Pharmacokinetics and Tolerability of Lorcaserin in Special Populations: Elderly Patients and Patients with Renal or Hepatic Impairment.

PURPOSE: To determine whether dosage adjustment is likely to be necessary for effective and well-tolerated use of a pharmaceutical agent, guidance documents from the US Food and Drug Administration recommend pharmacokinetics studies in patients with impaired renal or impaired hepatic function and in the elderly population. Three studies were conducted to evaluate the pharmacokinetic properties and tolerability of lorcaserin in these populations. METHODS: Lorcaserin was evaluated in single-dose pharmacokinetics studies of 3 overweight/obese populations: (1) elderly (aged >65 years) patients; (2) patients with impaired renal function; and (3) those with impaired hepatic function. FINDINGS: In elderly patients, Cmax was lower (geometric mean ratio [GMR], 0.83; 90% CI, 0.71-0.97), but AUC was unchanged versus adult patients. In patients with renal impairment, Cmax was reduced versus that in patients with normal renal function (GMR: mild impairment, 0.99 [90% CI, 0.76-1.29]; moderate, 0.70 [90% CI, 0.54-0.90]; and severe, 0.69 [90% CI, 0.53-0.89]); no trend in AUC was observed in this group versus renal impairment. In patients with hepatic impairment, Cmax was decreased (GMR: mild impairment, 0.92 [90% CI, 0.76-1.11]; moderate, 0.86 [90% CI, 0.71-1.04]), and AUC was increased versus patients with normal hepatic function. IMPLICATIONS: Based on these findings, no lorcaserin dose adjustments are necessary in elderly patients with normal renal function or in patients with mild/moderate renal or hepatic impairment. ClinicalTrials.gov identifiers: NCT00828581, NCT00828438, and NCT00828932.

Echocardiographic assessment of cardiac valvular regurgitation with lorcaserin from analysis of 3 phase 3 clinical trials.

BACKGROUND: Lorcaserin is a selective 5-HT2C agonist evaluated for weight management in clinical trials. Echocardiographic monitoring was conducted to test the hypothesis that selective 5-HT2C agonism would avoid valvular heart disease. METHODS AND RESULTS: Echocardiographic and weight change data from 5249 obese and overweight patients in 3 phase 3 trials were integrated. Treatment duration with 10 mg lorcaserin twice daily or placebo was 52 weeks. The proportions of patients who developed Food and Drug Administration-defined valvulopathy (≥ mild aortic or ≥ moderate mitral regurgitation) and changes in regurgitant grade at each heart valve were evaluated. Possible associations between weight or body mass index change and valvulopathy were explored. New valvulopathy was present in 2.04% of placebo and 2.37% of lorcaserin recipients at 52 weeks (risk difference, 0.33%; 95% confidence interval, -0.46 to 1.13; risk ratio, 1.16 [all patients with sufficient echocardiographic data, last-observation-carried-forward imputation] or 1.03 [patients who completed 52 weeks]). Changes in weight and body mass index were negatively associated with presence of valvulopathy at week 52 (P=0.02 and P=0.04, respectively); a 5% decrease in weight was associated with an odds ratio of 1.15 for Food and Drug Administration-defined valvulopathy. Most changes in regurgitation were ±1 grade in both treatment groups at all heart valves. CONCLUSIONS: In 3 prospective placebo-controlled trials with integrated data for 5249 patients, the rate of echocardiographic valvulopathy was similar with lorcaserin and placebo. Point estimates for risk ratios ranged from 1.03 to 1.16 and may be at least partially influenced by greater weight loss in the lorcaserin group than in the placebo group. CLINICAL TRIAL REGISTRATION: URL: http://www.clinicaltrials.gov. Unique identifiers: NCT00395135, NCT00603291, NCT00603902.

Randomized placebo-controlled clinical trial of lorcaserin for weight loss in type 2 diabetes mellitus: the BLOOM-DM study.

