Increased glyceroneogenesis in adipose tissue from rats adapted to a high-protein, carbohydrate-free diet: role of dietary fatty acids.
We have previously shown in in vivo experiments that adipose tissue glyceroneogenesis is increased in rats adapted to a high-protein, carbohydrate-free (HP) diet. The objectives of the present study were (1) to verify if the increased glyceroneogenic activity is also observed in isolated adipocytes and (2) to investigate the role of preformed fatty acids in the production of the increased adipose tissue glyceroneogenesis. Control rats received a balanced diet, with the same lipid content of the HP diet. Glyceroneogenic activity was found to be higher in adipocytes from HP rats than in controls, as evidenced by increased rates of conversion of pyruvate and lactate to triacylglycerol (TAG)-glycerol. Administration of Triton WR 1339, which blocks the removal of TAG incorporated into circulating lipoproteins, to HP diet-adapted rats caused a significant reduction in the incorporation of 14C-pyruvate into TAG-glycerol by adipose tissue, which was accompanied by a marked inhibition of phosphoenolpyruvate carboxykinase activity, the key enzyme of glyceroneogenesis. The inhibitory effect of Triton on TAG-glycerol synthesis by adipose tissue was also observed in vivo, after administration of 3H2O. Adaptation to the HP diet induced a marked increase in the activity of retroperitoneal and epididymal fat LPL, which was restored to control values 24 hours after replacement of the HP diet by the balanced diet. The data suggest that in rats adapted to a carbohydrate-free diet, adipose tissue glyceroneogenesis is activated by an increased use of diet-derived fatty acids.
Brito
Salete Cipriano
SC
Department of Biochemistry-Immunology, School of Medicine, University of São Paulo, 14049-900 Ribeirão Preto, São Paulo, Brazil.
Festuccia
William Lara
WL
Kawashita
Nair Honda
NH
Moura
Maria Ferreira
MF
Xavier
Analúcia Rampazzo
AR
Garófalo
Maria Antonieta
MA
Kettelhut
Isis Carmo
IC
Migliorini
Renato Hélios
RH
D000222:Adaptation, Physiological / Q000502:physiology*; D000273:Adipose Tissue / Q000378:metabolism*; D000818:Animals; D002914:Chylomicrons / Q000378:metabolism; D004032:Diet; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D004044:Dietary Proteins / Q000494:pharmacology*; D005227:Fatty Acids / Q000494:pharmacology*; D005979:Glutathione Peroxidase / Q000378:metabolism; D005989:Glycerides / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism; D008071:Lipoprotein Lipase / Q000378:metabolism; D008077:Lipoproteins, LDL / Q000378:metabolism; D008297:Male; D011092:Polyethylene Glycols / Q000494:pharmacology; D019289:Pyruvic Acid / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
D002914:Chylomicrons; D004040:Dietary Carbohydrates; D004044:Dietary Proteins; D005227:Fatty Acids; D005989:Glycerides; D008077:Lipoproteins, LDL; C014149:phosphoenolpyruvate carboxykinase ferroactivator protein, rat; D019344:Lactic Acid; D011092:Polyethylene Glycols; D019289:Pyruvic Acid; D005979:Glutathione Peroxidase; D008071:Lipoprotein Lipase; D005990:Glycerol; C016811:tyloxapol