Genetics of type 2 diabetes and insulin resistance: knowledge from human studies

The quality and reliability analysis of YouTube videos about insulin resistance

AIM

There is an increasing trend in the use of internet as a search tool for health-related informations. Insulin resistance is one of the most searched subjects online and some of the videos about insulin resistance have been watched by millions of YouTube users. This study aims to determine the quality and reliability of the most popular videos about insulin resistance on YouTube.

METHODS

On March 1, 2022, the term "insulin resistance" was searched on YouTube. The videos' popularity was assessed with Video Power Index (VPI). The quality and reliability were assessed with DISCERN score, modified DISCERN score and global quality score (GQS).

RESULTS

A total of 100 most popular videos were evaluated after applying the exclusion criteria. Fifty-four percent of the videos were very poor-poor, 35 % moderate, and 11 % good-excellent quality. Although few in number, the videos with relatively higher quality and more reliable had higher numbers of views, likes and comments (p < 0.01). There was a positive correlation between DISCERN score and VPI, duration, view, like, dislike, comment numbers of the videos (p < 0.01). Healthcare providers uploaded 58 % of the videos, while independent users uploaded 42 %. Video like ratio (VLR) at healthcare providers' videos was significantly higher than independent users' videos (p = 0.001).

CONCLUSIONS

Despite the high viewing rates of YouTube videos about insulin resistance, the overall quality and reliability were found to be very low. However, when high quality content regarding popular medical topics is produced, more people can be informed correctly.

GPR119 agonists: Novel therapeutic agents for type 2 diabetes mellitus

Diabetes mellitus type 2 (T2D) is a group of genetically heterogeneous metabolic disorders whose frequency has gradually risen worldwide. Diabetes mellitus Type 2 (T2D) has started to achieve a pandemic level, and it is estimated that within the next decade, cases of diabetes might get double due to increase in aging population. Diabetes is rightly called the 'silent killer' because it has emerged to be one of the major causes, leading to renal failure, loss of vision; besides cardiac arrest in India. Thus, a clinical requirement for the oral drug molecules monitoring glucose homeostasis appears to be unmet. GPR119 agonist, a family of G-protein coupled receptors, usually noticed in β-cells of pancreatic as well as intestinal L cells, drew considerable interest for type 2 diabetes mellitus (T2D). GPR119 monitors physiological mechanisms that enhance homeostasis of glucose, such as glucose-like peptide-1, gastrointestinal incretin hormone levels, pancreatic beta cell-dependent insulin secretion and glucose-dependent insulinotropic peptide (GIP). In this manuscript, we have reviewed the work done in the last five years (2015-2020) which gives an approach to design, synthesize, evaluate and study the structural activity relationship of novel GPR119 agonist-based lead compounds. Our article would help the researchers and guide their endeavours in the direction of strategy and development of innovative, effective GPR119 agonist-based compounds for the management of diabetes mellitus type 2.

Schizophrenia, antipsychotics and diabetes: Genetic aspects

The relatively high comorbidity of type 2 diabetes and schizophrenia may suggest a shared biological susceptibility to these twoconditions. Family studies have demonstrated an increased risk of diabetes in unaffected relatives of patients with schizophrenia, consistent with a heritable susceptibility trait. Linkage analyses have identified several loci that are associated with schizophrenia and some of these, notably those on chromosomes 2p22.1-p13.2 and 6g21-824.1 have also been observed in linkage studies in type 2 diabetes. In addition, the dopamine D5 receptor on chromosome 5 and the tyrosine hydroxylase gene on chromosome 11 have both been suggested as candidate genes in schizophrenia and may also be implicated in susceptibility to poor glycaemic control. In addition, an increased rate of type II diabetes has been observed in some patients treated with antipsychotics. Potential neurochemical substrates of this effect include the histamine H1 receptor, the 5-HT2C serotonin receptor or the β3 adrenoreceptor. However, the search for a genetic basis to the association between diabetes and schizophrenia is still in its infancy, and much further work needs to be performed, including the systematic screening of all confirmed susceptibility loci and quantitative trait locus mapping of glycaemic control.

