A Gpr35-tuned gut microbe-brain metabolic axis regulates depressive-like behavior

Gene-environment interactions shape behavior and susceptibility to depression. However, little is known about the signaling pathways integrating genetic and environmental inputs to impact neurobehavioral outcomes. We report that gut G-protein-coupled receptor, Gpr35, engages a microbe-to-brain metabolic pathway to modulate neuronal plasticity and depressive behavior in mice. Psychological stress decreases intestinal epithelial Gpr35, genetic deletion of which induces depressive-like behavior in a microbiome-dependent manner. Gpr35-/- mice and individuals with depression have increased Parabacteroides distasonis, and its colonization to wild-type mice induces depression. Gpr35-/- and Parabacteroides distasonis-colonized mice show reduced indole-3-carboxaldehyde (IAld) and increased indole-3-lactate (ILA), which are produced from opposing branches along the bacterial catabolic pathway of tryptophan. IAld and ILA counteractively modulate neuroplasticity in the nucleus accumbens, a brain region linked to depression. IAld supplementation produces anti-depressant effects in mice with stress or gut epithelial Gpr35 deficiency. Together, these findings elucidate a gut microbe-brain signaling mechanism that underlies susceptibility to depression.

Identification of a Novel Strain Lactobacillus Reuteri and Anti-Obesity Effect through Metabolite Indole-3-Carboxaldehyde in Diet-Induced Obese Mice

The potentially beneficial effects of probiotics in the treatment of obesity have been generally demonstrated. In the present study, a new strain of Lactobacillus reuteri SY523 (L. reuteri SY523) with an anti-obesity effect was isolated from the fecal microbiota of diet-induced obese mice. Untargeted metabolomics analysis of mice serum showed that the significantly differential metabolite indole-3-carboxaldehyde (3-IAId) was markedly elevated in the L. reuteri SY523-treated group, and interestingly, the abundance of 3-IAId was significantly negatively associated with obesity-related indicators. As expected, in the HepG2 cell induced by free fatty acids, the potential activity of 3-IAId in restraining lipid deposition was verified. Further, we found that 3-IAId was involved in the anti-obesity effect of L. reuteri SY523 mainly via regulating the cGMP/cAMP signaling pathway. The highlight of this study lies in clarifying the pivotal role of metabolite 3-IAId in the anti-obesity effect induced by L. reuteri SY523, which is conducive to the development of probiotics for anti-obesity agents.

Design, synthesis, and biological evaluation of isatin-indole-3-carboxaldehyde hybrids as a new class of xanthine oxidase inhibitors

A novel series of triazole-linked isatin-indole-3-carboxaldehyde hybrids based on the febuxostat skeleton and its binding site interactions were rationally designed and synthesized as potential xanthine oxidase inhibitors. Among the synthesized hybrids, A19 showed the most potent xanthine oxidase inhibition (IC₅₀  = 0.37 µM) with the mixed-type inhibitory scenario. Structure-activity relationship studies revealed that methoxy (OCH₃ ) substitution on position 5 of the isatin nucleus and a two-carbon distance between isatin and the triazole moiety is most tolerable for the inhibitory potential. Various binding interactions of A19 with the binding site of xanthine oxidase are also streamlined by molecular docking studies, which showcase the favorable binding pattern for xanthine oxidase inhibition by the hybrid. Furthermore, molecular dynamic studies were performed that suggest the stability of the enzyme-hybrid complex. Overall, the study suggests that hybrid A19 can act as an effective hit lead for further development of potent xanthine oxidase inhibitors.

3-Indoleacetonitrile Is Highly Effective in Treating Influenza A Virus Infection In Vitro and In Vivo

Influenza A viruses are serious zoonotic pathogens that continuously cause pandemics in several animal hosts, including birds, pigs, and humans. Indole derivatives containing an indole core framework have been extensively studied and developed to prevent and/or treat viral infection. This study evaluated the anti-influenza activity of several indole derivatives, including 3-indoleacetonitrile, indole-3-carboxaldehyde, 3-carboxyindole, and gramine, in A549 and MDCK cells. Among these compounds, 3-indoleacetonitrile exerts profound antiviral activity against a broad spectrum of influenza A viruses, as tested in A549 cells. Importantly, in a mouse model, 3-indoleacetonitrile with a non-toxic concentration of 20 mg/kg effectively reduced the mortality and weight loss, diminished lung virus titers, and alleviated lung lesions of mice lethally challenged with A/duck/Hubei/WH18/2015 H5N6 and A/Puerto Rico/8/1934 H1N1 influenza A viruses. The antiviral properties enable the potential use of 3-indoleacetonitrile for the treatment of IAV infection.

