Reduced peripheral activity leading to hepato-preferential action of basal insulin peglispro compared with insulin glargine in patients with type 1 diabetes.

AIMS: Basal insulin peglispro (BIL), a novel PEGylated basal insulin with a large hydrodynamic size, has a delayed absorption and reduced clearance that prolongs the duration of action. The current study compared the effects of BIL and insulin glargine (GL) on endogenous glucose production (EGP), glucose disposal rate (GDR) and lipolysis in patients with type 1 diabetes. MATERIALS AND METHODS: This was a randomized, open-label, four-period, crossover study. Patients received intravenous infusions of BIL and GL, each at two dose levels selected for partial and maximal suppression of EGP, during an 8 to 10 h euglycemic clamp procedure with d-[3-3 H] glucose. RESULTS: Following correction for equivalent human insulin concentrations (EHIC), low-dose GL infusion resulted in similar EGP at the end of the clamp compared to low-dose BIL infusion (GL/BIL ratio of 1.03) but a higher GDR (GL/BIL ratio of 2.42), indicating similar hepatic activity but attenuated peripheral activity of BIL. Consistent with this, the EHIC-corrected GDR/EGP at the end of the clamp was 1.72-fold greater for GL than BIL following low-dose administration. At the lower dose of BIL and GL (concentrations in the therapeutic range), BIL produced less suppression of lipolysis compared with GL as indicated by free fatty acid and glycerol levels at the end of the clamp. CONCLUSIONS: Compared with GL, BIL restored the hepato-peripheral insulin action gradient seen in normal physiology via its peripherally restricted action on target tissues related to carbohydrate and lipid metabolism.

Improved glucose control with reduced hypoglycaemic risk when linagliptin is added to basal insulin in elderly patients with type 2 diabetes.

AIM: To assess the efficacy, hypoglycaemia risk and other safety markers of linagliptin as an additional therapy in older patients (aged ≥70 years) inadequately controlled with basal insulin. METHODS: A prespecified safety analysis from the linagliptin trials programme was carried out to explore the hypoglycaemia risk when linagliptin was added to background basal insulin therapy in elderly patients (≥70 years). To do this, two eligible, randomized, placebo-controlled, clinical trials (NCT00954447 and NCT01084005) of 24 and ≥52 weeks, respectively, were analysed. RESULTS: A total of 247 elderly individuals [mean ± standard deviation (s.d.) age 74 ± 4 years, glycated haemoglobin (HbA1c) 8.2 ± 0.8%] on basal insulin (mean ± s.d. baseline dose 36 ± 25 IU/day) were identified. Alongside placebo-adjusted change in HbA1c with linagliptin of -0.77% [95% confidence interval (CI) -0.95 to 0.59; p < 0.0001] after 24 weeks, the hazard ratios (HRs) of both overall and confirmed hypoglycaemia [blood glucose ≤3.9 mmol/l (70 mg/dl)], were significantly lower with linagliptin than with placebo: HR 0.61 (95% CI 0.39-0.97) versus 0.59 (95% CI 0.37-0.94), respectively (both p < 0.05). Moreover, significantly less confirmed hypoglycaemia was present in linagliptin-treated patients with renal impairment [HR 0.45 (95% CI 0.27-0.76)], moderate hyperglycaemia [HbA1c 7.5 to <9.0%; HR 0.51 (95% CI 0.27-0.99)], lower fasting plasma glucose levels [<152 mg/dl; HR 0.49 (95% CI 0.28-0.86)] and those treated with higher insulin doses [insulin ≥35.6 IU/day; HR 0.46 (95% CI 0.23-0.91); p < 0.05 for all]. Severe hypoglycaemia was rare and the incidence was lower with linagliptin (0.8%) versus placebo (2.5%): HR 0.21 (95% CI 0.02-2.30). CONCLUSIONS: Despite improvements in hyperglycaemia and no relevant on-trial insulin dose reductions, adding linagliptin to basal insulin appears to decrease hypoglycaemia risk. The biological basis of this phenomenon warrants further research but may involve counter-regulatory effects of incretin hormones.

Efficacy, safety and tolerability of aleglitazar in patients with type 2 diabetes: pooled findings from three randomized phase III trials.

