High glucose levels reduce fatty acid oxidation and increase triglyceride accumulation in human placenta

Placentas of women with gestational diabetes mellitus (GDM) exhibit an altered lipid metabolism. The mechanism by which GDM is linked to alterations in placental lipid metabolism remains obscure. We hypothesized that high glucose levels reduce mitochondrial fatty acid oxidation (FAO) and increase triglyceride accumulation in human placenta. To test this hypothesis, we measured FAO, fatty acid esterification, de novo fatty acid synthesis, triglyceride levels, and carnitine palmitoyltransferase activities (CPT) in placental explants of women with GDM or no pregnancy complication. In women with GDM, FAO was reduced by ~30% without change in mitochondrial content, and triglyceride content was threefold higher than in the control group. Likewise, in placental explants of women with no complications, high glucose levels reduced FAO by ~20%, and esterification increased linearly with increasing fatty acid concentrations. However, de novo fatty acid synthesis remained unchanged between high and low glucose levels. In addition, high glucose levels increased triglyceride content approximately twofold compared with low glucose levels. Furthermore, etomoxir-mediated inhibition of FAO enhanced esterification capacity by ~40% and elevated triglyceride content 1.5-fold in placental explants of women, with no complications. Finally, high glucose levels reduced CPT I activity by ~70% and phosphorylation levels of acetyl-CoA carboxylase by ~25% in placental explants of women, with no complications. We reveal an unrecognized regulatory mechanism on placental fatty acid metabolism by which high glucose levels reduce mitochondrial FAO through inhibition of CPT I, shifting flux of fatty acids away from oxidation toward the esterification pathway, leading to accumulation of placental triglycerides. © 2013 the American Physiological Society.This study was supported by a grant from the Carlos III Health Institute (CP08/00106), the Spanish Ministry of Science and Innovation (SAF2009-11282), and the FP7-PEOPLE-2009-RG (PIRG06-GA-2009-25369) to G. Perdomo; a grant from the Consejería de Salud, Junta de Andalucía (N°0269/05.2005) to J. L. Bartha; and grant from the Carlos III Health Institute (PI11/00676) to F. Bugatto.Peer Reviewe

Intestinal fructose and glucose metabolism in health and disease

The worldwide epidemics of obesity and diabetes have been linked to increased sugar consumption in humans. Here, we review fructose and glucose metabolism, as well as potential molecular mechanisms by which excessive sugar consumption is associated to metabolic diseases and insulin resistance in humans. To this end, we focus on understanding molecular and cellular mechanisms of fructose and glucose transport and sensing in the intestine, the intracellular signaling effects of dietary sugar metabolism, and its impact on glucose homeostasis in health and disease. Finally, the peripheral and central effects of dietary sugars on the gut–brain axis will be reviewed.Spanish MINISTERIO DE ECONOMÍA, INDUSTRIA Y COMPETITIVIDAD, grant numbers SAF2016-77871-C2-1-R and SAF2016-77871-C2-2-R to I.C-C. and G.P. respectively; the EFSD European Research Programme on New Targets for Type 2 Diabetes supported by an educational research grant from MSD to I.C-C. and G.P.; the FUNDACIÓN LA-CAIXA Y FUNDACIÓN CAJA DE BURGOS, grant number CAIXA-UBU001 to G.P

Leptolide improves insulin resistance in diet-induced obese mice

Producción CientíficaType 2 diabetes (T2DM) is a complex disease linked to pancreatic beta-cell failure and insulin resistance. Current antidiabetic treatment regimens for T2DM include insulin sensitizers and insulin secretagogues. We have previously demonstrated that leptolide, a member of the furanocembranolides family, promotes pancreatic beta-cell proliferation in mice. Considering the beneficial effects of leptolide in diabetic mice, in this study, we aimed to address the capability of leptolide to improve insulin resistance associated with the pathology of obesity. To this end, we tested the hypothesis that leptolide should protect against fatty acid-induced insulin resistance in hepatocytes. In a time-dependent manner, leptolide (0.1 µM) augmented insulin-stimulated phosphorylation of protein kinase B (PKB) by two-fold above vehicle-treated HepG2 cells. In addition, leptolide (0.1 µM) counteracted palmitate-induced insulin resistance by augmenting by four-fold insulin-stimulated phosphorylation of PKB in HepG2 cells. In vivo, acute intraperitoneal administration of leptolide (0.1 mg/kg and 1 mg/kg) improved glucose tolerance and insulin sensitivity in lean mice. Likewise, prolonged leptolide treatment (0.1 mg/kg) in diet-induced obese mice improved insulin sensitivity. These effects were paralleled with an ~50% increased of insulin-stimulated phosphorylation of PKB in liver and skeletal muscle and reduced circulating pro-inflammatory cytokines in obese mice. We concluded that leptolide significantly improves insulin sensitivity in vitro and in obese mice, suggesting that leptolide may be another potential treatment for T2DM.This research has been funded by Sociedad Española de Diabetes (Ayudas Investigación Básica 2014), Salud Castilla y León (BIO/VA40/15)Ministerio de Economía y Competitividad, (SAF2014-58702-C2-1-R),(SAF2014-58702-C2-2-R

