Effects of bezafibrate on receptor-mediated and receptor-independent low density lipoprotein catabolism in type II hyperlipoproteinaemic subjects

Serum lipids, lipoproteins and macrovascular disease in non-insulin-dependent diabetics: a possible new approach to prevention

The relationship between macrovascular disease and serum lipids, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL), and subfraction cholesterol, and apolipoproteins has been examined in 53 female and 95 male patients with non-insulin-dependent diabetes mellitus (NIDDM). In males, those with macrovascular disease had higher serum and LDL cholesterol concentrations than those without. In females, those with macrovascular disease had higher levels of serum triglyceride, cholesterol, LDL cholesterol, as well as lower HDL, HDL2, and HDL3 cholesterol and apoprotein A-1, than those without. On multivariate analysis, LDL cholesterol was the most important association with macrovascular disease in males and apoprotein A-1 in females. In a subgroup of 36 patients, a double-blind placebo controlled study using bezafibrate or placebo, in addition to conventional oral hypoglycaemic therapy over 4 months, showed falls in serum and LDL cholesterol and in serum triglyceride and a rise in HDL cholesterol in the treated group. These changes should reduce the incidence of macrovascular disease in NIDDM and we suggest further prospective studies of such therapy in addition to conventional oral hypoglycaemic agents.

Influence of etofibrate on low density lipoprotein metabolism

This study examined the effect of single dose etofibrate (1.0 g/day) on plasma lipids and lipoproteins in a group of eleven hypercholesterolemic individuals. The drug lowered plasma triglyceride and cholesterol by 32% and 14%, respectively (P less than 0.005). The cholesterol reduction came from a decrement in both VLDL and LDL. The cholesterol content of HDL did not change although its mass as determined by analytical ultracentrifugation rose by 29%. LDL metabolism was followed before and during drug therapy. Treatment increased catabolism of this lipoprotein by 14%, without affecting synthesis. The increased clearance resulted from activation (64%) of the LDL receptor pathway. There was a reciprocal decrease in the amount of lipoprotein channelled into the receptor-independent route.

Simvastatin and bezafibrate: effects on serum lipoproteins and lecithin: cholesterol acyltransferase activity in familial hypercholesterolaemia

Sixteen subjects with familial hypercholesterolaemia were randomly assigned to treatment with simvastatin 20-40 mg/day (an inhibitor of 3-hydroxy-3-methylglutaryl CoA reductase) or with bezafibrate 600 mg/day (a clofibrate analogue) for 12 weeks. Both drugs produced significant reductions in serum and LDL cholesterol; mean percentage fall -30.5% and -38.1% (simvastatin) and -17.8% and -20.6% (bezafibrate), respectively. Both drugs also caused a decrease in VLDL cholesterol, while only bezafibrate decreased the serum and VLDL triglyceride levels and increased HDL cholesterol and serum apolipoprotein A-I and A-II levels. Serum apolipoprotein B fell by 33.3% (simvastatin) and 15.7% (bezafibrate). Simvastatin and bezafibrate produced significant increases in the mean fractional esterification rate of LCAT, by +124.1% and +20.6%, respectively. Thus simvastatin was clearly more effective than bezafibrate in lowering LDL by enhancing its turnover, but bezafibrate had specific effects on VLDL and HDL that might be favourable in combined treatment regimens.

Changes in lipid and lipoprotein levels and Achilles tendon diameters and indices in familial hypercholesterolaemic patients with tendinous xanthomatosis treated by diet and bezafibrate for 2 years

Thirteen young adult patients suffering from heterozygotic familial hypercholesterolaemia with tendinous xanthomatosis, previously treated with a suitable special diet, were studied to assess the effect of bezafibrate, given for 2 years at a dose of 800 mg/day, on plasma lipid and lipoprotein levels and on changes in size of the Achilles tendon xanthomas. Measurements were made before and at intervals during treatment, the tendinous xanthomas being measured by an echographic procedure to give data on antero-posterior and lateral diameters, thus enabling an Achilles tendon index to be defined. The results confirm the hypolipidaemic activity of bezafibrate, changes in the levels of total cholesterol, triglycerides, lipids and lipoproteins (LDL, VLDL and HDL) being similar in direction and magnitude to those reported previously. A significant regression in the size of the Achilles tendon xanthomas was observed in 11 of the 13 patients, and the regression in the Achilles tendon index correlated significantly with a favourable change in the ratio HDL/LDL + VLDL. It is suggested that, as a result of this objective observation, a favourable effect of bezafibrate treatment would possibly be seen on the anatomical atheromatous lesions which are usual in this type of hyperlipidaemia.

