3-hydroxybutanoic acid (BHBA, Figure ), was found with statistically higher levels in AD compared to the other two groups. BHBA is the most abundant ketone in the human circulation and may be involved in many brain functions including neurotransmission, neuroinflammation and myelination . The higher levels in the AD group may be due to increased fat degradation and thus ketone formation as a physiological response to energy shortage in the brain . Ketogenic diets, which elevate BHBA concentrations, may also contribute to increased levels, but dietary information was not available for these samples.