Glucose effectiveness is a critical pathogenic factor leading to glucose intolerance and type 2 diabetes: An ignored hypothesis

BACKGROUND

Although the ability of glucose to mediate its own in vivo metabolism is long documented, the quantitative measurement of whole body glucose-mediated glucose disposal at basal insulin levels (glucose effectiveness [GE]), followed the introduction of the Minimal Model intravenous glucose tolerance test technique.

METHODS

A literature review, combined with our own studies, of the role of GE in glucose metabolism in normal and "at risk" individuals, was undertaken to determine GE's contribution to glucose homeostasis.

RESULTS

GE accounts for ~45% to 65% of glucose disposal in man. A negative association between GE and insulin meditated glucose disposal (Si), is present in normal subjects without a family history of type 2 diabetes mellitus but is absent in normoglycaemic "at risk" relatives with a positive family history of diabetes mellitus. Intracellular GE disposal is mediated by mass action of glucose through the skeletal muscle membrane via facilitated Glut 4 transporters. However, GE is frequently forgotten as a significant contributor to the development of glucose intolerance in "at risk" individuals. Only limited studies have examined the role of a lower GE in such normoglycemic subjects with preexisting mild insulin resistance and β-cell dysfunction. These studies demonstrate that in "at risk" individuals, an initial low GE is a key contributor and predictor of future glucose intolerance, whereas an initial raised GE is protective against future glucose intolerance.

CONCLUSION

In "at risk" individuals, a low GE and genetically determined vulnerable β-cell function are more critical determinants of future glucose intolerance than their preexisting insulin-resistant state.

Associations between birth size and later height from infancy through adulthood: An individual based pooled analysis of 28 twin cohorts participating in the CODATwins project

BACKGROUND

There is evidence that birth size is positively associated with height in later life, but it remains unclear whether this is explained by genetic factors or the intrauterine environment.

AIM

To analyze the associations of birth weight, length and ponderal index with height from infancy through adulthood within mono- and dizygotic twin pairs, which provides insights into the role of genetic and environmental individual-specific factors.

METHODS

This study is based on the data from 28 twin cohorts in 17 countries. The pooled data included 41,852 complete twin pairs (55% monozygotic and 45% same-sex dizygotic) with information on birth weight and a total of 112,409 paired height measurements at ages ranging from 1 to 69 years. Birth length was available for 19,881 complete twin pairs, with a total of 72,692 paired height measurements. The association between birth size and later height was analyzed at both the individual and within-pair level by linear regression analyses.

RESULTS

Within twin pairs, regression coefficients showed that a 1-kg increase in birth weight and a 1-cm increase in birth length were associated with 1.14-4.25 cm and 0.18-0.90 cm taller height, respectively. The magnitude of the associations was generally greater within dizygotic than within monozygotic twin pairs, and this difference between zygosities was more pronounced for birth length.

CONCLUSION

Both genetic and individual-specific environmental factors play a role in the association between birth size and later height from infancy to adulthood, with a larger role for genetics in the association with birth length than with birth weight.

Early-onset type 2 diabetes: Age gradient in clinical and behavioural risk factors in 5115 persons with newly diagnosed type 2 diabetes-Results from the DD2 study

AIM

To examine the association between early onset of type 2 diabetes mellitus (DM) and clinical and behavioural risk factors for later complications of diabetes.

METHODS

We conducted a cross-sectional study of 5115 persons with incident type 2 DM enrolled during 2010-2015 in the Danish Centre for Strategic Research in Type 2 Diabetes-cohort. We compared risk factors at time of diagnosis among those diagnosed at ≤45 years (early onset) with diagnosis age 46 to 55, 56 to 65 (average onset = reference), 66 to 75, and >75 years (late onset). Prevalence ratios (PRs) were computed by using Poisson regression.

RESULTS

Poor glucose control, ie, HbA1c ≥ 75 mmol/mol (≥9.0%) in the early-, average-, and late-onset groups was observed in 12%, 7%, and 1%, respectively (PR 1.70 [95% confidence intervals (CI) 1.27, 2.28] and PR 0.17 [95% CI 0.06, 0.45]). A similar age gradient was observed for severe obesity (body mass index > 40 kg/m² : 19% vs. 8% vs. 2%; PR 2.41 [95% CI 1.83, 3.18] and 0.21 (95% CI 0.08, 0.57]), dyslipidemia (90% vs. 79% vs. 68%; PR 1.14 [95% CI 1.10, 1.19] and 0.86 [95% CI 0.79, 0.93]), and low-grade inflammation (C-reactive protein > 3.0 mg/L: 53% vs. 38% vs. 26%; PR 1.41 [95% CI 1.12, 1.78] and 0.68 [95% CI 0.42, 1.11]). Daily smoking was more frequent and meeting physical activity recommendations less likely in persons with early-onset type 2 DM.

CONCLUSIONS

We found a clear age gradient, with increasing prevalence of clinical and behavioural risk factors the younger the onset age of type 2 DM. Younger persons with early-onset type 2 DM need clinical awareness and support.

Comparing effects of insulin analogues and human insulin on nocturnal glycaemia in hypoglycaemia-prone people with Type 1 diabetes

AIMS

To assess the difference between analogue and human insulin with regard to nocturnal glucose profiles and risk of hypoglycaemia in people with recurrent severe hypoglycaemia.

METHODS

A total of 72 people [46 men, mean ± sd age 54 ± 12 years, mean ± sd HbA_1c 65 ± 12 mmol/mol (8.1 ± 1.1%), mean ± sd duration of diabetes 30 ± 14 years], who participated in a 2-year randomized, crossover trial of basal-bolus therapy with insulin detemir/insulin aspart or human NPH insulin/human regular insulin (the HypoAna trial) were studied for 2 nights during each treatment. Venous blood was drawn hourly during sleep. Primary endpoints were nocturnal glucose profiles and occurrence of hypoglycaemia (blood glucose ≤ 3.9 mmol/l).

RESULTS

During insulin analogue treatment, the mean nocturnal plasma glucose level was significantly higher than during treatment with human insulin (10.6 vs 8.1 mmol/l). The fasting plasma glucose level was similar between the treatments. Nocturnal hypoglycaemia was registered during 41/101 nights (41%) in the human insulin arm and 19/117 nights (16%) in the insulin analogue arm, corresponding to a hazard ratio of 0.26 (95% CI 0.14 to 0.45; P < 0.0001) with insulin analogue.

CONCLUSIONS

Treatment with insulin analogue reduces the occurrence of nocturnal hypoglycaemia assessed by nocturnal glucose profiles in people with Type 1 diabetes prone to severe hypoglycaemia. Nocturnal glucose profiles provide a more comprehensive assessment of clinical benefit of insulin regimens as compared to conventional recording of hypoglycaemia.

Prescribing practices and clinical predictors of glucose-lowering therapy within the first year in people with newly diagnosed Type 2 diabetes

AIM

To examine prescribing practices and predictors of glucose-lowering therapy within the first year following diagnosis of Type 2 diabetes mellitus in a clinical care setting.

METHODS

We followed people enrolled in the Danish Centre for Strategic Research in Type 2 Diabetes (DD2) cohort from outpatient hospital clinics and general practices throughout Denmark in 2010-2013. We used Poisson regression to compute age- and gender-adjusted risk ratios (RRs).

RESULTS

Among 1158 new Type 2 diabetes mellitus patients, 302 (26%) did not receive glucose-lowering therapy within the first year, 723 (62%) received monotherapy [685 (95%) with metformin], and 133 (12%) received more than one drug. Predictors of receiving any vs. no therapy and combination vs. monotherapy were: age < 40 years [RR: 1.29 (95% CI: 1.16-1.44) and 3.60 (95% CI: 2.36-5.50)]; high Charlson Comorbidity Index [RRs: 1.20 (95% CI: 1.05-1.38) and 2.08 (95% CI: 1.16-3.72)]; central obesity [RRs: 1.23 (95% CI: 1.04-1.44) and 1.93 (95% CI: 0.76-4.94)]; fasting blood glucose of ≥ 7.5 mmol/l [RRs: 1.25 (95% CI: 1.10-1.42) and 1.94 (95% CI: 1.02-3.71)]; and HbA1c ≥ 59 mmol/mol (≥ 7.5%) [RR: 1.26 (95% CI: 1.20-1.32) and 2.86 (95% CI: 1.97-4.14)]. Weight gain ≥ 30 kg since age 20, lack of physical exercise and C-peptide of < 300 pmol/l also predicted therapy.

