Abstract
We examined the effect of dietary protein manipulation (DPM: habitual vs. experimental) on fasting protein kinetics (PK) in 112 community‐dwelling healthy 65–90 yr old men. 13C2‐Leu infusion and muscle sampling were used to quantify PK; whole‐body proteolysis per lean body mass (WBP), muscle protein fractional synthetic rate and muscle proteolytic enzyme activities; chymotrypsin, trypsin, and peptidylglutamyl‐peptide. Mean habitual intake assessed by 3‐day food diaries was the basis for experimental meals (27.8 kcal, 1.0 g protein, 4.2 g carbohydrate per kg body weigh per day) that were provided to participants for 3 days prior to isotope studies. Protein intake in the experimental meals differed from habitual intake by at least 0.2 g/kg/day for 70 participants (range −1.3 to +0.6). Stepwise linear regression was used to determine associations between PK and DPM. Age, BMI, testosterone, IGF‐1, physical activity, quality of life, creatinine clearance, serum albumin, and insulin resistance (HOMA‐IR) or sensitivity (QUICKI) with univariate p<0.10 were entered in the models. Only QUICKI predicted WBP (r2=0.21, p<0.0001). PK measures were not affected when habitual and experimental dietary protein and energy intakes differed in these elderly men. This suggests that such differences do not alter whole‐body and muscle protein kinetics. Support: NIH R01 AG18169 & RR000954, NCRR‐GCRC, USDA‐ARS.
Published Version
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