Postheparin Plasma Lipase Activities Research Articles

An automated method for measuring lipoprotein lipase and hepatic triglyceride lipase activities in post-heparin plasma

BackgroundLipoprotein lipase (LPL) and hepatic triglyceride lipase (HTGL) play a central role in triglyceride-rich lipoprotein metabolism by catalyzing the hydrolysis of triglycerides. Quantification of LPL and HTGL activity is useful for diagnosing lipid disorders, but there has been no automated method for measuring these lipase activities. MethodsThe automated kinetic colorimetric method was used for assaying LPL and HTGL activity in the post-heparin plasma using the natural long-chain fatty acid 2-diglyceride as a substrate. LPL activity was determined with apoCII and HTGL activity was determined without apoCII with 2 channel of auto-analyzer. ResultsThe calibration curve for dilution tests of the LPL and HTGL activity assay ranged from 0.0 to 500 U/L. Within-run CV was obtained within a range of 5%. No interference was observed in the testing of specimens containing potentially interfering substances. The measurement range of LPL activity in the post-heparin plasma was 30–153 U/L, while HTGL activity was 135–431 U/L in normal controls. ConclusionsThe L PL and HTGL activity assays are applicable to quantitating the LPL and HTGL activity in the post-heparin plasma. This assay is more convenient and faster than radiochemical assay and highly suitable for the detection of lipid disorders.

ANGPTL3 is part of the machinery causing dyslipidemia majorily via LPL inhibition in mastitis mice

Previous investigations have shown that inflammation induces changes in lipid and lipoprotein metabolism, and increased expression of angiopoietin-like protein 3 (ANGPTL3) contributes to the development of dyslipidemia. Here we investigated whether there is a correlation between increased ANGPTL3 expression and dyslipidemia in mastitis mice. Thirty mice were divided into two groups: control group and Staphylococcus aureus (S. aureus)–induced mastitis mice group. Changes in the levels of blood lipids [total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C)]; activity of myeloperoxidase (MPO); concentrations of plasma inflammation biomarkers [interferon-γ (IFNγ), tumor necrosis factor α (TNFα), and interleukin-1α (IL-1α)]; concentration of plasma ANGPTL3 protein; lipoprotein lipase (LPL) activities in postheparin plasma; expressions of hepatic N-acetylgalactosaminyltransferase 2 (GALNT2), hepatic ANGPTL3 and adipose LPL were determined. The major results indicated specific pathological mammary tissue changes, elevated MPO activity, reduced GALNT2 mRNA expression, elevated ANGPTL3 mRNA and protein expression and reduced LPL mRNA and protein expression. In plasma samples the S.aureus infused mice displayed elevated ANGPTL3 protein concentration, TG, TC and LDL-C levels, and reduced postheparin LPL activities and HDL-C level. The data suggests that ANGPTL3 is part of the machinery causing dyslipidemia majorily via LPL inhibition in mastitis mice.

Angptl3 Deficiency Is Associated With Increased Insulin Sensitivity, Lipoprotein Lipase Activity, and Decreased Serum Free Fatty Acids

Angiopoietin-like 3 (Angptl3) is a regulator of lipoprotein metabolism at least by inhibiting lipoprotein lipase activity. Loss-of-function mutations in ANGPTL3 cause familial combined hypolipidemia through an unknown mechanism. We compared lipolytic activities, lipoprotein composition, and other lipid-related enzyme/lipid transfer proteins in carriers of the S17X loss-of-function mutation in ANGPTL3 and in age- and sex-matched noncarrier controls. Gel filtration analysis revealed a severely disturbed lipoprotein profile and a reduction in size and triglyceride content of very low density lipoprotein in homozygotes as compared with heterozygotes and noncarriers. S17X homozygotes had significantly higher lipoprotein lipase activity and mass in postheparin plasma, whereas heterozygotes showed no difference in these parameters when compared with noncarriers. No changes in hepatic lipase, endothelial lipase, paraoxonase 1, phospholipid transfer protein, and cholesterol ester transfer protein activities were associated with the S17X mutation. Plasma free fatty acid, insulin, glucose, and homeostatic model assessment of insulin resistance were significantly lower in homozygous subjects compared with heterozygotes and noncarriers subjects. These results indicate that, although partial Angptl3 deficiency did not affect the activities of lipolytic enzymes, the complete absence of Angptl3 results in an increased lipoprotein lipase activity and mass and low circulating free fatty acid levels. This latter effect is probably because of decreased mobilization of free fatty acid from fat stores in human adipose tissue and may result in reduced hepatic very low density lipoprotein synthesis and secretion via attenuated hepatic free fatty acid supply. Altogether, Angptl3 may affect insulin sensitivity and play a role in modulating both lipid and glucose metabolism.

