Biomedical subjects

F Blachier

Publications and source records attributed to F Blachier.

60 records · Page 4Linked to original sources

PubMed1987

Metabolic and secretory response of tumoral-insulin producing cells to D-fructose and D-galactose.

At variance with normal islet cells, tumoral insulin-producing cells of the RINm5F line were found to display a positive secretory response not solely to D-glucose and D-mannose, but also to D-fructose and D-galactose. All hexoses increased the ATP/ADP ratio, exerted a sparing action upon the oxidation of endogenous nutrients in cells prelabelled with either L-[U-14C]glutamine or [U-14C]palmitate, increased the output of lactic acid and, as judged from data collected in the presence of D-[U-14C]hexoses, underwent oxidation in the RINm5F cells. The secretory response to these four hexoses appeared commensurate with the extent of their metabolic effects.

Adenine Nucleotides↗

PubMed1987

Unresponsiveness of phospholipase C to the regulatory proteins Ns and Ni in pancreatic islets.

The possible participation of the regulatory proteins Ns and Ni in the regulation of phospholipase C activity in rat pancreatic islets was investigated. The islets were preincubated for 120 min with myo-[2-3H]inositol and the fractional outflow rate of [3H]inositol or production of [3H]inositol 1-phosphate was then measured. Glucagon failed to affect these metabolic variables, whether in the absence or presence of D-glucose. Pretreatment of the islets with cholera toxin also failed to affect basal or glucose-stimulated [3H]inositol outflow. Likewise, clonidine, which abolished insulin release evoked by D-glucose and carbamylcholine, failed to prevent the stimulant action of these secretagogues upon either [3H]inositol outflow or [3H]inositol 1-phosphate production. It is concluded that the regulatory proteins Ns and Ni apparently do not play any major role in the regulation of phosphoinositide phosphodiesterase activity in islet cells.

Animals↗

PubMed1987

Possible role of a GTP-binding protein in the activation of phospholipase C by carbamylcholine in tumoral insulin-producing cells.

Carbamylcholine, but not GTP gamma S, stimulated the production of [3H]inositol mono-, bis- and trisphosphate in intact tumoral insulin-producing cells (RINm5F line) prelabelled with myo-[2-3H(N)]inositol. On the contrary, GTP gamma S, but not carbamylcholine, stimulated the production of [3H]inositol mono-, bis- and trisphosphates in a subcellular particulate fraction derived from the prelabelled RINm5F cells. When the latter cells were first treated by digitonine, carbamylcholine or GTP caused a modest stimulation of [3H]inositol 1-phosphate production. However, in the presence of both GTP and carbamylcholine, the production of [3H]inositol 1-phosphate was much higher: it exceeded the value computed by summing the individual responses to each of these two agents, and reached the same level as that recorded in the presence of GTP gamma S. It is speculated that a GTP-binding regulatory protein, probably distinct from either Ns or Ni, couples the occupancy of muscarinic receptor to the activation of phospholipase C in pancreatic islet cells.

Carbachol↗

PubMedDate not supplied

Portal hyperglutamatemia after dietary supplementation with monosodium glutamate in pigs.

The aim of the present work was to examine in pigs the effect of a dietary supplementation with the flavor enhancer monosodium glutamate (MSG) on intestinal amino acid metabolism. For this purpose, pigs weighing 60 +/- 2 kg received a standard meal twice a day for 1 week, supplemented with either 10 g MSG per meal or, as control experiments, an isonitrogenous amount of glycine together with an equal amount of sodium in the form of NaCl, the animals being their own control in all experiments. At the end of this period, pigs received a MSG or glycine-NaCl-supplemented meal and samples of portal and arterial blood were collected for amino acid analysis in plasma. The results demonstrate after MSG supplementation rapid significant increases in glutamate concentration in the portal and arterial blood plasma after a test meal which resulted in a positive portoarterial difference. In comparison, after glycine-NaCl supplementation, glutamate concentrations were almost identical in portal and arterial plasma. Furthermore, significant increased aspartate concentration in the portal blood plasma was observed after MSG supplementation when compared with control experiments. When enterocytes were isolated at the end of the supplementation period from the jejunum and examined for their metabolic capacities towards L-glutamate and L-glutamine, it was found that metabolism did not differ according to the supplement used, with glutamate and glutamine being oxidized and transaminated at a similar level. It is concluded that the portal hyperglutamatemia observed shortly after the ingestion of a MSG- supplemented meal is likely due to the saturation of the intestinal capacity to metabolize glutamate with no measurable adaptation of the metabolic pathways controlling glutamate metabolism in enterocytes.

