Conjugated linoleic acid inhibits glucose metabolism, leptin and adiponectin secretion in primary cultured rat adipocytes.

Conjugated linoleic acid (CLA) supplementation has been reported to induce insulin resistance in animals and humans, however, the underlying mechanisms remain unclear. The aim of this study was to examine the direct effects of CLA on leptin and adiponectin secretion, two hormones with actions known to influence insulin sensitivity. Isolated rat adipocytes were incubated with CLA (1-200microM) in the absence and presence of insulin (1.6nM). CLA inhibited both basal and insulin-stimulated leptin gene expression and secretion (-30 to -40%, P<0.05-0.01). CLA also inhibited basal adiponectin production (-20 to -40%, P<0.05-0.01), but not in the presence of insulin. CLA (50-200muM) decreased basal glucose uptake (P<0.05-0.01) and significantly increased the proportion of glucose metabolized to lactate (P<0.01). Insulin treatment partially prevented the inhibitory effects of CLA on glucose uptake and induced a significant increase (P<0.05-0.01) in the percentage of glucose metabolized to lactate. A strong inverse relationship was observed between the increase in the anaerobic utilization of glucose and the decreases of both leptin and adiponectin secretion. In addition, lipolysis and the expression of the adipogenic transcription factor PPARgamma were decreased by CLA. These results indicate that CLA inhibits leptin and adiponectin secretion and suggest that increased anaerobic metabolism of glucose may be involved in these effects. The inhibition of PPARgamma could also mediate the inhibition of adiponectin induced by CLA. Furthermore, the inhibition of leptin and adiponectin production induced by CLA may contribute to insulin resistance observed in CLA-treated animals and humans.

Effect of misoprostol on the enzyme ontogeny of the rat intestine.

The effect of Misoprostol (an analog of PGE1) on the biochemical changes in the small intestine of suckling rats was studied. Misoprostol increases sucrase activities in the proximal and the distal small intestine. Jejunal aminopeptidase N activity is higher in Misoprostol-treated rats than in the control rats. This drug also modifies the relative weight of the small intestine and the mucosal ratio of DNA to RNA. Misoprostol effects appear to be mediated by corticosterone release.

Effect of lindane on galactose and leucine transport in chicken enterocytes.

Lindane (gamma-hexachlorocyclohexane) influence on the in vitro intestinal transport of D-galactose and L-leucine has been studied in isolated chicken enterocytes. Animals were injected i.p. with 30 mg/kg b.w. of the pesticide over 7 days. Total uptake of D-galactose and L-leucine was significantly decreased by lindane action. There was no alteration in the non-mediated component, but the mediated transport was markedly inhibited in both cases. Furthermore, the exit of D-galactose across the basolateral membrane, as well as (Na(+)-K+)-ATPase activity, was significantly decreased in pesticide-treated chickens.

Eicosapentaenoic fatty acid increases leptin secretion from primary cultured rat adipocytes: role of glucose metabolism.

Eicosapentaenoic acid (EPA), one of the n-3 polyunsaturated fatty acids, has been shown to stimulate leptin mRNA expression and secretion in 3T3-L1 cells. However, other studies have reported inhibitory effects of EPA on leptin expression and secretion in vivo and in vitro. To determine the direct effects of EPA on basal and insulin-stimulated leptin secretion, isolated rat adipocytes were incubated with EPA in the absence and presence of insulin. EPA (10, 100, and 200 microM) increased basal leptin gene expression and secretion (+43.8%, P < 0.05; +71.1%, P < 0.01; and +73.7%, P < 0.01, respectively). EPA also increased leptin secretion in the presence of 1.6 nM insulin; however, the effect was less pronounced than in the absence of it. Because adipocyte glucose and lipid metabolism are involved in the regulation of leptin production, the metabolic effects of this fatty acid were also examined. EPA (200 microM) increased basal glucose uptake in isolated adipocytes (+50%, P < 0.05). Anaerobic metabolism of glucose, as assessed by lactate production and proportion of glucose metabolized to lactate, has been shown to be inversely correlated to leptin secretion and was decreased by EPA in both the absence and presence of insulin. EPA increased basal glucose oxidation as determined by the proportion of (14)C-labeled glucose metabolized to CO(2). Lipogenesis ((14)C-labeled glucose incorporation into triglyceride) was decreased by EPA in the absence of insulin, whereas lipolysis (glycerol release) was unaffected. The EPA-induced increase of basal leptin secretion was highly correlated with increased glucose utilization (r = +0.89, P < 0.01) and inversely related to the anaerobic glucose metabolism to lactate. EPA's effect on insulin-stimulated leptin secretion was not related to increased glucose utilization but was inversely correlated with anaerobic glucose metabolism to lactate (r = -0.84, P < 0.01). Together, the results suggest that EPA, like insulin, stimulates leptin production by increasing the nonanaerobic/oxidative metabolism of glucose.

