To determine whether proanthocyanidins can protect against dyslipidemia induced by a high-fat die... more To determine whether proanthocyanidins can protect against dyslipidemia induced by a high-fat diet (HFD) and to address the mechanisms that underlie this hypolipidemic effect. Female Wistar rats were fed on a HFD for 13 weeks. They were divided into two groups, one of which was treated with a grape seed proanthocyanidin extract (25 mg kg(-1) of body weight) for 10 days. Plasma and liver lipids were measured by colorimetric and gravimetric analysis. Liver, muscle and adipose tissue were used to study the expression of genes involved in the synthesis and oxidation of fatty acids and lipoprotein homeostasis by real-time RT-PCR. The administration of proanthocyanidins normalized plasma triglyceride and LDL-cholesterol (both parameters significantly increased with the HFD) but tended to decrease hypercholesterolemia and fatty liver. Gene expression analyses revealed that proanthocyanidins repressed both the expression of hepatic key regulators of lipogenesis and very low density lipoprotein (VLDL) assembling such as SREBP1, MTP and DGAT2, all of which were overexpressed by the HFD. These findings indicate that natural proanthocyanidins improve dyslipidemia associated with HFDs, mainly by repressing lipogenesis and VLDL assembly in the liver, and support the idea that they are powerful agents for preventing and treating lipid altered metabolic states.
Critical Reviews in Food Science and Nutrition, 2012
This review analyses the potential beneficial effects of procyanidins, the main class of flavonoi... more This review analyses the potential beneficial effects of procyanidins, the main class of flavonoids, in situations in which glucose homeostasis is disrupted. Because the disruption of glucose homeostasis can occur as a result of various causes, we critically review the effects of procyanidins based on the specific origin of each type of disruption. Where little or no insulin is present (Type I diabetic animals), summarized studies of procyanidin treatment suggest that procyanidins have a short-lived insulin-mimetic effect on the internal targets of the organism, an effect not reproduced in normoglycemic, normoinsulinemic healthy animals. Insulin resistance (usually linked to hyperinsulinemia) poses a very different situation. Preventive studies using fructose-fed models indicate that procyanidins may be useful in preventing the induction of damage and thus in limiting hyperglycemia. But the results of other studies using models such as high-fat diet treated rats or genetically obese animals are controversial. Although the effects on glucose parameters are hazy, it is known that procyanidins target key tissues involved in its homeostasis. Interestingly, all available data suggest that procyanidins are more effective when administered in one acute load than when mixed with food.
Flavonoids are beneficial compounds against risk factors for metabolic syndrome, but their effect... more 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.
We have developed a method for reconstructing gene association networks and have applied this met... more We have developed a method for reconstructing gene association networks and have applied this method to gene profiles from 3T3-L1 cells. Priorization of the candidate genes pinpointed a transcript annotated as APMAP (adipocyte plasma membrane-associated protein). Functional studies showed that APMAP is upregulated in murine and human adipogenic cell models as well as in a genetic mouse model of obesity. Silencing APMAP in 3T3-L1 cells strongly impaired the differentiation into adipocytes. Moreover, APMAP expression was strongly induced by the PPARγ ligand rosiglitazone in adipocytes in vitro and in vivo in adipose tissue. Using ChIP-qPCR and luciferase reporter assays, we show a functional PPARγ binding site. In addition, we provide evidence that the extracellular C-terminal domain of APMAP is required for the function of APMAP in adipocyte differentiation. Finally, we demonstrate that APMAP translocates from the endoplasmatic reticulum to the plasma membrane during adipocyte differentiation.
