Potassium reduction with sodium zirconium cyclosilicate in patients with heart failure.

AIMS: Several patients with heart failure and reduced ejection fraction (HFrEF) do not receive renin-angiotensin-aldosterone system (RAAS) inhibitors at the recommended dose or at all, frequently due to actual or feared hyperkalaemia. Sodium zirconium cyclosilicate (SZC) is an orally administered non-absorbed intestinal potassium binder proven to lower serum potassium concentrations. METHODS AND RESULTS: PRIORITIZE-HF was an international, multicentre, parallel-group, randomized, double-blind, placebo-controlled study to evaluate the benefits and risks of using SZC to intensify RAAS inhibitor therapy. Patients with symptomatic HFrEF were eligible and randomly assigned to receive SZC 5 g or placebo once daily for 12 weeks. Doses of study medication and RAAS inhibitors were titrated during the treatment period. The primary endpoint was the proportion of patients at 12 weeks in the following categories: (i) any RAAS inhibitor at less than target dose, and no MRA; (ii) any RAAS inhibitor at target dose and no MRA; (ii) MRA at less than target dose; and (iv) MRA at target dose. Due to challenges in participant management related to the COVID-19 pandemic, the study was prematurely terminated with 182 randomized patients. There was no statistically significant difference in the distribution of patients by RAAS inhibitor treatment categories at 3 months (P = 0.43). The proportion of patients at target MRA dose was numerically higher in the SZC group (56.4%) compared with the placebo group (47.0%). Overall, SZC was well tolerated. CONCLUSIONS: PRIORITIZE-HF was terminated prematurely due to COVID-19 and did not demonstrate a statistically significant increase in the intensity of RAAS inhibitor therapies with the potassium-reducing agent SZC compared with placebo.

Lifetime cost-effectiveness simulation of once-weekly exenatide in type 2 diabetes: A cost-utility analysis based on the EXSCEL trial.

AIMS: The Exenatide Study of Cardiovascular Event Lowering (EXSCEL) trial assessed once-weekly exenatide (EQW) vs. placebo, added to usual care in 14,752 patients with type 2 diabetes mellitus (Clinicaltrials.gov: NCT01144338). We assessed the lifetime cost-effectiveness of adding EQW vs. usual care alone from a healthcare perspective. METHODS: Medical resource use and EQ-5D utilities were collected throughout the study. Within-trial results were extrapolated to a lifetime horizon using the UK Prospective Diabetes Study Outcomes Model version 2 (UKPDS-OM2), predicting predict cardiovascular and microvascular events. Cost-effectiveness was evaluated separately for US and UK settings, with outcomes measured in quality-adjusted life-years (QALYs). RESULTS: EQW plus usual care gained 0.162 QALYs at an additional cost of $41,545/patient, compared with usual care in a US setting. The incremental cost-effectiveness ratio (ICER) was $259,223/QALY. In a UK setting, the QALY gain was 0.151 at an additional cost of £6357: an ICER of £42,589/QALY. Sensitivity analyses ranged between $34,369-$269,571 and £3430-£46,560 per QALY gained. CONCLUSIONS: In a lifetime extrapolation, adding EQW to usual care increased QALYs and costs compared with usual care alone. The base-case ICERs exceeded the commonly-cited cost-effectiveness thresholds of $100,000/QALY and £20,000/QALY. However, ICERs were considerably lower in some subgroups, and in sensitivity analyses.

Exploring the Possible Impact of Unbalanced Open-Label Drop-In of Glucose-Lowering Medications on EXSCEL Outcomes.

