Body fat accumulation is possibly responsible for lower dehydroepiandrosterone circulating levels in premenopausal obese women

OBJECTIVE

To determine whether any androgen is independently related with parameters of body fat accumulation and distribution in obese women.

DESIGN

Circulating insulin and androgen levels (total testosterone (T), free testosterone (FT), dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulfate (DHEAS), androstenedione, sex hormone binding globulin (SHBG)) and the parameters of body fat accumulation and distribution (body mass index, waist-to-hip ratio, total body fat volume (TBF), visceral adipose tissue area (VAT) and subcutaneous adipose tissue area (SAT) were determined in a population of non-diabetic obese women.

SUBJECTS

28 premenopausal obese women, recruited at the Verona University Hospital Outpatient Clinic.

MEASUREMENTS

TBF, VAT and SAT area were quantified by computed tomography. Hormone levels were measured by RIA.

RESULTS

SHBG showed an inverse correlation with BMI (r: -0.452, P < 0.05), WHR (r: -0.388, P < 0.05), TBF (r: -0.509, P < 0.01), VAT (r: -0.378, P < 0.05) and SAT (r: -0.449, P < 0.05). DHEA was negatively associated with BMI (r: -0.376, P < 0.05), TBF (r: -0 < 0.05), VAT (r: -0.662, P < 0.001) and SAT (r: -0.401, p < 0.05). T was found to be inversely related with VAT (r: -0.401, P < 0.05). Androstenedione was positively correlated with WHR (r: 0.383, P < 0.05). DHEAS and FT did not show significant associations with BMI, WHR, or any CT-parameters. Stepwise multiple regressions were performed for all androgens: one of the age-adjusted androgens was considered as the dependent variable for each analysis, and insulin, VAT, SAT and all other androgens were entered into the regression model. DHEA was the only hormone to show an independent association (negative) with both SAT (t-value: -3.683, P < 0.01) and VAT (t-value: -2.252, P < 0.05), whereas DHEAS showed an independent positive correlation with SAT (t-value: -2.241, P < 0.05).

CONCLUSIONS

Among the androgens, DHEA seems to be the most sensitive to body fat accumulation in premenopausal obese women.

34-day total fast in an adult man

The aim of this work was to investigate the changes of cardiac performance by both electrocardiography (ECG) and echocardiography (ECHOc), in addition to anthropometric and hormonal variables before, during and after prolonged total fasting (TF) and re-feeding in an overweight adult man. Physical examination, laboratory and hormonal measurements, ultrasonographic study of body fat distribution, ECG and ECHOc study were performed before during and after 34 days of TF and after 17 days of isocaloric re-feeding. The subject was a 52-year old Caucasian who was overweight with increased abdominal fat content (BMI: 28.6; W/H ratio: 0.95) and increased levels of arterial systolic and diastolic blood pressure (SBP, DBP). HPLC measurements of urinary catecholamine levels (HPLC), ECHOc study of cardiac performance, ultrasonographic study of body fat distribution were performed. The subject starved for 34 days losing 22kg, but after that time he was compelled to re-feed because of nausea and severe vomiting. A marked ketosis (ketonuria > 1200mg/day) was already present after 6 days of TF. After 17 days of TF norepinephrine (NE) and epinephrine (EPI) urinary levels showed a two-fold and nine-fold increase respectively, but they became undetectable at the end of TF. After 17 days of re-feeding catecholamine urinary levels were similar to those measured after 17 days of TF. After both TF and 17-day isocaloric re-feeding we found a decrease of visceral fat content and W/H ratio reached the normal values for age-matched subjects (W/H ratio after TF: 0.80, after re-feeding: 0.80).(ABSTRACT TRUNCATED AT 250 WORDS)

The free testosterone to dehydroepiandrosterone sulphate molar ratio as a marker of visceral fat accumulation in premenopausal obese women

The aim of this paper was to investigate the relationship between sex hormones and fat distribution in premenopausal obese women. Serum concentrations of sex hormones, glucose tolerance and fat distribution were determined in a population of non-diabetic obese women, in the outpatient clinic of University Hospital, Bari, Italy. The subjects were 40 consecutive premenopausal obese women (BMI > 25). The amounts of visceral, abdominal subcutaneous, and femoral subcutaneous fat, and the visceral to abdominal subcutaneous fat ratio were measured by ultrasound techniques. Serum concentrations of total testosterone (T), free testosterone (FT), dehydroepiandrosterone sulphate (DHEAS), delta 4-androstenedione (A), 17-beta-estradiol (E2), sex hormone binding globulin (SHBG), and the FT to DHEAS molar ratio were measured during the follicular phase. Plasma glucose and insulin concentrations were evaluated during an oral glucose tolerance test. Of all sex hormones, the FT/DHEAS molar ratio was the parameter that most closely related to the amount of visceral fat (r: 0.544, P < 0.001), and this positive association was maintained (P < 0.01) after adjustment for age, BMI and insulin levels (fitted model: R2 adjusted: 0.504; F ratio: 14.73; P-value: < 0.0001). DHEAS was inversely correlated with the amount of visceral fat (r: -0.324, P < 0.05). T was inversely correlated with the amounts of both abdominal subcutaneous (r: -0.409, P < 0.01) and visceral fat (r: -0.324, P < 0.05). The FT to DHEAS molar ratio is the androgenic parameter that most closely relates to the accumulation of visceral fat in premenopausal obese women.

