Sex hormone-binding globulin in the diagnosis of peripheral tissue resistance to thyroid hormone: the value of changes after short term triiodothyronine administration

Thyroid hormone is one of several factors that modulate the level of sex hormone-binding globulin (SHBG) in serum. SHBG levels are usually elevated in thyrotoxicosis and have been reported to be normal in a few patients with generalized resistance to thyroid hormone (GRTH). This study was designed to determine whether basal serum SHBG levels or the SHBG response to short term T3 administration could be used as an index of thyroid hormone action and thus serve as a test for the evaluation of patients suspected of having peripheral tissue resistance to thyroid hormone. Serum SHBG, total T4, free T4 index (FT4I), total T3, and TSH levels were measured in 21 normal subjects, 28 hypothyroid patients, 20 thyrotoxic patients, and 10 patients with GRTH. Excluding patients with GRTH, serum basal SHBG values were correlated with FT4I values (r = 0.66; P less than 0.0001). Mean SHBG levels in the patients with GRTH [37.6 +/- 16.2 (+/- SD) nmol/L] were not significantly different from those in the normal subjects (35.1 +/- 19.3 nmol/L) or hypothyroid patients (26.3 +/- 17.1 nmol/L), but were significantly lower than those in the thyrotoxic group (64.7 +/- 19.2 nmol/L; P less than 0.001). All 10 patients with GRTH had basal SHBG values in the normal range, but 7 of 20 (35%) thyrotoxic patients also had normal basal SHBG values. T3 was given orally for three sequential 3-day periods at doses of 50, 100, and 200 micrograms daily to 7 normal subjects, 11 hypothyroid and 3 thyrotoxic patients, and all 10 patients with GRTH. The serum SHBG concentration was measured on the last day at each dosage level. During T3 administration, SHBG levels increased in all individuals with normal tissue responsiveness. The increase above the basal value (delta SHBG) at each T3 dose was similar in normal, hypothyroid, and thyrotoxic individuals (non-resistant subjects). After administration of 50 micrograms T3 daily, the mean delta SHBG level was decreased [-2.9 +/- 5.3 (+/- SD) nmol/L] in the resistant patients and increased (4.0 +/- 4.9 nmol/L; P less than 0.005) in the nonresistant subjects. After administration of 100 micrograms T3 daily, the mean delta SHBG was -4.5 +/- 6.8 nmol/L in the resistant patients and 8.6 +/- 5.1 nmol/L (P less than 0.0001) in the nonresistant subjects. Serum SHBG decreased by more than 2 nmol/L in 6 of 10 (60%) resistant patients, but in no nonresistant subject.(ABSTRACT TRUNCATED AT 400 WORDS)     

Bioavailability of carotenoids from spinach and tomatoes

BACKGROUND AND AIM: Few published studies have described the bioavailability of the different carotenoids in spinach. This was designed to evaluate the effects on plasma carotenoid concentrations of a daily consumption of spinach (rich in lutein and beta-carotene), alone or together with lycopene-rich tomato puree. METHODS AND RESULTS: Nine healthy young women consumed a standard low-carotenoid diet during the pre-study phase, the spinach diet (standard diet plus 150 g spinach: 9 mg lutein, 4 mg beta-carotene) from day 0 to day 21, and then, after a wash-out period, the spinach-tomato diet (standard diet plus 150 g spinach and 25 g tomato puree: 9 mg lutein, 4.3 mg beta-carotene and 7 mg lycopene) from day 35 to day 56. The spinach and spinach-tomato supplements were consumed together with 10 g olive oil. Fasting blood samples were collected on day -7, and every week thereafter. Plasma carotenoid concentrations significantly decreased during the standard low-carotenoid diet. Lutein levels gradually increased after spinach consumption from 0.36+/-0.05 to 1.59+/-0.19 micromol/L (p<0.0001), decreased during the wash-out period from 1.59+/-0.19 to 0.62+/-0.07 micromol/L (p<0.001), and rose again after the intake of spinach-tomato puree from 0.62+/-0.07 to 1.55+/-0.17 micromol/L (p<0.0001). beta-carotene levels also increased during both dietary supplementation periods. Lycopene decreased during the spinach diet from 0.20+/-0.03 to 0.07+/-0.01 micromol/L (p<0.001) and increased during the spinach-tomato diet from 0.05+/-0.01 to 0.52+/-0.06 micromol/L (p<0.0001). CONCLUSIONS: The results of this study confirm that a regular intake of selected vegetables leads to a progressive increase in plasma carotenoid concentrations. The addition of tomato puree to spinach does not decrease lutein plasma concentrations. Furthermore, baseline plasma levels of lutein and lycopene are important variables affecting the relative increase in their levels after supplementation: ie more depleted subjects are expected to have a greater percent rise in plasma carotenoid concentrations.     

