Tauroursodeoxycholic Acid Mitigates Oxidative Stress and Promotes Differentiation in High Salt-Stimulated Osteoblasts via NOX1 Mediated by PGC-1α.

BACKGROUND: High-salt diet (HSD) is a pivotal risk factor for osteoporosis (OP). Accumulating evidence has supported that tauroursodeoxycholic acid (TUDCA), a naturally produced hydrophilic bile acid, exerts positive effects on the treatment of OP. This study is committed to shedding light on the impacts of TUDCA on high salt-treated osteoblasts and probing into its underlying mechanisms of action. METHODS: Cell counting kit-8 (CCK-8) assay was used to determine the viability of osteoblasts. Alkaline phosphatase (ALP) staining and Alizarin red S (ARS) staining were used to measure osteoblast differentiation. Reverse transcription-quantitative PCR (RT-qPCR) and western blot were used to examine the expression of osteogenic markers. Western blot was also used to analyze the expression of superoxide dismutase-2 (SOD2), peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC-1α), and NADPH oxidase 1 (NOX1). The production of reactive oxygen species (ROS) was evaluated via dichloro-dihydro-fluorescein diacetate (DCFH-DA) assay. Following PGC-1α knockdown in TUDCA-pretreated osteoblasts exposed to NaCl, the aforementioned functional experiments were implemented again. RESULTS: MC3T3-E1 cell viability was not significantly impacted by increasing concentrations of TUDCA. However, in NaCl-exposed MC3T3-E1 cells, the viability loss, oxidative stress, and decline of differentiation were all dose-dependently obstructed by TUDCA treatment. Moreover, NaCl exposure reduced PGC-1α expression and increased NOX1 expression, which was then reversed by TUDCA. PGC-1α deletion partially abolished the effects of TUDCA on PGC-1α and NOX1, differentiation, and oxidative stress in NaCl-treated osteoblasts. CONCLUSIONS: TUDCA might protect against high salt-induced OP via modulation of NOX1 mediated by PGC-1α.

Investigating the effects of tauroursodeoxycholic acid (TUDCA) in mitigating endoplasmic reticulum stress and cellular responses in Pak choi.

The accumulation of misfolded proteins in the endoplasmic reticulum (ER) within plant cells due to unfavourable conditions leads to ER stress. This activates interconnected pathways involving reactive oxygen species (ROS) and unfolded protein response (UPR), which play vital roles in regulating ER stress. The aim of this study is to investigate the underlying mechanisms of tunicamycin (TM) induced ER stress and explore the potential therapeutic applications of tauroursodeoxycholic acid (TUDCA) in mitigating cellular responses to ER stress in Pak choi (Brassica campestris subsp. chinensis). The study revealed that ER stress in Pak choi leads to detrimental effects on plant morphology, ROS levels, cellular membrane integrity, and the antioxidant defence system. However, treatment with TUDCA in TM-induced ER stressed Pak choi improved morphological indices, pigment contents, ROS accumulation, cellular membrane integrity, and antioxidant defence system restoration. Additionally, TUDCA also modulates the transcription levels of ER stress sensors genes, ER chaperone genes, and ER-associated degradation (ERAD) genes during ER stress in Pak choi. Furthermore, TUDCA has demonstrated its ability to alleviate ER stress, stabilize the UPR, reduce oxidative stress, prevent apoptosis, and positively influence plant growth and development. These results collectively comprehend TUDCA as a promising agent for mitigating ER stress-induced damage in Pak choi plants and provide valuable insights for further research and potential applications in crop protection and stress management.

SEPN1-related myopathy depends on the oxidoreductase ERO1A and is druggable with the chemical chaperone TUDCA.

