Preference for wine is associated with lower hip fracture incidence in post-menopausal women

Resveratrol inhibits basic fibroblast growth factor-induced macrophage colony-stimulating factor synthesis via the PI3-kinase/Akt pathway in osteoblasts

Resveratrol is a natural polyphenol found in grapes and beneficial for human health. Resveratrol regulates basic fibroblast growth factor (bFGF)-induced osteoprotegerin synthesis through Akt pathway in osteoblast-like MC3T3-E1 cells. In this study, we investigated resveratrol effects on bFGF-induced macrophage colony-stimulating factor (M-CSF) synthesis in MC3T3-E1 cells. bFGF significantly stimulated release and mRNA expression of M-CSF, which was reduced by resveratrol and SRT1720, sirtuin 1 (SIRT1) activator. Inauhzin, SIRT1 inhibitor, reversed inhibitory effects of resveratrol on bFGF-induced mRNA expression of M-CSF. Deguelin, Akt inhibitor, and LY294002, phosphatidylinositol 3-kinase (PI3-kinase) inhibitor, reduced bFGF-induced M-CSF synthesis. Inauhzin reversed inhibitory effects of resveratrol on bFGF-induced Akt phosphorylation. Suppressive effect of resveratrol on bFGF-induced osteoprotegerin mRNA expression was confirmed in the identical samples using in experiment of M-CSF mRNA expression. Therefore, resveratrol reduces bFGF-induced M-CSF synthesis in addition to osteoprotegerin synthesis by inhibiting PI3-kinase/Akt pathway and suppressive effects are mediated through SIRT1 activation in osteoblasts.

Why Is Iron Deficiency/Anemia Linked to Alzheimer's Disease and Its Comorbidities, and How Is It Prevented?

Impaired iron metabolism has been increasingly observed in many diseases, but a deeper, mechanistic understanding of the cellular impact of altered iron metabolism is still lacking. In addition, deficits in neuronal energy metabolism due to reduced glucose import were described for Alzheimer's disease (AD) and its comorbidities like obesity, depression, cardiovascular disease, and type 2 diabetes mellitus. The aim of this review is to present the molecular link between both observations. Insufficient cellular glucose uptake triggers increased ferritin expression, leading to depletion of the cellular free iron pool and stabilization of the hypoxia-induced factor (HIF) 1α. This transcription factor induces the expression of the glucose transporters (Glut) 1 and 3 and shifts the cellular metabolism towards glycolysis. If this first line of defense is not adequate for sufficient glucose supply, further reduction of the intracellular iron pool affects the enzymes of the mitochondrial electron transport chain and activates the AMP-activated kinase (AMPK). This enzyme triggers the translocation of Glut4 to the plasma membrane as well as the autophagic recycling of cell components in order to mobilize energy resources. Moreover, AMPK activates the autophagic process of ferritinophagy, which provides free iron urgently needed as a cofactor for the synthesis of heme- and iron-sulfur proteins. Excessive activation of this pathway ends in ferroptosis, a special iron-dependent form of cell death, while hampered AMPK activation steadily reduces the iron pools, leading to hypoferremia with iron sequestration in the spleen and liver. Long-lasting iron depletion affects erythropoiesis and results in anemia of chronic disease, a common condition in patients with AD and its comorbidities. Instead of iron supplementation, drugs, diet, or phytochemicals that improve energy supply and cellular glucose uptake should be administered to counteract hypoferremia and anemia of chronic disease.

