Effects of captopril and enalapril on zinc metabolism in hypertensive patients

Do medicines commonly used by older adults impact their nutrient status?

Background

Chronic health conditions and polypharmacy are common among the older population and associated with increased risks of adverse events, medicine-interactions, geriatric syndromes, falls and mortality. Poor nutrition is also common in older people. Causal associations between medication use and older people's nutrient status is seldom discussed.

Objectives

The objectives of this review were to summarise the literature reporting associations between medicines commonly prescribed to older adults and nutrient deficiencies, and to discuss the clinical implications and management.

Methods

Medicine information resources (n = 5) were searched for information about nutrient deficiencies associated with common medicines used by older people and listed within the top 50 medicines prescribed by volume on the Australian Pharmaceutical Benefits Scheme. This was followed by a search for clinical studies published on PubMed from inception to April 2020. Data was extracted, tabulated and summarised with clinical information relevant to pharmacists and clinicians involved in the care of older people taking medicines.

Results

A total of 23 clinical studies were identified reporting medicine-induced nutrient deficiencies in older adults. Vitamin B12, sodium, magnesium were identified as the 3 main nutrients susceptible to deficiency by medicines used to treat cardiovascular disease, neurological conditions, gastrointestinal conditions, and diabetes. The coenzyme CoQ10 was depleted by statins.

Conclusion: Certain medicines commonly prescribed to older adults are associated with nutrient deficiencies that may be clinically significant. Given the high prevalence of comorbidities and polypharmacy it is possible that some of these individual drug-induced nutrient deficiencies are compounded, warranting both clinical and research attention.

Intra-nasal zinc level relationship to COVID-19 anosmia and type 1 interferon response: A proposal

Anosmia is common among COVID-19 patients and anosmia assessment is proposed to be useful in the early diagnosis and prognosis of patients. Data on the pathogenesis of anosmia during COVID-19 suggest potential olfactory nerve involvement. Zinc is an essential micronutrient that regulates the immune responses, and zinc deficiency is known to induce anosmia and ageusia. We previously proposed that a drop in nasal zinc level is a normal nasal immune response to acute viral infections, including SARS-CoV-2 infection, and play a role in the pathogenesis of anosmia. The drop in the local zinc level in response to SARS-CoV-2 may lead to lower type 1 interferons and shift toward Th2 immune responses; if prolonged, it may lead to increased viral replication and more severe disease. In people who are at risk for baseline systemic zinc deficiency, such as the elderly and those with chronic diseases such as, chronic lung disease, diabetes, cardiovascular disease, and cancer, SARS-CoV-2 infection-induced drop in nasal zinc level may be more severe and prolonged and lead to an insufficient anti-viral nasal immune response and control the spread of the virus systemically and to the lungs. A better understanding of the clinical implications of baseline systemic zinc deficiency on anosmia and nasal immune responses may allow the development of new treatment strategies to slow down or stop the systemic invasion of SARS-CoV-2.

Dietary Sodium Intake is Predicted by Antihypertensive Medication Regimen in Patients With Heart Failure

BACKGROUND

Low-sodium diet adherence is foundational to heart failure (HF) self-management. Altered salt taste perception caused by angiotensin-converting enzyme (ACE) inhibitors commonly prescribed to patients with HF may increase sodium consumption. We hypothesized sodium intake, indicated by dietary sodium density, would be significantly higher among patients with HF prescribed ACE inhibitors compared with those not prescribed the drug.

OBJECTIVE

The aim of this study was to assess the association between prescribed ACE inhibitors and dietary sodium density in patients with HF.

METHODS

We conducted a secondary analysis of baseline data from patients with HF in an observational longitudinal study. Sodium density was derived by dividing averaged daily sodium intake from 4-day food diaries by averaged kilocalories consumed. Medical chart review was conducted to ascertain prescribed medications. Patients were categorized as prescribed and not prescribed an ACE inhibitor. t Tests were conducted to compare sodium intake between groups, and linear regression was conducted to examine whether prescribed ACE inhibitors independently predicted sodium density controlling for age, gender, New York Heart Association class, prescribed diuretics, and β-blockers.

RESULTS

Analyses included 255 patients with HF aged 61 ± 12 years, with 67% male, 44% New York Heart Association class III/IV, and 68% prescribed an ACE inhibitor. Compared with those not prescribed an ACE inhibitor, 13% more sodium per kilocalorie was consumed by patients prescribed an ACE inhibitor. Prescribed ACE inhibitor independently predicted dietary sodium density (β = 0.238, P = .009).

CONCLUSIONS

Sodium intake was higher among patients prescribed ACE inhibitors. Interventions to assist patients with HF with dietary sodium adherence can be informed by assessing medication regimens.

