Emilia Muñoz-Martínez

Grape Antioxidant Dietary Fiber Stimulates Lactobacillus Growth in Rat Cecum

UNLABELLED The digesta is a highly active biological system where epithelial cells, microbiota, nondigestible dietary components, and a large number of metabolic products interact. The gut microbiota can be modulated by both endogenous and exogenous substrates. Undigested dietary residues are substrates for colonic microbiota and may influence gut microbial ecology. The objective of this work was to study the capacity of grape antioxidant dietary fiber (GADF), which is rich in polyphenols, to modify the bacterial profile in the cecum of rats. Male adult Wistar rats were fed for 4 wk with diets containing either cellulose or GADF as dietary fiber. The effect of GADF on bacterial growth was evaluated in vitro and on the cecal microbiota of rats using quantitative real time polymerase chain reaction (RT-PCR). The results showed that GADF intake stimulates proliferation of Lactobacillus and slightly affects the composition of Bifidobacterium species. GADF was also found to have a stimulative effect on Lactobacillus reuteri and Lactobacillus acidophilus in vitro. These findings suggest that the consumption of a diet rich in plant foods with high dietary fiber and polyphenol content may enhance the gastrointestinal health of the host through microbiota modulation. PRACTICAL APPLICATION Grape antioxidant fiber combines nutritional and physiological properties of dietary fiber and natural antioxidants from grapes. Grape antioxidant fiber could be used as an ingredient for functional foods and as a dietary supplement to increase the intake of dietary fiber and bioactive compounds.

Grape antioxidant dietary fibre reduced apoptosis and induced a pro-reducing shift in the glutathione redox state of the rat proximal colonic mucosa.

Grape antioxidant dietary fibre (GADF) is a grape product rich in dietary fibre and natural antioxidants. We showed previously that the GADF intake induced an epithelial hypoplasia in the rat colonic mucosa. In the present study, we propose that the antioxidant effect of GADF could modulate mucosal apoptosis via modulation of the cellular redox environment. Male Wistar rats (n 20) were fed with diets containing either cellulose (control diet group) or GADF (GADF diet group) as fibre for 4 weeks. The GSH:GSSG ratio, the redox state of the GSSG/2GSH couple (Ehc), the mitochondrial and/or cytosolic antioxidant enzyme activities (superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx)), lipid peroxidation (LPO) and apoptosis were evaluated. GADF enhanced the cytosolic GSH:GSSG ratio, shifting the redox potential (Ehc) to a more pro-reducing status. Decreased Cu,ZnSOD:CAT, Cu,ZnSOD:GPx and MnSOD:GPx ratios could indicate an enhanced capacity for reducing H2O2, contributing to decreased cytosolic LPO. Reduced apoptosis in GADF-treated mucosa was inversely related to MnSOD activity. Furthermore, apoptosis increased directly as GSSG content increased. These results suggest that the reduction in apoptosis associated with GADF intake may be due to a modulation of the glutathione redox system and endogenous antioxidant enzymes.

Grape antioxidant dietary fibre prevents mitochondrial apoptotic pathways by enhancing Bcl-2 and Bcl-xL expression and minimising oxidative stress in rat distal colonic mucosa.

Grape antioxidant dietary fibre (GADF) is a grape product rich in dietary fibre and natural antioxidants. We reported previously that GADF intake reduced apoptosis and induced a pro-reducing shift in the glutathione (GSH) redox status of the rat proximal colonic mucosa. The aim of the study was to elucidate the molecular mechanisms responsible for the anti-apoptotic effect of GADF and their association with the oxidative environment of the distal colonic mucosa. The ability of GADF to modify colonic crypt cell proliferation was also investigated. Male Wistar rats (n 20) were fed with diets containing either cellulose (control group) or GADF (GADF group) as fibre for 4 weeks. GADF did not modify cell proliferation but induced a significant reduction of colonic apoptosis. The anti-apoptotic proteins Bcl-2 (B-cell lymphoma-2) and Bcl-xL (B-cell lymphoma extra large) were up-regulated in the mitochondria and down-regulated in the cytosol of the GADF mucosa, whereas the opposite was found for the pro-apoptotic protein Bax (Bcl-2-associated X protein), leading to an anti-apoptotic shift in the pattern of expression of the Bcl-2 family. Cytosolic cytochrome c and cleaved caspase-3 levels and caspase-3 activity were reduced by GADF. The modulation of the antioxidant enzyme system and the increase of the cytosolic GSH:glutathione disulfide (GSSG) ratio elicited by GADF helped to reduce oxidative damage. The cytosolic GSH:GSSG ratio was negatively related to apoptosis. These results indicate that GADF acts on the expression of the pro- and anti- apoptotic Bcl-2 proteins, attenuating the mitochondrial apoptotic pathway in the distal colonic mucosa. This effect appears to be associated with the antioxidant properties of GADF.

