Salivary Amylase Gene (AMY1) Copy Number Variation Has Only Minor Correlation with Body Composition in Chinese Adults

Abstract

Background: According to the WHO, about 39% of the global adult population were overweight or obese in 2016. Obesity has high heritability, with more than 1000 variants so far identified. There have been reports indicating that salivary amylase gene (AMY1) copy number was one of these variants, yet its association with obesity remains controversial. Objective: Our research aimed to provide more evidence on the relationship of AMY1 copy number variation (CNV) with body mass index (BMI) and body composition. Methods: We recruited 133 Chinese adults (65 males, 68 females, 18-25 years old) with normal fasting blood glucose and blood pressure levels. 19 males were selected for a 10-week intervention to change body composition. After anthropometric measurements, BMI was calculated, and body composition was measured using dual energy X-ray absorptiometry (DEXA). For the 19 selected participants, we collected their height, weight, and body composition data one more time after intervention. All participants were required to leave their saliva samples and their AMY1 copy number was determined by real-time fluorescence quantitative PCR. Results: We failed to find any significant difference in BMI and body composition between different copy number groups. Only a weak correlation was found between body muscle mass and body fat mass. After adjusted for height and weight, AMY1 CNV explained 4.83% of the variance and one single increase in AMY1 CNV can increase 0.214kg of the body muscle mass, while one single increase in AMY1 CNV can decrease 0.217kg of the body fat mass and explained 4.69% of the variance. Conclusions: As a genetic factor, the AMY1 gene copy number variation has only a minor correlation with BMI and body composition, and its effect can easily be hidden by other factors such as individual diet and exercise habit.