Molecular Basis of Bone Aging

The importance of the UGT1A1 variants in the development of osteopenia and osteoporosis in postmenopausal women

The UDP-glucuronosyltransferase 1A1 (UGT1A1) is involved in the process of estrogen conjugation and elimination. The aim of the study was to analyze whether the UGT1A1 genetic variants are associated with the development of osteopenia and osteoporosis in postmenopausal women. The analysis of the rs4148323 (UGT1A1*6) and rs3064744 (UGT1A1*28) variants in the UGT1A1 gene was conducted using real-time PCR. A significant correlation was observed between the genotypes of the rs3064744 (UGT1A1*28) sequence variant and body mass in women with osteoporosis. The analysis of the Z-score values revealed that women with osteoporosis and carrying the 6/6 variant had the lowest Z-score values as compared to women with the 6/7 and the 7/7 variants (− 1.966 ± 0.242 vs. − 1.577 ± 0.125 and − 1.839 ± 0.233). In addition, the odds ratio for the investigated genotypes (6/6, 6/7, 7/7) indicated an increased risk for osteopenia and osteoporosis in women with the 7/7 homozygous genotype. The analysis of the frequencies of the GG, GA and AA genotypes of the rs4148323 UGT1A1 gene showed no statistically significant differences between the groups. Our analysis revealed that the UGT1A1 rs3064744 variant may affect the risk of developing osteoporosis in postmenopausal Polish women. The UGT1A1 rs4148323 variant is not directly associated with the development of osteopenia and osteoporosis.

Age-related alterations and senescence of mesenchymal stromal cells: Implications for regenerative treatments of bones and joints

The most common clinical manifestations of age-related musculoskeletal degeneration are osteoarthritis and osteoporosis, and these represent an enormous burden on modern society. Mesenchymal stromal cells (MSCs) have pivotal roles in musculoskeletal tissue development. In adult organisms, MSCs retain their ability to regenerate tissues following bone fractures, articular cartilage injuries, and other traumatic injuries of connective tissue. However, their remarkable regenerative ability appears to be impaired through aging, and in particular in age-related diseases of bones and joints. Here, we review age-related alterations of MSCs in musculoskeletal tissues, and address the underlying mechanisms of aging and senescence of MSCs. Furthermore, we focus on the properties of MSCs in osteoarthritis and osteoporosis, and how their changes contribute to onset and progression of these disorders. Finally, we consider current treatments that exploit the enormous potential of MSCs for tissue regeneration, as well as for innovative cell-free extracellular-vesicle-based and anti-aging treatment approaches.

Relationship of Bone Status with Serum Uric Acid and Bilirubin in Men with Type 2 Diabetes: A Cross-Sectional Study

Background

Accumulating evidence has shown that serum uric acid and bilirubin are associated with some chronic diseases, owing to their antioxidant capacity, but the previous research produced discrepant results regarding the relation between uric acid, as well as bilirubin, and bone health. This study was designed to assess the relationship of serum uric acid and total bilirubin with bone mineral density and bone turnover markers in men with type 2 diabetes.

Material/Methods

In total, 631 male patients with type 2 diabetes were included. Data of patients’ medical history, biochemical index, bone mineral density of the lumbar vertebra, femoral neck, and total hip, and bone turnover markers including osteocalcin (OC), amino-terminal propeptide of type I procollagen (PINP), type I collagen carboxy-terminal peptide (CTX), and parathyroid hormone were collected and retrospectively analyzed.

Results

Both serum uric acid and total bilirubin were positively related to bone mineral density of the lumbar vertebra (β=0.179, p<0.001; β=0.095, p=0.030), femoral neck (β=0.133, p=0.002; β=0.089, p=0.029), and total hip (β=0.142, p=0.001; β=0.087, p=0.032), respectively. Serum uric acid concentration was negatively related to bone turnover markers (OC: r=−0.148, p=0.037; PINP: r=−0.139, p=0005; CTX: r=−0.200, p=0.005). Each unit increase of serum uric acid and total bilirubin was associated with a 0.4% and 5.6% lower risk of osteoporosis or osteopenia (OR=0.996, 95% CI=0.994–0.998; OR=0.944, 95% CI=0.899–0.992), respectively. The risk of osteoporosis and osteopenia in patients with low-tertile concentrations of serum uric acid and total bilirubin was increased (OR=3.486, 95% CI=1.535–7.913).

