A history of previous gestational diabetes mellitus is associated with adverse changes in insulin secretion and VLDL metabolism independently of increased intrahepatocellular lipid.

AIMS/HYPOTHESIS: We have previously reported a high prevalence of non-alcoholic fatty liver disease (NAFLD) among women with previous gestational diabetes mellitus (pGDM). We wanted to confirm that intrahepatocellular lipid (IHCL) is associated with pGDM independently of adiposity and determine: (1) if VLDL metabolism is dysregulated; and (2) the extent to which NAFLD and IHCL account for the dysmetabolic phenotype in pGDM. METHODS: We analysed data from a cohort of 234 women (114 with pGDM) and identified effects of pGDM on lipid and glucoregulation that were independent of ultrasound-diagnosed NAFLD. We then measured IHCL by MR spectroscopy in a representative subgroup (n = 36) and conducted detailed metabolic studies (IVGTT, VLDL apolipoprotein B [apoB] kinetics and palmitate turnover) and measurement of regional body fat by MRI to demonstrate effects of IHCL that were independent of a history of pGDM. RESULTS: pGDM was associated with increased IHCL (p = 0.04) after adjustment for adiposity. Independently of IHCL, pGDM was associated with a lower IVGTT disposition index (p = 0.02) and acute insulin response to glucose (pGDM+/NAFLD-, 50% lower; pGDM+/NAFLD+, 36% lower; effect of pGDM, p = 0.03), increased VLDL apoB pool size (pGDM+/NAFLD-, 3.1-fold higher; pGDM+/NAFLD+, 1.2-fold higher; effect of pGDM, p = 0.02) and, at borderline significance (p = 0.05), increased rate of VLDL apoB synthesis. CONCLUSIONS/INTERPRETATION: pGDM is associated with increased IHCL independently of adiposity. The increased liver fat contributes to the phenotype, but pGDM status is independently associated with diminished insulin secretion and (shown for the first time) augmented VLDL metabolism. IHCL with pGDM may compound a dysmetabolic phenotype.

Free radicals and the pH of topical glaucoma medications: a lifetime of ocular chemical injury?

INTRODUCTION: Preservatives in ophthalmic preparations are known to cause ocular surface damage. Excipients can also contribute to oxidative stress in the compromised ocular surface. We evaluated commonly used topical glaucoma medications to ascertain pH levels and the intrinsic presence of free radicals. METHODS: Samples of 27 topical glaucoma preparations were analysed for total free radical presence using a Randox Kit for total antioxidant status. Analytical grade indicator paper was used to ascertain pH levels. RESULTS: Free radical concentrations for these 27 glaucoma preparations ranged from 0 to 4.54 mmol/l, with a median value of 0.66 mmol/l (mean value of 0.662 mmol/l, SD 0.839). Levels of pH ranged from 4.0 to 7.4, with a median value of 6.5 (mean 6.252, SD 0.826). There was no evidence of a direct correlation between these two variables (r=0.232, P=0.275). CONCLUSION: This study is the first to document the range of pH and concentrations of free radicals intrinsically present in commonly used glaucoma medications. Long-term exposure to preservatives, free radicals, and pH levels could all contribute to ocular surface damage. The effect of excipients could be responsible for patient intolerance when changing products in the compromised ocular surface.

Triglycerides and small dense low density lipoprotein in the discrimination of coronary heart disease risk in South Asian populations.

INTRODUCTION: Coronary heart disease (CHD) is exceptionally prevalent amongst globally dispersed migrant groups originating from the Indian subcontinent, but the contribution of dyslipidaemia to their increased risk remains poorly defined. METHODS: Fasting lipids and lipoproteins, apolipoproteins (Apo), low density lipoprotein (LDL) diameter and oxidised LDL were measured amongst rural Indians in India (n=294) and their migrant contemporaries in the UK (n=242). The performance of qualitative and quantitative measures of lipid metabolism were compared in the discrimination of WHO defined metabolic risk and raised Framingham CHD risk scores (>15%) using Receiver Operating Characteristic (ROC) curves. RESULTS: LDL diameter was correlated with triglycerides (R(2)=0.12, P<0.001) and with high density lipoprotein (HDL) cholesterol levels (R(2)=0.15, P<0.001) in both groups. Migrants had less small dense LDL (95% CI: 12.5-14.2%) vs. rural Indians (15.7-17.2, P<0.05). On ROC analysis, triglycerides were the only consistent discriminators of metabolic and CHD risk scores (all P< or =0.001). Apo B was also a strong indicator of raised CHD risk scores. Irrespective of site, individuals with raised triglycerides also had higher total cholesterol and Apo B, denser LDL, lower HDL and more oxidised LDL (all P< or =0.01). DISCUSSION: Fasting triglycerides reflect both qualitative and quantitative aspects of lipid metabolism, and are a comprehensive discriminator of CHD risk in this South Asian population.

