Diabetes: mellitus or lipidus?

Alogliptin: a DPP-4 inhibitor modulating adipose tissue insulin resistance and atherogenic lipid

AIMS

The purpose of this study is to investigate the regulation of adipose tissue insulin resistance with DPP-4 inhibitors in treatment-naive subjects with T2DM and to examine its relation to other diabetic parameters.

SUBJECTS AND METHODS

A total of 147 subjects were treated with alogliptin 12.5-25 mg/day (n = 55), sitagliptin 25-50 mg/day (n = 49), or teneligliptin 10-20 mg/day (n = 43) monotherapy for 3 months. Changes in adipo-IR, a mathematical model used to evaluate adipose tissue insulin resistance, and various diabetic parameters were analyzed in this prospective, non-randomized observational study.

RESULTS

Among these three drugs, only alogliptin significantly reduced adipo-IR (-25.9%, p < 0.004) and some lipid parameters, such as LDL-C, T-C/HDL-C, log(TG)/HDL-C, non-HDL-C/HDL-C, and LDL-C/HDL-C. Subjects in the alogliptin group were divided into two groups with distinct changes in adipo-IR. Group A had a significant decrease in adipo-IR (-56.5%, p < 0.00001, n = 28), whereas group B had an insignificant increase (19.1%, p = 0.055, n = 27). Significant reductions in FBG or HbA1c were observed in groups A and B, respectively. Group A also showed significant reductions in HOMA-R, T-C/HDL-C, TG, log(TG)/HDL-C, non-HDL-C/HDL-C, LDL-C/HDL-C, and FFA, as well as increases in QUICKI or HDL-C. In contrast, group B showed significant reductions in QUICKI or LDL-C, and increases in HOMA-R, insulin, HOMA-B, C-peptide, or CPR-index.

CONCLUSIONS

In contrast to other tested DPP-4 inhibitors, alogliptin demonstrated the ability to down-regulate insulin resistance in adipose tissue, as well as certain atherogenic lipids. This study provides the initial evidence of a DPP-4 inhibitor's potential to regulate adipose tissue insulin resistance. Furthermore, adipo-IR is associated with non-LDL-C lipid parameters instead of glycemic control in those receiving alogliptin.

Age-Related Changes in Lipid and Glucose Levels Associated with Drug Use and Mortality: An Observational Study

Background: The pathogenesis of type 2 diabetes mellitus is complex and still unclear in some details. The main feature of diabetes mellitus is high serum glucose, and the question arises of whether there are other statistically observable dysregulations in laboratory measurements before the state of hyperglycemia becomes severe. In the present study, we aim to examine glucose and lipid profiles in the context of age, sex, medication use, and mortality. Methods: We conducted an observational study by analyzing laboratory data from 506,083 anonymized laboratory tests from 63,606 different patients performed by a regional laboratory in Slovenia between 2008 and 2019. Laboratory data-based results were evaluated in the context of medication use and mortality. The medication use database contains anonymized records of 1,632,441 patients from 2013 to 2018, and mortality data were obtained for the entire Slovenian population. Results: We show that the highest percentage of the population with elevated glucose levels occurs approximately 20 years later than the highest percentage with lipid dysregulation. Remarkably, two distinct inflection points were observed in these laboratory results. The first inflection point occurs at ages 55 to 59 years, corresponding to the greatest increase in medication use, and the second coincides with the sharp increase in mortality at ages 75 to 79 years. Conclusions: Our results suggest that medications and mortality are important factors affecting population statistics and must be considered when studying metabolic disorders such as dyslipidemia and hyperglycemia using laboratory data.

Is type 2 diabetes an adiposity-based metabolic disease? From the origin of insulin resistance to the concept of dysfunctional adipose tissue

In the last decades of the past century, a remarkable amount of research efforts, money and hopes was generated to unveil the basis of insulin resistance that was believed to be the primary etiological factor in the development of type 2 diabetes. From the Reaven's insulin resistance syndrome to the DeFronzo's triumvirate (skeletal muscle, liver and beta-cell) and to Kahn's discovery (among many others) of insulin receptor downregulation and autophosphorylation, an enthusiastic age of metabolic in vivo and in vitro research took place, making the promise of a resolutory ending. However, from many published data (those of insulin receptoropathies and lipodystrophies, the genome-wide association studies results, the data on reversibility of type 2 diabetes after bariatric surgery or very-low-calorie diets, and many others) it appears that insulin resistance is not a primary defect but it develops secondarily to increased fat mass. In particular, it develops from a mismatch between the surplus caloric intake and the storage capacity of adipose tissue. On this basis, we propose to change the today's definition of type 2 diabetes in adiposity-based diabetes.Level of Evidence as a narrative review a vast array of studies have been included in the analysis, ranging from properly designed randomized controlled trials to case studies; however, the overall conclusion may be regarded as level IV.

100th anniversary of the discovery of insulin perspective: insulin and adipose tissue fatty acid metabolism

Insulin inhibits systemic nonesterified fatty acid (NEFA) flux to a greater degree than glucose or any other metabolite. This remarkable effect is mainly due to insulin-mediated inhibition of intracellular triglyceride (TG) lipolysis in adipose tissues and is essential to prevent diabetic ketoacidosis, but also to limit the potential lipotoxic effects of NEFA in lean tissues that contribute to the development of diabetes complications. Insulin also regulates adipose tissue fatty acid esterification, glycerol and TG synthesis, lipogenesis, and possibly oxidation, contributing to the trapping of dietary fatty acids in the postprandial state. Excess NEFA flux at a given insulin level has been used to define in vivo adipose tissue insulin resistance. Adipose tissue insulin resistance defined in this fashion has been associated with several dysmetabolic features and complications of diabetes, but the mechanistic significance of this concept is not fully understood. This review focusses on the in vivo regulation of adipose tissue fatty acid metabolism by insulin and the mechanistic significance of the current definition of adipose tissue insulin resistance. One hundred years after the discovery of insulin and despite decades of investigations, much is still to be understood about the multifaceted in vivo actions of this hormone on adipose tissue fatty acid metabolism.

