Non-alcoholic fatty liver disease is associated with dysregulated bile acid synthesis and diarrhea: A prospective observational study

Background

Non-alcoholic fatty liver disease (NAFLD) may be associated with changes in bile acid (BA) metabolism. Hepatic BA production, measured by serum levels of the precursor 7α-hydroxy-4-cholesten-3-one (C4), is regulated by the farnesoid-X-receptor (FXR)-dependent ileal hormone fibroblast growth factor 19 (FGF19). Low FGF19 and high C4 are features of chronic BA diarrhea. Obeticholic acid, an FXR agonist, stimulates FGF19 and has shown therapeutic potential in both BA diarrhea and in NAFLD. We hypothesized there are associations of FGF19, C4 and BA diarrhea with NAFLD.

Methods and findings

127 patients with known NAFLD were recruited prospectively. Clinical features, including metformin use, markers of NAFLD severity and BA synthesis were analyzed. The overall incidence of chronic diarrhea was 25%, with features of BA diarrhea in 12%. FGF19 negatively correlated with C4 (r_s = -0.43, p = 0.001) and with alanine aminotransferase (r_s = -0.22, p = 0.03), but not with either NAFLD fibrosis or Fibroscan scores. High C4 was associated with a higher NAFLD fibrosis score (p < 0.05), and with diarrhea (p = 0.001). The median NAFLD fibrosis score was higher in those with diarrhea (p = 0.002). Metformin use, in 44% overall, was particularly associated with diarrhea (in 36% vs 17%, p = 0.02), and a lower median FGF19 (74 vs 105 pg/mL, p < 0.05).

Conclusions

Increased hepatic BA production and diarrhea, but not low FGF19, were associated with increased NAFLD fibrosis score, indicating dysregulation of the FXR-FGF19 axis and suggesting hepatic FGF19 resistance. Metformin use was an important factor in a subgroup, lowering FGF19, and resulting in bile acid diarrhea.

[Prognostic factors of patients with T3N0M0 renal cell carcinoma: a single-center retrospective study of 182 patients]

OBJECTIVE

To evaluate the impacts of clinical, pathological, and laboratory factors on oncological outcomes of patients with T3N0M0 renal cell carcinoma.

METHODS

The clinical data, laboratory exam results, and follow-up outcomes of 182 patients with T3N0M0 renal cell carcinoma who underwent nephrectomy from 2007 to 2012 in Peking University First Hospital were retrospectively collected. The 5-year cancer-specific survival and 5-year recurrence-free survival of all the patients were calculated using Kaplan-Meier method, and the statistical significance between the survival curves were compared using the Log-rank test. Variables with significant differences in the univariate analysis were subjected to the multivariate analysis by Cox regression model. All the comparisons were conducted using two-tailed test and P<0.05 was considered statistically significant.

RESULTS

A total of 182 patients were included in this study. Of all the 182 patients, 126 were male (69.23%) and 56 were female (30.77%). The mean age was (56.75±12.45) years. The median follow-up time was 48 months (3-99 months). At the end of the follow-up, 50 patients (27.47%) died due to the disease after a median of 29.74 months and 59 patients (32.42%) had tumor recurrence after a median of 22.12 months. The 5-year cancer-specific survival of all patients was 68.30% (95% CI: 60.16%-75.84%); the 5-year recurrence-free survival was 60.70% (95% CI: 53.16%-68.84%). In the univariate analysis, diabetes mellitus, tumor invasion status, Fuhrman grade, serum album, serum cholestenone, anemia, and neutrophils percentage were associated with the cancer-specific survival and Fuhrman grade, serum album and anemia were associated with the recurrence-free survival. Variables with significant differences on univariate analysis were included in Cox multivariate regression analysis. Multivariate Logistic regression analysis showed that diabetes mellitus (HR=2.434, 95% CI: 1.243-4.769, P=0.010), hypoalbuminemia (HR=2.188, 95% CI: 1.074-1.074, P=0.031), and anemia (HR=3.320, 95% CI: 1.839-5.991, P<0.001) were independent risk factors significantly associated with cancer-specific survival; and higher Fuhrman grade (HR=2.552, 95% CI: 1.433-4.545, P=0.001), anemia (HR=2.535, 95% CI: 1.497-4.293, P=0.001) were independent factors significantly associated with recurrence-free survival.

CONCLUSION

Diabetes mellitus, hypoalbuminemia, and anemia were independent risk factors significantly associated with cancer-specific survival of T3N0M0 renal cell carcinoma patients; higher Fuhrman grade and anemia were independent risk factors significantly associated with tumor recurrence of T3N0M0 renal cell carcinoma patients.

Genetic variation in GPBAR1 predisposes to quantitative changes in colonic transit and bile acid excretion

The pathobiology of irritable bowel syndrome (IBS) is multifaceted. We aimed to identify candidate genes predisposing to quantitative traits in IBS. In 30 healthy volunteers, 30 IBS-constipation, and 64 IBS-diarrhea patients, we measured bowel symptoms, bile acid (BA) synthesis (serum 7α-hydroxy-4-cholesten-3-one and FGF19), fecal BA and fat, colonic transit (CT by scintigraphy), and intestinal permeability (IP by 2-sugar excretion). We assessed associations of candidate genes controlling BA metabolism (KLB rs17618244 and FGFR4 rs351855), BA receptor (GPBAR1 rs11554825), serotonin (5-HT) reuptake (SLC6A4 through rs4795541 which encodes for the 44-bp insert in 5HTTLPR), or immune activation (TNFSF15 rs4263839) with three primary quantitative traits of interest: colonic transit, BA synthesis, and fecal BA excretion. There were significant associations between fecal BA and CT at 48 h (r = 0.43; P < 0.001) and IP (r = 0.23; P = 0.015). GPBAR1 genotype was associated with CT48 (P = 0.003) and total fecal BA [P = 0.030, false detection rate (FDR) P = 0.033]. Faster CT48 observed with both CC and TT GPBAR1 genotypes was due to significant interaction with G allele of KLB, which increases BA synthesis and excretion. Other univariate associations (P < 0.05, without FDR correction) observed between GPBAR1 and symptom phenotype and gas sensation ratings support the role of GPBAR1 receptor. Associations between SLC6A4 and stool consistency, ease of passage, postprandial colonic tone, and total fecal BA excretion provide data in support of future hypothesis-testing studies. Genetic control of GPBAR1 receptor predisposing to pathobiological mechanisms in IBS provides evidence from humans in support of the importance of GPBAR1 to colonic motor and secretory functions demonstrated in animal studies.

A sensitive spectrofluorometric method for determination of ergosta-4,6,8(14),22-tetraen-3-one in rat plasma, feces, and urine for application to pharmacokinetic studies using cerium(III) as a probe

Ergosta-4,6,8(14),22-tetraen-3-one (ergone) isolated from Polyporus umbellatus possesses a variety of pharmacological activities in vivo and in vitro, including cytotoxic, diuretic, and immunosuppressive effect. The interaction of cerium ions (Ce(3+)) with ergone was studied by fluorescence and absorption spectroscopy. Spectra data revealed that Ce(3+) ions exhibited emission maxima around 350 nm when the excitation wavelength was fixed at 255 or 290 nm, and the fluorescence of Ce(3+) ions was quenched by the addition of ergone, indicating that a Ce(3+)-ergone complex was formed. According to the modified Benesi-Hildebrand equation, the binding constant of interaction of Ce(3+) ions with ergone was obtained at room temperature. Based on this, a sensitive spectrofluorometric method using Ce(3+) ions as a probe was applied for the identification and quantification of ergone in rat plasma, feces, and urine. The linear ranges of the calibration curves were 1.31 to 4.50 μM for plasma, 1.12-9.87 μM for feces, and 1.28-3.42 μM for urine, and the ergone recoveries were found to be 97.1 ± 0.9%, 98.2 ± 0.7% and 96.5 ± 1.4% for plasma, feces, and urine, respectively. The intraday and inter-day relative standard deviations were less than 9.7%. The proposed spectrofluorometric method is simple and rapid for the quantitative determination of ergone in rat plasma, feces, and urine, and it is affordable for most laboratories because it has few requirements and uses low cost, easy to operate equipment.

Bile acid metabolites in serum: intraindividual variation and associations with coronary heart disease, metabolic syndrome and diabetes mellitus

Bile acids (BAs) regulate glucose and lipid metabolism. In longitudinal and case-control-studies, we investigated the diurnal variation of serum concentrations of the 15 major BAs as well as the biosynthetic precursor 7α-hydroxy-4-cholesten-3-one (C4) and their associations, respectively, with coronary artery disease (CAD), diabetes mellitus type 2 (T2DM), and non-diabetic metabolic syndrome (MetS). In hourly taken blood samples of four healthy probands, the intraindividual 24 h variation of C4, conjugated and unconjugated BAs ranged from 42% to 72%, from 23% to 91%, and from 49% to 90%, respectively. Conjugated BA concentrations mainly increased following food intake. Serum levels of C4 and unconjugated BAs changed with daytime with maxima varying interindividually between 20h00 and 1h00 and between 3h00 and 8h00, respectively. Comparisons of data from 75 CAD patients with 75 CAD-free controls revealed no statistically significant association of CAD with BAs or C4. Comparisons of data from 50 controls free of T2DM or MetS, 50 MetS patients, and 50 T2DM patients revealed significantly increased fasting serum levels of C4 in patients with MetS and T2DM. Multiple regression analysis revealed body mass index (BMI) and plasma levels of triglycerides (TG) as independent determinants of C4 levels. Upon multivariate and principle component analyses the association of C4 with T2DM and/or MetS was not independent of or superior to the canonical MetS components. In conclusion, despite large intra- and interindividual variation, serum levels of C4,are significantly increased in patients with MetS and T2DM but confounded with BMI and TG.

