The Panacea for Obesity: Fat!

Hello fellow science lovers!  Since my last blog post[i], I have been quite busy and have generated exciting and perplexing data.  As a brief reminder, I am working within the Division of Endocrinology, Diabetes and Metabolism at Beth Israel Deaconess Medical Center and Harvard Medical School[ii], focusing on hydrogen sulfide signaling using genetic knockout mouse models.  In particular, I am focusing my research on a knockout (KO) mouse strain for the major hepatic (liver) endogenous hydrogen sulfide producing enzyme, cystathionine gamma lyase (CGL). When I wrote my last blog post, I was beginning to examine key gene expression and protein expression levels between wild type (WT) control mice and CGLKO mice by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR)[iii] and Western Blots[iv] respectively.  I continue to rely on these powerful molecular biology methods, where I attempt to connect the dots between differential gene and protein expression levels.  Recently, my data has lead me towards a nutritional framework, where I have been particularly interested in dietary-induced and dietary-resistant obesity.

Pictured on the right is the ob/ob mouse strain compared to a normal, wild type mouse strain on the left. Ob/ob mice are deficient in the feeding inhibiting hormone leptin, and thus are used in obesity and diabetes research [vii].
Given the pervasive rise in obesity and diabetes within the United States (US), therapeutic targets for dietary-resistance to obesity are a “hot” research topic within the field of Endocrinology and Metabolism.  In a special report published in 2005 within the New England Journal of Medicine (NEJM), the authors predict “that as a result of the substantial rise in the prevalence of obesity and its life-shortening complications such as diabetes, life expectancy at birth and at older ages could level off or even decline within the first half of this century.”[v] This stands in stark contrast to human trends, where human life expectancy has steadily increased over the past thousand years [v].  Thus, the need for breakthrough research discoveries regarding obesity, metabolic disease, and diabetes has never been more imperative.  A major research target in recent publications has been the heat-generating, master energy consuming mammalian brown fat, or brown adipose tissue (BAT) [vi].

In mammals, BAT is a major tissue site for chemical production of heat (thermogenesis) from fats, which has made BAT a promising target to induce weight loss[vi].  Traditionally, when exposed to cold temperatures, humans generate heat by shivering [vi].  However, mammals such as mice and human infants possess vast BAT depots, allowing thermogenesis during cold exposure to be driven by the chemical uncoupling of cellular energy production, oxidative phosphorylation [vi].  This chemical uncoupling of oxidative phosphorylation is achieved in part through expression of uncoupling protein-1 (Ucp1) [vi]. Additionally, white fat or white adipose tissue (WAT), the classic form of stomach fat we all attempt to minimize, can be induced into a BAT like state, known as “beige” or “brite” fat [vi].  This beige fat has thermogenic capacity, and because thermogenesis relies on the breakdown of fat depots in order to generate heat, beige fat has the ability to burn excess fat depots and promote a healthier metabolic system [vi].  Countless studies have demonstrated that “expanding the activity of brown fat, beige fat or both in mice through genetic manipulation, drugs or transplantation suppresses metabolic disease.”[vi] One such stimulus for expanding beiging of WAT is dietary control.  Thus, because of the vast therapeutic potential of beige fat and BAT, I have been particularly fascinated by diets that can induce beige fat and or increase BAT activity.  Such a diet could have broad reaching implications for metabolic disease, and could help reduce the estimated 300,000 deaths per year related to obesity [v].

Here, major anatomical depots of brown adipose tissue (BAT), white adipose tissue (WAT) and beige adipocytes are depicted. This figure portrays differences between fat locations in (a) mice and (b) humans.   Genetic markers are given for each adipocyte type in the lower right hand corner  [viii].
Compared to my classroom studies at Brandeis, working in a biomedical research lab allows me to explore complex physiological topics that I would never confront in an undergraduate class, such as BAT and beige fat thermogenesis.  After running experiments on RNA, DNA, and proteins extracted from both control (WT) and CGLKO mice, the results almost always spur me to read a slew of research papers and reviews, which guide me towards a holistic understanding of what is occurring inside my mice. For example, I have examined Ucp1 expression levels in my mice, leading me towards reviews regarding thermogenesis. This ability to read beyond only what is assigned to me is a wonderful aspect of research which is mostly absent as an undergraduate at Brandeis.  I find this freedom allows me to become more excited about the material, and often causes me to gleefully share theories of mine with my co-workers, most of whom are post-doctoral fellows.

Similar to last summer, I am loving the environment of working in a basic science research lab.  I am continually refining my molecular techniques, learning new assays weekly, such as the protein concentration quantification bicinchoninic acid (BCA) assay[ix].  With each data result or conversation with the post-doctoral fellow I work alongside, I learn new complex signaling pathways within mammalian physiology.  After each biweekly lab meeting, I learn new elements of modern thyroid research, continually building upon my knowledge base of intricate thyroid endocrine regulation.  These molecular biology techniques combined with novel biology concepts will serve me well both in my future Biology coursework at Brandeis and in my future pursuits in and after medical school. Who knows, I may even end up a practicing Endocrinologist and participating in BAT thermogenesis research!  Only time will tell.

– Josh Lepson

[i] Brandeis University Hiatt Career Center. 2017. World of Work (WOW) Summer Internship Blog: Harnessing Science for the Common Good. Accessed on July 2.