Biological and functional characteristics of a novel low–molecular weight antagonist of glucose‐dependent insulinotropic polypeptide receptor, SKL‐14959, in vitro and in vivo

We recently discovered a glucose-dependent insulinotropic polypeptide (GIP) receptor antagonist, SKL-14959. GIP plays a role in the glucose and lipid metabolism, and is associated with obesity and insulin resistance. Therefore, we aimed to ascertain the inhibitory potency and glucose and lipid metabolism of SKL-14959. SKL-14959 was evaluated for its binding affinity to each GIP, glucagon-like peptide-1 (GLP-1) and glucagon receptors by each labelled and non-labelled ligand; GIP-stimulated cyclic AMP (cAMP) production in CHO cells expressing human GIP receptor in vitro. Oral and intraperitoneal glucose tolerance tests (OGTT and IPGTT) were performed to examine the insulinotropic effect on endogenous and exogenous GIP. Oil tolerance tests were also conducted to examine the lipid metabolism and the postheparin plasma lipase activity, lipoprotein lipase (LPL) and hepatic lipase (HL). SKL-14959 selectively bound to GIP receptor and inhibited GIP-stimulated cAMP production with the Ki value of 55 nM and an IC(50) value of 2.9 µM, respectively. SKL-14959·Na significantly increased blood glucose levels, inhibited insulin secretion in OGTT and inhibited the plasma glucose lowering of exogenous GIP in IPGTT. Furthermore, SKL-14959 increased plasma triacylglycerol (TG) levels as well as suppressed the postheparin plasma lipase activity in an oil load test. These data indicate that SKL-14959 is distinguished in the physiological phenotype of GIP following direct binding to the receptor.

Characterization of a hypertriglyceridemic transgenic miniature pig model expressing human apolipoprotein CIII

Hypertriglyceridemia has recently been considered to be an independent risk factor for coronary heart disease, in which apolipoprotein (Apo)CIII is one of the major contributory factors, as it is strongly correlated with plasma triglyceride levels. Although ApoCIII transgenic mice have been generated as an animal model for the study of hypertriglyceridemia, the features of lipoprotein metabolism in mice differ greatly from those in humans. Because of the great similarity between pigs and humans with respect to lipid metabolism and cardiovascular physiology, we generated transgenic miniature pigs expressing human ApoCIII by the transfection of somatic cells combined with nuclear transfer. The expression of human ApoCIII was detected in the liver and intestine of the transgenic pigs. As compared with nontransgenic controls, transgenic pigs showed significantly increased plasma triglyceride levels (83 ± 36 versus 38 ± 4 mg·dL(-1), P < 0.01) when fed a chow diet. Plasma lipoprotein profiling by FPLC in transgenic animals showed a higher peak in large-particle fractions corresponding to very low-density lipoprotein/chylomicrons when triglyceride content in the fractions was assayed. There was not much difference in cholesterol content in FPLC fractions, although a large low-density lipoprotein peak was identified in both nontransgenic and transgenic animals, resembling that found in humans. Further analysis revealed markedly delayed clearance of plasma triglyceride, accompanied by significantly reduced lipoprotein lipase activity in post-heparin plasma, in transgenic pigs as compared with nontransgenic controls. In summary, we have successfully generated a novel hypertriglyceridemic ApoCIII transgenic miniature pig model that could be of great value for studies on hyperlipidemia in relation to atherosclerotic disorders.

