The Impact of Leptin and Additive Sugars on Obesity

    Obesity is a widespread condition that affects millions of people across the world. Obesity is a health concern and puts a person at higher risk for complications when exposed to diseases such as COVID-19. There is a need to understand the effects on the brain and the human body of an obese person. This will help to treat and combat this important issue that affects a large portion of the world’s population. The brain has been found to regulate eating habits through the leptin pathway, which can be affected by sugar intake.

    In the article “A Leptin Analog Locally Produced in the Brain Acts via a conserved Neural Circuit to Modulate Obesity-Linked Behaviors in Drosophila” Dr. Beshel and colleagues analyzed the role of leptin and analog unpaired 1 (upd1) in Drosophila. This study found that when upd 1 in flies was deleted, flies had more attraction to eating, which resulted in weight gain. In more general terms, leptin is a hormone that is secreted by adipose cells. The levels of leptin in a person are directly correlated with their body fat. When a person has extra body fat, they release more leptin into the bloodstream that signals to the person’s brain that they are no longer hungry. However, in obesity, there is a constant high level of leptin in the bloodstream, which prevents receptors from being as sensitive to leptin and result in hunger signals not being turned off. Dr. Beshel’s findings point to triggers not only genetically based but also on the food availability that a fly consumed. Therefore, understanding the homeostasis of the leptin pathway is essential, but what types of food a fly or person consumes can also play a significant role in weight gain and affect leptin levels. 

 

    Another article that talks about obesity include, “Sugar consumption, metabolic disease and obesity: The state of controversy” by Kimber Stanhope, mentions the critical impact of sugar consumption on metabolism levels and obesity. This study has shown that added sugars in food can interrupt metabolic behavior in the body. Fructose consumption can interrupt the metabolic regulation of lipids and carbohydrates. This interference can lead to weight gain in a person. This study’s findings suggest that when there is increased fructose intake, the leptin levels are reduced. The reduction in leptin could be because fructose increases energy and reduces spent energy, resulting in stored fat. Many of the foods we eat have added sugars. These added sugars could be what is disrupting the homeostasis of our body weight. Therefore, this study argues that more research needs to be done, but limiting the number of additive sugars in our diets could prevent dysfunction in the leptin pathway and body fat produced within the body. 

 

    In conclusion, both of these articles are making strides towards preventing and finding a cause for obesity. The world needs a treatment or advice on how to prevent obesity. This would greatly help improve the life spans of those affected by obesity. Obesity is a complicated disorder because it is thought to be a human responsibility to eat the right food. However, this is not the case. There is a dysfunction in the leptin pathway that causes a person to eat more in many cases. Like many other diseases when homeostasis within the body cannot be reached, there is an issue. Due to the production or the lack of leptin production, a person’s diet and eating patterns vary. This leptin pathway can be impacted by consuming certain sugars like fructose. Overall, it is important to take information from both of these studies to better understand the cause of obesity and ways to treat or combat the disorder.

 

Works Cited:

 

 

Beshel, J., Dubnau, J., & Zhong, Y. (2017). A Leptin Analog Locally Produced in the Brain Acts via a Conserved Neural Circuit to Modulate Obesity-Linked Behaviors in Drosophila. Cell metabolism, 25(1), 208–217. https://doi.org/10.1016/j.cmet.2016.12.013

 

 

Stanhope K. L. (2016). Sugar consumption, metabolic disease and obesity: The state of the controversy. Critical reviews in clinical laboratory sciences, 53(1), 52–67. https://doi.org/10.3109/10408363.2015.1084990

 