Selenoprotein N (SEPN1) is a protein of the endoplasmic reticulum (ER) whose inherited defects originate SEPN1-related myopathy (SEPN1-RM). Here, we identify an interaction between SEPN1 and the ER-stress-induced oxidoreductase ERO1A. SEPN1 and ERO1A, both enriched in mitochondria-associated membranes (MAMs), are involved in the redox regulation of proteins. ERO1A depletion in SEPN1 knockout cells restores ER redox, re-equilibrates short-range MAMs, and rescues mitochondrial bioenergetics. ERO1A knockout in a mouse background of SEPN1 loss blunts ER stress and improves multiple MAM functions, including Ca2+ levels and bioenergetics, thus reversing diaphragmatic weakness. The treatment of SEPN1 knockout mice with the ER stress inhibitor tauroursodeoxycholic acid (TUDCA) mirrors the results of ERO1A loss. Importantly, muscle biopsies from patients with SEPN1-RM exhibit ERO1A overexpression, and TUDCA-treated SEPN1-RM patient-derived primary myoblasts show improvement in bioenergetics. These findings point to ERO1A as a biomarker and a viable target for intervention and to TUDCA as a pharmacological treatment for SEPN1-RM.

Novel insight on IRE1 in the regulation of chondrocyte dedifferentiation through ER stress independent pathway.

Inositol-requiring enzyme-1 (IRE1) is the master regulator of the unfolded protein response pathway, associated with the endoplasmic reticulum (ER) in sensing and regulating cell stress. The activity of IRE1 is highly explored and well-characterized in cancer and other cells. However, the IRE1 molecular mechanism in chondrocytes is poorly understood. The present study explored the effect of IRE1 on chondrocytes regarding its chondrogenic gene expression and its correlation with different cellular pathways and cell behavior. Chondrocytes transfected with the cDNA of IRE1 reduced the expression of type II collagen, disrupting chondrocyte differentiation as confirmed by western blotting and immunofluorescence. Upon siRNA treatment, the influence of IRE1 on chondrocyte differentiation is restored by reviving the normal expression of type II collagen. Different molecular pathways were explored to investigate the role of IRE1 in causing chondrocyte dedifferentiation. However, we found no significant correlation, as IRE1 induces dedifferentiation through independent pathways. In response to various endoplasmic reticulum (ER) agonists (2-deoxy-D-glucose), and ER stress antagonists (tauroursodeoxycholic acid and salubrinal), IRE1 overexpression did not affect GRP78/94, as implicated in the pathogenesis of ER stress. Moreover, when IRE1 overexpression was correlated with the inflammation pathway, nuclear factor-kappa B (NFκB), IRE1 substantially increased the expression of p50 while decreasing the expression of nuclear factor kappa light polypeptide alpha (IκBα). These results suggest that IRE1 induces dedifferentiation in chondrocytes by modulating inflammatory pathways that cause dedifferentiation by disrupting type II collagen expression.

Tauroursodeoxycholic Acid Supplementation in In Vitro Culture of Indicine Bovine Embryos: Molecular and Cellular Effects on the In Vitro Cryotolerance.

During embryo development, the endoplasmic reticulum (ER) acts as an important site for protein biosynthesis; however, in vitro culture (IVC) can negatively affect ER homeostasis. Therefore, the aim of our study was to evaluate the effects of the supplementation of tauroursodeoxycholic acid (TUDCA), an ER stress inhibitor, in the IVC of bovine embryos. Two experiments were carried out: Exp. 1: an evaluation of blastocyst rate, hatching kinetics, and gene expression of hatched embryos after being treated with different concentrations of TUDCA (50, 200, or 1000 µM) in the IVC; Exp. 2: an evaluation of the re-expansion, hatching, and gene expression of hatched embryos previously treated with 200 µM of TUDCA at IVC and submitted to vitrification. There was no increase in the blastocyst and hatched blastocyst rates treated with TUDCA in the IVC. However, embryos submitted to vitrification after treatment with 200 µM of TUDCA underwent an increased hatching rate post-warming together with a down-regulation in the expression of ER stress-related genes and the accumulation of lipids. In conclusion, this work showed that the addition of TUDCA during in vitro culture can improve the cryotolerance of the bovine blastocyst through the putative modulation of ER and oxidative stress.

