Comparative efficacy and potency of long-term therapy with glipizide or glyburide in patients with type 2 diabetes mellitus

Targeted pancreatic beta cell imaging for early diagnosis

Pancreatic beta cells are important in blood glucose level regulation. As type 1 and 2 diabetes are getting prevalent worldwide, we need to explore new methods for early detection of beta cell-related afflictions. Using bioimaging techniques to measure beta cell mass is crucial because a decrease in beta cell density is seen in diseases such as diabetes and thus can be a new way of diagnosis for such diseases. We also need to appraise beta cell purity in transplanted islets for type 1 diabetes patients. Sufficient amount of functional beta cells must also be determined before being transplanted to the patients. In this review, indirect imaging of beta cells will be discussed. This includes membrane protein on pancreatic beta cells whereby specific probes are designed for different imaging modalities mainly magnetic resonance imaging, positron emission tomography and fluorescence imaging. Direct imaging of insulin is also explored though probes synthesized for such function are relatively fewer. The path for successful pancreatic beta cell imaging is fraught with challenges like non-specific binding, lack of beta cell-restricted targets, the requirement of probes to cross multiple lipid layers to bind to intracellular insulin. Hence, there is an urgent need to develop new imaging techniques and innovative probing constructs in the entire imaging chain of bioengineering to provide early detection of beta cell-related pathology.

Glycemic Variability: Assessing Glycemia Differently and the Implications for Dietary Management of Diabetes

The primary therapeutic target for diabetes management is the achievement of good glycemic control, of which glycated hemoglobin (HbA1c) remains the standard clinical marker. However, glycemic variability (GV; the amplitude, frequency, and duration of glycemic fluctuations around mean blood glucose) is an emerging target for blood glucose control. A growing body of evidence supports GV as an independent risk factor for diabetes complications. Several techniques have been developed to assess and quantify intraday and interday GV. Additionally, GV can be influenced by several nutritional factors, including carbohydrate quality, quantity; and distribution; protein intake; and fiber intake. These factors have important implications for clinical nutrition practice and for optimizing blood glucose control for diabetes management. This review discusses the available evidence for GV as a marker of glycemic control and risk factor for diabetes complications. GV quantification techniques and the influence of nutritional considerations for diabetes management are also discussed.

Incretin, insulinotropic and glucose-lowering effects of whey protein pre-load in type 2 diabetes: a randomised clinical trial

AIMS/HYPOTHESIS

Since protein ingestion is known to stimulate the secretion of glucagon-like peptide-1 (GLP-1), we hypothesised that enhancing GLP-1 secretion to harness its insulinotropic/beta cell-stimulating activity with whey protein pre-load may have beneficial glucose-lowering effects in type 2 diabetes.

METHODS

In a randomised, open-label crossover clinical trial, we studied 15 individuals with well-controlled type 2 diabetes who were not taking any medications except for sulfonylurea or metformin. These participants consumed, on two separate days, 50 g whey in 250 ml water or placebo (250 ml water) followed by a standardised high-glycaemic-index breakfast in a hospital setting. Participants were randomised using a coin flip. The primary endpoints of the study were plasma concentrations of glucose, intact GLP-1 and insulin during the 30 min following meal ingestion.

RESULTS

In each group, 15 patients were analysed. The results showed that over the whole 180 min post-meal period, glucose levels were reduced by 28% after whey pre-load with a uniform reduction during both early and late phases. Insulin and C-peptide responses were both significantly higher (by 105% and 43%, respectively) with whey pre-load. Notably, the early insulin response was 96% higher after whey. Similarly, both total GLP-1 (tGLP-1) and intact GLP-1 (iGLP-1) levels were significantly higher (by 141% and 298%, respectively) with whey pre-load. Dipeptidyl peptidase 4 plasma activity did not display any significant difference after breakfast between the groups.

