Project description:The protective effects of lower body subcutaneous adiposity are linked to the depot functioning as a "metabolic sink" receiving and sequestering excess lipid. This postulate, however, is based on indirect evidence. Mechanisms that mediate this protection are unknown. Here we directly examined this with progressive subcutaneous adipose tissue removal. Ad libitum chow fed mice underwent sham surgery, unilateral or bilateral removal of inguinal adipose tissue or bilateral removal of both inguinal and dorsal adipose tissue. Subsequently mice were separated into 5 week chow or 5 or 13 week HFD groups (N = 10 per group). Primary outcome measures included adipocyte distribution, muscle and liver triglycerides, glucose tolerance, circulating adipocytokines and muscle insulin sensitivity. Subcutaneous adipose tissue removal caused lipid accumulation in femoral muscle proximal to excision, however, lipid accumulation was not proportionally inverse to adipose tissue quantity excised. Accumulative adipose removal was associated with an incremental reduction in systemic glucose tolerance in 13 week HFD mice. Although insulin-stimulated pAkt/Akt did not progressively decrease among surgery groups following 13 weeks of HFD, there was a suppressed pAkt/Akt response in the non-insulin stimulated (saline-injected) 13 week HFD mice. Hence, increases in lower body subcutaneous adipose removal resulted in incremental decreases in the effectiveness of basal insulin sensitivity of femoral muscle. The current data supports that the subcutaneous depot protects systemic glucose homeostasis while also protecting proximal muscle from metabolic dysregulation and lipid accumulation. Removal of the "metabolic sink" likely leads to glucose intolerance because of decreased storage space for glucose and/or lipids.
Project description:Abdominal fat (AF) and intramuscular fat (IMF) are key carcass traits in broilers but managing both is challenging due to their contrasting effects. Arginine (Arg) supplementation has potential effect in lipid metabolism, however its tissue specific effect remains poorly understood. The objective of this study was to investigate the tissue specific effect of Arg supplementation on growth performance and fat metabolism in both liver and pectoral muscle in broilers. A total of 480 Arbor Acre chicks were randomly assigned to four groups: Control (0 g/kg), Arg (1.8 g/kg), 5X Arg (9 g/kg) and 10X Arg (18g/kg), with 12 replicates of 10 birds each. Overall, high Arg supplementation (5X, 10X) significantly impaired growth performance, reducing average daily gain and feed intake, accompanied by elevated serum AST and IFN-γ levels (p<0.05). Liver transcriptomics analysis revealed that 10X Arg significantly enriched PPAR signaling pathway, promoting fatty acid oxidation while suppressing lipogenic genes. Conversely, in pectoral muscle, high Arg (10X) promoted intramuscular fat deposition which was associated with downregulation of PPAR-α (p<0.05) and increased expression of key lipogenic genes involved in de novo lipogenesis (SREBP-1c, FAS, ACC and SCD). Moreover, Arg supplementation modulated drug metabolism genes in liver, including EPX and RRM2, suggesting potential impacts on detoxification pathways. These findings underscore the importance of precise Arg dosing to optimize broiler growth, immune function, and carcass quality by targeting its tissue specific metabolic effect.
Project description:Like the morphology of native tissue fiber arrangement (such as skeletal muscle), unidirectional anisotropic scaffolds are highly desired as a means to guide cell behavior in anisotropic tissue engineering. In contrast, contour-like staircases exhibit directional topographical cues and are judged as an inevitable defect of fused deposition modeling (FDM). In this study, we will translate this staircase defect into an effective bioengineering strategy by integrating FDM with surface coating technique (FCT) to investigate the effect of topographical cues on regulating behaviors of human mesenchymal stem cells (hMSCs) toward skeletal muscle tissues. This integrated approach serves to fabricate shape-specific, multiple dimensional, anisotropic scaffolds using different biomaterials. 2D anisotropic scaffolds, first demonstrated with different polycaprolactone concentrations herein, efficiently direct hMSC alignment, especially when the scaffold is immobilized on a support ring. By surface coating the polymer solution inside FDM-printed sacrificial structures, 3D anisotropic scaffolds with thin wall features are developed and used to regulate seeded hMSCs through a self-established rotating bioreactor. Using layer-by-layer coating, along with a shape memory polymer, smart constructs exhibiting shape fix and recovery processes are prepared, bringing this study into the realm of 4D printing. Immunofluorescence staining and real-time quantitative polymerase chain reaction analysis confirm that the topographical cues created via FCT significantly enhance the expression of myogenic genes, including myoblast differentiation protein-1, desmin, and myosin heavy chain-2. We conclude that there are broad application potentials for this FCT strategy in tissue engineering as many tissues and organs, including skeletal muscle, possess highly organized and anisotropic extracellular matrix components.
