Vitamin B6 deficiency experimentally-induced bone and joint disorder: microscopic, radiographic and biochemical evidence

Altered gut microbe metabolites in patients with alcohol‑induced osteonecrosis of the femoral head: An integrated omics analysis

Excessive alcohol consumption is considered to be a major risk factor of alcohol-induced osteonecrosis of the femoral head (AONFH). The gut microbiota (GM) has been reported to aid in the regulation of human physiology and its composition can be altered by alcohol consumption. The aim of the present study was to improve the understanding of the GM and its metabolites in patients with AONFH. Metabolomic sequencing and 16S rDNA analysis of fecal samples were performed using liquid chromatography-mass spectrometry to characterize the GM of patients with AONFH and healthy normal controls (NCs). Metagenomic sequencing of fecal samples was performed to identify whether GM changes on the species level were associated with the expression of gut bacteria genes or their associated functions in patients with AONFH. The abundance of 58 genera was found to differ between the NC group and the AONFH group. Specifically, Klebsiella, Holdemanella, Citrobacter and Lentilactobacillus were significantly more abundant in the AONFH group compared with those in the NC group. Metagenomic sequencing demonstrated that the majority of the bacterial species that exhibited significantly different abundance in patients with AONFH belonged to the genus Pseudomonas. Fecal metabolomic analysis demonstrated that several metabolites were present at significantly different concentrations in the AONFH group compared with those in the NC group. These metabolites were products of vitamin B6 metabolism, retinol metabolism, pentose and glucuronate interconversions and glycerophospholipid metabolism. In addition, these changes in metabolite levels were observed to be associated with the altered abundance of specific bacterial species, such as Basidiobolus, Mortierella, Phanerochaete and Ceratobasidium. According to the results of the present study, a comprehensive landscape of the GM and metabolites in patients with AONFH was revealed, suggesting the existence of interplay between the gut microbiome and metabolome in AONFH pathogenesis.

Importance of micronutrients in bone health of monogastric animals and techniques to improve the bioavailability of micronutrient supplements - A review

Vitamins and minerals categorized as micronutrients are the essential components of animal feed for maintaining health and improving immunity. Micronutrients are important bioactive molecules and cofactors of enzymes as well. Besides being cofactors for enzymes, some vitamins such as the fat-soluble vitamins, vitamin A and D have been shown to exhibit hormone-like functions. Although they are required in small amount, they play an influential role in the proper functioning of a number of enzymes which are involved in many metabolic, biochemical and physiological processes that contribute to growth, production and health. Micronutrients can potentially have a positive impact on bone health, preventing bone loss and fractures, decreasing bone resorption and increasing bone formation. Thus, micronutrients must be provided to livestock in optimal concentrations and according to requirements that change during the rapid growth and development of the animal and the production cycle. The supply of nutrients to the animal body not only depends on the amount of the nutrient in a food, but also on its bioavailability. The bioavailability of these micronutrients is affected by several factors. Therefore, several technologies such as nanoparticle, encapsulation, and chelation have been developed to improve the bioavailability of micronutrients associated with bone health. The intention of this review is to provide an updated overview of the importance of micronutrients on bone health and methods applied to improve their bioavailability.

B-vitamins and bone health--a review of the current evidence

Because of ongoing global ageing, there is a rapid worldwide increase in incidence of osteoporotic fractures and the resultant morbidity and mortality associated with these fractures are expected to create a substantial economic burden. Dietary modification is one effective approach for prevention of osteoporosis in the general population. Recently, B vitamins have been investigated for their possible roles in bone health in human studies. In this review, we provide different lines of evidence and potential mechanisms of individual B vitamin in influencing bone structure, bone quality, bone mass and fracture risk from published peer-reviewed articles. These data support a possible protective role of B vitamins, particularly, B2, B6, folate and B12, in bone health. However, results from the clinical trials have not been promising in supporting the efficacy of B vitamin supplementation in fracture reduction. Future research should continue to investigate the underlying mechanistic pathways and consider interventional studies using dietary regimens with vitamin B enriched foods to avoid potential adverse effects of high-dose vitamin B supplementation. In addition, observational and interventional studies conducted in Asia are limited and thus require more attention due to a steep rise of osteoporosis and hip fracture incidence projected in this part of the world.