A Low-Protein, High-Carbohydrate Diet Exerts a Neuroprotective Effect on Mice with 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine-Induced Parkinson's Disease by Regulating the Microbiota-Metabolite-Brain Axis and Fibroblast Growth Factor 21.

Parkinson's disease (PD) is closely linked to lifestyle factors, particularly dietary patterns, which have attracted interest as potential disease-modifying factors. Eating a low-protein, high-carbohydrate (LPHC) diet is a promising dietary intervention against brain aging; however, its protective effect on PD remains elusive. Here, we found that an LPHC diet ameliorated 1-methyl-4-phenyl-1,2,3,6-tetrathydropyridine (MPTP)-induced motor deficits, decreased dopaminergic neuronal death, and increased the levels of striatal dopamine, serotonin, and their metabolites in PD mice. Levels of fibroblast growth factor 21 (FGF-21), a member of the fibroblast growth factor family, were elevated in PD mice following LPHC treatment. Furthermore, the administration of FGF-21 exerted a protective effect on MPTP-induced PC12 cells, similar to the effect of an LPHC diet in MPTP-induced mice. Sequencing of the 16S rDNA from fecal microbiota revealed that an LPHC diet normalized the gut bacterial composition imbalance in PD mice, as evidenced by the increased abundance of the genera Bifidobacterium, Ileibacterium, Turicibacter, and Blautia and decreased abundance of Bilophila, Alistipes, and Bacteroides. PICRUSt-predicted fecal microbiome function revealed that an LPHC diet suppressed lipopolysaccharide biosynthesis and the citrate cycle (TCA cycle), biosynthesis of ubiquinone and other terpenoid-quinones, and oxidative phosphorylation pathways caused by MPTP, and enhanced the biosynthesis of amino acids, carbohydrate metabolism, and biosynthesis of other secondary metabolites. A nonmetabolomic analysis of the serum and feces showed that an LPHC diet significantly increased the levels of aromatic amino acids (AAAs), including tryptophan, tyrosine, and phenylalanine. In addition, an LPHC diet elevated the serum concentrations of bile acids (BAs), particularly tauroursodeoxycholic acid (TUDCA) and taurine. Collectively, our current findings point to the potential mechanism of administering an LPHC diet in attenuating movement impairments in MPTP-induced PD mice, with AAAs, microbial metabolites (TUDCA and taurine), and FGF-21 as key mediators along the gut-microbiota-brain axis.

Taurochenodeoxycholic acid inhibits intestinal epithelial cell proliferation and induces apoptosis independent of the farnesoid X receptor.

Bile acids, such as taurochenodeoxycholic acid (TCDCA), are considered as functional small molecules involved in nutrition regulation or acting with adjuvant therapeutic effects against metabolic or immune diseases. The homeostasis of the intestinal epithelium depends on the conventional cellular proliferation and apoptosis of cells. Herein, mice and normal intestinal epithelial cells (IPEC-J2, a widely used normal intestinal epithelial cell line derived from porcine) were used as models to explore the regulatory effect of TCDCA on the proliferation of intestinal epithelial cells (IECs). In the mouse study, the oral gavage of TCDCA led to a significant reduction in weight gain, small intestinal weight, and the villus height of the intestinal epithelium while inhibiting the gene expression of Ki-67 in the intestinal epithelial crypts of mice (P < 0.05). TCDCA significantly downregulated the expression of the farnesoid X receptor (FXR) and upregulated the expression of caspase-9 in the jejunum (P < 0.05). The results of real-time quantitative PCR (RT-qPCR) suggested that TCDCA significantly inhibited the expression of tight junction proteins zonula occludens (ZO)-1, occludin, claudin-1, and mucin-2 (P < 0.05). In terms of apoptosis-related genes, TCDCA significantly inhibited the expression of Bcl2 and increased the expression of caspase-9 (P < 0.05). At the protein level, TCDCA decreased the expression of Ki-67 and PCNA, as well as FXR (P < 0.05). Caspase inhibitor Q-VD-OPh and guggulsterone, an FXR antagonist, significantly improved the inhibition of TCDCA-induced cell proliferation. Moreover, guggulsterone enhanced TCDCA-induced cell late apoptosis through flow cytometry and significantly lowered the TCDCA-induced up-regulated gene expression of caspase 9, despite both TCDCA and guggulsterone down-regulating the expression of FXR (P < 0.05). Overall, the effect of TCDCA on the induction of apoptosis is not dependent on FXR, whereas it would function via the activation of the caspase system. This provides a new perspective for the application of TCDCA or bile acid as functional small molecules in food, additives, and medicine.

