Development and significance of antibodies to salmon calcitonin in patients with Paget's disease on long-term treatment

Leptin and the Blood-Brain Barrier: Curiosities and Controversies

Leptin for over 25 years has been a central theme in the study of appetite, obesity, and starvation. As the major site of leptin production is peripheral, and the site of action of greatest interest is the hypothalamus, how leptin accesses the central nervous system (CNS) and crosses the blood-brain barrier (BBB) has been of great interest. We review here the ongoing research that addresses fundamental questions such as the sites of leptin resistances in obesity and other conditions, the causes of resistances and their relations to one another, the three barrier sites of entry into the CNS, why recent studies using suprapharmacological doses cannot address these questions but give insight into nonsaturable entry of leptin into the CNS, and how that might be useful in using leptin therapeutically. The current status of the controversy of whether the short form of the leptin receptor acts as the BBB leptin transporter and how obesity may transform leptin transport is reviewed. Review of these and other topics summarizes in a new appreciation of what leptin may have actually evolved to do and what physiological role leptin resistance may play. © 2021 American Physiological Society. Compr Physiol 11:1-19, 2021.

Immunogenicity of xenopeptide hormone therapies

Peptides are a growing class of agents whose therapeutic use originated with non-human treatments such as animal insulins. Xenopeptides continue to be explored for biotherapeutic development using genetic engineering, and through the rich resource of animal and plant polypeptides. One of the major concerns of therapeutic administration of xenopeptides is the potential for untoward immune responses that may lead to loss of drug efficacy or adverse events in recipients. An increased risk of immunogenicity is perceived with xenopeptides, however, human-derived therapies also induce antibody formation that in some cases has been associated with severe clinical sequelae. In this review, antibody responses to xenopeptides are highlighted looking at current hormone therapies used to treat endocrine disorders. Similar to clinical experiences with peptide-based agents in general, antibody responses against xenopeptide hormone therapies in majority of cases have been benign in nature with minimal clinical impact.

Biological properties of salmon calcitonin IV

In this study we characterized the biological activity of the recently identified salmon calcitonin (sCT) IV, in order to evaluate its potential therapeutic value. In the rat bioassay, sCT IV exhibited a 30% higher hypocalcemic activity than sCT I. The capacity of the molecule to inhibit bone resorption was assessed in vitro by the bone resorbing assay and the pit assay. An inhibitory effect, similar to that of sCT I, was observed in both assays. The interaction of sCT IV with the rabbit CT receptor was also studied. The affinity of sCT IV for the receptor was similar to that of sCT I, as was the potency for stimulating cAMP production. The antigenicity of the two molecules was not identical. Thus, this new CT could represent a useful novel therapeutic agent for the treatment of bone disorders.

Induction of antibodies to methadone during methadone maintenance treatment of heroin addicts and its possible clinical implications

By means of two different types of enzyme-linked immunosorbent assay (ELISA) techniques, antibodies to methadone were detected in blood plasma of heroin addicts on methadone maintenance treatment. In 11-15% of cases immunoglobulin (Ig) M antibodies were detected, while IgG antibodies were observed in 33-40%. At least two types of antibodies to methadone were induced-antibodies with high affinity to methadone and low-affinity antibodies more specific for morphine than for methadone. The methadone antibody-positive group of patients had a significantly higher plasma methadone concentration--440 ng/ml, than the antibody-negative group--250 ng/ml (P < 0.005) despite almost the same mean therapeutic doses of methadone. Of patients with all types of antibodies to methadone 52% were human immunodeficiency virus (HIV)-positive, whereas in the group without antibodies, HIV-positive reactions were observed in 10.5% only (P < 0.002). Alternatively, 87.5% of HIV-positive patients had antibodies to methadone, a fact which should be taken into consideration during methadone dose adjustment.

