Increased apoprotein B in very low density lipoproteins of patients with peripheral vascular disease

Lipoprotein compositional studies were carried out in 20 patients with atherosclerotic peripheral vascular disease. Twelve of these patients were normolipidemic, the other eight, hypertriglyceridemic. Ten normolipidemic and 10 hypertriglyceridemic age-matched subjects were used as controls. High density lipoprotein cholesterol levels were markedly reduced in the hypertriglyceridemic subjects, both with (35.1 +/- 5.0 mg/dl) and without (36.2 +/- 11.7 mg/dl) peripheral vascular disease, as compared to the normolipidemic patients (47.0 +/- 6.3 mg/dl) and controls (48.1 +/- 10.0 mg/dl). A decreased relative content of apo C-11 in very low density lipoproteins in the hypertriglyceridemic subjects, as compared to the normolipidemics, was detected by isoelectric focusing. Hypertriglyceridemia in patients with peripheral vascular disease shows a typical Type IV lipoprotein and apoprotein profile. Apoprotein B levels in very and low density lipoproteins were determined by electroimmunodiffusion and selective precipitation with tetramethylurea (r = 0.981 between the two methods). All the patients with peripheral vascular disease showed an increased apo B content in very low density lipoproteins vascular disease showed an increased apo B content in very low density lipoproteins (VLDL) as compared to controls (apo B cholesterol in VLDL = 0.341 +/- 0.124 for peripheral vascular disease patients and 0.236 +/- 0.086 for controls, p less than 0.001). A significant correlation between VLDL cholesterol and apo b levels was detected both in peripheral vascular disease patients and in controls; however, two distinct populations could be clearly separated (slopes of the regression lines: peripheral vascular disease patients = 0.350; controls = 0.215, p less than 0.001). The data suggest a possible discriminatory power of VLDL-apo B levels in patients with peripheral vascular disease independent from other lipoprotein and lipid parameters.

Pharmacological studies on tiadenol in type IV patients. Evidence for a mechanism of action different from other lipid-lowering drugs

Tiadenol [bis(hydroxyethylthio) 1-10 decane], a new absorbable hypolipidemic agent differing in chemical structure from clofibrate and related compounds, was tested in hypertriglyceridemic patients, both responsive and nonresponsive to dietary treatment. Tiadenol administration was remarkably effective in inhibiting fructose induced hypertriglyceridemia in diet responsive type IV patients; it was ineffective in patients with stable, diet refractory, hypertriglyceridemia. The significant reduction of plasma triglycerides (-42%) in sensitive patients, was not accompanied in this study, by the activation of plasma lipoprotein and hepatic lipases. In a second, longer term investigation of stable type IV patients, tiadenol administration resulted in significant triglyceride decreases in the very low density lipoproteins (VLDL) (-45%), as well as in the low and high density lipoproteins (LDL and HDL) (both -25%). The cholesterol content of LDL and HDL was not modified. In VLDL a significant reduction of apoprotein E was observed (from 15.2 +/- 4.9 to 11.9 +/- 5.9% of VLDL proteins). The reported observations are consistent with a difference in the mode of action of tiadenol from that of other lipid lowering agents, particularly of the clofibrate type.

Relation between the HDL apoproteins and AI isoproteins in subjects with the AIMilano abnormality

The apoprotein AIMilano (AIM) is the first described molecular abnormality of human apolipoproteins. In order to achieve a better understanding of the biochemical role of high density lipoproteins (HDL) and of their subcomponents, nine members of the AIM family were studied. Five showed the characteristic biochemical features of the AIM abnormality. All were hypertriglyceridemic; their plasma and very low density lipoprotein (VLDL) triglycerides had a significant negative correlation with the HDL cholesterol (HDL-C) levels (r = -0.961, p less than 0.01 and r = -0.939, p less than 0.05, respectively). Compositional studies of HDL in these subjects revealed a marked triglyceride (TG) enrichment, with reduced cholesterol content. HDL-C and/or phospholipid (PL) levels correlated significantly with the AIM apoprotein in HDL (r = 0.995, p less than 0.001 for HDL-C and r = 0.994, p less than 0.001 for HDL-PL) but not with the other HDL apoproteins, suggesting that only apo AIM in monomeric form, can bind lipids. Isoelectric focusing studies on the isolated AIM isoproteins from the five affected subjects revealed an isoprotein distribution markedly different from normal AI. A possible structural role for isoprotein AI1 is suggested by the strong correlation between HDL content of this isoprotein and HDL-C and HDL-PL levels (r = 0.965 and r = -0.990 respectively, both p less than 0.001). AI4 and AIM was nearly doubled, as compared to normal AI. The reported results may be of help for a better understanding of the role of the major HDL apoprotein and of its isoproteins in lipid binding and lipoprotein metabolism.

Reduced triglyceridemia and increased high density lipoprotein cholesterol levels after treatment with acipimox, a new inhibitor of lipolysis

Acipimox (5-methylpyrazine carboxylic acid 4-oxide) is a new inhibitor of lipolysis with long-lasting activity, whose plasma lipid lowering potential was demonstrated in early clinical trials. The hypolipidemic effect of acipimox was investigated in two double-blind cross-over trials versus placebo. The first trial, carried out in 12 type IV patients, showed a significant triglyceride lowering effect (-35%) following 4 weeks of drug administration at a 250 tid dose. The same regimen, maintained for 9 weeks in 18 type IIA patients, failed to induce a significant reduction of total cholesterolemia. However, in 10 subjects, in whom lipoprotein cholesterol fractionation was carried out, a significant reduction of low density and highly significant increase in high density lipoprotein cholesterol levels (respectively -11% and +20%) were observed.

