Additive glucose-lowering effects of glucagon-like peptide-1 and metformin in type 2 diabetes

OBJECTIVE: The incretin hormone glucagon-like peptide-1 (GLP-1) reduces plasma glucose in type 2 diabetic patients by stimulating insulin secretion and inhibiting glucagon secretion. The biguanide metformin is believed to lower plasma glucose without affecting insulin secretion. We conducted this study to investigate the effect of a combination therapy with GLP-1 and metformin, which could theoretically be additive, in type 2 diabetic patients. RESEARCH DESIGN AND METHODS: In a semiblinded randomized crossover study, seven patients received treatment with metformin (1,500 mg daily orally) alternating with GLP-1 (continuous subcutaneous infusion of 2.4 pmol x kg(-1) x min(-1)) alternating with a combination of metformin and GLP-1 for 48 h. Under fixed energy intake, we examined the effects on plasma glucose, insulin, C-peptide, glucagon, and appetite. RESULTS: Fasting plasma glucose (day 2) decreased from 13.9 +/- 1 (no treatment) to 11.2 +/- 0.4 (metformin) and 11.5 +/- 0.5 (GLP-1) and further decreased to 9.4 +/- 0.7 (combination therapy) (P = 0.0005, no difference between monotherapy with GLP-1 and metformin). The 24-h mean plasma glucose (day 2) decreased from 11.8 +/- 0.5 (metformin) and 11.7 +/- 0.8 (GLP-1) to 9.8 +/- 0.5 (combination) (P = 0.02, no difference between GLP-1 and metformin). Insulin levels were similar between the three regimens, but glucagon levels were significantly reduced with GLP-1 compared with metformin (P = 0.0003). Combination therapy had no additional effect on appetite scores. CONCLUSIONS: Monotherapy with GLP-1 and metformin have equal effects on plasma glucose and additive effects upon combination.     

Continuous subcutaneous infusion of glucagon-like peptide 1 lowers plasma glucose and reduces appetite in type 2 diabetic patients.

OBJECTIVE: The gut hormone glucagon-like peptide 1 (GLP-1) has insulinotropic and anorectic effects during intravenous infusion and has been proposed as a new treatment for type 2 diabetes and obesity. The effect of a single subcutaneous injection is brief because of rapid degradation. We therefore sought to evaluate the effect of infusion of GLP-1 for 48 h in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: We infused GLP-1 (2.4 pmol.kg-1.min-1) or saline subcutaneously for 48 h in randomized order in six patients with type 2 diabetes to evaluate the effect on appetite during fixed energy intake and on plasma glucose, insulin, glucagon, postprandial lipidemia, blood pressure, heart rate, and basal metabolic rate. RESULTS: The infusion resulted in elevations of the plasma concentrations of intact GLP-1 similar to those observed after intravenous infusion of 1.2 pmol.kg-1.min-1, previously shown to lower blood glucose effectively in type 2 diabetic patients. Fasting plasma glucose (day 2) decreased from 14.1 +/- 0.9 (saline) to 12.2 +/- 0.7 mmol/l (GLP-1), P = 0.009, and 24-h mean plasma glucose decreased from 15.4 +/- 1.0 to 13.0 +/- 1.0 mmol/l, P = 0.0009. Fasting and total area under the curve for insulin and C-peptide levels were significantly higher during the GLP-1 administration, whereas glucagon levels were unchanged. Neither triglycerides nor free fatty acids were affected. GLP-1 administration decreased hunger and prospective food intake and increased satiety, whereas fullness was unaffected. No side effects during GLP-1 infusion were recorded except for a brief cutaneous reaction. Basal metabolic rate and heart rate did not change significantly during GLP-1 administration. Both systolic and diastolic blood pressure tended to be lower during the GLP-1 infusion. CONCLUSIONS: We conclude that 48-h continuous subcutaneous infusion of GLP-1 in type 2 diabetic patients 1) lowers fasting as well as meal-related plasma glucose, 2) reduces appetite, 3) has no gastrointestinal side effects, and 4) has no negative effect on blood pressure.     

Effect of initial combination therapy with sitagliptin, a dipeptidyl peptidase-4 inhibitor, and pioglitazone on glycemic control and measures of β-cell function in patients with type 2 diabetes

