Absence of clinical relationship between oxidized low density lipoproteins and diabetic peripheral neuropathy: a case control study

Correlation Between Serum β2-GPI/oxLDL and the Risk of Cerebral Infarction in Patients with T2DM

Objective

This study aims to study the correlation between serum β2-glycoprotein I (β2-GPI)/oxidized low-density lipoprotein (oxLDL) and the risk of cerebral infarction in patients with type 2 diabetes (T2DM).

Methods

From January 2019 to March 2021, 56 patients with T2DM combined with cerebral infarction were chosen as a diabetic cerebral infarction (DCI) group, and 60 patients with simple T2DM were chosen as a T2DM group. In addition, 60 healthy volunteers were recruited as a control group. The essential information of each group was collected, and the serum β2-GPI/oxLDL and inflammatory factor levels in each group were compared. The clinical factors that affect the risk of ischemic cerebral infarction in patients with T2DM were analyzed by a logistic model.

Results

Compared with the control group, the level of serum β2-GPI/oxLDL in the T2DM and DCI groups increased significantly, P < 0.001. Compared with the T2DM group, the serum β2-GPI/oxLDL level in the DCI group increased significantly, P < 0.05. The result of Pearson’s correlation analysis showed that serum β2-GPI/oxLDL was positively correlated with total cholesterol, triglycerides, fasting blood glucose, 2-h postprandial blood glucose, glycosylated hemoglobin, interleukin-6, and tumor necrosis factor (TNF)-α (all P’s < 0.05). Serum TNF-α and β2-GPI/oxLDL were independent risk variates for DCI (P < 0.05). Based on the receiver operating characteristic curve analysis, the values of the area under the curve for TNF-α, serum β2-GPI/oxLDL, and the combined diagnosis of DCI were 0.653 (0.552–0.753), 0.680 (0.583–0.777), 0.739 (0.647–0.831), respectively.

Conclusion

In DCI patients, the levels of serum oxLDL/β2-GPI are significantly increased. Serum oxLDL/β2-GPI is an independent risk factor that affects the occurrence of DCI. In addition, the serum β2-GPI/oxLDL level implicates the lipid metabolism and inflammatory status of the internal environment of DCI patients to a certain extent.

Biomarkers of dyslipidemia in patients with diabetic foot

Diabetic foot (DF) is one of the most severe complications of diabetes that significantly reduces the quality of life and survival of patients. Besides firmly established risk factors, novel data indicate that alterations in lipid metabolism might also be implicated in the development and progression of DF. Diabetic dyslipidemia is characterized by the atherogenic triad, consisting of increased triglycerides (TG), decreased high-density lipoprotein cholesterol (HDL-C) levels and the presence of small, dense low-density lipoprotein (LDL) particles. Accumulating evidence suggests that profound hypertriglyceridemia and HDL-C reduction are common findings in patients with diabetic neuropathy and significantly contribute to an increased risk for DF, amputation and mortality. Small, dense LDL particles play an important role in the development of cardiovascular complications of diabetes, but their clinical importance in patients with DF remains to be established. In this paper, we will discuss the significance of standard and novel lipid biomarker determination in the assessment of the risk for the development and progression of DF.

Lipids and peripheral neuropathy

PURPOSE OF REVIEW

Hyperlipidaemia is associated with the development of neuropathy. Indeed, a mechanistic link between altered lipid metabolism and peripheral nerve dysfunction has been demonstrated in a number of experimental and clinical studies. Furthermore, post hoc analyses of clinical trials of cholesterol and triglyceride-lowering pharmacotherapy have shown reduced rates of progression of diabetic neuropathy. Given, there are currently no FDA approved disease-modifying therapies for diabetic neuropathy, modulation of lipids may represent a key therapeutic target for the treatment of diabetic nerve damage. This review summarizes the current evidence base on the role of hyperlipidaemia and lipid lowering therapy on the development and progression of peripheral neuropathy.

RECENT FINDINGS

A body of literature supports a detrimental effect of dyslipidaemia on nerve fibres resulting in somatic and autonomic neuropathy. The case for an important modulating role of hypertriglyceridemia is stronger than for low-density lipoprotein cholesterol (LDL-C) in relation to peripheral neuropathy. This is reflected in the outcomes of clinical trials with the different therapeutic agents targeting hyperlipidaemia reporting beneficial or neutral effects with statins and fibrates. The potential concern with the association between proprotein convertase subtilisin/kexin type 9 (PCSK9) inhibitor therapy and cognitive decline raised the possibility that extreme LDL-C lowering may result in neurodegeneration. However, studies in murine models and data from small observational studies indicate an association between increased circulating PCSK9 levels and small nerve fibre damage with a protective effect of PCSK9i therapy against small fibre neuropathy. Additionally, weight loss with bariatric surgery leads to an improvement in peripheral neuropathy and regeneration of small nerve fibres measured with corneal confocal microscopy in people with obesity with or without type 2 diabetes. These improvements correlate inversely with changes in triglyceride levels.

