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

M Loredana Marcovecchio,Francesco Chiarelli,Rosalba Florio,Alessandro Cama,Laura De Lellis,Delfina Verzilli,Fabio Verginelli,Cristian Capelli,Angelika Mohn,Andrea S Wiley

doi:10.1371/journal.pone.0154961

M Loredana Marcovecchio, Francesco Chiarelli + Show 8 more

Open Access

https://doi.org/10.1371/journal.pone.0154961

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Journal: PloS one	Publication Date: May 5, 2016
Citations: 48	License type: CC BY 4.0

Affiliation: University of Chieti-Pescara, University of Oxford

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.

Highlights

Body mass index (BMI) is a highly heritable trait with up to 80% of its variance being attributable to genetic factors based on twin and family studies [1,2]
A 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
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. In this pediatric-only, population-based study, a lower AMY1 copy number emerged to be associated with increased BMI in boys

Summary

Introduction

Body mass index (BMI) is a highly heritable trait with up to 80% of its variance being attributable to genetic factors based on twin and family studies [1,2]. Over the last years a large number of common variants has been associated with BMI in genome-wide association studies, each accounting for only a small proportion of the predicted heritability [3] This has led to the suggestion that copy number variation of genes involved in the metabolic response to diet may explain at least in part the missing heritability. The first genetic link between carbohydrate metabolism and BMI has recently emerged from a large study of European and Asian adults, where the authors clearly demonstrated that reduced AMY1 copy number was related to decreased salivary amylase levels, and to increased BMI [8]. We assessed the potential association between AMY1 copy number and a wide range of BMI in a population of Italian school-children

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