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.

Rationale: Obesity increases the risk of cardiovascular disease (CVD) through mechanisms that remain incompletely defined. Metabolic dysfunction, especially hyperglycemia, is thought to be a major contributor but how glucose impacts vascular function is unclear. Galectin-3 (GAL3) is a sugar binding lectin upregulated by hyperglycemia but its role as a causative mechanism of CVD remains poorly understood. Objective: To determine the role of GAL3 in regulating microvascular endothelial vasodilation in obesity. Methods and Results: GAL3 was markedly increased in the plasma of overweight and obese patients, as well as in the microvascular endothelium of diabetic patients. To investigate a role for GAL3 in CVD, mice deficient in GAL3 were bred with obese db/db mice to generate lean, lean GAL3 knockout (KO), obese, and obese GAL3 KO genotypes. GAL3 KO did not alter body mass, adiposity, glycemia or lipidemia, but normalized elevated markers of reactive oxygen species (TBARS) in plasma. Obese mice exhibited profound endothelial dysfunction and hypertension, both of which were rescued by GAL3 deletion. Isolated microvascular endothelial cells (EC) from obese mice had increased NOX1 expression, which we have previously shown to contribute to increased oxidative stress and endothelial dysfunction, and NOX1 levels were normalized in EC from obese mice lacking GAL3. EC-specific GAL3 knockout mice made obese using a novel AAV-approach recapitulated whole-body knockout studies, confirming that endothelial GAL3 drives obesity-induced NOX1 overexpression and endothelial dysfunction. Improved metabolism through increased muscle mass, enhanced insulin signaling, or metformin treatment, decreased microvascular GAL3 and NOX1. GAL3 increased NOX1 promoter activity and this was dependent on GAL3 oligomerization. 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. Figure 8. Visual

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: 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.