Abstract
Obesity is frequently associated with excessive accumulation of lipids in ectopic tissue and presents a major risk factor for type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD). Diacylglycerols (DAGs) and ceramides (CERs) were identified as key players in lipid-induced insulin resistance, typical for such diseases. Recent results suggest that the subcellular distribution of these lipids affects their lipotoxic properties. However, the subcellular dynamics of these lipids and the role of lipid droplets (LDs) as a potential storage site is not understood. Here, we developed a liquid chromatography triple quadrupole mass spectrometry (LC-MS/MS)-method for the rapid and simultaneous quantification of DAG and CER species in tissue sample fractions. The assay is characterized by excellent recovery of analytes, limit of quantification, accuracy and precision. We established a fractionation protocol that allows the separation of subcellular tissue fractions. This method was subsequently tested to measure the concentration of DAGs and CERs in subcellular fractions of human muscle and several mouse tissues. In a mouse model of NAFLD, application of this method revealed a prominent role for LDs as repository for lipotoxic DAG and CER species. In conclusion, the new method proved as a valuable tool to analyse the subcellular dynamics of lipotoxins, related to the pathogenesis of insulin resistance, T2D and NAFLD.
Highlights
Lipids present a versatile group of molecules with a broad spectrum of functions [1]
It is well accepted that the dysregulation of lipid metabolism represents a hallmark of the most common metabolic diseases worldwide, such as obesity, type 2 diabetes (T2D) and non-alcoholic fatty liver disease (NAFLD) [2,3,4,5]
CERs, which were shown to induce insulin resistance [18,39]. Their lipotoxic properties are most likely influenced by their subcellular localization
Summary
Lipids present a versatile group of molecules with a broad spectrum of functions [1]. Fatty acids are taken up and channelled into the triglyceride (TAG) synthesis pathway. Subsequent reactions in the ER lead to the formation of the lipid intermediate diacylglycerol (DAG) which can be further esterified to TAG. DAG can be channelled into LDs for localized synthesis of TAGs on LDs [10,11]. Lipolysis of TAGs leads to the formation of DAGs which can be further hydrolysed to provide FAs for energy production or channelled back into the ER for membrane lipid synthesis or very-low-density lipoprotein (VLDL) synthesis in the liver [12,13]. FAs, such as palmitate, can be channelled into the ceramide (CER) synthesis pathway [15,16]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
