Pathological Mechanism of “Phlegm, Blood stasis, Toxin ”in a Rabbit Model of Carotid Atherosclerosis Based on Gut Microbiota-host Metabolism Interactions

Background:In Traditional Chinese Medicine(TCM)theory,"phlegm,blood stasis and toxin"are the pathogenesis of carotid atherosclerosis(CAS).The rabbit carotid atherosclerosis(CAS),which is induced by high-cholesterol diet combined with carotid artery balloon injury,is a classic model for studying CAS.Many studies indicate that gut microbiota and host metabolic disorders are involved in the pathogenesis of rabbit CAS.However,the TCM pathological features and syndromes of this classic rabbit CAS model have not been reported.Objective:To explore the pathogenesis of the rabbit CAS model and its TCM syndrome types from the perspective of"phlegm,blood stasis,and toxin".Methods:Twelve male New Zealand white rabbits were randomly divided into NC group and CAS group according to their body weight,followed by feeding of basic feed and a 1%high cholesterol diet,respectively.After two weeks,the rabbits in the CAS group underwent common carotid artery(CCA)balloon injury,while the rabbits in the NC group underwent only CCA separation without balloon injury.The two groups received differential feed postoperatively for six more weeks,after which,changes in lipids,hemorheology,inflammation,oxidative stress,and CAS phenotypes were analyzed.In addition,the colon contents and serum were collected for 16S rRNA sequencing and ^(1)H-NMR metabonomic analysis.Results:The CAS rabbits were observed to form noticeable abnormalities in lipid metabolism and blood rhe-ology,a sharp increase in oxidative stress levels,excessive release of inflammatory factors and apparent CAS plaque formation.Furthermore,10 specific gut microbiota(such as Akkermansia muciniphila,Barnesiellaceae and Faecalibacterium)and 14 characteristic metabolites(such as trimethylamine oxide,acetic acid and L-carnitine)were identified in the CAS rabbits,which were significantly related to the CAS phenotypes.The pathway func-tion analysis showed that the gut microbiota and its metabolites mainly affected cholesterol metabolism,energy metabolism,inflammation and oxidative stress.Conclusion:The rabbit CAS model conforms to the“phlegm,blood stasis and toxin damage”theory.The gut microbiota and host metabolic disorders of the CAS rabbits interact and promote internal and external toxins,aggravating the progression of CAS.Our study provided experimental evidence for the application of this model in the TCM-based research of CAS.

Cross-talk between bile acids and intestinal microbiota in host metabolism and health

Bile acid（BA） is de novo synthesized exclusively in the liver and has direct or indirect antimicrobial effects. On the other hand, the composition and size of the BA pool can be altered by intestinal microbiota via the biotransformation of primary BAs to secondary BAs, and subsequently regulate the nuclear farnesoid X receptor（FXR; NR1H4）. The BA-activated FXR plays important roles in BA synthesis and metabolism, glucose and lipid metabolism, and even hepatic autophagy. BAs can also play a role in the interplays among intestinal microbes. In this review, we mainly discuss the interactions between BAs and intestinal microbiota and their roles in regulating host metabolism, and probably the autophagic signaling pathway.

NAD^(+) and its possible role in gut microbiota:Insights on the mechanisms by which gut microbes influence host metabolism

Nicotinamide adenine dinucleotide(NAD^(+))is an enzyme cofactor,co-substrate,and redox factor in all living cells and is necessary for maintaining cell metabolism.It has been shown that appropriate supplementation of NAD^(+)precursors or inhibition of NAD^(+)-depleting enzymes can promote mitochondrial oxidative phosphorylation and improve host energy utilization efficiency.In addition,increasing evidence indicates that the gut microbiota plays a pivotal role in host metabolism.Theoretically,there should be a close correlation among NAD^(+),gut microbiota,and host metabolism;however,the information is limited.In this review,we summarize the metabolic process of NAD^(+)and its impact on host metabolism,the link between gut microbiota and host metabolism,as well as the potential effects of NAD^(+)on microbial metabolism,providing a new perspective on the interaction between gut microbiota and host metabolism.

