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

Advanced lipoprotein profile identifies atherosclerosis better than conventional lipids in type 1 diabetes at high cardiovascular risk

BACKGROUND AND AIMS

People with type 1 diabetes (T1D) present lipoprotein disturbances that could contribute to their increased cardiovascular disease (CVD) risk. We evaluated the relationship between lipoprotein alterations and atherosclerosis in patients with T1D.

METHODS AND RESULTS

Cross-sectional study in subjects with T1D, without previous CVD, but high-risk (≥40 years, nephropathy, or ≥10 years of evolution of diabetes with another risk factor). The presence of plaque (intima-media thickness ≥1.5 mm) in the different carotid segments was determined by ultrasound. The advanced lipoprotein profile was analysed by magnetic resonance imaging (¹H NMR). We included 189 patients (42% women, 47.8 ± 10.7 years, duration of diabetes 27.3 ± 10.1 years, HbA1c 7.5% [7-8]). Those with carotid plaques (35%) were older, with longer diabetes duration, had a higher prevalence of hypertension, and showed lower and smaller LDL particles (LDL-P) and HDL particles (HDL-P), but higher VLDL particles (VLDL-P). Some LDL, HDL and VLDL-related parameters were associated with atherosclerosis in sex, age and statin use adjusted models (p < 0.05), but after adjusting for multiple confounders, including conventional lipid parameters, only HDL-P (OR 0.440 [0.204-0.951]; p = 0.037), medium HDL-P (OR 0.754 [0.590-0.963]; p = 0.024), HDL-P cholesterol content (OR 0.692 [0.495-0.968]; p = 0.032), ¹H NMR LDL-P number/conventional LDL-cholesterol (OR 1.144 [1.026-1.275]; p = 0.015), and ¹H NMR non-HDL particle number/conventional non-HDL-cholesterol ratios (OR 1.178 [1.019-1.361], p = 0.026) remained associated with atherosclerosis.

CONCLUSIONS

In adults with T1D at high-risk, variables related to HDL, LDL and total atherogenic particle number are independently associated with preclinical atherosclerosis. Advanced lipoprotein profiling could be used to identify those at the highest risk of CVD.

Children and adolescents with diabetes at Tygerberg Hospital – at risk of cardiovascular complications?

Background. In South Africa, the prevalence of dyslipidaemia and hypertension (HT) in paediatric diabetes patients is unknown. Objectives. To determine the prevalence of dyslipidaemia and HT in paediatric diabetic patients seen at Tygerberg Hospital (TBH) and establish whether either is associated with body mass index (BMI), glycosylated haemoglobin (HbA1c) or duration of diabetes. Further, to determine whether the prevalence differs between two specified periods.Methods. A retrospective study of 154 diabetic patients, aged 1 - 19 years, seen at TBH between 2007 and 2017, was undertaken. The following data were recorded: age; sex; duration of disease (time since diagnosis); height; weight; blood pressure; HbA1c; high-density lipoprotein cholesterol (HDL-C); triglycerides (TG); and low-density lipoprotein cholesterol (LDL-C).Results. More than half of the patients (57.8%; n=89/154; 95% confidence interval (CI) 51.7 - 65.0) had dyslipidaemia, 16.3% (n=24/147) had low HDL-C levels, 53.8% (n=78/145) had high LDL-C levels and 14.9% (n=22/148) had raised TG levels. Nearly half of the patients (48.7%; n=75/154; 95% CI 41.6 - 55.1) were hypertensive and 93.5% (n=144/154) were poorly controlled (HbA1c >7.5%). Dyslipidaemia was not associated with HT or BMI percentile and its prevalence did not change between the two specified periods. Prevalence of dyslipidaemia and HT was not associated with duration of diabetes. About one-third (30.8% (n=4/13); 95% CI 11.9 - 59.3) of the pre-adolescents and 60.3% (n=85/141; 95% CI 51.9 - 68.1) of the adolescents had dyslipidaemia (p=0.04). Dyslipidaemia was diagnosed in 62.6% (n=82/131) of adolescents with poorly controlled diabetes (p=0.04) and in 71.7% (95% CI 59.0 - 81.7) of patients ≥16 years of age (p=0.005).Conclusions. Poor glycaemic control, dyslipidaemia and HT are common in diabetic children, putting them at risk of cardiovascular complications in adulthood.

Obesity and Diabetic Complications: A Study from the Nationwide Diabetes Report of the National Program for Prevention and Control of Diabetes (NPPCD-2021) Implications for Action on Multiple Scales

BACKGROUND

Obesity plays a major role in the pathogenesis and development of macro- and microvascular complications of type 2 diabetes (T2D) and type 1 diabetes (T1D). We aimed to assess the association between obesity and macrovascular and microvascular complications of diabetes.

METHODS

This study consisted of 111,830 patients (age range: 1-106) with diabetes including 10,641 T1D (3187 obese [38.2% men] and 7454 non-obese [45.5% men]) and 101,189 T2D (51,873 obese [27.5% men] and 49,316 non-obese [33.4% men]) from the National Program for Prevention and Control of Diabetes (NPPCD-2021) in Iran, who attended academic tertiary care outpatient clinics from February 2016 to April 2021. A pooled logistic regression model was used to examine the association between obesity and diabetic complications.

RESULTS

Among patients with T1D, a significant association was found between obesity and cardiovascular disease (CVD), neuropathy, nephropathy and retinopathy (OR= 1.75, 1.56, 1.80 and 1.92, P-value= 0.001, 0.004, 0.001 and <0.001, respectively). In T2D, a statistically significant association was found between obesity and CVD, neuropathy and nephropathy (OR= 1.63, 1.98, 1.21, respectively, P-values <0.001).

CONCLUSION

Obesity was independently associated with CVD, neuropathy and nephropathy in patients with T1D and T2D and with retinopathy only in T1D, to different degrees. The association between obesity and retinopathy and neuropathy was the strongest among T1D and T2D, respectively. Findings from this study suggest that obesity affects diabetic complications differently among the two types of diabetes, in terms of epidemiology and pathophysiology. This signifies the importance of different preventive and therapeutic approaches to obesity in T1D compared to T2D, on a national and global scale.

Antiplatelet and Antithrombotic Therapy in Type I Diabetes Mellitus: Update on Current Data

Diabetes mellitus type 1 (T1DM) is an autoimmune disease characterized by a markedly elevated cardiovascular (CV) risk due to premature atherosclerosis. Previous studies have shown that intense glycemic control reduces the incidence of CV disease. Antiplatelet therapy is considered to be a very important therapy for secondary prevention of recurrent atherothrombotic events in patients with DM, while it may be considered for primary prevention in individuals with T1DM with additional CV risk factors. The aim of the present review is to summarize existing literature data regarding the thrombotic risk in T1DM patients and discuss current treatment strategies.

