Raúl López-Grueso

Properties of Resveratrol: In Vitro and In Vivo Studies about Metabolism, Bioavailability, and Biological Effects in Animal Models and Humans

Plants containing resveratrol have been used effectively in traditional medicine for over 2000 years. It can be found in some plants, fruits, and derivatives, such as red wine. Therefore, it can be administered by either consuming these natural products or intaking nutraceutical pills. Resveratrol exhibits a wide range of beneficial properties, and this may be due to its molecular structure, which endow resveratrol with the ability to bind to many biomolecules. Among these properties its activity as an anticancer agent, a platelet antiaggregation agent, and an antioxidant, as well as its antiaging, antifrailty, anti-inflammatory, antiallergenic, and so forth activities, is worth highlighting. These beneficial biological properties have been extensively studied in humans and animal models, both in vitro and in vivo. The issue of bioavailability of resveratrol is of paramount importance and is determined by its rapid elimination and the fact that its absorption is highly effective, but the first hepatic step leaves little free resveratrol. Clarifying aspects like stability and pharmacokinetics of resveratrol metabolites would be fundamental to understand and apply the therapeutic properties of resveratrol.

Direct antioxidant and protective effect of estradiol on isolated mitochondria

Estrogens have antioxidant properties which are due to their ability to bind to estrogen receptors and to up-regulate the expression of antioxidant enzymes via intracellular signalling pathways. Mitochondria are key organelles in the development of age-associated cellular damage. Recently, estrogen receptors were identified in mitochondria. The aim of this paper was to test whether estradiol directly affects mitochondria by preventing oxidative stress and protecting frail mitochondria. Incubation with estradiol at normal intracellular concentrations prevents the formation of reactive oxygen species by mitochondria in a saturable manner. Moreover, estradiol protects mitochondrial integrity as indicated by an increase in mitochondrial membrane potential. It also prevents the apoptogenic leakage of cytochrome c from mitochondria and as a result the mitochondrial content of this cytochrome c is maintained high. Thus, estradiol prevents the onset of the mitochondrial pathway of apoptosis by a direct effect on the organelle. Genistein, a phytoestrogen present at high concentration in soy, mimics the protective effect of estradiol by both decreasing the rate of formation of reactive oxygen species and preventing the release of cytochrome c from mitochondria.

Females Live Longer than Males: Role of Oxidative Stress

One of the most significant achievements of the twentieth century is the increase in human lifespan. In any period studied, females live longer than males. We showed that mitochondrial oxidative stress is higher in males than females and that the higher levels of estrogens in females protect them against ageing, by up-regulating the expression of antioxidant, longevity-related genes. The chemical structure of estradiol confers antioxidant properties to the molecule. However, the low concentration of estrogens in females makes it unlikely that they exhibit significant antioxidant capacity in the organism. Therefore we studied the mechanisms enabling estradiol to be antioxidant at physiological levels. Our results show that physiological concentrations of estrogens activate estrogen receptors and the MAPK and NFKB pathway. Activation of NFkB by estrogens subsequently activates the expression of Mn-SOD and GPx. Moreover, we have demonstrated that genistein, the most abundant phytoestrogen in soya, reproduces the antioxidant effect of estradiol at nutritionally relevant concentrations by the same mechanism, both in healthy ageing and in Alzheimers disease. We conclude that estrogens and phytoestrogens up-regulate expression of antioxidant enzymes via the estrogen receptor and MAPK activation, which in turn activate the NFkB signalling pathway, resulting in the up-regulation of the expression of longevity-related genes.

Free [NADH]/[NAD(+)] regulates sirtuin expression.

Sirtuins are deacetylases involved in metabolic regulation and longevity. Our aim was to test the hypothesis that they are subjected to redox regulation by the [NADH]/[NAD(+)] ratio. We used NIH3T3 fibroblasts in culture, Drosophila fed with or without ethanol and exercising rats. In all three models an increase in [NADH]/[NAD(+)] came up with an increased expression of sirtuin mRNA and protein. PGC-1α (a substrate of sirtuins) protein level was significantly increased in fibroblasts incubated with lactate and pyruvate but this effect was lost in fibroblasts obtained from sirtuin-deficient mice. We conclude that the expression of sirtuins is subject to tight redox regulation by the [NADH]/[NAD(+)] ratio, which is a major sensor for metabolite availability conserved from invertebrates to vertebrates.

