Sex-specific regulation of ENaC and androgen receptor in female rat kidney

With the beginning of puberty blood pressure increases and is persistently higher in men than in premenopausal women. Sex steroids are known to have complex effects on the renal and cardiovascular system and are involved in blood pressure regulation. The epithelial sodium channel (ENaC) modulates sodium reabsorption in the kidney, but little is known about sex-specific regulation of ENaC subunit expression. Regulation of the androgen receptor (AR) is known to be tissue-specific and age-dependent, but not well studied in the kidney. We investigated the effects of sex steroids on ENaC subunits and renal AR expression in an in vivo rat model. Ovariectomized female Wistar rats were treated with placebo, testosterone, 5 alpha-dihydrotestosterone (DHT) or 17 beta-estradiol (E2) for 14 days, and quantitative PCR and Western immunoblots were performed. DHT significantly decreased expression of all ENaC subunits in female rats, whereas testosterone showed only a trend to lower ENaC expression. These results are in contrast to previous studies where stimulating effects of androgens on the alpha-subunit of ENaC were seen. AR mRNA expression showed a trend to lower levels in females after testosterone treatment in this study. However, estrogen treatment significantly downregulated AR mRNA expression. In male control animals we were able to show a significantly increased expression of AR mRNA upon testosterone treatment. Our data demonstrate that AR and ENaC are regulated by sex steroids. That way sex steroids might modulate renal sodium reabsorption and therefore provide a possible explanation for sex differences in blood pressure.

Cardiovascular and cerebrovascular comorbidities of hypokalemic and normokalemic primary aldosteronism: results of the German Conn's Registry

CONTEXT

Primary aldosteronism (PA) is associated with vascular end-organ damage.

OBJECTIVE

Our objective was to evaluate differences regarding comorbidities between the hypokalemic and normokalemic form of PA.

DESIGN AND SETTING

This was a retrospective cross-sectional study collected from six German centers (German Conn's registry) between 1990 and 2007.

PATIENTS

Of 640 registered patients with PA, 553 patients were analyzed.

MAIN OUTCOME MEASURES

Comorbidities depending on hypokalemia or normokalemia were examined.

RESULTS

Of the 553 patients (61 +/- 13 yr, range 13-96), 56.1% had hypokalemic PA. The systolic (164 +/- 29 vs. 155 +/- 27 mm Hg; P < 0.01) and diastolic (96 +/- 18 vs. 93 +/- 15 mm Hg; P < 0.05) blood pressures were significantly higher in hypokalemic patients than in those with the normokalemic variant. The prevalence of cardiovascular events (angina pectoris, myocardial infarction, chronic cardiac insufficiency, coronary angioplasty) was 16.3%. Atrial fibrillation occurred in 7.1% and other atrial or ventricular arrhythmia in 5.2% of the patients. Angina pectoris and chronic cardiac insufficiency were significantly more prevalent in hypokalemic PA (9.0 vs. 2.1%, P < 0.001; 5.5 vs. 2.1%, P < 0.01). Overall, cerebrovascular comorbidities were not different between hypokalemic and normokalemic patients, however, stroke tended to be more prevalent in normokalemic patients.

CONCLUSIONS

Our data indicate a high prevalence of comorbidities in patients with PA. The hypokalemic variant is defined by a higher morbidity than the normokalemic variant regarding some cardiovascular but not cerebrovascular events. Thus, PA should be sought not only in hypokalemic but also in normokalemic hypertensives because high-excess morbidity occurs in both subgroups.

[Obesity and heart failure]

Obesity doubles the risk of heart failure independent of comorbidities like hypertension or coronary artery disease potentially mediated by altered hemodynamics to compensate increased mass and metabolic activity. Symptoms of obesity cardiomyopathy do not differ from other forms of cardiomyopathy, but may be easily mixed up with obesity associated symptoms. The diagnosis can be made with imaging techniques like echocardiography or magnetic resonance imaging. Therapeutic approaches include weight control by dietary intervention and exercise, as well as bariatric surgery for the morbidly obese. Heart failure treatment should otherwise follow the general heart failure guidelines.

Detrimental effects of testosterone on post-myocardial infarction remodelling in female rats

Clinical data suggest an association of increased serum androgens with cardiovascular mortality in females, but not in males. Therefore, we examined effects of chronic anabolic testosterone administration on left ventricular remodeling after myocardial infarction in female rats. Ovariectomized adult female rats were treated with placebo, supraphysiologic testosterone undecanoate (T), estradiol (E(2)), or T+E(2). Two weeks after ovarcectomy, animals underwent sham-operation or coronary artery ligation. Left ventricular remodeling and function were assessed by echocardiography and hemodynamic investigation. In sham operated animals T administration increased serum T levels and led to cardiac hypertrophy, with an increase in the beta/alpha-MHC-ratio and in IGF-1 expression. After coronary artery ligation, infarct size and mortality were similar among the groups. T treatment aggravated left ventricular hypertrophy and chamber dilatation (end-diastolic diameter, E(2) vs. T vs. E(2)+T, 8.6 +/- 0.6 vs. 9.9 +/- 0.3 vs. 9.8 +/- 0.3 mm, p<0.05) and reduced fractional shortening 8 weeks after myocardial infarction. Extracellular matrix remodeling was not altered by hormonal treatment. In conclusion, chronic anabolic T treatment causes myocardial hypertrophy under basal conditions and adversely affects left ventricular remodeling following myocardial infarction in female rats.

