NAC Prevents Bone Loss in Diabetic Rats

Abstract

N-acetylcysteine decreases alveolar bone loss on experimental periodontitis in streptozotocin-induced diabetic rats.

The purpose of this study was to evaluate the morphometric and histopathological changes associated with experimental periodontitis in diabetic rats in response to systemic administration of N-acetylcysteine (NAC), a sulfhydryl-containing thiol antioxidant.
Sixty Wistar rats were divided into six experimental groups: nonligated (NL) group; ligature-only (L) group; streptozotocin-only (STZ) group; STZ and ligature (STZ + L) group; and systemic administration of NAC and ligature (70 and 100 mg/kg body weight per day, respectively) (NAC70 and NAC100 groups). Diabetes mellitus was induced by 60 mg/kg of streptozotocin. Silk ligatures were placed at the gingival margin of the lower first molars of the mandibular quadrant. The study duration was 30 d and the animals were killed at the end of this period. Changes in alveolar bone levels were clinically measured and tissues were histopathologically examined to assess the differences among the study groups.
At the end of the 30-d study period, alveolar bone loss was significantly higher in the STZ + L group compared with the other groups (p < 0.05). Also, alveolar bone loss in all the NAC groups was significantly lower than in the STZ + L and L groups (p < 0.05). The osteoblastic activity in the NAC100 group was significantly higher than in the other groups (p < 0.05).
Within the limits of this study, it can be suggested that NAC, when administered systemically, prevents alveolar bone loss in the diabetic rat model.

Toker H, Ozdemir H, Balcı H, Ozer H
J. Periodont. Res. Dec 2012
PMID: 22712627

Folate + B12 Offer No Sensomotor Speed Benefit Despite Decreasing Homocysteine

Abstract

The association of betaine, homocysteine and related metabolites with cognitive function in Dutch elderly people.

The importance of the one-carbon metabolites, choline and homocysteine, to brain function is well known. However, the associations between the one-carbon metabolites choline, betaine, methionine and dimethylglycine with cognition in elderly are unclear. We therefore examined the associations of these metabolites with cognition in a double-blind, placebo-controlled trial. Individuals (n 195) were randomized to receive daily oral capsules with either 1000 microg cobalamin (vitamin B12), or 1000 microg cobalamin plus 400 microg folic acid, or placebo for 24 weeks. Concentrations of homocysteine, methionine, choline, betaine and dimethylglycine were assessed before and after 12 and 24 weeks of treatment. Cognitive function, including domains of attention, construction, sensomotor speed, memory and executive function, was assessed before and after 24 weeks of treatment. At baseline, elevated plasma homocysteine was associated with lower performance of attention, construction, sensomotor speed and executive function. In addition, betaine was positively associated with better performance of construction, sensomotor speed and executive function, whereas elevated concentrations of methionine were positively associated with sensomotor speed. Daily combined supplementation with cobalamin plus folic acid decreased total homocysteine concentrations by 36%, and increased betaine concentrations by 38%. Participants with the largest increases in betaine concentrations showed a borderline significant (P = 0.07) higher memory performance compared to those without it. Although this trial observed associations of homocysteine and betaine with cognitive domains prior to supplementation, decreased concentrations of homocysteine were not related to improved cognitive performance. There was a tendency of participants with the largest increases in betaine concentrations to show the greatest improvement in memory function.

Eussen SJ, Ueland PM, Clarke R, Blom HJ…
Br. J. Nutr. Nov 2007
PMID: 17537289

Folate, but Not Vitamin B2 or B12, Associated with Increased Done Density in Postmenopausal Women

Abstract

Dietary intake of folate, but not vitamin B2 or B12, is associated with increased bone mineral density 5 years after the menopause: results from a 10-year follow-up study in early postmenopausal women.

Folate, vitamin B2 (riboflavin), and vitamin B12 may affect bone directly or through an effect on plasma homocysteine levels. Previously, a positive association has been found between plasma levels and bone mineral density (BMD) as well as risk of fracture. However, there are limited data on whether dietary intakes affect bone. Our aim was to investigate whether intake of folate, vitamin B2) and vitamin B12, as assessed by food records affects BMD and fracture risk. In a population-based cohort including 1,869 perimenopausal women from the Danish Osteoporosis Prevention Study, associations between intakes and BMD were assessed at baseline and after 5 years of follow-up. Moreover, associations between intakes and 5- and 10-year changes in BMD as well as risk of fracture were studied. Intakes of folate, vitamin B2, and vitamin B12 were 417 (range 290-494) microg/day, 2.70 (range 1.70-3.16) mg/day, and 4.98 (range 3.83-6.62) microg/day, respectively, i.e., slightly above the intakes recommended by the United Nations Food and Agriculture Organization. At year 5, but not at baseline, cross-sectional analyses showed positive correlations between daily intake from diet and from diet plus supplements of folate and BMD at the femoral neck (P < 0.01). However, no associations were found between intakes and changes in BMD. During 10 years of follow-up, 360 subjects sustained a fracture. Compared with 1,440 controls, logistic regression analyses revealed no difference in intakes between cases and controls. A high dietary intake of folate, but not vitamin B2 or B12, exerts positive effects on BMD; but further studies are needed to confirm this association.

