Proceedings of The Physiological Society

Mitochondria: Form and function (London, UK) (2017) Proc Physiol Soc 38, PC04

Poster Communications

Studying mitochondrial bioenergetics in ghrelin-mediated neuroprotection

M. Carisi1, D. J. Rees1, A. H. Morgan1, J. S. Davies1

1. Medical School, Swansea University, Swansea, Wales, United Kingdom.

Alzheimer's disease (AD) is an age-related neurodegenerative disorder characterised by progressive memory loss and cognitive decline. Calorie restriction (CR) is known to prevent cognitive deficits in mouse models of AD and in aged humans. Our group showed that CR-mediated neuroprotection, neurogenesis and memory are dependent on the hormone ghrelin, produced in the stomach in response to changes in the body's metabolic status. Acyl-ghrelin (AG) activates Growth Hormone Secretagogue Receptor-1a (GHSR) in several areas of the brain. In the arcuate nucleus of the hypothalamus, AG regulates food intake, adiposity and insulin secretion during CR, through AMP-activated kinase (AMPK). In the hippocampus, AG affects neurogenesis and synaptic density, increases long-term potentiation and enhances learning and memory1,2. Recent evidences showed that ghrelin activity involves mitochondrial signalling. Cells treated with serum from calorie-restricted rats, displayed reduced mitochondrial membrane potential (MMP) and ROS production, increased mitochondrial biogenesis and bioenergetics capacity3. Neurons pre-treated with ghrelin exhibit increased resistance to rotenone-induced toxicity and reduced cytocrome C release4. Increased ghrelin levels activate mitochondrial respiration, increase mitochondrial number, and contribute to fatty acids oxidation and ROS clearance5. Preliminary data from our group, in in-vitro and in-vivo models of Parkinson's Disease, showed that AG attenuates rotenone-induced dopamine neurone loss in nutrient restricted media; induces phosphorylation of AMPK and Acetyl-CoA carboxylase, a fatty acid biosynthesis regulator; promotes MMP and partially prevents rotenone-induced mitochondrial fragmentation (unpublished). Our hypothesis is that AG-mediated neuroprotection may occur though regulation of mitochondrial energetic metabolism and fusion/fission balance. To investigate this, human neural stem cells (ReN VM, Merk Millipore) will be differentiated to mature neurones and treated for 5 days with AG before being incubated for 24h with amyloid-beta(1-42)oligomers (AβOs) - a peptide known to induce neuronal toxicity and mitochondrial dysfunction in AD patients1. To assess mitochondrial respiration and bioenergetics we will use an Agilent Seahorse XF system and MMP and mitochondrial fusion/fission will be quantified using confocal microscopy (HCS Mitohealth assay, Life Tech). Finally, using post-mortem human brain tissue (Brains for Dementia Research), we will determine GHSR expression in hippocampus and entorhinal cortex in AD and whether this correlates with expression of mitochondrial proteins.

Where applicable, experiments conform with Society ethical requirements