Insulin/IGF-1 enhances intestinal epithelial crypt proliferation through PI3K/Akt, and not ERK signaling in obese humans

Christensenellaceae minuta modulates epithelial healing via PI3K-AKT pathway and macrophage differentiation in the colitis

Ulcerative colitis (UC) is a chronic inflammatory disorder with an unsatisfactory cure rate and mucosal healing is a key treatment objective. Christensenellaceae minuta (C. minuta) has emerged as a next-generation of probiotic for maintaining intestinal health. We investigated the therapeutic efficacy of C. minuta in dextran sulfate sodium (DSS)-induced colitis, focusing on mucosal healing and the underlying mechanisms. C. minuta effectively alleviated colitis and promoted the regeneration of intestinal epithelial cells (IECs). Using 16S rRNA sequencing and metabolomics, we found that C. minuta administration increased beneficial bacteria, decreased pathogenic bacteria, and significantly elevated propionic acid levels. Additionally, C. minuta activated the PI3K-AKT pathway by upregulating systemic and local IGF-1 expression. Inhibiting the PI3K-AKT pathway reduced the therapeutic effects of C. minuta and impaired IEC regeneration. Furthermore, C. minuta promoted macrophage differentiation into the M2 phenotype and decreased proinflammatory factors. We propose that C. minuta alleviates colitis by regulating the gut microbiota, modulating macrophage differentiation, and enhancing mucosal healing by activating the PI3K-AKT pathway via IGF-1 secretion induced by short-chain fatty acids. Our findings provide evidence from animal experiments to support future clinical trials and the therapeutic translation of C. minuta.

Insulin promotes the bone formation capability of human dental pulp stem cells through attenuating the IIS/PI3K/AKT/mTOR pathway axis

BACKGROUND

Insulin has been known to regulate bone metabolism, yet its specific molecular mechanisms during the proliferation and osteogenic differentiation of dental pulp stem cells (DPSCs) remain poorly understood. This study aimed to explore the effects of insulin on the bone formation capability of human DPSCs and to elucidate the underlying mechanisms.

METHODS

Cell proliferation was assessed using a CCK-8 assay. Cell phenotype was analyzed by flow cytometry. Colony-forming unit-fibroblast ability and multilineage differentiation potential were evaluated using Toluidine blue, Oil red O, Alizarin red, and Alcian blue staining. Gene and protein expressions were quantified by real-time quantitative polymerase chain reaction and Western blotting, respectively. Bone metabolism and biochemical markers were analyzed using electrochemical luminescence and chemical colorimetry. Cell adhesion and growth on nano-hydroxyapatite/collagen (nHAC) were observed with a scanning electron microscope. Bone regeneration was assessed using micro-CT, fluorescent labeling, immunohistochemical and hematoxylin and eosin staining.

RESULTS

Insulin enhanced the proliferation of human DPSCs as well as promoted mineralized matrix formation in a concentration-dependent manner. 10- 6 M insulin significantly up-regulated osteogenic differentiation-related genes and proteins markedly increased the secretion of bone metabolism and biochemical markers, and obviously stimulated mineralized matrix formation. However, it also significantly inhibited the expression of genes and proteins of receptors and receptor substrates associated with insulin/insulin-like growth factor-1 signaling (IIS) pathway, obviously reduced the expression of the phosphorylated PI3K and the ratios of the phosphorylated PI3K/total PI3K, and notably increased the expression of the total PI3K, phosphorylated AKT, total AKT and mTOR. The inhibitor LY294002 attenuated the responsiveness of 10- 6 M insulin to IIS/PI3K/AKT/mTOR pathway axis, suppressing the promoting effect of insulin on cell proliferation, osteogenic differentiation and bone formation. Implantation of 10- 6 M insulin treated DPSCs into the backs of severe combined immunodeficient mice and the rabbit jawbone defects resulted in enhanced bone formation.

CONCLUSIONS

Insulin induces insulin resistance in human DPSCs and effectively promotes their proliferation, osteogenic differentiation and bone formation capability through gradually inducing the down-regulation of IIS/PI3K/AKT/mTOR pathway axis under insulin resistant states.

