Variants in GLIS3 and CRY2 are associated with type 2 diabetes and impaired fasting glucose in Chinese Hans

Background

Recent genome-wide association studies have identified a number of common variants associated with fasting glucose homeostasis and type 2 diabetes in populations of European origin. This is a replication study to examine whether such associations are also observed in Chinese Hans.

Methods

We genotyped nine variants in or near MADD, ADRA2A, CRY2, GLIS3, PROX1, FADS1, C2CD4B, IGF1 and IRS1 in a population-based cohort including 3,210 unrelated Chinese Hans from Beijing and Shanghai.

Results

We confirmed the associations of GLIS3-rs7034200 with fasting glucose (beta = 0.07 mmol/l, P = 0.03), beta cell function (HOMA-B) (beta = −3.03%, P = 0.009), and type 2 diabetes (OR [95%CI]  = 1.27 [1.09–1.49], P = 0.003) after adjustment for age, sex, region and BMI. The association for type 2 diabetes remained significant after adjusting for other diabetes related risk factors including family history of diabetes, lipid profile, medication information, hypertension and life style factors, while further adjustment for HOMA-B abolished the association. The A-allele of CRY2-rs11605924 was moderately associated with increased risk of combined IFG/type 2 diabetes (OR [95%CI]  = 1.15[1.01–1.30], P = 0.04). SNPs in or near MADD, ADRA2A, PROX1, FADS1, C2CD4B, IGF1, and IRS1 did not exhibit significant associations with type 2 diabetes or related glycemic traits (P≥0.10).

Conclusions

In conclusion, our results indicate the associations of GLIS3 locus with type 2 diabetes and impaired fasting glucose in Chinese Hans, partially mediated through impaired beta-cell function. In addition, we also found modest evidence for the association of CRY2-rs11605924 with combined IFG/type 2 diabetes.     

Mechanisms for abnormal postprandial glucose metabolism in type 2 diabetes

To assess mechanisms for postprandial hyperglycemia, we used a triple-isotope technique ([\3-(3)H]glucose and [(14)C]bicarbonate and oral [6,6-dideutero]glucose iv) and indirect calorimetry to compare components of glucose release and pathways for glucose disposal in 26 subjects with type 2 diabetes and 15 age-, weight-, and sex-matched normal volunteers after a standard meal. The results were as follows: 1) diabetic subjects had greater postprandial glucose release (P<0.001) because of both increased endogenous and meal-glucose release; 2) the greater endogenous glucose release (P<0.001) was due to increased gluconeogenesis (P<0.001) and glycogenolysis (P=0.01); 3) overall tissue glucose uptake, glycolysis, and storage were comparable in both groups (P>0.3); 4) glucose clearance (P<0.001) and oxidation (P=0.004) were reduced, whereas nonoxidative glycolysis was increased (P=0.04); and 5) net splanchnic glucose storage was reduced by approximately 45% (P=0.008) because of increased glycogen cycling (P=0.03). Thus in type 2 diabetes, postprandial hyperglycemia is primarily due to increased glucose release; hyperglycemia overcomes the effects of impaired insulin secretion and sensitivity on glucose transport, but intracellular defects persist so that pathways of glucose metabolism are abnormal and glucose is shunted away from normal sites of storage (e.g., liver and muscle) into other tissues.     

Postprandial metabolite profiles associated with type 2 diabetes clearly stratify individuals with impaired fasting glucose

Introduction

Fasting metabolite profiles have been shown to distinguish type 2 diabetes (T2D) patients from normal glucose tolerance (NGT) individuals.

Objectives

We investigated whether, besides fasting metabolite profiles, postprandial metabolite profiles associated with T2D can stratify individuals with impaired fasting glucose (IFG) by their similarities to T2D.

