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

Update on the combination of myo-inositol/d-chiro-inositol for the treatment of polycystic ovary syndrome

In this article, we present a narrative review on the use of inositol in the treatment of polycystic ovary syndrome (PCOS). Of the different inositols that exist, only myo-inositol (MYO) and D-chiro inositol (DCI) have been studied in the treatment of PCOS. The results of the studies show that there is insufficient or controversial evidence to recommend the use of DCI alone, while MYO alone shows positive results and, above all, the MYO/DCI combination is effective when used at a ratio of at least 40:1, but there is enough rationale to further study ratios such as 66:1 to 100:1 as other possible effective combinations.

Macromolecules from mushrooms, venoms, microorganisms, and plants for diabetes treatment - Progress or setback?

Diabetes is a substantial public health issue, while its prevalence continues to rise worldwide, affecting millions of persons between the ages of 20 and 80, the development of new therapeutic classes improving glycemic control and consequently micro and macrovascular complications are needed. Today, diabetes treatment is daily for life, and should not be interrupted. However, insulin secretagogues medications, and exogenous self-administration of insulin provide efficient antidiabetic effects, but their misuse leads to hypoglycemic complications besides other risks, hence the need to look for other natural products not to use solely but in concert with others types of medications. In this review, we will highlight briefly the pathophysiology of diabetes and its complications, then we will report the main bioactive macromolecules derived from various sources of natural products providing anti-diabetic properties. However, further researches need to be carried out to face the limitations hampering the development of effective natural drugs for diabetes treatment.

Comparative Determination of Mitochondrial Biomarkers and Their Relationship With Insulin Resistance in Type 2 Diabetic Patients: An Observational Cross-Sectional Study

INTRODUCTION

Data suggest malfunctioning mitochondria reduce oxidation and adenosine triphosphate (ATP) production, disrupting insulin signalling. Cytochrome c (CC), acylcarnitine (AC) and citrate synthase (CS) are essential components of the mitochondria machinery and can be used as reliable biomarkers of mitochondrial dysfunction. This study aimed to determine whether mitochondrial biomarkers (AC, CS and CC) are altered in individuals with type 2 diabetes mellitus (T2DM) and to examine the association between these biomarkers and insulin resistance.

METHODOLOGY

A cross-sectional observational study that recruited 170 participants (88 with T2DM and 82 without DM) was conducted. Blood samples were collected from the recruits and analysed for levels of fasting glucose (FBG), AC, CS, CC, insulin, total cholesterol, triglycerides (TG), glycated haemoglobin (HbA1c) and magnesium. Blood pressure (BP) and anthropometric characteristics of participants were also taken. Appropriate formulas were used to determine %body fat, body mass index (BMI), waist-to-hip ratio (WHR), the homeostatic model assessment for insulin resistance (HOMA-IR) and insulin sensitivity (HOMA-β).

RESULTS

Patients with T2DM had higher levels of CC, %body fat, FBG, TG, HbA1c, BMI and HOMA-IR than controls (p < 0.05, respectively). Results showed a significant relationship between circulating CC levels versus HOMA-β (r = -0.40, p = 0.001), CS (r = -0.70, p = 0.001) and AC (r = -0.72, p = 0.001) levels in patients with T2DM. The adjusted odds increased in the T2DM patients for VLDL (OR = 6.66, p = 0.002), HbA1c (OR = 6.50, p = 0.001), FPG (OR = 3.17, p = 0.001), TG (OR = 2.36, p = 0.010), being female (OR = 2.09, p = 0.020) and CC (OR = 1.14, p = 0.016).

CONCLUSION

Overall, alterations in mitochondrial biomarkers, measured by AC, CC and CS, were observed in people with T2DM and showed a direct relationship with insulin resistance. These findings are potentially significant in Africa, although additional confirmation from a larger cohort is necessary.

The association between the size of adipocyte-derived extracellular vesicles and fasting serum triglyceride-glucose index as proxy measures of adipose tissue insulin resistance in a rat model of early-stage obesity

Introduction

Obesity is a complex disease that predisposes individuals to cardiometabolic alterations. It leads to adipose tissue (AT) dysfunction, which triggers insulin resistance (IR). This suggests that people with obesity develop local IR first and systemic IR later. AT secretes extracellular vesicles, which may be physiopathologically associated with the development of IR. Our aim was to evaluate the effect of a high-fat diet on different parameters of adiposity in a rat model of early-stage obesity and to determine if these parameters are associated with markers of systemic IR. In addition, we sought to explore the relationship between fasting blood measures of IR (Triglycerides/High Density Lipoprotein-cholesterol [TAG/HDL-c] and Triglycerides-Glucose Index [TyG Index]) with the size of adipocyte-derived extracellular vesicles (adEV).

Methods

We used a model of diet-induced obesity for ten weeks in Wistar rats exposed to a high-fat diet. Final weight gain was analyzed by Dual X-ray absorptiometry. Visceral obesity was measured as epididymal AT weight. IR was evaluated with fasting TyG Index & TAG/HDL-c, and adEV were isolated from mature adipocytes on ceiling culture.

Results

In the high-fat diet group, glucose and triglyceride blood concentrations were higher in comparison to the control group (Log2FC, 0.5 and 1.5 times higher, respectively). The values for TyG Index and adEV size were different between the control animals and the high-fat diet group. Multiple linear regression analyses showed that adEV size can be significantly associated with the TyG Index value, when controlling for epididymal AT weight.

Conclusion

Our results show that lipid and glucose metabolism, as well as the size and zeta potential of adEV are already altered in early-stage obesity and that adEV size can be significantly associated with liver and systemic IR, estimated by TyG Index.

Pathogenesis of MASLD and MASH - role of insulin resistance and lipotoxicity

BACKGROUND

Insulin resistance and lipotoxicity are extremely interconnected but fundamental in setting the stage for the development of MASLD/MASH.

AIM/METHODS

A comprehensive literature search was performed and key themes were synthesised to provide insight into the underlying molecular mechanisms of insulin resistance and lipotoxicity in the liver, muscle, pancreas and adipose tissue and how organ cross-talk is fundamental to driving disease pathogenesis.

RESULTS

Classical thinking postulates that excess FFA load exceeds the storage capacity of adipose tissue, which is predicated upon both genetic and environmental factors. This results in insulin resistance and compensatory hyperinsulinaemia by pancreatic beta cells to overcome target organ insulin resistance. As adipocyte dysfunction worsens, not only are excess FFA delivered to other organs, including skeletal muscle, pancreas and liver but a pro-inflammatory milieu is established with increases in IL-6, TNF-α and changes in adipokine levels (increased leptin and decreased adiponectin). With increased intramuscular lipid accumulation, lipotoxic species decrease insulin signalling, reduce glucose uptake by downregulation of GLUT4 and decrease glycogen synthesis. With this additional reduced capacity, hyperglycaemia is further exacerbated and increased FFA are delivered to the liver. The liver has the largest capacity to oxidise fat and to adapt to these stressors and, therefore, has become the last line of defence for excess lipid storage and utilisation, the capacity of which may be impacted by genetic and environmental factors. However, when the liver can no longer keep up with increasing FFA delivery and DNL, lipotoxic species accumulate with ensuing mitochondrial dysfunction, increased ER stress, oxidant stress and inflammasome activation, all of which drive hepatocyte injury and apoptosis. The resulting wound healing response, marked by stellate cell activation, drives collagen accumulation, progressive fibrosis, and, ultimately, end organ failure and death. This vicious cycle and complex interplay between insulin resistance, hyperinsulinaemia, lipotoxicity and multi-directional cross-talk among different target organs are critical drivers of MASLD/MASH.

CONCLUSIONS

Targeting tissue-specific insulin resistance and hyperinsulinaemia while decreasing FFA load (lipotoxicity) through dietary and lifestyle changes remain the best upstream interventions.

