Healthy Subcutaneous and Omental Adipose Tissue Is Associated with High Expression of Extracellular Matrix Components

Obesity is associated with extensive expansion and remodeling of the adipose tissue architecture, including its microenvironment and extracellular matrix (ECM). Although obesity has been reported to induce adipose tissue fibrosis, the composition of the ECM under healthy physiological conditions has remained underexplored and debated. Here, we used a combination of three established techniques (picrosirius red staining, a colorimetric hydroxyproline assay, and sensitive gene expression measurements) to evaluate the status of the ECM in metabolically healthy lean (MHL) and metabolically unhealthy obese (MUO) subjects. We investigated ECM deposition in the two major human adipose tissues, namely the omental and subcutaneous depots. Biopsies were obtained from the same anatomic region of respective individuals. We found robust ECM deposition in MHL subjects, which correlated with high expression of collagens and enzymes involved in ECM remodeling. In contrast, MUO individuals showed lower expression of ECM components but elevated levels of ECM cross-linking and adhesion proteins, e.g., lysyl oxidase and thrombospondin. Our data suggests that subcutaneous fat is more prone to express proteins involved in ECM remodeling than omental adipose tissues. We conclude that a more dynamic ability to deposit and remodel ECM may be a key signature of healthy adipose tissue, and that subcutaneous fat may adapt more readily to changing metabolic conditions than omental fat.

The Omentum in Obesity-Associated Cancer: A Hindrance to Effective Natural Killer Cell Migration towards Tumour Which Can Be Overcome by CX3CR1 Antagonism

Oesophagogastric adenocarcinomas (OAC) are obesity-associated malignancies, underpinned by severe immune dysregulation. We have previously shown that natural killer (NK) cells preferentially migrate to OAC omentum, where they undergo phenotypic and functional alterations and apoptosis. Furthermore, we have identified the CX3CR1:fractalkine (CX3CL1) pathway as pivotal in their recruitment to omentum. Here, we elucidate whether exposure to the soluble microenvironment of OAC omentum, and in particular fractalkine and IL-15 affects NK cell homing capacity towards oesophageal tumour. Our data uncover diminished NK cell migration towards OAC tumour tissue conditioned media (TCM) following exposure to omental adipose tissue conditioned media (ACM) and reveal that this migration can be rescued with CX3CR1 antagonist E6130. Furthermore, we show that fractalkine has opposing effects on NK cell migration towards TCM, when used alone or in combination with IL-15 and uncover its inhibitory effects on IL-15-mediated stimulation of death receptor ligand expression. Interestingly, treatment with fractalkine and/or IL-15 do not significantly affect NK cell adhesion to MAdCAM-1, despite changes they elicit to the expression of integrin α4β7. This study provides further evidence that CX3CR1 antagonism has therapeutic utility in rescuing NK cells from the deleterious effects of the omentum and fractalkine in OAC, thus limiting their dysfunction.

Fibrogenesis marker PRO-C3 is higher in advanced liver fibrosis and improves in patients undergoing bariatric surgery

Objectives Serum propeptides of type III and type VI collagen (PRO-C3 and PRO-C6) are elevated in advanced nonalcoholic fatty liver disease, but their value in patients with severe obesity and their evolution after bariatric surgery (BS) is unknown. It is unclear if these markers of fibrogenesis are affected by adipose tissue fibrosis (ATF). We studied the association of PRO-C3 and PRO-C6 with liver fibrosis before BS, examined their evolution after BS and how much patients’ ATF contribute to their levels. Methods Serum PRO-C3 and PRO-C6 were measured in 158 BS patients and compared with liver, subcutaneous and omental adipose tissue histology obtained during surgery. PRO-C3 and PRO-C6 levels of 63 patients were determined in follow-up at 3 and 12 months post BS. Results Patients in the highest quartile of PRO-C3 had a higher risk of advanced liver fibrosis (stage F3-4; odds ratio 5.8; 95% CI [1.5-29.9]; p=0.017) compared to the lowest quartile (adjustment for age, gender and BMI). PRO-C3 was positively correlated with markers of insulin resistance and liver enzymes. After BS, PRO-C3 levels decreased in patients with high baseline liver fibrosis. This decrease correlated with improvement of metabolic and liver parameters. PRO-C6 was not related to stage of liver fibrosis. ATF did not correlate with PRO-C3 or PRO-C6 levels at baseline or after BS. Conclusions PRO-C3 was associated with advanced liver fibrosis in patients with severe obesity, and decreased after BS, without being affected by ATF. These data suggest that BS prominently eliminates drivers of hepatic fibrogenesis in NAFLD.