Methods

Three groups of individuals (age 45–65 years) without any history of IFG or T2D were selected from the Netherlands Epidemiology of Obesity study and stratified by baseline fasting glucose concentrations (NGT (n?=?176), IFG (n?=?186), T2D (n?=?171)). 163 metabolites were measured under fasting and postprandial states (150 min after a meal challenge). Metabolite profiles specific for a high risk of T2D were identified by LASSO regression for fasting and postprandial states. The selected profiles were utilised to stratify IFG group into high (T2D probability?≥?0.7) and low (T2D probability?≤?0.5) risk subgroups. The stratification performances were compared with clinically relevant metabolic traits.

Results

Two metabolite profiles specific for T2D (n_fasting = 12 metabolites, n_postprandial = 4 metabolites) were identified, with all four postprandial metabolites also being identified in the fasting state. Stratified by the postprandial profile, the high-risk subgroup of IFG individuals (n?=?72) showed similar glucose concentrations to the low-risk subgroup (n?=?57), yet a higher BMI (difference: 3.3 kg/m² (95% CI 1.7–5.0)) and postprandial insulin concentrations (21.5 mU/L (95% CI 1.8–41.2)).

Conclusion

Postprandial metabolites identified T2D patients as good as fasting metabolites and exhibited enhanced signals for IFG stratification, which offers a proof of concept that metabolomics research should not focus on the fasting state alone.

     

Postprandial low-density lipoproteins in type 2 diabetes are oxidized more extensively than fasting diabetes and control samples

This study examined the kinetics of low-density lipoprotein (LDL) oxidation in the fasting and postprandial states of diabetic and control subjects to determine if LDL oxidation may contribute to accelerated atherosclerosis in diabetes. We compared in vitro oxidation of LDL from 12 control and 13 Type 2 diabetic subjects in the fasting and postprandial states. The extent of oxidation was assessed by length of lag phase, formation of conjugated dienes (CD), lipid peroxides, thiobarbituric acid reactive substances (TBARS), and percentage reduction in free amine groups. Diabetic subjects were significantly older and heavier. Comparisons between control and diabetic subjects in the postprandial state showed that the lag phase was significantly shorter in diabetic subjects than controls (P = 0.005), TBARS were significantly higher (P = 0.006), and levels of CD were higher at 60, 65, and 70 min (P < 0.01). In the fasting state, however, these comparisons were not significant. In diabetic subjects, postprandial samples had a significantly shorter lag phase (P = 0.003), higher TBARS (P = 0.006), and higher levels of CD at 60, 65 (P < 0.001), and 70 min (P = 0.0013) compared to fasting samples. Elevated levels of serum triglycerides in diabetic subjects were negatively correlated to lag phase, in fasting (P = 0.06) and postprandial states (P = 0.002). We conclude that accelerated oxidation of LDL seen in postprandial states in diabetes may be a critical contributor to cardiovascular risks. Elevated levels of serum triglycerides may contribute to the rapid oxidation of LDL seen in diabetic subjects.     

Lipid-lowering therapy in people with type 2 diabetes

PURPOSE OF REVIEW: The risk of cardiovascular disease is markedly increased in people with type 2 diabetes. There is abundant epidemiological and clinical trial evidence that lipid abnormalities play a major role in the pathogenesis of atherosclerotic vascular disease in diabetes. Although the benefits of lipid-lowering therapy are well established in people without diabetes, the evidence in people with diabetes is not as well established. RECENT FINDINGS: Recent population studies of lipid-lowering therapy and cardiovascular disease outcomes that included people with diabetes and performed a separate subgroup analysis were reviewed. Lipid lowering with statins and fibrates is effective in improving cardiovascular disease outcomes in diabetes, and their effectiveness is similar to that in the non-diabetic population. This effect is well established in secondary prevention and is accumulating for primary prevention. SUMMARY: Individuals with diabetes require aggressive management of dyslipidaemia as part of an overall management strategy to reduce the risk of cardiovascular disease. Individuals with a previous cardiovascular disease event should be on lipid-lowering therapy, whereas in those who have not had a previous cardiovascular disease event, the decision to use lipid-lowering therapy should be based on lipid levels and the overall risk of a future event. The results of large studies that are currently in progress specifically in people with diabetes should resolve outstanding questions in relation to lipid-lowering therapy in diabetes.     

