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.

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.

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.

Effects of saxagliptin on β-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 β-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 β-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 β-cell is warranted.

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 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.

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.

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.

GSK-3beta and control of glucose metabolism and insulin action in human skeletal muscle

The involvement of the beta-isoform of glycogen synthase kinase (GSK-3) in glucose metabolism and insulin action was investigated in cultured human skeletal muscle cells. A 60% reduction in GSK-3beta protein expression was attained by treatment with siRNA; GSK-3alpha expression was unaltered. GSK-3beta knockdown did not influence total glycogen synthase (GS) activity, but increased the phosphorylation-dependent activity (fractional velocity-FV) in the basal state. Insulin responsiveness of GSFV was doubled by GSK-3beta knockdown (p<0.05). Basal rates of glucose uptake (GU) were not significantly influenced by GSK-3beta knockdown, while insulin stimulation of GU was increased. Improvements in insulin action on GS and GU did not involve changes in protein expression of either IRS-1 or Akt 1/2. Maximal insulin stimulation of phosphorylation of Akt was unaltered by GSK-3beta knockdown. Unlike GSK-3alpha, GSK-3beta directly regulates both GS activity in the absence of added insulin and through control of insulin action.

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.

Effects of the long-acting insulin analog insulin glargine on cultured human skeletal muscle cells: comparisons to insulin and IGF-I

The aim of this study was to determine whether the long-acting insulin analog, insulin glargine, behaves like human insulin for metabolic and mitogenic responses in differentiated cultured human skeletal muscle cells from nondiabetic and diabetic subjects. Human insulin and insulin glargine were equipotent in their ability to compete for [(125)I]insulin binding. Insulin glargine displaced [(125)I]IGF-I from the IGF-I-binding site with approximately 0.5% the potency of IGF-I. In nondiabetic muscle cells, all three ligands stimulated glucose uptake similarly, whereas the sensitivity of glucose uptake was greatest in response to IGF-I and lower and equal for human insulin and insulin glargine. In diabetic muscle cells, the final responsiveness of glucose uptake was greatest for IGF-I and equivalent for human insulin and insulin glargine; sensitivities were the same as those for nondiabetic cells. Thymidine uptake into DNA was stimulated foremost by IGF-I, whereas human insulin and insulin glargine showed equivalent, but greatly reduced, sensitivities and potencies (<1% IGF-I). Stimulation of Akt phosphorylation was slightly more responsive to IGF-I compared with human insulin and insulin glargine, with sensitivities similar to glucose uptake stimulation. We conclude that in human skeletal muscle cells, insulin glargine is equivalent to human insulin for metabolic responses and does not display augmented mitogenic effects.

Verbal working memory storage and processing deficits in HIV-1 asymptomatic and symptomatic individuals

BACKGROUND

Verbal working memory (WM), which relies on intact functioning of frontostriatal circuits, has been suggested as a cognitive domain that is preferentially affected in HIV-1 infection. Although several studies have found WM impairments in HIV-1 infected patients, Baddeley's classic WM model has not been studied extensively in this population.

METHODS

We used two cognitive neuropsychological approaches to examine verbal WM deficits in 18 HIV-1 seronegative, 16 HIV-1 asymptomatic, and 20 HIV-1 symptomatic patients. First, based on Baddeley's WM model of the Phonological Loop, we used the phonological similarity effect and the irrelevant speech effect to evaluate each individual's phonological store, and the word-length effect and the articulatory suppression effect to evaluate the articulatory control process. Secondly, an individual differences approach, which focuses on the capacity limitation of the WM system and potentially integrates the functions of Baddeley's Central Executive component with the Phonological Loop, was adopted. We evaluated each patient's simultaneous storage and processing of auditory material using the Verbal Memory Span test.

RESULTS

The HIV-1 symptomatic individuals, but not the HIV-1 asymptomatic subjects, demonstrated impaired short-term storage of verbal material in the phonological store on Baddeley's measures. Although the HIV-1 asymptomatic and symptomatic subjects demonstrated intact rehearsal of speech-based material in the articulatory control process, both groups demonstrated impairment on the Verbal Memory Span test.

CONCLUSIONS

These findings suggest that deficits in simultaneous short-term storage and processing occur during both early and later stages of HIV-1 infection.

Effect of pravastatin-to-simvastatin conversion on low-density-lipoprotein cholesterol

The effects of a pravastatin-to-simvastatin conversion program on low-density-lipoprotein (LDL) cholesterol levels were studied. Patients receiving pravastatin at a Veterans Affairs medical center were switched to simvastatin beginning in 1997. The dosage of simvastatin was based on the additional percent reduction in LDL cholesterol needed to achieve the goal specified by the National Cholesterol Education Program. The primary endpoint was the change in the percentage of patients meeting their LDL cholesterol goal at baseline and follow-up. Changes in lipid indices, the relative risk (RR) of coronary heart disease (CHD), and program costs were also evaluated. A total of 1032 patients completed the program. The mean +/- S.D. daily doses of pravastatin and simvastatin were 25.2 +/- 11.3 and 22.7 +/- 13.3 mg, respectively. Median baseline and follow-up LDL cholesterol concentrations were 116 and 99 mg/dL, respectively (p < 0.001). Overall, 44% of the patients met their LDL cholesterol goal while taking pravastatin, compared with 69% after conversion to simvastatin (p < 0.001). The predicted mean RR of a future CHD event (based on changes in serum lipids) was 0.87 (95% confidence interval, 0.83-0.91) four years after conversion. The total cost of the program was $40,644 in the first year, and there was a net saving thereafter. Therapeutic interchange between pravastatin and simvastatin increased the number of patients meeting their LDL cholesterol goal.

