Serum Lp(a) lipoprotein concentrations in insulin dependent diabetic patients with microalbuminuria

Elevated Plasma Lipoprotein(a) Levels and Hypoalbuminemia in Peritoneal Dialysis Patients

Plasma lipoprotein(a), Lp(a), is strongly and independently associated with atherosclerosis, and levels are elevated in hemodialysis (HD) patients and in some studies of those on peritoneal dialysis (PD). We hypothesized that protein losses and hypoalbuminemia could stimulate hepatic Lp(a) synthesis, and this effect would be accentuated in PD patients with malnutrition. The PD subjects (n=24) had higher plasma Lp(a) levels than those (n=10) on HD (median 34.4 vs 21.0 mg/dl, p<0.05), and values exceed normal in 62.5% vs 20% of the subjects (p<0.03), respectively. The serum albumin levels inversely correlated with concentrations of Lp(a) and apolipoprotein B, as well as the apolipoprotein B/AI ratio. In conclusion, plasma Lp(a) concentrations are frequently elevated in PD as well as HD patients. Measuring Lp(a) levels is useful in identifying patients at increased atherogenic risk, which may not be reflected in routine lipid profiles. The negative correlation between plasma Lp(a) and albumin levels suggests that the latter may be linked pathophysiologically to hepatic Lp(a) production. The association of hypoalbuminemia with higher Lp(a) values is of particular concern because malnutrition frequently occurs in PD patients.

Kidney disease and cardiovascular disease: implications of dyslipidemia

Cardiovascular complications are common inpatients with kidney disease. Regulating the lipid levels in these patients is important so that the risks of kidney and cardiovascular complications can be minimized. Lipid regulation decreases the incidence of coronary vascular events and other vascular complications in patients with kidney disease; however, whether lipid regulation slows progression of kidney disease is not yet known. Additional studies of the implications of dyslipidemia in patients with kidney disease are needed.

Insulin sensitivity and Lp(alpha) concentrations in normoglycemic offspring of type 2 diabetic parents

Background

Offspring of at least 1 parent with type 2 diabetes are more resistant to the insulin action, exhibit higher incidence of dyslipidemia and are more prone to cardiovascular diseases. The association between Lp(α) and coronary heart disease is well established. An association between Lp(α) concentration and insulin sensitivity was examined in this study.

We investigated the serum LP(α) in 41 offspring of 41 families of type 2 diabetic subjects (group I) with normal glucose tolerance, compared to 49 offspring who their parents had no history of type 2 diabetes, matched for sex, age, BMI, WHR and blood pressure (group II). Serum Lp(α), triglycerides, insulin resistant index, HDL, LDL-cholesterol and insulin were measured.

Results

The offspring of type 2 diabetic subjects had higher fasting serum triglycerides (mean ± SD 199.3 ± 184.2 vs. 147.1 ± 67.9 ng/dl, p < 0.05) lower HDL-cholesterol (37.3 ± 9.0 vs. 44.6 ± 7.8, p < 0.001) and particularly higher Insulin resistance Index (HOMA-IR) (2.84 ± 1.39 vs. 1.67 ± 0.77, p < 0.001).

They also had higher serum LP(α) concentration (15.4 ± 6.7 vs. 8.6 ± 6.0, p < 0.001). By simple linear analysis in the offspring of type 2 diabetic parents there was no correlation of Lp(α) concentration with insulin resistance index Homa-IR (r = 0,016 p = NS).

Conclusions

We conclude that serum LP(α) is significantly increased in offspring of type 2 diabetic subjects but was not related to insulin sensitivity.

Antiproteinuric effect of niceritrol, a nicotinic acid derivative, in chronic renal disease with hyperlipidemia: a randomized trial

PURPOSE

Lipoprotein (a) [Lp(a)] levels increase in patients with renal disease. We administered niceritrol, a nicotinic acid derivative, to patients with chronic renal disease and a high serum Lp(a) level, and studied its effects on lipid metabolism, proteinuria, and renal function.

METHODS

Thirty-three patients with chronic renal disease whose serum Lp(a) levels were > or = 15 mg/dL were randomly (but not blindly) assigned to treatment with niceritrol (n = 16) or to an untreated control group (n = 17). Parameters of lipid metabolism, excretion of urinary protein, and renal function were examined for 12 months.

RESULTS

Changes in urinary protein excretion, as well as Lp(a) levels, differed significantly between the two groups. The mean (+/- SD) change from baseline in excretion of urinary protein was 0.77 +/- 1.23 g/d in the control group compared with -1.41 +/- 2.26 g/d in the niceritrol group at 12 months (P =0.003). Mean Lp(a) levels increased by 3 +/- 10 mg/dL in the control group compared with a decrease of 10 +/- 13 mg/dL in the niceritrol group at 12 months (P =0.004). The mean creatinine clearance declined by 10 +/- 12 mL/min in the control group, compared with 1 +/- 13 mL/min in the niceritrol group at 12 months (P =0.06).

CONCLUSION

Lipid levels improved with niceritrol treatment, whereas the excretion of urinary protein decreased, perhaps slowing the rate of loss of renal function in chronic renal disease.

Microalbuminuria in essential hypertension: significance, pathophysiology, and therapeutic implications

Some patients with essential hypertension manifest greater than normal urinary albumin excretion (UAE). The significance of this association, which is the object of this review, is not well established. Hypertensive patients with microalbuminuria manifest greater levels of blood pressure, particularly at night, and higher serum levels of cholesterol, triglycerides, and uric acid than patients with normal UAE. Levels of high-density lipoprotein cholesterol, on the other hand, were lower in patients with microalbuminuria than in those with normal UAE. Patients with microalbuminuria manifested greater incidence of insulin resistance and thicker carotid arteries than patients with normal UAE. After a follow-up of 7 years, we observed that 12 cardiovascular events occurred among 54 (21.3%) patients with microalbuminuria and only two such events among 87 patients with normal UAE (P < 0.0002). Stepwise logistic regression analysis showed that UAE, cholesterol level, and diastolic blood pressure were independent predictors of the cardiovascular outcome. Rate of creatinine clearance from patients with microalbuminuria decreased more than that from those with normal UAE. In conclusion, these studies suggest that hypertensive individuals with microalbuminuria manifest a variety of biochemical and hormonal derangements with pathogenic potential, which results in hypertensive patients having a greater incidence of cardiovascular events and a greater decline in renal function than patients with normal UAE.

The relationship of prorenin values to microvascular complications in patients with insulin-dependent diabetes mellitus

We have performed a cross-sectional analysis of the relationship between prorenin values and the microvascular complications of diabetes in a well controlled population of insulin-dependent diabetes mellitus (IDDM) subjects. One hundred and thirty-nine subjects (75 men, 64 women, age 44 +/- 17 years; duration of diabetes 19 +/- 15 years), formed the study group. Sixty-seven subjects (48.2%) had no complications, 55 (39.6%) had retinopathy alone, and 17 (12.2%) had retinopathy and albuminuria. Patients with no complications had lower prorenin values than those with microvascular complications (p < 0.001), whilst patients with both albuminuria and retinopathy had higher values than those with retinopathy alone (p < 0.05). Retinopathy was associated with duration of diabetes (p < 0.0001), diastolic blood pressure (p < 0.02) and albuminuria (p < 0.0001) while albuminuria was associated with prorenin (p < 0.02), serum triglyceride (p < 0.01) and retinopathy (p < 0.001). Patients with albuminuria were 5.5 times more likely to have raised prorenin values (>80 ng/mL/h) than those with normal albumin excretion [95% confidence interval (CI): 1.48-20.12] and those with retinopathy alone were 2.5 times as likely (95% CI: 1.19-5.15). Eighty patients with IDDM (40 males, 40 females; age: 47 +/- 17 years; duration of diabetes: 20 +/- 15 years), had retinal photography performed to determine the association between the severity of retinopathy and prorenin values. Retinopathy was more severe in patients with retinopathy and albuminuria than in those with retinopathy alone (p < 0.002). When the prorenin values of patients with more marked retinopathy (eye grade greater than 3) were compared, prorenin values of those with retinopathy and albuminuria were greater than those of patients with retinopathy alone [269 (139-1406) versus 91 (41-273) ng/mL/h: geometric mean (range); p < 0.05]. Furthermore, when patients without albuminuria were considered, there was no significant difference between the prorenin levels of patients with more severe retinopathy (eye grade >3) when compared to patients with lesser degrees of retinopathy [91 (41-273) versus 69 (23-375). In patients with microvascular complications, prorenin values were independently predicted by albuminuria (p < 0.0001) and diastolic blood pressure (p < 0.02) but not the severity of retinopathy. In conclusion, prorenin values are significantly associated with the presence of microvascular complications in patients with IDDM. The association with albuminuria may be stronger than the association with retinopathy.

