Serum levels of endotrophin are associated with nonalcoholic steatohepatitis

Endotrophin as a Biomarker for Severe Acute Kidney Injury and Major Adverse Kidney Events

Key Points

Endotrophin (ETP), a circulating marker of fibroinflammation, is elevated in critically ill patients with AKI. ETP is independently associated with major adverse kidney events at hospital discharge. Sustained elevations of ETP at 5–7 days are associated with major adverse kidney events.

Background

The search for novel biomarkers in AKI continues, both for being able to predict adverse events in AKI but also for confirming pathogenic pathways as potential therapeutic targets. Endotrophin (ETP) is an emerging biomarker in a number of fibroinflammatory diseases. We sought to test the association of ETP with the development of a major adverse kidney event (MAKE) in critically ill adult patients.

Methods

Single-center prospective study of critically ill adult patients with stage 2–3 AKI and patients without AKI. Serum ETP was measured early in the first 3 days of critical care admission, 5–7 days later, and in some patients, 4–6 weeks later. The primary outcome was MAKE assessed at hospital discharge, a composite of mortality, RRT at discharge, and eGFR reduction of ≥25% from baseline.

Results

Among 121 patients evaluated in this study, serum ETP was significantly higher in patients with AKI versus those without (P < 0.05). In multivariable logistic regression analysis, higher tertiles of ETP were significantly associated with MAKE at discharge, controlled for relevant covariates. Furthermore, sustained elevations in ETP 5–7 days later, as opposed to reductions toward normal, were also associated with MAKE. In patients seen in the clinic 4–6 weeks post-AKI, ETP remained elevated. In the acute period, ETP levels correlated most with TNF-α and neutrophil gelatinase-associated lipocalin.

Conclusions

Higher levels of serum ETP early in the intensive care unit admission, as well as sustained elevations of ETP within a 5-day to 7-day period, are associated with MAKE at hospital discharge. ETP is a potential biomarker of AKI-related outcomes and a promising therapeutic target to minimize sequelae of AKI.

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.

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.

Extracellular matrix remodeling facilitates obesity-associated cancer progression

Obesity, a global public health concern, is an important risk factor for metabolic diseases and several cancers. Fibro-inflammation in adipose tissues (ATs) is tightly associated with the pathologies of obesity; excessive or uncontrolled extracellular matrix (ECM) production in AT has a crucial role in this pathogenesis. The ECM is a critical and functional component of various tissues, providing a mechanical and chemical network of proteins that controls cell survival, development, and tissue repair. The ECM is tightly regulated and dynamically remodeled; this is an important factor for AT expansion and can result in modifications to the physical shape and biological function of AT. Here, we focus on ECM remodeling in AT and how it affects obesity-related cancer progression.