Obesity and Insulin Resistance: A Review of Molecular Interactions

Cimifugin inhibits adipogenesis and TNF-α-induced insulin resistance in 3T3-L1 cells

To investigate the effects of cimifugin on adipogenesis and tumor necrosis factor (TNF-α)-induced insulin resistance (IR) and inflammation in 3T3-L1 adipocytes. 3T3-L1 adipocytes were treated with 3-isobutyl-1-methyl-xanthine, dexamethasone, and insulin or cimifugin and then Oil Red O staining and intracellular triglyceride content detection were performed to assess adipogenesis. Subsequently, after cimifugin treatment, TNF-α was used to induce IR and inflammation. The results showed that cimifugin reduced intracellular lipids accumulation of 3T3-L1 adipocytes. Cimifugin improved IR of 3T3-L1 adipocytes induced by TNF-α, as reflected in decreased adiponectin, GLUT-4, and IRS-1 mRNA and protein expression. Moreover, cimifugin reduced TNF-α-induced pro-inflammatory factors production and phospho-P65 expression, and MAPK pathway activation in the 3T3-L1 adipocytes. These findings suggested that cimifugin might be useful for the prevention and therapy of obesity-related IR and inflammation.

Anthropometric Indices With Insulin Resistance in Obese Patients: A Literature Review

The hormone insulin is responsible for regulating the metabolism of proteins, carbs, and lipids by promoting the absorption of molecules such as glucose from the bloodstream into fat, the liver, and skeletal muscle cells. Insulin resistance (IR) is considered to be a physiological response to obesity that inhibits fat from accumulating and supports weight stabilization. People with IR gain less weight than those with insulin sensitivity, and therefore IR individuals have a three-fold increased likelihood of losing more weight when compared with insulin-sensitive individuals. A person's health is jeopardized by obesity, which is defined as excessive or unusual storage of fat in adipose tissue. Early identification using different anthropometric measuring parameters and proper and suitable therapy is essential as the incidence of obesity cases is increasing as a result of sedentary lifestyles, bad eating habits, a lack of physical exercise, and a lack of knowledge among young adults. The review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, following which based on inclusion and exclusion criteria, eight articles were considered for the review. The analysis showed that all the parameters are easily accessible and hence can be used in daily practices. Due to being readily available, body mass index (BMI) and waist circumference (WC) constituted the most often employed anthropometric measures in everyday practices. In addition, variances in the values of the variables were seen due to differences in gender.

Prevalence and correlates of pre-diabetes in adults of mixed ethnicities in the South African population: A systematic review and meta-analysis

INTRODUCTION

Pre-diabetes is a metabolic condition characterised by moderate glycaemic dysregulation and is a frontline risk factor for multiple metabolic complications such as type 2 diabetes mellitus. To the best of our knowledge, this will be the first systematic review and meta-analysis focusing on generating a comprehensive pooling of studies reporting on pre-diabetes prevalence in South Africa. Therefore, the review's purpose will be to screen and select reports that can be used to synthesise and provide the best estimate prevalence of pre-diabetes and its associated correlates in the South African population.

METHODS AND ANALYSIS

To determine the prevalence and correlates of pre-diabetes in South Africa, we searched PubMed, Web of Science, Google scholar and African Journal online for published or unpublished studies reporting the prevalence of pre-diabetes in South Africa starting from the year 2000 to 2020. Studies were assessed for eligibility by checking if they met the inclusion criteria.

RESULTS & CONCLUSION

The total number of studies deemed eligible is 13 and from these studies, an overall prevalence of pre-diabetes was reported to be 15,56% in the South African population. Hypertension, obesity and sedentary lifestyle were the common correlates recorded for the population of interest. Therefore, the review highlights the disturbingly high prevalence of pre-diabetes in South Africa and necessitates further investigations into the possible genetics, biochemical and hormonal changes in pre-diabetes.

ETHICS AND DISSEMINATION

The review will not require ethics clearance because non-identifiable data will be used. The review outcomes will give insight into the current burden that pre-diabetes has in South Africa.

PROSPERO REGISTRATION NUMBER

CRD42020182430.

Peppers in Diet: Genome-Wide Transcriptome and Metabolome Changes in Drosophila melanogaster

The habanero pepper (Capsicum chinense) is an increasingly important spice and vegetable crop worldwide because of its high capsaicin content and pungent flavor. Diets supplemented with the phytochemicals found in habanero peppers might cause shifts in an organism's metabolism and gene expression. Thus, understanding how these interactions occur can reveal the potential health effects associated with such changes. We performed transcriptomic and metabolomic analyses of Drosophila melanogaster adult flies reared on a habanero pepper diet. We found 539 genes/59 metabolites that were differentially expressed/accumulated in flies fed a pepper versus control diet. Transcriptome results indicated that olfactory sensitivity and behavioral responses to the pepper diet were mediated by olfactory and nutrient-related genes including gustatory receptors (Gr63a, Gr66a, and Gr89a), odorant receptors (Or23a, Or59a, Or82a, and Orco), and odorant-binding proteins (Obp28a, Obp83a, Obp83b, Obp93a, and Obp99a). Metabolome analysis revealed that campesterol, sitosterol, and sucrose were highly upregulated and azelaic acid, ethyl phosphoric acid, and citric acid were the major metabolites downregulated in response to the habanero pepper diet. Further investigation by integration analysis between transcriptome and metabolome data at gene pathway levels revealed six unique enriched pathways, including phenylalanine metabolism; insect hormone biosynthesis; pyrimidine metabolism; glyoxylate, and dicarboxylate metabolism; glycine, serine, threonine metabolism; and glycerolipid metabolism. In view of the transcriptome and metabolome findings, our comprehensive analysis of the response to a pepper diet in Drosophila have implications for exploring the molecular mechanism of pepper consumption.

