Effect of short-term ACE inhibitor treatment on peripheral insulin sensitivity in obese insulin-resistant subjects

Aims/hypothesis This study was designed to investigate the effect of short-term ACE inhibitor treatment on insulin sensitivity and to examine possible underlying metabolic and haemodynamic effects in obese insulin-resistant subjects.Methods A randomised, double-blind placebo-controlled trial was performed in 18 obese insulin-resistant men (age, 53 ± 2 years; BMI, 32.6 ± 0.8 kg/m²; homeostasis model assessment of insulin resistance, 5.6 ± 0.5; systolic blood pressure [SBP], 140.8 ± 3.2; diastolic blood pressure [DBP], 88.8 ± 1.6 mmHg), who were free of any medication. The aim was to examine the effects of 2 weeks of ACE inhibitor treatment (ramipril, 5 mg/day) on insulin sensitivity, forearm blood flow, substrate fluxes across the forearm, whole-body substrate oxidation and intramuscular triacylglycerol (IMTG) content.Results Ramipril treatment decreased ACE activity compared with placebo (−22.0 ± 1.7 vs 0.2 ± 1.1 U/l, respectively, p < 0.001), resulting in a significantly reduced blood pressure (SBP, −10.8 ± 2.1 vs −2.7 ± 2.0 mmHg, respectively, p = 0.01; DBP, −10.1 ± 1.3 vs −4.2 ± 2.1 mmHg, respectively, p = 0.03). Ramipril treatment had no effect on whole-body insulin-mediated glucose disposal (before: 17.9 ± 2.0, after: 19.1 ± 2.4 μmol kg body weight⁻¹ min⁻¹, p = 0.44), insulin-mediated glucose uptake across the forearm (before: 1.82 ± 0.39, after: 1.92 ± 0.29 μmol 100 ml forearm tissue⁻¹ min⁻¹, p = 0.81) and IMTG content (before: 45.4 ± 18.8, after: 48.8 ± 27.5 μmol/mg dry muscle, p = 0.92). Furthermore, the increase in carbohydrate oxidation (p < 0.001) and forearm blood flow (p < 0.01), and the decrease in fat oxidation (p < 0.001) during insulin stimulation were not significantly different between treatments.Conclusions/interpretation Short-term ramipril treatment adequately reduced ACE activity and blood pressure, but had no significant effects on insulin sensitivity, forearm blood flow, substrate fluxes across the forearm, whole-body substrate oxidation and IMTG content in obese insulin-resistant subjects.     

Sex-related psychological effects on metabolic control in type 2 diabetes mellitus

Aims/hypothesis  Women are at higher risk of diabetes-related cardiovascular complications than men. We tested the hypothesis that there are sex-specific differences in glucometabolic control, and in social and psychological factors. We also examined the influence of these factors on glucometabolic control. Methods  We examined 257 (126 men/131 women) consecutive patients (64 ± 9 years, means ± SD) of a metropolitan diabetes outpatient service employing clinical testing and standardised psychological questionnaires. Results  Mean HbA_1c (7.6 ± 1.2%) was not different between women and men. Women patients on oral hypoglycaemic agents were better informed about diabetes (p = 0.012). They employed more strategies for coping with diabetes, including religion (p = 0.0001), active coping (p = 0.048) and distraction (p = 0.007). Women reported lower satisfaction with social support (p = 0.034), but not more depression than men. Although no differences were observed in compliance, insulin-treated patients were more satisfied with their therapy (p = 0.007). Variables predicting poor metabolic control were different in men (R ² = 0.737, p = 0.012) and women (R ² = 0.597, p = 0.019). Major predictors of high HbA_1c included depressive coping, lower sexual desire, quality of life and internal locus of control, but high external doctor-related locus of control in women and frequent emotional experiences of hyperglycaemia in men. Conclusions/interpretation  Lower quality of life, internal control and socioeconomic status, and higher prevalence of negative emotions probably prevented woman patients from achieving improved glucose control despite their better knowledge of and greater efforts to cope with diabetes. We suggest that women patients would benefit from individualised diabetes care offering social support, whereas men would benefit from knowledge-based diabetes management giving them more informational and instrumental support.     

Variations in the four and a half LIM domains 1 gene (<Emphasis Type="Italic">FHL1</Emphasis>) are associated with fasting insulin and insulin sensitivity responses to regular exercise