CONCLUSIONS

Comorbidity, young age, central obesity and poor baseline glycaemic control are important predictors of therapy one year after Type 2 diabetes mellitus debut.

Metabolic effects of lifestyle intervention in obese pregnant women. Results from the randomized controlled trial 'Lifestyle in Pregnancy' (LiP)

AIMS

The Lifestyle in Pregnancy intervention in obese pregnant women resulted in significantly lower gestational weight gain compared with the control group, but without improvement in rates of clinical pregnancy complications. The impact of the lifestyle intervention on metabolic measurements in the study participants is now reported.

METHODS

The Lifestyle in Pregnancy study was a randomized controlled trial among 360 obese women (BMI 30-45 kg/m²) who were allocated in early pregnancy to lifestyle interventions with diet counselling and physical activities or to the control group. Fasting blood samples, including plasma glucose, insulin, lipid profile and capillary blood glucose during a 2-h oral glucose tolerance test were carried out three times throughout pregnancy. Insulin resistance was estimated with the homeostasis model assessment of insulin resistance.

RESULTS

Three hundred and four women (84%) were followed until delivery. Women in the intervention group had a significantly lower change in insulin resistance (HOMA-IR) from randomization to 28-30 weeks' gestation compared with control subjects (mean ± SD: 0.7 ± 1.3 vs. 1.0 ± 1.3, P = 0.02). Despite a significantly lower gestational weight gain in the intervention group, there was no difference between the groups with respect to total cholesterol, HDL, LDL or triglycerides.

CONCLUSIONS

Lifestyle intervention in obese pregnant women resulted in attenuation of the physiologic pregnancy-induced insulin resistance. Despite restricted gestational weight gain, there were no changes in glucose or lipid metabolism between the groups.

Infant twin mortality and hospitalisations after the perinatal period - a prospective cohort study from Guinea-Bissau

OBJECTIVE

To examine mortality and hospitalisations among infant twins and singletons after the perinatal period in Guinea-Bissau.

METHODS

The study was conducted from September 2009 to November 2012 by the Bandim Health Project (BHP). Newborn twins and unmatched singleton controls were included at the National Hospital Simão Mendes in the capital Bissau. Children were examined clinically at enrolment. Maternal, pregnancy and obstetric information was collected and HIV testing offered at birth. Follow-up occurred at home at 2, 6 and 12 months and through linkage with the paediatric admission register at the National Hospital.

RESULTS

About 495 twins and 333 singletons were alive on day 7 after birth. In total, 36 twins and 12 singletons died during follow-up, the post-perinatal infant mortality rate being 91/1000 person-years for twins and 42/1000 for singletons (HR = 2.11, 95% CI: 1.09-4.07). In a multivariable analysis among twins only, birth weight <2000 g [3.32, (1.36-8.07)], death of the cotwin perinatally [2.54, (1.16-5.57)] and severe maternal illness during pregnancy [2.35, (1.00-5.51)] were significant risk factors for twin death. In the subgroup with available HIV status, maternal HIV infection was strongly associated with twin mortality [3.16, (1.24-8.05)]. Death occurred at home for 60% of twins and 67% of singletons. During follow-up, 90 first-time hospital admissions were registered, with similar rates observed for twins (139/1000) and singletons (143/1000) [0.97, (0.61-1.52)].

CONCLUSION

The post-perinatal infant mortality rate of twins was double that of singletons. No excess in twin hospitalisations was observed, possibly implying obstacles to hospital admission for twins in case of severe illness.

Glucose effectiveness in nondiabetic relatives: dysglycemia and β-cell function at 10 years

AIMS

Reduced glucose effectiveness is a predictor of future glucose tolerance in individuals with a family history of type 2 diabetes. We examined retrospectively at 10 years in normoglycemic relatives of diabetic subjects (RELs) the pathophysiological role of glucose effectiveness in the development of isolated impaired fasting glucose, glucose intolerance, and acute insulin release.

METHODS

At 0 years, 19 RELs and 18 matched control subjects had glucose effectiveness (GE), insulin sensitivity, acute insulin release (AIR)IVGTT, and disposition index measured during an iv glucose tolerance test (IVGTT), using the minimal model analysis. At 0 and 10 years, oral glucose tolerance (OGTT) and AIROGTT were determined.

RESULTS

At 0 years, fasting glucose (FG) and GE were raised in RELs, but insulin sensitivity and AIROGTT were reduced (P ≤ .05) compared with controls. At 10 years, RELs developed raised fasting and 2-hour OGTT glucose. FG10y correlated significantly with FG0y and body mass index0y and negatively with √GE and 2-hour OGTT glucose10y with FG0y and negatively with AIRIVGTT0y and AIROGTT0y. Log AIROGTT10y correlated with √GE, log AIRIVGTT0y and log AIROGTT0y. Multiple regression analyses demonstrated the following: REL FG10y was predicted by combined FG0y, √GE and body mass index0y (radj(2) = 56%; P ≤ .001) and 2-hour OGTT glucose10y weakly related by FG0y,and √GE (r(adj)(2) = 25%; P = .06). Log AIROGTT10y was predicted by AIRIVGTT0y and √GE (r(adj)(2) = 46%; P ≤ .004).

CONCLUSION

In normoglycemic RELs, a relative reduction of glucose effectiveness is an important contributor over 10 years to the development of isolated impaired fasting glucose and reduced acute insulin secretion.

Structured personal care of type 2 diabetes: a 19 year follow-up of the study Diabetes Care in General Practice (DCGP)

AIMS/HYPOTHESIS

This study is a 19 year observational follow-up of a pragmatic open multicentre cluster-randomised controlled trial of 6 years of structured personal diabetes care starting from diagnosis.

METHODS

A total of 1,381 patients aged ≥ 40 years and newly diagnosed with type 2 diabetes were followed up in national registries for 19 years. Clinical follow-up was at 6 and 14 years after diabetes diagnosis. The original 6 year intervention included regular follow-up and individualised goal setting, supported by prompting of doctors, clinical guidelines, feedback and continuing medical education (ClinicalTrials.gov NCT01074762). The registry-based endpoints were: incidence of any diabetes-related endpoint; diabetes-related death; all-cause mortality; myocardial infarction (MI); stroke; peripheral vascular disease; and microvascular disease.

RESULTS

At 14 year clinical follow-up, group differences in risk factors from the 6 year follow-up had levelled out, although the prevalence of (micro)albuminuria and level of triacylglycerols were lower in the intervention group. During 19 years of registry-based monitoring, all-cause mortality was not different between the intervention and comparison groups (58.9 vs 62.3 events per 1,000 patient-years, respectively; for structured personal care, HR 0.94, 95% CI 0.83, 1.08, p = 0.40), but a lower risk emerged for fatal and non-fatal MI (27.3 vs 33.5, HR 0.81, 95% CI 0.68, 0.98, p = 0.030) and any diabetes-related endpoint (69.5 vs 82.1, HR 0.83, 95% CI 0.72, 0.97, p = 0.016). These differences persisted after extensive multivariable adjustment.

CONCLUSIONS/INTERPRETATION

In concert with features such as prompting, feedback, clinical guidelines and continuing medical education, individualisation of goal setting and drug treatment may safely be applied to treat patients newly diagnosed with type 2 diabetes to lower the risk of diabetes complications.

Oral salmon calcitonin attenuates hyperglycaemia and preserves pancreatic beta-cell area and function in Zucker diabetic fatty rats

BACKGROUND AND PURPOSE

Oral salmon calcitonin (sCT), a dual-action amylin and calcitonin receptor agonist, improved glucose homeostasis in diet-induced obese rats. Here, we have evaluated the anti-diabetic efficacy of oral sCT using parameters of glycaemic control and beta-cell morphology in male Zucker diabetic fatty (ZDF) rats, a model of type 2 diabetes.

EXPERIMENTAL APPROACH

Male ZDF rats were treated with oral sCT (0.5, 1.0 or 2 mg·kg(-1) ) or oral vehicle twice daily from age 8 to 18 weeks. Zucker lean rats served as control group. Fasting and non-fasted blood glucose, glycosylated haemoglobin (HbA1c) and levels of pancreas and incretin hormones were determined. Oral glucose tolerance test and i.p. glucose tolerance test were compared, and beta-cell area and function were evaluated.