Catapol reduced the cognitive and mood dysfunctions in post-stroke depression mice via promoting PI3K-mediated adult neurogenesis

Adult hippocampal neurogenesis provides a regenerative resource for neural tissue and enhances neural plasticity, which is beneficial for brain functional rehabilitation post stroke. Recently, an increasing number of metabolic drugs have been reported to attenuate behavioral symptoms in neurodegeneration or psychiatric disorders via promoting adult hippocampal neurogenesis. Bioeffects of catapol show its potential as an antidiabetic though it has been previously widely indicated to perform the neuroprotective functions. However, the systematic evidence to support the behavioral effects of catapol to PSD model and what is the role of adult neurogenesis in such effects remains unexplored. In current study, we created the PSD model by combining MCAO procedure and CORT feeding. The treatment of catapol strikingly reduced the depressive/anxiety behavior in PSD model. Moreover, treatment of catapol also improved the cognitive functions. Immunofluorescence indicates that catapol could promote adult hippocampal neurogenesis in PSD model, and TMZ treatment further confirmed the role of the hippocampal neurogenesis in catapol's therapeutic effects to PSD. Cultural neurons also indicates that PI3K is the key signal in regulating catapol mediated neurogenesis. By administrating the PI3K specific inhibitor, we found that PI3K is the key to mediate the behavioral effects of catapol to PSD. In conclusion, catapol could perform as the effective drug to treat PSD via the PI3K mediated adult hippocampal neurogenesis.

Colostrum insulin supplementation to neonatal Holstein bulls affects small intestinal histomorphology, mRNA expression, and enzymatic activity with minor influences on peripheral metabolism

The objectives of this study were to evaluate how varying colostral insulin concentrations influenced small intestinal development and peripheral metabolism in neonatal Holstein bulls. Insulin was supplemented to approximately 5× (70.0 μg/L; n = 16) or 10× (149.7 μg/L; n = 16) the basal colostrum insulin (12.9 μg/L; BI, n = 16) concentration to maintain equivalent macronutrient intake (crude fat: 4.1 ± 0.06%; crude protein: 11.7 ± 0.05%; and lactose: 1.9 ± 0.01%) among treatments. Colostrum was fed at 2, 14, and 26 h postnatal and blood metabolites and insulin concentration were measured at 0, 30, 60, 90, 120, 180, 240, 360, 480, and 600 min postprandial respective to the first and second colostrum meal. At 30 h postnatal, a subset of calves (n = 8/treatment) were killed to excise the gastrointestinal and visceral tissues. Gastrointestinal and visceral gross morphology and dry matter and small intestinal histomorphology, gene expression, and carbohydrase activity were assessed. Insulin supplementation tended to linearly reduce the glucose clearance rate following the first meal, whereas after the second meal, supplementation linearly increased the rate of glucose absorption and nonesterified fatty acid clearance rate, decreased the time to maximum glucose concentrations, and decreased the time to reach minimum nonesterified fatty acid concentrations. Additionally, insulin clearance rate was linearly increased by insulin supplementation following the second colostrum feeding. However, there were no overall differences between treatments in the concentrations of glucose, nonesterified fatty acids, or insulin in plasma or serum. With respect to macroscopic intestinal development, dry rumen tissue mass linearly decreased when insulin was supplemented in colostrum, and supplementation linearly increased duodenal dry tissue density (g dry matter/cm) while tending to increase duodenal dry tissue weight. Increasing the colostrum insulin concentration improved small intestinal histomorphological development in the distal small intestine, as ileal villi height and mucosal-serosal surface area index were increased by supplementing insulin. Lactase enzymatic activity linearly increased in the proximal jejunum while ileal isomaltase activity linearly decreased with insulin supplementation. These data indicate that changes in colostrum insulin concentrations rapidly affect gastrointestinal growth prioritization and carbohydrase activity. The changes in gastrointestinal ontology result in minor changes in postprandial metabolite availability and clearance.

Effects of hormones on intestinal stem cells

The maintenance of intestinal renewal and repair mainly depends on intestinal stem cells (ISCs), which can also contribute to the growth of intestinal tumours. Hormones, which are vital signalling agents in the body, have various effects on the growth and replacement of intestinal stem cells. This review summarises recent progress in the identification of hormones associated with intestinal stem cells. Several hormones, including thyroid hormone, glucagon-like peptide-2, androgens, insulin, leptin, growth hormone, corticotropin-releasing hormone and progastrin, promote the development of intestinal stem cells. However, somatostatin and melatonin are two hormones that prevent the proliferation of intestinal stem cells. Therefore, new therapeutic targets for the diagnosis and treatment of intestinal illnesses can be identified by examining the impact of hormones on intestinal stem cells.

