Increased clearance of cortisol by 5beta-reductase in a subgroup of women with adrenal hyperandrogenism in polycystic ovary syndrome.

OBJECTIVE: Increased peripheral metabolism of cortisol may explain compensatory ACTH-dependent adrenal steroidogenesis and hence hyperandrogenism in polycystic ovary syndrome (PCOS). Previous studies have described an increased 5alpha-reduction of cortisol or impaired regeneration of cortisol by 11beta-HSD1 in PCOS. However, these observations may be confounded by obesity. Moreover, the relationship between alterations in cortisol metabolism and the extent of adrenal androgen hyper-secretion in response to ACTH has not been established. This study aimed to examine the association between cortisol metabolism and ACTH-dependent adrenal hyperandrogenism in PCOS, independently of obesity. DESIGN: We compared 90 PCOS women (age 18-45 yr) stratified by adrenal androgen responses to ACTH1-24 and 45 controls matched for age and body weight. METHODS: PCOS women were stratified as normal responders (NR), intermediate responders (IR), and high responders (HR) to 250 microg ACTH1-24: NR (no.=27) had androstenedione and DHEA responses within 2 SD of the mean in controls; IR (no.=43) had DHEA responses >2 SD above controls; HR (no.=20) had both androstenedione and DHEA responses >2 SD above controls. RESULTS: All groups were similar for age, body weight, and body fat distribution. Basal testosterone, androstenedione, and 5alpha-dihydrotestosterone plasma levels were similarly elevated among the 3 groups of PCOS compared with controls, whereas basal DHEA-S was higher in HR (2.8+/-1.2 microg/ml) and IR (2.4+/-1.1 microg/ml) than in NR (1.8+/-0.8 microg/ml) and controls (1.7+/-0.6 microg/ml). The HR group had the lowest basal plasma cortisol levels (101+/-36 ng/ml vs IR 135+/-42 ng/ml, NR 144+/-48 ng/ml, and controls 165+/-48 ng/ml; all p<0.01), but the greatest cortisol response to ACTH1-24 (Delta(60-0)cortisol 173+/-60 ng/ml vs IR 136+/-51 ng/ml, NR 114+/-50 ng/ml, and controls 127+/-50 ng/ml; all p<0.01), and the highest urinary excretion of total and 5beta-reduced cortisol metabolites (eg 5beta-tetrahydrocortisol/ cortisol ratio 25.2+/-15.3 vs IR 18.8+/-10.7, NR 19.7+/-11.4, and controls 17.2+/-13.7; all p<0.05). There were no differences in urinary excretion of 5alpha-reduced cortisol metabolites or in 5alpha-dihydrotestosterone/testosterone ratio between groups. CONCLUSIONS: Adrenal androgen excess in PCOS is associated with increased inactivation of cortisol by 5beta-reductase that may lower cortisol blood levels and stimulate ACTH-dependent steroidogenesis.

Polyunsaturated fatty acids and inflammatory bowel disease.

The rationale for supplementation with n-3 fatty acids to promote the health of the gastrointestinal tract lies in the antiinflammatory effects of these lipid compounds. The first evidence of the importance of dietary intake of n-3 polyunsaturated fatty acids was derived from epidemiologic observations of the low incidence of inflammatory bowel disease in Eskimos. The aim of this paper was to briefly review the literature on the use of n-3 fatty acids in inflammatory bowel disease (ulcerative colitis and Crohn disease), the results of which are controversial. The discrepancies between studies may reside in the different study designs used as well as in the various formulations and dosages used, some of which may lead to a high incidence of side effects. Choosing a formulation that lowers the incidence of side effects, selecting patients carefully, and paying strict attention to experimental design are critical when investigating further the therapeutic potential of these lipids in inflammatory bowel disease.

Lipid peroxidation and antioxidant status in adults receiving lipid-based home parenteral nutrition.

