Effective Tetradentate Compound Complexes against Leishmania spp. that Act on Critical Enzymatic Pathways of These Parasites.

The spectrum and efficacy of available antileishmanial drugs is limited. In the present work we evaluated in vitro the antiproliferative activity of 11 compounds based on tetradentate polyamines compounds against three Leishmania species (L. braziliensis, L. donovani and L. infantum) and the possible mechanism of action. We identified six compounds (3, 5, 6, 7, 8 and 10) effective against all three Leishmania spp both on extracellular and intracellular forms. These six most active leishmanicidal compounds also prevent the infection of host cells. Nevertheless, only compound 7 is targeted against the Leishmania SOD. Meanwhile, on the glucose metabolism the tested compounds have a species-specific effect on Leishmania spp.: L. braziliensis was affected mainly by 10 and 8, L. donovani by 7, and L. infantum by 5 and 3. Finally, the cellular ultrastructure was mainly damaged by 11 in the three Leishmania spp. studied. These identified antileishmania candidates constitute a good alternative treatment and will be further studied.

Effects of flavanols on the enteroendocrine system: Repercussions on food intake.

Flavanols are plant-derived bioactive compounds for which several beneficial effects have been described. When ingested, they reach the gastrointestinal tract, where they can interact with the enteroendocrine cells. In this paper, we consider the possibility that flavanols modulate enterohormone secretion. Because the regulation of food intake is among the principal functions of the hormones that are secreted in the gastrointestinal tract, we also compile the literature that covers how the effects of flavanols on food intake are measured. Although there are some papers showing the effects of flavanols on the regulation of enterohormones, there are very few papers that have addressed the specific effects at the food intake level. Instead, most of the findings are secondary to the study of the action of flavanols on body weight, which makes it difficult to reach a clear conclusion regarding the effects of flavanols on food intake.

A specific dose of grape seed-derived proanthocyanidins to inhibit body weight gain limits food intake and increases energy expenditure in rats.

PURPOSE: Several studies have suggested that flavanols may have antiobesity effects; however, those effects clearly depend on the experimental conditions. In a previous study, we found that a single acute dose of grape seed proanthocyanidin extract (GSPE) has satiating effects. We therefore hypothesise that satiating doses of GSPE could be used to reduce body weight gain, and our present objective was to define the most effective dose. METHODS: We assayed two GSPE doses in aged male Wistar rats. First we performed a subchronic (8-day) treatment by intragastric administration, which was repeated after a washout period. We measured body weight, energy intake and faeces composition; we performed indirect calorimetry; and we analysed the mRNA expression of genes involved in lipid metabolism to determine the target tissue for the GSPE. RESULTS: We observed that 0.5 g GSPE/kg BW significantly reduced food intake and thus the amount of energy absorbed. This dosage also increased lipid oxidation in subcutaneous adipose tissue, thus causing a higher total energy expenditure. These combined effects caused a decrease in body weight. Conversely, 1 g GSPE/kg BW, which also reduced energy absorption after the first treatment, had a rebound effect on body weight gain which resulted in a lower response to the proanthocyanidin extract. That is, after the second treatment, the GSPE did not reduce the energy absorbed or modify energy expenditure and body weight. CONCLUSION: GSPE at a dose of 0.5 g/kg can reduce body weight by limiting food intake and activating energy expenditure in subcutaneous adipose tissue.

Antioxidant effects of proanthocyanidin-rich natural extracts from grape seed and cupuassu on gastrointestinal mucosa.

