Adrenomedullin: possible predictor of insulin resistance in women with polycystic ovary syndrome

The aim of the study was to investigate adrenomedullin (ADM) levels and its relation with insulin resistance in women with polycystic ovary syndrome (PCOS). Twenty-nine women with PCOS and 29 age- and body mass index (BMI)- matched control subjects were included in the study. PCOS was defined according to criteria by the Rotterdam European Society of Human Reproduction and Embryology/American Society for Reproductive Medicine (ESHRE/ASRM)-sponsored PCOS consensus workshop group. A full clinical and biochemical examination including basal hormones and metabolic profile was performed. Insulin resistance was calculated by using the homeostasis model assessment of insulin resistance index (HOMA-IR). Plasma ADM levels were measured by high performance liquid chromatographic (HPLC) method. Plasma ADM, fasting insulin levels and HOMA-IR were significantly higher in patients with PCOS than the control group. ADM levels were positively correlated with insulin levels and HOMA-IR index. The best cut-off value of ADM levels to identify the presence of insulin resistance (HOMA-IR≥2.7) was 30.44 ng/ml. Calculated odds ratio of insulin resistance by using logistic regression analysis, as predicted by ADM, was 0.15 (95% confidence interval, 0.037-0.628; p=0.009). In multiple regression analysis, ADM level was an independent predictor of HOMA-IR index. Our finding indicated that ADM levels increased in women with PCOS in accordance with HOMA-IR. ADM could be a significant independent determinant of insulin resistance in women with PCOS.

Adrenomedullin and nitrite levels in children with dilated cardiomyopathy

Dilated cardiomyopathy (DCM) is an important cause of chronic congestive cardiac failure in children. In patients with idiopathic DCM, endothelium vasomotor function is disturbed. There are many studies on the roles of nitric oxide (NO) and adrenomedullin (AM) in adult patients with DCM. However, to our knowledge, no studies have investigated the level of AM and NO in children with idiopathic DCM. We determined plasma and urinary AM and total nitrite concentrations in children with idiopathic DCM and investigated the correlation between these and other clinical and laboratory findings. Eleven patients with DCM, ranging in age from 5 month to 14 years, were compared to 10 healthy age- and sex-matched controls. Plasma (pmol/ml) and urinary (pmol/mg creatinine) AM levels were significantly lower than in the healthy controls (19.55 +/- 2.36 vs 51.61 +/- 7.22 and 28.29 +/- 20.66 vs 68.87 +/- 40.23, respectively; p <0.001). Plasma and urinary AM levels were negatively correlated with ejection fraction (EF) and fractional shortening (FS). The plasma (Mmol/L) and urinary nitrite levels (Mmol/mg creatinine) were not different between patients and controls [50.90 +/- 17.50 VS 53.40 +/- 26.05 (P > 0.05) and 1.98 +/- 1.24 vs 2.75 +/- 1.68 (p > 0.05), respectively]. In our study, the first to analyze AM and nitrite levels in children with DCM, plasma and urinary AM levels were found to be decreased. A possible explanation for this reduction could be depletion of the viable myocyte population. However, this hypothesis must be clarified by further studies.

Contribution of adrenomedullin to homeostatic response to cold stress in rat model

Acute stress known to stimulate sympathetic activity as well as the hypothalamo-pituitary-adrenal (HPA) axis, produces a significant increase in adrenomedullin (ADM) levels in the pituitary gland, plasma and adrenal glands, all of which are key components of HPA axis, suggesting a regulatory or protective role for ADM in countering HPA activation following a variety of physiological and psychological stressors. This study was conducted to assess a rat model for in depth investigation of biochemical mechanisms and consequences of cold stress. Four groups of Sprague-Dawley rats were observed for their serum total protein, glucose, trigliceride and cholesterol levels as well as their blood pressures after housing at room temperature, administration of ADM (1.0 nm/kg), exposing to cold stress (8 degrees C for 48 h) and exposing to ADM injection in addition to cold stress. The results suggest that application of ADM in addition to cold stress may act via receptors on different end-organs and causes altered metabolic regulation taking partial or total occupation of ADM receptors, stimulated in response to cold application induced physiologic ADM release before pharmacological ADM administration.

Adrenomedullin and nitrite levels in children with Bartter syndrome

Children with Bartter syndrome have lower than normal vascular reactivity with normotension in spite of biochemical and hormonal abnormalities which are typical of hypertension. Nitric oxide (NO) is a potent endogenous vasodilator, and plays an important role in the control of vascular tone. Adrenomedullin (AM) is a novel hypotensive peptide originally isolated from human pheochromocytoma. The possible role of NO and AM in maintaining this reduced vascular reactivity was examined by studying plasma and urinary nitrite, a stable metabolite of NO, and AM levels in ten children with Bartter syndrome, ten healthy controls, and five children with hypokalemia of causes other than Bartter syndrome (pseudo-Bartter). Urinary excretion of nitrite (mumol/mg urinary creatinine) was 8.9 +/- 1.2 in children with Bartter syndrome, 4.7 +/- 0.9 in healthy controls, and 2.9 +/- 0.8 in pseudo-Bartter (P < 0.05). Plasma nitrite levels (mumol/l) were 101.9 +/- 23.4, 59.9 +/- 14.7, and 65.0 +/- 29.7, respectively (P < 0.05), in the three groups. Urinary excretion of AM (pmol/mg urinary creatinine) was 187 +/- 40, 65 +/- 10, and 160 +/- 50, respectively (P < 0.05), in the three groups. Plasma AM levels were 47.4 +/- 1.8, 39.9 +/- 5.9, and 42.4 +/- 3.9, respectively (P > 0.05), in the three groups. The same parameters were repeated in the two groups of controls and in the Bartter patients in the 6th month of therapy. Urinary nitrite and AM levels were still higher in the Bartter patients than in the other groups. We conclude that in Bartter syndrome the increased NO production may be responsible for the reduced vascular response of the disease. Initially, increased levels of AM in Bartter syndrome and pseudo-Bartter may be a compensatory response to acute hypokalemia; however, continuation of a high level of urinary excretion of AM in children with Bartter syndrome may suggest also the possible role of AM in the reduced vascular response of the disease.