Fourier transform Infrared spectroscopic characterization of mineralizing type I collagen enzymatic trivalent cross-links

The most abundant protein of bone's organic matrix is collagen. One of its most important properties is its cross-linking pattern, which is responsible for the fibrillar matrices' mechanical properties such as tensile strength and viscoelasticity. We have previously described a spectroscopic method based on the resolution of the Amide I and II Fourier transform Infrared (FTIR) bands to their underlying constituent peaks, which allows the determination of divalent and pyridinoline (PYD) collagen cross-links in mineralized thin bone tissue sections with a spatial resolution of ~6.3 μm. In the present study, we used FTIR analysis of a series of biochemically characterized collagen peptides, as well as skin, dentin, and predentin, to examine the potential reasons underlying discrepancies between two different analytical methodologies specifically related to spectral processing. The results identified a novel distinct FTIR underlying peak at ~1,680 cm(-1), correlated with deoxypyridinoline (DPD) content. Furthermore, the two different methods of spectral resolution result in widely different results, while only the method employing well-established spectroscopic routines for spectral resolution provided biologically relevant results, confirming our earlier studies relating the area of the underlying 1,660 cm(-1) with PYD content. The results of the present study describe a new peak that may be used to determine DPD content, confirm our earlier report relating spectroscopic parameters to PYD content, and highlight the importance of the selected spectral resolution methodology.

Lathyrism-induced alterations in collagen cross-links influence the mechanical properties of bone material without affecting the mineral

In the present study a rat animal model of lathyrism was employed to decipher whether anatomically confined alterations in collagen cross-links are sufficient to influence the mechanical properties of whole bone. Animal experiments were performed under an ethics committee approved protocol. Sixty-four female (47 day old) rats of equivalent weights were divided into four groups (16 per group): Controls were fed a semi-synthetic diet containing 0.6% calcium and 0.6% phosphorus for 2 or 4 weeks and β-APN treated animals were fed additionally with β-aminopropionitrile (0.1% dry weight). At the end of this period the rats in the four groups were sacrificed, and L2-L6 vertebra were collected. Collagen cross-links were determined by both biochemical and spectroscopic (Fourier transform infrared imaging (FTIRI)) analyses. Mineral content and distribution (BMDD) were determined by quantitative backscattered electron imaging (qBEI), and mineral maturity/crystallinity by FTIRI techniques. Micro-CT was used to describe the architectural properties. Mechanical performance of whole bone as well as of bone matrix material was tested by vertebral compression tests and by nano-indentation, respectively. The data of the present study indicate that β-APN treatment changed whole vertebra properties compared to non-treated rats, including collagen cross-links pattern, trabecular bone volume to tissue ratio and trabecular thickness, which were all decreased (p<0.05). Further, compression tests revealed a significant negative impact of β-APN treatment on maximal force to failure and energy to failure, while stiffness was not influenced. Bone mineral density distribution (BMDD) was not altered either. At the material level, β-APN treated rats exhibited increased Pyd/Divalent cross-link ratios in areas confined to a newly formed bone. Moreover, nano-indentation experiments showed that the E-modulus and hardness were reduced only in newly formed bone areas under the influence of β-APN, despite a similar mineral content. In conclusion the results emphasize the pivotal role of collagen cross-links in the determination of bone quality and mechanical integrity. However, in this rat animal model of lathyrism, the coupled alterations of tissue structural properties make it difficult to weigh the contribution of the anatomically confined material changes to the overall mechanical performance of whole bone. Interestingly, the collagen cross-link ratio in bone forming areas had the same profile as seen in actively bone forming trabecular surfaces in human iliac crest biopsies of osteoporotic patients.

Bone tissue and hyperhomocysteinemia

Bone tissue quality is determined not only by multiple architectural variables, but also by the mechanical properties of collagen type 1. Homocysteinuria is a genetic disease whose manifestations include severe hyperhomocysteinemia and decreased bone strength. The effects of smaller homocysteine elevations on bone tissue are difficult to demonstrate in clinical studies. Studies in animals and in humans suggest that homocysteine may weaken collagen crosslinks and, if present in large amounts, interfere with bone remodeling. Whether routine homocysteine assays should be performed to detect bone frailty remains unclear. In clinical practice, the focus should be on identifying patients with potential causes of homocysteine elevation (e.g., medications), who should then be given vitamin D and folic acid supplementation if needed. This approach may improve not only bone health, but also vascular and general health.

