Gut microbiota remodeling reverses aging-associated inflammation and dysregulation of systemic bile acid homeostasis in mice sex-specifically

Dietary nutrients mediate crosstalk between bile acids and gut microbes in animal host metabolism

Bile acids (BAs) are synthesized by liver, then gut microbes embellish primary BAs into secondary BAs with diverse and biological functions. Over the past few decades, amounts of evidences demonstrated the importance of gut microbes in BA metabolism. There is also significant evidence that BAs are regarded as cell signals in gut-liver, gut-brain, and gut-testis axis. Moreover, the interaction between BAs and gut microbes plays a key role not only in the absorption and metabolism of nutrients, but the regulation of immune function. Herein, we collected the major information of the BA metabolism-related bacteria, nutrients, and cell signals, focused on the possible molecular mechanisms by "Microbes-Bile acids" crosstalk, highlighted the gut-liver, gut-brain, and gut-testis axis, and discussed the possibility and application of the regulation of BA metabolism by nutrients.

Fecal microbiota transfer between young and aged mice reverses hallmarks of the aging gut, eye, and brain

BACKGROUND

Altered intestinal microbiota composition in later life is associated with inflammaging, declining tissue function, and increased susceptibility to age-associated chronic diseases, including neurodegenerative dementias. Here, we tested the hypothesis that manipulating the intestinal microbiota influences the development of major comorbidities associated with aging and, in particular, inflammation affecting the brain and retina.

METHODS

Using fecal microbiota transplantation, we exchanged the intestinal microbiota of young (3 months), old (18 months), and aged (24 months) mice. Whole metagenomic shotgun sequencing and metabolomics were used to develop a custom analysis workflow, to analyze the changes in gut microbiota composition and metabolic potential. Effects of age and microbiota transfer on the gut barrier, retina, and brain were assessed using protein assays, immunohistology, and behavioral testing.

RESULTS

We show that microbiota composition profiles and key species enriched in young or aged mice are successfully transferred by FMT between young and aged mice and that FMT modulates resulting metabolic pathway profiles. The transfer of aged donor microbiota into young mice accelerates age-associated central nervous system (CNS) inflammation, retinal inflammation, and cytokine signaling and promotes loss of key functional protein in the eye, effects which are coincident with increased intestinal barrier permeability. Conversely, these detrimental effects can be reversed by the transfer of young donor microbiota.

CONCLUSIONS

These findings demonstrate that the aging gut microbiota drives detrimental changes in the gut-brain and gut-retina axes suggesting that microbial modulation may be of therapeutic benefit in preventing inflammation-related tissue decline in later life. Video abstract.

Age-dependent effects of a high-fat diet combined with dietary advanced glycation end products on cognitive function and protection with voluntary exercise

To determine whether a high fat diet (HFD) combined with an advanced glycation end products (AGEs) diet will induce worse cognitive impairment than a HFD alone and to investigate whether voluntary exercise is capable of improving cognitive function after the combined diet, young and middle-aged male C57BL/6J mice were randomly assigned to four groups, i.e., control, HFD, combined diet, and combined diet treated with voluntary exercise. Compared to HFD, combined diet induced worse memory abilities only in middle-aged mice, as exhibited by the reduced number of crossings and reduced distance in the target zone during a probe trial. Exercise reversed combined-diet-induced cognitive impairment for both ages of mice. For young mice, the neuro-protective effects of exercise were mainly associated with inhibition of NLRP3, Dnmt3a, Dnmt3b, and H3K9me2 and elevation of OST48; it also elevated Bacilli and reduced Epsilonproteobacteria, Campylobacterales, and Helicobacter. For middle-aged mice, exercise elevated Tet2, inhibited NF-κB and NLRP3, and rebalanced circadian clock proteins and the RAGE-OST48 axis; also, exercise elevated Coriobacteriia/Coriobacteriaceae, Erysipelotrichaceae, and Allobaculum and restored intestinal permeability.

