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PubMed2006

Carbohydrate metabolism during prolonged exercise and recovery: interactions between pyruvate dehydrogenase, fatty acids, and amino acids.

During prolonged exercise, carbohydrate oxidation may result from decreased pyruvate production and increased fatty acid supply and ultimately lead to reduced pyruvate dehydrogenase (PDH) activity. Pyruvate also interacts with the amino acids alanine, glutamine, and glutamate, whereby the decline in pyruvate production could affect tricarboxycylic acid cycle flux as well as gluconeogenesis. To enhance our understanding of these interactions, we studied the time course of changes in substrate utilization in six men who cycled at 44+/-1% peak oxygen consumption (mean+/-SE) until exhaustion (exhaustion at 3 h 23 min+/-11 min). Femoral arterial and venous blood, blood flow measurements, and muscle samples were obtained hourly during exercise and recovery (3 h). Carbohydrate oxidation peaked at 30 min of exercise and subsequently decreased for the remainder of the exercise bout (P<0.05). PDH activity peaked at 2 h of exercise, whereas pyruvate production peaked at 1 h of exercise and was reduced (approximately 30%) thereafter, suggesting that pyruvate availability primarily accounted for reduced carbohydrate oxidation. Increased free fatty acid uptake (P<0.05) was also associated with decreasing PDH activity (P<0.05) and increased PDH kinase 4 mRNA (P<0.05) during exercise and recovery. At 1 h of exercise, pyruvate production was greatest and was closely linked to glutamate, which was the predominant amino acid taken up during exercise and recovery. Alanine and glutamine were also associated with pyruvate metabolism, and they comprised approximately 68% of total amino-acid release during exercise and recovery. Thus reduced pyruvate production was primarily associated with reduced carbohydrate oxidation, whereas the greatest production of pyruvate was related to glutamate, glutamine, and alanine metabolism in early exercise.

Adult↗
PubMed1990

Arterial LDH, 2,3-DPG, lactate, pyruvate and acid-base balance in hypoxic albino rats of first or second generation.

Arterial acid-base balance, lactate, pyruvate, lactate dehydrogenase activity (LDH), 2,3-diphosphoglycerate content (2,3-DPG) of normoxic control rats were compared with those of rats exposed to a hypoxic normobaric environment (10% O2 in N2) within a few hours after birth (hypoxic animals of first generation or H1), and with those of rats of second generation (H2) conceived and born in the above mentioned hypoxic environment of H1 parents and maintained always in the same place since their utilization. The H1 rats showed a displacement of acid-base balance towards acidosis and an increase of lactate, pyruvate, LDH and 2,3-DPG in comparison with normoxic controls. The H2 rats showed a significant attenuation of acidosis in comparison with H1 rats; the values of lactate, pyruvate, LDH and 2,3-DPG were intermediate between those found in H1 and normoxic control rats. We believe that these results are in relation with the evolution of adaptative processes to hypoxic environment in hypoxic animals of second generation.

Acid-Base Equilibrium↗
PubMed1985

Pyruvylated glycolipids from Mycobacterium smegmatis. Nature and location of the lipid components.

The dipyruvylated glycolipid from Mycobacterium smegmatis (Saadat, S., and Ballou, C.E. (1983) J. Biol. Chem. 258, 1813-1818) has been shown to have the following structure in which FA1 is tetra- or hexadecanoic acid and FA2 is 2,4-dimethyl-2-eicosenoic acid. (formula; see text) The fast atom bombardment mass spectrum showed two major ions [M - H]- at m/z 1511 and 1539 (Mr 1512 and 1540) in a ratio of 1.4:1, suggesting that the glycolipid was a mixture of homologs that differed in fatty acid composition by 2 methylene groups. Analysis revealed C14, C16, and C22 fatty acids in ratios of 0.6:0.4:1.0, indicating that 60% of the molecules contained a C14 and C22 fatty acid whereas 40% contained a C16 and C22 fatty acid. The fragmentation pattern showed that a single glucose unit along with the smaller fatty acid could be lost to yield a tetrasaccharide with attached C22 fatty acid, and a second fragmentation yielded a trisaccharide containing 2 pyruvic acids but without attached fatty acid. The C14 and C16 fatty acids were identified as myristic and palmitic acid, whereas the C22 fatty acid was 2,4-dimethyl-2-eicosenoic acid. Precise localization of the fatty acids came from periodate oxidation and methylation analysis.

