LEP and obesity due to melanocortin 4 receptor deficiency: Inasmuch as leptin and insulin are potent inhibitors of arcuate neuronal AgRP and NPY expression and activity under normal metabolic conditions [89,90,91,92], and these neurons lose their responsiveness to such leptin and insulin actions during high fat feeding and obesity [93,94,95,96,97], these present findings strongly imply an improvement in AgRP/NPY neuronal leptin and insulin sensitivity to reduce AgRP and NPY expression, even during prolonged high fat diet feeding by ZT 13 bromocriptine treatment.