RESUMO
Hypothalamic detection of elevated circulating glucose triggers suppression of endogenous glucose production (EGP) to maintain glucose homeostasis. Antipsychotics alleviate symptoms associated with schizophrenia but also increase the risk for impaired glucose metabolism. In the current study, we examined whether two acutely administered antipsychotics from different drug classes, haloperidol (first generation antipsychotic) and olanzapine (second generation antipsychotic), affect the ability of intracerebroventricular (ICV) glucose infusion approximating postprandial levels to suppress EGP. The experimental protocol consisted of a pancreatic euglycemic clamp, followed by kinomic and RNA-seq analyses of hypothalamic samples to determine changes in serine/threonine kinase activity and gene expression, respectively. Both antipsychotics inhibited ICV glucose-mediated increases in glucose infusion rate during the clamp, a measure of whole-body glucose metabolism. Similarly, olanzapine and haloperidol blocked central glucose-induced suppression of EGP. ICV glucose stimulated the vascular endothelial growth factor (VEGF) pathway, phosphatidylinositol 3-kinase (PI3K) pathway, and kinases capable of activating KATP channels in the hypothalamus. These effects were inhibited by both antipsychotics. In conclusion, olanzapine and haloperidol impair central glucose sensing. Although results of hypothalamic analyses in our study do not prove causality, they are novel and provide the basis for a multitude of future studies.
Assuntos
Antipsicóticos , Antipsicóticos/farmacologia , Glucose/metabolismo , Fosfatidilinositol 3-Quinases , Fator A de Crescimento do Endotélio Vascular , Olanzapina/farmacologia , Olanzapina/metabolismo , Benzodiazepinas/farmacologiaRESUMO
The NAD-dependent deacetylase SIRT1 improves ß cell function. Accordingly, nicotinamide mononucleotide (NMN), the product of the rate-limiting step in NAD synthesis, prevents ß cell dysfunction and glucose intolerance in mice fed a high-fat diet. The current study was performed to assess the effects of NMN on ß cell dysfunction and glucose intolerance that are caused specifically by increased circulating free fatty acids (FFAs). NMN was intravenously infused, with or without oleate, in C57BL/6J mice over a 48-h-period to elevate intracellular NAD levels and consequently increase SIRT1 activity. Administration of NMN in the context of elevated plasma FFA levels considerably improved glucose tolerance. This was due not only to partial protection from FFA-induced ß cell dysfunction but also, unexpectedly, to a significant decrease in insulin clearance. However, in conditions of normal FFA levels, NMN impaired glucose tolerance due to decreased ß cell function. The presence of this dual action of NMN suggests caution in its proposed therapeutic use in humans.
Assuntos
Ácidos Graxos não Esterificados/sangue , Intolerância à Glucose/tratamento farmacológico , Glucose/efeitos adversos , Insulina/metabolismo , Mononucleotídeo de Nicotinamida/administração & dosagem , Ácido Oleico/efeitos adversos , Animais , Intolerância à Glucose/sangue , Intolerância à Glucose/induzido quimicamente , Células Hep G2 , Humanos , Infusões Intravenosas , Masculino , Camundongos , Camundongos Endogâmicos C57BL , NAD/metabolismo , Mononucleotídeo de Nicotinamida/farmacologia , Sirtuína 1/metabolismo , Regulação para CimaRESUMO
We have shown that both insulin and resveratrol (RSV) decrease neointimal hyperplasia in chow-fed rodents via mechanisms that are in part overlapping and involve the activation of endothelial nitric oxide synthase (eNOS). However, this vasculoprotective effect of insulin is abolished in high-fat-fed insulin-resistant rats. Since RSV, in addition to increasing insulin sensitivity, can activate eNOS via pathways that are independent of insulin signaling, such as the activation of sirtuin 1 (SIRT1) and AMP-activated kinase (AMPK), we speculated that unlike insulin, the vasculoprotective effect of RSV would be retained in high-fat-fed rats. We found that high-fat feeding decreased insulin sensitivity and increased neointimal area and that RSV improved insulin sensitivity (p < 0.05) and decreased neointimal area in high-fat-fed rats (p < 0.05). We investigated the role of SIRT1 in the effect of RSV using two genetic mouse models. We found that RSV decreased neointimal area in high-fat-fed wild-type mice (p < 0.05), an effect that was retained in mice with catalytically inactive SIRT1 (p < 0.05) and in heterozygous SIRT1-null mice. In contrast, the effect of RSV was abolished in AMKPα2-null mice. Thus, RSV decreased neointimal hyperplasia after arterial injury in both high-fat-fed rats and mice, an effect likely not mediated by SIRT1 but by AMPKα2.