The limited role of midnight salivary cortisol levels in the diagnosis of subclinical hypercortisolism in patients with adrenal incidentaloma

OBJECTIVE

The criteria for defining subclinical hypercortisolism (SH) are debated and a real gold standard test or combination of tests is lacking. Recently, late-night salivary cortisol (MSC) has been described as a sensitive and easy-to-perform marker for diagnosing overt hypercortisolism. No data are available on the role of MSC in the diagnosis of SH. The aim of this study was to evaluate the sensitivity and specificity of MSC levels in the diagnosis of SH in patients with adrenal incidentalomas (AI).

METHODS

In 103 (females/males, 69/34) patients with AI, MSC levels were studied. One milligram overnight dexamethasone suppression test (DST), urinary-free cortisol (UFC), and ACTH plasma levels were also evaluated. Patients were defined as affected by SH if they showed two of the following criteria: DST>83 nmol/l, ACTH <2.2 pmol/l, and UFC >193 nmol/24 h.

RESULTS

No difference in MSC levels in patients with SH (3.1+/-3.1 nmol/l) compared with patients without SH (2.2+/-2.8 nmol/l) was observed. In patients with SH, MSC levels were significantly correlated with DST (r=0.4, P<0.05). Using the cut-off of 5.1 nmol/l, the sensitivity and specificity of MSC levels for diagnosis of SH is 22.7 and 87.7% respectively.

CONCLUSION

In patients with AI, normal levels of MSC do not exclude SH, whereas high levels may suggest the presence of SH identified by conventional tests. Thus, MSC is not suitable as a screening test, although it may be used in conjunction with other tests as the confirming test in selected patients.

Increased activity of hepatic microsomal triglyceride transfer protein and bile acid synthesis in gallstone disease

A strong interrelationship exists between the regulation of bile acid (BA) metabolism and hepatic very low density lipoprotein (VLDL) production. We have recently shown that BA synthesis is increased in gallstone disease. We investigated the activity of hepatic microsomal triglyceride transfer protein (MTTP) as a surrogate of VLDL production, BA synthesis, and mRNA expression levels of proteins that regulate fatty acid (FA) metabolism in the liver of gallstone (GS) patients compared with GS-free patients. Twenty-seven volunteers subjected to elective surgery; 9 were GS-free and 18 with GS agreed to have a liver biopsy. We quantified by a fluorescence assay the activity of MTTP and by quantitative reverse-transcription PCR (RT-PCR) the mRNA content of hepatic MTTP and genes that regulate hepatic sterol and FA metabolism. Plasma was assayed for lathosterol and 7alpha-hydroxy-4-cholesten-3-one. Liver histology was normal in GS and GS-free patients. Serum VLDL triglycerides and apoB were significantly increased in GS. Hepatic triglycerides tripled in GS (P<0.001) compared with GS-free. MTTP activity increased 70% (P<0.001). Serum lathosterol and hepatic cholesterol concentrations, and mRNA expressions of MTTP, CD36, and FABP1 were similar in GS-free and GS patients. Hepatic mRNA expression of hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR) and 3-hydroxyl-3-methyl-glutaryl-CoA synthase (HMGS) were significantly decreased--40% and 27%, respectively--in GS. Serum 7alpha-hydroxy-4-cholesten-3-one was 75% higher, and mRNA expression of CYP7A1 was increased sevenfold (P<0.001) in GS.

CONCLUSION

Hepatic MTTP activity and BA synthesis are increased in GS. Results suggest that hepatic VLDL production and trafficking of BA are increased in gallstone patients.

Oat bran rapidly increases bile acid excretion and bile acid synthesis: an ileostomy study

OBJECTIVE

To study whether oat bran with native beta-glucans increases bile acid excretion and bile acid synthesis as measured by serum concentrations of 7alpha-hydroxy-4-cholesten-3-one (7alpha-HC).

DESIGN

Short-term interventional crossover study evaluating cholesterol absorption, ileal excretion of cholesterol and bile acids, and serum levels of cholesterol and bile acid metabolites. Differences between diets evaluated with Wilcoxon's signed rank-sum test.

SETTING

Outpatients at a metabolic-ward kitchen.

SUBJECTS

Nine volunteers with conventional ileostomies.

METHODS

Two 3-day-diet periods, with controlled, blinded basal diet including 75 g extruded oat bran breakfast cereal daily, with either 11.6 g native or hydrolysed beta-glucans.

RESULTS

Native oat bran increased median excretion of bile acids by 144% (P=0.008). Cholesterol excretion remained unchanged, cholesterol absorption decreased by 19% (P=0.013), whereas the sum of bile acid and cholesterol excretion increased by 40% (P=0.008) compared with hydrolysed oat bran. 7alpha-HC reflecting bile acid synthesis increased by 57% (P=0.008) within 24 h of consumption, whereas serum lathosterol concentration reflecting cholesterol synthesis increased by 12% (P=0.015).

CONCLUSIONS

Oat bran with native beta-glucans increases bile acid excretion within 24 h of consumption and this increase can also be detected by rising serum concentrations of 7alpha-HC. Thus, 7alpha-HC could be used for rapid detection of dietary effects on bile acid metabolism. These effects could possibly be explained by entrapment of whole micelles in the gut owing to higher viscosity.

Highly sensitive quantification of 7alpha-hydroxy-4-cholesten-3-one in human serum by LC-ESI-MS/MS

We describe a highly sensitive and specific method for the quantification of serum 7alpha-hydroxy-4-cholesten-3-one (C4), which has been used as a biomarker for bile acid biosynthesis. This method is based upon a stable isotope dilution technique by liquid chromatography-tandem mass spectrometry (LC-MS/MS). C4 was extracted from human serum (2-50 mul) by a salting-out procedure, derivatized into the picolinoyl ester (C4-7alpha-picolinate), and then purified using a disposable C(18) cartridge. The resulting picolinoyl ester derivative of C4 was quantified by LC-MS/MS using the electrospray ionization mode. The detection limit of the C4 picolinoyl ester was found to be 100 fg (signal-to-noise ratio = 10), which was approximately 1,000 times more sensitive than the detection limit of C4 with a conventional HPLC-ultraviolet method. The relative standard deviations between sample preparations and between measurements by our method were calculated to be 5.7% and 3.9%, respectively, by one-way layout analysis. The recovery experiments were performed using serum spiked with 20.0-60.0 ng/ml C4 and were validated by a polynomial equation. The results showed that the estimated concentration with 95% confidence limit was 23.1 +/- 2.8 ng/ml, which coincided completely with the observed X(0) +/- SD = 23.3 +/- 1.0 ng/ml with a mean recovery of 93.4%. This method provides highly reliable and reproducible results for the quantification of C4, especially in small volumes of blood samples.

Biliary lipids, cholesterol and bile synthesis: different adaptive mechanisms to dietary cholesterol in lean and obese subjects

BACKGROUND

Increased biliary cholesterol secretion together with elevated cholesterol synthesis may predispose obese subjects to cholesterol gallstone formation.

AIM

To investigate whether processing of dietary cholesterol is altered in obesity, we enrolled eight lean and seven obese subjects in a double-blind crossover study.

METHODS

Cholesterol consumption was 300 mg/day on low and 1300 mg/day on high cholesterol diet. After 3 weeks on either diet, hepatic bile was collected to determine biliary lipid secretion, and bile salt composition by high-performance liquid chromatography and cholesterol saturation index was calculated. Cholesterol synthesis was measured employing mass isotopomer distribution analysis. Bile acid synthesis via neutral and acidic pathway was assessed by serum levels of 7alpha-hydroxy-4-cholesten-3-one and 27-hydroxycholesterol.

RESULTS

Cholesterol synthesis was increased in obese compared with lean and feedback inhibited only in obese. On low cholesterol diet, cholesterol secretion was doubled in obese but bile acid composition and synthesis was similar between the two groups. After high cholesterol diet, cholesterol saturation index and bile secretion were unchanged. In contrast to obese, lean increased bile acid synthesis only via the acidic pathway.

CONCLUSIONS

Dietary cholesterol appears to preferentially induce bile acid synthesis via the acidic pathway in lean, whereas cholesterol synthesis was inhibited in obese. Thus, stable cholesterol saturation index may be achieved by different mechanisms.

Decreased hepatic expression of PPAR-gamma coactivator-1 in cholesterol cholelithiasis

BACKGROUND

Cholesterol cholelithiasis (gallstone disease) is a common disease in the Western world. The aim of the present study was to analyze the hepatic expression of a number of nuclear receptors involved in bile acid metabolism in human cholesterol gallstone disease.

MATERIALS AND METHODS

Surgical liver biopsies were obtained from 11 patients with untreated cholesterol cholelithiasis and nine gallstone-free subjects; mRNA levels of cholesterol 7alpha-hydroxylase (CYP7A1) and related nuclear receptors and coactivators were assayed by quantitative real-time RT-PCR.

RESULTS

No differences between the two groups were detected in mRNA levels of CYP7A1 and related nuclear receptors, with the exception of peroxysome proliferator-activated receptor-gamma coactivator 1 (PGC-1), which was significantly (P < 0.01) less expressed in gallstone subjects. Expression of PGC-1 was linearly correlated with farnesoid X receptor (FXR) in gallstone patients (r = 0.87 on a log scale, P < 0.01), but not in control subjects; in gallstone patients PGC-1 expression was also correlated with hepatocyte nuclear factor 4 (HNF-4) (r = 0.78, P < 0.01).

CONCLUSION

These findings suggest that PGC-1 can play a role in the prevention of cholesterol gallstone disease in humans; this might take place via interaction with the bile acid receptor FXR, whose protective role in cholelithiasis has been suggested by recent evidence in animal models and other coactivators. The present data might help to understand the pathophysiology and possibly focus on new therapeutical targets in cholesterol gallstone disease.