The influence of low-carbohydrate diets on the metabolic response to androgen-deprivation therapy in prostate cancer

BACKGROUND

Prostate cancer (PC) is the second most lethal cancer for men. For metastatic PC, standard first-line treatment is androgen deprivation therapy (ADT). While effective, ADT has many metabolic side effects. Previously, we found in serum metabolome analysis that ADT reduced androsterone sulfate, 3-hydroxybutyric acid, acyl-carnitines but increased serum glucose. Since ADT reduced ketogenesis, we speculate that low-carbohydrate diets (LCD) may reverse many ADT-induced metabolic abnormalities in animals and humans.

METHODS

In a multicenter trial of patients with PC initiating ADT randomized to no diet change (control) or LCD, we previously showed that LCD intervention led to significant weight loss, reduced fat mass, improved insulin resistance, and lipid profiles. To determine whether and how LCD affects ADT-induced metabolic changes, we analyzed serum metabolites after 3-, and 6-months of ADT on LCD versus control.

RESULTS

We found androsterone sulfate was most consistently reduced by ADT and was slightly further reduced in the LCD arm. Contrastingly, LCD intervention increased 3-hydroxybutyric acid and various acyl-carnitines, counteracting their reduction during ADT. LCD also reversed the ADT-reduced lactic acid, alanine, and S-adenosyl methionine (SAM), elevating glycolysis metabolites and alanine. While the degree of androsterone reduction by ADT was strongly correlated with glucose and indole-3-carboxaldehyde, LCD disrupted such correlations.

CONCLUSIONS

Together, LCD intervention significantly reversed many ADT-induced metabolic changes while slightly enhancing androgen reduction. Future research is needed to confirm these findings and determine whether LCD can mitigate ADT-linked comorbidities and possibly delaying disease progression by further lowering androgens.

Indole-3-Carboxaldehyde Restores Gut Mucosal Integrity and Protects from Liver Fibrosis in Murine Sclerosing Cholangitis

Primary sclerosing cholangitis (PSC) is a long-term liver disease characterized by a progressive course of cholestasis with liver inflammation and fibrosis. Intestinal barrier dysfunction has been implicated in the pathogenesis of PSC. According to the "leaky gut" hypothesis, gut inflammation alters the permeability of the intestinal mucosa, with the translocation of gut-derived products that enter the enterohepatic circulation and cause hepatic inflammation. Thus, the administration of molecules that preserve epithelial barrier integrity would represent a promising therapeutic strategy. Indole-3-carboxaldehyde (3-IAld) is a microbial-derived product working at the interface between the host and the microbiota and is able to promote mucosal immune homeostasis in a variety of preclinical settings. Herein, by resorting to a murine model of PSC, we found that 3-IAld formulated for localized delivery in the gut alleviates hepatic inflammation and fibrosis by modulating the intestinal microbiota and activating the aryl hydrocarbon receptor-IL-22 axis to restore mucosal integrity. This study points to the therapeutic potential of 3-IAld in liver pathology.

