Comparative responsiveness to prolonged hyperinsulinemia between adipose-tissue and mammary-gland lipoprotein lipase activities in pregnant rats

The present study was addressed to determining the comparative responsiveness of lipoprotein lipase (LPL) activity, in white adipose tissue and mammary gland, to a prolonged hyperinsulinemic stimulus, in pregnant and virgin rats. Pregnant rats at the 17th day of gestation and virgin animals were subjected, under conscious and unrestrained conditions, to a continuous infusion with either 50% glucose or double-distilled water (controls) (35 ml/day) for 72 h through a catheter in the jugular vein. The basal plasma-glucose levels were lower in pregnant than in virgin rats. After the glucose infusion plasma-glucose levels remained unchanged but plasma-insulin levels were much higher, and this effect was greater in pregnant than in virgin rats. Whereas LPL activity in white adipose tissue in the controls was lower in pregnant than in virgin rats, in rats receiving the glucose infusion it increased more in pregnant than in virgin rats. However, LPL activity in the mammary gland was already higher in control pregnant rats than in virgin controls and the glucose infusion caused a similar increase in both groups. Although there was a linear correlation when individual values, from all the studied rats, for LPL activity in both tissues were plotted against plasma insulin levels, the correlation coefficient was much higher for mammary-gland LPL activity than for adipose-tissue LPL activity. Plasma-triglyceride levels were higher in pregnant than in virgin rats. The glucose infusion did not modify this parameter, probably because of the changes in LPL activity in other tissues which are known to occur in the opposite direction to those observed in this study for adipose tissue and mammary gland. The present results support the notion that the insulin resistant condition which normally occurs during late gestation is responsible for the decreased LPL activity in adipose tissue, but that the mammary gland remains sensitive to insulin and so maternal hyperinsulinemia would contribute to the induction of LPL activity in this organ prior to parturition.

Longitudinal study on lipoprotein profile, high density lipoprotein subclass, and postheparin lipases during gestation in women

To understand the mechanism responsible for maternal hyperlipidemia, 25 healthy pregnant women were studied longitudinally during the three trimesters of gestation and at post-partum, and 11 were studied again at post-lactation. Triglyceride and cholesterol levels increased with gestation in all the lipoprotein fractions. However, the greatest change appeared in low density (LDL) and high density (HDL) lipoproteins, both of which showed an increase in their triglyceride/cholesterol ratio. The proportional distribution of HDL subfractions showed that the HDL2b fraction was the only one that increased with gestation, whereas both HDL3a and HDL3b had the greatest decrease. Cholesteryl ester transfer protein activity increased during the second trimester of gestation. While postheparin lipoprotein lipase activity decreased during the third trimester, postheparin hepatic lipase activity progressively decreased from the first trimester. The 17 beta-estradiol, progesterone, and prolactin hormones progressively increased from the first trimester of gestation. The lipoprotein-triglyceride values correlated linearly and negatively with the logarithm of either postheparin lipase activities, HDL-triglycerides showing the highest correlation coefficient when plotted against the hepatic lipase values (r = -0.757). It appeared that the highest correlation between any of the HDL subclasses and the activity of the enzymes was for hepatic lipase activity versus HDL2b (r = 0.456) or HDL3a (r = 0.519). A significant lineal correlation also appeared between the postheparin hepatic lipase activity and the logarithm of any of the sex hormones studied, the highest value corresponding to estradiol (r = -0.783). Therefore, during gestation, the effect of estrogen in enhancing very low density lipoprotein (VLDL) production and decreasing hepatic lipase activity plays a key role in the accumulation of triglycerides in lipoproteins of density higher than VLDL.

