Vitamin D fortification of milk products does not resolve hypovitaminosis D in young Finnish men.

OBJECTIVE: To study if vitamin D fortification of milk products started in February 2003 has improved vitamin D status of young Finnish men, which has been poor before. DESIGN: A longitudinal study of one cohort. SETTING: Helsinki University Central Hospital. SUBJECTS: Sixty-five healthy men, studied for the first time in January 2001, were re-examined in January 2004. They were aged 18-21 years in 2001. METHODS: Blood was sampled for determination of serum 25-hydroxyvitamin D (25-OHD) and intact parathyroid hormone (iPTH). 25-OHD was measured by both radioimmunoassay (RIA) and high-pressure liquid chromatography (HPLC). Consumption of milk, sour milk and fish and use of vitamin D supplements were assessed using a questionnaire. RESULTS: In January 2004, vitamin D fortification had raised serum 25-OHD level, with the mean of individual percent changes being 20.4% measured with RIA (P=0.0015). The correlation between the RIA and HPLC methods was high (r=0.85). Nineteen men (29.2%) had vitamin D deficiency (25-OHD

Quantitative ultrasound variables of the heel in Finnish men aged 18-20 yr: predictors, relationship to bone mineral content, and changes during military service.

INTRODUCTION: Determinants of BUA and SOS and their changes during military service-associated physical training were studied in 196 army recruits and 50 control men, aged 18-20 years. METHODS: Heel ultrasound measurement, DXA, muscle strength test, Cooper's running test and genetic analyses were performed. Lifestyle factors were recorded. Sex steroids and bone turnover markers were determined. Heel ultrasound was repeated after six months. RESULTS: Exercise was the most significant determinant of both BUA (p<0.0001) and SOS (p<0.0001). There were 10% and 1.3% differences in BUA (p=0.006) and SOS (p=0.0001), respectively, between men belonging to the lowest and highest quartiles of exercise index. Weight associated with BUA (p=0.005) and height with SOS (p=0.03). BUA and SOS correlated with BMC and BMD (p<0.0001) but explained only up to 21% of their variance. Over six months SOS increased more in recruits than in control men (p=0.0043), the increase being higher, the lower muscle strength at baseline (r =-0.27, p=0.0028). CONCLUSION: Exercise is the most important determinant of ultrasonographic variables in men, aged 18-20 years. Physical loading during military training increases SOS.

Molecular basis for action of bioactive glasses as bone graft substitute.

Bone grafting procedures are undergoing a major shift from autologous and allogeneic bone grafts to synthetic bone graft substitutes. Bioactive glasses are a group of synthetic silica-based bioactive materials with bone bonding properties first discovered by Larry Hench. They have several unique properties compared with other synthetic bioresorbable bioactive ceramics, such as calcium phosphates, hydroxyapatite (HA) and tricalcium phosphate (TCP). Bioactive glasses have different rates of bioactivity and resorption rates depending on their chemical compositions. The critical feature for the rate of bioactivity is a SiO2 content < 60% in weight. In vivo, the material is highly osteoconductive and it seems to promote the growth of new bone on its surface. In a recent study, the activity of the material was found even to overshadow the effect of BMP-2 gene therapy. In vivo, there is a dynamic balance between intramedullary bone formation and bioactive glass resorption. Recent studies of molecular biology have shown that bioactive glass induces a high local turnover of bone formation and resorption. Many osteoporotic fracture patients are candidates for concurrent treatment with bisphosphonates and bioceramic bone graft substitutes. Since osteopromotive silica-based bioactive glasses induce accelerated local bone turnover, adjunct antiresorptive agents may affect the process. However, a recent study showed that an adjunct antiresorptive therapy (zoledronic acid) is even beneficial for bone incorporation of bioactive glass. Based on these observations, bioactive glasses are a promising group of unique biomaterials to act as bone graft substitutes.

Combined effect of BMP-2 gene transfer and bioactive glass microspheres on enhancement of new bone formation.

Adenovirus-mediated recombinant human BMP-2 (RAdBMP-2) gene transfer has been found to have significant osteoinductive properties. The hypothesis of the current study was that bioactive glass surface could provide favorable osteoconductive conditions for cellular action of osteoinductive RAdBMP-2 gene transfer. In the rat proximal tibia, a portion of the medullary cavity was evacuated and filled with bioactive glass microspheres and injected with adenovirus carrying the human BMP-2 gene (BG/RAdBMP-2). Control defects filled with BG microspheres were injected with adenovirus carrying the LacZ reporter gene (BG/RAdLacZ) or saline (BG). Empty control defects were also used. Bone healing response was analyzed at 4 days, and at 2 and 8 weeks by radiography, peripheral quantitative computed tomography (pQCT), histomorphometry, and backscattered electron imaging of scanning electron microscopy (BEI-SEM) equipped with energy dispersive X-ray analysis (EDXA). In empty controls, the amount of intramedullary new bone peaked at 2 weeks, whereas defects filled with bioactive glass with and without RAdBMP-2 gene transfer showed a constant time-related increase of intramedullary new bone. At 8 weeks, there was significantly more new bone in defects treated with BG and RAdBMP-2 than in defects left to heal without filling (p < 0.001). Compared with the other controls (BG only or BG/RAdLacZ), the difference was not significant. In the current model, the osteopromotive effect of bioactive glass microspheres appears synergistic with the osteoinductive action of BMP-2 gene transfer, or one overshadows the other, as no additive effect was observed.

