Role of opioid tone in the pathophysiology of hyperinsulinemia and insulin resistance in polycystic ovarian disease

Hypothetical physiological and molecular basis for the effect of acupuncture in the treatment of polycystic ovary syndrome

Clinical and experimental evidence indicates that acupuncture may be a safe alternative or complement in the treatment of endocrine and reproductive function in women with polycystic ovary syndrome (PCOS). This review describes potential etiological factors of PCOS with the aim to support potential mechanism of action of acupuncture to relieve PCOS related symptoms. The theory that increased sympathetic activity contributes to the development and maintenance of PCOS is presented, and that the effects of acupuncture are, at least in part, mediated by modulation of sympathetic outflow. While there are no relevant randomized controlled studies on the use of acupuncture to treat metabolic abnormalities in women with PCOS, a number of experimental studies indicate that acupuncture may improve metabolic dysfunction. For each aspect of PCOS, it is important to pursue new treatment strategies that have fewer negative side effects than drug treatments, as women with PCOS often require prolonged treatment.

Effects of naltrexone on food intake and body weight gain in olanzapine-treated rats

Blockade of opioidergic neurotransmission contributes to reduction in body weight. However, how such blockade affects body weight gain (BWG) attributed to second generation antipsychotic agents (SGAs) has not yet been established. Here we examined the effects of an opioid receptor antagonist, naltrexone (NTX), on food intake and BWG associated with an SGA, olanzapine (OL). Four groups of Wistar Han IGS rats were treated for 28 days with either OL (2 mg/kg twice daily, intraperitoneal (IP)), a combination of OL (2 mg/kg twice daily, IP) + extended-release NTX (50 mg/kg, one-time, intramuscular (IM)), extended-release NTX (50 mg/kg, one-time, IM) or vehicle and their food intake and body weight were measured daily for the first nine days and every other day thereafter. Food intake and BWG that were increased by OL were decreased by the added NTX while NTX alone had no significant effects on food intake or on BWG. Plasma leptin concentrations were significantly elevated in the three groups receiving pharmacological agents, but did not differ among each other, suggesting that changes in leptin secretion and/or clearance alone would not explain the food intake and the body weight findings. Our results extend prior reports on anorexigenic effects of opioid antagonists by demonstrating that such effects may generalize to food intake increases and BWG arising in the context of OL pharmacotherapy.

Cortisol and the polycystic ovary syndrome

Adrenal steroidogenesis is under the control of the hypothalamic-pituitary-adrenal (HPA) axis. Furthermore, metabolic factors including insulin and obesity-related signals may play a role in the regulation of both enzymes involved in the steroidogenetic pathways, as well as in the regulation of the HPA axis. In women with the polycystic ovary syndrome (PCOS), cortisol production rate is probably normal, although adrenal androgens can be overproduced in a subset of affected women. Cortisol metabolism and regeneration from inactive glucocorticoids can also be disrupted in PCOS, thereby contributing to determining an adrenal hyperandrogenic state. Finally, overactivity of the HPA axis may be related to the high prevalence of psychopathological and eating disorders in women with PCOS, implying a maladaptive allostatic load in the adaptive mechanisms to chronic stress exposure.

The role of opioid system and its interaction with sympathetic nervous system in the processing of polycystic ovary syndrome modeling in rat

BACKGROUND

This study was conducted to evaluate the effect of interaction of sympathetic and opioid systems in the processing of polycystic ovary syndrome modeling in rat.

METHODS

Ninety adult female rats (7-8 weeks of age) were treated with EV for 60 days for induction of follicular cysts (PCO modeling). Clonidine and yohimbine were used for sympathic agonist and antagonist and nalterxone was used for opioid system inhibition. Interactions of two systems were studied.

RESULTS

Our results indicate that both systems and interaction of two systems are effective in processing modeling of PCOS in rat. Interaction of two system drugs decreased estradiol (P < 0.05). Qualitative analysis showed that the bulk of cysts and corpus lutea and dominant follicles were increased in PCO rats in comparison with control group.

CONCLUSION

Therefore there could been an alternative in the treatment of the polycystic ovary syndrome in the rat by using adrenergic agonist and antagonists in combination with naltrexone.