Aim/hypothesis: To assess the safety and efficacy of initial combination therapy with sitagliptin and pioglitazone compared with pioglitazone monotherapy in drug‐naïve patients with type 2 diabetes. Methods: A total of 520 patients were randomised to initial combination therapy with sitagliptin 100 mg q.d. and pioglitazone 30 mg q.d. or pioglitazone 30 mg q.d. monotherapy for 24 weeks. Results: Initial combination therapy with sitagliptin and pioglitazone led to a mean reduction from baseline in A1C of ?2.4% compared with ?1.5% for pioglitazone monotherapy (p < 0.001). Mean reductions from baseline were greater in patients with a baseline A1C ≥ 10% (?3.0% with combination therapy vs. ?2.1% with pioglitazone monotherapy) compared with patients with a baseline A1C < 10% (?2.0% with combination therapy vs. ?1.1% with pioglitazone monotherapy). Sixty percent of patients in the combination therapy group vs. 28% in the pioglitazone monotherapy group had an A1C of < 7% at week 24 (p < 0.001). Fasting plasma glucose decreased by ?63.0 mg/dl (?3.5 mmol/l) in the combination therapy group compared with ?40.2 mg/dl (?2.2 mmol/l) for pioglitazone monotherapy (p < 0.001), and 2‐h post meal glucose decreased by ?113.6 mg/dl (?6.3 mmol/l) with combination therapy compared with ?68.9 mg/dl (?3.8 mmol/l) for pioglitazone monotherapy (p < 0.001). Measures related to β‐cell function also improved significantly with combination therapy compared with pioglitazone monotherapy. Combination therapy was generally well‐tolerated compared with pioglitazone monotherapy, with similar incidences of hypoglycemia (1.1% and 0.8%, respectively), gastrointestinal adverse events (5.7% and 6.9%, respectively), and oedema (2.7% and 3.5%, respectively). Conclusion/interpretation: Initial combination therapy with sitagliptin and pioglitazone substantially improved glycemic control and was generally well‐tolerated compared with pioglitazone monotherapy.     

Effect of repaglinide addition to metformin monotherapy on glycemic control in patients with type 2 diabetes.

OBJECTIVE: To compare the effect of repaglinide in combination with metformin with monotherapy of each drug on glycemic control in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: A total of 83 patients with type 2 diabetes who had inadequate glycemic control (HbA1c > 7.1%) when receiving the antidiabetic agent metformin were enrolled in this multicenter, double-blind trial. Subjects were randomized to continue with their prestudy dose of metformin (n = 27), to continue with their prestudy dose of metformin with the addition of repaglinide (n = 27), or to receive repaglinide alone (n = 29). For patients receiving repaglinide, the optimal dose was determined during a 4- to 8-week titration and continued for a 3-month maintenance period. RESULTS: In subjects receiving combined therapy, HbA1c was reduced by 1.4 +/- 0.2%, from 8.3 to 6.9% (P = 0.0016) and fasting plasma glucose by 2.2 mmol/l (P = 0.0003). No significant changes were observed in subjects treated with either repaglinide or metformin monotherapy in HbA1c (0.4 and 0.3% decrease, respectively) or fasting plasma glucose (0.5 mmol/l increase and 0.3 mmol/l decrease respectively). Subjects receiving repaglinide either alone or in combination with metformin, had an increase in fasting levels of insulin between baseline and the end of the trial of 4.04 +/- 1.56 and 4.23 +/- 1.50 mU/l, respectively (P < 0.02). Gastrointestinal adverse events were common in the metformin group. An increase in body weight occurred in the repaglinide and combined therapy groups (2.4 +/- 0.5 and 3.0 +/- 0.5 kg, respectively; P < 0.05). CONCLUSIONS: Combined metformin and repaglinide therapy resulted in superior glycemic control compared with repaglinide or metformin monotherapy in patients with type 2 diabetes whose glycemia had not been well controlled on metformin alone. Repaglinide monotherapy was as effective as metformin monotherapy.     

Characterization of GLP-1 effects on beta-cell function after meal ingestion in humans

OBJECTIVE: Glucagon-like peptide 1 (GLP-1) is an incretin that augments insulin secretion after meal intake and is developed for treatment of type 2 diabetes. As a novel therapeutic agent, characteristics of its beta-cell effects are important to establish. Previously, beta-cell effects of GLP-1 have been characterized in humans during graded intravenous infusions of glucose, whereas its effects after more physiological stimuli, like meal intake, are not known. RESEARCH DESIGN AND METHODS: Eight women (aged 69 years, fasting glucose 3.7-10.3 mmol/l, BMI 22.4-43.9 kg/m(2)) who had fasted overnight were served a breakfast (450 kcal) with intravenous infusion of saline or synthetic GLP-1 (0.75 pmol x kg(-1) x min(-1)), and beta-cell function was evaluated by estimating the relationship between glucose concentration and insulin secretion (calculated by deconvolution of C-peptide data). RESULTS:-GLP-1 markedly augmented insulin secretion, despite lower glucose. Total insulin secretion was 29.7 +/- 4.2 nmol/m(2) with GLP-1 versus 21.0 +/- 1.6 nmol/m(2) with saline (P = 0.048). GLP-1 increased the dose-response relationship between glucose concentration and insulin secretion (70 +/- 26 with GLP-1 versus 38 +/- 16 pmol insulin. min(-1 x m(2). mmol(-1) glucose. l without, P = 0.037) and augmented the potentiation factor that modulates the dose response (2.71 +/- 0.42 with GLP-1 versus 0.97 +/- 0.17 without, P = 0.005). The potentiation factor correlated to GLP-1 concentration (r = 0.53, P < 0.001); a 10-fold increase in GLP-1 levels produced a twofold increase in the potentiation factor. These effects of GLP-1 did not correlate with fasting glucose levels or BMI. CONCLUSIONS: Administration of GLP-1 along with ingestion of a meal augments insulin secretion in humans by a dose-dependent potentiation of the dose-response relationship between plasma glucose and insulin secretion.     