Alcohol Consumption and Risk of Fractures: A Systematic Review and Dose-Response Meta-Analysis of Prospective Cohort Studies

Alcohol consumption remains inconsistently correlated with fracture risk, and a dose-response meta-analysis for specific outcomes is lacking. The objective of this study was to quantitatively integrate the data on the relationship between alcohol consumption and fracture risk. Pertinent articles were identified in PubMed, Web of Science, and Embase databases up to 20 February 2022. Combined RRs and 95% CIs were estimated by random- or fixed-effects models. Restricted cubic splines were used to model linear or nonlinear relationships. Forty-four articles covering 6,069,770 participants and 205,284 cases of fracture were included. The combined RRs and 95% CIs for highest compared with lowest alcohol consumption were 1.26 (1.17-1.37), 1.24 (1.13-1.35), and 1.20 (1.03-1.40) for total, osteoporotic, and hip fractures, respectively. A linear positive relationship between alcohol consumption and total fracture risk was detected (Pnonlinearity = 0.057); the risk was correlated with a 6% increase (RR, 1.06; 95% CI: 1.02, 1.10) per 14 g/d increment of alcohol consumption. J-shaped relationships of alcohol consumption with risk of osteoporotic fractures (Pnonlinearity < 0.001) and hip fractures (Pnonlinearity < 0.001) were found. Alcohol consumption of 0 to 22 g/d was linked to a reduced risk of osteoporotic fractures and hip fractures. Our findings show that any level of alcohol consumption is a risk factor for total fractures. Moreover, this dose-response meta-analysis shows that an alcohol consumption level of 0 to 22 g/d is related to a reduction in the risk of osteoporotic and hip fractures. The protocol was registered in the International Prospective Register of Systematic Reviews (CRD42022320623).

Comorbidity of osteoporosis and Alzheimer's disease: Is `AKT `-ing on cellular glucose uptake the missing link?

Osteoporosis and Alzheimer's disease (AD) are both degenerative diseases. Osteoporosis often proceeds cognitive deficits, and multiple studies have revealed common triggers that lead to energy deficits in brain and bone. Risk factors for osteoporosis and AD, such as obesity, type 2 diabetes, aging, chemotherapy, vitamin deficiency, alcohol abuse, and apolipoprotein Eε4 and/or Il-6 gene variants, reduce cellular glucose uptake, and protective factors, such as estrogen, insulin, exercise, mammalian target of rapamycin inhibitors, hydrogen sulfide, and most phytochemicals, increase uptake. Glucose uptake is a fine-tuned process that depends on an abundance of glucose transporters (Gluts) on the cell surface. Gluts are stored in vesicles under the plasma membrane, and protective factors cause these vesicles to fuse with the membrane, resulting in presentation of Gluts on the cell surface. This translocation depends mainly on AKT kinase signaling and can be affected by a range of factors. Reduced AKT kinase signaling results in intracellular glucose deprivation, which causes endoplasmic reticulum stress and iron depletion, leading to activation of HIF-1α, the transcription factor necessary for higher Glut expression. The link between diseases and aging is a topic of growing interest. Here, we show that diseases that affect the same biochemical pathways tend to co-occur, which may explain why osteoporosis and/or diabetes are often associated with AD.

A systematic review and meta-analysis of prospective cohort studies on the association between alcohol intake and risk of fracture

Previous studies on the association between alcohol intake and risk of fracture have reached conflicting findings. The aim of this systematic review and meta-analysis of prospective cohort studies was to summarize earlier studies on the association of alcohol intake with risk of fracture. A systematic search of PubMed, Scopus, and ISI Web of Science was conducted up to November 2020. Prospective cohort studies that had considered alcohol consumption as the exposure variable and fracture as the main outcome or as one of the outcome variables were included in this systematic review. Publications in which odds ratios (ORs), rate or risk ratios (RRs), or hazard ratios (HRs) and 95% confidence intervals (CIs) were reported, were included in the meta-analysis. In total, 40 prospective cohort studies including 5,084,303 participants and 170,916 subjects with fracture were included in this systematic review; of them 38 studies with a total sample size of 5,053,117 participants and 169,560 cases of fracture were included in the meta-analysis. Using a random-effects meta-analysis, we found a significant positive association between alcohol consumption and risk of total fractures (RR: 1.35; 95% CI: 1.01, 1.81) and any fractures (RR: 1.24; 95% CI: 1.11, 1.38). However, no significant association was observed between alcohol intake and risk of hip fractures (RR: 1.19; 95% CI: 0.96, 1.48), osteoporotic fractures (RR: 2.01; 95% CI: 0.76, 5.34), vertebral fractures (RR: 0.98; 95% CI: 0.68, 1.40), and wrist fractures (RR: 0.99; 95% CI: 0.85, 1.16). In conclusion, we found that alcohol consumption was positively associated with risk of total fractures and any fractures. However, we did not observe any significant association between alcohol consumption and risk of hip, osteoporotic, vertebral, and wrist fractures.

