Relationship between abnormal cholesterol synthesis and retarded learning in rats

We examined the relationship between brain sterol composition and associative learning (classical conditioning of the eyeblink response) in newly weaned rats fed BM 15.766 (BM) for 4 months. This compound inhibits 7-dehydrocholesterol-delta7-reductase, which catalyzes the conversion of 7-dehydrocholesterol to cholesterol, the last step in the synthetic pathway. As countertreatment, half of the BM-treated rats were fed 2% cholesterol during the last 2 months. With BM, cholesterol concentrations declined 91% in plasma, but with cholesterol feeding, the levels increased 50% compared with baseline values. 7-Dehydrocholesterol, which was not detected at baseline, increased to 55% of plasma sterols with BM but decreased to 5% of total plasma sterols when cholesterol was added. With BM, brain cholesterol levels decreased 60% and did not increase after cholesterol was added. However, 7-dehydrocholesterol, which comprised 39% of brain sterols with BM, decreased to 31% (P < .05) when cholesterol was fed. Hydroxymethyl glutaryl coenzyme A (HMG-CoA) reductase activity in the liver increased 2.2-fold with BM and declined 95% after adding cholesterol, but did not change in the brain. BM treatment for 4 months prevented learning of the conditioned eyeblink response as compared with controls. In contrast, BM-treated rats supplemented with cholesterol acquired the conditioned eyeblink response. Chronic inhibition of 7-dehydrocholesterol-delta7-reductase reduced cholesterol and increased 7-dehydrocholesterol levels in plasma and brain, and was associated with impaired learning. Cholesterol feeding corrected plasma and hepatic sterol levels and reduced brain 7-dehydrocholesterol concentrations to reestablish normal learning.

Sitosterolemia: exclusion of genes involved in reduced cholesterol biosynthesis

Sitosterolemia (phytosterolemia) is a rare autosomal recessively inherited disorder that is characterized by premature coronary artery disease, xanthomas, and increased plasma plant sterols and 5alpha-stanols. Affected individuals show an increased absorption of both cholesterol and sitosterol from the diet, decreased bile clearance of these sterols and their metabolites resulting in markedly expanded whole body cholesterol and sitosterol pools. Biochemical studies have shown that the regulation of the cholesterol biosynthetic pathway may be abnormal in this condition. In particular, the activities and mRNA for the biosynthetic enzymes, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and HMG-CoA synthase are low in liver biopsy specimens isolated from affected individuals, suggesting replete intracellular cholesterol pools. However, the membrane expression of hepatocyte low density lipoprotein receptors was increased, suggesting discordant regulation. Segregation analyses in three families for the genes for HMG-CoA reductase, HMG-CoA synthase, and LDL-receptor excluded these as sites of mutation. In view of the previously described discordant regulation of the above genes in sitosterolemia, the two major regulatory genes for this pathway, sterol regulatory element binding proteins (SREBP-1 and -2), were also examined. These genes did not segregate with the disease and were thus excluded. Two other genes involved in cholesterol absorption and chylomicron secretion, namely acyl coenzyme A:cholesterol acyltransferase (ACAT) and microsomal triglyceride transfer protein (MTP) were also examined for segregation and similarly excluded. Although the gene defect in sitosterolemia therefore remains to be elucidated, important candidate genes have been excluded.

Enrichment of the more hydrophilic bile acid ursodeoxycholic acid in the fecal water-soluble fraction after feeding to rats with colon polyps