BACKGROUND: EXSCEL (Exenatide Study of Cardiovascular Event Lowering) assessed the impact of once-weekly exenatide 2 mg versus placebo in patients with type 2 diabetes mellitus, while aiming for glycemic equipoise. Consequently, greater drop-in of open-label glucose-lowering medications occurred in the placebo group. Accordingly, we explored the potential effects of their unbalanced use on major adverse cardiovascular events (MACE), defined as cardiovascular death, nonfatal myocardial infarction or nonfatal stroke, and all-cause mortality (ACM), given that some of these agents are cardioprotective. METHODS: Cox hazard models were performed by randomized treatment for drug classes where >5% open-label drop-in glucose-lowering medication occurred, and for glucagon-like peptide-1 receptor agonists (GLP-1 RAs; 3.0%) using three methodologies: drop-in visit right censoring, inverse probability for treatment weighting (IPTW), and applying drug class risk reductions. RESULTS: Baseline glucose-lowering medications for the 14 752 EXSCEL participants (73.1% with previous cardiovascular disease) did not differ between treatment groups. During median 3.2 years follow-up, open-label drop-in occurred in 33.4% of participants, more frequently with placebo than exenatide (38.1% versus 28.8%), with metformin (6.1% versus 4.9%), sulfonylurea (8.7% versus 6.9%), dipeptidyl peptidase-4 inhibitors (10.6% versus 7.5%), SGLT-2i (10.3% versus 8.1%), GLP-1 RA (3.4% versus 2.4%), and insulin (13.8% versus 9.4%). The MACE effect size was not altered meaningfully by right censoring, but the favorable HR for exenatide became nominally significant in the sulfonylurea and any glucose-lowering medication groups, while the ACM HR and p-values were essentially unchanged. IPTW decreased the MACE HR from 0.91 (P=0.061) to 0.85 (P=0.008) and the ACM HR from 0.86 (P=0.016) to 0.81 (P=0.012). Application of literature-derived risk reductions showed no meaningful changes in MACE or ACM HRs or P values, although simulations of substantially greater use of drop-in cardioprotective glucose-lowering agents demonstrated blunting of signal detection. CONCLUSIONS: EXSCEL-observed HRs for MACE and ACM remained robust after right censoring or application of literature-derived risk reductions, but the exenatide versus placebo MACE effect size and statistical significance were increased by IPTW. Effects of open-label drop-in cardioprotective medications need to be considered carefully when designing, conducting, and analyzing cardiovascular outcome trials of glucose-lowering agents under the premise of glycemic equipoise. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT01144338.

Within-Trial Evaluation of Medical Resources, Costs, and Quality of Life Among Patients With Type 2 Diabetes Participating in the Exenatide Study of Cardiovascular Event Lowering (EXSCEL).

OBJECTIVE: To compare medical resource use, costs, and health utilities for 14,752 patients with type 2 diabetes who were randomized to once-weekly exenatide (EQW) or placebo in addition to usual diabetes care in the Exenatide Study of Cardiovascular Event Lowering (EXSCEL). RESEARCH DESIGN AND METHODS: Medical resource use data and responses to the EuroQol 5-Dimension (EQ-5D) instrument were collected at baseline and throughout the trial. Medical resources and medications were assigned values by using U.S. Medicare payments and wholesale acquisition costs, respectively. Secondary analyses used English costs. RESULTS: Patients were followed for an average of 3.3 years, during which time those randomized to EQW experienced 0.41 fewer inpatient days (7.05 vs. 7.46 days; relative rate ratio 0.91; P = 0.05). Rates of outpatient medical visits were similar, as were total inpatient and outpatient costs. Mean costs for nonstudy diabetes medications over the study period were ∼$1,600 lower with EQW than with placebo (P = 0.01). Total within-study costs, excluding study medication, were lower in the EQW arm than in the placebo arm ($28,907 vs. $30,914; P ≤ 0.01). When including the estimated cost of EQW, total mean costs were significantly higher in the EQW group than in the placebo group ($42,697 vs. $30,914; P < 0.01). With English costs applied, mean total costs, including exenatide costs, were £1,670 higher in the EQW group than the placebo group (£10,874 vs. £9,204; P < 0.01). There were no significant differences in EQ-5D health utilities between arms over time. CONCLUSIONS: Medical costs were lower in the EQW arm than the placebo arm, but total costs were significantly higher once the cost of branded exenatide was incorporated.

Confirming the Bidirectional Nature of the Association Between Severe Hypoglycemic and Cardiovascular Events in Type 2 Diabetes: Insights From EXSCEL.

