M. Teresa Macarulla

Effects of the whole seed and a protein isolate of faba bean ( Vicia faba ) on the cholesterol metabolism of hypercholesterolaemic rats

The aim of the present work was to analyse the hypocholesterolaemic efficiency of a Vicia faba-protein 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 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 whole-seed 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.

Beneficial Effects of Quercetin on Obesity and Diabetes

Scientific research is constantly looking for new molecules that could be used as dietary functional ingredients in the fight against obesity and diabetes, two pathologies highly prevalent in Western societies. In this context, flavonoids represent a group of molecules of increasing interest. The major flavonoid is Quercetin, which belongs to the class called flavonols and is mainly found in apples, tea, onions, nuts, berries, cauliflower, cabbage and many other foods. It exhibits a wide range of biological functions including anticarcenogenic, anti-inflammatory and antiviral; it also inhibits lipid peroxidation, platelet aggregation and capillary permeability. This review focuses on the main effects of Quercetin on obesity and diabetes. The mechanisms of action explaining the effects of Quercetin on these two metabolic disturbances are also considered. Good perspectives have been opened for Quercetin, according to the results obtained either in cell cultures or in animal models. Nevertheless, further studies are needed to better characterize the mechanisms of action underlying the beneficial effects of this flavonoid on these pathologies. Moreover, the body fat-lowering effect and the improvement of glucose homeostasis need to be confirmed in humans. Animal studies have consistently failed to demonstrate adverse effects caused by Quercetin. In contrast, due to inhibitory effect of Quercetin in cytochrome P450, interactions with drugs can be taken into account when they are administered at the same time than Quercetin.

Hepatic lipid metabolic pathways modified by resveratrol in rats fed an obesogenic diet.

OBJECTIVE The scientific community is on the look-out for safe biomolecules useful in the prevention of obesity and related aberrations such as fatty liver. This study analyzed the influence of resveratrol on hepatic triacylglycerol metabolism. METHODS Male Sprague-Dawley rats were divided into control and resveratrol-treated groups (30 mg/kg of body weight per day) and fed a commercial obesogenic diet for 6 wk. Liver triacylglycerol content and the activity of carnitine palmitoyl transferase-Ia (CPT-Ia), acyl-coenzyme A oxydase (ACO), fatty acid synthase (FAS), glucose-6-phosphate dehydrogenase (G6PDH), malic enzyme (ME), acetyl-coenzyme A carboxylase (ACC), adenosine monophosphate-activated protein kinase (AMPK), and peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) activation were measured. Mitochondrial protein cytochrome C oxidase subunit 2 (COXII), mitochondrial transcription factor A (TFAM), sterol regulatory element-binding protein-1c (SREBP-1c), peroxisome proliferator-activated receptor-α (PPAR-α), sirtuin-1 (SIRT1), hepatocyte nuclear factor receptor-4α (HNF-4α), and PGC-1α mRNA levels were also analyzed. Serum insulin was quantified. RESULTS Resveratrol decreased liver fat accumulation, increased CPT-Ia and ACO, and decreased ACC activities. Other lipogenic enzymes, FAS, ME, and G6PDH were not modified. The polyphenol activated AMPK and PGC-1α. The expression of SRBP-1c, PPAR-α, SIRT1, PGC-1α, HNF-4α, TFAM, and COXII was not modified. No changes in serum insulin levels were observed. CONCLUSION Resveratrol partly prevents the increase in liver fat accumulation induced by high-fat high-sucrose feeding by increasing fatty acid oxidation and decreasing lipogenesis. These effects are mediated by the activation of the AMPK/SIRT1 axis.

Thermogenesis is involved in the body-fat lowering effects of resveratrol in rats.

The effect of resveratrol on thermogenesis in skeletal muscle and interscapular brown adipose tissue (IBAT) was investigated. Rats were fed an obesogenic diet supplemented with resveratrol (30mg/kg/day) or not supplemented for 6weeks. Resveratrol intake led to increased gene expression of mitochondrial-transcription-factor-A (TFAM), mitochondrial-protein-cytochrome-C-oxidase subunit-2 (COX2), sirtuin-1 (SIRT1), peroxisome-proliferator-activated-receptor-β/δ (PPARβ/δ) and proliferator-activated-receptor-gamma-coactivator1-α (PGC-1α) in IBAT and increased UCP1protein expression; however, peroxisome-proliferator-activated-receptor-α (PPARα) expression remained unchanged. In gastrocnemius muscle, resveratrol increased the gene expression of TFAM and COX2; however, no changes were observed in levels of SIRT1, PGC-1α and PPARβ/δ. Acetylated-PGC-1α was decreased in the resveratrol-treated group, indicating a higher level of activation, and a significant increase of UCP3 protein expression was observed in this group. The increases in UCP protein expression in two important thermogenic tissues after resveratrol treatment may contribute to increased whole-body energy dissipation, which may help to better understand the body-fat lowering effect of this polyphenol.

