Gene for the rat atrial natriuretic peptide is regulated by glucocorticoids in vitro.

Glucocorticoids regulate the expression of the gene for atrial natriuretic peptide (ANP) in neonatal cardiocytes. Dexamethasone (Dex) increased cytoplasmic ANP mRNA levels and media ANP immunoreactivity in a dose-dependent fashion. These effects were not shared by the other classes of steroid hormones and were reversed by the glucocorticoid antagonist RU 38486. The effect on ANP mRNA levels resulted, at least in part, from enhanced transcription of the gene. Dex effected a two-fold increase in ANP gene activity assessed using a run-on transcription assay. The turnover of the ANP transcript was approximated using a standard pulse-chase technique. The half-life of the ANP mRNA was 18 h in hormone-free media. In the presence of Dex this half-life increased modestly to 30 h, although the increase relative to the control did not reach statistical significance. The effect of Dex at the level of the individual myocardial cell was assessed by in situ hybridization analysis using a specific [3H]cRNA probe. These studies demonstrated a significant level of ANP expression within a subpopulation of cells in the cultures. Exposure of the cells to Dex for 24 h did not recruit additional cells into the expressing pool (27.3% cells/high power field vs. 31.3% for the control) but did increase the level of expression (i.e., grain density) within individual cells. These findings indicate that glucocorticoids stimulate expression of the ANP gene directly at the level of the myocardial cell. This results predominantly from transcriptional activation in cells already expressing the gene rather than through recruitment of previously quiescent cells.

Effects of a novel cholecystokinin (CCK) receptor antagonist, MK-329, on gallbladder contraction and gastric emptying in humans. Implications for the physiology of CCK.

To explore the physiology of cholecystokinin (CCK) in humans, we investigated the effect on gallbladder contraction and gastric emptying of a recently developed CCK receptor antagonist, MK-329. In a double-blind, four-period crossover study eight subjects received single doses of 0.5, 2, or 10 mg MK-329, or placebo, followed by an intravenous infusion of CCK-8 (30 pmol/kg.h). In placebo-treated subjects gallbladder volumes decreased on average to 43% of initial volumes after 2 h of CCK infusion. MK-329 caused a dose-dependent inhibition of CCK-stimulated gallbladder contraction with 10 mg producing complete blockade (P less than 0.01, cf. placebo). Gallbladder contraction and gastric emptying rates after a mixed meal were then measured in a two-period crossover study. Subjects received placebo or 10 mg of MK-329 2 h before eating. Gastric emptying of both solids and liquids was measured simultaneously by gamma scintigraphy. In placebo-treated subjects plasma CCK levels increased postprandially to 2.3 pM, gallbladder volumes decreased 68.4 +/- 3.8% (SE), and the times for 50% emptying of liquids and solids from the stomach were 58 +/- 10 and 128 +/- 8 min, respectively. In MK-329-treated subjects there was a marked elevation in peak CCK levels to 13.8 pM (P less than 0.01, cf. placebo), and gallbladder contraction was completely inhibited. Solid and liquid emptying rates were unaffected. These findings demonstrate that (a) MK-329 is a potent, orally active antagonist of CCK in humans, and (b) CCK is the major regulator of postprandial gallbladder contraction. These data also support the concept of negative feedback regulation of CCK secretion and suggest that mechanisms other than CCK play a dominant role in the regulation of postprandial gastric emptying rates.

Cardiovascular thrombotic events in controlled, clinical trials of rofecoxib.

BACKGROUND: In comparing aspirin, nonselective nonsteroidal antiinflammatory agents (NSAIDs), and cyclooxygenase (COX)-2 inhibitors, variation in platelet inhibitory effects exists that may be associated with differential risks of cardiovascular (CV) thrombotic events. Among the randomized, controlled trials with the COX-2 inhibitor rofecoxib, one study demonstrated a significant difference between rofecoxib and its NSAID comparator (naproxen) in the risk of CV thrombotic events. A combined analysis of individual patient data was undertaken to determine whether there was an excess of CV thrombotic events in patients treated with rofecoxib compared with those treated with placebo or nonselective NSAIDs. METHODS AND RESULTS: CV thrombotic events were assessed across 23 phase IIb to V rofecoxib studies. Comparisons were made between patients taking rofecoxib and those taking either placebo, naproxen (an NSAID with near-complete inhibition of platelet function throughout its dosing interval), or another nonselective NSAIDs used in the development program (diclofenac, ibuprofen, and nabumetone). The major outcome measure was the combined end point used by the Antiplatelet Trialists' Collaboration, which includes CV, hemorrhagic, and unknown deaths; nonfatal myocardial infarctions; and nonfatal strokes. More than 28 000 patients, representing >14 000 patient-years at risk, were analyzed. The relative risk for an end point was 0.84 (95% CI: 0.51, 1.38) when comparing rofecoxib with placebo; 0.79 (95% CI: 0.40, 1.55) when comparing rofecoxib with non-naproxen NSAIDs; and 1.69 (95% CI: 1.07, 2.69) when comparing rofecoxib with naproxen. CONCLUSIONS: This analysis provides no evidence for an excess of CV events for rofecoxib relative to either placebo or the non-naproxen NSAIDs that were studied. Differences observed between rofecoxib and naproxen are likely the result of the antiplatelet effects of the latter agent.

