LMNA, encoding lamin A/C, is mutated in partial lipodystrophy.

The lipodystrophies are a group of disorders characterized by the absence or reduction of subcutaneous adipose tissue. Partial lipodystrophy (PLD; MIM 151660) is an inherited condition in which a regional (trunk and limbs) loss of fat occurs during the peri-pubertal phase. Additionally, variable degrees of resistance to insulin action, together with a hyperlipidaemic state, may occur and simulate the metabolic features commonly associated with predisposition to atherosclerotic disease. The PLD locus has been mapped to chromosome 1q with no evidence of genetic heterogeneity. We, and others, have refined the location to a 5.3-cM interval between markers D1S305 and D1S1600 (refs 5, 6). Through a positional cloning approach we have identified five different missense mutations in LMNA among ten kindreds and three individuals with PLD. The protein product of LMNA is lamin A/C, which is a component of the nuclear envelope. Heterozygous mutations in LMNA have recently been identified in kindreds with the variant form of muscular dystrophy (MD) known as autosomal dominant Emery-Dreifuss MD (EDMD-AD; ref. 7) and dilated cardiomyopathy and conduction-system disease (CMD1A). As LMNA is ubiquitously expressed, the finding of site-specific amino acid substitutions in PLD, EDMD-AD and CMD1A reveals distinct functional domains of the lamin A/C protein required for the maintenance and integrity of different cell types.

Protection Against Nephropathy in Diabetes with Atorvastatin (PANDA): a randomized double-blind placebo-controlled trial of high- vs. low-dose atorvastatin(1).

AIMS: To compare the renal effects of low- vs. high-dose atorvastatin in patients with Type 2 diabetes mellitus and optimally managed early renal disease. METHODS: We compared the 2-year progression of nephropathy in a double-blind randomized controlled trial of atorvastatin 80 mg/day (n = 60) vs. 10 mg/day (n = 59) in patients with Type 2 diabetes with microalbuminuria or proteinuria [mean (sd): age 64 years (10 years); HbA(1c) 7.7% (1.3%), 61 mmol/mol (10 mmol/mol); blood pressure 131/73 mmHg; renin-angiotensin system blocker use > 80%; dual blockade > 67%] recruited from diabetes clinics in Greater Manchester. RESULTS: Over (mean) 2.1 years of follow-up, the Modification of Diet in Renal Disease estimated glomerular filtration rate declined by 3 ml min(-1) 1.73 m(-2) in the combined group. The mean (95% CI) between-group difference during follow-up was not significant [2.2 ml min(-1) 1.73 m(-2) (-1.1 to 5.4 ml min(-1) 1.73: m(-2) ), P = 0.20] after adjusting for baseline differences in renal function; positive difference favours 80 mg dose. Similarly, there was no significant difference in creatinine clearance by Cockcroft and Gault [2.5 ml/min (-2.4 to 7.3 ml/min), P = 0.32]; serum creatinine/24-h urine collections [4.0 ml/min (-4.8 to 12.7 ml/min), P = 0.38]; cystatin C (P = 0.69); or 24-h urine protein or albumin excretion (P = 0.92; P = 0.93). We recorded no significant between-group differences in deaths or adverse events. CONCLUSIONS: In patients with Type 2 diabetes with early renal disease, we found no statistical difference in renal function between those taking high- or low-dose atorvastatin over 2 years. We cannot exclude a beneficial effect of < 1.6 ml min(-1) 1.73 m(-2) year(-1) on Modification of Diet in Renal Disease estimated glomerular filtration rate, or if blood pressure management or if renin-angiotensin system blocker use had not been optimized.

Apolipoproteins, cardiovascular risk and statin response in type 2 diabetes: the Collaborative Atorvastatin Diabetes Study (CARDS).