Rejnmark L, Vestergaard P, Hermann AP, Brot C…
Calcif. Tissue Int. Jan 2008
PMID: 18175033

Homocysteine Correlates with Dizziness and Poor Posture

Abstract

Biological determinants of postural disorders in elderly women.

Postural control impairments and dizziness, which are major health problems with high secondary morbidity and mortality, increase with aging. Elevated homocysteine (Hcy) level is an age-related metabolic disorder, known to be involved in cardiovascular, neurological, and multisensory dysfunctions. Elevated Hcy level might be involved in sensory balance control systems impairment and dizziness occurrence. Dizziness, fitness Instrumental Activity of Daily Living scale (fitness IADL), systolic arterial pressure with ankle-brachial blood pressure index and homocysteinemia were studied in 61 noninstitutionized elderly women. Clinical balance tests (timed “Up and Go”, 10-m walking and one-leg balance) and posturography (including sensory conflicting situations [SCS] and cognitive conflicting situations [CCS]) were performed. Clinical balance control was lower in dizzy women who presented particularly poor stability in SCS. Dizziness was related to low fitness IADL scores (odds ratio [OR] 0.452, 95% CI 0.216-0.946) and to elevated Hcy (OR 8.084, 95% CI 1.992-32.810). Elevated Hcy was correlated with balance disorders both in SCS and CCS. Dizziness is associated with a reduced ability in balance control management. Hcy is related both to dizziness and low postural performance. This relation between elevated Hcy levels and balance impairments, resulting in dizziness, may be explained by its angiotoxicity and neurotoxicity.

Lion A, Spada RS, Bosser G, Gauchard GC…
Int. J. Neurosci. Jan 2013
PMID: 22909193

Vitamins D + B Improve Bone Markers in Elderly

Abstract

One year B and D vitamins supplementation improves metabolic bone markers.

Vitamin D and vitamin B deficiency are common in elderly subjects and are important risk factors for osteoporosis and age-related diseases. Supplementation with these vitamins is a promising preventative strategy. The objective of this study was to evaluate the effects of vitamins D3 and B supplementation on bone turnover and metabolism in elderly people.
Healthy subjects (n=93; >54 years) were randomly assigned to receive either daily vitamin D3 (1200 IU), folic acid (0.5 mg), vitamin B12 (0.5 mg), vitamin B6 (50 mg), and calcium carbonate (456 mg) (group A) or only vitamin D3 plus calcium carbonate (group B) in a double blind trial. We measured at baseline and after 6 and 12 months of supplementation vitamins, metabolites, and bone turnover markers.
At baseline mean plasma 25-hydroxy vitamin D [25(OH)D] was low (40 or 30 nmol/L) and parathormone was high (63.7 or 77.9 pg/mL). 25(OH)D and parathormone correlated inversely. S-Adenosyl homocysteine and S-adenosyl methionine correlated with bone alkaline phosphatase, sclerostin, and parathormone. One year vitamin D3 or D3 and B supplementation increased plasma 25(OH)D by median 87.6% (group A) and 133.3% (group B). Parathormone was lowered by median 28.3% (A) and 41.2% (B), bone alkaline phosphatase decreased by 2.8% (A) and 16.2% (B), osteocalin by 37.5% (A) and 49.4% (B), and tartrate-resistant-acid-phosphatase 5b by 6.1% (A) and 36.0% (B). Median total homocysteine (tHcy) was high at baseline (group A: 12.6, group B: 12.3 µmol/L) and decreased by B vitamins (group A) to 8.9 µmol/L (29.4%). tHcy lowering had no additional effect on bone turnover.
One year vitamin D3 supplementation with or without B vitamins decreased the bone turnover significantly. Vitamin D3 lowered parathormone. The additional application of B vitamins did not further improve bone turnover. The marked tHcy lowering by B vitamins may modulate the osteoporotic risk.

Herrmann W, Kirsch SH, Kruse V, Eckert R…
Clin. Chem. Lab. Med. Mar 2013
PMID: 23183751

Review: Homocysteine in Bone Remodeling

Abstract

The role of homocysteine in bone remodeling.