Dose-response study of alendronate sodium for the treatment of cancer-associated hypercalcemia.

PURPOSE: A randomized, double-blind, dose-ranging study of single-dose intravenous (IV) therapy with alendronate sodium (aminohydroxybutylidene bisphosphonate) was performed in patients with cancer-associated hypercalcemia. PATIENTS AND METHODS: Patients with hypercalcemia who had not received antitumor therapy in the preceding 7 days were treated with 48 hours of IV hydration. Patients with persistent hypercalcemia (albumin-corrected serum calcium concentration [CSCC] > or = 11.5 mg/dL) were randomly assigned to receive 2.5, 5, 10, or 15 mg of alendronate infused over 2 hours, or 10 mg of alendronate infused over 24 hours. Fifty-nine patients were treated and 50 patients were assessable for the dose-response relationship. RESULTS: Normalization of CSCC (< or = 10.5 mg/dL) was achieved in 22%, 82%, 75%, and 90% of assessable patients in the 2.5-, 5-, 10- (2- and 24-hour groups pooled), and 15-mg dose groups, respectively, within 8 days of therapy. Doses > or = 5 mg were significantly superior to the 2.5-mg dose level (P < .05). There was no significant difference in the minimum CSCC achieved between the 2- and 24-hour infusions of the 10-mg dose. Based on an intent-to-treat analysis of all randomized patients, the overall complete response rate was 74% for dose levels greater than 2.5 mg. For assessable patients who responded to > or = 5 mg of alendronate, the estimated median duration of normocalcemia was 10 days (range, 1 to 25). The estimated median time to relapse (CSCC > 11.5 mg/dL) was 15 days from initial treatment and 12 days from initial response, respectively. Adverse events included a transient febrile response in 34% of patients and eight episodes of reversible elevations in serum transaminase levels among treated patients. CONCLUSION: While a statistically significant dose-response relationship was not clearly evident at doses greater than 5 mg, single doses of > or = 5 mg alendronate sodium effectively lowered serum calcium concentrations and were well tolerated in the treatment of cancer-associated hypercalcemia.

Prevention of cisplatin-induced emesis by the oral neurokinin-1 antagonist, MK-869, in combination with granisetron and dexamethasone or with dexamethasone alone.

PURPOSE: The NK1-receptor antagonist MK-869 (L-754,030) has demonstrated antiemetic activity in humans receiving chemotherapy. Objectives of the present trial included the first assessment of oral MK-869 plus dexamethasone compared with a 5HT(3) antagonist plus dexamethasone for prevention of acute and delayed emesis after high-dose cisplatin. Furthermore, the study sought to confirm that addition of MK-869 to a 5HT(3) antagonist plus dexamethasone was more effective than just the 5HT(3) antagonist plus dexamethasone for prevention of acute and delayed emesis. METHODS: This multicenter, double-blind, parallel-group trial in 351 cisplatin-naïve patients evaluated prevention of acute (0 to 24 hours) and delayed emesis (primary efficacy parameter; days 2 to 5) after cisplatin (> or =70 mg/m(2)). Patients were randomized to four groups (I to IV) (n = number randomized; number evaluable): granisetron (10 microg/kg intravenously) pre-cisplatin followed by placebo on days 2 to 5 (group I) (n = 90; 90); granisetron and MK-869 (400 mg PO [by mouth]) pre-cisplatin, followed by MK-869 (300 mg PO) on days 2 to 5 (group II) (n = 86; 84); MK-869 (400 mg PO) the evening before and pre-cisplatin, followed by MK-869 (300 mg PO) on days 2 to 5 (group III) (n = 89; 88); or MK-869 (400 mg PO) pre-cisplatin, followed by MK-869 (300 mg PO) on days 2 to 5 (group IV) (n = 86; 84). All patients also received dexamethasone (20 mg PO) before cisplatin. Additional medication was available to treat emesis or nausea at any time. RESULTS: In the acute period, 57%, 80%, 46%, and 43% of patients were without emesis in groups I, II, III, and IV, respectively (P <.01 for group II v group I). In the delayed period, the proportion of patients without emesis in groups I, II, III, and IV was 29%, 63%, 51%, and 57%, respectively (P <.01 for groups II, III, and IV v group I). The distribution of nausea scores in the delayed period was lower when comparing group II with group I (P <.05 for days 1 to 5 and days 2 to 5). One serious adverse event (dizziness) was rated as possibly related to MK-869. CONCLUSION: Once daily oral administration of MK-869 was effective in reducing delayed emesis and nausea after high-dose cisplatin. However, the combination of the 5HT3 antagonist plus dexamethasone was numerically superior to MK-869 plus dexamethasone in reducing acute emesis. Confirming and extending previous findings, the triple combination of a 5HT(3) antagonist, MK-869, and dexamethasone provided the best control of acute emesis.

