Long-term effects of ileal bypass on lipoproteins in patients with familial hypercholesterolemia

Importance of Coagulation Factors as Critical Components of Premature Cardiovascular Disease in Familial Hypercholesterolemia

For almost a century, familial hypercholesterolemia (FH) has been considered a serious disease, causing atherosclerosis, cardiovascular disease, and ischemic stroke. Closely related to this is the widespread acceptance that its cause is greatly increased low-density-lipoprotein cholesterol (LDL-C). However, numerous observations and experiments in this field are in conflict with Bradford Hill’s criteria for causality. For instance, those with FH demonstrate no association between LDL-C and the degree of atherosclerosis; coronary artery calcium (CAC) shows no or an inverse association with LDL-C, and on average, the life span of those with FH is about the same as the surrounding population. Furthermore, no controlled, randomized cholesterol-lowering trial restricted to those with FH has demonstrated a positive outcome. On the other hand, a number of studies suggest that increased thrombogenic factors—either procoagulant or those that lead to high platelet reactivity—may be the primary risk factors in FH. Those individuals who die prematurely have either higher lipoprotein (a) (Lp(a)), higher factor VIII and/or higher fibrinogen compared with those with a normal lifespan, whereas their LDL-C does not differ. Conclusions: Many observational and experimental studies have demonstrated that high LDL-C cannot be the cause of premature cardiovascular mortality among people with FH. The number who die early is also much smaller than expected. Apparently, some individuals with FH may have inherited other, more important risk factors than a high LDL-C. In accordance with this, our review has shown that increased coagulation factors are the commonest cause, but there may be other ones as well.

Liver transplantation in patients with homozygotic familial hypercholesterolemia previously treated by end-to-side portocaval shunt and ileal bypass

Familial hypercholesterolemia is the result of mutations in the gene that encodes the synthesis of the cellular receptor for low density lipoprotein (LDL). In the homozygous form of the disease (HFHC), cellular LDL receptors either do not form, or, when present, cannot bond LDL and mediate its cellular uptake LDL, and the cholesterol that it transports accumulate in plasma, producing severe premature atherosclerosis and death from coronary artery disease usually before the age of 20. Currently, the only effective treatment is liver transplantation, which, alone or in association with medications, normalizes plasma cholesterol levels. The authors report the cases of 2 siblings with HFHC who underwent portocaval shunt at the ages of 2.5 and 1.5 years, respectively. Portocaval shunt produced an immediate, but insufficient decrease in cholesterol (by 40% and 35%, respectively), leaving them with cholesterol concentrations of about 500 mg/dL. One year later they each underwent ileal bypass without obtaining any significant response. Liver transplantation at the ages of 18 and 16 years, respectively, reduced plasma cholesterol concentrations to 129 and 225 mg/dL, respectively. The earlier operations seriously increased the technical difficulty of liver transplantation and did not produce a favorable effect on the natural course of the disease, so portocaval shunt and ileal bypass are not indicated in HFHC, not even for the purpose of delaying liver transplantation.

Enhanced plasma cholesterol lowering effect of retrovirus-mediated LDL receptor gene transfer to WHHL rabbit liver after improved surgical technique and stimulation of hepatocyte proliferation by combined partial liver resection and thymidine kinase--ganciclovir treatment

In this study we report an improved method for in vivo gene transfer to liver. Repeated injections of Moloney murine leukemia virus-derived retroviruses containing LDL receptor cDNA were given to the portal vein in combination with a 10% partial liver resection and stimulation of hepatocyte proliferation by plasmid/liposome-mediated thymidine kinase gene transfer and ganciclovir treatment. The method was used for the treatment of LDL receptor deficiency in Watanabe heritable hyperlipidemic rabbits. We demonstrate an increase in hepatocyte proliferation index by thymidine kinase and ganciclovir treatment from 0.9 to 1.35% and a maximum of 35% decrease in total plasma cholesterol level 2-3 months after the gene transfer. A 20% decline was still present after a 52-week follow-up period. A 50% decrease was also observed in plasma triglycerides. Liver function tests indicated a transient increase in plasma alkaline phosphatase level up to 12 weeks after the gene transfer. In situ PCR and RT-PCR analyses indicated that the transgene was present in periportal areas and was transcribed to mRNA 1 week after the gene transfer. Because of the relatively simple and controllable technique we suggest that repeated retrovirus injections via a portal vein catheter together with the limited partial liver resection and plasmid/liposome-mediated thymidine kinase gene transfer-ganciclovir treatment may be used to improve the results of retrovirus-mediated liver gene therapy.

