Metformin and dietary restriction pathway are associated with neuroprotection in Alzheimer’s disease context. A key role for glial autophagy

Abstract

AbstractBackgroundThe global rise of type 2 diabetes and obesity prevalence has elicited a great interest in understanding how changes in metabolic function lead to premature brain aging. The inflammation and insulin resistance interplay represent a potential target to prevent neurodegeneration.MethodWe evaluated the effect of the antidiabetic drug metformin‐considered a dietary restriction (DR) mimetic‐ on patients enrolled in ADNI, an observational and longitudinal study including patients from all around the world. We employed data from patients diagnosed with mild cognitive impairment (MCI) due to AD and we performed a principal component analysis focusing on biomarkers associated to AD measured in cerebrospinal fluid.We analyzed memory performance and hippocampal alterations in a model of AD, the PDAPP‐J20 transgenic mouse (Tg) and evaluated the effects of a periodic DR protocol (3 cycles of 40% DR for 5 days and ad libitum diet for 9 days).ResultMCI metformin‐treated patients were characterized as subjects with a better CSF biomarkers profile than the mean population of MCI patients (p<0.05). Control subjects and T2D patients were paired by age, gender, ApoE allele and education, defining three groups: MCI, MCI+T2D and MCI+T2D+metformin. We evaluated the effect of T2D and metformin treatment employing the PACC score and composites defined from standardized ADNI variables to evaluate the memory/learning function. We found that MCI+T2D patients have a worse cognitive performance than MCI patients (p<0.01), but this effect was absent in MCI+T2D+metformin patients. These cognitive variations were associated with changes in cortical thickness and hippocampal volume (p<0.001). Our study shows a beneficial effect of metformin treatment on cognitive performance, CSF biomarkers profile and neuroanatomical measures in MCI due to AD patients.We observed cognitive impairment, low adult neurogenesis and progressive Aβ deposition in the hippocampus of Tg mice. Periodic DR was associated to cognitive improvement, increased hippocampal neurogenesis, and reduced hippocampal amyloid load; we found that autophagy is modulated in Tg mice with a high proportion of LC3/Aβ colocalizing in astrocytes, probably contributing to the reduction in amyloid plaques associated to DR.ConclusionOur data suggest that metformin and DR may be potential interventions to promote healthy aging and prevent dementia.