Effects of long-term intake of lactotripeptides on cardiovascular risk factors in hypertensive subjects.

BACKGROUND/OBJECTIVES: Lactobacillus helveticus LBK-16H-fermented milk products containing tripeptides isoleucine-proline-proline and valine-proline-proline lower blood pressure in hypertensive subjects using office and home blood pressure registration. The present study was aimed to evaluate the effects of two doses of these lactotripeptides on 24-h ambulatory blood pressure and lipidomics profiles in mildly hypertensive subjects. SUBJECTS/METHODS: In a randomized, double-blind, placebo-controlled parallel group study, 89 mildly hypertensive subjects ingested, after a 1-month run-in period, a fermented milk drink with 5 mg per day of lactotripeptides during 3 months, and a milk drink with 50 mg per day of lactotripeptides for the following 3 months, or a placebo milk drink without lactotripeptides. Ambulatory blood pressure (24 h) was recorded at baseline and at the end of the intervention periods. Lipidomics profiles were characterized before and after the 6-month intervention. RESULTS: After the second intervention period (50 mg per day of lactotripeptides), systolic and diastolic 24-h blood pressures decreased significantly in the peptide, but not in the placebo group. However, the treatment effects -2.6 mm Hg (95% confidence interval (CI): -5.7 to 0.4) in systolic and -1.3 mm Hg (95% CI: -3.4 to 0.8) in diastolic blood pressure did not reach statistic significance. Ingestion of 5 mg per day of lactotripeptides for 3 months did not lower blood pressure. The peptide group was dominated by decrease in multiple phospholipids (PL). CONCLUSIONS: Ingestion of fermented milk with daily dose of 50 mg of lactotripeptides appears to lower elevated blood pressure slightly from the baseline, but not significantly compared with the placebo group and to induce significant decreases in multiple PL.

Rabbit atherosclerotic lesions express scavenger receptor AIII mRNA, a naturally occurring splice variant that encodes a non-functional, dominant negative form of the macrophage scavenger receptor.

Macrophage class A scavenger receptor types I and II (SR-AI and II) mediate the uptake of oxidized LDL in atherosclerotic lesions. The recently described type III receptor (SR-AIII), which lacks amino acids encoded by exon 10 of the SR-A gene, is unable to mediate the uptake of ligands and acts as a dominant negative regulator in the trimeric SR-A molecule. To find out whether SR-AIII might play a role in the regulation of SR-A activity in the arterial wall, we studied its expression in normal and atherosclerotic aortic intima-medias of Watanabe heritable hyperlipidemic (WHHL) and cholesterol-fed New Zealand white (NZW) rabbits. SR-A mRNA was amplified by reverse transcription-polymerase chain reaction (RT-PCR) with a SR-AIII-specific primer pair and with a primer pair suitable for both SR-AI and III. Very low SR-AI expression and no SR-AIII expression was found in the lesion-free aortic intima-medias of WHHL rabbits and control NZW rabbits. WHHL rabbit fatty streaks contained abundant SR-AI expression and low-level SR-AIII expression. In contrast, the numerous fatty streaks and fatty plaques appearing in the aortas of cholesterol-fed (14 weeks) NZW rabbits, and the fatty plaques of WHHL rabbits contained clearly detectable SR-AIII expression in addition to the abundant SR-AI expression. In addition, SR-AIII mRNA was detected in NZW and WHHL rabbit livers. The results suggest that in advanced atherosclerotic lesions, cells may protect themselves from the excessive uptake of oxidized lipoproteins by generating SR-A molecules which cannot bind modified LDL.

Relationship of angiotensin-converting enzyme gene polymorphism to carotid wall thickness in middle-aged men.

The insertion/deletion (I/D) polymorphism of the human angiotensin-converting enzyme (ACE) gene is a major determinant of circulating ACE levels. The D allele has been suggested to be a potent risk factor for coronary artery disease; however, the effect of the ACE gene on carotid atherosclerosis remains controversial. We therefore studied the relationship between the ACE gene I/D polymorphism and carotid artery intima-media thickness (IMT). A random sample of 300 men aged 50-59 years living in southern Finland were selected, and 233 agreed to participate (74%). Data were collected in 219 subjects. Quantitative B-mode ultrasonography was used to measure the maximum near and far wall IMT of right and left common, bifurcation, and internal carotid artery. The mean maximum IMT (overall mean) was calculated as the mean of 12 maximum IMTs at 12 standard sites. Patients with an IMT higher than 1.7 mm in at least one of 12 standard sites were assumed to have carotid atherosclerosis. The I/D polymorphism was determined by polymerase chain reaction. Overestimation of the frequency of the DD genotype was eliminated by insertion-specific primer and the inclusion of 5% dimethylsulfoxide. No significant differences were found in carotid wall thickness between the three genotypes; the overall mean IMT were 1.18 +/- 0.30, 1.22 +/- 0.24, and 1.08 +/- 0.40 mm in genotypes of II, ID, and DD, respectively. Similarly, the ACE genotypes and allele frequencies did not differ significantly between the subjects with and those without carotid atherosclerosis. There was no association in the subgroups among only nonsmoking subjects or subjects without chronic medication. The present data indicate that the I/D polymorphism of the ACE gene is not related to carotid IMT and is unlikely to play a major role in carotid atherosclerosis.

