Increased hepatic secretion of very-low-density lipoprotein apolipoprotein B-100 in NIDDM.

We measured the hepatic secretion of very-low-density lipoprotein apolipoprotein B-100 (VLDL apoB) using a stable isotope gas-chromatography mass-spectrometry method in six patients with non-insulin-dependent diabetes mellitus (NIDDM) (four males, two females, age 57.5 +/- 2.2 years (mean +/- SEM), weight 88.2 +/- 5.5 kg, glycated haemoglobin (HbA1) 8.5 +/- 0.5%, plasma total cholesterol concentration 5.7 +/- 0.5 mmol/l, triglyceride 3.8 +/- 0.9 mmol/l, high-density lipoprotein (HDL) cholesterol 1.0 +/- 0.1 mmol/l) and six non-diabetic subjects matched for age, sex and weight (four males, two females, age 55.7 +/- 2.8 years, weight 85.8 +/- 5.6 kg, HbA1 6.5 +/- 0.1%, plasma total cholesterol concentration 5.7 +/- 0.5 mmol/l, triglyceride 1.2 +/- 0.1 mmol/l, HDL cholesterol 1.4 +/- 0.1 mmol/l). HbA1, plasma triglyceride and mevalonic acid (an index of cholesterol synthesis in vivo) concentrations were significantly higher in the diabetic patients than in the non-diabetic subjects (p = 0.006, p = 0.02 and p = 0.004, respectively). VLDL apoB absolute secretion rate was significantly higher in the diabetic patients compared with the non-diabetic subjects (2297 +/- 491 vs 921 +/- 115 mg/day, p < 0.05), but there was no significant difference in the fractional catabolic rate of VLDL apoB. There was a positive correlation between VLDL apoB secretion rate and (i) fasting C-peptide (r = 0.84, p = 0.04) and (ii) mevalonic acid concentration (r = 0.83, p < 0.05) in the diabetic patients but not in the non-diabetic subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Direct correlation between cholesterol synthesis and hepatic secretion of apolipoprotein B-100 in normolipidemic subjects.

The regulation of apolipoprotein B-100 (apo B) metabolism in man is not fully understood. In vitro studies suggest a key role for the hepatic availability of cholesterol substrate. We therefore examined whether there was a direct association between plasma mevalonic acid (MVA) concentration (an index of in vivo cholesterol synthesis) and hepatic secretion of very-low-density lipoprotein (VLDL) apo B in eight normolipidemic, healthy adult subjects. Hepatic secretion of VLDL apo B was estimated by endogenous labeling of apo B with an 8-hour primed, constant infusion of 1-13C-leucine. Isotopic enrichment of VLDL apo B was measured by gas chromatography-mass spectrometry (GCMS), from which the fractional secretion rate (FSR) was derived by a modified monoexponential function. Plasma concentration of MVA was measured by gas chromatography-electron-capture mass spectrometry in blood samples taken at 9 AM. The absolute secretion rate (ASR) of VLDL apo B (mean +/- SD) was 9.7 +/- 2.6 mg/kg/d, and MVA concentration was 5.0 +/- 2.5 ng/mL. There was a highly significant positive correlation between ASR of VLDL apoB and plasma MVA (r = .88, P = .004), which persisted after adjusting for apo E phenotype. The findings suggest that in vivo cholesterol synthesis is a determinant of hepatic secretion of apo B in normolipidemic subjects.

Lipoprotein(a) as a determinant of the severity of angiographically defined carotid atherosclerosis.