We recently showed that feeding the cytoprotective bile acid ursodeoxycholic acid (UDCA) to rats resulted in significant reduction in polyps and especially cancers, both in number and size (D. L. Earnest et al., Cancer Res., 54: 5071-5074, 1994). Because fecal secondary bile acids [particularly deoxycholic acid (DCA)] are considered to promote formation of colon adenomas and cancer, we have now attempted to find a relationship between polyp reduction and fecal secondary bile acids after feeding UDCA to these rats. We examined the fecal bile acids in rats with polyps and compared them with fecal bile acids in control rats and also determined the bile acid composition in fecal aqueous phase, which is in direct contact with the colon epithelium and may be physiologically more active. Treatment with azoxymethane did not significantly alter fecal bile acid composition in the rats. Cholic acid feeding resulted in greatly increased proportions of DCA (82% of total bile acids versus 18% in control rats). On the other hand, UDCA feeding significantly reduced the proportion of fecal DCA (2% in control rats fed UDCA and 3% in rats also treated with azoxymethane). In control rats, 96% of the bile acids were present in the water-insoluble fraction and 4% in the water-soluble fraction. The major insoluble bile acids included DCA and hyodeoxycholic acid (73% of total bile acids). In contrast, the muricholic acids were concentrated in the soluble fraction (37%). When 0.4% UDCA was added to the diet, lithocholic acid increased in the insoluble fraction (40 versus 1%), but the hydrophilic UDCA and muricholic acids were enriched in the water-soluble fraction (37 and 43%, respectively). Thus, the hydrophobic bile acids were distributed predominantly in the water-insoluble fraction, whereas the hydrophilic bile acids were distributed preferentially in the water-soluble fraction. These data suggest that UDCA may prevent colon tumors and polyps by countering the toxic effect of DCA and enhancing the possible cytoprotective effects of UDCA and muricholic acids in the water-soluble fraction in the feces of rat.

Capillary gas chromatographic analysis of serum bile acids as the n-butyl ester-trimethylsilyl ether derivatives

Gas chromatographic separations of n-butyl ester-trimethylsilyl ether derivatives of several common bile acids were compared with those of the corresponding methyl ester-trimethylsilyl ether derivatives on a CP-Sil-5 CB capillary column. Both types of derivatives were similarly resolved from each other. However, the n-butyl ester-trimethylsilyl ether derivatives of the bile acids showed longer retention times than the corresponding methyl ester-trimethylsilyl ethers and unlike the methyl ester-trimethylsilyl ether derivatives, were completely resolved from and eluted later than the trimethylsilyl ethers of common plasma sterols including sitosterol. A simplified method of plasma work-up for quantitation of bile acids and application of the above method in quantification of plasma bile acids in humans is described.

Down-regulation of cholesterol biosynthesis in sitosterolemia: diminished activities of acetoacetyl-CoA thiolase, 3-hydroxy-3-methylglutaryl-CoA synthase, reductase, squalene synthase, and 7-dehydrocholesterol delta7-reductase in liver and mononuclear leukocytes

Sitosterolemia is a recessively inherited disorder characterized by abnormally increased plasma and tissue plant sterol concentrations. Patients have markedly reduced whole body cholesterol biosynthesis associated with suppressed hepatic, ileal, and mononuclear leukocyte 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate-controlling enzyme in cholesterol biosynthetic pathway, coupled with significantly increased low density lipoprotein (LDL) receptor expression. To investigate the mechanism of down-regulated cholesterol biosynthesis, we assayed several other key enzymes in the cholesterol biosynthetic pathway including acetoacetyl-CoA thiolase, HMG-CoA synthase, squalene synthase, and 7-dehydrocholesterol delta7-reductase activities in liver and freshly isolated mononuclear leukocytes from four sitosterolemic patients and 19 controls. Hepatic acetoacetyl-CoA thiolase, HMG-CoA synthase, reductase, and squalene synthase activities were significantly decreased (P < 0.05) -39%, -54%, -76%, and -57%, respectively, and 7-dehydrocholesterol delta7-reductase activity tended to be lower (-35%) in the sitosterolemic compared with control subjects. The reduced HMG-CoA synthase, reductase, and squalene synthase activities were also found in mononuclear leukocytes from a sitosterolemic patient. Thus, reduced cholesterol synthesis is caused not only by decreased HMG-CoA reductase but also by the coordinate down-regulation of entire pathway of cholesterol biosynthesis. These results suggest that inadequate cholesterol production in sitosterolemia is due to abnormal down-regulation of early, intermediate, and late enzymes in the cholesterol biosynthetic pathway rather than a single inherited defect in the HMG-CoA reductase gene.

