Jesús M. Porres

Phytase enzymology, applications, and biotechnology

Phytases are phosphohydrolases that initiate the step-wise removal of phosphate from phytate. These enzymes have been widely used in animal feeding to improve phosphorus nutrition and to reduce phosphorus pollution of animal waste. The potential of phytases in improving human nutrition of essential trace minerals in plant-derived foods is being explored. This review covers the basic biochemistry and application of phytases, and emphasizes the emerging biotechnology used for developing new effective phytases with improved properties.

The role of phytic acid in legumes: antinutrient or beneficial function?

This review describes the present state of knowledge about phytic acid (phytate), which is often present in legume seeds. The antinutritional effects of phytic acid primarily relate to the strong chelating associated with its six reactive phosphate groups. Its ability to complex with proteins and particularly with minerals has been a subject of investigation from chemical and nutritional viewpoints. The hydrolysis of phytate into inositol and phosphates or phosphoric acid occurs as a result of phytase or nonenzymatic cleavage. Enzymes capable of hydrolysing phytates are widely distributed in micro-organisms, plants and animals. Phytases act in a stepwise manner to catalyse the hydrolysis of phytic acid. To reduce or eliminate the chelating ability of phytate, dephosphorylation of hexa- and penta-phosphate forms is essential since a high degree of phosphorylation is necessary to bind minerals. There are several methods of decreasing the inhibitory effect of phytic acid on mineral absorption (cooking, germination, fermentation, soaking, autolysis). Nevertheless, inositol hexaphosphate is receiving increased attention owing to its role in cancer prevention and/or therapy and its hypocholesterolaemic effect.ResumenEsta revisión describe el estado actual de conocimientos sobre el ácido fítico, presente de forma natural en muchos alimentos derivados de plantas, y, sobre todo, en las legumbres. Sus efectos antinutritivos se relacionan con su fuerte capacidad para formar complejos con proteínas y minerales. La hidrólisis del fitato en inositol y fosfatos se produce por acción de fitasas, ampliamente distribuidas en microorganismos, plantas y animales, y también por procesos no enzimáticos. Las fitasas actúan de forma escalonada siendo necesario conseguir la defosforilación del inositol hexa y penta fosfato, ya que estas son las formas con mayor capacidad quelante. Hay varios métodos para disminuir el efecto antinutricional del ácido fítico, tales como el remojo, cocinamiento, la germinación, fermentación y adición de enzimas. Sin embargo, el inositol hexafosfato está siendo objeto de nuevo interés por su papel en la prevención del cáncer y/o en su terapia, y por su efecto anticolesterolémico.

Effects of high-whey-protein intake and resistance training on renal, bone and metabolic parameters in rats

Consumption of high-protein (HP) diets is postulated to exert a negative influence on bone and renal health. However, no conclusive evidence has been presented related to this issue or to the potential protective action of resistance training on HP-induced systemic effects. We examined the effects of HP diet consumption on food intake, body-weight gain, body composition, and renal, bone and metabolic parameters of rats performing resistance training. A total of ninety-six adult male Wistar rats were randomly distributed in twelve experimental groups (n 8): normal-protein (10%) or HP (45%) diets, with or without resistance training, killed for experimental periods of 1, 2 or 3 months. Diets were based on a commercial whey protein hydrolysate. Consumption of HP diets and resistance training significantly affected food intake, body weight and body composition, as well as the plasma levels of total cholesterol, HDL-cholesterol and TAG. The buffering action of resistance training on such diet-induced alterations was especially evident in the levels of plasma TAG. Consumption of HP diets led to a considerable increase in kidney weight, urinary volume and acidity, as well as in the urinary excretion of Ca, with a parallel reduction in the urinary excretion of citrate (P < 0·05). No apparent deleterious effect on bone mineral content was found. In conclusion, consumption of HP diets caused alterations in renal health status and some metabolic parameters, but did not seem to affect bone status. Resistance training had a protective action against alterations of renal health status and some metabolic parameters such as plasma TAG.

Influence of intracerebroventricular or intraperitoneal administration of cannabinoid receptor agonist (WIN 55,212-2) and inverse agonist (AM 251) on the regulation of food intake and hypothalamic serotonin levels.

The effect of intracerebroventricular or intraperitoneal administration of cannabinoid receptor agonist WIN 55,212-2 or inverse agonist AM 251 on food intake and extracellular levels of serotonin and acetic acid 5-hydroxy-indol from presatiated rats was studied. Compared to the vehicle-injected control, the intracerebroventricular administration of WIN 55,212-2 was associated with a significant increase in food intake, whereas the administration of AM 251 caused a significant reduction in this respect. These results were accompanied by considerable reductions or increases in serotonin and acetic acid 5-hydroxy-indol levels compared to the vehicle-injected control and the baseline values for the different experimental groups studied. Intraperitoneal administration of WIN 55,212-2 at doses of 1 and 2 mg/kg promoted hyperphagia up to 6 h after injection, whereas administration of a higher dose (5 mg/kg) significantly inhibited food intake and motor behaviour in partially satiated rats. Administration of any of the AM 251 doses studied (0.5, 1, 2, 5 mg/kg) led to a significant decrease in the amount of food ingested from 2 h after the injection, compared to the vehicle-injected control group, with the most striking effect being observed when the 5 mg/kg dose was injected.