Serum concentrations of nitric oxide, tumor necrosis factor (TNF)-alpha and TNF soluble receptors in women with overweight and obesity

The aims of the present study was to examine how overweight and obesity affect serum concentrations nitric oxide (NO) metabolites and to determine whether there is association between serum concentrations tumor necrosis factor (TNF)-alpha and TNF soluble receptors (sTNF-R) in subjects with overweight and obesity. The study groups involved 154 women: 102 obese (81 obese with body mass index [BMI] 30 to 40 kg/m2 and 21 obese with BMI > 40 kg/m2), 24 overweight patients, and 28 lean controls. Serum concentrations of NO metabolites and of TNF-alpha and its soluble receptors (sTNF-R1, sTNFR-2) were measured by enzyme-linked immunosorbent assay (ELISA) kits. Serum concentration of insulin was measured by radioimmunoassay (RIA). Plasma glucose, cholesterol, high-density lipoprotein (HDL)-cholesterol, and triglicerydes were determined by enzymatic procedure. Body composition was determined by impedance analysis using Bodystat (Douglas, British Isles). Serum concentrations of NO in the overweight group (35.1 +/- 12.1 micromol/L) and the obese groups with BMI 30 to 40 kg/m2 (32.8 +/- 9.3 micromol/L) and with BMI greater than 40 kg/m2 (33.3 +/- 8.5 micromol/L) were significantly higher when compared to controls (28.2 +/- 8.1 micromol/L): P < .05; P < .01, and P < .01, respectively. There was no difference in levels of NO between the overweight group and both obese groups. Serum concentration of TNF-alpha was also significantly higher in the group with overweight (6.5 +/- 3.1 pg/mL), in the obese group with BMI 30 to 40 kg/m2 (6.8 +/- 3.1 pg/mL), and in the obese group with BMI greater than 40 kg/m2 (7.4 +/- 2.6 pg/mL) when compared to controls (2.9 +/- 2.2 pg/mL): P < .00005; P < .00005, and P < .0000001, respectively. However, serum concentrations of sTNF-R1 and -R2 did not differ significantly between the overweight group, both obese groups, and controls. In conclusion, we observed increased serum concentrations of TNF-alpha and NO in overweight and obese women. It seems that there is an association between serum concentrations of TNF-alpha and NO; however, this relationship depends on the degree of obesity.     

The phytoestrogen genistein produces acute nitric oxide-dependent dilation of human forearm vasculature with similar potency to 17beta-estradiol

BACKGROUND: Genistein, a phytoestrogen, may have estrogenic cardioprotective actions. We investigated whether genistein influences endothelium-dependent vasodilation in forearm vasculature of healthy human subjects and compared the effects of genistein with those of 17beta-estradiol. METHODS AND RESULTS: The brachial arterial was cannulated with a 27-gauge needle for drug infusion. Forearm blood flow responses were measured with strain-gauge plethysmography. Genistein (10 to 300 nmol/min, each dose for 6 minutes) produced a dose-dependent increase in forearm blood flow from 3.4+/-0.3 to 9.6+/-1.3 mL x min(-1) x 100 mL forearm(-1) (mean+/-SEM) in men (n=9, P:<0.0001 by ANOVA). The mean forearm venous concentration of genistein during infusion of the highest dose was 1.8+/-0.3 micromol/L in 6 additional men. Genistein produced a similar increase in blood flow in premenopausal women. Daidzein, another phytoestrogen, was ineffective, but equimolar concentrations of 17beta-estradiol caused similar vasodilation to genistein. Responses to genistein and 17beta-estradiol were inhibited to the same degree by the NO synthase inhibitor N:(G)-monomethyl-L-arginine. A threshold dose of genistein potentiated the endothelium-dependent vasodilator acetylcholine but not the endothelium-independent vasodilator nitroprusside. CONCLUSIONS: Genistein causes L-arginine/NO-dependent vasodilation in forearm vasculature of human subjects with similar potency to 17beta-estradiol and potentiates endothelium-dependent vasodilation to acetylcholine.     

The effect of the phytoestrogen genistein on plasma nitric oxide concentrations,endothelin-1 levels and endothelium dependent vasodilation in postmenopausal women

The phytoestrogen genistein improves endothelial dysfunction in ovariectomized rats through a nitric oxide-dependent mechanism. We investigated whether genistein alters the balance between the nitric oxide products and endothelin-1 and influences endothelium-dependent vasodilation in postmenopausal women. Sixty healthy postmenopausal women were enrolled in the study. A double-blind, placebo controlled, randomized design was employed. After a 4-week stabilization on a standard fat-reduced diet, participants to the study were randomly assigned to receive either genistein (n=30; 54 mg/day) or placebo (n=30). Flow-mediated, endothelium-dependent vasodilation of the brachial artery, plasma nitric oxide breakdown products and endothelin-1 levels were measured at baseline and after 6 months of genistein therapy. The mean baseline level of nitrites/nitrates was 22+/-10 micromol/l and increased to 41+/-10 micromol/ml after 6 months of treatment. The mean baseline plasma endothelin-1 level was 14+/-4 pg/ml and decreased to 7+/-1 pg/ml following 6 months of treatment with genistein. The mean baseline ratio of nitric oxide to endothelin also significantly increased at the end of treatment. Flow-mediated, endothelium-dependent vasodilation of the brachial artery was 3.9+/-0.8 mm at baseline and increased to 4.4+/-0.7 mm after 6 months of treatment. Placebo-treated women showed no changes in plasma nitrites/nitrates, endothelin-1 levels and flow-mediated vasodilation. Genistein therapy improves flow-mediated endothelium dependent vasodilation in healthy postmenopausal women. This improvement may be mediated by a direct effect of genistein on the vascular function and could be the result of an increased ratio of nitric oxide to endothelin.     

