Type 2 diabetes: principles of pathogenesis and therapy

Telmisartan in the Treatment of Cohen-Rosenthal Diabetic Hypertensive Rats: The Benefit of PPAR-γ Agonism

The antihypertensive and hypoglycemic effects of telmisartan, which has dual angiotensin II antagonist-PPAR-gamma agonist properties, was studied in Cohen-Rosenthal Diabetic Hypertensive rats (CRDH), a model in which hypertension, insulin resistance, and diabetes co-exist. CRDH, Cohen-diabetic rats (CDR), and SHR received telmisartan (3 mg/kg/day in drinking water) for five months. Telmisartan significantly lowered systolic and diastolic BP in SHR and CRDH, independent of body weight, and remained fairly constant in controls throughout the experiment. Blood glucose levels fell rapidly in the treated animals and remained steady in controls. Results indicate that telmisartan is a prototype of a new approach to treating coexisting diabetes and hypertension.

Involvement of 4E-BP1 in the protection induced by HDLs on pancreatic beta-cells

High-density lipoproteins (HDLs) protect pancreatic beta-cells against apoptosis. This property might relate to the increased risk to develop diabetes in patients with low HDL blood levels. However, the mechanisms by which HDLs protect beta-cells are poorly characterized. Here we used a transcriptomic approach to identify genes differentially modulated by HDLs in beta-cells subjected to apoptotic stimuli. The transcript encoding 4E-binding protein (4E-BP)1 was up-regulated by serum starvation, and HDLs blocked this increase. 4E-BP1 inhibits cap-dependent translation in its non- or hypophosphorylated state but it loses this ability when hyperphosphorylated. At the protein level, 4E-BP1 was also up-regulated in response to starvation and IL-1beta, and this was blunted by HDLs. Whereas an ectopic increase of 4E-BP1 expression induced beta-cell death, silencing 4E-BP1 increase with short hairpin RNAs inhibited the apoptotic-inducing capacities of starvation. HDLs can therefore protect beta-cells by blocking 4E-BP1 protein expression, but this is not the sole protective mechanism activated by HDLs. Indeed, HDLs blocked apoptosis induced by endoplasmic reticulum stress with no associated decrease in total 4E-BP1 induction. Although, HDLs favored the phosphorylation, and hence the inactivation of 4E-BP1 in these conditions, this appeared not to be required for HDL protection. Our results indicate that HDLs can protect beta-cells through modulation of 4E-BP1 depending on the type of stress stimuli.

Metabolic links between diabetes and Alzheimer's disease

There is a cluster of risk factors for Type 2 diabetes and vascular disease that include high blood glucose, obesity, high blood pressure, increased blood triacylglycerols and insulin resistance. All of these factors, both individually and collectively, increase the risk of Alzheimer's disease (AD) and vascular dementia. Alterations in insulin signaling, glucose and fatty acid metabolism, as well as the accumulation of oxidatively modified and glycated proteins, are associated with both diabetes and the dementias. Data from animal and cell culture models have shown that there is a synergistic interaction between most of these stresses in both AD and diabetes, and with the elevated beta-amyloid peptide levels that are also linked to AD. Some of these parameters can be modified by diet and others may require novel drugs. However, because of the multiplicity of physiological pathways involved, conventional drug therapies directed against a single target are not going to be effective in treating AD or the complications of diabetes. It is therefore likely that the only successful therapy will involve the use of drugs with multiple targets in concert with changes in diet and lifestyle.

Persistent oxidative stress due to absence of uncoupling protein 2 associated with impaired pancreatic beta-cell function

Uncoupling protein (UCP) 2 is a widely expressed mitochondrial protein whose precise function is still unclear but has been linked to mitochondria-derived reactive oxygen species production. Thus, the chronic absence of UCP2 has the potential to promote persistent reactive oxygen species accumulation and an oxidative stress response. Here, we show that Ucp2-/- mice on three highly congenic (N >10) strain backgrounds (C57BL/6J, A/J, 129/SvImJ), including two independently generated sources of Ucp2-null animals, all exhibit increased oxidative stress. Ucp2-null animals exhibit a decreased ratio of reduced glutathione to its oxidized form in blood and tissues that normally express UCP2, including pancreatic islets. Islets from Ucp2-/- mice exhibit elevated levels of numerous antioxidant enzymes, increased nitrotyrosine and F4/80 staining, but no change in insulin content. Contrary to results in Ucp2-/- mice of mixed 129/B6 strain background, glucose-stimulated insulin secretion in Ucp2-/- islets of each congenic strain was significantly decreased. These data show that the chronic absence of UCP2 causes oxidative stress, including in islets, and is accompanied by impaired glucose-stimulated insulin secretion.

The Joint Asia Diabetes Evaluation (JADE) Program: a web-based program to translate evidence to clinical practice in Type 2 diabetes

AIMS

The Joint Asia Diabetes Evaluation (JADE) Program is the first web-based program incorporating a comprehensive risk engine, care protocols, clinical decision and self-management support to improve ambulatory diabetes care. The aim was to validate the risk stratification system of the JADE Program using a large prospective cohort.

METHODS

The JADE interactive risk engine stratifies patients into different risk levels using results from an annual comprehensive assessment of complications and risk factors. We used a prospective registry consisting of 7534 Type 2 diabetic patients [45.6% men, median (range) age 57 years (13-92)] to perform internal validation of the risk engine.

RESULTS

The JADE Risk Engine categorized patients into four risk levels (from low to high): level 1, n = 4520 (6%); level 2, n = 1468 (19.5%); level 3, n = 4476 (59.4%); and level 4, n = 1138 (15.1%). After a median follow-up period of 5.5 years (mean +/- sd 5.4 +/- 2.81 years), 763 (10.1%) died, 1129 (14.9%) developed cardiovascular disease (CVD), 282 (3.7%) developed end-stage renal disease and 1400 (18.6%) had at least one of these events. Compared with risk level 1, levels 2, 3 and 4 were associated with 2.8-, 4.7- and 8.6-fold increased risk of clinical end-points. Risk levels 3 and 4 were, respectively, associated with 2.2- and 3.9-fold increased risk for all-cause death and 4.8- and 12.1-fold increased CVD risks.

CONCLUSION

Based on results from a comprehensive assessment, the JADE Risk Engine successfully categorizes patients into different risk levels to guide clinical management.

Pomegranate flower ameliorates fatty liver in an animal model of type 2 diabetes and obesity

AIMS OF THE STUDY

Fatty liver is the most common cause of abnormal liver function tests. We investigated the effect and its underlying mechanism of pomegranate flower (PGF), a traditional antidiabetic medicine, on fatty liver.

