Lipoprotein (a) is not significantly associated with type 2 diabetes mellitus: cross-sectional study of 1604 cases and 7983 controls

Is inverse association between lipoprotein(a) and diabetes mellitus another paradox in cardiometabolic medicine?

INTRODUCTION

The impact of Type II Diabetes mellitus (T2DM) on cardiovascular disease (CVD) is well-established, while lipoprotein(a) [Lp(a)] has recently emerged as a recognized CVD risk factor. The rising prevalence of T2DM resulting from modern lifestyles and the development of specific Lp(a)-lowering agents brought the association between T2DM and Lp(a) in the forefront.

AREAS COVERED

Despite advancements in T2DM treatment, diabetic patients remain at very-high risk of CVD. Lp(a) may, to some extent, contribute to the persistent CVD risk seen in diabetic patients, and the coexistence of T2DM and elevated Lp(a) levels appears to synergistically amplify overall CVD risk. The relationship between T2DM and Lp(a) is paradoxical. On one hand, high Lp(a) plasma concentrations elevate the risk of diabetic microvascular and macrovascular complications. On the other hand, low Lp(a) plasma concentrations have been linked to an increased risk of developing T2DM.

EXPERT OPINION

Comprehending the association between T2DM and Lp(a) is critical due to the pivotal roles both entities play in overall CVD risk, as well as the unique aspects of their relationship. The mechanisms underlying the inverse association between T2DM and Lp(a) remain incompletely understood, necessitating further meticulous research.

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.

Association between Serum Uric Acid and Hypertension in a Large Cross-Section Study in a Chinese Population

Background: The association of serum uric acid (SUA) with hypertension has been well established in Caucasian populations. However, its association with hypertension in Chinese remained to be clarified. Methods: Consecutive patients, homogeneous in Chinese Han ethnicity, aged ≥18 years, abstracted from the database, admitted from 1 January 2010 to 31 December 2013, were included for potential analysis. The patients were grouped according to the presence or absence of hypertension. Unconditional logistic regression was performed to estimate the association between SUA and hypertension. Its possible interactions with risk factors on hypertension were also explored. Results: A total of 9587 patients were finally analyzed in the current study, where 5692 were with hypertension and 3895 were without hypertension. Per 100 μmol/L higher SUA concentration was associated with multivariable-adjusted odds ratios (95% CI) of 1.25 (1.08−1.22) in males, 1.10 (1.01−1.20) in females, and 1.19 (1.13−1.24) in total. On a categorical scale, when compared with the first quintile, the multivariable-adjusted odds ratios (95% CI) were 1.40 (1.20−1.64) for the 2nd quintile, 1.48 (1.27−1.74) for the 3rd quintile, 1.55 (1.32−1.82) for the 4th quintile, and 1.92 (1.63−2.26) for the 5th quintile, with a p for trend < 0.01. Conclusions: SUA is associated with hypertension in a dose-response manner among the Chinese hospitalized population. Management of SUA could help to the prevention and control of hypertension.

Clinical investigation of lipoprotein (a) levels in type 2 diabetics for cariovascular diseases prediction and prognosis

OBJECTIVES

We aimed to evaluate the levels of serum lipoprotein a, LP (a), in Jordanian patients with type 2 diabetes mellitus (DM); and to examine its relation to glycemic control, metabolic syndrome (MS) and duration of DM. The LP (a) is considered one of the independent risk factors for coronary artery disease (CAD) in the general population.

METHODS

Fasting blood samples were drawn from 51 diabetic patients with type 2 DM and 31 non-diabetic age and sex control subjects. Serum LP (a) was measured along with other parameters, including triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-c), low-density lipoprotein cholesterol (LDL-c) and glycosylated haemoglobin (HbA_1c). Correlation analyses were performed between LP (a) and the various variables measured.

RESULTS

LP (a) measurement showed a skewed distribution towards the lower levels in both groups. Mean LP (a) levels showed a statistically insignificant difference between the two groups. No correlations of LP (a) were observed with age, sex or body mass index (BMI). No correlations of LP (a) with LDL-c, HDL-c, TG, TC, MS, DM duration or HbA_1c were observed. The LP (a) serum levels were significantly higher in type 2 diabetic patients with retinopathy.

CONCLUSIONS

LP (a) serum levels are not increased in type 2 diabetic patients; so, LP (a) may not be a reliable marker for early therapeutic interventions in DM patients, even in high-risk for thrombosis groups.

