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

Lipoprotein(a) plasma levels are not associated with incident microvascular complications in type 2 diabetes mellitus

AIMS/HYPOTHESIS

Microvascular disease in type 2 diabetes is a significant cause of end-stage renal disease, blindness and peripheral neuropathy. The strict control of known risk factors, e.g. lifestyle, hyperglycaemia, hypertension and dyslipidaemia, reduces the incidence of microvascular complications, but a residual risk remains. Lipoprotein (a) [Lp(a)] is a strong risk factor for macrovascular disease in the general population. We hypothesised that plasma Lp(a) levels and the LPA gene SNPs rs10455872 and rs3798220 are associated with the incident development of microvascular complications in type 2 diabetes.

METHODS

Analyses were performed of data from the DiaGene study, a prospective study for complications of type 2 diabetes, collected in the city of Eindhoven, the Netherlands (n = 1886 individuals with type 2 diabetes, mean follow-up time = 6.97 years). To assess the relationship between plasma Lp(a) levels and the LPA SNPs with each newly developed microvascular complication (retinopathy n = 223, nephropathy n = 246, neuropathy n = 236), Cox proportional hazards models were applied and adjusted for risk factors for microvascular complications (age, sex, mean arterial pressure, non-HDL-cholesterol, HDL-cholesterol, BMI, duration of type 2 diabetes, HbA_1c and smoking).

RESULTS

No significant associations of Lp(a) plasma levels and the LPA SNPs rs10455872 and rs3798220 with prevalent or incident microvascular complications in type 2 diabetes were found. In line with previous observations the LPA SNPs rs10455872 and rs3798220 did influence the plasma Lp(a) levels.

CONCLUSIONS/INTERPRETATION

Our data show no association between Lp(a) plasma levels and the LPA SNPs with known effect on Lp(a) plasma levels with the development of microvascular complications in type 2 diabetes. This indicates that Lp(a) does not play a major role in the development of microvascular complications. However, larger studies are needed to exclude minimal effects of Lp(a) on the development of microvascular complications.

Effects of lipids and lipoproteins on diabetic foot in people with type 2 diabetes mellitus: a meta-analysis

BACKGROUND

To conduct a meta-analysis of case-control studies to determine the effects of lipids and lipoproteins on morbidity of diabetic foot in adults with type 2 diabetes.

METHODS

We searched the PubMed and EMBASE to identify eligible studies. The Newcastle-Ottawa Quality Assessment Scale was used to determine the quality of selected studies. We assessed the strength of associations using standardized mean differences with 95% confidence intervals.

RESULTS

A total of 4 articles were found. Decreased HDL-cholesterol had a significant association with diabetic foot susceptibility in fixed-effects model, but no significant associations were found between diabetic foot and LDL-cholesterol, TC or TG levels.

CONCLUSIONS

Our results suggested that decreased HDL-cholesterol was associated with diabetic foot, so possible measures to prevent diabetic foot should include targeting increases in HDL-cholesterol.

Lipoprotein(a) is not related to markers of insulin resistance in pregnancy

BACKGROUND

Dyslipidemia, a major risk factor for cardiovascular disease is a common finding in patients with type 2 diabetes and among women with gestational diabetes. Elevated levels of lipoprotein(a) [Lp(a)] are linked to increased risk of cardiovascular disease. However, its relationship with insulin resistance, type 2 diabetes and gestational diabetes is controversial and unproven. Here we aimed to clarify whether Lp(a) levels are associated with insulin sensitivity in pregnancy.

METHODS

Sixty-four women with gestational diabetes and 165 with normal glucose tolerance were enrolled in the study. Fasting Lp(a) serum levels were measured in all women at 24-28 weeks of gestation.

RESULTS

In pregnancy, there was no significant difference in serum Lp(a) concentrations between the two groups. Its level did not correlate with markers of insulin resistance (HOMA-IR), insulin sensitivity (HOMA-S%), pancreatic beta-cell function (HOMA-B%) and insulin sensitivity in dynamic conditions (OGIS). In addition, fasting glucose and insulin levels and those throughout an oral glucose tolerance test were independent of Lp(a) concentrations in our study group.

CONCLUSIONS

Lp(a) levels in pregnant women do not differ with respect to the presence or absence of gestational diabetes. Although influenced by some components of the lipid profile, such as triglycerides and HDL-C, insulin resistance in pregnancy is not affected by Lp(a).

Lipoprotein(a) in type 2 diabetic subjects and its relationship to diabetic microvascular complications

AIM: To estimate the level of serum lipoprotein (a) [Lp (a)] in type 2 diabetes mellitus patients and to determine the relationship between Lp(a) in type 2 diabetes mellitus patients and micro-vascular complications.

METHODS: A cross sectional study was performed that enrolled 144 subjects with type 2 diabetes mellitus above the age of 25 years attending outpatient clinic of Government Medical College, Kozhikode. Lp(a) levels were measured quantitatively in venous samples using Turbidimetric Immunoassay in all subjects. Each patient was evaluated for micro vascular complications, namely diabetic retinopathy, nephropathy and neuropathy. The relationship between Lp(a) levels and the micro vascular complications was assessed by univariate analysis.