Association of Alcohol Intake and Fracture Risk in Elderly Varied by Affected Bones: A Nationwide Longitudinal Study

OBJECTIVE

Previous studies investigating association of alcohol intake and fracture risk in elderly yielded conflicting results. We first examined the association between alcohol intake and total fracture risk in elderly subjects and further analyzed whether the association varied by fracture locations.

METHODS

This is a nationwide population-based cohort study which included all people aged 66 (n=1,431,539) receiving the National Screening Program during 2009-2014. Time-to-event were defined as duration from study recruitment, the day they received health screening, to the occurrence of fracture.

RESULTS

Total fracture was significantly lower in mild drinkers [adjusted hazard ratio (aHR)=0.952; 95% confidence interval (95% CI) =0.931-0.973] and higher in heavy drinkers (aHR=1.246; 95% CI=1.201-1.294) than non-drinkers. Risk pattern of alcohol consumption and fracture differed according to affected bones. Similar J-shaped trends were observed for vertebra fractures, but risk of limb fracture showed a linear relationship with alcohol intake. For hip fracture, risk decrement was more pronounced in mild and moderate drinkers, and significant increment was noted only in very severe drinkers [≥60 g/day; (aHR)=1.446; 1.162-1.801].

CONCLUSION

Light to moderate drinking generally lowered risk of fractures, but association between alcohol and fracture risk varied depending on the affected bone lesions.

Resveratrol suppresses insulin-like growth factor I-induced osteoblast migration: attenuation of the p44/p42 MAP kinase pathway

Resveratrol is a natural polyphenol with beneficial antioxidant properties. It suppresses the migration of osteoblast-like MC3T3-E1 cells induced by epidermal growth factor, via SIRT1-mediated inhibition of SAPK/JNK and Akt. Moreover, insulin-like growth factor-I (IGF-I) stimulates the migration involving the pathways of p44/p42 mitogen-activated protein (MAP) kinase and Akt. Therefore, we investigated the effects of resveratrol on IGF-I-induced cell migration. Resveratrol and SRT1720, an activator of SIRT1, suppressed IGF-I-induced migration. Inauhzin, a SIRT1 inhibitor, significantly rescued the inhibition of IGF-I-induced cell migration by resveratrol. Resveratrol inhibited IGF-I-induced phosphorylation of p44/p42 MAP kinase but not Akt. SRT1720 inhibited IGF-I-induced phosphorylation of p44/p42 MAP kinase. Furthermore, PD98059, p44/p42 MAP kinase inhibitor, alone suppressed IGF-I-induced osteoblast migration, but did not affect the suppressive effect of resveratrol when administered concomitantly. These findings strongly suggest that resveratrol suppresses IGF-I-induced osteoblast migration via SIRT1 activation at least partially by attenuating the p44/p42 MAP kinase pathway.

