Chronic dietary vitamin A supplementation regulates obesity in an obese mutant WNIN/Ob rat model.
OBJECTIVE
To understand the possible role of chronic dietary high vitamin A supplementation in body weight regulation and obesity using a novel WNIN/Ob obese rat model developed at the National Centre for Laboratory Animal Sciences of National Institute of Nutrition, India.


METHODS
Thirty-six 7-month-old male rats of lean, carrier, and obese phenotypes were broadly divided into two groups; each group was subdivided into three subgroups consisting of six lean, six carrier, and six obese rats and received diets containing either 2.6 or 129 mg vitamin A/kg of diet for 2 months. Body weight gain, food intake, and weights of various organs were recorded. Adiposity index and BMI were calculated. Serum and liver retinol and brown adipose tissue (BAT)-uncoupling protein1 (UCP1) mRNA expression levels were quantified.


RESULTS
Chronic feeding of high but non-toxic doses of vitamin A through diet significantly reduced (P < or = 0.05) body weight gain, adiposity index, and retroperitoneal white adipose tissue mass (without affecting food intake) in obese rats compared with their lean and carrier counterparts. In general, vitamin A treatment significantly improved hepatic retinol stores (P < or = 0.05) in all phenotypes without affecting serum free retinol levels. However, augmented BAT-UCP1 expression was observed only in carrier and obese rats (whose basal expression was low).


CONCLUSIONS
Our data suggest that chronic dietary vitamin A supplementation at high doses effectively regulates obesity in obese phenotype of the WNIN/Ob strain, possibly through up-regulation of the BAT-UCP1 gene and associated adipose tissue loss. However, in vitamin A-supplemented lean and carrier rats, changes in adiposity could not be related to BAT-UCP1 expression levels.
Department of Biochemistry, National Institute of Nutrition (ICMR), Jamai Osmania, Hyderabad 500 007, Andra Pradesh, India.
Shanmugam M
SM
Jeyakumar
Ayyalasomayajula
A
Vajreswari
Nappan V
NV
Giridharan
D000273:Adipose Tissue / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D002149:Energy Intake / Q000187:drug effects*; D007473:Ion Channels; D008099:Liver / Q000378:metabolism; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D024101:Mitochondrial Proteins; D009765:Obesity / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D011897:Random Allocation; D051381:Rats; D011919:Rats, Inbred Strains; D000071256:Uncoupling Protein 1; D014801:Vitamin A / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D014815:Vitamins / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology*; D015430:Weight Gain / Q000187:drug effects*
D002352:Carrier Proteins; D007473:Ion Channels; D008565:Membrane Proteins; D024101:Mitochondrial Proteins; C000604373:Ucp1 protein, rat; D000071256:Uncoupling Protein 1; D014815:Vitamins; D014801:Vitamin A