Do total and high density lipoprotein cholesterol and triglycerides act independently in the prediction of ischemic heart disease? Ten-year follow-up of Caerphilly and Speedwell Cohorts.

Several studies have suggested that men with raised plasma triglycerides (TGs) in combination with adverse levels of other lipids may be at special risk of subsequent ischemic heart disease (IHD). We examined the independent and combined effects of plasma lipids at 10 years of follow-up. We measured fasting TGs, total cholesterol (TC), and high density lipoprotein cholesterol (HDLC) in 4362 men (aged 45 to 63 years) from 2 study populations and reexamined them at intervals during a 10-year follow-up. Major IHD events (death from IHD, clinical myocardial infarction, or ECG-defined myocardial infarction) were recorded. Five hundred thirty-three major IHD events occurred. All 3 lipids were strongly and independently predictive of IHD after 10 years of follow-up. Subjects were then divided into 27 groups (ie, 3(3)) by the tertiles of TGs, TC, and HDLC. The number of events observed in each group was compared with that predicted by a logistic regression model, which included terms for the 3 lipids (without interactions) and potential confounding variables. The incidence of IHD was 22.6% in the group with the lipid risk factor combination with the highest expected risk (high TGs, high TC, and low HDLC) and 4.7% in the group with the lowest expected risk (P<0.01). A comparison of the predicted number of events in the 27 groups with the number of events observed showed that a logistic regression provided an adequate fit without the need to incorporate interactions between lipids in the model. Conclusions are as follows: (1) Serum TGs, TC, and HDLC are independently predictive of IHD at 10 years of follow-up. (2) Combinations of adverse levels of the 3 major lipid risk factors have no greater impact on IHD than that expected from their individual contributions in a logistic regression model. There was no evidence that men with low HDL/raised TGs were at significantly greater risk than that predicted from the independent effects of the 2 lipids considered individually.

Endothelial dysfunction in chronic renal failure: roles of lipoprotein oxidation and pro-inflammatory cytokines.

BACKGROUND: Chronic renal failure (CRF) is associated with an increased risk of ischaemic heart disease (IHD), but the mechanisms responsible are controversial. We investigated the relationship of two sets of candidate mechanisms-indices of LDL oxidation and markers of inflammatory activity-with vascular endothelial dysfunction (VED). METHODS: We carried out cross-sectional analysis of 23 dialysed and 16 non-dialysed CRF patients, 28 healthy controls, and 20 patients with stable angina and normal renal function. The following were determined: (i) LDL oxidation by Cu(2+) and ultraviolet light, serum autoantibodies to oxidized LDL (oxLDL); (ii) forearm flow-mediated vasodilatation, plasma concentrations of adhesion molecules, and von Willebrand factor (vWF); and (iii) circulating levels of TNF-alpha and IL-6, C-reactive protein (CRP), and fibrinogen. RESULTS: Endothelium-dependent vasodilatation (EDV) was lower in angina, pre-dialysis, and dialysis CRF patients than in controls (all P<0.005). Compared with controls, vWf (P<0.005) and adhesion molecules (vCAM-1, P<0.005; iCAM-1, P=0.01; E-selectin, P=0.05) were raised in dialysis, and vCAM-1 (P=0.01) in pre-dialysis CRF patients. Dialysed patients had lower HDL cholesterol (P=0.01) and higher triglyceride (P=0.05) than controls, but LDL-oxidation was similar in all groups. Autoantibodies to oxLDL were raised in angina (P<0.005) and pre-dialysis (P=0.006), but were absent in most dialysed patients. Concentrations of IL-6, TNF-alpha, CRP and fibrinogen were elevated in CRF compared with control and angina patients (P<0.005). In the whole population, IL-6 and TNF-alpha correlated negatively with EDV, HDL cholesterol, and positively with triglyceride, blood pressure, vWf, iCAM-1, vCAM-1 and E-selectin (r=-0.43 to +0.70, all P<0.05). CONCLUSIONS: Endothelial dysfunction is unrelated to LDL oxidation, suggesting that LDL oxidation might not be a major cause of VED in CRF. In contrast VED was more severe in CRF than in angina patients and is associated with increased acute-phase proteins and plasma cytokines, demonstrating a chronic inflammatory state. These observations may explain the VED and increased IHD risk of patients with CRF.

Prospective trial evaluating early initiation of feeding in patients with newly placed one-step button gastrostomy devices.