Acupuncture in polycystic ovary syndrome: current experimental and clinical evidence

This review describes the aetiology and pathogenesis of polycystic ovary syndrome (PCOS) and evaluates the use of acupuncture to prevent and reduce symptoms related with PCOS. PCOS is the most common female endocrine disorder and it is strongly associated with hyperandrogenism, ovulatory dysfunction and obesity. PCOS increases the risk for metabolic disturbances such as hyperinsulinaemia and insulin resistance, which can lead to type 2 diabetes, hypertension and an increased likelihood of developing cardiovascular risk factors and impaired mental health later in life. Despite extensive research, little is known about the aetiology of PCOS. The syndrome is associated with peripheral and central factors that influence sympathetic nerve activity. Thus, the sympathetic nervous system may be an important factor in the development and maintenance of PCOS. Many women with PCOS require prolonged treatment. Current pharmacological approaches are effective but have adverse effects. Therefore, nonpharmacological treatment strategies need to be evaluated. Clearly, acupuncture can affect PCOS via modulation of endogenous regulatory systems, including the sympathetic nervous system, the endocrine and the neuroendocrine system. Experimental observations in rat models of steroid-induced polycystic ovaries and clinical data from studies in women with PCOS suggest that acupuncture exert long-lasting beneficial effects on metabolic and endocrine systems and ovulation.

Assessment of insulin sensitivity from measurements in the fasting state and during an oral glucose tolerance test in polycystic ovary syndrome and menopausal patients

BACKGROUND

Polycystic ovary syndrome (PCOS) and menopausal subjects are characterized by an increased cardiovascular and type 2 diabetes mellitus risk, at least partially related to insulin disturbances. The evaluation of insulin resistance in these patients could be useful as primary prevention. The aim of the study was to verify the validity of several indexes of insulin sensitivity in PCOS and menopausal subjects by comparing the data obtained by these indexes to those of euglycemic-hyperinsulinemic clamp studies.

METHODS

One hundred PCOS and 110 menopausal subjects were analyzed; all subjects underwent an oral glucose tolerance test (75 g) and euglycemic-hyperinsulinemic clamp study. Seven PCOS patients and 13 menopausal subjects had impaired glucose tolerance or type 2 diabetes mellitus and were excluded from the study. After analysis of correlation coefficients between the evaluated indexes and the clamp studies, the sensitivity and specificity of different cut-off values for each parameter were analyzed by receiver operating characteristic (ROC) curves.

RESULTS

The best correlation coefficients with clamp studies were obtained with the Avignon insulin sensitivity index (SiM) (R(s) = 0.7812) in PCOS patients and the Matsuda and De Fronzo index (R(s) = 0.6178) in menopausal patients. The best predictive index of insulin resistance in PCOS was a Avignon insulin sensitivity basal index (SibB) value of 62 or less (78% sensitivity, 95% specificity) and an insulin area under the curve (AUC) of 7,000 microIU/ml or more (>/=50,225 pmol/liter) x 120 min (83% sensitivity, 90% specificity). In the menopausal population, the best predictive performance was obtained by an insulin AUC of 10,000 microIU/ml or more (>/=71,750 pmol/liter) x 240 min (70% sensitivity, 88% specificity).

CONCLUSIONS

The presence of high correlation coefficients does not necessarily mean that the indexes of insulin resistance have an optimal predictive performance; this is probably due to the presence of many borderline values. The simple evaluation of insulin AUC seems to effectively replace the euglycemic-hyperinsulinemic clamp in routine clinical practice, allowing results superimposable to those obtained by minimal model analysis.

A role for the endogenous opioid beta-endorphin in energy homeostasis

Proopiomelanocortin (POMC) neurons in the hypothalamus are direct targets of the adipostatic hormone leptin and contribute to energy homeostasis by integrating peripheral and central information. The melanocortin and beta-endorphin neuropeptides are processed from POMC and putatively coreleased at axon terminals. Melanocortins have been shown by a combination of pharmacological and genetic methods to have inhibitory effects on appetite and body weight. In contrast, pharmacological studies have generally indicated that opioids stimulate food intake. Here we report that male mice engineered to selectively lack beta-endorphin, but that retained normal melanocortin signaling, were hyperphagic and obese. Furthermore, beta-endorphin mutant and wild-type mice had identical orexigenic responses to exogenous opioids and identical anorectic responses to the nonselective opioid antagonist naloxone, implicating an alternative endogenous opioid tone to beta-endorphin that physiologically stimulates feeding. These genetic data indicate that beta-endorphin is required for normal regulation of feeding, but, in contrast to earlier reports suggesting opposing actions of beta-endorphin and melanocortins on appetite, our results suggest a more complementary interaction between the endogenously released POMC-derived peptides in the regulation of energy homeostasis.

