Regulation of Energy Metabolism by Dietary pH and Protein Source in Diet-induced Obese Mice and Female Mice.

Consumption of foods with acidic pH has been proposed as a potential contributor to negative metabolic health outcomes. Thus, in this work, we determined the main effects of dietary pH during onset of obesity in male and female B6 mice. We hypothesized that metabolic health will be improved by consuming a diet containing pH-enhanced ground beef or casein diets, compared to a non-pH-enhanced diets. To test this hypothesis, we designed a mouse study using the following 8 groups: Low-fat diet + casein protein (LFC), LF + casein with pH enhanced/ammonia (LFCN), LF + beef protein (LFB), LFB with pH enhanced (LFBN), High-fat diet + casein protein (HFC), HF + casein with pH enhanced (HFCN), HF + beef protein (HFB) and HFB with pH enhanced (HFBN). Mice were fed these diets for 12 weeks, during which we measured changes in body weight and food intake. Mice were individually placed in metabolic cages (TSE PhenoMaster System) at ambient temperature and a 12-hour light/dark cycle at week 11. The relationship between metabolic rate and body mass was normalized, and we evaluated energy balance (H), respiratory exchange ratio (RER), VCO2, VO2, feed, drink and distance traveled by the mice. These metabolic data were analyzed in both day and night periods. Blood and tissues were collected at the end of the study and fat pad weights were measured. Results showed that in males, body weight was increased in all HF groups, regardless of the protein source, while females did not exhibit any differences across groups. However, for energy metabolism, overall, females exhibited the main changes, especially for the interaction between LF and HF groups. These findings suggest that despite the lack of significant weight gain in females, they used fat as energy source based on their RER, VCO2 and VO2 data. During the day, only HF females had decreased VCO2, and at night both male and female exhibited the same pattern of decreased VCO2. During the night, only males from HF groups had reduced VO2. Regarding energy intake, only HF females had increased food consumption compared to males. The main effects of RER in both males and females were related to diet (LF x HF), in both day and night periods. Interestingly, females also presented differences for the interactions of the protein content (casein vs beef) during the day (p<0.0115). The latter suggests that in females, the protein source may be related to energy consumption and substrate utilization. Fat pad weights were increased in males from all HF groups compared to all LF groups. However, in females, only HFC groups had higher fat pad weights compared to LFC. The reduced RER, observed in both male and female mice from HF groups indicates that fat was oxidized and used as the main energy source in these groups, consistent with higher dietary fat content. Taken together, our data suggest that metabolic changes and substrate utilization are affected by dietary fat content (HF) and are more pronounced in female mice. Further analyses in metabolically active tissues from these mice will help elucidate the mechanisms mediating sex-dependent differences in metabolic effects of dietary pH enhancement, fat content and source of protein.