Hyperinsulinemic-euglycemic Clamp Test Research Articles

Central Administration of Galanin Receptor 1 Agonist Boosted Insulin Sensitivity in Adipose Cells of Diabetic Rats.

Our previous studies testified the beneficial effect of central galanin on insulin sensitivity of type 2 diabetic rats. The aim of the study was further to investigate whether central M617, a galanin receptor 1 agonist, can benefit insulin sensitivity. The effects of intracerebroventricular administration of M617 on insulin sensitivity and insulin signaling were evaluated in adipose tissues of type 2 diabetic rats. The results showed that central injection of M617 significantly increased plasma adiponectin contents, glucose infusion rates in hyperinsulinemic-euglycemic clamp tests, GLUT4 mRNA expression levels, GLUT4 contents in plasma membranes, and total cell membranes of the adipose cells but reduced the plasma C-reactive protein concentration in nondiabetic and diabetic rats. The ratios of GLUT4 contents were higher in plasma membranes to total cell membranes in both nondiabetic and diabetic M617 groups than each control. In addition, the central administration of M617 enhanced the ratios of pAkt/Akt and pAS160/AS160, but not phosphorylative cAMP response element-binding protein (pCREB)/CREB in the adipose cells of nondiabetic and diabetic rats. These results suggest that excitation of central galanin receptor 1 facilitates insulin sensitivity via activation of the Akt/AS160 signaling pathway in the fat cells of type 2 diabetic rats.

Training Does Not Alter Muscle Ceramide and Diacylglycerol in Offsprings of Type 2 Diabetic Patients Despite Improved Insulin Sensitivity.

Ceramide and diacylglycerol (DAG) may be involved in the early phase of insulin resistance but data are inconsistent in man. We evaluated if an increase in insulin sensitivity after endurance training was accompanied by changes in these lipids in skeletal muscle. Nineteen first-degree type 2 diabetes Offsprings (Offsprings) (age: 33.1 ± 1.4 yrs; BMI: 26.4 ± 0.4 kg/m2) and sixteen matched Controls (age: 31.3 ± 1.5 yrs; BMI: 25.3 ± 0.7 kg/m2) performed 10 weeks of endurance training three times a week at 70% of VO2max on a bicycle ergometer. Before and after the intervention a hyperinsulinemic-euglycemic clamp and VO2max test were performed and muscle biopsies obtained. Insulin sensitivity was significantly lower in Offsprings compared to control subjects (p < 0.01) but improved in both groups after 10 weeks of endurance training (Off: 17 ± 6%; Con: 12 ± 9%, p < 0.01). The content of muscle ceramide, DAG, and their subspecies were similar between groups and did not change in response to the endurance training except for an overall reduction in C22:0-Cer (p < 0.05). Finally, the intervention induced an increase in AKT protein expression (Off: 27 ± 11%; Con: 20 ± 24%, p < 0.05). This study showed no relation between insulin sensitivity and ceramide or DAG content suggesting that ceramide and DAG are not major players in the early phase of insulin resistance in human muscle.

Inhibition of MEK1 Signaling Pathway in the Liver Ameliorates Insulin Resistance.

Although mitogen-activated protein kinase kinase (MEK) is a key signaling molecule and a negative regulator of insulin action, it is still uncertain whether MEK can be a therapeutic target for amelioration of insulin resistance (IR) in type 2 diabetes (T2D) in vivo. To clarify whether MEK inhibition improves T2D, we examined the effect of continuous MEK inhibition with two structurally different MEK inhibitors, RO5126766 and RO4987655, in mouse models of T2D. RO5126766 and RO4987655 were administered via dietary admixture. Both compounds decreased blood glucose and improved glucose tolerance in doses sufficient to sustain inhibition of extracellular signal-regulated kinase (ERK)1/2 phosphorylation downstream of MEK in insulin-responsive tissues in db/db mice. A hyperinsulinemic-euglycemic clamp test showed increased glucose infusion rate (GIR) in db/db mice treated with these compounds, and about 60% of the increase was attributed to the inhibition of endogenous glucose production, suggesting that the liver is responsible for the improvement of IR. By means of adenovirus-mediated Mek1 shRNA expression, we confirmed that blood glucose levels are reduced by suppression of MEK1 expression in the liver of db/db mice. Taken together, these results suggested that the MEK signaling pathway could be a novel therapeutic target for novel antidiabetic agents.