Interactive effects ofAPOEhaplotype, sex, and exercise on postheparin plasma lipase activities

Hepatic lipase (HL) and lipoprotein lipase (LPL) activities (HLA, LPLA) modify lipoproteins and facilitate their binding to hepatic receptors. Apolipoprotein E (APOE) physically interacts with the lipases, and the three common haplotypes of the APOE gene (ε2, ε3, and ε4) yield protein isoforms (E2, E3, and E4, respectively) that are functionally different. Lipase activities themselves differ by sex and exercise training status. The interaction of APOE genotype, exercise training, and sex effects on lipase activities has not been studied. We measured postheparin plasma lipase activities in normolipidemic men and women with the three most common APOE genotypes, which are the haplotype combinations ε2/ε3 (n = 53 ), ε3/ε3 (n = 62), and ε4/ε3 (n = 52), enrolled in 6 mo of aerobic exercise training. These haplotype combinations comprise an estimated 11.6, 62.3, and 21.3% of the population, respectively. Baseline HLA was 35% lower in women than in men (P < 0.0001). In men but not women, HLA was higher in ε2/ε3 group compared with ε4/ε3 (P = 0.01) and ε3/ε3 (P = 0.05). Neither sex nor APOE genotype affected baseline LPLA. Training decreased HLA by 5.2% (P = 0.018) with no APOE effect. The apparent increase in LPLA following exercise was significant and APOE dependent only when corrected for baseline insulin (P < 0.05). Exercise decreased LPLA by 0.8 μmol free fatty acid (FFA)·ml⁻¹·h⁻¹ (-6%) in ε3/ε3 compared with the combined increases of 6.6% in ε2/ε3 and 12% in ε4/ε3 (P = 0.018 vs. ε3/ε3). However, these differences were statistically significant only after correcting for baseline insulin. We conclude that common APOE genotypes interact with 1) sex to modulate HLA regardless of training status, with ε2/ε3 men demonstrating higher HLA than ε3/ε3 or ε4/ε3 men, and 2) aerobic training to modulate LPLA, regardless of sex, with ε3/ε3 subjects showing a significant decrease compared with an increase in ε2/ε3 and ε3/ε4 after controlling for baseline insulin.

Pathogenetic role of adipose tissue lipase deficit for development of hypertriglyceridaemia.

In 87 patients (74 males, 13 females; age 43 +/- 9.2 years) covering a wide range of triglyceride (TG) concentrations (8.8 to 80.7 mmol/l) the turnover of total serum TG has been measured using the technique of labelling endogenously synthesized TG with 3H-glycerol. In parallel, lipoprotein lipase activity in adipose tissue and the adipose-tissue lipase activity in post-heparin plasma have been assessed following an oral 50 g glucose load. Despite the well-recognized function of this enzyme for intravascular lipolysis no direct relationship between lipase activities and fractional catabolic rates (FCR), reflecting TG removal processes, was found. On the other hand, relative enzyme activities (per TG moles) are positively correlated with the FCR. However, a detailed analysis of this relationship revealed that only in HTG patients whose FCR are below 0.210 h-1 a rate-limiting influence of a relative lipase deficit can be shown. In these patients, a statistically significant elevation of concentrations of free fatty acids is supposed to contribute to the impairment of the TG removal.

A novel method for measuring human lipoprotein lipase and hepatic lipase activities in postheparin plasma

The objective of this study was to establish a new lipoprotein lipase (LPL) and hepatic lipase (HL) activity assay method. Seventy normal volunteers were recruited. Lipase activities were assayed by measuring the increase in absorbance at 546 nm due to the quinoneine dye. Reaction mixture-1 (R-1) contained dioleoylglycerol solubilized with lauryldimethylaminobetaine, monoacylglycerol-specific lipase, glycerolkinase, glycerol-3-phosphate oxidase, peroxidase, ascorbic acid oxidase, and apolipoprotein C-II (apoC-II). R-2 contained Tris-HCl (pH 8.7) and 4-aminoantipyrine. Automated assay of lipase activities was performed with an automatic clinical analyzer. In the assay for HL + LPL activity, 160 microl R-1 was incubated at 37 degrees C with 2 microl of sample for 5 min, and 80 microl R-2 was added. HL activities were measured under the same conditions without apoC-II. HL and LPL activities were also measured by the conventional isotope method and for HL mass by ELISA. Lipase activity detected in a 1.6 M NaCl-eluted fraction from a heparin-Sepharose column was enhanced by adding purified apoC-II in a dose-dependent manner, whereas that eluted by 0.8 M NaCl was not. Postheparin plasma-LPL and HL activities measured in the present automated method had high correlations with those measured by conventional activity and mass methods. This automated assay method for LPL and HL activities is simple and reliable and can be applied to an automatic clinical analyzer.

