LDL subclasses in IDDM patients: relation to diabetic nephropathy

Protective effect of phospholipids in lipoproteins against diabetic kidney disease: A Mendelian randomization analysis

BACKGROUND

The etiology of diabetic kidney disease is complex, and the role of lipoproteins and their lipid components in the development of the disease cannot be ignored. However, phospholipids are an essential component, and no Mendelian randomization studies have yet been conducted to examine potential causal associations between phospholipids and diabetic kidney disease.

METHODS

Relevant exposure and outcome datasets were obtained through the GWAS public database. The exposure datasets included various phospholipids, including those in LDL, IDL, VLDL, and HDL. IVW methods were the primary analytical approach. The accuracy of the results was validated by conducting heterogeneity, MR pleiotropy, and F-statistic tests. MR-PRESSO analysis was utilized to identify and exclude outliers.

RESULTS

Phospholipids in intermediate-density lipoprotein (OR: 0.8439; 95% CI: 0.7268-0.9798), phospholipids in large low- density lipoprotein (OR: 0.7913; 95% CI: 0.6703-0.9341), phospholipids in low- density lipoprotein (after removing outliers, OR: 0.788; 95% CI: 0.6698-0.9271), phospholipids in medium low- density lipoprotein (OR: 0.7682; 95% CI: 0.634-0.931), and phospholipids in small low-density lipoprotein (after removing outliers, OR: 0.8044; 95% CI: 0.6952-0.9309) were found to be protective factors.

CONCLUSIONS

This study found that a higher proportion of phospholipids in intermediate-density lipoprotein and the various subfractions of low-density lipoprotein, including large LDL, medium LDL, and small LDL, is associated with a lower risk of developing diabetic kidney disease.

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

BACKGROUND

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

AIM

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Lipid disorders in type 1 diabetes

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

Efeitos fisiológicos do treinamento físico em pacientes portadores de diabetes tipo 1

Insulinoterapia, atividade física regular e planejamento alimentar, em conjunto, consistem na abordagem mais completa no tratamento de portadores de diabetes mellitus tipo 1 (DM1). Estudos clínicos e experimentais têm evidenciado os benefícios do treinamento físico em indivíduos com DM1, tais como melhora na sensibilidade à insulina, redução das doses de insulina e atenuação das disfunções autonômicas e cardiovasculares. Essa revisão aborda as adaptações fisiológicas ao treinamento físico no indivíduo com DM1 e discute as recomendações e prescrição de atividade física para esta população.

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.

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.

Cost-effective strategies in the prevention of diabetic nephropathy

A significant subgroup of patients with diabetes mellitus are predisposed to developing diabetic nephropathy and it is in this subgroup that other diabetes- related complications, and in particular greatly increased cardiovascular disease risk, are concentrated. The high personal, social and financial costs of managing end-stage renal failure and the other complications associated with diabetic nephropathy make a powerful case for screening and effective intervention programmes to prevent the condition or retard its progression. As major breakthroughs in finding genetic susceptibility factors remain elusive, screening efforts continue to be based on microalbuminuria testing, despite increasing recognition of its limitations as a positive predictor of nephropathy. Interventions have been extensively studied, but results remain conflicting. Economic evaluations of such screening and intervention programmes are essential for health planners, yet models of the cost/benefit ratio of such interventions often rely on a rather slim evidence base. Where economic models are developed, they are frequently based on those papers that propound the greatest clinical benefits of a given intervention, leading to a possible over-estimation of the advantages of the chosen approach. Furthermore, the benefits of even such generally accepted interventions as ACE inhibitor treatment are less firmly established than generally appreciated. Lifestyle interventions are instinctively attractive, but are by no means a low-cost option (as is often assumed by both medical professionals and politicians). This review critically assesses the evidence for clinical efficacy and economic benefit of microalbuminuria screening and interventions such as intensive glycaemic control, antihypertensive treatment, ACE inhibition and angiotensin receptor blockade, dietary protein restriction and lipid-modifying therapy. The various costs associated with diabetic nephropathy are so great that even expensive interventions may have a favourable cost/benefit ratio, provided they are truly effective.