Conclusions

In men with type 2 diabetes, serum uric acid level and total bilirubin were significantly associated with bone mineral density and were protective factors against osteoporosis and osteopenia.

Circulating Alpha-Tocopherol Levels, Bone Mineral Density, and Fracture: Mendelian Randomization Study

Recent cohort studies indicate a potential role of the antioxidant α-tocopherol in reducing bone loss and risk of fractures, especially hip fractures. We performed a Mendelian randomization investigation of the associations of circulating α-tocopherol with estimated bone mineral density (eBMD) using heel ultrasound and fractures, identified from hospital records or by self-reports and excluding minor fractures. Circulating α-tocopherol was instrumented by three genetic variants associated with α-tocopherol levels at p < 5 × 10^-8 in a genome-wide association meta-analysis of 7781 participants of European ancestry. Summary-level data for the genetic associations with eBMD in 426,824 individuals and with fracture (53,184 cases and 373,611 non-cases) were acquired from the UK Biobank. Two of the three genetic variants were strongly associated with eBMD. In inverse-variance weighted analysis, a genetically predicted one-standard-deviation increase of circulating α-tocopherol was associated with 0.07 (95% confidence interval, 0.05 to 0.09) g/cm² increase in BMD, which corresponds to a >10% higher BMD. Genetically predicted circulating α-tocopherol was not associated with odds of any fracture (odds ratio 0.97, 95% confidence interval, 0.91 to 1.05). In conclusion, our results strongly strengthen a causal link between increased circulating α-tocopherol and greater BMD. Both an intervention study in those with a low dietary intake of α-tocopherol is warranted and a Mendelian randomization study with fragility fractures as an outcome.

Different Training Durations and Frequencies of Tai Chi for Bone Mineral Density Improvement: A Systematic Review and Meta-Analysis

Objective

Tai Chi shows potential as a safe and cost-effective intervention to improve bone mineral density (BMD). However, the various effects caused by different training durations and frequencies have not been evaluated. This updated systematic review aims to explore the effectiveness of Tai Chi in attenuating bone mineral density loss based on different training durations and frequencies.

Methods

We conducted an extensive database search in Cochrane Central Register of Controlled Trials, PubMed, EMBASE, Web of Science, Chinese Biomedical Literature Database, China Knowledge Resource Integrated Database, Wanfang Data, and China Science and Technology Journal Database on randomized controlled trials that examined Tai Chi for BMD improvement. Two reviewers independently performed data screening and extraction. Study quality was evaluated using the Cochrane Handbook for Systematic Reviews of Interventions.

Results

A total of 23 randomized controlled trials involving 1582 patients were identified. The aggregated results have shown significant benefits in favor of Tai Chi on BMD improvement in the lumbar spine (SMD = 0.36, 95% [0.13, 0.59], P=0.002), femoral neck (SMD = 0.40, 95% [0.16, 0.63], P=0.0009), femoral trochanter (SMD = 0.43, 95% CI [0.20, 0.66], P=0.0002), and Ward's triangle (SMD = 0.31, 95% [0.15, 0.48], P=0.002). Such favorable benefits in Tai Chi can only be seen when compared with the nonexercise group, and Tai Chi showed no significant improvement in BMD change when compared with other exercises group. Subgroup analyses showed various effects of BMD improvement based on different training durations and frequencies of Tai Chi. Tai Chi is effective in attenuating BMD loss with an intervention frequency of >4 days/week in the lumbar spine, with an intervention frequency of >4 days/week or an intervention duration of >10 months in the femoral neck, and with an intervention duration of >10 months or a frequency of ≤4 days/week in Ward's triangle.

Conclusions

The results demonstrated that Tai Chi may have benefits in attenuating BMD loss. Different training durations and frequencies may result in variable effectiveness. Researchers should focus more on the training durations and frequencies of Tai Chi so that a more definitive claim can be made regarding the beneficial effects for BMD improvement.