Impaired muscle glycogen synthase in type 2 diabetes is associated with diminished phosphatidylinositol 3-kinase activation

Insulin signaling pathways potentially involved in regulation of skeletal muscle glycogen synthase were compared in differentiated human muscle cell cultures from nondiabetic and type 2 diabetic patients. Insulin stimulation of glycogen synthase activity as well as phosphorylation of MAPK, p70 S6 kinase, and protein kinase B (Akt) were blocked by the phosphatidylinositol 3-kinase inhibitors wortmannin (50 nM) and LY294002 (10 microM). In contrast to lean and obese nondiabetic subjects, where there were minimal effects (15-20% inhibition), insulin stimulation of glycogen synthase in muscle cultures from diabetic subjects was greatly diminished ( approximately 75%) by low concentrations of wortmannin (25 nM) or LY294002 (2 microM). This increased sensitivity of diabetic muscle to impairment of insulin-stimulated glycogen synthase activity occurs together with diminished insulin-stimulation (by 40%) of IRS-1-associated phosphatidylinositol 3-kinase activity in the same cells. Protein expression of IRS-1, p85, p110, Akt, p70 S6 kinase, and MAPK were normal in diabetic cells, as was insulin-stimulated phosphorylation of Akt, p70 S6 kinase, and MAPK. These studies indicate that, despite prolonged growth and differentiation of diabetic muscle under normal metabolic culture conditions, defects of insulin-stimulated phosphatidylinositol 3-kinase and glycogen synthase activity in diabetic muscle persist, consistent with intrinsic (rather than acquired) defects of insulin action.

Effects of home environment, socioeconomic status, and health status on cognitive functioning in children with HIV-1 infection

OBJECTIVE

To investigate the effects of the home environment, socioeconomic status (SES), and health status on cognitive functioning in a sample of children with HIV-1 infection in a cross-sectional study.

METHODS

Forty-three caregivers and their children (2.5 to 12 years) participated. Caregivers completed two self-report measures of the home environment that included questions regarding the organization of the environment, play materials, parental involvement, variety of stimulation, and parental attitudes toward the provision of a cognitively stimulating environment. Cognitive functioning was assessed using a standardized intelligence (IQ) test. Children's medical charts were reviewed for HIV-1 classification status (CDC, 1994), CD4 cell counts, and current medication.

RESULTS

This study revealed two primary findings. First, measures of the home environment mediated the association between SES and child IQ. Second, measures of the home environment had a stronger association with child IQ during the advanced stages of disease than earlier stages of disease.

CONCLUSIONS

The home environment is associated with cognitive functioning among children with HIV-1 infection. Moreover, interventions aimed at enhancing the quality of the home environment may have a positive impact on these children's cognitive development.

Retinoid X receptor expression in skeletal muscle of nondiabetic, obese and type 2 diabetic individuals

Retinoid X receptor (RXR) is a nuclear receptor that functions as an obligate heterodimeric partner of peroxisome proliferator-activator receptor (PPAR). Studies have shown that the alpha isoform of RXR and PPARgamma act synergistically to regulate gene expression and insulin action. The aim of the current study was to compare the expression and regulation of RXR in the primary insulin-sensitive tissue, skeletal muscle, of various degrees of insulin-resistant states including obese type 2 diabetic (T2D), obese nondiabetic (OND), and lean nondiabetic (LND) subjects. Insulin action/resistance was determined by a 3-hour hyperinsulinemic, euglycemic (5.0 to 5.5 mmol/L) clamp. Percutaneous biopsy of the vastus lateralis muscle was performed before and after the clamp. RXRalpha mRNA was measured using a quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay, while protein was determined by Western blotting. All 3 isoforms of RXR, alpha, beta, and gamma, were present in skeletal muscle. Protein expression of RXR isoforms did not differ between groups; RXR alpha mRNA was also similar between groups. Neither RXR alpha mRNA, RXR -beta nor -gamma protein displayed significant relationships with any of the clinical or laboratory parameters measured, including insulin sensitivity. RXR alpha exhibited a negative correlation with free fatty acids levels (r, -.42, P <.05). There was also no relationship between RXR alpha and PPARgamma protein levels. RXR alpha mRNA was unaltered following insulin infusion. We conclude that RXR isoform (alpha, beta, gamma) expression is not tightly controlled by insulin, insulin resistance or type 2 diabetes. Instead, RXR isoforms are likely constitutive proteins or controlled by other factors.

New oral therapies for type 2 diabetes mellitus: The glitazones or insulin sensitizers

Type 2 diabetes mellitus is a growing problem not only in the United States but also across the world. There is now strong evidence that intensive control of blood glucose can significantly reduce and retard the microvascular complications of retinopathy, nephropathy, and neuropathy. Ultimately however, up to 80% of type 2 diabetics die from macrovascular cardiovascular disease. This increased incidence of atherosclerotic disease is intricately associated with insulin resistance, which is a major pathophysiologic abnormality in type 2 diabetes. There is strong evidence that insulin resistance is involved in the development of not only hyperglycemia, but also dyslipidemia, hypertension, hypercoagulation, vasculopathy, and ultimately atherosclerotic cardiovascular disease. This cluster of metabolic abnormalities has been termed the insulin resistance or cardiovascular dysmetabolic syndrome. The thiazolidinediones (rosiglitazone and pioglitazone), a new class of oral antidiabetic agents, are "insulin sensitizers" and exert direct effects on the mechanisms of insulin resistance. These effects not only improve insulin sensitivity and glycemic control with reduced insulin requirements, but also have potentially favorable effects on other components of the cardiovascular dysmetabolic syndrome. Long-term studies are needed to determine whether the insulin-sensitizing effects of the glitazones can prevent or delay premature atherosclerotic cardiovascular disease, morbidity, and death.

Peroxisome proliferator-activated receptor (PPAR) gamma and retinoid X receptor (RXR) agonists have complementary effects on glucose and lipid metabolism in human skeletal muscle

AIMS/HYPOTHESIS

To determine the independent and potentially synergistic effects of agonists for PPAR gamma and RXR on glucose and lipid metabolism, as well as gene expression, in human skeletal muscle cell cultures.