Distinct patterns of heparin affinity chromatography VLDL1 and VLDL2 subfractions in the different dyslipidaemias.

Very low density lipoprotein (VLDL) 1 and 2 were fractionated by heparin affinity chromatography into a bound and an unbound fraction and the different subfractions were quantified in 17 normolipidaemic (NL), 13 hypercholesterolaemic (HC), 10 hypertriglyceridaemic (HTG) and 11 combined hyperlipidaemic subjects (CHL). Unbound VLDL1 and VLDL2 were, respectively, 1.9- and 2.2-fold richer in triglycerides than bound VLDL1 and VLDL2. In HTG and CHL the concentration of all the VLDL subfractions was increased and plasma triglyceride level was correlated to unbound VLDL1 and to bound VLDL1 (respectively, r=0.86 (p<0.001) and r=0.77 (p<0.01) in HTG and r=0.73 (p<0.001) and r=0.62 (p<0.05) in CHL). In HC unbound VLDL2 and bound VLDL2 concentration were increased compared to NL and in CHL, the concentration of bound VLDL2 was particularly increased (3.2-fold compared to NL (p<0.001)). In both HC and CHL bound VLDL2 concentration was correlated to low density lipoprotein cholesterol (LDL-C) concentration (respectively, r=0.67 (p<0.01) and r=0.62 (p<0.05)). In hypertriglyceridaemic states the intravascular accumulation of both unbound and bound VLDL1 appears as the determinant of plasma triglyceride concentration, whereas in moderately hypercholesterolaemic states the concentration of bound VLDL2 is strikingly correlated to LDL-C concentration, suggesting that these two species are linked metabolically, e.g. bound VLDL2 contain the precursor pool of LDL.

Energy replacement attenuates the effects of prior moderate exercise on postprandial metabolism in overweight/obese men.

BACKGROUND: The extent to which exercise-induced changes to postprandial metabolism are dependant on the associated energy deficit is not known. OBJECTIVE: To determine the effects of exercise, with and without energy replacement, on postprandial metabolism. DESIGN: Each subject underwent three 2-day trials in random order. On day 1 of each trial subjects rested (control), walked at 50% maximal oxygen uptake to induce a net energy expenditure of 27 kJ kg(-1) body mass (energy-deficit) or completed the same walk with the net energy expended replaced (energy-replacement). On day 2 subjects completed an 8.5-h metabolic assessment. For 3 days prior to day 2, subjects consumed an isocaloric diet, avoided planned exercise (apart from exercise interventions) and alcohol. SUBJECTS: A total of 13 overweight/obese men (age: 40+/-8 years, body mass index: 31.1+/-3.0 kg m(-2)). MEASUREMENTS: Postprandial triglyceride, insulin, glucose, non-esterified fatty acid and 3-hydroxybutyrate concentrations and substrate utilization rates were determined. RESULTS: Energy-deficit lowered postprandial triglyceride concentrations by 14 and 10% compared with control and energy-replacement (P<0.05 for both). Energy-deficit increased postprandial 3-hydroxybutyrate concentrations by 40 and 19% compared with control and energy-replacement (P<0.05 for both). Postprandial insulin concentrations were 18 and 10% lower for energy-deficit and energy-replacement compared with control and 10% lower for energy-deficit than energy-replacement (P<0.05 for all). Postprandial fat oxidation increased by 30 and 14% for energy-deficit and energy-replacement compared to control and was 12% higher for energy-deficit than energy-replacement (P<0.05 for all). CONCLUSION: Exercise with energy replacement lowered postprandial insulinaemia and increased fat oxidation. However an exercise-induced energy deficit augmented these effects and was necessary to lower postprandial lipaemia.

Acute suppression of VLDL1 secretion rate by insulin is associated with hepatic fat content and insulin resistance.

