I am Dr Rajeswaran, an endocrinologist and diabetologist. I want to discuss an emerging research area in diabetes, how tiny RNA molecules carried by exosomes from fat cells can influence insulin sensitivity.   

I have treated many patients with diabetes and have witnessed firsthand how this condition progresses differently in each individual. Recent advances in our understanding of cell-to-cell communication have highlighted why this happens, particularly through tiny vesicles called exosomes. 

Exosomes are nan-sized vesicles, roughly 30-150 nanometers in diameter, released by virtually all cells in our body, including fat cells, or what we medically call adipocytes. These vesicles travel through bodily fluids like blood, carrying important signalling molecules such as proteins, lipids, and non-coding RNAs, especially microRNAs. 

Why does this matter in diabetes?

In type 2 diabetes, one of the key issues is insulin resistance, where the body’s cells become less responsive to insulin, making it harder to regulate blood glucose levels. And here’s where exosomes come into action. 

Recent studies have shown that adipocyte-derived exosomes are not just metabolic bystanders. They actively communicate with other organs, especially the liver and muscle tissue, both of which are central in glucose metabolism. When adipose tissue becomes inflamed or dysfunctional, as often happens in obesity, it releases exosomes packed with specific miRNAs that can impair insulin signalling in these distant tissues. 

For example, miR-27a and miR-15, which are elevated in exosomes from obese fat tissue, have been shown to downregulate insulin receptor substrates in muscle cells and hepatocytes. This leads to a cascade of reduced glucose uptake and increased blood sugar levels. 

On the other hand, in a healthy state, exosomes may carry beneficial miRNAs like miR-99b or miR-223, which can enhance insulin sensitivity and reduce inflammation. 

So essentially, these exosomes are like messengers, and their message depends on the health of the fat cells they come from. When adipose tissue is healthy, it helps maintain metabolic balance, but in obesity or chronic inflammation, the message becomes harmful, promoting systemic insulin resistance. 

This opens some possibilities. 

Firstly, exosomal miRNAs might become early biomarkers that could potentially detect shifts in their levels in the blood before insulin resistance becomes clinically apparent. Secondly, researchers are now exploring ways to modify exosomes or block the harmful RNA signals as a potential therapeutic approach. 

 We used to think of fat as passive storage. But now, we are learning that fat talks to the rest of the body sometimes in helpful ways, and sometimes in ways that promote diabetes.