Aims/hypothesis The expression of the four and a half LIM domains 1 gene (FHL1) is increased in the muscle of individuals who show an improvement in insulin sensitivity index (S _I) after 20 weeks of exercise training. The aim of the present study was to investigate associations between three FHL1 single nucleotide polymorphisms (SNPs) and variables derived from an IVGTT, both in the sedentary state and in response to exercise training, in participants in the HERITAGE Family Study. Materials and methods SNPs were typed using fluorescence polarisation methodology. Analyses were performed separately by sex and in black and white individuals. Results In black participants, no associations were found with any of the SNPs. In white women (n = 207), SNP rs9018 was associated with the disposition index (D _I), which is calculated as S _I generated from the MINMOD program (×10⁻⁴ min⁻¹[μU/ml]⁻¹) multiplied by acute insulin response to glucose (AIR_g; pmol/l × 10 min), and the glucose disappearance index (K _g) training responses (p = 0.016 and p = 0.008, respectively). In white men (n = 222), all SNPs were associated with fasting glucose levels (p ≤ 0.05) and SNP rs2180062 with the insulin sensitivity index (S _I) (p = 0.04) in the sedentary state. Two SNPs were associated with fasting insulin training response. Fasting insulin decreased to a greater extent in carriers of the rs2180062 C allele (p = 0.01) and rs9018 T allele (p = 0.04). With exercise training, S _I (×10⁻⁴ min⁻¹[μU/ml]⁻¹: 0.68 ± 0.20 vs −0.77 ± 0.44, p = 0.046), D _I (319 ± 123 vs –528 ± 260, p = 0.006) and K _g (per 100 min: 0.09 ± 0.04 vs −0.14 ± 0.8, p = 0.03) improved more in the C allele carriers at rs2180062 than in the T allele carriers. Conclusions/interpretation Fasting insulin and S _I responses to exercise training were associated with DNA sequence variation in FHL1 in white men. Whether these associations exist only in white men remains to be investigated. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

Common variants in the TCF7L2 gene help to differentiate autoimmune from non-autoimmune diabetes in young (15–34 years) but not in middle-aged (40–59 years) diabetic patients

Aims/hypothesis  Type 1 diabetes in children is characterised by autoimmune destruction of pancreatic beta cells and the presence of certain risk genotypes. In adults the same situation is often referred to as latent autoimmune diabetes in adults (LADA). We tested whether genetic markers associated with type 1 or type 2 diabetes could help to discriminate between autoimmune and non-autoimmune diabetes in young (15–34 years) and middle-aged (40–59 years) diabetic patients. Methods  In 1,642 young and 1,619 middle-aged patients we determined: (1) HLA-DQB1 genotypes; (2) PTPN22 and INS variable-number tandem repeat (VNTR) polymorphisms; (3) two single nucleotide polymorphisms (rs7903146 and rs10885406) in the TCF7L2 gene; (4) glutamic acid decarboxylase (GAD) and IA-2-protein tyrosine phosphatase-like protein (IA-2) antibodies; and (5) fasting plasma C-peptide. Results  Frequency of risk genotypes HLA-DQB1 (60% vs 25%, p  = 9.4×10⁻³⁴; 45% vs 18%, p  = 1.4 × 10⁻¹⁶), PTPN22 CT/TT (34% vs 26%, p  = 0.0023; 31% vs 23%, p  = 0.034), INS VNTR class I/I (69% vs 53%, p  = 1.3 × 10⁻⁸; 69% vs 51%, p  = 8.5 × 10⁻⁵) and INS VNTR class IIIA/IIIA (75% vs 63%, p  =  4.3 × 10⁻⁶; 73% vs 60%, p  = 0.008) was increased in young and middle-aged GAD antibodies (GADA)-positive compared with GADA-negative patients. The type 2 diabetes-associated genotypes of TCF7L2 CT/TT of rs7903146 were significantly more common in young GADA-negative than in GADA-positive patients (53% vs 43%; p  = 0.0004). No such difference was seen in middle-aged patients, in whom the frequency of the CT/TT genotypes of TCF7L2 was similarly increased in GADA-negative and GADA-positive groups (55% vs 56%). Conclusions/interpretation  Common variants in the TCF7L2 gene help to differentiate young but not middle-aged GADA-positive and GADA-negative diabetic patients, suggesting that young GADA-negative patients have type 2 diabetes and that middle-aged GADA-positive patients are different from their young GADA-positive counterparts and share genetic features with type 2 diabetes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users. G. Sundkvist died in September 2006.     

The effect of salsalate on insulin action and glucose tolerance in obese non-diabetic patients: results of a randomised double-blind placebo-controlled study

Aim/hypothesis  Low-grade inflammation may contribute to obesity-related insulin resistance and has been associated with increased risk of type 2 diabetes mellitus. The present study evaluated whether treatment with salsalate, a traditional anti-inflammatory medication, would improve insulin action in obese non-diabetic individuals. Methods  The study was a randomised, double-blind, placebo-controlled, parallel trial conducted at the inpatient clinical research unit of the NIDKK (Phoenix, AZ, USA). Participants were 54 adults (18 to 45 years of age) with BMI ≥ 30 kg/m². The intervention was salsalate (3 g/day, n = 28) or identical placebo (n = 26) for 7 days. The allocation was kept concealed by giving the investigator only a number corresponding to a vial of placebo or salsalate sequentially randomised in blocks by sex. Main outcomes were changes in insulin action assessed as rate of glucose disposal (R _d) by euglycaemic–hyperinsulinaemic clamp (insulin infusion rate 40 mU m⁻² min⁻¹) and glucose tolerance by 75 g OGTT. Results  The study was completed by 47 participants, of which 40 were analysed (salsalate n = 22, placebo n = 18). Salsalate treatment resulted in decreased fasting plasma glucose concentration (mean [SD]; 4.83 [0.28] vs 5.11 [0.33] mmol/l, p = 0.001) and glucose AUC during the OGTT (p = 0.01), and in increased R _d (20 [8] vs 18 [6] μmol [kg estimated metabolic body size]⁻¹ min⁻¹, p = 0.002), while there was no significant change in these variables with placebo (p > 0.3 for all). The effect of salsalate on R _d disappeared (p = 0.9) after normalising to increased insulin concentrations (701 [285] vs 535 [201] pmol/l, p < 0.0001) measured during the clamp. No side effects of salsalate were observed during the study. Conclusions/interpretation  The glucose-lowering potential of salicylates appears to be due to effects on insulin concentration rather than improved insulin action. Salicylate-based compounds may be useful for the treatment and prevention of type 2 diabetes. Trial registration: ClinicalTrials.gov NCT 00339833. Funding: Intramural research programme of the NIDDK/NIH/DHHS. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users. J. Koska and E. Ortega contributed equally to this work.     

