The CC Genotype of Insulin-Induced Gene 2 rs7566605 Is a Protective Factor of Hypercholesteremia Susceptible to Mild Cognitive Impairment, Especially to the Executive Function of Patients with Type 2 Diabetes Mellitus

Abstract

Backgrounds and Aims. Insulin-induced gene 2 (INSIG-2) is closely related to hypercholesteremia, which is a well-recognized risk factor of mild cognitive impairment (MCI) in type 2 diabetes mellitus (T2DM). We aim to investigate the association between promoter of the INSIG-2 rs7566605 single-nucleotide polymorphism (SNP) and T2DM with MCI. Methods. 233 T2DM patients with MCI or without MCI were recruited. Baseline data and genotype frequency were compared between MCI and non-MCI groups. Demographic parameters and neuropsychological tests results were analyzed among patients with different genotypes. Further correlation and regression analysis were conducted to find the association between cognition and cholesterol. Results. Despite no significant statistical difference was detected, we observed higher levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL) in patients with MCI than those without MCI. In addition, we observed higher TC and LDL levels in patients with GG or GC genotypes than those with CC genotype (P<0.001, P=0.004, or P<0.001, P=0.002). Interestingly, increased MoCA and decreased TMTB scores were found in patients with CC genotype, compared to those with GG or CG genotype (P=0.009, P=0.024, or P=0.005, P=0.109). Moreover, partial correlation (P=0.030 and P=0.004, respectively) and multiple linear regression (P=0.030 and P=0.005, respectively) showed that TC and LDL levels are associated with the TMTB score, indicating the executive function. Conclusions. CC genotype of INSIG-2 rs7566605 may be a protective factor of hypercholesteremia susceptible to MCI, especially to the executive function of T2DM. This trial is registered with ChiCTROCC15006060.