Effects of gender on exercise-induced growth hormone release.

We examined gender differences in growth hormone (GH) secretion during rest and exercise. Eighteen subjects (9 women and 9 men) were tested on two occasions each [resting condition (R) and exercise condition (Ex)]. Blood was sampled at 10-min intervals from 0600 to 1200 and was assayed for GH by chemiluminescence. At R, women had a 3.69-fold greater mean calculated mass of GH secreted per burst compared with men (5.4 +/- 1.0 vs. 1.7 +/- 0.4 microg/l, respectively) and higher basal (interpulse) GH secretion rates, which resulted in greater GH production rates and serum GH area under the curve (AUC; 1,107 +/- 194 vs. 595 +/- 146 microg x l(-1) x min, women vs. men; P = 0.04). Compared with R, Ex resulted in greater mean mass of GH secreted per burst, greater mean GH secretory burst amplitude, and greater GH AUC (1,196 +/- 211 vs. 506 +/- 90 microg x l(-1) x min, Ex vs. R, respectively; P < 0.001). During Ex, women attained maximal serum GH concentrations significantly earlier than men (24 vs. 32 min after initiation of Ex, respectively; P = 0.004). Despite this temporal disparity, both genders had similar maximal serum GH concentrations. The change in AUC (adjusted for unequal baselines) was similar for men and women (593 +/- 201 vs. 811 +/- 268 microg x l(-1) x min), but there were significant gender-by-condition interactive effects on GH secretory burst mass, pulsatile GH production rate, and maximal serum GH concentration. We conclude that, although women exhibit greater absolute GH secretion rates than men both at rest and during exercise, exercise evokes a similar incremental GH response in men and women. Thus the magnitude of the incremental secretory GH response is not gender dependent.     

Type II collagen peptides for measuring cartilage degradation

This paper describes two new immunoassays for a peptide of the triple helix of type II collagen (Coll 2-1) and its nitrated form (Coll 2-1 NO(2)). In healthy subjects aged between 20 and 65 years old, Coll 2-1 and Coll 2-1 NO(2) levels in serum were in means 125.13+/-3.71 and 0.16+/-0.08 nmol/l, respectively. These levels did not significantly vary with age. However, up to 45 years of age, Coll 2-1 NO(2) levels in women were significantly higher than in men. In patients with knee osteoarthritis (OA), Coll 2-1 in serum was found to be elevated compared to healthy controls (267.45+/-26.42 nmol/l vs 126.78+/-6.61 nmol/l). Further, we have demonstrated that an increase of the urinary levels of Coll 2-1 or Coll 2-1 NO(2) over 1 year was predictive of joint space narrowing progression in OA patients. In conclusion, these preliminary results indicate that Coll 2-1 could be a predictive marker of knee OA progression.     

Cholesterol and mortality in New Zealand Maoris.

The relation between serum cholesterol concentration and mortality was studied prospectively over 11 years in 630 New Zealand Maoris aged 25-74. Serum cholesterol concentration was measured at initial examination in 1962-3 in 94% of the subjects and whether each was dead or alive was determined in 1974. The causes of death were divided into three categories: cancer, cardiovascular disease, and "other." The Mantel-Haenszel method of analysis of survivorship data showed a significant inverse relation between serum cholesterol concentration and overall mortality in men (x 2/2 = 11.6; p = 0.003) and women (x 2/2 = 7.6; p = 0.02) with odds ratios of 2.3 and 1.9 respectively. Similar significant inverse relations were found for cancer and "other" causes of death. These relations remained significant when baseline age, systolic blood pressure, and the Quetelt index were controlled in Cox''s proportional hazards regression model. The results of this study provide evidence for a potentially deleterious effect of low serum cholesterol concentration. Hence, further research is needed before indiscriminate efforts are made to lower serum cholesterol concentrations in New Zealand Maoris.     

