Obesity remains the most common risk factor for cardiovascular disease in Western nations. While considerable effort has focused on identifying risk factors, which contribute to the increase incidence of complications and disease, an emerging concept is the existence of resilience factors, which mitigate disease. An important resilience factor gaining increased appreciation is the amount of skeletal muscle mass. In this review, we will explore how obesity increases the most-identified vascular component of metabolic vascular disease - endothelial dysfunction-how increases in muscle mass may protect vascular function in the obese population. This review advances the concept the obesity is less a disease of body mass than body composition which is reflected in the degree of negative vascular outcomes and may be of increased relevance in consideration of therapies that promote loss of muscle mass while reducing overall body size.

Obesity is a foremost risk factor for the development of cardiovascular disease, a hallmark of which is chronic vascular inflammation and overproduction of reactive oxygen species (ROS). NADPH oxidases (NOX) are central mediators of ROS overproduction in the obese vasculature, yet a complete understanding of the mechanism underlying their dysregulation in obesity remains poorly understood. Herein, we investigated the contribution of NOX1 in obesity-associated hypertension and evaluated the therapeutic potential of pharmacologically targeting NOX1 using the novel inhibitor GKT771. In obese db/db mice, NOX1 deletion ameliorated hypertension independent of metabolic improvements such as weight loss or improved glucose handling. Furthermore, NOX1 deletion improved renal sodium handling with no compensatory upregulation of other NOX isoforms. Importantly, treatment with the NOX1-specific inhibitor GKT771 rescued endothelial function in obese mice, restoring microvascular function to levels observed in lean controls. These data highlight the importance of NOX1 as a driver of endothelial dysfunction in obesity and suggest that NOX1 inhibition may offer a novel therapeutic strategy for obesity-associated endothelial dysfunction and its downstream cardiovascular complications.

Angiogenesis plays a vital role for postnatal development and tissue repair following ischemia. Reactive oxygen species (ROS) generated by NADPH oxidases (NOXes) and mitochondria act as signaling molecules that promote angiogenesis in endothelial cells (ECs) which mainly relies on aerobic glycolysis for ATP production. However, the connections linking redox signaling with glycolysis are not well understood. The GTPase Drp1 is a member of the dynamin superfamily that moves from cytosol to mitochondria through posttranslational modifications to induce mitochondrial fission. The role of Drp1 in ROS-dependent VEGF signaling and angiogenesis in ECs has not been previously described. Here, we identify an unexpected function of endothelial Drp1 as a redox sensor, transmitting VEGF-induced H 2 O 2 signals to enhance glycolysis and angiogenesis. Loss of Drp1 expression in ECs inhibited VEGF-induced angiogenic responses. Mechanistically, VEGF rapidly induced the NOX4-dependent sulfenylation (CysOH) of Drp1 on Cys 644 , promoting disulfide bond formation with the metabolic kinase AMPK and subsequent sulfenylation of AMPK at Cys 299/304 via the mitochondrial fission-mitoROS axis. This cysteine oxidation of AMPK, in turn, enhanced glycolysis and angiogenesis. In vivo, mice with EC-specific Drp1 deficiency or CRISPR/Cas9-engineered “redox-dead” (Cys to Ala) Drp1 knock-in mutations exhibited impaired retinal angiogenesis and post-ischemic neovascularization. Our findings uncover a novel role for endothelial Drp1 in linking VEGF-induced mitochondrial redox signaling to glycolysis through a cysteine oxidation-mediated Drp1-AMPK redox relay, driving both developmental and reparative angiogenesis.

Background: Streptococcus pneumonia is the primary etiological agent of community-acquired pneumonia (CAP). Pneumococci promote severe lung injury through the release of virulence factors, including pneumolysin (PLY). Obesity/diabetes increases pneumonia-associated mortality, but the mechanisms remain elusive. We found that obese db/db mice have increased pulmonary barrier disruption to PLY. Previously we showed that upregulation of NOX1 in endothelial cells (EC) of db/db mice drives endothelial dysfunction, but a role for NOX1 in PLY-induced lung injury, especially in diabetic conditions, has not yet been described. Results: Increased NOX1 in lung ECs dose-dependently increased superoxide and EC barrier disruption (p < 0.05). Even at low activity levels, NOX1 greatly potentiated PLY-induced EC barrier disruption, whereas loss of NOX1 activity, either pharmacological or genetic, reduced barrier disruption (p < 0.05). Blockade of calcium entry protected the EC barrier from combined PLY and NOX1, indicating a key role for calcium. Hyperglycemia amplified PLY-enduced EC barrier disruption and intracellular calcium and these effects were mitigated by NOX1 inhibition and silencing (p < 0.05). NOX1-enhanced calcium entry was reduced by knockout of calcium sensor STIM1, and PLY-induced barrier disruption was reduced by STIM1 inhibition. Levels of STIM1, Orai1, TRPV4, or TRPC4 were unchanged by HG, but TRPC1 significantly increased (p < 0.05). NOX1 and HG promoted increased STIM1 and TRPC1 binding, and silencing TRPC1 ameliorated PLY-induced barrier disruption (p < 0.05). Increased calcium promoted mitochondrial permeability transition pore (MPTP) opening and PPIF inhibition protected EC barrier function (p < 0.05). Conclusions: These results suggest that elevated glucose levels in obesity primes EC barrier disruption by amplifying PLY-induced calcium influx via a novel NOX1, STIM1, TRPC1 and MPTP signaling axis.