SUMMARY

Hyperlipidaemia, particularly hypertriglyceridemia, is associated with the development and progression of neuropathy. Lipid modifying agents may represent a potential therapeutic option for peripheral neuropathy. Post hoc analyses indicate that lipid-lowering therapies may halt the progression of neuropathy or even lead to regeneration of nerve fibres. Well designed randomized controlled trials are needed to establish if intensive targeted lipid lowering therapy as a part of holistic metabolic control leads to nerve fibre regeneration and improvement in neuropathy symptoms.

A systematic review and meta-analysis of the serum lipid profile in prediction of diabetic neuropathy

Whether the lipid profile in diabetic patients is associated with diabetic neuropathy (DN) development remains ambiguous, as does the predictive value of serum lipid levels in the risk of DN. Here, we performed the first meta-analysis designed to investigate the relationship between DN and the serum levels of triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL), and low-density lipoprotein cholesterol (LDL). Candidate studies were comprehensively identified by searching PubMed, Embase, Cochrane Library and Web of Science databases up to May 2020. Observational methodological meta-analysis was conducted to assess the relationships of TG, TC, HDL, and LDL levels with DN. Changes in blood lipids were used to estimate the effect size. The results were pooled using a random-effects or fixed-effects model. Potential sources of heterogeneity were explored by subgroup analysis. Various outcomes were included, and statistical analyses were performed using STATA (Version 12.0). Mean differences (MDs) and odds ratios (ORs) with 95% confidence intervals (CIs) were estimated. The Newcastle–Ottawa Scale (NOS) was applied to assess the methodological quality. I2 statistics were calculated to evaluate statistical heterogeneity. Funnel plots were utilized to test for publication bias. A sensitivity analysis was performed by omitting each study one by one. Thirty-nine clinical trials containing 32,668 patients were included in the meta-analysis. The results demonstrated that DN patients showed higher TG and lower HDL levels (MD = 0.34, 95% CI: 0.20–0.48 for TG; MD = -0.05, 95% CI: -0.08–-0.02, I² = 81.3% for HDL) than controls. Subgroup analysis showed that patients with type 1 diabetes mellitus (T1DM) neuropathy had elevated TG levels in their serum (MD = 0.25, 95% CI: 0.16–0.35,I² = 64.4% for T1DM). However, only patients with T1DM neuropathy had reduced serum HDL levels, and there was no significant difference in serum HDL levels between patients with T2DM neuropathy and controls (MD = -0.07, 95% CI: -0.10–-0.03, I² = 12.4% for T1DM; MD = -0.02, 95% CI: -0.07–0.03, I² = 80.2% for T2DM). TC and LDL levels were not significantly different between DN patients and controls (MD = -0.03, 95% CI: -0.14–0.09, I² = 82.9% for TC; MD = -0.00, 95% CI: -0.08–0.08, I² = 78.9% for LDL). In addition, compared with mild or painless DN patients, those with moderate or severe pain DN pain had significantly reduced serum TC and LDL levels (MD = -0.31, 95% CI: -0.49–-0.13, I² = 0% for TC; MD = -0.19, 95% CI: -0.32–-0.08, I² = 0% for LDL). TG levels and HDL levels did not vary considerably between patients with mild or painless DN and those with moderate or severe DN pain patients (MD = 0.12, 95% CI: -0.28–0.51, I² = 83.2% for TG; MD = -0.07, 95% CI:-0.14–0.01, I² = 58.8% for HDL). Furthermore, people with higher TG and LDL levels had higher risk of DN (OR = 1.36, 95% CI: 1.20–1.54, I² = 86.1% for TG and OR = 1.10, 95% CI: 1.02–1.19, I² = 17.8% for LDL). Conversely, high serum HDL levels reduced the risk of DN (OR = 0.85, 95% CI: 0.75–0.96, I² = 72.6%), while TC levels made no significant difference with the risk of DN (OR = 1.02, 95% CI: 1.00–1.04, I² = 84.7%). This meta-analysis indicated that serum lipid profile changes are among the biological characteristics of DN. Lipid levels should be explored as routine laboratory markers for predicting the risk of DN, as they will help clinicians choose appropriate therapies, and thus optimize the use of available resources.

Designing a Logistic Regression Model for a Dataset to Predict Diabetic Foot Ulcer in Diabetic Patients: High-Density Lipoprotein (HDL) Cholesterol Was the Negative Predictor

OBJECTIVES

Although the risk factors for diabetic neuropathy and diabetic foot ulcer have been detected, there was no practical modeling for their prediction. We aimed to design a logistic regression model on an Iranian dataset to predict the probability of experiencing diabetic foot ulcers up to a considered age in diabetic patients.