BACKGROUND: The gastrointestinal tract (GI) is constantly exposed to reactive species released by the GI tract itself, and those present in food and beverages. Phenolic compounds may help in protecting the GI tract against damage produced by the reactive species. In this paper we have analyzed the effects of a grape seed proanthocyanidin extract (GSPE) on reactive oxygen species (ROS) production in two different intestinal cell types: the absorptive cell line Caco-2 and the enteroendocrine cell line STC-1. RESULTS: We show that GSPE prevents tert-butylhydroperoxide-induced oxidative stress in both cell lines, and that the effects are dose and time dependent. We have also analyzed whether GSPE has any in vivo effect, and found that 25 mg kg(-1) body weight cannot counteract the increase in intestinal ROS induced by the cafeteria diet. However, an acute (1 h) treatment of 1 g GSPE kg(-1) body weight reduced ROS in fasted animals and also decreased ROS induction by food. These effects were found only after a short-term treatment. Furthermore, we have compared the in vitro GSPE effects with those of another proanthocyanidin-rich extract from cupuassu seeds, though it has compounds with different structures. Cupuassu extract also shows antioxidant effects in both cell types, which suggests different mechanisms from those of GSPE. CONCLUSION: Natural proanthocyanidin-rich extracts have an antioxidant effect in the GI tract, acting on absorptive cells and enterohormone-secreting cells, although the effects depend on the dose and period of treatment. © 2015 Society of Chemical Industry.

The TAS1R2 G-protein-coupled receptor is an ambient glucose sensor in skeletal muscle that regulates NAD homeostasis and mitochondrial capacity.

The bioavailability of nicotinamide adenine dinucleotide (NAD) is vital for skeletal muscle health, yet the mechanisms or signals regulating NAD homeostasis remain unclear. Here, we uncover a pathway connecting peripheral glucose sensing to the modulation of muscle NAD through TAS1R2, the sugar-sensing G protein-coupled receptor (GPCR) initially identified in taste perception. Muscle TAS1R2 receptor stimulation by glucose and other agonists induces ERK1/2-dependent phosphorylation and activation of poly(ADP-ribose) polymerase1 (PARP1), a major NAD consumer in skeletal muscle. Consequently, muscle-specific deletion of TAS1R2 (mKO) in male mice suppresses PARP1 activity, elevating NAD levels and enhancing mitochondrial capacity and running endurance. Plasma glucose levels negatively correlate with muscle NAD, and TAS1R2 receptor deficiency enhances NAD responses across the glycemic range, implicating TAS1R2 as a peripheral energy surveyor. These findings underscore the role of GPCR signaling in NAD regulation and propose TAS1R2 as a potential therapeutic target for maintaining muscle health.

The TAS1R2 sweet taste receptor regulates skeletal muscle mass and fitness.

Muscle fitness and mass deteriorate under the conditions of obesity and aging for reasons yet to be fully elucidated. Herein, we describe a novel pathway linking peripheral nutrient sensing and skeletal muscle function through the sweet taste receptor TAS1R2 and the involvement of ERK2-PARP1-NAD signaling axis. Muscle-specific deletion of TAS1R2 (mKO) in mice produced elevated NAD levels due to suppressed PARP1 activity, improved mitochondrial function, increased muscle mass and strength, and prolonged running endurance. Deletion of TAS1R2 in obese or aged mice also ameliorated the decline in muscle mass and fitness arising from these conditions. Remarkably, partial loss-of-function of TAS1R2 (rs35874116) in older, obese humans recapitulated the healthier muscle phenotype displayed by mKO mice in response to exercise training. Our findings show that inhibition of the TAS1R2 signaling in skeletal muscle is a promising therapeutic approach to preserve muscle mass and function.

The Ile191Val Variant of the TAS1R2 Subunit of Sweet Taste Receptors Is Associated With Reduced HbA1c in a Human Cohort With Variable Levels of Glucose Homeostasis.

The Ile191Val variant of the TAS1R2 gene of sweet taste receptors causes a partial loss-of-function and is associated with reduced glucose excursions in a healthy lean cohort. However, it is unclear whether this polymorphism contributes to the regulation of glucose homeostasis in metabolically unhealthy individuals. Thus, we used participants with variable glycemic profiles and obesity to assess the effects of the TAS1R2-Ile191Val variant. We found that the Val minor allele carriers had lower HbA1c at all levels of fasting glucose and glucose tolerance. These effects were not due to differences in beta-cell function or insulin sensitivity assessed with a frequently sampled intravenous glucose tolerance test. This study extends our previous findings and provides further evidence that sweet taste receptor function may contribute to glucose regulation in humans.

Saccharin Stimulates Insulin Secretion Dependent on Sweet Taste Receptor-Induced Activation of PLC Signaling Axis.