OBJECTIVE: We sought to confirm a bidirectional association between severe hypoglycemic events (SHEs) and cardiovascular (CV) event risk and to characterize individuals at dual risk. RESEARCH DESIGN AND METHODS: In a post hoc analysis of 14,752 Exenatide Study of Cardiovascular Event Lowering (EXSCEL) participants, we examined time-dependent associations between SHEs and subsequent major adverse cardiac events (CV death, nonfatal myocardial infarction [MI] or stroke), fatal/nonfatal MI, fatal/nonfatal stroke, hospitalization for acute coronary syndrome (hACS), hospitalization for heart failure (hHF), and all-cause mortality (ACM), as well as time-dependent associations between nonfatal CV events and subsequent SHEs. RESULTS: SHEs were uncommon and not associated with once-weekly exenatide therapy (hazard ratio 1.13 [95% CI 0.94-1.36], P = 0.179). In fully adjusted models, SHEs were associated with an increased risk of subsequent ACM (1.83 [1.38-2.42], P < 0.001), CV death (1.60 [1.11-2.30], P = 0.012), and hHF (2.09 [1.37-3.17], P = 0.001), while nonfatal MI (2.02 [1.35-3.01], P = 0.001), nonfatal stroke (2.30 [1.25-4.23], P = 0.007), hACS (2.00 [1.39-2.90], P < 0.001), and hHF (3.24 [1.98-5.30], P < 0.001) were all associated with a subsequent increased risk of SHEs. The elevated bidirectional time-dependent hazards linking SHEs and a composite of all CV events were approximately constant over time, with those individuals at dual risk showing higher comorbidity scores compared with those without. CONCLUSIONS: These findings, showing greater risk of SHEs after CV events as well as greater risk of CV events after SHEs, validate a bidirectional relationship between CV events and SHEs in patients with high comorbidity scores.

Effects of exenatide and open-label SGLT2 inhibitor treatment, given in parallel or sequentially, on mortality and cardiovascular and renal outcomes in type 2 diabetes: insights from the EXSCEL trial.

BACKGROUND: Sodium-glucose cotransporter-2 inhibitors (SGLT2i) and glucagon-like peptide-1 receptor agonists (GLP-1 RA) improve cardiovascular and renal outcomes in patients with type 2 diabetes through distinct mechanisms. However, evidence on clinical outcomes in patients treated with both GLP-1 RA and SGLT2i is lacking. We aim to provide insight into the effects of open-label SGLT2i use in parallel with or shortly after once-weekly GLP-1 RA exenatide (EQW) on cardiorenal outcomes. METHODS: In the EXSCEL cardiovascular outcomes trial EQW arm, SGLT2i drop-in occurred in 8.7% of participants. These EQW+SGLT2i users were propensity-matched to: (1) placebo-arm participants not taking SGLT2i (n = 572 per group); and to (2) EQW-arm participants not taking SGLT2i (n = 575), based on their last measured characteristics before SGLT2i initiation, and equivalent study visit in comparator groups. Time-to-first major adverse cardiovascular event (MACE) and all-cause mortality (ACM) were compared using Cox regression analyses. eGFR slopes were quantified using mixed model repeated measurement analyses. RESULTS: In adjusted analyses, the risk for MACE with combination EQW+SGLT2i use was numerically lower compared with both placebo (adjusted hazard ratio 0.68, 95% CI 0.39-1.17) and EQW alone (0.85, 0.48-1.49). Risk of ACM was nominally significantly reduced compared with placebo (0.38, 0.16-0.90) and compared with EQW (0.41, 0.17-0.95). Combination EQW+SGLT2i use also nominally significantly improved estimated eGFR slope compared with placebo (+ 1.94, 95% CI 0.94-2.94 mL/min/1.73 m2/year) and EQW alone (+ 2.38, 1.40-3.35 mL/min/1.73 m2/year). CONCLUSIONS: This post hoc analysis supports the hypothesis that combinatorial EQW and SGLT2i therapy may provide benefit on cardiovascular outcomes and mortality. Trial registration Clinicaltrials.gov, Identifying number: NCT01144338, Date of registration: June 15, 2010.

Changes in Serum Calcitonin Concentrations, Incidence of Medullary Thyroid Carcinoma, and Impact of Routine Calcitonin Concentration Monitoring in the EXenatide Study of Cardiovascular Event Lowering (EXSCEL).