Distribution of resveratrol metabolites in liver, adipose tissue, and skeletal muscle in rats fed different doses of this polyphenol.

This study aimed to characterize resveratrol metabolite profiles in liver, skeletal muscle, and adipose tissue in rats treated for 6 weeks with 6, 30, or 60 mg of trans-resveratrol/kg body weight/d. Resveratrol metabolites were quantified by liquid chromatography-tandem mass spectrometry. The greatest number of metabolites was found in liver followed by adipose tissue. A great number of metabolites in muscle was below the limit of detection. The amounts of sulfate conjugates tended to increase when resveratrol dosage was enhanced, while the glucuronide ones increased only between 6 and 30 mg/kg/d. Microbiota metabolites were detected in higher amounts than resveratrol conjugates in liver, while the opposite occurred in adipose tissue and muscle. So, the largest amounts of resveratrol metabolites were found in liver, intermediate amounts in adipose tissue, and the lowest amounts in muscle. Sulfate conjugates, but not glucuronides, showed a dose-response pattern. Microbiota metabolites were predominant in liver.

The trans-10,cis-12 isomer of conjugated linoleic acid reduces hepatic triacylglycerol content without affecting lipogenic enzymes in hamsters

Conjugated linoleic acid (CLA) refers to the positional and geometric dienoic isomers of linoleic acid. The dietary intake of CLA has been associated with changes in lipid metabolism. The aim of the present work was to assess the effects of the two main isomers of CLA on sterol regulatory element binding protein (SREBP)-1a and SREBP-1c mRNA levels, as well as on mRNA levels and the activities of several lipogenic enzymes in liver. For this purpose hamsters were fed an atherogenic diet supplemented with 5 g linoleic acid, cis-9,trans-11 or trans-10,cis-12 CLA/kg diet for 6 weeks. The trans-10,cis-12 isomer intake produced significantly greater liver weight, but also significantly decreased liver fat accumulation. No changes in mRNA levels of SREBP-1a, SREBP-1c and lipogenic enzymes, or in the activities of these enzymes, were observed. There was no effect of feeding cis-9,trans-11 CLA. These results suggest that increased fat accumulation in liver does not occur on the basis of liver enlargement produced by feeding the trans-10,cis-12 isomer of CLA in hamsters. The reduction in hepatic triacylglycerol content induced by this isomer was not attributable to changes in lipogenesis.

trans-10, cis-12 Conjugated linoleic acid inhibits lipoprotein lipase but increases the activity of lipogenic enzymes in adipose tissue from hamsters fed an atherogenic diet

The aim of the present work was to investigate the effects of trans-10,cis-12 conjugated linoleic acid (CLA) on the activity and expression of lipogenic enzymes and lipoprotein lipase (LPL), as well as on the expression of transcriptional factors controlling these enzymes, in adipose tissue from hamsters, and to evaluate the involvement of these changes in the body fat-reducing effect of this CLA isomer. Thirty male hamsters were divided into three groups and fed atherogenic diets supplemented with 0 (linoleic group), 5 or 10 g trans-10,cis-12 CLA/kg diet, for 6 weeks. Body and adipose tissue weights, food intake and serum insulin were measured. Total and heparin-releasable LPL and lipogenic enzyme activities (acetyl-CoA carboxylase (ACC); fatty acid synthase (FAS); glucose-6-phosphate dehydrogenase (G6PDH); and malic enzyme (ME)) were assessed. ACC, FAS, LPL, sterol regulatory element-binding proteins (SREBP-1a), SREBP-1c and PPARgamma mRNA levels were also determined by real-time PCR. CLA did not modify food intake, body weight and serum insulin level. CLA feeding reduced adipose tissue weight, LPL activity and expression, and increased lipogenic enzyme activities, despite a significant reduction in ACC and FAS mRNA levels. The expression of the three transcriptional factors analysed (SREBP-1a, SREBP-1c and PPARgamma) was also reduced. These results appear to provide a framework for partially understanding the reduction in body fat induced by CLA. Inhibition of LPL activity seems to be an important mechanism underlying body fat reduction in hamsters. Further research is needed to better characterize the effects of CLA on lipogenesis and the role of these effects in CLA action.