Allergen degradation of bee pollen by lactic acid bacteria fermentation and its alleviatory effects on allergic reactions in BALB/c mice

Food allergy as a global health problem threatens food industry.Bee pollen(BP)is a typical food with allergenic potentials,although it performs various nutritional/pharmacological functions to humans.In this study,lactic acid bacteria(LAB)were used to ferment Brassica napus BP for alleviating its allergenicity.Four novel allergens(glutaredoxin,oleosin-B2,catalase and lipase)were identified with significant decreases in LAB-fermented BP(FBP)than natural BP by proteomics.Meanwhile,metabolomics analysis showed significant increases of 28 characteristic oligopeptides and amino acids in FBP versus BP,indicating the degradation of LAB on allergens.Moreover,FBP showed alleviatory effects in BALB/c mice,which relieved pathological symptoms and lowered production of allergic mediators.Microbial high-throughput sequencing analysis showed that FBP could regulate gut microbiota and metabolism to strengthen immunity,which were closely correlated with the alleviation of allergic reactivity.These findings could contribute to the development and utilization of hypoallergenic BP products.

Targeting host factors:A novel rationale for the management of hepatitis C virus

Hepatitis C is recognized as a major threat to global public health. The current treatment of patients with chronic hepatitis C is the addition of ribavirin to interferon-based therapy which has limited efficacy, poor tolerability, and significant expense. New treatment options that are more potent and less toxic are much needed. Moreover, more effective treatment is an urgent priority for those who relapse or do not respond to current regimens. A major obstacle in combating hepatitis C virus （HCV） infection is that the fidelity of the viral replication machinery is notoriously low, thus enabling the virus to quickly develop mutations that resist compounds targeting viral enzymes. Therefore, an approach targeting the host cofactors, which are indispensable for the propagation of viruses, may be an ideal target for the development of antiviral agents because they have a lower rate of mutation than that of the viral genome, as long as they have no side effects to patients. Drugs targeting, for example, receptors of viral entry, host metabolism or nuclear receptors, which are factors required to complete the HCV life cycle, may be more effective in combating the viral infection. Targeting host cofactors of the HCV life cycle is an attractive concept because it imposes a higher genetic barrier for resistance than direct antiviral compounds. However the principle drawback of this strategy is the greater potential for cellular toxicity.

Gut microbiota-derived metabolites are novel targets for improving insulin resistance

The gut microbiota plays a key role in metabolic diseases.Gut-microbiota-derived metabolites are found in different dietary sources,including:Carbohydrate(acetate,propionate,butyrate,also known as short-chain fatty acids,as well as succinate);protein(hydrogen sulfide,indole,and phenylacetic acid);and lipids(resveratrol-,ferulic acid-,linoleic acid-,catechin-and berry-derived metabolites).Insulin resistance,which is a global pandemic metabolic disease that progresses to type 2 diabetes mellitus,can be directly targeted by these metabolites.Gutmicrobiota-derived metabolites have broad effects locally and in distinct organs,in particular skeletal muscle,adipose tissue,and liver.These metabolites can modulate glucose metabolism,including the increase in glucose uptake and lipid oxidation in skeletal muscle,and decrease in lipogenesis and gluconeogenesis associated with lipid oxidation in the liver through activation of phosphatidylinositol 3-kinase-serine/threonine-protein kinase B and AMP-activated protein kinase.In adipose tissue,gut-microbiota-derived metabolites stimulate adipogenesis and thermogenesis,inhibit lipolysis,and attenuate inflammation.Importantly,an increase in energy expenditure and fat oxidation occurs in the whole body.Therefore,the therapeutic potential of current pharmacological and non-pharmacological approaches used to treat diabetes mellitus can be tested to target specific metabolites derived from intestinal bacteria,which may ultimately ameliorate the hyperglycemic burden.