METHODS

Fully differentiated myotubes from non-diabetic subjects and subjects with Type II (non-insulin-dependent) diabetes mellitus were chronically (2 days) treated with LG100268 (4 mumol/l), an RXR agonist, or troglitazone (4.6 mumol/l), a PPAR gamma agonist or both, to determine the effects on glucose uptake, activity of glycogen synthase and palmitate oxidation.

RESULTS

The combination of both agents increased glucose uptake (60 +/- 9% compared to control subjects) but not either agent alone (16 +/- 9 and 26 +/- 6% for LG100268 and troglitazone, p < 0.01, respectively). The agent LG100268 alone had little effect on the activity of glycogen synthase but the effect of troglitazone increased with LG100268 (p < 0.05). With chronic exposure, LG100268 upregulated palmitate oxidation (53 +/- 12% increase, p < 0.005), in a way similar to troglitazone (68 +/- 23%, p < 0.005). Synergism was observed when both agonists were combined (146 +/- 38%, p < 0.005 vs either agent alone). Treatment with either agent led to about a twofold increase in the expression of fatty acid transporter (FAT/CD36). Troglitazone upregulated PPAR gamma protein expression, whereas LG100268 had no effect. Furthermore, neither LG100268 nor troglitazone had any effect on the protein expression of RXR isoforms or PPAR alpha.

CONCLUSION/INTERPRETATION

Co-activation of PPAR gamma and RXR results in additive or synergistic effects on glucose and lipid metabolism in skeletal muscle, but unlike troglitazone, LG100268 does not alter expression of its own receptor.

Early alteration in glomerular reserve in humans at genetic risk of essential hypertension: mechanisms and consequences

Essential hypertension has a familial predisposition, but the phenotype of elevated blood pressure has delayed penetrance. Because the kidney is a crucial determinant of blood pressure homeostasis, we studied early glomerular alterations in still-normotensive young subjects at genetic risk of hypertension. Thirty-nine normotensive adults (mean age 29 to 31 years), stratified by genetic risk (parental family history [FH]) of hypertension (26 with positive FH [FH+], 13 with negative FH [FH-]), underwent intravenous infusion of mixed amino acids. Before and during amino acid administration, we measured glomerular filtration rate (GFR), putative second messengers of amino acids (nitric oxide [NO.] metabolites and cGMP), serum insulin and amino acid concentrations, and the FE(Li)+ as an index of renal proximal tubular reabsorption. The FH+ group had a blunted GFR rise in response to amino acids (2.43+/-8.16% versus 31.0+/-13.4% rise, P:=0.0126). The amino acid-induced change in GFR correlated (r=0.786, P:<0.01) with the change in urinary NO. metabolite excretion; a diminished rise in urinary NO. metabolite excretion in the FH+ group (P:=0.0105) suggested a biochemical mechanism for the different GFR responses between FH groups: a relative inability to convert arginine to NO. The FH+ group had a far lower initial cGMP excretion at baseline (261+/-21.1 versus 579+/-84.9 nmol. h(-1)/1.73 m(2), P:=0.001), although cGMP did not change during the amino acid infusion (P:=0.703). FH status, baseline GFR, and baseline serum insulin jointly predicted GFR response to amino acids (P:=0.0013), accounting for approximately 45% of the variance in GFR response. Decline in FE(Li)+, an inverse index of proximal tubular reabsorption, paralleled increase in GFR (r=-0.506, P:=0.01), suggesting differences in proximal tubular reabsorption during amino acids between the FH groups. GFR response to amino acid infusion was blunted in the FH+ group despite significantly higher serum concentrations of 6 amino acids (arginine, isoleucine, leucine, methionine, phenylalanine, and valine) in the FH+ group, suggesting a novel form of insulin resistance (to the amino acid-translocating action of insulin) in FH+ subjects. We conclude that blunted glomerular filtration reserve in response to amino acids is an early-penetrance phenotype seen even in still-normotensive subjects at genetic risk of hypertension and is linked to impaired formation of NO. in the kidney. Corresponding changes in GFR and fractional excretion of Li(+) suggest that altered proximal tubular reabsorption after amino acids is an early pathophysiologic mechanism. Resistance to the amino acid-translocating actions of insulin may play a role in the biological response to amino acids in this setting. This glomerular reserve phenotype may be useful in genetic studies of renal traits preceding or predisposing to hypertension.

Pharmacodynamic and pharmacokinetic properties of a premixed 85/15 human insulin preparation

BACKGROUND

Many patients with diabetes use mixtures of fast-acting (regular human) insulin and intermediate-acting (neutral protamine Hagedorn [NPH]) insulin to control their blood glucose levels. Premixed insulin is available in a 70%/30% mixture and a 50%/50% mixture of NPH/regular human insulin. For some patients, however, a premixed formulation containing > or =30% regular human insulin can provide too much fast-acting insulin, potentially causing an increased risk for hypoglycemia in the early hours after injection.

OBJECTIVE

The pharmacokinetic and pharmacodynamic properties of a premixed formulation of 85% NPH insulin and 15% regular human insulin (85/15) were compared with those of a premixed 70%/30% NPH/regular human insulin preparation and 100% NPH insulin.

METHODS

A 12-hour euglycemic clamp approach was used to assess glucose-lowering effects and serum insulin levels in 36 healthy male volunteers in a single-dose (0.5 U/kg), randomized, double-blind, 3-period, crossover study.

RESULTS

From 0 to 8 hours after injection, the glucose-lowering effects and serum insulin levels for the 85/15 premixed insulin preparation were significantly greater than those for NPH insulin (P < or = 0.05) but significantly less than those for the 70/30 premixed insulin preparation. The mean (+/- SEM) maximum glucose infusion rate (GIRmax) was 8+/-0.6 mg/(min x kg) for the 85/15 preparation, 7+/-0.6 mg/(min x kg) for NPH, and 9+/-0.6 mg/(min x kg) for the 70/30 preparation, with time to peak GIR (tmax(GIR)) occurring at 313, 360, and 272 minutes, respectively. Time to peak insulin levels did not differ significantly for the 3 preparations, but maximum serum insulin concentration (Cmax(ins)) was significantly different between the groups (70/30 premix: 54+/-2.2 microU/mL; 85/15 premix: 44+/-2.4 microU/mL; NPH: 35+/-1.7 microU/mL). Glucodynamic effect and serum insulin levels did not differ significantly among preparations during the interval from 8 to 12 hours after injection. Mean serum C-peptide levels ranged from -0.6 to 1.0 ng/mL for each preparation during the 12-hour period after injection.