Appraisal of hepatic lipase and lipoprotein lipase activities in mice

A variety of methods are currently used to analyze HL and LPL activities in mice. In search of a simple methodology, we analyzed mouse preheparin and postheparin plasma LPL and HL activities using specific polyclonal antibodies raised in rabbit against rat HL (anti-HL) and in goat against rat LPL (anti-LPL). As an alternative, we analyzed HL activity in the presence of 1 M NaCl, a condition known to inhibit LPL activity in humans. The assays were validated using plasma samples from wild-type and HL-deficient C57BL/6 mice. We now show that the use of 1 M NaCl for the inhibition of plasma LPL activity in mice may generate incorrect measurements of both LPL and HL activities. Our data indicate that HL can be measured directly, without heparin injection, in preheparin plasma, because virtually all HL is present in an unbound form circulating in plasma. In contrast, measurable LPL activity is present only in postheparin plasma. Both HL and LPL can be measured using the same assay conditions (low salt and the presence of apolipoprotein C-II as an LPL activator). Total lipase activity in postheparin plasma minus preheparin HL activity reflects LPL activity. Specific antibodies are not required.

The effect of exercise on postprandial lipidemia in type 2 diabetic patients

To elucidate if postprandial exercise can reduce the exaggerated lipidemia seen in type 2 diabetic patients after a high-fat meal. Two mornings eight type 2 diabetic patients (males) (58 +/- 1.2 years, BMI 28.0 +/- 0.9 kg m(-2)) and seven non-diabetic controls ate a high-fat breakfast (680 kcal m(-2), 84% fat). On one morning, 90 min later subjects cycled 60 min at 57% VO(2max). Biopsies from quadriceps muscle and abdominal subcutaneous adipose tissue were sampled after exercise or equivalent period of rest and arterialized blood for 615 min. Postprandial increases in serum total-triglyceride (TG) (incremental AUC: 1,702 +/- 576 vs. 341 +/- 117 mmol l(-1) 600 min), chylomicron-TG (incremental AUC: 1,331 +/- 495 vs. 184 +/- 55 mmol l(-1) 600 min) and VLDL-TG as well as in insulin (incremental AUC: 33,946 +/- 7,414 vs. 13,670 +/- 3,250 pmol l(-1) 600 min), C-peptide and glucose were higher in diabetic patients than in non-diabetic controls (P < 0.05). In diabetic patients these variables were reduced (P < 0.05) by exercise (total-TG incremental AUC being 1,110 +/- 444, chylomicron-TG incremental AUC 1,043 +/- 474 mmol l(-1) 600 min and insulin incremental AUC 18,668 +/- 4,412 pmol l(-1) 600 min). Lipoprotein lipase activity in muscle (11.0 +/- 2.0 vs. 24.1 +/- 3.4 mU g per wet weight, P < 0.05) and post-heparin plasma at 615 min were lower in diabetic patients than in non-diabetic controls, but did not differ in adipose tissue and did not change with exercise. In diabetic patients, 210 min after exercise oxygen uptake (P < 0.05) and fat oxidation (P < 0.1) were still higher than on non-exercise days. In type 2 diabetic patients, after a high-fat meal exercise reduces the plasma concentrations of triglyceride contained in both chylomicrons and VLDL as well as insulin secretion. This suggests protection against progression of atherosclerosis and diabetes.