OBJECTIVE: Increases in serum calcitonin, a tumor marker for medullary thyroid carcinoma (MTC), have been associated with glucagon-like peptide 1 receptor agonist use in some preclinical studies. We report calcitonin changes in exenatide-treated and placebo-administered participants and MTC incidence in the EXenatide Study of Cardiovascular Event Lowering (EXSCEL) and consider the impact of within-trial calcitonin monitoring. RESEARCH DESIGN AND METHODS: EXSCEL participants were randomized 1:1 to once-weekly exenatide 2 mg or placebo. Serum calcitonin was measured at baseline (with trial medication discontinued if >40 ng/L) and annually thereafter (with trial medication discontinued if ≥50 ng/L). Median calcitonin concentrations were calculated at each time point, and thyroid malignancies were collected prospectively. Data regarding follow-up after an elevated calcitonin were collected retrospectively. RESULTS: At baseline, 52 (30 exenatide and 22 placebo) participants had calcitonin >40 ng/L, and during follow-up an additional 23 participants (15 exenatide and 8 placebo) had calcitonin ≥50 ng/L in the intention-to-treat population. Median calcitonin concentrations were similar between treatment groups at baseline with no increase over time. Confirmed MTC occurred in three participants (2 exenatide and 1 placebo), all of whom had significantly elevated baseline calcitonin values (413, 422, and 655 ng/L). CONCLUSIONS: During a median 3.2 years' follow-up, no change in serum calcitonin was seen with exenatide therapy. The three confirmed cases of MTC all occurred in participants with markedly elevated baseline calcitonin levels, measured prior to trial medication administration. Regular calcitonin monitoring identified no additional cases of MTC, suggesting no benefit of routine calcitonin monitoring during exenatide treatment.

Effect of Once-Weekly Exenatide on Clinical Outcomes According to Baseline Risk in Patients With Type 2 Diabetes Mellitus: Insights From the EXSCEL Trial.

Background In the EXSCEL (Exenatide Study of Cardiovascular Event Lowering), exenatide once-weekly resulted in a nonsignificant reduction in major adverse cardiovascular events ( MACEs ) and a nominal 14% reduction in all-cause mortality in 14 752 patients with type 2 diabetes mellitus (T2 DM ) with and without cardiovascular disease. Whether patients at increased risk for events experienced a comparatively greater treatment benefit with exenatide is unknown. Methods and Results In the EXSCEL population, we created risk scores for MACEs and all-cause mortality using step-wise selection of baseline characteristics. A risk score was calculated for each patient, and a time-to-event model for each end point was developed including the risk score, treatment assignment, and risk-treatment interaction. Interaction P values evaluating for a differential treatment effect by baseline risk were reported. Over a median follow-up of 3.2 years (interquartile range, 2.2, 4.4), 1091 (7.4%) patients died and 1744 (11.8%) experienced a MACE . Independent predictors of MACEs and all-cause mortality included age, sex, comorbidities (eg, previous cardiovascular event), body mass index, blood pressure, hemoglobin A1c, and estimated glomerular filtration rate. The all-cause mortality and MACE risk models had modest discrimination with optimism-corrected c-indices of 0.73 and 0.71, respectively. No interaction was observed between treatment effect and risk profile for either end point (both interactions, P>0.1). Conclusions Baseline characteristics (eg, age, previous cardiovascular events) and routine laboratory values (eg, hemoglobin A1c, estimated glomerular filtration rate) provided modest prognostic value for mortality and MACEs in a broad population of patients with type 2 diabetes mellitus. Exenatide's effects on mortality and MACEs were consistent across the spectrum of baseline risk. Clinical Trial Registration URL: https://www.clinicaltrials.gov . Unique identifier: NCT 01144338.

Cardiovascular outcomes with glucagon-like peptide-1 receptor agonists in patients with type 2 diabetes: a meta-analysis.