Ultrasound triggered topical delivery of Bmp7 mRNA for white fat browning induction via engineered smart exosomes

Background Efficient and topical delivery of drugs is essential for maximized efficacy and minimized toxicity. In this study, we aimed to design an exosome-based drug delivery platform endowed with the ability of escaping from phagocytosis at non-target organs and controllably releasing drugs at targeted location. Results The swtichable stealth coat CP05-TK-mPEG was synthesized and anchored onto exosomes through the interaction between peptide CP05 and exosomal surface marker CD63. Chlorin e6 (Ce6) was loaded into exosomes by direct incubation. Controllable removal of PEG could be achieved by breaking thioketal (TK) through reactive oxygen species (ROS), which was produced by Ce6 under ultrasound irradiation. The whole platform was called SmartExo. The stealth effects were analyzed in RAW264.7 cells and C57BL/6 mice via tracing the exosomes. To confirm the efficacy of the engineered smart exosomes, Bone morphogenetic protein 7 (Bmp7) mRNA was encapsulated into exosomes by transfection of overexpressing plasmid, followed by stealth coating, with the exosomes designated as SmartExo@Bmp7. Therapeutic advantages of SmartExo@Bmp7 were proved by targeted delivering Bmp7 mRNA to omental adipose tissue (OAT) of obese C57BL/6 mice for browning induction. SmartExo platform was successfully constructed without changing the basic characteristics of exosomes. The engineered exosomes effectively escaped from the phagocytosis by RAW264.7 and non-target organs. In addition, the SmartExo could be uptaken locally on-demand by ultrasound mediated removal of the stealth coat. Compared with control exosomes, SmartExo@Bmp7 effectively delivered Bmp7 mRNA into OAT upon ultrasound irradiation, and induced OAT browning, as evidenced by the histology of OAT and increased expression of uncoupling protein 1 (Ucp1). Conclusions The proposed SmartExo-based delivery platform, which minimizes side effects and maximizing drug efficacy, offers a novel safe and efficient approach for targeted drug delivery. As a proof, the SmartExo@Bmp7 induced local white adipose tissue browning, and it would be a promising strategy for anti-obesity therapy. Graphical Abstract

Chronic binge alcohol and ovariectomy dysregulate omental adipose tissue metaboproteome in simian immunodeficiency virus-infected female macaques

Effective antiretroviral therapy (ART) has significantly reduced mortality of people living with HIV (PLWH), and the prevalence of at-risk alcohol use is higher among PLWH. Increased survival and aging of PLWH is associated with increased prevalence of metabolic comorbidities especially among menopausal women, and adipose tissue metabolic dysregulation may be a significant contributing factor. We examined the differential effects of chronic binge alcohol (CBA) administration and ovariectomy (OVX) on the omental adipose tissue (OmAT) proteome in a subset of simian immunodeficiency virus (SIV)-infected macaques of a longitudinal parent study. Quantitative discovery-based proteomics identified 1429 differentially expressed proteins. Ingenuity Pathway Analysis (IPA) was used to calculate z-scores, or activation predictions, for functional pathways and diseases. Results revealed protein changes associated with functional pathways centered around the "OmAT metaboproteome profile". Based on z-scores, CBA did not affect functional pathways of metabolic disease but dysregulated proteins involved in AMPK signaling and lipid metabolism. OVX-mediated proteome changes were predicted to promote pathways involved in glucose- and lipid-associated metabolic disease. Proteins involved in apoptosis, necrosis, and reactive oxygen species (ROS) pathways were also predicted to be activated by OVX, and these were predicted to be inhibited by CBA. These results provide evidence for the role of ovarian hormone loss in mediating OmAT metaboproteome dysregulation in SIV and suggest that CBA modifies OVX-associated changes. In the context of OVX, CBA administration produced larger metabolic and cellular effects, which we speculate may reflect a protective role of estrogen against CBA-mediated adipose tissue injury in female SIV-infected macaques.

