Why Cleaning our Oceans Could Also Reduce Obesity

Samera Mulatu, Georgia Southern University

The problem: Charleston Harbor is undergoing massive dredging to make way for super tankers. There are concerns that banned legacy compounds buried in the sediments, such as tributyltin (TBT), will be brought up into the harbor waters as a result of the dredging. A related concern is that oil spills will become more common and involve the release of cleanup compounds into the water column, including Span 80 and dioctyl sodium sulfosuccinate (DOSS). These three compounds and others are known to act as endocrine disrupting compounds (EDCs), which disrupt the Retinoid X Receptor (RXR) pathway. In mollusks, RXR disruption induces imposex development (when female mollusks develop male sex traits). One goal of my project is to measure the rates of imposex in the Eastern mud snail (Tritia obsoleta) within different sites in Charleston Harbor and to see if these rates increase over time with dredging.

The same chemicals that cause imposex are used in medications, processed foods (e.g. homogenized milk), textiles, paints, and cosmetics.  Because the identification and study of many EDCs is fairly new and upcoming, their effects on the human body are still not fully understood. Those EDCs found to promote weight gain are called “obesogens.” Early exposure to obesogens can detrimentally affect a child’s health into adulthood! These obesogens can persistently alter hormonal signaling pathways in children, which can lead to permanent metabolic damage.

Obesity in the United States is at an all-time high. Approximately half of the population is predicted to be obese by 2020.  This is a serious health problem because obesity can drastically increase the likelihood of developing cancer, diabetes, and heart disease. Many people associate obesity with lack of exercise. However, it should be noted that obesogens can reduce energy, increase appetite and change behaviors associated with weight gain.

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The author (right) collecting mud snails (Tritia obsoleta).  Photo: Dr. Spyropoulos.

I would like to give a big thank to Dr. Demetri Spyropoulos for guiding me in my research. Also to the Fort Johnson REU Program, NSF DBI- 1757899, for providing me with the funds to complete this project.

Related research

Hotchkiss, A.K, A.G.Leblanc, R.M. Sternberg. 2002. Synchronized expression of Retinoid X Receptor mRNA with Reproductive Tract Recrudescence in an Imposex- Susceptible Mollusc. Environ. Sci Technol. 42: 1345- 1351.

Ravitchandirane, V. S, M.Thangaraj. 2013. Phylogenetic Status of Babylonia Zeylanica (Family Babyloniidae) Based on 18S rRNA GENE FRAGMENT.Annals of West University of Timisoara, ser. Biology. 1(2): 135- 140.

Barron- Vivanco, B.S, D. Dominguez- Ojeda, I.M. Medina- Diaz, A.E. Rojas- Garcia, M.L. Robledo- Marenco. 2014. Exposure to tributyltin chloride induces penis and vas deferns development and increases RXR expression in females of the purple snail (Plicopurpura pansa). Invertebrate Survival Journal. 11: 204-2012.

Horiguchi, T., M. Morita, T. Nishikawa, Y. Ohta, H. Shiraishi. 2007. Retinoid X Receptor gene expression and protein content in tissues of the rock shell Thais clavigera. Aquatic Toxicology. 84: 379-388.


		
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Humans and gators and chickens, oh my!

Jimena B. Pérez-Viscasillas, University of Puerto Rico at Mayaguez

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When I first applied to this Marine Biology REU, in a lab that works mostly with alligators, at a Marine Science Campus right by the Charleston shore, I never thought I’d end up working with chickens. Yes, you read correctly: chickens, of the Chick-Fill-A and Kentucky Fried sort. I was surprised too, naturally, but it turns out the reason behind it is actually pretty important.

A couple of years ago, a group of scientists noticed some alligator populations in Florida weren’t doing too well. Their fertility levels were decreasing and a lower percentage of the eggs laid were hatching. Upon further study, evidence pointed towards a likely culprit: anthropogenic chemical contaminants in the environment. These contaminants were negatively affecting the gators’ hormone production and, in turn, their reproductive systems.

What do these gators have to do with chickens, though? Perhaps more importantly, what do they have to do with us? Let’s review some basic bio…

Figure 1: Vertebrate phylogenetic tree. Amniotes are organisms which have adapted to terrestrial reproduction. This group includes birds, reptiles, and mammals. (Graphic taken from: UCL)

There are some terrestrial animals which lay eggs (like chickens and gators) and some that carry their young in the womb, inside the placenta (like us). Both types of organisms, collectively called amniotes, have much of the same tissues surrounding their embryos during development. This shared characteristic means that we may be able to study some egg-laying animals to better understand our own reproductive systems.

Figure 2: A chick embryo and membrane. The membrane I’m going to be studying is that which lines the inside of the shell. Its called the chorioallantoic membrane, and it allows gas and waste exchange between the embryo and the environment. (Taken from Angiogenesis Laboratory Amsterdam)

Before we can use these organisms’ tissues as models of our own, however, we have to make sure we understand how they function. This is where I (and the chickens) come in. This summer, I’m going to be measuring how (and if), at different stages of development, the egg membrane of chickens produces hormones called prostaglandins. Prostaglandins play a major role in the immune system, as well as the body’s general regulation and reproduction. This preliminary research would help us better understand these sentinel species and allow us to later assess how their endocrine, immune and reproductive systems are being compromised by environmental pollutants. If we know how chemical contaminants in the environment are having negative effects on their reproduction, what might it tell us about how they’re affecting our health and reproduction?

To learn more about my project, check back for further posts!

Acknowledgements

This research, conducted at Dr. Louis Guillete’s MUSC Laboratory, is made possible thanks to funding from NSF and the College of Charleston. Further equipment and facilities are provided by the Hollings Marine Laboratory.

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References:

Bellairs, Ruth & Osmond, Mark. The Atlas of Chick Development.  San Diego, California: Elsevier Academic Press, 2005. Print.

Guillette LJ Jr. “The evolution of viviparity in amniote vertebrates—new insights, new questions.” J Zool  223 (1991): 521–526. Web. 10 June 2015.

Guillette LJ Jr. “The evolution of viviparity in lizards.” Bioscience 43 (1993): 742–751. Print.

Kalinski P. “Regulation of Immune Responses by Prostaglandin E2.” J Immunol 188 (2012):21-28. Web. 10 June 2015.

Kluge AG. Chordate Structure and Function. New York: Macmillan Publishing Co., Inc.; 1977. Print.

Milnes MR, Guillette LJ Jr. “Alligator Tales: New Lessons about Environmental Contaminants from a Sentinel Species.” BioScience 58.11 (2008): 1027-1036. Web. 15 June 2015.  doi:10.1641/B581106