Effect of Therapeutic Ultrasound on the Release of Insulin, Glucagon, and Alpha-Amylase from Ex Vivo Pancreatic Models.

Abstract

Our previously published studies showed the potential of therapeutic ultrasound (US) as a novel non-pharmacological alternative for the treatment of secretory deficiencies in type 2 diabetes. Despite showing enhanced insulin release from beta cells, these studies did not explore the potential effects of US treatment on other cells in the islets of Langerhans such as glucagon-secreting alpha cells or acinar cells of the exocrine pancreas. We applied US parameters found capable of safely stimulating insulin secretion from pancreatic beta cells (f=800 kHz, ISPTA =0.5-1 W/cm2 , 5 minutes) to a diced rabbit pancreas model in culture plates (n=6 per group). Released quantities of insulin and glucagon in response to US treatment were measured by collecting aliquots of the extracellular medium prior to the start of the treatment (t=0 minute), immediately after treatment (t=5 minutes) and 30 minutes after the end of treatment (t=35 minutes). Potential release of digestive enzyme alpha-amylase as a result of US treatment was evaluated in rabbit pancreas experiments. Preliminary studies were also performed in a small number of human pancreatic islets in culture plates (n=3 per group). The general integrity of the US-treated rabbit pancreatic tissue and human pancreatic islets was evaluated through histological analysis. While sham-treated rabbit pancreas samples showed decreased extracellular insulin content, there was an increase in insulin release at t=5 minutes from samples treated with US at 800 kHz and 1 W/cm2 (P <.005). Furthermore, no further insulin release was detected at t=35 minutes. No statistically significant difference in extracellular glucagon and alpha-amylase concentrations was observed between US-treated and sham rabbit pancreas groups. Preliminary studies in human islets appeared to follow trends observed in rabbit pancreas studies. Islet and other pancreatic tissue integrity did not appear to be affected by the US treatment. A potential US-based strategy for enhanced insulin release would require optimization of insulin secretion from pancreatic beta cells while minimizing glucagon and pancreatic enzyme secretions.