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.

Benefícios da atividade física no perfil lipídico de pacientes com diabetes tipo 1

Avaliamos a resposta do perfil lipídico a uma intervenção não-farmacológica de curta duração, e investigamos se alterações nas lipoproteínas estavam presentes, antes da nefropatia diabética (ND) clínica, em 46 pacientes jovens com diabetes tipo 1 (DM1), com idade de 15,5±1,5 anos submetidos a um programa de 8 dias de dieta apropriada e exercícios, durante controle glicêmico estável (glicemia média 110,3±27,1mg/dl e HbA1c 6,9±1,3%). No início, 65% dos jovens apresentavam colesterol total > 160mg/dl (IC 95% 0,51-0,78), enquanto que ao final somente 38% (IC 95% 0,24-0,51) tinham tais níveis. A melhora no perfil lipídico foi ainda melhor para a fração LDL, considerando que inicialmente 67% mostravam valores acima de 100mg/dl (IC 95% 0,55-0,78) e 24% (IC 95% 0,12-0,36) ao final. Valores de HDL-colesterol subnormais (< 40mg/dl) ocorreram em 38% (95% IC 0,24-0,51) e 11% (IC 95% 0,02-0,20) deles, no início e final do período. A razão albumina/creatinina média foi 9,0±8,0mg/g de creatinina. Encontramos fracas correlações entre a razão albumina/creatinina e os níveis de colesterol total (r= 0,21), LDL (r= 0,24), VLDL (r= 0,30), HDL (r= -0,17) e de triglicérides (r= 0,31). Dentro da faixa de referência de albuminúria, não foi encontrada nenhuma associação entre a excreção urinária de albumina e os níveis de lípides nos pacientes com DM1 estável. Um programa de exercícios regulares é eficaz em otimizar o perfil lipídico nestes pacientes, independentemente do controle glicêmico. Nossos dados não apoiam a hipótese de que mudanças no metabolismo lipídico precederiam a microalbuminúria no curso da ND.

Lipoprotein subclasses and particle sizes and their relationship with coronary artery calcification in men and women with and without type 1 diabetes

Type 1 diabetes is associated with increased coronary atherosclerosis, especially in women, even though such patients often have an apparently normal lipid profile. We examined whether lipoprotein particle sizes and subclasses differed between type 1 diabetic subjects (n = 194, age 30-55 years) and age- and sex-matched control subjects (n = 195). We examined whether any abnormalities were of similar magnitude in men and women. The relationship of particle size to electron beam computer tomography-defined coronary artery calcification, a measure of atherosclerosis, was also examined. Proton nuclear magnetic resonance (NMR) spectroscopy was used to quantify VLDL, LDL, and HDL subclass levels and average particle size on fasting samples. LDL size and subclass were similar in diabetic and nondiabetic men. In contrast, in women diabetes was associated with less large and more small LDL and a reduced LDL size (mean difference 0.2 nm; P = 0.0009). This greater effect of diabetes on LDL size in women compared with men was significant (P = 0.007). Diabetes was associated with more large and less small HDL and, to a similar degree in both sexes, a higher HDL size (difference of 0.4 nm in men and 0.3 nm in women; both P < 0.0001). There were no definitive abnormalities in VLDL size. In nondiabetic subjects, lower average HDL particle size, lower LDL size, and higher VLDL size were significantly associated with coronary calcification (P = 0.001, 0.02, and 0.04, respectively). Thus the HDL size differences with diabetes would be expected to be antiatherogenic and the LDL size differences pro-atherogenic. However, there was no clear relationship between particle size and calcification in diabetic subjects. We conclude that in the general population NMR spectroscopy-derived particle size reveals important information about the atherogenicity of lipoprotein profile. Type 1 diabetes is associated with differences in NMR-derived particle size, but their pathogenic significance is unclear.

Homocysteine levels during fasting and after methionine loading in adolescents with diabetic retinopathy and nephropathy

OBJECTIVE

To assess plasma homocysteine levels in adolescents and young adults with type 1 (insulin-dependent) diabetes with and without microvascular complications.

