Translating depression biomarkers for improved targeted therapies

PCOS and Depression: Common Links and Potential Targets

PCOS or polycystic ovary syndrome is a common endocrine disorder that occurs during the reproductive age in females. It manifests in the form of a wide range of symptoms including (but not limited to) hirsutism, amenorrhea, oligomenorrhea, obesity, acne vulgaris, infertility, alopecia, and insulin resistance. The incidence of depression in PCOS population is increasing as compared to the general population. Increased depression in PCOS significantly alters the quality of life (QOL) of affected females. Also, self-esteem is found to be low in both depression and PCOS. The loss in self-esteem in such patients can be largely attributed to the associated factors including (but not limited to) obesity, acne, androgenic alopecia, and hirsutism. The reason behind the occurrence of depression in PCOS remains elusive to date. Literature suggests that there is an overlap of clinical symptoms between depression and PCOS. As the symptoms overlap, there is a possibility of common associations between depression, PCOS, and PCOS-associated abnormalities including insulin resistance (IR), obesity, CVD, and androgen excess. Studies demonstrate that depression is an inflammatory disorder marked with increased levels of inflammatory markers. On the other hand, PCOS is also regarded as a pro-inflammatory state that is characterized by increased levels of pro-inflammatory markers. Thus, there is a possibility of an inflammatory relationship existing between depression and PCOS. It is also possible that the inflammatory markers in PCOS can cross the blood-brain barrier (BBB) leading to the development of depression. Through the present review, we have attempted to shed light on common associations/shared links between depression and PCOS with respect to the levels of cortisol, androgen, vitamin D, neurotransmitters, monoaminoxidase (MAO), and insulin-like growth factor-1 (IGF-1). Tracking down common associations between depression and PCOS will help find potential drug therapies and improve the QOL of females with depression in PCOS.

Study of Frontal Alpha Asymmetry in Mild Depression: A Potential Biomarker or Not?

Background:

Depression, despite being the most common of mental illness lacks any quantifiable and absolute biomarker. Frontal alpha asymmetry (FAA) is proposed as biomarker of depression both in resting and activated state. Yet, the location of extraction of alpha, clinical utility as well as validity of FAA is uncertain. With aim of obtaining clarity on this confusion we conducted this study.

Methodology:

Electroencephalographic frontal alpha power was calculated in patients of depression (n = 24) and compared with healthy controls (n = 17) for the assessment of FAA. Both groups were studied for resting phase and activation phase changes in FAA. For activation phase, auditory stimuli in the form of Indian classical music were used.

Results:

Frontal alpha power was measured across FP1, FP2, F3, F4, F7, and F8. Mean powers were compared in resting (before), activated (during) and postactivated resting stage (after). FAA was statistically significant in F7–F8 pair of electrodes and on F7 electrode when compared between cases and controls.

Conclusion:

Quest for biomarker for depression churned out FAA as frontrunner. Despite of vast amount of research on it, practical utility eludes us. We need to revisit our approach from conventional search of the diagnostic biomarker; as FAA might reflect component of depression but not totally disorder. In our opinion, we are not yet ready for it and have a road ahead to travel.

Depression: more treatment but no drop in prevalence: how effective is treatment? And can we do better?

PURPOSE OF REVIEW

Since the 70s, treatment of depression, especially pharmacologically, has expanded enormously. However, epidemiological studies show that 12-month population prevalence rates have not dropped. This observation raises multiple questions. How good are treatments of depression actually? Do they improve long-term outcomes? Have the treatment gaps narrowed? And how can we make mental healthcare more effective at the population level?

RECENT FINDINGS

Recent publications suggest some answers. Controlled treatment trials show that effectiveness of specific treatments (pharmacological, psychological) is modest and probably overestimated owing to substantial spontaneous recovery and nonspecific therapeutic effects. Treatment gaps are still substantial and prevention has unclear long-term effects and is not structurally embedded. Future relevance of genetic information for better personalized treatment is potentially high but uncertain. Increasingly, the potential of treatment to improve long-term outcome is being questioned.

SUMMARY

To reduce prevalence, it is essential to narrow the treatment gaps, provide timely interventions and high-quality treatment, eradicate waiting lists, prescribe antidepressants more cautiously and better managed, consider psychological alternatives, and provide more psychosocial treatment in primary care with physician-assistants. In addition, research is needed on long-term outcome of different treatment modalities, and least but not last the value of structurally socially embedded preventive interventions.

