Dietary Protein Modulates the Efficacy of Taurine Supplementation on Adaptive Islet Function and Morphology in Obesity.

Adaptation of islet ß-cell mass and function under limiting or excess nutrient availability is critical for maintenance of glucose homeostasis. Taurine regulates islet function of obese mice in normal and low dietary protein conditions, but whether this involves remodeling of the endocrine pancreas architecture is not well understood. Here, we carried functional and morphometric evaluation of the endocrine pancreas of normal and protein-restricted mice fed a high-fat diet (HFD) and investigated the role of taurine supplementation. Weaned mice were placed in a normal (C) or a low-protein diet (R) for 6 weeks, followed by HFD for 8 weeks (CH and RH). Half of HFD groups received 5% taurine supplementation since weaning (CHT and RHT) until the end of the experiment. Isolated islets from both CH and RH groups showed increased insulin release in association with increased pancreas weight and independently of changes in islet or ß-cell area. In normal protein CHT mice, taurine supplementation prevented obesity-induced insulin hypersecretion and promoted increased islet and ß-cell areas in association with increased protein expression of the proliferation marker, PCNA. On a low-protein background, taurine effects on islet function and morphology were blunted, but it prevented obesity-induced DNA fragmentation. In summary, taurine regulates islet function and morphology to improve the adaptive response to diet-induced obesity, but these effects are dependent on adequate dietary protein levels.

Beneficial effects of physical exercise for ß-cell maintenance in a type 1 diabetes mellitus animal model.

NEW FINDINGS: What is the central question of this study? Type 1 diabetes mellitus (T1D) leads to hyperglycaemia owing to pancreatic ß-cell destruction by the immune system. Physical exercise has been shown to have potentially beneficial protective roles against cytokine-induced pancreatic ß-cell death, but its benefits are yet to be proved and should be understood better, especially in the islet environment. What is the main finding and its importance? Physical exercise protects against ß-cell loss in a well-described animal model for T1D, induced by multiple low doses of streptozotocin. This seems to be related to reduced cytokine-induced ß-cell death and increased islet cell proliferation. Contributions of islet neogenesis and/or transdifferentiation of pancreatic non-ß-cells into ß-cells cannot be excluded. ABSTRACT: Physical exercise has beneficial effects on pancreatic ß-cell function and survival in a pro-inflammatory environment. Although these effects have been linked to decreased islet inflammation and modulation of pro-apoptotic pathways, little is known about the islet microenvironment. Our aim was to evaluate the effects of physical exercise in islet histomorphology in a mouse model of type 1 diabetes mellitus induced by multiple low doses of streptozotocin. As expected, induction of type 1 diabetes mellitus led to ß-cell loss and, consequently, decreased islet area. Interestingly, although the decrease in islet area was not prevented by physical exercise, this was not the case for the decrease in ß-cell mass. This was probably related to induction of ß-cell regeneration, because we observed increased proliferation and regeneration markers, such as Ki67 and Pcna, in islets of trained mice. These were found in the central and peripheral regions of the islets. An increase in the percentage of α- and δ-cells in these conditions, combined with an increase in proliferation and Pax4 labelling in peripheral regions, suggest that ß-cell regeneration might also occur by transdifferentiation. This agrees with the presence of cells double stained for insulin and glucagon only in islets of diabetic trained mice. In addition, this group had more extra-islet insulin-positive cells and islets associated with ducts than diabetic mice. Physical exercise also decreased nuclear factor-κB activation in islet cells of diabetic trained compared with diabetic untrained mice, indicating a decrease in pro-inflammatory cytokine-induced ß-cell death. Taken together, these findings indicate that preservation of ß-cell mass induced by physical exercise involves an increase in ß-cell replication and decrease in ß-cell death, together with islet neogenesis and islet cell transdifferentiation.

Augmentation index, a predictor of cardiovascular events, is increased in children and adolescents with primary nephrotic syndrome.

