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

Development and External Validation of Machine Learning Models for Diabetic Microvascular Complications: Cross-Sectional Study With Metabolites

BACKGROUND

Diabetic kidney disease (DKD) and diabetic retinopathy (DR) are major diabetic microvascular complications, contributing significantly to morbidity, disability, and mortality worldwide. The kidney and the eye, having similar microvascular structures and physiological and pathogenic features, may experience similar metabolic changes in diabetes.

OBJECTIVE

This study aimed to use machine learning (ML) methods integrated with metabolic data to identify biomarkers associated with DKD and DR in a multiethnic Asian population with diabetes, as well as to improve the performance of DKD and DR detection models beyond traditional risk factors.

METHODS

We used ML algorithms (logistic regression [LR] with Least Absolute Shrinkage and Selection Operator and gradient-boosting decision tree) to analyze 2772 adults with diabetes from the Singapore Epidemiology of Eye Diseases study, a population-based cross-sectional study conducted in Singapore (2004-2011). From 220 circulating metabolites and 19 risk factors, we selected the most important variables associated with DKD (defined as an estimated glomerular filtration rate <60 mL/min/1.73 m2) and DR (defined as an Early Treatment Diabetic Retinopathy Study severity level ≥20). DKD and DR detection models were developed based on the variable selection results and externally validated on a sample of 5843 participants with diabetes from the UK biobank (2007-2010). Machine-learned model performance (area under the receiver operating characteristic curve [AUC] with 95% CI, sensitivity, and specificity) was compared to that of traditional LR adjusted for age, sex, diabetes duration, hemoglobin A1c, systolic blood pressure, and BMI.

RESULTS

Singapore Epidemiology of Eye Diseases participants had a median age of 61.7 (IQR 53.5-69.4) years, with 49.1% (1361/2772) being women, 20.2% (555/2753) having DKD, and 25.4% (685/2693) having DR. UK biobank participants had a median age of 61.0 (IQR 55.0-65.0) years, with 35.8% (2090/5843) being women, 6.7% (374/5570) having DKD, and 6.1% (355/5843) having DR. The ML algorithms identified diabetes duration, insulin usage, age, and tyrosine as the most important factors of both DKD and DR. DKD was additionally associated with cardiovascular disease history, antihypertensive medication use, and 3 metabolites (lactate, citrate, and cholesterol esters to total lipids ratio in intermediate-density lipoprotein), while DR was additionally associated with hemoglobin A1c, blood glucose, pulse pressure, and alanine. Machine-learned models for DKD and DR detection outperformed traditional LR models in both internal (AUC 0.838 vs 0.743 for DKD and 0.790 vs 0.764 for DR) and external validation (AUC 0.791 vs 0.691 for DKD and 0.778 vs 0.760 for DR).

CONCLUSIONS

This study highlighted diabetes duration, insulin usage, age, and circulating tyrosine as important factors in detecting DKD and DR. The integration of ML with biomedical big data enables biomarker discovery and improves disease detection beyond traditional risk factors.

Triglyceride content of lipoprotein subclasses and kidney hemodynamic function and injury in adolescents with type 1 diabetes

AIMS

Elevated triglycerides (TG) are associated with development and progression of kidney disease, and TG distributions across lipoprotein subclasses predict kidney dysfunction in adults with type 1 diabetes (T1D). Little is known regarding these relationships in youth.

METHODS

In this single center study conducted from October 2018-2019, lipid constituents from lipoprotein subclasses were quantified by targeted nuclear magnetic resonance spectroscopy. Glomerular filtration rate (GFR), renal plasma flow (RPF), afferent arteriolar resistance (RA), efferent arteriolar resistance (RE), intraglomerular pressure (PGLO), urine albumin-to-creatinine ratio (UACR), and chitinase-3-like protein 1 (YKL-40), a marker of kidney tubule injury, were assessed. Cross-sectional relationships were assessed by correlation and multivariable linear regression (adjusted for age, sex, HbA1c) models.

RESULTS

Fifty youth with T1D (age 16 ± 3 years, 50 % female, HbA1c 8.7 ± 1.3 %, T1D duration 5.7 ± 2.6 years) were included. Very-low-density lipoprotein (VLDL)-TG concentrations correlated and associated with intraglomerular hemodynamic function markers including GFR, PGLO, UACR, as did small low-density lipoprotein (LDL)-TG and small high-density lipoprotein (HDL)-TG. YKL-40 correlated with all lipoprotein subclasses.

CONCLUSION

TG within lipoprotein subclasses, particularly VLDL, associated with PGLO, GFR, albuminuria, and YKL-40. Lipid perturbations may serve as novel targets to mitigate early kidney disease.

FBXW7 alleviates hyperglycemia-induced endothelial oxidative stress injury via ROS and PARP inhibition

Diabetic retinopathy (DR) and other diabetic vascular complications are the leading cause of death and disability in patients with suboptimum glycemic control. In the pathogenesis of diabetic vascular diseases, hyperglycemia-induced oxidative stress, DNA damage, and poly-ADP-ribose-polymerase (PARP) hyperactivation play important roles in endothelial cell impairment. Adipose differentiation-related protein FBXW7 was reported to regulate PGC-1α stability and mitochondrial homeostasis. Here, we investigated the role and mechanism of FBXW7 in repairing endothelial oxidative stress injuries under hyperglycemic conditions. FBXW7 promoted the hampered activity of homologous recombination and non-homologues end joining pathway for repairing DNA double-strand breaks damage, an initiating factor for PARP hyperactivation and diabetic vascular complications. The abundant mobilization of DNA damage repair mediated by FBXW7 suppressed PARP activation, leading to downregulation of PARP expression and activity in both human endothelial cells and diabetic rat retinas. This provided a new method for PARP inhibition, superior to PARP inhibitors for treating diabetic vascular complication. Furthermore, FBXW7 rescued downregulated NAD+ levels and ameliorated mitochondrial dysfunction, thereby reducing superoxide production under hyperglycemic conditions. These effects reversed oxidative injury and vascular leakage in diabetic rat retina, providing a potential future treatment strategy.

Diabetes Dyslipidemia

Diabetes mellitus is associated with a considerably increased risk of premature atherosclerotic cardiovascular disease. Intensive glycemic control has essentially failed to significantly improve cardiovascular outcomes in clinical trials. Dyslipidemia is common in diabetes and there is strong evidence that cholesterol lowering improves cardiovascular outcomes, even in patients with apparently unremarkable lipid profiles. Here, the authors review the pathophysiology and implications of the alterations in lipoproteins observed in both type 1 and type 2 diabetes, the effect of medications commonly used in the management of diabetes on the lipid profile, the evidence for lifestyle and pharmaceutical interventions, and national and international recommendations for the management of dyslipidemia in patients with diabetes.