Bile acids and salt-sensitive hypertension: a role of the gut-liver axis

Salt-sensitivity of blood pressure (SSBP) affects 50% of the hypertensive and 25% of the normotensive populations. Importantly, SSBP is associated with increased risk for mortality in both populations independent of blood pressure. Despite its deleterious effects, the pathogenesis of SSBP is not fully understood. Emerging evidence suggests a novel role of bile acids in salt-sensitive hypertension and that they may play a crucial role in regulating inflammation and fluid volume homeostasis. Mechanistic evidence implicates alterations in the gut microbiome, the epithelial sodium channel (ENaC), the farnesoid X receptor, and the G protein-coupled bile acid receptor TGR5 in bile acid-mediated effects on cardiovascular function. The mechanistic interplay between excess dietary sodium-induced alterations in the gut microbiome and immune cell activation, bile acid signaling, and whether such interplay may contribute to the etiology of SSBP is still yet to be defined. The main goal of this review is to discuss the potential role of bile acids in the pathogenesis of cardiovascular disease with a focus on salt-sensitive hypertension.

Decline in Liver Mitochondria Metabolic Function Is Restored by Hochuekkito Through Sirtuin 1 in Aged Mice With Malnutrition

Malnutrition impairs basic daily activities and leads to physical frailty, which is aggravated in the elderly compared with young adults. It is also well-known that the elderly are more vulnerable to metabolic stress. Therefore, in this study, using a food restricted (FR) mouse, we aimed to evaluate the effect of aging on locomotor activity and liver metabolic function. Further, we also investigated the involvement of hepatic mitochondria in liver metabolic function during aging, as well as the therapeutic benefit of the traditional Japanese medicine, hochuekkito (HET). Our findings indicated that following food restriction provided as 30% of ad libitum intake for 5 days, the locomotor activity was lower in 23–26-month-old (aged) mice than in 9-week-old (young) mice. Further, compared with young mice, aged mice exhibited significant decreases in the levels of metabolites related to the urea cycle, mitochondrial function, and anti-oxidative stress. The livers of the aged mice also showed a greater decrease in mitochondrial DNA copy number than young mice. Furthermore, the gene expression levels of sirtuin 1 (SIRT1) and mitochondrial biogenesis-related regulators were attenuated in aged mice. However, these changes were partially restored by HET treatment, which also improved locomotor activity, and combined treatment with alanine resulted in more significant effects in this regard. Therefore, our findings suggested that the decrease in locomotor activity in aged FR mice was associated with a decline in the metabolic function of hepatic mitochondria via decreased SIRT1 expression, which was restored by HET treatment. This implies that enhancing the metabolic function of liver mitochondria can contribute to alleviating energy deficiency in the elderly.

The Intestinal Barrier Dysfunction as Driving Factor of Inflammaging

The intestinal barrier, composed of the luminal microbiota, the mucus layer, and the physical barrier consisting of epithelial cells and immune cells, the latter residing underneath and within the epithelial cells, plays a special role in health and disease. While there is growing knowledge on the changes to the different layers associated with disease development, the barrier function also plays an important role during aging. Besides changes in the composition and function of cellular junctions, the entire gastrointestinal physiology contributes to essential age-related changes. This is also reflected by substantial differences in the microbial composition throughout the life span. Even though it remains difficult to define physiological age-related changes and to distinguish them from early signs of pathologies, studies in centenarians provide insights into the intestinal barrier features associated with longevity. The knowledge reviewed in this narrative review article might contribute to the definition of strategies to prevent the development of diseases in the elderly. Thus, targeted interventions to improve overall barrier function will be important disease prevention strategies for healthy aging in the future.

