Sex, Dietary pH, and Protein‐dependent effects in Diet‐induced Obese Mice

Abstract

Western diets, characterized by lower amounts of fruits, vegetables and lean proteins compared to higher quantities of saturated fats, fatty meats and sugar sweetened foods and beverages, have been implicated in metabolic diseases (e.g., obesity), in part, through low‐grade metabolic acidosis. Hence, the purpose of this study was to assess the effects of pH‐enhanced diets rich in beef or casein in diet induced obese B6 mice, compared to low fat‐fed mice. We hypothesized that metabolic health will be improved by consuming a diet containing pH‐enhanced cooked ground beef or casein, compared to a non pH‐enhanced beef or casein diets.Male and female mice were randomized (n=10) into 8 groups by protein source (beef protein or casein); fat content (low fat (LF) or high fat (HF)), and with or without pH‐enhancement with ammonia (N): LF casein (LFC) or LFCN; LF beef (LFB) or LFBN; HFC or HFCN; HFB, or HFBN. Weight gain and food intake were measured weekly (for 12 weeks); body composition was measured at weeks 7, 11; and glucose tolerance test (GTT) was performed at week 10.Body weight was significantly higher in all male HF groups (HF, HFN, HFB and HFBN: regardless of the protein source) compared to low fat groups (LFC, LFN, LFB, LFBN) except for the LFB group; however, no significant differences were observed in females. Male mice (but not females) fed lean beef (LFB, LFBN) exhibited significantly lower fat mass compared to mice fed HF diets with or without beef (HFC, HFB). Moreover, a significant main effect was observed for dietary fat (LF vs HF), protein source (casein vs beef) and pH (pH enhanced (N) vs not enhanced) in males’ fat mass, whereas females demonstrated a significant main effect for dietary fat (LF vs HF) but not for pH or protein source. Additionally, glucose clearance was increased (p=0.05) in LF groups compared to HF groups for both male and females. Interestingly, pH enhanced groups (HFN and HFBN) demonstrated higher glucose clearance (p=0.05) compared to HF group in both male and female mice. Surprisingly, glucose clearance was not improved by pH enhancement in the LFN group with trends towards worsening glucose intolerance (p value 0.08), compared to LF casein groups in both male and female mice. While there were differences in main effects and interactions among diet, protein source and pH enhancement in males compared to females, a significant (p=0.0001) main effect was observed in all parameters (fat mass, lean mass, final body weight, glucose clearance and serum insulin and leptin levels) among males and female mice, further confirming the sex‐dependent impact on metabolism regardless of the diet, protein source or the whether the diet pH is enhanced or not.Our findings suggest potential metabolic benefits of increasing dietary pH, as indicated by improved glucose clearance. The main effects and interactions observed in diet and protein source further indicate that it may be the amount of fat rather than the protein source, which contributes to metabolic dysfunctions. Additional research is warranted to determine sex dependent mechanisms underlying the metabolic effects of dietary fat content, protein source and interactions with dietary pH.