The angiotensin I-converting enzyme (kininase II): molecular organization and regulation of its expression in humans

Bradykinin actions in the central nervous system: historical overview and psychiatric implications

Bradykinin (BK), a well-studied mediator of physiological and pathological processes in the peripheral system, has garnered less attention regarding its function in the central nervous system, particularly in behavioural regulation. This review delves into the historical progression of research focused on the behavioural effects of BK and other drugs that act via similar mechanisms to provide new insights into the pathophysiology and pharmacotherapy of psychiatric disorders. Evidence from experiments with animal models indicates that BK modulates defensive reactions associated with panic symptoms and the response to acute stressors. The mechanisms are not entirely understood but point to complex interactions with other neurotransmitter systems, such as opioids, and intracellular signalling cascades. By addressing the existing research gaps in this field, we present new proposals for future research endeavours to foster a new era of investigation regarding BK's role in emotional regulation. Implications for psychiatry, chiefly for panic and depressive disorders are also discussed.

Structural insights into the inhibitory mechanism of angiotensin-I-converting enzyme by the lactotripeptides IPP and VPP

Human somatic angiotensin-1-converting enzyme (sACE) is composed of a catalytic N-(nACE) and C-domain (cACE) of similar size with different substrate specificities. It is involved in the regulation of blood pressure by converting angiotensin I to the vasoconstrictor angiotensin II and has been a major focus in the development of therapeutics for hypertension. Bioactive peptides from various sources, including milk, have been identified as natural ACE inhibitors. We report the structural basis for the role of two lacototripeptides, Val-Pro-Pro and Ile-Pro-Pro, in domain-specific inhibition of ACE using X-ray crystallography and kinetic analysis. The lactotripeptides have preference for nACE due to altered polar interactions distal to the catalytic zinc ion. Elucidating the mechanism of binding and domain selectivity of these peptides also provides important insights into the functional roles of ACE.

Subfornical organ interleukin 1 receptor: A novel regulator of spontaneous and conditioned fear associated behaviors in mice

Impaired threat responding and fear regulation is a hallmark of psychiatric conditions such as post-traumatic stress disorder (PTSD) and Panic Disorder (PD). Most studies have focused on external psychogenic threats to study fear, however, accumulating evidence suggests a primary role of homeostatic perturbations and interoception in regulating emotional behaviors. Heightened reactivity to interoceptive threat carbon dioxide (CO₂) inhalation associates with increased risk for developing PD and PTSD, however, contributory mechanisms and molecular targets are not well understood. Previous studies from our group suggested a potential role of interleukin 1 receptor (IL-1R1) signaling within BBB-devoid sensory circumventricular organ, the subfornical organ (SFO) in CO₂-evoked fear. However, the necessity of SFO-IL-1R1 in regulating CO₂-associated spontaneous fear as well as, long-term fear potentiation relevant to PD/PTSD has not been investigated. The current study tested male mice with SFO-targeted microinfusion of the IL-1R1 antagonist (IL-1RA) or vehicle in a recently developed CO₂-startle-fear conditioning-extinction paradigm. Consistent with our hypothesis, SFO IL-1RA treatment elicited significant attenuation of freezing and increased rearing during CO₂ inhalation suggesting SFO-IL1R1 regulation of spontaneous fear to CO₂. Intriguingly, SFO IL-1RA treatment normalized CO₂-associated potentiation of conditioned fear and impaired extinction a week later suggesting modulation of long-term fear by SFO-IL-1R1 signaling. Post behavior FosB mapping revealed recruitment of prefrontal cortex-amygdala-periaqueductal gray (PAG) areas in SFO-IL-1RA mediated effects. Additionally, we localized cellular IL-1R1 expression within the SFO to blood vessel endothelial cells and observed CO₂-induced alterations in IL-1β/IL-1R1 expression in peripheral mononuclear cells and SFO. Lastly, CO₂-evoked microglial activation was attenuated in SFO-IL-1RA treated mice. These observations suggest a peripheral monocyte-endothelial-microglia interplay in SFO-IL-1R1 modulation of CO₂-associated spontaneous fear and delayed fear memory. Collectively, our data highlight a novel, "bottom-up" neuroimmune mechanism that integrates interoceptive and exteroceptive threat processing of relevance to fear-related pathologies.

