Minimal effect of a low-fat/high soy diet for asymptomatic, hormonally naive prostate cancer patients

PURPOSE

The effects of a low-fat diet or a low-fat diet with the addition of a soy supplement were investigated in a pilot Phase II study for asymptomatic, hormonally naive prostate cancer patients with rising prostate-specific antigen (PSA) levels.

EXPERIMENTAL DESIGN

A two-step intervention was implemented. During step 1 patients were begun on a low-fat diet with a goal to reduce fat intake to 15% of total daily calories. On PSA progression, a soy protein supplement was added to the diet (step 2). The primary end point was PSA reduction by 50%. Secondary end points were PSA doubling time and time to progression (TTP). Serum was analyzed for changes in the sex hormone and insulin-like growth factor (IGF-I) axes.

RESULTS

Among 18 evaluable patients, (median follow-up on study 10.5 months), no patient on either step had a PSA reduction by 50% at any time. There was a trend toward a longer PSA doubling time (P = 0.06) and a prolongation in estimated median TTP of approximately 3 months (P = 0.018) during step 2 compared with step 1 of the study. During step 1, free testosterone levels decreased by 5% (P < 0.01), and during step 2, IGF-I levels increased by 22% (P = 0.02).

CONCLUSIONS

A low-fat diet with the subsequent addition of a soy supplement did not result in a significant decline in PSA levels. The addition of soy protein had a modest effect on TTP. A potentially undesirable effect associated with the administration of soy was an increase in IGF-I serum levels.

Leptin mediates Clostridium difficile toxin A-induced enteritis in mice

BACKGROUND & AIMS

Leptin regulates energy homeostasis and participates in the regulation of the hypothalamic-pituitary-adrenal axis. Although hyperleptinemia is described in experimental colitis, its role in the pathophysiology of enterotoxin-mediated diarrhea and inflammation remains unclear. We examined the role of leptin in the inflammatory diarrhea induced by toxin A from Clostridium difficile, the causative agent of antibiotic-related colitis.

METHODS

Toxin A (10 microg) or buffer were administered in ileal loops of leptin-deficient (ob/ob), leptin-resistant (db/db), or wild-type mice and enterotoxic responses were measured.

RESULTS

In toxin A-treated wild-type mice, circulating leptin and corticosterone levels were increased compared with buffer-injected animals. Toxin A also stimulated increased mucosal expression of the Ob-Rb at the messenger RNA (mRNA) and protein level. Ob/ob and db/db mice were partially protected against toxin A-induced intestinal secretion and inflammation, and this effect was reversed by leptin administration in ob/ob, but not db/db, mice. Basal- and toxin A-stimulated plasma corticosterone levels in ob/ob and db/db mice were higher compared with toxin A-treated wild-type mice. To assess whether the effect of leptin in intestinal inflammation is mediated by corticosteroids we performed adrenalectomy experiments in db/db and wild-type mice. Our results suggested that the diminished intestinal response to toxin A in db/db mice was related only in part to increased levels of corticosteroids.

CONCLUSIONS

Leptin plays an important role in regulating the severity of enterotoxin-mediated intestinal secretion and inflammation by activating both corticosteroid-dependent and -independent mechanisms.

Plasma adiponectin concentrations in relation to endometrial cancer: a case-control study in Greece

Adiponectin is a hormone secreted exclusively by adipocytes, and obesity is an established risk factor for endometrial cancer. We have, thus, evaluated the association of adiponectin with the occurrence of endometrial cancer. Questionnaire information and blood samples were taken before treatment from 84 women with newly diagnosed, histologically confirmed endometrial cancer and 84 control women who were admitted for minor gynecologic problems, mainly pelvic prolapse. Adiponectin levels were measured by immunoassay. The results were analyzed through multiple logistic regression and controlled for known risk factors for endometrial cancer, leptin, as well as major components of the IGF system (IGF-I, IGF-II, and IGF-binding protein 3). Among control women, there was no significant association of adiponectin with age or parity. Although there was no association of adiponectin with endometrial cancer among women 65 yr or older, there was an inverse, fairly strong, and statistically significant inverse association among younger women. Among women younger than 65 yr, an increase of adiponectin by 1 SD was associated with a more than 50% reduction of the risk for endometrial cancer [odds ratio (OR) 0.44; 95% confidence interval (CI) 0.24-0.81], even after controlling for body mass index and other potential confounders. Among all women, the adjusted OR for a 1 SD increase in adiponectin was not significant (OR, 0.78; 95% CI, 0.56-1.10) but was significant for a one quintile increase in adiponectin (OR, 0.74; 95% CI, 0.56-0.97). In women younger than 65 yr, among whom obesity represents a powerful risk factor for endometrial cancer, adiponectin is inversely and significantly related to the risk of this disease. This association is independent of possible effects of major components of the IGF system, leptin, body mass index, sociodemographic variables, and known endometrial cancer risk factors. Future studies are needed to prove causality and provide insight on both the mechanism of action of this hormone and its potential role in endometrial cancer.