Exploring the impact of lipid droplets on the evolution and progress of hepatocarcinoma

Over the past 10 years, the biological role of lipid droplets (LDs) has gained significant attention in the context of both physiological and pathological conditions. Considerable progress has been made in elucidating key aspects of these organelles, yet much remains to be accomplished to fully comprehend the myriad functions they serve in the progression of hepatic tumors. Our current perception is that LDs are complex and active structures managed by a distinct set of cellular processes. This understanding represents a significant paradigm shift from earlier perspectives. In this review, we aim to recapitulate the function of LDs within the liver, highlighting their pivotal role in the pathogenesis of metabolic dysfunction-associated steatotic liver disease (MASLD) (Hsu and Loomba, 2024) and their contribution to the progression towards more advanced pathological stages up to hepatocellular carcinoma (HC) (Farese and Walther, 2009). We are aware of the molecular complexity and changes occurring in the neoplastic evolution of the liver. Our attempt, however, is to summarize the most important and recent roles of LDs across both healthy and all pathological liver states, up to hepatocarcinoma. For more detailed insights, we direct readers to some of the many excellent reviews already available in the literature (Gluchowski et al., 2017; Hu et al., 2020; Seebacher et al., 2020; Paul et al., 2022).

Modulation of adipose tissue metabolism by exosomes in obesity

Obesity and its related metabolic complications represent a significant global health challenge. Central to this is the dysregulation of glucolipid metabolism, with a predominant focus on glucose metabolic dysfunction in the current research, whereas adipose metabolism impairment garners less attention. Exosomes (EXs), small extracellular vesicles (EVs) secreted by various cells, have emerged as important mediators of intercellular communication and have the potential to be biomarkers, targets, and therapeutic tools for diverse diseases. In particular, EXs have been found to play a role in adipose metabolism by transporting cargoes such as noncoding RNAs (ncRNA), proteins, and other factors. This review article summarizes the current understanding of the role of EXs in mediating adipose metabolism disorders in obesity. It highlights their roles in adipogenesis (encompassing adipogenic differentiation and lipid synthesis), lipid catabolism, lipid transport, and white adipose browning. The insights provided by this review offer new avenues for developing exosome-based therapies to treat obesity and its associated comorbidities.

Resveratrol relieves HFD-induced insulin resistance in skeletal muscle tissue through antioxidant capacity enhancement and the Nrf2-Keap1 signaling pathway

BACKGROUND

Resveratrol has received much attention due to its beneficial effects including antioxidant activity. The purpose of this study was to investigate the therapeutic effects of resveratrol treatment on oxidative stress and insulin resistance in the skeletal muscle of high-fat diet (HFD)-fed animals.

METHODS AND RESULTS

A total of 30 six-week-old C57BL/6J mice were randomly allocated to three groups (10 animals in each group): The control group in which mice were fed a normal chow diet (NCD); the HFD group in which mice were fed an HFD for 26 weeks; and the HFD-resveratrol group in which HFD was replaced by a resveratrol supplemented-HFD (400 mg/kg diet) after 10 weeks of HFD feeding. At the end of this period, gastrocnemius muscle samples were examined to determine insulin resistance and the oxidative status in the presence of HFD and resveratrol. Resveratrol supplementation in HFD-fed mice reduced body and adipose tissue weight, improved insulin sensitivity, and decreased oxidative stress as indicated by lower malonaldehyde (MDA) levels and higher total antioxidant capacity. The supplement also increased the expression and activity of antioxidative enzymes in gastrocnemius muscle and modulated Nrf2 and Keap1 expression levels.

CONCLUSIONS

These results suggest that resveratrol is effective in improving the antioxidant defense system of the skeletal muscle in HFD-fed mice, indicating its therapeutic potential to combat diseases associated with insulin resistance and oxidative stress.

Beta-Cell Tipe1 Orchestrates Insulin Secretion and Cell Proliferation by Promoting Gαs/cAMP Signaling via USP5

Inadequate β-cell mass and insulin secretion are essential for the development of type 2 diabetes (T2D). TNF-α-induced protein 8-like 1 (Tipe1) plays a crucial role in multiple diseases, however, a specific role in T2D pathogenesis remains largely unexplored. Herein, Tipe1 as a key regulator in T2D, contributing to the maintenance of β cell homeostasis is identified. The results show that the β-cell-specific knockout of Tipe1 (termed Ins2-Tipe1BKO) aggravated diabetic phenotypes in db/db mice or in mice with high-fat diet-induced diabetes. Notably, Tipe1 improves β cell mass and function, a process that depends on Gαs, the α subunit of the G-stimulating protein. Mechanistically, Tipe1 inhibited the K48-linked ubiquitination degradation of Gαs by recruiting the deubiquitinase USP5. Consequently, Gαs or cAMP agonists almost completely restored the dysfunction of β cells observed in Ins2-Tipe1BKO mice. The findings characterize Tipe1 as a regulator of β cell function through the Gαs/cAMP pathway, suggesting that Tipe1 may emerge as a novel target for T2D intervention.

The potential of therapeutic strategies targeting mitochondrial biogenesis for the treatment of insulin resistance and type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a persistent metabolic disorder marked by deficiencies in insulin secretion and/or function, affecting various tissues and organs and leading to numerous complications. Mitochondrial biogenesis, the process by which cells generate new mitochondria utilizing existing ones plays a crucial role in energy homeostasis, glucose metabolism, and lipid handling. Recent evidence suggests that promoting mitochondrial biogenesis can alleviate insulin resistance in the liver, adipose tissue, and skeletal muscle while improving pancreatic β-cell function. Moreover, enhanced mitochondrial biogenesis has been shown to ameliorate T2DM symptoms and may contribute to therapeutic effects for the treatment of diabetic nephropathy, cardiomyopathy, retinopathy, and neuropathy. This review summarizes the intricate connection between mitochondrial biogenesis and T2DM, highlighting the potential of novel therapeutic strategies targeting mitochondrial biogenesis for T2DM treatment and its associated complications. It also discusses several natural products that exhibit beneficial effects on T2DM by promoting mitochondrial biogenesis.

Celebrating a decade of exercise physiology and metabolism research in physiological reports

During its first decade of life, Physiological Reports has become a home for well-conceived and rigorously performed exercise physiology and metabolism studies. The breadth of research within this area is impressive, covering exercise-induced increases in skeletal muscle gene expression to the effects of exercise on the gut microbiome. The purpose of the current review is to highlight some of the impactful exercise physiology and metabolism papers published in the journal and to look ahead to what areas exercise physiology publications might address in the next 10 years.

SGLT2 inhibitor improves the prognosis of patients with coronary heart disease and prevents in-stent restenosis

Coronary heart disease is a narrowing or obstruction of the vascular cavity caused by atherosclerosis of the coronary arteries, which leads to myocardial ischemia and hypoxia. At present, percutaneous coronary intervention (PCI) is an effective treatment for coronary atherosclerotic heart disease. Restenosis is the main limiting factor of the long-term success of PCI, and it is also a difficult problem in the field of intervention. Sodium-glucose cotransporter 2 (SGLT2) inhibitor is a new oral glucose-lowering agent used in the treatment of diabetes in recent years. Recent studies have shown that SGLT2 inhibitors can effectively improve the prognosis of patients after PCI and reduce the occurrence of restenosis. This review provides an overview of the clinical studies and mechanisms of SGLT2 inhibitors in the prevention of restenosis, providing a new option for improving the clinical prognosis of patients after PCI.

Consumption of a Taiwanese cafeteria diet induces metabolic disorders and fecal flora changes in obese rats

OBJECTIVES

Among diet-induced obesity animal models, the cafeteria diet, which contains human junk food and processed foods, is a popular experimental animal diets in Western countries. Consumption of a cafeteria diet can lead to the development of obesity and non-alcoholic liver disease in as soon as 2 mo, which more accurately reflects human eating patterns. The aim of this study was to establish a Taiwanese cafeteria diet and compare it with a traditional lard-based, 60% high-fat diet in a 12-wk animal model.

METHODS

Six-wk-old male Wistar rats were assigned to the following three groups: control diet (C; LabDiet 5001); high-fat diet (HFD; 60% HFD); and the Taiwanese cafeteria diet (CAF).