Angiotensin-converting enzyme gene polymorphism is associated with coronary heart disease in non-insulin-dependent diabetic patients evaluated for 9 years.

The insertion/deletion (I/D) polymorphism of the human angiotensin-converting enzyme (ACE) gene is a major determinant of circulating ACE levels. Recent studies have found the ACE D allele to be associated with an increased risk for coronary heart disease (CHD) in diabetic and nondiabetic subjects. This association has not been evaluated in prospective studies. We therefore studied the relationship between ACE gene I/D polymorphism and CHD in patients with non-insulin-dependent diabetes mellitus (NIDDM) evaluated for 9 years. The I/D polymorphism was determined by polymerase chain reaction (PCR). Overestimation of the frequency of the DD genotype was eliminated by insertion-specific primers and inclusion of 5% dimethylsulfoxide (DMSO). Eighty-three patients were evaluated for a mean period of 9.1 years (range, 7.4 to 10.5). Among them, 64 patients showed no CHD at entry. During the follow-up period, 21 patients (37.5%) developed CHD. The systolic blood pressure (P = .046), fasting blood glucose (P < .01), and prevalence of hypertension (P < .001) increased, while high-density lipoprotein (HDL) cholesterol (P < .001) decreased. Patients who developed CHD were older than those who did not; the mean age was 59.3 and 53.2 years, respectively (P = .003). The prevalence of albuminuria at follow-up examination was higher in CHD subjects versus non-CHD subjects (61.9% v 20.9%, P = .012). The D allele of the ACE gene was significantly more frequent in subjects with CHD versus those without CHD in both follow-up (P = .028, chi2 test) and cross-sectional (P = .033, chi2 test) settings. No difference could be detected between the three genotypes in age, body mass index (BMI), blood pressure, or plasma lipid levels. In our logistic regression analysis, the best model selected the DD genotype (P = .0105) and age (P = .0407) as significant risk factors for CHD. This model classified 89% of the subjects correctly. In conclusion, this 9-year prospective study supports the hypothesis that the ACE I/D polymorphism is an important and independent risk factor for CHD in patients with NIDDM.

Angiotensin-converting enzyme insertion/deletion polymorphism and diabetic albuminuria in patients with NIDDM followed Up for 9 years.

Nephropathy is a major cause of premature morbidity and mortality in patients with non-insulin-dependent diabetes mellitus (NIDDM). The insertion/deletion (I/D) polymorphism of angiotensin-converting enzyme (ACE) is a genetic determinant of plasma ACE levels. Recent studies have found I/D polymorphism of the ACE gene to be associated with nephropathy in NIDDM. This association has not been evaluated in prospective studies. We, therefore, studied the relationship between ACE gene I/D polymorphism and diabetic albuminuria and glomerular filtration rate (GFR) in 83 NIDDM patients followed up for 9 years. At baseline, 29% (24 of 83) of the diabetic patients had an increased (>30 mg/24 h) urinary albumin excretion rate (UAER) and the prevalence of albuminuria at the 9-year examination was 35% (29 of 83). During the follow-up period, systolic blood pressure (p = 0.044), prevalence of hypertension (p < 0.01), and fasting blood glucose levels (p < 0.01) increased, while high-density lipoprotein cholesterol (p < 0.01) decreased. The declines of GFR during the follow-up period were 8.5, 14.1, and 16.3% within genotype groups of II, ID, and DD, respectively (p values for decreases: NS for II, <0.001 for ID, and <0.001 for DD). Patients with the DD genotype tended to have a steeper decrease of GFR, but the change was not statistically significant between the genotype groups. The increases of UAER during the follow-up period were 35.1, 8.3, and 122.4% within genotype groups of II, ID, and DD, respectively, but p values for all increases were not significant. Parallel to GFR, patients with the DD genotype tended to have a steeper increase of UAER, but the change was not statistically significant between the genotype groups. There were no differences in the ACE genotype distribution and allele frequencies between the patients with or without albuminuria either at follow-up or in cross-sectional settings. In conclusion, this 9-year follow-up study does not support the hypothesis that the ACE I/D polymorphism is a major genetic marker of diabetic nephropathy in NIDDM patients.

Expression of lipoprotein receptors in atherosclerotic lesions.