Combining three different sources as a valid tool to identify known diabetic patients: use in a prevalence study in an Italian local health unit

This study was carried out to validate the prevalence of known diabetes estimated from three different simultaneous sources (medical records from out-patient departments, registers and pharmaceutical prescriptions) as against the diagnosis of family doctors who had received ad hoc training before the study. To this effect, a selected Local Health Unit (Unità Sanitaria Locale or USL) in Bari, southern Italy, was examined. 2917 diabetic patients were found, with a 2.82% prevalence. The prevalence of known diabetes estimated from separate sources was 1.41% from medical records, 1.52% from the registers and 1.59% from prescriptions. With reference to the family doctor's conclusions, sensitivity, positive predictive value and efficiency of medical records were 49.8%, 92.5% and 57.4% of USL registers 53.8%, 95.6% and 61.8% of prescriptions 56.3%, 71.2% and 47.9%. 46% of the diabetic subjects were only identified from one source. In conclusion, by combining several sources of information together, a higher number of diabetic patients are identified than would be done by using separate sources; also, active cooperation from the family practitioners seems to be needed to correct the large number of false positive patients (n = 798) mostly identified from prescriptions.

Messenger RNA of G-proteins alpha-subunit in rat brown adipose tissue

The present study was addressed to quantify the steady-state mRNA levels for the alpha subunit of stimulatory (Gs) and inhibitory (Gi-1 and Gi-2) G-proteins in brown (interscapular) male rat adipose tissue (n = 6 rats). The quantification of specific mRNA, estimated using a solution hybridization RNAse protection assay, showed that the amounts of G alpha i-1, G alpha i-2 and G alpha s mRNA were 0.88 +/- 0.28 amol/microgram DNA, 76 +/- 4 amol/micrograms DNA and 460 +/- 16 amol/micrograms DNA, respectively. When the amounts of G alpha i-1 and G alpha i-2 and G alpha s mRNA in brown adipose tissue were compared with those in epididymal white adipose tissue (obtained from the same rats), G alpha i-1 and G alpha i-2 mRNA levels were very similar between brown and white adipose tissue, whereas the level of G alpha s mRNA was significantly higher in brown than in white fat tissue (P < 0.001). In conclusion, the present study shows the steady-state levels of mRNA for the alpha subunit of Gs, Gi-1 and Gi-2 in rat brown fat and suggests that the quantity of G alpha s mRNA is higher in brown than in white adipose tissue. Further studies are needed to explain the possible physiological importance of these findings.

Reduced effectiveness of atrial natriuretic factor in pre-menopausal obese women

It is well-known that the prevalence of hypertension progressively increases with body weight. Since the major physiological activities of atrial natriuretic factor (ANF) are its natriuretic, diuretic and vasodilatory effects, the aim of the present study was to investigate the ANF basal plasma levels and platelet receptor number in 15 young normotensive obese (O) and 12 age-matched normal weight healthy (C) women. ANF effectiveness was also studied in eight of the obese and seven of the control women, after an intravenous bolus of the hormone (human ANF (99-126): 0.5 mg/kg body weight). Results are expressed as means+s.d. Basal ANF plasma levels were similar between obese (18.2 +/- 9.7 pg/ml) and control women (12.3 +/- 7.7 pg/ml), whereas obese patients showed an increase density of platelet ANF-binding sites (clearance receptors) (C: 28.7 +/- 33.5 fmol/10(9) cells; O: 39.6 +/- 4.6 fmol/10(9) cells; P < 0.001), without apparent differences in receptor affinity (Kd) (C: 6.0 +/- 3.0 pM; O: 7.0 +/- 2.0 pM). The biological response to ANF, evaluated by changes of mean blood pressure levels (C: 5 +/- 1 mmHg; O: 1 +/- 1 mmHg; P < 0.001) and the percentage increase of diuresis (C: 159 +/- 52%; O: 81 +/- 62%; P < 0.01) and natriuresis (C: 205 +/- 129%; O: 99 +/- 41%; P < 0.05) was significantly reduced in obese patients. The percentage increase in sodium excretion was inversely related to the basal insulin concentrations in the obese group (r = 0.64, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Estradiol regulation of mRNA expression of stimulatory G-protein alpha-subunit in white adipose tissue from female rats

