Abstract
Fructose consumption has increased substantially in the past few decades and has been linked with metabolic maladaptations. Whether increased physical activity (PA) may confer protection against these maladaptations is yet to be determined. Although the glucose and insulin response to fructose ingestion has been well studied, the incretin response is not well understood.
PURPOSE: The purpose of this study was to determine the interaction between high fructose consumption and PA levels on the incretin response to a fructose rich meal in normal weight individuals.
METHODS: Twenty normal weight men and women (age: 21-30 yr) consumed an additional 64 g high fructose corn syrup for 14 days on 2 occasions. During these 14 days, subjects maintained either low PA (4,500 steps/day) or high PA (12,500 steps/day). Each condition was followed by a study day where subjects were given a fructose-rich meal (600 calorie mixed meal (45% carbohydrate [7.3% fructose], 40% fat, and 15% protein)) in the morning after a 12 h overnight fast, and blood was sampled at baseline and for 6 h after the meal. Samples were analyzed for glucagon-like peptide 1 (GLP-1), glucose-dependent insulinotropic peptide (GIP) and insulin concentrations. The incremental area under the curve (iAUC) was calculated to quantify the postprandial responses.
RESULTS: GIP concentrations showed a significant PA by fructose loading interaction (P=0.00) such that fructose increased the GIP iAUC levels from pre to post-loading more so in the physically inactive condition (pre 14,575±2339; post 30,431±3502 pg/ml) than in the high PA condition (pre 12,812±1303; post 14,938±1834 pg/ml). GLP-1 concentrations also demonstrated a significant interaction (P=0.05, n=13) such that high PA lowered the GLP-1 levels (pre 8203±1484; post 6248±1678 pg/ml) during fructose loading, while low PA resulted in an increase in GLP-1 levels (pre 6977±1508; post 8432±1539 pg/ml). The glucose and insulin response to the fructose challenge showed no changes with the loading or PA changes. There were no sex differences.
CONCLUSIONS: The combination of high fructose intake in conjunction with more sedentary behavior results a larger incretin response to a fructose-rich meal, while glucose levels are maintained. High PA appears to protect the incretin response to increased fructose loading.