Bone remodeling is a very complex process. Homocysteine (Hcy) is known to modulate this process via several known mechanisms such as increase in osteoclast activity, decrease in osteoblast activity and direct action of Hcy on bone matrix. Evidence from previous studies further support a detrimental effect on bone via decrease in bone blood flow and an increase in matrix metalloproteinases (MMPs) that degrade extracellular bone matrix. Hcy binds directly to extracellular matrix and reduces bone strength. There are several bone markers that can be used as parameters to determine how high levels of plasma Hcy (hyperhomocysteinemia, HHcy) affect bone such as: hydroxyproline, N-terminal collagen 1 telopeptides. Mitochondrion serves an important role in generating reactive oxygen species (ROS). Mitochondrial abnormalities have been identified during HHcy. The mechanism of Hcy-induced bone remodeling via the mitochondrial pathway is largely unknown. Therefore, we propose a mitochondrial mechanism by which Hcy can contribute to alter bone properties. This may occur both through generations of ROS that activate MMPs and could be extruded into matrix to degrade bone matrix. However, there are contrasting reports on whether Hcy affects bone density, with some reports in favour and others not. Earlier studies also found an alteration in bone biomechanical properties with deficiencies of vitamin B12, folate and HHcy conditions. Moreover, existing data opens speculation that folate and vitamin therapy act not only via Hcy-dependent pathways but also via Hcy-independent pathways. However, more studies are needed to clarify the mechanistic role of Hcy during bone diseases.

Vacek TP, Kalani A, Voor MJ, Tyagi SC…
Clin. Chem. Lab. Med. Mar 2013
PMID: 23449525

Homocysteine Decreases Bone Quality and is Antagonized by NAC

Abstract

Homocysteine alters the osteoprotegerin/RANKL system in the osteoblast to promote bone loss: pivotal role of the redox regulator forkhead O1.

In this study we determined the molecular mechanisms of how homocysteine differentially affects receptor activator of nuclear factor-κB ligand (RANKL) and osteoprotegerin (OPG) synthesis in the bone. The results showed that oxidative stress induced by homocysteine deranges insulin-sensitive FOXO1 and MAP kinase signaling cascades to decrease OPG and increase RANKL synthesis in osteoblast cultures. We observed that downregulation of insulin/FOXO1 and p38 MAP kinase signaling mechanisms due to phosphorylation of protein phosphatase 2A (PP2A) was the key event that inhibited OPG synthesis in homocysteine-treated osteoblast cultures. siRNA knockdown experiments confirmed that FOXO1 is integral to OPG and p38 synthesis. Conversely homocysteine increased RANKL synthesis in osteoblasts through c-Jun/JNK MAP kinase signaling mechanisms independent of FOXO1. In the rat bone milieu, high-methionine diet-induced hyperhomocysteinemia lowered FOXO1 and OPG expression and increased synthesis of proresorptive and inflammatory cytokines such as RANKL, M-CSF, IL-1α, IL-1β, G-CSF, GM-CSF, MIP-1α, IFN-γ, IL-17, and TNF-α. Such pathophysiological conditions were exacerbated by ovariectomy. Lowering the serum homocysteine level by a simultaneous supplementation with N-acetylcysteine improved OPG and FOXO1 expression and partially antagonized RANKL and proresorptive cytokine synthesis in the bone milieu. These results emphasize that hyperhomocysteinemia alters the redox regulatory mechanism in the osteoblast by activating PP2A and deranging FOXO1 and MAPK signaling cascades, eventually shifting the OPG:RANKL ratio toward increased osteoclast activity and decreased bone quality.

Vijayan V, Khandelwal M, Manglani K, Singh RR…
Free Radic. Biol. Med. Mar 2013
PMID: 23500899

Folic Acid and B12 Lowers Homocysteine but not Bone Turnover

Abstract

Folic acid and vitamin B(12) supplementation lowers plasma homocysteine but has no effect on serum bone turnover markers in elderly women: a randomized, double-blind, placebo-controlled trial.

