Low AMY1 Gene Copy Number Is Associated with Increased Body Mass Index in Prepubertal Boys

Abstract

BackgroundGenome-wide association studies have identified more than 60 single nucleotide polymorphisms associated with Body Mass Index (BMI). Additional genetic variants, such as copy number variations (CNV), have also been investigated in relation to BMI. Recently, the highly polymorphic CNV in the salivary amylase (AMY1) gene, encoding an enzyme implicated in the first step of starch digestion, has been associated with obesity in adults and children. We assessed the potential association between AMY1 copy number and a wide range of BMI in a population of Italian school-children.Methods744 children (354 boys, 390 girls, mean age (±SD): 8.4±1.4years) underwent anthropometric assessments (height, weight) and collection of saliva samples for DNA extraction. AMY1 copies were evaluated by quantitative PCR.ResultsA significant increase of BMI z-score by decreasing AMY1 copy number was observed in boys (β: -0.117, p = 0.033), but not in girls. Similarly, waist circumference (β: -0.155, p = 0.003, adjusted for age) was negatively influenced by AMY1 copy number in boys. Boys with 8 or more AMY1 copy numbers presented a significant lower BMI z-score (p = 0.04) and waist circumference (p = 0.01) when compared to boys with less than 8 copy numbers.ConclusionsIn this pediatric-only, population-based study, a lower AMY1 copy number emerged to be associated with increased BMI in boys. These data confirm previous findings from adult studies and support a potential role of a higher copy number of the salivary AMY1 gene in protecting from excess weight gain.

Dietary starch intake modifies the relation between copy number variation in the salivary amylase gene and BMI

“…The overall lack of an observed pattern of decrease in obesity traits with an increase in AMY1 copy number contrasts with some recent findings in both adults and children, whereby increasing AMY1 copy numbers were associated with a decrease in BMI and common obesity traits (5,6,20). For example, high AMY1 copy numbers were strongly associated with a lower risk of being obese in both the French DESIR (Epidemiological Study on the Insulin Resistance syndrome) and TwinsUK cohorts (5).…”

“…194 (12) 201 (13) 184 (12) 0.60 Dietary change in the past 313 (20) 394 (25) 439 (28) ,0.001 Underreporting 188 (12) 347 (22) 230 (14) ,0.001…”

“…For example, high AMY1 copy numbers were strongly associated with a lower risk of being obese in both the French DESIR (Epidemiological Study on the Insulin Resistance syndrome) and TwinsUK cohorts (5). In addition, studies have shown an association with a lower risk of obesity in Mexican children (6), and with decreased BMI in Italian primary school-age boys but not girls (20). Another study suggested an association of AMY1 CNVs with childhood-onset obesity in females only (21).…”

Starch Digestion–Related Amylase Genetic Variant Affects 2-Year Changes in Adiposity in Response to Weight-Loss Diets: The POUNDS Lost Trial

“…The A allele of SNP rs11185098 was nominally associated with a lower risk of obesity in the Estonian population; however, no relation was reported between the variant and BMI in a well-powered analysis (7). Previous studies reported that low AMY1 gene copies were associated with obesity (5,12–14), although the findings were not consistent (7,15). Studies have shown that the AMY1 gene copy number is positively correlated with salivary amylase activity and serum amylase levels (8–10), and observational studies have consistently reported that low serum amylase concentrations are associated with obesity, insulin resistance, and metabolic abnormalities (16–21,27).…”

“…Increasing evidence suggests that low AMY1 gene copy numbers are associated with obesity (5,12–14), although the findings are not entirely consistent (7,15). In epidemiological studies, low serum concentrations of amylase have been associated with elevated BMI (16–19), waist circumference (WC) (16,20), or visceral adipose tissue area (21).…”