Spatiotemporal dynamics of triglyceride storage in unilocular adipocytes.
Bottom Line: Exogenously added free fatty acids are rapidly adsorbed by mLDs and concurrently get esterified to TG.This process is greatly accelerated by insulin. mLDs transfer their content to the cLD, serving as intermediates that mediate packaging of newly synthesized TG in the large interior of a unilocular adipocyte.This study reveals novel cell biological features that may contribute to the mechanism of adipocyte hypertrophy.
Affiliation: Division of Endocrinology, Diabetes, and Clinical Nutrition, Department of Medicine, Portland, OR 97239.Show MeSH
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Mentions: To achieve better understanding of intracellular organization of unilocular adipocytes, we infected visceral WAT explants of nonhuman primates with an adenoviral vector encoding enhanced green fluorescent protein (eGFP) and examined living tissue by confocal microscopy. GFP labeled the cytoplasm and nuclei of adipocytes and stromo-vascular cells (Figure 1, A–F, large spherical and fibroblast-like cells, respectively). The cytoplasm of unilocular adipocytes appeared as a series of perforated nodules scattered around the cell surface (Figure 1, A–D). In addition, a thicker cytoplasmic layer surrounded adipocyte nuclei (Figure 1E). Perforated nodules were connected by a thin layer of GFP-positive cytoplasm (Figure 1, B and C). Each nodule harbored fluorescence-negative cavities that appeared as uniformly sized spheres. We hypothesized that these spheres represent preexisting micro-LDs (mLDs) filled with lipids. cLDs of each adipocyte were fluorescence-free (Figure 1B). A schematic diagram representing the spatial organization of a unilocular adipocyte is given in Figure 1G.
Affiliation: Division of Endocrinology, Diabetes, and Clinical Nutrition, Department of Medicine, Portland, OR 97239.