Complex characterization and formation mechanism of scallop (Patinopecten yessoensis) protein hydrolysates/κ-carrageenan/konjac gum composite gels.

The combination of κ-Carrageenan (KC) and konjac gum (KGM) were introduced to examine the impact on gelation and microstructural behaviors of scallop male gonads hydrolysates (SMGHs) and the involvement of intermolecular forces. In terms of G' response of SMGHs/KGM/KC, it obviously enhanced by 3.6- and 108.5-fold than controls of KGM/KC and SMGHs/KC at 0.1 Hz, accompanying increasing melting temperatures from 27.9 (KGM/KC) and 30.0 (SMGHs/KC) to 33.7°C (SMGHs/KGM/KC), respectively. Additionally, SMGHs/KGM/KC with decreasing relaxation time T23 and blue shift of hydroxyl group than controls suggested higher water retention capacity and ordered conformation. Moreover, SMGHs/KGM/KC formed compact networks with thick walls as reflected by cryo-SEM and showed rougher surface with more aggregation as reflected by AFM. Furthermore, electrostatic in couple with hydrophobic interactions were dominant interactions, while hydrogen bonds were involved in subordinately in SMGHs/KGM/KC. PRACTICAL APPLICATION: Scallop (Patinopecten yessoensis) male gonads are always discarded during processing despite high-protein content and edibility. In the current research, scallop male gonad hydrolysates (SMGHs) exhibited gelation behavior, which have a potential role in developing marine source protein as a functional food base such as kamaboko gels, can, sausage and spread and even delivery vehicles for bioactive compounds.

Functional properties of gonad protein isolates from three species of sea urchin: a comparative study.

Sea urchin Mesocentrotus nudus, Glyptocidaris crenularis, and Strongylocentrotus intermedius gonad protein isolates (mnGPIs, gcGPIs, and siGPIs) were extracted by isoelectric solubilization/precipitation (ISP) from the defatted gonads, and their functional properties were compared. Sodium dodecyl sulfate polyacrylamide gel electrophoresis results showed the similar protein pattern between each protein isolate and defatted gonad, indicating the high efficiency of ISP processing for protein recovery. Amino acid profileconfirmed that the mnGPIs and siGPIs could be potential sources of essential amino acid in nature. As regard to functional properties, mnGPIs showed higher water- and oil- holding capacities followed bysiGPIs and gcGPIs and all protein isolates presented great foaming property. As for emulsifying activity index (EAI), mnGPIs, gcGPIs, and siGPIs showed the minimum solubility and EAI at pH 5, 3, and 4, respectively, and behaved a pH-dependent manner. The gcGPIs revealed the highest EAI from pH 6 to 8 among the samples. In addition, circular dichroism showed increased content of ß-sheet at the expense of α-helix and ß-turn, suggesting the structure denaturation of the protein isolates. Indeed, no statistical difference was observed between secondary structure of mnGPIs and siGPIs. Moreover, ISP processing increased free sulfhydryl content of sea urchin protein isolates, but no difference was observed among the samples. Furthermore, siGPIs revealed the highest amount of total sulfhydryl and disulfide bonds, whereas both defatted gonads and protein isolates from G. crenularis presented the maximum surface hydrophobicity. These results suggest that gonad protein isolates from three species of sea urchin possess various functionalities and therefore can be potentially applied in food system. PRACTICAL APPLICATION: Sea urchin M. nudus, G. crenularis, and S. intermedius gonads are edible, whereas the functional properties of protein isolates from sea urchin gonad remain unknown. In this case, the extraction and comparison of three species of sea urchin gonad protein isolates will not only confirm functional properties but also screen food ingredients with suitable functions. In this study, functionalities of protein isolates derived from M. nudus, G. crenularis, and S. intermedius gonads would provide potential application in bakery food and meat products or as emulsifier candidates in food system.

Associations of urinary, glomerular, and tubular markers with the development of diabetic kidney disease in type 2 diabetes patients.

OBJECTIVES: To evaluate the associations of urinary markers (eg albumin), glomerular (eg transferrin [TRF], immunoglobulin G [IgG]), and tubular (eg α1-microglobulin [α1-MG], ß2-microglobulin [ß2-MG]) markers with the development of diabetic kidney disease (DKD) in type 2 diabetes patients, as assessed by estimated glomerular filtration rate (eGFR) and albuminuria. MATERIAL AND METHODS: A total of 252 type 2 diabetes patients and 50 nondiabetic controls from Tianjin, China, were selected. Diabetic patients were divided into three groups according to eGFR levels, including groups A, B, and C with eGFR ≥90 (n=94), 60-89 (n=94), and 30-59 (n=64) mL/min/1.73 m2 . Urine levels of glomerular and tubular markers were detected in first morning urine samples, and their associations with eGFR and albuminuria analyzed. RESULTS: Urinary levels of IgG, TRF, and ß2-MG were significantly elevated in diabetic patients with normal eGFR compared with nondiabetic control subjects. Urinary levels of all markers increased per eGFR stratum. All kidney damage markers were significantly associated with eGFR in univariate analysis (standard ß between -0.35 and -0.28; all P<.001). After adjusting for known confounders, only the tubular markers α1-MG (standard ß=-0.25; P=.013) and ß2-MG (standard ß=-0.18; P=.039) retained significant associations with eGFR. All kidney damage markers were significantly associated with albuminuria, independent of age, duration of diabetes, and eGFR (standard ß between 0.45 and 0.86; all P<.001). CONCLUSION: Only the tubular markers α1 -MG and ß2 -MG were associated with eGFR independent of albuminuria, suggesting that they may play an important role in the development of DKD.