BACKGROUND: Glucagon-like peptide-1 (GLP-1) receptor agonists are effective glucose-lowering drugs. Findings from cardiovascular outcome trials showed cardiovascular safety of GLP-1 receptor agonists, but results for cardiovascular efficacy were varied. We aimed to examine overall cardiovascular efficacy for lixisenatide, liraglutide, semaglutide, and extended-release exenatide. METHODS: In this systematic review and meta-analysis, we analysed data from eligible trials that assessed the safety and efficacy of GLP-1 receptor agonists compared with placebo in adult patients (aged 18 years or older) with type 2 diabetes and had a primary outcome including, but not limited to, cardiovascular mortality, non-fatal myocardial infarction, and non-fatal stroke. We searched PubMed and MEDLINE without language restrictions up to Sept 18, 2017, for eligible trials. We did a meta-analysis of available trial data using a random-effects model to calculate overall hazard ratios (HRs) for cardiovascular efficacy outcomes and odds ratios for key safety outcomes. FINDINGS: Of 12 articles identified in our search and screened for eligibility, four trials of cardiovascular outcomes of GLP-1 receptor agonists were identified: ELIXA (lixisenatide), LEADER (liraglutide), SUSTAIN 6 (semaglutide), and EXSCEL (extended-release exenatide). Compared with placebo, GLP-1 receptor agonist treatment showed a significant 10% relative risk reduction in the three-point major adverse cardiovascular event primary outcome (cardiovascular mortality, non-fatal myocardial infarction, and non-fatal stroke; HR 0·90, 95% CI 0·82-0·99; p=0·033), a 13% RRR in cardiovascular mortality (0·87, 0·79-0·96; p=0·007), and a 12% relative risk reduction in all-cause mortality (0·88, 0·81-0·95; p=0·002), with low-to-moderate between-trial statistical heterogeneity. No significant effect of GLP-1 receptor agonists was identified on fatal and non-fatal myocardial infarction, fatal and non-fatal stroke, hospital admission for unstable angina, or hospital admission for heart failure. Overall, no significant differences were seen in severe hypoglycaemia, pancreatitis, pancreatic cancer, or medullary thyroid cancer reported between GLP-1 receptor agonist treatment and placebo. INTERPRETATION: Our findings show cardiovascular safety across all GLP-1 receptor agonist cardiovascular outcome trials and suggest that drugs in this class can reduce three-point major adverse cardiovascular events, cardiovascular mortality, and all-cause mortality risk, albeit to varying degrees for individual drugs, without significant safety concerns. GLP-1 receptor agonists have a favourable risk-benefit balance overall, which should allow the choice of drug to be individualised to each patient's needs. FUNDING: Amylin Pharmaceuticals (AstraZeneca).

Effects of Once-Weekly Exenatide on Cardiovascular Outcomes in Type 2 Diabetes.

BACKGROUND: The cardiovascular effects of adding once-weekly treatment with exenatide to usual care in patients with type 2 diabetes are unknown. METHODS: We randomly assigned patients with type 2 diabetes, with or without previous cardiovascular disease, to receive subcutaneous injections of extended-release exenatide at a dose of 2 mg or matching placebo once weekly. The primary composite outcome was the first occurrence of death from cardiovascular causes, nonfatal myocardial infarction, or nonfatal stroke. The coprimary hypotheses were that exenatide, administered once weekly, would be noninferior to placebo with respect to safety and superior to placebo with respect to efficacy. RESULTS: In all, 14,752 patients (of whom 10,782 [73.1%] had previous cardiovascular disease) were followed for a median of 3.2 years (interquartile range, 2.2 to 4.4). A primary composite outcome event occurred in 839 of 7356 patients (11.4%; 3.7 events per 100 person-years) in the exenatide group and in 905 of 7396 patients (12.2%; 4.0 events per 100 person-years) in the placebo group (hazard ratio, 0.91; 95% confidence interval [CI], 0.83 to 1.00), with the intention-to-treat analysis indicating that exenatide, administered once weekly, was noninferior to placebo with respect to safety (P<0.001 for noninferiority) but was not superior to placebo with respect to efficacy (P=0.06 for superiority). The rates of death from cardiovascular causes, fatal or nonfatal myocardial infarction, fatal or nonfatal stroke, hospitalization for heart failure, and hospitalization for acute coronary syndrome, and the incidence of acute pancreatitis, pancreatic cancer, medullary thyroid carcinoma, and serious adverse events did not differ significantly between the two groups. CONCLUSIONS: Among patients with type 2 diabetes with or without previous cardiovascular disease, the incidence of major adverse cardiovascular events did not differ significantly between patients who received exenatide and those who received placebo. (Funded by Amylin Pharmaceuticals; EXSCEL ClinicalTrials.gov number, NCT01144338 .).

Baseline characteristics of patients enrolled in the Exenatide Study of Cardiovascular Event Lowering (EXSCEL).