Comprehension of complex instructions deteriorates with age and vascular morbidity

Verbal comprehension is critical to the success of medical counseling. Here, we tested how age and vascular risk factors affect the ability to understand complex instructions. Verbal comprehension, cognitive functions, and vascular risk factors were assessed in 39 mid- and 38 late-life community-dwelling individuals (48 to 59 years and >59 years of age, respectively). To test for verbal comprehension, we used a modified version of the Token Test (TT). In midlife individuals, education (β = 0.572, p < 0.05) was the only predictor for extended-TT performance. In late-life individuals, age (β = −1.015, p < 0.001) and body mass index (β = −0.651, p = 0.003) were significantly correlated with extended-TT performance and explained 50% of the variance in extended-TT performance (adjusted R ² = 0.503). This relation is only partly explained by conventional neuropsychological measures as the ones used in our test battery. These results indicate that aging and overweight impair comprehension of complex instructions. Therefore, medical counseling appropriate for midlife individuals may be less successful in elderly people and particularly in those with metabolic disturbances.     

Changes in plasma endocannabinoid levels in viscerally obese men following a 1 year lifestyle modification programme and waist circumference reduction: associations with changes in metabolic risk factors

Aims/hypothesis  We previously reported that the plasma levels of the endocannabinoid, 2-arachidonoylglycerol (2-AG), in a cohort of viscerally obese men are directly correlated with visceral adipose tissue (VAT) accumulation and metabolic risk factors including low HDL-cholesterol and high triacylglycerol. It is not known, however, if such correlations persist after vigorous lifestyle interventions that reduce metabolic risk factors. We analysed the changes in endocannabinoid levels in a subsample from the same cohort following a 1 year lifestyle modification programme, and correlated them with changes in VAT and metabolic risk factors. Methods  Forty-nine viscerally obese men (average age 49 years, BMI 30.9 kg/m², waist 107.3 cm) underwent a 1 year lifestyle modification programme including healthy eating and physical activity. Plasma levels of 2-AG and the other most studied endocannabinoid, anandamide, were measured by liquid chromatography–mass spectrometry. Anthropometric and metabolic risk factors, including VAT, insulin resistance and glucose intolerance, HDL-cholesterol and triacylglycerol, were measured. Results  Most risk factors were improved by the intervention, which led to a significant decrease in body weight (−6.4 kg, p < 0.0001), waist circumference (−8.0 cm, p < 0.0001) and VAT (−30%, p < 0.0001), and in plasma 2-AG (−62.3%, p < 0.0001) and anandamide (−7.1%, p = 0.005) levels. The decrease in levels of 2-AG but not those of anandamide correlated with decreases in VAT and triacylglycerol levels, and with the increase in HDL₃-cholesterol levels. Multivariate analyses suggested that decreases in 2-AG and VAT were both independently associated with decreases in triacylglycerol. Conclusions/interpretation  This study shows that a strong correlation exists between 2-AG levels and high plasma triacylglycerol and low HDL₃-cholesterol in viscerally obese men. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

Common genetic variation in the melatonin receptor 1B gene (MTNR1B) is associated with decreased early-phase insulin response

Aims/hypothesis  We investigated whether variation in MTNR1B, which was recently identified as a common genetic determinant of fasting glucose levels in healthy, diabetes-free individuals, is associated with measures of beta cell function and whole-body insulin sensitivity. Methods  We studied 1,276 healthy individuals of European ancestry at 19 centres of the Relationship between Insulin Sensitivity and Cardiovascular disease (RISC) study. Whole-body insulin sensitivity was assessed by euglycaemic–hyperinsulinaemic clamp and indices of beta cell function were derived from a 75 g oral glucose tolerance test (including 30 min insulin response and glucose sensitivity). We studied rs10830963 in MTNR1B using additive genetic models, adjusting for age, sex and recruitment centre. Results  The minor (G) allele of rs10830963 in MTNR1B (frequency 0.30 in HapMap Centre d’Etude du Polymorphisme [Utah residents with northern and western European ancestry] [CEU]; 0.29 in RISC participants) was associated with higher levels of fasting plasma glucose (standardised beta [95% CI] 0.17 [0.085, 0.25] per G allele, p = 5.8 × 10⁻⁵), consistent with recent observations. In addition, the G-allele was significantly associated with lower early insulin response (−0.19 [−0.28, −0.10], p = 1.7 × 10⁻⁵), as well as with decreased beta cell glucose sensitivity (−0.11 [−0.20, −0.027], p = 0.010). No associations were observed with clamp-assessed insulin sensitivity (p = 0.15) or different measures of body size (p > 0.7 for all). Conclusions/interpretation  Genetic variation in MTNR1B is associated with defective early insulin response and decreased beta cell glucose sensitivity, which may contribute to the higher glucose levels of non-diabetic individuals carrying the minor G allele of rs10830963 in MTNR1B. Electronic supplementary material  The online version of this article (doi:) contains a list of the members of the RISC Consortium, which is available to authorised users.     

