Alterations in serum lipids and apolipoproteins in male type 1 (insulin-dependent) diabetic patients with microalbuminuria

Both LDL and HDL particle concentrations associate positively with an increased risk of developing microvascular complications in patients with type 2 diabetes: lost protection by HDL (Zodiac-63)

BACKGROUND

Triglyceride-rich lipoproteins (TRL) and low-density lipoproteins (LDL) are associated positively whereas high-density lipoproteins (HDL) are associated inversely with the development of new-onset type 2 diabetes (T2D). Here we studied potential associations between these lipoprotein particle concentrations and the risk of developing microvascular complications in patients with established T2D.

METHODS

Lipoprotein particle concentrations (TRLP, LDLP, and HDLP) were determined in 278 patients with T2D participating in a primary care-based longitudinal cohort study (Zwolle Outpatient Diabetes project Integrating Available Care [ZODIAC] study) leveraging the Vantera nuclear magnetic resonance (NMR) platform using the LP4 algorithm. Associations between lipoprotein particles and incident microvascular complications (nephropathy, neuropathy, and retinopathy) were assessed using Cox proportional hazards regression models.

RESULTS

In total, 136 patients had microvascular complications at baseline. During a median follow-up of 3.2 years, 49 (34.5%) of 142 patients without microvascular complications at baseline developed new-onset microvascular complications. In multivariable Cox proportional hazards regression analyses, both total LDLP and HDLP concentrations, but not total TRLP concentrations, were positively associated with an increased risk of developing any microvascular complications after adjustment for potential confounding factors, including age, sex, disease duration, HbA1c levels, history of macrovascular complications, and statin use (adjusted hazard ratio [HR] per 1 SD increment: 1.70 [95% CI 1.24-2.34], P < 0.001 and 1.63 [95% CI 1.19-2.23], P = 0.002, respectively). When analyzing each microvascular complication individually, total LDLP concentrations were positively associated with retinopathy (adjusted HR 3.35, 95% CI 1.35-8.30, P = 0.009) and nephropathy (adjusted HR 2.13, 95% CI 1.27-3.35, P = 0.004), and total HDLP concentrations with neuropathy (adjusted HR 1.77, 95% CI 1.15-2.70, P = 0.009). No significant associations were observed for lipoprotein particle subfractions.

CONCLUSIONS

Total lipoprotein particle concentrations of both LDL and HDL associate positively with an increased risk of developing microvascular complications in T2D. We propose that the protective role of HDL on the development of microvascular complications may be lost in established T2D.

Associations Among Biomarkers of Inflammation, Tubular Injury and Lipid Metabolism With Gestational Diabetes Mellitus Status, Microalbuminuria and Retinopathy in the Microalbuminuria and Retinopathy in Gestational Diabetes Study

OBJECTIVES

Pregnancy may be complicated by gestational diabetes mellitus (GDM) and/or microvascular complications like albuminuria, retinopathy and pre-eclampsia. In this study we aimed to identify whether mechanistic pathways associated with microvascular complications are active in pregnant women with GDM or microvascular disease.

METHODS

Urinary albumin excretion and biomarkers of inflammation, lipoprotein metabolism and tubular injury were quantified in 355 pregnant women with and without GDM. Participants underwent fundus photography graded for retinopathy. Adjusted associations between individual biomarkers and each outcome variable of interest, including GDM status, albuminuria and retinopathy, were performed using logistic regression.

RESULTS

After adjusting for age, systolic blood pressure, body mass index and ethnicity, significant associations between GDM status and apolipoprotein A1, interleukin (IL)-6, IL-8, soluble tumour necrosis factor receptor-I and -II (sTNFR-I and -II), vascular endothelial growth factor and von Willebrand factor were observed. Increased high-sensitivity C-reactive protein (hsCRP) and sTNFR-II were associated with higher levels of albuminuria. hsCRP and previous GDM were associated with retinopathy.

CONCLUSION

Mechanistic pathways associated with microvascular complications appear to be active in pregnant women with GDM or microvascular disease.