Improvement of the antioxidant and hypolipidaemic effects of cowpea flours (Vigna unguiculata) by fermentation: results of in vitro and in vivo experiments

BACKGROUND The antioxidant capacity and hypolipidaemic effects of Vigna unguiculata, as well as their potential improvement by different fermentation and thermal processes were studied using in vitro and in vivo methods. RESULTS Phenolic content and reducing capacity of legume acetone extract were significantly increased by different fermentation processes, and by the thermal treatment of fermented legume flours. TBARS inhibiting capacity was increased by fermentation but not by thermal treatment. A higher ability to decrease Cu(2+)/H2O2-induced electrophoretic mobility of LDL was found in fermented when compared to raw legume extracts, and a higher protective effect on short term metabolic status of HT-29 cells was found for raw and lactobacillus-fermented Vigna followed by naturally fermented Vigna extracts. Significant improvements in plasma antioxidant capacity and hepatic activity of antioxidant enzymes were observed in rats that consumed fermented legume flours when compared to the untreated legume or a casein-methionine control diet. In addition, liver weight and plasma levels of cholesterol and triglycerides were also positively affected by untreated or naturally fermented Vigna. CONCLUSION V. unguiculata has demonstrated its potential as a functional food with interesting antioxidant and lipid lowering properties, which can be further augmented by fermentation processes associated or not to thermal processing.

Ergogenic effects of quercetin supplementation in trained rats

BackgroundQuercetin is a natural polyphenolic compound currently under study for its ergogenic capacity to improve mitochondrial biogenesis. Sedentary mice have exhibited increased endurance performance, but results are contradictory in human models.MethodsWe examined the effects of six weeks of endurance training and quercetin supplementation on markers of endurance performance and training in a rodent model. Rats were randomly assigned to one of the following groups: placebo+sedentary (PS), quercetin+sedentary (QS), placebo+endurance training (PT) and quercetin+endurance training (QT). Quercetin was administered at a dose of 25 mg/kg on alternate days. During six weeks of treatment volume parameters of training were recorded, and after six weeks all groups performed a maximal graded VO2 max test and a low-intensity endurance run-to-fatigue test.ResultsNo effects were found in VO2 peak (p>0.999), nor in distance run during low-intensity test, although it was 14% greater in QT when compared with PT (P = 0.097). Post-exercise blood lactate was increased in QT when compared with PT (p=0.023) and also in QS compared with PS (p=0.024).ConclusionsThis study showed no effects in VO2 peak, speed at VO2 peak or endurance time to exhaustion after six weeks of quercetin supplementation compared with placebo in trained rats. Quercetin was show to increase blood lactate production after high-intensity exercise.

High-protein diets and renal status in rats

INTRODUCTION High-protein (HP) diets might affect renal status. We aimed to examine the effects of a HP diet on plasma, urinary and morphological renal parameters in rats. MATERIAL AND METHODS Twenty Wistar rats were randomly distributed in 2 experimental groups with HP or normal-protein (NP) diets over 12 weeks. RESULTS AND DISCUSSION Final body weight was a 10%lower in the HP group (p < 0.05) whereas we have not observed differences on food intake, carcass weight and muscle ashes content. No significant clear differences were observed on plasma parameters, whereas urinary citrate was an 88% lower in the HP group (p = 0.001) and urinary pH a 15% more acidic (p < 0.001). Kidney wet mass was ~22 heavier in the HP group (p < 0.001). Renal mesangium area was a 32% higher in the HP group (p < 0.01). Glomerular 1 and 2 were also ~30 higher in the HP diet (p < 0.01 and p < 0.05, respectively) and glomerular area a 13% higher (p < 0.01). CONCLUSION High-protein diet promoted a worse renal profile, especially on urinary and morphological markers, which could increase the risk for developing renal diseases in the long time.

Effect of heat treatment and mineral and vitamin supplementation on the nutritive use of protein and calcium from lentils (Lens culinaris M.) in growing rats.

