Type 2 Diabetes Associated Changes in the Plasma Non-Esterified Fatty Acids, Oxylipins and Endocannabinoids

<div><p>Type 2 diabetes has profound effects on metabolism that can be detected in plasma. While increases in circulating non-esterified fatty acids (NEFA) are well-described in diabetes, effects on signaling lipids have received little attention. Oxylipins and endocannabinoids are classes of bioactive fatty acid metabolites with many structural members that influence insulin signaling, adipose function and inflammation through autocrine, paracrine and endocrine mechanisms. To link diabetes-associated changes in plasma NEFA and signaling lipids, we quantitatively targeted >150 plasma lipidome components in age- and body mass index-matched, overweight to obese, non-diabetic (n = 12) and type 2 diabetic (n = 43) African-American women. Diabetes related NEFA patterns indicated ∼60% increase in steroyl-CoA desaturase activity and ∼40% decrease in very long chain polyunsaturated fatty acid chain shortening, patterns previously associated with the development of nonalcoholic fatty liver disease. Further, epoxides and ketones of eighteen carbon polyunsaturated fatty acids were elevated >80% in diabetes and strongly correlated with changes in NEFA, consistent with their liberation during adipose lipolysis. Endocannabinoid behavior differed by class with diabetes increasing an array of N-acylethanolamides which were positively correlated with pro-inflammatory 5-lipooxygenase-derived metabolites, while monoacylglycerols were negatively correlated with body mass. These results clearly show that diabetes not only results in an increase in plasma NEFA, but shifts the plasma lipidomic profiles in ways that reflect the biochemical and physiological changes of this pathological state which are independent of obesity associated changes.</p> </div

The type 2 diabetes-associated lipidomic changes projected in context of their biological relationships in obese African-American women.

<p>Metabolites are represented by circular “nodes” linked by “edges” with arrows designating the direction of the biosynthetic gradient (i.e. substrate to product). Some metabolites are linked by more than one enzymatic step. Node sizes represent magnitudes of differences in plasma metabolite geometric means (ΔGM). Arrow widths represent magnitudes of changes in product over substrate ratios (ΔP:S). Colors of node borders and arrows represent the significance and direction of changes relative to non-diabetics as per the figure legend. Differences are significant at p<0.05 by Mann-Whitney U test adjusted for FDR (q = 0.1).</p

Concentrations of selected plasma oxylipins (nM) in BMI-matched obese non-diabetic and type 2 diabetic African-American women.^*.

*<p>Values are reported as geometric means [ranges] if changes in geometric means between groups are significant (Mann-Whitney U-test, p<0.05 with FDR adjustment at q = 0.1). For remaining measurements see <b><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048852#pone.0048852.s006" target="_blank">Tables S6</a></b> and <b><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048852#pone.0048852.s007" target="_blank">Table S7</a></b>.</p

Characteristics of overweight diabetic and non-diabetic African American Gullah-speaking female study participants.

*<p>p<0.0001 by Mann-Whitney U-test.</p

An OPLS-DA model built from 15 plasma lipids discriminates non-diabetic and diabetic cohorts.

<p>Horizontal scatter plots of the log transformed concentrations for each model variable are shown. The horizontal arrangement of metabolite scatter plots is scaled to their loading in the discriminant model. A given species importance in the classification increases with increasing displacement from the origin (broken line). The direction of the displacement, left or right, designates whether the species was decreased (left) or increased (right) in the diabetic relative to the non-diabetic patients. The overall model discrimination performance is presented as a scatter plot of subject model scores (inset).</p

Analysis of correlations among all measured variables and estimated enzyme activities in non-diabetic and type 2 diabetic African-American women.

<p>Significant (p<0.05) non-parametric Spearman’s correlations for non-diabetic (top left triangle) and type 2 diabetic (bottom right triangle) subjects are indicated by orange (positive) and blue (negative) intersections.</p

Plasma non-esterified fatty acids (µM) in BMI-matched obese non-diabetic and type 2 diabetic African-American women.^*.

*<p>Values are reported as geometric means [ranges] if changes in geometric means between groups are significant (Mann-Whitney U-test, p<0.05 with FDR adjustment at q = 0.1). For remaining measurements see <b><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048852#pone.0048852.s005" target="_blank">Table S5</a></b>.</p

Plasma N-acylamides and lipoamino acids (nM) in BMI-matched obese non-diabetic and type 2 diabetic African-American women.^*

*<p>Values are reported as geometric means [ranges] if changes in geometric means between groups are significant (Mann-Whitney U-test, p<0.05 with FDR adjustment at q = 0.1). For remaining measurements see <b><a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0048852#pone.0048852.s008" target="_blank">Table S8</a></b>.</p

Correlation Heat Map for HDL and LDL.

<p>The Pearson correlation coefficient (r) among lipoprotein-oxylipins for HDL (<b>A</b>) and LDL (<b>B</b>) is shown before treatment <b>(top)</b>, after treatment <b>(middle)</b> as correlation of nM oxylipin/mM PL along with the change in oxylipins due to treatment <b>(bottom)</b> expressed as ln(nM oxylipin<i>_final</i>/mM PL<i>_final</i>)/ln(nM oxylipin<i>_baseline</i>/mM PL<i>_baseline</i>).</p

Effect of Omega-3 Fatty Acid Ethyl Esters on the Oxylipin Composition of Lipoproteins in Hypertriglyceridemic, Statin-Treated Subjects

<div><p>Background</p><p>Oxylipins mediate inflammation, vascular tension, and more. Their presence in lipoproteins could explain why lipoproteins mediate nearly identical activities.</p><p>Methods</p><p>To determine how oxylipins are distributed in the lipoproteins of hypertriglyceridemic subjects, and whether omega-3 fatty acids alter them in a manner consistent with improved cardiovascular health, we recruited 15 dyslipidemic subjects whose levels of low density lipoprotein cholesterol (LDL-C) were at goal but who remained hypertriglyceridemic (200–499 mg/dL). They were treated them with the indicated dose of 4 g/d omega-3 acid ethyl esters (P-OM3) for 8 weeks. Measured oxylipins included mid-chain alcohols (HETEs, HEPEs and HDoHEs), ketones (KETEs), epoxides (as EpETrEs, EpETEs, and EpDPEs).</p><p>Results</p><p>At baseline, arachidonate-oxylipins (HETEs, KETEs, and EpETrEs) were most abundant in plasma with the greatest fraction of total abundance (mean |95% CI|) being carried in high density lipoproteins (HDL); 42% |31, 57| followed by very low density lipoproteins (VLDL); 27% |20, 36|; and LDL 21% |16, 28|. EPA- and DHA-derived oxylipins constituted less than 11% of total. HDL carried alcohols and epoxides but VLDL was also rich in ketones. Treatment decreased AA-derived oxylipins across lipoprotein classes (−23% |−33, −12|, p = 0.0003), and expanded EPA−(322% |241, 422|, p<0.0001) and DHA-derived oxylipins (123% |80, 176|, p<0.0001).</p><p>Conclusions</p><p>Each lipoprotein class carries a unique oxylipin complement. P-OM3 treatment alters the oxylipin content of all classes, reducing pro-inflammatory and increasing anti-inflammatory species, consistent with the improved inflammatory and vascular status associated with the treatment.</p><p>Trial Registration</p><p>ClinicalTrials.gov <a href="http://www.clinicaltrials.gov/ct2/show/NCT00959842" target="_blank">NCT00959842</a></p></div