Project description:Irisin is an exercise-induced hormone that regulates lipid metabolism. The present study investigates whether the anti-obesity effect of the natural flavonoid pentamethylquercetin (PMQ) is related to irisin secretion from skeletal muscle in whole animals and cultured cells. Obese mice induced by monosodium glutamate were administered oral PMQ to determine blood irisin level and in vivo parameters of lipid metabolism, and cultured mouse C2C12 myoblasts and 3T3-L1 preadipocytes were employed to investigate the related molecular identities. PMQ increased circulating irisin and decreased bodyweight, insulin, and lipid levels accompanied with increasing brown-like adipocyte formation in obese mice. The brown adipocyte marker uncoupling protein 1 (UCP-1) and other brown-like adipocyte-specific genes and/or markers were increased in mouse white fat tissue, while PMQ treatment reversed the above changes. PMQ also dose-dependently increased the reduced levels of AMP-activated protein kinase (AMPK), peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), and fibronectin type III domain-containing 5 (FNDC5) signal molecules in obese mice. Interestingly, the irisin level was increased in the culture medium of C2C12 cells treated with PMQ, and the conditioned medium stimulated the brown-like transition of 3T3-L1 preadipocytes with the increased expression of PGC-1α, FNDC5, UCP-1, and other brown-like adipocyte-specific genes. The effects of conditioned culture medium were abolished in C2C12 cells with silenced PGC-1α. On the other hand, PMQ-induced upregulation of PGC-1α and FNDC5 expression was reduced by AMPK inhibitor Compound C in C2C12 cells. Our results demonstrate the novel information that PMQ-induced irisin secretion from skeletal muscle involves the improvement of metabolic dysfunction in obese mice via activating the AMPK/PGC-1α/FNDC5 signal pathway, suggesting that PMQ modulates skeletal muscle-adipose tissue crosstalk and may be a promising drug candidate for treating obesity and obesity-related metabolic diseases.
Project description:The mineralocorticoid receptor (MR) is able to regulate the transcription of a number of genes in the myotube, although its roles in skeletal muscle (SM) metabolism still await demonstration. SM represents a major site for glucose uptake, and its metabolic derangements play a pivotal role in the development of insulin resistance (IR). The aim of this study was to investigate the contribution of SM MR in mediating derangements of glucose metabolism in a mouse model of diet-induced obesity. We observed that mice fed a high-fat diet (HFD mice) showed impaired glucose tolerance compared to mice fed a normal diet (ND mice). Mice fed a 60% HFD treated with the MR antagonist Spironolactone (HFD + Spiro) for 12 weeks revealed an improvement in glucose tolerance, as measured with an intraperitoneal glucose tolerance test, compared with HFD mice. To investigate if blockade of SM MR could contribute to the favorable metabolic effects observed with pharmacological MR antagonism, we analyzed MR expression in the gastrocnemius, showing that SM MR protein abundance is downregulated by HFD compared to ND mice and that pharmacological treatment with Spiro was able to partially revert this effect in HFD + Spiro mice. Differently from what we have observed in adipose tissue, where HDF increased adipocyte MR expression, SM MR protein was down-regulated in our experimental model, suggesting a completely different role of SM MR in the regulation of glucose metabolism. To confirm this hypothesis, we investigated the effects of MR blockade on insulin signaling in a cellular model of IRin C2C12 myocytes, which were treated with or without Spiro. We confirmed MR protein downregulation in insulin-resistant myotubes. We also analyzed Akt phosphorylation upon insulin stimulation, and we did not observe any difference between palmitate- and palmitate + Spiro-treated cells. These results were confirmed by in vitro glucose uptake analysis. Taken together, our data indicate that reduced activity of SM MR does not improve insulin signaling in mouse skeletal myocytes and does not contribute to the favorable metabolic effects on glucose tolerance and IR induced by systemic pharmacological MR blockade.