Clinical features, functional consequences, and rescue pharmacology of missense GRID1 and GRID2 human variants.

GRID1 and GRID2 encode the enigmatic GluD1 and GluD2 proteins, which form tetrameric receptors that play important roles in synapse organization and development of the central nervous system. Variation in these genes has been implicated in neurodevelopmental phenotypes. We evaluated GRID1 and GRID2 human variants from the literature, ClinVar, and clinical laboratories and found that many of these variants reside in intolerant domains, including the amino terminal domain of both GRID1 and GRID2. Other conserved regions, such as the M3 transmembrane domain, show different intolerance between GRID1 and GRID2. We introduced these variants into GluD1 and GluD2 cDNA and performed electrophysiological and biochemical assays to investigate the mechanisms of dysfunction of GRID1/2 variants. One variant in the GRID1 distal amino terminal domain resides at a position predicted to interact with Cbln2/Cbln4, and the variant disrupts complex formation between GluD1 and Cbln2, which could perturb its role in synapse organization. We also discovered that, like the lurcher mutation (GluD2-A654T), other rare variants in the GRID2 M3 domain create constitutively active receptors that share similar pathogenic phenotypes. We also found that the SCHEMA schizophrenia M3 variant GluD1-A650T produced constitutively active receptors. We tested a variety of compounds for their ability to inhibit constitutive currents of GluD receptor variants and found that pentamidine potently inhibited GluD2-T649A constitutive channels (IC50 50 nM). These results identify regions of intolerance to variation in the GRID genes, illustrate the functional consequences of GRID1 and GRID2 variants, and suggest how these receptors function normally and in disease.

An epilepsy-associated KV1.2 charge-transfer-center mutation impairs KV1.2 and KV1.4 trafficking.

We report on a heterozygous KCNA2 variant in a child with epilepsy. KCNA2 encodes KV1.2 subunits, which form homotetrameric potassium channels and participate in heterotetrameric channel complexes with other KV1-family subunits, regulating neuronal excitability. The mutation causes substitution F233S at the KV1.2 charge transfer center of the voltage-sensing domain. Immunocytochemical trafficking assays showed that KV1.2(F233S) subunits are trafficking deficient and reduce the surface expression of wild-type KV1.2 and KV1.4: a dominant-negative phenotype extending beyond KCNA2, likely profoundly perturbing electrical signaling. Yet some KV1.2(F233S) trafficking was rescued by wild-type KV1.2 and KV1.4 subunits, likely in permissible heterotetrameric stoichiometries: electrophysiological studies utilizing applied transcriptomics and concatemer constructs support that up to one or two KV1.2(F233S) subunits can participate in trafficking-capable heterotetramers with wild-type KV1.2 or KV1.4, respectively, and that both early and late events along the biosynthesis and secretion pathway impair trafficking. These studies suggested that F233S causes a depolarizing shift of ∼48 mV on KV1.2 voltage dependence. Optical tracking of the KV1.2(F233S) voltage-sensing domain (rescued by wild-type KV1.2 or KV1.4) revealed that it operates with modestly perturbed voltage dependence and retains pore coupling, evidenced by off-charge immobilization. The equivalent mutation in the Shaker K+ channel (F290S) was reported to modestly affect trafficking and strongly affect function: an ∼80-mV depolarizing shift, disrupted voltage sensor activation and pore coupling. Our work exposes the multigenic, molecular etiology of a variant associated with epilepsy and reveals that charge-transfer-center disruption has different effects in KV1.2 and Shaker, the archetypes for potassium channel structure and function.

Tracking the motion of the KV1.2 voltage sensor reveals the molecular perturbations caused by a de novo mutation in a case of epilepsy.

