[Effect of high selenium on insulin signaling pathway PI3K-AKT-mTOR in L02 cells].

OBJECTIVE: To observe the effect of high selenium on insulin signaling pathway PI3K-AKT-mTOR in L02 cells. METHODS: One group of L02 cell was treated with different concentrations of selenomethionine(SeMet, 0.001, 0.0025, 0.005, 0.0075, 0.01, 0.025, 0.05, 0.075 and 0.1µmol/L) for 48 h, then cultured with serum-free medium for 4 h and stimulated with 1 µmol/L insulin for 15 min. The insulin signaling pathway(PI3K-AKT-mTOR) was detected by WB. Another group of L02 cell was treated with the same concentrations of SeMet as above for 48 h. The cell supernatant and lysates were collected for the analysis of SELENOP and GPX1, respectively by WB. RESULTS: The expressions of P-AKT-(Ser-473), P-AKT-(Thr-308), PI3K and mTOR in L02 cells under high-Se were decreased with the increase of SeMet concentration. The expressions of GPX1 and SELENOP were enhanced with the increase of SeMet. CONCLUSION: The insulin signaling pathway, PI3K-AKT-mTOR, was damaged in L02 cell under high-Se stress.

[Study of high selenium interfering with glucose and one-carbon metabolism in hepatocytes in vitro].

OBJECTIVE: To investigate the effects of high selenium environment on the expression of selenoproteins and enzymes related to glucose and one-carbon metabolism in normal human hepatocytes. METHODS: Ten different concentrations of selenomethionine(SeMet, 0, 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 5 and 10 µmol/L) was added into the normal human hepatocyts and incubated for 48 hours. The expressions of selenoprotein(GPX1 and SELENOP1) and metabolic enzymes(PHGDH, SHMT1, MTHFR and MS) were analyzed by Western blot. RESULTS: When the concentration of SeMet was 0-10 µmol/L, the expression trend of selenoprotein(GPX1 and SELENOP1) is similar, which first increases and then decreases. There is a slight difference between the inflection points of GPX1 and SELENOP1, which are respectively 0.5 µmol/L and 0.1 µmol/L. The expression trend of serine de novo synthesis pathway key enzymes(PHGDH) and folate cycle metabolizing enzymes(SHMT1, MTHFR and MS) is similar to that of selenoproteins, which also increases first and then decreases, but the inflection points are different, which are respectively 0.1 µmol/L(PHGDH and SHMT1) and 0.01 µmol/L(MTHFR and MS). CONCLUSION: Under the high selenium environment, the glycolytic bypass-serine de novo synthesis pathway is activated to synthesize endogenous serine due to the insufficient intracellular serine supply, causing abnormal glucose metabolism, which is an important extension to the hypothesis of the molecular mechanism of high selenium causing IR.

[Intervention study to inhibit the glucose metabolic remodeling in hepatocytes induced by high-selenium in vitro].

OBJECTIVE: To observe the effect of exogenous serine or glycine on the synthesis of selenoprotein and endogenous serine and the expression of metabolic enzymes in hepatocytes cultured with high-selenium in vitro and its dose-response relationship. METHODS: The experiment was divided into two parts, namely a inhibition experiment and a dose-response experiment, using L02 cells as the intervention target. In the inhibition experiment, the blank control group, high-Se(SeMet) group, serine intervention group and high-Se+serine intervention group were set up. Both SeMet and serine were given at a level of 0.05 µmol/L, and the blank control group was given the same volumes of saline. In the dose-response experiment, the concentration of SeMet was 0.05 µmol/L, and the intervention concentration gradients of serine or glycine were 0, 0.05, 0.1, 0.5, 1, 5, 10, 50, 100 and 500 µmol/L. The expression of phosphoglycerate dehydrogenase(PHGDH)、serine hydroxymethyltransferase 1(SHMT1)、methylenetetrahydrofolate reductase(MTHFR)、selenoprotein P(SELENOP) and glutathione peroxidase 1(GPX1)was detected by Western Blot(WB). RESULTS: (1)In the inhibition experiment, compared with the blank control group, the expression of selenium proteins(GPX1 and SELENOP) in L02 cells of the other three groups were significantly increased(P<0.05). Compared with the high expression of PHGDH in L02 cells of high-Se group, the expressions of PHGDH, SHMT1 and MTHFR in high-Se + serine group were significantly decreased(P<0.05). (2) In the dose-response experiment, the expression of PHGDH enzyme in L02 cells gradually decreased with the increase of the concentration of exogenous serine or glycine, showing an obvious dose-dependent effect. In contrast, none of the other metabolic enzymes(SHMT1 and MTHFR) showed similar trends in protein expression. CONCLUSION: The upregulated expression of PHGDH, the key enzyme in the de novo synthesis pathway of serine in hepatocytes cultured with high-selenium can be inhibited feedback by exogenous serine or endogenous serine transformed from exogenous glycine directly.