Apolipoprotein B attenuates albuminuria-associated cardiovascular disease in prevention of renal and vascular endstage disease (PREVEND) participants

Whether urinary albumin excretion relates to higher levels of atherogenic apolipoprotein B fractions in the nondiabetic population is uncertain. Such a relationship could explain, in part, the association of elevated urinary albumin excretion with cardiovascular disease risk. We assessed the relationship of urinary albumin excretion with apolipoprotein B fractions and determined whether the association of elevated urinary albumin excretion with incident cardiovascular events is modified by high apolipoprotein B fraction levels. We performed a prospective study on 8286 nondiabetic participants (580 participants with cardiovascular disease; 4.9 years median follow-up time) with fasting lipids, apolipoprotein B, and urinary albumin excretion determined at baseline. With adjustment for sex and age, micro- and macroalbuminuria were associated with increased apolipoprotein B fractions (non-HDL cholesterol, LDL cholesterol, triglycerides, and apolipoprotein B). All four apolipoprotein B fractions modified associations of urinary albumin excretion with incident cardiovascular disease (hazard ratios for interaction terms ranged from 0.89 to 0.94 with 95% confidence intervals ranging from 0.84 to 0.99 and P values ranging from 0.001 to 0.02 by Cox proportional hazards modeling). These interactions remained present after additional adjustment for conventional risk factors, eGFR, cardiovascular history, and lipid-lowering and antihypertensive drug treatments. Such modification was also observed when urinary albumin excretion was stratified into normo-, micro-, and macroalbuminuria. We conclude that there is an association between elevated urinary albumin excretion and apolipoprotein B fraction levels and a negative interaction between these variables in their associations with incident cardiovascular events. Elevated urinary albumin excretion may share common causal pathways with high apolipoprotein B fractions in the pathogenesis of cardiovascular disease.

Lower levels of total HDL and HDL3 cholesterol are associated with albuminuria in normoalbuminuric Type 1 diabetic patients

BACKGROUND

Previous studies have suggested a positive association between dyslipidemia and chronic kidney disease, but sparse data are available on the relation of lipids and urinary albumin excretion rate (UAE) in normoalbuminuric patients with normal renal function.

AIM

The aim of this study was to evaluate the associations of serum lipids, including total, LDL, HDL, HDL2, HDL3 cholesterol, and triglyceride levels with UAE in normoalbuminuric Type 1 diabetic (T1D) patients.

METHODS

Study included 313 normoalbuminuric T1D patients with normal renal function and before any interventions with statins, ACE inhibitors or angiotensin II receptor blockers. Subjects were classified as low-normoalbuminuric (UAE<11.0 mg/24h) or high-normoalbuminuric (UAE≥11.0 mg/24h) based on median UAE of at least two 24- h urine collections. Correlations and multiple linear regressions analysis were performed to identify relationships between serum lipids and UAE in normoalbuminuric subjects.

RESULTS

Total HDL (p=0.02) and HDL3 cholesterol (p=0.01) levels were higher in low-normoalbuminuric subjects compared to high-normoalbuminuric subjects. In logistic regression analysis, after adjustment for age, sex, BMI, duration of diabetes and HbA1c, lower total HDL and HDL3 cholesterol levels were significantly associated with risk of higher UAE in our normoalbuminuric subjects (p≤0.01), with odds ratios of 0.34 to 0.43.

CONCLUSIONS

Elevated total HDL and HDL3 cholesterol levels are associated with lower UAE in normoalbuminuric T1D patients. However, whether the detection of elevated total HDL and HDL3 cholesterol levels in T1D patients has protective value for development of microalbuminuria needs to be assessed in further follow-up studies.

