Diabetic hope of end to injections

Press, 21 February 1987, Page 21

Diabetic hope of end to injections

By

ROBIN McKIE,

London “Observer*’

science correspondent

Daily insulin injections for diabetics may be .replaced by a revolutionary one-off injection of living insulin-making cells. The single annual treatments would consist of pig or cow pancreas cells — each half a millimetre in diameter and wrapped in a special biological membrane. Indeed, scientists believe the technique, called micro-encapsu-lation, could ultimately help people with other conditions — for instance by membrane-wrap-ping brain cells which could be used to treat Parkinson’s disease and coma victims.

Researchers have already carried out successful insulin cell transplants in rats and mice, in which diabetes has been artifically induced, using micro-en-capsulation. The animals survived without insulin injections for more than a year. The cells are placed in the special membranes, which are derived from seaweed, to protect them from attacks by the body’s defence systems. “It is an extremely exciting technique and a great deal of progress is being made,” says Dr Joyce Baird, of the metabolic unit at the Western General Hospital, Edinburgh, and whose team is working on micro-encap-sulation research. “If successful, it will allow diabetics to avoid the considerable discomfort of daily injections and will also mean their blood insulin levels are kept at exactly the right levels.” Diabetes, in its most, serious form, is caused by destruction of the part of the pancreas that contains clusters of cells called the islets of Langerhans. Some of these cells make insulin, a chemical that carries glucose, the blood’s main form of fuel, into cells. Without it, tissues and muscles starve. The first symptoms are fatigue, weight loss and thirst, and ultimately, without treatment, sufferers-die.

To replace lost insulin, diabetics inject themselves daily with insulin that is derived from cows or pigs, or which is genetically engineered. However, these only crudely deal with fluctuating levels of glucose in the blood, variations that can later lead to kidney, heart and eye problems. So, researchers asked,, why not "transplant” living insulin cells? To do this, they, have had to develop the micro-encapsulation membranes that are made of two layers of a substance called sodium algenate, a seaweed derivative, between which is sandwiched a thin layer of a chemical called polylysine. These membranes, which protect the foreign insulin cells from

the body’s defence system, must be made of a chemical that does not damage the sensitive cells that lie within. In addition, the membrane must be covered with tiny holes big enough to allow nutrients in the blood to enter and provide food, and which permit insulin to be released. However, they must also be small enough to block out the large marauding cells of the immune systems which would otherwise enter and devour the foreign “islets” inside. Dr William Cochrane, of Connaught Laboratories, Toronto, a company which is one of the leaders in micro-encapsulation development, says: “When we perfect the technique, we will use cells taken from cows and pigs and which are known to make insulin similar to the human variety,- to inject in diabetics.”