Association of glucokinase regulatory protein polymorphism with type 2 diabetes and fasting plasma glucose: a meta-analysis

Glucokinase regulatory protein (GCKR) which binds to glucokinase (GCK) in the nucleus and inhibits its activity in the presence of fructose-6-phosphate is critical for glucose metabolism. In the past few years, a number of case–control studies have been carried out to investigate the relationship between the GCKR polymorphism and type 2 diabetes (T2D) since it was first identified to be associated with fasting plasma glucose levels, insulin resistance through genome-wide association approach. After that, a number of studies reported that the rs780094 polymorphism in GCKR has been implicated in T2D risk. However, these studies have yielded contradictory results. To investigate this inconsistency, we performed a meta-analysis of 19 studies involving a total of 298,977 subjects for GCKR rs780094 to evaluate its effect on genetic susceptibility for T2D. In a combined analysis, the summary per-allele odds ratio for T2D of the rs780094 polymorphism was 1.11 (95 % CI: 1.07–1.14, P < 10^?5). Significant results were also observed using dominant (OR = 1.18, 95 % CI: 1.05–1.34, P < 10^?5) or recessive genetic model (OR = 1.20, 95 % CI: 1.12–1.28, P < 10^?5). Significant results were found in Asians and Caucasians when stratified by ethnicity. Besides, the polymorphism was found to be significantly associated with increased fasting plasma glucose level. There was strong evidence of heterogeneity, which largely disappeared after stratification by ethnicity. This meta-analysis suggests that the rs780094 polymorphism in GCKR is associated with elevated T2D risk, but these associations vary in different ethnic populations.     

Indomethacin does not affect endogenous glucose production in type 2 diabetes mellitus.

In healthy subjects, basal endogenous glucose production is partly regulated by paracrine intrahepatic factors. It is currently unknown whether paracrine intrahepatic factors also influence the increased basal endogenous glucose production in patients with type 2 diabetes mellitus. Administration of indomethacin to patients with type 2 diabetes mellitus stimulates endogenous glucose production and inhibits insulin secretion. Our aim was to evaluate whether this stimulatory effect on glucose production is solely attributable to inhibition of insulin secretion. In order to do this, we administered indomethacin to 5 patients with type 2 diabetes during continuous infusion of somatostatin to block endogenous insulin and glucagon secretion and infusion of basal concentrations of insulin and glucagon in a placebo-controlled study. Endogenous glucose production was measured 3 hours after the start of the somatostatin, insulin and glucagon infusion, for 4 hours after administration of placebo/indomethacin, by primed, continuous infusion of [6,6-(2)H(2)] glucose. At the time of administration of placebo or indomethacin, there were no significant differences in plasma glucose concentrations and endogenous glucose production rates between the two experiments (16.4 +/- 2.09 mmol/l vs. 16.6 +/- 1.34 mmol/l and 17.7 +/- 1.05 micromol/kg/min and 17.0 +/- 1.06 micromol/kg/min), control vs. indomethacin). Plasma glucose concentration did not change significantly in the four hours after indomethacin or placebo administration. Endogenous glucose production in both experiments was similar after both placebo and indomethacin. Mean plasma C-peptide concentrations were all below the detection limit of the assay, reflecting adequate suppression of endogenous insulin secretion by somatostatin. There were no differences in plasma concentrations of insulin (76 +/- 5 vs. 74 +/- 4 pmol/l) and glucagon (69 +/- 8 vs. 71 +/- 6 ng/l) between the studies with levels remaining unchanged in both experiments. Plasma concentrations of cortisol, epinephrine, and norepinephrine were similar in the two studies and did not change significantly. We conclude that indomethacin stimulates endogenous glucose production in patients with type 2 diabetes mellitus by inhibition of insulin secretion.     