KEY RESULTS

Oral sCT treatment dose-dependently attenuated fasting and non-fasted hyperglycaemia during the intervention period. At the end of the study period, oral sCT treatment by dose decreased diabetic hyperglycaemia by ∼9 mM and reduced HbA1c levels by 1.7%. Furthermore, a pronounced reduction in glucose excursions was dose-dependently observed for oral sCT treatment during oral glucose tolerance test. In addition, oral sCT treatment sustained hyperinsulinaemia and attenuated hyperglucagonaemia and hypersecretion of total glucagon-like peptide-1 predominantly in the basal state. Lastly, oral sCT treatment dose-dependently improved pancreatic beta-cell function and beta-cell area at study end.

CONCLUSIONS AND IMPLICATIONS

Oral sCT attenuated diabetic hyperglycaemia in male ZDF rats by improving postprandial glycaemic control, exerting an insulinotropic and glucagonostatic action in the basal state and by preserving pancreatic beta-cell function and beta-cell area.

Adult glucose metabolism in extremely birthweight-discordant monozygotic twins

AIMS/HYPOTHESIS

Low birthweight (BW) is associated with increased risk of type 2 diabetes. We compared glucose metabolism in adult BW-discordant monozygotic (MZ) twins, thereby controlling for genetic factors and rearing environment.

METHODS

Among 77,885 twins in the Danish Twin Registry, 155 of the most BW-discordant MZ twin pairs (median BW difference 0.5 kg) were assessed using a 2 h oral glucose tolerance test with sampling of plasma (p-)glucose, insulin, C-peptide, glucose-dependent insulinotropic polypeptide and glucagon-like peptide-1. HOMA for beta cell function (HOMA-β) and insulin resistance (HOMA-IR), and also insulin sensitivity index (BIGTT-SI) and acute insulin response (BIGTT-AIR), were calculated. Subgroup analyses were performed in those with: (1) double verification of BW difference; (2) difference in BW >0.5 kg; and (3) no overt metabolic disease (type 2 diabetes, hyperlipidaemia or thyroid disease).

RESULTS

No intra-pair differences in p-glucose, insulin, C-peptide, incretin hormones, HOMA-β, HOMA-IR or BIGTT-SI were identified. p-Glucose at 120 min was higher in the twins with the highest BW without metabolic disease, and BIGTT-AIR was higher in those with the highest BW although not in pairs with a BW difference of >0.5 kg.

CONCLUSIONS/INTERPRETATION

BW-discordant MZ twins provide no evidence for a detrimental effect of low BW on glucose metabolism in adulthood once genetic factors and rearing environment are controlled for.

Pregestational body mass index is related to neonatal abdominal circumference at birth--a Danish population-based study

OBJECTIVES

To examine the impact of maternal pregestational body mass index (BMI) and smoking on neonatal abdominal circumference (AC) and weight at birth. To define reference curves for birth AC and weight in offspring of healthy, nonsmoking, normal weight women.

DESIGN

Population-based study.

SETTING

Data from the Danish Medical Birth Registry.

POPULATION

All live singletons without congenital malformations in Denmark 2004-10.

METHODS

Data on 366,886 singletons at 35(+0) to 41(+6) weeks(+days) of gestation were extracted and analysed using multivariate linear regressions.

MAIN OUTCOME MEASURES

Birth AC and weight in relation to pregestational maternal BMI, maternal smoking and medical conditions (any).

RESULTS

Birth AC and weight increased with increasing pregestational BMI, and decreased with smoking (P < 0.0001). Reference curves were created for offspring of healthy, nonsmoking mothers with normal pregestational BMI. Mean AC ranged from 30.1 cm and 30.2 cm at 35 weeks of gestation to 33.9 cm and 34.1 cm at 41 weeks of gestation, for girls and boys, respectively. Mean birthweight ranged from 2581 and 2666 g at 35 weeks to 3705 and 3852 g at 41 weeks of gestation for girls and boys, respectively. Pregestational BMI correlated more to the Z score of birthweight than to the Z score of AC (P < 0.0001).

CONCLUSION

Birth AC and weight are affected by maternal smoking status and pregestational BMI. Pregestational BMI correlated more to birthweight than to AC. Using data from healthy, nonsmoking mothers with normal pregestational BMI we have provided new reference curves for birth AC and birthweight.

Hyperglycaemia normalises insulin action on glucose metabolism but not the impaired activation of AKT and glycogen synthase in the skeletal muscle of patients with type 2 diabetes

AIMS/HYPOTHESIS

In type 2 diabetes, reduced insulin-stimulated glucose disposal, primarily glycogen synthesis, is associated with defective insulin activation of glycogen synthase (GS) in skeletal muscle. Hyperglycaemia may compensate for these defects, but to what extent it involves improved insulin signalling to glycogen synthesis remains to be clarified.

METHODS

Whole-body glucose metabolism was studied in 12 patients with type 2 diabetes, and 10 lean and 10 obese non-diabetic controls by means of indirect calorimetry and tracers during a euglycaemic-hyperinsulinaemic clamp. The diabetic patients underwent a second isoglycaemic-hyperinsulinaemic clamp maintaining fasting hyperglycaemia. Muscle biopsies from m. vastus lateralis were obtained before and after the clamp for examination of GS and relevant insulin signalling components.

RESULTS

During euglycaemia, insulin-stimulated glucose disposal, glucose oxidation and non-oxidative glucose metabolism were reduced in the diabetic group compared with both control groups (p < 0.05). This was associated with impaired insulin-stimulated GS and AKT2 activity, deficient dephosphorylation at GS sites 2 + 2a, and reduced Thr308 and Ser473 phosphorylation of AKT. When studied under hyperglycaemia, all variables of insulin-stimulated glucose metabolism were normalised compared with the weight-matched controls. However, insulin activation and dephosphorylation (site 2 + 2a) of GS as well as activation of AKT2 and phosphorylation at Thr308 and Ser473 remained impaired (p < 0.05).

CONCLUSIONS/INTERPRETATIONS

These data confirm that hyperglycaemia compensates for decreased whole-body glucose disposal in type 2 diabetes. In contrast to previous less well-controlled studies, we provide evidence that the compensatory effect of hyperglycaemia in patients with type 2 diabetes does not involve normalisation of insulin action on GS or upstream signalling in skeletal muscle.

Insulin analogues and severe hypoglycaemia in type 1 diabetes

INTRODUCTION

The effect of insulin analogues on glycaemic control is well-documented, whereas the effect on avoidance of severe hypoglycaemia remains tentative. We studied the frequency of severe hypoglycaemia in unselected patients with type 1 diabetes treated with insulin analogues, human insulin, or mixed regimens.

METHODS

A questionnaire was posted from six Danish diabetes clinics to 6112 unselected patients with type 1 diabetes and filled in by 3861 patients (63.2%). Primary endpoint was number of episodes of severe hypoglycaemia in the preceding year. Mild hypoglycaemia was also reported.

RESULTS

The frequency of severe hypoglycaemic episodes per patient-year in patients receiving long-acting insulin analogues was 1.47±0.18 versus 1.09±0.10 in patients on long-acting human insulin (p=0.01). The frequency of severe hypoglycaemic episodes per patient-year was 1.09±0.11 in patients on short-acting insulin analogues versus 1.26±0.13 in patients on short-acting human insulin (p=0.15), which was statistically significant in an adjusted analysis.

CONCLUSIONS

Severe hypoglycaemia is more frequent in patients with type 1 diabetes treated with long-acting insulin analogues. Confounding by indication may be involved. Clinical intervention trials using insulin analogues in patients prone to severe hypoglycaemia are highly needed.

The proteomic signature of insulin-resistant human skeletal muscle reveals increased glycolytic and decreased mitochondrial enzymes

AIMS/HYPOTHESIS

The molecular mechanisms underlying insulin resistance in skeletal muscle are incompletely understood. Here, we aimed to obtain a global picture of changes in protein abundance in skeletal muscle in obesity and type 2 diabetes, and those associated with whole-body measures of insulin action.

METHODS

Skeletal muscle biopsies were obtained from ten healthy lean (LE), 11 obese non-diabetic (OB), and ten obese type 2 diabetic participants before and after hyperinsulinaemic-euglycaemic clamps. Quantitative proteome analysis was performed by two-dimensional differential-gel electrophoresis and tandem-mass-spectrometry-based protein identification.