Effects of 3 months of continuous subcutaneous administration of glucagon-like peptide 1 in elderly patients with type 2 diabetes

OBJECTIVE: Glucagon-like peptide 1 (GLP-1) is an insulinotropic gut hormone that, when given exogenously, may be a useful agent in the treatment of type 2 diabetes. We conducted a 3-month trial to determine the efficacy and safety of GLP-1 in elderly diabetic patients. RESEARCH DESIGN AND METHODS: A total of 16 patients with type 2 diabetes who were being treated with oral hypoglycemic agents were enrolled. Eight patients (aged 75 +/- 2 years, BMI 27 +/- 1 kg/m(2)) remained on usual glucose-lowering therapy and eight patients (aged 73 +/- 1 years, BMI 27 +/- 1 kg/m(2)), after discontinuing hypoglycemic medications, received GLP-1 delivered by continuous subcutaneous infusion for 12 weeks. The maximum dose was 120 pmol x kg(-1). h(-1). Patients recorded their capillary blood glucose (CBG) levels (four times per day, 3 days per week) and whenever they perceived hypoglycemic symptoms. The primary end points were HbA(1c) and CBG determinations. Additionally, changes in beta-cell sensitivity to glucose, peripheral tissue sensitivity to insulin, and changes in plasma ghrelin levels were examined. RESULTS: HbA(1c) levels (7.1%) and body weight were equally maintained in both groups. The usual treatment group had a total of 87 CBG measurements of 相似文献   

Glucagon-like peptide-1 can reverse the age-related decline in glucose tolerance in rats.

Wistar rats develop glucose intolerance and have a diminished insulin response to glucose with age. The aim of this study was to investigate if these changes were reversible with glucagon-like peptide-1 (GLP-1), a peptide that we have previously shown could increase insulin mRNA and total insulin content in insulinoma cells. We infused 1.5 pmol/ kg-1.min-1 GLP-1 subcutaneously using ALZET microosmotic pumps into 22-mo-old Wistar rats for 48 h. Rat infused with either GLP-1 or saline were then subjected to an intraperitoneal glucose (1 g/kg body weight) tolerance test, 2 h after removing the pump. 15 min after the intraperitoneal glucose, GLP-1-treated animals had lower plasma glucose levels (9.04+/-0.92 mmol/liter, P < 0.01) than saline-treated animals (11.61+/-0.23 mmol/liter). At 30 min the plasma glucose was still lower in the GLP-1-treated animals (8.61+/-0.39 mmol/liter, P < 0.05) than saline-treated animals (10.36+/-0.43 mmol/liter). This decrease in glucose levels was reflected in the higher insulin levels attained in the GLP-1-treated animals (936+/-163 pmol/liter vs. 395+/-51 pmol/liter, GLP-1 vs. saline, respectively, P < 0.01), detected 15 min after glucose injection. GLP-1 treatment also increased pancreatic insulin, GLUT2, and glucokinase mRNA in the old rats. The effects of GLP-1 were abolished by simultaneous infusion of exendin [9-39], a specific antagonist of GLP-1. GLP-1 is therefore able to reverse some of the known defects that arise in the beta cell of the pancreas of Wistar rats, not only by increasing insulin secretion but also by inducing significant changes at the molecular level.     

Addition of nateglinide to rosiglitazone monotherapy suppresses mealtime hyperglycemia and improves overall glycemic control

OBJECTIVE: To determine the effects of nateglinide added to rosiglitazone monotherapy on glycemic control and on postprandial glucose and insulin levels in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: This 24-week, multicenter, double-blind, randomized study compared the efficacy of nateglinide (120 mg a.c.) and placebo added to rosiglitazone monotherapy (8 mg q.d.) in 402 patients with type 2 diabetes with HbA(1c) between 7 and 11% (inclusive). Efficacy parameters tested included HbA(1c) and plasma glucose and insulin levels in the fasting state and after a standardized meal challenge. Safety data were also collected. RESULTS: In placebo-treated patients, HbA(1c) did not change (Delta = 0.0 +/- 0.1%). In patients randomized to nateglinide, HbA(1c) decreased from 8.3 to 7.5% (Delta = -0.8 +/- 0.1%, P < 0.0001 vs. placebo). Target HbA(1c) (<7.0%) was achieved by 38% of patients treated with combination therapy and by 9% of patients remaining on rosiglitazone monotherapy. In nateglinide-treated patients, fasting plasma glucose levels decreased by 0.7 mmol/l, 2-h postprandial glucose levels decreased by 2.7 mmol/l, and 30-min insulin levels increased by 165 pmol/l compared with no changes from baseline of these parameters with placebo added to rosiglitazone (P < 0.001). CONCLUSIONS: By selectively augmenting early insulin release and decreasing prandial glucose excursions, nateglinide produced a clinically meaningful improvement in overall glycemic exposure in patients with type 2 diabetes inadequately controlled with rosiglitazone. Therefore, nateglinide substantially improves the likelihood of achieving a therapeutic target of HbA(1c) <7.0%.     