Combined intervention with pioglitazone and n-3 fatty acids in metformin-treated type 2 diabetic patients: improvement of lipid metabolism.

BackgroundThe marine n-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) exert numerous beneficial effects on health, but their potency to improve treatment of type 2 diabetic (T2D) patients remains poorly characterized. We aimed to evaluate the effect of a combination intervention using EPA + DHA and the insulin-sensitizing drug pioglitazone in overweight/obese T2D patients already treated with metformin.MethodsIn a parallel-group, four-arm, randomized trial, 69 patients (66 % men) were assigned to 24-week-intervention using: (i) corn oil (5 g/day; Placebo), (ii) pioglitazone (15 mg/day; Pio), (iii) EPA + DHA concentrate (5 g/day, containing ~2.8 g EPA + DHA; Omega-3), or (iv) pioglitazone and EPA + DHA concentrate (Pio& Omega-3). Data from 60 patients were used for the final evaluation. At baseline and after intervention, various metabolic markers, adiponectin and cytokines were evaluated in serum using standard procedures, EPA + DHA content in serum phospholipids was evaluated using shotgun lipidomics and mass spectrometry, and hyperinsulinemic-euglycemic clamp and meal test were also performed. Indirect calorimetry was conducted after the intervention. Primary endpoints were changes from baseline in insulin sensitivity evaluated using hyperinsulinemic-euglycemic clamp and in serum triacylglycerol concentrations in fasting state. Secondary endpoints included changes in fasting glycemia and glycated hemoglobin (HbA1c), changes in postprandial glucose, free fatty acid and triacylglycerol concentrations, metabolic flexibility assessed by indirect calorimetry, and inflammatory markers.ResultsOmega-3 and Pio& Omega-3 increased EPA + DHA content in serum phospholipids. Pio and Pio& Omega-3 increased body weight and adiponectin levels. Both fasting glycemia and HbA1c were increased by Omega-3, but were unchanged by Pio& Omega-3. Insulin sensitivity was not affected by Omega-3, while it was improved by Pio& Omega-3. Fasting triacylglycerol concentrations and inflammatory markers were not significantly affected by any of the interventions. Lipid metabolism in the meal test and metabolic flexibility were additively improved by Pio& Omega-3.ConclusionBesides preventing a modest negative effect of n-3 fatty acids on glycemic control, the combination of pioglitazone and EPA + DHA can be used to improve lipid metabolism in T2D patients on stable metformin therapy.Trial registrationEudraCT number 2009-011106-42.Electronic supplementary materialThe online version of this article (doi:10.1186/s12986-015-0047-9) contains supplementary material, which is available to authorized users.

Body Mass Index below Obesity Threshold Implies Similar Cardiovascular Risk among Various Polycystic Ovary Syndrome Phenotypes

Objective: The aim of this study was to determine the cardiometabolic risk factors in different polycystic ovary syndrome (PCOS) phenotypes. Subjects and Methods: This cross-sectional study was performed between 2010 and 2011. Eighty-nine patients with PCOS and 25 age- and weight-matched healthy controls were included in the study. Patients were grouped using the Rotterdam 2003 criteria as: group 1, oligomenorrhea and/or anovulation (ANOV) and hyperandrogenemia (HA) and/or hyperandrogenism (n = 23); group 2, ANOV and polycystic ovaries (PCO; n = 22); group 3, HA and PCO (n = 22); group 4, ANOV, HA and PCO (n = 22); group 5, controls (n = 25). Laboratory blood tests for diagnosis and cardiometabolic risk assessments were performed. Insulin resistance (IR) was calculated in all patients with the homeostasis model assessment of IR (HOMA-IR) formula. An euglycemic hyperinsulinemic clamp test was performed on 5 randomly selected cases in each subgroup, making 25 cases in total, and indicated as the ‘M' value (mg/kg/min), which is the total body glucose disposal rate. Results: The mean BMl values of the groups were: group 1, 26.1 ± 5.3; group 2, 27.9 ± 5.2; group 3, 24.3 ± 4.2; group 4, 27.9 ± 7.5; group 5, 24.7 ± 5.2 (p > 0.05). There were no differences in the lipid profile, plasma glucose, HOMA-IR, insulin and M values between the groups (p > 0.05). Phenotypes with oligomenorrhea/anovulation (groups 1, 2 and 4) were more obese than group 3 (p = 0.039). Conclusions: The cardiometabolic risk profile was similar among the PCOS subgroups. This finding could be attributed to the mean BMl values, which, being below 30, were not within the obesity range. Obesity appeared to be an important determinant of high cardiovascular risk in PCOS.