AIMS: To evaluate the potential efficacy, safety and tolerability of aleglitazar as monotherapy or add-on therapy to metformin or to a sulphonylurea (either alone or in combination with metformin). METHODS: We conducted a pooled analysis of data from three randomized phase III clinical trials of aleglitazar in patients with type 2 diabetes (n = 591). The three studies focused on: (i) aleglitazar alone; (ii) aleglitazar and metformin; and (iii) aleglitazar and sulphonylurea with or without metformin. Patients were randomized to 26 weeks' treatment with aleglitazar 150 µg/day or placebo. The primary endpoint was change in glycated haemoglobin (HbA1c) concentration from baseline to week 26. Secondary endpoints included changes in lipids, fasting plasma glucose and homeostatic model assessment of insulin resistance (HOMA-IR) at week 26. RESULTS: Reductions in HbA1c concentration from baseline to week 26 were statistically significantly greater with aleglitazar than with placebo. Aleglitazar treatment was associated with more beneficial changes in lipid profiles and HOMA-IR values than was placebo. Aleglitazar was generally well tolerated, with no reports of congestive heart failure. The incidence of peripheral oedema was similar in both groups. Change in body weight was +1.37 kg with aleglitazar and -0.53 kg with placebo. Hypoglycaemia was more frequently reported with aleglitazar (7.8%) than with placebo (1.7%), a result probably driven by the type of background medication. CONCLUSIONS: Development of aleglitazar was halted because of a lack of cardiovascular efficacy and peroxisome proliferator-activated receptor-related side effects in patients with type 2 diabetes post-acute coronary syndrome; however, in the present studies, aleglitazar was well tolerated and effective in improving HbA1c, insulin resistance and lipid variables.

Efficacy and safety of initial combination treatment with sitagliptin and pioglitazone--a factorial study.

AIM: To evaluate the efficacy and safety of initial combination therapy of sitagliptin 100 mg/day coadministered with all marketed doses of pioglitazone in patients with type 2 diabetes. METHODS: Patients with A1c ≥7.5 and ≤11.0% were randomized among seven arms that received, once daily, 100 mg sitagliptin alone; 15, 30 or 45 mg pioglitazone alone, or 100 mg sitagliptin plus 15, 30 or 45 mg pioglitazone for 54 weeks. The primary endpoint was change from baseline in A1c at week 24. Protocol-specified analyses compared combination therapies with monotherapies at respective dose-strengths and combination of sitagliptin plus pioglitazone 30 mg with pioglitazone 45 mg monotherapy. Post-hoc analyses compared sitagliptin plus pioglitazone 15 mg with pioglitazone monotherapy at the two higher doses. RESULTS: Initial combination therapy with sitagliptin and pioglitazone provided significantly greater reductions in A1c (0.4-0.7% differences) and other glycaemic endpoints than either monotherapy at the same doses. Combining sitagliptin with low-dose pioglitazone generally produced greater glycaemic improvements than higher doses of pioglitazone monotherapy (0.3-0.4% differences in A1c). Combination therapy was generally well tolerated; adverse events (AEs) of hypoglycaemia were reported with similar incidence (7.8-11.1%) in all treatment groups over the 54 weeks of study; oedema was reported in 0.5% of patients in the sitagliptin monotherapy group and 2.7-5.3% among pioglitazone-treated groups. Significant weight gain was observed in all combination-treated groups compared with the sitagliptin monotherapy group. CONCLUSIONS: Initial combination therapy with sitagliptin and pioglitazone provided better glycaemic control than either monotherapy and was generally well tolerated.

Effect of pioglitazone on body composition and bone density in subjects with prediabetes in the ACT NOW trial.

AIMS: This study examined the effects of pioglitazone on body weight and bone mineral density (BMD) prospectively in patients with impaired glucose tolerance as pioglitazone (TZD) increases body weight and body fat in diabetic patients and increases the risk of bone fractures. METHODS: A total of 71 men and 163 women aged 49.3 (10.7) years [mean (s.d.)]; body mass index (BMI), 34.5 (5.9) kg/m(2) were recruited at five sites for measurements of body composition by dual energy X-ray absorptiometry at baseline and at conversion to diabetes or study end, if they had not converted. RESULTS: Mean follow-up was 33.6 months in the pioglitazone group and 32.1 months in the placebo group. Body weight increased 4.63 ± 0.60 (m ± s.e.) kg in the pioglitazone group compared to 0.98 ± 0.62 kg in the PIO group (p < 0.0001). Body fat rose 4.89 ± 0.42 kg in the pioglitazone group compared to 1.41 ± 0.44 kg, (p < 0.0001) in placebo-treated subjects. The increase in fat was greater in legs and trunk than in the arms. BMD was higher in all regions in men and significantly so in most. PIO decreased BMD significantly in the pelvis in men and women, decreased BMD in the thoracic spine and ribs of women and the lumbar spine and legs of men. Bone mineral content also decreased significantly in arms, legs, trunk and in the total body. CONCLUSIONS: Pioglitazone increased peripheral fat more than truncal fat and decreased BMD in several regions of the body.

The incretin hormones: from scientific discovery to practical therapeutics.

