Utilisation of triacylglycerol and non-esterified fatty acid by the working rat heart: myocardial lipid substrate preference

Utilisation and subsequent metabolic fate (oxidation. tissue lipid depositi on) of non-esterified fatty acid (NEFA), very-low-density lipoprotein-triac ylglycerol (VLDL-TAG), and chylomicron-triacylglycerol (CM-TAG) alone or in combination by isolated working rat heart were examined. Cardiac mechanica l function was maintained regardless of lipid substrate used. NEFA and CM-T AG were assimilated to a greater extent than VLDL-TAG; CM-TAG utilisation ( 76 +/- 10 nmol fatty acid/min per g wet wt.; n = 8), but not VLDL-TAG utili sation (16 +/- 2 nmol fatty acid/min per g wet wt.; n = 8), was suppressed in the presence of NEFA, but TAG (CM or VLDL) did not alter NEFA utilisatio n (57 +/- 9 nmol fatty acid/min per g wet wt., n = 8). Most (about 75%) of the lipid utilised was oxidised. In the presence of NEFA, CM-TAG deposition as tissue lipid was preserved, despite decreased CM-TAG oxidation; metabol ic fate of VLDL-TAG was unaffected by NEFA. TAG (CM or VLDL) in the perfusa te tended to decrease lipoprotein lipase (LPL) activity; this may be a refl ection of increased LPL turnover in the presence of lipoproteins. (C) 2001 Elsevier Science B.V. All rights reserved.