Inhibition of dipeptidyl peptidase IV improves metabolic control over a 4-week study period in type 2 diabetes

OBJECTIVE: Glucagon-like peptide-1 (GLP-1) has been proposed as a new treatment modality for type 2 diabetes. To circumvent the drawback of the short half-life of GLP-1, inhibitors of the GLP-1-degrading enzyme dipeptidyl peptidase IV (DPP IV) have been examined. Such inhibitors improve glucose tolerance in insulin-resistant rats and mice. In this study, we examined the 4-week effect of 1-[[[2-[(5-cyanopyridin-2-yl)amino]ethyl]amino]acetyl]-2-cyano-(S)-pyrrolidine (NVP DPP728), a selective, orally active inhibitor of DPP IV, in subjects with diet-controlled type 2 diabetes in a placebo-controlled double-blind multicenter study. RESEARCH DESIGN AND METHODS: A total of 93 patients (61 men and 32 women), aged 64 +/- 9 years (means +/- SD) and with BMI 27.3 +/- 2.7 kg/m(2), entered the study. Fasting blood glucose was 8.5 +/- 1.5 mmol/l, and HbA(1c) was 7.4 +/- 0.7%. Before and after treatment with NVP DPP728 at 100 mg x 3 (n = 31) or 150 mg x 5 (n = 32) or placebo (n = 30), subjects underwent a 24-h study with standardized meals (total 2,000 kcal). RESULTS: Compared with placebo, NVP DPP728 at 100 mg t.i.d. reduced fasting glucose by 1.0 mmol/l (mean), prandial glucose excursions by 1.2 mmol/l, and mean 24-h glucose levels by 1.0 mmol/l (all P < 0.001). Similar reductions were seen in the 150-mg b.i.d. treatment group. Mean 24-h insulin was reduced by 26 pmol/l in both groups (P = 0.017 and P = 0.023). Although not an efficacy parameter foreseen in the study protocol, HbA(1c) was reduced to 6.9 +/- 0.7% in the combined active treatment groups (P < 0.001). Laboratory safety and tolerability was good in all groups. CONCLUSIONS: We conclude that inhibition of DPP IV is a feasible approach to the treatment of type 2 diabetes in the early stage of the disease.     

Comparison of effect of pioglitazone with metformin or sulfonylurea (monotherapy and combination therapy) on postload glycemia and composite insulin sensitivity index during an oral glucose tolerance test in patients with type 2 diabetes

OBJECTIVE: Pioglitazone, metformin, and gliclazide lower HbA(1c) and fasting plasma glucose in patients with type 2 diabetes. We compared the effects of these three drugs, used as monotherapy and in combination, on postload glycemia and composite insulin sensitivity index (CISI) in these patients. RESEARCH DESIGN AND METHODS: Postload glycemia and CISI were analyzed for 940 patients who had oral glucose tolerance tests (OGTTs) in four multicenter, randomized, double-blind, double-dummy, parallel group clinical trials (pioglitazone versus metformin, pioglitazone versus gliclazide, pioglitazone plus sulfonylurea versus metformin plus sulfonylurea, and pioglitazone plus metformin versus gliclazide plus metformin). Plasma glucose and insulin were determined during the 3-h OGTT performed at baseline and after 1 year of therapy. Incremental area under the curve for glucose was the surrogate for postload glycemia. CISI was calculated using the formula {10,000/ radical of [(fasting glucose x fasting insulin) x (mean glucose x mean insulin)]} during the OGTT. RESULTS: In monotherapy, pioglitazone reduced postload glycemia and enhanced CISI more than metformin and gliclazide. In combination therapy, pioglitazone plus sulfonylurea reduced postload glycemia and increased CISI more than metformin plus sulfonylurea. Pioglitazone plus metformin also decreased postload glycemia and increased CISI more than gliclazide plus metformin. CONCLUSIONS: Pioglitazone improves postload glycemia and CISI more than metformin or gliclazide when used as monotherapy or in combination therapy in patients with type 2 diabetes.     

One-year glycemic control with a sulfonylurea plus pioglitazone versus a sulfonylurea plus metformin in patients with type 2 diabetes