Serum urate and cardiovascular events in the DCCT/EDIC study

In type 2 diabetes, hyperuricemia is associated with cardiovascular disease (CVD) and the metabolic syndrome (MetS), but associations in type 1 diabetes (T1D) have not been well-defined. This study examined the relationships between serum urate (SU) concentrations, clinical and biochemical factors, and subsequent cardiovascular events in a well-characterized cohort of adults with T1D. In 973 participants with T1D in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications Study (DCCT/EDIC), associations were defined between SU, measured once in blood collected 1997–2000, and (a) concurrent MetS and (b) incident ‘any CVD’ and major adverse cardiovascular events (MACE) through 2013. SU was higher in men than women [mean (SD): 4.47 (0.99) vs. 3.39 (0.97) mg/dl, respectively, p < 0.0001], and was associated with MetS features in both (men: p = 0.0016; women: p < 0.0001). During follow-up, 110 participants (11%) experienced “any CVD”, and 53 (5%) a MACE. Analyzed by quartiles, SU was not associated with subsequent CVD or MACE. In women, SU as a continuous variable was associated with MACE (unadjusted HR: 1.52; 95% CI 1.07–2.16; p = 0.0211) even after adjustment for age and HbA1c (HR: 1.47; 95% CI 1.01–2.14; p = 0.0467). Predominantly normal range serum urate concentrations in T1D were higher in men than women and were associated with features of the MetS. In some analyses of women only, SU was associated with subsequent MACE. Routine measurement of SU to assess cardiovascular risk in T1D is not merited.

Trial registration clinicaltrials.gov NCT00360815 and NCT00360893.

Neuronal Lipoprotein Lipase Deficiency Alters Neuronal Function and Hepatic Metabolism

The autonomic regulation of hepatic metabolism offers a novel target for the treatment of non-alcoholic fatty liver disease (NAFLD). However, the molecular characteristics of neurons that regulate the brain-liver axis remain unclear. Since mice lacking neuronal lipoprotein lipase (LPL) develop perturbations in neuronal lipid-sensing and systemic energy balance, we reasoned that LPL might be a component of pre-autonomic neurons involved in the regulation of hepatic metabolism. Here, we show that, despite obesity, mice with reduced neuronal LPL (NEXCreLPL^flox (LPL KD)) show improved glucose tolerance and reduced hepatic lipid accumulation with aging compared to wilt type (WT) controls (LPL^flox). To determine the effect of LPL deficiency on neuronal physiology, liver-related neurons were identified in the paraventricular nucleus (PVN) of the hypothalamus using the transsynaptic retrograde tracer PRV-152. Patch-clamp studies revealed reduced inhibitory post-synaptic currents in liver-related neurons of LPL KD mice. Fluorescence lifetime imaging microscopy (FLIM) was used to visualize metabolic changes in LPL-depleted neurons. Quantification of free vs. bound nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) revealed increased glucose utilization and TCA cycle flux in LPL-depleted neurons compared to controls. Global metabolomics from hypothalamic cell lines either deficient in or over-expressing LPL recapitulated these findings. Our data suggest that LPL is a novel feature of liver-related preautonomic neurons in the PVN. Moreover, LPL loss is sufficient to cause changes in neuronal substrate utilization and function, which may precede changes in hepatic metabolism.

Advanced lipoprotein profile disturbances in type 1 diabetes mellitus: a focus on LDL particles

Background

Lipoprotein disturbances have been associated with increased cardiovascular disease (CVD) risk in type 1 diabetes mellitus (T1DM). We assessed the advanced lipoprotein profile in T1DM individuals, and analysed differences with non-diabetic counterparts.

Methods

This cross-sectional study involved 508 adults with T1DM and 347 controls, recruited from institutions in a Mediterranean region of Spain. Conventional and advanced (assessed by nuclear magnetic resonance [NMR] spectroscopy) lipoprotein profiles were analysed. Crude and adjusted (by age, sex, statin use, body mass index and leukocyte count) comparisons were performed.

Results

The median (interquartile range) age of the study participants was 45 (38–53) years, 48.2% were men. In the T1DM group, the median diabetes duration was 23 (16–31) years, and 8.1% and 40.2% of individuals had nephropathy and retinopathy, respectively. The proportion of participants with hypertension (29.5 vs. 9.2%), and statin use (45.7% vs. 8.1%) was higher in the T1DM vs. controls (p < 0.001). The T1DM group had a better conventional (all parameters, p < 0.001) and NMR-lipid profile than the control group. Thus, T1DM individuals showed lower concentrations of atherogenic lipoproteins (VLDL-particles and LDL-particles) and higher concentrations of anti-atherogenic lipoproteins (HDL-particles) vs. controls, even after adjusting for several confounders (p < 0.001 for all). While non-diabetic women had a more favourable lipid profile than non-diabetic men, women with T1DM had a similar concentration of LDL-particles compared to men with T1DM (1231 [1125–1383] vs. 1257 [1128–1383] nmol/L, p = 0.849), and a similar concentration of small-LDL-particles to non-diabetic women (672.8 [614.2–733.9] vs. 671.2 [593.5–761.4] nmol/L, respectively; p = 0.790). Finally, T1DM individuals showed higher discrepancies between NMR-LDL-particles and conventional LDL-cholesterol than non-diabetic subjects (prevalence of LDL-cholesterol < 100 mg/dL & LDL-particles > 1000 nmol/L: 38 vs. 21.2%; p < 0.001). All these differences were largely unchanged in participants without lipid-lowering drugs (T1DM, n = 275; controls, n = 317).

Conclusions

Overall, T1DM participants showed a more favourable conventional and NMR-lipid profile than controls. However, the NMR-assessment identified several lipoprotein derangements in LDL-particles among the T1DM population (higher discrepancies in NMR-LDL-particles vs. conventional LDL-cholesterol; a worse profile in T1DM women) that were overlooked in the conventional analysis. Further studies are needed to elucidate their role in the development of CVD in this population.

Sex Difference Impacts on the Relationship between Paraoxonase-1 (PON1) and Type 2 Diabetes

Type-2 diabetes (T2D) and its cardiovascular complications are related to sex. Increasing evidence suggests that paraoxonase 1 (PON1) activity, an antioxidant enzyme bound to high-density lipoproteins (HDL), is implicated in the onset and clinical progression of T2D. Since we previously showed that PON1 is a sexual dimorphic protein, we now investigated whether sex might impact the relationship between PON1 and this chronic disease. To address this aim, we assessed PON1 activity in the sera of 778 patients, including controls (women, n = 383; men, n = 198) and diabetics (women, n = 79; men = 118). PON1 activity decreased in both women and men with T2D compared with controls (p < 0.05 and p > 0.001, respectively), but the change was 50% larger in the female cohort. In line with this result, the enzyme activity was associated with serum glucose level only in women (r = -0.160, p = 0.002). Notably, only within this gender category, lower PON1 activity was independently associated with increased odds of being diabetic (odds ratio (95% Confidence interval: 2.162 (1.075-5.678)). In conclusion, our study suggests that PON1-deficiency in T2D is a gender-specific phenomenon, with women being more affected than men. This could contribute to the partial loss of female cardiovascular advantage associated with T2D.

Effect of oral magnesium sulfate administration on lectin-like oxidized low-density lipoprotein receptor-1 gene expression to prevent atherosclerosis in diabetic rat vessels

AIMS/INTRODUCTION

The purpose of the present study was to investigate the possible effect of oral magnesium sulfate (MgSO4 ) in the reduction of atherosclerosis plaques through inhibition of lectin-like low-density lipoprotein receptor-1 (LOX-1) gene expression in diabetic vessels.

