Salivary composition in obese vs normal-weight subjects: towards a role in postprandial lipid metabolism?

In the pathophysiological context of obesity, oral exposure to dietary fat can modulate lipid digestion and absorption but underlying in-mouth mechanisms have not been clearly identified. Therefore we tested the hypothesis that salivary components related to dietary fat sensitivity would differ according to BMI and postprandial lipid metabolism in young men. Saliva was collected from 9 normal-weight (BMI=22.3±0.5 kg/m2) and 9 non-morbid obese (BMI=31.7±0.3 kg/m2) men before a 8 h-postprandial metabolic exploration test involving the consumption of a 40 g fat-meal, in which obese subjects revealed a delayed postprandial lipid metabolism. Nine salivary characteristics (flow, protein content, lipolysis, amylase, proteolysis, total antioxidant status, lysozyme, lipocalin 1, carbonic anhydrase-VI) were investigated. We show that under fasting conditions, salivary lipolysis was lower in obese vs normal-weight subjects, while proteolysis and CAVI were higher. We reveal through multivariate and Mann-Whitney analysis that differences in fasting salivary lipolysis and proteolysis between both groups are related to differences in postprandial lipid metabolism including exogenous fatty acid absorption and beta-oxidation. These results suggest a potential role of salivary composition on postprandial lipid metabolism and bring novel causal hypotheses on the links between salivary composition, sensitivity to dietary fat oral income and postprandial lipid metabolism according to BMI.International Journal of Obesity accepted article preview online, 28 April 2015. doi:10.1038/ijo.2015.71