Moti L. Kashyap

Activation of fibrinolysis by apolipoproteins of high density lipoproteins in man.

The effects on fibrinolysis of purified normal human plasma lipoproteins and their apolipoproteins (apo) were assessed in an in vitro system containing urokinase, plasminogen, and fibrin. High and very low density lipoproteins (HDL and VLDL, respectively) but not low density lipoproteins (LDL) significantly increased lysis of radiolabeled fibrin or lysis area of plated fibrin compared to controls. Apo HDL, apo HDL2, apo HDL3, apo VLDL (buffer soluble apo), apo AI and AII activated fibrinolysis by 1.3-1.4 fold of control values, whereas apo B (as a narrow density cut of LDL) and non-lipoprotein control proteins (albumin and myoglobin) did not. Addition of HDL in the absence of urokinase failed to activate fibrin lysis. These data demonstrate that the major proteins of HDL - apo AI and apo AII - and possibly certain minor constituent(s) common to HDL and VLDL participate in the fibrinolytic process.

Hyperalpha- and hypobeta-lipoproteinemia in octogenarian kindreds☆

Abstract To assess factors related to distinctive longevity, lipoprotein and kindred studies were carried out in 22 octogenarian kindreds self-referred by virtue of either two siblings or a parent and child living to age 80 or over. There was evidence for familial hyperalpha-lipoproteinemia in 7 kindreds, for familial hypobeta-lipoproteinemia in 3 kindreds, and for primary hyperalpha-lipoproteinemia and hypobeta-lipoproteinemia in an additional 2 and 2 kindreds respectively. First degreee relatives of probands with primary or familial hyperalpha- or hypobeta-lipoproteinemia had sharply reduced morbidity and mortality from myocardial infarction when compared to population controls, P P P

Apolipoprotein AI and AII metabolism in patients with primary high-density lipoprotein deficiency associated with familial hypertriglyceridemia

Plasma high-density lipoproteins (HDL) and their major proteins--apolipoprotein (apo) AI and apo AII--are subnormal in most patients with familial hypertriglyceridemia. However, the pathophysiology of low-plasma apo AI and apo AII is unclear. The kinetic parameters (turnover) of HDL apo AI and apo AII were studied in six lean patients with primary HDL deficiency associated with familial hypertriglyceridemia and five normolipidemic controls. Autologous 125I labeled HDL were injected intravenously (IV; 25 microCi) and blood samples drawn ten minutes after the injection and periodically thereafter for 12 days. Urine samples were collected daily and their radioactivity measured. Kinetic parameters were calculated from the area under the decay curve using three exponentials. Mean plasma apo AI and apo AII were significantly lower (P less than 0.001) in patients than normals (70.4 +/- 2.7 v 106.9 +/- 7.0; 24.2 +/- 1.6 v 39.2 +/- 0.9 mg/dL, respectively). The mean fractional catabolic rates (FCR) obtained from plasma 125I-HDL, apo AI, apo AII radioactivity decay curves and by Berson and Yalows method (urine/plasma radioactivity ratios) were significantly greater (P less than 0.05) in patients than in controls (0.387 v 0.299; 0.391 v 0.309; 0.361 v 0.275; 0.272 v 0.207/d; respectively). The mean synthetic rates (SR) of apo AI and apo AII were significantly lower in patients than in controls (11.12 v 14.17 mg/kg body weight/d, P less than 0.05; 3.53 v 4.68 mg/kg body weight/d, P less than 0.05, respectively). In vitro lipolysis of triglyceride (TG) rich lipoproteins by bovine lipoprotein lipase, and measurement of hepatic TG lipase and lipoprotein lipase in postheparin plasma were similar in patients and controls, indicating no abnormality in these factors that are linked to HDL and TG catabolism. However, a significant positive correlation between hepatic TG lipase and the FCR of apo AI and apo AII was found. The data suggest that in this series of patients with HDL deficiency the low plasma HDL-cholesterol, apo AI, and apo AII levels resulted from decreased synthesis and an increased fractional catabolic rate of apo AI and apo AII, the major proteins of HDL.

Abnormal preponderance of sialylated apolipoprotein CIII in triglyceride rich lipoproteins in type V hyperlipoproteinemia