MATERIALS AND METHODS

A total of 50 rats were divided into five groups, including non-diabetic control, Mg-treated non-diabetic control, chronic diabetic, Mg-treated chronic diabetic and insulin-treated chronic diabetic. The induction of diabetes was carried out by streptozotocin. The Mg-treated chronic diabetic and Mg-treated non-diabetic control groups were treated with 10 g/L of MgSO4 added to their drinking water. The insulin-treated chronic diabetic group received 2.5 U/kg of insulin twice per day. The fasting blood glucose level and bodyweight were determined weekly. Blood pressure measurement and the intraperitoneal glucose tolerance test were carried out after 16 weeks, and the plasma levels of Mg, lipid profile and oxidized low-density lipoprotein cholesterol (oxLDL) were determined. The mesenteric bed was isolated and perfused according to the McGregor method. The aorta was isolated for LOX-1 genes and proteins expression, and pathological investigation.

RESULTS

MgSO4 administration improved blood pressure, sensitivity to phenylephrine, intraperitoneal glucose tolerance test, lipid profile and plasma ox-LDL level, and also lowered the blood glucose level to the normal range, and decreased LOX-1 gene and protein expressions. Insulin decreased blood pressure, sensitivity to phenylephrine, blood glucose, lipid profiles and plasma oxLDL level, but it did not decrease LOX-1 gene and protein expressions.

CONCLUSIONS

The present findings suggested that MgSO4 improves blood pressure and vessel structure through decreasing oxLDL, and LOX-1 gene and protein expressions; however, insulin did not repair vessel structure, and LOX-1 gene and protein expressions.

Apolipoprotein-defined lipoprotein subclasses, serum apolipoproteins, and carotid intima-media thickness in T1D

Circulating apolipoprotein-defined lipoprotein subclasses (ADLS) and apolipoproteins predict vascular events in the general and type 2 diabetes populations, but data in T1D are limited. We examined associations of ADLS, serum apolipoproteins, and conventional lipids with carotid intima-media thickness (IMT) measured contemporaneously and 6 years later in 417 T1D participants [men: n = 269, age 42 ± 6 y (mean ± SD); women: n = 148, age 39 ± 8 y] in the Epidemiology of Diabetes Interventions and Complications study, the follow-up of the Diabetes Control and Complications Trial (DCCT). Date were analyzed by multiple linear regression stratified by sex, and adjusted for time-averaged hemoglobin A1C, diabetes duration, hypertension, BMI, albuminuria, DCCT randomization, smoking, statin treatment, and ultrasound devices. In cross-sectional analyses, lipoprotein B (Lp-B), Lp-B:C, Lp-B:E+Lp-B:C:E, Apo-A-II, Apo-B, Apo-C-III-HP (heparin precipitate; i.e., Apo-C-III in Apo-B-containing lipoproteins), and Apo-E were positively associated with common and/or internal carotid IMT in men, but only Apo-C-III (total) was (positively) associated with internal carotid IMT in women. In prospective analyses, Lp-B, Apo-B, and Apo-C-III-HP were positively associated with common and/or internal carotid IMT in men, while Lp-A1:AII and Apo-A1 were inversely associated with internal carotid IMT in women. The only significant prospective association between conventional lipids and IMT was between triacylglycerols and internal carotid IMT in men. ADLS and apolipoprotein concentrations may provide sex-specific biomarkers and suggest mechanisms for IMT in people with T1D.

Association Between Inflammatory Markers and Progression to Kidney Dysfunction: Examining Different Assessment Windows in Patients With Type 1 Diabetes

OBJECTIVE

To determine whether biomarkers of inflammation and endothelial dysfunction are associated with the development of kidney dysfunction and the time frame of their association.

RESEARCH DESIGN AND METHODS

Biomarkers were measured at four time points during 28 years of treatment and follow-up in patients with type 1 diabetes in the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) cohort. In addition to traditional biomarkers of inflammation (C-reactive protein and fibrinogen), we measured interleukin-6 (IL-6) and soluble tumor necrosis factor receptors 1 and 2 (sTNFR-1/2), markers of endothelial dysfunction (soluble intracellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin [sE-selectin]), and fibrinolysis (total and active plasminogen activator inhibitor-1 [PAI-1]). Renal outcomes were defined as progression to incident chronic kidney disease (stage 3 or more severe) or macroalbuminuria (albumin excretion rate ≥300 mg/24 h). Prospective multivariate event-time analyses were used to determine the association of each biomarker with each subsequent event within prespecified intervals (3-year and 10-year windows).

RESULTS

Multivariate event-time models indicated that several markers of inflammation (sTNFR-1/2), endothelial dysfunction (sE-selectin), and clotting/fibrinolysis (fibrinogen and PAI-1) are significantly associated with subsequent development of kidney dysfunction. Although some markers showed variations in the associations between the follow-up windows examined, the results indicate that biomarkers (sTNFR-1/2, sE-selectin, PAI-1, and fibrinogen) are associated with progression to chronic kidney disease in both the 3-year and the 10-year windows.

CONCLUSIONS

Plasma markers of inflammation, endothelial dysfunction, and clotting/fibrinolysis are associated with progression to kidney dysfunction in type 1 diabetes during both short-term and long-term follow-up.

Lipoprotein subfraction cholesterol distribution is more atherogenic in insulin resistant adolescents with type 1 diabetes

AIMS/HYPOTHESIS

Adolescents with type 1 diabetes (T1D) often have a less atherogenic-appearing fasting lipid profile than controls, despite increased rates of cardiovascular disease (CVD) as adults. We previously reported an atherogenic lipoprotein subfraction cholesterol distribution associated with insulin resistance (IR) in T1D adults. We sought to determine if T1D youth have more atherogenic profile than controls via a cross-sectional study.

METHODS

Following 3 days of controlled diet and restricted exercise, fasting plasma samples were drawn from 28 T1D youth [50% female, age 15.3 ± 2 yr, body mass index (BMI) 48%ile; diabetes duration 73 ± 52 months, hemoglobin A1c (HbA1c) 8.3 ± 1.4%] and 17 non-diabetic controls (47% female, age: 15.0 ± 2 yr, BMI 49%ile) prior to a hyperinsulinemic euglycemic clamp. Lipoproteins were fractionated by fast protein liquid chromatography (FPLC) and lipoprotein cholesterol distribution determined. Outcome measures were IR assessed by glucose infusion rate (GIR) and FPLC lipoprotein subfraction cholesterol distribution.

RESULTS

T1D youth were more IR (GIR 9.1 ± 3.6 vs. 14.7 ± 3.9 mg/kg/min, p < 0.0001) and had more cholesterol distributed as small dense low density lipoprotein-cholesterol (LDL-C) and less as large buoyant high density lipoprotein-cholesterol (HDL-C) than controls (p < 0.05), despite no differences in the fasting lipid panel. T1D girls lacked the typical female less-atherogenic profile, whereas control girls tended to have a shift toward less dense LDL-C and HDL-C vs. control boys. Among T1D, IR but not HbA1c was associated with a more atherogenic lipoprotein profile.