Intracerebroventricular Injection of Alarin Increased Glucose Uptake in Skeletal Muscle of Diabetic Rats.

In order to investigate the central effect of alarin on glucose uptake, we administered alarin and/ or its inhibitor, ala6-25Cys into the cerebral ventricles of the type 2 diabetic rats. Then the relative parameters about glucose uptake in skeletal muscles were measured. We found that central treatment with alarin significantly increased the food intake, body weight and glucose infusion rates in hyperinsulinemic euglycemic clamp tests of the animals. Besides, the treatment also enhanced 2-deoxy-[3H]-D-glucose uptake, vesicle-associated membrane protein 2 contents, glucose transporter 4 protein and mRNA expression, as well as pAktThr308, pAktSer473 and total Akt levels in muscle cells, but reduced plasma glucose and insulin levels of the rats. All of the alarin-inducing events may be antagonised by central injection of ala6-25Cys. These results suggest that central administration of alarin stimulates glucose uptake mediated by activation of Akt signal pathway in type 2 diabetic animals.

Effects of Estrogen on Insulin Sensitivity and Adipokines in Mice.

To study the potential mechanisms via which estrogen exerts its effects on the insulin sensitivity in mice. Totally 36 female C57BL/6J mice aged 6 weeks were randomly divided into six groups:normal diet (NOR) group, normal diet with ovariectomy (NOR+OVX) group, normal diet with ovariectomy and estrogen replacement (NOR+OVX+E2) group,high-fat diet (HF) group, high-fat diet with ovariectomy (HF+OVX) group, and high-fat diet with ovariectomy and estrogen replacement (HF+OVX+E2) group. There were six mice in each group. After the ovariectomy based on the grouping, the mice were given normal diet or high-fat diet for 20 weeks. The intervention groups were given estrogen (5 μg/d,subcutaneous injection) for 20 days. Then,the body weight,visceral fat weight,oral glucose tolerance and insulin sensitivity (by euglycemic hyperinsulinemic clamp test), and serum leptin, adiponectin,and resistin levels were compared among these six groups. Compared with HF group, the HF+OVX group had significantly higher body weight and visceral fat weight and lower glucose tolerance, which were significantly improved after estrogen replacement therapy (all P<0.05). However, these indicators showed no significant differences among groups with normal diets (all P>0.05). The insulin sensitivity of ovariectomized mice was significantly decreased in both high-fat and normal diet groups and was also improved significantly after estrogen replacement (P<0.05). The serum leptin was increased and adiponectin was decreased significantly in ovariectomized mice, and the improvements of these two adipokines were also statistically significant after estrogen therapy (P<0.05): however,the serum resistin level was not significantly different among these 6 groups (P>0.05). Estrogen replacement therapy can improve insulin resistance by lowering body weight. In addition, it can exert its effect directly on adipose tissue,improve the levels of adipokines,reduce the amount of visceral fat, and improve insulin sensitivity in mice.

Effect of Chronic Pioglitazone Treatment on Hepatic Gene Expression Profile in Obese C57BL/6J Mice.

