How does obesity lead to insulin resistance?

Molecular Processes Involved in the Shared Pathways between Cardiovascular Diseases and Diabetes

Cardiovascular diseases and diabetes mellitus are currently among the diseases with the highest morbidity and mortality. The pathogenesis and development of these diseases remain strongly connected, along with inflammation playing a major role. Therefore, the treatment possibilities showing a positive impact on both of these diseases could be especially beneficial for patients. SGLT-2 inhibitors and GLP-1 receptor agonists present this dual effect. Moreover, the hostile composition of the gut microbiota could influence the progression of these conditions. In this review, the authors present the latest knowledge on and innovations in diabetes mellitus and CVD-with the focus on the molecular mechanisms and the role of the microbiota.

Stable Binding of Full-Length Chemerin Is Driven by Negative Charges in the CMKLR1 N Terminus

The adipokine chemerin is the endogenous ligand of the chemokine-like receptor 1 (CMKLR1), a member of the family of G protein-coupled receptors (GPCRs). This protein ligand plays an important role in obesity and inflammatory processes. Stable receptor-ligand interactions are highly relevant for its different physiological effects such as the migration of immune cells towards sites of inflammation. Here, we demonstrate that negative charges in the CMKLR1 N terminus are involved in the formation of strong contacts with a specific positively charged patch at the surface of full-length chemerin, which is absent in the short nonapeptide agonist chemerin-9, thus explaining its reduced affinity. Using receptor chimera of G protein-coupled receptor 1 (GPR1) and CMKLR1, we were able to identify the residues of this interaction and its relevance for stable full-length chemerin binding. This could help to develop more potent ligands for the treatment of inflammation-related diseases.

Sema7A protects against high-fat diet-induced obesity and hepatic steatosis by regulating adipo/lipogenesis

OBJECTIVE

Obesity and related diseases are becoming a growing risk for public health around the world due to the westernized lifestyle. Sema7A, an axonal guidance molecule, has been known to play a role in neurite growth, bone formation, and immune regulation. Whether Sema7A participates in obesity and metabolic diseases is unknown. As several SNPs in SEMA7A and its receptors were found to correlate with BMI and metabolic parameters in the human population, we investigated the potential role of Sema7A in obesity and hepatic steatosis.

METHODS

GWAS and GEPIA database was used to analyze SNPs in SEMA7A and the correlation of Sema7A expression with lipid metabolism related genes. Sema7A-/- mice and recombinant Sema7A (rSema7A) were used to study the role of Sema7A in HFD-induced obesity and hepatic steatosis. Adipose tissue-derived mesenchymal stem cells (ADSCs) were used to examine the role of Sema7A in adipogenesis, lipogenesis and downstream signaling.

RESULTS

Deletion of Sema7A aggravated HFD-induced obesity. Sema7A deletion enhanced adipogenesis in both subcutaneous and visceral ADSCs, while the addition of rSema7A inhibited adipogenesis of ADSCs and lipogenesis of differentiated mature adipocytes. Sema7A inhibits adipo/lipogenesis potentially through its receptor integrin β1 and downstream FAK signaling. Importantly, administration of rSema7A had protective effects against diet-induced obesity in mice. In addition, deletion of Sema7A led to increased hepatic steatosis and insulin resistance in mice.

CONCLUSIONS

Our findings reveal a novel inhibitory role of Sema7A in obesity and hepatic steatosis, providing a potential new therapeutic target for obesity and metabolic diseases.

Aerobic Versus Resistance Training: Leptin and Metabolic Parameters Improvement in Type 2 Diabetes Obese Men

Purpose: The purpose of the research was to determine the changes in metabolic parameters, leptin, and irisin levels after aerobic and resistance training in type-2 diabetes obese men. Methods: Forty-five participants in the age range of 17-25 years were randomized into three groups: aerobic training (AT), resistance training (RT), and control (CO). All training sessions were fulfilled 4 days per week for two months. The aerobic training began with intensity of 65% of the maximum aerobic power and finished with 90%. The resistance program started with 50% of one-repetition maximum and reached 70% in the 8th week. Results: Factorial analysis of variance and Bonferroni post-hoc test revealed significant decreases in leptin (p = .043), fasting blood sugar (FBS) (p = .023), insulin (p = .001), homeostasis model assessment for insulin resistance (HOMA-IR) (p = .022) in AT compared with CO and insulin (p = .006) in AT compared with RT. The change of percent body fat (PBF) was positively correlated only with change of HOMA-IR in AT group (p = .032) at p < .05. Conclusion: The result suggests that, compared to resistance training, aerobic training can control metabolic situations such as insulin resistance through the leptin hormone function, and not irisin in type-2 diabetes obese men.