CONCLUSIONS/INTERPRETATIONS

Normal weight T1D youth, especially females, had more atherogenic LDL-C and HDL-C distributions which correlated with lower insulin sensitivity. IR may contribute to the increased CVD burden in T1D.

Associations between intensive diabetes therapy and NMR-determined lipoprotein subclass profiles in type 1 diabetes

Our objective is to define differences in circulating lipoprotein subclasses between intensive versus conventional management of type 1 diabetes during the randomization phase of the Diabetes Control and Complications Trial (DCCT). NMR-determined lipoprotein subclass profiles (NMR-LSPs), which estimate molar subclass concentrations and mean particle diameters, were determined in 1,294 DCCT subjects after a median of 5 years (interquartile range: 4-6 years) of randomization to intensive or conventional diabetes management. In cross-sectional analyses, we compared standard lipids and NMR-LSPs between treatment groups. Standard total, LDL, and HDL cholesterol levels were similar between randomization groups, while triglyceride levels were lower in the intensively treated group. NMR-LSPs showed that intensive therapy was associated with larger LDL diameter (20.7 vs. 20.6 nm, P = 0.01) and lower levels of small LDL (median: 465 vs. 552 nmol/l, P = 0.007), total IDL/LDL (mean: 1,000 vs. 1,053 nmol/l, P = 0.01), and small HDL (mean: 17.3 vs. 18.6 μmol/l, P < 0.0001), the latter accounting for reduced total HDL (mean: 33.8 vs. 34.8 μmol/l, P = 0.01). In conclusion, intensive diabetes therapy was associated with potentially favorable changes in LDL and HDL subclasses in sera. Further research will determine whether these changes contribute to the beneficial effects of intensive diabetes management on vascular complications.

Data on carotid intima-media thickness and lipoprotein subclasses in type 1 diabetes from the Diabetes Control and Complications Trial and the Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC)

Type 1 diabetes (T1DM) is associated with increased risk of macrovascular complications. We examined longitudinal associations of serum conventional lipids and nuclear magnetic resonance (NMR)-determined lipoprotein subclasses with carotid intima-media thickness (IMT) in adults with T1DM (n=455) enrolled in the Diabetes Control and Complications Trial (DCCT). Data on serum lipids and lipoproteins were collected at DCCT baseline (1983-89) and were correlated with common and internal carotid IMT determined by ultrasonography during the observational follow-up of the DCCT, the Epidemiology of Diabetes Interventions and Complications (EDIC) study, at EDIC 'Year 1' (199-1996) and EDIC 'Year 6' (1998-2000). This article contains data on the associations of DCCT baseline lipoprotein profiles (NMR-based VLDL & chylomicrons, IDL/LDL and HDL subclasses and 'conventional' total, LDL-, HDL-, non-HDL-cholesterol and triglycerides) with carotid IMT at EDIC Years 1 and 6, stratified by gender. The data are supplemental to our original research article describing detailed associations of DCCT baseline lipids and lipoprotein profiles with EDIC Year 12 carotid IMT (Basu et al. in press) [1].

Nuclear magnetic resonance-determined lipoprotein subclasses and carotid intima-media thickness in type 1 diabetes

BACKGROUND

Dyslipidemia has been linked to vascular complications of Type 1 diabetes (T1DM). We investigated the prospective associations of nuclear magnetic resonance-determined lipoprotein subclass profiles (NMR-LSP) and conventional lipid profiles with carotid intima-media thickness (IMT) in T1DM.

METHODS

NMR-LSP and conventional lipids were measured in a subset of Diabetes Control and Complications Trial (DCCT) participants (n = 455) at study entry ('baseline', 1983-89), and were related to carotid IMT determined by ultrasonography during the observational follow-up of the DCCT, the Epidemiology of Diabetes Interventions and Complications (EDIC) study, at EDIC Year 12 (2004-2006). Associations were defined using multiple linear regression stratified by gender, and following adjustment for HbA1c, diabetes duration, body mass index, albuminuria, DCCT randomization group, smoking status, statin use, and ultrasound devices.

RESULTS

In men, significant positive associations were observed between some baseline NMR-subclasses of LDL (total IDL/LDL and large LDL) and common and/or internal carotid IMT, and between conventional total- and LDL-cholesterol and non-HDL-cholesterol and common carotid IMT, at EDIC Year 12; these persisted in adjusted analyses (p < 0.05). Large LDL particles and conventional triglycerides were positively associated with common carotid IMT changes over 12 years (p < 0.05). Inverse associations of mean HDL diameter and large HDL concentrations, and positive associations of small LDL with common and/or internal carotid IMT (all p < 0.05) were found, but did not persist in adjusted analyses. No significant associations were observed in women.

CONCLUSION

NMR-LSP-derived LDL particles, in addition to conventional lipid profiles, may help in identifying men with T1DM at highest risk for vascular disease.

High HDL-C prevalence is common in type 1 diabetes and increases with age but is lower in Hispanic individuals

High HDL-cholesterol (HDL-C) based on the 85th percentile of the 2009-2010 National Health and Education Survey (NHANES) was present in more than a third of 194 unselected subjects with type 1 diabetes (T1D). Age was associated with an increase and Hispanic ethnicity with a decrease in the prevalence of high HDL-C.

Novel effective drugs for diabetic kidney disease? or not?

INTRODUCTION

Diabetes mellitus is increasingly common worldwide and is expected to affect 592 million people by 2035. The kidney is often involved. A key goal in treating diabetes is to reduce the risk of development of kidney disease and, if kidney disease is already present, to delay the progression to end-stage renal disease (ESRD). This represents a social and ethical issue, as a significant proportion of patients reaching ESRD in developing countries do not have access to renal replacement therapy.

AREAS COVERED

The present review focuses on novel therapeutic approaches for diabetic nephropathy (DN), implemented on the basis of recent insights on its pathophysiology, which might complement the effects of single inhibition of the renin-angiotensin-aldosterone system (RAAS), the cornerstone of renoprotective interventions in diabetes, along with glycemic and blood pressure control.

EXPERT OPINION

Although a plethora of new treatment options has arisen from experimental studies, the number of novel renoprotective molecules successfully implemented in clinical practice over the last two decades is disappointingly low. Thus, new investigational strategies and diagnostic tools - including the appropriate choice of relevant renal end points and the study of urinary proteome of patients - will be as important as new therapeutic interventions to fight DN. Finally, in spite of huge financial interests in replacing the less expensive ACE inhibitors and angiotensin II receptor blockers with newer drugs, any future therapeutic approach has to be tested on top of - rather than instead of - optimal RAAS blockade.

