INS and obesity due to melanocortin 4 receptor deficiency: In high fat-diet-induced obesity models beginning at 4 weeks of age, treatment with the FABP4 inhibitor for 4 weeks improved insulin sensitivity in 24-week-old mice [33], which had severe macrophage infiltration in adipose tissue, but not in 20-week-old mice, which had much less macrophage accumulation in adipose tissue (Furuhashi M and Hotamisligil GS.