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Lesões das Artérias Carótidas/tratamento farmacológico , Artéria Carótida Primitiva/efeitos dos fármacos , Dieta Hiperlipídica , Artéria Femoral/efeitos dos fármacos , Neointima , Resveratrol/farmacologia , Sirtuína 1/metabolismo , Lesões do Sistema Vascular/tratamento farmacológico , Proteínas Quinases Ativadas por AMP/genética , Animais , Lesões das Artérias Carótidas/enzimologia , Lesões das Artérias Carótidas/patologia , Artéria Carótida Primitiva/enzimologia , Artéria Carótida Primitiva/patologia , Modelos Animais de Doenças , Artéria Femoral/enzimologia , Artéria Femoral/lesões , Artéria Femoral/patologia , Resistência à Insulina , Camundongos Knockout , Ratos Sprague-Dawley , Transdução de Sinais , Sirtuína 1/genética , Lesões do Sistema Vascular/enzimologia , Lesões do Sistema Vascular/patologiaRESUMO
Insulin resistance, a main characteristic of type 2 diabetes mellitus (T2DM), is linked to obesity and excessive levels of plasma free fatty acids (FFA). Studies indicated that significantly elevated levels of FFAs lead to skeletal muscle insulin resistance, by dysregulating the steps in the insulin signaling cascade. The polyphenol resveratrol (RSV) was shown to have antidiabetic properties but the exact mechanism(s) involved are not clearly understood. In the present study, we examined the effect of RSV on FFA-induced insulin resistance in skeletal muscle cells in vitro and investigated the mechanisms involved. Parental and GLUT4myc-overexpressing L6 rat skeletal myotubes were used. [3H]2-deoxyglucose (2DG) uptake was measured, and total and phosphorylated levels of specific proteins were examined by immunoblotting. Exposure of L6 cells to FFA palmitate decreased the insulin-stimulated glucose uptake, indicating insulin resistance. Palmitate increased ser307 (131% ± 1.84% of control, p < 0.001) and ser636/639 (148% ± 10.1% of control, p < 0.01) phosphorylation of IRS-1, and increased the phosphorylation levels of mTOR (174% ± 15.4% of control, p < 0.01) and p70 S6K (162% ± 20.2% of control, p < 0.05). Treatment with RSV completely abolished these palmitate-induced responses. In addition, RSV increased the activation of AMPK and restored the insulin-mediated increase in (a) plasma membrane GLUT4 glucose transporter levels and (b) glucose uptake. These data suggest that RSV has the potential to counteract the FFA-induced muscle insulin resistance.
Assuntos
Adenilato Quinase/fisiologia , Ácidos Graxos não Esterificados/toxicidade , Resistência à Insulina/fisiologia , Músculo Esquelético/efeitos dos fármacos , Resveratrol/farmacologia , Proteínas Quinases S6 Ribossômicas 70-kDa/fisiologia , Serina-Treonina Quinases TOR/fisiologia , Animais , Linhagem Celular , Glucose/metabolismo , Transportador de Glucose Tipo 4/metabolismo , Humanos , Proteínas Substratos do Receptor de Insulina/metabolismo , Células Musculares/efeitos dos fármacos , Células Musculares/metabolismo , Músculo Esquelético/metabolismo , Palmitatos/farmacologia , Palmitatos/toxicidade , Fosforilação , Processamento de Proteína Pós-Traducional/efeitos dos fármacos , Transporte Proteico/efeitos dos fármacos , Ratos , Transdução de Sinais/efeitos dos fármacosRESUMO
Since the serendipitous discovery of the first antipsychotic (AP) drug in the 1950s, APs remain the cornerstone of treatment for schizophrenia. A shift over the past two decades away from first-generation, conventional APs to so-called "atypical" (or 2nd/3rd generation) APs parallels acknowledgment of serious metabolic side-effects associated in particular with these newer agents. As will be reviewed, AP drugs and type 2 diabetes are now inextricably linked, contributing to the three- to fivefold increased risk of type 2 diabetes observed in schizophrenia. However, this association is not straightforward. Biological and lifestyle-related illness factors contribute to the association between type 2 diabetes and metabolic disease independently of AP treatment. In addition, APs have a well-established weight gain propensity which could also account for elevated risk of insulin resistance and type 2 diabetes. However, compelling preclinical and clinical evidence now suggests that these drugs can rapidly and directly influence pathways of glucose metabolism independently of weight gain and even in absence of psychiatric illness. Mechanisms of these direct effects remain poorly elucidated but may involve central and peripheral antagonism of neurotransmitters implicated not only in the therapeutic effects of APs but also in glucose homeostasis, possibly via effects on the autonomic nervous system. The clinical relevance of studying "direct" effects of these drugs on glucose metabolism is underscored by the widespread use of these medications, both on and off label, for a growing number of mental illnesses, extending safety concerns well beyond schizophrenia.
