Effects of angiotensin II type 1 receptor blocker and adiponectin on adipocyte dysfunction in stroke-prone spontaneously hypertensive rats

Benefits of Valsartan and Amlodipine in Lipolysis through PU.1 Inhibition in Fructose-Induced Adiposity

High fructose intake has been implicated in obesity and metabolic syndrome, which are related to increased cardiovascular mortality. However, few studies have experimentally examined the role of renin–angiotensin system blockers and calcium channel blockers (CCB) in obesity. We investigated the effects of valsartan (an angiotensin II receptor blocker) and amlodipine (a CCB) on lipolysis through the potential mechanism of PU.1 inhibition. We observed that high fructose concentrations significantly increased adipose size and triglyceride, monoacylglycerol lipase, adipose triglyceride lipase, and stearoyl-CoA desaturase-1 (SCD1), activating transcription factor 3 and PU.1 levels in adipocytes in vitro. Subsequently, PU.1 inhibitor treatment was able to reduce triglyceride, SCD1, and PU.1 levels. In addition, elevated levels of triglyceride and PU.1, stimulated by a high fructose concentration, decreased with valsartan and amlodipine treatment. Overall, these findings suggest that high fructose concentrations cause triacylglycerol storage in adipocytes through PU.1-mediated activation. Furthermore, valsartan and amlodipine treatment reduced triacylglycerol storage in adipocytes by inhibiting PU.1 activation in high fructose concentrations in vitro. Thus, the benefits of valsartan and amlodipine in lipolysis may be through PU.1 inhibition in fructose-induced adiposity, and PU.1 inhibition might have a potential therapeutic role in lipolysis in fructose-induced obesity.

Angiotensin II Inhibits Insulin Receptor Signaling in Adipose Cells

Angiotensin II (Ang II) is a critical regulator of insulin signaling in the cardiovascular system and metabolic tissues. However, in adipose cells, the regulatory role of Ang II on insulin actions remains to be elucidated. The effect of Ang II on insulin-induced insulin receptor (IR) phosphorylation, Akt activation, and glucose uptake was examined in 3T3-L1 adipocytes. In these cells, Ang II specifically inhibited insulin-stimulated IR and insulin receptor substrate-1 (IRS-1) tyrosine-phosphorylation, Akt activation, and glucose uptake in a time-dependent manner. These inhibitory actions were associated with increased phosphorylation of the IR at serine residues. Interestingly, Ang II-induced serine-phosphorylation of IRS was not detected, suggesting that Ang II-induced desensitization begins from IR regulation itself. PKC inhibition by BIM I restored the inhibitory effect of Ang II on insulin actions. We also found that Ang II promoted activation of several PKC isoforms, including PKCα/βI/βII/δ, and its association with the IR, particularly PKCβII, showed the highest interaction. Finally, we also found a similar regulatory effect of Ang II in isolated adipocytes, where insulin-induced Akt phosphorylation was inhibited by Ang II, an effect that was prevented by PKC inhibitors. These results suggest that Ang II may lead to insulin resistance through PKC activation in adipocytes.

Countering adipose tissue dysfunction could underlie the superiority of telmisartan in the treatment of obesity-related hypertension

BACKGROUND

The prevalence of hypertension and obesity has increased significantly in recent decades. Hypertension and obesity often coexist, and both are associated with increased cardiovascular mortality. Obese hypertensive patients usually require special anti-hypertensive treatment strategy due to the increased risk of treatment resistance. Molecules that can target both obesity and hypertension underlying pathologies should get more attention. Herein, we evaluated the therapeutic effects of telmisartan, with special interest in visceral adipose tissue dysfunction, in obesity-related hypertension rat model.

METHODS

Thirty male Wistar rats weighing 150-200 g were equally divided into: 1-Control group (fed normal laboratory diet for 24 weeks), 2-Diet-induced obesity group (DIO, fed high fat diet for 24 weeks), and 3-Diet-induced obesity treated with telmisartan group (DIO + Tel, fed high fat diet and received telmisartan for 24 weeks). At the end of the study, anthropometrical parameters were evaluated. Systolic blood pressure and heart rate were measured. Blood samples were collected for the measurement of serum lipids, adipokines, cardiac, renal, inflammatory, and oxidative stress biomarkers. Kidneys were removed and used for histopathological studies, and visceral adipose tissue was utilized for histopathological, immunohistochemical and RT-PCR studies.

RESULTS

High fat diet resulted in obesity-related changes in anthropometrical parameters, elevation of blood pressure, increase in heart rate, higher serum levels of cardiac, inflammatory and kidney function biomarkers, with altered serum lipids, adipokines and oxidative stress markers. Morphological changes (H&E and PAS-stained sections) were noticed in kidneys and visceral adipose tissue. Immunohistochemistry and RT-PCR studies confirmed adipose tissue dysfunction and over-expression of inflammatory and oxidative stress proteins. Telmisartan countered obesity-induced alterations in cardiovascular, renal, and adipose tissue functions.

