The cholesterol-lowering property of soybeans fed to rats is related to the fasting duration

Numerous factors affect plasma cholesterol and, therefore, representpotential interferences with the specific effects of diet on lipid metabolism.After casein intake, serum cholesterol levels depend on many experimentalconditions in rats, such as the type of casein, the presence or absence ofcholesterol in the diet, the age and strain of rat, the diet composition, thenutritional status. The effect of fasting duration on selected parameters wasstudied in adult male Wistar rats fed a 20% casein and 1% cholesterol-based diet. No changes were observed in total serum, lipoproteins-B andHDL cholesterol and in triglyceride values after an 8 h-fast compared tonon-fasted animals. A significant decrease was induced in total andlipoproteins-B cholesterol with a 12 h-fast. A prolonged fast resulted ina significant decrease in these parameters and in triglycerides and inHDL-cholesterol levels.Fasted animals fed heated soybean meal instead of casein did not display amarked decrease in serum lipids. It appeared that the fasting effect wasmore marked in animals fed casein than in animals fed soybeans. Theseresults showed the importance of experimental conditions such as nutritional status ofanimals when blood samples are taken in studies of the hypocholesterolemiceffect of soy protein compared to casein.     

Consumption of resistant starch decreases lipogenesis in adipose tissues but not in muscular tissues of growing pigs

The aim of the present study was to evaluate the effect of two different sources of starch on plasma glucose, acetate and insulin responses and peripheral lipogenesis in adipose and skeletal muscle tissues. Eighteen male growing pigs were fed a diet containing 250 g native corn starch/kg (CS; 26% amylose, 74% amylopectin) or 250 g raw potato starch/kg (RPS; 20% amylose, 80% amylopectin) as examples of digestible and resistant starch (type II), respectively. After 38 days on the experimental diets, twelve pigs (6 per treatment, Experiment 1) were killed and samples of adipose and muscular tissues were analysed for intramuscular lipid content and lipogenic enzyme activity. Lipogenic enzyme activities were significantly higher for CS than RPS in adipose tissues but not in muscular tissues. No differences were detected on the lipid content of the muscles tested. The six remaining pigs (3 per treatment, Experiment 2) were fitted with catheters in the saphenous vein and femoral artery after 28 days on the experimental diets. After feeding restoration to a level of 1.1 kg/day, they received a primed constant infusion of 1-¹³C acetate for a period of 90 min, starting 5 h after feeding the meal ingestion, and a primed constant infusion of 6,6-D₂ glucose for 7 h, starting 1 h before the following meal ingestion. No differences were observed between diets on peripheral acetate entry rate. Glucose concentration, the rate of peripheral glucose appearance and insulin concentration were quantitatively higher after the meal for CS than for RPS diet. This shows the importance of type of dietary starch on lipogenesis as a result of changes in glycemia and insulinemia in adipose but not in muscular tissues of growing pigs.     

Inhibition of glucose intestinal absorption by kaempferol 3-O-α-rhamnoside purified from Bauhinia megalandra leaves

Glucose intestinal absorption (GIA) is one of the factors that increase glycemia. Its reduction could be an important factor in decreasing hyperglycemia in diabetic patients. It has been shown that the aqueous extract of Bauhinia megalandra leaves inhibits GIA. In the present study we identified a compound present in the extract of B. megalandra responsible for the biological effect. The methanol extract of B. megalandra leaves was fractionated using different solvents, and high-speed counter-current chromatography yielding two pure compounds identified by ¹H NMR and ¹³C NMR as kaempferol 3-O-α-rhamnoside and quercetin 3-O-α-rhamnoside. The first one increased the K_M without changes in the V_MAX of GIA. In addition it exerted an additive inhibitory effect, on GIA, when combined with phlorizin. We suggest that kaempferol 3-O-α-rhamnoside is a competitive inhibitor of intestinal SGLT1 cotransporter.     

Yam Contributes to Improvement of Glucose Metabolism in Rats

To investigate whether yam improves glucose metabolism, yam-containing diets were given to Wistar rats. In a short-term experiment, fasted-rats were given 1.0 g of a control and 20% yam-containing diets. At 60 min after start of the feeding, glucose level in the yam diet group was lower or tended to be lower than that in the control diet. Insulin levels at 30 min and 60 min were significantly lower than those in the control group. In a long-term experiment, a normal diet (N) or 25% high fat diets with (Y) or without 15% yam powder (HF) were given to rats for 4 weeks. At 4 weeks, in an oral glucose tolerance test, the area under the curve (AUC) of plasma glucose level was higher in the HF group than that in the N group, whereas those in the Y groups did not differ from that in the N group. Glycosylated hemoglobin levels had similar tendency to the AUCs. Plasma leptin levels in the Y groups were significantly higher than that in the N group. In conclusion, yam may contribute to improvement of glucose metabolism. Additionally, we speculated that leptin level is possibly involved in the insulin-response to yam diets.     

Potential insulin secretagogue effects of isovitexin and swertisin isolated from Wilbrandia ebracteata roots in non-diabetic rats

The antihyperglycemic effect and mechanism of action of extracts, fractions and compounds from Wilbrandia ebracteata was studied. The crude extract reduced the glycemia, increased glycogen content and serum insulin in hyperglycemic rats. Also, a significant effect was observed with the n-butanol and metanol subfraction. However, the antihyperglycemic effect of the n-butanol fraction was not observed in diabetic rats. The C-glycosylflavones isovitexin and swertisin showed a strong antihyperglycemic action compared with the extracts and fractions. These results show that the extracts, fractions, and isolated C-glycosylflavones have an antihyperglycemic action that was reinforced by the stimulation on in vivo insulin secretion.     

Digestibility of Nutrients and Digestive Health in Horses Submitted to Moderate Exercise and Supplemented With Diets Formulated With Soybean Hulls

Soybean hulls (SHs) are a feedstuff that has been widely studied as an alternative ingredient in horse diets because of its fermentable carbohydrates with low glycemic index. The objective was to assess the influence of the inclusion of SH, in substitution for 0%, 10%, 20%, 30%, and 40% of the concentrate (kg/kg), on the apparent digestibility of nutrients, fecal pH and score, and the postprandial glycemic responses of five geldings submitted to moderate-intensity exercise. The study lasted 50 days, divided into five 10-day periods of 7 days for diet adaptation and 3 days for total feces collection. For the glycemic tests, blood was collected 30 minutes before and 30, 60, 90, 120, 180, 240, and 300 minutes after the administration of SH. Data were submitted to analyses of variance in a Latin square (5 × 5) design, and means were compared by the Tukey test at 5% of significance. There were no effects of treatments on the apparent digestibility of nutrients (P > .05), except for acid detergent fiber and hydrolyzable carbohydrate in 30% and 40% SH diets, and on slowly fermented carbohydrate in the 40% SH diet. Fecal parameters, glucose levels, and peak were not influenced (P > .05) by the increasing levels of SH in the diet. The use of SHs replacing up to 40% of the concentrate supplementation in a diet (kg/kg) improved the digestibility of fermentable carbohydrates and did not impair glycemia of horses under moderate-intensity exercise.