First trimester insulin resistance and subsequent preeclampsia: a prospective study

Insulin resistance is implicated in the pathogenesis of preeclampsia, but prospective data are limited. SHBG, a marker of insulin resistance among nonpregnant individuals, has not been studied in detail during pregnancy. We conducted a prospective, nested, case-control study to test the hypothesis that increased insulin resistance, marked by reduced first trimester SHBG levels, is associated with increased risk of subsequent preeclampsia. First trimester SHBG levels were measured in 45 nulliparous women who subsequently developed preeclampsia (blood pressure, > or =140/90 mm Hg; proteinuria, either > or =2+ by dipstick or > or =300 mg/24 h, after 20 wk gestation) and in 90 randomly selected normotensive nulliparous controls. Compared with controls, women who developed preeclampsia had significantly reduced first trimester SHBG levels (302 +/- 130 vs. 396 +/- 186 nmol/liter; P < 0.01). Every 100 nmol/liter increase in SHBG was associated with a 31% reduced risk of preeclampsia [odds ratio (OR), 0.69; 95% confidence interval (CI), 0.55, 0.88; P < 0.01]. After adjusting for covariates in a multiple logistic regression model, the association between first trimester SHBG and preeclampsia remained significant (per 100 nmol/liter increase; OR, 0.66; 95% CI, 0.47, 0.92; P = 0.01). When subjects were stratified by body mass index (lean: body mass index, < 25 kg/m(2); overweight: body mass index, > or =25 kg/m(2)), overweight women had lower SHBG levels than lean women (286 +/- 156 vs. 410 +/- 166 nmol/liter; P < 0.01), and within each stratum, women with preeclampsia had lower SHBG levels than their respective controls. In a multivariable analysis, the association between SHBG and preeclampsia strengthened among lean women, such that every 100 nmol/liter increase in serum SHBG was associated with a 55% reduction in the risk of preeclampsia (OR, 0.45; 95% CI, 0.27, 0.77; P < 0.01), whereas in overweight women, the association was mitigated (OR, 1.02; 95% CI, 0.62, 1.69; P = 0.9). We conclude that increased early pregnancy insulin resistance is independently associated with subsequent preeclampsia. First trimester SHBG levels may be a useful biomarker for preeclampsia, especially among lean women who otherwise would be perceived to be at low risk.     

Methylenetetrahydrofolate reductase mutation (677C-->T) negatively influences plasma homocysteine response to marginal folate intake in elderly women

Individuals who are homozygous for the methylenetetrahydrofolate reductase (MTHFR) 677C --> T mutation have depressed serum folate (SF) and elevated plasma total homocysteine (tHcy) concentrations, which may affect folate requirements and increase the risk for coronary artery disease. A controlled metabolic study (14 weeks) using a depletion/repletion protocol was performed in women (aged 60 to 85 years, N = 33) to provide age-specific data on the effects of the MTHFR mutation on SF and tHcy status. Subjects consumed a moderately folate-deplete diet (118 microg/d) for 7 weeks, followed by 7 weeks of folate repletion with 200 or 415 microg/d provided as two different treatments. Following folate depletion, the mean SF concentration was lower for homozygous (P = .017) versus heterozygous subjects. Homozygotes for the 677C --> T mutation showed a higher (P = .015) percent increase in plasma tHcy (44%) than heterozygous (20%) or normal (15%) subjects. At week 7, the mean plasma tHcy concentration was higher in homozygous subjects (12.5 +/- 5.3 micromol/L, mean +/- SD) versus the heterozygous (10.8 +/- 3.8 micromol/L, P = .008) or normal (11.3 +/- 2.7 micromol/L, P = .001) genotype groups. Following folate repletion, plasma tHcy concentrations were not different between genotype groups, despite a higher (P < .016) SF concentration in subjects with the homozygous genotype. These data suggest that older women who are homozygous for the MTHFR 677C --> T mutation may be at risk for greater elevations in plasma tHcy in response to moderately low folate intake as compared with individuals with the normal or heterozygous genotypes.     

Cellular-free magnesium depletion in brain and muscle of normal and preeclamptic pregnancy: a nuclear magnetic resonance spectroscopic study

Preeclampsia is a pregnancy disorder of unknown origin, characterized by vasospasm, elevated blood pressure, and increased neuromuscular irritability, features common to syndromes of magnesium deficiency. Evidence of serum and ionized magnesium metabolism disturbances have been observed in women with preeclampsia. This and the therapeutic utility of magnesium in preeclampsia led us to investigate the extent to which an endogenous tissue magnesium deficiency might be present in and contribute to its pathophysiology. We used (31)P nuclear magnetic resonance spectroscopy to noninvasively measure in situ intracellular-free magnesium levels in brain and skeletal muscle of fasting nonpregnant women (n=12), and of third trimester women with uncomplicated pregnancies (n=11) and preeclampsia (n=7). Compared with nonpregnant controls (brain 519+/-59 micromol/L; muscle 604+/-34 micromol/L), brain and skeletal muscle intracellular magnesium levels were significantly lower in both normal pregnant (brain 342+/-23 micromol/L; muscle 482+/-40 micromol/L; P=0.05 for both tissues) and preeclamptic women (brain 229+/-17 micromol/L; muscle 433+/-46 micromol/L; P=0.05 for both tissues). Brain intracellular magnesium was further reduced in preeclamptics compared with normal pregnant subjects (P=0.05). For all pregnant subjects, blood pressure was significantly and inversely related to the concomitantly measured intracellular magnesium level in brain (systolic, r=-0.59, P=0.01; diastolic, r=-0.52, P=0.02) but not in muscle. Cellular magnesium depletion is characteristic of normal pregnancy and may be one factor contributing to the pathophysiology of preeclampsia. Furthermore, the influence of central nervous system factors on blood pressure may be mediated, at least in part, by ambient intracellular magnesium levels.     