Obesity and cancer stem cells: Roles in cancer initiation, progression and therapy resistance

Obesity, the global pandemic since industrialization, is the number one lifestyle-related risk factor for premature death, which increases the incidence and mortality of various diseases and conditions, including cancer. In recent years, the theory of cancer stem cells (CSCs), which have the capacity for self-renewal, metastasis and treatment resistance, has been bolstered by increasing evidence. However, research on how obesity affects CSCs to facilitate cancer initiation, progression and therapy resistance is still in its infancy, although evidence has already begun to accumulate. Regarding the ever-increasing burden of obesity and obesity-related cancer, it is pertinent to summarize evidence about the effects of obesity on CSCs, as elucidating these effects will contribute to the improvement in the management of obesity-related cancers. In this review, we discuss the association between obesity and CSCs, with a particular focus on how obesity promotes cancer initiation, progression and therapy resistance through CSCs and the mechanisms underlying these effects. In addition, the prospect of preventing cancer and targeting the mechanisms linking obesity and CSCs to reduce cancer risk or to improve the survival of patients with cancer is considered.

Declined adipogenic potential of senescent MSCs due to shift in insulin signaling and altered exosome cargo

Multipotent mesenchymal stromal cells (MSCs) maintain cellular homeostasis and regulate tissue renewal and repair both by differentiating into mesodermal lineage, e.g., adipocytes, or managing the functions of differentiated cells. Insulin is a key physiological inducer of MSC differentiation into adipocytes, and disturbances in MSC insulin sensitivity could negatively affect adipose tissue renewal. During aging, regulation and renewal of adipose tissue cells may be disrupted due to the altered insulin signaling and differentiation potential of senescent MSCs, promoting the development of serious metabolic diseases, including metabolic syndrome and obesity. However, the potential mechanisms mediating the dysfunction of adipose-derived senescent MSC remains unclear. We explored whether aging could affect the adipogenic potential of human adipose tissue-derived MSCs regulated by insulin. Age-associated senescent MSCs (isolated from donors older than 65 years) and MSCs in replicative senescence (long-term culture) were treated by insulin to induce adipogenic differentiation, and the efficiency of the process was compared to MSCs from young donors. Insulin-dependent signaling pathways were explored in these cells. We also analyzed the involvement of extracellular vesicles secreted by MSCs (MSC-EVs) into the regulation of adipogenic differentiation and insulin signaling of control and senescent cells. Also the microRNA profiles of MSC-EVs from aged and young donors were compared using targeted PCR arrays. Both replicatively and chronologically senescent MSCs showed a noticeably decreased adipogenic potential. This was associated with insulin resistance of MSCs from aged donors caused by the increase in the basal level of activation of crucial insulin-dependent intracellular effectors ERK1/2 and Akt. To assess the impact of the paracrine cross-talk of MSCs, we analyzed microRNAs profile differences in MSC-EVs and revealed that senescent MSCs produced EVs with increased content of miRNAs targeting components of insulin-dependent signaling cascade PTEN, MAPK1, GAREM1 and some other targets. We also confirmed these data by differentiation of control MSCs in the presence of EVs from senescent cells and vice versa. Thus, aging attenuated the adipogenic potential of MSCs due to autocrine or paracrine-dependent induction of insulin resistance associated with the specific changes in MSC-EV cargo.

Intestinal plasticity and metabolism as regulators of organismal energy homeostasis

The small intestine displays marked anatomical and functional plasticity that includes adaptive alterations in adult gut morphology, enteroendocrine cell profile and their hormone secretion, as well as nutrient utilization and storage. In this Perspective, we examine how shifts in dietary and environmental conditions bring about changes in gut size, and describe how the intestine adapts to changes in internal state, bowel resection and gastric bypass surgery. We highlight the critical importance of these intestinal remodelling processes in maintaining energy balance of the organism, and in protecting the metabolism of other organs. The intestinal resizing is supported by changes in the microbiota composition, and by activation of carbohydrate and fatty acid metabolism, which govern the intestinal stem cell proliferation, intestinal cell fate, as well as survivability of differentiated epithelial cells. The discovery that intestinal remodelling is part of the normal physiological adaptation to various triggers, and the potential for harnessing the reversible gut plasticity, in our view, holds extraordinary promise for developing therapeutic approaches against metabolic and inflammatory diseases.