Molecularly defined lactose malabsorption, peak bone mass and bone turnover rate in young finnish men.

Lactose malabsorption (LM; adult-type hypolactasia), an autosomal recessive condition, results from the down-regulation of the activity of lactase enzyme in the intestinal wall. In previous studies the effect of LM on bone mass, bone turnover rate, development of osteoporosis and osteoporotic fractures has remained controversial. We have recently identified a single nucleotide polymorphism (SNP), a C to T change residing 13910 base pairs upstream of the lactase (LCT) gene at chromosome 2q21-22, which shows complete association with lactase persistence, with the C/C-13910 genotype defining LM and the genotypes C/T-13910 and T/T-13910 lactase persistence. The present study was undertaken to examine the relationship of the C/T-13910 polymorphism to peak bone mass, bone turnover rate, and stress fractures among young Finnish men. The study population comprised 234 young men, aged 18.3 to 20.6 years, 184 men were recruits of the Finnish Army, and 50 were men of similar age who had postponed their military service for reasons not related to health. Bone mineral content (BMC), density (BMD), and scan area were measured in the lumbar spine and upper femur by dual-energy X-ray absorptiometry (DXA). Blood was sampled for genotyping of the C/T-13910 polymorphism and determination of serum 25-hydroxyvitamin D (25OHD), intact parathyroid hormone (iPTH), type I procollagen aminoterminal propeptide (PINP), and tartrate-resistant acid phosphatase 5b (TRACP5b). Second-void urine samples were collected for the determination of type I collagen aminoterminal telopeptide (NTX). The prevalence of the C/C-13910-genotype of these young adults did not differ significantly from the corresponding population prevalence of C/C-13910 (17.1% vs 18.1%) among Finnish blood donors. Fifteen recruits of the army experienced a stress fracture; 3 of them (20%) had the C/C-13910-genotype. Calcium intake was similar for the three genotypes as were the unadjusted BMCs, scan areas, and BMDs at different measurement sites. The adjustments for age, height, weight, smoking, alcohol consumption, and physical exercise in the multiple regression analysis did not reveal any significant relationships between the lactase genotypes and BMDs at lumbar (P = 0.16), femoral neck (P = 0.99) or total hip (P = 0.96) sites. Serum 25OHD, iPTH, and bone marker levels were similar for the C/C-13910 C/T-13910 and T/T-13910 genotypes. In summary, in young Finnish men, molecularly defined lactose malabsorption does not alter bone turnover rate and impair the acquisition of peak bone mass. Moreover, the C/C-13910 genotype does not seem to be a risk factor for stress fractures in army recruits.

Molecular biologic comparison of new bone formation and resorption on microrough and smooth bioactive glass microspheres.

In a recent in vitro study, chemical microroughening of a bioactive glass surface was shown to enhance attachment of MG-63 osteoblastic cells to glass. The current study was designed to delineate the effects of microroughening on the gene expression patterns of bone markers during osteogenesis and new bone remodeling on bioactive glass surface in vivo. With the use of a rat model of paired comparison, a portion of the medullary canal in the proximal tibia was evacuated through cortical windows and filled with microroughened or smooth bioactive glass microspheres. The primary bone-healing response and subsequent remodeling were analyzed at 1, 2, and 8 weeks, respectively, by radiography, pQCT, histomorphometry, BEI-SEM, and molecular biologic analyses. The expression of various genes for bone matrix components (type I collagen, osteocalcin, osteopontin, osteonectin) and proteolytic enzymes (cathepsin K, MMP-9) were determined by Northern analysis of the respective mRNAs. Paired comparison showed significant differences in the mRNAs levels for specific bone matrix components at 2 weeks: osteopontin was significantly higher (p =.01) and osteonectin significantly lower (p =.05) in bones filled with microroughened microspheres than in those filled with smooth microspheres. Bones filled with microrough microspheres also showed significantly increased ratios of cathepsin K and MMP-9 (both markers of osteoclastic resorption) to type I collagen (p =.02 and p =.02, respectively) at 2 weeks and a significantly increased expression of MMP-9 at 8 weeks (p =.05). The pQCT, histomorphometric, and BEI-SEM analyses revealed no significant differences in the pattern of bone-healing response. Based on these results, microroughening of a bioactive glass surface could trigger temporal changes in the expression of specific genes especially by promoting the resorption part of new bone-remodeling processes. Future studies are needed to evaluate if the observed changes of gene expression are directly related to the microrough surface of any biomaterial or are biomaterial specific.