Effect of SCD probiotics supplemented with tauroursodeoxycholic acid (TUDCA) application on the aged rat gut microbiota composition.

AIMS: In this study, the effects of SCD Probiotics with tauroursodeoxycholic acid (TUDCA) application on the aged rat gut microbiota (GM) composition were investigated. METHODS AND RESULTS: Twenty-four-month-old Sprague-Dawley rats were given 300 mg/kg of TUDCA along with 3 mL (1 × 108 CFU) of SCD probiotics for 7 days. The bacterial profile was determined by the metagenome applied to the cecum content. TUDCA, SCD probiotics, and TUDCA with SCD probiotics designed GM differently. TUDCA and SCD probiotics have the most different dominant species profiles. CONCLUSIONS: SCD probiotics and TUDCA have their own unique effects on the species found in GM, and when they are evaluated together, the species found in GM are restructured differently.

Taurochenodeoxycholic acid reduces astrocytic neuroinflammation and alleviates experimental autoimmune encephalomyelitis in mice.

OBJECTIVE: Multiple sclerosis (MS) is an immune regulatory disease that affects the central nervous system (CNS). The main pathological features include demyelination and neurodegeneration, and the pathogenesis is associated with astrocytic neuroinflammation. Taurochenodeoxycholic acid (TCDCA) is one of the conjugated bile acids in animal bile, and it is not clear whether TCDCA could improve MS by inhibiting the activation of astrocytes. This study was aimed to evaluate the effects of TCDCA on experimental autoimmune encephalomyelitis (EAE)-a classical animal model of MS, and to probe its mechanism from the aspect of suppressing astrocytic neuroinflammation. It is expected to prompt the potential application of TCDCA for the treatment of MS. RESULTS: TCDCA effectively alleviated the progression of EAE and improved the impaired neurobehavior in mice. It mitigated the hyperactivation of astrocytes and down-regulated the mRNA expression levels of inducible nitric oxide synthase (iNOS), cyclooxygenase 2 (COX2), tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß) and IL-6 in the brain cortex. In the C6 astrocytic cell line induced by lipopolysaccharide (LPS), TCDCA treatment dose-dependently decreased the production of NO and the protein expression of iNOS and glial fibrillary acidic protein (GFAP). TCDCA consistently inhibited the mRNA expressions of COX2, iNOS and other inflammatory mediators. Furthermore, TCDCA decreased the protein expression of phosphorylated serine/threonine kinase (AKT), inhibitor of NFκB α (IκBα) and nuclear factor κB (NFκB). And TCDCA also inhibited the nuclear translocation of NFκB. Conversely, as an inhibitor of the G-protein coupled bile acid receptor Gpbar1 (TGR5), triamterene eliminated the effects of TCDCA in LPS-stimulated C6 cells. CONCLUSION: TCDCA improves the progress of EAE by inhibiting the astrocytic neuroinflammation, which might be exerted by the regulation of TGR5 mediated AKT/NFκB signaling pathway. These findings may prompt the potential application of TCDCA for MS therapy by suppressing astrocyte inflammation.

Insights by which TUDCA is a potential therapy against adiposity.