Cardiovascular disease and type 1 diabetes: prevalence, prediction and management in an ageing population

Cardiovascular disease (CVD) is a major cause of mortality in type 1 diabetes mellitus (T1D). However, evidence of its risks and management is often extrapolated from studies in type 2 diabetic (T2D) patients or the general population. This approach is unsatisfactory given that the underlying pathology, demographics and natural history of the disease differ between T1D and T2D. Furthermore, with a rising life expectancy, a greater number of T1D patients are exposed to the cardiovascular (CV) risk factors associated with an ageing population. The aim of this review is to examine the existing literature around CVD in T1D. We pay particular attention to CVD prevalence, how well we manage risk, potential biomarkers, and whether the studies included the older aged patients (defined as aged over 65). We also discuss approaches to the management of CV risk in the older aged. The available data suggest a significant CVD burden in patients with T1D and poor management of CV risk factors. This is underpinned by a poor evidence base for therapeutic management of CV risk specifically for patients with T1D, and in the most relevant population - the older aged patients. We would suggest that important areas remain to be addressed, particularly exploring the risks and benefits of therapeutic approaches to CVD management in the older aged.

Exome sequencing identifies novel ApoB loss-of-function mutations causing hypobetalipoproteinemia in type 1 diabetes

AIM

Diabetic patients commonly suffer from disturbances in production and clearance of plasma lipoproteins, known as diabetic dyslipidemia, resulting in an increased risk of coronary heart disease. The study aimed to examine the cause of hypobetalipoproteinemia in two patients with type 1 diabetes.

METHODS

The Diabetes Control and Complications Trial (DCCT) is a study demonstrating that intensive blood glucose control delays the onset and progression of type 1 diabetes complications. Hypobetalipoproteinemia was present in two DCCT subjects, IDs 1427 and 1078, whose LDL-C levels were 36 and 28 mg/dL, respectively, and triglyceride levels were 20 and 28 mg/dL, respectively. We performed exome sequencing on genomic DNA from the two patients with hypobetalipoproteinemia.

RESULTS

The subjects 1427 and 1078 had heterozygous loss-of-function mutations in the gene apolipoprotein B (ApoB), and these mutations resulted in premature stop codons at amino acid 1333 (ApoB-29) and 3680 (ApoB-81), respectively. Indeed, the plasma ApoB level of subject 1427 (19 mg/dL) was the lowest and that of subject 1078 (26 mg/dL) was the second to the lowest among all the 1,441 DCCT participants. Sequencing genomic DNA of family members showed that probands 1427 and 1078 inherited the mutations from the father and the mother, respectively.

CONCLUSIONS

The identification of ApoB loss-of-function mutations in type 1 diabetic patients presents innovative cases to study the interaction between hypobetalipoproteinemia and insulin deficiency.

Atherogenic lipids and vascular complications in a selected diabetic population with normal urinary albumin/creatinine ratios

OBJECTIVE

To test the hypothesis that at different urinary albumin/creatinine ratios within the normal ranges, diabetics have low but similar prevalence of metabolic and micro vascular disease.

METHODS

The study sample consisted of normotensive diabetics not taking any medications known to effect blood pressure and lipids. The data were collected from the Diabetes Register. The diabetics were subgrouped according to the urinary albumin/creatinine ratios. MA is defined as present if the albumin/creatinine ratio (ACR) is more than 2 mg/mmol.

RESULTS

MA was present in 16% of the 152 diabetics. Total cholesterol, systolic BP, and triglycerides were significantly high in diabetics with ACR≥1<2 compared with <1. The prevalence rates for retinopathy and neuropathy in the MA group were also significantly high. However, a large number of diabetics without MA had had established complications (37% retinopathy, 40% neuropathy, and 16% peripheral vascular disease). Because these results were based on single early morning urine samples, we looked at their MA in the past year. After exclusion of regressed and progressed groups, the complications rate remained the same.

CONCLUSION

The high prevalence of metabolic and vascular complications seen even in absence of MA indicates an early intervention and those diabetics should not wait unitl CVD risk scores raise to receive preventive treatment.

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.

Apolipoprotein-defined lipoproteins and apolipoproteins: associations with abnormal albuminuria in type 1 diabetes in the diabetes control and complications trial/epidemiology of diabetes interventions and complications cohort

AIMS

Dyslipoproteinemia has been associated with nephropathy in diabetes, with stronger correlations in men than in women. We aimed to characterize and compare plasma lipoprotein profiles associated with normal and increased albuminuria in men and women using apolipoprotein-defined lipoprotein subclasses and simple apolipoprotein measures.

METHODS

This is a cross-sectional study in a subset (154 women and 282 men) of the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) cohort, using samples obtained in 1997-9. Immunochemical methods were used to quantify plasma apolipoprotein-based lipoprotein subclasses and individual apolipoprotein levels.

RESULTS

In adjusted analyses, elevated Lipoprotein-B (Lp-B) was significantly associated with macroalbuminuria in men [odds ratios (OR) and 95% confidence interval (CI): 2.13 (1.15-3.97)] and women [3.01 (1.11-8.12)], while association with Lp-B:C was observed only in men [1.84 (1.19-2.86)]. For individual apolipoproteins the following significant associations with macroalbuminuria were observed in men only: Apolipoprotein B (ApoB) [1.97 (1.20-3.25)], Apo-AII [0.52 (0.29-0.93)], ApoC-III [1.95 (1.16-3.30)], "ApoC-III in VLDL" (heparin-manganese precipitate) [1.88 (1.16-3.04)], and "ApoCIII in HDL" (heparin-manganese supernatant) [2.03 (1.27-3.26)], all P<0.05).

CONCLUSIONS

Atherogenic apolipoprotein-based profiles are associated with nephropathy in Type 1 diabetic men and to a lesser extent in women. The difference could result from the greater prevalence and severity of dyslipoproteinemia, and from the greater prevalence of renal dysfunction, in men vs women.

Higher levels of small dense low-density lipoprotein (LDL) are associated with cardiac autonomic neuropathy in patients with type 2 diabetes

AIM

To investigate the relationship between small dense LDL cholesterol and cardiac autonomic neuropathy among patients with Type 2 diabetes.

METHODS

A total of 175 patients who had not taken lipid-lowering agents previously were enrolled consecutively in this study. Small dense LDL cholesterol level was measured using polyacrylamide tube gel electrophoresis, which fractionates LDL cholesterol into seven components according to particle size and charge. We analysed the mean LDL cholesterol particle size and the proportion of small dense LDL cholesterol.

RESULTS

The mean (± sd) patient age was 56 (± 14) years, the mean (± sd) duration of diabetes was 10.3 (± 8.3) years, the mean (± sd) proportion of small dense LDL cholesterol was 21.3 (± 17.6)% and the mean (± sd) LDL cholesterol size was 26.33 (± 0.8) nm. Men with cardiac autonomic neuropathy had a longer duration of diabetes compared with those without cardiac autonomic neuropathy. Women with cardiac autonomic neuropathy had a larger waist circumference, higher plasma triglyceride levels, smaller mean (± sd) LDL cholesterol size [26.8 (± 4.3) nm vs 26.4 (± 6.9) nm; P < 0.01] and larger mean (± sd) proportion of small dense LDL cholesterol [10.1 (± 9.9)% vs 19.1 (± 16.8)%; P < 0.01] compared with those without cardiac autonomic neuropathy. After adjusting for other confounding risk factors, the triglyceride/ HDL cholesterol ratio (odds ratio = 1.698, 95% CI: 1.07-2.69; P = 0.025) and mean LDL cholesterol size (odds ratio = 0.873, 95% CI: 0.77-0.99; P = 0.038) remained as independent risk factors for cardiac autonomic neuropathy in women.

