DFCP1 associates with lipid droplets.

Double FYVE-containing protein 1 (DFCP1) is ubiquitously expressed, participates in intracellular membrane trafficking and labels omegasomes through specific interactions with phosphatidylinositol-3-phosphate (PI3P). Previous studies showed that subcellular DFCP1 proteins display multi-organelle localization, including in the endoplasmic reticulum (ER), Golgi apparatus and mitochondria. However, its localization and function on lipid droplets (LDs) remain unclear. Here, we demonstrate that DFCP1 localizes to the LD upon oleic acid incubation. The ER-targeted domain of DFCP1 is indispensable for its LD localization, which is further enhanced by double FYVE domains. Inhibition of PI3P binding at the FYVE domain through wortmannin treatment or double mutation at C654S and C770S have no effect on DFCP1's LD localization. These show that the mechanisms for DFCP1 targeting the omegasome and LDs are different. DFCP1 deficiency in MEF cells causes an increase in LD number and reduces LD size. Interestingly, DFCP1 interacts with GTP-bound Rab18, an LD-associated protein. Taken together, our work demonstrates the dynamic localization of DFCP1 is regulated by nutritional status in response to cellular metabolism.

Control of lipid droplet fusion and growth by CIDE family proteins.

Cell death-inducing DFF45-like effector (CIDE) family proteins including Cidea, Cideb and Cidec/Fsp27 are expressed in many different tissues and are known as lipid droplet (LD)-and ER-associated proteins. Systematic analyses using genetically modified animal models have demonstrated that CIDE proteins play important roles in regulating various aspects of lipid homeostasis, including lipid storage, lipolysis and lipid secretion. Recent research in ours and other laboratories has revealed that CIDE proteins are crucial regulators of LD fusion and growth in the adipose tissue, liver, skin and mammary glands. CIDE-mediated LD fusion and growth is different from other membrane fusions in that it requires CIDE proteins to be enriched and clustered at the LD-LD contact sites (LDCS). The enriched CIDE proteins then allow the recruitment of other proteins to the LDCS and the formation of potential fusion pores. Neutral lipids in the smaller LDs of the contacted pair are transferred to the larger LDs, owing to the internal pressure difference, thus resulting in the fusion and growth of the LDs. This review summarizes the physiological roles of CIDE proteins in controlling lipid homeostasis, insulin sensitivity and the development of metabolic diseases including obesity, diabetes and fatty liver, with a particular focus on the role of CIDE proteins in controlling LD fusion and growth. This article is part of a Special Issue entitled: Recent Advances in Lipid Droplet Biology edited by Rosalind Coleman and Matthijs Hesselink.

The progress and challenges in metabolic research in China.

Metabolism refers to a chain of chemical reactions converting food/fuel into energy to conduct cellular processes, including the synthesis of the building blocks of the body, such as proteins, lipids, nucleic acids, and carbohydrates, and the elimination of nitrogenous wastes. Metabolic chain reactions are catalyzed by various enzymes that are orchestrated in specific pathways. Metabolic pathways are important for organisms to grow and reproduce, maintain their structures, and respond to their environments. The coordinated regulation of metabolic pathways is important for maintaining metabolic homeostasis. The key steps and crucial enzymes in these pathways have been well investigated. However, the crucial regulatory factors and feedback (or feedforward) mechanisms of nutrients and intermediate metabolites of these biochemical processes remain to be fully elucidated. In addition, the roles of these enzymes and regulatory factors in controlling metabolism under physiological and pathological conditions are largely unknown. In particular, metabolic dysregulation is closely linked to the development of many diseases, including obesity, fatty liver, diabetes, cancer, cardiovascular, cerebrovascular, and neurodegenerative diseases. Therefore, metabolism, an old area of biochemistry, has attracted much attention in the last decade. With substantially increased government funding, the involvement of talented researchers, an improved infrastructure and scientific environment over the last ten years, the basic research in the field of metabolism in China has dramatically advanced. Here, we have summarized the major discoveries of scientists in China in the last decade in the area of metabolism. Due to the vast amount of information, we focused this review on specific aspects of metabolism, particularly metabolic regulation and lipid metabolism in vertebrates. © 2016 IUBMB Life, 68(11):847-853, 2016.

Enhanced effect of daytime restricted feeding on the circadian rhythm of streptozotocin-induced type 2 diabetic rats.

There is increasing awareness of the link between impaired circadian clocks and multiple metabolic diseases. However, the impairment of the circadian clock by type 2 diabetes has not been fully elucidated. To understand whether and how the function of circadian clock is impaired under the diabetic condition, we examined not only the expression of circadian genes in the heart and pineal gland but also the behavioral rhythm of type 2 diabetic and control rats in both the nighttime restricted feeding (NRF) and daytime restricted feeding (DRF) conditions. In the NRF condition, the circadian expression of clock genes in the heart and pineal gland was conserved in the diabetic rats, being similar to that in the control rats. DRF shifted the circadian phases of peripheral clock genes more efficiently in the diabetic rats than those in the control rats. Moreover, the activity rhythm of rats in the diabetic group was completely shifted from the dark phase to the light phase after 5 days of DRF treatment, whereas the activity rhythm of rats in the control group was still under the control of the suprachiasmatic nucleus (SCN) after the same DRF treatment. Furthermore, the serum glucose rhythm of type 2 diabetic rats was also shifted and controlled by the external feeding schedule, ignoring the SCN rhythm. Therefore, DRF shows stronger effect on the reentrainment of circadian rhythm in the type 2 diabetic rats, suggesting that the circadian system in diabetes is unstable and more easily shifted by feeding stimuli.