STUDY DESIGN

Homocysteine levels were measured during fasting and after methionine loading in plasma of 61 patients with onset of diabetes before the age of 12 years and duration of disease longer than 7 years. They had an albumin excretion rate (AER) between 20 and 200 microg/min in 2 of 3 overnight urine collections in a period of 6 months and/or retinopathy. Patients with persistent microalbuminuria were divided into 2 groups: subjects with AER of 20 to 70 microg/min and patients with AER of 70 to 200 microg/min. Adolescents (n = 54) without signs of diabetic retinopathy or nephropathy and matched control subjects (n = 63) were also studied.

RESULTS

Homocysteine concentrations before and after methionine load were higher in adolescents with diabetic complications than in healthy subjects (fasting values: 12. 4 +/- 7.9 micromol/L vs 7.8 +/- 4.2 micromol/L; P <.01; after methionine load: 28.1 +/- 13.2 micromol/L vs 16.6 +/- 7.3 micromol/L; P <.005). Values of 11.9 micromol/L or higher were considered to constitute fasting hyperhomocysteinemia. The increase of homocysteine concentrations was particularly evident in young diabetic patients with AER >70 microg/min (fasting values: 14.7 +/- 5.6 micromol/L; after methionine load: 34.2 +/- 12.6 micromol/L) and in patients with proliferative retinopathy (fasting values: 15.1 +/- 5.0 micromol/L; after methionine load: 36.8 +/- 12.5 micromol/L).

CONCLUSIONS

Increased plasma homocysteine concentrations may contribute to increased morbidity and death from cardiovascular disease in adolescents and young adults with diabetic retinopathy and nephropathy.

A nine-month, placebo-controlled study of the effects of growth hormone treatment on lipoproteins and LDL size in abdominally obese men

Abdominal/visceral obesity is associated with blunted growth hormone (GH) secretion and an unfavourable lipoprotein pattern. In this study, the effect of GH treatment on LDL size and on serum lipoprotein concentrations was determined in abdominally obese men. Thirty men, aged 48-66 years, with a body mass index (BMI) of 25-35 kg/m(2)and a waist:hip ratio of >0.95, received treatment with GH (9. 5 microg/kg/day) or placebo for 9 months. Serum concentrations of total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C) and apolipoprotein B (apoB) were reduced (P<0.05, P<0.05 and P<0.001 vs placebo, respectively). Serum lipoprotein(a) [Lp(a)] concentration increased (P<0.05 vs. placebo). Mean low density lipoprotein (LDL) particle diameter was marginally increased by active treatment as compared with placebo (P =0.08). No changes were observed in the serum concentrations of high density lipoprotein-cholesterol (HDL-C), apolipoprotein A-I (apoA-I) and apolipoprotein E (apoE). In conclusion, 9 months of GH treatment in abdominally obese men beneficially reduced serum concentrations of TC, LDL-C and apoB, and marginally increased mean LDL diameter, while serum Lp(a) increased. The ultimate effect of GH therapy on the cardiovascular risk remains, however, to be determined.

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

OBJECTIVE

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

RESEARCH DESIGN AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Treatment of obese subjects with the oral growth hormone secretagogue MK-677 affects serum concentrations of several lipoproteins, but not lipoprotein(a)

