Enhanced bone metabolism in vegetarians--the role of vitamin B12 deficiency.

BACKGROUND: Vitamin B12 deficiency and bone fractures are common in vegetarians. However, a direct relationship between vitamin B12 status and bone metabolism in vegetarians has not been tested sufficiently. METHODS: Our study included 96 vegetarians (23 German vegans, and 54 German and 19 Indian lacto-, lacto-ovo-vegetarians) and 89 omnivores (Germans and Asian-Indian immigrants in Oman). Blood concentrations of total vitamin B12, holotranscobalamin (holoTC), 25OH-vitamin D (25(OH)D), total homocysteine (tHcy), methylmalonic acid (MMA), and the bone turnover markers (BTMs) bone alkaline phosphatase (BAP), osteocalcin (OC), pro-collagen type I N-terminal peptide (PINP) and C-terminal telopeptides of collagen I (CTx) were measured. RESULTS: Vegetarians from both population groups exhibited significantly higher concentrations of tHcy, MMA, folate, and BAP, but lower concentrations of holoTC and cobalamin compared with omnivores from the same population. Additionally, German vegetarians had higher circulating activities of BAP as well as higher CTx, OC, and PINP compared with their omnivorous controls. HoloTC and MMA were correlated with OC, CTx and BAP. Subjects with low vitamin B12 status (holoTC < or =35 pmol/L and MMA >271 nmol/L) had significantly lower serum concentrations of 25(OH)D, but higher tHcy and the BTMs P1NP, BAP, OC, and CTx, compared with subjects with normal vitamin B12 status. Multiple regression analysis showed that the association between BTMs and markers of vitamin B12 status was independent from the association with 25(OH)D. Approximately 12%-14% of the variation in the concentration of BTMs was explained by a regression model including holoTC, MMA and 25(OH)D. The strictness of the diet was not related to the magnitude of change in BTMs. CONCLUSIONS: Low vitamin B12 status is related to increased bone turnover in vegetarians which is independent from vitamin D status.

The effect of endurance exercise-induced lactacidosis on biochemical markers of bone turnover.

BACKGROUND: Stress fractures are frequent injuries among athletes. In vitro, decreases in pH stimulate osteoclasts and inhibit osteoblasts. We hypothesized that exercise-induced lactacidosis stimulates osteoclasts and reduces osteoblast activity in vivo. METHODS: A total of 32 volunteers (MA, male athletes; MCo, male controls; female athletes; and female controls) performed three 60-min cycle ergometer tests at 75%, 95% and 110% of their individual anaerobic threshold (IAT). Blood was taken before and at 3 and 24 h after exercise. Osteocalcin (OC), pro-collagen type I N-terminal peptide (PINP), C-terminal telopeptides of collagen I (CTx) and tartrate-resistant acid phosphatase (TRAP) were measured. RESULTS: At 75% and 95% IAT, pH did not change. At 110% IAT, pH decreased in MA by 0.08 units (p=0.041) and in MCo by 0.03 units (p=0.017). The pH results were substantiated by circulating lactate concentrations. The bone resorption markers TRAP and CTx were not consistently modified by any of the exercise tests. Exercise at 75% decreased OC and PINP in all groups. Exercise at 95% and 110% did not induce homogeneous effects. CONCLUSIONS: Anaerobic exercise does not systemically affect bone turnover, suggesting that exercise-induced acidosis is not involved in the pathogenesis of stress fractures.

Relation between homocysteine and biochemical bone turnover markers and bone mineral density in peri- and post-menopausal women.