The common rs13266634 C > T variant in SLC30A8 contributes to the heterogeneity of phenotype and clinical features of both type 1 and type 2 diabetic subtypes

AIMS

T2D and T1D are phenotypically heterogeneous. This study aims to reveal the relationship between the common SLC30A8 rs13266634 variant and subgroups of T2D and T1D and their clinical characteristics.

METHODS

We included 3158 OGTT-based healthy controls, unrelated 1754 T2D, and 1675 autoantibody-positive T1D individuals. The associations between rs13266634 and subtypes of T2D, T1D, autoantibody status and glycemic-related quantitative traits were performed by binary logistic regression analysis under the additive model and multiple linear regression with appropriate adjustment.

RESULTS

We found that the T allele of rs13266634 was protectively associated with lean (OR = 0.810, P = 6.91E-04) but not obese T2D with considerable heterogeneity (P = 0.018). This allele also conferred significant protection with T1D of single (OR = 0.847, P = 9.76E-03), but not multi autoantibodies with substantial heterogeneity (P = 0.005). This variant significantly affected OGTT-related insulin release in lean (P = 2.66E-03, 3.88E-03 for CIR and DI, respectively) but not obese healthy individuals. Furthermore, rs13266634 T allele correlated with the risk of ZnT8A (OR = 1.440, P = 3.31E-05) and IA-2A (OR = 1.219, P = 1.32E-03) positivity, with more effect size in children/adolescents compared with adult-onset T1D subtypes.

CONCLUSIONS

These suggested that the SLC30A8 rs13266634 variant might be put into genetic risk scores to assess the risk of the subtypes of T1D and T2D and their related clinical features.

Role of the voltage-gated proton channel Hv1 in insulin secretion, glucose homeostasis, and obesity

Diabetes is characterized by an absolutely inadequate insulin secretion (type 1 diabetes mellitus) or a relative deficit in insulin secretion due to insulin resistance (type 2 diabetes mellitus), both of which result in elevated blood glucose. Understanding the molecular mechanisms underlying the pathophysiology of diabetes could lead to the development of new therapeutic approaches. The voltage-gated proton channel Hv1 is an ion channel with specific selectivity for protons, which is regulated by membrane potential and intracellular pH. Recently, our studies showed that Hv1 is expressed in β cells of the endocrine pancreas. Knockout of Hv1 reduces insulin secretion and results in hyperglycemia and glucose intolerance, but not insulin resistance. Furthermore, knockout of Hv1 leads to diet-induced obesity due to inflammation and hepatic steatosis. Increasing evidence suggests that Hv1 plays a pivotal role in glucose homeostasis and lipid metabolism. This review aims to summarize advances made so far in our understanding of the roles of Hv1 in the regulation of insulin secretion in β cells, glucose homeostasis, and obesity.

Associations of Dietary Inflammatory Index With Prediabetes and Insulin Resistance

BACKGROUND AND AIMS

Previous studies suggested that dietary inflammatory index (DII) was associated with a variety of adverse health conditions. However, less is known about the role of DII in prediabetes and insulin resistance (IR). Therefore, this study aimed to investigate whether DII is associated with prediabetes and IR in American adults.

METHOD AND RESULTS

DII scores were calculated using the average of two 24-hour dietary recalls. Linear regression models were performed to evaluate the associations of DII with markers of Type 2 diabetes (T2D) risk, and the associations of DII with prediabetes and IR were estimated using logistic regression model. The diet of the participants showed an anti-inflammatory potential, with a mean DII score of -0.14 (range: -5.83 to +5.32). After controlling for multiple potential confounders, DII scores were positively associated with fasting plasma glucose (FPG) (β: 0.009; 95%CI: 0.005 to 0.012), fasting serum insulin (FSI) (β: 0.083; 95%CI: 0.067 to 0.099) and homeostatic model assessment of insulin resistance (HOMA-IR) (β: 0.092; 95%CI: 0.075 to 0.109). Participants in the highest tertile of DII score have increased odds of prediabetes (OR: 1.40; 95%CI: 1.17 to 1.69; P for trend <0.001) and IR (OR: 1.79; 95%CI: 1.49 to 2.14; P for trend <0.001) compared with those in the first tertile of DII score.

