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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Weanling rats were fed diets containing various levels (0 to 40% of total dietary acids) of long chain, odd-carbon fatty acids (OCFA, 15:0 + 17:0) for 5 weeks. The OCFA did not significantly alter growth or feed efficiency and the OCFA were deposited in the carcass fat in proportion to their concentration in the diet fat. After the 5-week ingestion period, the rats were starved for 48 hours and the effect of carcass OCFA content on weight loss, fat loss, urinary total nitrogen, plasma glucose concentration and plasma ketone body concentrations was determined as a function of starvation time. The results demonstrate that OCFA catabolism during starvation results in a dose related increase in plasma glucose and dose related decrease in plasma ketone bodies without significantly altering the total weight loss, carcass fat loss, or urinary total nitrogen. Finally, the carcass percentage of OCFA did not change during starvation showing that these acids are as readily lost from the carcass during starvation as even chain fatty acids.
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PMID:Carcass deposition of dietary long-chain odd carbon fatty acids by rats and their effect on plasma glucose and ketone bodies during starvation. 49 Feb 17

Fat cells isolated from rat epididymal adipose tissue were incubated with albumin-bound [14C]palmitate. Incorporation of 14C into 14CO2 and glycerides was measured. Some evidence is presented to suggest that the exogenous palmitate pool is in isotopic equilibrium with intracellular precursors for these metabolic processes. Precautions were taken to minimize dilution of the exogenous palmitate pool by fatty acids released from the cells. 14CO2 production from [1-14C]palmitate was 3 times that from [16-14C]palmitate. Octanoate increased this differential oxidation of palmitate carbons and also inhibited palmitate oxidation without similarly affecting esterification. Glucose increases palmitate esterification in cells from fed or starved rats. Insulin potentiated this effect of glucose. Glucose influenced palmitate oxidation in a more complex manner, dependent upon the glucose concentration. Both the observation that esterification constitutes 99% of the metabolic flux of fatty acid and the manner in which glucose, insulin, or starvation influence palmitate esterification and oxidation suggested that factors controlling esterification may alter oxidation as a secondary effect, but not vice versa. It is suggested that oxidation and esterification compete for a single intracellular precursor, possibly extramitochondrial long chain fatty acyl CoA.
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PMID:Factors affecting fatty acid oxidation in fat cells isolated from rat white adipose tissue. 96 42

Rats starved for 96 hr were shown to have a 94% reduction in liver triacylglycerol. Among the long chain fatty acids in liver triacylglycerol, only stearic acid and arachidonic acid were proportionally increased (2.5 and 6 times, respectively); palmitic and linoleic acids were unchanged, and palmitoleic and oleic acids were proportionally decreased. Stearic and arachidonic acids (mg%) were correlated positively within the triacylglycerol fraction, and both fatty acids varied inversely with total triacylglycerol (mg/g) in fed and starved rats. The utilization of long chain fatty acids from liver triacylglycerol during starvation resulted in selective retention of arachidonic acid and stearic acid and suggests that differential hydrolysis of liver triacylglycerol by hepatic lipase may occur or selective reacylation of these specific fatty acids may occur during starvation.
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PMID:Differential utilization of long chain fatty acids during triacylglycerol depletion. II. Rat liver after starvation. 339 26

Fatty acid metabolism was examined in Escherichia coli plsB mutants that were conditionally defective in sn-glycerol-3-phosphate acyltransferase activity. The fatty acids synthesized when acyl transfer to glycerol-3-phosphate was inhibited were preferentially transferred to phosphatidylglycerol. A comparison of the ratio of phospholipid species labeled with 32Pi and [3H]acetate in the presence and absence of glycerol-3-phosphate indicated that [3H]acetate incorporation into phosphatidylglycerol was due to fatty acid turnover. A significant contraction of the acetyl coenzyme A pool after glycerol-3-phosphate starvation of the plsB mutant precluded the quantitative assessment of the rate of phosphatidylglycerol fatty acid labeling. Fatty acid chain length in membrane phospholipids increased as the concentration of the glycerol-3-phosphate growth supplement decreased, and after the abrupt cessation of phospholipid biosynthesis abnormally long chain fatty acids were excreted into the growth medium. These data suggest that the acyl moieties of phosphatidylglycerol are metabolically active, and that competition between fatty acid elongation and acyl transfer is an important determinant of the acyl chain length in membrane phospholipids.
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PMID:Fatty acid metabolism in sn-glycerol-3-phosphate acyltransferase (plsB) mutants. 354 64

