FOXO1 and Glucose intolerance: Changes in muscle morphology and insulin sensitivity were noted, with a reduction in type II muscle fiber diameter and overexpression of forkhead Box O1 (FOXO1) protein resulting in glucose intolerance.(46) In the second model, significant reductions in lean mass, voluntary physical function, and grip strength in muscle‐specific VDRKO mice, underpinned by key morphologic changes in muscle fibers, were demonstrated.(47) The presence of central nucleoli in muscle fibers of knockout mice suggested an underlying defect in muscle repair in the absence of VDR.