THE DETERMINATION OF PLASMA TRIGLYCERIDES

Serum cholesterol, triglycerides and heart disease of nomadic and sedentary tribesmen consuming isoenergetic diets of high and low fat content

1. The effects were examined of two approximately isoenergetic diets differing widely in saturated fat content on the levels of serum cholesterol and triglycerides of nomads and non-nomads in eastern Niger. Each person was also examined for clinical and electrocardiographic evidence of heart disease. 2. No significant differences could be found between serum cholesterol and triglyceride levels of 297 Anagamba nomad men consuming 73% energy as fat and 303 Kanouri sedentary men consuming 9% energy as fat. 3. Rheumatic heart disease was common in nomads and four possible cases of ischaemic heart disease were found in sedentary men only.

Plasma lipids and lipoproteins in protein-calorie malnutrition

Plasma triglycerides, phospholipids and total cholesterol estimations and lipoprotein electrophoresis on agarose gel were done in control, Kwashiorkor, and marasmic kwashiorkor children. The beta lipoprotein percentage in both conditions is reduced to a statistically significant extent, whereas there is a statistically significant increase in plasma triglycerides in both conditions. Pre-beta fraction was present in all cases, and even increased in marasmic kwashiorkor, which is found to be significant. The results do not support the hypothesis that fatty liver in kwashiorkor is due to impaired release of triglycerides from liver.

Hyperglucagonemia and blood glucose regulation in normal, obese and diabetic subjects

Glucagon was infused to maintain plasma concentrations three to six times the basal level (300 to 600 pg per milliliter) into 16 normal and seven non-diabetic obese subjects. Hyperglucagonemia caused only a transient rise of 5 to 10 mg per 100 ml in basal glucose levels and had no effect on oral glucose tolerance or plasma insulin. In three patients with adult and two with juvenile-onset diabetes on maintenance insulin, hyperglucagonemia maintained for two to four days caused no change in plasma glucose of ketone concentration. In contrast, in nine insulin-withdrawn patients the glycemic response to hyperglucagonemia was five to 15 times greater (P less then 0.05) than in normal controls. Hyperglucagonemia does not cause glucose intolerance in normal subjects or bring about deterioration of diabetic control when insulin is available. Glucagon in the insulin-deprived patient can worsen the diabetic state. These findings suggest the primary role of insulin deficiency in the diabetogenic action of glucagon.

Mechanism of triglyceridemia in hypercholesterolemic rabbits

To elucidate mechanisms responsible for the increased plasma triglyceride (TG) which occurs in diet-induced hypercholesterolemia in rabbits, albino rabbits were fed a 3% cholesterol diet for various durations, and the following determinations were carried out: plasma lipid levels; turnover rate of plasma TG (labeled very low density lipoprotein, or glycerol-2- 3 H method); lipoprotein lipase activity of the heart and plasma; fatty acid and acetate incorporation into TG in the liver (homogenates and slices). Plasma levels of both free and esterified cholesterol and phospholipid increased rapidly, while TG increased relatively slowly during cholesterol feeding without change in hepatic TG synthesis. The fractional turnover was, on the other hand, depressed within a week. The decrease in plasma TG in response to a heparin injection was less in hypercholesterolemic rabbits than in normal animals. However, the measured activity of heart lipoprotein lipase of cholesterol-fed rabbits was higher than that of the control group. When the effects of two substrates (very low density lipoprotein from normo- and from hypercholesterolemic plasma) were compared, the apparent activity was lower with the latter. The Degrees of this inhibition was proportional to the amount of cholesterol in the lipoproteins. The inhibition of lipoprotein lipase activity was also observed with the addition of cholesterol to activated Ediol, but not with addition of esterified cholesterol. Lineweaver-Burk plots were constructed using partially purified plasma lipoprotein lipase, and Km values for Ediol, Ediol plus protamine sulphate, and Ediol plus cholesterol were calculated. The presence of cholesterol in the substrate of lipoprotein lipase competitively inhibits the enzyme activity, and this is the mechanism of hyperglyceridemia observed in diet-induced hypercholesterolemic rabbits.

Studies on the metabolic error in Refsum's disease

Studies utilizing mevalonic acid-2-(14)C and D(2)O as precursors failed to provide evidence for an appreciable rate of endogenous biosynthesis of phytanic acid in a patient with Refsum's disease. Orally administered tracer doses of phytol-U-(14)C were well absorbed both by seven normal control subjects (61 to 94%) and by two patients with Refsum's disease (74 and 80%). The fraction of the absorbed dose converted to (14)CO(2) in 12 hours was 3.5 and 5.8% in Refsum's disease patients and averaged 20.9% in seven control subjects. Labeled phytanic acid was demonstrated in the plasma of both control subjects and patients given phytol-U-(14)C, establishing phytol in the diet as a potential precursor of phytanic acid. This labeled phytanic acid had disappeared almost completely from the plasma of the seven control subjects by 24 to 48 hours, whereas it persisted at high concentrations in the plasma of the two patients for many days. We conclude that the phytanic acid accumulating in Refsum's disease is primarily of exogenous origin and that patients with Refsum's disease have a relative block in the degradation of phytanic acid and possibly other similar branched-chain compounds. This may relate to a deficiency in mechanisms for release of phytanic acid from stored ester forms or, more probably, to reactions essential to oxidative degradation of the carbon skeleton.

The lipoproteins and lipid transport in abetalipoproteinemia

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The nature of pre beta (very low density) lipoproteins

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The differentiation of exogenous and endogenous hyperlipemia by paper electrophoresis

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