Adipose tissue has been recognized as a major peripheral metabolic target of estrogens. The present study was addressed to examine in female rats whether differences in the adipose tissue mRNA expression of alpha-subunit of stimulatory (Gs) and/or inhibitory (Gi) G-proteins exist between intact and ovariectomized rats, the latter with or without estradiol or testosterone treatment. The fat cell membrane protein amount of Gs and Gi alpha-subunit also was examined. All these parameters were evaluated in parametrial fat tissue samples obtained from 40 female Sprague-Dawley rats. A group of rats (N = 20) was investigated for evaluation of mRNA expression and another group (N = 20) for quantification of the protein amount of Gs and Gi alpha-subunit. Each group was represented by five control rats (sham-operated), five ovariectomized (OVX) rats, five ovariectomized rats treated with estradiol (OVXE) and five ovariectomized rats treated with testosterone (OVXT). Ribonucleic acid extracted from adipose tissue and analyzed by northern blot with G alpha s, G alpha i-3 cRNA probes revealed three major bands with estimated sizes of 1.9, 3.5 and 2.35 kb, respectively. Messenger RNA quantitative analysis, by a solution of hybridization RNAase protection assay on total nucleic acid samples, showed that the amount of G alpha i-1 and G alpha i-2 mRNA was similar within the different groups, whereas the G alpha s mRNA was significantly less abundant (p < 0.01) in OVX and OVXT rats than in control or OVXE rats. No difference in G alpha s mRNA content was found between control and OVXE rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Amount of G-protein alpha-subunit in rat white adipocytes: lack of difference between subcutaneous and visceral fat

It has been the purpose of this study to examine possible differences in the amount of stimulatory (Gs) and inhibitory (Gi) G-protein alpha-subunits (measured with a quantitative enzyme-linked immunosorbent assay in fat cell membrane preparation) between subcutaneous and intra-abdominal regions in rats. The lipolytic response to isoproterenol and the number of beta-adrenergic binding sites were also examined. These parameters were all evaluated simultaneously in subcutaneous (inguinal), epididymal and perirenal fat samples collected from six male Sprague-Dawley rats. The membrane contents of the Gs and Gi alpha-subunits were similar in the three depots. Moreover, no difference was found among the different regions with regard to isoproterenol-stimulated glycerol release and beta-adrenoceptor number, expressed per cell number. In conclusion, the present study shows for the first time in rats that the abundance of inhibitory and stimulatory G-protein alpha-subunits is similar in subcutaneous and in visceral adipocytes. Moreover, the number of beta-adrenoceptors and the lipolytic response to isoproterenol do not show significant variations with the anatomical site. As the present results are apparently in contrast with those obtained previously in human adipocytes, there is a possibility that the different results observed in rat and in human fat cells could be explained by species differences.

Insulin-like growth factor-1 (IGF-1) and dehydroepiandrosterone sulphate in obese women

Severe obesity is known to reduce either dehydroepiandrosterone circulating levels or growth hormone (GH) and insulin-like growth factor-1 (IGF-1) secretion. The present study was undertaken to evaluate the possibility of a relationship between the circulating levels of IGF-1 and those of dehydroepiandrosterone sulphate (DHEAS) in 25 fertile obese women. A logarithmic transformation of the values of non-normally distributed variables was performed before statistical analysis. We found a significant positive correlation between DHEAS and IGF-1 (r = 0.615, P < 0.01). In addition, stepwise multiple regression analysis showed that IGF-1 maintained a strong positive relationship with DHEAS (P < 0.01) when adjusted for other variables such as age, body mass index (BMI), waist:hip ratio (WHR) and insulin levels (adjusted R2 = 0.373; P < 0.01). These findings suggest that IGF-1 may independently influence the DHEAS circulating levels. ADG (5 alpha-androstan-3 alpha, 17 beta-diol-glucuronide) was also positively correlated to IGF-1 (r = 0.436, P < 0.05). However, when ADG concentrations were adjusted for DHEAS levels, this metabolite was not significantly correlated with IGF-1, thus excluding a direct influence of IGF-1 on the 5-alpha-reductase activity. Therefore, although our data represent only a preliminary study, they seem to suggest a possible influence of IGF-1 on circulating levels of DHEAS in obese women.

Relation between sex hormones and serum lipoprotein and lipoprotein(a) concentrations in premenopausal obese women