We measured fasting serum lipids, lipoproteins, apolipoproteins and lipoprotein(a) [Lp(a)] in 49 Caucasian patients with transient ischaemic attacks undergoing carotid angiography. The severity of extracranial cerebrovascular disease was assessed visually by a highly reproducible grading system that focused on the internal carotid artery and carotid bifurcation. Compared with a healthy reference group, patients had significantly higher serum concentrations of: total cholesterol (mean +/- SD), 6.2 +/- 1.6 vs. 5.6 +/- 1.0 mmol/l, p = 0.02; apolipoprotein B, 1.4 +/- 0.5 vs. 1.2 +/- 0.3 g/l, p = 0.03; triglyceride [geometric mean(95% CI)], 2.02(1.75-2.32) vs. 1.66(0.67-4.06) mmol/l, p = 0.03; and Lp(a), 0.33(0.26-0.42) vs. 0.17(0.40-0.76) g/l, p < 0.001. Regression analysis showed that of the lipoprotein-related variables, only Lp(a) was significantly related to the severity of carotid artery disease (p = 0.04) in the patients; this association remained significant after adjusting for age, sex, blood pressure, and a history of stroke. Serum Lp(a) concentration was significantly higher in patients with carotid artery disease severity score above the median value of the sample population compared with those below the median: 0.45 vs. 0.24 g/l (95% CI for difference 0.35-0.88), p = 0.01. Elevated serum Lp(a) is a significant determinant of the extent of carotid atherosclerosis and may be useful in identifying patients most at risk of stroke.

Metabolic determinants of the course of coronary artery disease in men.

We examined associations between metabolic variables and changes in coronary artery disease (CAD) in the St. Thomas' Atherosclerosis Regression Study (STARS). The course of CAD over 3 years was measured continually by quantitative coronary angiography, i.e., as the per patient change in the mean absolute width of coronary segments (delta MAWS). The decrease in MAWS (progression of CAD) was significantly correlated with in-trial plasma concentrations of cholesterol (P = 0.002), low-density lipoprotein (LDL) cholesterol (P = 0.001), apolipoprotein B (apoB) (P = 0.008), and lipoprotein(a) [Lp(a)] (P = 0.004); no significant associations were found with high-density lipoprotein (HDL) cholesterol, apoA-I, vitamin E, thyroid hormones, fibrinogen, von Willebrand factor, or post-load plasma glucose and insulin concentrations. By multiple regression analysis, LDL cholesterol was the best predictor of delta MAWS, the adjusted model explaining 22% of the variance (P = 0.04). Thus, in men with symptomatic CAD the most important metabolic predictor of change in CAD is plasma LDL cholesterol, there being no advantage in measuring other variables, in particular, apoB or Lp(a).

Serum lipids, lipoproteins and apolipoproteins in pregnant non-diabetic patients.

AIMS: To investigate the effect of pregnancy on serum concentrations of lipids, lipoproteins, and apolipoproteins. METHODS: Fasting serum concentrations of total cholesterol, triglyceride, low density lipoprotein cholesterol (LDL), high density lipoprotein cholesterol (HDL), apolipoproteins AI, AII, and B, and lipoprotein (a) were measured in 178 women with normal glucose tolerance in the second and third trimesters of pregnancy and in a control group of 58 non-pregnant women of similar age. Data were analysed using the unpaired t test and by one-way analysis of variance. RESULTS: The pregnant women had significantly higher concentrations of total cholesterol, triglyceride, LDL cholesterol, HDL cholesterol, and apolipoproteins AI and B (p < 0.001) and apolipoprotein AII (p = 0.003) than the control women. The ratio of apolipoprotein B:apolipoprotein AI was significantly higher in the pregnant women than in the controls (p < 0.001), but the total cholesterol:HDL cholesterol ratio was not significantly different. No significant difference was found in the concentration of lipoprotein (a). CONCLUSIONS: Hyperlipidaemia is common in the second half of pregnancy. This may be a purely physiological response to pregnancy or it may be indicative of pathology in some women. These results warrant a follow up study to investigate whether the hyperlipidaemic response to pregnancy is variable and if so, whether it can predict future hyperlipidaemia in a manner analogous to that of impaired glucose tolerance during pregnancy, predicting non-insulin dependent diabetes in later life.

Comparison of immunoturbidimetric and Lowry methods for measuring concentration of very low density lipoprotein apolipoprotein B-100 in plasma.

