From Pharmacology to Physiology: Endocrine Functions of μ-Opioid Receptor Networks

Cancer cachexia as a blueprint for treating obesity

Effective pharmacological treatments to achieve significant and sustained weight loss in obese individuals remain limited. Here, we apply a 'reverse engineering' approach to cancer cachexia, an extreme form of dysregulated energy balance resulting in net catabolism. We discuss three phenotypic features of the disease, summarize the underlying molecular checkpoints, and explore their translation to obesity research. We then provide examples for established pharmaceuticals, which follow a reverse engineering logic, and propose additional targets that may be of relevance for future studies. Finally, we argue that approaching diseases from this perspective may prove useful as a generic strategy to fuel the development of innovative therapies.

Mu Opioid Receptor Dynamics in Healthy Volunteers with a History of Childhood Maltreatment

Evidence suggests that adults with a history of childhood maltreatment, the experience of emotional or physical neglect and/or abuse within the family during childhood, have blunted reward and stress processing, and higher risk of depression. The mu opioid receptor rich nucleus accumbens and amygdala are critical to reward and stress processing respectively. We hypothesized that nucleus accumbens and amygdala mu opioid receptor densities and activity (change in receptor binding due to endogenous opioid release or receptor conformation change) were negatively associated with childhood maltreatment in healthy young adults. Maltreatment was assessed with the Childhood Trauma Questionnaire (CTQ). Healthy participants, n = 75 (52% female) completed [11C]carfentanil positron emission tomography imaging labeling mu opioid receptors. The relationship between CTQ score and binding potential (BPND, proportional to density of unoccupied receptors) was evaluated with a linear mixed effects model. No significant relationship was found between CTQ score and BPND (f = 3.28; df = 1, 73; p = 0.074) or change in BPND (activity) (t = 1.48; df = 198.3; p = 0.14). This is the first investigation of mu opioid receptors in those with childhood maltreatment. We did not identify a significant relationship between mu opioid receptor dynamics and severity of maltreatment in those without psychopathology. Because this cohort has a low CTQ score average, this may indicate that those with low severity of maltreatment may not have associated changes in mu opioid receptor dynamics. Future directions include evaluating a cohort with increased severity of childhood maltreatment.

Androgens, brain and androgen deprivation therapy in paraphilic disorders: A narrative review

Sexual delinquency is a global problem where those with paraphilic disorders, such as paedophiles, are more likely to commit and reoffend. Androgen deprivation therapy (ADT) has been suggested as a solution. The objective of this narrative review is to present current information on its risks, benefits and limitations as a treatment for paraphilias. The importance of testosterone in sexual function, the effect of its deficiency by age or by pharmacological treatment (anti-androgens, GnRH agonists and GnRH antagonists) and the effect of testosterone replacement therapy will be reviewed. The relationship between androgens, brain, sexual behaviour and pathophysiology of paraphilic disorders will also be explored. ADT reduces sexual urges, but has adverse effects and, because its reversible nature, it does not ensure less recidivism. Likewise, the research quality of ADT drugs is limited and not enough to support their use. Child sex offenders, and not paraphilic subjects who have not committed assaults, show signs of elevated prenatal exposure to androgens and a higher methylation state of the androgen receptor gene. Sexual behaviour is regulated by subcortical (hypothalamus, brainstem and spinal cord) and cortical structures of the brain, in addition to brain circuits (dopaminergic, serotonergic). Those with paraphilic disorders show abnormalities at these levels that could relate to the risk of sexual offences. In conclusion, androgens represent a significant part of the pathophysiology of paraphilias and therefore, ADT seems promising. Nonetheless, more studies are needed to make definite conclusions about the efficacy of long-term ADT in paraphilic patients.

New pharmacological perspectives and therapeutic options for opioids: Differences matter

Opioids remain the major drug class for the treatment of acute, chronic and cancer pain, but have major harmful effects such as dependence and opioid-induced ventilatory impairment. Although no new typical opioids have come onto the market in the past almost 50 years, a plethora of new innovative formulations has been developed to meet the clinical need. This review is intended to shed light on new understanding of the molecular pharmacology of opioids, which has arisen largely due to the genomic revolution, and what new drugs may become available in the coming years. Atypical opioids have and are being developed which not only target the mu opioid receptor but other targets in the pain pathway. Biased mu agonists have been developed but remain 'unbiased' clinically. The contribution of drugs targeting non-mu opioid receptors either alone or as heterodimers shows potential promise but remains understudied. That gene splice variants of the mu opioid receptor produce multiple receptor isoforms in different brain regions, and may change with pain chronicity and phenotype, presents new challenges but also opportunities for precision pain medicine. Finally, that opioids also have pro-inflammatory effects not aligned with mu opioid receptor binding affinity implicates a fresh understanding of their role in chronic pain, whether cancer or non-cancer. Hopefully, a new understanding of opioid analgesic drug action may lead to new drug development and better precision medicine in acute and chronic pain relief with less patient harm.

