Morris Schambelan

Liddle's syndrome: Heritable human hypertension caused by mutations in the β subunit of the epithelial sodium channel

Liddles syndrome (pseudoaldosteronism) is an autosomal dominant form of human hypertension characterized by a constellation of findings suggesting constitutive activation of the amiloride-sensitive distal renal epithelial sodium channel. We demonstrate complete linkage of the gene encoding the beta subunit of the epithelial sodium channel to Liddles syndrome in Liddles original kindred. Analysis of this gene reveals a premature stop codon that truncates the cytoplasmic carboxyl terminus of the encoded protein in affected subjects. Analysis of subjects with Liddles syndrome from four additional kindreds demonstrates either premature termination or frameshift mutations in this same carboxy-terminal domain in all four. These findings demonstrate that Liddles syndrome is caused by mutations in the beta subunit of the epithelial sodium channel and have implications for the regulation of this epithelial ion channel as well as blood pressure homeostasis.

Expression of AT2 receptors in the developing rat fetus.

Angiotensin II is known primarily for its effects on blood pressure and electrolyte homeostasis, but recent studies suggest that angiotensin II may play a role in the regulation of cellular growth. This study was undertaken to identify the angiotensin II receptor subtypes expressed during fetal and neonatal development and to characterize their cellular localization. Using an in situ receptor binding assay on sagittal frozen sections of fetal and neonatal rats, bound 125I-[Sar1,Ile8]-angiotensin II was visualized by film and emulsion autoradiography. Bound radioligand was detected by E11 (embryonic day 11) and maximal binding occurred by E19-21. Radioligand binding remained unaltered 30 min after birth, whereas a noticeable and stable decrease was observed 12 h postparturition. The highly abundant angiotensin II receptors were shown to be AT2 by the marked reduction in radioligand binding achieved with PD123177 (10(-7)M), a specific AT2 receptor antagonist, whereas DuP 753 (10(-5)M), an AT1 receptor antagonist, had little effect. Emulsion autoradiography showed radioligand binding in the undifferentiated mesenchyme of the submucosal layers of the intestine and stomach, connective tissue and choroid surrounding the retina, subdermal mesenchyme adjacent to developing cartilage, diaphragm, and tongue. Residual AT2 receptors were found on the dorsal subdermal region of the tongue 72 h after birth. AT1 receptors were detected in the placenta at E13 and in the aorta, kidney, lung, liver, and adrenal gland at E19-21, consistent with an adult distribution. The transient expression of AT2 receptors in the mesenchyme of the fetus suggests a role of angiotensin II in fetal development.

Hyperlipidemia and insulin resistance are induced by protease inhibitors independent of changes in body composition in patients with HIV infection.

Summary: Although protease inhibitor (PI) therapy has improved the clinical status of patients with HIV infection, concerns have arisen that such treatment may have deleterious effects on glucose control, lipid metabolism, and body fat distribution. To determine whether initiation of PI therapy uniquely affects glucose and lipid metabolism, we analyzed paired data in HIV‐infected patients before and after beginning antiretroviral therapy that included a PI (PI; N = 20) or lamivudine (3TC) but no PI (3TC; N = 9); and a control group on stable regimens that included neither of these agents (CONT; N = 12). Measurements included fasting glucose; insulin; triglycerides; total, high‐density lipoprotein (HDL) and low‐density lipoprotein (LDL) cholesterol; HIV RNA; CD4+ lymphocytes; weight; and total and regional body composition. Neither weight nor total or regional fat content changed significantly in any group during the period of observation. Nonetheless, in patients beginning PI therapy, there were significant increases in glucose (+9 ± 3 mg/dl; p = .0136), insulin (+12.2 ± 4.9 U/ml; p = .023), triglycerides (+53 ± 17 mg/dl; p = .0069), and total and LDL cholesterol (+32 ± 11 and +18 ± 5 mg/dl; p = .0082 and .0026, respectively). None of these parameters changed significantly in the 3TC or CONT groups. The PI and 3TC groups experienced comparable increases in CD4+ lymphocytes, suggesting that the observed metabolic effects may be associated with PIs uniquely, rather than improvement in clinical status. However, it is also possible that the metabolic effects of PIs are associated with more effective viral suppression, because a greater proportion of patients in the PI group achieved undetectable levels of virus. We conclude that changes in glucose and lipid metabolism are induced by PI therapy in the absence of significant changes in weight or fat distribution. Longer periods of follow‐up will be required to determine the clinical significance of these changes. However, at the moment, the risks associated with these metabolic effects do not appear to outweigh improvements in survival seen with PI therapy.

