Obesity alters the peripheral circadian clock in the aorta and microcirculation

OBJECTIVE

Perturbation of daily rhythm increases cardiovascular risk. The aim of this study was to determine whether obesity alters circadian gene expression and microvascular function in lean mice and obese (db/db) mice.

METHODS

Mice were subjected to normal LD or DD to alter circadian rhythm. Metabolic parameters and microvascular vasoreactivity were evaluated. Array studies were conducted in the am and pm cycles to assess the rhythmicity of the entire genomics. Rhythmic expression of specific clock genes (Bmal1, Clock, Npas2, Per1, Per2, and Cry1), clock output genes (dbp), and vascular relaxation-related genes (eNOS, GTPCH1) were assessed.

RESULTS

Obesity was associated with metabolic dysfunction and impaired endothelial dilation in the microvasculature. Circadian rhythm of gene expression was suppressed 80% in both macro- and microcirculations of obese mice. Circadian disruption with DD increased fasting serum glucose and HbA1c in obese but not lean mice. Endothelium-dependent dilation was attenuated in obese mice and in lean mice subjected to DD. Rhythmic expression of per1 and dbp was depressed in obesity. Expression of eNOS expression was suppressed and GTPCH1 lost rhythmic expression both in obesity and by constant darkness.

CONCLUSION

These results suggest that obesity reduces circadian gene expression in concert with impaired endothelial function. The causal relationship remains to be determined.

Anti-angiogenic actions of the mangosteen polyphenolic xanthone derivative α-mangostin

Retinal neovascularization is a major cause of vision loss in diseases characterized by retinal ischemia and is characterized by the pathological growth of abnormal vessels. Vascular endothelial growth factor (VEGF) is known to play an important role in this process. Oxidative stress has been strongly implicated in up-regulation of VEGF associated with neovascularization in various tissues. Hence, compounds with anti-oxidant actions can prevent neovascularization. α-Mangostin, a component of mangosteen (Garcinia mangostana Linn), has been shown to have an anti-oxidant property in pathological conditions involving angiogenesis such as cancer. However, the effect of α-mangostin on ROS formation and angiogenic function in microvascular endothelial cells has not been studied. Hence, this study demonstrated the anti-angiogenic effects of α-mangostin in relation to ROS formation in bovine retinal endothelial cells (REC). α-Mangostin significantly and dose-dependently reduced formation of ROS in hypoxia-treated REC. α-Mangostin also significantly and dose-dependently suppressed VEGF-induced increases in permeability, proliferation, migration and tube formation in REC and blocked angiogenic sprouting in the ex vivo aortic ring assay. In addition, α-mangostin inhibited VEGF-induced phosphorylation of VEGFR2 and ERK1/2-MAPK. According to our results, α-mangostin reduces oxidative stress and limits VEGF-induced angiogenesis through a process involving abrogation of VEGFR2 and ERK1/2-MAPK activation.

Anti-hyperlipidemic and cardioprotective effects of Ocimum sanctum L. fixed oil in rats fed a high fat diet

Ocimum sanctum (OS) has a lipid-lowering action in both normal and diabetic animals. Because OS leaves are rich in oil, the present study was conducted to explain the anti-hyperlipidemic and organ-protective effect of OS fixed oil in rats fed with a high fat (HF) diet. OS fixed oil was extracted by hexane and the fatty acids composition identified by GC-MS. Four groups of male Wistar rats included a normal control group, a high fat fed-diet (HF) group, a HF group treated with OS fixed oil, and a HF group treated with a reference drug simvastatin. The results show that OS fixed oil contains five kinds of fatty acids, of which alpha-linolenic acid was the major fatty acid. OS fixed oil depressed high serum levels of total cholesterol, triglyceride, LDL-C, and AI, whereas no significant effect on HDL-C was observed. OS fixed oil also suppressed high levels of liver cholesterol and triglyceride with no significant effect on both lipids in feces. In addition, OS fixed oil normalized the high serum levels of LDH and CK-MB but no significant effect on high serum levels of ALT, AST, and ALP was obtained. We conclude that treatment with OS fixed oil during the last three weeks of HF diet feeding decreased the high serum lipid profile and expressed antiartherogenic and cardioprotective actions against hyperlipidemia. The anti-hyperlipidemic action of OS fixed oil was mainly resulted from the suppression of liver lipid synthesis. Linolenic acid and linoleic acid contained in OS fixed oil were possibly responsible for both lipid-lowering and cardiac protective action against hyperlipidemia.

Effects of Kaempferia parviflora Wall. Ex Baker on endothelial dysfunction in streptozotocin-induced diabetic rats

AIM OF THE STUDY

The aim of the present study was to investigate an ethanolic extract of Kaempferia parviflora (KPE) reduces oxidative stress and preserves endothelial function in aortae from diabetic rats.

MATERIALS AND METHODS

Diabetes was induced in Sprague-Dawley rats by streptozotocin (STZ) treatment (55 mg/kg i.v.). Vascular reactivity and superoxide generation were assessed in aortic rings using standard organ bath techniques and lucigenin-enhanced chemiluminescence, respectively.