To assess whether the Lowry-tetramethylurea method for measuring apolipoprotein B-100 (apo-B) in very low density lipoprotein (VLDL) could be replaced by direct assay of VLDL apo-B using a highly practicable immunological method. Seventy five fasting blood samples were collected from patients attending the lipid clinic at this hospital. Plasma was separated immediately and VLDL isolated by preparative ultracentrifugation at solution density 0.93-1.006 kg/l. Apo-B was precipitated from an aliquot of the VLDL fraction using the tetramethylurea (TMU) technique and protein mass determined by the Lowry method (LM); mean apo-B 83.02 micrograms/ml (SD 74.85). Apo-B was also measured in VLDL using direct immunoturbidimetry on the Cobas-Fara analyser; mean apo-B 82.32 micrograms/ml (SD 72.88). There was a very close correlation between methods (immunoturbidimetry = 0.94.LM + 3.95, r = 0.97, p < 0.001). The mean difference between methods (constant error) was small (0.70 microgram/ml) and not significant (p = 0.742). Random error was 13.01 micrograms/ml by analysis of variance. It is concluded that immunoturbidimetry, a more rapid and convenient test, may replace the LM and TMU techniques for measuring VLDL apo-B concentration and that this method could be applied to research studies requiring analysis of large numbers of samples.

Independent associations between plasma lipoprotein subfraction levels and the course of coronary artery disease in the St. Thomas' Atherosclerosis Regression Study (STARS).

Associations between plasma lipoprotein subfractions and changes in coronary artery diseases (CAD) were examined in 74 men who completed the St. Thomas' Atherosclerosis Regression Study (STARS). Plasma lipoproteins were isolated by stepwise, preparative ultracentrifugation at repeated intervals during the 38-month trial. Paired coronary angiograms were quantitatively analyzed by a computerized method. In univariate linear regression analysis, changes in mean absolute width (delta MAWS) and minimum absolute with (delta MinAWS) of coronary segments were significantly correlated with in-trial concentrations of cholesterol in intermediate-density lipoprotein ([IDL] d = 1.006 to 1.019 kg/L), low-density lipoprotein ([LDL2] d = 1.019 to 1.040 kg/L; LDL3, d = 1.040 to 1.063 kg/L), and high-density lipoprotein ([HDL3] d = 1.125 to 1.210 kg/L) subfractions; no significant associations were found with other lipoproteins. IDL, LDL3, and HDL3 cholesterol were then selected for multiple linear regression analysis because these variables were not co-correlated and because they attained a significance of P less than or equal to .1 in univariate regression. In this analysis, only LDL3 cholesterol level was a significant negative predictor (P < .05) of both delta MAWS and delta MinAWS; a positive association between delta MinAWS and HDL3 cholesterol level just failed to reach conventional statistical significance (P = .066). Correlations between changes in coronary luminal dimensions and LDL3 cholesterol level were independent of age, smoking, weight, and blood pressure. Most patients showing regression of coronary atherosclerosis had an LDL3 cholesterol level of less than 1.8 mmol/L. The findings suggest that LDL3 is the plasma lipoprotein subfraction that exerts the single most powerful effect on the course of CAD in middle-aged men with hypercholesterolemia.

Gender and employment grade differences in blood cholesterol, apolipoproteins and haemostatic factors in the Whitehall II study.

In the first Whitehall study, plasma cholesterol was a strong predictor of coronary heart disease (CHD) but it showed a positive association with grade of employment: the higher the grade the higher the level. Because it could not explain the higher rate of CHD in lower employment grades, further investigation of biochemical CHD risk factors has been conducted with data from the baseline examination of the Whitehall II cohort in 1985-88. These data also allow investigation of gender differences and the effect of menopause. Serum cholesterol (6860 men and 3374 women) and apolipoproteins A-I and B (apo AI and apo B) were measured in those aged 35-55 working in the London offices of twenty Civil Service departments. Plasma fibrinogen and factor VII were determined in 45-55 year olds. The apo B/apo AI ratio (95% confidence interval) after age adjustment is lowest in premenopausal women: 0.557 (0.549-0.565), intermediate in postmenopausal women: 0.601 (0.589-0.613) and highest in men: 0.703 (0.698-0.709). After age adjustment fibrinogen is higher in postmenopausal (2.90 (2.85-2.95) g/l) than in premenopausal women (2.78 (2.71-2.84) g/l), who have higher levels than men (2.64 (2.62-2.67) g/l). A positive association with employment grade is seen for apo AI and a negative association is seen for fibrinogen, apo B (women only) and the apo B/apo AI ratio, after age adjustment. These patterns are consistent with the higher rates of CHD in lower grades. Cholesterol and factor VII show no gradient with our sensitive measure of social position. After adjusting for the effects of smoking rates, alcohol consumption, exercise and dietary pattern, as well as age, ethnicity, body mass index and report of symptoms, the regression coefficient for apo AI on employment grade is reduced by 43% in men and 70% in women. Corresponding reductions for fibrinogen are 53% and 65%. These attenuations suggest that a considerable part of the social gradients in apo AI and fibrinogen are explained by variations in health related behaviours. The remaining gradients may represent effects independent of these behaviours.