BACKGROUND: Saccharin is a common artificial sweetener and a bona fide ligand for sweet taste receptors (STR). STR can regulate insulin secretion in beta cells, so we investigated whether saccharin can stimulate insulin secretion dependent on STR and the activation of phospholipase C (PLC) signaling. METHODS: We performed in vivo and in vitro approaches in mice and cells with loss-of-function of STR signaling and specifically assessed the involvement of a PLC signaling cascade using real-time biosensors and calcium imaging. RESULTS: We found that the ingestion of a physiological amount of saccharin can potentiate insulin secretion dependent on STR. Similar to natural sweeteners, saccharin triggers the activation of the PLC signaling cascade, leading to calcium influx and the vesicular exocytosis of insulin. The effects of saccharin also partially require transient receptor potential cation channel M5 (TRPM5) activity. CONCLUSIONS: Saccharin ingestion may transiently potentiate insulin secretion through the activation of the canonical STR signaling pathway. These physiological effects provide a framework for understanding the potential health impact of saccharin use and the contribution of STR in peripheral tissues.

Cardiac-derived TGF-ß1 confers resistance to diet-induced obesity through the regulation of adipocyte size and function.

Regulation of organismal homeostasis in response to nutrient availability is a vital physiological process that involves inter-organ communication. Understanding the mechanisms controlling systemic cross-talk for the maintenance of metabolic health is critical to counteract diet-induced obesity. Here, we show that cardiac-derived transforming growth factor beta 1 (TGF-ß1) protects against weight gain and glucose intolerance in mice subjected to high-fat diet. Secretion of TGF-ß1 by cardiomyocytes correlates with the bioavailability of this factor in circulation. TGF-ß1 prevents adipose tissue inflammation independent of body mass and glucose metabolism phenotypes, indicating protection from adipocyte dysfunction-driven immune cell recruitment. TGF-ß1 alters the gene expression programs in white adipocytes, favoring their fatty acid oxidation and consequently increasing their mitochondrial oxygen consumption rates. Ultimately, subcutaneous and visceral white adipose tissue from cadiac-specific TGF-ß1 transgenic mice fail to undergo cellular hypertrophy, leading to reduced overall adiposity during high-fat feeding. Thus, TGF-ß1 is a critical mediator of heart-fat communication for the regulation of systemic metabolism.

The Ile191Val is a partial loss-of-function variant of the TAS1R2 sweet-taste receptor and is associated with reduced glucose excursions in humans.

OBJECTIVE: Sweet taste receptors (STR) are expressed in the gut and other extra-oral tissues, suggesting that STR-mediated nutrient sensing may contribute to human physiology beyond taste. A common variant (Ile191Val) in the TAS1R2 gene of STR is associated with nutritional and metabolic outcomes independent of changes in taste perception. It is unclear whether this polymorphism directly alters STR function and how it may contribute to metabolic regulation. METHODS: We implemented a combination of in vitro biochemical approaches to decipher the effects of TAS1R2 polymorphism on STR function. Then, as proof-of-concept, we assessed its effects on glucose homeostasis in apparently healthy lean participants. RESULTS: The Ile191Val variant causes a partial loss of function of TAS1R2 through reduced receptor availability in the plasma membrane. Val minor allele carriers have reduced glucose excursions during an OGTT, mirroring effects previously seen in mice with genetic loss of function of TAS1R2. These effects were not due to differences in beta-cell function or insulin sensitivity. CONCLUSIONS: Our pilot studies on a common TAS1R2 polymorphism suggest that STR sensory function in peripheral tissues, such as the intestine, may contribute to the regulation of metabolic control in humans.

High-dose saccharin supplementation does not induce gut microbiota changes or glucose intolerance in healthy humans and mice.

