Ontogenic transformation of the ankle from the initial mediolateral arrangement of the calcaneus and talus: A histological study of human embryos and early fetuses.

The human calcaneus is robust and provides a prominent heel for effective bipedal locomotion, although the adjacent talus has no muscle attachments. However, there is incomplete information about the morphological changes in these prominent bones during embryo development. We examined serial histological sections of 23 human embryos and early-term fetuses (approximately 5-10 weeks' gestational age [GA]). At a GA of 5 weeks, the precartilage talus was parallel to and on the medial side of the calcaneus, which had a prolate spheroid shape and consisted of three masses. At a GA of 6 weeks, the cartilaginous talus extended along the proximodistal axis, and the tuber calcanei became long and bulky, with a small sustentaculum talus at the "distal" side. At a GA of 6 to 8 weeks, the sustentaculum had a medial extension below the talus so that the talus "rode over" the calcaneus. In contrast, the talus had a more complex shape, depending on the growth of adjacent bones. At a GA of 9 to 10 weeks, the talus was above the calcaneus, but the medial part still faced the plantar subcutaneous tissue because of the relatively small sustentaculum. Therefore, the final morphology appeared after an additional several weeks. Muscle activity seemed to facilitate growth of the tuber calcanei, but growth of the other parts of calcaneus, including the sustentaculum, seemed to depend on active proliferation at the different sites of cartilage. Multiple tendons and ligaments seemed to fix the talus so that it remained close to the calcaneus.

Growth patterns of facial muscles at the angle of the mouth: A histological study using midterm and near-term human fetuses.

At the angle of the mouth, spoke-like muscle bundles converge at the "modiolus," which is believed to appear in utero. The aim of this study was to investigate the growth of the modiolus histologically. We studied frontal histological sections of the face from 12 midterm and six near-term fetuses. At midterm, a convergence of the levator anguli oris (LAOM) and depressor anguli oris (DAOM) was frequently present, and another convergence of the LAOM with the platysma (PM) or orbicularis oris (OOM) was also often evident. At near-term, muscle fiber merging or interdigitation was classified into nine combinations, five of which were frequently seen: LAOM-PM, LAOM-DAOM, zygomaticus major (ZMM)-orbicularis oris (OOM), buccinator (BM)-LAOM, and BM-PM. These combinations existed at slightly different depths and/or sites, thus allowing the angle of the mouth to receive multiple muscles. Notably, tissues interposed between the muscle fibers were limited to a thin epimysium at each crossing or interdigitation. Therefore, the LAOM, DAOM, OOM, BM, and PM appear to form a basic configuration at birth, but the development and growth were much delayed than the classical description. The modiolus is not a specific fibromuscular structure but simply represents a cluster of muscle convergence sites. Even at meeting between an elevator and depressor, a specific fibrous structure seems unlikely to connect the epimysium for the muscle convergence. Instead, the central nervous system appears to regulate the activity of related muscles to minimize tension or friction stress at the meeting site.

Differences in iron balance observed with dietary cholic acid supplementation and marginal iron deficiency in rats.

We investigated whether a cholic acid (CA)-supplemented diet and marginal iron deficiency (MID) diet influence hepatic lipid accumulation and iron balance in rats for 2 weeks. The CA diet enhanced hepatic lipid accumulation and modulated iron metabolism such as enhancement of fecal iron excretion, reduction in iron absorption, and no alteration in plasma iron levels. The MID diet did not alter hepatic lipid concentrations with reduced iron concentration in the liver and plasma. In combination, influence of the CA supplementation on the hepatic iron concentration was opposite between iron-sufficient and MID conditions. In the liver, the CA diet enhanced lipocalin 2 expression, whereas the MID diet enhanced transferrin receptor 1 expression and reduced hepcidin expression. This study revealed an involvement of 12-hydroxylated bile acids in regulation of hepatic iron concentration under MID condition.

A diet supplemented with cholic acid elevates blood pressure accompanied by albuminuria in rats.