Prognostic interaction patterns in diabetes mellitus II: A random-matrix-theory relation

We analyze protein-protein interactions in diabetes mellitus II and its normal counterpart under the combined framework of random matrix theory and network biology. This disease is the fifth-leading cause of death in high-income countries and an epidemic in developing countries, affecting around 8% of the total adult population in the world. Treatment at the advanced stage is difficult and challenging, making early detection a high priority in the cure of the disease. Our investigation reveals specific structural patterns important for the occurrence of the disease. In addition to the structural parameters, the spectral properties reveal the top contributing nodes from localized eigenvectors, which turn out to be significant for the occurrence of the disease. Our analysis is time-efficient and cost-effective, bringing a new horizon in the field of medicine by highlighting major pathways involved in the disease. The analysis provides a direction for the development of novel drugs and therapies in curing the disease by targeting specific interaction patterns instead of a single protein.

Life-threatening infectious diseases of childhood: single-gene inborn errors of immunity?

The hypothesis that inborn errors of immunity underlie infectious diseases is gaining experimental support. However, the apparent modes of inheritance of predisposition or resistance differ considerably among diseases and among studies. A coherent genetic architecture of infectious diseases is lacking. We suggest here that life-threatening infectious diseases in childhood, occurring in the course of primary infection, result mostly from individually rare but collectively diverse single-gene variations of variable clinical penetrance, whereas the genetic component of predisposition to secondary or reactivation infections in adults is more complex. This model is consistent with (i) the high incidence of most infectious diseases in early childhood, followed by a steady decline; (ii) theoretical modeling of the impact of monogenic or polygenic predisposition on the incidence distribution of infectious diseases before reproductive age; (iii) available molecular evidence from both monogenic and complex genetics of infectious diseases in children and adults; (iv) current knowledge of immunity to primary and secondary or latent infections; (v) the state of the art in the clinical genetics of noninfectious pediatric and adult diseases; and (vi) evolutionary data for the genes underlying single-gene and complex disease risk. With the recent advent of new-generation deep resequencing, this model of single-gene variations underlying severe pediatric infectious diseases is experimentally testable.

Gene expression in skeletal muscle biopsies from people with type 2 diabetes and relatives: differential regulation of insulin signaling pathways

BACKGROUND

Gene expression alterations have previously been associated with type 2 diabetes, however whether these changes are primary causes or secondary effects of type 2 diabetes is not known. As healthy first degree relatives of people with type 2 diabetes have an increased risk of developing type 2 diabetes, they provide a good model in the search for primary causes of the disease.

METHODS/PRINCIPAL FINDINGS

We determined gene expression profiles in skeletal muscle biopsies from Caucasian males with type 2 diabetes, healthy first degree relatives, and healthy controls. Gene expression was measured using Affymetrix Human Genome U133 Plus 2.0 Arrays covering the entire human genome. These arrays have not previously been used for this type of study. We show for the first time that genes involved in insulin signaling are significantly upregulated in first degree relatives and significantly downregulated in people with type 2 diabetes. On the individual gene level, 11 genes showed altered expression levels in first degree relatives compared to controls, among others KIF1B and GDF8 (myostatin). LDHB was found to have a decreased expression in both groups compared to controls.

CONCLUSIONS/SIGNIFICANCE

We hypothesize that increased expression of insulin signaling molecules in first degree relatives of people with type 2 diabetes, work in concert with increased levels of insulin as a compensatory mechanism, counter-acting otherwise reduced insulin signaling activity, protecting these individuals from severe insulin resistance. This compensation is lost in people with type 2 diabetes where expression of insulin signaling molecules is reduced.

Metabolomics in evaluation of glucose disorders

PURPOSE OF REVIEW

Recent advances in metabolomic tools now permit to characterize dysregulated metabolic pathways in various diseases associated with the identification of sensitive and specific early responding biomarkers that are critical both for the diagnosis of the type of insult as well as for the selection and evaluation of therapy.

RECENT FINDINGS

This short review describes progresses made in analytical science and their applications in the field of glucose disorders. Recent studies focused mainly on type 2 diabetes both in human and animal models in order to validate early biomarkers and effects of drugs on disease progression. The potential of using the metabolomic approach was also demonstrated for diagnosing diabetic complications such as diabetic nephropathy.

SUMMARY

In addition to its application in the discovery of disease biomarkers, metabolomics can contribute to the elucidation of pathophysiological mechanisms.

