Partial ileal bypass in type II familial hypercholesterolemia. Eleven-year experience at the Montreal Heart institute

The National Heart, Lung, and Blood Institute is currently sponsoring a multicenter clinical trial to evaluate the long-term efficacy of partial ileal bypass in the prevention of recurrent myocardial infarction in hypercholesterolemia patients. Thus we felt that a report of our clinical results with this intervention at the Montreal Heart Institute during the last 11 years would be of interest. Twenty patients with type II hyperlipoproteinemia and a mean age of 38 (range 25-54) years underwent partial ileal bypass between March 1971 and April 1978. This intervention was associated with aortocoronary bypass surgery in 11 patients. All patients were followed at regular intervals. The mean survival time was 70.7 (range 1-123) months. Two deaths were observed during follow-up, one from an acute myocardial infarction and the other from ventricular fibrillation, respectively, 1 month and 1 and one-half years after partial ileal bypass. The ileal bypass was undone twice because of gastrointestinal problems including a malabsorption syndrome and repeated episodes of subocclusion. A progressive decrease of the effects of the operation on serum cholesterol was noted, from a 33 per cent reduction at 3 months to 43 per cent at 2 years and 16 per cent at 6 years. Two patients presented an acute myocardial infarction respectively 3 and 4 years after the operation, respectively, and one patient suffered a right-sided hemiplegia at age 30, 12 months after the operation. Of 14 patients with angina pectoris preoperatively (class III in 10), eight remained symptomatic postoperatively (class I and II angina in five).(ABSTRACT TRUNCATED AT 250 WORDS)

Bile acid drainage by partial small bowel bypass or cholestyramine. Effects on serum cholesterol in Watanabe heritable hyperlipidemic rabbits

The effects of bile acid drainage on serum cholesterol levels have been investigated in Watanabe heritable hyperlipidemic rabbits, a unique model for homozygous familial hypercholesterolemia. Cholestyramine medication lowered serum cholesterol concentrations with 38%, while a 33% and a 50% small bowel bypass resulted in a decrease of 56 and 48%, respectively. Cholestyramine treatment after either bypass induced a minor additional fall in serum cholesterol. Ileal bypass and ileal resection were equally effective in reducing serum cholesterol. These results indicate the necessity for further investigation into the potential of bile acid drainage as a therapy in homozygous familial hypercholesterolemia.

Effects of probucol on homozygous cases of familial hypercholesterolemia

A marked reduction of serum cholesterol was obtained by treatment with probucol in heterozygous as well as in homozygous cases of familial hypercholesterolemia. A strict dietary regimen (low-fat, low-calories) intensified the hypocholesterolemic effect of the drug. The drug was also useful in diminishing the rebound of serum cholesterol after plasma exchange. Probucol reduced serum triglycerides in heterozygous cases of familial hypercholesterolemia, but there was a slight increase in triglycerides in homozygous cases. Treatment with probucol resulted in the regression of cutaneous and tendon xanthomas. Although it caused a decrease in HDL, it seems to be very effective in the treatment of familial hypercholesterolemia.

Fenofibrate and human liver. Lack of proliferation of peroxisomes

In rodents fenofibrate shares with other triglyceride-lowering agents the potential to increase the liver peroxisome population. It was therefore of interest to look for this effect in hyperlipoproteinemic patients receiving this drug. Light and electron microscopy of liver biopsies from a group of 10 patients treated with fenofibrate and from another group of 15 receiving diet only, show no morphological difference between both groups. In contrast with the rodent data the morphometric study reveals no significant changes in the number (fenofibrate group: 7.96 10(10) cm-3; group receiving diet alone: 8.41 10(10) peroxisomes/cm3 of liver tissue) or in the size (fenofibrate group: Diameter = 0.53 +/- 0.07 micrometer--group receiving diet alone: 0.50 +/- 0.06) of peroxisomes. The difference between our results and those obtained consistently in rodents may be due to the relatively low dose in man and/or a species-dependent difference in enzyme content of liver peroxisomes, itself related to an apparent difference in the way in which lipids are handled.