Resveratrol: distribución, propiedades y perspectivas

Resveratrol is a natural polyphenol which can be found in many plants and fruits, such as peanuts, mulberries, blueberries and, above all, in grapes and red wine. Its synthesis is regulated by the presence of stressful factors, such as fungal contamination and ultra-violet radiation. In plants, it plays a role as a phytoalexin, showing a capacity to inhibit the development of certain infections. Plant extracts which contain resveratrol have been employed by traditional medicine for more than 2000 years. Resveratrol was first isolated, and its properties were initially studied with scientific methods, thirty years ago. Its in vitro properties have been extensively studied and demonstrated. It is worth highlighting its activity as an anti-cancer agent, platelet anti-aggregation agent, anti-inflammatory, antiallergenic, etc. The activity of its in vivo properties are not so clear. There are many studies that report benefits on the cardiovascular system, illnesses such as diabetes, and in longevity. However, other authors did not find any agreement between in vitro and in vivo studies. This discrepancy is due to the bioavailability of resveratrol. After an oral dose, it has been demonstrated that the absorption is very high, but the metabolic pathways leave just a little free resveratrol in blood, therefore the bioavailability in the target tissues is very low and the concentrations used in in vitro studies are not found in these tissues. Thus, resveratrol is a very active molecule for maintaining health, but due to the low bioavailability not all the in vitro effects can be translated to in vivo. This opens a new potential approach, seeking derivatives of resveratrol that can be measured in the desired tissues.

Metabolomic analysis of long-term spontaneous exercise in mice suggests increased lipolysis and altered glucose metabolism when animals are at rest

Exercise has been associated with several beneficial effects and is one of the major modulators of metabolism. The working muscle produces and releases substances during exercise that mediate the adaptation of the muscle but also improve the metabolic flexibility of the complete organism, leading to adjustable substrate utilization. Metabolomic studies on physical exercise are scarce and most of them have been focused on the effects of intense exercise in professional sportsmen. The aim of our study was to determine plasma metabolomic adaptations in mice after a long-term spontaneous exercise intervention study (18 mo). The metabolic changes induced by long-term spontaneous exercise were sufficient to achieve complete discrimination between groups in the principal component analysis scores plot. We identified plasma indicators of an increase in lipolysis (elevated unsaturated fatty acids and glycerol), a decrease in glucose and insulin plasma levels and in heart glucose consumption (by PET), and altered glucose metabolism (decreased alanine and lactate) in the wheel running group. Collectively these data are compatible with an increase in skeletal muscle insulin sensitivity in the active mice. We also found an increase in amino acids involved in catecholamine synthesis (tyrosine and phenylalanine), in the skeletal muscle pool of creatine phosphate and taurine, and changes in phospholipid metabolism (phosphocholine and choline in lipids) between the sedentary and the active mice. In conclusion, long-term spontaneous wheel running induces significant plasma and tissue (heart) metabolic responses that remain even when the animal is at rest.

Low in vivo brain glucose consumption and high oxidative stress in accelerated aging

The validity of the free radical theory of aging has been recently questioned. Our aim was to test whether there is oxidative stress in tissues critically involved in accelerated aging (senescence‐accelerated mice, SAM) and whether this correlates with lower glucose consumption in vivo and behavioural tests. Positron emission tomography shows that brains of old SAM‐prone animals consume less glucose than young ones. Behavioural characteristics, mitochondrial peroxide production, and damage in both the central nervous system and bone marrow stem cells also indicate that SAM‐prone animals age faster than SAM‐resistant ones. Our results support the role of the free radical theory of aging in critical tissues involved in aging and that this correlates with glucose consumption.

