Link between diabetes and TB in the spotlight

A recent study found that in the South African Coloured population in the Western Cape Province, up to 25% of people have diabetes.
World Health Day was marked annually on 7 April and the theme for this year’s celebration was “Beat Diabetes”. Stellenbosch University’s Faculty of Medicine and Health Sciences is doing important research to elucidate the diabetes epidemic in local communities also affected by tuberculosis.
 
Globally more TB patients simultaneously have diabetes than TB patients co-infected with HIV – and the number is steadily rising.
 
This is according to Dr Katharina Ronacher, a medical biologist at Stellenbosch University (SU), who is leading a research group
studying the TB-diabetes co-epidemic.
 
“In the South African population about 12% of TB patients also have type 2 diabetes,” says Ronacher. She notes that this number is expected to rise, as the prevalence of diabetes is increasing dramatically in developing countries like South Africa as more people are adopting a Western lifestyle.
 
People with diabetes have a three times higher risk of developing TB than those without the disease.
 
Diabetes mellitus (DM) - commonly referred to as “diabetes” - is a metabolic disease that causes high blood sugar levels, and is increasingly common among South Africans. 
 
A recent study found that in the South African Coloured population in the Western Cape Province, up to 25% of people have diabetes. “This is very high,” says Ronacher, who is part of the SU Immunology Research Group at the Faculty of Medicine and Health Sciences.
 
Research has shown that one fifth of people (19%) with diabetes are not aware that they have the disease. In South Africa the lack of early diagnosis of diabetes is exacerbated by poor screening services, and most people are diagnosed only once they develop complications from the disease.
 
“The dual burden of TB and diabetes is greater in certain regions than in others,” Ronacher explains. “In India, for example, up to 50% of TB patients also have diabetes.”
 
“Not only are people with diabetes more likely to get TB, they are also less likely to respond to treatment, which can lead to relapse or even death,” explains Ronacher.
 
One reason for this could be that the levels of TB medication are generally lower in diabetes patients than patients without diabetes comorbidity. The cause for this is unknown and it is unclear whether it is due to interaction between the two diseases, or because people with diabetes generally have a higher body mass index and medication doses are not adjusted correctly.
 
Ronacher’s research group also investigates whether patients with poorly-controlled diabetes (mostly due to not taking medication regularly), have reduced immune responses to the germs that cause TB than patients whose diabetes are controlled.
 
Ronacher has recently been awarded a grant of R25 million by the American National Institutes of Health to explore the risk of developing TB from household contacts with diabetes, compared to household contact without diabetes.
 
The Immunology Research Group is also involved in a project to screen TB patients for diabetes, and vice versa, to gain a better understanding of how these two diseases interact.
 
Thato Motlhokodi