Production of Reactive Oxygen Species by Epicardial Adipocytes Is Associated with an Increase in Postprandial Glycemia, Postprandial Insulin, and a Decrease in Serum Adiponectin in Patients with Severe Coronary Atherosclerosis

Purpose. This work investigates the relations between the production of reactive oxygen species (ROS) by epicardial adipose tissue (EAT) adipocytes and parameters of glucose/insulin metabolism, circulating adipokines levels, and severity of coronary atherosclerosis in patients with coronary artery disease (CAD); establishing significant determinants describing changes in ROS EAT in this category of patients. Material and methods. This study included 19 patients (14 men and 5 women, 53−72 y.o., 6 patients with diabetes mellitus type 2; 5 patients with prediabetes), with CAD, who underwent coronary artery bypass graft surgery. EAT adipocytes were isolated by the enzymatic method from intraoperative explants obtained during coronary artery bypass grafting. The size of EAT adipocytes and ROS level were determined. Results. The production of ROS by EAT adipocytes demonstrated a direct correlation with the level of postprandial glycemia (rs = 0.62, p < 0.05), and an inverse correlation with serum adiponectin (rs = −0.50, p = 0.026), but not with general and abdominal obesity, EAT thickness, and dyslipidemia. Regression analysis demonstrated that the increase in ROS of EAT adipocytes occurs due to the interaction of the following factors: postprandial glycemia (β = 0.95), postprandial insulin (β = 0.24), and reduced serum adiponectin (β = −0.20). EAT adipocytes in patients with diabetes and prediabetes manifested higher ROS production than in patients with normoglycemia. Although there was no correlation between the production of ROS by EAT adipocytes and Gensini score in the total group of patients, higher rates of oxidative stress were observed in EAT adipocytes from patients with a Gensini score greater than median Gensini score values (≥70.55 points, Gr.B), compared to patients with less severe coronary atherosclerosis (<70.55 points, Gr.A). Of note, the frequency of patients with diabetes and prediabetes was higher among the patients with the most severe coronary atherosclerosis (Gr.B) than in the Gr.A. Conclusions. Our data have demonstrated for the first time that systemic impairments of glucose/insulin metabolism and a decrease in serum adiponectin are significant independent determinants of oxidative stress intensity in EAT adipocytes in patients with severe coronary atherosclerosis. The possible input of the interplay between oxidative stress in EAT adipocytes and metabolic disturbances to the severity of coronary atherosclerosis requires further investigation.

Effect of Mori ramulus on the postprandial blood glucose levels and inflammatory responses of healthy subjects subjected to an oral high-fat/sucrose challenge: A double-blind, randomized, crossover clinical trial

Blood glucose is inadequately controlled in diabetes mellitus, causing various inflammation-related complications. This study aimed to investigate responses to an oral sucrose/lipid challenge in the context of glucose metabolism after consumption of Mori ramulus (MR) extract. In this study on healthy subjects, the optimal dose and safety of MR were confirmed in a preliminary pilot trial (n = 24), meanwhile, blood glucose, insulin, and inflammatory marker levels were detected via an oral sucrose/lipid tolerance test in the main trial (n = 36). In the main study, the blood glucose response was significantly decreased after 240 min in the MR group. Compared to the placebo group, the treatment group exhibited plasma insulin levels that were significantly increased at 120 min and decreased at 240 min. In conclusion, a single MR extract dose protects against inflammation induced by high-fat/sugar to maintain normal insulin secretion and thus helps to maintain postprandial blood glucose levels via an inflammatory mechanism.

Association of serum kynurenine/tryptophan ratio with poor glycemic control in patients with type2 diabetes

Purpose

The role of indoleamine 2,3-dioxygenase (IDO) has been shown in insulin resistance and metabolic syndrome. The present study aimed to measure serum IDO activity in patients with type 2 diabetes (T2DM) and to determine its association with glycemic control, oxidative stress, and insulin resistance.

Methods

Seventy-four patients with T2DM and 74 healthy subjects were selected to participate in this study. Fasting serum biochemical parameters including fasting blood sugar (FBS), HbA1c, insulin, uric acid, albumin, tryptophan, kynurenine, and total antioxidant capacity (TAC) were measured. HOMA-IR, QUICKI, and HOMA-B were calculated using serum FBS and insulin values. IDO activity was estimated using kynurenine/tryptophan ratio (KTR). Data were analyzed using SPSS software (Version 15) and p < 0.05 was considered as a significant difference.

