Increment of subcutaneous adipose tissue is associated with decrease of elastic fibres in the dermal layer.

Obesity is a significant risk factor for various skin disorders, including pressure ulcer and delayed wound healing. We previously showed that increment of subcutaneous adipose tissue contributes to poor skin condition by decreasing dermal elasticity. Here, we examined the mechanism involved. Histologic observation of abdominal skin from middle-aged females with a wide range of body mass index (BMI), an indicator of subcutaneous fat mass, showed that dermal elastic fibre abundance was significantly decreased with increment of BMI. Concomitantly, adipocytes were significantly enlarged. Adipocyte enlargement was significantly negatively correlated with dermal elastic fibre abundance. We hypothesized that enlarged adipocytes negatively influence dermal elastic fibres, so we investigated elastic fibre-degrading factors in in vitro-cultured enlarged adipocytes. MMP9 gene expression and secretion were significantly increased; further, these changes were blocked by extracellular signal-regulated kinase (ERK) inhibitor. Nuclear translocation (activation) of AP-1, a downstream ERK signalling molecule, was also observed in enlarged adipocytes. MMP9 abundance was significantly increased in skin of subjects with high BMI and enlarged adipocytes. These results suggest that increment of subcutaneous adipose tissue leads to adipocyte enlargement together with increased degradation of dermal elastic fibres, mediated at least in part by an ERK signalling-mediated increase of MMP9 in enlarged adipocytes.