AIMS/HYPOTHESIS: Overproduction of VLDL(1) seems to be the central pathophysiological feature of the dyslipidaemia associated with type 2 diabetes. We explored the relationship between liver fat and suppression of VLDL(1) production by insulin in participants with a broad range of liver fat content. METHODS: A multicompartmental model was used to determine the kinetic parameters of apolipoprotein B and TG in VLDL(1) and VLDL(2) after a bolus of [(2)H(3)]leucine and [(2)H(5)]glycerol during a hyperinsulinaemic-euglycaemic clamp in 20 male participants: eight with type 2 diabetes and 12 control volunteers. The participants were divided into two groups with low or high liver fat. All participants with diabetes were in the high liver-fat group. RESULTS: The results showed a rapid drop in VLDL(1)-apolipoprotein B and -triacylglycerol secretion in participants with low liver fat during the insulin infusion. In contrast, participants with high liver fat showed no significant change in VLDL(1) secretion. The VLDL(1) suppression following insulin infusion correlated with the suppression of NEFA, and the ability of insulin to suppress the plasma NEFA was impaired in participants with high liver fat. A novel finding was an inverse response between VLDL(1) and VLDL(2) secretion in participants with low liver fat: VLDL(1) secretion decreased acutely after insulin infusion whereas VLDL(2) secretion increased. CONCLUSIONS/INTERPRETATION: Insulin downregulates VLDL(1) secretion and increases VLDL(2) secretion in participants with low liver fat but fails to suppress VLDL(1) secretion in participants with high liver fat, resulting in overproduction of VLDL(1). Thus, liver fat is associated with lack of VLDL(1) suppression in response to insulin.

Serum lipid and lipoprotein profile of patients with glycogen storage disease types I, III and IX.

With current dietary therapy, life expectancy in glycogen storage disease (GSD) has improved considerably and more children reach adulthood. Notwithstanding intensive dietary therapy, moderate to severe hyperlipidaemia is still observed frequently. There is limited information about the type and extent of hyperlipidaemia. We studied the lipid profile in 20 patients, aged 8-54 years, of the three (types I, III and IX) most common forms of adult GSD. Hyperlipidaemia was shown to be type-specific, affecting predominantly patients with GSD type Ia, who showed marked combined hypercholesterolaemia and hypertriglyceridaemia. By contrast, a heterogeneous distribution of HDL was found in patients with GSD I and III. There was no significant difference in Apo Al and Apo B concentrations between groups. In addition, mass measurements of the fractions of VLDL1, VLDL2 and IDL were raised in all patients with GSD Ia by comparison with all other patients with GSD. Patients with GSD type Ia have lipid concentrations and individual mass measurements that are consistent with ranges found in patients who have a significant risk of atherosclerosis. Accumulated evidence, however, suggest GSD type Ia patients do not have an increased risk of atherosclerotic cardiovascular disease (CVD) but the reason remains unknown. Intervention to reduce their lipid levels could therefore be on the basis of seeking to prevent the risk of pancreatitis rather than that of CVD.

Overproduction of large VLDL particles is driven by increased liver fat content in man.

AIMS/HYPOTHESIS: We determined whether hepatic fat content and plasma adiponectin concentration regulate VLDL(1) production. METHODS: A multicompartment model was used to simultaneously determine the kinetic parameters of triglycerides (TGs) and apolipoprotein B (ApoB) in VLDL(1) and VLDL(2) after a bolus of [(2)H(3)]leucine and [(2)H(5)]glycerol in ten men with type 2 diabetes and in 18 non-diabetic men. Liver fat content was determined by proton spectroscopy and intra-abdominal fat content by MRI. RESULTS: Univariate regression analysis showed that liver fat content, intra-abdominal fat volume, plasma glucose, insulin and HOMA-IR (homeostasis model assessment of insulin resistance) correlated with VLDL(1) TG and ApoB production. However, only liver fat and plasma glucose were significant in multiple regression models, emphasising the critical role of substrate fluxes and lipid availability in the liver as the driving force for overproduction of VLDL(1) in subjects with type 2 diabetes. Despite negative correlations with fasting TG levels, liver fat content, and VLDL(1) TG and ApoB pool sizes, adiponectin was not linked to VLDL(1) TG or ApoB production and thus was not a predictor of VLDL(1) production. However, adiponectin correlated negatively with the removal rates of VLDL(1) TG and ApoB. CONCLUSIONS/INTERPRETATION: We propose that the metabolic effect of insulin resistance, partly mediated by depressed plasma adiponectin levels, increases fatty acid flux from adipose tissue to the liver and induces the accumulation of fat in the liver. Elevated plasma glucose can further increase hepatic fat content through multiple pathways, resulting in overproduction of VLDL(1) particles and leading to the characteristic dyslipidaemia associated with type 2 diabetes.

Fetal cord plasma lipoprotein status in uncomplicated human pregnancies and in pregnancies complicated by pre-eclampsia and intrauterine growth restriction.