Changes in lipoprotein kinetics during therapy with fenofibrate and other fibric acid derivatives

The fibric acid derivatives, including fenofibrate, significantly reduce very low-density lipoprotein triglyceride concentrations by stimulating lipoprotein lipase activity, thereby increasing very low-density lipoprotein catabolism. These agents may also reduce the hepatic secretion of nascent very low-density lipoprotein, but this effect is less consistent. Effects on low-density lipoprotein metabolism appear to depend upon the lipid disorder present before therapy. If hypertriglyceridemia and normal or low low-density lipoprotein levels are present, fibrate therapy is associated with a rise in low-density lipoprotein levels. This is due to a decreased fractional catabolism of low-density lipoprotein from an unusually high clearance to a more normal value. Treating pre-existing hypercholesterolemia usually results in a significant decrease in low-density lipoprotein levels. In this disorder, there is a demonstrable increase in low-density lipoprotein receptor-mediated clearance. It is not known at which site these drugs act to increase low-density lipoprotein receptor function in the latter patients. Some studies suggest that fibrate therapy increases high-density lipoprotein apolipoprotein AI production, but how this occurs has not been defined.

Effect of fibric acid derivatives on blood lipid and lipoprotein levels

The literature for the last seven years was reviewed in terms of the effect of the various fibric acid derivatives on blood lipid and lipoprotein levels. The criteria for review resulted in a greater focus on three of the newer fibric acid derivatives: bezafibrate, ciprofibrate, fenofibrate. In type II A hyperlipoproteinemia, all fibric acid derivatives produce modest reductions in total plasma cholesterol and low-density lipoprotein cholesterol. The evidence suggests that bezafibrate, ciprofibrate, and fenofibrate may produce greater reductions in low-density lipoprotein cholesterol than those usually observed with clofibrate and gemfibrozil. All fibric acid derivatives produce modest reductions in triglycerides and modest increases in high-density lipoprotein cholesterol in type II A hyperlipoproteinemia. In type II B hyperlipoproteinemia, the low-density lipoprotein cholesterol lowering effect of fibric acid derivatives is generally less than that observed in type II A hyperlipoproteinemia. In type II B hyperlipoproteinemia, there is a mean decrease in low-density lipoprotein cholesterol for all patients studied. However, there is a considerable interpatient variation ranging from significant decreases to significant increases in low-density lipoprotein cholesterol. Further studies are required to assess whether the low-density lipoprotein cholesterol lowering effect is greater with the newer fibric acid derivatives. All fibric acid derivatives produce clinically significant decreases in triglyceride levels in type II B. There is also an associated increase in high-density lipoprotein cholesterol. In type IV hyperlipoproteinemia, all fibric acid derivatives produce clinically significant reductions in triglyceride. There is also an associated increase in high-density lipoprotein cholesterol and generally also an increase in low-density lipoprotein cholesterol levels. The available data do not suggest a clinically significant difference in the hypotriglyceridemic effect of the various fibric acid derivatives in type IV hyperlipoproteinemia. The lipid-altering effects of the various fibric acid derivatives were usually less in those studies that contained placebo and dietary controls. Additional controlled clinical trials are needed to accurately discriminate the relative lipid-and lipoprotein-altering effects of the various fibric acid derivatives.

