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Analysis of the protein related receptor GPR92 in G-cells.

Rettenberger AT, Schulze W, Breer H, Haid D - Front Physiol (2015)

Bottom Line: Our previous studies have shown that G-cells express suitable receptor types, most notably the peptone-receptor GPR92 and the amino acid receptors GPRC6A and CaSR; however, their relative importance remained unclear.The results indicate that the relative amount of receptor protein for GPR92 was much higher than for the receptor types GPRC6A and CaSR.These findings support the notion that the peptone-receptor GPR92 may be particularly relevant for sensing partially digested protein products.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physiology, University of Hohenheim Stuttgart, Germany.

ABSTRACT
A continuous assessment of ingested food in the gastric lumen is essential for fine-tuning the digestive activities, including the secretion of the regulatory hormones such as gastrin. It has been proposed that G-cells may be able to sense the amount of ingested proteins and adjust the secretion of gastrin accordingly. Our previous studies have shown that G-cells express suitable receptor types, most notably the peptone-receptor GPR92 and the amino acid receptors GPRC6A and CaSR; however, their relative importance remained unclear. To determine the relative quantity of each receptor type, individual G-cells isolated from the transgenic mouse line mGas-EGFP were analyzed by means of a Liquid Chromatography Tandem-Mass Spectrometry (LC-MS/MS) procedure. The results indicate that the relative amount of receptor protein for GPR92 was much higher than for the receptor types GPRC6A and CaSR. These findings support the notion that the peptone-receptor GPR92 may be particularly relevant for sensing partially digested protein products. This view was supported by the finding that a high-protein diet affected the expression level of the peptone-receptor GPR92 in the gastric antrum as well as in the circumvallate papillae.

No MeSH data available.


Related in: MedlinePlus

Effects of high-protein (HP) feeding for different time intervals on the relative amount of mRNA for GPR92 in the murine gastric antrum and circumvallate papillea (CV). The results of the qPCR analyses revealed that HP feeding resulted in time-dependent alterations of transcript levels: After 2 days the relative amount of mRNA for GPR92 were significantly reduced (P < 0.001) in the antrum region whereas mRNA quantities in the CV were significantly increased (P < 0.001). 21 days of HP feeding did not lead to significant changes of transcript levels. However, after 35 days only in the gastric antrum a strong increase of GPR92 mRNA amount was observed (P = 0.0094). After 84 days the HP diet induced increase of GPR92 transcripts in the antrum was no longer detectable. Instead, there was a decrease of circumvallate GPR92 mRNA level (P = 0.0493). Relative expressions were calculated using the formula: ΔΔCt = (E(target)ΔCt(target(control−HP)))/(E(reference)ΔCt(reference(control−HP))) with corresponding efficiencies (EGPR92: 1.988, EGPRC6A: 1.967 and ECaSR: 1.965). Data are expressed as mean ± S.E.M. Dashed line denotes baseline levels corresponding to no relative changes of mRNA expression (values = 1). Data were generated in triplicate with n = 4−5 mice in each group. Significant results were determined by the unpaired t-test (*P < 0.05; **P < 0.005; ***P < 0.001 against baseline level).
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Figure 4: Effects of high-protein (HP) feeding for different time intervals on the relative amount of mRNA for GPR92 in the murine gastric antrum and circumvallate papillea (CV). The results of the qPCR analyses revealed that HP feeding resulted in time-dependent alterations of transcript levels: After 2 days the relative amount of mRNA for GPR92 were significantly reduced (P < 0.001) in the antrum region whereas mRNA quantities in the CV were significantly increased (P < 0.001). 21 days of HP feeding did not lead to significant changes of transcript levels. However, after 35 days only in the gastric antrum a strong increase of GPR92 mRNA amount was observed (P = 0.0094). After 84 days the HP diet induced increase of GPR92 transcripts in the antrum was no longer detectable. Instead, there was a decrease of circumvallate GPR92 mRNA level (P = 0.0493). Relative expressions were calculated using the formula: ΔΔCt = (E(target)ΔCt(target(control−HP)))/(E(reference)ΔCt(reference(control−HP))) with corresponding efficiencies (EGPR92: 1.988, EGPRC6A: 1.967 and ECaSR: 1.965). Data are expressed as mean ± S.E.M. Dashed line denotes baseline levels corresponding to no relative changes of mRNA expression (values = 1). Data were generated in triplicate with n = 4−5 mice in each group. Significant results were determined by the unpaired t-test (*P < 0.05; **P < 0.005; ***P < 0.001 against baseline level).