BACKGROUND: EXSCEL is a randomized, double-blind, placebo-controlled trial examining the effect of exenatide once-weekly (EQW) versus placebo on time to the primary composite outcome (cardiovascular death, nonfatal myocardial infarction or nonfatal stroke) in patients with type 2 diabetes mellitus (DM) and a wide range of cardiovascular (CV) risk. METHODS: Patients were enrolled at 688 sites in 35 countries. We describe their baseline characteristics according to prior CV event status and compare patients with those enrolled in prior glucagon-like peptide-1 receptor agonist (GLP-1RA) outcomes trials. RESULTS: Of a total of 14,752 participants randomized between June 2010 and September 2015, 6,788 (46.0%) patients were enrolled in Europe; 3,708 (25.1%), North America; 2,727 (18.5%), Latin America; and 1,529 (10.4%), Asia Pacific. Overall, 73% had at least one prior CV event (70% coronary artery disease, 24% peripheral arterial disease, 22% cerebrovascular disease). The median (IQR) age was 63 years (56, 69), 38% were female, median baseline HbA1c was 8.0% (7.3, 8.9) and 16% had a prior history of heart failure. Those without a prior CV event were younger with a shorter duration of diabetes and better renal function than those with at least one prior CV event. Compared with prior GLP-1RA trials, EXSCEL has a larger percentage of patients without a prior CV event and a notable percentage who were taking a dipeptidyl peptidase-4 inhibitor at baseline (15%). CONCLUSIONS: EXSCEL is one of the largest global GLP-1RA trials, evaluating the safety and efficacy of EQW with a broad patient population that may extend generalizability compared to prior GLP-1RA trials (ClinicalTrials.gov number, NCT01144338).

Comparison of the circulating metabolite profile of PF-04991532, a hepatoselective glucokinase activator, across preclinical species and humans: potential implications in metabolites in safety testing assessment.

A previous report from our laboratory disclosed the identification of PF-04991532 [(S)-6-(3-cyclopentyl-2-(4-trifluoromethyl)-1H-imidazol-1-yl)propanamido)nicotinic acid] as a hepatoselective glucokinase activator for the treatment of type 2 diabetes mellitus. Lack of in vitro metabolic turnover in microsomes and hepatocytes from preclinical species and humans suggested that metabolism would be inconsequential as a clearance mechanism of PF-04991532 in vivo. Qualitative examination of human circulating metabolites using plasma samples from a 14-day multiple ascending dose clinical study, however, revealed a glucuronide (M1) and monohydroxylation products (M2a and M2b/M2c) whose abundances (based on UV integration) were greater than 10% of the total drug-related material. Based on this preliminary observation, mass balance/excretion studies were triggered in animals, which revealed that the majority of circulating radioactivity following the oral administration of [¹4C]PF-04991532 was attributed to an unchanged parent (>70% in rats and dogs). In contrast with the human circulatory metabolite profile, the monohydroxylated metabolites were not detected in circulation in either rats or dogs. Available mass spectral evidence suggested that M2a and M2b/M2c were diastereomers derived from cyclopentyl ring oxidation in PF-04991532. Because cyclopentyl ring hydroxylation on the C-2 and C-3 positions can generate eight possible diastereomers, it was possible that additional diastereomers may have also formed and would need to be resolved from the M2a and M2b/M2c peaks observed in the current chromatography conditions. In conclusion, the human metabolite scouting study in tandem with the animal mass balance study allowed early identification of PF-04991532 oxidative metabolites, which were not predicted by in vitro methods and may require additional scrutiny in the development phase of PF-04991532.

Effects of multiple doses of the DPP-IV inhibitor PF-734200 on the relationship between GLP-1 and glucose in subjects with type 2 diabetes mellitus.

A randomized, placebo-controlled study evaluated the effects multiple-doses (28 days) dipeptidyl peptidase-IV (DPP-IV) inhibitor PF-734200 on DPP-IV activity, glucose, glucagon-like peptide-1 (GLP-1), glucagon and insulin levels in 72 subjects with type 2 diabetes. The relationship between changes in active GLP-1 and glucose during a meal test appeared non-linear.

Intraportal administration of neuropeptide Y and hepatic glucose metabolism.

We examined whether intraportal delivery of neuropeptide Y (NPY) affects glucose metabolism in 42-h-fasted conscious dogs using arteriovenous difference methodology. The experimental period was divided into three subperiods (P1, P2, and P3). During all subperiods, the dogs received infusions of somatostatin, intraportal insulin (threefold basal), intraportal glucagon (basal), and peripheral intravenous glucose to increase the hepatic glucose load twofold basal. Following P1, in the NPY group (n = 7), NPY was infused intraportally at 0.2 and 5.1 pmol.kg(-1).min(-1) during P2 and P3, respectively. The control group (n = 7) received intraportal saline infusion without NPY. There were no significant changes in hepatic blood flow in NPY vs. control. The lower infusion rate of NPY (P2) did not enhance net hepatic glucose uptake. During P3, the increment in net hepatic glucose uptake (compared with P1) was 4 +/- 1 and 10 +/- 2 micromol.kg(-1).min(-1) in control and NPY, respectively (P < 0.05). The increment in net hepatic fractional glucose extraction during P3 was 0.015 +/- 0.005 and 0.039 +/- 0.008 in control and NPY, respectively (P < 0.05). Net hepatic carbon retention was enhanced in NPY vs. control (22 +/- 2 vs. 14 +/- 2 micromol.kg(-1).min(-1), P < 0.05). There were no significant differences between groups in the total glucose infusion rate. Thus, intraportal NPY stimulates net hepatic glucose uptake without significantly altering whole body glucose disposal in dogs.

