Journal of Lipid Research, Vol. 9, 19-26, January 1968
Copyright © 1968 by Lipid Research, Inc.

Lipogenesis in human adipose tissue

David J. Galton

New England Medical Center Hospitals, and the Department of Medicine, Tufts University School of Medicine, Boston, Massachusetts 02111

The pathways and some critical enzymes involved in lipogenesis in adipose tissue from 82 patients have been studied. Of the glucose-¹⁴C metabolized to lipid by isolated adipose cells, approximately 0.6% was recovered in fatty acids and the rest in glyceride-glycerol. Palmitate-1-¹⁴C was readily incorporated into neutral lipid.

Homogenates of human adipose tissue contained an active -glycerophosphate dehydrogenase which was approximately twice as active as malate dehydrogenase. Mitochondria of human adipose tissue contained an NAD-independent -glycerophosphate dehydrogenase; the reaction product, di-hydroxyacetone phosphate, was recovered extramitochondrially.

Homogenates of human adipose tissue also contained an active fatty acyl CoA synthetase which required ATP, CoA, and Mg⁺⁺ for maximal activity. The activity of acyl CoA synthetase varied greatly in a group of 40 patients. By contrast, the range of activity of malate dehydrogenase assayed in the same group of patients was much smaller.

When palmitate or palmitoyl CoA was used as substrate, no difference was found in the rate of incorporation of -glycerol-1,3-¹⁴C phosphate into neutral lipid. If time was allowed for activation of palmitate, the incorporation of -glycerol-1,3-¹⁴C phosphate into lipid was 3.5 times greater than for unactivated palmitate.

Palmitate (200 µm) stimulated lipogenesis in homogenates of human adipose tissue and then caused a severe inhibition at 700 µm. Arachidate over the same concentration range did not depress lipogenesis below initial values.

Supplementary key words adipose tissue • lipogenesis • incorporation • glucose-¹⁴C • palmitate-¹⁴C • l--glycerophosphate dehydrogenase and oxidase • fatty acyl-CoA synthetase • inhibition by fatty acids

Submitted on May 8, 1967
Accepted on September 13, 1967

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