Inar Alves de Castro

Leptin’s effect on puberty in mice is relayed by the ventral premammillary nucleus and does not require signaling in Kiss1 neurons

Studies in humans and rodents indicate that a minimum amount of stored energy is required for normal pubertal development. The adipocyte-derived hormone leptin is a key metabolic signal to the neuroendocrine reproductive axis. Humans and mice lacking leptin or the leptin receptor (LepR) (ob/ob and db/db mice, respectively) are infertile and fail to enter puberty. Leptin administration to leptin-deficient subjects and ob/ob mice induces puberty and restores fertility, but the exact site or sites of leptin action are unclear. Here, we found that genetic deletion of LepR selectively from hypothalamic Kiss1 neurons in mice had no effect on puberty or fertility, indicating that direct leptin signaling in Kiss1 neurons is not required for these processes. However, bilateral lesions of the ventral premammillary nucleus (PMV) of ob/ob mice blunted the ability of exogenous leptin to induce sexual maturation. Moreover, unilateral reexpression of endogenous LepR in PMV neurons was sufficient to induce puberty and improve fertility in female LepR-null mice. This LepR reexpression also normalized the increased hypothalamic GnRH content characteristic of leptin-signaling deficiency. These data suggest that the PMV is a key site for leptins permissive action at the onset of puberty and support the hypothesis that the multiple actions of leptin to control metabolism and reproduction are anatomically dissociated.

Phenolic composition of South American red wines classified according to their antioxidant activity, retail price and sensory quality

In this study, 73 South American red wines (Vitis vinifera) from 5 varietals were classified based on sensory quality, retail price and antioxidant activity and characterised in relation to their phenolic composition. ORAC and DPPH assays were assessed to determine the antioxidant activity, and sensory analysis was conducted by seven professional tasters using the Wine & Spirits Education Trusts structured scales. The use of multivariate statistical techniques allowed the identification of wines with the best combination of sensory characteristics, price and antioxidant activity. The most favourable varieties were Malbec, Cabernet Sauvignon, and Syrah produced in Chile and Argentina. Conversely, Pinot Noir wines displayed the lowest sensory characteristics and antioxidant activity. These results suggest that the volatile compounds may be the main substances responsible for differentiating red wines on the basis of sensory evaluation.

Viability of Lactobacillus acidophilus in synbiotic guava mousses and its survival under in vitro simulated gastrointestinal conditions

The effects of refrigeration, freezing and substitution of milk fat by inulin and whey protein concentrate (WPC) on Lactobacillus acidophilus La-5 viability and resistance to gastric and enteric simulated conditions in synbiotic guava mousses effects were investigated. Refrigerated mousses supplemented with WPC presented the best probiotic viability, ranging from 7.77 to 6.24 log cfu/g during 28 days of storage. The highest probiotic populations, above 7.45 log cfu/g, were observed for all frozen mousses during 112 days of storage. Decreased L. acidophilus survival during the in vitro gastrointestinal simulation was observed both for refrigerated and frozen mousses. Nonetheless, for the refrigerated mousses, the addition of inulin enhanced the probiotic survival during the in vitro assays in the first week of storage. L. acidophilus survival in simulated gastrointestinal fluids was also improved through freezing. The frozen storage may be used to provide increased shelf-life for synbiotic guava mousses. Even though the protective effect of inulin and WPC on the probiotic microorganism tested was shown to be more specific for the refrigerated products, the partial replacement of milk fat by these ingredients may also help, as it improves the nutritional value of mousses in both storage conditions.

Effect of red wines with different in vitro antioxidant activity on oxidative stress of high-fat diet rats.