OBJECTIVE:This study utilized AAV gene delivery as an approach to induce and reverse hyperphagia in mice. We hypothesized that the delivery of orexigenic neuropeptides to the brain via AAV precipitates obesity and that the implementation of genetic switches to reverse transgene expression would elicit weight loss. METHODS:We utilized capsid-modified AAV-PHP.eB and AAV-CAP.B10 to deliver AgRP, NPY, a leptin superantagonist, and ghrelin to the mouse brain. Cre-LoxP, TETOFF, and cumate expression systems were used to alter transgene expression. RESULTS:Delivery of three out of four orexigenic neuropeptides to the brain precipitated severe obesity. Cre-mediated excision of AgRP from the brain caused a return to baseline weight, confounded by tamoxifen-associated weight loss. Doxycycline-mediated suppression of AgRP in a TETOFF vector paused weight gain but did not elicit weight loss. Cumate induction of AgRP in the brain was unaffected by systemic administration, suggesting that cumate inadequately penetrates the blood-brain barrier. CONCLUSIONS:Brain-targeted delivery of orexigenic peptides induces obesity in mice. This allows for temporally controlled, convenient, and robust preclinical models of obesity. The implementation of genetic switches enabled suppression/removal of AgRP expression, but we unexpectedly observed that removal of hyperphagic stimuli does not elicit robust weight loss.

BACKGROUND: Although combination antiretroviral therapy has increased life expectancy in people living with HIV, it has led to a marked increase in the prevalence of hypertension, the cause of which is unknown. Despite combination antiretroviral therapy, HIV-derived proteins remain expressed and produced by CD4 + T lymphocytes in people living with HIV. However, their contribution to HIV-associated hypertension and impaired endothelium-dependent relaxation remains ill defined. METHODS: Here, we tested the hypothesis that CD4 + T cells expressing viral proteins contribute to endothelial dysfunction and hypertension using the Tg26 mouse model of HIV that expresses 7 of the 9 HIV proteins under the long terminal repeat promoter. We used male and female mice, bone marrow transplantation (BMT), adoptive transfer of CD4 + T cells, and aorta specimen discarded from people living with HIV. RESULTS: We reported that intact Tg26 mice and mice receiving BMT (Tg26→WT) or CD4 + T cells from Tg26 mice display impaired endothelium-dependent relaxation and hypertension. Conversely, BMT from WT mice into Tg26 mice, inhibition of T cell activation, and CD4 + T cell depletion restored endothelial function and blood pressure in Tg26 mice. Cytokine profiling revealed that Tg26 mice, Tg26→WT, and Tg26 CD4 + T cells consistently exhibit high interleukin 1α (IL-1α) levels with no significant increase in other cytokines, whereas BMT from WT mice into Tg26 mice reduced IL-1α levels. IL-1α neutralization reduced blood pressure and restored endothelial function in Tg26 mice. To investigate the role of CD4 + T cells and IL-1α in endothelial dysfunction, we developed an aorta-immune cell coculture system. Exposure of WT aortas to Tg26 CD4 + T cells impaired endothelium-dependent relaxation, which was blocked by IL-1α–neutralizing antibody. While investigating the mechanisms of endothelial dysfunction, we reported that Tg26 mice, Tg26→WT aorta exhibit high NADPH oxidase (NOX) 1 expression. IL-1α exposure increased NOX1 in human microvascular endothelial cells, and NOX1 blockade restored endothelial function in Tg26 and Tg26→WT arteries, whereas NOX1 deficiency protected against Tg26 BMT-induced impaired endothelium-dependent relaxation and hypertension. Aortas from people living with HIV exhibit high NOX1 levels, and exposure of human aorta to Tg26 T cells increased NOX1 expression. CONCLUSIONS: We provide the first evidence that CD4 + T cells expressing HIV viral proteins induced hypertension through IL-1α–mediated increases in vascular NOX1, which impairs endothelial function in males and females.

