Glycogen synthase kinase-3 regulates production of amyloid-ß peptides and tau phosphorylation in diabetic rat brain.

The pathogenesis of diabetic neurological complications is not fully understood. Diabetes mellitus (DM) and Alzheimer's disease (AD) are characterized by amyloid deposits. Glycogen synthase kinase-3 (GSK-3) plays an important role in the pathogenesis of AD and DM. Here we tried to investigate the production of amyloid-ß peptides (A ß) and phosphorylation of microtubule-associated protein tau in DM rats and elucidate the role of GSK-3 and Akt (protein kinase B, PKB) in these processes. Streptozotocin injection-induced DM rats displayed an increased GSK-3 activity, decreased activity and expression of Akt. And A ß 40 and A ß 42 were found overproduced and the microtubule-associated protein tau was hyperphosphorylated in the hippocampus. Furthermore, selective inhibition of GSK-3 by lithium could attenuate the conditions of A ß overproduction and tau hyperphosphorylation. Taken together, our studies suggest that GSK-3 regulates both the production of A ß and the phosphorylation of tau in rat brain and may therefore contribute to DM caused AD-like neurological defects.

[Mechanism of tau hyperphosphorylation in brain cortex of diabetic rats and effect of LiCl].

OBJECTIVE: To explore the mechanism of tau hyperphosphorylation and the effect of LiCl on tau phosphorylation and the memory retention deficits in streptozotocin-induced diabetes mellitus (DM) rats. METHODS: The rats were randomly divided into control, DM, DM + NaCl, and DM + LiCl groups and diabetes was induced by streptozotocin. The activity of glycogen synthase kinase-3 (GSK-3) was measured by 32P-labelling. The level of tau phosphorylated and changes of memory retention were examined by Western blotting and step down test, respectively. RESULTS: Compared with control group, the activity of GSK-3 and tau phosphorylation was increased, and the memory retention was impaired in DM group. When the rats were treated with LiCl, the activity of GSK-3 and hyperphosphorylation of tau were significantly arrested (P < 0.05, P < 0.01), and the memory retention deficit was significantly improved (P < 0.05). CONCLUSION: The hyperphosphorylation of tau can be induced by activation of GSK-3 in diabetic rats. Lithium protects tau from hyperphosphorylation and may rescue memory retention in the rats by inhibiting GSK-3 activity.

[Alteration of beta-amyloid and glutamate transporter in the brain of diabetes rats and the underlying mechanism].

OBJECTIVE: To investigate the alteration of beta-amyloid (Abeta) and glutamate transporter in the brain cortex of diabetes mellitus (DM) rats and the underlying mechanism. METHODS: The rats were randomly divided into control, DM, DM +NaCl, and DM +LiCl groups and diabetes was induced by streptozotocin. The activity of glycogen synthase kinase-3 (GSK-3) and the function of glutamate transporter were measured by 32P-labelling. The amount of Abeta was determined by enzyme-linked immunosorbentassay. RESULTS: In DM group, the level of Abeta40 increased (P < 0.01), but the function of glutamate transporter was impaired (P < 0.05). The activity of GSK-3 was stimulated (P < 0.05). Compared with DM group, the level of Abeta40 was restored (P < 0.01), and the function of glutamate transporter was enhanced (P < 0.05) in LiCl treated group, accompanied by a decreased activity of GSK-3. CONCLUSION: Overproduction of Abeta and impaired glutamate transporter exist in DM rats, and increase of GSK-3 may play a crucial role in this process.

Impact of low-dose urokinase in peritoneal dialysis on serum oxidative stress, nitric oxide and endothelin in cerebral infarction complicated with uremia.

BACKGROUND: Cerebrovascular accident is an important cause of death in patients with chronic renal failure. METHODS: This study evaluated the interference of low-dose urokinase in peritoneal dialysis solution on uremic serum superoxide dismutase (SOD), malondialdehyde (MDA), nitric oxide (NO) and endothelin (ET) dynamics in patients with a cerebral infarction complicated by uremia. RESULTS: Both the urokinase and conventional treatment groups showed decreased SOD activities, increased MDA content, and elevated serum NO and ET levels at the initiation stage of treatment. Antiplatelet and cerebral protection therapy slightly reduced body MDA content and increased SOD activity at the early stage of treatment, and its effects on reducing serum NO and ET-1 are also limited. CONCLUSION: Our results revealed that a small amount of urokinase in peritoneal dialysis can reduce body MDA content, increase SOD activity and decrease serum levels of NO and ET-1 at the early stage of cerebral infarction complicated by uremia. We also found that continuous treatment for 8 weeks may provide a potential treatment of cerebral infarction complicated with uremia.

The serum levels of MMP-9, MMP-2 and vWF in patients with low doses of urokinase peritoneal dialysis decreased uremia complicated with cerebral infarction.

To investigate the effect of MMP-9, MMP-2 and vWF in patients with low doses of urokinase peritoneal dialysis decreased uremia complicated with cerebral infarction. 112 cases of uremia complicated with cerebral infarction were randomly divided into the peritoneal dialysate with urokinase treatment group (66 cases) and the conventional treatment group (46 cases). At the same time, 50 cases of healthy people who were more than 45 years old were enrolled in the control group. The basic treatment in both treatment groups was the same. In urokinase therapy group based on the conventional treatment, urokinase was added into peritoneal dialysis fluid, and changes of serum MMP-9, MMP-2 and vWF were observed by drawing blood at different time points within 8 weeks. The changes of serum MMP-2, MMP-9 and vWF were detected by enzyme-linked immunosorbent assay. At the time of the onset of uremia complicated with cerebral infarction patients the serum MMP-9, MMP-2, vWF were significantly higher (P<0.05, P<0.05, P<0.01). Conventional antiplatelet therapy in brain protection only reduce MMP-9 to the normal range (P>0.05) within 8 weeks. But the MMP-2 and vWF cannot be reduced to the normal range (P<0.01, P<0.01). Low doses of urokinase can reduce MMP-9 (7 d) and MMP-2 (14 d) to the normal range (P>0.05, P>0.05) at the early stage and decrease the vWF to a normal range within 8 weeks (P>0.05). At the time of the onset of uremia complicated with cerebral infarction patients the serum MMP-9, MMP-2 and vWF increased significantly. Low doses of urokinase dialysis can reduce serum MMP-9, MMP-2, and vWF in acute uremia complicated with cerebral infarction without recurrence of cerebral infarction and cerebral hemorrhagic transformation, indicating that low dose of urokinase peritoneal dialysis may have a certain effect on the early treatment of this disease.