A diet supplemented with cholic acid (CA), the primary 12α-hydroxylated bile acid, can induce hepatic lipid accumulation in rats without obesity. This study examined the effects of a CA-supplemented diet on blood pressure (BP). After acclimation, WKAH/HkmSlc rats (3 weeks old) were divided into two groups and fed with a control AIN-93-based diet or a CA-supplemented diet (0.5 g CA/kg) for 13 weeks. The CA diet increased systolic and diastolic BP as well as hepatic lipid concentrations in the rats. No changes were found in the blood sodium concentration. Urinary albumin concentration increased in CA-fed rats. An increase was observed in the hepatic expression of ATP-binding cassette subfamily B member 1B that correlated BPs and urinary albumin concentration accompanied by an increase in portal taurocholic acid concentration. These results suggest that 12α-hydroxylated bile acids are involved in increased BP and albuminuria via alteration of hepatic function.

Chronological Changes in the Expression and Localization of Sox9 between Achilles Tendon Injury and Functional Recovery in Mice.

Tendons help transmit forces from the skeletal muscles and bones. However, tendons have inferior regenerative ability compared to muscles. Despite studies on the regeneration of muscles and bone tissue, only a few have focused on tendinous tissue regeneration, especially tendon regeneration. Sex-determining region Y-box transcription factor 9 (Sox9) is an SRY-related transcription factor with a DNA-binding domain and is an important control factor for cartilage formation. Sox9 is critical to the early-to-middle stages of tendon development. However, how Sox9 participates in the healing process after tendon injury is unclear. We hypothesized that Sox9 is expressed in damaged tendons and is crucially involved in restoring tendon functions. We constructed a mouse model of an Achilles tendon injury by performing a 0.3 mm wide partial excision in the Achilles tendon of mice, and chronologically evaluated the function restoration and localization of the Sox9 expressed in the damaged sites. The results reveal that Sox9 was expressed simultaneously with the formation of the pre-structure of the epitenon, an essential part of the tendinous tissue, indicating that its expression is linked to the functional restoration of tendons. Lineage tracing for Sox9 expressed during tendon restoration revealed the tendon restoration involvement of cells that switched into Sox9-expressing cells after tendon injury. The stem cells involved in tendon regeneration may begin to express Sox9 after injury.

Supplementary effect of whey components on the monascin productivity of Monascus sp.

BACKGROUND: Monascus sp. has been used in fermented foods for centuries. It can synthesize yellow, red, and orange pigments as secondary metabolites. Here, we focused on yellow pigment monascin, responsible for anti-inflammation and antidiabetic effects, and investigated whether whey could be a suitable substrate with or without rice powder for monascin production using M. purpureus AHU 9085, M. pilosus NBRC 4520 and M. ruber NBRC 32318. RESULTS: The growth and monascin production of the three Monascus strains were dependent on three liquid media consisting of whey and/or rice. All strains showed the best growth in a rice and whey mixed medium, in which M. ruber NBRC 32318 exhibited the highest total monascin production. Subsequent investigation of the effects of whey components indicated that a mineral cocktail in whey was particularly effective in stimulating the monascin production efficiency of M. ruber NBRC 32318. However, this recipe exhibited less stimulation, or even inhibition, for M. pilosus NBRC 4520 and M. purpureus AHU 9085, respectively. In terms of total monascin production, rice with whey provided the highest amount due to growth promotion along with relatively high production efficiency. CONCLUSION: The effect of whey on growth and monascin production was strongly dependent on the Monascus strains. Even a mineral cocktail in whey could regulate monascin productivity in a strain-specific manner. Further studies are needed to elucidate the mechanism behind the diverse responses by the minerals in the production of monascin from Monascus. © 2023 Society of Chemical Industry.

Dietary raffinose ameliorates hepatic lipid accumulation induced by cholic acid via modulation of enterohepatic bile acid circulation in rats.

