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Can obesity-induced inflammation in skeletal muscle and intramuscular adipose tissue accurately detect liver fibrosis?

ABSTRACT: OBJECTIVES:Obesity is characterized by a chronic, low grade, systemic inflammation. However, little is known about the role of skeletal muscle, which represents an active metabolic organ whose activities need to be determined. The purpose of our study was to detect relationships between skeletal muscle and adipose tissue inflammation with nonalcoholic fatty liver disease (NAFLD) and diabetes, as well as to explore associations with clinicopathological parameters. METHODS:Our study population consisted of 50 morbidly obese patients undergoing planned bariatric surgery. Biopsies were taken from visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), skeletal muscle (SM), extramyocellular adipose tissue (EMAT) and liver. The expression of CD68 and CD3 was assessed by immunohistochemistry. RESULTS:Our findings suggest a complex inter- and intra-tissue co-expression network that links obesity-induced inflammation in adipose depots and skeletal muscle with NAFLD. A novel finding is the intricate cross-talk between SM, EMAT and the liver and the probable correlation between SM, EMAT inflammation and the presence of liver fibrosis. CONCLUSIONS:Although the mechanisms of obesity-induced inflammation and its association with NAFLD and liver fibrosis are incompletely understood, our findings indicate an extensive and complex tissue network that needs to be further investigated.

SUBMITTER: Chasapi A

PROVIDER: S-EPMC6313048 | biostudies-other | 2018 Dec

REPOSITORIES: biostudies-other

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Can obesity-induced inflammation in skeletal muscle and intramuscular adipose tissue accurately detect liver fibrosis?

Chasapi Athina A Balampanis Kostas K Kourea Eleni E Kalfarentzos Fotios F Lambadiari Vaia V Lambrou George I GI Melachrinou Maria M Sotiropoulou-Bonikou Georgia G

Journal of musculoskeletal & neuronal interactions 20181201 4

<h4>Objectives</h4>Obesity is characterized by a chronic, low grade, systemic inflammation. However, little is known about the role of skeletal muscle, which represents an active metabolic organ whose activities need to be determined. The purpose of our study was to detect relationships between skeletal muscle and adipose tissue inflammation with nonalcoholic fatty liver disease (NAFLD) and diabetes, as well as to explore associations with clinicopathological parameters.<h4>Methods</h4>Our study ...[more]

PMID: 30511955

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Project description:Key pointsMuscle infiltration with adipose tissue (IMAT) is common and associated with loss of skeletal muscle strength and physical function across a diverse set of pathologies. Whether the association between IMAT and muscle weakness is causative or simply correlative remains an open question that needs to be addressed to effectively guide muscle strengthening interventions in people with increased IMAT. In the present studies, we demonstrate that IMAT deposition causes decreased muscle strength using mouse models. These findings indicate IMAT is a novel therapeutic target for muscle dysfunction.AbstractIntramuscular adipose tissue (IMAT) is associated with deficits in strength and physical function across a wide array of conditions, from injury to ageing to metabolic disease. Due to the diverse aetiologies of the primary disorders involving IMAT and the strength of the associations, it has long been proposed that IMAT directly contributes to this muscle dysfunction. However, infiltration of IMAT and reduced strength could both be driven by muscle disuse, injury and systemic disease, making IMAT simply an 'innocent bystander.' Here, we utilize novel mouse models to evaluate the direct effect of IMAT on muscle contraction. First, we utilize intramuscular glycerol injection in wild-type mice to evaluate IMAT in the absence of systemic disease. In this model we find that, in isolation from the neuromuscular and circulatory systems, there remains a muscle-intrinsic association between increased IMAT volume and decreased contractile tension (r2 > 0.5, P < 0.01) that cannot be explained by reduction in contractile material. Second, we utilize a lipodystrophic mouse model which cannot generate adipocytes to 'rescue' the deficits. We demonstrate that without IMAT infiltration, glycerol treatment does not reduce contractile force (P > 0.8). Taken together, this indicates that IMAT is not an inert feature of muscle pathology but rather has a direct impact on muscle contraction. This finding suggests that novel strategies targeting IMAT may improve muscle strength and function in a number of populations.

