Renal sympathetic nerve activity is increased in monosodium glutamate induced hyperadipose rats

Differential benefits of physical training associated or not with L-arginine supplementation in rats with metabolic syndrome: evaluation of cardiovascular, autonomic and metabolic parameters

Metabolic syndrome (MetS) is characterized by endocrine-metabolic and cardiac alterations that increase the risk of cardiovascular disease, dyslipidemia, and type-2 diabetes mellitus. Dietary supplementation with L-Arginine (L-Arg) is beneficial for fat loss, while chronic aerobic exercise has several benefits in reversing cardiovascular, autonomic, and metabolic dysfunctions caused by obesity. However, the association between these two approaches has not yet been described. This study aimed to evaluate the possible benefits of physical training, with or without L-Arg supplementation, on cardiovascular, autonomic, and metabolic parameters in rats with MetS, which was induced by the subcutaneous administration of monosodium glutamate at 4 mg g^-1day^-1 in rats from the first to fifth day of life. Physical training on a treadmill and supplementation with L-Arg in adulthood were carried out concomitantly for 8 weeks. After this, the animals underwent femoral artery catheterization to record their cardiovascular parameters and autonomic modulation. Organs and blood were removed to measure levels of nitrite, glucose, and hepatic steatosis. In adult rats with MetS, supplementation with L-Arg in combination with physical training reduced hypertension, tachycardia, adipose tissue mass, free fatty acids, and hepatic steatosis. Supplementation with L-Arg and physical training separately was beneficial in reducing several aspects of MetS, but a combination of both was especially effective in reducing adipose tissue and hepatic steatosis. Together, the two therapies can form a good strategy to combat MetS.

The methanol extract of Ceiba pentandra reverses monosodium glutamate-induced cardiometabolic syndrome in rats via the regulation of dyslipidemia, inflammation, oxidative stress, and insulin sensitization

The antidiabetic effects of the methanol extract of the stem bark of Ceiba pentandra (Cp) have been demonstrated in various experimental models. Besides, this extract is rich in 8-formyl-7-hydroxy-5-isopropyl-2-methoxy-3-methyl-1,4-naphthaquinone, 2,4,6-Trimethoxyphenol and vavain. However, it remains unknown whether Cp can mitigate cardiometabolic syndrome (CMS). The present study assessed the curative properties of Cp against Monosodium Glutamate (MSG)-induced CMS in rats. Male neonate Wistar rats were intraperitoneally administered with MSG (4 mg/g/day) during the first 5 days of life (postnatal days 2-6). They were kept under standard breeding conditions up to 5 months of age for the development of CMS. Diseased animals were then orally treated with atorvastatin (80 mg/kg/d) or Cp (75 and 150 mg/kg/day) for 28 days during which food intake, body mass, blood pressure, heart rate, glucose, and insulin tolerance were monitored. Plasma and tissues were collected on day 29th to assess the lipid profile, oxidative stress, and inflammatory parameters. The histomorphology of the adipose tissue was also evaluated. Cp significantly (p < 0.001) reduced the obesogenic and lipid profiles, adipocyte size, blood pressure, and oxidative and inflammatory status in MSG-treated rats. Cp also ameliorated glucose (p < 0.05) and insulin sensitivities (p < 0.001) hence, reducing animals' cardiometabolic risk score (p < 0.001). The curative effect of Cp on cardiometabolic syndrome is related to its capacity to reduce oxidative stress, inflammation, dyslipidemia, and increase insulin sensitivity. These results demonstrate the potential of Cp as a good candidate for alternative treatment of CMS.

Antioxidant therapy reverses sympathetic dysfunction, oxidative stress, and hypertension in male hyperadipose rats

AIMS

The rostral ventrolateral medulla (RVLM) is the main sympathetic output of the central nervous system to control blood pressure. Reportedly, reactive oxygen species (ROS) can increase arterial pressure, leading to hypertension. As ROS increase the sympathetic tone in RVLM and obese animals present grater oxidative stress, it would be important to note this relationship.

