Telomere length as a predictive biomarker in osteoporosis (Review)

Telomeres are the ends of chromosomes that protect them from DNA damage. There is evidence to suggest that telomere shortening appears with advanced age. Since aging is a significant risk factor for developing age-related complications, it is plausible that telomere shortening may be involved in the development of osteoporosis. The present review summarizes the potential of telomere shortening as a biomarker for detecting the onset of osteoporosis. For the purposes of the present review, the following scientific databases were searched for relevant articles: PubMed/NCBI, Cochrane Library of Systematic Reviews, Scopus, Embase and Google Scholar. The present review includes randomized and non-randomized controlled studies and case series involving humans, irrespective of the time of their publication. In six out of the 11 included studies providing data on humans, there was at least a weak association between telomere length and osteoporosis, with the remaining studies exhibiting no such association. As a result, telomere shortening may be used as a biomarker or as part of a panel of biomarkers for tracking the onset and progression of osteoporosis.

Protein structural and mechanistic basis of progeroid laminopathies

Progeroid laminopathies are characterized by the premature appearance of certain signs of physiological aging in a subset of tissues. They are caused by mutations in genes coding for A-type lamins or lamin-binding proteins. Here, we review how different mutations causing progeroid laminopathies alter protein structure or protein-protein interactions and how these impact on mechanisms that protect cell viability and function. One group of progeroid laminopathies, which includes Hutchinson-Gilford progeria syndrome, is characterized by accumulation of unprocessed prelamin A or variants. These are caused by mutations in the A-type lamin gene (LMNA), altering prelamin A itself, or in ZMPSTE24, encoding an endoprotease involved in its processing. The abnormally expressed farnesylated proteins impact on various cellular processes that may contribute to progeroid phenotypes. Other LMNA mutations lead to the production of nonfarnesylated A-type lamin variants with amino acid substitutions in solvent-exposed hot spots located mainly in coil 1B and the immunoglobulin fold domain. Dominant missense mutations might reinforce interactions between lamin domains, thus giving rise to excessively stabilized filament networks. Recessive missense mutations in A-type lamins and barrier-to-autointegration factor (BAF) causing progeroid disorders are found at the interface between these interacting proteins. The amino acid changes decrease the binding affinity of A-type lamins for BAF, which may contribute to lamina disorganization, as well as defective repair of mechanically induced nuclear envelope rupture. Targeting these molecular alterations in A-type lamins and associated proteins identified through structural biology studies could facilitate the design of therapeutic strategies to treat patients with rare but severe progeroid laminopathies.