Antonio S. Del Barrio

Nutritional evaluation and metabolic effects in rats of protein isolates obtained from seeds of three legume species

Three legume seeds, peas (Pisum sativum L), faba bean (Vicia faba L) and soybean (Glycine max L) and their respective protein isolates, were assayed for their nutritional value and metabolic effects. Feeding rats with either the legume seeds or the protein isolates resulted in an impairment in growth and significantly lower nutritional indices as compared to the control group. Protein apparent digestibility improved in the protein isolate fed rats, with similar digestibility data to those observed in the casein fed group. Liver, gastrocnemius muscle and spleen weights were decreased by legume consumption, and the enlargement detected in the small intestine weight in the animals fed on the legume seeds, was partially reversed in the animals receiving the protein isolate. This reversal was significant in rats offered faba bean protein isolate. Biochemical parameters were consistent in the legume groups, and hypoglycaemic and hypotriacylglycaemic responses were observed for the legume meals. Lower uric acid levels were found in some of the legume fed animals. Serum free amino acid profiles were affected by the legume intake, as compared with casein. Methionine and taurine concentrations decreased, whereas serine concentrations were augmented. Other amino acids, particularly glycine and valine, also showed modified plasma concentrations. These results suggest that the preparation of protein isolates, following an easy protocol, yield products with better digestibility, which keep the positive effects on glucose and triacylglyceride plasma levels, and partially reduce some other undesirable consequences related to legume consumption.

Responses to dietary macronutrient distribution of overweight rats under restricted feeding.

Changes in protein and amino acid balance after energy-restricted feeding have scarcely been studied, although it has been suggested that protein utilization may depend on the macronutrient composition of the restricted diet. The aim of this study is to investigate the influence of dietary fat quality and content, during an energy-restricted regime, on body composition and protein metabolism. Therefore, diet-induced overweight rats were divided into three dietary groups: one group was fed on a control diet ad libitum (control) and the other two groups were fed energy-restricted diets (about 60% of control group), which provided a standard amount (20%) of fat (SFR), based on olive oil, or a high amount (60%) of saturated fat (HFR), based on coconut oil. Measurements of body weight, body composition, serum biochemical parameters and the assessment of the hepatic and muscular protein response were performed. Similar results were found comparing weight losses and serum parameters in both deprived groups, although the high-fat-restricted rats (HFR group) showed a greater reduction in the subcutaneous fat depot and of total body fat. After both energy-restricted treatments, the serum amino acid concentration was reduced while the urinary amino acid excretion increased. Muscle and liver protein metabolism was affected by energy restriction, which produced a decrease in protein synthesis capacity (RNA content) in both tissues and a higher muscle proteolysis (catepsin activity), more marked in the SFR group, while no changes were found in liver protein breakdown. Hepatic glycogen and glycogenic amino acid were also altered, reaching significant differences in the HFR group. Thus, dietary macronutrient composition during energy restriction seems to be involved in the metabolic adaptative response.

Desensitization effect of in vivo treatment with metaproterenol on β1, β2 and β3-adrenergic responsiveness in rat adipocytes

Abstract The desensitization process of β-adrenergic system was assessed by in vivo administration to 7-week old rats of a mixed β-agonist, metaproterenol (3, 5-dyhydroxyphenyl-N-isopropyl-amine-β-ethanol sulphate; T1/2 = 6 hours), (2 mg/kg/d) in treatments of 12 hours, 2 days and 10 days. The in vitro lipolytic effect of selective β-adrenergic agonists, dobutamine, salbutamol and BRL 37344, as well as plasma free fatty acid concentrations were measured in treated and control animals given vehicle. Different times of exposure to a β-agonist induced a loss of responsiveness on lipolytic response mediated by β 1 and β 2 -adrenoceptors, as demonstrated by decreased affinity and intrinsic activity (maximal effect) of dobutamine and salbutamol. In contrast, no changes were found in β 3 -mediated lipolysis. These observations suggest that β 1 , β 2 and β 3 -adrenoceptors follow different regulatory patterns. Lack of β 3 -adrenoceptor desensitization may have important physiological and therapeutic consequences in the treatment of diseases such as obesity and heart failure.