Serum levels of insulin-like growth factor-1 and insulin-like growth factor-1 binding proteins after radical prostatectomy

PURPOSE

Elevated serum levels of insulin-like growth factor-1 (IGF-1) have been consistently shown to be a risk factor for prostate cancer. Alterations in serum IGF-1 binding proteins 1 to 3 have also been associated with prostate cancer risk. A potentially important complication in these studies is that prostate tissue, perhaps especially malignant prostate tissue, may secrete IGF-1 and its binding proteins into serum. In fact, it is possible that altered levels of these proteins observed in subjects at risk for prostate cancer are the result of prostate cancer rather than related to its cause.

MATERIALS AND METHODS

The contribution of prostate cancer to serum levels of IGF-1 and IGF-1 binding proteins was determined by analyzing serum samples from 86 patients with prostate cancer 2 weeks before and 8 weeks after radical prostatectomy. Preoperative and postoperative values for IGF-1 and its 3 major binding proteins were analyzed using univariate and multivariate analysis models.

RESULTS

On univariate analysis significant increases and not decreases in IGF-1, IGF binding protein-1 and 3 were observed after prostatectomy. On multivariate analysis a significant post-prostatectomy increase was observed for IGF-1 binding proteins 1 and 3 but the increase in IGF-1 was not significant.

CONCLUSIONS

Increased levels of IGF-1 and IGF-1 binding proteins were unexpected after prostatectomy. This result makes it extremely unlikely that secretion from the prostate, even if it contains cancer, affects serum levels of these proteins. The implication of these findings is that endocrine production of IGF-1 is a factor in prostate cancer risk. Therefore, strategies to lower serum IGF-1 may be potentially useful.

Serum levels of insulin-like growth factor-1 and insulin-like growth factor-1 binding proteins after radical prostatectomy

PURPOSE

Elevated serum levels of insulin-like growth factor-1 (IGF-1) have been consistently shown to be a risk factor for prostate cancer. Alterations in serum IGF-1 binding proteins 1 to 3 have also been associated with prostate cancer risk. A potentially important complication in these studies is that prostate tissue, perhaps especially malignant prostate tissue, may secrete IGF-1 and its binding proteins into serum. In fact, it is possible that altered levels of these proteins observed in subjects at risk for prostate cancer are the result of prostate cancer rather than related to its cause.

MATERIALS AND METHODS

The contribution of prostate cancer to serum levels of IGF-1 and IGF-1 binding proteins was determined by analyzing serum samples from 86 patients with prostate cancer 2 weeks before and 8 weeks after radical prostatectomy. Preoperative and postoperative values for IGF-1 and its 3 major binding proteins were analyzed using univariate and multivariate analysis models.

RESULTS

On univariate analysis significant increases and not decreases in IGF-1, IGF binding protein-1 and 3 were observed after prostatectomy. On multivariate analysis a significant post-prostatectomy increase was observed for IGF-1 binding proteins 1 and 3 but the increase in IGF-1 was not significant.

CONCLUSIONS

Increased levels of IGF-1 and IGF-1 binding proteins were unexpected after prostatectomy. This result makes it extremely unlikely that secretion from the prostate, even if it contains cancer, affects serum levels of these proteins. The implication of these findings is that endocrine production of IGF-1 is a factor in prostate cancer risk. Therefore, strategies to lower serum IGF-1 may be potentially useful.

Estrogens, testosterone and sex hormone binding globulin in relation to liver cancer in men

OBJECTIVE

Liver disease in men has been associated with an imbalance of serum estradiol and testosterone. We have evaluated whether serum estradiol and testosterone levels are altered in male liver cancer patients as a result of a specific effect of the disease or because of the associated liver damage.