A study on the biological reference interval of urinary alpha 1-microglobulin in a group of Chinese people.

OBJECTIVE: The aim of this study was to explore the possible influences of age and gender on urinary Alpha 1-Microglobulin (α1-MG) concentrations and establish specific reference values of urinary α1-MG in a group of healthy adults. METHODS: Two hundred and ninety-nine adults (141 males and 158 females) aged 20-60 were selected and grouped by gender and age. Urinary levels of α1-MG were detected in morning spot-urine samples, and statistical analysis was performed to explore the association between urinary α1-MG and clinical parameters, and the differences between groups were compared. The 95th percentile of distribution was used as the normal upper limit. RESULTS: The value of urinary α1-MG was sex-dependent (P<0.001), the 95th percentile of urinary α1-MG of males was 26.4 mg/L, whereas females was 8.6 mg/L. Whereas urinary α1-microglobulin-to-creatinine ratio (α1-MG/Cr) was both gender-and age-dependent (both P<0.001), and age 30 may be the cut-off point in this study. The 95th percentile of males and females aged 20-30 was 16.9 mg/g, of males aged 31-60 was 19.8 mg/g, of females aged 31-60 was 28.5 mg/g. DISCUSSIONS: The relationship between urinary α1-MG concentrations and gender, age is different from previous studies. It is recommended that hospitals and laboratories should develop their own α1-MG reference intervals based on their experimental conditions.

Second Morning ACR Could Be the Alternative to First Morning ACR to Assess Albuminuria in Elderly Population.

BACKGROUND: Albumin/creatinine ratio (ACR) from a first morning urine is recommended as a early indicator for diabetic nephropathy. However, it is not always feasible to collect the first morning urine for outpatients. We aimed to explore whether ACR from a second morning urine had a good consistency with that from a first morning urine to predict albuminuria in Chinese elderly citizens. METHOD: One hundred and ninety-one elderly citizens (≧60 years old) from Junliangcheng community, Dongli district, Tianjin, China were included. A first and second morning urine was collected from each participants, successfully and detected the urinary albumin and creatinine of each urine sample. Albumin to creatinine ratio from a first morning urine (ACR1) was compared with that from a second morning urine (ACR2), and the ability of ACR1 and ACR2 to predict albuminuria was assessed. RESULT: ACR1 and ACR2 were highly correlated (r = 0.901), especially in male and hypertension group (r = 0.938 and 0.904). The slope and intercept were 0.93 and 0.11 after log-transformed. And there was no statistical difference between values of ACR1 and ACR2 (P = 0.271). Overall, 26.2% participants were detected with albuminuria when judged by ACR1 and 28.3% by ACR2. A good concordance of ACR category (normal or albuminuria) was found between ACR1 and ACR2 (Kappa value = 0.815 in overall; in male and hypertension group were 0.900 and 0.850). CONCLUSION: A second morning urine ACR could be the alternative to a first morning urine ACR for albuminuria detection in elderly population.

Tubular proteinuria is the dominant type of proteinuria in an elderly community population in China.

PURPOSE: To explore the types of proteinuria in the elderly population in China. METHODS: Seven hundred and fourteen elderly people (≥ 60 years old) from Tianjin, China, were selected for the study. The albumin-to-creatinine ratio and α1-microglobulin-to-creatinine ratio from morning urine samples were used as indicators of proteinuria. The prevalence of proteinuria was evaluated and the proportion of three different types of proteinuria (mixed, glomerular, and tubular) was assessed in the subjects by analyzing these indicators. RESULTS: Of the 714 subjects, 29.13 % had elevated ACR and 46.36 % had elevated MCR. The proportion of subjects with either elevated ACR or MCR was 53.78 %. The correlation between MCR and ACR was moderate (r = 0.58, R (2) = 0.34, P < 0.001). Overall, tubular proteinuria was dominant (45.83 %), followed by mixed glomerular and tubular proteinuria (35.68 %), and significantly higher than glomerular proteinuria. A diet high in salt was the independent risk factor for tubular proteinuria; physical activity was the independent risk factor for glomerular proteinuria. The risk of glomerular proteinuria was lower in males than in females, but the risk of tubular proteinuria was higher in males. CONCLUSIONS: The prevalence of tubular proteinuria was higher than that of glomerular proteinuria, and the risk factors are different, in the elderly in China; therefore, tubular damage markers should get more attention in the overall population.

Methodological evaluation and comparison of five urinary albumin measurements.

BACKGROUND: Microalbuminuria is an indicator of kidney damage and a risk factor for the progression kidney disease, cardiovascular disease, and so on. Therefore, accurate and precise measurement of urinary albumin is critical. However, there are no reference measurement procedures and reference materials for urinary albumin. METHODS: Nephelometry, turbidimetry, colloidal gold method, radioimmunoassay, and chemiluminescence immunoassay were performed for methodological evaluation, based on imprecision test, recovery rate, linearity, haemoglobin interference rate, and verified reference interval. Then we tested 40 urine samples from diabetic patients by each method, and compared the result between assays. RESULTS: The results indicate that nephelometry is the method with best analytical performance among the five methods, with an average intraassay coefficient of variation (CV) of 2.6%, an average interassay CV of 1.7%, a mean recovery of 99.6%, a linearity of R=1.00 from 2 to 250 mg/l, and an interference rate of <10% at haemoglobin concentrations of <1.82 g/l. The correlation (r) between assays was from 0.701 to 0.982, and the Bland-Altman plots indicated each assay provided significantly different results from each other. CONCLUSION: Nephelometry is the clinical urinary albumin method with best analytical performance in our study.