The diabetes control and complications trial/epidemiology of diabetes interventions and complications study at 30 years: summary and future directions

OBJECTIVE The Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) study continues to address knowledge gaps in our understanding of type 1 diabetes and the effects of intensive therapy on its long-term complications. RESEARCH DESIGN AND METHODS During the DCCT (1982-1993), a controlled clinical trial of 1,441 subjects with type 1 diabetes, and the EDIC (1994-present), an observational study of the DCCT cohort, core data collection has included medical history questionnaires, surveillance health exams, and frequent laboratory and other evaluations for microvascular and macrovascular disease. Numerous collaborations have expanded the outcome data with more detailed investigations of cardiovascular disease, cognitive function, neuropathy, genetics, and potential biological pathways involved in the development of complications. RESULTS The longitudinal follow-up of the DCCT/EDIC cohort provides the opportunity to continue monitoring the durability of intensive treatment as well as to address lingering questions in type 1 diabetes research. Future planned analyses will address the onset and progression of microvascular triopathy, evidence-based screening for retinopathy and nephropathy, effects of glycemic variability and nonglycemic risk factors on outcomes, long-term impact of intensive therapy on cognitive decline, and health economics. Three new proposed investigations include an examination of residual C-peptide secretion and its impact, prevalence of hearing impairment, and evaluation of gastrointestinal dysfunction. CONCLUSIONS With the comprehensive data collection and the remarkable participant retention over 30 years, the DCCT/EDIC continues as an irreplaceable resource for understanding type 1 diabetes and its long-term complications.

Bixin and norbixin have opposite effects on glycemia, lipidemia, and oxidative stress in streptozotocin-induced diabetic rats

The present study investigated the effects of oral administration of annatto carotenoids (bixin (BIX) and norbixin (NBIX)) on glucose levels, lipid profiles, and oxidative stress parameters in streptozotocin (STZ)-induced diabetic rats. Animals were treated for 30 days in the following groups: nondiabetic control, diabetic vehicle, diabetic 10 mg/kg BIX, diabetic 100 mg/kg BIX, diabetic 10 mg/kg NBIX, diabetic 100 mg/kg NBIX, diabetic metformin, and diabetic insulin. Blood glucose, LDL cholesterol, and triglyceride levels were reduced in the diabetic rats treated with BIX. BIX treatment prevented protein oxidation and nitric oxide production and restored superoxide dismutase activity. NBIX treatment did not change most parameters assessed, and at the highest dose, it increased LDL cholesterol and triglycerides levels and showed prooxidant action (increased protein oxidation and nitric oxide levels). These findings suggested that BIX could have an antihyperglycemic effect, improve lipid profiles, and protect against damage induced by oxidative stress in the diabetic state. Because NBIX is a water-soluble analog of BIX, we propose that lipophilicity is crucial for the protective effect of annatto carotenoids against streptozotocin-induced diabetes.

Diabetic nephropathy: diagnosis and treatment

Nephropathy remains a major cause of morbidity and a key determinant of mortality in patients with type 1 or type 2 diabetes mellitus. Research is ongoing to identify biomarkers that in addition to albuminuria and glomerular filtration rate assist in the prediction and monitoring of renal disease in diabetes mellitus. Current strategies to treat this condition focus on intensification of glycaemic control and excellent control of blood pressure using regimens based on blockade of the renin-angiotensin system. Other approaches to control blood pressure and afford renoprotection are under active clinical investigation, including renal denervation and endothelin receptor antagonism. With increasing understanding of the underlying pathophysiological processes implicated in diabetic nephropathy, new specific renoprotective treatment strategies are anticipated to become available over the next few years.

New automated assay of small dense low-density lipoprotein cholesterol identifies risk of coronary heart disease: the Multi-ethnic Study of Atherosclerosis

OBJECTIVE

Coronary heart disease (CHD) is the leading cause of death in the United States, yet assessing risk of its development remains challenging. The present study evaluates a new automated assay of small dense low-density lipoprotein cholesterol content (sdLDL-C) and whether sdLDL-C is a risk factor for CHD compared with LDL-C or small LDL particle concentrations derived from nuclear magnetic resonance spectroscopy.

APPROACH AND RESULTS

sdLDL-C was measured using a new automated enzymatic method, and small LDL concentrations were obtained by nuclear magnetic resonance in 4387 Multi-Ethnic Study of Atherosclerosis participants. Cox regression analysis estimated hazard ratios for developing CHD for 8.5 years after adjustments for age, race, sex, systolic blood pressure, hypertension medication use, high-density lipoprotein cholesterol, and triglycerides. Elevated sdLDL-C was a risk factor for CHD in normoglycemic individuals. Those in the top sdLDL-C quartile showed higher risk of incident CHD (hazard ratio, 2.41; P=0.0037) compared with those in the bottom quartile and indicated greater CHD risk than the corresponding quartile of LDL-C (hazard ratio, 1.75; P=0.019). The association of sdLDL-C with CHD risk remained significant when LDL-C (<2.57 mmol/L) was included in a multivariate model (hazard ratio, 2.37; P=0.012). Nuclear magnetic resonance-derived small LDL concentrations did not convey a significant risk of CHD. Those with impaired fasting glucose or diabetes mellitus showed higher sdLDL-C and small LDL concentrations but neither was associated with higher CHD risk in these individuals.

CONCLUSIONS

This new automated method for sdLDL-C identifies risk for CHD that would remain undetected using standard lipid measures, but only in normoglycemic, nondiabetic individuals.

Glycemic control and high-density lipoprotein characteristics in adolescents with type 1 diabetes

BACKGROUND

Recent evidence suggests that high-density lipoprotein (HDL) physicochemical characteristics and functional capacity may be more important that HDL-C levels in predicting coronary heart disease. There is little data regarding HDL subclasses distribution in youth with type 1 diabetes.

OBJECTIVE

To assess the relationships between glycemic control and HDL subclasses distribution, composition, and function in adolescents with type 1 diabetes.

METHODS

This cross-sectional study included 52 adolescents with type 1 diabetes aged 12-16 years and 43 age-matched non-diabetic controls. Patients were divided into two groups: one in fair control [hemoglobin A1c (HbA1c) < 9.6%] and the second group with poor glycemic control (HbA1c ≥ 9.6%). In all participants, we determined HDL subclasses distribution, composition, and the ability of plasma and of isolated HDL to promote cellular cholesterol efflux. Levels of soluble adhesion molecules were also measured.

RESULTS

Although both groups of patients and the control group had similar HDL-C levels, linear regression analyses showed that compared with non-diabetic subjects, the poor control group had a lower proportion of HDL2b subclass (p = 0.029), triglyceride enriched (p = 0.045), and cholesteryl ester depleted (p = 0.028) HDL particles. Despite these HDL changes, cholesterol efflux was comparable among the three groups. The poor control group also had significantly higher intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 plasma concentrations.

CONCLUSIONS

In adolescents with type 1 diabetes, poor glycemic control is associated with abnormalities in HDL subclasses distribution and HDL lipid composition, however, in spite of these HDL changes, the ability of HDL to promote cholesterol efflux remains comparable to that of healthy subjects.

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.

Effect of the administration of Solanum nigrum fruit on blood glucose, lipid profiles, and sensitivity of the vascular mesenteric bed to phenylephrine in streptozotocin-induced diabetic rats

Background

Solanum nigrum fruit is traditionally used in Asia to manage, control, and treat diabetes but there is no scientific evidence of the efficacy of Solanum nigrum fruit in treatment of diabetes. We designed this study to investigate the effect of the administration of oral doses of aqueous extract from Solanum nigrum fruit on plasma glucose, lipid profiles, and the sensitivity of the vascular mesenteric bed to Phenylephrine in diabetic and non-diabetic rats.

