We have previously reported that the fractalkine (FKN)/CX3CR1 system represents a novel regulatory mechanism for insulin secretion and β cell function. Here, we demonstrate that chronic administration of a long-acting form of FKN, FKN-Fc, can exert durable effects to improve glucose tolerance with increased glucose-stimulated insulin secretion and decreased β cell apoptosis in obese rodent models. Unexpectedly, chronic FKN-Fc administration also led to decreased α cell glucagon secretion. In islet cells, FKN inhibited ATP-sensitive potassium channel conductance by an ERK-dependent mechanism, which triggered β cell action potential (AP) firing and decreased α cell AP amplitude. This results in increased glucose-stimulated insulin secretion and decreased glucagon secretion. Beyond its islet effects, FKN-Fc also exerted peripheral effects to enhance hepatic insulin sensitivity due to inhibition of glucagon action. In hepatocytes, FKN treatment reduced glucagon-stimulated cAMP production and CREB phosphorylation in a pertussis toxin–sensitive manner. Together, these results raise the possibility of use of FKN-based therapy to improve type 2 diabetes by increasing both insulin secretion and insulin sensitivity.
Matthew Riopel, Jong Bae Seo, Gautam K. Bandyopadhyay, Pingping Li, Joshua Wollam, Heekyung Chung, Seung-Ryoung Jung, Anne Murphy, Maria Wilson, Ron de Jong, Sanjay Patel, Deepika Balakrishna, James Bilakovics, Andrea Fanjul, Artur Plonowski, Duk-Su Koh, Christopher J. Larson, Jerrold M. Olefsky, Yun Sok Lee
Electrophysiology studies in α cells.