Management of metabolic complications associated with antiretroviral therapy for HIV-1 infection: recommendations of an International AIDS Society-USA panel.

Objective: Alterations in glucose and lipid metabolism, lactic acidemia, bone disorders, and abnormal body fat distribution have been recognized recently as frequent complications associated with HIV‐1 infection and potent antiretroviral therapy, but limited data ate available regarding the appropriate management of these disorders. These recommendations were developed to guide physicians actively involved in HIV care in the management of metabolic complications that occur primarily within the context of potent antiretroviral therapy. Participants: A 12‐member panel representing international expertise in HIV‐1 patient care, antiretroviral therapy, and endocrine and metabolic disorders was selected in the spring of 2000 by the International AIDS Society‐USA, a not‐for‐profit physician education organization. Panel members met in closed meetings beginning in May 2000. All work was funded by the International AIDS Society‐USA; the panel members are not compensated for their participation. Evidence: The panel reviewed published results of clinical, epidemiologic, and basic science studies and data and abstracts presented at research conferences, primarily from 1997 to 2002. The panel also considered studies of the pathophysiology and treatment of similar metabolic abnormalities in noninfected persons. Emphasis was placed on results from prospective, randomized, controlled clinical trials when available. Process: For each metabolic complication, 1 or more member(s) reviewed and presented all available evidence to the panel, and then wrote a summary of the evidence and preliminary recommendations. Final recommendations were determined by full group consensus. The summaries were combined into a single working document and all panel members edited and approved all subsequent drafts. Conclusions: Carefully controlled studies to determine the incidence, etiology, risk factors, and most appropriate treatments for metabolic complications in HIV‐1 infection are urgently needed. In the absence of these data, and to prevent acute illness and mitigate long‐term risks, the panel recommends routine assessment and monitoring of glucose and lipid levels and assessment and monitoring of lactic acidemia and bone abnormalities if clinical signs or symptoms are detected. With the exception of body fat distribution abnormalities, specific treatments for these complications are also recommended. Successful long‐term antiretroviral therapy will require diligent monitoring and preemptive treatment of metabolic complications to optimize the riskbenefit ratio of antiretroviral therapies.

Metabolic effects of indinavir in healthy HIV-seronegative men

BackgroundTherapy with HIV protease inhibitors (PI) has been associated with hyperglycemia, hyperlipidemia and changes in body composition. It is unclear whether these adverse effects are drug related, involve an interaction with the host response to HIV or reflect changes in body composition. MethodsIndinavir 800 mg twice daily was given to 10 HIV-seronegative healthy men to distinguish direct metabolic effects of a PI from those related to HIV infection. Fasting glucose and insulin, lipid and lipoprotein profiles, oral glucose tolerance (OGTT), insulin sensitivity by hyperinsulinemic euglycemic clamp, and body composition were measured prior to and after 4 weeks of indinavir therapy. ResultsFasting glucose (4.9 ± 0.1 versus 5.2 ± 0.2 mmol/l; P = 0.05) insulin concentrations (61.7 ± 12.2 versus 83.9 ± 12.2 pmol/l; P < 0.05), insulin : glucose ratio (12.6 ± 1.7 versus 15.9 ± 1.9 pmol/mmol; P < 0.05) and insulin resistance index by homeostasis model assessment (1.9 ± 0.3 versus 2.8 ± 0.5; P < 0.05) all increased significantly. During OGTT, 2 h glucose (5.1 ± 0.4 versus 6.5 ± 0.6 mmol/l; P < 0.05) and insulin levels (223.1 ± 48.8 versus 390.3 ± 108.8 pmol/l; P =0.05) also increased significantly. Insulin-mediated glucose disposal decreased significantly (10.4 ± 1.4 versus 8.6 ± 1.2 mg/kg ⋅ min per μU/ml insulin; 95% confidence interval 0.6–3.0; P < 0.01). There was no significant change in lipoprotein, triglycerides or free fatty acid levels. There was a small loss of total body fat (15.8 ± 1.4 versus 15.2 ± 1.4 kg; P = 0.01) by X-ray absorptiometry without significant changes in weight, waist : hip ratio, and visceral or subcutaneous adipose tissue by computed tomography. ConclusionsIn the absence of HIV infection, treatment with indinavir for 4 weeks causes insulin resistance independent of increases in visceral adipose tissue or lipid and lipoprotein levels.