Serum IRAP, a Novel Direct Biomarker of Prediabetes and Type 2 Diabetes?

Insulin resistance (IR), currently called prediabetes (PD), affects more than half of the adult population worldwide. Type 2 diabetes (T2D), which often follows in the absence of treatment, affects more than 475 million people and represents 10–20% of the health budget in industrialized countries. A preventive public health policy is urgently needed in order to stop this constantly progressing epidemic. Indeed, early management of prediabetes does not only strongly reduce its evolution toward T2D but also strongly reduces the appearance of cardiovascular comorbidity as well as that of associated cancers. There is however currently no simple and reliable test available for the diagnosis or screening of prediabetes and it is generally estimated that 20–60% of diabetics are not diagnosed. We therefore developed an ELISA for the quantitative determination of serum Insulin-Regulated AminoPeptidase (IRAP). IRAP is associated with and translocated in a stoechiometric fashion to the plasma membrane together with GLUT4 in response to insulin in skeletal muscle and adipose tissue which are the two major glucose storage sites. Its extracellular domain (IRAPs) is subsequently cleaved and secreted in the blood stream. In T2D, IRAP translocation in response to insulin is strongly decreased. Our patented sandwich ELISA is highly sensitive (≥10.000-fold “normal” fasting concentrations) and specific, robust and very cost-effective. Dispersion of fasting plasma concentration values in a healthy population is very low (101.4 ± 15.9 μg/ml) as compared to those of insulin (21–181 pmol/l) and C-peptide (0.4–1.7 nmol/l). Results of pilot studies indicate a clear correlation between IRAPs levels and insulin sensitivity. We therefore think that plasma IRAPs may be a direct marker of insulin sensitivity and that the quantitative determination of its plasma levels should allow large-scale screening of populations at risk for PD and T2D, thereby allow the enforcement of a preventive health policy aiming at efficiently reducing this epidemic.

Human sperm testicular angiotensin-converting enzyme helps determine human embryo quality

Angiotensin-converting enzyme functions in the male reproductive system, but the extent of its function in reproduction is not fully understood. The primary objective of this work was to investigate the relationship between the testicular isoform of angiotensin-converting enzyme present in human spermatozoa and semen parameters, human embryo quality, and assisted reproduction success. A total of 81 semen samples and 635 embryos from couples undergoing oocyte donation cycles at the IVI Bilbao Clinic were analyzed. Semen parameters, embryos quality, and blastocyst development were examined according to the World Health Organization standards and the Spanish Association of Reproduction Biology Studies criteria. The percentage of testicular angiotensin-converting enzyme-positive spermatozoa and the number of molecules per spermatozoon were analyzed by flow cytometry. Both parameters were inversely correlated with human sperm motility. Higher percentages of testicular angiotensin-converting enzyme-positive spermatozoa together with fewer enzyme molecules per spermatozoon were positively correlated with better embryo quality and development. Our results suggest that embryos with a higher implantation potential come from semen samples with higher percentages of testicular angiotensin-converting enzyme-positive cells and fewer enzyme molecules per spermatozoon. Based on these findings, we propose that testicular angiotensin-converting enzyme could be used to aid embryologists in selecting better semen samples for obtaining high-quality blastocysts during in vitro fertilization procedures.

Aerobic exercise training differentially affects ACE C- and N-domain activities in humans: Interactions with ACE I/D polymorphism and association with vascular reactivity

Introduction:

Previous studies have linked angiotensin-converting enzyme (ACE) insertion (I)/deletion (D) polymorphism (II, ID and DD) to physical performance. Moreover, ACE has two catalytic domains: NH2 (N) and COOH (C) with distinct functions, and their activity has been found to be modulated by ACE polymorphism. The aim of the present study is to investigate the effects of the interaction between aerobic exercise training (AET) and ACE I/D polymorphism on ACE N- and C-domain activities and vascular reactivity in humans.

Materials and methods:

A total of 315 pre-selected healthy males were genotyped for II, ID and DD genotypes. Fifty completed the full AET (II, n = 12; ID, n = 25; and DD, n = 13), performed in three 90-minute sessions weekly, in the four-month exercise protocol. Pre- and post-training resting heart rate (HR), peak O₂ consumption (VO₂ peak), mean blood pressure (MBP), forearm vascular conduction (FVC), total circulating ACE and C- and N-domain activities were assessed. One-way ANOVA and two-way repeated-measures ANOVA were used.