Lipid disorders in type 1 diabetes

Patients with type 1 diabetes (T1D) also present with lipid disorders. Quantitative abnormalities of lipoproteins are observed in T1D patients with poor glycaemic control (increased plasma triglycerides and low-density lipoprotein [LDL] cholesterol) or nephropathy (increased triglycerides and LDL cholesterol, low level of high density lipoprotein [HDL] cholesterol). In cases of T1D with optimal glycaemic control, plasma triglycerides and LDL cholesterol are normal or slightly decreased, while HDL cholesterol is normal or slightly increased. Several qualitative abnormalities of lipoproteins, which are potentially atherogenic, are observed in patients with T1D, even in those with good metabolic control. These abnormalities include increased cholesterol-to-triglyceride ratios within very low-density lipoprotein (VLDLs), increased triglycerides in LDLs and HDLs, compositional changes in the peripheral layer of lipoproteins, glycation of apolipoproteins, increased oxidation of LDLs and an increase in small, dense LDL particles. These qualitative changes in lipoproteins are likely to impair their function. In vitro, VLDLs and LDLs from patients with T1D induced abnormal responses in the cellular cholesterol metabolism of human macrophages. HDLs from patients with T1D are thought to be less effective in promoting cholesterol efflux from cells, and have been shown to have reduced antioxidative and vasorelaxant properties. These qualitative abnormalities are not fully explained by hyperglycaemia and may be partly due to peripheral hyperinsulinaemia associated with subcutaneous insulin administration. However, the precise consequences of these qualitative lipid changes on the development of cardiovascular disease in T1D are, as yet, unknown.

Higher levels of HDL cholesterol are associated with a decreased likelihood of albuminuria in patients with long-standing type 1 diabetes

OBJECTIVE

The objective of this study was to determine whether high levels of HDL cholesterol are associated with a lower prevalence of albuminuria

RESEARCH DESIGN AND METHODS

We analyzed the lipid profiles of patients with type 1 diabetes of > or = 20 years duration in 42 patients with albuminuria (28 microalbuminuria and 14 macroalbuminuria) and 65 patients without increased albumin excretion before any interventions with either statins or ACE inhibitors.

RESULTS

Several characteristics were similar in the two groups: sex, age, duration of diabetes, total cholesterol, LDL cholesterol, and triglycerides. By univariate analysis, significant differences (P < 0.01) were found in HDL cholesterol (albuminuria 1.42 mg/dl, no albuminuria 1.71 mg/dl, P < 0.01), HbA1c (A1C) (albuminuria 8.5%, no albuminuria 7.5%), and proportions with no, background, and proliferative retinopathy (albuminuria 2.4, 16.7, and 81%; no albuminuria 24.6, 52.3, and 23.1%, respectively). When adjusted for age and sex, a 0.26-mmol/l (10-mg/dl) increase in HDL cholesterol is associated with an odds ratio (OR) of 0.70 (95% CI 0.54-0.90) for having albuminuria. In a multivariate model that adjusted for age, sex, diabetes duration, and A1C, for every 0.54-mmol/l (21-mg/dl) increase in HDL cholesterol, patients are approximately half (OR 0.51 [95% CI 0.30-0.86]) as likely to have albuminuria, even after controlling for A1C.

CONCLUSIONS

Higher HDL cholesterol levels may be protective against the development of albuminuria in patients with type 1 diabetes. Whether this is due to the HDL cholesterol levels or whether they serve as a marker for some other mechanism remains to be determined.

Plasma lipids and urinary albumin excretion rate in Type 1 diabetes mellitus: the EURODIAB IDDM Complications Study

AIMS

To examine the relationship between increased urinary albumin excretion rate and fasting plasma lipids among male and female respondents to the EURODIAB IDDM Complications Study, and attempt to explain inconsistencies in previous reports.

METHODS

A cross-sectional study of 3250 randomly selected Type 1 diabetic patients from 31 diabetes clinics in 16 European countries was carried out between 1989 and 1990. Plasma lipids and urinary albumin were measured centrally. The present analysis was confined to the subgroup of 2205 patients attending after a 10-12 h overnight fast. Mean age was 33 years (SD 10) and mean duration of Type 1 diabetes mellitus was 15 years (SD 9).

RESULTS

The prevalence of microalbuminuria (24-h urinary albumin excretion rate 20-200 microg/min) was 21.7% (95% confidence interval 19.9-23.5) and macroalbuminuria (24-h urinary albumin excretion rate > 200 microg/min) 7.8% (6.6-9.0). In comparison to patients with normal urinary albumin excretion rate (< 20 microg/min), and after controlling for age, sex, glycaemic control, duration of diabetes and current smoking, macroalbuminuria was associated with significantly (P<0.01) increased fasting plasma triglycerides, cholesterol, LDL-cholesterol, cholesterol:HDL-cholesterol ratio and, in women, reduced HDL-cholesterol. In men and women with microalbuminuria, the only significant association was with increased plasma triglycerides.