Effect of diabetes on protein synthesis rate and eukaryotic initiation factor activities in the liver of virgin and pregnant rats

To study the effect of prolonged diabetes on protein synthesis and on the activities of initiation factors eIF-2 and eIF-2B in the liver, female rats were treated with streptozotocin. Some animals were mated and studied on day 20 of pregnancy, whereas others were kept virgin and studied in parallel. The protein synthesis rate was measured with an "in vitro' cellfree system, and was lower in diabetic pregnant and virgin animals than in pregnant and virgin controls (30-60%). The fetuses of diabetic rats had a lower protein synthesis rate than those from controls, although they always showed a higher protein synthesis rate than their mothers or virgin rats. Protein synthesis rate, RNA concentration, and initiation factor 2 activity were higher in pregnant than in virgin rats. Both activity and level of eIF-2 factor changed in parallel to the protein synthesis rate, although no differences could be detected between control and diabetic animals. The eIF-2B activity in tissue extracts from diabetic virgin rats and fetuses was lower than in extracts from their controls, whereas no differences could be detected between pregnant and virgin control rats nor between pregnant control and pregnant diabetic animals. The percentage of the phosphorylated form of eIF-2 factor, eIF-2(alpha P), was slightly lower in virgin than in pregnant rats but was unaffected by the diabetic condition, while in diabetic fetuses this parameter was lower than in their corresponding controls. The cyclic adenosine monophosphate dependent protein kinase level was lower in diabetic rats than in controls, whereas no changes in the activity of casein kinase II were found. The isoelectric forms of the beta subunit of eIF-2 factor, eIF-2 beta, were different in the diabetic and the control animals, indicating that insulin deficiency modifies the phosphorylation of specific substrates. Since no differences were detected in RNA or eIF-2 content between control and diabetic rats, translation may, at least partly, be inhibited in the liver by an impairment of peptide chain initiation caused by the decreased eIF-2B activity which nevertheless is independent of eIF-2 alpha phosphorylation.

Reversion of insulin resistance in the rat during late pregnancy by 72-h glucose infusion

To determine whether sustained exaggerated hyperinsulinemia in normoglycemic rats modifies insulin responsiveness during pregnancy, 17-day-pregnant and virgin rats were studied after receiving a continuous intravenous infusion (35 ml/day) of either 50% glucose or bidistilled water (controls) for 72 h. Plasma glucose was unchanged, whereas insulin was highly increased, and the effect was more marked in pregnant than in virgin rats. Insulin responsiveness, estimated under the hyperinsulinemic euglycemic clamp with 0.8 IU insulin.h-1.kg-1, was lower in control pregnant than in virgin rats but higher in pregnant than in virgin rats in those that had received the glucose infusion. The tissue glucose utilization metabolic index (GUI) was estimated with 2-deoxy-D-[1-3H]glucose in the clamped rats. The GUI was lower in heart, white- and red-fiber skeletal muscle, and adipose tissue in control pregnant rats than in control virgin rats, and, although the glucose infusion decreased that index in both red-fiber muscle and adipose tissue in virgin rats, glucose increased the index in red-fiber muscle in pregnant rats to the level found in virgin controls. Results therefore show that, when unaccompanied by hypoglycemia, sustained exaggerated hyperinsulinemia decreases insulin responsiveness in virgin rats but reverts insulin resistance in late-pregnant rats.

Sperm migration through the female genital tract of the New World monkey Cebus apella

This study was designed to characterize sperm migration in the female genital tract of Cebus apella. Forty-eight cycles of eighteen females mated during the periovulatory period were studied. Eggs were searched for and spermatozoa were counted in segmental flushings of the genital tract performed in situ 1-7 h, 19-31 h, or 45-56 h after coitus. Of 14 eggs recovered, 8 were fertilized, thus assuring a reasonable normality of prefertilization phenomena in both males and females. A downward gradient of several orders of magnitude in sperm numbers was recognized from cervix to ampulla, particularly over the first interval. The population in the cervix and uterus decreased progressively between the first and last interval. Spermatozoa were recovered from the ampulla as early as 1 h after mating. Different trends were observed in the isthmus and ampulla. From the first to the last interval, sperm numbers decreased in the ampulla, but not in the isthmus. The number of spermatozoa recovered from the ampulla of the ovulatory side 1-31 h postcoitum was higher in postovulatory than in preovulatory monkeys, while in the nonovulatory side, recovery was similar in the two conditions. This findings suggests that the passage of spermatozoa up to the site of fertilization is under local control and is synchronized with ovulation. The pattern of sperm migration that emerges from these data bears similarities to the pattern in nonprimate species as well as distinctive features. A unique feature in common with the pattern in human is the early establishment of a fairly abundant and persistent sperm population in the ampulla.

