Consumption of out-of-season orange modulates fat accumulation, morphology and gene expression in the adipose tissue of Fischer 344 rats

PURPOSE

According to the xenohormesis theory, animals receive signals from plants that give clues about the changing environment, and thus, depending on the season of the year, animals develop physiological changes to adapt in advance to the seasonal changes. Our objective was to study how the same fruit cultivated during two different seasons could affect the adipose tissue of rats.

METHODS

Thirty-six Fischer 344 rats were acclimated for 4 weeks to long-day or short-day (SD) photoperiods. After adaptation, three groups (n = 6) from each photoperiod were supplemented either with orange from the northern (ON) or southern (OS) hemispheres harvested in the same month or a vehicle (VH) for 10 weeks. Biometric measurements, postprandial plasmatic parameters, gene expression of the inguinal white adipose tissue (IWAT) and brown adipose tissue (BAT), and the histology of the IWAT were analysed.

RESULTS

The OSSD group increased its fat content compared to the VHSD, while the ON groups showed no biometric differences. The OS groups were further studied, and the IWAT showed increased levels of Pparγ gene expression and a higher percentage of larger adipocytes compared to the VH group. The BAT showed down-regulation of Lpl, Cpt1b and Pparα in the OSSD group compared to that in the VHSD group, suggesting an inhibition of BAT activity, however, Ucp1 gene expression was up-regulated.

CONCLUSIONS

We observed a different effect from both fruits, with the OS promoting a phenotype prone to fat accumulation when consumed in an SD photoperiod, which might be explained by the xenohormesis theory.

Consumption of Cherry out of Season Changes White Adipose Tissue Gene Expression and Morphology to a Phenotype Prone to Fat Accumulation

The aim of this study was to determine whether the consumption of cherry out of its normal harvest photoperiod affects adipose tissue, increasing the risk of obesity. Fischer 344 rats were held over a long day (LD) or a short day (SD), fed a standard diet (STD), and treated with a cherry lyophilizate (CH) or vehicle (VH) (n = 6). Biometric measurements, serum parameters, gene expression in white (RWAT) and brown (BAT) adipose tissues, and RWAT histology were analysed. A second experiment with similar conditions was performed (n = 10) but with a cafeteria diet (CAF). In the STD experiment, Bmal1 and Cry1 were downregulated in the CHSD group compared to the VHSD group. Pparα expression was downregulated while Ucp1 levels were higher in the BAT of the CHSD group compared to the VHSD group. In the CAF-fed rats, glucose and insulin serum levels increased, and the expression levels of lipogenesis and lipolysis genes in RWAT were downregulated, while the adipocyte area increased and the number of adipocytes diminished in the CHSD group compared to the VHSD group. In conclusion, we show that the consumption of cherry out of season influences the metabolism of adipose tissue and promotes fat accumulation when accompanied by an obesogenic diet.

Proanthocyanidins in health and disease

Proanthocyanidins (PAs) are the most abundant flavonoids in the human diet. Several epidemiological studies connect PA consumption and health benefits and the designation of PAs as healthy compounds started at the early stages of the 20th century. The beneficial health properties of PAs are attributed to their conjugated and colonic metabolites. Therefore, gut microbial compositions can determine the effectiveness of PAs. Reciprocally, dietary polyphenols can act as prebiotics. Recently, it has also been described that PAs modulate the circadian rhythm. Biochemical and epigenetic mechanisms, including the modulation of microRNAs, allow PAs to modulate cell functionality. PA effects in metabolic diseases are also reviewed.

Long-term supplementation with a low dose of proanthocyanidins normalized liver miR-33a and miR-122 levels in high-fat diet-induced obese rats

Deregulation of miR-33 and miR-122, as major regulators of lipid metabolism in liver, has been related to obesity and metabolic syndrome. Proanthocyanidins repress these microRNAs in healthy animals. Hence, we hypothesized that long-term consumption of dietary proanthocyanidins can normalize the expression of miR-33a and miR-122. Therefore, the objective of this work was to determine whether the long-term consumption of proanthocyanidins could effectively normalize the expression of miR-33a and miR-122 in rats made obese by a high-fat diet and to determine the effective dose. Rats were maintained on the high-fat diet with or without supplementation with a grape seed proanthocyanidin extract at low, medium, or high dose in relation to human consumption. Results show that 3 weeks of supplementation with grape seed proanthocyanidin extract normalized the overexpression of miR-33a and miR-122 in obese rats' liver for all doses studied, with no dose-dependent outcome, and also reduced the levels of plasma and liver lipids in a dose-dependent manner. In conclusion, a low sustained dose of proanthocyanidins, lower than the estimated mean intake for a European population, is enough to normalize miR-33a and miR-122 levels in the livers of obese rats. Therefore, a proanthocyanidin-rich diet during obesity can improve some of the metabolic syndrome symptoms at least at the molecular level.

Roles of proanthocyanidin rich extracts in obesity

Obesity is a multifactorial disorder involving an abnormal or excessive amount of body fat.

