The mosquito’s immune system is suppressed by human insulin, which could be bad news for the spread of malaria if the number of people in Africa with diabetes type 2 continues to grow at its present rate, researchers from the University of California, Davis, explained in the journal Infection and Immunity. The authors added that the malaria parasite spread is slowed down by the mosquitoes’ immunological resistance.
First author, Nazzy Pakpour, said “A fair portion actually fight off the infection.”
Type 2 diabetes rates in Africa, as in the rest of the world, are rising rapidly. According to experts in the area, approximately one in every five African adults will be afflicted with the disease by 2030.
If more people have diabetes, there will be a higher prevalence of hyperinsulinemia – high levels of insulin in the blood. If more people have high blood insulin levels, this means more human insulin entering mosquitoes when they take blood meals, and a lower immune response by these insects to Plasmodium falciparum, the protozoan parasite that causes malaria in humans. Put simply – more cases of hyperinsulinemia in Africa encourages the spread of malaria.
“It’s crazy to think something in our blood could change how mosquitoes respond to parasites.”
The scientists say they see this situation as both horrific and scientifically intriguing.
In a previous study, Pakpour and colleagues demonstrated that ingested human insulin triggers or activates the insulin/IGF-1 signaling pathway in mosquitoes that transmit malaria – Anopheles stephensi – making them more vulnerable to invasion by the P. falciparum parasite.
They explained that in their latest study, they showed that insulin signaling reduced expression of some specific mosquito genes involved in immunity that are under the same regulatory control. Human insulin, they added, suppresses mosquito immunity by activating the PI3K pathway. If the pathway could be artificially inhibited, the effects of human insulin on the mosquitoes’ immune system might be reversed.
Written by Christian Nordqvist