Gut chemosensing: implications for disease pathogenesis

Ingestible Smart Capsules for Chemical Sensing in the Gut

The development of novel ingestible sensors can aid physicians and patients in obtaining precise data on the health status of the gut at a local level. This in turn can facilitate earlier and more accurate disease diagnosis, improve the delivery of point-of-care medicine, and allow monitoring of the gastrointestinal (GI) tract status. This Tutorial overviews characteristics of the gut for inexpert readers and reviews emerging chemical sensing technologies for the GI tract from an analytical chemistry viewpoint.

Chemosensory function of Varroa gnathosoma: transcriptomic and proteomic analyses

In this study, we evaluated the role of the gnathosoma (mouthparts) in chemosensing of the most devastating honey bee parasite, Varroa destructor mite. Through transcriptomic analysis, we compared the expression of putative chemosensory genes between the body parts containing the main chemosensory organs (the forelegs), gnathosoma and the rest of the body devoid of these two body parts. Furthermore, we checked the presence of chemosensory-related transcripts in the proteome of the gnathosoma. Our comparative transcriptomic analysis revealed the presence of 83 transcripts with known characteristic conserved domains belonging to eight chemosensory gene families in the three Varroa transcriptomes. Among these transcripts, 11 were significantly upregulated in the mite's forelegs, compared to 8 and 10 in the gnathosoma and body devoid of both organs, respectively. Whilst the gnathosoma and the forelegs share similar expression of some putative lipid carrier proteins, membrane-bound receptors, and associated proteins, they also differ in the expression profiles of some transcripts belonging to these protein families. This suggests two functional chemosensory organs that may differ in their chemosensory function according to specific characteristics of compounds they detect. Moreover, the higher expression of some chemosensory transcripts in the body devoid of forelegs and gnathosoma compared to the gnathosoma alone, may suggest the presence of additional function of these transcripts or alternatively presence of additional external or internal chemosensory organs. Insights into the functional annotation of a highly expressed gustatory receptor present in both organs using RNA interference (RNAi) are also revealed.

Gut-brain axis: Mechanisms and potential therapeutic strategies for ischemic stroke through immune functions

After an ischemic stroke (IS) occurs, immune cells begin traveling to the brain and immune system from the gut and gastrointestinal tract, where most of them typically reside. Because the majority of the body's macrophages and more than 70% of the total immune cell pool are typically found within the gut and gastrointestinal tract, inflammation and immune responses in the brain and immune organs require the mobilization of a large number of immune cells. The bidirectional communication pathway between the brain and gut is often referred to as the gut-brain axis. IS usually leads to intestinal motility disorders, dysbiosis of intestinal microbiota, and a leaky gut, which are often associated with poor prognosis in patients with IS. In recent years, several studies have suggested that intestinal inflammation and immune responses play key roles in the development of IS, and thus may become potential therapeutic targets that can drive new therapeutic strategies. However, research on gut inflammation and immune responses after stroke remains in its infancy. A better understanding of gut inflammation and immune responses after stroke may be important for developing effective therapies. This review discusses the immune-related mechanisms of the gut-brain axis after IS and compiles potential therapeutic targets to provide new ideas and strategies for the future effective treatment of IS.

Appetite-Regulating Hormones in Human Milk: A Plausible Biological Factor for Obesity Risk Reduction?

BACKGROUND

Human milk contains appetite-regulating hormones that may influence infant growth and obesity risk.

RESEARCH AIMS

We evaluated whether leptin, peptide tyrosine-tyrosine (PYY), glucagon-like peptide-1 (GLP-1), and ghrelin concentrations in human milk (1) changed during feeding (from foremilk to hindmilk) and during the first 6 months of infancy; (2) were explained by maternal factors; and (3) were associated with infant anthropometrics and growth.

METHODS

Mother-infant dyads (N = 22) participated. Samples of foremilk and hindmilk at 1 month postpartum were collected and analyzed for leptin, PYY, GLP-1, and ghrelin via radioimmunoassay and milkfat percentage estimated via creamatocrit. Samples were also collected in mothers (n = 15) who breastfed through 6 months. Anthropometrics were obtained on all mother-infant dyads at 1 month and all infants at 6 months and 12 months.

