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PubMed1987

Effects of gemfibrozil on plasma lipoprotein-apolipoprotein distribution and platelet reactivity in patients with hypertriglyceridemia.

The effects of gemfibrozil on plasma lipoprotein distribution and composition and on platelet function were investigated in 11 patients with stable hypertriglyceridemia, six belonging to Fredrickson type IIb and five to type IV. Gemfibrozil (600 mg twice a day) significantly reduced total and very low density lipoprotein (VLDL)--associated triglyceridemia (respectively-32.4% and -40.4%, after 6 weeks of treatment). No significant variations were noted in the lipid components of low-density lipoproteins; by contrast, a marked increase (18%) was detected in high-density lipoprotein (HDL)--associated cholesterol. Comparison of the two patient groups (type IIb and type IV) showed that those with type IIb had both a more significant reduction of triglyceridemia and a more marked increase of HDL-cholesterol. Apolipoprotein B levels were reduced in both groups (-12%) with no change in apolipoprotein AI. The cholesterol content in the HDL subfractions, separated by rate zonal ultracentrifugation, was raised in HDL3 (18%) and in HDL2 (14%). Both particles also showed significant increases of the cholesterol/protein and the cholesterol/phospholipid ratios. A non-statistically significant decrease in collagen-induced aggregation and in the release of thromboxane B2 was noted after treatment. These findings suggest that, similar to what was recently reported in normal individuals and in laboratory animals, the probable mode of action of gemfibrozil is in reducing the secretion of atherogenic lipoproteins, particularly VLDL, while stimulating the production of small HDL particles.

Adult↗
PubMed2000

Selective inhibition of reactions involved in methanogenesis and fatty acid production on rice roots.

Washed excised roots of rice (Oryza sativa) produced H(2), CH(4) and fatty acids (millimolar concentrations of acetate, propionate, butyrate; micromolar concentrations of isovalerate, valerate) when incubated under anoxic conditions. Surface sterilization of the root material resulted in the inactivation of the production of CH(4), a strong reduction of the production of fatty acids and a transient (75 h) but complete inhibition of the production of H(2). Radioactive bicarbonate was incorporated into CH(4), acetate, propionate and butyrate. About 20-40% of the fatty acid carbon originated from CO(2) reduction. In the presence of phosphate, CH(4) was exclusively produced from H(2)/CO(2), since phosphate selectively inhibited acetoclastic methanogenesis. Acetoclastic methanogenesis was also selectively inhibited by methyl fluoride, while chloroform or 2-bromoethane sulfonate inhibited CH(4) production completely. Production of CH(4), acetate, propionate and butyrate from H(2)/CO(2) was always exergonic with Gibbs free energies <-20 kJ mol(-1) product. Chloroform inhibited the production of acetate and the incorporation of radioactive CO(2) into acetate. Simultaneously, H(2) was no longer consumed and accumulated, indicating that acetate was produced from H(2)/CO(2). Chloroform also resulted in increased production of propionate and butyrate whose formation from CO(2) became more exergonic upon addition of chloroform. Nevertheless, the incorporation of radioactive CO(2) into propionate and butyrate was inhibited by chloroform. The accumulation of propionate and butyrate in the presence of chloroform probably occurred by fermentation of organic matter, rather than by reduction of acetate and CO(2). [U-(14)C]Glucose was indeed converted to acetate, propionate, butyrate, CO(2) and CH(4). Radioactive acetate, CO(2) and CH(4) were also products of the degradation of [U-(14)C]cellulose and [U-(14)C]xylose. Addition of chloroform and methyl fluoride did not affect the product spectrum of [U-(14)C]glucose degradation. The application of combinations of selective inhibitors may be useful to elucidate anaerobic metabolic pathways in mixed microbial cultures and natural microbial communities.

Journal Article↗
PubMed1981

Effects induced by two different estrogens on serum individual phospholipids and serum lecithin fatty acid composition.