Comprehensive Reviews in Food Science and Food Safety, 2008
ABSTRACT: Flavonoids are usually found in fruits and other plant organs and therefore widely con... more ABSTRACT: Flavonoids are usually found in fruits and other plant organs and therefore widely consumed. They are antioxidants, anti-inflammatory, anticarcinogenic, and protective against coronary disease and metabolic disorders. These beneficial effects make them good candidates for the development of new functional foods with potential protective/preventive properties against several diseases. We must consider that this fact could lead to a higher intake of some of these flavonoids. Most of the studies concerning their beneficial effects showed peripheral activity of these molecules, but there is no clear information about their central effects on a key organ on metabolic control: the endocrine pancreas. The pancreas has an endocrine function of major importance to regulate nutrient metabolism, such as control of glucose homeostasis via insulin and glucagon secretion. Its importance in whole body nutrient equilibrium is highlighted by the fact that several pathologies, such as type 1 and/or 2 diabetes, are related at some point to a pancreatic cell deregulation. In this review, we compile the most relevant results concerning the effects of flavonoids on several aspects of pancreatic functionality. Studies using animals with drug-induced diabetes support the hypothesis that flavonoids can ameliorate this pathogenesis. The great diversity of flavonoid structures makes it difficult to establish common effects in the pancreas. Published data suggest that there might be direct effects of flavonoids on insulin secretion, as well as on prevention of beta-cell apoptosis, and they could even act via modulation of proliferation. The mechanisms of action involve mainly their antioxidant properties, but other pathways might also take place.
... Insulin (Actrapid) was from Novo Nordisk. Bradford protein reagent was from Bio-Rad Laborator... more ... Insulin (Actrapid) was from Novo Nordisk. Bradford protein reagent was from Bio-Rad Laboratories. ... Glucose transport values were corrected for protein content, which was determined by the Bradford method (Bradford, 1976). Each condition was run in triplicate. 2.7. ...
Critical Reviews in Food Science and Nutrition, 2011
This review analyses the potential beneficial effects of procyanidins, the main class of flavonoi... more This review analyses the potential beneficial effects of procyanidins, the main class of flavonoids, in situations in which glucose homeostasis is disrupted. Because the disruption of glucose homeostasis can occur as a result of various causes, we critically review the effects of procyanidins based on the specific origin of each type of disruption. Where little or no insulin is present (Type I diabetic animals), summarized studies of procyanidin treatment suggest that procyanidins have a short-lived insulin-mimetic effect on the internal targets of the organism, an effect not reproduced in normoglycemic, normoinsulinemic healthy animals. Insulin resistance (usually linked to hyperinsulinemia) poses a very different situation. Preventive studies using fructose-fed models indicate that procyanidins may be useful in preventing the induction of damage and thus in limiting hyperglycemia. But the results of other studies using models such as high-fat diet treated rats or genetically obese animals are controversial. Although the effects on glucose parameters are hazy, it is known that procyanidins target key tissues involved in its homeostasis. Interestingly, all available data suggest that procyanidins are more effective when administered in one acute load than when mixed with food.
Natural plant extracts are candidates for the development of new functional foods. Most of them a... more Natural plant extracts are candidates for the development of new functional foods. Most of them are usually complex mixtures of molecules of uncertain bioavailability that are often partially metabolized before they finally reach the target cells IN VIVO. IN VITRO studies of the bioactivity of these extracts suggest that their direct application to some cell cultures might be a long way from becoming a reality. To overcome this limitation, we seeded Caco-2 cells onto culture inserts and after 21 days, cocultured these with INS-1E on the base of the well. After 24 hours of coculture, TEER (transepithelium electrical resistance) measurements indicated no changes in the permeability of the Caco-2 barrier. We also found no changes in either the ability of Caco-2 cells to metabolize the flavan-3-ol component of a grape-seed procyanidin-rich extract, or in the flavanols' ability to pass through the barrier. However, the expression of the Caco-2 SGLT-1 gene increased due to the coculture. GSIS (glucose stimulated insulin secretion) was maintained in the INS-1E cells with higher levels of insulin secretion despite the fact that the insulin gene expression was unmodified by the cocultivation. Furthermore, we found that in some of the assays requiring several medium changes there was a tendency to lose β-cells. Neutral red assay showed that seeded cells should only be cocultured for a short time to obtain a higher consistency. In conclusion, four hours coculture with Caco-2 cells and INS-1E is a suitable method for checking the bioactivity of natural plant extracts of unknown bioavailability on β-cells.
Procyanidins are bioactive flavonoid compounds from fruits and vegetables that possess insulinomi... more 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.
