Dr. Crowthers is the STEM teacher at Mass Academy. The main focus of STEM I class is our five month long research project of choice. This project culminates in early February when we present our projects at the Mass Academy science fair. You can read more about my project below!

Impact of Curcumin on Depressive Symptoms in Drosophila melanogaster
Project Overview:

Depression is one of the most common mental disorders, impacting over 300 million individuals globally. One of the oldest psychiatric disorders that scientists have evidence for, depression accounts for nearly 13% of all mental illness diagnoses. Additionally, scientists have estimated that depression can be a factor for 15 – 20% of a patient’s life. Now with the ongoing COVID-19 pandemic, a global environment of isolation was created. Those already suffering from poor mental health, and even those with no history, felt its impact and the number of those diagnosed with clinical depression is estimated to have nearly tripled. The prevalence and debilitating nature of this disorder compels society to find a safe and effective remedy. The most clinically prescribed current treatments for depression include cognitive behavioral therapy (CBT) and prescription antidepressants. Unfortunately, CBT requires a time commitment as well as access to CBT trained therapists, and nearly a third of patients find antidepressants to be ineffective due to their numerous side effects, low probability of remission, and long latency period (American Psychological Association, 2021). Additionally, cultural stigmas against mental illness and lack of resources prevent many suffering individuals from receiving the care that they need. These multiple factors drive the need for the creation of a natural, common, and inexpensive treatment. A possible solution to this problem could be found in turmeric, more specifically in its principal active component called curcumin. Turmeric has for hundreds of years been used in Ayurvedic medicine to treat numerous medical conditions, including anxiety and depression.

Major Depressive Disorder (MDD) is one of the most common mental disorders, impacting over 300 million individuals, and causing a variety of physical and behavioral symptoms. However, current treatment methods such as antidepressants are not wholly effective as they have numerous side effects and low remission periods, leading many patients to cease treatment. Given the reach and impact of MDD, the need for more effective treatments is necessary. Curcumin, the principal component of the spice turmeric, shows potential as an effective treatment for MDD. The purpose of this experiment was to evaluate the impact of curcumin in reducing depressive symptoms in Drosophila melanogaster. In this project, behavioral assays measuring depression-influenced behaviors such as aggression, food intake, and locomotion, were used as proxies through which neurotransmitter levels were gauged. Measurements of dissimilarities between curcumin-treated Drosophila melanogaster model for depression and a control group provided insight into the efficacy of this treatment. From these experiments, it was concluded that curcumin had an increased the level of neurotransmitters and consequently had a significant impact on the prevalence of depressive symptoms. In comparison to non-depressed Drosophila melanogaster, curcumin was able to return the depression-impacted behaviors back to standard behaviors. Given the link between humans and Drosophila melanogaster, this finding stipulates curcumin to be a viable treatment option for humans suffering from MDD. Clinical trials measuring the effectiveness of curcumin as a stand-alone method of treatment versus its synergistic use with current antidepressants would assist in providing a better understanding of the optimal use of curcumin.

Supporting Documents:
Click here to view my supporting documents
Hypothesis: If curcumin is given to a Drosophila melanogaster model for depression, then the prevalence of depressive symptoms like aggression, reduced locomotion, and lowered food intake will decrease in Drosophila melanogaster.
Researchable Question: How does the consumption of curcumin impact the prevalence and severity of depressive symptoms in a Drosophila melanogaster model for depression?

