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Lactate, Pyruvate and Acetate Interactions during in Vitro Lipogenesis in Bovine Adipose Tissue

US Department of Agriculture^,2, Clay Center, NE 68933

Abstract

In vitro fatty acid synthesis in bovine adipose tissue was studied; [U-¹⁴C] -acetate, (U-¹⁴C]-lactate, [¹⁴C]-pyruvate and [³H]-acetate were used as substrates. Acetate inhibited lactate utilization for fatty acid synthesis, regardless of whether glucose (2 mM) and insulin (33 milliunits/ml) were present in the incubation media. Lactate (1-10 mM) stimulated acetate incorporation into fatty acids. Lactate (2 mM) also stimulated acetate incorporation into fatty acids in the presence of glucose (2 mM) and insulin (33 milliunits/ml). The D-isomer of lactic acid (1 to 10 mM) did not significantly alter fatty acid synthesis from acetate. Pyruvate at 10 mM, but not at 1 or 5 mM, final concentration slightly stimulated acetate incorporation into fatty acids. The fact that much less [1-¹⁴C]-pyruvate than [2-¹⁴C]-pyruvate was incorporated into fatty acids in bovine adipose tissue indicates that pyruvate and lactate are decarboxylated in position 1 before incorporation into fatty acids. Acetate (1 to 10 mM) inhibited [¹⁴C]-pyruvate and [¹⁴C]-lactate incorporation into fatty acids with or without glucose and insulin in the incubation media. Acetate did not significantly alter pyruvate or lactate metabolism to CO₂. These data show that lactate can be used for fatty acid synthesis in vitro and that lactate at physiological concentrations found in vivo can augment acetate incorporation into fatty acids, whereas physiological concentrations of acetate inhibit lactate incorporation into fatty acids in bovine adipose tissue.

¹ The assistance of Messrs. Dave Higbea, B. Rosenkranz, and G. Johnson and Ms. K. L'Heureux with care and biopsy of the animals and the secretarial assistance of Ms. M. Stones were gratefully appreciated.

² Roman L. Hruska US Meat Animal Research Center, Science and Education Administration, Agricultural Research. Mention of a trade name, proprietary product, or specific equipment does not constitute a guarantee or warranty by the USDA and does not imply its approval to the exclusion of other products that may be suitable.