Lipoprotein(a) (Lp[a]) is generally considered to be a risk factor for the development of cardiovascular disease, but little is known about the possible influence of obesity on the circulating levels of this lipoprotein. The present study was undertaken to examine this aspect in 136 menstrually active women by comparing the serum concentrations of Lp(a) between 72 obese and 64 age-matched nonobese women. Since an adverse effect of androgens and a protective effect of estrogens have been described for plasma lipoprotein profiles in obese women, the relation between the circulating levels of Lp(a) and those of these other hormones was also investigated in obese patients. In addition, other lipoproteins, anthropometric parameters (body mass index and waist-to-hip ratio), and insulin were evaluated. The levels of Lp(a) were not significantly different (Mann-Whitney U test chi 2, 3.59; p = 0.0582 [NS]) between obese (rank sum, 5,367) and control (rank sum, 3,949) women; in addition, the percentage of patients with high Lp(a) levels (cutoff defined at 30 mg/dL) did not differ between the two groups (obese women, 30%; control, 21.8%; chi 2, 0.90; two-sided p = 0.341 [NS]). Moreover, no correlation was found between Lp(a) and body mass index. Lastly, when the Lp(a) prevalence odds ratio for obesity was examined by adjusting the levels of this lipoprotein for age, triglycerides, total cholesterol, and high density lipoprotein cholesterol, the probability value (0.88) was far from significant. In obese women, no correlation was found between the logarithmically transformed Lp(a) concentrations and all the other variables evaluated in the study. In conclusion, the present study shows that the circulating levels of Lp(a) are not influenced by body weight and cardiovascular risk factors commonly associated with obesity, such as enhanced androgenic activity, hyperinsulinemia, adverse lipoprotein profile, and abdominal fat accumulation.

Postreceptor events involved in the up-regulation of beta-adrenergic receptor mediated lipolysis by testosterone in rat white adipocytes

In the previous studies we have shown that testosterone increases lipolytic responsiveness to catecholamines in rat white adipocytes, and that is associated with an up-regulation of beta-adrenergic receptor density. However, the postreceptor events involved in the testosterone induced enhancement of beta-adrenergic receptor activated lipolysis in these cells have not been adequately studied, and were therefore investigated in the present study. Male Sprague Dawley rats were divided into three groups: control, castrated, and castrated treated with testosterone. The beta-adrenergic receptor-mediated cAMP accumulation, measured with RIA after isoproterenol (a beta-adrenergic agonist) stimulation was decreased in castrated rats, and reversed by testosterone treatment, suggesting a testosterone effect at or proximal to adenylate cyclase. However, no differences between the groups were found in abundance of G alpha protein messenger RNAs (G alpha s, G alpha i-1, and G alpha i-2) as analyzed by Northern blot and a solution hybridization RNase protection assay, or in G protein mass measured with a quantitative enzyme-linked immunosorbent assay in fat cell membrane preparation. Lipolysis stimulated by N6-monobutyryl-cAMP was reduced in castrated rats and recovered by testosterone treatment, suggesting that components distal to the adenylate cyclase, i.e. protein kinase A (PKA) and/or hormone sensitive lipase (HSL) also are involved in testosterone regulation of lipolysis. In conclusion, these and previous results suggest that the testosterone-induced increase in lipolytic response to catecholamines in rat white adipocytes is mediated through several events including an increased beta-adrenergic receptor density, probably an increased adenylate cyclase activity and an increased protein kinase A/hormone sensitive lipase activity at the postreceptor level with apparent absence of effect on the expression of G-proteins.

High systolic blood pressure increases prevalence and severity of retinopathy in NIDDM patients

OBJECTIVE

To determine whether the severity of retinopathy is higher in a group of NIDDM patients with sBP greater than or equal to 140 mmHg compared with NIDDM patients with sBP less than 140 mmHg.

RESEARCH DESIGN AND METHODS

Ophthalmoscopy and FAG were conducted among a group of NIDDM patients with either a sBP above (n = 54) or below (n = 55) 140 mmHg. The groups were matched according to diabetes duration, metabolic control (HbA1c), and AER.

RESULTS

Patients with sBP greater than 140 mmHg had a higher prevalence of retinopathy, as established according to a rating scale (4.9 +/- 3.8 vs. 3.2 +/- 3.3, P less than 0.02); furthermore, their BMI values were higher (28.1 +/- 4.5 vs. 24.9 +/- 4.1 kg/m2, P less than 0.001). The group of normotensive subjects showed the highest rate of low grading (0-2) values. However, the highest prevalence rates of 8-10 grading values (proliferative retinopathy) were found in the hypertensive group.

CONCLUSIONS

These data suggest that sBP values greater than or equal to 140 mmHg favor the onset of retinopathy in NIDDM patients during their 1st 10 yr of disease.

Increased free testosterone but normal 5 alpha-reduced testosterone metabolites in obese premenopausal women

OBJECTIVE

The aim of the study was to investigate whether the absence of increased 5 alpha-reductase activity explained the absence of hirsutism in premenopausal obese women with increased free testosterone (FT) levels.

DESIGN

As in hyperandrogenicity there generally exists evidence for increased 5 alpha-reductase activity, we measured, as parameters of 5 alpha-reductase activity, plasma levels of 5 alpha-androstane-3 alpha,17 beta-diol glucuronide (ADG) and androsterone glucuronide (ADTG) as well as their precursor levels in obese women without hirsutism, obese hirsute women, non-obese hirsute women, and non-obese, non-hirsute women.

