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The aim of the present study was to evaluate the effect of dietary lactoferrin on bone metabolism in vivo using a postmenopausal animal model. We investigated whether bovine lactoferrin (bLF) ingestion could prevent bone loss in ovariectomized mice. Twelve-week-old female C3H mice either ovariectomized or sham operated were fed for 27 wk with the control diet (AIN-93M with 140 g of total milk protein as a protein source per kg of diet). Four groups of ovariectomized mice received diets including different concentrations of bLF (1, 5, 10, or 20 g of total milk protein were replaced by bLF). Ovariectomy induced a decreased uterine weight and a smaller gain of bone mineral density. Immunoreactive bLF was detected in the peripheral blood, and its concentration was related to the amount of bLF ingestion. bLF supplementation to the diet improved bone mineral density (BMD) and femoral failure load in a dose-dependent manner. We confirmed the direct effects of bLF in vitro using established and primary cultures of murine bone cells. Addition of bLF to the culture medium at a concentration of between 1 and 1,000 microg/ml stimulated both cell growth and differentiation of osteoblastic MC3T3 cells while inhibiting the growth of preosteoclastic RAW 267.4 cells. In primary culture of mixed bone cells, an enhanced osteoblast differentiation was associated with an inhibition of osteoclast differentiation at lower bLF concentrations (1-10 microg/ml). In conclusion, these findings suggest that dietary lactoferrin supplementation can have a beneficial effect on postmenopausal bone loss by modulating bone formation and resorption.

This study was designed to determine whether (1) protein type and (2) the dietary carbohydrate to lipid content affected daily energy intake, body weight and adiposity in rats receiving high-protein diets ad libitum over a 25 d period. Each of the ten groups (n 8) consumed ad libitum one of the diets described below. A normal protein diet (P14C56L30, containing whole milk protein) and nine high-protein diets were used. The composition of the high-protein diets varied in terms of two parameters: macronutrient composition and protein type. Three macronutrient compositions (P55C35L10, P55C15L30 and P55L45) combined with three protein types (Milk, Whey and bLac) allowed us to test nine diets. The results show that both protein type (bLac . Whey . Milk) and the carbohydrate to lipid ratio (P55L45 . P55C35L10 or P55C15L30) modulated reductions in energy intake, body weight and adiposity in rats receiving high-protein diets ad libitum, when compared with rats fed a normal diet under the same conditions. By contrast, blood lipid profiles were mainly influenced by the carbohydrate to lipid ratio (P55C15L30 . P55L45 or P55C35L10). Moreover, bLac protein was also the most efficient in tending to preserve lean body mass at the expense of fat mass, and improve blood metabolism hormones (insulin, leptin). Taken together, the present results show that whey-derived protein sources, and particularly b-lactoglobulin-enriched fraction, are of considerable value because of their ability to reduce both body weight gain and the adiposity index.Body composition: Energy intake: High-protein diet: Whey-protein fractionThe macronutrient composition of a diet is known to influence energy intake, energy metabolism and long-term changes to body weight and body composition. High-protein diets (HP diets) have been studied extensively for their ability to reduce total energy intake and body weight, and to limit lipid deposition 1 -5 . Of the dietary proteins, dairy proteins are widely employed as ingredients in order to increase the protein content in the formulation of high protein-containing foods. Dairy proteins comprise two major fractions, i.e. casein and whey protein, that represent 80 and 20 % of the total protein, respectively. Both caseins and whey proteins are considered to be high-quality proteins but they differ markedly with respect to their physicochemical properties, their amino acid composition, and their behaviour during digestion and absorption in the intestine 6 . These differences give rise to different patterns and kinetics of amino acid delivery to the blood, and are responsible for a variety of effects on protein metabolism following the ingestion of either casein or whey protein 4,7 . Whether these differences might also affect energy intake, energy metabolism and long-term changes to body weight and body composition in response to high-protein foods formulated with casein or whey protein, remains poorly documented. Moreover, not only the protein content but also the associated carbohydrate to lipid (C/L) ratio has bee...

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A lactoferrin receptor has been found on the brush-border membrane of intestinal epithelial cells of several species, including humans. A role for this receptor in intestinal iron absorption, which is well regulated in response to body iron stores, has been proposed. We have investigated the effect of intracellular iron depletion by picolinic acid, an iron chelator, on the cell surface binding of human lactoferrin to human enterocytes and its intracellular uptake, using HT29-18-C1 cells, an enterocyte-like differentiable cell line. The confluent cells exhibited 5.8 x 10(6) specific binding sites per cell for diferric human 125I-labelled lactoferrin with relatively low affinity (Kd 8.4 x 10(-7) M). The addition of picolinic acid to the culture medium resulted in a concentration- and time-dependent increase in lactoferrin binding that was correlated with a decrease in intracellular iron content. The maximum effect of picolinic acid on lactoferrin binding (approx. 2-fold increase), which appeared between 12 and 18 h after its addition, was obtained at a picolinic acid concentration of 2 mM. Scatchard analysis showed that the enhanced lactoferrin binding resulted from an increase in the number of lactoferrin receptors rather than an alteration in the binding affinity for lactoferrin. The time-dependent effect of picolinic acid was completely abolished in the presence of 1 microM anisomycin, a protein synthesis inhibitor, indicating that ongoing protein synthesis is involved in this effect. The enhanced lactoferrin binding induced by picolinic acid produced an increase of approx. 30% in the uptake of lactoferrin-bound 59Fe, indicating the existence of functional receptors. These results suggest that biosynthesis of lactoferrin receptors in intestinal epithelial cells can be regulated in response to the levels of intracellular chelatable iron, consistent with intestinal iron absorption dependent on body iron stores.