BACKGROUND: Arterial stiffness is associated with an increased risk of cardiovascular diseases. Augmentation index (AIx@75), a measure of arterial stiffness and wave reflection, has not been evaluated in patients with primary nephrotic syndrome (PNS). We investigated whether central and peripheral vascular profiles, hemodynamic parameters, and biochemical tests are associated with AIx@75 in PNS patients. METHODS: This observational study involved 38 children and adolescents with PNS (12.14 ± 3.65 years) and 37 healthy controls (13.28 ± 2.80 years). Arterial stiffness and vascular and hemodynamic parameters were measured noninvasively using the Mobil-O-Graph® (IEM, Stolberg, Germany). In the PNS group, biochemical tests and corticosteroid dosage/treatment time were analyzed. RESULTS: Peripheral and central systolic blood pressure (SBPp, SBPc) Z-scores were significantly higher in the PNS patients. AIx@75 was significantly higher in the PNS patients (25.14 ± 9.93%) than in controls (20.84 ± 7.18%). In the control group, AIx@75 negatively correlated with weight (r = - 0.369; p = 0.025), height (r = - 0.370; p = 0.024), and systolic volume/body surface (r = - 0.448; p = 0.006). In the PNS group, a univariate linear correlation showed that AIx@75 negatively correlated with weight (r = - 0.360; p = 0.027), height (r = 0.381; p = 0.18), and systolic volume/body surface (r = - 0.447; p < 0.002) and positively with the Z-score of SBPp (r = 0.407; p = 0.011), peripheral diastolic blood pressure (DBPp, r = 0.452; p = 0.004), SBPc (r = 0.416; p = 0.009), DBPc (r = 0.407; p = 0.011), triglycerides (r = 0.525; p = 0.001), and cholesterol [total (r = 0.539; p < 0.001), LDLc (r = 0.420; p = 0.010), and non-HDLc (r = 0.511; p = 0.001)]. CONCLUSIONS: Early abnormalities of AIx@75 and vascular parameters suggest that patients with PNS, even in stable condition, present subclinical indicators for the development of cardiovascular disease.

Protein malnutrition blunts the increment of taurine transporter expression by a high-fat diet and impairs taurine reestablishment of insulin secretion.

Taurine (Tau) restores ß-cell function in obesity; however, its action is lost in malnourished obese rodents. Here, we investigated the mechanisms involved in the lack of effects of Tau in this model. C57BL/6 mice were fed a control diet (CD) (14% protein) or a protein-restricted diet (RD) (6% protein) for 6 wk. Afterward, mice received a high-fat diet (HFD) for 8 wk [CD + HFD (CH) and RD + HFD (RH)] with or without 5% Tau supplementation after weaning on their drinking water [CH + Tau (CHT) and RH + Tau (RHT)]. The HFD increased insulin secretion through mitochondrial metabolism in CH and RH. Tau prevented all those alterations in CHT only. The expression of the taurine transporter (Tau-T), as well as Tau content in pancreatic islets, was increased in CH but had no effect on RH. Protein malnutrition programs ß cells and impairs Tau-induced restoration of mitochondrial metabolism and biogenesis. This may be associated with modulation of the expression of Tau-T in pancreatic islets, which may be responsible for the absence of effect of Tau in protein-malnourished obese mice.-Branco, R. C. S., Camargo, R. L., Batista, T. M., Vettorazzi, J. F., Borck, P. C., dos Santos-Silva, J. C. R., Boschero, A. C., Zoppi, C. C., Carneiro, E. M. Protein malnutrition blunts the increment of taurine transporter expression by a high-fat diet and impairs taurine reestablishment of insulin secretion.

Taurine supplementation induces long-term beneficial effects on glucose homeostasis in ob/ob mice.

The sulfur-containing amino acid, taurine (Tau), regulates glucose and lipid homeostasis under normal, pre- and diabetic conditions. Here, we aimed to verify whether Tau supplementation exerts its beneficial effects against obesity, hyperglycemia and alterations in islet functions, in leptin-deficient obese (ob/ob), over a long period of treatment. From weaning until 12 months of age, female ob/ob mice received, or not, 5% Tau in drinking water (obTau group). After this period, a reduction in hypertriglyceridemia and an improvement in glucose tolerance and insulin sensitivity were observed in obTau mice. In addition, the daily metabolic flexibility was restored in obTau mice. In the gastrocnemius muscle of obTau mice, the activation of AMP-activated protein kinase (AMPK) was increased, while total AMPK protein content was reduced. Finally, isolated islets from obTau mice expressed high amounts of pyruvate carboxylase (PC) protein and lower glucose-induced insulin secretion. Taking these evidences together Tau supplementation had long-term positive actions on glucose tolerance and insulin sensitivity, associated with a reduction in glucose-stimulated insulin secretion, in ob/ob mice. The improvement in insulin actions in obTau mice was due, at least in part, to increased activation of AMPK in skeletal muscle, while the increased content of the PC enzyme in pancreatic islets may help to preserve glucose responsiveness in obTau islets, possibly contributing to islet cell survive.