Maternal lipids have been studied extensively in pre-eclampsia (PE) and intrauterine growth restriction (IUGR) but little is known about fetal lipids. We hypothesised that the maternal lipid perturbations in PE and IUGR pregnancies would result in similar alterations in the fetal lipid profile. We performed a cross-sectional case control study of maternal and fetal (delivery venous cord blood) lipid and lipoprotein concentrations in third trimester uncomplicated pregnancies (n = 81) and in pregnancies complicated by PE (n = 23) or IUGR (n = 17). In uncomplicated pregnancies, fetal log total cholesterol (TC), log triglyceride (TG) and high-density lipoprotein cholesterol (HDL-C) levels were significantly affected by mode of delivery. Fetal log TC (r = 0.37, P = 0.02), log TG (r = 0.34, P = 0.04) and TC/HDL-C ratio (r = 0.31, P = 0.05) were positively correlated with placental weight. Maternal TC (r = 0.35, P = 0.03) and LDL levels (r = 0.36, P = 0.02) were associated with fetal HDL-C levels. Maternal TC was significantly elevated in PE [mean 6.75 (standard deviation 1.14) mmol/L] compared to BMI-matched controls [5.94 (0.89) mmol/L P = 0.04]. In PE, fetal log TC [mean 0.36 (0.23) versus 0.11 (0.15) log mmol/L, P = 0.03], fetal log TG [-0.21 (0.32) versus -0.49 (0.26) log mmol/L, P = 0.02] and fetal TC/HDL-C ratio [3.64 (1.62) versus 1.80 (0.86), P = 0.001] were higher than in controls, after adjustment for mode of delivery. In IUGR, fetal log TG [-0.17 (0.35) versus -0.57 (0.10) log mmol/L, P = 0.01] was higher than controls, after adjustment for mode of delivery. There were no correlations between maternal and fetal lipid levels, or between fetal birth weight and either maternal or fetal lipids in the PE or IUGR groups. We conclude that although fetal lipids do not show a direct correlation with maternal lipids in PE or IUGR, these complications of pregnancy significantly impact upon fetal lipid levels possibly due to increased fetal stress or compromised placental lipid transport. Our findings are potentially pertinent to understanding the future cardiovascular health of the offspring.

Remodelling of cerebrospinal fluid lipoproteins after subarachnoid hemorrhage.

Lipoprotein particles (Lps) in normal human cerebrospinal fluid (CSF) are distinct from those found in plasma and include unique apolipoprotein E (apoE indicates protein; APOE, gene) containing lipoproteins rarely seen in human plasma. Less favourable neurological recovery after subarachnoid hemorrhage (SAH) has been observed in patients who possess the APOE epsilon4 allele raising the possibility that apoE influences neuronal survival after brain injury. We analysed Lps from control and SAH CSF testing the hypotheses that following brain injury CSF Lps undergo remodelling and apoE containing Lps are selectively depleted from brain injury CSF. Lipoproteins were fractionated using CSF from six control pools and six patients with SAH on a sepharose 6HR 10/30 size exclusion column. Fractions were assayed for total cholesterol (TC), free cholesterol (FC), phospholipid, triglyceride (TG), apoE, apolipoprotein B (apoB), and apolipoprotein AI (apoAI). Compared to control CSF there were significant (P<0.05) increases in TC, FC, TG, and apoAI in SAH CSF. Plasma sized apoB-containing lipoproteins and a very small apoAI-containing Lps were identified in the SAH CSF, which were not present in controls. However, despite the release of plasma lipoproteins into the subarachnoid space, there was no significant increase in CSF apoE. These data provide novel indirect evidence suggesting that after SAH CSF Lps undergo remodelling and apoE containing Lps are selectively reduced in brain injury CSF. The remodelling of CSF Lps and selective reduction of apoE containing lipoproteins may reflect an important response of the human brain to injury.

Protease inhibitor related type III hyperlipoproteinaemia is common and not associated with apolipoprotein-E E2/E2 phenotype.