Bile acid synthesis in humans has a rapid diurnal variation that is asynchronous with cholesterol synthesis

BACKGROUND & AIMS

The conversion of cholesterol to bile acids by the liver is an important regulator of body cholesterol homeostasis. In rodents, both cholesterol and bile acid synthesis have marked diurnal rhythms that peak synchronously at midnight. The aim of this study was to establish whether such diurnal rhythms are also present in healthy humans.

METHODS

Serum levels of the markers 7alpha-hydroxy-4-cholesten-3-one (C4) monitoring bile acid biosynthesis and lathosterol reflecting cholesterol synthesis were determined at 90-minute intervals in 8 human volunteers during standardized dietary conditions.

RESULTS

Serum C4 showed 2 distinct peaks (2- to 4-fold above baseline) during a 24-hour period, the first at 1:00 pm and the second at 9:00 pm. During the night, C4 levels declined, and they returned to baseline levels the next morning. In contrast, serum lathosterol levels peaked at night, between midnight and 4:00 am. The diurnal changes of C4 were not synchronous with serum lipid changes or with the postprandial increase in serum bile acids and were maintained in cholecystectomized subjects.

CONCLUSIONS

Bile acid synthesis in humans has a diurnal rhythm, with 2 peaks during the daytime, that is opposite from the circadian rhythm of cholesterol synthesis. This is completely different from the pattern in rodents and indicates the presence of an important species variation in the regulation of cholesterol homeostasis.

Pituitary control of cholesterol metabolism in normal and LDL receptor knock-out mice: Effects of hypophysectomy and growth hormone treatment

The pituitary is important in the control of lipid metabolism and studies of hypophysectomized (Hx) rats have shown strong effects of growth hormone (GH) on bile acid synthesis, hepatic LDL receptor (LDLR) expression and on the sensitivity to dietary cholesterol. It is unclear if mice may be used in such studies. The aim of the current study was to evaluate if Hx mice may be used to further explore how GH modulates cholesterol and bile acid metabolism, and to define the importance of the LDLR in this regulation by studying LDLR-deficient mice (LDLRko). Experiments on three mouse strains showed that, following Hx, HDL were reduced and LDL increased. Cholesterol/fat feeding of Hx mice increased serum cholesterol levels 2- to 3-fold. Serum triglycerides were reduced 50% in Hx mice; a further 30% reduction was seen after dietary cholesterol/fat. A serum marker for CYP7A1-mediated bile acid synthesis (C4) increased 2-fold in intact mice on cholesterol/fat diet. In Hx mice C4 levels were reduced by 50% as compared to intact controls, but were unexpectedly increased to levels seen in normal mice upon cholesterol/fat feeding. Hx of LDLRko mice moderately increased LDL-cholesterol and reduced triglycerides and GH treatment attenuated these effects; serum C4 levels were increased by GH treatment in all groups. In conclusion, mice can be used to explore the role of the pituitary in lipid metabolism. CYP7A1 is generally reduced in Hx mice but has a normal stimulatory response following dietary cholesterol suggesting that faulty regulation of CYP7A1 is not important for the reduced resistance to dietary cholesterol in Hx mice. Further, the LDLR is only to a minor part involved in the pituitary regulation of serum cholesterol in mice.

High serum phytosterol levels in short bowel patients on parenteral nutrition support

BACKGROUND & AIMS

Patients with short bowel syndrome (SBS) are often depending on parenteral nutrition support (PNS), sometimes complicated by liver dysfunction. Phytosterols in parenteral lipid emulsions have been suspected to be responsible for cholestasis in paediatric nutrition support. The aim of the present study was to evaluate phytosterol intake and serum phytosterol levels in adult SBS patients.

METHODS

We quantified serum levels of phytosterols, cholesterol, and markers for bile acid and cholesterol synthesis, by gas or liquid chromatography in 21 healthy controls, and in 24 adult SBS-patients, 8 with and 16 without PNS. Phytosterols and cholesterol in parenteral lipid emulsions were also quantified.

RESULTS

Serum levels in SBS-patients without PNS; with PNS; and in controls, were on average for phytosterols 11; 63; and 23 micromol/l (P<0.05 for differences), cholesterol 4,2; 3,8; and 5,1 mmol/l, lathosterol 808; 824; and 228 micromol/100 mmol cholesterol, and 7alpha-hydroxy-4-cholesten-3-one 207;191; and 18 nmol/l, respectively (P<0.05 between controls and SBS). Phytosterols in lipid emulsions ranged from 591 to 958 micromol/l.

CONCLUSIONS

SBS-patients on PNS have higher serum levels of phytosterols than other SBS-patients and controls, possibly because of phytosterols in lipid emulsions. Patients with SBS, regardless of nutrition support, have lower serum levels of cholesterol but higher cholesterol and bile acid synthesis compared to controls.

Common polymorphisms in the CYP7A1 gene do not contribute to variation in rates of bile acid synthesis and plasma LDL cholesterol concentration

Transcriptional regulation of the cholesterol 7alpha-hydroxylase (CYP7AI) gene is of critical importance for bile acid and cholesterol metabolism. We evaluated the physiological significance of two common polymorphisms (-203C/A and -469T/C) in the promoter region of the CYP7AI gene. No evidence was found for physiological differences between either the -203C and -203A alleles or the -469T and -469C alleles in transient transfection studies using native 834bp promoter constructs. Moreover, no association was observed between the CYP7AI promoter polymorphisms and the hepatic cholesterol 7alpha-hydroxylase activity and parameters of bile acid synthesis rates, as analyzed in subjects with gallstone disease. In addition, no relationships were found between the promoter polymorphisms and plasma LDL cholesterol concentration in association studies conducted in three different groups of middle-aged Swedish men. Finally, near complete allelic association was found between the two promoter polymorphisms and the IVS6+363G/A polymorphism at the 3' end of the CYP7AI gene (|D'|=0.98), indicating strong linkage disequilibrium across the whole CYP7AI gene. It is concluded that common polymorphisms of the CYP7A1 gene do not contribute to variation in cholesterol 7alpha-hydroxylase activity, rates of bile acid synthesis and plasma LDL cholesterol concentration in humans.

Coffee oil consumption increases plasma levels of 7alpha-hydroxy-4-cholesten-3-one in humans

Unfiltered coffee brews such as French press and espresso contain a lipid from coffee beans named cafestol that raises serum cholesterol in humans. Cafestol decreases the expression and activity of cholesterol 7alpha-hydroxylase, the rate-limiting enzyme in the classical pathway of bile acid synthesis, in cultured rat hepatocytes and livers of APOE3Leiden mice. Inhibition of bile acid synthesis has been suggested to be responsible for the cholesterol-raising effect of cafestol. Therefore, we assessed whether cafestol decreases the activity of cholesterol 7alpha-hydroxylase in humans. Because liver biopsies were not feasible, we measured plasma levels of 7alpha-hydroxy-4-cholesten-3-one, a marker for the activity of cholesterol 7alpha-hydroxylase in the liver. Plasma 7alpha-hydroxy-4-cholesten-3-one was measured in 2 separate periods in which healthy volunteers consumed coffee oil containing cafestol (69 mg/d) for 5 wk. Plasma levels of 7alpha-hydroxy-4-cholesten-3-one increased by 47 +/- 13% (mean +/- SEM, n = 38, P = 0.001) in the first period and by 23 +/- 10% (n = 31, P = 0.03) in the second treatment period. Serum cholesterol was raised by 23 +/- 2% (P < 0.001) in the first period and by 18 +/- 2% (P < 0.001) in the second period. We corrected individual 7alpha-hydroxy-4-cholesten-3-one levels for serum cholesterol levels, because coffee oil increases serum cholesterol and 7alpha-hydroxy-4-cholesten-3-one is probably present in the lipoprotein fraction of serum. After correction, the increase in 7alpha-hydroxy-4-cholesten-3-one was 24 +/- 11% (P = 0.04) in the first period and there was no effect in period 2. Our study showed that coffee oil did not decrease, and actually increased, plasma levels of 7alpha-hydroxy-4-cholesten-3-one in humans in 2 separate treatment periods. Therefore, this study does not support the hypothesis that cafestol decreases bile acid synthesis in humans.

Bile acid synthesis is increased in Chilean Hispanics with gallstones and in gallstone high-risk Mapuche Indians

BACKGROUND & AIMS

Gallstone disease is an important, costly health-care problem in Western societies. It is still unclear whether hepatic lipid regulatory enzymes play primary or secondary roles in gallstone formation. In this study, the aim was to investigate whether the synthesis of bile acids and cholesterol is increased in gallstone disease and to test whether such a metabolic change, if present, might occur before gallstone formation.

METHODS

A total of 125 Chilean Hispanic women (80 without gallstones and 45 with gallstones) matched for age and body mass index were investigated, along with 40 Chilean Mapuche Indian women (20 without gallstones and 20 with gallstones), a population group in which the prevalence for gallstone disease is very high. Fasting blood plasma samples were assayed for 7 alpha-hydroxy-4-cholesten-3-one and lathosterol, 2 strong indicators for hepatic bile acid and body cholesterol synthesis, respectively.

RESULTS

Plasma 7 alpha-hydroxy-4-cholesten-3-one levels, corrected for plasma cholesterol, were significantly increased by 50% in Hispanic women with gallstones as compared with gallstone-free Hispanics (P < 0.006). As compared with Hispanic women without gallstones, plasma 7 alpha-hydroxy-4-cholesten-3-one levels were increased by > or =100% (P < 0.002) in Mapuche Indian women, independently of whether gallstones were present. Plasma lathosterol, corrected for plasma cholesterol, was significantly increased by 22% in Hispanic women with gallstones and in Mapuche Indian women compared with Hispanic women.