KEY POINTS: KV1.2 channels, encoded by the KCNA2 gene, regulate neuronal excitability by conducting K+ upon depolarization. A new KCNA2 missense variant was discovered in a patient with epilepsy, causing amino acid substitution F302L at helix S4, in the KV1.2 voltage-sensing domain. Immunocytochemistry and flow cytometry showed that F302L does not impair KCNA2 subunit surface trafficking. Molecular dynamics simulations indicated that F302L alters the exposure of S4 residues to membrane lipids. Voltage clamp fluorometry revealed that the voltage-sensing domain of KV1.2-F302L channels is more sensitive to depolarization. Accordingly, KV1.2-F302L channels opened faster and at more negative potentials; however, they also exhibited enhanced inactivation: that is, F302L causes both gain- and loss-of-function effects. Coexpression of KCNA2-WT and -F302L did not fully rescue these effects. The proband's symptoms are more characteristic of patients with loss of KCNA2 function. Enhanced KV1.2 inactivation could lead to increased synaptic release in excitatory neurons, steering neuronal circuits towards epilepsy. ABSTRACT: An exome-based diagnostic panel in an infant with epilepsy revealed a previously unreported de novo missense variant in KCNA2, which encodes voltage-gated K+ channel KV1.2. This variant causes substitution F302L, in helix S4 of the KV1.2 voltage-sensing domain (VSD). F302L does not affect KCNA2 subunit membrane trafficking. However, it does alter channel functional properties, accelerating channel opening at more hyperpolarized membrane potentials, indicating gain of function. F302L also caused loss of KV1.2 function via accelerated inactivation onset, decelerated recovery and shifted inactivation voltage dependence to more negative potentials. These effects, which are not fully rescued by coexpression of wild-type and mutant KCNA2 subunits, probably result from the enhancement of VSD function, as demonstrated by optically tracking VSD depolarization-evoked conformational rearrangements. In turn, molecular dynamics simulations suggest altered VSD exposure to membrane lipids. Compared to other encephalopathy patients with KCNA2 mutations, the proband exhibits mild neurological impairment, more characteristic of patients with KCNA2 loss of function. Based on this information, we propose a mechanism of epileptogenesis based on enhanced KV1.2 inactivation leading to increased synaptic release preferentially in excitatory neurons, and hence the perturbation of the excitatory/inhibitory balance of neuronal circuits.

Compression-induced HIF-1 enhances thrombosis and PAI-1 expression in mouse skin.

Pressure ulcers result from tissue hypoxia caused by external forces. Thrombosis due to external forces is considered important, and hypoxia inducible factor-1 (HIF-1) is a master regulator of pressure ulcer development. To date, however, their causal relationship has not been determined. This study therefore investigated the mutual relationship between thrombosis and HIF-1 activation in compressed mouse skin, based on a hypothesis that HIF-1 regulation by plasminogen activator inhibitor-1 (PAI-1) enhances thrombosis. Compression of mouse skin significantly increased the numbers of thrombi and HIF-1α-positive cells compared with control skin. A thrombosis inhibitor significantly reduced the numbers of HIF-1α-positive cells and an HIF-1 inhibitor significantly inhibited thrombosis in compressed skin tissue, suggesting a mutual relationship between thrombosis and HIF-1 activation. Compression of mouse skin also enhanced the level of Pai-1 messenger RNA expression, but this increase was significantly reduced by treatment with an HIF-1 inhibitor, whereas a thrombosis inhibitor had no effect. These results suggested the involvement of PAI-1 in HIF-1-enhanced thrombosis and that an additional factor participates in regulating Pai-1 expression in compressed skin. These findings may suggest new strategies in pressure ulcer management.

Diagnostic Yield of Epilepsy-Genes Sequencing and Chromosomal Microarray in Pediatric Epilepsy.