OBJECTIVE: The goal was to assess the 1-year efficacy and safety of the addition of pioglitazone or metformin to existing sulfonylurea (SU) therapy in patients with inadequately controlled type 2 diabetes. RESEARCH DESIGN AND METHODS: In this multicenter, double-blind study, patients were randomized to receive either pioglitazone 15 mg (n = 319) or metformin 850 mg (n = 320) and up to 45 mg/day and 2,550 mg/day, respectively. The primary efficacy endpoint was HbA(1c) at week 52. Fasting plasma glucose, insulin, and lipid profiles were also measured. RESULTS: HbA(1c) was reduced by 1.20% in the SU plus pioglitazone group and 1.36% in the SU plus metformin group, and fasting plasma glucose was reduced by 2.2 and 2.3 mmol/l in the respective groups. Fasting insulin levels were also reduced (pioglitazone arm -1.3 micro IU/ml; metformin arm -0.8 micro IU/ml). There were no significant between-treatment differences in these three parameters. Pioglitazone addition to SU significantly reduced triglycerides (-16 vs. -9%; P = 0.008) and increased HDL cholesterol (14 vs. 8%; P < 0.001) compared with metformin addition. LDL cholesterol was increased 2% by the addition of pioglitazone and decreased 5% by the addition of metformin to SU (P < 0.001). Urinary albumin-to-creatinine ratio was reduced by 15% in the SU plus pioglitazone group and increased 2% in the SU plus metformin group (P = 0.017). Both combinations were well tolerated with no evidence of hepatic or cardiac toxicity in either group. CONCLUSIONS: Clinically equivalent improvements in glycemic control were observed for both combinations. Compared with metformin plus SU, addition of pioglitazone to SU resulted in a reduction of the urinary albumin-to-creatinine ratio, a small but significant rise in LDL cholesterol, and significantly greater improvements in triglyceride levels and HDL cholesterol levels. Metformin plus SU was associated with a significant reduction in LDL cholesterol. SU plus pioglitazone is an effective and well-tolerated combination regimen that may provide additional beneficial effects for patients with type 2 diabetes.     

Effects of pioglitazone and glimepiride on glycemic control and insulin sensitivity in Mexican patients with type 2 diabetes mellitus: A multicenter, randomized, double-blind, parallel-group trial

BACKGROUND: Pioglitazone and glimepiride improve glycemic control in patients with type 2 diabetes mellitus by different mechanisms. Pioglitazone is a thiazolidinedione that reduces insulin resistance, and glimepiride is a sulfonylurea insulin secretagogue. OBJECTIVE: The goals of this study were to compare changes in measures of glycemic control and insulin sensitivity in Mexican patients with type 2 diabetes who received pioglitazone or glimepiride for 1 year. METHODS: This was a multicenter, 52-week, double-blind, parallel-group trial. Patients were randomized to receive monotherapy with either glimepiride (2 mg QD initially) or pioglitazone (15 mg QD initially). Doses were titrated (maximal doses: pioglitazone 45 mg, glimepiride 8 mg) to achieve glycemic targets (fasting blood glucose < or =7 mmol/L and 1-hour postprandial blood glucose < or =10 mmol/L). Insulin sensitivity (primary end point) was evaluated in terms of the Homeostasis Model Assessment for Insulin Sensitivity (HOMA-S), the Quantitative Insulin Sensitivity Check Index (QUICKI), and fasting serum insulin (FSI) concentrations. Glycemic control was evaluated in terms of glycosylated hemoglobin (HbA(1c)) values and fasting plasma glucose (FPG) concentrations. Patients were encouraged to maintain their individual diet and exercise regimens throughout the study. RESULTS: Two hundred forty-four patients (125 women, 119 men; all but 1 Hispanic) were randomized to receive pioglitazone (n = 121) or glimepiride (n = 123). In the intent-to-treat sample, pioglitazone and glimepirede produced comparable reductions in HbA(1c) from baseline to the end of the study (-0.78% and -0.68%, respectively). The pioglitazone group had significantly higher HbA(1c) values compared with the glimepiride group after 12 weeks of therapy (8.66% vs 7.80%; P = 0.007) but had significantly lower values after 52 weeks (7.46% vs 7.77%; P = 0.027). Pioglitazone significantly reduced FPG compared with glimepiride (-0.6 vs 0.6 mmol/L; P = 0.01). Pioglitazone therapy was associated with significant increases in insulin sensitivity (reduced insulin resistance), whereas glimepiride had no effect. HOMA-S values changed 18.0% for pioglitazone and -7.9% for glimepiride (P < 0.001), QUICKI values changed a respective 0.013 and -0.007 (P < 0.001), and FSI values were -21.1 and 15.1 pmol/L (P< 0.001). Both drugs were well tolerated, with pioglitazone associated with more peripheral edema (number of treatment-emergent cases: 35/121[28.9%] vs 17/123 [13.8%]; P = 0.005) and fewer hypoglycemic episodes (19 [15.7%] vs 38 [30.9%]; P = 0.024). The incidence of weight gain was not significantly different between treatment groups. Conclusions: These data suggest that long-term treatment with pioglitazone enhances insulin sensitivity relative to glimepiride in Mexican patients with type 2 diabetes and that pioglitazone may have a more sustained antihyperglycemic effect.     

