A low-protein, high-carbohydrate diet increases the adipose lipid content without increasing the glycerol-3-phosphate or fatty acid content in growing rats

• Published in: Canadian Journal of Physiology and Pharmacology 2010, Vol.88 (12), p.1157
• Main Authors: Buzelle, Samyra L, Santos, Maisa P, Baviera, Amanda M, Lopes, Carbene F, Garofalo, Maria A.R, Navegantes, Luiz C.C, Kettelhut, Isis C, Chaves, Valeria E, Kawashita, Nair H
• Format: Report
• Language: English
• Subjects: Adipose tissues; Carbohydrates; Diet; Fatty acids; Food and nutrition; Glycerin; Glycerol; Health aspects; Lipids; Physiological aspects; Properties; Proteins; Rats; Rattus
• ISSN: 0008-4212
• DOI: 10.1139/Y10-096

The amount of triacylglycerol (TAG) that accumulates in adipose tissue depends on 2 opposing processes: lipogenesis and lipolysis. We have previously shown that the weight and lipid content of epididymal (EPI) adipose tissue increases in growing rats fed a low-protein, high-carbohydrate (LPHC) diet for 15 days. The aim of this work was to study the pathways involved in lipogenesis and lipolysis, which ultimately regulate lipid accumulation in the tissue. De novo fatty acid synthesis was evaluated in vivo and was similar for rats fed an LPHC diet or a control diet; however, the LPHC-fed rats had decreased lipoprotein lipase activity in the EPI adipose tissue, which suggests that there was a decreased uptake of fatty acids from the circulating lipoproteins. The LPHC diet did not affect synthesis of glycerol-3phosphate (G3P) via glycolysis or glyceroneogenesis. Glycerokinase activity--i.e., the phosphorylation of glycerol from the hydrolysis of endogenous TAG to form G3P--was also not affected in LPHC-fed rats. In contrast, adipocytes from LPHC animals had a reduced lipolytic response when stimulated by norepinephrine, even though the basal adipocyte lipolytic rate was similar for both of the groups. Thus, the results suggest that the reduction of lipolytic activity stimulated by norepinephrine seems essential for the TAG increase observed in the EPI adipose tissue of LPHC animals, probably by impairment of the process of activation of lipolysis by norepinephrine. Key words: phosphoenolpyruvate carboxykinase, glyceroneogenesis, glycerokinase, glycerol-3-phosphate, fatty acids, lipolysis, epididymal adipose tissue, low-protein and high-carbohydrate diet. Le taux de triacylglycerol (TAG) qui s'accumule dans le tissu adipeux depend de 2 meecanismes opposes : la lipogenese et la lipolyse. Nous avons montre anteerieurement que le poids des lipides du tissu adipeux de l'epididyme (EPI) de mieme que leur taux augmentent chez les rats en croissance soumis a une diete hypoproteique hyperglucidique (HPHG) pendant 15 jours. La presente etude a eu pour but d'examiner les voies impliquees dans la lipogenese et la lipolyse qui regulent l'accumulation des lipides dans le tissu. On a evaluee in vivo la synthase de novo des acides gras, qui s'est revekee similaire chez les rats soumis a la diete HPHG ou a une diete temoin; toutefois, chez les rats soumis a la diete HPHG, une diminution de l'activite de la lipoproteeine lipase dans le tissus adipeux de l'EPI a ete observeee, c