Association Between Serum Lipoprotein(a) and Diabetic Retinopathy in Han Chinese Patients With Type 2 Diabetes

Lipoprotein (a) as a predictor of diabetic retinopathy in patients with type 2 diabetes: A systematic review

BACKGROUND

Lipoprotein a (LP(a)), an LDL-like lipoprotein, known as a risk factor for cardiovascular diseases, has a controversial association with diabetic retinopathy in patients with type 2 diabetes-the current systematic review aimed to critically assess the association between LP(a) and diabetic retinopathy.

METHODS

A systematic review of relevant studies was conducted after a thorough search in PubMed, Scopus, and Google Scholar electronic databases. We used English observational, case-control, and prospective cohort studies published up to August 2022, including type 2 diabetic patients as the population, diabetic retinopathy as the outcome, and LP(a) as the intervention.

RESULT

17 relevant studies, including 4688 patients with diabetes, were included in this systematic review. While in 13 studies, Lipoprotein(a) was recognized as a risk factor for diabetic retinopathy, only three studies reported no evidence of a relationship between the two. Also, another study showed a mixed outcome of the relationship between LP(a) and diabetic retinopathy.

CONCLUSION

High serum lipoprotein(a) in patients with type 2 diabetes is considered a risk factor for diabetic retinopathy. However, further large-scaled cohort studies are still required to validate this finding.

Circulating level of homocysteine contributes to diabetic retinopathy associated with dysregulated lipid profile and impaired kidney function in patients with type 2 diabetes mellitus

BACKGROUND

To test the hypothesis that elevated plasma levels of homocysteine (Hcy) and lipoprotein (a) (LPA) contribute to diabetic retinopathy (DR) associated with dysregulated lipid profile, dyslipidaemia, and kidney function.

METHODS

A total of 83 patients with type 2 diabetes mellitus (T2DM) were enrolled in this prospective case-control study. Patients were categorized into those with no DR (DM), non-proliferative DR (NPDR), and proliferative DR (PDR). Age and sex-matched individuals with no diabetes were included in the control group. Biochemical tests, including fasting blood glucose (FBG), glycated hemoglobin (HbA1c), Hcy, LPA, lipid profile, and urine microalbumin (UMA), were evaluated.

RESULTS

Hcy was negatively correlated with high-density lipoprotein-cholesterol (HDL-C) (p < 0.05), but positively correlated with [total cholesterol (TC)-HDL-C)/HDL-C] (p < 0.05), low-density lipoprotein cholesterol (LDL-C)/HDL-C (p < 0.05), and UMA (p < 0.05). Traditional risk factors, Hcy, arteriosclerosis-associated plasma indices, and UMA, resulted as the independent risk factors for the occurrence of DM and DR. After controlling for age, sex, duration of DM, and FBG, a multiple ordinal logistic regression model showed that LPA [OR = 2.90, 95% confidence interval (95% CI) 1.16-7.23, p = 0.023)], LDL-C (OR = 4.28, 95% CI 1.24-14.79, p = 0.021), and (TC-HDL-C)/HDL-C (OR = 1.92, 95% CI 1.05-3.53, p = 0.035) were risk factors for DM and DR.

CONCLUSIONS

Hcy and LPA contributed to DM and DR. Hcy was positively correlated with kidney dysfunction and the ratios of lipid profiles, and negatively with HDL-C, LPA, LDL-C, and (TC-HDL-C)/HDL-C resulted as predictors of the occurrence of DM and severity of DR.

Exploring the role of lipoprotein(a) in cardiovascular diseases and diabetes in Chinese population

A high level of lipoprotein (a) in the plasma has been associated with a variety of cardiovascular diseases and is considered to be an independent predictor of some other diseases. Based on recent studies, the concentration levels of Lp(a) in the Chinese population exhibit a distinctive variation from other populations. In the Chinese population, a high level of Lp(a) indicates a higher incidence of revascularization, platelet aggregation, and thrombogenicity following PCI. Increased risk of atherosclerotic cardiovascular disease (ASCVD) in Chinese population has been linked to higher levels of Lp(a), according to studies. More specifically, it has been found that in Chinese populations, higher levels of Lp(a) were linked to an increased risk of coronary heart disease, severe aortic valve stenosis, deep vein thrombosis in patients with spinal cord injuries, central vein thrombosis in patients receiving hemodialysis, and stroke. Furthermore, new and consistent data retrieved from several clinical trials also suggest that Lp (a) might also play an essential role in some other conditions, including metabolic syndrome, type 2 diabetes and cancers. This review explores the clinical and epidemiological relationships among Lp(a), cardiovascular diseases and diabetes in the Chinese population as well as potential Lp(a) underlying mechanisms in these diseases. However, further research is needed to better understand the role of Lp(a) in cardiovascular diseases and especially diabetes in the Chinese population.

