Investigations of cellular glucose transport and its regulation under the influence of insulin in human peripheral blood lymphocytes.

INTRODUCTION: We investigated the effects of insulin on glucose transport in human peripheral lymphocytes using flow cytometry. We hypothesized that lymphocytes could be used as tools to study insulin action at the cellular level and facilitate the investigation of mechanisms that lead to insulin resistance. MATERIAL AND METHODS: Blood was withdrawn from 25 healthy subjects. The expression of glucose transporter (GLUT) isoforms in plasma membrane and the rates of glucose transport were determined with and without insulin (10 to 100 mU/L). Anti-CD3 phycoerythrin monoclonal antibody was used for lymphocyte gating. GLUT1, GLUT3, and GLUT4 isoforms were determined after staining cells with specific monoclonal antibodies to GLUT1, 3, and 4. Glucose transport was monitored with deoxy-D-glucose, 2-[3H(G)] - 185-370 GBq. RESULTS: Insulin increased the uptake of deoxy-D-glucose and the expression of GLUT1, GLUT3, and GLUT4 isoforms in the plasma membrane. The optimal effects were always reached at 50 mU/L of insulin with the increase in GLUT1, 3, and 4 expression of 12%, 44%, and 38%, respectively. Mean baseline values of deoxy-D-glucose uptake were 3409 ccpm at 15 min., 6587 ccpm at 30 min., and 12525 ccpm at 60 min. of investigation. The maximal uptake in insulin-stimulated conditions was reached with 50 mU/L of insulin and went up to 12450 ccpm at 15 min., 37482 ccpm at 30 min., and 37916 ccpm at 60 min. of investigation (p < 0.01). CONCLUSIONS: Peripheral blood lymphocytes may become an interesting model system to study the effects of insulin on cellular glucose transport. Flow cytometry is suitable for this investigation and may be used as a method to estimate the influence of insulin on GLUTprotein translocation and the dynamics of glucose uptake by lymphocytes.

Does cellular glucose transport respond to a controlled diet and sulfonylurea therapy in type 2 diabetes mellitus?

INTRODUCTION: The normalization of cellular glucose assimilation is the basic aim of therapy in diabetes mellitus. This process should be accompanied by a proportional increase of the cellular glucose transport (CGT). The level of CGT should react to therapy typically recommended in Type 2 diabetes mellitus (T2DM), composed of diet and sulfonylurea. In order to explore this clinically significant hypothesis, a clinical-experimental study was undertaken. Its aim was to determine the clinical pharmacotherapeutic significance of CGT measurements. MATERIAL AND METHODS: CGT testing was performed on peripheral blood lymphocytes. CGT was assessed with 2-[(3)H(G)] glucose: before, and after the addition of sulfonylurea or sulfonylurea plus insulin to the incubation medium. Tests were performed at baseline in 28 persons with newly diagnosed, "therapeutically naive" T2DM and in 20 control subjects. In diabetic patients the tests for CGT were repeated after 3 months of routine diet and sulfonylurea therapy. In addition, the level of GLUT4 expression was assessed by flow cytometry before and after this therapy. RESULTS: Before treatment, CGT was significantly decreased in all subjects with T2DM. Incubated in-vitro cells responded directly to the addition of sulfonylurea with a moderate increase of CGT. This response was augmented by the addition of insulin to sulfonylurea in the incubation medium. The monitored three-month routine, controlled therapy with diet and sulfonylurea resulted in a significant increase of CGT process in all types of incubation tests. CONCLUSIONS: The basal and reactive CGT is significantly decreased in lymphocytes of persons with T2DM before the introduction of therapy. Effective therapy with diet and sulfonylurea normalizes both types of CGT - basal and reactive. It is related to the near normalization of GLUT4 expression in the studied cells. This phenomenon may be used as a new marker for diabetes mellitus pharmacotherapy. (Pol J Endocrinol 2010; 61 (1): 75-81).

Insulin as the main regulator of cellular glucose utilization--aetiological aspects of insulin resistance.

