Binds to lipid droplets and regulates their enlargement, thereby restricting lipolysis and favoring storage. At focal contact sites between lipid droplets, promotes directional net neutral lipid transfer from the smaller to larger lipid droplets. The transfer direction may be driven by the internal pressure difference between the contacting lipid droplet pair. Its role in neutral lipid transfer and lipid droplet enlargement is activated by the interaction with PLIN1. May act as a CEBPB coactivator in the white adipose tissue to control the expression of a subset of CEBPB downstream target genes, including SOCS1, SOCS3, TGFB1, TGFBR1, ID2 and XDH. When overexpressed in preadipocytes, induces apoptosis or increases cell susceptibility to apoptosis induced by serum deprivation or TGFB treatment. As mature adipocytes, that express high CIDEC levels, are quite resistant to apoptotic stimuli, the physiological significance of its role in apoptosis is unclear. May play a role in the modulation of the response to osmotic stress by preventing NFAT5 to translocate into the nucleus and activate its target genes expression. a triacyl-sn-glycerol(in) = a triacyl-sn-glycerol(out) Homodimer. Interacts with CIDEA. Interacts with NFAT5; this interaction is direct and retains NFAT5 in the cytoplasm (By similarity). Interacts with CEBPB. Interacts with PLIN1. Diffuses quickly on lipid droplet surface, but becomes trapped and clustered at lipid droplet contact sites, thereby enabling its rapid enrichment at lipid droplet contact sites. Expressed almost exclusively in adipose tissue, including subcutaneous and epididymal white adipose tissue (at protein level). Although abundantly present in brown adipose tissue at the mRNA level, the protein is almost undetectable in this tissue (PubMed:18654663), or at moderate levels (PubMed:22245780, PubMed:12910269). Expressed in the mammary gland, in stromal adipose tissue, but becomes undetectable at the end of pregnancy and during lactation (at protein level). Expressed at low levels in skeletal muscle and heart. Up-regulated during differentiation into adipocytes in various cell lines, including TA1 and 3T3-L1. Decreases in the mammary gland during pregnancy from day 14.5 until 18.5, when it becomes hardly detectable, and during lactation. Up-regulated under conditions that enhance triacylglycerol deposition, including rosiglitazone treatment and high-fat diet. This up-regulation is mediated by PPARG. Up-regulated by isoproterenol, a beta-agonist, and oleic acid treatment. This induction is due to protein stabilization. Down-regulated upon hypertonic conditions. The CIDE-N domain is involved in homodimerization which is crucial for its function in promoting lipid exchange and transfer. Ubiquitinated and targeted to proteasomal degradation, resulting in a short half-life (about 15 minutes in 3T3-L1 cells). Protein stability depends on triaclyglycerol synthesis, fatty acid availability and lipid droplet formation. Mutant animals are born in a Mendelian ratio and appear physically normal at birth. The body weights of wild-type and mutant mice fed a standard diet do not differ up to 14 weeks of age, nor does food intake. From 16 weeks of age, the body weight of mutant mice significantly decreases compared with that of wild-type mice. When animals are fed a high-fat diet, the gain in body weight is significantly smaller for mutant mice than for wild-type. Under these feeding conditions, mutant mice are also protected from insulin resistance and from accumulation of fat in the liver. The body temperature do not differ significantly between mutant and wild-type mice maintained at room temperature, but the basal rate of oxygen consumption is significantly increased in mutants.