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Lipid droplets (LDs) are key subcellular organelles for regulating lipid metabolism. Although several subcellular organelles participate in lipid metabolism, it remains elusive whether physical contacts between subcellular organelles and LDs might be involved in lipolysis upon nutritional deprivation. Here, we demonstrate that peroxisomes and peroxisomal protein PEX5 mediate fasting-induced lipolysis by stimulating adipose triglyceride lipase (ATGL) translocation onto LDs. During fasting, physical contacts between peroxisomes and LDs are increased by KIFC3-dependent movement of peroxisomes toward LDs, which facilitates spatial translocations of ATGL onto LDs. In addition, PEX5 could escort ATGL to contact points between peroxisomes and LDs in the presence of fasting cues. Moreover, in adipocytespecific PEX5-knockout mice, the recruitment of ATGL onto LDs was defective and fastinginduced lipolysis is attenuated. Collectively, these data suggest that physical contacts between peroxisomes and LDs are required for spatiotemporal translocation of ATGL, which is escorted by PEX5 upon fasting, to maintain energy homeostasis.

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Oral steroid treatment is the first line of therapy for childhood nephrotic syndrome (NS). Nonetheless, some patients are resistant to this treatment. Many efforts have been made to explain the differences in the response to steroid treatment in patients with NS based on the genetic background. We have investigated single nucleotide polymorphisms of the MDR1 [C1236T (rs1128503), G2677T/A (rs2032582), and C3435T (rs1045642)] and MIF (G-173C, rs755622) genes in 170 children with NS. Of these children, 69 (40.6%) were initial steroid non-responders, and 23 (13.5% of total) developed chronic kidney disease. Renal biopsy findings, which were available for 101 patients, showed that 35 patients had minimal change lesion and 66 had focal segmental glomerulosclerosis. The frequencies of the MDR1 1236 CC (18.8 vs 7.2%) or TC (53.5 vs 43.5%) genotype and C allele (45.5 vs 29.0%) were significantly higher in the initial steroid responders than in the non-responders. Analysis of MDR1 three-marker haplotypes revealed that the frequency of the TGC haplotype was significantly lower in the initial steroid responders than in the non-responders (15.8 vs 29.0%). There was no association between the MIF G-173C polymorphism and clinical parameters, renal histological findings, and steroid responsiveness. These data suggest that the initial steroid response in children with NS may be influenced by genetic variations in the MDR1 gene.