Serum endotrophin levels in patients with heart failure with reduced and mid-range ejection fraction

Endotrophin, a Key Marker and Driver for Fibroinflammatory Disease

Our overview covers several key areas related to recent results obtained for collagen type VI and endotrophin (ETP). (1) An introduction to the history of ETP, including how it was identified, how it is released, and its function and potential receptors. (2) An introduction to the collagen family, with a focus on what differentiates collagen type VI from an evolutionary standpoint. (3) An overview of collagen type VI, the 6 individual chains (COL6A1, A2, A3, A4, A5, and A6), their differences and similarities, as well as their expression profiles and function. (4) A detailed analysis of COL6A3, including the cleaved product endotrophin, and what separates it from the other 5 collagen 6 molecules, including its suggested function based on insights gained from knockout and gain of function mouse models. (5) The pathology of ETP. What leads to its presence and release and what are the consequences thereof? (6) Functional implications of circulating ETP. Here we review the data with the functional roles of ETP in mind. (7) We propose that ETP is a mediator for fibrotic (or fibroinflammatory) disorders. Based on what we know about ETP, we have to consider it as a target for the treatment of fibrotic (or fibroinflammatory) disorders. What segment(s) of the patient population would most dramatically respond to an ETP-targeted intervention? How can we find the population that would profit most from an intervention? We aim to present a broad overview over the ETP field at large, providing an assessment of where the future research efforts need to be placed to tap into the vast potential of ETP, both as a marker and as a target in different diseases.

Expression of Adipose Tissue Extracellular Matrix-Related Genes Predicts Weight Loss after Bariatric Surgery

BACKGROUND

We evaluated the association between white adipose tissue parameters before bariatric surgery (BS) and post-surgical weight loss, with an especial focus on extracellular matrix (ECM) gene expression.

METHODS

Paired samples from subcutaneous (SAT) and visceral adipose tissue (VAT) were obtained from 144 subjects undergoing BS. The association between total body weight loss (%TBWL) at 12 months after BS and the histological characteristics and gene expression of selected genes in SAT and VAT was analyzed.

RESULTS

Fat cell area, size-frequency distribution, and fibrosis in SAT or VAT prior to surgery were not associated with %TBWL. On the contrary, the SAT expression of COL5A1 and COL6A3 was associated with %TBWL after BS (both p < 0.001), even after adjusting for age, gender, baseline BMI, and type 2 diabetes status (T2D). Furthermore, in logistic regression analyses, the expression of these genes was significantly associated with insufficient WL (IWL = TBWL < 20%) after BS (respectively, p = 0.030 and p = 0.031). Indeed, in ROC analysis, the prediction of IWL based on sex, age, BMI, T2D, and the type of surgery (AUC = 0.71) was significantly improved with the addition of SAT-COL5A1 gene expression (AUC = 0.88, Z = 2.13, p = 0.032).

CONCLUSIONS

Our data suggest that the expression of SAT ECM-related genes may help explain the variability in TBWL following BS.

Plasma endotrophin, reflecting tissue fibrosis, is associated with graft failure and mortality in KTRs: results from two prospective cohort studies

BACKGROUND

Fibrosis is a suggested cause of graft failure and mortality among kidney transplant recipients (KTRs). Accumulating evidence suggests that collagen type VI is tightly linked to fibrosis and may be a marker of systemic fibrosis and ageing. We studied whether plasma endotrophin, a pro-collagen type VI fragment, is associated with graft failure and mortality among KTRs.

METHODS

In cohort A (57% male, age 53 ± 13 years), we measured plasma endotrophin in 690 prevalent KTRs ≥1 year after transplantation. The non-overlapping cohort B included 500 incident KTRs with serial endotrophin measurements before and after kidney transplantation to assess trajectories and intra-individual variation of endotrophin.

RESULTS

In cohort A, endotrophin was higher in KTRs compared with healthy controls. Concentrations were positively associated with female sex, diabetes, cardiovascular disease, markers of inflammation and kidney injury. Importantly, endotrophin was associated with graft failure {hazard ratio [HR] per doubling 1.87 [95% confidence interval (CI) 1.07-3.28]} and mortality [HR per doubling 2.59 (95% CI 1.73-3.87)] independent of potential confounders. Data from cohort B showed that endotrophin concentrations strongly decrease after transplantation and remain stable during post-transplantation follow-up [intra-individual coefficient of variation 5.0% (95% CI 3.7-7.6)].

CONCLUSIONS

Plasma endotrophin is strongly associated with graft failure and mortality among KTRs. These findings suggest a key role of abnormal extracellular matrix turnover and fibrosis in graft and patient prognosis among KTRs and highlight the need for (interventional) studies targeting the profibrotic state of KTRs. The intra-individual stability after transplantation indicates potential use of endotrophin as a biomarker and outcome measure of fibrosis.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02811835.

