pituitrin and acetoacetic-acid

[Arg8]Vasopressin (AVP) has an antilipolytic action on adipocytes, but little is known about the mechanisms involved. Here, we examined the involvement of the V1a receptor in the antilipolytic effect of AVP using V1a receptor-deficient (V1aR-/-) mice. The levels of blood glycerol were increased in V1aR-/- mice. The levels of ketone bodies, such as acetoacetic acid and 3-hydroxybutyric acid, the products of the lipid metabolism, were increased in V1aR-/- mice under a fasting condition. Triacylglyceride and free fatty acid levels in blood were decreased in V1aR-/- mice. Furthermore, measurements with tandem mass spectrometry determined that carnitine and acylcarnitines in serum, the products of beta-oxidation, were increased in V1aR-/- mice. Most acylcarnitines were increased in V1aR-/- mice, especially in the case of 2-carbon (C2), C10:1, C10, C14:1, C16, C18:1, and hydroxy-18:1-carbon (OH-C18:1)-acylcarnitines under feeding rather than under fasting conditions. The analysis of tissue C2-acylcarnitine level showed that beta-oxidation was promoted in muscle under the feeding condition and in liver under the fasting condition. An in vitro assay using brown adipocytes showed that the cells of V1aR-/- mice were more sensitive to isoproterenol for lipolysis. These results suggest that the lipid metabolism is enhanced in V1aR-/- mice. The cAMP level was enhanced in V1aR-/- mice in response to isoproterenol. The phosphorylation of Akt by insulin stimulation was reduced in V1aR-/- mice. These results suggest that insulin signaling is suppressed in V1aR-/- mice. In addition, the total bile acid, taurine, and cholesterol levels in blood were increased, and an enlargement of the cholecyst was observed in V1aR-/- mice. These results indicated that the production of bile acid was enhanced by the increased level of cholesterol and taurine. Therefore, these results indicated that AVP could modulate the lipid metabolism by the antilipolytic action and the synthesis of bile acid via the V1a receptor.

Topics: 3-Hydroxybutyric Acid; Acetoacetates; Adipocytes; Adipose Tissue; Animals; Cholesterol; Fatty Acids; Glycerol; Ketone Bodies; Lipids; Mice; Mice, Knockout; Receptors, Vasopressin; Triglycerides; Vasopressins

Atractyloside inhibited gluconeogenesis from dihydroxyacetone in hepatocytes from fasted rats and increased lactate synthesis. In the presence of atractyloside, lactate/pyruvate and beta-hydroxybutyrate/aceto-acetate ratios were increased and the accumulation of Fru-2,6-P2 was prevented. In the absence of atractyloside, gluconeogenesis from dihydroxyacetone was stimulated by dibutyryl-cAMP and, to a much lesser extent, by norepinephrine and vasopressin. Omission of Ca2+ increased the stimulation by norepinephrine but prevented that by vasopressin. High concentrations (greater than or equal to 40 microM) of atractyloside abolished the stimulation of gluconeogenesis by dibutyryl-cAMP but not that by norepinephrine or vasopressin. Exogenous Ca2+ was not required for hormonal stimulation in the presence of atractyloside. The stimulation by norepinephrine was inhibited by ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N-tetraacetic acid or prazosin but not by propranolol. Atractyloside caused decreases of all glycolytic intermediates and an activation of pyruvate kinase. Norepinephrine partially reversed these effects. The mitochondrial and cytosolic ATP/ADP ratios were determined by digitonin fractionation of hepatocytes. Norepinephrine or vasopressin increased the cytosolic ATP/ADP in the presence of atractyloside. We suggest that the increased availability of cytosolic ATP could be responsible for the stimulation of gluconeogenesis by these hormones.

Topics: 3-Hydroxybutyric Acid; Acetoacetates; Adenosine Diphosphate; Adenosine Triphosphate; Animals; Atractyloside; Bucladesine; Calcium; Cytosol; Dihydroxyacetone; Fructosediphosphates; Glucagon; Gluconeogenesis; Glycosides; Hydroxybutyrates; Lactates; Lactic Acid; Liver; Male; Mitochondria, Liver; NAD; Norepinephrine; Pyruvates; Pyruvic Acid; Rats; Rats, Inbred Strains; Trioses; Vasopressins