Concentration/activity of superoxide dismutase isozymes and the pro-/antioxidative status, in context of type 2 diabetes and selected single nucleotide polymorphisms (genes: INS, SOD1, SOD2, SOD3) - Preliminary findings

The alterations in concentration/activity of superoxide dismutase isozymes in the context of type 2 diabetes or obesity are well-described. Moreover, many hereditary factors, including single-nucleotide polymorphisms (SNPs) of genes for coding insulin, insulin receptors, or insulin receptor substrates (INS, INSR, IRS1, IRS2) or superoxide dismutase isozymes (SOD1, SOD2, SOD3), have been linked with the incidence of obesity and diabetes. However, the underlying changes in the plasma concentration/activity of superoxide dismutase isozymes and their potential connection with the said hereditary factors remain unexplored. Previously, we have observed that the plasma concentration/activity of superoxide dismutase isozymes differs in the context of obesity and/or rs2234694 (SOD1) and rs4880 (SOD2) and that the concentrations of SOD1, SOD2, SOD3 are correlated with each other. Intersexual variability of SOD1 concentration was detected regardless of obesity. In this study, the variability of concentration/activity of superoxide dismutase isozymes in plasma is considered in the context of type 2 diabetes and/or SNPs: rs2234694 (SOD1), rs5746105 (SOD2), rs4880 (SOD2), rs927450 (SOD2), rs8192287 (SOD3). Genotypic variability of SNP rs3842729 (INS), previously studied in the context of insulin-dependent diabetes, is investigated in terms of selected clinical parameters associated with type 2 diabetes. This study revealed higher SOD1 concentration in diabetic men compared to women, and extremely high SOD1 concentration, higher total superoxide dismutase, and copper-zinc superoxide dismutase activity, and lower superoxide dismutase and copper-zinc superoxide dismutase activity (when adjusted for the concentration of SODs) in the diabetic group regardless of sex. Multiple logistic regression, applied to explore possible links between the studied SNPs and other factors with the odds of type 2 diabetes or obesity, revealed that the genotypic variability of rs4880 (SOD2) could affect these odds, supporting the findings of several other studies.

Dyslipidaemia was correlated to the posterior circulation infarction in non-diabetic populations

Background

Diabetes mellitus (DM) was prone to happening in posterior circulation infarction (POCI) and DM also has the impact on the lipids, our study was to investigate the correlation between lipid compositions and POCI.

Methods

Data was collected from the patients with acute ischemic stroke (AIS) hospitalization in Affiliated Drum Tower Hospital of Nanjing University Medical School from October 2008 to May 2012. Lipids and other risk factors in the different populations were investigated in relation to occurrence of POCI based on the infarction location.

Results

Six hundred ten patients with AIS were included in this study, which had 428 with anterior circulation infarction (ACI) and 182 with POCI. Elevated Triglyceride (TG) and decreased High density lipoprotein cholesterol (HDL-C) were seen in the POCI of total populations and AIS without DM compared to the ACI, but not in the populations of AIS with DM, so did the elevated TG/HDL-C ratios. Also, the percent of low HDL-C level and high TG level were higher in POCI group than that in ACI group. Furthermore, single factors logistic regression demonstrated that TG, HDL-C and TG/HDL-C ratio were correlated to the POCI whatever in the total populations or AIS without DM, but this kind of trend just maintained in the populations of AIS without DM after adjusting by relative interference factors.

Conclusion

Dyslipidaemia was prone to happening in POCI compared to ACI in the non-diabetic populations, which was correlated to the pathogenesis of POCI.

Pharmacological inhibition of diacylglycerol acyltransferase-1 and insights into postprandial gut peptide secretion

AIM

To examine the role that enzyme Acyl-CoA:diacylglycerol acyltransferase-1 (DGAT1) plays in postprandial gut peptide secretion and signaling.

METHODS

The standard experimental paradigm utilized to evaluate the incretin response was a lipid challenge. Following a lipid challenge, plasma was collected via cardiac puncture at each time point from a cohort of 5-8 mice per group from baseline at time zero to 10 h. Incretin hormones [glucagon like peptide-1 (GLP-1), peptide tyrosine-tyrosine (PYY) and glucose dependent insulinotropic polypeptide (GIP)] were then quantitated. The impact of pharmacological inhibition of DGAT1 on the incretin effect was evaluated in WT mice. Additionally, a comparison of loss of DGAT1 function either by genetic ablation or pharmacological inhibition. To further elucidate the pathways and mechanisms involved in the incretin response to DGAT1 inhibition, other interventions [inhibitors of dipeptidyl peptidase-IV (sitagliptin), pancreatic lipase (Orlistat), GPR119 knockout mice] were evaluated.

RESULTS

DGAT1 deficient mice and wildtype C57/BL6J mice were lipid challenged and levels of both active and total GLP-1 in the plasma were increased. This response was further augmented with DGAT1 inhibitor PF-04620110 treated wildtype mice. Furthermore, PF-04620110 was able to dose responsively increase GLP-1 and PYY, but blunt GIP at all doses of PF-04620110 during lipid challenge. Combination treatment of PF-04620110 and Sitagliptin in wildtype mice during a lipid challenge synergistically enhanced postprandial levels of active GLP-1. In contrast, in a combination study with Orlistat, the ability of PF-04620110 to elicit an enhanced incretin response was abrogated. To further explore this observation, GPR119 knockout mice were evaluated. In response to a lipid challenge, GPR119 knockout mice exhibited no increase in active or total GLP-1 and PYY. However, PF-04620110 was able to increase total GLP-1 and PYY in GPR119 knockout mice as compared to vehicle treated wildtype mice.

CONCLUSION

Collectively, these data provide some insight into the mechanism by which inhibition of DGAT1 enhances intestinal hormone release.

Diabetes and dyslipidemia: characterizing lipoprotein metabolism

Premature atherosclerosis in diabetes accounts for much of the decreased life span. New treatments have reduced this risk considerably. This review explores the relationship among the disturbances in glucose, lipid, and bile salt metabolic pathways that occur in diabetes. In particular, excess nutrient intake and starvation have major metabolic effects, which have allowed us new insights into the disturbance that occurs in diabetes. Metabolic regulators such as the forkhead transcription factors, the farnesyl X transcription factors, and the fibroblast growth factors have become important players in our understanding of the dysregulation of metabolism in diabetes and overnutrition. The disturbed regulation of lipoprotein metabolism in both the intestine and the liver has been more clearly defined over the past few years, and the atherogenicity of the triglyceride-rich lipoproteins, and - in tandem - low levels of high-density lipoproteins, is seen now as very important. New information on the apolipoproteins that control lipoprotein lipase activity has been obtained. This is an exciting time in the battle to defeat diabetic atherosclerosis.