Material/Methods

Animals were divided into 5 groups (n=10): 2 groups served as non-diabetic controls (NDC), and the other groups had diabetes induced with a single injection of streptozotocin (STZ). Solanum nigrum-treated chronic diabetic (CD-SNE) and Solanum nigrum-treated controls (ND-SNE) received 1g/l of Solanum nigrum added to drinking water for 8 weeks. The mesenteric vascular beds were prepared using the McGregor method.

Results

Administration of Solanum nigrum caused Ca/Mg ratio, plasma glucose, high-density lipoprotein (HDL), low-density lipoprotein (LDL), very low-density lipoprotein (VLDL), total cholesterol, and triglyceride concentrations to return to normal levels, and was shown to decrease alteration in vascular reactivity to vasoconstrictor agents.

Conclusions

Our results support the hypothesis that Solanum nigrum could play a role in the management of diabetes and the prevention of vascular complications in STZ-induced diabetic rats.

Triglyceride-cholesterol imbalance across lipoprotein subclasses predicts diabetic kidney disease and mortality in type 1 diabetes: the FinnDiane Study

BACKGROUND

Circulating cholesterol (C) and triglyceride (TG) levels are associated with vascular injury in type 1 diabetes (T1DM). Lipoproteins are responsible for transporting lipids, and alterations in their subclass distributions may partly explain the increased mortality in individuals with T1DM.

DESIGN AND SUBJECTS

A cohort of 3544 individuals with T1DM was recruited by the nationwide multicentre FinnDiane Study Group. At baseline, six very low-density lipoprotein VLDL, one intermediate-density lipoprotein IDL, three low-density lipoprotein LDL and four higher high-density lipoprotein HDL subclasses were quantified by proton nuclear magnetic resonance spectroscopy. At follow-up, the baseline data were analysed for incident micro- or macroalbuminuria (117 cases in 5.3 years), progression from microalbuminuria (63 cases in 6.1 years), progression from macroalbuminuria (109 cases in 5.9 years) and mortality (385 deaths in 9.4 years). Univariate associations were tested by age-matched cases and controls and multivariate lipoprotein profiles were analysed using the self-organizing map (SOM).

RESULTS

TG and C levels in large VLDL were associated with incident albuminuria, TG and C in medium VLDL were associated with progression from microalbuminuria, and TG and C in all VLDL subclasses were associated with mortality. Large HDL-C was inversely associated with mortality. Three extreme phenotypes emerged from SOM analysis: (i) low C (<3% mortality), (ii) low TG/C ratio (6% mortality), and (iii) high TG/C ratio (40% mortality) in all subclasses.

CONCLUSIONS

TG-C imbalance is a general lipoprotein characteristic in individuals with T1DM and high vascular disease risk.

Association of apolipoprotein B and nuclear magnetic resonance spectroscopy-derived LDL particle number with outcomes in 25 clinical studies: assessment by the AACC Lipoprotein and Vascular Diseases Division Working Group on Best Practices

BACKGROUND

The number of circulating LDL particles is a strong indicator of future cardiovascular disease (CVD) events, even superior to the concentration of LDL cholesterol. Atherogenic (primarily LDL) particle number is typically determined either directly by the serum concentration of apolipoprotein B (apo B) or indirectly by nuclear magnetic resonance (NMR) spectroscopy of serum to obtain NMR-derived LDL particle number (LDL-P).

CONTENT

To assess the comparability of apo B and LDL-P, we reviewed 25 clinical studies containing 85 outcomes for which both biomarkers were determined. In 21 of 25 (84.0%) studies, both apo B and LDL-P were significant for at least 1 outcome. Neither was significant for any outcome in only 1 study (4.0%). In 50 of 85 comparisons (58.8%), both apo B and LDL-P had statistically significant associations with the clinical outcome, whereas in 17 comparisons (20.0%) neither was significantly associated with the outcome. In 18 comparisons (21.1%) there was discordance between apo B and LDL-P.

CONCLUSIONS

In most studies, both apo B and LDL-P were comparable in association with clinical outcomes. The biomarkers were nearly equivalent in their ability to assess risk for CVD and both have consistently been shown to be stronger risk factors than LDL-C. We support the adoption of apo B and/or LDL-P as indicators of atherogenic particle numbers into CVD risk screening and treatment guidelines. Currently, in the opinion of this Working Group on Best Practices, apo B appears to be the preferable biomarker for guideline adoption because of its availability, scalability, standardization, and relatively low cost.

Diabetic atherosclerosis in APOE*4 mice: synergy between lipoprotein metabolism and vascular inflammation

Diabetes is a major risk factor for cardiovascular disease. To examine how diabetes interacts with a mildly compromised lipid metabolism, we introduced the diabetogenic Ins2(C96Y/+) (Akita) mutation into mice expressing human apoE4 (E4) combined with either an overexpressing human LDL receptor gene (hLDLR) or the wild-type mouse gene. The hLDLR allele caused 2-fold reductions in plasma HDL-cholesterol, plasma apoA1, and hepatic triglyceride secretion. Diabetes increased plasma total cholesterol 1.3-fold and increased apoB48 secretion 3-fold, while reducing triglyceride secretion 2-fold. Consequently, diabetic E4 mice with hLDLR secrete increased numbers of small, cholesterol-enriched, apoB48-containing VLDL, although they have near normal plasma cholesterol (<120 mg/dl). Small foam cell lesions were present in the aortic roots of all diabetic E4 mice with hLDLR that we analyzed at six months of age. None were present in nondiabetic mice or in diabetic mice without hLDLR. Aortic expression of genes affecting leukocyte recruitment and adhesion was enhanced by diabetes. ApoA1 levels, but not diabetes, were strongly correlated with the ability of plasma to efflux cholesterol from macrophages. We conclude that the diabetes-induced proinflammatory changes in the vasculature and the hLDLR-mediated cholesterol accumulation in macrophages synergistically trigger atherosclerosis in mice with human apoE4, although neither alone is sufficient.

Cardiovascular disease risk in young people with type 1 diabetes

Cardiovascular disease (CVD) is the most frequent cause of death in people with type 1 diabetes (T1D), despite modern advances in glycemic control and CVD risk factor modification. CVD risk identification is essential in this high-risk population, yet remains poorly understood. This review discusses the risk factors for CVD in young people with T1D, including hyperglycemia, traditional CVD risk factors (dyslipidemia, smoking, physical activity, hypertension), as well as novel risk factors such as insulin resistance, inflammation, and hypoglycemia. We present evidence that adverse changes in cardiovascular function, arterial compliance, and atherosclerosis are present even during adolescence in people with T1D, highlighting the need for earlier intervention. The methods for investigating cardiovascular risk are discussed and reviewed. Finally, we discuss the observational studies and clinical trials which have thus far attempted to elucidate the best targets for early intervention in order to reduce the burden of CVD in people with T1D.

ApoA-1 mimetic restores adiponectin expression and insulin sensitivity independent of changes in body weight in female obese mice

BACKGROUND

We examined the ability of the apolipoprotein AI mimetic peptide L-4F to improve the metabolic state of female and male ob mice and the mechanisms involved.

METHODS

Female and male lean and obese (ob) mice were administered L-4F or vehicle for 6 weeks. Body weight was measured weekly. Fat distribution, serum cytokines and markers of cardiovascular dysfunction were determined at the end of treatment.