Enteroendocrine cells sense bacterial tryptophan catabolites to activate enteric and vagal neuronal pathways

The intestinal epithelium senses nutritional and microbial stimuli using epithelial sensory enteroendocrine cells (EEC). EECs communicate nutritional information to the nervous system, but whether they also relay signals from intestinal microbes remains unknown. Using in vivo real-time measurements of EEC and nervous system activity in zebrafish, we discovered that the bacteria Edwardsiella tarda activate EECs through the receptor transient receptor potential ankyrin A1 (Trpa1) and increase intestinal motility. Microbial, pharmacological, or optogenetic activation of Trpa1⁺EECs directly stimulates vagal sensory ganglia and activates cholinergic enteric neurons by secreting the neurotransmitter 5-hydroxytryptamine (5-HT). A subset of indole derivatives of tryptophan catabolism produced by E. tarda and other gut microbes activates zebrafish EEC Trpa1 signaling. These catabolites also directly stimulate human and mouse Trpa1 and intestinal 5-HT secretion. These results establish a molecular pathway by which EECs regulate enteric and vagal neuronal pathways in response to microbial signals.

Metabolomic effects of androgen deprivation therapy treatment for prostate cancer

Androgen deprivation therapy (ADT) is the main treatment strategy for men with metastatic prostate cancer (PC). However, ADT is associated with various metabolic disturbances, including impaired glucose tolerance, insulin resistance and weight gain, increasing risk of diabetes and cardiovascular death. Much remains unknown about the metabolic pathways and disturbances altered by ADT and the mechanisms. We assessed the metabolomic effects of ADT in the serum of 20 men receiving ADT. Sera collected before (baseline), 3 and 6 months after initiation of ADT was used for the metabolomics and lipidomics analyses. The ADT‐associated metabolic changes were identified by univariable and multivariable statistical analysis, ANOVA, and Pearson correlation. We found multiple key changes. First, ADT treatments reduced the steroid synthesis as reflected by the lower androgen sulfate and other steroid hormones. Greater androgen reduction was correlated with higher serum glucose levels, supporting the diabetogenic role of ADT. Second, ADT consistently decreased the 3‐hydroxybutyric acid and ketogenesis. Third, many acyl‐carnitines were reduced, indicating the effects on the fatty acid metabolism. Fourth, ADT was associated with a corresponding reduction in 3‐formyl indole (a.k.a. indole‐3‐carboxaldehyde), a microbiota‐derived metabolite from the dietary tryptophan. Indole‐3‐carboxaldehyde is an agonist for the aryl hydrocarbon receptor and regulates the mucosal reactivity and inflammation. Together, these ADT‐associated metabolomic analyses identified reduction in steroid synthesis and ketogenesis as prominent features, suggesting therapeutic potential of restricted ketogenic diets, though this requires formal testing. ADT may also impact the microbial production of indoles related to the immune pathways. Future research is needed to determine the functional impact and underlying mechanisms to prevent ADT‐linked comorbidities and diabetes risk.

as an anti-biofilm agent against Vibrio cholerae O1

Biofilm formation is a major contributing factor in the pathogenesis of Vibrio cholerae O1 (VCO1) and therefore preventing biofilm formation could be an effective alternative strategy for controlling cholera. The present study was designed to explore seawater bacteria as a source of anti-biofilm agents against VCO1. Indole-3-carboxaldehyde (I3C) was identified as an active principle component in Marinomonas sp., which efficiently inhibited biofilm formation by VCO1 without any selection pressure. Furthermore, I3C applications also resulted in considerable collapsing of preformed pellicles. Real-time PCR studies revealed the down-regulation of virulence gene expression by modulation of the quorum-sensing pathway and enhancement of protease production, which was further confirmed by phenotypic assays. Furthermore, I3C increased the survival rate of Caenorhabditis elegans when infected with VCO1 by significantly reducing in vivo biofilm formation, which was corroborated by a survivability assay. Thus, this study revealed, for the first time, the potential of I3C as an anti-biofilm agent against VCO1.

Update of spectroscopic data for 4-hydroxydictyolactone and dictyol E isolated from a Halimeda stuposa - Dictyota sp. assemblage

The methanol extract of an assemblage of Halimeda stuposa and a Dictyota sp., yielded three natural products characteristic of Dictyota sp., and one of Halimeda sp. These included the xenicane diterpene 4-hydroxydictyolactone (1), and the diterpenes dictyol E (2), 8a,11-dihydroxypachydictyol A (3) and indole-3-carboxaldehyde (4). A minor revision of 1 and new spectroscopic data for 1 and 2 are provided, along with associated anti-cancer activities of compounds.