Malay S. Gandhi

Coupled calcium and zinc dyshomeostasis and oxidative stress in cardiac myocytes and mitochondria of rats with chronic aldosteronism.

A dyshomeostasis of extra- and intracellular Ca2+ and Zn2+ occurs in rats receiving chronic aldosterone/salt treatment (ALDOST). Herein, we hypothesized that the dyshomeostasis of intracellular Ca2+ and Zn2+ is intrinsically coupled that alters the redox state of cardiac myocytes and mitochondria, with Ca2+ serving as a pro-oxidant and Zn2+ as an antioxidant. Toward this end, we harvested hearts from rats receiving 4 weeks of ALDOST alone or cotreatment with either spironolactone (Spiro), an aldosterone receptor antagonist, or amlodipine (Amlod), an L-type Ca2+ channel blocker, and from age/sex-matched untreated controls. In each group, we monitored cardiomyocyte [Ca2+]i and [Zn2+]i and mitochondrial [Ca2+]m and [Zn2+]m; biomarkers of oxidative stress and antioxidant defenses; expression of Zn transporters, Zip1 and ZnT-1; metallothionein-1, a Zn2+-binding protein; and metal response element transcription factor-1, a [Zn2+]i sensor and regulator of antioxidant defenses. Compared with controls, at 4-week ALDOST, we found the following: (a) increased [Ca2+]i and [Zn2+]i, together with increased [Ca2+]m and [Zn2+]m, each of which could be prevented by Spiro and attenuated with Amlod; (b) increased levels of 3-nitrotyrosine and 4-hydroxy-2-nonenal in cardiomyocytes, together with increased H2O2 production, malondialdehyde, and oxidized glutathione in mitochondria that were coincident with increased activities of Cu/Zn superoxide dismutase and glutathione peroxidase; and (c) increased expression of metallothionein-1, Zip1 and ZnT-1, and metal response element transcription factor-1, attenuated by Spiro. Thus, an intrinsically coupled dyshomeostasis of intracellular Ca2+ and Zn2+ occurs in cardiac myocytes and mitochondria in rats receiving ALDOST, where it serves to alter their redox state through a respective induction of oxidative stress and generation of antioxidant defenses. The importance of therapeutic strategies that can uncouple these two divalent cations and modulate their ratio in favor of sustained antioxidant defenses is therefore suggested.

Causes and Consequences of Zinc Dyshomeostasis in Rats With Chronic Aldosteronism

Iterations in Ca2+ and Mg2+ balance accompany aldosteronism (inappropriate for dietary Na+ intake). Increased Zn excretion and Zn translocation to injured tissues, including the heart, also occurs. Several causes and consequences of Zn dyshomeostasis in rats receiving aldosterone/salt treatment (ALDOST) were examined. (1) To study the role of urinary acidification in promoting hyperzincuria, acetazolamide (75 mg/kg), a carbonic anhydrase inhibitor, was used as cotreatment to raise urinary HCO3- excretion. (2) To assess Zn levels in the heart, including cardiomyocyte cytosolic free [Zn2+]i and mitochondrial Zn, the expression of metallothionein (MT-I), a Zn binding protein, and biomarkers of oxidative stress were examined. (3) Oxidative stress and cardiac pathology in response to ZnSO4 supplement (40 mg/d) were also studied. Comparison of controls and rats receiving 4 weeks ALDOST revealed the following: (1) an acidification of urine and metabolic alkalosis associated with increased urinary Zn excretion and hypozincemia, each of which were prevented by acetazolamide; (2) a rise in cardiac Zn, including increased [Zn2+]i and mitochondrial Zn, associated with increased tissue MT-I, 8-isoprostane, malondialdehyde, and gp91phox, coupled with oxidative stress in plasma and urine; (3) ZnSO4 prevented hypozincemia, but not ionized hypocalcemia, and attenuated oxidative stress and microscopic scarring without preventing the vasculitis and perivascular fibrosis of intramural coronary arteries. Thus, the hyperzincuria seen with ALDOST is due to urinary acidification. The oxidative stress that appears in the heart is accompanied by increased tissue Zn serving as an antioxidant. Cotreatment with ZnSO4 attenuated cardiomyocyte necrosis; however, polynutrient supplement may be required to counteract the dyshomeostasis of all 3 cations that accompanies aldosteronism and contributes to cardiac pathology.