CONCLUSIONS

The 85/15 premixed insulin preparation demonstrated clinical pharmacokinetic and pharmacodynamic properties that were intermediate between, and significantly different from, those of NPH insulin and the 70/30 premixed insulin preparation.

Circulating amylin in human essential hypertension: heritability and early increase in individuals at genetic risk

BACKGROUND

Human essential hypertension is a complex trait with poorly understood genetic determination. Insulin resistance is frequently associated with this trait.

OBJECTIVE

To determine whether a potentially pathogenic feature of the insulin-resistant state, circulating amylin (islet amyloid polypeptide, co-released with insulin from pancreatic islet beta-cells), is already increased in prehypertensive individuals (normotensive persons at genetic risk of hypertension because of family history), whether such individuals already differ in their amylin response to beta-cell stimulation, and whether plasma amylin concentration is heritable. Such features could establish increased circulating amylin as a hereditary 'intermediate phenotype' useful in genetic analyses of hypertension.

METHODS

Plasma amylin and insulin were measured in 283 medication-free individuals stratified by blood pressure status (82 hypertensive and 201 normotensive), and genetic risk (family history) of hypertension. Differences in means were tested by ANOVA, variances by F test, and frequency distributions by maximum likelihood analysis. Co-release of amylin and insulin was provoked by intravenous infusion of mixed amino acids. The effect of antihypertensive treatment was evaluated after monotherapy with either angiotensin converting enzyme inhibition or calcium-channel blockade in hypertension.

RESULTS

Plasma amylin was increased in hypertension (P= 0.027), and body mass index was a strong predictor of increased circulating amylin (P = 0.0001). Plasma amylin and plasma renin activity were not correlated (P = 0.395), and effective antihypertensive monotherapy with either angiotensin converting enzyme inhibition or calcium-channel blockade did not affect either amylin (P = 0.87-0.97) or insulin (P= 0.55-0.59). Among normotensive individuals, those at genetic risk of hypertension (with positive family history) already had increased concentrations of amylin (P< 0.001), despite exhibiting no difference in blood pressure or body mass index compared with the family-history-negative group; however, among normotensive individuals, both family history (P = 0.043) and body mass index (P= 0.0059) were significant predictors of increased concentrations of amylin. By maximum likelihood analysis, plasma amylin was distributed heterogeneously in the normotensive individuals, with two modes best explaining the distribution (chi2 = 77.4, P< 0.001), and family-history-positive individuals completely accounting for the upper mode (chi2 = 4.63, P = 0.031). Family-history-positive normotensive individuals showed greater plasma amylin concentrations both before and during beta-cell stimulation by amino acid infusion (P = 0.014). Black (n = 111) and white (n = 172) individuals did not differ in mean (P = 0.946) or variance (P = 0.172) of plasma amylin concentrations.

CONCLUSIONS

These results suggest that plasma amylin concentration is in part determined by heredity. Both basal and stimulated plasma amylin excess may identify a subgroup of individuals bearing an inherited predisposition to hypertension. Measurement of amylin might identify a useful 'intermediate phenotype' in the genetic analysis of essential hypertension and its relationship to insulin resistance.

Protein kinase Ctheta expression is increased upon differentiation of human skeletal muscle cells: dysregulation in type 2 diabetic patients and a possible role for protein kinase Ctheta in insulin-stimulated glycogen synthase activity

Protein kinase C (PKCtheta) is a key enzyme in regulating a variety of cellular functions, including growth and differentiation. PKCtheta is the most abundant PKC isoform expressed in skeletal muscle; however, its role in differentiation and metabolism is not clear. We examined the effect of muscle cell differentiation on PKCtheta expression in human skeletal muscle cells from normal and type 2 diabetic subjects. Low levels of PKCtheta messenger RNA (mRNA) and protein were detected in human myoblasts from both types of subjects. Upon differentiation into myotubes, PKCtheta mRNA and protein were increased 12-fold in myotubes from normal subjects. In human skeletal muscle cells obtained from type 2 diabetic subjects, increases in PKCtheta mRNA and protein were not observed upon differentiation into myotubes although expression of other markers of differentiation and fusion increased. Cells from type 2 diabetic subjects also exhibited decreased insulin-stimulated glycogen synthase activity. To determine whether the up-regulation of PKCtheta was important for the metabolic actions of insulin, PKCtheta was overexpressed in L6 rat skeletal muscle cells. Increased expression of PKCtheta occurred with differentiation of skeletal muscle myoblasts to myotubes. Glycogen synthase activity was further increased in L6 myotubes stably transfected with the complementary DNA for PKCtheta. The decreased expression of PKCtheta found in cells from type 2 diabetic subjects may be linked to insulin resistance and decreased glycogen synthase activity.

Induction of insulin resistance in human skeletal muscle cells by downregulation of glycogen synthase protein expression

Glycogen synthase (GS) is the rate-limiting enzyme controlling nonoxidative glucose disposal in skeletal muscle. A reduction in GS activity and an impaired insulin responsiveness are characteristic features of skeletal muscle in type 2 diabetes. These properties also exist in human skeletal muscle cell cultures from type 2 diabetic subjects. To determine the effect of an isolated reduction in GS on skeletal muscle insulin action, cultures from nondiabetic subjects were treated with antisense oligonucleotides (ODNs) to GS to interfere with expression of the gene. Treatment with antisense ODNs reduced GS protein expression by 70% compared with control (scrambled) ODNs (P < .01). GS activity measured at 0.01 mmol/L glucose-6-phosphate (G-6-P) was reduced by antisense ODN treatment. The insulin responsiveness of GS was impaired. Insulin also failed to stimulate glucose incorporation into glycogen after antisense ODN treatment. The cellular glycogen content was lower in antisense ODN-treated cells compared with control ODN. The insulin responsiveness of glucose uptake was abolished by antisense ODN treatment. Thus, reductions in GS expression in human skeletal muscle cells lead to impairments in insulin responsiveness and may play an important role in insulin-resistant states.