RESULTS

Forty-four protein spots displayed significant (p < 0.05) changes in abundance by at least a factor of 1.5 between groups. Several proteins were identified in multiple spots, suggesting post-translational modifications. Multiple spots containing glycolytic and fast-muscle proteins showed increased abundance, whereas spots with mitochondrial and slow-muscle proteins were downregulated in the OB and obese type 2 diabetic groups compared with the LE group. No differences in basal levels of myosin heavy chains were observed. The abundance of multiple spots representing glycolytic and fast-muscle proteins correlated negatively with insulin action on glucose disposal, glucose oxidation and lipid oxidation, while several spots with proteins involved in oxidative metabolism and mitochondrial function correlated positively with these whole-body measures of insulin action.

CONCLUSIONS/INTERPRETATION

Our data suggest that increased glycolytic and decreased mitochondrial protein abundance together with a shift in muscle properties towards a fast-twitch pattern in the absence of marked changes in fibre-type distribution contribute to insulin resistance in obesity with and without type 2 diabetes. The roles of several differentially expressed or post-translationally modified proteins remain to be elucidated.

Plasma sCD36 is associated with markers of atherosclerosis, insulin resistance and fatty liver in a nondiabetic healthy population

OBJECTIVES

Insulin resistance is associated with increased CD36 expression in a number of tissues. Moreover, excess macrophage CD36 may initiate atherosclerotic lesions. The aim of this study was to determine whether plasma soluble CD36 (sCD36) was associated with insulin resistance, fatty liver and carotid atherosclerosis in nondiabetic subjects.

METHODS

In 1296 healthy subjects without diabetes or hypertension recruited from 19 centres in 14 European countries (RISC study), we determined the levels of sCD36, adiponectin, lipids and liver enzymes, insulin sensitivity (M/I) by euglycaemic-hyperinsulinaemic clamp, carotid atherosclerosis as intima-media thickness (IMT) and two estimates of fatty liver, the fatty liver index (FLI) and liver fat percentage (LF%).

RESULTS

IMT, FLI, LF%, presence of the metabolic syndrome, impaired glucose regulation, insulin and triglycerides increased across sCD36 quartiles (Q2-Q4), whereas adiponectin and M/I decreased (P ≤ 0.01). sCD36 was lower in women than in men (P = 0.045). Log sCD36 showed a bimodal distribution, and amongst subjects with sCD36 within the log-normal distribution (log-normal population, n = 1029), sCD36 was increased in subjects with impaired glucose regulation (P = 0.045), metabolic syndrome (P = 0.006) or increased likelihood of fatty liver (P < 0.001). sCD36 correlated significantly with insulin, triglycerides, M/I and FLI (P < 0.05) after adjustment for study centre, gender, age, glucose tolerance status, smoking habits and alcohol consumption. In the log-normal population, these relationships were stronger than in the total study population and, additionally, sCD36 was significantly associated with LF% and IMT (P < 0.05).

CONCLUSIONS

In this cross-sectional study of nondiabetic subjects, sCD36 was significantly associated with indices of insulin resistance, carotid atherosclerosis and fatty liver. Prospective studies are needed to further evaluate the role of sCD36 in the inter-relationship between atherosclerosis, fatty liver and insulin resistance.

Common variation in oxidative phosphorylation genes is not a major cause of insulin resistance or type 2 diabetes

AIMS/HYPOTHESIS

There is substantial evidence that mitochondrial dysfunction is linked to insulin resistance and is present in several tissues relevant to the pathogenesis of type 2 diabetes. Here, we examined whether common variation in genes involved in oxidative phosphorylation (OxPhos) contributes to type 2 diabetes susceptibility or influences diabetes-related metabolic traits.

METHODS

OxPhos gene variants (n = 10) that had been nominally associated (p < 0.01) with type 2 diabetes in a recent genome-wide meta-analysis (n = 10,108) were selected for follow-up in 3,599 type 2 diabetic and 4,956 glucose-tolerant Danish individuals. A meta-analysis of these variants was performed in 11,729 type 2 diabetic patients and 43,943 non-diabetic individuals. The impact on OGTT-derived metabolic traits was evaluated in 5,869 treatment-naive individuals from the Danish Inter99 study.

RESULTS

The minor alleles of COX10 rs9915302 (p = 0.02) and COX5B rs1466100 (p = 0.005) showed nominal association with type 2 diabetes in our Danish cohort. However, in the meta-analysis, none of the investigated variants showed a robust association with type 2 diabetes after correction for multiple testing. Among the alleles potentially associated with type 2 diabetes, none negatively influenced surrogate markers of insulin sensitivity in non-diabetic participants, while the minor alleles of UQCRC1 rs2228561 and COX10 rs10521253 showed a weak (p < 0.01 to p < 0.05) negative influence on indices of glucose-stimulated insulin secretion.

CONCLUSIONS/INTERPRETATION

We cannot rule out the possibility that common variants in or near OxPhos genes may influence beta cell function in non-diabetic individuals. However, our quantitative trait studies and a sufficiently large meta-analysis indicate that common variation in proximity to the examined OxPhos genes is not a major cause of insulin resistance or type 2 diabetes.

A novel oral form of salmon calcitonin improves glucose homeostasis and reduces body weight in diet-induced obese rats

AIM

To investigate the effects of acute and chronic administration of a novel oral formulation of salmon calcitonin (sCT) on glycaemic control, glucose homeostasis and body weight regulation in diet-induced obese (DIO) rats-an animal model of obesity-related insulin resistance and type 2 diabetes.

METHODS

DIO rats were acutely given a single dose of oral sCT (0.5 and 2 mg/kg), its oral vehicle N-(5-chlorosalicyloyl)-8-aminocaprylic acid (5-CNAC) or injectable sCT (5 and 10 µg/kg) (n = 8), followed by oral glucose tolerance test (OGTT). Other DIO rats were chronic treated twice daily with oral vehicle 5-CNAC (n = 6), oral sCT (0.5 and 2 mg/kg) or injectable sCT (10 µg/kg) (n = 8). Fasting and postprandial glucose and pancreatic hormones, body weight and insulin sensitivity were assessed.

RESULTS

A single dose of oral sCT acutely reduced glucose and insulin area under the curve during OGTT by approximately 65 and 85%, respectively, compared with vehicle (p < 0.001). Chronic treatment with oral sCT significantly reduced both fasting and postprandial glucose and insulin levels by approximately 1.5 mM and 65%, respectively, compared with vehicle. Oral sCT concomitantly improved insulin sensitivity (homeostatic model assessment, HOMA). In contrast, injectable sCT resembling higher systemic exposure did not improve glycaemic control, either acutely or during chronic treatment. Furthermore, both oral and injectable sCT reduced body weight by 15% compared with vehicle (p < 0.05).

CONCLUSION

A novel oral form of sCT showed antidiabetic effects in DIO rats by improving glycaemic control, glucose homeostasis, insulin sensitivity and body weight.

No evidence of a higher 10 year period prevalence of diabetes among 77,885 twins compared with 215,264 singletons from the Danish birth cohorts 1910-1989

AIMS/HYPOTHESIS

Previous Danish twin studies have found a highly increased risk of precursors of type 2 diabetes as well as a higher prevalence of type 2 diabetes among twins compared with singletons. Likewise, small-scale studies of Danish twins have shown that monozygotic twins have a higher risk of developing precursors of type 2 diabetes compared with dizygotic twins. In the present register-based study, the 10 year period diabetes prevalence in Danish twins is compared with that in a random sample of Danish citizens. Furthermore, the 10 year period prevalence of diabetes in monozygotic twins is compared with that in dizygotic twins.

METHODS

The study population consisted of twins (n = 77,885) identified in the Danish Twin Registry, and a 5% random sample (n = 215,264) from the birth cohorts 1910-1989. We identified diabetes patients by means of three nationwide Danish health registers.

RESULTS

The number of identified diabetes cases among males was 6,677 (6.24%) for singletons vs 2,271 (5.68%) for twins (difference = 0.56% [0.29-0.83%]). The number among females was 6,143 (5.67%) for singletons and 1,722 (4.54%) for twins (difference = 1.13% [0.88-0.38%]). Restriction to various birth cohorts, known zygosity and known type 2 diabetes did not alter the overall conclusions. The difference between monozygotic twins (males, 5.29%; females, 4.40%) and dizygotic twins (males, 5.77%; females, 4.63%) was non-significant.

CONCLUSIONS/INTERPRETATION

Danish twins do not have an increased risk of developing diabetes compared with singletons, and the risk of diabetes among monozygotic twins does not differ from that of dizygotic twins.