MATERIALS AND METHODS

At the endpoint of treatment of male Zucker diabetic fatty (ZDF) rats with PGF extract (500 mg/kg, p.o. x 6 weeks), liver weight index, hepatic lipid contents (enzymatic colorimetric methods) and droplet accumulation (Oil Red O staining) were determined. Gene profiles (RT-PCR) were analyzed in the liver of ZDF rats and in human liver-derived HepG2 cell line.

RESULTS

PGF-treated ZDF rats showed reduced ratio of liver weight to tibia length, hepatic triglyceride contents and lipid droplets. These effects were accompanied by enhanced hepatic gene expression of peroxisome proliferator-activated receptor (PPAR)-alpha, carnitine palmitoyltransferase-1 and acyl-CoA oxidase (ACO), and reduced stearoyl-CoA desaturase-1. In contrast, PGF showed minimal effects on expression of genes responsible for synthesis, hydrolysis or uptake of fatty acid and triglycerides. PGF treatment also increased PPAR-alpha and ACO mRNA levels in HepG2 cells.

CONCLUSION

Our findings suggest that this Unani medicine ameliorates diabetes and obesity-associated fatty liver, at least in part, by activating hepatic expression of genes responsible for fatty acid oxidation.

ROS signaling, oxidative stress and Nrf2 in pancreatic beta-cell function

This review focuses on the emerging evidence that reactive oxygen species (ROS) derived from glucose metabolism, such as H(2)O(2), act as metabolic signaling molecules for glucose-stimulated insulin secretion (GSIS) in pancreatic beta-cells. Particular emphasis is placed on the potential inhibitory role of endogenous antioxidants, which rise in response to oxidative stress, in glucose-triggered ROS and GSIS. We propose that cellular adaptive response to oxidative stress challenge, such as nuclear factor E2-related factor 2 (Nrf2)-mediated antioxidant induction, plays paradoxical roles in pancreatic beta-cell function. On the one hand, induction of antioxidant enzymes protects beta-cells from oxidative damage and possible cell death, thus minimizing oxidative damage-related impairment of insulin secretion. On the other hand, the induction of antioxidant enzymes by Nrf2 activation blunts glucose-triggered ROS signaling, thus resulting in reduced GSIS. These two premises are potentially relevant to impairment of beta-cells occurring in the late and early stage of Type 2 diabetes, respectively. In addition, we summarized our recent findings that persistent oxidative stress due to absence of uncoupling protein 2 activates cellular adaptive response which is associated with impaired pancreatic beta-cell function.

The emerging role of TRIB3 as a gene affecting human insulin resistance and related clinical outcomes

Type 2 diabetes is becoming epidemic. The personal and social burden imposed by diabetes will increase in the close future as its prevalence is expected to double in the next 15-20 years. Type 2 diabetes is caused by the combination of resistance to insulin action and inadequate insulin secretion. Despite the role of profound changes in individual environmental exposure is incontrovertible, several findings clearly indicate that type 2 diabetes and insulin resistance are also heritable. Among the several inhibitors of insulin signalling, which have been recently proposed as determinants of insulin resistance, is TRIB3, a mammalian tribbles homolog which affects insulin signalling at the level of Akt-2, a key modulator of insulin action in target cells. We here report data on a prevalent Q84R TRIB3 missense single nucleotide polymorphism (rs2295490) we first described few years ago. Several lines of evidences indicate that this amino-acid change is, in fact, a gain of function mutation with the potential to affect insulin signalling and thus, to increase the risk of insulin resistance and related clinical outcomes.

Fixed-dose single tablet antidiabetic combinations

Combinations of two or more oral agents with different mechanisms of action are often used for the management of hyperglycaemia in type 2 diabetes. While these combinations have customarily been taken as separate tablets, several fixed-dose single tablet combinations are now available. These are based on bioequivalence with the separate tablets, giving similar efficacy to the separate tablets and necessitating the same cautions and contraindications that apply to each active component. Fixed-dose combinations can offer convenience, reduce the pill burden and simplify administration regimens for the patient. They increase patient adherence compared with equivalent combinations of separate tablets, and this is associated with some improvements in glycaemic control. Presently available antidiabetic fixed-dose combinations include metformin combined with a sulphonylurea, thiazolidinedione, dipeptidylpeptidase-4 inhibitor or meglitinide as well as thiazolidinedione-sulphonylurea combinations, each at a range of dosage strengths to facilitate titration. Anticipated future expansion of multiple drug regimens for diabetes management is likely to increase the use of fixed-dose single tablet combinations.

Horror autoinflammaticus: the molecular pathophysiology of autoinflammatory disease (*)

The autoinflammatory diseases are characterized by seemingly unprovoked episodes of inflammation, without high-titer autoantibodies or antigen-specific T cells. The concept was proposed ten years ago with the identification of the genes underlying hereditary periodic fever syndromes. This nosology has taken root because of the dramatic advances in our knowledge of the genetic basis of both mendelian and complex autoinflammatory diseases, and with the recognition that these illnesses derive from genetic variants of the innate immune system. Herein we propose an updated classification scheme based on the molecular insights garnered over the past decade, supplanting a clinical classification that has served well but is opaque to the genetic, immunologic, and therapeutic interrelationships now before us. We define six categories of autoinflammatory disease: IL-1beta activation disorders (inflammasomopathies), NF-kappaB activation syndromes, protein misfolding disorders, complement regulatory diseases, disturbances in cytokine signaling, and macrophage activation syndromes. A system based on molecular pathophysiology will bring greater clarity to our discourse while catalyzing new hypotheses both at the bench and at the bedside.

Impaired PRMT1 activity in the liver and pancreas of type 2 diabetic Goto-Kakizaki rats

AIMS

Arginine methylation catalyzed by protein N-arginine methyltransferase (PRMT) 1 is implicated in a variety of cellular processes, although the potential role of PRMT1-mediated methylation in glucose intolerance has not been defined. This study aims to investigate whether alteration of PRMT1 activity contributes to the clinical features of type 2 diabetes.

MAIN METHODS

Goto-Kakizaki (GK) rats were used as a rodent model of type 2 diabetes. Catalytic activity of PRMT1 and arginine methylation were determined by an in vitro methyltransferase assay and immunoblotting, respectively. Hepatic insulin signaling events, insulin secretion, and pancreatic glucose metabolism were assessed by studies using HepG2 hepatoma cells and isolated pancreatic islets. Methyltransferase activity was attenuated by transfection of a small interfering RNA against PRMT1 (PRMT1-siRNA) or by pretreatment with an inhibitor of methyltransferase, 5'-deoxy-5'-(methylthio)adenosine (MTA).