It is not known if there is a correlation between in vitro and in vivo antioxidant activity of wines. Thus, in the present study, rats were fed with a high-fat diet to induce inflammation and oxidative stress, and received supplementation (1.0 mL/day) containing water or three red wine samples characterised by high (41.1 mmol TE/L), medium (35.7 mmol TE/L) and low (14.4 mmol TE/L) in vitro antioxidant activity. A correlation was observed between in vitro antioxidant activity measured in the wines and in vivo antioxidant activity measured in plasma (r=+0.49, p=0.011). In liver, only the wine containing the highest in vitro antioxidant activity was able to reduce malondialdehyde concentration. Groups supplemented with wines containing lower in vitro antioxidant activity showed an increase in antioxidant enzyme activity. We concluded that the correlation between in vitro and in vivo antioxidant activity depends on the biomarker selected to evaluate the oxidative stress.

Characterization of red wines from South America based on sensory properties and antioxidant activity

BACKGROUND It is widely accepted that red wines constitute one of the most important sources of dietary polyphenolic antioxidants. However, it is still not known how some variables such as variety, vintage, country of origin, and retail price are associated with the antioxidant activity and sensory profile of South American red wines. In this regard, 80 samples produced in Brazil, Chile and Argentina were assessed in relation to their sensory properties, color and in vitro antioxidant activity, and results were subjected to multivariate statistical techniques. RESULTS Samples were grouped in clusters, characterized by high, intermediate and low in vitro antioxidant activity, sensory properties and prices. It was possible to observe that wines with high antioxidant activity were associated to high retail prices and overall perception of sensory quality. CONCLUSION South American wines produced from Vitis vinifera such as Syrah, Malbec and Cabernet Sauvignon had higher in vitro antioxidant activity and also higher sensory quality than wines produced from Vitis labrusca. This result was independent of vintage (2002-2010), corroborating the idea that the same grape varietal, even when produced in different years, displays similar sensory characteristics and antioxidant activity.

Free radical scavenger and antioxidant capacity correlation of α-tocopherol and Trolox measured by three in vitro methodologies

The objective of this study was to correlate the free radical scavenging and antioxidant activity of two known substances (Trolox and α-tocopherol), using three in vitro methods (linoleic acid emulsion, brain homogenate and 2,2-diphenyl-1-picryl-hydrazyl [DPPH]). At steady state, α-tocopherol showed a greater inhibition of spontaneous oxidation of brain homogenate (59.42%±1.91) than Trolox (38.50%±2.38), while the latter showed a better antioxidant activity performance regarding inhibition of linoleic acid peroxidation (100% versus 84.02%±1.98) and free radical scavenging activity (93.56%±5.71 versus 66.72%±6.28). When the IC50 value was used as a parameter, α-tocopherol presented greater antioxidant activity than Trolox evaluated in brain homogenate and DPPH, without a significant difference when using linoleic acid emulsion. Both compounds showed the same antioxidant efficiency measured by DPPH kinetics (0.37 mM). Antioxidant activity significantly changed according to the substrate, the parameter adopted to compare the substances in the same method and the form used to express antioxidant concentration.

Protein mixtures and their nutritional properties optimized by response surface methodology

Abstract Three protein ingredients (hydrolyzed gelatin, HG, wheat gluten, WG and soybean protein isolate, SPI) were mixed at different proportions in order to partially replace milk proteins in food formulations. The nutritional quality of the mixtures was evaluated by the Protein Digestibility-Corrected Amino Acid Score (PDCAAS) and Net Protein Ratio (NPR) methods. The results obtained experimentally were used to elaborate polynomial equations that would describe the effect of the proportion of each component on the final nutritional quality of the product. The PDCAAS method showed good correlation with the NPR method in terms of growth (r = 0.85). A optimum formulation containing 25% HG, 15% WG and 60% SPI, supplemented with calcium, was developed and used to substitute about 42% of the milk proteins in the formulation that is usually consumed by Nutrition Programs. The reformulated product showed the same nutritional quality, evaluated by the PDCAAS method, as the original product formulated with only integral milk, and its cost was cheaper. The Mixture Response Surface Methodology proved to be an indispensable tool for the optimization of the nutritional quality of protein mixtures.