METHODS

We have performed a hospital-based case-control study in Greece. The study subjects were all men; 73 patients with hepatocellular carcinoma (HCC), 25 with metastatic liver cancer (MLC) patients and 111 control subjects. Serum estradiol, testosterone and sex hormone binding globulin (SHBG) levels were measured for each subject. Data were analyzed by multiple linear regression.

RESULTS

Mean serum estradiol levels were significantly higher among HCC patients as well as among patients with MLC compared to controls. Mean serum testosterone levels were significantly lower among HCC patients as well as among patients with MLC compared to controls. The mean SHBG levels did not differ significantly between the groups. After controlling for the degree of liver damage, the elevated serum estradiol and reduced serum testosterone levels among HCC and MLC patients were no longer significant.

CONCLUSIONS

Changes in sex steroid levels among patients with liver damage are due to the liver damage per se and not to specific disease processes.

Insulin-like growth factor binding protein-3 predicts survival from acute childhood leukemia

OBJECTIVE

To investigate whether the three principal components of the insulin-like growth factor (IGF) system, IGF-1, IGF-2 and IGF binding protein-3 (IGFBP-3), are associated with survival from childhood leukemia.

PATIENTS AND METHODS

116 children, 0--14 years old, with newly diagnosed and bone-marrow-biopsy-confirmed acute childhood leukemia between 1993 and 1996 were followed up until death or March 31, 1998. IGF-1, IGF-2 and IGFBP-3 were measured at diagnosis and clinical data, including presence of hepatosplenomegaly and number of white blood cells, were available.

RESULTS

After controlling for gender, age, indicators of clinical severity and the other measured components of the IGF system there was a statistically significant (p < 0.05) inverse association of IGFBP-3 with survival. An increment of one standard deviation in IGFBP-3 was associated with a 65% reduction of the death hazard among the children with leukemia. Neither IGF-1 nor IGF-2 was associated with survival in this data set.

CONCLUSION

The presented empirical evidence in conjunction with the fact that IGFBP-3 modulates IGF-1 and IGF-2 bioavailability and is likely to have proapoptotic effects makes this compound a plausible independent predictor of survival from childhood leukemia.

Decreased serum leptin in bulimia nervosa

The eating disorder bulimia nervosa has been associated with impaired satiety, decreased resting metabolic rate, and abnormal neuroendocrine regulation. Preclinical studies suggest that such alterations could be associated with impaired leptin function. Thus, the goal of this study was to assess whether leptin function is decreased in bulimia nervosa. Serum leptin levels measured in women with bulimia nervosa (n = 18) and in women who had maintained stable recovery from bulimia nervosa (n = 15) were compared with values in healthy female controls (n = 20). Subjects were studied during the follicular phase of their menstrual cycle after an overnight fast and bed rest. Baseline serum samples were analyzed for leptin concentration by RIA. Subject groups were matched for age and body weight. Analysis of covariance, adjusting for percent body fat, demonstrated abnormally low serum leptin levels in the bulimia nervosa group (P: = 0.02), with a trend toward an inverse correlation between frequency of binge episodes and serum leptin concentration (P: < 0.1). Additionally, the remitted patient group demonstrated abnormally low leptin values (P: = 0.01). These results are consistent with the hypothesis that decreased leptin function may be associated with alterations in eating patterns, metabolic rate, and neuroendocrine regulation in bulimia nervosa.

Endocrinologic and psychological effects of short-term dexamethasone in anorexia nervosa

Patients with anorexia nervosa (AN) have hyperactivity of their hypothalamic-pituitary-adrenal (HPA) axis, sometimes accompanied by elevations of cortisol. We examined whether the normal effects of short-term dexamethasone treatment upon HPA axis suppression and appetite stimulation are observed in these patients. Five young women with AN and ten healthy female controls received one week of high-dose oral dexamethasone (2 mg/m2/d) preceded and followed by hormonal evaluation of sensitivity to glucocorticoids and psychological assessments. No differences in hormone levels of the HPA axis were observed between the two groups and control groups at baseline, after dexamethasone suppression, or following ACTH stimulation testing. However, fasting insulin levels were significantly lower in the AN group, both before and after dexamethasone therapy and their serum leptin levels were also significantly lower. The AN group had significantly lower scores on the Anorexia Nervosa Subtest and the Beck Depression Inventory after dexamethasone compared to controls. On daily analog scales, AN patients had higher anxiety scores while on dexamethasone. Normal sensitivity to glucocorticoids was observed in all parameters examined except for mild abnormalities in pancreatic beta-cell function. These data suggest that AN may represent a state of partial glucocorticoid resistance, as in other states of restricted food intake. Furthermore, these pilot data, including the effects of dexamethasone upon psychological outlook in AN, suggest that glucocorticoids are not an effective therapy for these patients.