Triglyceride rich lipoproteins contain apolipoproteins (apo) CII and CIII. Apo CII and CIII activate and inhibit tissue lipoprotein lipase, respectively. Apo CIII is a glycoprotein containing 0, 1 or 2 moles of sialic acid (designated apo CIII0, CIII1 and CIII2, respectively). This study was designed to determine whether an abnormal distribution of these biologically active apoproteins occurred in triglyceride rich lipoproteins isolated from hypertriglyceridemic individuals. Triglyceride rich lipoproteins were isolated by preparative ultracentrifugation from 10 patients with primary type V hyperlipoproteinemia, eight patients with primary type IV hyperlipoproteinemia, and 11 normal healthy normolipidemic matched control subjects. After delipidation with tetramethyl urea, apo CII and CIII subspecies were separated by analytical isoelectric focussing with a pl range between 3.5 and 5.0. This technique allows a clear separation of apo CIII0 from its sialylated subspecies and also from apo CII. The ratios of the individual apo CIII subspecies to each other and to apo CII were calculated from densitometric scanning of the stained gels. Desialylated apo CIII0 comprised 3.3 ± 1.9% (M ± SD.) of total apo CIII in patients with type V hyperlipoproteinemia and was significantly lower (p = 0.0001) than the proportion found in normal subjects (14.3 ± 5.9%) and patients with primary type IV hyperlipoproteinemia (16.7 ± 6.2%). Apo CIII1 comprised 62.4 ± 5.9% of total apo CIII in type V patients being significantly higher than that in normal subjects (52.6 ± 6.9%; p = 0.003) and patients with primary type IV hyperlipoproteinemia (47.1 ± 3.7%; p = 0.0001). Apo CIII2 as percent of total apo CIII was similar in the three groups. The distribution of the apo CIII subspecies in patients with primary type IV hyperlipoproteinemia was similar to control subjects. In patients with type V hyperlipoproteinemia, the ratio of apo CIII0; CII (0.11 ± 0.05) was significantly lower than normal (0.47 ± 0.26; p = 0.002), and also lower than the mean ratio observed in patients with primary type IV hyperlipoproteinemia (0.60 ± 0.25; p = 0.0001). Apo CIII1;CII ratio in type V hyperlipoproteinemia (2.24 ± 0.58) was significantly higher than normal (1.64 ± 0.41; p = 0.02) and type IV hyperlipoproteinemia (1.67 ± 0.32; p = 0.047). Apo CIII2:CII ratio was similar in the three groups. Total apo CIII:CII ratio in types IV and V (3.5 ± 0.86 and 3.55 ± 0.66, respectively) was higher than normal (3.15 ± 0.83), but the differences were not statistically significant. These data indicate that type V hyperlipoproteinemia is associated with an abnormal preponderance of sialylated to the desialylated apo CIII in triglyceride rich lipoproteins. Further work is needed to define the precise mechanism(s) responsible for this abnormality.

In vitro catabolism of human plasma very low density lipoproteins. Effects of VLDL concentration on the interconversion of high density lipoprotein subfractions.

The effect of lipolysis of human plasma very low density lipoproteins (VLDL) on the distribution of high density lipoprotein subfractions was studied in an in vitro system consisting of purified bovine milk lipoprotein lipase and albumin. The distribution of lipids and apoproteins (apoC-II and apoC-III) within the lipoprotein fractions corresponding to HDL2 (d = 1.063-1.120 g/ml) and HDL3 (d = 1.120-1.210 g/ml) was dependent upon the concentration of VLDL in the incubation mixture. After lipolysis of an incubation mixture containing VLDL-triglyceride (0.6 mg triglyceride/ml) and HDL3 (0.1 mg protein/ml), most of the lipid and apoproteins were recovered in HDL3. At higher concentrations of VLDL-triglyceride relative to HDL3-protein (1.8 or 2.4 mg of VLDL-triglyceride and 0.1 mg of HDL3-protein) the amount of lipid and apoprotein isolated in the HDL3 density fraction decreased after lipolysis and there was an increase in the amount isolated between d 1.063-1.120 g/ml. These results provide additional evidence for the conversion of HDL3 to HDL2 during lipolysis. Furthermore, they suggest that the relative distribution of plasma HDL2 and HDL3 is related to the rate of catabolism of triglyceride-rich lipoproteins.

Carbohydrate and lipid metabolism during human labor: Free fatty acids, glucose, insulin, and lactic acid metabolism during normal and oxytocin-induced labor for postmaturity☆

This investigation was performed to study the metabolism of the major body fuels (viz. glucose and free fatty acids), insulin, and lactic acid during the stress of human labor. In addition, the role of the normal placenta in the transport of these substances between mother and the fetus was evaluated by measuring them in the mother and cord blood at delivery. To study possible alterations of this role in the placenta which had exceeded the normal period of gestation, a second comparable group of women had labor induced with oxytocin 16-18 days beyond the expected date of delivery. A dramatic twofold increase in maternal plasma free fatty acids was observed during labor. There was a lesser but definite increase in blood glucose concentrations. No rise in serum insulin levels was noted which coincided with the changes in blood glucose. Lactic acid concentrations during the course of labor were variable from baseline but at delivery, the concentrations rose to very significant levels. Free fatty acids and blood glucose levels were significantly higher in the maternal than in the fetal side. A significantly positive correlation was noted between the maternal and cord blood values except for free fatty acids in the postmature group. No significant difference, nor a correlation was found between the two compartments in the insulin nor lactic acid levels. These results suggest that during human labor free fatty acids are the principal metabolic fuel. This increase in maternal free fatty acids may serve to spare glucose as a metabolic fuel in the fetus. The mechanism responsible for the increase maternal free fatty acid mobilization remains to be determined. It is not possible to discern any consistant alteration in placental function as a consequence of prolonged gestation.