CONCLUSIONS

The results indicate that the synthesis of bile acids and cholesterol is induced in gallstone disease and precedes gallstone development. These inductions presumably occur as a response to an increased intestinal loss of bile acids.

Significance of plasma 7alpha-hydroxy-4-cholesten-3-one and 27-hydroxycholesterol concentrations as markers for hepatic bile acid synthesis in cholesterol-fed rabbits

Plasma 7alpha-hydroxy-4-cholesten-3-one has been used as an index of hepatic bile acid synthesis. The aim of the current study was to ascertain whether the level of this oxysterol reflects hepatic cholesterol 7alpha-hydroxylase activity when plasma cholesterol concentrations are markedly changed. In addition, the relationship of hepatic sterol 27-hydroxylase activity with plasma concentrations of 27-hydroxycholesterol and 3beta-hydroxy-5-cholestenoic acid was studied. We used New Zealand white rabbits fed 2% cholesterol for 5 or 10 days and/or constructed bile fistula. Feeding cholesterol markedly increased and bile drainage reduced plasma cholesterol concentrations. Initially, in these models there was no correlation between plasma 7alpha-hydroxy-4-cholesten-3-one concentrations and hepatic cholesterol 7alpha-hydroxylase activities (r = -0.24, n = 10). Cholesterol feeding was associated with downregulated 7alpha-hydroxylase activities, while plasma 7alpha-hydroxy-4-cholesten-3-one concentrations were elevated in the presence of increased plasma cholesterol levels. However, this discrepancy was overcome and significant correlation was observed (r = 0.73, P <.05, n = 10) by expressing 7alpha-hydroxy-4-cholesten-3-one levels relative to cholesterol. In contrast, hepatic sterol 27-hydroxylase activities were not significantly correlated with plasma absolute (r = 0.23, difference not significant [NS], n = 10) nor cholesterol-related levels of 27-hydroxycholesterol (r = -0.13, NS, n = 10), or 3beta-hydroxy-5-cholestenoic acid concentrations (r = 0.30, NS, n = 10). In conclusion, plasma 7alpha-hydroxy-4-cholesten-3-one concentrations reflected hepatic cholesterol 7alpha-hydroxylase activities when the sterol levels were adjusted to plasma cholesterol concentrations in rabbits with hypercholesterolemia. The results suggest that plasma 7alpha-hydroxy-4-cholesten-3-one relative to cholesterol is a better marker for hepatic cholesterol 7alpha-hydroxylase activity than the absolute concentration when hypercholesterolemia is present. In contrast, 27-hydroxycholesterol and 3beta-hydroxy-5-cholestenoic acid levels in plasma did not reflect hepatic sterol 27-hydroxylase activities even if the levels were adjusted to plasma cholesterol concentrations.

On the origin of the cholestenoic acids in human circulation

3 Beta-hydroxy-5-cholestenoic acid, 3 beta,7 alpha-dihydroxy-5-cholestenoic acid, and 7 alpha-hydroxy-3-oxo-4-cholestenoic acid are metabolites of cholesterol present at significant concentrations (40-80 ng/ml) in human circulation. The 7 alpha-hydroxylated acids may be formed from cholesterol via two major pathways initiated by oxidations at either the 7 alpha- or 27-positions. In an attempt to clarify the origin and possible precursor-product relationships between these cholestenoic acids, we measured their deuterium enrichment in a unique experiment, after infusion of 10 g of [2H(6)]-cholesterol to a healthy volunteer. The observed extent and time-course of deuterium enrichment of circulating 3 beta-hydroxy-5-cholestenoic and 3 beta,7 alpha-dihydroxy-5-cholestenoic acid were almost identical, while different from that of cholesterol and 7 alpha-hydroxycholesterol. Notably, the deuterium enrichment of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid was similar to that of 7 alpha-hydroxycholesterol (and its metabolite 7 alpha-hydroxy-4-cholesten-3-one), though distinct from the other cholestenoic acids. Finally, the enrichment of unesterified 27-hydroxycholesterol followed a similar, though less pronounced, time curve to the delta(5)-cholestenoic acids. In conclusion, these results suggest that plasma 3 beta-hydroxy-5-cholestenoic acid is formed from a pool of cholesterol distinct from that used for the formation of the bulk of 27-hydroxycholesterol. The results are also in accordance with a formation of 3 beta,7 alpha-dihydroxy-5-cholestenoic acid directly from 3 beta-hydroxy-5-cholestenoic acid, and a formation of most of the circulating 7 alpha-hydroxy-4-cholesten-3-one from 7 alpha-hydroxycholesterol. These results are consistent with a flux of 7 alpha-hydroxycholesterol from the liver into the circulation, and an extrahepatic metabolism of this steroid into 7 alpha-hydroxy-3-oxo-4-cholestenoic acid.

Monitoring hepatic cholesterol 7alpha-hydroxylase activity by assay of the stable bile acid intermediate 7alpha-hydroxy-4-cholesten-3-one in peripheral blood

We describe an accurate method for monitoring the enzymatic activity of hepatic cholesterol 7alpha-hydroxylase (C7alphaOH; CYP7A1), the rate-limiting and major regulatory enzyme in the synthesis of bile acids. Assay of 7alpha-hydroxy-4-cholesten-3-one (C4), an intermediate in bile acid synthesis, revealed that the level of C4 in peripheral blood serum or plasma showed a strong correlation to the enzymatic activity of hepatic C7alphaOH, both at steady-state conditions (r = 0.929) as well as during the rapid changes that occur during the diurnal phases. This assay should be of value in clarifying the regulation of bile acid synthesis in vivo in laboratory animals and humans since it allows for the monitoring of hepatic C7alphaOH activity using peripheral blood samples.

Oat bran stimulates bile acid synthesis within 8 h as measured by 7alpha-hydroxy-4-cholesten-3-one

BACKGROUND

Oat bran contains soluble fibers, such as beta-glucan, that increase bile acid excretion and thus decrease serum cholesterol. Bile acid synthesis correlates with serum concentrations of the metabolite 7alpha-hydroxy-4-cholesten-3-one (alpha-HC).

OBJECTIVE

The objective was to investigate whether consumption of beta-glucan from oat bran increases bile acid synthesis, as measured by the serum alpha-HC concentration, within hours after consumption in response to the loss of bile acids from the liver.

DESIGN

In a randomized, single-blind, wheat bran-controlled study with crossover design, 8 subjects were served a controlled diet during 2 periods of 3 d each, with an 11-d washout between the periods. Breakfast included either 75 g extruded oat bran, of which 11 g was beta-glucan, or 75 g wheat bran, of which 1 g was beta-glucan. Alpha-HC was measured by HPLC on each day at 0, 12, and 24 h after breakfast and also at 8 h after breakfast on the first day.

RESULTS

After 8 and 12 h of the oat bran diet period, the serum alpha-HC concentration was 84% (P = 0.012) and 92% (P = 0.017) higher, respectively, than that before breakfast. Serum concentrations returned to the baseline value after 24 h. Wheat bran did not influence serum alpha-HC concentrations.

CONCLUSIONS

Consumption of beta-glucan from oat bran nearly doubled the serum alpha-HC concentration within 8 h, indicating increased bile acid synthesis. alpha-HC in serum could be used as a marker of increased bile acid excretion induced by the diet.

Cholesterol catabolism in patients with acute myelogenous leukemia and hypocholesterolemia: suppressed levels of a circulating marker for bile acid synthesis

Hypocholesterolemia is a frequent finding in patients with acute myelogenous leukemia (AML) and in other types of malignancies. Since bile acids are major excretion products of cholesterol, the hepatic degradation of cholesterol to bile acids was investigated in AML patients by analyzing a circulating marker for bile acid synthesis. In addition, plasma levels of a marker for cholesterol synthesis were determined. The plasma levels of 7alpha-hydroxy-4-cholesten-3-one, reflecting bile acid production, were markedly lower in patients with AML than in healthy controls. The median levels were 3.3 and 18.5ng/ml (P<0.0001) in the AML patients (n=29) and the healthy subjects (n=16), respectively. The plasma levels of 7-dehydrocholesterol, reflecting hepatic cholesterol synthesis, were similar for the AML patients and the controls. The results show that the conversion of cholesterol to bile acids was suppressed in AML patients, a phenomenon that may result in a decreased intestinal absorption of cholesterol and subsequent hypocholesterolemia.

Determinants of Variable Response to Statin Treatment in Patients With Refractory Familial Hypercholesterolemia

Abstract —Interindividual variability in low density lipoprotein (LDL) cholesterol (LDL-C) response during treatment with statins is well documented but poorly understood. To investigate potential metabolic and genetic determinants of statin responsiveness, 19 patients with refractory heterozygous familial hypercholesterolemia were sequentially treated with placebo, atorvastatin (10 mg/d), bile acid sequestrant, and the 2 combined, each for 4 weeks. Levels of LDL-C, mevalonic acid (MVA), 7-α-OH-4-cholesten-3-one, and leukocyte LDL receptor and hydroxymethylglutaryl coenzyme A reductase mRNA were determined after each treatment period. Atorvastatin (10 mg/d) reduced LDL-C by an overall mean of 32.5%. Above-average responders (ΔLDL-C −39.5%) had higher basal MVA levels (34.4±6.1 μmol/L) than did below-average responders (ΔLDL-C −23.6%, P <0.02; basal MVA 26.3±6.1 μmol/L, P <0.01). Fewer good responders compared with the poor responders had an apolipoprotein E4 allele (3 of 11 versus 6 of 8, respectively; P <0.05). There were no baseline differences between them in 7-α-OH-4-cholesten-3-one, hydroxymethylglutaryl coenzyme A reductase mRNA, or LDL receptor mRNA, but the latter increased in the good responders on combination therapy ( P <0.05). Severe mutations were not more common in poor than in good responders. We conclude that poor responders to statins have a low basal rate of cholesterol synthesis that may be secondary to a genetically determined increase in cholesterol absorption, possibly mediated by apolipoprotein E4. If so, statin responsiveness could be enhanced by reducing dietary cholesterol intake or inhibiting absorption.