CONCLUSIONS/INTERPRETATION

In summary, consumption of whey protein shortly before a high-glycaemic-index breakfast increased the early prandial and late insulin secretion, augmented tGLP-1 and iGLP-1 responses and reduced postprandial glycaemia in type 2 diabetic patients. Whey protein may therefore represent a novel approach for enhancing glucose-lowering strategies in type 2 diabetes. Trial registration ClinicalTrials.gov NCT01571622 Funding The Israeli Ministry of Health and Milk Council funded the research.

Hypoglycaemia due to interaction of glimepiride with isoniazid in a patient with type 2 diabetes mellitus

Hypoglycaemia is a well-recognised untoward effect of sulfonylureas. We report a case of severe hypoglycaemia after isoniazid initiation in a type 2 diabetic patient. An oral glucose tolerance test revealed high serum insulin and C peptide, suggesting hyperinsulinaemia, and it was used to ascertain the relationship between insulin, glucose and C peptide levels. Insulin and C peptide elevation was attributed to the interaction between the two drugs. As a cytochrome inhibitor, isoniazid increased serum glimepiride concentration, resulting in hyperinsulinaemia. The diagnosis of occult insulinoma or nesidioblastosis was ruled out by CT and MRI, as we could not perform more sensitive, still invasive, diagnostic procedures. After isoniazid withdrawal, hypoglycaemia regressed and glimepiride was reinitiated. In conclusion, this case illustrates the need of caution when prescribing isoniazid in patients with type 2 diabetes mellitus receiving glimepiride to avoid hypoglycaemia.

Effect of sulfonylurea dose escalation on hemoglobin A1c in Veterans Affairs patients with type 2 diabetes

Sulfonylureas are often titrated to maximum doses despite evidence that their efficacy plateaus above half-maximum doses. The aim of this study was to determine the impact of doubling the dose of glyburide and glipizide to high doses on hemoglobin A1c (HbA1c) in Veterans Affairs patients with type 2 diabetes. A retrospective review of 131 patient cases with prescriptions for high-dose glyburide or glipizide from July 1 through December 18, 2008, was conducted. Three dosage groups were examined: glyburide 5 mg twice daily increased to 10 mg twice daily (GLYB), glipizide 5 mg twice daily increased to 10 mg twice daily (GLIPA), and glipizide 10 mg twice daily increased to 20 mg twice daily (GLIPB). Each patient served as his or her own control; HbA1c after at least 75 days on each dose was compared. There was a statistically significant decrease in HbA1c in GLIPA only (mean ± SD 8.0 ± 1.0 vs. 7.6 ± 1.0%, P = 0.03). No significant change in HbA1c was detected in GLYB (8.1 ± 1.1 vs. 8.1 ± 1.3%, P = 0.80) and the evaluation of GLIPB (8.6 ± 1.7 vs. 8.2 ± 1.1%, P = 0.41) was not adequately powered due to the small sample size. In this small retrospective study, increasing glipizide, but not glyburide, from 5 mg to 10 mg twice daily significantly decreased HbA1c in patients with diabetes.

Biochemical and metabolic mechanisms by which dietary whey protein may combat obesity and Type 2 diabetes

Consumption of milk and dairy products has been associated with reduced risk of metabolic disorders and cardiovascular disease. Milk contains two primary sources of protein, casein (80%) and whey (20%). Recently, the beneficial physiological effects of whey protein on the control of food intake and glucose metabolism have been reported. Studies have shown an insulinotropic and glucose-lowering properties of whey protein in healthy and Type 2 diabetes subjects. Whey protein seems to induce these effects via bioactive peptides and amino acids generated during its gastrointestinal digestion. These amino acids and peptides stimulate the release of several gut hormones, such as cholecystokinin, peptide YY and the incretins gastric inhibitory peptide and glucagon-like peptide 1 that potentiate insulin secretion from β-cells and are associated with regulation of food intake. The bioactive peptides generated from whey protein may also serve as endogenous inhibitors of dipeptidyl peptidase-4 (DPP-4) in the proximal gut, preventing incretin degradation. Indeed, recently, DPP-4 inhibitors were identified in whey protein hydrolysates. This review will focus on the emerging properties of whey protein and its potential clinical application for obesity and Type 2 diabetes.