Assuntos
Antipsicóticos/uso terapêutico , Diabetes Mellitus Tipo 2/metabolismo , Glucose/metabolismo , Esquizofrenia/tratamento farmacológico , Animais , Sistema Nervoso Autônomo/metabolismo , Clozapina/uso terapêutico , Diabetes Mellitus Tipo 2/epidemiologia , Técnica Clamp de Glucose , Humanos , Resistência à Insulina , Receptores de Dopamina D2/metabolismo , Receptores 5-HT2 de Serotonina/metabolismo , Aumento de PesoRESUMO
Our aim was to examine longitudinal associations of triacylglyceride fatty acid (TGFA) composition with insulin sensitivity (IS) and ß-cell function. Adults at risk for T2D (n = 477) had glucose and insulin measured from a glucose challenge at three time points over 6 years. The outcome variables Matsuda insulin sensitivity index, homeostatic model of assessment 2-percent sensitivity (HOMA2-%S), Insulinogenic Index over HOMA-IR (IGI/IR), and Insulin Secretion-Sensitivity Index-2 were computed from the glucose challenge. Gas chromatography quantified TGFA composition from the baseline. We used adjusted generalized estimating equation (GEE) models and partial least squares (PLS) regression for the analysis. In adjusted GEE models, four TGFAs (14:0, 16:0, 14:1n-7, and 16:1n-7 as mol%) had strong negative associations with IS, whereas others (e.g., 18:1n-7, 18:1n-9, 20:2n-6, and 20:5n-3) had strong positive associations. Few associations were seen for ß-cell function, except for 16:0, 18:1n-7, and 20:2n-6. PLS analysis indicated four TGFAs (14:0, 16:0, 14:1n-7, and 16:1n-7) that clustered together and strongly related with lower IS. These four TGFAs also correlated highly (r > 0.4) with clinically measured triacylglyceride. We found that higher proportions of a cluster of four TGFAs strongly related with lower IS as well as hypertriglyceridemia, suggesting that only a few FAs within the TGFA composition may primarily explain lipids' role in glucose dysregulation.
Assuntos
Diabetes Mellitus Tipo 2/sangue , Ácidos Graxos/química , Triglicerídeos/sangue , Triglicerídeos/química , Estudos de Coortes , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , RiscoRESUMO
AIMS/HYPOTHESIS: Our aim was to determine the longitudinal associations of individual NEFA with the pathogenesis of diabetes, specifically with differences in insulin sensitivity and beta cell function over 6 years in a cohort of individuals who are at risk for diabetes. METHODS: In the Prospective Metabolism and Islet Cell Evaluation (PROMISE) longitudinal cohort, 477 participants had serum NEFA measured at the baseline visit and completed an OGTT at three time points over 6 years. Outcome variables were calculated using the OGTT values. At each visit, insulin sensitivity was assessed using the HOMA2 of insulin sensitivity (HOMA2-%S) and the Matsuda index, while beta cell function was assessed using the insulinogenic index over HOMA-IR (IGI/IR) and the insulin secretion-sensitivity index-2 (ISSI-2). Generalised estimating equations were used, adjusting for time, waist, sex, ethnicity, baseline age, alanine aminotransferase (ALT) and physical activity. NEFA were analysed as both concentrations (nmol/ml) and proportions (mol%) of the total fraction. RESULTS: Participants' (73% female, 70% with European ancestry) insulin sensitivity and beta cell function declined by 14-21% over 6 years of follow-up. In unadjusted models, several NEFA (e.g. 18:1 n-7, 22:4 n-6) were associated with lower insulin sensitivity, however, nearly all of these associations were attenuated in fully adjusted models. In adjusted models, total NEFA, 16:0, 18:1 n-9 and 18:2 n-6 (as concentrations) were associated with 3.7-8.0% lower IGI/IR and ISSI-2, while only 20:5 n-3 (as mol%) was associated with 7.7% higher HOMA2-%S. CONCLUSIONS/INTERPRETATION: Total NEFA concentration was a strong predictor of lower beta cell function over 6 years. Our results suggest that the association with beta cell function is due to the absolute size of the serum NEFA fraction, rather than the specific fatty acid composition.