Hypertriglyceridemia: a too long unfairly neglected major cardiovascular risk factor

The existence of an independent association between elevated triglyceride (TG) levels, cardiovascular (CV) risk and mortality has been largely controversial. The main difficulty in isolating the effect of hypertriglyceridemia on CV risk is the fact that elevated triglyceride levels are commonly associated with concomitant changes in high density lipoprotein (HDL), low density lipoprotein (LDL) and other lipoproteins. As a result of this problem and in disregard of the real biological role of TG, its significance as a plausible therapeutic target was unfoundedly underestimated for many years. However, taking epidemiological data together, both moderate and severe hypertriglyceridaemia are associated with a substantially increased long term total mortality and CV risk. Plasma TG levels partially reflect the concentration of the triglyceride-carrying lipoproteins (TRL): very low density lipoprotein (VLDL), chylomicrons and their remnants. Furthermore, hypertriglyceridemia commonly leads to reduction in HDL and increase in atherogenic small dense LDL levels. TG may also stimulate atherogenesis by mechanisms, such excessive free fatty acids (FFA) release, production of proinflammatory cytokines, fibrinogen, coagulation factors and impairment of fibrinolysis. Genetic studies strongly support hypertriglyceridemia and high concentrations of TRL as causal risk factors for CV disease. The most common forms of hypertriglyceridemia are related to overweight and sedentary life style, which in turn lead to insulin resistance, metabolic syndrome (MS) and type 2 diabetes mellitus (T2DM). Intensive lifestyle therapy is the main initial treatment of hypertriglyceridemia. Statins are a cornerstone of the modern lipids-modifying therapy. If the primary goal is to lower TG levels, fibrates (bezafibrate and fenofibrate for monotherapy, and in combination with statin; gemfibrozil only for monotherapy) could be the preferable drugs. Also ezetimibe has mild positive effects in lowering TG. Initial experience with en ezetimibe/fibrates combination seems promising. The recently released IMPROVE-IT Trial is the first to prove that adding a non-statin drug (ezetimibe) to a statin lowers the risk of future CV events. In conclusion, the classical clinical paradigm of lipids-modifying treatment should be changed and high TG should be recognized as an important target for therapy in their own right. Hypertriglyceridemia should be treated.

Effects of lipids and lipoproteins on diabetic foot in people with type 2 diabetes mellitus: a meta-analysis

BACKGROUND

To conduct a meta-analysis of case-control studies to determine the effects of lipids and lipoproteins on morbidity of diabetic foot in adults with type 2 diabetes.

METHODS

We searched the PubMed and EMBASE to identify eligible studies. The Newcastle-Ottawa Quality Assessment Scale was used to determine the quality of selected studies. We assessed the strength of associations using standardized mean differences with 95% confidence intervals.

RESULTS

A total of 4 articles were found. Decreased HDL-cholesterol had a significant association with diabetic foot susceptibility in fixed-effects model, but no significant associations were found between diabetic foot and LDL-cholesterol, TC or TG levels.

CONCLUSIONS

Our results suggested that decreased HDL-cholesterol was associated with diabetic foot, so possible measures to prevent diabetic foot should include targeting increases in HDL-cholesterol.

Pharmacological inhibition to examine the role of DGAT1 in dietary lipid absorption in rodents and humans

Alterations in fat metabolism, in particular elevated plasma concentrations of free fatty acids and triglycerides (TG), have been implicated in the pathogenesis of Type 2 diabetes, obesity, and cardiovascular disease. Acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1), a member of the large family of membrane-bound O-acyltransferases, catalyzes the final step in triacylglycerol formation. In the intestine, DGAT1 is one of the acyltransferases responsible for the reesterficiation of dietary TG. Following a single dose of a selective pharmacological inhibitor of DGAT1, PF-04620110, a dose-dependent inhibition of TG and vitamin A absorption postprandially was demonstrated in rodents and human subjects. In C57/BL6J mice, acute DGAT1 inhibition alters the temporal and spatial pattern of dietary lipid absorption. To understand the impact of DGAT1 inhibition on enterocyte lipid metabolism, lipomic profiling was performed in rat intestine and plasma as well as human plasma. DGAT1 inhibition causes an enrichment of polyunsaturated fatty acids within the TG class of lipids. This pharmacological intervention gives us insight as to the role of DGAT1 in human dietary lipid absorption.

Evidence for tuning adipocytes ICER levels for obesity care

Abnormal adipokine production, along with defective uptake and metabolism of glucose within adipocytes, contributes to insulin resistance and altered glucose homeostasis. Recent research has highlighted one of the mechanisms that accounts for impaired production of adiponectin (ADIPOQ) and adipocyte glucose uptake in obesity. In adipocytes of human obese subjects and mice fed with a high fat diet, the level of the inducible cAMP early repressor (ICER) is diminished. Reduction of ICER elevates the cAMP response element binding protein (CREB) activity, which in turn increases the repressor activating transcription factor 3. In fine, the cascade triggers reduction in the ADIPOQ and GLUT4 levels, which ultimately hampers insulin-mediated glucose uptake. The c-Jun N-terminal kinase (JNK) interacting-protein 1, also called islet brain 1 (IB1), is a target of CREB/ICER that promotes JNK-mediated insulin resistance in adipocytes. A rise in IB1 and c-Jun levels accompanies the drop of ICER in white adipose tissues of obese mice when compared with mice fed with a chow diet. Other than the expression of ADIPOQ and glucose transport, decline in ICER expression might impact insulin signaling. Impairment of ICER is a critical issue that will need major consideration in future therapeutic purposes.

Lipid profile and nutritional intake in children and adolescents with Type 1 diabetes improve after a structured dietician training to a Mediterranean-style diet

AIM

To evaluate if nutritional intakes and lipid profile fulfill international guidelines and recommendations before and after a structured dietician training to a Mediterranean- style diet in an Italian pediatric population with Type 1 diabetes.

METHODS

A 6-month prospective cohort study. Baseline and after-intervention nutritional intakes, lipid profile, glycated hemoglobin (HbA(1c)), and clinical parameters of 96 children and adolescents with Type 1 diabetes were assessed. A comparative computerized system which was approved and validated by the Italian Diabetologist Association was used to define the amounts of nutrients.