Results:

In pre-training, all variables were similar among the three genotypes. In post-training, a similar increase in FVC (35%) was observed in the three genotypes. AET increased VO₂ peak similarly in II, ID and DD (49±2 vs. 57±1; 48±1 vs. 56±3; and 48±5 vs. 58±2 ml/kg/min, respectively). Moreover, there were no changes in HR and MBP. The DD genotype was also associated with greater ACE and C-domain activities at pre- and post-training when compared to II. AET decreased similarly the total ACE and C-domain activities in all genotypes, while increasing the N-domain activity in the II and DD genotypes. However, interestingly, the measurements of N-domain activity after training indicate a greater activity than the other genotypes. These results suggest that the vasodilation in response to AET may be associated with the decrease in total ACE and C-domain activities, regardless of genotype, and that the increase in N-domain activity is dependent on the DD genotype.

Conclusions:

AET differentially affects the ACE C- and N-domain activities, and the N-domain activity is dependent on ACE polymorphism.

The ACE DD genotype and D-allele are associated with exceptional longevity: a meta-analysis

The ACE I/D polymorphism has been associated with longevity, although not consistently. The objective of this study was to detect the possible unequal distribution of the alleles and genotypes of this polymorphism among centenarians and younger segments of the population. Relevant data were extracted from studies in the literature, comparing genotype and allele frequencies between centenarians and younger controls. The association of ACE I/D polymorphism with exceptional longevity was analyzed in a total of 1803 centenarians and 10,484 controls using the chi-square test with the Yates correction. We conducted combined analyses for all ethnic groups studied in the literature (Caucasian, Chinese and Korean) as well as for Caucasians only. The DD genotype (odds ratio (OR): 1.25 (95% confidence interval (CI): 1.02-1.54), P=0.032) and the D-allele were more frequent in Caucasian centenarians compared with their younger controls (OR: 1.16 (95% CI: 1.05-1.28), P<0.001). Similar findings were obtained when all ethnic origin groups were included in the analyses, with no evidence of publication bias or heterogeneity (P>0.05). The present meta-analysis indicates that the ACE D-allele and the DD genotype might confer a modest, albeit significant advantage to reach exceptional longevity.

Is the ACE I/D polymorphism associated with extreme longevity? A study on a Spanish cohort

The 287 bp Ins(I)/Del(D) polymorphism [rs1799752] in intron 16 of the angiotensin-converting enzyme ( ACE) gene has been associated with extreme longevity (≥ 100 years) in some Caucasian and Asian cohorts, but this finding was not corroborated in other reports. We compared the allelic/genotypic frequency of the ACE I/D polymorphism among centenarians ( N = 64, 100—108 years, 89.1% female) and nonagenarians ( N = 47, 90—97 years, 76.6% female), and a control group of healthy young adults ( n = 434, age 20—40 years, 50% female). All participants were of the same Caucasian (Spanish) descent. The ACE I/D genotype met Hardy—Weinberg expectations in all the cohorts. Allelic and genotypic frequencies did not differ by sex in any of the study groups (all p > 0.2). There were no differences in allelic or genotypic frequencies between groups, for example the frequency of the D allele was 62.3% in controls vs. 65.3% in the elderly (64.8% in centenarians). In summary, the ACE I/D polymorphism is not significantly associated with extreme longevity in the Spanish population. Further research is, however, necessary using other approaches. It also remains to be determined if the interaction of ACE genotypes with some other genetic variants exerts a potential effect on longevity.

The antihypertensive effect of peptides: a novel alternative to drugs?

Many types of bioactive peptides that inhibit angiotensin I, angiotensin I converting enzyme (ACE) and Ang II type 1 receptor (AT1) in the cardiovascular system contribute to the prevention and treatment of hypertension. These inhibitory peptides are derived from many food proteins or artificial synthetic products. Further research examining the bioavailability of ACE inhibitory peptides will lead to the development of more effective ACE inhibitory peptides and foods. Our research also demonstrates that ACE inhibitory peptide LAP may lower blood pressure with no adverse effects.