Multicentre study of soybean protein diet for outpatient hyper-cholesterolaemic patients

The animal proteins in a low-lipid, low-cholesterol diet were substituted with a textured soybean preparation for 127 outpatients with stable type II hyperlipoproteinaemia selected from eight Italian and one Swiss lipid clinics. Eight weeks of the modified diet reduced plasma cholesterol by 23.1% in the 67 participating male patients and by 25.3% in the 60 females. No significant changes in plasma triglycerides, high-density lipoprotein cholesterol, and body weight were recorded. Better reductions in plasma cholesterol occurred in non-familial cases and in very young male patients. The acceptable taste of the soybean preparation used in this study, and its easy handling, indicate that this type of dietary treatment may be suitable for outpatients.

Clinical experience with the soybean protein diet in the treatment of hypercholesterolemia

The efficacy of the total substitution of animal proteins with a textured soybean protein in hypercholesterolemic individuals was assayed in 42 in-patients and 18 out-patients. The in-patients studied followed one of three different crossover protocols: in protocol A, the soybean diet was compared with a standard low lipid diet; protocol B compared two soybean diets, one with added cholesterol, one without; and protocol C compared a soybean diet containing a high P/S fatty acid ratio to one with a low P/S ratio. In all three protocols, the soybean regimen provided valid and reproducible hypocholesterolemic effects that were not modified by the addition of cholesterol. P/S variations appeared, however, to modify the final effect: soybean definitely had a decreased effectiveness with a low P/S (0.1) regimen. The overall plasma cholesterol changes in the 42 in-patients after 3 weeks on the different soybean diet protocols was -20%. Patients with type IIA and IIB hypercholesterolemia provided almost equivalent results, whereas patients with mixed phenotypes (IIB-III) appeared somewhat more sensitive to the dietary effect. Cholesterol decreased mostly in the low density lipoprotein fraction, but some very low density lipoprotein changes were also noted upon variation of the P/S ratio. The out-patients studied provided less satisfactory results. possibly due to the difficulty of adequately complying with the diet. These studies indicate that treatment with the soybean diet is an effective regimen for inducing a significant cholesterol reduction in type II patients refractory to standard low lipid regimens.

Kinetics of insulin secretion following glucose infusion in patients with atherosclerotic peripheral vascular disease

Kinetics of insulin secretion following an i.v. glucose infusion, according to the protocol described by Cerasi and Luft, were studied in 19 patients with angiographically documented atherosclerotic peripheral vascular disease and in a group of appropriate controls without clinical signs of disease. No significant differences were noted between patients and controls in plasma cholesterol levels and in the K value following a standard i.v. glucose tolerance test. Blood glucose levels were significantly lower in the patients, whereas mean plasma insulin and triglyceride levels were significantly higher. Analysis of the glucose and insulin responses to the glucose infusion test indicated that 31.6% of the patients had a delayed and sluggish insulin response to the glucose load, fitting the criteria suggested for the diagnosis of prediabetes, versus 10% of the appropriate controls. In particular, simulation of the plasma insulin responses by a square-wave glucose stimulus, confirmed that in a significantly higher number of patients the early insulin peak was below normal limits. The results of this study suggest that increased insulin secretion is not present in patients with atherosclerotic vascular disease, in contrast to reports by other authors, and that inefficient insulin secretory mechanisms may be observed in these patients, thus possibly contributing to the development of the atherosclerotic disease.

Platelet aggreation malondialdehyde formation in type IIA hypercholesterolemic patients

Platelet aggregation induced by threshold concentrations of ADP, adrenaline, collagen and Thrombofax was evaluated in 25 type IIA hypercholesterolemic patients in comparison with 15 control subjects. Malondialdehyde (MDA) formation induced by collagen and thrombin was also studied in a subgroup of 8 patients. In the patient group, irreversible platelet aggregation was induced by significantly lower concentrations of both adrenaline (p is less than 0.05) and Thrombofax (p is less than 0.01). MDA formation induced by both aggregating agents was markedly increased (p is less than 0.01) in type IIA hypercholesterolemic patients.

New microporous cholestyramine analog for treatment of hypercholesterolemia

A new, microporous, uniformly reticulated preparation of cholestyramine is described. The preparation, cholpor, has a higher exchange capacity for chloride than does cholestyramine and swells very little in water. It is 15--20% more potent than chloestyramine in the in vitro binding of sodium cholate; moreover, the binding velocity is considerably higher than that of cholestyramine. Colestipol hydrochloride, also used as a reference anion-exchange resin, is about half as potent as the other two resins; its binding velocity is similar to that of cholpor. Cholpor may be prepared in a suspension form of good palatability. Preliminary clinical findings in short-term trials showed a cholesterol-lowering effect similar to that of cholestyramine with lower doses and fewer side effects.

Treatment of hypertriglyceridemia with metformin. Effectiveness and analỳsis of results

The triglyceride-lowering effect of metformin (N,N-dimethylbiguanide) was tested in a series of patients with stable hypertriglyceridemia (types IIB, III and IV) and with variable degrees of glucose intolerance. Metformin caused a 38% mean decrease of plasma triglycerides. A selective decrease of very low density lipoprotein cholesterol was observed without reciprocal increase of low density lipoproteins. Thirty patients completed the study. Eighteen, who showed a hypotriglyceridemic effect exceeding 30%, were considered as "Responders"; the other 12, where the effect was negligible, were considered as "Non-Responder". Analysis of the pre-and post-treatment glucose tolerance tests of Responders and Non-Responders showed that the former had, on the average, a normal glucose tolerance and insulin secretion, whereas the latter had an impaired glucose tolerance with increased insulin secretion. These parameters were only slightly modified by metformin. The conclusions of this study support the hypothesis that biguanides exert a triglyceride-lowering effect by decreasing lipoprotein secretion, independent of changes in glucose tolerance and/or insulin secretion.