Enterohepatic circulation of 12α-hydroxylated (12αOH) bile acid (BA) is enhanced depending on the energy intake in high-fat diet-fed rats. Such BA metabolism can be reproduced using a diet supplemented with cholic acid (CA), which also induces simple steatosis, without inflammation and fibrosis, accompanied by some other symptoms that are frequently observed in the condition of non-alcoholic fatty liver in rats. We investigated whether supplementation of the diet with raffinose (Raf) improves hepatic lipid accumulation induced by the CA-fed condition in rats. After acclimation to the AIN-93-based control diet, male Wistar rats were fed diets supplemented with a combination of Raf (30 g/kg diet) and/or CA (0·5 g/kg diet) for 4 weeks. Dietary Raf normalised hepatic TAG levels (two-way ANOVA P < 0·001 for CA, P = 0·02 for Raf and P = 0·004 for interaction) in the CA-supplemented diet-fed rats. Dietary Raf supplementation reduced hepatic 12αOH BA concentration (two-way ANOVA P < 0·001 for CA, P = 0·003 for Raf and P = 0·03 for interaction). The concentration of 12αOH BA was reduced in the aortic and portal plasma. Raf supplementation increased acetic acid concentration in the caecal contents (two-way ANOVA P = 0·001 as a main effect). Multiple regression analysis revealed that concentrations of aortic 12αOH BA and caecal acetic acid could serve as predictors of hepatic TAG concentration (R2 = 0·55, P < 0·001). However, Raf did not decrease the secondary 12αOH BA concentration in the caecal contents as well as the transaminase activity in the CA diet-fed rats. These results imply that dietary Raf normalises hepatic lipid accumulation via suppression of enterohepatic 12αOH BA circulation.

Development and Regeneration of Muscle, Tendon, and Myotendinous Junctions in Striated Skeletal Muscle.

Owing to a rapid increase in aging population in recent years, the deterioration of motor function in older adults has become an important social problem, and several studies have aimed to investigate the mechanisms underlying muscle function decline. Furthermore, structural maintenance of the muscle-tendon-bone complexes in the muscle attachment sites is important for motor function, particularly for joints; however, the development and regeneration of these complexes have not been studied thoroughly and require further elucidation. Recent studies have provided insights into the roles of mesenchymal progenitors in the development and regeneration of muscles and myotendinous junctions. In particular, studies on muscles and myotendinous junctions have-through the use of the recently developed scRNA-seq-reported the presence of syncytia, thereby suggesting that fibroblasts may be transformed into myoblasts in a BMP-dependent manner. In addition, the high mobility group box 1-a DNA-binding protein found in nuclei-is reportedly involved in muscle regeneration. Furthermore, studies have identified several factors required for the formation of locomotor apparatuses, e.g., tenomodulin (Tnmd) and mohawk (Mkx), which are essential for tendon maturation.

Primary 12α-Hydroxylated Bile Acids Lower Hepatic Iron Concentration in Rats.

BACKGROUND: Primary 12α-hydroxylated bile acids (12αOH BAs) enhance intestinal iron uptake due to their ability ex vivo to chelate iron. However, no information is available on their role in vivo, especially in the liver. OBJECTIVES: To investigate the effects and mechanisms of primary 12αOH BAs on hepatic iron concentration in vivo. METHODS: Male Wistar King A Hokkaido male rats (WKAH/HkmSlc) rats aged 4-5 weeks were fed a control diet or a diet with cholic acid (CA; 0.5 g/kg diet), the primary 12αOH BA, for 2 weeks (Study 1) or 13 weeks (Study 2). In Study 3, rats fed the same diets were given drinking water either alone or containing vancomycin (200 mg/L) for 6 weeks. The variables measured included food intake (Studies 1-3), bile acid profiles (Studies 1 and 3), hepatic iron concentration (Studies 1-3), fecal iron excretion (Studies 1 and 2), iron-related liver gene expression (Studies 2 and 3), and plasma iron-related factors (Studies 2 and 3). RESULTS: In Study 1, CA feed reduced the hepatic iron concentration (-16%; P = 0.005) without changing food intake or fecal iron excretion. In Study 2, we found a significant increase in the aortic plasma concentration of lipocalin 2 (LCN2; +65%; P < 0.001), an iron-trafficking protein. In Study 3, we observed no effect of vancomycin treatment on the CA-induced reduction of hepatic iron concentration (-32%; P < 0.001), accompanied by increased plasma LCN2 concentration (+72%; P = 0.003), in the CA-fed rats despite a drastic reduction in the secondary 12αOH BA concentration (-94%; P < 0.001) in the aortic plasma. CONCLUSIONS: Primary 12αOH BAs reduced the hepatic iron concentration in rats. LCN2 may be responsible for the hepatic iron-lowering effect of primary 12αOH BAs by transporting iron out of the liver.

