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 elucidate the spatiotemporal dynamics of TG synthesis and packaging in unilocular adipocytes, we labeled WAT explants with the fluorescent FFA analogue BODIPY-C12. Previously, we and others demonstrated that BODIPY-FFA is transported into in vitro–differentiated adipocytes and WAT explants by an insulin-stimulated mechanism (Li et al., 2005; Liao et al., 2005; Wu et al., 2006a, b; Varlamov et al., 2010, 2012, 2013; Somwar et al., 2011) and is esterified to BODIPY-TG in 3T3-L1 adipocytes (Sun et al., 2013). Confocal microscopy analysis unveiled a striking, previously unobserved staining pattern that appeared as clusters of bright fluorescent mLDs scattered around the surface of the cLD (Figure 2, A and D, green). Each group of mLDs was surrounded by a distinct ER patch (Figure 2, red, and Supplemental Video S1). Three-dimensional reconstitution of confocal scans revealed “eggs-in-a-nest”-like structures, with mLDs occupying spherical cavities within each ER patch (Figure 2, B and E).
Affiliation: Division of Endocrinology, Diabetes, and Clinical Nutrition, Department of Medicine, Portland, OR 97239.