Genetic variability in noncoding RNAs: involvement of miRNAs and long noncoding RNAs in osteoporosis pathogenesis

Circulating MicroRNAs as Biomarkers of Osteoporosis and Fragility Fractures

CONTEXT

Measurement of circulating microRNAs (miRNAs) as potential biomarkers of fragility fracture risk has recently become a subject of investigation.

OBJECTIVE

Measure by next-generation sequencing (NGS), global miRNA expression in serum samples of osteoporotic subjects vs individuals with normal bone mineral density (BMD).

DESIGN

Samples were collected from patients with different bone phenotypes and/or fragility fractures who did not receive any antiresorptive and/or bone-forming drug at the time of blood collection.

SETTING

Samples and data were collected at 7 medical centers in Italy.

PATIENTS

NGS prescreening: 50 osteoporotic patients vs 30 individuals with normal BMD. Droplet digital polymerase chain reaction (ddPCR) validation: 213 patients with different bone phenotypes, including the NGS-analyzed cohort.

RESULTS

NGS identified 5 miRNAs (miR-8085, miR-320a-3p, miR-23a-3p, miR-4497, miR-145-5p) differentially expressed in osteoporosis cases without fractures vs controls. ddPCR validation confirmed lower c-miR-23a-3p expression in osteoporotic patients, with or without fracture, than in osteopenic and normal subjects and increased c-miR-320a-3p expression in osteoporotic patients with fracture and lower expression in osteoporotic patients without fracture. ddPCR analysis showed a significantly increased expression of miR-21-5p in osteoporotic patients, with or without fracture, than in osteopenic and normal subjects, not evidenced by the NGS prescreening.

DISCUSSION

Our study confirmed levels of c-miR-23a-3p and c-miR-21-5p as able to distinguish osteoporotic patients and subjects with normal BMD. Increased levels of c-miR-320a-3p specifically associated with fractures, independently by BMD, suggesting c-miR-320a-3p as a prognostic indicator of fracture risk in osteoporotic patients, to be confirmed in prospective studies on incident fractures.

Correlation between methylene tetrahydrofolate reductase (MTHFR) gene rs1801133 C>T polymorphisms and risk of osteoporosis

Objective

To evaluate the correlation between methylene tetrahydrofolate reductase (MTHFR) gene rs1801133 C>T polymorphisms and risk of osteoporosis.

Methods

We searched the clinical studies related to MTHFR gene rs1801133 C>T polymorphisms and risk of osteoporosis in the electronic databases of PubMed, Web of Science, EMBASE, China National Knowledge Infrastructure (CNKI), Chinese BioMedical Literature Database (CBM) and included the suitable publications in the present meta-analysis according to the inclusion and exclusion criteria. The data of included studies were extracted and pooled by a random or fixed-effect model. The odds ratio (OR) and 95% confidence interval (95% CI) were applied to demonstrate the correlation between MTHFR gene rs1801133 C>T polymorphisms and the risk of osteoporosis. Publication bias was assessed by Begg’s funnel plot and Egger’s line regression test.

Results

Seven case–control clinical studies were included and a data combination was made. The data was pooled by the fixed effect model because of no obvious statistical heterogeneity. The pooled results indicated that people with the T allele had increased risk of developing osteoporosis under the homologous gene model (TT vs CC) (OR = 2.36, 95% CI: 1.81–3.08, p < 0.05), dominant gene model (TT + CT) vs CC (OR = 1.47, 95% CI: 1.21–1.77, p < 0.05) and recessive gene model TT vs (CC + CT) (OR = 2.16, 95% CI: 1.71–2.74, p < 0.05). Egger’s line regression test indicated no significant publication bias for the present meta-analysis in the above homologous, dominant, and recessive gene models.

Conclusion

The MTHFR gene rs1801133 C>T polymorphisms are associated with osteoporosis and subjects with the T allele have an increased risk of developing osteoporosis.

DNA Methylation Signatures of Bone Metabolism in Osteoporosis and Osteoarthritis Aging-Related Diseases: An Updated Review

DNA methylation is one of the most studied epigenetic mechanisms that play a pivotal role in regulating gene expression. The epigenetic component is strongly involved in aging-bone diseases, such as osteoporosis and osteoarthritis. Both are complex multi-factorial late-onset disorders that represent a globally widespread health problem, highlighting a crucial point of investigations in many scientific studies. In recent years, new findings on the role of DNA methylation in the pathogenesis of aging-bone diseases have emerged. The aim of this systematic review is to update knowledge in the field of DNA methylation associated with osteoporosis and osteoarthritis, focusing on the specific tissues involved in both pathological conditions.