Biomedical subjects
Publications and source records attributed to J Frohlich.
The current status of dietary fibre and fibre supplements in health and disease is reported, and the components of dietary fibre and its respective mechanical and metabolic effects with emphasis on its therapeutic potential are reviewed. Practical management guidelines are provided to help physicians encourage patients identified as having fibre deficiency to increase dietary fibre intake to the recommended level.
Familial hypoalphalipoproteinemias (HA) are a heterogenous group of disorders characterized by various degrees of HDL deficiency. Differential diagnosis involves clinical and biochemical evaluation after intervention designed to correct known secondary causes of low HDL. Two specific HAs are discussed in this report: 1. primary isolated HA (PIHA) is a poorly characterized entity with an apparent autosomal dominant transmission and distinct abnormalities in the structure and function of HDL. 2. Lecithin: cholesterol acyltransferase (LCAT) deficiency syndromes are caused by a number of different genetic defects that lead to at least two distinct clinical presentations i.e. familial LCAT deficiency and fish eye disease. PIHA is an example of a genetic disorder whose diagnosis would greatly be improved by the availability of molecular diagnostic tests. Conversely, the effect of the genetic heterogeneity of LCAT deficiency syndromes on diagnosis is best overcome by utilizing existing biochemical measurement of LCAT activity and the plasma cholesterol esterification rate.
Explore the source record for details and available documents.
Hereditary high phosphatidylcholine hemolytic anemia (HHPCHA) is a hematological disorder characterized by chronic hemolytic anemia with a dominant pattern of inheritance. The affected members show increased numbers of target cells and/or stomatocytes in peripheral blood smears, have reduced erythrocyte osmotic fragility, increased autohemolysis as well as markedly increased erythrocyte membrane Na+, K(+)-ATPase activity. Erythrocyte membrane phosphatidylcholine is increased but plasma levels of this phospholipid are normal. Only 10 families affected with this disorder have been described in the literature. We are reporting a new family with HHPCHA in which there are two affected and four presumed affected members. In addition to anomalies commonly reported in HHPCHA, we found alterations in erythrocyte membrane acetylcholinesterase kinetics (low Vmax), reduced erythrocyte superoxide dismutase activity and increased susceptibility of erythrocytes to glutathione depletion on in vitro exposure to hydrogen peroxide. The pathogenesis and clinical features of previously reported cases of HHPCHA are also discussed.
The familial hypoalphalipoproteinemias are a heterogeneous group of rare lipoprotein disorders characterized by extremely low levels of plasma high density lipoproteins (HDL) and, in most cases, autosomal recessive inheritance. Most of these conditions present distinctive and diagnostic clinical and laboratory abnormalities. In spite of the marked reductions in HDL, however, many of these conditions are not associated with premature atherosclerosis. This is true of Tangier disease, Fish Eye disease, lecithin: cholesterol acyltransferase deficiency, and of some variants of apo Al. Another condition, defined as a primary and familial decrease in HDL-cholesterol levels in the absence of other lipoprotein abnormalities. that is associated with premature atherosclerosis was originally called Familial Hypoalphalipoproteinemia but is better referred as to Familial Isolated Hypoalphalipoproteinemia. At present, the prevalence, inheritance, and the underlying defect(s) in this disorder are unknown. Decreased or absent synthesis of apo A-I due to a gene defect is the cause of apo A-I/C-III and apo A-I/C-III/A-IV deficiency. However, the etiology of the low levels of HDL is unclear for most of the remaining familial hypoalphalipoproteinemias. Increased catabolism, decreased synthesis and altered equilibration of HDL between intra- and extravascular spaces have all been suggested as underlying causes of low plasma HDL. Whatever their causes, these disorders are associated with altered HDL composition and altered equilibration of cholesterol amongst the various lipoprotein classes. The absence of consistent correlation with premature atherosclerosis in many of these conditions suggests that the protective effect of HDL may reside in a quantitatively small, but metabolically active subfraction of HDL particles.