Chronic consumption of dietary proanthocyanidins modulates peripheral clocks in healthy and obese rats

Circadian rhythm plays an important role in maintaining homeostasis, and its disruption increases the risk of developing metabolic syndrome. Circadian rhythm is maintained by a central clock in the hypothalamus that is entrained by light, but circadian clocks are also present in peripheral tissues. These peripheral clocks are trained by other cues, such as diet. The aim of this study was to determine whether proanthocyanidins, the most abundant polyphenols in the human diet, modulate the expression of clock and clock-controlled genes in the liver, gut and mesenteric white adipose tissue (mWAT) in healthy and obese rats. Grape seed proanthocyanidin extracts (GSPEs) were administered for 21 days at 5, 25 or 50 mg GSPE/kg body weight in healthy rats and 25 mg GSPE/kg body weight in rats with diet-induced obesity. In healthy animals, GSPE administration led to the overexpression of core clock genes in a positive dose-dependent manner. Moreover, the acetylated BMAL1 protein ratio increased with the same pattern in the liver and mWAT. With regards to clock-controlled genes, Per2 was also overexpressed, whereas Rev-erbα and RORα were repressed in a negative dose-dependent manner. Diet-induced obesity always resulted in the overexpression of some core clock and clock-related genes, although the particular gene affected was tissue specific. GSPE administration counteracted disturbances in the clock genes in the liver and gut but was less effective in normalizing the clock gene disruption in WAT. In conclusion, proanthocyanidins have the capacity to modulate peripheral molecular clocks in both healthy and obese states.

Chronic intake of proanthocyanidins and docosahexaenoic acid improves skeletal muscle oxidative capacity in diet-obese rats

Obesity has become a worldwide epidemic. The cafeteria diet (CD) induces obesity and oxidative-stress-associated insulin resistance. Polyunsaturated fatty acids and polyphenols are dietary compounds that are intensively studied as products that can reduce the health complications related to obesity. We evaluate the effects of 21 days of supplementation with grape seed proanthocyanidins extract (GSPE), docosahexaenoic-rich oil (DHA-OR) or both compounds (GSPE+DHA-OR) on skeletal muscle metabolism in diet-obese rats. The supplementation with different treatments did not reduce body weight, although all groups used more fat as fuel, particularly when both products were coadministered; muscle β-oxidation was activated, the mitochondrial functionality and oxidative capacity were higher, and fatty acid uptake gene expressions were up-regulated. In addition to these outcomes shared by all treatments, GSPE reduced insulin resistance and improved muscle status. Both treatments increased 5'-AMP-activated protein kinase (AMPK) phosphorylation, which was consistent with higher plasma adiponectin levels. Moreover, AMPK activation by DHA-OR was also correlated with an up-regulation of peroxisome proliferator-activated receptor alpha (Pparα). GSPE+DHA-OR, in addition to activating AMPK and enhancing fatty acid oxidation, increased the muscle gene expression of uncoupling protein 2 (Ucp2). In conclusion, GSPE+DHA-OR induced modifications that improved muscle status and could counterbalance the deleterious effects of obesity, and such modifications are mediated, at least in part, through the AMPK signaling pathway.

Combination of grape seed proanthocyanidin extract and docosahexaenoic acid-rich oil increases the hepatic detoxification by GST mediated GSH conjugation in a lipidic postprandial state

The ingestion of dietary lipids leads to oxidative stress. This postprandial oxidative stress may potentiate the adverse effects of postprandial hyperlipidaemia. Proanthocyanidins have been shown to alleviate oxidative stress and hypertriglyceridaemia associated with the postprandial state. Additionally, omega-3 polyunsaturated fatty acids (PUFAs) also have beneficial effects on lipoprotein metabolism and oxidative stress. The present study was designed to investigate the possible additive effects in liver of an acute dose of grape seed proanthocyanidins extract (GSPE) and oil rich in docosahexaenoic acid (DHA-OR) on lipidic postprandial oxidative stress in Wistar rats. GSPE+DHA-OR modifies the hepatic antioxidant enzymatic activities (GST and GPx), clearly showing that this combination increases the detoxification of postprandial xenobiotics via the GST action mediated hepatic GSH conjugation. In conclusion, this study provides evidence that the combination of GSPE and DHA-OR ameliorate the transient imbalance between the lipid hydroperoxide level and antioxidant status related to a lipidic postprandial state.

Omega-3 polyunsaturated fatty acids and proanthocyanidins improve postprandial metabolic flexibility in rat

Postprandial lipemia influences the development of atherosclerosis, which itself constitutes a risk factor for the development of cardiovascular diseases. The introduction of bioactive compounds may prevent these deleterious effects. Proanthocyanidins are potent antioxidants that have hypolipidemic properties, while omega-3 polyunsaturated fatty acids (ω3 PUFAs) stimulate fatty acid oxidation and gene expression programs, controlling mitochondrial functions. In this study, we investigated the effects of acute treatment of ω3 PUFAs and proanthocyanidins on the metabolic flexibility and lipid handling profiles in the skeletal muscle and adipose tissue of rats that were raised on diets, high in saturated fatty acids. For this, oil rich in docosahexaenoic (DHA-OR), grape seed proanthocyanidins extract (GSPE), or both substances (GSPE + DHA-OR) were administered with an overload of lard oil to healthy Wistar rats. Our results indicate that the addition of DHA-OR to lard oil increases insulin sensitivity and redirects fatty acids toward skeletal muscle, thereby activating fatty acid oxidation. We also observed an improvement in adipose mitochondrial functionality and uncoupling. In contrast, GSPE lowers lipidemia, prevents muscle reactive oxygen species (ROS) production and damage, furthermore, activates mitochondrial biogenesis and lipogenesis in adipose tissue. The addition of GSPE+DHA-OR to lard resulted in nearly all the effects of DHA-OR and GSPE administered individually, but the combined administration resulted in a more attenuated profile.