Distribution of peroxisome proliferator-activated receptors (PPARs) in human skeletal muscle and adipose tissue: relation to insulin action

AIMS/HYPOTHESIS

To evaluate the tissue distribution and possible role of the peroxisome proliferator-activated receptors (PPARs) in insulin action in fat and muscle biopsy specimens from lean, obese and subjects with Type II (non-insulin-dependent) diabetes mellitus.

METHODS

We measured PPAR alpha, PPAR beta (delta) and PPAR gamma protein expression by western blot analysis. The PPAR gamma protein was also measured in muscle before and after 3-h hyperinsulinaemic (300 mU.m-2.min-1) euglycaemic clamps.

RESULTS

The PPAR alpha protein was expressed preferentially in muscle relative to fat (more than sevenfold). The PPAR beta protein was similar in fat and muscle. The amount of PPAR gamma protein found in muscle was, on average, two-thirds of that present in fat. There was no statistically significant difference between non-diabetic and diabetic subjects in baseline (preclamp) muscle PPAR (alpha, beta or gamma) protein expression. Subgroup analysis showed, however, significantly higher PPAR gamma protein in the most insulin resistant diabetic subjects with glucose disposal rates of 3-6 mg.kg-1.min-1 compared with their age and weight matched counterparts with glucose disposal rates of 6-9 (147 +/- 23 vs 88 +/- 10 AU/microgram protein, p < or = 0.01 in diabetic and vs 94 +/- 15, p < or = 0.04 in non-diabetic subjects). Muscle PPAR gamma protein and glucose disposal rates were inversely correlated in diabetic subjects (r = -0.47, p < or = 0.05).

CONCLUSION/INTERPRETATION

All PPARs (alpha, beta or gamma) are present in skeletal muscle and adipose tissue with different relative distributions. The PPAR gamma protein is abundant in skeletal muscle as well as adipose tissue. The altered expression of skeletal muscle PPAR gamma is consistent with a role for this nuclear protein in the impaired insulin action of Type II diabetes.

Duck immune responses to Riemerella anatipestifer vaccines

Riemerella anatipestifer (Ra) infection is probably the most economically important infectious disease of farm ducks worldwide but the immune responses to natural infection and vaccines are poorly understood. We have used the lymphocyte transformation test (LTT) to study the expression of cell-mediated immunity (CMI), and the enzyme-linked immunosorbent assay to monitor antibody (Ab) production following administration of formalin-inactivated and live attenuated serotype 2 (= G) Ra vaccines. Lymphocytes (8x10(5) in 200 microl of RPMI + 10% duck serum, in 96 well trays) were stimulated with Ra antigen, prepared by freeze-thaw and sonication; optimum responses were obtained with antigen at 6.25 microg/ml. Cells were cultured for 3 days at 41.6 degrees C/5% CO(2), prior to assessing 3H-thymidine uptake. Ra bacterin, incorporating aluminium hydroxide as adjuvant, stimulated strong but transient (about 4 weeks) LTT response; there was some cross-reaction of the LTT to proteins derived from other serotypes of Ra. Revaccination stimulated slightly stronger responses with the same time course. The Ab response to each vaccination was longer-lived than the LTT response. Vaccination with a live, attenuated strain of Ra stimulated weaker but longer lasting LTT responses, but similar Ab responses compared to the bacterin. It is apparent, therefore, that the transient protection reported using Ra bacterins is due to the fact that the CMI response to these vaccines is transient; and that it is possible for ducks to have detectable levels of serum Ab at times when CMI is not detectable by LTT. These observations are important in terms of our understanding of immunopathogenesis, immunoprophylaxis, and immunodiagnosis in Ra.

Potential role of glycogen synthase kinase-3 in skeletal muscle insulin resistance of type 2 diabetes

Glycogen synthase (GS) activity is reduced in skeletal muscle of type 2 diabetes, despite normal protein expression, consistent with altered GS regulation. Glycogen synthase kinase-3 (GSK-3) is involved in regulation (phosphorylation and deactivation) of GS. To access the potential role of GSK-3 in insulin resistance and reduced GS activity in type 2 diabetes, the expression and activity of GSK-3 were studied in biopsies of vastus lateralis from type 2 and nondiabetic subjects before and after 3-h hyperinsulinemic (300 mU x m(-2) x min(-1))-euglycemic clamps. The specific activity of GSK-3alpha did not differ between nondiabetic and diabetic muscle and was decreased similarly after 3-h insulin infusion. However, protein levels of both alpha and beta isoforms of GSK-3 were elevated (approximately 30%) in diabetic muscle compared with lean (P < 0.01) and weight-matched obese nondiabetic subjects (P < 0.05) and were unchanged by insulin infusion. Thus, both basal and insulin-stimulated total GSK-3 activities were elevated by approximately twofold in diabetic muscle. GSK-3 expression was related to in vivo insulin action, as GSK-3 protein was negatively correlated with maximal insulin-stimulated glucose disposal rates. In summary, GSK-3 protein levels and total activities are 1) elevated in type 2 diabetic muscle independent of obesity and 2) inversely correlated with both GS activity and maximally insulin-stimulated glucose disposal. We conclude that increased GSK-3 expression in diabetic muscle may contribute to the impaired GS activity and skeletal muscle insulin resistance present in type 2 diabetes.