Cholesteryl ester transfer from solid-phase bound HDL to endogenous plasma HDL or VLDL/LDL was determined in 50 patients with primary disorders of lipid metabolism and 27 normolipidemic subjects. Transfer to the plasma HDL pool was significantly reduced in familial hypercholesterolemia, familial combined hyperlipidemia, hypoalphalipoproteinemia and dysbetalipoproteinemia. Subfractionation of HDL revealed that the lipid transfer to HDL3 was significantly reduced in all patient groups while transfer to HDL2 was increased in those with dysbetalipoproteinemia and familial hypertriglyceridemia. Transfer to LDL and VLDL was increased only in patients with dysbetalipoproteinemia and hypoalphalipoproteinemia. Reduced transfer to HDL occurred in samples with altered HDL composition; particularly where HDL-triglyceride was significantly increased and HDL-cholesteryl esters were reduced. Transfer of cholesteryl ester to HDL3 was significantly decreased in patients with vascular disease. These findings indicate that impaired interaction of cholesteryl ester transfer protein with the HDL3 pool may contribute to the risk of coronary heart disease in patients with specific plasma lipid abnormalities.
Explore the source record for details and available documents.
The proton NMR spectra of the N-methyl choline region of normal and lecithin:cholesterol acyltransferase (LCAT)-deficient lipoproteins and of egg yolk phosphatidylcholine-cholesterol 55:45 (mol %) vesicle mixtures have been examined in the presence and absence of manganous sulfate as a line-broadening reagent. Manganous ions quenched all of the signal arising from normal lipoproteins and only part of the vesicle signal corresponding to the outer monolayer. There was no net loss of vesicular phospholipid when vesicles were added to normal lipoproteins and as little as 5% (or 100 micrograms) of the vesicular phospholipid could be detected and quantitated in the mixture of lipoproteins. Similar experiments performed on plasma lipoproteins from an LCAT-deficient patient indicated that 42% of the phospholipid was associated with vesicular lipoproteins. These experiments demonstrate that this technique can be used to detect and quantify small amounts of vesicular structures directly in a mixture of micellar lipoproteins.
Hyperlipidemia is a common complication of PBC. Ten patients with serologically and histologically defined PBC were randomized to receive either oral cyclosporin A (CyA) or placebo for one year. Fasting blood samples were obtained from subjects at the beginning, and following one year of treatment, for plasma lipids, apolipoproteins AI (apo AI) and B (apo B), and lecithin-cholesterol acyltransferase (LCAT) activity. On entry to the study there were no significant differences between groups for serum concentrations of total cholesterol (TC), low density lipoprotein cholesterol (LDL-C), high density lipoprotein cholesterol (HDL-C), free cholesterol (FC), total phospholipids (TPL), apo AI, apo B and LCAT activity. Compared to normal laboratory values, baseline TC was elevated in 5/10, LDL-C in 5/10, TPL in 6/10, while LCAT activity was decreased in 8/10 patients. The percent change after one year for CyA group vs the placebo group are as follows: total cholesterol, -22 vs -8%; LDL cholesterol -33 vs -25%; free cholesterol, -39 vs -14%; total phospholipids, -46 vs -23%; and LCAT activity, +/- 236 vs +/- 43%. The decrease in TC, LDL-C, FC, TPL with increase in LCAT activity suggests that CyA administration is associated with improvement in the lipid abnormalities of PBC.
Explore the source record for details and available documents.
These studies were performed to investigate the relationship between the enzyme lecithin:cholesterol acyltransferase and plasma lipoproteins in Tangier disease, a condition characterized by a virtual absence of high-density lipoproteins (HDLs) and an accumulation of cholesteryl esters in peripheral tissues. Apolipoprotein A-I was nearly absent from the patient's plasma (1% of the normal levels were found). However, apolipoprotein A-I purified from the plasma of the Tangier disease patient, was found to activate both purified and the plasma enzyme. At lower apolipoprotein concentrations (up to 25 micrograms/ml), about twice the amount of Tangier apolipoprotein A-I was required to achieve a certain level of lecithin:cholesterol acyltransferase activity as compared with the activating potential of the normal apolipoprotein. Gel chromatography studies revealed that as in normal plasma, lecithin:cholesterol acyltransferase in Tangier plasma was associated with an HDL-size lipoprotein fraction. However, unlike in normal plasma, this lipoprotein complex (containing lecithin:cholesterol acyltransferase) was not removed from Tangier plasma by immunoaffinity chromatography utilizing immobilized anti-apolipoprotein A-I antibodies. Plasma incubation studies showed that free cholesterol was primarily supplied by LDL in normal plasma, whereas both LDL and VLDL donated the free cholesterol for lecithin:cholesterol acyltransferase reaction in Tangier plasma. The majority of the cholesteryl esters, generated during the incubation experiments, were transferred back to LDL in normal plasma, whereas in Tangier plasma both LDL and VLDL served as cholesteryl ester acceptors. The cholesteryl ester transfer from HDL to lower-density lipoproteins was lower in Tangier plasma as compared to this process in a normal control, suggesting that a minimal cholesteryl ester core may be required for the stability of HDL.