MAIN METHODS

Therefore, we evaluated the systemic and central effects (in the RVLM) of vitamin C (vit C, an antioxidant) on the redox balance and cardiovascular and autonomic profiles in hyperadipose male rats. We also evaluated the neurotransmission by L-glutamate (L-glu) and vit C in the RVLM of awake hyperadipose rats.

KEY FINDINGS

Our study confirmed that hyperadipose rats were hypertensive and tachycardic, presented increased sympathetic and decreased parasympathetic modulation of the heart, and had increased plasma lipoperoxidation compared with the control rats (CTR). Oral vitamin C treatment reverted cardiovascular, autonomic, and plasma redox dysfunction. Hyperadipose rats presented a higher blood pressure increase after L-glu microinjection and a lower response to vit C in the RVLM compared with the CTR group. Biochemical analysis of redox balance in RVLM punches showed that hyperadipose rats have increased NBT and T-BARS, and after treatment with vit C, the oxidative profile decreased. The antioxidative activity of vit C reduced the amount of ROS in the RVLM area that might have resulted in lowered blood pressure and sympathetic modulation.

SIGNIFICANCE

Our data suggest central and peripheral benefits of vit C treatment on cardiovascular, autonomic, and oxidative dysfunctions in hyperadipose animals.

Metabolic syndrome improves cardiovascular dysfunction and survival during cecal ligation and puncture-induced mild sepsis in mice

AIMS

Sepsis is a potentially fatal systemic inflammatory response and its underlying pathophysiology is still poorly understood. Studies suggest that obesity, a component of metabolic syndrome (MS), is associated with sepsis survival. Therefore, this study focused on investigating the influence of MS on mortality and cardiovascular dysfunction induced by sublethal cecal ligation and puncture (SL-CLP).

MAIN METHODS

Newborn Swiss mice received monosodium glutamate (MSG) (4 mg kg^-1 day^-1, s.c.) during the first 5 d of life for MS induction, while the control pups received equimolar saline solution. On the 75th day, SL-CLP was used to induce mild sepsis (M-CLP) in the MS (MS-M-CLP) and control (SAL-M-CLP) mice. The effect of MS on sepsis in mice was assessed by determining the survival rate and quantification of nitric oxide (NO) in the plasma, and associating this data with hematological and cardiovascular parameters.

KEY FINDINGS

MS improved the survival of septic mice, preventing impairment to hematological and cardiovascular parameters. In addition, MS attenuated plasmatic NO increase, which is a typical feature of sepsis.

SIGNIFICANCE

These findings provide new insights into the relationship between obesity and mild sepsis in mice, thus revealing an approach in favor of the "obesity paradox."

Physical exercise associated with vitamin D chronic supplementation reduces kidney injury induced by monosodium glutamate

The aim was to evaluate the effects of chronic vitamin D (VD) supplementation associated with regular swimming over renal histomorphometric aspects in obese rats. Thirty Wistar male rats (5 days old) were used. Twenty four rats were given subcutaneous injections of monosodium glutamate (MSG; 4 g/kg), and six control rats were given an equimolar saline solution. At 21-days-old, the MSG-treated rats were randomly distributed among sedentary animals (S) and exercised (E, swimming; 3x/week). These groups were subdivided into groups orally supplemented with VD (12 μg/kg; 3x/week) or not supplemented (NS), totaling Five experimental groups (n = 6 rats/group): MSG, MSG-SVD, MSG-ENS, MSG-EVD and control groups. In MSG-obese rats, there was such as a decrease in the diameter of the, glomerular tuft, Bowman's capsule, Bowman's space areas, and renal cortical thickness, compared to the control group. In MSG-SVD, MSG-ENS, and MSG-EVD animals, there was an increase in the cortical thickness in relation to the MSG group. In MSG-ENS and MSG-EVD animals, there was a reduction of tubular degeneration in relation to the MSG group. We conclude that physical exercise associated with Vitamin D supplementation can prevent of renal injury, increasing the thickness of the renal cortex and decrease the tubular degeneration.