BACKGROUND: Around 40% of individuals with epilepsy have an underlying identifiable genetic etiology. Common methods for epilepsy genetic testing are chromosomal microarray (CMA) and epilepsy-genes sequencing (EGS). Historically, CMA was the first-line test for patients with epilepsy, but recent studies have shown that EGS has a superior diagnostic yield. To further optimize testing algorithms for epilepsy, we compared these tests' diagnostic yields and explored how they are influenced by age of onset and phenotype complexity. METHODS: Genetic test results from a cohort of patients with epilepsy were used to determine the diagnostic yield of CMA (n = 366) versus EGS (n = 370) for genetic epilepsy etiologies. Further analysis examined the probability of diagnostic results based on age of seizure onset and patients' phenotype complexity. RESULTS: For patients who underwent CMA, causative variants were found in 28 of 366 cases (7.7%), and 60 of 366 patients (16.4%) had at least one variant of uncertain significance (VUS). For EGS, 65 of 370 (17.6%) cases had causative variants, whereas 155 of 370 (41.9%) had at least one VUS. EGS had a significantly higher diagnostic yield than CMA (odds ratio [OR] = 2.63, P < 0.001). This difference in diagnostic yield was further pronounced among patients with infantile seizure onset (OR = 4.69, P < 0.001) and patients with additional neurological findings (OR = 2.99, P < 0.001). CONCLUSION: To minimize the time and resources required to reach a diagnosis, clinicians and insurers alike should consider using EGS as an initial diagnostic tool.

Factors predictive of adverse events associated with endoscopic ultrasound-guided fine needle aspiration of pancreatic solid lesions.

BACKGROUND: Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) provides high diagnostic accuracy with a low incidence of procedural complications. However, it occasionally causes serious complications, and factors that increase the susceptibility to such adverse events remain unknown. AIMS: We aimed to examine post-procedural events and determine risk factors associated with EUS-FNA of pancreatic solid lesions. METHODS: This single-center retrospective study included 316 consecutive patients with pancreatic solid lesions who underwent 327 EUS-FNA procedures from April 2003 to September 2011. We registered all patients undergoing EUS-FNA in the database and retrospectively ascertained the presence/absence of post-procedural adverse events. RESULTS: The incidence of post-procedural adverse events, including moderate to mild pancreatitis, mild abdominal pain, and mild bleeding, was 3.4 %. Univariate analysis showed that the incidence of post-procedural events was significantly increased in patients with tumors less than or equal to 20 mm in diameter (P < 0.001), those with pancreatic neuroendocrine tumors (PNET) (P = 0.012), and patients who had intervening normal pancreas for accessing the lesion (P = 0.048). Multivariate analysis identified tumors measuring less than or equal to 20 mm in diameter (OR 18.48; 95 % CI 3.55-96.17) and case of PNETs (OR 36.50; 95 % CI 1.73-771.83) were an independent risk factors. CONCLUSIONS: EUS-FNA of pancreatic solid lesions is a safe procedure. However, pancreatic lesions with small diameters and pancreatic neuroendocrine tumors are important factors associated with adverse events after EUS-FNA.

[A case of adenoendocrine cell carcinoma on the ampulla of Vater].

The occurrence of an adenoendocrine cell carcinoma on the ampulla of Vater is rare, especially when the component of adenocarcinoma is not located on the mucosa of the ampulla. A 76-year-old man was referred to our hospital for further investigation of a mass lesion on the ampulla. EGD revealed SMT like mass lesion on the ampulla. Endoscopic ultrasonography showed an ampullary hypoechoic mass. We performed pylorus-preserving pancreatoduodenectomy on the basis of the diagnosis of poorly differentiated adenocarcinoma of the ampulla of Vater. Postoperative pathological examinations revealed two different components of the tumor;malignant endocrine cells, and adenocarcinoma. The component of adenocarcinoma was located on the Ap lesion. We deducted that the adenocarcinoma appeared on the epithelium of Ap, then grew and spread into the direction of duodenum lumen, degenerating to endocrine cells.

Large ventral lateral neurons modulate arousal and sleep in Drosophila.