Sulfonylurea receptor as a target for molecular imaging of pancreas beta cells with (99m)Tc-DTPA-glipizide

OBJECTIVE

This study was aimed to assess pancreas beta cell activity using (99m)Tc-diethyleneaminepentaacetic acid-glipizide (DTPA-GLP), a sulfonylurea receptor agent. The effect of DTPA-GLP on the blood glucose level in rats was also evaluated.

METHODS

DTPA dianhydride was conjugated with GLP in the presence of sodium amide, yielding 60%. Biodistribution and planar images were obtained at 30-120 min after injection of (99m)Tc-DTPA-GLP (1 mg/rat, 0.74 and 11.1 MBq per rat, respectively) in normal female Fischer 344 rats. The control group was given (99m)Tc-DTPA. To demonstrate pancreas beta cell uptake of (99m)Tc-DTPA-GLP via a receptor-mediated process, a group of rats was pretreated with streptozotocin (a beta cell toxin, 55 mg/kg, i.v.) and the images were acquired at immediately-65 min on day 5 post-treatment. The effect on the glucose levels after a single administration (ip) of DTPA-GLP was compared to glipizide (GLP) for up to 6 h.

RESULTS

The structure of DTPA-GLP was confirmed by NMR, mass spectrometry and HPLC. Radiochemical purity assessed by ITLC was >96%. (99m)Tc-DTPA-GLP showed increased pancreas-to-muscle ratios, whereas (99m)Tc-DTPA showed decreased ratios at various time points. Pancreas could be visualized with (99m)Tc-DTPA-GLP in normal rat, however, (99m)Tc-DTPA has poor uptake suggesting the specificity of (99m)Tc-DTPA-GLP. Pancreas beta cell uptake could be blocked by pre-treatment with streptozotocin. DTPA-GLP showed an equal or better response in lowering the glucose levels compared to the existing GLP drug.

CONCLUSIONS

It is feasible to use (99m)Tc-DTPA-GLP to assess pancreas beta cell receptor recognition. (99m)Tc-DTPA-GLP may be helpful in evaluating patients with diabetes, pancreatitis and pancreatic tumors.

Sustained-release versus immediate-release glipizide for treatment of type 2 diabetes mellitus in chinese patients: A randomized, double-blind, double-dummy, parallel-group, 12-week clinical study

BACKGROUND

Few data exist that have compared sulfonylurea formulations in differing ethnic populations. Most studies of sulfonylureas have been performed in white patients with type 2 diabetes mellitus.

OBJECTIVE

The aim of this study was to compare the efficacy and tolerability of a sustained-release glipizide (GSR) formulation with those of immediate-release glipizide (GIR) in Chinese patients with type 2 diabetes mellitus.

METHODS

This randomized, double-blind, double-dummy, placebo-controlled, parallel-group, clinical study enrolled adult patients with type 2 diabetes mellitus who were already being treated with diet and a sulfonylurea. Patients were randomized to receive either GSR 10 mg PO QD or GIR 5 mg PO BID for 12 weeks. Because these 2 formulations differed in appearance, each patient also received placebo resembling the alternate formulation, to be received at the alternate frequency. Drugs dispensed but not used were returned to the investigators and counted to monitor compliance with the protocol. For efficacy assessment, fasting plasma glucose (FPG) and glycosylated hemoglobin (HbA(1c)) were measured before and after treatment. Tolerability was measured by adverse events (AEs), which were evaluated by the attending physician during each clinical visit.

