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High caloric intake and aging: consequences for synaptic plasticity and rat behaviour performance

Sara L. Paulo1, 2, Catarina Miranda-Lourenço1, 2, Rita F. Belo1, 2, Rui S. Rodrigues1, 2, Sara R. Tanqueiro1, 2, João Fonseca-Gomes1, 2, Ana M. Sebastião1, 2, Sara Xapelli1, 2* and Maria José Diógenes1, 2*
  • 1 Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Portugal
  • 2 Institute of Molecular Medicine, Faculty of Medicine, University of Lisbon, Portugal

The alarming increase in sugar and fat consumption over the last decades, leading to overweight and obesity, is one of the major health concerns nowadays, being associated with a higher risk of metabolic and cardiovascular diseases (World Health Organization, 2018). Recent evidence suggests a possible deleterious effect of this type of diet on cognitive function (Beilharz et al., 2015, 2016; Yeomans, 2017), which may act to exacerbate natural age-related cognitive decline. Thus, we aimed at unravelling the effects of a high caloric diet (HCD) in aged rats upon synaptic plasticity and memory performance. To obtain a model of obesity, male Wistar rats were fed from 1 to 24-months-old with a sucrose solution (33%), a solid mixture of lard (33%) and powdered sucrose (66%), and standard rat chow. All analyses were performed at 24 months-old. The weight and glycemia levels of the animals were measured. The open field (OF) and novel object recognition (NOR) behaviour tests were performed. Field excitatory postsynaptic potentials (fEPSPs) were recorded upon induction of a long-term potentiation (LTP) protocol. Since brain-derived neurotrophic factor TrkB receptor, and adenosine A2A receptor (A2AR) mediated signalling have been shown to be altered during aging, the levels of these receptors were appraised in the hippocampus. The number of immature neurons in the dentate gyrus (DG) of the hippocampus was also evaluated. Results show that while HCD animals were obese (n=6-7; p<0.001), glycemia levels were significantly decreased (n=3-6; p<0.05). Anxious-related behaviour (OF) was greater for the HCD group (n=6-7; p<0.01), without associated changes in locomotor activity (OF). Moreover, HCD animals presented significant changes in cognitive performance, denoting an episodic long-term memory impairment (NOR) (n=6; novel vs familiar object: CTL, p<0.05, HCD, p>0.05), accompanied by a significant reduction in LTP (n=3-4; p<0.05). A significant decrease in the levels of TrkB full-length receptors was found in the hippocampus of HCD animals (n=7; p<0.05). However, no changes were observed concerning the levels of A2AR in the hippocampus, or the number of immature neurons (doublecortin immune-positive cells, DCX+) in the DG. These results suggest that a HCD leading to obesity impairs memory performance and synaptic plasticity at old-age, even in the absence of compromised glucose metabolism, possibly due to changes in TrkB receptors.

Acknowledgements

The authors would like to acknowledge the Institute of Physiology (Faculty of Medicine, University of Lisbon, Lisbon, Portugal) for the animal donation.

References

Beilharz, J. E., Maniam, J., and Morris, M. J. (2016). Short-term exposure to a diet high in fat and sugar, or liquid sugar, selectively impairs hippocampal-dependent memory, with differential impacts on inflammation. Behav. Brain Res. 306, 1–7. doi:10.1016/j.bbr.2016.03.018. Beilharz, J., Maniam, J., Morris, M., Beilharz, J. E., Maniam, J., and Morris, M. J. (2015). Diet-Induced Cognitive Deficits: The Role of Fat and Sugar, Potential Mechanisms and Nutritional Interventions. Nutrients 7, 6719–6738. doi:10.3390/nu7085307. World Health Organization (2018). Obesity and overweight. Available at: https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight [Accessed February 27, 2019]. Yeomans, M. R. (2017). Adverse effects of consuming high fat–sugar diets on cognition: implications for understanding obesity. Proc. Nutr. Soc. 76, 455–465. doi:10.1017/S0029665117000805.

Keywords: high caloric diet, Obesity, Aging, Memory, Long-term potentation, adult hippocampal neurogenesis

Conference: XVI Meeting of the Portuguese Society for Neuroscience (SPN2019), Lisboa, Portugal, 30 May - 1 Jun, 2019.

Presentation Type: Pitch communication + Poster presentation

Topic: Cellular and Molecular Neurosciences

Citation: Paulo SL, Miranda-Lourenço C, Belo RF, Rodrigues RS, Tanqueiro SR, Fonseca-Gomes J, Sebastião AM, Xapelli S and Diógenes M (2019). High caloric intake and aging: consequences for synaptic plasticity and rat behaviour performance. Front. Cell. Neurosci. Conference Abstract: XVI Meeting of the Portuguese Society for Neuroscience (SPN2019). doi: 10.3389/conf.fncel.2019.01.00037

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Received: 03 Mar 2019; Published Online: 27 Sep 2019.

* Correspondence:
Prof. Sara Xapelli, Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Lisbon, Portugal, sxapelli@medicina.ulisboa.pt
Prof. Maria José Diógenes, Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Lisbon, Portugal, diogenes@medicina.ulisboa.pt