-added agent for the development of new nutraceutical and or pharmaceutical approaches.

Flavonoids and type 2 diabetes: Evidence of efficacy in clinical and animal studies and delivery strategies to enhance their therapeutic efficacy

Diabetes mellitus type 2 (T2DM) is a metabolic disorder develops due to the overproduction of free radicals where oxidative stress could contribute it. Possible factors are defective insulin signals, glucose oxidation, and degradation of glycated proteins as well as alteration in glutathione metabolism which induced hyperglycemia. Previous studies revealed a link between T2DM with oxidative stress, inflammation and insulin resistance which are assumed to be regulated by numerous cellular networks such as NF-κB, PI3K/Akt, MAPK, GSK3 and PPARγ. Flavonoids are ubiquitously present in the nature and classified according to their chemical structures for example, flavonols, flavones, flavan-3-ols, anthocyanidins, flavanones, and isoflavones. Flavonoids indicate poor bioavailability which could be improved by employing various nano-delivery systems against the occurrences of T2DM. These bioactive compounds exert versatile anti-diabetic activities via modulating targeted cellular signaling networks, thereby, improving glucose metabolism, α -glycosidase, and glucose transport or aldose reductase by carbohydrate metabolic pathway in pancreatic β-cells, hepatocytes, adipocytes and skeletal myofibres. Moreover, anti-diabetic properties of flavonoids also encounter diabetic related complications. This review article has designed to shed light on the anti-diabetic potential of flavonoids, contribution of oxidative stress, evidence of efficacy in clinical, cellular and animal studies and nano-delivery approaches to enhance their therapeutic efficacy. This article might give some new insights for therapeutic intervention against T2DM in near future.

Chronic Stress and Diabetes Mellitus: Interwoven Pathologies

Stress threatens the homeostasis and mobilizes a plethora of adaptive physiological and behavioral changes via the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system. The HPA axis influences the pituitary gland, hypothalamus and adrenal gland via a complex set of positive and negative feedback system. The feedback system operates in a well regulated neuroendocrine manner to reestablish the threatened body equilibrium. The HPA axis secreted major product is a glucocorticoid (cortisol) which is kept within a physiologically optimal range and serves to accomplish the various physiological functions crucial for survival. In chronically stressed individuals dishabituation of HPA axis is followed by increased release of glucocorticoids and catecholamines. Higher secretion of glucocorticoids influences glucose metabolism by promoting gluconeogenesis in the liver, suppressing glucose uptake (adipocytes and skeletal muscles), promoting lipolysis in adipocytes, suppressing insulin secretion, inflicting insulin resistance and inflammation. These biological changes alter neuroendocrine mechanisms and lead to maladaptive congregation of events that form the underlying cause of development of Type 2 diabetes (T2D). The currently reviewed evidences advocate that targeting stress mediated hypersecretion of glucocorticoids may be a viable approach for the treatment of T2D and to reinstate glucose homeostasis.

Increased Insulin Sensitivity by High-Altitude Hypoxia in Mice with High-Fat Diet-Induced Obesity Is Associated with Activated AMPK Signaling and Subsequently Enhanced Mitochondrial Biogenesis in Skeletal Muscles

BACKGROUND

This study aimed to investigate whether and how high altitude-associated ambient hypoxia affects insulin sensitivity in mice fed a high-fat diet (HFD).

METHODS

Mice were randomly divided into a control group (with normal diet feeding and low-altitude housing), LA/HFD group (with HFD feeding and low-altitude housing), and HA/HFD group (with HFD feeding and high-altitude housing).

RESULTS

After 8 weeks, mice in the HA/HFD group showed improved insulin sensitivity-related indices compared with the LA/HFD group. In mice residing in a low-altitude region, HFD significantly impaired mitochondrial respiratory function and mitochondrial DNA content in skeletal muscles, which was partially reversed in mice in the HA/HFD group. In addition, the fatty acid oxidation-related enzyme gene CPT1 (carnitine palmitoyltransferase 1) and genes related to mitochondrial biogenesis such as peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), nuclear respiratory factor 1 (NRF1), and mitochondrial transcription factor A (Tfam) were upregulated in the skeletal muscles of mice housed at high altitude, in comparison to in the LA/HFD group. Furthermore, AMPK (adenosine monophosphate-activated protein kinase) signaling was activated in the skeletal muscles, as evidenced by a higher expression of phosphorylated AMPK (p-AMPK) and protein kinase B (p-AKT) in the HA/HFD group than in the LA/HFD group.

