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Biomedical subjects

A Honda

Publications and source records attributed to A Honda.

At least 91 records · Page 5Linked to original sources
PubMed1998

Effects of progestins on the metabolism of cancellous bone in aged oophorectomized rats.

The effects of progestins on bone loss in female oophorectomized (ovx) rats were evaluated. One-year-old Sprague-Dawley rats were divided into eight groups: (1) beginning controls (control); (2) sham-operated controls (sham); (3) ovx; (4) ovx treated with estrogen (ovx + E); (5) ovx treated with progesterone (ovx + P); (6) ovx treated with estrogen and progesterone (ovx + E + P); (7) sham group treated with estrogen (sham + E); and (8) sham group treated with progesterone (sham + P). Immediately after surgery, the rats in the hormone injected groups were subcutaneously (s.c.) injected daily for 15 weeks with estrogen (17-beta-estradiol, 0.01 mg/kg in ethanol), or progesterone (4-pregnene-3,20-dione, 0.1 mg/kg in ethanol), or both. At the end of 15 weeks, the bone mineral density (BMD) and bone histomorphometry of the rats' lumbar vertebrae and serological parameters were measured. In the sham, ovx, and ovx + P groups, treatment with progesterone alone did not maintain the BMD in the lumbar vertebrae, but in the ovx + E and ovx + E + P, sham + E, and sham + P groups, progesterone did not inhibit the action of estrogen in the aged ovx rat model. BMD in the sham + P group was significantly higher than in the sham group (270.8+/-10.8 mg/cm2 versus 253.6+/-10.2 mg/cm2; p < 0.01). Bone histomorphometry revealed that bone volume (BV/TV) increased more in the ovx + E + P group than in the ovx + E group and more in the sham + P group than in the sham group, but not significantly. The ovx + E, ovx + E + P, sham + E, and sham + P groups showed no significant differences in the bone formation and resorption parameters, but the bone formation variables tended to increase in the ovx + E + P and sham + P groups. We concluded that progesterone alone cannot prevent bone loss or the increase in turnover after ovx and that estrogen, not progesterone, accounted for all of the bone activity in this study. It seems doubtful that progesterone inhibits the action of estrogen, and in fact may have a beneficial effect on bone metabolism.

Animals↗
PubMed1998

Accurate detection of Smith-Lemli-Opitz syndrome carriers by measurement of the rate of reduction of the ergosterol C-7 double bond in cultured skin fibroblasts.

The activity of ergosterol delta 7-reductase (3 beta-hydroxysteroid delta 7-reductase) was measured in cultured skin fibroblasts from 7 controls, 10 Smith-Lemli-Opitz syndrome (SLOS) patients, and 10 parents (obligate carriers). The fibroblasts were exposed to delipidated medium supplemented with lovastatin for 24 h and the enzyme activity was determined by incubating cell-free homogenate with ergosterol (ergosta-5,7,22-trien-3 beta-ol) and measuring the mass of brassicasterol (ergosta-5,22-dien-3 beta-ol) formed by gas chromatography-mass spectrometry with selected-ion monitoring. In carriers, the activity was significantly lower than in controls (22 +/- 2 vs 65 +/- 10 pmol/min per mg protein, p < 0.0005), and no overlap was observed. The mean activity in carriers' fibroblasts was more than 100 times higher than in patients' cells (0.2 pmol/min per mg protein). The use of ergosterol avoids the many problems caused by the instability and lack of availability of radiolabelled 7-dehydrocholesterol. The present method makes it possible to discriminate SLOS carriers from both controls and patients using a commercially available substrate and common analytical equipment.

Cells, Cultured↗
PubMed1998

Cholesterol and oxygenated cholesterol concentrations are markedly elevated in peripheral tissue but not in brain from mice with the Niemann-Pick type C phenotype.

