Glucocorticoids, stress and obesity

Obesity and the associated metabolic syndrome have been suggested to be the consequence of a maladaptation to chronic stress exposure mediated by a dysregulation of neuroendocrine axes. The hypothalamic-pituitary-adrenal (HPA) axis represents the major hormone system responsible for maintenance of the homeostatic balance in response to stress. The brainstem nuclei and the limbic regions are strongly involved in stressor neural processing and represent a regulatory network for the HPA axis. Moreover, the same neuroendocrine stress centers are involved in the regulation of feeding behavior following acute and chronic stress exposure. Studies performed in experimental animals suggest that consumption of so-called comfort foods, while favoring an adaptation to the detrimental impact of chronic stress on the reward system, may, in turn, lead to the rapid development of obesity. Available data also indicate that the endocannabinoid system modulates the HPA axis and that its type 1 receptors, which are extensively localized in the hypothalamus and in limbic structures, are involved in the regulation of the stress response and the reward mechanisms. Based on extensive clinical experience and studies performed in experimental animals, we developed the concept that there is a specific phenotype of individuals who may become obese as a result of exposure to major stressful events.

CB(1) signaling in forebrain and sympathetic neurons is a key determinant of endocannabinoid actions on energy balance

The endocannabinoid system (ECS) plays a critical role in obesity development. The pharmacological blockade of cannabinoid receptor type 1 (CB(1)) has been shown to reduce body weight and to alleviate obesity-related metabolic disorders. An unsolved question is at which anatomical level CB(1) modulates energy balance and the mechanisms involved in its action. Here, we demonstrate that CB(1) receptors expressed in forebrain and sympathetic neurons play a key role in the pathophysiological development of diet-induced obesity. Conditional mutant mice lacking CB(1) expression in neurons known to control energy balance, but not in nonneuronal peripheral organs, displayed a lean phenotype and resistance to diet-induced obesity. This phenotype results from an increase in lipid oxidation and thermogenesis as a consequence of an enhanced sympathetic tone and a decrease in energy absorption. In conclusion, CB(1) signaling in the forebrain and sympathetic neurons is a key determinant of the ECS control of energy balance.

Body mass index-independent metabolic alterations in narcolepsy with cataplexy

STUDY OBJECTIVES

To contribute to the anthropometric and metabolic phenotyping of orexin-A-deficient narcoleptic patients, and to explore a possible risk of their developing a metabolic syndrome.

DESIGN

We performed a cross-sectional study comparing metabolic alterations in patients with narcolepsy with cataplexy (NC) and patients with idiopathic hypersomnia without long sleep time.

SETTING

University hospital.

PATIENTS

Fourteen patients with narcolepsy with cataplexy and 14 sex and age-matched patients with idiopathic hypersomnia without long sleep time.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

Metabolic parameters were evaluated by measuring body mass index (BMI), waist circumference (also with abdominal computed tomography), blood pressure, and daily calorie intake (3-day diary). Chronotypes were assessed through the morningness-eveningness questionnaire. Lumbar puncture for cerebrospinal fluid orexin-A determination and HLA typing were performed. Patients with narcolepsy with cataplexy (all HLA DQB1*0602 positive and with cerebrospinal fluid orexin-A levels < 110 pg/mL) had a higher BMI and BMI-independent metabolic alterations, namely waist circumference, high-density lipoprotein cholesterol, and glucose/insulin ratio (an insulin resistance index), with respect to patients with idiopathic hypersomnia without long sleep time (cerebrospinal fluid orexin-A levels > 300 pg/mL). Despite lower daily food intake, patients with narcolepsy with cataplexy displayed significant alterations in metabolic parameters resulting in a diagnosis of metabolic syndrome in more than half the cases.

CONCLUSIONS

BMI-independent metabolic alterations and the relative hypophagia of patients with narcolepsy with cataplexy, as compared with patients with idiopathic hypersomnia without long sleep time, suggest that orexin-A influences the etiology of this phenotype. Moreover, considering that these dysmetabolic alterations are present from a young age, a careful metabolic follow-up of patients diagnosed with narcolepsy with cataplexy is mandatory.