CONCLUSIONS

These data confirm that there is an association between fasting plasma lipids and increasing urinary albumin excretion rate in European Type 1 diabetic patients. In microalbuminuric patients, however, the association was weaker than previously reported and partly explained by confounding factors.

Peritoneal dialysis in diabetic patients

Diabetes mellitus is the fastest growing cause of end-stage renal disease (ESRD) and has become the leading cause of such ESRD worldwide. In the United States, between 1984 and 1997, the proportion of new patients starting renal replacement therapies whose ESRD was caused by diabetes increased from 27% to 44.4%. Canada saw an increase from 16.5% in 1984 to 28.9% in 1997, and many European countries had similar increases. Among the modes of renal replacement, many clinicians have favored continuous ambulatory peritoneal dialysis (CAPD) for the treatment of diabetic ESRD for several reasons. Many studies have compared clinical outcomes in diabetic patients undergoing CAPD, and nondiabetic patients undergoing CAPD, or diabetic patients undergoing peritoneal dialysis (PD) and those undergoing hemodialysis (HD). However, only a small number of diabetic dialysis patients have been followed up for more than 5 years, largely because of the presence of several comorbid conditions at the start of dialysis and the coexistence of far-advanced target-organ damage at dialysis initiation and its progression during the course of dialysis. Diabetic patients undergoing PD and HD probably have similar survival, and those undergoing CAPD have lower survival and technique success rates than nondiabetic patients of comparable age. This article reviews the literature and our experience with diabetic patients undergoing PD and compares clinical outcomes in diabetic patients undergoing PD and HD.

Increased small dense LDL and intermediate-density lipoprotein with albuminuria in type 1 diabetes

OBJECTIVE

This population study examines the relationship between LDL density and persistent albuminuria in subjects with type 1 diabetes at the end of the Diabetes Control and Complications Trial (DCCT).

RESEARCH DESIGN AND METHODS

Subjects were classified as persistently normoalbuminuric (albumin excretion rate [AER] < 30 mg/d, n = 1,056), microalbuminuric (AER > or = 30-299 mg/day, n = 80), and macroalbuminuric (AER = 300 mg/day, n = 24) based on the last two AER measures.

RESULTS

Triglyceride (P < 0.01) and LDL cholesterol (P < 0.01) levels were higher in macroalbuminuric subjects compared with normoalbuminuric subjects. Cholesterol distribution by density-gradient ultracentrifugation showed an increase in intermediate-density lipoprotein (IDL) and a shift in peak LDL from buoyant toward more dense particles with progressive albuminuria. In the entire group, there was a significant negative correlation between the peak buoyancy of LDL particles and albuminuria (r = -0.238, P < 0.001, n = 1,160). This correlation persisted in the normoalbuminuric DCCT group (r = -0.138, P < 0.001, n = 1,056).

CONCLUSIONS

As albuminuria increases in subjects with type 1 diabetes, dyslipidemia occurs with an increase in IDL and dense LDL that may lead to increased cardiovascular disease.

Microalbuminuria: a marker to increased renal and cardiovascular risk in diabetes mellitus