RESULTS: Mean age of cases was 53.93 ± 10.74 years with a male to female ratio of 1.3:1. Mean duration of diabetes was 9.53 ± 7.3 years. Abnormal Lp(a) levels (≥ 30 mg/dL) were observed in 38 (26.4%) diabetic subjects. Seventy-eight (54.16%) cases had diabetic nephropathy and significantly higher Lp(a) levels were found among these cases [Median 28.2 mg/dL (Interquartile range; IQR 24.4-33.5) vs 19.3 mg/dL (IQR 14.7-23.5); P < 0.05]. Retinopathy was present among 66 (45.13%) cases and peripheral neuropathy was detected among 54 (37.5%) cases. However, Lp(a) levels were not significantly different among those with or without retinopathy and neuropathy. Positive correlation was found between higher Lp(a) levels and duration of diabetes (r = 0.165, P < 0.05) but not with HbA1c values (r = – 0.083).

CONCLUSION: Abnormal Lp(a) levels were found among 26.4% of diabetic subjects. Patients with diabetic nephropathy had higher Lp(a) levels. No association was found between Lp(a) levels and diabetic retinopathy or neuropathy. Longer duration of diabetes correlated with higher Lp(a) levels.

Lipoprotein(a) and Other Cardiovascular Metabolic Risk Factors in Kuwaiti Children with Type-1 Diabetes

BACKGROUND/AIMS

Lipoprotein(a) synthesis and catabolism could be influenced by insulin or by diabetes metabolic complications in patients with type-1 diabetes. The aim of the study was to investigate the relation of plasma lipoprotein(a) concentrations with metabolic cardiovascular risk factors in Kuwaiti children with uncomplicated type-1 diabetes.

METHODS

This case-control study included 115 (44 males and 71 females) diabetic children aged 6-18 years matched by age and sex to 115 non-diabetic children as controls.

RESULTS

There was no significant difference between the mean lipoprotein(a) concentrations in type-1 diabetic children (27.34 mg/dl) and their controls (22.80 mg/dl). Total cholesterol, apolipoprotein A1 and B levels were significantly higher in diabetic children than controls. In diabetic children, significant correlations were found between lipoprotein(a) levels and glycated hemoglobin (r = 0.249, p = 0.011), total cholesterol (r = 0.208, p = 0.025), and apolipoprotein B (r = 0.349, p < 0.001). The proportion of diabetic children with lipoprotein(a) >30 mg/dl was significantly higher in those having poor glycemic control (glycated hemoglobin >9.0%, p = 0.013), raised total cholesterol (p = 0.033), or with a family history of cardiovascular disease (p = 0.006).

CONCLUSION

Plasma lipoprotein(a) levels were not elevated in young type-1 diabetic children compared to non-diabetic controls; however, lipoprotein(a) levels were significantly higher in diabetic children with poor glycemic control. Moreover, there were significant correlations between lipoprotein(a) and the metabolic cardiovascular risk factors total cholesterol, atherogenic index, apolipoprotein B and apolipoprotein B/A1 ratio.

The role of lipids in the development of diabetic microvascular complications: implications for therapy

Dyslipidemia is a major factor responsible for coronary heart disease and its reduction decreases coronary risk in patients with diabetes mellitus. However, the association of dyslipidemia with microvascular complications and the effect of intervention with lipid-lowering therapy in diabetes have been less investigated. We present the systematic review of association and intervention studies pertaining to dyslipidemia and microvascular disease in diabetes and also review possible mechanisms. Dyslipidemia may cause or exacerbate diabetic retinopathy and nephropathy by alterations in the coagulation-fibrinolytic system, changes in membrane permeability, damage to endothelial cells and increased atherosclerosis. Hyperlipidemia is associated with faster decline in glomerular filtration rate and progression of albuminuria and nephropathy. Recent evidence also suggests a role of lipoprotein(a) in progression of retinopathy and nephropathy in patients with diabetes mellitus. Lipid-lowering therapy, using single agents or a combination of drugs may significantly benefit diabetic retinopathy and diabetic nephropathy. In particular, hydroxymethyl glutaryl coenzyme A reductase inhibitors may be effective in preventing or retarding the progression of microvascular complications because of their powerful lipid-lowering effects and other additional mechanisms. However, most of the data are based on short-term studies, and need to be ascertained in long-term studies. Until more specific guidelines are available, aggressive management of diabetic dyslipidemia, according to currently accepted guidelines, should be continued for the prevention of macrovascular disease which would also benefit microvascular complications.