Collagen cross-linking influences osteoblastic differentiation

Osteoblasts synthesize collagen matrix, which itself regulates the differentiation of precursor cells into mature osteoblasts. They express lysyl oxidase (LOX), which is involved in the collagen cross-linking process. Lathyrogens, like ss-aminopropionitrile (ssAPN), inhibit the formation of a stable matrix. The aim of the present study was to investigate the influence of cross-linking on osteoblastic differentiation. MC3T3-E1 cells were seeded and treated with or without 400 muM ssAPN for 1 week. Thereafter, living cells were removed and, on this extracellular matrix, new MC3T3-E1 cells were seeded and cultured for 1 week without ssAPN. RNA was isolated, and expression of specific marker genes was determined by quantitative reverse transcription-polymerase chain reaction. Changes in specific cross-links after ssAPN treatment were measured with Fourier-transform infrared spectroscopy. The collagen matrix that formed showed a significant reduction of two major cross-links of bone collagen, deH-DHLNL and pyr, compared to control cultures. Gene expression studies showed an increase of collagen alpha1 (I) (COL1A1) to 150%. Expression of LOX and osteocalcin (OCN) mRNA was significantly downregulated to about 75%. When fresh MC3T3-E1 cells were seeded on this altered matrix without ssAPN, COL1A1 mRNA expression was upregulated (140%), OCN was downregulated (60%), and LOX mRNA expression remained unaffected. These results indicate that ssAPN treatment not only disrupts collagen cross-link formation but also affects osteoblastic activity and expression. In conclusion, the disrupted matrix produced in the presence of lathyrogen influences, even in its absence, the expression of osteoblastic genes.

B vitamins, homocysteine, and bone disease: epidemiology and pathophysiology

Observational studies indicate that mildly elevated homocysteine is a strong risk factor for osteoporotic fracture, yet there is no clear biologic mechanism for an effect of homocysteine on bone. The association could instead be attributed to B vitamins (folate, vitamin B(12), vitamin B(6)), as low levels of these nutrients are the primary determinants of homocysteine and may be associated with lower bone quality. Discovery of a direct effect of homocysteine or B vitamins on bone would be important in terms of interventions, as these factors can be modified with changes in diet or supplementation. This article reviews the connections of homocysteine and B vitamins to measures of bone quality and osteoporotic fracture. Although the literature suggests that these factors may be associated with bone health, most of the epidemiologic studies are observational, limiting conclusions regarding causality. More controlled -trials are needed to determine whether treatment with B vitamins would reduce fracture rates among community-dwelling cohorts.

Bone material properties in trabecular bone from human iliac crest biopsies after 3- and 5-year treatment with risedronate

Long-term effects of risedronate on bone mineral maturity/crystallinity and collagen cross-link ratio in triple iliac crest biopsies of osteoporotic women were evaluated. In this double-blinded study, 3- and 5-year treatment with risedronate arrested the tissue aging encountered in untreated osteoporosis and in osteoporosis treated with other antiresorptives. This effect may be contributing to risedronate's antifracture efficacy.

INTRODUCTION

Risedronate is widely used in the treatment of osteoporosis. It reduces bone turnover, increases BMD, and decreases fracture risk. To date, there are no data available on the long-term effects of risedronate on bone material properties in humans.

MATERIALS AND METHODS

Osteoporotic women enrolled in the VERT-NA trial received either risedronate (5 mg/day, orally) or placebo for up to 5 years. All subjects received calcium. They also received vitamin D supplementation if deficient at baseline. Triple iliac crest biopsies were collected from a subset of these subjects at baseline, 3 years, and 5 years. Mineral maturity/crystallinity and collagen cross-link ratio was measured in these biopsies using Fourier transform infrared imaging.

