Renal protective effects of induction of haem oxygenase-1 combined with increased adiponectin on the glomerular vascular endothelial growth factor-nitric oxide axis in obese rats

Empagliflozin Attenuates Obesity-Related Kidney Dysfunction and NLRP3 Inflammasome Activity Through the HO-1-Adiponectin Axis

Empagliflozin (EMPA) is a novel sodium-glucose cotransporter 2 inhibitor (SGLT2i) that produces protective cardiovascular-renal outcomes in patients with diabetes. However, the effects of EMPA on obesity-related kidney disease have not been determined. The heme oxygenase-1 (HO-1)-adiponectin axis is an essential antioxidant system with anti-apoptotic and anti-inflammatory properties. This study explored whether EMPA improves obesity-related kidney disease through regulation of the renal HO-1-mediated adiponectin axis. C57BL/6J mice were assigned to control, high-fat diet (HFD) groups, and EMPA (10 mg/kg) groups. HFD mice showed metabolic abnormality and renal injury, including increased urinary albumin excretion, morphologic changes, and lipid accumulation. EMPA treatment improved metabolic disorders and attenuated lipotoxicity-induced renal injury. Furthermore, EMPA treatment ameliorated renal NLRP3 inflammasome activity and upregulated the HO-1-adiponectin axis. Our findings indicate that EMPA improves obesity-related kidney disease through reduction of NLRP3 inflammasome activity and upregulation of the HO-1-adiponectin axis, suggesting a novel mechanism for SGLT2i-mediated renal protection in obesity.

Heme Degradation in Pathophysiology of and Countermeasures to Inflammation-Associated Disease

The class of tetrapyrrol "coordination complexes" called hemes are prosthetic group components of metalloproteins including hemoglobin, which provide functionality to these physiologically essential macromolecules by reversibly binding diatomic gasses, notably O₂, which complexes to ferrous (reduced/Fe(II)) iron within the heme porphyrin ring of hemoglobin in a pH- and PCO₂-dependent manner-thus allowing their transport and delivery to anatomic sites of their function. Here, pathologies associated with aberrant heme degradation are explored in the context of their underlying mechanisms and emerging medical countermeasures developed using heme oxygenase (HO), its major degradative enzyme and bioactive metabolites produced by HO activity. Tissue deposits of heme accumulate as a result of the removal of senescent or damaged erythrocytes from circulation by splenic macrophages, which destroy the cells and internal proteins, including hemoglobin, leaving free heme to accumulate, posing a significant toxicogenic challenge. In humans, HO uses NADPH as a reducing agent, along with molecular oxygen, to degrade heme into carbon monoxide (CO), free ferrous iron (FeII), which is sequestered by ferritin protein, and biliverdin, subsequently metabolized to bilirubin, a potent inhibitor of oxidative stress-mediated tissue damage. CO acts as a cellular messenger and augments vasodilation. Nevertheless, disease- or trauma-associated oxidative stressors sufficiently intense to overwhelm HO may trigger or exacerbate a wide range of diseases, including cardiovascular and neurologic syndromes. Here, strategies are described for counteracting the effects of aberrant heme degradation, with a particular focus on "bioflavonoids" as HO inducers, shown to cause amelioration of severe inflammatory diseases.

Liraglutide improves obesity-induced renal injury by alleviating uncoupling of the glomerular VEGF-NO axis in obese mice

Obesity-related kidney disease is associated with generalized endothelial dysfunction. Liraglutide, a glucagon-like peptide-1 agonist, has cardiovascular-renal protective effects in patients with diabetes. In this study, the ability of liraglutide to reduce urinary albumin excretion by alleviating glomerular vascular endothelial growth factor-nitric oxide (VEGF-NO) axis uncoupling was assessed in high fat diet-induced obese mice. C57BL/6J mice were divided into control and obesity groups, treated with or without liraglutide (200 μg/kg/day). Blood biochemistry and urinary albumin excretion were measured. Glomerular VEGF and the AMPK-endothelial nitric oxide synthase (eNOS) pathway were assayed by western blotting. Glomerular NO, renal haeme oxygenase-1 activity, and malondialdehyde levels were also measured. Treatment of obese mice with liraglutide led to significant reductions in body weight gain (46 ± 1 g vs 55 ± 1 g, P < .0001), visceral fat (8.9 ± 0.6 g vs 14.5 ± 0.6 g, P < .0001), perirenal fat (2.9 ± 0.2 g vs 5.4 ± 0.3 g, P < .0001), and free fatty acid (1.71 ± 0.12 mmol/L vs 1.02 ± 0.08 mmol/L, P < .0001). Liraglutide significantly improved glucose homeostasis, which was impaired in obese mice. Liraglutide reduced urinary albumin excretion and glomerular hypertrophy in obese mice. Additionally, liraglutide significantly decreased VEGF and increased glomerular NO production in glomeruli, indicating restoration of the glomerular VEGF-NO axis. Furthermore, liraglutide activated the glomerular AMPK-eNOS pathway in obese mice, upregulated renal haeme oxygenase-1 activity, and reduced the renal malondialdehyde levels in obese mice. In conclusion, liraglutide reduced microalbuminuria and ameliorated renal injury by alleviating the uncoupling of the glomerular VEGF-NO axis.

