George D. Michaels

Calories do count

Abstract There have been statements in the medical and the lay literature to the effect that weight loss occurs more rapidly with diets high in fat and protein asc compared to equi-caloric diets containing large amounts of carbohydrate. In the present study, subjects have been maintained for many weeks on constant calorie intake. At intervals, the composition of the diet has been changed, the fat intake varying from 12 to 83 per cent, protein from 14 to 36 per cent, and carbohydrate from 3 to 64 per cent of total calories. In any given subject, the rate of weight loss was essentially constant throughout the entire study. It is therefore obvious that the significant factor responsible for weight loss is reduction of calories, irrespective of the composition of the diet.

The Effect of a Fish-oil Fraction on Plasma Lipids

Since the original report from this laboratory in 1952 many investigators have confirmed that the substitution in the diet of vegetable fats containing large amounts of linoleic acid (e.g., corn, cottonseed, safflower, soy oil) for fats containing predominantly saturated fatty acids (e.g., fat from meat, eggs, and dairy products) will result in a marked fall in plasma lipids in most human subjects. It has further been demonstrated that the addition of sufficient amounts of polyunsaturated fats to (a) fat-free diets or (b) diets containing significant amounts of saturated fats will result in a significant fall in the level of plasma lipids. The amount of vegetable fat required under the latter set of conditions is of considerable magnitude and from a clinical standpoint is unfeasible because of the increase in dietary calories. Recently, Ahrens and his associates reported that menhaden oil, a fish oil with an iodine value in excess of 150, had at least as great an effect upon plasma lipids as an equal amount of vegetable oil containing more than 50 per cent of linoleic acid. On the basis of existing information there is some reason to believe that the efficacy of a fat in lowering plasma lipids may be in a measure proportional to the total number of double bonds present in its fatty acids. Conceivably, a highly unsaturated fat containing fatty acids of proper molecular configuration would be capable of lowering plasma lipids when added in relatively small quantities to a diet containing considerable quantities of saturated fat. Accordingly, the ethyl esters of menhaden oil were fractionated by appropriate methods with the yield of the fish oil fraction shown in figure 1. The gas-liquid chromatographic pattern of menhaden oil fatty acids is shown at the top of this figure, the menhaden ethyl ester fraction in the center, and a standard fatty acid mixture is shown at the bottom for orientation purposes. It is apparent that the fractionated material contains very much larger amounts of long-chain highly unsaturated material than the original menhaden oil. The

The correlation of hepatic structure and function.

Abstract From study of liver biopsy sections and chemical liver function tests one can only hope for present purposes to obtain rather gross information as to the activity of the process which has resulted or is resulting in liver damage, and information as to the extent and duration of the process. Activity is correlated histologically with phagocytic cell infiltration and with hepatocellular change as manifested by widespread multinucleation, abnormalities of cell shape and size, and abnormalities of staining characteristics. The chemical abnormalities which indicate activity are the cephalin cholesterol flocculation and thymol turbidity tests as well as elevation of the serum bilirubin and/or icterus index. Extent and duration of the hepatotoxic process are manifested histologically by hepatocellular change and by fibrosis. The chemical changes which are found in liver damage of widespread extent and/or long duration are abnormal bromsulfalein retention, diminished hepatic glycogen storage and elevation of the serum bilirubin and/or icterus index. It is to be emphasized that the above observations are extremely superficial and have nothing to recommend them but their simplicity. From the foregoing it is evident that our knowledge of liver histology and physiology is in need of many additions; and that when such additional knowledge is obtained, revision of the present archaic classification of liver disease will be in order. An approach to such a reclassification is presented.

Technics for Separation of Plasma Cholesterol Esters for Determination of Iodine Value, and of Cholesterol.

Summary 1. A method for quantitative chromatographic separation of cholesterol esters from other blood lipids is presented. 2. A colorimetric micromethod for determination of the iodine number of plasma lipid is described. 3. A more stable reagent and a more stable color reaction than the Liebermann-Burchard reaction for the determination of plasma cholesterol is presented. 4. Employment of the above methods, together with determination of total lipids by the method of Bragdon, permits determinations of net unsaturation of the fatty acids esterified with cholesterol in the plasma.

