Acute oral amino acid intake increases both secretion and breakdown of very low density lipoprotein‐triacylglycerol

Abstract

We have previously reported a reduced plasma triacylglycerol (TAG) concentration in elderly individuals following chronic intake of amino acids (AAs), but it is unclear how acute intake of AAs affects plasma TAG kinetics. We used dual stable isotope tracer methodology in this study to investigate the effect of acute AA intake on the fractional secretion rate (FSR) and fractional breakdown rate (FBR) of VLDL‐TAG derived from plasma fatty acids. Eight hypertriacylglycerolaemic volunteers (mean ± standard deviation (SD): age 63.4 ± 7.7 years; BMI 29.6 ± 5.0 kg·m−2; fasting TAG 191 ± 52 mg·dl−1) were studied during a 5‐h basal period and a 5‐h period of acute AA intake. Infusions of U‐13C16‐palmitate and 2H2‐palmitate were started and stopped at specific time points to allow VLDL‐TAG secretion and breakdown to be calculated. VLDL‐TAG FSR was significantly higher during the AA intake period than during the basal period (mean ± SEM: 12.9 ± 2.6 vs. 8.7 ± 1.4 %·h−1; P < 0.05), as was VLDL‐TAG FBR (13.8 ± 4.0 vs. 4.9 ± 1.6 %·h−1; P < 0.05). We conclude that acute amino acid intake increases fractional secretion and breakdown rates of VLDL‐TAG, and may promote a state of net breakdown, which lowers the plasma TAG concentration. The study is sponsored by 1R01 AG033761 NIH/NIA and P30 AG024832 NIH/NIA. Screenings and study visits are being undertaken within the ITS‐Clinical Research Center at UTMB, funded by grant 1 U54RR026141 NIH/NCRR.