RESUMEN
BACKGROUND: Oestrogen deficiency leads to metabolic disturbances such as insulin resistance and impairment of adipose tissue or lipid metabolism. Marantodes pumilum (Blume) Kuntze (Primulaceae) is believed to have phytoestrogenic properties and is claimed to have beneficial effects in the treatment of diabetes mellitus (DM), but the mechanism behind its phytoestrogenic effects on estrogen-deficient diabetic condition have not been fully examined. PURPOSE: The present study investigated the effects of oral treatment with M. pumilum var. alata (MPA) extracts on the estrogen receptor, metabolic characteristics and insulin signaling pathway in pancreas and liver of ovariectomised nicotidamide streptozotocin-induced diabetes in female rats. MATERIALS AND METHODS: Ovariectomised diabetic (OVXS) Sprague-Dawley rats were orally administered with either aqueous leaf extract and ethanol (50%) stem-root extract of MPA (50 or 100â¯mg/kg) respectively for 28 days. Metabolic parameters were evaluated by measuring fasting blood glucose, serum insulin, oral glucose and insulin tolerance test. Distribution and expression level of insulin, oxidative stress and inflammatory marker in the pancreatic islets and liver were evaluated by immunohistochemistry and western blot, respectively. RESULTS: Oral treatment with aqueous leaf and ethanol (50%) stem-root extracts of MPA (100â¯mg/kg) significantly reversed the elevated fasting blood glucose, impaired glucose and insulin tolerance. The protein expression of insulin, glucose transporter (GLUT-2 and GLUT-4) increased in the pancreatic islets and liver. Furthermore, marked improvement in the tissue morphology following treatment with MPA was observed. Similarly, the western blots analysis denotes improved insulin signaling in the liver and decreased reactive oxygen species producing enzymes, inflammatory and pro-apoptotic molecules with MPA treatment. CONCLUSIONS: Taken together, this work demonstrate that 100â¯mg/kg of aqueous leaf extract and ethanol (50%) stem-root extract of MPA improves ß-cell function and insulin signaling in postmenopausal diabetes through attenuation of oxidative stress and partially mediated by oestrogen receptor stimulation.
Asunto(s)
Diabetes Mellitus Experimental/prevención & control , Células Secretoras de Insulina/efectos de los fármacos , Insulina/metabolismo , Extractos Vegetales/farmacología , Primulaceae/química , Animales , Glucemia/metabolismo , Diabetes Mellitus Experimental/tratamiento farmacológico , Femenino , Transportador de Glucosa de Tipo 2/metabolismo , Transportador de Glucosa de Tipo 4/metabolismo , Células Secretoras de Insulina/fisiología , Hígado/efectos de los fármacos , Hígado/metabolismo , Estrés Oxidativo/efectos de los fármacos , Páncreas/efectos de los fármacos , Páncreas/metabolismo , Extractos Vegetales/administración & dosificación , Posmenopausia , Ratas Sprague-Dawley , Receptores de Estrógenos/metabolismo , Transducción de Señal/efectos de los fármacosRESUMEN
ETHNOPHARMACOLOGICAL RELEVANCE: The leaves extract of Apocynum venetum (AVLE), also known as "luobuma", have long been used in traditional Chinese medicine to treat hypertension and depression in parts of China and it has been shown to possess anti-oxidant and anti-lipid peroxidation effects. AVLE (10 µg/ml) has been reported to have a long-lasting endothelium-dependent relaxant effect and this effect has been proposed to be due to its nitric oxide(NO)-releasing and superoxide anion(SOA)-scavenging properties. AIM OF THE STUDY: The present study seeks to evaluate the differential actions of AVLE extract between Ang II- and PE-induced vasoconstriction and the involvement of superoxide anions. MATERIALS AND METHODS: Single dose of Ang II (100 nM and 1 nM)- or PE (0.1 µM)-induced contraction were assessed in both endothelium-intact and -denuded aortic rings after pre-incubation of AVLE (10 µg/ml) for 15 min. The experiment was repeated in either the presence of NO synthase inhibitor, L-NAME (300 µM) or selective AT(1) receptor inhibitor, losartan (0.1 nM), or superoxide scavenger, tiron (1 mM) or a combination of L-NAME and AVLE. Superoxide production was measured by using enhanced-chemiluminescence assay. RESULTS: We have demonstrated that AVLE (10 µg/ml) effectively suppressed the Ang II-induced contraction (100 nM and 1 nM) of both endothelium-intact and -denuded rat aortic rings. In endothelium-intact rings, L-NAME, reversed AVLE-induced inhibition of Ang II-contraction. PE-induced contraction was significantly inhibited by AVLE in endothelium-intact rings, but not in endothelium-denuded rings. The inhibition by AVLE of PE-induced contraction was totally abolished in the presence of L-NAME. Ang II-induced SOA production concentration dependently with the optimal effect seen at 100 nM of Ang II, and AVLE (0.3, 1, 10 µg/ml) reduced this effect. SOA production in Ang II-stimulated rings was significantly higher than unstimulated control rings, while PE did not stimulate SOA production at all. SOA formation in the presence of Ang II was also inhibited in the presence of SOD (superoxide scavenger), DPI (NADPH inhibitor) and losartan (specific AT(1) receptor antagonist). CONCLUSION: These results collectively suggest that the ability of AVLE in inhibiting Ang II-induced contraction via its SOA scavenging properties and nitric oxide releasing effect may account for its usage as an antihypertensive treatment in traditional folk medicine.