RESULTS

At baseline mean daily dietary intakes of carbohydrates, proteins, and lipids were respectively (mean ± SEM) 51.8 ± 0.5, 15.9 ± 0.2, 33.8 ± 0.6%, with a contribution of cholesterol of 248.7 ± 12.5 mg/day. Fiber assumption was 18.0 ± 0.4 g/day. The 64.5% and 29.1% (p<0.0001) of subjects had at least one lipid parameter higher than 75(th) and 95(th) percentiles, respectively, of selected cut points (American Diabetes Association guidelines for total and LDL-cholesterol and American Academy of Pediatrics standards for HDL-cholesterol and triglycerides). Six months after the dietician intervention, dietary lipids and cholesterol decreased (p<0.0001) while fibers (p<0.0001) increased. LDL-cholesterol, non-HDL-cholesterol, and total cholesterol:HDL-cholesterol ratios significantly decreased (p<0.001) with a reduction of rate of subjects with at least one pathological lipid parameter (p<0.01) independently by weight and glucose control.

CONCLUSIONS

Italian pediatric subjects with Type 1 diabetes present a balanced diet with exception of lipids intake and a suboptimal lipid profile. A structured dietician training to a Mediterranean-style diet improves the quality of nutrient intakes being followed by a reduction of LDL-cholesterol, non- HDL-cholesterol, and total cholesterol:HDL-cholesterol ratios.

Atypical antipsychotics rapidly and inappropriately switch peripheral fuel utilization to lipids, impairing metabolic flexibility in rodents

Patients taking atypical antipsychotics are frequented by serious metabolic (eg, hyperglycemia, obesity, and diabetes) and cardiac effects. Surprisingly, chronic treatment also appears to lower free fatty acids (FFAs). This finding is paradoxical because insulin resistance is typically associated with elevated not lower FFAs. How atypical antipsychotics bring about these converse changes in plasma glucose and FFAs is unknown. Chronic treatment with olanzapine, a prototypical, side effect prone atypical antipsychotic, lowered FFA in Sprague-Dawley rats. Olanzapine also lowered plasma FFA acutely, concomitantly impairing in vivo lipolysis and robustly elevating whole-body lipid oxidation. Increased lipid oxidation was evident from accelerated losses of triglycerides after food deprivation or lipid challenge, elevated FFA uptake into most peripheral tissues (∼2-fold) except heart, rises in long-chain 3-hydroxylated acyl-carnitines observed in diabetes, and rapid suppression of the respiratory exchange ratio (RER) during the dark cycle. Normal rises in RER following refeeding, a sign of metabolic flexibility, were severely blunted by olanzapine. Increased lipid oxidation in muscle could be explained by ∼50% lower concentrations of the negative cytoplasmic regulator of carnitine palmitoyltransferase I, malonyl-CoA. This was associated with loss of anapleurotic metabolites and citric acid cycle precursors of malonyl-CoA synthesis rather than adenosine monophosphate-activated kinase activation or direct ACC1/2 inhibition. The ability of antipsychotics to lower dark cycle RER in mice corresponded to their propensities to cause metabolic side effects. Our studies indicate that lipocentric mechanisms or altered intermediary metabolism could underlie the FFA lowering and hyperglycemia (Randle cycle) as well as some of the other side effects of atypical antipsychotics, thereby suggesting strategies for alleviating them.

Comparison of effect of resveratrol and vanadium on diabetes related dyslipidemia and hyperglycemia in streptozotocin induced diabetic rats

PURPOSE

Resveratrol a natural polyphenolicstilbene derivative has wide variety of biological activities. There is also a large body of evidence demonstrating positive effect of resveratrol in treatment of various metabolic complications including metabolic syndrome, obesity, diabetes and dyslipidemia in adults. The purpose of this study was to investigate anti-hyperglycemic and anti-dyslipidemic effects of resveratrol.

METHODS

We used 40 diabetic streptozotocin Wistar rats. Rats were randomly divided into 5 treatment groups (n=8 in each) including normal control, normal treated with resveratrol, diabetic control, diabetic treated with vanadium , diabetic treated with resveratrol . Resveratrol (25 mg/kgbw) and vanadate (0.2 mg/kgbw) was orally gavaged for 40 days and blood samples were directly collected from heart.

RESULTS

Diabetic rats treated with resveratrol in comparison to control diabetic rats demonstrated a significant (p = 0.001) decline in serum glucose concentration, and high plasma concentrations of total cholesterol and LDL-c were reduced (p = 0.031, p = 0.004 respectively). Furthermore, body weight loss trend that observed in diabetic rats alleviated by resveratrol and vanadate. However triglyceride, VLDL-c and HDL-c levels did not changed significantly.

CONCLUSION

In conclusion Resveratrol ameliorated dyslipidemia and hyperglycemia in diabetic rats. However further investigations in peculiar human studies are required.

Age-related autocrine diabetogenic effects of transgenic resistin in spontaneously hypertensive rats: gene expression profile analysis

Increased circulating levels of resistin have been proposed as a possible link between obesity and insulin resistance; however, many of the potential metabolic effects of resistin remain to be investigated, including systemic versus local resistin action. We investigated potential autocrine effects of resistin on lipid and glucose metabolism in 2- and 16-mo-old transgenic spontaneously hypertensive rats (SHR) expressing a nonsecreted form of mouse resistin under control of the aP2 promoter. To search for possible molecular mechanisms, we compared gene expression profiles in adipose tissue in 6-wk-old transgenic SHR versus control rats, before development of insulin resistance, by digital transcriptional profiling using high-throughput sequencing. Both young and old transgenic rats showed moderate expression of the resistin transgene in adipose tissue but had serum resistin levels similar to control SHR and undetectable levels of transgenic resistin in the circulation. Young transgenic rats exhibited mild glucose intolerance. In contrast, older transgenic rats displayed marked glucose intolerance in association with near total resistance of adipose tissue to insulin-stimulated glucose incorporation into lipids (6 ± 2 vs. 77 ± 19 nmol glucose·g(-1)·2 h(-1), P < 0.00001). Ingenuity Pathway Analysis of differentially expressed genes revealed calcium signaling, Nuclear factor-erythroid 2-related factor-2 (NRF2)-mediated oxidative stress response, and actin cytoskeletal signaling canonical pathways as those most significantly affected. Analysis using DAVID software revealed oxidative phosphorylation, glutathione metabolism, pyruvate metabolism, and peroxisome proliferator-activated receptor (PPAR) signaling as top Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. These results suggest that with increasing age autocrine effects of resistin in fat tissue may predispose to diabetes in part by impairing insulin action in adipose tissue.