Retinol-binding protein 4 is associated with components of the metabolic syndrome, but not with insulin resistance, in men with type 2 diabetes or coronary artery disease

AIMS/HYPOTHESIS

Retinol-binding protein 4 (RBP4) has recently been reported to be associated with insulin resistance and the metabolic syndrome. This study tested the hypothesis that RBP4 is a marker of insulin resistance and the metabolic syndrome in patients with type 2 diabetes or coronary artery disease (CAD) or in non-diabetic control subjects without CAD.

METHODS

Serum RBP4 was measured in 365 men (126 with type 2 diabetes, 143 with CAD and 96 control subjects) and correlated with the homeostasis model assessment of insulin resistance index (HOMA-IR), components of the metabolic syndrome and lipoprotein metabolism. RBP4 was detected by ELISA and validated by quantitative Western blotting.

RESULTS

RBP4 concentrations detected by ELISA were shown to be strongly associated with the results gained in quantitative Western blots. There were no associations of RBP4 with HOMA-IR or HbA(1c) in any of the groups studied. In patients with type 2 diabetes there were significant positive correlations of RBP4 with total cholesterol, LDL-cholesterol, VLDL-cholesterol, plasma triacylglycerol and hepatic lipase activity. In patients with CAD, there were significant associations of RBP4 with VLDL-cholesterol, plasma triacylglycerol and hepatic lipase activity, while non-diabetic control subjects without CAD showed positive correlations of RBP4 with VLDL-cholesterol and plasma triacylglycerol.

CONCLUSIONS/INTERPRETATION

RBP4 does not seem to be a valuable marker for identification of the metabolic syndrome or insulin resistance in male patients with type 2 diabetes or CAD. Independent associations of RBP4 with pro-atherogenic lipoproteins and enzymes of lipoprotein metabolism indicate a possible role of RBP4 in lipid metabolism.

DHEA: why, when, and how much--DHEA replacement in adrenal insufficiency

In recent years it has been demonstrated that current replacement therapy with glucocorticoids and mineralocorticoids fails to fully restore health-related quality of life in patients with adrenal insufficiency (AI). Accordingly, replacement of zona reticularis function by DHEA is of considerable interest. Available studies have demonstrated beneficial effects of DHEA on health perception, vitality, fatigue, and (in women) sexuality. DHEA restores low circulating androgens in women into the normal range and increases IGF-1 levels. Side effects are mostly mild and related to androgenic activity of DHEA in women and include increased sebum production, facial acne, and changes in hair status. Replacement consists of a single oral dose of 25-50 mg DHEA in the morning. However, not all investigators have found effects of DHEA on well-being, most likely because of small sample size and short duration of treatment. Thus, to fully explore the role of DHEA in the treatment of AI large trials for 12-24 months are still urgently needed. Until the results of such trials are available DHEA cannot be considered part of standard replacement in AI, but compassionate use of DHEA in individual patients with AI and impaired well-being may be justified.

Epidermal growth factor receptor (EGFR) as a potential new target in the treatment of patients with adrenocortical carcinoma: Results of pre-clinical studies

21025

Background: Adrenocortical carcinoma (ACC) is a rare malignancy with incompletely understood pathogenesis and poor prognosis. Overexpression of epidermal growth factor receptor (EGFR) has been demonstrated in several tumors and is partly associated with a more aggressive phenotype and a worse prognosis. In addition, targeting the EGFR tyrosine kinase represents a successful new therapeutic strategy, e.g. in non-small cell lung cancer. Therefore, we investigated the role of EGFR in ACC as a potential therapeutic target. Methods: EGFR expression was analyzed by immunohistochemistry in 115 ACCs and 5 normal adrenals using paraffin sections and tissue arrays (scoring of expression: 0–3). Utilizing the clinical data from the German ACC registry, Kaplan Meier survival analyses were performed. In 30 patients the tumor DNA was sequenced for mutations of the “hot spot” exons 19–21 of the EGFR gene. In addition, cells of the ACC cell line NCI-h295 were incubated with the EGFR antibody cetuximab (1–100 μg/ml) and cell proliferation was measured by MTT tests. Results: Immunohistochemistry revealed EGFR expression in 78% of ACCs. In 67/115 (58%) of the ACCs and 0/5 of the normal adrenals the expression level was judged as moderate-to-high (score 2 or 3). However, the expression level did not correlate with the clinical outcome in these patients. In addition, none of the sequenced tumor DNA samples showed a mutation in exons 19–21. Cetuximab exhibited a dose dependent antiproliferative effect in NCI-H295 cells (cell viability: 1μg/ml: 95±2%; 10μg/ml 90±3%*; 100 μg/ml 85±4%* vs untreated control cells: 100±3%; * = p<0.01). Conclusion: EGFR is overexpressed in the majority of ACC. Moreover, in vitro experiments demonstrated that inhibition of EGFR signalling lead to moderate growth inhibition in ACC cells. Therefore, in patients with ACC refractory to established cytotoxic therapies the experimental use of EGFR inhibitors (combined with cytotoxic therapy) seems to be justified.

No significant financial relationships to disclose.