Abstract
Studies assessing the impact of amylase genes copy number (CN) on adiposity report conflicting findings in different global populations, likely reflecting the impact of ancestral and ethnic-specific environment and lifestyle on selection at the amylase loci. Here, we leverage population size and detailed adiposity measures from a large population biobank to resolve confounding effects and determine the relationship between salivary (AMY1) and pancreatic (AMY2A) amylase genes CN and adiposity in 2935 Qatari individuals who underwent whole-genome sequencing (WGS) as part of the Qatar Genome Programme. We observe a negative association between AMY1 CNs and trunk fat percentage in the Qatari population (P = 7.50 × 10−3) and show that Qataris of Arab descent have significantly lower CN at AMY1 (P = 1.32 × 10−10) as well as less favorable adiposity and metabolic profiles (P < 1.34 × 10−8) than Qataris with Persian ancestry. Indeed, lower AMY1 CN was associated with increased total and trunk fat percentages in Arabs (P < 4.60 × 10−3) but not in Persians. Notably, overweight and obese Persians reported a significant trend towards dietary restraint following weight gain compared to Arabs (P = 4.29 × 10−5), with AMY1 CN showing negative association with dietary self-restraint (P = 3.22 × 10−3). This study reports an association between amylase gene CN and adiposity traits in a large Middle Eastern population. Importantly, we leverage rich biobank data to demonstrate that the strength of this association varies with ethnicity, and may be influenced by population-specific behaviors that also contribute to adiposity traits.
Highlights
Salivary (AMY1) and pancreatic (AMY2A) amylase enzymes are responsible for starch digestion, which begins in the oral cavity and continues in the small intestine
All the adiposity traits under study were significantly higher in female than in male subjects (Table 1, Fig. 1; Wilcoxon’s P < 5.08 × 10−5), with the strongest difference being observed for total fat percentage (Wilcoxon’s P = 1.54 × 10−295)
The national STEPwise survey conducted in Qatar in 2012 reported an obesity epidemic (>70% of the adult population had a body mass index (BMI) ≥ 25 kg/m2), accompanied by an alarming rate of comorbidities in the affected population, such as hypertension (32.9% of respondents aged 18–64) and type II diabetes (17.6% of men and 15.9% of women)[23]
Summary
Salivary (AMY1) and pancreatic (AMY2A) amylase enzymes are responsible for starch digestion, which begins in the oral cavity and continues in the small intestine. Previous works exploring the relationship between AMY1 CN and diet revealed a significant effect of the interaction between AMY1 CN and starch intake on BMI in 4800 nondiabetic adults from Sweden[13], and greater weight and central adiposity loss following randomized low-calorie diet interventions among carriers of the allele rs11185098-A (a proxy of higher AMY1 CN and activity3), compared to noncarriers, among 692 Europeans from The POUNDS Lost Trial[14] Taken together, these studies suggest that environmental factors, and dietary choices, may play a role in modulating the observed association between AMY1 CN and adiposity. Our findings help explain trans-ethnic differences in the effect of amylase CN on adiposity and introduce a role for subpopulation-specific traditional dietary and lifestyle choices in determining the strength of association between amylase and adiposity in global populations
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