Obesity and type 2 diabetes (T2D) increase cardiovascular risk, largely due to altered metabolic state. An early consequence of T2D/obesity is the loss of endothelial function and impaired nitric oxide (NO) signaling. In blood vessels, endothelial nitric oxide synthase (eNOS) synthesizes NO to maintain vessel homeostasis. The biological actions of NO are compromised by superoxide that is generated by NADPH oxidases (NOXs). Herein we investigated how altered metabolism affects superoxide/NO balance in obesity. We found that eNOS expression and NO bioavailability are significantly decreased in endothelial cells (ECs) from T2D patients and animal models of obesity. In parallel, PFKFB3, a key glycolytic regulatory enzyme, is significantly increased in ECs of obese animals. EC overexpression of wild-type and a cytosol-restricted mutant PFKFB3 decreased NO production due to increased eNOS-T495 phosphorylation. PFKFB3 also blunted Akt-S473 phosphorylation, reducing stimulus-dependent phosphorylation of S1177 and the activation of eNOS. Furthermore, PFKFB3 enhanced the activities of NOX1 and NOX5, which are major contributors to endothelial dysfunction. Prolonged exposure of ECs to high glucose or TNFα, which are hallmarks of T2D, leads to increased PFKFB3 expression. These results demonstrate a novel functional relationship between endothelial metabolism, ROS, and NO balance that may contribute to endothelial dysfunction in obesity.

Objective: To test the hypothesis that restored muscle quality achieved through myostatin KO improves angiogenesis in obese mice through the resolution of GAL3-NOX1-mediated endothelial dysfunction.Methods: db/db mice, a well-described model of obesity, were crossed with mice lacking myostatin (MSTN KO), a myokine that negatively regulates muscle differentiation and growth, galectin-3 (GAL3 KO), a pro-inflammatory/atherogenic RAGE (receptor for advanced glycation endproducts), and NADPH oxidase-1 (NOX1 KO), a TGF-b-stimulated primary producer of the reactive oxygen species (ROS) O2−, to generate db+/−-MSTN+/−, db+/−-GAL3+/−, and db+/−-NOX1+/− mice. We utilized nuclear magnetic resonance (NMR) spectroscopy to assess skeletal muscle (SKM) lean/fat content in db+/−-MSTN+/− mice. Muscle and plasma lipid content were analyzed via mass spectrometry. Mice were placed in metabolic cages and monitored with CLAMS (Comprehensive Lab Animal Monitoring System) in order to determine their whole-body metabolism. Insulin metabolism indices were determined via appropriate blood and plasma testing kits. Morphology of SKM was determined via microscopy of H&E and Mason’s Trichrome-stained gastrocnemius cross sections. Femoral artery ligation was used to stimulate in vivo angiogenesis in response to hind limb ischemia (HLI); whereas 1mm aortic rings cultured in ECBM (2% FBS) were used to study ex vivo angiogenesis. Gene expression was assessed by RNA-Seq and RT-qPCR. Results: MSTN deletion results in significantly increased SKM mass and restored SKM quality (i.e. morphology and metabolic function) without altering whole-body mass, fat percentage, or activity in obese (db−) mice. We observed that obesity inhibits and MSTN KO restores angiogenesis in both HLI and aortic ring assay models. Previous studies in our lab revealed that MSTN deletion was suffcient to restore endothelial function in db/db mice. Additionally, our lab has shown that GAL3 or NOX1 KO in db/db mice phenocopied the vascular improvements seen in db−-MSTN− mice without restoring SKM size or quality. RNA-Seq and RT-qPCR analysis of SKM and endothelial cells (ECs) revealed significant upregulation of GAL3 and NOX1 expression in db−-MSTN+ mice but not in db−-MSTN− and db−-GAL3− mice. Finally, either GAL3 or NOX1 deletion results in amended angiogenesis in obese animals. Conclusion: In summary, restoration of muscle quality in obese individuals provides potent protection of vascular and metabolic health. A correlate of this improvement is the attenuation of a novel MSTN-GAL3-NOX1 axis, which we have shown to mediate vascular inflammation/redox signaling in obesity. These data suggest that pharmacological targeting of upstream MSTN, downstream GAL3 and/or NOX1 could be effective in treating cardiovascular disease in the context of obesity and metabolic syndrome. A. C. Speese is supported by NIH 1F31HL165858-01A1. D.W. Stepp and D. J. Fulton are supported by NIH 1R01HL147159. