Intermittent administration of parathyroid hormone ameliorated alveolar bone loss in experimental periodontitis in streptozotocin-induced diabetic rats.

OBJECTIVE: Intermittent administration of parathyroid hormone (PTH) has been demonstrated to have anabolic effects on bone metabolism and is approved for use in the treatment of osteoporosis. This study evaluates the role of intermittent PTH administration on alveolar bone loss in streptozotocin (STZ)-induced diabetic rats. DESIGN: Fifty male Sprague Dawley rats were randomly divided into the following five groups: (1) a control group (saline placebo without ligature and STZ injection), (2) a PTH group (PTH administration without ligature and STZ injection), (3) an L group (saline placebo with ligature), (4) an L+STZ group (saline placebo with ligature and STZ injection), and (5) an L+STZ+PTH group (PTH administration with ligature and STZ injection). PTH was administered at 75µg/kg per dose four times a week for 28days. Subsequently, all rats were sacrificed, and their mandibles were extracted for micro-computed tomography (micro-CT) scanning, as well as histological and immunochemical evaluation. RESULTS: Micro-CT scanning demonstrated the anabolic effect of PTH on alveolar bone metabolism in STZ-induced diabetic rats (P<0.05), and histomorphometry indicated that PTH inhibited inflammation of the periodontium and increased the level of osteoblastic activity (P<0.05). Immunochemical evaluation showed that rats subjected to both ligature placement and STZ injection had the highest receptor activator of nuclear factor kappa B ligand (RANKL)/osteoprotegerin (OPG) ratio and that PTH administration decreased this ratio. CONCLUSION: Intermittent systemic PTH administration effectively reduced alveolar bone loss and ameliorated the manifestation of experimental periodontitis in STZ-induced diabetic rats.

Oral administration of 5-hydroxytryptophan aggravated periodontitis-induced alveolar bone loss in rats.

OBJECTIVE: 5-Hydroxytryptophan (5-HTP) is the precursor of serotonin and 5-HTP has been widely used as a dietary supplement to raise serotonin level. Serotonin has recently been discovered to be a novel and important player in bone metabolism. As peripheral serotonin negatively regulates bone, the regular take of 5-HTP may affect the alveolar bone metabolism and therefore influence the alveolar bone loss induced by periodontitis. The aim of this study was to investigate the effect of 5-HTP on alveolar bone destruction in periodontitis. DESIGN: Male Sprague-Dawley rats were randomly divided into the following four groups: (1) the control group (without ligature); (2) the 5-HTP group (5-HTP at 25 mg/kg/day without ligature); (3) the L group (ligature+saline placebo); and (4) the L+5-HTP group (ligature+5-HTP at 25 mg/kg/day). Serum serotonin levels were determined by ELISA. The alveolar bones were evaluated with micro-computed tomography and histology. Tartrate-resistant acid phosphatase staining was used to assess osteoclastogenesis. The receptor activator of NF-kB ligand (RANKL) and osteoprotegerin (OPG) expression in the periodontium as well as the interleukin-6 positive osteocytes were analysed immunohistochemically. RESULTS: 5-HTP significantly increased serum serotonin levels. In rats with experimental periodontitis, 5-HTP increased alveolar bone resorption and worsened the micro-structural destruction of the alveolar bone. 5-HTP also stimulated osteoclastogenesis and increased RANKL/OPG ratio and the number of IL-6 positive osteocytes. However, 5-HTP treatment alone did not cause alveolar bone loss in healthy rats. CONCLUSION: The present study showed that 5-HTP aggravated alveolar bone loss, deteriorated alveolar bone micro-structure in the presence of periodontitis, which suggests 5-HTP administration may increase the severity of periodontitis.