AIMS/HYPOTHESIS: Controversy surrounds whether the ratio of apolipoprotein B (ApoB) to apolipoprotein A-I (ApoA-I) is the best lipoprotein discriminator of CHD risk in non-diabetic populations, but the issue has never been investigated in type 2 diabetes. METHODS: In 2,627 participants without known vascular disease in the Collaborative Atorvastatin Diabetes Study, ApoB, ApoA-I, LDL-cholesterol (LDLC) and HDL-cholesterol (HDLC) were assayed at baseline. RESULTS: There were 108 CHD and 59 stroke endpoints over 3.9 years. The ApoB:A-I ratio at baseline was the lipoprotein variable most closely predicting CHD risk both by comparison of the hazard ratio for a 1 SD change or tertiles of frequency distribution. The areas under the receiver-operator curve for the ApoB:ApoA-I and the LDLC to HDLC [corrected] ratios, although not significantly different from each other, were greater (p = 0.0005 and p = 0.0125 respectively) than that of non-HDLC:HDLC. The 27% decrease in the ApoB:ApoA-I ratio on atorvastatin predicted a 32% (95% CI 5.4-51.2%) risk reduction in CHD, close to the 36% decrease observed. Neither the ApoB:ApoA-I nor any other lipoprotein concentration or ratio predicted the stroke outcome. CONCLUSIONS/INTERPRETATION: Overall, the ApoB:ApoA-I ratio improved on the non-HDLC:HDLC ratio in predicting CHD, but, depending on the assessment chosen, its superiority over LDLC:HDLC may be marginal. The statin-induced decrease in stroke risk may not be lipoprotein mediated. TRIAL REGISTRATION: ClinicalTrials.gov NCT00327418. FUNDING: The study was supported by unrestricted grants from Diabetes UK, the Department of Health and Pfizer to the University of Manchester and to University College, London.

Ezetimibe monotherapy for cholesterol lowering in 2,722 people: systematic review and meta-analysis of randomized controlled trials.

OBJECTIVES: To study the evidence on the efficacy and safety of ezetimibe monotherapy for the treatment of primary (heterozygous familial and non-familial) hypercholesterolaemia. DESIGN: Systematic review and meta-analysis of randomized controlled trials (RCTs). METHODS: Eleven electronic bibliographic databases covering the biomedical, scientific and grey literature were searched from inception and supplemented by contact with experts in the field. Two reviewers independently determined the eligibility of RCTs, with a minimum treatment duration of 12 weeks, which compared ezetimibe monotherapy (10 mg per day) with placebo. RESULTS: In the absence of data from clinical outcome trials, surrogate endpoints such as changes in lipid concentrations were used as indicators of clinical outcomes. A meta-analysis of eight randomized, double-blind, placebo-controlled trials (all 12 weeks) showed that ezetimibe monotherapy was associated with a statistically significant mean reduction in LDL cholesterol (from baseline to endpoint) of -18.58%, (95% CI: -19.67 to -17.48, P < 0.00001) compared with placebo. Significant (P < 0.00001) changes were also found in total cholesterol (-13.46%, 95% CI: -14.22 to -12.70), HDL cholesterol (3.00%, 95% CI: 2.06-3.94) and triglyceride levels (-8.06%, 95% CI: -10.92 to -5.20). Ezetimibe monotherapy appeared to be well tolerated with a safety profile similar to placebo. CONCLUSIONS: In a meta-analysis restricted to short-term trials in hypercholesterolaemia, significant potentially favourable changes in lipid and lipoprotein levels relative to baseline occurred with ezetimibe monotherapy. Further long-term studies with cardiovascular and other clinical outcome data are needed to assess the efficacy and safety of ezetimibe more fully.

Estimated 10-year cardiovascular risk in a British population: results of a national screening project.