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Objective: Myostatin deletion improves cardiometabolic disease outcomes observed in obesity without any changes in activity in mice. Hormone balance is dysregulated in obesity, resulting in low testosterone and high estradiol levels, which have been shown to correlate with higher risk for developing associated cardiometabolic disease outcomes. However, the basis of these alterations and how they impact factors that improve obese cardiometabolic outcomes are unknown. Methods: Control and obese mice ( db/db) with or without myostatin deletion to induce hypermuscularity were used. Plasme from mice were analyzed for hormone levels via radioimmunoassay (RIA). Aromatase inhibition was performed via dosing 10mg/kg/day via water. Quantitative PCR was used cytochrome P450 enzymes involved in estrogen metabolism in the liver, skeletal muscle, and visceral white adipose tissue. C2C12 overexpression of CYP1B1 and treatment with hydroxyestrogens in vitro was performed and respective enzyme mRNA expression assessed. Results: Deletion of myostatin increased muscle mass by >30% and resulted in and improved glucose tolerance in the context of obesity without any changes in activity. Obesity decreased plasma testosterone 30% and increased estrogen 20% with no change in gonadal weight, which was improved in the absence of myostatin. CYP1B1, an enzyme that converts estradiol to toxic hydroxy estrogens, showed 2.5-fold expression in obese skeletal muscle, which is reduced in the absence of myostatin, with no change in other cytochrome P450s involved in estrogen metabolism. Inhibition of aromatase reduces estrogen and improves testosterone plasma concentration, indicating the excess estrogen in obesity is derived primarily from testosterone conversion. Aromatase expression was increased in obesity but unaffected by changes in muscle mass, this indicates an alteration to downstream estrogen metabolism. In C2C12 cells, overexpression of myostatin recapitulated changes in CYP1B1 expression seen in vivo, suggesting a direct link between the myokine and sex hormone metabolism. In addition, treatment of C2C12 cells with CYP1B1 derived hydroxyestrogens caused a tandem increase in SCD1 expression, indicating a causal link between CYP1B1 activity in obesity to increased triglyceride synthesis. Conclusion: In summary, obesity causes a shift in sex hormone levels towards estrogen production, which is improved by myostatin deletion. A potential mechanism responsible could be altered estrogen metabolism, leading to decreased estrogen levels without restoration of androgen levels. These data suggest CYP1B1 drives the conversion of estrogen to hydroxestrogens, known to harbor carcinogenic and pro-lipidemic influences, in skeletal muscle which may also contribute to cardiometabolic disease. Whether targeting CYP1B1 improves cardiometabolic function in obesity remains to be determined. D.W. Stepp and D.J. Fulton are supported by NIH 1R01HL147159. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Exercise as a lifestyle modification is a frontline therapy for nonalcoholic fatty liver disease (NAFLD), but how components of exercise attenuate steatosis is unclear. To uncouple the effect of increased muscle mass from weight loss in obesity, myostatin knockout mice were bred on a lean and obese db/db background. Myostatin deletion increases gastrocnemius (Gastrocn.) mass and reduces hepatic steatosis and hepatic sterol regulatory element binding protein 1 (Srebp1) expression in obese mice, with no impact on adiposity or body weight. Interestingly, hypermuscularity reduces hepatic NADPH oxidase 1 (Nox1) expression but not NADPH oxidase 4 (Nox4) in db/db mice. To evaluate a deterministic function of Nox1 on steatosis, Nox1 knockout mice were bred on a lean and db/db background. NOX1 deletion significantly attenuates hepatic oxidant stress, steatosis, and Srebp1 programming in obese mice to parallel hypermuscularity, with no improvement in adiposity, glucose control, or hypertriglyceridemia to suggest off-target effects. Directly assessing the role of NOX1 on SREBP1, insulin (Ins)-mediated SREBP1 expression was significantly increased in either NOX1, NADPH oxidase organizer 1 (NOXO1), and NADPH oxidase activator 1 (NOXA1) or NOX5-transfected HepG2 cells versus ?-galactosidase control virus, indicating superoxide is the key mechanistic agent for the actions of NOX1 on SREBP1. Metabolic Nox1 regulators were evaluated using physiological, genetic, and diet-induced animal models that modulated upstream glucose and insulin signaling, identifying hyperinsulinemia as the key metabolic derangement explaining Nox1-induced steatosis in obesity. GEO data revealed that hepatic NOX1 predicts steatosis in obese humans with biopsy-proven NAFLD. Taken together, these data suggest that hypermuscularity attenuates Srebp1 expression in db/db mice through a NOX1-dependent mechanism.NEW & NOTEWORTHY This study documents a novel mechanism by which changes in body composition, notably increased muscle mass, protect against fatty liver disease. This mechanism involves NADPH oxidase 1 (NOX1), an enzyme that increases superoxide and increases insulin signaling, leading to increased fat accumulation in the liver. NOX1 may represent a new early target for preventing fatty liver to stave off later liver diseases such as cirrhosis or liver cancer.

