S20G mutation of the amylin gene in Japanese patients with type 2 diabetes.

Amylin is a major protein component of islet amyloid, and thought to be a pancreatic islet hormone that plays a role similar to insulin and glucagon in the maintenance of glucose homeostasis [1]. Recently, Sakagashira et al. [2] reported that a serine to glycine missense mutation at position 20 of the amylin molecule (S20G) was found in 4.1% of Japanese patients with type 2 diabetes and 10% of those with early-onset type 2 diabetes, whereas the mutation was not found in non-diabetic subjects and type 1 diabetic patients. Racial differences have been noted in the frequency and role of the S20G mutation in association with the development of diabetes. No mutation was found in Caucasians [3–5]. The mutation was found in Chinese and Taiwanese subjects, but an association with diabetes was only established among the former [6,7]. In contrast to the findings of Sakagashira et al., Yamada et al. [8] reported that the frequency of the mutation was not statistically different between Japanese type 2 diabetic patients and subjects with normal glucose tolerance (NGT). To help clarify this apparent inconsistency in the role of the S20G mutation in the development of diabetes in Japanese subjects, we investigated the mutation in 308 Japanese patients with type 2 diabetes aged from 20 to 89 years (60.9912.2 years, mean9SD), and 149 NGT subjects with no family histories of diabetes aged from 40 to 67 years (50.996.3 years, mean9SD). Type 2 diabetes and NGT were defined by the World Health Organization (WHO) criteria. In the type 2 diabetic patients (a total of 175 men and 133 women), 150 subjects had family histories of dia* Corresponding author. Tel.: +81-76-2652234; fax: +8176-2344250.