A novel genetically-obese rat model with elevated 11 beta-hydroxysteroid dehydrogenase type 1 activity in subcutaneous adipose tissue.

11 ß-hydroxysteroid dehydrogenase type 1 (11 ß-HSD1) catalyzes the conversion of inactive glucocorticoids to active glucocorticoids and plays an important role in the development of obesity and metabolic syndrome. 11 ß-HSD1 activity is lower in liver and higher in omental adipose tissue of obese rodent models like obese zucker rats, Ob/Ob and db/db mice. Here, we report the 11 ß-HSD1 activity in liver and adipose tissue of lean and obese rats of WNIN/Ob strain, a new genetic rat model of obesity. 11 ß-HSD1 activity in liver, omental and subcutaneous adipose tissues of 3 month-old male WNIN/Ob lean and obese rats was assayed. As observed in other rodent models, 11 ß-HSD1 activity was lower in liver and higher in omental adipose tissue. In contrast to other rodent obese models, WNIN/Ob obese rats had elevated 11 ß-HSD1 activity in subcutaneous adipose tissue, which is in line with the observation in human obesity. Here, we conclude that dysregulation of 11 ß-HSD1 in WNIN/Ob obese rat model is identical to human obesity, which makes it an excellent model for studying the effect of 11 ß-HSD1 inhibitors in ameliorating obesity and metabolic syndrome.

Vitamin A-enriched diet modulates reverse cholesterol transport in hypercholesterolemic obese rats of the WNIN/Ob strain.

AIM: Vitamin A plays a major role in lipid metabolism. Previously, we reported that chronic vitamin A feeding (129 mg/kg) for two months normalized the abnormally high plasma HDL-cholesterol (HDL-C) levels in hypercholesterolemic obese rats by upregulating the hepatic scavenger receptor class B type 1 (SR-BI) expression. In this report, we hypothesize that the administration of a dose less than 129 mg of vitamin A/kg would also be effective in lowering the plasma HDL-C levels in these rats. METHODS: Changes in the activity and expression of proteins related to RCT were analyzed together with blood parameters in five-month-old male lean and obese rats supplemented with 2.6 (control group), 26, 52 and 129 mg of vitamin A/kg as retinyl palmitate for 20 weeks. RESULTS: Vitamin A supplementation in the obese rats decreased the plasma HDL-C levels with a concomitant increase in the hepatic SR-BI expression and lipase activity compared to that observed in the control diet-fed obese rats treated with 2.6 mg of vitamin A/kg diet. Furthermore, vitamin A supplementation at doses of 52 and 129 mg/kg diet reduced the plasma lecithin cholesterol acyltransferase activity and increased the hepatic ATP-binding cassette transporter protein A1 expression in the obese rats. Interestingly, most of these changes were not observed in the lean rats fed a vitamin A-enriched diet. CONCLUSIONS: Chronic feeding of a vitamin A-enriched diet in hypercholesterolemic obese rats normalizes the plasma HDL-C level and presumably improves RCT, with an effective dose of 52 mg/kg diet. Further studies should focus on the pharmacological potential of vitamin A supplementation to correct an abnormal human obesity-associated lipoprotein metabolism.

Mitochondriogenesis and apoptosis: possible cause of vitamin A-mediated adipose loss in WNIN/Ob-obese rats.