BACKGROUND: Non-caloric artificial sweeteners (NCAS) are widely used as a substitute for dietary sugars to control body weight or glycemia. Paradoxically, some interventional studies in humans and rodents have shown unfavorable changes in glucose homeostasis in response to NCAS consumption. The causative mechanisms are largely unknown, but adverse changes in gut microbiota have been proposed to mediate these effects. These findings have raised concerns about NCAS safety and called into question their broad use, but further physiological and dietary considerations must be first addressed before these results are generalized. We also reasoned that, since NCAS are bona fide ligands for sweet taste receptors (STRs) expressed in the intestine, some metabolic effects associated with NCAS use could be attributed to a common mechanism involving the host. RESULTS: We conducted a double-blind, placebo-controlled, parallel arm study exploring the effects of pure saccharin compound on gut microbiota and glucose tolerance in healthy men and women. Participants were randomized to placebo, saccharin, lactisole (STR inhibitor), or saccharin with lactisole administered in capsules twice daily to achieve the maximum acceptable daily intake for 2 weeks. In parallel, we performed a 10-week study administering pure saccharin at a high dose in the drinking water of chow-fed mice with genetic ablation of STRs (T1R2-KO) and wild-type (WT) littermate controls. In humans and mice, none of the interventions affected glucose or hormonal responses to an oral glucose tolerance test (OGTT) or glucose absorption in mice. Similarly, pure saccharin supplementation did not alter microbial diversity or composition at any taxonomic level in humans and mice alike. No treatment effects were also noted in readouts of microbial activity such as fecal metabolites or short-chain fatty acids (SCFA). However, compared to WT, T1R2-KO mice were protected from age-dependent increases in fecal SCFA and the development of glucose intolerance. CONCLUSIONS: Short-term saccharin consumption at maximum acceptable levels is not sufficient to alter gut microbiota or induce glucose intolerance in apparently healthy humans and mice. TRIAL REGISTRATION: Trial registration number NCT03032640 , registered on January 26, 2017. Video abstract.

Long Term Exposure to a Grape Seed Proanthocyanidin Extract Enhances L-Cell Differentiation in Intestinal Organoids.

SCOPE: A grape-seed proanthocyanidin extract (GSPE) interacts at the intestinal level, enhancing glucagon-like peptide-1 (GLP-1) and peptide YY (PYY) release, which modulate appetite and glucose homeostasis. Thus, enhancing L-cell numbers could be a strategy to promote hormone production, providing a potential strategy for obesity and type-2 diabetes mellitus (T2DM) treatment. METHODS AND RESULTS: Mice ileum organoids are used to evaluate the long-term effects of GSPE and two of its main components, epicatechin (EC) and gallic acid (GA), on intestinal differentiation. Hormone levels are determined using RIA and ELISA kits, and gene expression of transcription factors involved in intestinal cell differentiation, as well as markers of different cell types, are assessed by real-time qPCR. GSPE upregulates enterohormone gene expression and content, as well as the pan-endocrine marker chromogranin A. GSPE also modulates the temporal gene expression profile of early and late transcription factors involved in L-cell differentiation. Furthermore, GSPE upregulates goblet cell (Muc2) and enterocyte (sucraseisomaltase) markers, while downregulating stem cell markers (Lgr5+). Although EC and GA modified enterohormone release, they do not reproduce GSPE effects on transcription factor's profile. CONCLUSIONS: This study shows the potential role of GSPE in promoting enteroendocrine differentiation, effect that is not mediated by EC or GA.

Antihyperglycemic effect of a chicken feet hydrolysate via the incretin system: DPP-IV-inhibitory activity and GLP-1 release stimulation.

Herein, the potential of hydrolysates of chicken feet proteins as natural dipeptidyl-peptidase IV (DPP-IV) inhibitors was investigated; moreover, three hydrolysates were selected due to their high DPP-IV inhibitory capacity (>80% inhibition), showing the IC50 values of around 300 µg estimated protein per mL; one of them (named p4H) was selected for the posterior analysis. In addition, its effect on glucose tolerance was investigated in two rat models (diet and age-induced) of glucose-intolerance and healthy animals; the amount of 300 mg estimated peptide per kg body weight improved the plasma glucose profile in both glucose-intolerance models. Moreover, it stimulated active GLP-1 release in the enteroendocrine STC-1 cells and rat ileum tissue. In conclusion, our results indicate that chicken feet proteins are a good source of bioactive peptides as DPP-IV inhibitors. Moreover, our results highlight the potential of the selected hydrolysate p4H in the management of type 2 diabetes due to its dual function of inhibition of the DPP-IV activity and induction of the GLP-1 release.

Proanthocyanidins Limit Adipose Accrual Induced by a Cafeteria Diet, Several Weeks after the End of the Treatment.

