Obesity is a risk factor for developing type 2 diabetes and cardiovascular diseases. These diseases may, in turn, increase the risk for dementia and Alzheimer’s disease. Previous research has shown that a diet rich in fat and sugar induces obesity and diabetes in mice, and may impact their memory. Until now, it has been unknown whether the damage to the brain is temporary or permanent.
Researchers at Lund University have investigated how a diet rich in fat and sugar altered the hippocampus and cortex in mice of both genders. Their study shows that animals who were given a diet rich in fat and sugar displayed major metabolic alterations in the hippocampus and cortex, and also had impaired memory.
“An important result of this study is that we could see that the impairments does not have to be permanent. We saw the same results in mice of both genders,” says Joao Duarte, a researcher in diabetes and brain function at Lund University Diabetes Centre (LUDC) and one of the main authors behind the study in the scientific journal Aging and Disease.
A total of 72 mice were included in the study and randomly assigned to three experimental groups. One group had a diet that consisted of 60 percent saturated fat and sugary drink for four months followed by a diet low in fat for two months. Another group was given the diet of 60 percent fat and sugary drink during six months. The third group was given a control diet of ten percent fat.
The researchers assessed brain metabolites over time with magnetic resonance spectroscopy (MRS). A metabolite is a byproduct of breakdown of any substance in tissues and organs. The metabolic profile of the brain may reflect alterations in energy levels, neuron communication and cell death. Several behavioral experiments were carried out to study the impact of the diet in the memory functions of the mice.
“Our measurements with magnetic resonance spectroscopy show that mice who had been given unhealthy foods had an altered metabolic profile compared to animals who had eaten more healthy foods. We could also see that an unhealthy diet led to memory impairment. However, the brain structure and important memory functions were restored in mice who were assigned to the group who first had a diet high in fat followed by a reversed diet low in fat. This is a very positive result,” Joao Duarte.
Memory functions were studied in object recognition tasks, where the ability to recognise new objects was assessed. Animals who were given a diet high in fat did not explore new objects to the same extent as mice who had a diet low in fat. Mice who were assigned to the group who had a high fat diet followed by a period of a diet low in fat recovered their ability to recognise new objects.
The knowledge may contribute to a healthier ageing for people with type 2 diabetes. The disease requires lifelong treatment and may lead to different complications. There is no cure against dementia and Alzheimer’s disease.
“It is hard to conduct a similar study in human beings, and we have to keep in mind that research on mice has its limitations. However, metabolism supporting brain function is very similar in the two species. We believe that our results are robust and add to the evidence base that an unhealthy diet may harm important cognitive functions. It is important that people with type 2 diabetes are encouraged to develop a healthy lifestyle, as this may contribute to better ageing without dementia,” says Joao Duarte, affiliated with Wallenberg Centre for Molecular Medicine (WCMM).