The effect of intranasal salmon calcitonin on postmenopausal bone turnover as assessed by biochemical markers: evidence of maximal effect after 8 weeks of continuous treatment

Although treatment with intranasal salmon calcitonin (sCT) has been shown to effectively inhibit postmenopausal bone loss, there is still controversy over both timing and the duration of its application. In an open prospective study, we therefore assessed the effect of shortterm intranasal sCT on postmenopausal bone turnover, employing biochemical markers of bone metabolism. Ten early postmenopausal, previously untreated women (1-5 years after menopause) with biochemical evidence of increased bone resorption and a low bone mineral density at baseline were treated with intranasal sCT (100 IU B.I.D.) for a period of 3 months. Oral calcium (500 mg/day) was administered simultaneously, and during a further 3 month follow-up interval. Treatment with sCT resulted in a pronounced suppression of bone resorption markers with a maximum effect reached after 8 weeks of therapy: as compared to the respective baseline values, mean levels decreased by -26.2% +/- 3.4% (P < 0.001) for pyridinoline, -32.7% +/- 3.5% (P < 0.001) for deoxypyridinoline, -32.7% +/- 3.3% (P < 0.001) for hydroxyproline, and -24.1% +/- 8.2% (P < 0.001) for the amino-terminal telopeptide. In contrast, changes in bone formation markers of osteocalcin (-14.4% +/- 4.8%, P < 0.05) and C-terminal procollagen type I propetide (-7.9% +/- 3.9%, ns) were much less pronounced. Unexpectedly, after week 8 of the study all resorption markers showed a plateau and a trend to increase, although intranasal sCT was continued for a total of 12 weeks. This effect could not be attributed to the formation of anti-sCT antibodies. After cessation of treatment, both bone formation and resorption markers rapidly returned to baseline levels. Bone mineral density of both spine and hip showed no significant change during the observation period. Our results demonstrate that in postmenopausal women with a high bone turnover, intranasal treatment with 200 IU of sCT effectively reduces bone turnover and maintains bone mass, the maximum effect being reached after 8 weeks of treatment.

A double-blind, placebo-controlled, dose-finding trial of intermittent nasal salmon calcitonin for prevention of postmenopausal lumbar spine bone loss

PURPOSE

Nasal administration of salmon calcitonin (SCT) has been suggested for preventing trabecular bone loss during the first years following the menopause, but no conclusive evidence has appeared about the minimal effective dose. Since nasal calcitonin is highly expensive, it makes sense to define this dose.

PATIENTS AND METHODS

We performed a double-blind, placebo-controlled, randomized, single-center study with a 3-arm parallel-group design. The subjects were 251 healthy women who had experienced natural menopause within the past 6 to 72 months and were not affected by any diseases or treatments that interfere with calcium metabolism. They were randomly allocated in groups of 6 to receive intranasal SCT 50 IU (n = 84), SCT 200 IU (n = 84), or placebo (n = 83). All treatments were given on 5 consecutive days per week. Statistical analysis was based on two populations: intention-to-treat (IT) and valid completers (VC). The main assessments performed were bone mineral density of the lumbar spine (LSBMD) and biochemical parameters reflecting bone turnover (serum alkaline phosphatase, urinary calcium/creatinine, and hydroxyproline/creatinine ratios).

RESULTS

Changes over the treatment period were comparable in the IT and VC populations. In the group receiving the placebo, LSBMD decreased from baseline to end point by a mean of 6.28% (95% confidence interval [CI] -7.69 to -4.89) in the IT population and 6.98% (95% CI -8.86 to -5.11) in the VC population (P = 0.0001, end LSBMD versus baseline LSBMD). LSBMD increased slightly with the 50-IU/d dose of SCT, by 0.82% (95% CI -0.26 to 1.89) in the IT population, and 0.51% (95% CI -0.69 to 1.72) in the VC (P = NS, versus baseline). Subjects who received SCT 200 IU/d experienced significant increases of 2.03% (95% CI 0.92 to 3.15) in the IT population and 2.26% (95% CI 1.01 to 3.51) in the VC (both P = 0.001). The difference between the evolution of the combined groups receiving nasal SCT and the group treated with the placebo was highly significant (P = 0.0001). No significant changes were recorded in biochemical parameters reflecting bone turnover.