RESULTS

At the end of the study, weight gain and steatosis were observed in the HF and CAF groups. Compared with the HFD group, rats in the CAF group showed significantly higher plasma triacylglycerol concentrations and insulin resistance, which may have been correlated with increased inflammatory responses. Significantly lower hepatic sterol regulatory element-binding protein-1c and insulin receptor substrate-1 protein expressions were observed in the CAF group compared with the HFD group. Additionally, disruption of the microbiotic composition followed by increased obesity-related bacteria was observed in the CAF group.

CONCLUSIONS

The present study confirmed that the Taiwanese cafeteria diet-induced rat model provided a potential platform for investigating obesity-related diseases.

Momordica balsamina improves glucose handling in a diet-induced prediabetic rat model

Prolonged exposure to high energy diets has been implicated in the development of pre-diabetes, a long-lasting condition that precedes type 2 diabetes mellitus (T2DM). A combination of pharmacological treatment and dietary interventions are recommended to prevent the progression of pre-diabetes to T2DM. However, poor patient compliance leads to negligence of the dietary intervention and thus reduced drug efficiency. Momordica balsamina (MB) has been reported to possess anti-diabetic effects in type 1 diabetic rats. However, the effects of this medicinal plant in conjunction with dietary intervention on pre-diabetes have not yet been established. Consequently, this study sought to evaluate the effects of MB on glucose homeostasis in a diet-induced pre-diabetes rat model in the presence and absence of dietary intervention. Pre-diabetes was induced on male Sprague Dawley rats by a high fat high carbohydrate (HFHC) diet for a period of 20 weeks. Pre-diabetic male Sprague Dawley rats were treated with MB (250 mg/kg p.o.) in both the presence and absence of dietary intervention once a day every third day for a period of 12 weeks. The administration of MB with and without dietary intervention resulted in significantly improved glucose homeostasis through reduced caloric intake, body weights, with reduced plasma ghrelin concentration and glycated hemoglobin by comparison to the pre-diabetic control. MB administration also improved insulin sensitivity as evidenced by the expression of glucose transporter 4 (GLUT 4) and glycogen synthase on the prediabetic treated animals. These results suggest that MB has the potential to be used to manage pre-diabetes and prevent the progression to overt type 2 diabetes as it demonstrated the ability to restore glucose homeostasis even in the absence of dietary and lifestyle intervention.

No net utilization of intramuscular lipid droplets during repeated high-intensity intermittent exercise

Intramuscular lipids are stored as subsarcolemmal or intramyofibrillar droplets with potential diverse roles in energy metabolism. We examined intramuscular lipid utilization through transmission electron microscopy during repeated high-intensity intermittent exercise, an aspect that is hitherto unexplored. Seventeen moderately to well-trained males underwent three periods (EX1-EX3) of 10 × 45-s high-intensity cycling [∼100%-120% Wattmax (Wmax)] combined with maximal repeated sprints (∼250%-300% Wmax). M. vastus lateralis biopsies were obtained at baseline, after EX1, and EX3. During the complete exercise session, no net decline in either subsarcolemmal or intermyofibrillar lipid volume density occurred. However, a temporal relationship emerged for subsarcolemmal lipids with an ∼11% increase in droplet size after EX1 (P = 0.024), which reverted to baseline levels after EX3 accompanied by an ∼30% reduction in the numerical density of subsarcolemmal lipid droplets compared with both baseline (P = 0.019) and after EX1 (P = 0.018). Baseline distinctions were demonstrated with an approximately twofold higher intermyofibrillar lipid volume in type 1 versus type 2 fibers (P = 0.008), mediated solely by a higher number rather than the size of lipid droplets (P < 0.001). No fiber-type-specific differences were observed in subsarcolemmal lipid volume although type 2 fibers exhibited ∼17% larger droplets (P = 0.034) but a lower numerical density (main effect; P = 0.010) including 3% less droplets at baseline. Collectively, these findings suggest that intramuscular lipids do not serve as an important substrate during high-intensity intermittent exercise; however, the repeated exercise pattern mediated a temporal remodeling of the subsarcolemmal lipid pool. Furthermore, fiber-type- and compartment-specific differences were found at baseline underscoring the heterogeneity in lipid droplet deposition.NEW & NOTEWORTHY Undertaking a severe repeated high-intensity intermittent exercise protocol led to no net decline in neither subsarcolemmal nor intermyofibrillar lipid content in the thigh muscle of young moderately to well-trained participants. However, a temporal remodeling of the subsarcolemmal pool of lipid droplets did occur indicative of potential transient lipid accumulation. Moreover, baseline fiber-type distinctions in subcellular lipid droplet deposition were present underscoring the diversity in lipid droplet storage among fiber types and subcellular regions.

The effect of chronic high-intensity interval training programs on glycaemic control, aerobic resistance, and body composition in type 2 diabetic patients: a meta-analysis

BACKGROUND

Type 2 diabetes is an increasing health problem worldwide. HIIT has been proposed as an exercise alternative to be part of integral type 2 diabetes treatment.

OBJECTIVE

The aim of this meta-analysis was to determine the effect of different types of chronic HIIT on glycaemic control, aerobic resistance, and body composition in individuals above 18 years with T2D.

DESIGN

This meta-analysis was conducted in accordance with the Preferred Reporting Items for Systematic Review and Meta-analysis (PRISMA) statement and was registered with PROSPERO on November 21st, 2021.

DATA SOURCES

A systematic literature search of the following databases: EbscoHost (Academic Search Ultimate, Fuente Académica Plus, MEDline and SportDiscus), Web of Science, PubMed, and EMBASE between April of 2021 and April of 2023 was conducted.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Eligibility criteria included (1) participants aged ≥ 18 years with a diagnosis of type 2 diabetes, (2) an HIIT protocol with detailed description, (3) control group and/or continuous aerobic training comparison group, (4) report of pre-test and post-test values for at least one of the studied variables (from glycaemic control, aerobic resistance, and/or body composition), and (5) experimental or quasi-experimental intervention design.

ANALYSES

Meta-analysis was made by a pre-post-test between-group analysis following the inverse variance heterogeneity model for each variable, and then, a subgroup analysis by type of HIIT was conducted.

RESULTS

Of the 2817 records obtained, 180 records were included for meta-analysis. Significant improvements were found in the most part of the variables when HIIT was compared to control group, while fat-free mass kept without changes. HIIT vs. continuous aerobic training results showed and advantage in favor of HIIT for fasting blood glycemia. Subgroup analysis refers a possible advantage of SI-HIIT and SIT-HIIT in the improvement of fasting glycemia and SIT-HIIT advantage in HOMA 1-IR decrease.

CONCLUSIONS

HIIT improves glycaemic control, aerobic resistance, and % fat and waist circumference, and kept fat-free mass unchanged in individuals with T2D. SI-HIIT and SIT-HIIT could be better than the other types of HIIT. HIIT benefit is similar to continuous aerobic training except for fasting blood glycemia.

Calcium's Role and Signaling in Aging Muscle, Cellular Senescence, and Mineral Interactions

Calcium research, since its pivotal discovery in the early 1800s through the heating of limestone, has led to the identification of its multi-functional roles. These include its functions as a reducing agent in chemical processes, structural properties in shells and bones, and significant role in cells relating to this review: cellular signaling. Calcium signaling involves the movement of calcium ions within or between cells, which can affect the electrochemical gradients between intra- and extracellular membranes, ligand binding, enzyme activity, and other mechanisms that determine cell fate. Calcium signaling in muscle, as elucidated by the sliding filament model, plays a significant role in muscle contraction. However, as organisms age, alterations occur within muscle tissue. These changes include sarcopenia, loss of neuromuscular junctions, and changes in mineral concentration, all of which have implications for calcium's role. Additionally, a field of study that has gained recent attention, cellular senescence, is associated with aging and disturbed calcium homeostasis, and is thought to affect sarcopenia progression. Changes seen in calcium upon aging may also be influenced by its crosstalk with other minerals such as iron and zinc. This review investigates the role of calcium signaling in aging muscle and cellular senescence. We also aim to elucidate the interactions among calcium, iron, and zinc across various cells and conditions, ultimately deepening our understanding of calcium signaling in muscle aging.

