Thiamine Deficiency Induces Alzheimer's-like Pathology In C57 Mice And Benfotiamine Ameliorates Cognitive Dysfunction And Pathologic Alterations In APP/PS1 Transgenic Mice

Alzheimer's disease is the most prevalent neurodegenerative disorder marked by memory loss and cognitive impairment that occurred mainly in elder people.The etiology of AD is stilled to be clarified.Current drugs for AD do not prevent or reverse the disease,and provide only modest symptomatic benefits.Hitherto, hyperglycemia and diabetes mellitus has been considered as the independent risk of development of AD.The impairments of AD patients in cerebral glucose utilization and energy metabolism represent very early abnormalities that precede or accompany the initial stages of cognitive impairment.Animal experiments also suggested that abnormality of cerebral glucose metabolism could be the key etiological factor. Declined energy metabolism induced dysfunction of brain and mitochondria,which triggers generation of reactive oxygen species.Further studies on enzyme activity involved in abnormality of cerebral glucose utilization and energy metabolism demonstrated that the most significant reduction of enzymes activities occurred in thiamine-dependent enzymes,such as pyruvate dehydrogenase,α-ketoglutarate dehydrogenase,and transketolase.The highest correlation with the clinical state was with pyruvate dehydrogenase andα-ketoglutarate dehydrogenase.Epidemiology survey showed that lower thiamine pyrophosphate concentrations in elderly people appeared to be related more to age itself than to co-existent illnesses.Gold's study found that a significantly higher number of AD patients had plasma thiamine deficiencies than PD patients.Experimental research also indicated that thiamine deficiency(TD) promoted brain Aβdeposit in APP/PS1 transgenic mouse model.All these studies suggested that TD or abnormal metabolism of thiamine and reduced thiamine-dependent enzymes activities may play an important role in development of AD.However,nobody knows whether TD can induces brain Aβdeposit and tau hyperphosphorylation in non-transgenic mouse.Herein,we investigate the effect of TD on brain Aβdeposition and tau hyperphosphorylation in wild mouse.In addition, clinicla trial has demonstrated that thiamine supplement does not exhibit any prevention and treatment to AD.Could the lipid-soluble derivates of thiamine that possess better biological availability and effect ameliorate dysfunction of mitochondria and cerebral energy metabolism,rivalry oxidative injury,and diminish the pathological lesions? We first established TD mouse model and explored the effects of TD on Aβdeposition and tau hyperphosphorylation.The second part of the study was designed to test whether 8-week treatment of benfotiamine in double-transgenic APP/PS1 mice could lead to behavioral improvement and pathologic lesions reduction.Part 1.Thiamine Deficiency Induces AβDeposition and Tau HyperphosphorylationAim:To explore the effects of TD on Aβdeposition and tau hyperphosphorylation.Methods:TD animal model was produced by administrating thiamine-deprived diet combined with daily intraperitoneal injections of pyrithiamine.The control mice were fed with thiamine-containing diet and injecting saline intraperitoneally.All animals were sacrificed and the brain tissues were obtained at 13th day after treatment.The pathological lesions of vulnerable regions in brain were observed by HE staining.Aβdeposition,tau hyperphosphorylation and P-secretase expression were observed by immuno-histochemical staining.Results:TD led to pathological lesions characterized by symmetric petechial hemorrhage mainly in submedian thalamus,and induced Aβdeposition in cortex, hippocampus and thalamus.As the vulnerable regions of TD,thalamus exhibited more Aβdeposition.TD also exacerbated tau hyperphosphorylation and up-regulatedβ-secretase expression.Control mice did not appear any damage of brain region neither did Aβdeposition.Meanwhile,phosphorylated tau andβ-secretase positive cells were significantly lower than that of TD mice(P<0.05).Conclusion:TD could induce Aβdeposition and promoted tau hyperphosphorylation. The up-regulateion of P-secretase expression may be involved in Aβdeposition induced by TD.Part 2.Benfotiamine Ameliorates Cognitive Dysfunction and Pathologic Alterations in APP/PS1 transgenic MiceAim:To investigate whether benfotiamine could lead to behavioral improvement and pathologic lesions reduction in double-transgenic APP/PS1 mice.Methods:Twenty-week-old male APP/PS1 double-transgenic mice were divided into six groups,which were control group(0.7%CMC),fursutiamine group(100mg/kg),huperzine group(66.7ug/kg),and high-dose group(200mg/kg),moderate-dose group(100mg/kg), and low-dose group(50mg/kg) of benfotiamine.Mice of each group were intragastrically administrated daily with the above drugs for eight weeks.At the end of the period,half mice of each group were subjected to observe recognitive testing by morris water maze.The other half were sacrificed for investigate Aβdeposition and tau hyperphosphorylation by immuno-histochemical staining.Results:In probe trials conducted 24h after the last training trial,200mg/kg group and 100mg/kg group of benfotiamine and huperzine group exhibited more frequency of platform location crosses compared to control group(P<0.01).Although 50mg/kg group of benfotiamine and fursutiamine group also increase the numbers of crossing the platform,they showed no significant deference compared to control group.All the benfotiamine groups and huperzine group spent more time and path inⅣquadrant compared to control group(P<0.01),but fursutiamine group showed no significant deference compared to control group.The control group exhibited more Aβdeposition. Huperzine group and fursutiamine group showed no significant deference compared to control group.50mg/kg group of benfotiamine exhibited less Aβaccumulation compared to control group(P<0.05),while 200mg/kg group and 100mg/kg group of benfotiamine reduced Ap deposition significantly(P<0.01).All benfotiamine groups and huperzine group reduced tau pathology in the cortex significantly(huperzine group,P<0.05;benfotiamine groups,P<0.01),but fursutiamine group showed no significant deference compared to control group.Conclusion:Benfotiamine demonstrated the efficiency to ameliorates cognitive dysfunction and pathologic alterations in APP/PS1 transgenic mice.