The BLOOM-DM (Behavioral Modification and Lorcaserin for Obesity and Overweight Management in Diabetes Mellitus) study evaluated efficacy and safety of lorcaserin for weight loss in patients with type 2 diabetes. Secondary objectives included evaluations of glycemic control, lipids, blood pressure, and quality of life. This 1-year, randomized, placebo-controlled trial enrolled 604 patients 1:1:1 to placebo, lorcaserin 10 mg once daily (QD) or lorcaserin 10 mg twice daily (BID). Patients were treated with metformin, a sulfonylurea (SFU) or both; had glycated hemoglobin (HbA(1c)) 7-10%; were 18-65 years old; and had BMI 27-45 kg/m(2). Patients received diet and exercise counseling. Safety monitoring included serial echocardiograms. Mean (± SD) age was 52.7 ± 8.7; 54.2% were women; 60.5% were white, 20.9% were African American, and 13.8% were Hispanic. Mean (± SD) weight was 103.6 ± 17.8 kg; BMI was 36.0 ± 4.5 kg/m(2). Most patients (91.7%) took metformin; 50.2% took a SFU. More patients lost ≥5% body weight with lorcaserin BID (37.5%; P < 0.001) or lorcaserin QD (44.7%; P < 0.001) vs. placebo (16.1%; modified intent to treat (MITT)/last observation carried forward (LOCF)). Least square mean (± SEM) weight change was -4.5 ± 0.35% with lorcaserin BID and -5.0 ± 0.5% with lorcaserin QD vs. -1.5 ± 0.36% with placebo (P < 0.001 for each). HbA(1c) decreased 0.9 ± 0.06 with lorcaserin BID, 1.0 ± 0.09 with lorcaserin QD, and 0.4 ± 0.06 with placebo (P < 0.001 for each); fasting glucose decreased 27.4 ± 2.5 mg/dl, -28.4 ± 3.8 mg/dl, and 11.9 ± 2.5 mg/dl, respectively (P < 0.001 for each). Symptomatic hypoglycemia occurred in 7.4% of patients on lorcaserin BID, 10.5% on lorcaserin QD, and 6.3% on placebo. Common adverse events were headache, back pain, nasopharyngitis, and nausea. Lorcaserin was associated with significant weight loss and improvement in glycemic control in patients with type 2 diabetes.

A one-year randomized trial of lorcaserin for weight loss in obese and overweight adults: the BLOSSOM trial.

CONTEXT: Lorcaserin is a novel selective agonist of the serotonin 2C receptor. OBJECTIVE: Our objective was to evaluate the effects of lorcaserin on body weight, cardiovascular risk factors, and safety in obese and overweight patients. DESIGN AND SETTING: This randomized, placebo-controlled, double-blind, parallel arm trial took place at 97 U.S. research centers. PATIENTS: Patients included 4008 patients, aged 18-65 yr, with a body mass index between 30 and 45 kg/m(2) or between 27 and 29.9 kg/m(2) with an obesity-related comorbid condition. INTERVENTIONS: Patients were randomly assigned in a 2:1:2 ratio to receive lorcaserin 10 mg twice daily (BID), lorcaserin 10 mg once daily (QD), or placebo. All patients received diet and exercise counseling. MAIN OUTCOME MEASURES: The ordered primary endpoints were proportion of patients achieving at least 5% reduction in body weight, mean change in body weight, and proportion of patients achieving at least 10% reduction in body weight at 1 yr. Serial echocardiograms monitored heart valve function. RESULTS: Significantly more patients treated with lorcaserin 10 mg BID and QD lost at least 5% of baseline body weight (47.2 and 40.2%, respectively) as compared with placebo (25.0%, P < 0.001 vs. lorcaserin BID). Least squares mean (95% confidence interval) weight loss with lorcaserin BID and QD was 5.8% (5.5-6.2%) and 4.7% (4.3-5.2%), respectively, compared with 2.8% (2.5-3.2%) with placebo (P < 0.001 vs. lorcaserin BID; least squares mean difference, 3.0%). Weight loss of at least 10% was achieved by 22.6 and 17.4% of patients receiving lorcaserin 10 mg BID and QD, respectively, and 9.7% of patients in the placebo group (P < 0.001 vs. lorcaserin BID). Headache, nausea, and dizziness were the most common lorcaserin-related adverse events. U.S. Food and Drug Administration-defined echocardiographic valvulopathy occurred in 2.0% of patients on placebo and 2.0% on lorcaserin 10 mg BID. CONCLUSIONS: Lorcaserin administered in conjunction with a lifestyle modification program was associated with dose-dependent weight loss that was significantly greater than with placebo.

