Abstract
The association of salivary α-amylase activity (SAA) activity or low copy number of its coding gene AMY1 with diabetes remains controversial. We aimed to reinvestigate the association of these factors with diabetes in Qatar, where diabetes prevalence is about 16%. We obtained cross-sectional data of 929 Qataris (age > 18 years) from the Qatar Biobank. We estimated AMY1 copy number variants (CNV) from whole-genome data, and quantified the SAA activity in plasma (pSAA). We used adjusted logistic regression to examine the association between pSAA activity or AMY1 CNV and diabetes odds. We found a significant association between high pSAA activity, but not AMY1 CNV, and reduced odds of diabetes in Qatari women. The OR per pSAA activity unit was 0.95 [95% CI 0.92, 0.98] (p = 0.002) (pSAA activity range: 4.7 U/L to 65 U/L) in women. The association is driven largely by the highest levels of pSAA activity. The probability of having diabetes was significantly lower in the fifth pSAA activity quintile relative to the first (0.21 ± 0.03 (Q1) versus 0.82 ± 0.02 (Q5)), resulting in significantly reduced diabetes prevalence in Q5 in women. Our study indicates a beneficial effect of high pSAA activity, but not AMY1 CN, on diabetes odds in Qatari women, and suggests pSAA activity levels as a potential marker to predict future diabetes in Qatari women.
Highlights
The association of salivary α-amylase activity (SAA) activity or low copy number of its coding gene AMY1 with diabetes remains controversial
This study shows a significant association of high levels pSAA activity, but not AMY1 copy number variants (CNV), with lower odds of having diabetes exclusively in adult Qatari women (OR per pSAA activity unit 0.95 [95% CI 0.92, 0.98] (p = 0.002); with pSAASAA activity varying from 4.7 to 65 U/L in the population)
Our results are in line with a previous w ork[25], which reported that pSAA activity, but not AMY1 CNV, was significantly associated with lower fasting plasma glucose levels in a French study of 3500 adults
Summary
The association of salivary α-amylase activity (SAA) activity or low copy number of its coding gene AMY1 with diabetes remains controversial. AMY1 is one of the most variable loci in the human genome, ranging from 2 to 20 diploid copies[3,4,5,6] Both the saliva and serum levels of SAA correlate positively with the number of copies of the AMY1 g ene[3,4,5,7]. Some recent studies reported the opposite, i.e. higher post-prandial glycaemia in individuals with low AMY1 gene CN in response to starch ingestion but not to glucose or maltose ingestion[7,22,23,24] These findings suggest that people with low pSAA activity might be at greater risk of glucose intolerance if they chronically consume starch-rich. The observations above suggest that the pSAA activity and AMY1 CN could serve as potential markers to predict metabolic disorders, in populations where starch is a staple food
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