J. David Schnatz

Lipid and Carbohydrate Studies in Coronary Artery Disease

Twenty-seven patients with arteriographically proved coronary artery disease, aged 27 to 59 years, were studied for abnormalities of lipid or carbohydrate metabolism. All patients were referred because of cardiac symptoms and none had any prior history of lipid or carbohydrate abnormality. Twenty-three patients were found to have some abnormality of carbohydrate or lipid metabolism, and four had none. Seventeen patients had an abnormal lipoprotein electrophoretic pattern, 12 had elevated serum cholesterol concentrations, and 15 elevated serum triglyceride values. Eighteen patients had an abnormality of carbohydrate metabolism, 11 as determined on standard glucose tolerance tests and seven on cortisone glucose tolerance tests. These abnormalities of carbohydrate and lipid metabolism were not related to age or ponderal-index ratio. This high incidence of carbohydrate and lipid abnormalities in association with coronary artery disease may be important in the pathogenesis of the vascular disease as well as management of these patients and their progeny.

Localization in the ventromedial hypothalamic nuclei of an area affecting plasma triglyceride and cholesterol levels

In three experiments exploratory lesions were placed in anterior, medial, dorsal and posterior hypothalamic areas of weanling female rats to determine the localization and the extent of the area affecting plasma triglyceride and cholesterol levels. In another experiment, lesions of various sizes were placed in the ventromedial hypothalamic area to define the size of the lesions necessary to elevate plasma triglyceride and cholesterol levels. Three or more weeks after the hypothalamic operation, trunk blood was obtained after decapitation. Only lesions destroying primarily the ventromedial hypothalamic nuclei resulted in significant elevations of both lipid fractions. Small lesions, confined to the medial area of the VMN in antero-posterior respect did not produce the above alterations, but with increasing lesion size significant positive correlations between lesion size and plasma lipid levels were evident. The data suggest that the ventromedial hypothalamic nuclei are a hypothalamic site which influences lipid metabolism. In drei Experimenten wurden elektrolytische Läsionen im vorderen bzw. medialen, dorsalen und hinteren Gebiet des Hypothalamus der weiblichen abgesetzten Ratte plaziert, um den Locus zu bestimmen, dessen Zerstörung Hypertriglyceridämie und Hypercholesterinämie verursacht. In einem weiteren Experiment wurden Läsionen verschiedener Größe im ventromedialen Hypothalamus plaziert, um die Ausdehnung der verantwortlichen Nervenmasse zu definieren. Nur Läsionen, welche hauptsächlich den ventromedialen hypothalamischen Kern zerstören, verursachen bedeutende Erhöhungen von Triglyceriden und Cholesterinspiegeln. Kleine Läsionen, welche auf das mittlere Gebiet des ventromedialen Kernes beschränkt sind, verursachen die erwähnten Erscheinungen nicht. Mit größer werdendem Läsionsherd werden die Änderungen der Plasmalipide aber größer. Die Ergebnisse weisen darauf hin, daß die ventromedialen hypothalamischen Kerne und ihr unmittelbares Grenzgebiet den Fettstoffwechsel beeinflussen.

Neutral and alkaline lipolytic activities in human adipose tissue

Abstract Previous work from this laboratory suggested that human adipose tissue contains at least 2 lipolytic activities. Assay systems have been developed for the optimal demonstration of these activities in cell-free preparations of human adipose tissue, and additional differences have been demonstrated. Neutral lipolytic activity was assayed at pH 7.0, 37° with olive oil as substrate, and alkaline lipolytic activity at pH 8.0, 47° with tributyrin as substrate. Studies which related triglyceride concentration to both lipolysis and absorbance of the assay system suggested that neutral lipolytic activity represents hydrolysis of an emulsified ester and alkaline lipolytic activity hydrolysis of a soluble ester. In general, neutral lipolytic activity was augmented considerably by albumin, 50 mg/ml, but alkaline activity was not. In addition to the differences in assay conditions the 2 activities differed in their thermal stability, pH dependence, and inhibition characteristics. These activities differ in their hydrophilic tendencies as seen by the fact that they were partially separated by centrifugation of an adipose tissue homogenate, or by extraction of an adipose tissue preparation with diethyl ether. In addition each activity differs from lipoprotein lipase activity.

Electrophoretic behavior of alkaline lipolytic activity in human adipose tissue

Abstract 1. (1) Alkaline lipolytic activity (ALA), a soluble esterase found in human adipose tissue, has been visualized on starch gel after electrophoresis by a staining method which employs naphthol esters as substrates and Fast Blue B as a coupling agent 2. (2) The electrophoretic phenotype is manifest as five bands of esterase activity (ALA I-5) with similar substrate and inhibitor specificity, consistent with the isoenzyme concept 3. (3) The effects of time and temperature suggest that ALA 5 is a subunit of ALA i -4) 4. (4) I 8 2 fresh adipose tissue preparations have been carefully studied and no genetic variations observed 5. (5) The characteristic electrophoretic bands of ALA have also been found in human liver, lung, heart, kidney, adrenal, spleen, thyroid, ovary, testis, brain and muscle 6. (6) The physiological function is not known, but their ability to hydrolize emulsions of long-chain fatty acid esters suggests a role in lipolysis.

Effect of dorsomedial hypothalamic lesions before and after placement of obesity-producing ventromedial hypothalamic lesions in the weanling male rat.

