Serum Unconjugated Bile Acids Research Articles

Serum Unconjugated Bile Acids and Small Bowel Bacterial Overgrowth in Pediatric Intestinal Failure: A Pilot Study.

We determined qualitative and quantitative serum unconjugated bile acid (SUBA) levels among children with history of intestinal failure (IF) and suspected small bowel bacterial overgrowth (SBBO). This was a single-center, case-control pilot study conducted at Cincinnati Children's Hospital Medical Center. Children with history of IF and suspected SBBO were enrolled as subjects. Age-matched children without IF or suspected SBBO served as controls. All participants underwent small bowel fluid sampling for microbial culture analysis. Additionally, serum fractionated and total bile acids were measured by liquid chromatography-mass spectrometry at enrollment and following treatment for SBBO. SUBA concentrations were elevated in IF subjects (median 1.16 μM, range 0.43-10.65 μM) compared with controls (median 0.10 μM, range 0.05-0.18 μM, P = 0.001). Among SUBA, chenodeoxycholic acid (CDCA) was significantly elevated in subjects (median 0.8 μM, range 0-7.08 μM) compared with controls (median 0 μM, range 0-0.03 μM, P = 0.012). When controls were excluded from analysis, IF subjects with positive aspirates for SBBO demonstrated higher concentration of CDCA (median 7.36 μM, range 1.1-8.28 μM) compared with IF subjects with negative aspirates (median 0.18 μM, range 0-1.06 μM, P = 0.017). Treatment for SBBO did not alter SUBA concentration. SUBA concentrations are elevated in children with history of IF and presumed SBBO compared with non-IF controls. CDCA was more prevalent in IF subjects with positive aspirates for SBBO compared with IF subjects with negative aspirates. The determination of SUBA concentration may be a useful surrogate to small bowel fluid aspiration in the diagnosis of SBBO in children with history of IF.

P.04.3 SERUM CHENODEOXYCHOLIC ACID, BMI AND TG, ARE INDEPENDENTLY RELATED TO INSULIN-RESISTANCE IN BLOOD DONORS: AN INTERIM ANALYSIS OF AN ONGOING PROSPECTIVE STUDY

Background and aim: Although the lack of extensive data in humans, bile acids (BAs) and particularly CDCA a potent FXR and TGR5 ligand, are signaling molecules in glucose, lipid and energy metabolism. Aim of our study was to evaluate serum BA profile including Glycine (G), Taurine (T) and Unconjugated (U)-Bas in blood donors (BD) and to identify correlations between individual BA concentration in normal and insulin-resistant (IR) subjects. Material and methods:We prospectively enrolled 160 blood donors from our Transfusion Center, from January to June 2011. Exclusion criteria were: alteration in blood tests, history of liver or GI disease, previous abdominal surgery and treatment with metabolic and GI medications. All patients underwent biochemistry tests (fasting glucose and insulin, total cholesterol, HDL, LDL, triglycerides (TG), ALT, GammaGT, ALP) and serum BA profile measurement (HPLC-ESI-MS/MS). All patients underwent an abdominal ultrasound within a week from enrollment. Medical history, laboratory parameters and ultrasonographic findings of all subjects were reviewed from our physicians and subjects were classified as Healthy (H, n=120), IR (n=28) and gallstone subjects (GS, n=12, excluded from analysis). Results: 148 subjects (84 male/64 female; mean age 41.7±12.6) met the inclusion criteria. BMI was 25.1±3.7; total cholesterol 194.6±35.6; HDL 60.5±15.2; TG 91.8±48.7; ALT, GammaGt, ALP and other mean biochemical index were within normal limits. In IR subjects, total serum BAs (5.02±2.39 vs 3.56±2.55 μmol/l; P= 0.0017), serum unconjugated BAs (1.95±1.25 vs 1.40±1.17 μmol/l; P= 0.025) and CDCA (2.28±1.39 vs 1.63±1.43; P=0.03) were significantly higher than in healthy subjects. On multivariate analysis, BMI (r=0.35; P<0.0001), CDCA (r= 0.194; P= 0.0033) and TG (r=0.26; P=0.0134) were independently and directly related to the HOMA-IR. No significant correlation were found between serum cholesterol or triglycerides levels and serum BA profile. Conclusions: Total serum Bas (U-Bas, G-Bas, T-Bas) and particularly CDCA are significantly increased in patients with IR. CDCA, together with BMI and TG are independently related to insulin-resistance.

