Kiliaan, Amanda J.

Abstract The obesity epidemic increases the interest to elucidate impact of short‐chain fatty acids on metabolism, obesity, and the brain. We investigated the effects of propionic acid (PA) and caproic acid (CA) on metabolic risk factors, liver and adipose tissue pathology, brain function, structure (by MRI), and gene expression, during obesity development in Ldlr −/− .Leiden mice. Ldlr −/− .Leiden mice received 16 weeks either a high‐fat diet (HFD) to induce obesity, or chow as reference group. Next, obese HFD‐fed mice were treated 12 weeks with (a) HFD + CA (CA), (b) HFD + PA (PA), or (c) a HFD‐control group. PA reduced the body weight and systolic blood pressure, lowered fasting insulin levels, and reduced HFD‐induced liver macrovesicular steatosis, hypertrophy, inflammation, and collagen content. PA increased the amount of glucose transporter type 1‐positive cerebral blood vessels, reverted cerebral vasoreactivity, and HFD‐induced effects in microstructural gray and white matter integrity of optic tract, and somatosensory and visual cortex. PA and CA also reverted HFD‐induced effects in functional connectivity between visual and auditory cortex. However, PA mice were more anxious in open field, and showed reduced activity of synaptogenesis and glutamate regulators in hippocampus. Therefore, PA treatment should be used with caution even though positive metabolic, (cerebro) vascular, and brain structural and functional effects were observed.

Alzheimer’s disease (AD) is a severe neurodegenerative disorder for which the exact etiology is largely unknown. An increasingly recognized and investigated notion is the pathogenic role of mitochondrial dysfunction in AD. We assessed mitochondrial oxidative-phosphorylation (OXPHOS) enzyme activities in the APPswe/PS1ΔE9 mouse model from 4.5 to 14 months of age. We show an age-dependent decrease in mitochondrial complex-II activity starting at 9 months in APP/PS1 mice. Other enzymes of the OXPHOS do not show any alterations. Since amyloid-β (Aβ) plaques are already present from 4 months of age, mitochondrial dysfunction likely occurs downstream of Aβ pathology in this mouse model.