CONCLUSIONS

A more atherogenic lipid profile such as the triglyceride: HDL cholesterol ratio and a smaller mean LDL cholesterol particle size were related to the prevalence of cardiac autonomic neuropathy in women with Type 2 diabetes.

Prevalence and control of dyslipidaemia among diabetic patients with microalbuminuria in a Chinese hospital

BACKGROUND

Accumulating evidence indicates that dyslipidaemia plays an important role in the progression of kidney disease in patients with diabetes. Hyperlipidaemia is a risk factor for microalbuminuria in patients with diabetes. Little information exists on the prevalence and control of dyslipidaemia among diabetic patients with microalbuminuria in China. The aims of this study were to investigate the prevalence and control of dyslipidaemia among diabetic patients with microalbuminuria in a Chinese hospital as well as factors affecting the disease.

METHODS

A total of 1060 type 2 diabetic inpatients were assigned to the with-microalbuminuria group (n = 635) or the without-microalbuminuria group on the basis of urinary albumin-to-creatinine ratios (UACRs = 30-299 mg/g). Serum levels and the control of lipid profiles were assessed and classified according to the 2011 American Diabetes Association (ADA) guidelines, and low-density lipoprotein-cholesterol (LDL-C) was also assessed and classified according to Chinese intensified control criteria. Multiple regression analyses were performed to examine the factors affecting lipid variables.

RESULTS

Among patients with microalbuminuria, a significantly lower prevalence was found (33.1% vs. 58.6%; 35.3% vs. 52.5%, all p < 0.001) at target levels [LDL-C < 2.60 mmol/L or high-density lipoprotein-cholesterol (HDL-C) > 1.0 mmol/L for men and >1.3 mmol/L for women]. According to the intensified LDL-C goal (<2.07 mmol/L), a lower prevalence was found in male patients (15.5% vs. 32.7%, p < 0.001). Fewer patients with microalbuminuria were adherent to the therapy prescribed for dyslipidaemia (28.8% vs. 43.3%, p < 0.001). Even among patients who were on lipid-lowering treatment, the majority of individuals remained uncontrolled for all three lipid fractions [LDL-C, HDL-C and triglyceride (TG)] (82.5% vs. 69.0%, p = 0.003). Lipid and lipoprotein parameters were associated with gender and age.

CONCLUSION

In China, diabetic patients with microalbuminuria displayed typical dyslipidaemias and were not adequately controlled. Intensified LDL-C and overall lipid-lowering clinical goals are potential precautions taken against diabetic nephropathy.

Macrovascular angiopathy in children and adolescents with type 1 diabetes

Diabetes represents one of the most common diseases globally. Worryingly, the worldwide incidence of type 1 diabetes (T1D) is rising by 3% per year. Despite the rapid increase in diabetes incidence, recent advances in diabetes treatment have been successful in decreasing morbidity and mortality from diabetes-related retinopathy, nephropathy, and neuropathy. In contrast, there is clear evidence for the lack of improvement in mortality for cardiovascular diseases (CVDs). This emphasizes the importance of focusing childhood diabetes care strategies for the prevention of CVD in adulthood. Furthermore, although most work on diabetes and macrovascular disease relates to type 2 diabetes, it has been shown that the age-adjusted relative risk of CVD in T1D far exceeds that in type 2 diabetes. As T1D appears predominantly during childhood, those with T1D are at greater risk for coronary events early in life and require lifelong medical attention. Because of the important health effects of CVDs in children and adolescents with T1D, patients, family members, and care providers should understand the interaction of T1D and cardiovascular risk. In addition, optimal cardiac care for the patient with diabetes should focus on aggressive management of traditional cardiovascular risk factors to optimize those well-recognized as well as new specific risk factors which are becoming available. Therefore, a complete characterization of the molecular mechanisms involved in the development and progression of macrovascular angiopathy is needed. Furthermore, as vascular abnormalities begin as early as in childhood, potentially modifiable risk factors should be identified at an early stage of vascular disease development.

Competing-risk analysis of ESRD and death among patients with type 1 diabetes and macroalbuminuria

Patients with both type 1 diabetes and CKD have an increased risk of adverse outcomes. The competing risks of death and ESRD may confound the estimates of risk for each outcome. Here, we sought to determine the major predictors of the cumulative incidence of ESRD and pre-ESRD mortality in patients with type 1 diabetes and macroalbuminuria while incorporating the competing risk for the alternate outcome into a Fine-Gray competing-risks analysis. We followed 592 patients with macroalbuminuria for a median of 9.9 years. During this time, 56 (9.5%) patients died and 210 (35.5%) patients developed ESRD. Predictors of incident ESRD, taking baseline renal function and the competing risk for death into account, included an elevated HbA(1c), elevated LDL cholesterol, male sex, weight-adjusted insulin dose, and a shorter duration of diabetes. By contrast, predictors of pre-ESRD death, taking baseline renal function and the competing risk for ESRD into account, included only age, the presence of established macrovascular disease, and elevated cholesterol levels. This competing-risks approach has potential to highlight the appropriate targets and strategies for preventing premature mortality in patients with type 1 diabetes.

Strawberries decrease atherosclerotic markers in subjects with metabolic syndrome

Strawberries have been reported to be potent antioxidants and reduce cardiovascular risk factors, such as elevated blood pressure, hyperglycemia, dyslipidemia, and inflammation in limited studies. We hypothesized that freeze-dried strawberry supplementation will improve blood pressure, impaired glucose, dyslipidemia, or circulating adhesion molecules in obese subjects with metabolic syndrome, thereby lowering cardiovascular risk factors in these subjects. Twenty-seven subjects with metabolic syndrome (2 males and 25 females; body mass index, 37.5 +/- 2.15 kg/m(2); age, 47.0 +/- 3.0 years [means +/- SE]) consumed 4 cups of freeze-dried strawberry beverage (50 g freeze-dried strawberries approximately 3 cups fresh strawberries) or equivalent amounts of fluids (controls, 4 cups of water) daily for 8 weeks in a randomized controlled trial. Anthropometrics and blood pressure measurements, assessment of dietary intakes, and fasting blood draws were conducted at screen and 8 weeks of the study. Strawberry supplementation significantly decreased total and low-density lipoprotein cholesterol (5.8 +/- 0.2 to 5.2 +/- 0.2 mmol/L and 3.5 +/- 0.2 to 3.1 +/- 0.1 mmol/L, respectively [means +/- SE], P < .05) and small low-density lipoprotein particles using nuclear magnetic resonance-determined lipoprotein subclass profile vs controls at 8 weeks (794.6 +/- 94.0 to 681.8 +/- 86.0 nmol/L [means +/- SE], P < .05). Strawberry supplementation further decreased circulating levels of vascular cell adhesion molecule-1 vs controls at 8 weeks (272.7 +/- 17.4 to 223.0 +/- 14.0 ng/mL [means +/- SE], P < .05). Serum glucose, triglycerides, high-density lipoprotein cholesterol, blood pressure, and waist circumference were not affected. Thus, short-term freeze-dried strawberry supplementation improved selected atherosclerotic risk factors, including dyslipidemia and circulating adhesion molecules in subjects with metabolic syndrome, and these results need confirmation in future trials.