Competitive inhibition of hepatic sterol 27-hydroxylase by sitosterol: decreased activity in sitosterolemia

We investigated the effect of sitosterol on hepatic sterol 27-hydroxylase activities in subjects with sitosterolemia, a recessive inherited disease associated with accelerated atherosclerosis and increased levels of sitosterol and other plant sterols and stanols in tissues. Hepatic activities of mitochondrial sterol 27-hydroxylase, which catalyzes the first step in the conversion of cholesterol to bile acids via the acidic bile acid synthetic pathway, were measured in liver tissues and related to hepatic microsomal cholesterol 7 alpha-hydroxylase, which controls the rate of bile acid synthesis via the neutral synthetic pathway. These measurements of cholesterol catabolism were correlated to sterol concentrations and composition in plasma and liver. Sterol 27-hydroxylase activities in liver mitochondria of three homozygous sitosterolemic subjects were 68% lower than in 10 control subjects (p < .05) and were associated with increased levels of plant sterols in both plasma and liver (13% and 16% of total sterols, respectively, compared to trace amounts in controls). Analysis of Lineweaver-Burk double reciprocal plots of sterol 27-hydroxylase activities in control human liver specimens (where mitochondrial sterol 27-hydroxylase activities were measured with increasing concentrations of the cholesterol substrate, in the absence and presence of 100 microM and 300 microM sitosterol) revealed that sitosterol inhibited mitochondrial sterol 27-hydroxylase activity up to 50% by a competitive mechanism. In sitosterolemic subjects, competitive inhibition of hepatic sterol 27-hydroxylase activity by sitosterol was associated with competitively inhibited microsomal cholesterol 7 alpha-hydroxylase activity (averages from 4 sitosterolemic homozygotes and 14 controls were 12.4 +/- 1.9 and 23.6 +/- 2.5 pmol/mg/min, respectively). Furthermore, decreased cholesterol catabolism in sitosterolemic subjects was associated with significantly elevated plasma cholesterol concentrations (232 +/- 17 mg/dl, as compared to 180 +/- 13 mg/dl in controls) but with no change in hepatic cholesterol concentrations. In an animal model (rats infused intravenously with sitosterol-containing liposomes that increased sitosterol in the liver and plasma to levels similar to those found in sitosterolemic subjects), hepatic mitochondrial sterol 27-hydroxylase and microsomal cholesterol 7 alpha-hydroxylase activities also decreased significantly and were coupled to markedly elevated plasma sterol concentrations (120.7 +/- 12.5 mg/dl, as compared to 59.2 +/- 6.3 mg/dl in control animals; p < .05) but to no change in hepatic cholesterol concentrations. Thus, decreased cholesterol catabolism due to competitive inhibition of both microsomal cholesterol 7 alpha-hydroxylase and mitochondrial sterol 27-hydroxylase by elevated hepatic sitosterol concentrations contributes to hypercholesterolemia and increased risk of atherosclerosis in sitosterolemia.

Regulation of early cholesterol biosynthesis in rat liver: effects of sterols, bile acids, lovastatin, and BM 15.766 on 3-hydroxy-3-methylglutaryl coenzyme A synthase and acetoacetyl coenzyme A thiolase activities

Cytosolic 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase catalyzes the formation of HMG-CoA, the substrate for the rate-controlling enzyme in the cholesterol biosynthetic pathway. To explore the regulation in liver, we developed a new, accurate, and reliable reversed-phase ion-pair chromatographic assay that uses nonradioactive substrates and n-propionyl coenzyme A as an internal recovery standard. The hepatic activities were measured in rats treated with cholesterol, sitosterol, cholic acid, deoxycholic acid, ursodeoxycholic acid, cholestyramine, bile fistula, lovastatin, and BM 15.766, an inhibitor of 7-dehydrocholesterol delta7-reductase, and were compared with microsomal HMG-CoA reductase and cytosolic acetoacetyl coenzyme A (AcAc-CoA) thiolase activities. HMG-CoA synthase activity was effectively suppressed in synchrony with HMG-CoA reductase activity by treatments with cholesterol (-41%, P < .05), cholic acid (-72%, P < .005), and deoxycholic acid (-62%, P < .05). However, ursodeoxycholic acid increased activity 84% (P < .05) and intravenous sitosterol did not change activity. AcAc-CoA thiolase activities also paralleled HMG-CoA reductase and HMG-CoA synthase activities, but differences were not statistically significant. In contrast to inhibition, up-regulation of hepatic HMG-CoA synthase activities by cholestyramine, bile fistula, and lovastatin was much less than HMG-CoA reductase activities. In addition, BM 15.766 did not stimulate synthase activity, whereas lovastatin increased activity 2.4-fold. Thus, hepatic HMG-CoA synthase activity was regulated coordinately with HMG-CoA reductase, and responded more forcefully to regulatory stimuli than acetoacetyl-CoA thiolase activity but usually less than HMG-CoA reductase.

