Gonadal effects on food intake and adiposity: a metabolic hypothesis

Management of anorexic patients in radiotherapy: a prospective randomized comparison of megestrol and prednisolone

Megestrol acetate and corticosteroid have been demonstrated to be effective in the treatment of anorexia in patients with advanced cancer. The purpose of this preliminary study is to evaluate the role of megestrol acetate and prednisolone in the treatment of anorexia induced during whole pelvis external irradiation. Fifty-two patients were randomized in this prospective study to either receive megestrol acetate (40 mg orally four times a day), prednisolone (10 mg orally three times a day), or placebo (1 tablet orally three times a day) for 21 consecutive days. Body weight, appetite, performance status, sense of well-being, and complications were assessed every 3 days. Both the megestrol acetate group and the prednisolone group showed improvement in body weight gain, appetite, performance status, and sense of well-being. Appetite improvement was statistically significant in the megestrol acetate group (P = 0.024) when compared with the placebo group. There were no complications during the 21-day trial.

Antagonism of estrogenic effects on feeding behavior by central implants of anisomycin

The following experiment determined whether the estrogenic suppression of food intake is dependent upon changes in protein synthesis within neurons of the paraventricular nucleus of the hypothalamus (PVN). Ovariectomized rats were treated centrally with anisomycin-filled or empty (control) cannulae in the PVN. Females were injected with either 2.0 micrograms of estradiol benzoate (EB) or the oil vehicle and the inner cannulae were removed 2 h later. EB injections significantly lowered food and water intake in the central control group but not in animals given PVN implants of anisomycin. Body weight gain decreased for all females. EB induced comparable levels of female sexual behavior in both groups, demonstrating that anisomycin implants did not affect the ability of estradiol to stimulate lordosis. These findings indicate that the effects of estradiol on food intake require the activation of protein synthesis in estrogen-sensitive PVN neurons.

Threshold photoperiods for the induction of short day traits in collared lemmings (Dicrostonyx groenlandicus)

When exposed to short photoperiod collared lemmings undergo a number of physiological and morphological changes including an increase in body weight, a change in body composition, development and enlargement of the bifid "digging" claw, and a molt to a white winter pelage. We investigated the threshold photoperiods for the induction of these traits in male and female lemmings born and raised under a 22L:2D photoperiod and transferred at weaning (19 days of age) to various other photoperiods. Male lemmings showed the characteristic increase in body weight when exposed to 16 hr of light or less per day whereas females required a photoperiod of 14 hr of light or less per day to elicit an increase in body weight. The threshold photoperiods for the increase in bifid claw size were 16 and 18 hr of light per day in male and female lemmings, respectively. The molt to the white winter pelage began under a longer photoperiod in females (16L:8D) than in males (14L:10D). Testes and seminal vesicles were significantly inhibited by photoperiods of 22L:2D and 20L:4D. Likewise, uterine weights were inhibited by maintenance on a photoperiod of 22L:2D. Taken together, these data show that the threshold photoperiods for the induction of the short day traits in collared lemmings are both trait- and sex-dependent. These observations also suggest that under some conditions, exposure to long photoperiods can inhibit sexual maturation.

Effects of castration, estrogen replacement and estrus cycle on monoamine metabolism in the nucleus accumbens, measured by microdialysis

Changes in monoamine concentration in the nucleus accumbens were measured by microdialysis during the estrus cycle of intact females rats as well as untreated ovariectomized rats and ovariectomized rats treated with estrogen and progesterone. Norepinephrine (NE), 3-methoxy-4-hydroxyphenylglycol (MHPG) dopamine (DA), 3,4-dihydroxyphenylacetic acid, (DOPAC), serotonin (5-HT) and 5-hydroxy-3-indoleacetic acid (5-HIAA) were measured by high performance liquid chromatography. The ratio of MHPG to NE and DOPAC to DA were significantly increased during proestrus when compared to other phases of the estrus cycle. The ratio of 5-HIAA:5-HT, however, was significantly reduced during proestrus. Treatment of ovariectomized rats with estradiol at either 1 microgram/day or 10 micrograms/day significantly increased the ratio of MHPG:NE and DOPAC:DA. In contrast, the ratio of 5-HIAA:5-HT decreased significantly. Progesterone had no significant effect on the concentrations of 5-HT or 5-HIAA, but attenuated the effect of estrogen on the ratio of MHPG:NE and similarly reduced the ratio of DOPAC:DA. These studies are consistent with the hypothesis that estrogens are associated with enhanced metabolism of NE and decreased metabolism of 5-HT and dopamine in the nucleus accumbens of freely moving rats.

Ovariectomy increases the level of estrogen receptor mRNA and estrogen receptor binding sites in female rat adipose tissue

The roles of estrogen in the changes in estrogen receptor (ER) mRNA and ER binding sites in rat adipose tissue were studied in female rats. To elucidate the mechanism(s) behind ovariectomy (OVX)-induced obesity, the levels of ER mRNA and ER binding sites in adipose tissue were analyzed three weeks after OVX using Northern blot analysis of ER mRNA and the [3H]E2 binding assay, respectively. OVX induced an increase in body weight, and replacement of estradiol (E2) prevented that increase. Significant increases in the amounts of ER mRNA and in [3H]E2-specific binding were observed after OVX, and E2 replacement reduced both of those increases. These results suggest that E2 may regulate rat obesity directly through ER in adipose tissues.

Involvement of epidermal growth factor in inducing obesity in ovariectomized mice

Ovariectomy (Ovx) of mice significantly increases the epidermal growth factor (EGF) concentration in the submandibular gland. To elucidate the role of this elevated EGF in obesity of Ovx mice, we examined the effects of sialoadenectomy (Sx) and anti-EGF rabbit antiserum administration on the body weight (BW) gain and carcass fat deposition in Ovx animals. Studies were performed in four groups of mice consisting of control, Ovx, Ovx+Sx, and Ovx+anti-EGF groups. Ovx increased the BW gain compared with the control animals, whereas Sx and anti-EGF significantly reduced it. Although the relative weights (weight ratio to BW) of the liver and kidney were not significantly changed by Ovx, Sx, or anti-EGF treatment of Ovx mice, the relative weights of mesenteric, parametrial, and subcutaneous fat tissues were increased in Ovx mice, and this increase was significantly reduced by Sx or anti-EGF administration. Ovx induced adipocyte hypertrophy, and this effect was eliminated by Sx and anti-EGF. Moreover, acyl-CoA synthetase mRNA level was increased by Ovx, and this increase was reduced by Sx and anti-EGF in mesenteric fat tissue. These findings suggest that elevation of EGF may play a role in the induction of obesity in Ovx mice.