Asunto(s)
Antihipertensivos/farmacología , Aorta Torácica/efectos de los fármacos , Apocynum , Extractos Vegetales/farmacología , Vasoconstricción/efectos de los fármacos , Vasodilatadores/farmacología , Angiotensina II , Animales , Aorta Torácica/fisiología , Técnicas In Vitro , Masculino , Medicina Tradicional Tibetana , Óxido Nítrico/fisiología , Hojas de la Planta , Ratas , Ratas Sprague-Dawley , Superóxidos/metabolismo , Vasoconstricción/fisiologíaRESUMEN
Angiotensin II is known to act primarily on the angiotensin AT(1) receptors to mediate its physiological and pathological actions. Des-aspartate-angiotensin I (DAA-I) is a bioactive angiotensin peptide and have been shown to have contrasting vascular actions to angiotensin II. Previous work in this laboratory has demonstrated an overwhelming vasodepressor modulation on angiotensin II-induced vasoconstriction by DAA-I. The present study investigated the involvement of the AT(1) receptor in the actions of DAA-I on angiotensin II-induced vascular actions in the renal vasculature of normotensive Wistar-Kyoto rats (WKY), spontaneously hypertensive rats (SHR) and streptozotocin (STZ)-induced diabetic rats. The findings revealed that the angiotensin receptor in rat kidney homogenate was mainly of the AT(1) subtype. The AT(1) receptor density was significantly higher in the kidney of the SHR. The increase in AT(1) receptor density was also confirmed by RT-PCR and Western blot analysis. In contrast, AT(1) receptor density was significantly reduced in the kidney of the streptozotocin-induced diabetic rat. Perfusion with 10(-9)M DAA-I reduced the AT(1) receptor density in the kidneys of WKY and SHR rats suggesting that the previously observed vasodepressor modulation of the nonapeptide could be due to down-regulation or internalization of AT(1) receptors. RT-PCR and Western blot analysis showed no significant changes in the content of AT(1) receptor mRNA and protein. This supports the suggestion that DAA-I causes internalization of AT(1) receptors. In the streptozotocin-induced diabetic rat, no significant changes in renal AT(1) receptor density and expression were seen when its kidneys were similarly perfused with DAA-I.
Asunto(s)
Angiotensina I/análogos & derivados , Riñón , Receptor de Angiotensina Tipo 1/metabolismo , Angiotensina I/genética , Angiotensina I/metabolismo , Angiotensina I/farmacología , Angiotensina II/química , Angiotensina II/genética , Angiotensina II/metabolismo , Bloqueadores del Receptor Tipo 1 de Angiotensina II/metabolismo , Animales , Diabetes Mellitus Experimental , Riñón/irrigación sanguínea , Riñón/efectos de los fármacos , Losartán/metabolismo , Masculino , Ratas , Ratas Endogámicas SHR , Ratas Endogámicas WKY , Receptor de Angiotensina Tipo 1/genéticaRESUMEN
The trace elements copper, zinc, and selenium are important immune modulators and essential cofactors of the antioxidant enzymes. In the present study, the proliferative effect of human peripheral mononuclear cells (PBMCs) that have been exposed to copper, zinc, and selenium and the corresponding activities of antioxidant enzymes, namely superoxide dismutase (SOD), glutathione peroxidase (GPx), and catalase, were determined. Zinc and copper stimulated the PBMC proliferation in a dose-dependent manner within the dose range 25-200 micromol/L. SOD and GPx activities in PBMCs exposed to zinc were inhibited, whereas catalase activity was unaffected. All the three antioxidant enzymes in the cells exposed to copper were inhibited. Selenium exerted more potent inhibition of the cell proliferation while causing stimulation of the antioxidant enzymes at the lowest dose (25 micromol/L) than at the highest dose (200 micromol/L) tested. A significant negative correlation was observed between proliferation and antioxidant enzyme (SOD and GPx) activities in trace-element-exposed PBMC. The present findings substantiate the importance of trace elements as immune modulators and the involvement of enzymatic antioxidant system in the immune cell regulation.