A novel method for measuring human hepatic lipase activity in postheparin plasma

The objective of this study was to establish a hepatic lipase (HL) assay method that can be applied to automatic clinical analyzers. Seventy-four hyperlipidemic subjects (men/women 45/29) were recruited. Lipase activity was assayed measuring the increase in absorbance at 546 nm due to quinonediimine dye production. Reaction mixture R-1 contained 50 mM Tris-HCl (pH 9.5), 0.5 mM glycerol-1,2-dioleate, 0.4% (unless otherwise noted) polyoxyethylene-nonylphenylether, 3 mM ATP, 3 mM MgCl(2), 1.5 mM CaCl(2), monoacylglycerol-specific lipase, glycerol kinase, glycerol-3-phosphate oxidase, 0.075% N,N-bis-(4-sulfobutyl)-3-methylaniline-2 Na, peroxidase, ascorbic acid oxidase. Reaction mixture R-2 contained 50 mM Tris-HCl (pH9.5), 0.15% 4-aminoantypirine. Automated assay for activity was performed with a Model 7080 Hitachi analyzer. In the lipase assay, 160 microl of R-1 was incubated at 37 degrees C with 3 microl of samples for 5 min, and 80 microl of R-2 was added. Within-run coefficient of variations was 0.9-1.0%. Calibration curve of lipase activity was linear (r = 0.999) between 0 and 320 U/l. Analytical recoveries of purified HL added to plasma were 96.6-99.8%. HL activity in postheparin plasma measured in this method had a closer correlation with HL mass by a sandwich ELISA (r = 0.888, P < 0.0001) than those in the conventional method using [(14)C-]triolein (r = 0.730, P < 0.0001). This assay method for HL activity can be applied to an automatic clinical analyzer.

Apolipoprotein e genotype and changes in serum lipids and maximal oxygen uptake with exercise training

Physical activity improves lipid levels by altering triglyceride (TG) metabolism. Apolipoprotein E (Apo E) facilitates TG clearance by mediating lipoprotein binding to hepatic receptors, but Apo E also has less defined roles in skeletal muscle and nervous tissue. This study examined if variants in Apo E genotype affect the lipid and physiologic response to exercise training. Seven centers genetically screened 566 individuals to recruit 120 subjects into 6 gender-specific cohorts equal for the most common Apo E genotypes: E2/3, E3/3, and E3/4. Anthropometics, exercise capacity (V o 2max), serum lipids, and post heparin (PH) plasma lipase activities were measured before and after 6 months of supervised exercise training. Difference in the response (Δ) to training among the Apo E genotypes was the primary outcome variable. Differences in pretraining serum lipids among the Apo E genotypes mimicked those observed in population studies: TGs were slightly higher in E2/3 subjects, whereas low-density lipoprotein (LDL)-cholesterol (C) was lower ( P = not significant [NS] ). TGs decreased 11% with training for the entire cohort ( P < .0001) and 7%, 12%, and 14% for the Apo E 2/3, 3/3 and 3/4 groups, respectively ( P = NS for Δ). LDL-C did not change in the entire cohort, but decreased slightly in the 2/3 and 3/3 subjects and increased 4% in the 3/4 group ( P = NS for Δ). High-density lipoprotein (HDL)-C increased 2% for the entire cohort ( P = .06) due to a 6% increase in the 3/3 group ( P = .07 for Δ). Total cholesterol (TC)/HDL and LDL/HDL decreased with training in the 2/3 and 3/3 groups, but increased in the 3/4 subjects and these responses differed among the genotypes ( P < .05 for Δ). V o 2max increased 9% to 10% for the entire cohort, but only 5% in the 3/3 subjects versus 13% in the 2/3 and 3/4 groups and these differences were significantly different among the genotypes ( P < .01 for Δ). This is the first prospective study to demonstrate that the serum lipid response to exercise training differs by Apo E genotype in a pattern consistent with known metabolic differences among the variants. Surprisingly, Apo E genotype also affected the increase in aerobic capacity produced by exercise training possibly via undefined effects on nerve and skeletal muscle function.

Increased serum triglyceride clearance and elevated high-density lipoprotein 2 and 3 cholesterol during treatment of primary hypertriglyceridemia with bezafibrate