OBJECTIVE: To determine the prevalence of type III hyperlipoproteinaemia in a cohort of HIV infected patients taking protease inhibitors and its correlation with the apolipoprotein-E2 isoform. DESIGN: Cross sectional study of 57 consecutive HIV infected subjects taking protease inhibitor therapy for a median of 12.5 (1-29) months, seen in an outpatient HIV clinic. Controls were 17 patients on non-nucleoside reverse transcriptor inhibitor therapy (NNRTI) for 9 (1-19) months and 50 antiviral naive patients. METHODS: Fasting cholesterol, triglyceride, HDL cholesterol, lipoprotein (a), and glucose were measured. Lipoprotein electrophoresis was performed on patients with a cholesterol >6.5 mmol/l and a triglyceride concentration of >4.5 mmol/l. Apolipoprotein-E phenotype was determined in serum. RESULTS: Dyslipidaemia was found in 43 (75%) PI treated patients-37 with triglyceride >2.3 mmol/l, 30 with cholesterol >6.5 mmol/l, and nine with HDL cholesterol <0.9 mmol/l. 38% had a lipoprotein (a) >300 mg/l. 11 patients (19.3%) had a type III hyperlipoproteinaemia pattern. Only one was homozygous for the E2 phenotype and none had clinical diabetes. An additional patient had a serum lipid profile compatible with type III hyperlipoproteinaemia and an E3/E2 phenotype in whom electrophoresis was not carried out before treatment. Six (35%) of the NNRTI and 16 (32%) of the antiviral naive patients had dyslipidaemia. 18 (31.6%) of the PI and none of the control patients had a cholesterol and/or triglyceride >8 mmol/l. CONCLUSION: Type III hyperlipoproteinaemia is common in this group of patients and need not be associated with the apolipoprotein-E2/E2 isoform. HIV protease inhibitors may interfere with lipoprotein receptor related protein.

The atherogenic lipoprotein phenotype: small dense LDL and lipoprotein remnants in nephrotic range proteinuria.

The dyslipidaemia in nephrotic-range proteinuria is believed to contribute to the increased atherogenesis associated with the condition. Excess small dense low density lipoprotein (LDLIII) contributes to this risk. Lipoprotein remnants (RLP) may also be implicated but have not been studied in this population. We measured the plasma concentration of low density lipoprotein (LDL) subfractions (by density gradient ultracentrifugation), RLP (by immunoaffinity gel), very low density lipoprotein (VLDL) subfractions, post heparin lipases and cholesteryl ester transfer protein (CETP) activity in 27 patients with glomerular disease and albuminuria >2.0g. These were compared with 27 age and sex matched controls. Proteinuric patients had increased LDLIII concentration (patients 182 (84:267) vs. controls 31 (27:62); P<0.0001) with reduced lighter LDLI (36 (24:43) vs 69 (46:101); P<0.0005) and LDLII (124 (79:220) vs 178 (129:236); P<0.04, all mg/dl, median+interquartile range). RLP-cholesterol (RLP-C) and triglyceride (RLP-TG) were increased in proteinuric patients (RLP-C 18.9 (11.0:26.9) vs 7.7 (6.0:8.8); P<0.0001, RLP-TG 35.8 (11.8:54.7) vs. 7.2 (4.3:10.0); P<0.0001, all mg/dl). Increased LDLIII and RLP were independent of renal function. VLDL(1) and VLDL(2) concentrations were increased by 258 and 260% (both P<0.0001). CETP activity was increased by 46% (P<0.005). Lipoprotein and hepatic lipase activities did not differ from control values. LDLIII concentration (r(2)=45.7%, P<0.001), RLP-C (r(2)=85.2%, P<0.001) and RLP-TG (r(2)=87.5%, P<0.001) all correlated positively with plasma triglyceride. Moreover, increased LDLIII was associated with both RLP-C (r(2)=31.3%, P<0.002) and RLP-TG (r(2)=33.6%, P<0.002). Excess LDLIII and RLP are present in nephrotic-range proteinuria and add to the spectrum of cardiovascular risk factors present in proteinuric patients. Increases in LDLIII and RLP are closely related to plasma triglyceride. The association between excess RLP and LDLIII suggests that RLP contribute to the increased atherogenicity attributed to the atherogenic lipoprotein phenotype.

Insulin resistance in the St. Thomas' mixed hyperlipidaemic (SMHL) rabbit, a model for familial combined hyperlipidaemia.

