Lipogenic Enzyme Activity in Adipose Tissue During the Growth of Swine With Different Propensities to Fatten

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Abstract
Adipose tissue from three depots in swine of three breeding groups with different propensities to fatten was assayed for NADP-malate dehydrogenase (ME), NADP-isocitrate dehydrogenase (ICDH), glucose-6-phosphate dehydrogenase (G-6-PDH), 6-phosphogluconate dehydrogenase (6-PGDH) and acetyl CoA carboxylase (CBX). Net de novo synthesis was estimated by calculation to account for 73 and 82% of the total body fat accumulated during the growth of Hampshire × Yorkshire (H × Y) and Minnesota 3 × 1 (Minn 3 × 1) pigs, respectively. In porcine adipose tissue, growth to 109 kg live weight was accompanied by a progressive increase in the activity of ME, G-6-PDH and 6-PGDH when the activity was expressed per adipose organ or per 105 adipose cells. The activity of ICDH on a cellular basis increased only in the adipose tissue of the fatter Minn 3 × 1 pigs. The activities of ME, G-6-PDH, 6-PGDH and CBX were greater in perirenal tissue, intermediate in middle subcutaneous tissue and least in outer subcutaneous tissue. All enzyme activities were greater in the tissues of the fatter Minn 3 × 1 pigs than the respective tissues from the leaner H × Y pigs, while tissues from the Hormel Miniature pigs contained higher activities (cell basis) than the conventional pigs at equivalent live weights. Enzyme activities expressed on a cellular basis were found to be positively correlated with the weight of extramuscular fat, mean adipose cell volume and cellular soluble protein content and negatively correlated with chronological age and total number of extramuscular adipose cells at constant live weight. The soluble protein content of adipose cells was observed to increase with increasing mean cell volume.