Zinc as nutritional intervention and prevention measure for COVID-19 disease

The present spread of severe acute respiratory syndrome coronavirus 2, provoking COVID–19 disease, progresses rapidly worldwide. In current absence of a curative treatment and an effective, safe vaccine, there is a pressing need to focus on identifying and correcting deficits in immune function in order to reduce risk of severe progress of the disease and to lower the number of infections and fatalities. This paper evaluates the most recent literature on zinc status related to antiviral immunity and its possible role in COVID–19. It is concluded that zinc is a critical factor for antiviral immunity. There is ample evidence suggesting that zinc depletion, also prevalent in high–income nations, compromises immune functions. Notably, major risk groups for COVID–19, the elderly, men more than women, obese individuals and patients with diabetes are all at risk of zinc deficiency. Moreover, various widely used antihypertensive drugs and statin therapy have been reported to negatively influence zinc status. As zinc depletion impairs antiviral immunity, it is hypothesised to increase susceptibility for COVID–19. Therefore, dietary preventive measures and prompt implementation of zinc supplementation for risk groups should be considered. Large–scale studies are urgently needed to investigate the role of micronutrients and antiviral immunity, in particular drug–micronutrient immunity interaction.

Zinc Deficiency and Heart Failure: A Systematic Review of the Current Literature

Zinc is an essential micronutrient that impacts the cardiovascular system through modulation of oxidative stress. It is unknown whether zinc levels are affected in heart failure (HF), and whether the association, if present, is causal. A systematic search for publications that report coexisting zinc deficiency in patients with HF was performed to provide an overview of the pathophysiological and epidemiological aspects of this association (last search April 2019). Review of the literature suggests multiple potential pathophysiologic causes for zinc deficiency in HF as a result of impaired micronutrient consumption, hyper-inflammatory state, upregulation of the renin-angiotensin-aldosterone axis, diminished absorption, and hyperzincuria from HF medications. In a longitudinal study of patients with HF in the setting of intestinal malabsorption, there was partial cardiomyocyte and left ventricular ejection fraction recovery with intravenous selenium and zinc supplementation. Two randomized double-blind control trials evaluating micronutrient and macronutrient supplementation including zinc in patients with HF found improvement in echocardiographic findings compared with placebo. Two recently completed studies evaluated the role for zinc supplementation in 2 different HF populations: a trial of zinc supplementation in patients with non-ischemic HF, and a trial of micronutrient supplementation (including B vitamins, vitamin D, and zinc) in veterans with systolic dysfunction; the results of which are still pending. Several pathobiological pathways to link zinc deficiency with the development and deterioration of HF are presented. Preliminary clinical data are supportive of such an association and future studies should further investigate the effects of zinc supplementation on outcomes in patients with HF.

Diuretics, Ca-Antagonists, and Angiotensin-Converting Enzyme Inhibitors Affect Zinc Status in Hypertensive Patients on Monotherapy: A Randomized Trial

Background: Antihypertensive drugs affect mineral metabolism, inflammation, and the oxidative state. The aim of this study was to evaluate the effects of antihypertensive monopharmacotherapy with diuretics, β-blockers, calcium antagonists (Ca-antagonists), angiotensin-converting enzyme inhibitors (ACE-I), and angiotensin II receptor antagonists (ARBs) on zinc (Zn), iron (Fe), and copper (Cu) status, parameters of oxidative and inflammatory states, and glucose and lipid metabolism in patients with newly diagnosed primary arterial hypertension (AH). Methods: Ninety-eight hypertensive subjects received diuretics, β-blockers, Ca-antagonists, ACE-I, or ARB for three months. Zn, Fe, and Cu concentrations were determined in blood, urine, and hair. Results: A decrease in zinc serum and erythrocyte concentration and an increase in zinc urine concentration were registered after diuretic administration. Ca-antagonists led to a decrease in erythrocyte zinc concentration. A decrease in serum zinc concentration was observed after ACE-I. A decrease in triglyceride serum concentration was noted after ACE-I therapy, and a decrease in tumor necrosis factor-α serum concentration was seen following administration of Ca-antagonists. Hypotensive drugs led to decreases in catalase and superoxide dismutase serum concentrations. Conclusions: Three-months of monotherapy with diuretics, Ca-antagonists, or ACE-I impairs zinc status in patients with newly diagnosed primary AH. Antihypertensive monopharmacotherapy and zinc metabolism alterations affect lipid metabolism, the oxidative state, and the inflammatory state.

Evidence of Drug-Nutrient Interactions with Chronic Use of Commonly Prescribed Medications: An Update

The long-term use of prescription and over-the-counter drugs can induce subclinical and clinically relevant micronutrient deficiencies, which may develop gradually over months or even years. Given the large number of medications currently available, the number of research studies examining potential drug-nutrient interactions is quite limited. A comprehensive, updated review of the potential drug-nutrient interactions with chronic use of the most often prescribed medications for commonly diagnosed conditions among the general U.S. adult population is presented. For the majority of the interactions described in this paper, more high-quality intervention trials are needed to better understand their clinical importance and potential consequences. A number of these studies have identified potential risk factors that may make certain populations more susceptible, but guidelines on how to best manage and/or prevent drug-induced nutrient inadequacies are lacking. Although widespread supplementation is not currently recommended, it is important to ensure at-risk patients reach their recommended intakes for vitamins and minerals. In conjunction with an overall healthy diet, appropriate dietary supplementation may be a practical and efficacious way to maintain or improve micronutrient status in patients at risk of deficiencies, such as those taking medications known to compromise nutritional status. The summary evidence presented in this review will help inform future research efforts and, ultimately, guide recommendations for patient care.