BACKGROUND: Infusion of lipid emulsions rich in polyunsaturated fatty acids (PUFAs) may increase lipid peroxidation, which is counteracted mainly by superoxide dismutase (SOD) (a zinc-, copper-, and manganese-dependent enzyme), selenium-dependent glutathione peroxidase (Se-GSHPx), and alpha-tocopherol. OBJECTIVE: We investigated lipid peroxidation and antioxidant status in patients receiving home parenteral nutrition (HPN) providing variable amounts of a lipid emulsion rich in PUFAs, and alpha-tocopherol, zinc, copper, and manganese as recommended by the American Medical Association, and no selenium. DESIGN: Serum malondialdehyde, plasma alpha-tocopherol, selenium, Se-GSHPx, PUFAs, and red blood cell Se-GSHPx and SOD were evaluated in 12 patients and in 25 healthy control subjects. Malondialdehyde was also assessed in a group of 40 healthy control subjects. RESULTS: Patients had significantly higher concentrations of malondialdehyde and SOD and lower alpha-tocopherol concentrations and selenium nutritional status. Linear regression analysis showed that malondialdehyde was associated with the daily PUFA load (r=0.69, P< 0.03) and with plasma alpha-tocopherol (r=-0.59, P< 0.05), but stepwise multiple regression analysis confirmed only the association between malondialdehyde and alpha-tocopherol; plasma alpha-tocopherol was associated with the daily PUFA load (r=-0.65, P< 0.04) and with the duration of HPN (r=-0.74, P< 0.02). CONCLUSIONS: In HPN patients, the peroxidative stress due to lipid emulsions rich in PUFAs is counteracted primarily by alpha-tocopherol. The dosages of alpha-tocopherol, zinc, copper, and manganese recommended by the American Medical Association appear sufficient to sustain SOD activity but inadequate to maintain alpha-tocopherol nutritional status. HPN formulations should be supplemented with selenium.

Evidence for a neurotransmitter role of aspartate and/or glutamate in the projection from the torus longitudinalis to the optic tectum of the goldfish.

Different experimental approaches have been used to demonstrate that aspartate and/or glutamate is a transmitter(s) in the projection from the torus longitudinalis to the marginal layer of the optic tectum in the goldfish. Slices of the optic tectum incubated in vitro in the presence of D-[3H]aspartate and processed for light microscopic autoradiography, demonstrated a preferential accumulation of the labeled compound in the marginal layer. Under the same experimental conditions several neurons in the central part of the torus longitudinalis selectively accumulated D-[3H]aspartate. Synaptosome-enriched preparations from the optic tectum showed high-affinity uptake for D-[3H]aspartate and the rate of the uptake was significantly decreased after disconnection from the ipsilateral torus longitudinalis. The same subcellular preparations showed Ca2+-dependent release of previously accumulated D-[3H]aspartate under high potassium stimulation. This release was significantly reduced in preparations from optic tecta 5 days after cutting their connection with the ipsilateral torus longitudinalis. Finally, D-[3H]aspartate injected in the optic tectum retrogradely labeled the fiber systems connecting the marginal layer with the ipsilateral torus longitudinalis as well as neuronal cell bodies in the torus longitudinalis itself. From autoradiographic experiments it was, in addition, noticed that several tectal neurons selectively accumulated D-[3H]aspartate in the cell bodies as well as in main dendritic trunks. This observation suggests tht aspartate and/or glutamate may be a transmitter(s) in some intrinsic circuits and extrinsic projections of the optic tectum.

Characterization of a Na+/K+-ATPase inhibitor from human plasma: preliminary data.

The role of an endogenous sodium pump inhibitor in the pathogenesis of hypertension has been reported in several papers. Unfortunately, because of the unknown structure and lack of biochemical characterization, some discrepancies have arisen. In this study we report a method to obtain extracts from human plasma that are able to inhibit Na+/K+-ATPase in vitro. Preliminary characterization was carried out, which showed that the extracts are able to inhibit Na+/K+-ATPase, pNPPase, and [3H]ouabain binding to red blood cells. The enzyme inhibition is not due to vanadate, FFA, or bivalent cations, and it seems to be reversible, dose-dependent, and largely prevented in E1 conformation of the enzyme. These results seem to support the hypothesis that human plasma contains a sodium pump inhibitor with many characteristics of a "ouabainlike" compound.