Exercise is not an effective weight loss modality in women

The excess caloric expenditure which results from physical activity should lead to weight loss if caloric expenditure at other times remains constant. Unfortunately, while there is good evidence for such an effect in men, there is little if any evidence for a similar effect in women. Weight loss with exercise does not readily occur in women unless accompanied by caloric restriction. Further, the role of exercise in maintaining resting metabolic rate while dieting has only marginal support. Potential reasons for the ineffectiveness of exercise in inducing weight loss in women include smaller body size and lower aerobic capacity, under-reporting of caloric intake, differences in body fat distribution and sensitivity to catecholamines, a different gonadal hormone milieu, and energy conservation resulting from evolutionary pressures. Nevertheless, regular exercise in women has many beneficial effects on lipids, glucose homeostasis and bone metabolism even if weight loss does not occur.

Prostaglandin E2 administered by subcutaneous pellets causes local inflammation and systemic bone loss: a model for inflammation-induced bone disease

The effects of prostaglandin E2 (PGE2) given in controlled-release pellets or by daily sc injection for 21 days on mineral homeostasis and bone histomorphometry were compared in 7-week-old female rats. Sham operation and ovariectomy were performed at the beginning of the studies. In experiment 1, 7.5 mg PGE2 or drug-free, controlled-release pellets were implanted sc at the back of the neck on day 7. In experiment 2, 3 mg/kg body weight of PGE2 or vehicle was injected sc daily beginning on day 7. The animals were sacrificed on day 28 of the two experiments, and the tibiae were removed for histomorphometric analysis of the diaphysis and metaphysis. When administered by pellets in experiment 1, PGE2 lowered serum 1,25-dihydroxyvitamin D and did not influence weight gain, serum calcium, phosphorus, or magnesium, cross-sectional or medullary areas, periosteal bone formation and apposition rates, endosteal bone formation and apposition rates, or endosteal tetracycline-labeled perimeter. PGE2 lowered cancellous bone area and cancellous bone perimeter in both the sham-operated and ovariectomized rats. In contrast, when administered by sc injection in experiment 2, PGE2 reduced weight gain, increased serum magnesium, increased cortical area, and reduced medullary area without changing cross-sectional area, increased periosteal bone formation and apposition rates and endosteal bone and apposition rates, did not alter endosteal tetracycline-labeled perimeter, and increased cancellous bone area and cancellous bone perimeter in both sham-operated and ovariectomized animals. PGE2 produced local inflammation when given by pellets, and the serum concentration of 13,14-dihydro-15-ketoprostaglandin E2, the major metabolite of PGE2, increased when PGE2 was given by sc injection but not when administered by pellets. Thus, PGE2 given sc by controlled-release pellets (1) produces local inflammation and systemic bone loss without increasing PGE2 systemically and (2) provides a model for inflammation-induced loss of cancellous bone. The results also indicate that the pellet is not a valid means for the delivery of PGE2 to the general circulation.

Treatment with alpha-helical-CRF(9-41) prevents the anorectic effect of 17-beta-estradiol

The role of corticotropin-releasing factor (CRF) in the anorexia induced by 17-beta-estradiol (E2) has been assessed in castrated female rats that were trained to eat their daily food ration in three separate meals. Each rat was implanted with a permanent guide cannula that was aimed at the right lateral ventricle of the brain. Seven days after the brain surgery each rat was also subcutaneously implanted with an osmotic minipump containing Buserelin, a potent GnRH agonist that induces reversible castration in rats. Eight rats were used in the study, and each of them underwent four experimental treatments that consisted of a) a subcutaneous (SC) injection of oil combined with an intracerebroventricular (ICV) infusion of saline, b) a SC injection of E2 combined with an ICV infusion of saline c) a SC injection of oil combined with an ICV infusion of alpha-helical CRF(9-41), and d) a SC injection of E2 combined with an ICV injection of alpha-helical CRF(9-41). Subcutaneous injections of E2 or oil were carried out the day before the ICV infusions of alpha-helical CRF(9-41) or saline. Intracerebroventricular infusions were performed 30 min before the meal for which the interaction effect of E2 and alpha-helical CRF(9-41) on food intake was determined. E2 and alpha-helical CRF(9-41) interacted on food intake; E2 brought about a 33% reduction in food intake in rats when infused with saline, whereas it was without effect when infused with alpha-helical-CRF(9-41)-treated rats. The present results provide evidence that CRF is involved in the anorectic effect of E2.

Nutrition in advanced cancer: anorexia as an outcome variable and target of therapy

The endpoints used as outcome variables in clinical cancer treatment trials, including nutrition intervention studies, should contain items that are meaningful to the patient. Variables to consider are appetite, food intake, physical performance, psychological and social functioning, response to cancer therapies, survival time, nutrition status, associated morbidity, and costs. Ideally, the design and conduct of nutrition trials should be carried out by a multidisciplinary team comprising medical oncologists, physician specialists in nutrition, dietitians, and social scientists. Anorexia has not been a focus of nutrition support trials in the past partly because of the lack of effective strategies to reverse it. Anorexia is one important cause of cancer starvation, and it also causes patient discomfort. This paper describes outcome variables that include patient derived subjective factors such as anorexia, and outlines new strategies to reverse anorexia. Pharmacologic strategies tested to reverse anorexia include corticosteroids, anabolic steroids, cyproheptadine, hydrazine sulfate, cannabinoids, and megestrol acetate. Of these, only the latter has been consistently well tolerated and effective, with significant improvements in appetite and food intake demonstrated in large-scale, randomized, controlled trials involving more than 600 cancer patients. Dose-response studies have demonstrated increasing efficacy with increasing doses of megestrol acetate from 160 to 800 mg/day. Doses in excess of 800 mg/day are not currently recommended. The mechanisms of action of megestrol acetate involve both behavioral and metabolic effects, and its impact on energy expenditure, appetite, body composition, endocrine function, and lipid metabolism is the subject of ongoing research.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous display of sexual and ingestive behaviour by rats

