Shotgun Lipidomics Identifies Cardiolipin Depletion in Diabetic Myocardium Linking Altered Substrate Utilization with Mitochondrial Dysfunction

Abstract

Diabetic cardiomyopathy is characterized by excessive utilization of fatty acid substrate, diminished glucose transport, and mitochondrial dysfunction. However, the chemical mechanisms linking altered substrate utilization to mitochondrial dysfunction are unknown. Herein, we use shotgun lipidomics and multidimensional mass spectrometry to identify dramatic decreases in the critical mitochondrial inner membrane lipid, cardiolipin, in diabetic murine myocardium (from 7.2 +/- 0.3 nmol/mg of protein in control hearts to 3.1 +/- 0.1 nmol/mg of protein in diabetic myocardium; p < 0.001, n = 7). Moreover, the direct metabolic precursor of cardiolipin, phosphatidylglycerol, was also substantially depleted (2.5 +/- 0.2 nmol/mg of protein in control hearts vs 1.3 +/- 0.1 nmol/mg of protein in diabetic myocardium; p < 0.001, n = 7). Similarly, glycerol 3-phosphate, necessary for the penultimate step in phosphatidylglycerol production, decreased by 58% in diabetic myocardium (from 4.9 +/- 0.9 to 2.2 +/- 0.3 nmol/mg of protein; n = 4). Since Barth's syndrome (a disorder of cardiolipin metabolism) induces mitochondrial dysfunction and cardiomyopathy, and since decreases in cardiolipin content precipitate mitochondrial dysfunction, these results provide a unifying hypothesis linking altered substrate utilization and metabolic flux in diabetic myocardium with altered lipid metabolism, cardiolipin depletion, mitochondrial dysfunction, and resultant hemodynamic compromise.

Genetic Ablation of Calcium-independent Phospholipase A2γ Leads to Alterations in Hippocampal Cardiolipin Content and Molecular Species Distribution, Mitochondrial Degeneration, Autophagy, and Cognitive Dysfunction

“…Peak heights represent the relative intensity (%) of the individual molecular species to the intensity of the CL internal standard. The asterisks indicate doubly charged CL plusone isotopologues whose ion peak intensities were utilized to quantify individual CL molecular species as described previously (37,78). The results indicate an increase in multiple CL species in the iPLA 2 ␥ Ϫ/Ϫ mice and especially those containing shorter chain length aliphatic chains.…”

“…The results indicate an increase in multiple CL species in the iPLA 2 ␥ Ϫ/Ϫ mice and especially those containing shorter chain length aliphatic chains. B, the levels of total CL molecular species were calculated in comparison with internal standard after 13 C deisotoping as described previously (37,78). A 1.5-fold increase in total cardiolipin content was observed in the iPLA 2 ␥ Ϫ/Ϫ hippocampus in comparison to WT littermates (Total CL, p Ͻ 0.05).…”

Direct MALDI-MS analysis of cardiolipin from rat organs sections

“…Although MALDI-MS has the advantage of generating singly charged molecular ions over ESI-MS, the latter will always be the technique of choice for quantitative analysis [26]. In addition, due to instrumental limitation, we could only perform MS/MS on the precursor ions.…”

Lipids and lipidomics in brain injury and diseases

“…Despite these setbacks, there have been impressive achievements during the last few years. [10][11][12][13][14][15] The main progress that has spurred advances in lipid analysis has been the development of new mass spectroscopic (MS) techniques, particularly the " soft ionization " techniques electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI). Conventional mass spectral analyses used electron impact ionization, a method widely employed for small, volatile molecules but not applicable to complex biological molecules.…”

“…54 Studies have indicated that degradation of mitochondrial phospholipids also occurs and could affect the cellular energy metabolism via mitochondrial functions during ischemia/reperfusion. 13 , 55 , 56 Loss of cardiolipin has been implicated as a causative factor in mitochondrial dysfunction and release of cytochrome c. 13 Another lipid alteration implicated in initiation of apoptosis is translocation of phosphatidylserine (PtdSer) from the inner to the outer leafl et of the membrane lipid bilayer. 57 , 58 We have previously demonstrated signifi cant loss of PtdCho, PtdIns, PtdSer, sphingomyelin, and cardiolipin, along with alterations in the fatty acid composition of PtdCho and PtdEtn, phosphatidyl ethanolamine, in transient cerebral ischemia.…”