(P15-032-24) Effects of Diets Containing Ammoniated Beef on Markers of Ammonia Metabolism in Livers From Diet-Induced Obese Mice

Objectives: Diets high in fat, sugar and sodium and low in fruits and vegetables, especially leafy greens, tend to have an acidic pH, which may partly contribute to metabolic dysregulations including acidosis. We have previously reported physiological improvements from pH-enhanced beef with ammonium hydroxide, but the underlying mechanisms remain unknown. Therefore, we hypothesized that these metabolic ameliorations, in obese mice consuming diets containing ammoniated beef, compared to non-ammoniated beef, are mediated by changes in hepatic ammonia metabolism.

Methods: Male and female B6 mice were fed 4 diets for 12 weeks: Low Fat Beef, High Fat Beef, without (LFB or HFB, respectively) or with ammoniation (LFBN and HFBN). Mice were metabolically phenotyped and fecal samples collected during the interventions. Tissues including liver and cecal samples were collected after the intervention and stored for further analyses. Using qPCR, expression of genes involved in ammonia metabolism were determined, and included markers of the urea cycle (Arg1, Asl, Ass1, Cps, Ornt1, Otc, Nags), ammonia transport (Rhbg), bicarbonate synthesis (Ca5a), polyamine synthesis (Odc), and glutamine synthesis (Gs).

Results: Histological analysis of male liver triglyceride content via AdipoGuage software revealed high-fat diets increased liver TG accumulation [P < 0.0001], with no significant effects from ammonia. In female livers, HF decreased mRNA levels of both Ass1 [P=0.0005] and Ornt1 [P=0.0049]; while in males only Ornt1 mRNA levels were decreased by HF [P=0.0043]. Moreover, ammoniation led to trends of increased expression of Asl [P=0.0544] and Ass1 [P=0.0716] in females. Also, ammoniation increased Ca5a mRNA levels in females [P=0.0022]. By contrast, limited changes were observed in male liver.

Conclusions: Our results indicate that both ammoniation and fat content sex-dependently regulate hepatic urea cycle metabolism at the mRNA levels. Experiments are ongoing to measure these changes at the protein level, as well as in other target ammonia metabolizing tissues such as the kidneys. This research will help enhance our understanding of the effects of dietary pH, fat content, and sex in metabolic diseases, and warrants further translational research in this area.

Funding Sources: Funded by Empirical Foods Inc.