This review presents the advances in the molecular biology and the pathophysiology of insulin resistance with emphasis on disturbances in cellular glucose transport. New scientific information about the structure and function of glucotransporters from the GLUT4 and SLGT families underline their significance in endocrinopathies and metabolic disease pathogenesis as related to insulin resistance. The new discoveries in this area also contribute to a better understanding of the regulation of insulin receptor and post-receptor reactivity by hormones and by drugs. They refer to the regulation of glycaemia and to its disturbances in diabetes mellitus, particularly of type 2, to metabolic syndrome, and, in general, to the pathogenesis of many syndromes and clinical disturbances caused by insulin resistance. Impairment of cellular glucose transport may be one of the primary aetiological factors in this respect. Therefore, studies of cellular glucotransporters expression and function promise new clinical and pharmacotherapeutic developments. Progress in this area has already been transformed into many practical proposals which are improving clinical practice.

Cellular glucose transport disturbances in the pathogenesis and therapy of type 2 diabetes mellitus.

The current world epidemic of type 2 diabetes mellitus results from two general groups of causative factors. One is the influence of strong pathogenetic environmental pressures - also described as negative civilizational influence - on the very large subpopulation, assessed at 30% of the total world population, which is genetically predisposed to react to this external stress with the symptoms of type 2 diabetes mellitus. Such a pathogenetic reaction is based on the appearance of cellular and organ resistance to insulin. A second factor involves the beta cells of the pancreatic islets and their dysfunction. For these reasons, studies on the aetiology of insulin resistance have significance, both theoretical and practical. There are many biological deviations that can produce cellular insulin resistance and underutilization of glucose. The mechanism that is always present is the decrease of cellular glucose transport. For this reason, it should be approached as a potential target for preventive and therapeutic actions. These pathophysiological and clinical circumstances were the motivation for presenting a review of cellular glucose transport pathophysiology, which contributes to the aetiology of insulin resistance, cellular underutilization of glucose, and type 2 diabetes mellitus. They underline the significance of cellular glucose transport as a target for prevention and therapy of type 2 diabetes mellitus and other insulin resistant conditions. This review presents comments about the influence on cellular glucose transport of diet, physical exercise, and pharmacotherapeutic agents, based on the authors' studies. The review could contribute to an innovative approach to the pathogenesis, prevention, and therapy of type 2 diabetes mellitus and other conditions related to insulin resistance.

Molecular physiology of cellular glucose transport - a potential area for clinical studies in diabetes mellitus.

The normalization of cellular glucose assimilation is the basic aim of metabolic therapy in type 2 diabetes mellitus (T2DM). It requires parallel changes in the process of cellular glucose transport (CGT). This review presents the pathophysiological and clinical outlines of CGT. Sequentially, the advances in the mechanisms and classification of CGT and their physiological and molecular base are described. The role of CGT pathogenetic significance in diabetes mellitus is stressed. Finally, the opinion is expressed that the CGT study is a potentially important approach to clinical interpretation of glucose metabolism disturbances and their pharmacotherapy.

Glucose transport in human peripheral blood lymphocytes influenced by type 2 diabetes mellitus.

INTRODUCTION: The objective of this study was to evaluate glucose transport into lymphocytes in healthy subjects and patients with type 2 diabetes mellitus (DM) treated either with diet only or with insulin and to propose peripheral blood lymphocytes as a convenient model for cellular glucose transport studies. MATERIALS AND METHODS: Sixty subjects with type 2 DM, 30 treated with diet only and 30 with insulin, were investigated. Thirty healthy subjects matched for age, weight, and sex served as a control group. Deoxy-D-glucose, 2-[(3)H(G)] transport was studied in isolated peripheral blood lymphocytes. Expression of glucose transporters was ascertained by immunocytochemical identification and by Western blotting. RESULTS: In lymphocytes from the control group, deoxy-D-glucose uptake increased gradually with the duration of the experiment. In diabetics treated with insulin, the maximal increase in deoxy-D-glucose uptake was observed after 30 min of the investigation, followed by a plateau phase. In diabetics treated with diet, deoxy-D-glucose uptake increased slowly during the first 30 min. The presence of GLUT1 and GLUT3 in lymphocytes was confirmed in this study. CONCLUSIONS: Glucose transport into lymphocytes is altered in type 2 DM. In lymphocytes from diabetics, the dynamics of deoxy-D-glucose uptake significantly differed from that in healthy subjects. There was also a significant difference between the diabetic groups, representing different modes of therapy and stages of the disease. Glucose transport into lymphocytes is apparently influenced by DM as well as by the mode of therapy. We suggest that peripheral blood lymphocytes may become a promising model for studies on glucose transport in diabetes.