P.04.4 SVR TO ANTIVIRAL TREATMENT FOR POST-OLT RECURRENT HCV HEPATITIS CAN BE IMPROVED BY THE USE OF GROWTH FACTORS

Background and aim: Although the lack of extensive data in humans, bile acids (BAs) and particularly CDCA a potent FXR and TGR5 ligand, are signaling molecules in glucose, lipid and energy metabolism. Aim of our study was to evaluate serum BA profile including Glycine (G), Taurine (T) and Unconjugated (U)-Bas in blood donors (BD) and to identify correlations between individual BA concentration in normal and insulin-resistant (IR) subjects. Material and methods:We prospectively enrolled 160 blood donors from our Transfusion Center, from January to June 2011. Exclusion criteria were: alteration in blood tests, history of liver or GI disease, previous abdominal surgery and treatment with metabolic and GI medications. All patients underwent biochemistry tests (fasting glucose and insulin, total cholesterol, HDL, LDL, triglycerides (TG), ALT, GammaGT, ALP) and serum BA profile measurement (HPLC-ESI-MS/MS). All patients underwent an abdominal ultrasound within a week from enrollment. Medical history, laboratory parameters and ultrasonographic findings of all subjects were reviewed from our physicians and subjects were classified as Healthy (H, n=120), IR (n=28) and gallstone subjects (GS, n=12, excluded from analysis). Results: 148 subjects (84 male/64 female; mean age 41.7±12.6) met the inclusion criteria. BMI was 25.1±3.7; total cholesterol 194.6±35.6; HDL 60.5±15.2; TG 91.8±48.7; ALT, GammaGt, ALP and other mean biochemical index were within normal limits. In IR subjects, total serum BAs (5.02±2.39 vs 3.56±2.55 μmol/l; P= 0.0017), serum unconjugated BAs (1.95±1.25 vs 1.40±1.17 μmol/l; P= 0.025) and CDCA (2.28±1.39 vs 1.63±1.43; P=0.03) were significantly higher than in healthy subjects. On multivariate analysis, BMI (r=0.35; P<0.0001), CDCA (r= 0.194; P= 0.0033) and TG (r=0.26; P=0.0134) were independently and directly related to the HOMA-IR. No significant correlation were found between serum cholesterol or triglycerides levels and serum BA profile. Conclusions: Total serum Bas (U-Bas, G-Bas, T-Bas) and particularly CDCA are significantly increased in patients with IR. CDCA, together with BMI and TG are independently related to insulin-resistance.

High serum and urinary unconjugated bile acid concentrations are associated with homozygous mutation in bile acid coenzyme A: Amino acid N-acyltransferase (BAAT)

The final step in bile acid synthesis involves conjugation with the amino acids glycine and taurine. Conjugated bile acids have low pKa values and self-associate efficiently to form micelles and facilitate fat absorption. Recently, we discovered two Amish children, aged 2 and 5, with pruritus, fat malabsorption and vitamin K coagulopathy and high serum bile acid concentrations. Both showed homozygous mutation in BAAT, an enzyme that conjugates bile acids with glycine and taurine. Total serum bile acid concentrations were elevated (53.05 and 9.55 mg/ml, respectively; 1.4 mg/ml in control children, and 53.4 and 45.6 mg/ml after treatment with 300 mg/day ursodeoxycholic acid). No amino acid conjugates were found. in contrast, a cholestaric pauent with BRIC (due to a mutation in FIC1) showed elevated serum bile acid concentrations (151 mg/ml) that were almost entirely (96%) amino acid conjugated. Urinary bile acid outputs in the Amish patients were 30.3 and 17.3 mg/ml, respectively, with 18 and 34% unconjugated and the rest as glucuronide/sulfates. The patient with BRIC had 192.1 mg/ml bile acids in the anne, but more than 50% were glycine and taurine conjugated. These resuhs suggest that the bile salt export pump has a requirement for amino acid conjugated bile acids in order to transport them from liver into the bile. Patients that are homozygous for BAAT mutation show high levels of serum unconjugated bile acids and increased urinary excretion of bile acids, composed chiefly of unconjugated and glucuronidated/sulfated bile acids, in contrast, patients with BRIC also show elevated serum and urinary bile acids, but these are predominantly conjugated with glycine and taurine. The presence of unconjugated bile acids leads to their backup and overflow into the serum and excretion into urine. Clinically, elevated serum unconjugated bile acids are associated with pruritus while the deficiency of amino acid conjugated bile acids in the intestine results in tat malabsorption and vitamin K coagulopathy.