High-density lipoprotein apolipoprotein AI and AII turnover in moderate and severe proteinuria.

The kinetic parameters of high-density lipoprotein (HDL) and its major apolipoproteins (Apo) AI and Apo AII were studied in 2 patients with moderate and severe proteinuria and 2 normal controls after intravenous injection of autologous 125I-HDL. The fractional catabolic rates (FCR) of HDL estimated by urine/plasma radioactivity ratio, and FCR of Apo AI and Apo AII calculated from the radioactivity decay curves were higher in the patients. These results support the concept that high-density lipoproteinuria and renal parenchymal sequestration of HDL found in the nephrotic syndrome contribute to accelerated HDL catabolism.

Dietary fat in experimental nephrotic syndrome: Beneficial effects of fish oil on serum lipids and, indirectly, on the kidney

Three isocaloric diets with different fat composition were fed to rats for seven weeks after the production of nephrotic syndrome by adriamycin. The effects of feeding 3% and 14% fish oil were compared with those of feeding beef fat. At the fourth week of feeding the levels of triglycerides and cholesterol were lower in both fish oil fed groups. At the seventh week these levels, and the LDL cholesterol, were lower only in the 14% fish oil group. In rats fed beef fat, but not in those fed fish oil, there was a striking positive correlation of the four-week serum triglycerides and cholesterol with the seven-week serum creatinine level and with the degree of glomerular hyalinosis and endothelial swelling. The favorable effects of fish oil feeding on serum lipids may have a protective effect on the development of glomerular damage.

Diet and HDL Metabolism: High Carbohydrate vs. High Fat Diets

An increased level of plasma low density lipoproteins (LDL) is a major risk factor in the development of coronary artery disease (1). Conversely, plasma high density lipoproteins (HDL) and apolipoprotein A-I, the major protein constituent of HDL, are inversely related to the disease (2-4). In an attempt to reduce the incidence of heart disease, a number of organizations have suggested that dietary fat intake be reduced to 30% of calories (5). Since the protein intake of the U.S. population is approximately 20%, the resultant diet would result in an increase in dietary carbohydrate (CARB). Although high CARB diets reduce LDL-cholesterol, they also produce fasting hypertriglyceridemia, hyperinsulinemia (6) and decreased levels of HDL-cholesterol (6-8), all of which may be associated with increased risk of heart disease. Lipoprotein lipase (LpL) and hepatic triglyceride lipase are key enzymes in lipoprotein metabolism (9). LpL catalyzes the hydrolysis of chylomicron triacylglycerols and very low density lipoproteins (VLDL). The lipoprotein substrates for H-TGL are less well defined, although most evidence suggests that the enzyme plays a role in the catabolism of remnant lipoproteins (intermediate density lipoproteins) and in the degradation of HDL, particularly the HDL subfraction corresponding to HDL2.The purpose of the present study was to determine whether the effect of a high CARB diet on plasma lipids, and lipoproteins is correlated with changes in the activity of LpL and H-TGL. The results show that the dietary CARB-induced changes in HDL-cholesterol and HDL2, is significantly correlated to changes in LpL activity whereas H-TGL activity does not vary on a high CARB diet.

Renal handling of high-density lipoproteins by isolated perfused kidneys

Recent studies show that the normal and diseased kidney is an important organ in the catabolism of high-density lipoproteins (HDL). However, little is known about the renal handling of HDL. To investigate this aspect, kidneys were isolated from normal rats and rats made nephrotic with puromycin aminonucleoside. They were perfused in a chamber at 37 degrees C with a modified Krebs-Hensleit Bicarbonate Buffer containing 1%, 3%, 6%, and 10% Bovine Serum Albumin (BSA). Presence of 10% BSA in the perfusate prevented glomerular filtration and urine formation. Thus, the filtering and the nonfiltering kidney perfusion models distinguish the renal parenchymal function independently of luminal events that follow filtration. 125I-labeled rat HDL was injected into the perfusate and radioactivity in perfusate, urine, and kidney was examined. At the end of perfusion (30 minutes or four hours), each kidney was flushed with 125I-HDL-free perfusate and kidney radioactivity was measured. At four hours, 1.9% +/- 0.5% of injected radioactivity was present in urine from kidneys perfused with 6% BSA. Kidneys with intact glomerular filtration sequestered significantly more radioactivity (1.1% +/- 0.2% of injected radioactivity) than nonfiltering kidneys (0.7% +/- 0.2%); P less than 0.05. Radioactivity in filtering kidneys was significantly higher than in nonfiltering kidneys (33.9 +/- 7.8 v 15.6 +/- 2.6 cpm/mg kidney tissue protein, respectively; P less than 0.001). Nephrotic kidneys (filtering and nonfiltering) sequestered two to four times more 125I-HDL than normal kidneys. These data support the hypothesis that prior to urinary excretion, partial reabsorption of filtered HDL (or subfractions) occurs in the normal kidney.(ABSTRACT TRUNCATED AT 250 WORDS)