Increased serum GDF11 concentration is associated with a high prevalence of osteoporosis in elderly native Chinese women

The correlation between circulating growth differentiation factor 11 and the risk of osteopenia/osteoporosis in men

Our results suggest that the serum GDF11 concentration is significantly associated with the risk of bone metabolism dysfunction in men and may be a useful target for prediction of osteopenia/osteoporosis to enable prompt intervention for this common but invariably under- or misdiagnosed condition in men.

PURPOSE

Male osteopenia/osteoporosis remains a neglected subject or is under- or misdiagnosed. Many studies have confirmed the role of growth differentiation factor 11 (GDF11) in bone metabolism, although its role in bone metabolism remains controversial. In this study, we aimed to investigate the association between serum GDF11 levels and the prevalence of osteopenia/osteoporosis (OP) in a male cohort and explore the possibility of GDF11 to be a useful target for prediction of osteopenia/osteoporosis to enable prompt intervention for this disease.

METHODS

This cross-sectional study included 121 native Chinese men randomly aged 20-87 years, excluded the subjects who had the conditions of bone metabolism-related disease and administration of hormonal drugs, and grouped the subjects to OP and non-OP, based on the WHO definition and latest guidelines of OP. The serum GDF11 concentration was determined using a GDF11-specific immunoassay. Bone mineral density (BMD) was measured using dual-energy X-ray absorptiometry. Tartrate-resistant acid phosphatase 5b (TRAP-5b) were measured in serum samples with ELISA method.

RESULTS

We observed a negative correlation between serum GDF11 levels and age, a positive correlation between serum GDF11 levels and the femoral neck BMD, and a negative correlation between serum GDF11 levels and TRAP-5b in men. The prevalence and risk of OP were significantly higher in men with low serum GDF11 levels.

CONCLUSIONS

The serum GDF11 concentration is significantly associated with the risk of bone metabolism dysfunction and may be a useful target for prediction of OP in male cohort.

Bioinformatics identification and experimental validation of m6A-related diagnostic biomarkers in the subtype classification of blood monocytes from postmenopausal osteoporosis patients

BACKGROUND

Postmenopausal osteoporosis (PMOP) is a common bone disorder. Existing study has confirmed the role of exosome in regulating RNA N6-methyladenosine (m6A) methylation as therapies in osteoporosis. However, it still stays unclear on the roles of m6A modulators derived from serum exosome in PMOP. A comprehensive evaluation on the roles of m6A modulators in the diagnostic biomarkers and subtype identification of PMOP on the basis of GSE56815 and GSE2208 datasets was carried out to investigate the molecular mechanisms of m6A modulators in PMOP.

METHODS

We carried out a series of bioinformatics analyses including difference analysis to identify significant m6A modulators, m6A model construction of random forest, support vector machine and nomogram, m6A subtype consensus clustering, GO and KEGG enrichment analysis of differentially expressed genes (DEGs) between different m6A patterns, principal component analysis, and single sample gene set enrichment analysis (ssGSEA) for evaluation of immune cell infiltration, experimental validation of significant m6A modulators by real-time quantitative polymerase chain reaction (RT-qPCR), etc.

RESULTS

In the current study, we authenticated 7 significant m6A modulators via difference analysis between normal and PMOP patients from GSE56815 and GSE2208 datasets. In order to predict the risk of PMOP, we adopted random forest model to identify 7 diagnostic m6A modulators, including FTO, FMR1, YTHDC2, HNRNPC, RBM15, RBM15B and WTAP. Then we selected the 7 diagnostic m6A modulators to construct a nomogram model, which could provide benefit with patients according to our subsequent decision curve analysis. We classified PMOP patients into 2 m6A subtypes (clusterA and clusterB) on the basis of the significant m6A modulators via a consensus clustering approach. In addition, principal component analysis was utilized to evaluate the m6A score of each sample for quantification of the m6A subgroups. The m6A scores of patients in clusterB were higher than those of patients in clusterA. Moreover, we observed that the patients in clusterA had close correlation with immature B cell and gamma delta T cell immunity while clusterB was linked to monocyte, neutrophil, CD56dim natural killer cell, and regulatory T cell immunity, which has close connection with osteoclast differentiation. Notably, m6A modulators detected by RT-qPCR showed generally consistent expression levels with the bioinformatics results.