A study on biliary ductal system and bile fistula in the American alligator, Alligator mississippiensis

The anomalous arrangement of bile ducts in the Crocodylia has not been fully appreciated. A clear understanding of biliary anatomy is necessary in order to create complete bile drainage in these reptiles. The object of this study was to clarify the anatomy of the bile ductal system and to establish total bile fistulas in the American alligator, Alligator mississippiensis. Bile duct anatomy was studied in 104 juvenile alligators, and bile fistulas were constructed in seven alligators. In 93 out of 104 (89%) of the juveniles dissected there was an interconnection between the right and left hepatic duct before the right hepatic duct emptied into the gallbladder. The left hepatic duct then entered the duodenum independently of the cystic duct which drained the gallbladder directly into the duodenum. In 8% of the animals, the left hepatic duct did not enter the duodenum but joined with the right duct, forming a common hepatic duct that emptied into the gallbladder. In 3% of the cases, the right hepatic duct emptied into the gallbladder, while the left duct had no communication with the right hepatic duct and drained separately into the duodenum. This arrangement of bile ducts is similar to that seen in birds and reflects the common ancestry of crocodiles and birds. In other reptiles, the biliary system shows much more variability and is different from the alligator. In five of seven alligators in which total biliary diversion was attempted, the biliary catheter remained in place and stayed patent from 2-7 weeks. Bile flow was extremely low (1.5-2.5 ml/24 h) when compared to that of mammals (80-100 ml/24 h). This study demonstrates the variable nature of the biliary ductal system in Alligator mississippiensis and suggest a method for constructing an effective total bile fistula in these animals.

Increased bile acid pool inhibits cholesterol 7 alpha-hydroxylase in cholesterol-fed rabbits

BACKGROUND & AIMS

Cholesterol feeding unexpectedly inhibits cholesterol 7 alpha-hydroxylase in rabbits. The aim of this study was to explore the mechanism.

METHODS

Twenty male New Zealand white rabbits were fed regular chow with and without 2% cholesterol for 10 days followed by 7 days of bile drainage. The activities of hepatic cholesterol 7 alpha-hydroxylase and sterol 27-hydroxylase that control bile acid synthesis in classic and alternative pathways were related to the size and composition of bile acid pool.

RESULTS

After feeding cholesterol, plasma and hepatic cholesterol concentrations increased, the bile acid pool doubled (from 254 +/- 44 to 533 +/- 51 mg; P < 0.001), cholesterol 7 alpha-hydroxylase activity decreased 68% (P < 0.01), but sterol 27-hydroxylase activity increased 66% (P < 0.05) with increased cholic acid synthesis (P < 0.01). Bile drainage in the cholesterol-fed rabbits depleted the bile acid pool and stimulated down-regulated cholesterol 7 alpha-hydroxylase activity 11.4-fold (P < 0.001), although hepatic cholesterol remained elevated. Hepatic sterol 27-hydroxylase activity was unaffected.

CONCLUSIONS

Feeding cholesterol increased hepatic cholesterol and stimulated sterol 27-hydroxylase and alternative bile acid synthesis, which expanded the bile acid pool and inhibited cholesterol 7 alpha-hydroxylase in rabbits. In distinction, hepatic sterol 27-hydroxylase was insensitive to changes in the bile acid pool.

Comparative effect of dietary sitosterol on plasma sterols and cholesterol and bile acid synthesis in a sitosterolemic homozygote and heterozygote subject

OBJECTIVE

Sitosterolemia is a genetic disorder characterized by an increased plasma plant sterol concentration due to enhanced sterol absorption coupled with reduced steroid excretion. The purpose of the present investigation was two-fold; first to assess the effects of a "basal" low sitosterol metabolic diet on plasma sterols and sterol balance, and, secondly, to quantify the relative influence of graduated increase in dietary sitosterol intake on a metabolic diet in a sitosterolemic homozygote, obligate heterozygote, and controls.