Lipoprotein(a) and Atherosclerotic Cardiovascular Diseases: Evidence from Chinese Population

Cardiovascular disease (CVD) is the leading cause of mortality worldwide. Multiple factors are involved in CVD, and emerging data indicate that lipoprotein(a) (Lp(a)) may be associated with atherosclerotic cardiovascular disease (ASCVD) independent of other traditional risk factors. Lp(a) has been identified as a novel therapeutic target. Previous studies on the influence of Lp(a) in CVD have mainly used in western populations. In this review, the association of plasma Lp(a) concentration with ASCVD was summarized, with regards to epidemiological, population-based observational, and pathological studies in Chinese populations. Lp(a) mutations and copy number variations in Chinese populations are also explored. Finally, the impact of plasma Lp(a) levels on patients with type 2 diabetes mellitus, cancer, and familial hypercholesterolemia are discussed.

Cholesterols, Apolipoproteins, and Their Associations with the Presence and Severity of Diabetic Retinopathy: A Systematic Review

Serum apolipoproteins have been reported as a more significant marker for diabetic retinopathy (DR) compared with serum cholesterols. This article aims to review the associations between serum cholesterols and apolipoproteins, and the presence and severity of DR. The protocol of this systematic review was registered at the PROSPERO registry (CRD42022303331). We conducted a systematic search of literature published between 2011 to 2022 using the search terms "serum cholesterol" AND/OR "lipoprotein" AND/OR "apolipoprotein" AND/OR "diabetic retinopathy". Fifteen studies were included in this review. Six studies assessed the association between serum cholesterols, apolipoproteins, and the presence of DR. Three studies reported lower levels of apolipoprotein A1, and one study reported higher levels of apolipoprotein B in patients with DR. The remaining nine studies compared serum cholesterol and apolipoprotein levels according to DR severity. Patients with more severe grades of DR presented with lower apolipoprotein A1 in six (66.7%) studies, higher apolipoprotein B levels in seven (77.8%) studies, and a higher apolipoprotein B/apolipoprotein A1 ratio in six out of seven (85%) studies. In conclusion, serum apolipoproteins, in particular the apolipoprotein B/apolipoprotein A1 ratio, were a more consistent marker for DR severity compared with serum cholesterols.

Correlation between Imaging Morphological Findings and Laboratory Biomarkers in Patients with Diabetic Macular Edema

PURPOSE

To investigate the potential association between peripheral blood biomarkers and morphological characteristics of retinal imaging in patients with diabetic macular edema (DME).

METHODS

Participants in this cross-sectional study were 36 consecutive patients (36 eyes) with treatment-naïve DME, who underwent spectral domain-optical coherence tomography (SD-OCT), fundus photography, and fundus fluorescein angiography (FFA). In addition, peripheral blood samples were taken to evaluate full blood count and biochemical parameters. Correlation between imaging characteristics and laboratory parameters was examined.

RESULTS

Eyes with central subfield thickness greater than 405 μm presented significantly higher neutrophils/lymphocytes (p = 0.043) and higher lipoprotein (a) compared to eyes with CST < 405 μm (p = 0.003). Presence of hyperreflective foci on SD-OCT was associated with significantly higher white blood cell count (p = 0.028). Ellipsoid zone disruption was associated with significantly lower hematocrit (p = 0.012), hemoglobin (p = 0.009), and red blood cell count (p = 0.026), as well as with higher lipoprotein (a) (p = 0.015). Macular ischemia on FFA was associated with significantly higher monocytes (p = 0.027) and monocytes/HDL (p = 0.019). No significant associations were found between laboratory parameters and subretinal fluid, intraretinal fluid, exudates, cysts, disorganization of inner retinal layers, epiretinal membrane, and external limiting membrane condition.

CONCLUSION

Specific imaging morphological characteristics were found to be associated with laboratory parameters in patients with DME. These findings may shed light on the pathophysiology of DME and its correlation with the development of specific clinical signs.

Serum lipoprotein (a) associates with a higher risk of reduced renal function: a prospective investigation

