Inhibiting myeloperoxidase prevents onset and reverses established high-fat diet-induced microvascular insulin resistance

Rationale and design of ENDEAVOR: A sequential phase 2b-3 randomized clinical trial to evaluate the effect of myeloperoxidase inhibition on symptoms and exercise capacity in heart failure with preserved or mildly reduced ejection fraction

AIMS

Mitiperstat (formerly AZD4831) is a novel selective myeloperoxidase inhibitor. Currently, no effective therapies target comorbidity-induced systemic inflammation, which may be a key mechanism underlying heart failure with preserved or mildly reduced ejection fraction (HFpEF/HFmrEF). Circulating neutrophils secrete myeloperoxidase, causing oxidative stress, microvascular endothelial dysfunction, interstitial fibrosis, cardiomyocyte remodelling and diastolic dysfunction. Mitiperstat may therefore improve function of the heart and other organs, and ameliorate heart failure symptoms and exercise intolerance. ENDEAVOR is a combined, seamless phase 2b-3 study of the efficacy and safety of mitiperstat in patients with HFpEF/HFmrEF.

METHODS

In phase 2b, approximately 660 patients with heart failure and ejection fraction >40% are being randomized 1:1:1 to mitiperstat 2.5 mg, 5 mg or placebo for 48 weeks. Eligible patients have baseline 6-min walk distance (6MWD) of 30-400 m with a <50 m difference between screening and randomization and Kansas City Cardiomyopathy Questionnaire total symptom score (KCCQ-TSS) ≤90 points at screening and randomization. The dual primary endpoints are change from baseline to week 16 in 6MWD and KCCQ-TSS. The sample size provides 85% power to detect placebo-adjusted improvements of 21 m in 6MWD and 6.0 points in KCCQ-TSS at overall two-sided alpha of 0.05. Safety is monitored throughout treatment, with a focus on maculopapular rash. In phase 3 of ENDEAVOR, approximately 820 patients will be randomized 1:1 to mitiperstat or placebo.

CONCLUSION

ENDEAVOR is the first phase 2b-3 study to evaluate whether myeloperoxidase inhibition can improve symptoms and exercise capacity in patients with HFpEF/HFmrEF.

A cross-sectional study to correlate antioxidant enzymes, oxidative stress and inflammation with prevalence of hypertension

AIMS

Hypertension a multifactorial consequence of environmental factors, life style and genetics is the well-recognized risk factor contributing to coronary heart diseases. The antioxidant imbalance, excessive reactive oxygen species (ROS) leads to oxidative stress which is pivotal in progression of hypertension. The present study aims to understand the complex interaction between oxidative stress, inflammation and antioxidant system which is crucial to maintain cellular homeostasis which further can exaggerate hypertension pathophysiology.

MATERIALS AND METHODS

The metabolic profile of hypertensive and normotensive subjects from Malwa region, Punjab was compared by estimating lipid profile, cardiac, hepatic and renal markers. The oxidative stress markers (protein carbonyls and lipid peroxidation), inflammatory markers (Nitric oxide, Myeloperoxidase and advanced oxygen protein products), and antioxidant enzymes (Superoxide Dismutase, Catalase, and Total Antioxidant Capacity) were analyzed.

KEY FINDINGS

It is observed that the metabolic markers are altered in hypertensive subjects which further these subjects showed increased oxidative, inflammatory profile and compromised antioxidant status when compared with normotensive subjects. Co-relation analysis validated the involvement of inflammation and oxidative stress in impaired endothelial function and vital organ damage.

SIGNIFICANCE OF STUDY

These markers may act as early indicators of hypertension which usually do not show any physical symptoms, thus can be diagnosed and treated at the earliest. The current study suggests that disturbed homeostasis, a consequence of altered interaction between antioxidant system and inflammatory events raises the oxidative stress levels which eventually leads to hypertension and associated complications. These indicators can serve as early indicators of future chronic complications of hypertension.

COVID-19 induces new-onset insulin resistance and lipid metabolic dysregulation via regulation of secreted metabolic factors

Abnormal glucose and lipid metabolism in COVID-19 patients were recently reported with unclear mechanism. In this study, we retrospectively investigated a cohort of COVID-19 patients without pre-existing metabolic-related diseases, and found new-onset insulin resistance, hyperglycemia, and decreased HDL-C in these patients. Mechanistically, SARS-CoV-2 infection increased the expression of RE1-silencing transcription factor (REST), which modulated the expression of secreted metabolic factors including myeloperoxidase, apelin, and myostatin at the transcriptional level, resulting in the perturbation of glucose and lipid metabolism. Furthermore, several lipids, including (±)5-HETE, (±)12-HETE, propionic acid, and isobutyric acid were identified as the potential biomarkers of COVID-19-induced metabolic dysregulation, especially in insulin resistance. Taken together, our study revealed insulin resistance as the direct cause of hyperglycemia upon COVID-19, and further illustrated the underlying mechanisms, providing potential therapeutic targets for COVID-19-induced metabolic complications.

Increased concentrations of myeloperoxidase in serum and serum extracellular vesicles are associated with type 2 diabetes mellitus

BACKGROUND

Inflammatory response plays a critical role in the initiation and progression of type 2 diabetes mellitus (T2DM). Myeloperoxidase (MPO), a leukocyte-derived protagonist, exerts its proinflammatory properties in many complications. We explored the associations between serum extracellular vesicle (EV)-derived MPO as well as serum MPO and T2DM.