Autoregulation of endogenous glucose production during hyperglucagonemia

Increased endogenous glucose production (EGP) contributes to fasting hyperglycemia in type II diabetes. In nondiabetic subjects, increased gluconeogenesis from lactate does not increase EGP. Type 2 diabetes is associated with hyperglucagonemia. The present study was undertaken to examine whether physiologic elevation of plasma glucagon overrides autoregulation of EGP. Eight healthy volunteers were studied on 2 occasions, once during a 3-hour infusion of 30 micromol/kg/min Na-lactate and once during a control infusion of Na-bicarbonate. Plasma glucagon, insulin, and growth hormone were clamped at identical levels in both experiments. Rates of appearance of glucose, lactate, and gluconeogenesis from lactate were measured by tracer techniques. Glucagon infusion rate was elevated when the lactate or bicarbonate infusions were started to induce physiologic hyperglucagonemia. Plasma glucagon increased from baseline levels (234 +/- 21 ng/L and 211 +/- 23 ng/L) to 313 +/- 47 ng/L (bicarbonate experiments) and 329 +/- 43 ng/L (lactate experiments, means +/- SE, P >.3). Lactate infusion increased plasma lactate concentrations from 1.1 +/- 0.9 to 4.6 +/- 0.5 mmol/L (P =.0003). Lactate conversion to glucose increased from 1.5+/-0.3 to 2.8+/-0.8 micromol/kg/min (P =.03) and from 1.7 +/- 0.3 to 8.1 +/- 0.8 micromol/kg/min (P =.0003) in the bicarbonate and lactate experiments, respectively. The increments in lactate conversion to glucose differed significantly (P =.0008). Nevertheless, plasma glucose and EGP were not different in the bicarbonate and lactate experiments: 5.4 +/- 0.5 versus 6.6 +/- 0.7 mmol/L (P =.21), and 10.5 +/- 0.6 versus 11.6 +/- 0.6 micromol/kg/min (P =.19). We conclude that in normal volunteers, neither hyperglucagonemia nor the combination of hyperglucagonemia and increased substrate availability alters the autoregulation of EGP.     

Effects of gender on neuroendocrine and metabolic counterregulatory responses to exercise in normal man

Significant, sexual dimorphisms exist in counterregulatory responses to commonly occurring stresses, such as hypoglycemia, fasting, and cognitive testing. The question of whether counterregulatory responses differ during exercise in healthy men and women remains controversial. The aim of this study was to determine whether a sexual dimorphism exists in neuroendocrine, metabolic, or cardiovascular responses to prolonged moderate exercise. Sixteen healthy (eight men and eight women) subjects matched for age (28+/-2 yr), body mass index (22+/-1 kg/m2), nutrient intake, and spectrum of physical fitness were studied in a randomized fashion during 90 min of exercise on a cycle ergometer at 80% of their anaerobic threshold (approximately 50% VO2 max). Respiratory quotient and oxygen consumption relative to body weight were identical in men and women. Glycemia was equated (5.3+/-0.2 mmol/L) during exercise via an exogenous glucose infusion. Gender had significant effects on counterregulatory responses during exercise. Arterialized epinephrine (1.05+/-0.2 vs. 0.45+/-0.04 nmol/L), norepinephrine (9.2+/-1.1 vs. 5.8+/-1.1 nmol/L), and pancreatic polypeptide (52+/-6 vs. 37+/-6 pmol/L) were significantly (P<0.01) increased in men compared to women, respectively. Plasma glucagon, cortisol, and GH levels responded similarly in men and women. Insulin values were higher at baseline in men and fell by a greater amount to reach similar levels during exercise compared to those in women. Endogenous glucose production, measured with [3-3H]glucose was similar in men and women. Carbohydrate oxidation was significantly increased in men relative to women (21.2+/-2 vs. 15.6+/-2 mg/kg fat free mass x min; P<0.05). Despite reduced sympathetic nervous system (SNS) drive, lipolytic responses were increased in women. Arterialized blood glycerol (215+/-30 vs. 140+/-20 micromol/L), beta-hydroxybutyrate (54+/-9 vs. 25+/-10 micromol/L), and plasma nonesterified fatty acids (720+/-56 vs. 469+/-103 micromol/L) were significantly (P<0.01) increased in women. In keeping with increased SNS activity, systolic blood pressure and mean arterial pressure were significantly increased (P<0.01) in men. In summary, this study demonstrates that a significant sexual dimorphism exists in neuroendocrine, metabolic, and cardiovascular counterregulatory responses to prolonged moderate exercise in man. We conclude that during exercise, men have increased autonomic nervous system (epinephrine, norepinephrine, pancreatic polypeptide), cardiovascular (systolic, mean arterial pressure) and certain metabolic (carbohydrate oxidation) counterregulatory responses, but that women have increased lipolytic (glycerol, nonesterified fatty acids) and ketogenic (beta-hydroxybutyrate) responses. Women may compensate for diminished SNS activity during exercise by increased lipolytic responses.     