IGF1R and LOX Modules Are Related to Antler Growth Rate Revealed by Integrated Analyses of Genomics and Transcriptomics

Deer antlers are organs of bone and have an extremely rapid growth rate. Thus far, the molecular mechanism underlying rapid antler growth has not been properly elucidated, and key genes driving this growth rate have not been fully identified. In this study, based on the newly assembled high-quality sika deer genome, we conducted an integrated analysis of genome-wide association analysis (GWAS) and weighted gene co-expression network analysis (WGCNA) using genome resequencing data from our previous GWAS, with weight and transcriptome sequencing data of faster- vs. slower-growing antlers of sika deer. The expressions of key genes were verified using Fragments Per Kilobase of transcript per Million fragments mapped (FPKM) in different tissue zones of the antler growth center, different types of sika deer tissues and antler tissues collected from faster and slower growth rates. The results show that a total of 49 genes related to antler growth rate were identified, and most of those genes were enriched in the IGF1R and LOX modules. The gene regulation network of antler growth rate through the IGF1R pathway was constructed. In conclusion, the integration of GWAS and WGCNA analyses had great advantages in identifying regulatory genes of complex antler growth traits over using singular methods individually, and we believe that our findings in the present study can provide further insight into unveiling the mechanism underlying extraordinary fast antler growth rate in particular, as well as the regulatory mechanism of rapid tissue proliferation in general.

Identification of crucial factors involved in Cynoglossus semilaevis sexual size dimorphism by GWAS and demonstration of zbed1 regulatory network by DAP-seq

Sexual size dimorphism (SSD), whereby females and males exhibit different body sizes, are widely documented in animals. To explore crucial regulators implicated in female-biased SSD of Chinese tongue sole (Cynoglossus semilaevis), GWAS was conducted on 350 females and 59 males. Twenty SNPs and 25 genes including zbed1, nsd3, cdc45, klhl29, and smad4 with -log(p) > 7 were screened, mainly mapping to sex chromosome. The chromosome W-linked gene zbed1 attracted particular attention because it is a master key for cell proliferation. Thus, the regulatory network of zbed1 in C. semilaevis was explored by DAP-seq and 1352 peaks were discovered in the female brain. Moreover, zbed1 potentially regulated hippo signaling pathway, cell cycle, translation, and PI3k-Akt signaling pathway in C. semilaevis. These findings identify crucial SNPs and genes associated with female-biased SSD in C. semilaevis, also provide the first genome-wide survey for the zbed1 regulatory network in fish species.

Lepr+ mesenchymal cells sense diet to modulate intestinal stem/progenitor cells via Leptin-Igf1 axis

Diet can impact on gut health and disease by modulating intestinal stem cells (ISCs). However, it is largely unknown if and how the ISC niche responds to diet and influences ISC function. Here, we demonstrate that Lepr⁺ mesenchymal cells (MCs) surrounding intestinal crypts sense diet change and provide a novel niche signal to maintain ISC and progenitor cell proliferation. The abundance of these MCs increases upon administration of a high-fat diet (HFD) but dramatically decreases upon fasting. Depletion of Lepr⁺ MCs resulted in fewer intestinal stem/progenitor cells, compromised the architecture of crypt-villus axis and impaired intestinal regeneration. Furthermore, we showed that IGF1 secreted by Lepr⁺ MCs is an important effector that promotes proliferation of ISCs and progenitor cells in the intestinal crypt. We conclude that Lepr⁺ MCs sense diet alterations and, in turn, modulate intestinal stem/progenitor cell function via a stromal IGF1-epithelial IGF1R axis. These findings reveal that Lepr⁺ MCs are important mediators linking systemic diet changes to local ISC function and might serve as a novel therapeutic target for gut diseases.

Injury-Induced Cellular Plasticity Drives Intestinal Regeneration

The epithelial lining of the intestine, particularly the stem cell compartment, is affected by harsh conditions in the luminal environment and also is susceptible to genotoxic agents such as radiation and chemotherapy. Therefore, the ability for intestinal epithelial cells to revert to a stem cell state is an important physiological damage response to regenerate the intestinal epithelium at sites of mucosal injury. Many signaling networks involved in maintaining the stem cell niche are activated as part of the damage response to promote cellular plasticity and regeneration. The relative contribution of each cell type and signaling pathway is a critical area of ongoing research, likely dependent on the nature of injury as well as the regional specification within the intestine. Here, we review the current understanding of the multicellular cooperation to restore the intestinal epithelium after damage.