Regulation of endogenous glucose production after a mixed meal in type 2 diabetes

The extent and time course of suppression of endogenous glucose production (EGP) in type 2 diabetes after a mixed meal have been determined using a new tracer methodology. Groups of age-, sex-, and weight-matched normal controls (n = 8) and diet-controlled type 2 diabetic subjects (n = 8) were studied after ingesting a standard mixed meal (550 kcal; 67% carbohydrate, 19% fat, 14% protein). There was an early insulin increment in both groups such that, by 20 min, plasma insulin levels were 266 +/- 54 and 190 +/- 53 pmol/l, respectively. EGP was similar basally [2.55 +/- 0.12 mg x kg(-1) x min(-1) in control subjects vs. 2.92 +/- 0.16 mg x kg(-1) x min(-1) in the patients (P = 0.09)]. After glucose ingestion, EGP declined rapidly in both groups to approximately 50% of basal within 30 min of the meal. Despite the initial rapid decrease, the EGP was significantly greater in the diabetic group at 60 min (1.75 +/- 0.12 vs. 1.05 +/- 0.14 mg x kg(-1) x min(-1); P < 0.01) and did not reach nadir until 210 min (0.96 +/- 0.17 mg x kg(-1) x min(-1)). Between 60 and 240 min, EGP was 47% higher in the diabetic group (0.89 +/- 0.09 vs. 1.31 +/- 0.13 mg x kg(-1) x min(-1), P < 0.02). These data quantitate the initial rapid suppression of EGP after a mixed meal in type 2 diabetes and the contribution of continuing excess glucose production to subsequent hyperglycemia.     

Effects of 16 genetic variants on fasting glucose and type 2 diabetes in South Asians: ADCY5 and GLIS3 variants may predispose to type 2 diabetes

BackgroundThe Meta-Analysis of Glucose and Insulin related traits Consortium (MAGIC) recently identified 16 loci robustly associated with fasting glucose, some of which were also associated with type 2 diabetes. The purpose of our study was to explore the role of these variants in South Asian populations of Punjabi ancestry, originating predominantly from the District of Mirpur, Pakistan.Conclusions/SignificanceAlthough only the SLC30A8 rs11558471 SNP was nominally associated with fasting glucose in our study, the finding that 12 out of 16 SNPs displayed a direction of effect consistent with European studies suggests that a number of these variants may contribute to fasting glucose variation in individuals of South Asian ancestry. We also provide evidence for the first time in South Asians that alleles of SNPs in GLIS3 and ADCY5 may confer risk of type 2 diabetes.     

Disrupted circadian rhythms of body temperature,heart rate and fasting blood glucose in prediabetes and type 2 diabetes mellitus

We report a progressive disruption of 24-h rhythms in fasting blood glucose (FBG), body temperature (BT) and heart rate (HR) associated with metabolic dysfunction and the development of prediabetes (PD) and type 2 diabetes mellitus (T2DM) in overweight middle-aged (40–69 years old) humans. Increasing BT and HR mean values and declining 24-h BT and HR amplitudes accompany adverse changes in metabolic state. Increased nocturnal BT and a phase delay of the 24-h BT rhythm, deviant 24-h HR profile and a phase advance of the 24-h HR and FBG rhythms are early signs of the PD metabolic state. In T2DM, the 24-h FBG rhythm is no longer detectable, and the 24-h amplitudes of BT and HR are greatly diminished. In addition, lepton and creatinine values were lowered in T2DM. Moreover, positive correlations between FBG and body mass index, BMI, and negative correlations between the 24-h amplitude of FBG and BMI indicate that overweight is an additional factor causing disruption of the circadian rhythms. Further studies on circadian disruption as a consequence of metabolic dysfunction are necessary. The quantitative analysis of changing circadian BT and HR rhythms may provide prognostic markers of T2DM and therapeutic targets for its prevention and correction.     

