Defective extracellular matrix remodeling in brown adipose tissue is associated with fibro-inflammation and reduced diet-induced thermogenesis

Effects of Extracellular Matrix Changes Induced by a High-Fat Diet on Gallbladder Smooth Muscle Dysfunction

BACKGROUND

Gallstone formation is a common digestive ailment, with unclear mechanisms underlying its development. Dysfunction of the gallbladder smooth muscle (GSM) may play a crucial role, particularly with a high-fat diet (HFD). This study aimed to investigate the effects of an HFD on GSM and assess how it alters contractility through changes in the extracellular matrix (ECM).

METHODS

Guinea pigs and C57BL/6 mice were fed either an HFD or normal diet (ND). Primary cultures of their (guinea pigs) gallbladder smooth muscle cells (GSMCs) were used for in vitro experiments. Histological stains, RNA-sequencing, bioinformatics analysis, three-dimensional tissue culture, real-time polymerase chain reaction (PCR), Western blot, atomic force microscopy, and muscle tension measurements were performed.

RESULTS

Histological evidence indicated structural changes in the gallbladder muscle layer and ECM collagen deposition in the HFD group. The HFD group also showed increased expression of collagen, integrin family, and matrix metalloproteinase (MMP) and the phosphoinositide 3-kinase (PI3K)-protein kinase B (PKB/Akt) signaling pathway. Compared with GSMCs cultured on Matrigel containing 1 mg/mL of collagen I, those cultured with 2 mg/mL showed a phenotype change from contractile to synthetic cells. Consistent with these findings, the HFD group also demonstrated increased ECM stiffness and decreased smooth muscle contractility.

CONCLUSIONS

Our findings reveal a mechanism by which an HFD alters the ECM composition of the gallbladder muscle, activating the integrin/PI3K-Akt/MMP signaling pathway, thereby impacting GSMC phenotype and contractility. These insights enhance the understanding of gallstone formation mechanism and provide potential therapeutic targets to treat gallbladder dysfunction.

Spatiotemporally cascade-driven "Lipomicelles" enhance extracellular matrix penetration and remodel intercellular crosstalk in pulmonary fibrosis

Pulmonary fibrosis (PF) is an inevitable phase of many respiratory diseases with high mortality and limited effective treatments in the clinic. In PF, aberrant extracellular matrix (ECM) deposition is a significant pathological structural alteration that blocks intercellular crosstalk and hinders the deep penetration of therapeutics into lung tissues, reducing the effectiveness of conventional treatment strategies. Herein, a penetrating enhancer (Lipomicelles) composed of thermosensitive liposome shells loaded with collagenase IV and micellar cores containing thioketal bonds encapsulated with curcumin and decorated with cyclic RGDfc, is developed to alleviate PF. Specifically, Lipomicelles exhibit a cascade-responsive pattern to achieve precision delivery of curcumin through thermosensitivity, enhanced ECM penetration, site-specific targeting, and rapid release in injured alveolar epithelial type II cells (CellAEC2s). Subsequently, intercellular crosstalk is remodeled through the curcumin-mediated repair of CellAEC2s, combined with collagenase IV-mediated ECM degradation to inhibit myofibroblasts, ultimately achieving PF reversal. This work provides an innovative approach to enhance ECM penetration of therapeutics before remodeling intercellular crosstalk, addressing multi-phase PF therapy.

Engineering an energy-dissipating hybrid tissue in vivo for obesity treatment

Obesity is a global health challenge with limited therapeutic solutions. Here, we demonstrate the engineering of an energy-dissipating hybrid tissue (EDHT) in the body for weight control. EDHT is constructed by implanting a synthetic gel matrix comprising immunomodulatory signals and functional cells into the recipient mouse. The immunomodulatory signals induce the host stromal cells to create an immunosuppressive niche that protects the functional cells, which are overexpressing the uncoupling protein 1 (UCP1), from immune rejection. Consequently, these endogenous and exogenous cells co-develop a hybrid tissue that sustainedly produces UCP1 to accelerate the host's energy expenditure. Systematic experiments in high-fat diet (HFD) and transgenic (ob/ob) mice show that EDHT efficiently reduces body weight and relieves obesity-associated pathological conditions. Importantly, an 18-month observation for safety assessment excludes cell leakage from EDHT and reports no adverse physiological responses. Overall, EDHT demonstrates convincing efficacy and safety in controlling body weight.