Recombinant Human Growth Hormone in Patients with HIV-Associated Wasting: A Randomized, Placebo-Controlled Trial

Body wasting is an increasingly frequent acquired immunodeficiency syndrome (AIDS)-defining condition [1, 2]. Wasting is associated with impaired functional performance and quality of life [3]. Prospective [4-6] and retrospective [7-9] studies have shown that loss of weight [4, 7-9] and body cell mass [5-7] are statistically related to death in patients with human immunodeficiency virus (HIV) infection. The effect of weight and body composition on survival was notably independent of other factors that were thought to influence mortality. Nutritional supplementation [10, 11] and appetite stimulation [12, 13] can increase body weight and body fat in patients with HIV-associated wasting, but these treatments do not consistently restore lean tissue. The apparent failure of nutritional therapy to restore lean tissue suggests that, in some HIV-infected patients, metabolic alterations either promote nitrogen wasting or at least prevent repletion of lean tissue during periods when the patients presumably have adequate energy intake. Although increases in body fat in this setting may not be intrinsically harmful, body fat content is not correlated with survival [5, 7]. Thus, optimal therapy for patients with HIV-associated wasting should specifically reverse or forestall loss of lean tissue. Pharmacologic doses of growth hormone have induced nitrogen retention and increased protein synthesis and lean body mass in other catabolic states [14-17]. This treatment has also produced weight gain and nitrogen retention in a short-term study [18] of patients with HIV-associated wasting. The results of an open-label study [19] of a small group of patients with HIV-associated wasting suggested that growth hormone may have a sustained effect on lean body mass. We report the results of a randomized, multicenter, double-blind, placebo-controlled study that assessed the effects of growth hormone therapy on weight, body composition, functional performance, and quality of life in patients with HIV-associated wasting. Methods Patients Eligible patients were 18 years of age or older and had antibodies to HIV type 1, documented unintentional weight loss of at least 10% or weight less than 90% of the lower limit of ideal body weight [20], a Karnofsky score of 50 or greater, and life expectancy of 4 months or longer. Patients had to be able to consume at least 75% of maintenance energy requirement based on concurrent body weight. Patients had to have been receiving a stable regimen of antiretroviral therapy for at least 30 days before study entry and had to continue to receive antiretroviral therapy during the study. Exclusion criteria included pregnancy; severe diarrhea ( 6 stools per day); use of anabolic agents, glucocorticoids, appetite stimulants, or parenteral or tube feeding; initiation of therapy for a systemic infection within 30 days of enrollment; an active malignant condition other than localized Kaposi sarcoma (<10 cutaneous lesions, <2 cm in diameter); recent radiotherapy or systemic chemotherapy; untreated hypertension; history of diabetes mellitus, significant cardiovascular disease, chronic edema, or the carpal tunnel syndrome; fasting glucose level greater than 6.7 mmol/L; triglyceride level greater than 5.6 mmol/L; amylase level more than 3 times the upper limit of normal; or hemoglobin level less than 85 g/L. The study was approved by the institutional review board at each participating center, and signed informed consent was obtained before patients were enrolled. Baseline measures included results of history and physical examination; weight; body composition; assessment of treadmill work output and quality of life; routine hematologic and biochemical assessments; and measurement of insulin-like growth factor 1 levels, CD4+ and CD8+ lymphocyte counts, and p24 antigen levels. Plasma HIV RNA levels were measured in a subset of patients from whom appropriate samples were available. Patients were randomly assigned to receive recombinant human growth hormone derived from mammalian cells (Serostim, Serono Laboratories, Norwell, Massachusetts), 0.1 mg/kg of body weight subcutaneously every evening (average dosage, 6 mg/d), or an equivalent amount of placebo. This dose of growth hormone caused weight gain and nitrogen retention in a short-term study of patients with HIV-associated wasting [18]. Patients were randomly assigned according to a computer-generated randomization list that was balanced across all patients and within sites. Kits that contained either the active study drug or placebo in identical vials were given to the study sites. Patients and investigators were blinded to the content of the vials until the study was complete. Patients were reevaluated at weeks 1, 2, 6, and 12; adverse events were recorded and laboratory assessments were done at these evaluations. Doses were reduced for patients with fasting triglyceride levels greater than 7.9 mmol/L, fasting