Postprandial changes in serum unconjugated bile acid concentrations in healthy beagles.

To investigate postprandial changes in serum concentrations of unconjugated bile acids in healthy Beagles. 7 healthy Beagles. Blood samples were obtained from dogs at regular intervals up to 8 hours after consumption of a meal. Serum concentrations of 5 unconjugated bile acids were determined at each time point, using gas chromatography-mass spectrometry with selected ion monitoring. Total serum unconjugated bile acid concentration was significantly increased, relative to baseline values, at 360, 420, and 480 minutes after feeding. Unconjugated cholic acid was significantly increased at 360, 420, and 480 minutes. The proportion of total unconjugated bile acids represented by cholic acid was significantly increased at 240 to 480 minutes. Deoxycholic acid was significantly increased at 360 and 420 minutes. Chenodeoxycholic acid was significantly increased at 360 to 480 minutes. Lithocholic acid was significantly increased at 180 minutes, whereas no significant changes in ursodeoxycholic acid were detected at any time point. Healthy Beagles had significant increases in serum concentrations and changes in the profile of unconjugated bile acids after a meal. These increases persisted > 8 hours, indicating that prolonged withholding of food is necessary to avoid the risk of a false-positive diagnosis when assessing serum unconjugated bile acid concentrations in dogs.

Serum unconjugated bile acids as a test for intestinal bacterial overgrowth in dogs.

Small intestinal bacterial overgrowth (SIBO) has a high incidence in dogs and, as in humans, is difficult to diagnose. The aim of this study was to determine the diagnostic significance of serum unconjugated bile acid concentrations in dogs with bacterial overgrowth. Fasting sera were obtained from 23 dogs: 10 with culture-proven SIBO, 8 with indirectly diagnosed SIBO (normal pancreatic function but small intestinal disease associated with subnormal serum cobalamin and supranormal folate concentrations), and 5 healthy controls. Unconjugated bile acids were determined using gas chromatography-mass spectrometry after isolation by liquid-solid extraction and anion-exchange chromatography. Mean serum unconjugated bile acid concentrations were significantly elevated in dogs with SIBO (mean +/- SD: 0.91 +/- 1.03 micromol/liter), and in dogs with indirectly diagnosed SIBO (2.11 +/- 2.20 micromol/liter) compared to clinically healthy dogs (0.015 +/- 0.015 micromol/liter, P < 0.005). Cholic acid was the predominant unconjugated bile acid in the serum of dogs with SIBO. In conclusion serum unconjugated bile acid concentrations of healthy dogs are significantly lower than reported values for humans, and this fraction represents a relatively small proportion (0-2.3%; mean 0.8%) of the total bile acids in dogs. Unconjugated bile acids increased 10- to 20-fold in dogs with SIBO indicating the clinical utility of serum unconjugated bile acids for diagnosis of intestinal bacterial overgrowth in dogs.

Effect of ageing on postprandial conjugated and unconjugated serum bile acid levels in healthy subjects.