Treatment of hypercholesterolemia with heparin-induced extracorporeal low-density lipoprotein precipitation (HELP)

Familial hypercholesterolemia (FH) can cause early disability and death from premature atherosclerotic cardiovascular disease. Patients homozygous for the disease have very high plasma cholesterol, extensive xanthomatosis, and die from atherosclerosis in childhood or early adulthood. Past attempts to improve the prognosis included removal of cholesterol from the circulation by ileal bypass or biliary diversion. Neither treatment was successful. Direct removal by plasmapheresis of low-density lipoprotein (LDL), the primary carrier of cholesterol in plasma, was first performed on an FH homozygous patient in 1966. The treatment was well tolerated and led to rapid diminution of xanthomas. Other experimental treatments included selective LDL apheresis with monoclonal or polyclonal antibody affinity columns. A method for selective LDL apheresis was developed in 1983 by Armstrong, Seidel, and colleagues based on heparin precipitation of LDL at low pH. This method, called HELP, removes all apolipoprotein B-containing lipoproteins including LDL and lipoprotein (a), as well as some fibrinogen. LDL apheresis by HELP is well tolerated; the incidence of side effects is low, and the treatment has been associated with regression of cardiovascular disease. LDL apheresis, rather than liver transplantation, is the treatment of choice for patients with severe, life-threatening hypercholesterolemia which does not respond to diet and drug therapy.

The HELP-LDL-apheresis multicentre study, an angiographically assessed trial on the role of LDL-apheresis in the secondary prevention of coronary heart disease. II. Final evaluation of the effect of regular treatment on LDL-cholesterol plasma concentrations and the course of coronary heart disease. The HELP-Study Group. Heparin-induced extra-corporeal LDL-precipitation

The efficacy of the heparin-induced extracorporeal LDL-precipitation (HELP)-apheresis procedure has been studied in an open prospective multicentre trial. After 2 years of regular weekly HELP-treatment the data from 39 of 51 patients could be evaluated according to the study criteria. Twelve of the initially recruited study patients were omitted from the evaluation either because of premature termination of the treatment or because they did not fulfil the exact guidelines of the study protocol. A mean of 2.831 plasma was regularly treated on average every 7.85 days. The mean pre-/post-apheresis LDL-cholesterol levels decreased from 286/121 mg dl-1 at the first HELP treatment to 203/77 mg dl-1 after 1 year and to 205/77 mg dl-1 after 2 years of regular apheresis; the corresponding values for fibrinogen were 314/144, 246/98 and 250/105 mg dl-1, respectively. In contrast, the mean pre-/post-apheresis HDL-cholesterol levels rose from 41/38 through 51/44 mg dl-1 after 1 year to 52/43 mg dl-1 after 2 years of treatment. The overall result was a normalization of the atherogenic index (LDL-/HDL-cholesterol ratio) from 6.9/3.2 to 4.0/1.9. The angiographies from 33 patients obtained before and after 2 years of regular treatment could be evaluated blindly using the cardiovascular angiography analysis system. The mean degree of stenosis of all segments decreased from 32.5% (SD = 16) to 30.6% (SD = 16.8) over the 2 years. A regression > 8% was observed in 50/187 (26.7%) segments, whereas 29/187 (15.5%) segments showed progression. In 108/187 (57.8%) segments the lesions were stable (< 8% deviation) over 2 years. We conclude that regular treatment with HELP-LDL-apheresis is able to stabilize progressive atherosclerotic disease and to induce almost twice as much regression as progression of atherosclerotic lesions.