glucose levels greater than 8.9 mmol/L, moderate hypertension, arthralgia that did not respond to anti-inflammatory therapy, the carpal tunnel syndrome, edema that did not respond to diuretics, moderate systemic allergic reaction, or severe paresthesia. The dose was reduced by 50% and again by 50% if symptoms did not resolve within 10 days. Patients in whom symptoms persisted at the lowest dose were withdrawn from the study. Severe events that required suspension of treatment included fasting triglyceride levels of 16.9 mmol/L or greater, glucose levels of 22.2 mmol/L or greater, pseudotumor cerebri, congestive heart failure, pancreatitis, marked hypertension (blood pressure > 200/110 mm Hg), intolerable paresthesia, or severe systemic allergic reaction. If symptoms resolved within 5 days, patients could resume therapy at 50% of the dose used at the time of the event. Treatment was discontinued immediately and not resumed in patients who developed a new occurrence of cancer (including Kaposi sarcoma) and in patients who had progression of existing Kaposi sarcoma (new lesions or >50% growth of existing lesions). Patients who had acute infections could remain in the study at the discretion of the investigator. Outcome Assessments All measurements were done by investigators and their associates at each study site; investigators and associates were unaware of assignment to growth hormone or placebo. At baseline and 6 and 12 weeks, weight and body composition were measured after overnight fasting and voiding. Patients wore only a hospital gown. Weights were measured on the same calibrated scales (certified to have an accuracy to 0.2 kg and a coefficient of variation of 0.3%) throughout the study; the average of three determinations was used. Weight was also recorded at weeks 1 and 2 but not necessarily in the fasting state. Body fat, lean body mass, and bone mineral content were measured by dual-energy x-ray absorptiometry [21-23] with either a Lunar model DPX (Madison, Wisconsin) or Hologics model QDR-1000W or QDR-2000W (Waltham, Massachusetts). Scanning was done with the same equipment and software throughout the study. Total body water was measured by deuterium oxide dilution [24], and extracellular water was measured by sodium bromide dilution [25]. Plasma samples were collected at baseline and 3 hours after patients ingested 10 g of deuterium oxide and 5 g of 4 M sodium bromide. Patients fasted throughout the test period. For assessment of work output, patients walked on a treadmill at increasing workloads according to an adaptation of a protocol for patients with limited exercise capacity [26]. Speed or grade was increased at 3-minute intervals, and exercise was terminated when patients reached volitional exhaustion or estimated maximal heart rate [26]. Work output was calculated from body weight and treadmill speed and grade [27]. Changes in overall health status, functioning, disability, and symptoms were assessed by having patients complete a visual analogue self-appraisal (on a scale of 1 to 10) of overall quality of life and a self-administered questionnaire, the HIV-Patient Assessed Report of Status and Experience (HIV-PARSE) [28]. The HIV-PARSE questionnaire contains modified items and scales from the Medical Outcomes Study that can be analyzed separately or as an overall index [29] and that have been shown to reflect differences in quality-of-life outcomes with HIV therapies [30]. Laboratory Assessments Routine hematologic and biochemical variables were measured in the clinical laboratories at each site. Enrichment of deuterium oxide in plasma was determined by isotope ratio mass spectrometry [24]. Concentration of bromide in plasma was determined by ion chromatography [25]. Levels of plasma insulin-like growth factor 1 were measured by radioimmunoassay [31]. Levels of immune-complex dissociated p24 antigen were measured in acid-treated sera [32]; a change in p24 antigen levels was defined as an increase or decrease from baseline of 50% or greater, as long as one sample was 30 pg/mL or greater. Levels of HIV RNA in plasma were measured by branched-DNA assay [33, 34]. Statistical Analysis Sample size was calculated to detect a 2% difference between groups in weight change at week 12 with at least 80% power for a two-sided test with 5% type I error, assuming an SD of 4%. The groups were compared at baseline using analysis of variance. Analysis of variance was also used to compare changes in weight and body composition in patients who had measurement at baseline and week 12 and at least 80% compliance with the dosing regimen. An intention-to-treat analysis using the Wilcoxon rank-sum test was done on changes from baseline to the last postbaseline value measured in each patient, regardless of whether they completed the study or complied with the dosing regimen. The Wilcoxon rank-sum test was also used to evaluate the change in work output during treadmill exercise. We investigated a treatment-by-center interaction for data that did not have a normal distri

