Dietary effects of barley fibre, wheat bran and rye bran on bile composition and gallstone formation in hamsters

Metabolic effects of whole grain wheat and whole grain rye in the C57BL/6J mouse

OBJECTIVE

A diet rich in whole grain cereals is suggested to protect against type 2 diabetes and facilitate body weight regulation. However, little is known about the impact of different cereals and the underlying mechanisms. The objective of this study was to compare the long-term metabolic effects of diets supplemented with whole grain wheat or whole grain rye in the C57BL/6J mouse.

METHODS

Mice were fed the whole grain supplements in a low-fat background diet for 22 wk. Oral and intravenous glucose tolerance tests were performed during the study and in vitro insulin secretion assays were performed at the end of the study. Body weight, energy intake, body fat content, and plasma parameters were measured during the study.

RESULTS

A dietary supplement of whole grain rye suppressed body weight gain and resulted in significantly decreased adiposity, plasma leptin, total plasma cholesterol, and triacylglycerols compared with a supplement of whole grain wheat. Also, a slight improvement in insulin sensitivity was observed in the rye group compared with the wheat group. The decreases in body weight and adiposity were observed in the absence of differences in energy intake.

CONCLUSION

Long-term administration of whole grain rye evokes a different metabolic profile compared with whole grain wheat in the C57BL/6J mouse, the primary difference being that whole grain rye reduces body weight and adiposity compared with whole grain wheat. In addition, whole grain rye slightly improves insulin sensitivity and lowers total plasma cholesterol.

Rye bread decreases serum total and LDL cholesterol in men with moderately elevated serum cholesterol

The objective of this study was to determine the hypocholesterolemic effects of whole meal rye and white wheat breads in healthy humans with elevated serum cholesterol concentrations, and the changes in plasma glucose and insulin concentrations during rye and wheat bread periods. The subjects were 18 men and 22 women with baseline serum cholesterol concentration of 6.4+/-0.2 mmol/L. The study design was a 2x4-wk crossover trial during which each subject randomly consumed rye and wheat breads (20% of daily energy) as part of their usual diet for 4 wk. The bread periods were separated by a 4-wk washout period. Blood samples (after fasting) were collected on two consecutive days at the beginning and end of the bread periods. Serum total cholesterol decreased by 8% (P = 0.002) in men but was not significantly altered in women during the rye bread period. The wheat bread period did not affect any of the variables studied. Analysis of the serum lipids in tertiles of rye bread consumption confirmed the reduction in total cholesterol (P = 0.048) in men and revealed the reduction in LDL cholesterol (P = 0.032); both were dependent on the amount of rye bread consumed (-2, -14 and -10% in total cholesterol and 0, -12 and -12% in LDL cholesterol). Neither rye nor wheat bread influenced the concentrations of glucose and insulin. In conclusion, rye bread is effective in reducing serum total and LDL cholesterol concentrations in men with elevated serum cholesterol. Good compliance with consuming a relatively large amount of rye bread in the usual diet indicates that rye bread offers a practical dietary means of reducing serum cholesterol in men.

Effects of rye bran, oat bran and soya-bean fibre on bile composition, gallstone formation, gall-bladder morphology and serum cholesterol in Syrian golden hamsters (Mesocricetus auratus)

The effects of rye bran, oat bran and soya-bean fibre on serum lipids, bile composition and gallstone formation were studied in male Syrian golden hamsters (Mesocricetus auratus). The control groups received fibre-free stone-provoking (O1 diet) or non-stone-provoking (O2 diet) diets. The serum cholesterol levels were lower for all groups fed on the diets supplemented with the dietary fibre sources compared with the control groups. The total content of bile acids in bile was higher in groups given rye-bran diets compared with the corresponding controls. The proportion of cholic acid was higher and that of chenodeoxycholic and lithocholic acid lower in the groups given rye-bran-, oat-bran- or soya-bean-fibre-supplemented diets, compared with the corresponding controls. The secondary:primary bile acid ratio was lower in the group given the rye-bran-supplemented O1 diet. The lithocholic:deoxycholic acid ratio was lower in the groups given rye-bran-, oat-bran- or soya-bean-fibre-supplemented diets than in the corresponding controls. A lower frequency of gallstones was observed only for the group receiving the rye-bran-supplemented O1 diet while the lithogenic index was lower in the groups given the rye-bran-supplemented O2 diet. A decreased epithelial volume density of the gall-bladder and an increased smooth muscular volume density were observed in animals given oat-bran- and rye-bran-supplemented O1 diets, whereas for the soya-bean-fibre-supplemented O1 diet, only the smooth muscular volume density was increased.