The presence of persistent microalbuminuria in IDDM is strongly predictive of the future development of end stage renal failure and of cardiovascular disease to a lesser extent. Screening for microalbuminuria is an essential component of modern diabetes practice, as effective antihypertensive therapy, and particularly, the use of angiotensin converting enzyme inhibitors is of proven benefit in retarding progression of renal disease. Cost benefit analysis justifies the expense of microalbuminuria screening programmes and early intervention. It has been estimated that the use of angiotensin converting enzyme inhibitors in microalbuminuric IDDM will save 5200 Pounds-11,000 Pounds per year of life saved. Angiotensin converting enzyme inhibitors are not free of side-effects, and it is therefore essential, given the intrinsic variability of the albumin excretion rate, and the regression to normoalbuminuria of a significant proportion of patients, to confirm the diagnosis of microalbuminuria by repeated measurements prior to the commencement of treatment. The value of intensive glycaemic control is unproven, and further prospective studies are required. There are no proven therapies for the prevention of macrovascular disease in IDDM, although the value of cessation of smoking and aggressive blood pressure control are undoubted in the non-diabetic population. Controversy persists about the value of lipid lowering therapy, especially in young patients, although even in this group there is an increased risk of cardiovascular disease. Microalbuminuria is the strongest known predictor of cardiovascular disease in NIDDM; in contrast to the situation in the non-diabetic population, active lipid lowering therapy is not of proven cardiac benefit, but intervention seems justifiable when taken in the context of the very high prevalence of cardiovascular disease. Microalbuminuria is also predictive of end stage renal disease in NIDDM. Although intervention with angiotensin converting enzyme inhibitors has not been proven to prevent end stage renal disease, stabilisation of albumin excretion rate and creatinine clearance have been demonstrated in normotensive NIDDM, and it seems likely that longer term follow-up studies will confirm the benefit of angiotensin converting enzyme inhibitors in the prevention of end-stage renal disease. The observed predictive power of microalbuminuria as regards both cardiac and renal risk in NIDDM when considered in conjunction with the preliminary results of the benefits of angiotensin converting enzyme inhibition lend further support to the employment of microalbuminuria screening in NIDDM.

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.

Lipids, lipoproteins, antioxidants and glomerular and tubular dysfunction in type 1 diabetes

We aimed to examine the relationship of serum lipids, lipoproteins, apolipoproteins and antioxidants with renal dysfunction as measured by urinary excretion of albumin and of retinol binding protein (RBP) in insulin-dependent diabetes mellitus (IDDM). We studied 121 patients with IDDM. Glomerular function was assessed as the urinary albumin/creatinine ratio (UA/UC), and tubular function as the urinary retinol-binding protein/creatinine ratio (UR/UC), both measured in three early morning spot urine samples. The mean (range) UA/UC was 1.95 mg/mmol (0.3-476.5) and UR/UC was 17.5 micrograms/mmol (1.0-1853.8). 17% of the patients had a UA/UC > 3 mg/mmol and 33% had a UR/UC > 20 micrograms/mmol. Significant positive correlations were observed between both UA/UC and UR/UC and the following: serum total cholesterol (P < 0.005); triglycerides (P < 0.001); apolipoproteins A-I (P < 0.05), A-II (P < 0.02) and B (P < 0.002); glycated haemoglobin (P < 0.002). No significant associations were found with serum vitamin E, beta-carotene or total antioxidant activity. In multiple regression, only UA/UC was independently associated with serum apo B and cholesterol concentrations. In conclusion, in IDDM glomerular dysfunction, as measured by UA/UC, is associated with elevated serum cholesterol, triglycerides, apo B, apo A-I and apo A-II, but not with HDL cholesterol or antioxidant status. Tubular dysfunction tends to occur with increasing albuminuria, but it is not independently associated with serum lipid, lipoprotein, apolipoprotein or antioxidant levels.

Serum sialic acid concentration is elevated in IDDM especially in early diabetic nephropathy

OBJECTIVES

Elevated serum sialic acid concentration is a strong predictor of cardiovascular mortality in non-diabetic subjects. Because patients with insulin-dependent diabetes mellitus (IDDM) and albuminuria have a highly increased cardiovascular morbidity and mortality, we hypothesized that IDDM patients with albuminuria would have an increased concentration of serum sialic acid.

DESIGN

Cross-sectional study.

SETTING

Outpatient clinic at Steno Diabetes Centre, Gentofte, Denmark.

SUBJECTS

Twenty-six non-diabetic controls and 74 IDDM patients with normoalbuminuria (urinary albumin excretion [UAE] < 30 mg 24 h-1; n = 37), incipient nephropathy (UAE 30-300 mg 24 h-1; n = 20) and clinical nephropathy (UAE > 300 mg 24 h-1; n = 17), matched for sex, age and body mass index (BMI).

