Stereospecificity of lipoprotein lipase is an intrinsic property of the active site of the enzyme protein.
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Animals↗
Biomedical subjects
T Kuusi
Publications and source records attributed to T Kuusi.
The stability properties of golden beet and red beet pigments: influence of pH, temperature, and some stabilizers.
Golden beet (Beta vulgaris var. lutea) color was found to contain 8 components, of which the most important seemed to be vulgaxanthin-I and -II. Purified vulgazanthin -I solutions are easily degraded at high temperatures. The stability is, however, strongly dependent on pH: the stability is best at pH values between 5 and 6, the poorest at low pH values, but at pH 7 the stability is better than that of betanin. Vulgaxanthin-I is more stable in the raw extract than in a purified solution. EDTA, even in ppm amounts, was found to improve the stability of betanin. The effect was dependent on pH value, being most efficient at pH 2.0 and 5.0. Stability of vulgaxanthin-I was not improved by EDTA. Tannin did not show stabilizing influence. Ascorbic acid was found to have an unfavorable influence on stability, especially in the case of betanin.
Drug Stability↗
The effect of iron, tin, aluminium, and chromium on fading, discoloration, and precipitation in berry and red beet juices.
The effect of iron(II), tin(II), aluminium(III), and chromium(III) on the properties of red whortleberry, blackcurrant, and red beet juices was followed during storage for 10 months at 5 degrees C. The colour and pH changes were studied, and the precipitates formed were weighed and their metal contents assayed. Of the metals tested, only tin caused bluish discoloration in the berry juices. In the case of iron, aluminium, and chromium the low pH prevented this type of discoloration. In berry juices, some increases in colour intensity took place with the lowering of pH value, whereas in red beet juice the opposite change occurred. The colour changes due to storage appear to take place irrespective of the metals. Precipitation is enhanced in red whortleberry juice only by tin, and in blackcurrant juice by tin and iron. In red beet juice, precipitation is increased by the lowering of pH resulting from metal salt addition. In general, increase in the amount of metal added increased the metal content of the precipitate. Iron showed the greatest tendency to become bound in the precipitate, particularly in blackcurrant and red beet juice. The suitabilities of the metals for canning purposes are considered. Chromium, in particular, has interesting possibilities in view of the low degree of colour change associated with it.
Aluminum↗
Formation of malonaldehyde in frozen baltic herring and its influence on the changes in proteins.
The relationship between the malonaldehyde formed as oxidation product of lipids, and changes of proteins in frozen Baltic herring (Clupea harengus var. membranus) was studied. Changes occurred in the muscle proteins due to freezing, so that water-binding capacity, solubility, and the amount of free epsilon-amino groups in these proteins decreased. A close relationship was found between the amount of malonaldehyde and changes of proteins in the different phases of storage. The reaction of malonaldehyde with the free amino groups of the proteins may be one of the factors on which the changes of proteins during frozen storage are based.
Animals↗
Effect of probucol on cholesterol synthesis, plasma lipoproteins and the activities of lipoprotein and hepatic lipase in the rat.
The postheparin plasma lipoprotein lipase (LPL) activity and plasma HDL and LDL cholesterol concentrations, decreases significantly during probucol treatment of the rat. The reduction of the LPL activity obviously took place in adipose tissue. The activity of hepatic lipase and the in vitro synthesis of cholesterol in the liver or isolated jejunal villous cells were unaffected by the probucol treatment. Plasma triglyceride and VLDL cholesterol concentrations remained similar in the control and probucol groups despite the difference in the LPL activity, whereas the esterified VLDL cholesterol level was significantly reduced in the probucol group. The results suggest that the HDL lowering action of probucol is contributed by the reduced LPL activity probably via impaired VLDL metabolism.
Animals↗
Different effects of two progestins on plasma high density lipoprotein (HDL2) and postheparin plasma hepatic lipase activity.
Two progestins with different androgenic activity were compared for their effects on plasma high density lipoproteins and postheparin plasma lipase activities in premenopausal women. Levonorgestrel, a nortestosterone-derived steroid with androgenic activity reduced plasma HDL cholesterol by 17% (P less than 0.05) and HDL2 cholesterol by 30% (P less than 0.05), without changing the HDL3 cholesterol concentration. At the same time the postheparin plasma hepatic lipase activity was increased by 56% (P less than 0.01) whereas the lipoprotein lipase was not changed. None of these effects was reproduced during administration of medroxyprogesterone acetate, a progestin with low androgenic activity. The results suggest, first, that the decrease of HDL cholesterol observed during treatment with progestins is related to the androgenic activity of the steroid used, and, second, that the change in HDL (HDL2) is caused by androgen-induced increase of hepatic lipase activity.
Adult↗
Persistent abnormalities in lipoprotein composition in noninsulin-dependent diabetes after intensive insulin therapy.