Adipose tissue is an organ with metabolic and endocrine activity. White, brown and ectopic adipose tissues have different structure, location, and function. Adipose tissue regulates energy homeostasis, providing energy in nutrient-deficient conditions and storing it in high-supply conditions. To attend to the high demand for energy storage during obesity, the adipose tissue undergoes morphological, functional and molecular changes. Endoplasmic reticulum (ER) stress has been evidenced as a molecular hallmark of metabolic disorders. In this sense, the ER stress inhibitor tauroursodeoxycholic acid (TUDCA), a bile acid conjugated to taurine with chemical chaperone activity, has emerged as a therapeutic strategy to minimize adipose tissue dysfunction and metabolic alterations associated with obesity. In this review, we highlight the effects of TUDCA and receptors TGR5 and FXR on adipose tissue in the setting of obesity. TUDCA has been demonstrated to limit metabolic disturbs associated to obesity by inhibiting ER stress, inflammation, and apoptosis in adipocytes. The beneficial effect of TUDCA on perivascular adipose tissue (PVAT) function and adiponectin release may be related to cardiovascular protection in obesity, although more studies are needed to clarify the mechanisms. Therefore, TUDCA has emerged as a potential therapeutic strategy for obesity and comorbidities.

Evaluating the potential of tauroursodeoxycholic acid as add-on therapy in amelioration of streptozotocin-induced diabetic kidney disease.

The bile acid tauroursodeoxycholic acid (TUDCA) is of natural origin and is used in traditional Chinese medicine for centuries. Earlier its use was limited to biliary disorders but owing to its pleiotropic effects dietary TUDCA supplementation is under clinical trials for diseases including type 1 and 2 diabetic complications. The current study aims to evaluate the potential and underlying molecular mechanism of the TUDCA as a monotherapy and as an add-on therapy to telmisartan, an angiotensin II type 1 receptor (AT1R) blocker against diabetic kidney disease (DKD). We employed both in-vitro and in-vivo approaches where NRK-52E cells were incubated with high glucose, and DKD was induced in Wistar rats using streptozotocin (55 mg/kg, i.p.). After 4 weeks, animals were administered with TUDCA (250 mg/kg, i.p.), telmisartan (10 mg/kg, p.o.), and their combination for 4 weeks. Plasma was collected for the biochemical estimation and kidneys were used for immunoblotting, PCR, and histopathological analysis. Similarly, for in-vitro experiments, cells were exposed to 1000 µM of TUDCA and 10 µM of telmisartan, and their combination, followed by cell lysate collection and immunoblotting analysis. We observed that the addition of TUDCA to conventional telmisartan treatment was more effective in restoring the renal function decline and suppressing the apoptotic and fibrotic signaling as compared to monotherapies of AT1R blocker and ER stress inhibitor. The results implicate the utility of traditionally used TUDCA as a potential renoprotective compound. Since, both TUDCA and telmisartan are approved for clinical usage, thus concomitant administration of them could be a novel therapeutic strategy against DKD.

Is TGR5 a therapeutic target for the treatment of spinal cord injury?

Bile acids, which are synthesized in liver and colon, facilitate the digestion of dietary lipids. In addition to this metabolic function, they also act as molecular signals with activities in the nervous system. These are mediated primarily by a G-protein-coupled bile acid receptor (known as TGR5). Preceded by a long tradition in Chinese medicine, bile acids are now being investigated as therapeutic options in several neuropathologies. Specifically, one bile acid, tauroursodeoxycholic acid (TUDCA), which passes the blood-brain barrier and shows anti-inflammatory and anti-apoptotic effects, has been tested in animal models of spinal cord injury (SCI). In this review, we discuss the evidence for a therapeutic benefit in these preclinical experiments. At the time of writing, 12 studies with TGR5 agonists have been published that report functional outcomes with rodent models of SCI. Most investigations found cytoprotective effects and benefits regarding the recovery of sensorimotor function in the subacute phase. When TUDCA was applied in a hydrogel into the lesion site, a significant improvement was obtained at 2 weeks after SCI. However, no lasting improvements with TUDCA treatment were found, when animals were assessed in later, chronic stages. A combination of TUDCA with stem cell injection failed to improve the effect of the cellular treatment. We conclude that the evidence does not support the use of TUDCA as a treatment of SCI. Nevertheless, cytoprotective effects suggest that different modes of application or combinatorial therapies might still be explored.