Lp(a) lipoprotein is a major risk factor for cardiovascular disease: pathogenic mechanisms and clinical significance

The results of two previous and two recent studies of middle-aged males and females are presented to exemplify the clinical importance of lipoprotein(a) (Lp(a)) as a risk factor for atherosclerosis and coronary heart disease. In these studies various conventional and recently suggested risk factors were included and different methods for Lp(a) quantification were used. Lp(a) was a significant risk factor in all four studies. In the recent prospective case-control study, Lp(a) and cholesterol were found to act synergistically and predict primary acute myocardial infarction in Swedish males. A cholesterol level above 6.5 mmol/l increased the risk of acute myocardial infarction if the Lp(a) level was above 200 mg/l. The plasma apo A-I level was a protective factor. In the other recent case-control study, an Lp(a) level above 500 mg/l was a highly significant risk factor in Black and White US women with myocardial infarction or advanced coronary artery disease in addition to low density lipoprotein cholesterol levels above 130 mg/dl. A high apo A-I level was a protective factor. In these studies no other factors tested reached significance in multivariate logistic regression analysis. A hypothetical association between high Lp(a) levels and intracellular infection with Chlamydia pneumoniae is discussed. The results suggest that the Lp(a) level is useful in identifying high-risk individuals. Lowering low density lipoprotein cholesterol below 100 mg/dl (<2.6 mmol/l) seems to be most important in both males and females with high-risk Lp(a) levels.

Effects of visceral fat and weight loss on lipoprotein(a) concentration in subjects with obesity

We studied the relationships between regional body fat distribution and metabolic variables with lipoprotein(a) [Lp(a)] as well as the effects of weight loss on Lp(a) in 25 women and 9 men with obesity. Regional body fat distribution, as evaluated by the use of computed tomography; Lp(a); and fasting glucose, insulin, cholesterol, and triglycerides were analyzed before and after a very low-energy diet. No significant correlations were found between visceral, subcutaneous, and total fat and Lp(a) or between metabolic variables and Lp(a). All anthropometric variables significantly decreased after a very low-energy diet. Fasting glucose, insulin, triglycerides, and cholesterol significantly decreased after a very low-energy diet. No significant changes in Lp(a) concentration after a very low-energy diet were found. The correlation between the initial values of Lp(a) and changes of Lp(a) after a very low-energy diet was slightly significant (rho = 0.33, p < 0.06). In conclusion, our study shows that Lp(a) is not influenced by obesity, visceral fat, metabolic variables, or weight loss induced by a very low-energy diet.

Apolipoprotein B independently predicts progression of very-low-level albuminuria in insulin-dependent diabetes mellitus

The purpose of the study was to examine the contribution of alterations in lipoprotein metabolism to the progression of very-low-level albuminuria in insulin-dependent diabetes mellitus (IDDM). We measured serum concentrations of lipids, lipoproteins, and apolipoproteins in 53 normoalbuminuric diabetic patients without overt hypertension, whom we restudied after 10 years. Albuminuria was measured as the urinary albumin to creatinine ratio (UA/UC) in repeated early-morning samples. Over 10 years, UA/UC increased significantly (P < .001), and five patients (9.4%) progressed to microalbuminuria. The increase in albuminuria was significantly and positively related to the baseline serum concentrations of total cholesterol (P < .05), low-density lipoprotein (LDL) cholesterol (P = .05), non-high-density lipoprotein (HDL) cholesterol (P < .05), and apolipoprotein (apo) B (P < .001), but no significant associations were found with triglycerides, HDL cholesterol, apo A-1, or lipoprotein(a) [Lp(a)]. The relative risk of developing microalbuminuria for a serum apo B concentration more than 1.1 g/L was 3.8 (95% confidence interval [CI], 1.9 to 7.7). In multiple linear regression analysis, serum apo B (P < .05) and glycated hemoglobin ([HbA] P < .05) at baseline were significant independent predictors of the increase in albuminuria, with no significant associations found for sex, smoking, duration of diabetes, mean arterial blood pressure (BP), or family history of cardiovascular disease and hypertension; the regression model predicted 42% of the variation in UA/UC at 10 years. The findings suggest that an abnormality in the metabolism of apo B may be independently associated with progression of very-low-level albuminuria and possibly with the development of early nephropathy in IDDM patients.

Lipoprotein(a) concentrations and non-insulin-dependent diabetes mellitus: relationship to glycaemic control and diabetic complications

The aim of our study was to determine the lipoprotein(a) (Lp(a)) levels in patients with non-insulin-dependent diabetes mellitus (NIDDM) and to evaluate Lp(a) concentrations in relation to glycaemic control and diabetic complications. We evaluate in a cross-sectional study a total of 103 NIDDM patients (52 males and 51 females; mean age of 62.5 years; mean of diabetes duration: 12 years) referred to our hospital because of poor glycaemic control, and a group of 108 non-diabetic subjects (57 males and 51 females).

RESULTS

mean Lp(a) concentration did not significantly differ between NIDDM patients and non-diabetic subjects (11.1 +/- 14 vs. 16.2 +/- 14 mg/dl). The distribution of Lp(a) levels was highly skewed towards the lower levels in both groups, being over 30 mg/dl in only 6% of NIDDM patients and 12% of controls. Patients with Lp(a) levels over 10 mg/dl had lower haemoglobin Alc (HbA1c) than patients with Lp(a) levels over 10 mg/dl (8.5% vs. 10.4%; P < 0.01). Lp(a) concentration was positively correlated with body mass index (BMI) (P < 0.05) and HbA1c (P < 0.05). No association was found between Lp(a) and sex, age, other lipidic parameters, microalbuminuria, type of treatment and presence of cardiovascular disease. These findings may suggest that glycaemic control could have a modulatory role on Lp(a) concentration in NIDDM patients. In this study, diabetic complications did not seem to be associated with higher Lp(a) concentrations.

Lipoprotein (a) concentrations and apolipoprotein (a) phenotypes in normoglycaemic relatives of type 2 diabetic patients

Serum lipoprotein (a) concentrations (Lp(a)) are largely under genetic control, and are strong predictors of coronary heart disease. It has been hypothesised that Lp(a) may contribute to the increased risk of coronary heart disease in familial Type 2 diabetes mellitus. We therefore examined the Lp(a) concentrations and the apolipoprotein (a) (apo(a)) phenotypes in 126 normoglycaemic first degree relatives from families with two or more living Type 2 diabetic patients. These were compared with 147 sex matched normoglycaemic control subjects with no family history of diabetes. Lp(a) concentrations were measured using an enzyme-linked immunosorbent assay (ELISA), and apo(a) isoforms were determined and classified according to the relative mobility of apo(a) on sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), relative to that of apolipoprotein B-100. There were no significant differences in Lp(a) concentrations between the relatives (R) and controls (C): 11.2 (R) vs. 11.1 (C) mg/dl (median). The distribution of apo(a) phenotypes was not significantly different between groups 0.65 (R) vs. 0.67 (C). These results show that first degree relatives at risk of developing Type 2 diabetes do not have abnormal Lp(a) concentrations or apo(a) phenotypes.