Atherosclerosis is characterized by the presence of lipid-loaded cells which are derived from macrophages and smooth muscle cells. Several lipoprotein receptors may be involved in cellular lipid uptake. These receptors include: scavenger receptor(s); LDL receptor-related protein/alpha2-macroglobulin receptor (LRP); LDL receptor; and VLDL receptor. With the exception of the LDL receptor, all of these receptors are expressed in atherosclerotic lesions. While scavenger receptors are mostly expressed in macrophages, the LRP and VLDL receptor may play an important role in mediating lipid uptake in smooth muscle cells. It is evident that no single receptor pathway is solely responsible for the increased lipid uptake in lesion cells but several redundant mechanisms may contribute to the uptake and degradation of lipoproteins in atherosclerotic lesions.

Expression of LDL receptor, VLDL receptor, LDL receptor-related protein, and scavenger receptor in rabbit atherosclerotic lesions: marked induction of scavenger receptor and VLDL receptor expression during lesion development.

BACKGROUND: Atherosclerotic lesions contain foam cells that arise from monocyte-macrophages and smooth muscle cells (SMCs) by excessive uptake of lipoproteins. There are many candidate receptors for the lipid accumulation, such as LDL receptor (LDLR), VLDL receptor (VLDLR), LDL receptor-related protein (LRP), and scavenger receptors (SRs). However, little quantitative information exists on the expression of these receptors in normal and atherosclerotic arteries. METHODS AND RESULTS: Competitive reverse transcription-polymerase chain reaction and in situ hybridization were used for the studies in New Zealand White (NZW) and Watanabe heritable hyperlipidemic (WHHL) rabbit aortic intima-medias. NZW rabbits were fed a 1% cholesterol diet for 0 (control group), 3, 6, or 14 weeks. LDLR mRNA expression was low in aortic intima-medias of all groups. Of the analyzed receptors, LRP had the highest expression in the control group, and its mRNA was induced threefold in the 14-week group, the aortas of which had extensive lesions. SR expression was low and VLDLR expression moderate in the control group. Both receptors were highly induced during cholesterol feeding (SRs, 3-fold and 270-fold induction; VLDLR, 15-fold and 100-fold induction in the 3-week and 14-week groups, respectively). Comparable results were obtained from WHHL rabbits: high basal LRP mRNA in normal intima-medias; moderate induction of LRP and marked induction of SRs and VLDLR in fatty streaks and fatty plaques. In situ hybridization indicated that LRP and VLDLR were expressed in SMCs and macrophages. VLDLR expression was also observed in endothelial cells. SR expression was detected only in macrophages. CONCLUSIONS: SR and VLDLR mRNAs were highly induced in atherosclerotic lesions. VLDLR and LRP may be involved in the formation of both SMC-and macrophage-derived foam cells, whereas SRs play an important role in lipid uptake in macrophages.

Expression of extracellular SOD and iNOS in macrophages and smooth muscle cells in human and rabbit atherosclerotic lesions: colocalization with epitopes characteristic of oxidized LDL and peroxynitrite-modified proteins.

Oxidative processes play an important role in atherogenesis. Because superoxide anion and nitric oxide (NO) are important mediators in vascular pathology, we studied the expression of extracellular superoxide dismutase (EC-SOD) and inducible nitric oxide synthase (iNOS) in human and rabbit atherosclerotic lesions by using simultaneous in situ hybridization and immunocytochemistry and EC-SOD enzyme activity measurements. We also analyzed the presence in the arterial wall of oxidized lipoproteins and peroxynitrite-modified proteins as indicators of oxidative damage and possible mediators in vascular pathology. EC-SOD and iNOS mRNA and protein were expressed in smooth muscle cells and macrophages in early and advanced lesions. The expression of both enzymes was especially prominent in macrophages. As measured by enzyme activity, EC-SOD was the major SOD isoenzyme in the arterial wall. EC-SOD activity was higher in highly cellular rabbit lesions but lower in advanced, connective tissue-rich human lesions. Despite the abundant expression of EC-SOD, malondialdehyde-lysine and hydroxynonenal-lysine epitopes characteristic of oxidized lipoproteins and nitrotyrosine residues characteristic of peroxynitrite-modified proteins were detected in iNOS-positive, macrophage-rich lesions, thus implying that malondialdehyde, hydroxynonenal, and peroxynitrite are important mediators of oxidative damage. We conclude that EC-SOD, iNOS, and the balance between NO and superoxide anion play important roles in atherogenesis. EC-SOD and iNOS are highly expressed in lesion macrophages. High EC-SOD expression in the arterial wall may be required not only to prevent deleterious effects of superoxide anion but also to preserve NO activity and prevent peroxynitrite formation. Modulation of arterial EC-SOD and iNOS activities could provide means to protect arteries against atherosclerotic vascular disease.