The incretins are gut hormones secreted in response to nutrient/carbohydrate ingestion and act on the pancreatic beta cell to amplify glucose-stimulated insulin secretion. Incretin hormone-based treatments for patients with type 2 diabetes represent a major advance in diabetes therapeutics. The ability of the incretin agents (glucagon-like peptide 1 [GLP-1] agonists and dipeptidyl peptidase IV [DPP-4] inhibitors) to improve glycaemia with a low associated risk of hypoglycaemia, together with beneficial/neutral effects on body weight, offers a significant advantage for both patients and treating clinicians. In this edition of 'Then and Now,' it is useful to look back 25 years and reflect upon the developments in this field since Nauck and colleagues published two seminal papers. In 1986 they first documented a reduced incretin effect in patients with type 2 diabetes (Diabetologia 29:46-52), and then in 1993 they demonstrated that, in patients with poorly controlled type 2 diabetes, a single exogenous infusion of an incretin (GLP-1) increased insulin levels in a glucose-dependent manner and normalised fasting hyperglycaemia (Diabetologia 36:741-744). In the ensuing 26 years, progress in the field of incretin hormones has resulted in a greater understanding of the relative roles of GLP-1 and glucose-dependent insulinotropic polypeptide secretion and activity in the pathogenesis of type 2 diabetes and the important recognition that native GLP-1 is quickly degraded by the ubiquitous protease DPP-4. This has led to the development of GLP-1 agonists that are resistant to degradation by DPP-4 and of selective inhibitors of DPP-4 activity as therapeutic agents. GLP-1 agonists (exenatide and liraglutide) and DPP-4 inhibitors (sitagliptin, vildagliptin, saxagliptin and linagliptin) currently represent effective treatment options for patients with type 2 diabetes. Several additional agents are in the pipeline, including longer acting DPP-4-resistant GLP-1 agonists. More exciting, however, is the increasing recognition that the incretin agents have numerous extra-glycaemic effects that could translate into potential cardiovascular and other benefits.

Effects of colesevelam on glucose absorption and hepatic/peripheral insulin sensitivity in patients with type 2 diabetes mellitus.

AIM: Colesevelam lowers glucose and low-density lipoprotein cholesterol levels in patients with type 2 diabetes mellitus. This study examined the mechanisms by which colesevelam might affect glucose control. METHODS: In this 12-week, randomized, double-blind, placebo-controlled study, subjects with type 2 diabetes and haemoglobin A(1c) (HbA(1c)) ≥7.5% on either stable diet and exercise or sulphonylurea therapy were randomized to colesevelam 3.75 g/day (n = 16) or placebo (n = 14). Hepatic/peripheral insulin sensitivity was evaluated at baseline and at week 12 by infusion of (3) H-labelled glucose followed by a 2-step hyperinsulinemic-euglycemic clamp. Two 75-g oral glucose tolerance tests (OGTTs) were conducted at baseline, one with and one without co-administration of colesevelam. A final OGTT was conducted at week 12. HbA(1c) and fasting plasma glucose (FPG) levels were evaluated pre- and post-treatment. RESULTS: Treatment with colesevelam, compared to placebo, had no significant effects on basal endogenous glucose output, response to insulin or on maximal steady-state glucose disposal rate. At baseline, co-administration of colesevelam with oral glucose reduced total area under the glucose curve (AUC(g)) but not incremental AUC(g). At week 12, neither total AUC(g) nor incremental AUC(g) were changed from pre-treatment values in either group. Post-load insulin levels increased with colesevelam at 30 and 120 min, but these changes in total area under the insulin curve (AUC(i)) and incremental AUC(i) did not differ between groups. Both HbA(1c) and FPG improved with colesevelam, but treatment differences were not significant. CONCLUSIONS: Colesevelam does not affect hepatic or peripheral insulin sensitivity and does not directly affect glucose absorption.

Dapagliflozin, metformin XR, or both: initial pharmacotherapy for type 2 diabetes, a randomised controlled trial.