Platelet function and lipoprotein levels after plasma-exchange in patients with familial hypercholesterolaemia

1. Repeated plasma exchange was carried out on three young patients with severe familial hypercholesterolaemia. There was a 3 week interval between each exchange. After a single exchange, plasma cholesterol, apolipoprotein B and low density lipoprotein-cholesterol levels decreased markedly, but pre-exchange levels were not achieved within 2 weeks. High density lipoprotein-cholesterol and apolipoprotein A-I levels also fell but returned to the original concentration after only 5 days. 2. Platelet aggregation and [14C]serotonin release were increased in all three patients and dropped by 20% and 13% respectively after a single plasma exchange. Platelet function in vitro returned to pre-exchange levels with similar kinetics to that observed with the low density lipoprotein concentration. On removal of 100 g of plasma cholesterol, after repeated exchanges, low density lipoprotein concentration and platelet function were significantly decreased in comparison with values before initiation of plasma exchange. In addition there was a marked regression of xanthoma in all three patients. 3. Since this procedure is instrumental in achieving a negative cholesterol balance as well as inhibiting hypersensitive platelets, it may well result in a downgrading of the atherosclerotic risk.

Treatment of familial hypercholesterolemia by portacaval anastomosis: effect on cholesterol metabolism and pool sizes

Measurements of the key parameters of cholesterol homeostasis and the mass of the body pools of cholesterol were carried out in two patients with familial hypercholesterolemia (FH), one homozygote and one heterozygote, before and 28 and 18 months, respectively, after portacaval anastomosis (PCA). In both patients the procedure significantly reduced the plasma concentrations of total and low density lipoprotein cholesterol and the daily rate of whole body cholesterol and bile acid synthesis. In addition, PCA caused a net efflux of accumulated tissue cholesterol as demonstrated by reductions in the rapidly exchangeable and total exchangeable masses of body cholesterol. Shunt patency was verified by demonstration of increased bile acids in serum from fasting patients and from patients 2 hr after a meal and by increased plasma glucagon before and after arginine infusion. Other than a persistently increased level of serum alkaline phosphatase, liver function tests have fallen within the normal range in both patients; there has been no evidence of hepatic encephalopathy. In the homozygous patient there has also been a striking resolution in xanthoma size and distribution. These multiple effects on cholesterol homeostasis and pool sizes strongly suggest that PCA can reverse the progressive accumulation of cholesterol in body tissues of FH patients.

Partial Ileal Bypass in Treatment of Familial Hypercholesterolemia

The effects of partial ileal bypass have been studied in 7 patients with heterozygous familial hypercholesterolaemia. By the seventh to ninth postoperative day there was a significant fall in plasma cholesterol of 42.8% compared with levels at initial presentation. Thereafter, plasma levels of cholesterol rose by varying degrees, but had stabilized by 3 months with average values 29.5% lower than pretreatment. Debilitating diarrhoea or severe weight loss were not troublesome features of the operation in most patients.

Protection of myocardium by the compensatory mechanism of coronary collaterals after total occlusion of major coronary arteries shown in patients with familial hypercholesterolemia

We report 11 in a group of 21 asymptomatic patients with heterozygous familial hypercholesterolemia (FH) and progressive coronary artery disease to evaluate the role of compensatory mechanism(s), especially coronary collaterals, in providing adequate blood supply to the myocardium, following complete occlusion of one or more major coronary arteries. Diet-colestipol-nicotinic acid treatment decreased their plasma total cholesterol and low density lipoprotein cholesterol (mg/dl, mean +/- SEM) from 442.9 +/- 25.8 and 363.0 +/-24.1, respectively, to 231.2 +/- 11.8 and 185.3 +/- 14.2, respectively, for 6 to 9 years. The initially stenotic lesions of these 11 patients slowly progressed to complete occlusion, while the patients remained free of myocardial ischemia or infarction and exhibited no abnormality on 24-hour ambulatory ECG monitoring, exercise stress, and thallium 201 stress tests. We conclude that coronary occlusion can be retarded in FH patients by strenuous hypocholesterolemic therapy to allow the development of compensatory mechanism including coronary collaterals. Apparently, the angiographically visualizable collaterals combined with subendocardial anastomosis can give adequate myocardial blood supply to this series of FH patients following occlusion of one or more of their major coronary arteries.