Asunto(s)
Antioxidantes/farmacología , Leucocitos Mononucleares/citología , Leucocitos Mononucleares/efectos de los fármacos , Oligoelementos/metabolismo , Antioxidantes/metabolismo , Catalasa/metabolismo , Proliferación Celular , Cobre/metabolismo , Glutatión Peroxidasa/metabolismo , Humanos , Selenio/farmacología , Superóxido Dismutasa/metabolismo , Temperatura , Zinc/metabolismo , Sulfato de Zinc/farmacologíaRESUMEN
The present study investigated the action of des-aspartate-angiotensin I (DAA-I) on the pressor action of angiotensin II in the renal and mesenteric vasculature of WKY, SHR and streptozotocin (STZ)-induced diabetic rats. Angiotensin II-induced a dose-dependent pressor response in the renal vasculature. Compared to the WKY, the pressor response was enhanced in the SHR and reduced in the STZ-induced diabetic rat. DAA-I attenuated the angiotensin II pressor action in renal vasculature of WKY and SHR. The attenuation was observed for DAA-I concentration as low as 10(-18) M and was more prominent in SHR. However, the ability of DAA-I to reduce angiotensin II response was lost in the STZ-induced diabetic kidney. Instead, enhancement of angiotensin II pressor response was seen at the lower doses of the octapeptide. The effect of DAA-I was not inhibited by PD123319, an AT2 receptor antagonist, and indomethacin, a cyclo-oxygenase inhibitor in both WKY and SHR, indicating that its action was not mediated by angiotensin AT2 receptor and prostaglandins. The pressor responses to angiotensin II in mesenteric vascular bed were also dose-dependent but smaller in magnitude compared to the renal vasculature. The responses were significantly smaller in SHR but no significant difference was observed between STZ-induced diabetic and WKY rat. Similarly, PD123319 and indomethacin had no effect on the action of DAA-I. The findings reiterate a regulatory role for DAA-I in vascular bed of the kidney and mesentery. By being active at circulating level, DAA-I subserves a physiological role. This function appears to be present in animals with diseased state of hypertension and diabetes. It is likely that DAA-I functions are modified to accommodate the ongoing vascular remodeling.
Asunto(s)
Angiotensina Amida/metabolismo , Angiotensina II/administración & dosificación , Angiotensina I/administración & dosificación , Diabetes Mellitus Experimental/metabolismo , Circulación Renal/efectos de los fármacos , Circulación Esplácnica/efectos de los fármacos , Vasoconstrictores/administración & dosificación , Angiotensina I/análogos & derivados , Animales , Presión Sanguínea/efectos de los fármacos , Vasos Sanguíneos/metabolismo , Riñón/irrigación sanguínea , Riñón/metabolismo , Masculino , Ratas , Ratas Endogámicas SHR , Ratas Endogámicas WKY , Circulación Renal/fisiología , Circulación Esplácnica/fisiologíaRESUMEN
An earlier study showed that des-aspartate-angiotensin I (DAA-I) attenuated the pressor action of angiotensin III in aortic rings of the spontaneously hypertensive rat (SHR) but not the normotensive Wistar Kyoto (WKY) rat. The present study investigated similar properties of DAA-I in isolated perfused kidneys and mesenteric beds of WKY and SHR. In the renal vasculature, angiotensin III induced a dose-dependent pressor response, which was more marked in the SHR than WKY in terms of significant greater magnitude of response and lower threshold. DAA-I attenuated the pressor action of angiotensin III in both the WKY and SHR. The attenuation in SHR was much more marked, occurring at doses as low as 10(-15) M DAA-I, while effective attenuation was only seen with 10(-9) M in WKY. The effects of DAA-I was not inhibited by PD123319 and indomethacin, indicating that its action was not mediated by angiotensin AT2 receptors and prostaglandins. However, the direct pressor action of angiotensin III in the SHR but not the WKY was attenuated by indomethacin suggesting that this notable difference could be due to known decreased response of renal vasculature to vasodilator prostaglandins in the SHR. Pressor responses to angiotensin III in the mesenteric vascular bed was also dose dependent, but smaller in magnitude compared to the renal response. The responses in the SHR, though generally smaller, were not significantly different from those of the WKY. This trend is in line with the similar observations with angiotensin III and II by other investigators. In terms of the effect of DAA-I, indomethacin and PD123319 on angiotensin III action, similar patterns to those of the renal vasculature were observed. This reaffirms that in the perfused kidney and mesenteric bed, where the majority of the vessels are contractile, femtomolar concentrations of DAA-I attenuates the pressor action of angiotensin III. The attenuation is not indomethacin sensitive and does not involve the angiotensin AT2 receptor. The findings suggest that DAA-I possesses protective vascular actions and is involved in the pathophysiology of hypertension.