Vitamin D, Bone Metabolism, and Fracture Risk in Polycystic Ovary Syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder among premenopausal women. PCOS may have reproductive, metabolic, cardiovascular, and psychological implications. Vitamin D deficit is often encountered in PCOS women and may contribute to the pathophysiology of this disorder. As of the key role of vitamin D in bone and mineral metabolism, and because the vitamin D status appears to be closely linked with the PCOS manifestations including insulin resistance, obesity, ovulatory and menstrual irregularities, oxidative stress and PTH elevation, hypovitaminosis D may directly and indirectly via the different facets of PCOS impair bone health in these women. Although limited data are available on life-long fracture risk in women with PCOS, the importance of preserving bone health in youth and adults to prevent osteoporosis and related fractures is also recognized in PCOS women. Evidence of the association between vitamin D and the clinical hallmarks of PCOS are summarized and discussed. Vitamin D arises as a cornerstone in women with PCOS and contributes to the pathophysiological link between PCOS and bone metabolism.

Osteoprotective Roles of Green Tea Catechins

Osteoporosis is the second most common disease only secondary to cardiovascular disease, with the risk of fracture increasing with age. Osteoporosis is caused by an imbalance between osteoblastogenesis and osteoclastogenesis processes. Osteoclastogenesis may be enhanced, osteoblastogenesis may be reduced, or both may be evident. Inflammation and high reactive oxygen enhance osteoclastogenesis while reducing osteoblastogenesis by inducing osteoblast apoptosis and suppressing osteoblastic proliferation and differentiation. Catechins, the main polyphenols found in green tea with potent anti-oxidant and anti-inflammatory properties, can counteract the deleterious effects of the imbalance of osteoblastogenesis and osteoclastogenesis caused by osteoporosis. Green tea catechins can attenuate osteoclastogenesis by enhancing apoptosis of osteoclasts, hampering osteoclastogenesis, and prohibiting bone resorption in vitro. Catechin effects can be directly exerted on pre-osteoclasts/osteoclasts or indirectly exerted via the modulation of mesenchymal stem cells (MSCs)/stromal cell regulation of pre-osteoclasts through activation of the nuclear factor kB (RANK)/RANK ligand (RANKL)/osteoprotegerin (OPG) system. Catechins also can enhance osteoblastogenesis by enhancing osteogenic differentiation of MSCs and increasing osteoblastic survival, proliferation, differentiation, and mineralization. The in vitro effects of catechins on osteogenesis have been confirmed in several animal models, as well as in epidemiological observational studies on human subjects. Even though randomized control trials have not shown that catechins provide anti-fracture efficacy, safety data in the trials are promising. A large-scale, placebo-controlled, long-term randomized trial with a tea regimen intervention of optimal duration is required to determine anti-fracture efficacy.

Is a Healthy Diet Also Suitable for the Prevention of Fragility Fractures?

Osteoporosis and sarcopenia contribute to the risk of fracture in the population. These conditions share common features, and it is known that a healthy diet may have beneficial effects on both, theoretically resulting in fewer fractures. The present narrative review gives an overview of recent epidemiological research related to the association between healthy diets/dietary patterns, bone health and fragility fractures. The review also gives a brief overview on general dietary recommendations and advice as the cornerstone of public health nutrition. Although muscle health and sarcopenia contribute to the risk of fractures, these endpoints were not the focus of this review. Healthy diets are nutrient dense and contain bioactive components that are needed for the constant remodeling of the skeleton and to slow the rate of bone loss and muscle wasting, thus contributing to the prevention of fragility fractures. Compliance with healthy dietary patterns were predominantly found to be inversely associated with bone outcomes, although this was not entirely consistent across all studies. Different a priori diet scores, such as the Mediterranean diet score and the Dietary Inflammatory Index, as well as a posteriori data driven dietary patterns, such as the prudent or healthy dietary pattern, were inversely associated with fragility fractures in different populations. In conclusion, different healthy dietary patterns may contribute to bone health and less fractures. Following current dietary guidelines is thus advisable for the prevention of fragility fractures.