This study was designed to determine whether mean values for lipids and lipoproteins changed during the 21 days on oral contraceptive (OC) preparations and during the seven days off the pills. The design allowed for comparison of the effects of Triphasil and Ortho 777 and for examining the consistency over two pill cycles. The mean values for total cholesterol, HDL-cholesterol, LDL-cholesterol and HDL3-subfraction were consistently lower on Day 20 when compared to Day 2 (p less than 0.05) for the two cycles and higher on Day 2 of Cycle II when compared to Day 20 of Cycle I. This fall-rise-fall pattern was consistent for cholesterol in 17 out of 28 of the women studied and these women were heavier (p less than 0.05), had a greater mean Quetelet Index (p less than 0.05) and had been using OCs for a shorter mean period of time (p less than 0.05). Consistently higher apolipoprotein A1 mean values were found on Day 20 of both cycles for Triphasil users compared to Ortho 777 users (p less than 0.02). This paper discusses the importance of these findings in relation to study design when measuring for differences between OC preparations and changes over time.
A randomized double blind, placebo-controlled crossover design was used to determine the efficacy of gemfibrozil and clofibrate in the treatment of familial combined hyperlipidemia and to determine which one of these agents would be more effective. Sixteen patients, 12 men and 4 women, mean age 49.5 years (40-68 yrs), had the entry criteria of increased cholesterol and/or triglyceride with an increase in triglyceride and/or cholesterol in one or more first degree relatives and/or family history of premature cardiovascular disease. Patients received 6 weeks of placebo followed by clofibrate 1000 mg bid or gemfibrozil 600 mg bid for 12 weeks, placebo for 6 weeks and the other drug for 12 weeks. Plasma total cholesterol, triglycerides, HDL-C, LDL-C, apo B and apo A-I were measured every 6 weeks during the study. Gemfibrozil was associated with a significant (P less than 0.05) decrease in plasma triglyceride concentration compared to placebo but it was not significantly different compared to clofibrate. For ease of comparison, the mean value for serum triglycerides during gemfibrozil treatment (average of the 6 and 12 week measurements) was calculated and was 232 +/- 198 mg/dl (mean +/- 1 SD) compared to the average of the placebo treatment values of 381 +/- 410 mg/dl and the average value during the clofibrate treatment period of 217 +/- 178 mg/dl. HDL-C was significantly (P less than 0.05) increased with both drugs and to the same extent.(ABSTRACT TRUNCATED AT 250 WORDS)
Measurement of plasma lecithin:cholesterol acyltransferase (LCAT) activity was used to segregate unaffected family members (n = 8) from heterozygotes (n = 8) and homozygotes (n = 2) in a large LCAT-deficient kindred. The activity was absent in the homozygotes and was decreased to 50% of normal in the heterozygotes. Endogenous cholesterol esterification rate measurements did not differentiate the heterozygotes from the unaffected family members or normal subjects. The heterozygotes had significantly higher fasting plasma triglycerides, apo B, and lower HDL-cholesterol and apo AI than the unaffected family members. The HDL of the heterozygotes had the same mass of free cholesterol and triglyceride, but the mass of cholesteryl ester was reduced by 47%. The differences were not related to abnormal postheparin lipolytic activities. However, cholesteryl ester transfer activity in the lipoprotein-free (d greater than 1.21 bottom) fraction of plasma was significantly (P less than .05) decreased in the heterozygotes when compared to unaffected members. We conclude that the low LCAT activity is the likely cause of the qualitative and quantitative differences in the plasma lipoproteins of the heterozygotes in this family with LCAT deficiency. However, the low HDL and apo A-I levels are not associated with either a family or personal history of premature atherosclerosis.
