Glucokinase (Gck) functions as a glucose sensor for insulin secretion, and in mice fed standard chow, haploinsufficiency of β cell–specific Gck (Gck+/–) causes impaired insulin secretion to glucose, although the animals have a normal β cell mass. When fed a high-fat (HF) diet, wild-type mice showed marked β cell hyperplasia, whereas Gck+/– mice demonstrated decreased β cell replication and insufficient β cell hyperplasia despite showing a similar degree of insulin resistance. DNA chip analysis revealed decreased insulin receptor substrate 2 (Irs2) expression in HF diet–fed Gck+/– mouse islets compared with wild-type islets. Western blot analyses confirmed upregulated Irs2 expression in the islets of HF diet–fed wild-type mice compared with those fed standard chow and reduced expression in HF diet–fed Gck+/– mice compared with those of HF diet–fed wild-type mice. HF diet–fed Irs2+/– mice failed to show a sufficient increase in β cell mass, and overexpression of Irs2 in β cells of HF diet–fed Gck+/– mice partially prevented diabetes by increasing β cell mass. These results suggest that Gck and Irs2 are critical requirements for β cell hyperplasia to occur in response to HF diet–induced insulin resistance.
Yasuo Terauchi, Iseki Takamoto, Naoto Kubota, Junji Matsui, Ryo Suzuki, Kajuro Komeda, Akemi Hara, Yukiyasu Toyoda, Ichitomo Miwa, Shinichi Aizawa, Shuichi Tsutsumi, Yoshiharu Tsubamoto, Shinji Hashimoto, Kazuhiro Eto, Akinobu Nakamura, Mitsuhiko Noda, Kazuyuki Tobe, Hiroyuki Aburatani, Ryozo Nagai, Takashi Kadowaki
Guidelines: The Editorial Board will only consider letters that we deem relevant and of interest to our readers. We will not post data that have not been subjected to peer review, nor will we post letters that are essentially a reiteration of another letter. All accepted letters will be posted on our website within one week of acceptance. We reserve the right to edit any letter for length, content, and clarity. Authors of all accepted letters will be asked to preview any changes. Authors will be notified by e-mail if their letters were not accepted. As this is a final decision, no appeals will be considered.
Specific requirements: All letters must be 400 words or fewer. You may enter the letter as plain text or HTML. The author's name and e-mail address are required, and will be posted with the letter. All possible conflicts of interest must be noted, even if they are not posted. If you wish to include a figure (keep in mind that non-peer-reviewed data will not be posted), please contact the editors directly at email@example.com.