Purine nucleoside phosphorylase and the enzymatic antioxidant defense system in breast milk from women with different levels of arsenic exposure.

Purine nucleoside phosphorylase (PNP) is an ubiquitous enzyme which plays an important role in arsenic (As) detoxification. As is a toxic metalloid present in air, soil and water; is abundant in the environment and is readily transferred along the trophic chain, being found even in human breast milk. Milk is the main nutrient source for the growth and development of neonates. Information on breast milk synthesis and its potential defense mechanism against As toxicity is scarce. In this study, PNP and antioxidant enzymes activities, as well as glutathione (GSH) and total arsenic (TAs) concentrations, were quantified in breast milk samples. PNP, superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), glutathione peroxidase (GPx), glutathione reductase (GR) activities and GSH concentration were determined spectrophotometrically; TAs concentration ([TAs]) was measured by atomic absorption spectrometry. Data suggest an increase in PNP activity (median = 0.034 U mg protein-1) in the presence of TAs (median = 1.16 g L(-1)). To explain the possible association of PNP activity in breast milk with the activity of the antioxidant enzymes as well as with GSH and TAs concentrations, generalized linear models were built. In the adjusted model, GPx and GR activities showed a statistically significant (p<0.01) association with PNP activity. These results may suggest that PNP activity increases in the presence of TAs as part of the detoxification mechanism in breast milk.

Purina nucleósido fosforilasa (PNP) es una enzima ubicua que desempeña un papel importante en la desintoxicación del arsénico (As). As es un metaloide tóxico presente en el aire, el suelo y el agua; es abundante en el medio ambiente y se transfiere fácilmente a lo largo de la cadena trófica, encontrándose incluso en la leche materna humana. Información sobre la síntesis de la leche materna y su potencial mecanismo de defensa contra tóxicos es escasa. En este estudio, se cuantificó la actividad de PNP y de las enzimas antioxidantes así como la concentración de glutatión (GSH) y de arsénico total ([TAs]) en muestras de leche materna. La actividad de PNP, superóxido dismutasa (SOD), catalasa (CAT), glutatión S-transferasa (GST), glutatión peroxidasa (GPx), glutatión reductasa (GR) y la concentración de GSH se determinaron por espectrofotometría; la [TAs] se midió por espectrometría de absorción atómica. Los datos sugieren un incremento en la actividad de PNP (mediana= 0.034 U mg proteína-1) con la presencia de TAs (mediana= 1.16 g L-1). Para explicar la posible asociación de la actividad de las enzimas antioxidantes y la concentración de GSH, así como [TAs], con la actividad de PNP en la leche materna, se construyeron modelos lineales generalizados. En el modelo ajustado, la actividad de GPx y GR presentó una asociación estadística (p.

Immunoglobulin A with protease activity secreted in human milk activates PAR-2 receptors, of intestinal epithelial cells HT-29, and promotes beta-defensin-2 expression.

Secretory antibodies of the immunoglobulin A (sIgA) class constitute the first line of antigen-specific immune protection against pathogens and other antigens at mucosal surfaces. Although initially perceived as potentially deleterious, catalytic antibodies have been proposed to participate in the removal of metabolic wastes and in protection against infection. Here we show that the presence of sIgA endowed with serine protease-like hydrolytic activity in milk strongly correlates with PAR-2 activation in human intestinal epithelial cells. F(ab')(2) fragments of sIgA activated the epithelial cells in culture to produce beta-defensin-2 (hBD2). Intracellular Ca(2+) mobilization was induced by treatment with (1) sIgA-F(ab')(2) fragments; (2) trypsin, a recognized PAR-2 agonist; or (3) a synthetic PAR-2 agonist peptide (SLIGKV). The co-treatment with a synthetic PAR-2 antagonist peptide (FSLLRY) and sIgA-F(ab')(2) fragments eliminates the latter's effect; nevertheless, cells were not refractory to subsequent stimulation with sIgA-F(ab')(2) fragments. Both the induction of hBD-2 expression in epithelial cells and the increase in intracellular [Ca(2+)] stimulated by sIgA-F(ab')(2) fragments were inhibited by treatment with serine protease inhibitors or pertussis toxin (PTX). These findings suggest that catalytic antibodies can activate intestinal epithelial cells through G-protein-coupled PAR-2, and could actively participate in the immune system of breastfed babies inducing the production of peptides related to innate defense, such as defensins.

Effect of pasteurization on long chain polyunsaturated fatty acid levels and enzyme activities of human milk.

Milk fatty acids, including the polyunsaturated long chain fatty acids essential for retinal function and brain development, are not affected by pasteurization (62.5 degrees C for 30 min). Milk lipases are completely destroyed by pasteurization, whereas amylase lost only 15% of initial activity. Thus, certain bioactive components are stable to pasteurization of donor milk and can benefit the recipient infants.