Endogenous risk factors for childhood leukemia in relation to the IGF system (Greece). The Childhood Haematologists-Oncologists Group

OBJECTIVE

Insulin-like growth factor-1 (IGF-1) and its principal binding protein-3 (IGFBP-3) are central in the mediation of the effect of growth hormone, and the IGF system has been reported to play a role in the pathogenesis of childhood leukemia.

METHODS

To further evaluate the hypothesis connecting the IGF system to this disease, we have examined whether IGF-1 and IGFBP-3 are associated with the two main endogenous risk factors for childhood leukemia, namely gender and birth weight, since boys and heavier newborns are known to be at higher risk. IGF-1 and IGFBP-3 were measured under code in the serum of 118 apparently healthy children aged 0-14 years and the values of each of these components were regressed on age, gender and birth weight. Insulin-like growth factor-2 (IGF-2), as a dependent variable, and anemia during the corresponding pregnancy, as a predictor variable, were also evaluated for exploratory purposes.

RESULTS

In the total data set, IGF-1 was positively associated with birth weight (p = 0.0001), whereas girls had higher levels of IGFBP-3 (p = 0.01).

CONCLUSIONS

It appears that the associations of measured components of the IGF system with the examined risk factors for childhood leukemia are largely compatible with those that would have been expected, if this system played a role in the pathogenesis of childhood leukemia.

Insulin-like growth factor 1 in hepatocellular carcinoma and metastatic liver cancer in men

The insulin-like growth factor (IGF) axis has important autocrine, paracrine, and endocrine roles in the promotion of growth. Alterations of the IGF system have recently been implicated in the pathogenesis of several malignancies, but the relation to hepatocellular carcinoma (HCC) risk is unclear. To address this issue, we used an immunoradiometric assay to quantify IGF-1 levels in serum samples in a hospital-based, case-control study in Greece. The study subjects were all men and included 53 patients with HCC positive for hepatitis B and/or hepatitis C virus infections, 20 virus-negative HCC patients, 25 virus-negative patients with metastatic liver cancer (MLC), and 111 virus-negative control subjects. Data were analyzed by multiple linear regression, using IGF-1 as the dependent variable. The mean value of IGF-1 was 65.9 ng/ml among virus-positive HCC patients, 79.5 ng/ml among virus-negative HCC patients, 110.8 ng/ml among patients with MLC, and 174.7 ng/ml among hospital controls. After controlling for the degree of liver damage, as assessed by prothrombin time and serum albumin level, the reduction in IGF-1 level among HCC patients was found to be more than could be attributed to liver damage alone. This finding may have both diagnostic and pathophysiological implications.

Insulin-like growth factor 1 in hepatocellular carcinoma and metastatic liver cancer in men

The insulin-like growth factor (IGF) axis has important autocrine, paracrine, and endocrine roles in the promotion of growth. Alterations of the IGF system have recently been implicated in the pathogenesis of several malignancies, but the relation to hepatocellular carcinoma (HCC) risk is unclear. To address this issue, we used an immunoradiometric assay to quantify IGF-1 levels in serum samples in a hospital-based, case-control study in Greece. The study subjects were all men and included 53 patients with HCC positive for hepatitis B and/or hepatitis C virus infections, 20 virus-negative HCC patients, 25 virus-negative patients with metastatic liver cancer (MLC), and 111 virus-negative control subjects. Data were analyzed by multiple linear regression, using IGF-1 as the dependent variable. The mean value of IGF-1 was 65.9 ng/ml among virus-positive HCC patients, 79.5 ng/ml among virus-negative HCC patients, 110.8 ng/ml among patients with MLC, and 174.7 ng/ml among hospital controls. After controlling for the degree of liver damage, as assessed by prothrombin time and serum albumin level, the reduction in IGF-1 level among HCC patients was found to be more than could be attributed to liver damage alone. This finding may have both diagnostic and pathophysiological implications.

Effects of protease inhibitors on hyperglycemia, hyperlipidemia, and lipodystrophy: a 5-year cohort study

BACKGROUND

Although human immunodeficiency virus (HIV)-related morbidity and mortality rates in patients with advanced HIV infection who are treated with combination antiretroviral drugs have declined, significant metabolic adverse effects associated with these regimens have been increasingly recognized. However, since data from patients studied before and after initiation of protease inhibitor (PI) therapy are scant, the true effect of PIs on these metabolic changes remains unknown.