Human glomerular endothelium: interplay among glucose, free fatty acids, angiotensin II, and oxidative stress

Glomerular endothelial cells (GEC) are strategically situated within the capillary loop and adjacent to the glomerular mesangium. GEC serve as targets of metabolic, biochemical, and hemodynamic signals that regulate the glomerular microcirculation. Unequivocally, hyperglycemia, hypertension, and the local renin-angiotensin system partake in the initiation and progression of diabetic nephropathy (DN). Whether free fatty acids (FFA) and reactive oxygen species (ROS) that have been associated with the endothelial dysfunction of diabetic macrovascular disease also contribute to DN is not known. Since endothelial cells from different organs and from different species may display different phenotypes, we employed human GEC to investigate the effect of high glucose (22.5 mmol/l), FFA (800 micromol/l), and angiotensin II (ANG II; 10(-7) mol/l) on the genesis of ROS and their effects on endothelial nitric oxide synthase (eNOS), cyclooxygenase-2 (COX-2), and the synthesis of prostaglandins (PGs). We demonstrated that high glucose but not high FFA increased the expression of a dysfunctional eNOS as well as increased ROS from NADPH oxidase (100%) and likely from uncoupled eNOS. ANG II also induced ROS from NADPH oxidase. High glucose and ANG II upregulated (100%) COX-2 via ROS and significantly increased the synthesis of prostacyclin (PGI(2)) by 300%. In contrast, FFA did not upregulate COX-2 but increased PGI(2) (500%). These novel studies are the first in human GEC that characterize the differential role of FFA, hyperglycemia, and ANG II on the genesis of ROS, COX-2, and PGs and their interplay in the early stages of hyperglcyemia.

Statins, ACE inhibitors and ARBs in cardiovascular disease

Atherosclerotic cardiovascular disease (CVD) is the main cause of death in developed and developing countries. It is well accepted that several diseases - including hypertension, dyslipidemia and diabetes mellitus - increase CVD. More recently also chronic inflammatory diseases, such as rheumatoid arthritis, have been shown to accelerate CVD. This association further supports a responsible role for inflammatory processes in all stages of CVD pathophysiology. Clinically, CVD ranges through different acute and chronic syndromes with ischemic symptoms in distal tissues, including heart, cerebral region or peripheral arteries. Several treatments for reducing CVD are under investigation. In this review we focus on statins, angiotensin-converting-enzyme (ACE) inhibitors, and angiotensin-II receptor blockers (ARBs), updating therapeutic evidence from the last clinical trials with particular relevance to diabetic patients.

Modulating effects of chlorogenic acid on lipids and glucose metabolism and expression of hepatic peroxisome proliferator-activated receptor-alpha in golden hamsters fed on high fat diet

OBJECTIVE

To examine the effects of chlorogenic acid (CGA) on lipid and glucose metabolism under a high dietary fat burden and to explore the possible role of peroxisome proliferator-activated receptor-alpha (PPAR-alpha) in these effects.

METHODS

Twenty male golden hamsters were randomly divided into CGA treatment group (n=10, given peritoneal injection of CGA solution prepared with PBS, 80 mg CGA/kg body weight daily), and control group (n=10, given PBS i.p. at the average volume of the treatment group). Animals in both groups were given 15% high fat diet. Eight weeks after treatment with CGA, the level of biochemical parameters in fasting serum and tissues and the expression of hepatic mRNA and protein PPAR-alpha were determined.

RESULTS

Eight weeks after treatment with CGA, the levels of fasting serum triglyceride (TG), free fatty acid (FFA), total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), glucose (FSG), and insulin (FSI) were significantly lower in the GGA treatment group than in the control group. CGA also led to higher activity of hepatic lipase (HL), lower contents of TG and FFA in liver, and lower activity of lipoprotein lipase (LPL) in skeletal muscle. Furthermore, CGA significantly elevated significantly elevated the expression level of mRNA and protein expression in hepatic PPAR-alpha.

CONCLUSION

CGA can modify lipids and glucose metabolism, which may be attributed to PPAR-alpha facilitated lipid clearance in liver and improved insulin sensitivity.

The effect of antidiabetic drugs on genes regulating lipid metabolism

PURPOSE OF REVIEW

Hyperglycaemia and dyslipidaemia are closely linked, yet, there has been difficulty in demonstrating that lowering blood sugar reduces cardiovascular events. The pathways linking abnormalities in fatty acid metabolism, insulin resistance and diabetes with abnormalities in cholesterol metabolism are being rapidly unravelled with new understandings of the effect of antidiabetic drugs on lipoprotein metabolism. The purpose of this review is to explore the recent literature.

RECENT FINDINGS

Postprandial lipoproteins are now firmly established as a postprandial risk factor. Both insulin resistance and diabetes are associated with abnormalities in chylomicron production, and clearance and regulatory genes have been identified. Metformin, the most commonly used drug in type 2 diabetes, has multiple actions affecting numerous genes. The peroxisome proliferator-activated receptor-gamma regulation of insulin sensitivity and the important effects on lipoproteins are described. The entero-insulin axis and glucagon-like peptide-1 agonists, together with inhibitors of dipeptidyl peptidase 4 may have lipoprotein implications, but the evidence at present is sparse even though glucagon-like peptide-1 is found in high concentrations in the lymph.

SUMMARY

Although antidiabetic drugs affect lipid metabolism, there is little evidence to suggest that these drugs can prevent atherosclerosis in diabetes and some may promote atherosclerosis through their adverse effect on lipoproteins.

Body composition, insulin sensitivity, and cardiovascular disease profile in healthy Europeans

OBJECTIVE

To assess whether insulin sensitivity can explain the associations of leg-fat mass (LFM) and trunk-fat mass (TFM) with the cardiovascular disease (CVD) risk profile in healthy European men and women.

METHODS AND PROCEDURES

We studied 142 healthy men and women of a multicenter European study on insulin sensitivity, aged 30-60 years, from the centres in Hoorn, the Netherlands and Rome, Italy. Whole-body dual-energy X-ray absorptiometry (DXA) was used to determine fat and lean soft tissue mass in the trunk and legs. Fasting glucose, insulin, and lipid levels were measured. Insulin sensitivity (M/I-ratio) was measured during a euglycemic-hyperinsulinemic clamp. Associations between fat distribution and CVD risk factors were studied with linear regression analyses with adjustment for other body compartments, and subsequent adjustment for insulin sensitivity.