Genetic and environmental influences on factors associated with cardiovascular disease and the metabolic syndrome

The relative influence of genetics and the environment on factors associated with cardiovascular disease (CVD) and metabolic syndrome (MetS) remains unclear. We performed model-fitting analyses to quantify genetic, common environmental, and unique environmental variance components of factors associated with CVD and MetS [waist circumference, blood pressure, fasting plasma glucose and insulin, homeostatic model assessment of insulin resistance (HOMA-IR), and fasting plasma lipids] in adult male and female monozygotic twins reared apart or together. We also investigated whether MetS components share common influences. Plasma cholesterol and triglyceride concentrations were highly heritable (56-77%, statistically significant). Waist circumference, plasma glucose and insulin, HOMA-IR, and blood pressure were moderately heritable (43-57%, statistically significant). Unique environmental factors contributed to the variance of all variables (20-38%, perforce statistically significant). Common environmental factors contributed 23, 30, and 42% (statistically significant) of the variance of waist circumference, systolic blood pressure, and plasma glucose, respectively. Two shared factors influenced MetS components; one influenced all components except HDL cholesterol, another influenced only lipid (triglyceride and HDL cholesterol) concentrations. These results suggest that genetic variance has a dominant influence on total variance of factors associated with CVD and MetS and support the proposal of one or more underlying pathologies of MetS.

The identification of potential factors associated with the development of type 2 diabetes: a quantitative proteomics approach

Type 2 diabetes (T2D) arises when pancreatic beta-cells fail to compensate for systemic insulin resistance with appropriate insulin secretion. However, the link between insulin resistance and beta-cell failure in T2D is not fully understood. To explore this association, we studied transgenic MKR mice that initially develop insulin resistance in skeletal muscle but by 8 weeks of age have T2D. In the present study, global islet protein and gene expression changes were characterized in diabetic MKR versus non-diabetic control mice at 10 weeks of age. Using a quantitative proteomics approach (isobaric tags for relative and absolute quantification (iTRAQ)), 159 proteins were differentially expressed in MKR compared with control islets. Marked up-regulation of protein biosynthesis and endoplasmic reticulum stress pathways and parallel down-regulation in insulin processing/secretion, energy utilization, and metabolism were observed. A fraction of the differentially expressed proteins identified (including GLUT2, DNAJC3, VAMP2, RAB3A, and PC1/3) were linked previously to insulin-secretory defects and T2D. However, many proteins for the first time were associated with islet dysfunction, including the unfolded protein response proteins (ERP72, ERP44, ERP29, PPIB, FKBP2, FKBP11, and DNAJB11), endoplasmic reticulum-associated degradation proteins (VCP and UFM1), and multiple proteins associated with mitochondrial energy metabolism (NDUFA9, UQCRH, COX2, COX4I1, COX5A, ATP6V1B2, ATP6V1H, ANT1, ANT2, ETFA, and ETFB). The mRNA expression level corresponding to these proteins was examined by microarray, and then a small subset was validated using quantitative real time PCR and Western blot analyses. Importantly approximately 54% of differentially expressed proteins in MKR islets (including proteins involved in proinsulin processing, protein biosynthesis, and mitochondrial oxidation) showed changes in the proteome but not transcriptome, suggesting post-transcriptional regulation. These results underscore the importance of integrated mRNA and protein expression measurements and validate the use of the iTRAQ method combined with microarray to assess global protein and gene changes involved in the development of T2D.

Adiposity and insulin sensitivity derived from intravenous glucose tolerance tests in antipsychotic-treated patients

Cardiovascular disease is more common in schizophrenia patients than in the general population, with a hypothesized contribution from increases in adiposity produced by antipsychotic medications. We sought to test the relationship between adiposity and insulin resistance using frequently sampled intravenous glucose tolerance tests (FSIVGTTs) to quantify whole-body insulin sensitivity in chronically treated patients with schizophrenia or schizoaffective disorder and untreated healthy controls. FSIVGTTs, body mass index (BMI), and waist circumference were obtained in nondiabetic patients (n=63) receiving olanzapine, risperidone, ziprasidone, or first generation antipsychotics, as well as in healthy controls (n=14). Subject groups (including untreated healthy controls) were matched for BMI and all treated patient groups were additionally matched for age. Bergman's minimal model (MinMod) was used to calculate insulin sensitivity (S(I)), as well as secondary measures of interest. BMI and waist circumference significantly predicted insulin sensitivity measured as MinMod S(I) (F(1,62)=35.11, p<0.0001 and F(1,46)=24.48, p<0.0001, respectively). In addition, BMI and waist circumference significantly predicted the acute plasma insulin response to the glucose challenge (AIR(G)), consistent with a beta cell compensatory response to insulin resistance (MinMod AIR(G) F(1,65)=22.42, p<0.0001 and F(1,49)=11.72, p=0.0013, respectively). Adiposity levels occurring during antipsychotic treatment are strongly related to insulin resistance, confirming that antipsychotic-induced weight gain can contribute to increased cardiometabolic risk in this population.