The St. Thomas mixed hyperlipidaemic (SMHL) rabbit exhibits an inherited hyperlipidaemia similar to that seen in familial combined hyperlipidaemia (FCHL). In this study, we investigated whether the SMHL rabbit is insulin resistant, a condition often associated with FCHL. Six young and six mature combined hyperlipidaemic SMHL rabbits, age/sex matched New Zealand White (NZW) control rabbits and six young hypercholesterolaemic Watanabe heritable hyperlipidaemic (WHHL) control rabbits were fed a 0.08% (w/w) cholesterol-enriched diet for at least 1 month prior to the start of the experiment. We performed an oral glucose tolerance test after an overnight fast by dosing the rabbits with a solution of 1 g of glucose per kg body weight. Blood was withdrawn just before and 15, 30, 45, 60 and 120 min after administration of the oral glucose dose. Plasma glucose levels were similar in SMHL, WHHL and NZW rabbits throughout the oral glucose tolerance test. Fasting glucose levels were slightly increased in WHHL rabbits but not in young and adult SMHL rabbits as compared to NZW rabbits. The area under the curve (AUC) for the insulin response was significantly increased for both young (P<0.05) and mature (P<0.05) SMHL rabbits, and in WHHL rabbits, compared with NZW rabbits. The AUC for the ratio of glucose:insulin response to the glucose dose was decreased in young and mature SMHL rabbits (P<0.05 and P<0.01, respectively) and in young WHHL rabbits (P<0.05), compared with NZW rabbits. Only WHHL rabbits showed an increased AUC for the non-esterified fatty acid response compared to NZW rabbits. Log-transformed plasma triglycerides values were significantly correlated with the log-transformed AUC for the insulin response in young SMHL rabbits (r=0.81; P<0.05) and with the AUC for the insulin response in mature SMHL rabbits (r=0.84; P<0.05). WHHL rabbits showed no significant correlation. In conclusion, SMHL rabbits are insulin resistant, the severity of which appears to increase with age. Therefore, the SMHL rabbit offers a valuable animal model in which to study the relation between hypertriglyceridaemia and insulin resistance.

The coffee diterpene cafestol increases plasma triacylglycerol by increasing the production rate of large VLDL apolipoprotein B in healthy normolipidemic subjects.

BACKGROUND: Cafestol is a diterpene in unfiltered coffee that raises plasma triacylglycerol in humans. OBJECTIVE: We studied whether cafestol increases plasma triacylglycerol by increasing the production rate or by decreasing the fractional catabolic rate of VLDL(1) [Svedberg flotation unit (S(f)) 60-400] apolipoprotein (apo) B. In addition, we studied the effect of cafestol on the composition of VLDL(1) and VLDL(2) (S(f) 20-60). DESIGN: Eight healthy normolipidemic men were administered a daily dose of 75 mg cafestol for 2 wk. A bolus injection of 7 mg L-[5,5,5-(2)H(3)]leucine/kg body wt was given after a baseline period with no cafestol and again after treatment with cafestol. We derived kinetic constants to describe the metabolism of VLDL(1) apo B by using a multicompartmental model. RESULTS: Cafestol significantly increased plasma triacylglycerol by 31% or 0.32 mmol/L (95% CI: 0.03, 0.61); the increase was due mainly to a nonsignificant rise in VLDL(1) triacylglycerol of 57% or 0.23 mmol/L (95% CI: -0.02, 0.48). Cafestol significantly increased the mean rate of VLDL(1) apo B production by 80% or 755 mg/d (95% CI: 0.2, 5353), whereas it did not significantly change the mean fractional catabolic rate of VLDL(1) apo B (mean increase of 3 pools/d; 95% CI: -4, 10]). Cafestol did not change the composition of VLDL(1). A significant increase in the ratio of VLDL(2) cholesteryl ester to triacylglycerol indicates that VLDL(2) became enriched with cholesteryl esters at the cost of triacylglycerol. CONCLUSION: Cafestol increases plasma triacylglycerol by increasing the production rate of VLDL(1) apo B, probably via increased assembly of VLDL(1) in the liver.

Lipoprotein-associated phospholipase A2 as an independent predictor of coronary heart disease. West of Scotland Coronary Prevention Study Group.

