An emerging challenge for tuberculosis (TB) control is the steadily rising number of individuals with type 2 diabetes mellitus, particularly in developing countries where TB is endemic. Diabetes significantly increases an individual’s susceptibility for TB and although the link between diabetes and TB has been recognised for several decades, more research on the interaction between non-communicable and communicable diseases is needed.
The National Institutes of Health (NIH) has recently awarded a grant of $1,75 million towards an international collaborative research project on the diabetes and tuberculosis co-epidemic.
Dr Katharina Ronacher, senior researcher with the Stellenbosch University Immunology Research Group, has been appointed as the principle investigator of this NIH-SAMRC RO1 Award towards the study titled “Altered endocrine axis during type 2 diabetes and tuberculosis risk”, which will investigate population groups in South Africa and America.
According to Ronacher, a better understanding of the link between TB and diabetes is essential to identify individuals at increased risk for TB progression. The study’s hypothesis is that house hold contacts of TB cases (HHCs) with latent Mycobacterium tuberculosis (Mtb) infection and diabetes are characterised by a systemic dysregulation of immune-endocrine networks that lead to compromised immunity to Mtb.
“Diabetes increases the risk of TB by a factor of three and there are now more people affected by TB-DM co-morbidity than TB-HIV infection,” says Ronacher. “TB patients with diabetes have much poorer treatment outcomes than patients with only one of the two diseases and face an increase in risk of treatment failure, mortality and post-treatment relapse.”
In diabetes patients, the interplay of hormones under neuroendocrine regulation, adipokines and insulin, and chronic low grade inflammation are likely to contribute to compromised immune responses to Mycobacterium tuberculosis (Mtb). “We propose studies in HHCs in two populations with different background ethnicities: Coloureds in South Africa and Hispanics in Texas,” she explained.
The five year study will be carried out in collaboration with Dr Blanca Restrepo from the University of Texas, Prof Larry Schlesinger from Ohio State University and Prof Gerhard Walzl from Stellenbosch University (SU).
Ronacher said that at the completion of the study, they will have gained critical and fundamental new insights into the interplay between the immune and endocrine systems, both in the periphery and lung; thereby helping to identify underlying risk factors in diabetes patients for progression to active TB.
A further intended outcome of the study is capacity building amongst young researchers. Four postgraduate students from previously disadvantaged backgrounds have been appointed to the research team.
----------
Stellenbosch University Immunology Research Group (SUN-IRG), is a specialist Tuberculosis Immunology Group in the Department of Biomedical Sciences of the Faculty of Medicine & Health Sciences, led by Prof Gerhard Walzl. Dr Ronacher is leading the immune-endocrine studies within the SUN-IRG and with her team is trying to identify the underlying molecular mechanisms of the interplay between the immune and endocrine systems.
Photo: Dr Katharina Ronacher