Effects of the Non-Alcoholic Fraction of Beer on Abdominal Fat, Osteoporosis, and Body Hydration in Women

Several studies have shown that binge drinking of alcoholic beverages leads to non-desirable outcomes, which have become a serious threat to public health. However, the bioactive compounds in some alcohol-containing beverages might mitigate the negative effects of alcohol. In beer, the variety and concentration of bioactive compounds in the non-alcoholic fraction suggests that its consumption at moderate levels may not only be harmless but could also positively contribute to an improvement of certain physiological states and be also useful in the prevention of different chronic diseases. The present review focuses on the effects of non-alcoholic components of beer on abdominal fat, osteoporosis, and body hydration in women, conditions selected for their relevance to health and aging. Although beer drinking is commonly believed to cause abdominal fat deposition, the available literature indicates this outcome is inconsistent in women. Additionally, the non-alcoholic beer fraction might improve bone health in postmenopausal women, and the effects of beer on body hydration, although still unconfirmed seem promising. Most of the health benefits of beer are due to its bioactive compounds, mainly polyphenols, which are the most studied. As alcohol-free beer also contains these compounds, it may well offer a healthy alternative to beer consumers.

The Role and Mechanism of SIRT1 in Resveratrol-regulated Osteoblast Autophagy in Osteoporosis Rats

Osteoporosis is widely regarded as one of the typical aging-related diseases due to the impairment of bone remodeling. The silent information regulator of transcription1 (SIRT1) is a vital regulator of cell survival and life-span. SIRT1 has been shown to be activated by resveratrol treatment, and also has been proved to prevent aging-related diseases such as osteoporosis. However, the role of SIRT1 about autophagy or mitophagy of osteoblasts in resveratrol-regulated osteoporotic rats remains unclear. This study seeks to investigate the role of SIRT1 about autophagy or mitophagy in osteoblasts through PI3K/Akt signaling pathway in resveratrol-regulated osteoporotic rats. The vivo experiment results have revealed that resveratrol treatment significantly improved bone quality and reduced the levels of serum alkaline phosphatase and osteocalcin in osteoporotic rats. Moreover, Western bolt analysis showed that expression of SIRT1, LC3, and Beclin-1 in osteoblasts increased, while p-AKT and p-mTOR were downregulated in osteoporosis rats with high dose resveratrol treatment. On the other hand, resveratrol treatment increased the SIRT1 activity, LC3 and Beclin-1 mRNA expression in the dexamethasone (DEX)-treated osteoblasts. More mitophagosomes were observed in the DEX-treated osteoblasts with resveratrol. Meanwhile, the TOM20, Hsp60, p-Akt and p-mTOR activities were decreased in the DEX-treated osteoblasts with resveratrol. Resveratrol treatment did not change the p-p38 and p-JNK activities in the osteoblasts. These results revealed that resveratrol treatment protected osteoblasts in osteoporosis rats by enhancing mitophagy by mediating SIRT1 and PI3K/AKT/mTOR signaling pathway.

Alcohol intake, specific alcoholic beverages, and risk of hip fractures in postmenopausal women and men age 50 and older

BACKGROUND

Although a number of studies have examined the association between alcohol intake and hip fractures, few have considered specific alcoholic beverages separately.

OBJECTIVES

We prospectively assessed total alcohol and specific alcoholic beverage consumption and risk of hip fractures in US men and women.

METHODS

Health, lifestyle information, and hip fractures were self-reported on biennial questionnaires between 1980 and 2014 in 75,180 postmenopausal women from the Nurses' Health Study, and between 1986 and 2014 in 38,398 men aged ≥50 y from the Health Professionals Follow-Up Study. Diet was assessed approximately every 4 y with a semiquantitative FFQ. RRs were computed for hip fracture using Cox proportional hazards models, adjusting for potential confounders.

RESULTS

We ascertained 2360 incident low trauma hip fractures in women and 709 in men. Among women, RRs for low trauma hip fractures compared with nondrinkers were 0.89 (95% CI: 0.80, 0.99) for an average daily consumption of <5.0 g, 0.81 (95% CI: 0.70, 0.94) for 5.0 to <10.0 g, 0.83 (95% CI: 0.71, 0.96) for 10.0 to <20.0 g, and 0.93 (95% CI: 0.78, 1.10) for ≥20.0 g. Among men, risk declined linearly with higher alcohol consumption (P-trend = 0.002). Multivariable RR compared with nondrinkers was 0.77 (95% CI: 0.59, 1.01), 0.69 (0.49, 0.96), and 0.67 (0.48, 0.95) for an average intake of 10 g/d to <20 g/d, 20 g/d to <30 g/d, and 30.0 g/d or more, respectively. In women, the alcoholic beverage most significantly associated with hip fracture risk was red wine (RR per serving = 0.59; 95% CI: 0.45, 0.79). In men, there was no clear association with specific alcoholic beverages.