Importance of plasma renin activity suppression and venous distensibility on pressor and natriuretic responses to intravenous salt load in borderline hypertension.

Cardiopulmonary receptors influence renin release in a variety of physiological situations and in a fashion related to the degree of peripheral venous distensibility. We studied two groups of borderline hypertensives (BHTs) with different capacities to suppress plasma renin activity in response to saline infusion (0.20 mL/kg/per minute for 2 hours). Those BHTs with low suppressive capacity (L-supp) showed an increased venous distensibility in comparison with those with high suppressive capacity (H-supp). Saline infusion led to a significant increase in blood pressure only in L-supp BHTs, which was associated with enhanced 24-hour postloading natriuresis and raised plasma levels of an Na/K ATPase inhibitor (+12.2%). This result underlines the importance of venous distensibility as a determinant of pressor and humoral response to acute volume expansion.

Short-term plasma renin activity suppression by saline and release of a plasma endogenous Na/K ATPase inhibitor in essential hypertension.

The present study was conducted in 15 essential hypertensives to evaluate the modifications of plasma levels of an endogenous Na/K ATPase inhibitor, blood pressure, forearm hemodynamics and plasma renin activity (PRA) elicited by an intravenous saline infusion (0.9% NaCl at the mean rate of 0.22 mL/min/kg body weight for 2 h). The response to saline was determined in the whole hypertensive population as well as in two subgroups of patients classified according to their rate of PRA suppression in response to volume expansion by comparison with normotensive controls (Normal- and Low-suppressors: N-S, L-S). Over the whole group of hypertensive patients, NaCl load provoked an increase in Na/K ATPase inhibitory activity, measured by enzyme-coupled assay, which was linearly related to PRA decline (r = 0.73) and to the increase in mean blood pressure (r = 0.57). These effects were clearly enhanced by considering L-S patients alone. Urinary Na/K ratio after saline infusion was significantly higher in L-S as result of a lesser potassium excretion in this subgroup. Our results support the hypothesis that acute volume expansion with saline causes an increase in plasma levels of an endogenous sodium pump inhibitor with hemodynamic effects and whose release is related to the individual handling of infused fluids and to the degree of renin-angiotensin-aldosterone suppression.

Erythrocyte Na-K-ATPase membrane activity in obese patients fed over a long-term period with a very-low-calorie diet.

In a search for the role of long-term hypocaloric feeding on the expression of the erythrocyte Na pump in obesity, we examined three groups of subjects. Group 1 consisted of 10 obese subjects who had been under treatment for a long period of time with a very-low-calorie diet (500 kcal/d) while group 2 consisted of 10 age-, sex-, and body mass index-matched obese subjects on their usual diet; in the third group, 12 normal-weight subjects on a free diet served as controls. There was no difference between the groups in the number of erythrocyte binding sites per cell. On the contrary, the Na-K-ATPase activity was significantly lower in the obese group 1 (0.35 +/- 0.09 mumol Pi x mg protein-1 x h-1) compared to that observed in the obese group 2 (0.42 +/- 0.07, P less than .05) and in control subjects (0.45 +/- 0.06, P less than .05). Sex, duration of hypocaloric feeding, and the amount of weight loss before the study in the obese group 1 seemed not to be related to the Na pump parameters. We conclude that long-term severe hypocaloric feeding may be a factor in altered erythrocyte Na-K-ATPase in obese individuals.

The omega-3 polyunsaturated fatty acid eicosapentaenoic acid inhibits mouse MC-26 colorectal cancer cell liver metastasis via inhibition of PGE2-dependent cell motility.