Association between prefrontal glutamine levels and neuroticism determined using proton magnetic resonance spectroscopy

There is growing evidence for GABA and glutamate-glutamine dysfunction in the pathogenesis of mood and anxiety disorders. It is important to study this pathology in the early phases of the illness in order to develop new approaches to secondary prevention. New magnetic resonance spectroscopy (MRS) measures allow determining glutamine, the principal metabolite of synaptic glutamate that is directly related to glutamate levels in the synaptic cleft, as well as glutamate and GABA. In contrast to previous investigations, this study used community-based recruitment methods and a combined categorical and dimensional approach to psychopathology. In the study protocol, neuroticism was defined as the primary outcome. Neuroticism shares a large proportion of its genetic variance with mood and anxiety disorders. We examined young adult participants recruited from the general population in a cross-sectional study using 3-T 1H-MRS with one voxel in the left dorsolateral prefrontal cortex (DLPFC). The total sample of N = 110 (61 females) included 18 individuals suffering from MDD and 19 individuals suffering from DSM-IV anxiety disorders. We found that glutamine and glutamine-to-glutamate ratio were correlated with neuroticism in the whole sample (r = 0.263, p = 0.005, and n = 110; respectively, r = 0.252, p = 0.008, and n = 110), even when controlling for depression and anxiety disorder diagnoses (for glutamine: beta = 0.220, p = 0.047, and n = 110). Glutamate and GABA were not significantly correlated with neuroticism (r = 0.087, p = 0.365, and n = 110; r = -0.044, p = 0.645, and n = 110). Lack of self-confidence and emotional instability were the clinical correlates of glutamate-glutamine dysfunction. In conclusion, this study suggests that prefrontal glutamine is increased in early phases of mood and anxiety disorders. Further understanding of glutamate-glutamine dysfunction in stress-related disorders may lead to new therapeutic strategies to prevent and treat these disorders.

Review of the neurological benefits of phytocannabinoids

Background:

Numerous physical, psychological, and emotional benefits have been attributed to marijuana since its first reported use in 2,600 BC in a Chinese pharmacopoeia. The phytocannabinoids, cannabidiol (CBD), and delta-9-tetrahydrocannabinol (Δ9-THC) are the most studied extracts from cannabis sativa subspecies hemp and marijuana. CBD and Δ9-THC interact uniquely with the endocannabinoid system (ECS). Through direct and indirect actions, intrinsic endocannabinoids and plant-based phytocannabinoids modulate and influence a variety of physiological systems influenced by the ECS.

Methods:

In 1980, Cunha et al. reported anticonvulsant benefits in 7/8 subjects with medically uncontrolled epilepsy using marijuana extracts in a phase I clinical trial. Since then neurological applications have been the major focus of renewed research using medical marijuana and phytocannabinoid extracts.

Results:

Recent neurological uses include adjunctive treatment for malignant brain tumors, Parkinson's disease, Alzheimer's disease, multiple sclerosis, neuropathic pain, and the childhood seizure disorders Lennox-Gastaut and Dravet syndromes. In addition, psychiatric and mood disorders, such as schizophrenia, anxiety, depression, addiction, postconcussion syndrome, and posttraumatic stress disorders are being studied using phytocannabinoids.

Conclusions:

In this review we will provide animal and human research data on the current clinical neurological uses for CBD individually and in combination with Δ9-THC. We will emphasize the neuroprotective, antiinflammatory, and immunomodulatory benefits of phytocannabinoids and their applications in various clinical syndromes.

New targets for rapid antidepressant action

Current therapeutic options for major depressive disorder (MDD) and bipolar disorder (BD) are associated with a lag of onset that can prolong distress and impairment for patients, and their antidepressant efficacy is often limited. All currently approved antidepressant medications for MDD act primarily through monoaminergic mechanisms. Glutamate is the major excitatory neurotransmitter in the central nervous system, and glutamate and its cognate receptors are implicated in the pathophysiology of MDD, and in the development of novel therapeutics for this disorder. The rapid and robust antidepressant effects of the N-methyl-d-aspartate (NMDA) antagonist ketamine were first observed in 2000. Since then, other NMDA receptor antagonists have been studied in MDD. Most have demonstrated relatively modest antidepressant effects compared to ketamine, but some have shown more favorable characteristics. This article reviews the clinical evidence supporting the use of novel glutamate receptor modulators with direct affinity for cognate receptors: (1) non-competitive NMDA receptor antagonists (ketamine, memantine, dextromethorphan, AZD6765); (2) subunit (GluN2B)-specific NMDA receptor antagonists (CP-101,606/traxoprodil, MK-0657); (3) NMDA receptor glycine-site partial agonists (GLYX-13); and (4) metabotropic glutamate receptor (mGluR) modulators (AZD2066, RO4917523/basimglurant). We also briefly discuss several other theoretical glutamate receptor targets with preclinical antidepressant-like efficacy that have yet to be studied clinically; these include α-amino-3-hydroxyl-5-methyl-4-isoxazoleproprionic acid (AMPA) agonists and mGluR2/3 negative allosteric modulators. The review also discusses other promising, non-glutamatergic targets for potential rapid antidepressant effects, including the cholinergic system (scopolamine), the opioid system (ALKS-5461), corticotropin releasing factor (CRF) receptor antagonists (CP-316,311), and others.