Lipoprotein (a) as an independent risk factor for myocardial infarction in patients with common hypercholesterolaemia.

AIMS: To examine whether lipoprotein (a) (Lp(a)) increases the risk of myocardial infarction (MI) in patients with common hypercholesterolaemia. METHODS: 15 middle aged men with common hypercholesterolaemia (mean serum low density lipoprotein (LDL) cholesterol 4.94 mmol/l, SD 1.0) and a history of MI were selected consecutively from referrals to a lipid clinic. A control group that had not sustained an MI and with similar age, sex, cigarette smoking and blood pressure characteristics was also selected from the same clinic. Serum cholesterol, triglyceride, LDL cholesterol, high density lipoprotein cholesterol, apolipoproteins AI and B and Lp(a) were measured in both groups. Lp(a) was assayed by immunoturbidity. RESULTS: The serum concentration of Lp(a) was significantly higher in patients with MI (geometric mean 0.64 (95% confidence interval 0.36 to 1.14) v 0.30 (0.21 to 0.42) g/l, p = 0.02), but there were no significant differences in other variables. Stepwise logistic regression analysis showed that Lp(a) was the only significant predictor of MI (p < 0.02). The odds ratio of MI (adjusted for age, smoking, blood pressure and apolipoprotein B) for an Lp(a) of > 0.57 g/l was 16.5, 95% confidence interval 2.3 to 125.4 (p = 0.001). CONCLUSION: In middle aged men with common hypercholesterolaemia the serum concentration of Lp(a) is a powerful and independent risk factor for MI. Lp(a) should probably be routinely measured in all patients referred to a lipid clinic.

Determination of serum cholesterol concentration in the presence of ascorbate.

Pretreatment of a serum or plasma sample with ascorbate oxidase removed interfering ascorbate and allowed the determination of cholesterol to be carried out by a current enzymatic cholesterol method available in kit form. The Cobas-Fara was programmed to carry out pretreatment of the sample with ascorbate oxidase before addition of the cholesterol colour reagent.

Insulin therapy in type 2 diabetic subjects suppresses plasminogen activator inhibitor (PAI-1) activity and proinsulin-like molecules independently of glycaemic control.

Eleven Type 2 diabetic subjects (10 male 1 female: age 56.2 +/- 9.7 (SD) yr) were treated in random order either with insulin or with sulphonylureas for 8 weeks each, without attempting to alter glycaemic control between the two treatment periods. Insulin treatment was associated with suppression of endogenous insulin secretion (fasting C-peptide levels -35.0 +/- 24.2%; p = 0.006), and of intact proinsulin (-43.1 +/- 36.8%; p = 0.03) and 32,33 split proinsulin -20.1 +/- 27.0%; p = 0.03). Activity of plasminogen activator inhibitor (PAI-1), a fast acting inhibitor of fibrinolysis, decreased significantly (-14.3% +/- 27.5%; p = 0.02) but no changes occurred in concentration of lipoproteins or apoproteins between therapies. Changes in concentrations of 32,33 split and intact proinsulin were closely and significantly related (rs = 0.83; p < 0.001) to each other but not with changes in concentrations of C-peptide (intact proinsulin rs = -0.41; p = 0.11) and 32,33 split proinsulin rs = -0.27; (p = 0.21). Percentage changes in intact proinsulin concentrations were positively correlated with those in PAI-1 (rs = 0.51; p = 0.05). There was, however a paradoxical negative relationship between changes in C-peptide concentrations and those of PAI-1 (rs = -0.73; p = 0.006). These preliminary observations suggest that insulin treatment in Type 2 diabetic subjects without any changes in glycaemic control is associated with a reduced activity of PAI-1, but is without effect on any other cardiovascular risk factors. Concentrations of insulin precursor molecules may play a role in determining fibrinolytic activity.