A Sustainable Wholesome Foodstuff; Health Effects and Potential Dietotherapy Applications of Yacon.

A sustainable food supply is an ever-growing public and planetary health concern influenced by food culture, food practices, and dietary patterns. Globally, the consumption of plant foods that offer physiological and biochemical benefits is increasing. In recent years, products made from yacon (Smallanthus sonchifolius) tubers and leaves, e.g., in the form of syrup, powder, and herbal tea, have steadily emerged with scientific evidence to validate their possible health claims. Yacon was introduced to New Zealand in 1966, and its products can now be produced on a commercial scale. This paper reviews literature published mainly in the last 10 years concerning the health-related properties of yacon as a wholesome foodstuff and its bioactive components, e.g., fructooligosaccharides. Literature was sourced from Web of Science, PubMed, EBSCO Health, and Google Scholar up to June 2019. The potential markets for yacon in the field of food technology and new dietotherapy applications are discussed. Furthermore, the unique features of New Zealand-produced yacon syrup are introduced as a case study. The paper explores the scientific foundation in response to the growing public interest in why and how to use yacon.

[Effects of biotin on blood glucose regulation in type 2 diabetes rat model].

OBJECTIVE: To explore the effect of biotin on blood glucose regulation in rats and its possible mechanism. METHODS: According to initial body weight and blood glucose, we randomly divided the 90 Wistar rats into 5 groups: the normal control group, model group, biotin low-dose group (0. 6mg/kg BW), biotin medium-dose group (3. 0 mg/kg BW) and biotin high-dose group (6. 0 mg/kg BW). After 2 months, the rats with HFS feed were injected with STZ (25 mg/kg BW) to manufacture diabetic rat model. After the OGTT experiment at 10th week, the blood glucose, insulin, liver/muscle glycogen and other biochemical indexes were detected. The GCK, PCK1 mRNA expression were measured with RT-PCR method. RESULTS: Biotin has a certain improvement on postprandial glucose in diabetic rats. Compared with the model group, the AUC and the 30min postprandial blood glucose of biotin high-dose group were significantly decreased (P <0. 05). Biotin can affect some key enzyme gene in glucose metabolism, such as GCK, PCK1. CONCLUSION: The possible mechanism of the decreasing biotin blood sugar in diabetic rats may by promoting the synthesis of glycogenand reducing gluconeogenesis.

Suppression effects of betaine-enriched spinach on hyperhomocysteinemia induced by guanidinoacetic acid and choline deficiency in rats.

Betaine is an important natural component of rich food sources, especially spinach. Rats were fed diets with betaine or spinach powder at the same level of betaine for 10 days to investigate the dose-dependent effects of spinach powder supplementation on hyperhomocysteinemia induced by guanidinoacetic acid (GAA) addition and choline deprivation. The GAA-induced hyperhomocysteinemia in rats fed 25% casein diet (25 C) was significantly suppressed by supplementation with betaine or spinach, and it was completely suppressed by taking 11.0% spinach supplementation. The choline deprivation-induced enhancement of plasma homocysteine concentration in rats fed 25% soybean protein diet (25S) was markedly suppressed by 3.82% spinach. Supplementation with betaine or spinach partially prevented the effects of GAA on hepatic concentrations of methionine metabolites. The decrease in activity of betaine-homocysteine S-methyltransferase (BHMT) and cystathionine ß-synthase (CBS) in GAA-induced hyperhomocysteinemia was recovered by supplementation with betaine or spinach. Supplementation with betaine or spinach did not affect BHMT activity, whereas it partially restored CBS activity in choline-deprived 25S. The results indicated that betaine or spinach could completely suppress the hyperhomocysteinemia induced by choline deficiency resulting from stimulating the homocysteine removal by both remethylation and cystathionine formation.

[Effect on the quality of corn oil in different cooking temperature and time].

OBJECTIVE: To research the effect on fatty acid and oxidation products of corn oil under different temperature and time. METHODS: Corn oil was heated in 140 degrees C, 200 degrees C, 240 degrees C, after 60 s-300 s, then detected the fatty acid, POV and AV. RESULTS: Corn oil was heated in 240 degrees C, after 138 s, the corn oil started to fire, the contains of SFA rised from 14.18 g/100 g to 20.29 g/100 g, the contains of MUFA rised from 28. 30 g/100 g to 33. 33 g/100 g, the contains of PUFA reduced from 53. 13 g/100 g to 28.98 g/100 g, and tFA, POV, AV, TOV arrived to the highest value, they were 11.29 g/100 g, 108.9, 17.12 mmol/kg, 177.37 mmol/kg respectively. CONCLUSION: As the cooking time and the cooking temperature increased, the MUFA, tFA and the TV of the corn oil increased, on the contrary the PUFA reduced.