Non-linear increase in GLP-1 levels in response to DPP-IV inhibition in healthy adult subjects.

AIM: Dipeptidyl peptidase-IV (DPP-IV) inhibitors represent a new promising therapeutic intervention for the treatment of type 2 diabetes mellitus. The aim of this study was to investigate the effects of DPP-IV inhibition by PF-00734200, a potent competitive DPP-IV inhibitor, on the dynamics of DPP-IV activity and glucagon-like peptide-1 (GLP-1) kinetics in healthy adult subjects. METHODS: This was a prospective randomized, crossover, placebo-controlled, ascending, single, oral dose study conducted at a clinical research centre. Twenty-seven healthy adult subjects were randomized to receive placebo or PF-00734200 with doses ranging from 0.3 to 300 mg (n = 9 per dose group). Pharmacokinetic and pharmacodynamic end points (DPP-IV activity and GLP-1) were measured prior to, and various times after, dosing. RESULTS: PF-00734200 was well tolerated in all subjects. Pharmacokinetics (PK) data indicate that the drug was rapidly absorbed and declined in a biphasic fashion. Mean maximum concentration and area under concentration curve appeared to increase with doses proportionally. DPP-IV inhibition increased with PF-00734200 concentrations, which can be described by an E(max) model with EC50 approximately being 14 ng/ml. DPP-IV inhibition led to greater GLP-1 level accumulation compared with placebo. Plasma GLP-1 levels stimulated by meals were augmented by DPP-IV inhibition. However, the increase in GLP-1 with DPP-IV inhibition was non-linear and maximized at 10 mg, a dose which resulted in about 75% weighted average DPP-IV inhibition over 24 h and a 2.3-fold increase in GLP-1 over placebo. Moreover, even with near complete inhibition of DPP-IV for over 24 h at the highest PF-00734200 dose levels, the GLP-1 levels actually declined during the night compared with postdinner levels. CONCLUSION: DPP-IV inhibition by PF-00734200 resulted in a non-linear increase in plasma GLP-1 level, suggesting GLP-1 levels may be limited by meal stimulus or by production capacity. In addition, GLP-1 level declined even during maximal DPP-IV inhibition, suggesting that there may be additional pathways of GLP-1 elimination other than DPP-IV enzymatic breakdown.

Stimulation of both type I and type II corticosteroid receptors blunts counterregulatory responses to subsequent hypoglycemia in healthy man.

Antecedent increases of corticosteroids can blunt counterregulatory responses to subsequent stress. Our aim was to determine whether prior activation of type I corticosteroid (mineralocorticoid) or type II corticosteroid (glucocorticoid) receptors blunts counterregulatory responses to subsequent hypoglycemia. Healthy volunteers participated in five randomized 2-day protocols. Day 1 involved morning and afternoon 2-h hyperinsulinemic (9 pmol.kg(-1).min(-1)) euglycemic clamps (PE; n = 14), hypoglycemic clamps (PH; n = 14), or euglycemic clamps with oral fludrocortisone (PE + F; type I agonist, 0.2 mg, n = 14), oral dexamethasone (PE + D; type II agonist, 0.75 mg, n = 13), or both (PE + F + D; n = 14). Day 2 was identical in all protocols and consisted of a 2-h hyperinsulinemic hypoglycemic clamp. Day 2 insulin (625 +/- 40 pmol/l) and glucose (2.9 +/- 0.1 mmol/l) levels were similar among groups. Levels of epinephrine, norepinephrine, glucagon, growth hormone, and MSNA were significantly blunted by prior activation of both type I and type II corticosteroid receptors to PE. Prior activation of both corticosteroid receptors also significantly blunted NEFA during subsequent hypoglycemia. Thus, levels of a wide spectrum of key counterregulatory mechanisms (neuroendocrine, ANS, and metabolic) were blunted by antecedent pharmacological stimulation of either type I or type II corticosteroid receptors in healthy man. These data suggest that activation of type I corticosteroid receptors in man can have acute and profound regulating effects on physiological stress in man. Both type I and type II corticosteroid receptors may be involved in the multiple mechanisms controlling counterregulatory responses to hypoglycemia in healthy man.