BACKGROUND AND PURPOSE: The omega-3 polyunsaturated fatty acid (PUFA) eicosapentaenoic acid (EPA) has antineoplastic activity at early stages of colorectal carcinogenesis, relevant to chemoprevention of colorectal cancer (CRC). We tested the hypothesis that EPA also has anti-CRC activity at later stages of colorectal carcinogenesis, relevant to treatment of metastatic CRC, via modulation of E-type PG synthesis. EXPERIMENTAL APPROACH: A BALB/c mouse model, in which intrasplenic injection of syngeneic MC-26 mouse CRC cells leads to development of liver metastases, was used. Dietary EPA was administered in the free fatty acid (FFA) form for 2 weeks before and after ultrasound-guided intrasplenic injection of 1 × 10(6) MC-26 cells (n= 16 each group). KEY RESULTS: Treatment with 5% (w w(-1)) EPA-FFA was associated with a reduced MC-26 mouse CRC cell liver tumour burden compared with control animals (median liver weight 1.03 g vs. 1.62 g; P < 0.034). Administration of 5% EPA-FFA was also linked to a significant increase in tumour EPA incorporation and lower intratumoural PGE(2) levels (with concomitant increased production of PGE(3)). Liver tumours from 5% EPA-FFA- treated mice demonstrated decreased 5-bromo-2-deoxyuridine-positive CRC cell proliferation and reduced phosphorylated ERK 1/2 expression at the invasive edge of tumours. A concentration-dependent reduction in MC-26 CRC cell Transwell® migration following EPA-FFA treatment (50-200 µM) in vitro was rescued by exogenous PGE(2) (10 µM) and PGE(1)-alcohol (1 µM). CONCLUSIONS AND IMPLICATIONS: EPA-FFA inhibits MC-26 CRC cell liver metastasis. EPA incorporation is associated with a 'PGE(2) to PGE(3) switch' in liver tumours. Inhibition of PGE(2)-EP(4) receptor-dependent CRC cell motility probably contributes to the antineoplastic activity of EPA.

Modification of ultrastructural and neurochemical parameters in synaptosomes of the retino-deprived goldfish optic tectum.

Neurochemical parameters associated with cholinergic and excitatory amino acid transmission, were measured in synaptosomes of the goldfish optic tectum at different times after unilateral eye ablation. Significant decreases in choline acetyltransferase and acetylcholinesterase were measured 12 and 30 days after enucleation. The high affinity choline uptake did not parallel the decrease in cholinergic enzymes. Instead there was a significant increase of the uptake per unit of protein (though not relative to the total number of tectal synaptosomes). No decrease of the high affinity D-3H aspartate uptake was measured in the deafferentated optic tectum. Electron microscopic observations showed a correspondence between the time course of cholinergic enzyme decrease and the degeneration of retinal afferents to the tectum. The present results support the notion that acetylcholine is a better candidate than the excitatory amino acids for a neurotransmitter role in the fish optic tectum.

Purification of a Na+/K+ ATPase inhibitor from borderline hypertensives' plasma.

Increasing experimental evidences suggest an involvement of an endogenous Na+/K+ ATPase inhibitor in regulating water and electrolytes balance as well as in the pathogenesis of hypertension. However, conflicting results on the nature and the chemical structure of this substance still make it difficult to understand exactly its physiological mechanism of action. In the present study an attempt was made to purify a Na+/K+ ATPase inhibitor from hypertensives' plasma by solid phase extraction followed by 2 HPLC steps using reverse and normal phase columns. The fractions, from both columns, were able to inhibit Na+/K+ ATPase, 3H-ouabain binding to enzyme, ouabain sensitive 86Rb uptake and pNPPase activity in a manner not affected by boiling. Ultrafiltration experiments demonstrate that inhibitory activity is largely due to a low-molecular weight substance. These findings seem to confirm the presence in hypertensives plasma of a Na+/K+ ATPase inhibitor with some similarities with ouabain.