Lithocholic acid increases intestinal phosphate and calcium absorption in a vitamin D receptor dependent but transcellular pathway independent manner.

Phosphate/calcium homeostasis is crucial for health maintenance. Lithocholic acid, a bile acid produced by intestinal bacteria, is an agonist of vitamin D receptor. However, its effects on phosphate/calcium homeostasis remain unclear. Here, we demonstrated that lithocholic acid increases intestinal phosphate/calcium absorption in an enterocyte vitamin D receptor-dependent manner. Lithocholic acid was found to increase serum phosphate/calcium levels and thus to exacerbate vascular calcification in animals with chronic kidney disease. Lithocholic acid did not affect levels of intestinal sodium-dependent phosphate transport protein 2b, Pi transporter-1, -2, or transient receptor potential vanilloid subfamily member 6. Everted gut sac analyses demonstrated that lithocholic acid increased phosphate/calcium absorption in a transcellular pathway-independent manner. Lithocholic acid suppressed intestinal mucosal claudin 3 and occludin in wild-type mice, but not in vitamin D receptor knockout mice. Everted gut sacs of claudin 3 knockout mice showed an increased permeability for phosphate, but not calcium. In patients with chronic kidney disease, serum 1,25(OH)2 vitamin D levels are decreased, probably as an intrinsic adjustment to reduce phosphate/calcium burden. In contrast, serum and fecal lithocholic acid levels and fecal levels of bile acid 7α-dehydratase, a rate-limiting enzyme involved in lithocholic acid production, were not downregulated. The effects of lithocholic acid were eliminated by bile acid adsorptive resin in mice. Thus, lithocholic acid and claudin 3 may represent novel therapeutic targets for reducing phosphate burden.

Correlation between 12α-hydroxylated bile acids and insulin secretion during glucose tolerance tests in rats fed a high-fat and high-sucrose diet.

BACKGROUND: Previously, we found a significant relationship in a rat study between energy intake and bile acid (BA) metabolism especially 12α-hydroxylated (12αOH) BAs. The present study was designed to reveal relationships among BA metabolism, glucose tolerance, and cecal organic acids in rats fed a high-fat and high-sucrose diet (HFS) by using multivariate and multiple regression analyses in two types of glucose tolerance tests (GTTs). METHODS: Male WKAH/HkmSlc rats were fed with a control or a HFS for 13 weeks. Oral glucose tolerance test (OGTT) and intraperitoneal glucose tolerance test (IPGTT) were performed at week 9 and 11, respectively. BAs were analyzed by using ultra high-performance liquid chromatography-mass spectrometry. Organic acid concentrations in cecal contents were analyzed by using ultra high-performance liquid chromatography with post-column pH buffered electric conductivity method. RESULTS: A positive correlation of aortic 12αOH BA concentration was observed with energy intake and visceral adipose tissue weight. We found that an increase of 12αOH BAs in enterohepatic circulation, intestinal contents and feces in the HFS-fed rats compared to those in control rats regardless of no significant increase of total BA concentration in the feces in the test period. Fecal 12αOH BA concentration was positively correlated with maximal insulin level in OGTT and area under curve of insulin in IPGTT. There was a positive correlation between aortic 12αOH BAs concentration and changes in plasma glucose level in both OGTT and IPGTT. In contrast, a decrease in the concentration of organic acids was observed in the cecal contents of the HFS-fed rats. Multiple linear regression analysis in the IPGTT revealed that the concentrations of aortic 12αOH BA and cecal acetic acid were the predictors of insulin secretion. Moreover, there was a positive correlation between concentration of portal 12αOH BAs and change in insulin concentration of peripheral blood in the IPGTT. CONCLUSION: The distribution analysis of BA compositions accompanied by GTTs revealed a close relationship between 12αOH BA metabolism and insulin secretion in GTTs in rats.