Identification of type 2 diabetes genes in Mexican Americans through genome-wide association studies

OBJECTIVE

The objective of this study was to identify DNA polymorphisms associated with type 2 diabetes in a Mexican-American population.

RESEARCH DESIGN AND METHODS

We genotyped 116,204 single nucleotide polymorphisms (SNPs) in 281 Mexican Americans with type 2 diabetes and 280 random Mexican Americans from Starr County, Texas, using the Affymetrix GeneChip Human Mapping 100K set. Allelic association exact tests were calculated. Our most significant SNPs were compared with results from other type 2 diabetes genome-wide association studies (GWASs). Proportions of African, European, and Asian ancestry were estimated from the HapMap samples using structure for each individual to rule out spurious association due to population substructure.

RESULTS

We observed more significant allelic associations than expected genome wide, as empirically assessed by permutation (14 below a P of 1 x 10(-4) [8.7 expected]). No significant differences were observed between the proportion of ancestry estimates in the case and random control sets, suggesting that the association results were not likely confounded by substructure. A query of our top approximately 1% of SNPs (P < 0.01) revealed SNPs in or near four genes that showed evidence for association (P < 0.05) in multiple other GWAS interrogated: rs979752 and rs10500641 near UBQLNL and OR52H1 on chromosome 11, rs2773080 and rs3922812 in or near RALGPS2 on chromosome 1, and rs1509957 near EGR2 on chromosome 10.

CONCLUSIONS

We identified several SNPs with suggestive evidence for replicated association with type 2 diabetes that merit further investigation.

Network-based analysis of affected biological processes in type 2 diabetes models

Type 2 diabetes mellitus is a complex disorder associated with multiple genetic, epigenetic, developmental, and environmental factors. Animal models of type 2 diabetes differ based on diet, drug treatment, and gene knockouts, and yet all display the clinical hallmarks of hyperglycemia and insulin resistance in peripheral tissue. The recent advances in gene-expression microarray technologies present an unprecedented opportunity to study type 2 diabetes mellitus at a genome-wide scale and across different models. To date, a key challenge has been to identify the biological processes or signaling pathways that play significant roles in the disorder. Here, using a network-based analysis methodology, we identified two sets of genes, associated with insulin signaling and a network of nuclear receptors, which are recurrent in a statistically significant number of diabetes and insulin resistance models and transcriptionally altered across diverse tissue types. We additionally identified a network of protein–protein interactions between members from the two gene sets that may facilitate signaling between them. Taken together, the results illustrate the benefits of integrating high-throughput microarray studies, together with protein–protein interaction networks, in elucidating the underlying biological processes associated with a complex disorder.

Type 2 diabetes mellitus currently affects millions of people. It is clinically characterized by insulin resistance in addition to an impaired glucose response and associated with numerous complications including heart disease, stroke, neuropathy, and kidney failure, among others. Accurate identification of the underlying molecular mechanisms of the disease or its complications is an important research problem that could lead to novel diagnostics and therapy. The main challenge stems from the fact that insulin resistance is a complex disorder and affects a multitude of biological processes, metabolic networks, and signaling pathways. In this report, the authors develop a network-based methodology that appears to be more sensitive than previous approaches in detecting deregulated molecular processes in a disease state. The methodology revealed that both insulin signaling and nuclear receptor networks are consistently and differentially expressed in many models of insulin resistance. The positive results suggest such network-based diagnostic technologies hold promise as potentially useful clinical and research tools in the future.