Do Medications Commonly Prescribed to Patients with Peripheral Arterial Disease Have an Effect on Nutritional Status? A Review of the Literature

BACKGROUND

Polypharmacy is common among patients with peripheral arterial disease (PAD) with a combination of medications used for risk-factor modification and medical management of the disease itself. Interaction between commonly prescribed medications and nutritional status has not previously been well described. This review aims to critically appraise evidence exploring associations between medications commonly prescribed to patients with PAD and nutritional status and provide recommendations for practice.

METHODS

A comprehensive literature search was conducted to locate studies relating to nutrient interactions among lipid-lowering, antihypertensive, antiplatelet, and oral hypoglycemic drug classes. Quality of the evidence was rated on the basis of recommendations by the National Health and Medical Research Council.

RESULTS

A total of 25 articles were identified as suitable and included in the review. No studies were specific to patients with PAD, and hence findings highlighting risk of ubiquinone (coenzyme Q10 [CoQ10]) depletion with lipid-lowering medications, zinc depletion with antihypertensive medications, and vitamin B12 depletion with oral hypoglycemic medications are extrapolated from heterogeneous groups of patients and healthy adults. The body of evidence ranged in quality from satisfactory to poor.

CONCLUSIONS

High-quality research is required to confirm the interactions suggested by the included studies in patients with PAD specifically. It is, however, recommended that patients with PAD that are long-term consumers of the selected medications are monitored for CoQ10, zinc, and vitamin B12 to facilitate early identification of deficiencies and initiation of treatment. Treatment may involve dietary intervention and/or supplementation.

Aroma and taste perceptions with Alzheimer disease and stroke

Chemosensory disorders of smell or taste in humans have been attributed to various physiological and environmental factors including aging and disease conditions. Aroma and taste greatly condition our food preference, selection and, consumption; the decreased appetite in patients with known neurodegenerative diseases may lead to dietary restrictions that could negatively impact nutritional and health status. The decline in olfactory and gustatory systems in patients with Alzheimer disease and various types of stroke are described.

Effects of widely used drugs on micronutrients: a story rarely told

Vitamins and trace elements are essential to the body, however, deficiencies are frequently observed in the general population. Diet is mostly responsible for these deficiencies but drugs also may play a significant role by influencing their metabolism. These effects are rarely assessed in clinical practice, in part because of limited data available in the literature. Drug-induced micronutrient depletions, however, may be the origin of otherwise unexplained symptoms that might sometimes influence medication compliance. We present various examples of widely prescribed drugs that can precipitate micronutrient deficiencies. This review aims at sensitizing physicians on drug-micronutrient interactions. High-risk population groups also are presented and supplementation protocols are suggested.

Pharmaco-nutrient interactions - a systematic review of zinc and antihypertensive therapy

BACKGROUND

Antihypertensive medicines are to known to cause diverse disturbances to electrolyte homeostasis; however, their potential to affect zinc is less well known. The primary aim was to explore whether antihypertensive medicines have the potential to affect zinc status.

METHODS

A review of electronic databases was undertaken. Full-length English language articles describing clinical trials involving antihypertensive medicines and reporting on zinc measurements were reviewed.

RESULTS

Eight eligible studies were identified which involved the use of ACE inhibitors, thiazide diuretics, beta blockers, or ARB drugs of which five included a control group Studies used urinary zinc excretion, plasma zinc levels or erythrocyte zinc as key measures of zinc status. Studies reported increased urinary zinc losses for captopril (from 50 mg/day), enalapril (20 mg/day), losartan (50 mg/day), losartan (50 mg/day) together with hydrochlorothiazide (12.5 mg/day), captopril (75 mg/day) together with frusemide (40 mg/day) and stand-alone hydrochlorothiazide (25 mg/day). Serum levels of zinc decreased with captopril (50-150 mg/day), verapamil (240 mg/day), atenolol (50-150 mg/day) and the combination of losartan (50 mg/day) and hydrochlorothiazide (12.5 mg/day), eryrthrocyte levels decreased with use of valsartan (80 mg/day) and in some studies for captopril, but not for metoprolol (100 mg/day), atenolol (50-150 mg/day), verapamil (240 mg/day), doxazosin (4 mg/day) or amlodipine 10 mg/day). Major limitations were that most studies were small and did not report on dietary zinc intake.