Twelve- and 52-week efficacy of the dipeptidyl peptidase IV inhibitor LAF237 in metformin-treated patients with type 2 diabetes

OBJECTIVE: To assess the 12- and 52-week efficacy of the dipeptidyl peptidase IV inhibitor LAF237 versus placebo in patients with type 2 diabetes continuing metformin treatment. RESEARCH DESIGN AND METHODS: We conducted a 12-week, randomized, double-blind, placebo-controlled trial in 107 patients with type 2 diabetes with a 40-week extension in those completing the core study and agreeing, together with the investigator, to extend treatment to 1 year. Placebo (n=51) or LAF237 (50 mg once daily, n=56) was added to ongoing metformin treatment (1,500-3,000 mg/day). HbA1c and fasting plasma glucose (FPG) were measured periodically, and standardized meal tests were performed at baseline, week 12, and week 52. RESULTS: In patients randomized to LAF237, baseline HbA1c averaged 7.7 +/- 0.1% and decreased at week 12 (Delta=-0.6 +/- 0.1%), whereas HbA1c did not change from a baseline of 7.9 +/- 0.1% in patients given placebo (between-group difference in DeltaHbA1c=-0.7 +/- 0.1%, P <0.0001). Mean prandial glucose and FPG were significantly reduced in patients receiving LAF237 versus placebo by 2.2 +/- 0.4 mmol/l (P <0.0001) and 1.2 +/- 0.4 mmol/l (P=0.0057), respectively, but plasma insulin levels were not affected. At end point of the extension, the between-group differences in change in mean prandial glucose, insulin, and FPG were -2.4 +/- 0.6 mmol/l (P=0.0001), 40 +/- 16 pmol/l (P=0.0153), and -1.1 +/- 0.5 mmol/l (P=0.0312), respectively. HbA1c did not change from week 12 to week 52 in LAF237-treated patients (n=42) but increased in participants given placebo (n=29). The between-group difference in DeltaHbA1c after 1 year was -1.1 +/- 0.2% (P <0.0001). CONCLUSIONS: Data from this study demonstrate that LAF237 effectively prevents deterioration of glycemic control when added to metformin monotherapy in type 2 diabetes.     

Glucagon-like peptide 1 enhances glucose tolerance both by stimulation of insulin release and by increasing insulin-independent glucose disposal.

Glucagon-like peptide 1 [7-36 amide] (GLP-1) has been shown to enhance insulin secretion in healthy and type II diabetic humans, and to increase glucose disposal in type I diabetic patients. To further define its action on glucose kinetics, we studied six healthy subjects who received either GLP-1 (45 pmol/kg per h) or 150 mM saline on two mornings during which a modified intravenous glucose tolerance test was performed. Plasma insulin and glucose levels were analyzed using Bergman's minimal model of glucose kinetics to derive indices of insulin sensitivity (SI) and glucose effectiveness at basal insulin (SG), the latter a measure of glucose disposition independent of changes in insulin. In addition, basal insulin concentrations, the acute insulin response to glucose (AIRg), plasma glucagon levels, and the glucose disappearance constant (Kg) were measured on the days that subjects received GLP-1 or saline. Compared with saline infusions, GLP-1 increased the mean Kg from 1.61 +/- 0.20 to 2.65 +/- 0.25%/min (P = 0.022). The enhanced glucose disappearance seen with GLP-1 was in part the result of its insulinotropic effect, as indicated by a rise in AIRg from 240 +/- 48 to 400 +/- 78 pM (P = 0.013). However, there was also an increase in SG from 1.77 +/- 0.11 to 2.65 +/- 0.33 x 10(-2).min-1 (P = 0.038), which was accounted for primarily by insulin-independent processes, viz glucose effectiveness in the absence of insulin. There was no significant effect of GLP-1 on SI or basal insulin, and glucagon levels were not different during the glucose tolerance tests with or without GLP-1. Thus, GLP-1 improves glucose tolerance both through its insulinotropic action and by increasing glucose effectiveness. These findings suggest that GLP-1 has direct effects on tissues involved in glucose disposition. Furthermore, this peptide may be useful for studying the process of insulin-independent glucose disposal, and pharmacologic analogues may be beneficial for treating patients with diabetes mellitus.     

Effect of glucagon-like peptide 1 (7-36 amide) on insulin-mediated glucose uptake in patients with type 1 diabetes

OBJECTIVE: To examine the insulinomimetic insulin-independent effects of glucagon-like peptide (GLP)-1 on glucose uptake in type 1 diabetic patients. RESEARCH DESIGN AND METHODS: We used the hyperinsulinemic-euglycemic clamp (480 pmol. m(-2) x min(-1)) in paired randomized studies of six women and five men with type 1 diabetes. In the course of one of the paired studies, the subjects also received GLP-1 at a dose of 1.5 pmol. kg(-1) x min(-1). The patients were 41 +/- 3 years old with a BMI of 25 +/- 1 kg/m(2). The mean duration of diabetes was 23 +/- 3 years. RESULTS: Plasma glucose was allowed to fall from a fasting level of approximately 11 mmol/l to 5.3 mmol/l in each study and thereafter was held stable at that level. Plasma insulin levels during both studies were approximately 900 pmol/l. Plasma C-peptide levels did not change during the studies. In the GLP-1 study, plasma total GLP-1 levels were elevated from the fasting level of 31 +/- 3 to 150 +/- 17 pmol/l. Plasma glucagon levels fell from the fasting levels of approximately 14 pmol/l to 9 pmol/l during both paired studies. Hepatic glucose production was suppressed during the glucose clamps in all studies. Glucose uptake was not different between the two studies ( approximately 40 micromol. kg(-1) x min(-1)). CONCLUSIONS: GLP-1 does not augment insulin-mediated glucose uptake in lean type 1 diabetic patients.     

