title: Chronic vitamin A-enriched diet feeding induces body weight gain and adiposity in lean and glucose-intolerant obese rats of WNIN/GR-Ob strain.
abstract: What is the central question of this study? Previously, we reported that chronic feeding of a vitamin A-enriched diet to euglycaemic obese rats (WNIN/Ob) ameliorated obesity. Does this diet exert similar effects even with a different genetic background, i.e. obese rats of the WNIN/GR-Ob strain with impaired glucose tolerance? What is the main finding and its importance? Vitamin A-enriched diet aggravated weight gain and adiposity/obesity in both lean and glucose-intolerant obese rats of the WNIN/GR-Ob strain. Therefore, the role of genetic factors and their regulation by nutrients in determining health and disease conditions assumes greater significance in experimental and clinical research. Vitamin A and its metabolites are key regulators of the development of adipose tissue and its associated metabolic complications. Here, we tested, in a glucose-intolerant obese rat model (the WNIN/GR-Ob stain), whether feeding a vitamin A-enriched diet alters adiposity and its associated changes. For this purpose, 30-week-old male lean and obese rats were divided into two groups and received either stock diet or vitamin A-enriched diet [2.6 or 129 mg vitamin A (kg diet)(-1) , respectively] for 14 weeks. At the end, feeding of the vitamin A-enriched diet resulted in increased body weight gain/obesity and retroperitoneal white adipose tissue (RPWAT) in both lean and obese rats of the WNIN/GR-Ob strain, when compared with their respective control animals receiving stock diet, without affecting food intake. An improvement in hypertriglyceridaemia and circulatory non-esterified fatty acid levels and unaltered hepatic fatty acid oxidative and triglyceride secretory pathway proteins with vitamin A-enriched diet feeding are suggestive of enhanced hepatic clearance of circulatory lipids, resulting in increased hepatic triglyceride accumulation. Transcriptional analysis of RPWAT showed that feeding the vitamin A-enriched diet augmented the expression of adipogenic/adipose tissue-specific genes; peroxisome proliferator-activated receptor-γ, stearoyl CoA desaturase 1, retinol saturase, leptin and lipoprotein lipase and vitamin A metabolic pathway genes; retinoic acid receptors, retinoid X receptors and cytochrome P450 26B1. Besides, RPWAT-lipoprotein lipase-mediated clearance of triglyceride could also have contributed to increased adiposity and improved hypertriglyceridaemia. In conclusion, chronic feeding of vitamin A-enriched diet induces weight gain and adiposity in both lean and obese rats of the WNIN/GR-Ob strain, possibly through transcriptional regulation of key adipogenic pathway genes of RPWAT, but improves dyslipidaemia.
authors.affiliation: Lipid Biochemistry Division, National Institute of Nutrition, Jamai-Osmania, Hyderabad, 500 007, India.
authors.forename: Shanmugam M
authors.initials: SM
authors.lastname: Jeyakumar
authors.affiliation: Lipid Biochemistry Division, National Institute of Nutrition, Jamai-Osmania, Hyderabad, 500 007, India.
authors.forename: Alex
authors.initials: A
authors.lastname: Sheril
authors.affiliation: Lipid Biochemistry Division, National Institute of Nutrition, Jamai-Osmania, Hyderabad, 500 007, India.
authors.forename: Ayyalasomayajula
authors.initials: A
authors.lastname: Vajreswari
mesh_terms: D050156:Adipogenesis / Q000235:genetics; D050154:Adiposity / Q000187:drug effects*; D000818:Animals; D004032:Diet; D005786:Gene Expression Regulation; D005947:Glucose; D015228:Hypertriglyceridemia / Q000473:pathology; D008099:Liver / Q000737:chemistry; D008297:Male; D009765:Obesity / Q000473:pathology*; D051381:Rats; D011919:Rats, Inbred Strains; D014280:Triglycerides / Q000737:chemistry; D014801:Vitamin A / Q000008:administration & dosage*; D015430:Weight Gain / Q000187:drug effects*
chemical_list: D014280:Triglycerides; D014801:Vitamin A; D005947:Glucose