The polymerase chain reaction (PCR) has helped researchers discover abnormal gut taste mechanisms in diabetes, the first time that this has been described. The researchers, from the University of Adelaide, have linked these abnormalities with problems in glucose uptake in patients with diabetes.
The tongue isn’t the only place where we detect sweetness, as Richard Young of the University of Adelaide’s Nerve-Gut Research Laboratory explains: “When we talk about ‘sweet taste’, most people think of tasting sweet food on our tongue, but scientists have discovered that sweet taste receptors are present in a number of sites in the human body. We’re now just beginning to understand the importance of the sweet taste receptors in the human intestine and what this means for sufferers of type 2 diabetes.”
The researchers focused on the intestinal sweet taste receptors (STRs), T1R2 and T1R3, in 14 healthy people and 13 people with type 2 diabetes. They took biopsies from the gut before and after an infusion of glucose directly into the duodenum and measured the levels of STR transcripts using RT-PCR.
Before the glucose infusion, the levels of intestinal STR transcript levels were not affected by changes in levels of blood glucose in either group. After the infusion, the levels of T1R2 transcripts increased in both groups while blood glucose levels were normal, but decreased in the healthy people and increased in the people with type 2 diabetes while blood glucose was raised (hyperglycaemia). The levels of hyperglycaemia were higher in people with diabetes than in healthy people.
This suggests that while intestinal expression of the T1R2 sweet taste receptor is regulated by raised levels of glucose in the gut in healthy people, it’s disordered in people with diabetes when blood glucose levels are raised. This means that while healthy people can regulate glucose intake 30 minutes after exposure to glucose, people with diabetes take the glucose up more rapidly and in greater quantities. This could make episodes of hyperglycaemia after meals even worse.
“This shows that diabetes is not just a disorder of the pancreas and of insulin – the gut plays a bigger role than researchers have previously considered,” says Young. “This is because the body’s own management of glucose uptake may rely on the actions of sweet taste receptors, and these appear to be abnormally controlled in people with type 2 diabetes.”
Taste receptors in the gut were first identified in 2007, and linked with the development of diabetes and obesity. As these regulate secretion of insulin and hormones that regulate appetite, this may help to explain why using artificial sweeteners does not always lead to weight loss.
The next step is to see what happens over the whole period of digestion, and also to see what the impact of artificial sweeteners is, and PCR could play a role here too. As Young adds: “By gaining a better understanding of how these mechanisms in the gut work, we hope that eventually this will assist to better manage or treat diabetes in the future.”
This project shows the power of PCR in research to work out the underlying mechanisms of disease, which could lead to better diagnostics and therapeutics in the future.
Suzanne Elvidge is a freelance science, biopharma, business and health writer with more than 20 years of experience. She has written for a range of online and print publications including FierceBiomarkers, FierceDrugDelivery, European Life Science, the Journal of Life Sciences (now the Burrill Report), In Vivo, Life Science Leader, Nature Biotechnology, New Scientist, PR Week and Start-Up. She specialises in writing on pharmaceuticals, biotechnology, healthcare, science, lifestyle and green living, but can write on any topic given enough tea and chocolate biscuits. She lives just beyond the neck end of nowhere in the Peak District with her second-hand bookseller husband and two second-hand cats.