PATIENTS

Eighty-two premenopausal women (20-45 years old) were studied, in four age matched groups: 39 controls, 18 obese without hirsutism, 11 non-obese hirsute and 14 obese hirsute women.

MEASUREMENTS

Blood samples were taken between days 5 and 7 of the menstrual cycle. Steroid hormone levels were measured by radioimmunoassay. Free testosterone levels were measured by equilibrium dialysis.

RESULTS

Compared to controls, mean free testosterone levels were increased (P less than 0.01) in obese, obese hirsute and hirsute patients, whereas mean DHEAS levels were increased in hirsute and obese hirsute (P less than 0.01), but not in obese, women. Mean androstanediol glucuronide levels were markedly increased in hirsute and obese hirsute patients (P less than 0.01), but not in obese women. Plasma androsterone glucuronide levels were increased in hirsute (P less than 0.01), in the normal range in obese hirsute, and decreased in obese women (P less than 0.01).

CONCLUSIONS

These results show that, despite the presence of higher free testosterone levels, neither 5 alpha-reductase activity (as suggested by normal androstanediol glucuronide levels) nor adrenal androgen precursor levels (DHEAS) are increased in obese women without hirsutism.

Influence of free testosterone on antigen levels of plasminogen activator inhibitor-1 in premenopausal women with central obesity

Women with upper body obesity are at increased risk for cardiovascular disease (CVD). Several studies have demonstrated a reduced fibrinolytic activity in these patients, mainly due to an enhanced activity of plasminogen activator inhibitor-1 (PAI-1). Since an increase of androgenic activity is a feature of central obesity in women, the present study was aimed at evaluating the possibility of a relationship between androgens and PAI-1 (antigen and activity) in 20 premenopausal women, 10 with upper body obesity and 10 controls. In obese women, PAI-1 antigen showed a positive Pearson correlation with free testosterone (FT), insulin, c-peptide, triglycerides (TG), and waist to hip ratio (WHR) (P less than .01), whereas PAI-1 activity correlated positively only with insulin and WHR (P less than .01). In control women, PAI-1 antigen and activity were positively related only to TG (P less than .01). When we applied the multiple regression model with stepwise backward method to our data, both PAI-1 antigen and activity did not maintain any significant association. However, when the data from both the groups were pooled (n = 20), and PAI-1 antigen was considered as the dependent variable, body weight (Sig T = 0.0001), TG (Sig T = 0.0053), FT (Sig T = 0.013), and luteinizing hormone (LH) (Sig T = 0.0474) met the stepwise criteria, suggesting an independent effect of each of these parameters on PAI-1 antigen. On the other hand, when PAI-1 activity was tested as the dependent variable, only body weight maintained a significant relationship with this parameter (Sig T = 0.0006).(ABSTRACT TRUNCATED AT 250 WORDS)

Phorbol esters do not influence the maturation and the beta-adrenergic responsiveness of differentiated adipose precursor cells, cultured in a charcoal-treated serum medium

Phorbol esters are a well defined group of tumor-promoting substances, which influence the proliferation, the differentiation and the hormonal responsiveness of a wide variety of cell types through the activation of protein-kinase C. Opposite effects have been described on the beta-adrenoceptors and the adenylate cyclase activity, depending on the cell type. Since there is no information about the influence of these substances on lipolysis in adipose precursor cells, the aim of the present study was to examine the effect of 7 days exposure to phorbol esters on the differentiation and the lipolytic responsiveness of rat preadipocytes, cultured in 10% charcoal-treated fetal calf serum. Our results demonstrate that prolonged exposure to these tumor promoters does not influence the differentiation, the beta-adrenoceptors number and the lipolytic response to adenylate cyclase or beta-adrenergic agonists in differentiated cells.

Inverse relationship between cortisol excretion rate and plasminogen activator inhibitor-1 (PAI-1) antigen and activity in premenopausal obese women

The present study was undertaken in order to investigate the possibility of a relationship between plasminogen activator inhibitor-1 (PAI-1) and cortisol excretion rate in 15 obese women. We found a highly significant linear inverse correlation between cortisol excretion rate and both PAI-1 antigen (r = 0.79, P less than 0.001) and activity (r = 0.77, P less than 0.001). In addition, stepwise regression analysis showed that cortisol excretion rate maintained a strong negative relationship with PAI-1 antigen (significance level 0.03) and activity (significance level 0.003), when adjusted for other variables taken in examination (waist to hip ratio, body mass index, insulin, DHEAS, age). Even though this study only demonstrates a negative correlation, the possibility of a direct inhibitory effect of cortisol on PAI-1 production should be considered. In conclusion, the present study demonstrates an inverse correlation between cortisol excretion rate and PAI-1 antigen and activity, suggesting a possible role for cortisol in protecting obese women from reduced fibrinolytic activity.