RESULTS

Of the 57 patients (37 men, 20 women) enrolled in the study, 41 completed it. All were Han Chinese of Taiwanese origin, and had the following characteristics: age range, 33 to 69 years; mean (SE) height, 161.99 (9.42) cm; and mean (SE) body mass index, 25.21 (3.43) kg/m2. An intent-to-treat analysis found that the mean (SE) changes from baseline in FPG (-30.00 [10.67] vs -25.96 [11.15] mg/dL) and in HbA(1c) (-0.08% [0.24%] vs +0.14% [0.22%]) during the 12-week period of the study were not significantly different between the 2 formulations. For patients in the per-protocol analysis, mean (SE) changes from baseline in FPG (-30.00 [10.67] vs -16.52 [7.79] mg/dL) and HbA(1c) (-0.08% [0.24%] vs +0.11% [0.25%]) were also not significantly different. The most frequently reported AEs were urinary abnormality (22.2%) and tachycardia (6.7%) for the GSR group and GIR group, respectively. No serious drug-related AEs were observed in either group.

CONCLUSION

In this small study, treatment with oral GSR (10 mg QD) was not significantly different from that of treatment with GIR (5 mg BID) with respect to short-term (12 weeks) FPG and HbA(1c) reductions in these ethnic Chinese adults with type 2 diabetes mellitus receiving treatment with a sulfonylurea.

Effect of whey on blood glucose and insulin responses to composite breakfast and lunch meals in type 2 diabetic subjects

BACKGROUND

Whey proteins have insulinotropic effects and reduce the postprandial glycemia in healthy subjects. The mechanism is not known, but insulinogenic amino acids and the incretin hormones seem to be involved.

OBJECTIVE

The aim was to evaluate whether supplementation of meals with a high glycemic index (GI) with whey proteins may increase insulin secretion and improve blood glucose control in type 2 diabetic subjects.

DESIGN

Fourteen diet-treated subjects with type 2 diabetes were served a high-GI breakfast (white bread) and subsequent high-GI lunch (mashed potatoes with meatballs). The breakfast and lunch meals were supplemented with whey on one day; whey was exchanged for lean ham and lactose on another day. Venous blood samples were drawn before and during 4 h after breakfast and 3 h after lunch for the measurement of blood glucose, serum insulin, glucose-dependent insulinotropic polypeptide (GIP), and glucagon-like peptide 1 (GLP-1).

RESULTS

The insulin responses were higher after both breakfast (31%) and lunch (57%) when whey was included in the meal than when whey was not included. After lunch, the blood glucose response was significantly reduced [-21%; 120 min area under the curve (AUC)] after whey ingestion. Postprandial GIP responses were higher after whey ingestion, whereas no differences were found in GLP-1 between the reference and test meals.

CONCLUSIONS

It can be concluded that the addition of whey to meals with rapidly digested and absorbed carbohydrates stimulates insulin release and reduces postprandial blood glucose excursion after a lunch meal consisting of mashed potatoes and meatballs in type 2 diabetic subjects.

The role of glimepiride in the effective management of Type 2 diabetes

Type 2 diabetes mellitus, a disorder of impaired insulin secretion and insulin resistance, has reached epidemic proportions. The effective management of Type 2 diabetes is of vital concern to clinicians. The identification of high-risk individuals and lifestyle management can help control diabetes; however, most patients require pharmacologic intervention. The goals of pharmacologic therapy are to achieve adequate glycemic control while avoiding hypoglycemia and weight gain and to minimize the risk of future micro- and macrovascular complications. There are a number of available glucose-lowering agents from which to choose. This review focuses on the sulfonylureas, the first oral agents introduced for the management of Type 2 diabetes, which are effective, well-tolerated, and well-established drugs, Second-generation sulfonylureas are now widely used in the management of Type 2 diabetes. The most recent addition, glimepiride, can be used in combination with metformin, the thiazolidinediones, alpha-glucosidase inhibitors, and insulin. The unique properties of glimepiride may provide advantages over other currently available insulin secretagogues.