Thyroid hormone increases rat atrial natriuretic peptide messenger ribonucleic acid accumulation in vivo and in vitro.

Thyroid hormone has a number of effects on cardiovascular and renal function which are shared by the atrial natriuretic peptide (ANP). We attempted to demonstrate a relationship between the two by studying the effects of thyroid hormone on the expression of the ANP gene and the secretion of its encoded protein. Thyroid hormone, when given to thyroidectomized rats, increased plasma ANP levels by approximately 2-fold in both watered and dehydrated animals. Cardiac ANP mRNA in dehydrated animals fell to 25% of that in the water-replete controls. T4 increased cardiac ANP mRNA 3-fold in dehydrated animals, but failed to alter ANP mRNA in those animals allowed free access to water. The effect of thyroid hormone appeared to take place, at least in part, at the level of the ANP-synthesizing cardiocyte. T3, at concentrations ranging from 10(-10)-10(-8) M, increased ANP mRNA levels a maximum of 2-fold in primary cultures of neonatal cardiocytes. Both basal and T3-stimulated ANP transcripts appeared to be identical to their counterparts in the adult atria, as assessed by blot hybridization and S1 nuclease analysis. T3 (10(-8) M) also effected a 2-fold increase in media ANP immunoreactivity. These data indicate that thyroid hormone increases the secretion and genetic expression of ANP in vivo and in vitro and suggests a role for the peptide as a mediator of at least some thyroid hormone effects in the cardiovascular system.

Glucocorticoid control of rat growth hormone gene expression: effect on cytoplasmic messenger ribonucleic acid production and degradation.

The effect of the glucocorticoid dexamethasone on the production and degradation of rat GH (rGH) cytoplasmic mRNA was studied in cultured rat pituitary tumor (GC) cells. The incorporation of [3H]uridine into both rGH cytoplasmic mRNA and the pyrimidine nucleotide precursor pool was determined in hormone-treated and control cells. From these measurements glucocorticoid effects on absolute production rates of rGH cytoplasmic mRNA were determined and compared to effects on rGH mRNA accumulation. Rat GH mRNA half-life was then calculated based on a first-order decay model. Rat GH mRNA half-life was also directly assayed by: 1) pulse-chase studies and 2) measuring the kinetics of decay of rGH mRNA in cells after transfer from serum-containing to hormone-deficient media. From these independent analyses rGH mRNA half-life estimates ranged from 28-55 h in different experiments. Within individual experiments there was little variability of rGH mRNA decay rates; glucocorticoids were found not to alter the stability of rGH cytoplasmic mRNA. Glucocorticoid induction of rGH cytoplasmic mRNA accumulation was accounted for solely on the basis of increased mRNA production.

Effects of five daily 1 h infusions of alendronate in Paget's disease of bone.

We report a randomized placebo-controlled double-blind study of amino-hydroxybutylidene bisphosphonate (alendronate), infused over 1 h, in 15 patients with Paget's disease of bone. Alendronate, 10 mg/day for 5 days, suppressed urinary hydroxyproline to 44.9 +/- 4.8% and serum alkaline phosphatase to 74.6 +/- 5.4% of their pretreatment values within 1 month of the start of treatment. Within 5 months of the start of treatment serum alkaline phosphatase fell to 47.9 +/- 6.3% of pretreatment values. These effects were associated with a decrease in serum calcium and phosphate and in urinary calcium excretion and with a rise in serum iPTH values. A transient fever was observed in 3 of 10 patients who received alendronate during the course of the infusions, and this was associated with a decrease in the total and differential white cell count. No adverse effects were noted on renal function as judged by glomerular filtration rate and indices of proximal and distal tubular function. This regimen may simplify the management of patients with Paget's disease of bone.

Oral administration of the growth hormone secretagogue MK-677 increases markers of bone turnover in healthy and functionally impaired elderly adults. The MK-677 Study Group.