CONCLUSION

Our study suggests that high-altitude hypoxia improves insulin sensitivity in mice fed an HFD, which is associated with AMPK activation in the skeletal muscle and consequently enhanced mitochondrial biogenesis and fatty acid oxidation. This work provides a molecular explanation for why high altitude is associated with a reduced incidence of insulin resistance in the obese population.

Sera Anti-P53 Antibody Provides New Information Which Explains the Link Between Diabetes and Cancer

INTRODUCTION

Abnormalities in glucose metabolism in diabetic patients may lead to an increased risk of certain cancers. Epidemiological studies and meta-analysis have shown that factors such as gender, age, obesity, and insulin resistance are related to cancer incidence. The anti-p53 antibody is a known cancer marker due to tumor-associated p53 accumulation. Many studies have aimed to unravel the link between diabetes and cancer. Here, we aimed to elucidate the impact of diabetes on malignancies by analyzing anti-p53 antibody in sera of type 2 diabetes mellitus (T2DM) patients.

MATERIALS AND METHODS

We conducted an observational study with a cross-sectional design. A total of 149 subjects comprised of 78 T2DM patients (32 with cancer risk and 46 subjects without cancer risk), 51 T2DM patients with cancer, and 20 healthy subjects as controls from multisites. The anti-p53 antibody was measured by enzyme-linked immunosorbent assay, while HbA1c was measured using the NGSP standardized method.

RESULTS

We observed an 8.3-fold (p<0.05) increase of anti-p53 antibody in the sera of T2DM patients and a 24-fold increase (p<0.001) in T2DM patients with cancer compared to healthy subjects. The anti-p53 antibodies significantly increased almost three times (p<0.05) in T2DM patients with cancer (0.72 U/mL±0.20) compared to T2DM patients (0.25 U/mL±0.05). Meanwhile, this antibody was almost undetectable in healthy subjects as a control group (0.03 U/mL±0.03). The anti-p53 antibody level was higher in T2DM with cancer risk patients. However, we did not find a significant difference for it in T2DM without cancer risk patients (0.19 U/mL±0.03) and T2DM with cancer risk patients (0.29 U/mL±0.08). Multivariate regression analysis showed that T2DM with cancer was the only one independent factor (beta=0.218, p=0.019) that could predict the increase of anti-p53 antibody, controlled by age, gender, BMI, DM duration, and HbA1c.

CONCLUSION

Our results showed that anti-p53 antibody almost not detected in healthy subjects, but 8.3-fold increase in the sera of T2DM patients and 24-fold increase in T2DM patients with cancer. Therefore, this biomarker provides new information which explains the link between diabetes and cancer.

The effects of acute BPA exposure on skeletal muscle mitochondrial function and glucose metabolism

Bisphenol A (BPA) is an environmental pollutant that has been associated with adverse health effects including skeletal muscle insulin resistance, a major contributor to the pathogenesis of type 2 diabetes (T2D). Early mitochondrial dysfunction and oxidative stress are linked to impaired glucose metabolism in skeletal muscle. In this study, we investigated the effects of BPA on skeletal muscle mitochondrial function and insulin sensitivity. L6 myotubes were treated with BPA (1 nM-10⁵ nM) during the last 24 h of differentiation. Following exposure to 10⁵ nM of BPA, resting and maximal oxygen consumption rates were decreased, whereas mitochondrial proton leak was increased. Overall metabolic activity, measured by redox ability, was decreased in L6 myotubes exposed to 10⁵ nM of BPA. At this concentration, insulin-stimulated glucose uptake was increased, which corresponded to an increased phosphorylation of the insulin signaling protein Akt, and increased glycolysis measured by extracellular acidification rate (ECAR). Acute BPA exposure did not alter levels of oxidative stress markers in muscle cells, but significantly increased mitochondrial proton leak, which is known to be involved in decreased ROS production. The effects of BPA on glucose uptake, but not mitochondrial function, were reversed by the use of an estrogen receptor antagonist. These results suggest that acute exposure of L6 myotubes at only high concentrations of BPA alters glucose metabolism, which is likely a compensatory response to reduced mitochondrial energy production capacity.