Modelling depression in animals: at the interface of reward and stress pathways

RATIONALE

Despite substantial research efforts the aetiology of major depressive disorder (MDD) remains poorly understood, which is due in part to the heterogeneity of the disorder and the complexity of designing appropriate animal models. However, in the last few decades, a focus on the development of novel stress-based paradigms and a focus on using hedonic/anhedonic behaviour have led to renewed optimism in the use of animal models to assess aspects of MDD.

OBJECTIVES

Therefore, in this review article, dedicated to Athina Markou, we summarise the use of stress-based animal models for studying MDD in rodents and how reward-related readouts can be used to validate/assess the model and/or treatment.

RESULTS

We reveal the use and limitations of chronic stress paradigms, which we split into non-social (i.e. chronic mild stress), social (i.e. chronic social defeat) and drug-withdrawal paradigms for studying MDD and detail numerous reward-related readouts that are employed in preclinical research. Finally, we finish with a section regarding important factors to consider when using animal models.

CONCLUSIONS

One of the most consistent findings following chronic stress exposure in rodents is a disruption of the brain reward system, which can be easily assessed using sucrose, social interaction, food, drug of abuse or intracranial self-stimulation as a readout. Probing the underlying causes of such alterations is providing a greater understanding of the potential systems and processes that are disrupted in MDD.

Duality of Antidepressants and Neuroprotectants

The co-morbidity of neuropsychiatric disorders, particularly major depressive disorder (MDD) with neurodegenerative diseases, in particular Parkinson's disease (PD) is now well recognized. Indeed, it is suggested that depressive disorders, especially in late life, may be an indication of latent neurodegeneration. Thus, it is not unreasonable to expect that deterrents of MDD may also deter the onset and/or progression of the neurodegenerative diseases including PD. In this review, examples of neuroprotective efficacy of established as well as prospective antidepressants are provided. Conversely, mood-regulating effects of some neuroprotective drugs are also presented. Thus, in addition to currently used antidepressants, ketamine, nicotine, curcumin, and resveratrol are discussed for their dual efficacy. In addition, potential neurobiological substrates for their actions are presented. It is concluded that pharmacological developments of mood-regulating or neuroprotective drugs can have cross benefit in co-morbid conditions of neuropsychiatric and neurodegenerative disorders and that inflammatory and neurotrophic factors play important roles in both conditions.

Cannabidiol, neuroprotection and neuropsychiatric disorders

Cannabidiol (CBD) is a non-psychotomimetic phytocannabinoid derived from Cannabis sativa. It has possible therapeutic effects over a broad range of neuropsychiatric disorders. CBD attenuates brain damage associated with neurodegenerative and/or ischemic conditions. It also has positive effects on attenuating psychotic-, anxiety- and depressive-like behaviors. Moreover, CBD affects synaptic plasticity and facilitates neurogenesis. The mechanisms of these effects are still not entirely clear but seem to involve multiple pharmacological targets. In the present review, we summarized the main biochemical and molecular mechanisms that have been associated with the therapeutic effects of CBD, focusing on their relevance to brain function, neuroprotection and neuropsychiatric disorders.

The Beneficial Impact of Antidepressant Drugs on Prenatal Stress-Evoked Malfunction of the Insulin-Like Growth Factor-1 (IGF-1) Protein Family in the Olfactory Bulbs of Adult Rats

Insulin-like growth factor-1 (IGF-1) promotes the growth, differentiation, and survival of both neurons and glial cells, and it is believed to exert antidepressant-like activity. Thus, disturbances in the IGF-1 system could be responsible for the course of depression. To date, there have been no papers showing the impact of chronic antidepressant treatment on the IGF-1 network in the olfactory bulb (OB) in an animal model of depression. Prenatal stress was used as model of depression. Twenty-four 3-month-old male offspring of control and stressed mothers were subjected to behavioral testing (forced swim test). The mRNA expression of IGF-1 and IGF-1 receptor (IGF-1R) and the protein level of IGF-1 and its phosphorylation, as well as the concentrations of IGF-binding proteins (IGFBP-2, -4, -3, and -6), were measured in OBs before and after chronic imipramine, fluoxetine, or tianeptine administration. Adult rats exposed prenatally to stressful stimuli displayed not only depression-like behavior but also decreased IGF-1 expression, dysregulation in the IGFBP network, and diminished mRNA expression, as well as IGF-1R phosphorylation, in the OB. The administration of antidepressants normalized most of the changes in the IGF-1 system of the OB evoked by prenatal stress. These results suggested a beneficial effect of chronic antidepressant drug treatment in the alleviation of IGF-1 family malfunction in OBs in an animal model of depression.