Project description:Abstract: Background: The severity of visceral adipose tissue (VAT) inflammation in individuals with obesity is thought to signify obesity sub-phenotype(s) associated with higher cardiometabolic risk. Yet, this tissue is not accessible for direct sampling in the non-surgical patient. We hypothesized that circulating miRNAs (circ-miRs) could serve as biomarkers to distinguish human obesity subgroups with high or low extent of VAT-inflammation. Methods: Discovery and validation cohorts of patients living with obesity undergoing bariatric surgery (n=35 and 51, respectively) were included. VAT inflammation was classified into low/high based on an expression score derived from the mRNA levels of TNFA, IL6 and CCL2 (determined by rtPCR). Differentially-expressed circ-miRs were identified, and their discriminative power to detect low/high VAT inflammation was assessed by ROC-AUC analysis. Results: Fifty three out of 263 circ-miRs (20%) were associated with high VAT inflammation according to Mann-Whitney analysis in the discovery cohort. Of those, 12 (12/53=23%) were differentially expressed according to Deseq2, and 6 significantly discriminated between high and low VAT inflammation with ROC-AUC>0.8. Of the resulting 5 circ-miRs that were differentially abundant in all three statistical approaches, 3 were unaffected by hemolysis and validated in an independent cohort. Circ-miRs 181b-5p, 1306-3p, and 3138 combined with HOMA-IR exhibited ROC-AUC of 0.951 (95%CI:0.865-1) and 0.808 (95%CI:0.654-0.963) in the discovery and validation cohorts, respectively, providing strong discriminative power between participants with low versus high VAT inflammation. Predicted target genes of these miRNAs are enriched in pathways of insulin and inflammatory signaling, circadian entrainment, and cellular senescence. Conclusions: Circ-miRs that identify patients with low versus high VAT inflammation constitute a putative tool to improve personalized care of patients with obesity.

Project description:OBJECTIVES:High-fat diet (HFD) feeding in mice is characterized by accumulation of ?? T cells in adipose tissue. However, the contribution of ?? T cells to obesity-induced inflammation of skeletal muscle, a major organ of glucose uptake, is unknown. This study was undertaken to evaluate the effect of ?? T cells on insulin sensitivity and inflammatory state of skeletal muscle and adipose tissue in obesity. Furthermore, we investigated whether CD4+IFN?+ (TH1) cells are involved in skeletal muscle and adipose tissue metabolic dysfunction that accompanies obesity. METHODS:Mice lacking ?? T cells (T cell receptor beta chain-deficient [TCRb-/-] mice) were fed HFD for 12 weeks. Obesity-induced skeletal muscle and adipose tissue inflammation was assessed by flow cytometry and quantitative RT-PCR. To investigate the effect of TH1 cells on skeletal muscle and adipose tissue inflammation and metabolic functions, we injected 5×10(5) TH1 cells or PBS weekly over 12 weeks into HFD-fed TCRb-/- mice. We also cultured C2C12 myofibers and 3T3-L1 adipocytes with TH1-conditioned medium. RESULTS:We showed that similar to adipose tissue, skeletal muscle of obese mice have higher ?? T cell content, including TH1 cells. TCRb-/- mice were protected against obesity-induced hyperglycemia and insulin resistance. We also demonstrated suppressed macrophage infiltration and reduced inflammatory cytokine expression in skeletal muscle and adipose tissue of TCRb-/- mice on HFD compared to wild-type obese controls. Adoptive transfer of TH1 cells into HFD-fed TCRb-/- mice resulted in increased skeletal muscle and adipose tissue inflammation and impaired glucose metabolism. TH1 cells directly impaired functions of C2C12 myotubes and 3T3-L1 adipocytes in vitro. CONCLUSIONS:We conclude that reduced adipose tissue and skeletal muscle inflammation in obese TCRb-/- mice is partially attributable to the absence of TH1 cells. Our results suggest an important role of TH1 cells in regulating inflammation and insulin resistance in obesity.

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Can obesity-induced inflammation in skeletal muscle and intramuscular adipose tissue accurately detect liver fibrosis?

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Can obesity-induced inflammation in skeletal muscle and intramuscular adipose tissue accurately detect liver fibrosis?

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