Stimulation of brush border enzyme activity along the rat small intestine by misoprostol.

The effect of Misoprostol (0.3 mg/kg b.w., orally for four weeks) on the brush border membrane enzyme activity, is studied in growing rats. Misoprostol enhanced stomach and intestine relative weights as well as the mucosal weight of the duodenum and proximal jejunum. In treated rats, disaccharidases, alkaline phosphatase and aminopeptidase enzyme activity were measured in brush border purified fraction throughout the small intestine. Sucrase, maltase, aminopeptidase and alkaline phosphatase specific activities were significantly increased along the small intestine. In the proximal jejunum, sucrase (62%; p < 0.001) and maltase (42%; p < 0.01) activities were significantly greater. Sucrase activity was also significantly (p < 0.001) increased by about 103% in the distal jejunum. There was also a significant (p < 0.05) increment of 32% in the duodenal and ileal alkaline phosphatase activity after treatment. Similarly, aminopeptidase activity was significantly (p < 0.05) higher in duodenum (67%) and jejunum (24%). In conclusion, Misoprostol appreciably increased the ability of the small intestine to perform its digestive functions although further studies will be necessary to examine the cellular and molecular mechanism(s) which may be responsible for these effects.

Effect of carbaryl on the respiration, glycolysis and gluconeogenesis in isolated liver cells.

The effects of 1-naphthyl-N-methylcarbamate (carbaryl) upon respiration, glycolysis and gluconeogenesis in isolated rat hepatocytes was studied. The carbaryl at 0.01; 0.1 and 1.0 mM were dissolved in 1% dimethylsulphoxide. Concentrations of carbaryl at 1.0 mM reduces oxygen consumption. The decrease in the metabolic production of CO2 is significant at even the lowest of the concentrations. The utilization of glucose and the endogenous production of lactic is unaffected by treatment with carbaryl. The net glycolytic flux is decreased. On the other hand, the carbaryl inhibits lactate-gluconeogenesis at all concentrations of substrate studied. Gluconeogenesis from fructose or pyruvate or alanine is also inhibited by carbaryl 1 mM. Carbaryl decreases the lactic dehydrogenase activity but this diminution is only significant for the greatest concentration assayed. The activity of glucose-6-phosphatase is enhanced by carbaryl, but the increase is only significant for 1 mM carbaryl. The glutamic-oxalacetic transferase cytoplasmic and mitochondrial activities are inhibited by 0.1 mM and 1.0 mM carbaryl. Carbaryl decreases glucose production by hepatic cells, and suggests that the carbaryl-induced hyperglycemia in the fasted animal would be due to deficiencies in the peripheral utilization of the glucose.

Prostaglandin E2 accelerates enzymatic and morphological maturation of the small intestine in suckling rats.

