The implants, islet cells of the pancreas, can potentially cure many cases of diabetes. A prime obstacle to wide use—lack of a safe way to avoid immune attacks on the grafts—now seems to be crumbling by Paul E. Lacy
Until about 75 years ago, the form of diabetes that usually strikes children and young adults was invariably lethal. Families and physicians watched helplessly as robust youngsters wasted away and died within weeks or months of diagnosis. By the early 1900s investigators knew the problem lay with small clusters of pancreatic cells called the islets of Langerhans. It was evident these islets normally secreted a critical hormone, later named insulin, that enabled other cells to take up the sugar glucose from the blood for energy. It was also apparent that in the diabetic patients (today said to have type I, or insulin-dependent, diabetes mellitus) insulin production had ceased. Consequently, glucose from food accumulated in the blood while other tissues starved People with the more prevalent, later-
onset form of diabetes—type II, or non-insulin-dependent—fared better because they continued to make at least some insulin.
Prospects for type I diabetics improved dramatically in the early 1920s, when insulin extracted from animals proved lifesaving. Indeed, for decades thereafter most people assumed daily injections of the hormone were tantamount to a cure. Sadly, they were mistaken. Over the years clinicians gradually came to realize that many patients eventually suffer from potentially devastating diabetes-related disorders. Microscopic blood vessels can slowly become damaged, often culminating in blindness or kidney failure, or both.
Larger vessels may become prematurely narrowed by atherosclerosis, and nerves may be disrupted as well, leading to numbness and pain in the extremities. The cause of these "long-term complications" has now been shown to be excess glucose in the blood and the consequent alteration of tissues exposed to the extra sugar. Clearly, the insulin injections on which type I diabetics depend for survival cannot precisely mimic the ability of the normal pancreas to sense blood glucose levels and put out exactly the amount of insulin needed to keep the body healthy.
The key to ensuring long-term health, then, is to provide therapy that can
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