Changes in glucose transporter expression and nitric oxide production are associated with liver injury in diabetes

In diabetes mellitus (DM), both hyperglycaemia and hyperlipidaemia can initiate accumulation of fat in the liver, which might be further mediated by inducible nitric oxide synthase. We have studied changes in GLUT1, nitric oxide (NO^·) concentration and liver damage in two rat DM models. STZ model was induced by strepozotocin 50 mg/kg. HS model was induced by high‐fat diet and 30 mg/kg streptozotocin. GLUT1 expression was studied by means of real‐time RT‐PCR and immunohistochemistry. Production of NO^· was monitored by means of erythrocyte sedimentation rate spectroscopy of Fe‐DETC‐NO complex. Liver damage was assessed using histological activity index (HAI). NO^· concentration was increased in the liver of STZ rats, but it did not change in HS rats (control 36.8 ± 10.3; STZ 142.1 ± 31.1; HS 35.4 ± 9.8 ng/g). Liver HAI was higher in STZ group, 8.6 ± 0.17 versus HS 4.7 ± 0.31, p < 0.05. GLUT1 protein expression was elevated only in STZ group, 16 ± 3 cells/mm² versus Control 5 ± 2 cells/mm², p = 0.007. Hyperglycaemia sooner causes severe liver damage in rat models of DM, compared with hyperlipidaemia, and is associated with increased NO^· production. GLUT1 transporter expression might be involved in toxic effects of glucose in the liver. We have obtained novel data about association of GLUT1 expression and NO^· metabolism in the pathogenesis of liver injury in DM. Increased GLUT1 expression was observed together with overproduction of NO^· and pronounced liver injury in severely hyperglycaemic rats. On the contrary, moderately hyperglycaemic hyperlipidaemic rats developed only moderate liver steatosis and no increase in GLUT1 and NO^·. GLUT1 overexpression might be implicated in the toxic effects of glucose in the liver. Glycotoxicity is associated with oxidative stress and NO^· hyperproduction. GLUT1 and NO^· metabolism might become novel therapeutic targets in liver steatosis. Copyright © 2015 John Wiley & Sons, Ltd.     

Heparanase levels are elevated in the urine and plasma of type 2 diabetes patients and associate with blood glucose levels

Heparanase is an endoglycosidase that specifically cleaves heparan sulfate side chains of heparan sulfate proteoglycans. Utilizing an ELISA method capable of detection and quantification of heparanase, we examined heparanase levels in the plasma and urine of a cohort of 29 patients diagnosed with type 2 diabetes mellitus (T2DM), 14 T2DM patients who underwent kidney transplantation, and 47 healthy volunteers. We provide evidence that heparanase levels in the urine of T2DM patients are markedly elevated compared to healthy controls (1162 ± 181 vs. 156 ± 29.6 pg/ml for T2DM and healthy controls, respectively), increase that is statistically highly significant (P<0.0001). Notably, heparanase levels were appreciably decreased in the urine of T2DM patients who underwent kidney transplantation, albeit remained still higher than healthy individuals (P<0.0001). Increased heparanase levels were also found in the plasma of T2DM patients. Importantly, urine heparanase was associated with elevated blood glucose levels, implying that glucose mediates heparanase upregulation and secretion into the urine and blood. Utilizing an in vitro system, we show that insulin stimulates heparanase secretion by kidney 293 cells, and even higher secretion is observed when insulin is added to cells maintained under high glucose conditions. These results provide evidence for a significant involvement of heparanase in diabetic complications.     

Adipokine pattern in subjects with impaired fasting glucose and impaired glucose tolerance in comparison to normal glucose tolerance and diabetes

Aim

Altered adipokine serum concentrations early reflect impaired adipose tissue function in obese patients with type 2 diabetes (T2D). It is not entirely clear whether these adipokine alterations are already present in prediabetic states and so far there is no comprehensive adipokine panel available. Therefore, the aim of this study was to assess distinct adipokine profiles in patients with normal glucose tolerance (NGT), impaired fasting glucose (IFG), impaired glucose tolerance (IGT) or T2D.

Methods

Based on 75 g oral glucose tolerance tests, 124 individuals were divided into groups of IFG (n = 35), IGT (n = 45), or NGT (n = 43). Furthermore, 56 subjects with T2D were included. Serum concentrations of adiponectin, chemerin, fetuin-A, leptin, interleukin (IL)-6, retinol-binding protein 4 (RBP4), monocyte chemoattractant protein (MCP)-1, vaspin, progranulin, and soluble leptin receptor (sOBR) were measured by ELISAs.