BACKGROUND: Combining metformin (XR) with dapagliflozin to initiate pharmacotherapy in patients with type 2 diabetes (T2D) and high baseline HbA1c may be advantageous. We conducted two randomised, double-blind, three-arm 24-week trials in treatment-naïve patients to compare dapagliflozin plus metformin, dapagliflozin alone and metformin alone. METHODS: Eligible patients had baseline HbA1c 7.5-12%. Each trial had three arms: dapagliflozin plus metformin, dapagliflozin monotherapy and metformin monotherapy. Dapagliflozin in combination and as monotherapy was dosed at 5 mg (Study 1) and 10 mg (Study 2). Metformin in combination and as monotherapy was titrated to 2000 mg. The primary endpoint was HbA1c change from baseline; secondary endpoints included change in fasting plasma glucose (FPG) and weight. RESULTS: In both trials, combination therapy led to significantly greater reductions in HbA1c compared with either monotherapy: -2.05 for dapagliflozin + metformin, -1.19 for dapagliflozin, and -1.35 for metformin (p < 0.0001) (Study 1); -1.98 for dapagliflozin + metformin, -1.45 for dapagliflozin and -1.44 for metformin (p < 0.0001) (Study 2). Combination therapy was statistically superior to monotherapy in reduction of FPG (p < 0.0001 for both studies); combination therapy was more effective than metformin for weight reduction (p < 0.0001). Dapagliflozin 10 mg was non-inferior to metformin in reducing HbA1c (Study 2). Events suggestive of genital infection were reported in 6.7%, 6.9% and 2.0% (Study 1) and 8.5%, 12.8% and 2.4% (Study 2) of patients in combination, dapagliflozin and metformin groups; events suggestive of urinary tract infection were reported in 7.7%, 7.9% and 7.5% (Study 1) and 7.6%, 11.0% and 4.3% (Study 2) of patients in the respective groups. No major hypoglycaemia was reported. CONCLUSION: In treatment-naïve patients with T2D, dapagliflozin plus metformin was generally well tolerated and effective in reducing HbA1c, FPG and weight. Dapagliflozin-induced glucosuria led to an increase in events suggestive of urinary tract and genital infections.

Liraglutide, a once-daily human glucagon-like peptide 1 analogue, provides sustained improvements in glycaemic control and weight for 2 years as monotherapy compared with glimepiride in patients with type 2 diabetes.

AIMS: Most treatments for type 2 diabetes fail over time, necessitating combination therapy. We investigated the safety, tolerability and efficacy of liraglutide monotherapy compared with glimepiride monotherapy over 2 years. METHODS: Participants were randomized to receive once-daily liraglutide 1.2 mg, liraglutide 1.8 mg or glimepiride 8 mg. Participants completing the 1-year randomized, double-blind, double-dummy period could continue open-label treatment for an additional year. Safety data were evaluated for the full population exposed to treatment, and efficacy data were evaluated for the full intention-to-treat (ITT) and 2-year completer populations. Outcome measures included change in glycosylated haemoglobin (HbA1c), fasting plasma glucose (FPG), body weight and frequency of nausea and hypoglycaemia. RESULTS: For patients completing 2 years of therapy, HbA1c reductions were -0.6% with glimepiride versus -0.9% with liraglutide 1.2 mg (difference: -0.37, 95% CI: -0.71 to -0.02; p = 0.0376) and -1.1% with liraglutide 1.8 mg (difference: -0.55, 95% CI: -0.88 to -0.21; p = 0.0016). In the ITT population, HbA1c reductions were -0.3% with glimepiride versus -0.6% with liraglutide 1.2 mg (difference: -0.31, 95% CI: -0.54 to -0.08; p = 0.0076) and -0.9% with liraglutide 1.8 mg (difference: -0.60, 95% CI: -0.83 to -0.38; p < 0.0001). For both ITT and completer populations, liraglutide was more effective in reducing HbA1c, FPG and weight. Over 2 years, rates of minor hypoglycaemia [self-treated plasma glucose <3.1 mmol/l (<56 mg/dl)] were significantly lower with liraglutide 1.2 mg and 1.8 mg compared with glimepiride (p < 0.0001). CONCLUSION: Liraglutide monotherapy for 2 years provides significant and sustained improvements in glycaemic control and body weight compared with glimepiride monotherapy, at a lower risk of hypoglycaemia.

Effects of intensive insulin therapy alone and in combination with pioglitazone on body weight, composition, distribution and liver fat content in patients with type 2 diabetes.

AIM: To evaluate the effects of intensive insulin therapy alone and with added pioglitazone on body weight, fat distribution, lean body mass (LBM) and liver fat in type 2 diabetic patients. METHODS: Twenty-five insulin-treated, obese patients with type 2 diabetes were randomized to addition of pioglitazone 45 mg (n = 12) or placebo (n = 13) and treated intensively for 12-16 weeks. Dual-energy X-ray absorptiometry/abdominal computed tomography scans were performed before/after treatment. LBM, visceral/subcutaneous adipose tissue (VAT/SAT) and liver/spleen (L/S) attenuation ratios were measured pre-/posttreatment (a ratio <1 represents fatty liver). RESULTS: Intensive insulin alone and insulin + pioglitazone significantly improved glycaemic control (7.8 ± 0.3 to 7.2 ± 0.3% and 7.6 ± 0.3 to 7.1 ± 0.4%, respectively). Body weight gain was greater with insulin + pioglitazone (4.9 ± 4.5 kg) versus insulin therapy alone (1.7 ± 0.7 kg). SAT increased significantly with pioglitazone + insulin therapy (393.9 ± 48.5 to 443.2 ± 56.7 cm(2) , p < 0.01) compared to a non-significant increase with insulin therapy alone (412.9 ± 42.5 to 420.8 ± 43.8 cm(2) ). VAT decreased non-significantly in both groups (240.3 ± 41.7 to 223.8 ± 38.1 cm(2) with insulin + pioglitazone and 266.6 ± 27.4 to 250.5 ± 22.2 cm(2) with insulin therapy). LBM increased significantly by 1.92 ± 0.74 kg with insulin + pioglitazone treatment. The L/S attenuation ratio in the placebo + insulin group decreased from 1.08 ± 0.1 to 1.04 ± 0.1 (p = ns) and increased from 1.00 ± 0.1 to 1.08 ± 0.05 (p = 0.06) in the pioglitazone + insulin group. CONCLUSIONS: Intensification of insulin therapy in type 2 diabetic patients causes modest weight gain and no change in body fat distribution, LBM or liver fat. In contrast, the addition of pioglitazone, at equivalent glycaemia, increases weight gain, fat mass and SAT; increases LBM and tends to decrease liver fat. These changes in fat distribution may contribute to the beneficial effects of pioglitazone, despite greater weight gain.

