April 15 (UPI) -- Some influenza strains may trigger the same over-active immune system responses as COVID-19, and it may be determined by how the body metabolizes sugar, a new analysis, published Wednesday by the journal Science Advances, suggests.
If true, the findings add to the similarities between the two viruses, which are both highly contagious and share many of the same basic symptoms, including cough, fever and, in some cases, shortness of breath.
However, COVID-19, the disease caused by the new coronavirus, has posed a unique challenge, given that there is no effective vaccine or treatment against it. It has been well-documented that those with underlying health conditions, including diabetes, are at higher risk for serious illness and death from the infection.
"We believe that glucose metabolism contributes to various COVID-19 outcomes since both influenza and COVID-19 can induce a cytokine storm, and since COVID-19 patients with diabetes have shown higher mortality," study co-author Shi Liu, a researcher at Wuhan Hospital in China, said in a press release issued by the journal.
Cytokines are proteins that circulate in the bloodstream and send messages to immune cells throughout the body to fortify its response to a virus or other pathogen. When too many cytokines are released -- the so-called "storm" -- they can cause the body's immune system to attack healthy tissue.
Instead of making people better, these attacks actually worsen health. A study published earlier this month in the journal Nature Review Immunology found that people with serious, life-threatening illness from COVID-19 had elevated levels of up to 14 cytokines in the blood.
Many of these patients developed severe pneumonia, as well as heart-related symptoms.
In general, according to the authors of the current study, the mechanisms that promote cytokine storms, remain unknown. Although research suggests that glucose -- or blood sugar -- metabolism and cytokine signal networks are known to have evolved together, it has not been clear how, if at all, they interact during flu infection.
To attempt to answer this question, at least for influenza A, a highly contagious form of the virus that causes annual epidemics worldwide, the authors examined blood glucose levels and cytokine production in mice with the flu.
Researchers found that those treated with glucosamine -- a naturally occurring amino sugar found in the body that is sold as a supplement for joint stiffness -- produced significantly higher levels of inflammatory cytokines than mice that did not receive glucosamine.
Additionally, the researchers analyzed blood sugar levels in samples from patients diagnosed with influenza A and compared them with those in samples collected from healthy patients.
They found that the hexosamine biosynthesis pathway -- a process the body uses to process sugars -- plays an essential role in cytokine storms triggered by the flu virus, causing some people to suffer more serious illness from influenza A.
The researchers are now investigating how glucose metabolism affects patients with COVID-19, in the hope that observations from the study "provide new avenues for prognosis and therapy" of the pandemic illness.