Pentamethylquercetin Attenuates Cardiac Remodeling via Activation of the Sestrins/Keap1/Nrf2 Pathway in MSG-Induced Obese Mice

Objective

Obesity causes a variety of metabolic alterations that may contribute to abnormalities of the cardiac structure and function (obesity cardiomyopathy). In previous works, we have shown that pentamethylquercetin (PMQ) significantly improved metabolic disorders in obese mice and it inhibited pressure overload-induced cardiac remodeling in mice. However, its potential benefit in obesity cardiomyopathy remains unclear. The aim of this study was to investigate the effects of PMQ on cardiac remodeling in obese mice.

Methods

We generated a monosodium glutamate-induced obese (MSG-IO) model in mice, which were treated with PMQ (5, 10, and 20 mg/kg) for 16 weeks consecutively. We examined the metabolic parameters and observed cardiac remodeling by performing cardiac echocardiography and Masson's staining. The expression levels of molecules associated with the endogenous antioxidant system, including the sestrins/kelch-like ECH-associated protein 1 (Keap1)/Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) signaling pathway, were analyzed by western blotting and immunofluorescent staining.

Results

We found that PMQ treatment significantly ameliorated obesity phenotypes and improved metabolic disorders in MSG-IO mice. PMQ decreased the heart wall thickness and attenuated cardiac fibrosis. Further study revealed that the protective effects of PMQ might be mediated by promoting Keap1 degradation and augmenting sestrins expression and Nrf2 nuclear translocation.

Conclusion

Our findings indicated that PMQ ameliorated cardiac remodeling in obese mice by targeting the sestrins/Keap1/Nrf2 signaling pathway.

Mechanisms mediating renal sympathetic nerve activation in obesity-related hypertension

Excessive renal sympathetic nerve activation may be one of the mechanisms underlying obesity-related hypertension. Impaired baroreflex sensitivity, adipokine disorders-such as leptin, adiponectin, and resistin-activation of the renin-angiotensin system, hyperinsulinemia, insulin resistance, and renal sodium retention present in obesity increase renal sympathetic nerve activity, thus contributing to the development of hypertension. Renal sympathetic denervation reduces both renal sympathetic activity and blood pressure in patients with obesity-related hypertension.

Decreased endothelial nitric oxide, systemic oxidative stress, and increased sympathetic modulation contribute to hypertension in obese rats

We investigated the involvement of nitric oxide (NO) and reactive oxygen species (ROS) on autonomic cardiovascular parameters, vascular reactivity, and endothelial cells isolated from aorta of monosodium glutamate (MSG) obese rats. Obesity was induced by administration of 4 mg/g body wt of MSG or equimolar saline [control (CTR)] to newborn rats. At the 60th day, the treatment was started with N(G)-nitro-L-arginine methyl ester (L-NAME, 20 mg/kg) or 0.9% saline. At the 90th day, after artery catheterization, mean arterial pressure (MAP) and heart rate were recorded. Plasma was collected to assess lipid peroxidation. Endothelial cells isolated from aorta were evaluated by flow cytometry and fluorescence intensity (FI) emitted by NO-sensitive dye [4,5-diaminofluoresceindiacetate (DAF-2DA)] and by ROS-sensitive dye [dihydroethidium (DHE)]. Vascular reactivity was made by concentration-response curves of acetylcholine. MSG showed hypertension compared with CTR. Treatment with L-NAME increased MAP only in CTR. The MSG induced an increase in the low-frequency (LF) band and a decrease in the high-frequency band of pulse interval. L-NAME treatment increased the LF band of systolic arterial pressure only in CTR without changes in MSG. Lipid peroxidation levels were higher in MSG and were attenuated after L-NAME. In endothelial cells, basal FI to DAF was higher in CTR than in MSG. In both groups, acetylcholine increased FI for DAF from basal. The FI baseline to DHE was higher in MSG than in CTR. Acetylcholine increased FI to DHE in the CTR group, but decreased in MSG animals. We suggest that reduced NO production and increased production of ROS may contribute to hypertension in obese MSG animals.