Insulin aspart (B28 asp-insulin): a fast-acting analog of human insulin: absorption kinetics and action profile compared with regular human insulin in healthy nondiabetic subjects

OBJECTIVE

To study the pharmacokinetic and pharmacodynamic profile of insulin aspart (a new fast-acting human insulin analog) after subcutaneous administration in the deltoid, abdominal, and thigh sites and to compare this profile with regular human insulin (Novolin; Novo Nordisk A/S, Copenhagen).

RESEARCH DESIGN AND METHODS

A total of 20 healthy subjects were studied in a single-center six-period double-blind randomized crossover trial with 6 study days and a washout period of 1 week between each single daily dose of the trial drug. Subjects were randomized to receive a single dose of 0.2 U/kg of insulin aspart or regular insulin on each of the 6 study days in three different sites (the deltoid, the abdomen, and the thigh) during a 10-h euglycemic clamp (two drugs and three injection sites). Pharmacokinetic and pharmacodynamic measurements were derived from blood sample measurements of glucose, insulin, and C-peptide during these clamps.

RESULTS

The pharmacodynamic data from the euglycemic clamp study showed that, regardless of injection site, the maximal glucose infusion rate (GIR Cmax) was greater and occurred at an earlier time (GIR Tmax) after administration of insulin aspart than regular insulin (GIR Cmax: abdomen 813 vs. 708, deltoid 861 vs. 736, and thigh 857 vs. 720 g/min, P < 0.05 for all; GIR Tmax: abdomen 94 vs. 173, deltoid 111 vs. 192, and thigh 145 vs. 193 g/min, P < 0.05 for all). Pharmacokinetic parameters were also consistent with faster absorption and higher peak insulin concentrations after insulin aspart administration. From all sites, the peak insulin concentration (Cmax) was higher and occurred earlier (Tmax) after administration of insulin aspart than of regular insulin (Cmax: abdomen 501 vs. 260, deltoid 506 vs. 252, thigh 422 vs. 220 pmol/l, P < 0.001 for all sites; Tmax: abdomen 52 vs. 109, deltoid 54 vs. 98, and thigh 60 vs. 107 min, P < 0.01 for all sites). The absorption and glucose-lowering action of insulin aspart did not differ between sites (similar GIR Cmax, Tmax, and area under the curve parameters). However, the duration of the glucose-lowering effect was up to 34 min shorter (P < 0.01) for the abdomen injections than for the deltoid or thigh injections (lower time of 50% glucose disposal). In addition, the amount of glucose infused was significantly lower by 10-14% in the abdomen than in other sites.

CONCLUSIONS

Subcutaneous administration of insulin aspart causes a more rapid and intense maximal effect compared with regular insulin during euglycemic clamp studies in nondiabetic subjects. Abdominal administration of insulin aspart has a shorter duration of glucose-lowering effect compared with administration in the deltoid or thigh.

Glucosamine regulation of glucose metabolism in cultured human skeletal muscle cells: divergent effects on glucose transport/phosphorylation and glycogen synthase in non-diabetic and type 2 diabetic subjects

Chronic exposure (48 h) to glucosamine resulted in a dose-dependent reduction of basal and insulin-stimulated glucose uptake activities in human skeletal muscle cell cultures from nondiabetic and type 2 diabetic subjects. Insulin responsiveness of uptake was also reduced. There was no change in total membrane expression of either GLUT1, GLUT3, or GLUT4 proteins. While glucosamine treatment had no significant effects on hexokinase activity measured in cell extracts, glucose phosphorylation in intact cells was impaired after treatment. Under conditions where glucose transport and phosphorylation were down regulated, the fractional velocity (FV) of glycogen synthase was increased by glucosamine treatment. Neither the total activity nor protein expression of glycogen synthase were influenced by glucosamine treatment. The stimulation of glycogen synthase by glucosamine was not due totally to soluble mediators. Reflective of the effects on transport/phosphorylation, total glycogen content and net glycogen synthesis were reduced after glucosamine treatment. These effects were similar in nondiabetic and type 2 cells. In summary: 1) Chronic treatment with glucosamine reduces glucose transport/phosphorylation and storage into glycogen in skeletal muscle cells in culture and impairs insulin responsiveness as well. 2) Down-regulation of glucose transport/phosphorylation occurs at a posttranslational level of GLUTs. 3) Glycogen synthase activity increases with glucosamine treatment. 4) Nondiabetic and type 2 muscle cells display equal sensitivity and responsiveness to glucosamine. Increased exposure of skeletal muscle to glucosamine, a substrate/precursor of the hexosamine pathway, alters intracellular glucose metabolism at multiple sites and can contribute to insulin resistance in this tissue.

Normal insulin-dependent activation of Akt/protein kinase B, with diminished activation of phosphoinositide 3-kinase, in muscle in type 2 diabetes

To determine whether the serine/threonine kinase Akt (also known as protein kinase B) is activated in vivo by insulin administration in humans, and whether impaired activation of Akt could play a role in insulin resistance, we measured the activity and phosphorylation of Akt isoforms in skeletal muscle from 3 groups of subjects: lean, obese nondiabetic, and obese type 2 diabetic. Vastus lateralis biopsies were taken in the basal (overnight fast) and insulin-stimulated (euglycemic clamp) states. Insulin-stimulated glucose disposal was reduced 31% in obese subjects and 63% in diabetic subjects, compared with lean subjects. Glycogen synthase (GS) activity in the basal state was reduced 28% in obese subjects and 49% in diabetic subjects, compared with lean subjects. Insulin-stimulated GS activity was reduced 30% in diabetic subjects. Insulin treatment activated the insulin receptor substrate-1-associated (IRS-1-associated) phosphoinositide 3-kinase (PI 3-kinase) 6.1-fold in lean, 3.7-fold in obese, and 2.4-fold in diabetic subjects. Insulin also stimulated IRS-2-associated PI 3-kinase activity 2.2-fold in lean subjects, but only 1.4-fold in diabetic subjects. Basal activity of Akt1/Akt2 (Akt1/2) and Akt3 was similar in all groups. Insulin increased Akt1/2 activity 1.7- to 2. 0-fold, and tended to activate Akt3, in all groups. Insulin-stimulated phosphorylation of Akt1/2 was normal in obese and diabetic subjects. In lean subjects only, insulin-stimulated Akt1/2 activity correlated with glucose disposal rate. Thus, insulin activation of Akt isoforms is normal in muscle of obese nondiabetic and obese diabetic subjects, despite decreases of approximately 50% and 39% in IRS-1- and IRS-2-associated PI 3-kinase activity, respectively, in obese diabetic subjects. It is therefore unlikely that Akt plays a major role in the resistance to insulin action on glucose disposal or GS activation that is observed in muscle of obese type 2 diabetic subjects.