Body growth and substrate partitioning for fat and protein gain in weaned BALB/c mice treated with growth hormone

Previously we have found that recombinant human growth hormone (rhGH) (GH; 74 ng g body wt.(-1)) administration to weaned BALB/c male mice (fed 12% or 20% protein diet) induced a growth lag and subsequent repletion similar to the catch-up growth process. We studied the partitioning of feed and protein intakes between adipose and protein body stores through the linear relationships among them. The non-linear relationship of protein intake with body fat gain/protein gain (FG/PG) ratio was especially adequate in determining the partitioning of substrates. rhGH induced an increase in feed and protein intake utilization for body weight gain (50%) and fat gain (75-140%) over saline; macronutrient utilization was the greatest in rhGH-treated mice fed 20% protein. However, growth recovery of rhGH mice was anomalous and protein intake was derived primarily for fat gain. Mice fed 12% protein (treated and control) also derived protein intake in preference to fat stores. Treatment and diet had a cumulative effect with the result that rhGH-treated animals fed 12% protein showed the greatest FG/PG ratio (1.6), and therefore, the lowest efficiency to gain protein. Weaning is a critical stage in mice when treating with rhGH, as this could provoke a growth lag. The study showed that a high protein level is required to surpass the rhGH-induced lag, but it is not enough to obtain an enhanced protein deposition. Feeding a 12% protein diet was even worse as mice did not improve on the growth lag and substrates were directed mainly to body fat.

Growth hormone administration produces a biphasic cellular muscle growth in weaning mice.

The present study was undertaken to elucidate the effect of the exogenous administration of rhGH on the time course of the cellular muscle growth in male and female BALB/c mice fed 20% dietary protein between weaning and 50 days of age. Also, the efficiency of utilization of protein and energy intake to muscle DNA content and protein per cell (protein to DNA ratio) storage were studied. 120 weaned mice (21 d) were assigned to four groups based on rhGH-treatment (rhGH-treated: 7.4 ng.g−1 BW and control: saline vehicle; via s.c. every two days) and gender. Feed intake was measured daily. At 25, 30, 35, 40, 45 and 50 days of age twenty mice were killed by cervical dislocation and the samples of gastrocnemius muscles were isolated, weighed and protein and DNA contents were measured. The rhGH administration caused a biphasic response altering the muscle cellular growth as a consequence of age-specific feed intake changes. The GH-induced fall of feed intake between 25 and 30 days of age caused decreases in muscle weight and myonuclei number (DNA), whereas muscle cell size was maintained. Later on, the self-controlled increase of feed intake led to the muscle weight recovery to control level, in spite of the irreversible DNA fall, as a consequence of the increase of cellular protein deposition and an enhancement of utilization of protein and energy intakes to deposit protein per cell. These results demonstrate that in spite of the initial (25–30 d of age) muscle DNA fall, rhGH-administration from weaning ensures the recovery of cellular muscle growth to control level through a compensatory muscle hypertrophy.ResumenSe estudia el efecto de la administración exógena de la hormona de crecimiento recombinante humana (rhGH) sobre el crecimiento celular del músculo esquelético, así como la eficacia de utilización de la ingesta en el depósito de DNA y proteína/DNA muscular en ratones BALB/c de ambos sexos entre el destete y 50 días de vida, alimentados con una dieta del 20% de proteína. Una vez destetados (21 días), los animales se distribuyen en 4 grupos según sexo (macho y hembra) y tratamiento: rhGH-tratados (74ng/g vía s.c) y controles (solución salina). A los 25, 30, 35, 40, 45 y 50 días de vida se sacrifican 20 ratones por dislocación cación cervical, se extrae el músculo gastrocnemio y se determinan el peso muscular y el contenido de proteína y DNA. La administración de rhGH da lugar a una respuesta bifásica alterando la forma del crecimiento celular en relación con los cambios en la ingesta. La caída inicial de la ingesta (entre 25 y 30 días) induce una drástica disminución en el peso muscular y el número de mionúcleos (DNA), mientras que el tamaño celular (proteína/DNA) se mantiene. Sin embargo, la posterior hiperfagia (35–50 días) facilita la recuperación del peso muscular a valor control, pese a la irreversibilidad de la pérdida del DNA. Esto se produce a consecuencia del incremento del tamaño celular, al cual contribuye el aumento en la eficacia de utilización de la energía y la proteína de la dieta en el depósito proteico muscular. Ello sugiere que, a pesar de la deplección inicial de sustratos, la administración de rhGH a ratones en el momento del destete asegura la recuperación del crecimiento celular del músculo gastrocnemio a través de un mecanismo de hipertrofia compensadora.