Fibric acids: effects on lipids and lipoprotein metabolism

The major effect of the fibrates on triglycerides is to promote triglyceride-rich lipoprotein catabolism through increased lipoprotein lipase activity. Fibrates also enhance lipolysis of plasma triglycerides by a means different from that of caloric restriction. Their effect on very low-density lipoprotein metabolism also differs from that of nicotinic acid. The effect of fibrate therapy upon low-density lipoprotein-cholesterol concentrations depends upon the patients' overall lipoprotein status. The responsible mechanisms are not understood. In hypertriglyceridemic patients, fibrates often reverse abnormal changes in low-density lipoprotein composition; low-density lipoprotein heterogeneity is reduced and small dense low-density lipoproteins are eliminated, apparently secondary to reduced levels of triglyceride-rich lipoproteins. Kinetic studies indicate that fibrates do not enhance low-density lipoprotein formation rates, thus contradicting the idea that fibrate therapy causes increased low-density lipoprotein cholesterol levels via increased conversion of very low-density lipoprotein to low-density lipoprotein. Though enhanced low-density lipoprotein catabolism in hypertriglyceridemia could occur via several mechanisms, the responsible factors are largely reversed by fibrate therapy. In non-hypertriglyceridemic patients, fibrates may actually enhance the fractional clearance of low-density lipoprotein and thus reduce low-density lipoprotein levels. Fibrate therapy reverses the typical high-density lipoprotein pattern of hypertriglyceridemic patients, producing more high-density lipoprotein2a and less high-density lipoprotein2b. Such treatment also increases high-density lipoprotein cholesterol levels in patients without definite hypertriglyceridemia. Synthesis rates of apolipoproteins AI and AII may be affected by fibrates. The fibrates' major effects on sterol metabolism are interference with cholesterol and bile acid synthesis and increased cholesterol secretion into bile. Although bile saturation increases in most patients, in only a relatively small percentage do gallstones actually develop; super-saturated bile is not sufficient to induce gallstone formation in most patients. Available data strongly imply that fibrates mobilized cholesterol out of tissue pools, perhaps by altering tissue cell membranes to allow cholesterol release from the cell surfaces.

High density lipoprotein alterations induced by bezafibrate in healthy male volunteers

The alterations of HDL structure and metabolism induced by bezafibrate administration were studied in healthy male volunteers. As usually observed in hyperlipaemic patients, bezafibrate induced a decrease of the plasma concentrations of apo B and LDL-cholesterol and an increase of that of HDL-cholesterol. Analysis of HDL by gradient polyacrylamide gel electrophoresis revealed that bezafibrate administration resulted in a change of the particle size distribution likely suggesting a drop of the HDL2/HDL3 ratio. This was accompanied by a 30% enhancement of the plasma concentration of apoprotein A-II, while that of apoprotein A-I remained unchanged. These data suggest an increase of the HDL concentration, preferentially in the HDL3 subfraction. In spite of these HDL alterations, there was no evidence of change in the three stages of the reverse pathway of cholesterol, since bezafibrate did not induce any significant alteration in the in vitro properties of plasma with respect to (a) cholesterol transport from cultured cells, (b) cholesterol esterification, and (c) transfer of cholesteryl esters from HDL to VLDL-LDL.

Bezafibrate. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in hyperlipidaemia

Bezafibrate is a lipid-lowering drug, chemically related to clofibrate. At its recommended dosage of 200 mg 3 times daily, or alternatively 400 mg once daily as a sustained-release preparation, it produces substantial reductions in plasma triglyceride and cholesterol concentrations in patients with hypertriglyceridaemia and hypercholesterolaemia, respectively. Preliminary investigations indicate that a single daily dose of 400 mg in a sustained-release preparation is as effective as 200 mg 3 times daily. In patients with any type of hyperlipoproteinaemia bezafibrate also increases the plasma HDL-cholesterol concentration. These effects are equivalent in patients with primary hyperlipoproteinaemia or hyperlipoproteinaemia secondary to diabetes or renal disease, although dosage adjustment is important in the latter group. During long term therapy (2 to 4 years) the influence of bezafibrate on the lipid profile is sustained. The lipid-lowering effects of bezafibrate are at least equivalent to those of clofibrate, fenofibrate, colestipol, probucol or sustained release etofibrate. In addition, the increase in HDL-cholesterol tends to be at least as great as with all alternative treatments studied. Bezafibrate is rapidly eliminated, and thus does not accumulate during prolonged administration in patients with normal renal function. Experimental studies have shown bezafibrate to have a complex range of effects on lipoproteins and on the enzymes and receptors involved in lipid metabolism. However, its exact mechanism of lipid-lowering action is unclear. Bezafibrate enhances anticoagulation in hyperlipoproteinaemic patients requiring anticoagulant therapy, and preliminary investigations indicate that it reduces the plasma fibrinogen concentration, especially in patients with hyperfibrinogenaemia. These properties of bezafibrate could contribute to an antiatherogenic effect of the drug, but further investigation is required to establish the drug's potential as chronic therapy in patients with hyperfibrinogenaemic atherosclerosis. Adverse reactions to bezafibrate have largely been restricted to gastrointestinal disturbances, with some cutaneous reactions and central nervous system effects. The incidence of side effects has been no greater than with comparative lipid-lowering drugs. In patients with renal disease, a few cases of marked elevation of serum creatine phosphokinase and myoglobin, and associated muscle cramps, have been reported (diagnosed as rhabdomyolysis). Hepatic enzyme induction by bezafibrate in rats results in hepatomegaly, but there has been no case of significant hepatotoxicity in man.(ABSTRACT TRUNCATED AT 400 WORDS)

