Lamin A/C deficiency is associated with fat infiltration of muscle and bone

Sarcopenia and osteopenia are two common components of the frailty syndrome that may share a common underlying mechanism. Since frailty has been associated with increased fat infiltration in muscle and bone, we hypothesized that lamin A/C, a protein of the nuclear envelope that regulates adipose differentiation, could be associated with the pathophysiology of both osteo and sarcopenia in the frailty syndrome. Four-week-old lamin A/C null (Lmna(-/-)), heterozygous (Lmna(+/-)) and wild type (WT) mice were sacrificed and their mid-thigh analyzed for fat infiltration using invasive (histology) and non-invasive (μCT) methods. Lmna(-/-) mice showed a significant increase in inter- (~4-fold) and intra-myofiber (~2.5-fold) fat and marrow fat infiltration (~40-fold), with a significant decrease in muscle volume (-42.8%) and bone volume (-21.8%), as compared with WT controls. Furthermore, fat infiltration happened concomitantly with a significant decline in muscle and bone strength in Lmna(-/-) mice. From a mechanistic approach, high levels of pro-adipogenic factors PPARγ and C/EBPα were associated with a reduction in myogenic and osteogenic factors from the Wnt-10b/β-catenin signalling pathway in Lmna(-/-) mice. In conclusion, lamin A/C could constitute the determinant factor in the pathogenesis and potential treatment of both sarcopenia and osteopenia, which are commonly observed in the frailty syndrome.