CONCLUSION

The available evidence suggests that use of ACE inhibitors and angiotensin 2 receptor antagonists or thiazide diuretics have the potential to reduce zinc levels in hypertensive patients. Additional research using larger participant numbers and accounting for dietary zinc intakes are required.

Mineralocorticoid receptor antagonism confers cardioprotection in heart failure

The symptoms and signs constituting the congestive heart failure (CHF) syndrome have their pathophysiologic origins rooted in a salt-avid renal state mediated by effector hormones of the renin-angiotensin-aldosterone and adrenergic nervous systems. Controlled clinical trials, conducted over the past decade in patients having minimally to markedly severe symptomatic heart failure, have demonstrated the efficacy of a pharmacologic regimen that interferes with these hormones, including aldosterone receptor binding with either spironolactone or eplerenone. Potential pathophysiologic mechanisms, which have not hitherto been considered involved for the salutary responses and cardioprotection provided by these mineralocorticoid receptor antagonists, are reviewed herein. In particular, we focus on the less well-recognized impact of catecholamines and aldosterone on monovalent and divalent cation dyshomeostasis, which leads to hypokalemia, hypomagnesemia, ionized hypocalcemia with secondary hyperparathyroidism and hypozincemia. Attendant adverse cardiac consequences include a delay in myocardial repolarization with increased propensity for supraventricular and ventricular arrhythmias, and compromised antioxidant defenses with increased susceptibility to nonischemic cardiomyocyte necrosis.

Zinc deficiency and taste perception in the elderly

Taste, one of the major senses in humans, is the ability to detect the flavor of substances such as food, certain minerals, and poisons. Taste distortions in human beings have been attributed to various physiological and environmental factors including aging and disease conditions. Given the fact that taste is one of the most important factors in food preference, selection, and consumption, the decreased appetite in the elderly, probably due to disease conditions, may lead to dietary restrictions that could negatively impact nutritional and health status. The role of zinc on taste distortion in the elderly population and taste impairment are described. Although several studies demonstrate the associative nature of taste degeneration with age, additional investigations are required to clarify the mechanisms by which taste perception is altered with age.

Disturbances in calcium metabolism and cardiomyocyte necrosis: the role of calcitropic hormones

A synchronized dyshomeostasis of extra- and intracellular Ca(2+), expressed as plasma ionized hypocalcemia and excessive intracellular Ca(2+) accumulation, respectively, represents a common pathophysiologic scenario that accompanies several diverse disorders. These include low-renin and salt-sensitive hypertension, primary aldosteronism and hyperparathyroidism, congestive heart failure, acute and chronic hyperadrenergic stressor states, high dietary Na(+), and low dietary Ca(2+) with hypovitaminosis D. Homeostatic responses are invoked to restore normal extracellular [Ca(2+)](o), including increased plasma levels of parathyroid hormone and 1,25(OH)(2)D(3). However, in cardiomyocytes these calcitropic hormones concurrently promote cytosolic free [Ca(2+)](i) and mitochondrial [Ca(2+)](m) overloading. The latter sets into motion organellar-based oxidative stress, in which the rate of reactive oxygen species generation overwhelms their detoxification by endogenous antioxidant defenses, including those related to intrinsically coupled increments in intracellular Zn(2+). In turn, the opening potential of the mitochondrial permeability transition pore increases, allowing for osmotic swelling and ensuing organellar degeneration. Collectively, these pathophysiologic events represent the major components to a mitochondriocentric signal-transducer-effector pathway to cardiomyocyte necrosis. From necrotic cells, there follows a spillage of intracellular contents, including troponins, and a subsequent wound healing response with reparative fibrosis or scarring. Taken together, the loss of terminally differentiated cardiomyocytes from this postmitotic organ and the ensuing replacement fibrosis each contribute to the adverse structural remodeling of myocardium and progressive nature of heart failure. In conclusion, hormone-induced ionized hypocalcemia and intracellular Ca(2+) overloading comprise a pathophysiologic cascade common to diverse disorders and that initiates a mitochondriocentric pathway to nonischemic cardiomyocyte necrosis.

Stressor states and the cation crossroads

Neurohormonal activation involving the hypothalamic-pituitary-adrenal axis and adrenergic nervous and renin-angiotensin-aldosterone systems is integral to stressor state-mediated homeostatic responses. The levels of effector hormones, depending upon the degree of stress, orchestrate the concordant appearance of hypokalemia, ionized hypocalcemia and hypomagnesemia, hypozincemia, and hyposelenemia. Seemingly contradictory to homeostatic responses wherein the constancy of extracellular fluid would be preserved, upregulation of cognate-binding proteins promotes coordinated translocation of cations to injured tissues, where they participate in wound healing. Associated catecholamine-mediated intracellular cation shifts regulate the equilibrium between pro-oxidants and antioxidant defenses, a critical determinant of cell survival. These acute and chronic stressor-induced iterations in extracellular and intracellular cations are collectively referred to as the cation crossroads. Intracellular cation shifts, particularly excessive accumulation of Ca2+, converge on mitochondria to induce oxidative stress and raise the opening potential of their inner membrane permeability transition pores (mPTPs). The ensuing loss of cationic homeostasis and adenosine triphosphate (ATP) production, together with osmotic swelling, leads to organellar degeneration and cellular necrosis. The overall impact of iterations in extracellular and intracellular cations and their influence on cardiac redox state, cardiomyocyte survival, and myocardial structure and function are addressed herein.

