Understanding Genetic Heterogeneity in Type 2 Diabetes by Delineating Physiological Phenotypes:SIRT1and its Gene Network in Impaired Insulin Secretion

Abstract

■ AbstractType 2 diabetes (T2D) is a chronic metabolic disease which shows an exponential increase in all parts of the world. However, the disease is controllable by early detection and modified lifestyle. A series of factors have been associated with the pathogenesis of diabetes, and genes are considered to play a critical role. The individual risk of developing T2D is determined by an altered genetic background of the enzymes involved in several metabolism-related biological mechanisms, including glucose homeostasis, insulin metabolism, the glucose and ion transporters involved in glucose uptake, transcription factors, signaling intermediates of insulin signaling pathways, insulin production and secretion, pancreatic tissue development, and apoptosis. However, many candidate genes have shown heterogeneity of associations with the disease in different populations. A possible approach to resolving this complexity and understanding genetic heterogeneity is to delineate the physiological phenotypes one by one as studying them in combination may cause discrepancies in association studies. A systems biology approach involving regulatory proteins, transcription factors, and microRNAs is one way to understand and identify key factors in complex diseases such as T2D. Our earlier studies have screened more than 100 single nucleotide polymorphisms (SNPs) belonging to more than 60 globally known T2D candidate genes in the Indian population. We observed that genes invariably involved in the activity of pancreatic β-cells provide susceptibility to type 2 diabetes (T2D). Encouraged by these results, we attempted to delineate in this review one of the commonest physiological phenotypes in T2D, namely impaired insulin secretion, as the cause of hyperglycemia. This review is also intended to explain the genetic basis of the pathophysiology of insulin secretion in the context of variations in the SIRT1 gene, a major switch that modulates insulin secretion, and a set of other genes such as HHEX, PGC-α, TCF7L2, UCP2, and ND3 which were found to be in association with T2D. The review aims to look at the genotypic and transcriptional regulatory relationships with the disease phenotype.

The Regulatory Effect of SIRT1 on Extracellular Microenvironment Remodeling

“…SIRT1 has got long-term attention and well known for playing a pivotal role in glucose homeostasis and Type 2 Diabetes 11 , 12 . One of its functions is to regulate insulin secretion.…”

Recent advances and perspectives in next generation sequencing application to the genetic research of type 2 diabetes

“…In different populations, heterogeneity in association of genetic variants with the disease was demonstrated, apparently related to the design of the study, in particular the results of a large meta-analysis that combines cases of T2D with different origins or signs and evaluates them with a generalized intermediate hyperglycemia phenoty-pe, despite the fact that the phenotype may differ due to a multitude of unrelated causes within the physiology of the body or the environment[134]. In recent years, a large number of projects have been carried out to study the causes of diabetes, large-scale studies have been created and huge biobanks of samples of these patients have been collected.…”

Exercise Training-Induced Changes in MicroRNAs: Beneficial Regulatory Effects in Hypertension, Type 2 Diabetes, and Obesity

“…Different gene variants have been reported to increase the susceptibility or to participate in the pathogenesis of T2D [ 161 , 162 ]. SNPs in different genes involved in T2D pathogenesis were reported, including transcription factor 7-like 2-TCF7L2 [ 163 ], Angiotensin-converting enzyme [ 164 ], Adiponectin [ 165 ], IGF2 receptor [ 166 ], and Sirtuins—SIRT [ 167 ]. Insulin-like growth factor (IGF) and its receptor (IGF type 2 receptor: IGF2R) are involved in a variety of physiological events including glucose homeostasis [ 168 ].…”