Cyclic relationships between diabetic nephropathy and cardiovascular risk factors

The most common cause of death in diabetes is cardiovascular. Diabetic nephropathy has an important role in cardiovascular disease among susceptible diabetic patients. What is not well appreciated is that independent cardiovascular death risk factors (e.g., hypertension, hyperglycemia, dyslipidemias and microalbuminuria) may each have a cyclic relationship with diabetic nephropathy. Thus, as discussed in this review, each risk factor may aggravate diabetic nephropathy, increasing the likelihood of end-stage renal disease. Diabetic nephropathy in turn may aggravate each of the risk factors, increasing the likelihood of a cardiovascular event. These cardiovascular risk factors, amplified by vicious cycles with diabetic nephropathy, may then lead to accelerated cardiovascular morbidity and mortality.

Mild elevations of urine albumin excretion are associated with atherogenic lipoprotein abnormalities in the Multi-Ethnic Study of Atherosclerosis (MESA)

OBJECTIVE

Elevated urine albumin excretion is an established risk factor for cardiovascular disease. Increased cardiovascular risk may be partly mediated by abnormalities in lipoprotein metabolism. We examined cross-sectional associations of urine albumin-creatinine ratio (ACR) with standard lipid measurements and with lipoprotein particle concentrations measured by nuclear magnetic resonance (NMR) in the Multi-Ethnic Study of Atherosclerosis.

METHODS AND RESULTS

Among 5633 participants who were not using lipid-lowering medications, greater ACR was associated with greater triglyceride concentration and lesser high density lipoprotein cholesterol concentration (women only), but not with low density lipoprotein (LDL) cholesterol calculated using conventional methods. In contrast, unadjusted mean small LDL particle concentrations measured by NMR were 770, 827 and 935 nmol/L for women (p<0.001) and 996, 1030 and 1040 nmol/L for men (p=0.037) among participants with normal, high normal and elevated ACR. Adjusting for age, race/ethnicity, diabetes, impaired fasting glucose, hypertension, smoking, medications, body mass index and serum creatinine, each two-fold greater ACR was associated with an increase in small LDL particle concentration of 27 nmol/L for women (p<0.001) and 14 nmol/L for men (p=0.008). Greater ACR was also associated with greater intermediate density lipoprotein particle concentration and smaller mean LDL particle size.

CONCLUSIONS

Mild elevations of urine ACR are associated with atherogenic lipoprotein abnormalities that are not directly observed with a standard lipid panel.

Divergent in vitro and in vivo lipid peroxidation in the postprandial phase of patients with type I diabetes mellitus

OBJECTIVE

The two- to fourfold higher risk of cardiovascular disease in diabetes mellitus is more strongly predicted by the postprandial than by the fasting blood glucose and lipids. We aimed to investigate the impact of postprandial changes in serum lipoprotein fractions on lipid peroxidation in type I diabetes mellitus (T1DM).

DESIGN

This was a prospective observational study.

SETTING

The study was performed at Antwerp University Hospital, Belgium.

SUBJECTS

Twenty-three well-controlled T1DM patients were included.

INTERVENTION

Patients received a standard breakfast and lunch (>50% energy as fat). Blood was sampled at fasting (F), after the post-breakfast hyperglycemic peak (BP), just before lunch (B), after the post-lunch hyperglycemic peak (LP), after the post-lunch dale (LD) and 5 h after lunch (L) for the measurement of serum lipids, lipoprotein subfraction composition, alpha-tocopherol and lipid peroxidation in vivo and in vitro.

RESULTS

Serum triacylglycerols (Tgs) increased (from 1.03+/-0.40 at F to 1.60+/-0.87 mmol/l at LP, P=0.001), but cholesterol decreased by 12% in parallel with alpha-tocopherol (from 4.43+/-0.76 at F to 4.12+/-0.82 micromol/mmol total lipid at B, P=0.006). Although plasma malondialdehyde increased from 1.02+/-0.36 at F to 1.14+/-0.40 micromol/L at LP, P=0.03, copper-induced in vitro peroxidation decreased in the low-density lipoprotein and high-density lipoprotein fractions.

CONCLUSIONS

In well-controlled T1DM patients moderate postprandial increases in serum Tgs are accompanied by a relative deficiency in alpha-tocopherol. Lipid peroxidation in vivo increases but cannot be ascribed to changes in the susceptibility of lipoproteins to copper-induced in vitro peroxidation.

Central obesity, incident microalbuminuria, and change in creatinine clearance in the epidemiology of diabetes interventions and complications study

Weight gain and central obesity are associated with insulin resistance, hypertension, and dyslipidemia in type 1 diabetes. These metabolic abnormalities are risk factors for kidney disease in the general population, but data addressing the relationship of central obesity with kidney disease in type 1 diabetes are limited. Whether waist circumference is associated with incident microalbuminuria and change in creatinine clearance was examined among 1279 participants who had type 1 diabetes and were enrolled in the Epidemiology of Diabetes Interventions and Complications Study, the observational extension of the Diabetes Control and Complications Trial (DCCT). Ninety-three of 1105 participants with normal albumin excretion rate (AER) at DCCT closeout developed incident microalbuminuria over 5.8 yr of follow-up. The hazard ratio for incident microalbuminuria that was associated with each 10-cm greater waist circumference at DCCT closeout was 1.34 (95% confidence interval 1.07 to 1.68), after adjustment for DCCT closeout age, gender, duration of diabetes, treatment group, smoking status, glycosylated hemoglobin, and AER. This increased risk was modestly attenuated when additional adjustment was made for levels of BP and serum lipids. Creatinine clearance declined by an average of 0.34 ml/min per 1.73 m2 each yr over 8 yr of follow-up. Greater rate of decline in creatinine clearance was associated with greater age, conventional insulin therapy during the DCCT, smoking, and greater glycosylated hemoglobin and AER at DCCT closeout but not with waist circumference. In conclusion, waist circumference predicts the subsequent development of microalbuminuria in type 1 diabetes. In contrast, no association of waist circumference with decline in creatinine clearance was observed.