RESULTS

L-4F significantly decreased serum interleukin (IL)-6, tumor necrosis factor-α and IL-1β. L-4F improved vascular function, and increased serum adiponectin levels and insulin sensitivity compared with untreated mice. In addition, L-4F treatment increased heme oxygenase (HO)-1, pAKT and pAMPK levels in kidneys of ob animals. pAKT and pAMPK levels were significantly reduced in the presence of an HO inhibitor. Interestingly, L4F did not alter body weight in female mice, but caused a significant reduction in males.

CONCLUSIONS

L-4F treatments reduced cardiovascular risk factors and improved insulin sensitivity in female ob mice independent of body fat changes. Reduced inflammatory cytokine levels accompanied by increased HO activity, serum adiponectin and improved insulin sensitivity suggest that L-4F may promote the conversion of visceral fat to a healthier phenotype. Therefore, L-4F appears to be a promising therapeutic strategy for treating both cardiovascular risk factors and insulin resistance in obese patients of either gender.

Electrophoretic Mobility of Lipoprotein Nanoparticle Mimics

Lipoprotein particles (LPPs) are biological nanoparticles whose physiological roles are greatly influenced by their sizes. The four major classes of LP are: very low density lipoprotein, intermediate density lipoprotein, low density lipoprotein (LDL) and high density lipoprotein. Since the predominance of small, dense LDLs is associated with increased risk of coronary artery disease (CAD) and diabetes mellitus, LPP profiling can be used to predict metabolic risk factors. Highly tunable LPP mimics can be synthesized using nanoparticles to carefully control for size, lipid composition and surface charge to facilitate the study LPPs in CAD. Here, we engineered LPP mimics using gold nanoparticles between 10-50 nm in diameters. We measured the mobility and zeta potential of these LPP mimics and showed that each mimics have distinct electrokinetic properties and are electrostatically stable.

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.

Cardiovascular function/dysfunction in adolescents with type 1 diabetes

Type 1 diabetes mellitus (T1D) is associated with an increased risk of cardiovascular disease (CVD) that begins in childhood. Youth with T1D develop concerning functional cardiac and vascular defects and evidence of early atherosclerosis, despite modern advancements in risk reduction and glycemic management. Such early defects predict poor long-term outcomes. Women with T1D also have higher CVD risk than expected for unexplained reasons. Insulin resistance (IR) is recently recognized as a prominent factor in T1D youth and adults, but with an atypical clinical phenotype. This IR may contribute to early cardiac and vascular dysfunction and long-term CVD in T1D. A better understanding of potential contributors to cardiovascular dysfunction in T1D youth such as IR and its unique phenotype in T1D, subtle lipid abnormalities, and gender differences is now required to address the current knowledge gaps and to prevent cardiovascular morbidity and mortality in T1D.

LDL-containing immune complexes in the DCCT/EDIC cohort: associations with lipoprotein subclasses

Immune complexes containing modified LDL (LDL-IC) and NMR-determined Total LDL particle concentrations are significantly associated with intima-media thickness (IMT). We analyzed the associations between concentrations of NMR-determined lipoprotein subclasses and LDL-IC in the DCCT/EDIC cohort. LDL-IC concentrations in women and men of the DCCT/EDIC cohort did not differ significantly and were positively associated with Total LDL particle concentrations in men and women (r=0.34, r=0.32, respectively; P<.01) and with Small LDL concentration (r=0.22, r=0.13, respectively; P<.01). In women, Large LDL concentrations were also associated with LDL-IC (r=0.20, P<.01) while in men, the association was more modest (r=0.11, P<.05). Thus, both Small and Large LDL are associated with LDL-IC formation. Based on the results from statistical mediation analyses, we concluded that plasma concentrations of LDL-IC may provide a physiological link between the statistically significant association of Total LDL particle concentration with carotid artery IMT in subjects with Type 1 diabetes. Furthermore, after adjusting for conventional risk factors, there was a decrease in LDL-IC concentration even in the presence of high Total LDL particle concentrations in those women with high concentrations of Large HDL, but the association was not evident in men. This suggests that the associations between Large HDL and Total LDL particle concentrations, and their associations with LDL-IC levels, differ by gender and suggest that LDL-IC partially mediate the contribution of Total LDL particle concentration to increased carotid IMT in diabetic men.

Lipoprotein subfraction cholesterol distribution is proatherogenic in women with type 1 diabetes and insulin resistance

OBJECTIVE

Individuals with type 1 diabetes have a less atherogenic fasting lipid profile than those without diabetes but paradoxically have increased rates of cardiovascular disease (CVD). We investigated differences in lipoprotein subfraction cholesterol distribution and insulin resistance between subjects with and without type 1 diabetes to better understand the etiology of increased CVD risk.

RESEARCH DESIGN AND METHODS

Fast protein liquid chromatography was used to fractionate lipoprotein cholesterol distribution in a substudy of the Coronary Artery Calcification in Type 1 Diabetes (CACTI) study (n = 82, age 46 +/- 8 years, 52% female, 49% with type 1 diabetes for 23 +/- 8 years). Insulin resistance was assessed by a hyperinsulinemic-euglycemic clamp.

RESULTS

Among men, those with type 1 diabetes had less VLDL and more HDL cholesterol than control subjects (P < 0.05), but among women, those with diabetes had a shift in cholesterol to denser LDL, despite more statin use. Among control subjects, men had more cholesterol distributed as VLDL and LDL but less as HDL than women; however, among those with type 1 diabetes, there was no sex difference. Within sex and diabetes strata, a more atherogenic cholesterol distribution by insulin resistance was seen in men with and without diabetes, but only in women with type 1 diabetes.

CONCLUSIONS

The expected sex-based less atherogenic lipoprotein cholesterol distribution was not seen in women with type 1 diabetes. Moreover, insulin resistance was associated with a more atherogenic lipoprotein cholesterol distribution in all men and in women with type 1 diabetes. This lipoprotein cholesterol distribution may contribute to sex-based differences in CVD in type 1 diabetes.

Diabetes reduces the cholesterol exporter ABCA1 in mouse macrophages and kidneys

Accumulation of cholesterol in arterial macrophages may contribute to diabetes-accelerated atherosclerotic cardiovascular disease. The ATP-binding cassette transporter ABCA1 is a cardioprotective membrane protein that mediates cholesterol export from macrophages. Factors elevated in diabetes, such as reactive carbonyls and free fatty acids, destabilize ABCA1 protein in cultured macrophages, raising the possibility that impaired ABCA1 plays an atherogenic role in diabetes. We therefore examined the modulation of ABCA1 in two mouse models of diabetes. We isolated peritoneal macrophages, livers, kidneys, and brains from type 1 non-obese diabetic (NOD) mice and mice made diabetic by viral-induced autoimmune destruction of pancreatic beta-cells, and we measured ABCA1 protein and mRNA levels and cholesterol contents. ABCA1 protein levels and cholesterol export activity were reduced by 40-44% (P<0.01) in peritoneal macrophages and protein levels by 48% (P<0.001) in kidneys in diabetic NOD mice compared with nondiabetic animals, even though ABCA1 mRNA levels were not significantly different. A similar selective reduction in ABCA1 protein was found in peritoneal macrophages (33%, P<0.05) and kidneys (35%, P<0.05) from the viral-induced diabetic mice. In liver and brain, however, diabetes had no effect or slightly increased ABCA1 protein and mRNA levels. The reduced ABCA1 in macrophages and kidneys was associated with increased cholesterol content. Impaired ABCA1-mediated cholesterol export could therefore contribute to the increased atherosclerosis and nephropathy associated with diabetes.

