Adipocyte heme oxygenase-1 induction attenuates metabolic syndrome in both male and female obese mice

Obesity and mitochondrial uncoupling - an opportunity for the carbon monoxide-based pharmacology of metabolic diseases

Obesity, a chronic and progressive disease with a complex etiology, remains a significant global health challenge. Despite advancements in lifestyle interventions, pharmacological therapies, and bariatric surgery, substantial barriers to effective and sustained obesity management persist. Resistance to weight loss and gradual weight regain are commonly reported, limiting the long-term success of both non-pharmacological and pharmacological strategies. A possible contributor is metabolic adaptation, a phenomenon characterized by reduced metabolic rate and energy expenditure following weight loss, which hinders therapeutic efficacy. To address these challenges, increasing attention has been directed toward strategies that counteract maladaptive mechanisms by modulating metabolic rate and enhancing energy expenditure. One promising approach involves mitochondrial uncoupling, where electron transport and oxygen consumption are disconnected from ATP synthesis, promoting energy dissipation. Preclinical studies have demonstrated the potential of various chemical compounds with uncoupling activity as anti-obesity agents. Additionally, carbon monoxide (CO) has emerged as a significant gaseous signaling molecule in human physiology, with anti-inflammatory, antioxidative, and cytoprotective properties. Advances in CO-based pharmacology have led to the development of controlled-release CO donors, enabling precise therapeutic application. Experimental studies suggest that CO modulates mitochondrial bioenergetics, induces mild mitochondrial uncoupling, and regulates mitochondrial biogenesis. By integrating these findings, this review uniquely connects scientific threads, offering a comprehensive synthesis of current knowledge while proposing innovative directions in mitochondrial, metabolic and CO-based pharmacological research. It highlights the potential of CO-based pharmacology to regulate metabolic rate, support weight loss, and address obesity-related dysfunctions, thus suggesting novel pathways for advancing obesity treatment.

Heme oxygenase, biliverdin reductase, and bilirubin pathways regulate oxidative stress and insulin resistance: a focus on diabetes and therapeutics

Metabolic and insulin-resistant diseases, such as type 2 diabetes mellitus (T2DM), have become major health issues worldwide. The prevalence of insulin resistance in the general population ranges from 15.5% to 44.6%. Shockingly, the global T2DM population is anticipated to double by 2050 compared with 2021. Prior studies indicate that oxidative stress and inflammation are instrumental in causing insulin resistance and instigating metabolic diseases. Numerous methods and drugs have been designed to combat insulin resistance, including metformin, thiazolidinediones (TZDs), sodium-glucose cotransporter 2 inhibitors (SGLT2i), glucagon-like peptide 1 receptor agonists (GLP1RA), and dipeptidyl peptidase 4 inhibitors (DPP4i). Bilirubin is an antioxidant with fat-burning actions by binding to the PPARα nuclear receptor transcription factor, improving insulin sensitivity, reducing inflammation, and reversing metabolic dysfunction. Potential treatment with antioxidants like bilirubin and increasing the enzyme that produces it, heme oxygenase (HMOX), has also gained attention. This review discusses the relationships between bilirubin, HMOX, and insulin sensitivity, how T2DM medications affect HMOX levels and activity, and potentially using bilirubin nanoparticles to treat insulin resistance. We explore the sex differences between these treatments in the HMOX system and how bilirubin levels are affected. We discuss the emerging concept that bilirubin bioconversion to urobilin may have a role in metabolic diseases. This comprehensive review summarizes our understanding of bilirubin functioning as a hormone, discusses the HMOX isoforms and their beneficial mechanisms, analyzes the sex differences that might cause a dichotomy in responses, and examines the potential use of HMOX and bilirubin nanoparticle therapies in treating metabolic diseases.

Serum total bilirubin is a risk factor of metabolic syndrome and its components in obese Egyptians

Background/Aim

The link between serum total bilirubin and metabolic syndrome and its components has been previously proposed. However, it is unknown whether total bilirubin is a risk factor of metabolic syndrome and its components in obese Egyptians. Therefore, this study was conducted to clarify the association of total bilirubin levels with metabolic syndrome and its components in obese Egyptians.

Methods

A total of 200 adults with obesity were enrolled in this study. Obese participants were evaluated for metabolic syndrome; there were 92 obese participants with metabolic syndrome and 108 obese participants without metabolic syndrome. Anthropometric measurements, fasting blood glucose (FBG), fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), HOMA-β (%), lipid profile, uric acid, alanine aminotransferase, aspartate aminotransferase, and serum total bilirubin were assessed.

Results

Total bilirubin was significantly lower in obese participants with metabolic syndrome than in those without metabolic syndrome. Compared with middle bilirubin tertile, high and low bilirubin tertiles were independently associated with metabolic syndrome. Regarding metabolic syndrome components, a significant positive association between low bilirubin tertile and hypertension was found independent of the all studied confounding factors, whereas the association of total bilirubin level with waist circumference (WC), FBG, high-density lipoprotein cholesterol, and triglycerides was dependent on body mass index (BMI), HOMA-IR, and high sensitive C-reactive protein (hs-CRP).

Conclusion

Total bilirubin is an independent risk factor of metabolic syndrome in obese Egyptians. We have found an independent association between high bilirubin level and reduced risk of metabolic syndrome, whereas low bilirubin level was associated with increased risk of metabolic syndrome. Bilirubin is also independently associated with hypertension, but its association with other components of metabolic syndrome is mainly dependent on BMI, HOMA-IR, and hs-CRP.

On the Therapeutic Potential of Heme Oxygenase-1 and Its Metabolites

Over the past 55 years, the heme oxygenase (HO) system has emerged as a pivotal player in a myriad of cellular, tissue, and integrative physiological processes [...].

Heme Oxygenase-1, Cardiac Senescence, and Myocardial Infarction: A Critical Review of the Triptych

PURPOSE

Heme oxygenase-1 (HO-1) is a crucial enzyme in heme metabolism, facilitating the breakdown of heme into biliverdin, carbon monoxide, and free iron. Renowned for its potent cytoprotective properties, HO-1 showcases notable antioxidant, anti-inflammatory, and anti-apoptotic effects. In this review, the authors aim to explore the profound impact of HO-1 on cardiac senescence and its potential implications in myocardial infarction (MI).

RESULTS

Recent research has unveiled the intricate role of HO-1 in cellular senescence, characterized by irreversible growth arrest and functional decline. Notably, cardiac senescence has emerged as a pivotal factor in the development of various cardiovascular conditions, including MI. Notably, cardiac senescence has emerged as an important factor in the development of various cardiovascular conditions, including myocardial infarction (MI). The accumulation of senescent cells, spanning vascular endothelial cells, vascular smooth muscle cells, cardiomyocytes, and progenitor cells, poses a significant risk for cardiovascular diseases such as vascular aging, atherosclerosis, myocardial infarction, and ventricular remodeling. Inhibition of cardiomyocyte senescence not only reduces senescence-associated inflammation but also impacts other myocardial lineages, hinting at a broader mechanism of propagation in pathological remodeling. HO-1 has been shown to improve heart function and mitigate cardiomyocyte senescence induced by ischemic injury and aging. Furthermore, HO-1 induction has been found to alleviate H2O2-induced cardiomyocyte senescence. As we grow in our understanding of antiproliferative, antiangiogenic, anti-aging, and vascular effects of HO-1, we see the potential to exploit potential links between individual susceptibility to cardiac senescence and myocardial infarction.

CONCLUSIONS

This review investigates strategies for upregulating HO-1, including gene targeting and pharmacological agents, as potential therapeutic approaches. By synthesizing compelling evidence from diverse experimental models and clinical investigations, this study elucidates the therapeutic potential of targeting HO-1 as an innovative strategy to mitigate cardiac senescence and improve outcomes in myocardial infarction, emphasizing the need for further research in this field.

Association between heme oxygenase-1 and hyperlipidemia in pre-diabetic patients: a cross-sectional study

Background

Although the importance and benefit of heme oxygenase-1 (HO-1) in diabetes rodent models has been known, the contribution of HO-1 in the pre-diabetic patients with hyperlipidemia risk still remains unclear. This cross-sectional study aims to evaluate whether HO-1 is associated with hyperlipidemia in pre-diabetes.

Methods

Serum level of HO-1 was detected using commercially available ELISA kit among 1,425 participants aged 49.3-63.9 with pre-diabetes in a multicenter Risk Evaluation of cAncers in Chinese diabeTic Individuals: A lONgitudinal (REACTION) prospective observational study. Levels of total cholesterol (TC) and triglyceride (TG) were measured and used to defined hyperlipidemia. The association between HO-1 and hyperlipidemia was explored in different subgroups.

Result

The level of HO-1 in pre-diabetic patients with hyperlipidemia (181.72 ± 309.57 pg/ml) was obviously lower than that in pre-diabetic patients without hyperlipidemia (322.95 ± 456.37 pg/ml). High level of HO-1 [(210.18,1,746.18) pg/ml] was negatively associated with hyperlipidemia (OR, 0.60; 95% CI, 0.37-0.97; p = 0.0367) after we adjusted potential confounding factors. In subgroup analysis, high level of HO-1 was negatively associated with hyperlipidemia in overweight pre-diabetic patients (OR, 0.50; 95% CI, 0.3-0.9; p = 0.034), especially in overweight women (OR, 0.42; 95% CI, 0.21-0.84; p = 0.014).