The effect of weight loss on serum concentrations of nitric oxide, TNF-alpha and soluble TNF-alpha receptors

INTRODUCTION: The aims of the present study were to evaluate the effect of weight-loss treatment on serum concentrations of NO and TNF-alpha and to examine whether there is an association between TNF-system activity and serum concentrations of NO after weight loss. MATERIAL AND METHODS: The study group involved 43 obese women (aged 41.8 +/- 11.9 years, weight 95.2 +/- 15.0 kg, BMI 36.5 +/- 4.6 kg/m(2)). The women were subjected to three-month complex weight-loss treatment. Patients were advised to keep to a 1000-1200 kcal diet and to exercise regularly. Pharmacological treatment was not administered. Serum concentrations of nitric oxide metabolites, TNF-alpha and its soluble receptors (sTNFR1, sTNFR2) were measured by ELISA kits; insulin was measured by RIA and glucose, cholesterol, HDL cholesterol and triglicerydes by an enzymatic procedure before and after weight loss. Body composition was determined by impedance analysis using Bodystat. RESULTS: The mean weight loss during treatment was 8.3 +/- 4.3 kg. The serum concentrations of TNF-alpha decreased significantly (p < 0.000) and both receptors sTNFR1 and sTNFR2 increased significantly (p < 0.000) after weight loss. No significant changes in serum concentrations of NO were observed after weight loss. A multiple regression analysis was performed using DeltaTNF-alpha, DeltasTNFR1, DeltaTNFR2 and DeltaNO as dependent variables. A significant correlation was observed between DNO and initial plasma concentrations of TNF-alpha, sTNFR1 and sTNFR2. CONCLUSIONS: This study demonstrates a decrease in serum TNF-alpha concentration as well as an increase in plasma concentration of both TNF receptors but does not show any change in serum concentrations of NO after weight-loss treatment in obese women. It seems that changes in TNF-system activity may be a counter-regulating mechanism, which inhibits further body mass loss. We did not observe any association between changes in TNF-system activity and serum concentrations of NO after weight loss.     

Assessment of the levels of nitric oxide (NO) and cytokines (IL-5, IL-6, IL-13, TNF, IFN-gamma) in giardiosis

The current study aims to determine the involvement of cellular responses in combating Giardia intestinalis invasion. The study group consisted of 44 women and 18 men, aged 18-72 years, infected with G. intestinalis. The diagnosis was established based on laboratory investigations (examination of stool, choloscopy, GSA-65). Blood for analysis was collected before antiparasitic treatment and two weeks after treatment termination. The control group consisted of 22 women and 18 men aged 20-45 years. The serum concentrations of IL-5, IL-6, IL-13, TNF, IFN-g were assayed using a set of Quantikine human. The concentrations of NO in the serum were determined using a set of Total Nitric Oxide Assay. Patients infected with G. intestinalis showed a statistically significant increase in the levels of NO, IFN-g and IL-13. Even the antiparasitic treatment applied did not reduce the levels of these parameters and only caused a rise in IL-6. Our study showed a lack of acute inflammatory state in the course of G. intestinalis infection.     

Evaluation of tumour necrosis factor alpha, interleukin-2 soluble receptor, nitric oxide metabolites, and lipids as inflammatory markers in type 2 diabetes mellitus

This study compared the results of tumour necrosis factor alpha (TNF-alpha), interleukin-2 soluble receptor (sIL-2R), nitric oxide metabolites (NO(x)), C-reactive protein (CRP), and lipids (total cholesterol, high-density lipoprotein (HDL-cholesterol), low-density lipoprotein (LDL-cholesterol), and triglycerides) between control group (nondiabetic subjects) and overweight type 2 DM subjects. To restrict the influence of variables that could interfere in the interpretation of data, subjects with obesity and/or acute or chronic inflammatory disease, haemoglobinopathies, recent use of antibiotics, antiinflammatory drugs, and trauma were excluded. Type 2 DM patients (n = 39; age 53.3 +/- 9.0 years; median glycated haemoglobin A(1c)< 8%) presented higher levels of TNF-alpha, triglycerides (P < .01), NO(x) and sIL-2R (P < .05) than control group (n = 28; age 39.7 +/- 14.1 years). CRP, LDL-cholesterol, total cholesterol, and HDL-cholesterol did not differ among groups. Diabetic women (n = 21) had higher levels of TNF-alpha, total cholesterol, LDL-cholesterol, and HDL-cholesterol than diabetic men (n = 18) (P < .05), but there were no differences among sexes in the control group. This study indicates that increased level of proinflammatory markers occurs in type 2 DM even in the absence of obesity and marked hyperglycaemia, confirming that the inflammation course of the atherosclerotic process is more severe in diabetic patients than in nondiabetic subjects.     