An elevated homocysteine level is a newly recognized risk factor for osteoporosis. Older individuals may have elevated homocysteine levels due to inadequate folate intake and/or lower absorption of vitamin B(12). The aim of this study was to determine whether there is an impact of folic acid and vitamin B(12) supplementation on homocysteine levels and, subsequently, on bone turnover markers in older women with mildly to moderately elevated homocysteine levels. It is hypothesized that supplementation with folic acid and vitamin B(12) will improve homocysteine levels and, in turn, positively modify bone turnover markers in this population. This randomized, double-blind, placebo-controlled trial included 31 women (65 to 93 years) with homocysteine levels greater than 10 μmol/L. Participants were randomly assigned to receive either a daily folic acid (800 μg) and vitamin B(12) (1000 μg) (n = 17) or a matching placebo (n = 14) for 4 months. The results showed significantly lower homocysteine concentrations in the vitamin group compared to the placebo group (10.6 vs 18.5 μmol/L, P = .007). No significant difference in serum alkaline phosphatase or C-terminal cross-linking telopeptide of type I collagen was found between the vitamin and placebo groups before or after supplementation. The use of folic acid and vitamin B(12) as a dietary supplement to improve homocysteine levels could be beneficial for older women, but additional research must be conducted in a larger population and for a longer period to determine if there is an impact of supplementation on bone turnover markers or other indicators of bone health.

Keser I, Ilich JZ, Vrkić N, Giljević Z…
Nutr Res Mar 2013
PMID: 23507227

B12 Decreases Fracture Risk

Abstract

Vitamin B12, folate, homocysteine, and bone health in adults and elderly people: a systematic review with meta-analyses.

Elevated homocysteine levels and low vitamin B12 and folate levels have been associated with deteriorated bone health. This systematic literature review with dose-response meta-analyses summarizes the available scientific evidence on associations of vitamin B12, folate, and homocysteine status with fractures and bone mineral density (BMD). Twenty-seven eligible cross-sectional (n = 14) and prospective (n = 13) observational studies and one RCT were identified. Meta-analysis on four prospective studies including 7475 people showed a modest decrease in fracture risk of 4% per 50 pmol/L increase in vitamin B12 levels, which was borderline significant (RR = 0.96, 95% CI = 0.92 to 1.00). Meta-analysis of eight studies including 11511 people showed an increased fracture risk of 4% per μ mol/L increase in homocysteine concentration (RR = 1.04, 95% CI = 1.02 to 1.07). We could not draw a conclusion regarding folate levels and fracture risk, as too few studies investigated this association. Meta-analyses regarding vitamin B12, folate and homocysteine levels, and BMD were possible in female populations only and showed no associations. Results from studies regarding BMD that could not be included in the meta-analyses were not univocal.

van Wijngaarden JP, Doets EL, Szczecińska A, Souverein OW…
J Nutr Metab 2013
PMID: 23509616 | Free Full Text

MMPs a Potential Target

Abstract

Hydrogen sulfide and sodium nitroprusside compete to activate/deactivate MMPs in bone tissue homogenates.

Bone microvascular remodeling is the primary predictor of bone structure and function. Remodeling by its very nature implies synthesis and degradation of the extracellular matrix. Normally, 50% of total protein in the vessel wall is elastin. During remodeling, elastin is degraded by specialized matrix metalloproteinases (MMPs). Because the turnover of elastin is 1000-fold slower than that of collagen, most of the elastin is replaced by stiffer collagen. Stiffer vessels impose pressure on the aortic valve, causing regurgitation and increased pulse pressure. On the other hand, high MMP activity will cause vascular dilatation, leading to aneurysm. Therefore, balanced constitutive remodeling is necessary for adequate bone structure and function. Interestingly, collagen-degrading MMPs are involved in various pathological conditions, including osteoporosis, osteoarthritis, and cardiovascular disease.

Sodium nitroprusside is a nitric oxide donor that could potentially alter MMP activity via vasodilation in vivo, but can also produce peroxynitrite, which activates MMPs by combining with superoxide. Moreover, hydrogen sulfide is a known antioxidant as well as a vasodilator, and is also speculated to contribute directly to MMP activity. We hypothesized that hydrogen sulfide reduced activity of MMP in ex vivo bone tissue homogenates and that sodium nitroprusside would increase MMP activity in vitro.
We surgically removed the tibia and femur from anesthetized mice, and prepared bone tissue homogenates using a mortar and pestle, measured the protein concentration with a spectrophotometer, and detected MMP activity using gelatin gel zymography.
Our data showed increased MMP activity at a sodium nitroprusside concentration of 1 μM, and MMP activity increased exponentially. There was a decrease in MMP activity with increasing hydrogen sulfide, beginning at 16 μM (P < 0.01) and continuing to 40 μM. Moreover, sodium nitroprusside 3 μM was able to overcome the decrease in MMP activity that occurred with hydrogen sulfide 40 μM; this resulted in a more pronounced exponential increase in MMP activity.
There are several substances that can potentially be used to decrease MMP activity and to alleviate pathological remodeling by MMPs.

Vacek TP, Qipshidze N, Tyagi SC
Vasc Health Risk Manag 2013
PMID: 23658491 | Free Full Text