CONCLUSIONS

SCT 50 IU/d administered nasally and intermittently appears to prevent lumbar bone loss in nonobese early postmenopausal women.

Formation of neutralizing antibodies after treatment with human calcitonin

PURPOSE

Calcitonin is used for the treatment of Paget's disease of bone, hypercalcemia, and postmenopausal osteoporosis. The formation of antibodies against heterologous calcitonins, such as salmon calcitonin (sCT), has been described frequently. Neutralizing effects of these antibodies have been demonstrated in many cases. As far as antibody formation against human calcitonin (hCT) is concerned, only a single case has been reported in the literature; however, investigations concerning the biologic activity of the antibodies were not performed. We have now assessed the sera of 33 patients treated with hCT for postmenopausal osteoporosis for a period of at least 12 months to evaluate the occurrence of hCT-binding and hCT-neutralizing antibodies.

PATIENTS AND METHODS

Binding antibodies were detected by incubation of patient sera with 125I-labeled hCT; neutralizing activity was assessed in an in vitro bioassay that measured the impairment of the hCT-induced cyclic adenosine monophosphate (cAMP) formation in the human breast cancer cell line T47D.

RESULTS

Prior to hCT treatment, none of the patients showed evidence of the presence of either binding or neutralizing antibodies. During the course of treatment, binding antibodies occurred in a single patient. These antibodies had a neutralizing activity characterized by 15% impairment of cAMP formation after 6 months and 27% impairment after 12 months of treatment compared with pretreatment control values. The neutralizing effect observed in this particular patient was comparatively mild compared with the effects seen after the formation of neutralizing antibodies against sCT, so major clinical sequelae were not expected in this patient. This may be due to the lower antigenicity of hCT as compared with sCT.

CONCLUSION

Although antibody formation against hCT is a rare phenomenon, we nonetheless recommend monitoring of postmenopausal osteoporosis patients treated with sCT or hCT for neutralizing antibody formation in order to evaluate the therapeutic effect of treatment.

Prevention of osteoporosis with nasal salmon calcitonin: effect of anti-salmon calcitonin antibody formation

The amino acid sequence of salmon calcitonin (SCT) differs considerably from that of the human hormone and specific antibodies (Ab) develop in a significant proportion of patients after parenteral or nasal administration of SCT. Controversy remains regarding the functional importance of these Ab. We report on the development of specific anti-SCT Ab in a population of postmenopausal women receiving nasal SCT for prevention of postmenopausal bone loss, and compare the effects of nasal SCT in women with or without Ab. Thirty-nine per cent of women developed Ab after 6 months of treatment with SCT, 52% after 12 months, and 61% after 18 and 24 months. After 24 months the AB titre was 3.47-17.7 x 10(-9) M/l (mean +/- SD: 13.3 +/- 3.1 x 10(-9) M/l). No significant differences appeared between the changes in lumbar bone mineral density (BMD) measured in the whole population (n = 44) (mean +/- SD: +1.06 +/- 3.9%), the patients without Ab (n = 17) (+0.05 +/- 3.7%) or in those with Ab (n = 27) (+1.7 +/- 4.6%). During the same period, a control population randomly assigned to a 500 mg/day calcium intake showed a significant loss of lumbar BMD (-4.57 +/- 4.9%) (p < 0.01). In conclusion, in healthy postmenopausal women nasal SCT seems to maintain the same preventive effect against bone loss whether or not Ab are present.

Immune response to opiates: new findings in heroin addicts investigated by means of an original enzyme immunoassay and morphine determination in hair

