Renal denervation ameliorates cardiac metabolic remodeling in diabetic cardiomyopathy rats by suppressing renal SGLT2 expression.

This study aimed to investigate the effects of renal denervation (RDN) on diabetic cardiomyopathy (DCM) and explore the related mechanisms. Male Sprague-Dawley rats were fed high-fat chow and injected with low-dose streptozotocin to establish a DCM model. Six rats served as controls. The surviving rats were divided into three groups: control group, DCM group and DCM + RDN group. RDN surgery was performed in the fifth week. At the end of the experiment, all rats were subjected to 18F-FDG PET/CT and metabolic cage studies. Cardiac function and structure were evaluated by echocardiography and histology. Myocardial substrate metabolism and mitochondrial function were assessed by multiple methods. In the 13th week, the DCM rats exhibited cardiac hypertrophy and interstitial fibrosis accompanied by diastolic dysfunction. RDN ameliorated DCM-induced cardiac dysfunction (E/A ratio: RDN 1.07 ± 0.18 vs. DCM 0.93 ± 0.12, P < 0.05; E/E' ratio: RDN 10.74 ± 2.48 vs. DCM 13.25 ± 1.99, P < 0.05) and pathological remodeling (collagen volume fraction: RDN 5.05 ± 2.05% vs. DCM 10.62 ± 2.68%, P < 0.05). Abnormal myocardial metabolism in DCM rats was characterized by suppressed glucose metabolism and elevated lipid metabolism. RDN increased myocardial glucose uptake and oxidation while reducing the absorption and utilization of fatty acids. Meanwhile, DCM decreased mitochondrial ATP content, depolarized the membrane potential and inhibited the activity of respiratory chain complexes, but RDN attenuated this mitochondrial damage (ATP: RDN 30.98 ± 7.33 µmol/gprot vs. DCM 22.89 ± 5.90 µmol/gprot, P < 0.05; complexes I, III and IV activity: RDN vs. DCM, P < 0.05). Furthermore, both SGLT2 inhibitor and the combination treatment produced similar effects as RDN alone. Thus, RDN prevented DCM-induced cardiac dysfunction and pathological remodeling, which is related to the improvement of metabolic disorders and mitochondrial dysfunction.

Effects of Angiotensin Receptor Neprilysin Inhibitors on Inducibility of Ventricular Arrhythmias in Rats with Ischemic Cardiomyopathy.

The aims of the present study were to investigate the effects of angiotensin receptor neprilysin inhibitors (ARNi) on the susceptibility of ventricular arrhythmias (VAs) in rats with myocardial infarction (MI) and to explore the related mechanisms.A total of 32 adult male Sprague-Dawley rats were divided into 3 groups: a control group, MI group, and MI+ARNi group. MI was generated by ligation of the left anterior descending coronary artery. ARNi was given at 68 mg/kg/day for 4 weeks after MI surgery. At 4 weeks after MI, electrical programmed stimulation (EPS) was performed in all groups for the evaluation of VAs, and echocardiography was used to evaluate cardiac function. Indicators of sympathetic neural remodeling and cardiac remodeling were detected to further explore the related mechanisms.Four weeks after MI, rats in the ARNi group exhibited low susceptibility of VAs in comparison with that in the MI group, which was coincident with the attenuation of sympathetic nerve remodeling, amelioration of cardiac fibrosis, and regulation of Cx43 expression.ARNi is effective in reducing VAs in rats with ischemic cardiomyopathy, which is associated with attenuating sympathetic nerve remodeling and myocardial fibrosis.

Trimethylamine N-oxide facilitates the progression of atrial fibrillation in rats with type 2 diabetes by aggravating cardiac inflammation and connexin remodeling.

Diabetes is an independent risk factor for atrial fibrillation (AF). This study aimed to elucidate the pathophysiology of diabetes-related AF from the perspective of the gut microbial metabolite trimethylamine N-oxide (TMAO). In the present study, male rats received either a normal diet to serve as the control group or a high-fat diet/streptozotocin to induce type 2 diabetes mellitus. Then, diabetic rats were divided into two groups based on the presence or absence of 3,3-dimethyl-1-butanol (DMB, a specific TMAO inhibitor) in drinking water: the diabetic cardiomyopathy (DCM) group and the DCM + DMB group. Eight weeks later, compared with control rats, rats in the DCM group exhibited gut microbiota dysbiosis and systemic TMAO elevation. The inflammatory cytokines IL-1ß, IL-6, and TNF-α were markedly increased in the atria of rats in the DCM group. Downregulated expression of connexin 40 and lateralized distribution of connexin 43 were also observed in the atria of DCM rats. AF inducibility was significantly higher in DCM rats than in control rats. Furthermore, DMB treatment effectively ameliorated atrial inflammation and connexin remodeling while markedly reducing plasma TMAO levels. DMB treatment also decreased the vulnerability of diabetic rats to AF. In conclusion, TMAO might promote atrial inflammation and connexin remodeling in the development of diabetes, which may play a key role in mediating diabetes-related AF.