RESULTS

In men, larger LFM was significantly and independently associated with lower triglyceride levels (TGs) and higher high-density lipoprotein (HDL) cholesterol (P < 0.10) and tended to be associated also with lower low-density lipoprotein (LDL) cholesterol, and lower fasting insulin levels. In women, larger LFM was associated with favorable values of all CVD risk factors, although the associations were not statistically significant. In both sexes, larger TFM was independently and significantly associated with unfavorable values of most CVD risk factors, and most associations did not markedly change after adjustment for insulin sensitivity.

DISCUSSION

In a relatively young and healthy European population, larger LFM is associated with a lower and TFM with a higher cardiovascular and metabolic risk, which can not be explained by insulin sensitivity.

Insulin resistance: a proinflammatory state mediated by lipid-induced signaling dysfunction and involved in atherosclerotic plaque instability

The dysregulation of the insulin-glucose axis represents the crucial event in insulin resistance syndrome. Insulin resistance increases atherogenesis and atherosclerotic plaque instability by inducing proinflammatory activities on vascular and immune cells. This condition characterizes several diseases, such as type 2 diabetes, impaired glucose tolerance (IGT), impaired fasting glucose (IFG), obesity, hypertension, dyslipidemia, and other endocrinopathies, but also cancer. Recent studies suggest that the pathophysiology of insulin resistance is closely related to interferences with insulin-mediated intracellular signaling on skeletal muscle cells, hepatocytes, and adipocytes. Strong evidence supports the role of free fatty acids (FFAs) in promoting insulin resistance. The FFA-induced activation of protein kinase C (PKC) delta, inhibitor kappaB kinase (IKK), or c-Jun N-terminal kinase (JNK) modulates insulin-triggered intracellular pathway (classically known as PI3-K-dependent). Therefore, reduction of FFA levels represents a selective target for modulating insulin resistance.

Scanning electron microscopic analysis of intramyocellular lipid droplets in an animal model of type 2 diabetes

OBJECTIVE

To evaluate the accumulation pattern of intramyocellular lipids (IMCLs) in striated muscle during the development and progression of diabetes, using a novel scanning electron microscopic method.

METHODS AND PROCEDURES

Hyperglycemia was induced by feeding diabetes-prone (DP) Psammomys obesus a high-energy (HE) diet. Lipid accumulation within gastrocnemius muscle fibers was assessed in formalin-fixed muscle samples during the development of hyperglycemia using high resolution imaging in a scanning electron microscope. We evaluated the temporal relationship between changes in IMCL quantity and morphology and the altered glucose metabolism and assessed the effect of reversal of hyperglycemia on IMCL level and morphology. Diabetes-resistant (DR) P. obesus served as controls.

RESULTS

Lipid accumulation in the muscle fibers of DP animals was increased with the development of hyperglycemia. This was characterized by increased lipid density as well as by an abundance of large lipid droplets. Reversal of the phenotype resulted in the disappearance of large lipid droplets. The IMCL level and the distribution of lipid droplet size were similar in muscles of both the normoglycemic DR and DP animals, with an abundance of small lipid droplets. This profile was changed following a HE diet only in the DP animals.

DISCUSSION

Lipid accumulation in the muscle of P. obesus during the development of hyperglycemia is characterized by increased quantity and accumulation of large lipid droplets. These changes were reversible upon normalization of blood glucose. The evaluated methodology is a useful tool for the study of the dynamics of lipid accumulation in different metabolic conditions.

Targets for intervention in dyslipidemia in diabetes

Treatment for dyslipidemia in diabetes reduces cardiovascular events. Diabetes is associated with major abnormalities in fatty acid metabolism. The resulting disturbance results in an abnormal lipoprotein cascade from the large chylomicron through to the small HDL particle. This suggests that drugs that alter formation of the chylomicron particle might have a very important role in diabetic dyslipidemia. Achieving normal glycemia will reverse the abnormalities in fatty acid metabolism, but this is difficult, particularly as the disease progresses. Genes that regulate cholesterol absorption and excretion have been described (Niemann Pick C1-like 1 [NPC1-L1] and ATP binding cassette proteins [ABC] G5 and G8). An effective NPC1-L1 inhibitor (ezetimibe) improves the reduction in cholesterol caused by statins. Agonists of ABCG5 and G8 may become important in the treatment of dyslipidemia. Microsomal triglyceride transfer protein (MTP) is responsible for the assembly of the chylomicron and VLDL particles. New MTP inhibitors, acting only on the intestine, are exciting possible treatments. The advisability of sitosterol-enriched foods to lower cholesterol may have to be reassessed for patients with diabetes, since these products may lead to an increase in chylomicron sitosterol in diabetic patients. More successful treatment of diabetic dyslipidemia is essential if we are to reduce the burden of cardiovascular disease so commonly found in diabetes.

The different effect of pioglitazone as compared to insulin on expression of hepatic and intestinal genes regulating post-prandial lipoproteins in diabetes

This study investigates lipoprotein composition in diabetes before and after treatment with insulin or pioglitazone and its relationship to gene expression of five genes found in liver and intestine which are involved in cholesterol homeostasis. Thirty zucker diabetic fatty fa/fa and 10 lean rats were examined. mRNA for 3-hydroxy3-methylglutaryl coenzyme A reductase (HMGCoA), microsomal triglyceride transfer protein (MTTP), Niemann Pick C1-like 1 (NPC1L1) and ATP binding cassette transporters (ABC) G5 and G8 was determined using real-time, reverse transcriptase (RT-PCR). Cholesterol, triglyceride, apo B48 and apo B100 were elevated in chylomicrons and very low density lipoproteins (VLDL) of untreated diabetic animals (p<0.02). For similar blood glucose pioglitazone was more effective than insulin in normalising the lipoproteins. In diabetic animals, HMGCoA reductase, MTTP and NPC1L1 mRNA were significantly elevated (p<0.02) and ABCG5 and ABCG8 were significantly reduced (p<0.02) in the liver. Pioglitazone significantly reduced hepatic MTTP and NPC1L1 mRNA (p<0.0001) and significantly increased ABCG5 and G8 mRNA (p<0.0001) as compared to insulin. In conclusion diabetes was associated with major changes in mRNA levels of proteins involved in the regulation of post-prandial lipoproteins. Pioglitazone and insulin have different effects on post-prandial lipoprotein metabolism in part due their effect on genes regulating cholesterol synthesis and lipoprotein assembly.