Effect of the opioid blockade on the feeding-induced growth hormone response to growth hormone-releasing hormone in women with polycystic ovary syndrome

OBJECTIVE

To investigate the effect of naloxone, an opioid receptor antagonist, on the release of growth hormone (GH) induced by the growth hormone-releasing hormone (GHRH) in normal-weight and obese women with PCOS in relation to feeding.

DESIGN

Prospective clinical study.

SETTING

Academic research center.

PATIENT(S)

Seventeen women with PCOS (10 who were normal weight and 7 who were obese) and 14 control women (7 who were normal weight and 7 who were obese).

INTERVENTION(S)

A GHRH test (50 microg i.v.) and, on a different day, a GHRH test during a naloxone infusion (1.6 mg/h) during fasting. The same tests were repeated after a standard meal.

MAIN OUTCOME MEASURE(S)

GH response to GHRH (expressed as the area under the curve [AUC]) in different experimental conditions.

RESULT(S)

All normal-weight women showed a significantly higher AUC-GH compared with obese women in the fasting state. Normal-weight controls had a decrease in GH response to GHRH after feeding, and naloxone did not reverse the decrease. In obese controls, feeding increased the GH response but naloxone induced a decrease in the AUC. In fasting, normal-weight women with PCOS, naloxone significantly decreased the AUC-GH; in these patients, food intake induced an inhibition of GH response to GHRH, reversed by naloxone infusion. In obese PCOS patients, GH levels did not increase significantly after GHRH stimulation, either in the fasting state or after a meal, and naloxone did not affect these responses.

CONCLUSION(S)

Factors other than obesity and insulin may be involved in disruption of GH secretion in women with PCOS.

N-acetyl-cysteine treatment improves insulin sensitivity in women with polycystic ovary syndrome

OBJECTIVE

To evaluate the effect of N-acetyl-cysteine (NAC) on insulin secretion and peripheral insulin resistance in subjects with polycystic ovary syndrome (PCOS).

DESIGN

Prospective data analysis.

SETTING

Volunteer women in an academic research environment.

PATIENT(S)

Six lean and 31 obese subjects, aged 19-33 years.

INTERVENTION(S)

Patients were treated for 5-6 weeks with NAC at a dose of 1.8 g/day orally. A dose of 3 g/day was arbitrarily chosen for massively obese subjects. Six of 31 obese patients with PCOS were treated with placebo and served as controls.

MAIN OUTCOME MEASURE(S)

Before and after the treatment period, the hormonal and lipid blood profile and insulin sensitivity, assessed by an hyperinsulinemic euglycemic clamp, were evaluated and an oral glucose tolerance test (OGTT) was performed.

RESULT(S)

Fasting glucose, fasting insulin, and glucose area under curve (AUC) were unchanged after treatment. Insulin AUC after OGTT was significantly reduced, and the peripheral insulin sensitivity increased after NAC administration, whereas the hepatic insulin extraction was unaffected. The NAC treatment induced a significant fall in T levels and in free androgen index values (P<.05). In analyzing patients according to their insulinemic response to OGTT, normoinsulinemic subjects and placebo-treated patients did not show any modification of the above parameters, whereas a significant improvement was observed in hyperinsulinemic subjects.

CONCLUSION(S)

NAC may be a new treatment for the improvement of insulin circulating levels and insulin sensitivity in hyperinsulinemic patients with polycystic ovary syndrome.

Effect of long-term naltrexone treatment on endocrine profile, clinical features, and insulin sensitivity in obese women with polycystic ovary syndrome

OBJECTIVE

Evaluation of clinical and endocrine effects of naltrexone administration in obese women with PCOS.

DESIGN

Open, controlled, clinical study.

SETTING

Department of Reproductive Medicine and Child Development, Section of Gynecology and Obstetrics, University of Pisa, Pisa, Italy.

PATIENT(S)

Ten PCOS women were studied.

INTERVENTION(S)

Women were treated with naltrexone (50 mg/day) for 6 months.

