NDRG1 Activity in Fat Depots Is Associated With Type 2 Diabetes and Impaired Incretin Profile in Patients With Morbid Obesity.

Objective: We aimed to investigate insulin-, mTOR- and SGK1-dependent signaling basal states in morbidly obese patients' fat. We analyzed the correlation between the signaling activity, carbohydrate metabolism, and incretin profiles of patients. Methods: The omental and subcutaneous fat was obtained in patients with obesity. The omental study included 16 patients with normal glucose tolerance (NGT) and 17 patients with type 2 diabetes mellitus (T2DM); the subcutaneous study included 9 NGT patients and 12 T2DM patients. Insulin resistance was evaluated using the hyperinsulinemic euglycemic clamp test and HOMA-IR index. The oral glucose tolerance test (OGTT) for NGT patients and mixed meal tolerance test (MMTT) for T2DM patients were performed. The levels of incretins (GLP-1, GIP, oxyntomodulin) and glucagon were measured during the tests. Signaling was analyzed by Western blotting in adipose tissue biopsies. Results: We have shown equal levels of basal phosphorylation of insulin- and mTOR-dependent signaling in omental fat depot in NGT and T2DM obese patients. Nevertheless, pNDRG1-T346 was decreased in omental fat of T2DM patients. Correlation analysis has shown an inverse correlation of pNDRG1-T346 in omental fat and diabetic phenotype (HbA1c, impaired incretin profile (AUC GLP-1, glucagon)). Moreover, pNDRG1-T346 in subcutaneous fat correlated with impaired incretin levels among obese patients (inverse correlation with AUC glucagon and AUC GIP). Conclusions: According to results of the present study, we hypothesize that phosphorylation of pNDRG1-T346 can be related to impairment in incretin hormone processing. pNDRG1-T346 in adipose tissue may serve as a marker of diabetes-associated impairments of the systemic incretin profile and insulin sensitivity.

Decreased UCP-1 expression in beige adipocytes from adipose-derived stem cells of type 2 diabetes patients associates with mitochondrial ROS accumulation during obesity.

OBJECTIVE: Adipose derived stem cells (ADSC) are defective in metabolic disorders in various functionalities and properties including differentiation, multipotent state, metabolism and immunomodulation. However, the role of ADSC beiging potential in promoting of type 2 diabetes mellitus (T2DM) development remains unclear. Here we uncover association between potential of subcutaneous ADSC to beige differentiation and T2DM in patients with obesity. METHODS: ADSC were isolated from subcutaneous adipose tissue of patients with long morbid obesity (BMI > 35 kg/m2) and normal glucose tolerance (NGT) or T2DM. ADSC were differentiated into white or beige adipocytes and levels of thermogenic markers, lipid metabolism and electron transport chain (ETC) genes was analyzed by Western blotting and RT-PCR. ROS production was estimated by fluorescent microscopy. RESULTS: We have shown decreased UCP-1 expression in beige adipocytes from T2DM patients. Nevertheless, signal and expression activities of lipolysis were equal in NGT and T2DM beige adipocytes. Expression analysis of ETC genes also has not shown any statistically significant differences. Interestingly, we revealed increased mitochondrial ROS production in T2DM beige adipocytes during beige differentiation. CONCLUSIONS: In summary, compromised UCP1 expression in beige adipocytes of T2DM patients may cause increase of mitochondrial ROS. Elevated oxidative level is liable to act as damaging mechanism leading to insulin resistance or, alternatively, serve as compensatory mechanism for thermogenesis activation.

Low AS160 and high SGK basal phosphorylation associates with impaired incretin profile and type 2 diabetes in adipose tissue of obese patients.

OBJECTIVE: To compare basal insulin and mTOR signaling in subcutaneous fat of obese T2DM vs. obese subjects with normal glucose tolerance (NGT), and correlate it with clinical parameters of carbohydrate metabolism and incretin secretion profiles. METHODS: Recruited were 22 patients with long (>10 years) and morbid (BMI > 35 kg/m2) obesity, 12 of which had NGT and 10 had T2DM. Hyperinsulinemic-euglycemic clamp test and HOMA-IR were used to measure insulin resistance. Blood samples taken at 0, 30 and 120 min of food load test were used to assess incretin profile, insulin and glucose levels. Amount of total and visceral fat was determined by bioelectrical impedance analysis. Subcutaneous fat biopsies were obtained during bariatric surgery for all patients and analyzed by western blots. RESULTS: As assessed by western blots of insulin receptor substrate (IRS), Akt, Raptor, Rictor, mTOR and S6K1, the basal insulin signaling and mTORC activities were comparable in NGT and T2DM groups, whereas phosphorylation of AS160 was significantly lower and that of serum and glucocorticoid-induced kinase (SGK) was significantly higher in T2DM group. Various correlations were found between the degree of insulin resistance and amount of visceral fat, changes in incretin profile, glucose metabolic parameters and phosphorylation level of AS160, incretin secretion profile and phosphorylated levels of AS160 or SGK1. CONCLUSION: Altered phosphorylation of AS160 and SGK1 is associated with obese T2DM phenotype.