Lorcaserin, a 5-HT(2C) receptor agonist, reduces body weight by decreasing energy intake without influencing energy expenditure.

CONTEXT: Lorcaserin, a selective 5-hydroxytryptamine (5-HT)(2C) receptor agonist, reduces body weight. It is unclear whether weight loss is due to reduced energy intake (EI) or also to enhanced energy expenditure (EE). OBJECTIVE: This study tested the effect of lorcaserin on EI and EE. DESIGN, PARTICIPANTS, AND INTERVENTION: In a double-blind, randomized, placebo-controlled trial, 57 (39 women) overweight and obese (body mass index, 27-45 kg/m(2)) adults were randomized to placebo (n = 28) or 10 mg twice daily lorcaserin (n = 29) for 56 d. Weight maintenance was imposed during d 1-7. Beginning on d 8, participants followed a diet and exercise plan targeting a 600 kcal/d deficit. OUTCOMES: At baseline and after 7 and 56 d of treatment, we measured body weight, body composition (dual x-ray absorptiometry), blood pressure, heart rate, EI at lunch and dinner, subjective appetite ratings, and 24-h EE and 24-h-respiratory quotient (RQ), measured by indirect calorimetry in a respiratory chamber. RESULTS: After 7 d of weight maintenance, EI was significantly (P < 0.01) reduced with lorcaserin but not placebo (mean ± sem for lorcaserin, -286 ± 86 kcal; placebo, -147 ± 89 kcal). After 56 d, lorcaserin resulted in significantly larger reductions in body weight (lorcaserin, -3.8 ± 0.4 kg; placebo, -2.2 ± 0.5 kg; P < 0.01), EI (lorcaserin, -470 ± 87 kcal; placebo, -205 ± 91 kcal; P < .05), and appetite ratings than in placebo. Changes in 24-h EE and 24-h RQ did not differ between groups, even after 24-h EE was adjusted for body weight and composition. Compared with placebo, lorcaserin had no effect on systolic or diastolic blood pressure or heart rate after 56 d. CONCLUSIONS: Lorcaserin reduces body weight through reduced EI, not altered EE or RQ.

Glucagon-like peptide-1 and the exenatide analogue AC3174 improve cardiac function, cardiac remodeling, and survival in rats with chronic heart failure.

BACKGROUND: Accumulating evidence suggests glucagon-like peptide-1 (GLP-1) exerts cardioprotective effects in animal models of myocardial infarction (MI). We hypothesized that chronic treatment with GLP-1 or the exenatide analog AC3174 would improve cardiac function, cardiac remodeling, insulin sensitivity, and exercise capacity (EC) in rats with MI-induced chronic heart failure (CHF) caused by coronary artery ligation. METHODS: Two weeks post-MI, male Sprague-Dawley rats were treated with GLP-1 (2.5 or 25 pmol/kg/min), AC3174 (1.7 or 5 pmol/kg/min) or vehicle via subcutaneous infusion for 11 weeks. Cardiac function and morphology were assessed by echocardiography during treatment. Metabolic, hemodynamic, exercise-capacity, and body composition measurements were made at study end. RESULTS: Compared with vehicle-treated rats with CHF, GLP-1 or AC3174 significantly improved cardiac function, including left ventricular (LV) ejection fraction, and end diastolic pressure. Cardiac dimensions also improved as evidenced by reduced LV end diastolic and systolic volumes and reduced left atrial volume. Vehicle-treated CHF rats exhibited fasting hyperglycemia and hyperinsulinemia. In contrast, GLP-1 or AC3174 normalized fasting plasma insulin and glucose levels. GLP-1 or AC3174 also significantly reduced body fat and fluid mass and improved exercise capacity and respiratory efficiency. Four of 16 vehicle control CHF rats died during the study compared with 1 of 44 rats treated with GLP-1 or AC3174. The cellular mechanism by which GLP-1 or AC3174 exert cardioprotective effects appears unrelated to changes in GLUT1 or GLUT4 translocation or expression. CONCLUSIONS: Chronic treatment with either GLP-1 or AC3174 showed promising cardioprotective effects in a rat model of CHF. Hence, GLP-1 receptor agonists may represent a novel approach for the treatment of patients with CHF or cardiovascular disease associated with type 2 diabetes.

