Endocrine impact of Helicobacter pylori:Focus on ghrelin and ghrelin o-acyltransferase

Ghrelin is predominantly produced by the gastric enteroendocrine cell compartment and is octanoylated by the recently discovered ghrelin o-acyltransferase （GOAT） before secretion into the bloodstream. This octanoylation is essential for many of the biological properties of ghrelin including appetite stimulation and anti-inflammatory properties as only the acylated form of ghrelin binds to the ghrelin receptor, the growth hormone secretagogue receptor （GHS-R）. Given the gastric location of ghrelin production, it is perhaps not surprising that insult to the gastric mucosa affects circulating ghrelin levels in humans. Helicobacter pylori （H. pylon） infects more than fifty percent of the world＇s population and once established within the gastric mucosa, can persist for life. Infection is associated with chronic gastritis, gastric atrophy and ulceration, reduced appetite and a lower body mass index （BMI）. The large majority of studies investigating levels of circulating ghrelin and ghrelin expression in the stomach in patients with H. pylori infection indicate that the bacterium has a negative impact on ghrelin production and/or secretion. Eradication of infection restores ghrelin, improves appetite and increases BMI in some studies, however, a causative relationship between H. pylori-associated serum ghrelin decline and food intake and obesity has not been established. Most studies measure total ghrelin in the circulation although the measurement of the ratio of acyl/total ghrelin gives a clearer indication that the ghrelin acylation process is altered during infection and atrophy. GOAT is essential for the production of biologically-active, acyl ghrelin and the impact of H. pylori on GOAT expression and activity will be highly informative in the future.

Regular moderate aerobic exercise improves high-fat diet-induced nonalcoholic fatty liver disease via monoacylglycerol O-acyltransferase 1 pathway suppression

Purpose:Monoacylglycerol O-acyltransferase 1(MGAT1)is reported to play a key role in the development of diet-induced nonalcoholic fatty liver disease(NAFLD).Thus,this study investigated the effect of exercise on suppression of the MGAT1 pathway in NAFLD tissue of high-fat diet(HFD)-induced obese rats.Methods:Male Sprague-Dawley rats were fed an HFD containing 45%fat for 6 weeks.Upon confirmation that NAFLD had been induced in the obese animals,they were divided into HFD-fed groups provided with exercise(HFD+EXE)or without exercise(HFD)and a group given dietary adjustment(DA)only,for a further 6 weeks of intervention treatment.The 6-week regular moderate aerobic exercise consisted of an accommodation phase with increasing exercise.Lipid accumulation in the liver tissue was determined by Oil Red O staining.The MGAT1 and liver lipogenic gene mRNA levels were measured by qPCR,and their protein levels by western blot assay.Results:Oil Red O staining showed that NAFLD was successfully induced by HFD-fed.The gene expression of MGAT1 was significantly lower in HFD+EXE than HFD.However,there was no significant difference between HFD+EXE and DA.The protein expression of MGAT1 was significantly lower in HFD+EXE than both HFD and DA.Messenger RNA and protein expression of other lipogenic genes were not different among groups.These data indicate that exercise suppresses MGAT1 pathway regardless of HFD feeding;in part,this effect could be greater than DA.Conclusion:Our data suggest that exercise can improve NAFLD,which is probably due to suppression of MGAT1 pathway.

Comprehensive prognostic and immune analysis of sterol Oacyltransferase 1 in patients with hepatocellular carcinoma