Indinavir acutely inhibits insulin-stimulated glucose disposal in humans: a randomized, placebo-controlled study.

Background Therapy with HIV protease inhibitors (PI) causes insulin resistance even in the absence of HIV infection, hyperlipidemia or changes in body composition. The mechanism of the effects on insulin action is unknown. In vitro studies suggest that PI selectively and rapidly inhibit the activity of the insulin-responsive glucose transporter GLUT-4. We hypothesized that a single dose of the PI indinavir resulting in therapeutic plasma concentrations would acutely decrease insulin-stimulated glucose disposal in healthy human volunteers. Methods Randomized, double-blind, cross-over study comparing the effect of 1200 mg of orally administered indinavir and placebo on insulin-stimulated glucose disposal during a 180-min euglycemic, hyperinsulinemic clamp. Six healthy HIV-seronegative adult male volunteers were studied twice with 7 to 10 days between studies. Results There were no significant differences in baseline fasting body weight, or plasma glucose, insulin, lipid and lipoprotein levels between placebo- and indinavir-treated subjects. During steady-state (t60−−180 min) insulin reached comparable levels (394 ± 13 versus 390 ± 11 pmol/l) and glucose was clamped at approximately 4.4 mmol/l under both conditions. The average maximum concentration of indinavir was 9.4 ± 2.2 μM and the 2-h area under the curve was 13.5 ± 3.1 μM⋅h. Insulin-stimulated glucose disposal per unit of insulin (M/I) decreased in all subjects from 14.1 ± 1.2 to 9.2 ± 0.8 mg/kg⋅min per μ UI/ml (95% confidence interval for change, 3.7–6.1;P < 0.001) on indinavir (average decrease, 34.1 ± 9.2%). The non-oxidative component of total glucose disposal (storage) decreased from 3.9 ± 1.8 to 1.9 ± 0.9 mg/kg⋅min (P < 0.01). Free fatty acid levels were not significantly different at baseline and were suppressed equally with insulin administration during both studies. Conclusions A single dose of indinavir acutely decreases total and non-oxidative insulin-stimulated glucose disposal during a euglycemic, hyperinsulinemic clamp. Our data are compatible with the hypothesis that an acute effect of indinavir on glucose disposal in humans is mediated by a direct blockade of GLUT-4 transporters.

Characterization of angiotensin II receptor subtypes in rat heart.