Alanine↗

PubMedDate not supplied

Effect of an elemental vs a complex diet on polyamine metabolism in rat isolated enterocytes.

BACKGROUND: Polyamines play an important role in the proliferation and differentiation of enterocytes. Ornithine decarboxylase (ODC) is the rate-limiting enzyme for polyamine biosynthesis. Elemental diets, providing easily absorbable nutrients such as free amino acids, are used in clinical practice to treat growth failure and malnutrition. They are very different from complex diets normally consumed. Little information is available about the influence of elemental diets on metabolic capacities of enterocytes. This study was undertaken in rats to assess the effects on polyamine metabolism of an elemental diet compared with a complex diet. METHODS: Rats were fed the elemental diet (group ED) or the control diet (group C) for 14 days. The dietary intakes were isocaloric and isonitrogenous in groups C and ED. Villous enterocytes were then isolated and metabolic capacities or enzyme activities were assessed. RESULTS: Both the enterocyte capacity to decarboxylate ornithine through ODC (measured in viable enterocytes) and ODC activity (measured in homogenates) were severely decreased in group ED. The polyamine content in enterocytes, however, was maintained at a similar level in both groups. This coincided with a decrease in the main enzymatic activity responsible for putrescine catabolism (ie, diamine oxidase activity) in group ED. CONCLUSIONS: Although nutrition manipulation was shown to alter polyamine biosynthesis in this study, the polyamine homeostasis was probably maintained, at least in part, through down-regulation of diamine oxidase.

Amine Oxidase (Copper-Containing)↗

PubMedDate not supplied

Effect of an elemental vs a complex diet on L-citrulline production from L-arginine in rat isolated enterocytes.

BACKGROUND: L-Arginine and L-glutamine are highly metabolized by intestinal cells, leading to various metabolites, including L-citrulline, which is required for optimal growth. Elemental diets, used in clinical practice to treat growth failure and malnutrition, are very different from complex diets normally consumed. The aim of the present study was to assess the effects of an elemental diet compared with a complex diet on L-arginine metabolism in rat isolated enterocytes and its modulation by L-glutamine. METHODS: Rats were fed the elemental diet (group ED) or the control diet (group C) for 14 days. Villus enterocytes then were isolated, and metabolic capacities or enzyme activities were assessed. RESULTS: The incubation of enterocytes isolated from group C with 0.1 mmol/L L-[U-14C]-arginine led to the production of 125 +/- 25 pmol L-citrulline/10(6) cells per 30 minutes. This production showed a twofold increase in the presence of 2 mmol/L L-glutamine. In group ED, L-citrulline synthesis from L-arginine was markedly lower in the absence or in the presence of L-glutamine. This coincided with lower carbamoylphosphate synthase I activity and carbamoylphosphate (CP) content of enterocytes. Other L-arginine and L-glutamine metabolic pathways were not affected. Similar results were obtained when the elemental diet was administered continuously through a gastric catheter or fed by mouth. CONCLUSIONS: L-Glutamine favors the synthesis of L-citrulline from L-arginine in isolated enterocytes, probably via an increase in CP production. Changing the diet composition, from a complex to an elemental diet, results in an alteration of the enterocyte capacity to synthesize L-citrulline from L-arginine, irrespective of the rhythm of delivery.

Animals↗