Combination Therapy For Type 2 Diabetes

OBJECTIVE

To discuss a rational approach to improvement of glycemic control in patients with type 2 diabetes mellitus with use of combination therapy.

METHODS

We review the mechanisms of action and clinical applications for the various antidiabetic agents alone and in various combinations. Relevant studies in the literature are reviewed.

RESULTS

Although diet and exercise remain the cornerstones of treatment, in most patients with type 2 diabetes, pharmacologic agents are needed to achieve optimal glycemic control and likely reduce the incidence of microvascular and possibly macrovascular complications as well. Sulfonylureas have long been the foundation of oral pharmacologic therapy and provide adequate glycemic control for most patients for 5 to 10 years or longer. In the past, when treatment with sulfonylureas was no longer effective, insulin therapy was inevitable. With the approval of several new pharmacologic agents for the treatment of type 2 diabetes, however, the addition of one or more orally administered agents to sulfonylurea therapy or use of other oral combination therapy is rapidly evolving as a means of optimizing glycemic control. In many patients, combination therapy can delay the need to add or switch to insulin, or it can enhance glycemic control in patients already receiving insulin. In selected patients treated solely with insulin, discontinuation of insulin treatment and reinitiation of oral therapy may even be possible.

CONCLUSION

Currently, four classes of orally administered antidiabetic agents are available for use in patients with type 2 diabetes: insulin secretagogues, biguanides, a-glucosidase inhibitors, and thiazolidinediones. By taking advantage of differing mechanisms of action, combination therapy is evolving as a means of optimizing glycemic control in patients in whom a single agent or insulin is inadequate. Combinations of orally administered agents can often delay the need for insulin or in combination with insulin aid in achieving glycemic goals. Continuing research will help optimize combination therapies even further.

Inhibition of LDL oxidation in vitro but not ex vivo by troglitazone

Diabetic subjects are at increased risk for developing coronary artery disease, in part because of increased oxidation of LDL, which promotes atherogenesis. Troglitazone, a new antidiabetic drug of the thiazolidinedione class, acts as an insulin sensitizer and improves hyperglycemia. Structurally, it contains a tocopherol moiety similar to vitamin E and has been shown to have antioxidant properties in vitro. Therefore, we evaluated whether troglitazone inhibited LDL oxidation both in vitro and in type 2 diabetic subjects ex vivo. Troglitazone inhibited oxidation of LDL induced by Cu2+ or 2'2'-azobis-2-amidinopropane hydrochloride (AAPH) with 50% inhibition at 1 micromol/l and 100% inhibition at 5-10 micromol/l troglitazone. The inhibition of LDL oxidation by troglitazone also was time dependent. In addition, troglitazone inhibited oxidation of 125I-labeled LDL and its subsequent uptake and degradation by macrophages. To determine whether troglitazone was incorporated into LDL particles or acted in the aqueous milieu, troglitazone was incubated overnight at 37 degrees C with LDL or plasma before LDL re-isolation. After re-isolation, LDL that was incubated with troglitazone was no longer protected from oxidation, compared with probucol-treated LDL, which remained protected. Further, [14C]troglitazone did not get incorporated into LDL. This suggests that troglitazone exerts its antioxidant effect in the aqueous milieu of LDL. Consistent with this was the observation that the lag phases of copper-induced conjugated diene formation, a measure of the susceptibility in vivo, was similar for subjects taking troglitazone (76 +/- 5 min, n = 9) to subjects not taking the drug (77 +/- 3 min, n = 11; NS). Thus, troglitazone may be of value as an aqueous-phase antioxidant in addition to its effect on glucose homeostasis.

Measles, Hmong, and metaphor: culture change and illness management under conditions of immigration

When 19 Hmong families and three healers in St. Paul, Minnesota, were interviewed regarding their understanding of measles and the ways in which they cared for children with the disease, their responses spanned the range between Hmong animistic cosmology and Western theories of disease. The metaphors of growth that were used to describe the disease link language, cosmology, causation, body processes, and illness management practices. This study discusses the themes of cyclical time, disease-causing spirits, the natural/supernatural dichotomy, and agricultural metaphors as applied to disease, as well as the growing adaptation to, use of, and interpretation of Western medicine by these immigrants.

Effects of tumor necrosis factor-alpha on glucose metabolism in cultured human muscle cells from nondiabetic and type 2 diabetic subjects

The effects of tumor necrosis factor-alpha (TNF alpha) on glucose uptake and glycogen synthase (GS) activity were studied in human skeletal muscle cell cultures from nondiabetic and type 2 diabetic subjects. In nondiabetic muscle cells, acute (90-min) exposure to TNF alpha (5 ng/ml) stimulated glucose uptake (73 +/- 14% increase) to a greater extent than insulin (37 +/- 4%; P < 0.02). The acute uptake response to TNF alpha in diabetic cells (51 +/- 6% increase) was also greater than that to insulin (31 +/- 3%; P < 0.05). Prolonged (24-h) exposure of nondiabetic muscle cells to TNF alpha resulted in a further stimulation of uptake (152 +/- 31%; P < 0.05), whereas the increase in cells from type 2 diabetics was not significant compared with that in cells receiving acute treatment. After TNF alpha treatment, the level of glucose transporter-1 protein was elevated in nondiabetic (4.6-fold increase) and type 2 (1.7-fold) cells. Acute TNF alpha treatment had no effect on the fractional velocity of GS in either nondiabetic or type 2 cells. Prolonged exposure reduced the GS fractional velocity in both nondiabetic and diabetic cells. In summary, both acute and prolonged treatment with TNF alpha up-regulate glucose uptake activity in cultured human muscle cells, but reduce GS activity. Increased skeletal muscle glucose uptake in conditions of TNF alpha excess may serve as a compensatory mechanism in the insulin resistance of type 2 diabetes.