The Source Of Leptin-resistance And Its Effect On Obesity

    Obesity is prevalent today all over the world and in some places more than others. Not only does it take a significant toll on an individual’s health and cause different kinds of complications, it takes a toll on a person’s family and their loved ones who watch them struggle. Researchers like Dr. Jen Beshel, John Dubnau, Holger Henneicke, and Sarah Kim have discovered promising information to help us combat the ongoing pandemic of obesity. 
In the article A Leptin Analog Locally Produced in the Brain Acts via a Conserved Neural Circuit to Modulate Obesity-Linked Behaviors in Drosophila, Dr. Jennifer Beshel, Josh Dubnau, and others have all studied the neuropeptide Leptin which is typically an adipose tissue derived hormone which has a function in weight regulation. Dr. Beshel and the researchers all found that in drosophila there is an unpaired 1 ligand that acts to regulate feeding behaviors just as leptin does in human brains. Also, they found that the neuropeptide F that has regulatory effects on feeding behavior and mediates other obesity-type traits is homologous to the Neuropeptide Y regulator that is found in humans. These findings are significant in the search of obesity treatments because they allow scientists to manipulate the variables in drosophila to attempt to decrease weight gain or obesity related behaviors. However, this search has not been easy, the search for an effective treatment has been made increasingly difficult since leptin receptors can develop a resistance causing excess leptin not to bind to the receptors and thereby inhibiting the suppression of obese-type traits and behaviors causing further weight gain. 
Because Leptin resistance is what prevents doctors from prescribing leptin to obese patients for weight loss, it is important that researchers find out the source of leptin resistance. In the article Skeletal glucocorticoid signaling determines leptin resistance and obesity in aging mice, Holger Henneicke, Sarah Kim, and others found that skeletal glucocorticoid signaling determines leptin resistance and obesity in aging mice. The researchers studied mice that were lacking glucocorticoid signaling in osteoblasts and osteocytes (HSD2OB/OCY mice), and their wild-type littermates for 3, 6. 12 and 18 months of age. They also assessed leptin sensitivity by the arcuate nucleus STAT3 phosphorylation and the resulting inhibition of feeding. The researchers found that as the mice aged, wild-type mice became obese. The obesity that resulted from leptin resistance because of an impaired ability of exogenous leptin to suppress food intake and phosphorylate hypothalamic STAT3 from 6 months of age and onwards. This information is significant because it underlines the importance of the skeletal system in regulating weight and highlights a factor associated to the cause of leptin resistance. 
These studies open a door of opportunity to finding a new treatment for obesity that will help contain and reverse this global issue. By combining the information learned about leptin resistance in humans with the information about a potential source of the resistance, researchers might be able to target the source and develop different therapies that way.

Citations:

Beshel J, Dubnau J, Zhong Y. A Leptin Analog Locally Produced in the Brain Acts via a Conserved                    Neural Circuit to Modulate Obesity-Linked Behaviors in Drosophila.

Henneicke, Holger, et al. “Skeletal Glucocorticoid Signalling Determines Leptin Resistance and Obesity             in Aging Mice.” Molecular Metabolism, Elsevier, 10 Oct. 2020, 

Is Aesthetic Value Determined by Motivation?

Is beauty in the eye of the beholder? Scientists and philosophers alike have been trying to answer this question for years. Many years ago, beauty was seen as objective. According to philosophers like Plato and Aristotle, certain features, such as proportion and symmetry, give beauty to something (Sartwell, 2017). However, by the end of the 17th century, people began to take a subjective view of beauty (Aleem et al., 2019). Although more arguments are being made toward the subjective view of beauty, and much more research is needed to make any conclusions, I will argue an objective viewpoint. As mentioned in the study by Aleem et al., learning and motivation tie into what is considered aesthetically pleasing (Aleem et al., 2019). I will examine this study as well as a study conducted in 2016 by Domagoj Švegar that summarizes past empirical research. 

In the study by Aleem et al. conducted in 2019, participants were placed in an fMRI scanner and asked to determine if they liked or disliked a painting presented by the researcher. Many different areas were activated, such as visual, motor, and sensory pathways. To determine which brain networks are used for determining the beauty of something, Aleem and his team looked at a meta-analysis of 93 fMRI studies. The results of this analysis showed that the orbitofrontal cortex (OFC), anterior insula, and ventral basal ganglia are most highly activated when making these determinations (Brown et al., 2011). Aleem’s team then went on to discuss how these areas are involved in behavior. They discuss how the OFC is involved in integrating and tracking reward values, the anterior insula is involved in interoception and determining valence, and the basal ganglia are involved in predictions and errors (Aleem et al., 2019). Overall, these structures are important for reward-based learning. This is important for determining the aesthetic value of something because this motivational learning may lead to certain things being found as more aesthetically pleasing for various reasons. The example given in the study is of an apple. If one determines from experience that the redder an apple is, the sweeter it will be, they will be motivated to eat more red apples in the future (Aleem et al., 2019). This can translate to aesthetics in that redder apples will be viewed as more beautiful due to their reward value. If this is true, then beauty and aesthetics are more objective than subjective. Since most people have the same motivations in terms of survival instincts, it would make sense that certain qualities would nearly always be considered beautiful while others are nearly always considered aesthetically unpleasing. 