Extracellular Matrix (ECM) and Fibrosis in Adipose Tissue: Overview and Perspectives

Fibrosis in adipose tissue is a major driver of obesity-related metabolic dysregulation. It is characterized by an overaccumulation of extracellular matrix (ECM) during unhealthy expansion of adipose tissue in response to over nutrition. In obese adipose-depots, hypoxia stimulates multiple pro-fibrotic signaling pathways in different cell populations, thereby inducing the overproduction of the ECM components, including collagens, noncollagenous proteins, and additional enzymatic components of ECM synthesis. As a consequence, local fibrosis develops. The result of fibrosis-induced mechanical stress not only triggers cell necrosis and inflammation locally in adipose tissue but also leads to system-wide lipotoxicity and insulin resistance. A better understanding of the mechanisms underlying the obesity-induced fibrosis will help design therapeutic approaches to reduce or reverse the pathological changes associated with obese adipose tissue. Here, we aim to summarize the major advances in the field, which include newly identified fibrotic factors, cell populations that contribute to the fibrosis in adipose tissue, as well as novel mechanisms underlying the development of fibrosis. We further discuss the potential therapeutic strategies to target fibrosis in adipose tissue for the treatment of obesity-linked metabolic diseases and cancer. © 2023 American Physiological Society. Compr Physiol 13:4387-4407, 2023.

Caudamins, a new subclass of protein hormones

Hormones have traditionally been classified by their mode of biosynthetic origin. We postulate a mode of hormone biosynthesis that leads to a new subclass of protein hormones. Members of this class are derived from a cleavage event that also generates a much larger, functionally unrelated, nonhormonal protein. Here, we examine four representative members of this group: endostatin, endotrophin, asprosin, and placensin. We have named this subclass of protein hormones caudamins, from the Latin word cauda meaning 'tail'. These four caudamins have shown promise in understanding and treating diseases like metabolic syndrome and cancer. Identification of the rest of the caudamins will likely provide a plethora of drug targets for a variety of diseases.

Endotrophin as a novel marker in PCOS and its relation with other adipokines and metabolic parameters: a pilot study

BACKGROUND

Polycystic ovary syndrome is known to be the most common hormonal disorder in women of reproductive age. Current evidence shows that regulatory proteins secreted from the adipose tissue called adipokines may have a role in polycystic ovary syndrome. We planned to investigate the role of endotrophin that has never been researched in polycystic ovary syndrome before and its correlation with other metabolic parameters and adipokines such as adiponectin and ghrelin in patients with polycystic ovary syndrome.

METHODS

Forty-three women (n: 43) with polycystic ovary syndrome and 43 (n: 43) women as a control group were enrolled in this cross-sectional study. Serum levels of endotrophin, adiponectin, and ghrelin levels were measured with the enzyme-linked immunosorbent assay method. High-density lipoprotein cholesterol, low-density lipoprotein cholesterol, total cholesterol levels, luteinizing hormone/follicle-stimulating hormone ratio, total testosterone, and triglyceride levels were measured. Homeostasis model assessment for insulin resistance index, body mass index, Ferriman Gallwey Score, and waist-to-hip ratio were also evaluated.

RESULTS

Total testosterone, homeostasis model assessment for insulin resistance, C-reactive protein, luteinizing hormone/follicle-stimulating hormone ratio, and triglyceride levels were higher in patients with polycystic ovary syndrome (p < 0.01). No difference was detected between the groups in terms of body mass index, Ferriman Gallwey Score, waist-to-hip ratio, total cholesterol, low-density lipoprotein, and high-density lipoprotein levels (p > 0.05). We did not observe any significant difference in adiponectin and ghrelin levels between the groups (p > 0.05). Patients with polycystic ovary syndrome had significantly higher endotrophin levels (p < 0.01). According to our regression analyses [area under the curve: 0.973 (0.935-1.000), 95% confidence interval, 95.2% sensitivity, and 100% specificity], it was shown that endotrophin greater than 92 ng/ml and homeostasis model assessment for insulin resistance greater than 2.5 might be good predictors for polycystic ovary syndrome diagnosis.

CONCLUSION

We demonstrated that endotrophin level is higher in patients with polycystic ovary syndrome and may have predicted polycystic ovary syndrome with increased homeostasis model assessment for insulin resistance index. There was no significant difference in adiponectin and ghrelin levels in the polycystic ovary syndrome group. Endotrophin may have a role in polycystic ovary syndrome etiology rather than other adipokines.

Critical Role of Matrix Metalloproteinase 14 in Adipose Tissue Remodeling during Obesity

Fibrosis is recognized as the major pathological change in adipose tissue during the development of obesity. However, the detailed mechanisms governing the interactions between the fibrotic components and their modifiers remain largely unclear. Here, we reported that matrix metalloproteinase 14 (MMP14), a key pericellular collagenase, is dramatically upregulated in obese adipose tissue. We generated a doxycycline-inducible adipose tissue-specific MMP14 overexpression model to study its regulatory function. We found that overexpression of MMP14 in the established obese adipose tissue leads to enlarged adipocytes and increased body weights in transgenic mice. Furthermore, the mice exhibited decreased energy expenditure, impaired lipid metabolism, and insulin resistance. Mechanistically, we found that MMP14 digests collagen 6α3 to produce endotrophin, a potent costimulator of fibrosis and inflammation. Unexpectedly, when overexpressing MMP14 in the early-stage obese adipose tissue, the transgenic mice showed a healthier metabolic profile, including ameliorated fibrosis and inflammation, as well as improved lipid and glucose metabolism. This unique metabolic phenotype is likely due to digestion/modification of the dense adipose tissue extracellular matrix by MMP14, thereby releasing the mechanical stress to allow for its healthy expansion. Understanding these dichotomous impacts of MMP14 provides novel insights into strategies to treat obesity-related metabolic disorders.