Resveratrol as a potential protective compound against skeletal muscle insulin resistance

The increasing prevalence of type 2 diabetes has become a major global problem. Insulin resistance has a central role in pathophysiology of type 2 diabetes. Skeletal muscle is responsible for the disposal of most of the glucose under conditions of insulin stimulation, and insulin resistance in skeletal muscle causes dysregulation of glucose homeostasis in the whole body. Despite the current pharmaceutical and non-pharmacological treatment strategies to combat diabetes, there is still a need for new therapeutic agents due to the limitations of the therapeutic agents. Meanwhile, plant polyphenols have attracted the attention of researchers for their use in the treatment of diabetes and have gained popularity. Resveratrol, a stilbenoid polyphenol, exists in various plant sources, and a growing body of evidence suggests its beneficial properties, including antidiabetic activities. The present review aimed to provide a summary of the role of resveratrol in insulin resistance in skeletal muscle and its related mechanisms. To achieve the objectives, by searching the PubMed, Scopus and Web of Science databases, we have summarized the results of all cell culture, animal, and human studies that have investigated the effects of resveratrol in different models on insulin resistance in skeletal muscle.

The Impact of Taurine on Obesity-Induced Diabetes Mellitus: Mechanisms Underlying Its Effect

This review explores the potential benefits of taurine in ameliorating the metabolic disorders of obesity and type 2 diabetes (T2D), highlighting the factors that bridge these associations. Relevant articles and studies were reviewed to conduct a comprehensive analysis of the relationship between obesity and the development of T2D and the effect of taurine on those conditions. The loss of normal β-cell function and development of T2D are associated with obesity-derived insulin resistance. The occurrence of diabetes has been linked to the low bioavailability of taurine, which plays critical roles in normal β-cell function, anti-oxidation, and anti-inflammation. The relationships among obesity, insulin resistance, β-cell dysfunction, and T2D are complex and intertwined. Taurine may play a role in ameliorating these metabolic disorders through different pathways, but further research is needed to fully understand its effects and potential as a therapeutic intervention.

Plant-derived cell-penetrating microprotein α-astratide aM1 targets Akt signaling and alleviates insulin resistance

Insulin-resistant diabetes is a common metabolic disease with serious complications. Treatments directly addressing the underlying molecular mechanisms involving insulin resistance would be desirable. Our laboratory recently identified a proteolytic-resistant cystine-dense microprotein from huáng qí (Astragalus membranaceus) called α-astratide aM1, which shares high sequence homology to leginsulins. Here we show that aM1 is a cell-penetrating insulin mimetic, enters cells by endocytosis, and activates the PI3K/Akt signaling pathway independent of the insulin receptor leading to translocation of glucose transporter GLUT4 to the cell surface to promote glucose uptake. We also showed that aM1 alters gene expression, suppresses lipid synthesis and uptake, and inhibits intracellular lipid accumulation in myotubes and adipocytes. By reducing intracellular lipid accumulation and preventing lipid-induced, PKCθ-mediated degradation of IRS1/2, aM1 restores glucose uptake to overcome insulin resistance. These findings highlight the potential of aM1 as a lead for developing orally bioavailable insulin mimetics to expand options for treating diabetes.

Implications of receptor for advanced glycation end products for progression from obesity to diabetes and from diabetes to cancer

Obesity and type 2 diabetes mellitus (T2DM) are chronic pathologies with a high incidence worldwide. They share some pathological mechanisms, including hyperinsulinemia, the production and release of hormones, and hyperglycemia. The above, over time, affects other systems of the human body by causing tissue hypoxia, low-grade inflammation, and oxidative stress, which lay the pathophysiological groundwork for cancer. The leading causes of death globally are T2DM and cancer. Other main alterations of this pathological triad include the accumulation of advanced glycation end products and the release of endogenous alarmins due to cell death (i.e., damage-associated molecular patterns) such as the intracellular proteins high-mobility group box protein 1 and protein S100 that bind to the receptor for advanced glycation products (RAGE) - a multiligand receptor involved in inflammatory and metabolic and neoplastic processes. This review analyzes the latest advanced reports on the role of RAGE in the development of obesity, T2DM, and cancer, with an aim to understand the intracellular signaling mechanisms linked with cancer initiation. This review also explores inflammation, oxidative stress, hypoxia, cellular senescence, RAGE ligands, tumor microenvironment changes, and the “cancer hallmarks” of the leading tumors associated with T2DM. The assimilation of this information could aid in the development of diagnostic and therapeutic approaches to lower the morbidity and mortality associated with these diseases.

The circadian rhythm: an influential soundtrack in the diabetes story

Type 2 Diabetes Mellitus (T2DM) has been the main category of metabolic diseases in recent years due to changes in lifestyle and environmental conditions such as diet and physical activity. On the other hand, the circadian rhythm is one of the most significant biological pathways in humans and other mammals, which is affected by light, sleep, and human activity. However, this cycle is controlled via complicated cellular pathways with feedback loops. It is widely known that changes in the circadian rhythm can alter some metabolic pathways of body cells and could affect the treatment process, particularly for metabolic diseases like T2DM. The aim of this study is to explore the importance of the circadian rhythm in the occurrence of T2DM via reviewing the metabolic pathways involved, their relationship with the circadian rhythm from two perspectives, lifestyle and molecular pathways, and their effect on T2DM pathophysiology. These impacts have been demonstrated in a variety of studies and led to the development of approaches such as time-restricted feeding, chronotherapy (time-specific therapies), and circadian molecule stabilizers.

Fine particulate matter (PM2.5)-induced pulmonary oxidative stress contributes to increases in glucose intolerance and insulin resistance in a mouse model of circadian dyssynchrony

Results of human and animal studies independently suggest that either ambient fine particulate matter (PM2.5) air pollution exposure or a disturbed circadian rhythm (circadian dyssynchrony) are important contributing factors to the rapidly evolving type-2-diabetes (T2D) epidemic. The objective of this study is to investigate whether circadian dyssynchrony increases the susceptibility to PM2.5 and how PM2.5 affects metabolic health in circadian dyssynchrony. We examined systemic and organ-specific changes in glucose homeostasis and insulin sensitivity in mice maintained on a regular (12/12 h light/dark) or disrupted (18/6 h light/dark, light-induced circadian dyssynchrony, LICD) light cycle exposed to air or concentrated PM2.5 (CAP, 6 h/day, 30 days). Exposures during Zeitgeber ZT3-9 or ZT11-17 (Zeitgeber in circadian time, ZT0 = begin of light cycle) tested for time-of-day PM2.5 sensitivity (chronotoxicity). Mice transgenic for lung-specific overexpression of extracellular superoxide dismutase (ecSOD-Tg) were used to assess the contribution of CAP-induced pulmonary oxidative stress. Both, CAP exposure from ZT3-9 or ZT11-17, decreased glucose tolerance and insulin sensitivity in male mice with LICD, but not in female mice or in mice kept on a regular light cycle. Although changes in glucose homeostasis in CAP-exposed male mice with LICD were not associated with obesity, they were accompanied by white adipose tissue (WAT) inflammation, impaired insulin signaling in skeletal muscle and liver, and systemic and pulmonary oxidative stress. Preventing CAP-induced oxidative stress in the lungs mitigated the CAP-induced decrease in glucose tolerance and insulin sensitivity in LICD. Our results demonstrate that circadian dyssynchrony is a novel susceptibility state for PM2.5 and suggest that PM2.5 by inducing pulmonary oxidative stress increases glucose intolerance and insulin resistance in circadian dyssynchrony.

