Exploratory Analysis Of Protein Metabolism Sex Difference Following Feeding

PURPOSE: One of the principal roles of dietary protein is to increase muscle protein synthesis (MPS), whole-body protein synthesis (WBPS), WB net balance (WBNB), with a reduction in WB protein breakdown (WBPB). Although multiple investigations have examined sex difference in the basal state of these variables, little attention has been given to feeding induced changes from the basal to postprandial (Δ) state. Thus, the purpose of this study was to perform an exploratory analysis of a recently completed study using whole-food protein sources to investigate sex differences in ΔMPS, ΔWBPS, ΔWBPB, and ΔWBNB. METHODS: Participants were aged 18 to 40 years of age with a BMI between 20 and 32 kg/m. Written informed consent was obtained from all participants, and approved by UAMS IRB. Participants were assigned to one of three intervention groups via a single-blinded permuted block randomization, stratified for sex: 4 oz beef patty; 4 oz impossible burger; 8 oz impossible burger. Stable isotopes were infused to assess protein metabolism. Appropriate muscle and blood samples were obtained. Enrichment was measured with mass spectrometry. Independent samples t-test on ΔMPS, ΔWBPS, ΔWBPB, and ΔWBNB were used to identify sex difference in response to feeding. Significance was accepted at p ≤ 0.05. RESULTS: Women (MPS = 0.12 ± 0.01 %/hour: WBNB = 12.5 ± 6.1 grams per 360 minutes) displayed higher means than men (MPS = 0.11 ± 0.01 %/hour: WBNB = 10.8 ± 5.2 grams per 360 minutes). Nonetheless, independent samples t-test indicated that ΔMPS (p = 0.876), ΔWBPS (p = 0.239), ΔWBPB (p = 0.244), ΔWBNB (p = 0.244) were not significantly different between sexes. Post-hoc power analysis indicated a total sample size of 76 and 358 are required to detect statistically significant differences in ΔMPS and ΔWBNB, respectively. CONCLUSIONS: In this exploratory analysis, whole-food protein sources resulted in small to moderate effect sizes for feeding induced increases in protein metabolism between sexes. Supported by: National Cattleman's Beef Association