Niemann-Pick disease type C (NP-C) is a rare genetic disorder characterized by progressive neurodegeneration, frequent developmental delay and early death. Tissues of affected individuals accumulate large quantities of free cholesterol in lysosomes. Because cytotoxic oxygenated derivatives of cholesterol are known to form readily when cholesterol concentrations are elevated, we searched for these compounds in liver, kidney, spleen and brain from mice with the NP-C phenotype. In order of abundance, we identified 7 alpha- and 7 beta-hydroxycholesterol, 5 alpha, 6 alpha-epoxycholestan-3 beta-ol, 4 beta-hydroxycholesterol, cholest-4-en-3 beta, 7 alpha-diol and cholest-4-en-3 beta, 6 beta-diol in most tissue samples. Cholesterol concentrations in affected mice were increased 3-fold in kidney and 7- to 8-fold in spleen and liver compared to controls (all p < 0.001) but were unchanged in brain. Although oxysterol levels were markedly elevated in nonbrain tissue, the oxysterol and cholesterol concentrations increased proportionally so that oxysterols expressed as percentage of total sterols were the same for all animals (0.34 +/- 0.19% averaged over all organs in affected animals vs 0.40 +/- 0.42% in control mice). In contrast to peripheral tissue, we could not detect any increase in either absolute or relative oxysterol levels in the brains of affected and control mice (49 +/- 61 vs 53 +/- 43 micrograms/g wet weight and 0.45 +/- 0.52 vs 0.47 +/- 0.37%, respectively). Thus, brain sterols are normal in NP-C mice and it is unlikely that an accumulation of cytotoxic oxygenated derivatives of cholesterol could account for the progressive neuropathology seen in the disease.

Animals↗
PubMed1998

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.

Acetyl-CoA C-Acetyltransferase↗
PubMed1998

[A case of primary lung cancer presenting as pneumothorax].

A 62-year-old man presented pneumothorax as a first manifestation of lung cancer was described. The patient complained right side chest pain and dry cough of 6 days duration. On the day of admission, a chest radiograph showed a large pneumothorax on the right. After 3 days of tube drainage, the lung was re-expanded and a chest radiograph showed a mass density above the right hilum. A chest CT revealed a cavitating tumor of the right upper lobe with a fistula to the pleural space. Right upper lobectomy was performed, and the histology was squamous cell carcinoma. The cause of pneumothorax was bronchopleural fistula secondary to rapid growth of the cancer. Pneumothorax due to primary lung cancer is rare and the prognosis is poor because the cancer was advanced stage or diagnosis of cancer was delayed in the literature review. Lung cancer should always be considered as a possible cause of pneumothorax, and it is important to diagnose lung cancer as soon as possible.

Carcinoma, Squamous Cell↗
PubMed1998

[An operative case of primitive neuroectodermal tumor in the posterior mediastinum].

A primitive neuroectodermal tumor (PNET) is very rare and the prognosis of this tumor is poor. A 32-year-old woman complaining of dysphagia and back pain was admitted to our hospital for the posterior mediastinal tumor. The tumor originated from the muscle layer of esophagus and en bloc resection of the tumor combined with the affected part of esophagus was performed. Histopathological diagnosis of the resected tumor was PNET. She received adjuvant chemotherapy. Eight months after the surgery, recurrent tumors in the right mediastinum and the retrooperitoneal space was resected completely. But after the second surgery, dissemination occurred recurrently. These recurrent tumors revealed high sensitivity for radio-therapy. However, she died of rapid recurrence 22 months after the first surgery. In Japan, our case is the second case of PNET in the posterior mediastinum and the first case of PNET arising from the muscle layer of esophagus.

Adult↗
PubMed1998

7-Dehydrocholesterol down-regulates cholesterol biosynthesis in cultured Smith-Lemli-Opitz syndrome skin fibroblasts.