Serum lipoprotein-a levels and glyco-metabolic control in insulin and non-insulin dependent diabetes mellitus

OBJECTIVES

Conflicting results for lipoprotein-a (Lp(a)) levels in diabetic patients exist in the literature. Normal, increased, and decreased values are described, and a relation to glycometabolic control is not unequivocally established.

DESIGN AND METHODS

In our study Lp(a) was measured in a large group of diabetiee (80 patients with IDDM and 90 patients with NIDDM) in relation to glycometabolic control and the presence of microalbuminuria, retino and/or neuropathy. Long-term and short-term glycometabolic control were assessed by HbA1 and fructosamine assays, respectively.

RESULTS

Statistically significant differences between Lp(a) levels in IDDM and NIDDM-and a control group of 110 healthy nondiabetics could not be established. It appeared that the level of Lp(a) in IDDM and NIDDM is independent of short-term and long-term glycometabolic control or the occurrence of microalbuminuria, neuro or retinopathy. However, poor glycometabolic control affected the number of Lp(a) levels elevated above a threshold of 0.25 g/L in IDDM.

CONCLUSION

These results suggest that the level of Lp(a) in serum is not influenced by diabetes mellitus, glycemic control, or the occurrence of microalbuminuria, neuro or retinopathy.

Factors influencing plasma lipid profiles including lipoprotein (a) concentrations in renal transplant recipients

Fasting plasma cholesterol, triglycerides, high-density lipoprotein (HDL) and apoprotein (apo) B were elevated in 214 nondiabetic renal transplant recipients when compared to a reference group. Apo (a) was slightly but not significantly lower in transplant recipients (median 118 mg/dl, range 16-1680 vs 130 mg/dl, 10-1176) and this difference could be predicted from Lp (a) isoform analysis. Cholesterol, triglyceride, apo B and apo (a) concentrations correlated negatively with creatinine clearance but none of these parameters showed a significant association with proteinuria. Patients treated with steroids had higher plasma HDL concentrations than those receiving cyclosporin monotherapy (P < 0.01). The use of diuretics was associated with raised triglycerides (P < 0.001) and cholesterol (P < 0.01) and with reduced HDL (P < 0.01) whilst patients receiving beta-blockers had significantly higher triglycerides (P < 0.01) and lower HDL levels (P < 0.02). In multiple regression analysis, age (P < 0.01), creatinine clearance (P < 0.05) and diuretic therapy (P < 0.005) were independent risk factors for increased cholesterol whilst apo (a) levels correlated negatively with creatinine clearance (P < 0.005). These results suggest that impaired renal function, steroids and non-immunosuppressive drugs contribute to lipid abnormalites in renal transplant recipients.

Lipoprotein(a) is not elevated in non-diabetic microalbuminuric subjects. A longitudinal study of lipoprotein(a) concentrations and apolipoprotein(a) size isoforms

Microalbuminuric non-diabetic subjects have an increased risk of cardiovascular disease which is not explained by standard risk factors. In diabetic patients, microalbuminuria is associated with increased lipoprotein(a) concentrations. We have determined lipoprotein(a) concentrations and duplicate measures of albumin excretion rate, on two occasions separated by around 3 years, in 125 Europid subjects aged 40-75 years without hypertension or glucose intolerance and in 49 offspring aged 15-40 years. The apolipoprotein(a) isoform size, the major genetic determinant of lipoprotein(a) concentration, was also determined. There were no differences in lipoprotein(a) concentration between the 42 subjects who were microalbuminuric on either or both samples at screening (median 9.4 mg/dl, 20th and 80th percentiles 2.6 and 46.3 mg/dl) and the 79 who had been normoalbuminuric at both collections (median 10.9 mg/dl, 20th and 80th percentiles 2.9 and 53.0 mg/dl; P = 0.58). Lipoprotein(a) concentrations were not significantly different between subjects with or without microalbuminuria at recell (P = 0.55) or between those with or without microalbuminuria classified by mean albumin excretion rate in either collection (P = 0.24 and P = 0.73, respectively). There were no significant relationships between albumin excretion rate as a continuous variable and lipoprotein(a) concentration, or between changes in the two variables over 3 years. The microalbuminuric and normoalbuminuric subjects had similar distributions of size isoforms. There were also no differences in lipoprotein(a) concentration or isoform distribution between offspring of microalbuminuric and of normoalbuminuric subjects. In conclusion, we found no evidence that microalbuminuric subjects with normal blood pressure and normal glucose tolerance have elevated concentrations of lipoprotein(a) to explain their increased cardiovascular risk.

Lipoprotein(a) in health and disease

Lipoprotein(a) [Lp(a)] represents an LDL-like particle to which the Lp(a)-specific apolipoprotein(a) is linked via a disulfide bridge. It has gained considerable interest as a genetically determined risk factor for atherosclerotic vascular disease. Several studies have described a correlation between elevated Lp(a) plasma levels and coronary heart disease, stroke, and peripheral atherosclerosis. In healthy individuals, Lp(a) plasma concentrations are almost exclusively controlled by the apo(a) gene locus on chromosome 6q2.6-q2.7. More than 30 alleles at this highly polymorphic gene locus determine a size polymorphism of apo(a). There exists an inverse correlation between the size (molecular weight) of apo(a) isoforms and Lp(a) plasma concentrations. The standardization of Lp(a) quantification is still an unresolved task due to the large particle size of Lp(a), the presence of two different apoproteins [apoB and apo(a)], and the large size polymorphism of apo(a) and its homology with plasminogen. A working group sponsored by the IFCC is currently establishing a stable reference standard for Lp(a) as well as a reference method for quantitative analysis. Aside from genetic reasons, abnormal Lp(a) plasma concentrations are observed as secondary to various diseases. Lp(a) plasma levels are elevated over controls in patients with nephrotic syndrome and patients with end-stage renal disease. Following renal transplantation, Lp(a) concentrations decrease to values observed in controls matched for apo(a) type. Controversial data on Lp(a) in diabetes mellitus result mainly from insufficient sample sizes of numerous studies. Large studies and those including apo(a) phenotype analysis came to the conclusion that Lp(a) levels are not or only moderately elevated in insulin-dependent patients. In noninsulin-dependent diabetics, Lp(a) is not elevated. Conflicting data also exist from studies in patients with familial hypercholesterolemia. Several case-control studies reported elevated Lp(a) levels in those patients, suggesting a role of the LDL-receptor pathway for degradation of Lp(a). However, recent turnover studies rejected that concept. Moreover, family studies also revealed data arguing against an influence of the LDL receptor for Lp(a) concentrations. Several rare diseases or disorders, such as LCAT- and LPL-deficiency as well as liver diseases, are associated with low plasma levels or lack of Lp(a).

Prevalence of microalbuminuria, lipoprotein (a) and coronary artery disease in the lipid clinic

AIMS

To assess the prevalence of microalbuminuria (MA) and elevated serum lipoprotein (a) (Lp (a)) concentration, and their association with coronary artery disease (CAD) and other conventional cardiovascular risk factors in non-diabetic patients attending a lipid clinic.

METHODS

Clinical details were obtained from 96 consecutive non-diabetic patients from whom a fasting blood sample was taken to measure serum lipid, lipoprotein, apolipoprotein and plasma glucose, urea, and electrolyte concentrations. The urine albumin/creatinine ratio (Ua/Uc) was estimated from a random clinic sample.