Cellular and molecular pathways to myocardial necrosis and replacement fibrosis

Fibrosis is a fundamental component of the adverse structural remodeling of myocardium present in the failing heart. Replacement fibrosis appears at sites of previous cardiomyocyte necrosis to preserve the structural integrity of the myocardium, but not without adverse functional consequences. The extensive nature of this microscopic scarring suggests cardiomyocyte necrosis is widespread and the loss of these contractile elements, combined with fibrous tissue deposition in the form of a stiff in-series and in-parallel elastic elements, contributes to the progressive failure of this normally efficient muscular pump. Cellular and molecular studies into the signal-transducer-effector pathway involved in cardiomyocyte necrosis have identified the crucial pathogenic role of intracellular Ca2+ overloading and subsequent induction of oxidative stress, predominantly confined within its mitochondria, to be followed by the opening of the mitochondrial permeability transition pore that leads to the destruction of these organelles and cells. It is now further recognized that Ca2+ overloading of cardiac myocytes and mitochondria serves as a prooxidant and which is counterbalanced by an intrinsically coupled Zn2+ entry serving as antioxidant. The prospect of raising antioxidant defenses by increasing intracellular Zn2+ with adjuvant nutriceuticals can, therefore, be preferentially exploited to uncouple this intrinsically coupled Ca2+ - Zn2+ dyshomeostasis. Hence, novel yet simple cardioprotective strategies may be at hand that deserve to be further explored.

Cation dyshomeostasis and cardiomyocyte necrosis: the Fleckenstein hypothesis revisited

An ongoing loss of cardiomyocytes to apoptotic and necrotic cell death pathways contributes to the progressive nature of heart failure. The pathophysiological origins of necrotic cell loss relate to the neurohormonal activation that accompanies acute and chronic stressor states and which includes effector hormones of the adrenergic nervous system. Fifty years ago, Albrecht Fleckenstein and coworkers hypothesized the hyperadrenergic state, which accompanies such stressors, causes cardiomyocyte necrosis based on catecholamine-initiated excessive intracellular Ca(2+) accumulation (EICA), and mitochondrial Ca(2+) overloading in particular, in which the ensuing dysfunction and structural degeneration of these organelles leads to necrosis. In recent years, two downstream factors have been identified which, together with EICA, constitute a signal-transducer-effector pathway: (i) mitochondria-based induction of oxidative stress, in which the rate of reactive oxygen metabolite generation exceeds their rate of detoxification by endogenous antioxidant defences; and (ii) the opening of the mitochondrial inner membrane permeability transition pore (mPTP) followed by organellar swelling and degeneration. The pathogenesis of stress-related cardiomyopathy syndromes is likely related to this pathway. Other factors which can account for cytotoxicity in stressor states include: hypokalaemia; ionized hypocalcaemia and hypomagnesaemia with resultant elevations in parathyroid hormone serving as a potent mediator of EICA; and hypozincaemia with hyposelenaemia, which compromise antioxidant defences. Herein, we revisit the Fleckenstein hypothesis of EICA in leading to cardiomyocyte necrosis and the central role played by mitochondria.

Congestive heart failure: where homeostasis begets dyshomeostasis

Despite today's standard of care, aimed at preventing homeostatic neurohormonal activation, one in every five patients recently hospitalized with congestive heart failure (CHF) will be readmitted within 30 days of discharge because of a recurrence of their symptoms and signs. In light of recent pathophysiological insights, it is now propitious to revisit CHF with a view toward complementary and evolving management strategies. CHF is a progressive systemic illness. Its features include: oxidative stress in diverse tissues; an immunostimulatory state with circulating proinflammatory cytokines; a wasting of soft tissues; and a resorption of bone. Its origins are rooted in homeostatic mechanisms gone awry to beget dyshomeostasis. For example, marked excretory losses of Ca2+ and Mg2+ accompany renin-angiotensin-aldosterone system activation, causing ionized hypocalcemia and hypomagnesemia that lead to secondary hyperparathyroidism with consequent bone resorption and a propensity to atraumatic fractures. Parathyroid hormone accounts for paradoxical intracellular Ca2+ overloading in diverse tissues and consequent systemic induction of oxidative stress. In cardiac myocytes and mitochondria, these events orchestrate opening of the mitochondrial permeability transition pore with an ensuing osmotic-based destruction of these organelles and resultant cardiomyocyte necrosis with myocardial scarring. Contemporaneous with Ca2+ and Mg2+ dyshomeostasis is hypozincemia and hyposelenemia, which compromise metalloenzyme-based antioxidant defenses, whereas hypovitaminosis D threatens Ca2+ stores needed to prevent secondary hyperparathyroidism. An intrinsically coupled dyshomeostasis of intracellular Ca2+ and Zn2+, representing pro-oxidant and antioxidant, respectively, is integral to regulating the mitochondrial redox state; it can be uncoupled by a Zn2+ supplement in favor of antioxidant defenses. Hence, the complementary use of nutriceuticals to nullify dyshomeostatic responses involving macro- and micronutrients should be considered. Evolving strategies with mitochondria-targeted interventions interfering with their uptake of Ca2+ or serving as selective antioxidant or mitochondrial permeability transition pore inhibitor may also prove efficacious in the overall management of CHF.