In order to examine if motivation influences a person’s aesthetic views in other aspects, I looked at a study conducted by Domagoj Švegar in 2016. In this study, Švegar summarized past empirical research that had been done regarding the associations between symmetry and the health and personality of humans. He also conducted a meta-analysis to show the overall results of the studies. To begin, Švegar first examined studies regarding facial symmetry and attractiveness. From a study conducted by Quist et al., it was concluded that women prefer symmetric men, and these men are rated as more attractive (Quist et al., 2012). Several other studies examined had results that were in line with this data. The next relationship examined was facial symmetry and health. Švegar went into detail about a study conducted by Shackelford and Larsen that examined both perceived and actual health. This study used several measures to determine if there is a correlation between facial symmetry and attractiveness and perceived health. This study had a variety of results, but overall, asymmetrical participants report more health issues than symmetric participants, and symmetric photos were perceived as more healthy (Shackelford & Larsen, 1997). Several other studies also showed similar results; however, the association between symmetry and actual health was much weaker than the association with perceived health. However, a study conducted by Little et al. showed that even a weak link between symmetry and health may be enough to create selection pressure. This study showed that individuals who were more concerned with disease had elevated preferences for symmetric faces (Little et al., 2008). Therefore, if one is more concerned about the traits being passed to offspring, they will choose a mate that they believe has good genes. Aleem et al. then conducted a meta-analysis of 19 studies. This meta-analysis showed that there was a moderately strong relationship between facial symmetry and perceived health ( p < 0.01) (Aleem et al., 2019). Furthermore, there was a low, but significant, correlation between facial symmetry and actual health (p = 0.05) (Aleem et al., 2019). Throughout this study, Švegar determined that results were in line with the evolutionary hypothesis that we select attractive and symmetric mates because it is an indicator of good health and genes (Švegar, 2016). 

Overall, both studies examined show that motivation has a role in what is deemed aesthetically pleasing. As mentioned in the study by Aleem et al., we may view certain features as beautiful because they are indicators of something beneficial. For example, it is beneficial to be able to tell the difference between ripe and rotten fruit, and ripe fruit may be considered more beautiful due to features such as color or texture. Švegar examined this principle in human mate choices. It was concluded that more symmetric faces are perceived are more attractive, as well as more healthy. While there was only a small association between symmetry and actual health, but a large association for perceived health, this association can be enough to create a selection pressure that motivates individuals to choose mates with more symmetric faces since it may be a cue to good health and genes. Since these aspects are heritable and will be passed down to offspring, it is beneficial to choose a mate with good traits. Overall, it seems that motivation has a large role in determining the aesthetic value of things. However, more research is needed in order to determine the exact pathways and processes involved in determining beauty. 

References

Aleem, H., Pombo, M., Correa-Herran, I., & Grzywacz, N. M. (2019, November 16). Is Beauty in the Eye of the Beholder or an Objective Truth? A Neuroscientific Answer. https://link.springer.com/chapter/10.1007/978-3-030-24326-5_11. 

Brown, S., Gao, X., Tisdelle, L., Eickhoff, S.B., Liotti, M.: Naturalizing aesthetics: brain areas for aesthetic appraisal across sensory modalities. Neuroimage58(1), 250–258 (2011).

Little, A. C., Jones, B. C., Waitt, C., Tiddeman, B. P., Feinberg, D. R., Perrett, D. I., Apicella, C. R., & Marlowe, F. W. (2008). Symmetry is related to sexual dimorphism in faces: data across culture and species. PLoS One, 3(5), e2106.