NF-κB-Inducing Kinase Provokes Insulin Resistance in Skeletal Muscle of Obese Mice

Skeletal muscle is crucial for preserving glucose homeostasis. Insulin resistance and abnormalities in glucose metabolism result from a range of pathogenic factors attacking skeletal muscle in obese individuals. To relieve insulin resistance and restore glucose homeostasis, blocking the cell signaling pathways induced by those pathogenic factors seems an attractive strategy. It has been discovered that insulin sensitivity in obese people is inversely linked with the activity of NF-κB inducing kinase (NIK) in skeletal muscle. In order to evaluate NIK's pathological consequences, mechanism of action, and therapeutic values, an obese mouse model reproduced by feeding a high-fat diet was treated with a NIK inhibitor, B022. C2C12 myoblasts overexpressing NIK were utilized to assess insulin signaling and glucose uptake. B022 thus prevented high-fat diet-induced NIK activation and insulin desensitization in skeletal muscle. The insulin signaling in C2C12 myoblasts was compromised by the upregulation of NIK brought on by oxidative stress, lipid deposition, inflammation, or adenoviral vector. This inhibition of insulin action is mostly due to an inhibitory serine phosphorylation of IRS1 caused by ERK, JNK, and PKC that were activated by NIK. In summary, NIK integrates signals from several pathogenic factors to impair insulin signaling by igniting a number of IRS1-inhibiting kinases, and it also has significant therapeutic potential for treating insulin resistance.

FALCON systematically interrogates free fatty acid biology and identifies a novel mediator of lipotoxicity

Cellular exposure to free fatty acids (FFAs) is implicated in the pathogenesis of obesity-associated diseases. However, there are no scalable approaches to comprehensively assess the diverse FFAs circulating in human plasma. Furthermore, assessing how FFA-mediated processes interact with genetic risk for disease remains elusive. Here, we report the design and implementation of fatty acid library for comprehensive ontologies (FALCON), an unbiased, scalable, and multimodal interrogation of 61 structurally diverse FFAs. We identified a subset of lipotoxic monounsaturated fatty acids associated with decreased membrane fluidity. Furthermore, we prioritized genes that reflect the combined effects of harmful FFA exposure and genetic risk for type 2 diabetes (T2D). We found that c-MAF-inducing protein (CMIP) protects cells from FFA exposure by modulating Akt signaling. In sum, FALCON empowers the study of fundamental FFA biology and offers an integrative approach to identify much needed targets for diverse diseases associated with disordered FFA metabolism.

Dysregulated autophagy: A key player in the pathophysiology of type 2 diabetes and its complications

Autophagy is essential in regulating the turnover of macromolecules via removing damaged organelles, misfolded proteins in various tissues, including liver, skeletal muscles, and adipose tissue to maintain the cellular homeostasis. In these tissues, a specific type of autophagy maintains the accumulation of lipid droplets which is directly related to obesity and the development of insulin resistance. It appears to play a protective role in a normal physiological environment by eliminating the invading pathogens, protein aggregates, and damaged organelles and generating energy and new building blocks by recycling the cellular components. Ageing is also a crucial modulator of autophagy process. During stress conditions involving nutrient deficiency, lipids excess, hypoxia etc., autophagy serves as a pro-survival mechanism by recycling the free amino acids to maintain the synthesis of proteins. The dysregulated autophagy has been found in several ageing associated diseases including type 2 diabetes (T2DM), cancer, and neurodegenerative disorders. So, targeting autophagy can be a promising therapeutic strategy against the progression to diabetes related complications. Our article provides a comprehensive outline of understanding of the autophagy process, including its types, mechanisms, regulation, and role in the pathophysiology of T2DM and related complications. We also explored the significance of autophagy in the homeostasis of β-cells, insulin resistance (IR), clearance of protein aggregates such as islet amyloid polypeptide, and various insulin-sensitive tissues. This will further pave the way for developing novel therapeutic strategies for diabetes-related complications.

Association of skeletal muscle mass and its change with diabetes occurrence: a population-based cohort study

BACKGROUND

Low muscle mass likely results in reduced capacity for glucose disposal, leading to a significant but under-appreciated contribution to increasing the risk of diabetes. But few prospective studies have investigated the association between the loss of muscle mass and the occurrence of diabetes. We aimed to investigate whether short-term changes in muscle mass affect the incidence of diabetes in a Chinese population.

METHODS

This study included 1275 individuals without evident diabetes at baseline. In the baseline and re-examination, individuals completed the risk factors survey and underwent body composition measurement. Muscle mass index was defined as the percentage skeletal muscle mass, which was measured by an automatic bioelectric analyzer.

RESULTS

After a median follow-up of 2.1 years, 142 individuals developed diabetes (11.1%). There was an inverse association between basal skeletal muscle mass index and the risk of diabetes in participants with impaired glucose regulation but not in those with normal glucose tolerance. Multivariate-adjusted hazard ratios for the risk of developing diabetes were 0.85 (95% CI: 0.74-0.98) and 1.15 (95% CI: 0.98-1.34), respectively. Furthermore, Cox regression analysis revealed that a two-year change in skeletal muscle mass was also inversely associated with the incidence of diabetes in both participants with normal glucose tolerance and with impaired glucose regulation (HR: 0.76, 95% CI: 0.65-0.89; HR: 0.81, 95% CI: 0.71-0.91).

CONCLUSIONS

These findings emphasized the importance of early detection and control of muscle mass loss for the prevention of diabetes.

Antimicrobial protein REG3A regulates glucose homeostasis and insulin resistance in obese diabetic mice

Innate immune mediators of pathogen clearance, including the secreted C-type lectins REG3 of the antimicrobial peptide (AMP) family, are known to be involved in the regulation of tissue repair and homeostasis. Their role in metabolic homeostasis remains unknown. Here we show that an increase in human REG3A improves glucose and lipid homeostasis in nutritional and genetic mouse models of obesity and type 2 diabetes. Mice overexpressing REG3A in the liver show improved glucose homeostasis, which is reflected in better insulin sensitivity in normal weight and obese states. Delivery of recombinant REG3A protein to leptin-deficient ob/ob mice or wild-type mice on a high-fat diet also improves glucose homeostasis. This is accompanied by reduced oxidative protein damage, increased AMPK phosphorylation and insulin-stimulated glucose uptake in skeletal muscle tissue. Oxidative damage in differentiated C2C12 myotubes is greatly attenuated by REG3A, as is the increase in gp130-mediated AMPK activation. In contrast, Akt-mediated insulin action, which is impaired by oxidative stress, is not restored by REG3A. These data highlight the importance of REG3A in controlling oxidative protein damage involved in energy and metabolic pathways during obesity and diabetes, and provide additional insight into the dual function of host-immune defense and metabolic regulation for AMP.

Causal relationship between insulin resistance and sarcopenia

Sarcopenia is a multifactorial disease characterized by reduced muscle mass and function, leading to disability, death, and other diseases. Recently, the prevalence of sarcopenia increased considerably, posing a serious threat to health worldwide. However, no clear international consensus has been reached regarding the etiology of sarcopenia. Several studies have shown that insulin resistance may be an important mechanism in the pathogenesis of induced muscle attenuation and that, conversely, sarcopenia can lead to insulin resistance. However, the causal relationship between the two is not clear. In this paper, the pathogenesis of sarcopenia is analyzed, the possible intrinsic causal relationship between sarcopenia and insulin resistance examined, and research progress expounded to provide a basis for the clinical diagnosis, treatment, and study of the mechanism of sarcopenia.

4-PBA inhibits hypoxia-induced lipolysis in rat adipose tissue and lipid accumulation in the liver through regulating ER stress

High-altitude hypoxia may disturb the metabolic modulation and function of both adipose tissue and liver. The endoplasmic reticulum (ER) is a crucial organelle in lipid metabolism and ER stress is closely correlated with lipid metabolism dysfunction. The aim of this study is to elucidate whether the inhibition of ER stress could alleviate hypoxia-induced white adipose tissue (WAT) lipolysis and liver lipid accumulation-mediated hepatic injury. A rat model of high-altitude hypoxia (5500 m) was established using hypobaric chamber. The response of ER stress and lipolysis-related pathways were analyzed in WAT under hypoxia exposure with or without 4-phenylbutyric acid (PBA) treatment. Liver lipid accumulation, liver injury, and apoptosis were evaluated. Hypoxia evoked significant ER stress in WAT, evidenced by increased GRP78, CHOP, and phosphorylation of IRE1α, PERK. Moreover, Lipolysis in perirenal WAT significantly increased under hypoxia, accompanied with increased phosphorylation of hormone-sensitive lipase (HSL) and perilipin. Treatment with 4-PBA, inhibitor of ER stress, effectively attenuated hypoxia-induced lipolysis via cAMP-PKA-HSL/perilipin pathway. In addition, 4-PBA treatment significantly inhibited the increase in fatty acid transporters (CD36, FABP1, FABP4) and ameliorated liver FFA accumulation. 4-PBA treatment significantly attenuated liver injury and apoptosis, which is likely resulting from decreased liver lipid accumulation. Our results highlight the importance of ER stress in hypoxia-induced WAT lipolysis and liver lipid accumulation.

