Aging Exacerbates Binge Ethanol-Mediated Bone Toxicity in Mice

Alcohol consumption and aging are factors promoting osteopenia and osteoporosis. How these factors interact is poorly understood. To investigate this relationship, a binge ethanol exposure model in mice was used to determine how aging affects skeletal responses to binge ethanol.

Dmp1-Cre TdTomato mice with the fluorescent marker TdTomato expressed in osteoblasts and osteocytes, and control mice without Cre expression were used. Mice of both sexes at 12 weeks and 78 weeks of age were gavaged for four consecutive days with 3, 3, 4, and 4.5 g of ethanol/kg of body weight or with PBS (control). Skeletal responses were determined by serum bone turnover markers using ELISA and by gene expression and protein measurement in the femoral shaft and lumbar vertebrae using qRT-PCR and western blots.

Ethanol and aging both significantly decreased serum levels of Procollagen Type I (P1NP) and osteocalcin, indicating reduced bone formation. Serum levels of C-terminal telopeptide of type I collagen (CTX-1) increased significantly with ethanol exposure in the aging mice, reflecting enhanced bone resorption. In the femoral shaft, ethanol and aging increased the expression of genes involved in osteoclast activation, Calcitonin receptor (Calcr) and RANKL, with a significantly larger induction of receptor activator of nuclear factor-κB ligand (RANKL) mRNA in 78-week-old than 12-week-old mice. Expression of osteoblast-associated genes, Collagen Type I Alpha 1 Chain (Col1a1), Collagen Type I Alpha 2 Chain (Col1a2), and Sphingomyelin phosphodiesterase 3 (Smpd3), was downregulated by ethanol, with stronger ethanol-mediated reduction in the 78-week-old than 12-week-old mice. Aging did not decrease the expression of TdTomato mRNA or TdTomato protein, indicating no overall loss of osteoblasts and osteocytes.

Binge ethanol exposure and aging independently and synergistically disrupt bone remodeling by inhibiting bone formation and enhancing bone resorption.