Multifactorial causation of early onset colorectal cancer

The multiple-hit hypothesis of cancer, including colorectal cancer (CRC), states that neoplastic development requires a sequence of mutations and epigenetic changes in driver genes. We have previously proposed that obesity increases CRC risk by supporting neoplastic development through adipokine-induced signaling, and this proliferative signaling substitutes for specific driver gene mutations. In support of this hypothesis, analyses of The Cancer Genome Atlas (TCGA) mutation data have revealed that obese patients with microsatellite stable CRC exhibit fewer driver gene mutations than CRC patients with normal body mass index. The lower number of driver gene mutations required for cancer development may shorten the neoplastic process and lead to an early onset of CRC. Therefore, obesity could be one factor explaining the rise of CRC incidence among younger individuals (< 50 years of age); furthermore, early onset CRC has been associated with the increasing incidence of metabolic syndrome and obesity in this age group. However, CRC incidence among older individuals (> 50 years of age) is stable or declining, despite the high rates of metabolic syndrome and obesity in this age group. In search for explanations of this phenomenon, we discuss several factors that may contribute to the divergent CRC incidence trends in populations under, and above, the age of 50, despite the rising levels of metabolic syndrome and obesity across all ages. First, older individuals with metabolic dysregulation are more frequently on maintenance medications, such as aspirin, β-blockers, lipid-lowering drugs, ACE inhibitors, metformin, etc., compared to younger individuals. Such treatments may suppress specific adipokine-induced proliferative signaling pathways, and therefore counteract and slow down neoplastic development in medicated overweight/obese individuals. Second, in the past decades, the incidence of infectious diseases accompanied by febrile episodes has been decreasing and the use of antipyretics increasing. Compared to normal cells, neoplastic cells are more sensitive to high body temperature; therefore, the decreased number of febrile episodes in childhood and adolescence may contribute to increased cancer incidence before the age of 50. Third, obesity at younger age may expand the stem cell compartment. An increased number of intestinal stem cells and stem cell divisions translates into a higher probability of sporadic mutations in the stem cells, and therefore, a greater chance of neoplasia. In conclusion, we hypothesize that early onset CRC has multifactorial causation and the proposed associations could be examined through analyses of existing data.

Mitochondrial transcription factor A in RORγt+ lymphocytes regulate small intestine homeostasis and metabolism

RORγt+ lymphocytes, including interleukin 17 (IL-17)-producing gamma delta T (γδT17) cells, T helper 17 (Th17) cells, and group 3 innate lymphoid cells (ILC3s), are important immune regulators. Compared to Th17 cells and ILC3s, γδT17 cell metabolism and its role in tissue homeostasis remains poorly understood. Here, we report that the tissue milieu shapes splenic and intestinal γδT17 cell gene signatures. Conditional deletion of mitochondrial transcription factor A (Tfam) in RORγt+ lymphocytes significantly affects systemic γδT17 cell maintenance and reduces ILC3s without affecting Th17 cells in the gut. In vivo deletion of Tfam in RORγt+ lymphocytes, especially in γδT17 cells, results in small intestine tissue remodeling and increases small intestine length by enhancing the type 2 immune responses in mice. Moreover, these mice show dysregulation of the small intestine transcriptome and metabolism with less body weight but enhanced anti-helminth immunity. IL-22, a cytokine produced by RORγt+ lymphocytes inhibits IL-13-induced tuft cell differentiation in vitro, and suppresses the tuft cell-type 2 immune circuit and small intestine lengthening in vivo, highlighting its key role in gut tissue remodeling.