Fatty Acids↗
PubMed1977

Heart mitochondrial metabolism after feeding herring oil to rats and monkeys.

Heart mitochondrial oxidation of palmityl CoA and pyruvic acid was studied in rats and in the monkey Macaca fascicularis to determine the effects of feeding partially hydrogenated herring oil. Herring oil glycerides contain cetoleic acid (cis-11-docosenoic) which could have a similar effect to erucic acid (cis-13-docosenoic) in causing a rat cardiomyopathy. The initial rat heart mitochondrial response to dietary cetoleic acid (67% cis, 33% trans) was an in vitro decrease in palmityl CoA oxidation. Pronlonged feeding of cetoleic acid mixture was associated with a significant metabolic adaptation, increasing pyruvate and palmityl CoA oxidation above control levels. In vitro addition of cetoleyl CoA (pure cis isomer) stimulated pyruvate dehydrogenase activity, a possible response to decreased B-oxidation. There was no significant adaptive change in pyruvate or palmityl CoA use in monkeys after prolonged feeding of partially hydrogenated herring oil. Cetoleyl CoA was a good substrate for monkey heart carnitine acyl transferase even in the presence of palmityl CoA. These observations suggest that C22 fatty acids may be metabolized more rapidly in monkey heart than in rat heart. Metabolic differences argue against using the rat as an experimental model for studying possible cardiotoxic effects of docosenoic acids in primates.

Animals↗
PubMed1988

Oxidative decarboxylation of salsolinol-1-carboxylic acid to 1,2-dehydrosalsolinol: evidence for exclusive catalysis by particulate factors in rat kidney.

The decarboxylation of salsolinol-1-carboxylic acid (1-methyl-6,7-dihydroxy-1,2,3,4- tetrahydroisoquinoline-1-carboxylic acid), a novel endogenous catecholic adduct of dopamine and pyruvic acid, was examined in nuclei-free homogenates of rat liver, whole brain, and kidney, as well as in buffer only. Liquid chromatographic analysis of incubations for varying times (30 min to 5 h) showed that the tetrahydroisoquinoline substrate decarboxylated oxidatively, forming one product, 1-methyl-6,7-dihydroxy-3,4-dihydroisoquinolines (1,2-dehydrosalsolinol). No salsolinol was apparent, even with added NADPH. In buffer, decarboxylation occurred by an apparent oxygen radical-mediated process: it was stimulated by cupric ion or elevated pH, and was suppressed by EDTA, superoxide dismutase, metal ion removal with Chelex-100, or low pH (less than 6). In liver or brain, the conversion was qualitatively and quantitatively similar to that in buffer; thus there was no evidence for enzyme involvement. In kidney, however, dehydrosalsolinol formation was significantly greater than that in liver, brain, or buffer, and preboiling reduced it nearly to buffer values. The heat-labile kidney activity, displaying a pH maximum ca. 9, was localized in the particulate fractions. It was blocked completely by N-ethylmaleimide. Added superoxide dismutase was only slightly inhibitory; catalase and dimethyl sulfoxide, a hydroxyl radical trap, were uneffective. Lack of inhibition by indomethacin ruled against peroxidative involvement of kidney prostaglandin synthetase. Physiological amounts of a cofactor for amino acid decarboxylases, pyridoxal-5'-phosphate, also had no effect. The oxidative decarboxylation of 1-carboxylated salsolinol by kidney fractions appears mainly due to a sulfhydryl-containing particulate factor unique to or relatively concentrated in that organ. Its identity, substrate specificity, and possible significance, particularly in alcoholism, where elevated salsolinol-1-carboxylic acid levels have been reported, remain to be ascertained.

Animals↗
PubMed1976

Glutaric aciduria type II: report on a previously undescribed metabolic disorder.

