- Type 2 diabetes is known to affect nervous functions like memory due to the impaired glucose metabolism.
- Glycogen levels are significantly higher in the hippocampal neurons of diabetics due to impaired monocarboxylate transporters (MCT2) expression.
- But moderate levels of exercise helped to minimize MCT2 expression in the hippocampus and improve memory.
The impaired glycogen metabolism due to type 2 diabetes affects the hippocampal-mediated memory in patients.
Normal memory function relies on the hippocampal area of the brain.
‘Memory impairment in people with type 2 diabetes could be treated with moderate levels of physical activity, which promotes the levels of lactate in the hippocampal neurons.’
Type 2 diabetes
Type 2 diabetes is an inheritable metabolic disorder which is characterized by serious health implications. Type 2 diabetes occurs when the cells in the muscles, liver, and fat tissues fail to utilize insulin, a hormone secreted by pancreas, effectively. This results in a rise in the blood glucose levels with the cells remaining deprived of energy.
Increased levels of blood glucose eventually damage the nerves and blood vessels leading to severe health complications such as heart disease, stroke, kidney disease, infections in the gum, and also eye problems leading to blindness.
It is reported that nearly 8% of the adults in USA have type 2 diabetes. India has more than 30 million diabetics. According to WHO, India will have the maximum number of diabetics in the world by 2025.
Memory Impairment Test
The impaired glucose metabolism can cause central nervous system-related complications, such as memory dysfunction.
The study by researchers at the University of Tsukaba investigated whether hippocampal glucose metabolism and memory function gets altered in a rat model of type 2 diabetes.
To test whether exercise normalizes glucose metabolism and improves memory function, the research team also investigated the effects of exercise on hippocampal glycometabolism and memory formation.
The rat was placed in a circular pool and the hippocampal function was evaluated by testing its ability to remember the location of a platform that would help it to escape from the water.
"This is a well-established method for measuring spatial learning and memory," study first author Takeru Shima says.
How Exercise Alter MCT2 Expression
Rats who had type 2 diabetes needed more time to escape the water and find the platform.
But moderate levels of exercise for 4 weeks helped improve memory and the rats were able to find the platform much faster.
"This indicated that exercise significantly improved spatial memory impairments in type 2 diabetic rats," Shima explains.
Glycogen levels in the hippocampus were not investigated in the past and the researchers found that glycogen levels are significantly higher in the hippocampus of diabetic rats.
But engaging in a single bout of exercise reduced hippocampal glycogen levels because it led to an increase in lactate levels. Lactate is an energy substrate and neuromodulator in the hippocampus. It is transferred to neurons through monocarboxylate transporters (MCTs). Lactate is known to enhance memory formation.
"MCT2 expression was significantly lower in the hippocampus of type 2 diabetic rats," corresponding author Hideaki Soya says, "dysregulated MCT2-mediated neuronal uptake of lactate is a possible etiology of memory dysfunction in type 2 diabetes, and that elevated hippocampal glycogen may be an adaptive change to compensate for the decreased lactate utilization".
Four weeks of moderate exercise normalized MCT2 expression in the hippocampus of type 2 diabetic rats.
Memory dysfunction in type 2 diabetic rats is caused by disrupted MCT2-mediated uptake of lactate by neurons.
Moderate exercise could be used to treat memory impairment in patients with type 2 diabetes by promoting the transfer of glycogen-derived lactate to hippocampal neurons.
- Type 2 Diabetes - Risk Factors - Symptoms & Signs - Management - Prevention - (//www.medindia.net/patients/patientinfo/type-2-diabetes.htm)
- Takeru Shima et al. Moderate exercise ameliorates dysregulated hippocampal glycometabolism and memory function in a rat model of type 2 diabetes. Diabetologia; (2016)