RESULTS

Of the patients, 26% had MA (defined as a Ua/Uc > 2.2 mg/mumol), 38% had an elevated Lp (a) concentration (defined as > 0.4 g/l), 36% were hypertensive (blood pressure > 160/95) or were taking antihypertensive medication, and 25% had established CAD defined on clinical criteria. In men the Ua/Uc ratio was highly associated with age, plasma low density lipoprotein cholesterol, and triglyceride concentrations. In women there was no association between the Ua/Uc ratio and variables examined. Lp (a) concentration was not associated with variables examined in either sex. In multiple logistic regression analysis adjusted for age and sex, serum Lp (a) concentration, diastolic blood pressure and treatment of hyperlipidaemia were highly associated with CAD. MA was not, however, associated with CAD.

CONCLUSIONS

MA is common in a lipid clinic and is more likely to be found among older male patients with hyperlipidaemia. However, in contrast with Lp (a) concentrations, MA is not a risk factor for CAD in this high risk population. Lp (a) concentration may be a useful tool in the lipid clinic, but there does not seem to be a justification for measuring the Ua/Uc ratio, at least in non-diabetic subjects.

Little association of lipid parameters and large sensory nerve fiber function in diabetes mellitus

The natural history of diabetic neuropathy and its risk factors are not well understood. The potential association of various lipids [e.g., high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, triglycerides], and lipoprotein(a) [Lp(a)] concentrations, with large sensory nerve fiber function as assessed by vibratory thresholds was examined in a group of 91 individuals with diabetes mellitus. In multivariate analyses, no independent relationships of any of the lipid or lipoprotein parameters measured in this study were found with vibratory thresholds (i.e., dependent variable). Independent associations of age, duration of diabetes, height, and medications that lower blood pressure with vibratory thresholds were shown and explained 51% of the overall variability of the model. In gender-specific models, age, height, and medications that lower blood pressure were statistically significant independent determinates (i.e., males R2 = 0.61, females R2 = 0.39). These cross-sectional data suggest that lipid and lipoprotein parameters measured in this study have little association with large sensory nerve fiber dysfunction. The interesting association with the use of medications that lower blood pressure and vibratory thresholds warrants further investigation.

Glomerular and tubular function in glycogen storage disease

Urinary protein and calcium excretion were assessed in 77 patients with the hepatic glycogen storage diseases (GSD): 30 with GSD-I (median age 12.4 years, range 3.2-32.9 years), 25 with GSD-III (median age 10.5 years, range 4.2-31.3 years) and 22 with GSD-IX (median age 11.8 years, range 1.2-35.4 years). Inulin (Cinulin) and para-aminohippuric acid (CPAH) clearances were also measured in 33 of these patients. Those with GSD-I had significantly greater albumin (F = 15.07, P < 0.001), retinol-binding protein (RBP) (F = 14.66, P < 0.001), N-acetyl-beta-D-glucosaminidase (NAG) (F = 9.41, P < 0.001) and calcium (F = 7.41, P = 0.001) excretion than those with GSD-III and GSD-IX. GSD-I patients (n = 18) also had significantly higher Cinulin (F = 5.57, P = 0.009), but CPAH did not differ (F = 0.77, NS). Renal function was normal in GSD-III and GSD-IX patients. In GSD-I, Cinulin (r = -0.51, P = 0.03) and NAG excretion (r = -0.40, P = 0.03) were inversely correlated with age, whereas albumin excretion was positively correlated with age (r = +0.41, P = 0.03). RBP and calcium excretion were generally high throughout all age groups. Hyperfiltration in GSD-I is associated with renal tubular proteinuria that occurs before the onset of significant albuminuria. Deficiency of glucose-6-phosphatase within the proximal renal tubule may primarily cause tubular dysfunction, glomerular hyperfiltration being a secondary phenomenon.

Lipoprotein(a) concentrations in non-insulin-dependent diabetes mellitus and borderline hyperglycemia: a population-based study

The objective of the study was to compare lipoprotein(a) [Lp(a)] concentrations in population-based samples of individuals with non-insulin-dependent diabetes mellitus (NIDDM), borderline hyperglycemia, and normoglycemia. From 2,740 male Italian Telephone Company employees aged 40 to 59 years participating in a health screening, we selected all those with NIDDM (n = 100) plus a random sample of 950 nondiabetic individuals. Diabetes was defined as fasting plasma glucose (FPG) of at least 140 mg/dL or current use of hypoglycemic drugs. Among nondiabetic individuals, 854 were defined as normoglycemic (FPG < 115 mg/dL) and 95 were defined as borderline hyperglycemic (115 < FPG < 140 mg/dL). Lp(a) level was measured on frozen plasma by enzyme-linked immunosorbent assay. Lp(a) concentrations were similar in people with NIDDM, borderline hyperglycemia, and normoglycemia: 11.2 +/- 14, 14.1 +/- 20, and 13.9 +/- 18 mg/dL, respectively (F = 1.03). Accordingly, the proportion of subjects with Lp(a) levels of at least 30 mg/dL was comparable in the three groups (12%, 15%, and 14%; chi 2 = 3.95, P = .41). Results were not confounded by differences in age, body mass index (BMI), waist to hip ratio, plasma lipids, alcohol consumption, physical activity, and use of drugs. Furthermore, within the diabetic group Lp(a) levels were not significantly different for those on diet only versus those on oral agents (10.8 +/- 14.1 v 11.7 +/- 14.7, P = .7) or for people with FPG of at least 180 as compared with people with FPG less than 180 mg/dL (9.9 +/- 12.8 v 11.5 +/- 14.8, P = .5).(ABSTRACT TRUNCATED AT 250 WORDS)

Lipoprotein (a)

Lipoprotein (a) is similar to low-density lipoprotein but is unique in having an additional apolipoprotein called apolipoprotein (a) (apo(a)) covalently linked to it. apo(a), which is a member of the plasminogen gene superfamily, has a protease domain which cannot be activated to cause fibrinolysis. Its sequence of kringles is much longer than that of plasminogen and there is remarkable genetic variation in its length. The consequent inherited differences in apo(a) molecular mass are largely responsible for the wide range of serum Lp(a) concentrations in different individuals with low levels predominating in Europid populations. Physiologically Lp(a) may participate in haemocoagulation or in wound-healing. Epidemiological evidence that it is a risk factor for atherosclerosis, particularly in populations with high serum LDL levels, has led to research to uncover its role in atherogenesis and thrombosis. Diseases such as renal disease, and probably atherogenesis and thrombosis. Diseases such as renal disease, and probably atherosclerosis itself, are associated with an increase in Lp(a) above its genetically determined level and it remains a subject of speculation as to whether such increases are as closely involved in atherothrombosis as are spontaneously high levels resulting from low-molecular-mass apo(a) variants.

Levels of lipoprotein(a), apolipoprotein B, and lipoprotein cholesterol distribution in IDDM. Results from follow-up in the Diabetes Control and Complications Trial

Levels of lipoprotein(a) [Lp(a)], apolipoprotein (apo) B, and lipoprotein cholesterol distribution using density-gradient ultracentrifugation were measured as part of a cross-sectional study at the final follow-up examination (mean 6.2 years) in the Diabetes Control and Complications Trial. Compared with the subjects in the conventionally treated group (n = 680), those subjects receiving intensive diabetes therapy (n = 667) had a lower level of Lp(a) (Caucasian subjects only, median 10.7 vs 12.5 mg/dl, respectively; P = 0.03), lower apo B (mean 83 vs. 86 mg/dl, respectively; P = 0.01), and a more favorable distribution of cholesterol in the lipoprotein fractions as measured by density-gradient ultracentrifugation with less cholesterol in the very-low-density lipoprotein and the dense low-density lipoprotein fractions and greater cholesterol content of the more buoyant low-density lipoprotein. Compared with a nondiabetic Caucasian control group (n = 2,158), Lp(a) levels were not different in the intensive treatment group (median 9.6 vs. 10.7 mg/dl, respectively; NS) and higher in the conventional treatment group (9.6 vs. 12.5 mg/dl, respectively; P < 0.01). No effect of renal dysfunction as measured by increasing albuminuria or reduced creatinine clearance on Lp(a) levels could be demonstrated in the diabetic subjects. Prospective follow-up of these subjects will determine whether these favorable lipoprotein differences in the intensive treatment group persist and whether they influence the onset of atherosclerosis in insulin-dependent diabetes.