BACKGROUND: Large ventral lateral clock neurons (lLNvs) exhibit higher daytime-light-driven spontaneous action-potential firing rates in Drosophila, coinciding with wakefulness and locomotor-activity behavior. To determine whether the lLNvs are involved in arousal and sleep/wake behavior, we examined the effects of altered electrical excitation of the LNvs. RESULTS: LNv-hyperexcited flies reverse the normal day-night firing pattern, showing higher lLNv firing rates at night and pigment-dispersing-factor-mediated enhancement of nocturnal locomotor-activity behavior and reduced quantity and quality of sleep. lLNv hyperexcitation impairs sensory arousal, as shown by physiological and behavioral assays. lLNv-hyperexcited flies lacking sLNvs exhibit robust hyperexcitation-induced increases in nocturnal behavior, suggesting that the sLNvs are not essential for mediation of arousal. CONCLUSIONS: Light-activated lLNvs modulate behavioral arousal and sleep in Drosophila.

Safety and long-term outcomes of endoscopic papillary balloon dilation in children with bile duct stones.

BACKGROUND: Although experience with diagnostic and therapeutic ERCP in children is growing, little is known about the safety and technical outcomes of endoscopic papillary balloon dilation (EPBD) in pediatric patients with bile duct stones (BDSs). OBJECTIVE: To assess the safety and long-term outcomes of EPBD in pediatric patients with BDSs. DESIGN: Case study. SETTING: Tertiary referral center. PATIENTS AND INTERVENTIONS: This study involved 5 children who had BDSs combined with gallstones who underwent EPBD. MAIN OUTCOME MEASUREMENTS: Successful EPBD, successful stone removal, procedure-related complications, and long-term outcomes. RESULTS: ERCP was successful in all cases, with cannulation and subsequent EPBD. Stone removal was performed in 1 session in all patients. No EPBD-related complications were observed in any patient. After EPBD, 1 patient subsequently underwent laparoscopic cholecystectomy for gallstones. The remaining 4 were followed without surgery. In 2 patients, gallstones were spontaneously passed from the bile duct into the duodenum. During the follow-up period, over a mean of 7.1 years (range 3.7-9.3 years), no recurrence of BDSs was observed in any patient. LIMITATIONS: Small number of patients. CONCLUSIONS: Although BDSs are rare in pediatric patients, EPBD may be a safe and effective technique for the management of such stones in some children.

The Drosophila circadian pacemaker circuit: Pas De Deux or Tarantella?

Molecular genetic analysis of the fruit fly Drosophila melanogaster has revolutionized our understanding of the transcription/translation loop mechanisms underlying the circadian molecular oscillator. More recently, Drosophila has been used to understand how different neuronal groups within the circadian pacemaker circuit interact to regulate the overall behavior of the fly in response to daily cyclic environmental cues as well as seasonal changes. Our present understanding of circadian timekeeping at the molecular and circuit level is discussed with a critical evaluation of the strengths and weaknesses of present models. Two models for circadian neural circuits are compared: one that posits that two anatomically distinct oscillators control the synchronization to the two major daily morning and evening transitions, versus a distributed network model that posits that many cell-autonomous oscillators are coordinated in a complex fashion and respond via plastic mechanisms to changes in environmental cues.

Dilated cardiomyopathy in a patient with autosomal dominant EEF1A2-related neurodevelopmental disorder.

The EEF1A2 gene encodes eukaryotic translation elongation factor 1α2, an integral component of the elongation factor complex. Heterozygous pathogenic variants in EEF1A2 are associated with neurodevelopmental disorders characterized by epilepsy, global developmental delay, and autism. To date, dilated cardiomyopathy has only been reported in two siblings with neurodevelopmental phenotypes and a homozygous missense variant in EEF1A2. This report describes a nine-year-old female patient who presented with neurodevelopmental phenotypes and dilated cardiomyopathy. Analysis of 193 epilepsy genes by focused exome sequencing revealed a novel heterozygous variant c.46G > C (p.Val16Leu; NM_001958.3) in EEF1A2. The variant was not detected in either parent, confirming its de novo origin. No additional variants that explain the patient's phenotypes were found by subsequent whole exome analysis. Copy number analysis of the exome data and exon-level microarray excluded a deletion in the other allele of EEF1A2. We present the first patient with a heterozygous pathogenic EEF1A2 variant who had dilated cardiomyopathy as well as neurodevelopmental phenotypes, suggesting that this cardiac phenotype may be associated with the autosomal dominant form of the EEF1A2-related disorder.

