Lipid peroxidation is involved in calcium dependent upregulation of mitochondrial metabolism in skeletal muscle

BACKGROUND: Skeletal muscle cells continuously generate reactive oxygen species (ROS). Excessive ROS can affect lipids resulting in lipid peroxidation (LPO). Here we investigated the effects of myotube intracellular calcium-induced signaling eliciting contractions on the LPO induction and the impact of LPO-product 4-hydroxynonenal (4-HNE) on physiology/pathology of myotubes using C2C12 myoblasts. METHODS: C2C12 myoblasts were differentiated into myotubes, stimulated with caffeine and analyzed for the induction of LPO and formation of 4-HNE protein adducts. Further effects of 4-HNE on mitochondrial bioenergetics, NADH level, mitochondrial density and expression of mitochondrial metabolism genes were determined. RESULTS: Short and long-term caffeine stimulation of myotubes promoted superoxide production, LPO and formation of 4-HNE protein adducts. Furthermore, low 4-HNE concentrations had no effect on myotube viability and cellular redox homeostasis, while concentrations from 10 μM and above reduced myotube viability and significantly disrupted homeostasis. A time and dose-dependent 4-HNE effect on superoxide production and mitochondrial NADH-autofluorescence was observed. Finally, 4-HNE had strong impact on maximal respiration, spare respiratory capacity, ATP production, coupling efficiency of mitochondria and mitochondrial density. CONCLUSION: Data presented in this work make evident for the first time that pathological 4-HNE levels elicit damaging effects on skeletal muscle cells while acute exposure to physiological 4-HNE induces transient adaptation. GENERAL SIGNIFICANCE: This work suggests an important role of 4-HNE on the regulation of myotube's mitochondrial metabolism and cellular energy production. It further signifies the importance of skeletal muscle cells hormesis in response to acute stress in order to maintain essential biological functions

Triglyceride profiling in adipose tissues from obese insulin sensitive, insulin resistant and type 2 diabetes mellitus individuals

Abstract Background Lipid intermediates produced during triacylglycerols (TAGs) synthesis and lipolysis in adipocytes interfere with the intracellular insulin signaling pathway and development of insulin resistance. This study aims to compare TAG species and their fatty acid composition in adipose tissues from insulin sensitive (IS), insulin resistant (IR) and type 2 diabetes mellitus (T2DM) obese individuals. Methods Human subcutaneous and omental adipose tissue biopsies were obtained from 64 clinically characterized obese individuals during weight reduction surgery. TAGs were extracted from the adipose tissues using the Bligh and Dyer method, then were subjected to non-aqueous reverse phase ultra-high performance liquid chromatography and full scan mass spectrometry acquisition and data dependent MS/MS on LTQ dual cell linear ion trap. TAGs and their fatty acid contents were identified and compared between IS, IR and T2DM individuals and their levels were correlated with metabolic traits of participants and the adipogenic potential of preadipocyte cultures established from their adipose tissues. Results Data revealed 76 unique TAG species in adipose tissues identified based on their exact mass. Analysis of TAG levels revealed a number of TAGs that were significantly altered with disease progression including C46:4, C48:5, C48:4, C38:1, C50:3, C40:2, C56:3, C56:4, C56:7 and C58:7. Enrichment analysis revealed C12:0 fatty acid to be associated with TAGs least abundant in T2DM whereas C18:3 was found in both depleted and enriched TAGs in T2DM. Significant correlations of various adipose tissue-derived TAG species and metabolic traits were observed, including age and body mass index, systemic total cholesterol, TAGs, and interleukin-6 in addition to adipogenic potential of preadipocytes derived from the same adipose tissues. Conclusion Pilot data suggest that adipose tissues from obese IR and T2DM individuals exhibit TAG-specific signatures that may contribute to their increased risk compared to their IS counterparts. Future experiments are warranted to investigate the functional relevance of these specific lipidomic profiles

MOESM1 of Triglyceride profiling in adipose tissues from obese insulin sensitive, insulin resistant and type 2 diabetes mellitus individuals

Additional file 1: Table S1. Comparison of participants’ characteristics by gender. Table S2. Differences between obese and morbidly obese subjects. Table S3. TAGs exhibiting BMI interaction

MOESM2 of Triglyceride profiling in adipose tissues from obese insulin sensitive, insulin resistant and type 2 diabetes mellitus individuals

Additional file 2: Figure S1. Adipogenic capacity of preadipocytes derived from subcutaneous (SC) and omental (OM) adipose tissues from insulin sensitive (IS), insulin resistant (IR) and type 2 diabetes mellitus (T2DM) patients. Representative images of SC and OM adipocytes form IS and IR individuals stained with DAPI in blue (nuclear staining) and lipidtox in green (lipid droplet staining) (A). A bar chart showing differences in the adipogenic capacity (percentage of differentiated adipocytes to total number of nuclei) in SC and OM preadipocytes derived from IS, IR and T2DM individuals (B). Significant differences in adipogenic capacity with disease progression were detected as reported previously [12, 15]