Total parenteral nutrition and plasma lipoproteins in the rat: evidence for accelerated clearance of apo-A-I-rich HDL

The effect of total parenteral nutrition (TPN) containing fat on plasma lipoproteins and apo-A-I-rich HDL catabolism was studied in the rat. TPN rats were intravenously infused for 5 days with a nutritive mixture containing amino acids, lipids (Intralipid 20%) and glucose. In spite of similar plasma levels of total cholesterol in TPN and control orally fed rats, density gradient ultracentrifugation of plasma samples gave evidence of marked differences in the lipoprotein profiles. In the density range 1.010-1.040, were found elevated amounts of apo-B-100 and apo-B-48 containing lipoproteins, as well as an increase in free cholesterol and phospholipids, the latter indicating that the plasma of TPN rats contained abnormal lipoprotein-X-like particles. The level of apo-E-rich HDL (density: 1.040-1.063) was not markedly changed, whereas that of typical HDL (d > 1.063) was lowered, with less apo-A-I and apo-A-IV, and low amounts of cholesterol and phospholipids were found in the most dense HDL3 fractions (d > 1.090) containing the bulk of apo-A-I-rich particles. After intravenous infusion of homologous [14C]sucrose-labelled HDL3, the clearance of these particles was 2-fold faster in TPN than in control rats, with a tissue uptake increased in the liver (+40%) and decreased in the small and large intestines (-60%). Because the pool of apo-A-I-rich HDL was dramatically reduced after 5 days of artificial feeding, the absolute catabolic rate of these lipoproteins was similar in the two groups. These data suggest that, in TPN rats lacking of chylomicron coat components as a source for HDL material, the fall in plasma levels of apo-A-I-rich HDL resulted mainly from accelerated turnover of these particles, mediated by increased uptake by the liver. Conversely, mucosa atrophy was probably involved in the reduced uptake of apo-A-I-rich HDL by the gastrointestinal tract.

The HELP-LDL-apheresis multicentre study, an angiographically assessed trial on the role of LDL-apheresis in the secondary prevention of coronary heart disease. I. Evaluation of safety and cholesterol-lowering effects during the first 12 months. HELP Study Group

Fifty-one patients with coronary heart disease (CHD) and LDL-cholesterol levels greater than or equal to 200 mg dl-1 despite diet and drug therapy have been recruited into an angiographically controlled, multicentre, two-year study to evaluate HELP-LDL-apheresis in the secondary prevention of CHD. There were five drop-outs in the first year and 46 patients completed one year of therapy. An average of 2.791 of plasma was treated per patient every 7.7 days. Treatment was well tolerated and the incidence of side effects was small (2.9% of treatments). Mean pre-/post-apheresis LDL-cholesterol levels decreased from 283/120 mg dl-1 at baseline to 207/78 mg dl-1 and 203/76 mg dl-1 after 6 and 12 months, respectively. Mean pre-/post-apheresis HDL-cholesterol levels rose significantly over the course of therapy from 40.5/36.6 mg dl-1 to 44.8/39.7 mg dl-1 and 48.2/41.3 mg dl-1 after 0, 6 and 12 months, respectively. No major derangement of pre-apheresis haemostasis nor of haematological or clinical chemical parameters had occurred after 12 months of treatment. The data from this study support the feasibility of HELP-LDL-apheresis as an adjunctive therapy for lowering cholesterol levels in CHD patients refractory to cholesterol-lowering drugs while substantially improving the HDL/LDL ratio.

Effect of partial ileal bypass surgery on mortality and morbidity from coronary heart disease in patients with hypercholesterolemia. Report of the Program on the Surgical Control of the Hyperlipidemias (POSCH)

BACKGROUND AND METHODS

The Program on the Surgical Control of the Hyperlipidemias (POSCH), a randomized clinical trial, was designed to test whether cholesterol lowering induced by the partial ileal bypass operation would favorably affect overall mortality or mortality due to coronary heart disease. The study population consisted of 838 patients (417 in the control group and 421 in the surgery group), both men (90.7 percent) and women, with an average age of 51 years, who had survived a first myocardial infarction. The mean follow-up period was 9.7 years.

