Early-Stage Alzheimer's Disease Is Associated with Simultaneous Systemic and Central Nervous System Dysregulation of Insulin-Linked Metabolic Pathways.

BACKGROUND: Brain insulin resistance is a well-recognized abnormality in Alzheimer's disease (AD) and the likely mediator of impaired glucose utilization that emerges early and progresses with disease severity. Moreover, the rates of mild cognitive impairment (MCI) or AD are significantly greater in people with diabetes mellitus or obesity.

OBJECTIVE: This study was designed to determine whether systemic and central nervous system (CNS) insulin resistant disease states emerge together and thus may be integrally related.

METHODS: Insulin-related molecules were measured in paired human serum and cerebrospinal fluid (CSF) samples from 19 with MCI or early AD, and 21 controls using a multiplex ELISA platform.

RESULTS: In MCI/AD, both the CSF and serum samples had significantly elevated mean levels of C-peptide and an incretin, and reduced expression of Visfatin, whereas only CSF showed significant reductions in insulin and leptin and only serum had increased glucagon, PAI-1, and ghrelin. Although the overall CSF and serum responses reflected insulin resistance together with insulin deficiency, the specific alterations measured in CSF and serum were different.

CONCLUSION: In MCI and early-stage AD, CNS and systemic insulin-related metabolic dysfunctions, including insulin resistance, occur simultaneously, suggesting that they are integrally related and possibly mediated similar pathogenic factors.