KEY FINDINGS

Non-obese, diabetic GK rats exhibited a decrease in their hepatic and pancreatic PRMT1 activity, as compared to the control Wistar rats, which was associated with the impaired arginine methylation of several proteins in the tissues. Transfection of PRMT1-siRNA diminished the agonist-induced activation of insulin signaling and the subsequent suppression of gluconeogenic genes expression in the liver-derived cells. Pretreatment with MTA attenuated the glucose-stimulated insulin secretion, but not glucose utilization, in isolated pancreatic islets of Wistar controls, and its pattern was comparable to that of the GK rats undergoing similar modulation.

SIGNIFICANCE

The present data demonstrates that the impaired PRMT1 activity may be implicated in glucose intolerance in GK rats through the disturbed hepatic glucose metabolism and insulin secretion.

Adipokines in the treatment of diabetes mellitus and obesity

BACKGROUND

The physiology of adipose tissue plays a main role in the pathogenesis of type 2 diabetes mellitus. The secretion of adipocyte-derived hormones, in either an autocrine or a paracrine manner, has been proposed as a relevant mechanism in this process. In this sense, the administration and regulation of hormones derived from adipose tissue arises as an attractive option for treating metabolic disorders.

OBJECTIVE

To review the current understanding of the implication of adipokines in the development of obesity and insulin resistance, as well as their potential use as therapeutic agents.

METHODOLOGY

Review of scientific literature.

CONCLUSIONS

This review describes the role of adipokines in generating insulin resistance and the chronic low-grade inflammatory profile accompanying visceral obesity.

Antioxidants prevent health-promoting effects of physical exercise in humans

Exercise promotes longevity and ameliorates type 2 diabetes mellitus and insulin resistance. However, exercise also increases mitochondrial formation of presumably harmful reactive oxygen species (ROS). Antioxidants are widely used as supplements but whether they affect the health-promoting effects of exercise is unknown. We evaluated the effects of a combination of vitamin C (1000 mg/day) and vitamin E (400 IU/day) on insulin sensitivity as measured by glucose infusion rates (GIR) during a hyperinsulinemic, euglycemic clamp in previously untrained (n = 19) and pretrained (n = 20) healthy young men. Before and after a 4 week intervention of physical exercise, GIR was determined, and muscle biopsies for gene expression analyses as well as plasma samples were obtained to compare changes over baseline and potential influences of vitamins on exercise effects. Exercise increased parameters of insulin sensitivity (GIR and plasma adiponectin) only in the absence of antioxidants in both previously untrained (P < 0.001) and pretrained (P < 0.001) individuals. This was paralleled by increased expression of ROS-sensitive transcriptional regulators of insulin sensitivity and ROS defense capacity, peroxisome-proliferator-activated receptor gamma (PPARgamma), and PPARgamma coactivators PGC1alpha and PGC1beta only in the absence of antioxidants (P < 0.001 for all). Molecular mediators of endogenous ROS defense (superoxide dismutases 1 and 2; glutathione peroxidase) were also induced by exercise, and this effect too was blocked by antioxidant supplementation. Consistent with the concept of mitohormesis, exercise-induced oxidative stress ameliorates insulin resistance and causes an adaptive response promoting endogenous antioxidant defense capacity. Supplementation with antioxidants may preclude these health-promoting effects of exercise in humans.

Oral antidiabetic drug metabolism: pharmacogenomics and drug interactions

BACKGROUND

Type 2 diabetes is progressive in nature and so to control cardiovascular risk, most patients need combinations of oral antidiabetic drugs (OADs) plus or minus insulin. Thus, drug-drug interactions may substantially contribute to harmful effects of intensive glucose lowering therapy.

METHODS

A PubMed literature search was performed to select the most recent and relevant publications examining OAD metabolism and the effects of concomitant use of OADs.

RESULTS/CONCLUSION

Considering the individual sensitivity to OADs, pharmacogenetic factors could be of critical importance. The therapeutic range and efficacy as well as adverse effects of OADs may be significantly affected by genetic polymorphisms of cytochrome P450 drug metabolising enzymes, organic cation transporters or organic anion transporting polypeptides. Although current data suggest that modest pharmacokinetics interferences among some OAD combinations exist, they do not seem to have substantial clinical consequences. As long-term adherence to multi-drug treatment is poor in diabetic patients, the future will show a strong move towards earlier treatment with combination therapies. As metformin is cardiovascular protective and is not metabolised through the hepatic cytochrome P450 system, it is a key compound for any OAD combination. There is an overwhelming amount of small-sized in vitro studies and investigations mostly including healthy volunteers dealing with short-term effects and surrogate parameters of concomitant OAD use. Further evidence from large-scale studies including typical subjects with type 2 diabetes, in particular multimorbid and geriatric patients with polypharmacy, is needed. Postmarketing surveillance using large patients' registries could be helpful to improve the early detection of clinically relevant drug-drug interactions.

AMP-activated protein kinase in the regulation of hepatic energy metabolism: from physiology to therapeutic perspectives

As the liver is central in the maintenance of glucose homeostasis and energy storage, knowledge of the physiology as well as physiopathology of hepatic energy metabolism is a prerequisite to our understanding of whole-body metabolism. Hepatic fuel metabolism changes considerably depending on physiological circumstances (fed vs. fasted state). In consequence, hepatic carbohydrate, lipid and protein synthesis/utilization are tightly regulated according to needs. Fatty liver and hepatic insulin resistance (both frequently associated with the metabolic syndrome) or increased hepatic glucose production (as observed in type 2 diabetes) resulted from alterations in substrates oxidation/storage balance in the liver. Because AMP-activated protein kinase (AMPK) is considered as a cellular energy sensor, it is important to gain understanding of the mechanism by which hepatic AMPK coordinates hepatic energy metabolism. AMPK has been implicated as a key regulator of physiological energy dynamics by limiting anabolic pathways (to prevent further ATP consumption) and by facilitating catabolic pathways (to increase ATP generation). Activation of hepatic AMPK leads to increased fatty acid oxidation and simultaneously inhibition of hepatic lipogenesis, cholesterol synthesis and glucose production. In addition to a short-term effect on specific enzymes, AMPK also modulates the transcription of genes involved in lipogenesis and mitochondrial biogenesis. The identification of AMPK targets in hepatic metabolism should be useful in developing treatments to reverse metabolic abnormalities of type 2 diabetes and the metabolic syndrome.