Propranolol treatment lowers blood pressure, reduces vascular inflammatory markers and improves endothelial function in obese mice.

Obesity-associated hypertension is accompanied by a number of cardiovascular risk factors including vascular insulin resistance (IR) and higher sympathetic nervous activity. Therefore, autonomic blockade was demonstrated to reverse hypertension, endothelial dysfunction and IR in obese individuals. We hypothesized that ß-AR blockade with propranolol would restore endothelial function and vascular insulin signaling in obesity, associated with an anti-inflammatory effect. Body weight, systolic blood pressure (SBP), plasma biochemical parameters and aortic endothelial function were analyzed in mice fed standard diet (control group) or a high fat diet (HFD) that were treated with vehicle (water) or propranolol (10mg/kg/day) for 8weeks. Propranolol treatment did not modify obesogenic effect of HFD feeding. However, propranolol was effective in preventing the rise in SBP, the hyperinsulinemia and the impaired endothelium-dependent relaxation to acetylcholine and to insulin in obese mice. Protective effect of propranolol administration in endothelial function was associated with increased nitric oxide (NO) production and phosphorylation of Akt (Ser473) and eNOS (Ser1177), but with reduced phospho-IRS-1(Ser307) and phospho-ERK1/2 (Thr202/Tyr204). In addition, ß-blocker propranolol prevented the NF-kB nuclear translocation and the increase in phospho-IκB-α (Ser32) and in interleukin(IL)-6 expression in aorta of obese mice, without significant changes in either aortic reactive oxygen species production or in circulating IL-6 and TNF-α levels. In ß2-AR knockout mice, despite increasing body weight and visceral fat, HFD did not increase SBP and showed a partial improvement of endothelial function, revealing a role of ß2-AR in cardiovascular effects of obesity. In conclusion, our results suggest that ß-AR blockade with propranolol is effective to prevent the endothelial dysfunction, vascular IR and pro-inflammatory state displayed in HFD-induced obesity, independent of changes in body weight.

Benefits of L-alanine or L-arginine supplementation against adiposity and glucose intolerance in monosodium glutamate-induced obesity.

PURPOSE: L-alanine (Ala) and L-arginine (Arg) have been reported to regulate pancreatic ß-cell physiology and to prevent body fat accumulation in diet-induced obesity. Here, we assessed growth and adiposity parameters, glucose tolerance, insulin secretion and the expression of insulin and nutrient-regulated proteins in monosodium glutamate (MSG)-obese mice supplemented with either Ala or Arg. METHODS: Male newborn C57Bl/6 mice received a daily subcutaneous injection of MSG or saline solution (CTL group), during the first 6 days of life. From 30 to 90 days of age, MSG and CTL mice received or not 2.55 % Ala (CAla or MArg groups) or 1.51 % Arg-HCl (CArg or MArg groups) in their drinking water. RESULTS: Adult MSG mice displayed higher adiposity associated with lower phosphorylation of the adipogenic enzyme, ACC, in adipose tissue. Glucose intolerance in MSG mice was linked to lower insulin secretion and to lower expression of IRß in adipose tissue, as well as AS160 phosphorylation in skeletal muscle. Perigonadal fat depots were smaller in Ala and Arg mice, while retroperitoneal fat pads were decreased by Ala supplementation only. Both Ala and Arg improved fed-state glycemia as well as IRß and pAS160 content, but only Ala led to improved glucose tolerance and insulin secretion. Adipostatic signals were increased in MAla mice, as indicated by enhanced AMPK phosphorylation and pACC content in fat depots. CONCLUSIONS: Ala supplementation led to more pronounced metabolic improvements compared to Arg, possibly due to suppression of lipogenesis through activation of the AMPK/ACC pathway.

Vagotomy Reduces Insulin Clearance in Obese Mice Programmed by Low-Protein Diet in the Adolescence.

