Effects of Exogenous Ketones on Cognitive Function in Older Adults With Prediabetes?

Inclusion Criteria: * Age 60 to 75 years * Able to provide written informed consent * Fluent in English * No diagnosed cognitive impairment or dementia Classified as either: * Prediabetes (based on American Diabetes Association criteria), or Normal glucose regulation (control group) * Medically stable and cleared to undergo positron emission tomography and magnetic resonance imaging * Willing to comply with study procedures, including metabolic testing, supplement ingestion, and neuroimaging Exclusion Criteria: * Diagnosis of mild cognitive impairment, dementia, or other neurodegenerative disorder * Diagnosis of type 1 diabetes or type 2 diabetes * Use of glucose-lowering medications (e.g., insulin, metformin, glucagon-like peptide-1 receptor agonists) * History of major neurological disorder (e.g., stroke, traumatic brain injury with loss of consciousness \>30 minutes, epilepsy, multiple sclerosis) * Major psychiatric disorder not stable on treatment * Uncontrolled hypertension or significant cardiovascular disease * Severe renal, hepatic, or gastrointestinal disease that may affect supplement metabolism * Contraindications to magnetic resonance imaging (e.g., non-compatible implanted devices, severe claustrophobia)