Effects of supplementation with essential amino acids on intrahepatic lipid concentrations during fructose overfeeding in humans
Theytaz F., Noguchi Y., Egli L., Campos V., Buehler T., Hodson L., Patterson BW., Nishikata N., Kreis R., Mittendorfer B., Fielding B., Boesch C., Tappy L.
Background: A high dietary protein intake has been shown to blunt the deposition of intrahepatic lipids in high-fat- and high-carbohydrate-fed rodents and humans. Objective: The aim of this study was to evaluate the effect of essential amino acid supplementation on the increase in hepatic fat content induced by a high-fructose diet in healthy subjects. Design: Nine healthy male volunteers were studied on 3 occasions in a randomized, crossover design after 6 d of dietary intervention. Dietary conditions consisted of a weight-maintenance balanced diet (control) or the same balanced diet supplemented with 3 g fructose·kg-1·d-1and 6.77 g of a mixture of 5 essential amino acids 3 times/d (leucine, isoleucine, valine, lysine, and threonine) (HFrAA) or with 3 g fructose·kg-1·d-1and a maltodextrin placebo 3 times/d (HFr); there was a washout period of 4 to 10 wk between each condition. For each condition, the intrahepatocellular lipid (IHCL) concentration, VLDL-triglyceride concentration, and VLDL-[13C]palmitate production were measured after oral loading with [13C]fructose. Results: HFr increased the IHCL content (1.27 ± 0.31 compared with 2.74 ± 0.55 vol %; P < 0.05) and VLDL-triglyceride (0.55 ± 0.06 compared with 1.40 ± 0.15 mmol/L; P < 0.05). HFr also enhanced VLDL-[13C]palmitate production. HFrAA significantly decreased IHCL compared with HFr (to 2.30 ± 0.43 vol%; P < 0.05) but did not change VLDL-triglyceride concentrations or VLDL-[13C]palmitate production. Conclusions: Supplementation with essential amino acids blunts the fructose-induced increase in IHCL but not hypertriglyceridemia. This is not because of inhibition of VLDL-[13C]palmitate production. This trial was registered at www.clinicaltrials.gov as NCT01119989. © 2012 American Society for Nutrition.