Molecular mechanisms of insulin resistance and associated diseases

Insulin resistance is a state in which higher than normal concentrations of insulin are required for normal response. The most common underlying cause is central obesity, although primary insulin resistance in normal-weight individuals is also possible. Excess abdominal adipose tissue has been shown to release increased amounts of free fatty acids which directly affect insulin signalling, diminish glucose uptake in muscle, drive exaggerated triglyceride synthesis and induce gluconeogenesis in the liver. Other factors presumed to play the role in insulin resistance are tumour necrosis factor alpha, adiponectin, leptin, IL-6 and some other adipokines. Hyperinsulinaemia which accompanies insulin resistance may be implicated in the development of many pathological states, such as hypertension and hyperandrogenaemia. Insulin resistance underlies metabolic syndrome and is further associated with polycystic ovary syndrome and lipodystrophies. When beta-cells fail to secrete the excess insulin needed, diabetes mellitus type 2 emerges, which is, besides coronary heart disease, the main complication of insulin resistance and associated diseases.

Role of impaired insulin secretion and insulin resistance in the pathogenesis of type 2 diabetes mellitus

Type 2 diabetes mellitus (T2DM) is a heterogeneous disorder caused by a combination of genetic and acquired abnormalities that affect insulin sensitivity and insulin secretion. Currently available data suggest that insulin resistance is the acquired defect largely secondary to unhealthy lifestyles and that the major genetic factor is impaired insulin secretion. The latter is the result of both reduced beta-cell mass and functional abnormalities makes the beta-cell unable to compensate for increased insulin requirements caused by insulin resistance. Targeting both insulin resistance and impaired insulin secretion is therefore appropriate to prevent T2DM and to improve glycemic control in those with the disorder.

Review article: diabetes, genetics and ethnicity

The prevalence of insulin resistance and diabetes has increased in the past decades at an alarming rate in all Western countries and in those countries which are adopting a 'western life style'. This trend suggests the impact of environmental factors such as diet, obesity and physical activity on the pathogenesis of diabetes. However it is known that the prevalence and variation of prevalence, as consequence of environmental changes, it is different in various ethnic groups. Studies conducted in multiethnic populations suggest that some ethnic groups, such as Hispanics or Asian Indians, might have a particular predisposition, possibly on genetic basis, to develop insulin resistance and diabetes, when exposed to adverse conditions. According to the 'thrifty gene' hypothesis, a clustering of different genetic defects or polymorphisms, developed as genetic advantage in some populations, could predispose some ethnic groups to insulin resistance and diabetes in presence of an increased food supply. Multiple mutations, associated with small changes in insulin sensitivity, when combined, may induce a significant reduction in insulin sensitivity. This review deals with the possible relevance of genetic factors in the expression of insulin resistance and diabetes in relation to ethnicity.

Type 2 diabetes mellitus in children and adolescents

Over the last decade, there has been an alarming increase of Type 2 diabetes mellitus (T2DM) in youths, concomitant with the rise of obesity in this age group. T2DM is a progressive disease with a gradual increase in insulin resistance associated later with a decline in insulin secretion with fasting hyperglycemia. Prevalence of T2DM in children is mostly linked to some risk factors: obesity and sedentary lifestyle, puberty, membership of ethnic minorities, features of insulin resistance, family history of T2DM, female gender and perinatal factors. Prevention is essential and can be considered a public health approach directed to the general population. Treatment of T2DM in youth is complex and based on different strategies: diet, exercise and pharmacotherapy. An appropriated intervention program must be started early, in order to prevent or retard the progression of the disease and associated comorbidities.

The effect of non-insulin dependent diabetes mellitus on uncontrolled hemorrhage in a rodent model

OBJECTIVE

Diabetes mellitus (DM) is an independent risk factor for higher morbidity and mortality rates from trauma. We tested the null hypothesis that there would be no difference in the hemorrhage volumes and hemodynamic responses to uncontrolled hemorrhage between Zucker Diabetic Fat rats (ZDF) and euglycemic Sprague-Dawley rats (SD).