Multicenter, placebo-controlled trial of lorcaserin for weight management.

BACKGROUND: Lorcaserin is a selective serotonin 2C receptor agonist that could be useful in reducing body weight. METHODS: In this double-blind clinical trial, we randomly assigned 3182 obese or overweight adults (mean body-mass index [the weight in kilograms divided by the square of the height in meters] of 36.2) to receive lorcaserin at a dose of 10 mg, or placebo, twice daily for 52 weeks. All patients also underwent diet and exercise counseling. At week 52, patients in the placebo group continued to receive placebo but patients in the lorcaserin group were randomly reassigned to receive either placebo or lorcaserin. Primary outcomes were weight loss at 1 year and maintenance of weight loss at 2 years. Serial echocardiography was used to identify patients in whom valvulopathy (as defined by the Food and Drug Administration) developed. RESULTS: At 1 year, 55.4% of patients (883 of 1595) receiving lorcaserin and 45.1% of patients (716 of 1587) receiving placebo remained in the trial; 1553 patients continued into year 2. At 1 year, 47.5% of patients in the lorcaserin group and 20.3% in the placebo group had lost 5% or more of their body weight (P<0.001), corresponding to an average loss of 5.8+/-0.2 kg with lorcaserin and 2.2+/-0.1 kg with placebo during year 1 (P<0.001). Among the patients who received lorcaserin during year 1 and who had lost 5% or more of their baseline weight at 1 year, the loss was maintained in more patients who continued to receive lorcaserin during year 2 (67.9%) than in patients who received placebo during year 2 (50.3%, P<0.001). Among 2472 patients evaluated at 1 year and 1127 evaluated at 2 years, the rate of cardiac valvulopathy was not increased with the use of lorcaserin. Among the most frequent adverse events reported with lorcaserin were headache, dizziness, and nausea. The rates of serious adverse events in the two groups were similar. CONCLUSIONS: In conjunction with behavioral modification, lorcaserin was associated with significant weight loss and improved maintenance of weight loss, as compared with placebo. (Funded by Arena Pharmaceuticals; ClinicalTrials.gov number, NCT00395135.)

Nelotanserin, a novel selective human 5-hydroxytryptamine2A inverse agonist for the treatment of insomnia.

5-Hydroxytryptamine (5-HT)(2A) receptor inverse agonists are promising therapeutic agents for the treatment of sleep maintenance insomnias. Among these agents is nelotanserin, a potent, selective 5-HT(2A) inverse agonist. Both radioligand binding and functional inositol phosphate accumulation assays suggest that nelotanserin has low nanomolar potency on the 5-HT(2A) receptor with at least 30- and 5000-fold selectivity compared with 5-HT(2C) and 5-HT(2B) receptors, respectively. Nelotanserin dosed orally prevented (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI; 5-HT(2A) agonist)-induced hypolocomotion, increased sleep consolidation, and increased total nonrapid eye movement sleep time and deep sleep, the latter marked by increases in electroencephalogram (EEG) delta power. These effects on rat sleep were maintained after repeated subchronic dosing. In healthy human volunteers, nelotanserin was rapidly absorbed after oral administration and achieved maximum concentrations 1 h later. EEG effects occurred within 2 to 4 h after dosing, and were consistent with vigilance-lowering. A dose response of nelotanserin was assessed in a postnap insomnia model in healthy subjects. All doses (up to 40 mg) of nelotanserin significantly improved measures of sleep consolidation, including decreases in the number of stage shifts, number of awakenings after sleep onset, microarousal index, and number of sleep bouts, concomitant with increases in sleep bout duration. Nelotanserin did not affect total sleep time, or sleep onset latency. Furthermore, subjective pharmacodynamic effects observed the morning after dosing were minimal and had no functional consequences on psychomotor skills or memory. These studies point to an efficacy and safety profile for nelotanserin that might be ideally suited for the treatment of sleep maintenance insomnias.