Manipulation of Transmembrane Transport by Synthetic K+ Ionophore Depsipeptides and Its Implications in Glucose‐Stimulated Insulin Secretion in β‐Cells

The cyclic depsipeptide cereulide toxin it is a very well-known potassium electrogenic ionophore particularly sensitive to pancreatic beta cells. The mechanistic details of its specific activity are unknown. Here, we describe a series of synthetic substituted cereulide potassium ionophores that cause impressive selective activation of glucose-induced insulin secretion in a constitutive manner in rat insulinoma INS1E cells. Our study demonstrates that the different electroneutral K+ transport mechanism exhibited by the anionic mutant depsipeptides when compared with classical electrogenic cereulides can have an important impact of pharmacological value on glucose-stimulated insulin secretion.Ministerio de Economía y Competitividad, Spain (Projects CTQ2015-71353-R, SAF2016-77871-C2-1-R and SAF2016-77871-C2-2-R), the Junta de Castilla y León, Consejería de Educación y Cultura y Fondo Social Europeo (Project BU263P18) and the EFSD European Research Programme on New Targets for Type 2 Diabetes supported by an educational research grant from Merck Sharp & Dohme to I.C.C. and G.P. (EFSD-2017). This work was also supported in part by the 1000 Talent Plan (WQ20144400255) of State Administration of Foreign Experts Affairs, China. Y.-H.L. wishes to thank the Innovation and Talent Introduction Base of Photoelectronic and Functional Molecular Solid Material (Grant No. 90002-18011002) from Sun Yat-sen University and the China Scholarship Council (No. 21606380054) for financial support

Ghrelin's effects on proinflammatory cytokine mediated apoptosis and their impact on β-cell functionality

Ghrelin is a peptidic hormone, which stimulates cell proliferation and inhibits apoptosis in several tissues, including pancreas. In preclinical stage of type 1 diabetes, proinflammatory cytokines generate a destructive environment for β-cells known as insulitis, which results in loss of β-cell mass and impaired insulin secretion, leading to diabetes. Our aim was to demonstrate that ghrelin could preserve β-cell viability, turnover rate, and insulin secretion acting as a counter balance of cytokines. In the present work we reproduced proinflammatory milieu found in insulitis stage by treating murine cell line INS-1E and rat islets with a cytokine cocktail including IL-1β, IFNγ, and TNFα and/or ghrelin. Several proteins involved in survival pathways (ERK 1/2 and Akt/PKB) and apoptosis (caspases and Bcl-2 protein family and endoplasmic reticulum stress markers) as well as insulin secretion were analyzed. Our results show that ghrelin alone has no remarkable effects on β-cells in basal conditions, but interestingly it activates cell survival pathways, downregulates apoptotic mediators and endoplasmic reticulum stress, and restores insulin secretion in response to glucose when beta-cells are cytokine-exposed. These data suggest a potential role of ghrelin in preventing or slowing down the transition from a preclinical to clinically established diabetes by ameliorating the effects of insulitis on β-cells.This work was funded by a grant by the Andalusian Government (PI 0765-2011).Peer Reviewe

Protective effects of epoxypukalide on pancreatic b-cells and glucose metabolism in STZ-induced diabetic mice

Producción CientíficaDiabetes is a consequence of a decrease on functional β-cell mass. We have recently demonstrated that epoxypukalide (Epoxy) is a natural compound with beneficial effects on primary cultures of rat islets. In this study, we extend our previous investigations to test the hypothesis that Epoxy protects β-cells and improves glucose metabolism in STZ-induced diabetic mice. We used 3-months old male mice that were treated with Epoxy at 200 μg/kg body weight. Glucose intolerance was induced by multiple intraperitoneal low-doses of streptozotocin (STZ) on 5 consecutive days. Glucose homeostasis was evaluated measuring plasma insulin levels and glucose tolerance. Histomorphometry was used to quantify the number of pancreatic β-cells per islet. β-cell proliferation was assessed by BrdU incorporation, and apoptosis by TUNEL staining. Epoxy treatment significantly improved glucose tolerance and plasma insulin levels. These metabolic changes were associated with increased β-cell numbers, as a result of a two-fold increase in β-cell proliferation and a 50% decrease in β-cell death. Our results demonstrate that Epoxy improves whole-body glucose homeostasis by preventing pancreatic β-cell death due to STZ-induced toxicity in STZ-treated mic