CONCLUSION

Adipose tissue dysfunction could be the core pathophysiology of obesity-related hypertension. Besides its anti-hypertensive effect, telmisartan had profound actions on visceral adipose tissue structure and function. Attention should be given to polymodal molecules targeting adipose tissue-related disorders.

Anti-aging properties of Dendrobium nobile Lindl.: From molecular mechanisms to potential treatments

ETHNOPHARMACOLOGICAL RELEVANCE

Dendrobium Nobile Lindl. (DNL) is one of the central herbs in traditional Chinese medicine which mainly distributes in Guizhou, Yunnan, Guangxi and other sub-tropical areas south of the Yangtze River. In the past decades, it has been used to treat tumors, hyperglycemia, hyperlipidemia, and diseases of the nervous system that may be caused by aging.

AIM OF THE REVIEW

The purpose of this review is to summarize the anti-aging information of DNL from the molecular mechanism level, including classic theories related to aging, main chemical components, pharmacological research and anti-aging theory based on traditional Chinese medicine theory, for exploring the future development and clinical treatment.

MATERIALS AND METHODS

The information in this paper has been collected from the scientific literature databases including PubMed, Google Scholar, Web of Science, Science Direct, Springer, China National Knowledge Infrastructure, published books, Ph.D. and M.S. dissertations systematically.

RESULTS

In this paper, we have reviewed the several mechanisms underlying the potential effects of DNL on the prevention of aging, including the scavenging of free radicals for oxidation, delaying of DNA impairment, inhibition of apoptosis, and alteration of DNA methylation. Together with the theory of telomeres, this review also has summarized recent research progress in the use of DNL and its traditional efficacy.

CONCLUSIONS

We conclude that "strengthening Yin and benefiting the spirit", "thickening the intestine and stomach", "lightning the body and prolonging the life-span", and delaying aging, are key effects of DNL that can be used to combat age-related diseases (ARDs) such as Alzheimer's disease, hyperlipidemia, and diabetes. This review provides a reference for future study of ARDs and the clinical application of DNL.

Adiponectin and Its Isoforms in Pathophysiology

Adiponectin circulates in blood in multiple isoforms. High molecular weight (HMW) adiponectin is thought to be most biologically active and promotes glucose uptake, insulin sensitivity, and fatty acid oxidation. In obesity, adiponectin isoform formation is disrupted, leading to an inverse association between metabolic disease and HMW and total adiponectin. Adiponectin isoforms also function as acute-phase reactants influencing inflammation in acute and chronic disease. Interestingly, adiponectin and mortality have a U-shaped association. Unfortunately, data concerning adiponectin and its pathophysiologic function conflict. This is predominantly due to difficulties in adequate measurement of adiponectin isoforms and lack of a gold standard. In this review we provide a general overview of the formation and function of adiponectin and its isoforms under physiologic conditions. We highlight the ways adiponectin isoform formation is disrupted in obesity and its ensuing pathologic conditions. Furthermore, we will elaborate on the role of adiponectin isoforms as inflammatory proteins with respect to cardiac and kidney disease and discuss the association of adiponectin with mortality. Finally, we will provide a historical perspective on the measurement of adiponectin isoforms, current limitations, and future challenges.

Fermented rice bran supplementation mitigates metabolic syndrome in stroke-prone spontaneously hypertensive rats

BACKGROUND

Previous study shown that enzyme treated-rice bran effectively improved hypertension and glucose intolerance in stroke-prone spontaneously hypertensive rat (SHRSP). However, dual fermentation of rice bran's efficacy against metabolic syndrome in SHRSP is still unknown.

METHODS

Fermented rice bran (FRB) was prepared by dual fermentation of rice bran using fungi and lactic acid bacteria. The effect of FRB on metabolic syndrome in stroke-prone spontaneously hypertensive rats (SHRSP) was investigated by single and chronic supplementation.

RESULTS

Dual fermentation of rice bran enriches the functional value of rice bran. Single-dose oral administration of FRB (2 g/kg body weight) reduced systolic blood pressure; however, chronic supplementation with 5 % FRB (4 weeks) significantly reduced both systolic and diastolic blood pressure. FRB supplementation improved leptin impairment and increased serum adiponectin levels and angiotensin-converting enzyme inhibitory activity. Furthermore, FRB supplementation improved glucose tolerance and insulin sensitivity as well as serum insulin levels. Lipid profiles were also improved by the regulation of 5' adenosine monophosphate-activated protein kinase activation. Moreover, supplementation with FRB reduced the expressions of hepatic transcription factors such as liver X receptor alpha, sterol regulatory element-binding protein 1c, and carbohydrate-responsive element-binding protein alpha, as well as their target genes. In conclusion, dietary supplementation with FRB may lower hypertension and alleviate metabolic syndrome.

CONCLUSION

Metabolic syndrome was better alleviated with FRB supplementation. We therefore suggest FRB as an alternative medicine to reduce the risks of lifestyle-related diseases.