High serum sex hormone-binding globulin (SHBG) and low serum non-SHBG-bound testosterone in boys with idiopathic hypopituitarism: effect of recombinant human growth hormone treatment

We measured serum sex hormone-binding globulin (SHBG), total testosterone (T), non-SHBG-bound T, albumin-bound T, free T, and SHBG-bound T in 19 prepubertal boys with hypopituitarism. Serum SHBG decreased with age with a slope similar to that in 91 normal prepubertal boys at higher level, and therefore, it reached similar values at a later age. Serum SHBG was significantly higher in hypopituitary prepubertal boys [mean, 123 +/- 12 (+/- SE) nmol/L] than in normal prepubertal boys (76 +/- 4; P less than 0.001) despite the fact that their mean age was also higher (10.0 +/- 4 vs. 7.1 +/- 4.1 yr; P less than 0.001). In 4 boys with isolated hypogonadotropic hypogonadism (Kallman's syndrome), aged 15.6 +/- 1.5 yr, serum SHBG was 21 +/- 14 nmol/L, a value below the 95% confidence limit of the regression line in GH-deficient boys. The affinity constants of association of the SHBG-DHT complex were similar in hypopituitary and normal boys. Eleven of the 19 hypopituitary boys (mean chronological age, 8.3 +/- 2.5 yr; mean bone age, 4.1 +/- 2.1 yr) were treated with recombinant hGH (0.5 U/kg BW.week) for 1 yr. Their mean serum SHBG level before treatment was 154 +/- 14 nmol/L, and it decreased gradually to 106 +/- 5 nmol/L (P less than 0.01) after 12 months of treatment. The tendency toward normalization of serum SHBG during treatment suggested that GH deficiency was responsible for the high serum SHBG levels. Serum SHBG correlated negatively with age in both treated hypopituitary and normal boys, but the slope of the regression line was significantly steeper in treated hypopituitary boys (P less than 0.01). On the other hand, the mean serum non-SHBG-bound T level was 0.10 +/- 0.02 (+/- SE) nmol/L in hypopituitary boys, significantly lower than that in normal boys (0.21 +/- 0.02 nmol/L; P less than 0.02). Since serum total T concentrations were similar in the two groups, the higher serum SHBG concentration resulted in lower serum bioavailable T levels in the hypopituitary boys. These changes might explain the poor response to T treatment reported in GH-deficient patients. The lower serum non-SHBG-bound T concentrations in the GH-deficient boys suggest there may be delayed exposure of central nervous system structures to increased levels of sex hormones, which, in turn, may slow body maturation. This mechanism might play a role in the delay of puberty that occurs in patients with isolated GH deficiency.     

Salt loading on plasma asymmetrical dimethylarginine and the protective role of potassium supplement in normotensive salt-sensitive asians

Asymmetrical dimethylarginine (ADMA) is an endogenous inhibitor of NO synthase. Because endothelial NO pathway is compromised in patients with salt-sensitive hypertension, we investigated whether the plasma ADMA can be modulated by chronic salt loading in normotensive salt-sensitive persons and its relationship with NO, and we further determined whether or not dietary potassium supplementation can reverse them. Sixty normotensive subjects (aged 20 to 60 years) were selected from a rural community of Northern China. All of the people were sequentially maintained on a low-salt diet for 7 days (3 g/day, NaCl), then a high-salt diet for 7 days (18 g/day), and high-salt diet with potassium supplementation for another 7 days (4.5 g/day, KCl). After salt loading, the plasma ADMA concentrations increased significantly in salt-sensitive subjects (0.89+/-0.02 micromol/L versus 0.51+/-0.02 micromol/L; P<0.05), whereas the plasma NOx levels reduced considerably (41.8+/-2.1 micromol/L versus 63.5+/-2.1 micromol/L; P<0.01). All of the abnormalities normalized when dietary potassium were supplemented (0.52+/-0.03 micromol/L versus 0.89+/-0.02 micromol/L for ADMA and 58.1+/-0.9 micromol/L versus 41.8+/-2.1 micromol/L for NOx). Statistically significant correlations were found among plasma ADMA level, the mean blood pressure, and the level of NO after salt loading in normotensive salt sensitive individuals. Our study indicates that high dietary potassium intake reduces blood pressure and ADMA levels while increasing NO bioactivity in normotensive salt-sensitive but not salt-resistant Asian subjects after salt loading.     

