ACE inhibitor captopril reduces ecdysteroids and oviposition in moths.

By using the selective ACE inhibitor captopril, we studied the effect of the angiotensin converting enzyme (ACE) on larval growth, metamorphosis, and reproduction in a lepidopteran species, the cotton leafworm, Spodoptera littoralis. Captopril was detrimental to adult formation and oviposition, and in female moths it elicited decreasing ecdysteroid levels, but increasing trypsin activities. Our results suggest that captopril downregulates oviposition by two independent pathways. Apparently, oviposition is influenced by a complex interaction of ACE, trypsin activity, and ecdysteroid levels.

The angiotensin converting enzyme inhibitor captopril reduces oviposition and ecdysteroid levels in Lepidoptera.

The role of angiotensin converting enzyme (ACE, peptidyl dipeptidase A) in metamorphic- and reproductive-related events in the Egyptian cotton leafworm, Spodoptera littoralis (Lepidoptera, Noctuidae) was studied by using the selective ACE inhibitor captopril. Although oral administration of captopril had no effect on larval growth, topical administration to new pupae resulted in a large decrease of successful adult formation. Oviposition and overall appearance of adults emerging from treated larvae did not differ significantly from those emerging from non-treated larvae. In contrast, topical or oral administration of captopril to newly emerged adults caused a reduction in oviposition. By evaluating the effect of captopril on ecdysteroid titers and trypsin activity, we revealed an additional physiological role for ACE. Captopril exerted an inhibitory effect on ecdysteroid levels in female but not in male adults. Larvae fed a diet containing captopril exhibited increased trypsin activity. A similar captopril-induced increase in trypsin activity was observed in female adults. In male adults, however, captopril elicited reduced levels of trypsin activity. Our results suggest that captopril downregulates oviposition by two independent pathways, one through ecdysteroid biosynthesis regulation, and the other through regulation of trypsin activity. Apparently, fecundity is influenced by a complex interaction of ACE, trypsin activity, and ecdysteroid levels.

The impact of fermentation and in vitro digestion on the formation of angiotensin-I-converting enzyme inhibitory activity from pea and whey protein.

Pea and whey protein were fermented by Lactobacillus helveticus and Saccharomyces cerevisiae in monoculture and in combination at 28 and 37 degrees C in order to release angiotensin-I-converting enzyme (ACE) inhibitory peptides. The fermentation products were subjected to in vitro gastrointestinal digestion, and the digests of nonfermented samples served as controls. After fermentation, the ACE inhibitory activity (%) increased by 18 to 30% for all treatments, except for the fermentations of whey protein with Saccharomyces cerevisiae at 28 degrees C, where no significant change was observed. After digestion, however, both fermented and nonfermented samples reached maximum ACE inhibitory activity. The whey digests tended to have lower (50%) inhibitory concentrations (IC50; 0.14 to 0.07 mg/ml), hence, higher ACE inhibitory activity, than the pea digests (0.23 to 0.11 mg/ml). The nonfermented whey protein digest showed the highest ACE inhibitory activity of all. For pea protein, the nonfermented sample had the lowest IC50 value. These results suggest that in vitro gastrointestinal digestion was the predominant factor controlling the formation of ACE inhibitory activity, hence, indicating its importance in the bioavailability of ACE inhibitory peptides.

Intestinal transport of the lactokinin Ala-Leu-Pro-Met-His-Ile-Arg through a Caco-2 Bbe monolayer.

ACE inhibitory peptides are biologically active peptides that play a role in blood pressure regulation. When derived from food proteins during food processing or gastrointestinal digestion, these peptides could function as efficient agents in treating and preventing hypertension. However, in order to exert an antihypertensive effect by inhibition of the ACE enzyme, they have to reach the bloodstream intact. The aim of this research was to assess if the known ACE inhibitory peptide Ala-Leu-Pro-Met-His-Ile-Arg, derived from a tryptic digest of beta-lactoglobulin, could be absorbed through a Caco-2 Bbe cell monolayer in an Ussing chamber and reach the serosal side undegraded. Samples of the mucosal compartment showed high ACE inhibitory activity. No or only little ACE inhibitory activity was detected in the serosal compartment. However, when the serosal sample was concentrated three-fold, a substantial ACE inhibitory activity was registered. Concomitantly, HPLC and MS clearly showed the presence of Ala-Leu-Pro-Met-His-Ile-Arg in the mucosal compartment, whereas in the serosal compartment only MS was able to detect the heptapeptide. In conclusion. under the observed experimental conditions, the ACE inhibitory peptide Ala-Leu-Pro-Met-His-Ile-Arg was transported intact through the Caco-2 Bbe monolayer, but in concentrations too low to exert an ACE inhibitory activity.