Assuntos
Ácidos Graxos não Esterificados/sangue , Teste de Tolerância a Glucose , Resistência à Insulina/fisiologia , Células Secretoras de Insulina/metabolismo , Insulina/sangue , Ilhotas Pancreáticas/metabolismo , Adulto , Idoso , Antropometria , Glicemia/metabolismo , Feminino , Humanos , Insulina/metabolismo , Testes de Função Hepática , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Ontário , Estudos Prospectivos , Índice de Gravidade de Doença , Classe Social , Resultado do TratamentoRESUMO
AIM: To investigate the specific effects of intranasal glucagon (ING) on plasma glucose, endogenous glucose production (EGP) and lipid concentration. METHODS: We conducted a single-blind, randomized, crossover study at our academic investigation unit. Under pancreatic clamp conditions with tracer infusion, 1 mg ING or intranasal placebo (INP) was administered to 10 healthy men. As pilot studies showed that ING transiently increased plasma glucagon, we infused intravenous glucagon for 30 minutes along with INP to ensure similar plasma glucagon concentrations between interventions. The main outcome measures were plasma glucose, EGP, free fatty acid (FFA) and triglyceride (TG) concentrations. RESULTS: In the presence of similar plasma glucagon concentrations, the increase in plasma glucose under these experimental conditions was attenuated with ING (mean plasma glucose analysis of variance P < .001) with reduction in EGP (P = .027). No significant differences were seen in plasma FFA and TG concentrations. CONCLUSION: ING raises plasma glucose but this route of administration attenuates the gluco-stimulatory effect of glucagon by reducing EGP. This observation invites speculation about a potential central nervous system effect of glucagon, which requires further investigation. If ING is developed as a treatment for hypoglycaemia, this attenuated effect on plasma glucose should be taken into account.
Assuntos
Glicemia/análise , Glucagon/administração & dosagem , Gluconeogênese/efeitos dos fármacos , Metabolismo dos Lipídeos/efeitos dos fármacos , Fígado/efeitos dos fármacos , Administração Intranasal , Estudos Cross-Over , Deutério , Jejum/sangue , Jejum/metabolismo , Ácidos Graxos não Esterificados/sangue , Glucagon/efeitos adversos , Glucagon/farmacocinética , Glucagon/farmacologia , Técnica Clamp de Glucose , Humanos , Infusões Intravenosas , Insulina/sangue , Fígado/metabolismo , Masculino , Pessoa de Meia-Idade , Absorção Nasal , Proteínas Recombinantes/administração & dosagem , Proteínas Recombinantes/efeitos adversos , Proteínas Recombinantes/farmacocinética , Proteínas Recombinantes/farmacologia , Método Simples-Cego , Triglicerídeos/sangueRESUMO
AIMS/HYPOTHESIS: We have previously shown that oxidative stress plays a causal role in beta cell dysfunction induced by fat. Here, we address whether the proinflammatory kinase inhibitor of (nuclear factor) κB kinase ß (IKKß), which is activated by oxidative stress, is also implicated. METHODS: Fat (oleate or olive oil) was infused intravenously in Wistar rats for 48 h with or without the IKKß inhibitor salicylate. Thereafter, beta cell function was evaluated in vivo using hyperglycaemic clamps or ex vivo in islets isolated from fat-treated rats. We also exposed rat islets to oleate in culture, with or without salicylate and 4(2'-aminoethyl)amino-1,8-dimethylimidazo(1,2-a)quinoxaline; BMS-345541 (BMS, another inhibitor of IKKß) and evaluated beta cell function in vitro. Furthermore, oleate was infused in mice treated with BMS and in beta cell-specific Ikkb-null mice. RESULTS: 48 h infusion of fat impaired beta-cell function in vivo, assessed using the disposition index (DI), in rats (saline: 1.41 ± 0.13; oleate: 0.95 ± 0.11; olive oil [OLO]: 0.87 ± 0.15; p < 0.01 for both fats vs saline) and in mice (saline: 2.51 ± 0.39; oleate: 1.20 ± 0.19; p < 0.01 vs saline) and ex vivo (i.e., insulin secretion, units are pmol insulin islet-1 h-1) in rat islets (saline: 1.51 ± 0.13; oleate: 1.03 ± 0.10; OLO: 0.91 ± 0.13; p < 0.001 for both fats vs saline) and the dysfunction was prevented by co-infusion of salicylate in rats (oleate + salicylate: 1.30 ± 0.09; OLO + salicylate: 1.33 ± 0.23) or BMS in mice (oleate + BMS: 2.25 ± 0.42) in vivo and by salicylate in rat islets ex vivo (oleate + salicylate: 1.74 ± 0.31; OLO + salicylate: 1.54 ± 0.29). In cultured islets, 48 h exposure to oleate impaired beta-cell function ([in pmol insulin islet-1 h-1] control: 0.66 ± 0.12; oleate: 0.23 ± 0.03; p < 0.01 vs saline), an effect prevented by both inhibitors (oleate + salicylate: 0.98 ± 0.08; oleate + BMS: 0.50 ± 0.02). Genetic inhibition of IKKß also prevented fat-induced beta-cell dysfunction ex vivo ([in pmol insulin islet-1 h-1] control saline: 0.16 ± 0.02; control oleate: 0.10 ± 0.02; knockout oleate: 0.17 ± 0.04; p < 0.05 control saline vs. control oleate) and in vivo (DI: control saline: 3.86 ± 0.40; control oleate: 1.95 ± 0.29; knockout oleate: 2.96 ± 0.24; p < 0.01 control saline vs control oleate). CONCLUSIONS/INTERPRETATION: Our results demonstrate a causal role for IKKß in fat-induced beta cell dysfunction in vitro, ex vivo and in vivo.