Exogenous nitric oxide increases basal leg glucose uptake in humans

This study addressed the role of blood flow and nitric oxide in leg glucose uptake. Seven subjects (5 men, 2 women) were studied during conditions of resting blood flow and increased blood flow, achieved by infusion of the nitric oxide (NO) donor sodium nitroprusside (SNP) into the femoral artery. Femoral arterial and venous blood samples were obtained and blood flow was determined by infusion of indocyanine green dye. SNP infusion significantly increased leg blood flow (769 +/- 103 v 450 +/- 65 mL. min(-1). leg(-1), P <.001), but did not affect arterial (4.68 +/- 0.13 mmol/L control, 4.63 +/- 0.09 mmol/L SNP) or venous (4.60 +/- 0.14 mmol/L control, 4.54 +/- 0.10 mmol/L SNP) glucose concentrations. Glucose uptake was significantly (P <.01) higher during SNP infusion (65 +/- 6 micromol. min(-1). leg(-1)) than during the basal period (34 +/- 6 micromol. min(-1). leg(-1)), whereas lactate release was unaffected (rest, 45 +/- 11 micromol. min(-1). leg(-1); SNP, 42 +/- 14 micromol. min(-1). leg(-1)). We conclude that blood flow and/or NO increase basal leg glucose uptake.     

Levels of steroid-binding proteins and steroids in human preovulatory follicle fluid and serum as predictors of success in in vitro fertilization-embryo transfer treatment

In an attempt to identify the embryos and cycles that have the best chances of resulting in establishment of pregnancies, after in vitro fertilization-embryo transfer (IVF-ET) treatment, the concentrations of sex hormone-binding globulin (SHBG) and cortisol-binding protein (CBP) were measured, using two new enzyme-linked immunosorbent assays in serum and follicle fluid (FF) from 30 women (125 FF) undergoing IVF-ET. The concentrations were compared to those of total estradiol and total progesterone, and correlated to oocyte cleavage and the establishment of pregnancies. Serum concentrations of CBP were significantly higher in women who became pregnant (1469 +/- 108) nM (+/- SEM] than in those who did not (CBP, 1200 +/- 58 nM; P less than or equal to 0.05). The concentrations of SHBG were not significant different in these two groups of women (72.4 +/- 9.3 and 60.8 +/- 4.2 nM, respectively; P greater than or equal to 0.10). By contrast, in FF significantly higher concentrations of both SHBG and CBP were found in women achieving pregnancy (SHBG, 56.1 +/- 2.8 nM; CBP, 1198 +/- 37 nM) than in those who did not (SHBG, 45.5 +/- 1.4 nM; P less than or equal to 0.001; CBP, 1079 +/- 29 nM; P less than or equal to 0.01). A positive correlation was found between serum and FF levels of both SHBG (r = 0.85; P less than or equal to 0.001) and CBP (r = 0.70; P less than or equal to 0.001). FF levels of estradiol and progesterone did not differ regardless of whether the oocyte cleaved. However, a significant reduction of estradiol was found in fluid from follicles in which the oocyte cleaved and resulted in pregnancy (3046 +/- 180 nM) than in fluid from follicles in which the oocyte cleaved but without establishment of pregnancy (4162 +/- 282 nM; P less than or equal to 0.001). There was no correlation between estradiol and SHBG and between progesterone and CBP. However, levels of FF progesterone above 15,000 nM combined with CBP concentrations above the mean concentration found in FF (1,127 nM) were related with oocyte cleavage in 87% of the cases. The overall cleavage rate is 56%. The higher levels of SHBG and CBP in serum compared to those in FF, and the positive relationship between serum and FF levels suggest that both proteins arise from the circulation. The similar levels in serum and FF indicate that neither SHBG nor CBP is responsible for maintaining the concentration gradient of estradiol and progesterone from follicle to plasma.(ABSTRACT TRUNCATED AT 400 WORDS)     

Associations among oral estrogen use, free testosterone concentration, and lean body mass among postmenopausal women

Circulating concentrations of sex hormone-binding globulin (SHBG) are increased by use of oral estrogen. The objective of this study was to determine whether postmenopausal women who used oral estrogen had higher serum concentrations of SHBG and lower serum concentrations of free testosterone (T) than nonusers, and whether free T was associated with lean body mass, particularly skeletal muscle mass. Subjects were 70 postmenopausal women, 46-55 yr old, 46 of whom used oral estrogen. Total and regional body composition were determined by dual-energy x-ray absorptiometry. Serum concentrations of SHBG, total T, and estradiol (E(2)) were determined by RIA. Free T was calculated from concentrations of total T and SHBG. Hormone users had higher serum concentrations of E(2) and SHBG (182.0 +/- 58. 5 vs. 82.9 +/- 41.1 nmol/L, mean +/- SD, P: < 0.001) and lower concentrations of free T (3.7 +/- 2.2 vs. 7.9 +/- 4.1 pmol/L, mean +/- SD, P: < 0.001); total T did not differ. Total lean mass and leg lean mass were significantly correlated with free, but not total T [r values of 0.29 (P: < 0.05) and 0.31 (P: < 0.01) for total and leg lean mass, respectively, vs. free T]; arm lean mass was not correlated with either measure of T. Serum E(2) was significantly correlated with SHBG (r = 0.50, P: < 0.001) and free T (r = -0.33, P: < 0.01). These observations imply that, by reducing the concentration of bioavailable T, oral estrogen therapy may accelerate or augment lean mass loss among postmenopausal women. This conclusion awaits confirmation by longitudinal observation.     