The Smith-Lemli-Opitz syndrome (SLOS) is a common birth defect-mental retardation syndrome caused by a defect in the enzyme that reduces 7-dehydrocholesterol to cholesterol. Because of this block, patients' plasma cholesterol levels are generally low while 7-dehydrocholesterol concentrations are markedly elevated. In addition, plasma total sterols are abnormally low and correlate negatively with the percent of 7-dehydrocholesterol (r = -0.65, P < 0.0001) suggesting that 7-dehydrocholesterol might inhibit the activity of HMG-CoA reductase. Cultured skin fibroblasts from SLOS patients grown in fetal bovine serum or for 1 day in delipidated medium contain little 7-dehydrocholesterol (3 +/- 1% of total sterols) and HMG-CoA reductase activities are indistinguishable from that measured in control cells. However, raising the 7-dehydrocholesterol concentration to 20 +/- 3% of total sterols, equal to the mean proportion in plasma of SLOS patients, by either growing cells for 1 week in delipidated medium or adding 20 microg/ml 7-dehydrocholesterol directly to the cells reduced HMG-CoA reductase activities from 74 +/- 7 to 9 +/- 2 pmol/min per mg protein, or from 92 +/- 22 to 16 +/- 4 pmol/min per mg protein, respectively (P < 0.01). In contrast, adding 20 microg/ml cholesterol evoked a 2- to 4-fold lesser suppression of activity (39 +/- 8 pmol/min per mg protein, P < 0.05, vs. 7-dehydrocholesterol). HMG-CoA synthase and LDL binding were inhibited equally by 7-dehydrocholesterol and cholesterol. Ketaconazole prevented the down-regulation of HMG-CoA reductase by 7-dehydrocholesterol, suggesting that an hydroxylated derivative of 7-dehydrocholesterol may be especially important in suppressing cholesterol synthesis. These results demonstrate that 7-dehydrocholesterol, perhaps as an hydroxylated derivative(s), is a very effective feedback inhibitor of HMG-CoA reductase.

Cells, Cultured↗
PubMed1998

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.

Adult↗
PubMed1998

[A case of pulmonary arteriovenous fistula beneath the surface of the lung].

A 19-year-old woman complaining of exertional dyspnea was admitted to our hospital with an abnormal shadow on the left side of the chest. Laboratory examination revealed polycythemia and hypoxemia. Pulmonary angiogram demonstrated a pulmonary arteriovenous fistula beneath the surface of the left S10. Partial resection of the left S10 was performed. The wall of the arteriovenous fistula was flimsy and seemed to rupture easily. The sister of this patient also had a peripheral pulmonary arteriovenous fistula and suffered from repeating epistaxis. Rendu-Osler-Weber disease was diagnosed in both, and the sister underwent partial resection of the right S7, which contained the fistula. Their postoperative courses were uneventful. Hemothorax and hemoptysis are lethal complications of arteriovenous fistulae. In order to avoid the rupture of fistulae, surgical resection is the most reliable treatment. Pulmonary arteriovenous fistulae beneath the surface of the lung should be resected.

Adolescent↗
PubMed1998

[Two cases of solitary peripheral pulmonary arterial aneurysm].

We report two very rare cases of solitary peripheral pulmonary arterial aneurysm. Case 1: An 83-year-old man treated for myocardial infarction died of multiple organ failure and hemoptysis. Autopsy disclosed rupture of a pulmonary arterial aneurysm 1.5 cm in diameter in the right A3. Case 2: A 75-year-old man was found to have a pulmonary arterial aneurysm, 3 cm in diameter of the right A1. Surgical treatment was not indicated, because of severe pulmonary emphysema. The aneurysms in these two cases were idiopathic: (1) there were no histologic findings that would implicate specific chronic inflammation. (2) the period from the occurrence of secondary pulmonary hypertension to hemoptysis was short, and there was no (3) history of trauma.

Aged↗
PubMed1998

Fetal Smith-Lemli-Opitz syndrome can be detected accurately and reliably by measuring amniotic fluid dehydrocholesterols.

