Beneficial and detrimental effects of intensive glycaemic control, with emphasis on type 2 diabetes mellitus

Inactivation of p66Shc Decreases Afferent Arteriolar KATP Channel Activity and Decreases Renal Damage in Diabetic Dahl SS Rats

Increased expression of adaptor protein p66Shc has been associated with progression of diabetic nephropathy. Afferent arteriolar dilation and glomerular hyperfiltration in diabetes are due to increased K_ATP channel availability and activity. Hyperglycemia was induced in Dahl salt-sensitive (SS) rats in a model of diabetes induced by streptozotocin (STZ). Renal injury was evaluated in SS rats and genetically modified SS rats either lacking p66Shc (p66Shc knockout [p66ShcKO]) or expressing p66Shc mutant (p66Shc-S36A). Afferent arteriolar diameter responses during STZ-induced hyperfiltration were determined by using the juxtamedullary nephron technique. Albuminuria and glomerular injury were mitigated in p66ShcKO and p66Shc-S36A rats with STZ-induced diabetes. SS rats with STZ-induced diabetes had significantly increased afferent arteriolar diameter, whereas p66ShcKO and p66Shc-S36A rats did not. SS rats with STZ-induced diabetes, but not p66ShcKO or p66Shc-S36A rats with STZ-induced diabetes, had an increased vasodilator response to the K_ATP channel activator pinacidil. Likewise, the K_ATP inhibitor glibenclamide resulted in a greater decrease in afferent arteriolar diameter in SS rats with STZ-induced diabetes than in STZ-treated SS p66ShcKO and p66Shc-S36A rats. Using patch-clamp electrophysiology, we demonstrated that p66ShcKO decreases K_ATP channel activity. These results indicate that inactivation of the adaptor protein p66Shc decreases afferent arteriolar K_ATP channel activity and decreases renal damage in diabetic SS rats.

Tissue response to subcutaneous implantation of glucose-oxidase-based glucose sensors in rats

Considerable progress in improved control of disturbed glucose metabolism can be expected by continuous glucose monitoring. The aim of the study was to evaluate in male Sprague-Dawley rats tissue response to implantation of a new amperometric glucose-oxidase-based glucose sensor (NTS) compared to a commercially available sensor system CGMS of MiniMed. Both sensors were tested under working conditions over a period of 3 days. Using NTS, glucose in interstitial fluid reflected glucose in arterial blood even in rapidly changing hyper- and hypoglycaemia whereas the CGMS did not detect the experimentally induced glucose changes adequately. Gene expression profiling was performed using Affymetrix chips. Acute phase response to injury by sensor application for a short time is indicated by down regulation of the increase in mRNA of proteases e.g. metallothionein-1alpha and matrix metalloprotease-3 at day 3. Improvement of anabolic situation is suggested by decrease in mRNA of insulin-like growth factor binding protein whereas increase of heme oxygenase and hypoxia-inducible factor may be related to defense mechanisms. Changes of mRNA together with slight fibrous capsule formation suggest good histocompatibility. Comparability of the patterns of changed mRNA in tissue surrounding SCGM with and without operating voltage as shown in dendrogram indicates no contribution of hydrogen peroxide to worsening biocompatibility. Beside established histological investigations of foreign body reaction weeks or months after implantation, gene expression profiling provides additional information to biocompatibility already early after implantation.

Culture-specific diabetes care for Surinam South Asians with a low socio-economic position: who benefits?

The South Asians in The Netherlands have a high diabetes prevalence in combination with a low socio-economic position. A new, culture-specific type of care was developed. This intervention study investigates which patient characteristics are associated with success and whether those in the lowest socio-economic position have been reached. Before and after the end of the intensive guidance, the HbAlc of the patients (n=101) was measured. The following variables were significantly related to success (defined as a decrease in HbAlc > or = 0.8%): a high initial HbAlc, a low BMI and presence of complications. The average improvement in HbAlc was significant only in the group with a higher socio-economic position. Although the patients with the lowest socio-economic position did not sufficiently benefit from this intervention, an overall improvement was achieved in this poorly educated study population. The further improvements in the care after the completion of this study should be evaluated.

Design of the cooperative study on glycemic control and complications in diabetes mellitus type 2: Veterans Affairs Diabetes Trial

INTRODUCTION

Long-term glycemic control trials in type 2 diabetes show as the main clinical benefit a difference in retinal photocoagulation (3/1000 in the UK Prospective Diabetes Study [UKPDS]), but no effect on visual acuity or renal failure. No intensive glycemic control trial has yet affected cardiovascular (CV) events, the main cause of morbidity and mortality. By contrast, modest blood pressure reduction has protective effects on visual acuity, renal function, CV events, and mortality. Optimal glycemic control goals are not established in elderly, obese persons with advanced complications, the most common patients in the Veterans Affairs (VA) system. The earlier feasibility trial in such patients (VA-CSDM) suggested potentially worse CV outcomes with lower attained hemoglobin A1c (HbA1c) levels.