Lipoprotein (a) [Lp(a)] is a well-known risk factor for cardiovascular disease, but analysis on Lp(a) and renal dysfunction is scarce. We aimed to investigate prospectively the association of serum Lp(a) with the risk of reduced renal function, and further investigated whether diabetic or hypertensive status modified such association. Six thousand two hundred and fifty-seven Chinese adults aged ≤40 years and free of reduced renal function at baseline were included in the study. Reduced renal function was defined as estimated glomerular filtration rate <60 ml/min/1.73 m2 During a mean follow-up of 4.4 years, 158 participants developed reduced renal function. Each one-unit increase in log10-Lp(a) (milligrams per deciliter) was associated with a 1.99-fold (95% CI 1.15-3.43) increased risk of incident reduced renal function; the multivariable-adjusted odds ratio (OR) for the highest tertile of Lp(a) was 1.61 (95% CI 1.03-2.52) compared with the lowest tertile (P for trend = 0.03). The stratified analysis showed the association of serum Lp(a) and incident reduced renal function was more prominent in participants with prevalent diabetes [OR 4.04, 95% CI (1.42-11.54)] or hypertension [OR 2.18, 95% CI (1.22-3.89)]. A stronger association was observed in the group with diabetes and high Lp(a) (>25 mg/dl), indicating a combined effect of diabetes and high Lp(a) on the reduced renal function risk. An elevated Lp(a) level was independently associated with risk of incident reduced renal function, especially in diabetic or hypertensive patients.

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.

Early-onset type 2 diabetes: A high-risk factor for proliferative diabetic retinopathy (PDR) in patients with microalbuminuria

We aim to explore the relationship between early-onset diabetes and proliferative diabetic retinopathy (PDR) in type 2 diabetes mellitus (T2DM) patients with microalbuminuria.A total of 461 T2DM patients with microalbuminuria were enrolled. Subjects were defined as early-onset or late-onset based on the age at which they were diagnosed with diabetes (<40 and ≥40 years, respectively). Medical history, anthropometry, and laboratory indicators were documented. PDR was defined as the presence of any of the following changes on fundus photography: neovascularization, vitreous hemorrhage, or preretinal hemorrhage.The prevalence of PDR was 6-fold higher in patients with early-onset than late-onset T2DM [(6.1% vs 1.0%), P = .004]. Univariate correlation analysis showed that early-onset diabetes, use of oral hypoglycemic drugs, and insulin therapy were risk factors for PDR. In multivariate logistic analysis, patients with early-onset diabetes exhibited a 7.00-fold [(95% confidence interval 1.40-38.26), P = .019] higher risk of PDR than subjects with late-onset diabetes after adjusting for sex; T2DM duration; systolic blood pressure; total triglyceride; glycated hemoglobin; insulin therapy; and the use of oral hypoglycemic drugs, antihypertensive drugs, and lipid-lowering drugs.In T2DM patients with microalbuminuria, early-onset diabetes is an independent risk factor for the development of PDR.

Lipoprotein(a) and Apolipoproteins as Predictors for Diabetic Retinopathy and Its Severity in Adults With Type 2 Diabetes: A Case-Cohort Study

OBJECTIVES

Our aim in this study was to assess the relationship between serum lipoprotein(a) [Lp(a)] and apolipoproteins and the risk of developing diabetic retinopathy (DR).

METHODS

One thousand fifty-seven patients with type 2 diabetes were divided into 2 main groups and followed for 5 years: 637 patients without DR and 420 patients with DR. A group of patients with DR were then divided into 2 subgroups: 162 patients with nonproliferative DR (NPDR) and 163 patients with proliferative DR (PDR). The association between serum Lp(a) and apolipoproteins with NPDR and PDR was assessed using univariate and multivariate regression analyses. Receiver-operating characteristic curve analysis was performed based on the new cutoff values.

RESULTS

There was a positive relationship between Lp(a) and the presence of DR as well as a negative correlation between ApoA and DR (p<0.001 and p=0.03, respectively). We also found a positive association between ApoB and the severity of DR (p=0.008). ApoA1 had an area under the curve of 55.0% for the prediction of DR. The calculated cutoff values of ApoB/ApoA1 ratio (0.58 g/L) and ApoB (77.5 g/L) in detection of DR were lower than their standard cutoff values of 0.8 and 90 g/L, respectively. Also, the sensitivity of new cutoff values for ApoB and ApoB/ApoA1 ratio was higher than the standard value, but the specificity of the standard cutoff values for both was higher than our new cutoff value.

CONCLUSIONS

Serum Lp(a) and ApoA1 levels were independently associated with DR, and serum ApoB correlated with severity of DR. These measurements can be used for assessment and early treatment of this vision-threatening complication of diabetes.

Elevated RBP4 plasma levels were associated with diabetic retinopathy in type 2 diabetes