Resveratrol and EGCG bind directly and distinctively to miR-33a and miR-122 and modulate divergently their levels in hepatic cells

Modulation of miR-33 and miR-122 has been proposed to be a promising strategy to treat dyslipidemia and insulin resistance associated with obesity and metabolic syndrome. Interestingly, specific polyphenols reduce the levels of these mi(cro)RNAs. The aim of this study was to elucidate the effect of polyphenols of different chemical structure on miR-33a and miR-122 expression and to determine whether direct binding of the polyphenol to the mature microRNAs (miRNAs) is a plausible mechanism of modulation. The effect of two grape proanthocyanidin extracts, their fractions and pure polyphenol compounds on miRNA expression was evaluated using hepatic cell lines. Results demonstrated that the effect on miRNA expression depended on the polyphenol chemical structure. Moreover, miR-33a was repressed independently of its host-gene SREBP2. Therefore, the ability of resveratrol and epigallocatechin gallate to bind miR-33a and miR-122 was measured using ¹H NMR spectroscopy. Both compounds bound miR-33a and miR-122 and differently. Interestingly, the nature of the binding of these compounds to the miRNAs was consistent with their effects on cell miRNA levels. Therefore, the specific and direct binding of polyphenols to miRNAs emerges as a new posttranscriptional mechanism by which polyphenols could modulate metabolism.

DHA sensitizes FaO cells to tert-BHP-induced oxidative effects. Protective role of EGCG

The excessive production of reactive oxygen species has been implicated in several pathologies, such as atherosclerosis, obesity, hypertension and insulin resistance. Docosahexaenoic acid (DHA) may protect against the above mentioned diseases, but paradoxically the main DHA treated pathologies are also associated with increased ROS levels. Therefore, the aim of this study was to explore if in vitro DHA supplementation may increase the sensitivity of cells to tert-BHP induced oxidative stress, and if the green tea polyphenol epigallocatechin-3-gallate (EGCG) is able to correct such detrimental effect. We found that DHA-enriched cells exacerbate ROS generation, decrease cell viability and increase Nrf2 nuclear translocation and HO-1 expression. Interestingly, cellular EGCG is able to counteract oxidative damage from either tert-BHP or DHA-enriched cells. In consequence, our results suggest that in a ROS enriched environment DHA could not always be beneficial for cells and can be considered a double-edged sword in terms of its benefits vs. risks. In this sense, our results propose that the supplementation with potent antioxidant molecules could be an appropriate strategy to reduce the risks related with the DHA supplementation in an oxidative stress-associated condition.

Grape seed proanthocyanidins repress the hepatic lipid regulators miR-33 and miR-122 in rats

SCOPE

One major health problem in westernized countries is dysregulated fatty acid and cholesterol metabolism that causes pathologies such as metabolic syndrome. Previous studies from our group have shown that proanthocyanidins, which are the most abundant polyphenols in the human diet, regulate lipid metabolism and are potent hypolipidemic agents. The noncoding RNAs, miR-33 and miR-122, regulate genes that are involved in lipid metabolism.

METHODS AND RESULTS

Here, we show that grape seed proanthocyanidins rapidly and transiently repressed the expression of miR-33 and miR-122 in rat hepatocytes in vivo and in vitro. Furthermore, the miR-33 target gene ATP-binding cassette A1 and the miR-122 target gene fatty acid synthase were also modulated by proanthocyanidins. Specifically, ATP-binding cassette A1 mRNA and protein levels were increased, and fatty acid synthase mRNA and protein levels were reduced after the miRNA levels were altered.

CONCLUSION

These results suggest that proanthocyanidin treatment increased hepatic cholesterol efflux to produce new HDL particles by repressing miR-33, and it reduced lipogenesis by repressing miR-122. These results highlight a new mechanism by which grape seed proanthocyanidins produce hypolipidemia through their effects on miRNA modulators of lipid metabolism.

Acute administration of grape seed proanthocyanidin extract modulates energetic metabolism in skeletal muscle and BAT mitochondria

Proanthocyanidin consumption might reduce the risk of developing several pathologies, such as inflammation, oxidative stress and cardiovascular diseases. The beneficial effects of proanthocyanidins are attributed to their antioxidant properties, although they also can modulate gene expression at the transcriptional level. Little is known about the effect of proanthocyanidins on mitochondrial function and energy metabolism. In this context, the objective of this study was to determine the effect of an acute administration of grape seed proanthocyanidin extract (GSPE) on mitochondrial function and energy metabolism. To examine this effect, male Wistar rats fasted for fourteen hours, and then they were orally administered lard oil containing GSPE or were administered lard oil only. Liver, muscle and brown adipose tissue (BAT) were used to study enzymatic activity and gene expression of proteins related to energetic metabolism. Moreover, the gastrocnemius muscle and BAT mitochondria were used to perform high-resolution respirometry. The results showed that, after 5 h, the GSPE administration significantly lowers plasma triglycerides, free fatty acids, glycerol and urea concentrations. In skeletal muscle, GSPE lowers FATP1 mRNA levels and increases mitochondrial oxygen consumption, using pyruvate as the substrate, suggesting a promotion of glycosidic metabolism. Furthermore, GSPE increased the genetic expression of key genes in energy metabolism such as peroxisome proliferator-activated receptor gamma, coactivator 1 alpha (PGC1α), and modulated the enzyme activity of proteins, which are involved in the citric acid cycle and electron transport chain (ETC) in BAT. In conclusion, GSPE affects mainly the skeletal muscle and BAT mitochondria, increasing their oxidative capacity rapidly after acute supplementation.