Exploration of the core gene signatures and mechanisms between NAFLD and sarcopenia through transcriptomic level

INTRODUCTION

The increased prevalence of non-alcoholic fatty liver disease (NAFLD) and sarcopenia among the elderly are facing a significant challenge to the world's health systems. Our study aims to identify the coexpressed genes in NAFLD and sarcopenia patients.

METHODS

We downloaded the transcriptome data of NAFLD tissue from patients, as well as muscle tissues from sarcopenia patients, from the GEO database in order to investigate the shared transcriptional regulation mechanisms between these two diseases. Then, focusing on the genes that were frequently expressed in these diseases, together with GSVA and WGCNA, we utilized a range of analysis methods to identify the main co-expressed genes in both diseases by taking intersections. We investigated these changes after learning that they mostly affected lipid metabolism and oxidative stress injury pathways.

RESULTS

By analyzing these genes and their interactions with transcription factors and proteins, we were able to identify 8 genes that share common patterns. From these 8 genes, we were possible to forecast potential future medicines. Our research raises the possibility of NAFLD and sarcopenia transcriptome regulatory pathways in aging populations.

DISCUSSION

In conclusion, a complete transcription pattern mapping was carried out in order to identify the core genes, underlying biological mechanisms, and possible therapeutic targets that regulate aging in NAFLD and sarcopenia patients. It provides novel insights and proof in favor of decreasing the increased prevalence of sarcopenia in the elderly caused by NAFLD.

The Trend of Organic Based Nanoparticles in the Treatment of Diabetes and Its Perspectives

Diabetes is an untreatable metabolic disorder characterized by alteration in blood sugar homeostasis, with submucosal insulin therapy being the primary treatment option. This route of drug administration is attributed to low patient comfort due to the risk of pain, distress, and local inflammation/infections. Nanoparticles have indeed been suggested as insulin carriers to allow the drug to be administered via less invasive routes other than injection, such as orally or nasally. The organic-based nanoparticles can be derived from various organic materials (for instance, polysaccharides, lipids, and so on) and thus are prevalently used to enhance the physical and chemical consistency of loaded bioactive compounds (drug) and thus their bioavailability. This review presents various forms of organic nanoparticles (for example, chitosan, dextron, gums, nanoemulsion, alginate, and so on) for enhanced hypoglycemic drug delivery relative to traditional therapies.

Transgenerational effects of zinc, selenium and chromium supplementation on glucose homeostasis in female offspring of gestational diabetes rats

Clinical studies have demonstrated that maternal gestational diabetes mellitus (GDM) increases the offspring's risk of developing glucose intolerance. Our previous study reported that co-supplementation with zinc, selenium, and chromium improved insulin resistance in diet-induced GDM rats. Here, Transgenerational effects of supplementation with zinc (10 mg/kg.bw), selenium (20 μg/kg.bw), and chromium (20 μg/kg.bw) in F1 female offspring of both zinc, selenium and chromium (ZnSeCr)-treated, and untreated GDM rats daily by gavage from weaning to the postpartum were investigated in the present study. Glucose homeostasis in the F1 female offspring of GDM at different stages were evaluated. Maternal GDM did increase the birth mass of newborn F1 female offspring, as well as the serum glucose and insulin levels. Zinc, selenium and chromium supplementation attenuated the GDM-induced mass gain, increased serum glucose and insulin levels in the female neonates. The high fat and sucrose (HFS) diet-fed GDM-F1 offspring developed GDM, with glucose intolerance, hyperglycemia and insulin resistance during pregnancy. Moreover, endoplasmic reticulum (ER) stress-related protein levels were increased and the activation of insulin signaling pathways were reduced in the liver of HFS-fed GDM-F1 offspring. Whereas glucose homeostasis in parallel with insulin sensitivity was normalized in the female offspring of GDM by supplementation both F0 dams and F1 offspring with zinc, selenium and chromium, not in those either F0 or F1 elements supplemented offspring. Therefore, we speculate that zinc, selenium and chromium supplementation may have a potential beneficial transgenerational effect on the glucose homeostasis in the female offspring of GDM.

Mitochondrial DNA Copy Number: Linking Diabetes and Cancer

Recent Advances: Various studies have suggested that mitochondrial DNA copy number (mtDNA-CN), a surrogate biomarker of mitochondrial dysfunction, is an easily quantifiable biomarker for chronic diseases, including diabetes and cancer. However, current knowledge is limited, and the results are controversial. This has been attributed mainly to methodology and study design. Critical Issues: The incidence of diabetes and cancer has increased significantly in recent years. Moreover, type 2 diabetes (T2D) has been shown to be a risk factor for cancer. mtDNA-CN has been associated with both T2D and cancer. However, it is not known whether mtDNA-CN plays any role in the association between T2D and cancer. Significance: In this review, we have discussed mtDNA-CN in diabetes and cancer, and reviewed the literature and methodology used in published studies so far. Based on the literature review, we have speculated how mtDNA-CN may act as a link between diabetes and cancer. Furthermore, we have provided some recommendations for reliable translation of mtDNA-CN as a biomarker. Future Directions: Further research is required to elucidate the role of mtDNA-CN in the association between T2D and cancer. If established, early lifestyle interventions, such as physical activity and diet control that improve mitochondrial function, may help preventing cancer in patients with T2D. Antioxid. Redox Signal. 37, 1168-1190.

Identification of the hub susceptibility genes and related common transcription factors in the skeletal muscle of Type 2 Diabetes Mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) and its related complications contribute to the high morbidity and mortality in worldwide. Skeletal muscle insulin resistance plays a critical role in the onset of T2DM due to the decreasing in the insulin-stimulated glucose uptake. T2DM is associated not only with the inherited factors but also with the noninherited factors. However, the susceptibility genes related with the two factors and the transcription factors (TF) regulating the susceptibility genes in skeletal muscle, which aggravate the development of T2DM were still ill-defined.

METHODS

In the present study, the expression profiles by the array of GSE25462 were retrieved from the GEO database. GEO2R was performed to validate the susceptibility differentially expressed genes (SDEG) in skeletal muscle of T2DM. Gene Ontology (GO) analysis and The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were conducted via The Database for Annotation, Visualization, and Integrated Discovery (DAVID). A Protein-Protein Interaction (PPI) network was performed with the STRING.

RESULTS

With the performance of GEO2R, 229 SDEGs in skeletal muscle of T2DM were identified. The biological processes (BP) of SDEGs was enriched in the cellular response to UV-B most significantly. KEGG pathway analysis revealed that the SDEGs were most significantly enriched in glycosaminoglycan degradation. 5 hub susceptibility genes (GPR84, CALCB, GCG, PTGDR, GNG8) in the skeletal muscle of T2DM were identified. Eventually, the common transcription factors regulating the hub susceptibility genes were identified by means of the online tool PROMO.

CONCLUSIONS

Five hub susceptibility genes (GPR84, CALCB, GCG, PTGDR, GNG8) in the skeletal muscle of T2DM and the common transcription factors were identified. The outputs would provide new clues on the novel potential targets and the therapeutic strategies for treating T2DM and its related diseases.