The cardioprotective effect of the sodium-glucose cotransporter 2 inhibitor dapagliflozin in rats with isoproterenol-induced cardiomyopathy.

Sodium-glucose cotransporter 2 inhibitor (SGLT2i) has been reported to improve glycemic control. This study was designed to investigate the effects of SGLT2i dapagliflozin (dapa) on cardiomyopathy induced by isoproterenol (ISO) and its potential mechanisms. Fifty male Sprague Dawley rats were randomly assigned to the control (n=10) and the ISO (2.5 mg/kg/day)-treated groups (n=40). After 2 weeks, the 28 surviving rats with obvious left ventricular dysfunction in the ISO group were randomized into three medication groups, including the angiotensin receptor neprilysin inhibitor (ARNI) sacubitril/valsartan group (S/V, n=9), the dapa group (n=9), and the ISO group (n=10) for 4 weeks. Next, electrical programmed stimulation was performed in all the groups to evaluate their susceptibility to ventricular arrhythmias (VAs). Compared to the ISO rats, the dapa administration not only effectively reduced the cumulative risk of death, the myocardial fibrosis, the plasma angiotensin II levels and its functional receptor AT1R protein expressions in the heart, and the proinflammatory cytokine levels in the cardiac tissue of the ISO-treated rats, but it also improved their cardiac function and inhibited oxidative stress. These effects were similar to S/V. However, dapa showed a greater efficacy than S/V in reducing the left ventricular end-diastolic volumes, lowing the heart rates and VAs, and decreasing the body weights and plasma glucose levels. The mechanisms by which dapa exerts protective effects on cardiomyopathy may be related to its indirect antioxidant capacity and direct hypoglycemic action.

Intestinal Barrier Dysfunction Exacerbates Neuroinflammation via the TLR4 Pathway in Mice With Heart Failure.

AIMS: The present study aimed to investigate alterations in neuroinflammation after heart failure (HF) and explore the potential mechanisms. METHODS: Male wild-type (WT) and Toll-like receptor 4 (TLR4)-knockout (KO) mice were subjected to sham operation or ligation of the left anterior descending coronary artery to induce HF. 8 weeks later, cardiac functions were analyzed by echocardiography, and intestinal barrier functions were examined by measuring tight junction protein expression, intestinal permeability and plasma metabolite levels. Alterations in neuroinflammation in the brain were examined by measuring microglial activation, inflammatory cytokine levels and the proinflammatory signaling pathway. The intestinal barrier protector intestinal alkaline phosphatase (IAP) and intestinal homeostasis inhibitor L-phenylalanine (L-Phe) were used to examine the relationship between intestinal barrier dysfunction and neuroinflammation in mice with HF. RESULTS: Eight weeks later, WT mice with HF displayed obvious increases in intestinal permeability and plasma lipopolysaccharide (LPS) levels, which were accompanied by elevated expression of TLR4 in the brain and enhanced neuroinflammation. Treatment with the intestinal barrier protector IAP significantly attenuated neuroinflammation after HF while effectively increasing plasma LPS levels. TLR4-KO mice showed significant improvements in HF-induced neuroinflammation, which was not markedly affected by intestinal barrier inhibitors or protectors. CONCLUSION: HF could induce intestinal barrier dysfunction and increase gut-to-blood translocation of LPS, which could further promote neuroinflammation through the TLR4 pathway.

Renal Denervation Attenuates Neuroinflammation in the Brain by Regulating Gut-Brain Axis in Rats With Myocardial Infarction.