Overview of Major Depressive Disorder Major Depressive Disorder (MDD) is a mental health disorder characterized by persistently depressed mood or loss of interest in activities, causing significant impairment in daily life. Symptoms of MDD include anhedonia (the inability to feel pleasure), constant negativity, lack of interest, feeling worthless, suicidal thoughts, low energy, reduced amount of energy of appetite, and aggression (American Psychological Association, 2021). These symptoms can vary from mild to severe and a diagnosis is made if these symptoms are persistent for more than 2 weeks and cause a change in the patient’s level of function (American Psychological Association, 2021). Some factors that can contribute to the development of depression are increased levels of stress, neurochemistry, innate personality, environmental factors, and genetics. The most clinically used methods in current-day medicine for treatment are cognitive behavioral therapy and prescription anti-depressants, known commonly as selective serotonin reuptake inhibitors (SSRI). However, one-third of patients find antidepressants to be ineffective due to their numerous side effects, low probability of remission, and long latency period (American Psychological Association, 2021). Sadly, depression is one of the most common mental disorders, estimated to impact over 300 million people globally. In 2013, Global Burden of Disease reported major depressive disorder (MDD) to be the 2nd highest illness causing loss of lifespan (Gibson-Smith et al., 2019).

At its most basic, depression is regulated by three major monoamines neurotransmitters –serotonin, dopamine, and norepinephrine– whose levels play a major role in either preventing or causing depression. These levels are affected by genetics, stressors, and physiologic responses to environmental factors. Connections between inflammatory pathways and neural circuits in the brain can lead to behavioral responses like avoidance and alarm, contributing to the development of depression (Miller et al., 2015). Additionally, the neurotrophin hypothesis of depression suggests that low levels of brain-derived neurotrophic factor (BDNF) can play an important role in the development of depression (Ramaholimihaso et al., 2020). BDNF refers to growth factors that lead to cell survival, differentiation, and death of particular neuronal cells that assist monoamine neurotransmitters. When levels of this neurotrophic factor are decreased, scientists have found that it results in chronic stress, and therefore leads to the development of depression (Shafiee et al., 2018).

The discovery of antidepressants in the 1950s led to a revolution in the treatment of depression and a sharp reduction in suicides by people with depression. Over time, these antidepressants have evolved and diversified into the numerous clinical options available today (Shafiee et al., 2018). The monoamine neurotransmitter deficiency theory is the idea that has spurred many of the medicines that have come about to combat depression, like SSRIs. This theory assumes that the lack of monoamines in the brain is the main cause for depression and therefore the medication that results from this theory (SSRIs) all attempt to increase the number of monoamines within the brain (Ramaholimihaso et al., 2020). Antidepressants have several limitations, inducing harmful side effects. Common side effects include dry mouth, weight gain, dizziness, headaches, sexual dysfunction, and emotional blunting (Shafiee et al., 2018). Additionally, most antidepressants have low probabilities of remission as more than 30% of patients fail to achieve remission as well as low tolerability; 28% of depressed patients stop taking their medication in the first month of treatment and 44% discontinue within 3 months (Shafiee et al., 2018).

Turmeric has been used for thousands of years in Ayurvedic medicine to treat numerous medical conditions, including anxiety and depression. Recent scientific studies have found that curcumin, the principal curcuminoid of turmeric, has the ability to regulate neurotransmitter concentrations, inflammatory pathways, neuroplasticity, hypothalamic–pituitary–adrenal (HPA) disturbances, insulin resistance, and oxidative stress - all of which of factors that can lead to depression (Ramaholimihaso et al., 2020). Additionally, studies conducted on the model organism of rats found that curcumin could increase norepinephrine, serotonin, and dopamine levels in the frontal cortex, hippocampus, and striatum in brains of these organisms. Further research has shown that curcumin leads to this decrease in inflammation in the hippocampus and prefrontal cortex by acting on pro-inflammatory cytokine pathways and decreasing their mRNA expression (Ramaholimihaso et al., 2020). Moreover, curcumin has also been found to have the ability to stimulate the production of BDNF (Ramaholimihaso et al., 2020). Though the impact of curcumin on depression is relatively new to study, there are many promising aspects of curcumin that may lead it to be a potential antidepressant.