Translocation of gut microbes to epididymal white adipose tissue drives lipid metabolism disorder under heat stress

Heat stress induces multi-organ damage and serious physiological dysfunction in mammals,and gut bacteria may translocate to extra-intestinal tissues under heat stress pathology.However,whether gut bacteria translocate to the key metabolic organs and impair function as a result of heat stress remains unknown.Using a heat stress-induced mouse model,heat stress inhibited epididymal white adipose tissue(eWAT)expansion and induced lipid metabolic disorder but did not damage other organs,such as the heart,liver,spleen,or muscle.Microbial profiling analysis revealed that heat stress shifted the bacterial community in the cecum and eWAT but not in the inguinal white adipose tissue,blood,heart,liver,spleen,or muscle.Notably,gut-vascular barrier function was impaired,and the levels of some bacteria,particularly Lactobacillus,were higher in the eWAT,as confirmed by catalyzed reporter deposition fluorescence in situ hybridization(CARD-FISH)staining when mice were under heat stress.Moreover,integrated multi-omics analysis showed that the eWAT microbiota was associated with host lipid metabolism,and the expression of genes involved in the lipid metabolism in eWAT was upregulated under heat stress.A follow-up microbial supplementation study after introducing Lactobacillus plantarum to heat-stressed mice revealed that the probiotic ameliorated heat stress-induced loss of eWAT and dyslipidemia and reduced gut bacterial translocation to the eWAT by improving gut barrier function.Overall,our findings suggest that gut bacteria,particularly Lactobacillus spp.,play a crucial role in heat stress-induced lipid metabolism disorder and that there is therapeutic potential for using probiotics,such as Lactobacillus plantarum.

Swine gut microbiota and its interaction with host nutrient metabolism

Gut microbiota is generally recognized to play a crucial role in maintaining host health and metabolism.The correlation among gut microbiota,glycolipid metabolism,and metabolic diseases has been well reviewed in humans.However,the interplay between gut microbiota and host metabolism in swine remains incompletely understood.Given the limitation in conducting human experiments and the high similarity between swine and humans in terms of anatomy,physiology,polyphagy,habits,and metabolism and in terms of the composition of gut microbiota,there is a pressing need to summarize the knowledge gained regarding swine gut microbiota,its interplay with host metabolism,and the underlying mechanisms.This review aimed to outline the bidirectional regulation between gut microbiota and nutrient metabolism in swine and to emphasize the action mechanisms underlying the complex microbiomeehost crosstalk via the gut microbiotaegutebrain axis.Moreover,it highlights the new advances in knowledge of the diurnal rhythmicity of gut microbiota.A better understanding of these aspects can not only shed light on healthy and efficient pork production but also promote our knowledge on the associations between gut microbiota and the microbiomeehost crosstalk mechanism.More importantly,knowledge on microbiota,host health and metabolism facilitates the development of a precise intervention therapy targeting the gut microbiota.

Mesenteric lymph system constitutes the second route in gut-liver axis and transports metabolism-modulating gut microbial metabolites

The gut-liver axis denotes the intricate connection and interaction between gut microbiome and liver, in which compositional and functional shifts in gut microbiome affect host metabolism. Hepatic portal vein of the blood circulation system has been thought to be the major route for metabolite transportation in the gut-liver axis, but the existence and importance of other routes remain elusive. Here, we perform metabolome comparison in blood circulation and mesenteric lymph systems and identify significantly shifted metabolites in serum and mesentery. Using cellular assays, we find that the majority of decreased metabolites in lymph system under high-fat diet are effective in alleviating metabolic disorders, indicating a high potential of lymph system in regulating liver metabolism. Among those, a representative metabolite, L-carnitine, reduces diet-induced obesity in mice. Metabolic tracing analysis identifies that L-carnitine is independently transported by the mesenteric lymph system, serving as an example that lymph circulation comprises a second route in the gut-liver axis to modulate liver metabolism. Our study provides new insights into metabolite transportation via mesenteric lymph system in the gut-liver axis, offers an extended scope for the investigations in host-gut microbiota metabolic interactions and potentially new targets in the treatment of metabolic disorders.