Hemodynamics of orthostatic intolerance: implications for gender differences

Women have a greater incidence of orthostatic intolerance than men. We hypothesized that this difference is related to hemodynamic effects on regulation of cardiac filling rather than to reduced responsiveness of vascular resistance during orthostatic stress. We constructed Frank-Starling curves from pulmonary capillary wedge pressure (PCWP), stroke volume (SV), and stroke index (SI) during lower body negative pressure (LBNP) and saline infusion in 10 healthy young women and 13 men. Orthostatic tolerance was determined by progressive LBNP to presyncope. LBNP tolerance was significantly lower in women than in men (626.8 +/- 55.0 vs. 927.7 +/- 53.0 mmHg x min, P < 0.01). Women had steeper maximal slopes of Starling curves than men whether expressed as SV (12.5 +/- 2.0 vs. 7.1 +/- 1.5 ml/mmHg, P < 0.05) or normalized as SI (6.31 +/- 0.8 vs. 4.29 +/- 0.6 ml.m-2.mmHg-1, P < 0.05). During progressive LBNP, PCWP dropped quickly at low levels, and reached a plateau at high levels of LBNP near presyncope in all subjects. SV was 35% and SI was 29% lower in women at presyncope (both P < 0.05). Coincident with the smaller SV, women had higher heart rates but similar mean arterial pressures compared with men at presyncope. Vascular resistance and plasma norepinephrine concentration were similar between genders. We conclude that lower orthostatic tolerance in women is associated with decreased cardiac filling rather than reduced responsiveness of vascular resistance during orthostatic challenges. Thus cardiac mechanics and Frank-Starling relationship may be important mechanisms underlying the gender difference in orthostatic tolerance.     

Endothelial function in highly endurance-trained men: effects of acute exercise

Exercise training reverses endothelial dysfunction, but the effect in young, healthy subjects is less clear. We determined the influence of maximal oxygen uptake (VO2max) and a single bout of high-intensity exercise on flow-mediated dilatation (FMD), brachial artery diameter, peak blood flow, nitric oxide (NO) bioavailability, and antioxidant status in highly endurance-trained men and their sedentary counterparts. Ten men athletes (mean +/- SEM age 23.5 +/- 0.9 years, height 182.6 +/- 2.4 cm, weight 72.5 +/- 2.4 kg, VO2max 75.9 +/- 0.8 mL.kg.min) and seven healthy controls (age 25.4 +/- 1.2 years, height 183.9 +/- 3.74 cm, weight 92.8 +/- 3.9 kg, VO2max 47.7 +/- 1.7 mL.kg.min) took part in the study. FMD, brachial artery diameter, and peak blood flow were measured using echo-Doppler before, 1 hour, 24 hours, and 48 hours after a single bout of interval running for 5 x 5 minutes at 90% of maximal heart rate. NO bioavailability and antioxidant status in blood were measured at all time points. Maximal arterial diameter and peak flow were 10-15% (P < 0.02) and 28-35% (P < 0.02) larger, respectively, in athletes vs. controls at all time points, and similar FMD were observed, apart from a transient decay of FMD in athletes 1 hour post exercise. NO bioavailability increased significantly after exercise in both groups and decreased to baseline levels after 24 hours in controls but remained increased 80% and 93% above baseline 24 and 48 hours post exercise in athletes. Antioxidant status was equal in the two groups at baseline and increased by approximately 10% 1 hour post exercise, an effect that lasted for 24 hours. Athletes had larger arterial diameter but similar FMD as untrained subjects, i.e., athletes had larger capacity for blood transport compared with their untrained counterparts. The observed FMD, bioavailability of NO, and antioxidant status in blood were highly dependent on the time elapsed after the exercise session.     