Effects of a grapeseed procyanidin extract (GSPE) on insulin resistance

Flavonoids are beneficial compounds against risk factors for metabolic syndrome, but their effects and the mechanisms on glucose homeostasis modulation are not well defined. In the present study, we first checked the efficacy of grapeseed procyanidin extract (GSPE) for stimulating glucose uptake in insulin-resistant 3T3-L1 adipocytes. Results show that when resistance is induced with chronic insulin treatment, GSPE maintain a higher stimulating capacity than insulin. In contrast, when dexamethasone is used as the resistance-inducing agent, GSPE is less effective. Next we evaluated how effective different GSPE treatments are at improving glucose metabolism in hyperinsulinemic animals (fed a cafeteria diet). GSPE reduced plasma insulin levels. The lower dose (25 mg GSPE/kg body weight per day) administered for 30 days improved the HOmeostasis Model Assessment-insulin resistance index. This was accompanied by down-regulation of Pparg2, Glut4 and Irs1 in mesenteric white adipose tissue. Similarly, a chronic GSPE treatment of insulin-resistant 3T3-L1 adipocytes down-regulated the mRNA levels of those adipocyte markers, although cells were still able to respond to the acute stimulation of glucose uptake. In summary, 25 mg/kg body weight per day of GSPE has a positive long-term effect on glucose homeostasis, and GSPE could be targeted at adipose tissue, where it might directly stimulate glucose uptake. This work also highlights the need to carefully consider the bioactive dose, since a higher dose does not necessarily correlate to a greater positive effect.

Dietary procyanidins enhance transcriptional activity of bile acid-activated FXR in vitro and reduce triglyceridemia in vivo in a FXR-dependent manner

Consumption of dietary flavonoids has been associated with reduced mortality and risk of cardiovascular disease, partially by reducing triglyceridemia. We have previously reported that a grape seed procyanidin extract (GSPE) reduces postprandial triglyceridemia in normolipidemic animals signaling through the orphan nuclear receptor small heterodimer partner (SHP) a target of the bile acid receptor farnesoid X receptor (FXR). Our aim was to elucidate whether FXR mediates the hypotriglyceridemic effect of procyanidins. In FXR-driven luciferase expression assays GSPE dose-dependently enhanced FXR activity in the presence of chenodeoxycholic acid. GSPE gavage reduced triglyceridemia in wild type mice but not in FXR-null mice, revealing FXR as an essential mediator of the hypotriglyceridemic actions of procyanidins in vivo. In the liver, GSPE downregulated, in an FXR-dependent manner, the expression of the transcription factor steroid response element binding protein 1 (SREBP1) and several SREBP1 target genes involved in lipogenesis, and upregulated ApoA5 expression. Altogether, our results indicate that procyanidins lower triglyceridemia following the same pathway as bile acids: activation of FXR, transient upregulation of SHP expression and subsequent downregulation of SREBP1 expression. This study adds dietary procyanidins to the arsenal of FXR ligands with potential therapeutic use to combat hypertriglyceridemia, type 2 diabetes and metabolic syndrome.

Oligomers of grape-seed procyanidin extract activate the insulin receptor and key targets of the insulin signaling pathway differently from insulin

Procyanidins are bioactive flavonoid compounds from fruits and vegetables that possess insulinomimetic properties, decreasing hyperglycaemia in streptozotocin-diabetic rats and stimulating glucose uptake in insulin-sensitive cell lines. Here we show that the oligomeric structures of a grape-seed procyanidin extract (GSPE) interact and induce the autophosphorylation of the insulin receptor in order to stimulate the uptake of glucose. However, their activation differs from insulin activation and results in differences in the downstream signaling. Oligomers of GSPE phosphorylate protein kinase B at Thr308 lower than insulin does, according to the lower insulin receptor activation by procyanidins. On the other hand, they phosphorylate Akt at Ser473 to the same extent as insulin. Moreover, we found that procyanidins phosphorylate p44/p42 and p38 MAPKs much more than insulin does. These results provide further insight into the molecular signaling mechanisms used by procyanidins, pointing to Akt and MAPK proteins as key points for GSPE-activated signaling pathways. Moreover, the differences between GSPE and insulin might help us to understand the wide range of biological effects that procyanidins have.