Islet auto-transplantation into an omental or splenic site results in a normal beta cell but abnormal alpha cell response to mild non-insulin-induced hypoglycemia.

The present studies were designed to determine if totally pancreatectomized dogs that underwent islet auto-transplantation retained a functional pancreatic counterregulatory response to mild non-insulin-induced hypoglycemia. Six dogs underwent total pancreatectomy followed by islet auto-transplantation to spleen or omentum. The animals recovered and fasting plasma glucose and insulin levels were normal. Each study consisted of a 40-min control and 2-h test period. At the onset of the test period, a glycogen phosphorylase inhibitor was administered to create mild hypoglycemia. Plasma glucose in the transplanted dogs fell from 120 +/- 4 to 80 +/- 3 mg/dL, similar to the minimum in control dogs without islet auto-transplantation (108 +/- 2 to 84 +/- 5 mg/dL). The fall in plasma insulin was similar in both groups. Glucagon, however, rose in response to hypoglycemia in the control dogs (Delta24 +/- 7 pg/mL; p < 0.05), but failed to rise significantly in the transplanted dogs (Delta9 +/- 6 pg/mL). In fact, only 1 of 7 control dogs failed to increase plasma glucagon by at least 25%, whereas 4 of 6 transplanted dogs failed to do so. In conclusion, in conscious dogs with successfully auto-transplanted islets, the beta cell response to mild non-insulin-induced hypoglycemia was normal, whereas the alpha cell response was not.

Effects of hyperglycemia, glucagon, and epinephrine on renal glucose release in the conscious dog.

The role of renal glucose production after an overnight fast and in response to different hormonal conditions has been debated. The aim of this study was to determine whether hyperglycemia, glucagon, or epinephrine can affect renal glucose production. In 18-hour fasted conscious dogs a pancreatic clamp initially fixed insulin and glucagon at basal levels, following which 1 of 4 protocols was instituted. In G+E glucagon (1.5 ng. kg(-1). min(-1); portally) and epinephrine (50 ng. kg(-1). min(-1); peripherally) were increased, in G glucagon was increased alone, in E epinephrine was increased alone, and in C neither were increased. In G, E, and C, glucose was infused to match the hyperglycemia in G+E (approximately 250 mg/dL). The average net renal glucose output during the last 2 hours was not different from the basal values in any group. Furthermore, the changes in unidirectional renal glucose production were not significantly different among groups. Therefore, after an overnight fast in the conscious dog, the kidneys do not significantly contribute to overall glucose production or respond to glucagon or epinephrine.

Selective stimulation of G-6-Pase catalytic subunit but not G-6-P transporter gene expression by glucagon in vivo and cAMP in situ.

We recently compared the regulation of glucose-6-phosphatase (G-6-Pase) catalytic subunit and glucose 6-phosphate (G-6-P) transporter gene expression by insulin in conscious dogs in vivo (Hornbuckle LA, Edgerton DS, Ayala JE, Svitek CA, Neal DW, Cardin S, Cherrington AD, and O'Brien RM. Am J Physiol Endocrinol Metab 281: E713-E725, 2001). In pancreatic-clamped, euglycemic conscious dogs, a 5-h period of hypoinsulinemia led to a marked increase in hepatic G-6-Pase catalytic subunit mRNA; however, G-6-P transporter mRNA was unchanged. Here, we demonstrate, again using pancreatic-clamped, conscious dogs, that glucagon is a candidate for the factor responsible for this selective induction. Thus glucagon stimulated G-6-Pase catalytic subunit but not G-6-P transporter gene expression in vivo. Furthermore, cAMP stimulated endogenous G-6-Pase catalytic subunit gene expression in HepG2 cells but had no effect on G-6-P transporter gene expression. The cAMP response element (CRE) that mediates this induction was identified through transient transfection of HepG2 cells with G-6-Pase catalytic subunit-chloramphenicol acetyltransferase fusion genes. Gel retardation assays demonstrate that this CRE binds several transcription factors including CRE-binding protein and CCAAT enhancer-binding protein.