Leptolide improves insulin resistance in diet-induced obese mice

Type 2 diabetes (T2DM) is a complex disease linked to pancreatic beta-cell failure and insulin resistance. Current antidiabetic treatment regimens for T2DM include insulin sensitizers and insulin secretagogues. We have previously demonstrated that leptolide, a member of the furanocembranolides family, promotes pancreatic beta-cell proliferation in mice. Considering the beneficial effects of leptolide in diabetic mice, in this study, we aimed to address the capability of leptolide to improve insulin resistance associated with the pathology of obesity. To this end, we tested the hypothesis that leptolide should protect against fatty acid-induced insulin resistance in hepatocytes. In a time-dependent manner, leptolide (0.1 µM) augmented insulin-stimulated phosphorylation of protein kinase B (PKB) by two-fold above vehicle-treated HepG2 cells. In addition, leptolide (0.1 µM) counteracted palmitate-induced insulin resistance by augmenting by four-fold insulin-stimulated phosphorylation of PKB in HepG2 cells. In vivo, acute intraperitoneal administration of leptolide (0.1 mg/kg and 1 mg/kg) improved glucose tolerance and insulin sensitivity in lean mice. Likewise, prolonged leptolide treatment (0.1 mg/kg) in diet-induced obese mice improved insulin sensitivity. These effects were paralleled with an ~50% increased of insulin-stimulated phosphorylation of PKB in liver and skeletal muscle and reduced circulating pro-inflammatory cytokines in obese mice. We concluded that leptolide significantly improves insulin sensitivity in vitro and in obese mice, suggesting that leptolide may be another potential treatment for T2DMSociedad Española de Diabetes (Ayudas Investigación Básica 2014), Salud Castilla y León (BIO/VA40/15) and Ministerio de Economía y Competitividad-Spain (SAF2014-58702-C2-1-R) to I.C. and Ministerio de Economía y Competitividad-Spain (SAF2014-58702-C2-2-R) to G.P

Chloro-Furanocembranolides from Leptogorgia sp. Improve Pancreatic Beta-Cell Proliferation

Type 2 diabetes (T2DM) is a complex disease linked to pancreatic beta-cell failure and insulin resistance. Current antidiabetic treatment regimens for T2DM include insulin sensitizers and insulin secretagogues. We have previously demonstrated that leptolide, a member of the furanocembranolides family, promotes pancreatic beta-cell proliferation in mice. Considering the beneficial effects of leptolide in diabetic mice, in this study, we aimed to address the capability of leptolide to improve insulin resistance associated with the pathology of obesity. To this end, we tested the hypothesis that leptolide should protect against fatty acid-induced insulin resistance in hepatocytes. In a time-dependent manner, leptolide (0.1 µM) augmented insulin-stimulated phosphorylation of protein kinase B (PKB) by two-fold above vehicle-treated HepG2 cells. In addition, leptolide (0.1 µM) counteracted palmitate-induced insulin resistance by augmenting by four-fold insulin-stimulated phosphorylation of PKB in HepG2 cells. In vivo, acute intraperitoneal administration of leptolide (0.1 mg/kg and 1 mg/kg) improved glucose tolerance and insulin sensitivity in lean mice. Likewise, prolonged leptolide treatment (0.1 mg/kg) in diet-induced obese mice improved insulin sensitivity. These effects were paralleled with an ~50% increased of insulin-stimulated phosphorylation of PKB in liver and skeletal muscle and reduced circulating pro-inflammatory cytokines in obese mice. We concluded that leptolide significantly improves insulin sensitivity in vitro and in obese mice, suggesting that leptolide may be another potential treatment for T2DMMinisterio de Ciencia e Innovación (SAF2009-0839 and RTA 2015-00010-C03-02). ARDM acknowledges funding from IMBRAIN project (FP7-REGPOT-2012-CT2012-31637-IMBRAIN) and from Cabildo de Tenerife (Agustín de Betancourt Programme). A.B.G. would like to thank Convenio Universidad de Magallanes (Chile) and CSIC, project 2009CL0031, for financial support

