Effect of Potassium Bicarbonate and Vitamin D Insufficiency on Aging Skeletal Muscle.
Age-associated, low-grade metabolic acidosis and vitamin D insufficiency are potential
contributors to skeletal muscle loss and impairment. Reducing endogenous acid production
with alkali therapy lowers markers of muscle protein breakdown, but effects on muscle
morphology are unknown. Also, whether alkali therapy modifies the effect of vitamin D
insufficiency on muscle h... read moreas not been studied. Objective: We conducted a pilot study to
investigate the impact of an alkaline salt, potassium bicarbonate (KHCO3), and a vitamin
D3-deficient diet, alone and in combination, on intermediate biomarkers of muscle
protein metabolism and muscle fiber size in rats on acid-producing diets for 12 weeks.
Design: Thirty-six 20-month-old rats on acid-producing diets were weight-matched and
randomly assigned in a 2x2 factorial design to one of two KHCO3-supplemented diets (with
or without vitamin D3) or one of two diets without KHCO3 (with or without vitamin D3)
and pair fed for 12 weeks. Main Outcomes: At 12 weeks, we measured 24h urinary
nitrogen-to-creatinine ratio (UNi/Cr), a ratio of type I muscle fiber cross-sectional
area (CSA) to soleus weight (CSA1/soleus), a ratio of type II fiber CSA to extensor
digitorum longus (EDL) muscle (CSA2/EDL), serum IGF-1 and IGFBP-3 levels. Results: KHCO3
supplementation, adjusted for vitamin D3 group, resulted in lower mean UNi/Cr (11.99
mg/mg [95%CI 8.16-15.83] with KHCO3; 19.17 mg/mg [95%CI 15.46-22.89] without KHCO3;
P=0.01), higher mean CSA1/soleus (123.78 μm2/mg [95%CI 116.80-130.76] with KHCO3;
112.14 μm2/mg [95%CI 105.39-118.89] without KHCO3; P=0.02), similar mean CSA2/EDL,
and similar IGF-1 and IGFBP-3 levels when compared to groups without KHCO3. Vitamin
D3-deficient diets, adjusted for KHCO3 group, had no significant effects on muscle
endpoints. We did not detect statistically significant interactions between the KHCO3
and vitamin D3 groups. Conclusion: A 12-week alkalinization of the diet with KHCO3
promoted nitrogen sparing and larger type I fibers in aged rats on acid-producing diets.
Conversely, vitamin D3-deficient diets had no significant effect on these muscle
outcomes over a 12-week period.
Thesis (M.S.)--Tufts University, 2011.
Submitted to the Dept. of Clinical & Translational Science.
Advisor: David Kent.
Committee: Bess Dawson-Hughes, Lori Lyn Price, and Roger Fielding.
Keywords: Medicine, and Nutrition.read less