OBJECTIVE: To estimate 10-year cardiovascular disease (CVD) risk using the risk equation and risk categories of the Joint British Societies' Guidelines on Prevention of Cardiovascular Disease in Clinical Practice (2005). METHODS: A cross-sectional CVD screening programme was conducted in 35 towns in Great Britain. In total, 27,776 men and 43,261 women aged at least 18 years were screened. The estimated 10-year risk of CVD was calculated and directly standardised to the population of Great Britain. RESULTS: The age standardised combined prevalence of known CVD, diabetes, lipid-lowering or antihypertensive drug therapy, which preclude multifactorial risk assessment, was 18.0% for men and 18.1% for women. CVD risk was calculated for 56,863 individuals, and the age-standardised prevalence of an estimated 10-year CVD risk < 10% was 42.7% (95% CI: 42.2-43.1) for men and 60.4% (95% CI: 60.1-60.7) for women; 10% to < 20% was 19.6% (19.1-20.6) and 15.6% (15.2-15.9); and > or = 20% was 19.6% (19.1-20.0) and 6.0% (5.8-6.2) respectively. After aggregating known CVD, diabetes, antihypertensive or lipid-lowering drug therapy, or an estimated CVD risk of > or = 20%, the combined standardised prevalence of high CVD risk for individuals aged 50 years or more was 74.1% (73.5-74.8) for men (n = 14,787) and 45.5% (44.8-46.2) for women (n = 24,400). CONCLUSIONS: Using current risk thresholds, there is a substantial unmet need for primary prevention of CVD, particularly among middle-aged men. The results emphasise the scale of intervention that a strategy of individual risk assessment and pharmacological intervention requires.

Coronary heart disease mortality in treated familial hypercholesterolaemia: Update of the UK Simon Broome FH register.

BACKGROUND AND AIMS: Patients with familial hypercholesterolaemia (FH) have an elevated risk of coronary heart disease (CHD). Here we compare changes in CHD mortality in patients with heterozygous (FH) pre 1992, before lipid-lowering therapy with statins was used routinely, and in the periods 1992-2008 and 2008-2016. METHODS: 1903 Definite (DFH) and 1650 Possible (PFH) patients (51% women) aged 20-79 years, recruited from 21 lipid clinics in the United Kingdom and followed prospectively between 1980 and 2016 for 67,060 person-years. The CHD standardised mortality ratio (SMR) compared to the population in England and Wales was calculated (with 95% Confidence intervals). RESULTS: There were 585 deaths, including 252 from CHD. Overall, the observed 2.4-fold excess coronary mortality for treated DFH post-1991 was significantly higher than the 1.78 excess for PFH (35% 95% CI 3%-76%). In patients with DFH and established coronary disease, there was a significant excess coronary mortality in all time periods, but in men it was reduced from a 4.83-fold excess (2.32-8.89) pre-1992 to 4.66 (3.46-6.14) in 1992-2008 and 2.51 (1.01-5.17) post-2008, while in women the corresponding values were 7.23 (2.65-15.73), 4.42 (2.70-6.82) and 6.34 (2.06-14.81). Primary prevention in men with DFH resulted in a progressive reduction in coronary mortality over the three time-periods, with no excess mortality evident post-2008 (0.89 (0.29-2.08)), although in women the excess persisted (post-2008 3.65 (1.75-6.72)). CONCLUSIONS: The results confirm the benefit of statin treatment in reducing CHD mortality, but suggest that FH patients with pre-existing CHD and women with FH may not be treated adequately.

Effects of insulin and glucose on very low density lipoprotein triglyceride secretion by cultured rat hepatocytes.

The effect of insulin on hepatic triglyceride synthesis and secretion is controversial. Previously, we have described a cell culture system of adult rat hepatocytes that synthesize and secrete very low density lipoprotein (VLDL) triglycerides with small and irreproducible effects of insulin on triglyceride metabolism. To study the primary effects of insulin on hepatic triglyceride metabolism a method was developed utilizing fibronectin-coated culture dishes that allowed adhesion, spreading, and maintenance of hepatocytes for 2-3 d in the absence of serum and insulin. This culture system allowed mass measurements of both cellular and secreted VLDL triglycerides for long time periods after the addition of physiological concentrations of insulin to hormone-free culture medium. In the absence of insulin and after an initial 4 h in culture, the medium was replenished and triglyceride mass was measured at the end of 18-h incubations. VLDL triglyceride accumulated in the culture medium at a linear rate over this time-course with increasing accumulation as the medium glucose concentration was raised from 2.5 to 25 mM glucose (1.77+/-0.24 to 3.09+/-0.76 mug triglyceride/mg cell protein per h). There was no apparent significant lipolysis or hepatocellular reuptake of secreted VLDL triglycerides. In the absence of insulin cellular triglyceride levels were unchanged between 3 and 24 h in culture while insulin (50-500 muU/ml) significantly increased cellular triglyceride content at all glucose concentrations tested (0-25 mM). The addition of insulin to the culture medium progressively reduced the rate of VLDL triglyceride secretion accompanied by an increase in cellular triglyceride at insulin concentrations > 50 muU/ml. Most or all of the observed increase in cell triglyceride content could in all experiments be accounted for by the insulin-induced inhibition of VLDL secretion. Incorporation of [2-(3)H]glycerol into cellular and VLDL triglycerides as a function of insulin concentration was also measured. Glycerol incorporation data at 20-22 h after plating of the cells closely paralleled the insulin-induced changes in cellular and VLDL triglyceride as determined by mass analysis. The observed effects of insulin occurred at concentrations close to the physiological range and suggest that the direct hepatic effect is to suppress VLDL secretion although the net effect in vivo will clearly reflect many additional accompanying changes.