Candesartan attenuates ischemic brain edema and protects the blood-brain barrier integrity from ischemia/reperfusion injury in rats

Background: Angiotensin II (Ang II) has an important role on cerebral microcirculation; however, its direct roles in terms of ischemic brain edema need to be clarified. This study evaluated the role of central Ang II by using candesartan, as an AT1 receptor blocker, in the brain edema formation and blood-brain barrier (BBB) disruption caused by ischemia/reperfusion (I/R) injuries in rat. Methods: Rats were exposed to 60-min middle cerebral artery (MCA) occlusion. Vehicle and non-hypotensive doses of candesartan (0.1 mg/kg) were administered one hour before ischemia. Neurological dysfunction scoring was evaluated following 24 h of reperfusion. Animals were then decapitated under deep anesthesia for the assessments of cerebral infarct size, edema formation, and BBB permeability. Results: The outcomes of 24 h reperfusion after 60-min MCA occlusion were severe neurological disability, massive BBB disruption (Evans blue extravasation = 12.5 ± 1.94 µg/g tissue), 4.02% edema, and cerebral infarction (317 ± 21 mm³). Candesartan at a dose of 0.1 mg/kg, without changing arterial blood pressure, improved neurological dysfunction scoring together with significant reductions in BBB disruption (54.9%), edema (59.2%), and cerebral infarction (54.9%). Conclusions: Inactivation of central AT1 receptors, if not accompanied with arterial hypotension, protected cerebral micro-vasculatures from damaging effects of acute stroke.

The impact of age-related dysregulation of the angiotensin system on mitochondrial redox balance

Aging is associated with the accumulation of various deleterious changes in cells. According to the free radical and mitochondrial theory of aging, mitochondria initiate most of the deleterious changes in aging and govern life span. The failure of mitochondrial reduction-oxidation (redox) homeostasis and the formation of excessive free radicals are tightly linked to dysregulation in the Renin Angiotensin System (RAS). A main rate-controlling step in RAS is renin, an enzyme that hydrolyzes angiotensinogen to generate angiotensin I. Angiotensin I is further converted to Angiotensin II (Ang II) by angiotensin-converting enzyme (ACE). Ang II binds with equal affinity to two main angiotensin receptors—type 1 (AT₁R) and type 2 (AT₂R). The binding of Ang II to AT₁R activates NADPH oxidase, which leads to increased generation of cytoplasmic reactive oxygen species (ROS). This Ang II-AT₁R–NADPH-ROS signal triggers the opening of mitochondrial K_ATP channels and mitochondrial ROS production in a positive feedback loop. Furthermore, RAS has been implicated in the decrease of many of ROS scavenging enzymes, thereby leading to detrimental levels of free radicals in the cell. AT₂R is less understood, but evidence supports an anti-oxidative and mitochondria-protective function for AT₂R. The overlap between age related changes in RAS and mitochondria, and the consequences of this overlap on age-related diseases are quite complex. RAS dysregulation has been implicated in many pathological conditions due to its contribution to mitochondrial dysfunction. Decreased age-related, renal and cardiac mitochondrial dysfunction was seen in patients treated with angiotensin receptor blockers. The aim of this review is to: (a) report the most recent information elucidating the role of RAS in mitochondrial redox hemostasis and (b) discuss the effect of age-related activation of RAS on generation of free radicals.

Blockade of Central Angiotensin II AT1 Receptor Protects the Brain from Ischemia/Reperfusion Injury in Normotensive Rats

BACKGROUND

Stroke is the third leading cause of invalidism and death in industrialized countries. There are conflicting reports about the effects of Angiotensin II on ischemia-reperfusion brain injuries and most data have come from chronic hypertensive rats. In this study, hypotensive and non-hypotensive doses of candesartan were used to investigate the effects of angiotensin II AT1 receptor blockade by transient focal cerebral ischemia in normotensive rats.

METHODS

In this experimental study, 48 male Sprague-Dawley rats were randomly divided into four groups (n=12). Sham group, the control ischemic group, and two ischemic groups received candesartan at doses of 0.1 or 0.5 mg/kg at one hour before ischemia. Transient focal cerebral ischemia was induced by 60 minutes occlusion of the middle cerebral artery, followed by 24 h reperfusion. The neurological deficit score was evaluated at the end of the reperfusion period. The total cortical and striatal infarct volumes were determined using triphenyltetrazolium chloride staining technique. Tissue swelling was calculated for the investigation of ischemic brain edema formation.

RESULTS

In comparison with the control ischemic group, AT1 receptor blockade with both doses of candesartan (0.1 or 0.5 mg/kg) significantly improved neurological deficit and lowered cortical and striatal infarct sizes. In addition, pretreatment with candesartan significantly reduced ischemia induced tissue swelling.

CONCLUSION

Angiotensin II by stimulating AT1 receptors, participates in ischemia-reperfusion injuries and edema formation. AT1 receptor blockade with candesartan decreased ischemic brain injury and edema and improved neurological outcome.