Low dehydroepiandrosterone circulating levels in premenopausal obese women with very high body mass index

Dehydroepiandrosterone (DHEA) has an anti-obesity effect in rodents and reduces body fat in normal men. Therefore, the plasma levels of DHEA were evaluated in nine premenopausal healthy women and in 13 menstrually active nondiabetic obese women, including patients (n = 6) with body mass index (BMI) over 40. In the obese group, a significant inverse correlation between DHEA levels and BMI was found. These results suggest that patients with severe obesity are unable to increase the DHEA adrenal production rate in order to parallel the increase in the hormone metabolic clearance rate (due to enlargement of body fat mass per se). The deficiency of this mechanism might itself contribute to the progressive fat accumulation in severe obesity.

Testosterone increases lipolysis and the number of beta-adrenoceptors in male rat adipocytes

The influence of androgen status on the regulation of lipolysis and number of beta-adrenoceptors in isolated adipocytes was studied in male rats. Castration resulted in decreased catecholamine-induced as well as forskolin-induced lipolysis. beta-adrenoceptor number, examined by a whole cell cyanopindolol binding assay, was also diminished to a similar extent. Testosterone treatment of castrated rats normalized lipolysis as well as beta-adrenoceptor number. These results demonstrate that testosterone stimulates catecholamine-induced lipolysis in vivo by increasing the number of beta-adrenoceptors as well as the activity of adenylate cyclase, confirming previous in vitro studies performed in adipose precursor cells.

Up-regulation of androgen receptor binding in male rat fat pad adipose precursor cells exposed to testosterone: study in a whole cell assay system

Binding of androgens to adipocytes has previously been evaluated using cytosol fractions without taking into account nuclear binding, although the latter is suggested to be close to the physiological site of action. In the present study, performed in differentiated fat pad adipose precursor cells, we describe a simple, reliable and reproducible androgen binding assay in a system with intact cells. Tritiated and unlabeled methyltrienolone (R1881) were used to define specific and unspecific androgen binding. Triamcinolone acetonide was added to prevent the binding of R1881 to other types of receptors. Differentiated adipose precursor cells contain a homogeneous class of high affinity androgen binding sites, and binding is saturable and reversible. Binding apparently occurs at one site, with a Kd in the range of physiological androgen concentration (about 4 nM). Competition studies indicate that the receptor is specific for R1881, testosterone and dihydrotestosterone, which have approximately the same affinity, while progesterone, estradiol and dexamethasone show much lower affinity. Androgen binding was markedly enhanced after cellular exposure to R1881 and testosterone but not dihydrotestosterone, and this increase was dependent on protein synthesis, suggesting the formation of new receptors by these androgens. In conclusion, fully differentiated adipocytes contain a specific, high affinity receptor, the density of which is dependent on androgens.

Testosterone treatment of ovariectomized rats: effects on lipolysis regulation in adipocytes

The effects of testosterone treatment (2 mg every 14 days, for three months) on adipocyte lipolysis of intact (250-300 g body weight) and ovariectomized female rats were studied. Testosterone treatment of intact rats had no effect. Ovariectomy was followed by an increase in fat cell size and a decrease of lipolysis stimulated by isoproterenol, norepinephrine, epinephrine, forskolin, cAMP and isobutylmethylxantine. The number of beta-adrenergic receptors was reduced. There was, however, no change in the antilipolytic effects of UK 14,304 (alpha 2-adrenergic agonist), nicotinic acid, N6-phenylisopropyladenosine or insulin. Testosterone treatment of ovariectomized rats restored the number of beta-adrenoceptors and lipolysis stimulated by cAMP and isobutylmethylxantine, but not lipolysis stimulated by catecholamines and forskolin, suggesting a remaining defect in the catalytic unit of adenylate cyclase. These results indicate that ovariectomy is followed by a profound derangement of the lipolytic pathway at several levels, from beta-adrenoceptors number to the triglyceride lipase activity. This is partially restored by treatment with testosterone, which, however, has no effect on intact female rats. This study emphasizes the importance of ovarian integrity for the lipolytic regulation and the inability of testosterone to replace ovarian function in this regard or to affect lipolysis in intact female rats.

Changes in overall plasma norepinephrine turnover and lymphomonocyte beta-adrenoceptor number during combined caloric and sodium restriction in normotensive obese subjects

The aim of the study was to evaluate in eight normotensive obese patients the influence of low sodium intake (9 mEq/day) on the sympathetic activity modifications induced by caloric restriction (2511 kJ/day). As compared to the isocaloric salt balanced diet, 7 days of normosodic underfeeding induced a decrease in the overall norepinephrine turnover (clearance and appearance rate) and 24 hours urinary output, whereas the combined caloric and salt restriction significantly increased the norepinephrine appearance rate and even more the norepinephrine clearance but, on the other hand, decreased the beta-adrenergic receptor number on the lymphomonocyte surface, suggesting a reduced peripheral sensitivity to catecholamines. Therefore, the utility of the combined sodium and caloric restriction in the treatment of the normotensive obese patients remains still questionable.

