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The storage and mobilization of lipid energy are central functions of adipocytes. Lipid energy is stored as triglyceride in lipid droplet structures that are now recognized as hona fide organelles and whose functions are greatly influenced by members of the perilipin family of lipid droplet scaffolds. Recent work indicates that the signaling events underlying fatty acid mobilization involve protein trafficking to a specialized subset of lipid droplets. Furthermore, the core lipolytic machinery is composed of evolutionarily conserved proteins whose functions are conserved in avian and mammalian production species. Lipolysis affects many aspects of animal nutrition and physiology, which can have an important influence on growth efficiency, lactation, and meat quality. This review focuses on recent research that addresses the organization and trafficking of key players in hormone-stimulated lipolysis, and the central role of perilipin 1A in adipocyte lipolysis. The review emphasizes recent work frpm the laboratories of the authors that utilizes imaging techniques to explore the organization and interactions among lipolytic effectors in live cells during lipolytic activation. A mechanistic understanding of lipolysis may lead to new strategies for promoting human and animal health. [ABSTRACT FROM AUTHOR]

Previous research has implicated linseed oil in altering lipid metabolism of dairy cattle when infused intravenously as lipid emulsion. The objective was to determine the effects of abomasal linseed oil (LO) infusion on liver triglyceride (TG) accumulation and subcutaneous adipose tissue lipolysis during fatty liver induction. Eight nonpregnant, nonlactating Holstein cows were randomly assigned to treatments in a replicated 4 x 4 Latin square design. Treatments included abomasal infusion of water (W), tallow (T), LO, or half tallow plus half LO (LOT) at a rate of 0.56 g/kg BW per day for 4 d. Daily treatments were administered directly into the abomasum, divided into 6 doses and administered every 4 h. Infusion of treatments was concurrent with a 4 d fast. Cows were fed ad libitum for 24 d between periods of fasting and lipid infusion. T contained 43% C18:1, 24% C16:0 and 14% C18:0. LO contained 51% C18:3, and 17% C18:2. For most parameters, contrasts were: W vs. LO + LOT + T (effect of lipid), LO vs. T (linear effect of LO), and LOT vs. LO + T (nonlinear dose effect of LO). For measurement of blood fatty acid composition, differences among treatment means were determined using the PDIFF procedure of PROC MIXED. Infusion of linseed oil (LO or LOT) increased α-linolenic acid (g/100 g fatty acid) in serum (P < 0.05) but not in the nonesterified fatty acid (NEFA) fraction of plasma. Treatments had no effect on plasma NEFA concentrations. Infusion of LO increased total serum fatty acid concentration (nonlinear dose effect; P = 0.06). Abomasal infusion of lipid significantly increased isoproterenol stimulated lipolysis by subcutaneous adipose tissue explants in vitro. Liver TG content increased 4.8, 4.9, 2.3 and 2.3 μg TG/ μg of DNA during the fast for W, LO, LOT and T, respectively; infusion of lipid decreased liver TG accumulation (P = 0.06) when compared to W, but this was due to T (LO vs. T; P = 0.03). Abomasal LO infusion failed to reduce liver TG accumulation, plasma NEFA concentration or alter subcutaneous adipose tissue lipolysis. [ABSTRACT FROM AUTHOR]