Novel double-congenic strain reveals effects of spontaneously hypertensive rat chromosome 2 on specific lipoprotein subfractions and adiposity

We have developed a new, double-congenic rat strain BN- Lx.SHR2, which carries two distinct segments of chromosome 2 introgressed from the spontaneously hypertensive rat strain (SHR) into the genetic background of congenic strain BN- Lx, which was previously shown to express variety of metabolic syndrome features. In 16-wk-old male rats of BN- Lx and BN- Lx.SHR2 strains, we compared their glucose tolerance and triacylglycerol and cholesterol concentrations in 20 lipoprotein subfractions and the lipoprotein particle sizes under conditions of feeding standard and high-sucrose diets. Introgression of two distinct SHR-derived chromosome 2 segments resulted in decreased adiposity together with aggravation of glucose intolerance in the double-congenic strain. The BN- Lx.SHR2 rats were more sensitive to sucrose-induced rise in triacylglycerolemia. Although the total cholesterol concentrations of the two strains were comparable after the standard diet and even lower in BN- Lx.SHR2 after sucrose feeding, detailed analysis revealed that under both dietary conditions, the double-congenic strain had significantly higher cholesterol concentrations in low-density lipoprotein fractions and lower high-density lipoprotein fractions. We established a new inbred model showing dyslipidemia and mild glucose intolerance without obesity, attributable to specific genomic regions. For the first time, the chromosome 2 segments of SHR origin are shown to influence other than blood pressure-related features of metabolic syndrome or to be involved in relevant nutrigenomic interactions.

Hypercytolipidemia-induced cellular lipoapoptosis: Cytostructural and endometabolic basis of progressive organo-involution following expression of diabetes (db/db) and obese (ob/ob) mutation syndromes

Onset expression of Type 2 (NIDDM) diabetes and obesity metabolic syndromes (DOS) are characterized by premature, progressive cytoatrophy and organo-involution induced by dysregulated cellular gluco- and lipo-metabolic cascades. The consequential systemic, interstitial and intracellular hyperlipidemia disrupts normal cytointegrity and metabolic responsivity to the established hypercaloric pericellular environments. The sequential cytostructural, metabolic and endocrine disturbances associated with the development of progressive DOS-associated hypercytolipidemia compromises cellular metabolic response cascades and promotes cytochemical disturbances which culminate with nuclear lipoapoptosis and cytoatrophy. The dramatic alterations in interstitial glucose and lipid (free fatty acids/triglycerides) concentrations are recognized to influence interstitial and cytoplasmic microchemical environments, which markedly alter cellular nutrient diffusion and active trans-membrane flux rates. The progressive exacerbation of interstitial and cytoplasmic lipid imbibition has been demonstrated to be associated with DNA fragmentation by lipo-infiltration into the chromatin matrix, inducing structural disruption and physical dissolution, indexed as nuclear lipoapoptosis. Therapeutic reduction of the severity of hypercytolipidemia-induced structural and cytochemical compromise promotes the restoration of homeostatic metabolic support for normalized cytostructural indices and supportive cellular gluco- and lipo-metabolic cascades. The re-establishment of a homeostatic interstitial microenvironment moderates the severity of cytolipidemic compromise within affected cell types, reduces nuclear lipo-infiltration and DNA lipo-dissolution, resulting in the preservation of cytostructural integrity. Through the therapeutic restoration of extra- and intra-cellular microchemical environments in genetically dysregulated metabolic syndrome models, the coincident cytochemical, endocrine and metabolic disturbances associated with progressive hypercytolipidemia, resulting from the expressed systemic hypercaloric environmental and hepato-pancreatic endometabolic disturbances which characterize Type 2 (NIDDM) diabetes-obesity and metabolic (X) syndromes, may be ameliorated.

Increased heat generation from atherosclerotic plaques in patients with type 2 diabetes: an increased local inflammatory activation

OBJECTIVE

Patients with coronary artery disease (CAD) and diabetes show increased inflammatory activation. Thermography detects local inflammatory involvement as heat generation. The aim of this study was to investigate whether patients with CAD and diabetes have increased local heat generation compared with nondiabetic patients.

RESEARCH DESIGN AND METHODS

We enrolled patients undergoing percutaneous coronary interventions: 45 diabetic patients and 63 nondiabetic patients, serving as the control group, matched for age, type of clinical syndrome, statin and aspirin intake, and angiographic stenosis (%). Coronary thermography was performed, and temperature difference (DeltaT) between the atherosclerotic plaque and the proximal vessel wall was measured.

RESULTS

Patients with diabetes had increased temperature difference compared with nondiabetic patients (DeltaT: 0.17 +/- 0.18 degrees C vs. 0.09 +/- 0.02 degrees C, P = 0.01). Twenty-one diabetic and 22 nondiabetic patients suffered from acute coronary syndromes (ACSs) (P = 0.22). Patients with diabetes and ACSs had increased temperature difference compared with nondiabetic patients with ACSs (DeltaT: 0.29 +/- 0.31 degrees C vs. 0.15 +/- 0.21 degrees C, P = 0.02), which is the same as patients with diabetes and chronic stable angina (DeltaT: 0.09 +/- 0.08 degrees C vs. 0.05 +/- 0.04 degrees C, P = 0.006). Twenty-three diabetic and 30 nondiabetic patients were under therapy with statins (P = 0.72). Patients with diabetes under statins had lower temperature difference compared with untreated patients (DeltaT: 0.11 +/- 0.12 degrees C vs. 0.22 +/- 0.21 degrees C, P = 0.02), which is the same as nondiabetic patients under statins (DeltaT: 0.05 +/- 0.04 degrees C vs. 0.13 +/- 0.18 degrees C, P = 0.01).

CONCLUSIONS

Patients with diabetes have increased temperature difference compared with nondiabetic patients. Patients with diabetes under statins showed decreased temperature difference compared with untreated patients, suggesting that statins have a favorable effect in patients with diabetes and CAD.

Metabolic syndrome in relationship to type 2 diabetes and atherosclerosis

Metabolic syndrome affects approximately one quarter of population in developed countries. Its presence is a major risk for development of both type 2 diabetes (T2DM) and atherosclerosis. The prevalence of cardiovascular disease is 2-3 times higher in individuals with metabolic syndrome than in age-matched controls. Most important components of metabolic syndrome are insulin resistance with or without glucose intolerance, abdominal obesity, atherogenic dyslipidaemia, hypertension, prothrombotic state and proinflammatory state. Early identification of subjects with metabolic syndrome is very important, since they represent a target group for multiple lifestyle and pharmacological interventions. Lifestyle interventions, antiobesity drugs and drugs increasing insulin sensitivity prevented development of T2DM in subjects with impaired glucose tolerance in randomized trials. Treatment of atherogenic dyslipidaemia to the therapeutic goals defined for diabetic patients seems reasonable and both statins and fibrates could be used based on evidence from clinical trials. Treatment of hypertension should also aim for target levels similar to those in diabetic patients. Using drugs affecting renin-angiotensin II axis, as first choice seems reasonable based on evidence from clinical trials showing the ability of these drugs to prevent T2DM and decrease albuminuria.