Colorectal cancer is a disease of elderly subjects. A decreased ileal absorption of bile acids in elderly subjects may lead to an increased exposure of the colonic mucosa to secondary bile acids. This may contribute to an enhanced risk of colorectal cancer. In this study fasting and postprandial conjugated and unconjugated serum levels of cholic, chenodeoxycholic, and deoxycholic acid in 12 elderly and 12 younger subjects were investigated. Intestinal transit time, gallbladder emptying and jejunal bacterial flora were also studied in both age groups. Fasting levels of conjugated and unconjugated serum bile acids were similar in both age groups. Postprandial levels of all individual conjugated bile acids increased to a significantly higher extent in the younger subjects. Postprandial unconjugated serum bile acid levels did not differ significantly between both age groups, although unconjugated deoxycholic levels tended to increase to higher levels in the elderly. Results of jejunal bacterial counts, gallbladder emptying and intestinal transit time were similar in both groups. These data suggest that conjugated bile acids are reabsorbed less effectively in elderly subjects.

Postprandial conjugated and unconjugated serum bile acid levels after proctocolectomy with ileal pouch-anal anastomosis.

In patients with ileal pouch-anal anastomosis (IPAA) bile acid reabsorption may be impaired, and stasis may lead to deconjugation and dehydroxylation of bile acids as a result of bacterial overgrowth. We therefore studied fasting and postprandial conjugated and unconjugated serum levels of cholic (CA), chenodeoxycholic (CDCA), and deoxycholic acid (DCA) in 11 patients who underwent proctocolectomy with IPAA and in 11 healthy controls. Fasting levels of conjugated DCA but not CA and CDCA were significantly lower in IPAA patients. Postprandially, conjugated bile acid levels were significantly lower in IPAA patients. Postprandial unconjugated CA levels were significantly higher and CDCA levels tended to be higher in IPAA patients, whereas unconjugated DCA levels were lower in IPAA patients. These data suggest that reabsorption of conjugated bile acids is impaired after IPAA; deconjugation of bile acids may result from bacterial overgrowth secondary to stasis in the pouch; and dehydroxylation of bile acids is decreased after proctocolectomy with IPAA.

A preliminary assessment of post prandial unconjugated bile acids in serum of cats with chronic diarrhoea and vomiting.

Increases in serum unconjugated bile acid concentrations have recently been shown to be diagnostic for small intestinal bacterial overgrowth in man. Similar increases in serum unconjugated bile acids were detected in three of nine cats with chronic diarrhoea and vomiting.

Unconjugated serum bile acids as a marker of small intestinal bacterial overgrowth

Non-invasive methods to detect small intestinal bacterial overgrowth often lack specificity in patients who have undergone an ileal resection or have an accelerated intestinal transit. Since elevated serum unconjugated bile acid levels have been found in patients with clinical signs of bacterial overgrowth, we studied the clinical value of unconjugated serum bile acids as a marker of small intestinal bacterial overgrowth. Patients with culture-proven bacterial overgrowth had significantly elevated fasting unconjugated serum bile acid levels (median and range: 4.5; 1.4-21.5 mumol l-1) as compared to healthy subjects (0.9; 0.3-1.7 mumol l-1, P less than 0.005), to persons with an accelerated intestinal transit (1.0; 0.3-1.9 mumol l-1, P less than 0.005) and to persons who have undergone an ileal resection (2.1; 0.7-3.6 mumol l-1, P less than 0.005). The same was true 30 and 60 min after ingestion of a Lundh meal. Serum unconjugated bile acid levels above 4 mumol l-1 were found in eight of 10 patients with culture-proven small intestinal bacterial overgrowth whereas serum levels above 4 mumol l-1 were found in none of the patients from the three control groups. These results suggest that determination of unconjugated serum bile acids is of clinical value in the evaluation of patients suspected of small intestine bacterial overgrowth.

Serum unconjugated bile acids in patients with small bowel bacterial overgrowth

Concentrations of total and unconjugated bile acids in serum were measured fasting and 2 h postprandially in 9 patients with a positive [ 14C]glycocholate breath test consistent with small bowel bacterial overgrowth and in 13 controls. Gas-liquid chromatography-mass spectrometry (GLC-MS) and enzymatic-fluorometric assays were both used. In contrast to previous work, total serum bile acids were only occasionally elevated in patients with bacterial overgrowth. Total 2 h postprandial unconjugated bile acids, however, were elevated in 7 9 patients when measured by GLC-MS and in 6 9 when measured by the enzymatic-fluorometric method. The best separation between patients and controls was achieved by GLC-MS determinations of 2 h postprandial unconjugated cholic acid or primary bile acids, which were abnormal in 8 9 patients. This study indicates that measurement of serum bile acids may be a useful approach to the diagnosis of bacterial overgrowth, but would require accessible methods for separating and measuring cholic acid or unconjugated primary bile acids in post-prandial sera.

