Fortification of water kefir with magnetite nanoparticles

The aim of this work was to evaluate the suitability of incorporating Fe₃O₄ (magnetite, M) NPs into water kefir (wKef) beverages. Magnetite NPs were synthesized and coated with pectins (cM), and incorporated into wKef beverages obtained by fermentation of a muscovado sugar solution with wKef grains. FeSO₄, usually employed as fortifier, was used as a control. Four different beverages were analyzed: wKef, wKef-cM, wKef-M, wKef-FeSO₄, indicating wKef beverages fortified with cM, M or FeSO₄, respectively. Their stability was assessed by determining the viability of total lactic acid bacteria and yeasts, and the composition of saccharides along storage at 4 °C for up to 30 days. The toxicity of M and cM was evaluated in an in vivo model of Artemia salina. The absorption of iron was quantified by determining ferritin values on intestinal Caco-2/TC7 cells, and its internalization mechanisms, by employing inhibitors of endocytic pathways and quantifying ferritin. M and cM were non-toxic on Artemia salina up to 500 µg/mL, a toxicity even lower than that of FeSO₄, which showed a LD50 of 304.08 µg/mL. After 30 days of storage, no significant decrease on yeasts viability was observed, and bacteria viability was above 6 log CFU/mL for the four beverages. In turn, sucrose decreased to undetectable values, concomitantly to an increase in the concentrations of glucose and fructose. Both wKef-M and wKef-cM led to a significant increase in the ferritin values (up to 2 folds) with regard to the basal state. The internalization of M NPs occurred via clathrins and caveolin pathways, whereas that of cM, by macropinocytosis. Safely incorporating M and cM NPs into wKef beverages appear as an innovative strategy for providing bioavailable iron aiming to ameliorate the nutritional status of populations at risk of iron deficiency (e.g., vegans).

Valorization of okara oil for the encapsulation of Lactobacillus plantarum

Oil-in-water (O/W) emulsions of okara oil-caseinate (1:2; 1:3 and 1:4 O/W ratios) were used to encapsulate Lactobacillus plantarum CIDCA 83114. Once encapsulated, microorganisms were freeze-dried or spray-dried, and observed by scanning electronic and confocal microscopies. A physical characterization of the dehydrated capsules was carried out by determining their moisture content, water activity, particle size, polydispersity index and zeta potential. Determining the induction times and peroxide values provided information about their susceptibility to oxidation. In turn, bacterial stability was analyzed by plate counting before and after freeze-drying and spray-drying, and during storage at 4°C. Spray-dried emulsions had lower Z-sizes and polydispersity indexes, higher induction times and lower peroxide values than the freeze-dried ones, thus resulting better systems to protect L. plantarum CIDCA 83114. In addition, the culturability of spray-dried bacteria did not decrease neither after spray-drying nor up to 60days of storage at 4°C. The results showed that the better physical-chemical stability of spray-dried capsules determined the greater stability of microorganisms. This demonstrates the importance of defining adequate emulsions' formulations for an efficient encapsulation of microorganisms, with promising applications in the development of novel functional foods.

Lipid hydroperoxide and markers of renal disease susceptibility in African-Caribbean and Caucasian patients with Type 2 diabetes mellitus

AIMS

The reasons for the increased incidence of diabetic nephropathy in African-Caribbean compared with Caucasian subjects are poorly understood. Increased oxidative stress is linked to the development of endothelial dysfunction and histological abnormalities associated with diabetic renal disease. Therefore, it was assessed whether a marker of oxidative stress, lipid hydroperoxide (LOOH) and endothelial damage, von Willebrand factor (vWF) varied according to ethnic origin in the presence or absence of early diabetic nephropathy.