Coronary heart disease in diabetes mellitus: three new risk factors and a unifying hypothesis

The standard risk factors--dyslipidaemia, hypertension and smoking--provide little help in explaining the raised cardiovascular risk in diabetes. It can be calculated that intervening for disturbances of these risk factors could do little to rectify the loss of life expectancy of around 10 years for a middle-aged diabetic man. Three new risk factors are discussed, which together may contribute to some of the excess cardiovascular risk in diabetes. Plasminogen activator inhibitor is an inhibitor of fibrinolysis which is elevated in concentration in diabetic subjects, and may increase both the incidence of thrombotic events and the risk of reinfarction after the initial infarct. Recent work also suggests that high activity of this substance may impair pharmacological fibrinolysis. Proinsulin-like molecules are elevated in concentration in diabetic patients and correlate with levels of a number of other risk factors. Whilst these correlations may represent cause and effect for plasminogen activator inhibitor, there is no evidence that changes in levels of proinsulin-like molecules influence levels of other risk factors. Microalbuminuria provides a powerful indicator of cardiovascular risk in both diabetic and non-diabetic subjects, but whilst the mechanisms for this association are unclear, they are again unlikely to be mediated through changes in levels of standard risk factors. Recent observations of an association between short stature and microalbuminuria suggest that intrauterine or early infant nutrition may represent a common antecedent, these having also been shown to predict both components of the insulin resistance syndrome and cardiovascular disease in adult life.

Lipoprotein (a) and vascular disease in diabetic patients

In order to assess the potential role of lipoprotein (a) as a risk factor for cardiovascular disease in diabetes mellitus, plasma concentrations were measured in a large group (n = 500) of non-insulin-dependent (NIDDM, n = 355) and insulin-dependent (IDDM, n = 145) patients. Concentrations of lipoprotein (a) were compared in diabetic patients with (n = 153) or without (347) documented vascular disease (ischaemic heart disease, peripheral vascular disease or macroangiopathy). They were significantly higher (p < 0.05) in patients with ischaemic heart disease (mean [interquartile range] 15.5 (5.0-38.0) vs 9.0 (4.5-26.0) mg/dl) or macroangiopathy (13.0 (5.0-38.0) vs 9.0 (4.0-25.0) mg/dl) compared to patients without manifestations of vascular disease. In addition, stepwise logistic regression analysis identified lipoprotein (a) levels > or = 30 mg/dl as being independently associated with the presence of cardiovascular disease. Lipoprotein (a) was an independent risk factor for ischaemic heart disease and macroangiopathy in this group of IDDM and NIDDM patients.

Longitudinal study of lipoprotein(a) in peripubertal children with insulin-dependent diabetes

We aimed to examine the longitudinal relationship between lipoprotein(a) and haemoglobin A1c, albumin excretion rate, and puberty in peripubertal children with insulin-dependent diabetes. A total of 114 patients aged 11.5 +/- 3.6 years (mean (SD)) were followed prospectively for 15.2 +/- 2.8 months. Lipoprotein(a), apolipoproteinB-100, haemoglobin A1c, mean overnight albumin excretion rate and Tanner stage were determined at the beginning and end of the study period. Lipoprotein(a) and apolipoproteinB-100 were measured using nephelometry. This method was correlated with radioimmunoassay and there was no significant change in mean bias during the study. Lipoprotein(a) fell significantly over time (214, (152, 276); 160 (84, 236) mg l-1 geometric mean (0.95 confidence intervals), p < 0.001); apolipoproteinB-100 did not change. Lipoprotein(a) and apolipoproteinB-100 did not differ in 233 cross-sectional controls of similar age. The change in lipoprotein(a) did not correlate with a small fall in haemoglobin A1c or with overnight albumin excretion rate, Tanner stage or insulin dose. Separate analysis of male and female patients and prepubertal and pubertal patients continued to show a significant fall in lipoprotein(a) independent of change in haemoglobin A1c or albumin excretion rate. Likewise, 53 patients with a change in haemoglobin A1c of greater than 1%, and 20 patients who progressed from normal albumin excretion rate to albumin excretion rate above the 95th centile, showed no relationship between lipoprotein(a) and haemoglobin A1c or albumin excretion rate. In conclusion, longitudinal changes in lipoprotein(a) do not relate to metabolic control or early changes in albuminuria in young patients with insulin-dependent diabetes.

The role of lipoprotein(a) in the vascular complications of diabetes mellitus

Lipoprotein(a) has been identified as an independent risk factor for atherosclerotic vascular disease in non-diabetic populations. Because of its potential role in the pathogenesis of both microvascular and macrovascular complications in diabetes, there have recently been many reports on lipoprotein(a) in diabetic populations. Some studies indicate an association between elevated lipoprotein(a) and macrovascular disease in non-insulin-dependent diabetes mellitus (NIDDM), but this link has not been found with insulin-dependent diabetes mellitus (IDDM). In IDDM, elevated lipoprotein(a) has been found in groups with diabetic nephropathy and retinopathy, raising the possibility that it plays a causative role. The relationship between glycaemic control and the lipoprotein(a) level has not been fully resolved. Most studies have not found any connection in NIDDM, but some found higher lipoprotein(a) levels in hyperglycaemic IDDM patients. Potentially, lipoprotein(a) is an important factor linking the microvascular and macrovascular complications of diabetes.

The hepatic glycogen storage diseases--problems beyond childhood

The introduction of continuous nocturnal enteral glucose feeds and uncooked cornstarch has improved the prognosis for patients with the hepatic glycogen storage diseases. An increasing number of patients are surviving into adulthood in better health, but still at some medical cost. In this review we examine bone mineralization, renal function, hepatic tumours, and vascular endothelial function in GSD I and cardiac function in GSD III. All females over the age of 5 years with GSD I, III, VI and IX had morphologically polycystic ovaries. Thirteen adult GSD I patients have been studied, and been found to have poor bone mineralization and marked renal glomerular and tubular dysfunction. More than half of these patients also had focal hepatic lesions on sonography and yet vascular endothelial function was preserved in the face of hyperlipidaemia. In 12 GSD III patients, one had a focal hepatic lesion and 6 had pronounced left ventricular hypertrophy, although cardiorespiratory function was normal. These data emphasize the multisystem nature of these disorders and highlight the need for careful longterm follow-up.

Selected aspects of ACE inhibitor therapy for patients with renal disease: impact on proteinuria, lipids and potassium

Overt proteinuria is often accompanied by hypercholesterolemia and is associated with increased lipoprotein(a) levels. These lipid abnormalities are probably involved in the high incidence of macrovascular complications associated with diabetic nephropathy and possibly other kinds of non-diabetic proteinuric renal disease. Over the last decade many studies have shown that ACE inhibitors can reduce urinary protein excretion but little attention was paid to the impact of this form of therapeutic intervention on the lipid profile. In this article we review our recent data showing that fosinopril administration was associated with significant decreases in both urinary protein excretion, serum total cholesterol levels, and plasma lp(a) levels. The use of ACE inhibitors in patients with renal impairment can result in the development of hyperkalemia as a result of suppression of angiotensin II-driven aldosterone secretion by the adrenal gland. Inhibition of aldosterone secretion may depend on the degree of inhibition of angiotensin II formation in the circulation and also locally in the adrenal gland. Because the various ACE inhibitors exhibit different degrees of ACE inhibition at the tissue level, we have postulated that angiotensin II-dependent aldosterone production will be inhibited to a lesser degree by agents that have low tissue affinity for the adrenal gland. The implication of this theoretical concept for the development of hyperkalemia in patients with impaired renal function treated with ACE inhibitors is discussed.

