High blood glucose and the brain

Many of us have had that feeling of brain fog, or that moment when something is on the tip of your tongue, but you can’t quite spit it out (and heaven forbid the deeper recesses of your memory give it over)!

Brain function, like memory, learning, concentration, and executive function, can be impacted for a variety of reasons, including diet and sleep. And recent research has been looking more closely at the relationship between these factors of brain function, and high blood glucose.

The brain and blood glucose

The brain consumes about 20% of the body’s energy. That is huge, and more than any other single organ. A majority of the energy is required to help brain cells fire and send signals, with some left over for cell health maintenance.¹

This means a large portion of the body’s blood is sent north to neurons, carrying with it glucose (whether ingested or produced endogenously) for mitochondria to metabolise into ATP – the energy carrying molecule found in cells of all living things.

However, a long-term state of hyperglycaemia can come at a cost to the brain, much like the damage seen in other parts of the body such as kidneys, blood vessels, and eyes.

It has been found there is a 65% increased risk for mild cognitive impairment in those with type 2 or mid-life onset diabetes, as well as impaired memory and thinking skills compared with healthy controls. And this may come down to the onslaught of chronically high glucose to the brain.^2;3

Altered connection

A recently released study revealed that in those with hyperglycaemia, the integrated communication between various parts of the brain are negatively impacted.⁴

A team of researchers from University of Ulsan College of Medicine in South Korea undertook MRI scans of participants with uncontrolled type 2 diabetes and high levels of HAb1c and fasting blood glucose, and compared them with scans of healthy controls. They analysed 144 different regions of the brain and the connections between them.

They found two factors in the brains of those with uncontrolled type 2 diabetes that were not present in healthy controls – a disrupted white matter configuration, and a longer length of connection pathways between brain regions.

The researchers surmised these two factors impact the function and efficiency of communication within the brain.

“Chronic, uncontrolled hyperglycemia may induce tiny changes in the white matter tract, which may force changes in the brain network,” said one study author Min-Seon Kim said.

The white matter of the brain is integral to transferring information between different areas of the brain, and the efficiency of this process depends on the structural integrity of the white matter.

Therefore cognitive deficits, like memory, learning, concentration and executive function can be caused by white matter structural abnormalities.

It is important to keep in mind this is a study in those with hyperglycaemia, so effects are likely very different in those with well-controlled type 2 diabetes.

Research continues

In other recent and interesting research, scientists have found that glial cells in the brain may have a role to play in regulating the amount of sugar taken up by the brain.⁵

Astrocytes, a type of glia cell, have a receptor that responds to insulin, influencing cell metabolism – and in those astrocytes missing the receptor, researchers found the ability to curb food intake was diminished.

Simultaneously, glucose transport across the blood brain barrier into the brain became less efficient, particularly in the satiety centre of the hypothalamus. The researchers believe this then impacts glucose sensing in the brain and therefore glucose metabolism systemically.

You can imagine if transport across into the brain or sensing the presence of glucose is compromised, coupled with an impaired ability to know when one is full, we could very well be on the track to eating more (especially the sweet stuff).

Comprehensive research into the intricate workings of the brain and glucose relationship continues, and while it does, it is best to focus on what we can do in our day-to-day to reduce any negative impact on the brain from chronically high blood glucose.

Diet, exercise and stress are all implicated in the pathogenesis of insulin resistance and type 2 diabetes – and fortunately, all these things are modifiable to improve health, and in some cases, reverse the condition altogether!

So eat well, move lots and breathe deeply. Your brain, in the long run, will thank you for it.

By Angela Johnson (BHSc Nut. Med.)

References:

1. Du, F, Zhu, X, Zhang, Y, Friedman, M, Zhang, N, Ugurbil, K, & Chen, W 2008, ‘Tightly coupled brain activity and cerebral ATP metabolic rate’, Proceedings of the National Academy of Sciences of the United States, no. 17, p. 6409.
2. Cooper, C, Sommerlad, A, Lyketsos, CG, & Livingston, G 2015, ‘Modifiable predictors of dementia in mild cognitive impairment: a systematic review and meta-analysis’, American Journal of Psychiatry, no. 4, p. 323.
3. Roberts, RO, Knopman, DS, Przybelski, SA, Mielke, MM, Kantarci, K, Preboske, GM, Senjem, ML, Pankratz, VS, Geda, YE, Boeve, BF, Ivnik, RJ, Rocca, WA, Petersen, RC, & Jack Jr, CR 2014, ‘Association of type 2 diabetes with brain atrophy and cognitive impairment’,Neurology, vol. 82, no. 13, pp. 1132-1141.
4. Kim, D, Yu, JH, Shin, M, Shin, Y, & Kim, M 2016, ‘Hyperglycemia Reduces Efficiency of Brain Networks in Subjects with Type 2 Diabetes’,PLoS ONE, vol. 11, no. 6, pp. 1-14.
5. García-Cáceres, C, Quarta, C, Varela, L, Gao, Y, Gruber, T, Legutko, B, Jastroch, M, Johansson, P, Ninkovic, J, Yi, C, Le Thuc, O, Szigeti-Buck, K, Cai, W, Meyer, CW, Pfluger, PT, Fernandez, AM, Luquet, S, Woods, SC, Torres-Alemán, I, & Kahn, CR 2016, ‘Astrocytic Insulin Signaling Couples Brain Glucose Uptake with Nutrient Availability’, Cell, vol. 166, no. 4, pp. 867-880.