The aim of this study was to investigate the effect of subdiaphragmatic vagotomy on insulin sensitivity, secretion, and degradation in metabolic programmed mice, induced by a low-protein diet early in life, followed by exposure to a high-fat diet in adulthood. Weaned 30-day-old C57Bl/6 mice were submitted to a low-protein diet (6% protein). After 4 weeks, the mice were distributed into three groups: LP group, which continued receiving a low-protein diet; LP + HF group, which started to receive a high-fat diet; and LP + HFvag group, which underwent vagotomy and also was kept at a high-fat diet. Glucose-stimulated insulin secretion (GSIS) in isolated islets, ipGTT, ipITT, in vivo insulin clearance, and liver expression of the insulin-degrading enzyme (IDE) was accessed. Vagotomy improved glucose tolerance and reduced insulin secretion but did not alter adiposity and insulin sensitivity in the LP + HFvag, compared with the LP + HF group. Improvement in glucose tolerance was accompanied by increased insulinemia, probably due to a diminished insulin clearance, as judged by the lower C-peptide : insulin ratio, during the ipGTT. Finally, vagotomy also reduced liver IDE expression in this group. In conclusion, when submitted to vagotomy, the metabolic programmed mice showed improved glucose tolerance, associated with an increase of plasma insulin concentration as a result of insulin clearance reduction, a phenomenon probably due to diminished liver IDE expression.

Reduced insulin secretion function is associated with pancreatic islet redistribution of cell adhesion molecules (CAMS) in diabetic mice after prolonged high-fat diet.

Intercellular junctions play a role in regulating islet cytoarchitecture, insulin biosynthesis and secretion. In this study, we investigated the animal metabolic state as well as islet histology and cellular distribution/expression of CAMs and F-actin in the endocrine pancreas of C57BL/6/JUnib mice fed a high-fat diet (HFd) for a prolonged time period (8 months). Mice fed a HFd became obese and type 2 diabetic, displaying significant peripheral insulin resistance, hyperglycemia and moderate hyperinsulinemia. Isolated islets of HFd-fed mice displayed a significant impairment of glucose-induced insulin secretion associated with a diminished frequency of intracellular calcium oscillations compared with control islets. No marked change in islet morphology and cytoarchitecture was observed; however, HFd-fed mice showed higher beta cell relative area in comparison with controls. As shown by immunohistochemistry, ZO-1, E-, N-cadherins, α- and ß-catenins were expressed at the intercellular contact site of endocrine cells, while VE-cadherin, as well as ZO-1, was found at islet vascular compartment. Redistribution of N-, E-cadherins and α-catenin (from the contact region to the cytoplasm in endocrine cells) associated with increased submembranous F-actin cell level as well as increased VE-cadherin islet immunolabeling was observed in diabetic mice. Increased gene expression of VE-cadherin and ZO-1, but no change for the other proteins, was observed in islets of diabetic mice. Only in the case of VE-cadherin, a significant increase in islet content of this CAM was detected by immunoblotting in diabetic mice. In conclusion, CAMs are expressed by endocrine and endothelial cells of pancreatic islets. The distribution/expression of N-, E- and VE-cadherins as well as α-catenin and F-actin is significantly altered in islet cells of obese and diabetic mice.

Taurine supplementation ameliorates glucose homeostasis, prevents insulin and glucagon hypersecretion, and controls ß, α, and δ-cell masses in genetic obese mice.

Taurine (Tau) regulates ß-cell function and glucose homeostasis under normal and diabetic conditions. Here, we assessed the effects of Tau supplementation upon glucose homeostasis and the morphophysiology of endocrine pancreas, in leptin-deficient obese (ob) mice. From weaning until 90-day-old, C57Bl/6 and ob mice received, or not, 5% Tau in drinking water (C, CT, ob and obT). Obese mice were hyperglycemic, glucose intolerant, insulin resistant, and exhibited higher hepatic glucose output. Tau supplementation did not prevent obesity, but ameliorated glucose homeostasis in obT. Islets from ob mice presented a higher glucose-induced intracellular Ca(2+) influx, NAD(P)H production and insulin release. Furthermore, α-cells from ob islets displayed a higher oscillatory Ca(2+) profile at low glucose concentrations, in association with glucagon hypersecretion. In Tau-supplemented ob mice, insulin and glucagon secretion was attenuated, while Ca(2+) influx tended to be normalized in ß-cells and Ca(2+) oscillations were increased in α-cells. Tau normalized the inhibitory action of somatostatin (SST) upon insulin release in the obT group. In these islets, expression of the glucagon, GLUT-2 and TRPM5 genes was also restored. Tau also enhanced MafA, Ngn3 and NeuroD mRNA levels in obT islets. Morphometric analysis demonstrated that the hypertrophy of ob islets tends to be normalized by Tau with reductions in islet and ß-cell masses, but enhanced δ-cell mass in obT. Our results indicate that Tau improves glucose homeostasis, regulating ß-, α-, and δ-cell morphophysiology in ob mice, indicating that Tau may be a potential therapeutic tool for the preservation of endocrine pancreatic function in obesity and diabetes.