Impact of olanzapine or risperidone treatment on insulin sensitivity in schizophrenia or schizoaffective disorder.

AIM: To assess changes in insulin sensitivity in non-diabetic adults with schizophrenia or schizoaffective disorder treated with olanzapine or risperidone. METHODS: One hundred and thirty patients were randomly assigned to 12 weeks double-blind treatment with olanzapine or risperidone. Insulin sensitivity was measured using a two-step euglycaemic, hyperinsulinaemic clamp procedure. Whole-body adiposity was measured using dual-energy X-ray absorptiometry. The primary endpoint was the within-group change from baseline in insulin sensitivity normalized to fat-free mass (M(ffm) /I) during the clamp procedure's low-insulin phase, using an analysis of covariance model including the covariate weight change. RESULTS: Forty-one olanzapine-treated and 33 risperidone-treated patients completed baseline and endpoint clamp measurements. Mean M(ffm) /I during the low-insulin phase declined 9.0% (p = 0.226) in olanzapine-treated patients and 13.2% (p = 0.047) in risperidone-treated patients (between-group difference p = 0.354). During the high-insulin phase, M(ffm) /I declined 10.4% (p = 0.036) in olanzapine-treated patients and 2.1% (p = 0.698) in risperidone-treated patients (between-group difference p = 0.664). Changes in M(ffm) /I correlated inversely with changes in body weight and adiposity, which were generally higher in olanzapine-treated patients. Significant within-group increases in fasting glucose, but not haemoglobin A1c (HbA1c), were observed during olanzapine treatment. The fasting glucose change was not correlated with M(ffm) /I changes. CONCLUSIONS: Small, but statistically significant, decrements in insulin sensitivity were observed in olanzapine- and risperidone-treated patients at 1 of 2 insulin doses tested. Significant increases in fasting glucose and insulin and total fat mass were observed only in olanzapine-treated patients. Changes in insulin sensitivity correlated significantly with changes in weight or adiposity, but not with changes in glucose.

Effects of saxagliptin on ß-cell stimulation and insulin secretion in patients with type 2 diabetes.

AIM: To study the effect of dipeptidyl peptidase-4 (DPP-4) inhibition with saxagliptin on ß-cell function as reflected by the stimulated insulin secretion rate after an enteral glucose load in patients with type 2 diabetes. METHODS: Patients in this randomized, parallel-group, double-blind, placebo-controlled study were drug-naïve, aged 43-69 years, with baseline haemoglobin A1c (HbA1c) 5.9-8.1%. Twenty patients received saxagliptin 5 mg once daily; 16 received placebo. Patients were assessed at baseline and week 12 by intravenous hyperglycaemic clamp (0-180 min, fasting state), and intravenous-oral hyperglycaemic clamp (180-480 min, postprandial state) following oral ingestion of 75 g glucose. Primary and secondary endpoints were percent changes from baseline in insulin secretion during postprandial and fasting states, respectively. Insulin secretion was calculated by C-peptide deconvolution. RESULTS: After 12 weeks, saxagliptin significantly increased insulin secretion percent change from baseline during the postprandial state by an 18.5% adjusted difference versus placebo (p = 0.04), an improvement associated with increased peak plasma concentrations of intact glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide. In the fasting state, saxagliptin significantly increased insulin secretion by a 27.9% adjusted difference versus placebo (p = 0.02). Saxagliptin also improved glucagon area under the curve in the postprandial state (adjusted difference -21.8% vs. placebo, p = 0.03). CONCLUSIONS: DPP-4 inhibition with saxagliptin improves pancreatic ß-cell function in postprandial and fasting states, and decreases postprandial glucagon concentration. Given the magnitude of enhancement of the insulin response in the fasting state, further study into the effect of DPP-4 inhibition on the ß-cell is warranted.