Thalamic neuronal dysfunction and chronic sensorimotor distal symmetrical polyneuropathy in patients with type 1 diabetes mellitus

Aims/hypothesis  Although clear peripheral nerve pathological abnormalities have been demonstrated in diabetic peripheral neuropathy (DPN), there is little information with regard to brain involvement. Our aim was to use in vivo proton magnetic resonance specroscopy (H-MRS) in patients with DPN in order to assess the neuro-chemical status of the thalamus, which acts as the gateway to the brain for somatosensory information. Methods  Participants included 18 type 1 diabetic men (eight without DPN, ten with DPN) and six non-diabetic healthy volunteers, who all underwent detailed clinical and neurophysiological assessments yielding a Neuropathy Composite Score (NCS) derived from Neuropathy Impairment Score of the Lower Limbs plus seven tests of nerve function prior to investigation via a single-voxel H-MRS technique, which was used to sample ventral posterior thalamic parenchyma. Spectroscopic resonances including those due to N-acetyl aspartate (NAA) were assessed at both short and long echo-time, providing putative indicators of neuronal function and integrity, respectively. Results  At long echo-time we observed significantly lower NAA:creatine (p = 0.04) and NAA:choline (p = 0.02) ratios in DPN patients than in the other groups. No group differences were detected at short echo-time. We found a significant positive association between both sural amplitude (ρ = 0.61, p = 0.004) and nerve conduction velocity (r = 0.58, p = 0.006) and NAA:creatine signal among participants with diabetes. Vibration detection threshold (ρ = −0.70, p = 0.004) was significantly related to NAA:choline ratio. Heart rate variability with deep breathing (ρ = −0.46, p = 0.05) and NCS (ρ = −0.53, p = 0.03) were significantly related to NAA:creatine ratio. Conclusions/interpretation  The significantly lower NAA:creatine ratio in DPN is suggestive of thalamic neuronal dysfunction, while the lack of difference in short echo-time between the groups does not suggest neuronal loss. Taken together with the observed correlations between NAA and neurophysiological assessments, these findings provide evidence for thalamic neuronal involvement in DPN.     

Use of cystatin C-based estimations of glomerular filtration rate in patients with type 2 diabetes

Aims/hypothesis  The Modification of Diet in Renal Disease (MDRD) equation has recognised limitations when using estimated GFR in persons at risk of chronic kidney disease. Equations based on cystatin C provide an alternative method. We compared performance of the MDRD equation with a selection of cystatin C-based formulae for estimation of GFR in normoalbuminuric patients with type 2 diabetes. Methods  Estimated GFR was calculated using the MDRD equation and the cystatin C formulae proposed by several investigator teams. Isotopic GFR was measured using plasma clearance of ⁵¹Cr-EDTA. Results  We studied 106 participants, of whom 83 (78%) were men with the following characteristics, mean (SD): age 61 (9) years, HbA_1c 7.10 (1.27)%, creatinine 89.0 (12.7) μmol/l, cystatin C 0.859 (0.234) mg/l and isotopic GFR 104.5 (20.1) ml min⁻¹ 1.73 m⁻². MDRD estimated GFR was 77.4 (13.6) ml min⁻¹ 1.73 m⁻² (p < 0.05 for difference from isotopic GFR). Cystatin C-based calculations of estimated GFR were: Perkins 124.5 (31.8), Rule 90.0 (30.0), Stevens (age) 96.0 (30.4) and Stevens (creatinine) 85.6 (19.0) ml min⁻¹ 1.73 m⁻² (p < 0.05 for difference with isotopic GFR). For Arnal’s, MacIsaac’s and Tan’s formulae cystatin-C estimated GFR were 101.7 (34.8), 102.1 (27.0) and 101.6 (27.8) ml min⁻¹ 1.73 m⁻², respectively (p = NS for difference with isotopic GFR). Cystatin C-based formulae were less biased and, with the exception of Perkins’ formula, more accurate to within 10% of isotopic GFR than MDRD. Conclusions/interpretation  Performance of cystatin C equations was superior to MDRD in normoalbuminuric patients with type 2 diabetes. These results support further evaluation of cystatin C for estimation of GFR in persons at risk of chronic kidney disease.     