MAIN OUTCOME MEASURES

Serum sialic acid concentration, concurrent fasting blood glucose, glycated haemoglobin (HbA1c), serum creatinine, plasma fibrinogen and erythrocyte sedimentation rate.

RESULTS

Normoalbuminuric patients had a higher serum sialic acid concentration (mmol L-1) than non-diabetic controls (1.83 +/- 0.24 vs. 1.67 +/- 0.26; P < 0.02). Serum sialic acid concentration was further increased in patients with incipient nephropathy (2.02 +/- 0.37; P < 0.03) and in patients with clinical nephropathy (2.13 +/- 0.33; P < 0.002) compared with normoalbuminuric IDDM patients. Serum sialic acid correlated strongly with plasma fibrinogen (r = 0.78; P < 0.0001) and erythrocyte sedimentation rate (r = 0.62; P < 0.0001). In a multiple regression analysis including UAE, retinopathy status, fasting blood glucose, HbA1c, mean blood pressure, serum creatinine, age, BMI, duration and smoking. UAE and fasting blood glucose were the independent variables which correlated significantly with serum sialic acid concentration (P < 0.0001 and P < 0.05, respectively).

CONCLUSION

Serum sialic acid is elevated in IDDM especially in albuminuric patients. Whether elevated serum sialic acid is predictive for early diabetic nephropathy and cardiovascular disease in IDDM has to be shown in the future.

Comparison of platelet aggregability in Japanese type 2 diabetic patients with and without microalbuminuria

Microalbuminuria is associated with higher cardiovascular morbidity and mortality in Type 2 (non-insulin-dependent) diabetic patients. This study was designed to assess whether Type 2 diabetic patients with microalbuminuria (urinary albumin excretion rate (AER) 20-200 microgram min-1) is associated with alterations in platelet aggregability as compared with those with normal urinary albumin excretion (AER < 20 microgram min-1). Platelet aggregability was compared between 21 Japanese Type 2 diabetic patients with microalbuminuria and 21 individually pair-matched (for age, sex, body mass index, treatment, and HbA1c level) patients with normoalbuminuria. The in vitro platelet aggregation induced by 1.0 and 3.0 mumol l-1 ADP and 0.5 and 1.0 mg l-1 collagen was measured using platelet-rich plasma. No significant differences were observed between the two groups in the values for maximum percent platelet aggregation, percent aggregation at 3 min, and aggregation velocities after adding ADP or collagen. Microalbuminuric patients had significantly higher mean values for systolic (p < 0.004) and diastolic (p < 0.02) blood pressures and plasma fibrinogen level (p < 0.03) as compared with the respective mean values in normoalbuminuric patients. The results suggest that Japanese microalbuminuric Type 2 diabetic patients do not differ in the degree of platelet aggregability as compared with normoalbuminuric patients, despite an increase in certain other coronary risk factors.

Dyslipoproteinemia in diabetic renal failure

Plasma concentrations of lipids and apolipoproteins (Apo) were determined in 34 patients with long-standing type I (insulin-dependent) diabetes mellitus. Twenty-four patients had renal insufficiency (GFR 4 to 55 ml/min) due to diabetic nephropathy, while 10 patients had no clinical signs of nephropathy. Results were compared with those in 42 non-diabetic patients with comparable degree of renal insufficiency and with asymptomatic control subjects. Diabetic patients without nephropathy had plasma lipid and apolipoprotein concentrations similar to those of the control subjects. Diabetic patients with renal insufficiency had a significant increase in triglycerides (TG) and, to a lesser extent, in total cholesterol (TC). The patients also had reduced levels of ApoA-I and ApoA-II, increased levels of ApoC-II and ApoC-III, while increases in levels of ApoB and ApoE were statistically significant in patients with GFR < 20 ml/min. These lipids and apolipoprotein abnormalities were accentuated with decreasing renal function. The reduction in the ApoA-I/ApoC-III ratio characteristic of renal insufficiency was found in normo- and hyper-TG diabetic patients with nephropathy; this ratio was correlated with the GFR levels. Patients with higher HbA1C values had higher levels of ApoC-II and ApoC-III. The findings in the diabetic patients corresponded with those in non-diabetic patients with renal insufficiency. However, diabetic patients had higher ApoC-III and ApoE levels. The abnormalities of lipid metabolism in diabetic renal insufficiency seem to reflect primarily metabolic impairments characteristic of renal insufficiency, but may be further accentuated by the diabetic state and the metabolic control.