Effect of etofibrate on bile production in the normolipidemic rat

1. The effect of etofibrate, the ethandiol-1,2 diester of nicotinic and clofibric acids on bile production was studied in male rats that received a daily dose of 300 mg of etofibrate/kg body weight by stomach tube for 10 days and were compared with control rats receiving the medium. 2. The bile duct was cannulated, animals were intravenously given 1 microCi (4-14C)-cholesterol/100 b.w. and bile was collected at different intervals for a total of 4 hr. 3. Etofibrate treatment decreased plasma cholesterol and triglyceride concentrations and increased the bile flow. The cummulative amount of both bile volume and total bile radioactivity secreted increased linearly in all the animals; the respective slopes being higher in etofibrate treated rats than in controls. 4. The main labelled component found in the bile was always bile acids rather than cholesterol and the proportion of each of these compounds was similar in both groups. Neither was any difference between the groups found in the concentration of bile acids, cholesterol and phospholipids nor in the cholesterol/(bile+phospholipid) ratio. 5. Besides other factors, the present results indicate that an increase in bile flow and biliary cholesterol excretion in its free form and after its conversion into bile acids should contribute to the hypocholesterolemic effect of etofibrate.

Effect of streptozotocin diabetes on polysomal aggregation and protein synthesis rate in the liver of pregnant rats and their offspring

To study the effect of diabetes on hepatic protein synthesis and polysomal aggregation in pregnant rats, female rats were treated with streptozotocin prior to conception. Some animals were mated, and studied at day 20 of pregnancy, whereas, others were studied in parallel under non pregnant conditions. The protein synthesis rate measured with an "in vitro" cell-free system was higher in pregnant than in virgin control rats. It decreased with diabetes in both groups, although values remained higher in diabetic pregnant rats than in the virgin animals. The fetuses of diabetic rats had a lower protein synthesis rate than those from controls, although they showed a higher protein synthesis rate than either their respective mothers or virgin rats. Liver RNA concentration was higher in control and diabetic, pregnant rats than in virgin rats, and the effect of diabetes decreasing this parameter was only significant for pregnant rats. Liver RNA concentration in fetuses was lower than in their mothers, and did not differ between control and diabetic animals. The decreased protein synthesis found in diabetic animals was accompanied by disaggregation of heavy polysomes into lighter species, indicating an impairment in peptide-chain initiation.

Glucose and insulin tolerance tests in the rat on different days of gestation

To study insulin/glucose relationship during gestation, rats were studied on days 6, 12, 15, 18, 20 or 21 of pregnancy and the results were compared to values in sex-matched virgin control rats. Blood glucose levels were decreased on days 20 and 21 of gestation whereas plasma insulin levels appeared decreased on days 6 and 12, unchanged on day 15 and enhanced on days 18, 20 and 21 of gestation. Total pancreas insulin content was already augmented on day 6 of gestation and continued to increase with gestational time. With the exception of an increase in the 6-day-pregnant rats 22.5 min after an oral glucose load, blood glucose levels did not differ between 6- or 12-day-pregnant rats and virgin controls although plasma insulin levels reached higher values on these days. However, in the 15-day-pregnant rats, glucose tolerance after the glucose load was enhanced while plasma insulin levels did not differ from those in virgin rats during the first 30 min. In the 18-day-pregnant rat blood glucose was more increased but plasma insulin did not differ after the glucose load when compared to virgin rats, whereas 20- or 21-day-pregnant rats showed a glucose tolerance similar to that of virgin rats but their insulin levels shortly after the glucose load were higher. The hypoglycemic response to a high intravenous dose of insulin was decreased in 12-, 18-, 20- and 21-day-pregnant rats. Therefore, whereas in both the 6- and 12-day-pregnant rats there is an enhanced beta-cell response to the glucose insulinotropic effect and insulin responsiveness is reduced in 12-day-pregnant rats, the 15-day pregnant rat is in a transitory stage where both insulin sensitivity and the beta-cell response return to nonpregnant values. However, from 18 days of gestation on, there is an intense insulin-resistant condition which is only partially compensated by an enormous accumulation of insulin in the pancreas followed by a faster and larger insulin release after a glucose load.