RESULTS

At 1 month, milk GLP-1 and milkfat concentration increased from foremilk to hindmilk (p ≤ .05) while leptin and PYY concentrations remained stable during feeding. Milk hormone concentrations and milkfat tended to decline overtime, with lower leptin, PYY, and ghrelin at 6 months versus 1 month (p < .05). At 1 month, milk leptin and milkfat content were associated with maternal markers of adiposity (r = 0.49-0.78, p < .001); whereas, milk PYY was correlated with maternal serum PYY concentration (r = 0.672, p = .001). Average 1-month milk concentrations of GLP-1 and leptin were negatively associated with weight-for-age z-scores at 6 months (r = -0.46, p < .05) and 12 months (r = -0.49, p < .05), respectively.

CONCLUSION

The content of certain appetite-regulating hormones in human milk may be influenced by maternal factors and play a role in infant growth; much needs to be learned about their role in the obesity protection of breastfed infants.

The Role of lncRNA PCAT6 in Cancers

Long non-coding RNA (lncRNA) PCAT6 is a member of the Prostate Cancer Associated Transcripts family of molecules. In this review, we focus on the latest studies involving PCAT6 in the diagnosis, treatment, and prognosis of malignant tumors of the digestive, respiratory, urinary, reproductive, motion, and nervous systems. PCAT6 was found to be highly expressed in gastric cancer, colon cancer, hepatocellular carcinoma, lung cancer, bladder cancer, ovarian cancer, breast cancer, cervical cancer, osteosarcoma, glioblastoma, and other tumors. PCAT6 can promote the development and progression of different types of malignant tumors through various mechanisms. Overall, these findings suggest that PCAT6 may play an increasingly vital role in the clinical assessment of these malignant tumors. It can function as an oncogene and may be used as a potential new prognostic biomarker of these tumors.

Ecological Sensing Through Taste and Chemosensation Mediates Inflammation: A Biological Anthropological Approach

Ecological sensing and inflammation have evolved to ensure optima between organism survival and reproductive success in different and changing environments. At the molecular level, ecological sensing consists of many types of receptors located in different tissues that orchestrate integrated responses (immune, neuroendocrine systems) to external and internal stimuli. This review describes emerging data on taste and chemosensory receptors, proposing them as broad ecological sensors and providing evidence that taste perception is shaped not only according to sense epitopes from nutrients but also in response to highly diverse external and internal stimuli. We apply a biological anthropological approach to examine how ecological sensing has been shaped by these stimuli through human evolution for complex interkingdom communication between a host and pathological and symbiotic bacteria, focusing on population-specific genetic diversity. We then focus on how these sensory receptors play a major role in inflammatory processes that form the basis of many modern common metabolic diseases such as obesity, type 2 diabetes, and aging. The impacts of human niche construction and cultural evolution in shaping environments are described with emphasis on consequent biological responsiveness.

Neuroimmunophysiology of the gut: advances and emerging concepts focusing on the epithelium

The epithelial lining of the gastrointestinal tract serves as the interface for digestion and absorption of nutrients and water and as a defensive barrier. The defensive functions of the intestinal epithelium are remarkable considering that the gut lumen is home to trillions of resident bacteria, fungi and protozoa (collectively, the intestinal microbiota) that must be prevented from translocation across the epithelial barrier. Imbalances in the relationship between the intestinal microbiota and the host lead to the manifestation of diseases that range from disorders of motility and sensation (IBS) and intestinal inflammation (IBD) to behavioural and metabolic disorders, including autism and obesity. The latest discoveries shed light on the sophisticated intracellular, intercellular and interkingdom signalling mechanisms of host defence that involve epithelial and enteroendocrine cells, the enteric nervous system and the immune system. Together, they maintain homeostasis by integrating luminal signals, including those derived from the microbiota, to regulate the physiology of the gastrointestinal tract in health and disease. Therapeutic strategies are being developed that target these signalling systems to improve the resilience of the gut and treat the symptoms of gastrointestinal disease.