The purpose of this study was to prospectively assess the feasibility and safety of early feeding in patients with newly placed one-step button (OSB) gastrostomy devices. Twenty-five patients who underwent percutaneous endoscopic button gastrostomy placement were prospectively enrolled. The patients underwent radiographic assessment (Gastrografin gastrograms) 3 hr after gastrostomy placement. Contrast extravasation was not documented in any patient. Aside from one patient who aspirated the contrast solution after the radiologic study, all others (96%) were successfully fed on the day the gastrostomy buttons were placed. In this prospective study of patients with newly placed OSB gastrostomy devices, early initiation of feeding was feasible and safe. In a fashion similar to their tube-style counterparts, button gastrostomy devices provide adequate apposition between the stomach and abdominal wall immediately after their initial placement.

Evidence for the regulation of levels of plasma adhesion molecules by proinflammatory cytokines and their soluble receptors in type 1 diabetes.

OBJECTIVES: To investigate the regulation of soluble adhesion molecules by tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), and relationships with circulating cytokine receptors, in vivo, in type 1 diabetes. DESIGN: Cross-sectional study. SETTING: University hospital diabetes clinic. SUBJECTS: A total of 47 non-nephropathic, Caucasian type 1 diabetics and 39 nondiabetic controls. OUTCOME MEASURES: Plasma levels of TNF-alpha, IL-6, their soluble receptors and adhesion molecules intercellular adhesion molecule-1 (sICAM-1), vascular cell adhesion molecule-1 (sVCAM-1), sE-selectin and von Willebrand factor (vWF), and risk factors for cardiovascular disease. RESULTS: Plasma concentrations of IL-6 were elevated in diabetic patients compared with controls [median (interquartiles) 1.28 (0.89-2.65) vs. 0.66 (0.45-1.73) pg mL(-1): P=0.016], and in these patients IL-6 and soluble IL-6 receptor (sIL-6R) levels correlated with concentrations of sICAM-1 (r = 0.41, P = 0.012 and r = 0.31, P = 0.04, respectively). Tumour necrosis factor-alpha soluble receptor-2 (sTN-FRII), but not TNF-alpha or tumour necrosis factor soluble receptor-1 (sTNFRI), was elevated in diabetic subjects (P = 0.027). Plasma TNF-alpha levels correlated with sVCAM-1 (r = 0.39, P = 0.008), triglycerides (r = 0.36, P = 0.02 1) and diastolic blood pressure (r = 0.35; P = 0.024). Both sTNFRI and sTNFRII correlated with blood pressure (r = 0.46, P = 0.002; r = 0.32, P = 0.034) and triglycerides (r = 0.33, P = 0.033; r = 0.29, P = 0.05). In contrast, HDL-cholesterol and triglyceride were related to sE-selectin (r = -0.45 and +0.45; both P < 0.001). Neither sE-selectin nor vWF were related to cytokine concentrations. Finally, both TNF-alpha and sIL-6R correlated sTNFRI and RII (r = 0.44-0.49, P < 0.001). None of these interactions were apparent in control subjects. CONCLUSIONS: (i) IL-6, through effects on sICAM-1, and TNF-alpha via effects on sVCAM-1, may promote vascular adhesion; (ii) plasma levels of TNF-alpha are associated with dyslipidaemia and increased blood pressure, adding to vascular disease risk; (iii) the actions of both cytokines are probably modified by altered production of soluble receptors in diabetic subjects.

Apolipoproteins A-I, A-II and B, lipoprotein(a) and the risk of ischaemic heart disease: the Caerphilly study.

Apolipoproteins B, A-I and Lp(a) have been proposed as independent predictors of subsequent ischaemic heart disease (IHD) improving on the prediction obtained by routine lipid measurements. In this report we have investigated the relative predictive ability of apolipoproteins and plasma lipids in a prospective study of middle aged men. 2398 men aged 49-65 years from the general population of Caerphilly, South Wales, UK were screened for evidence of IHD. After an overnight fast 2225 men each provided a venous blood sample on which plasma lipids, apolipoproteins B, A-I, A-II, and lipoprotein (a) (Lp(a)) were measured. Over a follow-up period of nearly 9 years, 282 (12%) men developed major IHD. Multiple logistic regression analysis showed that after adjusting for standard cardiovascular risk factors other than lipids there was a strong trend (standardised relative odds (SRO) = 1.20; P = 0.009) for incidence of IHD to increase with apolipoprotein B. However, on further adjusting for total cholesterol this trend largely disappeared (SRO = 1.05; P = 0.57). Similarly, a trend for incidence of IHD to increase with decreasing apolipoprotein A-I (SRO = 1.18; P = 0.02) disappeared when HDL cholesterol was added to the model. Levels of apolipoprotein A-II were not related to risk of subsequent IHD. Incidence of IHD was effectively constant over nearly 90% of the range of Lp(a). Only among the 5% of men with Lp(a) greater than 70 mg dL-1 was the risk of IHD significantly (P = 0.04) greater than among men with Lp(a) less than 10 mg dL-1. Apolipoproteins B and A-I do not improve on the prediction of risk of IHD provided by total and HDL cholesterol, respectively. Apolipoprotein A-II was not related to risk of IHD. Lp(a) may be independently associated with incident IHD among the 5-10% of men with the highest levels.