Comparison of the real-time use of glycosylated haemoglobin and plasma fructosamine in the diabetic clinic.

The within-clinic use of glycosylated haemoglobin (HbA1) and plasma fructosamine results in assessing blood glucose control and clinical management was compared in 1030 diabetic patients. The physician initially reviewed the patient with one randomly allocated measure (HbA1 or fructosamine) and completed a questionnaire concerning perception of blood glucose control, alteration to diet, alteration to medication, referral for diabetes education, and follow-up interval. The patient was then re-assessed using the second measure and the questionnaire repeated. Discordance rates for the study end-points, judged as binary outcomes, were: blood glucose control 15%; alteration to diet 7%; alteration to medication 9%; referral for education 3%; follow-up interval 4%. A significantly greater number of patients were rated as poorly controlled with HbA1 than with fructosamine (p less than 0.001) and were, in consequence, more frequently recommended alteration to diet and medication, referral for education and shorter follow-up interval; the rate of discordance for at least one of the management decisions was 16%. Multifactorial analysis showed that discordant management was dependent on the reviewing physician (p less than 0.001) and a history of cardiovascular disease (p less than 0.01); but neither type of diabetes, nor presence of nephropathy or variant haemoglobins, nor plasma glucose concentration, significantly influenced the likelihood of a discordance. Replacing HbA1 with fructosamine in the diabetic clinic may result in significant differences in the physician's perception of blood glucose control and in the management of patients.

The influence of zinc status and malnutrition on immunological function in Crohn's disease.

Cellular immunity is likely to be important in the pathogenesis of Crohn's disease; whether it is abnormal is not clear. The heterogeneity of patients with Crohn's disease probably underlies the disparity of reports, but attempts to determine which clinical features influence cellular immunity have been largely unsuccessful. This is probably caused by the omission of nutritional status as a potential factor, even though zinc deficiency has frequently been linked with abnormal immunity. Therefore, a detailed study of nutritional and tissue zinc status, nonspecific cellular immunity, and a measure of phagocytic function was performed in 32 patients with Crohn's disease and in a control group of 18 normal subjects and 12 patients with anorexia nervosa. Fourteen patients with Crohn's disease, all patients with anorexia nervosa, but none of the normal controls were malnourished. Peripheral blood lymphocyte population levels were normal in patients with Crohn's disease and in normal controls, but there was a small decrease in the levels of patients with anorexia nervosa. In vivo delayed hypersensitivity skin test responses were profoundly depressed in patients with anorexia nervosa and decreased in patients with Crohn's disease who were malnourished or receiving systemic glucocorticoids. In vitro lymphocyte transformation was reduced in malnourished patients with Crohn's disease, but there were only minor changes in patients with anorexia nervosa. There were alterations of in vitro immunoregulation in Crohn's disease, but they were not responsible for the abnormal lymphocyte transformation responses in malnourished patients. In vitro phagocytic function was reduced in patients with active Crohn's disease. These findings suggest that depressed in vivo and in vitro cellular immunity in malnourished patients with Crohn's disease is caused by a qualitative lymphocyte defect and that depressed in vivo but normal in vitro cellular immunity in anorexia nervosa is caused by a quantitative defect. Thus, malnutrition in Crohn's disease resembles kwashiorkor; in anorexia nervosa, it resembles marasmus. Tissue zinc status was mostly normal in Crohn's disease and anorexia nervosa, and zinc deficiency was not responsible for depressed nonspecific cellular immunity in either condition.

Zinc depletion and complications of surgery.

Zinc is essential for protein synthesis and reduced levels may impair recovery from surgery. To study this prospectively, clinical, anthropometric, haematological and biochemical indices of malnutrition were measured in 46 patients undergoing elective surgery and were related to the frequency and type of post-operative complications. In addition, leucocyte zinc levels, which are an estimate of tissue zinc levels, were measured. The diagnoses of the patients did not correlate with any of these parameters. Many patients were malnourished. 39% of the patients had a post-operative complication, of whom 8 had a wound complication. The frequency of complications as a whole was inversely related to serum albumin and transferrin levels, while wound complications were in addition associated with low leucocyte zinc levels. Malnutrition may therefore increase post-operative complications in general, but tissue zinc deficiency may contribute to wound problems.