BACKGROUND Sterol O-acyltransferase 1(SOAT1)is an important target in the diagnosis and treatment of liver cancer.However,the prognostic value of SOAT1 in patients with hepatocellular carcinoma(HCC)is still not clear.AIM To investigate the correlation of SOAT1 expression with HCC,using RNA-seq and gene expression data of The Cancer Genome Atlas(TCGA)-liver hepatocellular carcinoma(LIHC)and pan-cancer.METHODS The correlation between SOAT1 expression and HCC was analyzed.Cox hazard regression models were conducted to investigate the prognostic value of SOAT1 in HCC.Overall survival and disease-specific survival were explored based on TCGA-LIHC data.Biological processes and functional pathways mediated by SOAT1 were characterized by gene ontology(GO)analysis and the Kyoto Encyclopedia of Genes and Genomes(KEGG)analysis of differentially expressed genes.In addition,the protein-protein interaction network and co-expression analyses of SOAT1 in HCC were performed to better understand the regulatory mechanisms of SOAT1 in this malignancy.RESULTS SOAT1 and SOAT2 were highly expressed in unpaired samples,while only SOAT1 was highly expressed in paired samples.The area under the receiver operating characteristic curve of SOAT1 expression in tumor samples from LIHC patients compared with para-carcinoma tissues was 0.748,while the area under the curve of SOAT1 expression in tumor samples from LIHC patients compared with GTEx was 0.676.Patients with higher SOAT1 expression had lower survival rates.Results from GO/KEGG and gene set enrichment analyses suggested that the PI3K/AKT signaling pathway,the IL-18 signaling pathway,the calcium signaling pathway,secreted factors,the Wnt signaling pathway,the Jak/STAT signaling pathway,the MAPK family signaling pathway,and cell–cell communication were involved in such association.SOAT1 expression was positively associated with the abundance of macrophages,Th2 cells,T helper cells,CD56bright natural killer cells,and Th1 cells,and negatively linked to the abundance of Th17 cells,dendritic cells,and cytotoxic cells.CONCLUSION Our findings demonstrate that SOAT1 may serve as a novel target for HCC treatment,which is helpful for the development of new strategies for immunotherapy and metabolic therapy.

鳙goat基因序列特征及其时空表达模式分析

【目的】探究鳙的ghrelin O-acyltransferase(goat)基因序列特征及时空表达模式,解析goat基因的潜在生物学功能。【方法】通过RACE扩增得到goat基因cDNA全长序列,采用实时荧光定量PCR对其在早期发育阶段、各组织和冬夏季4个组织(脑、肠道、肌肉和肝脏)中的表达特征进行检测;结合原位杂交和免疫组化技术分别从基因和蛋白水平解析goat基因在肠组织中的分布特征,并通过实时荧光定量PCR评估goat基因及通路相关基因的共表达模式。【结果】鉴定得到goat基因cDNA序列全长2255 bp,开放阅读框(ORF)长1116 bp,共编码371个氨基酸残基。推导氨基酸序列含7个跨膜结构域,并包含参与催化的天冬酰胺(第251位)和组氨酸(第282位)。同源比对分析发现鳙GOAT氨基酸序列与鲤科鱼类相似度极高。鳙goat基因在早期孵化时和出膜后5 d的表达水平均显著高于其他时期(P<0.05,下同);成体组织差异表达分析发现goat基因在肠道中表达量最高;goat基因在夏季脑、肠道和肌肉组织的相对表达量均显著高于冬季。原位杂交试验结果显示goat基因在肠道中表达信号较强,且肠道切片的免疫组化试验显示肠黏膜中存在GOAT与GHRL共定位的阳性信号。goat基因与生长激素的合成、分泌和作用通路(ko04935)中相关基因存在共表达关系。【结论】goat基因具有MBOAT家族的典型结构特征,可能通过与摄食相关基因(ghrl等)协作来参与鳙摄食调控和生长代谢适应等生物学过程。

Ghrelin O-acyltransferase(GOAT) and energy metabolism

Ghrelin O-acyltransferase(GOAT), a member of MBOATs family, is essential for octanoylation of ghrelin, which is required for active ghrelin to bind with and activate its receptor. GOAT is expressed mainly in the stomach, pancreas and hypothalamus. Levels of GOAT are altered by energy status. GOAT contains 11 transmembrane helices and one reentrant loop. Its invariant residue His-338 and conserved Asn-307 are located in the endoplasmic reticulum lumen and cytosol respectively. GOAT contributes to the regulation of food intake and energy expenditure, as well as glucose and lipids homeostasis. Deletion of GOAT blocks the acylation of ghrelin leading to subsequent impairment in energy homeostasis and survival when mice are challenged with high energy diet or severe caloric restriction. GO-Co A-Tat, a peptide GOAT inhibitor, attenuates acyl-ghrelin production and prevents weight gain induced by a medium-chain triglycerides-rich high fat diet. Further, GO-Co A-Tat increases glucose-induced insulin secretion. Overall, inhibition of GOAT is a novel strategy for treatment of obesity and related metabolic disorders.