Mentions: As an independent approach to assess a possible role of GPR92 in protein sensing of G-cells it was hypothesized that a high-protein (HP) diet (59% calories from protein) may have an impact on the expression level of the peptone-receptor GPR92. Toward this goal, by means of real-time quantitative PCR (qPCR), the amounts of receptor mRNA were determined in antral tissue samples from mice which were fed the HP diet for different time periods. In addition, the transcript levels for GPR92 in the circumvallate papilla were determined, where the peptone-receptor is expressed in taste sensory cells (Haid et al., 2013). The results are depicted in Figure 4; it is evident that in the presence of high luminal protein concentration the relative amounts of mRNA for GPR92 changed over time. During a period of 2 days the level of transcripts for GPR92 in the circumvallate papillae was significantly increased in HP fed mice compared to controls (***P < 0.001) while no change was observed in antral tissue. In contrast after 35 days the relative amount of mRNA for GPR92 in the antrum was strongly increased in HP fed mice (**P = 0.0094). No difference was observed in the circumvallate papillae. After a period of 84 days the relative amount of mRNA for GPR92 was back to baseline level. Together the results demonstrate that the expression of the peptone-receptor GPR92 in in the stomach and in the taste buds was affected by feeding a protein enriched diet, but seems to be controlled by different parameters.


Analysis of the protein related receptor GPR92 in G-cells.

Rettenberger AT, Schulze W, Breer H, Haid D - Front Physiol (2015)