CONCLUSION

In these 2 US cohorts, low to moderate alcohol consumption, when compared with no consumption, was associated with a lower risk of hip fractures, particularly with red wine consumption among women.

The association between alcohol consumption and risk of hip fracture differs by age and gender in Cohort of Norway: a NOREPOS study

The association between alcohol consumption and hip fracture differed by gender: Men aged 30-59 years drinking frequently or 14+ gl/week had higher risk than moderate drinkers. No significant association was seen in older men. Women not drinking alcohol had higher risk than those drinking moderately both regarding frequency and amount.

INTRODUCTION

We aimed to examine alcohol consumption and risk of hip fracture according to age and gender in the population-based Cohort of Norway (1994-2003).

METHODS

Socio-demographics, lifestyle, and health were self-reported and weight and height were measured in 70,568 men and 71,357 women ≥ 30 years. Information on subsequent hip fractures was retrieved from hospitals' electronic patient registries during 1994-2013. Frequency of alcohol consumption was categorized: never/seldom, moderate (≤ 2-3 times/week), or frequent (≥ 4 times/week), and amount as number of glasses per week: 0, 1-6, 7-13, 14-27, and 28+. Type of alcohol (wine vs. beer/hard liquor) was also examined. Cox's proportional hazards regression was used to estimate hazard ratios (HRs) stratified on gender and baseline age < 60 and ≥ 60 years.

RESULTS

During median 15-year follow-up, 1558 men and 2511 women suffered a hip fracture. Using moderate drinkers as reference, men < 60 years drinking frequently had multivariable adjusted HR = 1.73 (CI 1.02-2.96) for hip fracture and more than 2.5 times higher risk if they consumed 14+ glasses compared to 1-6 glasses per week. In other groups of age and gender, no statistically significant increased risk was found in those consuming the highest levels of alcohol. Compared to women with moderate or frequent alcohol use, never/seldom-drinking women had the highest fracture risk. In women, use of wine was associated with lower fracture risk than other types of alcohol.

CONCLUSIONS

Risk of hip fracture was highest in men < 60 years with the highest frequency and amount of alcohol consumption and in non-drinking women.

Resveratrol suppresses thyroid hormone‑induced osteocalcin synthesis in osteoblasts

Resveratrol, a polyphenolic compound that is present in grape skins, berries and red wine, may be beneficial for human health through its anti‑inflammatory and anti‑oxidant effects. It has been previously demonstrated that resveratrol exerts its biological effects primarily via sirtuin 1 (SIRT1) activation. We previously reported that triiodothyronine (T3) induces osteocalcin synthesis in osteoblast‑like MC3T3‑E1 cells, and that p38 mitogen‑activated protein (MAP) kinase mediates the T3‑stimulated synthesis of osteocalcin. The present study investigated the effect of resveratrol on T3‑induced osteocalcin synthesis and its underlying mechanism in MC3T3‑E1 cells. Cultured cells were stimulated with T3, and osteocalcin release from MC3T3‑E1 cells was measured by ELISA and phosphorylation of p38 MAP kinase was analyzed by western blotting. Resveratrol significantly suppressed the release of osteocalcin stimulated by T3, and SRT1720, a SIRT1 activator, significantly reduced T3‑induced osteocalcin release. The expression level of osteocalcin mRNA stimulated by T3 was significantly attenuated by resveratrol and T3‑induced transactivation activity of the thyroid hormone‑responsive element was significantly diminished by resveratrol. However, only limited effects of resveratrol on the T3‑induced phosphorylation of p38 MAP kinase were observed. The results of the present study demonstrated that resveratrol suppresses T3‑stimulated osteocalcin synthesis at a point upstream of transcription in osteoblasts, and that the inhibitory effect of resveratrol is mediated, at least partially, through SIRT1 activation. These results indicate that there may be a novel role for the polyphenol in the modulation of bone metabolism.