In the early 1970's, some papers appeared reporting an immune response to opiates in animals treated with morphine and in heroin addicts, but further researches failed to confirm these results in humans. The aim of the present work is investigating with a newly developed enzyme immunoassay the existence of specific antibodies to morphine in a group of opiate chronic users, controlled by means of the toxicological analysis of hair. Twenty five opiate addicts inpatients for detoxication treatments were investigated for the presence of morphine specific antibodies and for the morphine content in hair, as a marker of addiction to opiates. Antibodies to morphine were investigated using an original ELISA method using a morphine-human serum albumin conjugate immobilized into the wells of polystyrene microtiter plates. Morphine determinations in hair were accomplished by a radioimmunologic screening followed by HPLC confirmation of positive results. The group of opiate users, in which all the subjects resulted positive for morphine content in hair, showed in the ELISA test an average D OD% value significantly higher than the control group (p < 0.001); in particular, 16 out of 25 addicts could be classified positive for anti-morphine antibodies, which were identified as IgM. Inhibition studies demonstrated Ka's for morphine ranging from 10(4) to 10(10) M-1 and a high cross reactivity for codeine. The presence of circulating antibodies specific to morphine in chronic users of opiates is strongly supported by the present findings.

Clinical experience with pamidronate in the treatment of Paget's disease of bone

Bisphosphonates have been shown to be effective in treating the increased bone turnover associated with Paget's disease of bone. In this study two groups of patients were treated with pamidronate by intravenous infusion. In group 1 (n = 15) 30 mg of pamidronate was given once a week for six weeks. A subgroup (group 1A, n = 6) of more severely affected patients (pretreatment serum alkaline phosphatase (ALP) greater than 1000 U/l, normal range 80-280 U/l) received a further 60 mg weekly for three weeks. Group 2 (n = 24) received 45 mg of pamidronate every three months for one year. In both groups the level of ALP in serum samples decreased steadily throughout the year. In group 1 the level decreased to a mean value of 230 U/l (95% confidence interval 188-281) and in group 2 to 297 U/l (227-389). Four of the six patients in group 1A achieved normal ALP, whereas ALP remained at an increased level in all of the 10 patients in group 2 whose pretreatment ALP was greater than 1000 U/l, suggesting that a dose-response effect exists. The lowest hydroxyproline to creatinine ratios (normal ratio less than 0.033) were observed at the end of treatment in group 1, with a mean ratio of 0.022 (range 0.015-0.033) and at three months after the start of treatment in group 2 with a mean ratio of 0.029 (range 0.022-0.037). There was a significant decrease in the turnover of bone, as measured by whole body retention of radiolabelled bisphosphonate, from a mean of 49.3 to 41.0% (p less than 0.01). These data confirm that pamidronate is effective in the management of Paget's disease of bone. For patients with levels of ALP in serum samples of up to four times above the upper limit of the normal reference range, an effective and convenient regimen is 45 mg every three months for one year. For patients with higher levels of ALP higher doses may be more effective.

Discontinuous calcitonin treatment of established osteoporosis--effects of withdrawal of treatment

PURPOSE

The purpose of this study was to examine the effects of discontinuous treatments with intranasal salmon calcitonin on bone and calcium metabolism in postmenopausal women and to establish the effects of withdrawing treatment.

PATIENTS AND METHODS

This report presents data from 26 postmenopausal women with established osteoporosis (forearm fracture) 12 months after withdrawal of a 1-year double-blind, placebo-controlled therapy with intranasal calcitonin. The women then resumed treatment with calcitonin 200 IU plus calcium 500 mg daily in an open design for an additional 1-year period. A control group of 19 age-matched women (no forearm fracture) did not receive any treatment.

RESULTS

At the end of the 3 years, the control group had lost significantly more bone in the forearm (single photon absorptiometry) and spine (dual photon absorptiometry) than had the group treated with intranasal calcitonin for 2 years, whereas the group receiving calcitonin for 1 year had intermediate values. During the year of withdrawal, the rate of bone loss was similar in the women who had received calcitonin and those who had received placebo. Calcitonin was especially effective in women with initially high bone turnover and low bone mass. The bone response in the spine could, furthermore, be estimated by the changes in bone turnover.

CONCLUSION

Discontinuous treatment with intranasal calcitonin affects bone and calcium metabolism in established osteoporosis. In women with high-turnover osteoporosis, therapy results in a net gain of bone in both the peripheral and axial skeleton. Response to treatment may be monitored by changes in bone turnover.