Pioglitazone, a selective ligand of peroxisome proliferator-activated receptor gamma (PPARγ), is an insulin sensitizer drug that is being used in a number of insulin-resistant conditions, including non-alcoholic fatty liver disease (NAFLD). However, there is a discrepancy between preclinical and clinical data in the literature and the benefits of pioglitazone treatment as well as the precise mechanism of action remain unclear. In the present study, we determined the effect of chronic pioglitazone treatment on hepatic gene expression profile in diet-induced obesity (DIO) C57BL/6J mice in order to understand the mechanisms of NAFLD induced by PPARγ agonists. DIO mice were treated with pioglitazone (25 mg/kg/day) for 38 days, the gene expression profile in liver was evaluated using Affymetrix Mouse GeneChip 1.0 ST array. Pioglitazone treatment resulted in exacerbated hepatic steatosis and increased hepatic triglyceride and free fatty acids concentrations, though significantly increased the glucose infusion rate in hyperinsulinemic-euglycemic clamp test. The differentially expressed genes in liver of pioglitazone treated vs. untreated mice include 260 upregulated and 86 downregulated genes. Gene Ontology based enrichment analysis suggests that inflammation response is transcriptionally downregulated, while lipid metabolism is transcriptionally upregulated. This may underlie the observed aggravating liver steatosis and ameliorated systemic insulin resistance in DIO mice.

Insulin response of the glucose and fatty acid metabolism in dry dairy cows across a range of body condition scores

The objective of the present research was to determine the insulin response of the glucose and fatty acid metabolism in dry dairy cows with a variable body condition score (BCS). Ten pregnant Holstein Friesian dairy cows (upcoming parity 2 to 5) were selected based on BCS at the beginning of the study (2mo before expected parturition date). During the study, animals were monitored weekly for BCS and backfat thickness and in the last 2wk, blood samples were taken for determination of serum nonesterified fatty acid (NEFA) concentration. Animals underwent a hyperinsulinemic euglycemic clamp test in the third week before the expected parturition date. The hyperinsulinemic euglycemic clamp test consisted of 4 consecutive insulin infusions with increasing insulin doses: 0.1, 0.5, 2, and 5mIU/kg per minute. For each insulin infusion period, a steady state was defined as a period of 30min where no or minor changes of the glucose infusion were necessary to keep the blood glucose concentration constant and near basal levels. During the steady state, the glucose infusion rate [steady state glucose infusion rate (SSGIR) in µmol/kg per minute] and NEFA concentration [steady state NEFA concentration (SSNEFA) in mmol/L] were determined and reflect the insulin response of the glucose and fatty acid metabolism. Dose response curves were created based on the insulin concentrations during the steady state and the SSGIR or SSNEFA. The shape of the dose response curves is determined by the concentration of insulin needed to elicit the half maximal effect (EC50) and the maximal SSGIR or the minimal SSNEFA for the glucose or fatty acid metabolism, respectively. The maximal SSGIR was negatively associated with variables reflecting adiposity of the cows (BCS, backfat thickness, NEFA concentration during the dry period, and absolute weight of the different adipose depots determined after euthanasia and dissection of the different depots), whereas the EC50 of the glucose metabolism was positively associated with these variables. These results reflect a decreased insulin sensitivity and a decreased insulin responsiveness of the glucose metabolism in overconditioned dry dairy cows. The minimal SSNEFA and the EC50 of the fatty acid metabolism were not associated with variables reflecting adiposity of the cows, meaning that the insulin response of the fatty acid metabolism was not associated with the level of fat accumulation in dry dairy cows. Additionally, within individual cows, the EC50 of the glucose metabolism was higher than the EC50 of the fatty acid metabolism, meaning that the response of the fatty acid metabolism occurs at lower insulin concentrations compared with the response of the glucose metabolism. It can be concluded that a negative association exists between the level of fat accumulation in pregnant dairy cows at the end of the dry period and the insulin response of the glucose metabolism.

Plasma Lactate Levels Increase during Hyperinsulinemic Euglycemic Clamp and Oral Glucose Tolerance Test.

