Deficiencies of folate and vitamin B12 do not affect fracture healing in mice
Introduction
In the Western civilization hyperhomocysteinemia (HHCY) represents a widespread metabolic disorder leading to cardiovascular disease and osteoporosis [1], [2]. Homocysteine (HCY) is a metabolite of the essential amino acid methionine [3]. Folate, vitamin B6, and vitamin B12 are essential co-enzymes of the HCY degrading remethylation and trans sulfuratin pathways [3]. In accordance, deficiencies of B vitamins are among the main causes of elevated HCY serum concentrations [4], [5]. In countries without folate supplementation of food, the prevalence of B vitamin deficiencies ranges between 20% and 45% [6], [7], [8].
Several clinical studies as well as some recent animal studies have indicated HHCY and B vitamin deficiency to be associated with an impaired bone quality [9], [10], [11], [12], [13], [14], [15]. Of interest, an additional animal study in mice has recently demonstrated that HHCY adversely affects also fracture healing [16]. In this study, HHCY was induced by a HCY-supplemented diet. Using a closed femur fracture model bone repair was analyzed at 4 weeks. Biomechanical testing of the healing bones revealed a significantly lower callus stiffness, while histomorphometric analyses showed a slightly smaller callus diameter in hyperhomocysteinemic animals when compared to normohomocysteinemic controls.
The induction of HHCY by a HCY-supplemented diet represents a relatively artificial model of HHCY, as B vitamin deficiency rather than an alimentary HCY overload is the most common cause of HHCY in humans. In accordance, the herein introduced study was conducted to investigate on whether also a folate- and vitamin B12-deficient diet might affect bone repair in mice.
Section snippets
Experimental design
For the present study we used two groups of adult CD-1 mice. The first group (n = 14) was fed a folate- and vitamin B12-deficient diet (TD 06250, Harlan), while the second group (n = 13) received the accordant equicaloric (3600 kcal/kg) standard diet (TD 06422, Harlan) for control. Based on data of pre-experiments the application of the folate- and vitamin B12-deficient diet was started 5 weeks prior to fracture, ensuring that animals were deficient in folate and vitamin B12 during the overall
Body weights
The body weights of the animals were recorded at 5 weeks before fracture as well a as at the day of fracture and the day of sacrifice. The body weights increased during the 5 weeks time period before fracture and remained constant during the following time period between fracture and sacrifice. At the different time points the body weights revealed no significant differences between folate- and vitamin B12-deficient animals and controls (Table 1).
Serum analysis
Animals, which were fed the folate- and vitamin
Discussion
The results of the herein introduced study demonstrate that an alimentary deficiency of folate and vitamin B12 is capable of inducing a moderate HHCY in mice. These nutritional and metabolic alterations do, however, not affect bone repair.
In the present study B vitamin deficiency was induced by a folate- and vitamin B12-deficient diet, which has been fed over a time period of 9 weeks. Pre-experiments in mice have confirmed that this diet leads to significantly decreased serum concentrations of
Acknowledgments
This work was supported by the research program of the Medical Faculty of the University of Saarland (1000/T201000138 HOMFOR 06/84).
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M. Herrmann and J. Schmalenbach contributed equally to this paper.