Genetic causes of familial hypercholesterolaemia in patients in the UK: relation to plasma lipid levels and coronary heart disease risk.

AIMS: To determine the relative frequency of mutations in three different genes (low-density lipoprotein receptor (LDLR), APOB, PCSK9), and to examine their effect in development of coronary heart disease (CHD) in patients with clinically defined definite familial hypercholesterolaemia in UK. PATIENTS AND METHODS: 409 patients with familial hypercholesterolaemia patients (158 with CHD) were studied. The LDLR was partially screened by single-strand conformational polymorphism (SSCP) (exons 3, 4, 6-10 and 14) and by using a commercial kit for gross deletions or rearrangements. APOB (p.R3500Q) and PCSK9 (p.D374Y) were detected by specific assays. Coding exons of PCSK9 were screened by SSCP. RESULTS: Mutations were detected in 253 (61.9%) PATIENTS: 236 (57.7%) carried LDLR, 10 (2.4%) carried APOB p.Q3500 and 7 (1.7%) PCSK9 p.Y374. No additional mutations were identified in PCSK9. After adjusting for age, sex, smoking and systolic blood pressure, compared to those with no detectable mutation, the odds ratio of having CHD in those with an LDLR mutation was 1.84 (95% CI 1.10 to 3.06), for APOB 3.40 (0.71 to 16.36), and for PCSK9 19.96 (1.88 to 211.5; p = 0.001 overall). The high risk in patients carrying LDLR and PCSK9 p.Y374 was partly explained by their higher pretreatment cholesterol levels (LDLR, PCSK9 and no mutation, 10.29 (1.85), 13.12 and 9.85 (1.90) mmol/l, respectively, p = 0.001). The post-statin treatment lipid profile in PCSK9 p.Y374 carriers was worse than in patients with no identified mutation (LDL-C, 6.77 (1.82) mmol/l v 4.19 (1.26) mmol/l, p = 0.001, HDL-C 1.09 (0.27) mmol/l v 1.36 (0.36) mmol/l, p = 0.03). CONCLUSIONS: The higher CHD risk in patients carrying PCSK9 p.Y347 or a detected LDLR mutation supports the usefulness of DNA testing in the diagnosis and management of patients with familial hypercholesterolaemia. Mutations in PCSK9 appear uncommon in patients with familial hypercholesterolaemia in UK.

Impact of migration on coronary heart disease risk factors: comparison of Gujaratis in Britain and their contemporaries in villages of origin in India.