To determine whether proanthocyanidins can protect against dyslipidemia induced by a high-fat die... more To determine whether proanthocyanidins can protect against dyslipidemia induced by a high-fat diet (HFD) and to address the mechanisms that underlie this hypolipidemic effect. Female Wistar rats were fed on a HFD for 13 weeks. They were divided into two groups, one of which was treated with a grape seed proanthocyanidin extract (25 mg kg(-1) of body weight) for 10 days. Plasma and liver lipids were measured by colorimetric and gravimetric analysis. Liver, muscle and adipose tissue were used to study the expression of genes involved in the synthesis and oxidation of fatty acids and lipoprotein homeostasis by real-time RT-PCR. The administration of proanthocyanidins normalized plasma triglyceride and LDL-cholesterol (both parameters significantly increased with the HFD) but tended to decrease hypercholesterolemia and fatty liver. Gene expression analyses revealed that proanthocyanidins repressed both the expression of hepatic key regulators of lipogenesis and very low density lipoprotein (VLDL) assembling such as SREBP1, MTP and DGAT2, all of which were overexpressed by the HFD. These findings indicate that natural proanthocyanidins improve dyslipidemia associated with HFDs, mainly by repressing lipogenesis and VLDL assembly in the liver, and support the idea that they are powerful agents for preventing and treating lipid altered metabolic states.
Critical Reviews in Food Science and Nutrition, 2012
This review analyses the potential beneficial effects of procyanidins, the main class of flavonoi... more This review analyses the potential beneficial effects of procyanidins, the main class of flavonoids, in situations in which glucose homeostasis is disrupted. Because the disruption of glucose homeostasis can occur as a result of various causes, we critically review the effects of procyanidins based on the specific origin of each type of disruption. Where little or no insulin is present (Type I diabetic animals), summarized studies of procyanidin treatment suggest that procyanidins have a short-lived insulin-mimetic effect on the internal targets of the organism, an effect not reproduced in normoglycemic, normoinsulinemic healthy animals. Insulin resistance (usually linked to hyperinsulinemia) poses a very different situation. Preventive studies using fructose-fed models indicate that procyanidins may be useful in preventing the induction of damage and thus in limiting hyperglycemia. But the results of other studies using models such as high-fat diet treated rats or genetically obese animals are controversial. Although the effects on glucose parameters are hazy, it is known that procyanidins target key tissues involved in its homeostasis. Interestingly, all available data suggest that procyanidins are more effective when administered in one acute load than when mixed with food.
Flavonoids are beneficial compounds against risk factors for metabolic syndrome, but their effect... more 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.
We have developed a method for reconstructing gene association networks and have applied this met... more We have developed a method for reconstructing gene association networks and have applied this method to gene profiles from 3T3-L1 cells. Priorization of the candidate genes pinpointed a transcript annotated as APMAP (adipocyte plasma membrane-associated protein). Functional studies showed that APMAP is upregulated in murine and human adipogenic cell models as well as in a genetic mouse model of obesity. Silencing APMAP in 3T3-L1 cells strongly impaired the differentiation into adipocytes. Moreover, APMAP expression was strongly induced by the PPARγ ligand rosiglitazone in adipocytes in vitro and in vivo in adipose tissue. Using ChIP-qPCR and luciferase reporter assays, we show a functional PPARγ binding site. In addition, we provide evidence that the extracellular C-terminal domain of APMAP is required for the function of APMAP in adipocyte differentiation. Finally, we demonstrate that APMAP translocates from the endoplasmatic reticulum to the plasma membrane during adipocyte differentiation.