Secondary prevention of macrovascular events in patients with type 2 diabetes in the PROactive Study (PROspective pioglitAzone Clinical Trial In macroVascular Events): a randomised controlled trial.

BACKGROUND: Patients with type 2 diabetes are at high risk of fatal and non-fatal myocardial infarction and stroke. There is indirect evidence that agonists of peroxisome proliferator-activated receptor gamma (PPAR gamma) could reduce macrovascular complications. Our aim, therefore, was to ascertain whether pioglitazone reduces macrovascular morbidity and mortality in high-risk patients with type 2 diabetes. METHODS: We did a prospective, randomised controlled trial in 5238 patients with type 2 diabetes who had evidence of macrovascular disease. We recruited patients from primary-care practices and hospitals. We assigned patients to oral pioglitazone titrated from 15 mg to 45 mg (n=2605) or matching placebo (n=2633), to be taken in addition to their glucose-lowering drugs and other medications. Our primary endpoint was the composite of all-cause mortality, non fatal myocardial infarction (including silent myocardial infarction), stroke, acute coronary syndrome, endovascular or surgical intervention in the coronary or leg arteries, and amputation above the ankle. Analysis was by intention to treat. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN NCT00174993. FINDINGS: Two patients were lost to follow-up, but were included in analyses. The average time of observation was 34.5 months. 514 of 2605 patients in the pioglitazone group and 572 of 2633 patients in the placebo group had at least one event in the primary composite endpoint (HR 0.90, 95% CI 0.80-1.02, p=0.095). The main secondary endpoint was the composite of all-cause mortality, non-fatal myocardial infarction, and stroke. 301 patients in the pioglitazone group and 358 in the placebo group reached this endpoint (0.84, 0.72-0.98, p=0.027). Overall safety and tolerability was good with no change in the safety profile of pioglitazone identified. 6% (149 of 2065) and 4% (108 of 2633) of those in the pioglitazone and placebo groups, respectively, were admitted to hospital with heart failure; mortality rates from heart failure did not differ between groups. INTERPRETATION: Pioglitazone reduces the composite of all-cause mortality, non-fatal myocardial infarction, and stroke in patients with type 2 diabetes who have a high risk of macrovascular events.

Cellular glucose transport and glucotransporter 4 expression as a therapeutic target: clinical and experimental studies.

INTRODUCTION: The normalization of cellular glucose assimilation is the basic aim of metabolic therapy in type 2 diabetes mellitus (T2DM). It requires parallel changes in the process of cellular glucose transport (CGT). Therefore the level of CGT could be regarded as a therapeutic target for oral hypoglycemic drugs in T2DM. To explore this hypothesis, CGT levels before and after sulfonylurea therapy were investigated. Peripheral blood lymphocytes were used as a cell model for testing CGT. MATERIALS AND METHODS: CGT was assessed by experimental in vitro tests allowing timed comparative observation of the transport process during the incubation of lymphocytes with 2-[(3)H(G)] glucose under basal conditions and after the addition of sulfonylurea or sulfonylurea plus insulin. The incubation tests were performed at baseline in 28 persons with newly diagnosed, therapy-naive T2DM and in 20 control subjects. In the diabetic patients the tests for CGT were repeated after 3 months of sulfonylurea therapy. The level of glucotransporter 4 (GLUT4) expression was also assessed by flow cytometry before and after the therapy. RESULTS: Before treatment, CGT was significantly lower in the subjects with T2DM. The cells responded to the addition of sulfonylurea by a moderate increase in CGT. This response was augmented by the addition of insulin to sulfonylurea in the culture medium. CONCLUSIONS: The three-month therapy with sulfonylurea resulted in a significant increase in CGT in all types of culture tests. This sulfonylurea-related improvement in CGT was associated with a near normalization of GLUT4 expression in the cells.

Oral sulodexide reduces albuminuria in microalbuminuric and macroalbuminuric type 1 and type 2 diabetic patients: the Di.N.A.S. randomized trial.

