L-carnitine supplementation and adipokines in patients with end-stage renal disease on regular hemodialysis.

Chronic hemodialysis (HD) patients frequently encounter carnitine depletion, elevated adipose tissue-derived hormones/cytokines, that may contribute to accelerated arteriosclerosis. 10 non-diabetic HD patients were studied over 28 weeks. In the 12 weeks treatment period 1 g L-carnitine was given iv after each HD session. Measurements of plasma free- and acylcarnitines, insulin, leptin, adiponectin, resistin and ghrelin were performed at baseline, at weeks 2, 4, 8, 12 (treatment period) and at weeks 24-28 (post-treatment period). L-carnitine supplementation resulted in progressive increase of free- and acylcarnitine levels. Plasma levels of insulin, resistin, leptin and ghrelin remained at the already elevated baseline values. L-carnitine therapy induced a significant increase in plasma adiponectin from 20.2 ± 12.7 µg/ml (baseline) to 32.7 ± 20.2 µg/ml in week 2 (p<0.05) and 35.4 ± 19.6 µg/ml in week 12 (p < 0.03), which remained unchanged in the post-carnitine period. Plasma insulin levels correlated positively with leptin (r = 0.525, p<0.0001) and resistin (r = 0.284, p<0.005); adiponectin levels correlated inversely with leptin (r = -0.255, p<0.02) and resistin (r = -0.213, p<0.04) irrespective of carnitine status. Plasma levels of adipokines and related hormones are greatly elevated in patients on regular HD. L-carnitine administration further augmented the plasma levels of protective adiponectin, therefore it may have a role in preventing cardiovascular complications of uremia.

Hyaluronan-related limited concentration by the immature kidney.

The limited renal concentration performance by the immature kidney traditionally is thought to be attributed to blunted renal response to arginine vasopressin (AVP) and medullary hypotonicity. The diminished AVP-dependent osmotic water permeability of the collecting duct is the result of decreased AVP binding and adenylate cyclase activation, and low expression of aquaporin-2 (AQP2) mRNA and low levels of AQP2 protein. Moreover, the immature kidney fails to establish deep cortico-papillary osmotic gradient because of structural immaturity, limited solute transport and increased medullary blood flow. Based on indirect clinical and experimental evidences this article puts forward a hypothesis that during perinatal period the abundant hyaluronan (HA) content in the renomedullary interstitium has a primary role in antagonizing water reabsorption and limiting concentration performance. Hydration-related alterations in renal HA appears to be mediated by antidiuretic hormone. The concept of HA-mediated renal water transport may imply that interfering selectively with renal HA metabolism may provide a new therapeutic approach to promote diuresis or antidiuresis, respectively, according to the elevation or reduction in renomedullary HA.

Urinary aquaporin-2 excretion in preterm and full-term neonates.

The study was undertaken to define the role of aquaporin-2 (AQP2) in renal concentrating performance by measuring urinary AQP2 excretion and urine osmolality in healthy preterm and full-term neonates during early postnatal life. Random urine samples were obtained from 9 full-term newborn infants (mean birth weight 3,218 g, mean gestational age 39.2 weeks) at postnatal ages of 1, 3 and 5 days. Five premature infants with a mean birth weight of 1,570 g and mean gestational age of 30.6 weeks were studied at the end of the 1st week and then weekly up to the 6th week. Urine osmolality (Knauer osmometer), creatinine (modified Jaffé's method) and AQP2 concentrations (radioimmunoassay) were measured. In full-term neonates, urinary AQP2 excretion showed no consistent changes over the age period studied, while urine osmolality decreased significantly with advancing age. In premature infants, urinary AQP2 excretion remained practically unchanged during the first 4 weeks followed by an abrupt increase thereafter. Urine osmolality did not follow the developmental pattern of AQP2 excretion; its mean values varied only from 78 +/- 39 to 174 +/- 146 mosm/l during the experimental period. It is concluded that during the early postnatal period, urinary AQP2 excretion does not serve as a direct marker of the renal action of AVP and the renal capacity to concentrate urine.