miR‑146a improves hepatic lipid and glucose metabolism by targeting MED1

Non-alcoholic fatty liver disease (NAFLD) is one of the most common chronic liver diseases worldwide. Increasing evidence has shown that microRNAs (miRNAs) play a vital role in the progression of NAFLD. The aim of the present study was to examine the expression level and roles of miR-146a in fatty liver of high-fat diet (HFD) and ob/ob mice and fatty acid-treated hepatic cells using RT-qPCR and western blot analysis. The results showed that the expression of miR-146a was significantly decreased in the livers of high-fat diet (HFD) and ob/ob mice and free fatty acid-stimulated cells by RT-qPCR. Overexpression of hepatic miR-146a improved glucose and insulin tolerance as well as lipid accumulation in the liver by promoting the oxidative metabolism of fatty acids. In addition, the overexpression of miR-146a increased the amount of mitochondria and promoted mitochondrial respiration in hepatocytes. Similarly, inhibition of miR-146a expression levels significantly reduced mitochondrial numbers in AML12 cells as well as the expression of mitochondrial respiration related genes. Additionally, MED1 was a direct target of miR-146a and restoring MED1 abolished the metabolic effects of miR-146a on lipid metabolism and mitochondrial function. Therefore, results of the present study identified a novel function of miR-146a in glucose and lipid metabolism in targeting MED1, suggesting that miR-146a serves as a potential therapeutic target for metabolic syndrome disease.

Mitochondrial Dysfunction in Heart Failure With Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is a complex syndrome with an increasingly recognized heterogeneity in pathophysiology. Exercise intolerance is the hallmark of HFpEF and appears to be caused by both cardiac and peripheral abnormalities in the arterial tree and skeletal muscle. Mitochondrial abnormalities can significantly contribute to impaired oxygen utilization and the resulting exercise intolerance in HFpEF. We review key aspects of the complex biology of this organelle, the clinical relevance of mitochondrial function, the methods that are currently available to assess mitochondrial function in humans, and the evidence supporting a role for mitochondrial dysfunction in the pathophysiology of HFpEF. We also discuss the role of mitochondrial function as a therapeutic target, some key considerations for the design of early-phase clinical trials using agents that specifically target mitochondrial function to improve symptoms in patients with HFpEF, and ongoing trials with mitochondrial agents in HFpEF.

Mitochondrial fission regulates germ cell differentiation by suppressing ROS-mediated activation of Epidermal Growth Factor Signaling in the Drosophila larval testis

Mitochondria are essential organelles that have recently emerged as hubs for several metabolic and signaling pathways in the cell. Mitochondrial morphology is regulated by constant fusion and fission events to maintain a functional mitochondrial network and to remodel the mitochondrial network in response to external stimuli. Although the role of mitochondria in later stages of spermatogenesis has been investigated in depth, the role of mitochondrial dynamics in regulating early germ cell behavior is relatively less-well understood. We previously demonstrated that mitochondrial fusion is required for germline stem cell (GSC) maintenance in the Drosophila testis. Here, we show that mitochondrial fission is also important for regulating the maintenance of early germ cells in larval testes. Inhibition of Drp1 in early germ cells resulted in the loss of GSCs and spermatogonia due to the accumulation of reactive oxygen species (ROS) and activation of the EGFR pathway in adjacent somatic cyst cells. EGFR activation contributed to premature germ cell differentiation. Our data provide insights into how mitochondrial dynamics can impact germ cell maintenance and differentiation via distinct mechanisms throughout development.