Guar by-product improves carbohydrate tolerance in healthy human subjects

Guar gum possesses distinct hypoglycemic properties. The other fraction of the guar bean, guar by-product (GBP), was studied to determine if it possesses any hypoglycemic properties. When 25 g GBP or wheat bran were consumed with a carbohydrate test meal by 10 healthy subjects, at 15 and 30 min after the GBP test meal significantly lower normalized plasma glucose responses were measured. Postprandial plasma insulin responses were similar after both test meals. During the first 60 min postprandially, the mean integrated plasma glucose response area was significantly lower after the GBP test meal. These data indicate that GBP, like guar gum, possesses hypoglycemic properties; because of the different chemical characteristics of these 2 guar bean fractions, it seems that their hypoglycemic properties are due probably to different mechanisms.

Guar by-product improves carbohydrate tolerance in rats

These studies were designed to assess the effect of guar by-product (GBP) upon carbohydrate tolerance in rats. Both 1% and 10% GBP suspensions administered immediately before a glucose challenge (1 g/kg body weight) caused a 31% reduction in the integrated plasma glucose response area during a 180 min test. Because 10% GBP caused a flattened glucose response curve, it was studied further. Ten percent GBP caused a similar reduction in plasma glucose during a 360-minute test; similar plasma insulin levels were measured in both 0% and 10% GBP groups throughout the 360-minute test. Ten percent oat bran and 10% soy bran had no effect upon plasma glucose responses. Ten percent GBP was effective in lowering glycemic excursions after sucrose and starch challenges. Rats fed pellet fractions from water and acid treated GBP had the lowest plasma glucose excursions after a glucose challenge; simulated gastric juice treatment of GBP reduced the hypoglycemic activity and simulated pancreatic juice treatment destroyed it. These studies demonstrate the ability of GBP suspensions to significantly reduce plasma glucose excursions after carbohydrate challenge.

Effect of histone H3 sulfhydryl modifications on histone-histone interactions and nucleosome formation and structure

The effect of histone H3 sulfhydryl mnodification and disulfide bridge formation on histone-histone interactions, nucleosome reconstitution and structure has been examined for calf and chicken mononucleosomes. For intramolecular disulfide bridge formation histone H3-H4 complexation is disrupted and no nucleosome-like particle containing all four of the histones could be prepared. Intermolecular disulfide bridge formation between H3 residues 110 and 110 as well as chemical modification of this site with small and with bulky groups allowed histone H3-H4 complexation and the reconstituatioin of a nucleosome-like particle. However, the yield of such particles is decreased and their thermal denaturation properties indicate a reduced stability. These results suggest that the histone core is destabilized or even structurally altered by even a minor modification at H3 position 110, such as carboxymethylation, and therefore this site must be used with caution for the attachment of reporter groups.

Rearrangements and reconstitution of mononucleosomes as monitored by thermal denaturation measurements

Derivative melting profiles of calf thymus mononucleosomes have been examined for changes resulting from variations in solvent pH and ionic strength, histone H1 content, and DNA size. Samples of mononucleosomes were found to rearrange during freeze-drying to form an altered monomer and a series of noncovalent multimers. The derivative melting profiles of these particles differ significantly from those for the untreated monomer and dimer. The noncovalent dimer exhibited a new melting transition at 66 degrees C involving approximately 18 base pairs of DNA normally associated with the highest melting transition. Mononucleosomes were reconstituted from 6 M guanidine hydrochloride to give particles with physical properties including melting profile which were virtually indistinguishable from those of the starting material. This result confirms the notion that no structural domains exist in the histone core that can be irreversible denatured by noncovalent perturbations.