METHODS

Patients were studied under strict metabolic conditions and fed a "basal" 30% fat, low-sitosterol (33 mg per 2000 kcal) diet. The level of dietary sitosterol was increased by addition of oils and resulted in final dietary sitosterol intakes of 1.8 mg/kg, 2.6 mg/kg and 3.5 mg/kg/day intakes of dietary sitosterol in the homozygote. These sitosterol dosages were selected based on sitosterol intakes equivalent to 2.6 mg/kg/day in the average American diet. Plasma cholesterol, sitosterol, and apolipoprotein A were measured, and stool collections assayed for sterol balance.

RESULTS

Fecal sterol excretion and cholesterol synthesis were depressed markedly by 50% in the homozygote compared to the heterozygous parent, whereas plasma sitosterol levels were increased over 50-fold. When the sitosterol content of the diet was increased three-fold and dietary cholesterol was maintained in the homozygous and hypercholesterolemic control, plasma levels did not increase in the homozygote. Plasma cholesterol and sitosterol levels were unaffected in the hypercholesterolemic control.

CONCLUSIONS

Plasma sterol levels remained elevated with the dietary sitosterol changes in the sitosterolemic homozygote. These findings were associated with a low fecal sterol excretion rate and depressed endogenous cholesterol synthesis. In this sitosterolemic patient, a very low sitosterol diet to curtail sterol input was of minimal therapeutic benefit. These results have important implications regarding the selection of therapy for this patient under these experimental conditions, but cannot be generalized to other homozygotes.

Synthesis of [3 alpha-3H]7-dehydrocholesterol via stable tritiated 4-phenyl-1,2,4-triazoline-3,5-dione derivative

Synthesis of [3 alpha-3H]7-dehydrocholesterol is described via protection of the 5,7-diene system in 7-dehydrocholesterol as the Diels-Alder adduct with 4-phenyl-1,2,4-triazoline-3,5-dione followed by oxidation of the hydroxyl group to give the 3-oxo adduct. Reduction of the keto adduct with [3H]sodium borohydride produced the adduct of [3 alpha-3H]7-dehydrocholesterol from which the radiolabeled sterol was obtained via treatment with lithium aluminum hydride. The advantage of the method is that highly labeled [3 alpha-3H]7-dehydrocholesterol can be prepared. Further, unlike 7-dehydrocholesterol, its adduct with 4-phenyl-1,2,4-triazoline-3,5-dione is stable and can be stored. This allows the preparation of small batches of [3 alpha-3H]7-dehydrocholesterol for immediate use in biological experiments, and losses due to decomposition of excess radiolabeled 7-dehydrocholesterol are minimized.

Rapid identification of Smith-Lemli-Opitz syndrome homozygotes and heterozygotes (carriers) by measurement of deficient 7-dehydrocholesterol-delta 7-reductase activity in fibroblasts

To extend the enzyme deficiency in Smith-Lemli-Opitz syndrome (SLOS) to extrahepatic tissues, 7-dehydrocholesterol-delta 7-reductase activity was measured in fibroblasts from 10 controls, five SLOS homozygotes, and five obligate heterozygotes. In cells grown almost to confluence in cholesterol-containing medium (4 mg/dL), the conversion of [1,2-3H]7-dehydrocholesterol to cholesterol (7-dehydrocholesterol-delta 7-reductase activity) was 3.8 times higher in control than in homozygote cells and 2.2 times higher than in heterozygote cells. After 24 hours' exposure of the fibroblasts to cholesterol-deficient medium supplemented with lovastatin, 7-dehydrocholesterol-delta 7-reductase activity increased twofold in controls, but did not change significantly in either heterozygous or homozygous cells. In contrast, the activities of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and lathosterol 5-dehydrogenase, two key enzymes that precede 7-dehydrocholesterol-delta 7-reductase in the cholesterol biosynthetic pathway, and low-density lipoprotein (LDL) receptor-mediated binding were equal in control, homozygote, and heterozygote fibroblasts. Further, HMG-CoA reductase activity and LDL receptor-mediated binding increased after exposure of the cells to cholesterol-deficient medium. Fibroblast cholesterol concentrations were approximately equal, although homozygote cells contained 30 times more 7-dehydrocholesterol. Thus, markedly reduced 7-dehydrocholesterol-delta 7-reductase activity that cannot be upregulated after exposure of the cells to cholesterol-deficient medium is diagnostic for the biochemical defect in SLOS. Significantly reduced enzyme activity between the levels in controls and homozygotes without accumulation of 7-dehydrocholesterol in fibroblasts identified heterozygotes.