Valores de carnitina en las leches de consumo masivo y leche materna de Venezuela / Cornitine values on the massive consumption milk and maternal milk from Venezuela

Bajos niveles individuales de Carnitina sérica podrían ser determinados por mecanismos genéticos, metabólicos o de ingesta. En una población básicamente sana podrían invocarse mecanismos más generales como los dietéticos. Decidimos evaluar el aporte de Carnitina a nuestra población infantil, a través de la medición en la principal fuente exógena de la infancia como es la leche, por haber detectado en un estudio previo niveles séricos bajos y por existir programas oficiales por más de 26 mil 517 millones de bolivares (482 millones de dolares) para subsidios de alimentación láctea. Se evaluaron: A) Leche materna humana (n=14) < 1sem, 15d, 3m y < = 6m con valores de medios de 25.5; 20.5; 11.7 y 5.7nmol/ml, B) Leches de vaca cruda (n=13) siendo 29.25;20.2 y 13.9 nmol/ml a los 15d, 1m y 3m. Ambos grupos mostraron decretar en el curso de tiempo postparto. C) Leches de vaca en planta pasteurizadora (n=4) 18.5 pre y 9.1 nmol/ml post pasteurización. D) Leches en polvo reconstituidas (n=9), con rangos en 7 de ellas, entre 16-26 nmol/ml. Las leches en polvo para consumo popular fueron las más bajo contenido con 12.2 nmol/ml. Las de mayor contenido, fueron las de soya adicionadas con Carnitina, pero no alcanzaron valores fisiológicos de 50 nmol/ml. Se concluye que existen bajos niveles de Carnitina en las leches de consumo infantil y masivo en Venezuela, pudiendo se la causa de los bajos niveles sanguíneos que se encuentran en la población

Enterohepatic circulation of nonconjugated bilirubin in rats fed with human milk.

To test the hypothesis that enhanced intestinal absorption of bilirubin may contribute to prolonged nonconjugated hyperbilirubinemia in human milk-fed infants, we studied a cross-section of 36 healthy infants and mothers. Milk from mothers and serum from infants were collected at 16.3 +/- 2.4 days. Milk was studied for its effect on the absorption of bilirubin labeled with carbon 14 in rats and compared with buffer and iron-fortified infant formula (Similac With Iron). The percentage of a 1 mg bilirubin dose absorbed by the rat was 25.29 +/- 4.0% when it was administered into the duodenum with buffer, 4.67 +/- 2.4% with Similac formula, and 7.7 +/- 2.9% with human milk. Linear regression analysis, using the infant's serum nonconjugated bilirubin level as the dependent variable and the percentage of (14C)bilirubin absorbed by the rat with the corresponding mother's milk as the independent variable, revealed a significant correlation (r = 0.40; p = 0.016). Inspection of the data suggested that absorptive permissiveness correlated closely with infant serum bilirubin values greater than 24 mumol/L (1.4 mg/dl) (r = 0.55; p = 0.007), whereas in those with bilirubin values less than or equal to 24 mumol/L, there was no apparent correlation. Milk was also analyzed for beta-glucuronidase, nonesterified fatty acids, and the ability to inhibit glucuronosyltransferase activity of rat liver microsomes in vitro, none of which correlated with the infant's serum bilirubin. These data support the theory that enhanced intestinal absorption of bilirubin contributes to the jaundice associated with breast-feeding.

Phosphoglucomutase proteins in human milk

O polimorfismo do loco 4 da fosfoglicomutase foi investigado em uma amostra de colostro obtida de 652 mulheres (60% brancas e 40% negras), coletada 24 a 48 hs. após o parto, em Porto Alegre, Brasil. Uma nova amostra de leite foi obtida de 175 dessas mulheres com cerca de 17 dias de lactaçäo. No colostro observou-se um acentuado desvio no equilíbrio de hardy-Weinberg, havendo em geral um excesso de homozigotos e deficiência de heterozigotos. No leite, no entanto, esse desequilíbrio näo ocorreu. As diferenças entre as duas distribuiçöes säo devidas à detecçäo de padröes nas amostras que näo apresentavam atividade no primeiro período, assim como a variabilidade na ativaçäo enzimática, que pode ocorrer no início da lactaçäo. As frequências gênicas no leite (n = 175) foram: brancos (n = 127) PGM4*1 = 0,20, PGM4*2 = 0,41, PGM4*3 = 0,38, PGM4*4 = 0,01; negróides (n = 48) PGM4*1 = 0,15, PGM4*2 = 0,52, PGM4*3 = 0,32 e PGM4*4 = 0,01

Host resistance factors in human milk.

PIP: This paper discusses the nature of host resistance factors in human milk and epidemiologic studies regarding infections and mortality rates in breastfed and nonbreastfed babies. The defense factors and their proposed modes of action are: 1) a growth enhancer of lactobacilli, which interferes with intestinal colonization of enteric pathogens; 2) antistaphylococcal factors, which inhibit staphylococci; 3) secretory IgA and other immunoglobulins, which protect the gut and respiratory tract; 4) C4 and C3 (complement components; C3 fragments have opsonic, chemotactic, and anaphylatoxic activities); 5) lysozome, lysis of bacterial cell wall; 6) lactoperoxidase, killing of streptococci; 7) lactoferrin, kills microorganism by chelating iron, and 8) macrophages and lymphocytes, phagocytosis and cell-mediated immunity. Although it can be postulated that the breastfed infant's resistance to infection would be superior on account of the greater presence of these factors in human milk compared to cow's milk, little is known about the effects of these defense factors on the infant. Epidemiologic studies have reported on the lower morbidity and mortality rates of breastfed infants as compared to bottlefed infants. Other studies have focused on the protective effects of human milk upon the infant, but these have been inconclusive. In countries with poor sanitation and high infection rates, the incidence of bacterial infections is lowest in breastfed infants. The advantages of human milk however are difficult to demonstrate in societies with high standards of sanitation and low infection rates. Infection and mortality rates in infants have in fact declined in developed countries as the practice of breastfeeding declined. Until it is established that immunity to common pathogens is transmitted to the infant by human milk, it will not be known whether human milk does have protective effects.^ieng