The importance of lipid-derived malondialdehyde in diabetes mellitus.

Malondialdehyde (MDA) is a highly toxic by-product formed in part by lipid oxidation derived free radicals. Many studies have shown that its concentration is increased considerably in diabetes mellitus. Malondialdehyde reacts both irreversibly and reversibly with proteins and phospholipids with profound effects. In particular, the collagen of the cardiovascular system is not only stiffened by cross-links mediated by malondialdehyde but then becomes increasingly resistant to remodelling. It is important in diabetes mellitus because the initial modification of collagen by sugar adducts forms a series of glycation products which then stimulate breakdown of the lipids to malondialdehyde and hence further cross-linking by malondialdehyde of the already modified collagen. Some progress is being made into the mechanisms of formation and the nature of the intermolecular cross-links induced by malondialdehyde which result in the stiffening of the collagenous tissues. Our recent studies indicate the formation of pyridyl cross-links. Malondialdehyde has been shown to react several orders of magnitude faster with the pre-existing collagen enzymic cross-links than the amino acid side-chains. Malondialdehyde modification of basic amino-acid side-chains also results in a change in properties, for example, in the charge profile of the molecule resulting in modified cell-matrix interactions. Although aspects of the biochemistry of malondialdehyde are still not fully understood its complex chemistry is being unravelled and this should lead to ways of preventing its damaging reactions, for example, through antioxidant therapy.

Measurement of N-methyl-2-pyridone-5-carboxamide in urine by high performance liquid chromatography.

We have previously described a simple and reproducible method for the measurement of nicotinamide and its major metabolite N-methyl-2-pyridone-5-carboxamide (2-pyr) in human plasma. We now describe a low-cost high-throughput method for measurement of urinary 2-pyr, and demonstrate that Isolute C18 bulk can replace use of the column to clean up the samples prior to injection into the HPLC apparatus. Using a standard curve together with an internal standard for each sample, with mean recovery of 2-pyr greater than 95%, the assay has proved reproducible, with considerable savings in cost and time. The principal advantages of this method are the rapid column clean up of samples prior to injection and the simple but effective methodology.

Measurement of nicotinamide and N-methyl-2-pyridone-5-carboxamide in plasma by high performance liquid chromatography.

We describe a simple and reproducible method for simultaneous determination of nicotinamide and its major human biological metabolite N-methyl-2-pyridone-5-carboxamide (2pyr). Previous assays for nicotinamide in plasma and in urine have been complicated by the use of tedious extraction procedures or HPLC conditions which, although often allowing simultaneous analysis of several metabolites, add to the difficulties of performing multiple analyses. The procedure we describe is simple, using a rapid column clean-up of samples prior to injection, which can then be done using an autosampler. Both nicotinamide and its major metabolite 2pyr can be assayed rapidly, with good reproducibility, and at the same time.

The lipoprotein profile of women with hyperprolactinaemic amenorrhoea.

The aim of this study was to evaluate the lipoprotein profile in women with hyperprolactinaemic amenorrhoea and to establish whether effective dopamine agonist therapy might have a beneficial effect. Blood samples were collected from women with hyperprolactinaemic amenorrhoea and from controls matched for age, body mass index and smoking. Follow-up blood samples were collected from women on dopamine agonist therapy as treatment for their hyperprolactinaemia. Plasma cholesterol, high density lipoprotein cholesterol, low density lipoprotein (LDL) cholesterol, very low density lipoprotein cholesterol, triglycerides, serum oestradiol and prolactin were measured. No statistically significant differences were found in the lipoprotein profile of the patient (n = 15) and control (n = 15) groups. During treatment with the dopamine agonist, bromocriptine (n = 9), significant reduction in total cholesterol [4.87 (3.98-5.87) versus 5.60 (4.55-6.61) mmol/l, P = 0.024] and LDL cholesterol [3.22 (2.01-4.23) versus 3.72 (2.59-4.93) mmol/l, P = 0.033] was noted. We conclude that beneficial alterations in the lipoprotein profile may occur in response to effective dopamine agonist therapy, presumably as a consequence of return of ovarian function and alleviation of oestrogen deficiency. Women with hyperprolactinaemic amenorrhoea should be encouraged to take effective therapy to improve their lipoprotein profile and potentially reduce their cardiovascular risk.