Insulin at the intersection of thermoregulation and glucose homeostasis

Mammals are protected from changes in environmental temperature by altering energetic processes that modify heat production. Insulin is the dominant stimulus of glucose uptake and metabolism, which are fundamental for thermogenic processes. The purpose of this work was to determine the interaction of ambient temperature induced changes in energy expenditure (EE) on the insulin sensitivity of glucose fluxes. Short-term and adaptive responses to thermoneutral temperature (TN, ∼28 °C) and room (laboratory) temperature (RT, ∼22 °C) were studied in mice. This range of temperature does not cause detectable changes in circulating catecholamines or shivering and postabsorptive glucose homeostasis is maintained. We tested the hypothesis that a decrease in EE that occurs with TN causes insulin resistance and that this reduction in insulin action and EE is reversed upon short term (<12h) transition to RT. Insulin-stimulated glucose disposal (Rd) and tissue-specific glucose metabolic index were assessed combining isotopic tracers with hyperinsulinemic-euglycemic clamps. EE and insulin-stimulated Rd are both decreased (∼50%) in TN-adapted vs RT-adapted mice. When RT-adapted mice are switched to TN, EE rapidly decreases and Rd is reduced by ∼50%. TN-adapted mice switched to RT exhibit a rapid increase in EE, but whole-body insulin-stimulated Rd remains at the low rates of TN-adapted mice. In contrast, whole body glycolytic flux rose with EE. This higher EE occurs without increasing glucose uptake from the blood, but rather by diverting glucose from glucose storage to glycolysis. In addition to adaptations in insulin action, 'insulin-independent' glucose uptake in brown fat is exquisitely sensitive to thermoregulation. These results show that insulin action adjusts to non-stressful changes in ambient temperature to contribute to the support of body temperature homeostasis without compromising glucose homeostasis.

Gelatin but not type I collagen promotes bacteria phagocytosis in PMA-treated U937 human lymphoma cells

PURPOSE

Besides comprising scaffolding, extracellular matrix components modulate many biological processes including inflammation and cell differentiation. We previously found precoating cell plates with extracellular matrix collagen I, or its denatured product gelatin, causes aggregation of macrophage-like human lymphoma U937 cells, which are induced to differentiation by phorbol myristate treatment. In the present study, we investigated the influence of gelatin or collagen I precoating on the bacteria phagocytosis in PMA-stimulated U937 cells.

MATERIALS AND METHODS

Colony forming units of phagocytosed bacteria, Giemsa-staining of cells with phagocytosed bacteria, confocal microscopic and flow cytometric analysis of cells with phagocytosed FITC-labeled bacteria and non-bioactive latex beats were conducted.

RESULTS

Gelatin precoating enhances the phagocytosis of both Gram-negative and positive bacteria, as shown by the increased colony forming units of bacteria phagocytosed by cells, and increased intracellular bacteria observed after Giemsa-staining. But collagen I has no marked influence. Confocal microscopy reveals that both live and dead FITC-bacteria were phagocytosed more in the cells with gelatin-coating but not collagen-coating. Of note, both gelatin and collagen I coating had no influence on the phagocytosis of non-bioactive latex beads. Since gelatin-coating increases autophagy but collagen I has no such impact, we are curious about the role of autophagy. Inhibiting autophagy reduced the phagocytosis of bacteria, in cells with gelatin-coating, while stimulating autophagy enhanced phagocytosis.

CONCLUSION

This study finds the bacteria-phagocytosis stimulatory effect of gelatin in PMA-treated U937 cells and reveals the positive regulatory role of autophagy, predicting the potential use of gelatin products in anti-bacterial therapy.