Antioxidant activity of phenolic compounds added to a functional emulsion containing omega-3 fatty acids and plant sterol esters

The effect of eleven compounds extracted from red propolis on the oxidative stability of a functional emulsion was evaluated. Emulsions prepared with Echium oil as omega 3 (ω-3 FA) source, containing 1.63 g/100mL of α-linolenic acid (ALA), 0.73 g/100 mL of stearidonic acid (SDA) and 0.65 g/100mL of plant sterol esters (PSE) were prepared without or with phenolic compounds (vanillic acid, caffeic acid, trans-cinnamic acid, 2,4-dihydroxycinnamic acid, p-coumaric acid, quercetin, trans-ferulic acid, trans,trans-farnesol, rutin, gallic acid or sinapic acid). tert-Butylhydroquinone and a mixture containing ascorbic acid and FeSO4 were applied as negative and positive controls of the oxidation. Hydroperoxide, thiobarbituric acid reactive substances (TBARS), malondialdehyde and phytosterol oxidation products (POPs) were evaluated as oxidative markers. Based on hydroperoxide and TBARS analysis, sinapic acid and rutin (200 ppm) showed the same antioxidant activity than TBHQ, representing a potential alternative as natural antioxidant to be applied in a functional emulsion containing ω-3 FA and PSE.

Effects of diet supplementation with three soluble polysaccharides on serum lipid levels of hypercholesterolemic rats

Some soluble polysaccharides have been explored as possible ingredients in the development of “functional foods” because of their ability to reduce plasma cholesterol and consequently contribute to the reduction of the risk of cardiovascular disease. However, this effect has been predominantly observed in studies using megadoses that are incompatible with the pattern of human consumption. On the basis of this limitation, the objective of the present study was to assess the hypocholesterolemic effect of the ingestion of three different hydrocolloids (guar gum, xanthan gum and pre-gelatinised cornstarch) at 1.5% concentration in an assay on rats. Cellulose was used as control. In the first stage of the experiment, all animals were fed a hypercholesterolemic diet that produced a mean concentration of total cholesterol (5.2 mmol/l) significantly higher than in the group fed a control diet (1.0 mmol/l). In the subsequent stage, 1.5% of the starch was replaced with each of the three hydrocolloids in the experimental ration. Food intake and body weight gain were not altered by the hydrocolloid diets (P<0.05). Serum cholesterol concentrations were 1.43, 1.41, 1.54 and 1.42 mmol/l for the diets containing guar gum, xanthan gum, pre-gelatinized cornstarch and cellulose, respectively. We conclude that, under the conditions of the present study, the hypocholesterolemic effect of hydrocolloid ingestion at a dose of 1.5% of the ration was not significant in comparison to the effect produced by the reduction and change of lipids in the diet. Thus, more attention should be paid to the use of hydrocolloids in functional foods, always considering the balance of the diet as a whole.

Effects of Diets Supplemented with Branched-Chain Amino Acids on the Performance and Fatigue Mechanisms of Rats Submitted to Prolonged Physical Exercise

This study aimed to determine the effects of diets chronically supplemented with branched-chain amino acids (BCAA) on the fatigue mechanisms of trained rats. Thirty-six adult Wistar rats were trained for six weeks. The training protocol consisted of bouts of swimming exercise (one hour a day, five times a week, for six weeks). The animals received a control diet (C) (n = 12), a diet supplemented with 3.57% BCAA (S1) (n = 12), or a diet supplemented with 4.76% BCAA (S2) (n = 12). On the last day of the training protocol, half the animals in each group were sacrificed after one hour of swimming (1H), and the other half after a swimming exhaustion test (EX). Swimming time until exhaustion was increased by 37% in group S1 and reduced by 43% in group S2 compared to group C. Results indicate that the S1 diet had a beneficial effect on performance by sparing glycogen in the soleus muscle (p < 0.05) and by inducing a lower concentration of plasma ammonia, whereas the S2 diet had a negative effect on performance due to hyperammonemia (p < 0.05). The hypothalamic concentration of serotonin was not significantly different between the 1H and EX conditions. In conclusion, chronic BCAA supplementation led to increased performance in rats subjected to a swimming test to exhaustion. However, this is a dose-dependent effect, since chronic ingestion of elevated quantities of BCAA led to a reduction in performance.