Addition of alendronate to ongoing hormone replacement therapy in the treatment of osteoporosis: a randomized, controlled clinical trial.

Alendronate and estrogen are effective therapies for postmenopausal osteoporosis, but their efficacy and safety as combined therapy are unknown. The objective of this study was to evaluate the addition of alendronate to ongoing hormone replacement therapy (HRT) in the treatment of postmenopausal women with osteoporosis. A total of 428 postmenopausal women with osteoporosis, who had been receiving HRT for at least 1 yr, were randomized to receive either alendronate (10 mg/day) or placebo. HRT was continued in both groups. Changes in bone mineral density (BMD) and biochemical markers of bone turnover were assessed. Compared with HRT alone, at 12 months, alendronate plus HRT produced significantly greater increases in BMD of the lumbar spine (3.6% vs. 1.0%, P < 0.001) and hip trochanter (2.7% vs. 0.5%, P < 0.001); however, the between-group difference in BMD at the femoral neck was not significant (1.7% vs. 0.8%, P = 0.072). Biochemical markers of bone turnover (serum bone-specific alkaline phosphatase and urine N-telopeptide) decreased significantly at 6 and 12 months with alendronate plus HRT, and they remained within premenopausal levels. Addition of alendronate to ongoing HRT was generally well tolerated, with no significant between-group differences in upper gastrointestinal adverse events or fractures. This study demonstrated that, in postmenopausal women with low bone density despite ongoing treatment with estrogen, alendronate added to HRT significantly increased bone mass at both spine and hip trochanter and was generally well tolerated.

Leukotrienes in ulcerative colitis: results of a multicenter trial of a leukotriene biosynthesis inhibitor, MK-591.

BACKGROUND & AIMS: Leukotrienes (LTs) are believed to be important in the pathogenesis of ulcerative colitis (UC). The aim of this study was to determine whether inhibition of LT biosynthesis with a 5-lipoxygenase inhibitor (MK-591) induces remission in patients with mild to moderate UC. METHODS: One hundred eighty-three patients with mild to moderately active UC enrolled in this randomized parallel group, double-blind study. Patients received placebo or MK-591 at a dose of 12.5, 50, or 100 mg twice daily for 8 weeks. A subset of patients underwent rectal dialysis to determine LTB4 concentration. RESULTS: MK-591 reduced LTB4 concentrations in rectal dialysate at the final determination. The median percent of baseline LTB4 concentration for 100 mg taken twice daily was 1.4% (n = 4); for 50 mg taken twice daily, 16.5% (n = 6); for 12.5 mg taken twice daily, 12% (n = 6); and for placebo, 78% (n = 6). There was no correlation between reduction of LTB4 and remission. Patients in remission at week 8 were as follows: placebo, 9 of 44 (20.5%); 100 mg taken twice daily, 11 of 43 (25.6%); 50 mg taken twice daily, 8 of 49 (16.3%); and 12.5 mg taken twice daily, 4 of 47 (8.5%) (P > 0.10). CONCLUSIONS: MK-591 markedly inhibited LT biosynthesis, but it did not differ significantly from placebo in clinical efficacy. Inhibition of LT biosynthesis was not effective as a single therapeutic modality in active UC.

Acid suppression by famotidine 20 mg twice daily or 40 mg twice daily in preventing relapse of endoscopic recurrence of erosive esophagitis.

Control of esophageal acid exposure is important in treating patients with gastroesophageal reflux disease (GERD). After complete healing of esophagitis, most patients will relapse within 6 months if left untreated. This multicenter, randomized, double-masked, placebo-controlled trial, conducted in the United States, examined whether two famotidine dosing regimens are effective in extending the time in remission for patients with moderate-to-severe erosive esophagitis. Of 172 patients enrolled, 31 received placebo, 69 received famotidine 20 mg twice daily (BID) , and 72 received famotidine 40 mg BID. Endoscopy was scheduled at baseline and at months 3 and 6. Patients assessed global heartburn and symptom relief at months 3 and 6 relative to the start of the study. Life table (Kaplan-Meier) relapse rates at 6 months were 22% (P < 0.001 vs placebo) for famotidine 20 mg BID, 11% (P < 0.001 vs placebo) for famotidine 40 mg BID, and 62% for placebo. Compared with placebo, patients in the famotidine groups were significantly less likely to note global symptomatic deterioration, as measured by the distribution of global assessment responses. The incidence of clinical and laboratory adverse experiences was similar among treatment groups. For maintenance treatment of GERD, famotidine 20 mg BID and 40 mg BID are more effective than placebo in extending the time in remission.

Point and counterpoint. Should healthcare ethics committee members be paid?