Quist, M. C., Watkins, C. D., Smith, F. G., Little, A. C., DeBruine, L. M., & Jones, B. C. (2012). Sociosexuality predicts women’s preferences for symmetry in men’s faces. Archives of Sexual Behavior, 41(6), 1415–1421. 

Sartwell, C.: “Beauty”. In: Zalta, E.N. (ed.) The Stanford Encyclopedia of Philosophy (Winter 2017). Metaphysics ResearchLab, Stanford University (2017).

Shackelford, T. K., & Larsen, R. J. (1997). Facial asymmetry as an indicator of psychological, emotional, and physiological distress. Journal of Personality and Social Psychology, 72(2), 456–466. 

Švegar, D. (2016). What does facial symmetry reveal about health and personality? Polish Psychological Bulletin, 47(3), 356–365. https://doi.org/10.1515/ppb-2016-0042.

Double Trouble: The Obesity Crisis Meets COVID-19

We’ve all seen plenty of news surrounding what has become known as the dreaded “Quarantine Fifteen”--much like the college “Freshman Fifteen”. A considerable number of Americans have reported changes in their diet, exercise habits, and weight since the coronavirus pandemic began. The way that these changes are affecting people’s health has also been quite dependent on other factors such as race/ethnicity and socioeconomic status. Stress from the pandemic has created two different food-related reactions within people: an increase in restrictive dieting and an increase in binge-eating. Both of these reactions can easily develop into serious eating disorders--which is why some behavioral medicine experts are seeing an overall rise in eating disorders since the pandemic began.

 [Eating disorders increase due to COVID-19 pandemic ]

Now, how does this relate to some recent findings in neuroscience? Dr. Jen Beshel’s lecture on the leptin conserved neural circuit in the brain provided excellent insight as to why obesity has become such a problem in modern times. The human body, as we know, evolves slowly over time, and as man makes more rapid innovations sometimes we outpace our bodies’ abilities to adjust to these innovations. One example is how drastically the food landscape has changed within the past 100 years. While food insecurity still exists all over the world, food accessibility has gone up tremendously due to the rise of cheap, processed, and fast food. The downside to this is that our bodies are not necessarily wired to ingest high-calorie, high-fat, and high-sugar foods on a regular basis--especially in those that have genetic predispositions to obesity. 

Dr. Beshel discussed a study done on mice in which one mouse had a mutated OB gene, which resulted in what we now refer to as an “obese” phenotype. This mouse was deficient for leptin--a hormone that is critical in the experience of satiety, or fullness. This deficiency led to the mouse essentially eating with no “off switch”, which resulted in rapid and dangerous levels of weight gain. Another finding from Dr. Beshel’s study also showed that elevated levels of leptin are typically found in obese individuals, as an increase in adipose tissue seems to increase leptin production. But instead of increasing feelings of satiety, these individuals seem to have a “leptin resistance” that inhibits their ability to limit food intake. High food intake mixed with an unhealthy diet can lead to becoming obese very quickly. 

So how does this relate back to the pandemic? During times of high stress, people tend to view food and food cues in one of two ways: as a way of controlling their life in an uncontrollable world or as a source of comfort. The first view tends to lead to restrictive dieting, excessive exercise, and body dysmorphia--all common symptoms of starvation eating disorders like anorexia or bulimia. But the eating disorder that has seen the greatest rise due to pandemic stress is binge eating disorder--a condition where individuals tend to overeat because they view food as a source of emotional comfort. 

Binge eating disorder is also on the rise because the pandemic has changed our food landscape yet again, especially for people with low socioeconomic status. Not everyone can afford to get fresh groceries delivered, not everyone can afford healthy takeout, some neighborhoods don’t have a supermarket around for miles, and some grocery delivery services don’t even deliver to low-income areas. People who were living in food deserts before the pandemic are finding their food options more limited than ever--especially during the “panic buying” phase of lockdown. The stress over all of these uncontrollable factors makes indulging in readily available “comfort food” almost too easy. 