Effect of cholestyramine on bile acid pattern and synthesis during administration of ursodeoxycholic acid in man

BACKGROUND

Cholestyramine is the first-line treatment for cholestasis-induced pruritus and is prescribed along with ursodeoxycholic acid (UDCA) in patients with cholestatic liver diseases. Impairment of the intestinal absorption of endogenous hydrophobic bile acids by cholestyramine is well known. It is unclear, however, whether cholestyramine also impairs the absorption of the hydrophilic bile acid, UDCA, in man.

AIMS

To study serum levels of UDCA and endogenous bile acids as well as endogenous bile acid synthesis during simultaneous or separate administration of UDCA and cholestyramine in vivo; and absorption of UDCA both in the presence and absence of its hydrophobic epimer, chenodeoxycholic acid (CDCA), by cholestyramine in vitro.

PATIENTS AND METHODS

Five healthy subjects received UDCA (12.5 +/- 0.5 mg kg-1 daily) as a single dose for periods of 14 days with or without cholestyramine (4 g daily). Fasting serum levels of bile acids and of 7alpha-hydroxy-4-cholesten-3-one (alpha-HC), a measure of endogenous bile acid synthesis, were determined by gas chromatography and high pressure liquid chromatography, respectively. In vitro, bile acid solutions were incubated for 24 h in the presence or absence of cholestyramine, and bile acid concentrations were determined in the supernatant.

RESULTS

Simultaneous administration of UDCA and cholestyramine in man led to a decrease of fasting serum levels of UDCA by 60% when compared to UDCA serum levels during administration of UDCA alone. In contrast, serum levels of endogenous bile acids were not affected and alpha-HC serum levels were found increased 2. 7-fold indicating stimulation of endogenous bile acid synthesis by cholestyramine. Administration of cholestyramine and UDCA at an interval of 5 h tended to diminish the effect of cholestyramine on UDCA serum levels. In vitro, conjugated and unconjugated UDCA were effectively bound by cholestyramine both in the presence and absence of hydrophobic bile acids.

CONCLUSIONS

The results strongly support the recommendation to administer UDCA and cholestyramine at different times of day.

Effect of inhibiting HMG-CoA reductase on 7 alpha-hydroxy-4-cholesten-3-one, a marker of bile acid synthesis: contrasting findings in patients with and without prior up-regulation of the latter pathway

BACKGROUND

Atorvastatin is a potent inhibitor of 3-hydroxy-3-methyl-glutaryl coenzyme A reductase, but its effect on bile acid synthesis is unknown. The objectives of the study were to determine the effect of atorvastatin on bile acid synthesis in patients in whom this process had not been or had been previously up-regulated by pharmacological or surgical means.

MATERIALS AND METHODS

Four patients with heterozygous familial hypercholesterolaemia (FH) and partial ileal bypass (PIB) and 19 FH heterozygotes without PIB were treated with placebo, atorvastatin 10 mg and atorvastatin 40 mg daily, each regimen for 4 weeks. The non-PIB group was subsequently treated with bile acid (BA) sequestrant 8-16 g daily followed by co-administration of atorvastatin 10 mg, each for 4 weeks. Plasma 7 alpha-hydroxy-4-cholesten-3-one (7 alpha-HCO), a well-validated marker of BA synthesis was measured using high-performance liquid chromatography with UV detection.

RESULTS

The plasma 7 alpha-HCO concentration was tenfold higher with placebo in the PIB than in the non-PIB group (418.5 ng mL-1 vs. 39.6 ng mL-1 p = 0.0001). Levels decreased in PIB patients treated with atorvastatin 10 mg and 40 mg daily (350.1 ng mL-1 and 174.0 ng mL-1, P = 0.007 respectively) but did not change significantly in the non-PIB group (44.7 ng mL-1 and 28.3 ng mL-1 respectively). Administration of BA sequestrant to non-PIB patients increased 7 alpha-HCO to 197.4 ng mL-1; this decreased to 106.0 ng mL-1 during co-administration of atorvastatin 10 mg daily (P = 0.0001).

CONCLUSION

Atorvastatin decreases the rate of BA synthesis only if the latter is up-regulated by PIB or BA sequestrants, presumably by limiting the supply of newly synthesized free cholesterol.

Plasma levels of mevalonate and 7alpha-hydroxy-4-cholesten-3-one in chronic liver disease

BACKGROUND AND AIMS

Cholesterol levels in blood tend to be preserved despite hepatic impairment, in contrast to albumin levels and other markers of liver function in patients with liver cirrhosis (LC). We reported previously that the levels of plasma mevalonate (MVA) and 7alpha-hydroxy-4-cholesten-3-one (7alpha3one) closely reflect hepatic synthetic rates of cholesterol and bile acids. The aim of this study was to examine the association between hepatic cholesterogenesis and bile acid synthesis in hepatocellular impairment using these indices.

METHODS

The plasma indices were measured in patients with LC (n = 38) or chronic hepatitis (CH; n = 11) and in normal controls (n = 22). The severity of LC was assessed by the Child-Pugh score.

RESULTS

There were no significant differences in plasma MVA levels between CH, LC and control groups. However, plasma 7alpha3one levels were significantly lower in LC than in CH and control groups (P< 0.01). While MVA levels did not correlate with the Child-Pugh score, there was a significant correlation between 7alpha3one level and Child-Pugh score (P< 0.005). The plasma 7alpha3one level in controls correlated positively with MVA levels (P< 0.01); however, there was no significant correlation between these indices in CH and LC.

CONCLUSION

In chronic liver disease, there was a tendency for hepatic cholesterogenesis to be sustained in the face of hepatocellular impairment, while bile acid synthesis declined in parallel with the severity of impairment.

Bile acid malabsorption as a cause of chronic diarrhea: diagnostic value of 7alpha-hydroxy-4-cholesten-3-one in serum

To evaluate the usefulness of 7a-hydroxy-4-cholesten-3-one (HCO) serum concentrations as a diagnostic marker of bile acid malabsorption, we determined the reference range of HCO in 106 normal subjects (age 40.2+/-16.8 years; 55 women, 51 men) and conducted a utility study in 23 patients with chronic diarrhea of unknown origin (age 49.4+/-15.3 years, 13 women, 10 men). The diagnosis of bile acid malabsorption was made on the basis of a decreased retention of [75Se]homocholyltaurine after oral application (75SeHCAT test). HCO (reference range: 6-48 ng/ml) and the 75SeHCAT test yielded the same results in 19/23 (83%) patients. Bile acid malabsorption was identified by an increase of HCO in serum with a sensitivity of 90% and a specificity of 79%. Analysis of HCO in serum may serve as a novel, simple, and sensitive method for the detection of bile acid malabsorption in patients with chronic diarrhea of unknown origin.

Progesterone metabolites and bile acids in serum of patients with intrahepatic cholestasis of pregnancy: effect of ursodeoxycholic acid therapy

The concentrations in serum of sulfated metabolites of progesterone are known to be elevated in patients with intrahepatic cholestasis of pregnancy (ICP). The profiles of these metabolites and conjugated bile acids were analyzed in serum from 11 patients with ICP before and during administration of ursodeoxycholic acid (UDCA) (8 patients) or placebo (3 patients). The clinical condition of 7 of the patients given UDCA improved markedly, and 1 patient given placebo had a spontaneous remission of the disease. The total concentration of conjugated bile acids in the 11 patients was 25 +/- 6 micromol/L (mean +/- SEM) and decreased to 6.3 +/- 3.5 micromol/L in the 7 patients responding to treatment with UDCA. The level of 7alpha-hydroxy-4-cholesten-3-one was significantly lower (7.2 +/- 2.2 ng/mL) in patients with ICP than in healthy pregnancy (18 +/- 4.6 ng/mL) (P < .05). The concentrations of 5alpha-pregnane-3alpha,20alpha-diol mono- and disulfates decreased by 52% +/- 7.9% and 68% +/- 5.5%, respectively, in the patients responding to treatment. Similar decreases were observed for the mono- and disulfates of 5alpha-pregnane-3alpha,20alpha,21-triol and 5beta-pregnane-3alpha,20alpha-diol. The disulfate of 5alpha-pregnane-3beta,20alpha-diol showed a smaller decrease, while glucuronidated steroids were not affected. The 3alpha-/3beta-hydroxysteroid ratio and di-/monosulfate ratio decreased significantly during UDCA. The magnitudes of the changes of bile acid and steroid concentrations during UDCA were not correlated to each other. The results suggest that UDCA stimulates the biliary excretion of steroids with a 3alpha-sulfoxy group and disulfates. This effect seems to be independent of the effect on bile acid excretion, indicating the use of different transport proteins. The possibility of an effect of UDCA on the formation of the steroid sulfates cannot be excluded.