RESULTS

Patients that received placebo exhibited increased mineral maturity/crystallinity and collagen cross-link ratio after 3 and 5 years compared with baseline values. On the contrary, patients that received risedronate retained baseline values in both bone material indices throughout. A more spatially detailed analysis revealed that this was achieved mainly through beneficial effects on active bone-forming areas. Surprisingly, patients that received risedronate achieved premenopausal values at bone-forming areas in both indices after 5 years of treatment.

CONCLUSION

Long-term treatment with risedronate affects bone material properties (mineral maturity/crystallinity and collagen cross-link ratio) and arrests the tissue aging apparent in untreated osteoporosis. These changes at the material level of the bone matrix may contribute to risedronate's rapid and sustained antifracture efficacy in osteoporotic patients.

B-6 vitamers and 4-pyridoxic acid in the plasma, erythrocytes, and urine of postmenopausal women

BACKGROUND

Although many studies have reported reduced vitamin B-6 status with aging, little information is available about the specific effects of menopause.

OBJECTIVE

We aimed to examine vitamin B-6 metabolism in premenopausal and early postmenopausal women.

DESIGN

We examined dietary intake and vitamin B-6 metabolites in the plasma, erythrocytes, and urine of 30 premenopausal women (x +/- SD age: 41.9 +/- 4.8 y) and 30 women (aged 54.0 +/- 3.8 y) who were 4.0 +/- 1.4 y past menopause.

RESULTS

Vitamin B-6 intake in the postmenopausal group (1.97 +/- 0.40 mg/d) was significantly greater than that in the premenopausal group (1.63 +/- 0.50 mg/d). Plasma pyridoxal phosphate (PLP) and pyridoxal concentrations and erythrocyte PLP, pyridoxal, and pyridoxamine phosphate concentrations were in the normal range in both groups and did not differ significantly between the 2 groups. Plasma and erythrocyte 4-pyridoxic acid (4-PA) concentrations were significantly higher in the postmenopausal group than in the premenopausal group, which may have been due at least partly to the slightly higher vitamin B-6 intake of the former group. Erythrocyte 4-PA was correlated (r = -0.37, P < 0.01) with serum estradiol in both groups. Urinary 4-PA did not differ significantly between the 2 groups. The serum phosphate concentration was higher in the postmenopausal group than in the premenopausal group, and it was correlated (r = 0.40, P < 0.01) with plasma PLP. Inhibition of alkaline phosphatase by the increased phosphate may help to increase plasma PLP.

CONCLUSION

Menopause may not necessarily be associated with a decrease in vitamin B-6 status.

Distribution of collagen cross-links in normal human trabecular bone

Infrared imaging analysis of normal human iliac crest biopsy specimens shows a characteristic spatial variation in the nonreducible:reducible collagen cross-links at trabecular surfaces, depending on the surfaces' metabolic status.

INTRODUCTION

Bone is a composite material consisting of mineral, collagen, non-collagenous proteins, and lipids. Bone collagen, mainly type I, provides the scaffold on which mineral is deposited and imparts specific mechanical properties, determined in part by the amount of collagen present, its orientation and fibril diameter, and the distribution of its cross-links.

MATERIALS AND METHODS

In this study, the technique of Fourier transform infrared imaging (FTIRI) was used to determine the ratio of nonreducible:reducible cross-links, in 2- to 4-microm-thick sections from human iliac crest biopsy specimens (N = 14) at trabecular surfaces as a function of surface activity (forming versus resorbing), with an approximately 6.3-mm spatial resolution. The biopsy specimens were obtained from patients devoid of any metabolic bone disease based on histomorphometric and bone densitometric parameters.

RESULTS AND CONCLUSIONS

Distributions of collagen cross-links within the first 50 mm at forming trabecular surfaces demonstrated a progressive increase in the nonreducible:reducible collagen cross-link ratio, unlike in the case of resorbing surfaces, in which the collagen cross-links ratio (as defined for the purposes of the present report) was relatively constant.

Chemical and biomechanical characterization of hyperhomocysteinemic bone disease in an animal model

BACKGROUND

Classical homocystinuria is an autosomal recessive disorder caused by cystathionine beta-synthase (CBS) deficiency and characterized by distinctive alterations of bone growth and skeletal development. Skeletal changes include a reduction in bone density, making it a potentially attractive model for the study of idiopathic osteoporosis.

