More toxic tangles, this time in diabetes.

For years, neurobiologists have debated the role of a peptide called beta-amyloid in the development of Alzheimer's disease (SN: 1/1/94, p.8). Now, it appears that a similar protein particle may be involved in type II diabetes, a disease that typically strikes adults.

Like the beta-amyloid peptide, this 37-amino-acid particle, called amylin, aggregates; but instead of forming plaques in the brain, as beta-amyloid does, amylin accumulates near insulin-producing beta cells located in the pancreas.

Scientists suspected that amylin interferes with the body's ability to regulate sugar (SN: 10/20/90, p.250). But they found that when clumps of amylin contact the surfaces of beta cells, the substance can also cause the cells to die, report Alfredo Lorenzo of Harvard Medical School and Children's Hospital in Boston and his colleagues.

For the experiments, they developed ways of growing rat and human pancreatic tissue in a laboratory dish. While aggregated human amylin killed the cells, dissolved amylin did not, the scientists report in the April 21 NATURE.

Amylin's toxicity seems to be related to its tendency to form tangled masses; beta-amyloid plaques have a similar, though weaker, effect on the pancreatic cells, says Harvard's Bruce A. Yankner. As with beta-amyloid, the amylin deposits somehow initiate the process of programmed cell death.