Lipoproteins, vascular-related genetic factors, and human longevity

The relationships among lipoprotein metabolism, genetic vascular factors, vascular disease, and Alzheimer's disease suggest that the examination of centenarian populations in relation to certain genes or lipoprotein metabolism provide insights into human longevity. The findings on the higher frequency of the apolipoprotein E epsilon4 allele in middle-aged subjects than in centenarians were substantially confirmed. On the contrary, recent findings did not confirm previous data on increased prevalence of the high-risk angiotensin I converting enzyme D allele in French centenarians. The variability in the strength of association between angiotensin I converting enzyme polymorphism and longevity could be related to regional differences in angiotensin I converting enzyme D allele frequency in Europe recently showed, as also recently reported for apolipoprotein Eepsilon2 and epsilon4 allele in centenarians. Indeed some studies of lipoprotein profiles in centenarians have also had contradictory outcomes, with evidence of lower serum levels of high-density lipoprotein cholesterol, with higher high-density lipoprotein 2 cholesterol subfraction, larger high-density lipoprotein and low-density lipoprotein particle sizes, and higher lipoprotein(a) concentration in centenarians, which is apparently disadvantageous for human longevity. Elevated lipoprotein(a) serum levels, increasing the risk for cerebrovascular disease, may play a role in determining clinical Alzheimer's disease, but lipoprotein(a) elevation in centenarians, in the absence of other coronary artery disease risk factors, appears as a positive survival factor. In different populations, there are significant trends in the reduction of serum apolipoprotein E levels from apolipoprotein E epsilon2- to epsilon4-carriers and significant differences in serum apolipoprotein E levels with respect to age in epsilon4-carriers but only after adjustment for high-density lipoprotein cholesterol. While further studies are needed to confirm the possible role of apolipoprotein E concentration as putative longevity factor this paper provides an overview of many of the investigated vascular factors with respect to longevity.

Angiotensin, bradykinin and the endothelium

Angiotensins and kinins are endogenous peptides with diverse biological actions; as such, they represent current and future targets of therapeutic intervention. The field of angiotensin biology has changed significantly over the last 50 years. Our original understanding of the crucial role of angiotensin II in the regulation of vascular tone and electrolyte homeostasis has been expanded to include the discovery of new angiotensins, their important role in cardiovascular inflammation and the development of clinically useful synthesis inhibitors and receptor antagonists. While less applied progress has been achieved in the kinin field, there are continuous discoveries in bradykinin physiology and in the complexity of kinin interactions with other proteins. The present review focuses on mechanisms and interactions of angiotensins and kinins that deal specifically with vascular endothelium.

Working outside the system: an update on the unconventional behavior of the renin–angiotensin system components

The renin-angiotensin system (RAS) plays an important role in regulating arterial pressure, blood volume, thirst, cardiac function, and cellular growth. Both a circulating and multiple tissue-localized systems have been identified, and are generally portrayed as a series of reactions that occur sequentially with a single outcome: angiotensinogen is cleaved by renin to form angiotensin I, which in turn is processed by angiotensin-converting enzyme (ACE) to angiotensin II, which then activates either the AT1 or the AT2 plasma membrane receptor. Evidence has emerged, however, showing that some RAS components play important roles outside of this canonical scheme. This article provides an overview of some recently identified extra-system functions. In addition to forming angiotensin II, ACE is a multifunctional enzyme equally important in the metabolism of vasodilator and antifibrotic peptides. As the membrane-bound form, ACE functions as a "receptor" that initiates intracellular signaling leading to gene expression. Both angiotensin I and II may lead to actions that are independent of, or even oppose, those of the RAS via their metabolism by the novel ACE-homologue ACE2. The two angiotensin II receptor types have ligand-independent roles that influence cellular signaling and growth, some of which may result from the ability to form hetero-dimers with other 7-transmembrane receptors. Finally, intracellular angiotensin II has been demonstrated to have actions on cell-communication, gene expression, and cellular growth, through both receptor-dependent and independent means. A greater understanding of these extra-system functions of the RAS components may aid in the development of novel treatments for hypertension, myocardial ischemia, and heart failure.