Taurine supplementation increases K(ATP) channel protein content, improving Ca2+ handling and insulin secretion in islets from malnourished mice fed on a high-fat diet.

Pancreatic ß-cells are highly sensitive to suboptimal or excess nutrients, as occurs in protein-malnutrition and obesity. Taurine (Tau) improves insulin secretion in response to nutrients and depolarizing agents. Here, we assessed the expression and function of Cav and KATP channels in islets from malnourished mice fed on a high-fat diet (HFD) and supplemented with Tau. Weaned mice received a normal (C) or a low-protein diet (R) for 6 weeks. Half of each group were fed a HFD for 8 weeks without (CH, RH) or with 5% Tau since weaning (CHT, RHT). Isolated islets from R mice showed lower insulin release with glucose and depolarizing stimuli. In CH islets, insulin secretion was increased and this was associated with enhanced KATP inhibition and Cav activity. RH islets secreted less insulin at high K(+) concentration and showed enhanced KATP activity. Tau supplementation normalized K(+)-induced secretion and enhanced glucose-induced Ca(2+) influx in RHT islets. R islets presented lower Ca(2+) influx in response to tolbutamide, and higher protein content and activity of the Kir6.2 subunit of the KATP. Tau increased the protein content of the α1.2 subunit of the Cav channels and the SNARE proteins SNAP-25 and Synt-1 in CHT islets, whereas in RHT, Kir6.2 and Synt-1 proteins were increased. In conclusion, impaired islet function in R islets is related to higher content and activity of the KATP channels. Tau treatment enhanced RHT islet secretory capacity by improving the protein expression and inhibition of the KATP channels and enhancing Synt-1 islet content.

Transcriptional regulation of tocopherol biosynthesis in tomato.

Tocopherols, compounds with vitamin E (VTE) activity, are potent lipid-soluble antioxidants synthesized only by photosynthetic organisms. Their biosynthesis requires the condensation of phytyl-diphosphate and homogentisate, derived from the methylerythritol phosphate (MEP) and shikimate pathways (SK), respectively. These metabolic pathways are central in plant chloroplast metabolism and are involved in the biosynthesis of important molecules such as chlorophyll, carotenoids, aromatic amino-acids and prenylquinones. In the last decade, few studies have provided insights into the regulation of VTE biosynthesis and its accumulation. However, the pathway regulatory mechanism/s at mRNA level remains unclear. We have recently identified a collection of tomato genes involved in tocopherol biosynthesis. In this work, by a dedicated qPCR array platform, the transcript levels of 47 genes, including paralogs, were determined in leaves and across fruit development. Expression data were analyzed for correlation with tocopherol profiles by coregulation network and neural clustering approaches. The results showed that tocopherol biosynthesis is controlled both temporally and spatially however total tocopherol content remains constant. These analyses exposed 18 key genes from MEP, SK, phytol recycling and VTE-core pathways highly associated with VTE content in leaves and fruits. Moreover, genomic analyses of promoter regions suggested that the expression of the tocopherol-core pathway genes is trancriptionally coregulated with specific genes of the upstream pathways. Whilst the transcriptional profiles of the precursor pathway genes would suggest an increase in VTE content across fruit development, the data indicate that in the M82 cultivar phytyl diphosphate supply limits tocopherol biosynthesis in later fruit stages. This is in part due to the decreasing transcript levels of geranylgeranyl reductase (GGDR) which restricts the isoprenoid precursor availability. As a proof of concept, by analyzing a collection of Andean landrace tomato genotypes, the role of the pinpointed genes in determining fruit tocopherol content was confirmed. The results uncovered a finely tuned regulation able to shift the precursor pathways controlling substrate influx for VTE biosynthesis and overcoming endogenous competition for intermediates. The whole set of data allowed to propose that 1-deoxy-D-xylulose-5-phosphate synthase and GGDR encoding genes, which determine phytyl-diphosphate availability, together with enzyme encoding genes involved in chlorophyll-derived phytol metabolism appear as the most plausible targets to be engineered aiming to improve tomato fruit nutritional value.