Counter-regulatory hormone responses to spontaneous hypoglycaemia during treatment with insulin Aspart or human soluble insulin: a double-blinded randomized cross-over study

AIMS

To compare insulin Aspart and human insulin with respect to glycaemic control, hypoglycaemic frequency and counter-regulatory responses to spontaneous hypoglycaemia.

METHODS

Glycaemic control, hypoglycaemic frequency, p-insulin concentrations, insulin dosages and patients' satisfaction were examined in a randomized, double-blinded cross-over study for two periods of 8 weeks. Sixteen patients with type 1 diabetes were subjected to three daily injections of human soluble insulin or Aspart in addition to Neutral Protamine Hagedorn (NPH) insulin twice daily. Each intervention period was followed by hospitalization where episodes of spontaneous hypoglycaemia and counter-regulatory hormone responses were evaluated from frequently obtained blood samples.

RESULTS

No difference between soluble insulin and insulin Aspart was found regarding HbA1c (7.0 ± 0.2 vs. 7.0 ± 0.2%, ns), hypoglycaemic frequency (1.1 ± 0.2 vs. 0.9 ± 0.1 events per patient per week, ns), nocturnal hypoglycaemia, severe hypoglycaemic events, dosages of bolus insulin (31.8 ± 0.4 vs. 30.0 ± 0.6 IU day(-1), ns), or NPH insulin (26.7 ± 1.8 vs. 26.0 ± 1.7 IU day(-1) , ns) or in patients satisfaction (ns). Modest differences existed in the counter-regulatory responses regarding growth hormone, glucagon and ghrelin whereas no differences were found in relation to free fatty acid, cortisol, insulin-like growth factor (IGF)-I, IGF-II and IGF-binding proteins 1 and 2. Treatment with insulin Aspart resulted in well-defined peaks in serum insulin concentrations as compared with more blunted insulin peaks using human soluble insulin.

CONCLUSION

Although insulin Aspart treatment was associated with clear postprandial insulin peaks, no improvement in glycaemic control was obtained and no difference in the hypoglycaemic frequency was observed. However, insulin Aspart elicited a slightly different physiological response to spontaneous hypoglycaemia compared with human insulin.

Natural history and physiological determinants of changes in glucose tolerance in a non-diabetic population: the RISC Study

AIMS/HYPOTHESIS

The natural history and physiological determinants of glucose intolerance in subjects living in Europe have not been investigated. The aim of this study was to increase our understanding of this area.

METHODS

We analysed the data from a population-based cohort of 1,048 non-diabetic, normotensive men and women (aged 30-60 years) in whom insulin sensitivity was measured by the glucose clamp technique (M/I index; average glucose infusion rate/steady-state insulin concentration) and beta cell function was estimated by mathematical modelling of the oral glucose tolerance test at baseline and 3 years later.

RESULTS

Seventy-seven per cent of the participants had normal glucose tolerance (NGT) and 5% were glucose intolerant both at baseline and follow up; glucose tolerance worsened in 13% (progressors) and improved in 6% (regressors). The metabolic phenotype of the latter three groups was similar (higher prevalence of familial diabetes, older age, higher waist-to-hip ratio, higher fasting and 2 h plasma glucose, higher fasting and 2 h plasma insulin, lower insulin sensitivity and reduced beta cell glucose sensitivity with increased absolute insulin secretion). Adjusting for these factors in a logistic model, progression was predicted by insulin resistance (bottom M/I quartile, OR 2.52 [95% CI 1.51-4.21]) and beta cell glucose insensitivity (bottom quartile, OR 2.39 [95% CI 1.6-3.93]) independently of waist-to-hip ratio (OR 1.44 [95% CI 1.13-1.84] for one SD). At follow up, insulin sensitivity and beta cell glucose sensitivity were unchanged in the stable NGT and stable non-NGT groups, worsened in progressors and improved in regressors.

CONCLUSIONS/INTERPRETATION

Glucose tolerance deteriorates over time in young, healthy Europids. Progressors, regressors and glucose-intolerant participants share a common baseline phenotype. Insulin sensitivity and beta cell glucose sensitivity predict and track changes in glucose tolerance independently of sex, age and obesity.

Impaired insulin-induced site-specific phosphorylation of TBC1 domain family, member 4 (TBC1D4) in skeletal muscle of type 2 diabetes patients is restored by endurance exercise-training

AIMS/HYPOTHESIS

Insulin-mediated glucose disposal rates (R(d)) are reduced in type 2 diabetic patients, a process in which intrinsic signalling defects are thought to be involved. Phosphorylation of TBC1 domain family, member 4 (TBC1D4) is at present the most distal insulin receptor signalling event linked to glucose transport. In this study, we examined insulin action on site-specific phosphorylation of TBC1D4 and the effect of exercise training on insulin action and signalling to TBC1D4 in skeletal muscle from type 2 diabetic patients.

METHODS

During a 3 h euglycaemic-hyperinsulinaemic (80 mU min⁻¹ m⁻²) clamp, we obtained M. vastus lateralis biopsies from 13 obese type 2 diabetic and 13 obese, non-diabetic control individuals before and after 10 weeks of endurance exercise-training.

RESULTS

Before training, reductions in insulin-stimulated R (d), together with impaired insulin-stimulated glycogen synthase fractional velocity, Akt Thr³⁰⁸ phosphorylation and phosphorylation of TBC1D4 at Ser³¹⁸, Ser⁵⁸⁸ and Ser⁷⁵¹ were observed in skeletal muscle from diabetic patients. Interestingly, exercise-training normalised insulin-induced TBC1D4 phosphorylation in diabetic patients. This happened independently of increased TBC1D4 protein content, but exercise-training did not normalise Akt phosphorylation in diabetic patients. In both groups, training-induced improvements in insulin-stimulated R(d) (~20%) were associated with increased muscle protein content of Akt, TBC1D4, α2-AMP-activated kinase (AMPK), glycogen synthase, hexokinase II and GLUT4 (20-75%).

CONCLUSIONS/INTERPRETATION

Impaired insulin-induced site-specific TBC1D4 phosphorylation may contribute to skeletal muscle insulin resistance in type 2 diabetes. The mechanisms by which exercise-training improves insulin sensitivity in type 2 diabetes may involve augmented signalling of TBC1D4 and increased skeletal muscle content of key insulin signalling and effector proteins, e.g., Akt, TBC1D4, AMPK, glycogen synthase, GLUT4 and hexokinase II.

Experience of malignancies with oral glucose-lowering drugs in the randomised controlled ADOPT (A Diabetes Outcome Progression Trial) and RECORD (Rosiglitazone Evaluated for Cardiovascular Outcomes and Regulation of Glycaemia in Diabetes) clinical trials

AIMS/HYPOTHESIS

Observational and mechanistic studies have suggested a possible relationship between treatment with metformin and decreased incidence of cancer in participants with type 2 diabetes. We extracted data for malignancies from the ADOPT (A Diabetes Outcome Progression Trial) and RECORD (Rosiglitazone Evaluated for Cardiovascular Outcomes and Regulation of Glycaemia in Diabetes) randomised controlled clinical trials, in which the efficacy and/or safety of metformin was assessed in comparison with sulfonylureas and rosiglitazone.

METHODS

Neoplasm occurrences were collected as adverse events in these studies. We reviewed and re-analysed the individual participant data in both studies for serious adverse events, malignancies reported as adverse events and related neoplasms of special interest.

RESULTS

In ADOPT, 50 participants (3.4%) on metformin and 55 (3.8%) on each of rosiglitazone and glibenclamide (known as glyburide in the USA and Canada) developed serious adverse event malignancies (excluding non-melanoma skin cancers). This corresponds to 1.03, 1.12 and 1.31 per 100 person-years, giving hazard ratios for metformin of 0.92 (95% CI 0.63-1.35) vs rosiglitazone and 0.78 (0.53-1.14) vs glibenclamide. In RECORD, on a background of sulfonylurea, 69 (6.1%) participants developed malignant neoplasms in the metformin group, compared with 56 (5.1%) in the rosiglitazone group (HR 1.22 [0.86-1.74]). On a background of metformin, 74 (6.7%) participants in the sulfonylurea group developed malignant neoplasms, compared with 57 (5.1%) in the rosiglitazone group (HR 1.33 [0.94-1.88]).

CONCLUSIONS/INTERPRETATION

The malignancy rates in these two randomised controlled clinical trials do not support a view that metformin offers any particular protection against malignancy compared with rosiglitazone. However, they do not refute the possibility of a difference compared with sulfonylureas.

