Serum leptin levels decline substantially during fasting, largely through increased uptake across the blood brain barrier, into the hypothalamus [21]. This decline was observed in our WT mice during a 4 hour morning fast (Figure 4B), but was substantially enhanced in the Cyp1b1-ko mice, particularly when fed the LFD. This was accompanied by a loss of BW, which was more than doubled in the Cyp1b1-ko mice on the LFD (Figure 4D). This acceleration of BW loss in Cyp1b1-ko mice was similar to losses observed in WT mice after a 16 hour fast.