Adrenomedullin and nitrite levels in children with minimal change nephrotic syndrome

Nitric oxide (NO) serves many functions within the kidney, and recent evidence suggests that NO contributes to glomerular injury. Adrenomedullin (AM) is a novel hypotensive peptide originally isolated from human pheochromocytoma. Recent studies showed that plasma AM concentrations correlated with the extent of proteinuria. We have examined the possible role of these two agents by studying plasma and urinary total nitrite (NO-2 + NO-3) and AM levels in children with minimal change nephrotic syndrome (MCNS). In comparison with healthy controls, children with MCNS had increased urinary nitrite excretion (micromol/mg urinary creatinine), irrespective of whether the disease was in relapse or remission (3.2+/-0.2 in relapse, n=13; 1.9+/-0.3 in remission, n=12; 1.0+/-0.2 in controls, n=10, P<0.05). Plasma nitrite levels (micromol/l) were high in relapse compared with controls (53.2+/-8.7 vs. 32+/-4.0, P<0.05). Plasma AM levels (pmol/ml) were decreased in relapse (27.6+/-1.4 in relapse, 43.3+/-1.2 in remission, 41.5+/-1.6 in controls, P<0.05). Urinary AM levels (pmol/mg urinary creatinine) were significantly higher in relapse than in remission and in controls (156+/-43 in relapse, 56+/-18 in remission, 36+/-16 in controls, P<0.05). Our data indicate that NO may play a role in mediating the clinical manifestations of MCNS in children. However, changes in AM levels may be the result of heavy proteinuria.

Exercise training reverses the age-related decline in tyrosine hydroxylase expression in rat hypothalamus

Tyrosine hydroxylase (TH) is the rate-limiting enzymatic step in the catecholamine biosynthesis pathway. Some studies have demonstrated that aging is associated with a decrease in TH activity and TH mRNA in rat hypothalamus. We previously demonstrated that exercise training can decrease TH gene expression in the adrenal medulla of young but not senescent rats. This study was designed to examine the effects of endurance training on the TH expression in hypothalamus with aging. To this end, we assessed TH mRNA, TH immunoreactivity, and TH activity with or without exercise training. Young and old F-344 female rats were trained by treadmill running for 8 weeks. All parameters examined were significantly lower in hypothalamus of old (25-month) compared with young (5-month) control animals (p < .05). Exercise training significantly elevated TH mRNA (n = 5-7 in each group), TH immunoreactivity (n = 5-8 in each group), and TH activity (n = 12-13 young groups and n = 6 old groups) in the hypothalamus of old animals (p < .05), but there was no significant change in any of these parameters in young animals following training. These data indicate that endurance training can reverse the age-related decline in catecholamine biosynthesis in the hypothalamus.

Effect of chronic treatment with prazosin and L-arginine on the elevation of blood pressure during cold exposure

Chronic exposure to cold (5 degrees C) is well known to increase both tyrosine hydroxylase (TH) activity in brown adipose tissue and systemic blood pressure. The effect of chronic dietary administration of the alpha-adrenergic antagonist, prazosin, and the amino acid, L-arginine, on both the elevation of blood pressure during exposure to cold and on TH activity and expression of TH mRNA in the adrenal glands of rats was studied. As observed previously, chronic exposure to cold increased systolic blood pressure significantly and induced cardiac hypertrophy. Chronic dietary treatment with prazosin (8 mg/kg food) and arginine (20 g/kg food) returned blood pressure to control levels, did not affect body weight significantly, but failed to prevent cardiac hypertrophy. Both prazosin and L-arginine reduced the drinking response to administration of angiotensin II. Treatment with arginine and prazosin was accompanied by a significant increase in the urinary outputs of dopamine and L-DOPA. The 3 cold-treated groups (control, L-arginine and prazosin) had increases in plasma T3 and decreases in plasma T4 and plasma renin activity. Plasma concentrations of epinephrine and norepinephrine were increased significantly in the L-arginine-treated group. TH mRNA and TH activity in the adrenal glands were increased in the 3 cold-treated groups and these measures were correlated directly and significantly with plasma norepinephrine and epinephrine concentrations. Although both prazosin and arginine prevented the cold-induced elevation of blood pressure, they did not prevent the increase in TH mRNA, TH activity or epinephrine in plasma. The protective effect of arginine and prazosin in cold-induced hypertension may be related both to their reduction in plasma renin activity and to a reduced responsiveness to angiotensin II, as well as to their abilities to increase the secretion of dopamine.