Vascular risk factors in Japanese non-insulin-dependent diabetic patients with microalbuminuria

To determine if non-insulin-dependent diabetes mellitus (NIDDM) patients with microalbuminuria would have augmented vascular risk factors, we studied the relationships between blood pressure, serum lipids, plasma fibrinogen, and uric acid concentrations and plasma lipoprotein (a) level in 25 Japanese NIDDM patients with microalbuminuria [albumin excretion rate (AER) 20-200 micrograms/min] and 25 individually pair-matched NIDDM patients with normal urinary albumin excretion (AER less than 20 micrograms/min), matched for age, sex, body mass index, treatment and HbAlc level. Microalbuminuric patients had significantly higher systolic blood pressure (p less than 0.05) and plasma fibrinogen level (p less than 0.05) and lower high-density lipoprotein (HDL) cholesterol concentration (p less than 0.05) as compared with those in normoalbuminuric patients, respectively, while there were no differences in serum triglycerides and uric acid levels between the two groups. Plasma lipoprotein (a) level, assessed in 15 microalbuminuric and 15 normoalbuminuric patients, was comparable in the two groups. The results suggest that some of the vascular risk factors are already present in microalbuminuric NIDDM patients when compared with normoalbuminuric patients.

Levels of cardiovascular risk factors in type 2 diabetes mellitus are dependent on the stage of proteinuria

Levels of cardiovascular risk factors were determined in 75 patients with Type 2 diabetes mellitus. The patients were divided into three groups according to their urinary protein excretion (UPE): (a) normal proteinuria (less than or equal to 70 mg d-1); (b) microproteinuria (70-500 mg d-1); and (c) macroproteinuria (greater than 500 mg d-1). A significant stepwise increase in mean systolic blood pressure, LDL-cholesterol and fibrinogen levels was observed from the first to the third investigated group of patients. Mean apoprotein B levels were significantly increased in the group with macroproteinuria compared to the other two groups. Significant linear correlations were found between UPE and LDL-cholesterol, total cholesterol, apoprotein B, creatinine, systolic blood pressure and diabetes duration. In summary, it is concluded that the levels of some cardiovascular risk factors increase with the stage of proteinuria in Type 2 diabetes mellitus.

Lipoprotein (a) and microvascular disease in type 1 (insulin-dependent) diabetes

The influence of albuminuria and proliferative retinopathy on concentration of serum lipoprotein (a) was examined cross-sectionally in 90 Type 1 diabetic patients. Concentrations of lipoprotein (a) were less in those with normoalbuminuria (90 (8-882) (median (range] U l-1) than in those with micro- or macro-albuminuria (137 (19-1722) U l-1, p less than 0.05). The prevalence of patients whose lipoprotein (a) concentrations were greater than 200 U l-1 was also greater (45% vs 24%, p = 0.03) among patients with albuminuria, but no difference was found between the microalbuminuric and macroalbuminuric groups (53 and 41%, respectively), or between those with or without proliferative retinopathy. The present finding that lipoprotein (a) concentrations may be increased at an early stage of diabetic renal disease may in part account for the excess ischaemic heart disease associated with diabetic nephropathy.