Ursocholic acid, a hydrophilic bile acid, fails to improve liver function parameters in primary biliary cirrhosis: comparison with ursodeoxycholic acid

OBJECTIVE

To compare the effect of short term feeding of ursocholic acid, a hydrophilic bile acid, as the unconjugated acid and the taurine conjugate, on clinical and biochemical features and bile acid metabolism with that of ursodeoxycholic acid in four patients with primary biliary cirrhosis.

METHODS

Four patients with stage II primary biliary cirrhosis were studied. Two were fed ursocholic acid (900 mg/day), and two were given tauroursocholate (900 mg/day) in three divided doses. After 1 month, all patients were given 900 mg/day of ursodeoxycholic acid. Fasting serum, bile, and 24-hour urine levels were measured before and at the end of ursocholic acid and tauroursocholate feeding and after 1 month of ursodeoxycholic acid feeding. Clinical and biochemical symptoms were measured by routine hospital methods, and bile acids were measured by gas-liquid chromatography.

RESULTS

One month of ursocholic acid or tauroursocholate feeding did not improve clinical or biochemical findings in any patient. Approximately 21-25% ursocholic acid was present in the serum and bile, with substantial metabolism to deoxycholic acid. Increased ursocholic acid was excreted in the urine. In comparison, ursodeoxycholic acid improved biochemical parameters and was 45-65% enriched in the serum and bile.

CONCLUSION

Ursocholic acid as the free bile acid or as taurine conjugate, although more hydrophilic, is poorly enriched in serum and bile and is ineffective in patients with primary biliary cirrhosis.

7 beta-hydroxy bile alcohols: facile synthesis and 2D 1H NMR studies of 5 beta-cholestane-3 alpha, 7 beta, 12 alpha, 25-tetrol

A rapid and easily performed procedure for the synthesis of 5 beta-cholestane-3 alpha, 7 beta, 12 alpha, 25-tetrol by means of an efficient homologation sequence of the intermediate, 3 alpha, 7 beta, 12 alpha-triformyloxy-24-oxo-25-diazo-25-homo-5 beta-cholane is described. The reaction sequence involved treating the intermediate, alpha-diazoketone in methanol with 3% AgNO3 or Ag2O, anhydrous Na2CO3, Na2S2O/H2O resulting in the formation of homoursocholic acid in high yield. Esterification of the homoursocholic acid in methanol containing a catalytic amount of methanesulfonic acid under microwave irradiation conditions gave methyl homourscholate. The subsequent treatment of methyl homoursocholate with methyl magnesium iodide provided 5 beta-cholestane-3 alpha, 7 beta, 12 alpha, 25-tetrol in 88% yield. The products and synthetic intermediates prepared in these studies were fully characterized by the results of 1D and 2D NMR, and high-resolution mass spectral studies. These studies will help in further investigation of the defect of cholic acid biosynthesis in patients with cerebrotendinous xanthomatosis (CTX) as well as other inborn errors of bile acid metabolism.

Rapid hydrogenation of unsaturated sterols and bile alcohols using microwaves

This paper describes an operationally simple, rapid hydrogenation of unsaturated sterols and bile alcohols in a domestic microwave oven. This has been achieved by the addition of catalytic amounts of Pd/C in methylene chloride/propylene glycol solvents in the presence of ammonium formate followed by microwave irradiation. It is suggested that this methodology will be helpful in the identification of saturated and unsaturated sterols with different side-chain structures in rare diseases: sitosterolemia, cerebrotendinous xanthomatosis (CTX), as well as atherosclerosis and diabetes mellitus. Sterols, such as cholesterol, campesterol, sitosterol, and bile alcohols with unsaturated side chains, were converted to their reduced congeners with high yield and purity.