Effect of a six-week national cholesterol education program step 1 diet on plasma sex hormone-binding globulin levels in overweight premenopausal women

Background: Low circulating sex hormone-binding globulin (SHBG) concentrations have been associated with the presence of several features of the metabolic syndrome in both men and women. Nutritional factors including dietary lipids and fibers in particular have been suggested to modulate plasma SHBG levels. Methods: The primary objective of the present study was to investigate the effect of an oat bran-rich supplement in conjunction with the National Cholesterol Education Program (NCEP) Step 1 diet (< 30% of total energy from fat, < 10% of energy from saturated fat, and < 300 mg cholesterol per day) on plasma SHBG levels in 35 overweight premenopausal women. Subjects (age 38.6 +/- 7.4 years) had normal menstrual cycles and were tested in the midluteal phase. Since no effect of the oat bran supplement was observed on plasma SHBG levels, data were analyzed according to the 6-week NCEP Step 1 diet. Results: The NCEP Step 1 nutritional intervention caused a significant decrease in energy intake ( -11%, p < 0.05), percent fat intake (-10%, p < 0.005), as well as saturated (-20%, p < 0.005) and monounsaturated (-10%, p < 0.05) fatty acid intake. Body mass index (BMI) decreased slightly but significantly (from 29.2 +/- 4.5 to 28.8 +/- 4.3 kg/m(2), p < 0.005). Plasma SHBG levels increased significantly (from 70.6 +/- 17.7 to 79.9 +/- 15.3 pmol/L, p < 0.0005) following the 6-week NCEP Step 1 diet, whereas plasma insulin levels were not modified significantly. Significant correlations were observed between the change in plasma SHBG levels and baseline BMI (r = 0.36, p < 0.04), as well as baseline (r = -0.42, p < 0.05) and postintervention (r = -0.35, p < 0.05) HDL cholesterol levels. Conclusions: We observed that a 6-week NCEP Step 1 diet significantly increased plasma SHBG levels, despite the finding that fasting insulin was not modified. Further studies are needed to elucidate physiological mechanisms underlying a direct effect of dietary composition on SHBG production by the liver.     

Plasma total and glycosylated corticosteroid-binding globulin levels are associated with insulin secretion.

In humans, steroid hormones circulate in the blood mainly bound to specific steroid transport proteins, namely corticosteroid-binding globulin (CBG) for cortisol and sex hormone-binding globulin (SHBG) for testosterone and estradiol. The binding activities of these proteins are believed to modulate the biodisposal of steroids to target cells. It has been shown in vitro that insulin is a potent inhibitor of both CBG and SHBG secretion by a human hepatoblastoma cell (HepG2) line. To further investigate this potential effect of insulin in vivo, we prospectively studied three groups of lean subjects, obese subjects, and obese subjects with glucose intolerance, all of whom were otherwise healthy. The three groups were comparable in sex and age, and in the two obese groups, body mass index, waist to hip ratio, and blood pressure were similar. Plasma total CBG concentrations (38.2 +/- 5.4 vs. 31.7 +/- 4.05 mg/L; P = 0.016) and glycosylated CBG levels (37.3 +/- 5.2 vs. 31 +/- 3.9 mg/L; P = 0.018) were significantly increased in obese subjects with glucose intolerance. Plasma CBG correlated positively with fasting glucose levels (r = 0.49; P = 0.002), hemoglobin A1c levels (r = 0.35; P = 0.03), and area under the curve of glucose after an oral glucose tolerance test (r = 0.45; P = 0.005) and correlated negatively with the insulin response to i.v. glucose (AIRg; -0.38, P = 0.02) as well as to oral glucose (r = -0.40; P = 0.01) challenge tests. CBG levels did not covariate with insulin sensitivity. Multiple linear regression analysis showed that only AIRg contributed to the variability of the CBG concentration (P = 0.03), explaining 41% of its variance. Morning cortisol levels did not differ between the groups and did not correlate to any of the glucose or insulin metabolism parameters. Because carbohydrate chains influence the biological activity and half-life of glycoproteins, we analyzed the migration profile of CBG by Western blot and the interaction of CBG with lectin, Con A. The results indicated that the CBG mol wt and interaction with Con A did not differ between lean and obese patients. These data favor the hypothesis that the inhibitory effect of insulin on CBG liver secretion might be relevant in vivo and therefore contribute to decrease CBG levels in obese patients with enhanced insulin secretion. In both men and women, SHBG levels correlated negatively with fasting glucose (r = -0.55; P < 0.0001) and hemoglobin A1c (r = -0.38; P = 0.02) and positively with insulin sensitivity (S(I); r = 0.65; P = 0.003 and r = 0.63; P = 0.007 in men and women, respectively), but not with insulin secretion. The disposition index (S(I) x AIRg) was significantly decreased in the obese, glucose-intolerant subjects, suggesting that AIRg was inadequate for their degree of insulin resistance. The disposition index correlated positively with plasma SHBG levels (r = 0.52; P = 0.001) and negatively with plasma CBG levels (r = -0.54; P = 0.001). Our data suggest that CBG is a marker of insulin secretion in a similar way as SHBG is a marker of insulin sensitivity. As high plasma CBG levels have been associated with increased incidence of type 2 diabetes, this important issue merits further investigations.     

