Back in 2012, a reader asked "Have you heard of a proposed new drug based on the hormone irisin?"
My reply to the reader was brief ("It's way too early to speculate whether this will lead to new therapy for any condition."), but I decided to have another look at irisin; I concluded "It's way too early to get anyone's hopes up that this putative hormone will make any difference in diabetes or any other condition. Come back in a few years, and ask again."
It's now a few years later, and we now have the answer. Irisin is a myth. And the company that was promoting it sputtered, and closed its doors, before being acquired by another company. And their corporate website is gone (except on the Wayback Machine).
The publication that debunked irisin is titled Irisin – a myth rather than an exercise-inducible myokine. The authors concluded that others had "raised the question whether irisin is a “Greek goddess or a Greek myth”. Our results provide experimental evidence for irisin being a myth." A detailed discussion of the new study is available on-line in a commentary "'Exercise Protein' Irisin Fades to Myth - Faulty assays undermine results of dozens of published studies." Basically, the method used to measure irisin activity was faulty.
This reinterpretation of the role, if any, of irisin leaves some folks look a little silly; for instance, Joslin bought into the concept: "Joslin Partners with Ember Therapeutics to Develop Drug Treatment Approaches from “Brown Fat” Findings".
But the main point of the present essay is simple: Whenever you read a press release about a new diabetes breakthrough, and your heart beats faster at the thought of how the breakthrough will transform diabetes care, take it with a grain of salt. (And if you might be tempted to invest in the company, remember another adage: "There's a sucker born every minute.")