METHODS

To investigate this aspect of hyperhomocysteinemia, we supplemented developing chicks (n = 8) with 0.6% dl-homocysteine (hCySH) for the first 8 weeks of life in comparison to controls (n = 10), and studied biochemical, biomechanical and morphologic effects of this nutritional intervention.

RESULTS

hCySH-fed animals grew faster and had longer tibiae at the end of the study. Plasma levels of hCySH, methionine, cystathionine, and inorganic sulfate were higher, but calcium, phosphate, and other indices of osteoblast metabolism were not different. Radiographs of the lower limbs showed generalized osteopenia and accelerated epiphyseal ossification with distinct metaphyseal and suprametaphyseal lucencies similar to those found in human homocystinurics. Although biomechanical testing of the tibiae, including maximal load to failure and bone stiffness, indicated stronger bone, strength was proportional to the increased length and cortical thickness in the hCySH-supplemented group. Bone ash weights and IR-spectroscopy of cortical bone showed no difference in mineral content, but there were higher Ca2+/PO4(3-) and lower Ca2+/CO3(2-) molar ratios than in controls. Mineral crystallization was unchanged.

CONCLUSION

In this chick model, hyperhomocysteinemia causes greater radial and longitudinal bone growth, despite normal indices of bone formation. Although there is also evidence for an abnormal matrix and altered bone composition, our finding of normal biomechanical bone strength, once corrected for altered morphometry, suggests that any increase in the risk of long bone fracture in human hyperhomocysteinemic disease is small. We also conclude that the hCySH-supplemented chick is a promising model for study of the connective tissue abnormalities associated with homocystinuria and an important alternative model to the CBS knock-out mouse.

Spectroscopic characterization of collagen cross-links in bone

Collagen is the most abundant protein of the organic matrix in mineralizing tissues. One of its most critical properties is its cross-linking pattern. The intermolecular cross-linking provides the fibrillar matrices with mechanical properties such as tensile strength and viscoelasticity. In this study, Fourier transform infrared (FTIR) spectroscopy and FTIR imaging (FTIRI) analyses were performed in a series of biochemically characterized samples including purified collagen cross-linked peptides, demineralized bovine bone collagen from animals of different ages, collagen from vitamin B6-deficient chick homogenized bone and their age- and sex-matched controls, and histologically stained thin sections from normal human iliac crest biopsy specimens. One region of the FTIR spectrum of particular interest (the amide I spectral region) was resolved into its underlying components. Of these components, the relative percent area ratio of two subbands at approximately 1660 cm(-1) and approximately 1690 cm(-1) was related to collagen cross-links that are abundant in mineralized tissues (i.e., pyridinoline [Pyr] and dehydrodihydroxylysinonorleucine [deH-DHLNL]). This study shows that it is feasible to monitor Pyr and DHLNL collagen cross-links spatial distribution in mineralized tissues. The spectroscopic parameter established in this study may be used in FTIRI analyses, thus enabling the calculation of relative Pyr/DHLNL amounts in thin (approximately 5 microm) calcified tissue sections with a spatial resolution of approximately 7 microm.

Perturbations in factors that modulate osteoblast functions in vitamin B6 deficiency

It was hypothesized that the widespread structural defect of collagen in connective tissue of vitamin B6deficient-animals and the consequent alteration in bone biomechanical properties cause an additional stress to their inflammed swollen tibiotarsometatarsal joints. The present study showed a 32% elevation (P &lt 0.02) in mean plasma free cortisol concentration. Vitamin D metabolism was impaired but without changing plasma calcium homeostasis and bone mineral content. Mean plasma calcitriol [1,25(OH)2D] concentration was significantly reduced (P < 0.001). Because plasma calcidiol concentration did not change, we speculated that either renal 25-hydroxycalciferol-1α-hydroxylase activity was reduced or 1,25(OH)2D turnover was increased. Plasma osteocalcin, an index of osteoblast function related to bone formation, was significantly decreased (P < 0.05). This adverse effect on osteoblasts was consistent with the reduction of bone specific alkaline phosphatase activity (another index of bone formation) found in a previous study. The excess of cortisol may have impaired these bone cells functions directly and (or) indirectly via the decline in calcitriol synthesis. Plasma hydroxyproline concentrations in B6-deficient animals were found to be significantly reduced (P < 0.001), suggesting that cortisol in excess had also a suppressive effect on another hydroxylase, namely tissue (mainly bone and liver) prolyl hydroxylase. The bone uncoupling (in formation and resoption) associated with vitamin B6deficiency seems to be due to secondary hypercortisolism and (or) another unknown factors but not related to a change in bone modulators such as IGF-1 and eicosanoids.Key words: collagen, vitamin B6, vitamin D, cortisol, osteocalcin, IGF-1, eicosanoids, PGE2.

