Effect of an α-lactalbumin-enriched infant formula with lower protein on growth.

BACKGROUND/OBJECTIVES: Protein concentration is lower in human milk (HM) than in infant formula. The objective of this study was to evaluate the effect of an α-lactalbumin-enriched formula with a lower protein concentration on infant growth, protein markers and biochemistries. SUBJECTS/METHODS: Healthy term formula-fed (FF) infants 5-14 days old were randomized in this controlled, double-blind trial to standard formula (SF: 14.1 g/l protein, 662 kcal/l) group (n=112) or experimental formula (EF: 12.8 g/l protein, 662 kcal/l) group (n=112) for 120 days; a HM reference group (n=112) was included. Primary outcome was weight gain (g/day) from D0 to D120. Secondary outcomes included serum albumin, plasma amino acids insulin and incidence of study events. Anthropometric measures were expressed as Z-scores using 2006 World Health Organization growth standards. RESULTS: A total of 321 of the 336 infants (96%) who enrolled, completed the study. Mean age was 9.6 (±2.9) days; 50% were girls. Mean weight gain (g/day) did not significantly differ between SF vs EF (P=0.67) nor between EF vs HM (P=0.11); however weight gain (g/day) was significantly greater in the SF vs HM group (P=0.04). At day 120, mean weight-for-age Z-score (WAZ) and weight-for-length Z-score (WLZ) did not significantly differ between SF vs EF nor EF vs HM; however the WAZ was significantly greater in SF vs HM (P=0.025). Secondary outcomes were within normal ranges for all groups. Incidence of study events did not differ among groups. CONCLUSIONS: α-Lactalbumin-enriched formula containing 12.8 g/l protein was safe and supported age-appropriate growth; weight gain with EF was intermediate between SF and HM groups and resulted in growth similar to HM-fed infants in terms of weight gain, WAZ and WLZ.

Expression of a constitutive mutant of iron regulatory protein 1 abolishes iron homeostasis in mammalian cells.

Iron regulatory proteins (IRPs) are iron-sensing proteins that bind to RNA stem-loop sequences known as iron-responsive elements (IREs) when cells are depleted of iron. Although IRPs have been shown to bind to IREs derived from ferritin and transferrin receptor (TfR) mRNAs in vitro, there has not been a direct demonstration of the impact of a recombinant IRP on the expression of endogenous IRE-containing transcripts. In this study, we evaluate the impact of expression of C437S, a mutant of IRP1 that binds IREs regardless of cellular iron status, on the regulation of biosynthesis of ferritin and TfR. Despite being made iron-replete, cells expressing C437S continue to synthesize and express high amounts of TfR, while the synthesis of ferritin is repressed. Thus, a single mutant IRP can prevent the usual homeostatic changes in ferritin and TfR biosynthesis. Cells expressing the mutant protein would therefore be predicted to be unable to defend against iron overload. Preliminary results show that cells treated with iron have diminished cell survival when C437S is expressed, and we have thus created a tissue culture model system for the study of iron toxicity.

Determination of intracellular free magnesium by nuclear magnetic resonance in human magnesium deficiency.

Magnesium (Mg) deficiency is a common clinical problem. As Mg is predominantly an intracellular cation and Mg deficiency may exist despite normal serum Mg (sMg) concentrations, we have utilized nuclear magnetic resonance (NMR) techniques in an attempt to measure intracellular free Mg (Mg2+) in red blood cells (RBC). Twenty normal subjects, 22 hypomagnesemic patients, and 17 normomagnesemic alcoholic patients were studied. Mean RBC Mg2+ in normal subjects (178 +/- 6.3 microM) was significantly greater than in hypomagnesemic patients (146 +/- 7.1 microM, p less than 0.002). RBC Mg2+ correlated with sMg concentration (r = 0.54, p less than 0.001). In addition, four normal subjects were given a low Mg diet for 3 weeks. There was a progressive fall in both the sMg concentration and RBC Mg2+ during Mg depletion, with a concomitant rise in retention of a parenterally administered Mg load. These data suggest that the determination of intracellular Mg2+ by NMR may be a useful research tool in assessing the effect of changes in Mg2+ on intracellular processes. Its utility in the clinical evaluation of disorders of Mg deficiency remains to be determined.

Mechanisms of blood pressure regulation by magnesium in man.

In order to determine the effect and mechanism of Mg on vascular tone, a 3-hour infusion of Mg (200 mg/h) was administered to normal subjects. The Mg infusion resulted in a drop in blood pressure (BP), a rise in renal blood flow, and an increase in urinary 6-keto-PGF1 alpha excretion. Cyclooxygenase inhibition with indomethacin and the calcium channel blocker, nifedipine, prevented these vascular effects of Mg. These data suggest that prostacyclin release via changes in Ca2+ flux may be the mechanism of Mg vasodilatory action. Since angiotensin II (AII) acts via the Ca2+ messenger system, we also studied the effects of Mg loading and dietary Mg depletion on AII responses. Mg loading blunted the rise in BP and the aldosterone-stimulating effect of AII, whereas Mg depletion significantly enhanced these AII effects. These results support the hypothesis that Mg may be an antagonist of the pressor and steroidogenic effects of AII.

Folate nutriture in pregnancy.

Folacin intakes from diet and supplements consumed during pregnancy were determined by interview in 566 women. Eight percent of this population (48 women) obtained folacin from diet only. Thirteen percent (76 women) received less than two-thirds of the RDA for folacin for pregnant women. Serum and erythrocyte folate levels in maternal and cord blood were correlated with dietary folacin intakes in subsamples of the group. Women who received their folate from diet alone showed marginal or deficient maternal serum folate levels. Of the group of women whose folacin intake was equal to or greater than the RDA for pregnant women, some had intakes as high as eight times the RDA from supplements. When, in a subsample, total folacin intake was correlated with maternal and cord folate levels, significant correlations were obtained. The high serum and erythrocyte folate levels resulting from self-medication with folate supplements are of concern because of possible deleterious interaction with other nutrients.

Preventive nutrition intervention in coronary heart disease: risk assessment and formulating dietary goals.

Risk factor screening and establishing realistic goals are key steps for the dietitian to follow in planning strategies to prevent coronary heart disease. The major risk factors that are responsive to dietary intervention include: elevated plasma total cholesterol and low-density-lipoprotein cholesterol, elevated blood pressure, glucose intolerance, and obesity. The criteria used in assessing nutrition-related risk in coronary heart disease are presented. The long-term goals of preventive nutrition intervention in heart disease are discussed, with emphasis on a unified and progressive approach to diet planning.