Plasma NOx concentrations in glucose intolerance and type 2 diabetes. A case-control study in a Vietnamese population.

AIM: The Vietnamese develop type 2 diabetes (T2D) and metabolic syndrome (MS) at a lower BMI than other ethnicities. Thus, biomarkers that identify subjects at an increased risk of T2D independently of obesity are being sought. Recent studies show that circulating NO metabolites (NOx) are increased in T2D. We investigated whether plasma NOx levels predict insulin resistance and glucose intolerance before the development of T2D, independently of obesity. METHODS: The current study was derived from a population-based study in HCMC, Vietnam, which was designed to investigate the prevalence of MS and T2D in a population aged 30-69 years. Four hundred and twenty-two subjects were recruited from the study and were stratified into 4 age- and gender-matched groups according to a glucose tolerance test {normal glucose tolerance (NGT), impaired fasting glucose (IFG), impaired glucose tolerance (IGT) and T2D}. RESULTS: Plasma NOx concentrations were significantly increased in T2D but not in IFG or IGT compared with NGT. Multiregression analysis showed that plasma NOx levels were inversely correlated with BMI in T2D whereas no association was found between plasma NOx levels and BMI in non-diabetic subjects. Moreover, there was no correlation between plasma NOx levels and homeostasis model assessment-insulin resistance (HOMA-IR) in both diabetic and non-diabetic subjects. CONCLUSION: Plasma NOx levels did not predict glucose intolerance or insulin resistance before the development of T2D and the increase in plasma NOx levels in T2D was not caused by adiposity. Thus, plasma NOx is not a useful marker for the prediction of high-risk subjects for T2D among Vietnamese.

Alpha-glucosidase inhibitory and antioxidant activities of Vietnamese edible plants and their relationships with polyphenol contents.

The prevention and treatment of non-communicable diseases by using the beneficial biological effects of polyphenolic plants have attracted increasing interest from nutritional scientists. The a-glucosidase inhibitory and antioxidant activities of aqueous and methanolic extracts from 28 common Vietnamese edible plants, comprising 4 groups (plants used for making drinks, edible wild vegetables, herbs, and dark green vegetables), were investigated in vitro. The polyphenol contents of these extracts were determined by the Folin-Ciocalteu method and calculated as catechin equivalents. The extracts from plants used for making drinks showed the highest activities for both a-glucosidase inhibition and as antioxidants, followed by edible wild vegetables, herbs, and dark green vegetables. Positive relationships among alpha-glucosidase inhibitory activities, antioxidant activities and polyphenol contents of these 28 edible plants were found in both aqueous and methanolic extracts. Four new promising materials that are similar to or better than guava leaf extract, including Syzygium zeylanicum, Cleistocalyx operculatus, Horsfieldia amygdalina and Careya arborea demonstrated high alpha-glucosidase inhibitory activity (93, 76, 68 and 67%, respectively) at the final concentration of 0.8 mg lyophilized material/mL solution and antioxidant activity (85, 87, 78 and 80%, respectively) at the final concentration of 30 pg lyophilized material/mL solution. These four edible plants contained significantly high polyphenol contents (equivalent to 251.7, 146.6, 136.6 and 168.6 mg of catechin/g dry weight, respectively). Thus, these four materials might be possible new sources of a-glucosidase inhibition and antioxidants suitable for use as functional foods in the future.

Inhibition of tumor growth and angiogenesis by water extract of Gac fruit (Momordica cochinchinensis Spreng).

The antitumor activity of the crude water extract from Gac fruit (Momordica cochinchinensis) was investigated in vivo and in vitro. A water extract prepared from 0.75 and 0.25 mg dry weight of Gac fruit per gram body weight was given daily to Balb/c mice (n=15/group). The water extract inhibited the growth of the colon 26-20 adenocarcinoma cell line, transplanted in Balb/c mice, reducing wet tumor weight by 23.6%. Histological and immunohistochemical results indicated that Gac water extract reduced the density of blood vessels around the carcinoma. The water extract also produced a marked suppression of cell proliferation in colon 26-20 and HepG2 cells. Cell cycle analysis demonstrated a significant accumulation of cells in the S phase by water extract. Immunoblotting showed that cyclin A, Cdk2, p27waf1/Kip1 were down-regulated, whereas the protein level of p21waf1/Cip1 was not decreased. Treatment of colon 26-20 cells with Gac extract induced necrosis rather than apoptosis. The antitumor component was confirmed as a protein with molecular weight of 35 kDa, retained in the water-soluble high molecular weight fraction. Thus, the bioactive antitumor compound in Gac extract is a protein, which is distinct from lycopene, another compound in Gac fruit with potential antitumor activity.