The aim of the present work was to analyse the hypocholesterolaemic efficiency of a Vicia fabaprotein isolate in relation to the intact legume. In addition, the mechanisms underlying the effects of this isolate were investigated. Hypercholesterolaemic rats were divided into three groups n10 Â 3 and fed high-fat diets rich in cholesterol-containing casein, whole seeds of Vicia faba or the protein isolate of faba beans as protein source, for 2 weeks ad libitum. The protein isolate was prepared by isoelectric precipitation and spray dried. Analyses of serum, liver and faeces, as well as of the activity of hepatic 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase, were assessed by enzymatic methods. The rats fed on Vicia faba diets showed significantly lower body weights and energy intakes than rats fed on casein diets. The wholeseed diet induced a significant reduction in plasma triacylglycerol. Feeding rats on diets containing faba bean seeds, or the protein isolate, induced a significant decrease in plasma (LDL+VLDL)-cholesterol but not in HDL-cholesterol. Hepatic cholesterol and triacylglycerol were also reduced. The hypocholesterolaemic effects of Vicia faba were not the result of a reduction in cholesterol synthesis as assessed from HMG-CoA reductase activity, but the result of an increase in steroid faecal excretion. The faba bean-protein isolate obtained under our experimental conditions was useful in improving the metabolic alterations induced by feeding with a hypercholesterolaemic diet compared with casein. The effectiveness of the whole seeds was higher than that of the protein isolate.
The purpose of this study was to differentiate between the effects of the amount and the type of dietary lipids on the expression of the retinoic acid receptor (RAR), but also the peroxisome proliferator-activated receptor (PPAR) and the receptor of the 9-cis retinoic acid (retinoid X receptor (RXR)) in rat liver. Six groups of eight rats (5-weeks old) were fed during 4 weeks on the following diets: control 50 g vegetable oil/kg, high-fat diet 250 g vegetable oil/kg. These oils were either coconut oil (rich in saturated fatty acids) or olive oil (rich in monounsaturated fatty acids) or saf¯ower oil (rich in polyunsaturated fatty acids, mainly as n-6). The three high-fat diets induced a signi®cant decrease of the maximal binding capacity of RAR and of the abundance of RARb mRNA. Simultaneously, an increased expression of PPARa mRNA was observed while no signi®cant difference on abundance of RXRa mRNA was observed. The mechanisms involved are probably multiple, but one hypothesis is that a modi®cation of the equilibrium between the nuclear receptors, resulting from an increased expression of PPAR, induces a decreased expression of RAR in rat liver.Rat liver: High-fat diet: Retinoic acid receptor expression
OBJECTIVE:To investigate in human adipose tissue a possible relationship between per oxisome proliferator-activated receptor gamma (PPARg) and retinoic acid receptor alpha (RARa) gene expression, two genes involved in the control of adipocyte differentiation. SUBJECTS: Ten lean control women (age 31 -60 y, body mass index (BMI) 18 -24.7 kg=m 2 ) and an obese group of 15 women (age 27 -62 y, BMI 30 -57.5 kg=m 2 ), of whom 10 subjects were in weight-gain phase and five were in weight-loss phase. MEASUREMENTS:We assessed the relative PPARg and RARa mRNA levels in subcutaneous abdominal adipose tissue using a realtime PCR method. RESULTS: PPARg mRNA level were significantly increased ( þ 91%; P < 0.01) in obese women compared to lean control women. In the obese group, we observed a PPARg mRNA level 42% lower in weight-loss obese than in weight-gain obese subjects. We obtained a positive correlation (r ¼ 0.56; P < 0.01) between PPARg mRNA level and the BMI of all subjects. Relative mRNA abundance level of RARa in subcutaneous adipose tissue of obese subjects is significantly lower than in control subjects ( 7 56%, P < 0.01), and a negative correlation was found between PPARg and RARa mRNA levels in subcutaneous adipose tissue of subjects study (r ¼ 7 0.75; P < 0.01). CONCLUSION: Our findings suggest that obesity is associated with an inverse relationship between PPARg and RARa expressions in human subcutaneous adipose tissue. Modulations of nuclear receptor profile could be an important event in the body's early adaptive mechanisms promoting adipose tissue plasticity and leading to the onset of obesity.
In order to study the effects of dietary lipids and vitamin A on the development of adipose tissues, young rats were submitted for 8 d to a control or to two cafeteria diets with normal (Caf) or higher (Caf þ ) vitamin A levels. Retinoid (retinoic acid receptor (RAR) a, RARg, retinoid X receptor (RXR) a) and fatty acid (PPARg) receptor mRNA was measured in the subcutaneous white adipose tissue (Swat) and in isolated mature adipocytes by RT-PCR. The stroma vascular fraction was cultured in vitro to test the capacities of the adipocyte precursors to proliferate and differentiate. The Caf diet enriched in vitamin A resulted in an increased adiposity, due to increased adipocyte hypertrophy. This was concomitant with a lower expression of RARa and RARg mRNA (234·6 and 238·6 %) and a higher expression of PPARg (þ 59 %) in the Swat and, to a less extent, in isolated adipocytes. Positive correlations were obtained between PPARg mRNA and Swat weights and between PPARg and RXRa mRNA. By contrast, RARg mRNA and Swat masses were negatively correlated. The adipocyte precursors from Caf þ Swat proliferated more, in vitro, at the beginning of the culture. This difference progressively disappeared and was totally absent after 8 d of culture, but with a higher percentage of differentiated preadipocytes (þ 80·3 %) in the Caf þ group. In conclusion, lipids and vitamin A act synergistically on the normal growth of the adipose tissue in young rats, concomitant with an imbalance in the pattern of the nuclear receptors. These changes influence the early normal development of the endogenous adipocyte precursors.Diet-induced obesity: Peroxisome proliferator-activated receptor: Retinoic acid receptor: Retinoid X receptor: Adipogenesis Today, it is clearly acknowledged that environmental factors and especially dietary factors may largely contribute to the development of obesity (1)
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