Intraoral infusion of sucrose activates consummatory ingestive behaviour in rats selectively, i.e. the rat only emits the responses used to ingest food. Activation of consummatory ingestive behaviour in this way had no effect on the subsequent display of sexual behaviour by male or female rats and vice versa. Rats infused intraorally with sucrose and presented with a sexual partner showed ingestive and sexual behaviour simultaneously. Pretreatment with cholecystokinin octapeptide inhibited the ingestion of sucrose in both males and females but had no effect on the simultaneous display of sexual behaviour. Ingestion of sucrose from a drinking spout, a test in which the rat has to emit responses to obtain food, i.e. show appetitive ingestive behaviour, was inhibited by the presentation of a sexual partner in rats of both sexes. These results show that the mechanisms controlling consummatory sexual and ingestive behaviour operate independently and that the presentation of a sexual partner inhibits appetitive ingestive behaviour. Daily intraoral infusion of sucrose reduced pellet intake in ovariectomized rats while the rats maintained their body weight. Implantation of an oestradiol-filled implant reduced body weight and inhibited daily intake of pellets but had no effect on the intake of intraorally administered sucrose. Subsequent removal of the oestradiol implant increased sucrose intake and body weight but did not have a marked effect on pellet intake. Thus, rats respond to a lowering of the set point for body weight by decreasing their intake of the least preferable kind of food and increase their intake of the most preferable kind of food in response to an elevation of the set point for body weight. Ovariectomized rats infused intraorally once daily with a highly nutritive milk diet in the absence of food pellets ingested very large amounts and reduced their intake in response to oestradiol implantation. Thus, although oestradiol can inhibit consummatory ingestive behaviour, its suppressive effect on ingestion cannot be described in terms of selective effects on appetitive and/or consummatory aspects of the behaviour nor in terms of an alteration in the preference for a sweet solution. Inhibition of ingestive behaviour occurred within 24 h after oestrogen treatment as opposed to stimulation of sexual behaviour which had a longer latency, suggesting that oestradiol affects ingestive and sexual behaviour via different mechanisms. While the mechanisms controlling consummatory ingestive and sexual behaviour must be different, there is evidence for a common mechanism mediating the incentive motivation and reward aspects of these behaviours. The mechanisms which enable rats to select between two, possibly equally rewarding courses of action, i.e. display of sexual or ingestive responses, however, are unknown.

Effects of testosterone and estrogen on hepatic levels of cytochromes P450 2C7 and P450 2C11 in the rat

The effects of exogenous hormone treatment on the expression of cytochromes P450 2C7 and P450 2C11 were studied in neonatally gonadectomized and sham-operated male and female rats. Hepatic levels of cytochrome P450 2C7 were found to be two- to threefold higher in intact adult female versus male rats. Neonatal gonadectomy resulted in a reversal of the relative cytochrome P450 2C7 levels in male and female animals at maturity. Expression of this isozyme was restored in ovariectomized females by estradiol treatment. Furthermore, neonatal and/or pubertal administration of estradiol to intact male rats induced cytochrome P450 2C7 to adult female levels. On the other hand, administration of testosterone at all times examined had no effect in intact female rats, but decreased cytochrome P450 2C7 to normal levels in neonatally castrated males treated during adulthood. Neonatal testosterone treatment also increased hepatic cytochrome P450 2C7 content in both ovariectomized females and intact males. These results indicate that estrogen is required for full expression of cytochrome P450 2C7 while the effect of testosterone is ambiguous. In comparison, neonatal gonadectomy of male rats abolished the adult expression of cytochrome P450 2C11. Normal levels were restored only by treatment with testosterone during adulthood. Neonatal testosterone treatment did not induce cytochrome P450 2C11 levels in gonadectomized rats of either sex. In contrast, neonatal estrogen treatment suppressed cytochrome P450 2C11 expression in intact adult male rats to the same extent as neonatal castration. These results indicate that androgen exposure during the adult, and not the neonatal, phase is essential for full expression of cytochrome P450 2C11.

Metabolic fuels and reproduction in female mammals

A complete reproductive cycle of ovulation, conception, pregnancy, and lactation is one of the most energetically expensive activities that a female mammal can undertake. A reproductive attempt at a time when calories are not sufficiently available can result in a reduced return on the maternal energetic investment or even in the death of the mother and her offspring. Numerous physiological and behavioral mechanisms link reproduction and energy metabolism. Reproductive attempts may be interrupted or deferred when food is scarce or when other physiological processes, such as thermoregulation or fattening, make extraordinary energetic demands. Food deprivation suppresses both ovulation and estrous behavior. The neural mechanisms controlling pulsatile release of gonadotropin-releasing hormone (GnRH) and, consequently, luteinizing hormone secretion and ovarian function appear to respond to minute-to-minute changes in the availability of metabolic fuels. It is not clear whether GnRH-secreting neurons are able to detect the availability of metabolic fuels directly or whether this information is relayed from detectors elsewhere in the brain. Although pregnancy is less affected by fuel availability, both lactational performance and maternal behaviors are highly responsive to the energy supply. When a reproductive attempt is made, changes in hormone secretion have dramatic effects on the partitioning and utilization of metabolic fuels. During ovulatory cycles and pregnancy, the ovarian steroids, estradiol and progesterone, induce coordinated changes in the procurement, ingestion, metabolism, storage, and expenditure of metabolic fuels. Estradiol can act in the brain to alter regulatory behaviors, such as food intake and voluntary exercise, as well as adenohypophyseal and autonomic outputs. At the same time, ovarian hormones act on peripheral tissues such as adipose tissue, muscle, and liver to influence the metabolism, partitioning and storage of metabolic fuels. During lactation, the peptide hormones, prolactin and growth hormone, rather than estradiol and progesterone, are the principal hormones controlling partitioning and utilization of metabolic fuels. The interactions between metabolic fuels and reproduction are reciprocal, redundant, and ubiquitous; both behaviors and physiological processes play vital roles. Although there are species differences in the particular physiological and behavioral mechanisms mediating nutrition-reproduction interactions, two findings are consistent across species: 1) Reproductive physiology and behaviors are sensitive to the availability of oxidizable metabolic fuels. 2) When reproductive attempts are made, ovarian hormones play a major role in the changes in ingestion, partitioning, and utilization of metabolic fuels.