CONCLUSIONS

This study indicates that DII was positively associated with FPG, FSI, and HOMA-IR, and a more pro-inflammatory diet was related to increased odds of insulin resistant and prediabetes.

Non-Alcoholic Fatty Liver Disease: Metabolic, Genetic, Epigenetic and Environmental Risk Factors

Non-alcoholic fatty liver disease (NAFLD) is one of the most frequent causes of chronic liver disease in the Western world, probably due to the growing prevalence of obesity, metabolic diseases, and exposure to some environmental agents. In certain patients, simple hepatic steatosis can progress to non-alcoholic steatohepatitis (NASH), which can sometimes lead to liver cirrhosis and its complications including hepatocellular carcinoma. Understanding the mechanisms that cause the progression of NAFLD to NASH is crucial to be able to control the advancement of the disease. The main hypothesis considers that it is due to multiple factors that act together on genetically predisposed subjects to suffer from NAFLD including insulin resistance, nutritional factors, gut microbiota, and genetic and epigenetic factors. In this article, we will discuss the epidemiology of NAFLD, and we overview several topics that influence the development of the disease from simple steatosis to liver cirrhosis and its possible complications.

Association of age at menarche with hypertension in rural Chinese women

OBJECTIVE

The study aimed to explore the association of age at menarche with hypertension and whether adiposity and insulin resistance mediated the association in rural Chinese women.

METHODS

We conducted a cross-sectional study enrolling 7518 women (median age 56 years) from a rural Chinese area from 2013 to 2014. Adiposity was measured by BMI and waist circumference, and insulin resistance was measured by the homeostasis model assessment of insulin resistance (HOMA-IR) index. Odds ratios (ORs) and 95% confidence limits (Cls) for the association of age at menarche with hypertension were estimated by using multivariate logistic regression models. The contribution of adiposity and insulin resistance to the association was estimated by mediation analysis.

RESULTS

Among 7518 women, 3187 (42.39%) had hypertension. Age at menarche was inversely associated with hypertension (per additional year of menarche, OR = 0.965, 95% Cl: 0.935-0.995). BMI or waist circumference and HOMA-IR completely mediated the association of age at menarche with hypertension (for BMI and HOMA-IR: total indirect effect: OR = 0.970, 95% Cl: 0.962-0.978 and direct effect: OR = 0.994, 95% Cl: 0.963-1.026; for waist circumference and HOMA-IR: total indirect effect: OR = 0.981, 95% Cl: 0.973-0.988 and direct effect: OR = 0.983, 95% Cl: 0.952-1.014).

CONCLUSION

Early age at menarche was positively associated with hypertension. Adiposity and insulin resistance seemed to be two vital mediators of the association between age at menarche and hypertension in rural Chinese women.

Association of triglycerides to high-density lipoprotein-cholesterol ratio with risk of incident hypertension

The triglyceride to high-density lipoprotein-cholesterol (TG/HDL-C) ratio is considered a simple surrogate of insulin resistance. The aim of this study was to explore the association of the TG/HDL-C ratio with the risk of incident hypertension and whether the TG/HDL-C ratio mediates the obesity-incident hypertension association. The study analyzed 9679 participants from a rural Chinese population. Demographic and anthropometric and laboratory data were collected at baseline (2007-2008) and follow-up (2013-2014) examinations. A multivariate logistic regression model was used to analyze the association of the TG/HDL-C ratio with incident hypertension, estimating odds ratios (ORs) and 95% confidence intervals (CIs). Mediation analysis was performed to examine the contribution of the TG/HDL-C ratio to obesity-related incident hypertension. During a median follow-up of 6.00 years, hypertension developed in 1880/9679 participants (19.42%). The risk of incident hypertension was higher in the highest TG/HDL-C ratio quartile than in the lowest quartile (OR = 1.21, 95% CI = 1.02-1.42). Subgroup analyses showed that the risk of incident hypertension was increased by 30%, 36%, and 33% among women, participants < 60 years old and those with prehypertension at baseline, respectively. The TG/HDL-C ratio partially mediated the obesity-incident hypertension association (indirect effect: OR = 1.04, 95% CI: 1.01-1.07; direct effect: OR = 1.36, 95% CI: 1.16-1.62). The TG/HDL-C ratio may be a risk factor for incident hypertension, especially in women, participants < 60 years old and those with prehypertension. The TG/HDL-C ratio may also play a mediating role in obesity-related incident hypertension.