Insulin resistance, which plays a central role in the pathogenesis of type 2 diabetes (T2D), is an early indicator that heralds the occurrence of T2D. It is imperative to understand the metabolic changes that occur at the cellular level in the early stages of insulin resistance. The objective of this study was to determine the pattern of circulating lactate levels during oral glucose tolerance test (OGTT) and hyperinsulinemic euglycemic clamp (HIEC) study in normal nondiabetic subjects. Lactate and glycerol were determined every 30 minutes during OGTT and HIEC on 22 participants. Lactate progressively increased throughout the HIEC study period (P < 0.001). Participants with BMI < 30 had significantly higher mean M-values compared to those with BMI ≥ 30 at baseline (P < 0.05). This trend also continued throughout the OGTT. In addition, those with impaired glucose tolerance test (IGT) had significantly higher mean lactate levels compared to those with normal glucose tolerance (P < 0.001). In conclusion, we found that lactate increased during HIEC study, which is a state of hyperinsulinemia similar to the metabolic milieu seen during the early stages in the development of T2D.

Assessment of insulin sensitivity/resistance.

Insulin resistance is one pretty troublesome entity which very commonly aggravates metabolic syndrome. Many methods and indices are available for the estimation of insulin resistance. It is essential to test and validate their reliability before they can be used as an investigation in patients. At present, hyperinsulinemic euglycemic clamp and intravenous glucose tolerance test are the most reliable methods available for estimating insulin resistance and are being used as a reference standard. Some simple methods, from which indices can be derived, have been validated e.g. homeostasis model assessment (HOMA), quantitative insulin sensitivity check index (QUICKI). For the clinical uses HOMA-insulin resistance, QUIKI, and Matsuda are suitable, while HES, McAuley, Belfiore, Cederholm, Avignon and Stumvoll index are suitable for epidemiological/research purposes. With increasing number of these available indices of IR, it may be difficult for clinicians to select the most appropriate index for their studies. This review provides guidelines that must be considered before performing such studies.

Clearance approach in hyperinsulinemic–euglycemic clamp evaluation in lean and obese subjects

Purpose/Aim: The main aim of this study was to propose a method to express whole body insulin sensitivity as estimated by a hyperinsulinemic–euglycemic clamp (HEC) as a dimensionless parameter. Materials and methods: Two groups of subjects were examined: The first group was comprised of seven healthy lean volunteers with BMI <25 kg/m2 and a second group comprised of four obese subjects with BMI ≥30 kg/m2. The dependence between the M/I index expressing the whole body insulin sensitivity, and the dimensionless whole human body effect E as a ratio of the clearance of glucose and the clearance of insulin after their exogenous administration during the last 40 min of the HEC test, was expressed by regression analysis. Unlike an expression of insulin sensitivity/resistance as a function of M taking into account the space corrections or the M/I index, our whole human body effect represents the insulin sensitivity/resistance as a dimensionless number. Results: A linear dependence between the M/I index and the dimensionless effect E with zero intercept and slope at 2.2623 ± 0.157, r = 0.914, and between the M/I index and the effect E recalculated per kg of human body weight with zero intercept and slope at 0.03164 ± 0.00127, r = 0.978, were observed. Conclusions: The high correlation between the M/I index and new effect E in lean and obese volunteers confirms our proposal that the HEC test could be evaluated by a dimensionless parameter which eliminates potential unit mismatches in the expression of clamp results.

Low-energy diets differing in fibre, red meat and coffee intake equally improve insulin sensitivity in type 2 diabetes: a randomised feasibility trial.