Effects of PVN lesions on the responsiveness of female rats to estradiol

Previous research has shown that the paraventricular nucleus of the hypothalamus (PVN) is an important site of action for the effects of estradiol on feeding behavior. The recent finding that estrogenic stimulation of the PVN lowers food intake without inducing lordosis suggests that the effects of estradiol on feeding and sexual behaviors are organized separately within the brain. Whether the effects of estradiol on food intake can be attenuated by PVN lesions is therefore a question of practical and theoretical interest. In this experiment we examined the behavioral responsiveness of females with PVN lesions to peripheral treatment with estradiol. 32 adult, female rats received either bilateral or sham lesions of the PVN. All subjects were ovariectomized 2 weeks after the lesion. 2 Weeks following ovariectomy, half of the animals were injected with 2 micrograms of estradiol benzoate (EB) for 3 days, and half were injected with the oil vehicle. 10 days later, the treatment conditions for each subject (oil or EB) were reversed. Histological analysis indicated that 9 females had bilateral lesions of the PVN and 4 had bilateral lesions of the dorsomedial nucleus of the hypothalamus (DMN); 11 animals received sham lesions. Compared with oil treatment, EB injections significantly lowered water intake and body weight gain in all groups. However, food intake was suppressed in the DMN and sham but not in PVN-lesioned females. In addition, statistical analyses indicated that EB treatment induced similar levels of female sexual behavior in all groups. Thus, PVN lesions did not interfere with the ability of estradiol to stimulate lordosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Testosterone and avian life histories: the effect of experimentally elevated testosterone on corticosterone and body mass in dark-eyed juncos

To assess whether alterations in the normal pattern of testosterone (T) secretion might be beneficial or detrimental, we studied a breeding population of dark-eyed juncos in which we elevated T experimentally and measured its effect on potential correlates of fitness. We treated both free-living and captive males with implants that were either empty (C-males, controls) or packed with T (T-males, experimentals). Timing of implant varied and was designed to mimic natural peak breeding levels except that peaks were either prolonged or premature. We bled the birds at recapture and analyzed their plasma, and that of their female mates, for T and corticosterone (B). We also measured body mass and fat score in free-living T- and C-males. In the field, T-implants elevated T and kept it elevated for at least a month. Experimental males also had higher B than controls. In captives, the effect of the implants on plasma T was detectable within 24 hr. B in captive T-males was again higher than in captive C-males. In females, neither T nor B differed between mates of T- and C-males. T-males implanted in early spring lost more mass between implant and recapture in late spring than did controls and also had lower fat scores when recaptured. When implants were inserted in summer, treatment did not influence mass. Elevated T in early spring apparently hastened the transition from the winter to the breeding mode of fat storage. We suggest that prolonged elevation of testosterone might be selected against because of the association between T and B. Premature elevation of T might be costly because of the resultant loss of mass and fat reserves, which could lead to mortality when spring snowstorms prevent access to food.

Serotonin-depleting midbrain lesions do not prevent ovariectomy-induced weight gain

Past research has shown that subdiaphragmatic vagotomy and midbrain raphe lesions are each effective in impeding the development of hypothalamic obesity while neither affects the development of genetic obesity in Zucker rats. To further test the parallels that may exist between these two manipulations on another putative obesity model, we studied the effects of midbrain raphe lesions on the development of ovariectomy-induced weight gain, previously shown to be unaffected by vagotomy. Ten adult female rats received thermal lesions of the dorsal and median raphe nuclei (RAPHE) while 7 served as sham controls (SHAM). Following a 26-day recovery period during which body weight, food intake and water intake were periodically monitored, bilateral ovariectomy (OVX) was performed on 7 RAPHEs and 4 SHAMs, with laparotomy (LAP) being performed on 3 RAPHEs and 3 SHAMs. Body weights and intake variables were monitored for an additional 58 days, then animals were sacrificed for brain histological and biochemical assessments. RAPHEs weighed less despite eating and drinking more than SHAMs throughout this study. Nevertheless, OVX rats gained more weight regardless of lesion (mean +/- SEM weight gain = 73.9 +/- 5.5 g for RAPHE + OVX and 67.0 +/- 6.6 g for SHAM + OVX vs. 30.7 +/- 3.0 g for RAPHE + LAP and 39.7 +/- 5.5 g for SHAM + LAP). This occurred without reliable changes in the food or water intakes of either OVX subgroup. Histology confirmed that RAPHE lesions were largely localized to the dorsal and median raphe nuclei, as planned.(ABSTRACT TRUNCATED AT 250 WORDS)

The relative contribution of androgens and insulin in determining abdominal body fat distribution in premenopausal women

To investigate the relative contribution of insulin and sex hormones in determining the abdominal pattern of fat distribution in premenopausal women, five groups of age-matched subjects were examined: Group 1 consisted of 14 normal weight eumenorrheic women (NO); Group 2 of 9 obese eumenorrheic women (OB); Group 3 of 14 normal weight hyperandrogenic women with polycystic ovary syndrome (NO-HA); Group 4 of 10 obese hyperandrogenic women with polycystic ovary syndrome (OB-HA) and, finally, Group 5 of 10 obese hyperandrogenic women with polycystic ovary syndrome and acanthosis nigricans (OB-HA-AN). Both the two normal weight groups and the three obese groups were matched for body mass index values. Sex hormone pattern showed significantly higher LH and testosterone levels in hyperandrogenic women with respect to NO and OB women but obese hyperandrogenic groups (OB-HA and OB-HA-AN) presented significantly lower LH concentrations than NO-HA. Fasting and glucose-stimulated insulin levels were significantly higher in OB than NO, in OB-HA and OB-HA-AN than in OB and NO-HA, and in OB-HA-AN than in OB-HA, without any significant difference between OB and NO-HA. Body fat distribution, expressed by the waist to hip ratio (WHR), showed progressively higher values (p less than 0.01) from NO to OB, NO-HA, OB-HA and, particularly, OB-HA-AN women. Determination coefficients r2 obtained from simple regression analysis showed that the sum of insulin values during the glucose tolerance test and testosterone levels had a more significant power in determining WHR variability.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of ovarian steroids on energy balance in rats fed a highly palatable diet

