Fatty Acid Synthesis from Lactate in Growing Cattle

Abstract

Rates of fatty acid synthesis from lactate and acetate and activities of selected lipogenic and NADPH-generating enzymes were determined in subcutaneous, intermuscular and intramuscular adipose tissues of cattle that were 11-19 months of age. Fatty acid synthesis from lactate and acetate increased from 11 to 13 months of age in subcutaneous and intermuscular adipose tissues; synthesis from lactate increased until 17 months of age. In intramuscular adipose tissue, synthesis from lactate also increased until 17 months of age while that from acetate continually increased. Activities of NADPH-generating enzymes increased in all three fat depots from 11 to 13 months of age, and little change occurred thereafter. Acetyl-CoA carboxylase activity was constant over entire growth period in all depots. Activity of ATP-citrate lyase increased from 11 to 13 months of age in subcutaneous and intermuscular adipose tissues, but did not increase until 19 months of age in intramuscular adipose tissue. In all cases, activities of ATP-citrate lyase were sufficient to support synthesis from lactate; therefore, lactate conversion to fatty acids in bovine adipose tissues seems to use the citrate cleavage pathway for generation of cytosolic acetyl-CoA.

Glucose-6-phosphate dehydrogenase and leptin are related to marbling differences among Limousin and Angus or Japanese Black × Angus steers1,2

“…adipose tissue are in agreement and supplement the data reported for enzymes involved in de novo lipogenesis in different breeds of growing meat cattle (Chakrabarty and Romans, 1972;Whitehurst et al, 1981;Smith and Crouse, 1984;Miller et al, 1991). These greater activities probably contribute to the greater lipid deposition in s.c. adipose tissue, as suggested by its lower protein content, and confirm the repeatedly observed later maturity of i.m.…”

“…Black cross steers. Indeed, lipogenic activities increased with age until 7 to 13 mo of age depending on the breed and the plane of nutrition (Hood and Allen, 1975;Whitehurst et al, 1981; and then decreased. Elsewhere, the greater LPL activity in Limousin s.c. adipose tissue may indicate a lack of relationship between its potential for circulating fatty acid uptake and carcass adiposity ( Figure 5A).…”

Influence of the diet and grazing on adipose tissue lipogenic activities and plasma leptin in steers

“…Adipose tissue lipogenesis in steers fed grass or maize with previous reports (Whitehurst et al, 1981;Mendizabal et al, 1999) in different breeds of steers. However, the absence of interaction between adipose depot and dietary treatments for most enzymes indicates that diet-induced changes in lipogenic enzyme activities are consistent across adipose depots.…”

mRNA expression of genes regulating oxidative phosphorylation in the muscle of beef cattle divergently ranked on residual feed intake

“…This phenotype ϫ dietary period interaction may have been mediated through a number of physiological processes. For example, 1) alterations in metabolism of end-products of fermentation due to differences in dietary substrates consumed (highstarch/low-fiber diets shift the pattern of end-products of ruminal fermentation toward greater propionate, providing readily available sources of energy for growing muscle)(37, 80); 2) differences in lipid metabolism (accretion vs. mobilization) (37), and subsequent adipogenic signals (83), and 3) differences in muscle metabolism during protein turnover, connective tissue remodeling, and muscle atrophy (90,107), which take place during periods of decreased energy intake, or indeed a combination of the above factors. Furthermore, negative associations were also detected between COX II gene expression with BHB and subcutaneous fat depth, indicating a potential link between tissue catabolism and the expression of this gene.…”