Reference Values for Serum Magnesium Levels in Young Adult Iranian Subjects

This study aims at determining the reference values for serum magnesium (Mg) concentrations in Iranian adults. Serum Mg level was measured using flame atomic absorption spectrometry in 491 subjects (233 men and 258 women), aged 20-50 years, randomly selected from a population-based study. The International Federation of Clinical Chemistry guidelines and the robust method were used for determining the reference values. The 95% reference values for serum Mg concentration were 1.83-2.49, 1.79-2.48, and 1.83-2.55 mg/dL in men, women, and total population, respectively. The prevalences of hypo- and hypermagnesemia, according to the reference values obtained in the current study, were 2.5% and 4.0%, respectively. In conclusion, this study reports serum Mg reference values based on current standards in a large healthy population of young Iranian adults.     

Comparison of whole-blood glutathione peroxidase activity,levels of serum selenium,and lipid peroxidation in subjects from the fishing and rural communities of "Rabo de Peixe" village,San Miguel Island,the Azores' Archipelago,Portugal

The activity of glutathione peroxidase (GSH-Px), serum selenium (Se), and thiobarbituric acid reactive substances (TBARS) were measured in the whole blood of 148 healthy adults aged 20–60 yr from the fishing and rural communities of “Rabo de Peixe,” The Azores, Portugal. The subjects did not live in the same household and had different socioeconomic profiles and dietary habits. The serum lipid profile and selected life habits were also considered in this study. No significant differences in the activity of GSH-Px were found in the interpopulation or intrapopulation analyses, classified by age or lipid profile. An age-dependent GSH-Px increase was noted in the younger male (M) subgroups (20–39 yr). The Se levels were higher in fishers (f) of both genders (M, F) than in subjects living in the rural (r) environment: 110±25 μg/L (f, M), 89±20 μg/L (f, F), 88±22 μg/L (r, M) and 80±17 μg/L (r, F). In the fishers, but not in the rural population, Se was higher in the males, but it did not show significant variation with age. The levels of TBARS were lower in the f than in the r male group. The Se level was lower and TBARS higher in the hyperlipemic women in the f group, compared to the corresponding controls. Our results suggest that the fishers (mainly men) show a better antioxidant status than that of their rural counterparts, due to differences in dietary habits between the study populations and between genders.     

Reference values for serum silicon in adults

Silicon is an essential nutrient of fundamental importance to human biology. It has been shown that silicon is required for bone, cartilage, and connective tissue formation. However, the assessment of silicon concentration is difficult as reference values are lacking. The aim of the present study was to establish reference values for apparently healthy individuals. Silicon concentrations were determined in serum of 1325 healthy subjects 18-91 years of age using atomic absorption spectrometry. Medians for serum silicon concentrations showed a statistically significant age and sex dependency. In men 18-59 years of age the median was 9.5 micromol/L and decreased to 8.5 micromol/L at 60-74 years of age. In women there was an increase in the median from age 18-29 years (10.00 micromol/L) to 30-44 years (11.10 micromol/L) followed by a decrease in the age group of 45-59 years (9.23 micromol/L). In subjects aged over 74 years the median serum silicon values were 7.70 micromol/L for men and 8.00 micromol/L for women. The most important findings in this study are the decrease of silicon and the course of the silicon concentrations with age, especially in women. The present study is an important prerequisite for studies that aim to identify the health effects and medical implications of silicon.     

Diagnostic value of serum IGF-I and IGFBP-3 in growth hormone disorders in adults

