IL-1β directly suppress ghrelin mRNA expression in ghrelin-producing cells

Tryptophan-sensing receptor GPR142 expression levels are directly regulated by proinflammatory cytokines in ghrelin-producing cells

GPR142 is a tryptophan-sensing receptor that has been implicated in the regulation of inflammation. In this study, we investigated the relationships between inflammatory cytokine and GPR142 expression by using cellular, animal models, and human stomach samples. We found that addition of TNF-α, IL-6, and IL-1β into the culture of ghrelin-producing cell line, MGN3-1 cells, increased GPR142 mRNA expression levels. Lipopolysaccharide (LPS) injection to mice significantly increased GPR142 expression in the stomach, confirming the results observed in the cellular model. GPR142 mRNA expression levels in the stomach samples of morbidly obese patients were positively correlated with TNF-α, IL-6, and IL-1β mRNA levels. Taken together our results suggest that GPR142 expression is under the direct control of proinflammatory cytokines and support further investigation of GPR142 potential roles in inflammation.

Influence of innate immune activation on endocrine and metabolic pathways in infancy

Prematurity is the leading cause of neonatal morbidity and mortality worldwide. Premature infants often require extended hospital stays, with increased risk of developing infection compared with term infants. A picture is emerging of wide-ranging deleterious consequences resulting from innate immune system activation in the newborn infant. Those who survive infection have been exposed to a stimulus that can impose long-lasting alterations into later life. In this review, we discuss sepsis-driven alterations in integrated neuroendocrine and metabolic pathways and highlight current knowledge gaps in respect of neonatal sepsis. We review established biomarkers for sepsis and extend the discussion to examine emerging findings from human and animal models of neonatal sepsis that propose novel biomarkers for early identification of sepsis. Future research in this area is required to establish a greater understanding of the distinct neonatal signature of early and late-stage infection, to improve diagnosis, curtail inappropriate antibiotic use, and promote precision medicine through a biomarker-guided empirical and adjunctive treatment approach for neonatal sepsis. There is an unmet clinical need to decrease sepsis-induced morbidity in neonates, to limit and prevent adverse consequences in later life and decrease mortality.

Ghrelin-cell physiology and role in the gastrointestinal tract

PURPOSE OF REVIEW

Ghrelin was discovered in 1999; extensive research and clinical studies on ghrelin have been published in the last 20 years. Physiological research on ghrelin ranges from its appetite-stimulating effects to its association with energy homeostasis. The physiological effects of ghrelin in the gastrointestinal tract and its relevance in the pathological conditions of the gastrointestinal tract have gradually become clearer. The purpose of the review is to provide current information on ghrelin cell biology and physiology, particularly in the gastrointestinal tract.

RECENT FINDINGS

Ghrelin-producing cells in the stomach are characterized as X/A-like cells, but immunohistochemical analyses have revealed co-expression of several secreted proteins and hormones in ghrelin-producing cells such as nesfatin-1, somatostatin, and pancreastatin. Furthermore, the local physiological roles and/or mechanisms of ghrelin in gastrointestinal functions such as gastric motility and inflammation are discussed.

SUMMARY

Ghrelin is a brain-gut hormone with a wide range of physiological actions; hence, it is important to understand its effects on the physiological functions of the gastrointestinal tract to elucidate the biological significance of ghrelin.

Interleukin-27 decreases ghrelin production through signal transducer and activator of transcription 3-mechanistic target of rapamycin signaling

Interleukin-27 (IL-27), a heterodimeric cytokine, plays a protective role in diabetes. Ghrelin, a gastric hormone, provides a hunger signal to the central nervous system to stimulate food intake. The relationship between IL-27 and ghrelin is still unexplored. Here we investigated that signal transducer and activator of transcription 3 (STAT3)—mechanistic target of rapamycin (mTOR) signaling mediates the suppression of ghrelin induced by IL-27. Co-localization of interleukin 27 receptor subunit alpha (WSX-1) and ghrelin was observed in mouse and human gastric mucosa. Intracerebroventricular injection of IL-27 markedly suppressed ghrelin synthesis and secretion while stimulating STAT3–mTOR signaling in both C57BL/6J mice and high-fat diet-induced-obese mice. IL-27 inhibited the production of ghrelin in mHypoE-N42 cells. Inhibition of mTOR activity induced by mTOR siRNA or rapamycin blocked the suppression of ghrelin production induced by IL-27 in mHypoE-N42 cells. Stat 3 siRNA also abolished the inhibitory effect of IL-27 on ghrelin. IL-27 increased the interaction between STAT3 and mTOR in mHypoE-N42 cells. In conclusion, IL-27 suppresses ghrelin production through the STAT3-mTOR dependent mechanism.

