Effects of Amino Acid Supplementation on Liver Lipid Content: A Randomized, Double-Blinded, Placebo-Controlled Trial

Abstract

Abstract Objectives To test whether chronic ingestion of essential amino acids (EAAs) plus arginine lowers liver lipid content when compared with a placebo (non-essential amino acids; NEAAs). Methods Older adults (50–75 y) with elevated fasting plasma triacylglycerol (TAG) concentrations were recruited into the study. After screening (week -2), all participants ingested placebo (NEAAs; alanine, aspartic acid, and serine) capsules twice daily (between meals) for two weeks and 3 T nuclear magnetic resonance spectroscopy scans were used to determine baseline (week 0) liver lipid percentage. Participants were then randomised to receive capsules containing 11 g of EAAs plus arginine (n = 10) or NEAAs (n = 9) twice daily for eight weeks, using a double-blinded design. Follow-up NMR spectroscopy scans were conducted at eight weeks after the onset of randomised supplementation (week 8) to determine the impact on liver lipids. Results Liver lipid percentage (mean ± standard deviation) was not significantly altered by randomised supplementation in either the EAAs plus arginine group (Pre: 9.08 ± 7.90%; Post: 8.94 ± 6.91%; P = 0.65) or the NEAAs group (Pre: 10.23 ± 7.20%; Post: 9.65 ± 7.70%; P = 0.18). Change in fasting plasma TAG during placebo run-in (Week 0 minus screening) was significantly negatively correlated with change in liver lipid content (week 8 minus week 0) for the EAAs plus arginine group (r = −0.722; P = 0.02), but not for the NEAAs group A (r = −0.479; P = 0.19). Conclusions Eight weeks of essential amino acids plus arginine ingestion did not significantly lower liver lipid content in older adults. However, ingestion of non-essential amino acids during the run-in period may have influenced the effect on liver fat of subsequent randomised amino acid supplementation, suggesting further investigation is warranted. Funding Sources The study was sponsored by NIH/NIA (award to EB), and the Roy and Christine Sturgis Charitable Trust (award to NMH). Screenings and study visits were undertaken within the ITS-Clinical Research Center at UTMB, funded by NIH/NCRR, and within the UAMS Donald W. Reynolds Institute on Aging at UAMS, funded by NIH/NIA. NMH and EB were also funded by the Arkansas Biosciences Institute, the major research component of the Arkansas Tobacco Settlement Proceeds Act of 2000.