Conclusions

In conclusion, elevated HO-1 level was negatively associated with risk of hyperlipidemia in overweight pre-diabetic patients, especially in female ones. Our findings provide information on the exploratory study of the mechanism of HO-1 in hyperlipidemia, while also suggesting that its mechanism may be influenced by body weight and gender.

In Vitro Assessment of Anti-Adipogenic and Anti-Inflammatory Properties of Black Cumin (Nigella sativa L.) Seeds Extract on 3T3-L1 Adipocytes and Raw264.7 Macrophages

Background and Objectives: This study evaluated the in vitro anti-adipogenic and anti-inflammatory properties of black cumin (Nigella sativa L.) seed extract (BCS extract) as a potential candidate for developing herbal formulations targeting metabolic disorders. Materials and Methods: We evaluated the BCS extract by assessing its 2,2-diphenyl-1-picrohydrazyl (DPPH) radical scavenging activity, levels of prostaglandin E2 (PGE2) and nitric oxide (NO), and mRNA expression levels of key pro-inflammatory mediators. We also quantified the phosphorylation of nuclear factor kappa light chain enhancer of activated B cells (NF-κB) and mitogen-activated protein kinases (MAPK) signaling molecules. To assess anti-adipogenic effects, we used differentiated 3T3-L1 cells and BCS extract in doses from 10 to 100 μg/mL. We also determined mRNA levels of key adipogenic genes, including peroxisome proliferator-activated receptor γ (PPARγ), CCAAT/enhancer binding protein α (C/BEPα), adipocyte protein 2 (aP2), lipoprotein lipase (LPL), fatty acid synthase (FAS), and sterol-regulated element-binding protein 1c (SREBP-1c) using real-time quantitative polymerase chain reaction (qPCR). Results: This study showed a concentration-dependent DPPH radical scavenging activity and no toxicity at concentrations up to 30 μg/mL in Raw264.7 cells. BCS extract showed an IC50 of 328.77 ± 20.52 μg/mL. Notably, pre-treatment with BCS extract (30 μg/mL) significantly enhanced cell viability in lipopolysaccharide (LPS)-treated Raw264.7 cells. BCS extract treatment effectively inhibited LPS-induced production of PGE2 and NO, as well as the expression of monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor-α (TNF-α), cyclooxygenase-2 (COX-2), inducible NO synthase (iNOS), interleukin (IL)-1β and IL-6, possibly by limiting the phosphorylation of p38, p65, inhibitory κBα (I-κBα), and c-Jun N-terminal kinase (JNK). It also significantly attenuated lipid accumulation and key adipogenic genes in 3T3-L1 cells. Conclusions: This study highlights the in vitro anti-adipogenic and anti-inflammatory potential of BCS extract, underscoring its potential as a promising candidate for managing metabolic disorders.

Gut microbiome and diet in populations with obesity: Role of the Na+/K+-ATPase transporter signaling in severe COVID-19

OBJECTIVE

The triad of obesity, a high-protein diet from animal sources, and disturbed gut microbiota have been linked to poor clinical outcomes in patients with COVID-19. In this report, the effect of oxidative stress resulting from the Na+ /K+ -ATPase transporter signaling cascade is explored as a driver of this poor clinical outcome.

METHODS

Protein-protein interactions with the SARS-CoV-2 proteome were identified from the interactome data for Na+ /K+ -transporting ATPase subunit α-1 (ATP1A1), epidermal growth factor receptor, and ERB-B2 receptor tyrosine kinase 2, using the curated data from the BioGRID Database of Protein Interactions. Data for the gene expression pattern of inflammatory response were from the Gene Expression Omnibus database for cardiomyocytes post SARS-CoV-2 infection (number GSE151879).

RESULTS

The ATP1A1 subunit of the Na+ /K+ -ATPase transporter is targeted by multiple SARS-CoV-2 proteins. Furthermore, receptor proteins associated with inflammatory response, including epidermal growth factor receptor and ERB-B2 receptor tyrosine kinase 2 (which interact with ATP1A1), are also targeted by some SARS-CoV-2 proteins. This heightened interaction likely triggers a cytokine release that increases the severity of the viral infection in individuals with obesity.

CONCLUSIONS

The similarities between the effects of SARS-CoV-2 proteins and indoxyl sulphate on the Na+ /K+ -ATPase transporter signaling cascade suggest the possibility of an augmentation of gene changes seen with COVID-19 infection that can result in a hyperinduction of cytokine release in individuals with obesity.

Cytochrome P450 epoxygenase-derived EPA and DHA oxylipins 17,18-epoxyeicosatetraenoic acid and 19,20-epoxydocosapentaenoic acid promote BAT thermogenesis and WAT browning through the GPR120-AMPKα signaling pathway

The mechanisms whereby fish oil rich in EPA and DHA promotes BAT thermogenesis and WAT browning are not fully understood. Thus, this study aimed to investigate the effects of cytochrome P450 (CYP) epoxygenase-derived EPA and DHA oxylipins 17,18-EpETE and 19,20-EpDPE on BAT thermogenesis and WAT browning and explore the underlying mechanism. Stromal vascular cells (SVCs) were subjected to 17,18-EpETE or 19,20-EpDPE treatment and mice were treated with the CYP epoxygenase inhibitor, the thermogenic marker genes were detected and the involvement of GPR120 and AMPKα were assessed. The in vitro results indicated that 17,18-EpETE and 19,20-EpDPE induced brown and beige adipocyte thermogenesis, with increased expression of thermogenic marker gene UCP1 in differentiated SVCs. Meanwhile, the expression of GPR120 and phosphorylation of AMPKα were increased in response to these two oxylipins. However, the inhibition of GPR120 and AMPKα inhibited the promotion of adipocyte thermogenesis. In addition, in the presence of CYP epoxygenase inhibitor MS-PPOH, EPA and DHA had no effect on increasing UCP1 expression in differentiated SVCs. Consistent with the in vitro results, the in vivo findings demonstrated that fish oil had no body fat-lowering effects and no effects on enhancing energy metabolism, iBAT thermogenesis and iWAT browning in mice fed HFD after intraperitoneal injection of CYP epoxygenase inhibitor SKF-525A. Moreover, fish oil had no effect on the elevation of GPR120 expression and activation of AMPKα in iBAT and iWAT in mice fed HFD after intraperitoneal injection of SKF-525A. In summary, our results showed that CYP epoxygenase-derived EPA and DHA oxylipins 17,18-EpETE and 19,20-EpDPE promoted BAT thermogenesis and WAT browning through the GPR120-AMPKα signaling pathway, which might contribute to the thermogenic and anti-obesity effects of fish oil.

Biliverdin reductase-A protein levels are reduced in type 2 diabetes and are associated with poor glycometabolic control

AIM

Biliverdin reductase-A (BVR-A) other than its canonical role in the degradation pathway of heme as partner of heme oxygenase-1 (HO1), has recently drawn attention as a protein with pleiotropic functions involved in insulin-glucose homeostasis. However, whether BVR-A expression is altered in type 2 diabetes (T2D) has never been evaluated.

MAIN METHODS

BVR-A protein levels were evaluated in T2D (n = 44) and non-T2D (n = 29) subjects, who underwent complete clinical workup and routine biochemistry. In parallel, levels HO1, whose expression is regulated by BVR-A as well as levels of tumor necrosis factor α (TNFα), which is a known repressor for BVR-A with pro-inflammatory properties, were also assessed.

KEY FINDINGS

BVR-A levels were significantly lower in T2D subjects than in non-T2D subjects. Reduced BVR-A levels were associated with greater body mass, systolic blood pressure, fasting blood glucose (FBG), glycated hemoglobin (HbA1c), triglycerides, transaminases and TNFα, and with lower high-density lipoprotein (HDL) levels. Lower BVR-A levels are associated with reduced HO1 protein levels and the multivariate analysis showed that BVR-A represented the main determinant of HO1 levels in T2D after adjustment. In addition, reduced BVR-A levels were able to predict the presence of T2D with AUROC = 0.69. for potential confounders.

SIGNIFICANCE

Our results demonstrate for the first time that BVR-A protein levels are reduced in T2D individuals, and that this alteration strictly correlates with poor glycometabolic control and a pro-inflammatory state. Hence, these observations reinforce the hypothesis that reduced BVR-A protein levels may represent a key event in the dysregulation of intracellular pathways finally leading to metabolic disorders.

Cytochrome P450 2F2 (CYP2F2) negatively regulates browning in 3T3-L1 white adipocytes

Cytochromes P450 (CYPs) are a multigene superfamily of constitutively expressed and inducible enzymes responsible for the detoxification of many endogenous and exogenous compounds and for the metabolism of numerous medications. The cytochrome P450 2F2 (CYP2F2) subfamily is preferentially expressed in the respiratory tract, but its functional role in adipocytes has never been explored. We found that CYP2F2 was highly expressed during the differentiation of the C3H10T1/2 murine mesenchymal stem cells to adipocytes and here we have explored its functional role in adipocytes. The expression of thermogenic marker proteins such as peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), PR domain containing 16 (PRDM16), and uncoupling protein 1 (UCP1) and beige-fat specific genes were significantly increased in Cyp2f2-deficient 3T3-L1 adipocytes. Moreover, Cyp2f2 silencing led to reduced adipogenesis and lipogenesis, and enhanced lipid catabolism through the increased expression of lipolytic and fatty acid oxidative enzymes. A mechanistic study to identify molecular signals for CYP2F2-mediated negative regulation in the browning of white adipocytes revealed that CYP2F2 impairs the beta-3 adrenergic receptor (β3-AR) activation as well as its downstream regulators including protein kinase A (PKA), p38 mitogen-activated protein kinase (p38 MAPK), and activating transcription factor 2 (ATF2). This data provides evidence that CYP2F2 is a negative regulator of lipid catabolism and browning in white adipocytes, suggesting that inhibitors of CYP2F2 could be potential drugs for the treatment of obesity with a focus on enhancing energy expenditure.