OBJECTIVE: To investigate the diagnostic value of serum insulin-like growth factor-I (IGF-I) and insulin-like growth factor-binding protein-3 (IGFBP-3) measurements in adult patients with acromegaly and GH deficiency (GHD). METHODS: Serum IGF-I and IGFBP-3 levels were measured in 39 active acromegalic patients, 34 adult patients with GHD and 150 healthy adults. Disease activity in patients with acromegaly was confirmed by nadir GH levels during an oral glucose tolerance test (OGTT). Among patients with acromegaly, 15 had not been treated previously and 24 had been treated but not cured. GHD in adults was diagnosed by an insulin tolerance test (ITT). Among patients with GHD, 15 were aged 20-40 years (9 men and 6 women) and 19 were aged over 40 years (9 men and 10 women). One hundred and fifty healthy subjects were recruited as a control group. To compare the individual serum IGF-I and IGFBP-3 levels of patients with the results of the gold standard, we calculated age- and sex-corrected standard deviation scores (SDS) for individual IGF-I and IGFBP-3 levels. The sensitivities of serum IGF-I and IGFBP-3 measurements for the disease diagnosis were analyzed using the mean +/- 2 SD of the values of healthy control subjects as a diagnostic cutoff, defining 95% specificity. RESULTS: The mean IGF-I and IGFBP-3 SDS levels were significantly higher in active acromegalic patients, both untreated and treated but not cured, than in the control subjects (p < 0.05). The sensitivities of serum IGF-I and IGFBP-3 measurements for the diagnosis of acromegaly were 97.4 and 81.8%, respectively. In untreated patients with acromegaly, the sensitivities of serum IGF-I and IGFBP-3 measurements for the diagnosis of disease were 100 and 100%, while these were 95.8 and 72.7% in treated patients with acromegaly. In adult patients with GHD, the mean IGF-I and IGFBP-3 SDS were significantly lower than those of the control subjects (IGF-I, -2.2 +/- 0.8 vs. 0.0 +/- 1.0 SDS, p < 0.0001); IGFBP-3, -1.7 +/- 1.2 vs. 0.0 +/- 1.0 SDS, p < 0.0001), but there was a considerable overlap between GHD in adults and the controls. In all patients with GHD, the sensitivities of serum IGF-I and IGFBP-3 measurements were 64.7 and 52.9%, respectively. In the group of women aged 20-40 years, the sensitivity of IGF-I measurement for the diagnosis of GHD was 100%, although the number of patients was only 6. CONCLUSION: Both serum IGF-I and IGFBP-3 measurements are comparable to an oral glucose tolerance test in patients with untreated acromegaly, but in acromegalic patients that have undergone surgery and/or radiotherapy, serum IGF-I is more valuable for determining disease activity than serum IGFBP-3. Serum IGF-I and IGFBP-3 measurements are not valuable for the diagnosis of GHD in adults, but in women aged 20-40 years serum IGF-I measurement appears to be useful in the diagnosis of GHD.     

Skeletal muscle fatigue, strength, and quality in the elderly: the Health ABC Study.

We examined the muscle fatigue characteristics in older men and women and determined whether these were related to the size, strength, or quality of muscle. A total of 1,512 men and women aged 70-79 yr from the Health, Aging, and Body Composition Study participated in this study. Muscle cross-sectional area and attenuation were determined with computed tomography. Skeletal muscle fatigue and strength (peak torque) of the knee extensors and flexors were measured using isokinetic dynamometry. Men were more fatigue resistant than women for both knee extension (fatigue index: 70.4 +/- 15.3 vs. 66.9 +/- 14.3%; P < 0.05) and knee flexion (67.9 +/- 16.4 vs. 64.9 +/- 17.6%; P < 0.05). Peak torque and muscle quality (specific torque) were higher in men than women for knee extension (99.6 +/- 28.2 vs. 63.0 +/- 16.8 N x m and 1.62 +/- 0.43 vs. 1.51 +/- 0.39 N x m/cm2; both P < 0.05) and for knee flexion (74.0 +/- 26.4 vs. 49.6 +/- 15.9 N x m and 2.47 +/- 1.29 vs. 2.22 +/- 0.78 N x m/cm2; both P < 0.05). Total work and power output was greater in men compared with women for both the quadriceps (1,353 +/- 451 vs. 832 +/- 264 J and 87.7 +/- 33.5 vs. 53.3 +/- 19.2 W; both P < 0.05) and the hamstrings (741 +/- 244 vs. 510 +/- 141 J and 35.4 +/- 16.0 vs. 23.7 +/- 10.2 W; both P < 0.05). In both genders, the quadriceps was able to perform more work with greater power compared with the hamstrings. Those who were stronger actually had greater fatigue after adjusting for age, race, physical activity, and total body fat. In conclusion, older men were more fatigue resistant than women, although in both men and women greater fatigue was not related to muscle weakness.     