Wine and bone health: a review

A light-to-moderate wine consumption has been shown to provide several beneficial effects on the skeletal system, including reduced risk of bone mass loss and fractures. Wine is rich in phenolic compounds, strong phytoestrogens and natural antioxidants, to which bone protection is mainly attributed. The objective of this review was to give an overview of the exact mechanisms by which wine consumption is involved in bone protection. We found a great variety of in vitro research on the beneficial effects of isolated wine phenolics on the skeletal system, with a significant lack of evidence of their in vivo effects. In addition, we found almost no studies investigating how wine, a mixture of these phenolics dissolved in ethanol, affects the skeletal system. Our results warrant further research on this interesting topic.

Resveratrol suppresses TGF-β-induced VEGF synthesis in osteoblasts: Inhibition of the p44/p42 MAPKs and SAPK/JNK pathways

Resveratrol, which is found in grape and berry skins and red wine, is generally known to be beneficial for human health due to its anti-inflammation and antioxidant effects. We have recently reported that transforming growth factor-β (TGF-β) stimulates vascular endothelial growth factor (VEGF) synthesis through Smad-independent pathways, such as the p38 mitogen-activated protein (MAP) kinase, p44/p42 MAP kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) pathways, in osteoblast-like MC3T3-E1 cells. The aim of the present study was to investigate the effect of resveratrol on the TGF-β-induced VEGF synthesis and the mechanism in osteoblast-like MC3T3-E1 cells. Resveratrol significantly suppressed the TGF-β-stimulated release of VEGF and the VEGF mRNA expression levels. SRT1720, a synthetic sirtuin 1 (SIRT1) activator, also reduced the VEGF release and the mRNA levels. With regard to the intracellular signaling in the TGF-β-stimulated VEGF synthesis, resveratrol and SRT1720 significantly attenuated the phosphorylation of p44/p42 MAP kinase and SAPK/JNK stimulated by TGF-β; however, the TGF-β-induced phosphorylation of Smad2 and p38 MAP kinase was hardly affected by resveratrol or SRT1720. These results strongly suggest that the TGF-β-stimulated VEGF synthesis is suppressed by resveratrol through the inhibition of p44/p42 MAP kinase and SAPK/JNK in osteoblasts, and that the suppressive effect is mediated, at least in part, via SIRT1 activation.

Alcohol consumption and hip fracture risk

SUMMARY

The present meta-analysis shows that a nonlinear association between alcohol consumption and the risk of hip fracture was observed. Light alcohol consumption was inversely significantly associated with hip fracture risk, whereas heavy alcohol consumption was associated with an elevated hip fracture risk.

INTRODUCTION

Previous studies examining the association between alcohol consumption and the risk of hip fracture have reported conflicting findings. Therefore, we conducted a meta-analysis of prospective cohort studies to assess the association between alcohol consumption and the risk of hip fracture.

METHODS

PubMed and EMBASE were searched for prospective cohort studies on the relationship between alcohol consumption and the risk of hip fractures. Relative risks (RR) with 95% confidence intervals (CI) were derived using random-effects models throughout the whole analysis.

RESULTS

Eighteen prospective cohort studies were included with 3,730,424 participants and 26,168 hip fracture cases. Compared with non-drinkers, the pooled RR of hip fractures for alcohol consumption was 1.03 (95% CI, 0.91-1.15), with high heterogeneity between studies (P<0.001, I2=72.6%). A nonlinear relationship between alcohol consumption and the risk of hip fracture was identified (P nonlinearity=0.003). Compared with non-drinkers, the pooled RRs of hip fractures were 0.88 (95% CI, 0.83-0.89) for light alcohol consumption (0.01-12.5 g/day), 1.00 (95% CI, 0.85-1.14) for moderate alcohol consumption (12.6-49.9 g/day), and 1.71 (95% CI, 1.41-2.01) for heavy alcohol consumption (≥50 g/day).