Effect of starvation on lipoprotein lipase activity in different tissues during gestation in the rat

This study was addressed to determine whether the tissue-specific LPL activity response to fasting differs between nonpregnant and pregnant rats over the course of pregnancy. Fed and 24-h fasted rats were studied at days 12, 15 or 20 of gestation and were compared to virgin controls. In fed rats at days 15 and 20 of gestation LPL activity decreased in lumbar adipose tissue and the heart and liver, and increased in mammary gland tissue. Fasting decreased LPL activity in lumbar adipose tissue in 12 day pregnant and virgin rats and in mammary gland tissue in pregnant rats at 15 and 20 days of gestation and in virgin rats, whereas it increased LPL activity in heart tissue in rats at day 15 and 20 and in liver at day 20 of gestation. Plasma triacylglycerols were higher in 20 day pregnant rats than in the other groups when fed and this difference was even more noticeable in the fasting condition where the plasma beta-hydroxybutyrate level also reached the highest value in the 20 day pregnant rats. Since tissue LPL activity controls the hydrolysis and uptake of circulating triacylgylcerols, the present results indicate that in fed rats after the 15th day of gestation circulating triacylglycerols are preferentially taken up by the mammary gland instead of being taken up by adipose tissue and heart. However, after fasting, circulating triacylglycerols are driven to the heart and liver in the late pregnant rat, and become a major source for fatty acid oxidation, an effect that seems to be specially evident in the liver of the 20 day pregnant rat where there is an intense increase in LPL activity and the triacylglycerols become preferential substrates for ketone body production.

Carbohydrate-lipid interactions during gestation and their control by insulin

1. During the first two thirds of gestation, coinciding with a minimal accretion by the conceptus, the mother is in an anabolic state which is supported by her hyperphagia and the more efficient conservation of exogenous nutrients when she eats. During this phase maternal fat deposits are accumulated thanks to the enhancement in adipose tissue lipogenic and glycerologenic activity. In contrast, in the latter part of gestation, the rapid fetal growth is sustained by the intense transfer of nutrients from maternal circulation. 2. Glucose is quantitatively the most abundant of the several substrates that cross the placenta and despite increased maternal gluconeogenesis this transfer is responsible for the maternal tendency to hypoglycemia. This causes a switch to a net catabolic state which is especially evident in the net breakdown of fat depots. 3. Enhanced release of adipose tissue lipolytic products, free fatty acids (FFA) and glycerol, facilitates the liver synthesis of triglycerides and their later release into circulation associated to very low-density lipoprotein (VLDL). Glycerol is also used as an important gluconeogenic substrate and FFAs are broken down through beta-oxidation for ketone body synthesis. Flow through these pathways becomes increased when food is withheld and this actively contributes to the availability of fuels to the fetus which becomes partially preserved from maternal metabolic insult. Increased liver production of VLDL-triglycerides and decreased extrahepatic lipoprotein lipase contribute to exaggerated maternal hypertriglyceridemia which, besides being a floating metabolic reserve for emergency conditions such as starvation, constitutes an essential substrate for milk synthesis around parturition in preparation for lactation. 4. While the maternal anabolic tendencies found during the first two-thirds of gestation seem to be facilitated by hyperinsulinemia in the presence of a normal responsiveness to the hormone, it is proposed that most of the metabolic changes taking place during the last third of gestation seem to be caused by the insulin-resistant state which is consistently present at this stage, since its reversion caused by sustained exaggerated hyperinsulinemia also reverts several of these metabolic adaptations.

