5-lipoxygenase activating protein signals adipose tissue inflammation and lipid dysfunction in experimental obesity.
The presence of the so-called low-grade inflammatory state is recognized as a critical event in adipose tissue dysfunction, leading to altered secretion of adipokines and free fatty acids (FFAs), insulin resistance, and development of hepatic complications associated with obesity. This study was designed to investigate the potential contribution of the proinflammatory 5-lipoxygenase (5-LO) pathway to adipose tissue inflammation and lipid dysfunction in experimental obesity. Constitutive expression of key components of the 5-LO pathway, as well as leukotriene (LT) receptors, was detected in adipose tissue as well as in adipocyte and stromal vascular fractions. Adipose tissue from obese mice, compared with that from lean mice, exhibited increased 5-LO activating protein (FLAP) expression and LTB(4) levels. Incubation of adipose tissue with 5-LO products resulted in NF-kappaB activation and augmented secretion of proinflammatory adipokines such as MCP-1, IL-6, and TNF-alpha. In addition, LTB(4), but not LTD(4), reduced FFA uptake in primary adipocytes, whereas 5-LO inhibition suppressed isoproterenol-induced adipose tissue lipolysis. In mice with dietary obesity, elevated FLAP expression in adipose tissue was paralleled with macrophage infiltration, increased circulating FFA levels, and hepatic steatosis, phenomena that were reversed by FLAP inhibition with Bay-X-1005. Interestingly, FLAP inhibition induced AMP-activated protein kinase phosphorylation in parallel with decreases in hormone-sensitive lipase activity and the expression and secretion of TNF-alpha and IL-6. Similar effects were observed in differentiated 3T3-L1 adipocytes incubated with either Bay-X-1005 or the selective LTB(4) receptor antagonist U-75302. Taken together, these findings indicate that the 5-LO pathway signals the adipose tissue low-grade inflammatory state and steatogenic potential in experimental obesity.
Horrillo
Raquel
R
Department of Biochemistry and Molecular Genetics, Hospital Clinic, August Pi i Sunyer Biomedical Research Institute, Esther Koplowitz Biomedical Research Center, University of Barcelona, Barcelona, Spain.
González-Périz
Ana
A
Martínez-Clemente
Marcos
M
López-Parra
Marta
M
Ferré
Natàlia
N
Titos
Esther
E
Morán-Salvador
Eva
E
Deulofeu
Ramon
R
Arroyo
Vicente
V
Clària
Joan
J
D058927:5-Lipoxygenase-Activating Proteins; D000273:Adipose Tissue / Q000378:metabolism* / Q000473:pathology; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D015777:Eicosanoids / Q000032:analysis / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D005227:Fatty Acids / Q000378:metabolism; D005234:Fatty Liver; D015870:Gene Expression; D020869:Gene Expression Profiling; D007150:Immunohistochemistry; D007249:Inflammation / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D050356:Lipid Metabolism; D008055:Lipids; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D016328:NF-kappa B / Q000378:metabolism; D009765:Obesity / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D020133:Reverse Transcriptase Polymerase Chain Reaction
D058927:5-Lipoxygenase-Activating Proteins; C548593:Alox5ap protein, mouse; D002352:Carrier Proteins; D016207:Cytokines; D015777:Eicosanoids; D005227:Fatty Acids; D008055:Lipids; D008565:Membrane Proteins; D016328:NF-kappa B