Novel Role of Ghrelin Receptor in Gut Dysbiosis and Experimental Colitis in Aging

Chronic low-grade inflammation is a hallmark of aging, which is now coined as inflamm-aging. Inflamm-aging contributes to many age-associated diseases such as obesity, type 2 diabetes, cardiovascular disease, and inflammatory bowel disease (IBD). We have shown that gut hormone ghrelin, via its receptor growth hormone secretagogue receptor (GHS-R), regulates energy metabolism and inflammation in aging. Emerging evidence suggests that gut microbiome has a critical role in intestinal immunity of the host. To determine whether microbiome is an integral driving force of GHS-R mediated immune-metabolic homeostasis in aging, we assessed the gut microbiome profiles of young and old GHS-R global knockout (KO) mice. While young GHS-R KO mice showed marginal changes in Bacteroidetes and Firmicutes, aged GHS-R KO mice exhibited reduced Bacteroidetes and increased Firmicutes, featuring a disease-susceptible microbiome profile. To further study the role of GHS-R in intestinal inflammation in aging, we induced acute colitis in young and aged GHS-R KO mice using dextran sulfate sodium (DSS). The GHS-R KO mice showed more severe disease activity scores, higher proinflammatory cytokine expression, and decreased expression of tight junction markers. These results suggest that GHS-R plays an important role in microbiome homeostasis and gut inflammation during aging; GHS-R suppression exacerbates intestinal inflammation in aging and increases vulnerability to colitis. Collectively, our finding reveals for the first time that GHS-R is an important regulator of intestinal health in aging; targeting GHS-R may present a novel therapeutic strategy for prevention/treatment of aging leaky gut and inflammatory bowel disease.

Ileal FXR-FGF15/19 signaling activation improves skeletal muscle loss in aged mice

Sarcopenia is the age-related decrease in skeletal muscle mass, and current therapies for this disease are ineffective. We previously showed that ileal farnesoid X receptor (FXR)-fibroblast growth factor 15/19 (FGF15/19) signaling acts as a regulator of gut microbiota to mediate host skeletal muscle. However, the therapeutic potential of this pathway for sarcopenia is unknown. This study showed that ileal FXR-FGF15/19 signaling was downregulated in older men and aged male mice due to changes in the gut microbiota and microbial bile acid metabolism during aging. In addition, the intestine-specific FXR agonist fexaramine increased skeletal muscle mass and improve muscle performance in aged mice. Ileal FXR activation increased skeletal muscle protein synthesis in a FGF15/19-dependent way, indicating that ileal FXR-FGF15/19 signaling is a potential therapeutic target for sarcopenia.

Alleviation effects of grape seed proanthocyanidin extract on inflammation and oxidative stress in a d-galactose-induced aging mouse model by modulating the gut microbiota

Grape seed proanthocyanidin extract delayed the d-galactose-induced aging process in mice through the gut microbiota–liver axis and microbiota–brain axis.

Impact of the Age of Cecal Material Transfer Donors on Alzheimer’s Disease Pathology in 5xFAD Mice

Alzheimer’s disease is a progressive neurodegenerative disorder affecting around 30 million patients worldwide. The predominant sporadic variant remains enigmatic as the underlying cause has still not been identified. Since efficient therapeutic treatments are still lacking, the microbiome and its manipulation have been considered as a new, innovative approach. 5xFAD Alzheimer’s disease model mice were subjected to one-time fecal material transfer after antibiotics-treatment using two types of inoculation: material derived from the caecum of age-matched (young) wild type mice or from middle aged, 1 year old (old) wild type mice. Mice were profiled after transfer for physiological parameters, microbiome, behavioral tasks, and amyloid deposition. A single time transfer of cecal material from the older donor group established an aged phenotype in the recipient animals as indicated by elevated cultivatable fecal Enterobacteriaceae and Lactobacillaceae representative bacteria, a decreased Firmicutes amount as assessed by qPCR, and by increased levels of serum LPS binding protein. While behavioral deficits were not accelerated, single brain regions (prefrontal cortex and dentate gyrus) showed higher plaque load after transfer of material from older animals. We could demonstrate that the age of the donor of cecal material might affect early pathological hallmarks of Alzheimer’s disease. This could be relevant when considering new microbiome-based therapies for this devastating disorder.