The ubiquitous role of zinc in health and disease

OBJECTIVE

To review zinc physiology and pathophysiology and the importance of zinc toxicity and deficiency in veterinary patients.

DATA SOURCES

A review of human and veterinary medical literature.

HUMAN DATA SYNTHESIS

There is a significant amount of original research in humans and animals on the role of zinc in multiple organ systems. There is also significant data available on human patients with zinc abnormalities.

VETERINARY DATA SYNTHESIS

Zinc deficiency has been studied in dogs with genetic disease and dietary deficiency leading to dermatological disease and immune deficiency. Zinc toxicity has been described after ingestion of metallic foreign bodies containing zinc.

CONCLUSIONS

Historically, the role of zinc in health and disease has been studied through patients with toxicity or severe deficiency with obvious clinical signs. As the ubiquitous contribution of zinc to structure and function in biological systems was discovered, clinically significant but subtle deficiency states have been revealed. In human medicine, mild zinc deficiencies are currently thought to cause chronic metabolic derangement leading to or exacerbating immune deficiency, gastrointestinal problems, endocrine disorders, neurologic dysfunction, cancer, accelerated aging, degenerative disease, and more. Determining the causal relationships between mild zinc deficiency and concurrent disease is complicated by the lack of sensitive or specific tests for zinc deficiency. The prevalence of zinc deficiency and its contribution to disease in veterinary patients is not well known. Continued research is warranted to develop more sensitive and specific tests to assess zinc status, to determine which patients are at risk for deficiency, and to optimize supplementation in health and disease.

A novel dietary-related model of esophagitis and Barrett's esophagus, a premalignant lesion

Barrett's esophagus (BE) is a premalignant lesion in which columnar epithelium (containing goblet cells) replaces esophageal squamous cells. Previous evidence suggested that hydrophobic bile acids and zinc deficiency each play a role in BE development. We fed wild-type C57BL/6 mice a zinc-deficient diet containing the hydrophobic bile acid, deoxycholic acid for various times up to 152 days. All mice fed this diet developed esophagitis by 69 days on the diet and 63% of the mice on this diet for 88 to 152 days also developed a BE-like lesion. Esophageal tissues showed thickened mucosa, increased proliferation, and increased expression of markers associated with oxidative and nitrosative stress. The newly formed BE-like lesions expressed Mucin-2, a marker of columnar differentiation. They also showed translocation of the p65 subunit of nuclear factor-kappaB and beta -catenin to the nucleus and typical histological changes associated with BE lesions. This mouse model of esophagitis and BE is expected to contribute to a deeper understanding of BE pathogenesis and to strategies for prevention of BE progression to cancer.

Nutrition in Pediatric Cardiomyopathy

Pediatric cardiomyopathies are heterogeneous groups of serious disorders of the heart muscle and are responsible for significant morbidity and mortality among children who have the disease. While enormous improvements have been made in the treatment and survival of children with congenital heart disease, parallel strides have not been made in the outcomes for cardiomyopathies. Thus, ancillary therapies, such as nutrition and nutritional interventions, that may not cure but may potentially improve cardiac function and quality of life, are imperative to consider in children with all types of cardiomyopathy. Growth failure is one of the most significant clinical problems of children with cardiomyopathy with nearly one-third of children with this disorder manifesting some degree of growth failure during the course of their illness. Optimal intake of macronutrients can help improve cardiac function. In addition, several specific nutrients have been shown to correct myocardial abnormalities that often occur with cardiomyopathy and heart failure. In particular, antioxidants that can protect against free radical damage that often occurs in heart failure and nutrients that augment myocardial energy production are important therapies that have been explored more in adults with cardiomyopathy than in the pediatric population. Future research directions should pay particular attention to the effect of overall nutrition and specific nutritional therapies on clinical outcomes and quality of life in children with pediatric cardiomyopathy.