Relation between dietary fat and fatty acid composition of “endogenous” and “exogenous” very low density lipoprotein triglycerides (D < 1.006)

Abstract Using methodology which permits of separation of “exogenous” and “endogenous” very low density lipoprotein triglycerides and subsequent identification of their fatty acid composition, it appears that in a normal subject, as well as in Types IV and V hyperglyceridemics, the dietary fatty acids are incorporated to a significant degree in endogenous as well as exogenous very low density lipoprotein triglycerides. Since the chylomicron triglycerides reflect the dietary fatty acid composition more rapidly than do the endogenous triglycerides, it seems probable that the latter are formed to some degree from the former, quite probably in the liver.

PLASMA LIPID FATTY ACIDS DURING FASTING.

T lIE FATTY acid composition of plasma lipids has been studied in five human subjects during six to fifteen day periods of starvation. Two of the subjects were women with simple exogenous obesity, one a diabetic man (noninsulin dependent) and two noninsulin dependent diabetic women with moderate obesity. According to current concepts, the plasma free fatty acids, particularly during fasting, are derived ahumost entirely from adipose tissue. Only small amounts originate froiri other tissues. Most of the plasma triglycerides are derived from the liver. Free fatty acids from adipose tissue contribute to the liver pool of glycenides.’ Hirsch reported that the mobilization of fatty acids from adipose tissue occurred at random and that no change in the composition of depot fatty acids occurred in human subjects during twenty days of starvation or several months of low calorie, low fat intake.2 He inferred that individual fatty acids are utilized at much the

PLASMA CHOLESTEROL FATTY ACIDS IN HUMAN SUBJECTS AS DETERMINED BY ALKALINE ISOMERIZATION AND BY GAS CHROMATOGRAPHY

Extraction procedure. Fasting plasma lipids are extracted with 25 volumes of solution containing equal parts of ethanol and acetone. The plasma is added slowly to the solvent with shaking; this is brought to a boil and filtered rapidly, using fat-free filter paper. Aliquots of this extract are used for the column separation of the cholesterol esters. Preparation of solution in petroleum ether. Two 50-ml. aliquots of the plasma filtrate, each representing 2 ml. of plasma, are evaporated to dryness under partial vacuum a t approximately 50” C. Five ml. of petroleum ether is added to the residue to dissolve the fat. This is added to the column. The tube is washed 3 times with 2-ml. portions of petroleum ether and these portions are added to the column. After the absorption of the petroleum ether by the Celite-silicic acid, 100 ml. of petroleum ether is added for complete elution of the cholesterol esters. The rate is adjusted by application of slight positive pressure to attain a flow rate of approximately 1 ml./min. Preparation of the column. The column consists of a 25-ml. burette with a self-lubricating Teflon plug assemblyt and a 125-ml. flask fused to the top of the burette as a reservoir. A glass wool plug is introduced and a mixture of equal parts by weight of Celite and silicic acid is added with tamping to a height of 10 cm. Many investigators who use silicic acid for the separation of the various fat components advise the use of certain mesh sizes and activation by heat’ or by dehydrating solvents? Such activation will increase the efficiency considerably if one is interested in obtaining the maximum amount of lipid adsorption per gram of silicic acid. However, dehydration of silicic acid below a certain point will eliminate its adsorptive power almost completely. The degree of activation affects not only the amount of fat adsorbed per gram, but also the elution of certain fats. When 100 ml. of petroleum ether is added to the col-

Plasma cholesterol ester fatty acid composition in relation to diet.

Summary Administration of large amounts of purified linoleic acid preparations to diabetic and non-diabetic patients results in a marked increase in the di-enoic acid content of the cholesterol esters, in association with a lowering in the mono-enoic acid content. When ethyl esters of oleic acid are substituted for the ethyl linoleate the opposite pattern is observed. A high carbohydrate, fat-free diet produces much the same pattern of cholesterol ester composition as that seen during oleate ingestion.

Accentuation of Human Diabetes by “Pituitary Growth Hormone”.

Summary Administration of “highly purified pituitary growth hormone” to a diabetic patient, under chemically controlled conditions, resulted in increased hyperglycemia and glycosuria, in minimal increase in blood and urinary ketones, and in minimal change in the nitrogen balance. The data support the concept that the increased hyperglycemia and glycosuria are probably attributable to diminished carbohydrate utilization rather than increased neoglucogenesis. The diminished utilization in turn may be referable to diminished endogenous insulin production as the result of the exhaustion of the beta cells of the islets.

PROTEIN BALANCE STUDIES IN PATIENTS WITH LIVER DAMAGE. II. THE RÔLE OF LIPOTROPIC AGENTS

Excerpt During the decade 1932-1942 a considerable body of data accumulated, which completely revamped prior concepts of liver damage, in that nutritional factors assumed a role of increasing impor...