Cortisol producing adrenal adenoma--a new manifestation of Gardner's syndrome.

INTRODUCTION: Familial adenomatous polyposis (FAP) is an autosomal dominant disorder which typically presents with colorectal cancer in early adult life secondary to extensive adenomatous polyps of the colon. Gardner's syndrome is a variant of FAP in which desmoid tumors, osteomas and pigmented retinal lesions occur together with intestinal manifestations. The APC gene (adenomatous polyposis coli) at 5q21 is a tumor suppressor gene which is mutant in FAP. PATIENT: A 36 year old woman presented with a history of polyposis ventriculi, ovarian desmoid cysts, and disseminated desmoid tumors. Her familial history was unremarkable. On admission she complained weight gain, secondary amenorrhea, and episodes of hypertension followed by paroxysmal headache. RESULTS: Elevated urinary free cortisol (878 microg/24h), suppressed basal ACTH (< 5 pg/ml) and insuppressible serum cortisol after low dose dexamethasone (189 ng/ml) revealed adrenal Cushing's syndrome. Abdominal NMR showed an adrenal mass two centimeter in diameter with inhomogeneous contrast enhancement. Unilateral adrenalectomy was performed and an adrenal adenoma was diagnosed by histological criteria. For mutational detection DNA from peripheral blood leucocytes was extracted. A protein truncation test was performed, which revealed a termination mutation between codon 1099 and 1623 of the APC gene. Direct sequencing showed a point mutation in exon 15 of the APC gene at position 1542 (CAG --> TAG). This region is known to be altered in patients with extraintestinal manifestation of FAP. CONCLUSION: In patients with Gardner's syndrome adrenal tumors leading to hormonal excess should be considered. Whether mutations in the APC gene have implications in sporadic adrenal tumorigenesis needs to be proven.

A phase II study of weekly 24-h infusion of high-dose 5-fluorouracil in advanced pancreatic cancer.

No single agent or combination chemotherapy protocol, with the exception of gemcitabine, has so far proven superior to standard bolus 5-fluorouracil regimes for the treatment of advanced pancreatic cancer. The present phase II trial was designed to study whether the effectivity of 5-fluorouracil can be improved with a weekly high-dose 5-fluorouracil schedule. 26 patients with cytologically or histologically verified, metastasized (n = 21) or locally advanced (n = 5) previously untreated adenocarcinoma of the pancreas were included in this study. Treatment consisted of weekly applications of 2,600 mg/m2 5-fluorouracil as 24-h infusion on days 1, 8, 15, 22, 29, 36. Treatment was repeated at day 50 and was continued until disease progression. Primary endpoints of the study were response rates and toxicity, secondary endpoints were survival and clinical benefit in terms of performance status, body weight and analgesia consumption. Toxicity of the regimen was mild with only four instances of grade-3 toxicity. Response rates were 8% (95% CI = 1.2-13.7) with two partial remissions. Improvement of at least one parameter of clinical benefit for > or = four weeks was observed for 11.5% of the study patients. The most prominent effect was a transient stabilization of objective tumor measurements (48% [95% CI = 27.8-68.7]) and individual parameters of clinical benefit (50-75%). Median survival was 248 days (95% CI = 164-459) for all patients included in the study. The present study indicates that the high-dose 5-fluorouracil regimen shows weak activity in advanced pancreatic cancer which seems comparable to gemcitabine.

Abnormalities in lipoprotein metabolism in hemodialysis patients.