Small intestinal transit, bacterial growth, and bowel habits in diabetes mellitus.

To investigate diabetic alterations of small intestinal transit and bacterial growth, we performed hydrogen breath tests (10 g lactulose via duodenal tube at the ligament of Treitz), bacterial cultures, and determinations of unconjugated serum bile acids in 19 patients with long-standing diabetes and 7 healthy controls. Asymptomatic diabetics had a late rise in breath hydrogen, indicating prolonged jejunal-cecal transit (86 +/- 10 min, p less than 0.05) as an early pathogenic event. Rise in breath hydrogen in symptomatic diabetics (constipation: 50 +/- 6 min; diarrhea: 41 +/- 11 min) was not significantly different from controls (57 +/- 8 min). Bacterial studies and increased unconjugated serum bile acids suggest bacterial overgrowth in some symptomatic diabetics. Bacterial overgrowth was associated more frequently (p less than 0.05) with a rise in breath hydrogen before 45 min or after 75 min. Changes in the hydrogen breath test, bacterial growth, or unconjugated serum bile acids did not correlate with gastrointestinal symptoms of diabetes.

Intestinal involvement in progressive systemic sclerosis detected by increased unconjugated serum bile acids.

In patients with progressive systemic sclerosis, impaired motor function of the small intestine may lead to bacterial overgrowth causing diarrhoea, steatorrhoea and malabsorption. As unconjugated serum bile acids have been proposed as markers for small bowel bacterial overgrowth, we studied individual unconjugated serum bile acids in 36 patients with progressive systemic sclerosis. These patients had significantly higher serum concentrations of unconjugated cholic acid (median 0.18; range 0.05-30.75 v 0.09; 0.01-0.19 mumol/l, p less than 0.001) and chenodeoxycholic acid (0.10; 0.01-6.83 v 0.04; 0.01-0.39 mumol/l, p less than 0.025) than healthy controls (n = 16). This difference was mainly due to patients with diarrhoea (n = 10), who had significantly higher concentrations of unconjugated serum bile acids than patients with normal bowel habit (cholic acid median 0.55 v 0.16 mumol/l, p less than 0.001; chenodeoxycholic acid 0.75 v 0.07 mumol/l; p less than 0.005). All patients with raised unconjugated serum bile acids had oesophageal motility disorders. These results confirm a relationship between motility disorders and bacterial overgrowth in patients with progressive systemic sclerosis.

Serum unconjugated bile acids: Qualitative and quantitative profiles in ileal resection and bacterial overgrowth

Qualitative and quantitative profiles of unconjugated bile acids in the serum obtained over a 24-h period from three patients with ileal resections and one with a bacterial overgrowth are described. Unconjugated serum bile acids were determined using the high sensitivity and resolution of capillary column gas liquid chromatography after their rapid extraction and isolation using reverse phase octadecylsilane bonded silica cartridges and the lipophilic gel Lipidex 1000. Unconjugated serum bile acid concentrations were elevated throughout the day in both ileum resected patients and in conditions involving bacterial overgrowth when compared to healthy subjects. Total conjugated cholic acid concentrations were expectedly low in both intestinal disorders and were without the postprandial increases generally observed in healthy subjects. Qualitative gas Chromatographic profiles of serum unconjugated bile acids in bacterial overgrowth distinctly revealed a predominance of deoxycholic acid and other secondary bile acids in all samples, while, in conditions of an impaired enterohepatic circulation, deoxycholic acid was absent or present in only trace amounts. The potential significance of measuring serum unconjugated bile acids in intestinal disorders is discussed.

