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Effects of High Glucose Levels and Glycated Serum on GIP Responsiveness in the Pancreatic Beta Cell Line HIT-T15.

Puddu A, Sanguineti R, Montecucco F, Viviani GL - J Diabetes Res (2015)

Bottom Line: The results showed that incubation with GS alone altered intracellular GIP signaling and decreased insulin secretion as compared to CTR.GS in combination with HG reduced the expression of GIPR and PI3K and abrogated GIP-induced AKT phosphorylation and GIP-stimulated insulin secretion.In conclusion, we showed that treatment with GS is associated with the loss of the insulinotropic effect of GIP in hyperglycemic conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, University of Genoa, Viale Benedetto XV, 16143 Genoa, Italy.

ABSTRACT
Glucose-dependent insulinotropic peptide (GIP) is an incretin hormone produced in the gastrointestinal tract that stimulates glucose dependent insulin secretion. Impaired incretin response has been documented in diabetic patients and was mainly related to the inability of the pancreatic beta cells to secrete insulin in response to GIP. Advanced Glycation End Products (AGEs) have been shown to play an important role in pancreatic beta cell dysfunction. The aim of this study is to investigate whether the exposure to AGEs can induce GIP resistance in the pancreatic beta cell line HIT-T15. Cells were cultured for 5 days in low (CTR) or high glucose (HG) concentration in the presence of AGEs (GS) to evaluate the expression of GIP receptor (GIPR), the intracellular signaling activated by GIP, and secretion of insulin in response to GIP. The results showed that incubation with GS alone altered intracellular GIP signaling and decreased insulin secretion as compared to CTR. GS in combination with HG reduced the expression of GIPR and PI3K and abrogated GIP-induced AKT phosphorylation and GIP-stimulated insulin secretion. In conclusion, we showed that treatment with GS is associated with the loss of the insulinotropic effect of GIP in hyperglycemic conditions.

No MeSH data available.


Related in: MedlinePlus

Treatment with GS reduces GIPR protein expression in cells cultured under HG. HIT-T15 cells were cultured for 5 days in media containing 5.6 mmol/L (CTR) or 11.1 mmol/L glucose (HG) supplemented with GS. Then cells were lysed and tested for protein expression of GIPR. (a) Representative western blot analysis. (b) Quantification of densitometries of western blot bands. Data were expressed as mean ± SE of fold induction relative to GAPDH (n = 3). ∗∗∗P < 0.001 versus CTR.
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fig1: Treatment with GS reduces GIPR protein expression in cells cultured under HG. HIT-T15 cells were cultured for 5 days in media containing 5.6 mmol/L (CTR) or 11.1 mmol/L glucose (HG) supplemented with GS. Then cells were lysed and tested for protein expression of GIPR. (a) Representative western blot analysis. (b) Quantification of densitometries of western blot bands. Data were expressed as mean ± SE of fold induction relative to GAPDH (n = 3). ∗∗∗P < 0.001 versus CTR.

Mentions: GIPR is expressed in several tissues, including pancreatic islets [32]. Firstly, we confirmed the protein expression of GIPR in the pancreatic beta cell lines HIT-T15 (Figures 1(a) and 1(b)). Then, we investigated whether treatments with HG or GS would affect GIPR protein expression. Incubation with GS or HG alone did not affect GIPR expression, while combined treatment with GS and HG significantly decreased GIPR protein expression (Figures 1(a) and 1(b)).


Effects of High Glucose Levels and Glycated Serum on GIP Responsiveness in the Pancreatic Beta Cell Line HIT-T15.

Puddu A, Sanguineti R, Montecucco F, Viviani GL - J Diabetes Res (2015)

Treatment with GS reduces GIPR protein expression in cells cultured under HG. HIT-T15 cells were cultured for 5 days in media containing 5.6 mmol/L (CTR) or 11.1 mmol/L glucose (HG) supplemented with GS. Then cells were lysed and tested for protein expression of GIPR. (a) Representative western blot analysis. (b) Quantification of densitometries of western blot bands. Data were expressed as mean ± SE of fold induction relative to GAPDH (n = 3). ∗∗∗P < 0.001 versus CTR.
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4499629&req=5

fig1: Treatment with GS reduces GIPR protein expression in cells cultured under HG. HIT-T15 cells were cultured for 5 days in media containing 5.6 mmol/L (CTR) or 11.1 mmol/L glucose (HG) supplemented with GS. Then cells were lysed and tested for protein expression of GIPR. (a) Representative western blot analysis. (b) Quantification of densitometries of western blot bands. Data were expressed as mean ± SE of fold induction relative to GAPDH (n = 3). ∗∗∗P < 0.001 versus CTR.
Mentions: GIPR is expressed in several tissues, including pancreatic islets [32]. Firstly, we confirmed the protein expression of GIPR in the pancreatic beta cell lines HIT-T15 (Figures 1(a) and 1(b)). Then, we investigated whether treatments with HG or GS would affect GIPR protein expression. Incubation with GS or HG alone did not affect GIPR expression, while combined treatment with GS and HG significantly decreased GIPR protein expression (Figures 1(a) and 1(b)).

Bottom Line: The results showed that incubation with GS alone altered intracellular GIP signaling and decreased insulin secretion as compared to CTR.GS in combination with HG reduced the expression of GIPR and PI3K and abrogated GIP-induced AKT phosphorylation and GIP-stimulated insulin secretion.In conclusion, we showed that treatment with GS is associated with the loss of the insulinotropic effect of GIP in hyperglycemic conditions.

View Article: PubMed Central - PubMed

Affiliation: Department of Internal Medicine, University of Genoa, Viale Benedetto XV, 16143 Genoa, Italy.

ABSTRACT
Glucose-dependent insulinotropic peptide (GIP) is an incretin hormone produced in the gastrointestinal tract that stimulates glucose dependent insulin secretion. Impaired incretin response has been documented in diabetic patients and was mainly related to the inability of the pancreatic beta cells to secrete insulin in response to GIP. Advanced Glycation End Products (AGEs) have been shown to play an important role in pancreatic beta cell dysfunction. The aim of this study is to investigate whether the exposure to AGEs can induce GIP resistance in the pancreatic beta cell line HIT-T15. Cells were cultured for 5 days in low (CTR) or high glucose (HG) concentration in the presence of AGEs (GS) to evaluate the expression of GIP receptor (GIPR), the intracellular signaling activated by GIP, and secretion of insulin in response to GIP. The results showed that incubation with GS alone altered intracellular GIP signaling and decreased insulin secretion as compared to CTR. GS in combination with HG reduced the expression of GIPR and PI3K and abrogated GIP-induced AKT phosphorylation and GIP-stimulated insulin secretion. In conclusion, we showed that treatment with GS is associated with the loss of the insulinotropic effect of GIP in hyperglycemic conditions.

No MeSH data available.


Related in: MedlinePlus