In vitro detection of neutralizing antibodies after treatment of Paget's disease of bone with nasal salmon calcitonin

To elucidate the biologic relevance of circulating sCT antibodies, an in vitro bioassay system for the detection of neutralizing antibodies was developed utilizing the human breast carcinoma cell line T47D. We reasoned that the inhibition of the dose-dependent cAMP response to sCT in the T47D assay system by anti-sCT antibodies could be used to determine the in vivo relevance of these antibodies. In this report the clinical course of nine patients with Paget's disease of bone treated with intranasal sCT was correlated with the presence of 125I-sCT binding and neutralizing antibodies. Of these seven patients, four were found to have neutralizing antibodies; the appearance of the antibodies coincided with the development of resistance. One of these patients was subsequently treated with human calcitonin and revealed a good response to the treatment. There was no clinical resistance observed in the three patients with 125I-sCT binding antibodies but no neutralizing antibodies; no resistance was observed in two patients without 125I-sCT binding or neutralizing antibodies. We conclude that this new technique to determine the biologic relevance of circulating anti-sCT antibodies may be an useful adjunct for determining the cause of resistance in patients treated with sCT.

Biochemical response to combination of disodium etidronate with calcitonin in Paget's disease

The biochemical responses to salmon calcitonin (SCT: 100 MRC units thrice weekly) and disodium etidronate (EHDP: 400 mg daily) alone and in combination for 6 months were compared in 72 patients with symptomatic Paget's disease of bone unresponsive to simple analgesic agents. SCT produced a 53% reduction in alkaline phosphatase (AP) and a 38% reduction in 24 h urinary hydroxyproline excretion (HYPRO). The response to EHDP was not significantly different--56% reduction in AP and 48% reduction in HYPRO. Their use in combination produced a significantly greater reduction of 71% in AP (P less than 0.002) and 69% reduction in HYPRO (P less than 0.0001). In those that remained symptomatic with increased disease activity treatment for longer than 6 months had a unpredictable effect and normal bone turnover was rarely achieved. Once therapy was withdrawn AP and HYPRO increased rapidly in those given SCT alone, returning to initial levels within 6 months. More sustained control of disease activity was achieved in those given EHDP either alone or with SCT but the combination retained the advantage obtained during treatment. Combinations of SCT + EHDP may find a place in the treatment of very active Paget's disease.

Chemical synthesis and expression in E. coli of a human Val8-calcitonin gene by fusion to a synthetic human interferon-gamma gene

A gene coding for human Val8-calcitonin (Val8-hCT) was synthesized by the solid-phase phosphite approach and fused to a synthetic human immune interferon-gamma (IFN-gamma) gene. The IFN gene was previously shown to be expressed at a very high level in E. coli [(1986) Gene, in press] due to the control of a strong synthetic promoter and strong ribosome binding site. The cells harboring the fused gene produced 100-150 micrograms per l of bacterial suspension of immunoreactive calcitonin in the form of hybrid IFN-gamma-Val8-hCT protein consisting of 140 amino acids. The Val8-hCT can be released from this protein by CNBr treatment.

Paget's disease of bone. An update on management

The essential requirement for effective treatment of Paget's disease of bone is that the characteristic abnormality of bone remodelling is predictably corrected without the occurrence of significant side effects. Although the ideal agent is not currently available, appropriate use of the calcitonins or diphosphonates goes a long way to achieving this goal. Calcitonin (50 to 100 MRC units subcutaneously daily or 3 times weekly) will generally reduce bone turnover by approximately 50% within 6 months. However, very active disease will not be controlled and bone turnover will generally increase once treatment is withdrawn. Calcitonin is without significant side effects, although some patients will develop antibody-mediated resistance to the exogenous calcitonin species. An advantage of calcitonin is that there is radiographic evidence of a return to normal bone remodeling during treatment. Although a number of diphosphonates (now more correctly termed bisphosphonates) are available for experimental use, only the first generation compound, disodium etidronate (EHDP) is commercially available. It too will reduce bone turnover by about 50% within 6 months when given in a dose of 5 mg/kg daily. Unlike calcitonin, it results in a more sustained control of bone turnover while having the additional advantage that it can be given by mouth. Although larger doses are more effective in controlling very active disease, there is a real risk of causing defective bone mineralisation which may result in the development of atraumatic long bone fractures or diffuse bone pains. Combinations of calcitonin and disodium etidronate in conventional dosage seem to result in an additive suppressant effect on bone turnover and may be indicated for more active disease. Advances in treatment are progressing rapidly and it seems likely that in the next few years the introduction of new agents for the control of Paget's disease will more nearly approach the ideal goal of treatment.