D-(-)-beta-hydroxybutyrate inhibits catecholamine-stimulated lipolysis and decreases beta-adrenoceptors' affinity in human fat cells but not in lymphomonocytes

The effect of D-(-)-beta-hydroxybutyrate, at concentrations commonly achieved during ketoacidosis in humans (10 mmol/l), on human fat cell lipolysis in vitro was the aim of this study. The basal lipolysis was not modified and beta-hydroxybutyrate did not affect forskolin- or dibutyryl-cAMP-stimulated glycerol release, whereas it markedly inhibited isoproterenol-stimulated lipolysis. In membranes of intact adipocytes exposed to D-(-)-beta-hydroxybutyrate for 1 h, we found a decrease in beta-adrenoceptor affinity in saturation experiments and a shift to the right of the isoproterenol-mediated radioligand [( 125I]-cyanopindolol) displacement curve. These findings suggest that beta-hydroxybutyrate inhibits catecholamine-stimulated lipolysis by decreasing beta-adrenoceptor affinity. No effect of beta-hydroxybutyrate was found on beta-adrenoceptor binding of intact mononuclear cells of peripheral blood. In conclusion, the beta-adrenoceptor affinity lowering effect of beta-hydroxybutyrate is seemingly specific to human fat cells and might represent a feed-back mechanism that prevents an uncontrolled breakdown of triglycerides and indirectly regulates its own production rate.

[Adenylate cyclase response to beta-adrenergic agonists in heart and brown adipose tissue]

Some sympathomimetic compounds (i.e. BRL37344) increase brown adipose tissue (BAT) thermogenesis with minimal cardiac effects. They act through an "atypical" beta-adrenergic receptor (beta-AR). Since beta-AR responses involve Adenylate Cyclase (AC) activation, we investigate the AC answer to isoproterenol and BRL37344 in rat plasmamembranes of heart (beta 1-ARs) and BAT (atypical beta-ARs). AC dose-response curves were obtained by incubating membrane fractions with different concentrations of isoproterenol and BRL37344 (1 nM-100 microM) at 25 degrees C for 15 min. In our study BRL37344 is 40-times more potent than isoproterenol in stimulating AC activity of BAT (EC50s: BRL37344 = 0.02 microM, isoproterenol = 0.7 microM). Furthermore it is more potent in stimulating BAT AC than heart AC (BRL37344 EC50 ratio heart/BAT = 38). However on BAT membranes, BRL37344 intrinsic sympathomimetic activity (ISA) vs. Isoproterenol is 0.87. Since isoproterenol and BRL37344 show a similar ISA for BAT respiration and lipolysis, we may argue that AC maximal activity is not required for maximal lipolytic and thermogenic responses.

The effects of androgens on the regulation of lipolysis in adipose precursor cells

Adipose precursor cells from male rats were exposed in primary culture to testosterone (T) or dihydrotestosterone (DHT), and their effects on the regulation of lipolysis were studied. T, but not DHT, stimulated catecholamine-induced lipolysis in a dose-dependent manner, including physiological concentrations. The effect was equally pronounced with isoproterenol (a pure beta-adrenergic agonist) and norepinephrine (a mixed alpha 2- and beta-adrenergic agonist). The higher lipolytic capacity of catecholamines on T-treated cells was paralleled by a similar increase in the number of beta-adrenoceptors in the cells, without a change in the receptor affinity, suggesting that T induced new synthesis or externalization of beta-adrenoceptors. Both T and DHT stimulated forskolin-induced lipolysis, suggesting an androgen effect at the level of the catalytic subunit of adenylate cyclase. The pertussis toxin-stimulated lipolysis was not influenced by the presence of androgens in the culture medium, and no effect was seen on the antilipolytic effect of insulin. These effects did not disappear in the presence of an aromatase inhibitor, suggesting that the T effects were not mediated by conversion to estrogens. These cells showed specific saturable binding for androgens, with a Kd in the range of androgen concentrations shown to be active. In conclusion, androgens enhance the lipolytic capacity of these cells by increasing the apparent number of beta-adrenoceptors (T only) and the activity of adenylate cyclase (both T and DHT). These changes are not mediated by conversion to estrogens. These effects probably occur via binding to specific androgen receptors.

