Visit-to-visit HbA1c variability, dementia, and hippocampal atrophy among adults without diabetes

Associations of Serum Insulin and Related Measures With Neuropathology and Cognition in Older Persons With and Without Diabetes

OBJECTIVE

To examine associations of serum insulin and related measures with neuropathology and cognition in older persons.

METHODS

We studied 192 older persons (96 with diabetes and 96 without, matched by sex and balanced by age-at-death, education, and postmortem interval) from a community-based, clinical-pathologic study of aging, with annual evaluations including neuropsychological testing (summarized into global cognition and 5 cognitive domains) and postmortem autopsy. We assessed serum insulin, glucose, leptin, adiponectin, hemoglobin A1C, advanced glycation-end products (AGEs), and receptors for advanced glycation-end products, and calculated the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR) and adiponectin-to-leptin ratio. Using adjusted regression analyses, we examined the associations of serum measures with neuropathology of cerebrovascular disease and Alzheimer's disease, and with the level of cognition proximate-to-death.

RESULTS

Higher HOMA-IR was associated with the presence of brain infarcts and specifically microinfarcts, and higher HOMA-IR and leptin were each associated with subcortical infarcts. Further, higher leptin levels and lower adiponectin-to-leptin ratios were associated with the presence of moderate-to-severe atherosclerosis. Serum insulin and related measures were not associated with the level of Alzheimer's disease pathology, as assessed by global, as well as amyloid burden or tau tangle density scores. Regarding cognitive outcomes, higher insulin and leptin levels, and lower adiponectin and receptors for advanced glycation-end products levels, respectively, were each associated with lower levels of global cognition.

INTERPRETATION

Peripheral insulin resistance indicated by HOMA-IR and related serum measures was associated with a greater burden of cerebrovascular neuropathology and lower cognition. ANN NEUROL 2024;95:665-676.

Glucose Metabolism and Cognitive Decline in Progressive Supranuclear Palsy and Corticobasal Syndrome: A Preliminary Study

Multiple studies have analyzed the possible correlations between diabetes and Alzheimer's disease. Less is known about the context of cognitive deterioration among patients with atypical Parkinsonian syndromes and glucose metabolism impairment. The aim of this study was to evaluate the association between the impaired glucose metabolism and cognitive decline among patients with progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS). The study included 22 patients with PSP and CBS with disease durations varying from 3 to 6 years. The levels of glycated hemoglobin (HbA1C), fasting blood glucose, fasting C-peptide and the presence of microalbuminuria were evaluated, and oral glucose tolerance tests (OGTT) were performed. Based on the OGTT results, the glycemic variability, mean glycemia, glycemia standard deviation (SD) and coefficient of variation (%CV) were calculated. All patients underwent a three-Tesla brain magnetic resonance (MRI) examination and neuropsychological cognitive assessment with the use of standardized scales: Montreal Cognitive Assessment (MoCA), Mini-Mental State Examination (MMSE) and Frontal Assessment Battery (FAB). A statistical analysis revealed that poor control of glycemia with high glycemic variability and increased atrophy of the medial temporal lobe among patients with PSP and CBS correlated with worse cognitive performance independent of age or sex, even among patients who did not fulfill the criteria for diabetes. The study results indicate the importance of glucose metabolism control and optimal treatment in the context of cognition maintenance among patients with PSP and CBS. Due to the relatively small number of analyzed patients, the issue requires further assessment. To the best of our knowledge, this is the first study discussing the role of glycemic variability in atypical Parkinsonian syndromes.