Effect of physical training on mitochondrial respiration and reactive oxygen species release in skeletal muscle in patients with obesity and type 2 diabetes

AIM/HYPOTHESIS

Studies have suggested a link between insulin resistance and mitochondrial dysfunction in skeletal muscles. Our primary aim was to investigate the effect of aerobic training on mitochondrial respiration and mitochondrial reactive oxygen species (ROS) release in skeletal muscle of obese participants with and without type 2 diabetes.

METHODS

Type 2 diabetic men (n = 13) and control (n = 14) participants matched for age, BMI and physical activity completed 10 weeks of aerobic training. Pre- and post-training muscle biopsies were obtained before a euglycaemic-hyperinsulinaemic clamp and used for measurement of respiratory function and ROS release in isolated mitochondria.

RESULTS

Training significantly increased insulin sensitivity, maximal oxygen consumption and muscle mitochondrial respiration with no difference between groups. When expressed in relation to a marker of mitochondrial density (intrinsic mitochondrial respiration), training resulted in increased mitochondrial ADP-stimulated respiration (with NADH-generating substrates) and decreased respiration without ADP. Intrinsic mitochondrial respiration was not different between groups despite lower insulin sensitivity in type 2 diabetic participants. Mitochondrial ROS release tended to be higher in participants with type 2 diabetes.

CONCLUSIONS/INTERPRETATION

Aerobic training improves muscle respiration and intrinsic mitochondrial respiration in untrained obese participants with and without type 2 diabetes. These adaptations demonstrate an increased metabolic fitness, but do not seem to be directly related to training-induced changes in insulin sensitivity.

Differential aetiology and impact of phosphoinositide 3-kinase (PI3K) and Akt signalling in skeletal muscle on in vivo insulin action

AIMS/HYPOTHESIS

Insulin resistance in skeletal muscle is a key factor in the development of type 2 diabetes and although some studies indicate that this could be partly attributed to reduced content and activity of various proximal and distal insulin signalling molecules, consensus is lacking. We therefore aimed to investigate the regulation of proximal insulin signalling in skeletal muscle and its effect on glucose metabolism in a large non-diabetic population.

METHODS

We examined 184 non-diabetic twins with gold-standard techniques including the euglycaemic-hyperinsulinaemic clamp. Insulin signalling was evaluated at three key levels, i.e. the insulin receptor, IRS-1 and V-akt murine thymoma viral oncogene (Akt) levels, employing kinase assays and phospho-specific western blotting.

RESULTS

Proximal insulin signalling was not associated with obesity, age or sex. However, birthweight was positively associated with IRS-1-associated phosphoinositide 3-kinase (PI3K; IRS-1-PI3K) activity (p = 0.04); maximal aerobic capacity (VO2(max)), paradoxically, was negatively associated with IRS-1-PI3K (p = 0.02) and Akt2 activity (p = 0.01). Additionally, we found low heritability estimates for most measures of insulin signalling activity. Glucose disposal was positively associated with Akt-308 phosphorylation (p < 0.001) and Akt2 activity (p = 0.05), but not with insulin receptor tyrosine kinase or IRS-1-PI3K activity.

CONCLUSIONS/INTERPRETATION

With the exception of birthweight, 'classical' modifiers of insulin action, including genetics, age, sex, obesity and VO2(max) do not seem to mediate their most central effects on whole-body insulin sensitivity through modulation of proximal insulin signalling in skeletal muscle. We also demonstrated an association between Akt activity and in vivo insulin sensitivity, suggesting a role of Akt in control of in vivo insulin resistance and potentially in type 2 diabetes.

Impaired beta cell glucose sensitivity rather than inadequate compensation for insulin resistance is the dominant defect in glucose intolerance

AIMS/HYPOTHESIS

It is commonly thought that hyperglycaemia results from insufficient compensation of insulin secretion for insulin resistance. To verify this hypothesis, we assessed beta cell function and insulin sensitivity (IS) in a large cohort of volunteers with normal glucose tolerance (NGT) or impaired glucose regulation (IGR), i.e. impaired glucose tolerance or impaired fasting glucose.

METHODS

In men and women with NGT (n=1,123) or IGR(n=156) (age 44 +/- 8 years, BMI 25+/-4 kg/m2, mean +/- SD)we measured: (1) IS by clamp; (2) insulin secretion rates(ISR) and beta cell glucose sensitivity (=slope of the insulin secretion/plasma glucose dose-response) by C-peptide deconvolution and OGTT modelling; and (3) acute insulin response to intravenous glucose.

RESULTS

After controlling for centre, sex, age and BMI, fasting and total ISR were inversely related to IS in both groups,whereas beta cell glucose sensitivity was not. Acute insulin response was reciprocally related to IS in both groups, but the relationships were incompatible with inadequate compensation and significance was lost after controlling for fasting ISR. InIGR vs NGT, IS was impaired (92 [75] vs 133 [86] micromol min(-1)[kg fat-free mass](-1) [nmol/l](-1), median [interquartile range],p<0.0001) as was beta cell glucose sensitivity (69 [46] vs 119[83] pmol min(-1) m(-2) [nmol/l](-1), p<0.0001), whereas fasting and total ISR were increased (35% and 25%, respectively, p<0.0001). In fully adjusted models, beta cell glucose sensitivity was the strongest determinant of OGTT glucose levels.

CONCLUSIONS/INTERPRETATION

Insulin resistance normally upregulates the secretory tone, with no evidence of defective compensation in IGR. In contrast, beta cell glucose sensitivity is independent of insulin resistance, but a key determinant of glucose tolerance. This suggests that hyperglycaemia results from an intrinsic beta cell defect rather than from inadequate compensation for insulin resistance.

Identification of asymptomatic type 2 diabetes mellitus patients with a low, intermediate and high risk of ischaemic heart disease: is there an algorithm?

AIMS/HYPOTHESIS

The leading cause of death in type 2 diabetes is cardiovascular disease (CVD). We examined the prevalence of myocardial ischaemia in type 2 diabetes patients and tried to establish an algorithm to identify patients with a high risk of ischaemic heart disease.

METHODS

Type 2 diabetes patients who had no known or suspected CVD, and had been referred consecutively to a diabetes clinic for the first time (n=305; age 58.6+/-11.3 years; diabetes duration 4.5+/-5.3 years) were screened for myocardial ischaemia using myocardial perfusion scintigraphy (MPS).

RESULTS

The univariate predictors of myocardial ischaemia were: atypical or typical angina pectoris, two or more traditional risk factors for CVD, BMI >32 kg/m2, systolic blood pressure >140 mmHg, HbA1c >8.5%, high-sensitivity C-reactive protein >4.0 mg/l, N-terminal pro-brain natriuretic peptide >300 pg/ml, left atrial volume index >32 ml/m2, left ventricular ejection fraction <50%, and carotid and peripheral arterial disease. The algorithm identified low (n=96), intermediate (n=65) and high risk groups (n=115), in which the prevalence of myocardial ischaemia was 15%,23% and 43%, respectively. Overall the algorithm reduced the number of patients referred to MPS from 305 to 144.However, the sensitivity and specificity of the algorithm was just 68% and 62%, respectively.

CONCLUSIONS/INTERPRETATION

Our algorithm was able to stratify which patients had a low, intermediate or high risk of myocardial ischaemia based on MPS. However, the algorithm had low sensitivity and specificity, combined with high cost and time requirements.

TRIAL REGISTRATION

clinicaltrials.gov NCT00298844 FUNDING: The study was funded by the Danish Cardio vascular Research Academy (DaCRA), The Danish Diabetes Association and The Danish Heart Foundation.

Human ATP synthase beta is phosphorylated at multiple sites and shows abnormal phosphorylation at specific sites in insulin-resistant muscle

AIMS/HYPOTHESIS

Insulin resistance in skeletal muscle is linked to mitochondrial dysfunction in obesity and type 2 diabetes. Emerging evidence indicates that reversible phosphorylation regulates oxidative phosphorylation (OxPhos) proteins. The aim of this study was to identify and quantify site-specific phosphorylation of the catalytic beta subunit of ATP synthase (ATPsyn-beta) and determine protein abundance of ATPsyn-beta and other OxPhos components in skeletal muscle from healthy and insulin-resistant individuals.