Butyrylated starch protects mice from DSS-induced colitis: combined effects of butyrate release and prebiotic supply

Butyrate has recently emerged as a promising substance for the therapy of colitis. To overcome the shortcomings implicated in the existing delivery systems of butyrate, we utilized butyrylated starch to specifically deliver butyrate to the colon. Herein, we describe the stable loading of butyrate via chemical bonds with a heterogeneous distribution throughout the particle. Butyrylated starch supply increased butyrate as well as total short-chain fatty acid contents at the end of the intervention period. Moreover, butyrylated starch showed multiple effects on the suppression of DSS-induced colitis. From the observation of the gut-liver axis, reduced hepatic inflammation and hepatocyte damage further confirmed alleviated colonic inflammation. Given that butyrylated starch has the combined effects of specific release of butyrate in the colon and extra supply of fermentable substrates for gut microbiota, this work provides an effective strategy for the assistant therapy of colitis.

Photodynamic Therapy of Novel Photosensitizer Ameliorates TNBS-Induced Ulcerative Colitis via Inhibition of AOC1

Ulcerative colitis (UC), a chronic, nonspecific inflammatory bowel disease characterized by continuous and diffuse inflammatory changes in the colonic mucosa, requires novel treatment method. Photodynamic therapy (PDT), as a promising physico-chemical treatment method, were used to treat UC rats’ model with novel photosensitizer LD₄ in this paper, the treatment effect and mechanism was investigated. LD₄-PDT could improve the survival rate of 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced UC model rats, decrease expression of interleukin (IL)-6, IL-1, tumor necrosis factor (TNF)-α, malondialdehyde (MDA), myeloperoxidase (MPO) and increase the expression of glutathione (GSH) and superoxide oxidase (SOD), while protecting the integrity of the intestinal epithelium. LD₄-PDT treatment could rebuild the intestinal microflora composition and reprogram the colonic protein profiles in TNBS-induced rats to almost the normal state. Proteomics analysis based upon TNBS-induced UC model rats revealed that Amine oxidase copper-containing 1 (AOC₁) was a potential target of LD₄-PDT. Novel photosensitizer agent LD₄-PDT represents an efficient treatment method for UC, and AOC₁ may be a promising target.

Host and microbiota metabolic signals in aging and longevity

Aging is an inevitable biochemical process that adversely affects personal health and poses ever-increasing challenges to society. Recent research has revealed the crucial role of metabolism in regulating aging and longevity. During diverse metabolic processes, the host organism and their symbiotic partners-the microbiota-produce thousands of chemical products (metabolites). Emerging studies have uncovered specific metabolites that act as signaling molecules to actively regulate longevity. Here we review the latest progress in understanding the molecular mechanisms by which metabolites from the host and/or microbiota promote longevity. We also highlight state-of-the-art technologies for discovering, profiling and imaging aging- and longevity-regulating metabolites and for deciphering the molecular basis of their actions. The broad application of these technologies in aging research, together with future advances, will foster the systematic discovery of aging- and longevity-regulating metabolites and their signaling pathways. These metabolite signals should provide promising targets for developing new interventions to promote longevity and healthy aging.

A botanical dietary supplement from white peony and licorice attenuates nonalcoholic fatty liver disease by modulating gut microbiota and reducing inflammation

BACKGROUND

Nonalcoholic fatty liver disease (NAFLD) is an obesity-related metabolic disease that is highly associated with gut dysbiosis and inflammation. A botanical dietary supplement, mainly containing an herbal pair of white peony root and licorice as well as grape seeds and broccoli extracts (WLT), exerts auxiliary protection against chemical liver injury. However, it is unclear whether WLT protects against the development of NAFLD induced by a high energy diet.

PURPOSE

To investigate the protective role of WLT against NAFLD development induced by a high-fat and high-sucrose (HFHS) diet and its mechanism of action.