Eleven oophorectomized women (mean age 34.5 +/- 5.9) received two treatment cycles, one of the 17-C-alkylated ethinyl estradiol 20 microgram per day, and the second of the non-alkylated estrogen, estradiol valerate 2 mg per day for six weeks in separate periods preceded by six weeks without hormonal replacement therapy. Blood samples were drawn before and after six weeks on each estrogen. The samples were assayed for individual phospholipids i.e. cephalin, lecithin, lysolecithin and sphingomyelin after separation of these lipids by thin layer chromatography. The relative fatty acid composition of serum and high density lipoprotein lecithin and serum cholesterol ester was determined by gas liquid chromatography. Both estrogens reversed the symptoms of estrogen deficiency and had similar effects on serum individual phospholipids i.e. causing an increase in lecithin concomitant with a decrease in lysolecithin. It is suggested that this lecithin-lysolecithin shift could depend on an inhibition of the hepatic lipase and its phospholipase A1-activity. Both estrogens increased serum lecithin arachidonic acid without causing any change in linoleic acid (the major essential fatty acid), which indicates that this increase in arachidonic acid could be an estrogenic effect independent of dietary factors. Ethinyl estradiol caused an increase in palmitic and a decrease in stearic acid in the 1-position of serum lecithin while estradiol valerate did not influence these fatty acids at all. This palmitic-stearic acid shift induced by ethinyl estradiol is interpreted as a non-hormonal "drug-effect" linked to the liver toxicity of 17-C-alkylated steroids in spite of the lack of influence on routine liver function tests.

Adult↗
PubMed1987

Butyrate kinase from Clostridium acetobutylicum.

Crude extracts of Clostridium acetobutylicum contain a butyrate kinase of high specific activity (5.2 mumol/min/mg of protein). The enzyme has been purified 77-fold in a six-step procedure to a specific activity of 402 mumol/min/mg of protein. The purified butyrate kinase showed a single band with a molecular weight of 85,000 on nondenaturing polyacrylamide gradient gel electrophoresis. Separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated that the enzyme is a dimer of two apparently identical subunits with molecular weights of 39,000. The pH optimum for the reaction in the butyryl phosphate-forming direction is 7.5, and the pI of the kinase is 5.6. The amino acid composition of the enzyme is also reported. It contains no tryptophan and is low in sulfur-containing amino acids. The kinase has a broad substrate specificity and exhibits its highest relative activities with butyrate and valerate. Butyrate kinase is rapidly inactivated at 50 degrees C in the absence of a fatty acid substrate. Although a reducing agent was required for maximum activity, treatment with several sulfhydryl-modifying agents failed to inhibit the enzyme.

Amino Acids↗
PubMed1985

Effect of single or repeated estrogen administration on tuberoinfundibular GABA neurons and anterior pituitary GABA receptors: biochemical and functional studies.

The effect of single or protracted administration of estradiol valerate on the hypothalamo-pituitary gamma-aminobutyric acid (GABA)ergic system and on plasma prolactin levels has been evaluated in female rats 2 months after the last (chronic treatment) or the single dose of the steroid. In the group of animals receiving one dose of estrogen, no modifications were detected in the activity of the tuberoinfundibular GABAergic neurons as implied by unchanged GABA accumulation either in the median eminence or the anterior pituitary after blockade of GABA catabolism with ethanolamine-O-sulphate. However, a complete disappearance of the low affinity population of GABA receptors in the anterior pituitary was observed. In this experimental condition, where baseline prolactin levels were 3-fold higher than in control rats, muscimol, a potent GABA agonist, was effective in significantly lowering plasma prolactin concentrations. Chronic estradiol valerate administration reduced GABA accumulation in the median eminence and the anterior pituitary at 4, but not at 2 h, after intracerebroventricular injection of ethanolamine-O-sulphate. Moreover, in this instance, a complete disappearance of the high affinity population of GABA receptors in the anterior pituitary was detected. Long-term estrogen administration induced also a 55-fold increase of plasma prolactin titers and muscimol was ineffective in reducing prolactin concentrations in plasma. The ability of muscimol to inhibit prolactin release only in single-estrogen-treated animals strongly suggests that the high affinity population of anterior pituitary GABA receptors is that involved in the mechanisms whereby GABA inhibits prolactin release from anterior pituitary.

Animals↗
PubMed1982

Specific binding of [3H]L-glutamate to cerebellar membranes: evidence for recognition site heterogeneity.