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.

Hepatic Gene Expression in Morbidly Obese Women: Implications for Disease Susceptibility

The objective of this study was to determine the molecular bases of disordered hepatic function and disease susceptibility in obesity. We compared global gene expression in liver biopsies from morbidly obese (MO) women undergoing gastric bypass (GBP) surgery with that of women undergoing ventral hernia repair who had experienced massive weight loss (MWL) following prior GBP. Metabolic and hormonal profiles were examined in MO vs. MWL groups. Additionally, we analyzed individual profiles of hepatic gene expression in liver biopsy specimens obtained from MO and MWL subjects. All patients underwent preoperative metabolic profiling. RNAs were extracted from wedge biopsies of livers from MO and MWL subjects, and analysis of mRNA expression was carried out using Affymetrix HG‐U133A microarray gene chips. Genes exhibiting greater than twofold differential expression between MO and MWL subjects were organized according to gene ontology and hierarchical clustering, and expression of key genes exhibiting differential regulation was quantified by real‐time–polymerase chain reaction (RT‐PCR). We discovered 154 genes to be differentially expressed in livers of MWL and MO subjects. A total of 28 candidate disease susceptibility genes were identified that encoded proteins regulating lipid and energy homeostasis (PLIN, ENO3, ELOVL2, APOF, LEPR, IGFBP1, DDIT4), signal transduction (MAP2K6, SOCS‐2), postinflammatory tissue repair (HLA‐DQB1, SPP1, P4HA1, LUM), bile acid transport (SULT2A, ABCB11), and metabolism of xenobiotics (GSTT2, CYP1A1). Using gene expression profiling, we have identified novel candidate disease susceptibility genes whose expression is altered in livers of MO subjects. The significance of altered expression of these genes to obesity‐related disease is discussed.

Effect of combination lipid-modifying therapy on the triglyceride lowering effect of fish oil

Background:Marine fish oil supplements are frequently administered with other lipid medications for treatment of hypertriglyceridemia. The efficacy of fish oil may be reduced in the presence of other lipid agents, particularly fibrates that also act as PPAR&agr; agonists. We therefore sought to determine the efficacy of fish-oil supplements when coadministered with other lipid-modifying agents. Methods:Patients receiving fish oil supplements were identified from the computer database of a large governmental HMO. Change in plasma lipoprotein levels after administration of fish oil was compared between patients receiving fish oil as their only treatment and those for whom fish oil was added to other drugs. Results:A total of 166 evaluable records were identified, 66 from patients treated with fish oil alone and 100 from patients for whom fish oil was added to another agent or other agents. Fish oil effectively reduced triglyceride levels to an equal extent in the fish oil only and fish oil added groups (−30% versus –27% respectively; P = 0.84). Conclusion:Fish oil effectively reduces plasma triglyceride levels when administered with concomitant lipid medications. These findings suggest the presence of additional and even complementary mechanisms of action of fish oil to lower triglyceride when added to other lipid drugs. These findings validate the common clinical practice of combining fish oil supplements with other lipid-lowering medications in patients with hypertriglyceridemia.

Bilateral Pleural Effusions in Congestive Heart Failure

The salt-avid state that accounts for the clinical syndrome congestive heart failure (CHF) leads to an initial expansion of intra- and subsequent rise in extravascular volumes that can include the appearance of pleural effusion. Herein, we present a 54-year-old man with a dilated cardiomyopathy who was hospitalized because of his CHF, which included bilateral pleural effusions, right hydrothorax greater than left. The pathophysiology of pleural fluid formation in CHF, previously debated, has now reached consensus, albeit not frequently reviewed. This index case offers such an opportunity.

An Unusual Cause of Muscle Weakness: A Case Report

Thyrotoxic hypokalemic periodic paralysis (THPP) has been reported earlier in the Asian population. However, it is now becoming increasingly common in the Western countries as well. Thus, its in-depth knowledge is a must for every physician so that this diagnosis is not overlooked in any case presenting with extremity weakness and paralysis, especially considering its reversible nature. We present an interesting case of THPP in a Vietnamese patient presenting with bilateral lower extremity weakness and extremely low serum potassium levels. We also present a comprehensive discussion and review of literature related to THPP, which would be helpful for the internists to diagnose and appropriately manage this disease.

