title: Coexisting role of fasting or feeding and dietary lipids in the control of gene expression of enzymes involved in the synthesis of saturated, monounsaturated and polyunsaturated fatty acids.
abstract: In the liver, maintaining lipid homeostasis is regulated by physiological and exogenous factors. These lipids are synthesized by Fasn, elongases and desaturases. Interactions in an organism among these factors are quite complex and, to date, relatively little is known about them. The aim of this study was to evaluate the coexisting role of physiological (insulin, fasting and feeding) and exogenous (dietary lipids) factors in the control of gene expression of Fasn, elongases and desaturases via Srebf-1c in liver from rats. Gene expression of encoding enzymes for fatty acid synthesis and fatty acid composition was evaluated in liver from rats in fasting and feeding (at 30, 60, 90 and 120 min after feeding) when food intake (adequate or high-lipid diet) was synchronized to a restricted period of 7h. Fasn, Scd and Fads2 were induced during 120 min after initial feeding in both dietary groups. This induction may be activated in part by insulin via Srebf-1c. Also, we showed for the first time that Elovl7 may be regulated by insulin and dietary lipids. The failure to synthesize saturated and monounsaturated fatty acids is consistent with a downregulation of Fasn and Scd, respectively, by dietary lipids. A higher content of LC-PUFAs was observed due to a high expression of Elovl2 and Elovl5, although Fads2 was suppressed by dietary lipids. Therefore, elongases may have a mechanism that is Srebf-1c-independent. This study suggests that a high-lipid diet triggers, during 120 min after initial feeding, a tight coordination among de novo lipogenesis, elongation, and desaturation and may not always be regulated by Srebf-1c. Finally, upregulation by feeding (insulin) of Fasn, Scd, Fads2 and Srebf-1c is insufficient to compensate for the inhibitory effect of dietary lipids.
authors.affiliation: Laboratorio de Biología Molecular, Unidad de Investigación Médica en Nutrición, Hospital de Pediatría, Centro Médico Nacional Siglo XXI, IMSS, México City, Mexico. maricela.rodriguez.cruz@gmail.com
authors.forename: Maricela
authors.initials: M
authors.lastname: Rodríguez-Cruz
authors.forename: Raúl
authors.initials: R
authors.lastname: Sánchez González
authors.forename: Apolos M
authors.initials: AM
authors.lastname: Sánchez García
authors.forename: Mardia
authors.initials: M
authors.lastname: Lòpez-Alarcòn
mesh_terms: D000818:Animals; D004041:Dietary Fats / Q000494:pharmacology*; D004435:Eating / Q000235:genetics / Q000502:physiology*; D004798:Enzymes / Q000235:genetics* / Q000378:metabolism; D005215:Fasting / Q000378:metabolism / Q000502:physiology*; D005227:Fatty Acids / Q000378:metabolism*; D005229:Fatty Acids, Monounsaturated / Q000378:metabolism; D005231:Fatty Acids, Unsaturated / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D007328:Insulin / Q000378:metabolism / Q000502:physiology; D000078790:Insulin Secretion; D050356:Lipid Metabolism / Q000187:drug effects / Q000235:genetics; D050155:Lipogenesis / Q000187:drug effects / Q000235:genetics; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D051780:Sterol Regulatory Element Binding Protein 1 / Q000235:genetics / Q000378:metabolism
chemical_list: D004041:Dietary Fats; D004798:Enzymes; D005227:Fatty Acids; D005229:Fatty Acids, Monounsaturated; D005231:Fatty Acids, Unsaturated; D007328:Insulin; C497389:Srebf1 protein, rat; D051780:Sterol Regulatory Element Binding Protein 1