A dose of proanthocyanidins with satiating properties proved to be able to limit body weight increase several weeks after administration under exposure to a cafeteria diet. Here we describe some of the molecular targets and the duration of the effects. We treated rats with 500 mg grape seed proanthocyanidin extract (GSPE)/kg BW for ten days. Seven or seventeen weeks after the last GSPE dose, while animals were on a cafeteria diet, we used reverse transcriptase-polymerase chain reaction (RT-PCR) to measure the mRNA of the key energy metabolism enzymes from the liver, adipose depots and muscle. We found that a reduction in the expression of adipose Lpl might explain the lower amount of adipose tissue in rats seven weeks after the last GSPE dose. The liver showed increased expression of Cpt1a and Hmgs2 together with a reduction in Fasn and Dgat2. In addition, muscle showed a higher fatty oxidation (Oxct1 and Cpt1b mRNA). However, after seventeen weeks, there was a completely different gene expression pattern. At the conclusion of the study, seven weeks after the last GSPE administration there was a limitation in adipose accrual that might be mediated by an inhibition of the gene expression of the adipose tissue Lpl. Concomitantly there was an increase in fatty acid oxidation in liver and muscle.

Grape seed proanthocyanidins influence gut microbiota and enteroendocrine secretions in female rats.

Grape seed proanthocyanidin extract (GSPE) modulates several parameters involved in metabolic syndrome. GSPE is a mixture of compounds, some which are rapidly absorbed, while others remain in the lumen where they might have effects that are translated to the whole organism. Our aim was to decipher if the 8-day treatment of GSPE, previously shown to reduce food intake, induces changes in the microbiota and enterohormone secretion. The ratio of Firmicutes : Bacteroidetes was lower in the microbiota of GSPE-treated rats compared to controls, and differences in several taxonomic families and genera were observed. Such modulation led to a reduction in cecal butyrate content. GSPE also increased plasma glucagon-like-peptide-1 (GLP-1). Gallic acid did not induce major changes in the microbiota profile nor in GLP-1 secretion. Correlations between several microbiota taxa and plasma triacylglycerol, adiposity, and enterohormones were observed. Modulation of microbiota may be one of the mechanism by which GSPE impacts metabolic health.

Effects of an Intermittent Grape-Seed Proanthocyanidin (GSPE) Treatment on a Cafeteria Diet Obesogenic Challenge in Rats.

Obesity is highly associated with the pathologies included in the concept of the Metabolic Syndrome. Grape-seed proanthocyanins (GSPE) have showed very positive effects against all these metabolic disruptions; however, there is, as yet, no consensus about their effectiveness against an obesogenic challenge, such as a cafeteria diet. We determined the effectiveness of a dose of 500 mg GSPE/kg b.w. (body weight) against the obesogenic effects of a 17-week cafeteria diet, administered as a sub-chronic treatment, 10-15 days before, intermittently and at the end of the diet, in Wistar rats. Body weight, adiposity, indirect calorimetry and plasma parameters were analyzed. GSPE pre-treatment showed a long-lasting effect on body weight and adiposity that was maintained for seven weeks after the last dose. A corrective treatment was administered for the last two weeks of the cafeteria diet intervention; however, it did not effectively correct any of the parameters assessed. The most effective treatment was an intermittent GSPE dosage, administered every second week during the cafeteria diet. This limited body weight gain, adiposity and most lipotoxic effects. Our results support the administration of this GSPE dose, keeping an intermittent interval between dosages longer than every second week, to improve obesogenic disruptions produced by a cafeteria diet.

Acute selective bioactivity of grape seed proanthocyanidins on enteroendocrine secretions in the gastrointestinal tract.