Functional effects of polymorphisms in the human gene encoding 11 beta-hydroxysteroid dehydrogenase type 1 (11 beta-HSD1): a sequence variant at the translation start of 11 beta-HSD1 alters enzyme levels

Regeneration of active glucocorticoids within liver and adipose tissue by the enzyme 11 beta-hydroxysteroid dehydrogenase type 1 (11 beta-HSD1) may be of pathophysiological importance in obesity and metabolic syndrome and is a therapeutic target in type 2 diabetes. Polymorphisms in HSD11B1, the gene encoding 11 beta-HSD1, have been associated with metabolic phenotype in humans, including type 2 diabetes and hypertension. Here, we have tested the functional consequences of two single nucleotide polymorphisms located in contexts that potentially affect tissue levels of 11 beta-HSD1. We report no effect of allelic variation at rs846910, a polymorphism within the 5'-flanking region of the gene on HSD11B1 promoter activity in vitro. However, compared with the common G allele, the A allele of rs13306421, a polymorphism located two nucleotides 5' to the translation initiation site, gave higher 11 beta-HSD1 expression and activity in vitro and was translated at higher levels in in vitro translation reactions, possibly associated with a lower frequency of "leaky scanning." These data suggest that this polymorphism may have direct functional consequences on levels of 11 beta-HSD1 enzyme activity in vivo. However, the rs13306421 A sequence variant originally reported in other ethnic groups may be of low prevalence because it was not detected in a population of 600 European Caucasian women.

Prominent role of low HDL-cholesterol in explaining the high prevalence of the metabolic syndrome in polycystic ovary syndrome

BACKGROUND AND AIMS

The main objective was to evaluate the prevalence of the metabolic syndrome in Caucasian women with PCOS, using either of the currently proposed definitions (NCEP/ATPIII, IDF and AHA/NHLBI) and, therefore, to estimate the concordance between these three classifications. Secondary objectives were to evaluate: i) which individual criterion of the metabolic syndrome is most strongly associated with PCOS; and ii) whether the severity of hyperandrogenemia, hyperinsulinemia and insulin resistance may influence the presence of the metabolic syndrome in PCOS women.

METHODS AND RESULTS

The metabolic syndrome was assessed in 200 Caucasian women with PCOS and in 200 Caucasian controls, matched for age and BMI, considering the NCEP/ATPIII, IDF and AHA/NHLBI definitions. PCOS women had an increased prevalence of the metabolic syndrome compared with controls: 32 versus 23% with the NCEP/ATPIII, 39 versus 25% with the IDF and 37 versus 24% with the AHA/NHLBI, respectively (Cohen's Kappa index between the three classifications, P < 0.001). Multivariate logistic regressions revealed that among the individual criteria of the metabolic syndrome, only low HDL-cholesterol levels were significantly associated with PCOS (P < 0.001) which, in turn, are related to insulin(AUC) (P = 0.029) but not to androgens.

CONCLUSION

This case-control study indicates a high prevalence of the metabolic syndrome in Caucasian PCOS women that is independent of the diagnostic classification used. Furthermore, it shows that low HDL-cholesterol is the criterion which best explains the high prevalence of the metabolic syndrome in PCOS subjects which, in turn, is influenced by hyperinsulinemia, rather than by hyperandrogenemia.

Targeting insulin sensitivity in the treatment of polycystic ovary syndrome

Targeting insulin resistance may result in a list of benefits for women with PCOS, including hormonal, metabolic and ovulatory (and fertility) improvements. The therapeutic strategy to treat PCOS should however depend on the clinical situation, the phenotype, the degree of androgen excess, age, the presence of infertility and the woman's desire to conceive, the presence of obesity and, finally, the spectrum of metabolic abnormalities and the need to treat or prevent long-term associated comorbidities. According to the needs, therapeutic options include, alone or in combination, lifestyle management, particularly in the presence of obesity, the use of insulin sensitizers, metformin and thiazolidinediones, antiandrogens or estro-progestins.