Clinical importance and therapeutic modulation of small dense low-density lipoprotein particles

The National Cholesterol Education Programme Adult Treatment Panel III accepted the predominance of small dense low-density lipoprotein (sdLDL) as an emerging cardiovascular disease (CVD) risk factor. Most studies suggest that measuring low-density lipoprotein (LDL) particle size, sdLDL cholesterol content and LDL particle number provides additional assessment of CVD risk. Therapeutic modulation of small LDL size, number and distribution may decrease CVD risk; however, no definitive causal relationship is established, probably due to the close association between sdLDL and triglycerides and other risk factors (e.g., high-density lipoprotein, insulin resistance and diabetes). This review addresses the formation and measurement of sdLDL, as well as the relationship between sdLDL particles and CVD. The effect of hypolipidaemic (statins, fibrates and ezetimibe) and hypoglycaemic (glitazones) agents on LDL size and distribution is also discussed.

Microalbuminuria

Microalbuminuria, originally described more than 3 decades ago as a predictor of nephropathy in patients who had type 1 diabetes mellitus and associated with higher cardiovascular risk, is now linked with increased risk for cardiovascular events rather than progression to end-stage kidney disease. This article reviews the role of microalbuminuria in the context of atherosclerotic vascular disease. It presents the methods for microalbuminuria assessment in clinical practice, its relations with other cardiovascular risk factors, and the pathophysiologic associations between microalbuminuria and vascular damage. In addition, this article discusses the prognostic significance of microalbuminuria for cardiovascular disease as well as existing therapeutic interventions for reducing urine albumin excretion in patients who are at high cardiovascular risk.

Serum lipids and the progression of nephropathy in type 1 diabetes

OBJECTIVE

Dyslipidemia contributes to the progression of microvascular disease in diabetes. However, different lipid variables may be important at different stages of nephropathy. This study examines the pattern of dyslipidemia associated with the progression of nephropathy in patients with type 1 diabetes.

RESEARCH DESIGN AND METHODS

A total of 152 patients with type 1 diabetes were recruited in order to represent various phases of nephropathy. Patients were followed for 8-9 years, during which time they received standard care. Renal progression was defined a priori as a doubling in albumin excretion (in patients with normo- or microalbuminuria) or a decline in creatinine clearance (in those with macroalbuminuria). A panel of lipid variables was determined and correlated with indexes of progression.

RESULTS

In patients with normoalbuminuria (n = 66), progression was associated with male sex (P < 0.05), borderline albuminuria (P = 0.02), and LDL-free cholesterol (P = 0.02). In patients with microalbuminuria (n = 51), progression was independently associated with triglyceride content of VLDL and intermediate-density lipoprotein (both P < 0.05). In patients with macroalbuminuria (n = 36), a significant decline in the renal function (>3 ml x min(-1) x year(-1)) was independently associated with poor glycemic control, hypertension, and LDL size (P < 0.05). When all patients with progressive nephropathy were analyzed together, only LDL cholesterol was predictive on multivariate analysis (P < 0.05), which masked the importance of triglyceride enrichment in microalbuminuria.

CONCLUSIONS

Lipid variables are associated with progression of diabetic kidney disease, but the relationship is not the same at all stages. This finding has implications for the design of renoprotective strategies and the interpretation of clinical trials in type 1 diabetes.

Spectrum and prevalence of atherogenic risk factors in 27,358 children, adolescents, and young adults with type 1 diabetes: cross-sectional data from the German diabetes documentation and quality management system (DPV)

OBJECTIVE

The aim of this data analysis was to ascertain the type and prevalence rate as well as age and sex distribution of cardiovascular risk factors in type 1 diabetic patients up to 26 years of age.

RESEARCH DESIGN AND METHODS

Cardiovascular risk factors such as obesity, hypertension, dyslipidemia, poor glycemic control, and smoking were analyzed in 27,358 patients who were divided into three groups (prepubertal, pubertal, and adult) using specifically designed diabetes software for prospective disease documentation.

RESULTS

More than half of the patients per age-group had at least one cardiovascular risk factor. Two risk factors were age dependently found in 6.2-21.7% and three or four risk factors in 0.5-4.7%. Elevated values of HbA(1c), total cholesterol, and BMI were found most frequently. Hypertension, smoking, and HDL cholesterol were observed more frequently in males, and elevated BMI, total cholesterol, and LDL cholesterol more often in females. Although 28.6% of the patients had dyslipidemia, merely 0.4% of them received medical treatment, and of the 8.1% of the patients with hypertension, only 2.1% of them were given antihypertensive medication.

CONCLUSIONS

With increasing age, a greater number of patients with cardiovascular risk factors were observed. Significant sex differences were seen in the majority of risk factors. Despite the high prevalence of risk factors, only a small minority of patients received antihypertensive or lipid-lowering treatment. Early identification, prevention, and treatment of additional risk factors seem to be necessary, particularly in light of the high incidence of future cardiovascular disease.

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.

Cardiovascular disease morbidity and mortality in patients with type 1 diabetes mellitus : management strategies

There is an increased risk of cardiovascular disease (CVD) mortality and morbidity in patients with type 1 diabetes mellitus compared with the general population as shown by epidemiologic studies measuring cardiovascular endpoints, as well as by autopsy, angiographic, and coronary calcification studies. Most of the excess CVD risk associated with type 1 diabetes is concentrated in the subset of approximately 35% of patients who develop diabetic nephropathy (after 20 years of diabetes duration), who also typically have dyslipidemias, elevated blood pressure, and hyperglycemia, factors contributing to CVD. For reasons that remain speculative, the relative risks from CVD are higher in women than in men with type 1 diabetes compared with the general population, which effectively eliminates the gender differences in CVD. As in the general population and in patients with type 2 diabetes, education and lifestyle changes, interventions to reduce hyperglycemia, blood pressure, micro-albuminuria, lipid control, and the use of aspirin are important management areas in order to reduce the increased risk of CVD. Whether management with aspirin and statins should be started in type 1 diabetic patients at a younger age or at a lower risk score than in the general population is still under investigation. There is a need for a better understanding of the pathophysiology of vascular complications in type 1 diabetes, more specific risk engines in type 1 diabetes, and accurate estimations of the absolute and relative risk for CVD in order to improve management of CVD in these high-risk patients.

Traditional and nontraditional cardiovascular risk factors in chronic kidney disease

Chronic kidney disease (CKD) is public health problem, with as many as 20 million individuals affected in the United States. Patients with CKD should be considered in the highest-risk group for development of cardiovascular disease (CVD), and aggressive treatment of traditional and nontraditional risk factors should be instituted. Additional randomized controlled trials are urgently needed to evaluate potential treatments in this population. This article focuses attention on the major modifiable cardiovascular risk factors in CKD.

Lipoprotein composition in children and adolescents with type 1 diabetes mellitus

Atherosclerotic cardiovascular diseases are the major causes of morbidity and mortality in patients with diabetes mellitus. Both quantitative and qualitative abnormalities of lipo-proteins are associated with the development of atherogenesis. In this study, the prevalence of dyslipidemia and the relative levels of glycosylated lipoproteins in 20 children and adolescents with type 1 diabetes mellitus were determined. Lipid profile, apolipoproteins A-I and B, Lp(a) and LpA-I in plasma were assayed. LpB and glycosylated HDL and LDL were evaluated by ELISA. Diabetic patients and controls had normal lipid profiles, but the diabetic group showed significantly higher LpA-I and lower LpA-I:A-II concentrations than controls. The diabetic group showed a significantly higher glycosylation level of HDL than controls and did not show a statistical difference for glycosylated LDL. No significant correlation between glycosylated lipoproteins, glycemia or HbA1c was found. In conclusion, these results suggest that type 1 diabetic patients develop important qualitative lipid abnormalities.