Capillary gas-liquid chromatography of acetate-methyl esters of bile acids

Gas-liquid chromatographic separations of acetate-methyl esters of several common bile acids with and without a hydroxyl group at C-6 are compared with those of the corresponding trimethylsilyl ether-methyl esters on a CP-Sil-5 CB capillary column. Unlike the trimethylsilyl ether derivatives, the retention indices of the corresponding acetates were greatly influenced by the number of hydroxyl groups in the ring system. Epimeric hydroxyl groups at carbons 6, 7 as well as 12 increased retention index of the acetate-methyl esters of the bile acids, the effect of the 7 beta-hydroxyl group being most prominent. The 6 beta-acetoxyl group increased the retention index more than the 6 alpha-acetoxy group and contrary to the trimethylsilyl ether derivatives, a 6 beta, 7 beta-diacetoxy group showed larger increase in the retention index than the corresponding 6 alpha, 7 beta-diacetoxy group. The acetate derivatives of bile acid-methyl esters show larger retention times and reduced sensitivity than the corresponding trimethylsilyl ether derivatives. However, gas chromatography of bile acid acetate-methyl esters can be very useful for the characterization of bile acids and for bile acid analysis in the rat where muricholic acids and hyodeoxycholic acid are in abundance, since these bile acids are difficult to resolve from each other and from other common bile acids as the trimethylsilyl ether derivatives.

Sterol concentrations in cultured Smith-Lemli-Opitz syndrome skin fibroblasts: diagnosis of a biochemically atypical case of the syndrome

The Smith-Lemli-Opitz syndrome is a common birth defect syndrome caused by a deficiency of 7-dehydrocholesterol delta 7-reductase, an essential enzyme in the biosynthesis of cholesterol. The syndrome can usually be diagnosed easily from the plasma markers of markedly elevated 7-dehydrocholesterol and reduced cholesterol concentrations. However, atypical cases with normal plasma levels of cholesterol with only moderately elevated 7-dehydrocholesterol have been reported. To establish a sensitive method for the biochemical diagnosis of the atypical cases of the syndrome, we measured sterol concentrations of cultured skin fibroblasts. 7-Dehydrocholesterol concentrations in patients' fibroblasts grown in the presence of 10% fetal bovine serum were significantly higher than those in controls and parents (P < 0.0005), but they were not elevated proportionately as much as in plasma. To re-produce the accumulation of 7-dehydrocholesterol, the cells were exposed to delipidated medium to induce sterol biosynthesis. After 4 weeks, 7-dehydrocholesterol concentrations in patients' fibroblasts increased from 2.8 +/- 0.3% to 34 +/- 3% of total sterols (cholesterol + 7-dehydrocholesterol + 8-dehydrocholesterol). The increase was also observed in fibroblasts from an atypical patient who has a normal plasma cholesterol level and a 7-dehydrocholesterol concentration of only 0.15 mg/dl. In contrast, cells from parents and controls accumulated very little 7-dehydrocholesterol (< 1% of total sterols). These results demonstrate that cultured fibroblasts exhibit abnormally high accumulation of 7-dehydrocholesterol after cells are exposed to delipidated medium not only in typical patients, but also in an atypical case. The present method is a sensitive procedure for the biochemical diagnosis of this syndrome.

Clinical effects of cholesterol supplementation in six patients with the Smith-Lemli-Opitz syndrome (SLOS)

We describe the clinical effects of cholesterol supplementation in 6 children with the RSH-"Smith-Lemli-Opitz" syndrome (SLOS). The children ranged in age from birth to 11 years at the onset of therapy, with pretreatment cholesterol levels ranging from 8 to 62 mg/dl. Clinical benefits of therapy were seen in all patients, irrespective of age at onset of treatment, or severity of cholesterol defect. Effects of treatment included improved growth, more rapid developmental progress, and a lessening of problem behaviors. Pubertal progression in older patients, a better tolerance of infection, improvement of gastrointestinal symptoms, and a diminution in photosensitivity and skin rashes were also noted. There were no adverse reactions to treatment with cholesterol. This preliminary study suggests that cholesterol supplementation may be of benefit to patients with the SLOS.

