Novel bromomelatonin derivatives as potentially effective drugs to treat bone diseases

Scientific basis for the potential use of melatonin in bone diseases: osteoporosis and adolescent idiopathic scoliosis

The objective of this paper was to analyze the data supporting the possible role of melatonin on bone metabolism and its repercussion in the etiology and treatment of bone pathologies such as the osteoporosis and the adolescent idiopathic scoliosis (AIS). Melatonin may prevent bone degradation and promote bone formation through mechanisms involving both melatonin receptor-mediated and receptor-independent actions. The three principal mechanisms of melatonin effects on bone function could be: (a) the promotion of the osteoblast differentiation and activity; (b) an increase in the osteoprotegerin expression by osteoblasts, thereby preventing the differentiation of osteoclasts; (c) scavenging of free radicals generated by osteoclast activity and responsible for bone resorption. A variety of in vitro and in vivo experimental studies, although with some controversial results, point toward a possible role of melatonin deficits in the etiology of osteoporosis and AIS and open a new field related to the possible therapeutic use of melatonin in these bone diseases.

Actions of melatonin mixed with collagenized porcine bone versus porcine bone only on osteointegration of dental implants

This study evaluated the effect of the topical application of melatonin mixed with collagenized porcine bone on the osteointegration on the rough discrete calcium deposit (DCD) surface implants in Beagle dogs 3 months after their insertion. In preparation for subsequent insertion of dental implants, lower molars were extracted from 12 Beagle dogs. Each mandible received two parallel wall expanded platform implants with a DCD surface of 4 mm in diameter and 10 mm in length. The implants were randomly assigned to the distal sites on each mandible in the molar area and the gaps were filled with 5 mg lyophilized powdered melatonin and porcine bone and collagenized porcine bone alone. Ten histological sections per implant were obtained for histomorphometric studies. After a 4-wk treatment period, melatonin plus porcine bone significantly increased the perimeter of bone that was in direct contact with the treated implants (P < 0.0001), bone density (P < 0.0001), and new bone formation (P < 0.0001) in comparison with porcine bone alone around the implants. Melatonin plus collagenized porcine bone on DCD surface may act as a biomimetic agent in the placement of endo-osseous dental implants and enhance the osteointegration. Melatonin combined with porcine bone on DCD implants reveals more bone in implant contact at 12 wk (84.5 +/- 1.5%) compared with porcine bone alone treated area (67.17 +/- 1.2%).

Association of disease-predisposition polymorphisms of the melatonin receptors and sunshine duration in the global human populations

Melatonin is predominantly involved in signaling circadian and seasonal rhythms, and its synthesis is regulated by the environmental light/dark cycle. The selection pressure by geographically different environmental light/dark cycles, which is predominantly determined by sunshine duration, on the global distribution of genetic polymorphisms in the melatonin pathway is not well understood. Recent genetic association studies identified various disease-predisposition polymorphisms in this pathway. We investigated the correlations between the prevalence of these clinically important single nucleotide polymorphisms (SNPs) and sunshine duration among worldwide human populations from twelve regions in the CEPH-HGDP database rs4753426, a recently reported predisposition SNP for type 2 diabetes in the promoter of the MT(2) melatonin receptor gene (MTNR1B), which was not included in the CEPH-HGDP genotyping array, was additionally genotyped. This SNP showed a marginally significant correlation in 760 CEPH-HGDP DNA samples (r = -0.5346, P = 0.0733), and it showed the most prominent association among the candidate melatonin pathway SNPs examined. To control for population structure, which may lead to a false positive correlation, we genotyped this SNP in a replication set of 1792 subjects from China. The correlation was confirmed among Chinese populations (r = -0.8694, P = 0.0002), and was also statistically significant after correction of other climatic and geographical covariants in multiple regression analysis (beta = -0.907, P = 1.94 x 10(-5)). Taken together, it suggests that the human melatonin signaling pathway, particularly MT(2) melatonin receptor may have undergone a selective pressure in response to global variation in sunshine duration.

Role of melatonin in metabolic regulation

Although the human genome has remained unchanged over the last 10,000 years, our lifestyle has become progressively more divergent from those of our ancient ancestors. This maladaptive change became apparent with the Industrial Revolution and has been accelerating in recent decades. Socially, we are people of the 21st century, but genetically we remain similar to our early ancestors. In conjunction with this discordance between our ancient, genetically-determined biology and the nutritional, cultural and activity patterns in contemporary Western populations, many diseases have emerged. Only a century ago infectious disease was a major cause of mortality, whereas today non-infectious chronic diseases are the greatest cause of death in the world. Epidemics of metabolic diseases (e.g., cardiovascular diseases, type 2 diabetes, obesity, metabolic syndrome and certain cancers) have become major contributors to the burden of poor health and they are presently emerging or accelerating, in most developing countries. One major lifestyle consequence is light at night and subsequent disrupted circadian rhythms commonly referred to as circadian disruption or chronodisruption. Mounting evidence reveals that particularly melatonin rhythmicity has crucial roles in a variety of metabolic functions as an anti-oxidant, anti-inflammatory chronobiotic and possibly as an epigenetic regulator. This paper provides a brief outline about metabolic dysregulation in conjunction with a disrupted melatonin rhythm.