Diabetic nephropathy may be effectively prevented and treated by controlling glycemia and administering angiotensin-converting enzyme (ACE) inhibitors. However, strict metabolic control can be difficult, and ACE inhibitors may be poorly tolerated and only partially effective, particularly in diabetes mellitus type 2 (DM2), warranting the search for ancillary treatment. Sulodexide is a glycosaminoglycan, a new class of drug that has demonstrated nephroprotective activity in experimental investigations. The Di.N.A.S. study was a randomized, double-blind, placebo-controlled, multicenter, dose-range finding trial to evaluate the extent and duration of the hypoalbuminuric effect of oral sulodexide in diabetic patients. A total of 223 microalbuminuric and macroalbuminuric DM1 and DM2 patients with serum creatinine < or =150 micromol/L and stable BP and metabolic control were recruited. They were randomly allocated to one of four groups: 50 mg/d, 100 mg/d, or 200 mg/d sulodexide daily or placebo for 4 mo (T0 to T4), with 4 mo of follow-up after drug suspension (T4 to T8). Treatment with 200 mg/d sulodexide for 4 mo significantly reduced log albumin excretion rate (logAER) from 5.25 +/- 0.18 at T0 to 3.98 +/- 0.11 at T4 (P < 0.05), which was maintained till T8 (4.11 +/- 0.13; P < 0.05 versus T0). Moreover, the sulodexide-induced percent reductions in AER at T4 were significantly different from the placebo value at T4 and approximately linear to dose increments (30% [confidence limits, 4 to 49%], P = 0.03; 49% [30 to 63%], P = 0.0001; and 74% [64 to 81%], P = 0.0001 in the sulodexide 50, 100, and 200 mg/d groups, respectively. At T8, the sulodexide 200 mg/d group maintained a 62% (45 to 73%) AER significant reduction versus placebo (P = 0.0001). Subanalysis by type of diabetes (DM1 versus DM2, microalbuminuric versus macroalbuminuric, or on concomitant ACE inhibitors versus not on ACE inhibitors) demonstrated similar findings. These effects were obtained without any significant variation in metabolic control and BP or serum creatinine. Very few adverse events were reported; none were serious. In conclusion, a 4-mo course of high doses of sulodexide significantly and dose-dependently improves albuminuria in DM1 and DM2 patients and micro- or macroalbuminuric patients with or without concomitant ACE inhibition. The effect on albuminuria is long-lasting and seemingly additive to the ACE inhibitory effect.

Effect of low-dose perindopril/indapamide on albuminuria in diabetes: preterax in albuminuria regression: PREMIER.

Microalbuminuria in diabetes is a risk factor for early death and an indicator for aggressive blood pressure (BP) lowering. We compared a combination of 2 mg perindopril/0.625 mg indapamide with enalapril monotherapy on albumin excretion rate (AER) in patients with type 2 diabetes, albuminuria, and hypertension in a 12-month, randomized, double-blind, parallel-group international multicenter study. Four hundred eighty-one patients with type 2 diabetes and hypertension (systolic BP > or =140 mm Hg, <180 mm Hg, diastolic BP <110 mm Hg) were randomly assigned (age 59+/-9 years, 77% previously treated for hypertension). Results from 457 patients (intention-to-treat analysis) were available. After a 4-week placebo period, patients with albuminuria >20 and <500 microg/min were randomly assigned to a combination of 2 mg perindopril/0.625 mg indapamide or to 10 mg daily enalapril. After week 12, doses were adjusted on the basis of BP to a maximum of 8 mg perindopril/2.5 mg indapamide or 40 mg enalapril. The main outcome measures were overnight AER and supine BP. Both treatments reduced BP. Perindopril/indapamide treatment resulted in a statistically significant higher fall in both BP (-3.0 [95% CI -5.6, -0.4], P=0.012; systolic BP -1.5 [95% CI -3.0, -0.1] diastolic BP P=0.019) and AER -42% (95% CI -50%, -33%) versus -27% (95% CI -37%, -16%) with enalapril. The greater AER reduction remained significant after adjustment for mean BP. Adverse events were similar in the 2 groups. Thus, first-line treatment with low-dose combination perindopril/indapamide induces a greater decrease in albuminuria than enalapril, partially independent of BP reduction. A BP-independent effect of the combination may increase renal protection.