Short-term effects of 3-hydroxy-3-methylglutaryl-CoA reductase inhibitor on cholesterol and bile acid synthesis in humans

Competitive inhibitors of 3-hydroxy-3-methylglutaryl-CoA reductase improve hypercholesterolemia. However, reports about the effects of these agents on bile acid synthesis, the metabolic pathway of cholesterol, are conflicting. We studied the short-term effect on one of these agents, pravastatin, on bile acid synthesis. Six male volunteers were given 40 mg of pravastatin. Plasma mevalonate level (which reflects cholesterol synthesis) and 7 alpha-hydroxy-4-cholesten-3-one level (which reflects bile acid synthesis) were measured every 2 h for 8 h. These plasma levels were compared to those of the same volunteers without pravastatin. Plasma mevalonate level after 2 h was lower than control (3.0 +/- 1.1 ng/mL vs. 6.7 +/- 2.5, mean +/- SD; P < 0.05). This decrease continued for 8 h (2.5 +/- 0.8 vs. 5.2 +/- 1.5; P < 0.05). On the other hand, plasma 7 alpha-hydroxy-4-cholesten-3-one level did not change until after 6 h; then at 8 h it was lower than control (15.7 +/- 11.8 ng/mL vs. 24.7 +/- 16.9; P < 0.05). According to three-way layout analysis of variance, mevalonate level was influenced by both pravastatin treatment (P < 0.01) and time-course (P < 0.01). On the other hand, the 7 alpha-hydroxy-4-cholesten-3-one level was affected by both individual difference (P < 0.01) and time course (P < 0.01), but pravastatin treatment did not influence this compound. This indicates that bile acid synthesis was influenced by pravastatin, although cholesterol synthesis was inhibited. The short-term inhibition of cholesterol synthesis did not affect bile acid synthesis.

Circulating markers for biosynthesis of cholesterol and bile acids are not depressed in asymptomatic gallstone subjects

BACKGROUND/AIMS

Cholesterol gallstone disease is often associated with an increased biliary secretion rate of cholesterol, which may be due to abnormalities in hepatic cholesterol metabolism. The aim of the present study was to investigate whether gallstone subjects may have an underlying defect in hepatic cholesterol and bile acid formation.

METHODS

In 41 asymptomatic gallstone subjects, randomly selected from a population of both sexes 40 and 60 years of age, and in 72 age- and sex-matched controls, plasma levels of lathosterol (reflecting hepatic HMG CoA reductase activity) and 7alpha-hydroxy-4-cholesten-3-one (reflecting cholesterol 7alpha-hydroxylase activity) were analysed. In a subgroup of gallstone subjects and controls, plasma levels of 27-hydroxy cholesterol were also determined.

RESULTS

The gallstone subjects had normal plasma levels of cholesterol but displayed 20-25% higher plasma levels of triglycerides compared with the controls. The plasma level of lathosterol was not significantly different between the two groups of subjects whereas the plasma level of 7alpha-hydroxy-4-cholesten-3-one was about 40% higher in the gallstone subjects compared with the controls. Positive correlations were obtained between plasma levels of 7alpha-hydroxy-4-cholesten-3-one and triglycerides in both groups of subjects. The plasma level of 27-hydroxy cholesterol was similar in gallstone subjects and controls.

CONCLUSIONS

The previously reported hypersecretion of cholesterol in gallstone patients is not due to a single metabolic defect leading to increased hepatic synthesis of cholesterol or decreased catabolism of cholesterol to bile acids via 7alpha-hydroxylation or 27-hydroxylation of cholesterol.

Cholesterol 7 alpha-hydroxylase activity in hypothyroidism and hyperthyroidism in humans

Alterations of serum cholesterol levels are well recognized findings in hypothyroidism and hyperthyroidism. It remains unclear, whether thyroid hormones may affect serum concentrations of cholesterol through changes in the activity of cholesterol 7 alpha-hydroxylase, the rate-limiting enzyme in the catabolic conversion of cholesterol to bile acids. We determined serum concentrations of the bile acid precursor 7 alpha-hydroxy-4-cholesten-3-one, which reflects cholesterol 7 alpha-hydroxylase activity in the liver, in 19 patients with hypothyroidism and in 10 patients with hyperthyroidism before and after treatment, respectively. In patients with hypothyroidism, serum concentrations of cholesterol and LDL-cholesterol decreased by 33% (p < 0.0005) and 39% (p < 0.0005), respectively, after replacement therapy with thyroid hormones. In contrast, serum concentrations of 7 alpha-hydroxy-4-cholesten-3-one (21.7 +/- 15.8 ng/ml vs 24.5 +/- 18.1 ng/ml before treatment, n.s.) as well as serum HDL-cholesterol were unchanged during substitution therapy. In patients with hyperthyroidism, serum concentrations of cholesterol and LDL-cholesterol increased by 27% (p < 0.01) and 39% (p < 0.01) after antithyroid treatment, respectively. Again, serum concentrations of 7 alpha-hydroxy-4-cholesten-3-one did not change significantly during treatment (15.8 +/- 12.6 ng/ml vs 14.7 +/- 8.1 ng/ml before treatment, n.s.). These findings indicate that in humans, thyroid hormones influence serum lipid concentrations by other mechanisms than by affecting the activity of cholesterol 7 alpha-hydroxylase.

Simultaneous determination of plasma mevalonate and 7alpha-hydroxy-4-cholesten-3-one levels in hyperlipoproteinemia: convenient indices for estimating hepatic defects of cholesterol and bile acid syntheses and biliary cholesterol supersaturation

The high prevalence of cholesterol gallstone disease in hypertriglyceridemic patients may be associated with frequent metabolic defects in cholesterol and bile acid syntheses and in the concomitant formation of bile supersaturated with cholesterol. This study had the two aims: 1) to assess whether the defects as well as the degree of biliary cholesterol supersaturation in patients with hyperlipoproteinemia (HLP) can be estimated by the simultaneous determination of plasma mevalonate (MVL) and 7alpha-hydroxy-4-cholesten-3-one (C4); and 2) to assess the possible application of an estimated cholesterol saturation index ([CSI]E) as a means of evaluating the clinical effects of simvastatin on biliary lipid composition. Biliary cholesterol supersaturation was observed in patients with both IIa and IV HLP types. Consistent with the high activity and steady-state messenger RNA level of 3-hydroxy-3 methylglutaryl coenzyme A (HMG-CoA) reductase, plasma MVL was significantly higher in 86 patients with HLP (38 type IIa, 44.1 +/- 2.4 nmol/L and 48 type IV, 56.7 +/- 2.3; P < .01) than in 41 normolipidemic subjects (34.2 +/- 1.5), closely correlating with the molar percentage of cholesterol in bile (r = .61, P = .0001; n = 86). On the other hand, consistent with the high activity and messenger RNA level of cholesterol 7alpha-hydroxylase, plasma C4 was significantly higher in patients with HLP (type IIa, 28.8 +/- 2.3 nmol/L and type IV, 38.3 +/- 2.7; P < .01) than in normolipidemic subjects (17.4 +/- 1.5). Plasma C4 was closely correlated with plasma MVL (r = .40, P = .0001; n = 86), but was inversely correlated with the molar percentage of bile acids in bile (r = .49, P = .0001; n = 86). Assuming that cholesterol supersaturation in patients with HLP may be governed by both an enhanced cholesterol secretion (closely reflected by plasma MVL) and a decreased secretion of bile acids (closely reflected by plasma C4), the multivariate linear regression-analyses revealed that an index defined as estimated CSI ([CSI]E) (%) in patients with HLP was given by the following equation using plasma MVL and C4 (nmol/L): [CSI]E = 1[MVL] + 0.7[C4] + 44.4. Biliary cholesterol supersaturation in patients treated with simvastatin improved in a manner parallel to the time course of decreases in plasma MVL and C4. The [CSI]E before and at the end of treatment were correlated with biliary CSI. These results indicate that defects of hepatic cholesterogenesis, and bile acid synthesis, and the degree of biliary cholesterol supersaturation in patients with HLP can be estimated exactly by the simultaneous determination of plasma MVL and C4; furthermore [CSI]E may be adopted for clinical use as a convenient index of biliary CSI.

Serum concentrations of 7alpha-hydroxy-4-cholesten-3-one reflect bile acid synthesis in humans

Serum concentrations of 7alpha-hydroxy-4-cholesten-3-one (alpha-HC) have recently been shown to reflect the activity of cholesterol 7 alpha-hydroxylase in humans. To evaluate the relationship between alpha-HC in serum and bile acid synthesis, serum concentrations of alpha-HC, and rates of bile acid synthesis, as measured by the isotope dilution technique using gas chromatography-mass spectrometry, were determined simultaneously. Regression analysis revealed a positive linear correlation of serum alpha-Hc with synthesis of cholic acid (CA) (r = .59, P = .02), chenodeoxycholic acid (CDCA) (r = .75, P = .001), and total synthesis of both primary bile acids (r = .83, P < .001) in patients with gallstones and normal liver function (n = 15). alpha-HC was also correlated to input rates of deoxycholic acid (DCA) (r = .53, P <.05). Addition of patients with chronic cholestatic liver disease (n = 5) improved the correlation between serum alpha-HC and synthesis of CA (r = .75, P < .001), CDCA (r = .77, P < .001), and both primary bile acid combined (r = .87), P < .001). Our data are in agreement with the concept that synthesis of bile acids is regulated by cholesterol 7 alpha-hydroxylase activity and that alpha-HC in serum may serve as a convenient marker for the semiquantitative assessment of bile acid synthesis in humans.

Serum 7 alpha-hydroxy-4-cholesten-3-one and selenohomocholyltaurine (SeHCAT) whole body retention in the assessment of bile acid induced diarrhoea

OBJECTIVE

To assess the reliability of serum 7 alpha-hydroxy-4-cholesten-3-one (7 alpha-3ox-C) in the differential diagnosis of bile acid induced diarrhoea by comparison with 75selenohomocholyltaurine whole body retention (SeHCAT WBR).

DESIGN

One hundred and sixty-four patients with chronic diarrhoea were investigated prospectively in two centres (Edinburgh and Sweden) by two different tests which measure bile acid loss or synthesis: the SeHCAT test which measures the 7-day SeHCAT WBR and serum 7 alpha-3ox-C which reflects the rate of bile acid synthesis.