The Diabetes Control and Complications Trial: the gift that keeps giving

The Diabetes Control and Complications Trial (DCCT) recruited its first patients in 1983. In 1993, the investigators reported that intensive glycemic treatment of patients with type 1 diabetes mellitus was superior to conventional therapy in preventing the development of microvascular and neurological complications and thus provided definitive proof of the relationship between hyperglycemia and the subsequent risk of diabetic retinopathy, nephropathy and neuropathy. The value of this study, however, did not end there. After the original trial, most participants of the DCCT continued to be followed up in the Epidemiology of Diabetes Interventions and Complications (EDIC) study, which demonstrated the long-term benefits of close glycemic control and provided observational data of a large epidemiological cohort of patients with type 1 diabetes mellitus. Stored samples from the DCCT have also provided an invaluable resource for the identification of new markers of the disease. Recently, the complete dataset of the DCCT and of the initial years of the EDIC have been made publicly available, which allowed independent investigators to help answer their own questions about diabetes. In conclusion, the DCCT continues to provide new insights into type 1 diabetes mellitus, which are of benefit to patients over a quarter of a century after the trial was started.

The cell cholesterol exporter ABCA1 as a protector from cardiovascular disease and diabetes

ATP-binding cassette transporter A1 (ABCA1) is an integral cell membrane protein that exports cholesterol from cells and suppresses macrophage inflammation. ABCA1 exports cholesterol by a multistep pathway that involves forming cell-surface lipid domains, solubilizing these lipids by apolipoproteins, binding of apolipoproteins to ABCA1, and activating signaling processes. Thus, ABCA1 behaves both as a lipid exporter and a signaling receptor. ABCA1 transcription is highly induced by sterols, and its expression and activity are regulated post-transcriptionally by diverse processes. ABCA1 mutations can reduce plasma HDL levels, accelerate cardiovascular disease, and increase the risk for type 2 diabetes. Genetic manipulations of ABCA1 expression in mice also affect plasma HDL levels, inflammation, atherogenesis, and pancreatic beta cell function. Metabolites elevated in individuals with the metabolic syndrome and diabetes destabilize ABCA1 protein and decrease cholesterol export from macrophages, raising the possibility that an impaired ABCA1 pathway contributes to the enhanced atherogenesis associated with common inflammatory and metabolic disorders. The ABCA1 pathway has therefore become a promising new therapeutic target for treating cardiovascular disease and diabetes.

NMR-determined lipoprotein subclass profile predicts type 2 diabetes

AIMS

To determine whether nuclear magnetic resonance (NMR)-determined lipoprotein profiles predict type 2 diabetes.

METHODS

Subjects were 813 male and female participants in the Melbourne Collaborative Cohort Study, aged 40-69 years at baseline (1990-1994), and with a baseline fasting plasma glucose <7.0 mmol/L. Incident type 2 diabetes was identified in 1994-1998 by self-report and confirmation from doctors. Eligible cases and a random group of controls were selected, with NMR data available for 59 cases and 754 non-cases.

RESULTS

Concentration of very low density lipoprotein (VLDL) particles (positive) and high density lipoprotein (HDL) particle size (negative) were selected by stepwise regression as predictors of type 2 diabetes. These associations were independent of other non-lipid risk factors, but not plasma triglycerides. Factor analysis identified a factor from NMR variables, explaining 47% of their variation, and characterized by a positive correlation with VLDL, particularly large and medium sized; more low density lipoprotein (LDL) that were smaller; and relatively smaller, but not more HDL particles. This factor was positively associated with diabetes incidence, but not independently of triglycerides.

CONCLUSIONS

We identified an atherogenic NMR lipoprotein profile in people who developed diabetes, but this did not improve diabetes prediction beyond conventional triglyceride levels.

Is nuclear magnetic resonance lipoprotein subclass related to diabetic retinopathy? The multi-ethnic study of atherosclerosis (MESA)

OBJECTIVE

To examine the associations between nuclear magnetic resonance (NMR) defined lipoproteins and diabetic retinopathy (DR) in a population-based sample of adults with type 2 diabetes.

RESEARCH DESIGN AND METHODS

In all, 921 persons with diabetes in the Multi-Ethnic Study of Atherosclerosis (MESA) were included. DR was assessed from retinal photographs. Lipoproteins were measured by NMR spectroscopy.

RESULTS

After controlling for age, race/ethnicity, study centre and diabetes and vascular risk factors, no consistent patterns of associations between NMR-defined lipoprotein particle concentrations and subclass with DR were evident.

CONCLUSION

The lack of association between NMR-defined lipoproteins and DR does not support clinical use of NMR spectroscopy for management of patients with DR.

Effect of obesity on the plasma lipoprotein subclass profile in normoglycemic and normolipidemic men and women

OBJECTIVE

To determine the effect of obesity without the confounding effect of metabolic complications on the lipoprotein subclass profile in men and women.

DESIGN

Cross-sectional study.

SUBJECTS

A total of 40 lean (body mass index (BMI): 18.5-25 kg/m(2)) and 40 obese (BMI: 30-45 kg/m(2)) subjects, with blood pressure <140/90 mm Hg, fasting plasma glucose concentration <100 mg per 100 ml and total triglyceride concentration <150 mg per 100 ml; all obese subjects had normal oral glucose tolerance.

MEASUREMENTS

Fasting concentrations of very low-, intermediate-, low- and high-density lipoproteins (VLDL, IDL, LDL, and HDL, respectively) and average VLDL, LDL and HDL particle sizes were evaluated by using proton nuclear magnetic resonance spectroscopy.

RESULTS

Obese compared with lean individuals of both sexes had increased plasma concentrations of VLDL (by approximately 50%), IDL (by approximately 100%), LDL (by approximately 50%), and to some extent HDL (by approximately 10%) particles (P<0.05). The contribution of large VLDL to total VLDL concentration, small LDL to total LDL concentration, and small HDL to total HDL concentration was greater in obese than lean subjects (P<0.05), resulting in larger average VLDL size but smaller average LDL and HDL sizes (P<0.05). Women, compared with men, had reduced concentrations of total VLDL particles (by approximately 10%) due to lower concentrations of large and medium VLDL and a shift toward large at the expense of small HDL particles (P<0.05), with no difference in total HDL particle concentration. IDL and total LDL concentrations and LDL subclass distribution were not different between men and women.

CONCLUSION

Obesity is associated with pro-atherogenic alterations in the lipoprotein subclass profile, which may increase cardiovascular disease risk even in the absence of classical metabolic risk factors. On the other hand, the female cardiovascular disease risk advantage is probably largely related to differences in traditional lipid risk factors (plasma triglyceride and HDL-cholesterol concentrations) because sex differences in the plasma lipoprotein subclass profile are minimal.