Evidence of a short-term effect of growth hormone on in vivo bone protein synthesis in normal rats

The growth of skeletal tissue is influenced by growth hormone (GH), whose effects are believed to be mediated, at least in part, by somatomedins or insulin-like growth factors (IGFs). This report describes an action of GH by increasing bone protein synthesis. This effect was not accompanied by changes in circulating IGFs. It is concluded that this experiment shows apparently for the first time in intact animals a short-term effect on bone turnover of GH.

Effects of the Beta-Adrenergic Agonist Salbutamol and Its Withdrawal on Protein Metabolism of Lambs

Rasa Aragonesa lambs were used to evaluate the repartitioning effects of a beta-adrenergic agonist and its withdrawal on nutrient metabolism. One group of animals (T-I) was fed salbutamol at a dose of 2 mg x kg-1 diet x day-1 for 38 days, while in another group (T-II) the beta-adrenergic agonist was discontinued in the diet 5 days before slaughter on the 43rd day. The semitendinosus muscle protein content increased (p < 0.05), while fat and collagen content decreased (p < 0.05) in the T-I group. These differences were not apparent in the group from which salbutamol was withdrawn. Muscle protein degradation was diminished (p < 0.05) in both treated groups. The serum free fatty acid level was markedly enhanced (p < 0.05) in the T-I group. Total essential amino acid serum levels were reduced (p < 0.05) after the withdrawal period. Ketogenic and urea cycle amino acids were reduced (p < 0.05) in the salbutamol-fed T-I group and glycogenic amino acids were diminished (p < 0.05) in the T-II experimental group. The data show that salbutamol is able to increase muscle content at the expense of fat stores in productive animals. However, these repartitioning effects are circumvented by a 5-day period of withdrawal, in which concomitant metabolic changes in lipid and protein turnover and plasma amino acid profiles occur.

A diet rich in coconut oil decreases the expression of retinoic acid and triiodothyronine nuclear receptors in rat liver

Abstract A considerable part of the total energy consumed by western populations is accounted for by lipids and particularly by lipids containing saturated fatty acids. A high level of dietary fat induces a lipid status characterized by a changing fatty acid profil which, in turn, could affect several hormonal actions. Thus, the aim of this study was to explore the effect of a high fat diet rich in saturated fatty acids on the expression of nuclear receptors of retinoic acid (RAR) and triiodothyronine (TR) in rat liver. This expression was mainly evaluated as binding properties of RAR and TR (evaluated by an isotopic displacement analysis), and quantitation of mRNAs of these receptors (using a semi-quantitative RT-PCR method). Following seven weeks of a diet containing 30% coconut oil and 5% olive oil, the maximum binding capacity of RAR and TR was decreased by 36% and 23%, respectively (the apparent affinity of the receptors was not affected). The abundance of mRNAs of these receptors was also lowered (by approximately 37–40%), suggesting that the decreased number of receptors results from a mechanism occuring, at least in part, at a transcriptional level.

Changes in Serum and Urinary Amino Acids after the Administration of a Mixed Beta-Adrenergic Agonist

The administration of the repartitioning agent metaproterenol, with affinity for beta 1- and beta 2-receptors, induced marked increases in gastrocnemius muscle and heart weights. The renal loss of essential amino acids was reduced in animals treated with beta-adrenergic agonists and a significant reduction in total serum amino acids was found as well. The assessment of urinary 3-methylhistidine suggests, that those changes were accompanied by a lower myofibrillar protein breakdown, while hydroxyproline output was increased as an indirect index of collagen turnover.

Effects of dexfenfluramine on weight loss and serum amino acids profile in obese subjects

Abstract The aim of this study was to investigate the effect of weight reduction on serum amino acids levels in 40 obese subjects (BMI in kg·m −2 : 38.8±1.5) achieved by hypocaloric (1200–1500 kcal/day) diets with dexfenfluramine (30 mg/day) or placebo for 6 months. The weight reduction was statistically different between placebo (P) and dexfenfluramine (dF) groups (P: −5.6±1.5 kg, dF: −8.8±1.1 kg; p