OBJECTIVES

To examine temporal trends in serum glucose and lipid levels after initiation of PI therapy, to assess whether changes are independent of virological response and improvement in disease severity, and to determine risk factors associated with the development of hyperglycemia, hyperlipidemia, and lipodystrophy.

METHODS

A 5-year historical cohort analysis in a population of 221 HIV-infected patients observed in the Infectious Diseases Clinic of a tertiary care center from October 1, 1993, through July 31, 1998. Clinical and laboratory data were retrieved from medical records and a computerized database. The main outcome measure was the incidence of hyperglycemia, hypercholesterolemia, hypertriglyceridemia, and lipodystrophy. Adjusted incidence rate ratios (IRRs) were estimated by means of Poisson regression. In addition, mixed regression analyses were performed to examine effects of PIs on serum lipid and glucose levels, modeled as continuous outcomes.

RESULTS

The cumulative incidence of new-onset hyperglycemia, hypercholesterolemia, hypertriglyceridemia, and lipodystrophy was 5%, 24%, 19%, and 13%, respectively. Most of these events occurred after initiation of PI therapy. Protease inhibitors were independently associated with hyperglycemia (adjusted IRR, 5.0; 95% confidence interval [CI], 1. 3-19.4), hypercholesterolemia (adjusted IRR, 2.8; 95% CI, 1.5-5.2), hypertriglyceridemia (adjusted IRR, 6.1; 95% CI, 3.1-11.7), and lipodystrophy (adjusted IRR, 5.1; 95% CI, 1.9-13.9). Anabolic steroids and psychotropic medications were also associated with lipodystrophy. Inclusion of potential intermediate variables (eg, virological suppression and increase in body weight) did not reduce the magnitude of the association with PIs. The association between hypertriglyceridemia and ritonavir was stronger than for other PIs (Wald test, P=.02). In contrast, the incidence of hyperglycemia, hypercholesterolemia, and lipodystrophy did not vary significantly across different PIs. Longitudinal mixed models confirmed that serum lipid levels were more substantially affected by antiretroviral therapy, particularly PIs, than serum glucose levels. Similarly, controlling for surrogate markers did not abolish the strong association between PIs and increase in serum lipid levels.

CONCLUSION

We found an independent association between PI use and hyperglycemia, hyperlipidemia, and lipodystrophy that is not explained by the antiviral and therapeutic effect of PIs.

Insulin-like growth factor 1 in hepatocellular carcinoma and metastatic liver cancer in men

The insulin-like growth factor (IGF) axis has important autocrine, paracrine, and endocrine roles in the promotion of growth. Alterations of the IGF system have recently been implicated in the pathogenesis of several malignancies, but the relation to hepatocellular carcinoma (HCC) risk is unclear. To address this issue, we used an immunoradiometric assay to quantify IGF-1 levels in serum samples in a hospital-based, case-control study in Greece. The study subjects were all men and included 53 patients with HCC positive for hepatitis B and/or hepatitis C virus infections, 20 virus-negative HCC patients, 25 virus-negative patients with metastatic liver cancer (MLC), and 111 virus-negative control subjects. Data were analyzed by multiple linear regression, using IGF-1 as the dependent variable. The mean value of IGF-1 was 65.9 ng/ml among virus-positive HCC patients, 79.5 ng/ml among virus-negative HCC patients, 110.8 ng/ml among patients with MLC, and 174.7 ng/ml among hospital controls. After controlling for the degree of liver damage, as assessed by prothrombin time and serum albumin level, the reduction in IGF-1 level among HCC patients was found to be more than could be attributed to liver damage alone. This finding may have both diagnostic and pathophysiological implications.

IGF-I and IGF-II in relation to colorectal cancer

Recent data suggest that the IGF system plays an important role in the pathogenesis of several forms of human cancer, and there is evidence that IGFs acting in an autocrine and paracrine manner may also affect colorectal cancer risk. We have conducted a case-control study on the island of Crete, Greece, to examine the potential relation between circulating IGF-I and -II and their major binding protein (IGF-BP3), on the one hand, and colorectal cancer, on the other. IGF-I, IGF-II and IGF-BP3 were determined in the serum from 41 patients with colorectal cancer and 50 healthy controls; data were analyzed using unconditional multiple logistic regression, adjusting for age, gender, education, height and BMI, as well as mutually. Both IGF-I and IGF-II were positively, while IGF-BP3 was inversely, associated with risk for colorectal cancer, though none of these relations reached statistical significance. However, individuals with IGF-I and -II values in the upper 2 tertiles of the respective distributions had a significantly elevated odds ratio for colorectal cancer (OR = 5.2, 95% confidence interval 1.0-26.8) compared with those in the lower tertile in both distributions. Our results provide evidence that high levels of circulating IGF-I and -II might be associated with colorectal cancer.