[Link to news article: Chicago Tackles COVID-19 Disparities In Hard-Hit Black And Latino Neighborhoods]

Putting all of these different ideas together, we can see why there is so much disparity between Covid cases in low versus high-income areas. Low-income individuals are more likely to have pre-existing conditions (like obesity), rely the most on fast food and cheap, processed food options, live in crowded homes or apartment buildings, and, of course, work many essential jobs. It’s the perfect storm to create the level of Covid disparity that we see when comparing northside Chicago Covid cases to southside Chicago Covid cases. 

All Americans, regardless of location and class, are going through a struggle with weight control during the pandemic. But this issue is hitting the communities that are most vulnerable to death or serious complications from Covid the hardest. A closer look at these two connected issues shows that increasing food accessibility is not enough, we must also be working to bring nutritious food to impoverished communities as a first step to diminishing health disparities. 

Neuroaesthetics and Photography

            The field of neuroaesthetics seeks to understand the perception of beauty through examining neuroanatomical and associated cognitive elements. It strives to understand what determines the degree of beauty of an object, and what neural processes underlie its visual perception.
            In the article, "Is Beauty in the Eye of the Beholder or an Objective Truth? A Neuroscientific Answer", Grzywacz et al. utilized the processing fluency theory to assess the extent of the influence of both objectivity and subjectivity on the individual and collective perception of aesthetics. Processing fluency theory states that every object differs in fluency or the level of ease with which a viewer can process that object. The level of an object's fluency determines whether it is perceived positively or negatively (greater fluency results in a more positive view) based both on learned individual preference and on the evolution of general human perception of characteristics such as symmetry, balance and complexity, the main foci of this study. Specifically, they compared these characteristics amongst grayscale versions of Early Renaissance paintings, posed and spontaneous photographs. Results showed that the paintings, on average, had greater symmetry, balance, and detail; however, they showed less variability in intensity, establishing a degree of objectivity within aesthetics. Furthermore, the researchers also examined cognitive components associated with the reward-learning pathway and their relationship to the subjective aesthetic perception. They found that reinforcement learning and motivation adapt an individual’s values according to their experience, evidenced in the assessment of complexity and balance aesthetic preferences in risk-taker and risk-averse individuals. A risk-taker individual initially preferred higher complexity, whereas a risk-averse individual preferred lower complexity; these preferences were maintained in the endpoints, suggesting motivation and prior learned experiences influence the individuality of aesthetic perception.
            Similarly, another more recent study focuses on the individual and collective contribution to the high aesthetic value of an iconic photograph, Migrant Mother. In the study, “Neuro-Aesthetics and the Iconography of Photography”, Jokeit and Blochwitz apply the predictive coding theory to develop a combined neuroscientific and socio contextual approach to determine the success of this particular photograph. The predictive coding theory highlights the idea that the brain actively processes the individual’s model of the environment, compares it to the new information that is presented, and revises the existing model in order to adapt to the presented information. Furthermore, the researchers explore the idea that emotions associated with the activation of the amygdala paired with repetition enhance the memorability of a particular object or environment. These ideas are similar to the attribution of subjective aesthetics to learning and motivation proposed in Grzywacz’s study. Additionally, they emphasize the balance between relatability/familiarity and unpredictability coexisting in an art piece in order to draw and maintain the viewer’s attention. In the case of the Migrant Mother, the researchers attributed its success to its composition and the socio-economic climate of the Great Depression, when it was created. The component of familiarity and relatability stems from the emotions evoked from the shared experience of that era in America and also the conventional portrayal of a mother and her children. Additionally, the unpredictability and complexity lie in the composition, utilizing imbalance and detail which extends the duration of the viewer’s attention in order to assess all the elements of the photograph such as the presence of a baby in the mother’s arms which does not stand out upon initial observation. 

            Both studies emphasize the importance of recognizing the roles of objectivity and subjectivity when assessing the individual and general perceptions of beauty. Evolution has presented elements of objectivity in aesthetics as a result of adaptations to the environment for survival, but, as a result, has also led to increased subjectivity between and within different communities. Further exploration into this emerging field would lead to fruitful insight into the neuroscientific basis for the differences of aesthetic preference and can be utilized for practical applications to contribute to successes in other fields such marketing and visual art.