METHODS

We investigated the anti-NAFLD effects of WLT on a HFHS diet-induced NAFLD C57BL/6J mouse model by detecting the hepatic triglyceride (TG) level, performing histological examination of the liver tissue, and evaluating glucose tolerance and systemic inflammation. Then, we analyzed the impact of WLT on gut microbiota by 16S rRNA gene sequencing, followed by fecal microbiota transplantation. Furthermore, we performed hepatic transcriptomic analysis of mice with or without WLT treatment using the RNA sequencing approach.

RESULTS

Our results showed that WLT supplement attenuated body weight gain, hepatic steatosis, glucose tolerance, and systemic inflammation in HFHS-fed mice. Moreover, WLT supplement altered the composition of gut microbiota, which contributed at least in part, to the anti-NAFLD effect. Meanwhile, WLT improved the intestinal integrity and comprehensively modulated the expression of hepatic genes in HFHS mice, particularly reducing the expression of genes in the toll-like receptor-mediated inflammatory pathway.

CONCLUSION

WLT is protective against NAFLD formation induced by an HFHS diet, and its effect is associated with the modulation of gut microbiota and inflammation, highlighting the potential of WLT to reduce the risk of metabolic disorders as a functional dietary supplement.

Perinatal High-Salt Diet Induces Gut Microbiota Dysbiosis, Bile Acid Homeostasis Disbalance, and NAFLD in Weanling Mice Offspring

A perinatal high-salt (HS) diet was reported to elevate plasma triglycerides. This study aimed to investigate the hypothesis that a perinatal HS diet predisposed offspring to non-alcoholic fatty liver disease (NAFLD), the hepatic manifestation of abnormal lipid metabolism, and the possible mechanism. Female C57BL/6 mice were fed a control diet (0.5% NaCl) or HS diet (4% NaCl) during pregnancy and lactation and their offspring were sacrificed at weaning. The perinatal HS diet induced greater variation in fecal microbial beta-diversity (β-diversity) and increased bacteria abundance of Proteobacteria and Bacteroides. The gut microbiota dysbiosis promoted bile acid homeostasis disbalance, characterized by the accumulation of lithocholic acid (LCA) and deoxycholic acid (DCA) in feces. These alterations disturbed gut barrier by increasing the expression of tight junction protein (Tjp) and occludin (Ocln), and increased systemic lipopolysaccharide (LPS) levels and hepatic inflammatory cytokine secretion (TNF-α and IL-6) in the liver. The perinatal HS diet also inhibited hepatic expression of hepatic FXR signaling (CYP7A1 and FXR), thus triggering increased hepatic expression of pro-inflammatory cytokines (TNF-α and IL-6) and hepatic lipid metabolism-associated genes (SREBP-1c, FAS, ACC), leading to unique characteristics of NAFLD. In conclusion, a perinatal HS diet induced NAFLD in weanling mice offspring; the possible mechanism was related to increased bacteria abundance of Proteobacteria and Bacteroides, increased levels of LCA and DCA in feces, and increased expressions of hepatic FXR signaling.

Integrated Metagenomic and Transcriptomic Analyses Reveal the Dietary Dependent Recovery of Host Metabolism From Antibiotic Exposure

The balance of gut microbiome is essential for maintaining host metabolism homeostasis. Despite widespread antibiotic use, the potential long-term detrimental consequences of antibiotics for host health are getting more and more attention. However, it remains unclear whether diet affects the post-antibiotic recovery of gut microbiome and host metabolism. In this study, through metagenomic sequencing and hepatic transcriptome analysis, we investigated the divergent impacts of short-term vancomycin (Vac), or combination of ciprofloxacin and metronidazole (CM) treatment on gut microbiome and host metabolism, as well as their recovery extent from antibiotic exposure on chow diet (CD) and high-fat diet (HFD). Our results showed that short-term Vac intervention affected insulin signaling, while CM induced more functional changes in the microbiome. However, Vac-induced long-term (45 days) changes of species were more apparent when recovered on CD than HFD. The effects of antibiotic intervention on host metabolism were long-lasting, antibiotic-specific, and diet-dependent. The number of differentially expressed gene was doubled by Vac than CM, but was comparable after recovery on CD as revealed by the hepatic transcriptomic analysis. In contrast, HFD intake during recovery could worsen the extent of post-antibiotic recovery by altering infection, immunity, and cancer-related pathways in short-term Vac-exposed rats and by shifting endocrine system-associated pathways in CM-exposed rats. Together, the presented data demonstrated the long-term recovery extent after different antibiotic exposure was diet-related, highlighting the importance of dietary management during post-antibiotic recovery.