Growth hormone (GH) stimulates osteoblasts in vitro and increases bone turnover and stimulates osteoblast activity when given to elderly subjects. Probably a major effect of GH on bone is mediated through stimulation of either circulating or locally produced insulin-like growth factor I (IGF-I). We determined the effect of chronic administration of the GH secretagogue, MK-677, on serum IGF-I and markers of bone turnover in 187 elderly adults (65 years or older) enrolled in three randomized, double-blind, placebo-controlled clinical studies lasting 2-9 weeks. Urine was collected for determination of N-telopeptide cross-links (NTXs), a marker of bone resorption, and blood was collected for determination of serum osteocalcin and bone-specific alkaline phosphatase (BSAP), as bone formation markers, and serum IGF-I levels pre- and post-treatment. Dose response data were initially obtained in healthy elderly subjects who received oral doses of 10 mg or 25 mg of MK-677 or placebo for 2 weeks (n = 10-12/group). Treatment with 10 mg and 25 mg of MK-677 for 2 weeks increased mean urine NTXs 10% and 17%, respectively (p < 0.05 vs. placebo). Additionally, 50 healthy elderly subjects received either placebo (n = 20) for 4 weeks or 25 mg of MK-677 (n = 30) daily for 2 weeks followed by 50 mg daily for 2 weeks. MK-677 increased mean serum osteocalcin by 8% (p < 0.05 vs. placebo). In both studies, MK-677 increased serum IGF-I levels significantly (55-94%). Subsequently, the biological effects of MK-677 were studied in 105 elderly subjects who met objective criteria for functional impairment. Subjects were randomized to receive oral doses of placebo for 9 weeks or either 5, 10, or 25 mg of MK-677 daily for an initial 2 weeks followed by 25 mg of MK-677 daily for the next 7 weeks(n = 63 on MK-677 and n = 28 on placebo completed 9 weeks of therapy). Treatment with MK-677 (all MK-677 groups combined) for 9 weeks increased mean serum osteocalcin by 29.4% and BSAP by 10.4% (p < 0.001 vs. placebo) and mean urinary NTX excretion by 22.6% (p < 0.05 vs. placebo). The change from baseline serum osteocalcin correlated with the change from baseline serum IGF-I in the MK-677 group (r = 0.37; p < 0.01). In conclusion, once daily dosing with MK-677, an orally active GH secretagogue, stimulates bone turnover in elderly subjects based on elevations in biochemical markers of bone resorption and formation.

Monitoring bone resorption in early postmenopausal women by an immunoassay for cross-linked collagen peptides in urine.

A new immunoassay using an ELISA approach for measuring urinary excretion of cross-linked N-telopeptides of type 1 collagen was evaluated as a specific measure of bone resorption. The assay was applied to 65 early postmenopausal women who participated in a placebo-controlled trial of the aminobisphosphonate, alendronate sodium. Eight blood and urine samples were collected over a 9 month interval. Baseline cross-linked peptide excretion varied from 26 to 216 pmol BCE (bone collagen/mumol Cr. Within-subject variability (CV) for cross-linked peptide excretion was 20.2% over the 9 months in placebo-treated subjects, substantially less than that observed for other biochemical markers of bone resorption: 45, 53, and 63% for fasting urinary calcium and hydroxyproline and 24 h urinary lysylpyridinoline (HPLC assay), respectively. Baseline cross-linked peptide excretion correlated significantly (p < 0.001) with baseline total urine lysylpyridinoline and serum osteocalcin, but not with the other biochemical markers. Initial peptide excretion also correlated inversely with lumbar spine bone mineral density at entry (r = -0.26, p < 0.05). Treatment for 6 weeks with alendronate produced a dose-dependent suppression of cross-linked peptide excretion (0 +/- 8, 29 +/- 6, 56 +/- 5, and 64 +/- 3% for 0, 5, 20, and 40 mg, respectively, p < 0.01 versus placebo for treatment effect), with a return toward pretreatment values during follow-up. Measurement of the urinary cross-linked N-telopeptides of type I collagen by this new ELISA approach appears promising as a simple and reliable method to assess overall bone resorption.(ABSTRACT TRUNCATED AT 250 WORDS)

Elimination and biochemical responses to intravenous alendronate in postmenopausal osteoporosis.

Postmenopausal women with established vertebral osteoporosis were studied for 2 years to determine the terminal elimination half-life and the duration of response to treatment with intravenous alendronate (30 mg) given over 4 days. The urinary excretion of alendronate followed a multiexponential decline. Approximately 50% of the total dose was excreted over the first 5 days, and a further 17% was excreted in the succeeding 6 months. Thereafter, there was a much slower elimination phase with an estimated mean terminal half-life of greater than 10 years (n = 11). Urinary excretion of hydroxyproline and calcium decreased significantly from pretreatment values by day 3, reaching a nadir by 1 week (40% and 67% decrease, respectively). Thereafter, hydroxyproline remained suppressed for the following 2 years. In contrast, urinary calcium excretion returned gradually toward pretreatment values over the first year and during the second year was comparable to pretreatment values. Serum activity of alkaline phosphatase activity decreased over 3 months (23% reduction), increased gradually thereafter, and returned to pretreatment values at month 24. Bone mineral density measured at the spine increased by approximately 5% during the first year and remained significantly higher than pretreatment values at 2 years. We conclude that a short course of high doses of intravenous alendronate is associated with a prolonged skeletal retention of the agent. This open study also suggests that this regimen has a sustained effect on bone turnover persisting for at least 1 year.

Chronic administration of corticotropin-releasing factor increases pituitary corticotroph number.