Lorcaserin (APD356), a selective 5-HT(2C) agonist, reduces body weight in obese men and women.

Lorcaserin (APD356) is a potent, selective 5-HT(2C) agonist with ~15-fold and 100-fold selectivity vs. 5-HT(2A) and 5-HT(2B) receptors, respectively. This study evaluated the safety and efficacy of lorcaserin for weight reduction in obese patients during a 12-week period. The randomized, double-blind, placebo-controlled, parallel-arm study enrolled 469 men and women between ages 18 and 65 and with BMI 30-45 kg/m(2). Patients received placebo, lorcaserin 10 mg q.d., lorcaserin 15 mg q.d., or lorcaserin 10 mg b.i.d. for 12 weeks, and were counseled to maintain their usual diet and activity. The primary end point was change in weight from baseline to day 85 by completer analysis. Safety analyses included echocardiograms at Screening and day 85/study exit. Lorcaserin was associated with progressive weight loss of 1.8 kg, 2.6 kg, and 3.6 kg at 10 mg q.d., 15 mg q.d., and 10 mg b.i.d., respectively, compared to placebo weight loss of 0.3 kg (P < 0.001 for each group). Similar results were seen by intent-to-treat last observation-carried forward (ITT-LOCF) analysis. The proportions of completers achieving > or =5% of initial body weight were 12.8, 19.5, 31.2, and 2.3% in the 10 mg q.d., 15 mg q.d., 10 mg b.i.d., and placebo groups, respectively. The most frequent adverse events (AEs) were transient headache, nausea, and dizziness. Echocardiograms showed no apparent drug-related effects on heart valves or pulmonary artery pressure (PAP). Lorcaserin was well tolerated and efficacious for weight reduction in this 12-week study. Longer-term trials employing behavior modification will be needed to more fully assess its safety and efficacy.

APD125, a selective serotonin 5-HT(2A) receptor inverse agonist, significantly improves sleep maintenance in primary insomnia.

INTRODUCTION: Insomnia is a condition affecting 10% to 15% of the adult population and is characterized by difficulty falling asleep, difficulty staying asleep, or nonrestorative sleep, accompanied by daytime impairment or distress. This study evaluates APD125, a selective inverse agonist of the 5-HT(2A) receptor, for treatment of chronic insomnia, with particular emphasis on sleep maintenance. In phase 1 studies, APD125 improved sleep maintenance and was well tolerated. METHODOLOGY: Adult subjects (n=173) with DSM-IV defined primary insomnia were randomized into a multicenter, double-blind, placebo-controlled, 3-way crossover study to compare 2 doses of APD125 (10 mg and 40 mg) with placebo. Each treatment period was 7 days with a 7- to 9-day washout period between treatments. Polysomnographic recordings were performed at the initial 2 screening nights and at nights (N) 1/2 and N 6/7 of each treatment period. RESULTS: APD125 was associated with significant improvements in key sleep maintenance parameters measured by PSG. Wake time after sleep onset decreased (SEM) by 52.5 (3.2) min (10 mg) and 53.5 (3.5) min (40 mg) from baseline to N 1/2 vs. 37.8 (3.4) min for placebo, (P < 0.0001 for both doses vs. placebo), and by 51.7 (3.4) min (P = 0.01) and 48.0 (3.6) min (P = 0.2) at N 6/7 vs. 44.0 (3.8) min for placebo. Significant APD125 effects on wake time during sleep were also seen (P < 0.0001 N 1/2, P < 0.001 N 6/7). The number of arousals and number of awakenings decreased significantly with APD125 treatment compared to placebo. Slow wave sleep showed a statistically significant dose-dependent increase. There was no significant decrease in latency to persistent sleep. No serious adverse events were reported, and no meaningful differences in adverse event profiles were observed between either dose of APD125 and placebo. APD125 was not associated with next-day psychomotor impairment as measured by Digit Span, Digit Symbol Copy, and Digit Symbol Coding Tests. CONCLUSIONS: APD125 produced statistically significant improvements in objective parameters of sleep maintenance and sleep consolidation and was well tolerated in adults with primary chronic insomnia.