KIE: Cain, an oncologist and chair of her medical center's ethics advisory committee, and Reagan, a clinical ethicist, debate the pros and cons of compensation for ethics committee members. Among the issues raised are the value of monetary compensation in our society, the assumption of virtue as its own reward, and the potential for conflict of interest if ethics committee members are paid.^ieng

Biological activity of parathyroid hormone antagonists substituted at position 13.

Lysine occupies position 13 in the parathyroid hormone (PTH) antagonist, [Nle8,18,Tyr34]bPTH(7-34)NH2. Acylation of the epsilon-amino group in lysine 13 by a hydrophobic moiety is well tolerated in terms of bioactivity: the analog [Nle8,18, D-Trp12,Lys 13 (epsilon-3-phenylpropanoyl),Tyr34]bPTH(7-34)NH2 is equivalent to the parent peptide in its affinity for PTH receptors and its ability to inhibit PTH-stimulated adenylate cyclase in both kidney- and bone-based assays. Truncation of this peptide by deletion of phenylalanyl7 with concomitant removal of the amino-terminal alpha-amino group yielded the analog desamino[Nle8,18,D-Trp12,Lys13 (epsilon-3-phenylpropanoyl),Tyr34]bPTH(8-34)NH2, an antagonist of high potency in vitro (Kb = 4 and 9 nM, Ki = 73 and 3.5 nM in kidney- and bone-based assays, respectively). Also this analog is potentially stable to aminopeptidases present in many biological systems.

Effects of hydrophobic substitutions at position 18 on the potency of parathyroid hormone antagonists.

Position 18 in a parathyroid hormone (PTH) antagonist, [Nle8,18,Tyr34]bPTH(7-34)NH2 (ii), was shown to tolerate substitutions by a range of amino acids with retention of inhibitory activity. The effects of hydrophobic substitutions at this position as a means of enhancing binding interactions with the receptor were evaluated. Substitution of Nle at position 18 with either D-Ala, D-Trp, or L-Trp in analog ii or with Trp (D or L) in the recently reported, highly potent antagonist, [Nle8,18,D-Trp12,Tyr34]bPTH(7-34)NH2 (in vitro activities; Kb = 15 nM and Ki = 125 nM), was performed. In terms of activity on renal receptors, one antagonist, [Nle8,D-Trp12,18,Tyr34]bPTH(7-34)NH2, is the most active in vitro PTH antagonist yet reported (Kb = 4 nM; Ki = 30 nM). The rationale for design of this antagonist and the conclusions regarding PTH-receptor interactions are discussed.

Modifications of position 12 in parathyroid hormone and parathyroid hormone related protein: toward the design of highly potent antagonists.

Truncated N-terminal fragments of parathyroid hormone (PTH), [Tyr34]bovine PTH(7-34)NH2, and parathyroid hormone related protein (PTHrP), PTHrP(7-34)NH2, inhibit [Nle8,18,[125I]iodo-Tyr34]-bPTH(1-34)NH2 binding and PTH-stimulated adenylate cyclase in bone and kidney assays. However, the receptor interactions of these peptides are 2-3 orders of magnitude weaker than those of their agonist counterparts. To produce an antagonist with increased receptor-binding affinity but lacking agonist-like properties, structure-function studies were undertaken. Glycine at position 12 (present in all homologues of PTH and in PTHrP), which is predicted in both hormones to participate in a beta-turn, was examined by substituting conformational reporters, such as D- or L-Ala, Pro, and alpha-aminoisobutyric acid (Aib), in both agonist and antagonist analogues. Except for N-substituted amino acids, which substantially diminished potency, substitutions were well tolerated, indicating that this site can accept a wide latitude of modifications. To augment receptor avidity, hydrophobic residues compatible with helical secondary structure were introduced. Incorporation of the nonnatural amino acids D-Trp, D-alpha-naphthylalanine (D-alpha-Nal), or D-beta-Nal into either [Tyr34]bPTH(7-34)NH2 or [Nle8,18,Tyr34]bPTH(7-34)NH2 resulted in antagonists that were about 10-fold more active than their respective 7-34 parent compound. Similarly, [D-Trp12]PTHrP(7-34)NH2 was 6 times more potent than the unsubstituted peptide but retained partial agonistic properties, although markedly reduced, similar to PTHrP(7-34)NH2. The antagonistic potentiating effect was configurationally specific.(ABSTRACT TRUNCATED AT 250 WORDS)

Avian (chicken) parathyroid hormone: synthesis and comparative biological evaluation of the 1-34 fragment.

The full-length amino acid sequence of the avian (chicken) form of parathyroid hormone (cPTH) has recently been elucidated. We have chemically synthesized, purified to a high degree, and analytically and biologically characterized the N-terminal 1-34 fragment of the avian hormone. The biological properties of cPTH-(1-34)NH2 were evaluated and compared to the bovine fragment bPTH-(1-34) in several assays. The potency of cPTH-(1-34)NH2 in binding to PTH receptors, in stimulating adenylate cyclase activity and in relaxing smooth muscle tissue was approximately one-tenth that of bPTH-(1-34). Comparison of the avian sequence to other native PTH related sequences suggests that changes in the binding domain of the 1-34 active fragment may account for the decline in potency.

