Effect of extrusion parameters on the interaction between rice starch and glutelin in the preparation of reconstituted rice.

Reconstituted rice produced by extrusion has been attracted attention due to nutritional fortification and convenient production. Nevertheless, how to achieve desirable qualities and physicochemical properties of reconstituted rice nearly to natural rice by regulating extrusion process parameters is difficult. Herein, rice starch/glutelin mixture as raw material of reconstituted rice was extruded at varying extrusion conditions. Specific mechanical energy (SME) and sectional expansion index (SEI) dropped with rise in density (R2 = 0.9117 and 0.8207). Solubility was enhanced with increase in product temperature (R2 = 0.9085), color darkened and shifted to reddish and yellowish as extrusion temperature increased (R2 = 0.8577). These trends were well fitted by sigmoid models. Furthermore, SME enhanced hydrophobic and electrostatic interactions between rice starch and glutelin and caused the reduction in crystallinity and thermal stability, promoting the formation of a bi-continuous matrix of protein aggregates with rice starch. The obtained results can be applied to guide the production of reconstituted rice with desirable qualities.

Insights into the interaction mechanism of glutelin and rice starch during extrusion processing: The role of specific mechanical energy.

Extruded glutelin/rice starch composites were prepared using twin-screw extrusion at various specific mechanical energies (SME), and the interaction mechanism of glutelin and rice starch was investigated at the molecular level. The results indicated that the structure of glutelin was destroyed, hydrophobic interactions and hydrogen bonds between rice starch and glutelin were formed and enhanced as the SME increased, and new hydrogen bonds were formed at the carbonyl (δ- and γ-carbons of glutelin) and C-1 of Tyr. Molecular docking studies confirmed that SME promoted the simultaneous occurrence of the Millard reaction and non-covalent reaction between glutelin and small molecular sugars produced by starch degradation, providing information on binding sites. Additionally, scanning electron microscopy (SEM) revealed dense and uniform flake-like structures induced by these binding interactions. Overall, insights into the interaction mechanism of rice starch and glutelin provide theoretical references for generating reconstituted rice products using extrusion processing.

[Characteristics of CO2 Flux in a Mature Apple (Malus demestica) Orchard Ecosystem on the Loess Plateau].

Apples (Malus demestica) in the Loess Plateau region are grown in the largest apple orchards in the world and China, playing an important role in the improvement of the ecological environment. However, there is little research on the scale of the ecological system of the apple orchard in the Loess Plateau region. In this study, the CO2 flux of a mature apple orchard in the Loess Plateau region was observed using an eddy covariance technique in the Shannxi Province. Based on the observation data sets observed from January 2016 to December 2016, a quantitative analysis of the apple orchard net ecosystem exchange (NEE), ecosystem respiration (Reco), total ecosystem primary productivity (GPP) changes at different time scales, changes in main meteorological factors, the effects of soil temperature (Ts) and air temperature (Ta) at different levels, and PAR on NEE were discussed. The results showed that during the study period, the apple orchard ecosystem NEE monthly totals were positive (as a carbon source) in the non-growing season in December, January, February and March, were negative (a carbon sink) in the growing season from April to November, and functioned as a strong carbon sink year round. The maximum peak NEE (absolute value) monthly average daily change appeared in August[-17.08 µmol ·(m2 ·s)-1], and the smallest peak appeared in November[-4.47 µmol ·(m2 ·s)-1] during the growing season. The NEE monthly average daily change value during the non-growing season is very weak, though the change is not obvious. GPP, Reco, and NEE maximum daily total values were 11.12, 5.04, and -7.34 g ·(m2 ·d)-1, respectively. GPP, Reco, and NEE maximum monthly total values were 238.97, 105.38, and -144.44 g ·(m2 ·month)-1, respectively, as GPP and NEE maintained high cumulative values that were relatively stable from May through August. The annual GPP, Reco, and NEE were 1223.2, 525.2, and -698.0 g ·(m2 ·a)-1. The observations show that the mature apple orchard ecosystem in the Chinese Loess Plateau has a relatively high carbon sequestration capacity. Nighttime ecosystem respiration Reco.n was positively correlated with the soil temperature and air temperature at different levels, and the correlation coefficients were Ts-5 cm > Ts-10 cm > Ta-4 m > Ta-8 m, The photosynthetic active radiation (PAR) can explain more than 80% of the daytime NEE changes.