The development of a functional human small intestinal epithelium model for drug absorption

Advanced technologies are required for generating human intestinal epithelial cells (hIECs) harboring cellular diversity and functionalities to predict oral drug absorption in humans and study normal intestinal epithelial physiology. We developed a reproducible two-step protocol to induce human pluripotent stem cells to differentiate into highly expandable hIEC progenitors and a functional hIEC monolayer exhibiting intestinal molecular features, cell type diversity, and high activities of intestinal transporters and metabolic enzymes such as cytochrome P450 3A4 (CYP3A4). Functional hIECs are more suitable for predicting compounds metabolized by CYP3A4 and absorbed in the intestine than Caco-2 cells. This system is a step toward the transition from three-dimensional (3D) intestinal organoids to 2D hIEC monolayers without compromising cellular diversity and function. A physiologically relevant hIEC model offers a novel platform for creating patient-specific assays and support translational applications, thereby bridging the gap between 3D and 2D culture models of the intestine.

Obesity and intestinal stem cell susceptibility to carcinogenesis

Background

Obesity is a top public health problem associated with an increase in colorectal cancer incidence. Stem cells are the chief cells in tissue homeostasis that self-renew and differentiate into other cells to regenerate the organ. It is speculated that an increase in stem cell pool makes cells susceptible to carcinogenesis. In this review, we looked at the recent investigations linking obesity/high-fat diet-induced obesity to intestinal carcinogenesis with regard to intestinal stem cells and their niche.

Findings

High-fat diet-induced obesity may rise intestinal carcinogenesis by increased Intestinal stem cells (ISC)/progenitor’s population, stemness, and niche independence through activation of PPAR-δ with fatty acids, hormonal alterations related to obesity, and low-grade inflammation. However, these effects may possibly relate to the interaction between fats and carbohydrates, and not a fatty acid per se. Nonetheless, literature studies are inconsistency in their results, probably due to the differences in the diet components and limitations of genetic models used.

Conclusion

High-fat diet-induced obesity affects carcinogenesis by changing ISC proliferation and function. However, a well-matched diet and the reliable colorectal cancer models that mimic human carcinogenesis is necessary to clearly elucidate the influence of high-fat diet-induced obesity on ISC behavior.

Altered intestinal epithelial nutrient transport: an underappreciated factor in obesity modulated by diet and microbiota

Dietary nutrients absorbed in the proximal small intestine and assimilated in different tissues have a profound effect on overall energy homeostasis, determined by a balance between body's energy intake and expenditure. In obesity, altered intestinal absorption and consequently tissue assimilation of nutrients may disturb the energy balance leading to metabolic abnormalities at the cellular level. The absorption of nutrients such as sugars, amino acids and fatty acids released from food digestion require high-capacity transporter proteins expressed in the intestinal epithelial absorptive cells. Furthermore, nutrient sensing by specific transporters/receptors expressed in the epithelial enteroendocrine cells triggers release of gut hormones involved in regulating energy homeostasis via their effects on appetite and food intake. Therefore, the intestinal epithelial cells play a pivotal role in the pathophysiology of obesity and associated complications. Over the past decade, gut microbiota has emerged as a key factor contributing to obesity via its effects on digestion and absorption of nutrients in the small intestine, and energy harvest from dietary fiber, undigested component of food, in the large intestine. Various mechanisms of microbiota effects on obesity have been implicated. However, the impact of obesity-associated microbiota on the intestinal nutrient transporters needs extensive investigation. This review marshals the limited studies addressing the altered structure and function of the gut epithelium in obesity with special emphasis on nutrient transporters and role of diet and microbiota. The review also discusses the thoughts and controversies and research gaps in this field.

Protectin DX promotes epithelial injury repair and inhibits fibroproliferation partly via ALX/PI3K signalling pathway

Acute respiratory distress syndrome/acute lung injury (ARDS/ALI) is histologically characterized by extensive alveolar barrier disruption and excessive fibroproliferation responses. Protectin DX (PDX) displays anti‐inflammatory and potent inflammation pro‐resolving actions. We sought to investigate whether PDX attenuates LPS (lipopolysaccharide)‐induced lung injury via modulating epithelial cell injury repair, apoptosis and fibroblasts activation. In vivo, PDX was administered intraperitoneally (IP) with 200 ng/per mouse after intratracheal injection of LPS, which remarkedly stimulated proliferation of type II alveolar epithelial cells (AT II cells), reduced the apoptosis of AT II cells, which attenuated lung injury induced by LPS. Moreover, primary type II alveolar cells were isolated and cultured to assess the effects of PDX on wound repair, apoptosis, proliferation and transdifferentiation in vitro. We also investigated the effects of PDX on primary rat lung fibroblast proliferation and myofibroblast differentiation. Our result suggests PDX promotes primary AT II cells wound closure by inducing the proliferation of AT II cells and reducing the apoptosis of AT II cells induced by LPS, and promotes AT II cells transdifferentiation. Furthermore, PDX inhibits transforming growth factor‐β₁ (TGF‐β₁) induced fibroproliferation, fibroblast collagen production and myofibroblast transformation. Furthermore, the effects of PDX on epithelial wound healing and proliferation, fibroblast proliferation and activation partly via the ALX/ PI3K signalling pathway. These data present identify a new mechanism of PDX which targets the airway epithelial cell and fibroproliferation are potential for treatment of ARDS/ALI.