The causes of the excess coronary heart disease (CHD) risk in South Asian migrants from the Indian subcontinent remain unclear. Comparisons of CHD risk factors amongst South Asian migrants living in Britain with those of the general UK population provide only a partial explanation. We compared Gujaratis in Britain with similar, non-migrant Gujaratis in India, to test the hypothesis that differences in CHD risk factors associated with migration would be more informative. Randomly sampled Gujaratis aged 25-79 years living in Sandwell (n = 242) were compared with age-, gender- and caste-matched contemporaries remaining in their villages of origin in Navsari, India (n = 295). Lifestyle indices, food intake and physical activity, were assessed with standardised questionnaires and energy expenditure and metabolic parameters measured. British Gujaratis had higher, mean body mass indices by 6 (4.5-7.4) kg/m(2) mean (95% CI), and greater dietary energy intake, fat intake, blood pressure, fasting serum cholesterol, apolipoprotein B, triglycerides, non-esterified fatty acid (NEFA) and C-reative protein concentrations than Gujaratis in India. Dietary folate and serum folate and Vitamin B(12) were lower and plasma homocysteine was higher in India. Smoking was less prevalent and high-density lipoprotein cholesterol tended to be higher in Britain. Diabetes prevalence was high in both populations and impaired fasting or 2 h post-glucose challenge plasma glucose was even more prevalent in Gujarat. In India, however, where insulin secretion and NEFA were lower diabetes and impaired glucose tolerance were less frequently accompanied by excess metabolic CVD risk factors. In conclusion, exposure to increased fat intake and obesity related to migration is likely to explain the disproportionate combination of established and emerging CHD risk factors prevalent in Gujaratis in Britain. Strategies to improve nutrition and to identify and treat cardiovascular risk factors such as dyslipidaemia and hypertension are urgently required.

Lipoprotein secretion by the human hepatoma cell line Hep G2: differential rates of accumulation of apolipoprotein B and lipoprotein lipids in tissue culture media in response to albumin, glucose and oleate.

Serum low-density lipoprotein (LDL) concentration is a major determinant of susceptibility to the development of atherosclerosis. A major component of the protein moiety of LDL and its precursor very-low-density lipoprotein is apolipoprotein B (apo B). The human hepatoma cell line, Hep G2, was used as a model for the investigation of mechanisms which control hepatic secretion of the apo B and lipid components of lipoproteins. Using a sensitive immunoradiometric assay for apo B developed in this laboratory, we showed that bovine serum albumin inhibited and glucose, and fatty acids enhanced the rate of accumulation of apo B in the culture medium of Hep G2 cells. However, these substances did not necessarily affect LDL lipids in the same way as apo B. This finding appeared to be due to Hep G2 cells expressing lipase activities which led to triacylglycerol and phospholipid hydrolysis and lipid reuptake. Reuptake of apo B also occurred, but its rate of accumulation in the culture medium suggested it was a closer reflection of its true secretory rate.

Serum esterase activities and hyperlipidaemia in the streptozotocin-diabetic rat.

The levels of activity of four serum esterases were measured in control and streptozotocin-diabetic rats for a period of 6 months. Pseudocholinesterase activity was significantly elevated in the diabetic rats at all time points tested, reaching 250% of the control activity at 6 months. Levels of paraoxonase activity progressively decreased with time in the diabetic rats, being 36% lower than in controls at 6 months. No significant differences in either serum arylesterase or carboxylesterase activity between control and diabetic rats were observed.

Effect of treatment with a hydroxymethylglutaryl coenzyme A reductase inhibitor on fasting and postprandial plasma lipoproteins and cholesteryl ester transfer activity in patients with NIDDM.

Patients with non-insulin-dependent diabetes mellitus (NIDDM) have a greater risk of developing coronary heart disease than would be expected from a similar degree of hyperlipidemia in nondiabetic populations. Accelerated transfer of cholesteryl esters (CET) from high-density lipoprotein (HDL) to low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL), a process that is associated with atherosclerosis, may be a possible explanation for this. CET, plasma lipoprotein concentration, and mass in the fasting and postprandial state have been examined in 31 hyperlipidemic patients with NIDDM before and after 8 weeks of treatment with the hydroxymethylglutaryl (HMG)-coenzyme A (CoA) reductase inhibitor pravastatin in a double-blind, placebo-controlled, parallel group study. Body mass index, glycemic control, and blood pressure remained unaltered during the study period. Compared with placebo, pravastatin decreased fasting serum cholesterol (P < 0.001) and LDL cholesterol (P < 0.002) levels. The high basal CET (34.4 +/- 13.1 nmol.ml-1.h-1) was decreased significantly by pravastatin treatment (27.5 +/- 13.7 nmol.ml-1.h-1, P = 0.013). There was a fall in the total cholesterol, free cholesterol, and phospholipid content of the Sf 0-12, 20-60, and 60-400 lipoproteins (all P = 0.001). Lecithin: cholesterol acyl transferase activity was not altered. The postprandial increase in VLDL cholesterol 5 h after a standardized mixed meal was attenuated after pravastatin treatment (P = 0.011). Inhibition of hepatic cholesterol synthesis with an HMG-CoA reductase inhibitor in hyperlipidemic patients with NIDDM decreased serum cholesterol content of triglyceride-rich lipoprotein, thereby decreasing the transfer of cholesteryl ester from HDL to LDL and VLDL.