Sex, age, geographical location, smoking, and alcohol consumption influence serum selenium concentrations in the USA: third National Health and Nutrition Examination Survey, 1988-1994.

Selenium has been reported to reduce the risk for heart diseases and cancer. We examined the association of sex, age, geographical location, serum cotinine concentrations, a measure of smoking intensity, and alcohol consumption with serum selenium concentrations in the third National Health and Nutrition Examination Survey (NHANES III), 1988-1994. Study sample consisted of 14,619 apparently healthy individuals (male: 7,102; female: 7,517) aged 14 to >90 years. Sex, age, geographical location, serum cotinine concentrations, and alcohol consumption significantly influenced serum selenium concentrations (P < 0.05). The mean (+/- standard error) serum selenium concentration in men (124.5 +/- 0.20 ng/mL) was significantly higher than in women (122.0 +/- 0.20 ng/mL) (P < 0.0001). Men in the 31-50 y age group had the highest mean serum selenium concentration. In the same age group, women had the lowest mean serum selenium concentration. In both sexes, participants living in the Midwest and West had significantly higher serum selenium concentrations than those living in South and Northeast geographical locations. Serum cotinine was negatively associated with serum selenium concentrations in both men (beta = -0.0108; P < 0.0001 for trend) and women (beta = -0.0097; P < 0.0001 for trend). Alcohol consumption is positively associated with serum selenium in women (beta = 0.0462; P = 0.0044 for trend) but not in men (beta = 0.0015; P = 0.8496 for trend). Although, sex, age, geographical location, smoking, and alcohol intake influenced serum selenium concentrations, clinically low serum selenium concentrations are not common in the USA.     

The effect of weight loss on serum concentrations of FAS and tumour necrosis factor alpha in obese women

INTRODUCTION: Apoptosis can influence both adipose tissue mass and its distribution. The suprafamily of tumour necrosis factor (TNF) receptors stimulate apoptosis. The aim of the study was to assess serum concentrations of tumour necrosis factor alpha (TNF-alpha), TNF soluble receptors (sTNFRs) and FAS in obese subjects and to examine the changes in these parameters after weight loss. MATERIAL AND METHODS: The study group consisted of 23 obese women without additional disease aged 36.6 +/- 10.9 years. These were examined before and after three-month weight reduction treatment consisting of a diet of 1000 kcal/day and physical exercise. The control group comprised 17 lean healthy women aged 40.3 +/- 5.5 years. Blood samples were taken in the morning after an overnight fast. Serum concentrations of TNF-alpha, sTNFRs and FAS were measured by enzyme linked immunosorbent assay (ELISA). Serum concentrations of insulin were measured by RIA. Serum concentrations of glucose, total cholesterol, HDL cholesterol and triglycerides were measured by an enzymatic procedure. RESULTS: The mean weight loss over the three-month treatment was 11.4 +/- 3.1 kg. Following weight loss, serum TNF-alpha concentrations decreased significantly (7.3 +/- 3.0 vs. 5.4 +/- 1.6 pg/ml; p < 0.005) and concentrations of sTNFRs increased significantly (1222.6 +/- 211.8 vs. 1325.6 +/- 261.6 pg/ml; p < 0.05 and 1881.5 +/- 337.2 vs. 2057.4 +/- 358.7 pg/ml; p < 0.05 respectively). However, no changes in serum concentrations of FAS were observed after weight loss. CONCLUSION: We observed increased serum concentrations of TNF-alpha but not of FAS in obese women. The concentrations of TNF decreased and those of sTNFRs increased after weight loss. However, the weight reduction therapy did not change serum concentrations of FAS.     