Duyun compound green tea extracts regulate bile acid metabolism on mice induced by high-fat diet.

Duyun compound green tea (DCGT) is a healthy beverage with lipid-lowering effect commonly consumed by local people, but its mechanism is not very clear. We evaluated the effect of DCGT treatment on bile acids (BA) metabolism of mice with high-fat diet (HFD) - induced hyperlipidaemia by biochemical indexes and metabolomics and preliminarily determined the potential biomarkers and metabolic pathways of hyperlipidaemia mice treated with DCGT as well as investigated its lipid-lowering mechanism. The results showed that DCGT treatment could reduce HFD - induced gain in weight and improve dyslipidaemia. In addition, a total of ten types of BA were detected, of which seven changed BA metabolites were observed in HFD group mice. After DCGT treatment, glycocholic acid, tauroursodeoxycholic acid and taurochenodeoxycholic acid were significantly down-regulated, while hyodeoxycholic acid, deoxycholic acid and chenodeoxycholic acid were markedly up-regulated. These results demonstrated that DCGT treatment was able to make the BA metabolites in the liver of hyperlipidaemia mice normal and alleviate hyperlipidaemia by regulating the metabolites such as glycocholic acid, tauroursodeoxycholic acid and taurochenodeoxycholic, as well as the BA metabolic pathway and cholesterol metabolic pathway involved.

Effects of Tauroursodeoxycholic Acid and 4-Phenylbutyric Acid on Selenium Distribution in Mice Model with Type 1 Diabetes.

The effect of selenium on diabetes is significant. As pharmaceutical chaperones, tauroursodeoxycholic acid (TUDCA) and 4-phenylbutyric acid (4-PBA) can effectively improve the oxidative stress of the endoplasmic reticulum. This study established a mice model with type 1 diabetes (T1D) to evaluate the effects of pharmaceutical chaperones on selenium distribution. Streptozotocin was used to induce Friend virus B-type mice to establish a T1D mice model. Mice were administered with TUDCA or 4-PBA. Selenium levels in different tissues were measured by inductively coupled plasma-mass spectroscopy (ICP-MS). After treatment with TUDCA and 4-PBA, related laboratory findings such as glucose and glycated serum protein were significantly reduced and were closer to normal levels. At 2 weeks, 4-PBA normalized selenium levels in the heart, and 4-PBA and TUDCA maintained the selenium in the liver, kidney, and muscle at normal. At 2 months, 4-PBA and TUDCA maintained the selenium in the heart, liver, and kidney at normal levels. The serum selenium had a positive correlation with zinc and copper in the diabetes group and the control group, while the serum selenium had no significant association with magnesium and calcium at 2 weeks and 2 months. TUDCA and 4-PBA have crucial effects on selenium distribution in diabetic mice, and further research is needed to research their internal mechanisms.

The bile acid TUDCA reduces age-related hyperinsulinemia in mice.

Aging is associated with glucose metabolism disturbances, such as insulin resistance and hyperinsulinemia, which contribute to the increased prevalence of type 2 diabetes (T2D) and its complications in the elderly population. In this sense, some bile acids have emerged as new therapeutic targets to treat TD2, as well as associated metabolic disorders. The taurine conjugated bile acid, tauroursodeoxycholic acid (TUDCA) improves glucose homeostasis in T2D, obesity, and Alzheimer's disease mice model. However, its effects in aged mice have not been explored yet. Here, we evaluated the actions of TUDCA upon glucose-insulin homeostasis in aged C57BL/6 male mice (18-month-old) treated with 300 mg/kg of TUDCA or its vehicle. TUDCA attenuated hyperinsulinemia and improved glucose homeostasis in aged mice, by enhancing liver insulin-degrading enzyme (IDE) expression and insulin clearance. Furthermore, the improvement in glucose-insulin homeostasis in these mice was accompanied by a reduction in adiposity, associated with adipocyte hypertrophy, and lipids accumulation in the liver. TUDCA-treated aged mice also displayed increased energy expenditure and metabolic flexibility, as well as a better cognitive ability. Taken together, our data highlight TUDCA as an interesting target for the attenuation of age-related hyperinsulinemia and its deleterious effects on metabolism.

