Tag Archives: quote

Resveratrol Enhances Osteogenesis via Runx2 and SIRT1 In Vitro

Abstract

Resveratrol mediated modulation of Sirt-1/Runx2 promotes osteogenic differentiation of mesenchymal stem cells: potential role of Runx2 deacetylation.

Osteogenic repair in response to bone injury is characterized by activation and differentiation of mesenchymal stem cells (MSCs) to osteoblasts. This study determined whether activation of Sirt-1 (a NAD(+)-dependent histone deacetylase) by the phytoestrogen resveratrol affects osteogenic differentiation.
Monolayer and high-density cultures of MSCs and pre-osteoblastic cells were treated with an osteogenic induction medium with/without the Sirt-1 inhibitor nicotinamide or/and resveratrol in a concentration dependent manner.
MSCs and pre-osteoblastic cells differentiated to osteoblasts when exposed to osteogenic-induction medium. The osteogenic response was blocked by nicotinamide, resulting in adipogenic differentiation and expression of the adipose transcription regulator PPAR-γ (peroxisome proliferator-activated receptor). However, in nicotinamide-treated cultures, pre-treatment with resveratrol significantly enhanced osteogenesis by increasing expression of Runx2 (bone specific transcription factor) and decreasing expression of PPAR-γ. Activation of Sirt-1 by resveratrol in MSCs increased its binding to PPAR-γ and repressed PPAR-γ activity by involving its cofactor NCoR (nuclear receptor co-repressor). The modulatory effects of resveratrol on nicotinamide-induced expression of PPAR-γ and its cofactor NCoR were found to be mediated, at least in part, by Sirt-1/Runx2 association and deacetylation of Runx2. Finally, knockdown of Sirt-1 by using antisense oligonucleotides downregulated the expression of Sirt-1 protein and abolished the inhibitory effects of resveratrol, namely nicotinamide-induced Sirt-1 suppression and Runx2 acetylation, suggesting that the acetylated content of Runx2 is related to downregulated Sirt-1 expression.
These data support a critical role for Runx2 acetylation/deacetylation during osteogenic differentiation in MSCs in vitro.

Shakibaei M, Shayan P, Busch F, Aldinger C…
PLoS ONE 2012
PMID: 22539994 | Free Full Text


From the introduction:

Resveratrol is a polyphenolic phytoestrogen (trans-3,5, 4′-trihydroxystilbene) found in the skin of red grapes, red vines, various other fruits, peanuts and root extracts of Polygonum cuspidatum [8]. Resveratrol acts as a mixed agonist/antagonist for the estrogen receptors alpha and beta [9]. Through binding to the estrogen receptor, resveratrol is thought to exert beneficial effects on the cardiovascular system and may reverse osteoporosis by a direct stimulatory effect on bone formation in osteoblastic cells [10]. Many of the biological effects of resveratrol have already been demonstrated in the literature; these include cardiovascular protection [11], anticancer activity [12] and stimulation of proliferation and osteoblastic differentiation in human and mouse MSCs [13], [14]. However, its effects on bone are less studied and are particularly relevant to this investigation.

From the discussion:

Resveratrol’s enhancement of osteogenesis was, at least in part regulated by Runx2 with additional contributions by Sirt-1. Resveratrol increases alkaline phosphatase activity in osteoblastic cells [10] an effect that is blocked by tamoxifen, an estrogen antagonist, suggesting that some of resveratrol’s stimulatory actions may be mediated through the estrogen receptor. Gehm et al. have reported that resveratrol acts as a phytoestrogen (i.e. activating the estrogen receptor) and decreases osteoporosis [43]. Moreover, resveratrol is one of the most potent Sirt-1 activators; through binding to a special binding site it induces a conformational change in Sirt-1, lowering the Km for both the acetylated substrate and NAD, thus resulting in increased enzymatic activity [18]. Sirt-1 facilitates the differentiation of MSCs to osteoblasts by directly regulating factors such as Runx2 and by modulation of nuclear receptor co-repressor NCoR and PPAR-γ.

Review: Vitamin K2 (MK-4) Monotherapy Modestly Increases Bone Density and Reduces Fractures in Eight Studies

Abstract

Vitamin k2 therapy for postmenopausal osteoporosis.

