F13A1 transglutaminase expression in human adipose tissue increases in acquired excess weight and associates with inflammatory status of adipocytes

High-intensity interval training and medium-intensity continuous training may affect cognitive function through regulation of intestinal microbial composition and its metabolite LPS by the gut-brain axis

AIMS

The gut-brain axis is the communication mechanism between the gut and the central nervous system, and the intestinal flora and lipopolysaccharide (LPS) play a crucial role in this mechanism. Exercise regulates the gut microbiota composition and metabolite production (i.e., LPS). We aimed to investigate the effects of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on cognitive function in C57BL/6 J mice through gut-brain axis regulation of gut microbiota composition and LPS displacement.

MAIN METHODS

C57BL/6 J male mice were randomly divided into sedentary, HIIT, and MICT groups. After 12 weeks of exercise intervention, the cognitive function of the brain and mRNA levels of related inflammatory factors were measured. RNA sequencing, Golgi staining, intestinal microbial 16 s rDNA sequencing, and ELISA were performed.

KEY FINDINGS

HIIT and MICT affect brain cognitive function by regulating the gut microbiota composition and its metabolite, LPS, through the gut microbiota-gut-brain axis. HIIT is suspected to have a risk: it can induce "intestinal leakage" by regulating intestinal permeability-related microbiota, resulting in excessive LPS in the blood and brain and activating M1 microglia in the brain, leading to reduced dendritic spine density and affecting cognitive function.

SIGNIFICANCE

This study revealed a potential link between changes in the gut microbiota and cognitive function. It highlighted the possible risk of HIIT in reducing dendritic spine density and affecting cognitive function.

Circulating plasma fibronectin affects tissue insulin sensitivity, adipocyte differentiation, and transcriptional landscape of adipose tissue in mice

Plasma fibronectin (pFN) is a hepatocyte-derived circulating extracellular matrix protein that affects cell morphology, adipogenesis, and insulin signaling of adipocytes in vitro. In this study, we show pFN accrual to adipose tissue and its contribution to tissue homeostasis in mice. Hepatocyte-specific conditional Fn1 knockout mice (Fn1-/-ALB) show a decrease in adipose tissue FN levels and enhanced insulin sensitivity of subcutaneous (inguinal), visceral (epididymal) adipose tissue on a normal diet. Diet-induced obesity model of the Fn1-/-ALB mouse showed normal weight gain and whole-body fat mass, and normal adipose tissue depot volumes and unaltered circulating leptin and adiponectin levels. However, Fn1-/-ALB adipose depots showed significant alterations in adipocyte size and gene expression profiles. The inguinal adipose tissue on a normal diet, which had alterations in fatty acid metabolism and thermogenesis suggesting browning. The presence of increased beige adipocyte markers Ucp1 and Prdm16 supported this. In the inguinal fat, the obesogenic diet resulted in downregulation of the browning markers and changes in gene expression reflecting development, morphogenesis, and mesenchymal stem cell maintenance. Epididymal adipose tissue showed alterations in developmental and stem cell gene expression on both diets. The data suggests a role for pFN in adipose tissue insulin sensitivity and cell profiles.

Serum proteomics analysis of drug-naïve patients with generalised anxiety disorder: Tandem mass tags and multiple reaction monitoring

OBJECTIVES

The prevalence of generalised anxiety disorder (GAD) is high. However, the underlying mechanisms remain elusive. Proteomics techniques can be employed to assess the pathological mechanisms involved in GAD.

METHODS

Twenty-two drug-naive GAD patients were recruited, their serum samples were used for protein quantification and identified using Tandem Mass Tag and Multiple Reaction Monitoring (MRM). Machine learning models were employed to construct predictive models for disease occurrence by using clinical scores and target proteins as input variables.

RESULTS

A total of 991 proteins were differentially expressed between GAD and healthy participants. Gene Ontology analysis revealed that these proteins were significantly associated with stress response and biological regulation, suggesting a significant implication in anxiety disorders. MRM validation revealed evident disparities in 12 specific proteins. The machine learning model found a set of five proteins accurately predicting the occurrence of the disease at a rate of 87.5%, such as alpha 1B-glycoprotein, complement component 4 A, transferrin, V3-3, and defensin alpha 1. These proteins had a functional association with immune inflammation.

CONCLUSIONS

The development of generalised anxiety disorder might be closely linked to the immune inflammatory stress response.

Limited Bariatric Surgery-induced Weight Loss in Subjects With Type 2 Diabetes: Predictor Variables in Adipose Tissue

CONTEXT

The impact of type 2 diabetes mellitus (T2D) at baseline on limited weight loss (WL) after bariatric surgery (BS) remains controversial, and the potential underlying mechanisms incompletely understood.