OBJECTIVE The effects of heat treatment, supplementation of a mineral and vitamin premix, and 4% olive oil on the bioavailability of protein and calcium from Lens culinaris M., var vulgaris, cultivar. magda-20 were studied in growing rats. METHODS Nutrition assessment was based on chemical analysis of lentil protein, energy, total and available starch, lipid and calcium composition, and the digestive and metabolic use of nitrogen and calcium by rats. Lentils used for the present study had crude protein and calcium contents of 25.5% and 0.07%, respectively. Heating lentils to 120 degrees C at 1 atm for 30 min decreased trypsin inhibitor activity, phytate, and tannin content by 76%, 8%, and 12%, respectively, but did not improve dietary intake or digestive use of protein compared with untreated raw control lentils. RESULTS Mineral, vitamin, and olive oil supplementation of raw or autoclaved lentils significantly improved daily food intake and nutritive use of nitrogen and calcium. The best results were obtained for the rats fed with a diet of raw lentils supplemented with a premix of minerals and vitamins. CONCLUSIONS There was a direct correlation between calcium balance and weight gain in animals (r = 0.89) and between the calcium balance and nitrogen balance (r = 0.86).

Effects of the dietary amount and source of protein, resistance training and anabolic-androgenic steroids on body weight and lipid profile of rats

INTRODUCTION Dietary protein amount and source, hypertrophy resistance training (RT) and anabolicandrogenic steroids (AAS) may affect body weight and plasma and hepatic lipid profile. MATERIAL AND METHODS 157 adult male Wistar rats were randomly distributed in 16 experimental groups resulting in: normal-protein (NP) or high-protein (HP) diets, whey or soy-protein diets, with or without RT and with or without AAS, for 3 months. RESULTS AND DISCUSSION Final body weight was lower in the RT and AAS groups compared to sedentary and non- AAS groups, respectively (all, p<0.001). Plasma total cholesterol (TC) was lower for the HP compared to the NP diets, for the whey compared to the soy-protein diets and for the AAS compared to the non-AAS groups (all, p<0.001). Plasma HDL-cholesterol was higher in the RT groups (p<0.05) but lower for the AAS groups (p<0.001), the HP and the soy-protein diets (p<0.05). Plasma triglycerides (TAG) were lower for the HP diet (p<0.001), for the RT (p=0.002) and the non-AAS groups (p=0.001). Liver TC was lower for the NP (p<0.01), for the soyprotein (p<0.05) and for the AAS groups (p<0.001). Liver TAG were lower for the whey-protein diet (p<0.001), RT and non-AAS groups (both, p<0.05). Some interactions were found, such as the greater effect of AAS on reducing body weight of rats that performed RT or ingested a HP diet (all, p<0.05). HDL-cholesterol was higher when RT was combined with HP diets (p=0.010) or non-AAS and when HP diets were combined with non-AAS (both,p<0.001). Groups that combined RT with non-AAS administration obtained the lowest hepatic TAG (p<0.05). CONCLUSION Among all the interventions tested, AAS was the factor that most negatively affected plasma and hepatic lipid profile, whereas HP diets and RT could benefit lipid profile, especially when combined.

Novel effects of the cannabinoid inverse agonist AM 251 on parameters related to metabolic syndrome in obese Zucker rats

BACKGROUND AND OBJECTIVE Recent research suggests that cannabinoid receptor CB1 antagonists can affect appetite and body weight gain, although their influence on other parameters related to metabolic syndrome is not well documented. The present study was designed to assess the effects of chronic treatment with the CB1 receptor inverse agonist AM 251 (3 mg/kg for 3 weeks) in obese and lean Zucker rats on parameters related to metabolic syndrome. MATERIALS AND METHODS Four groups of rats were used: lean Zucker rats, untreated obese Zucker rats, AM 251-treated obese Zucker rats and a pair-fed obese Zucker rat experimental group which received the same amount of food as that consumed by the animals treated with AM251. Food intake, body weight gain, energy expenditure, plasma biochemical parameters, leptin, insulin and hepatic status markers were analysed. RESULTS Daily injection of AM 251 in obese Zucker rats produced a marked and sustained decrease in daily food intake and body weight and a considerable increase in energy expenditure in comparison with untreated obese Zucker rats. AM 251 administration to obese rats significantly reduced plasma levels of glucose, leptin, AST, ALT, Gamma GT, total bilirubin and LDL cholesterol whereas HDL cholesterol plasma levels increased. The results also showed a decrease in liver/weight body ratio and total fat content in the liver. The main effects of AM251 (3 mg/kg) found in this study were not observed in pair-fed obese animals, highlighting the additional beneficial effects of treatment with AM 251. The results obtained in obese rats can be interpreted as a decrease in leptin and insulin resistance, thereby improving glucose and lipid metabolism, alleviating the steatosis present in the metabolic syndrome and thus favourably modifying plasma levels of hepatic biomarkers. CONCLUSION Our results indicate that the cannabinoid CB1 inverse agonist AM 251 represents a promising therapeutic strategy for the treatment of obesity and metabolic syndrome.