Differential effects of diets that provide different lipid sources on hepatic lipogenic activities in rats under ad libitum or restricted feeding.

This work was designed to study the effect of different lipid sources on hepatic lipogenic enzyme activity in rats fed ad libitum or energy-controlled diets. Male Wistar rats were fed diets containing 40% of energy as fat (olive oil, sunflower oil, palm oil, or beef tallow) for 4 wk. In experiment 1 rats had free access to food, and in experiment 2 rats were fed a controlled amount of food. In both experiments, rats fed the olive oil diets had higher activities of glucose-6-phosphate dehydrogenase, malic enzyme, fatty acid synthase, and acetyl-CoA carboxylase (P < 0.05) than rats fed the other fats. It is unlikely that this effect could be attributed to the stimulation by insulin or triiodothyronine because serum values did not differ among the groups. Enzymatic activities were positively and significantly correlated with liver triacylglycerol content, but not with serum triacylglycerol levels. No interaction between lipid source and feeding protocol was found. Oleic acid and components in olive oil other than fatty acids, such as phytosterols, may account for the effects of dietary fat on lipogenic enzyme activity.

Influence of different dietary fats on triacylglycerol deposition in rat adipose tissue

It has been demonstrated that triacylglycerol (TAG) mobilization from adipose tissue is selective and depends on fatty acid (FA) chain length, unsaturation and positional isomerism. The present study was performed to determine the influence of dietary fat on the composition of TAG stored in rat perirenal and subcutaneous adipose tissues. These results may provide information on the susceptibility of stored TAG to hydrolysis and further mobilization, and may help to establish an interrelationship between dietary composition and the FA efflux from adipose tissue. TAG molecular species and FA composition were determined by HPLC and GLC respectively. No significant differences were found in either FA or TAG composition between perirenal and subcutaneous adipose depots. The major FA in the dietary fats were present in the adipose tissues of the animals; in most cases, in similar proportions. However, differences were found between dietary and adipose tissue content of minor FA, which suggests that dietary FA composition is altered between ingestion and deposition in adipose tissue. The TAG molecular species of rat adipose tissue were enriched with the FA characteristic of each dietary fat. Dietary sunflower oil was responsible for enrichment with the most polar TAG. This finding may suggest easier mobilization of stored TAG. In conclusion, the process of fatty acid and TAG deposition in rat adipose tissue is selective, and depends on the composition of the diet.

Effects of trans-10, cis-12 conjugated linoleic acid on the expression of uncoupling proteins in hamsters fed an atherogenic diet

It is known that conjugated linoleic acid (CLA) feeding decreases body adiposity but the mechanisms involved are not clear. The aim of this study was to analyse whether alterations in uncoupling protein (UCP) expression in white and brown adipose tissues (WAT and BAT, respectively) and in skeletal muscle may be responsible for the effect of trans-10, cis-12 CLA on the size of body fat depots in hamsters. Animals were divided into three groups and fed an atherogenic diet with different amounts of trans-10, cis-12 CLA (0 control, 0.5, or 1 g/100 g diet) for 6 weeks. CLA feeding reduced adipose depot weights, but had no effect on body weight. Leptin mRNA expression decreased in both subcutaneous and perirenal WAT depots, in accordance with lower adiposity, whereas resistin mRNA expression was not changed. Animals fed CLA had lower UCP1 mRNA levels in BAT (both doses of CLA) and in perirenal WAT (the low dose), and lower UCP3 mRNA levels in subcutaneous WAT (the high dose). UCP2 mRNA expression in WAT was not significantly affected by CLA feeding. Animals fed the high dose of CLA showed increased UCP3 and carnitine palmitoyl transferase-I (CPT-I) mRNA expression levels in skeletal muscle. In summary, induction of UCP1 or UCP2 in WAT and BAT is not likely to be responsible for the fat-reduction action of CLA, but the increased expression of UCP3 in skeletal muscle, together with a higher expression of CPT-I, may explain the previously reported effects of dietary CLA in lowering adiposity and increasing fatty acid oxidation by skeletal muscle.