Assuntos
Ácidos Graxos não Esterificados/metabolismo , Quinase I-kappa B/antagonistas & inibidores , Células Secretoras de Insulina/efeitos dos fármacos , Ácido Oleico/farmacologia , Ácido Salicílico/farmacologia , Animais , Feminino , Imidazóis/farmacologia , Células Secretoras de Insulina/metabolismo , Camundongos , Estresse Oxidativo/efeitos dos fármacos , Quinoxalinas/farmacologia , Ratos , Ratos WistarRESUMO
BACKGROUND: Insulin receptors are widely expressed in the brain and may represent a crossroad between metabolic and cognitive disorders. Although antipsychotics, such as olanzapine, are the cornerstone treatment for schizophrenia, they are associated with high rates of type 2 diabetes and lack efficacy for illness-related cognitive deficits. Historically, this risk of diabetes was attributed to the weight gain propensity of antipsychotics, but recent work suggests antipsychotics can have weight-independent diabetogenic effects involving unknown brain-mediated mechanisms. Here, we examined whether antipsychotics disrupt central insulin action, hypothesizing that olanzapine would impair the well-established ability of central insulin to supress hepatic glucose production. METHODS: Pancreatic euglycemic clamps were used to measure glucose kinetics alongside a central infusion of insulin or vehicle into the third ventricle. Male rats were pretreated with olanzapine or vehicle per our established model of acute olanzapine-induced peripheral insulin resistance. Groups included (central-peripheral) vehicle-vehicle (n = 11), insulin-vehicle (n = 10), insulin-olanzapine (n = 10) and vehicle-olanzapine (n = 8). RESULTS: There were no differences in peripheral glucose or insulin levels. Unexpectedly, we showed that central insulin increased glucose uptake, and this effect was not perturbed by olanzapine. We replicated suppression of glucose production by insulin (clamp relative to basal: 77.9% ± 13.1%, all p < 0.05), an effect abolished by olanzapine (insulin-olanzapine: 7.7% ± 14%). LIMITATIONS: This study used only male rats and an acute dose of olanzapine. CONCLUSION: To our knowledge, this is the first study suggesting olanzapine may impair central insulin sensing, elucidating a potential mechanism of antipsychotic-induced diabetes and opening avenues of investigation related to domains of schizophrenia psychopathology.
Assuntos
Antipsicóticos/farmacologia , Benzodiazepinas/farmacologia , Glucose/metabolismo , Insulina/metabolismo , Animais , Encéfalo/efeitos dos fármacos , Encéfalo/metabolismo , Cateteres de Demora , Infusões Intraventriculares , Insulina/administração & dosagem , Resistência à Insulina/fisiologia , Masculino , Olanzapina , Ratos Sprague-Dawley , Absorção SubcutâneaRESUMO
It has been argued whether insulin accelerates or prevents atherosclerosis. Although results from in vitro studies have been conflicting, recent in vivo mice studies demonstrated antiatherogenic effects of insulin. Insulin is a known activator of endothelial nitric oxide synthase (NOS), leading to increased production of NO, which has potent antiatherogenic effects. We aimed to examine the role of NOS in the protective effects of insulin against atherosclerosis. Male apolipoprotein E-null mice (8 wk old) fed a high-cholesterol diet (1.25% cholesterol) were assigned to the following 12-wk treatments: control, insulin (0.05 U/day via subcutaneous pellet), N(ω)-nitro-l-arginine methyl ester hydrochloride (l-NAME, via drinking water at 100 mg/l), and insulin plus l-NAME. Insulin reduced atherosclerotic plaque burden in the descending aorta by 42% compared with control (plaque area/aorta lumen area: control, 16.5 ± 1.9%; insulin, 9.6 ± 1.3%, P < 0.05). Although insulin did not decrease plaque burden in the aortic sinus, macrophage accumulation in the plaque was decreased by insulin. Furthermore, insulin increased smooth muscle actin and collagen content and decreased plaque necrosis, consistent with increased plaque stability. In addition, insulin treatment increased plasma NO levels, decreased inducible NOS staining, and tended to increase phosphorylated vasodilator-stimulated phosphoprotein staining in the plaques of the aortic sinus. All these effects of insulin were abolished by coadministration of l-NAME, whereas l-NAME alone showed no effect. Insulin also tended to increase phosphorylated endothelial NOS and total neuronal NOS staining, effects not modified by l-NAME. In conclusion, we demonstrate that insulin treatment decreases atherosclerotic plaque burden and increases plaque stability through NOS-dependent mechanisms.