The Veterans Affairs Implantable Insulin Pump Study: effect on cardiovascular risk factors

OBJECTIVE

To determine whether implantable insulin pump (IIP) and multiple-dose insulin (MDI) therapy have different effects on cardiovascular risk factors in insulin-requiring patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

A randomized clinical trial was conducted at seven Veterans Affairs medical centers in 121 male patients with type 2 diabetes between the ages of 40 and 69 years receiving at least one injection of insulin per day and with HbA1c, levels of > or =8% at baseline. Weights, blood pressures, insulin use, and glucose monitoring data were obtained at each visit. Lipid levels were obtained at 0, 4, 8, and 12 months, and free and total insulin levels were obtained at 0, 6, and 12 months. All medications being taken were recorded at each visit.

RESULTS

No difference in absolute blood pressure, neither systolic nor diastolic, was seen between patients receiving MDI or IIP therapy, but significantly more MDI patients required anti-hypertensive medications. When blood pressure was modeled against weight and time, IIP therapy was significantly better than MDI therapy for systolic blood pressure in patients with BMI <33 and for diastolic blood pressure in patients with BMI >34 kg/m2. Total cholesterol levels decreased in the overall sample, but IIP patients exhibited significantly higher levels than MDI patients. Triglyceride levels increased over time for both groups, with IIP patients having significantly higher levels than patients in the MDI group. BMI was a significant predictor of, and inversely proportional to, HDL cholesterol level. No difference in lipid-lowering drug therapy was seen between the two groups. Free insulin and insulin antibodies tended to decrease in the IIP group as compared with the MDI group. C-peptide levels decreased in both groups.

CONCLUSIONS

IIP therapy in insulin-requiring patients with type 2 diabetes has advantages over MDI therapy in decreasing the requirement for antihypertensive therapy and for decreasing total and free insulin and insulin antibodies. Both therapies reduce total cholesterol and C-peptide levels.

Troglitazone effects on gene expression in human skeletal muscle of type II diabetes involve up-regulation of peroxisome proliferator-activated receptor-gamma

Troglitazone, besides improving insulin action in insulin-resistant subjects, is also a specific ligand for the nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma). To determine whether troglitazone might enhance insulin action by stimulation of PPARgamma gene expression in muscle, total PPARgamma messenger RNA (mRNA), and protein were determined in skeletal muscle cultures from nondiabetic control and type II diabetic subjects before and after treatment of cultures with troglitazone (4 days +/- troglitazone, 11.5 microM). Troglitazone treatment increased PPARgamma mRNA levels up to 3-fold in muscle cultures from type II diabetics (277 +/- 63 to 630 +/- 100 x 10(3) copies/microg total RNA, P = 0.003) and in nondiabetic control subjects (200 +/- 42 to 490 +/- 81, P = 0.003). PPARgamma protein levels in both diabetic (4.7 +/- 1.6 to 13.6 +/- 3.0 AU/10 microg protein, P < 0.02) and nondiabetic cells (7.4 +/- 1.0 to 12.7 +/- 1.8, P < 0.05) were also upregulated by troglitazone treatment. Increased PPARgamma was associated with stimulation of human adipocyte lipid binding protein (ALBP) and muscle fatty acid binding protein (mFABP) mRNA, without change in the mRNA for glycerol-3-phosphate dehydrogenase, PPARdelta, myogenin, uncoupling protein-2, or sarcomeric alpha-actin protein. In summary, we showed that troglitazone markedly induces PPARgamma, ALBP, and mFABP mRNA abundance in muscle cultures from both nondiabetic and type II diabetic subjects. Increased expression of PPARgamma protein and other genes involved in glucose and lipid metabolism in skeletal muscle may account, in part, for the insulin sensitizing effects of troglitazone in type II diabetes.

Type 2 diabetes care: the role of insulin-sensitizing agents and practical implications for cardiovascular disease prevention

Millions of Americans are at risk for cardiovascular morbidity and mortality related to disorders of glucose intolerance--particularly type 2 diabetes and prediabetic conditions, including the insulin resistance, or "cardiovascular dysmetabolic," syndrome. The latter is apparently more intricately associated with macrovascular disease--myocardial infarction, stroke, and peripheral vascular disease. In some situations the risk of cardiovascular disease might be reduced by the prevention of diabetes and also by prevention or treatment of the cardiovascular dysmetabolic syndrome. Studies have shown that intensive glycemic control can delay the development of microvascular complications in type 1, and possibly type 2, diabetes. Several longitudinal observational studies have demonstrated a relationship between glycemic control and the development of cardiovascular disease. Prospective clinical intervention trials to address this issue are underway. Insulin may have a role in atherogenesis, both directly and by promoting development of such risk factors as hypertension and dyslipidemia. Genetic factors and mechanisms promoting or discouraging development of glucose intolerance are also under investigation. Lifestyle changes--dietary and exercise modification, weight loss, and smoking cessation--have been shown to have a positive effect on cardiovascular disease risk. Clinical trials suggest that oral antidiabetic agents--particularly the new noninsulin secretagogues (including troglitazone and metformin, which act on the liver and on skeletal muscle)--may be useful in delaying or preventing development of type 2 diabetes and the cardiovascular dysmetabolic syndrome, as well as in their treatment, when present. Both agents, acting primarily by different mechanisms of action, have also demonstrated potential beneficial effects on serum lipid profiles and other cardiovascular risk factors and may be useful in patients with cardiovascular dysmetabolic syndrome who do not yet meet the criteria for diabetes.