Gliadin Fragments and a Specific Gliadin 33-mer Peptide Close KATP Channels and Induce Insulin Secretion in INS-1E Cells and Rat Islets of Langerhans

Abstract

In non-obese diabetic (NOD) mice, diabetes incidence is reduced by a gluten-free diet. Gluten peptides, such as the compound gliadin, can cross the intestinal barrier and may directly affect pancreatic beta cells. We investigated the effects of enzymatically-digested gliadin in NOD mice, INS-1E cells and rat islets. Six injections of gliadin digest in 6-week-old NOD mice did not affect diabetes development, but increased weight gain (20% increase by day 100). In INS-1E cells, incubation with gliadin digest induced a dose-dependent increase in insulin secretion, up to 2.5-fold after 24 hours. A similar effect was observed in isolated rat islets (1.6-fold increase). In INS-1E cells, diazoxide reduced the stimulatory effect of gliadin digest. Additionally, gliadin digest was shown to decrease current through KATP-channels. A specific gliadin 33-mer had a similar effect, both on current and insulin secretion. Finally, INS-1E incubation with gliadin digest potentiated palmitate-induced insulin secretion by 13% compared to controls. Our data suggest that gliadin fragments may contribute to the beta-cell hyperactivity observed prior to the development of type 1 diabetes.

Dietary gluten increases natural killer cell cytotoxicity and cytokine secretion

“…This raised beta-cell activity may contribute to an increase in surface Ags recruiting immune cells to the islets, along with increased secretion of cytokines. These findings correlate with a previous study showing that gliadin increases insulin secretion in rat islets and the INS-1E cell line [9].…”

“…This raised beta-cell activity may contribute to an increase in surface Ags recruiting immune cells to the islets, along with increased secretion of cytokines. These findings correlate with a previous study showing that gliadin increases insulin secretion in rat islets and the INS-1E cell line [9].In vivo, we found several gluten-induced effects in immunocompetent BALB/c mice and diabetes-prone NOD mice. We showed that an STD gluten-containing diet increased the amount of NKp46…”

“…HeLa cells (kindly provided by Lars H. Engelholm, Rigshospitalet, Copenhagen, Denmark) were cultured in DMEM (Lonza) supplemented with 10% FCS. Gliadin was enzymatically digested, prepared, and tested as described in [9]. In gliadin stimulation experiments, the cells were exposed to 300 μg/mL gliadin digest for 24 h, unless otherwise noted.…”

“…MIN6 cells [28] (kindly provided by J. Miyazaki, Osaka University) were grown at 37°C and 5% CO 2 Gliadin was enzymatically digested, prepared, and tested as described in [9]. In gliadin stimulation experiments, the cells were exposed to 300 μg/mL gliadin digest for 24 h, unless otherwise noted.…”

“…A recently published case report describes a boy with T1D who was able to maintain a low fasting blood glucose level without insulin therapy for more than 20 months after the time of diagnosis by adhering to a GF diet [8]. Lately, it has also been suggested that a family of gluten proteins known as gliadins may contribute directly to beta-cell hyperactivity, as enzymatically digested gliadin and a 33-mer gliadin fragment increase insulin secretion from beta cells by affecting the K ATP channel current [9]. This process could induce increased Ag expression of the beta-cell surface and prevent beta-cell rest [10].…”