High AMY1 copy number protects against obesity in Portuguese young adults.

BACKGROUND: The highly polymorphic copy number variation (CNV) in the salivary amylase gene (AMY1) has been associated with obesity in different populations. However, some authors have failed to reproduce these findings.

AIM: To investigate the association between AMY1 CNV and obesity in young adults of Portuguese origin.

SUBJECTS AND METHODS: This study evaluated AMY1 gene copy number (CN) in 262 individuals: 155 females and 107 males, aged 18-34 years-old (mean age = 21.08). The number of AMY1 copies was estimated in a QX100 droplet digital PCR (ddPCR) system (Bio-Rad Laboratories, Hercules, CA).

RESULTS: Defining a case group with obese and overweight individuals, logistic regression did not show a significant association between AMY1 CNV and risk of overweight/obesity in the whole population (p = 0.489). However, after testing case-control data in the sub-set of samples above the third quartile (CN ≥10), a significant association was found between lower AMY1 copy number and risk of obesity (OR = 0.532; p = 0.034), even when adjusted for age and sex (OR = 0.527; p = 0.039). In concordance, all participants with >10 AMY1 copies were normal weight controls (n = 20) or overweight (n = 6).

CONCLUSION: The results suggest that high AMY1 gene copy number protects against obesity in Portuguese young adults.