Vitamin K may play an important role in the prevention of fractures in postmenopausal women with osteoporosis. Menatetrenone is the brand name of a synthetic vitamin K2 that is chemically identical to menaquinone-4. The present review study aimed to clarify the effect of menatetrenone on the skeleton in postmenopausal women with osteoporosis, by reviewing the results of randomized controlled trials (RCTs) in the literature. RCTs that investigated the effect of menatetrenone on bone mineral density (BMD), measured by dual-energy X-ray absorptiometry and fracture incidence in postmenopausal women with osteoporosis, were identified by a PubMed search for literature published in English. Eight studies met the criteria for RCTs. Small RCTs showed that menatetrenone monotherapy decreased serum undercarboxylated osteocalcin (ucOC) concentrations, modestly increased lumbar spine BMD, and reduced the incidence of fractures (mainly vertebral fracture), and that combined alendronate and menatetrenone therapy enhanced the decrease in serum ucOC concentrations and further increased femoral neck BMD. This review of the literature revealed positive evidence for the effects of menatetrenone monotherapy on fracture incidence in postmenopausal women with osteoporosis. Further studies are required to clarify the efficacy of menatetrenone in combination with bisphosphonates against fractures in postmenopausal women with osteoporosis.

Iwamoto J
Nutrients 2014
PMID: 24841104 | Free Full Text


One interesting passage from the full text talks about the unpublished dose range study from Japan:

Orimo, H., et al. “Clinical evaluation of soft capsule menatetrenone (Ea-0167) in the treatment of osteoporosis: late phase II dose study.” J New Remedies Clinics 41 (1992): 1249-79.

A dose-finding study of menatetrenone in Japan [7] administered daily doses of 15, 45, 90, and 135 mg and revealed that 45 mg was the minimum effective dose for improving bone mass parameters evaluated by microdensitometry and/or single photon absorptiometry in postmenopausal women with osteoporosis. This optimal dose (45 mg/day) for the treatment of osteoporosis is about 150–180 times greater than the recommended daily dietary intake of vitamin K (250–300 μg) [8]. No toxic effects of menatetrenone (45 mg/day) have been reported [7]. High-dose vitamin K is needed to prevent fractures in postmenopausal women with osteoporosis [9]. However, the effect of menatetrenone on the skeleton remains a matter of controversy [10–17], and the role of menatetrenone in the treatment of osteoporosis therefore needs to be clarified.

Vitamin K1 and K2 (MK-4, MK-7) Don’t Prevent Bone Loss in Rats Fed Adequate Nutrients

Abstract

Vitamin K supplementation does not prevent bone loss in ovariectomized Norway rats.

Despite plausible biological mechanisms, the differential abilities of phylloquinone (PK) and menaquinones (MKn) to prevent bone loss remain controversial. The objective of the current study was to compare the effects of PK, menaquinone-4 (MK-4) and menaquinone-7 (MK-7) on the rate of bone loss in ovariectomized (OVX) Norway rats. A secondary aim was to compare the effects of vitamin K with those of bisphosphonates (BP) on bone loss.
Rats (n = 96) were randomized to 6 dosing groups [n = 16/group; Sham; OVX; OVX + BP (100 μg/kg/100 μg/mL saline sc); OVX + PK; OVX + MK-4; and OVX + MK-7] for 6 wk. Equimolar daily doses of 107 mg PK/kg, 147 mg MK-4/kg, and 201 mg MK-7/kg diet were provided.
BP significantly increased bone strength and bone mineral density (BMD) vs. OVX (P < 0.05). However, PK, MK-4 or MK-7 did not change bone strength or BMD compared to the OVX group. Whereas supplementation of PK, MK-4 and MK-7 increased serum and tibia concentrations of each respective form, PK concentrations were consistently higher despite equimolar intakes.
PK, MK-4, and MK-7 do not appear to prevent bone loss in OVX rats when administered concurrent with adequate intake of other nutrients.

Fu X, Moreines J, Booth SL
Nutr Metab (Lond) 2012
PMID: 22348311 | Free Full Text


In conclusion, supplementation of PK, MK-4 or MK-7 did not confer a beneficial effect on bone loss in ovariectomized Norway rats fed a diet that meets nutritional requirements for other nutrients, including calcium and vitamin D. This would suggest that equivocal findings in the literature regarding the effect of various forms of vitamin K on bone cannot be attributed to differences among the forms studied. These data are also consistent with a growing number of clinical studies that report no beneficial effect of vitamin K supplementation on bone loss in the elderly who are otherwise calcium and vitamin D-replete [1,18,19].