OBJECTIVES

The primary objective of the Veterans Affairs Diabetes Trial (VADT) is the assessment of the effect of intensive glycemic treatment on CV events. Other objectives are effects on microangiopathy, quality of life, and cost effectiveness.

RESEARCH DESIGN AND METHODS

The VADT, started in December 2000, is enrolling 1700 men and women previously uncontrolled on insulin or maximum doses of oral agents at 20 VA medical centers. Accrual is 2 years and follow-up is 5-7 years, with visits every 1.5 months. The study has a power of 86% to detect a 21% relative reduction in major CV events (CV death, myocardial infarction [MI], cerebrovascular accident [CVA], congestive heart failure [CHF], revascularization and amputation for ischemia). Subjects are randomized to an intensive arm aiming at normal HbA1c levels or to a standard arm with usual, improved glycemic control. An HbA1c separation of >1.5% is to be maintained (expected 2%). Both arms receive step therapy: glimepiride or metformin plus rosiglitazone and addition of insulin or other oral agents to achieve goals. Strict control of blood pressure and dyslipidemia, daily aspirin, diet, and education are identical in both arms. Plasma fibrinogen, plasminogen-activating inhibitor I (PAI-I), lipids, renal function parameters, and ECG are measured throughout. Stereo retinal photographs are obtained at entry and 5 years, eye examinations yearly, and intervention as needed to prevent visual deterioration. Recruitment is proceeding on schedule: the current mean HbA1c at entry is 9.4+/-1.6% and mean duration of diagnosed diabetes 11+/-8 years.

Comparison of glycaemic control and cardiovascular risk profile in patients with type 2 diabetes during treatment with either repaglinide or metformin

OBJECTIVE

To compare glycaemic control and cardiovascular risk profile in patients with type 2 diabetes following 12 months' treatment with either repaglinide or metformin.

STUDY DESIGN AND METHODS

This was an open uncontrolled randomised study in n=112 patients with inadequately controlled type 2 diabetes not previously treated with oral hypoglycaemic agents. Patients beginning treatment with either repaglinide or metformin entered an 8-week titration period (to optimise dosage: repaglinide, 2-4 mg/day; metformin, 1500-2500 mg/day) followed by a 12-month treatment period. Glycaemic control and cardiovascular risk factors were determined at baseline and at the end of the treatment period.

RESULTS

Mean (S.D.) final drug doses were 3 (+/-1) mg/day in the repaglinide group and 2000 (+/-500) mg/day in the metformin group. Significant improvements in glycaemic control [glycated haemoglobin, fasting and 2-h postprandial plasma glucose (PPG)] were demonstrated in both treatment groups. The decrease in PPG was significantly greater in the repaglinide group (P<0.05). During the treatment period, fasting plasma insulin (FPI) decreased significantly in both groups, more so with metformin (P<0.05). Two-hour postprandial plasma insulin (PPI) levels decreased only in the metformin group (P<0.05). Significant improvements between baseline and final visit were demonstrated in one or both groups in the following cardiovascular risk factors: total cholesterol, low-density lipoprotein cholesterol (LDL-C), triglycerides, plasminogen activator inhibitor, lipoprotein(a) and homocysteine. No changes were observed in high-density lipoprotein cholesterol (HDL-C), apolipoprotein A-I, apolipoprotein B, fibrinogen, body mass index (BMI) or blood pressure.

CONCLUSIONS

The use of repaglinide or metformin in drug therapy-nai;ve patients with type 2 diabetes over a 12-month period is associated with improvements in both glycaemic control and cardiovascular risk profile. The latter cannot necessarily be attributed to the pharmacotherapy per se, but provides reassurance in the context of initiating oral hypoglycaemic drug therapy with these agents.

Orlistat use in type 2 diabetes

OBJECTIVE

To review the use of orlistat in type 2 diabetes.

DATA SOURCES

A MEDLINE search of the English-language literature (1990-August 2001) was performed using the key terms orlistat, obesity, glucose, and diabetes.

DATA EXTRACTION

All articles pertaining to orlistat were considered for inclusion, with emphasis placed on randomized, placebo-controlled, double-blind clinical trials.

DATA SYNTHESIS

In April 1999, orlistat was approved by the Food and Drug Administration for the treatment of obesity. Of 13 randomized, placebo-controlled studies, only 2 reported specific data in individuals with type 2 diabetes. Both reported significant weight reduction and improved glycemic control over placebo.

CONCLUSIONS

Since weight loss is a difficult goal to achieve in patients with type 2 diabetes, orlistat can be a safe, effective addition to a multidisciplinary approach.