RESULTS

When compared with the control group at five years, the surgery group had a total plasma cholesterol level 23.3 percent lower (4.71 +/- 0.91 vs. 6.14 +/- 0.89 mmol per liter [mean +/- SD]; P less than 0.0001), a low-density lipoprotein cholesterol level 37.7 percent lower (2.68 +/- 0.78 vs. 4.30 +/- 0.89 mmol per liter; P less than 0.0001), and a high-density lipoprotein cholesterol level 4.3 percent higher (1.08 +/- 0.26 vs. 1.04 +/- 0.25 mmol per liter; P = 0.02). Overall mortality and mortality due to coronary heart disease were reduced, but not significantly so (deaths overall [control vs. surgery], 62 vs. 49, P = 0.164; deaths due to coronary disease, 44 vs. 32, P = 0.113). The overall mortality in the surgery subgroup with an ejection fraction greater than or equal to 50 percent was 36 percent lower (control vs. surgery, 39 vs. 24; P = 0.021). The value for two end points combined--death due to coronary heart disease and confirmed nonfatal myocardial infarction--was 35 percent lower in the surgery group (125 vs. 82 events; P less than 0.001). During follow-up, 137 control-group and 52 surgery-group patients underwent coronary-artery bypass grafting (P less than 0.0001). A comparison of base-line coronary arteriograms with those obtained at 3, 5, 7, and 10 years consistently showed less disease progression in the surgery group (P less than 0.001). The most common side effect of partial ileal bypass was diarrhea; others included occasional kidney stones, gallstones, and intestinal obstruction.

CONCLUSIONS

Partial ileal bypass produces sustained improvement in the blood lipid patterns of patients who have had a myocardial infarction and reduces their subsequent morbidity due to coronary heart disease. The role of this procedure in the management of hypercholesterolemia remains to be determined. These results provide strong evidence supporting the beneficial effects of lipid modification in the reduction of atherosclerosis progression.

Partial ileal bypass for hypercholesterolemia. 20- to 26-year follow-up of the first 57 consecutive cases

Between 1963 and 1968, 57 patients underwent partial ileal bypass (PIB) at the University of Minnesota for primary hypercholesterolemia. Preoperative total plasma cholesterol (TC) was 363.3 +/- 136.8 mg/dL (mean +/- SD) in these patients. Baseline and follow-up TC results demonstrated highly significant (p less than or equal to 0.001) TC reduction, 34% (n = 48), 28% (n = 49), 35% (n = 26), 35% (n = 11), and 30% (n = 25) at 1, 2 to 5, 6 to 10, 11 to 15, and more than 20 years, respectively, after PIB. In 21 patients with baseline, 1-year, and more than 20-year results TC decreased 33% by 1 year and remained 29% less than baseline more than 20 years after surgery (p = NS versus 1 year). Plasma triglyceride results were available in fewer patients, and no statistically significant changes developed after PIB. Two patients (3.5%) underwent PIB reversal, one for intractable diarrhea and one for recurrent nephrolithiasis. In the 25 nonreversed, long-term survivors, no statistically significant weight change was noted. Twenty-four per cent had 0 to 2, 52% had 3 to 5, and 24% had more than 5 bowel movements per day. Subsequent cholecystectomy was required in eight patients, and nephrolithiasis developed in 10 (40%). During 20 to 26 years, most survivors developed clinically apparent atherosclerosis: angina (60%), myocardial infarction (16%), or coronary artery bypass (28%). Coronary heart disease was the predominant cause of death among nonsurvivors (80%). Overall survival rates were 95% 88%, 75%, 59%, 53%, and 41% at 1, 5, 10, 15, 20, and 25 years, respectively, after PIB. Partial ileal bypass leads to highly significant TC reduction, which is sustained, essentially unchanged, more than 20 years after operation. In comparison to available epidemiologic and clinical trial data, these results support the hypothesis that TC reduction has a beneficial effect in patients with hypercholesterolemia.