The effect of prostaglandin E2 (PGE2) injection on the postnatal maturation of the 16-day-old rodent small intestine was studied. Previous studies have shown that 16,16-dimethyl PGE2 induced several morphological and biochemical parameters in the small intestine of 11-day-old rats. PGE2 was given subcutaneously daily at doses of 2 and 4 mg/kg body weight on postnatal days 11-15. After treatment there was a rise in the mean activities of sucrase, maltase, lactase and aminopeptidase. In rats receiving 4 mg/kg PGE2, sucrase activity was strongly stimulated (p < 0.001) in the proximal and the distal small bowel. In the duodenum, PGE2 treatment (4 mg/kg body weight) produced a significant increase in crypt depth (35%, p < 0.001), although villus height was not modified. Serum corticosterone levels were significantly increased in PGE2-treated rats. The results seem to indicate that PGE2 accelerates enzymatic and morphological intestinal maturation and this effect could be mediated by an increase in corticosterone.

[Effect of gamma-hexachlorocyclohexane (Lindane) on the brain and serum tryptophan (author's transl)]. / Influencia del gamma-hexaclorociclohexano (Lindano) sobre el triptófano sérico y cerebral.

The effect of convulsant doses of gamma-hexachlorocyclohexane (Lindane) on the brain and serum tryptophan contents as well as on the serum FFA contents was studied. The results indicate a possible correlation between the fluctuations in the FFA, free serum and brain tryptophan concentrations. The total tryptophan concentrations increase as well as the brain tryptophan/free tryptophan ratio, with both experimental doses.

[Response of pleural and peritoneal mastocyte populations in the rat to agents with different mechanisms of action]. / Respuesta de las poblaciones pleural y peritoneal de mastocitos de rata ante agentes con distintos mecanismos de acción.

Histamine release from rat pleural and peritoneal mast cells not previously purified is presented. Cells are stimulated by different mechanism-acting pharmacologic agents. FNa, theophylline, ruthenium red, chlorpromazine and propranolol are used. Results show that both cell populations are pharmacologically different, with distinct responses in the presence of FNa or chlorpromazine. Chlorpromazine and propranolol are cytolytic agents.

Effects of in situ and systemic lindane treatment on in vivo absorption of galactose and leucine in rat jejunum.

In vivo intestinal absorption of L-leucine is significantly decreased by the presence of lindane (0.3, 0.2 and 0.1 mM) in perfusion solution (in situ lindane treatment) for 5 min. The inhibitory effect is earlier when lindane concentration is higher, and it is irreversible. There are no changes in D-galactose absorption when lindane (0.3 and 0.2 mM) is perfused for 5 min, but a significant decrease in observed if pesticide is perfused for 10 min at 0.3 mM concentration. Subcutaneous lindane treatment at a dose of 68.76 mumol/kg over 7 days does not alter D-galactose and L-leucine absorption. In situ lindane treatment (0.3, 0.2 and 0.1 mM) induces a significant decrease in basolateral (Na(+)-K(+)-ATPase activity. In contrast, systemic lindane treatment (s.c. injection) at doses of 34.38 and 68.76 mumol/kg over 7 days does not alter this enzyme activity, although a significant decrease is observed in rats injected s.c. with 68.76 mumol/kg lindane over 15 days.

Effects of different subchronic treatments with lindane on some brush border enzymes in rat jejunum.

Subchronic lindane (gamma-HCH) intoxication by oral or s.c. injection over 7 and 15 days, induced a significant inhibition in rat jejunum maltase activity when the pesticide was administered at doses of 20 mg/kg b. wt. However, maltase levels remained unaffected in those animals injected with 10 mg/kg of lindane. A longer period of s.c. lindane exposure (30 days) at doses of 10 mg/kg induced a significant decrease in maltase activity, although the injection of 20 mg/kg over the same period did not alter this enzyme activity. When this lindane dose was s.c. injected over 20 days a significant inhibition of maltase activity was observed. However no changes in this enzyme were found in rats injected over 25 days. This fact seems to suggest that between 20-25 days of pesticide exposure the organism develops possible regulatory mechanisms to counteract the alterations induced by this dose of lindane on maltase activity. Lactase and alkaline phosphatase activities were not altered by lindane action in different treatments performed. Sucrase activity was only altered in oral injected rats at doses of 20 mg/kg over 15 days. In conclusion, maltase activity seems to be more sensitive to lindane action than other brush border enzymatic proteins; lindane effects on this enzyme depend on the injected dose and the pesticide administration period duration.

