Protection from vascular risk in diabetic hypertension

Current Research of Phytochemical, Medicinal and Non-Medicinal Uses of Uncaria gambir Roxb.: A Review

Uncaria gambir Roxb. is a plant from Southeast Asia and is widely used as an alternative medicine with various applications. This plant has been widely used in traditional medicine. This paper aims to provide information on U. gambir, a summary of data on phytochemicals and on medical and nonmedical activities. Phytochemical studies reveal biologically active constituents such as flavonoids, phenolics, and alkaloids. Various studies have shown that extracts and compounds obtained from U. gambir have medical uses for their antioxidant, antibacterial, anti-helminthic, anticancer, antifungal, anti-inflammatory, anti-hyperglycemic, anti-hyperuricemic, anti-lipid peroxidation, antihyperlipidemic and other properties. In addition, this extract has other uses, such as adsorbent for dyes and metal ions, as well as corrosion inhibition. Thus, U. gambir, which is commonly used in traditional medicine, is a potential plant for many therapeutic applications and prospects for drug development as well as other applications such as adsorbent and corrosion inhibition.

Regulation of insulin resistance by targeting the insulin-like growth factor 1 receptor with microRNA-122-5p in hepatic cells

Insulin resistance (IR) is a common etiology of type 2 diabetes (T2D) defined by a state of decreased reactivity to insulin in multiple organs, such as the liver. This study aims to investigate how microRNA-122-5p (miR-122) regulates the hepatic IR in vitro. We first found that the miR-122 level was upregulated in the liver of rats fed with a high-fat diet and injected with streptozotocin (T2D rats), while the expression level of insulin-like growth factor 1 receptor (IGF-1R), a potential target of miR-122, was downregulated in the diabetic liver. In vitro, glucosamine-induced IR was introduced in HepG2 hepatic cells, and the levels of miR-122 and IGF-1R were further assessed. An increase of miR-122 level and a decrease of IGF-IR level were observed in IR hepatic cells, which was the same as that in the diabetic liver. Results of the luciferase reporter assay validated IGF-1R as a direct target of miR-122. Moreover, in IR HepG2 cells, antagonizing miR-122 with its specific inhibitor enhanced glucose uptake and suppressed the expression of glucose 6-phosphatase and phosphoenolpyruvate carboxykinase, two key enzymes in regulating gluconeogenesis. Such alterations induced by the miR-122 inhibitor in IR hepatic cells were impaired when IGF-1R was simultaneously knocked down. In addition, the PI3K/Akt pathway was deactivated in IR cells, and then reactivated with miR-122 inhibitor transfection. In conclusion, our study demonstrates that miR-122 is able to regulate IR in hepatic cells by targeting IGF-1R.

Structure-Activity Relationships ofN-Cinnamoyl and Hydroxycinnamoyl Amides onα-Glucosidase Inhibition

Currently, there is an increasing interest towardsα-glucosidase inhibition of various diseases including diabetes mellitus type 2, cancer, HIV, and B- and C-type viral hepatitis. Cinnamic acid derivatives have been shown to be potentially valuable as a new group ofα-glucosidase inhibitors. Therefore, herein, theα-glucosidase inhibitory activity oftrans-N-cinnamoyl and hydroxycinnamoyl amides was studied in vitro. Results revealed that the tested hydroxycinnamoyl amides (1–16) inhibiteda-glucosidase with IC50s ranging between 0.76 and 355.1 μg/ml. Compounds1,2,5,6,9,14, and15showed significant inhibition of yeastα-glucosidase, being even more potent ones than the used positive inhibitor acarbose (IC50=2.50±0.21 μg/ml).