Naringin Ameliorates Skeletal Muscle Atrophy and Improves Insulin Resistance in High-Fat-Diet-Induced Insulin Resistance in Obese Rats

Obesity causes progressive lipid accumulation and insulin resistance within muscle cells and affects skeletal muscle fibres and muscle mass that demonstrates atrophy and dysfunction. This study investigated the effects of naringin on the metabolic processes of skeletal muscle in obese rats. Male Sprague Dawley rats were divided into five groups: the control group with normal diet and the obese groups, which were induced with a high-fat diet (HFD) for the first 4 weeks and then treated with 40 mg/kg of simvastatin and 50 and 100 mg/kg of naringin from week 4 to 8. The naringin-treated group showed reduced body weight, biochemical parameters, and the mRNA expressions of protein degradation. Moreover, increased levels of antioxidant enzymes, glycogen, glucose uptake, the expression of the insulin receptor substrate 1 (IRS-1), the glucose transporter type 4 (GLUT4), and the mRNA expressions of protein synthesis led to improved muscle mass in the naringin-treated groups. The in vitro part showed the inhibitory effects of naringin on digestive enzymes related to lipid and glucose homeostasis. This study demonstrates the potential benefits of naringin as a supplement for treating muscle abnormalities in obese rats by modulating the antioxidative status, regulating protein metabolism, and improved insulin resistance in skeletal muscle of HFD-induced insulin resistance in obese rats.

HM-Chromanone, a Major Homoisoflavonoid in Portulaca oleracea L., Improves Palmitate-Induced Insulin Resistance by Regulating Phosphorylation of IRS-1 Residues in L6 Skeletal Muscle Cells

This study investigated the effect of (E)-5-hydroxy-7-methoxy-3-(2-hydroxybenzyl)-4-chromanone (HM-chromanone) on palmitate-induced insulin resistance and elucidated the underlying mechanism in L6 skeletal muscle cells. Glucose uptake was markedly decreased due to palmitate-induced insulin resistance in these cells; however, 10, 25, and 50 µM HM-chromanone remarkably improved glucose uptake in a concentration-dependent manner. HM-chromanone treatment downregulated protein tyrosine phosphatase 1B (PTP1B) and phosphorylation of c-Jun N-terminal kinase (JNK) and inhibitor of nuclear factor kappa-B kinase subunit beta (IKKβ), which increased because of palmitate mediating the insulin-resistance status in cells. HM-chromanone promoted insulin receptor substrate-1 (IRS-1) tyrosine phosphorylation and suppressed palmitate-induced phosphorylation of IRS-1 serine. This activated phosphoinositide 3-kinase (PI3K) and stimulated protein kinase B (AKT) phosphorylation. Phosphorylated AKT promoted the translocation of Glucose transporter type 4 to the plasma membrane and significantly enhanced glucose uptake into muscle cells. Additionally, HM-chromanone increased glycogen synthesis through phosphorylating glycogen synthase kinase 3 alpha/beta (GSK3 α/β) via AKT. Consequently, HM-chromanone may improve insulin resistance by downregulating the phosphorylation of IRS-1 serine through inhibition of negative regulators of insulin signaling and inflammation-activated protein kinases in L6 skeletal muscle cells.

In vitro skeletal muscle models for type 2 diabetes

Type 2 diabetes mellitus, a metabolic disorder characterized by abnormally elevated blood sugar, poses a growing social, economic, and medical burden worldwide. The skeletal muscle is the largest metabolic organ responsible for glucose homeostasis in the body, and its inability to properly uptake sugar often precedes type 2 diabetes. Although exercise is known to have preventative and therapeutic effects on type 2 diabetes, the underlying mechanism of these beneficial effects is largely unknown. Animal studies have been conducted to better understand the pathophysiology of type 2 diabetes and the positive effects of exercise on type 2 diabetes. However, the complexity of in vivo systems and the inability of animal models to fully capture human type 2 diabetes genetics and pathophysiology are two major limitations in these animal studies. Fortunately, in vitro models capable of recapitulating human genetics and physiology provide promising avenues to overcome these obstacles. This review summarizes current in vitro type 2 diabetes models with focuses on the skeletal muscle, interorgan crosstalk, and exercise. We discuss diabetes, its pathophysiology, common in vitro type 2 diabetes skeletal muscle models, interorgan crosstalk type 2 diabetes models, exercise benefits on type 2 diabetes, and in vitro type 2 diabetes models with exercise.

Insight into Potential Interactions of Thyroid Hormones, Sex Hormones and Their Stimulating Hormones in the Development of Non-Alcoholic Fatty Liver Disease

Non-Alcoholic Fatty Liver Disease (NAFLD) is a common manifestation of metabolic syndrome. In addition to lifestyle, endocrine hormones play a role in the dysregulation of hepatic metabolism. The most common endocrine hormones contributing to metabolic syndrome are alterations in the levels of thyroid hormones (THs, predominantly in subclinical hypothyroidism) and of sex hormones (in menopause). These hormonal changes influence hepatic lipid and glucose metabolism and may increase hepatic fat accumulation. This review compares the effects of sex hormones, THs and the respective stimulating hormones, Thyroid-Stimulating Hormone (TSH) and Follicle-Stimulating Hormone (FSH), on the development of hepatosteatosis. TSH and FSH may be more relevant to the dysregulation of hepatic metabolism than the peripheral hormones because metabolic changes were identified when only levels of the stimulating hormones were abnormal and the peripheral hormones were still in the reference range. Increased TSH and FSH levels appear to have additive effects on the development of NAFLD and to act independently from each other.

Diabetic Muscular Atrophy: Molecular Mechanisms and Promising Therapies

Diabetes mellitus (DM) is a typical chronic disease that can be divided into 2 types, dependent on insulin deficiency or insulin resistance. Incidences of diabetic complications gradually increase as the disease progresses. Studies in diabetes complications have mostly focused on kidney and cardiovascular diseases, as well as neuropathy. However, DM can also cause skeletal muscle atrophy. Diabetic muscular atrophy is an unrecognized diabetic complication that can lead to quadriplegia in severe cases, seriously impacting patients' quality of life. In this review, we first identify the main molecular mechanisms of muscle atrophy from the aspects of protein degradation and synthesis signaling pathways. Then, we discuss the molecular regulatory mechanisms of diabetic muscular atrophy, and outline potential drugs and treatments in terms of insulin resistance, insulin deficiency, inflammation, oxidative stress, glucocorticoids, and other factors. It is worth noting that inflammation and oxidative stress are closely related to insulin resistance and insulin deficiency in diabetic muscular atrophy. Regulating inflammation and oxidative stress may represent another very important way to treat diabetic muscular atrophy, in addition to controlling insulin signaling. Understanding the molecular regulatory mechanism of diabetic muscular atrophy could help to reveal new treatment strategies.

Extracellular Vesicles from Adipose Tissue Could Promote Metabolic Adaptation through PI3K/Akt/mTOR

Extracellular vesicles (EVs) are nanoparticles secreted by cells under physiological and pathological conditions, such as metabolic diseases. In this context, EVs are considered potential key mediators in the physiopathology of obesity. It has been reported that EVs derived from adipose tissue (ADEVs) contribute to the development of a local inflammatory response that leads to adipose tissue dysfunction. In addition, it has been proposed that EVs are associated with the onset and progression of several obesity-related metabolic diseases such as insulin resistance. In particular, characterizing the molecular fingerprint of obesity-related ADEVs can provide a bigger picture that better reflects metabolic adaptation though PI3K/Akt/mTOR. Hence, in this review we describe the possible crosstalk communication of ADEVs with metabolically active organs and the intracellular response in the insulin signaling pathway.

