Low Copy Number of the Salivary Amylase Gene (AMY1) Is Associated with Obesity, Dyslipidemia, and Chronic Low-Grade Inflammation but Not Insulin Sensitivity and Secretion

Abstract

Low salivary amylase gene (AMY1) copy number variations (CNVs) are associated with low serum amylase concentrations which have been shown to correlate with obesity, metabolic syndrome and predict type 2 diabetes. Recently, AMY1 CNV below 4 has been associated higher risk of obesity. Only one study has shown an association between AMY1 CNV and insulin resistance (HOMA). We assessed the relationship between AMY1 CNVs and adiposity (body mass index and dual X-ray absorptiometry), fasting and 2 hour glucose (75g OGTT), insulin sensitivity (hyperinsulinemic euglycemic clamp) and total, first and second phase insulin secretion (intravenous glucose tolerance test), inflammatory markers and adipokines (multiplex assays, Biolegend, CA) in 58 overweight and obese but otherwise healthy individuals (age 31±9 years, BMI 31±4 kg/m2). Participants were non-smokers and had modest alcohol consumption. The participants were divided into two groups according to a median of 4 AMY1 CNVs. Individuals with less than 4 AMY1 CNVs had higher BMI (33±4 vs. 30±3 kg/m2, p=0.04), fat mass (41±12 vs. 34±8kg, p=0.01), LDL cholesterol (3.3 ± 0.8 vs. 2.8±0.7mmol/l, p= 0.02), plasma interleukin 6 (53±56 vs. 24±22 pg/ml, p= 0.02) and leptin concentrations (0.83±0.56 vs. 0.50±0.46 ng/ml, p=0.02) compared to individuals with more than 4 AMY1 CNVs. There was no relationship between AMY1 CNVs and insulin sensitivity, insulin secretion, plasma fasting and 2 hour glucose, high sensitivity C-reactive protein, adiponectin, resistin and adipsin levels (all p>0.1). Our data indicated that AMY1 CNVs are associated with obesity, dyslipidemia and chronic low-grade inflammation but not glucose metabolism. Further larger studies are needed to confirm whether AMY1 CNVs could be a genetic biomarker for metabolic syndrome and type 2 diabetes. Disclosure B. de Courten: None. N. Naderpoor: None.