METHODS

Twenty-four adult male rats (12 ZDF and 12 SD) were anesthetized with althesin via the intraperitoneal route. The femoral artery was cannulated by cut-down to monitor the heart rate (HR), mean arterial pressure (MAP) and to obtain blood samples for blood gas analysis. Twelve rats (6 ZDF and 6 SD) underwent uncontrolled hemorrhage by 50% tail amputation. Twelve rats (6 ZDF and 6 SD) served as non-hemorrhage controls. The HR, MAP, lactate (LAC), glucose levels (GL) and cumulative hemorrhage volume (CHV) were measured pre-hemorrhage and then every 15 min post-hemorrhage for 120 min. Data were reported as mean+/-S.E.M. Group comparisons were analyzed by ANOVA with repeated values; post hoc testing by Bonferroni (all tests were two-tailed, alpha = 0.05).

RESULTS

Pre-hemorrhage the SD and ZDF were evenly matched for LAC, HR and MAP. CHV (cm3/100 g) was significantly (p = 0.008) greater in the ZDF (1.49+/-0.12) as compared to the SD (0.38+/-0.11). The ZDF had significantly (p < 0.001) higher LAC (7.96+/-0.61 mmol/L) than the SD (2.0+/-0.41 mmol/L).

CONCLUSION

DM as compared to non-DM rats suffered a greater blood loss with a more severe lactic acidosis after a comparable uncontrolled vascular injury.

Emerging strategies and applications of pharmacogenomics

The rapid pace of genomic science advancements, including the completion of the human genome sequence, the extensive cataloguing of genetic variation and the acceleration of technologies to assess such variation, combined with clinical programmes with rich phenotypic data, serve as the foundation for the design and execution of pharmacogenomic studies which have an impact on the pharmaceutical pipeline from early discovery through to the marketplace. The authors discuss the required infrastructure to support pharmacogenomic studies and provide insight into the strategies and practical application to influence decision making in the pharmaceutical setting. Further, the influence of pharmacogenomics is currently affecting patient care in the oncology area and is highlighted as evident impact in the marketplace.

Genes and Type 2 Diabetes Mellitus

Type 2 diabetes (T2DM) comprises a group of entities with different genetic causes. In most patients, T2DM results from alterations of various genes, each having a partial and additive effect. The inheritance pattern is thus complex, and environmental factors play an important role in favoring or delaying the expression of the disease. The identification of susceptibility genes and genetic variants requires different methodological approaches. Here we address some of the most important strategies and findings on the genomic basis of T2DM, as well as evidence of genetic heterogeneity among populations. The identification of the underlying genetic causes of T2DM and other related traits such as obesity and hypertension will lead to the development of new therapeutic targets likely to impact the way we treat these diseases. Survival and quality of life for T2DM patients is expected to eventually increase, significantly lessening the socioeconomic burden of the disease.

Nonalcoholic fatty liver disease: a review of current understanding and future impact

Nonalcoholic fatty liver disease (NAFLD), already the most common form of liver disease in the United States, can be expected to increase in prevalence and severity in parallel with national epidemics of obesity and type 2 diabetes. NAFLD is frequently associated with insulin resistance. While insulin resistance, and thereby hyperinsulinemia, are, in large part, metabolic consequences of obesity, the basis of diversity in severity and progression of inflammation and fibrosis is not known. Increased susceptibility to oxidative stress is likely to play a role. Several patient characteristics have been associated with more severe histological findings in patients with NAFLD, including type 2 diabetes, hypertension, age over 40 years, and higher transaminases. Liver biopsy is, however, required to accurately grade and stage NAFLD histologically. Although the natural history of NAFLD is relatively poorly defined, NAFLD is increasingly recognized as an important cause of decompensated liver disease. Weight reduction and improved insulin sensitivity are associated with improved biochemical and histological parameters of NAFLD. There are, however, no proven safe and efficacious pharmacological treatments for NAFLD.

Antidiabetic effect of novel modulating peptides of G-protein-coupled kinase in experimental models of diabetes

AIMS/HYPOTHESIS

G-protein-coupled receptor kinases (GRKs) play a key role in agonist-induced desensitisation of G-protein-coupled receptors (GPCRs) that are involved in metabolic regulation and glucose homeostasis. Our aim was to examine whether small peptides derived from the catalytic domain of GRK2 and -3 would ameliorate Type 2 diabetes in three separate animal models of diabetes.