Results

The findings showed higher levels of FBS, HbA1c, HOMA-IR, and KTR in the patients compared to the controls. TAC and HOMA-B were significantly lowered in the T2DM patients compared to controls. KTR was significantly correlated with the level of HbA1c, and T2DM patients with poor glycemic control (HbA1c ≤ 8) had significantly higher level of KTR. HOMA-B was significantly correlated with serum tryptophan and inversely correlated with HbA1c.

Conclusion

Serum KTR is increased in T2DM patients with poor glycemic control. Potential clinical implications and possible pathogenic roles of IDO in T2DM development should be further elucidated.

Pathophysiology of Physical Inactivity-Dependent Insulin Resistance: A Theoretical Mechanistic Review Emphasizing Clinical Evidence

The modern lifestyle has a negative impact on health. It is usually accompanied by increased stress levels and lower physical activity, which interferes with body homeostasis. Diabetes mellitus is a relatively common metabolic disorder with increasing prevalence globally, associated with various risk factors, including lower physical activity and a sedentary lifestyle. It has been shown that sedentary behavior increases the risk of insulin resistance, but the intermediate molecular mechanisms are not fully understood. In this mechanistic review, we explore the possible interactions between physical inactivity and insulin resistance to help better understand the pathophysiology of physical inactivity-dependent insulin resistance and finding novel interventions against these deleterious pathways.

miR-139-5p mediates the palmitate-induced inhibition of insulin secretion by targeting neuronal pentraxin 1 in INS-1 cells

High fatty acid reduces insulin secretion in pancreatic β-cells and miR-139-5p is increased in diabetic pancreatic tissues and induces islet β-cell apoptosis. However, to date, there is no study exploring whether or not miR-139-5p is involved in high fatty acid-induced insulin secretion. In the present study, INS-1 cells were exposed to different concentrations (0.1, 0.2, and 0.4 mM) of palmitate for different time periods (12, 24, and 48 h). The expression levels of miR-139-5p and neuronal pentraxin 1 (NPTX1) were evaluated by real-time PCR and western blot analysis. The regulation of NPTX1 by miR-139-5p was examined by luciferase assay. Cell transfection was conducted using Lipo8000 or Lipofectamine RNAiMAX. Potassium or glucose-stimulated insulin secretion levels were used to verify the function of miR-139-5p or NPTX1 in insulin secretion. Insulin secretion levels were detected by radioimmunoassay. We found that miR-139-5p was increased in INS-1 cells stimulated with palmitate. In addition, miR-139-5p was also elevated in islets of high-fat diet-fed mice and db/db mice compared to those in islets of normal diet-fed mice and wild-type mice. Knockdown of miR-139-5p could reverse high fatty acid-induced insulin secretion defects in INS-1 cells. Furthermore, we demonstrated that NPTX1 is a target of miR-139-5p. miR-139-5p mediated palmitate-induced insulin secretion defects by targeting NPTX1. Moreover, palmitate treatment declined the expression of NPTX1 and the NPTX1 expression was also decreased in islets of high-fat diet-fed mice and db/db mice. Impaired NPTX1 expression is involved in fatty acid-induced insulin secretion defects. Collectively, our results illustrate that the induction of β-cell insulin secretion defects by fatty acids is mediated, at least in part, by miR-139-5p via downregulation of NPTX1 expression.

Pulmonary and vascular effects of acute ozone exposure in diabetic rats fed an atherogenic diet

Air pollutants may increase risk for cardiopulmonary disease, particularly in susceptible populations with metabolic stressors such as diabetes and unhealthy diet. We investigated effects of inhaled ozone exposure and high-cholesterol diet (HCD) in healthy Wistar and Wistar-derived Goto-Kakizaki (GK) rats, a non-obese model of type 2 diabetes. Male rats (4-week old) were fed normal diet (ND) or HCD for 12 weeks and then exposed to filtered air or 1.0 ppm ozone (6 h/day) for 1 or 2 days. We examined pulmonary, vascular, hematology, and inflammatory responses after each exposure plus an 18-h recovery period. In both strains, ozone induced acute bronchiolar epithelial necrosis and inflammation on histopathology and pulmonary protein leakage and neutrophilia; the protein leakage was more rapid and persistent in GK compared to Wistar rats. Ozone also decreased lymphocytes after day 1 in both strains consuming ND (~50%), while HCD increased circulating leukocytes. Ozone increased plasma thrombin/antithrombin complexes and platelet disaggregation in Wistar rats on HCD and exacerbated diet effects on serum IFN-γ, IL-6, KC-GRO, IL-13, and TNF-α, which were higher with HCD (Wistar>GK). Ex vivo aortic contractility to phenylephrine was lower in GK versus Wistar rats at baseline(~30%); ozone enhanced this effect in Wistar rats on ND. GK rats on HCD had higher aortic e-NOS and tPA expression compared to Wistar rats. Ozone increased e-NOS in GK rats on ND (~3-fold) and Wistar rats on HCD (~2-fold). These findings demonstrate ways in which underlying diabetes and HCD may exacerbate pulmonary, systemic, and vascular effects of inhaled pollutants.