High Omega-6:Omega-3 Ratios Increase Fracture Risk and Doubles Risk for Ratios > 6

Abstract

The association of red blood cell n-3 and n-6 fatty acids with bone mineral density and hip fracture risk in the women’s health initiative.

Omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acids (PUFA) in red blood cells (RBCs) are an objective indicator of PUFA status and may be related to hip fracture risk. The primary objective of this study was to examine RBC PUFAs as predictors of hip fracture risk in postmenopausal women. A nested case-control study (n = 400 pairs) was completed within the Women’s Health Initiative (WHI) using 201 incident hip fracture cases from the Bone Mineral Density (BMD) cohort, along with 199 additional incident hip fracture cases randomly selected from the WHI Observational Study. Cases were 1:1 matched on age, race, and hormone use with non-hip fracture controls. Stored baseline RBCs were analyzed for fatty acids using gas chromatography. After removing degraded samples, 324 matched pairs were included in statistical analyses. Stratified Cox proportional hazard models were constructed according to case-control pair status; risk of fracture was estimated for tertiles of RBC PUFA. In adjusted hazard models, lower hip fracture risk was associated with higher RBC α-linolenic acid (tertile 3 [T3] hazard ratio [HR]: 0.44; 95% confidence interval [CI], 0.23-0.85; p for linear trend 0.0154), eicosapentaenoic acid (T3 HR: 0.46; 95% CI, 0.24-0.87; p for linear trend 0.0181), and total n-3 PUFAs (T3 HR: 0.55; 95% CI, 0.30-1.01; p for linear trend 0.0492). Conversely, hip fracture nearly doubled with the highest RBC n-6/n-3 ratio (T3 HR: 1.96; 95% CI, 1.03-3.70; p for linear trend 0.0399). RBC PUFAs were not associated with BMD. RBC PUFAs were indicative of dietary intake of marine n-3 PUFAs (Spearman’s rho = 0.45, p < 0.0001), total n-6 PUFAs (rho = 0.17, p < 0.0001) and linoleic acid (rho = 0.09, p < 0.05). These results suggest that higher RBC α-linolenic acid, as well as eicosapentaenoic acid and total n-3 PUFAs, may predict lower hip fracture risk. Contrastingly, a higher RBC n-6/n-3 ratio may predict higher hip fracture risk in postmenopausal women.

Orchard TS, Ing SW, Lu B, Belury MA…
J. Bone Miner. Res. Mar 2013
PMID: 23018646 | Free Full Text


The full text has a nice chart showing the hazard ratios for the various fatty acids they looked at.

The Omega-6:Omega-3 ratios and their respective hazard ratios were:

Omega-6:Omega-3 Ratio 1.48–5.00 5.01–6.07 6.08–10.59
Hazard Ratio 1.00 1.28 (0.71–2.30) 1.96 (1.03–3.70)

[Hazard Ratios] for hip fracture by tertiles of RBC FAs with multivariate adjustment for risk factors per Robbins and colleagues37 are reported in Table 3. No significant associations were found between RBC total SFA, MUFA, or PUFA and risk of hip fracture. However, there was a significant inverse linear association between hip fracture risk and total n-3 FAs in RBCs (p for linear trend 0.0492). When examining individual n-3 FAs, there was a 56% lower relative risk of hip fracture with highest RBC ALA (tertile 3 [T3] hazard ratio [HR]: 0.44; 95% CI, 0.23–0.85; p for linear trend 0.0154), and a 54% lower hip fracture risk with highest EPA levels (T3 HR: 0.46; 95% CI, 0.24–0.87; p for linear trend 0.0181) compared to T1. Neither DHA nor the n-3 index was significantly associated with risk of fracture. In contrast, hip fracture risk nearly doubled in women in the highest tertile of the n-6/n-3 FA ratio (HR T3: 1.96; 95% CI, 1.03–3.70; p for linear trend 0.0399). Because the n-6/n-3 FA ratio in RBCs primarily reflects the ratio of AA to EPA and DHA, we further examined the relation of the AA/EPA + DHA ratio to hip fracture risk. Similar to the n-6/n-3 FA ratio, a higher AA/EPA + DHA ratio produced higher HR for hip fracture, but the association was not significant (T3 HR: 1.69; 95% CI, 0.86–3.31; p for linear trend 0.1242). Although the direction of association between total n-6 FAs, AA, and hip fracture was toward harm, there was no significant relation of either total n-6 FAs or AA with hip fracture. There was an inverse direction of association between LA and hip fracture risk, but again, this was not statistically significant (T3 HR: 0.77; 95% CI, 0.40–1.49; p for linear trend 0.5140). Inclusion of additional potential confounders (alcohol consumption, total energy intake, total calcium intake, total vitamin D intake, and multivitamin use) in the model produced similar results….