Heme-oxygenase and lipid mediators in obesity and associated cardiometabolic diseases: Therapeutic implications

Obesity-mediated metabolic syndrome remains the leading cause of death worldwide. Among many potential targets for pharmacological intervention, a promising strategy involves the heme oxygenase (HO) system, specifically its inducible form, HO-1. This review collects and updates much of the current knowledge relevant to pharmacology and clinical medicine concerning HO-1 in metabolic diseases and its effect on lipid metabolism. HO-1 has pleotropic effects that collectively reduce inflammation, while increasing vasodilation and insulin and leptin sensitivity. Recent reports indicate that HO-1 with its antioxidants via the effect of bilirubin increases formation of biologically active lipid metabolites such as epoxyeicosatrienoic acid (EET), omega-3 and other polyunsaturated fatty acids (PUFAs). Similarly, HO-1and bilirubin are potential therapeutic targets in the treatment of fat-induced liver diseases. HO-1-mediated upregulation of EET is capable not only of reversing endothelial dysfunction and hypertension, but also of reversing cardiac remodeling, a hallmark of the metabolic syndrome. This process involves browning of white fat tissue (i.e. formation of healthy adipocytes) and reduced lipotoxicity, which otherwise will be toxic to the heart. More importantly, this review examines the activity of EET in biological systems and a series of pathways that explain its mechanism of action and discusses how these might be exploited for potential therapeutic use. We also discuss the link between cardiac ectopic fat deposition and cardiac function in humans, which is similar to that described in obese mice and is regulated by HO-1-EET-PGC1α signaling, a potent negative regulator of the inflammatory adipokine NOV.

Serum Bilirubin Levels in Overweight and Obese Individuals: The Importance of Anti-Inflammatory and Antioxidant Responses

Obesity is a chronic condition involving low-grade inflammation and increased oxidative stress; thus, obese and overweight people have lower values of serum bilirubin. Essentially, bilirubin is a potent endogenous antioxidant molecule with anti-inflammatory, immunomodulatory, antithrombotic, and endocrine properties. This review paper presents the interplay between obesity-related pathological processes and bilirubin, with a focus on adipose tissue and adipokines. We discuss potential strategies to mildly increase serum bilirubin levels in obese patients as an adjunctive therapeutic approach.

Sex differences in the link between blood cobalt concentrations and insulin resistance in adults without diabetes

Background

Little is known about the effects of environmental cobalt exposure on insulin resistance (IR) in the general adult population. We investigated the association between cobalt concentration and IR.

Methods

A total of 1281 subjects aged more than 20 years with complete blood cobalt data were identified from the National Health and Nutrition Examination Survey (NHANES) 2015–2016 cycle. Blood cobalt levels were analyzed for their association with IR among all populations and subgroups by sex. Regression coefficients and 95% confidence intervals (CIs) of blood cobalt concentrations in association with fasting glucose, insulin and homeostatic model assessment of insulin resistance (HOMA-IR) were estimated using multivariate linear regression after adjusting for age, sex, ethnicity, alcohol consumption, body mass index, education level, and household income. A multivariate generalized linear regression analysis was further carried out to explore the association between cobalt exposure and IR.

Results

A negative association between blood cobalt concentration (coefficient = − 0.125, 95% CI − 0.234, − 0.015; P = 0.026) and HOMA-IR in female adults in the age- and sex-adjusted model was observed. However, no associations with HOMA-IR, fasting glucose, or insulin were found in the overall population. In the generalized linear models, participants with the lowest cobalt levels had a 2.74% (95% CI 0.04%, 5.50%) increase in HOMA-IR (P for trend = 0.031) compared with subjects with the highest cobalt levels. Restricted cubic spline regression suggested that a non-linear relationship may exist between blood cobalt and HOMA-IR.

Conclusions

These results provide epidemiological evidence that low levels of blood cobalt are negatively associated with HOMA-IR in female adults.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12199-021-00966-w.

Gasotransmitter signaling in energy homeostasis and metabolic disorders

Gasotransmitters are small molecules of gases, including nitric oxide (NO), hydrogen sulfide (H₂S), and carbon monoxide (CO). These three gasotransmitters can be endogenously produced and regulate a wide range of pathophysiological processes by interacting with specific targets upon diffusion in the biological media. By redox and epigenetic regulation of various physiological functions, NO, H₂S, and CO are critical for the maintenance of intracellular energy homeostasis. Accumulated evidence has shown that these three gasotransmitters control ATP generation, mitochondrial biogenesis, glucose metabolism, insulin sensitivity, lipid metabolism, and thermogenesis, etc. Abnormal generation and metabolism of NO, H₂S, and/or CO are involved in various abnormal metabolic diseases, including obesity, diabetes, and dyslipidemia. In this review, we summarized the roles of NO, H₂S, and CO in the regulation of energy homeostasis as well as their involvements in the metabolism of dysfunction-related diseases. Understanding the interaction among these gasotransmitters and their specific molecular targets are very important for therapeutic applications.

Natural Antioxidant and Anti-Inflammatory Compounds in Foodstuff or Medicinal Herbs Inducing Heme Oxygenase-1 Expression

Heme oxygenase-1 (HO-1) is an inducible antioxidant enzyme that catalyzes heme group degradation. Decreased level of HO-1 is correlated with disease progression, and HO-1 induction suppresses development of metabolic and neurological disorders. Natural compounds with antioxidant activities have emerged as a rich source of HO-1 inducers with marginal toxicity. Here we discuss the therapeutic role of HO-1 in obesity, hypertension, atherosclerosis, Parkinson's disease and hepatic fibrosis, and present important signaling pathway components that lead to HO-1 expression. We provide an updated, comprehensive list of natural HO-1 inducers in foodstuff and medicinal herbs categorized by their chemical structures. Based on the continued research in HO-1 signaling pathways and rapid development of their natural inducers, HO-1 may serve as a preventive and therapeutic target for metabolic and neurological disorders.

The Pivotal Role of Adipocyte-Na K peptide in Reversing Systemic Inflammation in Obesity and COVID-19 in the Development of Heart Failure

This review summarizes data from several laboratories that have demonstrated a role of the Na/K-ATPase, specifically its α1 subunit, in the generation of reactive oxygen species (ROS) via the negative regulator of Src. Together with Src and other signaling proteins, the Na/K-ATPase forms an oxidant amplification loop (NKAL), amplifies ROS, and participates in cytokines storm in obesity. The development of a peptide fragment of the α1 subunit, NaKtide, has been shown to negatively regulate Src. Several groups showed that the systemic administration of the cell permeable modification of NaKtide (pNaKtide) or its selective delivery to fat tissue-adipocyte specific expression of NaKtide-ameliorate the systemic elevation of inflammatory cytokines seen in chronic obesity. Severe acute respiratory syndrome - coronavirus 2 (SARS-CoV-2), the RNA Coronavirus responsible for the COVID-19 global pandemic, invades cells via the angiotensin converting enzyme 2 (ACE-2) receptor (ACE2R) that is appended in inflamed fat tissue and exacerbates the formation of the cytokines storm. Both obesity and heart and renal failure are well known risks for adverse outcomes in patients infected with COVID-19. White adipocytes express ACE-2 receptors in high concentration, especially in obese patients. Once the virus invades the white adipocyte cell, it creates a COVID19-porphyrin complex which degrades and produces free porphyrin and iron and increases ROS. The increased formation of ROS and activation of the NKAL results in a further potentiated formation of ROS production, and ultimately, adipocyte generation of more inflammatory mediators, leading to systemic cytokines storm and heart failure. Moreover, chronic obesity also results in the reduction of antioxidant genes such as heme oxygenase-1 (HO-1), increasing adipocyte susceptibility to ROS and cytokines. It is the systemic inflammation and cytokine storm which is responsible for many of the adverse outcomes seen with COVID-19 infections in obese subjects, leading to heart failure and death. This review will also describe the potential antioxidant drugs and role of NaKtide and their demonstrated antioxidant effect used as a major strategy for improving obesity and epicardial fat mediated heart failure in the context of the COVID pandemic.