The effects of progesterone and estradiol on body weight, energy intake, energy expenditure, body composition, and brown adipose tissue activity were investigated in female rats fed a highly palatable diet (association of chow and full milk with sugar), which, by itself, induced an increase in food intake and energy expenditure. Progesterone and estradiol were administered in the form of implants. Ovariectomized animals were used in the estradiol studies. Energy expenditure was assessed through oxygen consumption, body composition through carcass analysis, brown adipose tissue activity through measurements of uncoupling-protein, guanosine diphosphate (GDP) binding capacity, and assay of uncoupling-protein mRNA. Body weight and food intake were increased by progesterone and decreased by estradiol. Energy expenditure was not altered by progesterone. Indirect evidence showed that estradiol increased energy expenditure, but direct measurements showed no modification. Changes in body weight under progesterone or under estradiol were not due to brown adipose tissue activity. The results indicate that ovarian hormones act on energy balance mainly by altering food intake, and possibly in the case of estradiol by increasing energy expenditure. These effects persist in rats fed a highly palatable diet, despite increases in energy intake and expenditure induced by the diet alone.

Involvement of Cholecystokinin in Food Intake: III. Oestradiol Potentiates the Inhibitory Effect of Cholecystokinin Octapeptide on Food Intake in Ovariectomized Rats

Abstract The role of Cholecystokinin in a model of hypophagia, oestradiol-treated Ovariectomized rats, was investigated. Implantation of oestradiol-filled constant-release implants in rats made obese by ovariectomy potentiated the inhibitory effect of intraperitoneal injection of Cholecystokinin octapeptide on food intake after 24 h of food deprivation. The alterations in the concentration of Cholecystokinin in pjasma and of cholecystokinin-like immunoreactivity in cerebrospinal fluid produced by deprivation of food for 24 h and subsequent food intake for 1 h were unaffected by the oestradiol treatment as was the amount of food consumed during 1 h. Oestradiol-treated rats deprived of food for 6 h, however, consumed less food during a 15-min test than controls. Treatment with oestradiol blunted the decrease in the concentration of cholecystokinin-like immunoreactivity in the cerebrospinal fluid in response to 6 h of food deprivation. No alterations in the concentration of Cholecystokinin in plasma occurred after this period of food deprivation and subsequent feeding during 15 min in either oestradiol-treated or control rats. Thus, treatment with oestradiol enhances responsivity to exogenous Cholecystokinin octapeptide and changes the response of endogenous levels of cholecystokinin-like immunoreactivity in the cerebrospinal fluid to a short period of food deprivation. It is suggested that these effects are caused by an action of oestradiol on Cholecystokinin pathways in the brain. The results support the suggestion that hunger in the rat is inversely related to the decrease in the concentration of cholecystokinin-like immunoreactivity in the cerebrospinal fluid.

Relationship between the concentration of cholecystokinin-like immunoreactivity in plasma and food intake in male rats

In food-deprived male rats IP injection of cholecystokinin octapeptide (CCK-8, 5 micrograms), ingestion of food or ejaculation caused a comparable increase in plasma concentrations of CCK-8 and inhibited food intake. IV injection of 0.1 microgram CCK-8 interrupted ongoing feeding and greatly increased plasma CCK-8 levels. Osmotic minipumps delivering 0.5 micrograms CCK-8/h implanted IP reduced meal size and caused a modest increase in plasma CCK-8 levels. Injection of 5 micrograms CCK-8 IP produced an abrupt but transient increase in plasma CCK-8 concentrations whereas plasma concentrations of CCK-8 increased gradually with feeding. Injection of 5 micrograms CCK-8 IP, but not feeding, caused a marked increase in plasma oxytocin levels. The suppression of feeding, but not the increase in oxytocin, induced by IP CCK-8 was reversed by ICV injection of the CCK antagonist proglumide in a dose (100 micrograms) which failed to affect food intake if injected IP. Deprivation of food decreased and feeding increased the concentration of CCK-like immunoreactivity in the CSF. It is suggested that CCK-8 inhibits feeding in physiological doses by a specific mechanism in which peripheral as well as central neural CCK is involved.

The role of conditioned taste aversion in the suppression of food intake by estradiol

In three experiments, ovariectomized rats were given a familiar or novel diet prior to treatment with a brain-enhanced estradiol-chemical delivery system (E2-CDS, 1 mg/kg). Experiment 1 showed that food intake was suppressed in subjects receiving either diet, but animals given a novel diet initially showed a profound anorexia which eventually recovered to the moderate suppression of animals given the familiar diet. In Experiment 2, rats showed an aversion to a novel diet paired with the E2-CDS in a two-choice preference test given on Day 2 after the injection, indicating that the initial large reduction in intake was mediated by a conditioned taste aversion. However, no aversion was observed seven days after the E2-CDS, suggesting that the residual intake suppression was mediated by unconditioned aversion or appetite suppression. Experiment 3 showed that lengthening the postovariectomy time resulted in a taste aversion that persisted for a longer duration.

