Presence Of Exogenous Fatty Acids Research Articles

Fatty acid and glucose utilization in isolated, working newborn pig hearts.

The effects of exogenous fatty acids on glucose uptake were assessed in isolated, working newborn pig hearts in which great vessel pressures were controlled (mean 55 mmHg) and oxygenated nutrient buffer was recirculated through the heart for 30 or 60 min. When palmitate (1.5 mM) or octanoate (1.0 mM) were added to buffer containing 10 mM glucose and 100 mU insulin/ml, glucose uptake, as measured by 3H2O production from D-[2-3H]glucose, was suppressed to less than one-half that observed when glucose alone was present. Increased tissue levels of glucose 6-phosphate, fructose 6-phosphate, and citrate following perfusion in the presence of exogenous fatty acids were consistent with decreased glycolytic activity due to inhibition of phosphofructokinase. Measurements of carnitine in perfused and unperfused hearts indicated that total carnitine levels in neonatal hearts are similar to those of adult pigs. Increased tissue levels of long-chain acyl carnitine, acetyl carnitine, and citrate in hearts perfused with palmitate and glucose in combination with extensive fatty acid uptake and marked suppression of glycolysis indicated that the newborn pig heart is capable of utilizing fatty acids as a primary energy source.

Influence of Sphingolipid Bases, Fatty Acids and Tween 80 on the Folate Requirement of Tetrahymena pyriformis*

SYNOPSIS The fatty acids lauric, myristic, and oleic, as well as long‐chain bases (LCBs) obtained from sphingolipids, and Tween 80 “spare” the requirement for folate by Tetrahymena pyriformis W. Since LCBs are metabolized by the ciliate to ethanolamine phosphate and fatty aldehydes which can be converted to either fatty acids or fatty alcohols, the latter compounds are used as precursors of phospho‐ and phosphonolipids and ether phospholipids. It is suggested that lipid biosynthesis is a rate‐limiting step in growth of the ciliate as is the folate concentration. Removal of one restraint on growth rate mimics the effect of increased folate concentration. Alternatively, if the enzymes responsible for lipid synthesis are repressible, the presence of exogenous fatty acids would make available more formylmethionyl‐tRNA for the initiation of synthesis of other proteins.

Candida lipolytica mutants defective in an acyl-coenzyme A synthetase: isolation and fatty acid metabolism.

Mutant strains of Candida lipolytica defective in an acyl-CoA synthetase [acid:CoA ligase (AMP-forming); EC 6.2.1.3]were isolated. The mutant strains apparently exhibited no acyl-CoA synthetase activity in vitro and were, in contrast to the wild-type strain, incapable of growing in the presence of exogenous fatty acid when cellular synthesis de novo of fatty acid was blocked. However, the mutant strains grew on either fatty acid or n-alkane as a sole carbon source at rates comparable to that observed for the wild-type strain. Analysis of the fatty acid composition of the lipids from the mutant cells grown on odd-chain-length fatty acid as well as [14C]oleic acid incorporation studies have shown that the mutant cells, unlike the wild-type cells, cannot incorporate exogenous fatty acid as a whole into cellular lipids, but utilize the fatty acid that is synthesized de novo from acetyl-CoA produced by degradation of exogenous fatty acid. This finding indicates the presence of at least two acyl-CoA synthetases that activate long-chain fatty acid. One, designated acyl-CoA synthetase I, which is absent in the mutant strains, is responsible for the production of acyl-CoA to be utilized for the synthesis of cellular lipids. The other acyl-CoA synthetase provides actyl-CoA that is exclusively degraded via beta-oxidation to yield acetyl-CoA.

Glyceride metabolism in cultured cells dissociated from rat cerebral cortex.

Abstract— [1‐14C]stearic acid and [2‐3H]glycerol were rapidly taken up and esterified into triacylglycerol and phospholipids by rat brain cells cultivated in monolayers. Expressed in terms of pool size, the incorporation of glycerol and stearate into triacylglycerol was 6‐ and 8‐fold, respectively, higher than the incorporation into the choline phosphoglycerides. Tritium‐labelled glycerol in both triacylglycerol and glycerophosphatides was diluted more rapidly than the [14C] labelled fatty acids. Chase experiments indicated a transfer of fatty acid from one lipid class to another, mainly from triacylglycerol to phospholipids, with no apparent loss of radioactivity. The accumulation of triacylglycerol in the brain cells was a function of both the presence of exogenous fatty acids in the culture medium and the metabolic needs of the cells; as long as the cells were involved in active formation of membranes the proportion of triacylglycerol was relatively small; its concentration increased while cell division slowed down in older, fully monolayered cultures.

Inhibition of aromatic photometabolism in Rhodopseudomonas palustris by fatty acids

The photo-metabolism of aromatic acids by Rhodopseudomonas palustris is sensitive to the presence of exogenous fatty acids. Long-chain fatty acids produced during disruption of the cell and associated with the chromatophore particles cause severe inhibition of benzoate and p-hydroxybenzoate photoassimilation when added to a suspension of intact cells. The main component of the isolated fatty acids was an octadecamonoenoic acid with minor amounts of stearic, palmitic, and palmitoleic acids. The photometabolism of acetate or malate, or the aerobic oxidation of p-hydroxybenzoate, appeared not to be affected. Oleic or linolenic acids caused high inhibition while strong detergents had much less effect on benzoate photometabolism. Monocarboxylic acid homologues, as low as propionate, and dicarboxylic acids were also inhibitory.