RESULTS

Forty-six patients had SeHCAT WBR of less than 10% (19 with ileal disease or resection, nine with idiopathic bile acid induced diarrhoea and 18 with miscellaneous causes for bile acid induced diarrhoea). All patients with ileal or idiopathic disease showed a favorable response to treatment as did 13 of the miscellaneous group. Serum 7 alpha-3ox-C was raised in all subjects with ileal disease/resection, seven patients with idiopathic disease and all subjects in the miscellaneous group who responded to treatment. Sixteen out of 118 patients with SeHCAT WBR greater than or equal to 10% had raised serum 7 alpha-3ox-C.

CONCLUSION

The positive predictive value of serum 7 alpha-3ox-C was 74%. The high negative predictive value (98%) of serum 7 alpha-3ox-C indicates the possible use of this test for excluding bile acid malabsorption in this population. All but two subjects who responded to treatment had raised serum 7 alpha-3ox-C concentrations. The possibility that the sensitivity of the test can be improved by repeat testing needs to be further investigated. There was a significant correlation between fractional catabolic rate (FCR) SeHCAT and serum 7 alpha-3ox-C (r = 0.63, P < 0.0001). Further data are required to validate the reference range in women over 70 years of age.

Cholest-3,5-dien-7-one formation in peroxidized human plasma as an indicator of lipoprotein cholesterol peroxidation potential

Lipoprotein peroxidation susceptibility is routinely evaluated using products of unsaturated fatty acids as markers (e.g., malonaldehyde). The significance and factors influencing peroxidation of cholesterol moiety of lipoproteins are relatively unknown due to lack of a reliable marker product which can be measured easily. Under the influence of Cu2+ ions, the major product of lipoprotein cholesterol peroxidation (isolated after saponification) was cholest-3-5-dien-7-one (CSD). Apart from gas-liquid chromatography, this compound lends itself for measurement by alternative methods. Due to lack of the 3 beta-hydroxyl group, CSD was separated from the rest of the oxysterols and cholesterol by passing through digitonin-coated silica-gel G and its concentration was determined by absorption at 283 nm. The recovery of CSD by this method exceeded by 87%. The formation of CSD was also sensitive to vitamin E and therefore could be used as an index of lipoprotein cholesterol susceptibility to peroxidation.

High-performance liquid chromatographic analysis of human erythrocyte oxysterols as delta 4-3-ketone derivatives

Following oxidation by cholesterol oxidase human erythrocyte oxysterols were analyzed as the corresponding hydroxy-delta 4-3-ketones by HPLC with effluent monitoring at 235 nm. Variable amounts of epimeric cholest-5-ene-3 beta,7-diols, 3 beta-hydroxycholest-5-en-7-one, cholest-5-ene-3 beta,19-diol, cholest-5-ene-3 beta,20-diol, cholest-5-ene-3 beta,25-diol and cholest-5-ene-3 beta,26-diol were detected in erythrocyte membranes of patients with sickle cell anemia or sickle cell trait. Only 3 beta-hydroxycholest-5-en-7-one was detected in erythrocyte membranes of healthy donors.

Cholelithiasis and bile acid absorption after truncal vagotomy and gastroenterostomy

Gallbladder disease in the form of gallstones demonstrated by ultrasonography or previous cholecystectomy was found in 15 of 26 women of median age 69 (range 52-82) years who had had truncal vagotomy and gastroenterostomy performed a median of 27 (range 11-30) years previously, compared with eight of 31 healthy age- and sex-matched controls drawn from the community (P < 0.02). Bile acid malabsorption identified by retention of 23-selena, 25-homotaurocholate (75SeHCAT) occurred in only two of the 26 patients after vagotomy and there was no relationship between retention and the presence or absence of gallbladder disease. The serum concentration of 7 alpha-hydroxycholestenone, an indicator of bile acid turnover, was significantly lower in patients with gallbladder disease after vagotomy than in controls (mean(s.e.m.) 19.1(3.7) versus 31.4(4.4) ng/ml, P < 0.05). Bile acid malabsorption does not play a significant role in the pathogenesis of gallstones after vagotomy but decreased bile acid synthesis may be important. There is no correlation between retention of 75SeHCAT and 7 alpha-hydroxycholestenone levels in patients after vagotomy, indicating that bile acid synthesis and absorption are uncoupled in this situation.

Reversed-phase high-performance liquid chromatographic determination of 7 alpha-hydroxy-4-cholesten-3-one in human serum

A method for the determination of 7 alpha-hydroxy-4-cholesten-3-one in human serum has been developed. The method is based upon solid-phase (C18) extraction of serum after addition of 7-beta-hydroxy-4-cholesten-3-one as internal standard. The extract is analysed by reversed-phase HPLC using acetonitrile-water as a mobile phase. The effluent is monitored at 241 nm. The overall recoveries of the method range from 96% to 105%. The coefficient of variation for the within-run precision is 3.2% (n = 20, mean = 13.0 ng/ml) and for the between-run precision 3.8% (n = 32, mean = 13.3 ng/ml). The limit of detection is 3 ng at a signal-to-noise ratio of 3:1, which corresponds to 1 ng/ml using 3 ml of serum. The median value of 7 alpha-hydroxy-4-cholesten-3-one found in blood donors (n = 27) was 8.9 ng/ml (range 2-35 ng/ml).

Determination of 7 alpha-hydroxy-4-cholesten-3-one level in plasma using isotope-dilution mass spectrometry and monitoring its circadian rhythm in human as an index of bile acid biosynthesis

A highly sensitive and specific method has been developed for determination of the level of 7 alpha-hydroxy-4-cholesten-3-one in plasma. This method is based on a stable isotope-dilution technique by gas chromatography-selected-ion monitoring mass spectrometry. 7 alpha-Hydroxy-4-cholesten-3-one was extracted from plasma by saltingout extraction, and then purified by serial solid-phase extractions. The extract was treated with O-methylhydroxyl-amine hydrochloride and then dimethylethylsilylated. The resulting methyloxime-dimethylethylsilyl ether derivative was quantified by gas chromatography-selected-ion monitoring mass spectrometry with a high-resolution mode. The plasma levels of 7 alpha-hydroxy-4-cholesten-3-one were correlated with the cholesterol 7 alpha-hydroxylase activity to a higher degree than those of any other form of 7 alpha-hydroxycholesterol (r = 0.84, n = 16, p < 0.0001). The present method was applied to monitor the circadian rhythm of 7 alpha-hydroxy-4-cholesten-3-one levels in human plasma. It was concluded that the plasma level of 7 alpha-hydroxy-4-cholesten-3-one is a useful index for the monitoring of bile acid biosynthesis in the human liver.

Alterations of bile acid composition in gallstones, bile, and liver of patients with hepatolithiasis, and their etiological significance

A detailed comparison was made of the bile acid composition in gallstones (brown pigment stones) and paired bile and liver from both affected and unaffected lobes by gallstones, which were taken at operation from 16 patients with hepatolithiasis, with the aim of elucidating whether stone formation is derived from possible local disturbances limited to intrahepatic bile ducts. Brown pigment stones in the intrahepatic bile ducts, most of which were accompanied by bile with high cholesterol saturation, had significantly more cholesterol, and less calcium bilirubinate and bile acid than those found in the extrahepatic bile ducts. Intrahepatic gallstones had significantly lower amounts of secondary and unconjugated bile acids, the bile acids modified by bacterial intervention, than extrahepatic stones. Bile specimens from both affected and unaffected lobes showed significantly increased molar percentages of cholesterol and decreased percentages of bile acids than bile from controls. In contrast, liver specimens from both lobes showed significantly higher concentrations of total bile acids. Secondary bile acids were present in a much lower proportion in bile and liver from both lobes than in bile and liver from controls. On the other hand, unconjugated bile acids were present in a much higher proportion in bile and liver from patients and only in negligible amounts in bile from controls. Furthermore, the plasma levels of mevalonate and those of 7 alpha-hydroxy-4-cholestene-3-one were found to be significantly higher and lower in patients than in controls, respectively, indicating that in hepatolithiasis cholesterol synthesis might increase and bile acid synthesis might decrease in the liver. These findings suggested that alterations of bile acid composition in gallstones, bile, and liver of patients with hepatolithiasis may be attributed to not only secondary changes resulting from local disturbances limited to intrahepatic bile ducts but also possible primary alterations of hepatocyte metabolism, such as bile acid conjugation and primary defects in cholesterol and bile acid synthesis.

Serum 7 alpha-hydroxy-4-cholesten-3-one concentrations in the evaluation of bile acid malabsorption in patients with diarrhoea: correlation to SeHCAT test

The synthesis of bile acids is regulated by a homeostatic mechanism in which bile acids returning to the liver from the intestine inhibit their own synthesis. Serum concentrations of the bile acid intermediate 7 alpha-hydroxy-4-cholesten-3-one reflect the rate of bile acid synthesis whereas bile acid malabsorption can be determined by the SeHCAT test. This study was done to evaluate the correlation between the two tests in humans. Twenty eight patients with chronic diarrhoea were included in the study. Fasting serum was collected for the determination of 7 alpha-hydroxy-4-cholesten-3-one, and on the same day the gamma emitting bile acid analogue SeHCAT was given orally and its fractional catabolic rate assessed by repeated external counting over the upper abdomen during the next seven days. There was a highly significant positive correlation between the two tests (Rs = 0.80, p < 0.001). The results show a close relation between intestinal loss and hepatic synthesis of bile acids and imply that analysis of 7 alpha-hydroxy-4-cholesten-3-one in serum should now be evaluated as a possible convenient method for assessing bile acid malabsorption in patients with diarrhoea.

