The consequences of growth hormone-releasing hormone receptor haploinsufficiency for bone quality and insulin resistance

Objective Growth hormone (GH)/insulin-like growth factor (IGF) axis and insulin are key determinants of bone remodelling. Homozygous mutations in the GH-releasing hormone receptor (GHRHR) gene (GHRHR) are a frequent cause of genetic isolated GH deficiency (IGHD). Heterozygosity for GHRHR mutation causes changes in body composition and possibly an increase in insulin sensitivity, but its effects on bone quality are still unknown. The objective of this study was to assess the bone quality and metabolism and its correlation with insulin sensitivity in subjects heterozygous for a null mutation in the GHRHR. Patients and methods A cross-sectional study was performed on 76 normal subjects (68.4% females) (N/N) and 64 individuals (64.1% females) heterozygous for a mutation in the GHRHR (MUT/N). Anthropometric features, quantitative ultrasound (QUS) of the heel, bone markers [osteocalcin (OC) and CrossLaps], IGF-I, glucose and insulin were measured, and homeostasis model assessment of insulin resistance (HOMAIR) was calculated. Results There were no differences in age or height between the two groups, but weight (P = 0.007) and BMI (P = 0.001) were lower in MUT/N. There were no differences in serum levels of IGF-I, glucose, T-score or absolute values of stiffness and OC, but insulin (P = 0.01), HOMAIR (P = 0.01) and CrossLaps (P = 0.01) were lower in MUT/N. There was no correlation between OC and glucose, OC and HOMAIR in the 140 individuals as a whole or in the separate MUT/N or N/N groups. Conclusions This study suggests that one allele mutation in the GHRHR gene has a greater impact on energy metabolism than on bone quality.

The effects of conjugated estrogen, raloxifene and soy extract on collagen in rat bones

Objective To evaluate the action of conjugated equine estrogen, raloxifene and isolated or combined genistein-rich soy extracts on collagen fibers in the bones of oophorectomized rats. Materials and methods Seventy female rats received testosterone propionate (0.1 mu g/g) on the 9th day after birth. At 6 months of age, the rats were administered the vehicle (propylene glycol, 0.5 ml/day), and ten of the rats were randomly chosen to comprise the non-oophorectomized control group (GI). The other 60 rats were ovariectomized and randomized into six groups of ten as follows: GII, vehicle; GIII, conjugated equine estrogen (CEE), 50 mu g/kg/day; GIV, raloxifene (RAL), 0.75 mg/kg/day; GV, genistein-rich soy extract (GSE), 300 mg/kg/day; GVI, CEE + GSE, 50 mu g/kg/day + 300 mg/kg/day; and GVII, CEE + RAL, 50 mu g/kg/day + 0.75 mg/kg/day. Three months after surgery, the drugs were administered for 60 consecutive days. All rats were euthanized, and their left tibiae were removed for histological routine. The histological sections were stained with hematoxylin-eosin, and picrosirius for evaluating bone microarchitecture. Types I and II collagen fibers were analyzed by immunofluorescence. Data analysis was carried out with ANOVA and Tukey's test. Results Collagen reduction was significant in the GIII animals when compared to the other groups (p < 0.05). There was no significant difference in the thickness of collagen fibers among the groups. There was a greater quantity of type III collagen in GVI than in the other groups. Conclusion Our data indicate that conjugated equine estrogen improves bone quality because it increases the quantity of type I collagen while reducing the quantity of thin collagen fibers. In addition, the combination of CEE and raloxifene or genistein-rich soy extract is not as efficient as CEE itself to improve bone quality.