[Expression of aquaporin 7 in perirenal adipose tissue of Otsuka Long-Evans Tokushima Fatty diabetic rats].

OBJECTIVE: To observe perirenal adipose tissue aquaporin 7 (AQP7) mRNA and protein expression in the spontaneous type 2 diabetes animal model Otsuka Long-Evans Tokushima Fatty (OLETF) rats in different stages of diabetes and explore the role of AQP7 in obesity development and diabetes. METHODS: OLETF rats (n=30) were studied, with the same strains of non-diabetic Long-Evans Tokushima Otsuka (LETO) rats (n=18) used as age-matched normal controls. After 8 weeks (baseline), 6 rats in each of the two groups were sacrificed. Then the rest of the OLETF rats were divided into untreated group (OLETF group, n=12) and metformin hydrochloride treated group (OLETF/M group, n=12). At the age of 8 , 18 and 28 weeks, their body weights were obtained, and biochemical items were measured including serum triglyceride, cholesterol, glycerol, glucose and insulin levels with oral glucose tolerance test (OGTT), and the perirenal adipose tissue (PAT) was obtained to measure the AQP7 mRNA expression (by Real-time PCR) and AQP7 protein relative expression (by Western blotting). RESULTS: (1) OLETF group rats developed diabetes at week 18 [60 min glucose: (25.67 ± 6.78) mmol/L, 120 min glucose: (16.19 ± 2.98)mmol/L]. The body weights and biochemical items including serum triglyceride, serum cholesterol, glucose and insulin levels of OGTT, were increased with the rats' age. The serum glycerol level was increased at week 18, but decreased at week 28. The serum glycerol level at weeks 8, 18, 28 were(52.61 ± 11.80)µmol/L, (156.03 ± 39.56)µmol/L and (130.84 ± 25.46)µmol/L , respectively. (2) OLETF/M group rats developed diabetes at week 18 [60 min glucose: (18.64 ± 6.67)mmol/L, 120 min glucose: (14.13 ± 5.21)mmol/L], but the glucose level at week 28 [60 min glucose: (11.72 ± 3.06)mmol/L, 120 min glucose: (12.42 ± 2.30)mmol/L] became lower than that at week 18. The body weights and Biochemical items including serum triglyceride, serum cholesterol, serum glycerol and insulin levels of OGTT of the OLETF/M group rats, were of no significant difference from those of the OLETF group rats. The two groups were compared: in serum triglyceride [at week 18: (0.88 ± 0.14) vs. (1.09±0.44)mmol/L;at week 28 (1.06 ± 0.51) vs. (2.20 ± 1.51)mmol/L];serum cholesterol [at week 18 (2.18±0.14) vs. (2.30 ± 0.21)mmol/L,at week 28 (1.90 ± 0.19) vs. (2.36 ± 0.35) mmol/L,P<0.05];serum glycerol [at week 18 (77.28 ± .06) vs. (156.03 ± 39.56)µmol/L,P<0.05,at week 28 (58.44 ± 14.03) vs. (130.84 ± 25.46)µmol/L, P<0.01]. (3) Expression of perirenal adipose tissue AQP7 mRNA and protein levels: with rats age and obesity developed, compared with the same group rats at 8 week, the AQP7 mRNA expression of OLETF group increased 67.5% at 18 week and 41.7% at 28 week respectively, the AQP7 protein expression of OLETF group increased 21.9% at 18 week and 8.9% at 28 week respectively, the AQP7 mRNA expression of OLETF/M group increased 25% at 18 week and 8.3% at 28 week respectively, the AQP7 protein expression of OLETF/M group increased 14.6% at 18 week and 1.6% at 28 week respectively. AQP7 mRNA and protein expression were increased at 18 weeks and decreased at 28 weeks not only in OLETF groups but also in OLETF/M groups as it were consistent with serum glycerol. In the OLETF/M group, the expression of AQP7 mRNA and protein levels were lower than those in age-matched OLETF groups, though there was no statistic difference between the two groups. In the OLETF/M group, the expression of AQP7 mRNA and protein levels were lower than those in the age-matched OLETF group, though there was no statistic difference between the two groups. CONCLUSION: AQP7 of visceral adipose tissue may participate in glucose and lipid metabolism associated with diabetes and obesity. Metformin can improve OLETF rat glucose and lipid, but not contribute to AQP7 mRNA and AQP7 protein expression of perirenal adipose tissue.