β-estradiol adjusts intestinal function via ERβ and GPR30 mediated PI3K/AKT signaling activation to alleviate postmenopausal dyslipidemia

Decreases in estrogen secretion and estrogen receptor function lead to an increase in the incidence of dyslipidemia and cardiovascular disease (CVD) in postmenopausal women. We previously reported that β-estradiol has a significant regulatory effect on lipids in ApoE^-/- mice with bilateral ovariectomy. In the present study, we investigated how β-estradiol regulates intestinal function via estrogen receptors to alleviate postmenopausal dyslipidemia. Ovariectomized ApoE^-/- mice were treated with β-estradiol for 90 days, and we found that β-estradiol reduced TC, TG, LDL-c, IL-1β and IL-18 levels in serum and decreased lipid accumulation in the liver. β-estradiol reduced injury and inflammation in the jejunum in ovariectomized mice, and promoted the expression of tight junction-related proteins. Moreover, β-estradiol increased ERα, ERβ, GPR30 and ABCG5 protein expression, and decreased the levels of NPC1L1 and SR-B1 in the jejunum of ovariectomized mice. In Caco-2 cells incubated with cholesterol, β-estradiol up-regulated PI3K/AKT signaling, reduced cholesterol accumulation, suppressed inflammatory signaling, and increased the expression of tight junction-related proteins. ERβ or GPR30 inhibition decreased the protective effect of β-estradiol on cholesterol accumulation, tight junctions, and inflammation in cholesterol incubated Caco-2 cells, while silencing both ERβ and GPR30 completely eliminated the protective effect of β-estradiol. PI3K/AKT inhibition abolished the protective effect of β-estradiol on cholesterol accumulation, tight junction-related protein expression, and inflammation, but had no influence on ERα, ERβ or GPR30 expression in cholesterol incubated Caco-2 cells. Our results provide evidence that β-estradiol regulates intestinal function via ERβ and GPR30 mediated PI3K/AKT signaling activation to alleviate postmenopausal dyslipidemia.

Hyodeoxycholic acid (HDCA) suppresses intestinal epithelial cell proliferation through FXR-PI3K/AKT pathway, accompanied by alteration of bile acids metabolism profiles induced by gut bacteria

Bile acids (BAs) have been implicated in regulation of intestinal epithelial signaling and function. This study aimed to investigate the effects of hyodeoxycholic acid (HDCA) on intestinal epithelial cell proliferation and explore the underlying mechanisms. IPEC-J2 cells and weaned piglets were treated with HDCA and the contributions of cellular signaling pathways, BAs metabolism profiles and gut bacteria were assessed. In vitro, HDCA suppressed IPEC-J2 proliferation via the BAs receptor FXR but not TGR5. In addition, HDCA inhibited the PI3K/AKT pathway, while knockdown of FXR or constitutive activation of AKT eliminated the inhibitory effects of HDCA, suggesting that FXR-dependent inhibition of PI3K/AKT pathway was involved in HDCA-suppressed IPEC-J2 proliferation. In vivo, dietary HDCA inhibited intestinal expression of proliferative markers and PI3K/AKT pathway in weaned piglets. Meanwhile, HDCA altered the BAs metabolism profiles, with decrease in primary BA and increase in total and secondary BAs in feces, and reduction of conjugated BAs in serum. Furthermore, HDCA increased abundance of the gut bacteria associated with BAs metabolism, and thereby induced BAs profiles alternation, which might indirectly contribute to HDCA-suppressed cell proliferation. Together, HDCA suppressed intestinal epithelial cell proliferation through FXR-PI3K/AKT signaling pathway, accompanied by alteration of BAs metabolism profiles induced by gut bacteria.