MBX-102/JNJ39659100, a novel non-TZD selective partial PPAR-γ agonist lowers triglyceride independently of PPAR-α activation

MBX-102/JNJ-39659100 (MBX-102) is a selective, partial PPAR-γ agonist that lowers glucose in the absence of some of the side effects, such as weight gain and edema, that are observed with the TZDs. Interestingly MBX-102 also displays pronounced triglyceride lowering in preclinical rodent models and in humans. Although in vitro reporter gene studies indicated that MBX-102 acid is a highly selective PPAR-γ agonist that lacks PPAR-α activity, we sought to determine if PPAR-α activation in vivo could possibly contribute to the triglyceride lowering abilities of MBX-102. In vivo studies using ZDF and ZF rats demonstrated that MBX-102 lowered plasma triglycerides. However in ZF rats, MBX-102 had no effect on liver weight or on hepatic expression levels of PPAR-α target genes. Further in vitro studies in primary human hepatocytes supported these findings. Finally, the ability of MBX-102 to lower triglycerides was maintained in PPAR-α knockout mice, unambiguously establishing that the triglyceride lowering effect of MBX-102 is PPAR-α independent. The in vivo lipid lowering abilities of MBX-102 are therefore mediated by an alternate mechanism which is yet to be determined.

Metabolic syndrome and its components as predictors of incident type 2 diabetes mellitus in an Aboriginal community

BACKGROUND

Risk factors for type 2 diabetes remain poorly characterized among Aboriginal Canadians. We aimed to determine the incidence of type 2 diabetes in an Aboriginal community and to evaluate prospective associations with metabolic syndrome and its components.

METHODS

Of 606 participants in the Sandy Lake Health and Diabetes Project from 1993 to 1995 who were free of diabetes at baseline, 540 (89.1%) participated in 10-year follow-up assessments. Baseline anthropometry, blood pressure, fasting insulin and serum lipid levels were measured. Fasting and 2-hour postload glucose levels were obtained at follow-up to determine incident cases of type 2 diabetes.

RESULTS

The 10-year cumulative incidence of diabetes was 17.5%. High adiposity, dyslipidemia, hyperglycemia, hyperinsulinemia and hypertension at baseline were associated with an increased risk of diabetes after adjustment for age and sex (all p < or = 0.03). Metabolic syndrome had high specificity (75%-88%) and high negative predictive value (85%-87%) to correctly detect diabetes-free individuals at follow-up. It had low sensitivity (26%-48%) and low positive predictive value (29%-32%) to detect future diabetes. Metabolic syndrome at baseline was associated with incident diabetes after adjustment for age and sex, regardless of whether the syndrome was defined using the National Cholesterol Education Program criteria (odds ratio [OR] 2.03, 95% confidence interval [CI] 1.10-3.75) or the International Diabetes Federation criteria (OR 2.14, 95% CI 1.29-3.55). The association was to the same degree as that for impaired glucose tolerance assessed using the oral glucose tolerance test (OR 2.87, 95% CI 1.52-5.40; p > 0.05 for comparison of C statistics).

INTERPRETATION

Metabolic syndrome and its components can be identified with readily available clinical measures. As such, the syndrome may be useful for identifying individuals at risk of type 2 diabetes in remote Aboriginal communities.

Contribution of type 2 diabetes associated loci in the Arabic population from Tunisia: a case-control study

Background

Candidate gene and genome-wide association studies have both reproducibly identified several common Single Nucleotide Polymorphisms (SNPs) that confer type 2 diabetes (T2D) risk in European populations. Our aim was to evaluate the contribution to T2D of five of these established T2D-associated loci in the Arabic population from Tunisia.

Methods

A case-control design comprising 884 type 2 diabetic patients and 513 control subjects living in the East-Center of Tunisia was used to analyze the contribution to T2D of the following SNPs: E23K in KCNJ11/Kir6.2, K121Q in ENPP1, the -30G/A variant in the pancreatic β-cell specific promoter of Glucokinase, rs7903146 in TCF7L2 encoding transcription factor 7-like2, and rs7923837 in HHEX encoding the homeobox, hematopoietically expressed transcription factor.

Results

TCF7L2-rs7903146 T allele increased susceptibility to T2D (OR = 1.25 [1.06–1.47], P = 0.006) in our study population. This risk was 56% higher among subjects carrying the TT genotype in comparison to those carrying the CC genotype (OR = 1.56 [1.13–2.16], P = 0.002). No allelic or genotypic association with T2D was detected for the other studied polymorphisms.

Conclusion

In the Tunisian population, TCF7L2-rs7903146 T allele confers an increased risk of developing T2D as previously reported in the European population and many other ethnic groups. In contrast, none of the other tested SNPs that influence T2D risk in the European population was associated with T2D in the Tunisian Arabic population. An insufficient power to detect minor allelic contributions or genetic heterogeneity of T2D between different ethnic groups can explain these findings.

Type 2 Diabetes Mellitus: New Genetic Insights will Lead to New Therapeutics

Type 2 diabetes is a disorder of dysregulated glucose homeostasis. Normal glucose homeostasis is a complex process involving several interacting mechanisms, such as insulin secretion, insulin sensitivity, glucose production, and glucose uptake. The dysregulation of one or more of these mechanisms due to environmental and/or genetic factors, can lead to a defective glucose homeostasis. Hyperglycemia is managed by augmenting insulin secretion and/or interaction with hepatic glucose production, as well as by decreasing dietary caloric intake and raising glucose metabolism through exercise. Although these interventions can delay disease progression and correct blood glucose levels, they are not able to cure the disease or stop its progression entirely. Better management of type 2 diabetes is sorely needed. Advances in genotyping techniques and the availability of large patient cohorts have made it possible to identify common genetic variants associated with type 2 diabetes through genome-wide association studies (GWAS). So far, genetic variants on 19 loci have been identified. Most of these loci contain or lie close to genes that were not previously linked to diabetes and they may thus harbor targets for new drugs. It is also hoped that further genetic studies will pave the way for predictive genetic screening. The newly discovered type 2 diabetes genes can be classified based on their presumed molecular function, and we discuss the relation between these gene classes and current treatments. We go on to consider whether the new genes provide opportunities for developing alternative drug therapies.

Adiponectin multimers in maternal plasma

OBJECTIVE

Adiponectin is an anti-diabetic, anti-atherogenic, anti-inflammatory, and angiogenic adipokine that circulates in oligomeric complexes including: low molecular weight (LMW) trimers, medium molecular weight (MMW) hexamers, and high molecular weight (HMW) isoforms. The aim of this study was to determine whether there are changes in adiponectin multimers in pregnancy and as a function of maternal weight.