The kinetics of interaction of excitatory amino acid analogues and reputed antagonists with a specific binding site for [3H]L-glutamate, having a Kd of 600 nM, were examined in washed cerebellar membranes incubated at 37 degrees C. Displacement curves were analyzed by an iterative computer program for a non-cooperative two-site competitive inhibition model. L-Glutamate, D-glutamate and D-aspartate exhibited simple, mass action kinetics with Hill coefficients near unity and Kis of 1.1, 9.3 and 23.3 microM, respectively. Quisqualate, ibotenate and cyclopentylglutamate had Hill coefficients less than 0.85 and bound to an high affinity component with KHS of 0.4, 0.8 and 1.7 microM, respectively. Neither N-methyl-D-aspartate nor derivatives of kainate, with the exception of a-keto kainate, had KiS less than 0.1 mM. Linear analogues of glutamate with reputed antagonistic properties all exhibited shallow displacement curves with Hill coefficients less than 0.6 and KHS varying from 0.5 to 6.6 microM. Notably, 2-amino-6-phosphonocaproic acid had negligible affinity for the site in contrast to the valeric and pimelic phosphono analogues. The results indicate that [3H]L-glutamate labels a single class of sites that can be resolved into subpopulations by agonists and antagonists and provide additional evidence of excitatory amino acid receptor heterogeneity.

Amino Acids↗
PubMedDate not supplied

Short-chain carboxylic acid in the feces in patients with pancreatic insufficiency.

Short-chain carboxylic acids in the feces of 12 patients with chronic pancreatitis having steatorrhea and 18 healthy subjects were determined by high-performance liquid chromatography. The fecal amount of the patients with chronic pancreatitis was increased to about twice that of the control, and the fat in the feces increased to eight times. The excretion of short-chain carboxylic acids increased to about three times. The short-chain carboxylic acid concentration regarded as derived from protein or amino acid, such as iso-butyrate, isovalerate, and n-valerate, was significantly increased in patients with chronic pancreatitis. From the above results, our data suggest that there is maldigestion of protein besides that of carbohydrate. And we confirmed that these data are an in-vivo illustration of the phenomena which have been studied in-vitro experiments, when fecal bacteria were incubated with peptide or amino acids as a substrate.

Adult↗
PubMed1971

Growth of Escherichia coli on short-chain fatty acids: growth characteristics of mutants.

The parent Escherichia coli K-12 is constitutive for the enzymes of the glyoxylate bypass and adapts to growth on long-chain fatty acids (C(12) to C(18)). It does not utilize medium-chain (C(6) to C(11)) or short-chain (C(4), C(5)) n-monocarboxylic acids. Several mutants of this strain which grow using short- or medium-chain acids, or both, as the sole carbon source were selected and characterized. One mutant (D(1)) synthesizes the beta-oxidation enzymes constitutively and grows on medium-chain but not on short-chain acids. A second (N(3)) is partially derepressed for synthesis of these enzymes and grows both on medium-chain and on short-chain acids. Secondary mutants (N(3)V(-), N(3)B(-), N(3)OL(-)) were derived from N(3). N(3)V(-) grows on even-chain but not on odd-chain acids and exhibits a lesion in propionate oxidation. N(3)B(-) grows on odd-chain but not on even-chain acids and exhibits no crotonase activity as assayed by hydration of crotonyl-CoA. N(3)OL(-) grows on acetate and propionate but does not utilize fatty acids C(4) to C(18); it exhibits multiple deficiencies in the beta-oxidation pathway. Growth on acetate of N(3), but not of the parent strain, is inhibited by 4-pentenoate. Revertants of N(3) which are resistant to growth inhibition by 4-pentenoate (N(3)PR) exhibit loss of ability to grow on short-chain acids but retain the ability to grow on medium-chain and long-chain acids. The growth characteristics of these mutants suggest that in order to grow at the expense of butyrate and valerate, E. coli must be (i) derepressed for synthesis of the beta-oxidation enzymes and (ii) derepressed for synthesis of a short-chain fatty acid uptake system.

Acetates↗
PubMed1999

D-tagatose has low small intestinal digestibility but high large intestinal fermentability in pigs.