Response of Paget's disease to human calcitonin in patients resistant to porcine calcitonin

Eleven patients with Paget's disease of bone, treated intermittently for 2-4 years with porcine calcitonin (pCT) and clinically resistant to pCT [no modifications of serum alkaline phosphatase (ALP) and urinary hydroxyproline ( uHOP ) during pCT administration] were treated with 0.5-0.25 mg/day of human calcitonin (hCT) for 3-6 months. Nine of our patients showed biochemical improvement during the first 2 months of treatment, with reduction in ALP and uHOP . In one patient with slightly increased ALP and uHOP , and in another one during the second treatment course, hCT treatment did not modify the biochemical indices of bone disease. However all patients, including those with biochemical resistance, experienced a remarkable diminution of bone pain, which had not been observed during previous pCT treatment courses. Therefore, hCT appears to be indicated for therapeutic use in patients who are resistant to foreign calcitonins.

Calcitonin and diphosphonate in the treatment of Paget's disease of bone

The ideal treatment for Paget's disease of bone should control turnover irrespective of its initial activity and produce a sustained remission once treatment is withdrawn. Unfortunately, neither the calcitonins nor the diphosphonates currently available entirely fulfil these requirements. Preliminary studies suggest that combinations of calcitonin and EHDP produce significantly better responses than those of the individual agents alone. This proposition is examined critically in terms of the optimum effects achieved with calcitonin and EHDP alone paying particular attention to variables such as disease activity, dose and duration of treatment.

Salmon calcitonin therapy for Paget's disease of bone. The problem of acquired clinical resistance

During the initial months of long-term treatment of Paget's disease of bone with salmon calcitonin, circulating alkaline phosphatase activity and urinary hydroxyproproline excretion usually decrease by about 50%. In 22 of 85 patients these parameters returned to pretreatment levels despite continuous therapy. Nineteen patients who were resistant to salmon calcitonin had salmon calcitonin antibodies in high titer. Human calcitonin has been effective in suppressing disease activity in these patients. The pathogenesis of calcitonin resistance in patients without antibodies is unknown.

Functional significance of antibody formation after long-term salmon calcitonin therapy

Twenty patients with Paget's disease were challenged with porcine (PCT) and salmon (SCT) calcitonin before and after 6 months SCT therapy. Acute hypocalcaemia was clearly related to the prevailing rate of bone turnover but responses to PCT showed that treatment had not disturbed this relationship. Although antibodies to SCT developed in eight patients during the period of treatment the acute hypocalcaemic response to SCT was not diminished in relation to bone turnover. It is suggested that antibodies which develop during the course of SCT therapy do not necessarily exert a functionally effective neutralizing action.

Treatment of Paget's disease with the calcitonins

Calcitonin has been used in the treatment of Paget's Disease of bone because of its ability to inhibit osteoclastic bone resorption. This results in a return of bone turnover towards normal, as reflected by urinary hydroxyproline and serum alkaline phosphatase. A plateau is reached with these parameters, at about 50% of the pre-treatment level. The cause of this plateau is unknown, but does not indicate resistance to treatment, since it occurs with all forms of calcitonin. Most treated patients experience pain relief, and there is radiological and histological evidence of arrested progression of Paget's Disease in patients treated with calcitonin. Both primary and secondary resistance to calcitonin occur with all calcitonins, including homologous hormone. Antibodies develop commonly in patients treated with pig or salmon calcitonin, but antibody-based clinical resistance has been demonstrated only in a few patients. Methods of selection of patients for treatment and of assessment of response are discussed, and treatment schedules summarized.

Medical staff conference. Paget disease of bone

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