Dietary egg white protein (EWP) decreases serum cholesterol levels. We previously showed that EWP decreased cholesterol absorption in the intestine. Rats subjected to permanent lymph duct cannulation were used to investigate the effects of dietary EWP on lipid transport. They were fed diets with 20% EWP and casein, and their lymph was collected to quantify lymphatic lipid levels. Dietary EWP decreased lymphatic cholesterol transport compared with casein. It was previously shown that EWP excluded cholesterol from bile acid micelles. Therefore, pepsin-hydrolyzed EWP and casein were prepared. EWP was not completely digested. Ovalbumin, which is the most abundant protein in EWP, showed resistance to digestion by pepsin. This study investigated the effects of EWP pepsin hydrolysate (EWP-ph) on cholesterol micellar solubility, cholesterol transfer from the micellar to the oil phase, water-holding capacity (WHC), settling volume in water (SV), and relative viscosity and compared them with the effects of casein pepsin hydrolysate (C-ph). EWP-ph significantly decreased the micellar solubility and transfer rate and increased the WHC, SV, and relative viscosity compared with C-ph. Moreover, the pepsin hydrolysate of ovalbumin, a major protein in EWP, played a role in decreasing cholesterol micellar solubility, leading to the inhibition of cholesterol absorption. In conclusion, dietary EWP decreased cholesterol intestinal absorption by exerting combined effects of these physicochemical properties in the gut.

BackgroundKurozu concentrated liquid (KCL) is used as a health-promoting supplement for the treatment of disorders such as cancer, hyperlipidemia, and hypertension in Japan. We investigated the possible anti-obesity effects of KCL in rats.MethodsMale Sprague Dawley rats were fed American Institute of Nutrition 76 formula diet and were orally administrated KCL or acetic acid at a dose of 100 mg/kg body weight or deionized water for 4 weeks. Adipocyte size, DNA content in subcutaneous adipose tissue, lipid levels in the serum and liver, and the rate of fatty acid excretion were determined. Effects of KCL on pancreatic lipase activity and 3T3-L1 preadipocyte differentiation were investigated in vitro.ResultsIn the KCL group, the average adipocyte size in subcutaneous and perirenal adipose tissues was significantly reduced. The KCL-administered rats displayed greater numbers of small adipocytes in the subcutaneous, perirenal and mesenteric adipose tissues than did rats from the other groups. In the KCL group, the DNA content in subcutaneous adipose tissue was significantly increased. The rate of fatty acid excretion was significantly increased in the KCL group. Furthermore, KCL significantly inhibited pancreatic lipase activity in vitro, and also significantly inhibited fat accumulation and mRNA expression of fatty acid binding protein 2 (aP2) and peroxisome proliferator-activated γ (PPARγ) in 3T3-L1 preadipocyte. The levels of serum and liver lipids, the concentration of serum glucose, and the levels of adiponectin were similar among the 3 groups.ConclusionOral administration of KCL decreases the adipocyte size via inhibition of dietary fat absorption and reductions of PPARγ and aP2 mRNA expression levels in adipocytes.

Guar gum has a well-recognized hypolipidemic effect. This effect is thought to be due to the physicochemical properties of guar gum, which may cause changes in adsorption of lipids or the viscosity of the intestinal contents. Guar gum is a non-specific absorption inhibitor of any type of lipid-soluble compound. Permanent lymph duct cannulation was performed on rats to investigate the effects of dietary guar gum on lymph flow and lipid transport. Rats fed a 5% guar gum diet were compared with those fed a 5% cellulose diet, and lymph was collected after feeding. The water-holding capacity (WHC), settling volume in water (SV), and viscosity of guar gum were compared with those of cellulose. Rats fed with the guar gum diet had significantly lower lymph flow and lymphatic lipid transport than did rats fed with the cellulose diet. The WHC, SV, and viscosity of guar gum were significantly higher than those of cellulose. We propose that dietary guar gum reduces lymph flow and thereby diminishes lipid transport by means of its physicochemical properties related to water behavior in the intestine.

Summary Egg yolk is an important source of nutrients and contains different bioactive substances. In the present study, we studied the benefits of egg yolk in preventing low-protein-diet-induced fatty liver in rats. Rats were fed the following diets, which were based on the AIN-76 formula, for 2 wk: an adequate-protein diet containing 20% casein (C), a lowprotein diet containing 5% casein (LP-C), a low-protein diet supplemented with 12.5% egg yolk (LP-EY), and a low-protein diet supplemented with 4.1% egg yolk oil (LP-EYO). The lowprotein diets were adjusted to contain 4.13% protein and 4.7% lipids. The LP-C diet resulted in a greater increase in the liver trigriceride (TG) and the vacuolation and a greater decrease in the serum TG and free fatty acid (FFA) than did the C diet. These deviations in the serum and liver TG, serum FFA levels and the liver histopathology were corrected in rats fed the LP-EY diet but not in those fed the LP-EYO diet. Compared to rats fed the LP-C diet, although the activities of lipogenesis-related enzymes (fatty acid synthase, glucose-6-phosphate dehydrogenase, and malic enzyme) decreased in rats fed both of the LP-EY and LP-EYO diets, the level of the microsomal TG transfer protein (MTP) increased only in rats fed the LP-EY diet. Collectively, these results suggest that dietary egg yolk supplementation decreases the LP diet-induced accumulation of TG in the liver by increasing transport of TG in the liver, and egg yolk oil alone is not sufficient enough to bring about these benefits.