Increased plasma availability of l-arginine in the postprandial period decreases the postprandial lipemia in older adults

Objective: Older adults have exaggerated postprandial lipemia, which increases their risk for cardiovascular disease. We sought to determine the effects of increased plasma l-arginine (L-ARG) availability on the oxidation of ingested fat (enriched with [1,1,1-¹³C]-triolein) and plasma triacylglycerol (TG) concentrations during the postprandial period in older subjects. Methods: On one day, eight healthy subjects (67.8 ± 1.3 y old) received an intravenous infusion of L-ARG during the first hour of the postprandial period (L-ARG trial), while on a separate day, and in a randomized order, they received saline (control trial). Results: The 8-h area under the plasma concentration-time curve describing the postprandial plasma TG concentrations was considerably lower in the L-ARG trial than in the control trial (-4 ± 21 versus 104 ± 21 mg dL^-1 h^-1, P < 0.01). The rate of the postprandial oxidation of the ingested lipid was not different between the trials, but the average contribution of the ingested oleate to the oleate of the TG of the plasma small TG-rich lipoproteins (Svedberg flotation index 20-400) was lower in the L-ARG trial (11 ± 1 versus 18 ± 2%, P < 0.01). L-ARG infusion also decreased the 8-h area under the plasma concentration-time curve of the plasma free fatty acid concentrations derived from the ingested fat compared with the saline infusion (0.77 ± 0.09 versus 1.11 ± 0.08; mmol L^-1 h^-1, P < 0.01). Conclusion: Increasing the plasma L-ARG availability during the postprandial period decreases the postprandial lipemia in older adults, in association with a decrease in the postprandial contribution of ingested lipids into TGs of the plasma small TG-rich lipoproteins.