Influence of bezafibrate and colestipol on LDL-cholesterol, LDL-apolipoprotein B and HDL-cholesterol in hyperlipoproteinaemia

A significant increase of LDL-apolipoprotein B by 13% and LDL-cholesterol by 19% was observed in a group of 9 patients with hyperlipoproteinaemia Type III after bezafibrate treatment. Additional administration of colestipol caused a significant decrease of both LDL-apolipoprotein B by 18% and LDL-cholesterol by 25%. In 10 patients of hyperlipoproteinaemia Type IIb a significant decrease of both LDL-apolipoprotein B by 28% and LDL-apolipoprotein B by 18% was observed after bezafibrate therapy. When bezafibrate was given together with colestipol a further decrease of both LDL-cholesterol by 17% and LDL-apolipoprotein B by 16% occurred. HDL-cholesterol concentration increased significantly in both groups of hyperlipaemic patients during therapy. This may be the effect of both bezafibrate and colestipol. It is concluded that bile acid resins may effectively prevent the LDL-cholesterol concentration increase observed sometimes after clofibrate analogues.

The effect of combined fenofibrate and cholestyramine therapy on low-density lipoprotein kinetics in familial hypercholesterolemia patients

The effects of combined drug treatment (fenofibrate and cholestyramine) have been investigated in vivo by simultaneously determining total and receptor-independent LDL catabolism with 125I-labelled LDL and 131I-labelled LDL coupled with cyclohexanedione. Receptor-mediated catabolism of LDL determined as the difference between the turnover of 125I and 131I, was found to be reduced in heterozygotes with familial hypercholesterolemia. Treatment with combined fenofibrate and cholestyramine markedly stimulated both receptor-mediated (by more than 2-fold) and receptor-independent catabolism. LDL-Apo B and LDL-cholesterol levels were reduced by 38% and 36%, respectively. The combined treatment also reduced the absolute synthetic rate of LDL-Apo B (by 9%). The mechanisms responsible for these kinetic effects are discussed.

The fibrinolytic system and coagulation during bezafibrate treatment of hypertriglyceridemia

Bezafibrate was given to 23 hypertriglyceridemic but otherwise healthy middle-aged men in a double-blind, cross-over study to evaluate its effect on the components of the fibrinolytic system as well as on ATIII, FVIIIR: Ag, FVIII: C and platelet aggregation. Fibrinogen dropped markedly (P less than 0.05) and there was a small but significant fall of ATIII. The second wave of platelet aggregation was found much less frequently than in controls (P less than 0.001). Bezafibrate seemed to decrease the rate of formation of the first wave platelet aggregation.