Polyopes lancifolia Extract, a Potent α-Glucosidase Inhibitor, Alleviates Postprandial Hyperglycemia in Diabetic Mice

This study was designed to investigate the inhibitory effects of Polyopes lancifolia extract (PLE) on α-glucosidase activity, α-amylase activitiy, and postprandial hyperglycemia in streptozotocin (STZ)-induced diabetic mice. The results of this study revealed a marked inhibitory effect of PLE on α-glucosidase and α-amylase activities. The IC₅₀s of PLE against α-glucosidase and α-amylase were 0.20 mg/mL and 0.35 mg/mL, respectively. PLE was a more effective inhibitor of α-glucosidase and α-amylase activities than acarbose, the positive control. The postprandial blood glucose levels of STZ-induced diabetic mice were significantly lower in the PLE treated group than in the control group. Moreover, PLE administration was associated with a decreased area under the curve for the glucose response in diabetic mice. These results indicate that PLE may be a potent inhibitor of α-glucosidase and α-amylase activities and may suppress postprandial hyperglycemia.

Effect of Polyopes lancifolia Extract on Oxidative Stress in Human Umbilical Vein Endothelial Cells Induced by High Glucose

The protective effect of Polyopes lancifolia extract on high glucose-induced oxidative stress was investigated using human umbilical vein endothelial cells (HUVECs). High concentration of glucose (30 mM) treatment induced HUVECs cell death, but Polyopes lancifolia extract, at concentrations of 25, 50, and 100 μg/mL, protected cells from high glucose-induced damage. Furthermore, thiobarbituric acid reactive substances, intracellular reactive oxygen species, and nitric oxide levels increased by high glucose treatment were effectively decreased by treatment with Polyopes lancifolia extract in a dose-dependent manner. Also, Polyopes lancifolia extract treatment reduced the overexpressions of inducible nitric oxide synthase, cyclooxygenase-2, and nuclear factor-kappa B proteins activation that was induced by high glucose in HUVECs. These results indicate that Polyopes lancifolia extract is a potential therapeutic material that will reduce the damage caused by high glucose-induced-oxidative stress associated with diabetes.

Hypoglycemic Effect of Padina arborescens Extract in Streptozotocin-induced Diabetic Mice

This study investigated the hypoglycemic effect of the Padina arborescens extract in STZ-induced diabetic mice. Freeze-dried Padina arborescens were extracted with 80% methanol and concentrated for use in this study. The hypoglycemic effect was determined by inhibitory activities against α-glucosidase and α-amylase as well as the alleviation of postprandial blood glucose level. Padina arborescens extracts showed higher inhibitory activities than acarbose, a positive control against α-glucosidase and α-amylase. The IC₅₀ values of Padina arborescens extracts against α-glucosidase and α-amylase were 0.26 and 0.23 mg/mL, respectively, which evidenced as more effective than observed with acarbose. The increase of postprandial blood glucose levels were significantly suppressed in the Padina arborescens extract administered group than the control group in the streptozotocin induced diabetic mice. Furthermore, the area under the curve (AUC) was significantly lowered via Padina arborescens extract administration in diabetic mice (p < 0.05). These results indicated that the Padina arborescens extract might be used as an inhibitor of α-glucosidase and α-amylase and delay absorption of dietary carbohydrates.

Triterpene acids isolated from Lagerstroemia speciosa leaves as alpha-glucosidase inhibitors

The potential antidiabetic activity of ethyl acetate extract of the leaves of Lagerstroemia speciosa (LSL) was investigated by alpha-amylase and alpha-glucosidase inhibition assay. Six pentacyclic triterpenes (oleanolic acid, arjunolic acid, asiatic acid, maslinic acid, corosolic acid and 23-hydroxyursolic acid) were isolated from LSL. Their structures were determined by spectroscopic analysis and their alpha-glycosidase and alpha-amylase inhibitory activities were investigated. They exhibited no or weak inhibitory activity against alpha-amylase and middle alpha-glucosidase inhibitory activities. Corosolic acid, which shows best bioactivity against alpha-glucosidase (IC(50) = 3.53 microg/mL), contributes most to the alpha-glucosidase inhibitory activity of EtOAc extract. The kinetics of inhibition of corosolic acid was also discussed. Results from this study might provide the scientific evidence for LSL for the treatment of diabetes in traditional medicine.