Plasma and biliary cholestanol related to steroid metabolism in familial hypercholesterolemia patients with and without ileal exclusion

Plasma cholestanol is increased in cerebrotendinous xanthomatosis and in sitosterolemia with xanthomatosis. We measured plasma and biliary cholestanol in heterozygous familial hypercholesterolemia patients with (n = 10) and without (n = 12) ileal exclusion. In the unoperated patients plasma cholestanol concentration (12.9 mumol/l) and content (1.2 mmol/mol cholesterol) were slightly higher than in the nonhypercholesterolemic control subjects studied by us. Ileal exclusion had lowered plasma cholestanol concentration but only in proportion to the lowering of plasma cholesterol concentration, and plasma cholestanol content (mmol/mol cholesterol) was similar in the operated and unoperated subjects. Plasma and biliary cholestanol contents were positively associated. In the unoperated patients the fractional cholesterol absorption and plasma plant sterols, also reflecting sterol absorption, were positively correlated with plasma cholestanol content. Our study suggests, that plasma cholestanol is slightly elevated in familial hypercholesterolemia and that, in addition to plasma lipoprotein level, sterol absorption is important in the regulation of plasma cholestanol level. Ileal exclusion decreases plasma cholestanol in proportion to the decrement in the plasma cholesterol concentration.

Effect of ileal exclusion on lipoprotein sitosterol in familial hypercholesterolaemia

A plant sterol, sitosterol, was quantitated in very low density lipoproteins (VLDL), low density lipoproteins (LDL) and high density lipoproteins (HDL) and related to faecal steroids and cholesterol absorption in heterozygous familial hypercholesterolaemia patients with (n = 7) and without ileal bypass (n = 6). The latter had resulted in severe bile acid malabsorption but fractional cholesterol absorption was within low control limits. Serum total and LDL cholesterol and apoprotein B levels were reduced, whereas HDL cholesterol, apoprotein A-I, VLDL and HDL sitosterol concentrations were increased by the ileal exclusion, and the increase in LDL and serum total sitosterol levels was insignificant. In terms of mmol/mol of cholesterol or apoprotein B, however, the LDL and total sitosterol contents were higher in the subjects who had undergone operation. For an unknown reason the sitosterol content increased gradually within the lipoprotein particles from the lighter to the heavier lipoproteins, and the enrichment was similar in the two groups. Dietary sitosterol intake, indicated by faecal sitosterol excretion, was similar in the two groups. The contents of serum total and LDL sitosterol were positively correlated with the dietary sitosterol intake in both groups, and with the fractional cholesterol absorption only in the group not subject to operation. These associations were less consistent for sitosterol contents in other lipoproteins. We conclude that normally the serum sitosterol content reflects cholesterol absorption efficiency even in patients with familial hypercholesterolaemia, provided the dietary sitosterol intake is quite constant. In addition, for unknown reasons ileal exclusion leads to an increased lipoprotein sitosterol content.

Peripheral arterial disease in heterozygous familial hypercholesterolemia: no difference between patients with and without partial ileal bypass

We evaluated lower limb arterial circulation in 37 patients with heterozygous familial hypercholesterolemia using strain-gauge plethysmography. Nineteen patients were initially allocated to surgical therapy (ileal bypass operation), and 18 control patients were treated conservatively. After a follow-up period of 3-12 years (mean 10 yrs) the surgically treated patients had significantly lower serum total (9.4 vs. 11.9 mmol/l, P less than 0.001) and LDL (6.2 vs. 8.1 mmol/l, P less than 0.01) cholesterol and apoprotein B levels and higher HDL cholesterol (1.2 vs. 1.0 mmol/l, P less than 0.05) and apoprotein A-I levels compared with controls. There was no significant difference in the prevalence of intermittent claudication (16 vs. 6%) or coronary heart disease (68 vs. 61%) between the operated and control groups. The ankle-arm systolic blood pressure ratio was pathologically low in 53% of the operated and 72% of the control patients, and the toe-arm pressure ratio in 50% and 44%, respectively. These differences or the differences in the mean ankle-arm and toe-arm pressure ratios between the groups were not significant. The toe-ankle pressure gradient was normal in all but 2 patients indicating that atherosclerotic changes predominantly affect the more proximal arteries in familial hypercholesterolemia. Patients with peripheral arterial disease could not be differentiated by serum lipoprotein levels, blood pressure or the presence of coronary heart disease. However, smoking was more prevalent (38% vs. 0%, P less than 0.05) in patients with impaired peripheral circulation. We conclude that asymptomatic peripheral arterial disease is quite common in familial hypercholesterolemia, and that smoking increases its risk.(ABSTRACT TRUNCATED AT 250 WORDS)