Harnessing Science for the Common Good

[ii] Beth Israel Deaconess Medical Center. 2017. Endocrinology, Diabetes and Metabolism. Accessed on July 2.

http://www.bidmc.org/Centers-and-Departments/Departments/Medicine/Divisions/Endocrinology.aspx

[iii] ThermoFisher Scientific. Basic Principles of RT-qPCR: Introduction to RT-qPCR. Accessed on July 2.

https://www.thermofisher.com/us/en/home/brands/thermo-scientific/molecular-biology/molecular-biology-learning-center/molecular-biology-resource-library/basic-principles-rt-qpcr.html

[iv] ThermoFisher Scientific. Overview of Western Blotting. Accessed on July 2.

https://www.thermofisher.com/us/en/home/life-science/protein-biology/protein-biology-learning-center/protein-biology-resource-library/pierce-protein-methods/overview-western-blotting.html

[v] Olshansky, S.J., Passaro, D.J., Hershow, R.C., Layden, J., Carnes, B.A., Brody, J., Hayflick, L., Butler, R.N., Allison, D.B., Ludwig, D.S. 2005. A potential decline in life expectancy in the United States in the 21st century. N. Engl. J. Med. 352(11): 1138-1145.

[vi] Harms, M., Seale, P. 2013. Brown and beige fat: development, function and therapeutic potential. Nat. Med. 19(10): 1252-1263.

[vii] The Jackson Laboratory. B6.Cg-Lepob/J. Accessed on July 2. https://www.jax.org/strain/000632

[viii] Bartelt, A., Heeren, J. 2014. Adipose tissue browning and metabolic health. Nat. Rev. Endocrinol. 10(1): 24-36.

[ix] ThermoFisher Scientific. Pierce™ BCA Protein Assay Kit. Accessed on July 2.

https://www.thermofisher.com/order/catalog/product/23225

Harnessing Science for the Common Good

Division of Endocrinology, Diabetes & Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School

Working in a basic science biomedical research laboratory within the Division of Endocrinology, Diabetes and Metabolism at Beth Israel Deaconess Medical Center and Harvard Medical School[i] has been an incredibly exciting experience.  I started to work in the Lab two weeks ago, located within the Center for Life Science in the heart of the Longwood Medical area.  Since I worked in this same Laboratory during the Summer of 2016, I was welcomed into the research environment, and was able to pick up where I left off last summer.  After recently completing animal research facility training, I began working with laboratory mice, focusing on a knockout (KO) mouse strain of the major hepatic (liver) endogenous hydrogen sulfide producing enzyme, cystathionine gamma lyase (CGL).  The Lab I work in is interested in the regulation of human metabolism by master endocrine regulator, thyroid hormone.  Thus, I have been investigating the relationship between thyroid hormone and endogenous hydrogen sulfide production capacity, with an emphasis on extension of longevity using mouse models.

Inside the laboratory, much of my work consists of analyzing key gene expression and protein expression levels between wildtype (WT) control mice and CGLKO mice through various physiological states.  My research consists of dissecting mouse tissue ex vivo, performing an RNA extraction from that tissue type (i.e., liver tissue, brown adipose tissue, etc.), running a reverse transcriptase quantitative polymerase chain reaction (RT-qPCR)[ii] using several key gene markers, and performing statistical tests on differences in gene expression levels between WT and CGLKO mice.  For proteomic analysis, I perform Western Blots[iii] and statistical tests to establish potential differential protein expression in CGLKO mice.  Once I have gathered meaningful data, I present the results informally to the post-doctoral fellow I work alongside and to my Principal Investigator (PI).  However, living systems are complex, and bewilderment can punctuate results.  At these times, I turn to scientific journals for answers.

Pipettors and laboratory reagents (Sigma-Aldrich, Fisherbrand by ThermoFisher Scientific): friends of the biomedical researcher.

Biomedical literature publications, such as Brent et al. 2014[iv], have guided me through the complex physiology of thyroid endocrine regulation.  As an incoming third year undergraduate student, dissecting complex signaling pathways with my current learning foundation is a daunting task, especially considering the wealth of knowledge and graduate degrees that my co-workers possess.  However, my co-workers and PI have been and continue to be excellent learning resources.  Bouncing theories back and forth with the post-doctoral research fellow I work alongside is a daily occurrence.  This collaborative environment is characterized by persistent questioning of results and interpretations, which has filled my scientific soul with joy.  This stands in stark contrast to undergraduate classes, where the measure of performance is reflective of the individual, rather than a research team.

Looking forward, the skills I am learning, both in molecular methods and thinking as an experimentalist, will bolster my ability to succeed as a Biology major at Brandeis, and as physician scientist in the future.  I wish to exit this summer with the framework to think as a biomedical researcher, with the ultimate goal of generating meaningful research that can mitigate human suffering.  This can be easy to lose track of in the busyness of a lab, but I hope this goal remains tethered to my being; science for the common good.

[i] Beth Israel Deaconess Medical Center. 2017. Endocrinology, Diabetes and Metabolism. Accessed on June 4.

http://www.bidmc.org/Centers-and-Departments/Departments/Medicine/Divisions/Endocrinology.aspx

[ii] ThermoFisher Scientific. Basic Principles of RT-qPCR: Introduction to RT-qPCR. Accessed on June 4.

https://www.thermofisher.com/us/en/home/brands/thermo-scientific/molecular-biology/molecular-biology-learning-center/molecular-biology-resource-library/basic-principles-rt-qpcr.html

[iii] ThermoFisher Scientific. Overview of Western Blotting. Accessed on June 4.

https://www.thermofisher.com/us/en/home/life-science/protein-biology/protein-biology-learning-center/protein-biology-resource-library/pierce-protein-methods/overview-western-blotting.html

[iv] Mullur, R., Liu, Y.Y., Brent, G.A. 2014. Thyroid hormone regulation of metabolism. Physiol. Rev. 94(2): 355-382.

Josh Lepson