Association of Low Fecal Elastase-1 and Non-Ulcer Dyspepsia

Non-ulcer dyspepsia (NUD) is a term used to define a set of symptoms that are believed to originate from the gastroduodenal region, and no underlying organic, systemic, or metabolic reason can be found. The majority of patients suffer from chronic symptoms although half of the patients report improvement in symptoms with time. The potential role exocrine pancreatic insufficiency in NUD patients has not been clarified yet. We aimed to identify exocrine pancreas function with pancreatic fecal elastase-1 in patients diagnosed with non-ulcer dyspepsia and no typical exocrine pancreatic insufficiency (EPI) symptoms. Thirty-five patients referred to gastroenterology clinics with NUD and 35 people with no dyspeptic symptoms as a control group were included in this prospective study. Non-ulcer dyspepsia patients were classified as group 1 and control subjects classified as group 2. Upper gastrointestinal endoscopies were performed in both groups. Assessment of exocrine pancreatic function was performed by measuring fecal elastase-1 concentration with a commercial ELISA kit using polyclonal antibodies (BioServ Diagnostics) in NUD patients compared to control subjects. Mean fecal elastase-1 levels were significantly lower in group 1 patients compared with group 2 (367.47 ± 43.27; 502.48 ± 50.94 respectively; p = 0.04). The percentage of the patients with EPI was significantly higher in group 1 (p = 0.02). Patients with NUD should be re-evaluated if they do not show satisfactory improvement with treatment. Exocrine pancreatic insufficiency was significantly higher in patients with NUD in our study. Evaluation for the presence of EPI can be a cost effective approach in management of refractory patients during the process of ruling out organic reasons.

Anxiety, Depression, and the Microbiome: A Role for Gut Peptides

The complex bidirectional communication between the gut and the brain is finely orchestrated by different systems, including the endocrine, immune, autonomic, and enteric nervous systems. Moreover, increasing evidence supports the role of the microbiome and microbiota-derived molecules in regulating such interactions; however, the mechanisms underpinning such effects are only beginning to be resolved. Microbiota-gut peptide interactions are poised to be of great significance in the regulation of gut-brain signaling. Given the emerging role of the gut-brain axis in a variety of brain disorders, such as anxiety and depression, it is important to understand the contribution of bidirectional interactions between peptide hormones released from the gut and intestinal bacteria in the context of this axis. Indeed, the gastrointestinal tract is the largest endocrine organ in mammals, secreting dozens of different signaling molecules, including peptides. Gut peptides in the systemic circulation can bind cognate receptors on immune cells and vagus nerve terminals thereby enabling indirect gut-brain communication. Gut peptide concentrations are not only modulated by enteric microbiota signals, but also vary according to the composition of the intestinal microbiota. In this review, we will discuss the gut microbiota as a regulator of anxiety and depression, and explore the role of gut-derived peptides as signaling molecules in microbiome-gut-brain communication. Here, we summarize the potential interactions of the microbiota with gut hormones and endocrine peptides, including neuropeptide Y, peptide YY, pancreatic polypeptide, cholecystokinin, glucagon-like peptide, corticotropin-releasing factor, oxytocin, and ghrelin in microbiome-to-brain signaling. Together, gut peptides are important regulators of microbiota-gut-brain signaling in health and stress-related psychiatric illnesses.

Fatty acid and mineral receptors as drug targets for gastrointestinal disorders

Nutrient-sensing receptors, including fatty acid receptors (FFA1–FFA4), Ca2+-sensing receptors and Zn2+-sensing receptors, are involved in several biological processes. These receptors are abundantly expressed in the GI tract, where they have been shown to play crucial roles in regulating GI function. This review provides an overview of the GI functions of fatty acid and mineral receptors, including the regulation of gastric and enteroendocrine functions, GI motility, ion transport and cell growth. Recently, several lines of evidence have implicated these receptors as promising therapeutic targets for the treatment of GI disorders, for example, inflammatory bowel disease, colorectal cancer, metabolic syndrome and diarrheal diseases. A future perspective on drug discovery research targeting these receptors is discussed.