Obesity is associated with blunted GH secretion and an unfavorable lipoprotein pattern. The objective of this study was to investigate the effects of treatment with the oral GH secretagogue MK-677 on lipoproteins in otherwise healthy obese males. The study was randomized, double blind, and parallel. Twenty-four obese males, aged 18-50 yr, with body mass index greater than 30 kg/m2 and waist/hip ratio above 0.95 were treated with 25 mg MK-677 (n = 12) or placebo (n = 12) daily for 8 weeks. MK-677 treatment did not significantly change serum lipoprotein(a) [Lp(a)] levels. Serum apolipoprotein A-I and E (apoA-I and apoE) were increased at 2 weeks (P < 0.001 and P < 0.01 vs. placebo, respectively), but were not changed at study end. Serum total cholesterol and low density lipoprotein (LDL) cholesterol (LDL-C) levels were not significantly changed by MK-677 treatment. Serum high density lipoprotein (HDL) cholesterol (HDL-C) was increased at 2 weeks of MK-677 treatment (P < 0.01 vs. placebo), but not at 8 weeks. The LDL-C/HDL-C ratio was reduced after 8 weeks of MK-677 treatment (P < 0.05 vs. placebo). Mean LDL particle diameter was decreased at 2 weeks (P < 0.05 vs. placebo), but was unchanged compared with baseline values at 8 weeks (P = NS vs. placebo). The level of serum triglycerides was increased at 2 (P < 0.05 vs. placebo), but not at 8, weeks. Lipoprotein lipase activity in abdominal and gluteal sc adipose tissue was not affected by active treatment. In conclusion, treatment with the oral GH secretagogue MK-677 affected circulating lipoproteins. The effects on serum apoA-1, apoE, triglycerides, and mean LDL particle diameter were transient. At study end, the LDL-C/HDL-C ratio was decreased. MK-677 treatment did not significantly affect serum Lp(a) concentrations at the present dose and administration protocol.

High prevalence of small LDL particles in non-insulin-dependent diabetic patients with nephropathy

To determine whether small-sized low density lipoprotein (LDL) is associated with a high incidence of coronary heart disease in diabetic nephropathy, we measured the LDL particle size in non-insulin-dependent diabetes mellitus (NIDDM) patients with various degrees of albuminuria (n = 95) and age-, weight-matched non-diabetic control subjects (n = 31). The diabetic subjects were divided into three groups, normoalbuminuric, microalbuminuric and macroalbuminuric NIDDM, based on the amount of albuminuria. The average diameter of LDL particles was determined by non-denaturing polyacrylamide gradient (2-16%) gel electrophoresis. The plasma lipid and lipoprotein concentrations were comparable between the non-diabetic controls and normoalbuminuric NIDDM, whereas the plasma triglyceride, very-low-density lipoprotein (VLDL) or LDL concentration was significantly increased in diabetic nephropathy. The mean LDL particle size was significantly smaller in microalbuminuric NIDDM compared with the controls or normoalbuminuric NIDDM, and the LDL size was further decreased in macroalbuminuric NIDDM. The incidence of small LDL (diameter < 255 A) was remarkably increased in microalbuminuric (58%) and macroalbuminuric NIDDM (67%) compared to the control (13%) and normoalbuminuric NIDDM (27%). Corresponding to the decreased LDL size, the cholesterol content of the LDL was significantly depleted in NIDDM with nephropathy. The high prevalence of small LDL in diabetic nephropathy was also observed even when hypertriglyceridemic or hypertensive subjects were excluded from each group. The increment in triglyceride-rich lipoprotein (d < 1.006) after oral fat-loading was increased, and postheparin lipoprotein lipase activity was decreased significantly in diabetic nephropathy. These abnormalities were significantly associated with LDL particle size. Multivariate regression analysis revealed that the amount of albuminuria was closely associated with the average LDL particle size, and this association was independent of the plasma triglyceride level. Neither insulin resistance nor glycemic control was directly associated with LDL particle diameter. The present study indicates that LDL particles become smaller in diabetic nephropathy, and this may be associated primarily with abnormal triglyceride metabolism. However, in addition to hypertriglyceridemia, other metabolic abnormalities caused by diabetic nephropathy may also be involved in the pathogenesis of small LDL particles.

Epidemiology of late diabetic complications. A basis for the development and evaluation of preventive programs

This article examines the relationship between duration and level of glycemia in patients with diabetes and the occurrence of complications in the eyes, kidneys, and heart. Emphasis is placed on those aspects that are relevant to the development and evaluation of preventive and therapeutic programs against these complications. Data on patients with insulin-dependent diabetes mellitus are reviewed, and the similarities and differences with the data on patients with non-insulin-dependent diabetes mellitus are discussed.

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

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