Researchers have released what is possibly the most complex, time-lapse video of a functioning cell. The cell, taken from the kidney of an African green monkey, was analyzed with dyes, fluorescent proteins and a laser scanning microscope. The video shows the movement of fat droplets throughout the cell, and is color coded to indicate which oraganelles - the subunits of cells - are which. To make the video, the researchers tagged the cells' different organelles with proteins that glow different colors in light. They tracked 6 different organelles, which are color coded in the video: Lysosomes (cyan), mitochondria (green), endoplasmic reticulum (yellow), peroxisomes (red), Golgi apparatus (magenta) and Lipid (fat) droplets (blue).
Adipose (fat) tissue is a major site of energy storage that responds to fluctuations in nutrient availability to maintain systemic metabolic homeostasis (1). Adipocytes take up circulating free fatty acids (FFAs) from the blood and store them in lipid droplets in response to increased insulin concentrations (which occur after feeding); they then hydrolyze lipids to release FFAs under conditions of nutrient deprivation. A variety of other cell types are present within adipose tissue, including fibroblasts, endothelial cells, and adipose tissue macrophages (ATMs). In addition to their roles in immune surveillance and clearance of cellular debris, ATMs are important for lipid buffering and regulate adipose tissue function in both healthy and diseased states (2). Owing to the rising global incidence of chronic obesity and associated health issues, there is renewed interest in understanding how adipose tissue functions in physiological and pathological settings.
Toxoplasma parasites (blue), shown here in their encysted stage within liver tissue, compete with mitochondria for lipids. Mitochondria provide platforms for innate immunity. Pernas et al. wanted to understand the role of mitochondrial morphology in the control of Toxoplasma growth. They discovered that parasite-infected cells displayed a marked reduction in host lipid droplets caused by Toxoplasma-induced droplet autophagy (lipophagy). Fatty acid flux analysis revealed the path of fatty acids from the droplets to the Toxoplasma-containing vacuole.
Fat tissue is essential for the safe storage of excess calories and thereby plays a key role in metabolic health. By storing lipid droplets, fat cells (adipocytes) protect organs from the damaging effects of ectopic lipid accumulation (1). Understanding how to promote healthy fat expansion may therefore reveal treatments for obesity and related diseases. Such expansion depends on the formation of new adipocytes from progenitor cells within fat tissue (2). Distinct populations of adipocyte progenitor cells (APCs) have been identified, but their interrelationships and relevance to physiological and pathological fat expansion have remained poorly understood (3).
Inside a white fat cell sits a single large lipid (fat) droplet and not much else. That fatty deposit gives the cell its color and claim to fame, storing energy and providing a nice cushion for our internal organs. It also produces a whole bunch of hormones, like estrogen and leptin (which regulates hunger), and contain receptors for others like insulin.