A report is given on a hitherto undescribed metabolic disorder, characterized clinically by fatal neonatal acidosis, hypoglycemia and a strong 'sweaty-feet' odour. Biochemical features were a massive urinary excretion of glutaric and lactic acids. Isobutyric, isovaleric and alpha-methylbutyric acids were also greatly increased, followed by adipic, ethylmalonic, alpha-hydroxybutyric, n-butyric, beta-hydroxybutyric, sebacic, suberic, propionic, alpha-hydroxyisovaleric and hexanoic acids. The serum level of glutaric acid was highly elevated. In the serum there were also abnormal levels of lactic, alpha-hydroxybutyric, adipic, suberic, p-hydroxyphenyllactic, myristic, hexadecenoic, palmitic, oleic and stearic acids. Plasma lysine and valine were also elevated. Degradation of 14C-labelled glutaric acid and 14C-labelled branched-chain amino acids, alpha-ketoisovaleric and alpha-ketoisocaproic acids in intact fibroblasts was decreased, whereas that of pyruvic acid was normal. The defect was tentatively supposed to be localized at the level of the metabolism of a range of acyl-CoA compounds. The name glutaric aciduria 'type II' is proposed for the patient's disease.

Amino Acids↗
PubMed1997

Substrate and cofactor specificity and selective inhibition of lactate dehydrogenase from the malarial parasite P. falciparum.

Lactate dehydrogenase from the malarial parasite Plasmodium falciparum has many amino acid residues that are unique compared to any other known lactate dehydrogenase. This includes residues that define the substrate and cofactor binding sites. Nevertheless, parasite lactate dehydrogenase exhibits high specificity for pyruvic acid, even more restricted than the specificity of human lactate dehydrogenases M4 and H4. Parasite lactate dehydrogenase exhibits high catalytic efficiency in the reduction of pyruvate, kcat/Km = 9.0 x 10(8) min(-1) M(-1). Parasite lactate dehydrogenase also exhibits similar cofactor specificity to the human isoforms in the oxidation of L-lactate with NAD+ and with a series of NAD+ analogs, suggesting a similar cofactor binding environment in spite of the numerous amino acid differences. Parasite lactate dehydrogenase exhibits an enhanced kcat with the analog 3-acetylpyridine adenine dinucleotide (APAD+) whereas the human isoforms exhibit a lower kcat. This differential response to APAD+ provides the kinetic basis for the enzyme-based detection of malarial parasites. A series of inhibitors structurally related to the natural product gossypol were shown to be competitive inhibitors of the binding of NADH. Slight changes in structure produced marked changes in selectivity of inhibition of lactate dehydrogenase. 7-p-Trifluoromethylbenzyl-8-deoxyhemigossylic acid inhibited parasite lactate dehydrogenase, Ki = 0.2 microM, which was 65- and 400-fold tighter binding compared to the M4 and H4 isoforms of human lactate dehydrogenase. The results suggest that the cofactor site of parasite lactate dehydrogenase may be a potential target for structure-based drug design.

Allosteric Regulation↗
PubMed1990

Antihypertensive activity of indolepyruvic acid: a keto analogue of tryptophan.

We studied the effect of indole-3-pyruvic acid (IPA) on systolic blood pressure of normotensive, spontaneously hypertensive, DOCA + salt hypertensive, and Grollman hypertensive rats. Experiments were also carried out in order to investigate whether IPA may influence the development of hypertension in spontaneously hypertensive rats. Age-matched normotensive, spontaneously hypertensive, DOCA + salt hypertensive, and Grollman hypertensive rats treated with N-methylglucamine, were used as controls. Acute oral (up to 50 mg/kg) and intravenous (5 mg/kg) administration of IPA did not change systolic blood pressure in any models of hypertension. By contrast, a repeated administration of IPA (100 mg/kg/day, by oral gavage for 10 days) significantly decreased systolic blood pressure in all models of hypertension, while it elicited no significant effect in normotensive rats. Moreover, when IPA was given daily to 5-week-old spontaneously hypertensive rats for 7 weeks, it partially inhibited the development of hypertension. In addition, chronic administration of IPA caused enhanced levels of tryptophan and 5-hydroxyindoleacetic acid in the cortex and diencephalon. Brainstem serotonin content in both normotensive and spontaneously hypertensive rats was also enhanced by IPA treatment. Our results suggest that IPA lowers blood pressure in different rat models of hypertension and this effect seems to be correlated with an increase in cerebral serotonin metabolism.