In vivo, in vitro, and in silico studies of Cu/Zn-superoxide dismutase regulation by molecules in grape seed procyanidin extract

The potential beneficial effects of flavonoids on human health have aroused considerable interest and were initially attributed to their antioxidant activities. Recent studies have speculated that as well as their antioxidant role, flavonoids can act by modulating cell signaling pathways and/or gene expression. In this respect, we have used streptozotocin-induced diabetic rats as an oxidative stress model to study whether grape seed procyanidin extract (GSPE) regulates copper/zinc-superoxide dismutase (Cu/Zn-SOD), an enzyme that defends against oxidative stress. The results indicate that the expression profile of Cu/Zn-SOD in diabetic rats was similar to the profile in nondiabetic rats. Nevertheless, the administration of GSPE increased Cu/Zn-SOD activity in both diabetic and nondiabetic rats. Therefore, to evaluate whether this increase in activity was dose-dependent, we also studied the effect of GSPE on Cu/Zn-SOD expression by using an in vitro model (Fao cell line hepatocytes). The cells were exposed to GSPE doses between 0 and 150 mg/L for 24 h, and the results showed that enzyme activity was enhanced only with 15 mg/L of GSPE. Therefore, we decided to explore whether this increase in Cu/Zn-SOD activity was due to direct interaction between some of the molecules in GSPE and the enzyme (in vitro experiments) and, if so, to analyze how this interaction occurs (in silico experiments). The results of these studies showed that direct interaction between some small- or medium-sized GSPE components and the enzyme is responsible for the increase in Cu/Zn-SOD activity.

Procyanidin effects on adipocyte-related pathologies

Procyanidins, a class of flavonoids, have clear and well-defined beneficial effects against several pathologies including cardiovascular heart disease. Now, studies in vivo are revealing the effects of procyanidins against obesity, where they prevent weight gain and adipose tissue mass increase, and against diabetes and insulin resistance, where they act as antihiperglycemic agents. Several mechanisms may be responsible for these effects. One of these, due to the key role of adipose tissue in the development of obesity and insulin resistance, is their effect on adipocytes. In this review we compile the studies that indicate a protective role for procyanidins in obesity and insulin resistance, focusing on their effects on the adipocyte, where procyanidins modify lipid synthesis, lipid degradation, glucose uptake, and adipose differentiation.

Tetramethylated dimeric procyanidins are detected in rat plasma and liver early after oral administration of synthetic oligomeric procyanidins

Procyanidins (PC) are of great interest in nutrition because they account for a major fraction of the total flavonoids ingested in Western diets and have health benefits in humans. However, it remains unknown which species of PC, namely, monomers, oligomers, or aromatic acid derivatives of gut microflora, are responsible for their beneficial effects in vivo. The high molecular complexity of PC extracts and PC-rich foods is a major problem in absorption studies. To circumvent this difficulty, we have synthesized oligomeric PC consisting of (-)-epicatechin units linked by ethyl bridges. The synthetic PC (SPC) only contains dimers, trimers, tetramers, and nanomers. After oral gavage of this SPC (200 mg/kg body weight) to male Wistar rats, tetramethylated dimeric PC (TDPC) were detected in plasma and liver. TDPC were detected in plasma as soon as 1 h after intake, reaching maximum concentrations (14 mg/L) 2 h after gavage. At this time, liver contained as much as 15 mug of TDPC per gram of tissue. In conclusion, orally administered dimeric PC are rapidly absorbed and internally methylated in rats. To our knowledge, this is the first time that methylated dimeric PC have been detected in plasma and liver. We consider that plasma and liver concentrations of TDPC are sufficient to exert a hormone-like effect and, therefore, that PC dimers are good candidates as agents of the biological activities of PC extracts and PC-rich foods.

Grape seed procyanidins prevent oxidative injury by modulating the expression of antioxidant enzyme systems

In the present paper, we report the effect of a grape seed procyanidin extract (GSPE) on antioxidant enzyme systems (AOEs). Gene expression was tested using the hepatocarcinoma cell line HepG2 by exposing it to several GSPE doses between 0 and 100 mg/L for 24 h. We evaluated mRNA expression and enzyme activity levels using real time RT-PCR and spectrophotometry. The results suggested a transcriptional GSPE regulation of glutathione related enzymes caused by an increase both in mRNA and in enzyme activity levels overall at 15 mg/L. We also assessed the GSPE effect on AOEs in cells submitted to oxidative stress. Under oxidative conditions (1 mM H(2)O(2), 1 h), we found a decrease in GSH content and an increase in MDA, and we suggested a posttranslational regulation of GPx/GR mRNAs and a transcriptional enhancement of GST mRNA. The GSPE pretreatment (15 mg/L, 23 h) before HepG2 submission to H(2)O(2) (1 mM, 1 h) showed an increase of the mRNA of GPx/GR with respect to the H(2)O(2) group, whereas the GSH content was similar to the control group. However, the GPx/GR enzyme activities were not increased. We hypothesize that GSPE probably improves the cellular redox status via glutathione synthesis pathways instead of regulation of the GPx and/or GR activities protecting against oxidative damage.