Epidemiological studies have found that a diet high in fibre and coffee, but low in red meat, reduces the risk for type 2 diabetes. We tested the hypothesis that these nutritional modifications differentially improve whole-body insulin sensitivity (primary outcome) and secretion. Inclusion criteria were: age 18-69 years, BMI ≥ 30 kg/m(2), type 2 diabetes treated with diet, metformin or acarbose and known disease duration of ≤ 5 years. Exclusion criteria were: HbA1c >75 mmol/mol (9.0%), type 1 or secondary diabetes types and acute or chronic diseases including cancer. Patients taking any medication affecting the immune system or insulin sensitivity, other than metformin, were also excluded. Of 59 patients (randomised using randomisation blocks [four or six patients] with consecutive numbers), 37 (54% female) obese type 2 diabetic patients completed this controlled parallel-group 8-week low-energy dietary intervention. The participants consumed either a diet high in cereal fibre (whole grain wheat/rye: 30-50 g/day) and coffee (≥ 5 cups/day), and free of red meat (L-RISK, n = 17) or a diet low in fibre (≤ 10 g/day), coffee-free and high in red meat (≥ 150 g/day) diet (H-RISK, n = 20). Insulin sensitivity and secretion were assessed by hyperinsulinaemic-euglycaemic clamp and intravenous glucose tolerance tests with isotope dilution. Whole-body and organ fat contents were measured by magnetic resonance imaging and spectroscopy. Whole-body insulin sensitivity increased in both groups (mean [95% CI]) (H-RISK vs L-RISK: 0.8 [0.2, 1.4] vs 1.0 [0.4, 1.7]mg kg(-1) min(-1), p = 0.59), while body weight decreased (-4.8% [-6.1%, -3.5%] vs -4.6% [-6.0%, -3.3%], respectively). Hepatic insulin sensitivity remained unchanged, whereas hepatocellular lipid content fell in both groups (-7.0% [-9.6%, -4.5%] vs -6.7% [-9.5%, -3.9%]). Subcutaneous fat mass (-1,553 [-2,767, -340] cm(3) vs -751 [-2,047; 546] cm(3), respectively) visceral fat mass (-206 [-783, 371] cm(3) vs -241 [-856, 373] cm(3), respectively) and muscle fat content (-0.09% [-0.16%, -0.02%] vs -0.02% [-0.10%, 0.05%], respectively) decreased similarly. Insulin secretion remained unchanged, while the proinflammatory marker IL-18 decreased only after the L-RISK diet. No evidence of a difference between both low-energy diets was identified. Thus, energy restriction per se seems to be key for improving insulin action in phases of active weight loss in obese type 2 diabetic patients, with a potential improvement of subclinical inflammation with the L-RISK diet. Clinicaltrials.gov NCT01409330. This study was supported by the Ministry of Science and Research of the State of North Rhine-Westphalia (MIWF NRW), the German Federal Ministry of Health (BMG), the Federal Ministry for Research (BMBF) to the Center for Diabetes Research (DZD e.V.) and the Helmholtz Alliance Imaging and Curing Environmental Metabolic Diseases (ICEMED).

Mechanism of action of hypoglycemic effects of an intestine-specific inhibitor of microsomal triglyceride transfer protein (MTP) in obese rats

Diminished insulin sensitivity in the peripheral tissues and failure of pancreatic beta cells to secrete insulin are known major determinants of type 2 diabetes mellitus. JTT-130, an intestine-specific microsomal transfer protein inhibitor, has been shown to suppress high fat-induced obesity and ameliorate impaired glucose tolerance while enhancing glucagon-like peptide-1 (GLP-1) secretion. We investigated the effects of JTT-130 on glucose metabolism and elucidated the mechanism of action, direct effects on insulin sensitivity and glucose-stimulated insulin secretion in a high fat diet-induced obesity rat model. Male Sprague Dawley rats fed a high-fat diet were treated with a single administration of JTT-130. Glucose tolerance, hyperglycemic clamp and hyperinsulinemic-euglycemic testing were performed to assess effects on insulin sensitivity and glucose-stimulated insulin secretion, respectively. Plasma GLP-1 and tissue triglyceride content were also determined under the same conditions. A single administration of JTT-130 suppressed plasma glucose elevations after oral glucose loading and increased the disposition index while elevating GLP-1. JTT-130 also enhanced glucose-stimulated insulin secretion in hyperglycemic clamp tests, whereas increased insulin sensitivity was observed in hyperinsulinemic-euglycemic clamp tests. Single-dose administration of JTT-130 decreased lipid content in the liver and skeletal muscle. JTT-130 demonstrated acute and direct hypoglycemic effects by enhancing insulin secretion and/or insulin sensitivity.