Nobiletin ameliorates high-fat diet-induced vascular and renal changes by reducing inflammation with modulating AdipoR1 and TGF-β1 expression in rats

AIMS

We investigate the effect of nobiletin on vascular and renal alterations and possible mechanisms involved in high-fat diet (HFD)-fed rats.

MAIN METHODS

Male Sprague-Dawley rats were fed a HFD with fructose 15% in drinking water for 16 weeks. HFD-fed rats were treated with nobiletin (20 or 40 mg/kg/day) or vehicle for the last 4 weeks.

KEY FINDINGS

HFD-fed rats treated with nobiletin was significantly reduced obesity, hypertension, dyslipidemia and hyperinsulinemia. Nobiletin improved vascular endothelial function, restored creatinine clearance, and reduced plasma urea and creatinine levels, as well as urinary protein excretion. Nobiletin markedly alleviated vascular medial cross-sectional area (CSA) and collagen deposition, glomerular extracellular matrix (ECM) accumulation, and renal fibrosis. Nobiletin significantly elevated plasma adiponectin levels, together with upregulated adiponectin receptor 1 (AdipoR1) and suppressed transforming growth factor-β1 (TGF-β1) expression in kidney. In addition, an increase of plasma tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) was significantly attenuated after nobiletin treatment.

SIGNIFICANCE

Our results suggest that nobiletin attenuates HFD-induced vascular and renal alterations in rats, which is possibly related to the modulation of AdipoR1 and TGF-β1expression, and suppression of inflammation.

Hydrogen sulfide renal protective effects: possible link between hydrogen sulfide and endogenous carbon monoxide in a rat model of renal injury

Hydrogen sulfide (H2S), along with nitric oxide (NO) and carbon monoxide (CO), proved to have renoprotective effects in various renal diseases. Therefore, this study investigated the renoprotective effect of H2S, in a renal injury model, and its crosstalk with other gasotransmitters such as CO. Thirty-two adult rats were divided into four groups: control, gentamicin (GEN)-treated, GEN + sodium hydrosulfide (NaHS), and GEN + NaHS + zinc protoporphyrin (ZnPP) groups. GEN was used to induce renal injury, NaHS is a water-soluble H2S, and ZnPP is a selective heme oxygenase-1 (HO-1) inhibitor used to inhibit CO synthesis in vivo. NaHS improved kidney functions in the GEN group as evidenced by significantly lower levels of renal injury markers: serum urea, creatinine, uric acid, urinary albumin excretion, and urinary albumin/creatinine. Moreover, NaHS administration to the GEN-treated group significantly lowered renal levels of NO and tumor necrosis factor-α with an increase in total antioxidant, HO-1, and interleukin-10 levels. Furthermore, NaHS administration downregulated the GEN-induced overexpression of the renal inducible nitric oxide synthase (iNOS) and upregulated the suppression of endothelial nitric oxide synthase (eNOS) with improvement in the histological examination and periodic acid Schiff (PAS) staining. However, this improvement in kidney function produced by NaHS was reduced by combination with ZnPP but still improved as compared with the GEN-treated group. The renoprotective effects of H2S can be through its effects on renal tissue antioxidants, pro-inflammatory and anti-inflammatory cytokines, and expression of eNOS and iNOS which can be partially dependent on CO pathway via induction of HO-1 enzyme.

Mangifera indica L. Leaf Extract Induces Adiponectin and Regulates Adipogenesis

Natural bioactive compounds may be used in obese patients because of their ability to impact on various key mechanisms involved in the complex pathophysiological mechanisms of such condition. The aim of this study was to investigate the effect of a Mangifera indica L. leaf extract (MLE) on adipogenic differentiation of murine preadipocyte cells. 3T3-L1 cells were treated during their differentiation with various concentrations of (Mangifera indica L.) leaves extract (MLE) (750, 380, 150, 75 and 35 μg) in order to assess their lipid content, adiponectin production, expression profile of genes involved in lipid metabolism, oxidative stress and inflammation. Our results showed that MLE was particularly enriched in polyphenols (46.30 ± 0.083 mg/g) and that pharmacological treatment of cells resulted in a significant increase of adiponectin levels and reduction of intracellular lipid content. Consistently with these results, MLE resulted in a significant decrease of the expression of genes involved in lipid metabolism (FAS, PPARG, DGAT1, DGAT2, and SCD-1). In conclusion, our results suggest that MLE may represent a possible pharmacological tool for obese or metabolic syndrome patients.