Angiotensin-Converting Enzyme Inhibitor Attenuates Monocyte Adhesion to Vascular Endothelium through Modulation of Intracellular Zinc

To elucidate an anti-inflammatory role of angiotensin-converting enzyme inhibitors (ACEIs) in cardiovascular disease, we studied the effect of ACEIs in monocyte adhesion to endothelial cells and underlying molecular mechanisms. Treatment of human monocytic THP-1 cells with monocyte chemoattractant protein-1 (MCP-1; 100 ng/ml; 10 min) significantly increased their adhesion to human umbilical vein endothelial cells (HUVECs) under flow condition (P < 0.001). Preincubation of THP-1 cells with imidaprilat (50 nM; 4 h), an active metabolite of imidapril, reduced MCP-1-triggered THP-1 cell adhesion (P < 0.01). Similar effects were obtained with experiments using human peripheral monocytes (P < 0.05). MCP-1 activated protein kinase C (PKC)alpha in THP-1 cells, resulting in the up-regulation of alpha4 and beta2 integrin. Imidaprilat attenuated MCP-1-induced PKC activation and integrin up-regulation in THP-1 cells. Imidaprilat also inhibited THP-1 cell adhesion induced by phorbol 12-myristate 13-acetate (PMA), a potent PKC activator. In attempt to elucidate the mechanisms for the modulation of PKC activity by imidaprilat, we found that MCP-1 or PMA increased labile zinc in THP-1 cells, which was canceled by imidaprilat. Indeed, zinc/pyrithione activated PKC and increased THP-1 cell adhesion. Zinc chelator as well as PKC inhibitor inhibited these processes, suggesting the role for labile zinc in PKC activation and THP-1 cell adhesion. Imidaprilat attenuated zinc/pyrithione-induced PKC activation and THP-1 cell adhesion. These data suggest that ACEI reduces MCP-1 or PMA-triggered monocyte adhesion to activated HUVECs by modulating labile zinc in monocytes. Our findings may point out a novel anti-inflammatory mechanism of ACEIs in atherogenesis.

Effects of angiotensin-converting enzyme inhibitors (ACE i) on zinc metabolism in patients with heart failure

The aim of this study is to investigate the effects of angiotensin-converting enzyme (ACE) inhibitors and furosemide on zinc metabolism by assessing serum zinc and urine levels in hospitalized subjects. We recruited 11 patients with heart failure from the Internal Medicine Department; these patients had been hospitalized less than 72 h before. Heart failure was defined using clinical and radiological signs. Serum zinc concentrations were measured using an air/acetylene flame atomic absorption spectrophotometer. Urine zinc levels were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Data were obtained from the 11 patients and 24 healthy controls matched for age and sex. Results indicate higher urine zinc levels and lower concentrations of zinc in serum in heart failure patients vs matched controls (p<0.05). This study suggests that treating heart failure patients with ACE inhibitors may result in zinc deficiency.

Macro- and micronutrients in African-Americans with heart failure

An emerging body of evidence suggests secondary hyperparathyroidism (SHPT) may be an important covariant of congestive heart failure (CHF), especially in African-Americans (AA) where hypovitaminosis D is prevalent given that melanin, a natural sunscreen, mandates prolonged exposure of skin to sunlight and where a housebound lifestyle imposed by symptomatic CHF limits outdoor activities and hence sunlight exposure. In addition to the role of hypovitaminosis D in contributing to SHPT is the increased urinary and fecal losses of macronutrients Ca(2+) and Mg(2+) associated with the aldosteronism of CHF and their heightened urinary losses with furosemide treatment of CHF. Thus, a precarious Ca(2+) balance seen with reduced serum 25(OH)D is further compromised when AA develop CHF with circulating RAAS activation and are then treated with a loop diuretic. SHPT accounts for a paradoxical Ca(2+) overloading of diverse tissues and the induction of oxidative stress at these sites which spills over to the systemic circulation. In addition to SHPT, hypozincemia and hyposelenemia have been found in AA with compensated and decompensated heart failure and where an insufficiency of these micronutrients may have its origins in inadequate dietary intake, altered rates of absorption or excretion and/or tissue redistribution, and treatment with an ACE inhibitor or AT(1) receptor antagonist. Zn and Se deficiencies, which compromise the activity of several endogenous antioxidant defenses, could prove contributory to the severity of heart failure and its progressive nature. These findings call into question the need for nutriceutical treatment of heart failure and which is complementary to today's pharmaceuticals, especially in AA.

Micronutrients and their supplementation in chronic cardiac failure. An update beyond theoretical perspectives

Physicians' use of micronutrients to improve symptoms or outcomes in chronic illness has until recently been guided by limited data on the actions of individual agents in vitro or in animal studies. However several recently published clinical trials have provided information about which groups of patients are likely to benefit from which combination of micronutrients. Patients with chronic cardiac failure (CCF), particularly elderly individuals, have several reasons to be deficient in micronutrients including reduced intake, impaired gastrointestinal absorption and increased losses on the background of increased utilisation due for example to increased oxidative stress. Studies of nutritional supplementation in CCF patients have usually concentrated on specific agents. However given that many micronutrients have synergistic influences upon metabolic processes this strategy might merely lead to a shifting of a limiting step. Rather, a strategy of increasing the availability of multiple agents at once might be more logical. The aim of this article is to briefly review the experimental rationale for each of the micronutrients of potential benefit in chronic heart failure and examine the current clinical trial evidence supporting their use.