Trace element status (Se, Cu, Zn) in healthy portuguese subjects of Lisbon population

Serum levels of selenium, copper, and zinc were systematically determined in healthy subjects of the Lisbon population. The sample consisted of 183 blood donors of both genders who were divided into two age groups: 20–44 and 45–70 yr of age; relationships with gender, age, the lipid profile, and tobacco consumption were investigated. In the female group, the intake of oral contraceptives and pregnancy were considered for the youngest women, and hormonal replacement therapy (HRT) was taken into account for the oldest ones. Serum concentrations of these elements were in the same range as those found for populations of other European countries. Differences between genders were observed for the three elements studied, with serum selenium and zinc concentrations higher in men and copper levels higher in women. Age-dependent differences were found for selenium: The oldest subjects (regardless gender) presented the highest concentrations of selenium in serum as further demonstrated by the positive correlation with age. In both pregnant and contraceptive-using women, copper was greatly increased, confirming the influence of estrogen status and/or oral contraceptive intake on increased serum copper levels. However, in postmenopausal women, HRT did not significantly affect serum copper levels. Selenium, copper, and zinc status were not different between normolipidemic and hyperlipidemic subjects for the same gender and age range, but selenium levels tended to increase with hyperlipidemia when considering the whole group of subjects. With respect to the lifestyle, higher serum zinc levels were found in tobacco-consuming men. Albumin serum levels were similar for all considered subgroups, except for the pregnant women, for whom a decrease in this parameter was observed. The present study allowed one to obtain reference values for this healthy group of population, which will serve for a comparative study with groups having pathological conditions, such as cardiovascular disease.     

Leptin levels in obese children: effects of gender,weight reduction and androgens

Obesity in children is accompanied by increased circulating leptin concentrations. Girls have higher leptin concentrations than boys. The aim of our study was to compare serum leptin levels before and after a five-week weight reduction program and to study the relationship of leptin levels, serum total cholesterol, and androgens (testosterone, dehydroepiandrosterone, dehydroepiandrosterone sulphate) in 33 obese boys (age: 12.7+/-1.97 years, BMI: 30.46+/-4.54) and 66 obese girls (age: 12.7+/-2.51 years, BMI: 29.31+/-4.62). We found that serum leptin concentrations in obese children were significantly decreased after a weight reduction program (before 20.79+/-9.61 ng/ml, after 13.50+/-8.65 ng/ml in girls; before 12.25+/-10.09 ng/ml and after 5.18+/-3.56 ng/ml in boys, p<0.0001 in both genders). Leptin levels correlated positively with the body mass index before and after weight reduction. There was a positive association in obese boys and a negative one in obese girls between leptin levels and the WHR (waist to hip circumference ratio). Serum leptin also shows a strong relationship to fat distribution (p=0.02 in boys, p<0.0001 in girls). No significant correlation was found between leptin concentrations and total cholesterol or androgens. We confirmed that leptin is a sensitive parameter of body composition and weight reduction in obese children.     

Respiratory control stability and upper airway collapsibility in men and women with obstructive sleep apnea.

Obstructive sleep apnea (OSA) is two to three times more common in men as in women. The mechanisms leading to this difference are currently unclear but could include gender differences in respiratory stability [loop gain (LG)] or upper airway collapsibility [pharyngeal critical closing pressure (Pcrit)]. The aim of this study was to compare LG and Pcrit between men and women with OSA to determine whether the factors contributing to apnea are similar between genders. The first group of 11 men and 11 women were matched for OSA severity (mean +/- SE apnea-hypopnea index = 43.8 +/- 6.1 and 44.1 +/- 6.6 events/h). The second group of 12 men and 12 women were matched for body mass index (BMI; 31.6 +/- 1.9 and 31.3 +/- 1.8 kg/m2, respectively). All measurements were made during stable supine non-rapid eye movement sleep. LG was determined using a proportional assist ventilator. Pcrit was measured by progressively dropping the continuous positive airway pressure level for three to five breaths until airway collapse. Apnea-hypopnea index-matched women had a higher BMI than men (38.0 +/- 2.4 vs. 30.0 +/- 1.9 kg/m2; P = 0.03), but LG and Pcrit were similar between men and women (LG: 0.37 +/- 0.02 and 0.37 +/- 0.02, respectively, P = 0.92; Pcrit: 0.35 +/- 0.62 and -0.18 +/- 0.87, respectively, P = 0.63). In the BMI-matched subgroup, women had less severe OSA during non-rapid eye movement sleep (30.9 +/- 7.4 vs. 52.5 +/- 8.1 events/h; P = 0.04) and lower Pcrit (-2.01 +/- 0.62 vs. 1.16 +/- 0.83 cmH2O; P = 0.005). However, LG was not significantly different between genders (0.38 +/- 0.02 vs. 0.33 +/- 0.03; P = 0.14). These results suggest that women may be protected from developing OSA by having a less collapsible upper airway for any given degree of obesity.     