Stress-related development of obesity and cortisol in women

Chronic exposure to environmental stress may play a role in the development of obesity, through hyperactivation of the hypothalamic-pituitary-adrenocortical (HPA) axis. This study investigated the dynamics of weight gain and the activity of the HPA axis in women who developed weight gain after a stressful event. This is a case-control retrospective study. Two groups of age-matched premenopausal women were selected. One (n = 14) included women characterized by a rapid weight gain following a stressful event, defined as the "stress-related obesity " (SRO) group, and the other (n = 21) women with nonstress-related development of obesity, defined as the "nonstress-related obesity " (NSRO) group. Twenty-one healthy premenopausal women served as normal-weight controls. Baseline hormonal and metabolic parameters, and 24-h urinary free cortisol (UFC/24 h) excretion rate (as a measure of HPA-axis activity) were measured in all women. Anthropometry, diet, and physical activity were similar in both obese groups. Both obese groups showed similar metabolic and hormonal profiles, but the SRO group had UFC/24 h values (41.1 +/- 14.3 microg) significantly higher (P < 0.001) with respect to the NSRO (26.6 +/- 17.6 microg) or the normal-weight control groups (21.1 +/- 9.8 microg). Moreover, time (years) to achieve maximum Deltaweight gain (kg) and the Deltaweight gain/time ratio were significantly shorter (P < 0.001) and higher (P < 0.001) in the SRO group with respect to the NSRO group, respectively. In the SRO group, there was a tendency to a significant correlation between UFC/24 h and the Deltaweight gain/time ratio. These findings support the concept that SRO has distinct pathophysiological mechanisms, including hyperactivity of the HPA axis.

Increased clearance of cortisol by 5beta-reductase in a subgroup of women with adrenal hyperandrogenism in polycystic ovary syndrome

OBJECTIVE

Increased peripheral metabolism of cortisol may explain compensatory ACTH-dependent adrenal steroidogenesis and hence hyperandrogenism in polycystic ovary syndrome (PCOS). Previous studies have described an increased 5alpha-reduction of cortisol or impaired regeneration of cortisol by 11beta-HSD1 in PCOS. However, these observations may be confounded by obesity. Moreover, the relationship between alterations in cortisol metabolism and the extent of adrenal androgen hyper-secretion in response to ACTH has not been established. This study aimed to examine the association between cortisol metabolism and ACTH-dependent adrenal hyperandrogenism in PCOS, independently of obesity.

DESIGN

We compared 90 PCOS women (age 18-45 yr) stratified by adrenal androgen responses to ACTH1-24 and 45 controls matched for age and body weight.

METHODS

PCOS women were stratified as normal responders (NR), intermediate responders (IR), and high responders (HR) to 250 microg ACTH1-24: NR (no.=27) had androstenedione and DHEA responses within 2 SD of the mean in controls; IR (no.=43) had DHEA responses >2 SD above controls; HR (no.=20) had both androstenedione and DHEA responses >2 SD above controls.

RESULTS

All groups were similar for age, body weight, and body fat distribution. Basal testosterone, androstenedione, and 5alpha-dihydrotestosterone plasma levels were similarly elevated among the 3 groups of PCOS compared with controls, whereas basal DHEA-S was higher in HR (2.8+/-1.2 microg/ml) and IR (2.4+/-1.1 microg/ml) than in NR (1.8+/-0.8 microg/ml) and controls (1.7+/-0.6 microg/ml). The HR group had the lowest basal plasma cortisol levels (101+/-36 ng/ml vs IR 135+/-42 ng/ml, NR 144+/-48 ng/ml, and controls 165+/-48 ng/ml; all p<0.01), but the greatest cortisol response to ACTH1-24 (Delta(60-0)cortisol 173+/-60 ng/ml vs IR 136+/-51 ng/ml, NR 114+/-50 ng/ml, and controls 127+/-50 ng/ml; all p<0.01), and the highest urinary excretion of total and 5beta-reduced cortisol metabolites (eg 5beta-tetrahydrocortisol/ cortisol ratio 25.2+/-15.3 vs IR 18.8+/-10.7, NR 19.7+/-11.4, and controls 17.2+/-13.7; all p<0.05). There were no differences in urinary excretion of 5alpha-reduced cortisol metabolites or in 5alpha-dihydrotestosterone/testosterone ratio between groups.