Calcium Threonate may Influence Bone Mineralization Through its Action on Vitamin C

Abstract

Pharmacokinetics and safety of calcium L-threonate in healthy volunteers after single and multiple oral administrations.

To evaluate the pharmacokinetics of L-threonate after single or multiple oral administrations and its safety profile in healthy Chinese volunteers. This was an open-label, single- and multiple-dose study. The subjects were assigned to receive a single dose, 675, 2025, or 4050 mg, of calcium L-threonate (n=12) or repeated doses of 2025 mg twice daily for 4 d (n=12). Serial plasma and urine samples were analyzed with HPLC-MS/MS. Pharmacokinetic parameters of L-threonate were calculated using non-compartmental analysis with WinNonlin software.
In the single dose group, C(max) reached at 2.0 h and the mean t(1/2) was approximately 2.5 h. Area under curve (AUC) and C(max) increased with dose escalation, but dose proportionality was not observed over the range of 675 to 4050 mg. AUC and C(max) in the fasted subjects were lower compared with those in the non-fasted subjects. Cumulative urinary excretion of L-threonate over 24 h represented 5.9% of the administered dose with a mean Cl/r of 0.8 L/h. In the multiple-dose study, no accumulation appeared upon repeated doses of 2025 mg twice daily for 4 d. There were no serious adverse events that occurred during this study.
Calcium L-threonate was well tolerated in healthy Chinese subjects, with no pattern of dose-related adverse events. Plasma exposure increased with dose escalation, but linear pharmacokinetics were not observed over the studied doses. L-threonate was absorbed rapidly, and its absorption was enhanced by food intake. No systemic accumulation appeared after repeated administrations.

Wang HY, Hu P, Jiang J
Acta Pharmacol. Sin. Dec 2011
PMID: 21986570 | Free Full Text


The introduction is the most interesting part of the article.

L-Threonic acid is an active metabolite of vitamin C5, 6, 7, 8. It has been reported that L-threonic acid exhibits significant stimulatory action on vitamin C uptake and prolongs the retention of vitamin C in human T-lymphoma cells9, 10. It is also well known that vitamin C is a marker for osteoblast formation and has been shown to stimulate procollagen and enhance collagen synthesis11, 12, 13, 14. Therefore, L-threonic acid may play a role in the mineralization process through its positive action on vitamin C. This hypothesis was confirmed in 1999 by Rowe DJ15. It was reported that in vitro treatment with ascorbate-containing vitamin C metabolites enhanced the formation of the mineralized nodules and collagenous proteins and that L-threonate was one of the metabolites that was found to influence the mineralization process15. Recently, a preclinical study was performed to investigate the effect of L-threonate on bone resorption of rabbit osteoclasts16. This study contained a total of six culture groups, including one control group and five groups treated with drugs (calcium L-threonate, sodium L-threonate, alendronate, 17β-estradiol and calcium gluconate). The levels of type I collagen C-telopeptide (CTx) and bone slice resorptive area were measured. This study found that L-threonate, especially calcium L-threonate, inhibited the bone resorption of osteoclasts in vitro; however, the reductive effects on the CTx level and resorptive area were not as significant as alendronate and 17β-estradiol at the same concentration.

Calcium L-threonate ((2R,3S)-2,3,4-trihydroxy butyric acid calcium) (Figure 1) is a novel drug developed for the treatment of osteoporosis and as a calcium supplement. Phase I clinical trials of calcium L-threonate, including tolerance, pharmacokinetics and calcium absorption evaluation, were performed in Peking Union Medical College Hospital. In this paper, the pharmacokinetics of L-threonate after single or multiple oral administrations and its safety profile in healthy Chinese volunteers are presented.