Effects of high-protein (HP) feeding for different time intervals on the relative amount of mRNA for GPR92 in the murine gastric antrum and circumvallate papillea (CV). The results of the qPCR analyses revealed that HP feeding resulted in time-dependent alterations of transcript levels: After 2 days the relative amount of mRNA for GPR92 were significantly reduced (P < 0.001) in the antrum region whereas mRNA quantities in the CV were significantly increased (P < 0.001). 21 days of HP feeding did not lead to significant changes of transcript levels. However, after 35 days only in the gastric antrum a strong increase of GPR92 mRNA amount was observed (P = 0.0094). After 84 days the HP diet induced increase of GPR92 transcripts in the antrum was no longer detectable. Instead, there was a decrease of circumvallate GPR92 mRNA level (P = 0.0493). Relative expressions were calculated using the formula: ΔΔCt = (E(target)ΔCt(target(control−HP)))/(E(reference)ΔCt(reference(control−HP))) with corresponding efficiencies (EGPR92: 1.988, EGPRC6A: 1.967 and ECaSR: 1.965). Data are expressed as mean ± S.E.M. Dashed line denotes baseline levels corresponding to no relative changes of mRNA expression (values = 1). Data were generated in triplicate with n = 4−5 mice in each group. Significant results were determined by the unpaired t-test (*P < 0.05; **P < 0.005; ***P < 0.001 against baseline level).
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Figure 4: Effects of high-protein (HP) feeding for different time intervals on the relative amount of mRNA for GPR92 in the murine gastric antrum and circumvallate papillea (CV). The results of the qPCR analyses revealed that HP feeding resulted in time-dependent alterations of transcript levels: After 2 days the relative amount of mRNA for GPR92 were significantly reduced (P < 0.001) in the antrum region whereas mRNA quantities in the CV were significantly increased (P < 0.001). 21 days of HP feeding did not lead to significant changes of transcript levels. However, after 35 days only in the gastric antrum a strong increase of GPR92 mRNA amount was observed (P = 0.0094). After 84 days the HP diet induced increase of GPR92 transcripts in the antrum was no longer detectable. Instead, there was a decrease of circumvallate GPR92 mRNA level (P = 0.0493). Relative expressions were calculated using the formula: ΔΔCt = (E(target)ΔCt(target(control−HP)))/(E(reference)ΔCt(reference(control−HP))) with corresponding efficiencies (EGPR92: 1.988, EGPRC6A: 1.967 and ECaSR: 1.965). Data are expressed as mean ± S.E.M. Dashed line denotes baseline levels corresponding to no relative changes of mRNA expression (values = 1). Data were generated in triplicate with n = 4−5 mice in each group. Significant results were determined by the unpaired t-test (*P < 0.05; **P < 0.005; ***P < 0.001 against baseline level).
Mentions: As an independent approach to assess a possible role of GPR92 in protein sensing of G-cells it was hypothesized that a high-protein (HP) diet (59% calories from protein) may have an impact on the expression level of the peptone-receptor GPR92. Toward this goal, by means of real-time quantitative PCR (qPCR), the amounts of receptor mRNA were determined in antral tissue samples from mice which were fed the HP diet for different time periods. In addition, the transcript levels for GPR92 in the circumvallate papilla were determined, where the peptone-receptor is expressed in taste sensory cells (Haid et al., 2013). The results are depicted in Figure 4; it is evident that in the presence of high luminal protein concentration the relative amounts of mRNA for GPR92 changed over time. During a period of 2 days the level of transcripts for GPR92 in the circumvallate papillae was significantly increased in HP fed mice compared to controls (***P < 0.001) while no change was observed in antral tissue. In contrast after 35 days the relative amount of mRNA for GPR92 in the antrum was strongly increased in HP fed mice (**P = 0.0094). No difference was observed in the circumvallate papillae. After a period of 84 days the relative amount of mRNA for GPR92 was back to baseline level. Together the results demonstrate that the expression of the peptone-receptor GPR92 in in the stomach and in the taste buds was affected by feeding a protein enriched diet, but seems to be controlled by different parameters.

Bottom Line: Our previous studies have shown that G-cells express suitable receptor types, most notably the peptone-receptor GPR92 and the amino acid receptors GPRC6A and CaSR; however, their relative importance remained unclear.The results indicate that the relative amount of receptor protein for GPR92 was much higher than for the receptor types GPRC6A and CaSR.These findings support the notion that the peptone-receptor GPR92 may be particularly relevant for sensing partially digested protein products.

View Article: PubMed Central - PubMed

Affiliation: Institute of Physiology, University of Hohenheim Stuttgart, Germany.

ABSTRACT
A continuous assessment of ingested food in the gastric lumen is essential for fine-tuning the digestive activities, including the secretion of the regulatory hormones such as gastrin. It has been proposed that G-cells may be able to sense the amount of ingested proteins and adjust the secretion of gastrin accordingly. Our previous studies have shown that G-cells express suitable receptor types, most notably the peptone-receptor GPR92 and the amino acid receptors GPRC6A and CaSR; however, their relative importance remained unclear. To determine the relative quantity of each receptor type, individual G-cells isolated from the transgenic mouse line mGas-EGFP were analyzed by means of a Liquid Chromatography Tandem-Mass Spectrometry (LC-MS/MS) procedure. The results indicate that the relative amount of receptor protein for GPR92 was much higher than for the receptor types GPRC6A and CaSR. These findings support the notion that the peptone-receptor GPR92 may be particularly relevant for sensing partially digested protein products. This view was supported by the finding that a high-protein diet affected the expression level of the peptone-receptor GPR92 in the gastric antrum as well as in the circumvallate papillae.

No MeSH data available.


Related in: MedlinePlus