Non-coronary heart disease mortality and risk of fatal cancer in patients with treated heterozygous familial hypercholesterolaemia: a prospective registry study.

BACKGROUND: The prognosis from coronary heart disease (CHD) for patients with heterozygous familial hypercholesterolaemia has improved substantially since the introduction of HMG Co-A reductase inhibitors (statins), but the effect of lipid-lowering drug therapy combined with dietary and life style advice on non-coronary mortality and the risk of fatal cancer is unclear. METHODS: The cohort of 2871 patients was recruited from 21 outpatient lipid clinics in the UK from 1980 to 1998 and was followed for 22,992 person-years. The standardised mortality ratio (SMR) was calculated from the ratio of the number of deaths observed to the number expected in the general population of England and Wales. RESULTS: There were 169 deaths, including 102 (60.4%) from CHD, and 32 (18.9%) from cancer. The SMR for CHD was 2.5-fold higher than in the general population (95% CI 2.1, 3.1), but the all-cause SMR was not increased (1.1, 95% CI 0.9, 1.3) and non-coronary mortality was significantly lower in men (0.5, 95% CI 0.3, 0.7) and women (0.6, 95% CI 0.4, 0.9). The SMR for all cancers was significantly reduced (0.6, 95% CI 0.4, 0.8) with an 80% reduction in fatal cancers of the respiratory and intra-thoracic organs and a non-significant reduction in fatal cancers of the genitourinary and digestive organs. CONCLUSIONS: Although the study cannot exclude the possibility that statins have anti-cancer activity, the results strongly suggest that giving advice to consume a healthy diet, increase physical activity and stop smoking is associated with a substantial reduction in mortality from cancer.

Paraoxonase and atherosclerosis.

There is considerable evidence that the antioxidant activity of high density lipoprotein (HDL) is largely due to the paraoxonase-1 (PON1) located on it. Experiments with transgenic PON1 knockout mice indicate the potential for PON1 to protect against atherogenesis. This protective effect of HDL against low density lipoprotein (LDL) lipid peroxidation is maintained longer than is the protective effect of antioxidant vitamins and could thus be more important. There is evidence that the genetic polymorphisms of PON1 least able to protect LDL against lipid peroxidation are overrepresented in coronary heart disease, particularly in association with diabetes. However, these polymorphisms explain only part of the variation in serum PON1 activity; thus, a more critical test of the hypothesis is likely to be whether low serum PON1 activity is associated with coronary heart disease. Preliminary case-control evidence suggests that this is indeed the case and, thus, that the quest for dietary and pharmacological means of modifying serum PON1 activity may allow the oxidant model of atherosclerosis to be tested in clinical trials.

Paraoxonase status in coronary heart disease: are activity and concentration more important than genotype?

Human serum paraoxonase (PON1) hydrolyzes oxidized lipids in low density lipoprotein (LDL) and could therefore retard the development of atherosclerosis. In keeping with this hypothesis, several case-control studies have shown a relationship between the presence of coronary heart disease (CHD) and polymorphisms at amino acid positions 55 and 192 of PON1, which we associated with a decreased capacity of PON1 to protect LDL against the accumulation of lipid peroxides, but some other studies have not. However, the PON1 polymorphisms are only 1 factor in determining the activity and concentration of the enzyme. Only 3 of the previous 18 studies directly determined PON1 activity and concentration. Therefore, we studied PON1 activity, concentration, and gene distribution in 417 subjects with angiographically proven CHD and in 282 control subjects. We found that PON1 activity and concentration were significantly lower in subjects with CHD than in control subjects (activity to paraoxon 122.8 [3.3 to 802.8] versus 214.6 [26.3 to 620.8] nmol. min(-1). mL(-1), P<0.001; concentration 71.6 [11.4 to 489.3] versus 89.1 [16.8 to 527.4] microg/mL, P<0.001). There were no differences in the PON1-55 and -192 polymorphisms or clusterin concentration between patients with CHD and control subjects. These results indicate that lower PON1 activity and concentration and, therefore, the reduced ability to prevent LDL lipid peroxidation may be more important in determining the presence of CHD than paraoxonase genetic polymorphisms.