To determine whether rigorous insulin therapy, which normalized the routinely measured plasma lipids, also reversed qualitative abnormalities in the composition of lipoproteins in noninsulin-dependent diabetes mellitus (NIDDM), we studied 18 NIDDM patients (eight men and 10 women) before and 2 months after intensive insulin therapy. Glycosylated hemoglobin levels (11.7% vs. 8.7%), plasma triglyceride (TG) (250 +/- 91 vs. 164 +/- 56 mg/dl, p less than 0.001), and cholesterol (214 +/- 43 vs. 198 +/- 31 mg/dl, p less than 0.025) all fell, and both HDL2 cholesterol and HDL3 cholesterol increased (59.1% and 10.9%, respectively, p less than 0.001). However, abnormalities in two indices of lipoprotein surface constituents, which were present before insulin therapy, remained so thereafter. The first of these, the new cardiovascular risk factor, the plasma free cholesterol/lecithin ratio, which was increased before treatment, fell only slightly after therapy (pre-therapy 1.02 +/- 0.29 vs. post-therapy 0.90 +/- 0.17, p less than 0.4; reference group, 0.83 +/- 0.14), and remained elevated in very low density lipoprotein (VLDL) and low density lipoprotein (LDL). Secondly, the sphingomyelin/lecithin ratio, an index of the surface rigidity of lipoproteins, was abnormal before treatment in VLDL, HDL2, and HDL3, and this alteration persisted after insulin therapy in HDL3 (p less than 0.001). Lipoprotein core lipid abnormalities were also present before treatment: the TG/cholesteryl ester ratio was reduced in VLDL and increased in LDL, HDL2, and HDL3. Rigorous insulin therapy improved, but failed to fully correct, this disturbance.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Changes of high density lipoprotein subfraction concentration and composition by intralipid in vivo and by lipolysis of intralipid in vitro.
Serum lipoproteins were measured during a single infusion of intralipid and during parenteral nutrition with intralipid and glucose. Postheparin plasma lipolytic enzymes and plasma LCAT activity were assayed before and after the parenteral nutrition. Both single and repeated infusions of intralipid were followed by a significant rise of HDL2 concentration (p less than 0.01), whereas the HDL3 decreased. The composition of HDL subclasses altered. The HDL2 triglyceride and phospholipids increased, while the HDL3 esterified cholesterol and protein decreased. In vitro incubation of serum with intralipid alone caused no changes in the zonal profile of HDL subclasses, but hydrolysis of intralipid by lipoprotein lipase was followed by conversion of HDL3 into lighter particles floating in the density range of HDL2. The present results provide additional evidence for a precursor-product relationship between the HDL2 and HDL3. During 4 days of parenteral nutrition with intralipid, the basal (morning) values of serum total and VLDL triglyceride did not change. The LDL phospholipids increased progressively (from 67 to 98 mg/dl, p less than 0.05). The total HDL cholesterol decreased and this change was due to the fall of HDL3 cholesterol esters (from 19 to 12 mg/dl, p less than 0.05). Also the basal values of apo A-I and A-II in HDL3 decreased. The basal level of the HDL2 remained constant. Postheparin plasma LPL activity increased by 52% (p less than 0.01) but hepatic lipase activity fell by 49% (p less than 0.05). These changes may account for the maintenance of plasma HDL2, whereas the progressive fall of the basal HDL3 is probably due to the lack of intestinal apoprotein synthesis during absent intestinal absorption.
Adult↗
Lack of sex differences in high density lipoproteins in Pima Indians. Studies of obesity, lipase activities, and steroid hormones.
To investigate the reasons for the lack of sex differences in high density lipoproteins (HDL) observed in population studies of the Pima Indians, we selected 18 lean (9 men, 9 women, body mass index (BMI) less than 27) and 22 obese (12 men, 10 women, BMI greater than 27) Pima Indians for an inpatient study of HDL composition. We measured lipase activities and steroid hormone concentrations, both of which have previously been implicated in the control of HDL. The lean women had higher concentrations of HDL and HDL2 than did either the obese women or the lean or obese men. Lean women had significantly lower hepatic lipase activities and significantly higher concentrations of estradiol compared to obese women. Lean women also had different HDL2 composition, as indicated by the molar ratio of HDL2 cholesterol/A-I. Significant negative correlations between HDL and obesity measured by either BMI or percent body fat were observed in both sexes, but the slope of the relationship was steeper in women. Significant negative associations were observed between HDL or HDL2 concentrations and hepatic lipase in both sexes, and there were significant positive associations between HDL2 and plasma estradiol in women. The data suggest that obesity in this population has a stronger negative influence on HDL concentrations in women, possibly through changes in estradiol and hepatic lipase activities. Since there are so few lean women in the Pima population, the net result is that HDL levels in women in the population as a whole do not differ from those of men.
Adult↗
Inheritance of high density lipoprotein and lipoprotein lipase and hepatic lipase activity.