Effect of Tauroursodeoxycholic Acid on Inflammation after Ocular Alkali Burn.

Inflammation is the main cause of corneal and retinal damage in an ocular alkali burn (OAB). The aim of this study was to investigate the effect of tauroursodeoxycholic acid (TUDCA) on ocular inflammation in a mouse model of an OAB. An OAB was induced in C57BL/6j mouse corneas by using 1 M NaOH. TUDCA (400 mg/kg) or PBS was injected intraperitoneally (IP) once a day for 3 days prior to establishing the OAB model. A single injection of Infliximab (6.25 mg/kg) was administered IP immediately after the OAB. The TUDCA suppressed the infiltration of the CD45-positive cells and decreased the mRNA and protein levels of the upregulated TNF-α and IL-1ß in the cornea and retina of the OAB. Furthermore, the TUDCA treatment inhibited the retinal glial activation after an OAB. The TUDCA treatment not only ameliorated CNV and promoted corneal re-epithelization but also attenuated the RGC apoptosis and preserved the retinal structure after the OAB. Finally, the TUDCA reduced the expression of the endoplasmic reticulum (ER) stress molecules, IRE1, GRP78 and CHOP, in the retinal tissues of the OAB mice. The present study demonstrated that the TUDCA inhibits ocular inflammation and protects the cornea and retina from injury in an OAB mouse model. These results provide a potential therapeutic intervention for the treatment of an OAB.

Melatonin relieves hepatic lipid dysmetabolism caused by aging via modifying the secondary bile acid pattern of gut microbes.

It has been reported that aging-generated gut microecosystem may promote host hepatic lipid dysmetabolism through shaping the pattern of secondary bile acids (BAs). Then as an oral drug, melatonin (Mel)-mediated beneficial efforts on the communication between gut microbiota and aging host are still not clearly. Here, we show that aging significantly shapes the pattern of gut microbiota and BAs, whereas Mel treatment reverses these phenotypes (P < 0.05), which is identified to depend on the existence of gut microbiota. Mechanistically, aging-triggered high-level expression of ileac farnesoid X receptor (FXR) is significantly decreased through Mel-mediated inhibition on Campylobacter jejuni (C. jejuni)-induced deconjugation of tauroursodeoxycholic acid (TUDCA) and glycoursodeoxycholic acid (GUDCA) (P < 0.05). The aging-induced high-level of serum taurine chenodeoxycholic acid (TCDCA) activate trimethylamine-N-oxide (TMAO)-triggered activating transcriptional factor 4 (ATF4) signaling via hepatic FXR, which further regulates hepatic BAs metabolism, whereas TUDCA inhibits aging-triggered high-level of hepatic ATF4. Overall, Mel reduces C. jejuni-mediated deconjugation of TUDCA to inhibit aging-triggered high-level expression of hepatic FXR, which further decreases hepatic TMAO production, to relieve hepatic lipid dysmetabolism.

The Taurine-Conjugated Bile Acid (TUDCA) Normalizes Insulin Secretion in Pancreatic ß-Cells Exposed to Fatty Acids: The Role of Mitochondrial Metabolism.