Background Hypertriglyceridemia accompanied by low levels of high-density lipoprotein cholesterol (HDL-C) is a risk factor for coronary artery disease. High-density lipoprotein 2 (HDL 2) and 3 (HDL 3) are believed to suppress the progress of atherosclerosis through reverse cholesterol transport. As a result, peripheral tissues can be protected against excessive accumulation of cholesterol. Although bezafibrate is known to accelerate the increase of HDL-C, results are not standardized regarding increases of HDL 3 and HDL 2 subfractions. Objective This study assessed the effects of bezafibrate on serum triglyceride (TG) fractional clearance rate (K 2) and HDL 2 and HDL 3 cholesterol (HDL 2-C and HDL 3-C, respectively) levels in patients with primary hypertriglyceridemia (serum TG ≥150 mg/dL). Methods Outpatients with primary hypertriglyceridemia were enrolled in this 8-week study conducted at the Third Department of Internal Medicine, Nagoya City University Hospital (Nagoya, Japan). Oral bezafibrate was administered at a dose of 400 mg/d (200-mg tablet BID, morning and evening) for 8 weeks. After 8 weeks, serum levels of total cholesterol (TC), TG, HDL-C, HDL 2-C, and HDL 3-C were measured. A fat emulsion tolerance test to assess K 2 and measurements of plasma lipoprotein lipase (LPL) mass, LPL activity, and hepatic triglyceride lipase (HTGL) activity in postheparin plasma were performed before bezafibrate administration and after the course of treatment. Results Sixteen patients (10 men, 6 women; mean [SD] age, 54 [12] years [range, 30–69 years]; mean [SD] body mass index, 23 [2] kg/m 2) entered the study. The following findings were observed in male and female patients after 8 weeks of treatment. A statistically significant reduction was observed in mean serum TG level ( P<0.01). Significant increases were seen in HDL-C, HDL 2-C, and HDL 3-C (all P<0.01), K 2 ( P<0.01), and in plasma LPL mass ( P<0.01) and LPL activity ( P<0.05). TC level and HTGL activity did not change significantly. No adverse effects related to the use of bezafibrate were documented. Conclusions In this study, bezafibrate treatment resulted in significant decreases in serum TG level and significant increases in HDL 2-C and HDL 3-C levels and plasma LPL mass and activity. We hypothesize that bezafibrate may increase HDL 3-C by promoting TG-rich lipoprotein catabolism and may increase HDL 2-C by promoting the conversion of HDL 3 to HDL 2.

Apolipoprotein CIII deficiency prevents the development of hypertriglyceridemia in streptozotocin-induced diabetic mice

To explore the role of apolipoprotein (apo) CIII in the development of hypertriglyceridemia associated with diabetes mellitus, we examined triglyceride (TG) kinetics in apo CIII - deficient mice (apo CIII - null) and wild-type (WT) (C57BL/6J) mice with diabetes induced by the injection of streptozotocin (STZ). Plasma TG levels increased significantly in WT mice after diabetes was induced (102 ± 29 v 65 ± 33 mg/dL, P < .01). Apo CIII-null mice had a significantly lower TG level (35 ± 9 mg/dL) that remained unchanged even when diabetes was induced (35 ± 8 mg/dL). The TG secretion rate (TGSR) measured by the Triton WR1339 method tended to decrease in diabetic WT, indicating that catabolism of TG was impaired. Apo CIII-null mice showed 2-fold higher TG production than WT mice, indicating markedly faster clearance of TG. The high TGSR was halved when diabetes was induced in apo CIII-null mice, and the fractional catabolic rate (FCR) of TG was also halved, although it was still significantly higher than in WT mice. Lipoprotein lipase (LPL) activity in postheparin plasma was not significantly altered in WT or apo CIII-null mice regardless of the presence or absence of diabetes. [ 3H] very-low-density lipoprotein (VLDL)-TG from WT or apo CIII-null mice showed similar clearance by WT recipients, and this was also observed when VLDL was obtained from diabetic counterparts. In contrast, VLDL-TG was cleared faster by apo CIII-null recipients compared with WT recipients, regardless of the VLDL donors. These results suggest that apo CIII deficiency prevents the development of hypertriglyceridemia associated with diabetes by stimulating TG removal, possibly by promoting the interaction of VLDL with the TG removal system.

Exercise training, without weight loss, increases insulin sensitivity and postheparin plasma lipase activity in previously sedentary adults.