METHODS

Synthetic peptides derived from a kinase-substrate interaction site in GRK2/3 were initially screened for their effect on in vitro melanogenesis, a GRK-mediated process. The most effective peptides were administered intraperitoneally, utilising a variety of dosing regimens, to Psammomys obesus gerbils, Zucker diabetic fatty (ZDF) rats, or db/db mice. The metabolic effects of these peptides were assessed by measuring fasting and fed blood glucose levels and glucose tolerance.

RESULTS

Two peptides, KRX-683(107) and KRX-683(124), significantly reduced fed-state blood glucose levels in the diabetic Psammomys obesus. In animals treated with KRX-683(124) at a dose of 12.5 mg/kg weekly for 7 weeks, ten of eleven treated animals responded with mean blood glucose significantly lower than controls (4.7+/-0.4 vs 16.8+/-0.8 mmol/l, p</=0.0001). Significant reductions in blood glucose compared with controls were also seen in ZDF rats administered KRX-683(124) and in db/db mice, which had significantly reduced fasting and 2-hour postprandial glucose levels after the treatment.

CONCLUSIONS/INTERPRETATION

Sequence-based peptides derived from GRK2/3 have an antidiabetic effect demonstrated in three different animal models of Type 2 diabetes. By modulating GRK2/3 activity, these peptides enhance GPCR-initiated signal transduction, resulting in improved glucose homeostasis. Sequence-based peptide modulation of GRK could prove useful in the treatment of Type 2 diabetes.

The genetics and pathophysiology of diabetes mellitus type II

Type II diabetes is a common, complex and heterogeneous group of disorders of growing public health concern. Paradoxically, rare monogenic forms of diabetes mellitus have been the most informative regarding diabetes pathophysiology to date. We discuss disappointing results of genetic approaches thus far, emphasizing the genetic heterogeneity underlying the common phenotypic endpoint of elevated blood glucose level and the phenotypic misclassification in large studies resulting from this admixture and from the obligatory use of epidemiological or clinical surrogate measures. We suggest that novel approaches that take explicit account of the phenotypic, environmental and genetic complexities of type II diabetes are needed and discuss some principles that might underlie such approaches.

Genetic and environmental aspect of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a heterogeneous syndrome determined in most patients by the association of two main factors: hyperandrogenism and insulin resistance. These characters are probably independent of each other and seem to be inherited by several different mechanisms. In some patients homozygous gene alteration has been found but in most patients PCOS seems to be determined by the association of gene polymorphisms that are common in the general population but alone are unable to determine phenotypic consequences. Alteration of genes that regulate the initial steps of ovarian steroidogenesis is probably the main causal factor of hyperandrogenism. Insulin resistance may be the result of many different gene alterations including insulin receptor substrate (IRS)-1 and 2, calpain-10 and peroxisome proliferator-activated receptor gamma(PPARgamma). Some polymorphisms may be protective against other gene alterations. Insulin sensitivity is also modified by socioeconomic and cultural factors that influence quantity and quality of food and energy expenditure. However, even eating behavior and weight response to food intake may be under genetic regulation. Different combinations of multiple gene polymorphisms and of environmental factors explain the heterogeneity of PCOS.

Type 2 diabetes: an epidemic disease in childhood

Type 2 diabetes mellitus in the pediatric population is now a public health problem. It represents 8 to 45% of all diabetes reported among children and adolescents. Concurrently, childhood obesity has become an epidemic in the United States. Epidemiologic risk factors and diagnostic criteria have largely been established: The incidence of type 2 diabetes increases with age and obesity. Children and adolescents diagnosed with type 2 diabetes usually have a first- or second-degree relative with the disorder. Familial clustering and twin studies have suggested a genetic component for type 2 diabetes. However, the molecular mechanisms that promote diabetes in susceptible individuals, the best treatment plans, and methods of prevention of this disorder are not yet established.

Molecular and physiologic actions of insulin related to production of nitric oxide in vascular endothelium

Insulin has important vascular actions that regulate blood flow, in addition to its classical actions to coordinate glucose homeostasis. Insulin-stimulated production of nitric oxide in vascular endothelium results in capillary recruitment and vasodilation that diverts and increases blood flow to skeletal muscle and consequently increases glucose disposal. Thus, vascular actions of insulin may be essential for coupling hemodynamic and metabolic homeostasis. A complete biochemical signaling pathway linking the insulin receptor to activation of endothelial nitric oxide synthase in vascular endothelium has recently been elucidated. Moreover, the time course and dose response for capillary recruitment in response to physiologic concentrations of insulin parallels that of insulin-mediated glucose uptake in vivo. Taken together, these observations suggest a molecular mechanism that may help to explain how insulin resistance contributes to cardiovascular components of the metabolic syndrome and vascular complications of diabetes.