RESULTS

Eight weeks after STZ treatment blood glucose was elevated compared to citrate treated control rats and there was an increased aortic generation of superoxide anion. In aortic rings acetylcholine-induced relaxation was impaired whereas endothelium-independent relaxation to sodium nitroprusside was unaffected. When aortic rings were acutely exposed to KPE (1, 10 and 100 μg/ml) there was a significant reduction in the detection of superoxide anion and enhanced relaxation to acetylcholine. Two separate groups of rats (control and diabetic) were orally administered daily with KPE (100 mg/kg body weight) for 4 weeks. KPE treatment reduced superoxide generation and increased the nitrite levels in diabetic aortae, and enhanced acetylcholine-induced relaxation. In the presence of N(G)-nitro-L-arginine (L-NNA), the relaxation to acetylcholine in aortic rings of diabetic rats was only partially inhibited, but was totally abolished in aortic rings from the KPE-treated diabetic rats. Indomethacin did not affect relaxation to acetylcholine in aortic rings of any group.

CONCLUSIONS

These results suggest that KPE, acutely in vitro or after 4 weeks administration in vivo, reduces oxidant stress, increases NO bioavailability and preserves endothelium-dependent relaxation in aortae from diabetic rats.

Antioxidant Activity and Lipid-Lowering Effect of Essential Oils Extracted from Ocimum sanctum L. Leaves in Rats Fed with a High Cholesterol Diet

It has been reported that Ocimum sanctum L. (OS) leaves decrease serum lipid profile in normal and diabetic animals. No experimental evidences support the anti-hyperlipidemic and antioxidative actions against hypercholesterolemia. Moreover the identity of the specific chemical ingredients in OS leaves responsible for these pharmacological effects are unknown. Since OS leaves are rich in essential oil (EO). Therefore the present study was conducted to investigate the anti-hyperlipidemic and antioxidative activities of EO extracted from OS leaves in rats fed with high cholesterol (HC) diet. EO was extracted by the hydrodistillation method and the chemical constituents were then identified by Gas Chromatography-Mass Spectrometry. The experiment was performed in Male Wistar rats fed with 2.5 g%(w/w) of cholesterol diet for seven weeks. During the last 3 weeks, rats were daily fed with EO. The results showed that phenyl propanoid compounds including eugenol and methyl eugenol were the major constituents of EO. EO suppressed the high serum lipid profile and atherogenic index as well as serum lactate dehydrogenase and creatine kinase MB subunit without significant effect on high serum levels of aspartate aminotransferase, alanine aminotransferase and alkaline phosphatase in rats fed with HC diet. In addition, EO was found to decrease the high levels of thiobarbituric acid reactive substances (TBARS), glutathione peroxidase (GPx) and superoxide dismutase (SOD) without impacting catalase (CAT) in the cardiac tissue while in the liver, it decreased high level of TBARS without significantly effecting GPx, SOD and CAT. Histopathological results confirmed that EO preserved the myocardial tissue. It can be concluded that EO extracted from OS leaves has lipid-lowering and antioxidative effects that protect the heart against hypercholesterolemia. Eugenol that is contained in EO likely contribute to these pharmacological effects.

Type 1 diabetes and hypercholesterolaemia reveal the contribution of endothelium-derived hyperpolarizing factor to endothelium-dependent relaxation of the rat aorta

1. The present study evaluated the effect of diabetes, hypercholesterolaemia and their combination on the contribution of nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) to relaxation of rat isolated aortic rings and the potential contribution of oxidant stress to the disturbance of endothelial function. 2. Thoracic aortic rings from control, diabetic, hypercholesterolaemic and diabetic plus hypercholesterolaemic rats were suspended in organ baths for tension recording. Generation of superoxide by the aorta was measured using lucigenin-enhanced chemiluminescence. 3. The maximal response to acetylcholine (ACh) was significantly reduced in diabetic or hypercholesterolaemic rats compared with control rats. In rats with diabetes plus hypercholesterolaemia, both the sensitivity and maximal response to ACh was impaired. In control rats, the response to ACh was abolished by the NO synthase inhibitor N(G)-nitro-L-arginine (L-NNA) or inhibition of soluble guanylate cyclase with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ). In contrast, in rats with diabetes, hypercholesterolaemia or both, relaxation to ACh was resistant to inhibition by L-NNA or ODQ, but abolished by additional inhibition of K(Ca) channels with charybdotoxin plus apamin. 4. The generation of superoxide was not significantly enhanced in aortic rings from either diabetic or hypercholesterolaemic rats, but was significantly increased in aortic rings from rats with diabetes plus hypercholesterolaemia. 5. These results suggest that when diabetes and hypercholesterolaemia impair endothelium-dependent relaxation, due to a diminished contribution from NO, a compensatory contribution of EDHF to endothelium-dependent relaxation of the aorta is revealed. The attenuation of NO-mediated relaxation, at least in the presence of both diabetes and hypercholesterolaemia, is associated with enhanced superoxide generation.