Variants in KCNQ1 are associated with susceptibility to type 2 diabetes in the population of mainland China

Aims/hypothesis  Two recent genome-wide association studies have identified several novel type 2 diabetes susceptibility variants in intron 15 of the KCNQ1 gene. We aimed to evaluate the effects of the variants in KCNQ1 on type 2 diabetes and metabolic traits in the population of mainland China. Methods  Three candidate single nucleotide polymorphisms were genotyped in 1,912 individuals with type 2 diabetes and 2,041 normal controls using the ligase detection reaction method. Results  We confirmed the association of KCNQ1 with type 2 diabetes in the population of mainland China. Allele frequency ORs of the three single nucleotide polymorphisms (SNPs) were: rs2237892 (OR 1.19, 95% CI 1.08–1.31, p = 3.0 × 10⁻⁴); rs2237895 (OR 1.20, 95% CI 1.09–1.32, p = 1.9 × 10⁻⁴); and rs2237897 (OR 1.24, 95% CI 1.13–1.36, p = 3.9 × 10⁻⁵). We also found a significant difference in the distribution of the global haplotypes between the type 2 diabetes group and the normal control group (p = 2.6 × 10⁻⁵). In addition, in the control group SNP rs2237892 was marginally associated with increasing fasting plasma glucose and SNPs rs2237892 and rs2237897 were associated with HbA_1c. Furthermore, for all three variants, homozygous carriers of the diabetes-associated allele had significantly decreased BMI and waist circumferences. Conclusions/interpretation  Our investigation confirmed the effects of KCNQ1 variants on type 2 diabetes risk in the Chinese population. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users. Y. Liu and D. Z. Zhou contributed equally to this study.     

Circadian rhythms of GIP and GLP1 in glucose-tolerant and in type 2 diabetic patients after biliopancreatic diversion

Aims/hypothesis  We tested the hypothesis that the reversibility of insulin resistance and diabetes observed after biliopancreatic diversion (BPD) is related to changes in circadian rhythms of gastrointestinal hormones. Methods  Ten morbidly obese participants, five with normal glucose tolerance (NGT) and five with type 2 diabetes, were studied before and within 2 weeks after BPD. Within-day variations in glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide 1 (GLP1) levels were assessed using a single cosinor model. Insulin sensitivity was assessed by euglycaemic–hyperinsulinaemic clamp. Results  Basal GLP1 relative amplitude (amplitude/mesor × 100) was 25.82–4.06% in NGT; it increased to 41.38–4.32% after BPD but was unchanged in diabetic patients. GLP1 and GIP mesor were shifted in time after surgery in diabetic patients but not in NGT participants. After BPD, the GLP1 AUC significantly increased from 775 ± 94 to 846 ± 161 pmol l⁻¹ min in NGT, whereas GIP AUC decreased significantly from 1,373 ± 565 to 513 ± 186 pmol l⁻¹ min in diabetic patients. Two-way ANOVA showed a strong influence of BPD on both GIP (p = 0.010) and GLP1 AUCs (p = 0.033), which was potentiated by the presence of diabetes, particularly for GIP (BPD × diabetes, p = 0.003). Insulin sensitivity was markedly improved (p < 0.01) in NGT (from 9.14 ± 3.63 to 36.04 ± 8.55 μmol [kg fat-free mass]⁻¹ min⁻¹) and diabetic patients (from 9.49 ± 3.56 to 38.57 ± 4.62 μmol [kg fat-free mass]⁻¹ min⁻¹). Conclusions/interpretation  An incretin circadian rhythm was shown for the first time in morbid obesity. The effect of BPD on the 24 h pattern of incretin differed between NGT and diabetic patients. GLP1 secretion impairment was reversed in NGT and could not be overcome by surgery in diabetes. On the other hand, GIP secretion was blunted after the operation only in diabetic patients, suggesting a role in insulin resistance and diabetes.     

Glucokinase, the pancreatic glucose sensor, is not the gut glucose sensor

Aims/hypothesis  The incretin hormones glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotrophic peptide (GIP) are released from intestinal endocrine cells in response to luminal glucose. Glucokinase is present in these cells and has been proposed as a glucose sensor. The physiological role of glucokinase can be tested using individuals with heterozygous glucokinase gene (GCK) mutations. If glucokinase is the gut glucose sensor, GLP-1 and GIP secretion during a 75 g OGTT would be lower in GCK mutation carriers compared with controls. Methods  We compared GLP-1 and GIP concentrations measured at five time-points during a 75 g OGTT in 49 participants having GCK mutations with those of 28 familial controls. Mathematical modelling of glucose, insulin and C-peptide was used to estimate basal insulin secretion rate (BSR), total insulin secretion (TIS), beta cell glucose sensitivity, potentiation factor and insulin secretion rate (ISR). Results  GIP and GLP-1 profiles during the OGTT were similar in GCK mutation carriers and controls (p = 0.52 and p = 0.44, respectively). Modelled variables of beta cell function showed a reduction in beta cell glucose sensitivity (87 pmol min⁻¹ m⁻² [mmol/l]⁻¹ [95% CI 66–108] vs 183 pmol min⁻¹ m⁻² [mmol/l]⁻¹ [95% CI 155–211], p < 0.001) and potentiation factor (1.5 min [95% CI 1.2–1.8] vs 2.2 min [95% CI 1.8–2.7], p = 0.007) but no change in BSR or TIS. The glucose/ISR curve was right-shifted in GCK mutation carriers. Conclusions/interpretation  Glucokinase, the major pancreatic glucose sensor, is not the main gut glucose sensor. By modelling OGTT data in GCK mutation carriers we were able to distinguish a specific beta cell glucose-sensing defect. Our data suggest a reduction in potentiation of insulin secretion by glucose that is independent of differences in incretin hormone release.     

