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Spatiotemporal dynamics of triglyceride storage in unilocular adipocytes.

Chu M, Sampath H, Cahana DY, Kahl CA, Somwar R, Cornea A, Roberts CT, Varlamov O - Mol. Biol. Cell (2014)

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.

View Article: PubMed Central - PubMed

Affiliation: Division of Endocrinology, Diabetes, and Clinical Nutrition, Department of Medicine, Portland, OR 97239.

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Cytoarchitecture of primary unilocular adipocytes. Visceral WAT explants were infected with an adenoviral vector encoding eGFP as described in Materials and Methods. On day 2 after infection, live explants were examined for GFP expression using confocal microscopy. cLD, central LD; Cyt, cytoplasm; LDM, lipid droplet membrane; mLD, micro-LD; N, nucleus; PM, plasma membrane. (A) A field of view shows GFP-positive unilocular adipocytes (spheres) and stromovascular cells (asterisks) residing in WAT. The image represents the sum of confocal slices. Bar, 10 μm. (B) Single confocal section of the image in A. Enlarged areas of adipocytes containing cytoplasmic nodules (C, D) and perinuclear cytoplasm (E) filled with GFP-negative spherical cavities. Bar, 5 μm. (F) Portion of the GFP-infected WAT explant shown at lower magnification. Bar, 50 μm. (G) Schematic representation of the spatial organization of a unilocular adipocyte. The cLD of a unilocular adipocyte represents a single sphere tightly fitted inside the cell, whereas the cytoplasm forms multiple nodules containing various organelles.
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Figure 1: Cytoarchitecture of primary unilocular adipocytes. Visceral WAT explants were infected with an adenoviral vector encoding eGFP as described in Materials and Methods. On day 2 after infection, live explants were examined for GFP expression using confocal microscopy. cLD, central LD; Cyt, cytoplasm; LDM, lipid droplet membrane; mLD, micro-LD; N, nucleus; PM, plasma membrane. (A) A field of view shows GFP-positive unilocular adipocytes (spheres) and stromovascular cells (asterisks) residing in WAT. The image represents the sum of confocal slices. Bar, 10 μm. (B) Single confocal section of the image in A. Enlarged areas of adipocytes containing cytoplasmic nodules (C, D) and perinuclear cytoplasm (E) filled with GFP-negative spherical cavities. Bar, 5 μm. (F) Portion of the GFP-infected WAT explant shown at lower magnification. Bar, 50 μm. (G) Schematic representation of the spatial organization of a unilocular adipocyte. The cLD of a unilocular adipocyte represents a single sphere tightly fitted inside the cell, whereas the cytoplasm forms multiple nodules containing various organelles.

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.


Spatiotemporal dynamics of triglyceride storage in unilocular adipocytes.

Chu M, Sampath H, Cahana DY, Kahl CA, Somwar R, Cornea A, Roberts CT, Varlamov O - Mol. Biol. Cell (2014)

Cytoarchitecture of primary unilocular adipocytes. Visceral WAT explants were infected with an adenoviral vector encoding eGFP as described in Materials and Methods. On day 2 after infection, live explants were examined for GFP expression using confocal microscopy. cLD, central LD; Cyt, cytoplasm; LDM, lipid droplet membrane; mLD, micro-LD; N, nucleus; PM, plasma membrane. (A) A field of view shows GFP-positive unilocular adipocytes (spheres) and stromovascular cells (asterisks) residing in WAT. The image represents the sum of confocal slices. Bar, 10 μm. (B) Single confocal section of the image in A. Enlarged areas of adipocytes containing cytoplasmic nodules (C, D) and perinuclear cytoplasm (E) filled with GFP-negative spherical cavities. Bar, 5 μm. (F) Portion of the GFP-infected WAT explant shown at lower magnification. Bar, 50 μm. (G) Schematic representation of the spatial organization of a unilocular adipocyte. The cLD of a unilocular adipocyte represents a single sphere tightly fitted inside the cell, whereas the cytoplasm forms multiple nodules containing various organelles.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4263452&req=5

Figure 1: Cytoarchitecture of primary unilocular adipocytes. Visceral WAT explants were infected with an adenoviral vector encoding eGFP as described in Materials and Methods. On day 2 after infection, live explants were examined for GFP expression using confocal microscopy. cLD, central LD; Cyt, cytoplasm; LDM, lipid droplet membrane; mLD, micro-LD; N, nucleus; PM, plasma membrane. (A) A field of view shows GFP-positive unilocular adipocytes (spheres) and stromovascular cells (asterisks) residing in WAT. The image represents the sum of confocal slices. Bar, 10 μm. (B) Single confocal section of the image in A. Enlarged areas of adipocytes containing cytoplasmic nodules (C, D) and perinuclear cytoplasm (E) filled with GFP-negative spherical cavities. Bar, 5 μm. (F) Portion of the GFP-infected WAT explant shown at lower magnification. Bar, 50 μm. (G) Schematic representation of the spatial organization of a unilocular adipocyte. The cLD of a unilocular adipocyte represents a single sphere tightly fitted inside the cell, whereas the cytoplasm forms multiple nodules containing various organelles.
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.

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.

View Article: PubMed Central - PubMed

Affiliation: Division of Endocrinology, Diabetes, and Clinical Nutrition, Department of Medicine, Portland, OR 97239.

Show MeSH
Related in: MedlinePlus