The Smith-Lemli-Opitz syndrome, characterized by limb, face and organ abnormalities, and mental retardation, is caused by an inherited block in the step of cholesterol biosynthesis in which the delta 7 double bond of 7-dehydrocholesterol is reduced. It is diagnosed by the presence of markedly elevated levels of 7-dehydrocholesterol and 8-dehydrocholesterol in plasma and tissue. We measured amniotic fluid sterols in 15 pregnancies in 13 women who had previously carried an affected fetus. Cholesterol, 7-dehydrocholesterol and 8-dehydrocholesterol concentrations averaged 18 +/- 3, 9.8 +/- 2.9 and 5.0 +/- 1.7 micrograms/ml, respectively, in seven pregnancies with an affected fetus or child. In contrast, these levels were 19 +/- 3, 0.05 +/- 0.01 and < 0.005 micrograms/ml, respectively, in eight increased-risk pregnancies with normal outcomes and 16 +/- 2, 0.07 +/- 0.01 and < 0.005 micrograms/ml in normal controls. 7-dehydrocholesterol concentrations, 2.2-26 and 0.05-0.10 micrograms/ml in pregnancies with an affected and unaffected fetus, respectively, did not overlap. Thus, abnormally elevated amniotic fluid dehydrocholesterol concentrations are an accurate predictor of fetal Smith-Lemli-Opitz syndrome. A false-positive or a false-negative result is highly unlikely.

Adult↗
PubMed1998

Regulation of rat hepatic 3beta-hydroxysterol delta7-reductase: substrate specificity, competitive and non-competitive inhibition, and phosphorylation/dephosphorylation.

The mechanism for the catalytic reduction of the double bond at C-7, 8 in 7-dehydrocholesterol by 3beta-hydroxysterol Delta7-reductase was investigated by testing structurally related sterols as substrates and potential inhibitors. The hepatic smooth endoplasmic reticulum was identified as the site of enzyme activity. All putative substrates contained 27 carbons, but differed from 7-dehydrocholesterol by the addition of either an ethyl substituent at C-24 (7-dehydrositosterol), a double bond at C-22 with a methyl substituent at C-24 (ergosterol), epimerization of the hydroxyl from the 3beta- to 3alpha-configuration (7-dehydroepicholesterol), or a saturated double bond at C-5,6 (lathosterol). Two non-steroidal compounds that inhibit 3beta-hydroxysterol Delta7-reductase in vivo (AY 9944 and BM 15.766) were also tested. Ergosterol, 7-dehydrositosterol, and 7-dehydroepicholesterol were reduced at C-7, 8 to form brassicasterol, sitosterol, and epicholesterol, respectively, but 75% less efficiently than 7-dehydrocholesterol. Increasing concentrations of these sterols competitively inhibited 3beta-hydroxysterol Delta7-reductase activity. The double bond at C-7,8 in lathosterol was not reduced. AY 9944 and BM 15.766 inhibited 3beta-hydroxysterol Delta7-reductase activity non-competitively. 3beta-Hydroxysterol-Delta7-reductase activity declined after microsomes were exposed to alkaline phosphatase, and enzyme activity was increased by phosphorylation with Mg2+, and ATP. These results demonstrate that the reduction of the double bond at C-7,8 requires binding of the enzyme protein with the B-ring of the sterol substrate that contains a double bond at C-5,6. The reaction is hindered by substituents located on the apolar side-chain and epimerization of the hydroxyl group in ring A to a 3alpha-configuration. 3beta-Hydroxysterol Delta7-reductase exists in two forms: an active phosphorylated form and an inactive dephosphorylated form.

Animals↗
PubMed1997

A novel HSP70 gene of Schizosaccharomyces pombe that confers K-252a resistance.

A new gene encoding a heat shock protein 70 family protein of Schizosaccharomyces pombe (Sp), named sks2+, was cloned as a weak suppressor for the K-252a-sensitive mutation, ucm1. The nucleotide sequence of sks2+ revealed an open reading frame of a 613-amino-acid (aa) protein. The deduced aa sequence of sks2+ showed significant homology with Saccharomyces cerevisiae (Sc) Ssb1p and Ssb2p responsible for protein synthesis by non-organelle-localized ribosomes, as well as with other proteins of the HSP70 family. The cells lacking the functional sks2+ gene were viable and showed no increased sensitivity to K-252a but grew slowly with an elongated morphology. These results suggest that the sks2+ gene product plays a role in the cell cycle progression and is able to confer drug resistance in a multicopy state.

Amino Acid Sequence↗
PubMed1997

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.

Cells, Cultured↗
PubMed1997

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.

Adolescent↗
PubMed1997

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.

Adult↗
PubMed1997

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.

Fibroblasts↗