Treatment of Smith-Lemli-Opitz syndrome: results of a multicenter trial

Patients with the RSH or Smith-Lemli-Optiz syndrome (SLOS) have an inborn error of cholesterol biosynthesis which results in a deficiency of cholesterol and an elevation of the cholesterol precursor, 7-dehydrocholesterol. A treatment protocol consisting of administration of cholesterol +/- bile acids was initiated in an attempt to correct the biochemical abnormalities seen. Fourteen patients (8 female, 6 male: ages 2 months to 15 years) have now been treated for 6-15 months. Three patients received cholesterol alone, while 11 patients received cholesterol and one or more bile acids. Biochemical improvement in sterol levels and in the ratio of cholesterol to total sterols was noted in all patients. The most marked improvement was noted in patients presenting with initial cholesterol levels < 40 mg/dl. No toxicity was observed. Clinical improvement in growth and neurodevelopmental status was also observed.

Screening for abnormal cholesterol biosynthesis in the Smith-Lemli-Opitz syndrome: rapid determination of plasma 7-dehydrocholesterol by ultraviolet spectrometry

The Smith-Lemli-Opitz syndrome (SLOS) is a common condition caused by deficiency of 7-dehydrocholesterol delta 7-reductase. The syndrome can usually be diagnosed by demonstrating markedly increased plasma concentrations of the cholesterol precursor, 7-dehydrocholesterol. We describe a simple and rapid method for detection of plasma 7-dehydrocholesterol by use of ultraviolet (UV) spectrometry. Lipids were extracted from plasma by addition of ethanol and n-hexane, and the n-hexane phase was directly subjected to spectrometry. The absorption maxima characteristics of 7-dehydrocholesterol (lambda max 271, 282, and 294 nm) were observed in patients' plasma but not in controls. For quantitative measurements, absorbance at 282 nm was used. Since this absorbance is the sum of the absorbance derived from 7-dehydrocholesterol and background absorbance, the concentrations of 7-dehydrocholesterol in various plasma samples were quantified by subtracting estimated background absorbance at 282 nm from observed absorbance at 282 nm. The results correlated well with total (free plus esterified) 7-dehydrocholesterol concentrations measured by gas-liquid chromatographic method. The UV spectrometric assay was sensitive enough to detect increased 7-dehydrocholesterol in cultured skin fibroblasts from patients grown in delipidated medium. The present method will make it possible to screen plasma or fibroblasts to detect the syndrome rapidly in general clinical laboratories.

Cholesterol 7alpha-hydroxylase activities from human and rat liver are modulated in vitro posttranslationally by phosphorylation/dephosphorylation

Purified cholesterol 7alpha-hydroxylases (C7alphaH) from human and rat liver microsomes, and from transformed Escherichia coli expression systems, were incubated with 0.3 mmol/L [gamma-32P] adenosine triphosphate (ATP) in the presence and absence of bacterial alkaline phosphatase (AP) or rabbit muscle adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase. The amounts of 32P incorporation after separation of human and rat C7alphaH proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) were related to C7alphaH catalytic activities (determined by a radioisotope incorporation method) and enzyme protein mass (determined by Western blotting and laser densitometry). Both human and rat C7alphaH activities significantly decreased after dephosphorylation by AP (-57% - -72%) and increased up to twofold with phosphorylation by rabbit muscle cAMP-dependent protein kinase. The increases in C7alphaH activities were proportional to the amounts of cAMP-dependent protein kinase used, and were coupled to 32P incorporation into the purified enzymes. Both the activation of C7alphaH and the amounts of 32P incorporation were time-dependent and reached a maximum after 1 hour of incubation with 5 U of cAMP-dependent protein kinase. In a second set of experiments, purified human and rat liver C7alphaH were dephosphorylated by 30-minute incubation with AP, followed by inactivation of the phosphatase by the inhibitor NaF, and rephosphorylation of C7alphaH by 30-minute incubation with rabbit muscle cAMP-dependent protein kinase or bovine heart cAMP-independent protein kinase. Rephosphorylation of the dephosphorylated C7alphaH proteins by cAMP-dependent protein kinase increased C7alphaH catalytic activities up to fourfold, and the stimulation in catalytic activities paralleled the increases in 32P incorporation into the purified enzymes. Bovine heart protein kinase was as potent as rabbit muscle cAMP-dependent protein kinase in stimulating catalytic activity and 32P incorporation into the human C7alphaH protein. Because the protein mass of these purified enzymes did not change, the short-term regulation or catalytic efficiency of C7alphaH (activity per protein mass unit) is modulated, in vitro, posttranslationally by a phosphorylation/dephosphorylation mechanism in both the human and the rat enzymes.