Is proteinuria a plausible target of therapy?

Microalbuminuria is an independent marker of cardiovascular risk, irrespective of kidney disease. Recent pharmacologic interventions have resulted in a significant delay and even an arrest in the progression of microalbuminuria to macroalbuminuria or to chronic kidney disease. Focus should be placed on agents that not only lower blood pressure but also improve albuminuria levels. Current guidelines recommend that hypertensive patients with renal disease should be started on agents that block the renin-angiotensin-aldosterone system, such as angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs). The use of three to four different agents is frequently necessary to reach the guideline goal blood pressure of 130/80 mm Hg.

Serum cystatin C level is a marker of end-organ damage in patients with essential hypertension

High urinary albumin excretion rate (AER) has been associated with the presence of atherosclerotic vascular damages and is an independent risk factor for all causes of death and cardiovascular morbidity and mortality in essential hypertensive patients. Serum cystatin C (s-CC) is a recently identified nonglycosylated 13-kD basic protein that has been suggested to be a useful marker of glomerular filtration rate. In the present study, we investigated the relationship between s-CC level and end-organ damages in the kidney, heart, and vessels of patients with essential hypertension. Sixty patients with essential hypertension participated in the present study. Patients with renal failure were excluded. Serum-CC level was measured by a particle-enhanced turbidimetric assay. Left ventricular mass index (LVMI) and intima media thickness (IMT) in the common carotid arteries were evaluated by ultrasound images. Twenty-four-hour blood pressure was measured by a cuff-oscillometric method. Serum-CC level was negatively correlated with creatinine clearance (r=-0.617, p<0.0001). It was also correlated with mean 24-h systolic blood pressure (24h-SBP) (r=0.308, p= 0.0167), LVMI (r=0.528, p<0.0001), and IMT (r=0.539, p<0.0001). Both AER and s-CC level were independently associated with mean 24h-SBP. AER but not s-CC level was associated with HDL-cholesterol. The present study was the first to demonstrate that s-CC level is a useful and convenient parameter of renal function, and may also prove to be an early marker of the severity of end-organ damage in patients with essential hypertension.

Effect of glycated LDL on microvascular tone in mice: a comparative study with LDL modified in vitro or isolated from diabetic patients

AIMS/HYPOTHESIS

In vitro studies have suggested that glycation of LDL might be implicated in diabetic microangiopathy. We therefore investigated the in vivo effects of LDL glycated in vitro on the mouse skeletal muscle arteriolar tone. Since glycation naturally occurs during diabetes, we also tested the effects of LDL isolated from diabetic patients.

METHODS

In anaesthetized mice, the spinotrapezius muscle microcirculation was observed, in situ, using the orthogonal polarization spectral imaging technology. The diameter of terminal (<20 microm) and small arterioles (20-40 microm) was measured before and after a bolus intravenous injection of glycated LDL followed by a continuous perfusion (115 micro g/kg/min).

RESULTS

A slight decrease of terminal and small arterioles diameter (<10%) was observed with native LDL and LDL isolated from healthy subjects. In contrast, mildly glycated LDL induced a clear vasoconstriction of arterioles (>15%), which was further increased when highly glycated LDL was perfused (>22%). LDL isolated from diabetic patients mimicked the vasoconstriction obtained with in vitro mildly glycated LDL, which underwent similar glycation as those isolated from diabetic patients.

CONCLUSION/INTERPRETATION

Our results show in vivo that acute perfusion of both types of glycated LDL (artificially or naturally modified), cause major microvascular modification by enhancing arteriolar tone in skeletal muscle. These findings highlight a new role of glycated LDL at the level of microvessels. We suggest that glycation of LDL could contribute to the impaired vascular reactivity observed in diabetes.

Effects of Atorvastatin on LDL sub-fractions and peroxidation in type 1 diabetic patients: a randomised double-blind placebo-controlled study

BACKGROUND

Patients with diabetes have an increased risk of both developing and dying from cardiovascular disease, and, currently, more aggressive lipid-lowering targets are being recommended for these patients. Statins are widely and successfully used to correct dyslipidemia and prevent acute coronary episodes, but their effects on lipoprotein composition and peroxidation have not been fully investigated. We aimed to address this issue in type 1 diabetes mellitus.

METHODS

T1DM patients with atherogenic index (total/HDL-cholesterol > 4) were randomised double-blindly to group A (n = 12) that received Atorvastatin 40 mg/day and group P (n = 12) that received placebo. They were monitored for blood biochemistry, LDL sub-fractions and lipid peroxidation at inclusion, after 6 and after 12 weeks.

RESULTS

In group A, the 40% decrease in serum total and LDL cholesterol and 20% decrease in triglycerides was accompanied by a decrease in serum alpha-tocopherol from 46.4 +/- 16.3 (mean +/- SD) at inclusion to 32.2 +/- 11.8 and 32.6 +/- 14.0 micromol/L after 6 and 12 weeks respectively (p < 0.001 compared to group P by repeated-measures ANOVA). Relative to LDL + VLDL cholesterol, alpha-tocopherol increased by 40% (p < 0.001). Copper-induced LDL + VLDL peroxidation increased from 4891 +/- 1325 at inclusion to 6821 +/- 2291 and 7040 +/- 1712 nmol TBARS/mg LDL + VLDL cholesterol produced in 3 h (p = 0.004). LDL sub-fractions shifted towards the less dense regions (p = 0.03).

CONCLUSIONS

These results suggest that Atorvastatin lowers the antioxidant capacity of LDL and VLDL in T1DM. The mechanisms underlying these changes merit further investigation and should be taken into account when planning long-term primary prevention of CHD in diabetes.

Effect of diabetes on uremic dyslipidemia

Elevated intermediate-density lipoprotein (IDL), a remnant lipoprotein, is an independent risk factor for atherosclerosis in patients with end-stage renal disease (ESRD). Since the presence of diabetes mellitus further increases the risk of cardiovascular mortality in ESRD, we examined the effect of diabetes on IDL among ESRD patients. The subjects were 330 healthy control subjects and 287 patients with end-stage renal disease including 80 patients with type 2 diabetes. As compared with the healthy subjects, the nondiabetic ESRD patients had increased plasma triglyceride and IDL cholesterol. Diabetic patients with ESRD showed a further increase in plasma triglyceride and IDL cholesterol compared with the nondiabetic group. However, the difference in IDL levels between the ESRD groups was no longer significant when subjects were stratified by plasma triglyceride. Plasma triglyceride was correlated with IDL cholesterol. Increased hemoglobin A(1c) was significantly associated with IDL cholesterol in a multiple regression model including age, gender, and the presence of ESRD. Such an association was no longer significant in another model including plasma triglyceride as an additional covariate. Further analysis indicated the positive effects of diabetes and hyperglycemia on plasma triglyceride. These results indicate that increased IDL in ESRD is further deteriorated in the presence of diabetes, and that the adverse effect is accounted for at least partly by hypertriglyceridemia associated with chronic hyperglycemia.