Changes of Ghrelin/GOAT axis and m TOR pathway in the hypothalamus after sleeve gastrectomy in obese type-2 diabetes rats

AIM To examine the changes of the ghrelin/ghrelin O-acyltransferase(GOAT) axis and the mammalian target of rapamycin(m TOR) pathway in the hypothalamus after sleeve gastrectomy.METHODS A total of 30 obese type-2 diabetes Sprague-Dawley(SD) rats, 6 wk of age, fed with high-sugar and highfat fodder for 2 mo plus intraperitoneal injection of streptozotocin were randomly divided into three groups: non-operation group(S0 group, n = 10), sham operation group(Sh group, n = 10) and sleeve gastrectomy group(SG group, n = 10). Data of body mass, food intake, oral glucose tolerance test(OGTT), acylated ghrelin(AG) and total ghrelin(TG) were collected and measured at the first day(when the rats were 6 wk old), preoperative day 3 and postoperative week 8. The m RNA expression of preproghrelin, GOAT and neuropeptide Y(NPY), and protein expression of ghrelin, GOAT, GHSR and the m TOR pathway(p-Akt, p-m TOR and p-S6) were measured in the hypothalamus.RESULTS SG can significantly improve metabolic symptoms by reducing body mass and food intake. The obese rats showed lower serum TG levels and no change in AG, but the ratio of AG/TG was increased. When compared with the S0 and Sh groups, the SG group showed decreased TG(1482.03 ± 26.55, 1481.49 ± 23.30 and 1206.63 ± 52.02 ng/L, respectively, P < 0.05), but unchanged AG(153.06 ± 13.74, 155.37 ± 19.30 and 144.44 ± 16.689 ng/L, respectively, P > 0.05). As a result, the ratio of AG/TG further increased in the SG group(0.103 ± 0.009, 0.105 ± 0.013 and 0.12 ± 0.016, respectively, P < 0.05). When compared with the S0 group, SG suppressed m RNA and protein levels of preproghrelin(0.63 ± 0.12 vs 0.5 ± 0.11, P < 0.05) and GOAT(0.96 ± 0.09 vs 0.87 ± 0.08, P < 0.05), but did not change NPY m RNA expression(0.61 ± 0.04 vs 0.65 ± 0.07, P > 0.05) in the hypothalamus. The protein levels of p-Akt, p-m TOR and p-S6 were higher in the SG group, which indicated that the hypothalamic m TOR pathway was activated after SG at the postoperative week 8. CONCLUSION The reduction of ghrelin expression and activation of the m TOR pathway might have opposite effects on food intake, as SG improves obesity and T2 DM.

MBOAT1 homozygous missense variant causes nonobstructive azoospermia

Nonobstructive azoospermia(NOA)is a common cause of infertility and is defined as the complete absence of sperm in ejaculation due to defective spermatogenesis.The aim of this study was to identify the genetic etiology of NOA in an infertile male from a Chinese consanguineous family.A homozygous missense variant of the membrane-bound O-acyltransferase domain-containing 1(MBOAT1)gene(c.770C>T,p.Thr257Met)was found by whole-exome sequencing(WES).Bioinformatic analysis also showed that this variant was a pathogenic variant and that the amino acid residue in MBOAT1 was highly conserved in mammals.Quantitative polymerase chain reaction(Q-PCR)analysis showed that the mRNA level of MBOAT1 in the patient was 22.0%lower than that in his father.Furthermore,we screened variants of MBOAT1 in a broader population and found an additional homozygous variant of the MBOAT1 gene in 123 infertile men.Our data identified homozygous variants of the MBOAT1 gene associated with male infertility.This study will provide new insights for researchers to understand the molecular mechanisms of male infertility and will help clinicians make accurate diagnoses.