CONCLUSION

In general, m6A modulators exert integral function in the pathological process of PMOP. Our study of m6A patterns may provide diagnostic biomarkers and immunotherapeutic strategies for future PMOP treatment.

Challenges to Improve Bone Healing Under Diabetic Conditions

Diabetes mellitus (DM) can affect bone metabolism and the bone microenvironment, resulting in impaired bone healing. The mechanisms include oxidative stress, inflammation, the production of advanced glycation end products (AGEs), etc. Improving bone healing in diabetic patients has important clinical significance in promoting fracture healing and improving bone integration. In this paper, we reviewed the methods of improving bone healing under diabetic conditions, including drug therapy, biochemical cues, hyperbaric oxygen, ultrasound, laser and pulsed electromagnetic fields, although most studies are in preclinical stages. Meanwhile, we also pointed out some shortcomings and challenges, hoping to provide a potential therapeutic strategy for accelerating bone healing in patients with diabetes.

Detection of GDF11 by using a Ti3C2-MXene-based fiber SPR biosensor

In the research of resistant aging, the concentration of Growth differentiation factor-11(GDF11) is an indispensable parameter. So the accurate detection of GDF11 is very important in life science and medical cosmetology. Hereby, we proposed and demonstrated a simple method to detect low concentration GDF11 by using fiber surface plasmon resonance (SPR) sensor decorated with two-dimension (2D) material Ti₃C₂-MXene and gold nanosphere. The sensitivity of the fiber SPR sensor was increased to be 4804.64nm/RIU. After functionalized with GDF11 antibody, the fiber SPR sensor could specifically recognize GDF11, and the limit of detection (LOD) can reach 0.577pg/L which is 100 times lower than that of single-molecule ELISA method.

Serum levels of irisin in postmenopausal women with osteoporotic hip fractures

OBJECTIVE

The purpose of this study was to evaluate the role of circulating serum levels of irisin in predicting hip fracture occurrence in a cohort of Chinese postmenopausal women.

METHODS

This was a cross-section and case-control study. Four hundred and thirty postmenopausal women aged 50-90 years were included (215 with hip fractures and 215 age-matched cases without fracture). Clinical features, bone mineral density (BMD) and serum biomarkers levels including irisin were measured at baseline. Cox proportional hazards regression analysis was used to assess the correlation between irisin and fracture risk.

RESULTS

The mean age of those participants was 68.7 (S.D. 11.7) and 53.0% were order than 65. The irisin serum levels were positively related to total body BMD and total hip BMD. Women with hip fractures showed lower mean serum levels of irisin compared normal control women (457.6 ± 172.6 ng/ml vs. 602.2 ng/ml; P < 0.001). The irisin levels in third and fourth quartiles were associated with the risk of hip fracture (the lowest quartile of irisin levels as the reference), and risk of fracture reduced by 67% (hazard ratio [HR] = 0.33; 95 %CI: 0.18-0.54; P < 0.001) and 84% (HR = 0.16; 95 %CI: 0.09-0.29; P < 0.001). The irisin levels in third and fourth quartiles were also associated with the risk of osteoporosis, and risk of fracture reduced by 55% (HR = 0.45; 95 %CI: 0.21-0.63; P = 0.003) and 73% (HR = 0.27; 95 %CI: 0.15-0.47; P < 0.001).

CONCLUSION

Decreased serum levels of circulating irisin are associated with high risk of osteoporosis-related hip fractures and osteoporosis.

The relationship between transforming growth factor β superfamily members (GDF11 and BMP4) and lumbar spine bone mineral density in postmenopausal Chinese women

PURPOSE

The relationship between transforming growth factor β superfamily members (GDF11 and BMP4) and bone metabolism remains controversial. The aim of this study was to investigate the association between serum GDF11 and BMP4 levels and lumbar spine bone mineral density (LBMD) in a cohort of postmenopausal Chinese women.