Adiposity and insulin resistance as mediators between age at menarche and type 2 diabetes mellitus

OBJECTIVE

This study aimed to explore the association between age at menarche and type 2 diabetes mellitus (T2DM) and whether the association is mediated by adiposity and insulin resistance (IR) in rural Chinese women.

METHODS

This cross-sectional study analyzed data for 7,460 women (median age 56 y) from a rural Chinese area from 2013 to 2014. Data were collected by standardized interviews and anthropometric and laboratory measurements. Adiposity was measured by body mass index (BMI), and IR was measured by the homeostasis model assessment of IR (HOMA-IR) index. Multivariate logistic regression models were used to estimate odds ratios (ORs) and 95% confidence limits (CLs) for the association between age at menarche and T2DM. Mediation analysis was performed to explore the contribution of BMI and HOMA-IR to the association between age at menarche and T2DM.

RESULTS

Among 7,460 women, 840 (11.26%) had T2DM. After adjusting for potential confounding factors, the odds of T2DM with the latest age at menarche 18 years or older versus 13 years was reduced (OR = 0.65, 95% CL: 0.47, 0.91), and age at menarche was negatively associated with T2DM (per additional year of menarche, OR = 0.95, 95% CL: 0.91, 0.99). BMI and HOMA-IR completely mediated the association between age at menarche and T2DM (total indirect effect: OR = 0.973, 95% CL: 0.961, 0.986; direct effect: OR = 0.974, 95% CL: 0.930, 1.021).

CONCLUSIONS

Late menarche may be negatively associated with T2DM. The potential mechanism is adiposity and IR completely mediating the association between age at menarche and T2DM.

Chronic Adipose Tissue Inflammation Linking Obesity to Insulin Resistance and Type 2 Diabetes

Obesity is one of the major health burdens of the 21st century as it contributes to the growing prevalence of its related comorbidities, including insulin resistance and type 2 diabetes. Growing evidence suggests a critical role for overnutrition in the development of low-grade inflammation. Specifically, chronic inflammation in adipose tissue is considered a crucial risk factor for the development of insulin resistance and type 2 diabetes in obese individuals. The triggers for adipose tissue inflammation are still poorly defined. However, obesity-induced adipose tissue expansion provides a plethora of intrinsic signals (e.g., adipocyte death, hypoxia, and mechanical stress) capable of initiating the inflammatory response. Immune dysregulation in adipose tissue of obese subjects results in a chronic low-grade inflammation characterized by increased infiltration and activation of innate and adaptive immune cells. Macrophages are the most abundant innate immune cells infiltrating and accumulating into adipose tissue of obese individuals; they constitute up to 40% of all adipose tissue cells in obesity. In obesity, adipose tissue macrophages are polarized into pro-inflammatory M1 macrophages and secrete many pro-inflammatory cytokines capable of impairing insulin signaling, therefore promoting the progression of insulin resistance. Besides macrophages, many other immune cells (e.g., dendritic cells, mast cells, neutrophils, B cells, and T cells) reside in adipose tissue during obesity, playing a key role in the development of adipose tissue inflammation and insulin resistance. The association of obesity, adipose tissue inflammation, and metabolic diseases makes inflammatory pathways an appealing target for the treatment of obesity-related metabolic complications. In this review, we summarize the molecular mechanisms responsible for the obesity-induced adipose tissue inflammation and progression toward obesity-associated comorbidities and highlight the current therapeutic strategies.

Type 2 diabetes mellitus in children and adolescent: an Indonesian perspective

The prevalence of type 2 diabetes mellitus (T2DM) in children and adolescents has increased globally over the past 2 decades. Metabolic syndrome, including obesity and overweight at a young age, increases the occurrence of T2DM. Studies in Indonesia have found that obese children and adolescents are more likely to have insulin resistance, a risk factor for T2DM. There are no data on the current incidence of T2DM in youth in Indonesia, but there has been a significant rise in the prevalence of overweight in adolescents. The diagnosis of T2DM in youth is similar to that in adults, with special consideration of when to test asymptomatic children. Management of T2DM in Indonesia follows the recommendations of the Indonesian Pediatric Society, which include lifestyle modifications, such as improving dietary habits and exercise, as well as appropriate medications. Metformin is the drug of choice for young T2DM patients; if marked hyperglycemia is present, basal insulin is given with metformin. Monitoring of T2DM is generally done through selfmonitoring of blood glucose and glycosylated hemoglobin.