Opioids and pituitary function: expert opinion

PURPOSE

Opioids are highly addictive potent analgesics and anti-allodynics whose use has dramatically increased in recent decades. The precipitous rise in opioid dependency and opioid use disorder is an important public health challenge given the risks for severely adverse health outcomes. The long-term opioid impact on hypothalamic-pituitary axes is particularly underappreciated among both endocrinologists and primary care physicians. We review the effects of opioids on hypothalamic-pituitary-target gland function and their implications for clinical practice.

METHODS

Experts in hypothalamic-pituitary disorders and opioid pharmacology reviewed recently published literature and considered strategies for diagnosing and managing these opioid-induced endocrine effects.

RESULTS

Opioid suppression of hypothalamic-pituitary axes can lead to hypogonadotropic hypogonadism, central adrenal insufficiency, and hyperprolactinemia. These important clinical manifestations are often under-estimated, poorly evaluated, and typically either untreated or not optimally managed. Data on biochemical testing for diagnosis and on the effect of hormone replacement in these patients is limited and prospective randomized controlled studies for guiding clinical practice are lacking.

CONCLUSIONS

Patients should be informed about risks for hypogonadism, adrenal insufficiency, and hyperprolactinemia, and encouraged to report associated symptoms. Based on currently available evidence, we recommend clinical and biochemical evaluation for potential central adrenal insufficiency, central hypogonadism, and/or hyperprolactinemia in patients chronically treated with opioids as well as the use of current expert guidelines for the diagnosis and treatment of these conditions.

Co-occurrence of preconception maternal childhood adversity and opioid use during pregnancy: Implications for offspring brain development

Understanding of the effects of in utero opioid exposure on neurodevelopment is a priority given the recent dramatic increase in opioid use among pregnant individuals. However, opioid abuse does not occur in isolation-pregnant individuals abusing opioids often have a significant history of adverse experiences in childhood, among other co-occurring factors. Understanding the specific pathways in which these frequently co-occurring factors may interact and cumulatively influence offspring brain development in utero represents a priority for future research in this area. We highlight maternal history of childhood adversity (CA) as one such co-occurring factor that is more prevalent among individuals using opioids during pregnancy and which is increasingly shown to affect offspring neurodevelopment through mechanisms beginning in utero. Despite the high incidence of CA history in pregnant individuals using opioids, we understand very little about the effects of comorbid prenatal opioid exposure and maternal CA history on fetal brain development. Here, we first provide an overview of current knowledge regarding effects of opioid exposure and maternal CA on offspring neurodevelopment that may occur during gestation. We then outline potential mechanistic pathways through which these factors might have interactive and cumulative influences on offspring neurodevelopment as a foundation for future research in this area.

Effects of opioids on reproduction in Japanese medaka, Oryzias latipes

To study the effects of exposure of fish to opioid drugs, we exposed Japanese medaka (Oryzias latipes) over a full life cycle to codeine spiked into river water at nominal concentrations of 100, 1,000 and 25,000 ng/L and to fentanyl spiked into river water at nominal concentrations of 5, 25 and 1,000 ng/L. The measured concentrations during medaka exposures were consistent with the nominal concentrations. Treatments with codeine at all test concentrations reduced the number of eggs produced by female medaka, as well as the number of mature oocytes observed histologically in the ovaries. Exposures to codeine also resulted in altered concentrations of hormones within the hypothalamic-pituitary-gonadal axis, including reduced levels of 17β-estradiol in female medaka. Fentanyl did not affect reproduction or the levels of hormones in medaka at the concentrations tested. Monitoring of surface waters in southern Ontario, Canada downstream of wastewater treatment plants showed that the test concentrations of fentanyl and codeine were environmentally relevant. The results of this work contribute to the literature on the impacts of opioids and other drugs of abuse released into surface waters.