BACKGROUND: Patients on chronic hemodialysis treatment are at elevated atherogenic risk, and dyslipidemia appears to be one of the major risk factors. However, most of these patients exhibit elevated serum triglycerides, whereas serum cholesterol and low-density lipoprotein (LDL) cholesterol levels are in the normal range. This study was therefore designed to examine the influence of hypertriglyceridemia under the condition of hemodialysis and diabetes mellitus on LDL metabolism. METHODS: LDL was isolated from healthy controls, hypertriglyceridemic diabetic patients, and nondiabetic hemodialysis patients (N = 30, 10 in each group), which were separated into six subfractions by density gradient ultracentrifugation and were characterized concerning lipid/protein composition, degree of glycation, and oxidation. Uptake of 125I-labeled LDL was examined via LDL receptors of HepG2 cells and scavenger receptors of mouse peritoneal macrophages. RESULTS: In hemodialysis patients, serum triglycerides were significantly elevated, whereas cholesterol levels were within the normal range. Triglyceride enrichment occurred in the very low-density lipoprotein (VLDL) class and LDL class, and an accumulation of a highly atherogenic small dense LDL subfraction could be detected predominantly in patients with non-insulin-dependent diabetes mellitus. LDL of hemodialysis patients also contained elevated levels of lipid peroxidation products, which were even higher in diabetic patients. Alterations in composition, size, and configuration of LDL from diabetic and nondiabetic patients on hemodialysis impaired LDL receptor-mediated degradation and enhanced the uptake of these modified LDL particles via nonsaturable scavenger receptors. CONCLUSION: Diminished LDL receptor-mediated uptake of modified, triglyceride-rich, small dense LDL most likely leads to accumulation of these lipoproteins in vivo, favoring the development of atherosclerotic lesions. Future clinical studies must demonstrate whether patients will benefit from reducing these atherogenic particles by lipid-lowering intervention.

Structural and compositional modifications of diabetic low-density lipoproteins influence their receptor-mediated uptake by hepatocytes.

Dyslipoproteinaemia is an important risk factor for the development of atherosclerosis in noninsulin-dependent diabetes mellitus (NIDDM). This study shows that the uptake of low-density lipoproteins (LDLs) prepared from the plasma of patients with NIDDM in cultured human hepatoma cells is largely reduced. In addition, diabetic LDL was less effective in suppressing intracellular cholesterol synthesis. This is because of physicochemical and biochemical differences between lipoproteins from diabetic and from normal individuals. LDL from patients with NIDDM was abnormal with regard to charge, the degree of glycation, the lipid composition and the conformation of the apolipoprotein B receptor-binding domain. The diminished receptor-mediated uptake of apolipoprotein B-containing lipoproteins in diabetic individuals most probably leads to the accumulation of these lipoproteins in vivo and may be of great importance to the pathogenesis of atheroclerosis in these patients.

Receptor-mediated lipoprotein uptake by human glomerular cells: comparison with skin fibroblasts and HepG2 cells.

BACKGROUND: Currently the mechanisms of glomerular lipid accumulation are not completely understood. The present study characterizes the mechanisms of lipid uptake by glomerular cells. Since renal diseases are frequently associated with an accumulation of apoE-containing triglyceride-rich lipoproteins, we were interested to investigate whether glomerular epithelial or mesangial cells possess VLDL receptors besides the well established LDL receptors. METHODS: Uptake kinetics of 125I-labelled very-low-density lipoproteins (VLDL) and low-density lipoproteins (LDL) in human glomerular epithelial and mesangial cells were compared to lipid uptake in cells with established receptor status, i.e. human skin fibroblasts and HepG2 cells. RESULTS: Glomerular epithelial cells, mesangial cells, and skin fibroblasts as well as hepatocytes express VLDL receptor mRNA, indicating that they exhibit VLDL receptors. VLDL uptake in glomerular epithelial cells, mesangial cells and skin fibroblasts occurred with a lower specificity than in HepG2 cells (-25%). No differences were found for the specificity of LDL uptake. VLDL uptake in HepG2 cells was inhibited more effectively with VLDL than with LDL. In skin fibroblasts, glomerular epithelial and mesangial cells, VLDL and LDL were equally effective inhibitors of VLDL uptake. The degradation-uptake ratio of VLDL in glomerular cells was elevated 50% compared to HepG2 cells, suggesting highly efficient intracellular lipoprotein turnover in these cells. CONCLUSION: We conclude that glomerular epithelial and mesangial cells as well as skin fibroblasts and HepG2 exhibit VLDL receptors additionally to their LDL receptors, even though the regulation of the VLDL receptor in HepG2 cells seems to differ from the regulation in glomerular epithelial and mesangial cells. The high degradation-uptake-ratio in these renal cells suggests the presence of an effective clearance pathway which might serve as protection against lipoprotein accumulation.

