Impacts of abdominal fat distribution on body composition and islet function in type 2 diabetic patients

Abstract

Objective To analyze the differences of body composition and islet function between patients with or without nonalcoholic fatty liver disease (NAFLD), and between patients with or without visceral obesity in type 2 diabetes mellitus (T2DM). The effects of fatty liver and visceral fat on islet function were also investigated. Methods A total of 519 patients with T2DM were divided into 4 groups according to the presence or absence of fatty liver and visceral obesity. Group 1: 242 cases of T2DM+ NAFLD with visceral obesity, group 2: 59 cases of T2DM + NAFLD without visceral obesity, group 3: 101 cases of T2DM with visceral obesity but without NAFLD and group 4: 117 cases of T2DM without NAFLD and visceral obesity. Bioelectrical impedance method was used to analyze human body composition, including visceral fat area, skeletal muscle content, mineral content and other indicators. At the same time, biochemical indicators such as liver and kidney function, blood lipid, oral glucose tolerance and islet function were measured in all patients. Variance analysis or nonparametric test was used to compare the difference of body composition and biochemical indexes between groups. Spearman rank correlation was used for correlation analysis, and binary logistic regression was used for multivariate analysis. Results (1)The mineral content, protein content, total body water, body mass index in group 1 were higher than those in group 4 (F=16.202-100.482, all P<0.05); the percentage of fat was decreased gradually from group 1 to group 4 (T=47.027, P<0.05); the skeletal muscle content in group 2 was higher than that in group 1 (T=2.879, P<0.05). (2)The white blood cell, C-reactive protein, total protein, albumin, gamma glutamyl transferase, alanine aminotransferase, aspertate aminotransferase, estimated glomerular filtration rate, serum uric acid, triglyceride, low-density lipoprotein-cholesterol and very low-density lipoprotein-cholesterol showed a downward trend, and the level of high density lipoprotein-cholesterol was increased gradually (F/T=4.036-18.831, all P<0.05) from group 1 to group 4. (3)Among the four groups, homeostatic model assessment of insulin resistance, homeostasis model assessment of β cell function, insulin sensitivity index, area under curve of insulin and area under curve of C-peptide showed a downward trend from group 1 to group 4, with significant difference between group 1 and group 4 (F/T=5.757-13.860, all P<0.05). (4)After adjusting for age and sex, the visceral fat area was positively correlated with body mass index, waist to hip ratio, visceral fat content, subcutaneous fat content, basal metabolic volume, gamma glutamyl transferase, alanine aminotransferase, aspertate aminotransferase and serum uric acid(r=0.340-0.916, all P<0.05), and negatively correlated with high density lipoprotein-cholesterol(r=-0.442, P<0.05). (5)Visceral fat content(OR=5.463, 95% CI: 1.886-4.451, P=0.071)and low-density lipoprotein-cholesterol (OR=1.224, 95% CI: 1.180-1.227, P=0.025)were independent risk factors for NAFLD in patients with T2DM. Conclusions Both T2DM patients with NAFLD or visceral obesity have insulin resistance and compensatory increase of insulin secretion. The most serious insulin resistance is found in T2DM patients with NAFLD and visceral obesity simultaneously. Increasing skeletal muscle content is beneficial to control visceral obesity and improve islet function in patients with NAFLD. Reducing visceral fat area is beneficial to improve metabolic indicators. Key words: Type 2 diabetes mellitus; Non-alcoholic fatty liver disease; Visceral obesity; Body composition; Insulin resistance