Circulating progenitor and mature endothelial cells in deep vein thrombosis.

INTRODUCTION: Mature circulating endothelial cells (CEC) and circulating endothelial progenitor cells (EPC) have been described in several conditions associated with endothelial injury. Their role in deep vein thrombosis (DVT) has not been previously evaluated. PATIENTS AND METHODS: In this pilot study we evaluated the time course of CEC and EPC release after vena cava experimental DVT in mice, using the FeCl3 model. We also evaluated their presence in patients with DVT at different phases of the disease (acute and chronic phase). CEC and EPC were evaluated by Flow Cytometry. RESULTS: In mice, both CEC and EPC were increased 24 hours after DVT induction, peaking 48 hours thereafter. After 72 hours, CEC counts decreased sharply, whereas EPC counts decreased less substantially. In DVT patients we observed a significant increase in CEC counts immediately after DVT compared to healthy individuals. Patients with chronic disease also presented a significant elevation of these cell count. In a subgroup of patients for whom serial samples were available, CEC counts decreased significantly after 9-15 months of the acute event. CONCLUSIONS: Our results suggest the participation of these cells in the reparative processes that follows DVT, both at immediate and late time-points. The different kinetics of CEC and EPC release in experimental DVT suggests a heterogeneous role for these cells in the reparative events after DVT.

Taurine supplementation prevents morpho-physiological alterations in high-fat diet mice pancreatic ß-cells.

Taurine (Tau) is involved in beta (ß)-cell function and insulin action regulation. Here, we verified the possible preventive effect of Tau in high-fat diet (HFD)-induced obesity and glucose intolerance and in the disruption of pancreatic ß-cell morpho-physiology. Weaning Swiss mice were distributed into four groups: mice fed on HFD diet (36 % of saturated fat, HFD group); HTAU, mice fed on HFD diet and supplemented with 5 % Tau; control (CTL); and CTAU. After 19 weeks of diet and Tau treatments, glucose tolerance, insulin sensitivity and islet morpho-physiology were evaluated. HFD mice presented higher body weight and fat depots, and were hyperglycemic, hyperinsulinemic, glucose intolerant and insulin resistant. Their pancreatic islets secreted high levels of insulin in the presence of increasing glucose concentrations and 30 mM K(+). Tau supplementation improved glucose tolerance and insulin sensitivity with a higher ratio of Akt phosphorylated (pAkt) related to Akt total protein content (pAkt/Akt) following insulin administration in the liver without altering body weight and fat deposition in HTAU mice. Isolated islets from HTAU mice released insulin similarly to CTL islets. HFD intake induced islet hypertrophy, increased ß-cell/islet area and islet and ß-cell mass content in the pancreas. Tau prevented islet and ß-cell/islet area, and islet and ß-cell mass alterations induced by HFD. The total insulin content in HFD islets was higher than that of CTL islets, and was not altered in HTAU islets. In conclusion, for the first time, we showed that Tau enhances liver Akt activation and prevents ß-cell compensatory morpho-functional adaptations induced by HFD.

Cell-to-cell contact dependence and junctional protein content are correlated with in vivo maturation of pancreatic beta cells.

In this study, we investigated the cellular distribution of junctional proteins and the dependence on cell-cell contacts of pancreatic beta cells during animal development. Fetus and newborn rat islets, which display a relatively poor insulin secretory response to glucose, present an immature morphology and cytoarchitecture when compared with young and adult islets that are responsive to glucose. At the perinatal stage, beta cells display a low junctional content of neural cell adhesion molecule (N-CAM), α- and ß-catenins, ZO-1, and F-actin, while a differential distribution of N-CAM and Pan-cadherin was seen in beta cells and nonbeta cells only from young and adult islets. In the absence of intercellular contacts, the glucose-stimulated insulin secretion was completely blocked in adult beta cells, but after reaggregation they partially reestablished the secretory response to glucose. By contrast, neonatal beta cells were poorly responsive to sugar, regardless of whether they were arranged as intact islets or as isolated cells. Interestingly, after 10 days of culturing, neonatal beta cells, known to display increased junctional protein content in vitro, became responsive to glucose and concomitantly dependent on cell-cell contacts. Therefore, our data suggest that the developmental acquisition of an adult-like insulin secretory pattern is paralleled by a dependence on direct cell-cell interactions.