Assuntos
Aorta/efeitos dos fármacos , Inibidores Enzimáticos/farmacologia , Hipoglicemiantes/farmacologia , Insulina/farmacologia , NG-Nitroarginina Metil Éster/farmacologia , Óxido Nítrico Sintase/efeitos dos fármacos , Placa Aterosclerótica/metabolismo , Actinas/efeitos dos fármacos , Actinas/metabolismo , Animais , Aorta/metabolismo , Aorta/patologia , Apolipoproteínas E/genética , Colágeno/efeitos dos fármacos , Colágeno/metabolismo , Macrófagos/efeitos dos fármacos , Macrófagos/patologia , Masculino , Camundongos , Camundongos Knockout , Necrose , Óxido Nítrico Sintase/metabolismo , Óxido Nítrico Sintase Tipo I/efeitos dos fármacos , Óxido Nítrico Sintase Tipo I/metabolismo , Óxido Nítrico Sintase Tipo III/efeitos dos fármacos , Óxido Nítrico Sintase Tipo III/metabolismo , Fosfoproteínas/efeitos dos fármacos , Fosfoproteínas/metabolismo , Placa Aterosclerótica/patologia , Seio Aórtico/efeitos dos fármacos , Seio Aórtico/metabolismo , Seio Aórtico/patologiaRESUMO
Epidemiological studies have demonstrated clear associations between specific dietary and environmental risk factors and incidence of colorectal cancer, but the mechanisms responsible for these associations are not known. An animal model could facilitate such an understanding. Both genotoxic and nongenotoxic carcinogens induce aberrant crypt foci (ACF) in the colons of F344 rats. F344 rats were provided with diets that contained putative risk factors for CRC: low calcium and low vitamin D, high iron, high fructose, and decreased light (UV) exposure or a control diet for 14 wk. The rats were then assessed with biochemical measures and by topological examination for evidence of colon abnormalities. Circulating ionized calcium was decreased from 2.85 to 1.69 mmol/L, and ACF were increased from 0.7 to 13.6 lesions/colon (both P < 0.001). Rats exposed to the multiple environmental conditions associated with colon cancer, developed ACF similar to the heterogeneous or ill-defined ACF in the human colon. Heterogeneous ACF are the most frequently seen in humans and are also seen in rats shortly after exposure to the non-genotoxic colon carcinogen, dextransulfate sodium. The rodent model could be used to assess the pathways from diet and environment to colon cancer and to provide guidance for clinical studies.
Assuntos
Focos de Criptas Aberrantes/etiologia , Neoplasias Colorretais/etiologia , Animais , Cálcio/sangue , Colo/patologia , Modelos Animais de Doenças , Humanos , Masculino , Ratos , Ratos Endogâmicos F344 , Fatores de RiscoRESUMO
Severe malnutrition is a leading cause of global childhood mortality, and infection and hypoglycemia or hyperglycemia are commonly present. The etiology behind the changes in glucose homeostasis is poorly understood. Here, we generated an animal model of severe malnutrition with and without low-grade inflammation to investigate the effects on glucose homeostasis. Immediately after weaning, rats were fed diets containing 5 [low-protein diet (LP)] or 20% protein [control diet (CTRL)], with or without repeated low-dose intraperitoneal lipopolysaccharide (LPS; 2 mg/kg), to mimic inflammation resulting from infections. After 4 wk on the diets, hyperglycemic clamps or euglycemic hyperinsulinemic clamps were performed with infusion of [U-(13)C6]glucose and [2-(13)C]glycerol to assess insulin secretion, action, and hepatic glucose metabolism. In separate studies, pancreatic islets were isolated for further analyses of insulin secretion and islet morphometry. Glucose clearance was reduced significantly by LP feeding alone (16%) and by LP feeding with LPS administration (43.8%) compared with control during the hyperglycemic clamps. This was associated with a strongly reduced insulin secretion in LP-fed rats in vivo as well as ex vivo in islets but signficantly enhanced whole body insulin sensitivity. Gluconeogenesis rates were unaffected by LP feeding, but glycogenolysis was higher after LP feeding. A protein-deficient diet in young rats leads to a susceptibility to low-dose endotoxin-induced impairment in glucose clearance with a decrease in the islet insulin secretory pathway. A protein-deficient diet is associated with enhanced peripheral insulin sensitivity but impaired insulin-mediated suppression of hepatic glycogenolysis.