Endothelial dysfunction in Type 1 diabetes mellitus: relationship with LDL oxidation and the effects of vitamin E.

AIMS: To examine the hypothesis that increased susceptibility of low density lipoproteins (LDL) to oxidation predisposes to endothelial dysfunction in patients with Type 1 diabetes mellitus. METHODS: A cross-sectional study of 46 non-nephropathic diabetic and 39 control subjects and in the diabetic patients, a 3-month duration, randomized, placebo-controlled double-blind trial of vitamin E 500 U/day. Flow-mediated vasodilatation (FMD) was measured in the forearm by high resolution ultrasound. LDL oxidation by Cu2+ was measured in vitro. RESULTS: Diabetic patients had greater basal and reactive forearm blood flow (geometric mean (SD%) flow (ml/min) 110.15 (19.19%) vs. 74.99 (23.17%); P=0.045, and 344.35 (20.84%) vs. 205.17 (21.48%); P=0.007), compared with controls, but there was no difference in FMD (median (interquartile range) 0.00 (-0.01-0.02) vs. 0.02 (-0.01-0.02) cm2; P=0.78). Diabetic LDL oxidation lag time correlated with postdilatation brachial artery area (r= 0.32; P=0.05) but not with FMD. Lag-times and total LDL oxidation by Cu2+, lipoprotein and vitamin E concentrations were similar in diabetic and control groups. Antibody titres to oxidized LDL (oxLDL) were higher in non-diabetic than diabetic subjects, and were unrelated to FMD. In diabetic patients, vitamin E increased mean (SD) plasma vitamin E levels (24.0 (6.5) to 47.5 (7.5) gmol/l; P=0.0006) and resulted in increased FMD (delta 0.00 (-0.02-0.01) vs. 0.01 (0.01-0.02)) cm2; P=0.0036), but no changes in LDL Cu2+ oxidation profiles were observed. CONCLUSIONS: FMD is no different in Type 1 diabetic and non-diabetic subjects and nor are indices of lipid peroxidation and in vitro LDL oxidation although levels of antibody to oxLDL are lower in diabetes. Vitamin E supplementation increases plasma vitamin E levels and may enhance FMD in diabetes but, in the absence of changes in LDL oxidation, this may not be mediated by reduced oxidation of LDL.

The influence of lifestyle and diet on the lipoprotein profile of border collies.

Plasma lipoprotein cholesterol and triglycerides were determined in two groups of Border Collies, one actively working and the other pets. Baseline concentrations of total, low density lipoprotein (LDL) and high density lipoprotein (HDL) cholesterol were higher, and HDL triglyceride concentrations lower in the pet dogs. Lifestyle of the dogs was assessed by questionnaire completed by the owners. Measurement of exercise was made by visual observation and using a Caltrac activity monitor. The working dogs were a homogenous group with respect to lifestyle and diet, but the pet dogs showed differences in lipoprotein profile relating to housing, dietary fat and exercise intensity. Two diets with different levels of dietary fat (13 and 20 per cent dry weight) were given for two months each. After two months on either of the diets the cholesterol concentration of the working dogs increased and HDL triglyceride concentration decreased, and there were no significant differences between the groups, but very low density lipoprotein (VLDL) triglyceride increased significantly in the less active pet dogs.

Aspirin protects low density lipoprotein from oxidative modification.

OBJECTIVE: To examine the effects of aspirin on the potential for oxidative modification of low density lipoprotein (LDL). DESIGN: Before and after trial. SETTING: University department of medicine within a district general hospital campus. PATIENTS: Ten healthy normolipidaemic volunteers drawn from laboratory and medical staff. INTERVENTIONS: Aspirin (enteric coated) 300 mg daily for two weeks. MAIN OUTCOME MEASURES: In vitro oxidation of LDL following ultraviolet C (UVC) irradiation with measurements made of malondialdehyde, conjugated dienes, and electrophoretic mobility. RESULTS: There was a significant decrease in malondialdehyde production from LDL modified by aspirin in vivo following exposure to UVC irradiation for 90 minutes, culminating in a 30% decrease by 240 minutes (mean (SD) 64.2 (9.12) v 89.6 (11.6) nmol/mg LDL protein, P = 0.029). These observations were borne out using LDL modified by aspirin in vitro. The UVC induced increase in relative electrophoretic mobility of LDL was also significantly reduced following aspirin treatment (mean (SD) 2.17 (0.16) v 2.66 (0.24), P = 0.012). CONCLUSIONS: Aspirin, both in vivo and in vitro, protects LDL against subsequent oxidative modification, providing an additional mechanism whereby aspirin may protect against atherosclerosis.