The associations between some biological markers, obesity, and cardiovascular risk in Slovenian children and adolescents

INTRODUCTION

The occurrence of cardiovascular diseases and metabolic disorders steadily increases with the body mass index (BMI). Since the latter is not the best and earliest indicator of obesity and cardiovascular risk, the aim of the study was to evaluate some potential biological markers that would allow us to detect children and adolescents at higher risk at an early stage.

METHODS

A sample of 330 children and adolescents were included in the study and divided into four groups: obese patients with hypertension, normal-weight patients with hypertension, patients with mildly elevated lipids and a control group of healthy children and adolescents. Some clinical parameters (age, body weight, body height, BMI, waist circumference, hip circumference, blood pressure), biochemical parameters (glucose, total cholesterol, triglycerides, HDL, LDL, apolipoprotein A1, homocysteine) and biological markers of obesity (ghrelin, adiponectin, leptin) were evaluated.

RESULTS

Ghrelin and adiponectin were found to have a strong negative statistically significant correlation with BMI in all three observed groups (p < 0.001), but not in the control group (p = 0.053 and p = 0.316, respectively). In addition, leptin had a strong positive statistically significant correlation with BMI in all four groups (p < 0.001 for the research groups, p = 0.009 for the controls). In the group of obese patients with hypertension, statistically significant differences in all three markers of obesity were found in comparison to the control group (p < 0.001 for all markers). In the group of patients with mildly elevated lipids, ghrelin and leptin were significantly different (p = 0.002 and p < 0.001, respectively). In the group of normal-weight hypertensive patients, only values of ghrelin were different compared to the control group (p = 0.001).

CONCLUSION

In the research groups, significant differences were found in clinical, biochemical and biological parameters compared to the control group. The observed biological markers of obesity are useful early markers for identifying groups of patients that are at cardiovascular risk.

In Vitro and In Vivo Characterization of Novel Stable Peptidic Ghrelin Analogs: Beneficial Effects in the Settings of Lipopolysaccharide-Induced Anorexia in Mice

Ghrelin, the only known orexigenic gut hormone produced primarily in the stomach, has lately gained attention as a potential treatment of anorexia and cachexia. However, its biologic stability is highly limited; therefore, a number of both peptide and nonpeptide ghrelin analogs have been synthesized. In this study, we provide in vitro and in vivo characterization of a series of novel peptide growth hormone secretagogue receptor (GHS-R1a) agonists, both under nonpathologic conditions and in the context of lipopolysaccharide (LPS)-induced anorexia. These analogs were based on our previous series modified by replacing the Ser3 with diaminopropionic acid (Dpr), the N-terminal Gly with sarcosine, and Phe4 with various noncoded amino acids. New analogs were further modified by replacing the n-octanoyl bound to Dpr3 with longer or unsaturated fatty acid residues, by incorporation of the second fatty acid residue into the molecule, or by shortening the peptide chain. These modifications preserved the ability of ghrelin analogs to bind to the membranes of cells transfected with GHS-R1a, as well as the GHS-R1a signaling activation. The selected analogs exhibited long-lasting and potent orexigenic effects after a single s.c. administration in mice. The stability of new ghrelin analogs in mice after s.c. administration was significantly higher when compared with ghrelin and [Dpr3]ghrelin, with half-lives of approximately 2 hours. A single s.c. injection of the selected ghrelin analogs in mice with LPS-induced anorexia significantly increased food intake via the activation of orexigenic pathways and normalized blood levels of proinflammatory cytokines, demonstrating the anti-inflammatory potential of the analogs.

The effects of inflammatory cytokines on the expression of ghrelin

In the current study, we examined the effects of LPS and inflammatory cytokines including IL-1β, TNF-α, and IL-6 on the expression of ghrelin in MGN3-1 cells. We found that IL-1β, and TNF-α with lesser extent, significantly suppressed ghrelin mRNA expression in the cells. MGN3-1 cells expressed IL-1β receptor and IL-1β significantly stimulated NF-κB, p38, JNK, and ERK pathways. Knockdown of IKK2 by siRNA significantly attenuated the suppression of ghrelin mRNA by IL-1β. These results indicate that IL-1β directly suppressed ghrelin mRNA via NF-κB pathway at least partially, which may have a role in the regulation of appetite during inflammation.