METHODS

This was a non-prospective cross-sectional study of 350 postmenopausal women with a mean age of 63.13 ± 8.66 years who came from Shenyang, China. LBMD was measured using dual-energy X-ray absorptiometry. Serum GDF11 and BMP4 concentrations were detected using a sandwich enzyme immunoassay kit. Pearson's correlation analysis and regression analyses were carried out to investigate the relationships between LBMD and serum GDF11 and BMP4 levels.

RESULTS

A linear association between LBMD and serum LgGDF11 concentration was observed after adjusting for numerous confounders (P = 0.018). In addition, the osteoporosis (OP) was inversely related to LgGDF11 and the odds ratios for postmenopausal women with lumbar OP in LgGDF11 quartile group 2, group 3, and group 4 were 0.46 (95% CI 0.23-0.90, P < 0.05), 0.41 (95% CI 0.20-0.84, P < 0.05), and 0.30 (95% CI 0.14-0.63, P < 0.01), respectively (P = 0.001 for the trend), when compared to the highest quartile of LgGDF11 after adjustments for many confounding variables in this study.

CONCLUSIONS

This study showed that serum GDF11 levels were linearly related to LBMD, and it was also revealed that serum GDF11 levels were significantly associated with lumbar OP in postmenopausal women. However, serum BMP4 levels were not associated with LBMD and lumbar OP.

A Renewed Focus on GDF11 Level Fluctuation in Human Serum in Relation to Physical Examination Indicators

Growth and differentiation factor 11 (GDF11) is a member of the transforming growth factor β superfamily. Previous studies have shown that GDF11 decreases with age and has antiaging effects; however, such reports are controversial. We choose 152 subjects covering a large age range (2 hours to 75 years) to measure serum GDF11. Twenty-two hematological variables and 13 biochemical values were measured. Pearson's analysis found a significant correlation between GDF11 and age (p = .0000, r = .4898), as well as serum creatinine, uric acid, triglycerides, red blood cell count, hemoglobin, hematocrit, and platelet volume distribution width. GDF11 negatively correlated with aspartate transaminase, white blood cell count, platelet count, lymphocyte count, monocyte count, mean platelet volume, and plateletcrit. Interestingly, we found GDF11 increases in people aged 20-30 years, holds steady in people aged 30-50 years, and increases in people older than 50 years. The results suggest that GDF11 serves different roles along the life span. The current actual evidence supports that GDF11 is helpful to promote aging.

Circulating GDF11 levels are decreased with age but are unchanged with obesity and type 2 diabetes

Growth differentiation factor 11 (GDF11) is a member of the transforming growth factor β (TGFβ) superfamily which declines with age and exerts anti-aging regenerative effects in skeletal muscle in mice. However, recent data in humans and mice are conflicting casting doubts about its true functional actions. The aim of the present study was to compare the circulating concentrations of GDF11 in individuals of different ages as well as body weight and glycemic status. Serum concentrations of GDF11 were measured by ELISA in 319 subjects. There was a significant increase in GDF11 concentrations in people in the 41-50 y group and a decline in the elder groups (61-70 and 71-80 y groups, P=0.008 for the comparison between all age groups). However, no significant correlation between fat-free mass index (FFMI), a formula used to estimate the amount of muscle mass in relation to height, and logGDF11 was observed (r=0.08, P=0.197). Moreover, no significant differences in circulating concentrations of GDF11 regarding obesity or glycemic status were found. Serum GDF11 concentrations in humans decrease in older ages being unaltered in obesity and T2D. Further studies should determine the exact pathophysiological role of GDF11 in aging.

Inhibition of GDF11 could promote bone healing in the tooth extraction socket and facilitate mesenchymal stem cell osteogenic differentiation in T2DM pigs

BACKGROUND

Growth differentiation factor 11 (GDF11) might be a key factor responsible for the weakening of mesenchymal stem cell (MSC) osteogenic differentiation in tooth extraction sockets in patients with type 2 diabetes mellitus (T2DM). This study aimed to confirm that inhibition of GDF11 could promote bone healing in tooth extraction sockets and facilitate MSC osteogenic differentiation under T2DM conditions.