STUDY DESIGN

In this cross-sectional study, plasma concentrations of total, HMW, MMW, and LMW adiponectin were determined in women included in three groups: (1) normal pregnant women of normal body mass index (BMI) (n = 466), (2) overweight pregnant women (BMI >or=25; n = 257), and (3) non-pregnant women of normal weight (n = 40). Blood samples were collected once from each woman between 11 and 42 weeks of gestation. Plasma adiponectin multimer concentrations were determined by enzyme-linked immunosorbent assay (ELISA). Non-parametric statistics were used for analysis.

RESULTS

(1) The median HMW adiponectin concentration and the median HMW/total adiponectin ratio were significantly higher, and the median LMW adiponectin concentration was significantly lower in pregnant women than in non-pregnant women. (2) Among pregnant women, the median plasma concentration of total, HMW, and MMW adiponectin was significantly higher in normal weight women than in overweight patients. (3) Maternal HMW was the most prevalent adiponectin multimer regardless of gestational age or BMI status. (4) There were no significant differences in the median concentration of total, MMW, and LMW adiponectin and their relative distribution with advancing gestation.

CONCLUSION

Human pregnancy is characterized by quantitative and qualitative changes in adiponectin multimers, especially the most active isoform, HMW adiponectin.

How can antipsychotics cause Diabetes Mellitus? Insights based on receptor-binding profiles, humoral factors and transporter proteins

The prevalence of Diabetes Mellitus (DM) is becoming a serious public health problem. The use of atypical antipsychotics has been associated with disruption of the glucose metabolism and therefore with causing DM. The underlying mechanisms are unknown, but knowledge of the differences between the pharmacological features of various antipsychotics combined with their diabetogenic profile might help us to understand those mechanisms. This article describes how the binding of various essential receptors or transporters in essential body tissues, adipose tissue, pancreatic tissue and liver and skeletal muscle tissue can cause disruption of the glucose metabolism. With such knowledge in mind one can try to explain the differences between the diabetogenic propensities of various antipsychotics. It is well known that clozapine and olanzapine cause weight gain and DM, whereas aripiprazole and ziprasidone have much less disruptive clinical profiles. The most significant risk factor for adiposity seems to be strong blocking of histaminergic receptors. An agonistic activity on serotonergic-1a receptors, with a very low affinity for muscarinergic-3 receptors, might protect against the development of DM. More data will become available which may help to solve the puzzle.

Effects of acute intermittent hypoxia on glucose metabolism in awake healthy volunteers

Accumulating evidence suggests that obstructive sleep apnea is associated with alterations in glucose metabolism. Although the pathophysiology of metabolic dysfunction in obstructive sleep apnea is not well understood, studies of murine models indicate that intermittent hypoxemia has an important contribution. However, corroborating data on the metabolic effects of intermittent hypoxia on glucose metabolism in humans are not available. Thus the primary aim of this study was to characterize the acute effects of intermittent hypoxia on glucose metabolism. Thirteen healthy volunteers were subjected to 5 h of intermittent hypoxia or normoxia during wakefulness in a randomized order on two separate days. The intravenous glucose tolerance test (IVGTT) was used to assess insulin-dependent and insulin-independent measures of glucose disposal. The IVGTT data were analyzed using the minimal model to determine insulin sensitivity (S(I)) and glucose effectiveness (S(G)). Drops in oxyhemoglobin saturation were induced during wakefulness at an average rate of 24.3 events/h. Compared with the normoxia condition, intermittent hypoxia was associated with a decrease in S(I) [4.1 vs. 3.4 (mU/l)(-1).min(-1); P = 0.0179] and S(G) (1.9 vs. 1.3 min(-1)x10(-2), P = 0.0065). Despite worsening insulin sensitivity with intermittent hypoxia, pancreatic insulin secretion was comparable between the two conditions. Heart rate variability analysis showed the intermittent hypoxia was associated with a shift in sympathovagal balance toward an increase in sympathetic nervous system activity. The average R-R interval on the electrocardiogram was 919.0 ms during the normoxia condition and 874.4 ms during the intermittent hypoxia condition (P < 0.04). Serum cortisol levels after intermittent hypoxia and normoxia were similar. Hypoxic stress in obstructive sleep apnea may increase the predisposition for metabolic dysfunction by impairing insulin sensitivity, glucose effectiveness, and insulin secretion.

Effects of acute intermittent hypoxia on glucose metabolism in awake healthy volunteers

Accumulating evidence suggests that obstructive sleep apnea is associated with alterations in glucose metabolism. Although the pathophysiology of metabolic dysfunction in obstructive sleep apnea is not well understood, studies of murine models indicate that intermittent hypoxemia has an important contribution. However, corroborating data on the metabolic effects of intermittent hypoxia on glucose metabolism in humans are not available. Thus the primary aim of this study was to characterize the acute effects of intermittent hypoxia on glucose metabolism. Thirteen healthy volunteers were subjected to 5 h of intermittent hypoxia or normoxia during wakefulness in a randomized order on two separate days. The intravenous glucose tolerance test (IVGTT) was used to assess insulin-dependent and insulin-independent measures of glucose disposal. The IVGTT data were analyzed using the minimal model to determine insulin sensitivity (S(I)) and glucose effectiveness (S(G)). Drops in oxyhemoglobin saturation were induced during wakefulness at an average rate of 24.3 events/h. Compared with the normoxia condition, intermittent hypoxia was associated with a decrease in S(I) [4.1 vs. 3.4 (mU/l)(-1).min(-1); P = 0.0179] and S(G) (1.9 vs. 1.3 min(-1)x10(-2), P = 0.0065). Despite worsening insulin sensitivity with intermittent hypoxia, pancreatic insulin secretion was comparable between the two conditions. Heart rate variability analysis showed the intermittent hypoxia was associated with a shift in sympathovagal balance toward an increase in sympathetic nervous system activity. The average R-R interval on the electrocardiogram was 919.0 ms during the normoxia condition and 874.4 ms during the intermittent hypoxia condition (P < 0.04). Serum cortisol levels after intermittent hypoxia and normoxia were similar. Hypoxic stress in obstructive sleep apnea may increase the predisposition for metabolic dysfunction by impairing insulin sensitivity, glucose effectiveness, and insulin secretion.

General health and quality-of-life measures in active, recent, and comorbid mental disorders: a population-based health 2000 study

AIMS

We studied the impact of comorbidity and recency in psychiatric disorders on psychological well-being, perceived health, and quality of life and compared their effect with the effect of a chronic medical condition, type 2 diabetes mellitus.