1. Measurements were made of milk yield, mammary blood flow and mammary arteriovenous differences during the measurement of substrate entry rate by the isotope dilution method using [U-(14)C]glucose, acetate, palmitate, stearate or oleate in conscious lactating goats after 24 hr starvation.2. As previously reported, in fasting, milk yield fell to 40 +/- 3.4 (S.E.)%, lactose secretion to 31 +/- 3.4%, milk fat secretion to 81 +/- 6.7% and mammary blood flow fell to 53 +/- 7.5% of the values before fasting. Mammary O(2) uptake was only 45 +/- 5% of the mean value in fed animals and there were marked falls in the uptakes of glucose, acetate and triglycerides, a smaller fall in beta-hydroxybutyrate uptake, and a large increase in free fatty acid uptake.3. Glucose was found to enter the circulation of the fasting animal at 1-1.6 mg/min/kg body wt. (entry rate) and it gave rise to 3-5% of the total CO(2). The udder took up 10.7-16.1 mg/min/kg of tissue and 8-10% of mammary CO(2) was derived from glucose, although only 5-10% was oxidized. Mammary uptake accounted for 35-43% of the total glucose entering the circulation.4. In the whole animal acetate entry rate was 1-1.4 mg/min/kg and 9-10% of total CO(2) was derived from it. The udder used 0.8-2.4 mg/min/kg of tissue and 9-13% of mammary CO(2) was derived from acetate, 46-79% of that taken up being oxidized. Mammary uptake accounted for only 2-6% of the total acetate entry rate. Negligible quantities of isotope were found in milk fatty acids and there was a fall in the proportion of milk fatty acids of chain length up to C(14) which in fed animals are synthesized from acetate and beta-hydroxybutyrate.5. Palmitate, stearate and oleate entered the circulation as free fatty acids at 0.94-6.8 mg/min/kg and 6-9% of total CO(2) was derived from each. The udder took up 3.0-5.7 mg/min/kg of tissue and 4-8% of mammary CO(2) was derived from each acid. In the udder 8 and 5.5% of stearate and oleate were oxidized and 25% of palmitate. Mammary uptake of stearate was 31.5% of the total entry rate, palmitate 1%, and oleate 7.5%. Only long chain milk fatty acids were labelled.6. During fasting the mammary R.Q. was 0.85 +/- 0.045 compared with a value in fed animals of 1.24 +/- 0.02, when the udder is synthesizing fatty acids from acetate. The total mammary uptake of lipid precursors was only 74% of the rate of milk fat secretion and there was an 18% shrinkage in empty udder volume, suggesting the use of endogenous mammary tissue substrates.
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PMID:Mammary and whole animal metabolism of glucose and fatty acids in fasting lactating goats. 571 53

The requirement for carnitine and the malonyl-CoA sensitivity of carnitine palmitoyl-transferase I (EC 2.3.1.21) were measured in isolated mitochondria from eight tissues of animal or human origin using fixed concentrations of palmitoyl-CoA (50 microM) and albumin (147 microM). The Km for carnitine spanned a 20-fold range, rising from about 35 microM in adult rat and human foetal liver to 700 microM in dog heart. Intermediate values of increasing magnitude were found for rat heart, guinea pig liver and skeletal muscle of rat, dog and man. Conversely, the concentration of malonyl-CoA required for 50% suppression of enzyme activity fell from the region of 2-3 microM in human and rat liver to only 20 nM in tissues displaying the highest Km for carnitine. Thus, the requirement for carnitine and sensitivity to malonyl-CoA appeared to be inversely related. The Km of carnitine palmitoyltransferase I for palmitoyl-CoA was similar in tissues showing large differences in requirement for carnitine. Other experiments established that, in addition to liver, heart and skeletal muscle of fed rats contain significant quantities of malonyl-CoA and that in all three tissues the level falls with starvation. Although its intracellular location in heart and skeletal muscle is not known, the possibility is raised that malonyl-CoA (or a related compound) could, under certain circumstances, interact with carnitine palmitoyltransferase I in non-hepatic tissues and thereby exert control over long chain fatty acid oxidation.
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PMID:Observations on the affinity for carnitine, and malonyl-CoA sensitivity, of carnitine palmitoyltransferase I in animal and human tissues. Demonstration of the presence of malonyl-CoA in non-hepatic tissues of the rat. 661 66

1. An increase in the ionic strength of the assay medium markedly increased the basal activity of the malonyl-CoA-sensitive carnitine medium/long chain acyltransferases in peroxisomes and microsomes and decreased the malonyl-CoA inhibition. 2. ATP-Mg largely reversed the salt mediated stimulation of both the peroxisomal and the microsomal activities. 3. The octylglucoside solubilization of the peroxisomes and microsomes caused only marginal losses of their catalytic activity but the malonyl-CoA inhibition was nearly fully abolished. 4. Starvation increased the above activity of peroxisomes and microsomes and decreased their sensitivity to malonyl-CoA inhibition. Tritiated etomoxir labeled a approximately 47 kDa peptide in these organelles, the intensity of which was decreased on starvation. Collectively these findings strengthen the notion that the malonyl-CoA sensitive carnitine acyltransferases in mitochondria, microsomes, and peroxisomes are distinct proteins.
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PMID:Some properties of the malonyl-CoA sensitive carnitine long/medium chain acyltransferase activities of peroxisomes and microsomes of rat liver. 783 27