OBJECTIVE

We aimed at gaining further insight on this relationship and identifying novel associations between adipose tissue (AT) parameters and short-term WL outcomes in subjects with or without T2D undergoing BS.

METHODS

Mid-term WL trajectories after BS have been evaluated in a cohort of 1659 subjects (cohort 1) with (n = 543) and without T2D (n = 1116). Paired subcutaneous and visceral AT samples were obtained from a cohort of 48 pairs of subjects with and without T2D matched for age, sex, BMI, and type of BS (cohort 2). Differences in AT parameters between groups were evaluated and potential associations with WL response explored.

RESULTS

T2D was independently associated with a 5% lesser mid-term WL in cohort 1, while HbA1c, insulin treatment, and number of T2D medications prior to BS were only related to short-term WL outcomes. In cohort 2, a number of differentially expressed genes in AT were identified between groups, while fat cell size and fibrosis were comparable. Subcutaneous ATG7 expression was found as an independent predictor of limited WL 1 year after surgery (β: -12.21 ± 4.41, P = .008) and its addition to a clinical model significantly improved the amount of WL variability explained (R2 = 0.131 vs R2 = 0.248, F change P = .009).

CONCLUSION

Our results highlight the importance of T2D as determinant of limited WL following BS and suggest that dysregulated macroautophagy in subcutaneous AT may contribute to this association.

Collagens Regulating Adipose Tissue Formation and Functions

The globally increasing prevalence of obesity is associated with the development of metabolic diseases such as type 2 diabetes, dyslipidemia, and fatty liver. Excess adipose tissue (AT) often leads to its malfunction and to a systemic metabolic dysfunction because, in addition to storing lipids, AT is an active endocrine system. Adipocytes are embedded in a unique extracellular matrix (ECM), which provides structural support to the cells as well as participating in the regulation of their functions, such as proliferation and differentiation. Adipocytes have a thin pericellular layer of a specialized ECM, referred to as the basement membrane (BM), which is an important functional unit that lies between cells and tissue stroma. Collagens form a major group of proteins in the ECM, and some of them, especially the BM-associated collagens, support AT functions and participate in the regulation of adipocyte differentiation. In pathological conditions such as obesity, AT often proceeds to fibrosis, characterized by the accumulation of large collagen bundles, which disturbs the natural functions of the AT. In this review, we summarize the current knowledge on the vertebrate collagens that are important for AT development and function and include basic information on some other important ECM components, principally fibronectin, of the AT. We also briefly discuss the function of AT collagens in certain metabolic diseases in which they have been shown to play central roles.

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.

Comprehensive molecular and morphological resolution of blubber stratification in a deep-diving, fasting-adapted seal

Blubber is a modified subcutaneous adipose tissue in marine mammals that provides energy storage, thermoregulation, hydrodynamic locomotion, and buoyancy. Blubber displays vertical stratification by lipid content, fatty acid composition, and vascularization, leading to the assumption that deeper blubber layers are metabolically active, while superficial layers are mainly structural and thermoregulatory. However, few studies have examined functional stratification of marine mammal blubber directly, especially in pinnipeds. We characterized morphological and transcriptional differences across blubber layers in the northern elephant seal, a deep-diving and fasting-adapted phocid. We collected blubber from seals early in their fasting period and divided blubber cores into three similarly sized portions. We hypothesized that the innermost blubber portion would have higher 1) heterogeneity in adipocyte size, 2) microvascular density, and 3) expression of genes associated with metabolism and hormone signaling than outer blubber. We found that adipocyte area and variance increased from outermost (skin-adjacent) to innermost (muscle-adjacent) blubber layers, suggesting that inner blubber has a higher capacity for lipid storage and turnover than outer blubber. Inner blubber had a higher proportion of CD144+ endothelial cells, suggesting higher microvascular density. In contrast, outer blubber had a higher proportion of CD4+ immune cells than inner blubber, suggesting higher capacity for response to tissue injury. Transcriptome analysis identified 61 genes that were differentially expressed between inner and outer blubber layers, many of which have not been studied previously in marine mammals. Based on known functions of these genes in other mammals, we suggest that inner blubber has potentially higher 1) adipogenic capacity, 2) cellular diversity, and 3) metabolic and neuroendocrine signaling activity, while outer blubber may have higher 1) extracellular matrix synthesis activity and 2) responsiveness to pathogens and cell stressors. We further characterized expression of nine genes of interest identified by transcriptomics and two adipokines with higher precision across blubber layers using targeted assays. Our study provides functional insights into stratification of blubber in marine mammals and a molecular key, including CD144, CD4, HMGCS2, GABRG2, HCAR2, and COL1A2, for distinguishing blubber layers for physiological and functional studies in seals.