Targeting postprandial hyperglycemia: a comparative study of insulinotropic agents in type 2 diabetes

This study was designed to compare the efficacy of three insulinotropic agents in the control of postprandial hyperglycemia in type 2 diabetes. Fifteen subjects with noninsulin-requiring type 2 diabetes were admitted to the General Clinical Research Center on four separate occasions. During the control study and following 7-10 d on each study medication, daylong glucose profiles were performed to investigate the effects of the assigned medication on postprandial hyperglycemia. During each admission, placebo or study medications were administered before three isocaloric meals as follows: immediate-release glipizide 30 min before breakfast and 30 min before supper, glipizide gastrointestinal therapeutic system (GITS) 30 min before breakfast, or nateglinide 120 mg 10 min before breakfast, before lunch, and before supper. Blood was drawn for analysis of glucose, insulin, and C-peptide at -0.05, 0, 0.25, 0.5, 1, 2, 3, and 4 h relative to each test meal. Immediate-release glipizide, nateglinide, or glipizide GITS administration resulted in significantly lower integrated daylong (glucose area under the curve) and peak glucose levels, compared with placebo. There were no significant differences in the daylong integrated glucose levels among the three study medications. The peak postbreakfast glucose level (but not glucose area under the curve) was lower with nateglinide, compared with either immediate-release glipizide or glipizide GITS. Postlunch and postdinner integrated glucose levels were significantly lower with immediate-release glipizide or glipizide GITS, compared with nateglinide. C-peptide levels were significantly higher with immediate-release glipizide, compared with glipizide GITS. Insulin levels did not differ among the three study medications. Once-daily glipizide GITS, twice-daily immediate-release glipizide, or three-times-a-day administration of nateglinide results in equivalent control of postmeal hyperglycemia in type 2 diabetes. The decision to prescribe one of these three insulinotropic agents should be based on factors such as the patient's ability to comply with complex dosing regimens, the need to control fasting hyperglycemia, the risk of interprandial hypoglycemia, and pharmacoeconomic considerations, rather than postprandial glucose-lowering efficacy.

Are hypoglycaemia and other adverse effects similar among sulphonylureas?

This review provides an updated overview of the adverse effects of sulphonylureas and identifies factors associated with variation in adverse effect rates among sulphonylureas published by different studies. A search of Medline, Embase, Current Contents and Cochrane Library was conducted to identify all papers related to sulphonylureas and adverse effects published from 1950-2001. The reference lists of all relevant papers were also searched for additional articles. The frequency of sulphonylurea-induced hypoglycaemia varied from 1.8-59%. Severe hypoglycaemia due to sulphonylurea use has been reported from 1.9-3.5%. Variation in hypoglycaemia rates may be due to differences in definitions, methods to detect and to collect information, patient characteristics, patient knowledge of the condition, threshold for symptoms, and activity level during hypoglycaemia. Other adverse effects associated with sulphonylurea use include bodyweight gain, gastrointestinal distress, disulphiram-like syndrome, dermatological reactions, haematological changes, ocular problems, and the syndrome of inappropriate secretion of antidiuretic hormone. Bodyweight gain has been reported to vary from 1.7-4.8 kg, according to the United Kingdom Prospective Diabetes Study (UKPDS-33). Controversy exists regarding cardiovascular adverse effects, but the consensus is to exercise caution in the use of these drugs as first-line therapy for patients with diabetes mellitus and coronary artery disease. The benefits of sulphonylurea treatment should be weighed against the risks associated with them. More work in this area is needed to homogenise the definition of hypoglycaemia, to get consensus on the methods for detection and data collection, as well as to further patient and physician education.

Clinical significance of targeting postprandial and fasting hyperglycemia in managing type 2 diabetes mellitus