Change in very low-, low-, and high-density lipoproteins during lipid lowering (bezafibrate) therapy: studies in type IIA and type IIb hyperlipoproteinaemia

The effects of lipid lowering therapy (bezafibrate) on plasma lipoproteins was investigated in twelve patients with familial hypercholesterolaemia (type IIA) and eight with familial combined hyperlipidaemia (type IIB). Bezafibrate caused a decrease of plasma cholesterol, plasma triglycerides, plasma apolipoprotein B, VLDL cholesterol and LDL cholesterol and an increase of HDL cholesterol. Post-heparin plasma lipoprotein and hepatic lipase activities increased in both groups (significant only in type IIB). Lipoprotein composition showed the following changes: Increased protein and phospholipids and decreased triglycerides and cholesteryl esters in VLDL. Decreased protein and triglycerides and increased free and esterified cholesterol in LDL. Decreased triglycerides and increased phospholipids in HDL. Cholesteryl ester to protein ratios decreased in VLDL and increased in LDL. The hydrated density of LDL (both groups) and of HDL3 (type IIB) decreased following bezafibrate therapy. These changes were in general similar to those observed in hypertriglyceridaemic patients and could be ascribed, at least in part, to the increase of plasma lipase activities and the decrease of lipid transfer reactions. Comparing the present data with that previously reported, it was found that bezafibrate caused decreased LDL cholesterol in types IIA and IIB but increased levels in type IV. This change was correlated with the initial plasma triglycerides (r = 0.74, P less than 0.0001) and initial plasma LDL cholesterol (r = 0.66, P less than 0.001). It is concluded that varied response of LDL to therapy reflects a complex interaction of metabolic events, including changing rates of VLDL conversion to LDL, lipoprotein compositional changes and effects of therapy on LDL degradation rates.

Fenofibrate and colestipol: effects on serum and lipoprotein lipids and apolipoproteins in familial hypercholesterolaemia

Effects on serum lipoproteins were studied in ten patients with familial hypercholesterolaemia (FH) during consecutive eight-week treatment periods with fenofibrate 0.3 g/day, fenofibrate plus colestipol, 15 g/day, and fenofibrate 0.25 g/day plus colestipol. VLDL, LDL, HDL, HDL2, and HDL3 were isolated by ultracentrifugation and precipitation. Lipids and apolipoproteins A-I and B were determined by enzymatic and immunonephelometric techniques, respectively. Administration of fenofibrate alone resulted in decreases in VLDL and LDL cholesterol (-48% and -18%) and in serum apolipoprotein B (-10%), but in increases in HDL, HDL2, and HDL3 (+25%, +26%, and +24%), and in serum apolipoprotein A-I (+6%). Addition of colestipol produced a further reduction in LDL cholesterol (-31%) and in serum apolipoprotein B (-19%). The effects were maintained with less fenofibrate. In FH, an acceptable therapy combines the favourable effects of sufficient lowering of LDL and of a rise in HDL.

Changes in serum lipoprotein pattern following bezafibrate. Differential effects in type IIa and in type IIb hyperlipoproteinemic patients

Sixteen type IIb and 26 type IIa hyperlipoproteinemic patients were treated with bezafibrate 200 mg t.i.d. After 1 month VLDL-TG decreased by 54% in type IIb and by 43% in type IIa; LDL-C decreased by 13% in type IIb and by 23% in type IIa patients. HDL3-C rose in both group of patients, while HDL2-C significantly increased (52%) only in patients with phenotype IIb. The change in LDL-C and in HDL2-C concentrations resulted to be related to the pretreatment VLDL lipid concentration and to its change during the treatment. Twenty patients were treated with bezafibrate for 4 months. On the average, the changes in lipoprotein lipid concentration attained at the end of the first month of therapy remained substantially constant in the following 3 months.

Effects of fenofibrate on bile lipid composition

In humans, clofibrate increases the degree of bile cholesterol saturation and predisposes patients to cholesterol gallstone formation. To determine if this activity extends to the related hypolipidemic agent fenofibrate, duodenal bile lipid composition was studied in 15 subjects before they participated in a double-blind study of that drug. Eight subjects were studied again on fenofibrate and six on placebo; five placebo patients were also studied later on open-label fenofibrate. The results were similar in the double-blind and open-label studies, and changes in bile lipid composition were comparable to those seen in studies of clofibrate. Fenofibrate caused a significant decrease in the molar percentage of bile acids and increases in the molar percentage of phospholipids and cholesterol. The changes in bile acids and phospholipids had opposing effects on the cholesterol-holding capacity of bile. A statistically significant increase in the cholesterol saturation index was only apparent when all fenofibrate bile analyses were compared with all untreated bile analyses. The results demonstrated that fenofibrate has clear effects on bile lipid composition that may be associated with an increased propensity for gallstone formation, and when fenofibrate is used, patients should be monitored for this possibility.