Increase of endothelial nitric oxide synthase and endothelin-1 mRNA expression in human placenta during gestation.

OBJECTIVE: To investigate the maturation of the paracrine system's endothelial nitric oxide synthase (eNOS), inducible NOS (iNOS), endothelin-1 (ET-1) and adrenomedullin (AM) in human placenta during the 2nd and 3rd trimester of pregnancy. STUDY DESIGN: Placental tissue from 14 healthy women with normal pregnancy and from 13 patients giving birth to premature infants following premature labor was obtained. Messenger RNA expression was determined using quantitative TaqMan real-time PCR. RESULTS: Placental eNOS/GAPDH and ET-1/GAPDH mRNA expression significantly increased as a function of gestational age (r=0.63, P<0.001 and r=0.53, P=0.007, respectively). There was no change in gene expression of neither iNOS nor AM mRNA/GAPDH during gestation (r=0.02, P=0.75 and r=0.001, P=0.99, respectively). CONCLUSION: There is a maturation of eNOS and ET-1 in human placenta with gestation reflecting developmental changes of important paracrine endothelial and trophoblastic regulators. AM and iNOS show no maturation during pregnancy.

Increased endothelin-1 and decreased adrenomedullin gene expression in the stenotic tissue of congenital pelvi-ureteric junction obstruction in children.

OBJECTIVES: To test the hypothesis that the gene expression of endothelin-1 and adrenomedullin may be altered in stenotic tissues of patients with congenital hydronephrosis caused by pelvi-ureteric junction (PUJ) obstruction. MATERIALS AND METHODS: Using real-time reverse transcription-polymerase chain reaction, mRNA of smooth muscle-constricting endothelin-1 and of smooth muscle-relaxing adrenomedullin was quantified in tissue specimens of 20 patients with PUJ obstruction (mean age 5.1 years, SD 7.0) and of 21 controls with normal PUJs (mean age 23.5 years, SD 24.2). RESULTS: The amount of endothelin-1 mRNA in stenotic specimens was higher than in the controls, indicated by significantly lower threshold cycles (Ct values) in real-time PCR for the target gene in the obstructive tissue, with mean (SD) values of 24.9 (1.6) and 26.0 (2.1) (P < 0.05), respectively. The endothelin-1/CD31 ratio was significantly higher in the patients (P < 0.05) than in controls. In addition, adrenomedullin gene expression in the obstructed junctions was significantly lower than in normal junctions, with higher Ct values for the patient group of 26.7 (1.6) vs 25.2 (1.8) (P < 0.05) and lower adrenomedullin mRNA when standardized to glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (P < 0.05), CD31 (P < 0.01) and smooth muscle alpha-actin mRNA (P < 0.01). The two groups showed no significant differences for GAPDH and CD31 mRNA content, whereas there was about twice as much alpha-actin mRNA in stenotic tissues than in unaffected PUJs, shown by the lower Ct values for the patient group of 16.9 (2.0) vs 17.9 (2.6) (P < 0.05). Furthermore, endothelin-1, adrenomedullin and alpha-actin mRNA amounts were independent of age. CONCLUSION: Taken together these results provide evidence that the production of autocrine/paracrine acting endothelin-1 and adrenomedullin is altered in tissues of patients with genuine PUJ obstruction, and may be involved in the pathogenesis of congenital hydronephrosis.

Brain water and proton magnetic resonance relaxation in preterm and term rabbit pups: their relation to tissue hyaluronan.

The present study was performed to investigate simultaneously total brain water, T1 and T2 relaxation times, and hyaluronan (HA) in fetal and neonatal rabbits. Attempts were also made to establish the relationship of HA to total brain water and to T2-derived motionally distinct water fractions, since HA is known to bind water and to limit tissue water mobility. Experiments were carried out in fetal Pannon white rabbit pups at gestational ages of 25, 27, 29, and 31 days and at a postnatal age of 4 days. The brain tissue water content (desiccation method), T1 and T2 relaxation times (H1-NMR method), and HA concentration (radioassay HA 50) were measured, and free and bound water fractions were calculated by using multicomponent fits of the T2 relaxation curves. Compared with values in newborn pups, water and HA contents were found to be highly elevated in the preterm brain and decreased markedly during early postnatal life. The trends and time courses of T1 and T2 relaxation times proved to be similar, but the postnatal decrease in T2 was preceded by a significant decline in late gestation. Maturity-related changes occurred in the T2 relaxation derived bound water fraction which amounted to 4-19% of brain water. The bound water fraction appeared to be independent of total brain water and HA concentration, and HA is, therefore, unlikely to be the only factor controlling brain water mobility. The clear dissociation of bound water fraction from total water suggests restructuring of brain water during the perinatal period.