Selenium, zinc and copper plasma levels in intrahepatic cholestasis of pregnancy, in normal pregnancies and in healthy individuals, in Chile

BACKGROUND/AIMS: Low blood Se levels have been previously shown in normal pregnancies (third trimester) and significantly lower levels in patients with intrahepatic cholestasis of pregnancy (ICP), in Finland and in Chile, suggesting that a low or marginal dietary availability of Se may contribute to the pathogenesis of this disease. The aim of this study was to investigate whether a temporal change in plasma concentration of Se, and seasonal fluctuations in plasma concentrations of Se, Zn and Cu, could coincide with changes in the prevalence of ICP. METHODS: A cross-sectional cohort study was done including 21 ICP patients, 98 women in the third trimester of a normal pregnancy, 29 non-pregnant women, and also 13 individuals (seven non-pregnant women and six men) who had been studied 9 years before. Plasma Se, Zn and Cu were measured by atomic spectroscopy. Plasma Se levels in the present study were compared to the results obtained 5 to 7 years before, employing identical methodology in similar population samples. RESULTS: Plasma Se concentrations in non-pregnant women were higher than in the previous study: 1.43+/-0.34 micromol/l vs 0.85+/-0.13; p<0.001. In comparison to non-pregnant women, normal pregnancies near term had lower plasma levels of Se: 1.08+/-0.25 micromol/l; p<0.01, and Zn: 17.90+/-3.61 micromol/l vs 19.71+/-3.21; p<0.05, but higher plasma levels of Cu: 34.35+/-7.12 micromol/l vs 20.62+/-3.34; p<0.01. In normal pregnancies, plasma Se concentration was significantly higher in summer (1.34+/-0.19 micromol/l) than in the other seasons, while Zn and Cu diminished. Similar to previous studies, ICP patients had significantly lower Se plasma levels than normal pregnancies: 0.94+/-0.12 micromol/l, p<0.05, and Cu levels were significantly higher: 50.80+/-7.02 micromol/l, p<0.01. Cu plasma levels correlated with the biochemical severity of the disease. Zn did not change in ICP. CONCLUSIONS: The present study shows that the decrease in the prevalence of ICP in Chile during the last decade coincides with an increase in plasma Se levels. Its lower incidence during summer coincides with a higher plasma Se concentration in summer than in other seasons, as observed in normal pregnancies.     

Alterations of plasma calcium and intracellular and membrane calcium in erythrocytes of patients with pre-eclampsia

BACKGROUND: Changes in plasma and intracellular calcium levels have been suggested in the pathogenesis of pre-eclampsia, however, membrane calcium content has not been studied so far. We compared intracellular and membrane calcium concentrations in erythrocytes of women with pre-eclampsia, healthy pregnant woman and controls to determine a possible alteration of membrane calcium in pre-eclampsia. SUBJECTS AND METHODS: Eighteen untreated, healthy pregnant woman and 16 pregnant nulliparous women with manifest pre-eclampsia were included, 25 healthy, age-matched woman served as controls. Atomic absorption spectroscopy was used for measurement of intracellular and membrane calcium content in erythrocytes and plasmalemmal preparations. RESULTS: Plasma Ca++ concentrations were significantly lower in pre-eclamptic women (1.96 +/- 0.15 mmol/l, P < 0.01, mean +/- s.e.m.) compared to healthy controls (2.43 +/- 0.14 mmol/l) or women with uncomplicated pregnancies (2.20 +/- 0.10 mmol/l). Intracellular Ca++ concentrations were not different between groups, however, membrane Ca++ content was significantly increased in the pre-eclamptic patients (1.23 +/- 0.36 micromol/g membrane protein, P < 0.01) compared to control subjects (0.83 +/- 0.16 micromol/g) and healthy pregnant women (0.77 +/- 0.13 micromol/g). CONCLUSION: Membrane calcium content is significantly increased in pre-eclamptic women despite low plasma Ca++ concentrations. This finding suggests an altered membrane ion transport and may be of importance for the pathogenesis of pre-eclampsia.     

Normal serum alanine aminotransferase activity in uncomplicated obesity

AIM: To evaluate serum alanine aminotransferase (ALT) activity in a well-characterized group of uncomplicated obese subjects and its correlation with insulin resistance, plasma adiponectin, and leptin concentrations. METHODS: One hundred and five uncomplicated obese subjects (87 women, 18 men, age 34.3±9.6 years, BMI 39.9±8.3 kg/m2)were studied. Serum ALT activity was evaluated. Insulin sensitivity was assessed by euglycemic hyperinsulinemic clamp (M index) and fasting insulin. Plasma leptin and adiponectin levels were also measured. RESULTS: Serum ALT concentration in the whole group of uncomplicated obese subjects was 17.73±6.33 U/L with none of the subjects presenting ALT levels greater than 43 U/L and only 9 (11%) women and 3 (19%) men showed ALT levels >19 and >30 U/L for women and men, respectively. No significant difference was detected in serum ALT levels between severe obese subjects (BMI >40 kg/m2) and those with BMI <40 kg/m2 (18.63±6.25 vs 17.26±6.02 U/L). ALT was significantly correlated with fasting insulin (r=0.485, P= 0.02) and triglycerides (r= 0.358, P=0.03). CONCLUSION: Serum ALT activity is practically normal in uncomplicated obese subjects, independently of their obesity degree. These findings suggest the role of obesityrelated comorbidities and not of BMI as main risk factors for elevated ALT levels in obese subjects.