Simultaneous quantitation of ceramides and 1,2-diacylglycerol in tissues by Iatroscan thin-layer chromatography-flame-ionization detection

Astragalus polysaccharides repress myocardial lipotoxicity in a PPARalpha-dependent manner in vitro and in vivo in mice

BACKGROUND

The role of peroxisome proliferator-activated receptor alpha (PPARα) in the development of myocardial lipotoxicity is widely observed in diabetic disorders. Thus, we investigated if treatment of Astragalus polysaccharides modulates lipotoxic cardiomyopathy both in vivo and in vitro through PPARα mechanisms.

METHODOLOGY/PRINCIPAL FINDINGS

The effects of Astragalus polysaccharides (APS) on PPARα target gene expression and protein levels were tested in vitro and in vivo, including in mice with PPARα cardiac-restricted overexpression [myosin heavy chain (MHC)-PPARα] and in H9c2 embryonic rat cardiomyocytes with or without PPARα agonist. Echocardiographic studies, analyses of myocardial triglyceride and cardiac fuel utilization analyses were also performed in MHC-PPARα mice. Treatment with APS prevented myocardial triglyceride accumulation and cardiac dysfunction in the MHC-PPARα mice, with the normalization of energy metabolic derangements in hearts including reduced free fatty acids utilization and increased glucose uptake. Consistently, both in the MHC-PPARα hearts and H9c2 cardiomyocytes with PPARα agonist, the activation of PPARα gene regulatory pathway involved in FFA-oxidation was down-regulated by APS treatment, while the suppression of PPARα target genes involved in glucose uptake and oxidation was normalized by APS administration.

CONCLUSIONS

Therapy with APS could prevent the development of lipotoxic cardiomyopathy through a mechanism mainly dependent on the cardiac PPARα-mediated regulatory pathways.

Sphingolipidomics: methods for the comprehensive analysis of sphingolipids

Sphingolipids comprise a highly diverse and complex class of molecules that serve as both structural components of cellular membranes and signaling molecules capable of eliciting apoptosis, differentiation, chemotaxis, and other responses in mammalian cells. Comprehensive or "sphingolipidomic" analyses (structure specific, quantitative analyses of all sphingolipids, or at least all members of a critical subset) are required in order to elucidate the role(s) of sphingolipids in a given biological context because so many of the sphingolipids in a biological system are inter-converted structurally and metabolically. Despite the experimental challenges posed by the diversity of sphingolipid-regulated cellular responses, the detection and quantitation of multiple sphingolipids in a single sample has been made possible by combining classical analytical separation techniques such as high-performance liquid chromatography (HPLC) with state-of-the-art tandem mass spectrometry (MS/MS) techniques. As part of the Lipid MAPS consortium an internal standard cocktail was developed that comprises the signaling metabolites (i.e. sphingoid bases, sphingoid base-1-phosphates, ceramides, and ceramide-1-phosphates) as well as more complex species such as mono- and di-hexosylceramides and sphingomyelin. Additionally, the number of species that can be analyzed is growing rapidly with the addition of fatty acyl Co-As, sulfatides, and other complex sphingolipids as more internal standards are becoming available. The resulting LC-MS/MS analyses are one of the most analytically rigorous technologies that can provide the necessary sensitivity, structural specificity, and quantitative precision with high-throughput for "sphingolipidomic" analyses in small sample quantities. This review summarizes historical and state-of-the-art analytical techniques used for the identification, structure determination, and quantitation of sphingolipids from free sphingoid bases through more complex sphingolipids such as sphingomyelins, lactosylceramides, and sulfatides including those intermediates currently considered sphingolipid "second messengers". Also discussed are some emerging techniques and other issues remaining to be resolved for the analysis of the full sphingolipidome.

Sex-related survival differences in murine cardiomyopathy are associated with differences in TNF-receptor expression

Epidemiological evidence suggests that the prognosis of heart failure in women is better than in men. In our murine model of dilated cardiomyopathy arising from cardiac-specific overexpression of TNF-alpha, the 6-month survival rate was significantly better in females than in males. Young female transgenic mice exhibited left ventricular wall thickening without dilatation, whereas age-matched male transgenic hearts were markedly dilated. Basal and isoproterenol-stimulated fractional shortening was preserved in female transgenic mice, but not in male transgenic mice. Myocardial expression of proinflammatory cytokines and the extent of myocardial infiltrates were similar in male and female transgenic mice. Myocardial expression of TNF-receptor mRNAs (type I and type II) was significantly higher in male mice in both transgenic and wild-type littermates, whereas sex-specific differences were not observed in either peripheral white blood cells or liver tissue. After TNF-alpha challenge, myocardial but not liver production of ceramide was significantly higher in male than in female mice. Thus, differential expression of myocardial TNF receptors may contribute to sex differences in the severity of congestive heart failure and mortality consequent to cardiac-specific overexpression of TNF-alpha.

Measurements of 1,2-diacylglycerol and ceramide in hearts subjected to ischemic preconditioning

An accumulation of recent evidence suggests that the mechanism in ischemic preconditioning (IPC) may involve the activation of protein kinase C (PKC) regulatory pathway. In this study, we examined whether the content of 1,2-diacylglycerol (1,2-DAG) and ceramide, which are intracellular second messengers regulating PKC activity, change during IPC in isolated perfused rat hearts, and whether the observed change in 1,2-DAG is accompanied with alteration in its fatty acid composition. Hearts subjected to IPC, consisting of 5-min transient global ischemia followed by 5-min reperfusion, presented a significant functional recovery during subsequent 40-min reperfusion following 40-min global ischemia compared with non-preconditioned hearts. An increase in 1,2-DAG content was observed in hearts subjected to 5-min transient ischemia compared with non-ischemic control hearts, however this was not seen in hearts harvested after 5-min reperfusion following 5-min ischemia. While fatty acid composition in 1,2-DAG was virtually unchanged in hearts subjected to 5-min ischemia, saturated 1,2-DAG decreased and monounsaturated/polyunsaturated 1,2-DAG increased in hearts reperfused for 5-min following 5-min ischemia compared with the non-ischemic control hearts. Ceramide mass did not change significantly, suggesting that the contribution of ceramide may be small in IPC. These data are in concert with the hypothesis that 1,2-DAG is a second messenger in IPC and the changes in fatty acid composition of 1,2-DAG may add new insight concerning signal transduction pathway in IPC.