Heme Oxygenase 1 and 2 Differentially Regulate Glucose Metabolism and Adipose Tissue Mitochondrial Respiration: Implications for Metabolic Dysregulation

Heme oxygenase (HO) consists of inducible (HO-1) and constitutive (HO-2) isoforms that are encoded by Hmox1 and Hmox2 genes, respectively. As an anti-inflammatory and antioxidant molecule, HO participates in the development of metabolic diseases. Whether Hmox deficiency causes metabolic abnormalities under basal conditions remains unclear. We hypothesized that HO-1 and HO-2 differentially affect global and adipose tissue metabolism. To test this hypothesis, we determined insulin sensitivity, glucose tolerance, energy expenditure, and respiratory exchange ratio in global Hmox1^-/- and Hmox2^-/- mice. Body weight was reduced in female but not male Hmox1^-/- and Hmox2^-/- mice. Reduced insulin sensitivity and physical activity were observed in Hmox1^-/- but not Hmox2^-/- mice. Deletion of either Hmox1 or Hmox2 had no effects on glucose tolerance, energy expenditure or respiratory exchange ratio. Mitochondrial respiration was unchanged in gonadal fat pads (white adipose tissue, WAT) of Hmox1^-/- mice. Hmox2 deletion increased proton leak and glycolysis in gonadal, but not interscapular fat tissues (brown adipose tissue, BAT). Uncoupling protein and Hmox1 genes were unchanged in gonadal fat pads of Hmox2^-/- mice. Conclusively, HO-1 maintains insulin sensitivity, while HO-2 represses glycolysis and proton leak in the WAT under basal condition. This suggests that HO-1 and HO-2 differentially modulate metabolism, which may impact the metabolic syndrome.

Heme Oxygenase-1 Supports Mitochondrial Energy Production and Electron Transport Chain Activity in Cultured Lung Epithelial Cells

Heme oxygenase-1 is induced by many cellular stressors and catalyzes the breakdown of heme to generate carbon monoxide and bilirubin, which confer cytoprotection. The role of HO-1 likely extends beyond the simple production of antioxidants, for example HO-1 activity has also been implicated in metabolism, but this function remains unclear. Here we used an HO-1 knockout lung cell line to further define the contribution of HO-1 to cellular metabolism. We found that knockout cells exhibit reduced growth and mitochondrial respiration, measured by oxygen consumption rate. Specifically, we found that HO-1 contributed to electron transport chain activity and utilization of certain mitochondrial fuels. Loss of HO-1 had no effect on intracellular non-heme iron concentration or on proteins whose levels and activities depend on available iron. We show that HO-1 supports essential functions of mitochondria, which highlights the protective effects of HO-1 in diverse pathologies and tissue types. Our results suggest that regulation of heme may be an equally significant role of HO-1.

Therapeutic Efficacy of Antioxidants in Ameliorating Obesity Phenotype and Associated Comorbidities

Obesity has been a worldwide epidemic for decades. Despite the abundant increase in knowledge regarding the etiology and pathogenesis of obesity, the prevalence continues to rise with estimates predicting considerably higher numbers by the year 2030. Obesity is characterized by an abnormal lipid accumulation, however, the physiological consequences of obesity are far more concerning. The development of the obesity phenotype constitutes dramatic alterations in adipocytes, along with several other cellular mechanisms which causes substantial increase in systemic oxidative stress mediated by reactive oxygen species (ROS). These alterations promote a chronic state of inflammation in the body caused by the redox imbalance. Together, the systemic oxidative stress and chronic inflammation plays a vital role in maintaining the obese state and exacerbating onset of cardiovascular complications, Type II diabetes mellitus, dyslipidemia, non-alcoholic steatohepatitis, and other conditions where obesity has been linked as a significant risk factor. Because of the apparent role of oxidative stress in the pathogenesis of obesity, there has been a growing interest in attenuating the pro-oxidant state in obesity. Hence, this review aims to highlight the therapeutic role of antioxidants, agents that negate pro-oxidant state of cells, in ameliorating obesity and associated comorbidities. More specifically, this review will explore how various antioxidants target unique and diverse pathways to exhibit an antioxidant defense mechanism.

Cold Press Pomegranate Seed Oil Attenuates Dietary-Obesity Induced Hepatic Steatosis and Fibrosis through Antioxidant and Mitochondrial Pathways in Obese Mice

Aim: Obesity is associated with metabolic syndrome, hypertension, dyslipidemia, nonalcoholic fatty liver disease (NAFLD), and type 2 diabetes. In this study, we investigated whether the dietary supplementation of pomegranate seed oil (PSO) exerted a protective effect on liver lipid uptake, fibrosis, and mitochondrial function in a mouse model of obesity and insulin resistance. Method: In this in vivo study, eight-week-old C57BL/6J male mice were fed with a high fat diet (HFD) for 24 weeks and then were divided into three groups as follows: group (1) Lean; group (n = 6) (2) HF diet; group (n = 6) (3) HF diet treated with PSO (40 mL/kg food) (n = 6) for eight additional weeks starting at 24 weeks. Physiological parameters, lipid droplet accumulation, inflammatory biomarkers, antioxidant biomarkers, mitochondrial biogenesis, insulin sensitivity, and hepatic fibrosis were determined to examine whether PSO intervention prevents obesity-associated metabolic syndrome. Results: The PSO group displayed an increase in oxygen consumption, as well as a decrease in fasting glucose and blood pressure (p < 0.05) when compared to the HFD-fed mice group. PSO increased both the activity and expression of hepatic HO-1, downregulated inflammatory adipokines, and decreased hepatic fibrosis. PSO increased the levels of thermogenic genes, mitochondrial signaling, and lipid metabolism through increases in Mfn2, OPA-1, PRDM 16, and PGC1α. Furthermore, PSO upregulated obesity-mediated hepatic insulin receptor phosphorylation Tyr-⁹⁷², p-IRB tyr¹¹⁴⁶, and pAMPK, thereby decreasing insulin resistance. Conclusions: These results indicated that PSO decreased obesity-mediated insulin resistance and the progression of hepatic fibrosis through an improved liver signaling, as manifested by increased insulin receptor phosphorylation and thermogenic genes. Furthermore, our findings indicate a potential therapeutic role for PSO in the prevention of obesity-associated NAFLD, NASH, and other metabolic disorders.

Low molecular weight blue mussel hydrolysates inhibit adipogenesis in mouse mesenchymal stem cells through upregulating HO-1/Nrf2 pathway

Blue mussel proteins are a good source of bioactive peptides. In this study, blue mussel hydrolysate (BMH) with anti-adipogenic effect in mouse mesenchymal stem cells (mMSC) was produced by peptic hydrolysis at 1:500 of pepsin/substrate ratio for 120 min. Additionally, BMH with below 1 kDa (BMH < 1 kDa) showed the highest anti-adipogenic effect in mMSC. BMH < 1 kDa increased lipolysis and down-regulated adipogenic transcription factors including peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT/enhancer-binding protein α (C/EBPα), and sterol regulatory element-binding protein 1 (SREBP1). Generation of intracellular reactive oxygen species during adipogenesis was markedly decreased by BMH < 1 kDa treatment, which is attributed to the up-regulation of heme oxygenase-1 (HO-1) through Nrf2 translocation into the nucleus. Moreover, ZnPP, HO-1 inhibitor, treatment abolished BMH < 1 kDa-mediated HO-1 expression and anti-adipogenic effect in mMSCs through down-regulating adipogenic transcription factors. Taken together, BMH < 1 kDa may be a potential ingredient of nutraceuticals and/or functional foods in ameliorating obesity.

Proteomic analysis of oxidative stress response in human umbilical vein endothelial cells (HUVECs): role of heme oxygenase 1 (HMOX1) in hypoxanthine-induced oxidative stress in HUVECs

Background

Erectile dysfunction (ED) is a well-known complication of diabetes, affecting up to 75% of diabetic men. Although the etiology of diabetic ED is multifactorial, endothelial dysfunction is considered to be a pillar of its pathophysiology. Endothelial dysfunction is caused by the harmful effects of high glucose levels and increased oxidative stress on the endothelial cells that comprise the vascular endothelium. The aim of this study was to identify the proteomic changes caused by high glucose-induced oxidative stress and explore the role of heme oxygenase 1 (HMOX1) in it.

Methods

The cellular proteomic response to hypoxanthine-induced oxidative stress in human umbilical vein endothelial cells (HUVECs) was analyzed by isobaric tags for relative and absolute quantitation (iTRAQ) combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Differentially expressed proteins (DEPs) were analyzed through Network and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Further validation assays was performed to validate the role of HMOX1.

Results

The results showed that 66 and 76 DEPs were markedly upregulated and downregulated, respectively, for HUVECs oxidative stress. Among these proteins, we verified eight dysregulated genes by quantitative reverse transcription PCR, including nucleolin (NCL), X-ray repair cross-complementing protein 6 (XRCC6), ubiquinol-cytochrome C reductase binding protein (UQCRB), non-POU domain containing octamer binding (NONO), heme oxygenase 1 (HMOX1), nucleobindin 1 (NUCB1), DEK, and chromatin target of prmt1 (CHTOP). Further, using overexpression and genetic knockdown approaches, we found that HMOX1 was critical for the oxidative stress response in HUVECs.

Conclusions

We found that HMOX1 was closely related to the oxidative stress response induced by hypoxanthine. To the best of our knowledge, this study is the first overview of the responses of HUVECs to oxidative stress. The findings will contribute to analyses of the detailed molecular mechanisms involved in the pathogenesis of endothelial dysfunction and related molecular mechanisms in ED patients.