METHODS

Skeletal muscle biopsies were obtained from lean, healthy, obese, non-diabetic and type 2 diabetic volunteers (each group n = 10) for immunoblotting of proteins, and hypothesis-driven identification and quantification of phosphorylation sites on ATPsyn-beta using targeted nanospray tandem mass spectrometry. Volunteers were metabolically characterised by euglycaemic-hyperinsulinaemic clamps.

RESULTS

Seven phosphorylation sites were identified on ATPsyn-beta purified from human skeletal muscle. Obese individuals with and without type 2 diabetes were characterised by impaired insulin-stimulated glucose disposal rates, and showed a approximately 30% higher phosphorylation of ATPsyn-beta at Tyr361 and Thr213 (within the nucleotide-binding region of ATP synthase) as well as a coordinated downregulation of ATPsyn-beta protein and other OxPhos components. Insulin increased Tyr361 phosphorylation of ATPsyn-beta by approximately 50% in lean and healthy, but not insulin-resistant, individuals.

CONCLUSIONS/INTERPRETATION

These data demonstrate that ATPsyn-beta is phosphorylated at multiple sites in human skeletal muscle, and suggest that abnormal site-specific phosphorylation of ATPsyn-beta together with reduced content of OxPhos proteins contributes to mitochondrial dysfunction in insulin resistance. Further characterisation of phosphorylation of ATPsyn-beta may offer novel targets of treatment in human diseases with mitochondrial dysfunction, such as diabetes.

Evidence-based insulin treatment in type 1 diabetes mellitus

AIM

Evaluation of the evidence base for recommending different insulin treatment regimens in type 1 diabetes.

METHODS

A computerised literature survey was conducted using The Cochrane Controlled Trials Register and the Pub Med database for the period of 1982-2007.

RESULTS

A meta-analysis on only 49 out of 1295 references showed that CSII compared with conventional or multiple insulin injections therapy demonstrated a significant reduction in mean HbA1c (primary outcome) of 1.2% CI [0.73; 1.59] (P<0.001) without increasing the risk of hypoglycaemia. The evidence for using four versus two daily insulin injections was based on only one publication demonstrating an improved quality of life but no significant reduction in HbA1c or hypoglycaemia. A comparison of rapid-acting insulin analogues and human soluble insulin demonstrated a statistically significant reduction in HbA1c of 0.1% CI: [0.01; 0.16] (P=0.03) using rapid-acting insulin analogues. The mean frequency of hypoglycaemia was reduced with 14+/-3.7% (<0.05).

CONCLUSION

The scientific evidence supporting the three common insulin regimens was rather sparse. Only five studies during the past 25 years fulfil the optimal criteria for a clinical trial, and only 5 trials on insulin analogues were performed as double-blinded. Current evidence suggests that CSII treatment results in a significant reduction in HbA1c without inducing more hypoglycaemia. Rapid-acting insulin analogues compared to human soluble insulin provide statistically significant but clinically minor improvement in HbA1c but seem to reduce the risk for hypoglycaemia.

Maximal lipid oxidation in patients with type 2 diabetes is normal and shows an adequate increase in response to aerobic training

AIM

Insulin resistance in subjects with type 2 diabetes (T2D) and obesity is associated with an imbalance between the availability and the oxidation of lipids. We hypothesized that maximal whole-body lipid oxidation during exercise (FATmax) is reduced and that training-induced metabolic adaptation is attenuated in T2D.

METHODS

Obese T2D (n = 12) and control (n = 11) subjects matched for age, sex, physical activity and body mass index completed 10 weeks of aerobic training. Subjects were investigated before and after training with maximal and submaximal exercise tests and euglycaemic-hyperinsulinaemic clamps combined with muscle biopsies.

RESULTS

Training increased maximal oxygen consumption (VO(2max)) and muscle citrate synthase activity and decreased blood lactate concentrations during submaximal exercise in both groups (all p < 0.01). FATmax increased markedly (40-50%) in both T2D and control subjects after training (all p < 0.001). There were no significant differences in these variables and lactate threshold (%VO(2max)) between groups before or after training. Insulin-stimulated glucose disappearance rate (Rd) was lower in T2D vs. control subjects both before and after training. Rd increased in response to training in both groups (all p < 0.01). There was no correlation between Rd and measures of oxidative capacity or lipid oxidation during exercise or the training-induced changes in these parameters.

CONCLUSIONS

FATmax was not reduced in T2D, and muscle oxidative capacity increased adequately in response to aerobic training in obese subjects with and without T2D. These metabolic adaptations to training seem to be unrelated to changes in insulin sensitivity and indicate that an impaired capacity for lipid oxidation is not a major cause of insulin resistance in T2D.

Transcriptional profiling of myotubes from patients with type 2 diabetes: no evidence for a primary defect in oxidative phosphorylation genes

AIMS/HYPOTHESIS

Microarray-based studies of skeletal muscle from patients with type 2 diabetes and high-risk individuals have demonstrated that insulin resistance and reduced mitochondrial biogenesis co-exist early in the pathogenesis of type 2 diabetes independently of hyperglycaemia and obesity. It is unknown whether reduced mitochondrial biogenesis or other transcriptional alterations co-exist with impaired insulin responsiveness in primary human muscle cells from patients with type 2 diabetes.

METHODS

Using cDNA microarray technology and global pathway analysis with the Gene Map Annotator and Pathway Profiler (GenMapp 2.1) and Gene Set Enrichment Analysis (GSEA 2.0.1), we examined transcript levels in myotubes established from obese patients with type 2 diabetes and matched obese healthy participants, who had been extensively metabolically characterised both in vivo and in vitro. We have previously reported reduced basal lipid oxidation and impaired insulin-stimulated glycogen synthesis and glucose oxidation in these diabetic myotubes.

RESULTS

No single gene was differently expressed after correction for multiple testing, and no biological pathway was differently expressed using either method of global pathway analysis. In particular, we found no evidence for differential expression of genes involved in mitochondrial oxidative metabolism. Consistently, there was no difference in mRNA levels of genes known to mediate the transcriptional control of mitochondrial biogenesis (PPARGC1A and NRF1) or in mitochondrial mass between diabetic and control myotubes.

CONCLUSIONS/INTERPRETATION

These results support the hypothesis that impaired mitochondrial biogenesis is not a primary defect in the sequence of events leading to insulin resistance and type 2 diabetes.

Adiponectin and its response to thiazolidinediones are associated with insulin-mediated glucose metabolism in type 2 diabetic patients and their first-degree relatives

Patients with type 2 diabetes (T2D) and their first-degree relatives (FDRs) are characterized by hypoadiponectinaema and insulin resistance. In T2D patients, plasma adiponectin and insulin sensitivity (SI) increase in response to thiazolidinediones (TZDs). These findings suggest a role for adiponectin in the regulation of SI. We studied the relationship between plasma adiponectin and glucose and lipid metabolism and the effect of troglitazone (200 mg/day) for 12 weeks in 19 normoglycaemic, obese FDR and 20 obese T2D patients, using euglycaemic-hyperinsulinaemic clamps, glycolytic flux calculations and indirect calorimetry. Plasma adiponectin was similar in both groups, despite higher glucose disposal (Rd), glucose oxidation and glycolytic flux and lower lipid oxidation during insulin stimulation in FDR compared with T2D patients. Plasma adiponectin correlated with insulin-stimulated Rd, non-oxidative glucose disposal (NOGD), glucose storage and SI in both groups after adjustment for sex and body fat. The troglitazone-mediated upregulation of plasma adiponectin was associated with increased insulin-stimulated Rd, NOGD and glucose storage in both groups. No effect on endogenous glucose production was observed. In FDR, plasma adiponectin correlated with insulin-stimulated glycogen synthase activity and the troglitazone-induced increase in plasma adiponectin correlated with the improvement in insulin-stimulated Rd and SI after adjustment for sex and body fat. In conclusion, plasma adiponectin in weight-matched FDR and T2D patients is comparably low and correlates with insulin-mediated glucose uptake and storage. Moreover, these data provide evidence for an adiponectin-dependent insulin-sensitizing effect of TZDs at an early stage before development of T2D and that this effect is exerted mainly on insulin-mediated glucose metabolism.

Weight history of patients with newly diagnosed Type 2 diabetes

AIMS

To estimate and illustrate how the 10 years of weight change immediately preceding diabetes diagnosis vary with weight at the age of 20 years and with socio-demographic variables, risk factors and comorbidities at diagnosis.

METHODS

Data were from a population-based cohort of 1320 persons newly diagnosed with diabetes aged > or = 40 years. Patients' weight at diagnosis was measured by the doctor, while patients recalled their weight approximately 1, 5 and 10 years prior to diagnosis and at age 20 years.

