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Biomedical subjects

R I Levy

Publications and source records attributed to R I Levy.

At least 109 records · Page 6Linked to original sources
PubMed1975

Type III hyperlipoproteinemia: an analysis of two contemporary definitions.

Two current definitions of type III hyperlipoproteinemia, "floating beta" lipoproteins and an estimate of the relative content of cholesterol and triglyceride in lipoproteins of density less than 1,006 (very low-density [VLD] lipoproteins), have been compared. Over 3100 complete lipoprotein analyses of 182 adults with primary familial hyperglyceridemia, covering a wide range of plasma lipid concentrations, formed the data base for this retrospective analysis: The ratio of VLD lipoprotein cholesterol to the plasma triglyceride concentration (VLDL/TG=r) proved capable of segregating an apparently unique subpopulation with persistently abnormal very low-density lipoprotein composition. Although floating beta lipoproteins were present in nearly all patients with a high r value, they also appeared inconsistently in many other patients. It is concluded that the chemical index to VLD lipoprotein composition is the better, albeit, temporary definition for this disorder. When the plasma triglyceride concentration is between 150 and 1000 mg/100 ml, an r not less than 0.25 should be considered as suggestive and a value not less than 0.30 as diagnosttc of type III hyperlipoproteinemia.

Adult↗
PubMed1975

The biochemical, clinical, and genetic features of type III hyperlipoproteinemia.

The clinical and biochemical features of type III hyperlipoproteinemia are described in 49 patients from 23 to 70 years of age. An increase in very low-density lipoproteins (VLDL) of abnormal chemical composition was the basis for diagnosis. The untreated patients all had hypercholesterolemia and hyperglyceridemia, and, on the average, decreased concentrations of both low- and high-density lipoproteins. Seventy-four percent had xanthomas, and classic "xanthoma striata palmaris" was found in more than half. Twenty-seven percent had ischemic heart disease, detected earlier in men than in women. Twenty-seven percent had peripheral vascular disease (compared to 4% of subjects with type II hyperlipoproteinemia). Twenty-five of 35 subjects achieved normal lipid levels with dietary therapy alone. Analysis of 29 kindred showed hyperlipidemia in half of adult blood relatives; half of these had type III, the remainder usually had sample endogenous hyperglyceridemia (type IV). Only 2 of 55 children less than 20 years of age were affected, both with type IV.

Adult↗
PubMed1975

Pathophysiology of lipid transport disorders.

Over the past decade considerable insight into the mechanisms involved in normal and abnormal transport as well as the mode of action of hypolipidaemic drugs has been achieved. This progress has made the approach to the hyperlipidaemic patient increasingly more precise and effective.

Adipose Tissue↗
PubMed1974

Familial hypercholesterolemia (one form of familial type II hyperlipoproteinemia). A study of its biochemical, genetic and clinical presentation in childhood.

Primary hyperbetalipoproteinemia (type II hyperlipoproteinemia) is a common disorder associated with premature vascular disease. It is frequently due to genetic abnormalities, some of which are expressed in childhood. We have examined the manner in which that form of hyperbetalipoproteinemia known as familial hypercholesterolemia may be expressed in 236 children aged 1-19 born of 90 matings in which one parent had hyperbetalipoproteinemia of this variety and one parent did not.Two Gaussian populations were fitted to the distribution of both low density lipoprotein cholesterol (C(LDL)) and plasma cholesterol (C) in these children and a likelihood ratio test strongly favored a two over a one population model for both C(LDL) (X(2) = 18.41, P < 0.0005) and C (X(2) = 7.81, P < 0.025). 45% of the children were in the population identified as affected; their mean C(LDL) was 229. The remaining 55% were in the normal population with a mean C(LDL) of 110 which was indistinguishable from that of an unrelated control population, aged 1-19. On the basis of an assumed frequency of hyperbetalipoproteinemia in the general population of 5%, the Edwards' test indicated that a polygenic model of inheritance was highly unlikely (expected, 22%; observed, 45%). The segregation ratio obtained from the derived intersection between the two population curves (C(LDL), 164 mg/100 ml; C, 235 mg/100 ml) was 45/55 (abnormal/normal). The percentage of abnormal children in the first decade (52%) significantly exceeded that in the second (39%) (P < 0.01). The ratios (II/N) were 50/47 and 55/84 in the offspring of affected female and male parents, respectively (X(2) = 3.819, 0.05 < P < 0.10). Only 10% of hyperbetalipoproteinemic children were considered to have hyperglyceridemia. These children, frequently, but not invariably, had a parent with hyperglyceridemia in addition to hyperbetalipoproteinemia (P < 0.05). None of the affected children who were examined had ischemic heart disease (IHD) and 7% had tendon xanthomas. Half of the parents (mean age, 37.4 yr) who were examined had IHD and three-quarters had xanthomas. The data agree well with the hypothesis that hyperbetalipoproteinemia is inherited as a monogenic trait with early expression in these children. More than one genetic defect within the group is not excluded, but retrospective analyses of the 345 first-degree adult relatives of the affected parents indicated that most of the abnormal parents probably represented familial hypercholesterolemia, rather than combined hyperlipidemia, the other most generally recognized form of familial hyperbetalipoproteinemia.

Adult↗
PubMed1974

Selective measurement of two lipase activities in postheparin plasma from normal subjects and patients with hyperlipoproteinemia.

An assay has been developed for specific measurement of two different lipase activities in postheparin plasma. Lipoprotein lipase, derived from extrahepatic sources, is measured as protamine-inactivated lipase activity; hepatic lipase activity is protamine-resistant under the conditions of this assay. In 100 normal subjects, both enzyme activities were noted to be related to age and sex. Protamine-resistant lipase, which comprised 46-95% of the total activity, was highest in men over 18. Protamine-inactivated lipase activity was greatest in younger males and was age-correlated in women, doubling between the second and sixth decades. In 12 patients with hyperchylomicronemia, including five previously shown to have familial type I hyperlipoproteinemia, protamine-inactivated lipase activity was markedly reduced, whereas protamine-resistant lipase was below normal in only 1. The results were not due to lack of plasma activator, presence of plasma inhibitor, or diet, and the deficiency was not overcome by increasing the provoking dose of heparin from 10 U to 75 U/kg. Mean values for both lipase activities were not reduced in 32 other patients with hyperchylomicronemia, nine with "floating beta" lipoproteins (type III hyperlipoproteinemia), and 23 with hyperprebetalipoproteinemia (type IV). Mean protamine-resistant lipase activity was below normal in a group of four women with hypothyroidism, in whom protamine-inactivated lipase was not reduced. Both of the lipase activities were capable of hydrolyzing lipid in very low-density lipoproteins, but the relative rate of hydrolysis of chylomicrons by protamine-resistant lipase was markedly limited. These results indicate the importance of distinguishing between lipases of hepatic and extra-hepatic origin in the measurement of postheparin lipolytic activity.

Adipose Tissue↗