Effects of fenofibrate on high and low density lipoprotein metabolism in heterozygous familial hypercholesterolemia

This study investigates the influence of pharmacological doses of fenofibrate on HDL and LDL metabolism in 5 familial hypercholesterolemia heterozygotes. Fenofibrate lowered plasma low density lipoprotein cholesterol (20%, P less than 0.025), triglycerides (37%: P less than 0.005) and apolipoprotein B (14%: P less than 0.05) but increased apo A-I (20%; P = 0.01). Kinetic studies showed that the drug markedly increased the fractional catabolic rate of LDL-apo B by 59% and its synthetic rate by 36%. Fractional catabolic rate of apo A-I was also increased by 26% but accompanied by a much greater increase of its synthetic rate (49%). Thus the change in balance between catabolism and synthesis of both apoproteins affected by fenofibrate accounts for the observed plasma concentration changes, which may be considered as favourable with regard to the management of atherosclerosis.

Fenofibrate reduces low density lipoprotein catabolism in hypertriglyceridemic subjects

This study examines the kinetic basis for the increment in plasma low density lipoprotein (LDL) levels that accompanies the fenofibrate treatment of severely hypertriglyceridemic (HTG) patients. Seven HTG men with a mean plasma triglyceride level of 1470 mg/dl were treated for 6 weeks. During treatment, their plasma triglyceride level fell by 77% and their cholesterol level by 41%. The fall in very low density lipoprotein (VLDL) cholesterol level was reciprocated by increments in the cholesterol level in both LDL and high density lipoproteins (HDL); the rise in HDL was confined to HDL3. LDL catabolism was examined before and during therapy using native and chemically modified tracers in an attempt to distinguish receptor-mediated from non-receptor-mediated clearance. In their basal state, the hypertriglyceridemic subjects overcatabolized both the native and the modified lipoprotein, implying that the non-receptor pathways were hyperactive. The mean fractional clearance rate of LDL via the receptor pathway was not significantly different from normal. Fenofibrate therapy corrected the patients' hypercatabolism, reducing the receptor-independent fractional clearance of apo LDL by 50% (from 0.48 to 0.24 pools/day; p less than 0.05). The mean fractional catabolic activity of the receptor route did not change, but when the increment in the plasma apo LDL concentration was taken into account, it was clear that the drug treatment was associated with an increase in the net amount cleared by the receptor pathway and with a reduction of lipoprotein uptake into receptor-independent routes.

Correlation between plasma levels of fenofibrate and lipoprotein changes in hyperlipidaemic patients

Eleven hyperlipidaemic patients received two formulations of fenofibrate (differing in in vitro dissolution) in randomized sequence, each for 6 weeks. Formulation N, giving a 2-3-fold higher plasma fenofibrate level compared to R, lowered both the cholesterol and triglyceride levels far more than R. Changes in the total and high density lipoprotein cholesterol levels were not significantly correlated with the fenofibrate level. A highly significant correlation was detected for triglycerides in Type IV patients, and for changes both in very low density lipoprotein (VLDL) cholesterol and triglycerides in the entire group of patients. In conditions of widely distributed steady state levels of an absorbable hypolipidaemic drug, a significant correlation may thus be detected between the plasma level and the reduction of VLDL - associated lipids.

Apolipoprotein A and B (Sf 100-400) metabolism during bezafibrate therapy in hypertriglyceridemic subjects