[Characteristics of lipolysis in epididymal adipose tissues of OLETF rats with spontaneous type 2 diabetic mellitus].

OBJECTIVE: To observe the characteristics of lipolysis in epididymal adipose tissues of spontaneously type 2 diabetic animal model-Otsuka Long-Evans Tokushima Fatty (OLETF) rats-in different stages of disease and explore the possible molecular mechanism. METHODS: We adopted OLETF rats as subjects, and Long-Evans Tokushima Otsuka (LETO) rats were used as age-matched normal controls. Oral glucose tolerance tests (OGTT) and fasting serum insulin levels were performed respectively at the ages of 8, 18 and 28 weeks. The animals were sacrificed and epididymal fat pads were obtained in corresponding weeks. Glycerol released in the culture medium was determined by use of a colorimetric assay and served as an index of lipolysis. The protein levels of hormone-sensitive lipase (HSL), adipose triglyceride lipase (ATGL), perilipin, extracellular signal-regulated kinase (ERK) and its phosphorylated form (p-ERK) in epididymal fat were examined by immunoblotting. RESULTS: (1) Compared with the age-matched normal control, the ratio of epididymal adipose tissues to total body weight was heavier at the end of 18 weeks [(1.80±0.09)% vs (1.23±0.07)%, P<0.01] and 28 weeks [(2.51±0.12)% vs (1.56±0.08)%, P<0.01]; In OGTT 1 h plasma glucose levels of OLETF rats were higher at the age of 18 weeks [(26.00±3.09) vs (10.50±0.82) mmol/L, P<0.01] and 28 weeks [(23.15±0.55) vs (9.72±0.17) mmol/L, P<0.01] and 2 h plasma glucose levels were higher at the age of 18 weeks [(16.19±1.22) vs (7.47±0.35) mmol/L, P<0.01] and 28 weeks [(17.96±2.00) vs (9.24±0.47) mmol/L, P<0.01]. The level of fasting insulin was higher in OLETF rats than that of LETO rats only at the age of 28 weeks [(68.17±13.35)×10(-3) vs (19.61±0.20)×10(-3) U/L, P<0.01]. (2) Glycerol released from epididymal adipose tissues of OLETF rats was increased by 34.7% compared with LETO rats at the age of 18 weeks [(213.0±12.5) vs (158.2±11.7) nmol/(g×h), P<0.05], whereas at the age of 28 weeks, it was reduced by 33.5% [(210.2±37.8) vs (315.9±25.0) nmol/(g×h), P<0.05]. (3) In OLETF rats, HSL protein level was not altered at the age of 18 weeks, but down-regulated at the age of 28 weeks. Nevertheless, the expressions of ATGL and perilipin were decreased, while p-ERK protein expression was increased at the age of both 18 and 28 weeks. CONCLUSION: With the development of disease in spontaneously type 2 diabetic animal model of OLETF rats, the lipolysis in epididymal adipose tissue presented a pattern of initial increase followed by subsequent reduction. The earlier augment may contribute to the higher expression of p-ERK and the lower content of perilipin, however the later decrease may result from the reduction of both HSL and ATGL level.