Melatonin plus porcine bone on discrete calcium deposit implant surface stimulates osteointegration in dental implants

The aim of this study was to evaluate the effect of the topical application of melatonin mixed with collagenized porcine bone to accelerate the osteointegration on the rough discrete calcium deposit (DCD) surface implants in Beagle dogs 3 months after their insertion. In preparation for subsequent insertion of dental implants, lower premolars and molars were extracted from 12 Beagle dogs. Each mandible received three parallel wall implants with discrete calcium deposit (DCD) surface of 4 mm in diameter and 10 mm in length. The implants were randomly assigned to the distal sites on each side of the mandible in three groups: group I implants alone, group II implants with melatonin and group III implants with melatonin and porcine bone. Prior to implanting, 5 mg lyophylized powdered melatonin was applied to one bone hole at each side of the mandible. None was applied at the control sites. Ten histological sections per implant were obtained for histomorphometric studies. After a 4-wk treatment period, melatonin significantly increased the perimeter of bone that was in direct contact with the treated implants (P < 0.0001), bone density (P < 0.0001), new bone formation (P < 0.0001) in comparison with control implants. Topical application of melatonin on DCD surface may act as a biomimetic agent in the placement of endo-osseous dental implants and enhance the osteointegration. Melatonin combined with porcine bone on DCD implants reveals more bone to implant contact at 12 wk (84.5 +/- 1.5%) compared with melatonin treated (75.1 +/- 1.4%) and nonmelatonin treated surface implants (64 +/- 1.4%).

Melatonin and reproduction revisited

This brief review summarizes new findings related to the reported beneficial effects of melatonin on reproductive physiology beyond its now well-known role in determining the sexual status in both long-day and short-day seasonally breeding mammals. Of particular note are those reproductive processes that have been shown to benefit from the ability of melatonin to function in the reduction of oxidative stress. In the few species that have been tested, brightly colored secondary sexual characteristics that serve as a sexual attractant reportedly are enhanced by melatonin administration. This is of potential importance inasmuch as the brightness of ornamental pigmentation is also associated with animals that are of the highest genetic quality. Free radical damage is commonplace during pregnancy and has negative effects on the mother, placenta, and fetus. Because of its ability to readily pass through the placenta, melatonin easily protects the fetus from oxidative damage, as well as the maternal tissues and placenta. Examples of conditions in which oxidative and nitrosative stress can be extensive during pregnancy include preeclampsia and damage resulting from anoxia or hypoxia that is followed by reflow of oxygenated blood into the tissue. Given the uncommonly low toxicity of melatonin, clinical trials are warranted to document the protection by melatonin against pathophysiological states of the reproductive system in which free radical damage is known to occur. Finally, the beneficial effects of melatonin in improving the outcomes of in vitro fertilization and embryo transfer should be further tested and exploited. The information in this article has applicability to human and veterinary medicine.

The new frontier of bone formation: a breakthrough in postmenopausal osteoporosis?

OBJECTIVE

Osteoporosis is a chronic disease that accelerates after menopause in many women. Most of the pharmacologic attempts to control the disease, such as hormone therapy, have emphasized the constraint of bone resorption. Since recent years have witnessed important advances in the field of bone formation, this review aims to update the present knowledge on the mechanisms affecting osteoblastogenesis and on the therapeutic results achieved by recently approved drugs.

METHOD

We sought peer-reviewed, full-length basic and clinical articles published between 1995 and May 2008 using a PubMed search strategy, with the terms osteoporosis and osteoblast, osteoporosis and strontium ranelate, and osteoporosis and parathyroid hormone (PTH). This search was further supplemented by a hand-search of reference lists of selected review papers. After crossing-cleaning the reference lists, some 800 articles were selected. Articles on regulators of osteoblast differentiation and function, together with well-designed clinical studies, were surveyed.

RESULTS

A complex network of systemic and local factors regulates osteoblastogenesis. Advances in fracture protection have been published in clinical studies with PTH. Some investigators claim an anabolic effect for strontium ranelate, which also confers protection against fracture.

CONCLUSION

The control of bone formation offers new clinical potential. Stimulation of bone formation by PTH has translated into fracture protection. The action of strontium ranelate has been claimed to be mediated by some level of bone formation, but this hypothesis still needs clarification.

The depressive effects of 5,8,11-eicosatrienoic Acid (20:3n-9) on osteoblasts

In cases of essential fatty acid deficiency, 5,8,11-eicosatrienoic acid (Mead acid, 20:3n-9) is synthesized from oleic acid as a 20-carbon analog of arachidonic acid. It was reported that 20:3n-9 levels were markedly higher in human fetal cartilage than in the muscle, liver and spleen. We, therefore, hypothesized that 20:3n-9 decreased osteoblastic activity. Goldfish scales were incubated either with 20:3n-9 or with oleic acid at 15 degrees C for 6 and 18 h. Both osteoblastic and osteoclastic activities in the scale were assessed by measuring alkaline phosphatase (ALP) and tartrate-resistant acid phosphatase, respectively. MC3T3-E1 cells (an osteoblast cell line derived from the mouse) were incubated with 20:3n-9 or oleic acid at 37 degrees C for 6 and 18 h. ALP activity in cell lysate was measured. In the case of experiments with scales, 20:3n-9 (1-100 muM) significantly suppressed osteoblastic activity after 6 and 18 h of incubation, whereas oleic acid did not change this activity. Osteoclastic activity was not affected either by 20:3n-9 or by oleic acid. In the case with the cell line, osteoblastic activity was again significantly decreased with 20:3n-9 (10-30 muM) after 6-h incubation but not after 18 h incubation. The presence of 20:3n-9 in fetal cartilage may be important for the prevention of calcification in the cartilage. 20:3n-9 could be applied to some clinical situations where bone formation should be inhibited.