Glucagon-like peptide 1 promotes satiety and suppresses energy intake in humans.

We examined the effect of intravenously infused glucagon-like peptide 1 (GLP-1) on subjective appetite sensations after an energy-fixed breakfast, and on spontaneous energy intake at an ad libitum lunch. 20 young, healthy, normal-weight men participated in a placebo-controlled, randomized, blinded, crossover study. Infusion (GLP-1, 50 pmol/ kg.h or saline) was started simultaneously with initiation of the test meals. Visual analogue scales were used to assess appetite sensations throughout the experiment and the palatability of the test meals. Blood was sampled throughout the day for analysis of plasma hormone and substrate levels. After the energy-fixed breakfast, GLP-1 infusion enhanced satiety and fullness compared with placebo (treatment effect: P < 0.03). Furthermore, spontaneous energy intake at the ad libitum lunch was reduced by 12% by GLP-1 infusion compared with saline (P = 0.002). Plasma GLP-1, insulin, glucagon, and blood glucose profiles were affected significantly by the treatment (P < 0.002). In conclusion, the results show that GLP-1 enhanced satiety and reduced energy intake and thus may play a physiological regulatory role in controlling appetite and energy intake in humans.     

Initial Combination Therapy With Alogliptin and Pioglitazone in Drug-Na?ve Patients With Type 2 Diabetes

OBJECTIVE

To assess the efficacy and tolerability of alogliptin plus pioglitazone for initial combination therapy in drug-naïve type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

This 26-week, double-blind, parallel-group study randomized 655 patients with inadequately controlled type 2 diabetes to four arms: 25 mg alogliptin (A25) q.d. monotherapy, 30 mg pioglitazone (P30) q.d. monotherapy, or 12.5 (A12.5) or 25 mg alogliptin q.d. plus pioglitazone (P30) q.d. combination therapy. Primary efficacy was A1C change from baseline with the high-dose combination (A25 + P30) versus each monotherapy.

RESULTS

Combination therapy with A25 + P30 resulted in greater reductions in A1C (−1.7 ± 0.1% from an 8.8% mean baseline) vs. A25 (−1.0 ± 0.1%, P < 0.001) or P30 (−1.2 ± 0.1%, P < 0.001) and in fasting plasma glucose (−2.8 ± 0.2 mmol/l) vs. A25 (−1.4 ± 0.2 mmol/l, P < 0.001) or P30 (−2.1 ± 0.2 mmol/l, P = 0.006). The A25 + P30 safety profile was consistent with those of its component monotherapies.

CONCLUSIONS

Alogliptin plus pioglitazone combination treatment appears to be an efficacious initial therapeutic option for type 2 diabetes.Because the pathogenesis of type 2 diabetes involves defects in both insulin secretion and insulin action, simplified, well-tolerated, and durably effective combination therapies are being considered as potential standard initial treatment strategies to increase the likelihood of achieving sustained glycemic targets (1–3). Two drug classes that have complementary modes of action and may prove efficacious in combination are thiazolidinediones (TZDs), which are insulin sensitizers that increase peripheral glucose uptake, and dipeptidyl peptidase (DPP)-4 inhibitors, which augment pancreatic insulin secretion and also reduce hepatic glucose output through a suppressive effect on pancreatic glucagon secretion (4,5). This phase 3 study was conducted in drug-naïve patients with type 2 diabetes inadequately controlled with diet and exercise to evaluate the effects of initial combination therapy with the DPP-4 inhibitor alogliptin and the TZD pioglitazone versus either component used alone.     

Elimination of the action of glucagon-like peptide 1 causes an impairment of glucose tolerance after nutrient ingestion by healthy baboons.

Glucagon-like peptide 1 (GLP-1) is an insulinotropic hormone released after nutrient ingestion which is known to augment insulin secretion, inhibit glucagon release, and promote insulin-independent glucose disposition. To determine the overall effect of GLP-1 on glucose disposition after a meal we studied a group of healthy, conscious baboons before and after intragastric glucose administration during infusions of saline, and two treatments to eliminate the action of GLP-1: (a) exendin-[9-39] (Ex-9), a peptide receptor antagonist of GLP-1; or (b) an anti-GLP-1 mAb. Fasting concentrations of glucose were higher during infusion of Ex-9 than during saline (4.44 +/- 0.05 vs. 4.16 +/- 0.05 mM, P < 0.01), coincident with an elevation in the levels of circulating glucagon (96 +/- 10 vs. 59 +/- 3 ng/liter, P < 0.02). The postprandial glycemic excursions during administration of Ex-9 and mAb were greater than during the control studies (Ex-9 13.7 +/- 2.0 vs. saline 10.0 +/- 0.8 mM, P = 0.07; and mAb 13.6 +/- 1.2 vs. saline 10.6 +/- 0.9 mM, P = 0.044). The increments in insulin levels throughout the absorption of the glucose meal were not different for the experimental and control conditions, but the insulin response in the first 30 min after the glucose meal was diminished significantly during treatment with Ex-9 (Ex-9 761 +/- 139 vs. saline 1,089 +/- 166 pM, P = 0.044) and was delayed in three of the four animals given the neutralizing antibody (mAb 946 +/- 262 vs. saline 1,146 +/- 340 pM). Thus, elimination of the action of GLP-1 impaired the disposition of an intragastric glucose meal and this was at least partly attributable to diminished early insulin release. In addition to these postprandial effects, the concurrent elevation in fasting glucose and glucagon during GLP-1 antagonism suggests that GLP-1 may have a tonic inhibitory effect on glucagon output. These findings demonstrate the important role of GLP-1 in the assimilation of glucose absorbed from the gut.     