[Isolation of mastocytes from rat peritoneal fluid using continuous Ficoll gradients]. / Purificación de mastocitos de fluido peritoneal de rata utilizando gradientes continuos de Ficoll.

A method for mast cells purification from rat peritoneal fluid is described. The method consists of a continuous Ficoll gradient between 20 and 22,5% (w/v) Ficoll and the cells are obtained with an 88% retrieval. Purity and viability were of 95% and 97% respectively. The cells so purified were functional against the compound 48/80 and the spontaneous secretion value was less than 8%.

[Secretory activity of mast cells in the presence of cholinergic agonists]. / Estudio de la actividad secretora de mastocitos en presencia de agonistas colinérgicos.

Mast cells from rat peritoneal fluid were studied under cholinergic stimulus. The cells were purified by a continuous Ficoll gradient and were challenged with acetylcholine and carbamylcholine. The preparations showed the typical dose-response pattern against compound 48/80 with a dose interval of 0.5-1 microM that clearly increased the secretion. However, the histamine release elicited by increasing concentrations of acetylcholine and carbamylcholine was of little magnitude and similar for all the concentrations; this kind of response has not a dose-response profile and does not appear to be explained by the presence of a cholinergic receptor on the mast cell cellular membranes. The cholinergic agents neither stimulated directly the mast cells nor did they cause any variation in the 48/80 response. The histamine release pattern obtained with these agents cannot support the hypothesis of a primary cholinergic receptor on mast cells. However, if such receptor existed, its action could only be of secondary importance, and in fact such action was not manifested with the compound 48/80.

Influence of dimethylsulphoxide on the functional state of isolated rat hepatocytes.

The effect of dimethylsulphoxide upon respiration, glycolysis and gluconeogenesis in isolated rat hepatocytes was studied. The results show that the glycolysis pathway is strongly inhibited by the action of dimethylsulphoxide in the hepatocytes, with increased glucose uptake and reduced net flux. However, the alterations in respiration and the gluconeogenesis pathway are less pronounced, the only significant change being an increase in respiratory activity during the first 10 min of incubation with dimethylsulphoxide.

Changes in enzymatic activity of small intestine and kidney of rats by a methionine deficient diet.

The effect of methionine dietary deficiency on food intake, weight gain, liver and kidney weight, feed conversion rate, protein efficiency ratio, maltase and leucineaminopeptidase (LAPase) activities of the intestinal mucosa as well as renal LAPase activity was studied. Three groups of female Wistar rats, weighing between 40-60 g, were fed for 25 days on either Diet A (casein supplemented with 0.6% DL-methionine), Diet B (amino acid mixture simulating casein also supplemented with 0.6% methionine) or Diet C (amino acid mixture with 0.67% methionine deficiency with respect to Diet A). The results show no significant differences in either growth or enzymatic activity between the rats fed on Diet A and those on Diet B. The animals fed on Diet C show an increase in intestinal (P less than 0.01, vs Diet B) and renal (P less than 0.005, vs Diet A) LAPase activity, although intestinal maltase activity remained unchanged. Food intake, weight gain, organ weight and nutritional parameters obtained in rats fed on Diet C showed no statistically significant changes, with the exception of kidney weight which decreased (P less than 0.005) when compared to those fed on Diet B.

[Effect of colchicine on histamine secretion and calcium uptake in mast cells]. / Efecto de la colchicina sobre la secreción de histamina y captación de calcio en mastocitos.

