Figure 2.

Are ob/ob mice hypothermic?

(A) ob/ob mice have similar or even higher levels of energy expenditure than wild-type mice under thermoneutral conditions as well as under subthermoneutral conditions, at least on the C57BL/6 background. The limit of their thermoneutral zone, as indicated by the lower critical temperature (LCT), is similar in lean and ob/ob. (B) ob/ob mice have normal body temperature at thermoneutrality and defend a lower, but stable, body temperature when gradually exposed to subthermoneutral temperatures. (C, E) Differences in body temperature resulting from changes in the activation thresholds of thermoregulatory, but not behavioral, effectors. (D, F) Leptin-deficient ob/ob mice develop massive obesity because of excessive food intake, but not from reduced energy expenditure, which is similar or even higher than that in lean mice.