The effect of chronic administration of CRF on rat pituitary morphology was studied. Experimental animals received CRF (10 micrograms/day) over a period of 52 days by means of sc osmotic pumps changed at 10- to 14-day intervals. The average 0800 h plasma corticosterone levels in the treated animals were significantly greater than control values [7.52 +/- 0.99 (+/- SE) vs. 1.14 +/- 0.5 micrograms/dl; P less than 0.001]. The CRF-treated animals also had a significantly greater adrenal weight (16.44 +/- 1.38 vs. 12.24 +/- 0.85 mg; P less than 0.05) and lower thymus weight (164 +/- 12 vs. 248 +/- 27 mg; P less than 0.005). There was a marked increase in the number of ACTH-producing cells in the anterior pituitaries of the rats that received CRF (13.3 +/- 0.8% vs. 4.5 +/- 0.3% ACTH-producing cells; P less than 0.001), as determined by immunocytochemical methods. Corticotrophs of rats treated with CRF manifested a significant increase in nuclear area (24.0 +/- 0.7 vs. 21.4 +/- 0.4 micron 2; P less than 0.001) and an increased diameter of forming and storage granules (191.1 +/- 1.1 vs. 158.6 +/- 3.5 nm and 196.1 +/- 1.2 vs. 170.1 +/- 3.7 nm, respectively; P less than 0.001). There was no demonstrable increase in ACTH cell area. These data indicate that long term administration of CRF is capable of increasing the number of pituitary corticotrophs. It also supports the view that the corticotroph hyperplasia occurring after adrenalectomy, in unusual cases of ectopic CRF production, and in rare instances of Cushing's disease is a proliferative response to CRF.

The effect of short term treatment with alendronate on vertebral density and biochemical markers of bone remodeling in early postmenopausal women.

The effects of oral alendronate treatment on spinal bone mineral density and biochemical markers of bone turnover were assessed in women in the early postmenopausal period. Sixty-five women were treated with placebo or 5, 20, or 40 mg alendronate daily for 6 weeks in a double blind study. Treatment with alendronate decreased both urinary markers of bone resorption (pyridinolines, hydroxyproline, and calcium) and serum markers of bone formation (osteocalcin and alkaline phosphatase) in a dose-dependent fashion. This short term treatment with alendronate also produced a dose-dependent increase in lumbar bone mineral density measured 7.5 months after the completion of therapy. Median percent changes in integral spinal bone mineral density, as assessed by dual x-ray absorptiometry, were -2.3, -1.2, +0.7, and +1.2 after treatment with placebo and 5, 20, and 40 mg alendronate, respectively. Treatment with alendronate was well tolerated and produced no fever; gastrointestinal intolerance was no more common than with placebo treatment. Short term alendronate treatment in early postmenopausal women decreased bone turnover and increased vertebral density.

L-692,429, a nonpeptide growth hormone (GH) secretagogue, reverses glucocorticoid suppression of GH secretion.

The reversal of glucocorticoid-induced negative nitrogen balance by GH supports a possible therapeutic role for GH treatment in patients receiving these catabolic steroids. A GH secretagogue might be of similar utility. However, stimulated GH secretion is generally suppressed by glucocorticoids. To test whether L-692,429, a nonpeptide mimic of GH-releasing peptide-6, can overcome such suppression, a double blind, placebo-controlled, three-period, cross-over study was performed in nine healthy young men who received 0.2 mg/kg L-692,429, i.v., preceded by 4 days of prednisolone (20 mg, orally, three times daily) or placebo, and 0.75 mg/kg L-692,429 preceded by prednisolone only. The mean (SE) GH peak and area under the curve between 0-240 min after administration of 0.2 mg/kg L-692,429 in the absence of steroid were 53.8 (7.2) micrograms/L and 3481 (1005) micrograms/min.L, which were reduced to 25.1 (3.4) micrograms/L and 1342 (285) micrograms/min.L (P < or = 0.01) when treatment was preceded by 4 days of prednisolone. However, the suppressive influence of the steroid was attenuated by the high dose of L-692,429, which achieved a GH peak and area under the curve between 0-240 min of 42.6 (5.8) micrograms/L and 2298 (425) micrograms/min.L, respectively (P < 0.01 vs. 0.2 mg/kg L-692,429 plus prednisolone). L-692,429 stimulates GH secretion even in the setting of short term, high dose, concomitant glucocorticoid treatment, suggesting that such compounds might provide an alternative means of increasing circulating GH and reversing the catabolic effects of these steroids.

Growth hormone response in man to L-692,429, a novel nonpeptide mimic of growth hormone-releasing peptide-6.

