Amino acid supplementation decreases plasma and liver triacylglycerols in elderly

Abstract

Objective: Hypertriglyceridemia is a risk factor for coronary heart disease. The aim of this study was to determine the effect of amino acid (AA) supplementation on plasma, liver, and muscle lipid concentrations and insulin sensitivity in the elderly.

Methods: Twelve impaired glucose tolerant elderly (mean +/- SD 67.0 +/- 5.6 y of age, seven women and five men) ingested 11 g of essential AAs plus arginine twice a day for 16 wk, after a 7-wk control run-in. Diet and activity were not otherwise modified. Plasma lipid concentrations and oral glucose tolerance were measured every fourth week and tissue lipid concentrations (magnetic resonance spectroscopy) every eighth week.

Results: No changes in plasma lipids were observed during the control run-in. AA supplementation lowered plasma triacylglycerol (TG; P < 0.001), total cholesterol (P = 0.048), and very low-density lipoprotein cholesterol (P < 0.001) concentrations. Plasma TG decreased approximately 20% from the initial value of 1.45 +/- 0.18 mmol/L (mean +/- SE, 128 +/- 16 mg/dL), with the greatest decrease in the subjects starting out with the highest concentrations (r = -0.83). Similarly, liver fat content (liver TG/Intralipid standard) decreased approximately 50% from the initial value of 0.34 +/- 0.06 (P = 0.021, n = 8), with the greatest decrease in the subjects who initially had the highest values (r = -0.86). Intramuscular fat content and insulin sensitivity did not change.

Conclusion: Diet supplementation with AAs lowers plasma TG, total cholesterol, and very low-density lipoprotein cholesterol concentrations and liver lipid content in impaired glucose tolerant elderly. AA supplementation may have a potential role in the treatment of hypertriglyceridemia or hepatic steatosis.

Figures

Fig. 1

The average plasma triglyceride concentration changes from baseline during 16 weeks of amino acid supplementation in elderly that had baseline values between 0.56–1.12 mmol/l (50–99 mg/dl; left; n = 4), between 1.13–1.68 mmol/l (100–149 mg/dl; middle; n = 5) and >1.69 mmol/l (>150 mg/dl; right; n = 3). Normal reference range: 0.34–1.92 mmol/l (30–170 mg/dl). Data are mean ± SE; *P = 0.01 vs. zero; #P = 0.004 vs. zero.

Fig. 2

Liver lipids (liver TG/intralipid standard) at baseline, and after 8 and 16 weeks of amino acid supplementation (mean ± SE; n = 8 at week 0 and 16, n = 6 at week 8); *P < 0.05 vs. baseline.