Liver-specific ablation of insulin-degrading enzyme causes hepatic insulin resistance and glucose intolerance, without affecting insulin clearance in mice

The role of insulin-degrading enzyme (IDE), a metalloprotease with high affinity for insulin, in insulin clearance remains poorly understood. OBJECTIVE: This study aimed to clarify whether IDE is a major mediator of insulin clearance, and to define its role in the etiology of hepatic insulin resistance. Methods We generated mice with liver-specific deletion of Ide (L-IDE-KO) and assessed insulin clearance and action. Results L-IDE-KO mice exhibited higher (~20%) fasting and non-fasting plasma glucose levels, glucose intolerance and insulin resistance. This phenotype was associated with ~30% lower plasma membrane insulin receptor levels in liver, as well as ~55% reduction in insulin-stimulated phosphorylation of the insulin receptor, and its downstream signaling molecules, AKT1 and AKT2 (reduced by ~40%). In addition, FoxO1 was aberrantly distributed in cellular nuclei, in parallel with up-regulation of the gluconeogenic genes Pck1 and G6pc. Surprisingly, L-IDE-KO mice showed similar plasma insulin levels and hepatic insulin clearance as control mice, despite reduced phosphorylation of the carcinoembryonic antigen-related cell adhesion molecule 1, which upon its insulin-stimulated phosphorylation, promotes receptor-mediated insulin uptake to be degraded. Conclusion IDE is not a rate-limiting regulator of plasma insulin levels in vivoMinisterio de Economía, Industria y Competitividad: SAF2014-58702-C2-1-R and SAF2016-77871-C2-1-R to ICC; SAF2014-58702-C2-2-R and SAF2016-77871-C2-2-R to GP; supported by the EFSD European Research Programme on New Targets for Type 2 Diabetes supported by an educational research grant from MSD to ICC and GP; the National Institutes of Health: R01-DK054254, R01-DK083850 and RO1-HL-112248 to SMN, and R01-GM115617 to MAL; and the American Diabetes Association: Career Development Award 7-11-CD-13 to MAL

Genetic deficiency of apolipoprotein D in the mouse is associated with nonfasting hypertriglyceridemia and hyperinsulinemia

Apolipoprotein D (ApoD) is an atypical apolipoprotein with an incompletely understood function in the regulation of triglyceride and glucose metabolism. We have demonstrated that elevated ApoD production in mice results in improved postprandial triglyceride clearance. This work studies the role of ApoD deficiency in the regulation of triglyceride and glucose metabolism and its dependence on aging. We used ApoD knockout (ApoD-KO) mice of 3 and 21 months of age. Body weight and food intake were measured. Hepatic histology, triglyceride content, lipoprotein lipase levels, and plasma metabolites were studied. Phenotypic characterization of glucose metabolism was performed using glucose tolerance test. β-Cell mass, islet volume, and islet number were analyzed by histomorphometry. Apolipoprotein D deficiency results in nonfasting hypertriglyceridemia in young (P =.01) and aged mice (P =.002). In young ApoD-KO mice, hypertriglyceridemia was associated with 30% to 50% increased food intake in nonfasting and fasting conditions, respectively, without changes in body weight. In addition, lipoprotein lipase levels were reduced by 35% in adipose tissue (P =.006). In aged ApoD-KO mice, hypertriglyceridemia was not associated with changes in food intake or body weight, whereas hepatic triglyceride levels were reduced by 35% (P =.02). Furthermore, nonfasting plasma insulin levels were elevated by 2-fold in young (P =.016) and aged (P =.004) ApoD-KO mice, without changes in blood glucose levels, glucose tolerance, β-cell mass, or islet number. These findings underscore the importance of ApoD in the regulation of plasma insulin levels and triglyceride metabolism, suggesting that ApoD plays an important role in the pathogenesis of dyslipidemia. © 2011 Elsevier Inc. All rights reserved.This work was supported by grants from the Carlos III Health Institute (CP08/00106), the Spanish Ministry of Science and Innovation (SAF2009-11282), and the FP7-PEOPLE-2009-RG (PIRG06-GA-2009-256369) to GP; grant from the Spanish Ministry of Science and Innovation (BFU2008-01170) to MDG and DS; and grants from the Carlos III Health Institute (PS09/ 00671) and the FP7-PEOPLE-2009-RG (IRG247835) to IC. MJP was supported by the Carlos III Health Institute (Spain).Peer Reviewe