High lipoprotein(a) concentrations are associated with lower type 2 diabetes risk in the Chinese Han population: a large retrospective cohort study

Background

Lipoprotein (a) [Lp(a)] is a proven independent risk factor for coronary heart disease. It is also associated with type 2 diabetes mellitus (T2DM). However, the correlation between Lp(a) and T2DM has not been clearly elucidated.

Methods

This was a retrospective cohort study involving 9248 T2DM patients and 18,496 control individuals (1:2 matched). Patients were randomly selected from among inpatients in the Second Affiliated Hospital of Nanchang University between 2006 and 2017. Clinical characteristics were compared between the two groups. Spearman rank-order correlation coefficients were used to evaluate the strength and direction of monotonic associations of serum Lp(a) with other metabolic risk factors. Binary logistic regression analysis was used to establish the correlation between Lp(a) levels and T2DM risk.

Results

The median Lp(a) concentration was lower in T2DM patients than in controls (16.42 vs. 16.88 mg/dL). Based on four quartiles of Lp(a) levels, there was a decrease in T2DM risk from 33.7% (Q1) to 31.96% (Q4) (P for trend < 0.0001). Then, Lp(a) levels > 28.72 mg/dL (Q4) were associated with a significantly lower T2DM risk in the unadjusted model [0.924 (0.861, 0.992), P = 0.030]. Similar results were obtained in adjusted models 1 [Q4, 0.925 (0.862, 0.993), P = 0.031] and 2 [Q4, 0.919 (0.854, 0.990), P = 0.026]. Furthermore, in the stratified analysis, Q4 of Lp(a) was associated with a significantly lower T2DM risk among men [0.813 (0.734, 0.900), P < 0.001] and those age > 60 years [0.819 (0.737, 0.910), P < 0.001]. In contrast, the low-density lipoprotein cholesterol (LDL-C) levels and coronary heart disease (CHD) did not impact these correlations between Lp(a) and diabetes.

Conclusions

There is an inverse association between Lp(a) levels and T2DM risk in the Chinese population. Male patients, especially those aged more than 60 years with Lp(a) > 28.72 mg/dL, are low-risk T2DM individuals, regardless of LDL-C levels and CHD status.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12944-021-01504-x.

Lp(a) and Apo-lipoproteins as predictors for micro- and macrovascular complications of diabetes: A case-cohort study

AIMS

To investigate the associations between Lp(a), Apo A1, Apo B, and Apo B/Apo A1 ratio with micro- and macrovascular complications of diabetes.

METHODS AND RESULTS

In this case-cohort study, 1057 patients with type 2 diabetes (T2DM) were followed in the diabetes clinic of Vali-Asr Hospital from 2014 to 2019. The association between serum Lp (a) and apolipoproteins with cardiovascular disease (CVD), neuropathy, and nephropathy were assessed by using binary regression analysis. The ROC curve analysis was used to evaluate the predictive properties of proteins. Youden index was used to calculate cutoff values. Among patients with T2DM, 242, 231, and 91 patients developed CVD, neuropathy, and nephropathy, respectively. The serum Lp (a) level was positively correlated with the development of all three. (P-values = 0.022, 0.042, and 0.038, respectively). The Apo A1 level was negatively correlated with nephropathy. Among the biomarkers, Lp(a) had the highest AUC for prediction of CVD, neuropathy, and nephropathy. Calculated cutoff values of Lp(a), and Apo A1 levels were higher than the standard cutoff values.

CONCLUSION

Serum level of Lp(a) is a predictor for CVD, neuropathy, and nephropathy. Based on the calculated cutoff values in patients with T2DM, we should consider diabetic complications at higher levels of Lp(a).

Interaction between lipoprotein (a) levels and body mass index in first incident acute myocardial infarction

BACKGROUND

Possible interaction between Lipoprotein (a) (Lp(a)) and body mass index (BMI) was investigated with regard to the risk of first incident acute myocardial infarction (AMI).

METHODS

Cross-sectional study of 1522 cases with initial AMI and 1691 controls without coronary artery disease (CAD) were retrospectively analyzed using logistic regression model. Subjects were categorized based on Lp(a) and BMI and compared with regard to occurrence of AMI by calculating odds ratios (ORs) with 95% confidence intervals (CIs). A potential interaction between Lp(a) and BMI was evaluated by the measures of effect modification on both additive (Relative excess risk due to interaction, RERI) and multiplicative scales.