A comparison of lipid and glycemic effects of pioglitazone and rosiglitazone in patients with type 2 diabetes and dyslipidemia

OBJECTIVE: Published reports suggest that pioglitazone and rosiglitazone have different effects on lipids in patients with type 2 diabetes. However, these previous studies were either retrospective chart reviews or clinical trials not rigorously controlled for concomitant glucose- and lipid-lowering therapies. This study examines the lipid and glycemic effects of pioglitazone and rosiglitazone. RESEARCH DESIGN AND METHODS: We enrolled subjects with a diagnosis of type 2 diabetes (treated with diet alone or oral monotherapy) and dyslipidemia (not treated with any lipid-lowering agents). After a 4-week placebo washout period, subjects randomly assigned to the pioglitazone arm (n = 400) were treated with 30 mg once daily for 12 weeks followed by 45 mg once daily for an additional 12 weeks, whereas subjects randomly assigned to rosiglitazone (n = 402) were treated with 4 mg once daily followed by 4 mg twice daily for the same intervals. RESULTS: Triglyceride levels were reduced by 51.9 +/- 7.8 mg/dl with pioglitazone, but were increased by 13.1 +/- 7.8 mg/dl with rosiglitazone (P < 0.001 between treatments). Additionally, the increase in HDL cholesterol was greater (5.2 +/- 0.5 vs. 2.4 +/- 0.5 mg/dl; P < 0.001) and the increase in LDL cholesterol was less (12.3 +/- 1.6 vs. 21.3 +/- 1.6 mg/dl; P < 0.001) for pioglitazone compared with rosiglitazone, respectively. LDL particle concentration was reduced with pioglitazone and increased with rosiglitazone (P < 0.001). LDL particle size increased more with pioglitazone (P = 0.005). CONCLUSIONS: Pioglitazone and rosiglitazone have significantly different effects on plasma lipids independent of glycemic control or concomitant lipid-lowering or other antihyperglycemic therapy. Pioglitazone compared with rosiglitazone is associated with significant improvements in triglycerides, HDL cholesterol, LDL particle concentration, and LDL particle size.     

Improved glycemic control and enhanced insulin sensitivity in type 2 diabetic subjects treated with pioglitazone

OBJECTIVE: To elucidate the effects of pioglitazone treatment on glucose and lipid metabolism in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS: A total of 23 diabetic patients (age 30-70 years BMI < 36 kg/m2) who being treated with a stable dose of sulfonylurea were randomly assigned to receive either placebo (n = 11) or pioglitazone (45 mg/day) (n = 12) for 16 weeks. Before and after 16 weeks of treatment, all subjects received a 75-g oral glucose tolerance test (OGTT) and hepatic peripheral insulin sensitivity was measured with a two-step euglycemic insulin (40 and 160 mU x min(-1) x m(-2) clamp performed with 3-[3H]glucose and indirect calorimetry HbA1c measured monthly throughout the study period. RESULTS: After 16 weeks of pioglitazone treatment, the fasting plasma glucose (FPG; 184 +/- 15 to 135 +/- 11 mg/dl, P < 0.01), mean plasma glucose during OGTT(293 +/- 12 to 225 +/- 14 mg/dl, P < 0.01), and HbA1c (8.9 +/- 0.3 to 7.2 +/- 0.5%, P < 0.01 ) decreased significantly without change in fasting or glucose-stimulated insulin/C-peptide concentrations. Fasting plasma free fatty acid (FFA; 647 +/- 39 to 478 +/- 49) microEq/l, P < 0.01) and mean plasma FFA during OGTT (485 +/- 30 to 347 +/- 33 microEq/l, P < 0.01) decreased significantly after pioglitazone treatment. Before and after pioglitazone treatment, basal endogenous glucose prodution (EGP) and FPG were strongly correlated (r = 0.67, P < 0.01). EGP during the first insulin clamp step was significantly decreased after pioglitazone treatment (P < 0.05) whereas insulin-stimulated total and nonoxidative glucose disposal during the second insulin clamp was increased (P < 0.01). The change in FPG was related to the change in basal EGP, EGP during the first insulin clamp step, and total glucose disposal during the second insulin clamp step. The change in mean plasma glucose concentration during the OGGTT was strongly related to the change in total body glucose disposl during the second insulin clamp step. CONCLUSIONS: These results suggest that pioglitazone therapy in type 2 diabetic patients decreases lasting and postprandial plasma glucose levels by improving hepatic and peripheral (muscle) tissue sensitivity to insulin.