Vascular genetic factors and human longevity

Complex inter-relationships between age-associated illnesses, such as vascular disease and Alzheimer's disease (AD), suggest that biological and genetic pathways may be worthy of examination in centenarian populations to provide insights into human longevity. This is also borne out by the involvement of lipoprotein metabolism and a number of vascular genetic risk factors. Repeated findings of a higher frequency of the apolipoprotein E (APOE) epsilon4 allele in middle-aged subjects compared with centenarians were reported. Furthermore, we have also shown how in different populations there is a significant trend in reduction of serum APOE levels from APOE epsilon2- to epsilon4-carrier as well as significant differences in serum APOE levels respect to age in epsilon4-carriers but only after adjustment for HDL cholesterol. In contrast, findings of increased prevalence of the angiotensin I converting enzyme 1 (ACE1) D allele in French centenarians have not been replicated, suggesting the possibility that regional differences may occur in ACE1(*)D frequency within Europe in centenarians, as has been recently reported for APOE epsilon2 and epsilon4 alleles. A number of studies have examined the potential role in longevity of other genes involved in vascular risk, haemostasis, and blood pressure regulation [methyltetrahydrofolatereductase (MTHFR), apolipoprotein A1 (APOA-I), apolipoprotein C3 (APOC-III), apolipoprotein A4 (APOA-IV), paraoxonase 1 (PON1), plasminogen activator inhibitor type I (PAI-1)], with contrasting results. While further studies are needed to confirm the possible role of APOE concentration as putative longevity factor, this paper provides an overview of genetic vascular factors potentially involved in human longevity.

Species-specific splicing and expression of angiotensin converting enzyme

Angiotensin converting enzyme (ACE) is a critical determinant in the pathogenesis of various cardiovascular diseases and in the control of male fertility. Multiple isoforms of ACE protein are present in body fluids and tissues, but their formation and functions in vivo remain to be investigated. To determine whether alternative splicing contributes to the formation of ACE isoforms, this study was designed to clone all possible spliced transcripts in rat. We found that the splicing of intron 13 in testicular ACE was species-dependent. Compared with human and mouse testicular ACE, rat testicular ACE (rtACE) retained intron 13 in its mature transcripts. The insertion of the intron 13 did not change or shift the reading frame. Cloning and characterization of the rtACE showed that, in addition to testicular tissue, it was wildly expressed in somatic tissues, such as lung, kidney, cardiac ventricle, and skeletal muscle from both genders. Furthermore, we demonstrated that the expression of rtACE was developmentally up-regulated in testicular tissue and increased during cardiac hypertrophy. Our data suggests that the inclusion of intron 13 produces a novel ACE isoform. This isoform likely participates in local angiotensin II formation in both somatic and germinal tissues, and associates with certain physiological or pathophysiological events.

Angiotensin-converting enzyme gene and longevity in the Xin Jiang Uighur autonomous region of China: an association study

BACKGROUND

Longevity can be regarded as a multifactorial trait that results from an interaction between environmental factors and sets of epistatic alleles that have pleiotropic age-dependent effects. The Hotan district in the Xin Jiang Uighur Autonomous region of China is relatively isolated and is well known for an ethnic group that displays marked longevity.

METHODS

We performed a correlation study between the insertion/deletion (I/D) polymorphism of the angiotensin-converting enzyme (ACE) gene and longevity by comparing distributions of the polymorphism between three different ethnic groups in this region. We obtained data from 424 subjects comprising 227 Uighur individuals, 108 Kazakh individuals, and 89 Han individuals. All subjects in the latter two groups ranged in age from 65 to 70 years, whereas the Uighur subjects actually comprised two different age groups: those ranging in age from 59 to 70 years (Uighur older group in Hotan [UOH]) and those ranging in age from 90 to 113 years (Uighur longevity group in Hotan [ULH]). Genomic DNA was extracted from peripheral white blood cells. Polymerase chain reaction was performed to amplify the I/D polymorphic region of the ACE gene.

RESULTS

Frequencies of the insertion (I) and deletion (D) alleles were 0.596 (243/408) and 0.404 (165/408) in the Uighur group, 0.606 (130/216) and 0.394 (85/216) in the Kazakh group, and 0.657 (117/178) and 0.343 (61/178) in the Han group. The overall distributions of alleles in these three groups did not differ significantly (chi(2) = 4.6, p =.33). Within the Uighur group, frequency of the D allele was significantly higher in the ULH group (0.448) than in the UOH group (0.355) (p <.04).