Insulin at the Intersection of Thermoregulation and Glucose Homeostasis

Mammals are protected from changes in environmental temperature by altering energetic processes that modify heat production. Insulin is the dominant stimulus of glucose uptake and metabolism, which are fundamental for thermogenic processes. The purpose of this work was to determine the interaction of ambient temperature induced changes in energy expenditure (EE) on the insulin sensitivity of glucose fluxes. Short-term and adaptive responses to thermoneutral temperature (TN, ~28°C) and room (laboratory) temperature (RT, ~22°C) were studied in mice. This range of temperature does not cause detectable changes in circulating catecholamines or shivering and postabsorptive glucose homeostasis is maintained. We tested the hypothesis that a decrease in EE that occurs with TN causes insulin resistance and that this reduction in insulin action and EE is reversed upon short term (<12h) transition to RT. Insulin-stimulated glucose disposal (Rd) and tissue specific glucose uptake were assessed combining isotopic tracers with hyperinsulinemic-euglycemic clamps. EE and insulin-stimulated Rd are both decreased (~50%) in TN-adapted vs RT-adapted mice. When RT-adapted mice are switched to TN, EE rapidly decreases and Rd is reduced by ~50%. TN-adapted mice switched to RT exhibit a rapid increase in EE, but whole body insulin-stimulated Rd remains at the low rates of TN-adapted mice. In contrast, whole body glycolytic flux rose with EE. This higher EE occurs without increasing glucose uptake from the blood, but rather by diverting glucose from glucose storage to glycolysis. In addition to adaptations in insulin action, 'insulin-independent' glucose uptake in brown fat is exquisitely sensitive to thermoregulation. These results show that insulin action adjusts to non-stressful changes in ambient temperature to contribute to the support of body temperature homeostasis without compromising glucose homeostasis.

Cotadutide improves brown adipose tissue thermogenesis in obese mice

We studied the effect of cotadutide, a dual agonist glucagon-like peptide 1 (GLP1)/Glucagon, on interscapular brown adipose tissue (iBAT) remodeling and thermogenesis of obese mice. Twelve-week-old male C57BL/6 mice were fed a control diet (C group, n = 20) or a high-fat diet (HF group, n = 20) for ten weeks. Then, animals were redivided, adding cotadutide treatment: C, CC, HF, and HFC for four additional weeks. The multilocular brown adipocyte structure showed fat conversion (whitening), hypertrophy, and structural disarray in the HF group, which was reverted in cotadutide-treated animals. Cotadutide enhances the body temperature, thermogenesis, and sympathetic innervation (peroxisome proliferator-activated receptor-α, β3 adrenergic receptor, interleukin 6, and uncoupled protein 1), reduces pro-inflammatory markers (disintegrin and metallopeptidase domain, morphogenetic protein 8a, and neuregulin 4), and improves angiogenesis (vascular endothelial growth factor A, and perlecan). In addition, cotadutide enhances lipolysis (perilipin and cell death-inducing DNA fragmentation factor α), mitochondrial biogenesis (nuclear respiratory factor 1, transcription factor A mitochondrial, mitochondrial dynamin-like GTPase, and peroxisome proliferator-activated receptor gamma coactivator 1α), and mitochondrial fusion/fission (dynamin-related protein 1, mitochondrial fission protein 1, and parkin RBR E3 ubiquitin protein ligase). Cotadutide reduces endoplasmic reticulum stress (activating transcription factor 4, C/EBP homologous protein, and growth arrest and DNA-damage inducible), and extracellular matrix markers (lysyl oxidase, collagen type I α1, collagen type VI α3, matrix metallopeptidases 2 and 9, and hyaluronan synthases 1 and 2). In conclusion, the experimental evidence is compelling in demonstrating cotadutide's thermogenic effect on obese mice's iBAT, contributing to unraveling its action mechanisms and the possible translational benefits.

Mesenchymal stromal cells as conductors of adipose tissue remodeling

Adipose tissue exhibits a remarkable capacity to expand, contract, and remodel in response to changes in physiological and environmental conditions. Here, we describe recent advances in our understanding of how functionally distinct tissue-resident mesenchymal stromal cell subpopulations orchestrate several aspects of physiological and pathophysiological adipose tissue remodeling, with a particular focus on the adaptations that occur in response to changes in energy surplus and environmental temperature. The study of adipose tissue remodeling provides a vehicle to understand the functional diversity of stromal cells and offers a lens through which several generalizable aspects of tissue reorganization can be readily observed.