Metabolic fate of glucose on 3T3-L1 adipocytes treated with grape seed-derived procyanidin extract (GSPE). Comparison with the effects of insulin

In this paper we investigate the effects of a grape seed procyanidin extract (GSPE) on the metabolic fate of glucose in adipocytes. Differentiated 3T3-L1 cells were treated with 140 mg/L GSPE or 100 nM insulin for a short period (1 h, acute treatment) or for a long period (15 h, chronic treatment). 2-Deoxy-[1-(3)H]glucose uptake and [1-(14)C]glucose incorporation into cells, glycogen, and lipid were measured. We found that GSPE mimicked the anabolic effects of insulin but there were several important differences. GSPE stimulated glycogen synthesis less than insulin. After chronic exposure, GSPE induced a higher incorporation of glucose into lipid, mainly due to the increase in glucose directed to glycerol synthesis. Our main conclusions, therefore, are that GSPE has insulinomimetic properties and activates glycogen and lipid synthesis. However, the differences between the effects of GSPE and the effects of insulin indicate that GSPE uses mechanisms complementary to those of insulin signaling pathways to bring about these effects.

Grape-seed derived procyanidins interfere with adipogenesis of 3T3-L1 cells at the onset of differentiation

OBJECTIVE

Our group's previous results on the effects of a grape seed procyanidin extract (GSPE) on adipose metabolism showed that peroxisome proliferator-activated receptor-gamma (PPARgamma) plays a central role in the lipolytic effects of GSPE on adipocytes. Since PPARgamma2 is a main regulator of the differentiation process of adipocytes, we investigated whether GSPE affects the adipogenesis of 3T3-L1 cells.

DESIGN

We performed a time point screening by treating 3T3-L1 cells with GSPE during the differentiation process for 24 h.

MEASUREMENTS

Differentiation markers and differential gene expression due to GSPE treatment (using the microarray technique).

RESULTS

Twenty four hour-GSPE treatment at the onset of differentiation reduces adipose-specific markers and maintains the expression of preadipocyte marker preadipocyte factor-1 (Pref-1) significantly elevated. These effects were not found in other time points. Microarray analysis of gene expression after GSPE treatment at the early stage of differentiation showed a modified gene expression profile in which cell cycle and growth-related genes were downregulated by GSPE.

CONCLUSION

These results suggest that GSPE affects adipogenesis, mainly at the induction of differentiation, and that procyanidins may have a new role in which they impede the formation of adipose cells.

Intracellular mediators of procyanidin-induced lipolysis in 3T3-L1 adipocytes

We have previously reported that grape seed procyanidins stimulate long-term lipolysis on 3T3-L1 fully differentiated adipocytes. To unravel the molecular mechanism by which procyanidins exert this effect, we checked the involvement of two main cellular targets in adipose cells: protein kinase A (PKA) and peroxisome proliferator-activated receptor-gamma (PPAR-gamma). Procyanidin treatment increased intracellular cAMP levels in 3T3-L1 adipocytes, and their lipolytic effect was inhibited by simultaneous treatment with H89, a PKA specific inhibitor. BRL49653, a very highly specific ligand of PPAR-gamma, totally abolished the lipolytic effect of procyanidins. Simultaneous to this long-term lipolytic effect, the mRNA levels of some differentiation adipocyte markers decreased, although there were no changes in the triglyceride content of the cells. BRL49653 did not antagonize the decrements of differentiation markers. These results support a mediation of PPAR-gamma and PKA on the lipolytic effects of procyanidins on 3T3-L1 adipocytes.

Grape seed-derived procyanidins have an antihyperglycemic effect in streptozotocin-induced diabetic rats and insulinomimetic activity in insulin-sensitive cell lines

Flavonoids are functional constituents of many fruits and vegetables. Some flavonoids have antidiabetic properties because they improve altered glucose and oxidative metabolisms of diabetic states. Procyanidins are flavonoids with an oligomeric structure, and it has been shown that they can improve the pathological oxidative state of a diabetic situation. To evaluate their effects on glucose metabolism, we administered an extract of grape seed procyanidins (PE) orally to streptozotocin-induced diabetic rats. This had an antihyperglycemic effect, which was significantly increased if PE administration was accompanied by a low insulin dose. The antihyperglycemic effect of PE may be partially due to the insulinomimetic activity of procyanidins on insulin-sensitive cell lines. PE stimulated glucose uptake in L6E9 myotubes and 3T3-L1 adipocytes in a dose-dependent manner. Like insulin action, the effect of PE on glucose uptake was sensitive to wortmannin, an inhibitor of phosphoinositol 3-kinase and to SB203580, an inhibitor of p38 MAPK. PE action also stimulated glucose transporter-4 translocation to the plasma membrane. In summary, procyanidins have insulin-like effects in insulin-sensitive cells that could help to explain their antihyperglycemic effect in vivo. These effects must be added to their antioxidant activity to explain why they can improve diabetic situations.

Antigenotoxic effect of grape seed procyanidin extract in Fao cells submitted to oxidative stress

The protective effects of grape seed procyanidin extract on the repair of H(2)O(2)-induced DNA lesions were tested using Fao cells. Cells were exposed to 600 microM H(2)O(2) for 3 or 21 h. A procyanidin extract from grape seed (PE) was incubated or preincubated (1 h) during the exposure to H(2)O(2). The ability of procyanidins to protect against the genotoxicity of H(2)O(2) was compared with those of the monomeric flavanols (+)-catechin and (-)-epicatechin and the flavonol quercetin. After treatment, DNA damage was monitored using alkaline single-cell gel electrophoresis (the comet assay) (Aherne, S. A.; O'Brien, N. M. Nutr. Cancer 1999, 34, 160-166). At the end of the experiment, PE significantly decreased the damage caused by H(2)O(2). The results also showed that quercetin was the most effective of the flavonoids tested, which is consistent with its powerful antioxidant character. The results indicate that procyanidins are more effective than the corresponding individual monomers, catechin and epicatechin, at preventing DNA lesions in hepatocytes and that this protection is higher after preincubation than after co-incubation.