References

Grzywacz, Norberto M., et al. “Is Beauty in the Eye of the Beholder or an Objective Truth? A Neuroscientific Answer.” Springer Series on Bio- and Neurosystems Mobile Brain-Body Imaging and the Neuroscience of Art, Innovation and Creativity, 2019, pp. 101–110., doi:10.1007/978-3-030-24326-5_11.

Jokeit, Hennric, and Daniel Blochwitz. “Neuro‐Aesthetics and the Iconography in Photography.” PsyCh Journal, vol. 9, no. 4, 3 June 2020, pp. 444–457., doi:10.1002/pchj.379.

Gestures in Learning and Speech

 

Gestures are a large part of effective communication. When speaking, many people unknowingly gesture to support their points. These gestures suggest information that speech alone does not have. Gesturing supports communication thus supporting learning. The gestures that individuals use can give insight to their learning and thought processes. Gestures provide an avenue into new interpretations and ideas, and this highlights the importance of understanding why we gesture, what message these gestures convey, and how they can support learning. 

A study conducted by Elizabeth Wakefield titled, “Learning math by hand: The neural effects of gesture-based instruction in 8-year old children,” explores the connection between gestures and instruction in young students. Using fMRI, Wakefield and her team explored the neural circuitry that is associated with a child’s ability to solve and understand a mathematical problem. Two conditions were used, a speech+gesture group and a speech alone group. These students were between 8 to 10 years old, and they were randomly assigned into one of the groups. Each group viewed six videos that pertained to their group condition and were then asked to solve a math problem after an individual video, then completed a test after watching all of the videos. Wakefield et. al utilized eye tracking to collect data on the attention of the children. The researchers found that after completing the posttest, the children in the speech+gesture condition answered more problems correctly than the speech alone condition. 

The fMRI utilized in this study showed that both groups had brain issues associated with mathematical processing activated, but the speech+gesture group had the motor region, the inferior parietal gyrus, and the horizontal intraparietal sulcus activated. All of these regions are activated when children engage in action-based learning which suggest that actions and gestures are somehow related. Ultimately, Wakefield’s study suggests that gesture has an impact on neural traces of motor activity and visual attention. Those in the gesture+speech condition performed better leading to the conclusion that gesture supports learning. 

Columbia University is among many to utilize the power of gesture in analyzing people of power and their speeches. Notably, Donald Trump is an example of a speaker who uses excessive gesturing when presenting. Dr. Ronald Riggio has noted that Trump utilized 10 gestures frequently to communicate his message. An example of one is the “OK” symbol, showing a pinch between the thumb and forefinger. This gesture is understood to enforce the user’s precision and control of the statements they are making. Another common one is the “point” gesture. This is used to emphasize a statement or be accusatory; this often comes across as someone being too dominant. He is also infamous for using gestures to mimic others and their movements, such as mimicking the body language of his 2016 opponent Hilary Clinton in efforts to make her seem “stiff” and unqualified as noted by Kira Hall (2016).  The gestures that Donald Trump uses make his speeches memorable, both to his supporters and his critics. This created a spectacle and allowed some of his viewers to deem him comedic, trustworthy, and knowledgeable. 

Gestures are extremely powerful in communication. They play a role in learning and memory. It is a natural motion to many, and can be introduced into schools at a young age as shown in Wakefield’s study. Gestures carry on into adulthood and can be observed by many people in power. Therefore, it is important to study their origins and development in efforts to understand and improve our language processing.

Sources

Hall, K., Goldstein, D. M., & Ingram, M. B. (2016). The hands of Donald Trump. HAU: Journal of Ethnographic Theory,6(2), 71-100. doi:10.14318/hau6.2.009

Riggio, R. (n.d.). Understanding Trump's Non-Verbal Communication. Retrieved October 15, 2020, from http://www.columbia.edu/~st2839/midterm.html

Wakefield, E.M., Congdon, E.L., Novack, M.A. et al. (2019). Learning math by hand: The neural effects of gesture-based instruction in 8-year-old children. Atten Percept Psychophys 81, 2343–2353. https://doi.org/10.3758/s13414-019-01755-y

The Effects of Leptin and GIP on Food Related Behavior and Obesity

     Obesity is one of the leading health issues in America today, affecting around 40% of the US population, according to the CDC. As obesity is so prevalent and is associated with many significant health risks, research into obesity is very prominent and expansive in many fields of science today. In neuroscience, researchers have been looking at the role leptin plays in neural pathways that regulates food and appetite related behavior. This research helps in identifying the causes of obesity. 