Therapeutic approaches to diabetic cardiomyopathy: Targeting the antioxidant pathway

The global epidemic of cardiovascular disease continues unabated and remains the leading cause of death both in the US and worldwide. We hereby summarize the available therapies for diabetes and cardiovascular disease in diabetics. Clearly, the current approaches to diabetic heart disease often target the manifestations and certain mediators but not the specific pathways leading to myocardial injury, remodeling and dysfunction. Better understanding of the molecular events determining the evolution of diabetic cardiomyopathy will provide insight into the development of specific and targeted therapies. Recent studies largely increased our understanding of the role of enhanced inflammatory response, ROS production, as well as the contribution of Cyp-P450-epoxygenase-derived epoxyeicosatrienoic acid (EET), Peroxisome Proliferator-Activated Receptor Gamma Coactivator-1α (PGC-1α), Heme Oxygenase (HO)-1 and 20-HETE in pathophysiology and therapy of cardiovascular disease. PGC-1α increases production of the HO-1 which has a major role in protecting the heart against oxidative stress, microcirculation and mitochondrial dysfunction. This review describes the potential drugs and their downstream targets, PGC-1α and HO-1, as major loci for developing therapeutic approaches beside diet and lifestyle modification for the treatment and prevention of heart disease associated with obesity and diabetes.

Heme Oxygenase-1 Upregulation: A Novel Approach in the Treatment of Cardiovascular Disease

Significance: Heme oxygenase (HO) plays a pivotal role in both vascular and metabolic functions and is involved in many physiological and pathophysiological processes in vascular endothelial cells (ECs) and adipocytes. Recent Advances: From the regulation of adipogenesis in adipose tissue to the adaptive response of vascular tissue in the ECs, HO plays a critical role in the capability of the vascular system to respond and adjust to insults in homeostasis. Recent studies show that HO-1 through regulation of adipocyte and adipose tissue functions ultimately aid not only in local but also in systemic maintenance of homeostasis. Critical Issues: Recent advances have revealed the existence of a cross talk between vascular ECs and adipocytes in adipose tissue. In the pathological state of obesity, this cross talk contributes to the condition's adverse chronic effects, and we propose that specific targeting of the HO-1 gene can restore signaling pathways and improve both vascular and adipose functions. Future Directions: A complete understanding of the role of HO-1 in regulation of cardiovascular homeostasis is important to comprehend the homeostatic regulation as well as in cardiovascular disease. Efforts are required to highlight the effects and the ability to target the HO-1 gene in models of obesity with an emphasis on the role of pericardial fat on cardiovascular health.

The Effects of Heme Oxygenase Upregulation on Obesity and the Metabolic Syndrome

Significance: Obesity is a chronic condition that is characterized by inflammation and oxidative stress with consequent cardiovascular complications of hypertension, dyslipidemia, and vascular dysfunction. Obesity-induced metabolic syndrome remains an epidemic of global proportions. Recent Advances: Gene targeting of the endothelium with a retrovirus using an endothelium-specific promoter vascular endothelium cadherin (VECAD)-HO-1 offers a potential long-term solution to adiposity by targeting the endothelium. This has resulted in improvements of both vascular function and adiposity attenuation. Critical Issues: Heme oxygenase plays an ever-increasing role in the understanding of human biology in the complex conditions of obesity and the metabolic syndrome. The heme oxygenase 1 (HO-1) system creates biliverdin/bilirubin, which functions as an antioxidant, and carbon monoxide, which has antiapoptotic properties. Future Directions: Upregulation of HO-1 has been shown to improve adiposity as well as vascular function in both animal and human studies.

SERUM BILIRUBIN CORRELATES WITH SERUM ADIPOKINES IN NORMAL WEIGHT AND OVERWEIGHT ASYMPTOMATIC ADULTS

Overweight and obesity are considered as chronic low-grade inflammation accompanied by imbalanced production of adipokines. The aim of this study was to elucidate the relationship between serum bilirubin, which is an endogenous antioxidant with anti-inflammatory activity, and pro- and anti-inflammatory serum adipokines in asymptomatic normal weight and overweight individuals. Healthy men and women aged 25-49 participated in this cross-sectional study. All participants underwent fasting serological measurements of adipokines, interleukin-6, tumor necrosis factor alpha (TNF-α), C-reactive protein (CRP), total and direct serum bilirubin, and other biochemical parameters. Participants were divided into normal weight and overweight groups. We found a significant negative association between total bilirubin and CRP, TNF-α, visfatin and resistin values, and a significant positive association between total bilirubin and adiponectin values in both normal-weight and overweight groups. Importantly, after adjusting for body mass index, we also found a significant negative association between total serum bilirubin levels and both visfatin and CRP serum levels. Moreover, visfatin, resistin and CRP were predictors of the total serum bilirubin levels.

Adipocyte Specific HO-1 Gene Therapy is Effective in Antioxidant Treatment of Insulin Resistance and Vascular Function in an Obese Mice Model

Obesity is a risk factor for vascular dysfunction and insulin resistance. The study aim was to demonstrate that adipocyte-specific HO-1 (heme oxygenase-1) gene therapy is a therapeutic approach for preventing the development of obesity-induced metabolic disease in an obese-mice model. Specific expression of HO-1 in adipose tissue was achieved by using a lentiviral vector expressing HO-1 under the control of the adiponectin vector (Lnv-adipo-HO-1). Mice fed a high-fat diet (HFD) developed adipocyte hypertrophy, fibrosis, decreased mitochondrial respiration, increased levels of inflammatory adipokines, insulin resistance, vascular dysfunction, and impaired heart mitochondrial signaling. These detrimental effects were prevented by the selective expression of HO-1 in adipocytes. Lnv-adipo-HO-1-transfected mice on a HFD display increased cellular respiration, increased oxygen consumption, increased mitochondrial function, and decreased adipocyte size. Moreover, RNA arrays confirmed that targeting adipocytes with HO-1 overrides the genetic susceptibility of adiposopathy and correlated with restoration of the expression of anti-inflammatory, thermogenic, and mitochondrial genes. Our data demonstrate that HO-1 gene therapy improved adipose tissue function and had positive impact on distal organs, suggesting that specific targeting of HO-1 gene therapy is an attractive therapeutic approach for improving insulin sensitivity, metabolic activity, and vascular function in obesity.

Role of cytochrome P450-derived, polyunsaturated fatty acid mediators in diabetes and the metabolic syndrome

Over the last decade, cases of metabolic syndrome and type II diabetes have increased exponentially. Exercise and ω-3 polyunsaturated fatty acid (PUFA)-enriched diets are usually prescribed but no therapy is effectively able to restore the impaired glucose metabolism, hypertension, and atherogenic dyslipidemia encountered by diabetic patients. PUFAs are metabolized by different enzymes into bioactive metabolites with anti- or pro-inflammatory activity. One important class of PUFA metabolizing enzymes are the cytochrome P450 (CYP) enzymes that can generate a series of bioactive products, many of which have been attributed protective/anti-inflammatory and insulin-sensitizing effects in animal models. PUFA epoxides are, however, further metabolized by the soluble epoxide hydrolase (sEH) to fatty acid diols. The biological actions of the latter are less well understood but while low concentrations may be biologically important, higher concentrations of diols derived from linoleic acid and docosahexaenoic acid have been linked with inflammation. One potential application for sEH inhibitors is in the treatment of diabetic retinopathy where sEH expression and activity is elevated as are levels of a diol of docosahexaenoic acid that can induce the destabilization of the retina vasculature.

HO-1 overexpression and underexpression: Clinical implications

In this review we examine the effects of both over- and under-production of heme oxygenase-1 (HO-1) and HO activity on a broad spectrum of biological systems and on vascular disease. In a few instances e.g., neonatal jaundice, overproduction of HO-1 and increased HO activity results in elevated levels of bilirubin requiring clinical intervention with inhibitors of HO activity. In contrast HO-1 levels and HO activity are low in obesity and the HO system responds to mitigate the deleterious effects of oxidative stress through increased levels of bilirubin (anti-inflammatory) and CO (anti-apoptotic) and decreased levels of heme (pro-oxidant). Site specific HO-1 overexpression diminishes adipocyte terminal differentiation and lipid accumulation of obesity mediated release of inflammatory molecules. A series of diverse strategies have been implemented that focus on increasing HO-1 and HO activity that are central to reversing the clinical complications associated with diseases including, obesity, metabolic syndrome and vascular disease.

Heme, Heme Oxygenase, and Endoplasmic Reticulum Stress-A New Insight into the Pathophysiology of Vascular Diseases

The prevalence of vascular disorders continues to rise worldwide. Parallel with that, new pathophysiological pathways have been discovered, providing possible remedies for prevention and therapy in vascular diseases. Growing evidence suggests that endoplasmic reticulum (ER) stress is involved in a number of vasculopathies, including atherosclerosis, vascular brain events, and diabetes. Heme, which is released from hemoglobin or other heme proteins, triggers various pathophysiological consequence, including heme stress as well as ER stress. The potentially toxic free heme is converted by heme oxygenases (HOs) into carbon monoxide (CO), iron, and biliverdin (BV), the latter of which is reduced to bilirubin (BR). Redox-active iron is oxidized and stored by ferritin, an iron sequestering protein which exhibits ferroxidase activity. In recent years, CO, BV, and BR have been shown to control cellular processes such as inflammation, apoptosis, and antioxidant defense. This review covers our current knowledge about how heme induced endoplasmic reticulum stress (HIERS) participates in the pathogenesis of vascular disorders and highlights recent discoveries in the molecular mechanisms of HO-mediated cytoprotection in heme stress and ER stress, as well as crosstalk between ER stress and HO-1. Furthermore, we focus on the translational potential of HIERS and heme oxygenase-1 (HO-1) in atherosclerosis, diabetes mellitus, and brain hemorrhage.