Results

Chemerin, progranulin, fetuin-A, and RBP4, IL-6, adiponectin and leptin serum concentrations were differentially regulated among the four investigated groups but only circulating chemerin was significantly different in patients with IGT compared to those with IFG. Compared to T2D the IFG subjects had higher serum chemerin, progranulin, fetuin-A and RBP4 levels which was not detectable in the comparison of the T2D and IGT group.

Conclusion

Alterations in adipokine serum concentrations are already detectable in prediabetic states, mainly for chemerin, and may reflect adipose tissue dysfunction as an early pathogenetic event in T2D development. In addition, distinct adipokine serum patterns in individuals with IFG and IGT suggest a specific role of adipose tissue in the pathogenesis of these prediabetic states.     

Urine metabolites are associated with glomerular lesions in type 2 diabetes

Introduction

Little is known about the association of urine metabolites with structural lesions in persons with diabetes.

Objectives

We examined the relationship between 12 urine metabolites and kidney structure in American Indians with type 2 diabetes.

Methods

Data were from a 6-year clinical trial that assessed renoprotective efficacy of losartan, and included a kidney biopsy at the end of the treatment period. Metabolites were measured in urine samples collected within a median of 6.5 months before the research biopsy. Associations of the creatinine-adjusted urine metabolites with kidney structural variables were examined by Pearson’s correlations and multivariable linear regression after adjustment for age, sex, diabetes duration, hemoglobin A_1c, mean arterial pressure, glomerular filtration rate (iothalamate), and losartan treatment.

Results

Participants (n?=?62, mean age 45?±?10 years) had mean?±?standard deviation glomerular filtration rate of 137?±?50 ml/min and median (interquartile range) urine albumin:creatinine ratio of 34 (14–85) mg/g near the time of the biopsy. Urine aconitic and glycolic acids correlated positively with glomerular filtration surface density (partial r?=?0.29, P?=?0.030 and r?=?0.50, P?<?0.001) and total filtration surface per glomerulus (partial r?=?0.32, P?=?0.019 and r?=?0.43, P?=?0.001). 2-ethyl 3-OH propionate correlated positively with the percentage of fenestrated endothelium (partial r?=?0.32, P?=?0.019). Citric acid correlated negatively with mesangial fractional volume (partial r=-0.36, P?=?0.007), and homovanillic acid correlated negatively with podocyte foot process width (partial r=-0.31, P?=?0.022).

Conclusions

Alterations of urine metabolites may associate with early glomerular lesions in diabetic kidney disease.

     

Platelet biomarkers identifying mild cognitive impairment in type 2 diabetes patients

Type 2 diabetes mellitus (T2DM) is an independent risk factor of Alzheimer''s disease (AD). Therefore, identifying periphery biomarkers correlated with mild cognitive impairment (MCI) is of importance for early diagnosis of AD. Here, we performed platelet proteomics in T2DM patients with MCI (T2DM‐MCI) and without MCI (T2DM‐nMCI). Pearson analysis of the omics data with MMSE (mini‐mental state examination), Aβ1‐42/Aβ1‐40 (β‐amyloid), and rGSK‐3β(T/S9) (total to Serine‐9‐phosphorylated glycogen synthase kinase‐3β) revealed that mitophagy/autophagy‐, insulin signaling‐, and glycolysis/gluconeogenesis pathways‐related proteins were most significantly involved. Among them, only the increase of optineurin, an autophagy‐related protein, was simultaneously correlated with the reduced MMSE score, and the increased Aβ1‐42/Aβ1‐40 and rGSK‐3β(T/S9), and the optineurin alone could discriminate T2DM‐MCI from T2DM‐nMCI. Combination of the elevated platelet optineurin and rGSK‐3β(T/S9) enhanced the MCI‐discriminating efficiency with AUC of 0.927, specificity of 86.7%, sensitivity of 85.3%, and accuracy of 0.859, which is promising for predicting cognitive decline in T2DM patients.