CONCLUSIONS

This association reflects a genetic influence on differential survival and may point to pleiotropic age-dependent effects on longevity. Our data may help elucidate the relationship between natural longevity and race difference among individuals in the Xin Jiang Uighur Autonomous region of China.

Activity of testis angiotensin converting enzyme (ACE) in ejaculated human spermatozoa

Testicular angiotensin converting enzyme (ACE) isozyme is likely to play important functional roles in male reproduction. Several studies have shown that ACE is released from human spermatozoa during capacitation and that ACE is associated with reduced sperm motility. Recently, we established an assay to detect testicular ACE activity in human spermatozoa. The purpose of this study was to determine if testicular ACE activity is related to sperm motility in human ejaculates. Semen samples were collected from 80 infertile patients. According to the semen characteristics, they were divided into four (WHO) categories. Enzyme activities of ACE in spermatozoa (testicular ACE) and seminal plasma (somatic ACE) were spectrophotometrically determined. Total testicular ACE activity in spermatozoa was measured by solubilization of spermatozoa with Triton X-100. Membrane testicular ACE activity was measured in a sperm : PBS suspension. Sperm concentration and sperm motility were 136.6 +/- 154.1 x 10(6)/mL and 58.6 +/- 23.4%, respectively (mean +/- SD). Enzyme activities of membrane testicular ACE, total testicular ACE and somatic ACE were 0.273 +/- 1.219 microU/10(6) spermatozoa, 0.35 +/- 1.34 microU/10(6) spermatozoa and 684.7 +/- 226.6 mU/mL, respectively. A negative correlation was observed between sperm motility and membrane testicular ACE activity (p < 0.05). Membrane testicular ACE activity in 44 normal semen samples was 0.04 +/- 0.02 microU/10(6) spermatozoa, whilst that in 36 abnormal semen samples was 0.24 +/- 0.42 microU/10(6) spermatozoa. There was a significant difference between these two groups (p < 0.01). Membrane testicular ACE in sperm samples from normozoospermic men was significantly lower than that from oligoasthenozoospermic men (p < 0.05). These findings suggest that testicular ACE is released from normal functional spermatozoa for them to have fertilizing ability.

Kinin-mediated anaphylactoid reaction implicated in acute intra-operative pulseless electrical activity

A 65-year-old patient undergoing total hip replacement under general anaesthesia suffered acute pulseless electrical activity with a fatal outcome. A kinin-mediated analphylactoid reaction following administration of a polygeline plasma expander (Haemaccel) was implicated by in vitro testing. This case report illustrates the diagnostic difficulties posed by non-histaminoid anaphylactoid reactions and the resistance to epinephrine of kinin-mediated hypotension.

Pharmacology and cardiovascular implications of the kinin-kallikrein system

Kinins are peptide hormones that can exert a significant influence on the regulation of blood pressure and vascular tone due to their vasodilatatory, natriuretic and growth modulating activity. Their cardiovascular involvement in physiological and pathophysiological situations has been studied intensively since inhibitors for angiotensin I-converting enzyme and selective receptor antagonists have become available for pharmacologically potentiating or inhibiting kinin-mediated reactions. Molecular biological analysis and the establishment of genetically modified animal models have also allowed newer information to be acquired on this subject. In this review, the components and cardiovascularly relevant mechanisms of the kinin-kallikrein system shall be described. Organ-specific effects concerning the kidneys, the vascular system, the heart and nervous tissue shall also be illustrated. On this issue, the physiological functions and pathophysiological implications of the kinin-kallikrein system should be clearly distinguished from the many, mostly endothelium-mediated protective effects which occur during ACE inhibition due to the potentiation of kinin effects. Finally, a view shall also be cast upon newly discovered targets of action, which could be exploited for therapeutically altering the kinin-kallikrein system.