The role of genetic and environmental factors in the regulation of plasma high density lipoprotein (HDL) was estimated in 17 monozygotic (MZ) and 18 dizygotic (DZ) male twins randomly selected from the Finnish Twin Cohort Study. In addition to HDL cholesterol, we determined the HDL subfractions, HDL2 and HDL3, and the major HDL apoproteins (apo) A-I and A-II. The activities of lipoprotein lipase (LPL) and hepatic lipase (HL) were also assayed from postheparin plasma to get information on their possible contribution to the heritability of HDL. Evidence for the genetic component in the regulation of plasma HDL received support from the heritability estimate of 0.34. The different heritability estimates of HDL2 and HDL3 (h2 of 0.56 and less than 0, respectively) support the idea that the HDL subfraction distribution might be important in the genetic regulation of plasma HDL level. This also received support from the heritability of apo A-I (h2 = 0.66), mainly varying in HDL2, and the lack of it in apo A-II, found mainly in HDL3. These conclusions were strengthened by standardizing the data with relative ponderosity. Postheparin plasma HL activity had a high pairwise correlation coefficient in the MZ twins (r = 0.80, p less than 0.001), whereas LPL displayed no within-pair correlation. Neither of the lipolytic enzymes, LPL or HL, showed any correlation in the DZ twins. Therefore, it is suggested that part of the genetic regulation of the HDL and its subfraction distribution might be mediated through the activity of HL.
Apolipoprotein A-II↗
Insulin therapy induces antiatherogenic changes of serum lipoproteins in noninsulin-dependent diabetes.
To study the effects of rigorous insulin therapy on serum lipoproteins in patients with noninsulin-dependent diabetes not controlled with oral agents only, we measured serum lipoproteins, apoproteins, lipolytic enzymes, and glucose disposal using an insulin clamp technique before and after 4 weeks of insulin therapy. Lipoproteins were isolated by ultracentrifugation and high density lipoprotein (HDL) subfractions, by rate-zonal density gradient ultracentrifugation. The group included 11 women and eight men (age 58 +/- 1 years and RBW 125 +/- 4%). Body weight, glycosylated hemoglobin, mean diurnal glucose, plasma free insulin, and glucose uptake (M-value) were 75 vs. 76 kg; 11.9 vs. 8.9%; 234 vs. 124 mg/dl; 12 vs. 27 microU/ml; and 5.0 +/- 0.4 vs. 7.1 +/- 0.6 mg/kg/min before and after insulin therapy, respectively. After insulin therapy there was a decrease of very low density lipoprotein (VLDL) triglyceride (-60%, p less than 0.001) but an increase of HDL2 cholesterol (+21%, p less than 0.001); HDL2 phospholipids (+38%, p less than 0.001); HDL2 proteins (+23%, p less than 0.01); and HDL2 mass (127 +/- 11 vs. 158 +/- 12 mg/dl, p less than 0.001). There was a decrease of HDL3 cholesterol (-13%, p less than 0.05); HDL3 phospholipids (-16%, p less than 0.05); HDL3 proteins (-18%, p less than 0.001); and HDL3 mass (179 +/- 6 vs. 146 +/- 6, p less than 0.01). Zonal profiles showed a redistribution of particles from HDL3 to HDL2. Serum apo A-I increased (p less than 0.05), apo A-II remained constant, but apo B decreased (-29%, p less than 0.001). The most marked change during insulin therapy was a 2.3-fold increase in adipose tissue lipoprotein lipase (LPL) activity (p less than 0.001). The changes of VLDL and HDL subfractions were not explained by respective changes of the blood glucose, free insulin, or M-value. The data indicate that intensive insulin therapy induces antiatherogenic changes in serum lipids and lipoproteins and suggest that the induction of LPL by insulin is the major factor responsible for redistribution of HDL particles from HDL3 to HDL2.
Adult↗
Apoprotein E polymorphism and coronary artery disease. Increased prevalence of apolipoprotein E-4 in angiographically verified coronary patients.
Several studies have indicated that genetic polymorphism of apolipoprotein (apo) E is related to coronary artery disease (CAD). We therefore determined the apo E phenotype in 91 consecutive Finnish men with angiographically confirmed CAD. The apo E phenotype distribution differed significantly from that observed in the Finnish population (p less than 0.05). In the patient group, the frequency of the epsilon 4 allele was 0.324, which is 1.4-fold higher than in the normal Finnish population and twice as high as in other Caucasian populations. Serum lipoproteins and postheparin plasma lipase activities did not display any significant variation according to apo E phenotype. These studies confirm and extend, in a population with high epsilon 4 allele frequency, the previous data on the impact of the epsilon 4 allele on the risk of CAD and suggest that the high epsilon 4 allele frequency in the Finnish population may be one factor contributing to Finns' increased susceptibility to CAD.
Adult↗