Comprehensive Reviews in Food Science and Food Safety, 2008
ABSTRACT: Flavonoids are usually found in fruits and other plant organs and therefore widely con... more ABSTRACT: Flavonoids are usually found in fruits and other plant organs and therefore widely consumed. They are antioxidants, anti-inflammatory, anticarcinogenic, and protective against coronary disease and metabolic disorders. These beneficial effects make them good candidates for the development of new functional foods with potential protective/preventive properties against several diseases. We must consider that this fact could lead to a higher intake of some of these flavonoids. Most of the studies concerning their beneficial effects showed peripheral activity of these molecules, but there is no clear information about their central effects on a key organ on metabolic control: the endocrine pancreas. The pancreas has an endocrine function of major importance to regulate nutrient metabolism, such as control of glucose homeostasis via insulin and glucagon secretion. Its importance in whole body nutrient equilibrium is highlighted by the fact that several pathologies, such as type 1 and/or 2 diabetes, are related at some point to a pancreatic cell deregulation. In this review, we compile the most relevant results concerning the effects of flavonoids on several aspects of pancreatic functionality. Studies using animals with drug-induced diabetes support the hypothesis that flavonoids can ameliorate this pathogenesis. The great diversity of flavonoid structures makes it difficult to establish common effects in the pancreas. Published data suggest that there might be direct effects of flavonoids on insulin secretion, as well as on prevention of beta-cell apoptosis, and they could even act via modulation of proliferation. The mechanisms of action involve mainly their antioxidant properties, but other pathways might also take place.
... Insulin (Actrapid) was from Novo Nordisk. Bradford protein reagent was from Bio-Rad Laborator... more ... Insulin (Actrapid) was from Novo Nordisk. Bradford protein reagent was from Bio-Rad Laboratories. ... Glucose transport values were corrected for protein content, which was determined by the Bradford method (Bradford, 1976). Each condition was run in triplicate. 2.7. ...
Critical Reviews in Food Science and Nutrition, 2011
This review analyses the potential beneficial effects of procyanidins, the main class of flavonoi... more This review analyses the potential beneficial effects of procyanidins, the main class of flavonoids, in situations in which glucose homeostasis is disrupted. Because the disruption of glucose homeostasis can occur as a result of various causes, we critically review the effects of procyanidins based on the specific origin of each type of disruption. Where little or no insulin is present (Type I diabetic animals), summarized studies of procyanidin treatment suggest that procyanidins have a short-lived insulin-mimetic effect on the internal targets of the organism, an effect not reproduced in normoglycemic, normoinsulinemic healthy animals. Insulin resistance (usually linked to hyperinsulinemia) poses a very different situation. Preventive studies using fructose-fed models indicate that procyanidins may be useful in preventing the induction of damage and thus in limiting hyperglycemia. But the results of other studies using models such as high-fat diet treated rats or genetically obese animals are controversial. Although the effects on glucose parameters are hazy, it is known that procyanidins target key tissues involved in its homeostasis. Interestingly, all available data suggest that procyanidins are more effective when administered in one acute load than when mixed with food.
Natural plant extracts are candidates for the development of new functional foods. Most of them a... more Natural plant extracts are candidates for the development of new functional foods. Most of them are usually complex mixtures of molecules of uncertain bioavailability that are often partially metabolized before they finally reach the target cells IN VIVO. IN VITRO studies of the bioactivity of these extracts suggest that their direct application to some cell cultures might be a long way from becoming a reality. To overcome this limitation, we seeded Caco-2 cells onto culture inserts and after 21 days, cocultured these with INS-1E on the base of the well. After 24 hours of coculture, TEER (transepithelium electrical resistance) measurements indicated no changes in the permeability of the Caco-2 barrier. We also found no changes in either the ability of Caco-2 cells to metabolize the flavan-3-ol component of a grape-seed procyanidin-rich extract, or in the flavanols' ability to pass through the barrier. However, the expression of the Caco-2 SGLT-1 gene increased due to the coculture. GSIS (glucose stimulated insulin secretion) was maintained in the INS-1E cells with higher levels of insulin secretion despite the fact that the insulin gene expression was unmodified by the cocultivation. Furthermore, we found that in some of the assays requiring several medium changes there was a tendency to lose β-cells. Neutral red assay showed that seeded cells should only be cocultured for a short time to obtain a higher consistency. In conclusion, four hours coculture with Caco-2 cells and INS-1E is a suitable method for checking the bioactivity of natural plant extracts of unknown bioavailability on β-cells.
Procyanidins are bioactive flavonoid compounds from fruits and vegetables that possess insulinomi... more 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.
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