Determinants of glucose tolerance in impaired glucose tolerance at baseline in the Actos Now for Prevention of Diabetes (ACT NOW) study.

AIMS/HYPOTHESIS: The aim of the study was to examine the determinants of oral glucose tolerance in 602 persons with impaired glucose tolerance (IGT) who participated in the Actos Now for Prevention of Diabetes (ACT NOW) study. METHODS: In addition to the 602 IGT participants, 115 persons with normal glucose tolerance (NGT) and 50 with impaired fasting glucose (IFG) were identified during screening and included in this analysis. Insulin secretion and insulin sensitivity indices were derived from plasma glucose and insulin during an OGTT. The acute insulin response (AIR) (0-10 min) and insulin sensitivity (S(I)) were measured with the frequently sampled intravenous glucose tolerance test (FSIVGTT) in a subset of participants. RESULTS: At baseline, fasting plasma glucose, 2 h postprandial glucose (OGTT) and HbA(1c) were 5.8 +/- 0.02 mmol/l, 10.5 +/- 0.05 mmol/l and 5.5 +/- 0.04%, respectively, in participants with IGT. Participants with IGT were characterised by defects in early (DeltaI (0-30)/DeltaG (0-30) x Matsuda index, where DeltaI is change in insulin in the first 30 min and DeltaG is change in glucose in the first 30 min) and total (DeltaI(0-120)/DeltaG(0-120) x Matsuda index) insulin secretion and in insulin sensitivity (Matsuda index and S(I)). Participants with IGT in whom 2 h plasma glucose was 7.8-8.3 mmol/l had a 63% decrease in the insulin secretion/insulin resistance (disposition) index vs participants with NGT and this defect worsened progressively as 2 h plasma glucose rose to 8.9-9.94 mmol/l (by 73%) and 10.0-11.05 mmol/l (by 80%). The Matsuda insulin sensitivity index was reduced by 40% in IGT compared with NGT (p < 0.005). In multivariate analysis, beta cell function was the primary determinant of glucose AUC during OGTT, explaining 62% of the variance. CONCLUSION: Our results strongly suggest that progressive beta cell failure is the main determinant of progression of NGT to IGT.

Effects of intensive insulin therapy alone and with added pioglitazone on renal salt/water balance and fluid compartment shifts in type 2 diabetes.

OBJECTIVE: To evaluate the effects of intensive insulin therapy alone or with added pioglitazone on renal salt/water balance and body fluid compartment shifts in type 2 diabetes. METHODS: A total of 25 insulin-treated, obese patients with type 2 diabetes were randomized to pioglitazone 45 mg (n = 12) or placebo (n = 13) and treated intensively for 12-16 weeks to achieve equivalent glycaemic control. We measured total body water (TBW) and extracellular/intracellular fluid by bioimpedance analysis; plasma/RBC volume with I(131)albumin; sodium handling by fractional excretion of sodium/lithium (FeNa/FeLi) and other renal/hormonal parameters. RESULTS: Intensification of insulin therapy and the addition of pioglitazone significantly improved glycaemia (HbA1C 7.8-7.2% and 7.6-7.1%) and increased body weight (1.7 and 4.9 kg) respectively. TBW increased 1.7 l with insulin alone (65% intracellular) and 1.6 l with added pioglitazone (75% extracellular) (p = 0.06 and 0.09 respectively). Plasma volume increased 0.2 +/- 0.1 l with insulin alone (p = 0.05) and 0.4 +/- 0.1 l with added pioglitazone (p < 0.05). Extravascular, extracellular (interstitial) fluid increased significantly and more with added pioglitazone (0.8 +/- 0.2 l, p < 0.01) than with insulin alone (0.4 +/- 0.2 l, p = ns). At steady-state, FeLi (marker of proximal-tubular sodium delivery to the distal nephron) increased significantly with added pioglitazone (12.4 +/- 1.3 to 18.0 +/- 3.2%) vs. no significant change with insulin alone (15.4 +/- 1.2 to 14.5 +/- 2.3%). There were no significant changes in the other parameters. CONCLUSION: In intensively insulin-treated obese type 2 diabetic patients, at equivalent glycaemic control, the addition of pioglitazone causes greater weight gain, but a similar increase in body water that is mainly extracellular and interstitial compared with intracellular increase with insulin therapy alone. Pioglitazone also increases the filtered load of sodium reabsorbed at the distal nephron with no net change in FeNa.

Is adiposopathy (sick fat) an endocrine disease?

