hESC (WA01/H1 line; WiCell) were cultured on Matrigel-coated plates (BD Biosciences) in Essential 8 medium (A1517001; Life Technologies). Differentiation was carried out following a seven-stage protocol as previously described (21 (link)–23 (link)) with further modifications. The glucose concentration of each stage was as follows: S1–S4 cells were cultured in 10.5 mmol/L glucose; S5–S6 cells were cultured in 20.5 mmol/L glucose; and S7 cells were cultured in 5.5 mmol/L glucose.