Effect of endogenous galanin on glucose transporter 4 expression in cardiac muscle of type 2 diabetic rats

Although galanin has been shown to increase glucose transporter 4 (GLUT4) expression in skeletal muscle and adipocytes of rats, there is no literature available about the effect of galanin on GLUT4 expression in cardiac muscle of type 2 diabetic rats. In this study, we investigated the relationship between intracerebroventricular administration of M35, a galanin receptor antagonist, and GLUT4 expression in cardiac muscle of type 2 diabetic rats. The rats tested were divided into four groups: rats from healthy and type 2 diabetic drug groups were injected with 2μM M35 for three weeks, while both control groups with 2μl vehicle control. The euglycemic-hyperinsulinemic clamp test was conducted for an index of glucose infusion rates. The cardiac muscle was processed for determination of GLUT4 expression levels. The present study showed that the plasma insulin and retinol binding protein 4 (RBP4) levels were higher in both drug groups than controls respectively. Moreover, the results showed the inhibitive effect of central M35 treatment on glucose infusion rates in the euglycemic-hyperinsulinemic clamp test and GLUT4 expression levels in the cardiac muscle. These results demonstrate that endogenous galanin, acting through its central receptor, has an important attribute to increase GLUT4 expression, leading to enhance insulin sensitivity and glucose uptake in cardiac muscle of type 2 diabetic rats. Galanin and its fragment can play a significant role in regulation of glucose metabolic homeostasis in cardiac muscle and galanin is an important hormone relative to diabetic heart.

Effect of Hypericum perforatum L. extract on insulin resistance and lipid metabolic disorder in high-fat-diet induced obese mice.

Natural product Hypericum perforatum L. has been used in folk medicine to improve mental performance. However, the effect of H. perforatum L. on metabolism is still unknown. In order to test whether H. perforatum L. extract (EHP) has an effect on metabolic syndrome, we treated diet induced obese (DIO) C57BL/6J mice with the extract. The chemical characters of EHP were investigated with thin-layer chromatography, ultraviolet, high-performance liquid chromatography (HPLC), and HPLC-mass spectrometry fingerprint analysis. Oral glucose tolerance test (OGTT), insulin tolerance test (ITT), and the glucose infusion rate (GIR) in hyperinsulinemic–euglycemic clamp test were performed to evaluate the glucose metabolism and insulin sensitivity. Skeletal muscle was examined for lipid metabolism. The results suggest that EHP can significantly improve the glucose and lipid metabolism in DIO mice. In vitro, EHP inhibited the catalytic activity of recombinant human protein tyrosine phosphatase 1B (PTP1B) and reduced the protein and mRNA levels of PTP1B in the skeletal muscle. Moreover, expressions of genes related to fatty acid uptake and oxidation were changed by EHP in the skeletal muscle. These results suggest that EHP may improve insulin resistance and lipid metabolism in DIO mice. © 2014 The Authors. Phytotherapy Research published by John Wiley & Sons Ltd.

Central alarin ameliorated insulin resistance of adipocytes in type 2 diabetic rats.

Alarin, a regulatory peptide, belongs to the galanin family and plays the same regulatory roles as galanin in orexigenic activity and energy metabolism. Our previous studies had found that galanin might facilitate insulin sensitivity via activation of its central receptors. To date, little is known about whether central alarin may exert similar effects on insulin sensitivity. In order to investigate this, alarin and its specific antagonist, alarin 6-25Cys, were administered into the cerebral ventricles of type 2 diabetic rats (T2DR) to evaluate the changes in insulin resistance. The results indicated that central treatment with alarin significantly increased the body weight of animals, the 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose uptake, the plasma adiponectin levels, the glucose infusion rates in hyperinsulinemic-euglycemic clamp tests, the vesicle-associated membrane protein 2 as well as glucose transporter 4 (GLUT4 (SLC2A4)) protein and mRNA levels, and the ratios of GLUT4 contents in plasma membranes to total cell membranes in adipocytes, but reduced blood glucose and plasma retinol-binding protein 4 levels. These effects of alarin may be inhibited by pretreatment with alarin 6-25Cys. The above-mentioned results suggest that the central alarin projective system may facilitate insulin sensitivity and glucose uptake via the increase in GLUT4 content and GLUT4 translocation from intracellular pools to plasma membranes in T2DR.

Leukocyte profiles differ between type 1 and type 2 diabetes and are associated with metabolic phenotypes: results from the German Diabetes Study (GDS).