Animals↗
PubMed1980

The stimulus-secretion coupling of glucose-induced insulin release. XLVI. Physiological role of L-glutamine as a fuel for pancreatic islets.

Exogenous L-glutamine is actively metabolized in rat pancreatic islets. The rate of L-glutamine deamidation largely exceeds the rate of glutamate conversion to gamma-aminobutyrate and alpha-ketoglutarate. The latter conversion occurs in part by oxidative deamination, and in part by transamination reactions coupled with the conversion of 2-keto acids (pyruvate, oxaloacetate), themselves derived from the metabolism of glutamine, to their corresponding amino acids (alanine, aspartate). An important fraction of malate formed from alpha-ketoglutarate leaves the Krebs cycle and is converted to pyruvate, the process being apparently associated with the induction of a more reduced state in cytosolic redox couples. L-Glutamine abolishes the oxidation of endogenous nutrients is documented by the fact that the glutamine-induced increase in O2 consumption is much lower than expected from the rate of 14CO2 output from islets exposed to L-[U-14C]glutamine, L-Glutamine, although decreasing K+ conductance, fails to stimulate insulin release both in the absence and presence of D-glucose. It is proposed that L-glutamine represents a major fuel for pancreatic islets under physiological conditions.

Animals↗
PubMed1983

[Animal experiments on the gastric mucosa and demonstration of analgesic and antipyretic effects after combined administration of acetylsalicylic acid and sodium pyruvate].

Animal experimental examinations in guinea pigs and rats demonstrate the positive influence of sodium pyruvate on lesions of the gastric mucosa induced by acetylsalicylic acid. As compared to pure acetylsalicylic acid a combination of acetylsalicylic acid and sodium pyruvate reduces significantly the numbers of erosions, ulcers and hemorrhages on the gastric mucosa. Sodium pyruvate protects effectively against the undesired side-effects by acetylsalicylic acid. The analgetic and antipyretic effect of acetylsalicylic acid is not impaired by the addition of sodium pyruvate.

Analgesics↗
PubMed1975

Effects of insulin upon fatty acids synthesis from pyruvate, lactate, and glucose in rat mammary cells.

In isolated rat mammary secretory cells, insulin stimulated fatty acid synthesis from pyruvate three times, stimulated glucose conversion to fatty acids 1.2 to 1.5 times, and decreased lactate conversion to fatty acids 20 to 30%. Incubation of glucose and pyruvate together depressed fatty acid synthesis from glucose not attributable to isotope dilution. Glucose stimulated conversion of pyruvate-2-14 carbon to fatty acids without significantly affecting pyruvate-1-14 carbon conversion to 14-carbon dioxide. At differing concentrations, the electron acceptors phenazine methosulfate and N,N,N',N'-tetramethyl-p-phenylene-diamine alleviated the depression by insulin of lactate conversion to fatty acids. The data support concepts that: (1) insulin acts at important sites other than or in addition to glucose transport in regulating mammary secretory cell metabolism and, particularly, fatty acid synthesis; (2) insulin actions upon fatty acid synthesis can vary dependent upon cellular redox state (insulin increases fatty acid synthesis in cells with a low redox state and decreases fatty acid synthesis in cells in a very reduced state); and (3) pyruvate depresses glucose carbon flux through the Embden-Meyerhof pathway.

Animals↗
PubMed1990

Structural analysis of the specific capsular polysaccharide of Rhodococcus equi serotype 1.