A new highly potent parathyroid hormone antagonist: [D-Trp12,Tyr34]bPTH-(7-34)NH2.

Based upon N-terminal parathyroid hormone (PTH) analog structure-activity relationship studies, position 12 was found to possess a wide structural latitude and was chosen as a site for single amino acid substitutions. Replacement of the naturally-occurring Gly with D-Trp at position 12 in the PTH antagonists [Tyr34]bPTH-(7-34)NH2 and [Nle8,18,Tyr34]bPTH-(7-34)NH2 increased in vitro receptor affinity. The D-Trp12 containing analogs were 12-fold more potent than their unsubstituted counterparts as inhibitors of PTH binding to renal and bone PTH receptors and 13-27-fold more potent as inhibitors of PTH-stimulated renal and bone adenylate cyclase activity. Based upon Scatchard analyses of saturation binding experiments and Schild analyses of adenylate cyclase experiments, [D-Trp12,Tyr34]bPTH-(7-34)NH2 was shown to interact with PTH receptors in a competitive manner. These studies demonstrate, therefore, that D-Trp12 substitution in PTH antagonists improves inhibitory properties in vitro and is compatible with a helical conformation at this position as a new direction for the design of PTH antagonists.

Evaluation of novel parathyroid hormone analogs using a bovine renal membrane receptor binding assay.

A PTH membrane receptor binding assay based on a stable hormone analog radioligand was refined and used with bovine renal cortical membranes to evaluate PTH reference peptides and novel analogs of the hormone. Systematic studies were performed to optimize several aspects of the receptor binding assay. The sulfur-free agonist analog [Nle8,18,Tyr34]bovine PTH-(1-34)NH2 was iodinated using Iodogen. The monoiodinated derivative was purified and isolated by reverse phase HPLC. Immediate dilution of the purified radioligand in albumin-containing buffer and cold storage of aliquots yielded a tracer that was stable for at least 2 months. When used in the binding assay, the radioligand displayed specific, high affinity, and saturable binding to both bovine and canine renal cortical membranes. The Kd values were 0.47 +/- 0.07 and 0.63 +/- 0.08 nM for bovine and canine membranes, respectively. Maximum binding values were 475 +/- 46 and 395 +/- 48 fmol/mg protein for bovine and canine membranes, respectively. Furthermore, when used on a routine basis, this assay system proved reliable and reproducible. A series of previously characterized PTH agonists and antagonists was tested as reference peptides to validate this assay. Inhibition of binding by agents was dose dependent, parallel concentration-dependent binding curves were observed, and a close correlation between binding affinity and adenylate cyclase activity was obtained. In addition, a series of novel analogs designed to determine the consequences of sequence elongation at the N- and/or C-terminus or incorporation of amino acid substitutions to enhance resistance to enzymatic degradation were examined. With the exception of C-terminal extension from position 34 to position 38, which diminished receptor affinities, all modifications retained full biological activity. This refined receptor binding assay should facilitate future studies of newly designed PTH analogs.

Similarity of synthetic peptide from human tumor to parathyroid hormone in vivo and in vitro.

One mechanism considered responsible for the hypercalcemia that frequently accompanies malignancy is secretion by the tumor of a circulating factor that alters calcium metabolism. The structure of a tumor-secreted peptide was recently determined and found to be partially homologous to parathyroid hormone (PTH). The amino-terminal 1-34 region of the factor was synthesized and evaluated biologically. In vivo it produced hypercalcemia, acted on bone and kidney, and stimulated 1,25-dihydroxy-vitamin D3 formation. In vitro it interacted with PTH receptors and, in some systems, was more potent than PTH. These studies support a long-standing hypothesis regarding pathogenesis of malignancy-associated hypercalcemia.

Fasting and L-364,718 prevent cholecystokinin-induced elevations of plasma insulin levels.

Sulfated CCK-8 but not non-sulfated CCK-8 induced a dose-dependent increase in plasma insulin levels in fed mice. In fasted mice, however, the CCK peptides caused a non-significant to minimal elevation of plasma insulin. Refeeding fasted mice for 1 h prior to CCK-8-S administration was sufficient to cause a significant elevation of plasma insulin levels. The peripheral CCK antagonist, L-364,718, prevented the CCK-8-S-induced elevation of plasma insulin observed in fed mice. In conclusion, CCK produces a nutrition-dependent increase in plasma insulin levels in vivo via an action upon peripheral CCK receptors.