Background: Enteroendocrine cells respond to food components by secreting an array of hormones that regulate several functions. We have previously shown that grape seed proanthocyanidins (GSPE) modulate GLP-1 levels. Objective: To deepen on the knowledge of the mechanisms used by GSPE to increase GLP-1, and extend it to its role at modulation of other enterohormones. Design: We used an ex vivo system to test direct modulation of enterohormones; STC-1 cells to test pure phenolic compounds; and rats to test the effects at different gastrointestinal segments. Results: GSPE compounds act at several locations along the gastrointestinal tract modulating enterohormone secretion depending on the feeding condition. GSPE directly promotes GLP-1 secretion in the ileum, while unabsorbed/metabolized forms do so in the colon. Such stimulation requires the presence of glucose. GSPE enhanced GIP and reduced CCK secretion; gallic acid could be partly responsible for this effect. Conclusions: The activity of GSPE modulating enterohormone secretion may help to explain its effects on metabolism. GSPE acts through several mechanisms; its compounds and their metabolites are GLP-1 secretagogues in ileum and colon, respectively. In vivo GLP-1 secretion might also be mediated by indirect pathways involving modulation of other enterohormones that in turn regulate GLP-1 release.

Subchronic treatment with grape-seed phenolics inhibits ghrelin production despite a short-term stimulation of ghrelin secretion produced by bitter-sensing flavanols.

SCOPE: Grape-seed phenolic compounds have recently been described as satiating agents in rats when administered as a whole phenolic extract (GSPE). This satiating effect may involve the release of satiating gut hormones such as GLP-1, although a short-term increase in the orexigenic hormone ghrelin was also reported. In this study, we investigated the short- and long-term effects of GSPE in rats, focusing on the role of the main grape-seed phenolics in ghrelin secretion. METHODS AND RESULTS: GSPE produced a short-term increase in plasma ghrelin in rats after an acute treatment. A mouse ghrelinoma cell line was used to test the effects of the main pure grape-seed phenolic compounds on ghrelin release. Monomeric flavanols stimulated ghrelin secretion by activating bitter taste receptors. In contrast, gallic acid (GA) and oligomeric flavanols inhibited ghrelin release. The ghrelin-inhibiting effects of GA were confirmed in rats and in rat duodenal segments. One day after the last dose of a subchronic treatment, GSPE decreased plasma ghrelin in rats, ghrelin secretion in intestinal segments, and ghrelin mRNA expression in stomach. CONCLUSION: The sustained satiating effects of GSPE are related to a long-term decrease in ghrelin expression. GA and oligomeric flavanols play a ghrelin-inhibiting role in this process.

Acutely administered grape-seed proanthocyanidin extract acts as a satiating agent.

Grape-seed proanthocyanidins' role as stimulators of active GLP-1 in rats suggests that they could be effective as satiating agents. Wistar rats were used to study the effects of proanthocyanidins on food intake with different doses, administration times and proanthocyanidin extract compositions. A dose of 423 mg of phenolics per kg body weight (BW) of grape-seed proanthocyanidin extract (GSPE) was necessary to decrease the 12-hour cumulative food intake by 18.7 ± 3.4%. Proanthocyanidins were effective when delivered directly into the gastrointestinal tract one hour before, or simultaneously at the start of the feeding period. Proanthocyanidins without galloyl forms, such as those from cocoa extract, were not as effective as grape-seed derived forms. GSPE increased the portal levels of active GLP-1 and total ghrelin and decreased the CCK levels, simultaneously with a decrease in gastric emptying. In conclusion, grape-seed proanthocyanidins could be useful as a satiating agent under the conditions defined in this study.

Defining Conditions for Optimal Inhibition of Food Intake in Rats by a Grape-Seed Derived Proanthocyanidin Extract.

Food intake depends on homeostatic and non-homeostatic factors. In order to use grape seed proanthocyanidins (GSPE) as food intake limiting agents, it is important to define the key characteristics of their bioactivity within this complex function. We treated rats with acute and chronic treatments of GSPE at different doses to identify the importance of eating patterns and GSPE dose and the mechanistic aspects of GSPE. GSPE-induced food intake inhibition must be reproduced under non-stressful conditions and with a stable and synchronized feeding pattern. A minimum dose of around 350 mg GSPE/kg body weight (BW) is needed. GSPE components act by activating the Glucagon-like peptide-1 (GLP-1) receptor because their effect is blocked by Exendin 9-39. GSPE in turn acts on the hypothalamic center of food intake control probably because of increased GLP-1 production in the intestine. To conclude, GSPE inhibits food intake through GLP-1 signaling, but it needs to be dosed under optimal conditions to exert this effect.