Low serum folate and vitamin B6 are associated with an altered cancellous bone structure in humans

+1Holstein, J H; 2Herrmann, M; 1Splett, C; 1Herrmann, W; 1Garcia, P; 1Histing, T; 3Siebel, T; 3Kurz, K; 1Menger, M D; 1Pohlemann, T

+1University of Saarland, Germany, 2University of Sydney, Australia, 3Knappschaftskrankenhaus Püttlingen, Germany

tim.pohlemann@uks.eu

ABSTRACT INTRODUCTION:

Osteoporosis represents a widespread disease, which affects about 75

million people in Europe, the United States, and Japan. Osteoporosis is

characterized by a decrease of bone mass and an impairment of bone

microarchitecture, resulting in a decreased bone strength and hence an

increased fracture risk. In the United States, over 2 million incident

fractures occur annually, causing costs of 16.9 billion dollars.

Recent epidemiological studies have reported an increased serum

concentration of homocysteine (hyperhomocysteinemia) to be associated

with osteoporosis and osteoporotic fractures. Folate, vitamin B6, and

vitamin B12 are important co-enzymes of the homocysteine degrading

remethylation and trans-sulfuration pathways. In accordance,

deficiencies of folate, vitamin B6, and vitamin B12 lead to

hyperhomocysteinemia. Besides, B vitamins play a crucial role in the

reduction of oxidative stress as well as in the methylation of different

proteins. In countries without folate supplementation of food, the

prevalence of folate and vitamin B12 deficiencies ranges between 20%

and 45%. So far, there is no information on whether low serum B

vitamins are linked to an alteration of human bone properties. Therefore,

this study aimed to analyze the association between B vitamin serum

concentrations and structural properties of human bone.

METHODS:

For the present study, fasting blood samples and femoral heads were

obtained from 94 males and females who underwent elective hip

arthroplasty. According to the National Institute of Health guidelines,

the study was approved by the local Ethical Committee and was

performed with informed consent of the subjects.

Fasting blood samples were used to measure serum concentrations of

folate, vitamin B6, and vitamin B12. In addition, serum concentrations

of the bone formation marker osteocalcin (OC) and the bone resorption

marker tartrate-resistant acid phosphatase (TRAP) were determined.

Bones were assessed by histomorphometry. According to the median B

vitamin serum concentrations, results of the bone and serum analyses

were grouped for individuals with high and low serum concentrations of

folate, vitamin B6, and vitamin B12 (n=47 each).

All data are given as means±standard deviation (SD). The

comparison between the experimental groups was performed by Mann-

Whitney-U-test. A P value <0.05 was considered to indicate significant

differences.

RESULTS SECTION:

The bone formation marker OC was found significantly higher in

individuals with high serum B vitamins when compared to those with

low serum B vitamins (folate: 24.0±12.6µg/L vs. 19.4±7.8 µg/L,

P=0.04; vitamin B6: 23.9±12.2 µg/L vs. 19.6±8.5 µg/L, P=0.05; and

vitamin B12: 24.2±12.4 µg/L vs. 19.1±7.8 µg/L, P=0.02). The serum

concentration of the bone resorption marker TRAP was slightly but not

significantly higher in individuals with high serum vitamin B12 (3.3±2.6

U/L vs. 2.7±0.7 U/L, P=0.12), while it did not differ between individuals

with high and low serum folate and vitamin B6.

The histomorphometric analysis demonstrated a significantly lower

trabecular thickness and percent trabecular area in individuals with low

serum folate in comparison to individuals with high serum folate (Table

1 and Figure 1). Individuals with low serum vitamin B6 showed a

significantly lower trabecular number when compared to individuals

with high serum vitamin B6 (Table 1 and Figure 1). In contrast, we

found no significant differences in the histomorphometric analysis

between subjects with high and low serum vitamin B12 (Table 1).

DISCUSSION:

To our knowledge, this study evaluated for the first time the

association between serum B vitamins and bone properties in humans.

Of interest, we found a relation between low serum folate and an

impaired cancellous bone structure. Individuals with low serum vitamin

B6 demonstrated a minor alteration of cancellous bone structure, while

there was no association between low serum vitamin B12 and

deteriorated cancellous bone structure.

The alterations of cancellous bone structure might be explained by an

impaired osteoblast activity as indicated by low serum OC in subjects

with low serum folate and vitamin B6. In spite of a vitamin B12-related

elevation of serum OC, we found no association between serum vitamin

B12 and trabecular bone architecture. These results might be explained

by a concomitant vitamin B12-related elevation of ostoclast activity as

indicated by the slightly elevated serum TRAP in subjects with high

serum vitamin B12.

In general, it might be assumed that B vitamin deficiency affects

cancellous bone structure by inducing hyperhomocysteinemia. On the

other hand, B vitamins have also direct effects on bone metabolism.

Therefore, B vitamin deficiency might be related to altered bone

properties also independently of the homocysteine status.

In conclusion, this study provides to our knowledge the first evidence

that low serum folate and vitamin B6 are related to an altered cancellous

bone structure in humans.

Table 1

Tb.Th [mm] Tb.N [mm-1] Tb.Sp [mm] Tb.Ar [%]

________________________________________________________

Folate+ 0.35±0.14 0.36±0.15 2.4±0.8 14.2±8.0

Folate- 0.29±0.11 0.31±0.12 2.7±0.7 10.3±5.7

P 0.02 0.12 0.13 0.02

________________________________________________________

B6+ 0.34±0.13 0.37±0.13 2.4±0.8 13.8±7.6

B6- 0.30±0.13 0.30±0.13 2.7±0.8 10.9±6.7

P 0.15 0.03 0.12 0.07

________________________________________________________

B12+ 0.33±0.13 0.33±0.13 2.6±0.8 12.8±7.7

B12- 0.30±0.13 0.35±0.14 2.5±0.7 11.7±6.6

P 0.75 0.49 0.56 0.67

Histomorphometric analysis of trabecular thickness (Tb.Th), trabecular

number (Tb.N), trabecular separation (Tb.Sp), and percent trabecular

area (Tb.Ar) of individuals with high (+) and low (-) serum B vitamins.

Data are given as means±SD. Groups include n=47 each.

Figure 1. H&E stained histological sections of cancellous bone samples.

Figures A and C show bone samples of individuals with high serum

concentrations of folate (A) and vitamin B6 (C). Figures B and D

represent bone samples of individuals with low serum concentrations of

folate (B) and vitamin B6 (D). Scale bar represents 250 µm.

Poster No. 599 • 56th Annual Meeting of the Orthopaedic Research Society