METHODS

The present study was a statistical modeling on a previously published dataset. The covariates were sex, age, body mass index (BMI), fasting blood sugar (FBS), hemoglobin A1C (HbA1C), low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglyceride (TG), insulin dependency, and statin use. The final model of logistic regression was designed through a manual stepwise method. To study the performance of the model, an area under receiver operating characteristic (AUC) curve was reported. A scoring system was defined according to the beta coefficients to be used in logistic function for calculation of the probability.

RESULTS

The pretest probability for the outcome was 30.83%. The final model consisted of age (β1 = 0.133), BMI (β2 = 0.194), FBS (β3 = 0.011), HDL (β4 = -0.118), and insulin dependency (β5 = 0.986) (P < 0.1). The performance of the model was definitely acceptable (AUC = 0.914).

CONCLUSION

This model can be used clinically for consulting the patients. The only negative predictor of the risk is HDL cholesterol. Keeping the HDL level more than 50 (mg/dl) is strongly suggested. Logistic regression modeling is a simple and practical method to be used in the clinic.

Non-glucose risk factors in the pathogenesis of diabetic peripheral neuropathy

In this review, we consider the diverse risk factors in diabetes patients beyond hyperglycemia that are being recognized as contributors to diabetic peripheral neuropathy (DPN). Interest in such alternative mechanisms has been encouraged by the recognition that neuropathy occurs in subjects with metabolic syndrome and pre-diabetes and by the reporting of several large clinical studies that failed to show reduced prevalence of neuropathy after intensive glucose control in patients with type 2 diabetes. Animal models of obesity, dyslipidemia, hypertension, and other disorders common to both pre-diabetes and diabetes have been used to highlight a number of plausible pathogenic mechanisms that may either damage the nerve independent of hyperglycemia or augment the toxic potential of hyperglycemia. While pathogenic mechanisms stemming from hyperglycemia are likely to be significant contributors to DPN, future therapeutic strategies will require a more nuanced approach that considers a range of concurrent insults derived from the complex pathophysiology of diabetes beyond direct hyperglycemia.

Pain Control by Targeting Oxidized Phospholipids: Functions, Mechanisms, Perspectives

Within the lipidome oxidized phospholipids (OxPL) form a class of chemically highly reactive metabolites. OxPL are acutely produced in inflamed tissue and act as endogenous, proalgesic (pain-inducing) metabolites. They excite sensory, nociceptive neurons by activating transient receptor potential ion channels, specifically TRPA1 and TRPV1. Under inflammatory conditions, OxPL-mediated receptor potentials even potentiate the action potential firing rate of nociceptors. Targeting OxPL with D-4F, an apolipoprotein A-I mimetic peptide or antibodies like E06, specifically binding oxidized headgroups of phospholipids, can be used to control acute, inflammatory pain syndromes, at least in rodents. With a focus on proalgesic specificities of OxPL, this article discusses, how targeting defined substances of the epilipidome can contribute to mechanism-based therapies against primary and secondary chronic inflammatory or possibly also neuropathic pain.

Associations of serum low-density lipoprotein and systolic blood pressure levels with type 2 diabetic patients with and without peripheral neuropathy: systemic review, meta-analysis and meta-regression analysis of observational studies

BACKGROUND

Compositional abnormalities in lipoproteins and cardiovascular risk factors play an important role in the progression of diabetic peripheral neuropathy (DPN). This systematic review aimed to estimate the predicting value of low-density lipoprotein (LDL) and systolic blood pressure (SBP) level in type-2 diabetes mellitus (T2DM) patients with and without peripheral neuropathy. We also tried to determine whether LDL and SBP are associated with an increased collision risk of DPN.

METHODS

A systematic search was conducted for eligible publications which explored the LDL and SBP level in T2DM patients with and without peripheral neuropathy. The quality of the included studies was assessed by the QUADAS-2 tool. The standardized mean difference (SMD) with 95% CI of LDL and SBP level were pooled to assess the correlation between LDL and SBP level with DPN. We performed random effects meta-regression analyses to investigate factors associated with an increased collision risk of DPN.

RESULTS

There was a significant association between LDL and SBP with poor prognosis of DPN in those included studies (I₂ = 88.1% and I₂ = 84.9%, respectively, Both P < 0.001). European T2DM patients have higher serum level of LDL in compare with the European DPN patients (SMD = 0.16, 95% CI: - 0.06 - 0.38; P < 0.001). SBP level was associated with a 2.6-fold decrease in non-DPN patients of T2DM (SMD = - 2.63, 95% CI: - 4.00 - -1.27, P < 0.001). Old age European T2DM patients have significantly high risk for diabetes drivers. Furthermore, the results of the case-control study design model are more precise to show the accuracy of SBP in Asian T2DM patients.

CONCLUSION

Our finding supports the LDL and SBP status could be associated with increased risk of peripheral neuropathy in T2DM patients.