Type 2 diabetes-associated genetic variants discovered in the recent genome-wide association studies are related to gestational diabetes mellitus in the Korean population

Aims/hypothesis  New genetic variants associated with susceptibility to type 2 diabetes mellitus have been discovered in recent genome-wide association (GWA) studies. The aim of the present study was to examine the association between these diabetogenic variants and gestational diabetes mellitus (GDM). Methods  The study included 869 Korean women with GDM and 345 female and 287 male Korean non-diabetic controls. We genotyped the single nucleotide polymorphisms (SNPs) rs7756992 and rs7754840 in CDKAL1; rs564398, rs1333040, rs10757278 and rs10811661 in the CDKN2A−CDKN2B region; rs8050136 in FTO; rs1111875, rs5015480 and rs7923837 in HHEX; rs4402960 in IGF2BP2; and rs13266634 in SLC30A8. In addition, rs7903146 and rs12255372 in TCF7L2; rs5215 and rs5219 in KCNJ11; and rs3856806 and rs1801282 in PPARG were genotyped. The genotype frequencies in the GDM patients were compared with those in the non-diabetic controls. Results  Compared with controls (men and women combined), GDM was associated with rs7756992 and rs7754840 (OR 1.55, 95% CI 1.34–1.79, p = 4.17 × 10⁻⁹) in CDKAL1; rs10811661 (OR 1.49, 95% CI 1.29–1.72, p = 1.05 × 10⁻⁷) in the CDKN2A−CDKN2B region; rs1111875 (OR 1.27, 95% CI 1.09–1.49, p = 0.003), rs5015480, and rs7923837 in HHEX; rs4402960 (OR 1.18, 95% CI 1.01–1.38, p = 0.03) in IGF2BP2; rs13266634 (OR 1.24, 95% CI 1.07–1.43, p = 0.005) in SLC30A8; and rs7903146 (OR 1.58, 95% CI 1.03–2.43, p = 0.038) in TCF7L2. The risk alleles of the SNPs rs7756992 and rs7754840 in CDKAL1; rs10811661 in the CDKN2A–CDKN2B region; and rs1111875, rs5015480 and rs7923837 in HHEX were associated with significant decreases in the insulin AUC during a 100 g OGTT performed at the time of diagnosis of GDM. Conclusions/interpretation  Some of the type 2 diabetes-associated genetic variants that were discovered in the recent GWA studies are also associated with GDM in Koreans. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users. Y. M. Cho and T. H. Kim contributed equally to this study.     

GAD65 vaccination: 5?years of follow-up in a randomised dose-escalating study in adult-onset autoimmune diabetes

Aims/hypothesis  The aim of this study was to ascertain whether treatment of GAD65 autoantibody (GADA)-positive diabetic patients with alum-formulated recombinant GAD65 (GAD-alum) is safe and does not compromise beta cell function. Methods  This Phase 2, placebo-controlled, dose-escalation clinical trial, which was randomized through a central office, was performed in 47 GADA-positive type 2 diabetic patients, who received subcutaneous injections of GAD-alum (4 [n = 9], 20 [n = 8], 100 [n = 9] or 500 [n = 8] μg) or placebo (n = 13) at weeks 1 and 4 of the trial. Participants and caregivers were blinded to group assignments. The primary outcome was safety as assessed by neurological tests, medications and beta cell function evaluated over 5 years, representing the end of the trial. Results  No severe study-related adverse events occurred during the 5 year follow-up. None of the dose groups was associated with an increased risk of starting insulin treatment compared with the placebo group. The use of oral hypoglycaemic agents did not differ between the dose groups. After 5 years, fasting C-peptide levels declined in the placebo group (−0.24; 95% CI −0.41 to −0.07 log₁₀ nmol/l; p = 0.01) and the 500 μg dose group (−0.37; 95% CI −0.57 to −0.17 log₁₀ nmol/l; p = 0.003), but not in the 4 μg (−0.10; 95% CI −0.28 to 0.07 log₁₀ nmol/l; p = 0.20), 20 μg (0.04; 95% CI −0.12 to 0.19 log₁₀ nmol/l; p = 0.58) and 100 μg (0.00; 95% CI −0.20 to −0.20 log₁₀ nmol/l; p = 0.98) dose groups. Conclusions/interpretation  The primary outcome of safety was achieved, since no severe study-related adverse events occurred. Trial registration  Because the study was initiated before 1 July 2005, the protocol was not registered in a registry. Funding  This trial was funded by the National Institutes of Health (grant numbers DK26190 and DK53004), the Swedish Research Council (grant number 72X-14064) and Diamyd Therapeutics (Stockholm, Sweden). Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