Prevention of recurrent pancreatitis in familial lipoprotein lipase deficiency with high-dose antioxidant therapy.

We describe a dramatic response to antioxidant therapy in three patients with familial lipoprotein lipase deficiency complicated by frequent severe episodes of pancreatitis who had failed to respond to other dietary and pharmacological measures. Antioxidant therapy may be an important advance in the management of this type of patient.

Fetal and maternal lipoprotein metabolism in human pregnancy complicated by type I diabetes mellitus.

Serum lipid, apolipoprotein concentration, and lipoprotein composition were determined in maternal and umbilical venous cord blood at delivery by elective Cesarean section (CS) in 10 singleton, full-term pregnancies with maternal insulin-dependent diabetes mellitus (type I DM), which predated pregnancy, and in 22 nondiabetic pregnancies. The objectives of the study were to determine the influence of maternal type I DM, and hence potential fetal overnutrition on fetal lipid metabolism. There were no significant differences in gestational age, fetal weight, or fetal serum insulin concentration between the type I DM group and those with nondiabetic pregnancies, although fetal venous cord blood glucose was 3.4 mmol/L (3.0-4.5 mmol/L) (median and 25th-75th percentiles) and 2.9 mmol/L (2.0-3.4 mmol/L), respectively, and maternal Hemoglobin A1c [9.6% (8.2-10.7%) and 6.8% (6.3-7.8%), respectively], was significantly greater in the type I DM subjects (P < 0.02 and 0.002 respectively). Plasma nonesterified fatty acid (NEFA) concentrations were lower in the type I DM mothers [0.85 mmol/L (0.56-2.31 mmol/L) compared with 1.14 mmol/L (0.88-1.24 mmol/L] in nondiabetic pregnancies; P < 0.0001). Serum high-density lipoprotein phospholipids (HDL-PL) were increased in type I DM mothers because of elevated HDL2 phospholipid [0.39 mmol/L (0.27-0.48 mmol/L) compared with 0.12 mmol/L (0.06-0.21 mmol/L), respectively, P < 0.01). The maternal HDL cholesterol (C) concentration was not significantly different in the uncomplicated and type I DM pregnancies. However, in the umbilical venous cord blood, serum levels of NEFA [0.49 mmol/L (0.33-1.29 mmol/L) in type I DM compared with 0.13 mmol/L (0.06-0.33 mmol/L) in nondiabetics; P < 0.02)], total cholesterol (TC) [2.87 mmol/L (1.65-4.86 mmol/L) in type I DM compared with 1.65 mmol/L (1.46-1.87 mmol/L) in nondiabetics; P < 0.02]; free cholesterol (FC) [0.97 mmol/L (0.60-1.26 mmol/L) in type I DM compared with 0.62 mmol/L (0.37-0.75 mmol/L) in nondiabetics; P < 0.05), and cholesteryl ester (CE) [1.90 mmol/L (1.44-3.33 mmol/L) in type I DM compared with 1.01 mmol/L (0.83-1.24 mmol/L) in nondiabetics; P < 0.02), triglyceride (TG) (1.06 [0.50-1.91) mmol/L in type I DM compared with 0.29 [0.25-0.36] mmol/l in nondiabetics; P < 0.001), phospholipid (PL) (2.52 [1.73-3.03) mmol/L in type I DM compared with 1.34 [1.27-1.48] mmol/L in nondiabetics; P < 0.01], and the apolipoproteins A-I and B had significantly higher concentrations in type I DM. In umbilical venous cord blood, ratios of HDL-TC and HDL-PL to apo AI, reflecting the lipid content of HDL, were reduced when the mother had type I DM during pregnancy (P < 0.02 and P < 0.0001, respectively). These results indicate that maternal type I DM may lead to a fetal serum lipoprotein composition more closely resembling that seen in the adult. In type I DM, maternal TG and PL and fetal TC, TG, PL, CE, and FC were correlated to NEFA levels (P < 0.05), but not to glucose, insulin secretion, or maternal control of type I DM. These data suggest that the enhanced supply of NEFA to the fetus in type I DM pregnancies may drive the synthesis of cholesterol as well as TGs and PLs.