Cataracts are Associated with Osteoporosis

Abstract

Are cataracts associated with osteoporosis?

Calcium is considered an important factor in the development of both osteoporosis and cataract. This study evaluated the association between osteoporosis and cataracts.
To evaluate the prevalence of osteoporosis among patients undergoing cataract surgery, and the association between the two.
This was a retrospective observational case-control study, conducted in the Central District of Clalit Health Services (a district of the largest health maintenance organization in Israel). All Clalit members in the district older than 50 years who underwent cataract surgery from 2000 to 2007 (n=12,984) and 25,968 age- and sex-matched controls comprised the sample. Electronic medical records of all patients in the study were reviewed. The main outcome measure was the prevalence of osteoporosis and the odds ratio of having osteoporosis among cataract patients compared with controls.
Demographically, 41.8% were men with a mean age of 68.7 ± 8.2 years. A logistic regression model for osteoporosis showed that age, female sex, higher socioeconomic class, smoking, chronic renal failure, hyperthyroidism, rheumatoid arthritis, inflammatory bowel diseases, and cataract are all associated with increased prevalence of osteoporosis. Obesity is a protective factor for osteoporosis. In all age-groups, osteoporosis was more prevalent in cataract patients than in the control group.
Among other well-known risk factors, osteoporosis is associated with the presence of cataracts. Common pathophysiological associations with both conditions, such as calcium imbalance, hormonal abnormalities, and shared genetic predisposition, are discussed.

Nemet AY, Hanhart J, Kaiserman I, Vinker S
Clin Ophthalmol 2013
PMID: 24204110 | Free Full Text


We found a significant association between cataract and osteoporosis among women of all age-groups and in men older than 75 years. Smoking,8 obesity,9 chronic renal failure,10 hyperthyroidism,11 rheumatoid arthritis,12 inflammatory bowel diseases13 are well known to be associated with osteoporosis and have been reported on extensively. Obesity as a protective factor has already been reported.14 To the best of our knowledge, this is the first study to show this association. This section focuses on calcium imbalance as a common key event, hormonal abnormalities associated with both conditions, and shared ultrastructural abnormalities found in cataract and osteoporosis.

Review: Vitamin K Reviewed by European Vitamin K Experts

Abstract

Beyond deficiency: potential benefits of increased intakes of vitamin K for bone and vascular health.

Vitamin K is well known for its role in the synthesis of a number of blood coagulation factors. During recent years vitamin K-dependent proteins were discovered to be of vital importance for bone and vascular health. Recommendations for dietary vitamin K intake have been made on the basis of the hepatic requirements for the synthesis of blood coagulation factors. Accumulating evidence suggests that the requirements for other functions than blood coagulation may be higher. This paper is the result of a closed workshop (Paris, November 2002) in which a number of European vitamin K experts reviewed the available data and formulated their standpoint with respect to recommended dietary vitamin K intake and the use of vitamin K-containing supplements.

Vermeer C, Shearer MJ, Zittermann A, Bolton-Smith C…
Eur J Nutr Dec 2004
PMID: 15309455 | Free Full Text


Accumulating evidence suggests that in many aspects arterial calcification mimics bone formation, which prompts interest in the effects of vitamin K on the vasculature. Previous population-based studies reported a significant reduction in aortic calcification with high vitamin K1 [62] and vitamin K2 intake [63], and a significant inverse correlation was found between vitamin K2 intake, and the incidence of both ischaemic heart disease and cardiovascular mortality [63]. Based on these findings the effect of treatment on arterial characteristics was monitored in the Maastricht osteostudy. These unpublished findings clearly demonstrated that supplementation with vitamin K1 can protect against vascular hardening and loss of arterial elasticity. High dose MK-4 also seems to have cholesterol lowering properties as shown in studies in rabbits [64] and humans [65].

[…]

Extremely high doses (45–90mg/day) of MK-4 have been used for the treatment of postmenopausal osteoporosis in Japan for several years [66, 67]. After the positive outcomes of the first clinical trials, the treatment is now used on a large scale; thus far, no adverse side-effects have been reported. A number of independent groups have claimed that this medication results in complete prevention of further bone loss in postmenopausal women, and in some women even a significant gain in BMD [68, 69]. The treatment was also reported to be successful in other groups at risk for bone loss such as haemodialysis patients and those treated with corticosteroids.