METHODS

We performed a cross-sectional study in 151 individuals, including 93 patients with T2DM and 58 non-T2DM controls. The concentrations of serum EV-derived MPO and serum MPO were measured by Luminex Assay.

RESULTS

Our data showed that serum EV-derived MPO concentrations and serum MPO concentrations were significantly higher in T2DM patients compared with non-T2DM subjects. In addition, multivariate logistic regression analysis revealed that serum EV-derived MPO as well as serum MPO was independently associated with the presence of T2DM even after adjusting for confounding factors (OR = 1.836 /1 ng EV-derived MPO, 95% CI = 1.395-2.417, P < 0.001; OR = 4.135 /10 ng serum MPO, 95% CI = 2.285-7.483, P < 0.001). Furthermore, serum MPO showed marginally higher discriminatory accuracy than serum EV-derived MPO in screening T2DM (AUC = 0.858; AUC = 0.779).

CONCLUSION

Increased concentrations of the inflammatory marker MPO either in serum or in serum EVs were independently associated with T2DM.

Microbial-derived indoles inhibit neutrophil myeloperoxidase to diminish bystander tissue damage

During episodes of acute inflammation, polymorphonuclear leukocytes (PMNs) are actively recruited to sites of inflammation or injury where they provide anti-microbial and wound-healing functions. One enzyme crucial for fulfilling these functions is myeloperoxidase (MPO), which generates hypochlorous acid from Cl^- and hydrogen peroxide. The potential exists, however, that uncontrolled the extracellular generation of hypochlorous acid by MPO can cause bystander tissue damage and inhibit the healing response. Previous work suggests that the microbiota-derived tryptophan metabolites 1H-indole and related molecules ("indoles") are protective during intestinal inflammation, although their precise mechanism of action is unclear. In the present work, we serendipitously discovered that indoles are potent and selective inhibitors of MPO. Using both primary human PMNs and recombinant human MPO in a cell-free system, we revealed that indoles inhibit MPO at physiologic concentrations. Particularly, indoles block the chlorinating activity of MPO, a reliable marker for MPO-associated tissue damage, as measured by coulometric-coupled HPLC. Further, we observed direct interaction between indoles and MPO using the established biochemical techniques microscale thermophoresis and STD-NMR. Utilizing a murine colitis model, we demonstrate that indoles inhibit bystander tissue damage, reflected in decreased colon 3-chlorotyrosine and pro-inflammatory chemokine expression in vivo. Taken together, these results identify microbiota-derived indoles that acts as endogenous immunomodulatory compounds through their actions on MPO, suggesting a symbiotic association between the gut microbiota and host innate immune system. Such findings offer exciting new targets for future pharmacological intervention.

Neutrophil-Associated Inflammatory Changes in the Pre-Diabetic Pancreas of Early-Age NOD Mice

A growing body of evidence indicates that neutrophils are the first major leukocyte population accumulating inside the pancreas even before the onset of a lymphocytic-driven impairment of functional beta cells in type 1 diabetes mellitus (T1D). In humans, pancreata from T1D deceased donors exhibit significant neutrophil accumulation. We present a time course of previously unknown inflammatory changes that accompany neutrophil and neutrophil elastase accumulation in the pancreas of the non-obese diabetic (NOD) mouse strain as early as 2 weeks of age. We confirm earlier findings in NOD mice that neutrophils accumulate as early as 2 weeks of age. We also observe a concurrent increase in the expression of neutrophil elastase in this time period. We also detect components of neutrophil extracellular traps (NET) mainly in the exocrine tissue of the pancreas during this time as well as markers of vascular pathology as early as 2 weeks of age. Age- and sex-matched C57BL/6 mice do not exhibit these features inside the pancreas. When we treated NOD mice with inhibitors of myeloperoxidase and neutrophil elastase, two key effectors of activated neutrophil activity, alone or in combination, we were unable to prevent the progression to hyperglycemia in any manner different from untreated control mice. Our data confirm and add to the body of evidence demonstrating neutrophil accumulation inside the pancreas of mice genetically susceptible to T1D and also offer novel insights into additional pathologic mechanisms involving the pancreatic vasculature that have, until now, not been discovered inside the pancreata of these mice. However, inhibition of key neutrophil enzymes expressed in activated neutrophils could not prevent diabetes. These findings add to the body of data supporting a role for neutrophils in the establishment of early pathology inside the pancreas, independently of, and earlier from the time at onset of lymphocytic infiltration. However, they also suggest that inhibition of neutrophils alone, acting via myeloperoxidase and neutrophil elastase only, in the absence of other other effector cells, is insufficient to alter the natural course of autoimmune diabetes, at least in the NOD model of the disease.

Nucleotides released from palmitate-activated murine macrophages attract neutrophils

Obesity and elevation of circulating free fatty acids are associated with an accumulation and proinflammatory polarization of macrophages within metabolically active tissues, such as adipose tissue, muscle, liver, and pancreas. Beyond macrophages, neutrophils also accumulate in adipose and muscle tissues during high-fat diets and contribute to a state of local inflammation and insulin resistance. However, the mechanisms by which neutrophils are recruited to these tissues are largely unknown. Here we used a cell culture system as proof of concept to show that, upon exposure to a saturated fatty acid, palmitate, macrophages release nucleotides that attract neutrophils. Moreover, we found that palmitate up-regulates pannexin-1 channels in macrophages that mediate the attraction of neutrophils, shown previously to allow transfer of nucleotides across membranes. These findings suggest that proinflammatory macrophages release nucleotides through pannexin-1, a process that may facilitate neutrophil recruitment into metabolic tissues during obesity.