Influence of lactate on isoproterenol-induced lipolysis and beta-adrenoceptors distribution in human fat cells

The influence of lactate on human adipocytes lipolysis and the possible relationship between lactate-induced metabolic effects and beta-adrenoceptor binding sites were investigated. beta-sites were identified in membranes with (125I)-cyanopindolol and in intact cells with (125I)-cyanopindolol and (3H)-CGP 12177. Lactate reduced isoproterenol-induced lipolysis in a dose-response fashion and such inhibition became significant only at 16 mmol/l lactate. Exposure of human fat cells to 16 mmol/l lactate significantly reduced beta-adrenoceptors density on crude membranes. When the binding assay was performed on intact cells using (125I)-cyanopindolol at 37 degrees C, the radioligand identified the same number of receptors, regardless of the presence of lactate in the preincubation medium. When (3H)-CGP 12177 was used, it bound to about 35% less receptors in lactate pre-treated cells than in control. Seemingly, at 37 degrees C, because of its lipophilicity, (125I)-cyanopindolol can cross the plasma membrane and bind to intracellular sites whereas, (3H)-CGP 1277, due to its hydrophilicity, identifies surface receptors only. Thus, the present in vitro study provides evidence that high levels of lactate, similar to the concentrations usually achieved in overt lactic acidosis, are able per se to inhibit human lipolysis and to redistribute beta-adrenoceptors from cell surface to a domain not accessible to hydrophilic ligands.

Human fat cell beta-adrenergic receptors: beta-agonist-dependent lipolytic responses and characterization of beta-adrenergic binding sites on human fat cell membranes with highly selective beta 1-antagonists

Beta-adrenergic receptors were characterized in human fat cell membranes using 125I-labeled cyanopindolol (125I-labeled CYP) and highly selective beta 1-antagonists. The iodinated radioligand bound saturably and specifically to a single class of high affinity binding sites. The number of binding sites determined with 125I-labeled CYP closely agreed with that determined with two other tritiated radioligands: [3H]dihydroalprenolol and [3H]CGP-12,177. Since 125I-labeled CYP does not discriminate between beta 1- and beta 2-adrenoceptors, the densities of the two receptor subtypes were determined from the competition curves of 125I-labeled CYP by highly selective beta 1-antagonists (bisoprolol, ICI-89,406, CGP-20,712A, and LK-204,545). Moreover, in order to enable correlation with binding data, the regulation of adenylate cyclase activity and of lipolysis was tested with various beta-agonist and antagonist compounds. The results obtained on fat cell membranes from abdominal subcutaneous adipose tissue demonstrated the following. 1) 125I-labeled CYP represents a valuable tool for the quantification and the delineation of beta-receptor subtypes. 2) The presence of sodium ions in binding buffers causes a modification of the affinity of beta-sites for some beta-antagonists. 3) The human fat cell beta adrenergic receptor population defined by nonselective radioligands is composed of two subtypes that can be interpreted in terms of classic beta 1- and beta 2-adrenergic receptor subtypes as assessed by competition studies with highly selective antagonists; beta 2-sites are predominant (60-70% of 125I-labeled CYP sites) in the adipocytes of slightly overweight women. 4) Results support the idea that beta 1- as well as beta 2-adrenergic receptors are coupled with adenylate cyclase and involved in the induction of lipolysis. 5) The results focus on the interest in some beta 2-agonist drugs (zinterol, clenbuterol) as partial inductors of lipolysis, with the lipolytic efficacies of these compounds being well correlated with their efficacies at 125I-labeled CYP sites.

Arginine-vasopressin response to supine-erect posture change: an index for evaluation of the integrity of the afferent component of baroregulatory system in diabetic neuropathy

The arginine-vasopressin (AVP) response to supine-standing postural change was evaluated in eight healthy subjects and in fourteen diabetic patients. Plasma AVP levels were found to increase in the controls and in nine subjects from the diabetic group. In the controls the increase was 139% 5 min. after standing and 275% 120 min. after standing. In four of the diabetics affected by autonomic neuropathy AVP failed to increase in response to standing, thus suggesting lesions of the neurogenic pathways connecting baroreceptors to neurohypophysis. Consequently, a failure of the afferent limb in the baroregulatory system must be taken into account among other localizations of autonomic neuropathy. On this basis, AVP measurement both in supine and erect positions could represent an additional test for assessing the integrity of the autonomic nervous system.

[Determination of glycemia with a new reflex photometer (glucometer)]

The introduction on the market of small sized (easy to use) reflectance photometers for determination of blood glucose levels offers a new possibility in the monitoring homeostasis of glucose in diabetic patients. An evaluation of the system has been performed comparing the results with those obtained by spectrophotometer methods. Results by the two methods are quite comparable. A wide use of this system for blood monitoring should be encouraged especially among the diabetic patients in order to allow them to achieve a higher autonomy, particularly in emergency situations.

[Therapy of hepatic diseases with alpha-mercaptopropionylglycine]

Thiopronine has been used to treat 88 patients suffering from chronic hepatitis (65), liver cirrhosis in ascitic phase (14), alcoholic hepatosis(5) and acute hepatitis (4). The drug was employed at the attack stage i.v. at a daily dose of 1-2 grams, and at maintenance phase orally at a dose of 0.750-1 gram. It led to a gradual, significant improvement in clinical symptomatology and hepatofunctional haematochemical indices in all chronic forms, only decompensated cirrhosis showing a slight regression. In hepatic forms, normalisation of subjective and objective parameters was particularly fast, between the 4th and 7th days. Tolerance was very good in 98% of cases.