Angiotensin II exerts positive inotropic and chronotropic effects on the mammalian heart by binding to specific membrane receptors. Recently, two subtypes of angiotensin II receptors (AT1 and AT2) have been distinguished by using the nonpeptide antagonists losartan (previously known as DuP 753) and PD123177. To evaluate the tissue distribution and subtypes of angiotensin II receptors in rat heart, we performed a 125I-[Sar1,Ile8]angiotensin II in situ binding assay on tissue sections obtained from adult Sprague-Dawley rats (10 and 14 weeks old). Binding specificity was verified by competition with unlabeled [Sar1]angiotensin II. Distribution of AT1 and AT2 receptors was determined by competition with losartan and PD123177, respectively, and the density of the receptors was quantified by emulsion autoradiography. Angiotensin II receptors were widely distributed throughout the heart, with each receptor subtype accounting for approximately 50% of the specific binding. Binding density was comparable in the atria, right and left ventricles, intraventricular septum, and sinoatrial node, whereas it was significantly greater in the atrioventricular node. The AT1 receptor appears to interact with guanidine nucleotide regulatory proteins, because GTP-gamma-S causes dissociation of the radioligand from this receptor. In contrast, the AT2 receptor does not appear to directly interact with guanine nucleotide regulatory proteins, inasmuch as radioligand dissociation from this receptor subtype is not affected by GTP-gamma-S. Because angiotensin II has been reported to have growth-potentiating effects in several tissues, we examined angiotensin II receptors in fetal (embryonic days 16 and 19) and neonatal (1-, 2-, 3-, and 10-day-old) rats.(ABSTRACT TRUNCATED AT 250 WORDS)

RENAL-VEIN RENIN IN VARIOUS FORMS OF RENAL HYPERTENSION

Abstract Renal and peripheral venous plasmarenin activities were determined by radioimmunoassay of angiotensin I in 13 hypertensive patients with radiologically normal kidneys and in 110 patients with suspected renal hypertension. Renal-artery stenosis was present in 78 patients, while 32 had other abnormalities, including unilateral hydronephrosis, segmental renal infarction, and intrarenal vascular malformations. The results in 41 surgically treated patients confirm the predictive value of a renal-vein-renin ratio greater than 1·5 in patients with renal-artery stenosis and suggest that this ratio is also useful in patients with other types of renal hypertension. Evidence of suppression of renin release from the contralateral kidney seems to have additional value in predicting a response to surgery, but peripheral renin levels were normal in 14 out of 34 patients who benefited from surgery. The immunoassay has a high degree of precision, and the chance of an apparently significant ratio resulting from assay variation is negligible.

The metabolic effects of lopinavir/ritonavir in HIV-negative men.

Background: Therapy with HIV protease inhibitors (PI) has been shown to worsen glucose and lipid metabolism, but whether these changes are caused by direct drug effects, changes in disease status, or body composition is unclear. Therefore, we tested the effects of the PI combination lopinavir and ritonavir on glucose and lipid metabolism in HIV-negative subjects. Methods: A dose of 400 mg lopinavir/100 mg ritonavir was given twice a day to 10 HIV-negative men. Fasting glucose and insulin, lipid and lipoprotein profiles, oral glucose tolerance, insulin sensitivity by euglycemic hyperinsulinemic clamp, and body composition were determined before and after lopinavir/ritonavir treatment for 4 weeks. Results: On lopinavir/ritonavir, there was an increase in fasting triglyceride (0.89 ± 0.15 versus 1.63 ± 0.36 mmol/l; P = 0.007), free fatty acid (FFA; 0.33 ± 0.04 versus 0.43 ± 0.06 mmol/l; P = 0.001), and VLDL cholesterol (15.1 ± 2.6 versus 20 ± 3.3 mg/dl; P = 0.05) levels. There were no changes in fasting LDL, HDL, IDL, lipoprotein (a), or total cholesterol levels. Fasting glucose, insulin, and insulin-mediated glucose disposal were unchanged, but on a 2 h oral glucose tolerance test glucose and insulin increased. There were no changes in weight, body fat, or abdominal adipose tissue by computed tomography. Conclusion: Treatment with 4 weeks of lopinavir/ritonavir in HIV-negative men causes an increase in triglyceride levels, VLDL cholesterol, and FFA levels. Lopinavir/ritonavir leads to a deterioration in glucose tolerance at 2 h, but there is no significant change in insulin-mediated glucose disposal rate by euglycemic hyperinsulinemic clamp.