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

Arch Oral Biol. 2015 May;60(5):789-98. doi: 10.1016/j.archoralbio.2015.01.015. Epub 2015 Feb 21.

Abstract

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.

Keywords: 5-Hydroxytryptophan; Alveolar bone loss; Osteoclast; Osteocyte; Periodontitis; Serotonin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 5-Hydroxytryptophan / administration & dosage*
  • 5-Hydroxytryptophan / pharmacology*
  • Administration, Oral
  • Alveolar Bone Loss / chemically induced*
  • Alveolar Bone Loss / diagnostic imaging
  • Animals
  • Disease Progression
  • Enzyme-Linked Immunosorbent Assay
  • Immunoenzyme Techniques
  • Interleukin-6 / metabolism
  • Male
  • Osteoclasts / drug effects
  • Osteocytes / drug effects
  • Periodontitis / complications*
  • RANK Ligand / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptor Activator of Nuclear Factor-kappa B / metabolism
  • Serotonin / blood
  • X-Ray Microtomography

Substances

  • Interleukin-6
  • RANK Ligand
  • Receptor Activator of Nuclear Factor-kappa B
  • Serotonin
  • 5-Hydroxytryptophan