Antidiabetic effect of an active fraction extracted from dragon's blood (Dracaena Cochinchinensis)

The active fraction extracted from dragon's blood displayed an inhibitory effect on alpha-glucosidase activity with an IC50 of 0.152 microg/mL, which is nearly half of the crude material. Its inhibition on alpha-glucosidase was noncompetitive. In addition, when this fraction was orally administered to mice dosed with Acarbose (20 mg/kg), the active fraction (100, 300, 500 mg/kg) significantly suppressed increase of blood glucose levels after sucrose loading in a dose-dependent manner. These results suggest that this extract from dragon's blood exerts an anti-diabetic effect by suppressing intestinal carbohydrate absorption and thereby reducing the postprandial increase of blood glucose.

Neurovascular coupling is impaired in cerebral microangiopathy--An event-related Stroop study

Small-vessel disease or cerebral microangiopathy is a common finding in elderly people leading finally to subcortical ischemic vascular dementia. Because cerebral microangiopathy impairs vascular reactivity and affects mainly the frontal lobes, we hypothesized that brain activation decreases during an event-related color-word matching Stroop task. 12 patients suffering from cerebral microangiopathy were compared with 12 age-matched controls. As an imaging method we applied functional near-infrared spectroscopy, because it is particularly sensitive to the microvasculature. The Stroop task led to activations in the lateral prefrontal cortex. Generally, the amplitude of the hemodynamic response was reduced in patients in tight correlation with behavioral slowing during the Stroop task and with neuropsychological deficits, namely attentional and executive dysfunction. Interestingly, patients showed an early deoxygenation of blood right after stimulation onset, and a delay of the hemodynamic response. Whereas the amplitude of the hemodynamic response is reduced in the frontal lobes also with normal aging, data suggest that impairments of neurovascular coupling are specific for cerebral microangiopathy. In summary, our findings indicate frontal dysfunction and impairments of neurovascular coupling in cerebral microangiopathy.

Spontaneous slow hemodynamic oscillations are impaired in cerebral microangiopathy

Small-vessel disease or cerebral microangiopathy (CMA) is a common finding in elderly people. It is related to a variety of vascular risk factors and may finally lead to subcortical ischemic vascular dementia. Because vessel stiffness is increased, we hypothesized that slow spontaneous oscillations are reduced in cerebral hemodynamics. Accordingly, we examined spontaneous oscillations in the visual cortex of 13 patients suffering from CMA, and compared them with 14 age-matched controls. As an imaging method we applied functional near-infrared spectroscopy, because it is particularly sensitive to the microvasculature. Spontaneous low-frequency oscillations (LFOs) (0.07 to 0.12 Hz) were specifically impaired in CMA in contrast to spontaneous very-low-frequency oscillations (0.01 to 0.05 Hz), which remained unaltered. Vascular reagibility was reduced during visual stimulation. Interestingly, changes were tightly related to neuropsychological deficits, namely executive dysfunction. Vascular alterations had to be attributed mainly to the vascular risk factor arterial hypertension. Further, results suggest that the impairments might be, at least partly, reversed by medical treatment such as angiotensin-converting enzyme inhibitors/angiotensin II receptor blockers. Results indicate that functional near-infrared spectroscopy may detect changes in the microvasculature due to CMA, namely an impairment of spontaneous LFOs, and of vascular reagibility. Hence, CMA accelerates microvascular changes due to aging, leading to impairments of autoregulation.

Inhibitory effect of pine extract on alpha-glucosidase activity and postprandial hyperglycemia

OBJECTIVE

This study investigated the inhibitory effect of pine bark extract (PBE) and needle extract on carbohydrate-hydrolyzing enzymes and the hypoglycemic effect in diabetic mice (Lep(ob) [ob/ob]).

METHODS

Pine bark and needle were dried and then placed in ethanol, and the extracts were assayed for the measurement of inhibition mode of PBE against alpha-amylase (EC 3.2.1.1) and alpha-glucosidase (EC 3.2.1.20). We also investigated the effect of long-term treatment with extracts on levels of postprandial blood glucose, body weight, food efficiency ratio, and gene expression of glucose transporter-4 in quadriceps muscle in diabetic mice (Lep(ob) [ob/ob]).