Lipoproteins in the DCCT/EDIC cohort: associations with diabetic nephropathy

BACKGROUND

Lipoproteins may contribute to diabetic nephropathy. Nuclear magnetic resonance (NMR) can quantify subclasses and mean particle size of very low density lipoprotein (VLDL), low density lipoprotein (LDL), and high density lipoprotein (HDL), and LDL particle concentration. The relationship between detailed lipoprotein analyses and diabetic nephropathy is of interest.

METHODS

In a cross-sectional study, lipoproteins from 428 women and 540 men from the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) cohort were characterized by conventional lipid enzymology, NMR, apolipoprotein levels, and LDL oxidizibility. Linear regression was performed for each lipoprotein parameter versus log albumin excretion rate (AER), with and without covariates for age, diabetes duration, HbA1c, hypertension, body mass index, waist-hip ratio, and DCCT treatment group. Significance was taken at P < 0.05.

RESULTS

By multivariate analysis, conventional profile, total triglycerides, total- and LDL cholesterol, but not HDL cholesterol, were associated with AER. NMR-determined large, medium, and small VLDL were associated with AER in both genders (except large VLDL in women), and intermediate density lipoprotein (IDL) was associated with AER (men only). LDL particle concentration and ApoB were positively associated with AER (in men and in the total cohort), and there was a borderline inverse association between LDL diameter and AER in men. Small HDL was positively associated with AER and a borderline negative association was found for large HDL. No associations were found with ApoA1, Lp(a), or LDL oxidizibility.

CONCLUSION

Potentially atherogenic lipoprotein profiles are associated with renal dysfunction in type 1 diabetes and further details are gained from NMR analysis. Longitudinal studies are needed to determine if dyslipoproteinemia can predict patients at risk of nephropathy, or if lipoprotein-related interventions retard nephropathy.

Serum lipoproteins in the diabetes control and complications trial/epidemiology of diabetes intervention and complications cohort: associations with gender and glycemia

OBJECTIVE

To relate the nuclear magnetic resonance (NMR)-determined lipoprotein profile, conventional lipid and apolipoprotein measures, and in vitro oxidizibility of LDL with gender and glycemia in type 1 diabetes.

RESEARCH DESIGN AND METHODS

In the 1997-1999 Diabetes Control and Complications Trial/Epidemiology of Diabetes Intervention and Complications (DCCT/EDIC) cohort, serum from 428 women and 540 men were characterized by conventional lipids, NMR, apolipoprotein levels, and LDL susceptibility to in vitro oxidation. Simple and partial correlation coefficients were calculated for each lipoprotein-related parameter versus gender, with and without covariates (age, diabetes duration, concurrent HbA(1c), DCCT randomization, hypertension, BMI, waist-to-hip ratio, and albuminuria). For concurrent HbA(1c), data were analyzed as above, exchanging gender for HbA(1c). Associations were significant if P < 0.05.

RESULTS

Although men and women had similar total and LDL cholesterol and triglycerides, men exhibited the following significant percent differences in NMR profiles versus women: small VLDL 41; IDL -30; medium LDL 39; small LDL 21; large HDL -32; small HDL 35; LDL particle concentration 4; VLDL and HDL diameters -8 and -4, respectively. Small VLDL, small HDL, medium LDL (women only), small LDL (men only), and LDL particle concentration were positively correlated, and HDL size was inversely correlated, with concurrent HbA(1c). NMR profile was unrelated to prior DCCT randomization. Susceptibility of LDL to oxidation was unrelated to gender and glycemia.

CONCLUSIONS

Male gender and poor glycemia are associated with a potentially more atherogenic NMR lipoprotein profile. Neither gender nor glycemia influence LDL oxidation in vitro.

Paraoxonase gene cluster is a genetic marker for early microvascular complications in type 1 diabetes

BACKGROUND

Paraoxonase is a serum enzyme, which prevents oxidation of low-density lipoprotein (LDL) by hydrolyzing lipid peroxides. Two polymorphisms in PON1 gene have been associated with cardiovascular and microvascular diseases in both diabetic and non-diabetic patients.

AIMS

The current project was designed to investigate the association between the polymorphisms of two PON genes and diabetes microvascular diseases (retinopathy and microalbuminuria) and any potential linkage between Met54Leu of PON1 and Cys311Ser of PON2 gene.

METHODS

Diabetic retinopathy and albumin excretion rate were assessed in 372 adolescents with Type 1 diabetes who were genotyped for the two polymorphisms.

RESULTS

We confirmed the increased susceptibility for diabetic retinopathy for the Leu/Leu genotype (odds ratio (OR) 3.34 (confidence interval (CI) 1.95, 5.75), P < 0.0001). The Ser/Ser genotype was significantly more common in those patients with microalbuminuria (albumin excretion rate > or = 20 microg/min) compared with those with albumin excretion rate < 20 microg/min (OR 4.72 (CI 2.65, 8.41), P < 0.0001). The Ser311 of PON2 was in strong linkage disequilibrium with Leu54 of PON1 gene (Delta = 23 x 10(4), P < 0.001). The delta value was higher for those without complications (28 x 104, P < 0.001) compared with those with complications (15.5 x 10(4), P < 0.001).

CONCLUSIONS

This study supports the hypothesis that diabetic microangiopathy is genetically heterogeneous. PON1 Leu/Leu increases the risk for retinopathy and PON2 Ser/Ser increases the risk for microalbuminuria.

Microalbuminuria: marker of vascular dysfunction, risk factor for cardiovascular disease

Based on the data from large single and multi-center clinical trials, including the Heart Outcomes Prevention Evaluation (HOPE) study, it is clear that the presence of microalbuminuria is a signal from the kidney that cardiovascular risk is increased and that vascular responses are altered. This is exemplified by studies that have demonstrated that the compensatory vasodilation seen following relief from prolonged ischemia or infusion of vasodilators such as nitroglycerin is blunted in people with microalbuminuria. Thus, the presence of between 30 and 299 mg/day of albumin in the urine is associated with abnormal vascular responsiveness, which may be the result of more advanced atherosclerosis and not necessarily related to the presence of hypertension or renal disease. Agents known to reduce the rise in microalbuminuria or actually reduce the level of microalbuminuria, such as ACE inhibitors, angiotensin receptor blockers, HMG-CoA reductase inhibitors, beta blockers, non-dihydropyridine calcium channel blockers and diuretics, have all been shown to reduce cardiovascular mortality and in some cases preserve renal function. This article will present an overview of the data that support the assertion that a reduction in the rise of microalbuminuria is a significant consideration in the selection of agents to treat a given risk factor (cholesterol or blood pressure) to a recommended target goal. Achieving such a goal with agents that also impact microalbuminuria will provide for a more complete cardiovascular risk reduction.