METHODS

Established instruments for psychological distress (12-item General Health Questionnaire [GHQ-12]), self-rated general health, and health-related quality of life (EQ-5D and 15D) were administered for the participants of the nationwide Finnish Health 2000 survey. The diagnoses of depressive, anxiety, and alcohol use disorders and their unique comorbid combinations were based on the Munich version of the Composite International Diagnostic Interview (M-CIDI).

RESULTS

People with comorbid anxiety and depressive disorders had the highest distress and lowest health and quality-of-life ratings on all scales. The effects of mental disorders on health-related quality of life and self-rated health were comparable to the effects of diabetes. Type 2 diabetes mellitus and alcohol use disorder were associated with minimal, although statistically significant, increase of psychological distress. Symptom recovery from an active depressive disorder associated with improved well-being on all measures, but residual ill-being was also remarkably common among the partly or fully recovered in all disorder categories.

CONCLUSIONS

Even in comparison with a chronic physical illness such as diabetes, comorbid psychiatric disorders have a high impact on psychological well-being, perceived health, and quality of life, when evaluated by simple, useful, and feasible self-rating scales. The scales used may be useful in monitoring the severity and course of psychiatric conditions. Recognizing and treating psychiatric comorbidity is important in improving the quality of life of psychiatric patients.

Perinatal risk factors for diabetes in later life

OBJECTIVE

Low birth weight is consistently associated with an increased risk of type 2 diabetes in adulthood, but the individual contributions from poor fetal growth and preterm birth are not known. We therefore investigated the significance of these two factors separately.

RESEARCH DESIGN AND METHODS

We identified a cohort of subjects born preterm or with low birth weight at term at four major delivery units in Sweden from 1925 through 1949. A comparison cohort of subjects was identified from the same source population. Of 6,425 subjects in all, 2,931 were born at <37 weeks of gestation and 2,176 had a birth weight <2,500 g. Disease occurrence among participants was assessed through nationwide hospital registers from 1987 through 2006.

RESULTS

During follow-up, there were 508 cases of diabetes. Low birth weight was strongly negatively associated with risk of diabetes (P for trend <0.0001). Both short gestational duration and poor fetal growth were associated with later diabetes (P for trend <0.0001 and <0.0004, respectively). Very preterm birth (< or =32 weeks of gestation at birth) was associated with a hazard ratio (HR) of 1.67 (95% CI 1.33-2.11) compared with term birth. Birth weights below 2 SDs of mean birth weight for gestational age were associated with an HR of 1.76 (1.30-2.38) compared with birth weights between the mean weight and the weight at 1 SD above the mean.

CONCLUSIONS

Our results suggest that the association between low birth weight and diabetes is due to factors associated with both poor fetal growth and short gestational age.

Saxagliptin: a new DPP-4 inhibitor for the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a global epidemic with increasing impact on individuals and healthcare providers. Available treatments (such as metformin, sulfonylureas, glitazones, and insulin) have proven unsatisfactory in producing a long-lasting impact on glycemic control. In addition, most of these treatments have undesirable side effects such as weight gain and hypoglycemia. As a result, exploring new treatment targets and new therapies is mandatory in order to treat this condition. The incretin pathway, in particular glucagon-like peptide (GLP-1), plays an important pathological role in the development of T2DM, and treatments targeting the incretin system have recently become available. These can mainly be divided into two broad categories; GLP-1 agonists/analogs (exenatide, liraglutide), and dipeptidyl peptidase-4 (DPP-4; the enzyme responsible for rapid inactivation of incretins) inhibitors (sitagliptin, vildagliptin). Saxagliptin is a novel DPP-4 inhibitor that has recently completed phase 3 studies. Saxagliptin is a potent and specific inhibitor of DPP-4 (in comparison with other dipeptidyl peptidase enzymes) that is given once daily. Current data suggest that saxagliptin as monotherapy or in combination with metformin, glyburide, or a glitazone results in significant reductions in fasting and postprandial plasma glucose and hemoglobin A(1c) (HbA(1c)). Saxagliptin is well tolerated and does not increase hypoglycemia compared with the placebo, and is probably weight neutral. Saxagliptin will be a new effective drug in the currently available variety of antidiabetic medications for patients with T2DM.

Growth factor control of pancreatic islet regeneration and function

Type 1 and type 2 diabetes mellitus together are predicted to affect over 300 million people worldwide by the year 2020. A relative or absolute paucity of functional β-cells is a central feature of both types of disease, and identifying the pathways that mediate the embryonic origin of new β-cells and mechanisms that underlie the proliferation of existing β-cells are major efforts in the fields of developmental and islet biology. A poor secretory response of existing β-cells to nutrients and hormones and the defects in hormone processing also contribute to the hyperglycemia observed in type 2 diabetes and has prompted studies aimed at enhancing β-cell function. The factors that contribute to a greater susceptibility in aging individuals to develop diabetes is currently unclear and may be linked to a poor turnover of β-cells and/or enhanced susceptibility of β-cells to apoptosis. This review is an update on the recent work in the areas of islet/β-cell regeneration and hormone processing that are relevant to the pathophysiology of the endocrine pancreas in type 1, type 2 and obesity-associated diabetes.

Novel insights into glucocorticoid-mediated diabetogenic effects: towards expansion of therapeutic options?

At pharmacological concentrations, glucocorticoids (GCs) display potent anti-inflammatory effects, and are therefore frequently prescribed by physicians to treat a wide variety of diseases. Despite excellent efficacy, GC therapy is hampered by their notorious metabolic side effect profile. Chronic exposure to increased levels of circulating GCs is associated with central adiposity, dyslipidaemia, skeletal muscle wasting, insulin resistance, glucose intolerance and overt diabetes. Remarkably, many of these side-effects of GC treatment resemble the various components of the metabolic syndrome (MetS), in which indeed subtle disturbances in the hypothalamic-pituitary-adrenal (HPA) axis and/or increased tissue sensitivity to GCs have been reported. Recent developments have led to renewed interest in the mechanisms of GC's diabetogenic effects. First, 'selective dissociating glucocorticoid receptor (GR) ligands', which aim to segregate GC's anti-inflammatory and metabolic actions, are currently being developed. Second, at present, selective 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) inhibitors, which may reduce local GC concentrations by inhibiting cortisone to cortisol conversion, are evaluated in clinical trials as a novel treatment modality for the MetS. In this review, we provide an update of the current knowledge on the mechanisms that underlie GC-induced dysmetabolic effects. In particular, recent progress in research into the role of GCs in the pathogenesis of insulin resistance and beta-cell dysfunction will be discussed.

