To investigate the ameliorative effect of deferoxamine (DFO) on cognitive impairment in a rat model of type 1 diabetes mellitus (T1DM) and to elucidate the molecular mechanisms underlying cerebral iron overload in T1DM rats.

Thirty-six healthy male SD rats (weighing 180~250 g) were randomly assigned into a blank control group (Ctrl), a T1DM model group and a DFO group, with 12 rats in each group. A single dose of 65 mg/kg streptozotocin (STZ) was intraperitoneally injected to the rats to establish a T1DM model, and those with fasting blood glucose ≥16.7 mmol/L at 3 d later were designated as the T1DM group. Intracerebroventricular administration of DFO (5 μg/kg·d) was given to the DFO group for 28 consecutive days since 21 d after STZ injection. Morris water maze test was carried out to assess the spatial learning and memory abilities. Nissl staining and immunofluorescence assay were applied to observe neuronal morphology and number in the hippocampus and cortex. The iron content in the hippocampus was measured with inductively coupled plasma mass spectrometry (ICP-MS). The expression levels of iron metabolism related proteins were detected with Western blotting.

In the T1DM group, significant declines in learning and memory abilities (P<0.01) and impaired neuronal morphology and reduced neuronal counts in the hippocampal CA1 region (P<0.01), CA3 region (P<0.01), and cortex (P<0.05) were observed when compared with those in the Ctrl group. ICP-MS analysis showed a marked increase in the hippocampal iron content in the T1DM group (P<0.01). Western blot results demonstrated that T1DM rats exhibited obviously up-regulated expression of iron storage proteins FTH and FTL in both the hippocampus (P<0.01, P<0.05) and the cortex (P<0.05, P<0.01), enhanced expression of iron import protein DMT1 in both the hippocampus and the cortex (P<0.05), while decreased expression of iron export protein FPN1 in the hippocampus (P<0.01) and the cortex (P<0.05). DFO treatment significantly ameliorated all above abnormalities.

The declines in learning and memory in T1DM rats are closely associated with neuronal damage induced by cerebral iron overload. Iron import protein DMT1 and export protein FPN1 jointly regulate cerebral iron content in T1DM rats. DFO reduces brain iron levels and mitigates iron overload-mediated neuronal injury by modulating the expression of DMT1 and FPN1.