Body weight rhythmicity in the unweaned female rat following neonatal estrogen treatment

Male and female rats were weighted daily throughout this study to determine whether neonatal exposure to estrogens influences body weight (BW) patterns, particularly during the period before weaning when vaginal opening (VO) occurs as a consequence of this treatment. Females receiving estradiol benzoate (EB) at the age of 5 days had greater body weight than their controls soon after the treatment and until day 21. Clear 3-day periodic changes of BW, between days 9 and 20, were revealed by the spectral analysis of the results in EB-given females which did not occur in their controls. Changes of BW (at 4-day intervals) were verified in adult control females whereas age-matched EB-treated females did not show such a rhythm. Neither BW gain nor infradian rhythmicity were detected in infantile males after neonatal EB treatment. The results suggest that, as in spontaneous puberty, a relationship between the occurrence of VO and the establishment of the infradian body rhythmicity in the infantile estrogenized female may exist.

Effects of dexamethasone on multiplication and differentiation of rat adipose precursor cells

The effects of dexamethasone (DEX) on adipose precursor cells from rat adipose tissue were studied in primary culture. When added from the beginning of culture in media containing untreated fetal calf serum (SM), serum treated with charcoal to remove steroid hormones (CSM), or serum-free medium (SFM), DEX inhibited cellular growth. Lipoprotein lipase (LPL) as well as glycerophosphate dehydrogenase (GPDH) activities, markers of cellular differentiation, were also inhibited, except in CSM where LPL was stimulated. When added after cellular confluence, however, DEX had opposite effects and now stimulated cellular differentiation. This effect was highly dependent on insulin. These studies demonstrate that DEX affects adipose precursor cells in several ways, depending on the type of culture medium, the time period of exposure, and the presence of insulin.

Effect of gossypol on thyroid hormones in young female rats

The study was designed to examine the effect of gossypol on thyroid function in young female rats. Forty young Sprague-Dawley female rats were randomly assigned to four treatment groups. The dosages of gossypol acetic acid (gossypol) used for this experiment were 1, 5 and 10 mg/kg body weight/day in 0.5 ml potassium phosphate buffer subcutaneously started from day 34 of age for 15 consecutive days. The control group was treated with vehicle alone. Animals were sacrificed 15 days after gossypol treatment. Blood samples and sera were collected and prepared for measurement of thyroid hormones by radioimmunoassay. The levels of free thyroxine (T4), 3,5,3'-triiodothyronine (T3) and 3,3',5'-triiodothyronine (reverse T3, rT3) in control rats at age 49 days averaged 55.90 +/- 7.7, 670 +/- 90, and 71.7 +/- 5.7 pg/ml of serum, respectively. Fifteen days after gossypol treatment at 5 and 10 mg/kg/day, the free T4 levels significantly decreased to 21.96 +/- 2.1 and 11.12 +/- 1.5 pg/ml of serum, the T3 levels significantly decreased to 430 +/- 89, 359 +/- 90 pg/ml of serum and the rT3 levels were significantly decreased to 37.20 +/- 7.3, and 24.20 +/- 6.0 pg/ml of serum, respectively. However, the serum levels of free T4, T3 and rT3 in the 1 mg/kg/day of gossypol-treated animals were not significantly different from the controls. Five to 15 days after initiation of gossypol treatment, both body weight gain and food intake appeared to be significantly reduced at 5 and 10 mg/kg/day of gossypol treatment. This trend continued to the end of the 15-day gossypol treatment. The results provide new evidence that gossypol might have exerted its antithyroid function by an unknown mechanism that triggered an interference in body metabolism, thus causing the loss of food intake and body weight gain in young female animals.

Variations in food preference and consumption across the menstrual cycle

There is some evidence that food consumption changes across the menstrual cycle. However, archived studies tend to rely on self-report data and do not differentiate among types of food eaten. The present laboratory study was designed to measure women's taste preferences and specific food consumption across the menstrual cycle. Women came into the laboratory, consumed everyday foods, and rated them on taste judgment scales. The foods were weighed before and after the tasting session to determine amount eaten. After the tasting session, subjects completed several questionnaires (e.g., measures of affect, restrained eating, menstrual cycle and menstrual symptoms). Physical measurements (e.g., height, weight) were taken at the end of the session. Sweet food consumption and preference ratings were significantly higher during the premenstrual period. Consumption and ratings of other foods did not differ. There were no differences in levels of mood, obesity, or restrained eating across the menstrual cycle. Low restraint was associated with reporting fewer menstrual symptoms, in general, and slightly better mood. These results support the idea that specific taste preferences change over the menstrual cycle, and that endocrinological factors could be involved in this phenomenon.

Endocrine pathology of estrogens: species differences

The clinical uses of estrogens are associated with serious adverse effects, so the experimental toxicology of these compounds is under continuous review. Structurally different estrogens have qualitatively similar effects in animals when given in amounts way above the rodent uterotrophic dose. Toxicity still tends, however, to be related to estrogenic potency. Carnivores are more susceptible than rodents. Changes in reproductive, mammary and endocrine tissues are consistent with hyperestrogenism. Growth rate is decreased in rats and mice, but weight gains have been reported in other species. The weights of the liver, spleen, thymus and other organs are changed. Liver damage can occur. Susceptibility declines in the order cat, ferret, rat and mouse, dog. Clotting changes seen in the rat are secondary to liver damage. Moderate doses elicit anemia in rats, but lethal bone marrow depression in dogs and ferrets. Death is associated with hemorrhage. Antiestrogens modify aspects of estrogen toxicity in the rat, but not in the ferret. The predictive value of animal studies for humans has been disappointing. Interspecies variations at the hypothalamic-pituitary axis appear to have an important bearing on the differential activities of estrogens and antiestrogens across the species.

The significance of decreased ambulatory activity during the generation by long-term observation of obesity in ovariectomized rats

We attempted to determine the significance of ambulatory activity as a cause of overweight in ovariectomized rats. Drinking and ambulation were measured continuously and directly for periods up to 12 months in special apparatus developed at Gunma University. In older rats, ambulatory activity decreased much more in the ovariectomy group than in the control group. There was no difference in food intake between the ovariectomized and the control group. After 2 months, the ovariectomy group increased body weight more than the control group despite no difference in food intake. The decrease in ambulatory activity was consistent in the ovariectomy group, regardless of any differences in age and body weight. These results indicate that decrease of energy expenditure by gradual decrease in ambulatory activity may be an important factor as a cause of overweight in ovariectomized, obese rats.

