TNF-alpha interferes with lipid homeostasis and activates acute and proatherogenic processes.
The interaction between disrupted lipid homeostasis and immune response is implicated in the pathogenesis of several diseases, but the molecular bridges between the major players are still a matter of controversy. Our systemic study of the inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) in the livers of mice exposed to 20-h cytokine/fasting for the first time shows that TNF-alpha interferes with adaptation to fasting and activates harmful proatherogenic pathways, partially through interaction with the insulin-Insig-sterol regulatory element binding protein (Srebp) signaling pathway. In addition to the increased expression of acute-phase inflammatory genes, the most prominent alterations represent modified lipid homeostasis observed on the gene expression and metabolite levels. These include reduction of HDL-cholesterol, increase of LDL-cholesterol, and elevated expression of cholesterogenic genes, accompanied by increase of potentially harmful precholesterol metabolites and suppression of cholesterol elimination through bile acids, likely by farnesoid X receptor-independent mechanisms. On the transcriptional level, a shift from fatty oxidation toward fatty acid synthesis is observed. The concept of the influence of TNF-alpha on the Srebp regulatory network, followed by downstream effects on sterol metabolism, is novel. Observed acute alterations in lipid metabolism are in agreement with chronic disturbances found in patients.
Fon Tacer
Klementina
K
Center for Functional Genomics and Biochips, Institute of Biochemistry, Faculty of Medicine, University of Ljubljana, Slovenia.
Kuzman
Drago
D
Seliskar
Matej
M
Pompon
Denis
D
Rozman
Damjana
D
D000210:Acute-Phase Reaction / Q000235:genetics; D000818:Animals; D001647:Bile Acids and Salts / Q000096:biosynthesis; D002784:Cholesterol / Q000096:biosynthesis; D005215:Fasting / Q000502:physiology*; D005227:Fatty Acids / Q000378:metabolism; D025461:Feedback, Physiological; D006706:Homeostasis / Q000235:genetics; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D007249:Inflammation / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D007328:Insulin / Q000502:physiology; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D050356:Lipid Metabolism / Q000235:genetics / Q000502:physiology*; D008099:Liver / Q000187:drug effects; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D011994:Recombinant Proteins / Q000494:pharmacology; D013250:Steroid Hydroxylases / Q000096:biosynthesis / Q000235:genetics; D051779:Sterol Regulatory Element Binding Proteins / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology / Q000502:physiology*
D001647:Bile Acids and Salts; D005227:Fatty Acids; C506119:Insig1 protein, mouse; D007328:Insulin; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D011994:Recombinant Proteins; C102196:SREBP cleavage-activating protein; D051779:Sterol Regulatory Element Binding Proteins; D014409:Tumor Necrosis Factor-alpha; D002784:Cholesterol; D006903:Hydroxymethylglutaryl CoA Reductases; D013250:Steroid Hydroxylases