Lung water and proton magnetic resonance relaxation in preterm and term rabbit pups: their relation to tissue hyaluronan.

The present study was performed to investigate simultaneously total lung water, T(1) and T(2) relaxation times, and hyaluronan (HA) in preterm and term rabbits. Attempts were also made to establish the relationship of HA to total lung water and to T(2)-derived motionally distinct water fractions. Experiments were performed in fetal Pannon white rabbit pups at gestational ages of 25, 27, 29, and 31 d and at a postnatal age of 4 d. Lung tissue water content (desiccation method), T(1) and T(2) relaxation times (H(1)-NMR method), and HA concentration (radioassay) were measured, and free and bound water fractions were calculated by using multicomponent fits of the T(2) relaxation curves. Lung water content and T(1) and T(2) relaxation times were highest at a gestational age of 27 d and then declined steadily during the whole study period. Similar trends and time courses were seen for the fast and slow components of the T(2) relaxation curve. The T(2)-derived free water fraction remained unchanged at a gestational age of 25-29 d ( approximately 67%), but increased progressively to a value of 78.5 +/- 7.9% at 31 d (p < 0. 001) and to 83.4 +/- 9.4% at the postnatal age of 4 d (p < 0.01). Opposite changes occurred in the bound water fraction. Lung HA concentration decreased with advancing gestation from 870.8 +/- 205.2 microg/g dry weight at 25 d to 162.6 +/- 32.4 microg/g dry weight at 31 d (p < 0.001), but it was increased 2-fold postnatally. HA correlated positively with total lung water (r = 0.39; p < 0.001) but not with the bound water fraction. It is suggested that the physiologic lung dehydration is associated with macromolecule-related reorganization of lung water and that the role of HA in this process needs to be further investigated.

Urinary excretion of endogenous ouabain-like substance is reduced in NaCl supplemented premature infants.

Ouabain or an isomer has been identified as endogenous ouabain-like substance (EOLS). The role of EOLS in the adaptation of premature infants to alterations of sodium balance was investigated by measuring urinary ouabain excretion serially in 9 low birth weight premature infants with (group S, mean birth weight 1,578 g, mean gestational age 30.4 weeks) and without (group NS, mean birth weight 1,537 g, mean gestational age 30.8 weeks) NaCl supplementation. The study was performed on the 7th day and weekly thereafter until the 5th week of life. NaCl supplementation was given in a dose of 3-5 and 1.5-2.5 mmol/kg/day at the postnatal ages of 8-21 and 22-35 days, respectively. Prior to NaCl supplementation, urinary ouabain excretion was similar in the two groups (146.2 +/- 16.8 pg/kg/h in group S versus 180.0 +/- 9.6 pg/kg/h in group NS) and remained at about the same level throughout the study when supplemental NaCl was provided. In infants of group NS, urinary ouabain excretion increased significantly by the 3rd week (p < 0.01) and no consistent change occurred later on. As a result, the differences in urinary ouabain excretion between the two groups proved to be significant during weeks 2-5 (p < 0.001). Essentially the same pattern of ouabain excretion was seen when it was expressed in terms of pg/mg creatinine. In infants receiving high sodium diet there was a significant positive correlation between urinary sodium and ouabain excretion. It is concluded that premature infants receiving low sodium intake have elevated EOLS excretion by the 3rd week of life. Although the relationship between ouabain and sodium excretion in supplemented premature infants suggests some physiological significance for sodium excretion, ouabain does not appear to be regulated by extracellular volume.