El envejecimiento y la ovariectomía causan una disminución del consumo cerebral de glucosa in vivo en ratas Wistar

INTRODUCTION The life expectancy of the population has been increased steadily over the twentieth century in both genders. The survival of women has always been higher compared to men and these differences in longevity are reproduced in other animal species such as rats. There must be some biological basis to support the differences in longevity between males and females. Differences can be explained by the effects of estrogens because ovariectomy cancels out the benefits shown in females compared to males. AIM Our aims were to study the cerebral glucose consumption in vivo in young and old female Wistar rats and evaluate the effect of ovariectomy on the brain glucose uptake. MATERIAL AND METHODS We used female Wistar rats, divided into young (4-7 months), young control (Sham) and ovariectomized (3 or 6 weeks) and old (22-24 months) groups. After intravenous administration of 18F-fluorodeoxyglucose (FDG) the cerebral glucose uptake was measured in vivo by Positron Emission Tomography (PET). RESULTS There was a significant decrease in cerebral glucose consumption in old rats compared with young rats. Similar results were found in glucose uptake when comparing control rats with ovariectomized rats, i.e., ovariectomy significantly reduces the brain glucose consumption. CONCLUSIONS Aging causes a decrease in cerebral glucose metabolism. Ovariectomy reduces cerebral glucose consumption significantly compared to control rats and is similar to the old group.

ORIGINAL/Sección BiológicaEl envejecimiento y la ovariectomía causan una disminución del consumo cerebral de glucosa in vivo en ratas WistarAging and ovariectomy cause a decrease in brain glucose consumption in vivo in Wistar rats

INTRODUCTION The life expectancy of the population has been increased steadily over the twentieth century in both genders. The survival of women has always been higher compared to men and these differences in longevity are reproduced in other animal species such as rats. There must be some biological basis to support the differences in longevity between males and females. Differences can be explained by the effects of estrogens because ovariectomy cancels out the benefits shown in females compared to males. AIM Our aims were to study the cerebral glucose consumption in vivo in young and old female Wistar rats and evaluate the effect of ovariectomy on the brain glucose uptake. MATERIAL AND METHODS We used female Wistar rats, divided into young (4-7 months), young control (Sham) and ovariectomized (3 or 6 weeks) and old (22-24 months) groups. After intravenous administration of 18F-fluorodeoxyglucose (FDG) the cerebral glucose uptake was measured in vivo by Positron Emission Tomography (PET). RESULTS There was a significant decrease in cerebral glucose consumption in old rats compared with young rats. Similar results were found in glucose uptake when comparing control rats with ovariectomized rats, i.e., ovariectomy significantly reduces the brain glucose consumption. CONCLUSIONS Aging causes a decrease in cerebral glucose metabolism. Ovariectomy reduces cerebral glucose consumption significantly compared to control rats and is similar to the old group.

Estrogenic Modulation of Longevity by Induction of Antioxidant Enzymes

In many species including humans, females live longer than males. We and others have observed that mitochondria from females of Wistar rats and of OF1 mice produce half the amount of peroxide produced by males. We attributed this to a change in the expression of antioxidant, longevity-related genes. We have found that in those species in which females live longer than males, estrogens activate longevity-related genes, particularly antioxidant ones. It should be emphasized that estrogens do not act as antioxidants because of their phenolic ring but rather they act indirectly; that is, they behave as hormones and bind to estrogen receptors, which eventually leads to the upregulation of the expression of antioxidant genes. The pathway by which estrogens activate the expression of these genes has been elucidated, and we have traced it to the activation of the mitogen activated proteins (MAP) kinase pathway. It is remarkable that estrogens activate proliferation genes (related to their feminizing function and also to their cancer-promoting effects) by binding to estrogen receptor alpha whereas the longevity-related genes, in particular the antioxidant ones, are mediated by binding to estrogen receptor beta. Phytoestrogens, which in their vast majority bind to estrogen receptor beta, promote longevity-related genes without increasing the rate of cell division or promoting feminization. Thus, a practical approach discussed here is that administration of phytoestrogens may be very beneficial for longevity because they bind very preferentially to estrogen receptor beta and promote the upregulation of longevity-related genes.