Plasma levels of PBEF/Nampt/visfatin are decreased in patients with liver cirrhosis

Liver cirrhosis is a catabolic disease associated with a high incidence of insulin resistance and diabetes mellitus. Pre-B cell colony-enhancing factor/ nicotinamide phosphoribosyltransferase/visfatin has been characterized as a novel adipokine with a potential role in glucose metabolism and nicotinamide dinucleotide (NAD) generation. We studied plasma levels and metabolic relevance of visfatin in 19 patients with cirrhosis and 19 body mass index-, age-, and sex-matched controls. In addition, hepatic mRNA expression was assessed by qPCR in livers of seven patients with cirrhosis and four controls. Circulating visfatin was 78% lower in cirrhotics (P < 0.001) and decreased with worsening of the clinical stage of liver disease. Hepatic visfatin secretion decreased with clinical stage (P < 0.05) and reduced liver function (P = 0.01). Consistent with these data, hepatic visfatin mRNA expression was significantly lower in cirrhotic livers (P < 0.05). Circulating visfatin in cirrhosis was correlated with body cell mass (r = 0.72, P < 0.01) as well as with body fat mass (r = 0.53, P < 0.05) but not with plasma glucose, insulin, the degree of insulin resistance, or whole body glucose oxidation rates. Higher visfatin levels were associated with higher hepatic glucose production (r = 0.53, P < 0.05) and also with a higher arterial ketone body ratio (KBR) (r = 0.48, P < 0.05), an indicator of increased hepatic NAD generation. In conclusion, circulating visfatin levels are significantly decreased in liver cirrhosis, presumably attributable to decreased hepatic expression and production. Plasma visfatin in cirrhosis is not associated with insulin resistance but correlates with hepatic glucose production and the arterial KBR, indicating a potential link between the NAD-generating properties of visfatin and metabolism.

Berberine reduces insulin resistance through protein kinase C-dependent up-regulation of insulin receptor expression

Natural product berberine (BBR) has been reported to have hypoglycemic and insulin-sensitizing activities; however, its mechanism remains unclear. This study was designed to investigate the molecular mechanism of BBR against insulin resistance. Here, we identify insulin receptor (InsR) as a target of BBR to increase insulin sensitivity. In cultured human liver cells, BBR increased InsR messenger RNA (mRNA) and protein expression in a dose- and time-dependent manner. Berberine increased InsR expression in the L6 rat skeletal muscle cells as well. Berberine-enhanced InsR expression improved cellular glucose consumption only in the presence of insulin. Silencing InsR gene with small interfering RNA or blocking the phosphoinositol-3-kinase diminished this effect. Berberine induced InsR gene expression through a protein kinase C (PKC)-dependent activation of its promoter. Inhibition of PKC abolished BBR-caused InsR promoter activation and InsR mRNA transcription. In animal models, treatment of type 2 diabetes mellitus rats with BBR lowered fasting blood glucose and fasting serum insulin, increased insulin sensitivity, and elevated InsR mRNA as well as PKC activity in the liver. In addition, BBR lowered blood glucose in KK-Ay type 2 but not in NOD/LtJ type 1 diabetes mellitus mice that were insulin deficient. Our results suggest that BBR is a unique natural medicine against insulin resistance in type 2 diabetes mellitus and metabolic syndrome.

Robust signaling networks of the adipose secretome

Type 2 diabetes is a prototypical complex systems disease that has a strong hereditary component and etiologic links with a sedentary lifestyle, overeating and obesity. Adipose tissue has been shown to be a central driver of type 2 diabetes progression, establishing and maintaining a chronic state of low-level inflammation. The number and diversity of identified endocrine factors from adipose tissue (adipokines) is growing rapidly. Here, I argue that a systems biology approach to understanding the robust multi-level signaling networks established by the adipose secretome will be crucial for developing efficient type 2 diabetes treatment. Recent advances in whole-genome association studies, global molecular profiling and quantitative modeling are currently fueling the emergence of this novel research strategy.

Decreased hepatic RBP4 secretion is correlated with reduced hepatic glucose production but is not associated with insulin resistance in patients with liver cirrhosis

OBJECTIVE

Patients with liver cirrhosis have a high incidence of insulin resistance and diabetes. This study was designed to determine circulating levels and hepatic production of retinol-binding protein 4 (RBP4) in relation to parameters of hepatic and systemic metabolism in patients with liver cirrhosis.

DESIGN AND METHOD

Circulating RBP4 levels were measured in 19 patients with liver cirrhosis at different clinical stages of the disease and in 20 age-, sex- and body mass index (BMI)-matched controls. Hepatic production rates of RBP4 and glucose were assessed by measuring the arterial hepatic venous concentration difference together with hepatic blood flow. Insulin resistance was determined by the Quantitative Insulin Sensitivity Check Index (QUICKI) and the homeostasis model assessment of insulin resistance (HOMA-IR), energy expenditure by indirect calorimetry and body composition by bioelectrical impedance analysis (BIA).

RESULTS

Compared with controls, RBP4 levels in cirrhosis were decreased (8.1 +/- 1.8 vs. 22.6 +/- 2.4 mg/l, P < 0.001) due to decreased hepatic production (P < 0.05). RBP4 correlated with hepatic protein synthesis capacity (P < 0.01), but not with insulin resistance, energy expenditure, BMI or body fat mass. Plasma RBP4 correlated with hepatic glucose production (P < 0.05).

CONCLUSIONS

These data demonstrate that RBP4 in cirrhosis (i) is decreased due to reduced hepatic production, (ii) is not associated with insulin resistance, and (iii) might have a beneficial role by decreasing hepatic glucose production and could thus also be regarded as a hepatokine.

Causes and metabolic consequences of Fatty liver

Type 2 diabetes and cardiovascular disease represent a serious threat to the health of the population worldwide. Although overall adiposity and particularly visceral adiposity are established risk factors for these diseases, in the recent years fatty liver emerged as an additional and independent factor. However, the pathophysiology of fat accumulation in the liver and the cross-talk of fatty liver with other tissues involved in metabolism in humans are not fully understood. Here we discuss the mechanisms involved in the pathogenesis of hepatic fat accumulation, particularly the roles of body fat distribution, nutrition, exercise, genetics, and gene-environment interaction. Furthermore, the effects of fatty liver on glucose and lipid metabolism, specifically via induction of subclinical inflammation and secretion of humoral factors, are highlighted. Finally, new aspects regarding the dissociation of fatty liver and insulin resistance are addressed.