Sex- and age-specific variation of gut microbiota in Brandt's voles

Background

Gut microbiota plays a key role in the survival and reproduction of wild animals which rely on microbiota to break down plant compounds for nutrients. As compared to laboratory animals, wild animals face much more threat of environmental changes (e.g. food shortages and risk of infection). Therefore, studying the gut microbiota of wild animals can help us better understand the mechanisms animals use to adapt to their environment.

Methods

We collected the feces of Brandt’s voles in the grassland, of three age groups (juvenile, adult and old), in both sexes. We studied the gut microbiota by 16S rRNA sequencing.

Results

The main members of gut microbiota in Brandt’s voles were Firmicutes, Bacteroidetes and Proteobacteria. As voles get older, the proportion of Firmicutes increased gradually, and the proportion of Bacteroides decreased gradually. The diversity of the microbiota of juveniles is lower, seems like there is still a lot of space for colonization, and there are large variations in the composition of the microbiome between individuals. In adulthood, the gut microbiota tends to be stable, and the diversity is highest. In adult, the abundances of Christensenellaceae and Peptococcus of female were significantly higher than male voles.

Conclusions

The gut microbiota of Brandt’s vole was influenced by sex and age, probably due to growth needs and hormone levels. Gut microbiota of wild animals were much influenced by their life-history reflected by their age and sex. Future studies will be directed to identify functions of these “wild microbiota” in regulating physiological or behavioral processes of wild animals in different life stage or sexes.

Irritable bowel syndrome in midlife women: a narrative review

Midlife women between the ages of 40 and 65 years have reported multiple challenges due to menopausal, developmental, and situational transitions from younger to older adulthood. During the midlife period, many women seek health care for gastrointestinal symptoms and irritable bowel syndrome (IBS). Multiple factors including stress, poor sleep, diet, and physical inactivity may contribute to IBS or gastrointestinal symptoms in midlife women. As such, a comprehensive assessment and treatment approach is needed for midlife women suffering gastrointestinal symptoms. This article reviews the main aspects of the menopausal transition, sex hormonal changes, abdominal and pelvic surgery, psychosocial distress, behavioral factors, and gut microbiome, as well as their relevance on IBS and gastrointestinal symptoms in midlife women. Also, management strategies for IBS in midlife women are discussed. To date, gastrointestinal symptoms during midlife years remain a critical area of women’s health. Additional research is needed to better understand the contributors to gastrointestinal symptoms in this group. Such efforts may provide a new window to refine or develop treatments of gastrointestinal symptoms for midlife women.

Poria cocos could ameliorate cognitive dysfunction in APP/PS1 mice by restoring imbalance of Aβ production and clearance and gut microbiota dysbiosis

Alzheimer's disease (AD) is the most common neurodegenerative disorder. Amyloid beta-protein (Aβ) plaques, which are the hallmark of AD, are formed from the imbalance of Aβ production and clearance accompanied by neuroinflammation, gut dysbiosis, and metabolite dysfunction. All of these processes give rise to neurochemical deficiencies and synaptic dysfunction, which ultimately contribute to recognition dysfunction. Poria cocos (PC), which contains multiple active ingredients, plays a significant role in the treatment of multiple-pathogenesis senile diseases such as AD. Nevertheless, there are only very few investigations on the intricate action mechanism of PC for the treatment of AD. In this study, we evaluate the multi-target cure effect of PC on APP/PS1 mice by behavioral, immunohistochemical (IHC), targeted metabolomics, and 16S rRNA sequencing experiments. Mice treated with PC showed significant improvements in cognitive function as evaluated by the behavioral experiment. IHC revealed that PC treatment relieved Aβ deposition by reducing the formation of Aβ and increasing its clearance. Moreover, PC treatment improved gut dysbiosis, which reversed the metabolite dysfunction of bile acid. These findings reveal that PC is a promising therapeutic agent, which might ameliorate the cognitive function of AD by restoring the imbalance of Aβ production and clearance and gut microbiota dysbiosis.