Angiotensin I-converting enzyme insertion/deletion polymorphism: clinical implications

Since the identification of an Insertion/Deletion polymorphism in the ACE gene, numerous studies have evaluated the potential risk of the DD genotype in cardiovascular disease and hypertension. The report of many conflicting publications reveals a strong need for reviewing the most important data. There is evidence of the absence of an association between the ACE polymorphism and hypertension in Caucasians. In blacks a positive association between the D allele and high blood pressure was seen, Japanese studies show discrepant results. Several studies showed no association between the ACE polymorphism and the risk of myocardial infarction. However, in certain subpopulations, such as low risk patients or coronary care unit patients, an increased risk of myocardial infarction in DD type is present, and a meta-analysis supports this proposition. Because of conflicting data, the potential association between the ACE polymorphism and coronary artery disease, cerebrovascular disease, left ventricular hypertrophy, hypertrophic and idiopathic dilated cardiomyopathy, carotid artery disease and diabetic and immunoglobin A nephropathy, remains inconclusive.

Severe hypotension associated with angiotensin-converting enzyme inhibition in anaesthesia

Three cases of severe hypotension associated with the use of angiotensin-converting enzyme inhibitors (ACEIs) and intravenous administration of the synthetic colloid Gelofusin (Braun Medical Ltd) are presented. A possible mechanism of interaction between ACEIs and Gelofusin is discussed. All three patients were treated successfully.

Kinin receptors in human vascular tissue: their role in atheromatous disease

Using samples of many human blood vessels, obtained at autopsy and specific antibodies directed to peptide sequences of the kinin B1 and B2 receptors, we demonstrate the localisation of these receptors within the human vascular system using standard immunolabelling techniques. In large elastic arteries and veins, kinin receptors are present only in the endothelial cells whereas in all muscular arteries and arterioles, these receptors are present in both the endothelial and smooth muscle cells. The identification of kinin receptors in human blood vessels confirms that kinins may modulate both vascular permeability and contractility. The incidental finding at histology, of patchy atheromatous disease in the coronary, femoral, vertebral and pericallosal arteries, assisted in elucidating the role of these receptors in the commonest disease affecting human blood vessels. Intense labelling for B1 receptors was observed in the endothelial cells, foamy macrophages, inflammatory cells and fibroblasts within the thickened intima of the plaque as well as in smooth muscle cells of the underlying tunica media. Immunoreactive B2 receptors were also observed in these cells but with reduced intensity. The intense immunolabelling of B1 receptors in these regions suggest that these may be induced by atheromatous disease and may have therapeutic importance for the B1 receptor antagonists.

The angiotensin I-converting enzyme (ACE) locus is strongly associated with age and duration of diabetes in patients with type I diabetes

We have investigated the frequency of the angiotensin I-converting enzyme (ACE) insertion/ deletion (I/D) polymorphism in 249 patients with type I diabetes and 162 normal healthy controls. There was no significant difference in the frequency of ACE genotypes between those patients with diabetic nephropathy (n = 72) (nephropaths) compared to those with no proteinuria after 20 years duration of diabetes (n = 86) (normoalbuminurics). There was, however, a significant difference in the frequency of ACE genotypes between the short-duration and long-term normoalbuminuric group (chi = 11.5, p = 0.001). Analysis of the ACE genotypes with respect to age and duration of diabetes showed that homozygosity for the insertion (I/I) genotype was significantly decreased with longer duration of diabetes (r2 = 92.7%, p < 0.009). No association was found with age in the normal controls. In conclusion, these results suggest that the ACE locus may be associated with longevity and survival in patients with type I diabetes rather than diabetic nephropathy or microvascular disease per se.

Genetic associations with human longevity at the APOE and ACE loci

In an effort to dissect the genetic components of longevity, we have undertaken case-control studies of populations of centenarians (n = 338) and adults aged 20-70 years at several polymorphic candidate gene loci. Here we report results on two genes, chosen for their impact on cardiovascular risk, encoding apolipoprotein E (ApoE), angiotensin-converting enzyme (ACE). We find that the epsilon 4 allele of APOE, which promotes premature atherosclerosis, is significantly less frequent in centenarians than in controls (p < 0.001), while the frequency of the epsilon 2 allele, associated previously with type III and IV hyperlipidemia, is significantly increased (p < 0.01). A variant of ACE which predisposes to coronary heart disease is surprisingly more frequent in centenarians, with a significant increase of the homozygous genotype (p < 0.01). These associations provide examples of genetic influences on differential survival and may point to pleiotropic age-dependent effects on longevity.