Differential effects of gonadal function on bone histomorphometry in male and female rats

The effects of castration on bone histomorphometry and mineral homeostasis were compared in male and female rats. Measurements were performed 4 weeks after sham operation or gonadectomy. Orchiectomy produced increases in serum calcium and decreases in serum testosterone and androstenedione, whereas ovariectomy produced decreases in serum estradiol and testosterone. Orchiectomy did not alter static bone histomorphometric measurements of the tibial diaphysis, whereas ovariectomy increased cross-sectional and medullary areas, lowered endosteal tetracycline-labeled surface length, and markedly increased endosteal nonlabeled surface length. Orchiectomy decreased mean periosteal bone formation rate and mean periosteal bone apposition rate, whereas ovariectomy increased both measurements. Orchiectomy and ovariectomy markedly diminished trabecular area and trabecular surface length at the tibial metaphysis. Orchiectomy did not alter the number of osteoclasts per mm trabecular surface or the percentage of trabecular surface covered by osteoclasts, whereas ovariectomy increased both measurements. These findings indicate that gonadal hormones produce separate and distinct effects on bone metabolism as determined by histomorphometry in male and female rats.

Effects of a brain-enhanced chemical delivery system for estradiol on body weight and food intake in intact and ovariectomized rats

Studies were undertaken to determine the effects on body weight of a brain-enhanced chemical delivery system for estradiol. This estradiol-chemical delivery system (E2-CDS) has a long half-life in the brain, where it slowly releases estradiol but is quickly cleared from peripheral tissues. We administered, by a single iv injection, E2-CDS (0.2, 1.0, or 5.0 mg/kg), equimolar doses of another 17-hydroxy-substituted estrogen, estradiol valerate (E2-VAL), or the dimethyl sulfoxide (DMSO) vehicle to female rats. Daily food intake and body weight was determined for 24 days thereafter. E2-CDS caused an initial dose-dependent suppression in body weight for up to 8 days and a suppression in food intake for up to 4 days. In response to E2-VAL, the initial declines in body weight and food intake were lower in magnitude, were shorter in duration, and showed no dose dependency. Following this period of weight loss, E2-CDS-treated rats gained weight at a rate greater than that of the DMSO controls, and at the 0.2- and 1.0-mg/kg doses, body weights achieved were greater than control levels. To determine the role of the ovaries on this biphasic response to E2-CDS, long-term ovariectomized rats were treated with E2-CDS (1.0 mg/kg) or the vehicle and parameters of body weight regulation were determined for 25 days. Ovariectomized rats responded to E2-CDS with a prompt and sustained decrease in body weight which did not recover over the 25-day course of the study. The body-weight loss in ovariectomized rats was associated with a marked reduction in food intake for 8 days.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of the body weight increase induced by systemic sulpiride

Long-term intraperitoneal administration of sulpiride induced body weight increase in female but not in male rats. The hypothesis that systemic sulpiride causes an endocrine unbalance which in turn causes body weight gain and hyperphagia was tested in four experiments. First, it was shown that even when they are on a high-fat diet male rats do not show body weight gain induced by systemic sulpiride. Second, sulpiride suppressed the estrous cycle. Third, gonadectomy prevented the body weight gain induced by systemic sulpiride in female rats. Fourth, estradiol simultaneously administered with sulpiride prevented the expected sulpiride-induced body weight gain. These results are discussed in terms of an hypothetical functional castration produced by systemic sulpiride. The well known hyperprolactinemia, induced by the pituitary D2 dopamine receptor blockade, might bring about an impairment of the steroidogenesis with subsequent decrease in estrogens level, which in turn might be responsible for the hyperphagia and body weight increase induced by systemic injections of sulpiride.

Biology of regional body fat distribution: relationship to non-insulin-dependent diabetes mellitus

Our studies support the view that body fat distribution and the accompanying metabolic abnormalities could be exacerabated by variability in the androgenic/estrogenic balance. Sensitivity to the androgenic milieu might be initiated by an early developmental aberration in sexual dimorphism. The possible direct and indirect sites of interaction between androgenic activity and the abnormal metabolic pathways in upper body obesity are summarized in Figure 19.

Puberty modifies sulpiride effects on body weight in rats

Sulpiride (20 mg/kg, i.p.) for 21 days increased body weight in prepubertal, peripubertal and adult female rats. The increment was higher in the adult group, where a significant hyperphagia was also noted. In males, the same treatment tended to decrease body weight in the peripubertal and adult groups while in the prepubertal animals an increase of body weight without a significant hyperphagia was observed. These results are discussed in terms of an hypothetical sulpiride-induced reduction in serum gonadal steroid levels.

Regional adipocyte precursors in the female rat. Influence of ovarian factors

A flow cytometric immunofluorescence procedure utilizing a specific antibody to rat adipose tissue lipoprotein lipase (LPL) was developed to quantify differentiated and undifferentiated preadipocytes present in the adipose tissue vascular stroma. This method is highly sensitive and specific for cells capable of synthesizing LPL in significant quantities. Pubescence in female rats was associated with an increase in differentiated preadipocytes and in fat cell number with enlargement of the fat depots in the perirenal, parametrial, and the subcutaneous dorsal and femoral regions. A concomitant decline in the percentage of undifferentiated preadipocytes occurred in all but the femoral depot. Ovariectomy reduced pubertal adipose growth in the femoral and parametrial but not the dorsal or perirenal regions. Furthermore, the femoral undifferentiated preadipocyte pool was not preserved in the ovariectomized animals. Thus, ovarian factors influence the pubescence-associated regional preadipocyte differentiation and conversion to adipocytes. The femoral depot contains an ovarian-dependent infinite pool of fat cell precursors. These features could account for the association between ovarian hormones and body fat topography.

