Increased CD36 protein as a response to defective insulin signaling in macrophages.
Accelerated atherosclerosis is a major cause of morbidity and death in insulin-resistant states such as obesity and the metabolic syndrome, but the underlying mechanisms are poorly understood. We show that macrophages from obese (ob/ob) mice have increased binding and uptake of oxidized LDL, in part due to a post-transcriptional increase in CD36 protein. Macrophages from ob/ob mice are also insulin resistant, as shown by reduced expression and signaling of insulin receptors. Three lines of evidence indicate that the increase in CD36 is caused by defective insulin signaling: (a) Treatment of wild-type macrophages with LY294002, an inhibitor of insulin signaling via PI3K, results in an increase in CD36; (b) insulin receptor knockout macrophages show a post-transcriptional increase in CD36 protein; and (c) administration of thiazolidinediones to intact ob/ob mice and ob/ob, LDL receptor-deficient mice results in a reversal of macrophage insulin receptor defects and decreases CD36 protein. The last finding contrasts with the increase in CD36 that results from treatment of macrophages with these drugs ex vivo. The results suggest that defective macrophage insulin signaling predisposes to foam cell formation and atherosclerosis in insulin-resistant states and that this is reversed in vivo by treatment with PPAR-gamma activators.
Liang
Chien-Ping
CP
Department of Medicine, Division of Molecular Medicine, Columbia University, New York, New York 10032, USA. CL534@columbia.edu
Han
Seongah
S
Okamoto
Haruka
H
Carnemolla
Ronald
R
Tabas
Ira
I
Accili
Domenico
D
Tall
Alan R
AR
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D018955:CD36 Antigens / Q000096:biosynthesis*; D002867:Chromones / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005487:Foam Cells / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism; D007004:Hypoglycemic Agents / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D008077:Lipoproteins, LDL / Q000378:metabolism; D008264:Macrophages / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008820:Mice, Obese; D009025:Morpholines / Q000494:pharmacology; D010100:Oxygen / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D000077154:Rosiglitazone; D015398:Signal Transduction; D045162:Thiazolidinediones / Q000494:pharmacology; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D014443:Tyrosine / Q000378:metabolism
D018955:CD36 Antigens; D002867:Chromones; D004791:Enzyme Inhibitors; D007004:Hypoglycemic Agents; D007328:Insulin; D008077:Lipoproteins, LDL; D009025:Morpholines; D018160:Receptors, Cytoplasmic and Nuclear; D045162:Thiazolidinediones; D014157:Transcription Factors; D000077154:Rosiglitazone; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D014443:Tyrosine; C089946:2,4-thiazolidinedione; D019869:Phosphatidylinositol 3-Kinases; D005978:Glutathione; D010100:Oxygen