OBJECTIVE: To review current consensus and controversy regarding whether obesity is a 'disease', examine the pathogenic potential of adipose tissue to promote metabolic disease and explore the merits of 'adiposopathy' and 'sick fat' as scientifically and clinically useful terms in defining when excessive body fat may represent a 'disease'. METHODS: A group of clinicians and researchers, all with a background in endocrinology, assembled to evaluate the medical literature, as it pertains to the pathologic and pathogenic potential of adipose tissue, with an emphasis on metabolic diseases that are often promoted by excessive body weight. RESULTS: The data support pathogenic adipose tissue as a disease. Challenges exist to convince many clinicians, patients, healthcare entities and the public that excessive body fat is often no less a 'disease' than the pathophysiological consequences related to anatomical abnormalities of other body tissues. 'Adiposopathy' has the potential to scientifically define adipose tissue anatomic and physiologic abnormalities, and their adverse consequences to patient health. Adiposopathy acknowledges that when positive caloric balance leads to adipocyte hypertrophy and visceral adiposity, then this may lead to pathogenic adipose tissue metabolic and immune responses that promote metabolic disease. From a patient perspective, explaining how excessive caloric intake might cause fat to become 'sick' also helps provide a rationale for patients to avoid weight gain. Adiposopathy also better justifies recommendations of weight loss as an effective therapeutic modality to improve metabolic disease in overweight and obese patients. CONCLUSION: Adiposopathy (sick fat) is an endocrine disease.

Reversibility of defective adipocyte insulin receptor kinase activity in non-insulin-dependent diabetes mellitus. Effect of weight loss.

Insulin-stimulated kinase activity of adipocyte-derived insulin receptors is reduced in subjects with non-insulin-dependent diabetes mellitus (NIDDM) but normal in obese nondiabetics. To assess the reversibility of the kinase defect in NIDDM, insulin receptor kinase activity was measured before and after weight loss in 10 NIDDM and 5 obese nondiabetic subjects. Peripheral insulin action was also assessed in vivo by glucose disposal rates (GDR) measured during a hyperinsulinemic (300 mU/M2 per min) euglycemic clamp. In the NIDDMs, insulin receptor kinase activity was reduced by 50-80% and rose to approximately 65-90% (P less than 0.01) of normal after 13.2 +/- 2.0 kg (P less than 0.01) weight loss; comparable weight loss (18.2 +/- 1.5 kg, P less than 0.01) in the nondiabetics resulted in no significant change in insulin receptor kinase activity. Relative to GDR measured in lean nondiabetics, GDR in the NIDDMs was 35% of normal initially and 67% (P less than 0.01) of normal after diet therapy; weight loss in the nondiabetics resulted in an increase in GDR from 53 to 76% of normal (P less than 0.05). These results indicate that the insulin receptor kinase defect that is present in NIDDM is largely reversible after weight reduction. In contrast, the improvement in GDR, in the absence of any change in insulin receptor kinase activity in the nondiabetics, suggests that the main cause of insulin resistance in obesity lies distal to the kinase.

Intracellular glucose oxidation and glycogen synthase activity are reduced in non-insulin-dependent (type II) diabetes independent of impaired glucose uptake.

To examine whether reduced rates of oxidative (Gox) and non-oxidative (Nox) glucose metabolism in non-insulin-dependent diabetes mellitus (NIDDM) are due to reduced glucose uptake, intrinsic defects in intracellular glucose metabolism or increased fat oxidation (Fox), indirect calorimetry was performed at similar glucose uptake rates in eight nonobese NIDDM and eight comparable nondiabetic subjects. Three glucose clamp studies were performed: one in the nondiabetic and two in the NIDDM subjects. In the nondiabetic subjects, glucose uptake was increased to 7.62 +/- 0.62 mg/kg of fat-free mass (FFM) per min by increasing serum insulin to 309 pmol/liter at a glucose concentration of 5.1 mmol/liter. By raising the concentration of either serum glucose or insulin fourfold in the NIDDM subjects, glucose uptake was matched to nondiabetic subjects (8.62 +/- 0.49 and 8.59 +/- 0.51 mg/kg FFM per min, respectively, P = NS). Skeletal muscle glycogen synthase activity and plasma lactate levels were measured to characterize Nox. When glucose uptake was matched to nondiabetics by hyperglycemia or hyperinsulinemia, Gox was reduced by 26-28% in NIDDM (P less than 0.025) whereas Fox was similar. Nox was greater in NIDDM (P less than 0.01) and was accompanied by increases in circulating lactate levels. Glycogen synthase activity was reduced by 41% (P less than 0.025) when glucose uptake was matched by hyperglycemia. Glycogen synthase activity was normalized in NIDDM, however, when glucose uptake was matched by hyperinsulinemia. Therefore, a defect in Gox exists in nonobese NIDDM subjects which cannot be overcome by increasing glucose uptake or insulin. Since both glucose uptake and Fox were similar in the two subject groups these factors were not responsible for reduced Gox. Increased Nox in NIDDM is primarily into lactate. Reduced glycogen synthase activity in NIDDM is independent of glucose uptake but can be overcome by increasing the insulin concentration.