Paraoxonase prevents accumulation of lipoperoxides in low-density lipoprotein.

Oxidative modification of low-density lipoprotein (LDL) enhances its uptake by macrophages in tissue culture and in vivo may underly the formation of arterial fatty streaks, the progenitors of atheroma. We investigated the possible protection which high-density lipoprotein (HDL) affords against LDL oxidation. The formation of lipoperoxides and thiobarbituric acid reactive substances when LDL was incubated with copper ions was significantly decreased by HDL. The enzyme, paraoxonase (E.C. 3.1.8.1), purified from human HDL, had a similar effect and thus may be the component of HDL responsible for decreasing the accumulation of lipid peroxidation products.

Effect of the human serum paraoxonase 55 and 192 genetic polymorphisms on the protection by high density lipoprotein against low density lipoprotein oxidative modification.

Human serum paraoxonase (PON1) associated with high density lipoprotein (HDL) has been postulated to have a role in protecting low density lipoprotein (LDL) against oxidative modification, which has led to the proposal that PON1 is an anti-atherogenic, anti-inflammatory enzyme. PON1 has two genetically determined polymorphic sites giving rise to amino-acid substitutions at positions 55 (L-->M) and 192 (R-->Q) and therefore 4 potential alloenzymes. We have examined the effects of these molecular polymorphisms on the ability of HDL to protect LDL from oxidative modification. HDL protected LDL from oxidative modification, whatever the combination of PON1 alloenzymes present in it. However, HDL from QQ/MM homozygotes was most effective at protecting LDL while HDL from RR/LL homozygotes was least effective. Thus after 6 h of co-incubation of HDL and LDL with Cu2+ PON1-QQ HDL retained 57 +/- 6.3% of its original ability to protect LDL from oxidative modification, while PON1-QR HDL retained less at 25.1 +/- 4.5% (P < 0.01) and PON1-RR HDL retained only 0.75 +/- 0.40% (P < 0.005). In similar experiments HDL from LL and LM genotypes retained 21.8 +/- 7.5% and 29.5 +/- 6.6% (P = NS), respectively, of their protective ability, whereas PON1-MM HDL maintained 49.5 +/- 5.3% (P < 0.01). PON1 polymorphisms may affect the ability of HDL to impede the development of atherosclerosis and to prevent inflammation.

Presence of paraoxonase in human interstitial fluid.

Human serum paraoxonase (PON1) is postulated to have anti-atherosclerotic properties through its ability to prevent lipid peroxide generation on LDL. However, in order to perform this role it must be present in interstitial fluid, to prevent LDL oxidation which takes place in the sub-intimal space of the artery wall. The PON1 activity in interstitial fluid was 15.7 (2.3-183.0) (median (range)) nmol/min/ml compared to 105.3 (74.6-323.9) nmol/min/ml in serum. The PON1 concentration in interstitial fluid was found to be 20.2 (1.1-78.1) microg/ml (median (range)) compared to 109.6 (11.1-485.7) microg/ml in serum. Interstitial fluid PON1 concentration was dependent on the interstitial fluid apo AI concentration (r = 0.690, P < 0.005) indicating PON1 remained associated with HDL. However, the ratio of PON1 concentration to apo AI was lower in interstitial fluid (0.60 +/- 0.20) than in the serum (0.95 +/- 0.18) (P < 0.001) indicating sequestration of PON1 in the sub-intimal space. Therefore, PON1 is present and active in interstitial fluid where it can perform its anti-atherosclerotic function.