The use of various assays measuring symptoms of depression were utilized as markers to measure the extent of depressive symptoms displayed by Drosophila melanogaster. The Drosophila melanogaster utilized in this experiment were acquired from Bloomington Drosophila Stock Center at the University of Indiana Bloomington. These Drosophila melanogaster were taken care of using fly vials, potato flakes (dry media), ddH2O, and yeast. The specific breed of Drosophila melanogaster chosen for these experiments was Wild Type. Common symptoms of depression include irregularities in aggression, food intake, and locomotion. Therefore, the primary aim of the three main assays used in these experiments – measuring aggression, locomotion, and food intake - was to act as an indirect method through which neurotransmitter levels could be measured in the Drosophila melanogaster brain.

Levodopa (LDOPA) was utilized to incite depressive symptoms in Drosophila melanogaster. This chemical has been shown to induce dopaminergic misbalances and depressive symptoms in the brains of these organisms (Moulin et al., 2021). Additionally, turmeric, containing its principal curcuminoid of curcumin, was used as a method of treatment for the symptoms of depression caused by LDOPA.

An aggression assay developed by Dierick (2007) was replicated for this experiment as aggression is a behavior that is impacted by the onset of MDD. For this experiment, the materials used included Fluon, an iPhone X, a Plexiglas rectangular plate, fly anesthetic, and a microscope. Also utilized was a capillary feeding assay measuring food intake in Drosophila melanogaster conducted by Diegelmann et al. (2017). Blue and red food coloring, microcapillaries, sucrose, ddH2O, and fly vials were used for this assay. The final assay measured locomotion and required the materials of a ruler, red Sharpie, iPhone X, and fly vials. This locomotion assay was based on an assay conducted by Ali et al. (2011). However, multiple modifications were made to this assay. The original assay called for the use of a vortex and a dichotomous measurement of a result. However, the vortex was replaced by simply tapping flies to the bottom of the vial and the final measurement was not dichotomous, but instead measured the final height of the fly. These changes were made in the interest of time.
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The primary objective of this experiment was to measure the impact of curcumin on depressive symptoms using Drosophila melanogaster as models for depression. The hypothesis for this experiment proposed curcumin’s ability to act effectively against depressive symptoms. From the data collected and its subsequent analyzation, the null hypothesis – curcumin would have no impact on depressive symptoms in a depressed Drosophila melanogaster – can be rejected and the alternate hypothesis, as aforementioned, can be accepted in its place. The use of various assays measuring irregularities in aggression, food intake, and locomotive behaviors, allowed the researcher insight into the levels of neurotransmitters present in the brains of Drosophila melanogaster in each experimental group.

For this experiment, four different levels of an independent variable were represented by the four different experimental groups. These groups included two control groups – one treated with just curcumin and the other with neither curcumin nor LDOPA – and two additional experimental groups – one LDOPA-treated group (representing the depression model) and a final group treated with both LDOPA and curcumin. From the data collected and the significant differences in behaviors observed between the LDOPA group and the LDOPA and curcumin treated group as well as the similarities in behaviors displayed between the LDOPA and curcumin treated group with the control groups, it was concluded the curcumin does have the ability to act a mechanism of antidepressant action and increase the levels of neurotransmitters within the brains of depressed Drosophila melanogaster.
Future Steps:

It is clear from the data that curcumin has great potential to be both a safe and effective antidepressant for humans. However, a lack of studies on curcumin’s impacts on humans prevent this spice from being used commercially as an antidepressant medication. Additionally, it is unclear if curcumin could be used solely as an effective antidepressant or if this curcuminoid would need to be used in conjunction with current antidepressants to be effective. Studies specifically looking for the optimal amount of curcumin dosage per patient would also be necessary to solidify curcumin’s usage as an antidepressant. To bridge these gaps in knowledge, additional studies need to be conducted on animal models to ensure curcumin’s safety, prior to testing beginning on humans. Through these studies on animal models, the properties, and functions of curcumin in relation to depressive symptoms can be better understood, as well as increasing understanding about the impact of curcumin on the brain. Though this project took the first step in researching curcumin’s antidepressant potential through Drosophila melanogaster, there are many more steps that need to be taken for curcumin to be prescribed to human patients as an antidepressant.

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