AGE/RAGE/DIAPH1 axis is associated with immunometabolic markers and risk of insulin resistance in subcutaneous but not omental adipose tissue in human obesity

Background/objectives The incidence of obesity continues to increase worldwide and while the underlying pathogenesis remains largely unknown, nutrient excess, manifested by “Westernization” of the diet and reduced physical activity have been proposed as key contributing factors. Western-style diets, in addition to higher caloric load, are characterized by excess of advanced glycation end products (AGEs), which have been linked to the pathophysiology of obesity and related cardiometabolic disorders. AGEs can be “trapped” in adipose tissue, even in the absence of diabetes, in part due to higher expression of the receptor for AGEs (RAGE) and/or decreased detoxification by the endogenous glyoxalase (GLO) system, where they may promote insulin resistance. It is unknown whether the expression levels of genes linked to the RAGE axis, including AGER (the gene encoding RAGE), Diaphanous 1 (DIAPH1), the cytoplasmic domain binding partner of RAGE that contributes to RAGE signaling, and GLO1 are differentially regulated by the degree of obesity and/or how these relate to inflammatory and adipocyte markers and their metabolic consequences. Subjects/methods We sought to answer this question by analyzing gene expression patterns of markers of the AGE/RAGE/DIAPH1 signaling axis in abdominal subcutaneous (SAT) and omental (OAT) adipose tissue from obese and morbidly obese subjects. Results In SAT, but not OAT, expression of AGER was significantly correlated with that of DIAPH1 (n = 16; $$\hat \beta = 0.719$$ β ̂ = 0.719 , [0.260, 1.177]; q = 0.008) and GLO1 (n = 16; $$\hat \beta = 0.773$$ β ̂ = 0.773 , [0.364, 1.182]; q = 0.004). Furthermore, in SAT, but not OAT, regression analyses revealed that the expression pattern of genes in the AGE/RAGE/DIAPH1 axis is strongly and positively associated with that of inflammatory and adipogenic markers. Remarkably, particularly in SAT, not OAT, the expression of AGER positively and significantly correlated with HOMA-IR (n = 14; $$\hat \beta = 0.794$$ β ̂ = 0.794 , [0.338, 1.249]; q = 0.018). Conclusions These observations suggest associations of the AGE/RAGE/DIAPH1 axis in the immunometabolic pathophysiology of obesity and insulin resistance, driven, at least in part, through expression and activity of this axis in SAT.

Synergetic Action of Forskolin and Mevastatin Induce Normalization of Lipids Profile in Dyslipidemic Rats through Adenosine Monophosphate Kinase Upregulation

In the present study, we examined the synergetic effect of forskolin and mevastatin administration on lipid profile and lipid metabolism in omental adipose tissue in dyslipidemic rats. The study was conducted on forty male albino rats. The rats were randomly classified into four main groups of ten animals in each group as follows: group A, served as control nontreated; group B, rats that received Triton WR 1339 (500 mg/kg); group C, rats that received Triton WR 1339 with forskolin (100% FSK extract 0.5 mg/kg/day) for four weeks; and group D, dyslipidemic rats received both mevastatin and forskolin. At the end of the experimental period, blood and omental adipose tissue samples were collected, preserved, and used for biochemical determination of lipid profile and mRNA expression profile of adenylate cyclase (AC), hormone-sensitive lipase, respectively (HSL), and adenosine monophosphate-activated protein kinase (AMPK). The results showed a significant decline in the serum concentration of total cholesterol, LDL-cholesterol, and triglycerides, although there was a significant increase in serum levels of HDL-cholesterol and glycerol in rats received forskolin alone or with mevastatin when compared with control and dyslipidemic groups. The mRNA expression levels of AC, HSL, and AMPK were significantly increased in omental adipose tissue of rats received forskolin when compared with other groups. In conclusion, forskolin acts synergistically with mevastatin to lower lipid profile and improve lipid metabolism in dyslipidemic rats through upregulation of AMPK expression.