The skeletal muscles of mice infected with Plasmodium berghei and Plasmodium chabaudi reveal a crosstalk between lipid mediators and gene expression

Effects of a Laparotomy on Targeted Lipidomics Profiles in a Mouse Model of Surgical Stress During Aging

Laparotomy (EL) is one of the most common procedures performed among surgical specialties. Previous research demonstrates that surgery is associated with an increased inflammatory response. Low psoas muscle mass and quality markers are associated with increased mortality rates after emergency laparotomy. Analysis of lipid mediators in serum and muscle by using liquid chromatography-mass spectrometry (LC-MS)-based lipidomics has proven to be a sensitive and precise technique. In this chapter, we describe an LC-MS/MS protocol for the profiling and quantification of signaling lipids formed from Eicosapentaenoic Acid (EPA) and Eicosatetranoic acid (ETA) by 5, 12, or 15 lipoxynases. This protocol has been developed for and validated in serum and muscle samples in a mouse model of surgical stress caused by laparotomy.

Quantification of Endocannabinoids from Biological Samples Using Liquid Chromatography-Tandem Mass Spectrometry

Endocannabinoids (eCBs) are a family of lipid molecules with important regulatory function in the brain and immune system. The two well-studied eCBs are arachidonic acid derivatives, N-arachidonoylethanolamine (AEA) and 2-arachidonoylglycerol (2-AG). Currently one of the most important methods for quantitative analysis of eCBs and related lipids from biological matrices is liquid chromatographic separation coupled with tandem mass spectroscopy (LC-MS/MS) owing to its high sensitivity and selectivity, as well as no derivatization procedures needed. Here we describe pretreatment procedures using solid-phase extraction for tissue sampling and an in vivo brain microdialysis approach prior to LC-MS/MS analysis, followed by detailed steps of LC-MS/MS analytic method to demonstrate the potential and application of this method in quantification of eCBs and congeners from various biological matrices.

Mass Spectrometry Approaches for Detection and Determination of Prostaglandins from Biological Samples

Accurate determination of prostaglandins (PGs) from biological samples is critical for understanding their biological functions and interactions during physiological and pathological processes. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) is a highly sensitive, accurate, and high-throughput approach for simultaneous detection of ultra-trace PGs from a single biological sample. Here we describe LC-MS/MS techniques and related sample pretreatment methods including both off-line and on-line SPE for the determination of PGs in biological samples.

Comparative Analysis of Fat Composition in Marrow, Serum, and Muscle from Aging C57BL6 mice

Osteosarcopenia is an age-related condition characterized by fragile bone and low muscle mass and function. Fat infiltration concomitantly contributes to age-related bone and muscle decline. Fat-secreted factors could be locally secreted in the muscle and bone marrow milieu affecting cell function and survival. However, the specific fat-related secretory factors that may simultaneously affect those tissues remain unknown. Using targeted-lipidomics approach, we comprehensively quantified fat composition (lipid mediators [LMs]) in bone marrow flush, gastrocnemius and serum obtained from 6-, 24- and 42-week-old C57BL6 mice. Compared to young mice (6wks), all tissues in older mice showed significantly higher levels of arachidonic acid (AA) and AA-derived eicosanoids, PGA 2, TXB 2, and 11,12-EET, which are known to affect muscle and bone function. Moreover, Lipoxin B4, another AA product and an enhancer of bone turnover and negative regulator for muscle, showed significantly lower values in older mice compared to young mice in both genders. Furthermore, eicosapentaenoic acid and docosahexaenoic acid autoxidation products (20-HDoHE, 11-HDoHE, 7-HDoHE and 4-HDoHE), and omega-3 fatty acids that negatively regulate bone and muscle health, were significantly higher in older mice. In conclusion, these results suggest that LMs could play a role in modulating musculoskeletal function during aging.

Nampt activator P7C3 ameliorates diabetes and improves skeletal muscle function modulating cell metabolism and lipid mediators

BACKGROUND

Nicotinamide phosphoribosyltransferase (Nampt), a key enzyme in NAD salvage pathway is decreased in metabolic diseases, and its precise role in skeletal muscle function is not known. We tested the hypothesis, Nampt activation by P7C3 (3,6-dibromo-α-[(phenylamino)methyl]-9H-carbazol-9-ethanol) ameliorates diabetes and muscle function.

METHODS

We assessed the functional, morphometric, biochemical, and molecular effects of P7C3 treatment in skeletal muscle of type 2 diabetic (db/db) mice. Nampt^+/- mice were utilized to test the specificity of P7C3.