Cutaneous leishmaniasis in subtropical Ecuador: popular perceptions, knowledge, and treatment

Popular perceptions and knowledge about cutaneous leishmaniasis and its treatment were studied in an endemic area of subtropical Northwest Ecuador. Although most of the adults surveyed were familiar with the disease, the vector, and traditional treatments, many showed a lack of knowledge about transmission of the disease, ulcer healing, and conventional treatment. Gender was found to have a significant impact on disease risk, perceptions, and treatment knowledge. Males experienced a risk of contracting cutaneous leishmaniasis that was almost triple that of women. Men were also more likely to perceive that the disease seriously diminished the victim's capacity to work. Women, on the other hand, were more prone to perceive that cutaneous leishmaniasis was a serious disease that significantly decreased self-esteem. Although 80% of the subjects knew at least one method of treating the disease, women tended to know more methods than men. Most of 150 different therapies reported involved the use of indigenous plants, chemicals, acids, antibiotics, heat treatments, or petroleum by-products. Some of these treatments could have clinical value. However, only 7% of the subjects knew about pentavalent antimonials. Almost 70% of the subjects with a past or present infection history were treated solely by traditional methods; only 12% received a full course of Glucantime, while 7.5% got an incomplete course. The findings indicate that it will be important to consider the identified gaps in knowledge and gender perceptions regarding the disease and its treatment when planning future control programs.

Lipoprotein lipase and hormone-sensitive lipase activity and mRNA in rat adipose tissue during pregnancy

To investigate the factors controlling maternal depot fat accumulation during early pregnancy and net decrease during late pregnancy, the activity and mRNA expression of adipose tissue lipoprotein lipase (LPL) and hormone-sensitive lipase (HSL) were related to several other lipid metabolic parameters. Virgin control rats, pregnant rats (at days 12, 15, 19, and 21), and lactating rats (at days 5 and 10 postpartum) were studied. In adipose lumbar tissue of late pregnant rats, LPL activity decreased to about one-third that of the virgin control animals, with < 10% of initial LPL mRNA expressed as determined by Northern blots. HSL activity increased maximally 1.5-fold with a fourfold increase of HSL expression at days 12-15 of pregnancy and decreased to control levels after parturition. The HSL-to-LPL mRNA and activity ratios were enhanced from days 15 and 19 of pregnancy, respectively, and remained so even during lactation, mainly because of the marked lowering of the LPL values. This enhancement coincided with increments in plasma free fatty acids and glycerol levels indicating an increased depot fat breakdown. These results give no indication of an involvement of LPL and HSL gene expression changes in the accumulation of maternal depot during early pregnancy. In contrast, such changes could be responsible for the net breakdown of this fat depot during late gestation. Thus, during this physiological state, long-term (e.g., transcriptional) regulation of LPL and HSL gene expression could be an important mechanism for the control of adipose tissue mass breakdown during late gestation.

[Changes in the lipid profile in chronic hepatopathies]

BACKGROUND

The pattern of lipoproteins and apolipoproteins has been studied in a group of patients with chronic liver disease. The differences in this pattern were analysed in relation with the stage of liver disease and the presence of cholestasis.

METHODS

Twenty one patients with hepatic cirrhosis and 12 with primary biliary cirrhosis were studied. Two subgroups were established according to the disease severity and to the Scheuer classification, respectively. Plasma lipoproteins were separated by ultracentrifugation, and the lipid and apolipoprotein composition were determined. Lipoprotein X was identified by means of agarose gel electrophoresis.

RESULTS

In the subgroups with less severe liver disease, only minimal changes were found, such as the decreases in esterified cholesterol and Apo E contents in VLDL in the cirrhotic patients, and the increase of HDL-cholesterol in the patients with primary biliary cirrhosis in the first stages. In patients with severe hepatic cirrhosis, total esterified cholesterol, triglycerides, VLDL and HDL were diminished. Apo E in VLDL was undetectable whereas the different Apo C isoforms were in the normal proportion. Patients with severe biliary cirrhosis showed high levels of total cholesterol and triglycerides, elevated LDL-cholesterol, and decreased HDL-cholesterol and total esterified cholesterol. Apo C-IIO in VLDL was proportionally increased as related to both Apo E and Apo C-III. Lipoprotein X was detected in all these patients and in half of the patients with severe hepatic cirrhosis.