Multiple defects in muscle glycogen synthase activity contribute to reduced glycogen synthesis in non-insulin dependent diabetes mellitus.

To define the mechanisms of impaired muscle glycogen synthase and reduced glycogen formation in non-insulin dependent diabetes mellitus (NIDDM), glycogen synthase activity was kinetically analyzed during the basal state and three glucose clamp studies (insulin approximately equal to 300, 700, and 33,400 pmol/liter) in eight matched nonobese NIDDM and eight control subjects. Muscle glycogen content was measured in the basal state and following clamps at insulin levels of 33,400 pmol/liter. NIDDM subjects had glucose uptake matched to controls in each clamp by raising serum glucose to 15-20 mmol/liter. The insulin concentration required to half-maximally activate glycogen synthase (ED50) was approximately fourfold greater for NIDDM than control subjects (1,004 +/- 264 vs. 257 +/- 110 pmol/liter, P less than 0.02) but the maximal insulin effect was similar. Total glycogen synthase activity was reduced approximately 38% and glycogen content was approximately 30% lower in NIDDM. A positive correlation was present between glycogen content and glycogen synthase activity (r = 0.51, P less than 0.01). In summary, defects in muscle glycogen synthase activity and reduced glycogen content are present in NIDDM. NIDDM subjects also have less total glycogen synthase activity consistent with reduced functional mass of the enzyme. These findings and the correlation between glycogen synthase activity and glycogen content support the theory that multiple defects in glycogen synthase activity combine to cause reduced glycogen formation in NIDDM.

Glucose transport in cultured human skeletal muscle cells. Regulation by insulin and glucose in nondiabetic and non-insulin-dependent diabetes mellitus subjects.

A primary human skeletal muscle culture (HSMC) system, which retains cellular integrity and insulin responsiveness for glucose transport was employed to evaluate glucose transport regulation. As previously reported, cells cultured from non-insulin-dependent diabetic (NIDDM) subjects displayed significant reductions in both basal and acute insulin-stimulated transport compared to nondiabetic controls (NC). Fusion/differentiation of NC and NIDDM HSMC in elevated media insulin (from 22 pM to 30 microM) resulted in increased basal transport activities but reduced insulin-stimulated transport, so that cells were no longer insulin responsive. After fusion under hyperinsulinemic conditions, GLUT1 protein expression was elevated in both groups while GLUT4 protein level was unaltered. Fusion of HSMC under hyperglycemic conditions (10 and 20 mM) decreased glucose transport in NC cells only when combined with hyperinsulinemia. Hyperglycemia alone down-regulated transport in HSMC of NIDDM, while the combination of hyperglycemia and hyperinsulinemia had greater effects. In summary: (a) insulin resistance of glucose transport can be induced in HSMC of both NC and NIDDM by hyperinsulinemia and is accompanied by unaltered GLUT4 but increased GLUT1 levels; and (b) HSMC from NIDDM subjects demonstrate an increased sensitivity to impairment of glucose transport by hyperglycemia. These results indicate that insulin resistance in skeletal muscle can be acquired in NC and NIDDM from hyperinsulinemia alone but that NIDDM is uniquely sensitive to the additional influence of hyperglycemia.

In vivo stimulation of the insulin receptor kinase in human skeletal muscle. Correlation with insulin-stimulated glucose disposal during euglycemic clamp studies.

To assess the relationship between insulin receptor (IR) kinase activity and insulin action in vivo in humans, we measured glucose disposal rates (GDR) during a series of euglycemic clamp studies. Simultaneously, we measured IR kinase activity in IRs extracted from skeletal muscle obtained by needle biopsy at the end of each clamp. By preserving the phosphorylation state of the receptors as it existed in vivo at the time of biopsy, we could correlate GDR and IR kinase in skeletal muscle. Eight nondiabetic, nonobese male subjects underwent studies at insulin infusion rates of 0, 40, 120, and 1,200 mU/m2 per min. Kinase activity, determined with receptors immobilized on insulin agarose beads, was measured at 0.5 microM ATP, with 1 mg/ml histone, followed by SDS-PAGE. Insulin increased GDR approximately sevenfold with a half-maximal effect at approximately 100 microU/ml insulin and a maximal effect by approximately 400 microU/ml. Insulin also increased IR kinase activity; the half-maximal effect occurred at approximately 500-600 microU/ml insulin with a maximal 10-fold stimulation over basal. Within the physiologic range of insulin concentrations, GDR increased linearly with kinase activation (P less than 0.0006); at supraphysiologic insulin levels, this relationship became curvilinear. Half-maximal and maximal insulin-stimulated GDR occurred at approximately 20 and approximately 50% maximal kinase activation, respectively. These results are consistent with a role of the kinase in insulin action in vivo. Furthermore, they demonstrate the presence of a large amount of "spare kinase" for glucose disposal.