BACKGROUND:Pulmonary arterial hypertension (PAH) is high blood pressure in the lungs that originates from structural changes in small resistance arteries. A defining feature of PAH is the inappropriate remodeling of pulmonary arteries (PA) leading to right ventricle failure and death. Although treatment of PAH has improved, the long-term prognosis for patients remains poor, and more effective targets are needed. METHODS:Gene expression was analyzed by microarray, RNA sequencing, quantitative polymerase chain reaction, Western blotting, and immunostaining of lung and isolated PA in multiple mouse and rat models of pulmonary hypertension (PH) and human PAH. PH was assessed by digital ultrasound, hemodynamic measurements, and morphometry. RESULTS:Microarray analysis of the transcriptome of hypertensive rat PA identified a novel candidate, PBK (PDZ-binding kinase), that was upregulated in multiple models and species including humans. PBK is a serine/threonine kinase with important roles in cell proliferation that is minimally expressed in normal tissues but significantly increased in highly proliferative tissues. PBK was robustly upregulated in the medial layer of PA, where it overlaps with markers of smooth muscle cells. Gain-of-function approaches show that active forms of PBK increase PA smooth muscle cell proliferation, whereas silencing PBK, dominant negative PBK, and pharmacological inhibitors of PBK all reduce proliferation. Pharmacological inhibitors of PBK were effective in PH reversal strategies in both mouse and rat models, providing translational significance. In a complementary genetic approach, PBK was knocked out in rats using CRISPR/Cas9 editing, and loss of PBK prevented the development of PH. We found that PBK bound to PRC1 (protein regulator of cytokinesis 1) in PA smooth muscle cells and that multiple genes involved in cytokinesis were upregulated in experimental models of PH and human PAH. Active PBK increased PRC1 phosphorylation and supported cytokinesis in PA smooth muscle cells, whereas silencing or dominant negative PBK reduced cytokinesis and the number of cells in the G2/M phase of the cell cycle. CONCLUSIONS:PBK is a newly described target for PAH that is upregulated in proliferating PA smooth muscle cells, where it contributes to proliferation through changes in cytokinesis and cell cycle dynamics to promote medial thickening, fibrosis, increased PA resistance, elevated right ventricular systolic pressure, right ventricular remodeling, and PH.

Background & Aims Visceral smooth muscle cells (SMCs) are an integral component of the gastrointestinal (GI) tract that regulate GI motility. SMC contraction is regulated by posttranslational signaling and the state of differentiation. Impaired SMC contraction is associated with significant morbidity and mortality, but the mechanisms regulating SMC-specific contractile gene expression, including the role of long noncoding RNAs (lncRNAs), remain largely unexplored. Herein, we reveal a critical role of Carmn (cardiac mesoderm enhancer-associated noncoding RNA), an SMC-specific lncRNA, in regulating visceral SMC phenotype and contractility of the GI tract. Methods Genotype-Tissue Expression and publicly available single-cell RNA sequencing (scRNA-seq) data sets from embryonic, adult human, and mouse GI tissues were interrogated to identify SMC-specific lncRNAs. The functional role of Carmn was investigated using novel green fluorescent protein (GFP) knock-in (KI) reporter/knock-out (KO) mice. Bulk RNA-seq and single nucleus RNA sequencing (snRNA-seq) of colonic muscularis were used to investigate underlying mechanisms. Results Unbiased in silico analyses and GFP expression patterns in Carmn GFP KI mice revealed that Carmn is highly expressed in GI SMCs in humans and mice. Premature lethality was observed in global Carmn KO and inducible SMC-specific KO mice due to GI pseudo-obstruction and severe distension of the GI tract, with dysmotility in cecum and colon segments. Histology, GI transit, and muscle myography analysis revealed severe dilation, significantly delayed GI transit, and impaired GI contractility in Carmn KO vs control mice. Bulk RNA-seq of GI muscularis revealed that loss of Carmn promotes SMC phenotypic switching, as evidenced by up-regulation of extracellular matrix genes and down-regulation of SMC contractile genes, including Mylk, a key regulator of SMC contraction. snRNA-seq further revealed SMC Carmn KO not only compromised myogenic motility by reducing contractile gene expression but also impaired neurogenic motility by disrupting cell-cell connectivity in the colonic muscularis. These findings may have translational significance, because silencing CARMN in human colonic SMCs significantly attenuated contractile gene expression, including MYLK, and decreased SMC contractility. Luciferase reporter assays showed that CARMN enhances the transactivation activity of the master regulator of SMC contractile phenotype, myocardin, thereby maintaining the GI SMC myogenic program. Conclusions Our data suggest that Carmn is indispensable for maintaining GI SMC contractile function in mice and that loss of function of CARMN may contribute to human visceral myopathy. To our knowledge this is the first study showing an essential role of lncRNA in the regulation of visceral SMC phenotype.

