RESUMEN
The aim of this work was to assess the effects of temperature (T), time (t) and pH treatments and an in vitro digestion on the stability of the angiotensin I-converting-enzyme-inhibitory activity (ACEIA) and antithrombotic activity (ATA; assessed as inhibition of platelet aggregation) of selected protein hydrolysates of amaranth named Alb1H103 and GloH88 and GluH24 with dipeptidyl peptidase IV inhibitory activity (DPPIVIA). Heat treatment (40-100 °C) for 1 h showed no significant differences among ACEIA, DPPIVIA and ATA of the heated hydrolysates at pH 4 and 7. There was no statistically significant loss of any bioactivity under heat treatment for 3 h at pH 4.0. Alb1H103 and GluH24 maintained the inhibitory activity of ACE and ATA at pH 7.0 for 3 h, whereas GloH88 maintained ACEIA and ATA for 2.0 h at pH 7.0. The pH effect on hydrolysates bioactivity was assessed in the range of 2.0-12.0. This was negligible on ACEIA, ATA and DPPIVIA. The in vitro digestion was performed using pepsin, trypsin (T) and α-chymotrypsin (C). A previous treatment of hydrolysates with pepsin improved the proteolytic activities of T and C. The hydrolysates kept at 100 °C for 1 h at pH 4.0, showed a significant increase in bioactivity. Conversely, a treatment at pH 7.0 showed no significant difference (p < 0.05) in the hydrolysates bioactivities after their digestion. Thus, biological activity of hydrolysates may be preserved or enhanced, depending on their processing conditions.
RESUMEN
BACKGROUND: Lp(a) is a lipoparticle of unknown function mainly present in primates and humans. It consists of a low-density lipoprotein and apo(a), a polymorphic glycoprotein. Apo(a) shares sequence homology and fibrin binding with plasminogen, inhibiting its fibrinolytic properties. Lp(a) is considered a link between atherosclerosis and thrombosis. Marked inter-ethnic differences in Lp(a) concentration related to the genetic polymorphism of apo(a) have been reported in several populations. AIM: The study examined the structural and functional features of Lp(a) in three Native Mexican populations (Mayos, Mazahuas and Mayas) and in Mestizo subjects. METHODS: We determined the plasma concentration of Lp(a) by immunonephelometry, apo(a) isoforms by Western blot, Lp(a) fibrin binding by immuno-enzymatic assay and short tandem repeat (STR) polymorphic marker genetic analysis by capillary electrophoresis. RESULTS: Mestizos presented the less skewed distribution and the highest median Lp(a) concentration (13.25 mg dL(-1)) relative to Mazahuas (8.2 mg dL(-1)), Mayas (8.25 mg dL(-1)) and Mayos (6.5 mg dL(-1)). Phenotype distribution was different in Mayas and Mazahuas as compared with the Mestizo group. The higher Lp(a) fibrin-binding capacity was found in the Maya population. There was an inverse relationship between the size of apo(a) polymorphs and both Lp(a) levels and Lp(a) fibrin binding. CONCLUSION: There is evidence of significative differences in Lp(a) plasma concentration and phenotype distribution in the Native Mexican and the Mestizo group.
Asunto(s)
Etnicidad/genética , Indígenas Norteamericanos/genética , Lipoproteína(a)/genética , Polimorfismo Genético , Femenino , Fibrina/metabolismo , Marcadores Genéticos , Genética de Población , Humanos , Indígenas Norteamericanos/etnología , Lipoproteína(a)/sangre , Masculino , México/etnología , Fenotipo , Isoformas de Proteínas/sangre , Isoformas de Proteínas/genéticaRESUMEN
High plasma concentrations of lipoprotein (a) [Lp(a)] are now considered a major risk factor for atherosclerosis and cardiovascular disease. This effect of Lp(a) may be related to its composite structure, a plasminogen-like inactive serine-proteinase, apoprotein (a) [apo(a)], which is disulfide-linked to the apoprotein B100 of an atherogenic low-density lipoprotein (LDL) particle. Apo(a) contains, in addition to the protease region and a copy of kringle 5 of plasminogen, a variable number of copies of plasminogen-like kringle 4, giving rise to a series of isoforms. This structural homology endows Lp(a) with the capacity to bind to fibrin and to membrane proteins of endothelial cells and monocytes, and thereby inhibits binding of plasminogen and plasmin formation. This mechanism favors fibrin and cholesterol deposition at sites of vascular injury and impairs activation of transforming growth factor-beta (TGF-beta) that may result in migration and proliferation of smooth muscle cells into the vascular intima. It is currently accepted that this effect of Lp(a) is linked to its concentration in plasma, and an inverse relationship between apo(a) isoform size and Lp(a) concentrations that is under genetic control has been documented. Recently, it has been shown that inhibition of plasminogen binding to fibrin by apo(a) from homozygous subjects is also inversely associated with isoform size. These findings suggest that the structural polymorphism of apo(a) is not only inversely related to the plasma concentration of Lp(a), but also to a functional heterogeneity of apo(a) isoforms. Based on these pathophysiological findings, it can be proposed that the predictive value of Lp(a) as a risk factor for vascular occlusive disease in heterozygous subjects would depend on the relative concentration of the isoform with the highest affinity for fibrin.