Neuroprotective effects of Apium graveolens against focal cerebral ischemia occur partly via antioxidant, anti-inflammatory, and anti-apoptotic pathways

BACKGROUND

Stroke is a neurological disease caused by a sudden disturbance of cerebral blood flow to the brain, leading to loss of brain function. Recently, accumulating lines of evidence have suggested that dietary enrichment with nutritional antioxidants could reduce brain damage and improve cognitive function. In this study, we investigated the possible protective effects of Apium graveolens, a medicinal plant with putative neuroprotective activity, against oxidative-stress-related brain damage and brain damage due to inflammation induced by focal cerebral ischemia.

METHODS

Male adult Wistar rats were administered with an extract of A. graveolens orally 14 days before permanent occlusion of their right middle cerebral artery. The brain infarct volumes of rats in each group were determined by 2,3,5-triphenyltetrazolium chloride staining, and the density of neurons in the cortex and hippocampus of rats was determined by cresyl violet staining. The levels of malondialdehyde, catalase, glutathione peroxidase, and superoxide dismutase in the cerebral cortex and hippocampus of the rats were also quantified at the end of the study period.

RESULTS

Our results show that A. graveolens extract significantly decreased infarct volume and improved neuronal density in the cortex and hippocampus of rats receiving A. graveolens extract compared with those rats receiving no treatment. This neuroprotective effect was found to occur partly due to antioxidant, anti-inflammatory, and anti-apoptotic effects.

CONCLUSION

Our study demonstrates that A. graveolens helps to reduce the severity of cognitive damage caused by focal cerebral ischemia. © 2020 Society of Chemical Industry.

Age-specific microbiota in altering host inflammatory and metabolic signaling as well as metabolome based on the sex

Background

Metabolism is sex-different, and the direct link between gut microbiota and aging-associated metabolic changes needs to be established in both sexes.

Methods

Gene expression, metabolic and inflammatory signaling, gut microbiota profile, and metabolome were studied during aging and after fecal microbiota transplantation (FMT) in mice of both sexes.

Results

Our data revealed young female mice and aged male mice were the most insulin sensitive and resistant group, respectively. In addition, aging reduced sex difference in insulin sensitivity. Such age- and sex-dependent metabolic phenotypes were accompanied by shifted gut microbiota profile and altered abundance of bacterial genes that produce butyrate, propionate, and bile acids. After receiving feces from the aged males (AFMT), the most insulin-resistant group, recipients of both sexes had increased hepatic inflammation and serum endotoxin. However, AFMT only increased insulin resistance in female mice and abolished sex difference in insulin sensitivity. Additionally, such changes were accompanied by narrowed sex difference in metabolome. Metabolomics data revealed that age-associated insulin resistance in males was accompanied by increased sugar alcohols and dicarboxylic acids as well as reduced aromatic and branched-chain amino acids. Further, receiving feces from the young females (YFMT), the most insulin-sensitive group, reduced body weight and fasting blood glucose in male recipients and improved insulin sensitivity in females, leading to enhanced sex differences in insulin sensitivity and metabolome.

Conclusions

Aging systemically affected inflammatory and metabolic signaling based on the sex. Gut microbiome is age and sex-specific, which affects inflammation and metabolism in a sex-dependent manner.