Identification of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid in chronic subdural hematoma

We detected a novel kind of bile acid in the content of chronic subdural hematoma. This substance was specifically found in chronic subdural hematoma, and not in subdural hygroma, which is pathologically similar except for the lack of capsular membrane. The compound was identified as 7 alpha-hydroxy-3-oxo-4-cholestenoic acid by high performance liquid chromatography, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectrometry. The structure was confirmed by the comparison with the chemically synthesized compound. The average contents in chronic subdural hematoma were 658.09 +/- 137.53 ng/ml, while those in normal human plasma were 126.27 +/- 17.73 ng/ml. It was not detected in normal cerebrospinal fluid. The higher level in chronic subdural hematoma than human plasma strongly suggests the local, extrahepatic production of this type of C27 bile acids.

Oxidative status of lipoproteins in coronary disease patients

Oxidized low-density lipoprotein (LDL) may play an important role in atherogenesis. The oxidative status of isolated LDL and very low-density lipoprotein (VLDL) were investigated in 23 patients with proven coronary disease and in 23 healthy asymptomatic control subjects. Oxidized cholesterol (4-cholesten-3-one and 20 alpha-OH cholesterol) was identified in LDL and VLDL from both groups. The content of cholesterol and 4-cholesten-3-one in LDL from patients was significantly increased in comparison with values from the control subjects. Lipid peroxidation, as assessed by malondialdehyde (MDA) formation, was barely detectable in native LDL and VLDL from the two groups. However, after incubation with a free radical-producing system, MDA levels in LDL from patients were significantly higher than those in control subjects. Lysine reactivity in LDL after incubation with an oxidizing agent, CuSO4, was similar between groups. However, lysine reactivity to CuSO4 in VLDL from patients was less than that in control subjects. Our results suggest that LDL levels from patients with coronary disease have an elevated oxidized cholesterol content and are more susceptible to peroxidative modification. Conversely, the LDL apoprotein does not appear to have been oxidatively modified in these patients. The data are consistent with a role for oxidized LDL in coronary artery disease and indicate that the LDL lipid may be an important oxidation site.

The plasma level of 7 alpha-hydroxy-4-cholesten-3-one reflects the activity of hepatic cholesterol 7 alpha-hydroxylase in man

Circulating levels of 7 alpha-hydroxy-4-cholesten-3-one have been compared with activities of the rate-limiting enzyme in bile acid synthesis, microsomal cholesterol 7 alpha-hydroxylase, measured in liver biopsies obtained from patients undergoing surgery for gallstone disease. Some patients were treated with cholestyramine or bile acids prior to operation in order to alter the feed-back inhibition of the enzyme. The levels of the sterol were similar in untreated patients and in patients treated with ursodeoxycholic acid (median concentration 17 and 13 ng/ml, respectively), and so were the activities of the enzyme (median activity 7.0 and 5.5 pmol/min/mg protein, respectively). The sterol levels and enzyme activities were significantly increased in patients treated with cholestyramine (91 ng/ml and 45 pmol/min/mg protein) and decreased in patients treated with chenodeoxycholic acid (less than 2.0 ng/ml and 0.7 pmol/min/mg protein). There was a strong positive correlation (r = 0.90, P less than 0.00001) between levels of 7 alpha-hydroxy-4-cholesten-3-one in plasma and the activities of cholesterol 7 alpha-hydroxylase in the whole patient group. The results show that analysis of 7 alpha-hydroxy-4-cholesten-3-one in plasma is a sensitive and convenient method to determine relative rates of bile acid production in man.

Ethanol has an acute effect on bile acid biosynthesis in man

A single dose of ethanol, 0.4 g/kg body weight, was found to give a 5-15 fold increase of the plasma concentrations of 7 alpha-hydroxy-cholesterol and 7 alpha-hydroxy-4-cholesten-3-one in humans. The rise was maximal 4 h after ethanol ingestion, was dose-dependent and was not seen in a cholecystectomized subject. The effect was selective for these and some other 7 alpha-hydroxylated C27-intermediates in bile acid biosynthesis. The changes are compatible with an acute stimulation of cholesterol 7 alpha-hydroxylase possibly due to an ethanol-induced inhibition of gallbladder contraction resulting in an interruption of the enterohepatic circulation of bile acids. The effect is of interest in relation to the influence of ethanol consumption on cardiovascular and gallstone diseases.

Potential bile acid precursors in plasma--possible indicators of biosynthetic pathways to cholic and chenodeoxycholic acids in man

The plasma concentrations of 3 beta-hydroxy-5-cholestenoic acid, 3 beta,7 alpha-dihydroxy-5-cholestenoic acid and 7 alpha-hydroxy-3-oxo-4-cholestenoic acid have been compared with that of 7 alpha-hydroxy-4-cholesten-3-one in healthy subjects and in patients with an expected decrease or increase of the bile acid production. In controls and patients with liver disease, the level of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid was positively correlated to that of 3 beta,7 alpha-dihydroxy-5-cholestenoic acid and not to that of 7 alpha-hydroxy-4-cholesten-3-one. In patients with stimulated bile acid formation the levels of the acids were not correlated to each other but there was a significant positive correlation between the levels of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid and 7 alpha-hydroxy-4-cholesten-3-one. These findings indicate that the precursor of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid differs depending on the activity of cholesterol 7 alpha-hydroxylase. Since the activity of this enzyme is reflected by the level of 7 alpha-hydroxy-4-cholesten-3-one in plasma the findings are compatible with a formation of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid from 3 beta,7 alpha-dihydroxy-5-cholestenoic acid when the rate of bile acid formation is normal or reduced and from 7 alpha-hydroxy-4-cholesten-3-one under conditions of increased bile acid synthesis. In support of this interpretation, 7 alpha,26-dihydroxy-4-cholesten-3-one was identified at elevated levels in plasma from patients with ileal resection or treated with cholestyramine. The levels of 7 alpha,12 alpha-dihydroxy-4-cholesten-3-one were also higher than normal in these patients. Based on these findings and previous knowledge, a model is proposed for the biosynthesis of bile acids in man. Under normal conditions, two major pathways, one "neutral" and one "acidic" or "26-oxygenated", lead to the formation of cholic acid and chenodeoxycholic acid, respectively. These pathways are separately regulated. When the activity of cholesterol 7 alpha-hydroxylase is high, the "neutral" pathway is most important whereas the reverse is true when cholesterol 7 alpha-hydroxylase activity is low. In cases with enhanced activity of cholesterol 7 alpha-hydroxylase, the "neutral" pathway is connected to the "acidic" pathway via 7 alpha,26-dihydroxy-4-cholesten-3-one, whereas a flow from the acidic pathway to cholic acid appears to be of minor importance.

Concentrations of cholestenoic acids in plasma from patients with liver disease

The concentrations of 3 beta-hydroxy-5-cholestenoic acid, 3 beta,7 alpha-dihydroxy-5-cholestenoic acid, and 7 alpha-hydroxy-3-oxo-4-cholestenoic acid were determined in plasma from patients with different liver diseases and compared with those of unconjugated and conjugated C24 bile acids. The levels of the cholestenoic acids were similar in patients with extrahepatic cholestasis and in controls (median concentration 153 and 162 ng/ml, respectively), whereas significantly elevated levels were found in plasma from patients with primary biliary cirrhosis (median concentration 298 ng/ml) and alcoholic liver cirrhosis (median concentration 262 ng/ml). As expected, conjugated C24 bile acids were elevated in most patients whereas the corresponding unconjugated compounds were low in cholestasis and elevated in alcoholic liver cirrhosis. The levels of the individual C27 acids were usually positively correlated to each other and also to the levels of conjugated C24 bile acids in plasma from patients with liver cirrhosis. In contrast, there was no correlation between the levels of C27 acids and conjugated bile acids in patients with extrahepatic cholestasis. The levels of unconjugated C24 bile acids were not correlated to C27 acids or conjugated bile acids in any of the groups. The results indicate that there is a close metabolic relationship between the individual C27 acids, that they do not participate in an enterohepatic circulation, and that the liver is important for their elimination/metabolism.

Concentrations of cholestenoic acids in plasma from patients with reduced intestinal reabsorption of bile acids

The concentrations of 3 beta-hydroxy-5-cholestenoic acid, 3 beta,7 alpha-dihydroxy-5-cholestenoic acid, and 7 alpha-hydroxy-3-oxo-4-cholestenoic acid were determined in plasma from patients treated with cholestyramine or subjected to resection of the ileum or colon. The values were compared with those for conjugated and unconjugated C24 bile acids. Patients with an intact ileum but without colon had normal levels of cholestenoic acids. Patients treated with cholestyramine or with ileal resection had elevated levels of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid (median values 189 and 233 ng/ml, respectively, compared to 85 ng/ml in controls). The levels of the other two C27 acids were normal in cholestyramine-treated and low in ileoresected patients and were positively correlated to each other but not to the 3-oxo-delta 4 acid. There were no consistent correlations between the levels of C27 acids and those of conjugated or unconjugated C24 bile acids. The results indicate an increased formation of 7 alpha-hydroxy-3-oxo-4-cholestenoic acid in subjects having a stimulated activity of cholesterol 7 alpha-hydroxylase.

Levels of 7 alpha-hydroxy-4-cholesten-3-one in plasma reflect rates of bile acid synthesis in man

A method for analysis of 7 alpha-hydroxy-4-cholesten-3-one in plasma is described. Following solid-phase extraction/purification the compound is determined by high-performance liquid chromatography using a UV detector. The median concentration in healthy subjects was 12 ng/ml (range 3-40). The levels were lower in diseases associated with a low bile acid production: extrahepatic cholestasis, less than 1.5 ng/ml (range less than 0.9-3); liver cirrhosis less than 1.5 ng/ml (range less than 0.9-38), and higher in diseases associated with a high bile acid production: cholestyramine treatment, 188 ng/ml (range 54-477); ileal resection 397 ng/ml (range 128-750). The levels were essentially normal in patients with colon resection. The results are consistent with a strong positive correlation between the levels of 7 alpha-hydroxy-4-cholesten-3-one in plasma and the rate of bile acid synthesis.