Estradiol-mediated regulation of hepatic iNOS in obese rats: Impact of Src, ERK1/2, AMPKα, and miR-221.

PURPOSE: This study aimed to investigate in vivo effects of estradiol on the regulation of hepatic inducible nitric oxide synthase (iNOS) expression in the high fat (HF) diet-induced obesity. Also, we aimed to investigate whether activation of the extracellular signal-regulated kinase (ERK1/2), adenosine monophosphate-activated protein kinase (AMPK), Src kinase, and miR-221 is involved in estradiol-mediated regulation of iNOS in the liver of obese male Wistar rats. Male Wistar rats were fed a standard laboratory diet or a HF diet for 10 weeks. Half of HF rats were treated with estradiol intraperitoneally (40 µg/kg), whereas the other half were placebo-treated 24 H before euthanasia. Results show that estradiol treatment of HF rats decreased hepatic iNOS mRNA (P < 0.05) and protein expression (P < 0.01), the protein levels of p65 subunit of nuclear factor κB (P < 0.05) and ERα (P < 0.05), ERK1/2 phosphorylation (P < 0.001), and ERα/Src kinase association (P < 0.05). By contrast, hepatic Src protein level (P < 0.05), AMPKα phosphorylation (P < 0.05), and miR-221 expression (P < 0.05) were increased in HF rats after estradiol treatment. Our results indicate that estradiol in vivo regulates hepatic iNOS expression in obese rats via molecular mechanisms involving ERK1/2, AMPK, Src, and miR-221 signaling.

Regulation of hepatic Na+/K+-ATPase in obese female and male rats: involvement of ERK1/2, AMPK, and Rho/ROCK.

In this study, we assessed whether the disturbed regulation of sodium/potassium-adenosine-triphosphatase (Na+/K+-ATPase) occurs as a consequence of obesity-induced IR in sex-specific manner. We also assessed whether alterations of IRS/PI3K/Akt, ERK1/2, AMPKα, and RhoA/ROCK signaling cascades have an important role in this pathology. Female and male Wistar rats (150-200 g, 8 weeks old) were fed a standard laboratory diet or a high-fat (HF) diet (42% fat) for 10 weeks. The activity of hepatic Na+/K+-ATPase and Rho, and the association of IRS-1/p85 were assessed in liver. Furthermore, the protein level of α1 Na+/K+-ATPase in plasma membrane fractions, and protein levels of IRS-1, PI3K-p85, -p110, RhoA, ROCK1, ROCK2, ERK1/2, AMPKα, ERα, and ERß in liver lysates were assessed. The expression of hepatic α1 Na+/K+-ATPase mRNA was also analyzed by qRT-PCR. The results show that HF-fed female rats exhibited an increase in hepatic ERK1/2 (p < 0.05) and AMPKα (p < 0.05) phosphorylation levels, unchanged level of Na+/K+-ATPase α1 mRNA, decreased level of Na+/K+-ATPase activity (p < 0.05), and decreased α1 Na+/K+-ATPase protein expression (p < 0.01). In liver of HF-fed male rats, results show decreased levels of Na+/K+-ATPase activity (p < 0.01), both protein and mRNA of α1 subunit (p < 0.05), but significant increase in Rho activity (p < 0.05). Our results indicate significant sex differences in α1 Na+/K+-ATPase mRNA expression and activation of ERK1/2, AMPKα, and Rho in the liver. Exploring the sex-specific factors and pathways that promote obesity-related diseases may lead to a better understanding of pathogenesis and discovering new therapeutic targets.

Regulation of Na+/K+-ATPase by Estradiol and IGF-1 in Cardio-Metabolic Diseases.