The specific capsular polysaccharide produced by Rhodococcus equi serotype 1 was found to be a high molecular weight acidic polymer composed of D-glucose, D-mannose, and D-glucuronic acid. Structural analysis of the polysaccharide employed a combination of chemical and nuclear magnetic resonance techniques, from which it was determined that the polysaccharide possessed a linear repeating tetrasaccharide unit containing a single O-acetyl substituent and and acetal-linked pyruvic acid moiety: [formula: see text] The 1H and 13C nuclear magnetic resonances of O-deacetylated and pyruvic-free serotype 1 polysaccharides were fully assigned by homo- and hetero-nuclear chemical shift correlation methods.

Acetylation↗
PubMed1996

Age-related responses of right ventricle in swim-trained rats: changes in lactate and pyruvate contents and lactate dehydrogenase activity.

Age related changes in carbohydrate substrates such as, glucose, glycogen, pyruvic acid and lactic acid and the activity of lactate dehydrogenase (LDH) and LDH isoenzyme profile were evaluated in the right ventricle (RV) of swim-trained rats of 6- (adult), 12- (middle-aged) and 18- (old) months-of-age. Moderate hypertrophy was seen in the heart and RV in response to training in all age groups with the 12 months exhibiting a significant increase. While resting levels of pyruvate and glucose in the RV showed small elevations in adult and middle-aged rats, lactic acid showed reductions in all ages. Glycogen supercompensation was seen in the RV of trained animals. These age-related alterations in RV were associated with decreases in blood lactic acid and glucose in the trained rats belonging to all ages. Total protein of the RV decreased with age and exercise increased the content. Total LDH and M4-LDH activities decreased with age. However, training increased their activities in all ages. These changes in the RV suggests that swimming activity produces adaptations (e.g. increased LDH and M4) in all age groups. Considering the degree of adaptations, it can be suggested that adult and middle-aged are suitable for initiating swim-training programs, but not in old age.

Aging↗
PubMed1982

Metabolism of round spermatids from rats: lactate as the preferred substrate.

Round spermatids were prepared from rat testes and incubated with various substrates (glucose, fructose, pyruvate, lactate and acetate) to measure utilization of substrates and production of ATP in the presence of saturating levels of each substrate. By both criteria lactate is the preferred substrate by a factor of 3 or 4. Production of more than half of the ATP with lactate is substrate is prevented by addition of an inhibitor of alpha-ketoacid dehydrogenase (5-methoxyindole-2-carboxylic acid) Pyruvate and lactate are interconverted and pyruvate inhibits production of ATP from lactate. Synthesis of ATP with lactate and with pyruvate is inhibited by rotenone, rutamycin or 2,4-dinitrophenol. Utilization of glucose is limited by aldolase activity. These findings suggest that exogenous lactate is oxidized by lactate dehydrogenase followed by pyruvate dehydrogenase and Krebs; cycle enzymes under conditions which do not allow pyruvate to inhibit lactate dehydrogenase. ATP is synthesized through electron transport. Post-mitochondrial supernate from spermatids showed that high concentration of pyruvate (greater than 1 mM) inhibit lactate dehydrogenase with pyruvate as substrate and that with lactate as substrate, pyruvate behaves as a competitive inhibitor of lactate dehydrogenase. Evidently lactate is the preferred substrate for round spermatids and energy production is most efficient when this substance is present in high concentrations and pyruvate is present in low concentrations. Reasons are given for suggesting that Sertoli cells may provide the relatively large amounts of lactate required by round spermatids.

Adenosine Triphosphate↗
PubMed1985

Microbial preparation of L-[15N]tyrosine and [15N]tyramine and their gas chromatographic-mass spectrometric analyses.

The preparation of L-[15N]tyrosine and [15N]tyramine by microbial synthesis is described. Immobilized Erwinia herbicola cells were added to a reaction mixture containing phenol, pyruvic acid, and 15NH4Cl. The reaction was driven by excess nonlabeled pyruvate and phenol. Under these denaturing concentrations of phenol, immobilized cells were more effective than free ones. Gram quantities of L-[15N]tyrosine were obtained without label dilution. The conversion of this L-[15N]tyrosine into [15N]tyramine by Streptococcus faecalis was performed at maximal efficiency. Gas chromatographic-mass spectrometric studies and 1H and 15N NMR analyses of the labeled compounds are reported.

Enterococcus faecalis↗