(P04-014-25) Diets With Higher Slowly Digestible Starch Improve Metabolic Flexibility Using a New Assessment Approach

Objectives: The influence of dietary carbohydrate type on metabolic flexibility, or the ability to efficiently switch between oxidation of carbohydrate and fat, is incompletely understood. We sought to test the influence of dietary carbohydrate digestibility on metabolic flexibility and metabolic substrate utilization.

Methods: Adult wild-type mice (n=8) and mice lacking the mucosal maltase-glucoamylase enzyme (Mgam, n=8) were housed in indirect calorimetry cages and given a series of diets matched for total carbohydrate contents and containing different ratios of slowly digestible starch (SDS) and resistant starch (RS) [High SDS (53% RCS); Intermediate SDS (35% RCS + 18% HAS); Intermediate RS (18% RCS + 35% HAS); High RS (53% HAS)], or that were high in sucrose or fat [Sucrose (65% sucrose); and High-fat (42% fat)]. Exposure periods were 8 days per diet (4 days of acclimation, 4 days of data collection), and during the final 2 days of data collection fungal amyloglucosidase (AMG) was administered in drinking water to increase carbohydrate digestion rate. Respiratory exchange ratio (RER) data were examined using percent relative cumulative frequency (PRCF) analyses combined with a new application of modeling using the Mixed Weibull Cumulative Distribution function to assess metabolic substrate utilization and metabolic flexibility. We devised a Metabolic Flexibility Factor (MFF) to quantitate metabolic flexibility for each dietary condition and mouse genotype, with higher MFF indicating higher metabolic flexibility.

Results: Diets containing greater amounts of SDS exhibited lower average RER and higher metabolic flexibility (indicated by MFF) than diets high in RS, sucrose, or fat (P=0.0001 and P< 0.0001, respectively). Consumption of diets containing high and intermediate amounts of SDS resulted in a more complete shift to fat oxidation (Mixed Weibull Modeling, P< 0.05). Mouse genotype had minimal effects on substrate oxidation and metabolic flexibility. AMG supplementation shifted substrate utilization to carbohydrate oxidation (Mixed Weibull Modeling, P< 0.01) and generally decreased MFF (P=0.002).

Conclusions: Consumption of slowly digestible starch improved measures of metabolic substrate utilization at the whole-body level in adult mice.

Funding Sources: USDA, NIH, Whistler Center for Carbohydrate Research.