Lipoprotein(a) in type 1 diabetic patients with renal disease

Lp(a) was measured in 64 normoalbuminuric, 52 microalbuminuric, and 37 proteinuric Type 1 diabetic patients and 54 healthy subjects. Microalbuminuric and proteinuric Type 1 diabetic patients had higher median Lp(a) values (133 (16-1932) and 169 (17-1149) mg l-1) than patients with normal AER (73 (15-1078) mg l-1; p = 0.048 and p = 0.027). Lp(a) in healthy subjects (110 (15-1630)mg l-1) did not differ from the diabetic subgroups. The frequency of Lp(a) values in the upper quarter of the normal distribution was similar in the diabetic groups and did not differ between diabetic and control subjects. The cumulative distribution of Lp(a) was similar in all groups. Lp(a) concentrations were not related to AER, age, gender, duration of diabetes, body mass index, glycaemic control, serum creatinine, free insulin or systolic blood pressure. Cholesterol, LDL-cholesterol, triglycerides, and apo B were higher in microalbuminuric and proteinuric than in normoalbuminuric Type 1 diabetic patients. Lp(a) was independently related to diastolic blood pressure, fibrinogen, and macroangiopathy. In conclusion, median Lp(a) concentrations tend to be higher in Type 1 diabetic patients with early and established renal disease, although the differences are small and the overlap between groups large. Lp(a) is related to diastolic blood pressure and fibrinogen, and this association of powerful risk factors suggests that Lp(a) may play a role in the pathogenesis of cardiovascular disease in Type 1 diabetic patients with proteinuria. Whether Lp(a) is an independent determinant of increased cardiovascular risk in these patients needs to be elucidated by prospective studies.

Hyperlipidaemia does not impair vascular endothelial function in glycogen storage disease type 1a

Patients with glycogen storage disease type 1 (GSD-1) often have marked hyperlipidaemia with abnormal lipoprotein profiles. This metabolic abnormality improves, but is not fully corrected, with dietary therapy and therefore these patients may be at high risk for the development of atherosclerosis. Endothelial dysfunction is an early event in atherogenesis and can be detected in children and young adults at high risk. We studied endothelial function, using a non-invasive ultrasonographic method, in the brachial arteries of 6 adult GSD-1a patients (aged 23-33 years) with mean cholesterol of 7.9 mmol/l (range 4.7 to 14.6) and mean triglycerides of 9.1 mmol/l (range 4.1 to 21.3), and 12 age- and sex-matched normolipidaemic controls. Flow-mediated (endothelium-dependent) dilation was similar in patients and controls (8.2% vs. 10.5%; P = 0.20). Although the patient numbers are small, these results are consistent with the surprising lack of clinically evident atherosclerosis in GSD-1. The reasons these patients appear less susceptible to the damaging arterial effects of hyperlipidaemia are unknown. These results may have implications for others with secondary hyperlipidaemias.

A long-term, randomized, comparative study of insulin versus sulfonylurea therapy in type 2 diabetes

OBJECTIVES

To study the effect of insulin and sulfonylurea (SU) therapy on glycaemic control, insulin resistance and cardiovascular risk factors in type 2 diabetic subjects.

DESIGN

A prospective, parallel, randomized, controlled, long-term study.

SETTING

Outpatient clinic in tertiary referral centre.

SUBJECTS

Thirty-six type 2 diabetic subjects treated with diet and SU, aged 44-69 years and a duration of diabetes of between 2 and 14 years.

INTERVENTIONS

Individually adjusted doses of insulin and glibenclamide.

MAIN OUTCOME MEASURES

Glycosylated haemoglobin (HbA1c), insulin resistance (euglycaemic glucose clamp), levels of lipids, lipoproteins and blood pressure.

RESULTS

Glycaemic control improved during insulin treatment, but deteriorated on SU; HbA1c levels differed significantly between groups after 12 months of therapy (mean +/- SEM 7.9 +/- 0.3 vs. 9.5 +/- 0.4%, P = 0.004). Body mass index increased significantly during insulin treatment (26.4 +/- 0.7 to 27.8 +/- 0.7 kg/m2, P = 0.0001) and 30% of this increase was a result of an increase in lean body mass. The total glucose disposal rate showed a small increase in the insulin group. Levels of triglycerides and apolipoprotein B were significantly reduced during insulin treatment (1.8 +/- 0.2 to 1.5 +/- 0.2 mmol L-1, P = 0.03 and 1.58 +/- 0.1 to 1.40 +/- 0.08 g L-1, P = 0.003), and insulin prevented a reduction in the levels of high-density lipoprotein (HDL) cholesterol and apolipoprotein A-1 and an increase in Lp(a) lipoprotein observed in the SU group. Blood pressure levels did not change during therapy.

CONCLUSIONS

Insulin therapy was superior to SU treatment in achieving good metabolic control. Despite a modest improvement in cardiovascular risk factors in the insulin-treated group, no significant differences were observed between the groups after 1 year's treatment.

Dyslipoproteinemia and other risk factors for atherosclerosis in children and adolescents

The early lesions of atherosclerosis in youth are strongly related to antemortem levels of total and low density lipoprotein (LDL) cholesterol, very low density lipoprotein (VLDL) cholesterol, and triglyceride, to ponderal index and to systolic and diastolic blood pressure. The major apolipoproteins of LDL and high density lipoprotein (HDL), apo B and apo A1, respectively, as well as levels of Lp(a) lipoprotein are often abnormal in children born to a parent with coronary artery disease (CAD). Other risk factors for CAD include obesity, high blood pressure, cigarette smoking, diabetes mellitus, positive family history of CAD and physical inactivity. Children from families with premature CAD, familial dyslipidemia or hypertension, and/or two other risk factors should have a lipoprotein profile determined. The first form of treatment is a diet low in total fat, saturated fat and cholesterol, combined with treatment of overnutrition and obesity, if necessary, and regular habits of aerobic physical activity. Children with inherited disorders of LDL metabolism may require the addition of lipid lowering therapy. The early detection and treatment of youth at risk for premature CAD offers the greatest promise to decrease morbidity and mortality.

Microalbuminuria: prognostic and therapeutic implications in diabetes mellitus

Thirty years following the development of the first radioimmunoassay for albumin, microalbuminuria is widely acknowledged as an important predictor of overt nephropathy in patients with Type 1 diabetes and of cardiovascular mortality in Type 2 diabetes. In addition, there is accumulating evidence to suggest that diabetic patients with microalbuminuria may have more advanced retinopathy, higher blood pressure, and worse dyslipidaemia than patients with normal albumin excretion rates. Recent studies have focused on the role of intervention, principally with antihypertensive therapy and intensive glycaemic control, in reducing microalbuminuria. While successful in reducing urinary albumin excretion it remains to be established whether such therapies will be translated into a reduction in renal failure and decreased cardiovascular morbidity and mortality.