The retinol-binding protein 4 (RBP4) has been postulated to play a role in glucose homeostasis, insulin resistance, and diabetes mellitus in human and animal studies. The aim of the present study was to evaluate the role of RBP4 in Chinese patients with type 2 diabetes mellitus with and without diabetic retinopathy (DR). Plasma RBP4 concentrations were tested in 287 patients with type 2 diabetes. At baseline, demographic and clinical information including presence of DR and vision-threatening DR (VTDR) was collected. The relationship between RBP4 and DR (VTDR) was investigated using logistic regression. Patients with DR or VTDR had significantly higher plasma levels of RBP4 on admission (P<0.0001). Receiver operating characteristics (ROCs) to predict DR and VDTR demonstrated areas under the curve for RBP4 of 0.79 (95% confidence interval (CI): 0.73–0.85) and 0.90 (95% CI: 0.85–0.94), respectively, which were superior to other factors. For each 1 μg/ml increase in plasma level of RBP4, the unadjusted and adjusted risk of DR would be increased by 8% (with the odds ratio (OR) of 1.08 (95% CI: 1.05–1.13), P<0.001) and 5% (1.05 (1.02–1.11), P=0.001), respectively. It was 12% (with the OR of 1.12 (95% CI: 1.07–1.18), P<0.001) and 9% (1.09 (1.05–1.15), P<0.001) for VTDR. The present study shows that elevated plasma levels of RBP4 were associated with DR and VDTR in Chinese patients with type 2 diabetes, suggesting a possible role of RBP4 in the pathogenesis of DR complications. Lowering RBP4 could be a new strategy for treating type 2 diabetes with DR.

Circulating Serum Fatty Acid-Binding Protein 4 Levels Predict the Development of Diabetic Retinopathy in Type 2 Diabetic Patients

PURPOSE

Fatty acid-binding protein 4 (FABP4) has been implicated in the pathology of diabetes and macrovascular diseases. Serum FABP4 levels were determined in type 2 diabetic patients without diabetic retinopathy (DR) at admission in order to investigate a possible contribution of FABP4 to the increased risk of 5-year incidence of DR.

DESIGN

Cohort study.

METHODS

A total of 738 patients with type 2 diabetes without DR were consecutively enrolled and followed up prospectively. Retinopathy evaluation was annually performed by ophthalmologists in the following 5 years. Multivariate analyses were performed using logistic regression models.

RESULTS

During the follow-up period, 152 (20.60% [95% CI: 17.68%-23.51%]) patients developed DR and 60 (8.13% [95% CI: 6.16%-10.10%]) patients developed vision-threatening DR (VTDR). Nonparametric Spearman rank correlation revealed a statistically significant positive correlation between serum FABP 4 level and international Clinical Diabetic Retinopathy Severity Scales (r = 0.348; P < .001). After adjustment for other established risk factors, in multivariate models comparing the third and fourth quartiles against the first quartile of the FABP4, levels of FABP4 were associated with DR and the adjusted risk of DR increased by 124% (OR = 2.24 [95% CI 1.65-3.68], P = .006) and 227% (3.27 [2.04-5.56], P < .001), respectively. Similarly, the adjusted risk of VTDR increased by 140% (OR = 2.40 [95% CI 1.32-3.82], P = .001) and 278% (3.78 [2.17-6.59], P < .001), respectively.

CONCLUSION

FABP4 shows potential as a novel biomarker for DR prediction in Chinese patients with T2DM, and strict glycemic control and more frequent retinal examination should be highlighted for T2DM patients with the highest quartile range of FABP4.

Elevated Lipoprotein (a) and Risk of Poor Functional Outcome in Chinese Patients with Ischemic Stroke and Type 2 Diabetes

The aim of this study was to evaluate the short-term prognostic value of early measurement of serum lipoprotein (a) [Lp(a)] levels in Chinese patients with type 2 diabetes (T2D) and acute ischemic stroke (AIS). The study population comprised 232 consecutive patients with an AIS diagnosis complicated with T2D. Functional outcome was obtained on month 3 according to the modified Rankin Scale (mRS). Unfavorable functional outcome was defined as a mRS score of 3 to 6 points. The prognostic value of Lp(a) at admission to predict the unfavorable functional outcome 3 months after stroke onset was compared with the National Institutes of Health Stroke Scale score and other known outcome predictors. The Lp(a) levels in those patients were obtained with a median value of 16.8 mg/dl (IQR, 9.5-34.4 mg/dl). At 3-month follow-up, an unfavorable functional outcome was found in 86 patients (37.1%). In multivariate models comparing the second (Q2), third, and fourth quartiles against the first quartile of Lp(a), concentrations of Lp(a) in Q2, Q3, and Q4 were associated with unfavorable outcome, and increased risk of unfavorable outcome by 42, 131, and 211%. Interestingly, an elevated Lp(a, > 30 mg/dl) was also associated with unfavorable outcome, and with adjusted OR of 2.25 (95% CI 1.39-3.68). The AUC was significantly increased by adding Lp(a) to established risk factors (difference, 0.041 [95% CI, 0.034-0.053]; P = 0.02). The addition of Lp(a) to established risk factors significantly improved net reclassification improvement and integrated discrimination improvement. Higher Lp(a) levels at admission were associated with increased risk of unfavorable functional outcome and might be useful in identifying stroke patients with T2D at risk for unfavorable functional outcome for early prevention strategies.