Beneficial Role of HO-1-SIRT1 Axis in Attenuating Angiotensin II-Induced Adipocyte Dysfunction

Background: Angiotensin II (Ang II), released by the renin–angiotensin–aldosterone system (RAAS), contributes to the modulatory role of the RAAS in adipose tissue dysfunction. Investigators have shown that inhibition of AngII improved adipose tissue function and insulin resistance in mice with metabolic syndrome. Heme Oxygenase-1 (HO-1), a potent antioxidant, has been demonstrated to improve oxidative stress and adipocyte phenotype. Molecular effects of high oxidative stress include suppression of sirtuin-1 (SIRT1), which is amenable to redox manipulations. The mechanisms involved, however, in these metabolic effects of the RAAS remain incompletely understood. Hypothesis: We hypothesize that AngII-induced oxidative stress has the potential to suppress adipocyte SIRT1 via down regulation of HO-1. This effect of AngII will, in turn, upregulate mineralocorticoid receptor (MR). The induction of HO-1 will rescue SIRT1, hence improving oxidative stress and adipocyte phenotype. Methods and Results: We examined the effect of AngII on lipid accumulation, oxidative stress, and inflammatory cytokines in mouse pre-adipocytes in the presence and absence of cobalt protoporphyrin (CoPP), HO-1 inducer, tin mesoporphyrin (SnMP), and HO-1 inhibitor. Our results show that treatment of mouse pre-adipocytes with AngII increased lipid accumulation, superoxide levels, inflammatory cytokine levels, interleukin-6 (IL-6) and tumor necrosis factor α (TNFα), and adiponectin levels. This effect was attenuated by HO-1 induction, which was further reversed by SnMP, suggesting HO-1 mediated improvement in adipocyte phenotype. AngII-treated pre-adipocytes also showed upregulated levels of MR and suppressed SIRT1 that was rescued by HO-1. Subsequent treatment with CoPP and SIRT1 siRNA in mouse pre-adipocytes increased lipid accumulation and fatty acid synthase (FAS) levels, suggesting that beneficial effects of HO-1 are mediated via SIRT1. Conclusion: Our study demonstrates for the first time that HO-1 has the ability to restore cellular redox, rescue SIRT1, and prevent AngII-induced impaired effects on adipocytes and the systemic metabolic profile.

Identification of lncRNAs and Genes Responsible for Fatness and Fatty Acid Composition Traits between the Tibetan and Yorkshire Pigs

Tibetan pigs from the Tibetan Plateau are characterized with a significant phenotypic difference relative to lowland pigs. In this study, a significant difference of the fatness and fatty acid composition traits was observed between the Tibetan and Yorkshire pigs. To uncover the involved mechanism, the expression profile of long noncoding RNAs (lncRNAs) and genes was compared between them. After serial filtered steps, 1,964 lncRNAs were obtained through our computational pipeline. In total, 63 and 715 lncRNAs and genes were identified to be differentially expressed. Evidence from cis- and trans-targeting analysis of lncRNAs demonstrated that some lncRNAs, such as MSTRG.14097 and MSTRG.8034, played important roles in the fatness and fatty acid composition traits. Bioinformatics analysis revealed that many candidate genes were responsible for the two traits. Of these, FASN, ACACA, SCD, ME3, PDHB, ACSS1, ACSS2, and ACLY were identified, which functioned in regulating the level of hexadecanoic acid, hexadecenoic acid, octadecenoic acid, and monounsaturated fatty acid. And LPGAT1, PDK4, ACAA1, and ADIPOQ were associated with the content of stearic acid, octadecadienoic acid, and polyunsaturated fatty acid. Candidate genes, which were responsible for fatness trait, consisted of FGF2, PLAG1, ADIPOQ, IRX3, MIF, IL-34, ADAM8, HMOX1, Vav1, and TLR8. In addition, association analysis also revealed that 34 and 57 genes significantly correlated to the fatness and fatty acid composition trait, respectively. Working out the mechanism caused by these lncRNAs and candidate genes is proven to be complicated but is invaluable to our understanding of fatness and fatty acid composition traits.

Oxidized HDL, Adipokines, and Endothelial Dysfunction: A Potential Biomarker Profile for Cardiovascular Risk in Women with Obesity

OBJECTIVE

High BMI predicts adverse cardiovascular outcomes and positively correlates with increased levels of adipokines. The relationship among BMI, IL-6, TNFα, adiponectin, and oxidized high-density lipoprotein (Ox-HDL) with circulating endothelial cells (CECs) and endothelial progenitor cells (EPCs) has not been well studied. Elevated CEC levels have been described in both humans and mice with obesity and diabetes. Ox-HDL has been shown to be a potent driver of adipogenesis in vivo and in vitro. In this study, elevated BMI was examined in 2 groups of women studied in Brooklyn, New York, and Huntington, West Virginia, respectively.

METHODS

Twenty-six females with obesity and five lean controls without overt cardiovascular disease were enrolled, 13 from Huntington and 13 from Brooklyn. Cytokine levels, EPCs, and CECs were determined.

RESULTS

Females with obesity had elevated levels of leptin, IL-6, and Ox-HDL, increased CEC levels, and decreased EPC and adiponectin levels (all P < 0.01). The Ox-HDL levels were higher in women from Brooklyn versus Huntington (P < 0.01), possibly from higher TNFα levels in Brooklyn or higher adiponectin levels in Huntington. Seventy-five percent of the variance in Ox-HDL levels could be predicted in this population (P < 0.01).

CONCLUSIONS

This study reveals a unique inflammatory biomarker profile in females with obesity.

Carbon monoxide-induced metabolic switch in adipocytes improves insulin resistance in obese mice

Obesity is characterized by accumulation of adipose tissue and is one the most important risk factors in the development of insulin resistance. Carbon monoxide-releasing (CO-releasing) molecules (CO-RMs) have been reported to improve the metabolic profile of obese mice, but the underlying mechanism remains poorly defined. Here, we show that oral administration of CORM-401 to obese mice fed a high-fat diet (HFD) resulted in a significant reduction in body weight gain, accompanied by a marked improvement in glucose homeostasis. We further unmasked an action we believe to be novel, by which CO accumulates in visceral adipose tissue and uncouples mitochondrial respiration in adipocytes, ultimately leading to a concomitant switch toward glycolysis. This was accompanied by enhanced systemic and adipose tissue insulin sensitivity, as indicated by a lower blood glucose and increased Akt phosphorylation. Our findings indicate that the transient uncoupling activity of CO elicited by repetitive administration of CORM-401 is associated with lower weight gain and increased insulin sensitivity during HFD. Thus, prototypic compounds that release CO could be investigated for developing promising insulin-sensitizing agents.

Cardiotonic Steroids and the Sodium Trade Balance: New Insights into Trade-Off Mechanisms Mediated by the Na⁺/K⁺-ATPase

In 1972 Neal Bricker presented the "trade-off" hypothesis in which he detailed the role of physiological adaptation processes in mediating some of the pathophysiology associated with declines in renal function. In the late 1990's Xie and Askari published seminal studies indicating that the Na⁺/K⁺-ATPase (NKA) was not only an ion pump, but also a signal transducer that interacts with several signaling partners. Since this discovery, numerous studies from multiple laboratories have shown that the NKA is a central player in mediating some of these long-term "trade-offs" of the physiological adaptation processes which Bricker originally proposed in the 1970's. In fact, NKA ligands such as cardiotonic steroids (CTS), have been shown to signal through NKA, and consequently been implicated in mediating both adaptive and maladaptive responses to volume overload such as fibrosis and oxidative stress. In this review we will emphasize the role the NKA plays in this "trade-off" with respect to CTS signaling and its implication in inflammation and fibrosis in target organs including the heart, kidney, and vasculature. As inflammation and fibrosis exhibit key roles in the pathogenesis of a number of clinical disorders such as chronic kidney disease, heart failure, atherosclerosis, obesity, preeclampsia, and aging, this review will also highlight the role of newly discovered NKA signaling partners in mediating some of these conditions.

Ablation of soluble epoxide hydrolase reprogram white fat to beige-like fat through an increase in mitochondrial integrity, HO-1-adiponectin in vitro and in vivo

We have shown that epoxyeicosatrienoic acids (EETs), specifically 11,12- and 14,15-EETs, reduce adipogenesis in human mesenchymal stem cells and mouse preadipocytes (3T-3L1). In this study, we explore the effects of soluble epoxide hydrolase (sEH) deletion on various aspects of adipocyte-function, including programing for white vs. beige-like fat, and mitochondrial and thermogenic gene-expressions. We further hypothesize that EETs and heme-oxygenase 1 (HO-1) form a synergistic, functional module whose effects on adipocyte and vascular function is greater than the effects of sEH deletion alone. In in vitro studies, we examined the effect of sEH inhibitors on MSC-derived adipocytes. MSC-derived adipocytes exposed to AUDA, an inhibitor of sEH, exhibit an increased number of small and healthy adipocytes, an effect reproduced by siRNA for sEH. in vivo studies indicate that sEH deletion results in a significant decrease in adipocyte size, inflammatory adipokines NOV, TNFα, while increasing adiponectin (p < 0.05). These findings are associated with a decrease in body weight (p < 0.05), and visceral fat (p < 0.05). Importantly, sEH deletion was associated with a significant increase in Mfn1, COX 1, UCP1 and adiponectin (p < 0.03). sEH deletion was manifested by a significant increase in EETs isomers 5,6-EET, 8,9-EET, 11,12-EET, and 14,15-EET and an increased EETs/DHETEs ratio. Notably, activation of HO-1 gene expression further increased the levels of EETs, suggesting that the antioxidant HO-1 system protects EETs from degradation by ROS. These results are novel in that sEH deletion, while increasing EET levels, resulted in reprograming of white fat to express mitochondrial and thermogenic genes, a phenotype characteristic of beige-fat. Thus, EETs agonist(s) and sEH inhibitors may have therapeutic potential in the treatment of metabolic syndrome and obesity.