[…]

In considering the potential efficacy of pharmacological doses of MK-4 it should be noted that there is evidence for a secondary function of this analogue over and above its role in glutamate carboxylation. The available evidence (mainly from cell culture experiments) suggests that MK-4 (but not K1) may also be associated with production of interleukin-6, regulate the synthesis of PGE2 [83], or inhibit the mevalonate pathway in a comparable way to bisphosphonates [84], but at present only preliminary data exist.

[…]

Any risks associated with relatively high consumption of either K1 or K2 appear minimal, with intakes up to 1 mg/d K1 and 45 mg/d MK-4 often having been used without observed adverse events. Two possible exceptions exist. Firstly a potential problem relates to interference with oral anticoagulants. However, a systematic dose-response study among subjects on oral anticoagulant treatment demonstrated that the stability of anticoagulation was not significantly affected by vitamin K supplements at doses below 100 μg/day [14]. Secondly, preliminary studies have suggested that high vitamin K1 supplementation (i. e. above 1 mg/day) can contribute to periodontal disease via a bacterial mechanism on gingival tissue (S. Hodges, unpublished data).

 

 

Review: Vitamin K and Bone Health 1998-2008

Abstract

Update on the role of vitamin K in skeletal health.

A protective role for vitamin K in bone health has been suggested based on its role as an enzymatic cofactor. In observational studies, vitamin K insufficiency is generally associated with lower bone mass and increased hip fracture risk. However, these findings are not supported in randomized controlled trials (RCT) of phylloquinone (vitamin K(1)) supplementation and bone loss at the hip in the elderly. This suggests that increased vegetable and legume intakes may simultaneously improve measures of vitamin K status and skeletal health, even though the mechanisms underlying these improvements may be independent of each other. Menaquinone-4 (vitamin K(2)), when given at pharmacological doses, appears to protect against fracture risk and bone loss at the spine. However, there are emerging data that suggest the efficacy of vitamin K supplementation on bone loss is inconclusive.

Shea MK, Booth SL
Nutr. Rev. Oct 2008
PMID: 18826451 | Free Full Text


This is a great review of the different forms of Vitamin K and their benefits for bone. The full study includes a table listing many studies dated from 1998 to 2008 with their outcomes. I highly recommend reading the full text.

MK-4 in doses of 45 mg/d is used as a pharmacological treatment for osteoporosis in Japan, so there are numerous randomized control studies that have assessed the efficacy of MK-4 supplementation on skeletal health. Such doses cannot be attained from the diet, regardless of the form of vitamin K consumed. Phylloquinone from the diet is converted to MK-4 in certain tissues, including bone, but the proportion of phylloquinone that is converted is not known and no dose-dependent data are available for this conversion.

[…]

As reviewed in an earlier volume of this journal,60 studies indicate a therapeutic dose (45 mg/day) of MK-4 has a beneficial effect on spine or metacarpal BMD and fracture61–76 (Table 2). There is also improvement in bone turnover, as measured by circulating markers of bone formation and bone resorption, in response to MK-4 supplementation studies.71,72,76,77 In a separate systematic review and analysis of randomized clinical trials assessing the influence of vitamin K supplementation on hip fracture, Cockayne et al.78 concluded that supplementation with MK-4 for longer than 6 months reduces risk for hip and vertebral fracture. Included in that analysis were 12 studies that used daily doses of 45 mg/d of MK-4. As discussed by the authors, several of the studies used for the meta-analysis lacked sufficient sample size,64–66,70,73,79 were non-placebo-controlled intervention trials,70–74,76,77,80 and/or used concurrent treatment with calcium and/or vitamin D.62,69,75,76

It was subsequently disclosed that a large unpublished surveillance study conducted in Japan (n > 3000) did not find a protective effect of MK-4 supplementation (45 mg/day) on bone loss and fracture in the elderly, and that inclusion of this study may have altered the results of the meta-analysis.81 More recently, two placebo-controlled studies with large sample sizes reported no protective effect of 45 mg/d of MK-4 on hip BMD.59,67 Prior to these two publications, the majority of MK-4 supplementation studies did not report hip BMD as an outcome (Table 2). Given the heterogeneous quality of the studies used and considering the null findings of more recent, larger, placebo-controlled trials and unpublished surveillance data, prior systematic reviews and meta-analyses may need to be revisited.