Leptin is a hormone released by fat cells. It is thought to be a ‘satiety’ signal to the body, thereby controlling food intake and appetite. Leptin is thought to inhibit neurons in the brain that work in neural pathways that promote food intake and stimulate hunger. Dr. Jennifer Beshel conducted a study to see whether reducing expression of an leptin analog in the brain would lead to obesity phenotypes. In the article “A Leptin Analog Locally Produced in the Brain Acts via a Conserved Neural Circuit to Modulate Obesity-Linked Behaviors in Drosophila”, Dr. Jennifer Beshel and colleagues were studying a leptin analog, upd1, in Drosophila. Upd1 is thought to inhibit Drosophila neuropeptide F (npf), which functions in regulating food odor valuation and promotes food intake. They found that neurons expressing Upd1 are positioned in the brain to release upd1 on npf-positive neurons. This is a homologue of leptin acting on mammalian neuropeptide Y seen in humans which also regulates food related behavior. The researchers also showed that flies that were manipulated to stop expressing upd1 had a greater response to food odor cues, consumed more food per hour compared to controls, had a higher body mass and had increased sensitivity to an obesogenic environment. The results provide evidence for obesity being related to genetics, shown here in the case of leptin expression, and one’s food environment. 

Dr. Beshel’s study showed how leptin plays a role in obesity characteristics shown in the body through neural signalling. However, this study led to further questions regarding what controls and mediates leptin levels in the brain. An article published by Science Daily spoke about a recent study led by researchers at Baylor College of Medicine, which offered one explanation of how our 21st century food landscape controls leptin levels. It explained how the researchers were looking at a mechanism that influences ‘leptin resistance’. Leptin resistance is when the body is producing normal levels of leptin but does not respond to its satiety signal. It is thought that the majority of obsese individuals do not have a genetic mutation that stops them producing leptin, but instead have leptin resistance, making it an interesting subject of research. In “Gut-brain connection helps explain how overeating leads to obesity”, the article explained how the researchers were studying gastric inhibitory polypeptide (GIP), a hormone that is produced in the gut which travels to the brain and inhibits leptin. GIP functions in managing the body’s energy levels, and GIP production in the gut is increased when eating a high fat diet. The researchers fed mice a high fat diet, making them obese, and then blocked the GIP receptors in the brain. With GIP not functioning, the mice ate less and were able to reduce their fat mass. This suggests that leptin was now able to function correctly and control appetite. Interestingly, they found that normally fed, lean mice did not respond to blocking GIP receptors, indicating that diet influences this GIP and leptin interaction. The results of this study suggest that a high fat diet contributes to leptin resistance through the role of GIP. In our current food landscape in which more people are eating high fat diets, the interesting results of this study offers more insight into how this diet is affecting obesity. 

The results of Dr. Beshel’s and the Baylor College of Medicine’s studies provide us with great insight into starting to understand how obesity happens and how an individual might be predisposed to becoming obese. However, it is clear that more research into leptin, leptin resistance and the factors that influence these mechanisms needs to be done in order to improve our understanding of obesity and help lessen the rate of obesity in the U.S and the world today. 

WORKS CITED:

Baylor College of Medicine. (2018) "Gut-brain connection helps explain how overeating leads to obesity." ScienceDaily. ScienceDaily, 12 August 2019. <www.sciencedaily.com/releases/2019/08/190812160533.htm>. 

Beshel, J., Dubnau, J., & Zhong, Y. (2017). A Leptin Analog Locally Produced in the Brain Acts via a Conserved Neural Circuit to Modulate Obesity-Linked Behaviors in Drosophila. Cell metabolism, 25(1), 208–217. https://doi.org/10.1016/j.cmet.2016.12.013