Age, sex, and smoking are predictors of circulating insulin-like growth factor 1 and insulin-like growth factor-binding protein 3

PURPOSE

Insulin-like growth factor (IGF-1) and its major binding protein (IGF-BP3) have recently been implicated in the pathogenesis of several malignancies. However, anthropometric and lifestyle predictors of these hormones have not been elucidated. Here we report the results of a cross-sectional study.

SUBJECTS AND METHODS

This cross-sectional study examines the relationship of a series of epidemiologic parameters (age, sex, height, body mass index, smoking, alcohol consumption, and coffee drinking) with IGF-1 and IGF-BP3 in a sample of 130 healthy adults.

RESULTS

We observed that serum levels of IGF-1 are higher, whereas levels of IGF-BP3 are lower, in men than in women. In addition, serum levels of IGF-1 are independently and negatively associated with age and positively associated with pack-year history of smoking. Finally, serum levels of IGF-BP3 are independently and negatively associated with the number of cigarettes smoked per day or pack-year history of smoking.

CONCLUSION

Age, sex, and smoking are independent predictors of IGF-1 and/or IGF-BP3. The influence of these epidemiologic variables on the pathogenesis of disease states associated with IGF-1 and IGF-BP3 warrants further exploration.

Insulin-like growth factor-I and binding protein-3 in relation to childhood leukaemia

The aetiology of most cases of childhood leukaemia remains unknown, but several studies have indicated that increased birthweight and height are risk factors for the disease. Since insulin-like growth factor-I (IGF-I) mediates the effect of growth hormone and has been positively associated with prostate cancer, we have evaluated the role of this hormone and its principal binding protein, IGFBP-3, in the aetiology of childhood leukaemia. Incident cases of childhood leukaemia from those recorded by a national network of childhood oncologists were enrolled in our study. Controls were children hospitalised for acute conditions of no more than moderate severity with matching for gender, age and maternal place of residence. Blood measurements of IGF-I and IGFBP-3 were undertaken using commercially available radioimmunoassays. Serum IGF-I values decreased by about 1.7% per month, and the rate of decline was higher, though not significantly so, among cases (2.1% per month) than among controls (1.4%). There was no significant association between IGF-I and the likelihood of childhood leukaemia, but an increment of 1 microg/ml of IGFBP-3 was associated with a substantial and statistically significant reduction of childhood leukaemia by 28% (95% confidence interval 7% to 45%). Because IGFBP-3 is essentially a binding protein, we interpret our findings as indicating that bioavailable IGF-I may play an important role in the aetiology of childhood leukaemia. The much smaller quantities and the inherent instability of IGF-I in the blood in comparison to those of IGFBP-3 are likely to hinder documentation of an underlying positive association of IGF-I with the disease.

Sex differences in circulating human leptin pulse amplitude: clinical implications

Leptin, a product of fat cells, provides a signal of nutritional status to the central nervous system. Leptin concentrations have ultradian and diurnal fluctuations. We conducted this study to assess sex differences in the levels of organization of frequently sampled leptin concentrations in healthy, normal weight women and men. Leptin levels were sampled every 7 min for 24 h in 14 healthy, normal weight individuals (6 women and 8 men). The 14 leptin time series containing a total of 2898 leptin measurements were assessed by 1) algorithms that characterize statistically significant pulsatility, 2) Spectral (Fourier) analysis, 3) analysis of time intervals and variability, and 4) approximate entropy. We found that frequently sampled plasma leptin concentrations have a 24-h profile that is numerically more than twice as high in women as in men, and leptin pulse amplitude is likewise more than twice as high in women. However, healthy men and women have nearly identical concentration-independent and frequency-related 24-h and ultradian patterns. Leptin concentrations have nonrandom fluctuations over 24 h, independent of their absolute value and underlying 24-h periodicity, that are similar in men and women. Ultradian periodicities detected by Fourier time series have similar values in men and women. The strongest distinction between the sexes in the level of organization of leptin concentration is not at the level of pulse organization or oscillation frequency, but, rather, in the mass or amount of leptin released (or removed) per unit time, indicating that women might be more resistant to the effects of leptin than men. Because leptin is clinically relevant to the regulation of body weight, future studies should examine whether the relative leptin resistance exhibited by women might contribute to their increased susceptibility to disorders whose pathophysiology involves dysregulation of food intake and body weight.