HMOX1 as a marker of iron excess-induced adipose tissue dysfunction, affecting glucose uptake and respiratory capacity in human adipocytes

AIMS/HYPOTHESIS

Iron excess in adipose tissue is known to promote adipose tissue dysfunction. Here, we aimed to investigate the possible role of haem oxygenase 1 (HMOX1) in iron excess-induced adipose tissue dysfunction.

METHODS

Cross-sectionally, HMOX1 gene expression in subcutaneous and visceral adipose tissue was analysed in two independent cohorts (n = 234 and 40) in relation to obesity. We also evaluated the impact of weight loss (n = 21), weight gain (in rats, n = 20) on HMOX1 mRNA; HMOX1 mRNA levels during human adipocyte differentiation; the effects of inflammation and iron on adipocyte HMOX1; and the effects of HMOX1-induced activity on adipocyte mitochondrial respiratory function, glucose uptake and adipogenesis.

RESULTS

Adipose tissue HMOX1 was increased in obese participants (p = 0.01) and positively associated with obesity-related metabolic disturbances, and markers of iron accumulation, inflammation and oxidative stress (p < 0.01). HMOX1 was negatively correlated with mRNAs related to mitochondrial biogenesis, the insulin signalling pathway and adipogenesis (p < 0.01). These associations were replicated in an independent cohort. Bariatric surgery-induced weight loss led to reduced HMOX1 (0.024 ± 0.010 vs 0.010 ± 0.004 RU, p < 0.0001), whereas in rats, high-fat diet-induced weight gain resulted in increased Hmox1 mRNA levels (0.22 ± 0.15 vs 0.54 ± 0.22 RU, p = 0.005). These changes were in parallel with changes in BMI and adipose tissue markers of iron excess, adipogenesis and inflammation. In human adipocytes, iron excess and inflammation led to increased HMOX1 mRNA levels. HMOX1 induction (by haem arginate [hemin] administration), resulted in a significant reduction of mitochondrial respiratory capacity (including basal respiration and spare respiratory capacity), glucose uptake and adipogenesis in parallel with increased expression of inflammatory- and iron excess-related genes.

CONCLUSIONS/INTERPRETATION

HMOX1 is an important marker of iron excess-induced adipose tissue dysfunction and metabolic disturbances in human obesity.

Irisin improves perivascular adipose tissue dysfunction via regulation of the heme oxygenase-1/adiponectin axis in diet-induced obese mice

AIMS

To determine whether irisin could improve perivascular adipose tissue (PVAT) dysfunction via regulation of the heme oxygenase-1 (HO-1)/adiponectin axis in obesity.

MATERIALS AND METHODS

C57BL/6 mice were given chow or a high-fat diet (HFD) with or without treatment with irisin. The concentration-dependent responses of the thoracic aorta with or without PVAT (PVAT+ or PVAT-) to phenylephrine were studied in an organ bath. Protein levels of HO-1 and adiponectin were determined by western blot. UCP-1, Cidea, and TNF-α gene expression in PVAT were analyzed by real-time PCR.

RESULTS

Treatment of obese mice with irisin improved glucose and lipid metabolism, reduced plasma levels of TNF-α and malondialdehyde, and increased plasma adiponectin levels (P<0.01). The anti-contractile effects of PVAT were attenuated in HFD mice and this attenuation was restored in HFD mice treated with irisin (P<0.05). Incubation of aortas (PVAT+) with the HO-1 inhibitor and adiponectin receptor blocking peptide in irisin-treated HFD mice abolished the beneficial effects of irisin on PVAT function. The same results were also observed in HFD mice treated with irisin ex vivo. Treatment of HFD mice with irisin significantly enhanced protein levels of HO-1 and adiponectin, and reduced superoxide production and TNF-α expression in PVAT. Irisin treatment enhanced brown adipocyte markers UCP-1 and Cidea expression in PVAT from HFD mice.

CONCLUSION

Irisin improved the anti-contractile properties of PVAT from the thoracic aorta in diet-induced obese mice. The mechanism for protective effects of irisin appeared to be related to upregulation of the HO-1/adiponectin axis in PVAT and browning of PVAT.

Antioxidation Effect of Simvastatin in Aorta and Hippocampus: A Rabbit Model Fed High-Cholesterol Diet

We show that hypercholesterolemia contributes to oxidative stress injury progression in brain and simvastatin counteracts the cholesterol-induced peroxidation injury in rabbit hippocampus, and we demonstrate for the first time that the simvastatin is a critical role in brain protection and identify HO-1 and other related antioxidant enzymes as molecular target for active redox compounds. Second, our experiments have pointed out an association between statin treatment and a decrease in the risk of having peroxidation damage of brain. The balance effects of simvastatin to ROS and antioxidants enzymes network are most probably due to improved SOD functional activity, increase in GSH-Px, increase in HO-1 expression, and decrease of MDA generation.