The effect of dietary changes on plasma lipids and lipoproteins of six Labrador retrievers.

Six healthy, spayed female Labrador Retrievers (aged 5.5 to 11 years), kept under controlled conditions of exercise and housing, were fed a diet of 15 per cent fat, 24 per cent carbohydrate and 33 per cent protein for two weeks before and between each of three test diets, of differing fat to carbohydrate ratios (A 13:44, B 20:33, C 25:26 fat:carbohydrate gm per cent dry weight) given in a predetermined order for four weeks each. Fasting plasma lipoproteins and total fatty acids were measured weekly. In the fourth week of each test period post-prandial plasma lipoproteins were measured. Diets B and C increased total (P < 0.001) and LDL cholesterol (P < 0.05) whilst diet A increased HDL triglyceride (P < 0.05). Eicosapentaenoic acid (C20:5) increased on diets B and C, and oleic acid (C18:1) on diet A. Post-prandial hypertriglyceridaemia occurred on all diets. Chylomicron clearance was slower on higher fat diets. Relatively small dietary changes produced significant alterations of plasma lipids, lipoproteins and chylomicron clearance.

Associations of the HDL2 and HDL3 cholesterol subfractions with the development of ischemic heart disease in British men. The Caerphilly and Speedwell Collaborative Heart Disease Studies.

BACKGROUND: The relative importance of HDL2 and HDL3 cholesterol as risk factors for ischemic heart disease (IHD) is still uncertain. Their associations with the incidence of IHD in the Caerphilly and Speedwell prospective studies are described. METHODS AND RESULTS: The two studies have a common core protocol and are based on a total of 4860 middle-aged men from the general population. The first follow-up was at a nearly constant interval of 5.1 years in Caerphilly and 3.2 years in Speedwell: 251 major IHD events had occurred. Lipid levels were measured on fasting samples. Different laboratories were used by the two studies. Each laboratory used ultracentrifugation to separate HDL2 and HDL3. Both subfractions were inversely associated with risk of IHD. Standardized relative odds of developing major IHD were 0.95 (95% confidence interval [CI], 0.80 to 1.14) for HDL2 cholesterol and 0.83 (95% CI, 0.68 to 1.00) for HDL3 cholesterol in Caerphilly and 0.76 (95% CI, 0.57 to 1.01) for HDL2 and 0.64 (95% CI, 0.49 to 0.83) for HDL3 in Speedwell. The association with incident IHD appeared to be stronger for HDL3 in both areas. No linear combination of the two subfractions was a better predictor of IHD than total HDL cholesterol alone. CONCLUSIONS: In British men, both HDL2 and HDL3 cholesterol are inversely associated with the incidence of IHD. However, the prediction of the risk of IHD from total HDL cholesterol alone could not be improved upon by measurement of the two HDL subfractions. The relative value of the two HDL subfractions as predictors of risk is still unresolved. The uncertainty may be due, at least in part, to problems associated with their measurement.

Insulin in ischaemic heart disease: are associations explained by triglyceride concentrations? The Caerphilly prospective study.

OBJECTIVE: To investigate the predictive value of fasting insulin concentrations for subsequent fatal or non-fatal ischaemic heart disease at five year follow up and to examine the associations between insulin and other indicators of risk. DESIGN: A prospective population study among 2512 men aged 45 to 59 at recruitment. SETTING: A whole population sample of men resident in Caerphilly, South Wales. MEASUREMENTS: At recruitment fasting blood samples were taken for measurement of plasma lipids and serum insulin. Men were re-examined at a five year follow up and ischaemic heart disease events during this period were assessed from hospital notes, death certificates, and electrocardiograms. MAIN RESULTS: Diabetic men and those men with a fasting blood glucose of > or = 8 mmol/l were excluded from all analyses. In a univariate analysis the incidence of ischaemic heart disease increased with increasing concentration of fasting insulin, such that for men in the top 20% of the insulin distribution the odds of developing ischaemic heart disease were 1.87 relative to men in the bottom 20%. On multivariate analysis this relation disappeared on adjusting for plasma triglycerides, body mass index, and evidence of ischaemic heart disease at recruitment. CONCLUSION: In this population in South Wales there was no evidence that the fasting insulin concentration is an independent risk factor for ischaemic heart disease. The univariate association between insulin and incident disease was almost entirely explained by the association of both with triglycerides and body mass index.