A low coefficient of variation in hepatic triglyceride concentration in an inbred rat strain.

BACKGROUND: Inbred strains are characterized by less genetic variation, which suggests usefulness of inbred strains for evaluations of various parameters. In this study, experimental reproducibility in several parameters was compared between an outbred Wistar rat and Wistar King A Hokkaido (WKAH/HkmSlc) rat, the inbred strain that is originated from Wistar rats. METHODS: Difference of variations was investigated in parameters of body compositions and liver functions such as body weight, liver weight, liver triglycerides (TG), liver cholesterol and plasma alanine aminotransferase activity (ALT) between WKAH rats and outbred Wistar rats by using the coefficient of variation (CV). RESULTS: There was no difference in the CVs of body weight and relative liver weight between WKAH and Wistar rats. The CVs of body weight and relative liver weight were below 10% in both WKAH and Wistar rats. The CVs of TG, cholesterol, and ALT in Wistar rats were between 30 and 40%, whereas those in WKAH rats were between 10 and 25%. A low CV level of TG was observed in WKAH rats compared to that in Wistar rats regardless of the duration of the experimental period in those rat strains. CONCLUSION: The low CV values in metabolic parameters involved in liver functions in the inbred rats suggested an advantage of using inbred rather than outbred rats for the evaluation of liver lipid metabolism.

Ingestion of difructose anhydride III partially suppresses the deconjugation and 7α-dehydroxylation of bile acids in rats fed with a cholic acid-supplemented diet.

Difructose anhydride III (DFAIII) is a prebiotic involved in the reduction of secondary bile acids (BAs). We investigated whether DFAIII modulates BA metabolism, including enterohepatic circulation, in the rats fed with a diet supplemented with cholic acid (CA), one of the 12α-hydroxylated BAs. After acclimation, the rats were fed with a control diet or a diet supplemented with DFAIII. After 2 weeks, each group was further divided into two groups and was fed diet with or without CA supplementation at 0.5 g/kg diet. BA levels were analyzed in aortic and portal plasma, liver, intestinal content, and feces. As a result, DFAIII ingestion reduced the fecal deoxycholic acid level via the partial suppression of deconjugation and 7α-dehydroxylation of BAs following CA supplementation. These results suggest that DFAIII suppresses production of deoxycholic acid in conditions of high concentrations of 12α-hydroxylated BAs in enterohepatic circulation, such as obesity or excess energy intake. Abbreviation: BA: bile acid; BSH: bile salt hydrolase; CA: cholic acid; DCA: deoxycholic acid; DFAIII: difructose anhydride III; MCA: muricholic acid; MS: mass spectrometry; NCDs: non-communicable diseases; LC: liquid chromatography; SCFA: short-chain fatty acid; TCA: taurocholic acid; TCDCA: taurochenodeoxycholic acid; TDCA: taurodeoxycholic acid; TUDCA: tauroursodeoxychlic acid; TαMCA: tauro-α-muricholic acid; TßMCA: tauro-ß-muricholic acid; TωMCA: tauro-ω-muricholic acid.

Marginal iron deficiency enhances liver triglyceride accumulation in rats fed a high-sucrose diet.

We investigated whether marginal iron-deficiency (MID) without anemia influences liver lipid accumulation in rats. Ingestion of a MID diet in which the iron concentration was half of AIN-93 formulation (iron-adequate, IA) for 3 weeks decreased liver iron concentration without anemia. We then evaluated the influence of the MID diet on liver lipid accumulation in combination with a high-sucrose (HS) diet and confirmed that the HS-MID diet successfully decreased liver iron concentration without anemia. Additionally, a significant increase in liver triglyceride concentration was found, accompanied by upregulation of hepatic fatty acid synthase expression in the rats fed the HS-MID diet compared to those in the rats fed an HS-IA diet, although no difference was observed in plasma transaminase activity and hepatic interleukin-1ß expression. These results suggest that MID enhances de novo lipid synthesis via upregulation of lipogenic gene expression in combination with sucrose in the diet. Abbreviations: ALT, alanine aminotransferase; AST, aspartate aminotransferase; HS, high sucrose; IA, iron adequate; ID, iron deficiency; MID, marginal irondeficiency; NAFLD, non-alcoholic fatty liver disease.