Stability of dental implants after irradiation with an 830-nm low-level laser: a double-blind randomized clinical study

Little is known about the benefits of low-level laser therapy (LLLT) on improvement of stability of dental implants. The aim of this randomized clinical study was to assess the LLLT effect on implants stability by means of resonance frequency analysis (RFA). Thirty implants were distributed bilaterally in the posterior mandible of eight patients. At the experimental side, the implants were submitted to LLLT (830 nm, 86 mW, 92.1 J/cm(2), 0.25 J, 3 s/point, at 20 points), and on the control side, the irradiation was simulated (placebo). The first irradiation was performed in the immediate postoperative period, and it was repeated every 48 h in the first 14 days. The initial implant stability quotient (ISQ) of the implants was measured by means of RFA. New ISQ measurements were made after 10 days, 3, 6, 9, and 12 weeks. The initial ISQ values ranged from 65-84, with a mean of 76, undergoing a significant drop in stability from the 10th day to the 6th week in the irradiated group, and presenting a gradual increase from the 6th to the 12th week. The highest ISQ values were observed on the 10th day in the irradiated group, and the lowest in the 6th week in both groups. Under the conditions of this study, no evidence was found of any effect of LLLT on the stability of the implants when measured by RFA. Since high primary stability and good bone quality are of major relevancy for a rigid bone-implant interface, additional LLLT may have little impact macroscopically.

Effect of soft laser in bone repair after expansion of the midpalatal suture in dogs

Introduction: The purpose of this research was to study the influence of soft laser treatment on the process of bone repair after expansion of the midpalatal suture. Methods: The sample for this case-control experimental study was 11 dogs. They were randomly divided into 2 groups, both of which underwent rapid maxillary expansion with a hyrax appliance. The animals in group 1 were also treated with laser therapy. They were killed, and histologic specimens of the palatal suture were prepared. The Student t test was applied for independent data, and the Mann-Whitney test was used for nonparametric data. Results: A significant difference was observed in the quality of the palatal sutures between the animals in groups 1 and 2. The connective tissues of the sutures in the group 1 animals were similar to the original configurations, with more advanced osteogenesis and fibrogenesis, compared with those of group 2. Conclusions: Soft laser appears to influence the behavior of the repair process, contributing to suture reorganization and palatal bone osteogenesis during and after expansion. (Am J Orthod Dentofacial Orthop 2012; 142: 615-24)

Molecular features of sexual steroids on cartilage and bone

In Brazil, the increase in the reported cases of degenerative diseases of articular cartilage is 20% per year, meaning that 200,000 Brazilians develop degenerative joint diseases every year, which have a negative impact on bone mass. This study shows evidence that hormone production of sexual steroids (estrogens, progestogens, and androgens) have an influence on cartilage quality, as well as on bone mass. Therefore, this review aimed to analyze literature data on the molecular and genic action of sexual steroids on hyaline cartilage and bone physiology, as well as osteoarthritis interference on the quality of these structures.

Cigarette smoke inhalation influences bone healing of post-extraction tooth socket: a histometric study in rats

The aim of this study was to evaluate, histometrically, the bone healing of the molar extraction socket just after cigarette smoke inhalation (CSI). Forty male Wistar rats were randomly assigned to a test group (animals exposed to CSI, starting 3 days before teeth extraction and maintained until sacrifice; n=20) and a control group (animals never exposed to CSI; n=20). Second mandibular molars were bilaterally extracted and the animals (n=5/group/period) were sacrificed at 3, 7, 10 and 14 days after surgery. Digital images were analyzed according to the following histometric parameters: osteoid tissue (OT), remaining area (RA), mineralized tissue (MT) and non-mineralized tissue (NMT) in the molar socket. Intergroup analysis showed no significant differences at day 3 (p>0.05) for all parameters. On the 7th day, CSI affected negatively (p<0.05) bone formation with respect to NMT and RA (MT: 36%, NMT: 53%, RA: 12%; and MT: 39%, NMT: 29%, RA: 32%, for the control and test groups, respectively). In contrast, no statistically significant differences (p>0.05) were found at days 10 and 14. It may be concluded that CSI may affect socket healing from the early events involved in the healing process, which may be critical for the amount and quality of new-bone formation in smokers.