RESULTS

The PBE showed competitive inhibition against salivary alpha-amylase and the combination of non-competitive and uncompetitive inhibition against yeast alpha-glucosidase. In animal experiments, PBE effectively suppressed the increase of postprandial blood glucose level by delaying absorption of diet, and body weights of the group that received PBE were significantly lower than that in the group administered 0.5% carboxylmethyl cellulose (control) 21 d after administration.

CONCLUSIONS

PBE can be used to suppress postprandial hyperglycemia of diabetic patients. It also can be applied for control of obesity by decreasing the food efficiency ratio, especially carbohydrates.

Inhibitory effect of aqueous extract from the gall of Rhus chinensis on alpha-glucosidase activity and postprandial blood glucose

The present study examined the inhibitory effect of aqueous extract from the gall of Rhus chinensis (AEGRC) on alpha-glucosidase activity, an enzyme responsible for digestion of carbohydrate to monosaccharides in the process of intestinal absorption. AEGRC inhibited Bacillus alpha-glucosidase acitvity with an IC(50) of 0.9 micro g/ml. Its inhibition on alpha-glucosidase was determined to be noncompetitive and reversible when the enzyme-substrate mixture was simultaneously treated with AEGRC as an inhibitor. In addition, when it was orally administered to rats with sucrose (2g/kg), AEGRC (250-1000mg/kg) significantly suppressed the increase of blood glucose levels after sucrose loading in a dose dependent manner. These results suggest that AEGRC might exert anti-diabetic effect by suppressing carbohydrate absorption from intestine, and thereby reducing the postprandial increase of blood glucose.

Normal perivascular sensory dilator nerve function in arteries of Zucker diabetic fatty rats

BACKGROUND

Type II diabetes in humans is associated with pathology of both the cardiovascular and peripheral sensory nervous systems. Because abnormal vasodilator responses have been reported in animals of type II diabetes and perivascular sensory nerves are a source of vasodilator substances, we tested the hypothesis that sensory nerve-dependent relaxation is abnormal in arteries of the Zucker diabetic fatty (ZDF) rat model of type II diabetes.

METHODS

The ZDF rats and genetic controls were studied at 26 weeks of age. Tail-cuff systolic blood pressure (BP) was measured, serum was obtained for chemical determinations, and mesenteric branch arteries were isolated for wire myograph analysis and confocal-based measurement of calcitonin gene-related peptide (CGRP) positive nerve density.

RESULTS

No differences in BP were detected. Serum glucose, triglycerides, and cholesterol were significantly elevated in ZDF. Sensory nerve-dependent vasodilation was assessed by measuring relaxation of phenylephrine preconstricted arterial segments to cumulative addition of divalent calcium ion (Ca2+) or capsaicin. Neither Ca(2+)-nor capsaicin-induced relaxation were different in ZDF versus control (maximal ZDF response to Ca2+ = 64% +/- 2% v 59% +/- 4%; ED50 for Ca2+ = 3.7 +/- 0.5 mmol/L v 3.2 +/- 0.5 mmol/L; n = 5, P = not significant [NS]; maximal ZDF response to capsaicin = 68% +/- 9% v 74% +/- 4%; ZDF ED50 = 3.8 +/- 0.5 nmol/L v 9.8 +/- 7 nmol/L; n = 5, P = NS). In contrast, the maximal relaxation response to acetylcholine was impaired in ZDF (maximal ZDF response = 83% +/- 5% v 94% +/- 2%, n = 4, P = .039; ED50 for acetylcholine = 8.1 +/- 2.9 nmol/L for ZDF v 33.5 +/- 18.2; n = 4 per group, P = .086). The CGRP positive nerve density was not different between groups.

CONCLUSIONS

Blood pressure, perivascular sensory nerve CGRP content, and dilator function is normal in the ZDF model of type II diabetes, whereas endothelium-dependent relaxation is impaired.