CONCLUSIONS

Severe chronic liver disease is associated with a decrease of the concentration of hepatic lipoproteins and the absence of Apo E in VLDL, probably as a result of a defect in their synthesis. The lipid profile found in patients with biliary cirrhosis delineates the pattern of chronic cholestasis, which is characterized by the presence of lipoprotein X, a significant increase of free-cholesterol and a decrease of HDL-cholesterol; VLDL, which are increased, are rich in Apo C-II. Data show the distinct apolipoprotein composition of VLDL in the different hepatic diseases.

Changes in cholesteryl ester transfer protein activity during normal gestation and postpartum

Cholesteryl ester transfer protein (CETP) activity was measured in a d > 1.21 kg/L plasma fraction collected from healthy women at different times during gestation, postpartum, and in control women. CETP activity was highest in the second trimester of gestation, declined at the third trimester, and was lowest at postpartum. Only the value at the second trimester was significantly different from that of control women. This trend differed from that of circulating lipoproteins: very low-density lipoprotein (VLDL)-lipids, including triglycerides and cholesterol, increased progressively from the first to the third trimester, and then declined at postpartum. Low-density lipoprotein (LDL)-cholesterol levels, like VLDL levels, rose during gestation but then remained elevated at postpartum. High-density lipoprotein (HDL)-cholesterol as well as HDL-phospholipids and apolipoprotein A-I, peaked in the second trimester, remaining elevated in the third trimester and then fell at postpartum. Finally, HDL-triglyceride increased markedly from the first to the second trimester, rose somewhat higher during the third trimester, and declined at postpartum. When all the samples from pregnant women were considered together, CETP activity correlated significantly with HDL-triglyceride levels and the changes in CETP activity during gestation and postpartum paralleled those of the HDL-triglyceride/VLDL-triglyceride ratio. These results suggest that CETP contributes to the exaggerated accumulation of triglycerides in HDL that begins in the second trimester of human gestation.

Cholesteryl ester transfer activity in lipoprotein lipase deficiency and other primary hypertriglyceridemias

Cholesteryl ester transfer protein (CETP) activity was measured in d > 1.21 g/ml plasma from hypertriglyceridemic patients and compared with normolipidemic subjects. The assay consisted in measuring the specific transfer of [3H]cholesteryl oleate from a prelabelled, apo E-poor HDL fraction to VLDL after incubation at 37 degrees C in the presence of the d > 1.21 g/ml plasma sample: the lipoproteins were then separated by precipitation with dextran sulfate/Mg2+ solution. Increasing the volume of d > 1.21 g/ml plasma or purified human CETP in the assay produced linear responses in measured activity, whereas, either during incubation at 4 degrees C or in the presence of rat plasma instead of human plasma, the transfer of [3H]cholesteryl oleate to VLDL was not stimulated. Thus, the assay reflects changes in CETP in the sample and appears to be suitable for measuring CETP activity in d > 1.21 g/ml plasma. CETP activity was very similar in the two groups of normolipidemic subjects considered: adolescents (203 +/- 11 nmol esterified cholesterol transferred per 8 h/ml plasma) and adults (215 +/- 5). Patients were grouped into lipoprotein-lipase (LPL)-deficient and non-LPL-deficient according to their enzyme activity in postheparin plasma. CETP activity was highly increased in LPL-deficient, severe hyperchylomicronemic patients (430 +/- 42) and was directly correlated with VLDL levels in the non-LPL-deficient individuals. Marked differences were observed in the lipid composition of HDL and apolipoprotein A-I levels among patients and controls. In the control group, CETP activity was correlated only with HDL-triglyceride and HDL-triglyceride/apo A-I mass ratio, which is compatible with the physiological role of CETP in transferring triglyceride to HDL from other lipoprotein particles. When all hypertriglyceridemic patients were considered together, CETP activity was inversely correlated with apo A-I and HDL-cholesterol, whereas it was directly correlated with HDL-triglyceride/HDL-cholesterol and HDL-triglyceride/apo A-I mass ratios. The results indicate that the enhanced CETP activity associated with hypertriglyceridemia contributes to the compositional change of HDL, which in turn may be responsible for the reduction of HDL levels in this condition.