CONCLUSIONS

There was no evidence of publication bias. In conclusion, a nonlinear association between alcohol consumption and the risk of hip fracture was observed in this meta-analysis. Further, light alcohol consumption was inversely significantly associated with hip fracture risk, whereas heavy alcohol consumption was associated with an elevated hip fracture risk.

Down-regulation by resveratrol of basic fibroblast growth factor-stimulated osteoprotegerin synthesis through suppression of Akt in osteoblasts

It is firmly established that resveratrol, a natural food compound abundantly found in grape skins and red wine, has beneficial properties for human health. In the present study, we investigated the effect of basic fibroblast growth factor (FGF-2) on osteoprotegerin (OPG) synthesis in osteoblast-like MC3T3-E1 cells and whether resveratrol affects the OPG synthesis. FGF-2 stimulated both the OPG release and the expression of OPG mRNA. Resveratrol significantly suppressed the FGF-2-stimulated OPG release and the mRNA levels of OPG. SRT1720, an activator of SIRT1, reduced the FGF-2-induced OPG release and the OPG mRNA expression. PD98059, an inhibitor of upstream kinase activating p44/p42 mitogen-activated protein (MAP) kinase, had little effect on the FGF-2-stimulated OPG release. On the other hand, SB203580, an inhibitor of p38 MAP kinase, SP600125, an inhibitor of stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), and Akt inhibitor suppressed the OPG release induced by FGF-2. Resveratrol failed to affect the FGF-2-induced phosphorylation of p44/p42 MAP kinase, p38 MAP kinase or SAPK/JNK. The phosphorylation of Akt induced by FGF-2 was significantly suppressed by resveratrol or SRT1720. These findings strongly suggest that resveratrol down-regulates FGF-2-stimulated OPG synthesis through the suppression of the Akt pathway in osteoblasts and that the inhibitory effect of resveratrol is mediated at least in part by SIRT1 activation.

Suppression by resveratrol of prostaglandin D2-stimulated osteoprotegerin synthesis in osteoblasts

Resveratrol, a natural polyphenol with health-related properties mainly existing in grape skins and red wine, possesses beneficial effects on human being. We have previously reported that prostaglandin D2 (PGD2) stimulates heat shock protein 27 (HSP27) induction via activation of p44/p42 mitogen-activated protein (MAP) kinase, p38 MAP kinase and stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK) in osteoblast-like MC3T3-E1 cells. In the present study, we investigated the mechanism behind the effect of PGD2 on osteoprotegerin (OPG) synthesis and the effect of resveratrol on the OPG synthesis in MC3T3-E1 cells. PGD2 significantly stimulated both the OPG release and the expression levels of OPG mRNA. Resveratrol and SRT1720, an activator of SIRT1, markedly suppressed the PGD2-induced OPG release and the mRNA levels of OPG. PD98059, a specific MEK inhibitor, SB203580, a specific p38 MAP kinase inhibitor, and SP600125, a specific SAPK/JNK inhibitor suppressed the PGD2-stimulated OPG release. PGD2-induced phosphorylation of p38 MAP kinase and SAPK/JNK was attenuated by resveratrol or SRT1720. However, resveratrol or SRT1720 failed to affect the phosphorylation of myosin phosphatase-targeting subunit-1 (MYPT-1), a downstream substrate of Rho-kinase and p44/p42 MAP kinase. These results strongly suggest that resveratrol suppresses PGD2-stimulated OPG synthesis through inhibiting p38 MAP kinase and SAPK/JNK in osteoblasts, and that the suppressive effect is exerted at the point downstream of Rho-kinase but upstream of p38 MAP kinase or SAPK/JNK.