Abstract Bilateral electrolytic lesions in the ventromedial hypothalamic nuclei (VMN) were produced in two groups of weanling male rats. Two groups of rats received lesions in the dorsomedial hypothalamic nuclei (DMN). Six days later, one of the VMN groups received DMN lesions (VMN and DMN), while VMN lesions were produced in one of the DMN groups (DMN and VMN). Sham-operated animals served as controls. The animals were maintained for 18 days during which time food intake was measured. On the 19th day they were decapitated and the following parameters determined: carcass fat, plasma insulin, glucose, triglyceride and cholesterol, and body weight and length. DMN lesions failed to attenuate the ‘principal’ parameters of the weanling rat ventromedial syndrome: hyperinsulinemia, hyperlipidemia and increased carcass fat. This was irrespective of the sequence of the two hypothalamic operations. Food intake, body weight and length proved amenable to DMN lesions only when DMN were produced prior to VMN lesions, but it is noteworthy that in these animals plasma insulin and lipid levels remained elevated despite a reduced food intake. Neither of the groups with double lesions had glucose values which were significantly different from those of the controls. The data point to a profound autonomy of the ventromedial hypothalamic nuclei and their related circuits in the development of the weanling rat VMN syndrome.

Alkaline lipolytic activity of rabbit adipose tissue: Genotypes and their inheritance

A genetic variant of alkaline lipolytic activity (ALA), a soluble esterase found in mammalian adipose tissue, has previously been described. This “slow” variant was characterized by slower migration during starch gel electrophoresis, a decreased tendency to dimerize, and reduced enzymatic activity in constrast to the “fast” electrophoretic phenotype. The present paper identifies a homozygous (FF) and a heterozygous (Ff) “fast” phenotype which are differentiated after starch gel electrophoresis by the presence or absence of a slow band identical to that of the homozygous “slow” (ff)/it phenotype. In addition, ALA of homozygous and heterozygous “fast” rabbits differed in total enzymatic activity and its tendency to dimerize. The inheritance of this variant was proven to be Mendelian.

The effect of lateral hypothalamic lesions in weanling rats bearing lesions in the ventromedial hypothalamic nuclei.

Summary Lateral hypothalamic lesions in weanling rats bearing lesions in the ventromedial hypothalamic nuclei (VMN) did not eliminate the hypertriglyceridemia, hyper-insulinemia or changes in somatic parameters associated with VMN lesions. In conjunction with previous data, the present findings suggest that altered sympathetic nervous system activity, subsequent to ventromedial hypothalamic destruction, is important in the development of the syndrome of hypothalamic obesity. The authors appreciate the technical assistance of Diana Hojnicki, Maureen Mills, Betty Stone and Tom Vincent. This work was supported in part by a grant from the National Institutes of Health, NIAMD AM 14418.

Lipoprotein lipase activity and hypertriglyceridemia in alloxan diabetic rabbits.

Abstract Alloxan diabetic rabbits, deprived of insulin, had normal plasma post-heparin lipoprotein lipase activity. An associated hypertriglyceridemia developed on a high carbohydrate diet and had characteristics of an endogenous lipemia. These data indicate that (1) lipoprotein lipase activity of rabbits responds differently to acute insulin deficiency than that of rats, (2) additional factors may be important in the hypertriglyceridemia of uncontrolled diabetes, and (3) there is a possible similarity to the hypertriglyceridemia of ketoacidosis in humans where, although lipoprotein lipase activity may be decreased, other factors also appear to be operative.

The Hydrolysis of Tissue Triglyceride Emulsions by Homogenates of Normal, Adrenalin-Stimulated and Insulin-Deficient Rat Epididymal Adipose Tissue

Studies on lipolytic activity of rat epididymal adipose tissue are reported. A unique aspect consisted of using as substrate triglyceride which had been extracted from adipose tissue. The triglyceride was characterized by thin-layer and gas-liquid chromatography. Optimal conditions for hydrolysis of an emulsion of this triglyceride were determined to consist of pH 7.5, 0.05 M phosphate, 5 per cent albumin, and an incubation temperature between 20 and 30 C. Hydrolysis at 25 C. An investigation of the that at 37 C. An investigation of the intracellular location of this lipolytic activity in homogenates centrifuged at 800 x g for 10 minutes showed that it was associated with the fat layer which floated to the top. Hydrolysis of the triglyceride emulsion was not altered by preincubation of the tissue with adrenalin. This was in contrast to a significant increase in glycerol release observed during preincubation and in hydrolysis of homogenate triglyceride of the assay system. Hydrolysis of the triglyceride emulsion remained unaltered after 48 hours of in vivo insulin deficiency. The lipolytic activity described differs in a number of respects from those previously reported, suggesting the presence of a different enzyme or indicating additional factors which modify the in vitro reaction of previously described lipolytic enzymes.

Genetic variation of alkaline lipolytic activity in rabbits.

Abstract Rabbit adipose tissue extracts have been shown to have a “fast” and a “slow” phenotype of alkaline lipolytic activity which have been attributed to two genotypes, FS and SS. the “fast” phenotype is similar to the alkaline lipolytic activity of human adipose tissue in its migration during starch gel electrophoresis and elution from Sephadex G-200. The “slow” phenotype contains less activity, is electrophoretically different, and exists mainly as a smaller molecule than that which comprises the “fast” phenotype. The genetics of this alteration are not yet understood. However, some rabbits appear to inherit a subunit which is altered in charge and thus in electrophoretic mobility. Associated with this alteration is a decrease in measurable activity and a decreased tendency to dimerize.