Bacteroides species differentially modulate depression-like behavior via gut-brain metabolic signaling.

Gut microbiome disturbances have been widely implicated in major depressive disorder (MDD), although the identity of causal microbial species and the underlying mechanisms are yet to be fully elucidated. Here we show that Bacteroides species enriched in the gut microbiome from MDD patients differentially impact the susceptibility to depressive behaviors. Transplantation of fecal microbiome from MDD patients into antibiotic-treated mice induced anxiety and despair-like behavior and impaired hippocampal neurogenesis. Colonization of Bacteroides fragilis, Bacteroides uniformis, and, to a lesser extent, Bacteroides caccae, but not Bacteroides ovatus, recapitulated the negative effects of MDD microbiome on behavior and neurogenesis. The varying impacts of Bacteroides species were partially explained by differential alternations of tryptophan pathway metabolites and neurotransmitters along the gut-brain axis. Notably, an intensified depletion of cerebral serotonin concurred with the enhanced susceptibility to depression. Together, these findings identify select Bacteroidetes species that contribute to depression susceptibility in mice by metabolic regulation along the gut-brain axis.

Preclinical Pharmacokinetics, Tissue Distribution and Primary Safety Evaluation of a Novel Curcumin Analogue H10 Suspension, a Potential 17ß Hydroxysteroid Dehydrogenase Type 3 Inhibitor.

17ß Hydroxysteroid dehydrogenase type 3 (17ß-HSD3) is the key enzyme in the biosynthesis of testosterone, which is an attractive therapeutic target for prostate cancer (PCa). H10, a novel curcumin analogue, was identified as a potential 17ß-HSD3 inhibitor. The pharmacokinetic study of H10 in rats were performed by intraperitoneal (i.p.), intravenous (i.v.) and oral (p.o.) administration. In addition, the inhibitory effects of H10 against liver CYP3A4 were investigated in vitro using human liver microsomes (HLMs). The acute and chronic toxicological characteristics were characterized using single-dose and 30 d administration. All the mice were alive after i.p. H10 with dose of no more than 100 mg/kg which are nearly the maximum solubility in acute toxicity test. The pharmacokinetic characteristics of H10 fitted with linear dynamics model after single dose. Furthermore, H10 could bioaccumulate in testis, which was the target organ of 17ß-HSD3 inhibitor. H10 distributed highest in spleen, and then in liver both after single and multiple i.p. administration. Moreover, H10 showed weak inhibition towards liver CYP3A4, and did not cause significant changes in aspartate transaminase (AST) and alanine transaminase (ALT) levels after treated with H10 for continuously 30 d. Taken together, these preclinical characteristics laid the foundation for further clinical studies of H10.

Xyloketal B Attenuates Fatty Acid-Induced Lipid Accumulation via the SREBP-1c Pathway in NAFLD Models.

The goal of this study was to examine the effects of xyloketal B on nonalcoholic fatty liver disease (NAFLD) and to explore the molecular mechanisms underlying its effects in both in vivo and in vitro models. We discovered an association between xyloketal B and the sterol regulatory element-binding protein-1c (SREBP-1c) signaling pathway, which is related to lipid metabolism. Mice were dosed with xyloketal B (5, 10 and 20 mg/kg/d) and atorvastatin (15 mg/kg/d) via intraperitoneal injection once daily for 40 days after being fed a high fat diet plus 10% high fructose liquid (HFD+HFL) for 8 weeks. Xyloketal B significantly improved HFD+HFL-induced hepatic histological lesions and attenuated lipid and glucose accumulation in the blood as well as lipid accumulation in the liver. Xyloketal B increased the expression of CPT1A, and decreased the expression of SREBP-1c and its downstream targeting enzymes such as ACC1, ACL, and FAS. Xyloketal B also significantly reduced lipid accumulation in HepG2 cells treated with free fatty acids (FFAs). These data suggested that xyloketal B has lipid-lowering effects via the SREBP-1c pathway that regulate lipid metabolism. Thus, targeting SREBP-1c activation with xyloketal B may be a promising novel approach for NAFLD treatment.

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.

Psychological stress-induced microbial metabolite indole-3-acetate disrupts intestinal cell lineage commitment.

The brain and gut are intricately connected and respond to various stimuli. Stress-induced brain-gut communication is implicated in the pathogenesis and relapse of gut disorders. The mechanism that relays psychological stress to the intestinal epithelium, resulting in maladaptation, remains poorly understood. Here, we describe a stress-responsive brain-to-gut metabolic axis that impairs intestinal stem cell (ISC) lineage commitment. Psychological stress-triggered sympathetic output enriches gut commensal Lactobacillus murinus, increasing the production of indole-3-acetate (IAA), which contributes to a transferrable loss of intestinal secretory cells. Bacterial IAA disrupts ISC mitochondrial bioenergetics and thereby prevents secretory lineage commitment in a cell-intrinsic manner. Oral α-ketoglutarate supplementation bolsters ISC differentiation and confers resilience to stress-triggered intestinal epithelial injury. We confirm that fecal IAA is higher in patients with mental distress and is correlated with gut dysfunction. These findings uncover a microbe-mediated brain-gut pathway that could be therapeutically targeted for stress-driven gut-brain comorbidities.