Loss of decorin from the surface zone of articular cartilage in a chick model of osteoarthritis

The objective of this study was to immunolocalize decorin and to assess changes as a result of pyridoxine (PN) deficiency in chick articular cartilage from femoral condyles. After maintenance on a normal diet for the first two weeks after hatching, 15 broiler chickens were deprived of this vitamin for 6 weeks. It was previously shown that the ankle joints of PN-deficient animals are swollen with effusions. They also present an abnormal gait, enlarged bony margins, and fissuring of the articular cartilages. Milder changes (no fissures) were also shown in the knee joints. Data from a previous study were suggestive that sulfated glycosaminoglycans are lost from the knee cartilage surface into synovial fluid. The current study was focused on the small proteoglycan, decorin, which coats the surface of collagen fibrils and may regulate their morphology. To examine decorin in normal and PN-deficient articular cartilage, a monoclonal antibody to an epitope on the protein core of decorin was used for immunohistochemical staining of tissue sections and for Western Blot analysis of cartilage extracts. Reduction of staining with the antibody was demonstrated in the tangential surface zone of PN-deficient cartilage, and Western Blot analysis showed reduced intensity of decorin bands compared to normal controls. These data suggest that a lack of decorin may play a role in the enlargement of collagen bundles in the tangential zone of PN-deficient articular cartilage as observed in a previous electron microscopic study.

Pyridoxine deficiency affects biomechanical properties of chick tibial bone

The mechanical integrity of bone is dependent on the bone matrix, which is believed to account for the plastic deformation of the tissue, and the mineral, which is believed to account for the elastic deformation. The validity of this model is shown in this study based on analysis of the bones of vitamin B6-deficient and vitamin B6-replete chick bones. In this model, when B6-deficient and control animals are compared, vitamin B6 deficiency has no effect on the mineral content or composition of cortical bone as measured by ash weight (63 +/- 6 vs. 58 +/- 3); mineral to matrix ratio of the FTIR spectra (4.2 +/- 0.6 vs. 4.5 +/- 0.2), line-broadening analyses of the X-ray diffraction 002 peak (beta 002 = 0.50 +/- 0.1 vs. 0.49 +/- 0.01), or other features of the infrared spectra. In contrast, collagen was significantly more extractable from vitamin B6-deficient chick bones (20 +/- 2% of total hydroxyproline extracted vs. 10 +/- 3% p < or = 0.001). The B6-deficient bones also contained an increased amount of the reducible cross-links DHLNL, dehydro-dihydroxylysinonorleucine, (1.03 +/- 0.07 vs. 0.84 +/- 0.13 p < or = 0.001); and a nonsignificant increase in HLNL, dehydro-hydroxylysinonorleucine, (0.51 +/- 0.03 vs. 0.43 +/- 0.03, p < or = 0.10). There were no significant changes in bone length, bone diameter, or area moment of inertia. In four-point bending, no significant changes in elastic modulus, stiffness, offset yield deflection, or fracture deflection were detected. However, fracture load in the B6-deficient animals was decreased from 203 +/- 35 MPa to 151 +/- 23 MPa, p < or = 0.01, and offset yield load was decreased from 165 +/- 9 MPa to 125 +/- 14 MPa, p < or = 0.05. Since earlier histomorphometric studies had demonstrated that the B6-deficient bones were osteopenic, these data suggest that although proper cortical bone mineralization occurred, the alterations of the collagen resulted in changes to bone mechanical performance.