Beta cell glucose sensitivity is decreased by 39% in non-diabetic individuals carrying multiple diabetes-risk alleles compared with those with no risk alleles

Aims/hypothesis  Novel type 2 diabetes-susceptibility loci have been identified with evidence that individually they mediate the increased diabetes risk through altered pancreatic beta cell function. The aim of this study was to test the cumulative effects of diabetes-risk alleles on measures of beta cell function in non-diabetic individuals. Methods  A total of 1,211 non-diabetic individuals underwent metabolic assessment including an OGTT, from which measures of beta cell function were derived. Individuals were genotyped at each of the risk loci and then classified according to the total number of risk alleles that they carried. Initial analysis focused on CDKAL1, HHEX/IDE and TCF7L2 loci, which were individually associated with a decrease in beta cell function in our cohort. Risk alleles for CDKN2A/B, SLC30A8, IGF2BP2 and KCNJ11 loci were subsequently included into the analysis. Results  The diabetes-risk alleles for CDKAL1, HHEX/IDE and TCF7L2 showed an additive model of association with measures of beta cell function. Beta cell glucose sensitivity was decreased by 39% in those individuals with five or more risk alleles compared with those individuals with no risk alleles (geometric mean [SEM]: 84 [1.07] vs 137 [1.11] pmol min⁻¹ m⁻² (mmol/l)⁻¹, p = 1.51 × 10⁻⁶). The same was seen for the 30 min insulin response (p = 4.17 × 10⁻⁷). The relationship remained after adding in the other four susceptibility loci (30 min insulin response and beta cell glucose sensitivity, p < 0.001 and p = 0.003, respectively). Conclusions/interpretation  This study shows how individual type 2 diabetes-risk alleles combine in an additive manner to impact upon pancreatic beta cell function in non-diabetic individuals. Electronic supplementary material  The online version of this article (doi:) contains a list of the members of the RISC Consortium, which is available to authorised users.     

c-Jun N-terminal kinase 1 is deleterious to the function and survival of murine pancreatic islets

Aims/hypothesis  Inhibition of c-jun N-terminal kinase (JNK) favours pancreatic islet function and survival. Since two JNK isoforms are present in the pancreas (JNK1 and JNK2), we addressed their specific roles in experimental islet transplantation. Methods  C57BL/6J (wild-type [WT]), Jnk1 (also known as Mapk8)^−/− and Jnk2 (also known as Mapk9)^−/− mice were used as donor/recipients in a syngeneic islet transplantation model. Islet cell composition, function, viability, production of cytokines and of vascular endothelial growth factor (VEGF) were also studied in vitro. Results   Jnk1 ^−/− islets secreted more insulin in response to glucose and were more resistant to cytokine-induced cell death compared with WT and Jnk2 ^−/− islets (p < 0.01). Cytokines reduced VEGF production in WT and Jnk2 ^−/− but not Jnk1 ^−/− islets; VEGF blockade restored Jnk1 ^−/− islet susceptibility to cytokine-induced cell death. Transplantation of Jnk1 ^−/− or WT islets into WT recipients made diabetic had similar outcomes. However, Jnk1 ^−/− recipients of WT islets had shorter time to diabetes reversal (17 vs 55 days in WT, p = 0.033), while none of the Jnk2 ^−/− recipients had diabetes reversal (0% vs 71% in WT, p = 0.0003). Co-culture of WT islets with macrophages from each strain revealed a discordant cytokine production. Conclusions/interpretation  We have shown a deleterious effect of JNK2 deficiency on islet graft outcome, most likely related to JNK1 activation, suggesting that specific JNK1 blockade may be superior to general JNK inhibition, particularly when administered to transplant recipients.     

A common variant in PNPLA3, which encodes adiponutrin, is associated with liver fat content in humans

Aims/hypothesis  It has recently been suggested that the rs738409 G allele in PNPLA3, which encodes adiponutrin, is strongly associated with increased liver fat content in three different ethnic groups. The aims of the present study were as follows: (1) to try to replicate these findings in European individuals with quantitative measures of hepatic fat content; (2) to study whether the polymorphism influences hepatic and adipose tissue insulin sensitivity; and (3) to investigate whether PNPLA3 expression is altered in the human fatty liver. Methods  We genotyped 291 Finnish individuals in whom liver fat had been measured using proton magnetic resonance spectroscopy. Hepatic PNPLA3 expression was measured in 32 participants. Hepatic and adipose tissue insulin sensitivities were measured using a euglycaemic–hyperinsulinaemic (insulin infusion 0.3 mU kg⁻¹ min⁻¹) clamp technique combined with infusion of [3-³H]glucose in 109 participants. Results  The rs738409 G allele in PNPLA3 was associated with increased quantitative measures of liver fat content (p = 0.011) and serum aspartate aminotransferase concentrations (p = 0.002) independently of age, sex and BMI. Fasting serum insulin and hepatic and adipose tissue insulin sensitivity were related to liver fat content independently of genotype status. PNPLA3 mRNA expression in the liver was positively related to obesity (r = 0.62, p < 0.0001) and to liver fat content (r = 0.58, p = 0.025) in participants who were not morbidly obese (BMI < 40 kg/m²). Conclusions/interpretation  A common variant in PNPLA3 increases the risk of hepatic steatosis in humans. A. Kotronen and L. E. Johansson contributed equally to this study.     