Growth hormone excess and the effect of octreotide in cats with diabetes mellitus

In this prospective study 16 cats with diabetes mellitus were examined for concurrent acromegaly by measuring plasma growth hormone (GH) and insulin-like growth factor-I concentrations, and magnetic resonance imaging (MRI) of the pituitary fossa. Additionally, the effects of octreotide administration on the plasma concentrations of glucose, GH, alpha-melanocyte-stimulating hormone (alpha-MSH), adrenocorticotrophic hormone (ACTH), and cortisol were measured. Five cats were diagnosed with hypersomatotropism. The pituitary was enlarged in these 5 cats and in 2 other cats. Six cats that required a maximum lente insulin dosage >or=1.5 IU/kg body weight per injection had pituitary enlargement and 5 of these cats had acromegaly. Plasma concentrations of GH, ACTH, and cortisol decreased significantly after single intravenous administration of the somatostatin analogue octreotide in the acromegalic cats. The effect on GH concentrations was more pronounced in some of the acromegalic cats than in others. In the non-acromegalic cats only ACTH concentrations decreased significantly. In both groups plasma glucose concentrations increased slightly but significantly, whereas alpha-MSH concentrations were not significantly affected. In conclusion, the incidence of hypersomatotropism with concomitant pituitary enlargement appears to be high among diabetic cats with severe insulin resistance. Some of these cats responded to octreotide administration with a pronounced decrease in the plasma GH concentration, which suggests that octreotide administration could be used as a pre-entry test for treatment with somatostatin analogues.

New therapeutic approaches in type 2 diabetes

Type 2 diabetes is a progressive chronic disease resulting from a dynamic interaction between defects in insulin secretion and insulin action. New molecules have recently been launched and many others are under clinical investigation. Besides classical sulfonylureas and glinides, new insulin secretagogues are now available, which target the incretin gut hormone glucagon-like peptide-1 (GLP-1). Indeed, oral incretin enhancers acting as antagonists of the enzyme DPP-4 (dipeptidylpeptidase-4), which inactivates natural GLP-1,and injectable incretin mimetics (exenatide) or analogues (liraglutide), which reproduce the actions of GLP-1 while resisting to DPP-4, represent new opportunities to stimulate insulin secretion, without increasing the risk of hypoglycaemia and weight gain. Among insulin sensitizers, metformin remains unequivocally the first drug of choice for the treatment of type 2 diabetes, whereas promising drugs as thiazolidinediones (glitazones) were recently challenged because of various safety issues. When insulin is required, insulin analogues, both short-acting and basal ones, may offer some advantages regarding better control of postprandial hyperglycaemia, reduced risk of hypoglycaemia and/or lower weight gain in patients with type 2 diabetes. Emphasis should be put on early detection and intensive management of type 2 diabetes, individualized glucose lowering treatments and goals, stepwise pharmacological strategy avoiding therapeutic inertia, and multiple cardiovascular risk--targeted approach.

Predicting type 2 diabetes based on polymorphisms from genome-wide association studies: a population-based study

OBJECTIVE

Prediction of type 2 diabetes based on genetic testing might improve identification of high-risk subjects. Genome-wide association (GWA) studies identified multiple new genetic variants that associate with type 2 diabetes. The predictive value of genetic testing for prediction of type 2 diabetes in the general population is unclear.

RESEARCH DESIGN AND METHODS

We investigated 18 polymorphisms from recent GWA studies on type 2 diabetes in the Rotterdam Study, a prospective, population-based study among homogeneous Caucasian individuals of 55 years and older (genotyped subjects, n = 6,544; prevalent cases, n = 686; incident cases during follow-up, n = 601; mean follow-up 10.6 years). The predictive value of these polymorphisms was examined alone and in addition to clinical characteristics using logistic and Cox regression analyses. The discriminative accuracy of the prediction models was assessed by the area under the receiver operating characteristic curves (AUCs).

RESULTS

Of the 18 polymorphisms, the ADAMTS9, CDKAL1, CDKN2A/B-rs1412829, FTO, IGF2BP2, JAZF1, SLC30A8, TCF7L2, and WFS1 variants were associated with type 2 diabetes risk in our population. The AUC was 0.60 (95% CI 0.57-0.63) for prediction based on the genetic polymorphisms; 0.66 (0.63-0.68) for age, sex, and BMI; and 0.68 (0.66-0.71) for the genetic polymorphisms and clinical characteristics combined.

CONCLUSIONS

We showed that 9 of 18 well-established genetic risk variants were associated with type 2 diabetes in a population-based study. Combining genetic variants has low predictive value for future type 2 diabetes at a population-based level. The genetic polymorphisms only marginally improved the prediction of type 2 diabetes beyond clinical characteristics.

The diabetogenic effects of excessive ethanol: reducing beta-cell mass, decreasing phosphatidylinositol 3-kinase activity and GLUT-4 expression in rats

The diabetogenic impact of ethanol remains as a focal point of basic and clinical investigations. In this study, Wistar rats were subjected to daily intragastric ethanol administration (10 ml/kg body weight injection with 0 (control), 10, 20 and 33 % (v/v) ethanol in the injections, respectively) for 19 weeks. At the end of the administration, we found that the fasting plasma glucose level of the 33 % (v/v) ethanol-loaded group was 18 % higher than the control. Insulin sensitivity was decreased in a dose-dependent manner in all the ethanol-loaded groups (r - 0.842, P < 0.001) during intraperitoneal insulin tolerance test. Necrotic/haemorrhagic injury was detected in the pancreas and islet beta-cell mass was significantly reduced in the 33 % (v/v) ethanol-loaded rats by immunohistochemical and morphometric analysis. At the molecular level, we detected a dose-dependent attenuation of phosphatidylinositol 3-kinase activity (r - 0.956, P < 0.001) and GLUT-4 expression (GLUT-4 mRNA, r - 0.899, P < 0.001; GLUT-4 protein, r - 0.964, P < 0.001) in skeletal muscle. These results demonstrated that drinking is a conditional aetiological factor for diabetes and excessive ethanol intake is negatively associated with both insulin sensitivity and beta-cell mass. The whole-body insulin resistance might result from the ethanol-induced insulin signalling defects in muscle.

Type 2 diabetes: new genes, new understanding

Over the past two years, there has been a spectacular change in the capacity to identify common genetic variants that contribute to predisposition to complex multifactorial phenotypes such as type 2 diabetes (T2D). The principal advance has been the ability to undertake surveys of genome-wide association in large study samples. Through these and related efforts, approximately 20 common variants are now robustly implicated in T2D susceptibility. Current developments, for example in high-throughput resequencing, should help to provide a more comprehensive view of T2D susceptibility in the near future. Although additional investigation is needed to define the causal variants within these novel T2D-susceptibility regions, to understand disease mechanisms and to effect clinical translation, these findings are already highlighting the predominant contribution of defects in pancreatic beta-cell function to the development of T2D.