Interindividual variation in the partition of lipoprotein(a) into lipoprotein subfractions

In order to evaluate cardiovascular risk, we analyzed the lipid composition of HDL and the presence of lipoprotein(a) [Lp(a)] by both agarose gel electrophoresis and enzyme-linked immunoassay (ELISA). In 681 plasmas we found a close correspondence between the existence of a visible sinking pre-beta lipoprotein band and a concentration of Lp(a) higher than 300 mg/L. In the sinking pre-beta(+) samples, the HDL-cholesterol level obtained by differential ultracentrifugation was significantly higher than that obtained by precipitation with the MgCl2-phosphotungstic acid reagent; and the difference between these HDL-cholesterol values was linearly correlated with plasma Lp(a) concentration. Moreover, the other HDL lipid components and the lipid mass ratios of HDL isolated by ultracentrifugation were significantly different from those of HDL isolated by precipitation, and these changes were also correlated with plasma Lp(a). These differences are attributed to Lp(a) because it was detected in the 1.063-1.21 kg/L plasma fractions, whereas it was absent in the plasma supernates after precipitation with MgCl2-phosphotungstic acid. Although to a lesser extent, Lp(a) was also present in the LDL and VLDL density ranges and it directly depended on both the Lp(a) and the triglyceride plasma concentrations. The proportion of Lp(a) in HDL as related to that in LDL density fractions decreased as Lp(a) plasma levels increased, reflecting an interindividual variation of Lp(a) density species. Since 90% of our study population had detectable Lp(a) in plasma, the results reinforce the concept that the ultracentrifugation method is not equivalent to precipitation in most samples, and the contaminant effect of Lp(a) cannot be predicted because of Lp(a) partition into the different lipoprotein fractions.

Studies with etofibrate in the rat. Part II: A comparison of the effects of prolonged and acute administration on plasma lipids, liver enzymes and adipose tissue lipolysis

To contribute to the understanding of the hypolipidemic action of etofibrate, which is the 1,2-ethandiol ester of clofibric acid and nicotinic acid, 300 mg of this drug/kg body weight or of the medium were administered daily by a stomach tube to normolipidemic rats. Some animals were decapitated at the 10th day of daily treatment (prolonged treatment), whereas others were studied at different times after one single administration (acute treatment). In animals on prolonged treatment etofibrate decreased plasma levels of cholesterol, triacylglycerols, free fatty acids (FFA) and glycerol, as well as the total and unesterified cholesterol concentrations, in liver microsomes. In these rats, etofibrate increased the activity of liver cytosolic glycerol-3-P dehydrogenase, whereas it decreased the activity of both microsomal HMG-CoA reductase and cholesterol 7 alpha-hydroxylase and did not affect acyl-CoA: cholesterol acyltransferase (ACAT). At 3, 5 and 7 h after acute treatment, etofibrate decreased plasma levels of triacylglycerols, glycerol and FFA, and this effect disappeared at 24 h, whereas plasma cholesterol did not change 3 h after etofibrate but decreased at 5 and 7 h and remained low after 24 h, and a similar change was found in the liver microsomes free cholesterol concentration. However, with the exception of a significant reduction in cytosolic glycerol-3-P dehydrogenase at 7 h and in ACAT at 5 h, acute etofibrate treatment did not affect the activity of the liver enzymes studied. At low concentrations (10(-5) M) in the incubation medium, etofibrate decreased the release of both FFA and glycerol by epididymal fat pad pieces incubated in vitro. These findings together with those previously reported by us in rats using a similar etofibrate treatment protocol [6] indicate that etofibrate decreases the availability of lipolytic products in the liver by acting on their release from adipose tissue and on their intrinsic hepatic metabolism. Consequently, this drug would decrease liver VLDL triacylglycerol synthesis and secretion, which together with facilitating the clearance of circulating triacylglycerols causes its hypotriglyceridemic effect. The hypocholesterolemic effect of etofibrate after acute treatment may be a secondary consequence of the reduced liver VLDL production caused by decreased adipose tissue lipolysis, but after prolonged treatment, this effect also seems to be influenced by the inhibition of HMG-CoA reductase activity which would reduce cholesterol synthesis.

