GPR43 Suppresses Intestinal Tumor Growth by Modification of the Mammalian Target of Rapamycin Complex 1 Activity in ApcMin/+ Mice

OBJECTIVE

G protein-coupled receptor 43 (GPR43), a receptor for short-chain fatty acids, plays a role in suppressing tumor growth; however, the detailed underlying mechanism needs to be comprehensively elucidated. In this study, we investigated the role of GPR43 in inhibiting tumor growth using ApcMin/+, a murine model of intestinal tumors.

MATERIALS AND METHODS

Using GPR43-/- ApcMin/+ and GPR43+/- ApcMin/+ mice, the number of tumors was analyzed at the end of the experimental period. Immunohistochemistry, quantitative polymerase chain reaction, and Western blotting were performed to analyze cellular proliferation and proliferation-associated signal pathways.

RESULTS

Our results revealed that GPR43 deficiency resulted in increased tumor numbers in ApcMin/+ mice. Ki67 was highly expressed in GPR43-/- mice (p > 0.05). Increased expression levels of proinflammatory cytokines, including interleukin-6 and tumor necrosis factor-α, and amino acid transporters were not observed in GPR43-deficient mice compared to GPR43-sufficient mice. Furthermore, GPR43-deficient tumor tissues showed enhanced mammalian target of rapamycin-mediated phosphorylated ribosomal protein S6 kinase beta-1 (p > 0.05) and phosphorylated eukaryotic translation initiation factor 4E-binding protein 1 (p > 0.05), but not Akt (protein kinase B) phosphorylation (p = 0.7088).

CONCLUSION

Collectively, GPR43 affords protection against tumor growth at least partly through inhibition of the mammalian target of rapamycin complex 1 pathway.

Oral Administration of Compound Probiotics Ameliorates HFD-Induced Gut Microbe Dysbiosis and Chronic Metabolic Inflammation via the G Protein-Coupled Receptor 43 in Non-alcoholic Fatty Liver Disease Rats. Probiotics Antimicrob Proteins. 2019;11:175-185. [PMID: 29353414 DOI: 10.1007/s12602-017-9378-3]

The aim of this study was to investigate how the effects of compound probiotics modulate the gut microbiota, short-chain fatty acid (SCFA), body composition, serum and liver lipids, and inflammatory markers in non-alcoholic fatty liver disease (NAFLD) rats. Twenty-four male SD rats were randomly divided into 3 groups: normal control group (standard feed), high-fat diet (HFD) feeding group (83% standard feed + 10% lard oil + 1.5% cholesterol + 0.5% cholate + 5% sucrose), and compound probiotics intervention group (HFD + 0.6 g × kg^-1 × d^-1 compound probiotics). The microbial population was assessed by 16S rDNA amplification and sequence analysis. Body composition, serum and liver lipids, serum inflammatory markers, colonic SCFAs, and relative proteins were assessed. The results showed that compound probiotics significantly reduced body weight, visceral and total fat mass, and the levels of hepatic TC and TG and serum TG, FFA, ALT, LPS, IL-1β, and IL-18 (P < 0.05). The proportions of TM7 phylum (0.06 vs 1.57%, P < 0.05) clearly increased, while that of Verrucomicrobia phylum (5.69 vs 2.61%, P < 0.05) clearly decreased. Compound probiotics also increased the representation of Ruminococcus genus (0.95 vs 1.83%, P < 0.05), while the proportion of Veillonella genus decreased (0.10 vs 0.03%, P < 0.05). The levels of colonic SCFAs and GPR43, NLRP3, ASC, and CASPASE-1 proteins also changed significantly (P < 0.05). Compound probiotics modulated gut microbiota, SCFAs, and their receptor GPR43 in NAFLD rats. These changes might inhibit lipid deposition and chronic metabolic inflammation in response to the insult of HFD.

Implication of G Protein-Coupled Receptor 43 in Intestinal Inflammation: A Mini-Review

Short chain fatty acids (SCFAs, e.g., acetate, propionate, and butyrate) are a subset of fatty acids that are produced by gut microbiota during the fermentation of dietary fiber. They modulate different processes in the gastrointestinal tract and play various positive roles in mediating the intestinal health. Most beneficial roles of SCFAs in the gastrointestinal tract are mediated by directly activating its receptor, G protein-coupled receptor 43 (GPR43, also known as FFAR2). Various recent studies have demonstrated the role of GPR43 in intestinal inflammatory diseases, such as inflammatory bowel diseases. These SCFAs-mediated regulations of intestinal health are associated with neutrophil chemotaxis, T cell differentiation, activation, and subsequent cytokines production. Therefore, GPR43 could potentially be a drug target for intestinal inflammatory diseases. In this review, we review the current knowledge on the regulatory mechanisms associated with GPR43 in intestinal inflammation. The role of GPR43-mediated regulation of antibody responses is also discussed.

Function and clinical implications of short-chain fatty acids in patients with mixed refractory constipation

AIM

The present study was designed to investigate the function and clinical implications of stool short-chain fatty acids (SCFAs) in patients with mixed refractory constipation.

METHOD

Ascending colon specimens obtained from 30 patients with ascending colon cancer were regarded as the control group. Ascending colon specimens obtained from patients with mixed refractory constipation were regarded as the experimental group and were divided into three subgroups, according to Wexner scores [A constipation scoring system to simplify evaluation and management of constipated patients. Dis Colon Rectum 1996; 39: 681-5] of 16-20, 21-25 and 26-30, with 30 patients in each group. The stool SCFAs were extracted and quantitatively analysed using gas chromatography-mass spectrometry (GC-MS). The expression of G protein-coupled receptor 43 (GPR43) and of choline acetyltransferase (ChAT) were detected by immunofluorescence, reverse transcription-polymerase chain reaction (RT-PCR) and western blotting of colon samples.

RESULTS

The levels of acetate, propionate and butyrate were significantly lower in the experimental group than in the control group (P < 0.05). Compared with the control group, the densitometric quantification and mean density of GPR43 and ChAT proteins, and expression of GPR43 and CHAT genes, were significantly decreased in the patients with mixed refractory constipation (P < 0.05).

CONCLUSION

In the patients with mixed refractory constipation, the levels of stool SCFAs, including acetate, propionate and butyrate, as well as the levels of GPR43 and ChAT expressed in the colon, which were all negatively correlated with the Wexner score, were decreased and may be associated with the pathogenesis of mixed refractory constipation.