RESULTS

Insulin resistance increased 1.6-fold in diabetic mice compared with wild-type mice and after 4 weeks treatment with P7C3 rescued diabetes (P < 0.05). In the db-P7C3 mice fasting blood glucose levels decreased to 0.96-fold compared with C57Bl/6J wild-type naïve control mice. The insulin and glucose tolerance tests blood glucose levels were decreased to 0.6-fold and 0.54-folds, respectively, at 120 min along with an increase in insulin secretion (1.76-fold) and pancreatic β-cells (3.92-fold) in db-P7C3 mice. The fore-limb and hind-limb grip strengths were increased to 1.13-fold and 1.17-fold, respectively, together with a 14.2-fold increase in voluntary running wheel distance in db-P7C3 mice. P7C3 treatment resulted in a 1.4-fold and 7.1-fold increase in medium-sized and larger-sized myofibres cross-sectional area, with a concomitant 0.5-fold decrease in smaller-sized myofibres of tibialis anterior (TA) muscle. The transmission electron microscopy images also displayed a 1.67-fold increase in myofibre diameter of extensor digitorum longus muscle along with 2.9-fold decrease in mitochondrial area in db-P7C3 mice compared with db-Veh mice. The number of SDH positive myofibres were increased to 1.74-fold in db-P7C3 TA muscles. The gastrocnemius and TA muscles displayed a decrease in slow oxidative myosin heavy chain type1 (MyHC1) myofibres expression (0.46-fold) and immunostaining (6.4-fold), respectively. qPCR analysis displayed a 2.9-fold and 1.3-fold increase in Pdk4 and Cpt1, and 0.55-fold and 0.59-fold decrease in Fgf21 and 16S in db-P7C3 mice. There was also a 3.3-fold and 1.9-fold increase in Fabp1 and CD36 in db-Veh mice. RNA-seq differential gene expression volcano plot displayed 1415 genes to be up-regulated and 1726 genes down-regulated (P < 0.05) in db-P7C3 mice. There was 1.02-fold increase in serum HDL, and 0.9-fold decrease in low-density lipoprotein/very low-density lipoprotein ratio in db-P7C3 mice. Lipid profiling of gastrocnemius muscle displayed a decrease in inflammatory lipid mediators n-6; AA (0.83-fold), and n-3; DHA (0.69-fold) and EPA (0.81-fold), and a 0.66-fold decrease in endocannabinoid 2-AG and 2.0-fold increase in AEA in db-P7C3 mice.

CONCLUSIONS

Overall, we demonstrate that P7C3 activates Nampt, improves type 2 diabetes and skeletal muscle function in db/db mice.

RNA-sequencing Reveals a Gene Expression Signature in Skeletal Muscle of a Mouse Model of Age-associated Postoperative Functional Decline

This study aimed to characterize the effects of laparotomy on postoperative physical function and skeletal muscle gene expression in male C57BL/6N mice at 3, 20, and 24 months of age to investigate late-life vulnerability and resiliency to acute surgical stress. Pre and postoperative physical functioning was assessed by forelimb grip strength on postoperative day (POD) 1 and 3 and motor coordination on POD 2 and 4. Laparotomy-induced an age-associated postoperative decline in forelimb grip strength that was the greatest in the oldest mice. While motor coordination declined with increasing age at baseline, it was unaffected by laparotomy. Baseline physical function as stratified by motor coordination performance (low functioning vs high functioning) in 24-month-old mice did not differentially affect postlaparotomy reduction in grip strength. RNA sequencing of soleus muscles showed that laparotomy-induced age-associated differential gene expression and canonical pathway activation with the greatest effects in the youngest mice. Examples of such age-associated, metabolically important pathways that were only activated in the youngest mice after laparotomy included oxidative phosphorylation and NRF2-mediated oxidative stress response. Analysis of lipid mediators in serum and gastrocnemius muscle showed alterations in profiles during aging and confirmed an association between such changes and functional status in gastrocnemius muscle. These findings demonstrate a mouse model of laparotomy which recapitulated some features of postoperative skeletal muscle decline in older adults, and identified age-associated, laparotomy-induced molecular signatures in skeletal muscles. Future research can build upon this model to study molecular mechanisms of late-life vulnerability and resiliency to acute surgical stress.

Novel Insights Into Sterol Uptake and Intracellular Cholesterol Trafficking During Eimeria bovis Macromeront Formation

Apicomplexan parasites are considered as defective in cholesterol synthesis. Consequently, they need to scavenge cholesterol from the host cell by either enhancing the uptake of extracellular cholesterol sources or by upregulating host cellular de-novo biosynthesis. Given that Eimeria bovis macromeront formation in bovine lymphatic endothelial host cells in vivo is a highly cholesterol-demanding process, we here examined host parasite interactions based on host cellular uptake of different low-density lipoprotein (LDL) types, i.e., of non-modified (LDL), oxidized (oxLDL), and acetylated LDL (acLDL). Furthermore, the expression of lipoprotein-oxidized receptor 1 (LOX-1), which mediates acLDL and oxLDL internalization, was monitored throughout first merogony, in vitro and ex vivo. Moreover, the effects of inhibitors blocking exogenous sterol uptake or intracellular transport were studied during E. bovis macromeront formation in vitro. Hence, E. bovis-infected primary bovine umbilical vein endothelial cells (BUVEC) were treated with inhibitors of sterol uptake (ezetimibe, poly-C, poly-I, sucrose) and of intracellular sterol transport and release from endosomes (progesterone, U18666A). As a read-out system, the size and number of macromeronts as well as merozoite I production were estimated. Overall, the internalization of all LDL modifications (LDL, oxLDL, acLDL) was observed in E. bovis-infected BUVEC but to different extents. Supplementation with oxLDL and acLDL at lower concentrations (5 and 10 µg/ml, respectively) resulted in a slight increase of both macromeront numbers and size; however, at higher concentrations (25-50 µg/ml), merozoite I production was diminished. LOX-1 expression was enhanced in E. bovis-infected BUVEC, especially toward the end of merogony. As an interesting finding, ezetimibe treatments led to a highly significant blockage of macromeront development and merozoite I production confirming the relevance of sterol uptake for intracellular parasite development. Less prominent effects were induced by non-specific inhibition of LDL internalization via sucrose, poly-I, and poly-C. In addition, blockage of cholesterol transport via progesterone and U18666A treatments resulted in significant inhibition of parasite development. Overall, current data underline the relevance of exogenous sterol uptake and intracellular cholesterol transport for adequate E. bovis macromeront development, unfolding new perspectives for novel drug targets against E. bovis.