Leptin responsiveness restored by amylin agonism in diet-induced obesity: evidence from nonclinical and clinical studies.

Body weight is regulated by complex neurohormonal interactions between endocrine signals of long-term adiposity (e.g., leptin, a hypothalamic signal) and short-term satiety (e.g., amylin, a hindbrain signal). We report that concurrent peripheral administration of amylin and leptin elicits synergistic, fat-specific weight loss in leptin-resistant, diet-induced obese rats. Weight loss synergy was specific to amylin treatment, compared with other anorexigenic peptides, and dissociable from amylin's effect on food intake. The addition of leptin after amylin pretreatment elicited further weight loss, compared with either monotherapy condition. In a 24-week randomized, double-blind, clinical proof-of-concept study in overweight/obese subjects, coadministration of recombinant human leptin and the amylin analog pramlintide elicited 12.7% mean weight loss, significantly more than was observed with either treatment alone (P < 0.01). In obese rats, amylin pretreatment partially restored hypothalamic leptin signaling (pSTAT3 immunoreactivity) within the ventromedial, but not the arcuate nucleus and up-regulated basal and leptin-stimulated signaling in the hindbrain area postrema. These findings provide both nonclinical and clinical evidence that amylin agonism restored leptin responsiveness in diet-induced obesity, suggesting that integrated neurohormonal approaches to obesity pharmacotherapy may facilitate greater weight loss by harnessing naturally occurring synergies.

Effects of prior or concurrent food restriction on amylin-induced changes in body weight and body composition in high-fat-fed female rats.

Amylin infusion reduces food intake and slows body weight gain in rodents. In obese male rats, amylin (but not pair feeding) caused a preferential reduction of fat mass with protein preservation despite equal body weight loss in amylin-treated (fed ad libitum) and pair-fed rats. In the present study, the effect of prior or concurrent food restriction on the ability of amylin to cause weight loss was evaluated. Retired female breeder rats were maintained on a high-fat diet (40% fat) for 9 wk. Prior to drug treatment, rats were either fed ad libitum or food restricted for 10 days to lose 5% of their starting body weight. They were then subdivided into treatment groups that received either vehicle or amylin (100 microgxkg(-1)xday(-1) via subcutaneous minipump) and placed under either a restricted or ad libitum feeding schedule (for a total of 8 treatment arms). Amylin 1) significantly reduced body weight compared with vehicle under all treatment conditions, except in always restricted animals, 2) significantly decreased percent body fat in all groups, and 3) preserved lean mass in all groups. These results indicate that amylin's anorexigenic and fat-specific weight loss properties can be extended to a variety of nutritive states in female rats.

Biological activity of AC3174, a peptide analog of exendin-4.

Exenatide, the active ingredient of BYETTA (exenatide injection), is an incretin mimetic that has been developed for the treatment of patients with type 2 diabetes. Exenatide binds to and activates the known GLP-1 receptor with a potency comparable to that of the mammalian incretin GLP-1(7-36), thereby acting as a glucoregulatory agent. AC3174 is an analog of exenatide with leucine substituted for methionine at position 14, [Leu(14)]exendin-4. The purpose of these studies was to evaluate the glucoregulatory activity and pharmacokinetics of AC3174. In RINm5f cell membranes, the potency of AC3174 for the displacement of [(125)I]GLP-1 and activation of adenylate cyclase was similar to that of exenatide and GLP-1. In vivo, AC3174, administered as a single IP injection, significantly decreased plasma glucose concentration and glucose excursion following the administration of an oral glucose challenge in both non-diabetic (C57BL/6) and diabetic db/db mice (P<0.05 vs. vehicle-treated). The magnitude of glucose lowering of AC3174 was comparable to exenatide. The ED(50) values of AC3174 for glucose lowering (60 minute post-dose) were 1.2 microg/kg in db/db mice and 1.3 microg/kg in C57BL/6 mice. AC3174 has insulinotropic activity in vivo. Administration of AC3174 resulted in a 4-fold increase in insulin concentrations in normal mice following an IP glucose challenge. AC3174 was also shown to inhibit food intake and decrease gastric emptying in rodent models. AC3174 was stable in human plasma (>90% of parent peptide was present after 5 h of incubation). In rats, the in vivo half-life of AC3174 was 42-43 min following SC administration. In summary, AC3174 is an analog of exenatide that binds to the GLP-1 receptor in vitro and shares many of the biological and glucoregulatory activities of exenatide and GLP-1 in vivo.