Procyanidins protect Fao cells against hydrogen peroxide-induced oxidative stress

In this paper, we evaluate the extent to which flavonoids in red wine (catechin, epicatechin, quercetin and procyanidins) protect against hydrogen peroxide-induced oxidative stress in Fao cells. When cells were exposed to H(2)O(2), malondialdehyde (MDA) levels, oxidized glutathione (GSSG) levels and lactate dehydrogenase (LDH) release increased, indicating membrane damage and oxidative stress. All the flavonoids studied, and in particular epicatechin and quercetin, protected the plasma membrane. Only procyanidins lowered MDA levels and LDH leakage, maintained a higher reduced/oxidized glutathione ratio, and increased catalase/superoxide dismutase and glutathione peroxidase/superoxide dismutase ratios, and glutathione reductase and glutathione transferase activities. These results show that the procyanidin mixture has a greater antioxidant effect than the individual flavonoids studied, probably due to its oligomer content and/or the additive/synergistic effect of its compounds. This suggests that the mixture of flavonoids found in wine has a greater effect than individual phenols, which may explain many of the healthy effects attributed to wine.

Human apo A-I and rat transferrin are the principal plasma proteins that bind wine catechins

The processes of absorption, blood transport, tissular distribution, metabolism, and excretion are at present understood very little. The aim of this study was to investigate blood transport and identify which principal plasma proteins in humans and rats bind to monomeric catechin and procyanidins in red wine ex vivo. Human and rat plasma and serum were incubated with (+)-catechin and procyanidins from grape seed, the origin of red wine catechins. Proteins were separated by SDS-PAGE and native-PAGE to determine which proteins bound to these compounds. The principal protein that bound to (+)-catechin in each species was sequenced. SDS-PAGE showed that (+)-catechin and procyanidins mainly bound to a protein of about 80 kDa in rats and 35 kDa in humans. Their sequencing indicated that these proteins were apo A-I in humans and transferrin in rats. The fact that red wine procyanidins bind to both proteins suggests that they may have a role in reverse cholesterol transport and in the oxidizing action of iron.

Nonalcoholic components in wine reduce low density lipoprotein cholesterol in normocholesterolemic rats

Using an experimental model that enables the effects of alcohol to be distinguished from the effects of the nonalcoholic components present in wine, we determined whether wine has effects other than those of alcohol on the metabolism of cholesterol. Male rats were fed a standard diet and had free access to water and either wine or an equivalent alcohol solution for 45 d or 6 mon. Alcohol intake was similar in the two groups of animals. Consumption of the alcohol solution or wine did not influence plasma cholesterol or high density lipoprotein-cholesterol. At 45 d, the consumption both of wine and of alcohol solution reduced low density lipoprotein (LDL)-cholesterol and very low density lipoprotein cholesterol. At 6 mon, only the rats that consumed wine had reduced LDL-cholesterol. After 45 d of consuming alcohol solution, total cholesterol in the aorta was significantly increased mainly as a result of the rise in free cholesterol. In the aorta, the effect of wine consumption was similar to the effect of alcohol solution consumption, although it was less intense. The only clear effect that could be ascribed to the nonalcoholic components in wine was that the LDL-cholesterol was reduced in the long term, although aortic cholesterol was not.

Changes in lipolysis and hormone-sensitive lipase expression caused by procyanidins in 3T3-L1 adipocytes

OBJECTIVE

To find out whether lipid stores are influenced by phenolic compounds in wine.

DESIGN

Differentiated 3T3-L1 cells were treated with catechin, epicatechin or procyanidin extracts with different degrees of polymerization at 150 microM for different periods of time (0.5-24 h).

SUBJECTS

Cell line 3T3-L1.

MEASUREMENTS

Cellular viability, glycerol-3-phosphate dehydrogenase activity, glycerol release in the medium, HSL mRNA levels, triacylglycerols and protein.

RESULTS

Catechin, epicatechin and procyanidin extracts were not toxic for the 3T3-L1 cells in the conditions assayed. Glycerol-3-phosphate dehydrogenase activity was markedly decreased by 150 microM procyanidin extracts. The release of glycerol into the medium was increased in 150 microM procyanidin extract-treated cells and reached a plateau after 15 h exposure. Procyanidins caused a time-dependent reduction in the HSL mRNA levels.

CONCLUSIONS

These results suggest that procyanidins from grape and wine affect lipid metabolism whilst their monomers (catechin and epicatechin) do not. This effect is more pronounced when the degree of polymerization is higher. Procyanidin extracts cause a time-dependent reduction in the HSL mRNA levels, inhibit triacylglycerol synthesis and also favour triacylglycerol hydrolysis until the HSL mRNA had reached very low levels.

