One afternoon, Ivan Barriga woke up in his car on the side of the road with no memory of how he ended up there. Luckily, he was not injured, but his severe case of type 1 diabetes put him at risk for passing out again without warning.
"I was constantly frustrated and fearful of the next insulin reaction because it was a life and death situation," says Barriga, who at 18-years-old was diagnosed with type 1 diabetes, a condition in which the insulin-producing cells in the pancreas stop making enough insulin, a hormone needed to convert sugar into energy.
Type 1 diabetes is considered an autoimmune disease because the body's own immune system mistakenly attacks and destroys the pancreas' insulin-producing cells. In Barriga's case, the condition quickly advanced to what doctors call "brittle" diabetes, meaning that his blood sugar fluctuated wildly without warning, causing him to pass out before he was able to treat himself.
People with type 1 diabetes require multiple insulin injections each day in order to maintain safe blood sugar levels. Barriga gave himself insulin injections four times a day for 16 years and then began wearing an insulin pump in 2001, but still continued to pass out periodically from low blood sugar. The only curable treatment for type 1 diabetes is a pancreas transplant — a major surgery with a risk of organ rejection.
"I did consider a pancreas transplant," says Barriga, now 35-years-old. "But I didn't want to have a full organ transplant at the time, because the risks are great, the recovery process is long and the medications to prevent organ rejection are very strong."
To prevent organ rejection, a pancreas transplant recipient must take powerful anti-rejection medications for the rest of their life. These medications have a number of side effects and make the transplant recipient more susceptible to other illnesses.
However, now a different kind of non-surgical and minimally-invasive transplant involving islet cells can temporarily reverse diabetes, allowing patients like Barriga to live free from the condition for the first time in their lives. Barriga received islet transplants at UCSF in January 2004 and August 2005. He has been insulin free for the past nine months and no longer passes out due to low blood sugar.
"The transplants have been highly effective because I have hypoglycemic awareness, meaning that I now have the ability to notice if my blood sugars are low, so the chances of passing out have diminished greatly. This is a real life saving effect of the transplant," says Barriga. "My blood sugars have also improved dramatically which will help to lessen the long-term effects of diabetes."
During an islet transplant, insulin-producing beta cells contained in clusters called islets are isolated from a cadaver donor's pancreas, then injected through the skin into the portal vein of the recipient's liver, where they flow into the liver, lodge in small blood vessels, and release insulin. For an average-size person, a typical transplant requires about one million islets, equal to two donor organs.
"The isolation process is labor-intensive and takes several days, but for the recipient, the transplant is a relatively simple procedure that does not require major surgery or general anesthesia. Patients can usually go home in one to two days," says Dr. Andrew Posselt, who heads UCSF's Pancreatic Islet Transplantation Program. "Ivan's procedure took less than three hours and he was feeling great afterward. The islets begin working almost immediately, and within three or four weeks, most patients can completely stop using insulin."
In the past two years, it has become clear that islet transplantation works. Like Barriga, many recipients have been able to discard their blood glucose meters, their pumps and their syringes and live free of diabetes. Though in order to prevent rejection of the islets, patients must take immunosuppressive drugs for the rest of their lives.
Current treatment protocols for islet transplants require the use of insulin-producing cells from cadaveric pancreases, rather than embryonic stem cells that can be developed into islet cells. There are far too few donor pancreases available to provide islet cells necessary for the millions of diabetics.
Fortunately, though, with the passing of California's Proposition 71 and the recent formation of the California Institute of Regenerative Medicine, UCSF diabetes researchers and doctors are optimistic that stem cell research will yield a new, unlimited source of beta cells for use in islet transplantation. Known as the Diabetes Stem Cell Pipeline, UCSF is the only comprehensive and strategic stem cell therapy program in the country devoted to bringing together basic and clinical researchers to advance our understanding of type 1 and type 2 diabetes.
"The possibility for a global cure is within our grasp, but we need a lot more islets cells to help the 100 million diabetics in the world," says Barriga. "My hope is that through stem cell research we can duplicate these islet cells and provide them to all diabetics on a yearly basis."
Story written in August 2006.
Abby Sinnott is a freelance writer in San Francisco.