The pfk3 mutation of Saccharomyces cerevisiae causes glucose-negativity in a pfk1 genetic background, the mutant is temperature-sensitive for growth and homozygous diploids do not sporulate. It fails to accumulate trehalose, and has an altered glycogen accumulation profile under glucose-starvation conditions. pfk3-6, one of the alleles of pfk3, has an altered morphology, forming long chain-like structures at 36 degrees C. The PFK3 gene was cloned by complementation of the mutant phenotypes. Integrative transformation demonstrated that the complementing fragment encoded the authentic PFK3 gene. The disruption of the gene does not affect viability. Like the EMS-induced pfk3 mutant, the disruptants are temperature-sensitive and in a pfk1 genetic background are also glucose-negative. The PFK3 transcript is induced by heat-shock. Partial DNA sequence shows that PFK3 is identical to TPS2 (De Virgilio et al., 1993). We demonstrate that, apart from being a structural determinant of trehalose 6-phosphate phosphatase, PFK3 (TPS2) is required for PFKII synthesis and normal regulation of S. cerevisiae response to nutrient and thermal stresses.
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PMID:Analysis of PFK3--a gene involved in particulate phosphofructokinase synthesis reveals additional functions of TPS2 in Saccharomyces cerevisiae. 820 61

Short chain (SCAD), medium chain (MCAD), and long chain acyl-CoA dehydrogenases (LCAD) catalyze the first step of fatty acid oxidation, while isovaleryl-CoA dehydrogenase (IVD) is involved in leucine oxidation. They are homologous flavoproteins belonging to the acyl-CoA dehydrogenase (ACD) family. Electron transfer flavoprotein (ETF) serves as an obligatory electron acceptor for these reactions. We demonstrated that the expression of SCAD, MCAD, and LCAD and the alpha-subunit of ETF (alpha-ETF) showed a similar developmental pattern, while that of IVD was distinctly different from others. The ontogenic pattern of each enzyme in the liver differed distinctly from that in the heart. The degree of glucagon-enhanced ACD expression in vivo and in vitro in both the liver and heart was especially high in fasted rats. Dexamethasone induced all ACD mRNAs in the heart. In contrast, it strongly suppressed mRNAs of all ACDs and alpha-ETF mRNA in the liver, except IVD mRNA. Dexamethasone induced IVD mRNA in both the liver and heart. Starvation strongly stimulated expression of all five genes in various tissues, with the highest in the heart, except the IVD gene which was down-regulated. The degree of induction by 3-day starvation differed in different age groups of rats. Feeding the rats a fat-free diet for 7 days caused a marked increase of IVD mRNA in the heart, whereas the high fat diet for the same period resulted in a severe decrease of the same degree, suggesting a protein-sparing mechanism. However, these manipulations of dietary fat content had little effect on the expression of other ACD genes.
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PMID:Developmental, nutritional, and hormonal regulation of tissue-specific expression of the genes encoding various acyl-CoA dehydrogenases and alpha-subunit of electron transfer flavoprotein in rat. 822 58

In animal cells peroxisomes as well as mitochondria are capable of degrading lipids via beta-oxidation. Nevertheless, there are important differences between the two systems. 1) The peroxisomal and mitochondrial beta-oxidation enzymes are different proteins. 2) Peroxisomal beta-oxidation does not degrade fatty acids completely but acts as a chain-shortening system, catalyzing only a limited number of beta-oxidation cycles. 3) Peroxisomal beta-oxidation is not coupled to oxidative phosphorylation and is thus less efficient than mitochondrial beta-oxidation as far as energy conservation is concerned. 4) Peroxisomal beta-oxidation is not regulated by malonyl-CoA and--as a consequence--by feeding as opposed to starvation. Peroxisomes are responsible for the beta-oxidation of very long chain (> C20) fatty acids, dicarboxylic fatty acids, 2-methyl-branched fatty acids, prostaglandins, leukotrienes, and the carboxyl side chains of certain xenobiotics and of the bile acid intermediates di- and trihydroxycoprostanic acids. Mitochondria oxidize mainly long (C16-C20) chain fatty acids, which--because of their abundance--constitute a major source of metabolic fuel. The first step in peroxisomal beta-oxidation is catalyzed by two acyl-CoA oxidases in extrahepatic tissues and by three acyl-CoA oxidases in liver, each enzyme having its own substrate specificity. Palmitoyl-CoA oxidase and pristanoyl-CoA oxidase are found in liver and extrahepatic tissues. The former enzyme oxidizes the CoA esters of straight chain fatty acids, dicarboxylic fatty acids and prostaglandins; the latter enzyme oxidizes the CoA esters of branched fatty acids but also shows some activity towards straight chain and dicarboxylic fatty acids. Hepatic peroxisomes contain a third acyl-CoA oxidase, trihydroxycoprostanoyl-CoAA oxidase, which oxidizes the CoA esters of the bile acid intermediates di- an trihydroxycoprostanic acids. Treatment of rodents with a number of structurally diverse compounds called peroxisome proliferators, results in the proliferation of peroxisomes, especially in liver, and in the induction of the hepatic peroxisomal beta-oxidation enzymes except pristanoyl-CoA oxidase and trihydroxycoprostanoyl-CoA oxidase. There exist several inborn errors, in which peroxisomal beta-oxidation is deficient. These diseases are characterized by severe neurological symptoms. The biochemical findings in these diseases confirm the function of peroxisomal beta-oxidation as described above.
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PMID:[Peroxisomal beta-oxidation]. 848 Apr 47


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