title: Exacerbation of diabetic nephropathy by hyperlipidaemia is mediated by Toll-like receptor 4 in mice.
abstract: OBJECTIVE
  Hyperlipidaemia is an independent risk factor for the progression of diabetic nephropathy, but its molecular mechanism remains elusive. We investigated in mice how diabetes and hyperlipidaemia cause renal lesions separately and in combination, and the involvement of Toll-like receptor 4 (TLR4) in the process.
  
  
  METHODS
  Diabetes was induced in wild-type (WT) and Tlr4 knockout (KO) mice by intraperitoneal injection of streptozotocin (STZ). At 2 weeks after STZ injection, normal diet was substituted with a high-fat diet (HFD). Functional and histological analyses were carried out 6 weeks later.
  
  
  RESULTS
  Compared with treatment with STZ or HFD alone, treatment of WT mice with both STZ and HFD markedly aggravated nephropathy, as indicated by an increase in albuminuria, mesangial expansion, infiltration of macrophages and upregulation of pro-inflammatory and extracellular-matrix-associated gene expression in glomeruli. In Tlr4 KO mice, the addition of an HFD to STZ had almost no effects on the variables measured. Production of protein S100 calcium binding protein A8 (calgranulin A; S100A8), a potent ligand for TLR4, was observed in abundance in macrophages infiltrating STZ-HFD WT glomeruli and in glomeruli of diabetic nephropathy patients. High-glucose and fatty acid treatment synergistically upregulated S100a8 gene expression in macrophages from WT mice, but not from KO mice. As putative downstream targets of TLR4, phosphorylation of interferon regulatory factor 3 (IRF3) was enhanced in kidneys of WT mice co-treated with STZ and HFD.
  
  
  CONCLUSIONS
  Activation of S100A8/TLR4 signalling was elucidated in an animal model of diabetic glomerular injury accompanied with hyperlipidaemia, which may provide novel therapeutic targets in progressive diabetic nephropathy.
authors.affiliation: Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, 54 Shogoin Kawaharacho, Sakyoku, Kyoto, 606-8507, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Kuwabara
authors.forename: K
authors.initials: K
authors.lastname: Mori
authors.forename: M
authors.initials: M
authors.lastname: Mukoyama
authors.forename: M
authors.initials: M
authors.lastname: Kasahara
authors.forename: H
authors.initials: H
authors.lastname: Yokoi
authors.forename: Y
authors.initials: Y
authors.lastname: Saito
authors.forename: Y
authors.initials: Y
authors.lastname: Ogawa
authors.forename: H
authors.initials: H
authors.lastname: Imamaki
authors.forename: T
authors.initials: T
authors.lastname: Kawanishi
authors.forename: A
authors.initials: A
authors.lastname: Ishii
authors.forename: K
authors.initials: K
authors.lastname: Koga
authors.forename: K P
authors.initials: KP
authors.lastname: Mori
authors.forename: Y
authors.initials: Y
authors.lastname: Kato
authors.forename: A
authors.initials: A
authors.lastname: Sugawara
authors.forename: K
authors.initials: K
authors.lastname: Nakao
mesh_terms: D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000097:blood / Q000473:pathology*; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000473:pathology*; D003924:Diabetes Mellitus, Type 2 / Q000097:blood / Q000473:pathology*; D003928:Diabetic Nephropathies / Q000097:blood / Q000209:etiology / Q000473:pathology*; D018450:Disease Progression; D006801:Humans; D006949:Hyperlipidemias / Q000097:blood / Q000150:complications / Q000473:pathology*; D007668:Kidney / Q000473:pathology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D060888:Real-Time Polymerase Chain Reaction; D015398:Signal Transduction; D013311:Streptozocin / Q000494:pharmacology; D051197:Toll-Like Receptor 4 / Q000378:metabolism*
chemical_list: C495345:TLR4 protein, human; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D013311:Streptozocin