Rose myrtle (Rhodomyrtus tomentosa) extract and its component, piceatannol, enhance the activity of DNA polymerase and suppress the inflammatory response elicited by UVB­induced DNA damage in skin cells.

A number of naturally occurring agents are hypothesized to protect against ultraviolet (UV)­induced skin damage. The present study screened >50 plant extracts for inhibitors of UVB­induced cytotoxicity, using cultured normal human epidermal keratinocytes (NHEK), and identified that the fruit of rose myrtle (Rhodomyrtus tomentosa) was the most marked inhibitor of cell death. The protective effect of rose myrtle extract and the two key components, piceatannol and piceatannol­4'­O­ß­D­glucopyranoside, on UVB­induced damage and inflammation in cultured NHEK was investigated. The 80% ethanol extract from rose myrtle fruit with piceatannol exhibited protection of UVB­induced cytotoxicity in NHEK; however, piceatannol­4'­O­ß­D­glucopyranoside exhibited no protection, as determined by a 3­(4,5­dimethylthiazol­2­yl)­2,5­diphenyltetrazolium bromide assay. This extract and piceatannol reduced the production of UVB­induced cyclobutane pyrimidine dimers and enhanced the cellular enzyme activity of the DNA polymerases in UVB­irradiated NHEK, suggesting that UVB­stimulated DNA damage was repaired by the polymerases. In addition, the secretion of prostaglandin E2, which is an inflammatory mediator, was decreased. These results indicated that rose myrtle fruit extract and its key constituent, piceatannol, are potential photoprotective candidates for UV­induced skin damage.

Dietary egg white protein inhibits lymphatic lipid transport in thoracic lymph duct-cannulated rats.

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.

Rice α-globulin decreases serum cholesterol concentrations in rats fed a hypercholesterolemic diet and ameliorates atherosclerotic lesions in apolipoprotein E-deficient mice.

The hypocholesterolemic and antiatherogenic effects of rice α-globulin remain unclear. We investigated the hypocholesterolemic effect of rice α-globulin in rats fed a hypercholesterolemic diet. The rats were divided into 4 groups and were orally administrated the following three proteins or a vehicle for 4weeks: rice protein, rice α-globulin, or soy ß-conglycinin at a dose of 100mg/kg body weight or carboxymethylcellulose to the control rats. In the rice α-globulin group, serum cholesterol concentrations were 28% lower than the control group and fecal neutral steroid excretion was increased by 30%. The hypocholesterolemic effect of rice α-globulin was equal to soy ß-conglycinin in SD rats fed the hypercholesterolemic diet. However, the serum cholesterol concentrations in the rice protein group did not change compared to the control group. To investigate the antiatherogenic effects of rice α-globulin, male apolipoprotein E-deficient mice were orally administered the same dose of rice α-globulin for 9weeks. The en face lesion area in the aorta was 46% lower than in the control group. In conclusion, administration of rice α-globulin improves hypercholesterolemia in rats fed a hypercholesterolemic diet by increasing the fecal excretion of neutral sterols, and inhibits atherosclerosis development in apolipoprotein E-deficient mice. The anti-atherosclerotic effect exerts by mechanism(s) other than the regulation of serum MCP-1 and NO concentrations.

Dietary kakrol (Momordica dioica Roxb.) flesh inhibits triacylglycerol absorption and lowers the risk for development of fatty liver in rats.

Kakrol (Momordica dioica Roxb.) is a cucurbitaceous vegetable native to India and Bangladesh. Bitter gourd (Momordica charantia Linn.), a species related to kakrol, has been shown to have pharmacological properties including antidiabetic and antisteatotic effects. In this study, we investigated the effect of dietary kakrol on lipid metabolism in rats. Sprague-Dawley rats were fed AIN-76 formula diets containing 3% freeze-dried powders of whole kakrol or bitter gourd for two weeks. Results showed significantly lowered liver cholesterol and triacylglycerol levels in rats fed on both diets. Fecal lipid excretion increased in rats fed the kakrol diet, and lymphatic transport of triacylglycerol and phospholipids decreased in rats fed the kakrol diet after permanent lymph cannulation. Furthermore, n-butanol extract from kakrol caused a significant concentration-dependent decrease in the pancreatic lipase activity in vitro. These results indicate that the mechanisms of action on lipid metabolism in kakrol and bitter gourd are different and that dietary kakrol reduces liver lipids by inhibiting lipid absorption.

Dietary guar gum reduces lymph flow and diminishes lipid transport in thoracic duct-cannulated rats.

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.