Impact of Bariatric Surgery on Heme Oxygenase-1, Inflammation, and Insulin Resistance in Morbid Obesity with Obstructive Sleep Apnea

INTRODUCTION

Morbid obesity and obstructive sleep apnea (OSA) interact at an inflammatory level. Bariatric surgery reduces inflammatory responses associated with obesity. Heme oxygenase-1 (HO-1) is an enzyme with anti-inflammatory properties, which might be increased in morbid obesity or OSA. We studied morbidly obese patients with OSA to determine: (a) HO-1 plasma concentrations according to OSA severity and their relationship with insulin resistance and inflammation and (b) the impact of bariatric surgery on HO-1 and parameters of insulin resistance and inflammation.

MATERIAL AND METHODS

We analyzed the homeostasis model insulin resistance index (HOMA) and plasma concentrations of HO-1, tumor necrosis factor alpha, interleukin-6, interleukin-1-beta, C reactive protein (CRP), and adiponectin according to polysomnography findings in 66 morbidly obese patients before bariatric surgery and 12 months after surgery.

RESULTS

Before surgery, HO-1 plasma concentrations were similar in three groups of patients with mild, moderate, and severe OSA, and correlated with HOMA (r = 0.27, p = 0.02). Twelve months after surgery, low-grade inflammation and insulin resistance had decreased in all the groups, but HO-1 plasma concentration had decreased only in the severe OSA group (p = 0.02). In this group, the reduction in HO-1 correlated with a reduction in CRP concentrations (r = 0.43, p = 0.04) and with improved HOMA score (r = 0.37, p = 0.03).

CONCLUSIONS

Bariatric surgery decreases HO-1 concentrations in morbid obesity with severe OSA, and this decrease is associated with decreases in insulin resistance and in inflammation.

Direct Bilirubin Levels and Risk of Metabolic Syndrome in Healthy Chinese Men

Background

Serum bilirubin is a potent endogenous antioxidant with anti-inflammatory properties. Several cross-sectional studies have reported that bilirubin was negatively associated with metabolic syndrome. However, in recent longitudinal studies, the relations between bilirubin and metabolic syndrome are inconsistent. Moreover, previous studies mainly focused on serum total bilirubin which is the sum of direct bilirubin and indirect bilirubin. For these reasons, the longitudinal effect of bilirubin subtypes on incident metabolic syndrome was evaluated in Chinese men.

Methods

The study cohort involved 1339 Chinese men without metabolic syndrome. Metabolic syndrome was defined by the American Heart Association/National Heart, Lung and Blood Institute (AHA/NHLBI) criteria, using BMI for the replacement of waist circumference.

Results

There are 117 incident metabolic syndrome cases (8.7%) during 5 years of follow-up among 1339 metabolic syndrome-free participants at baseline. After adjusting for age, drinking, smoking, physical activity, TG, and LDL-C, the odd ratios (ORs) and 95% confidence intervals (CIs) for MetS incidence in the second, third, and fourth quartiles versus the first quartile of DBil concentration were 1.00 (0.61-1.63), 0.57 (0.32-1.02), and 0.51 (0.28-0.92) (P_trend = 0.031), respectively.

Conclusions

Our findings support the negative association between direct bilirubin and incident metabolic syndrome in healthy Chinese men over 5-year period.

β-Sarcoglycan Deficiency Reduces Atherosclerotic Plaque Development in ApoE-Null Mice

BACKGROUND

Smooth muscle cells are important for atherosclerotic plaque stability. Their proper ability to communicate with the extracellular matrix is crucial for maintaining the correct tissue integrity. In this study, we have investigated the role of β-sarcoglycan within the matrix-binding dystrophin-glycoprotein complex in the development of atherosclerosis.

RESULTS

Atherosclerotic plaque development was significantly reduced in ApoE-deficient mice lacking β-sarcoglycan, and their plaques contained an increase in differentiated smooth muscle cells. ApoE-deficient mice lacking β-sarcoglycan showed a reduction in ovarian adipose tissue and adipocyte size, while the total weight of the animals was not significantly different. Western blot analysis of adipose tissues showed a decreased activation of protein kinase B, while that of AMP-activated kinase was increased in mice lacking β-sarcoglycan. Analysis of plasma in β-sarcoglycan-deficient mice revealed reduced levels of leptin, adiponectin, insulin, cholesterol, and triglycerides but increased levels of IL-6, IL-17, and TNF-α.

CONCLUSIONS

Our results indicate that the dystrophin-glycoprotein complex and β-sarcoglycan can affect the atherosclerotic process. Furthermore, the results show the effects of β-sarcoglycan deficiency on adipose tissue and lipid metabolism, which may also have contributed to the atherosclerotic plaque reduction.

Ablation of adipose-HO-1 expression increases white fat over beige fat through inhibition of mitochondrial fusion and of PGC1α in female mice

Background Hmox1 plays an important role in the regulation of mitochondrial bioenergetics and function by regulating cellular heme-derived CO and bilirubin. Previous studies have demonstrated that global disruption of HO-1 in humans and mice resulted in severe organ dysfunction. Methods We investigated the potential role of adipose-specific-HO-1 genetic ablation on adipose tissue function, mitochondrial quality control and energy expenditure by generating an adipo-HO-1 knockout mouse model (Adipo-HO-1-/-) and, in vitro, adipocyte cells in which HO activity was inhibited. Adiposity, signaling proteins, fasting glucose and oxygen consumption were determined and compared to adipocyte cultures with depressed levels of both HO-1/HO-2. Results Adipo-HO-1-/- female mice exhibited increased adipocyte size, and decreases in the mitochondrial fusion to fission ratio, PGC1, and SIRT3. Importantly, ablation of HO-1 in adipose tissue resulted in fat acquiring many properties of visceral fat such as decreases in thermogenic genes including pAMPK and PRDM16. Deletion of HO-1 in mouse adipose tissue led to complete metabolic dysfunction, an increase in white adipose tissue, a reduction of beige fat and associated increases in FAS, aP2 and hyperglycemia. Mechanistically, genetic deletion of HO-1 in adipose tissues decreased the mitochondrial fusion to fission ratio; disrupted the activity of the PGC1 transcriptional axis and thermogenic genes both in vitro and in vivo. Conclusion Ablation of adipose tissue-HO-1 abridged PGC1 expression promoted mitochondrial dysfunction and contributed to an increase of pro-inflammatory visceral fat and abrogated beige-cell like phenotype.

Baicalein protects rat insulinoma INS-1 cells from palmitate-induced lipotoxicity by inducing HO-1

Objective

β-Cell dysfunction plays a central role in the pathogenesis of type 2 diabetes (T2D), and the identification of novel approaches to improve β-cell function is essential to treat this disease. Baicalein, a flavonoid originally isolated from the root of Scutellaria Baicalensis, has been shown to have beneficial effects on β-cell function. Here, the authors investigated the molecular mechanism responsible for the protective effects of baicalein against palmitate (PA)-induced impaired β-cell function, and placed focus on the role of heme oxygenase (HO)-1.

Methods

Rat pancreatic β-cell line INS-1 cells or mouse pancreatic islets were cultured with PA (500 μM) to induce lipotoxicity in the presence or absence of baicalein (50 μM), and the expressions of the ER stress markers, ATF-3, CHOP and GRP78 were detected by Western blotting and/or qPCR. The involvement of HO-1 was evaluated by HO-1 siRNA transfection and using the HO-1 inhibitor ZnPP.

Results

Baicalein reduced PA-induced ER stress and inflammation and enhanced insulin secretion, and these effects were associated with the induction of HO-1. Furthermore, these protective effects were attenuated by ZnPP and by HO-1 siRNA. Pretreatment of PD98059 (an ERK inhibitor) significantly inhibited the protective effects of baicalein and blocked HO-1 induction. On the other hand, CO production by RuCO (a CO donor) ameliorated PA-induced ER stress, suggesting that CO production followed by HO-1 induction may contribute to the protective effects of baicalein against PA-induced β-cell dysfunction.

Conclusion

Baicalein protects pancreatic β-cells from PA-induced ER stress and inflammation via an ERK-HO-1 dependent pathway. The authors suggest HO-1 induction in pancreatic β-cells appears to be a promising therapeutic strategy for T2D.

Low adiponectin is associated with diastolic dysfunction in women: a cross-sectional study from the Tromsø Study

Background

Heart failure with preserved ejection fraction is closely associated with diastolic dysfunction and related to obesity and female sex. We investigated whether adiponectin, an adipocyte-secreted protein hormone with cardioprotective effects, was associated with indices of diastolic dysfunction, and whether the association was sex dependent.