Influence of AHRR Pro189Ala polymorphism on kidney functions.

The function of aryl hydrocarbon receptor repressor (AHRR) in the kidney is unclear. The present study investigated associations between AHRR Pro189Ala polymorphism and estimated glomerular filtration rates (eGFR), serum creatinine, and hemoglobin levels in 2775 Japanese adults without diabetes. In addition, we examined whether AHRR expression levels in the kidney of control and chronic kidney disease (CKD) rats were changed. Multiple linear regression analyses showed that carriers of the Ala allele had increased eGFR and lower concentrations of serum creatinine and hemoglobin (p < 0.05). Immunohistochemical analysis showed that the expression of AHRR was upregulated in the kidneys of rats with CKD. These findings suggest that AHRR plays distinct roles in kidney functions and hemoglobin values. The effects of the AHRR polymorphism might be intensified in the kidneys of patients with CKD.

Combination of soya pulp and Bacillus coagulans lilac-01 improves intestinal bile acid metabolism without impairing the effects of prebiotics in rats fed a cholic acid-supplemented diet.

Intestinal bacteria are involved in bile acid (BA) deconjugation and/or dehydroxylation and are responsible for the production of secondary BA. However, an increase in the production of secondary BA modulates the intestinal microbiota due to the bactericidal effects and promotes cancer risk in the liver and colon. The ingestion of Bacillus coagulans improves constipation via the activation of bowel movement to promote defaecation in humans, which may alter BA metabolism in the intestinal contents. BA secretion is promoted with high-fat diet consumption, and the ratio of cholic acid (CA):chenodeoxycholic acid in primary BA increases with ageing. The dietary supplementation of CA mimics the BA environment in diet-induced obesity and ageing. We investigated whether B. coagulans lilac-01 and soya pulp influence both BA metabolism and the maintenance of host health in CA-supplemented diet-fed rats. In CA-fed rats, soya pulp significantly increased the production of secondary BA such as deoxycholic acid and ω-muricholic acids, and soya pulp ingestion alleviated problems related to plasma adiponectin and gut permeability in rats fed the CA diet. The combination of B. coagulans and soya pulp successfully suppressed the increased production of secondary BA in CA-fed rats compared with soya pulp itself, without impairing the beneficial effects of soya pulp ingestion. In conclusion, it is possible that a combination of prebiotics and probiotics can be used to avoid an unnecessary increase in the production of secondary BA in the large intestine without impairing the beneficial functions of prebiotics.

Activity of ERK regulates mucin 3 expression and is involved in undifferentiated Caco-2 cell death induced by 3-oxo-C12-homoserine lactone.

The signal molecule, 3-oxo-C12-homoserine lactone (3-oxo-C12-HSL), is similar to a mammalian hormone in bacteria. Although most studies have examined the effects of high 3-oxo-C12-HSL concentrations (>200 µM) on mammalian cellular functions because ~600 µM 3-oxo-C12-HSL can be secreted in biofilms of Pseudomonas aeruginosa grown in vitro, we previously showed that a low 3-oxo-C12-HSL concentration (30 µM) induces the apoptosis of undifferentiated Caco-2 cells through suppressing Akt activity. Here, we found that a low concentration of 3-oxo-C12-HSL-activated ERK1/2 in undifferentiated Caco-2 cells. Incubating cells with the ERK pathway inhibitor U0126 for 30 min alleviated the mucin 3 (MUC3) expression suppressed by 3-oxo-C12-HSL, and the upregulation of MUC3 expression induced by a 48-h incubation with U0126-reduced cell death. Thus, altered MUC3 expression caused by long-term attenuated ERK1/2 activity might correlate with the death of undifferentiated Caco-2 cells induced by 3-oxo-C12-HSL.

