14 August 2016
Lifestyle diseases, such as type II diabetes, are becoming a worldwide public health crisis. Diabetes can be triggered by excessive intake of sucrose, which causes a sudden peak in blood glucose. Now, Japanese researchers are using silkworms – which process sucrose remarkably similarly to mammals – to test potential diabetes treatments.
The digestive enzyme α-glycosidase breaks down sucrose into smaller molecules of glucose and fructose, which are absorbed from the gut into the bloodstream. A high sucrose diet results in high blood glucose, or hyperglycaemia, which, if left untreated, can be toxic to cells, causing diseases such as obesity and type II diabetes. Chemical inhibitors of α-glycosidase are already used as anti-diabetic agents, and certain bacteria are supposed to have similar effects. However, both types of treatment will require costly and unpopular animal testing before human clinical trials can begin.
A team led by microbiologist Yasuhiko Matsumoto at the University of Tokyo in Japan has identified a potential solution. Silkworms are small enough that a large number can be reared cheaply, yet large enough to be injected easily. Like all insects, silkworms have ‘haemolymph’ instead of blood. According to Matsumoto, haemolymph “has many similar functions to blood, such as the transport of hormones and nutrients.” Silkworms show similar responses to humans when treated with antibiotics or exposed to toxins.
Matsumoto bred a diabetic silkworm that can be used to test diabetes treatments. He believes this “original and unique” approach has promise and describes his team as “pioneers in the use of silkworms as an experimental animal.”
The team tested a group of bacteria, known as lactic acid bacteria, for their ability to inhibit the hyperglycaemic response in silkworms. One strain of bacteria in particular, Lactococcus lactis #Ll-1, had a strong inhibitory effect on the α-glycosidase enzyme, and therefore on hyperglycaemia, in the haemolymph. Matsumoto suggests that in humans, these bacteria could permanently colonize the gut, producing a “lasting suppressive effect on hyperglycaemia.”
Many type II diabetes patients find it hard to maintain a healthy lifestyle. The results reported by the Japanese team suggest lactic acid bacteria could be used as a supportive treatment for type II diabetes, or a preventative approach in those predisposed to the disease. Matsumoto’s silkworm model provides a low-cost way of screening bacteria for this purpose.
Matsumoto, Y., Ishii, M., & Sekimizu, K. An in vivo invertebrate evaluation system for identifying substances that suppress sucrose-induced postprandial hyperglycemia. Scientific Reports (2016).| article