Synchronicity of frequently sampled, 24-h concentrations of circulating leptin, luteinizing hormone, and estradiol in healthy women

Leptin, an adipocyte hormone, is a trophic factor for the reproductive system; however, it is still unknown whether there is a dynamic relation between fluctuations in circulating leptin and hypothalamic-pituitary-ovarian (HPO) axis hormones. To test the hypothesis that fluctuations in plasma leptin concentrations are related to the levels of luteinizing hormone (LH) and estradiol, we sampled plasma from six healthy women every 7 min for 24 h during days 8-11 of the menstrual cycle. Cross-correlation analysis throughout the 24-h cycle revealed a relation between release patterns of leptin and LH, with a lag of 42-84 min but no significant cross-correlation between LH and estradiol. The ultradian fluctuations in leptin levels showed pattern synchrony with those of both LH and estradiol as determined by cross-approximate entropy (cross-ApEn). At night, as leptin levels rose to their peak, the pulsatility profiles of LH changed significantly and became synchronous with those of leptin. LH pulses were fewer, of longer duration, higher amplitude, and larger area than during the day. Moreover, the synchronicity of LH and leptin occurred late at night, at which time estradiol and leptin also exhibited significantly stronger pattern coupling than during the day. We propose that leptin may regulate the minute-to-minute oscillations in the levels of LH and estradiol, and that the nocturnal rise in leptin may determine the change in nocturnal LH profile in the mid-to-late follicular phase that precedes ovulation. This may explain the disruption of hypothalamic-pituitary-ovarian function that is characteristic of states of low leptin release, such as anorexia nervosa and cachexia.

The influence of smoking habits on thyroid gland volume: an ultrasonic approach

The effects of smoking habits on thyroid function, echo-texture (nodules and/or cysts) and thyroid gland volume were determined by using ultrasound and measuring serum Thyroxin (T4), Triiodothyronine (T3), Thyrotropin (TSH) and TPO antibodies (ab-TPO) in 189 healthy smokers and non-smokers, randomly selected (111 females and 78 males) among the employees of our hospital and their relatives. When the entire group of subjects was considered the mean ratio of thyroid gland volume/body weight was found to be significantly higher in male (P < 0.05) and female (P < 0.05) smokers compared with non-smokers. In female smokers, mean serum thyroid-stimulating hormone (TSH) was lower (P < 0.05) and the degree of smoking was positively correlated with the ratio of thyroid gland volume/body weight (P < 0.05). However, when the subjects with a family history of goitre in first degree relatives were excluded from our study (14 females and 9 males), no significant differences in mean ratio of thyroid volume/weight or TSH between the remaining smokers and non-smokers were detected. In both sexes, the correlation between the degree of smoking and thyroid volume, although positive, did not reach statistical significance. No difference in prevalence of abnormal echogenicity and echo-texture (nodules and cysts) between smokers and non-smokers was detected. It is concluded that smoking habits present a goitrogenic effect only in subjects with a family history of goitre but have no influence on thyroid gland texture.

Cerebrospinal fluid leptin in anorexia nervosa: correlation with nutritional status and potential role in resistance to weight gain

Studies in rodents have shown that leptin acts in the central nervous system to modulate food intake and energy metabolism. To evaluate the possible role of leptin in the weight loss of anorexia nervosa, this study compared cerebrospinal fluid (CSF) and plasma leptin concentrations in anorexic patients and controls. Subjects included 11 female patients with anorexia nervosa studied at low weight and after treatment, and 15 healthy female controls. Concentrations of leptin in blood and CSF were measured by RIA. Patients with anorexia nervosa, compared to controls, had decreased concentrations of leptin in CSF (98 +/- 26 vs. 160 +/- 58 pg/mL; P < 0.0005) and plasma (1.75 +/- 0.46 vs. 7.01 +/- 3.92 ng/mL; P < 0.005). The CSF to plasma leptin ratio, however, was higher for patients (0.060 +/- 0.023) than for controls (0.025 +/- 0.007; P < 0.0001). At posttreatment testing, although patients had not yet reached normal body weight, CSF and plasma leptin concentrations had increased to normal levels. These results demonstrate the dynamic changes in plasma and CSF leptin during positive energy balance in anorexia nervosa. The results further suggest that normalization of CSF leptin levels before full weight restoration during treatment of anorexic patients could contribute to resistance to weight gain and/or incomplete weight recovery.

