Brain energy rescue with ketones improves cognitive outcomes in MCI

Abstract

AbstractBackgroundAn emerging strategy to delay the onset of Alzheimer disease (AD) is to use ketones to overcome the progressive brain energy deficit caused by deteriorating brain glucose metabolism in mild cognitive impairment (MCI). Ketones (acetoacetate and beta‐hydroxybutyrate) are the brain’s main alternative fuel to glucose; in contrast to glucose, ketone metabolism by the brain is now known to be unaffected in MCI and AD. Successful brain energy rescue with ketones in MCI was recently reported.MethodsIn the 6‐month, randomized, placebo‐controlled Benefic Trial (NCT02551419), the active arm was a ketogenic medium chain triglyceride (kMCT) supplement in a lactose‐free skim milk emulsion (15 g kMCT twice/day; n = 39 completers). The placebo arm was a non‐ketogenic iso‐energetic vegetable oil (n = 44 completers). Brain ketone and glucose metabolism were assessed by PET.ResultsPerformance on all five cognitive domains improved significantly over 6 months in the kMCT group: (i) Episodic memory (trial 1, Free and Cued Recall Test) increased by 1 word (+0.5 Δ Z‐score); (ii) Executive function (Verbal Fluency Test) correct answers increased by 2 words (+0.3 Δ Z‐score) but decreased by 1 word on placebo (‐0.1 Δ Z‐score), time taken on the Stroop Colour Naming Test decreased by 1 sec (p = 0.09), and errors on the Trail Making Test increased by 0.8 on placebo (p = 0.02); (iii) Language (Boston naming test) correct answers increased by 1.3 words. (iv) Processing speed increased directly with higher brain ketone uptake in several white matter tracts. (v) Improved attention was directly associated with increased ketone uptake and functional connectivity in the dorsal attention network.ConclusionsImproved cognition correlating positively with improved brain energy supply by ketones suggests a direct link to brain energy status. The moderate effect size of this kMCT intervention indicates a clinically meaningful benefit on certain cognitive outcomes, some of which relate directly to risk of MCI progressing to AD. Other potential ketogenic interventions that have been less well studied in MCI or AD include a ketogenic diet and ketone salts or esters. Whether brain energy rescue with ketones can delay the onset or progression of AD should now be assessed.