L-692,429, a substituted benzolactam, is a novel nonpeptide mimic of the GH secretagogue, GH-releasing peptide-6. The safety and GH secretory activity of L-692,429 (0.001-1.0 mg/kg, i.v.) were investigated in 24 healthy nonobese young (18-26 yr old) male volunteers who demonstrated a GH response of 7 micrograms/L or more after 1 microgram/kg, i.v. GH-releasing hormone [GH-releasing hormone-(1-29)NH2]. L-692,429 was administered as a 15-min iv infusion in an incremental dose, double blind, placebo-controlled, alternating panel fashion to 3 panels of 8 subjects each. Dose-dependent GH secretion was observed with a threshold dose of 0.05 mg/kg (4 of 6 subjects responded with peak GH > 7 micrograms/L), and 0.2 mg/kg produced a response in all 14 subjects tested (mean +/- SE peak GH, 41.0 +/- 6.3 micrograms/L). The maximum dose of 1.0 mg/kg L-692,429 resulted in a pronounced GH response (peak GH, 82.5 +/- 14.9 micrograms/L; n = 8). The GH peak was seen 30-45 min after initiation of the infusion. Small transient increases in cortical and PRL were observed (increases in cortical averaged 182.1 +/- 33.1 nmol/L and peak PRL was 21 +/- 2.6 micrograms/L after 1.0 mg/kg L-692,429, respectively), whereas no significant changes occurred in LH, FSH, TSH, insulin, or glucose concentrations. Plasma pharmacokinetic analysis revealed dose-related increases in plasma concentrations of L-692,429 and a half-life of 3.8 +/- 0.2 (+/- SE) h, a plasma clearance of 214 +/- 67 mL/min, and a steady state volume of distribution of 14.2 +/- 4.8 L. Facial flushing or a warm sensation were reported in 4 subjects, primarily at dose levels of 0.2 mg/kg L-692,429 or more, but no other clinical or laboratory adverse experiences appeared related to drug treatment. L-692,429, synthesized as a specific nonpeptide mimic of GH-releasing peptide-6, is thus a well tolerated, highly effective, and selective GH secretagogue in man.

Neuroendocrine responses to a novel growth hormone secretagogue, L-692,429, in healthy older subjects.

L-692,429 (L), a novel nonpeptide mimic of GH-releasing peptide (GHRP), is a potent GH secretagogue in animals and young men. To assess the safety and efficacy of L in stimulating GH release in healthy older men and women, 16 subjects were admitted to a randomized, double blind, cross-over comparison of i.v. administered placebo, GH-releasing hormone [GHRH-(1-29)-NH2; 1 microgram/kg] and two doses of L (0.2 and 0.75 mg/kg). Blood samples were obtained at 5-min intervals for 60 min before and 240 min after each dose for measurement of GH; cortisol, PRL, and insulin-like growth factor-I (IGF-I) were measured less frequently. Peak and integrated GH concentrations increased significantly after L in a dose-dependent manner. Responses to L at either dose were significantly greater than the response to GHRH: peak GH responses in older men and women were (mean +/- SE; micrograms per L): after placebo, 1.2 +/- 0.2; L (0.2 mg/kg), 16.5 +/- 1.8; L (0.75 mg/kg), 32.2 +/- 3.9; and GHRH, 7.6 +/- 1.3 (P < 0.05, L vs. placebo or GHRH). Serum cortisol and PRL concentrations increased after both doses of L, but to values within the respective normal ranges. Serum IGF-I values did not change consistently in any group. The GH responses to GHRH and L (0.75 mg/kg) were highly correlated (r2 = 0.61; P < 0.0004). Deconvolution analysis demonstrated that the increase in serum GH concentrations stimulated by L and GHRH resulted from enhanced GH secretion rates, with no change in the half-life of GH disappearance. Amplitudes of GH secretory pulses were increased 11-, 18-, and 4-fold after L (0.2 mg/kg), L (0.75 mg/kg), and GHRH treatments, respectively. The number of GH secretory pulses was significantly increased by L (0.75 mg/kg; 4.6 +/- 0.4) and GHRH (4.4 +/- 0.3) compared to placebo (2.6 +/- 0.5), but the interval between pulses was shorter after L (0.75 mg/kg; 28.6 +/- 3.6 min) than after GHRH (50.7 +/- 7.7 min; P < 0.05). Adverse experiences were limited to brief episodes of flushing or a warm sensation about the upper body. L-692,429 is a potent GH secretagogue that is well tolerated in healthy older men and women. At the doses employed in this study, L elicited greater increases in GH secretion rates and serum GH concentrations than GHRH. L-692,429 may have therapeutic advantages over peptide GH secretagogues to restore endogenous GH secretion in GH deficiency states or the hyposomatotropism of aging.

MK-677, an orally active growth hormone secretagogue, reverses diet-induced catabolism.

