Article

Diabetologia

, Volume 55, Issue 8, pp 2256-2266

First online:

Exacerbation of diabetic nephropathy by hyperlipidaemia is mediated by Toll-like receptor 4 in mice

  • T. KuwabaraAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine
  • , K. MoriAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine Email author 
  • , M. MukoyamaAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine
  • , M. KasaharaAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine
  • , H. YokoiAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine
  • , Y. SaitoAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine
  • , Y. OgawaAffiliated withDepartment of Nephrology, Osaka Redcross Hospital
  • , H. ImamakiAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine
  • , T. KawanishiAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine
    • , A. IshiiAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine
    • , K. KogaAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine
    • , K. P. MoriAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine
    • , Y. KatoAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine
    • , A. SugawaraAffiliated withDepartment of Nephrology, Osaka Redcross Hospital
    • , K. NakaoAffiliated withDepartment of Medicine and Clinical Science, Kyoto University Graduate School of Medicine

Abstract

Aims/hypothesis

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/interpretation

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.

Keywords

Diabetic nephropathy Glomerulus High-fat diet Hyperlipidaemia Macrophages S100A8 TLR4