To determine the effects of exercise, without weight loss, on insulin sensitivity (S(I)), postheparin plasma lipase activity (PHPL), intravenous fat clearance rate (K(2)), and fasting lipids in sedentary adults. At baseline and after 6 months of walk training (intensity 45-55 or 65-75% heart rate reserve, frequency 3-4 or 5-7 days/week, duration 30 min/session), anthropometric indexes, S(I), PHPL, K(2), and fasting lipids were measured in 18 sedentary adults (12 women, 6 men; 51.9 +/- 5.8 years of age, BMI 28.9 +/- 4.6 kg/m(2)). Exercise increased S(I) (2.54 +/- 2.74 vs. 4.41 +/- 3.30 microU ml(-1) x min(-1), P < 0.005) and both lipoprotein lipase (LPL) (1890 +/- 1380 vs. 4926 +/- 1858 nEq free fatty acid [FFA]. ml(-1). h(-1)) and hepatic lipase (HL) activities (3326 +/- 1605 vs. 4636 +/- 1636 nEq FFA. ml(-1) x h(-1)) (both P < 0.001), without altering BMI, waist circumference, K(2), or fasting lipids. Correlations between changes in LPL and the total:HDL cholesterol ratio (r = -0.54) and changes in the LPL:HL ratio and waist circumference (r = -0.50) were significant (P < 0.05). Exercise, without weight loss, increases S(I) and PHPL activity in previously sedentary adults, without changing K(2) or fasting lipid levels. Furthermore, increased LPL is associated with a decreased total:HDL ratio, and an increased LPL:HL ratio is associated with a decreased waist circumference. Therefore, even modest amounts of exercise in the absence of weight loss positively affect markers of glucose and fat metabolism in previously sedentary, middle-aged adults.

Insulin improves fasting and postprandial lipemia in type 2 diabetes

Background: The purpose of the investigation presented here was to study the effects of insulin therapy in type 2 diabetes mellitus (type 2 DM) not only on glycemic control but also on other components of the metabolic syndrome, including lipid metabolism, blood pressure, and body weight. Methods: Twelve patients with type 2 DM were studied before and after replacement of sulphonylurea treatment with insulin for 4 months. Results: Insulin therapy resulted in a significant decrease in fasting glucose levels by 26%; glycated hemoglobin decreased by 17% and fructosamine values by 19%. With insulin treatment, fasting plasma triglyceride levels decreased by 28% and total HDL cholesterol and HDL 3 cholesterol increased by 17 and 11%, respectively. Low-density lipoprotein (LDL) cholesterol showed no significant change. The magnitude of postprandial lipemia after ingestion of a standard fatty meal decreased by 38%. Insulin treatment was also accompanied by a 21% increase in lipoprotein lipase (LPL) activity in postheparin plasma and by a 20% increase in cholesteryl ester transfer protein (CETP) activity. Hepatic lipase activity was not changed significantly with insulin. Mean BMI decreased from 28.5±4.2 to 28.0±3.1 kg/m 2 ( P=0.02), which is in keeping with the finding that peripheral insulin levels did not increase and which can be explained by the fact that the insulin regimen was combined with dietary counseling. Accordingly, blood pressure showed no significant change. Conclusion: Our study demonstrates that judicious replacement of sulfonylurea treatment with insulin therapy, together with dietary counseling, can result in a simultaneous improvement in the major stigmata of the metabolic syndrome, i.e. a significant improvement in glycemic control and lipid metabolism without unfavorable effects on body weight and blood pressure.

Kinetics of an Intravenously Injected Fat Emulsion Reflect Postheparin Plasma Lipoprotein Lipase Mass and Activity

A study was conducted to determine whether the catabolism of an intravenously injected fat emulsion could be correlated with lipoprotein lipase (LPL) mass and activity in postheparin plasma. We observed the relationship between the fractional removal rate (K2) of an intravenously injected fat emulsion (Intralipid®) and LPL mass and activity in postheparin plasma of 20 normolipidemic and 21 hypertriglyceridemic subjects. The K2 level was determined by the intravenous fat emulsion tolerance test. LPL mass was measured by a sandwich enzyme immunoassay system. K2 was significantly correlated with the LPL mass in total group of subjects (r=0.51, p<0.001), as well as in normolipidemic (r=0.72, p<0.001) and hypertriglyceridemic (r=0.43, p<0.05) subgroups. K2 was also significantly correlated with LPL activity in the total group (r=0.40, p<0.05), as well as in the normolipidemic subjects (r=0.55, p<0.05). Kinetics following an intravenous injection of a fat emulsion reflect LPL mass and activity in postheparin plasma.

