Oxidized and electronegative low-density lipoprotein as potential biomarkers of cardiovascular risk in obese adolescents

Impaired HDL-associated enzymes and proteins in children and adolescents with weight disorders and their association with novel cardiometabolic indexes

BACKGROUND AND AIMS

Overweight/obesity (OW/OB) is associated with modifications in lipoprotein (Lp)-associated enzymes and proteins, such as cholesteryl ester transfer protein (CETP), Lp-associated phospholipase A2 (LpPLA2) and paraoxonase (PON)1. No evidence is available regarding underweight (UW). The following indexes have been proposed to better assess atherogenic risk related to weight alterations: triglycerides-glucose index (TyG), visceral adiposity index (VAI) and height-corrected lipid accumulation product (HLAP).

AIM

To analyze the presence of alterations in Lp-associated enzymes and proteins in children and adolescents with UW and OW/OB and their relation to novel cardiometabolic indexes.

METHODS AND RESULTS

Thirty male children and adolescents with UW, 66 with normal weight (NW) and 30 with OW/OB were included. Anthropometric parameters, glucose, Lp profile and the activities of CETP, LpPLA2 and PON1 were evaluated. Body mass index (BMI)-z, TyG, VAI and HLAP were calculated. UW and NW showed lower CETP activity than OW/OB (Mean ± SD) (218 ± 38vs.224 ± 26vs.237 ± 26%/mL.h; p < 0.05). UW and OW/OB showed lower PON1 activity than NW (318 ± 170vs.409 ± 200vs.310 ± 184 nmol/mL.min; p < 0.05). TyG was higher in OW/OB than UW (p < 0.01), whilst both HLAP (p < 0.05) and VAI (p < 0.01) followed a linear trend across weight categories. After adjusting for age and BMI-z, TyG was an independent predictor of CETP (r2 = 0.25, β = -0.22, p < 0.01) and LpPLA2 (r2 = 0.21,β = -0.21,p < 0.05), while VAI (r2 = 0.21,β = -0.32,p < 0.01) and HLAP (r2 = 0.20,β = -0.31,p < 0.01) of CETP.

CONCLUSIONS

Both UW and OW/OB showed impaired antioxidant PON1 activity. Moreover, TyG, VAI and HLAP were all capable of predicting alterations in crucial modulators of Lp metabolism and vascular inflammation in children and adolescents with varying degrees of alterations in body weight.

Changes in the Composition and Function of Lipoproteins after Bariatric Surgery in Patients with Severe Obesity

The effect of bariatric surgery on lipid profile and the qualitative characteristics of lipoproteins was analyzed in morbidly obese subjects. Thirteen obese patients underwent bariatric surgery. Plasma samples were obtained before surgery and at 6 and 12 months after the intervention. Thirteen healthy subjects comprised the control group. Lipid profile, hsCRP, and the composition and functional characteristics of VLDL, LDL, and HDL were assessed. At baseline, plasma from subjects with obesity had more triglycerides, VLDLc, and hsCRP, and less HDLc than the control group. These levels progressively normalized after surgery, although triglyceride and hsCRP levels remained higher than those in the controls. The main differences in lipoprotein composition between the obese subjects and the controls were increased apoE in VLDL, and decreased cholesterol and apoJ and increased apoC-III content in HDL. The pro-/anti-atherogenic properties of LDL and HDL were altered in the subjects with obesity at baseline compared with the controls, presenting smaller LDL particles that are more susceptible to modification and smaller HDL particles with decreased antioxidant capacity. Bariatric surgery normalized the composition of lipoproteins and improved the qualitative characteristics of LDL and HDL. In summary, patients with obesity present multiple alterations in the qualitative properties of lipoproteins compared with healthy subjects. Bariatric surgery reverted most of these alterations.

Clinical Significance of Electronegative Low-Density Lipoprotein Cholesterol in Atherothrombosis

Despite the numerous risk factors for atherosclerotic cardiovascular diseases (ASCVD), cumulative evidence shows that electronegative low-density lipoprotein (L5 LDL) cholesterol is a promising biomarker. Its toxicity may contribute to atherothrombotic events. Notably, plasma L5 LDL levels positively correlate with the increasing severity of cardiovascular diseases. In contrast, traditional markers such as LDL-cholesterol and triglyceride are the therapeutic goals in secondary prevention for ASCVD, but that is controversial in primary prevention for patients with low risk. In this review, we point out the clinical significance and pathophysiological mechanisms of L5 LDL, and the clinical applications of L5 LDL levels in ASCVD can be confidently addressed. Based on the previously defined cut-off value by receiver operating characteristic curve, the acceptable physiological range of L5 concentration is proposed to be below 1.7 mg/dL. When L5 LDL level surpass this threshold, clinically relevant ASCVD might be present, and further exams such as carotid intima-media thickness, pulse wave velocity, exercise stress test, or multidetector computed tomography are required. Notably, the ultimate goal of L5 LDL concentration is lower than 1.7 mg/dL. Instead, with L5 LDL greater than 1.7 mg/dL, lipid-lowering treatment may be required, including statin, ezetimibe or PCSK9 inhibitor, regardless of the low-density lipoprotein cholesterol (LDL-C) level. Since L5 LDL could be a promising biomarker, we propose that a high throughput, clinically feasible methodology is urgently required not only for conducting a prospective, large population study but for developing therapeutics strategies to decrease L5 LDL in the blood.

The effect of palmitic acid on inflammatory response in macrophages: an overview of molecular mechanisms

Palmitic acid is a saturated fatty acid whose blood concentration is elevated in obese patients. This causes inflammatory responses, where toll-like receptors (TLR), TLR2 and TLR4, play an important role. Nevertheless, palmitic acid is not only a TLR agonist. In the cell, this fatty acid is converted into phospholipids, diacylglycerol and ceramides. They trigger the activation of various signaling pathways that are common for LPS-mediated TLR4 activation. In particular, metabolic products of palmitic acid affect the activation of various PKCs, ER stress and cause an increase in ROS generation. Thanks to this, palmitic acid also strengthens the TLR4-induced signaling. In this review, we discuss the mechanisms of inflammatory response induced by palmitic acid. In particular, we focus on describing its effect on ER stress and IRE1α, and the mechanisms of NF-κB activation. We also present the mechanisms of inflammasome NLRP3 activation and the effect of palmitic acid on enhanced inflammatory response by increasing the expression of FABP4/aP2. Finally, we focus on the consequences of inflammatory responses, in particular, the effect of TNF-α, IL-1β and IL-6 on insulin resistance. Due to the high importance of macrophages and the production of proinflammatory cytokines by them, this work mainly focuses on these cells.