The digestibility of D-tagatose, its effect on the digestibility of macronutrients and the metabolic response of the microbiota of the gastrointestinal tract to the ingestion of this carbohydrate were studied in pigs. Eight pigs were fed a low fiber diet comprising 15% sucrose (control group). Another eight pigs were fed a similar diet except that 100 g sucrose per kg diet was replaced by D-tagatose (test group). After 18 d, the pigs were killed and the gastrointestinal contents removed for analysis. The digestibility of D-tagatose was 25.8 +/- 5.6% in the distal third of the small intestine. The small intestinal digestibilities of dry matter (86.9 +/- 1.3 vs. 92.9 +/- 0.9%), gross energy (74.4 +/- 1.6 vs. 80.7 +/- 1.8%) and sucrose (90.4 +/- 2.5 vs. 98.0 +/- 0.5%) were lower (P < 0. 05) in the pigs fed D-tagatose. Digestibilities of starch, protein and fat did not differ between groups. D-Tagatose, sucrose and starch were fully digested in the large intestine. The fecal digestibilities of energy, dry matter and fat did not differ between the two groups, whereas D-tagatose reduced the fecal digestibility of protein (91.1 +/- 0.6 vs. 93.5 +/- 0.7%, P < 0.05). D-Tagatose served as a substrate for the microbiota in the cecum and proximal colon as indicated by a reduced pH, and a greater ATP concentration, adenylate energy charge (AEC) ratio and concentration of short-chain fatty acids. In particular, the increase in the concentrations of propionate, butyrate and valerate suggests possible health benefits of this monosaccharide.

Adenosine Triphosphate↗
PubMed1978

Effects of corticosteroids on the growth and metabolism of fibroblasts cultured from human skin.

Hydrocortisone, betamethasone 17-valerate, clobetasone butyrate and clobetasol propionate were tested in vitro for effects on the proliferation and metabolism of six strains of fibroblasts from normal human skin. The different cell strains gave similar results: hydrocortisone and betamethasone valerate slightly enhanced growth at all concentrations (0.0001-10 microgram/ml), but high concentrations of clobetasone butyrate and clobetasol propionate significantly reduced proliferation. Secretion of acid mucopolysaccharide was most inhibited by clobetasone butyrate and clobetasol propionate, then by betamethasone valerate, with hydrocortisone having the least effect. Clobetasol propionate and betamethasone valerate at 10 microgram/ml both reduced collagen synthesis by about 50%; other protein synthesis was less affected.

Betamethasone↗
PubMed1981

Characteristics of the rumen proteolysis of fraction I (18S) leaf protein from lucerne (Medicago sativa L).

1. The rate of proteolysis of fraction I (18S) leaf protein in the rumen of sheep of cattle was affected by diet ans the rate on fresh lucerne (medicago sativa L) was three to nine times the rate on a hay + concentrate diet. 2. Simultaneous rumen fermentations in vivo and in an artificial rumen showed that the rates of proteolysis of fraction I in vitro was approximately 30% of the rates in sheep. 3. Using 14 C uniformly-labelled fraction I protein at low concentrations, proteolysis exhibited 1st-order kinetics. Over a wide range of protein concentrations the velocity v. substrate concentration curve showed Michaelis-Menten characteristics typical of an enzyme-catalysed reaction. With rumen fluid from a hay + concentrate-fed sheep the maximum velocity was 2.6 mg protein nitrogen/1 per min and the Michaelis constant was 75 mg nitrogen/l. 4. Rapid absorption of 14C-labelled fraction I protein onto bacterial cells preceded proteolysis. 5. Sucrose-density-gradient analysis showed initial incorporation of 14C from protein into rumen bacteria followed by partial transfer to rumen protozoa. 6. No peptides were detected during proteolysis showing that the rate-limiting step occurred during the initial stages of proteolysis. Only small amounts of free amino acids were released except for leucine, isoleucine, valine and ornithine, which showed significantly increased levels. 7. Volatile fatty acids were the main 14C-labelled end products and were rapidly produced in descending concentrations: acetate greater than propionate greater than 3-methyl + 2-methyl butyrate greater than butyrate greater than isobutyrate greater than valerate.

Amino Acids↗