Effect of dietary protein on whole-body protein turnover and endocrine functionality in geriatric and young-adult dogs

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Thirty-six adult female Beagles averaging 2 or 8 years of age were utilized to assess the effects of graded levels of dietary protein (16, 24, or 32%) on endocrine-controlled regulation of whole-body protein turnover. Rates of whole-body protein synthesis (WBPS) and degradation (WBPD) were estimated using 15N-glycine and total excreta collection. Although N balance averaged -0.5 g/d for all three diets, it responded quadratically (P<01) to increased dietary protein. There was a quadratic response (P<.05) to dietary protein for both WBPS and WBPD rates, with highest (P<.05) rates in dogs fed 32% protein. Regression analysis between age-dependent changes in WBPS and essential amino acid (EAA) concentrations revealed that every 1% increase in EAA resulted in a 13.5% increase in WBPS (r2=.984; y=13.5x+46.1). Serum IGF-I, IGF-I binding protein-3, and total IGF-I binding proteins were higher (P< .05) in geriatric dogs. Lower EAA and WBPS rates in geriatric dogs fed 16% protein indicate that low protein diets may compromise the health of the geriatric dog. Increased levels of dietary protein positively affected whole-body protein turnover which may prevent the loss of muscle mass associated with the aging process.

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FASEB Journal

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