Genetic dissection of vitamin E biosynthesis in tomato.

Vegetables are critical for human health as they are a source of multiple vitamins including vitamin E (VTE). In plants, the synthesis of VTE compounds, tocopherol and tocotrienol, derives from precursors of the shikimate and methylerythritol phosphate pathways. Quantitative trait loci (QTL) for α-tocopherol content in ripe fruit have previously been determined in an Solanum pennellii tomato introgression line population. In this work, variations of tocopherol isoforms (α, ß, γ, and δ) in ripe fruits of these lines were studied. In parallel all tomato genes structurally associated with VTE biosynthesis were identified and mapped. Previously identified VTE QTL on chromosomes 6 and 9 were confirmed whilst novel ones were identified on chromosomes 7 and 8. Integrated analysis at the metabolic, genetic and genomic levels allowed us to propose 16 candidate loci putatively affecting tocopherol content in tomato. A comparative analysis revealed polymorphisms at nucleotide and amino acid levels between Solanum lycopersicum and S. pennellii candidate alleles. Moreover, evolutionary analyses showed the presence of codons evolving under both neutral and positive selection, which may explain the phenotypic differences between species. These data represent an important step in understanding the genetic determinants of VTE natural variation in tomato fruit and as such in the ability to improve the content of this important nutriceutical.

Agomelatine reduces circulating triacylglycerides and hepatic steatosis in fructose-treated rats.

Agomelatine (AGO) is an antidepressant drug with agonistic activity at melatonin receptor 1 (MT1) and MT2 and with neutral antagonistic activity at serotonin receptor 5-HT2C. Although experimental studies show that melatonin reduces hypertriglyceridemia and hepatic steatosis induced by excessive fructose intake, no studies have tested if AGO exerts similar actions. To address this issue we have treated male Wistar rats with fructose (15% in the drinking water) and/or AGO (40 mg/kg/day) for two weeks. AGO reduced body weight gain, feeding efficiency and hepatic lipid levels without affecting caloric intake in fructose-treated rats. AGO has also decreased very low-density lipoprotein (VLDL) production and circulating TAG levels after an oral load with olive oil. Accordingly, treatment with AGO reduced the hepatic expression of fatty acid synthase (Fasn), a limiting step for hepatic de novo lipogenesis (DNLG). The expression of apolipoprotein B (Apob) and microsomal triglyceride transfer protein (Mttp) in the ileum, two crucial proteins for intestinal lipoprotein production, were also downregulated by treatment with AGO. Altogether, the present data show that AGO mimics the metabolic benefits of melatonin when used in fructose-treated rats. This study also suggests that it is relevant to evaluate the potential of AGO to treat metabolic disorders in future clinical trials.

Dexamethasone programs lower fatty acid absorption and reduced PPAR-γ and fat/CD36 expression in the jejunum of the adult rat offspring.

The progeny of rats born and breastfed by mothers receiving dexamethasone (DEX) during pregnancy exhibits permanent reduction in body weight and adiposity but the precise mechanisms related to this programming are not fully understood. In order to clarify this issue, the present study investigated key aspects of lipoprotein production and lipid metabolism by the liver and the intestine that would explain the reduced adiposity seen in the adult offspring exposed to DEX in utero. Female Wistar rats were treated with DEX (0.1 mg/kg/day) between the 15th and the 21st days of pregnancy, while control mothers were treated with vehicle. Male offspring born to control mothers were nursed by either adoptive control mothers (CTL/CTL) or DEX-treated mothers (CTL/DEX). Male offspring born to DEX-treated mothers were nursed by either control mothers (DEX/CTL) or adoptive DEX-treated mothers (DEX/DEX). We found that only the male DEX/DEX offspring had reduced adiposity. Additionally, male DEX/DEX progeny had lower circulating triacylglycerol (TAG) levels only in fed-state. The four groups of offspring presented similar energy expenditure, respiratory quotient and very low-density lipoprotein (VLDL) production. On the other hand, DEX/DEX rats displayed reduced TAG levels after gavage with olive oil and reduced expression of fatty acid translocase Cd36 (Fat/Cd36) and peroxisome proliferator-activated receptor γ (Pparg) in the jejunum. Altogether, our study supports the notion that reduced fat absorption by the jejunum may contribute to the lower adiposity of the adult offspring born and breastfed by mothers treated with DEX during pregnancy.