Human leptin levels are pulsatile and inversely related to pituitary-adrenal function

Leptin communicates nutritional status to regulatory centers in the brain. Because peripheral leptin influences the activity of the highly pulsatile adrenal and gonadal axes, we sought to determine whether leptin levels in the blood are pulsatile. We measured circulating leptin levels every 7 minutes for 24 hours, in six healthy men, and found that total circulating leptin levels exhibited a pattern indicative of pulsatile release, with 32.0 +/- 1.5 pulses every 24 hours and a pulse duration of 32.8 +/- 1.6 minutes. We also show an inverse relation between rapid fluctuations in plasma levels of leptin and those of adrenocorticotropic hormone (ACTH) and cortisol that could not be accounted for on the basis of glucocorticoid suppression of leptin. As leptin levels are pulsatile, we propose that a key function of the CNS is regulated by a peripheral pulsatile signal. In a separate pilot study we compared leptin pulsatility in 414 plasma samples collected every 7 minutes for 24 hours from one obese woman and one normal-weight woman. We found that high leptin levels in the obese subject were due solely to increased leptin pulse height; all concentration-independent pulsatility parameters were almost identical in the two women. Leptin pulsatility therefore can be preserved in the obese.

Role of leptin in the neuroendocrine response to fasting

A total deficiency in or resistance to the protein leptin causes severe obesity. As leptin levels rise with increasing adiposity in rodents and man, it is proposed to act as a negative feedback 'adipostatic signal' to brain centres controlling energy homeostasis, limiting obesity in times of nutritional abundance. Starvation is also a threat to homeostasis that triggers adaptive responses, but whether leptin plays a role in the physiology of starvation is unknown. Leptin concentration falls during starvation and totally leptin-deficient ob/ob mice have neuroendocrine abnormalities similar to those of starvation, suggesting that this may be the case. Here we show that preventing the starvation-induced fall in leptin with exogenous leptin substantially blunts the changes in gonadal, adrenal and thyroid axes in male mice, and prevents the starvation-induced delay in ovulation in female mice. In contrast, leptin repletion during this period of starvation has little or no effect on body weight, blood glucose or ketones. We propose that regulation of the neuroendocrine system during starvation could be the main physiological role of leptin.

Serum steroid hormone levels, sex hormone-binding globulin, and body mass index in the etiology of postmenopausal breast cancer

Serum concentrations of estrone, androstenedione, testosterone, and sex hormone-binding globulin (SHBG) were measured postoperatively in 122 postmenopausal women with incident breast cancer and 122 age-matched population controls. After mutual adjustment, through conditional logistic regression, between the hormonal variables and body mass index (BMI), the odds ratios for increasing control-defined quartiles of estrone and androstenedione, respectively, were 1.00, 1.44, 1.76, 1.94 and 1.00, 0.83, 0.97, 2.43; there was no association of testosterone with breast cancer risk. Moreover, the odds ratios for increasing quartiles of SHBG and BMI were 1.00, 0.72, 0.28, 0.25 and 1.00, 0.39, 0.28, 0.19, respectively. This study reveals sharp contrasts in breast cancer risk between women with high estrone and low BMI and SHBG, vs women with low estrone and high BMI and SHBG.

Genetic variability in the TNF-alpha promoter is not associated with type II diabetes mellitus (NIDDM)

Recent evidence suggests that expression of tumor necrosis factor-alpha (TNF-alpha) by adipocytes is a molecular mediator of insulin resistance in obesity. We have therefore tested the hypothesis that variations within the regulatory region of the TNF-alpha gene, which might cause increased adipocyte or generalized TNF-alpha synthesis, are associated with NIDDM, a state in which insulin resistance is routinely observed. Neither the previously known variants within the TNF-alpha promoter at position -308 and -238, nor two newly identified polymorphisms at position -376 and -163, were found at a significantly higher frequency in Caucasian NIDDM patients compared to non-diabetic controls. No genetic variants were found in Pima Indians. These data make it unlikely that mutations within regulatory elements of the TNF-alpha gene are associated with an increase in the prevalence of NIDDM.