BACKGROUND: Recently, increased plasma homocysteine (Hcy) has been suggested as an independent risk factor for osteoporotic fractures. Therefore, it is tempting to speculate that Hcy adversely affects bone metabolism. This study aimed to analyze the relation between Hcy and biochemical markers of bone metabolism and bone mineral density (BMD). MATERIALS AND METHODS: We investigated 143 peri- and post-menopausal women [median age (25th-75th percentile), 67 (57-75) years]. All subjects underwent a detailed medical examination, measurement of bone mineral density at lumbar spine (BMD-LS) and total hip (BMD-HIP), and fasting venous blood and urine sampling. Osteocalcin (OC), serum calcium (Ca), urinary desoxypyridinoline cross-links (DPD), osteoprotegerin (OPG) and soluble receptor activator of NF-kappaB ligand (sRANKL) were studied. RESULTS: According to BMD subjects were classified as normal (n=24), osteopenic (n=51) or osteoporotic (n=68). Median Hcy did not differ between normal, osteopenic and osteoporotic subjects (p=0.647). Partial correlation analysis, controlling for the major confounders, age, creatinine, menopause and previous fractures, revealed significant correlations between Hcy and DPD (r=0.193, p=0.022), as well as between Hcy and Ca (r=0.170, p=0.045). After adjustment for the same confounders, subsequent regression analysis confirmed significant associations of Hcy with DPD and Ca. No significant relations could be observed between Hcy and BMD-LS, BMD-HIP, OC, OPG or sRANKL. CONCLUSION: Our results demonstrate weak, but significant, relations between Hcy and markers of organic and inorganic bone resorption, suggesting a mechanistic role of Hcy in bone metabolism. The relation between Hcy and bone resorption was not dependent on OPG or sRANKL.

The measurement of complexed prostate-specific antigen has a better performance than total prostate-specific antigen.

The aim of this study was to compare the diagnostic utility of complexed prostate-specific antigen (cPSA) with total PSA (tPSA) in screening for prostate cancer. Serum concentrations of tPSA and cPSA were measured in 4479 adult men during the prostate cancer screening program in the Saarland region (Germany). The percentage of men with c/tPSA ratio above the cut-off value of 0.75 increased with increasing tPSA intervals: tPSA 0-0.9 microg/l, 4.4%; 1.0-1.9 microg/l, 24.3%; 2.0-2.9 microg/l, 43.9%; 3.0-3.9 microg/l, 50.4%; and 4.0-20 microg/l, 60.2%. The commonly accepted tPSA cut-off value of 3.9 microg/l matched to the 93rd percentile of the overall population (corresponding cPSA value, 2.9 microg/l). A total of 202 men out of 313 with increased cPSA had increased c/tPSA ratio (cut-off > or = 0.75) vs. 186 out of 312 men with increased tPSA. Thus, an additional 16 men at high risk for prostate cancer were selected only if cPSA was utilised as a first line parameter. Our data show that, compared to tPSA, cPSA measurement will always detect more high-risk patients, independent of the cut-off levels utilised for cPSA, tPSA and c/tPSA ratio. cPSA is more effective than tPSA in selecting subjects with an elevated c/tPSA ratio who are at high risk of prostate cancer. Thus, cPSA might be seen as the superior first-line parameter in screening for prostate cancer. Using lower cut-off values for tPSA or cPSA than the commonly accepted values seems reasonable for screening purposes.

Long-distance mountain biking does not disturb the measurement of total, free or complexed prostate-specific antigen in healthy men.

PURPOSE: Mechanical manipulation of the prostate is a generally accepted interfering factor for the measurement of prostate-specific antigen (PSA). However, only few studies have focused on common daily mechanical manipulations, such as bicycle riding. Furthermore, physical exercise is also supposed to modulate PSA serum concentration. Long-distance mountain biking is an excellent model to study the combined effect of mechanical prostate manipulation by bicycle riding and strenuous endurance exercise on total, free and complexed PSA (tPSA, fPSA, cPSA). MATERIALS AND METHODS: We investigated tPSA, fPSA and cPSA in 42 healthy male cyclists (mean age 35+/-6 years) before and after a 120 km off-road mountain bike race. Blood sampling was done before, 15 min and 3 h after the race. RESULTS: Mean race time was 342+/-65 min. All athletes had normal serum levels of tPSA, fPSA or cPSA. None of these parameters was modified by the race. CONCLUSIONS: In healthy men the measurement of tPSA, fPSA and cPSA is not disturbed by preceding long distance mountain biking or endurance exercise. Based on the present data, there is no evidence for a recommendation to limit bicycle riding or physical activity before the measurement of tPSA, fPSA or cPSA.