SIGNALLING INSTRUCTIONS: Obesity promotes insulin resistance via exosomal microRNAs, according to researchers at the University of California, San Diego. Macrophages associated with adipocytes in mouse fatty tissue package microRNAs into exosomes, which are released into circulation and are taken up by other cell types. When researchers treated lean mice with exosomes made by macrophages from obese mice, they found that despite remaining lean, recipient mice became insulin resistant. In contrast, treating obese mice with exosomes from lean mice improved the recipient animals’ insulin sensitivity, without reducing their weight.© LAURIE O'KEEFE
The paper
W. Ying et al., “Adipose tissue macrophage-derived exosomal miRNAs can modulate in vivo and in vitro insulin sensitivity,” Cell, 171:372-84.e12, 2017.
Jerrold Olefsky has spent much of the last decade trying to decipher the connection between obesity and the risk for type 2 diabetes. It’s now known that “in obesity, the adipose tissue becomes highly inflamed and fills up with macrophages and other immune cells,” Olefsky, an endocrinologist at the University of California, San Diego, explains. “This inflammation is very important for causing insulin resistance,” in which cells fail to respond to hormonal signals to take up glucose.
But a crucial piece of the puzzle has been missing. “Insulin resistance is a systemic thing,” Olefsky says. For inflamed fat tissue to trigger it, ...