Ginkgo biloba extract protects against depression-like behavior in mice through regulating gut microbial bile acid metabolism.

Depression is a mental disorder with high morbidity, disability and relapse rates. Ginkgo biloba extract (GBE), a traditional Chinese medicine, has a long history of clinical application in the treatment of cerebral and mental disorders, but the key mechanism remains incompletely understood. Here we showed that GEB exerted anti-depressant effect in mice through regulating gut microbial metabolism. GBE protected against unpredictable mild stress (UMS)-induced despair, anxiety-like and social avoidance behavior in mice without sufficient brain distribution. Fecal microbiome transplantation transmitted, while antibiotic cocktail abrogated the protective effect of GBE. Spatiotemporal bacterial profiling and metabolomics assay revealed a potential involvement of Parasutterella excrementihominis and the bile acid metabolite ursodeoxycholic acid (UDCA) in the effect of GBE. UDCA administration induced depression-like behavior in mice. Together, these findings suggest that GBE acts on gut microbiome-modulated bile acid metabolism to alleviate stress-induced depression.

Drug Discovery Inspired from Nuclear Receptor Sensing of Microbial Signals.

Host-microbiota interactions are vital for diverse pathophysiological events and may be targeted for innovative therapeutics. Nuclear receptors (NRs) are versatile host sensors of microbial signals that coordinate diverse environmental cues with local and remote adaptions. Harnessing NR-mediated sensory machinery could provide an alternative lynchpin for gut microbiota-oriented drug discovery strategy.

A diet-microbial metabolism feedforward loop modulates intestinal stem cell renewal in the stressed gut.

Dietary patterns and psychosocial factors, ubiquitous part of modern lifestyle, critically shape the gut microbiota and human health. However, it remains obscure how dietary and psychosocial inputs coordinately modulate the gut microbiota and host impact. Here, we show that dietary raffinose metabolism to fructose couples stress-induced gut microbial remodeling to intestinal stem cells (ISC) renewal and epithelial homeostasis. Chow diet (CD) and purified diet (PD) confer distinct vulnerability to gut epithelial injury, microbial alternation and ISC dysfunction in chronically restrained mice. CD preferably enriches Lactobacillus reuteri, and its colonization is sufficient to rescue stress-triggered epithelial injury. Mechanistically, dietary raffinose sustains Lactobacillus reuteri growth, which in turn metabolizes raffinose to fructose and thereby constituting a feedforward metabolic loop favoring ISC maintenance during stress. Fructose augments and engages glycolysis to fuel ISC proliferation. Our data reveal a diet-stress interplay that dictates microbial metabolism-shaped ISC turnover and is exploitable for alleviating gut disorders.

Paeoniflorin modulates gut microbial production of indole-3-lactate and epithelial autophagy to alleviate colitis in mice.

BACKGROUND: Total glucosides of peony (TGP), extracted from the root and rhizome of Paeonia lactiflora Pall, has well-confirmed immunomodulatory efficacy in the clinic. However, the mechanism and active ingredients remain largely unclear. HYPOTHESIS/PURPOSE: Our previous study revealed a low systemic exposure but predominant gut distribution of TGP components. The aim of this study was to investigate involvement of the gut microbiota in the immunoregulatory effects and identify the active component. METHODS: Mice received 3% DSS to establish a model of colitis. The treatment group received TGP or single paeoniflorin (PF) or albiflorin (AF). Body weight, colon length, inflammatory and histological changes were assessed. Gut microbiota structure was profiled by 16s rRNA sequencing. Antibiotic treatment and fecal transplantation were used to explore the involvement of gut microbiota. Metabolomic assay of host and microbial metabolites in colon was performed. RESULTS: TGP improved colonic injury and gut microbial dysbiosis in colitis mice, and PF was responsible for the protective effects. Fecal microbiota transfer from TGP-treated mice conferred resilience to colitis, while antibiotic treatment abrogated the protective effects. Both TGP and PF decreased colonic indole-3-lactate (ILA), a microbial tryptophan metabolite. ILA was further identified as an inhibitor of epithelial autophagy and ILA supplementation compromised the benefits of TGP. CONCLUSION: Our findings suggest that TGP acts in part through a gut microbiota-ILA-epithelial autophagy axis to alleviate colitis.