(P16-006-23) Determining Changes in Fecal Fermentation Profile and Weight Gain in a Murine Model Consuming a Mediterranean v. Western Diet

Objectives: This study aimed to evaluate physiological and microbiome differences in a murine model consuming a Mediterranean (M) v. Western (W) diet.

Methods: Study design: To investigate the potential of diets in modifying the fecal microbiota, we used 16 ICR mice per diet split evenly between males and females. Mice were acclimated for 5 weeks, consuming regular chow, before switching to M or W diets. Four same sex mice were housed per cage and randomly assigned M or W diets with 2 cages of male and female mice/diet. All animals were weighed weekly and stool samples collected, freeze-dried, ground. An aliquot was analyzed for short chain fatty acid (SCFA) to determine the fecal fermentation profile (FFP).

Diets: All animals were acclimated to their surroundings while consuming the standard mouse chow diet for 5 wks. Experimental diets were from Envigo for 5 wks. M vs. W diets were 24.2 v. 17.3% protein, 42.3 v. 48.5% carbohydrate, 13 v. 21.2 % fat, 9 vs. 5% fiber and energy density of 3.6 v. 4.5 kcal/g, and were offered ad libitum.

Fecal Fermentation Profile: Fecal samples had SCFA extracted and analyzed using a modified Schwiertz et al method via gas chromatography. The resulting SCFA profiles were used to determine differences between diets.

Statistical Model: General linear models examined main effects of diet, sex, and week while accounting for baseline value and a random effect for cage (SCFA) or mouse (weight).

Results: Diet effects for M v. W diets for SCFA were Acetate 50.12 v. 38.45% (p < 0.01), Propionate 14.19 v. 7.98% (p < 0.01), Butyrate 8.37 v. 17.27% (p < 0.01), Caproate 16.19 v. 23.68% (p < 0.01), and Caprillic 0.44 v. 0.68% (p < 0.01). Sex comparisons showed higher percentages of Butyrate (p < 0.05) for males and higher percentages of Isobutyrate (p < 0.01), Isovalerate (p < 0.01), and Propionate (p=0.02) for female mice. No differences were noted in weight gain for diet or sex.

Conclusions: Differences were noted between diets for FFP when looking at diet and sex effects. The M diet being less energy dense results in numerically lower weight gains while differences in diet composition results in significant changes in bacterial FFP. Hormonal status of male v. female mice may influence changes seen in FFP. Experimental feeding will continue through 8 wks where body composition, microbiome and physiological measures will be evaluated.

Funding Sources: ETSU Undergraduate Research Funding, CCRHS