CONCLUSIONS

Adrenal androgen excess in PCOS is associated with increased inactivation of cortisol by 5beta-reductase that may lower cortisol blood levels and stimulate ACTH-dependent steroidogenesis.

Clomiphene citrate, metformin or both as first-step approach in treating anovulatory infertility in patients with polycystic ovary syndrome (PCOS): a systematic review of head-to-head randomized controlled studies and meta-analysis

BACKGROUND

To date, no systematic review or meta-analysis has been published of direct head-to-head studies comparing clomiphene citrate (CC) vs. metformin, or the combination of both drugs as first-line therapy in anovulatory polycystic ovary syndrome (PCOS) patients seeking pregnancy. The aim of the current paper was to define, if possible, the best evidence-based recommendations regarding the use of CC and/or metformin as the initial treatment of PCOS women with anovulatory infertility.

DESIGN

Systematic review and meta-analysis of the head-to-head randomized controlled trials (RCTs) available in the literature.

METHODS

A bibliographic search was performed using the following bibliographic databases: Medline, EMBASE, Biological Abstracts, Cochrane Controlled Trials Register and Cochrane Database of Systematic Reviews. Reference lists of included studies, other relevant review articles and textbooks were checked for additional citations of interest.

RESULTS

Four head-to-head RCTs were identified and qualified for inclusion in the analysis. No difference in fertility improvement was observed comparing CC with metformin (OR = 1.22, 95% CI 0.23-6.55, P = 0.815), whereas a significant (P < 0.0001) heterogeneity was observed. Homogeneous data showed no difference in fertility improvement between the combination treatment and CC monotherapy (OR = 0.99, 95% CI 0.70-1.40, P = 0.982), but a significant difference in comparison with metformin monotherapy (OR = 0.23, 95% CI 0.14-0.37, P < 0.0001).

CONCLUSIONS

In PCOS patients with anovulatory infertility and not previously treated, the administration of metformin plus CC is not better than monotherapy (metformin alone or CC alone), whereas to date no specific recommendation can be given regarding the use of CC or metformin as first-step drug.

Feeding disorders and obesity

The ability of the endocannabinoid (EC) system to control appetite, food intake and energy balance has recently received great attention, particularly in the light of the different modes of action underlying these functions. The EC system modulates rewarding properties of food by acting at specific mesolimbic areas in the brain. In the hypothalamus, cannabinoid type 1 receptors (CB1) and ECs are integrated components of the networks controlling appetite and food intake. Interestingly, the EC system has recently been shown to control several metabolic functions by acting on peripheral tissues, such as adipocytes, hepatocytes, the skeletal muscles and the endocrine pancreas. The relevance of the system is further strengthened by the notion that visceral obesity seems to be a condition in which an overactivation of the EC system occurs; therefore, drugs interfering with this overactivation by blocking CB1 receptors are considered valuable candidates for the treatment of obesity and related cardiometabolic risk factors.

Monogenic polycystic ovary syndrome due to a mutation in the lamin A/C gene is sensitive to thiazolidinediones but not to metformin

CONTEXT

Despite the very high prevalence of the polycystic ovary syndrome (PCOS), the underlying pathogenetic mechanism has remained obscure.

OBJECTIVE

To determine the cause of two sisters' PCOS associated with severe insulin resistance.

DESIGN

Clinical case report. Methods Two sisters who presented with hyperandrogenism and menstrual disorders in the context of PCOS, and were subsequently found to be severely insulin resistant. Physical examination revealed muscular hypertrophy with a paucity of fat in the extremities, trunk and gluteal regions, in spite of excess fat deposits in the face, neck and dorsocervical region. Known genes involved in familial partial lipodystrophy were screened. At the same time, metformin (1700 mg/day) was commenced. After 2-3 years of uninterrupted therapy, lack of clinical improvement led to the introduction of pioglitazone (30 mg/day).