Chronic weight loss in lean and obese rats with a brain-enhanced chemical delivery system for estradiol

Studies were undertaken to determine the effects on body weight and food intake of a chemical delivery system which preferentially delivers estradiol (E2) to the brain and there serves as a source for the sustained release of the steroid. We injected intravenously various doses of this estradiol-chemical delivery system (E2-CDS), E2-valerate (E2-VAL) or the dimethyl sulfoxide (DMSO) vehicle to young lean male rats and monitored body weight and 24 hr food intake for 39 days postinjection. E2-VAL caused a transient reduction in food intake and body weight gain. By contrast, a single injection of E2-CDS caused a chronic, dose-dependent reduction in the rate of body weight gain. In these lean rats, the duration of reduced body weight gain was not correlated with the observed transient reduction in food intake. In aged, obese male rats, E2-CDS caused a marked and chronic dose-dependent reduction in body weight. In contrast to lean rats, E2-CDS caused a long-term reduction in food intake in obese rats. To evaluate the importance of the E2-CDS-induced reduction in food intake in the observed persistent weight loss in obese rats, E2-CDS was administered to a group of obese rats and a second group which received the DMSO vehicle was pair-fed an equivalent amount of food daily. The resulting weight loss in both groups was equivalent. These results show that the enhanced delivery of E2 to the brain with the E2-CDS causes sustained reduction in the rate of body weight gain in lean rats and persistent weight loss in obese animals.

Androgens exert opposite effects on body mass of heavy and light meadow voles

The influence of gonadal hormones on body mass of adult male meadow voles varied systematically as a function of the animals' baseline body weight; heavier voles decreased and lighter voles increased their body mass after castration. Testosterone replacement reversed the effects of castration; changes in body mass during hormone treatment were negatively correlated with changes observed after castration. Body mass of intact males was not correlated with plasma testosterone titers. Individual differences in body mass of male voles appear to reflect variations among animals in substrate responsiveness to hormones rather than differences in circulating hormone levels.

Sex steroid hormones and adipose tissue metabolism in ovariectomized and adrenalectomized rats

The effects of oestrogen and progesterone, alone or in combination, on regional adipose tissue metabolism and oestrogen binding were examined in rats which were not only ovariectomized but also adrenalectomized to allow a study under conditions such that no endogenous sex steroid production occurred. Under these conditions no effects on food intake of the sex steroid hormones were found. 17-beta-oestradiol plus progesterone tended to increase lipoprotein lipase in the parametrial but not retroperitoneal fat depot, but no effects were found of oestrogen or progesterone alone. Oestradiol alone or in combination with progesterone clearly increased basal and norepinephrine-stimulated lipolysis, most pronounced in the retroperitoneal depot. Progesterone alone had no effect. Cytoplasmic 17-beta-oestradiol binding was highest in the parametrial fat depot in non-substituted rats and decreased dramatically after oestrogen administration. It was concluded that in ovariectomized-adrenalectomized rats, oestrogen alone or in the presence of progesterone facilitates lipolysis, a clear effect which is thus possible to elicit without adrenal hormones. Both sex steroid hormones alone or in combination, have no or weak effects on food intake and lipoprotein lipase activity, respectively. These metabolic events as well as cytoplasmic oestrogen binding show regional variations.

Genetic association between nest building and brown adipose tissue thermogenesis in female house mice

Mice selectively bred for either high or low levels of thermoregulatory nest building were cold-acclimated (5 degrees C) for 3 weeks without nesting material; then body weight and food intake were measured. The mice selected for low nest building (Lows) of both sexes showed lower feed efficiencies than the high nest-building mice (Highs), although their body weights were not significantly different (Table 1). This adds to a large body of evidence which suggests that nest building and feed efficiency were influenced by a common mechanism (Lacy et al. 1978; Sulzbach and Lynch 1984; Lynch et al. 1981; Lynch and Roberts 1984). Brown adipose tissue mitochondrial GDP binding and cytochrome c oxidase activity were measured in the above mice. In females, the Lows had 100% higher levels of total GDP binding than the Highs, while no difference between the lines was seen in males. Thus in the High females, lower energy expenditure through brown fat thermogenesis may account for their greater feed efficiency. In males, the genetic differences in feed efficiency must be due to differences in either thermogenesis in tissues other than brown fat, or mechanisms which reduce heat loss.

Hyperprolactinemia stimulates food intake in the female rat

Lactation in the rat is marked by extreme hyperphagia. The present study examined the possibility that elevated prolactin levels contribute to this increase. It also evaluated the effects of hyperprolactinemia on brown adipose tissue and carcass composition. Virgin Osborne-Mendel rats were made hyperprolactinemic via ectopic pituitary transplants (PIT, n = 9) or were sham-operated (SHAM, n = 8). Eight lactating rats (LACT) served as additional controls. Food intake, body weight and rectal temperature were recorded daily. Eleven days postsurgery (or 11-12 days postpartum), the rats were sacrificed, and brown fat (scapular, axillary, cervical and thoracic) was excised, weighed, and assayed for GDP binding, one indicator of thermogenic capacity. Carcasses were subjected to body composition analysis. Although prior to surgery, PIT and SHAM rats weighed the same, PIT rats gained significantly more weight during the experiment than did SHAMs. Percent body fat and food intake (both total intake and intake relative to metabolic body size) were significantly elevated in the PIT rats. GDP binding in both PIT and LACT rats was significantly less than in SHAMs. This was true whether GDP binding was expressed per mg mitochondrial protein or per total amount of mitochondrial protein recovered. These data confirm that brown fat thermogenic capacity is suppressed during lactation. They also demonstrate that elevations of serum prolactin, to levels that are well within physiological limits, are capable of stimulating food intake and white fat deposition in the female rat. It is presently unclear whether these results are a direct or an indirect effect of hyperprolactinemia.

Circannual rhythms of ground squirrels: role of the hypothalamic paraventricular nucleus

Female golden-mantled ground squirrels, maintained in an LD 14:10 photoperiod at 23 degrees C, sustained lesions of the paraventricular nucleus (PVN) or sham operations. Body weight and reproductive status were recorded weekly pre- and postoperatively. Bilateral lesions of the PVN did not eliminate, phase-shift, or otherwise disrupt the circannual rhythms of body mass or reproduction. Absolute levels of body weight were unaffected by PVN ablation. The PVN is not an essential component of the oscillatory system that generates circannual cycles in ground squirrels.