Content area
Abstract
Added sugars from sweetened beverages contribute a substantial number of calories to the American diet with numerous associated negative health effects. There is a need to evaluate the different effects of fructose, glucose, and aspartame on healthy young adult metabolism to better understand the etiology of obesity and obesity-associated diseases. This study aims to evaluate differences in de novo lipogenesis in adipose tissue versus the liver when subjects consume differentially sweetened beverages, based on research in rodent models suggesting that the balance of hepatic vs. adipose tissue lipogenesis has substantial effects on energy and glucose homeostasis. Healthy young adults consumed a controlled and standardized diet with glucose-, fructose-, or aspartame-sweetened beverages as 25% of caloric intake for 8 day periods in a randomized double-blind cross-over study. After each diet period, subjects were admitted to the University of Washington Clinical Research Center where fasting plasma samples were obtained for later gas chromatographic measurement of palmitoleic acid in both phospholipid and free fatty acid fractions as a biomarker for de novo lipogenesis, in addition to lipid levels and inflammatory markers. There was no significant difference in palmitoleic acid levels in the free fatty acid fraction of plasma between the three diet periods (p=0.740). There was a significant difference in palmitoleic acid levels in the phospholipid fraction of plasma between the three diet periods (p=0.020). In post hoc analysis, there was significantly higher palmitoleic acid level in phospholipids in the fructose- than in the aspartame-sweetened beverage diet period (p=0.024, adjusted). These results indicate that while there was no significant difference in the effect of the different sugars on adipose tissue de novo lipogenesis, the sugars elicited differential effects on hepatic de novo lipogenesis. Phospholipid palmitoleic acid was positively associated with plasma fasting triglycerides, and inversely with resting energy expenditure. Taken together, these results suggest that dietary fructose, but not glucose, induces hepatic de novo lipogenesis and has detrimental effects for metabolic health.
