nth-old Sam68−/− mice in which all histomorphometric parameters, including marrow fat, resembled those of young mice of either genotype (Table 3). When cells were expressed as a function of the bone perimeter (nOB/BP, nOC/BP), there were no statistical differences and the ratio of osteoblasts to osteoclasts was similar in all groups of mice (Table 3).
Table 3  Histomorphometric Analysis of Long Bones from 4- and 12-Month-Old Mice Circulating levels of serum C-telopeptide (sCTX; Roche Diagnostics, Mannheim, Germany) and ALP showed little difference among the groups, except for a small decrease in 12-month-old Sam68−/− mice and (Dataset S3). Serum estrogen was significantly decreased in all 12-month-old mice regardless of genotype with a reciprocal increase in interleukin-6 levels (Dataset S3). Given the involvement of leptin in regulating body and bone mass, serum leptin was measured in Sam68+/+ and Sam68−/− mice. Twelve-month-old Sam68−/− mice had significantly lower levels than young and old Sam68+/+ mice and young Sam68−/− mice (Dataset S3). Taken together, these observations suggested that preservation of bone ma