METHODS

Three streptozotocin-induced T2DM pig models and two control pig models were established. The T2DM pigs were treated with an intrasocket injection of GDF11 inhibitor in the left mandible, whereas the right side was maintained for natural healing. The postextraction socket healing of the T2DM pigs was compared with that of nondiabetic controls. Healing was quantitatively verified by microcomputed tomography, and the GDF11 expression level was detected. MSCs from T2DM pig sockets were cultured and treated with a GDF11 inhibitor. The osteogenic differentiation ability of MSCs was also compared among groups.

RESULTS

The expression of GDF11 in the tooth extraction sockets from T2DM pigs increased significantly post extraction. Bone healing was promoted by periodic injection of the GDF11 inhibitor into the extraction sockets of T2DM pigs. Furthermore, the osteogenic differentiation ability of T2DM-MSCs was improved in pigs treated with the GDF11 inhibitor.

CONCLUSIONS

GDF11 inhibition could promote bone healing in the tooth extraction socket and facilitate MSC osteogenic differentiation under T2DM conditions. GDF11 could be a potential therapeutic target for undesirable alveolar bone healing in T2DM patients.

Gdf11 gene transfer prevents high fat diet-induced obesity and improves metabolic homeostasis in obese and STZ-induced diabetic mice

Background

The growth differentiation factor 11 (GDF11) was shown to reverse age-related hypertrophy on cardiomyocytes and considered as anti-aging rejuvenation factor. The role of GDF11 in regulating metabolic homeostasis is unclear. In this study, we investigated the functions of GDF11 in regulating metabolic homeostasis and energy balance.

Methods

Using a hydrodynamic injection approach, plasmids carrying a mouse Gdf11 gene were delivered into mice and generated the sustained Gdf11 expression in the liver and its protein level in the blood. High fat diet (HFD)-induced obesity was employed to examine the impacts of Gdf11 gene transfer on HFD-induced adiposity, hyperglycemia, insulin resistance, and hepatic lipid accumulation. The impacts of GDF11 on metabolic homeostasis of obese and diabetic mice were examined using HFD-induced obese and STZ-induced diabetic models.

Results

Gdf11 gene transfer alleviates HFD-induced obesity, hyperglycemia, insulin resistance, and fatty liver development. In obese and STZ-induced diabetic mice, Gdf11 gene transfer restores glucose metabolism and improves insulin resistance. Mechanism study reveals that Gdf11 gene transfer increases the energy expenditure of mice, upregulates the expression of genes responsible for thermoregulation in brown adipose tissue, downregulates the expression of inflammatory genes in white adipose tissue and those involved in hepatic lipid and glucose metabolism. Overexpression of GDF11 also activates TGF-β/Smad2, PI3K/AKT/FoxO1, and AMPK signaling pathways in white adipose tissue.

Conclusions

These results demonstrate that GDF11 plays an important role in regulating metabolic homeostasis and energy balance and could be a target for pharmacological intervention to treat metabolic disease.

Regulatory Role of RNA N6-Methyladenosine Modification in Bone Biology and Osteoporosis