Altered immune reactivity precedes and accompanies type 1 and type 2 diabetes. We hypothesized that the metabolic phenotype relates to the systemic cellular immune status. A total of 194 metabolically well-controlled patients with type 1 diabetes (n = 62, mean diabetes duration 1.29 years) or type 2 diabetes (n = 132, 1.98 years) and 60 normoglycemic persons underwent blood sampling for automated white blood cell counting (WBC) and flow cytometry. Whole-body insulin sensitivity was measured with hyperinsulinemic-euglycemic clamp tests. Patients with type 2 diabetes had higher WBC counts than control subjects along with a higher percentage of T cells and activated T helper (Th) and cytotoxic T (Tc) cells but lower proportions of natural killer (NK) cells. In type 1 diabetes, the percentage of activated Th and Tc cells was also higher compared with control subjects, whereas the ratio of regulatory T (Treg) cells to activated Th cells was lower, suggesting diminished regulatory capacity. Parameters of glycemic control related positively to Treg cells only in type 2 diabetes. Upon age, sex, and body mass adjustments, insulin sensitivity correlated positively with monocytes, while circulating lipids correlated positively with T cell subsets in type 1 diabetes. Immune cell phenotypes showed distinct frequencies of occurrence in both diabetes types and associate with insulin sensitivity, glycemia, and lipidemia.

Transcription factor NF-E2-related factor 1 impairs glucose metabolism in mice.

Nrf1 (NF-E2-related factor 1) is a basic region leucine zipper-type transcription factor belonging to the CNC (cap-'n'-collar) family. Major pathophysiological contribution of Nrf1 remains unclear. As single nucleotide polymorphism rs3764400 in 5'-flanking region of NRF1 gene appears to associate with obesity, in this study, we focused on the Nrf1 function on metabolism. We found that the risk C allele of rs3764400 increased NRF1 gene transcriptional activity compared with the T allele in hepatoma cell lines. Therefore, we newly established Nrf1 transgenic (Nrf1-Tg) mouse lines and examined roles that Nrf1 plays on the obesity and metabolism. Unexpectedly, Nrf1 over-expression repressed bodyweight gain in both lean and diet-induced obesity mice. Of note, Nrf1-Tg mice showed rise in blood glucose levels; Nrf1 strongly reduced glucose infusion rate in euglycemic-hyperinsulinemic clamp test and increased blood glucose levels in insulin tolerance test, indicating that Nrf1 induces insulin resistance in mice. Nrf1 repressed insulin-regulated glycolysis-related gene expression and gave rise to loss of glucose-6-phosphate and fructose-6-phosphate contents in liver. Consistently, Nrf1 heterozygote improved impaired glucose regulations in diet-induced obesity model. These results showed that Nrf1 contributes to metabolic regulation, which gain-of-function develops diabetes mellitus in mice.

Combined galanin with insulin improves insulin sensitivity of diabetic rat muscles

Although administration of galanin or insulin alone may enhance insulin sensitivity and glucose transporter 4 (GLUT4) trafficking, their cooperative effect on insulin sensitivity is still unclear. In the present study, we evaluated the cooperative effect of both reagents compared with solitary treatment with galanin or insulin in type 2 diabetic rats. Galanin and/or insulin were injected singly or together into type 2 diabetic rats once a day for 15 days. The results indicated that coadministration of both reagents compared with treatment with galanin or insulin alone significantly increased glucose infusion rates in euglycemic-hyperinsulinemic clamp tests, 2-deoxy-[(3)H]d-glucose contents, GLUT4 densities, and pAS160 and protein kinase C activity levels, but reduced blood glucose and insulin levels, as well as retinol-binding protein 4 contents, and did not affect Glut4 (Slc2a4) mRNA expression levels in myocytes. The changes in the ratios of GLUT4 immunoreaction in plasma membranes to total cell membranes of myocytes were higher in the coadministrative group compared with either the insulin or the galanin group. These results indicate that cooperation of the two hormones plays a synergic role to improve GLUT4 translocation and insulin sensitivity. This finding indicates the possibility of combining galanin with insulin with the aim of obtaining better antidiabetic efficacy than that of the canonical treatment with insulin alone.