Different hydrolytic efficiencies of adipose tissue lipoprotein lipase on very-low-density lipoprotein subfractions separated by heparin-Sepharose chromatography

Human very-low-density lipoproteins (VLDL) were subfractionated by heparin-Sepharose chromatography into an unbound (A) and three bound (B, C and D) populations at increasing ionic strengths. Subfractions were characterized regarding their chemical composition and efficiency of triacylglycerol hydrolysis by rat adipose tissue LPL. The triacylglycerol content decreased, whereas the cholesterol and protein contents increased from subfractions A and B to subfraction D. VLDL-D showed the highest apo E/apo C ratio, though all the subfractions contained appreciable apo E. Appearance of VLDL-A resulted from exceeding the binding capacity of the column, since practically all its particles eluted at positions of bound VLDL under re-chromatography. Subfractions B, C and D stimulated LPL activity on emulsified tri[14C]oleoylglycerol to a similar extent, indicating that their apo C-II content was equally effective activating LPL. Incubation of tri[14C]oleoylglycerol labeled VLDL subfractions with fat pad pieces in the presence or absence of heparin resulted in greater hydrolysis and fatty acid uptake for VLDL-B and -C than for VLDL-D, a pattern observed over a wide range of LPL activities in the media. We conclude: (1) any VLDL particle can interact with heparin, which is consistent with the presence of apo E in all the subfractions, and (2) triacylglycerols in apo E-rich VLDL are less efficiently hydrolyzed by LPL than those in apo E-poor particles. We propose that richness in apo E impairs LPL action upon VLDL and decreases the rate of delivery of fatty acids to peripheral tissues.

Longitudinal study of plasma lipoproteins and hormones during pregnancy in normal and diabetic women

Plasma lipoproteins were studied longitudinally at the 1st, 2nd, and 3rd trimester of gestation and at postpartum and postlactation in 12 age-matched PGDM women, 9 GDM women, and 12 healthy control subjects. FPG and HbA1c were higher in every case in PGDM women than in control subjects, whereas in GDM patients, glucose was augmented only after parturition. FFA and beta-hydroxybutyrate levels were higher in both PGDM and GDM patients than in control subjects during gestation but not after parturition. Total TGs and VLDL, LDL, and HDL TGs increased with gestational time in the three groups and declined at postpartum, and although total cholesterol and VLDL, LDL, and HDL cholesterol followed a similar trend, their rise was less pronounced, and the decline after parturition was slower than that of the TGs in the three groups, with no difference among them. The VLDL TG/cholesterol ratio declined in the three groups at the 3rd gestational trimester, whereas in both LDL and HDL, the TG/cholesterol ratio, but not the cholesterol/phospholipid ratio, increased during gestation in the three groups, indicating a specific enrichment of TGs in these particles. The increase in apoA-I and apoB with gestation was parallel to the respective changes in HDL and LDL cholesterol and, again, no difference was observed between the three groups. Plasma levels of beta-estradiol, progesterone, and prolactin increased sharply with gestation and declined at postpartum in the three groups, but absolute values of beta-estradiol and prolactin, at the three trimesters of gestation, were lower in PGDM patients, but progesterone levels were lower than controls in GDM women only at the 3rd trimester. (ABSTRACT TRUNCATED AT 250 WORDS)