Serum lipoprotein(a) concentration as a cardiovascular risk factor in Kuwaiti type 2 diabetic patients

Serum lipoprotein(a) [Lp(a)], a risk factor for coronary heart disease (CHD) in some nondiabetic populations, is largely under genetic control and varies among ethnic and racial groups. We evaluated serum Lp(a) concentration and its relationship with traditional CHD risk factors (age, sex, smoking, hypertension, dyslipidemia) as well as stage of diabetic nephropathy in 345 type 2 diabetic patients. Lp(a) concentration was skewed with median (2.5th, 97.5th percentiles) of 25.0 (8.1, 75.7) mg/dl. Twenty-three of 55 (41.8%) patients with CHD had increased (>30 mg/dl) Lp(a) compared with 102 of 290 (35.1%) patients without CHD (P=.35). Twelve of 27 (44.4%) female patients with CHD had increased Lp(a) compared to 11 of 28 (39.3%) males (P=.70). Lp(a) was significantly (P<.05) higher in females than males, but the logistic regression analysis showed significant association of Lp(a), LDL-C, and duration of diabetes mellitus (DM) with CHD in male patients only. Although female patients with CHD and macroalbuminuria had significantly (P<.05) higher Lp(a) than normoalbuminuric female patients without CHD, no such association was found in males and no significant association was found between Lp(a) and the degree of albuminuria. Partial correlation analysis controlling for age, sex, and BMI showed significant correlation of Lp(a) with total cholesterol only (P=.03) and no correlation was found with other lipid parameters. Multiple regression analysis did not show significant associations of Lp(a) with standard CHD risk factors, HbA(1c), and plasma creatinine. This study is in agreement with studies in other populations, which showed that Lp(a) may not be an independent risk factor for CHD in patients with DM. However, as Lp(a) could promote atherogenesis via several mechanisms, follow-up studies in our patients will confirm if increased Lp(a) concentration can partly account for the poorer prognosis when diabetic patients develop CHD.

Urinary excretion of apolipoprotein(a) fragments in type 1 diabetes mellitus patients

High levels of plasma lipoprotein(a) [Lp(a)] represent an independent risk factor for cardiovascular morbidity; however, Lp(a) has not yet been identified as a risk factor for type 1 diabetic patients. Results from the limited number of available studies on plasma Lp(a) levels in relation to renal function in type 1 diabetes mellitus are inconclusive. We hypothesized that only type 1 diabetes mellitus patients with impaired renal function show increased plasma Lp(a) levels, due to decreased urinary apolipoprotein(a) [apo(a)] excretion. We therefore measured urinary apo(a) levels in 52 type 1 diabetes mellitus patients and 52 matched controls, and related the urinary apo(a) concentration to the plasma Lp(a) level, kidney function, and metabolic control. Our findings indicate that patients with incipient diabetic nephropathy as evidenced by microalbuminuria (20 to 200 microg/min) exhibit significantly higher plasma Lp(a) levels (median, 15.6 mg/dL) in comparison to normoalbuminuric patients (median, 10.3 mg/dL) and healthy controls (median, 12.0 mg/dL). Urinary apo(a) normalized to creatinine excretion was significantly elevated in both normoalbuminuric (median, 22.3 microg/dL) and microalbuminuric type 1 diabetic patients (median, 29.1 microg/dL) compared with healthy subjects (median, 16.0 microg/dL) and correlated significantly with Lp(a) plasma levels in both patient and control groups (P < .003). No correlation existed between the Lp(a) plasma level or urinary apo(a) concentration and metabolic control in type 1 diabetes mellitus patients. From these studies, we conclude that urinary apo(a) excretion is significantly increased in type 1 diabetic patients and correlates with plasma Lp(a) levels, and only type 1 diabetic patients with microalbuminuria have higher plasma levels of Lp(a) compared with patients with normoalbuminuria and healthy controls.

Evaluation of serum glycated lipoprotein(a) levels in noninsulin-dependent diabetic patients

OBJECTIVE

Serum Lp(a) levels are generally considered unaffected by non-insulin-dependent diabetes mellitus (NIDDM). However, high Lp(a) concentrations as well as an increased rate of nonenzymatic glycation of proteins may be involved in degenerative diabetic complications.

DESIGN AND METHODS

We measured serum glycated Lp(a) levels in 17 NIDDM patients, as compared to 14 normoglycaemic controls. Glycated proteins were separated from nonglycated ones by boronate affinity chromatography, and specific proteins assayed by immunonephelometric methods in both fractions.

RESULTS

The percentage of glycated Lp(a) was 1.5 +/- 0.4% (mean +/- SD) in the control group, and was significantly higher in NIDDM patients: 4.3 +/- 1.5% (p < 0.01). The basal level of Lp(a) glycation was lower than that of other proteins, particularly apo B (4.0 +/- 0.7%). By contrast, the variations of glycated Lp(a) levels were of greater amplitude (+ 187%) than those of glycated apo B (+ 67%). Glycated Lp(a) values were significantly elevated in patients with micro and macrovascular complications in comparison with uncomplicated patients.

CONCLUSIONS

These results suggest that glycated Lp(a) may be considered a potentially interesting parameter in the pathophysiology of diabetic vascular complications.