Metallopeptide-promoted inactivation of angiotensin-converting enzyme and endothelin-converting enzyme 1: toward dual-action therapeutics

A series of metallopeptides based on the amino terminal copper/nickel (ATCUN) binding motif have been evaluated as classical inhibitors and catalytic inactivators of both rabbit and human angiotensin-converting enzyme (hACE), and human endothelin-converting enzyme 1 (hECE-1). The cobalt complex [KGHK-Co(NH3)2]2+, where KGHK is lysylglycylhistidyllysine, displayed similar K(I) and IC50 values to those found for [KGHK-Cu]+, in spite of the enhanced charge, and so either the influence of charge is offset by the steric influence of the axially coordinated ammine ligands, or binding is dominated by contributions from the amino acid side chains, especially the C-terminal lysine that mimics the binding pattern observed for lisinopril. Moreover, the inhibition observed for [KGHK-Co(NH3)2]2+ contrasts with the activation of hACE by Co2+(aq), reflecting the stimulation of enzyme activity following replacement of the catalytic zinc cofactor by cobalt ion at each of the two active sites. Quantitative analysis of the dose-dependent stimulation of activity by Co2+(aq) yielded apparent affinities of 1.3 +/- 0.2 and 56 +/- 8 microM for the two sites in the presence of saturating Zn2+ (10 microM). Catalytic inactivation of hACE by [KGHK-Cu]+ at subsaturating concentrations had previously been characterized, with k(obs) = 2.9 +/- 0.5 x 10(-2) min(-1). Under similar conditions, the same complex is found to catalytically inactivate hECE-1, with k(obs) = 2.12 +/- 0.16 x 10(-2) min(-1), demonstrating the potential for dual-action activity against two key drug targets in cardiovascular disease. Irreversible inactivation of a drug target represents a novel mechanism of drug action that complements existing classical inhibitor strategies that underlie current drug discovery efforts.

Zinc balance and medications commonly used in the management of heart failure

Heart failure (HF) is a prevalent syndrome resulting in a high mortality rate. HF may be associated with zinc deficiency through a reduction in dietary intake, decreased absorption due to gastrointestinal edema, impaired motility or intestinal zinc losses. Diseases concomitant with HF such as diabetes mellitus (DM) and hypertension may enhance zinc deficiency. Medications given for HF may affect zinc metabolism in different ways. It was shown that thiazides may cause zincuria and a decrease in tissue zinc concentration. There is conflicting evidence about furosemide, even though patients with chronic furosemide treatment showed low tissue zinc levels in autopsies. Treatment with angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs) resulted in zincuria and zinc deficiency, but this outcome was not consistent in all studies. Beta-blockers did not alter plasma zinc concentration. Matrix metalloproteinases (MMPs) and ACE are zinc-containing enzymes, which play a role in the process of remodeling in HF. It was shown that ACE inhibitors may inhibit the activity of different MMPs. The exact interrelationship between HF, zinc-containing enzymes, zinc deficiency and the clinical manifestation of HF has to be investigated.

Inactivation of human angiotensin converting enzyme by copper peptide complexes containing ATCUN motifs

The copper complex [KGHK-Cu]+ demonstrates catalytic inactivation of human angiotensin converting enzyme at sub-saturating concentrations, under oxidative conditions, with an observed rate constant k approximately 2.9 +/- 0.5 x 10(-2) min(-1).

A study of the determination of the hypertensive drug captopril by square wave cathodic adsorptive stripping voltammetry

In this work, the determination of captopril (CPL) was studied by square wave cathodic adsorptive stripping voltammetry (SWCAdSV) on a hanging mercury drop electrode (HMDE). CPL was adsorptively preconcentrated on the mercury surface as a sparingly soluble mercury salt under stirring of the solution and then the accumulated species was reduced by a cathodic square wave voltammetric scan. The reduction current was related to the CPL concentration in the sample. The chemical and instrumental parameters affecting the response were investigated and optimized for the CPL determination. The calibration curve was linear from 0.5 to 180 microg l(-1) of CPL (depending on the preconcentration time), the limit of detection at a S/N ratio of 3 was 0.5 microg l(-1) with 300 s of preconcentration and the relative standard deviation was 3.2% at the 20 microg l(-1) level (with 120 s of preconcentration, n=8). The method was applied to the determination of CPL in two pharmaceutical formulations with recoveries of 97.9 and 98.8%. Finally, the potential for applying the proposed method to the determination of CPL in biological media is briefly discussed.