Scientists from Melbourne’s Walter and
Eliza Hall Institute and the RIKEN Institute, Japan, have found that type
2 diabetes could be ‘reversed’ in laboratory models by dampening the
inflammatory responses in fat tissue. In the recently published article in
Nature Immunology, Dr Ajith Vasanthakumar, Dr Axel Kallies and
colleagues have reported that the regulatory T cells (Tregs) play a key role in
controlling inflammation in fat tissue and maintaining insulin sensitivity and
have published their findings in Nature Immunology1.
Type 2 diabetes is the most common type
of diabetes with an alarming rise in the prevalence rate. It is strongly linked
with ‘lifestyle’ factors, such as being obese or having hypertension and its long-term
complications include kidney, eye and heart disease, and there is no cure. People
with type 2 diabetes have reduced sensitivity to insulin, a hormone that
normally triggers uptake of glucose by cells, and their cells no longer respond
to insulin appropriately. This decrease in insulin sensitivity is thought to be
a result of long-term, low-level inflammation of fat tissue in people who are
obese.
According to Dr Vasanthakumar, Tregs
act as the guardians of the immune system, preventing the immune response from
getting out-of-hand and attacking the body’s own tissues and when the number of
Treg is reduced, it leads to inflammatory diseases such as diabetes and
rheumatoid arthritis.
Recent studies have demonstrated that
fat tissue has its own unique type of Tregs, which disappear from fat tissue
during obesity. This study has showed that the fat tissue of obese people has
lower numbers of Tregs than the fat tissue of people in a healthy weight range.
Without Tregs, the inflammation-causing cell levels increase, and this rise in
inflammation can lead to insulin resistance and high blood glucose levels, a
classic hallmark of type 2 diabetes. The researchers have discovered a key
hormone called IL-33 (interleukin-33), which was able to selectively boost Treg
populations in fat tissue, effectively halting the development of type 2
diabetes, or even reversing the disease in preclinical models. Treatments that
mimic IL-33 could have the potential to reduce obesity-related inflammation and
type 2 diabetes.
The findings of this research
underscore the importance of ‘healthy’ fat tissue in maintaining a healthy
body, rather than being thought as simply being an energy storage reservoir. Fat
tissue is increasingly being recognized as an important organ that releases
hormones and regulates development.
1. Vasanthakumar
A, Moro K, Xin A, Liao Y, Gloury R, Kawamoto S, et al. The transcriptional
regulators IRF4, BATF and IL-33 orchestrate development and maintenance of
adipose tissue-resident regulatory T cells. Nat Immunol. 2015 Jan 19;
Image courtesy: http://www.wehi.edu.au/
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