Moderate red wine consumption protects the rat against oxidation in vivo

The effect of the moderate consumption of red wine on the antioxidant system in rat liver, kidney and plasma has been evaluated. Wistar rats were treated in separate groups as follows: control; red wine for 45 days or 6 months; and 13.5% ethanol for 45 days or 6 months. The consumption of alcoholic beverages was free because the rat could always choose between the alcoholic beverage and the water. In liver, red wine ingestion resulted in higher hepatic superoxide dismutase and glutathione peroxidase activities after 45 days of treatment. The data indicate that wine and ethanol ingestion resulted in lower hepatic malondialdehyde and enhanced hepatic catalase activity in both of the periods studied. In kidney, the reduced glutathione/oxidized glutathione ratio was higher after 45 days of wine consumption, and the malondialdehyde was lower after 6 months of wine consumption. In plasma, malondialdehyde was lower after 6 months of both treatments, but plasmatic vitamin E was higher after red wine consumption while it was lower after ethanol consumption for this period of time. The present study shows that the moderate and prolonged consumption of red wine is consistent with higher protection against oxidation in vivo.

Model for voluntary wine and alcohol consumption in rats

It has been suggested that moderate consumption of ethanol and wine has a protective effect on human health. Animal models used to date for alcohol consumption can not mimic real situations in humans because the consumption is forced and/or excessive. The present study proposes to determine the effects of a voluntary and ad lib consumption model more similar to that of human behavior. Male Wistar rats had free access to either standard diet and water or the same diet plus red wine, sweet wine, or a solution equivalent to red wine (13.5% ethanol) or to sweet wine (20% ethanol + 130 g/L sucrose) for 30 days or 6 months. Daily wine consumption was 15.8 +/- 0.9 and 2.0 +/- 0.2 ml/day for sweet and red wines, respectively. The consumption of each of the alcoholic solutions was similar to that of the wine they were simulating. Drinking wine or ethanol did not affect food and water intakes or growth rate. Plasma metabolites were not substantially affected by consumption of wine or ethanol. Although moderate and high wine consumption did not change the activity of plasma marker enzymes of tissue damage, the consumption of the 2 alcoholic solutions caused a long-term increase in the activity of aspartate aminotransferase. It seems that wine consumption protects the organism from hepatic lesions induced by ethanol alone.

Plasma amino acids in hyperphagic pups subjected to a glucose gavage

An oral gavage of either glucose or saline was given to pups fed either standard diet or cafeteria diet. The plasma amino acid concentrations were measured by a radiochemical method. In the standard diet group, plasma Asn+Asp, Thr, Pro, Cit, Trp and Phe levels were higher in rats receiving a glucose solution than in those given saline solution; taurine (on day 20) and Ser (on day 30) showed also higher plasma values. Plasma Arg and taurine levels in rats receiving glucose were lower than those in rats receiving saline when these pups were fed the cafeteria diet. Tyr (on day 20) and Gly and Pro (on day 30), showed decreased plasma values. The diet consumed during the days preceding a glucose gavage may have pronounced effects on several metabolites, particularly on nitrogen metabolism. The homeostasis of plasma amino acids was held highly constant in spite of the variety of diets supplied, indicating a remarkable homeostatic capacity on amino acidemia against dietetic manipulation.

Glutamine force-feeding effect on plasma amino-acid concentrations in growing rats fed a cafeteria diet

The effect of a glutamine force-feeding on plasma amino-acid levels in rats fed either a reference diet or a cafeteria diet was studied during weaning. The increases in plasma amino-acid levels shown by rats eating the cafeteria diet were related to the force-feeding and/or the age studied. The glutamine solution decreased the levels of proline, ornithine and tyrosine in the plasma of rats eating the cafeteria diet. In rats fed the reference diet, glutamine solution increased the plasma concentrations of threonine and cysteine. A major effect of diet over force-feeding was shown.

The plasma amino acid response to cafeteria feeding and essential-amino acid gavage in weaning rats

The plasma amino acid concentrations of cafeteria-fed and standard-fed rats gavaged either an essential amino acid mixture or saline solution have been studied from 14 to 30 days after birth. The consumption of a cafeteria diet caused higher levels in many amino acids. The amino acid-gavaged cafeteria-fed rats showed the highest cysteine levels. The amino acid gavage produced lower concentrations of alanine, glutamate+glutamine, hydroxyproline, proline and ornithine, in both cafeteria-fed and standard-fed animals. The results show that the supply of amino acids has a positive effect on nitrogen retention and amino acid availability in cafeteria-fed pups.

Postnatal development of plasma amino acids in hyperphagic rats

The effect of feeding a highly palatable high-energy cafeteria diet on individual amino acid levels in plasma during postnatal development of the rat has been evaluated and compared to chow-fed controls. The cafeteria diet selected by the rats was hypercaloric and hyperlipidic, with practically the same amount of carbohydrate as the control diet, and slightly hyperproteic. In response to cafeteria feeding, significant decreases were observed in plasma serine and cysteine along the period studied. Significant changes with age during the growth period were shown by cafeteria-fed animals, which were not observed in control rats. Citrulline levels were lower on days 10 and 14 in cafeteria pups than in chow pups. Methionine was highest on day 30. Threonine was also higher at days 20 and 30, as was valine but with a nadir at day 10. Lysine showed maximal values on days 14 and 30.