RESULTS

Median weight gain from age 20 years to diabetes diagnosis at median age 65.3 years was 14.7 kg (interquartile range 6.0-23.0). Women gained weight more than men, and the lower the weight at age 20 years, the greater the weight gain. The average weight gain from 10 years prior to diabetes diagnosis until diagnosis, however, was only 1 kg and decreased markedly with age. These 10 years of weight change were also associated with sex and the following baseline characteristics: diagnostic plasma glucose, urinary glucose, urinary albumin, fasting triglycerides, systolic blood pressure, smoking habits, and presence of diabetic retinopathy.

CONCLUSIONS

The results add to the evidence that it is important to advise young patients in particular, especially women, who have gained and sustained considerable weight to curb this upward weight trend in order to prevent the development of diabetes.

Rosiglitazone RECORD study: glucose control outcomes at 18 months

AIMS

To compare glucose control over 18 months between rosiglitazone oral combination therapy and combination metformin and sulphonylurea in people with Type 2 diabetes.

METHODS

RECORD, a multicentre, parallel-group study of cardiovascular outcomes, enrolled people with an HbA(1c) of 7.1-9.0% on maximum doses of metformin or sulphonylurea. If on metformin they were randomized to add-on rosiglitazone or sulphonylurea (open label) and if on sulphonylurea to rosiglitazone or metformin. HbA(1c) was managed to < or = 7.0% by dose titration. A prospectively defined analysis of glycaemic control on the first 1122 participants is reported here, with a primary outcome assessed against a non-inferiority margin for HbA(1c) of 0.4%.

RESULTS

At 18 months, HbA(1c) reduction on background metformin was similar with rosiglitazone and sulphonylurea [difference 0.07 (95% CI -0.09, 0.23)%], as was the change when rosiglitazone or metformin was added to sulphonylurea [0.06 (-0.09, 0.20)%]. At 6 months, the effect on HbA(1c) was greater with add-on sulphonylurea, but was similar whether sulphonylurea was added to rosiglitazone or metformin. Differences in fasting plasma glucose were not statistically significant at 18 months [rosiglitazone vs. sulphonylurea -0.36 (-0.74, 0.02) mmol/l, rosiglitazone vs. metformin -0.34 (-0.73, 0.05) mmol/l]. Increased homeostasis model assessment insulin sensitivity and reduced C-reactive protein were greater with rosiglitazone than metformin or sulphonylurea (all P < or = 0.001). Body weight was significantly increased with rosiglitazone compared with sulphonylurea [difference 1.2 (0.4, 2.0) kg, P = 0.003] and metformin [difference 4.3 (3.6, 5.1) kg, P < 0.001].

CONCLUSIONS

In people with diabetes, rosiglitazone in combination with metformin or sulphonylurea was demonstrated to be non-inferior to the standard combination of metformin + sulphonylurea in lowering HbA(1c) over 18 months, and produces greater improvements in C-reactive protein and basal insulin sensitivity but is also associated with greater weight gain.

Changes in patient weight and the impact of antidiabetic therapy during the first 5 years after diagnosis of diabetes mellitus

AIMS/HYPOTHESIS

It is generally thought difficult for type 2 diabetic patients to lose weight. We monitored changes in patients' weight during the first 5 years after diabetes diagnosis in relation to initiation of antidiabetic treatment.

SUBJECTS AND METHODS

Data from 711 newly diagnosed diabetic patients aged 40 or over were analysed with a random-effect linear-regression model. Patients were included consecutively from a well-defined patient list in general practice.

RESULTS

In 245 patients whose only treatment was advice on diet, an initial weight loss of 6 to 7 kg was largely maintained over 5 years. Patients receiving metformin (n=86) or sulfonylureas (n=330) maintained an average weight loss of 2 to 4 kg that was dependent on age and sex. Patients' weight did not change on initiation of treatment with sulfonylureas or metformin. Over 5 years, median HbA(1c) increased from 7.0 to 7.8% (reference range 5.4-7.4%) in the diet-alone group. HbA(1c) was approximately 1 percentage point higher for most of the other treatment groups.

CONCLUSIONS/INTERPRETATION

In newly diagnosed type 2 diabetic patients, long-term weight loss was common and weight loss was not affected by sulfonylurea treatment. The measurements in the study are taken from treatment results achieved in the general population of diabetic patients, who are rarely treated in secondary care and seldom the subject of research; the results thus indicate that weight reduction is a practicable treatment in diabetic patients.

Partial rescue of in vivo insulin signalling in skeletal muscle by impaired insulin clearance in heterozygous carriers of a mutation in the insulin receptor gene

AIMS/HYPOTHESIS

Recently we reported the coexistence of postprandial hypoglycaemia and moderate insulin resistance in heterozygous carriers of the Arg1174Gln mutation in the insulin receptor gene (INSR). Controlled studies of in vivo insulin signalling in humans with mutant INSR are unavailable, and therefore the cellular mechanisms underlying insulin resistance in Arg1174Gln carriers remain to be clarified.

SUBJECTS, MATERIALS AND METHODS

We studied glucose metabolism and insulin signalling in skeletal muscle from six Arg1174Gln carriers and matched control subjects during a euglycaemic-hyperinsulinaemic clamp.

RESULTS

Impaired clearance of exogenous insulin caused four-fold higher clamp insulin levels in Arg1174Gln carriers compared with control subjects (p<0.05). In Arg1174Gln carriers insulin increased glucose disposal and non-oxidative glucose metabolism (p<0.05), but to a lower extent than in controls (p<0.05). Insulin increased Akt phosphorylation at Ser473 and Thr308, inhibited glycogen synthase kinase-3alpha activity, reduced phosphorylation of glycogen synthase at sites 3a+3b, and increased glycogen synthase activity in Arg1174Gln carriers (all p<0.05). In the insulin-stimulated state, Akt phosphorylation at Thr308 and glycogen synthase activity were reduced in Arg1174Gln carriers compared with controls (p<0.05), whereas glycogen synthase kinase-3alpha activity and phosphorylation of glycogen synthase at sites 3a+3b were similar in the two groups.

CONCLUSIONS/INTERPRETATION

In vivo insulin signalling in skeletal muscle of patients harbouring the Arg1174Gln mutation is surprisingly intact, with modest impairments in insulin-stimulated activity of Akt and glycogen synthase explaining the moderate degree of insulin resistance. Our data suggest that impaired insulin clearance in part rescues in vivo insulin signalling in muscle in these carriers of a mutant INSR, probably by increasing insulin action on the non-mutated insulin receptors.

Reduced plasma adiponectin concentrations may contribute to impaired insulin activation of glycogen synthase in skeletal muscle of patients with type 2 diabetes

AIMS/HYPOTHESIS

Circulating levels of adiponectin are negatively associated with multiple indices of insulin resistance, and the concentration is reduced in humans with insulin resistance and type 2 diabetes. However, the mechanisms by which adiponectin improves insulin sensitivity remain unclear.

SUBJECTS AND METHODS

Combining euglycaemic-hyperinsulinaemic clamp studies with indirect calorimetry and skeletal muscle biopsies, we examined the relationship between plasma adiponectin and parameters of whole-body glucose and lipid metabolism, and muscle glycogen synthase (GS) activity in 51 Caucasians (ten lean, 21 obese and 20 with type 2 diabetes).

RESULTS

Plasma adiponectin was significantly reduced in type 2 diabetic compared with obese and lean subjects. In lean and obese subjects, insulin significantly reduced plasma adiponectin, but this response was blunted in patients with type 2 diabetes. Plasma adiponectin was positively associated with insulin-stimulated glucose disposal (r = 0.48), glucose oxidation (r = 0.54), respiratory quotient (r = 0.58) and non-oxidative glucose metabolism (r = 0.38), and negatively associated with lipid oxidation during insulin stimulation (r = -0.60) after adjustment for body fat (all p < 0.01). Most notably, we found a positive association between plasma adiponectin and insulin stimulation of GS activity in skeletal muscle (r = 0.44, p < 0.01).

CONCLUSIONS/INTERPRETATION

Our results indicate that plasma adiponectin may enhance insulin sensitivity by improving the capacity to switch from lipid to glucose oxidation and to store glucose as glycogen in response to insulin, and that low adiponectin may contribute to impaired insulin activation of GS in skeletal muscle of patients with type 2 diabetes.