Copy Number Polymorphism of the Salivary Amylase Gene: Implications in Human Nutrition Research

Abstract Objectives The microbial metabolite trimethylamine n-oxide (TMAO) is associated with cardiovascular and renal disease. The dietary factors contributing to plasma TMAO concentrations are not well characterized in a generally healthy population unmedicated for metabolic diseases. The objective of this study was to assess the relationships among TMAO-precursor foods, TMAO, and classic cardiometabolic markers in a generally healthy population stratified for age, sex, and BMI. Methods Fasting plasma TMAO was quantified using liquid chromatography-mass spectrometry in 356 participants (n = 188 female, 18–65 yr, 18–40 BMI) enrolled in the cross-sectional Nutritional Phenotyping Study conducted as the USDA Western Human Nutrition Center. Diet was assessed by averaging 2 weekday and 1 weekend ASA-24hr recalls cleaned by NCBI guidelines. Fasting plasma analytes such as glucose, insulin, triglycerides, and cholesterol were measured using the Cobas Integra 400 Plus. Variables were transformed to conform to the normal distribution. Regression models assessing health parameters and TMAO were adjusted for age, sex, and the kidney function marker, cystatin C. Models assessing TMAO and diet variables were adjusted for age, sex, and energy intake. Composite variables describing average intake of red meat and TMAO-precursor foods were created by summing the appropriate ASA24 variables. Results TMAO was associated with age (P = 0.001), but not sex or BMI. A significant interaction (P = 0.006) between sex and age was used in all models. Of the variables analyzed, only refined grains and total energy intake were significantly associated with TMAO (r = −0.11, P = 0.04; r = 0.12, P = 0.03, respectively). Reduced renal function as assessed by circulating cystatin C concentrations was associated with plasma TMAO (r = 0.18, P < 0.001). Average daily red meat consumption as well as average daily TMAO-precursor consumption was not significantly associated with TMAO (P = 0.137, P = 0.554, respectively). In contrast, average daily fiber intake was marginally related to TMAO (B = −0.11, SE = 0.01, P = 0.07). Conclusions In this generally healthy population, no relationship between red meat or TMAO-precursor foods and TMAO was identified. Funding Sources The Beef Checkoff (R01HL128572); USDA/ARS/Western Human Nutrition Research Center project funds (2032–51,000-025–00D).

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Salivary amylase gene copy number and its association with fasting and postprandial glucose response

Proceedings of The Nutrition Society ◽

10.1017/s0029665120000853 ◽

2020 ◽

Vol 79 (OCE2) ◽

Author(s):

Mary Farrell ◽

Emily Sonestedt ◽

Anne Raben ◽

Juscelino Tovar ◽

Stina Ramne ◽

...

Keyword(s):

Observational Study ◽

Copy Number ◽

Fasting Glucose ◽

Postprandial Glucose ◽

Gene Copy ◽

Amylase Gene ◽

Salivary Amylase ◽

Glucose Levels ◽

Copy Numbers ◽

Meal Study

AbstractIntroductionWhen compared to other primates, humans elicit a large variation in the copy number for the salivary amylase gene, AMY1. This variation can range from 2 to 17 copies. The AMY1 gene is responsible for coding for salivary amylase, an enzyme needed to catalyze the hydrolysis of starch molecules into smaller sugars. AMY1 copy number correlates with the amount and activity of salivary amylase. Few studies have investigated the effect of amylase copy number on fasting and postprandial glucose levels. The aim was first to investigate the association between AMY1 copy numbers and fasting glucose in an observational study, and secondly to investigate the difference in postprandial effect of high-starch meals in individuals with either high or low AMY1 copy numbers.Materials and methodsFor the observational study, we used data from 436 participants from the Malmö Offspring Study (MOS) cohort whom have been genotyped for AMY1. For the meal study (conducted during May 2019), we used genotype-based-recall to recruit 24 participants from the observational study of the MOS cohort: 12 with low AMY1 copy number (from the lowest 20%) and 12 with high AMY1 copy numbers (from the highest 20%). Each subject will be served a breakfast meal of white wheat bread on two separate test days: one containing 40 g and the other containing 80 g of carbohydrates (mainly starch). Blood samples will then be taken at various time points to investigate postprandial glucose and insulin responses.ResultsWhen using linear regression analyses adjusting for age and sex, no significant association between AMY1 copy number and fasting glucose was observed (p = 0.23). However, there was a difference (p = 0.05) in fasting glucose levels between the lowest (2–4 copy numbers: 5.31 mmol/L; 95% CI: 5.13–5.50) and highest (10–16 copy numbers: 5.57 mmol/L; 95% CI: 5.39–5.75) copy number groups. The results for the meal study will be obtained in June 2019 and be presented at the conference.DiscussionOur findings of higher fasting glucose among the group with more than 10 AMY1 copy numbers is the first study to find this and needs to be replicated in other populations.

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