Preferential uptake of intermediate-density lipoproteins from nephrotic patients by human mesangial and liver cells.

Hyperlipidemia of nephrotic origin could potentially cause glomerular injury as well as increase the risk of atherosclerosis. The precise interaction of human lipoproteins abnormal in lipid and protein composition, with lipoprotein receptors has not been clearly defined. This study examines receptor-mediated uptake and intracellular cholesterol metabolism of apolipoprotein (apo)B,E containing intermediate-density lipoprotein (IDL) and apoB-100 containing low-density lipoprotein (LDL), isolated from patients with the nephrotic syndrome (N = 6), in human glomerular mesangial and HepG2 cells. In the patients, serum IDL and LDL cholesterol levels were significantly increased as compared with those of healthy subjects. The IDL of nephrotic patients contained 80% more cholesterol than the IDL of healthy controls. No differences in lipid/protein composition were found in the LDL density range. Therefore, nephrotic and control LDL showed identical affinities for receptor-mediated uptake. In contrast, the IDL of nephrotic patients was taken up by mesangial cells and HepG2 with higher affinity than the LDL. Intracellular sterol synthesis was suppressed more effectively and cholesterol esterification rate was enhanced 2.2-fold by nephrotic IDL as compared with control IDL. These data indicate that hypercholesterolemia of nephrotic origin cannot be explained by reduced ligand binding for LDL. ApoE-containing IDL of patients with the nephrotic syndrome were avidly taken up by glomerular mesangial cells and could therefore play the predominant role in the development of glomerulosclerosis and atherosclerosis associated with this disorder.

Dithiothreitol, an inhibitor of violaxanthin de-epoxidation, increases the susceptibility of leaves ofNerium oleander L. to photoinhibition of photosynthesis.

Leaves ofNerium oleander L. plants, which had been previously kept in a shaded glasshouse for at least two months, were fed 1 mM dithiothreitol (DTT) through their petioles, either for 12h in darkness (overnight) or for 2h in low light (28 µmol photons·m(-2)·s(-1)), in each case followed by a 3-h exposure to high light (1260 µmol photons·m(-2)·s(-1)). During exposure to high light, violaxanthin became converted to zeaxanthin in control leaves, to which water had been fed, whereas zeaxanthin did not accumulate in leaves treated with DTT. Total carbon gain was not reduced by DTT during the photoinhibitory treatment. Exposure to high light led to a decrease in the photochemical efficiency of photosystem II, measured as the ratio of variable over maximum fluorescence emission,F v/F M, at both 298 K and 77K. The decrease was much more pronounced in the presence of DTT, mainly owing to a sustained increase in the instantaneous fluorescence,F o. By contrast, in the control leaves,F o determined immediately after the high-light treatment showed a transient decrease below theF o value obtained before the onset of the photoinhibitory treatment (i.e. after 12 h dark adaptation), followed by a rapid return (within seconds) to this original level ofF o during the following recovery period in darkness. Incubation of leaves with DTT led to large, sustained decreases in the photon-use efficiency of photosynthetic O2 evolution by bright light, whilst the capacity of photosynthetic O2 evolution at light and CO2 saturation was less affected. In the control leaves, only small reductions in the photon yield and in the photosynthetic capacity were observed. These findings are consistent with previous suggestions that zeaxanthin, formed in the xanthophyll cycle by de-epoxidation of violaxanthin, is involved in protecting the photosynthetic apparatus against the adverse effects of excessive light.