Novel experimental protocol to increase specific plasma nonesterified fatty acids in humans

Abstract

This study reports a novel protocol to increase plasma monounsaturated, polyunsaturated, and saturated nonesterified fatty acids (NEFA) in eight healthy volunteers (age 29–54 yr, body mass index 23–26 kg/m2). This was achieved by feeding small boluses of fat at different time points (35 g at 0 min and 8 g at 30, 60, 90, 120, 150, 180, and 210 min) in combination with a continuous low-dose heparin infusion. Olive oil, safflower oil, or palm stearin were used to increase monounsaturated, polyunsaturated, or saturated NEFAs, respectively. Plasma NEFA concentrations were increased for 2 h, when fat and heparin were given (olive oil: 745 ± 35 μmol/l; safflower oil: 609 ± 37 μmol/l, and palm stearin: 773 ± 38 μmol/l) compared with the control test (no fat and no heparin: 445 ± 41 μmol/l). During the heparin infusion, 18:1 n-9 was the most abundant fatty acid for the olive oil test compared with 18:2 n-6 for the safflower oil test and 16:0 for the palm stearin test ( P < 0.01). The method described here successfully increases several types of plasma NEFA concentrations and could be used to investigate differential effects of elevated individual NEFAs on metabolic processes.