[Sarcomatoid carcinoma of the liver: a case report and review of the literature].

A 66-year-old woman presented to our outpatient clinic with abdominal discomfort in April, 2008. Ultrasound revealed a hypo-echoic 10cm mass in the right hepatic lobe but no indication of chronic liver disease, with similar results in her history, on physical exam, and imaging. Serum testing did not identify any systemic disease. The mass was suspected to be intrahepatic cholangiocarcinoma and right hepatic lobectomy was performed. Histologic examination of the specimen revealed numerous spindle cells, and immunostaining confirmed a definitive diagnosis of sarcomatoid carcinoma of the liver. On subsequent review of the case, an abdominal CT performed 2.5 years earlier for unrelated symptoms had shown a 1cm faint low density area in the same location as the mass. The doubling time of this tumor was about 95 days.

Electrochemical Determination of Titratable Acidity for the Discrimination of Schisandrae Chinensis Fructus and Schisandrae Sphenantherae Fructus.

A simple electrochemical procedure has been developed for determining the titratable acidity in Schisandrae Chinensis Fructus (SCF) and Schisandrae Sphenantherae Fructus (SSF) by means of reduction of quinone in the presence of acid compounds. To measure a voltammogram, a test solution was prepared by mixing a water extract from SCF or SSF and an electrolyte cocktail containing 3,5-di-tert-butyl-1,2-benzoquinone and NaCl. The quantitative results of titratable acidity in the SCF and SSF samples by the present voltammetry were in good agreement with those by neutralization titration using 0.1 M NaOH (r2 = 0.980): y = 1.003x + 0.010, where the y- and x-axes were the titratable acidity obtained by the present voltammetry and the neutralization titration, respectively. Further, the titratable acidities in the SSF samples were significantly lower than those in the SCF samples (p < 0.01). From these findings, we show that the titratable acidity is useful as an indicator to discriminate between SCF and SSF. Moreover, a prototype of electrochemical portable sensor for on-site analysis has been provided to perform this procedure.

Integration of read-across and artificial neural network-based QSAR models for predicting systemic toxicity: A case study for valproic acid.

We present a systematic, comprehensive and reproducible weight-of-evidence approach for predicting the no-observed-adverse-effect level (NOAEL) for systemic toxicity by using read-across and quantitative structure-activity relationship (QSAR) models to fill gaps in rat repeated-dose and developmental toxicity data. As a case study, we chose valproic acid, a developmental toxicant in humans and animals. High-quality in vivo oral rat repeated-dose and developmental toxicity data were available for five and nine analogues, respectively, and showed qualitative consistency, especially for developmental toxicity. Similarity between the target and analogues is readily defined computationally, and data uncertainties associated with the similarities in structural, physico-chemical and toxicological properties, including toxicophores, were low. Uncertainty associated with metabolic similarity is low-to-moderate, largely because the approach was limited to in silico prediction to enable systematic and objective data collection. Uncertainty associated with completeness of read-across was reduced by including in vitro and in silico metabolic data and expanding the experimental animal database. Taking the "worst-case" approach, the smallest NOAEL values among the analogs (i.e., 200 and 100 mg/kg/day for repeated-dose and developmental toxicity, respectively) were read-across to valproic acid. Our previous QSAR models predict repeated-dose NOAEL of 148 (males) and 228 (females) mg/kg/day, and developmental toxicity NOAEL of 390 mg/kg/day for valproic acid. Based on read-across and QSAR, the conservatively predicted NOAEL is 148 mg/kg/day for repeated-dose toxicity, and 100 mg/kg/day for developmental toxicity. Experimental values are 341 mg/kg/day and 100 mg/kg/day, respectively. The present approach appears promising for quantitative and qualitative in silico systemic toxicity prediction of untested chemicals.