RESULTS

Compared with reference group (BMI < 24 kg/m² and in the first quintile of Lp(a)), multivariable-adjusted analysis revealed that ORs(95%CI) of AMI were 2.27(1.46-3.52) for higher BMI alone; 1.79(1.11-2.90), 1.65(1.05-2.60), 1.96(1.20-3.20) and 2.34(1.47-3.71) for higher Lp(a) alone across its quintiles; and 2.86(1.85-4.40), 3.30(2.14-5.11), 4.43(2.76-7.09) and 5.98(3.72-9.60) for both higher BMI and higher Lp(a), greater than the sum of the both risks each. Prominent interaction was found between Lp(a) and BMI on additive scale (RERI = 2.45 (0.36-4.54) at the fifth quintile of Lp(a)) but not on multiplicative scale.

CONCLUSIONS

This study demonstrates that BMI and Lp(a) levels are important factors affecting the risk of AMI. Significant interaction is found between Lp(a) and BMI in initial AMI on additive scale, indicating that Lp(a) confers greater risk for initial AMI when BMI is elevated. For those whose BMIs are inadequately controlled, Lp(a) lowering may be an option.

TRIAL REGISTRATION

This clinical study was not registered in a publicly available registry because this study was a retrospective study first started in 2015. Data are available via the correspondent.

LPA kringle IV type 2 is associated with type 2 diabetes in a Chinese population with very high cardiovascular risk

The connection between lipoprotein (a) [Lp(a)] levels and the risks of cardiovascular disease and diabetes remains poorly understood. Lp(a) is encoded by the LPA gene, and evidence suggests that the kringle IV type 2 (KIV-2) variant is particularly important to Lp(a) isoform size. A large isoform size, represented as a high number of KIV-2 repeats in LPA, is associated with low serum Lp(a) concentrations and an increased risk of type 2 diabetes. We investigated the associations among Lp(a) concentrations, LPA KIV-2 repeats, and type 2 diabetes in a Chinese population of 1,863 consecutive patients with very high cardiovascular risk, as identified by coronary angiography. Individuals with Lp(a) levels in the top tertile [67.86 (35.34-318.50) mg/dl] had a lower risk of diabetes compared with those in the bottom tertile [7.38 (0.60-12.91) mg/dl]. There was an inverse association between the number of KIV-2 repeats and serum Lp(a) concentrations. This study demonstrated that a high number of LPA KIV-2 repeats are associated with increased risk of type 2 diabetes in a Chinese population with very high cardiovascular risk, which suggests that large Lp(a) isoform size, associated with low Lp(a) concentration, has a causal effect on type 2 diabetes.

Association between lipoprotein(a) level and type 2 diabetes: no evidence for a causal role of lipoprotein(a) and insulin

AIMS

Inverse relationships have been described between the largely genetically determined levels of serum/plasma lipoprotein(a) [Lp(a)], type 2 diabetes (T2D) and fasting insulin. Here, we aimed to evaluate the nature of these relationships with respect to causality.

METHODS

We tested whether we could replicate the recent negative findings on causality between Lp(a) and T2D by employing the Mendelian randomization (MR) approach using cross-sectional data from three independent cohorts, Berlin Aging Study II (BASE-II; n = 2012), LIFE-Adult (n = 3281) and LIFE-Heart (n = 2816). Next, we explored another frequently discussed hypothesis in this context: Increasing insulin levels during the course of T2D disease development inhibits hepatic Lp(a) synthesis and thereby might explain the inverse Lp(a)-T2D association. We used two fasting insulin-associated variants, rs780094 and rs10195252, as instrumental variables in MR analysis of n = 4937 individuals from BASE-II and LIFE-Adult. We further investigated causality of the association between fasting insulin and Lp(a) by combined MR analysis of 12 additional SNPs in LIFE-Adult.

RESULTS

While an Lp(a)-T2D association was observed in the combined analysis (meta-effect of OR [95% CI] = 0.91 [0.87-0.96] per quintile, p = 1.3x10^-4), we found no evidence of causality in the Lp(a)-T2D association (p = 0.29, fixed effect model) when using the variant rs10455872 as the instrumental variable in the MR analyses. Likewise, no evidence of a causal effect of insulin on Lp(a) levels was found.

CONCLUSIONS

While these results await confirmation in larger cohorts, the nature of the inverse Lp(a)-T2D association remains to be elucidated.