Differing associations of lipid and lipoprotein disturbances with the macrovascular and microvascular complications of type 1 diabetes

OBJECTIVE

Cardiovascular disease (CVD) is increased in patients with type 1 diabetes, but lipid and lipoprotein patterns remain favorable. In contrast, nephropathy is associated with an adverse distribution. We compared the associations and predictive power of lipid and lipoprotein disturbances with these complications.

RESEARCH DESIGN AND METHODS

A nested case-control study from the EURODIAB cohort of 140 case subjects with evidence of at least one complication and 84 control subjects with no complications were analyzed. Conventional and unconventional lipid and lipoprotein fractions, including apolipoprotein (apo)-A1, lipoprotein (Lp)-A1, LpA1/A2, apoB, and LDL particle size were measured centrally.

RESULTS

CVD was only associated with increased LDL cholesterol (3.6 vs. 3.0 mmol/l, P = 0.02). In contrast, albuminuria was associated with elevated cholesterol, triglyceride, LDL, and apoB and with diminished LDL particle size. No disturbances in HDL and related lipoproteins were noted. In normoalbuminuric patients, CVD was not associated with any significant changes in lipids. CVD in macroalbuminuric patients was associated with increased triglyceride level (2.37 vs. 1.07 mmol/l, P = 0.001; P = 0.02 for CVD/albuminuria interaction) and LDL cholesterol (5.4 vs. 3.3 mmol/l, P = 0.005; P = 0.004 for interaction). Independent associations were observed for total cholesterol and for LDL particle size and albuminuria.

CONCLUSIONS

Abnormalities in lipid and lipoprotein disturbances are more closely related to albuminuria than to CVD in patients with type 1 diabetes. Measurement of conventional parameters provide sufficient risk information. ApoB and LDL particle size offer limited extra information. HDL metabolism remains undisturbed in the presence of complications. These changes reflect associations with glycemic control, which is the key to understanding lipid and lipoprotein disturbances.

Microalbuminuria in type 1 diabetes: rates, risk factors and glycemic threshold

BACKGROUND

The occurrence of microalbuminuria in type 1 diabetes is strongly predictive of renal and cardiovascular disease and is still likely to occur despite improvements in glycemic control. A better understanding of microalbuminuria is required to inform new interventions. We determined the incidence and risk factors for microalbuminuria [albumin excretion rate (AER) 20 to 200 microg/min] in the EURODIAB Prospective Complications Study.

METHODS

This is a seven-year follow-up (between 1988 and 1991) of 1134 normoalbuminuric men and women (aged 15 to 60) with type 1 diabetes from 31 European centers. Risk factors and AER were measured centrally.

RESULTS

The incidence of microalbuminuria was 12.6% over 7.3 years. Independent baseline risk factors were HbA1c (7.1 vs. 6.2%, P = 0.0001) and AER (9.6 vs. 7.8 microg/min, P = 0.0001) and, independent of these, fasting triglyceride (0.99 vs. 0.88 mmol/L, P = 0.01), low-density lipoprotein cholesterol (3.5 vs. 3.2 mmol/L, P = 0.02), body mass index (24.0 vs. 23.4 kg/m2, P = 0.01), and waist to hip ratio (WHR; 0.85 vs. 0.83, P = 0.009). Triglyceride and WHR risk factors were nearly as strong as AER in predicting microalbuminuria (standardized regression effects of 1.3 for triglyceride and WHR and 1.5 for AER). Blood pressure at follow-up, but not at baseline, was also raised in those who progressed. There was no evidence of a threshold of HbA1c on microalbuminuria risk.

CONCLUSIONS

The incidence of microalbuminuria in patients with type 1 diabetes remains high, and there is no apparent glycemic threshold for it. Markers of insulin resistance, such as triglyceride and WHR, are strong risk factors. Systemic blood pressure is not raised prior to the onset of microalbuminuria.

Microalbuminuria: what is it? Why is it important? What should be done about it?

Microalbuminuria (MA) is defined as persistent elevation of albumin in the urine, of 30-300 mg/day (20-200 microg/min). These values are less than the values detected by routine urine dipstick testing, which does not become positive until protein excretion exceeds 300-500 mg/day. Use of the albumin-to-creatinine ratio is recommended as the preferred screening strategy for all diabetic patients. MA is measured in spot morning urine obtained from the patient in the office and sent for measurement of both albumin and creatinine. A value above 0.03 mg/mg suggests that albumin excretion is above 30 mg/day and therefore MA is present. MA should be checked annually in everyone, and every 6 months within the first year of treatment to assess the impact in patients started on antihypertensive therapy. MA is an established risk factor for renal disease progression in type 1 diabetes and its presence is the earliest clinical sign of diabetic nephropathy. In addition, a number of studies suggest that MA is an important risk factor for cardiovascular disease and defines a group at high risk for early cardiovascular mortality in both type 2 diabetes and essential hypertension. MA also signifies abnormal vascular permeability and the presence of atherosclerosis. Among nondiabetic patients with essential hypertension, MA is associated with higher blood pressures, increased serum total cholesterol, and reduced serum high-density lipoprotein cholesterol. Thus, taken together these data support the concept that the presence of MA is the kidney's notice to the physician/patient that there is a problem with the vasculature. MA can be reduced, and progression to overt proteinuria prevented, by aggressive blood pressure reduction. The National Kidney Foundation recommends that blood pressure levels be maintained at or below 130/80 mm Hg in anyone with diabetes or renal disease. This should be accomplished with antihypertensive agents that prevent the rise in MA and hence prevent development of proteinuria. Such agents are angiotensin-converting enzyme inhibitors, angiotensin receptor blockers and, to a lesser extent, Beta blockers, non-dihydropyridine calcium antagonists, and diuretics. In summary, the presence of MA is a marker of endothelial dysfunction and a harbinger of markedly enhanced cardiovascular risk. All patients with diabetes and/or hypertension should be screened for the presence of microalbuminuria with use of spot morning urine. To maximize prevention of MA development, the following goals should be instituted: 1) blood pressure should be maintained at less than 130/80 mm Hg and a low-salt, moderate-potassium diet instituted; 2) in diabetics, HbA1c should be kept at less than 7%; 3) in obese patients, a weight loss program should be implemented, with a goal BMI of less than 30; and 4) the physician and patient, working together, should maintain low-density lipoprotein cholesterol at less than 120 mg/dL, and less than 100 mg/dL if diabetes is present. (c)2001 by Le Jacq Communications, Inc.

Therapeutic modulation of low-density lipoprotein size

Small, dense LDL particles have been linked to atherosclerosis, often in a cluster of risk factors and affecting approximately 20% of adults. Over the past year, studies confirmed that small dense LDL is an autosomal dominant trait, influenced mainly by hypertriglyceridaemia and obesity, insulin resistance and diabetes mellitus and some incompletely investigated genetic loci. Compositional and functional differences have been observed in small LDL. Evidence is emerging that lifestyle as well as pharmacological intervention can modulate LDL size, but there is no proof yet that this is of clinical benefit.