Mucin 3 is involved in intestinal epithelial cell apoptosis via N-(3-oxododecanoyl)-L-homoserine lactone-induced suppression of Akt phosphorylation.

N-acyl-homoserine lactones (AHL) are quorum-sensing molecules in bacteria that play important roles in regulating virulence gene expression in pathogens such as Pseudomonas aeruginosa. The present study compared responses between undifferentiated and differentiated Caco-2 cells to N-(3-oxododecanoyl)-L-homoserine lactone (3-oxo-C12-HSL). A low concentration of 3-oxo-C12-HSL (30 µM) is sufficient to reduce viability accompanied by apoptosis via the suppression of phosphorylation by Akt in undifferentiated Caco-2 cells. The suppression of Akt phosphorylation appears specific in 3-oxo-C12-HSL, because other AHLs did not influence the phosphorylation status of Akt. The reduced viability induced by 3-oxo-C12-HSL was partially recovered by constitutively active Akt overexpression in undifferentiated Caco-2 cells. Since mucin is considered a vital component of the gut barrier, we investigated whether mucin protects cellular functions induced by 3-oxo-C12-HSL in undifferentiated Caco-2 cells. The results showed that mucin protected undifferentiated Caco-2 cells from apoptosis induced by 3-oxo-C12-HSL. 3-Oxo-C12-HSL did not induce cell death in differentiated Caco-2 cells that expressed higher levels of mucin 3 (MUC3) than undifferentiated Caco-2 cells. In addition, 3-oxo-C12-HSL promoted cell death in undifferentiated Caco-2 cells transfected with MUC3 siRNA and reduced MUC3 expression in undifferentiated Caco-2 cells. Therefore, MUC3 might be responsible for the survival of undifferentiated intestinal epithelial cells in the presence of 3-oxo-C12-HSL through regulating Akt phosphorylation. In conclusion, 3-oxo-C12-HSL might influence the survival of undifferentiated intestinal epithelial cells as well as interactions between these cells and pathogens.

Acyl-homoserine lactones suppresses IEC-6 cell proliferation and increase permeability of isolated rat colon.

We investigated to determine whether a variety of acyl-homoserine lactones (AHLs) influences epithelial cell proliferation and mucosal permeability. 3-Oxo-C12-homoserine lactone (HSL) and 3-oxo-C14-HSL significantly suppressed IEC-6 cell proliferation. A significant increase in mucosal permeability was observed in isolated rat colon tissue exposed to C12-HSL, 3-oxo-C12-HSL, and 3-oxo-C14-HSL. These data indicate that AHLs suppress epithelial proliferation and disrupt barrier function in intestinal mucosa.

Dietary Supplementation with Cholic Acid Reduces Insulin Secretion in Response to Intraperitoneal Glucose Administration in Rats.

The major characteristic of type 2 diabetes is insulin resistance, which is associated with plasma level of 12-hydroxylated bile acids (BAs) in humans. In this study, we investigated whether the rise of enterohepatic 12-hydroxylated BAs associates with glucose tolerance and/or insulin secretion using rats fed a diet supplemented with cholic acid (CA) at a level of 0.5 g/kg diet. Almost no increase was observed in plasma insulin in response to the intraperitoneal glucose administration in the CA-fed rats despite the significant increase of plasma insulin in control with the same treatment. In contrast, the changes in insulin secretion were observed in both groups and no difference was detected between the groups in the oral glucose tolerance test. Increases were observed in pancreatic expressions of Ins1 and Ins2 although the insulin protein content decreased in the pancreas without any sign in ectopic fat accumulation and histological damage in the CA-fed rats. Our results suggest that enterohepatic 12-hydroxylated BAs modulate insulin secretion in response to intraperitoneal glucose administration. The decrease in insulin store might be responsible for the reduction in the insulin secretion in the CA-fed rats.