Measurement of glycosylated hemoglobin (HbA1c) remains the gold standard for the assessment of glycemic control in patients with type 2 diabetes. Recent investigations have studied the correlations between HbA1c levels and other aspects of glucose metabolism, specifically, postprandial glucose (PPG) and fasting plasma glucose (FPG). The results suggest that PPG is also important to overall glycemic control and may be a better index of glucose regulation than FPG. Further, elevated PPG values have been associated with cardiovascular complications and cardiovascular mortality. Such evidence has led to recommendations that PPG levels be monitored as part of type 2 diabetes management, in addition to HbA1c and FPG. These glycemic parameters are differentially affected by the various classes of oral antidiabetic agents used in the treatment of type 2 diabetes--sulfonylureas, meglitinides, insulin sensitizers and alpha-glucosidase inhibitors. The sulfonylureas, for example, lower HbA1c, PPG and FPG, while the meglitinides have virtually no effect on FPG. The insulin sensitizer metformin, on the other hand, does not affect PPG levels, whereas the alpha-glucosidase inhibitors, in the presence of a high-carbohydrate diet, can effectively lower PPG. Many patients receive combination therapy, thereby benefiting from multiple mechanisms of glucose control, although in most cases insulin must later be added to the regimen in order to effectively suppress FPG. Thus, all aspects of glucose metabolism appear to be clinically relevant and should be monitored for effective diabetes management. Further study will more precisely define the clinical significance of PPG.

The effect of 3-month ingestion of Ginkgo biloba extract (EGb 761) on pancreatic beta-cell function in response to glucose loading in individuals with non-insulin-dependent diabetes mellitus

In the first report (Journal of Clinical Pharmacology 2000; 40:647-654), it was shown that ingestion of 120 mg of Ginkgo biloba extract (EGb 761) daily for 3 months by normal glucose-tolerant individuals caused a significant increase in pancreatic beta-cell insulin and C-peptide response, measured as the area under the curve (AUC0-->120) during a 2-hour standard (75 g) oral glucose tolerance test (OGTT). This follow-up study was designed to determine the effect of the same Ginkgo biloba treatment on glucose-stimulated pancreatic beta-cell function in non-insulin-dependent diabetes mellitus (NIDDM) subjects. In diet-controlled subjects (fasting plasma glucose [FPG], 117 +/- 16 mg/dl; fasting plasma insulin [FPI], 29 +/- 8 microU/ml; n = 6), ingestion of Ginkgo biloba produced no significant effect on the insulin AUC0-->120 (193 +/- 53 vs. 182 +/- 58 microU/ml/h, before and after ingesting Ginkgo biloba, respectively). In hyperinsulinemic NIDDM subjects taking oral hypoglycemic medications (n = 6) (FPG 143 +/- 48 mg/dl; FPI 46 +/- 13 microU/ml), ingestion of Ginkgo biloba caused blunted plasma insulin levels from 30 to 120 minutes during the OGTT, leading to a reduction of the insulin AUC0-->120 (199 +/- 33 vs. 147 +/- 58 microU/ml/h, before and after Ginkgo biloba, respectively). The C-peptide levels increased, and so the AUC0-->120 did not parallel the insulin AUC0-->120, creating a dissimilar insulin/C-peptide ratio indicative of an enhanced hepatic extraction of insulin relative to C-peptide. Thus, in pancreatic beta-cells that are already maximally stimulated, ingestion of Ginkgo biloba may cause a reduction in plasma insulin levels. Only in NIDDM subjects with pancreatic exhaustion (FPG 152 +/- 46 mg/dl; FPI 16 +/- 8 microU/ml; n = 8), who also took oral hypoglycemic agents, did Ginkgo biloba ingestion significantly increase pancreatic beta-cell function in response to glucose loading (insulin AUC0-->120 increased from 51 +/- 29 to 98 +/- 20 microU/ml/h, p < 0.0001), paralleled by a C-peptide AUC0-->120 increase from 7.2 +/- 2.8 to 13.7 +/- 6.8 (p < 0.0001). Whether this increase is due to "resuscitation" of previously exhausted islets or increased activity of only the remaining functional islets is unclear. However, not even in this group did increased pancreatic beta-cell activity cause a reduction of blood glucose during the OGTT. It is concluded that ingestion of Ginkgo biloba extract by an NIDDM subject may increase the hepatic metabolic clearance rate of not only insulin but also the hypoglycemic agents. The result is reduced insulin-mediated glucose metabolism and elevated blood glucose.