The reversal of diet-induced negative nitrogen balance by GH suggests a possible therapeutic role for GH treatment in catabolic patients. A double-blind, randomized, placebo-controlled, two-period cross-over study was designed to investigate whether MK-677, an orally active nonpeptide mimic of GH-releasing peptide, can reverse diet-induced protein catabolism. Eight healthy volunteers (ages 24-39 yr) were calorically restricted (18 kcal/kg.day) for two 14-day periods. During the last 7 days of each diet period, subjects received either oral MK-677 25 mg or placebo once daily. There was a 14- to 21-day washout interval between periods. During the first week of caloric restriction (i.e. diet alone), daily nitrogen losses were similar for both treatment groups (mean +/- SE; MK-677 group -2.67 +/- 0.40 g/day vs. placebo group -2.83 +/- 0.26 g/day). During the second week (diet and study drug), mean daily nitrogen balance was 0.31 +/- 0.21 g/day in the MK-677 treatment group compared with -1.48 +/- 0.21 g/day in the placebo group (P < 0.01). MK-677 improved nitrogen balance integrated over the 7 days of treatment; area under the curve day 8-14 nitrogen balance response was +2.69 +/- 5.0 (SE) for MK-677 and -8.97 +/- 5.26 g.day for placebo (P < 0.001). MK-677 produced a peak GH response of 55.9 +/- 31.7 micrograms/L after single dose (day 1 of treatment) and 22.6 +/- 9.3 micrograms/L after a week of dosing compared with placebo treatment peak GH values of approximately 9 (treatment day 1) and approximately 7 micrograms/L (treatment day 7). Following the initial 7-day caloric restriction, insulin-like growth factor-I (IGF-I) declined from 232 +/- 25 to 186 +/- 19 ng/mL in the MK-677 group and from 236 +/- 19 to 174 +/- 23 ng/mL in the placebo group. Mean IGF-I concentration increased significantly during MK-677 to 264 +/- 31 ng/mL (mean for the last 5 days of treatment) compared with 188 +/- 19 ng/mL with placebo (P < 0.01). No significant difference in IGF binding protein-2 was found between the MK-677 and placebo treatments. However, the mean in IGF binding protein-3 for the last 5 days of MK-677 treatment was also significantly increased to 3273 +/- 330 ng/mL (mean +/- SE) compared with placebo 2604 +/- 253 ng/mL (P < 0.01). Neither the serum cortisol nor the PRL response was significantly greater after 7 days of MK-677 dosing compared with 7 days of placebo. MK-677 (25 mg) was generally well tolerated and without clinically significant adverse experiences. In conclusion, MK-677 reverses diet-induced nitrogen wasting, suggesting that if these short-term anabolic effects are maintained in patients who are catabolic because of certain acute or chronic disease states, it may be useful in treating catabolic conditions.

Regulation of pancreatic endocrine function by cholecystokinin: studies with MK-329, a nonpeptide cholecystokinin receptor antagonist.

A cholecystokinin (CCK) receptor antagonist, MK-329, was used to explore the physiological role of CCK in regulating pancreatic endocrine function in humans. The ability of CCK to increase plasma pancreatic polypeptide (PP) concentrations and blockade of this effect with MK-329 were evaluated in a double blind, balanced, four-period cross-over study. Eight subjects received single oral doses of 0.5, 2, or 10 mg MK-329 or placebo, followed by an iv infusion of CCK-8 (34 ng/kg.h). In placebo-treated subjects, PP increased from basal levels of 70 +/- 15 (+/- SE) to peak values of 291 +/- 58 pg/mL after CCK infusion (P less than 0.05 compared to basal). This increase in plasma PP concentration was inhibited in a dose-dependent fashion by MK-329, with 10 mg antagonizing the stimulatory effect of CCK infusion by nearly 80%. Second, the effect of MK-329 on meal-stimulated pancreatic endocrine responses was evaluated by giving placebo or 10 mg MK-329 2 h before ingestion of a mixed meal. Eight subjects were treated in a randomized two-period cross-over fashion. With placebo treatment, peak postprandial plasma insulin, glucagon, and glucose concentrations were 101 +/- 8 microU/mL, 195 +/- 15 pg/mL, and 150 +/- 10 mg/dL, respectively (all P less than 0.05). The integrated PP response following the meal was 56.3 +/- 11.1 ng/mL.minute. With MK-329 treatment, the integrated PP concentration was reduced to 33.9 +/- 2.2 ng/mL.min (P less than 0.05 compared to placebo treatment). Mean postprandial insulin, glucagon, and glucose concentrations did not differ between placebo and MK-329 treatments. We conclude that CCK receptor blockade with 10 mg MK-329 does not alter plasma insulin, glucagon, or glucose responses to a mixed meal. However, the observation that physiological concentrations of CCK increase plasma levels of PP, and the finding that CCK receptor blockade selectively attenuates the postprandial increase in plasma PP concentrations support a physiological role for CCK in regulating PP secretion.

Effect of alendronate and MK-677 (a growth hormone secretagogue), individually and in combination, on markers of bone turnover and bone mineral density in postmenopausal osteoporotic women.