Aims: The development of neuroinflammation deteriorates the prognosis of myocardial infarction (MI). We aimed to investigate the effect of renal denervation (RDN) on post-MI neuroinflammation in rats and the related mechanisms. Methods and Results: Male adult Sprague-Dawley rats were subjected to sham or ligation of the left anterior descending coronary artery to induce MI. One week later, the MI rats received a sham or RDN procedure. Their cardiac functions were analyzed by echocardiography, and their intestinal structures, permeability, and inflammatory cytokines were tested. The intestinal microbiota were characterized by 16S rDNA sequencing. The degrees of neuroinflammation in the brains of rats were analyzed for microglia activation, inflammatory cytokines, and inflammation-related signal pathways. In comparison with the Control rats, the MI rats exhibited impaired cardiac functions, intestinal injury, increased intestinal barrier permeability, and microbial dysbiosis, accompanied by increased microglia activation and pro-inflammatory cytokine levels in the brain. A RDN procedure dramatically decreased the levels of renal and intestinal sympathetic nerve activity, improved cardiac functions, and mitigated the MI-related intestinal injury and neuroinflammation in the brain of MI rats. Interestingly, the RDN procedure mitigated the MI-increased intestinal barrier permeability and pro-inflammatory cytokines and plasma LPS as well as ameliorated the gut microbial dysbiosis in MI rats. The protective effect of RDN was not significantly affected by treatment with intestinal alkaline phosphatase but significantly reduced by L-phenylalanine treatment in MI rats. Conclusions: RDN attenuated the neuroinflammation in the brain of MI rats, associated with mitigating the MI-related intestinal injury.

Renal denervation attenuates pressure overload-induced cardiac remodelling in rats with biphasic regulation of autophagy.

AIM: This study aimed to investigate effects of renal denervation (RDN) on pressure overload-induced cardiac remodelling in rats and the related mechanisms. METHODS: Adult male Sprague-Dawley rats underwent transverse aortic constriction (TAC) to generate cardiac remodelling. RDN was performed 1 week after TAC. The animals were divided into four groups: control group, TAC group, TAC+RDN group and control+RDN group. Rats in all groups were studied at 3 and 10 weeks after TAC respectively. Echocardiography and histology were used to evaluate cardiac function and pathological changes. TUNEL staining and western blotting were used to assess apoptosis. Western blotting and transmission electron microscopy (TEM) were used to evaluate autophagy. RESULTS: Three weeks after TAC, the TAC rats exhibited cardiac hypertrophy with normal cardiac function and no myocardial interstitial fibrosis or apoptosis, accompanied by a lower LC3 II level and fewer autophagic vacuoles in the left ventricles, both in the presence and absence of chloroquine (CQ), indicating suppressed autophagy at this stage. RDN ameliorated these pathological changes and attenuated the decrease in autophagy. Ten weeks after TAC, the TAC rats had decreased cardiac function, obvious cardiac interstitial fibrosis and apoptosis, with increased autophagy. RDN prevented these pathological changes, coincident with attenuation of increased autophagy. CONCLUSION: Autophagy was suppressed at the early stage but activated at the late stage of TAC-induced cardiac remodelling. RDN attenuated the pathological changes of TAC rats, accompanied by attenuation of the changes in autophagy. Thus, RDN ameliorated TAC-induced cardiac remodelling partially associated with biphasic modulation of autophagy.

Renal denervation ameliorates post-infarction cardiac remodeling in rats through dual regulation of oxidative stress in the heart and brain.

BACKGROUND: Myocardial remodeling is the key step in the development of ischemic cardiomyopathy. We aimed to compare effects of renal denervation (RDN) with those of angiotensin receptor neprilysin inhibitors (ARNi) on cardiac remodeling after myocardial infarction (MI), and explore underlying mechanism. METHODS: Sprague-Dawley rats (n = 40; male) were subjected to ligation of left anterior descending coronary artery to induce MI; six rats served as controls. ARNi was administered at a dose of 60 mg/kg/day for 4 weeks starting 1 week after MI. An RDN/Sham-RDN procedure was performed 1 week after MI. Rats in all groups were studied 5 weeks after MI. Echocardiography was used to evaluate cardiac function. Masson staining and TUNEL staining were used to determine the extent of cardiac remodeling. Indicators of oxidative stress in heart and brain were used to analyze the potential mechanisms involved. RESULTS: Five weeks after MI, both RDN and ARNi significantly improved cardiac function and cardiac remodeling; however, RDN was superior to ARNi at attenuating myocardial apoptosis. Compared to ARNi, RDN was also more effective at decreasing the abnormal oxidative stress caused by MI; this was especially true in case of the brain and was confirmed by evaluating the changes in reactive oxygen species (ROS) levels and other oxidative stress parameters following MI. CONCLUSIONS: RDN is not inferior to ARNi with respect to the improvement of cardiac remodeling in rats with ischemic cardiomyopathy. The effect of RDN might be associated with effective inhibition of oxidative stress in both the heart and brain.