 

Vitamin K1 and K2 Reversed Bone Loss in Obese Mice

Abstract

Vitamin K1 (phylloquinone) and K2 (menaquinone-4) supplementation improves bone formation in a high-fat diet-induced obese mice.

Several reports suggest that obesity is a risk factor for osteoporosis. Vitamin K plays an important role in improving bone metabolism. This study examined the effects of vitamin K1 and vitamin K2 supplementation on the biochemical markers of bone turnover and morphological microstructure of the bones by using an obese mouse model. Four-week-old C57BL/6J male mice were fed a 10% fat normal diet group or a 45% kcal high-fat diet group, with or without 200 mg/1000 g vitamin K1 (Normal diet + K1, high-fat diet + K1) and 200 mg/1000 g vitamin K2 (Normal diet + K2, high-fat diet + K2) for 12 weeks. Serum levels of osteocalcin were higher in the high-fat diet + K2 group than in the high-fat diet group. Serum OPG level of the high-fat diet group, high-fat diet + K1 group, and high-fat diet + K2 group was 2.31 ± 0.31 ng/ml, 2.35 ± 0.12 ng/ml, and 2.90 ± 0.11 ng/ml, respectively. Serum level of RANKL in the high-fat diet group was significantly higher than that in the high-fat diet + K1 group and high-fat diet + K2 group (p<0.05). Vitamin K supplementation seems to tend to prevent bone loss in high-fat diet induced obese state. These findings suggest that vitamin K supplementation reversed the high fat diet induced bone deterioration by modulating osteoblast and osteoclast activities and prevent bone loss in a high-fat diet-induced obese mice.

Kim M, Na W, Sohn C
J Clin Biochem Nutr Sep 2013
PMID: 24062608 | Free Full Text


Vitamin K is related to blood coagulation, assisting the promotion of OC carboxylation of γ-glutamic acid, which is produced by osteoblasts, and aiding in bone formation by coupling carboxylated OC with phosphine.(15) Many studies have demonstrated that low intake of vitamin K decreases bone density, and that this is a factor that increases osteoporosis and bone fracture.(16) In the study by Booth et al.,(17) low intake of vitamin K1 led to low bone density, and was a factor for increased risk of bone fracture. When vitamin K1 was administered to human bone marrow culture, osteoclast formation was inhibited.(13) After administering vitamin K2 to osteoblasts, real-time gene expression analysis found that the OC, OPG, and RANKL genes were expressed, demonstrating that vitamin K2 has an influence on osteoblasts and osteoclasts.(18) In addition, vitamin K2 supplementation in patients with osteoporosis necessitated by the administration of glucocorticoids inhibited OPG decrease, and had effects of bone loss prevention.(19) Vitamin K2 supplementation in patients with rheumatoid arthritis accompanied with osteoporosis decreased RANKL levels and inhibited osteoclast activation.(20) Therefore, vitamin K affects bone condition both in healthy adults and in patients with specific diseases.

[…]

The results of the bone density analysis revealed an increase with the vitamin K1 and K2 supplementation in high-fat diets. Studies on the relationship between bone density and vitamin K generally have used dual-energy x-ray absorptiometry or ultrasonic densitometry,(32) but this study used high-resolution 3D micro-CT to analyze the morphologic microstructure of trabecular bone. In the study by Fujikawa et al.,(24) the Tb.N increased when vitamin K2 and calcium were fed to ovariectomized mice, and the Tb.Sp decreased. Yamaguchi et al.,(33) also fed vitamin K2 to ovariectomized rats, and reported that it prevented bone loss. These two studies used osteoporosis-induced animals, and the methods differed from those in this study, in which obesity-induced mice were fed vitamin K supplements. In this study, even though there was no significantly statistical difference in the microstructure analysis between the groups, but BV, Tb.N, and Tb.Sp were seemed to be better in the vitamin K2-supplemented group than those in the HF group, indicating that vitamin K2 may play a role in protecting the structures of trabecular bone.