Methods

We conducted a cross-sectional study on 1165 women and 896 men without diabetes. We stratified the multivariable adjusted logistic regression analyses and the fractional polynomial regression analyses according to sex, with echocardiographic markers of diastolic dysfunction as dependent variables, and adiponectin as the independent variable of interest.

Results

Decreased adiponectin was associated with higher odds of average tissue Doppler e’ < 9 in women (odds ratio [OR] 1.17 per 1 μg/mL adiponectin decrease, 95% confidence interval [CI] 1.04–1.30), but not in men (p for interaction with sex 0.04). Women, but not men, had higher odds of E/e’ ratio ≥ 8 with lower adiponectin (OR 1.12 per 1 μg/mL adiponectin decrease, 95% CI 1.02–1.24, p for interaction with sex 0.04). Adiponectin in the lower sex-specific tertile was associated with increased odds of concentric left ventricular hypertrophy in women (OR 2.44, 95% CI 1.03–5.77), but with decreased odds in men (OR 0.32, 95% CI 0.11–0.88, p for interaction with sex 0.002), and decreased odds of eccentric hypertrophy in men only (OR 0.53, 95% CI 0.33–0.88, p for interaction with sex 0.02). Adiponectin in the lower sex-specific tertile was associated with moderately enlarged left atria in women only (OR 1.43, 95% CI 1.01–2.03, p for interaction with sex 0.04). Finally, adiponectin had a non-linear relationship with left ventricular mass in women only, with exponentially increasing left ventricular mass with lower adiponectin levels (p for interaction with sex 0.01).

Conclusions

Low adiponectin was associated with higher odds of indices of diastolic dysfunction in women, but lower odds of indices of diastolic dysfunction in men. Lower adiponectin was associated with increased left ventricular mass in women only.

Sex-Dependent Effects of HO-1 Deletion from Adipocytes in Mice

Induction of heme oxygenase-1 (HO-1) has been demonstrated to decrease body weight and improve insulin sensitivity in several models of obesity in rodents. To further study the role of HO-1 in adipose tissue, we created an adipose-specific HO-1 knockout mouse model. Male and female mice were fed either a control or a high-fat diet for 30 weeks. Body weights were measured weekly and body composition, fasting blood glucose and insulin levels were determined every six weeks. Adipocyte-specific knockout of HO-1 had no significant effect on body weight in mice fed a high-fat diet but increased body weight in female mice fed a normal-fat diet. Although body weights were not different in females fed a high fat diet, loss of HO-1 in adipocytes resulted in significant alterations in body composition. Adipose-specific HO-1 knockout resulted in increased fasting hyperglycemia and insulinemia in female but not male mice on both diets. Adipose-specific knockout of HO-1 resulted in a significant loss of HO activity and a decrease in the protein levels of adiponectin in adipose tissue. These results demonstrate that loss of HO-1 in adipocytes has greater effects on body fat and fasting hyperglycemia in a sex-dependent fashion and that expression of HO-1 in adipose tissue may have a greater protective role in females as compared to males.

Butein induction of HO-1 by p38 MAPK/Nrf2 pathway in adipocytes attenuates high-fat diet induced adipose hypertrophy in mice

Adipose tissue inflammation and oxidative stress are key components in the development of obesity and insulin resistance. Heme oxygenase (HO)-1 in adipocytes protects against obesity and adipose dysfunction. In this study, we report the identification of butein, a flavonoid chalcone, as a novel inducer of HO-1 expression in adipocytes in vitro and in vivo. Butein upregulated HO-1 mRNA and protein expression in 3T3-L1 adipocytes, accompanied by Kelch-Like ECH-Associated Protein (Keap) 1 degradation and increase in the nuclear level of nuclear factor erythroid 2-related factor 2 (Nrf2). Butein modulation of Keap1 and Nrf2 as well as HO-1 upregulation was reversed by pretreatment with p38 MAPK inhibitor SB203580, indicating the involvement of p38 MAPK in butein activation of Nrf2 in adipocytes. In addition, HO-1 activation by butein led to the inhibitions of reactive oxygen species and adipocyte differentiation, as evidenced by the fact that butein repression of reactive oxygen species and adipogenesis was reversed by pretreatment with HO-1 inhibitor SnPP. Induction of HO-1 expression by butein was also demonstrated in the adipose tissue of C57BL/6 mice fed a high-fat diet administered along with butein for three weeks, and correlated with the inhibitions of adiposity and adipose tissue inflammation, which were reversed by co-administration of SnPP. Altogether, our results demonstrate that butein activates the p38 MAPK/Nrf2/HO-1 pathway to act as a potent inhibitor of adipose hypertrophy and inflammation in a diet-induced obesity model and thus has potential for suppressing obesity-linked metabolic syndrome.

Obesity, Oxidative Stress, and Their Effect on Serum Heme Oxygenase-1 Concentrations and Insulin in Children Aged 3 to 5 Years in a Pediatric Hospital of the Ministry of Health CDMX

BACKGROUND

Obesity during early stages of life may condition states of oxidative stress. Heme oxygenase-1 (HO-1) is an enzyme involved in oxidative metabolism; it has antioxidant and anti-inflammatory functions and is related in sensitivity to insulin. However, a high concentration of this enzyme has been described to cause alterations such as insulin resistance. The objective of this work was to study the relationship between obesity, oxidative stress, HO-1, and insulin in children aged 3 to 5 years.

METHODS

To achieve our objective, we studied a control group of children (n = 50) and a group of obese children (n = 50) who underwent an anthropometric evaluation. Additionally, we quantified peroxidized lipids, oxidized low-density lipoproteins (Ox-LDLs), oxidized and reduced glutathione, HO-1, and insulin. We also calculated the homeostasis model assessment of insulin resistance (HOMA-IR), HOMA-%B, and HOMA-%S indices. According to the data distribution, nonparametric and Spearman's rank correlation coefficient tests were conducted.

RESULTS

The results demonstrate that obese children show a statistically relevant increase in BMI/age, serum concentrations of peroxidized lipids, Ox-LDLs, oxidized glutathione, HO-1, and insulin (p < 0.005). In addition, there was an increase in the HOMA-IR and HOMA-%B (p < 0.0001) indices and a decrease of reduced glutathione, as well as a reduction in the HOMA-%S, compared with the children of the control group (p < 0.003).

CONCLUSIONS

With the results obtained, we can conclude that obese preschool children show a chronic state of oxidative stress, an increase of HO-1, and an incipient state of insulin resistance. Finally, the increased reactive oxygen species could be one of the leading factors involved in insulin resistance and Ox-LDL increase from the preschool stage.

The Role of Na/K-ATPase Signaling in Oxidative Stress Related to Obesity and Cardiovascular Disease

Na/K-ATPase has been extensively studied for its ion pumping function, but, in the past several decades, has been identified as a scaffolding and signaling protein. Initially it was found that cardiotonic steroids (CTS) mediate signal transduction through the Na/K-ATPase and result in the generation of reactive oxygen species (ROS), which are also capable of initiating the signal cascade. However, in recent years, this Na/K-ATPase/ROS amplification loop has demonstrated significance in oxidative stress related disease states, including obesity, atherosclerosis, heart failure, uremic cardiomyopathy, and hypertension. The discovery of this novel oxidative stress signaling pathway, holds significant therapeutic potential for the aforementioned conditions and others that are rooted in ROS.

Epoxyeicosatrienoic Acids Regulate Adipocyte Differentiation of Mouse 3T3 Cells, Via PGC-1α Activation, Which Is Required for HO-1 Expression and Increased Mitochondrial Function

Epoxyeicosatrienoic acid (EET) contributes to browning of white adipose stem cells to ameliorate obesity/diabetes and insulin resistance. In the current study, we show that EET altered preadipocyte function, enhanced peroxisome proliferation-activated receptor γ coactivator α (PGC-1α) expression, and increased mitochondrial function in the 3T3-L1 preadipocyte subjected to adipogenesis. Cells treated with EET resulted in an increase, P < 0.05, in PGC-1α and a decrease in mitochondria-derived ROS (MitoSox), P < 0.05. The EET increase in heme oxygenase-1 (HO-1) levels is dependent on activation of PGC-1α as cells deficient in PGC-1α (PGC-1α knockout adipocyte cell) have an impaired ability to express HO-1, P < 0.02. Additionally, adipocytes treated with EET exhibited an increase in mitochondrial superoxide dismutase (SOD) in a PGC-1α-dependent manner, P < 0.05. The increase in PGC-1α was associated with an increase in β-catenin, P < 0.05, adiponectin expression, P < 0.05, and lipid accumulation, P < 0.02. EET decreased heme levels and mitochondria-derived ROS (MitoSox), P < 0.05, compared to adipocytes that were untreated. EET also decreased mesoderm-specific transcript (MEST) mRNA and protein levels (P < 0.05). Adipocyte secretion of EET act in an autocrine/paracrine manner to increase PGC-1α is required for activation of HO-1 expression. This is the first study to dissect the mechanism by which the antiadipogenic and anti-inflammatory lipid, EET, induces the PGC-1α signaling cascade and reprograms the adipocyte phenotype by regulating mitochondrial function and HO-1 expression, leading to an increase in healthy, that is, small, adipocytes and a decrease in adipocyte enlargement and terminal differentiation. This is manifested by an increase in mitochondrial function and an increase in the canonical Wnt signaling cascade during adipocyte proliferation and terminal differentiation.