Serum lipids and lipoproteins in insulin-dependent diabetic patients with persistent microalbuminuria.

Serum lipid and lipoprotein concentrations were measured in 18 insulin-dependent diabetic patients with persistent microalbuminuria and an equal number with persistently normal albumin excretion. The groups were matched for sex, age, duration of diabetes, body mass index, insulin dose, and glycosylated haemoglobin. Diabetic patients with persistent microalbuminuria were found to have a significantly lower high density lipoprotein (HDL) cholesterol concentration (difference 0.29, 95% Cl 0.12 to 0.46, mmol l-1, p less than 0.01) and a higher low density lipoprotein (LDL) cholesterol:HDL cholesterol ratio (difference 0.97, 95% Cl 0.29 to 1.65, p less than 0.01) than patients with normal albumin excretion. No significant differences were found in total cholesterol, triglycerides, LDL cholesterol, apolipoprotein (apo) A-I and apo B concentrations. Compared to an age and sex-matched group of non-diabetic subjects with normal albumin excretion, diabetic patients with persistent microalbuminuria had significantly higher concentrations of total cholesterol (p less than 0.05), LDL cholesterol (p less than 0.05) and apo B (p less than 0.01), but a lower concentration of HDL cholesterol (p less than 0.05). No significant differences were found in serum lipids and lipoproteins between diabetic patients with normal albumin excretion and non-diabetic subjects.

Zinc status in inflammatory bowel disease.

1. The zinc contents of plasma, erythrocytes, polymorphonuclear leucocytes and mononuclear leucocytes from 18 normal control subjects, 31 patients with Crohn's disease and 15 patients with ulcerative colitis were measured. 2. Plasma zinc levels were low in Crohn's disease, particularly in malnourished patients, and related to plasma albumin concentrations, but were normal in ulcerative colitis. 3. Erythrocyte zinc levels were normal in both Crohn's disease and ulcerative colitis. 4. Mean polymorphonuclear leucocyte zinc levels were normal in Crohn's disease and ulcerative colitis. Ten per cent of Crohn's disease patients had subnormal levels, which were associated with inactive disease, while 10% had elevated levels, which were associated with active disease. Seven per cent of ulcerative colitis patients had subnormal levels. Mononuclear leucocyte zinc levels were normal in Crohn's disease and in ulcerative colitis. 5. Tissue zinc depletion occurs in only a few patients with Crohn's disease and ulcerative colitis.

Is alcohol hepatotoxic in the baboon?

The baboon is the only animal in which alcoholic fibrosis and cirrhosis of the liver has been produced with a nutritionally adequate diet. Zinc deficiency is associated with alcoholic liver disease and may contribute to liver damage. We have therefore investigated whether zinc supplementation would reduce liver damage in ten baboons receiving ethanol and an adequate diet. Eight received ethanol at up to 25 g/kg/day (70% of calories) for up to 60 months (four were supplemented with 50 mg zinc/day). All animals gained weight, and blood concentrations of ethanol were 63-342 mg/dl. Changes in liver blood tests were slight. Liver histology only showed fatty change in six animals, severe in two, and minor inflammatory changes but no significant fibrosis or cirrhosis. In one of the animals with severe fatty change there were also degenerative changes in parenchymal cells. There was thus no significant hepatic fibrosis or cirrhosis in baboons given large amounts of ethanol and an adequate diet for up to 5 years.

Immunoturbidimetric assays for serum apolipoproteins A1 and B using Cobas Bio centrifugal analyser.

Immunoturbidimetric assays for measuring the apolipoproteins A1 and B using the Cobas Bio centrifugal analyser are described. The methods were specific, offered good sensitivity (less than 0.05 g/l) and intrabatch variability, with coefficients of variation between 2.4% and 3.5%, and were cost effective. Reference ranges were calculated for a group of civil servants, aged 35 to 55 years.

Hereditary angioneurotic oedema: a neglected diagnosis.

A case of hereditary angioneurotic oedema, which was only diagnosed after presentation to several hospital departments, is reported. It was then discovered that the mother of the patient had the same condition but that, unusually, it appeared to have been in remission for more than 20 years. This disease, due to C1 esterase inhibitor deficiency, is potentially fatal but easily treatable. The diagnosis is often missed.