Leptin and Insulin and Diabetes   (August 26, 2008)

A news story today, UT Southwestern doctor reports 'intriguing' diabetes breakthrough, is indeed intriguing. A research team used high levels of leptin, a substance naturally produced by fat cells, to somehow reverse the otherwise fatal effects of diabetes in rodents.

Leptin, as you may or may not know, is a hormone. It gets very little respect -- it doesn't even have its own website (although a drug company owns the domain name leptin.com, there's nothing there). It's a protein hormone, made by fat cells, that influences how the brain perceives hunger or the reverse, satiety. After a meal, leptin signals to the brain that the body has had enough to eat. As obese people have a lot of fat, one might surmise that they have a lot of leptin, and they do. But apparently these folks are somehow resistant to the usual leptin effect. This phenomenon has become the subject of a great deal of interest, as pharmaceutical companies have been investigating leptin and other substances that influence satiety.

But I digress.

These latest findings were apparently just published yesterday in the Proceedings of the National Academy of Sciences. Sadly, the paper, titled Making insulin-deficient type 1 diabetic rodents thrive without insulin, is not available on-line as of this writing. It's a bummer that the media gets to report on research without the research itself being available; among other problems, I can't be at all sure how much of the breathless media hype is based on science, and how much on wishful thinking.

Anyway, according to the news story, the research team was looking at insulin and glucagon as well as leptin. They injected genetically modified viruses that infected the rodents' liver cells and somehow turned them into leptin-producers. In a matter of days, the rats' blood sugar levels reportedly dropped to "near normal." After a few weeks, the leptin levels went down and the blood sugar levels went back up - but not nearly as high as for untreated mice. Apparently, this is the first study to show such results without insulin. "Leptin seems to do everything that insulin does - and with a more prolonged effect," according to the lead researcher.

Hmmm. Maybe leptin will turn out to be important in the treatment of diabetes. Or maybe not. I've warned before of overinterpreting rat research in an essay, Rat research and media hype. It's a shame that this story about leptin is more media hype -- this time without even being able to read the scientific information on-line.