[…]

The effects of vitamin K1 and K2 supplementation in normal diet on bone metabolism were not statistically significant. However, vitamin K1 and K2 supplementation in a high-fat diet could prevent a decrease in bone density, and vitamin K2 had a greater effect on this parameter. Therefore, vitamin K2 increases OPG, a marker related to bone density and the metabolism of osteoclasts and osteoblasts, and it decreases RANKL, and thus has an influence on bone metabolism. This study has showed the effects of vitamin K on bone density and metabolism in animals, but further studies are needed to determine whether the same holds true for obese humans. Future studies would need to perform bone measurement and biochemical examinations on the bone microstructures and metabolism in humans.

 

Urine pH or Acid Excretion Doesn’t Predict Bone Density or Fractures

Abstract

Low urine pH and acid excretion do not predict bone fractures or the loss of bone mineral density: a prospective cohort study.

The acid-ash hypothesis, the alkaline diet, and related products are marketed to the general public. Websites, lay literature, and direct mail marketing encourage people to measure their urine pH to assess their health status and their risk of osteoporosis. The objectives of this study were to determine whether 1) low urine pH, or 2) acid excretion in urine [sulfate + chloride + 1.8x phosphate + organic acids] minus [sodium + potassium + 2x calcium + 2x magnesium mEq] in fasting morning urine predict: a) fragility fractures; and b) five-year change of bone mineral density (BMD) in adults.
Design: Cohort study: the prospective population-based Canadian Multicentre Osteoporosis Study. Multiple logistic regression was used to examine associations between acid excretion (urine pH and urine acid excretion) in fasting morning with the incidence of fractures (6804 person years). Multiple linear regression was used to examine associations between acid excretion with changes in BMD over 5-years at three sites: lumbar spine, femoral neck, and total hip (n = 651). Potential confounders controlled included: age, gender, family history of osteoporosis, physical activity, smoking, calcium intake, vitamin D status, estrogen status, medications, renal function, urine creatinine, body mass index, and change of body mass index.
There were no associations between either urine pH or acid excretion and either the incidence of fractures or change of BMD after adjustment for confounders.
Urine pH and urine acid excretion do not predict osteoporosis risk.

Fenton TR, Eliasziw M, Tough SC, Lyon AW…
BMC Musculoskelet Disord 2010
PMID: 20459740 | Free Full Text


The evidence to support the acid-ash hypothesis of osteoporosis predominantly comes from studies using changes in urine calcium as the outcome [6,8-12,46], some prospective observational studies [16,18,19,47] and one randomized trial [13]. Although one randomized trial has supported the hypothesis [13], another did not [40]. The randomized trial [13] supporting the hypothesis did not use concealment of allocation, a study quality indicator for randomized studies that is important to avoid bias during the randomization process [48]. Without concealment of allocation, investigators can influence the allocation of individuals into the treatment groups, invalidating the randomization. Trials that do not have concealed allocation can overestimate effectiveness of a therapy [49]. The more recent randomized trial, that concealed allocation, did not reveal any protective effect of either potassium citrate or increased fruit and vegetable consumption on change in BMD [14].

Three previous prospective cohort studies of the hypothesis reported some protective associations between fruit and vegetable, potassium, and/or vitamin C intakes and bone health [16,18,19], and thus may support the hypothesis, while two more recent cohort studies do not support it [50,51]. One of the positive reporting studies did not see a significant protective association for potassium once potential confounders were controlled [16]. Further, it is possible that the associations in agreement with the hypothesis in the cohort studies were due to uncontrolled confounding by estrogen status [19], baseline BMD [16,19], change of weight status during follow-up [18], and/or vitamin D status [16,18,19,47].

Further, three recent meta-analyses of the acid-ash hypothesis do not support the hypothesis. First, a meta-analysis of calcium balance studies, restricted to studies of superior methodology, revealed no association between net acid excretion and calcium balance, in spite of the strong relationship between net acid excretion and urinary calcium [52]. A systematic review and meta-analysis of the effect of protein intake on bone health revealed a small beneficial effect of protein supplementation on lumbar spine BMD in randomized placebo-controlled trials [53]. Further, the acid-ash hypothesis predicts higher phosphate intakes would be associated with increased urinary calcium and lower calcium balance, but this was not supported by a third recent meta-analysis [54].