GH increases bone turnover and stimulates osteoblast activity. We hypothesized that administration of MK-677, an orally active GH secretagogue, together with alendronate, a potent inhibitor of bone resorption, would maintain a higher bone formation rate relative to that seen with alendronate alone, thereby generating greater enhancement of bone mineral density (BMD) in women with postmenopausal osteoporosis. We determined the individual and combined effects of MK-677 and alendronate administration on insulin-like growth factor I levels and biochemical markers of bone formation (osteocalcin and bone-specific alkaline phosphatase) and resorption [urinary N-telopeptide cross-links (NTx)] for 12 months and BMD for 18 months. In a multicenter, randomized, double blind, placebo-controlled, 18-month study, 292 women (64-85 yr old) with low femoral neck BMD were randomly assigned in a 3:3:1:1 ratio to 1 of 4 daily treatment groups for 12 months: MK-677 (25 mg) plus alendronate (10 mg); alendronate (10 mg); MK-677 (25 mg); or a double dummy placebo. Patients who received MK-677 alone or placebo through month 12 received MK-677 (25 mg) plus alendronate (10 mg) from months 12-18. All other patients remained on their assigned therapy. All patients received 500 mg/day calcium. The primary results, except for BMD, are provided for month 12. MK-677, with or without alendronate, increased insulin-like growth factor I levels from baseline (39% and 45%; P < 0.05 vs. placebo). MK-677 increased osteocalcin and urinary NTx by 22% and 41%, on the average, respectively (P < 0.05 vs. placebo). MK-677 and alendronate mitigated the reduction in bone formation compared with alendronate alone based on mean relative changes in serum osteocalcin (-40% vs. -54%; P < 0.05, combination vs. alendronate) and reduced the effect of alendronate on resorption (NTx) as well (-52% vs. -61%; P < 0.05, combination vs. alendronate). MK-677 plus alendronate increased BMD at the femoral neck (4.2% vs. 2.5% for alendronate; P < 0.05). However, similar enhancement was not seen with MK-677 plus alendronate in BMD of the lumbar spine, total hip, or total body compared with alendronate alone. GH-mediated side effects were noted in the groups receiving MK-677, although adverse events resulting in discontinuation from the study were relatively infrequent. In conclusion, the anabolic effect of GH, as produced through the GH secretagogue MK-677, attenuated the indirect suppressive effect of alendronate on bone formation, but did not translate into significant increases in BMD at sites other than the femoral neck. Although the femoral neck is an important site for fracture prevention, the lack of enhancement in bone mass at other sites compared with that seen with alendronate alone is a concern when weighed against the potential side effects of enhanced GH secretion.

MK-386, an inhibitor of 5alpha-reductase type 1, reduces dihydrotestosterone concentrations in serum and sebum without affecting dihydrotestosterone concentrations in semen.

Two isozymes (types 1 and 2) of 5alpha-reductase (5alphaR; EC 1.3.99.5), with differential tissue distribution, catalyze the reduction of testosterone (T) to dihydrotestosterone (DHT) in humans. This study examined sequentially increasing oral doses of MK-386 (4,7beta-dimethyl-4-aza-5alpha-cholestan-3-one), an azasteroid that specifically inhibits the human 5alphaR1 isozyme in vitro. Finasteride, a selective inhibitor of 5alphaR2, was included for comparison. One hundred men were evaluated in a double blind, randomized, placebo-controlled, sequential, increasing dose, parallel group trial. Ten to 20 subjects received MK-386, and 2 to 5 received placebo in each of 6 panels. In 1 panel, 10 subjects received finasteride (5 mg), and 5 received placebo. Treatments were given once daily for 14 days, except in 1 panel in which MK-386 was administered 10 mg twice daily for comparison to 20 mg daily. Serum, sebum, and semen DHT concentrations and serum and sebum T concentrations were measured before and after treatment. The mean changes from baseline on day 14 for serum DHT after placebo and 0.1, 0.5, 5, 20, and 50 mg MK-386 were 6.9%, 4.6%, -2.7%, -1.2%, -14.1% (P < 0.05 vs. placebo), and -22.2% (P < 0.05 vs. placebo), respectively. No significant alterations in serum T were observed after any dose of MK-386. Serum DHT fell 65.8% from the baseline 14 days after finasteride treatment (P < 0.05 vs. placebo). The mean changes from baseline on day 14 in sebum DHT were 5.0%, 3.0%, -25.4% (P < 0.05 vs. placebo), -30.1% (P < 0.05 vs. placebo), and -49.1% (P < 0.05 vs. placebo) for the placebo and 0.5, 5, 20, and 50 mg MK-386 groups, respectively. Finasteride also reduced sebum DHT, but to a lesser extent (- 14.9%; P < 0.05 vs. placebo). Reciprocal increases in sebum T concentration were noted at doses of 5 mg or more of MK-386, but not with finasteride. The mean reduction in semen DHT with 5 mg finasteride was approximately 88% (P < 0.01 vs. placebo); no significant change in semen DHT was noted with 20 or 50 mg MK-386. Serum 3alpha-androstanediol glucuronide values were also reduced after the 20- and 50-mg MK-386 treatments in parallel with the changes in serum DHT. No meaningful changes were observed in serum LH after MK-386 treatment. MK-386 was generally well tolerated by all subjects; reversible aspartate aminotransferase/alanine aminotransferase elevations were observed in two subjects at the 50-mg dose. The differential responses in serum, sebum, and semen DHT concentrations associated with MK-386 and finasteride treatments are consistent with those changes anticipated for selective inhibitors of the human 5alphaR isozymes. Dose-dependent suppression of sebum DHT by a 5alphaR1 inhibitor suggests the potential utility of such compounds in the treatment of acne.