Recent evidence suggests a role for lipid deposition in the pathogenesis of some forms of glomerular disease. To gain further insight into this phenomenon guinea pigs (GP) were fed a 2% cholesterol (HC) diet and compared to GP on a normal diet (C). Serial observations were made 5, 10, 30 and 70 days after the initiation of the experiment. HC gained less weight than C (P less than 0.001) and developed hemolytic anemia after 30 days. At all time periods serum total cholesterol (TC) was significantly elevated in HC (P less than 0.001). High density lipoprotein-cholesterol and total phospholipids (PL) were significantly higher in HC at days 30 and 70. Lipoprotein-X was detected in HC serum. The relative proportion (%) of cholesteryl ester (CE) at day 70 was significantly higher in HC than in C when renal cortical lipids were analyzed (P less than 0.017). Renal function was normal in both groups throughout the 70 days. The HC group developed proteinuria and hematuria (proteinuria, HC = 22.1 +/- 7.2 mg/24 hr; C, 6.4 +/- 2.3 mg/24 hr), which was detected at day 70 but not at day 30. HC developed significant progressive mesangial expansion which was first evident at day 30. In HC only oil red 0 material was first detected in glomeruli at day 5 and was very conspicuous at day 70. Increased intraglomerular monocyte numbers were detected at day 70 (P less than 0.017) but not at day 30 in HC. No glomerulosclerosis was observed in GP's with drug-induced hemolysis on a normal diet. To see the effect of high protein intake on HC GP's, a group of GP's was put on a HC diet for 30 days followed by a 2% cholesterol-high protein (HCHP) diet for 40 days. Compared to HC GP's, the HCHP group showed significantly higher serum TC and PL (P less than 0.017), mesangial expansion (P less than 0.01) and proteinuria (P less than 0.01). The results indicate that hypercholesterolemia plays an important role in the pathogenesis of glomerulosclerosis in this model and that the process appears to be mediated, at least in part in the later stages, by monocytes. The addition of protein to the HC diet augments these effects.
Erythrocyte membrane (EM) abnormalities in a 16-yr-old boy with hypoalphalipoproteinemia resembling fish eye disease (FED-LS) were investigated. The proband's erythrocytes had markedly decreased osmotic fragility with target cells observed in the peripheral film. Analysis of his EM lipids revealed normal cholesterol and phospholipid content but a marked increase in phosphatidylcholine with concomitant decreases in phosphatidylethanolamine and sphingomyelin. Of the EM enzymes examined, acetylcholinesterase and superoxide dismutase activities were decreased while those of Na+-K+ ATPase, catalase and glutathione reductase were normal. 51Cr erythrocyte survival in the patient was slightly decreased. The observed changes in a number of structural and functional properties of erythrocytes in this disorder are indistinguishable from those previously described in homozygotes for familial lecithin:cholesterol acyltransferase (LCAT) deficiency. Thus, it is possible that in both of these disorders an abnormality of plasma LCAT activity causes, either directly or indirectly, functional and structural changes in the erythrocyte membrane.
Lecithin:cholesterol acyltransferase (LCAT) deficiency is a rare familial disease inherited in an autosomal recessive pattern. It is characterized by a combination of plasma lipoprotein, corneal, erythrocyte and, in most patients, renal changes. The corneal changes consist of scattered stromal dots that are lipid deposits. Their composition is unique and suggests an intrinsic corneal metabolic defect. The corneal clouding is usually asymptomatic. Patients with the condition must be followed closely because renal failure may develop. We describe a patient with LCAT deficiency.
We determined cholesteryl ester transfer activity in whole plasma and in lipoprotein-depleted plasma of normolipidemic subjects and of patients with severe high-density lipoprotein (HDL) deficiency: Tangier disease, lecithin:cholesterol acyltransferase (LCAT) deficiency, and "fish-eye" disease. Transfer rates in plasma were positively correlated (r = 0.950) with rates measured in the absence of the endogenous lipoproteins. This suggests that lipoprotein composition and content may not affect total cholesteryl ester transfer activity in normolipidemic and the HDL-deficient subjects. Cholesteryl ester transfer from solid-phase-bound HDL to plasma lipoproteins was decreased by 39% in fish-eye disease and 33% in LCAT deficiency but increased by 57% in Tangier disease, as compared with normal values. Changes were similar for lipoprotein-depleted plasma from the same individuals. Transfer to plasma HDL was significantly decreased in all HDL-deficient patients, whereas transfer to very-low- and low-density lipoproteins was increased only in Tangier disease. Differences in transfer rates between the patients studied appeared to reflect the LCAT activity and the need to transport cholesteryl ester rather than the HDL cholesterol concentration. Thus, the concentration of HDL in plasma does not directly affect total cholesteryl ester transfer activity in HDL deficiency.