40 MICROARRAY ANALYSIS OF HEPATIC GENE EXPRESSION IN OBESE HUMANS UNDERGOING BARIATRIC SURGERY.

Obesity is consistently accompanied by the development of resistance to the effect of insulin to promote glucose uptake in skeletal muscle. The resulting glucose intolerance leads to development of hyperinsulinemia, which, in turn, promotes synthesis of lipid by the liver (de novo lipogenesis and triglyceride synthesis). This leads to overproduction of VLDL and elevated levels of triglyceride-rich lipoproteins in the plasma. Excess lipid also accumulates in the liver to produce fatty liver (hepatic steatosis). Although these processes have been well characterized in animal models of obesity and hyperinsulinemia, little information is available regarding these processes in livers of obese humans. To gain insight into the pathophysiology of hepatic lipid production in obese humans we examined global gene expression using Affymetrix human HG-U133A microarray chip in liver biopsy samples obtained from obese patients who were undergoing gastric-bypass surgery for weight loss and from post-obese individuals who were undergoing abdominal wall revision (tummy tuck) after weight loss following prior gastric-bypass surgery. Of the 22,400 probe sets on the chip 3,576 genes were expressed at a 95% or greater level of detection certainty. From this dataset 39 genes were identified that were highly overexpressed (2-fold or greater) in obese livers, and 33 genes were identified that were underexpressed (22-fold or greater) in obese livers as compared to post-obese controls. Functional analysis of over- and underexpressed genes revealed altered expression of genes related to insulin signaling, lipid metabolism, inflammation, proliferation, and immunologic response. Several genes of specific interest for insulin resistance and hepatic lipid synthesis were highly regulated in obese human liver. These include genes related to insulin signaling [suppressor of cytokine signaling 2 (SOCS2) and leptin receptor (LEP)], inflammation [C-reactive protein (CRP) and superoxide dismutase (SOD2)], and lipid synthesis [fatty acid synthase (FASN)]. The potential significance of altered expression of these and other genes in obese human liver is discussed.

41 EFFECT OF CONCOMITANT HYPOLIPIDEMIC THERAPY ON THE TRIGLYCERIDE-LOWERING EFFECT OF FISH OIL.

Background Fish oil supplements are administered for treatment of hypertriglyceridemia, frequently in combination with other lipid-lowering agents. Given the presence of overlapping mechanisms of action of N-3 polyunsaturated fatty acids with that of other lipid-lowering agents, in particular fibrates, the efficacy of fish oil may be diminished with concomitant administration of other lipid-lowering agents. Objective To determine the efficacy (primarily triglyceride lowering) of fish oil supplements when co-administered with other lipid-lowering agents versus that of fish oil alone. Design/Setting Retrospective chart review. Outpatient clinics of large Gov. HMO (VA, Memphis). Patients Representative population of veterans attending outpatient clinics with active prescription for fish oil supplements at the time of survey, who had lipid profiles prior to and following initiation of fish oil. Results Over 500 individuals receiving fish oil supplements were identified. Of these, 94 individual patients had the required information available and were therefore evaluable for this study. Forty-eight were receiving fish oil alone and 46 had fish oil added to another hypolipidemic agent(s) (statin, fibrate, niacin). The average dose of fish oil administered in both groups was relatively low (3.2 and 3.3 grams per day in fish oil only and fish oil added groups), indicating use of relatively low doses of fish oil in many patients. Despite this, fish oil therapy effectively reduced triglyceride and to an equal extent in the fish oil only and fish oil added groups (228% versus 224% respectively, p = .24). Analysis of triglyceride response by type of lipid-lowering agent administered showed no significant attenuation of fish oil efficacy with concomitant administration of statin, niacin, or fibrate. Limitations A limited number of evaluable cases were identified. The study was not prospective or randomized. A limited effect of other hypolipidemic agents on triglyceride response to fish oil supplements may have gone undetected; however, the present study supports the hypothesis that fish oil supplements are effective when added to other hypolipidemic agents. Conclusions Fish oil supplements effectively reduce plasma triglyceride when administered alone or with concomitant lipid-lowering therapy. Submaximal doses of fish oil supplements are frequently used in this outpatient practice setting, thereby limiting the benefit gained.