RESULTS

Both sisters were found to be heterozygous for the R482Q mutation in the lamin A/C gene (LMNA) gene, establishing the definitive diagnosis as Dunnigan-type familial partial lipodystrophy complicated by severe insulin resistance and secondary PCOS. Treatment with pioglitazone resulted in progressive amelioration of insulin resistance, hyperinsulinaemia and hyperandrogenaemia. Menses also improved, with restoration of a eumenorrhoeic pattern, and the framework of ultrasound PCO was in complete remission.

CONCLUSIONS

Assessment of insulin sensitivity and adipose tissue topography should be a key part of the initial evaluation of patients with PCOS. Identifying such forms of PCOS with monogenic insulin resistance as the primary pathogenic abnormality may have practical implications for therapy, since they respond to thiazolidinediones, but not to metformin.

Cannabinoid type 1 receptor blockade promotes mitochondrial biogenesis through endothelial nitric oxide synthase expression in white adipocytes

OBJECTIVE

Cannabinoid type 1 (CB1) receptor blockade decreases body weight and adiposity in obese subjects; however, the underlying mechanism is not yet fully understood. Nitric oxide (NO) produced by endothelial NO synthase (eNOS) induces mitochondrial biogenesis and function in adipocytes. This study was undertaken to test whether CB1 receptor blockade increases the espression of eNOS and mitochondrial biogenesis in white adipocytes.

RESEARCH DESIGN AND METHODS

We examined the effects on eNOS and mitochondrial biogenesis of selective pharmacological blockade of CB1 receptors by SR141716 (rimonabant) in mouse primary white adipocytes. We also examined eNOS expression and mitochondrial biogenesis in white adipose tissue (WAT) and isolated mature white adipocytes of CB1 receptor-deficient (CB1(-/-)) and chronically SR141716-treated mice on either a standard or high-fat diet.

RESULTS

SR141716 treatment increased eNOS expression in cultured white adipocytes. Moreover, SR141716 increased mitochondrial DNA amount, mRNA levels of genes involved in mitochondrial biogenesis, and mitochondrial mass and function through eNOS induction, as demonstrated by reversal of SR141716 effects by small interfering RNA-mediated decrease in eNOS. While high-fat diet-fed wild-type mice showed reduced eNOS expression and mitochondrial biogenesis in WAT and isolated mature white adipocytes, genetic CB1 receptor deletion or chronic treatment with SR141716 restored these parameters to the levels observed in wild-type mice on the standard diet, an effect linked to the prevention of adiposity and body weight increase.

CONCLUSIONS

CB1 receptor blockade increases mitochondrial biogenesis in white adipocytes by inducing the expression of eNOS. This is linked to the prevention of high-fat diet-induced fat accumulation, without concomitant changes in food intake.

The endocannabinoid system and energy metabolism

Many different regulatory actions have been attributed to endocannabinoids, and their involvement in several pathophysiological conditions is under intense scrutiny. Cannabinoid receptors [cannabinoid receptor type 1 (CB1) and CB2] participate in the physiological modulation of many central and peripheral functions. The ability of the endocannabinoid system to control appetite, food intake and energy balance has recently received considerable attention, particularly in the light of the different modes of action underlying these functions. The endocannabinoid system modulates rewarding properties of food by acting at specific mesolimbic areas in the brain. In the hypothalamus, CB1 receptors and endocannabinoids are integrated components of the networks controlling appetite and food intake. Interestingly, the endocannabinoid system was recently shown to control several metabolic functions by acting on peripheral tissues such as adipocytes, hepatocytes, the gastrointestinal tract, the skeletal muscles and the endocrine pancreas. The relevance of the system is further strengthened by the notion that visceral obesity seems to be a condition in which an overactivation of the endocannabinoid system occurs, and therefore drugs interfering with this overactivation by blocking CB1 receptors are considered as potentially valuable candidates for the treatment of obesity and related cardiometabolic risk factors.