RESUMO
OBJECTIVE: Accumulating epidemiological studies have demonstrated that diabetes is an important risk factor for dementia. However, the underlying pathological and molecular mechanisms, and effective treatment, have not been fully elucidated. Herein, we investigated the effect of the dipeptidyl peptidase-4 (DPP-4) inhibitor, linagliptin, on diabetes-related cognitive impairment. METHOD: Streptozotocin (STZ)-induced diabetic mice were treated with linagliptin (3 mg/kg/24 h) for 17 weeks. The radial arm water maze test was performed, followed by evaluation of oxidative stress using DNP-MRI and the expression of NAD(P)H oxidase components and proinflammatory cytokines and of microglial activity. RESULTS: Administration of linagliptin did not affect the plasma glucose and body weight of diabetic mice; however, it improved cognitive impairment. Additionally, linagliptin reduced oxidative stress and the mRNA expression of NAD(P)H oxidase component and TNF-α, and the number and body area of microglia, all of which were significantly increased in diabetic mice. CONCLUSIONS: Linagliptin may have a beneficial effect on diabetes-related dementia by inhibiting oxidative stress and microglial activation, independently of glucose-lowering.
Assuntos
Diabetes Mellitus Experimental/tratamento farmacológico , Inibidores da Dipeptidil Peptidase IV/uso terapêutico , Linagliptina/farmacologia , Microglia/metabolismo , Estresse Oxidativo/efeitos dos fármacos , Animais , Glicemia/análise , Peso Corporal/efeitos dos fármacos , Encéfalo/metabolismo , Diabetes Mellitus Experimental/induzido quimicamente , Inibidores da Dipeptidil Peptidase IV/farmacologia , Linagliptina/uso terapêutico , Peroxidação de Lipídeos/efeitos dos fármacos , Masculino , Aprendizagem em Labirinto/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Microglia/citologia , Microglia/efeitos dos fármacos , NADPH Oxidases/genética , NADPH Oxidases/metabolismo , Estreptozocina/toxicidade , Fator de Necrose Tumoral alfa/genética , Fator de Necrose Tumoral alfa/metabolismoRESUMO
Accumlating evidence have suggested that diabetes mellitus links dementia, notably of Alzheimer's disease (AD). However, the underlying mechanism remains unclear. Several studies have shown oxidative stress (OS) to be one of the major factors in the pathogenesis of diabetic complications. Here we show OS involvement in brain damage in a diabetic animal model that is at least partially mediated through an AD-pathology-independent mechanism apart from amyloid-ß accumulation. We investigated the contribution of the p66Shc signaling pathway to diabetes-related cognitive decline using p66Shc knockout (-/-) mice. p66Shc (-/-) mice have less OS in the brain and are resistant to diabetes-induced brain damage. Moreover, p66Shc (-/-) diabetic mice show significantly less cognitive dysfunction and decreased levels of OS and the numbers of microglia. This study postulates a p66Shc-mediated inflammatory cascade leading to OS as a causative pathogenic mechanism in diabetes-associated cognitive impairment that is at least partially mediated through an AD-pathology-independent mechanism.