Supraphysiological hyperinsulinaemia is necessary to stimulate skeletal muscle protein anabolism in older adults: evidence of a true age-related insulin resistance of muscle protein metabolism

Aims/hypothesis  The physiological increase in muscle protein anabolism induced by insulin is blunted in healthy, glucose-tolerant older adults. We hypothesised that the age-related defect in muscle protein anabolism is a true insulin resistance state and can be overridden by supraphysiological hyperinsulinaemia. Methods  We used dye dilution, stable isotopic and immunoblotting techniques to measure leg blood flow, muscle protein synthesis, protein kinase B/mammalian target of rapamycin (Akt/mTOR) signalling, and amino acid kinetics in 14 healthy, glucose-tolerant older volunteers at baseline, and during an insulin infusion at postprandial (PD, 0.15 mU min⁻¹ 100 ml⁻¹) or supraphysiologically high (HD, 0.30 mU min⁻¹ 100 ml⁻¹) doses. Results  Leg blood flow, muscle protein synthesis, and Akt/mTOR signalling were not different at baseline. During hyperinsulinaemia, leg blood flow (p < 0.01) and muscle protein synthesis increased in the HD group only (PD [%/h]: from 0.063 ± 0.006 to 0.060 ± 0.005; HD [%/h]: from 0.061 ± 0.007 to 0.098 ± 0.007; p < 0.01). Muscle Akt phosphorylation increased in both groups, but the increase tended to be greater in the HD group (p = 0.07). The level of p70 ribosomal S6 kinase 1 (S6K1) phosphorylation increased in the HD group only (p < 0.05). Net amino acid balance across the leg improved in both groups, but a net anabolic effect was observed only in the HD group (p < 0.05). Conclusions/interpretation  We conclude that supraphysiological hyperinsulinaemia is necessary to stimulate muscle protein synthesis and anabolic signalling in healthy older individuals, suggesting the existence of a true age-related insulin resistance of muscle protein metabolism.     

Pioglitazone stimulates AMP-activated protein kinase signalling and increases the expression of genes involved in adiponectin signalling, mitochondrial function and fat oxidation in human skeletal muscle in vivo: a randomised trial

Aims/hypothesis  The molecular mechanisms by which thiazolidinediones improve insulin sensitivity in type 2 diabetes are not fully understood. We hypothesised that pioglitazone would activate the adenosine 5′-monophosphate-activated protein kinase (AMPK) pathway and increase the expression of genes involved in adiponectin signalling, NEFA oxidation and mitochondrial function in human skeletal muscle. Methods  A randomised, double-blind, parallel study was performed in 26 drug-naive type 2 diabetes patients treated with: (1) pioglitazone (n = 14) or (2) aggressive nutritional therapy (n = 12) to reduce HbA_1c to levels observed in the pioglitazone-treated group. Participants were assigned randomly to treatment using a table of random numbers. Before and after 6 months, patients reported to the Clinical Research Center of the Texas Diabetes Institute for a vastus lateralis muscle biopsy followed by a 180 min euglycaemic–hyperinsulinaemic (80 mU m⁻² min⁻¹) clamp. Results  All patients in the pioglitazone (n = 14) or nutritional therapy (n = 12) group were included in the analysis. Pioglitazone significantly increased plasma adiponectin concentration by 79% and reduced fasting plasma NEFA by 35% (both p < 0.01). Following pioglitazone, insulin-stimulated glucose disposal increased by 30% (p < 0.01), and muscle AMPK and acetyl-CoA carboxylase (ACC) phosphorylation increased by 38% and 53%, respectively (p < 0.05). Pioglitazone increased mRNA levels for adiponectin receptor 1 and 2 genes (ADIPOR1, ADIPOR2), peroxisome proliferator-activated receptor gamma, coactivator 1 gene (PPARGC1) and multiple genes involved in mitochondrial function and fat oxidation. Despite a similar reduction in HbA_1c and similar improvement in insulin sensitivity with nutritional therapy, there were no significant changes in muscle AMPK and ACC phosphorylation, or the expression of ADIPOR1, ADIPOR2, PPARGC1 and genes involved in mitochondrial function and fat oxidation. No adverse (or unexpected) effects or side effects were reported from the study. Conclusions/interpretations  Pioglitazone increases plasma adiponectin levels, stimulates muscle AMPK signalling and increases the expression of genes involved in adiponectin signalling, mitochondrial function and fat oxidation. These changes may represent an important cellular mechanism by which thiazolidinediones improve skeletal muscle insulin sensitivity. Trial registration: NCT 00816218 Funding: This trial was funded by National Institutes of Health Grant DK24092, VA Merit Award, GCRC Grant RR01346, Executive Research Committee Research Award from the University of Texas Health Science Center at San Antonio, American Diabetes Association Junior Faculty Award, American Heart Association National Scientist Development Grant, Takeda Pharmaceuticals North America Grant and Canadian Institute of Health Research Grant. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users.