Calibration, specificity and trueness of a postheparin plasma lipoprotein lipase assay.

Measurement of lipoprotein lipase activity in postheparin plasma is generally accompanied by moderate within-run variation CV(W-R) (<10%) and higher between-run variation CV(B-R) (5-25%). A calibration system was introduced in order to improve the reproducibility of measurements and to compare lipoprotein lipase activities from different days. Every day a calibration curve for lipoprotein lipase activity was constructed. Fifteen calibration curves designed over 2 years, show linearity over the whole biological spectrum and a considerable reduction of between-run variation in lipoprotein lipase activity, from 42% to 5.3% as estimated from two control postheparin plasma samples. The lipoprotein lipase calibration system is an easy and very cheap arrangement, which makes it possible to compare lipoprotein lipase activities achieved over years. When the lipoprotein lipase control values are compared with reference lipoprotein lipase samples determined in other lipase laboratories, the calibration-control system becomes an important tool for reducing analytical bias. The article reviews the original analytical criteria of catalytic measurement of lipoprotein lipase activity and describes the implementation of the calibration-control system. We describe a model for reduction of the analytical variability in the measurement of lipoprotein lipase activity. Other standardization efforts need to be made in the future, especially to define the reference material for calibration.

Energy intake-independent modulation of triglyceride metabolism by glucocorticoids in the rat.

This study aimed to dissociate the peripheral effects of adrenalectomy (ADX) on triglyceride (TG) metabolism from those it exerts centrally on energy intake and to determine the impact of diet composition therein. Rats were fed either rodent chow or a diet high in sucrose and fat (HSF) and were adrenalectomized or left intact and pair fed to the ADX animals. Liver TG content, an index of hepatic TG production, was not affected by ADX, but was increased twofold by the HSF diet. ADX decreased the rate of hepatic TG secretion by 41% in chow-fed but not in HSF-fed animals. Triglyceridemia and postheparin plasma lipase activities remained largely unchanged by treatments. ADX decreased insulinemia fivefold in chow-fed rats, but less so in HSF-fed animals. Likewise, subcutaneous and visceral adipose depots were 40-60% smaller in ADX than in intact pair-fed rats given chow, but the effect of ADX was dampened by consumption of the HSF diet. Although smaller, adipose tissues of ADX rats maintained a higher activity of lipoprotein lipase (LPL) than those of intact pair-fed rats, whereas muscle LPL was decreased. The study confirms that in the presence of reduced energy intake, corticosterone contributes to the maintenance of adipose stores and that the consequences of its absence tend to be attenuated when a high-energy diet is fed. The study further shows that, contrary to ad libitum feeding conditions, most determinants of TG metabolism, such as hepatic TG stores, triglyceridemia, postheparin plasma LPL, and adipose tissue LPL, are minimally affected by glucocorticoids when consumption of a high-energy diet is restricted, suggesting that glucocorticoids affect TG metabolism mostly indirectly through their central action on ingestive behavior.

Lipid Metabolism in Equines Fed a Fat-Rich Diet

The hypothesis tested was that dietary fat, when compared with an isoenergetic amount of non-structural carbohydrates, stimulates lipolysis in adipose tissue and also stimulates the fatty-acid oxidative capacity in skeletal muscle from horses. Six adult horses were fed a high-fat, glucose or starch containing diet according to a 3 x 3 Latin square design with feeding periods of three weeks. The diets were formulated so that the intake of soybean oil versus either glucose or corn starch were the only variables. In accordance with previous work, whole plasma triacylglycerol (TAG) concentration decreased significantly by 58% following fat supplementation. This fat effect was accompanied by a 247% increase in lipoprotein lipase (LPL) activity in post-heparin plasma. The dietary variables did neither significantly affect the basal in vitro lipolytic rate nor the lipolytic rate after adding noradrenaline. There was no significant diet effect on the activities of hexokinase and phosphofructokinase as indicators of glycolytic flux and citrate synthase and 3-hydroxy-acyl-CoA dehydrogenase as indicators of fatty-acid oxidative capacity. The concentrations of muscle glycogen and TAG were not affected by fat supplementation. It is concluded that our hypothesis is not supported by the present results.