Egg-white protein (EWP) is known to reduce lymphatic TAG transport in rats. In this study, we investigated the effects of dietary EWP on body fat mass. Male rats, 4 weeks old, were fed diets containing either 20 % EWP or casein for 28 d. Carcass protein levels and gastrocnemius leg muscle weights in the EWP group were significantly higher than those in the casein group. In addition, carcass TAG levels and abdominal fat weights in the EWP group were significantly lower than those in the casein group; adipocyte size in abdominal fat in the EWP group was smaller than that in the casein group. To identify the involvement of dietary fat levels in the rats, one of two fat levels (5 or 10 %) was added to their diet along with the different protein sources (EWP and casein). Abdominal fat weight and serum and hepatic TAG levels were significantly lower in the EWP group than in the casein group. Moreover, significantly higher values of enzymatic activity related to β-oxidation in the liver were observed in the EWP group compared with the casein group. Finally, abdominal fat weight reduction in the EWP group with the 10 % fat diet was lower than that in the EWP group with the 5 % fat diet. In conclusion, our results indicate that, in addition to the inhibition of dietary TAG absorption reported previously, dietary EWP reduces body fat mass in rats through an increase of body protein mass and the acceleration of β-oxidation in the liver.
BackgroundWe previously reported the abdominal fat-reducing effect of unheated egg white proteins (EWP); however, unheated egg white is actually rarely consumed. We thus investigated the effect of heated egg white on abdominal fat in rats.MethodsMale SD rats were divided into two groups that were allowed to consume different dietary preparations containing casein or heated egg white for 4 weeks (Trial 1). We studied whether a heated form and a lactic fermented form of egg white (FLE) are as effective as unheated egg white for reducing abdominal fat. For this, we divided male SD rats into four groups that were allowed to consume different dietary preparations containing casein, unheated egg white, heated egg white, or lactic fermented egg white for 4 weeks (Trial 2).ResultsAnimals in the heated egg white group showed no significant difference in abdominal fat weight compared with those in the casein group (Trial 1). Animals in the unheated egg white group and the FLE group had significantly lower levels of abdominal fat weight than those in the casein group (Trial 2). Ovalbumin in heated egg white was degraded by pepsin, whereas ovalbumin in unheated egg white and lactic acid fermented egg white was not degraded appreciably by pepsin. It was reported that EWP inhibit triglyceride absorption in rat. In the present study, EWP pepsin hydrolysate inhibited the micellar solubility of fatty acids in vitro. In particular, ovalbumin inhibited the micellar solubility of fatty acids.ConclusionsThese results indicate that lactic fermented egg white reduces visceral fat in rats and suggest that different levels of susceptibility of ovalbumin to pepsin digestion underlie the varying effectiveness among the egg white preparations.
Free plant sterols cannot be dissolved in oil or water. Using free plant sterols and egg yolks, we developed a plant sterol-egg yolk lipoprotein complex (PSY) that can be dispersed in water and considered suitable for use in processed foods. The cholesterol-lowering activity of PSY was equal to that of free plant sterols and plant sterol esters. Consumption of a freeze-dried PSY-containing omelet reduced serum and hepatic cholesterol concentrations. The results suggest that PSY has cholesterol-lowering activity equivalent to that of free plant sterols and plant sterol esters. Moreover, the cholesterol-lowering activity of PSY was maintained in processed foods.
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