Preventing peripheral intravenous catheter failure by reducing mechanical irritation.

Peripheral intravenous catheter failure is a significant concern in the clinical setting. We investigated the effectiveness of care protocols, including an ultrasonographic "pre-scan" for selecting a large-diameter vein before catheterization, a "post-scan" for confirming the catheter tip position after catheterization with ultrasonography, and the use of a flexible polyurethane catheter to reduce the mechanical irritation that contributes to the incidence of catheter failure. This intervention study was a non-randomized controlled trial to investigate the effectiveness of the abovementioned care protocols, the effects of which were compared to the outcomes in the control group, which received conventional care. For both groups, participants were selected from patients in two wards at the University of Tokyo in Japan between July and November 2017. Inverse probability score-based weighted methods (IPW) using propensity score were used to estimate the effectiveness of care protocols. The primary outcome was catheter failure, which was defined as accidental and unplanned catheter removal. We used Kaplan-Meier survival curves to compare rates of time until catheter failure. We analysed 189 and 233 catheters in the intervention and control groups, respectively. In the control group, 68 catheters (29.2%) were determined to have failed, whereas, in the intervention group, only 21 catheters (11.1%) failed. There was a significant difference between each group regarding the ratio of catheter failure adjusted according to IPW (p = 0.003). The relative risk reduction of the intervention for catheter failure was 0.60 (95% CI: 0.47-0.71). Care protocols, including assessment of vein diameter, vein depth, and catheter tip location using ultrasound examination for reducing mechanical irritation is a promising method to reduce catheter failure incidence.

Embryonal rhabdomyosarcoma in a patient with a germline CBL pathogenic variant.

Germline pathogenic variants in CBL are associated with an autosomal dominant RASopathy and an increased risk for malignancies, particularly juvenile myelomonocytic leukemia. Herein, we describe a patient with clinical features of a Noonan-spectrum disorder who developed embryonal rhabdomyosarcoma of the bladder at age two years. Tumor analysis using the OncoKids® cancer panel revealed a CBL pathogenic variant: NM_005188.3:c.1100A>C (p.Gln367Pro). Sanger sequencing of peripheral blood DNA confirmed a de novo heterozygous germline variant. This is the first report of embryonal rhabdomyosarcoma in association with a germline CBL pathogenic variant, further broadening the CBL cancer predisposition spectrum.

Isolated pancreatic metastasis from malignant melanoma: a case report and literature review.

Isolated pancreatic metastasis from malignant melanoma is rare. Pancreatic metastasis is difficult to diagnose in patients with unknown primary malignant melanoma. Endoscopic ultrasound-guided fine-needle aspiration plays an important role in confirming the diagnosis. A 67-year-old woman was referred to our institution because of a mass in her pancreas. Computed tomography and magnetic resonance imaging revealed a 35-mm mass localized on the pancreatic tail, with low attenuation, surrounded by a high-attenuation rim. Endoscopic ultrasonography revealed a hypoechoic mass with central anechoic areas. Endoscopic ultrasound-guided fine-needle aspiration of the mass was performed, and the pathological diagnosis was malignant melanoma. Intense fluorodeoxyglucose uptake was observed in the pancreatic tail on positron emission tomography-computed tomography. No other malignant melanoma was found. Distal pancreatectomy was performed. Six months postoperatively, positron emission tomography-computed tomography revealed high uptake in the left nasal cavity, and biopsy revealed the mass to be a malignant melanoma, indicating that the primary site of the malignant melanoma was the left nasal cavity and that the pancreatic mass and peritoneal lesion were metastases. The patient had survived > 2 years after the distal pancreatectomy. Pancreatic resection of isolated pancreatic metastasis can possibly prolong survival; however, metastatic melanoma usually has poor prognosis.

Light-dependent development of circadian gene expression in transgenic zebrafish.