Benefits of blood pressure reduction in diabetic patients

Hypertension is common among patients with type 2 diabetes mellitus, increasing their risk of cardiovascular morbidity and mortality. Such patients are also at risk of renal impairment and end-stage renal disease. Long-term, tight blood pressure control (ideally to a target of < 130/85 mmHg) in patients with type 2 diabetes is a highly effective strategy for reducing the risk of cardiovascular complications and is now embodied in the many guidelines of hypertension and diabetes management. More recent studies indicate that the choice of antihypertensive agent is also important. Drugs that block the renin-angiotensin-aldosterone system, such as the angiotensin-II receptor blockers (ARBs), may prevent the onset of diabetes and confer greater cardiovascular benefit among patients who already have this disease compared with some older antihypertensive agents. For example, in type 2 diabetic patients with renal dysfunction, ARBs exert a renal protective effect that extends beyond blood pressure reduction and may retard diabetic nephropathy. Antihypertensive therapy, together with lifestyle modification to address obesity and physical inactivity, can significantly reduce the risk of cardiovascular complications in patients with type 2 diabetes. The challenge is to achieve beneficial, hygienic measures in populations with diverse backgrounds and improve compliance with proven treatments that inevitably involve multiple drugs. Combination therapies comprising agents that offer good tolerability and do not exacerbate existing metabolic disturbances, as well as demonstrating benefit in preventing events in diabetic patients beyond blood pressure reduction itself, seem a likely way forward.

Contributions of insulin-resistance and insulin-secretory defects to the pathogenesis of type 2 diabetes mellitus

Controlled clinical trials have shown that optimal glycemic control can prevent the microvascular complications of type 2 diabetes mellitus; considerable epidemiological data suggest that this may also be true for macrovascular complications. However, this is frequently not achieved. Consequently, research efforts have been undertaken to better understand the pathophysiology of this disorder. It is now well recognized that 2 factors are involved: impaired beta-cell function and insulin resistance. Prospective studies of high-risk populations have shown insulin-resistance and/ or insulin-secretory defects before the onset of impaired glucose tolerance. Thus, there has been a long-standing debate whether an alteration in insulin sensitivity or in insulin secretion is the primary genetic factor. Most of the available evidence favors the view that type 2 diabetes is a heterogeneous disorder in which the major genetic factor is impaired beta-cell function and insulin resistance is the major acquired factor. Superimposition of insulin resistance on a beta cell that cannot appropriately compensate leads to deterioration in glucose tolerance. Therefore, clinicians managing type 2 diabetes must reduce insulin resistance and augment and/or replace beta-cell function.

The prevention of type 2 diabetes--lifestyle change or pharmacotherapy? A challenge for the 21st century

Diabetes mellitus is occurring in epidemic proportions in many countries. In Australia 7.4% of people over 25 years of age have diabetes (mostly type 2) and comparable or higher prevalences have been reported in the United States and a number of Asian countries. The enormous economic and social cost of this disease makes a compelling case for prevention. Epidemiological studies have shown clearly that type 2 diabetes results from an interaction between a genetic predisposition and lifestyle factors including obesity, sedentary behaviour and both calorie excess and various dietary constituents. The natural history of type 2 diabetes includes a preceding period of impaired glucose tolerance (IGT)/impaired fasting glucose (IFG) which provides an opportunity for targeted intervention within large communities. Lifestyle intervention studies have consistently shown that quite modest changes can reduce the progression from IGT to diabetes by 50-60%. It may, however, not be possible to translate these successful findings to larger cohorts or maintain the lifestyle changes longer term. This has lead to consideration of pharmacotherapy. While small studies with sulphonylureas are inconclusive, benefits have been found for metformin, acarbose and troglitazone. Big intervention studies with ramipril, rosiglitazone, valsartan and nateglinide are underway. Pharmacological intervention raises a whole range of ethical, economic and practical issues not the least of which is the problem of long term therapy of the 'otherwise well'.