BACKGROUND: Chronic inflammation is believed to increase the risk of coronary events by making atherosclerotic plaques in coronary vessels prone to rupture. We examined blood constituents potentially affected by inflammation as predictors of risk in men with hypercholesterolemia who were enrolled in the West of Scotland Coronary Prevention Study, a trial that evaluated the value of pravastatin in the prevention of coronary events. METHODS: A total of 580 men who had had a coronary event (nonfatal myocardial infarction, death from coronary heart disease, or a revascularization procedure) were each matched for age and smoking status with 2 control subjects (total, 1160) from the same cohort who had not had a coronary event. Lipoprotein-associated phospholipase A2, C-reactive protein, and fibrinogen levels, and the white-cell count were measured at base line, along with other traditional risk factors. The association of these variables with the risk of coronary events was tested in regression models and by dividing the range of values according to quintiles. RESULTS: Levels of C-reactive protein, the white-cell count, and fibrinogen levels were strong predictors of the risk of coronary events; the risk in the highest quintile of the study cohort for each variable was approximately twice that in the lowest quintile. However, the association of these variables with risk was markedly attenuated when age, systolic blood pressure, and lipoprotein levels were included in multivariate models. Levels of lipoprotein-associated phospholipase A2 (platelet-activating factor acetylhydrolase), the expression of which is regulated by mediators of inflammation, had a strong, positive association with risk that was not confounded by other factors. It was associated with almost a doubling of the risk in the highest quintile as compared with the lowest quintile. CONCLUSIONS: Inflammatory markers are predictors of the risk of coronary events, but their predictive ability is attenuated by associations with other coronary risk factors. Elevated levels of lipoprotein-associated phospholipase A2 appear to be a strong risk factor for coronary heart disease, a finding that has implications for atherogenesis and the assessment of risk.

Patients with nephrotic-range proteinuria have apolipoprotein C and E deficient VLDL1.

BACKGROUND: Impaired very low-density lipoprotein (VLDL) clearance contributes to dyslipidemia in nephrotic-range proteinuria. VLDL can be subdivided into large light VLDL1 (Sf 60 to 400) and smaller, denser VLDL2 (Sf 20 to 60). In nephrotic-range proteinuria, the clearance of VLDL1 is delayed. VLDL1 lipolysis is influenced by apolipoprotein CII (apoCII) and apoCIII, whereas apoE regulates receptor-mediated clearance. METHODS: To ascertain whether impaired VLDL1 clearance was related to a deficiency in apolipoproteins on VLDL1, we measured VLDL subfraction concentrations and VLDL1 apolipoprotein and lipid compositions in 27 patients with glomerular disease and urinary albumin> 2 g/24 h along with 27 age- and sex-matched controls. RESULTS: Proteinuric patients had increased plasma VLDL1, VLDL2, apoCII, apoCIII (all P < 0.001), and apoE concentration (P < 0.002). Patients appeared to have smaller VLDL1 particles, as assessed by triglyceride per particle (median + interquartile range, moles per VLDL1 particle): patients, 4.9 (3.0 to 7.9) x103; controls, 7.0 (4.6 to 15.7) x103, P < 0.05, with reduced apoCII, 4.2 (3.1 to 8.2) versus 9.9 (7.4 to 23.2), P < 0.0004; apoCIII, 16.6 (9.1 to 27.2) versus 29.3 (18.5 to 69.4), P < 0.02; and apoE content, 0.17 (0.08 to 0.44) versus 0.48 (0.31 to 1. 31), P < 0.006. The VLDL1 surface free cholesterol to phospholipid results were increased in proteinuric patients (0.55 +/- 0.17 vs. 0. 40 +/- 0.18, P < 0.002, all mean +/- SD). For all patients, VLDL1 apoCII, apoCIII, and apoE contents per particle were related to particle size (apoCII, r2 = 61.5%, P < 0.001; apoCIII, r2 = 75.8%, P < 0.001; apoE, r2 = 58.2%, P < 0.001) and inversely to the free cholesterol to phospholipid ratio (apoCII, r2 = 41.6%, P < 0.001; apoCIII, r2 = 38.8%, P < 0.001; apoE, r2 = 11.7%, P < 0.05). Multivariate analysis suggested that the relative lack of apoCII and apoCIII on patients VLDL1 was related to smaller particle size and increased free cholesterol:phospholipid (FC:PL) ratio. Particle size but not free cholesterol determined the apoE content of VLDL1. CONCLUSIONS: We postulate that impaired VLDL1 clearance in nephrotic-range proteinuria results from the appearance of particles deficient in apoCII, apoCIII, and apoE. VLDL1 apoC deficiency is associated with the formation of smaller particles with a high FC:PL ratio, and is likely to cause inefficient lipolysis. VLDL1 apoE deficiency is associated with smaller VLDL1 particles but not altered VLDL1 surface lipid content, and may reduce receptor-mediated clearance of this lipoprotein.

Lipoprotein-associated phospholipase A(2), platelet-activating factor acetylhydrolase: a potential new risk factor for coronary artery disease.