Fecal bile acids related to small-bowel length before and after ileal exclusion

We studied the relationship among the small-bowel length, the fecal excretion of bile acids and neutral steroids, and cholesterol synthesis in 16 patients with familial hypercholesterolemia before and 1 month after the ileal bypass operation. The mean small-bowel length measured during the operation was 6.3 +/- 0.3 (SEM) m before and 4.3 +/- 0.2 m after the bypass of the distal third of the small bowel. The preoperative fecal bile acid excretion was negatively correlated (r = 0.63, p less than 0.01) with the small-bowel length, whereas this correlation was insignificant for fecal neutral steroid excretion and cholesterol synthesis. Postoperative amounts of fecal bile acids and neutral steroids and cholesterol synthesis were negatively correlated with the length of the small bowel remaining in function (r = -0.52, -0.51, and -0.62, respectively). Our study suggests that fecal bile acid excretion and, hence, bile acid synthesis are related to the small-bowel length even under physiologic conditions.

High density lipoprotein, apoproteins A-I and A-II and postheparin plasma lipolytic enzymes after ileal bypass

Apoproteins A-I and A-II, and the activities of lipoprotein lipase (LPL) and hepatic lipase (HL), were studied in 16 patients 3-12 years after ileal bypass operation and in 13 controls, all heterozygous for familial hypercholesterolemia, to investigate why the operated subjects had a higher HDL cholesterol level than the unoperated controls. HDL- and HDL2-cholesterol and apoprotein A-I were higher, HDL3-cholesterol was similar and apoprotein A-II tended to be lower in the operated than the control subjects. The activities of LPL and HL were similar in the 2 groups. HL was negatively correlated with HDL2-cholesterol, whereas LPL was not associated with any of the HDL components. The controls had gained in weight during the follow-up, but the HDL components were not correlated with relative body weight. It is concluded that in familial hypercholesterolemia ileal bypass results in higher HDL- and HDL2-cholesterol and apoprotein A-I level than conservative treatment and that postheparin plasma lipolytic enzymes do not explain the higher level of these HDL components in the operated subjects.

Adaptation of cholesterol and bile acid metabolism and vitamin B12 absorption in the long-term follow-up after partial ileal bypass

Cholesterol and bile acid metabolism and vitamin B12 were studied in 19 patients with heterozygous familial hypercholesterolemia in an 8-yr follow-up (3-12 yr after ileal bypass operation), and in 11 unoperated controls. Absorption of cholesterol and vitamin B12 were decreased by the operation, but improved slowly, and at 8 yr cholesterol absorption was normal. Cholesterol excretion as fecal neutral steroids was not increased by the operation, and at 8 yr the flux of endogenous cholesterol to the gut was similar in the operated and control patients. Cholesterol absorption was positively correlated with mouth to anus transit time in the unoperated patients. Fecal bile acid excretion was increased immediately after the operation and continued to increase even after the second postoperative year. In the operated patients fecal excretion of fat, water, and dry matter were positively correlated with fecal bile acid excretion. Our study suggests that adaptive changes occur slowly after ileal bypass, resulting in gradual normalization of cholesterol absorption, despite continuing bile acid malabsorption, and that the intestinal transit time is related to steroid absorption even under physiologic conditions.