The detection of superoxide anion (O2●−) in biological tissues remains challenging. Barriers to convenient and reproducible measurements include expensive equipment, custom probes, and the need for high sensitivity and specificity. The luminol derivative, L-012, has been used to measure O2●− since 1993 with mixed results and concerns over specificity. The goal of this study was to better define the conditions for use and their specificity. We found that L-012 coupled with depolymerized orthovanadate, a relatively impermeable tyrosine phosphatase inhibitor, yielded a highly sensitive approach to detect extracellular O2●−. In O2●− producing HEK-NOX5 cells, orthovanadate increased L-012 luminescence 100-fold. The combination of L-012 and orthovanadate was highly sensitive, stable, scalable, completely reversed by superoxide dismutase, and selective for O2●− generating NOXes versus NOX4, which produces H2O2. Moreover, there was no signal from cells transfected with NOS3 (NO●) and NOS2(ONOO−). To exclude the effects of altered tyrosine phosphorylation, O2●− was detected using non-enzymatic synthesis with phenazine methosulfate and via novel coupling of L-012 with niobium oxalate, which was less active in inducing tyrosine phosphorylation. Overall, our data shows that L-012 coupled with orthovanadate or other periodic group 5 salts yields a reliable, sensitive, and specific approach to measuring extracellular O2●− in biological systems.

BACKGROUND:Obesity is associated with increased risk of cardiovascular disease, but underlying mechanisms remain elusive. Metabolic dysfunction, especially hyperglycemia, is thought to be a major contributor, but how glucose impacts vascular function is unclear. GAL3 (galectin-3) is a sugar-binding lectin upregulated by hyperglycemia, but its role as a causative mechanism of cardiovascular disease remains poorly understood. Therefore, the objective of this study was to determine the role of GAL3 in regulating microvascular endothelial vasodilation in obesity.METHODS:GAL3 was measured and found to be markedly increased in the plasma of overweight and obese patients, as well as in the microvascular endothelium of diabetic patients. To investigate causative mechanisms in cardiovascular disease, mice deficient in GAL3 were bred with obese db/db mice to generate lean, lean GAL3 knockout, obese, and obese GAL3 knockout genotypes. Endothelial cell-specific GAL3 knockout mice with novel AAV-induced obesity recapitulated whole-body knockout studies to confirm cell specificity.RESULTS:Deletion of GAL3 did not alter body mass, adiposity, or plasma indices of glycemia and lipidemia, but levels of plasma reactive oxygen species as assessed by plasma thiobarbituric acid reactive substances were normalized in obese GAL3 knockout mice. Obese mice exhibited profound endothelial dysfunction and hypertension, both of which were rescued by GAL3 deletion. Isolated microvascular endothelial cells from obese mice had increased expression of NOX1 (nicotinamide adenine dinucleotide phosphate oxidase 1), which we have previously shown to contribute to increased oxidative stress and endothelial dysfunction, which was normalized in microvascular endothelium from mice lacking GAL3. Cell-specific deletion confirmed that endothelial GAL3 regulates obesity-induced NOX1 overexpression and subsequent microvascular function. Furthermore, improvement of metabolic syndrome by increasing muscle mass, improving insulin signaling, or treating with metformin decreased microvascular GAL3, and thereby NOX1, expression levels.CONCLUSIONS:Deletion of GAL3 normalizes microvascular endothelial function in obese db/db mice, likely through a NOX1-mediated mechanism. Pathological levels of GAL3, and in turn NOX1, are amenable to improvements in metabolic status, presenting a potential therapeutic target to ameliorate pathological cardiovascular consequences of obesity.