Assuntos
Glicemia/metabolismo , Dieta com Restrição de Proteínas , Inflamação/metabolismo , Insulina/metabolismo , Ilhotas Pancreáticas/metabolismo , Lipopolissacarídeos/toxicidade , Fígado/metabolismo , Desnutrição Proteico-Calórica/metabolismo , Animais , Glicemia/efeitos dos fármacos , Isótopos de Carbono , Modelos Animais de Doenças , Gluconeogênese/efeitos dos fármacos , Gluconeogênese/fisiologia , Glucose/farmacologia , Técnica Clamp de Glucose , Glicerol/farmacologia , Glicogenólise/efeitos dos fármacos , Glicogenólise/fisiologia , Homeostase/efeitos dos fármacos , Inflamação/induzido quimicamente , Resistência à Insulina , Secreção de Insulina , Ilhotas Pancreáticas/efeitos dos fármacos , Desnutrição/metabolismo , RatosRESUMO
Glycogen synthesis is a major component of the insulin response, and defective glycogen synthesis is a major portion of insulin resistance. Insulin regulates glycogen synthase (GS) through incompletely defined pathways that activate the enzyme through dephosphorylation and, more potently, allosteric activation. We identify Epm2aip1 as a GS-associated protein. We show that the absence of Epm2aip1 in mice impairs allosteric activation of GS by glucose 6-phosphate, decreases hepatic glycogen synthesis, increases liver fat, causes hepatic insulin resistance, and protects against age-related obesity. Our work identifies a novel GS-associated GS activity-modulating component of insulin resistance.
Assuntos
Fosfatases de Especificidade Dupla/genética , Glicogênio Sintase/metabolismo , Glicogênio/biossíntese , Resistência à Insulina/genética , Obesidade/patologia , Envelhecimento/genética , Animais , Fosfatases de Especificidade Dupla/metabolismo , Glucose-6-Fosfato/metabolismo , Glicogênio/genética , Glicogênio Sintase/genética , Humanos , Insulina/genética , Insulina/metabolismo , Fígado/enzimologia , Fígado/metabolismo , Fígado/patologia , Camundongos , Obesidade/etiologia , Obesidade/genética , Fosforilação , Proteínas Tirosina Fosfatases não ReceptorasRESUMO
Fat-induced hepatic insulin resistance plays a key role in the pathogenesis of type 2 diabetes in obese individuals. Although PKC and inflammatory pathways have been implicated in fat-induced hepatic insulin resistance, the sequence of events leading to impaired insulin signaling is unknown. We used Wistar rats to investigate whether PKCδ and oxidative stress play causal roles in this process and whether this occurs via IKKß- and JNK-dependent pathways. Rats received a 7-h infusion of Intralipid plus heparin (IH) to elevate circulating free fatty acids (FFA). During the last 2 h of the infusion, a hyperinsulinemic-euglycemic clamp with tracer was performed to assess hepatic and peripheral insulin sensitivity. An antioxidant, N-acetyl-L-cysteine (NAC), prevented IH-induced hepatic insulin resistance in parallel with prevention of decreased IκBα content, increased JNK phosphorylation (markers of IKKß and JNK activation, respectively), increased serine phosphorylation of IRS-1 and IRS-2, and impaired insulin signaling in the liver without affecting IH-induced hepatic PKCδ activation. Furthermore, an antisense oligonucleotide against PKCδ prevented IH-induced phosphorylation of p47(phox) (marker of NADPH oxidase activation) and hepatic insulin resistance. Apocynin, an NADPH oxidase inhibitor, prevented IH-induced hepatic and peripheral insulin resistance similarly to NAC. These results demonstrate that PKCδ, NADPH oxidase, and oxidative stress play a causal role in FFA-induced hepatic insulin resistance in vivo and suggest that the pathway of FFA-induced hepatic insulin resistance is FFA â PKCδ â NADPH oxidase and oxidative stress â IKKß/JNK â impaired hepatic insulin signaling.
Assuntos
Ácidos Graxos não Esterificados/sangue , Glucose/metabolismo , Resistência à Insulina/fisiologia , Fígado/metabolismo , NADPH Oxidases/metabolismo , Estresse Oxidativo/fisiologia , Proteína Quinase C/metabolismo , Animais , Feminino , Ratos , Ratos WistarRESUMO
Metabolic tests are vital to determine in vivo insulin sensitivity and glucose metabolism in preclinical models, usually rodents. Such tests include glucose tolerance tests, insulin tolerance tests, and glucose clamps. Although these tests are not standardized, there are general guidelines for their completion and analysis that are constantly being refined. In this review, we describe metabolic tests in rodents as well as factors to consider when designing and performing these tests.
Assuntos
Resistência à Insulina , Humanos , Glicemia/metabolismo , Teste de Tolerância a Glucose , Técnica Clamp de Glucose , Insulina/metabolismoRESUMO
Restenosis following percutaneous revascularization is a major challenge in patients with insulin resistance and diabetes. Currently, the vascular effects of insulin are not fully understood. In vitro, insulin's effects on endothelial cells (ECs) are beneficial, whereas on vascular smooth muscle cells (SMCs), they are mitogenic. We previously demonstrated a suppressive effect of insulin on neointimal growth under insulin-sensitive conditions that was abolished in insulin-resistant conditions. Here, we aimed to determine the cell-specific effects of insulin on neointimal growth in a model of restenosis under insulin-sensitive and insulin-resistant conditions. Vascular cell-specific insulin receptor (IR)-deficient mice were fed a low-fat diet (LFD) or a high-fat, high-sucrose diet (HFSD) and implanted with an insulin pellet or vehicle prior to femoral artery wire injury. In insulin-sensitive conditions, insulin decreased neointimal growth only in controls. However, under insulin-resistant conditions, insulin had no effect in either control, EC-specific or SMC-specific IR-deficient mice. These data demonstrate that EC and SMC IRs are required for the anti-restenotic effect of insulin in insulin-sensitive conditions and that, in insulin resistance, insulin has no adverse effect on vascular SMCs in vivo.