The function of contractile system of microtubules on the mechanism of mast cell exocytosis by using colchicine, a depolymerizing alkaloid of the microtubular system, has been studied. The response of histamine release and 45Ca-uptake in isolated rat mast cells treated with colchicine has been determined. The incubation of mast cells in the presence of 10(-8)-10(-3) M colchicine slightly inhibits histamine secretion induced by the stimulant concentration 50 micrograms/ml of compound 48/80 (35 +/- 5%). Similarly colchicine does not significantly affect histamine values spontaneously elicited in unstimulated mast cells; the percentages of secretion are never greater than 10%. However, high doses of this alkaloid are found to markedly inhibit entry of calcium ions into the cell. These results suggest that microtubules do not participate in the secretory process of mast cells, although they significantly decrease calcium uptake. The microtubules might be connected to the membrane, so that the depolymerization of this contractile system could damage the membrane structures through which Ca2+ is transported.

Effect of calcium on histamine release from pleural and peritoneal mast cells induced by catechol.

Histamine release from rat pleural and peritoneal mast cells induced by catechol (1, 10, 50, 250 microM and 1 mM) has been studied. The dose-response induced by catechol is non-cytotoxic, is not modified by purification of mast cells and is calcium independent. The sensitivity and maximum response to catechol is the same irrespective of the presence or absence of Ca++, except on purified pleural mast cells, that showed a plateau response at 250 microM catechol in the absence of Ca++, and on unpurified peritoneal mast cells which exhibited a lower maximum response equally in the absence of Ca++. The release is induced by catechol at concentrations as low as 50 microM in all cases, and the maximum response is reached at 1 mM.

Action of actinomycin D on glycosidase levels in the small intestine of hamsters.

Actinomycin D affects a number of functions of the epithelial cells of the small intestine. Maltase, saccharase and lactase levels in the small intestine of hamsters treated with various dosages of actinomycin D over various periods of time, differed from those observed in control animals: administration of 0.25 micrograms/g body weight, gave rise to a statistically significant increase in the maltase and saccharase levels measured after 4 h and a statistically significant reduction in the lactase levels measured after 8 h; administration of 1.5 micrograms/g body weight reduced the activity of all three enzymes at all times post-administration, the decrease being statistically significant for maltase after 2 and 8 h.

Effects on energy utilization of a beta3-adrenergic agonist in rats fed on a cafeteria diet.

The antiobesity potential of a new beta3-adrenergic agonist (Trecadrine) was assessed in a cafeteria model of obesity through body composition, thermogenesis and oxygen consumption indicators. Animals fed on a cafeteria diet for 75 days increased body weight and fat content, while muscle mass as a percentage of body weight was reduced in relation to control fed rats. In addition, in vitro brown adipose tissue (BAT) and white adipose tissue (WAT) oxygen consumption was increased in these obese animals as compared with controls. Trecadrine administration reduced weight gain, BAT and WAT stores as well as the respiratory quotient, which was accompanied by an increase in WAT and BAT oxygen consumption and rectal temperature. Moreover, muscle mass as a percentage of body weight maintained the same values as non-obese animals, while an increase in absolute muscle weight was found in Trecadrine-treated obese rats. However, liver weights and in vitro oxygen consumption remained unaltered after cafeteria feeding and Trecadrine administration. Since chronic administration of Trecadrine had no effect on food intake, the stimulation of thermogenesis and oxygen consumption by the beta3-adrenergic agonist in white and brown adipose tissue are apparently responsible for the rise in energy expenditure as well as for the lower weight gain and fat deposition in obese treated rats. Thus, Trecadrine exhibits some promise as a potential treatment for obesity.

Actinomycin D and cycloheximide actions on activity of some intestinal enzymes of adult hamster.

Actinomycin D, at a dose of 0.25 micrograms/g body wt, produced slight increases in intestinal enzymatic activity on hamsters. At a high dose (1.5 micrograms/g body wt), actinomycin D produced inhibition of lactase activity, whereas maltase, sucrase and alkaline phosphatase activity decreased in males and increased in females. Cycloheximide (1.5 micrograms/g body wt), produced no changes in enzymatic activity. In the male and female hamster, the different actions of the antibiotic can be explained by the variations in the cortisol release produced by stress.