Structure and possible biological roles of Lp(a)

Lipoprotein(a) [Lp(a)] is a plasma macromolecular complex that is assembled from low-density lipoproteins (LDL) and a large hydrophilic glycoprotein, named apolipoprotein(a) [apo(a)], linked by a disulfide bond to apolipoprotein B-100. Apo(a) is formed by different structural domains one of which is present in multiple copies, the number of which is determined by variation in the hypervariable apo(a) gene. Sequence homology of apo(a) with plasminogen may explain the competition of Lp(a) for some physiological functions of plasminogen in the coagulation and fibrinolytic cascade in vitro. There is evidence that high plasma levels of Lp(a) may have atherogenic and/or thrombogenic potential. More work will have to be done to understand the exact role of Lp(a) in atherogenesis, to evaluate the potential synergy between Lp(a) and LDL in promoting coronary artery disease, and to assess the therapeutic benefits of a reduction of Lp(a) levels.

Lipids and Lp(a) lipoprotein levels and coronary artery disease in subjects with non-insulin-dependent diabetes mellitus

OBJECTIVE

To determine whether increased Lp(a) lipoprotein levels are associated with either non-insulin-dependent diabetes mellitus (NIDDM) or coronary artery disease (CAD) in patients with NIDDM and to examine the relationship between Lp(a) levels and glycemic control.

DESIGN

We conducted a cross-sectional study of subjects with NIDDM who were participants in the Rochester Diabetic Neuropathy Study and healthy control subjects from the population of Rochester, Minnesota.

MATERIAL AND METHODS

Lipids and Lp(a) lipoprotein levels were compared in 227 subjects with NIDDM and 163 control subjects and, among the subjects with NIDDM, in those with (N = 96) and without (N = 131) CAD. The correlation between Lp(a) levels and glycosylated hemoglobin was investigated.

RESULTS

Subjects with NIDDM had higher triglyceride and lower high-density lipoprotein cholesterol levels than did control subjects. Subjects with NIDDM and CAD had higher total cholesterol, triglyceride, and low-density lipoprotein cholesterol levels and lower high-density lipoprotein cholesterol levels than did subjects with NIDDM without CAD. Subjects with NIDDM had significantly higher Lp(a) levels than did control subjects, but subjects with NIDDM and CAD did not have significantly higher Lp(a) levels than did those without CAD. Among subjects with NIDDM, the level of Lp(a) was not significantly correlated with glycosylated hemoglobin.

CONCLUSION

Although subjects with NIDDM have higher Lp(a) levels than do control subjects, Lp(a) does not seem to be associated with CAD in subjects with NIDDM. In this study, no association was found between Lp(a) level and glycemic control.

Lipid abnormalities in the nephrotic syndrome: causes, consequences, and treatment

Hyperlipidemia so commonly complicates heavy proteinuria that it has come to be regarded as an integral feature of the nephrotic syndrome (NS). Characteristically, total plasma cholesterol and triglyceride levels are elevated, as are very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) cholesterol. Although high-density lipoprotein (HDL) concentrations may be normal, HDL subtypes are abnormally distributed, with a reduction of HDL2 and an increase in HDL3. In addition, lipoprotein (a) [Lp (a)] levels may be elevated. The mechanisms underlying these abnormalities are multifactorial, involving both increased rates of lipoprotein synthesis and defective clearance and catabolism of circulating particles. Although recent dietary and therapeutic studies have demonstrated that nephrotic hyperlipidemia can be effectively treated, the need for such intervention has not been clearly established. This pattern of lipoprotein abnormality is associated with an increased risk of cardiovascular disease in the general population, and several studies have suggested that nephrotic individuals are more likely to develop atherosclerosis. However, no prospective trials have evaluated the relationship between deranged lipid metabolism and coronary or cerebral artery disease in patients with NS. In addition, although recent experimental studies suggest that lipid abnormalities may accelerate renal injury and that lipid-lowering agents may protect renal function, there is little current evidence to suggest that such intervention is of value in preserving residual renal function in humans. Further studies are clearly required to assess the potential long-term benefits of lipid-lowering intervention in individuals with NS. In the meantime, based on data generated from other population groups, a rational approach to the clinical management of hyperlipidemia in these patients is presented.

Microalbuminuria in salt-sensitive patients. A marker for renal and cardiovascular risk factors

We previously showed that a high salt diet increases glomerular capillary pressure in salt-sensitive hypertensive patients and suggested that this may underlie the greater propensity of these patients to develop renal failure. Because microalbuminuria is considered an initial sign of renal damage, we have tested whether salt-sensitive patients display greater urinary albumin excretion than salt-resistant hypertensive patients. Twenty-two patients were placed on a low sodium intake (20 mEq/d) for 7 days followed by a high sodium diet (250 mEq/d) for 7 more days. Twelve patients were classified as salt sensitive and 10 as salt resistant. Urinary albumin excretion was greater in salt-sensitive than salt-resistant patients (54 +/- 11 versus 22 +/- 5 mg/24 h, P < .01). During the low sodium diet, glomerular filtration rate, renal plasma flow, and filtration fraction were similar between the two groups. During the high sodium intake, glomerular filtration, renal plasma flow, filtration fraction, and calculated intraglomerular pressure did not change in salt-resistant patients; in salt-sensitive patients, however, renal plasma flow decreased, and filtration fraction and intraglomerular pressure increased, whereas glomerular filtration rate did not change. Urinary albumin excretion was significantly correlated with glomerular capillary pressure. Salt-sensitive patients displayed higher serum levels of low-density lipoprotein cholesterol and lipoprotein(a) and lower levels of high-density lipoprotein cholesterol than salt-resistant patients. These studies have shown greater urinary albumin excretion and serum concentrations of atherogenic lipoproteins in salt-sensitive than in salt-resistant hypertensive patients, suggesting that salt sensitivity may be a marker for greater risk of renal and cardiovascular complications.

Lipoprotein disorders in diabetes mellitus

In IDDM or NIDDM, the total plasma cholesterol and triglycerides are usually within normal limits when the blood glucose is controlled. Marked hypertriglyceridemia can develop with loss of glycemic control and is often due to superimposed genetic abnormalities in lipoprotein metabolism. Tight control in IDDM usually reduces LDL and VLDL to normal levels and may raise HDL above the normal range. Low HDL cholesterol and mild to moderate elevations of VLDL triglyceride are common in NIDDM if obesity or proteinuria is also present. Both HDL and LDL may be smaller and more dense and may be enriched with triglyceride as compared with cholesterol. These abnormalities may require weight loss for control. The increased incidence of cardiovascular disease in diabetes is unexplained but is amplified by the well-defined cardiovascular risk factors. The new American Diabetes Association guidelines call for treatment of high triglycerides and LDL cholesterol to be aggressively reduced. Triglycerides should be under 200 mg/dL, are considered borderline high between 200 and 400 mg/dL, and high when above 400 mg/dL. Low HDL is defined as less than 35 mg/dL. Control of obesity with diet and exercise and reduced intake of saturated fat and cholesterol are important first steps. If needed, drug therapy is appropriate to reduce LDL to levels below 130 mg/dL in all adult diabetics and below 100 mg/dL in those with cardiovascular disease.

Lipid parameters including Lp(a) in hemodialysis patients

Chronic hemodialysis (CHD) patients have a high incidence and prevalence of atherosclerotic disease which may be related to numerous atherosclerotic risk factors. Among them dyslipidemia plays a significant role. Elevated Lp(a) levels, which are strongly associated with atherosclerosis, have been reported recently in uremic patients. The aim of our study was the determination of the levels of lipid parameters including Lp(a) in 151 CHD patients (76 male) aged 57 (12-81) years, who were on hemodialysis for a mean of 44.3 (range 1 to 189) months. Eighty-four normal individuals age and sex matched were used as controls. The median serum Lp(a) concentration in hemodialysis patients was 13 mg/dL compared with 6.5 mg/dL in healthy controls, p < 0.001 by distribution-free Mann-Whitney test. The prevalence of subjects with Lp(a) levels above 25 mg/dL was significantly higher in CHD patients compared to normal subjects (30% vs. 8%, p < 0.001). Even if CHD patients were matched for fasting lipid levels, they showed Lp(a) levels significantly higher than controls. No significant correlation was found between Lp(a) levels and either the age of the patients or the duration of hemodialysis. The etiology of primary renal disease did not influence the Lp(a) levels.