Fasting and postprandial serum bile acid concentration with special reference to variations in the conjugate profile.

Serum bile acids were group-separated by ion exchange chromatography on diethylaminohydroxypropyl Sephadex LH-20 into unconjugated bile acids and bile acids conjugated with either glycine, taurine, glucuronic acid or sulphuric acid. The conjugate moiety was hydrolysed by treatment with a combination of Helix pomatia and cholylglycine hydrolase and the released bile acids analysed by gas liquid chromatography/mass spectrometry. Analysis of fasting and postprandial serum from six healthy subjects showed that, in addition to the primary bile acids, cholic (C) and chenodeoxycholic acid (CDC), secondary bile acids were present to varying extents. Unconjugated serum bile acids were found in four of the six subjects. Glycine and taurine conjugates of C and CDC and their glucuronides and sulphates were found in all subjects. The postprandial increase of serum bile acids was mainly due to increase of the glycine conjugates of C and CDC. After the meal, the ratio C:CDC in glycine and taurine conjugates shifted to lower values.

Measurement of conjugated and unconjugated serum bile acid concentrations using 3 alpha-hydroxysteroid dehydrogenase.

Measurement of conjugated and unconjugated serum bile acid concentrations using 3 alpha-hydroxysteroid dehydrogenase.

Diurnal changes in serum unconjugated bile acids in normal man.

Unconjugated bile acids were measured using gas chromatography-mass spectrometry in the serum of two subjects throughout a 24 hour period and in two other subjects over a six hour period after breakfast. Unconjugated bile acids were found in all samples of serum and included cholic, chenodeoxycholic, deoxycholic, 3 beta, 7 alpha-dihydroxy-5 beta-cholanic (iso-chenodeoxycholic), ursodeoxycholic, 3 beta, 7 beta-dihydroxy-5 beta-cholanic (iso-ursodeoxycholic), 3 beta-hydroxy-5-cholenoic, and lithocholic acids. The maximum concentration of each bile acid generally occurred between breakfast and dinner and total unconjugated bile acid concentrations attained levels of between 2-3 mumol/l. Concentrations increased after breakfast and were often as high as 30-40% of the conjugated bile acid glycocholate, but returned to fasting levels in the absence of lunch. The intestinal absorption of unconjugated bile acids is therefore of greater quantitative importance than was previously thought.

Conjugated and Unconjugated Serum Bile Acid Levels in Patients with Hepatobiliary Diseases

Total and unconjugated bile acid levels in serum of patients with various hepatobiliary diseases were determined by gas-liquid chromatography. In normal serum, ranges of total serum bile acid were found as follows: deoxycholic acid 0.22 ± 0.14, chenodeoxycholic acid 0.23 ± 0.14, cholic acid 0.14 ± 0.09, and total amount of bile acid 0.59 ± 0.31 μg per ml. The cholic to chenodeoxycholic acid ratio (C:CDC) was 0.61 ± 0.30. In hepatobiliary diseases, the level of total serum bile acid rose. The increase was remarkable in acute early hepatitis and in obstructive jaundice but moderate or slight in active portal cirrhosis and chronic hepatitis. Changes in the composition of serum bile acid were also observed. The C:CDC ratio was 1.01 ± 0.43 in portal cirrhosis and 2.74 ± 1.42 in obstructive jaundice. A correlation was observed between the total serum bile acid level and the serum bilirubin concentration in obstructive jaundice and portal cirrhosis. Unconjugated serum bile acid levels in healthy persons showed a range of 0.26 ± 0.20 μg per ml; and the unconjugated to total bile acid ratio (U:T) was 51.4 ± 22.0 %;. In active portal cirrhosis, the amount of unconjugated bile acid increased (2.54 ± 1.83 μg per ml). The value was significantly higher than that in normal, chronic hepatitis, and obstructive jaundice groups. Contrary to portal cirrhosis, the whole increase in serum bile acid in obstructive jaundice was occupied by conjugated bile acid and the U:T ratio was very low (0.2 ± 0.4%). A possible cause for the rising of the total and unconjugated serum bile acid levels in hepatobiliary diseases is discussed.