Blood rheology and cardiovascular risk factors in type 1 diabetes: relationship with microalbuminuria

Whole blood and plasma viscosity, erythrocyte aggregation and deformability, plasma fibrinogen, lipids, lipoproteins, apolipoproteins, and measures of blood glucose control were compared between 21 Type 1 diabetic patients with microalbuminuria (overnight albumin excretion rate 30-200 micrograms min-1) and 21 patients with albumin excretion below this range matched for age, sex, and duration of diabetes. Patients with microalbuminuria had significantly higher glycosylated haemoglobin (9.4 +/- 1.6 (+/- SD) vs 7.9 +/- 1.8% (normal range 5.0 to 7.6%)), total-cholesterol (5.6 +/- 1.1 vs 4.6 +/- 1.3 mmol l-1), apolipoprotein B (0.82 +/- 0.21 vs 0.66 +/- 0.14 g l-1), and apolipoprotein B:A1 ratio (0.58 +/- 0.18 vs 0.50 +/- 0.15) than those without microalbuminuria (all p less than 0.05). HDL-cholesterol was also raised (1.71 +/- 0.46 vs 1.43 +/- 0.37 mmol l-1, p less than 0.05). Lipoprotein(a) concentration was possibly higher in the microalbuminuric group (median (95% Cl) 105 (82-140) vs 72 (52-114) mg l-1, p = 0.06). No differences were seen in any of the rheological measurements. These results confirm the presence of potentially atherogenic lipoprotein changes in Type 1 diabetic patients with microalbuminuria, but suggest that altered blood rheology does not predate the development of nephropathy.

Influence of early diabetic nephropathy on very low density lipoprotein (VLDL), intermediate density lipoprotein (IDL), and low density lipoprotein (LDL) composition

The procedure of discontinuous gradient ultracentrifugation (DGU) was used to characterize the influence of early diabetic nephropathy on the composition of very low density lipoprotein (VLDL, flotation density 60-400 Svedberg (Sf) units), low density lipoprotein (LDL, flotation density 0-12 Sf) and subfractions of intermediate density lipoprotein (IDL1 and IDL2, 20-60 and 12-20 Sf, respectively). Forty-six subjects with type 1 (insulin-dependent) diabetes and serum creatinine, less than 140 mumol/l were studied, of whom 23 consistently had normal rates of albumin excretion (AER less than 15 micrograms/min), and 23 had persistent albuminuria (AER 20.0-960.6 micrograms/min). The two groups were similar with respect to total serum lipids, glycaemic control, age and body mass. The composition (lipid, protein and phospholipid) and mass of VLDL, LDL and IDL2 was not appreciably altered by early nephropathy, but free and total cholesterol concentration in IDL1 (Sf 20-60) was increased (total cholesterol 0.68 (0.09) (mean (SE)) vs. 0.47 (0.07) mmol/l, and free cholesterol 0.27 (0.04) vs. 0.17 (0.03) mmol/l, both P less than 0.05). The explanation of these findings was probably an accumulation in the circulation of the remnants of chylomicron metabolism and/or intermediates in the conversion from VLDL to IDL1. In addition, there was a decrease in serum high density lipoprotein (HDL) cholesterol in early nephropathy (1.27 (0.06) vs. 1.38 (0.10) mmol/l, P less than 0.05), due to a decrease in the HDL2 cholesterol subfraction (P less than 0.05). These findings may in part explain the increased risk of premature atherosclerosis associated with the development of albuminuria.

Hyperlipidaemia in diabetes

Currently our knowledge of the role of lipid abnormalities as risk factors for CHD in diabetes is insufficient. We need to define exact risk parameters to target correctly the therapy of lipid disorders and to outline optimum therapeutic strategies. Therefore it is necessary to identify quantitative and qualitative abnormalities of lipoproteins and apoproteins which signify the risk of CHD and to define their predictive power in prospective trials. Obviously we need to know more about the pathophysiology of lipid abnormalities and the action of insulin. Because diabetic patients carry a high inherent risk of CHD, target values recommended for non-diabetic populations may not be optimal for diabetic populations, but should be lower. To date no primary or secondary intervention trials in diabetic populations have been carried out to show that the lowering of lipid values (serum and LDL cholesterol) will reduce the risk of CHD morbidity or mortality or will prevent the progression of CHD in diabetes. Since hypertriglyceridaemia and low HDL levels are typical abnormalities in NIDDM it is a unique target group to test whether lowering of triglycerides and raising of HDL cholesterol levels will reduce the risk of CHD. Therefore there is a pressing need for clinical trials in both IDDM and NIDDM to provide adequate information on the benefits of lipid-lowering therapy and to confirm treatment strategies.