The roles of environmental stimuli in initiation and synchronization of circadian oscillation during development appear to vary among different rhythmic processes. In zebrafish, a variety of rhythms emerge in larvae only after exposure to light-dark (LD) cycles, whereas zebrafish period3 (per3) mRNA has been reported to be rhythmic from day 1 of development in constant conditions. We generated transgenic zebrafish in which expression of the firefly luciferase (luc) gene is driven by the zebrafish per3 promoter. Live larvae from these lines are rhythmically bioluminescent, providing the first vertebrate system for high-throughput measurement of circadian gene expression in vivo. Circadian rhythmicity in constant conditions was observed only after 5-6 d of development, and only if the fish were exposed to LD signals after day 4. Regardless of light exposure, a novel developmental profile was observed, with low expression during the first few days and a rapid increase when active swimming begins. Ambient temperature affected the developmental profile and overall levels of per3 and luc mRNA, as well as the critical days in which LD cycles were needed for robust bioluminescence rhythms. In summary, per3-luc zebrafish has revealed complex interactions among developmental events, light, and temperature in the expression of a clock gene.

Effects of long-term ingestion of difructose anhydride III (DFA III) on intestinal bacteria and bile acid metabolism in humans.

Changes in the intestinal microbiota of 10 human subjects with long-term ingestion of 3 g/d difructose anhydride III (DFA III; 4 persons, 2 months; 3 persons, 6 months; and 3 persons, 12 months) were examined by denaturing gradient gel electrophoresis (DGGE). According to the answers to questionnaires, the subjects were divided into two groups (constipated and normal). The DGGE profile was different for every individual and each subject had unique profiles of intestinal microbiota. In the DGGE profiles of constipated subjects, the intensities of bands related to Bacteroides spp. increased. Moreover, the DFA III-assimilating bacteria, Ruminococcus sp. were isolated from subjects who ingested DFA III for 12 months. These strains showed 95% similarity of their 16S rDNA sequences with that of Ruminococcus obeum ATCC 29174(T) (X85101) and produced large amounts of acetic acid. DFA III ingestion for 2 months tended to increase total organic acids in feces, and tended to decrease fecal pH and the secondary bile acid (SBA) ratio in total bile acids. The SBA ratio in total bile acids corresponded to fecal pH. The production of SBA was decreased by low pH in vitro. These results indicated that DFA III ingestion in humans tended to lower intestinal pH, inhibited bile acid 7alpha-dehydroxylation activities and also tended to decrease the SBA ratios in total bile acids. Moreover, as another cause for the decrease in the SBA ratio in total bile acids, it was suggested that the number of bile acid 7alpha-dehydroxylating bacteria were decreased by DFA III ingestion.

Effects of difructose anhydride III (DFA III) administration on bile acids and growth of DFA III-assimilating bacterium Ruminococcus productus on rat intestine.

The growth of DFA III-assimilating bacteria in the intestines of rats fed 3% DFA III for 2 weeks was examined. Sixty-four percent of the DFA III intake had been assimilated on day 3 of ingestion, and almost all of the DFA III was assimilated at the end of the experiment. The DFA III-assimilating bacterium, Ruminococcus productus, in DFA III-fed rats was in the stationary state of 10(8)-10(9) cells/g dry feces within a week from 10(6) cells/g dry feces on day 1 of DFA III ingestion. The number of R. productus cells was associated with the amount of DFA III excreted in the feces. The acetic acid produced from DFA III by R. productus lowered the cecal pH to 5.8. In control-fed rats and DFA III-fed rats, 94% of secondary bile acids and 94% of primary bile acids, respectively, were accounted for in the total bile acids analyzed. DFA III ingestion increased the ratio of primary bile acids and changed the composition of fecal bile acids. In conclusion, R. productus assimilated DFA III, produced short chain fatty acids, and the cecal pH was lowered. The acidification of rat intestine perhaps inhibited secondary bile acid formation and decreased the ratio of secondary bile acids. Therefore, it is expected that DFA III may prevent colorectal cancer and be a new prebiotic candidate.