Platelet Lipidome Fingerprint: New Assistance to Characterize Platelet Dysfunction in Obesity

Abstract

Obesity is associated with a pro-inflammatory and pro-thrombotic state that supports atherosclerosis progression and platelet hyper-reactivity. During the last decade, the platelet lipidome has been considered a treasure trove, as it is a source of biomarkers for preventing and treating different pathologies. The goal of the present study was to determine the lipid profile of platelets from non-diabetic, severely obese patients compared with their age- and sex-matched lean controls. Lipids from washed platelets were isolated and major phospholipids, sphingolipids and neutral lipids were analyzed either by gas chromatography or by liquid chromatography coupled to mass spectrometry. Despite a significant increase in obese patient's plasma triglycerides, there were no significant differences in the levels of triglycerides in platelets among the two groups. In contrast, total platelet cholesterol was significantly decreased in the obese group. The profiling of phospholipids showed that phosphatidylcholine and phosphatidylethanolamine contents were significantly reduced in platelets from obese patients. On the other hand, no significant differences were found in the sphingomyelin and ceramide levels, although there was also a tendency for reduced levels in the obese group. The outline of the glycerophospholipid and sphingolipid molecular species (fatty-acyl profiles) was similar in the two groups. In summary, these lipidomics data indicate that platelets from obese patients have a unique lipid fingerprint that may guide further studies and provide mechanistic-driven perspectives related to the hyperactivate state of platelets in obesity.

Keywords: lipidomics; obesity; platelets.

Figure 1

Workflow of the experimental design. The figure was created with Biorender.

Figure 2

Platelet cholesterol and plasma HDL cholesterol levels are decreased in obese patients compared to lean controls, whereas no significant differences between groups exist in total plasma cholesterol levels. (A) Circulating cholesterol levels in blood from obese patients and their age- and gender-matched lean controls. Cholesterol levels were measured as milligrams of cholesterol per deciliter of blood. Results are represented as mean ± SD for each group (plasma cholesterol; HDL-cholesterol and LDL-cholesterol). * p < 0.05, according to unpaired t-test. (B) Mean cholesterol and cholesteryl ester levels in platelets from obese patients and their age- and gender-matched lean controls. Results are expressed as micrograms of lipid per milligrams of total platelet proteins and represented as mean ± SEM. * p < 0.05, according to unpaired t-test.

Figure 3

Triglyceride (TG) profile in obese patients and lean controls indicate higher plasma TG levels in the former, whereas no significant differences exist in platelet TG levels between groups. (A) Circulating total TG levels in blood from obese patients and their age- and gender-matched lean controls. TG levels were measured as milligrams of triglycerides per deciliter of blood. Results are represented as mean ± SD for each group. ** p < 0.01, according to unpaired t-test. Mean total TG levels (B) and levels of three major TG molecular species (C) in platelets from obese patients and their age- and gender-matched lean controls. Results are expressed as nanograms of lipids per milligrams of total platelet proteins and represented as mean ± SEM for each group.

Figure 4

Analysis of glycerophospholipid levels in platelets from obese patients and lean controls indicates decreased levels of PC and PE in obese patients. (A) Levels of PC (i) and their molecular species (ii) in platelets from obese patients and their age- and gender-matched lean controls. In the case of (i), for each obese patient, results are expressed as fold change of area ratio (sample signal/standard signal/mg of total platelet proteins), and represented as mean fold change ± SEM for each group. Significance level is included for those cases with statistically significant differences between both groups of patients. ** p < 0.01, according to unpaired t-test. In the case of (ii), for 21 different molecular species of PC, results are expressed as mean percentage of the different PC molecular species ± SEM from obese patients (pink) and from age- and gender-matched lean controls (purple). (B) Levels of PE (i) and their molecular species (ii) in platelets from obese patients and their age- and gender-matched lean controls. In the case of (i), for each obese patient results are expressed as fold change of area ratio (sample signal/standard signal/mg of total platelet proteins), and represented as mean fold change ± SEM for each group. * p < 0.05, according to unpaired t-test. In the case of (ii), for 18 different molecular species of PE, results are expressed as mean percentage of the different PE molecular species ± SEM from obese patients (pink) and from age- and gender-matched lean controls (purple). (C) Levels of total PI and PS in platelets from obese patients and their age- and gender-matched lean controls. For each obese patient, results are expressed as fold change of area ratio (sample signal/standard signal/mg of total platelet proteins) and represented as mean fold change ± SEM for each group. PC, phosphatidylcholine; PE, phosphatidylethanolamine; PI, phosphatidylinositol; PS, phosphatidylserine.

Figure 5

Analysis of sphingolipid levels in platelets from obese patients and lean controls shows a tendency for decreased levels of SM in the obese group. (A) Levels of SM (i) and their molecular species (ii) in platelets from obese patients and their age- and gender-matched lean controls. In the case of (i), for each obese patient, results are expressed as fold change of area ratio (sample signal/standard signal/mg of total platelet proteins) and represented as mean fold change ± SEM for each group. In the case of (ii), results are expressed as mean percentage of the different SM molecular species ± SEM from obese patients (pink) and from age- and gender-matched lean controls (purple). (B) Levels of Cers (i) and their molecular species (ii) in platelets from obese patients and their age- and gender-matched lean controls. In the case of (i), for each obese patient, results are expressed as fold change of area ratio (sample signal/standard signal/mg of total platelet proteins), and represented as mean fold change ± SEM for each group. In the case of (ii), results are expressed as mean percentage of the different Cer molecular species ± SEM from obese patients (pink) and from age- and gender-matched lean controls (purple). SM, sphingomyelin; Cers, ceramides.