Fig 1.
Involvement of Gαi/o signaling in NMU-suppressed GSIS.
Insulin secretion from MIN6-K8 cells (A) (n = 4), isolated mouse islets (B, C) (n = 4), and human islets (D) (n = 4) with or without PTX or YM254890 pretreatment. (E) Efficacy of Gαi/o knockdown in MIN6-K8 cells (n = 4). (F) NMU-induced suppression of GSIS after Gαi/o knockdown in MIN6-K8 cells (n = 4). (G) mRNA levels of Gnao1 or Gnai2 in MIN6-K8 cells after respective knockdown of Gnai2 or Gnao1 (n = 4). *P < 0.05, **P < 0.01, ***P < 0.001. n.s., not significant.
Fig 2.
Effects of NMU on intracellular cAMP production.
Intracellular cAMP levels in mouse islets (A) (n = 4) and human islets (B) (n = 4) with or without NMU or somatostatin treatment under 16.7 mM glucose. **P < 0.01.
Fig 3.
Effects of NMU on [Ca2+]i in β cells.
(A, C) Representative Fura-2-AM ratios in dispersed mouse β cells in response to NMU with PTX or YM254890 (A), β cell‒derived MIN6-K8 cells in response to ghrelin or somatostatin (C). (B, D) Average incremental AUC (iAUC) (8–15 min) for [Ca2+]i in (A) and (C), respectively (n = 16). **P < 0.01, ***P < 0.001. n.s., not significant.
Fig 4.
Effects of Gnai2 and Gnao1 knockdown on NMU-induced alterations related to mitochondrial function and ER stress in MIN6-K8 cells.
(A) mRNAs related to mitochondrial dynamics (n = 4). (B) Chop mRNA (n = 4). (C) Pgc-1α, Nrf1, and Tfam mRNAs (n = 4). (D) Atp2a3, Ryr2, and Itpr2 mRNAs (n = 4). (E, F) Mitochondrial membrane potential determined by TMRE staining (n = 4). (G) Intracellular ATP level (n = 4). *P < 0.05, **P < 0.01, ***P < 0.001.