Bile acid tauroursodeoxycholic (TUDCA), formed from the association of ursodeoxycholic acid (UDCA) with taurine, has already been shown to increase mitochondrial biogenesis and cell survival, in addition to reduce reticulum stress markers in different cell types. However, its mechanism of action upon insulin secretion control in obesity is still unknown. In this sense, we seek to clarify whether taurine, associated with bile acid, could improve the function of the pancreatic ß-cells exposed to fatty acids through the regulation of mitochondrial metabolism. To test this idea, insulin-producing cells (INS1-E) were exposed to a fatty acid mix containing 500 µM of each palmitate and oleate for 48 hours treated or not with 300 µM of TUDCA. After that, glucose-stimulated insulin secretion and markers of mitochondrial metabolism were evaluated. Our results showed that the fatty acid mix was efficient in inducing hyperfunction of INS1-E cells as observed by the increase in insulin secretion, protein expression of citrate synthase, and mitochondrial density, without altering cell viability. The treatment with TUDCA normalized insulin secretion, reducing the protein expression of citrate synthase, mitochondrial mass, and the mitochondrial membrane potential. This effect was associated with a decrease in the generation of mitochondrial superoxide and c-Jun N-terminal kinase (JNK) protein content. The findings are also consistent with the hypothesis that TUDCA normalizes insulin secretion by improving mitochondrial metabolism and redox balance. Thus, it highlights likely mechanisms of the action of this bile acid on the glycemic homeostasis reestablishment in obesity.

Tauroursodeoxycholic acid: a potential therapeutic tool in neurodegenerative diseases.

Most neurodegenerative disorders are diseases of protein homeostasis, with misfolded aggregates accumulating. The neurodegenerative process is mediated by numerous metabolic pathways, most of which lead to apoptosis. In recent years, hydrophilic bile acids, particularly tauroursodeoxycholic acid (TUDCA), have shown important anti-apoptotic and neuroprotective activities, with numerous experimental and clinical evidence suggesting their possible therapeutic use as disease-modifiers in neurodegenerative diseases. Experimental evidence on the mechanisms underlying TUDCA's neuroprotective action derives from animal models of Alzheimer's disease, Parkinson's disease, Huntington's diseases, amyotrophic lateral sclerosis (ALS) and cerebral ischemia. Preclinical studies indicate that TUDCA exerts its effects not only by regulating and inhibiting the apoptotic cascade, but also by reducing oxidative stress, protecting the mitochondria, producing an anti-neuroinflammatory action, and acting as a chemical chaperone to maintain the stability and correct folding of proteins. Furthermore, data from phase II clinical trials have shown TUDCA to be safe and a potential disease-modifier in ALS. ALS is the first neurodegenerative disease being treated with hydrophilic bile acids. While further clinical evidence is being accumulated for the other diseases, TUDCA stands as a promising treatment for neurodegenerative diseases.

Alleviation of Endoplasmic Reticulum Stress Enhances Human Corneal Epithelial Cell Viability under Hyperosmotic Conditions.

Tear hyperosmolarity plays an essential role in the initiation and progression of dry-eye disease. Under a hyperosmotic environment, corneal epithelial cells experience perturbations in endoplasmic reticulum function that can lead to proinflammatory signaling and apoptosis. In this study, we investigated the effect of tauroursodeoxycholic acid (TUDCA), a chemical chaperone known to protect against endoplasmic reticulum stress, on corneal epithelial cells exposed to hyperosmotic conditions. We found that the expression of the genes involved in the activation of the unfolded protein response and the pro-apoptotic transcription factor DDIT3 were markedly upregulated in patients with Sjögren's dry-eye disease and in a human model of corneal epithelial differentiation following treatment with hyperosmotic saline. Experiments in vitro demonstrated that TUDCA prevented hyperosmotically induced cell death by reducing nuclear DNA fragmentation and caspase-3 activation. TUDCA supplementation also led to the transcriptional repression of CXCL8 and IL5, two inflammatory mediators associated with dry-eye pathogenesis. These studies highlight the role of hyperosmotic conditions in promoting endoplasmic reticulum stress in the cornea and identify TUDCA as a potential therapeutic agent for the treatment of dry-eye disease.