BACKGROUND: Previously, we reported that vitamin A-enriched diet (129 mg/kg diet) intake reduces the adiposity development in obese rats of WNIN/Ob strain. Here, we hypothesize that dose lesser than 129 mg of vitamin A/kg diet would also be effective in ameliorating the development of obesity in these rats. METHODS: Five-month-old male lean and obese rats designated as A & B were divided into four subgroups (I, II, III and IV) consisting of 8 rats from each phenotype and received diets containing 2.6 mg (control group), 26 mg, 52 mg and 129 mg vitamin A/kg diet as retinyl palmitate for 20 weeks. Body composition and morphological analysis of brown adipose tissue (BAT) was analyzed. Expression of uncoupling protein 1 (UCP1), retinoic acid receptor α (RARα) and retinoid X receptor α (RXRα) in BAT and levels of Bcl2 and Bax in epididymal white adipose tissue (eWAT) were determined by immunoblotting. RESULTS: Vitamin A supplementation to obese rats at doses of 52 and 129 mg/kg diet showed reduced body weight gain and adiposity compared to control diet-fed obese rats receiving 2.6 mg of vitamin A/kg diet. In BAT of obese rats, vitamin A supplementation at doses of 26 and 52 mg of vitamin A/kg diet resulted in increased UCP1 expression with concomitant decrease in RARα and RXRα levels compared to control diet-fed obese rats. Further, transmission electron microscopy study revealed an increase in number of BAT mitochondria of obese rats supplemented with 26 and 52 mg of vitamin A/kg diet. Also, obese rats fed on 52 mg/kg diet resulted in increased apoptosis by altering the ratio of Bcl2 to Bax protein levels in eWAT. Notably, most of these changes were not observed in lean rats fed vitamin A-enriched diets. CONCLUSION: In conclusion, chronic consumption of 52 mg of vitamin A/kg diet seems to be an effective dose in ameliorating obesity possibly through mitochondriogenesis, UCP1-mediated thermogenesis in BAT and apoptosis in eWAT of obese rats. Therefore, the role of dietary vitamin A in correcting human obesity would be of unquestionable relevance and can only be addressed by future studies.

Studies on the molecular correlates of genomic stability in rat brain cells following Amalakirasayana therapy.

Adult Wistar NIN (WNIN) rats (6 months old) of both sexes were orally fed Amalakirasayana at a dose of 4.5 g per kg body weight, five days in a week. The Amalakirasayana was prepared by Arya Vaidya Sala, Kottakkal, Kerala, India, which is considered as gold standard. After 3, 9 and 15 months of such therapeutic regime, rats were sacrificed and various tissues including brain were removed. Isolated cell suspensions of neurons and astroglia were prepared from the cerebral cortex. DNA damage, as a prime indicator of the status of genomic stability was measured in terms of single (SSBs) and double strand breaks (DSBs) through (a). The "comet" assay and (b). The biochemical methods utilizing the unique properties of Escherichia coli DNA polymerase I (pol I) and calf thymus terminal transferase. The results convincingly indicate that while in control animals, there was a distinct increase in DNA damage with age in neurons and astrocytes, rasayana fed animals showed significantly less DNA damage in brain cells demonstrating beneficial effects of Rasayana therapy towards maintenance of genomic stability. DNA-damage may be the proximal cause of aging and strategies to reduce the rate of aging could be based on this fact.

Impact of feeding polyunsaturated fatty acids on cholesterol metabolism of dyslipidemic obese rats of WNIN/GR-Ob strain.

Dietary fatty acids are known to play an important role in the development as well as prevention of dyslipidemia. In this study, we evaluated the impact of feeding polyunsaturated fatty acids (PUFAs) for a period of 4 months on various aspects of cholesterol metabolism in genetically obese mutant rats of WNIN/GR-Ob strain. Based on their phenotype, lean and obese rats were divided into two groups, A and B respectively, and further subdivided depending on the type of dietary fat. Control groups of rats (AI and BI), were fed on 4% groundnut oil, which was replaced by safflower oil; n-6 PUFA diet (AII and BII) or oil blend of safflower and soybean oil, n-6 and n-3 PUFA diet (AIII and BIII) in the experimental groups. It was observed that feeding of diets with n-6 PUFA or a combination of n-6 and n-3 PUFAs resulted in marked elevation of plasma levels of total as well as HDL cholesterol and triglycerides in obese rats (BII and BIII), as compared to the control group (BI). Further, plasma HDL fraction of obese rats had elevated apolipoprotein E (apo E), while apo A1 levels remained unaltered. Increased lecithin: cholesterol acyltransferase (LCAT) activity and cholesteryl ester (CE) levels in the plasma and enhanced expression of hepatic scavenger receptor class B type1 (SR-B1) were also observed in PUFA-fed obese rats (BII and BIII). However, there was no change in hepatic ATP-binding cassette transporter protein A1 (ABCA1) levels in the obese rats fed on PUFA rich diets. Intriguingly, though these changes favor efficient removal of cholesterol from peripheral tissues, its esterification and enhanced clearance through reverse cholesterol transport (RCT); plasma HDL-C remained higher in these genetically dyslipidemic obese rats, thereby pointing at yet unknown mechanisms, involved in cholesterol homeostasis, which need to be studied.

