Effects of a dietary ketone ester on hippocampal glycolytic and tricarboxylic acid cycle intermediates and amino acids in a 3xTgAD mouse model of Alzheimer's disease

In patients with Alzheimer's disease (AD) and in a triple transgenic (3xTgAD) mouse model of AD low glucose metabolism in the brain precedes loss of memory and cognitive decline. The metabolism of ketones in the brain by-passes glycolysis and therefore may correct several deficiencies that are associated with glucose hypometabolism. A dietary supplement composed of an ester of D-beta-hydroxybutyrate and R-1,3 butane diol referred to as ketone ester (KE) was incorporated into a rodent diet and fed to 3xTgAD mice for 8 months. At 16.5 months of age animals were killed and brains dissected. Analyses were carried out on the hippocampus and frontal cortex for glycolytic and TCA (Tricarboxylic Acid) cycle intermediates, amino acids, oxidized lipids and proteins, and enzymes. There were higher concentrations of D-beta-hydroxybutyrate in the hippocampus of KE-fed mice where there were also higher concentrations of TCA cycle and glycolytic intermediates and the energy-linked biomarker, N-acetyl aspartate compared to controls. In the hippocampi of control-fed animals the free mitochondrial [NAD(+)]/[NADH] ratio were highly oxidized, whereas, in KE-fed animals the mitochondria were reduced. Also, the levels of oxidized protein and lipids were lower and the energy of ATP hydrolysis was greater compared to controls. 3xTgAD mice maintained on a KE-supplemented diet had higher concentrations of glycolytic and TCA cycle metabolites, a more reduced mitochondrial redox potential, and lower amounts of oxidized lipids and proteins in their hippocampi compared to controls. The KE offers a potential therapy to counter fundamental metabolic deficits common to patients and transgenic models.