Cholesterol reduction by a high-glucose diet in a patient with homozygous familial hypercholesterolemia. A preliminary report

Homozygous familial hypercholesterolemia is refractory to standard dietary or drug therapy. Recent studies, however, suggest that a high-carbohydrate/low-fat diet may reduce circulation cholesterol levels in normal or hyperlipidemic subjects. In this regard, we treated a nine year old boy with homozygous familial hypercholesterolemia with a liquid formula diet containing 82 to 90 percent of total calories as glucose. The diet was given as a constant nasogastric infusion or as intermittent daytime drinks followed by a nighttime infusion. Plasma total and low-density lipoprotein cholesterol fell from basal levels of 719 mg/dl and 676 mg/dl to 456 mg/dl and 434 mg/dl, respectively, after one week of therapy. After approximately 14 weeks of treatment, plasma total and low-density lipoprotein cholesterol levels were 311 mg/dl and 277 mg/dl, each representing approximately a 58 percent decrease from basal levels. The fall in circulating cholesterol levels was accompanied by a regression of xanthomatous skin lesions, a rise in plasma insulin levels and no change in plasma glucose or glucagon concentrations. No adverse effects of therapy occurred. We conclude that high-carbohydrate diets may be a safe and effective adjunct in the treatment of homozygous familial hypercholesterolemia.

The metabolism of very low density and intermediate density lipoproteins in patients with familial hypercholesterolaemia

The metabolism of apolipoprotein B (apoB) in very low density lipoprotein (VLDL) and intermediate density lipoprotein (IDL) was studied in normal subjects and in patients with familial hypercholesterolaemia (FH) after an intravenous injection of autologous VLDL labelled with 125I. There were no significant differences in half life, pool size and turnover rate (mg/kg/h) of VLDL-apoB between the normal subjects, the FH heterozygotes and the FH homozygotes. IDL-apoB metabolism in the FH patients differed significantly from that in the normal subjects. In the FH patients, the rise to the maximum of the specific activity curve was slower, the half life of the descending limb of the specific-activity curve was longer, the fractional rate of turnover was lower and the plasma concentration was higher than in the normals. The effect of cholestyramine on IDL-apoB metabolism in the normal subjects did not differ from that in the FH heterozygotes and homozygotes, though cholestyramine is known to stimulate hepatic uptake of low density lipoprotein (LDL) by the LDL receptor. It is suggested that in normal human subjects the LDL receptor makes some contribution to the hepatic uptake of IDL-apoB derived from VLDL, but that IDL uptake is mediated partly by a separate receptor that recognizes apolipoprotein E but not apoB.

Plasma methyl sterol sulfates in familial hypercholesterolemia after partial ileal bypass

We demonstrate, in this study, the presence of several unidentified components in the sterol sulfate fraction of familial hypercholesterolemia patients treated with partial ileal bypass surgery. The sterols obtained after solvolysis and derivatization of this fraction had a retention time, on gas-liquid chromatography, intermediate between cholesterol and beta-sitosterol. They were not present in the sterol sulfate fraction obtained from normal subjects, hypercholesterolemic patients, or ileal bypass subjects before surgery or after reanastomosis. The substances isolated from the sterol sulfate fraction were identified by combined gas-liquid chromatography and mass spectrometry to be 24,25-dihydrolanosterol, 4,4-dimethyl-5alpha-cholest-8-en-3beta-ol, 4,4-dimethyl-5alpha-cholest-9(11)-en-3beta-ol, 4alpha-methyl-5alpha-cholest-7-en-3beta-ol, and 4alpha-methyl-5alpha-cholest-8-en-3beta-ol. Their free forms are known to be biosynthetic intermediates in the transformation of lanosterol into cholesterol.

Treatment of hypercholesterolemia

After discussing the indications for treatment of familial hypercholesterolemia and the importance of a differential diagnosis, the authors describe drug therapy for the disorder with special attention to combined drug regimens. The surgical treatment of hypercholesterolemia and the treatment of homozygous and other forms of hypercholesterolemia are also detailed.

The LDL receptor defect in familial hypercholesterolemia. Implications for pathogenesis and therapy

Familial hypercholesterolemia results from one of several genetic defects in a cell surface receptor that normally controls the degradation of low density lipoprotein. The clinical and genetic features and the pathophysiology of these defects are discussed. Knowledge of the regulation of LDL receptors in the liver can be exploited in the design of a physiologically rooted therapy for familial hypercholesterolemia.