Genetic landscape in coagulation factor XIII associated defects – Advances in coagulation and beyond

Coagulation factor XIII (FXIII) acts as a fine fulcrum in blood plasma that maintains the balance between bleeding and thrombosis by covalently crosslinking the pre-formed fibrin clot into an insoluble one that is resistant to premature fibrinolysis. In plasma, FXIII circulates as a pro-transglutaminase complex composed of the dimeric catalytic FXIII-A encoded by the F13A1 gene and dimeric carrier/regulatory FXIII-B subunits encoded by the F13B gene. Growing evidence accumulated over decades of exhaustive research shows that not only does FXIII play major roles in both pathological extremes of hemostasis i.e. bleeding and thrombosis, but that it is, in fact, a pleiotropic protein with physiological roles beyond coagulation. However, the current FXIII genetic-epidemiological literature is overwhelmingly derived from the bleeding pathology associated with its deficiency. In this article we review the current clinical, functional, and molecular understanding of this fascinating multifaceted protein, especially putting into the same perspective its genetic landscape.

The role of cathepsin S in the pathophysiology of bronchial asthma

To date, the study of the role of proteases in the pathogenesis of various diseases remains relevant. The variety of cathepsin functions is associated with the peculiarities of their localization, expression, and regulation, due to which cathepsins are involved in development of many pathologies. Dysregulation of proteases, their inhibitors, and substrates can lead to the development of multiple organ dysfunction.

The review presents data on the characteristics of the entire family of cathepsins and cathepsin S, in particular. The pathophysiological role of cathepsin S in the formation of bronchopulmonary pathologies, as well as in bronchial asthma is described, and intraand extracellular implementation mechanisms are considered. The authors believe it is this enzyme that could be targeted in targeted asthma therapy to prevent airway wall remodeling at the earliest stages of the disease. The literature search was carried out in the search engines Medline, eLibrary, Scopus, the Cochrane Library, and RSCI.

Single-nuclei analysis reveals depot-specific transcriptional heterogeneity and depot-specific cell types in adipose tissue of dairy cows

Adipose tissue (AT) is an endocrine organ with a central role on whole-body energy metabolism and development of metabolic diseases. Single-cell and single-nuclei RNA sequencing (scRNA-seq and snRNA-seq, respectively) analyses in mice and human AT have revealed vast cell heterogeneity and functionally distinct subtypes that are potential therapeutic targets to metabolic disease. In periparturient dairy cows, AT goes through intensive remodeling and its dysfunction is associated with metabolic disease pathogenesis and decreased productive performance. The contributions of depot-specific cells and subtypes to the development of diseases in dairy cows remain to be studied. Our objective was to elucidate differences in cellular diversity of visceral (VAT) and subcutaneous (SAT) AT in dairy cows at the single-nuclei level. We collected matched SAT and VAT samples from three dairy cows and performed snRNA-seq analysis. We identified distinct cell types including four major mature adipocytes (AD) and three stem and progenitor cells (ASPC) subtypes, along with endothelial cells (EC), mesothelial cells (ME), immune cells, and pericytes and smooth muscle cells. All major cell types were present in both SAT and VAT, although a strong VAT-specificity was observed for ME, which were basically absent in SAT. One ASPC subtype was defined as adipogenic (PPARG+) while the other two had a fibro-adipogenic profile (PDGFRA+). We identified vascular and lymphatic EC subtypes, and different immune cell types and subtypes in both SAT and VAT, i.e., macrophages, monocytes, T cells, and natural killer cells. Not only did VAT show a greater proportion of immune cells, but these visceral immune cells had greater activation of pathways related to immune and inflammatory response, and complement cascade in comparison with SAT. There was a substantial contrast between depots for gene expression of complement cascade, which were greatly expressed by VAT cell subtypes compared to SAT, indicating a pro-inflammatory profile in VAT. Unprecedently, our study demonstrated cell-type and depot-specific heterogeneity in VAT and SAT of dairy cows. A better understanding of depot-specific molecular and cellular features of SAT and VAT will aid in the development of AT-targeted strategies to prevent and treat metabolic disease in dairy cows, especially during the periparturient period.

Factor XIII-A in Diseases: Role Beyond Blood Coagulation

Multidisciplinary research from the last few decades has revealed that Factor XIII subunit A (FXIII-A) is not only involved in blood coagulation, but may have roles in various diseases. Here, we aim to summarize data from studies involving patients with mutations in the F13A1 gene, performed in FXIII-A knock-out mice models, clinical and histological studies assessing correlations between diseases severity and FXIII-A levels, as well as from in vitro experiments. By providing a complex overview on its possible role in wound healing, chronic inflammatory bowel diseases, athe-rosclerosis, rheumatoid arthritis, chronic inflammatory lung diseases, chronic rhinosinusitis, solid tumors, hematological malignancies, and obesity, we also demonstrate how the field evolved from using FXIII-A as a marker to accept and understand its active role in inflammatory and malignant diseases.