A specific and robust immunoassay for the lipoprotein-associated phospholipase A(2) (Lp-PLA(2)), platelet-activating factor acetylhydrolase, is described for the first time. The immunoassay was used to evaluate possible links between plasma Lp-PLA(2) levels and atherosclerosis risk amongst susceptible individuals. Such an investigation was important because Lp-PLA(2) participates in the oxidative modification of low density lipoprotein by cleaving oxidised phosphatidylcholines, generating lysophosphatidylcholine and oxidised free fatty acids. The majority of Lp-PLA(2) was found associated with LDL (approximately 80%) and, as expected, enzyme levels were significantly positively correlated to LDL cholesterol. Plasma Lp-PLA(2) levels were significantly elevated in patients with angiographically proven coronary artery disease (CAD) when compared with age-matched controls, even though LDL cholesterol levels did not differ significantly. Indeed, when included in a general linear model with LDL cholesterol and other risk factors, Lp-PLA(2) appeared to be an independent predictor of disease status. We propose, therefore, that plasma Lp-PLA(2) mass should be viewed as a potential novel risk factor for CAD that provides information related to but additional to traditional lipoprotein measurements.

The role of small, dense low density lipoprotein (LDL): a new look.

Plasma low density lipoprotein (LDL) plays a central role in atherogenesis, and elevated levels of LDL are associated with an increased risk of coronary heart disease (CHD). Studies have now revealed that LDL is structurally heterogeneous, based on its size and density. Patients with combined hyperlipidemia exhibit a lipid profile - the so-called atherogenic lipoprotein phenotype - that is associated with elevated triglyceride levels, low levels of high density lipoprotein and a preponderance of atherogenic, small, dense LDL particles. Such individuals are at an increased risk of CHD events, regardless of their total LDL circulating mass. Evidence suggests that when plasma triglycerides exceed a critical threshold of approximately 133 mg/dl (1.5 mmol/l), this favours the formation of small, dense LDL from larger, less dense species. Lipid-lowering agents that are capable of lowering triglyceride levels below this threshold value will cause a shift to a less dense and, therefore, less atherogenic LDL profile. This effect has been demonstrated for the HMG-CoA reductase inhibitor atorvastatin which, in addition to its ability to markedly decrease the total LDL circulating mass, can also shift the LDL profile towards less dense, larger species. This suggests that atorvastatin may also affect the atherogenic lipoprotein phenotype found in patients with combined hyperlipidemia.

Atherogenic lipoprotein phenotype in end-stage renal failure: origin and extent of small dense low-density lipoprotein formation.

End-stage renal failure (ESRF) is associated with dyslipidemia and accelerated atherosclerosis. Triglyceride-rich lipoproteins accumulate and qualitative changes take place in low-density lipoprotein (LDL), with a predominance of the small dense LDL phenotype. Increased small dense LDL (LDLIII) is a known risk factor for cardiovascular disease. To assess the extent of LDLIII formation in ESRF and identify factors contributing to LDLIII production, we analyzed LDL subfractions by density-gradient ultracentrifugation, very low-density lipoprotein subfractions, and lipase activity in 75 patients with ESRF (25 hemodialysis [HD], 25 peritoneal dialysis [PD], and 25 predialysis patients) and 40 age- and sex-matched controls. The percentage of LDLIII was increased in all three patient groups compared with controls (PD, 33% +/- 29% [mean +/- SD]; P < 0.005; HD, 30% +/- 22%; P < 0.01; predialysis, 26% +/- 26%; P < 0.01; all versus controls, 14% +/- 10%). Plasma LDLIII concentration was increased only in PD patients (median, 84 mg/dL; interquartile range [IQR], 29 to 160 mg/dL versus controls; median, 31 mg/dL; IQR, 26 to 54 mg/dL). In other patient groups, total LDL level was less, with heterogeneity in LDLIII concentrations. Forty percent of PD patients and 28% of HD and predialysis patients had LDLIII concentrations greater than 100 mg/dL compared with 2.5% of controls (P = 0.002). Plasma triglyceride levels (r(2) = 38.4%; P < 0.001) and hepatic lipase activity (r(2) = 6.7%; P < 0.03) were independent predictors of LDLIII concentration. The strong association between LDLIII concentration and triglyceride level was present in all three patient groups (HD, r(2) = 47.9%; PD, r(2) = 45. 2%; predialysis, r(2) = 25.8%); plasma triglyceride levels greater than 177 mg/dL (2.0 mmol/L) had an 86% specificity and 79% sensitivity for predicting an LDLIII concentration greater than 100 mg/dL. We conclude that the atherogenic lipoprotein phenotype predominates in ESRF, with excess LDLIII particularly prominent in PD patients. Atherogenic levels of LDLIII are found in patients with triglyceride levels greater than 177 mg/dL. This is likely to represent a further cardiovascular risk factor in this population.