Chronic inflammation underlies many chronic diseases such as obesity and diabetes and can lead to vascular and organ dysfunction, disability and death. Inflammation has been widely studied due to its broad involvement in numerous disease states, but current models of inflammation suffer from limitations. Models such as LPS treatment are non-specific and require multiple doses over extended periods of time which can lead to septic shock. The goal of our study was to develop an alternative model offering cell and organ specificity using an AAV-based approach. We hypothesize that delivering Ikk2, a potent activator of NF-KB will lead to chronic inflammation in the targeted cells and tissues. This approach has the benefit of cell and tissue specificity using specialized promoters and modified AAV capsids. Additionally, it will allow for consistent and regulatable expression over time. In preliminary studies I compared two know activators of NFKB, IKBKE and IKK2 to investigate differences in expression of inflammatory markers. Western blot analysis revealed ICAM-1 and IRF-1 protein levels were increased with IKK2 expression. In comparison, the inhibitior of apoptosis, CIAP-2, was more highly increased under IKBKE expression. We conclude that IKK2 would be more suitable to induce inflammation in target cells. Future studies will employ qPCR, Western blot, cytokine analysis and vascular function studies to characterize the effects in vivo. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Objective: To test the hypothesis that restored muscle mass achieved through deletion of myostatin improves angiogenesis in obese mice through the resolution of myosteatosis. Methods: db/db mice, a well-described model of obesity, were crossed with mice lacking myostatin (MSTN KO), a myokine that negatively regulates muscle differentiation and growth, or stearoyl Co-A desaturase 1 (SCD1 KO), the rate limiting enzyme for oleate synthesis and subsequent triglyceride production, to generate db +/-_MSTN +/- and db +/-_SCD1 +/- mice. We utilized confocal and nuclear magnetic resonance (NMR) spectroscopy to assess skeletal muscle (SKM) histology and morphology in db +/-_MSTN +/- and db +/-_SCD1 +/- mice. Muscle lipid content was analyzed via mass spectrometry. Femoral artery ligation was used to stimulate in vivo angiogenesis in response to ischemia; whereas, 1mm aortic rings cultured in ECBM (2% FBS) were used to study ex vivo angiogenesis. Gene expression was assessed by RNA-Seq with protein expression follow-up in isolated gastrocnemius SKM via RT-qPCR and western blotting. Results: As previously described, MSTN deletion results in significantly increased muscle mass without altering whole-body mass or fat percentage in obese db/db mice. Additionally, we observed that obesity inhibits and MSTN deletion restores angiogenesis in both hind limb ischemia and aortic ring assay models. Despite persistent plasma lipedema, ectopic lipid deposition in SKM (Myosteatosis) was largely ameliorated in obese mice lacking MSTN, a reduction largely explained by a decrease in tissue triglyceride levels. Confocal microscopy revealed the accumulation of lipid in obese mouse myocytes that was lacking in obese mice with MSTN KO. RNA-Seq analysis of SKM exposed marked upregulation of lipogenesis pathways, notably the expression of SCD1. SCD1 was elevated at both the protein and RNA levels in db -_MSTN + SKM but not in db -_MSTN - SKM. Similar to MSTN KO, confocal imaging reveals that SCD1 deletion reverses lipid accumulation in obese mice. Conclusion: In summary, restored muscle mass in obese mice provides potent protection to vascular and metabolic health. A potential correlate of this improvement is the resolution of myosteatosis in obese MSTN KO mice. These data suggest that resolution of myosteatosis, independent of muscle mass, may afford similar protection, possibly by targeted deletion or blockade of SCD1. A. C. Guilfoyle-Speese is supported by Kirschstein National Research Service Award (NRSA) Institutional Research Training Grant (T32) T32HL155011. D.W. Stepp and D.J. Fulton are supported by NIH 1R01HL147159. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Obesity is a major risk factor for type 2 diabetes mellitus and cardiovascular diseases (CVD) such as atherosclerosis, hypertension and stroke, which account for a majority of worldwide deaths. The complications arising from excess adiposity are multiple and cumulative and thus, animal models are critical to interrogate the mechanisms arising from obesity that contribute to vascular disease. The commonly used models of obesity in mice, namely those with disturbed leptin signaling ( db/db, ob/ob) and use of high fat diets (HFD) mimic aspects of human obesity including increased adiposity, and metabolic and vascular derangement. However, these models also have substantial limitations including: 1) whole body loss of leptin signaling, 2) infertility, a major barrier to generating complex genetic obese mouse models, 3) hyperphagia from birth leading to an obesogenic milieu throughout development, 4) early onset of metabolic derangement inconsistent with the majority of human disease, and 5) HFD fed mice take months to develop a mild form of obesity and do so solely through increased dietary fat consumption outside of the range of normal human diet and not through hyperphagia, a key hallmark of human obesity. To address these limitations, while maintaining the strengths of the aforementioned models, we generated a blood brain barrier crossing AAV (AAV-PHP.eB) that expresses Agouti related peptide (AgRP) in the brains of C57BL/6J mice when administered