Fatty acid desaturation index correlates with body mass and adiposity indices of obesity in Wistar NIN obese mutant rat strains WNIN/Ob and WNIN/GR-Ob.

BACKGROUND: Microsomal stearoyl-CoA desaturase1 (SCD1) is the rate limiting enzyme involved in the biosynthesis of monounsaturated fatty acids (MUFAs); palmitoleic (16:1) and oleic (18:1) acid from their respective substrates palmitic (16:0) and stearic (18:0) acids. The ratio of 18:1 to 18:0 has been implicated in the regulation membrane fluidity and function. SCD1 is abundantly expressed in obese humans as well as rodent models. However, no studies have correlated the fatty acid desaturation index (16:1/16:0 and 18:1/18:0), an indicator of SCD1 activity with the markers of obesity in terms of body mass index (BMI) and adiposity index (AI). Therefore, here, we attempted to relate the fatty acid desaturation index with BMI and AI in Wistar NIN-obese mutant rat strains namely, WNIN/Ob and WNIN/GR-Ob (with impaired glucose tolerance). METHODS: For this purpose, 200 days old male 6 lean and 6 obese rats of both strains were taken. Fatty acid composition was analyzed in plasma, various tissues such as liver, white adipose tissues (retroperitoneal, epididymal, omental, and subcutaneous) and brown adipose tissue. RESULTS: Fatty acid composition data showed significant increase in palmitoleic (16:1) and oleic (18:1) acid levels, which were reflected in increased desaturation index (16:1/16:0 and 18:1/18:0) in plasma and all the tissues of obese rats of both strains, when compared with their respective age and sex-matched lean rats. Further, we found a strong positive correlation between desaturation index, BMI and AI in plasma and most of the tissues analyzed. CONCLUSION: So far, plasma Δ9 desaturation index has been well correlated with hypertriglyceridemia and we, by employing two models of obesity namely, WNIN/Ob and WNIN/GR-Ob, have shown Δ9 desaturation index of plasma correlated with physical markers of obesity such as BMI and AI. In conclusion, Δ9 desaturation index may serve as a potential sensitive biochemical marker to assess the degree of obesity and impact of therapeutic/nutritional interventions to combat obesity, along with other indicators.

Impact of vitamin A on high-density lipoprotein-cholesterol and scavenger receptor class BI in the obese rat.

OBJECTIVE: Scavenger receptor class BI (SR-BI), authentic high-density lipoprotein (HDL) receptors expressed in liver, are known to play an important role in HDL-cholesterol (C) metabolism and reverse cholesterol transport. Interestingly, obese rats of WNIN/Ob strain have abnormally elevated levels of serum HDL-C compared with their lean counterparts. Based on the well-established role of SR-B1 in HDL-C metabolism, it was hypothesized that these obese rats may have an underexpression of hepatic SR-B1 receptors. In view of the significant role of vitamin A in energy expenditure and obesity, we also tested whether vitamin A supplementation can correct abnormal HDL-C metabolism. RESEARCH METHODS AND PROCEDURES: To test this hypothesis, 7-month-old male lean and obese rats of WNIN/Ob strain were divided into two groups; each group was subdivided into two subgroups consisting of six lean and six obese rats and received diets containing either 2.6 or 129 mg vitamin A/kg diet for 2 months. RESULTS: At the end, obese rats receiving normal levels of vitamin A diet showed high serum HDL-C and lower hepatic SR-BI expression levels compared with lean counterparts. Furthermore, chronic dietary vitamin A supplementation resulted in overexpression of hepatic SR-BI receptors (protein and gene) with concomitant reduction in serum HDL-C levels in obese rats. DISCUSSION: Thus, our observations highlight the role of vitamin A in reverse cholesterol transport through up-regulation of hepatic SR-BI receptors and, thereby, HDL-C homeostasis in obese rats of WNIN/Ob strain.

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. RESEARCH METHODS AND PROCEDURES: 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). DISCUSSION: 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.