US studies, using animals, have uncovered new information about the long-term effects of Covid-19 and the health complications it can cause, opening the door to the development of new treatments.
Some people who contract Covid-19 develop long-lasting symptoms that persist even after they have recovered – a potentially serious group of conditions known as long Covid. Symptoms vary and can, for instance, affect a patient’s breathing, concentration or digestion.
Researchers led by the Tulane University School of Medicine, Louisiana, focused on a specific long Covid symptom – high blood sugar – which can induce diabetes and heart disease, but which is still not well understood in the context of Covid-19.
The team studied monkeys with Covid-19 and found that after a Covid-19 mRNA vaccination the animals had lower blood sugar levels which were sustained over time. Specific molecules were then identified in their bloodstream that are linked to high blood sugar and may provide insights into the virus’s mechanism of infection.
Meanwhile a study, at the University of Colorado Boulder, has looked at how neurological symptoms such as ‘brain fog’ and fatigue can arise from long Covid, which can happen when the Covid-19 virus leaves behind proteins in the blood after an infection.
The researchers saw that when rats were injected with these proteins, there was a significant drop in the levels of a hormone, in the brain region linked to memory and learning.
This hormone in rats is equivalent to the cortisol hormone, found in humans, that normally keeps inflammation in the brain at bay when there is stress or infection. Therefore, the lowering of cortisol due to long Covid could be causing the brain’s immune cells to overreact, leading to the symptoms.
Lead researcher Matthew Frank said: “This research gets us closer to understanding what, neurobiologically, is going on and how cortisol may be playing a role.”