systemically. Retro-orbital administration of AgRP-AAV.PHP.eB to 8-week-old mice resulted in the expression of AgRP in the brain, the onset of robust hyperphagia within 1 week of injection, and sustained weight gain to a median of 63.1±2.1g. Although male AgRP-AAV mice exhibited metabolic dysfunction as shown by increases in HbA1c, insulin, lipids and leptin at 20 weeks, the magnitude of these changes were less pronounced versus previous findings in db/db mice, suggesting a slower progression metabolic syndrome which is more in line with prediabetic humans. This metabolic phenotype was accompanied by a profound microvascular endothelial dysfunction in mesenteric arteries as determined by reduced dilation to acetylcholine. Strengths of this model include: 1) temporal control the onset of obesity, 2) it is effective in both males and females, 3) it does not depend on a restricted diet with the advantage that it can be combined with changes in diet, 4) AgRP expression is largely restricted to the brain, 5) leptin and leptin receptors are intact, and 6) it can easily be combined with most mouse genetic models without laborious breeding strategies to circumvent infertility. Supported by National Institutes of Health (NIH) 1F31HL154646 (CAP), 1F31HL165916 (HGS), R01HL147159 (DS, DF), HL125926-05A1 (DF) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Objective: Obesity alters sex hormone balance in males, resulting in low testosterone and altered metabolism of estrogen, independent risk factors for cardiometabolic dysfunction. The basis of these alterations and how they are impacted by factors that improve cardiometabolic outcomes in obesity are unknown. Methods: Control and obese mice ( db/db) with or without deletion of myostatin to induce hypermuscularity were used. Mice were analyzed for plasma sex hormones via mass-spectrometry with or without 10mg/kg/day fadrazole to inhibit aromatase. Quantitative PCR was used to measure aromatase along with cytochrome P450 enzymes involved in estrogen metabolism in the liver, skeletal muscle, and visceral adipose tissue. HEK293a cells were treated with myostatin in vitro and enzyme levels assessed. Results: Obesity decreased plasma testosterone 30% and increased estrogen 20% with no change in gonadal weight. Deletion of myostatin increased muscle mass >30% and resulted in a reduction in estrogen levels without a parallel increase in androgens in obese mice. Inhibition of aromatase restores estrogen levels indicating the excess estrogen in obesity is derived from testosterone conversion. Since estrogen was lowered without increasing testosterone and estrogen metabolism must be increased. Aromatase was increased in obesity but unaffected by changes in muscle mass. CYP1B1, an enzyme that converts estradiol to hydroxy estrogens, showed 2.5 fold expression in obese skeletal muscle, which is improved in the absence of myostatin, with no change in other P450s involved in estrogen metabolism. Moreover, changes in P450 enzymes in liver or fat were either absent or changed directionally opposite to observed hormone changes. In HEK cells, treatment with myostatin recapitulated changes in CYP1B1 expression seen in vitro, suggesting a direct link between the myokine and sex hormone metabolism by skeletal muscle. Conclusion: In summary, obesity causes a shift in sex hormone levels to estrogen production, which is improved by myostatin deletion, without restoration of androgens. A potential mechanism responsible could be altered estrogen catabolism, leading to decreased estrogen levels without the restoration of androgen levels. Together, these data suggest CYP1B1 drives the conversion of estrogen to hydroxestrogens, which are known pro-oxidant and pro-lipidemic influences that may contribute to cardiometabolic disease. Whether targeting CYP1B1 improves cardiometabolic function in obesity remains to be determined. D.W. Stepp and D.J. Fulton are supported by NIH 1R01HL147159 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Pneumolysin (PLY) is a bacterial pore forming toxin and primary virulence factor of Streptococcus pneumonia, a major cause of pneumonia. PLY binds cholesterol-rich domains of the endothelial cell (EC) plasma membrane resulting in pore assembly and increased intracellular (IC) Ca2+ levels that compromise endothelial barrier integrity. Caveolae are specialized plasmalemma microdomains of ECs enriched in cholesterol. We hypothesized that the abundance of cholesterol-rich domains in EC plasma membranes confers cellular susceptibility to PLY. Contrary to this hypothesis, we found increased PLY-induced IC Ca2+ following membrane cholesterol depletion. Caveolin-1 (Cav-1) is an essential structural protein of caveolae and its regulation by cholesterol levels suggested a possible role in EC barrier function. Indeed, Cav-1 and its scaffolding domain peptide protected the endothelial barrier from PLY-induced disruption. In loss of function experiments, Cav-1 was knocked-out using CRISPR-Cas9 or silenced in human lung microvascular ECs. Loss of Cav-1 significantly enhanced the ability of PLY to disrupt endothelial barrier integrity. Rescue experiments with re-expression of Cav-1 or its scaffolding domain peptide protected the EC barrier against PLY-induced barrier disruption. Dynamin-2 (DNM2) is known to regulate caveolar membrane endocytosis. Inhibition of endocytosis, with dynamin inhibitors or siDNM2 amplified PLY induced EC barrier dysfunction. These results suggest that Cav-1 protects the endothelial barrier against PLY by promoting endocytosis of damaged membrane, thus reducing calcium entry and PLY-dependent signaling.