METHODS

Eighty-eight patients with Type 2 diabetes mellitus of African-Caribbean or Caucasian origin without a history of cardiovascular disease or clinical proteinuria were studied. Patients were classified as having microalbuminuria or normal albumin excretion. Fasting plasma vWF and LOOH were measured by an inhouse enzyme-linked immunoassay and ferrous oxidation with xylenol orange (FOX) assay, respectively. The relationship of LOOH to urinary albumin status, the metabolic disturbances of diabetes, blood pressure and ethnic origin were assessed using multivariate analysis.

RESULTS

Compared with Caucasian patients those of African-Caribbean origin had higher systolic blood pressure and HDL-cholesterol (157.8 +/- 17.0 vs. 147.8 +/- 24.4, P = 0.041 and 1.6 +/- 0.4 vs. 1.3 +/- 0.5, P = 0.018) but lower total triglycerides (1.3 +/- 0.8 vs. 1.9 +/- 1.1, P = 0.008). LOOH was significantly higher in the African-Caribbean patients compared with Caucasians (5.98 +/- 2.49 vs. 4.49 +/- 2.19, P = 0.006). vWF tended to be higher in microalbuminuric patients but showed no variation with ethnicity. In logistic regression analysis, LOOH was the only independent predictor of a raised albumin excretion rate (P = 0.008). In multiple regression analysis, African-Caribbean ethnicity (P = 0.020) HDL-cholesterol (P = 0.036), total triglycerides (P = 0.002) and a raised albumin excretion rate (P = 0.002) were independent predictors of LOOH.

CONCLUSIONS

In this group of Type 2 diabetic patients an increase in LOOH is associated with abnormal urinary albumin excretion. African-Caribbean origin was a determinant of LOOH independently of microalbuminuria. It is postulated that increased oxidative stress is of pathophysiological significance in accelerating the development of renal disease in African-Caribbean patients.

Functional link between ataxia-telangiectasia and Nijmegen breakage syndrome gene products

Ataxia-telangiectasia (A-T) and Nijmegen breakage syndrome (NBS) are recessive genetic disorders with susceptibility to cancer and similar cellular phenotypes. The protein product of the gene responsible for A-T, designated ATM, is a member of a family of kinases characterized by a carboxy-terminal phosphatidylinositol 3-kinase-like domain. The NBS1 protein is specifically mutated in patients with Nijmegen breakage syndrome and forms a complex with the DNA repair proteins Rad50 and Mrel1. Here we show that phosphorylation of NBS1, induced by ionizing radiation, requires catalytically active ATM. Complexes containing ATM and NBS1 exist in vivo in both untreated cells and cells treated with ionizing radiation. We have identified two residues of NBS1, Ser 278 and Ser 343 that are phosphorylated in vitro by ATM and whose modification in vivo is essential for the cellular response to DNA damage. This response includes S-phase checkpoint activation, formation of the NBS1/Mrel1/Rad50 nuclear foci and rescue of hypersensitivity to ionizing radiation. Together, these results demonstrate a biochemical link between cell-cycle checkpoints activated by DNA damage and DNA repair in two genetic diseases with overlapping phenotypes.

Insulin and IGFs induce apoptosis in chick embryo retinas deprived of L-glutamine

In chick embryo retinas, cultured in serum-free medium lacking L-glutamine, IGF-I, IGF-II and insulin induced apoptotic DNA fragmentation and cell death, IGF-I being the most efficacious compound. The apoptotic effect, which was particularly evident in retinas removed from 7-day-old chick embryos, declined with the age of the embryos and disappeared after day 11. Apoptosis appeared after a time lag of 8 h and then increased with time up to 16 h. Cycloheximide, an inhibitor of protein synthesis, was capable of entirely abolishing apoptotic cell death. The effect induced by IGFs or insulin was suppressed by the addition of glutamine. Cytokine-mediated apoptosis was also observed after withdrawal of phosphate. We suggest that IGFs or insulin may produce, in retinas cultured in medium lacking L-glutamine or phosphate, a conflict of signals that could be lethal for retinal cells.

