Effect of methotrexate therapy on bone mineral density and body composition in rat adjuvant arthritis.
OBJECTIVE
To test whether methotrexate (MTX) therapy of rat adjuvant arthritis (AA) prevents loss of bone mineral density (BMD) and loss of adipose and lean body mass compared to pair-fed controls with untreated rat AA (positive controls) and rats without AA (negative controls).


METHODS
AA was induced by a Mycobacterium butyricum injection at the base of the tail of 5-week-old female Lewis rats. The MTX-treated group was injected with adjuvant and then treated twice weekly with MTX (1.0 mg/kg/wk intraperitoneally). To control for the effects of AA on appetite and weight, food given to control animals and MTX-treated rats with AA was limited to that consumed by rats with untreated AA. At 42 days post-adjuvant injection, the animals were sacrificed and tibial BMD was measured. Body composition was analyzed for percentage fat, protein, ash, and water.


RESULTS
There was no difference in ankle edema score or ankle width between the negative controls and MTX-treated group at necropsy. BMD was significantly higher in the negative controls versus positive controls and MTX-treated and in MTX-treated versus positive controls. There was significantly less body fat and protein and greater body water in the positive controls and MTX group compared to the negative controls.


CONCLUSIONS
MTX prevents loss of BMD in the tibia in the rat AA model compared to positive controls. While MTX is effective in lowering inflammation in rat AA, there are still significant losses in BMD and body composition, which may have implications for rheumatoid arthritis.
Morgan
Sarah L
SL
Department of Nutrition Sciences, University of Alabama at Birmingham, Birmingham, Alabama, USA. slmorgan@uab.edu
Chen
Dung-Tsa
DT
Carlee
Jodelle
J
Baggott
Joseph E
JE
D000818:Animals; D018501:Antirheumatic Agents / Q000494:pharmacology*; D001169:Arthritis, Experimental / Q000188:drug therapy* / Q000473:pathology; D001823:Body Composition / Q000187:drug effects*; D015519:Bone Density / Q000187:drug effects*; D005260:Female; D008727:Methotrexate / Q000494:pharmacology*; D051381:Rats; D011917:Rats, Inbred Lew; D013977:Tibia / Q000473:pathology
D018501:Antirheumatic Agents; D008727:Methotrexate