MAIN OUTCOME MEASURE(S)

Body mass index and the menstrual cyclicity during naltrexone treatment were assessed. Basal levels of LH, FSH, 17beta-estradiol (E(2)), 17-hydroxyprogesterone, total and free T, androstenedione, dehydroepiandrosterone sulfate, cortisol, sex hormone-binding globulin were evaluated before treatment and every 3 months. Progesterone levels were measured in the luteal phase during the sixth month. Gonadotropin response to GnRH administration (10 microg) and a 75-g oral glucose tolerance test were performed before and every 3 months.

RESULT(S)

Body mass index significantly decreased from 29.94 +/- 1.04 to 26.07 +/- 0.81 during treatment. The menstrual cyclicity improved in 80% of PCOS women: the mean cycle length was 40-360 days before treatment and ranged between 25 and 120 days and 28-120 days after 3 and 6 months of treatment. Plasma levels of free T, androstenedione, dehydroepiandrosterone sulfate, and cortisol significantly decreased. Fasting glucose-to-insulin ratio improved in women with insulin resistance.

CONCLUSION(S)

Naltrexone may have a beneficial effect on the clinical and endocrine-metabolic disturbances of obese PCOS women. Whether these effects are the consequences of weight loss or are due to changes in opioidergic tone is debatable.

Naltrexone effect on pulsatile GnRH therapy for ovulation induction in polycystic ovary syndrome: a pilot prospective study

The aim of the present study was to analyze the opioid influence on LH pulsatility in polycystic ovary syndrome (PCOS) patients and to evaluate the effectiveness of a long-term opioid antagonist (naltrexone) treatment in improving the pulsatile GnRH therapy which is successful in this syndrome. Ten obese women affected by PCOS participated in the study. Patients were hospitalized during the early follicular phase and underwent an oral glucose tolerance test (OGTT) with 75 g of glucose and a pulse pattern study followed by a GnRH test (100 pg i.v.). All patients were then treated for ovulation induction with pulsatile administration of GnRH (5 microg/bolus every 90 min). Since pregnancies did not occurr in any patient, after spontaneous or progestin-induced menstrual cycles, all patients received naltrexone at a dose of 50 mg/day orally for 8 weeks and during treatment repeated the basal protocol study and the ovulation induction cycle with the same modalities. The naltrexone treatment significantly reduced the insulin response to OGTT and the LH response to GnRH bolus, whereas it did not affect the FSH and LH pulsatility patterns. Concerning the ovulation induction by pulsatile GnRH, naltrexone treatment was able to improve, although not significantly, the ovulation rate (60% pre-treatment vs 90% post-treatment). Furthermore, the maximum diameter of the dominant follicle and the pre-ovulatory estradiol concentration were higher after long-term opioid blockade (follicular diameter 19.5+/-1.76 mm pre-treatment vs 21.6+/-2.19 mm post-treatment, p<0.001; maximum estradiol level 728.7+/-288.5 pmol/l pre-treatment vs 986.4+/-382.1 pmol/l post-treatment, p<0.05). During the naltrexone-pulsatile GnRH co-treatment two pregnancies occurred. In conclusion, our data show that naltrexone-pulsatile GnRH co-treatment is able to improve the ovarian responsiveness to ovulation induction in obese PCOS patients when compared to pulsatile GnRH alone. This action seems to be related to a decrease of insulin secretion. Further randomized studies should be performed in order to obtain significant conclusions on the possible clinical application.

Insulin and polycystic ovary syndrome: a new look at an old subject

In recent years the metabolic implications of polycystic ovary syndrome (PCOS) have received a great deal of attention; in fact 50% of women with PCOS are obese and a similar percentage of subjects was found to show exaggerated insulin secretion and reduced insulin-stimulated glucose uptake. The presence of these features in women with PCOS has profound clinical implications in terms of morbidity due to diabetes mellitus, dyslipidemia, hypertension and cardiovascular disease. Moreover, hyperinsulinemia has recently been proposed as a possible independent risk factor for endometrial and breast cancer. In the light of these considerations, the importance of metabolic screening in patients with PCOS in order to improve their quality of life cannot be underestimated. In this review we analyze all the clinical pathologies in which hyperinsulinemia of PCOS could be involved. Furthermore, in order to clarify the possible mechanisms leading to the insulin disorders of the syndrome, we review the available data about the insulin receptor abnormalities, as well as those concerning the insulin resistance and the exaggerated insulin secretion. Finally, we examine the main therapeutic strategies to ameliorate the insulinemic status of PCOS patients in order to potentially be able to prevent the long-term consequences of this syndrome.