Antiobesity effects of the beta-cell hormone amylin in diet-induced obese rats: effects on food intake, body weight, composition, energy expenditure, and gene expression.

Effects of amylin and pair feeding (PF) on body weight and metabolic parameters were characterized in diet-induced obesity-prone rats. Peripherally administered rat amylin (300 microg/kg.d, 22d) reduced food intake and slowed weight gain: approximately 10% (P<0.05), similar to PF. Fat loss was 3-fold greater in amylin-treated rats vs. PF (P<0.05). Whereas PF decreased lean tissue (P<0.05 vs. vehicle controls; VEH), amylin did not. During wk 1, amylin and PF reduced 24-h respiratory quotient (mean+/-se, 0.82+/-0.0, 0.81+/-0.0, respectively; P<0.05) similar to VEH (0.84+/-0.01). Energy expenditure (EE mean+/-se) tended to be reduced by PF (5.67+/-0.1 kcal/h.kg) and maintained by amylin (5.86+/-0.1 kcal/h.kg) relative to VEH (5.77+/-0.0 kcal/h.kg). By wk 3, respiratory quotient no longer differed; however, EE increased with amylin treatment (5.74+/-0.09 kcal/.kg; P<0.05) relative to VEH (5.49+/-0.06) and PF (5.38+/-0.07 kcal/h.kg). Differences in EE, attributed to differences in lean mass, argued against specific amylin-induced thermogenesis. Weight loss in amylin and pair-fed rats was accompanied by similar increases arcuate neuropeptide Y mRNA (P<0.05). Amylin treatment, but not PF, increased proopiomelanocortin mRNA levels (P<0.05 vs. VEH). In a rodent model of obesity, amylin reduced body weight and body fat, with relative preservation of lean tissue, through anorexigenic and specific metabolic effects.

Inhibition of mitochondrial Na+-Ca2+ exchanger increases mitochondrial metabolism and potentiates glucose-stimulated insulin secretion in rat pancreatic islets.

The mitochondrial Na(+)-Ca(2+) exchanger (mNCE) mediates efflux of Ca(2+) from mitochondria in exchange for influx of Na(+). We show that inhibition of the mNCE enhances mitochondrial oxidative metabolism and increases glucose-stimulated insulin secretion in rat islets and INS-1 cells. The benzothiazepine CGP37157 inhibited mNCE activity in INS-1 cells (50% inhibition at IC(50) = 1.5 micro mol/l) and increased the glucose-induced rise in mitochondrial Ca(2+) ([Ca(2+)](m)) 2.1 times. Cellular ATP content was increased by 13% in INS-1 cells and by 49% in rat islets by CGP37157 (1 micro mol/l). Krebs cycle flux was also stimulated by CGP37157 when glucose was present. Insulin secretion was increased in a glucose-dependent manner by CGP37157 in both INS-1 cells and islets. In islets, CGP37157 increased insulin secretion dose dependently (half-maximal efficacy at EC(50) = 0.06 micro mol/l) at 8 mmol/l glucose and shifted the glucose dose response curve to the left. In perifused islets, mNCE inhibition had no effect on insulin secretion at 2.8 mmol/l glucose but increased insulin secretion by 46% at 11 mmol/l glucose. The effects of CGP37157 could not be attributed to interactions with the plasma membrane sodium calcium exchanger, L-type calcium channels, ATP-sensitive K(+) channels, or [Ca(2+)](m) uniporter. In hyperglycemic clamp studies of Wistar rats, CGP37157 increased plasma insulin and C-peptide levels only during the hyperglycemic phase of the study. These results illustrate the potential utility of agents that affect mitochondrial metabolism as novel insulin secretagogues.