α-Linolenic acid rich-chia seed modulates visceral adipose tissue collagen deposition, lipolytic enzymes expression, insulin signaling and GLUT-4 levels in a diet-induced adiposity rodent model

Given obesity and its associated metabolic disorders have reached epidemic proportions, the study of therapeutic strategies targeting white adipose tissue (WAT) are of main research interest. We previously shown that α-linolenic acid-rich chia seed was able to ameliorate a wide range of metabolic disorders including body fat accretion in sucrose-rich diet (SRD)-fed rats, an experimental model of visceral adiposity and insulin resistance. However, the mechanisms involved are not fully clarified. The aim of this study was to evaluate the effect of chia seed administration upon WAT remodeling and key enzymes that controls lipolysis, insulin signaling (tAKT, pAKT), and GLUT-4 levels in different visceral fat pad depots (epididymal -eWAT- and retroperitoneal -rWAT- adipose tissues) of SRD-fed rats. Results showed that chia seed reduces adipocytes hypertrophy, the increased lipid content and collagen deposition in both WAT. These changes were accompanied by a significant reduction of HSL and ATGL protein levels in eWAT and HSL protein levels in rWAT. Moreover, chia seed restored the altered expression pattern of the pAKT observed in SRD-fed rats, and modulated GLUT-4 levels. Chia seed could be a dietary intervention of great relevance with potential beneficial effects in the management of body fat excess and WAT function.

Adipocyte Phenotype Flexibility and Lipid Dysregulation

The prevalence of obesity and associated cardiometabolic diseases continues to rise, despite efforts to improve global health. The adipose tissue is now regarded as an endocrine organ since its multitude of secretions, lipids chief among them, regulate systemic functions. The loss of normal adipose tissue phenotypic flexibility, especially related to lipid homeostasis, appears to trigger cardiometabolic pathogenesis. The goal of this manuscript is to review lipid balance maintenance by the lean adipose tissue’s propensity for phenotype switching, obese adipose tissue’s narrower range of phenotype flexibility, and what initial factors account for the waning lipid regulatory capacity. Metabolic, hypoxic, and inflammatory factors contribute to the adipose tissue phenotype being made rigid. A better grasp of normal adipose tissue function provides the necessary context for recognizing the extent of obese adipose tissue dysfunction and gaining insight into how pathogenesis evolves.

Systems-level analysis of insulin action in mouse strains provides insight into tissue- and pathway-specific interactions that drive insulin resistance

Skeletal muscle and adipose tissue insulin resistance are major drivers of metabolic disease. To uncover pathways involved in insulin resistance, specifically in these tissues, we leveraged the metabolic diversity of different dietary exposures and discrete inbred mouse strains. This revealed that muscle insulin resistance was driven by gene-by-environment interactions and was strongly correlated with hyperinsulinemia and decreased levels of ten key glycolytic enzymes. Remarkably, there was no relationship between muscle and adipose tissue insulin action. Adipocyte size profoundly varied across strains and diets, and this was strongly correlated with adipose tissue insulin resistance. The A/J strain, in particular, exhibited marked adipocyte insulin resistance and hypertrophy despite robust muscle insulin responsiveness, challenging the role of adipocyte hypertrophy per se in systemic insulin resistance. These data demonstrate that muscle and adipose tissue insulin resistance can occur independently and underscore the need for tissue-specific interrogation to understand metabolic disease.

Human placental mesenchymal stromal cell therapy restores the cytokine efflux and insulin signaling in the skeletal muscle of obesity-induced type 2 diabetes rat model

Obesity poses a significant risk factor for the onset of metabolic syndrome with allied complications, wherein mesenchymal stem cell therapy is seen as a promising treatment for obesity-induced metabolic syndrome. In the present study, we aim to explore the beneficial effects of the human placental mesenchymal stromal cells (P-MSCs) on obesity-associated insulin resistance (IR) including inflammation. To understand this, we have analyzed the peripheral blood glucose, serum insulin levels by ELISA, and the glucose uptake capacity of skeletal muscle by a 2-NBDG assay using flow cytometry in WNIN/GR-Ob rats treated with and without P-MSCs. Also, we have studied insulin signaling and cytokine profile in the skeletal muscle by western blotting, dot blotting, and Multiplex-ELISA techniques. The skeletal muscle of WNIN/GR-Ob rats demonstrates dysregulation of cytokines, altered glucose uptake vis-a-vis insulin signaling. However, P-MSCs' treatment was effective in WNIN/GR-Ob rats as compared to its control, to restore HOMA-IR, re-establishes dysregulated cytokines and PI3K-Akt pathway in addition to enhanced Glut4 expression and glucose uptake studied in skeletal muscle. Overall, our data advocate the beneficial effects of P-MSCs to ameliorate inflammatory milieu, improve insulin sensitivity, and normalize glucose homeostasis underlining the Ob-T2D conditions, and we attribute for immunomodulatory, paracrine, autocrine, and multipotent functions of P-MSCs.

Polycystic Ovary Syndrome: An Evolutionary Adaptation to Lifestyle and the Environment

Polycystic ovary syndrome (PCOS) is increasingly recognized as a complex metabolic disorder that manifests in genetically susceptible women following a range of negative exposures to nutritional and environmental factors related to contemporary lifestyle. The hypothesis that PCOS phenotypes are derived from a mismatch between ancient genetic survival mechanisms and modern lifestyle practices is supported by a diversity of research findings. The proposed evolutionary model of the pathogenesis of PCOS incorporates evidence related to evolutionary theory, genetic studies, in utero developmental epigenetic programming, transgenerational inheritance, metabolic features including insulin resistance, obesity and the apparent paradox of lean phenotypes, reproductive effects and subfertility, the impact of the microbiome and dysbiosis, endocrine-disrupting chemical exposure, and the influence of lifestyle factors such as poor-quality diet and physical inactivity. Based on these premises, the diverse lines of research are synthesized into a composite evolutionary model of the pathogenesis of PCOS. It is hoped that this model will assist clinicians and patients to understand the importance of lifestyle interventions in the prevention and management of PCOS and provide a conceptual framework for future research. It is appreciated that this theory represents a synthesis of the current evidence and that it is expected to evolve and change over time.

Impact of Sarcopenia and Myosteatosis in Non-Cirrhotic Stages of Liver Diseases: Similarities and Differences across Aetiologies and Possible Therapeutic Strategies

Sarcopenia is defined as a loss of muscle strength, mass and function and it is a predictor of mortality. Sarcopenia is not only a geriatric disease, but it is related to several chronic conditions, including liver diseases in both its early and advanced stages. Despite the increasing number of studies exploring the role of sarcopenia in the early stages of chronic liver disease (CLD), its prevalence and the relationship between these two clinical entities are still controversial. Myosteatosis is characterized by fat accumulation in the muscles and it is related to advanced liver disease, although its role in the early stages is still under researched. Therefore, in this narrative review, we firstly aimed to evaluate the prevalence and the pathogenetic mechanisms underlying sarcopenia and myosteatosis in the early stage of CLD across different aetiologies (mainly non-alcoholic fatty liver disease, alcohol-related liver disease and viral hepatitis). Secondly, due to the increasing prevalence of sarcopenia worldwide, we aimed to revise the current and the future therapeutic approaches for the management of sarcopenia in CLD.

Obesity, Body Image Dissatisfaction, and Sexual Dysfunction: A Narrative Review

With approximately two-thirds of the United States adult population classified as overweight or obese, obesity remains a critical public health concern. Obesity not only contributes to several health complications including type 2 diabetes mellitus and cardiovascular disease, but the condition is also associated with sexual dysfunction in both women and men. Despite evidence linking obesity and its concomitant pathophysiology to sexual problems, the potential roles of psychosocial factors such as body image are understudied. This narrative review evaluates the research linkages between obesity and sexual dysfunction, with particular attention to the potential effects of body image dissatisfaction. A literature search of biomedical and psychological databases was used to identify research pertaining to obesity, sexual function, and/or body image constructs. The pathophysiological effects of obesity on sexual function are well-documented in mechanistic studies and animal trials, often with corroboration in human clinical samples. However, very few studies examine obesity, body image, and sexual function in tandem. Body image dissatisfaction appears to independently impinge upon the sexual response cycle and mental health outcomes, irrespective of body weight. While obesity is often associated with negative body image appraisal, it is unclear whether these constructs exert additive, synergistic, or antagonistic effects on sexual responsivity. Additionally, overweight/obese individuals who exhibit higher levels of body image satisfaction or self-confidence appear to be protected from the deleterious effects of obesity on sexual satisfaction, at least to some extent. Greater reliance upon conceptual/theoretical models from the body image literature may better clarify the relationships between these constructs.