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

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.

[Physical dependence liability test of 4-(o-benzylphenoxy)-N-methylbutylamine hydrochloride (MCI-2016) in rats].

An acute administration of MCI-2016 at the doses of 30, 100 and 300 mg/kg (p.o.), and 10, 20 and 30 mg/kg (i.p.) produced a slight CNS depression in rats, such as, sedation, ptosis, decrease in motor activity and systemic muscle relaxation. In a direct physical dependence test, rats were fed the MCI-2016-admixed food together with drinking water ad libitum for 24 hours daily for 51-71 days (mean MCI-2016 intake 29.9-210.7 mg/kg/day), on the gradedly increased dosage schedule with a dosage level of 0.25 and 0.5 mg/g food to 4 mg/g food. In a natural withdrawal following administration of MCI-2016, no significant withdrawal signs were observed in any group. In a naloxone-precipitation test the rats that were treated with MCI-2016-admixed food did not show any withdrawal signs. In a substitution test in either morphine or barbital dependent rats, no suppression of withdrawal signs or maintenance of dependence were observed by cross-administration of MCI-2016. In conclusion, MCI-2016 was considered to have no physical dependence potential.