Bile Acids as Key Modulators of the Brain-Gut-Microbiota Axis in Alzheimer's Disease

Recently, the concept of the brain-gut-microbiota (BGM) axis disturbances in the pathogenesis of Alzheimer's disease (AD) has been receiving growing attention. At the same time, accumulating data revealing complex interplay between bile acids (BAs), gut microbiota, and host metabolism have shed new light on a potential impact of BAs on the BGM axis. The crosstalk between BAs and gut microbiota is based on reciprocal interactions since microbiota determines BA metabolism, while BAs affect gut microbiota composition. Secondary BAs as microbe-derived neuroactive molecules may affect each of three main routes through which interactions within the BGM axis occur including neural, immune, and neuroendocrine pathways. BAs participate in the regulation of multiple gut-derived molecule release since their receptors are expressed on various cells. The presence of BAs and their receptors in the brain implies a direct effect of BAs on the regulation of neurological functions. Experimental and clinical data confirm that disturbances in BA signaling are present in the course of AD. Disturbed ratio of primary to secondary BAs as well as alterations in BA concertation in serum and brain samples have been reported. An age-related shift in the gut microbiota composition associated with its decreased diversity and stability observed in AD patients may significantly affect BA metabolism and signaling. Given recent evidence on BA neuroprotective and anti-inflammatory effects, new therapeutic targets have been explored including gut microbiota modulation by probiotics and dietary interventions, ursodeoxycholic acid supplementation, and use of BA receptor agonists.

QiDiTangShen granules modulated the gut microbiome composition and improved bile acid profiles in a mouse model of diabetic nephropathy

QiDiTangShen granules (QDTS), a traditional Chinese herbal medicine, have been used in clinical practice for treating diabetic kidney disease for several years. In our previous study, we have demonstrated that QDTS displayed good efficacy on reducing proteinuria in mice with diabetic nephropathy (DN). However, the exact mechanism by which QDTS exerts its reno-protection remains largely unknown. To ascertain whether QDTS could target the gut microbiota-bile acid axis, the db/db mice were adopted as a mouse model of DN. After a 12-week of treatment, we found that QDTS significantly reduced urinary albumin excretion (UAE), and attenuated the pathological injuries of kidney in the db/db mice, while the body weight and blood glucose levels of those mice were not affected. In addition, we found that QDTS significantly altered the gut microbiota composition, and decreased serum levels of total bile acid (TBA) and BA profiles such as β-muricholic acid (β-MCA), taurocholic acid (TCA), tauro β-muricholic acid (Tβ-MCA) and deoxycholic acid (DCA). These BAs are associated with the activation of farnesoid X receptor (FXR), which is highly expressed in kidney. However, there was no significant difference between QDTS-treated and -untreated db/db mice regarding the renal expression of FXR, indicating that other mechanisms may be involved. Conclusively, our study revealed that QDTS significantly alleviated renal injuries in mice with DN. The gut microbiota-bile acid axis may be an important target for the reno-protection of QDTS in DN, but the specific mechanism merits further study.

Bile acid metabolism and circadian rhythms

Circadian rhythms are biological systems that synchronize cellular circadian oscillators with the organism's daily feeding-fasting or rest-activity cycles in mammals. Circadian rhythms regulate nutrient absorption and utilization at the cellular level and are closely related to obesity and metabolic disorders. Bile acids are important modulators that facilitate nutrient absorption and regulate energy metabolism. Here, we provide an overview of the current connections and future perspectives between the circadian clock and bile acid metabolism as well as related metabolic diseases. Feeding and fasting cycles influence bile acid pool size and composition, and bile acid signaling can respond to acute lipid and glucose utilization and mediate energy balance. Disruption of circadian rhythms such as shift work, irregular diet, and gene mutations can contribute to altered bile acid metabolism and heighten obesity risk. High-fat diets, alcohol, and gene mutations related to bile acid signaling result in desynchronized circadian rhythms. Gut microbiome also plays a role in connecting circadian rhythms with bile acid metabolism. The underlying mechanism of how circadian rhythms interact with bile acid metabolism has not been fully explored. Sustaining bile acid homeostasis based on circadian rhythms may be a potential therapy to alleviate metabolic disturbance.