Inducible expression of a dominant negative DNA polymerase-gamma depletes mitochondrial DNA and produces a rho0 phenotype.

We report the inducible, stable expression of a dominant negative form of mitochondria-specific DNA polymerase-gamma to eliminate mitochondrial DNA (mtDNA) from human cells in culture. HEK293 cells were transfected with a plasmid encoding inactive DNA polymerase-gamma harboring a D1135A substitution (POLGdn). The cells rapidly lost mtDNA (t1/2 = 2-3 days) when expression of the transgene was induced. Concurrent reduction of mitochondrial encoded mRNA and protein, decreased cellular growth rate, and compromised respiration and mitochondrial membrane potential were observed. mtDNA depletion was reversible, as demonstrated by restoration of mtDNA copy number to normal within 10 days when the expression of POLGdn was suppressed following a 3-day induction period. Long term (20 days) expression of POLGdn completely eliminated mtDNA from the cells, resulting in rho0 cells that were respiration-deficient, lacked electron transport complex activities, and were auxotrophic for pyruvate and uridine. Fusion of the rho0 cells with human platelets yielded clonal cybrid cell lines that were populated exclusively with donor-derived mtDNA. Respiratory function, mitochondrial membrane potential, and electron transport activities were restored to normal in the cybrid cells. Inducible expression of a dominant negative DNA polymerase-gamma can yield mtDNA-deficient cell lines, which can be used to study the impact of specific mtDNA mutations on cellular physiology, and to investigate mitochondrial genome function and regulation.

Efficient syntheses of benzothiazepines as antagonists for the mitochondrial sodium-calcium exchanger: potential therapeutics for type II diabetes.

Type II diabetes mellitus is a chronic metabolic disorder that can lead to serious cardiovascular, renal, neurologic, and retinal complications. While several drugs are currently prescribed to treat type II diabetes, their efficacy is limited by mechanism-related side effects (weight gain, hypoglycemia, gastrointestinal distress), inadequate efficacy for use as monotherapy, and the development of tolerance to the agents. Consequently, combination therapies are frequently employed to effectively regulate blood glucose levels. We have focused on the mitochondrial sodium-calcium exchanger (mNCE) as a novel target for diabetes drug discovery. We have proposed that inhibition of the mNCE can be used to regulate calcium flux across the mitochondrial membrane, thereby enhancing mitochondrial oxidative metabolism, which in turn enhances glucose-stimulated insulin secretion (GSIS) in the pancreatic beta-cell. In this paper, we report the facile synthesis of benzothiazepines and derivatives by S-alkylation using 2-aminobenzhydrols. The syntheses of other bicyclic analogues based on benzothiazepine, benzothiazecine, benzodiazecine, and benzodiazepine templates are also described. These compounds have been evaluated for their inhibition of mNCE activity, and the results from the structure-activity relationship (SAR) studies are discussed.

Reduced-median-network analysis of complete mitochondrial DNA coding-region sequences for the major African, Asian, and European haplogroups.

The evolution of the human mitochondrial genome is characterized by the emergence of ethnically distinct lineages or haplogroups. Nine European, seven Asian (including Native American), and three African mitochondrial DNA (mtDNA) haplogroups have been identified previously on the basis of the presence or absence of a relatively small number of restriction-enzyme recognition sites or on the basis of nucleotide sequences of the D-loop region. We have used reduced-median-network approaches to analyze 560 complete European, Asian, and African mtDNA coding-region sequences from unrelated individuals to develop a more complete understanding of sequence diversity both within and between haplogroups. A total of 497 haplogroup-associated polymorphisms were identified, 323 (65%) of which were associated with one haplogroup and 174 (35%) of which were associated with two or more haplogroups. Approximately one-half of these polymorphisms are reported for the first time here. Our results confirm and substantially extend the phylogenetic relationships among mitochondrial genomes described elsewhere from the major human ethnic groups. Another important result is that there were numerous instances both of parallel mutations at the same site and of reversion (i.e., homoplasy). It is likely that homoplasy in the coding region will confound evolutionary analysis of small sequence sets. By a linkage-disequilibrium approach, additional evidence for the absence of human mtDNA recombination is presented here.