Deletion of Gpr128 results in weight loss and increased intestinal contraction frequency

Abstract

AIM: To generate a Gpr128 gene knockout mouse model and to investigate its phenotypes and the biological function of the Gpr128 gene.

METHODS: Bacterial artificial chromosome-retrieval methods were used for constructing the targeting vector. Using homologous recombination and microinjection technology, a Gpr128 knockout mouse model on a mixed 129/BL6 background was generated. The mice were genotyped by polymerase chain reaction (PCR) analysis of tail DNA and fed a standard laboratory chow diet. Animals of both sexes were used, and the phenotypes were assessed by histological, biochemical, molecular and physiological analyses. Semi-quantitative reverse transcription-PCR and Northern blotting were used to determine the tissue distribution of Gpr128 mRNA. Beginning at the age of 4 wk, body weights were recorded every 4 wk. Food, feces, blood and organ samples were collected to analyze food consumption, fecal quantity, organ weight and constituents of the blood and plasma. A Trendelenburg preparation was utilized to examine intestinal motility in wild-type (WT) and Gpr128^-/- mice at the age of 8 and 32 wk.

RESULTS: Gpr128 mRNA was highly and exclusively detected in the intestinal tissues. Targeted deletion of Gpr128 in adult mice resulted in reduced body weight gain, and mutant mice exhibited an increased frequency of peristaltic contraction and slow wave potential of the small intestine. The Gpr128^+/+ mice gained more weight on average than the Gpr128^-/- mice since 24 wk, being 30.81 ± 2.84 g and 25.74 ± 4.50 g, respectively (n = 10, P < 0.01). The frequency of small intestinal peristaltic contraction was increased in Gpr128^-/- mice. At the age of 8 wk, the frequency of peristalsis with an intraluminal pressure of 3 cmH2O was 6.6 ± 2.3 peristalsis/15 min in Gpr128^-/- intestine (n = 5) vs 2.6 ± 1.7 peristalsis/15 min in WT intestine (n = 5, P < 0.05). At the age of 32 wk, the frequency of peristaltic contraction with an intraluminal pressure of 2 and 3 cmH₂O was 4.6 ± 2.3 and 3.1 ± 0.8 peristalsis/15 min in WT mice (n = 8), whereas in Gpr128^-/- mice (n = 8) the frequency of contraction was 8.3 ± 3.0 and 7.4 ± 3.1 peristalsis/15 min, respectively (2 cmH₂O: P < 0.05 vs WT; 3 cmH₂O: P < 0.01 vs WT). The frequency of slow wave potential in Gpr128^-/- intestine (35.8 ± 4.3, 36.4 ± 4.2 and 37.1 ± 4.8/min with an intraluminal pressure of 1, 2 and 3 cmH₂O, n = 8) was also higher than in WT intestine (30.6 ± 4.2, 31.4 ± 3.9 and 31.9 ± 4.5/min, n = 8, P < 0.05).

CONCLUSION: We have generated a mouse model with a targeted deletion of Gpr128 and found reduced body weight and increased intestinal contraction frequency in this animal model.

Keywords: G-protein-coupled receptors, Gpr128, Knockout mouse, Weight loss, Intestinal contraction frequency

Core tip: The Adhesion family is the second largest subfamily of the G-protein-coupled receptors (GPCR). The physiological function of the orphan Adhesion-GPCR Gpr128 is unknown. In the present study, we generated Gpr128 knockout mice and confirmed the selective expression of Gpr128 in the intestinal tissues. Phenotypic analysis revealed that targeted deletion of Gpr128 in the mouse resulted in reduced body weight gain and increased frequency of peristaltic contraction and slow wave potential in the small intestine. The physiological roles of Gpr128 in the gastrointestinal tract and its potential as a therapeutic target for obesity and nutritional disorders warrant further investigation.