This study describes the effects of bezafibrate, an analogue of clofibrate, on the plasma lipid and lipoprotein profiles of 11 hypertriglyceridemic subjects and on their metabolism of apolipoproteins A-I, A-II, and B. The major action of the drug was to lower plasma triglyceride (by 58%; P less than 0.01). This was accompanied by a reduction in the level of very low density lipoprotein apoprotein B (Svedberg units of flotation [Sf] 60-400), whose mean residence time in the plasma fell threefold (from 3.4 to 1.0 h). Synthesis of the B protein in this fraction was not significantly altered, so the drug acts to accelerate the transit of very low density lipoprotein particles down the delipidation cascade. The metabolism of very low density lipoprotein remnant apoprotein B (Sf 12-100) changed little in response to treatment, although we detected a 30% increment (P less than 0.05) in the plasma concentration of this fraction. The mean residence time of these remnant particles in the plasma did not correlate with that of Sf 100-400 very low density lipoprotein apoprotein B, nor was this parameter altered by the drug. The most consistent and significant perturbation seen in the Sf 0-12 fraction (low density lipoprotein) was a reduction in the fractional catabolism of its apoprotein B moiety (26%; P less than 0.05). In those subjects who were grossly hypertriglyceridemic and who responded well to treatment, the level of this protein rose substantially owing to a combined increase in its synthesis and a reduction in its catabolism. In the group as a whole, high density lipoprotein cholesterol rose 13% (P less than 0.02), and detailed examination showed that this was associated with a small but significant increment in the plasma concentration of the high density lipoprotein subfraction 2. High density lipoprotein subfraction 3 also rose on the average, but this was not a consistent feature in all patients. The plasma concentrations and turnovers of the A proteins (A-I and A-II) were not significantly altered by bezafibrate therapy.

Effect of fenofibrate on serum lipoproteins in subjects with familial hypercholesterolemia and combined hyperlipidemia

The effects on serum lipoproteins were studied in 8 patients with familial heterozygous hypercholesterolemia and 9 patients with familial combined hyperlipidemia during an 8-week treatment with fenofibrate. VLDL, IDL, LDL and HDL were isolated by ultracentrifugation and precipitation. Lipids and apolipoproteins A-I and B were determined by enzymatic and immunonephelometric techniques, respectively. In hypercholesterolemia, administration of fenofibrate resulted in decreases of VLDL, IDL, and LDL (cholesterol -58.3%, -28.6%, and -24.4%), while, in combined hyperlipidemia, treatment with the drug lowered VLDL and IDL (-33.3% and -42.9%). HDL cholesterol and apolipoprotein A-I increased only in hypercholesterolemia (+22.9% and +6.9%).

Abnormalities in very low, low and high density lipoproteins in hypertriglyceridemia. Reversal toward normal with bezafibrate treatment

The effects of triglyceridemia on plasma lipoproteins were investigated in 16 hypertriglyceridemic (HTG) subjects (222-2,500 mg/dl) before and after the initiation of bezafibrate therapy. Bezafibrate caused a mean reduction of 56% in plasma triglyceride and increased the levels of lipoprotein and hepatic triglyceride lipases by 260 and 213%, respectively. The natures of very low density lipoprotein (VLDL), isolated at plasma density and of low and high density lipoprotein (LDL and HDL), separated by zonal ultracentrifugation, were determined. HTG-LDL appears as multiple fractions whereas HTG-HDL is seen predominantly as HDL3. HTG-VLDL is relatively poor in apoproteins and triglycerides but enriched in free and esterified cholesterol. HTG-LDL (main fraction) is depleted of free and esterified cholesterol but enriched in apoprotein and triglyceride. It is also denser and smaller than normal. HTG-HDL3 is denser than N-HDL3 and demonstrates compositional abnormalities similar to those of HTG-LDL. With the reduction of the VLDL mass, all abnormalities revert towards normal. This is accompanied by an increase in LDL-apoprotein B and cholesterol levels, which indicates an increased conversion of VLDL to LDL. Significant correlations between plasma triglyceride and the degree of all abnormalities are shown. The data obtained during treatment corroborate these relationships. The observations support the concept that most abnormalities reflect the degree of triglyceridemia. We suggest that plasma core-lipid transfer protein(s) is an effector of the abnormal cholesteryl ester distribution. Its prolonged action on increasingly large and slowly metabolized VLDL populations would entail a correspondingly excessive transfer of cholesteryl ester to VLDL and of triglyceride to LDL and HDL. It is calculated that, in moderate HTG, LDL and HDL contain only 50% of the normal cholesterol load. It is suggested that cholesteryl ester redistribution in HTG might be important in regulating metabolic events.