Sex difference in the effect of obesity on 24-hour mean serum gonadotropin levels.

To determine the effect of obesity on serum gonadotropin levels and any possible sex difference in the effect, we measured the 24-hour mean serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) concentrations in 62 healthy men with Body Mass Index (BMI) ranging from 20 - 94 and 61 healthy, regularly cycling women with BMIs ranging from 19 - 76. We also measured free testosterone (T) and estradiol (E2) in these subjects. There was a significant negative correlation between serum FSH and BMI in men: FSH(IU/L) = 49.9 x BMI -0.567; r = - 0.376, p = 0.0026; but a significant positive correlation between serum FSH and BMI in women: FSH(IU/L) =7.66 +/- 0.071 x BMI; r = 0.302, p = 0.018. Serum LH was weight-invariant in both sexes. In men, free T was negatively correlated with BMI: Free T (nmol/L) = 0.74 - 0.0068 x BMI; r = 0.585, p = 0.0381; and free E2 was positively correlated with BMI: Free E2 (pmol/L) = - 1.03 +/- 0.057 x BMI; r = 0.50, p = 0.0014. In obese women as a group, free T was higher than in lean women (33 +/- 6.8 S.E.M. vs. 17.4 +/- 2.0 pmol/L; p < 0.0001), and free E2 was also higher than in lean women: (6.90 +/- 0.80 vs. 4.84 +/- 0.55 pmol/L; p = 0.046). Of the many cases of hypothalamic-pituitary hormonal dysregulation that have been reported in obesity, none has been studied for sex differences. Our results mandate that possible sex differences be investigated in all cases of dysregulation.     

Gender dimorphism in skeletal muscle leptin receptors, serum leptin and insulin sensitivity

To determine if there is a gender dimorphism in the expression of leptin receptors (OB-R170, OB-R128 and OB-R98) and the protein suppressor of cytokine signaling 3 (SOCS3) in human skeletal muscle, the protein expression of OB-R, perilipin A, SOCS3 and alpha-tubulin was assessed by Western blot in muscle biopsies obtained from the m. vastus lateralis in thirty-four men (age = 27.1+/-6.8 yr) and thirty-three women (age = 26.7+/-6.7 yr). Basal serum insulin concentration and HOMA were similar in both genders. Serum leptin concentration was 3.4 times higher in women compared to men (P<0.05) and this difference remained significant after accounting for the differences in percentage of body fat or soluble leptin receptor. OB-R protein was 41% (OB-R170, P<0.05) and 163% (OB-R128, P<0.05) greater in women than men. There was no relationship between OB-R expression and the serum concentrations of leptin or 17beta-estradiol. In men, muscle OB-R128 protein was inversely related to serum free testosterone. In women, OB-R98 and OB-R128 were inversely related to total serum testosterone concentration, and OB-R128 to serum free testosterone concentration. SOCS3 protein expression was similar in men and women and was not related to OB-R. In women, there was an inverse relationship between the logarithm of free testosterone and SCOS3 protein content in skeletal muscle (r = -0.46, P<0.05). In summary, there is a gender dimorphism in skeletal muscle leptin receptors expression, which can be partly explained by the influence of testosterone. SOCS3 expression in skeletal muscle is not up-regulated in women, despite very high serum leptin concentrations compared to men. The circulating form of the leptin receptor can not be used as a surrogate measure of the amount of leptin receptors expressed in skeletal muscles.