Assuntos
Modelos Animais de Doenças , Células Endoteliais , Resistência à Insulina , Insulina , Receptor de Insulina , Animais , Insulina/metabolismo , Insulina/farmacologia , Camundongos , Receptor de Insulina/metabolismo , Células Endoteliais/metabolismo , Células Endoteliais/efeitos dos fármacos , Miócitos de Músculo Liso/metabolismo , Miócitos de Músculo Liso/efeitos dos fármacos , Neointima/patologia , Neointima/metabolismo , Masculino , Músculo Liso Vascular/metabolismo , Músculo Liso Vascular/efeitos dos fármacos , Músculo Liso Vascular/patologia , Camundongos Endogâmicos C57BLRESUMO
In rats, cannulation of the jugular vein and the carotid artery precedes the use of the hyperinsulinemic euglycemic clamp to determine insulin sensitivity in vivo. Here, we present a vascular surgery protocol to allow the infusion of substances via the vein and the collection of blood samples from the artery on the day of the hyperinsulinemic euglycemic clamp. We describe steps for preparing for and performing catheterization surgery. We then detail procedures for clamp preparation and its use. For complete details on the use and execution of this protocol, please refer to Pereira et al.1,2,3.
RESUMO
Olanzapine is a second-generation antipsychotic that disrupts metabolism and is associated with an increased risk of type 2 diabetes. The hypothalamus is a key region in the control of whole-body metabolic homeostasis. The objective of the current study was to determine how acute peripheral olanzapine administration affects transcription and serine/threonine kinase activity in the hypothalamus. Hypothalamus samples from rats were collected following the pancreatic euglycemic clamp, thereby allowing us to study endpoints under steady state conditions for plasma glucose and insulin. Olanzapine stimulated pathways associated with inflammation, but diminished pathways associated with the capacity to combat endoplasmic reticulum stress and G protein-coupled receptor activity. These pathways represent potential targets to reduce the incidence of type 2 diabetes in patients taking antipsychotics.
Assuntos
Antipsicóticos , Diabetes Mellitus Tipo 2 , Humanos , Ratos , Animais , Olanzapina/farmacologia , Olanzapina/metabolismo , Diabetes Mellitus Tipo 2/tratamento farmacológico , Diabetes Mellitus Tipo 2/metabolismo , Benzodiazepinas/farmacologia , Benzodiazepinas/metabolismo , Antipsicóticos/farmacologia , Antipsicóticos/metabolismo , Hipotálamo/metabolismo , Perfilação da Expressão GênicaRESUMO
In the classical insulin target tissues of liver, muscle, and adipose tissue, chronically elevated levels of free fatty acids (FFA) impair insulin signaling. Insulin signaling molecules are also present in ß-cells where they play a role in ß-cell function. Therefore, inhibition of the insulin/insulin-like growth factor 1 pathway may be involved in fat-induced ß-cell dysfunction. To address the role of ß-cell insulin resistance in FFA-induced ß-cell dysfunction we co-infused bisperoxovanadate (BPV) with oleate or olive oil for 48 hours in rats. BPV, a tyrosine phosphatase inhibitor, acts as an insulin mimetic and is devoid of any antioxidant effect that could prevent ß-cell dysfunction, unlike most insulin sensitizers. Following fat infusion, rats either underwent hyperglycemic clamps for assessment of ß-cell function in vivo or islets were isolated for ex vivo assessment of glucose-stimulated insulin secretion (GSIS). We also incubated islets with oleate or palmitate and BPV for in vitro assessment of GSIS and Akt (protein kinase B) phosphorylation. Next, mice with ß-cell specific deletion of PTEN (phosphatase and tensin homolog; negative regulator of insulin signaling) and littermate controls were infused with oleate for 48 hours, followed by hyperglycemic clamps or ex vivo evaluation of GSIS. In rat experiments, BPV protected against fat-induced impairment of ß-cell function in vivo, ex vivo, and in vitro. In mice, ß-cell specific deletion of PTEN protected against oleate-induced ß-cell dysfunction in vivo and ex vivo. These data support the hypothesis that ß-cell insulin resistance plays a causal role in FFA-induced ß-cell dysfunction.