Osteoporosis is a metabolic skeletal disorder in which bone mass is depleted and bone structure is destroyed to the degree that bone becomes fragile and prone to fractures. Emerging evidence suggests that N⁶-methyladenosine (m⁶A) modification, a novel epitranscriptomic marker, has a significant role in bone development and metabolism. M⁶A modification not only participates in bone development, but also plays important roles as writers and erasers in the osteoporosis. M⁶A methyltransferase METTL3 and demethyltransferase FTO involves in the delicate process between adipogenesis differentiation and osteogenic differentiation, which is important for the pathological development of osteoporosis. Conditional knockdown of the METTL3 in bone marrow stem cells (BMSCs) could suppress PI3K-Akt signaling, limit the expression of bone formation-related genes (such as Runx2 and Osterix), restrain the expression of vascular endothelial growth factor (VEGF) and down-regulate the decreased translation efficiency of parathyroid hormone receptor-1 mRNA. Meanwhile, knockdown of the METTL3 significantly promoted the adipogenesis process and janus kinase 1 (JAK1) protein expression via an m⁶A-dependent way. Specifically, there was a negative correlation between METTL3 expression and porcine BMSCs adipogenesis. The evidence above suggested that the relationship between METTL3 expression and adipogenesis was inverse, and osteogenesis was positive, respectively. Similarly, FTO regulated for BMSCs fate determination during osteoporosis through the GDF11-FTO-PPARγ axis, prompting the shift of MSC lineage commitment to adipocyte and inhibiting bone formation during osteoporosis. In this systematic review, we summarize the most up-to-date evidence of m⁶A RNA modification in osteoporosis and highlight the potential role of m⁶A in prevention, treatment, and management of osteoporosis.

The GDF11-FTO-PPARγ axis controls the shift of osteoporotic MSC fate to adipocyte and inhibits bone formation during osteoporosis

During osteoporosis, the shift of bone mesenchymal stem cell (BMSC) lineage commitment to adipocyte leads to the imbalance between bone mass and fat, which increases the risk of fracture. The mechanism underlying this process is not fully understood. Fat mass and obesity-associated protein (FTO) is an RNA demethylase that demethylates various methylated nucleic acids and participates in various physiological and pathological processes. Here we identified FTO as a regulator for BMSC fate determination during osteoporosis. FTO was up-regulated in bone marrow during aging or osteoporosis in human and mice in a GDF11(growth differentiation factor 11)-C/EBPα-dependent mechanism. The expression of FTO was also up-regulated during adipocyte differentiation of BMSCs whereas its expression was down-regulated during osteoblast differentiation. Gain-of-function and loss-of-function experiments showed that FTO favored the BMSCs to differentiate to adipocytes rather than osteoblasts. Further mechanism study demonstrated that FTO bound and demethylated the mRNA of the Peroxisome proliferator-activated receptor gamma (Pparg), leading to the increase in the expression of Pparg mRNA. Reversely, Pparg knockdown blocked the function of GDF11-FTO during osteoblast differentiation of BMSCs. Furthermore, conditionally genetic knockout of Fto in osteoblasts inhibited the development of osteopenia in mice. Collectively, our findings demonstrated that GDF11-FTO-Pparg axis promoted the shift of osteoporotic BMSC fate to adipocyte and inhibited bone formation during osteoporosis.

Abdominal aortic calcification and the risk of bone fractures: a meta-analysis of prospective cohort studies

The relationship between abdominal aortic calcification (AAC) and bone fracture has been examined by some observational studies, but the results remain discordant. Therefore, we aimed to assess the link between them by conducting a meta-analysis of prospective studies. Relevant studies were identified by searching PubMed and EMBASE databases until the end of December 2016. Summary relative risks (RRs) and 95% confidence intervals (CIs) for associations between AAC and fracture risk were estimated with fixed- or random- effects models. Seven prospective studies were included in the final analysis. The summarized RRs of any type of fractures for the highest compared with the lowest category of AAC were 1.64 (95% CI 1.30-2.07, P = 0.000) with mild heterogeneity (I ² = 30.1%, P = 0.188). Subgroup analysis showed that the association between AAC and fracture was not significantly modified by gender and follow-up length. Risks were similar when analyses were restricted to the studies with adjustment for bone mineral density (BMD) (RR = 1.76, 95% CI 1.31-2.38, P = 0.000, I ² = 49.1%). For the specific type of fracture, severe AAC was significantly related with hip fracture (RR = 1.64, 95% CI 1.22-2.20, P = 0.001, n = 5), but not with vertebral (RR = 1.45, 95% CI 0.81-2.58, P = 0.213, n = 3) or non-vertebral fracture (RR = 1.35, 95% CI 0.96-1.88, P = 0.081, n = 3). There was no evidence of publication bias. Our findings demonstrated that AAC was significantly and independently associated with a higher fracture risk, especially for hip fracture.