BACKGROUND: The sodium/potassium- adenosine- triphosphatase (Na+/K+-ATPase) is an important mediator in vasculature tone and contractility, and its abnormal regulation has been implicated in many diseases such as obesity, insulin resistance, diabetes, and hypertension. Decreased Na+/K+-ATPase abundance and its altered isoform expression induce cardiomyocytes death and cardiac dysfunction, possibly leading to the development of myocardial dilation and heart failure. Therefore, the regulation of Na+/K+-ATPase activity/expression could be important in treatment and possible prevention of cardio-metabolic diseases. A number of hormones and environmental factors regulate the function of Na+/K+-ATPase in response to changing cellular requirements. Estradiol and insulin like growth factor-1 (IGF-1) are among potent hormones that positively regulate Na+/K+- ATPase activity or de novo synthesis of α - and ß - subunits. Both estradiol and IGF-1 have a huge therapeutic potential in treatment of vasculopathy in cardio-metabolic diseases. METHODS: We searched the MEDLINE and PUBMED databases for all English and non-English articles with an English abstract from April 1978 to May 2016. The main data search terms were: Na+/K+-ATPase; estradiol and Na+/K+-ATPase; estradiol, Na+/K+-ATPase and CVS; estradiol, Na+/K+-ATPase and CVD; estradiol, Na+/K+- ATPase and obesity; estradiol, Na+/K+-ATPase and diabetes; estradiol, Na+/K+-ATPase and hypertension; IGF-1; IGF-1 and Na+/K+-ATPase; IGF-1, Na+/K+-ATPase and CVS; IGF-1, Na+/K+-ATPase and CVD; IGF-1, Na+/K+- ATPase and obesity; IGF-1, Na+/K+-ATPase and diabetes; IGF-1, Na+/K+-ATPase and hypertension. RESULTS: The present review discusses the latest data from animal and human studies which focus on the effects of estradiol and IGF-1 on Na+/K+-ATPase regulation in physiological and pathophysiological conditions in cardiovascular system. CONCLUSION: Understanding the molecular mechanisms of estradiol and IGF-1 action on Na+/K+-ATPase in humans, may help resolving outstanding issues and developing new strategies for the protection and treatment of cardiovascular diseases.

Nitric Oxide as a Marker for Levo-Thyroxine Therapy in Subclinical Hypothyroid Patients.

Subclinical hypothyroidism (SH) is characterized by a mildly elevated concentration of thyroid stimulating hormone (TSH) despite free thyroxine (FT4) and triiodothyronine (FT3) levels within the reference range. Numerous studies revealed SH to be an independent risk factor for cardiovascular disease (CVD), including atherosclerosis, congestive heart failure, coronary heart disease, ischemic heart disease and the associated mortality. The relationship between SH and CVD is well documented, but the molecular mechanism underlying this correlation remain unknown. Endothelial dysfunction has been recognized as an initial step leading to CVD in patients with SH. Changes in lipid profile, inflammation and/or oxidative stress contribute to the endothelial dysfunction in SH. Moreover, the progression of SH is characterized by significantly decreased nitrite and nitrate levels. Recent animal and clinical studies discussed in this review suggest that nitric oxide (NO) levels could be a reliable biomarker for cardiovascular risk in SH. Understanding the regulation of NO production by thyroid hormone may provide novel and useful knowledge regarding how endothelial dysfunction in SH is linked with CVD and help us to uncover new treatments for SH. We suggest that serum NO level may be an indicator for the introduction and dosage of levothyroxine (LT4) replacement therapy in SH patients. Future studies should focus on understanding the molecular mechanisms underlying the effects of NO in physiological as well as in pathophysiological conditions such as hypothyroidism and their clinical relevance.

Benefits of L-Arginine on Cardiovascular System.

The amino acid, L-Arginine (L-Arg) plays an important role in the cardiovascular system. Data from the literature show that L-Arg is the only substrate for the production of nitric oxide (NO), from which L-Arg develops its effects on the cardiovascular system. As a free radical, NO is synthesized in all mammalian cells by L-Arg with the activity of NO synthase (NOS). In states of hypertension, diabetes, hypercholesterolemia and vascular inflammation a disorder occurs in the metabolic pathway of the synthesis of NO from L-Arg which all together bring alterations of blood vessels. Experimental results obtained on animals, as well as clinical studies show that L-Arg has an effect on thrombocytes, on the process of coagulation and on the fibrolytic system. This mini review represents a summary of the latest scientific animal and human studies related to L-Arg and its mechanisms of actions with a focus on the role of L-Arg via NO pathway in cardiovascular disorders. Moreover, here we present data from recent animal and clinical studies suggesting that L-Arg could be one of the possible therapeutic molecules for improving the treatment of different cardiovascular disorders.