Growth hormone improves lipoprotein concentration and arylesterase activity in mice with an atherogenic lipid profile induced by lactalbumin

The effect of growth hormone (GH) on arylesterase (AE), one of the activities of paraoxonase, has never been studied. The aims of the present study in mice were: (a) to compare the effect of age and sex on serum lipid and lipoprotein levels after consumption of lactalbumin- v. chow-based diets and (b) to study the effect of GH administration, age and sex on serum AE activity, lipid and lipoprotein and body fat levels in mice fed a lactalbumin diet. Seventy-two mice were divided into three age- and sex-matched experimental groups: (1) control chow (CC), (2) non-GH lactalbumin (NGL) and (3) GH-treated lactalbumin (GL) mice. Lactalbumin increased total cholesterol, (LDL+VLDL)-cholesterol and TAG and diminished HDL-cholesterol in all animals (P<0.05). In comparison with their NGL counterparts, old GL males presented lower total cholesterol (15%) and (LDL+VLDL)-cholesterol (17%) levels (P<0.05), whereas values of the same parameters were higher in adult GL males (P<0.05) (22 and 23%, respectively). Adult GL females displayed higher serum HDL-cholesterol concentrations (26%) (P<0.05) than adult NGL females. AE activity was lower in old GL females (78%) and old GL males (20%) (P<0.05), but higher in adult GL males (100%) (P<0.01). GH, that was inversely related to food intake, decreased abdominal and gonadal fat in all mice (P<0.05). To conclude, lactalbumin induced an atherogenic lipoprotein profile in NGL mice that was reverted by GH, preferentially in old males, suggesting that GH therapy will be more effective in aged men. The present results suggest that AE activity was age-, sex- and body fat level-dependent and that it diminished as a consequence of improved antioxidant status.

Influence of Hansenula anomala yeast intake on the liver and kidney metabolism of the trout (Salmo gairdneri)

The nutritional and metabolic effects of the use of Hansenula anomala yeast as the only protein source were studied in the trout. Food intake, weight and length increments significantly decreased in trout fed on yeast diet. Hepatosomatic index did not suffer any change. Soluble protein content in liver and kidney rose significantly. Liver alkaline phosphatase activity increased significantly. Liver lactate dehydrogenase (LDH) activity did not change in the experimental conditions. Glutamic-oxalacetic transaminase (GOT) activity appeared as the most affected parameter in both organs, increasing significantly in those trout fed on yeast diet.

Dietary α-lactalbumin induced fatty liver by enhancing nuclear liver X receptor αβ/sterol regulatory element-binding protein-1c/PPARγ expression and minimising PPARα/carnitine palmitoyltransferase-1 expression and AMP-activated protein kinase α phosphorylation associated with atherogenic dyslipidaemia, insulin resistance and oxidative stress in Balb/c mice

The effect and the role played by dietary α-lactalbumin (α-LAC) on hepatic fat metabolism are yet to be fully elucidated. We reported previously that α-LAC intake induced atherogenic dyslipidaemia in Balb/c mice. The aim of the present study was to investigate if this atherogenic effect could be due to a possible α-LAC-induced hepatic steatosis. We examine the ability of dietary α-LAC to induce liver steatosis, identifying the molecular mechanisms underlying hepatic lipid metabolism in association with the lipid profile, peripheral insulin resistance (IR) and changes in the hepatic oxidative environment. Male Balb/c mice (n 6) were fed with diets containing either chow or 14 % α-LAC for 4 weeks. The α-LAC-fed mice developed abdominal adiposity and IR. Moderate liver steatosis with increased TAG and NEFA contents was correlated with atherogenic dyslipidaemia. There was increased nuclear expression of liver X receptor αβ (LXRαβ), sterol regulatory element-binding protein-1c (SREBP-1c) and PPARγ transcription factors and of the cytosolic enzymes acetyl-CoA carboxylase 1 (ACC1) and fatty acid synthase involved in the hepatic de novo lipogenesis. The opposite was found for the nuclear receptor PPARα and the mitochondrial enzyme carnitine palmitoyltransferase-1 (CPT-1), leading to reduced fatty acid β-oxidation (FAO). These changes were associated with a significant decrease in both p-Thr172-AMP-activated protein kinase α (AMPKα) (inactivation) and p-Ser79-ACC1 (activation) and with a more oxidative liver environment increasing lipid peroxidation and protein oxidation and reducing GSH:GSSG ratio in the α-LAC-fed mice. In conclusion, 4 weeks of 14 % α-LAC feeding induced liver steatosis associated with atherogenic dyslipidaemia, IR and oxidative stress by enhancing nuclear LXRαβ/SREBP-1c/PPARγ expression and diminishing PPARα/CPT-1 expression and AMPKα phosphorylation shifting the hepatic FAO toward fatty acid synthesis in Balb/c mice.