Lp(a) lipoprotein: an overview

The Lp(a) lipoprotein, a distinct class of serum lipoproteins, was detected in 1962. It consists of an LDL particle to which a long polypeptide chain is attached by a disulfide bridge. The level of Lp(a) lipoprotein is genetically determined. Single locus control was suggested already in the very first report, and this has been conclusively confirmed by the demonstration of absolute genetic linkage to the plasminogen gene, from which the LPA gene is likely to have evolved. The detection in 1974 of an association between Lp(a) lipoprotein and coronary heart disease has been confirmed in numerous studies. The Lp(a) lipoprotein may have atherogenic as well as thrombogenic properties and thus form the bridge between atherogenesis and thrombogenesis. Genes determining a moderate level of Lp(a) lipoprotein may be longevity genes, and it seems possible that Lp(a) lipoprotein, because of its affinity to vessel walls, may also influence placental function. Lp(a) lipoprotein measurements should be included in the diagnostic work-up of people with premature coronary heart disease or with such disease in close relatives.

Metabolic effects of converting enzyme inhibitors: focus on the reduction of cholesterol and lipoprotein(a) by fosinopril

It is generally believed that the use of angiotensin-converting enzyme (ACE) inhibitors has no effect on the lipid profile. Our recent data show that in patients with proteinuric renal disease, serum levels of total cholesterol and lipoprotein(a) [Lp(a)] may be lowered during treatment with an ACE inhibitor, fosinopril sodium. During a 12-week randomized, placebo-controlled, double-blind study involving 26 patients with mild-to-moderate renal impairment, fosinopril administration was associated with significant decreases in both urinary protein excretion and serum total cholesterol levels, whereas placebo was not. During a 6-week washout phase, both parameters returned to baseline in fosinopril-treated patients and remained unchanged in placebo recipients. In addition, fosinopril-treated patients had a decrease in plasma levels of Lp(a), whereas this was not seen in placebo-treated patients. When data from a subset of 13 patients with proteinuric renal disease and hypertension were examined, a significant decrease in serum total cholesterol levels was observed; this decrease reversed after discontinuation of fosinopril. Analysis of the effect of fosinopril on plasma Lp(a) levels in a subset of patients who had type II diabetes mellitus and overt proteinuria revealed a significant decrease in plasma Lp(a) after administration of fosinopril. Moreover, fosinopril lowered plasma Lp(a) levels in blacks, whose pretreatment levels were higher than those of whites with comparable degrees of proteinuria and levels of serum total cholesterol. Thus, the reduction in serum Lp(a) levels may be related not only to amelioration of proteinuria, but also to another direct action of fosinopril on the metabolism of Lp(a).

Glycometabolic control, lipids, and coagulation parameters in patients with non-insulin-dependent diabetes mellitus

Diabetes mellitus and hyperlipidemia are associated with coronary heart disease and with hypercoagulability, another independent risk factor for coronary heart disease. In 65 non-insulin-dependent diabetes mellitus patients [41 females, 24 males, median age 66 years (range 43-81 years)] treated with antidiabetic agents glycometabolic control (HbA1c), lipids (Quetelet index and blood lipids), and several coagulation parameters were studied in comparison with a reference group. Serum triglycerides were elevated [median (interquartile range) 2.3 (1.3) mmol/l vs. 1.6 (0.7) mmol/l in the controls (P < 0.001)], whereas the median lipoprotein(a) concentration was 65 (157) mg/l in the diabetic patients versus 44 (114) mg/l in the control group (not significantly different). Median high-density lipoprotein-cholesterol concentrations were slightly decreased in the diabetic patients: 1.2 (0.3) mmol/l compared with 1.3 (0.4) mmol/l in the control group (P < 0.02). Elevated levels of fibrinogen, fibrin monomers, thrombin-antithrombin III complex, and factor VIIIc were found in the diabetic patients and factor VII in male diabetic patients. These elevated coagulation parameters are indicators of an activated coagulation system in this patient group. By Spearman's rank test, only HbA1c values correlated with anti-thrombin III (r = 0.27, P < 0.03) and showed a tendency towards a correlation with lipoprotein(a) (r = 0.23, P < 0.07). Triglycerides correlated with the Quetelet index (r = 0.27, P < 0.03), high-density lipoprotein-cholesterol (r = -0.41, P < 0.001), and factor VII (r = 0.35, P < 0.01), whereas serum cholesterol concentrations correlated with factor VII (r = 0.27, P < 0.04) and with fibrin monomers (r = 0.29, P < 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Elevated lipoprotein (a) levels in primary nephrotic syndrome

Elevated plasma levels of total cholesterol and increase in the hepatic synthesis of some apo B-containing lipoproteins have been noted in the nephrotic syndrome. Apoprotein (a), the apolipoprotein distinguishing lipoprotein (a) [Lp(a)] from low-density lipoprotein, is equally of hepatic origin, and Lp(a) recently has been shown to possess both atherogenic and thrombogenic activities. However, little is known of Lp(a) levels in nephrotic patients. We measured plasma Lp(a) concentrations in 11 patients with primary nephrotic syndrome in the absence of hematuria, hypertension, and renal insufficiency. Histologic lesions were minimal-change disease in five cases, membranous glomerulopathy in four cases, and focal and segmental glomerulosclerosis in two cases. Mean levels of Lp(a) (98 +/- 92 mg/dL [mean +/- SD]) were markedly elevated in the nephrotic patients as compared with the controls (14 +/- 13 mg/dL). No correlation was noted between plasma Lp(a) and proteinuria, albuminemia, total cholesterolemia, low-density lipoprotein cholesterol, apoprotein B100, or plasminogen. Furthermore, there was no correlation between Lp(a) levels and apoprotein (a) isoform size. In four patients, the level of Lp(a) decreased approximately fourfold after remission of the nephrotic syndrome under corticosteroid treatment. Our observation that Lp(a) levels are elevated in the nephrotic syndrome is consistent with the hypothesis that these patients may be at an increased risk of cardiovascular and thrombotic complications.

Lipoprotein(a) and treatment of chronic renal disease

OBJECTIVES

To compare lipoprotein(a) [Lp(a)] and albumin concentrations in patients with chronic renal disease receiving different forms of treatment and to determine, if any, the relationship between these variables.

DESIGN

A prospective cross-sectional, case-controlled study.

SETTING

A tertiary referral nephrology and dialysis unit.

SUBJECTS

Forty-four consecutive non-diabetic patients with chronic renal failure treated by renal transplantation (n = 18), haemodialysis (n = 18), continuous ambulatory peritoneal dialysis (CAPD; n = 8), and 30 healthy controls from subjects drawn from University personnel were studied.

INTERVENTIONS

Fasting morning venous blood was analysed for Lp(a), albumin, total cholesterol and glucose concentrations.

MAIN OUTCOME MEASURES

Comparison of plasma levels of these variables between the sub-groups.

RESULTS

Concentrations (median; 95% CI) of Lp(a) were significantly (P < 0.05) higher (38.4 mg dl-1; range 15.4-72.0) and of albumin lower (31.6 g l-1; range 28-35.2) in the CAPD group compared with both control subjects and other groups of chronic renal disease patients.

CONCLUSIONS

The elevated Lp(a) concentrations seen only in association with reduced albumin concentrations in CAPD patients suggest a regulatory role for albumin with albumin losses stimulating production of Lp(a).