The effects of TGF-beta1 on chick embryo retina development in vitro

This paper studies the effect exerted by TGF-beta1 on the development of chick embryo retina cultured in vitro. The addition of TGF-beta1 to retinal explants inhibited DNA synthesis, measured as 3H-thymidine incorporation into trichloroacetic acid-insoluble fraction, while it increased both wet weight and protein content, in particular that of extracellular matrix proteins. Lastly, in explants treated with TGF-beta1 an increment in the level of fibronectin was demonstrated by means of Western blotting analysis.

Differentiation of Y79 cells induced by prolonged exposure to insulin

Y79 human retinoblastoma cells are known to contain receptors for both insulin and insulin-like growth factors (IGFs), to produce these cytokines and release them in the culture medium. Previously we have demonstrated that IGFs and insulin stimulate Y79 cell proliferation through the involvement of type I IGF receptor and Insulin Receptor Substrate 1 (IRS-1). This paper studies the effect of prolonged exposure to insulin on Y79 cells. Cells grown for 10 days in the presence of insulin were reseeded and incubated once more with insulin. In the reseeded cells proliferation lowered and morphological changes appeared. After 10 days of reseeding, cells stopped proliferating and showed long ramifying neurite processes and varicosities consistent with neuronal differentiation. Morphological differentiation was accompanied by a marked increase in the content of total protein and in that of tubulin, the major protein constituent of microtubules, a marked increase in the content of specialized protein markers of dopaminergic and cholinergic differentiation (dopamine beta-hydroxylase and choline acetyltransferase activities, respectively); a contemporaneous decrease in the content of glial fibrillary acidic protein (GFAP), a specific marker of glial cells, was also observed. Our results demonstrate that prolonged exposure to insulin induces Y79 cells to differentiate into a neuronal-like phenotype. At this moment it is not possible to establish the mechanism by which insulin induces this differentiative effect.

Changes in protein composition during chick embryo retina development

Two dimensional gel electrophoresis was employed to analyse the protein composition of chick embryo retina during "in ovo" development in order to individuate some components which are typical of different stages of growth. The study of protein composition of 7-day-old chick embryo retinas revealed the presence of about eighty different soluble components. In four of these proteins the staining intensity decreased during retina development. One of these components, of 35 KD with an isoelectric point of about 5.15, was partially purified by means of preparative isoelectric focusing. Other components, which were absent at day 7 appeared during the second week of development and were clearly visualised at day 16. These results were also compared with those obtained by means of 2DGE performed on liver and brain of chick embryo at day 7 and 16 of development.

Insulin-like growth factors in chick embryo retina during development

Evidence exists supporting an important role for insulin-like growth factors (IGFs) during fetal growth. In the present report we performed studies to define whether developing chick retina contains IGFs and whether IGFs play a role in the growth of this tissue. We have shown that both IGF-I and IGF-II are present in chick embryo retina throughout development (7th-18th day). The highest values, when expressed as ng/g of tissue, were found in the youngest retinas studied (7th-9th day) and at 16th-18th day of development. During whole development the content of IGF-II was about two to three times higher than that ascertained for IGF-I. The tissue also contains cell-surface binding for IGFs. However, the developmental pattern of IGF-I binding was quite different from that found for IGFs, showing the highest values during the second week of development. Competitive studies showed that this receptor has a high affinity for IGF-I, a lower affinity for IGF-II, and a very much lower affinity for insulin. Also anti-IGF-I receptor antibody (alpha IR3) inhibited 125I-labeled IGF-I binding to the receptor. Such results indicate the presence of type I IGF receptor in chick embryo retina. Affinity labeling experiments have confirmed this hypothesis. We have also shown that cultured retinal explants contain, synthesize and release into the medium appreciable amounts of IGFs. Both exogenous IGF-I and IGF-II added to the culture medium stimulated DNA synthesis of retinal explants. Evidence that the retinas produce IGFs and possess IGF-IR together with the growth-promoting effect of IGFs suggests that these factors play an important role as regulators of retinal growth.