Can the atherosclerosis prevention targets be achieved in type 2 diabetes?

Type 2 diabetes mellitus is beside hyperglycemia frequently accompanied by dyslipidemia, arterial hypertension, obesity and other atherosclerosis risks. The article summarizes current status demonstrating that we are far from recommended targets, especially with diabetes, blood pressure and lipid controls. More aggressive drug treatment together with life style changes will be necessary to reach our goals in Type 2 diabetic patients.

Correction of insulin resistance and the metabolic syndrome

Insulin resistance is a common phenomenon of the metabolic syndrome, which is clinically characterized by a clustering of various cardiovascular risk factors in a single individual and a higher prevalence of respective complications, such as coronary heart disease and stroke. At the cellular level, insulin resistance is defined as a reduced insulin action, which can affect not only glucose uptake, but also gene regulation. Elucidation of novel signaling networks within the cell which are mediating and affecting insulin action will reveal many new genes and drug targets that are potentially of clinical relevance in the future. In this chapter, we propose that the metabolic syndrome might be a clinical consequence of altered gene regulation. This is illuminated in the context of transcription factors, e.g., sterol regulatory element binding proteins (SREBPs), coupling signals from nutrients, metabolites, and hormones at the gene regulatory level with pathobiochemical features of increased lipid accumulation in lean nonadipose tissues. The phenomenon of ectopic lipid accumulation (lipotoxicity) appears to be a novel link between insulin resistance, obesity, and possibly other features of the metabolic syndrome. Therefore, the investigation of specific gene regulatory networks and their alterations might be a clue to understanding the development and clustering of different cardiovascular risk factors in different individuals. As cellular sensors transcription factors--as common denominators of gene regulatory networks--might thereby also determine the susceptibility of individuals to cardiovascular risk factors and their complications.

Diabetes: insulin resistance and derangements in lipid metabolism. Cure through intervention in fat transport and storage

We present multiple findings on derangements in lipid metabolism in type 2 diabetes. The increase in the intracellular deposition of triglycerides (TG) in muscles, liver and pancreas in subjects prone to diabetes is well documented and demonstrated to attenuate glucose metabolism by interfering with insulin signaling and insulin secretion. The obesity often associated with type 2 diabetes is mainly central, resulting in the overload of abdominal adipocytes with TG and reducing fat depot capacity to protect other tissues from utilizing a large proportion of dietary fat. In contrast to subcutaneous adipocytes, the central adipocytes exhibit a high rate of basal lipolysis and are highly sensitive to fat mobilizing hormones, but respond poorly to lipolysis restraining insulin. The enlarged visceral adipocytes are flooding the portal circulation with free fatty acids (FFA) at metabolically inappropriate time, when FFA should be oxidized, thus exposing nonadipose tissues to fat excess. This leads to ectopic TG accumulation in muscles, liver and pancreatic beta-cells, resulting in insulin resistance and beta-cell dysfunction. This situation, based on a large number of observations in humans and experimental animals, confirms that peripheral adipose tissue is closely regulated, performing a vital role of buffering fluxes of FFA in the circulation. The central adipose tissues tend to upset this balance by releasing large amounts of FFA. To reduce the excessive fat outflow from the abdominal depots and prevent the ectopic fat deposition it is important to decrease the volume of central fat stores or increase the peripheral fat stores. One possibility is to downregulate the activity of lipoprotein lipase, which is overexpressed in abdominal relatively to subcutaneous fat stores. This can be achieved by gastrointestinal bypass or gastroplasty, which decrease dietary fat absorption, or by direct means that include surgical removal of mesenteric fat. Indirect treatment consists of the compliant application of drastic lifestyle change comprising both diet and exercise and pharmacotherapy that reduces mesenteric fat mass and activity. The first step should be an attempt to effectively induce a lifestyle change. Next comes pharmacotherapy including acarbose, metformin, PPARgamma, or PPARgammaalpha agonists, statins and orlistat, estrogens in postmenopausal women or testosterone in men. Among surgical procedures, gastric bypass has been proven to produce beneficial results in advance of other surgical techniques, the evidence basis of which still needs strengthening.

Analysis of the contribution to type 2 diabetes susceptibility of sequence variation in the gene encoding stearoyl-CoA desaturase, a key regulator of lipid and carbohydrate metabolism

AIMS/HYPOTHESIS

Stearoyl-CoA desaturase (SCD) is emerging as a key regulator of lipid and carbohydrate metabolism. Scd-null mice display a beneficial metabolic phenotype characterised by resistance to obesity, diabetes and hyperlipidaemia. The human homologue, SCD, maps to a region of chromosome 10 linked to type 2 diabetes, and SCD activity correlates with insulin sensitivity. Given this strong positional and biological candidacy, the present study sought to establish whether sequence variation in SCD influences susceptibility to type 2 diabetes and related traits.

METHODS

The SCD gene was resequenced in 23 diabetic subjects. Six variants within coding and adjacent sequence, including a non-synonymous SNP in exon 5 (M224L), were selected for genotyping in a primary set of 608 diabetic subjects and 600 control subjects.

RESULTS

There was no association (at the allele, genotype or haplotype level) with type 2 diabetes, although genotype frequencies at the +14301 A>C SNP in the 3' untranslated region showed borderline association (p~0.06) when evidence for linkage was taken into account. However, replication studies (350 young-onset diabetic patients; 747 controls) failed to confirm any relationship with diabetes for this variant. No significant associations were seen for diabetes-related traits including BMI and waist-to-hip ratio.

CONCLUSIONS/INTERPRETATION

The present study, the first reported analysis of this gene, indicates that the SCD variants typed do not explain chromosome-10-encoded susceptibility to type 2 diabetes. Although this study provided no evidence that SCD sequence variation influences diabetes susceptibility or related traits, SCD remains a major target for pharmaceutical and/or environmental manipulation.

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.