http://www.jbc.org/content/266/17/11341.full.pdf

Perilipin, a major hormonally regulated adipocyte-specific phosphoprotein associated with the periphery of lipid storage droplets.

Potential mechanism of insulin action on glucose transport in the isolated rat diaphragm. Apparent translocation of intracellular transport units to the plasma membrane.

Regulation of Wnt signaling during adipogenesis.

Adipose cell hyperplasia and enhanced glucose disposal in transgenic mice overexpressing GLUT4 selectively in adipose tissue.

Insulin-stimulated translocation of glucose transport systems in the isolated rat adipose cell. Time course, reversal, insulin concentration dependency, and relationship to glucose transport activity.

A method is described for preparing isolated rat adipose cells for electron microscopy. The ultrastructure of such cells and their production of 14CO2 from U-glucose-14C were studied simultaneously in the presence of insulin or epinephrine. Each adipose cell consists of a large lipid droplet surrounded by a thin rim of cytoplasm. In addition to typical subcellular organelles, a variety of small lipid droplets and an extensive system of membranes characterize the cell's cytoplasm. A fenestrated envelope surrounds the large, central lipid droplet. Similar envelopes surround cytoplasmic lipid droplets occurring individually or as aggregates of very small, amorphous droplets. Groups of individual droplets of smaller size also occur without envelopes. The system of membranes consists of invaginations of the cell membrane, vesicles possibly of pinocytic origin, simple and vesiculated vacuoles, vesicles deeper in the cytoplasm, flattened and vesicular smooth surfaced endoplasmic reticulum, and Golgi complexes. Neither insulin nor epinephrine produced detectable ultrastructural alterations even when cells were incubated under optimal conditions for the stimulation of 14CO2 evolution. Structural responses of the isolated adipose cell to hormones, if such occur, must, therefore, be dynamic rather than qualitative in nature; the extensive system of smooth surfaced membranes is suggestive of compartmentalized transport and metabolism.

/pdf/structure-function-relationships-in-the-adipose-cell-i-3qztbj4xue.pdf

Structure-function relationships in the adipose cell. I. Ultrastructure of the isolated adipose cell

Pinocytic activity in the adipose cell has been examined by measuring the uptake of colloidal gold. Pinocytic activity occurs in the isolated adipose cell under all experimental conditions; a portion of the vesicular elements of the cell can be identified by electron microscopy as pinocytic in origin. The isolated adipose cell appears to take up serum albumin by pinocytosis. Pinocytic activity in the isolated adipose cell is enhanced by epinephrine, but not by insulin. The relationship between pinocytosis and the metabolic activity of the adipose cell has been studied by measuring simultaneously the uptake of radioactive colloidal gold, the incorporation of (14)C-counts from U-glucose-(14)C into CO(2), total lipid, triglyceride glycerol and triglyceride fatty acids, and the release of nonesterified fatty acids in the absence of hormones and in the presence of insulin or epinephrine. Correlations between hormone-produced alterations in lipid metabolism and in pinocytic activity suggest that intracellular nonesterified fatty acid levels are a factor in the regulation of both the cell's pinocytic activity and its metabolism and that pinocytosis in the adipose cell functions in the extracellular-intracellular transport of nonesterified fatty acids.

https://rupress.org/jcb/article-pdf/46/2/342/1263364/342.pdf

Structure-function relationships in the adipose cell. II. Pinocytosis and factors influencing its activity in the isolated adipose cell.

Serum albumin stimulates the uptake of U-glucose-(14)C and the incorporation of (14)C-counts into triglyceride glycerol and inhibits the incorporation of (14)C-counts into triglyceride fatty acids by isolated adipose cells; insulin and epinephrine enhance these effects. In the absence of hormones, these responses to albumin increase with increasing albumin concentration. In the presence of insulin, a qualitatively similar pattern of increasing responses to albumin is observed; the enhancement of each response by insulin is, however, only slightly potentiated by higher albumin concentrations. In contrast, in the presence of epinephrine, these responses to albumin are maximal at the lowest albumin concentration tested, 0.1%; the enhancement of each response by epinephrine is similarly maximal at 0.1% albumin, but decreases rapidly as the albumin concentration is raised. Increasing serum albumin concentrations do, however, stimulate the release of fatty acids and glycerol by epinephrine-treated cells increasingly until a plateau, determined by the epinephrine dose, is reached. These data support the suggestion that intracellular fatty acid levels function in the regulation of adipose cell activity, and further suggest that serum albumin plays a role in determining the metabolic fate of these fatty acids.

https://rupress.org/jcb/article-pdf/46/2/354/1263488/354.pdf

STRUCTURE-FUNCTION RELATIONSHIPS IN THE ADIPOSE CELL III. Effects of Bovine Serum Albumin on the Metabolism of Glucose and the Release of Nonesterified Fatty Acids and Glycerol by the Isolated Adipose Cell

Samuel W. Cushman

Papers

Structure-function relationships in the adipose cell. I. Ultrastructure of the isolated adipose cell

Structure-function relationships in the adipose cell. II. Pinocytosis and factors influencing its activity in the isolated adipose cell.

STRUCTURE-FUNCTION RELATIONSHIPS IN THE ADIPOSE CELL III. Effects of Bovine Serum Albumin on the Metabolism of Glucose and the Release of Nonesterified Fatty Acids and Glycerol by the Isolated Adipose Cell