article Fall 2019

Organ Communication Through Lipids

Despite their bad image, fatty cells are helping biochemical researchers map the pathways of many organisms–from humans with metabolic diseases to livestock.

Fat has a negative reputation of being the junk of the body and something we should aim to rid ourselves of. We’ve heard it all–cardiovascular disease, diabetes, high blood pressure–all associated with excess fat and obesity. While it is true that excess adipose cells can cause various health issues, adipose tissue is a crucial endocrine organ that informs the body of available energy stores. Moreover, lipid-fat molecules that compose parts of cells and circulate through our bloodstream play a crucial role in every organism’s metabolic process. Lipids are responsible for duties ranging from storing excess energy to maintain body temperature.

Sustaining a body temperature that is favorable for biochemical reactions is paramount for survival. When an organism experiences extreme cold, there is a sudden increase in the demand for energy to produce the heat to maintain an optimal temperature. To sufficiently supply this increasing energy demand, our body utilizes types of fat cells called brown adipocytes. Brown adipocytes are tasked to increase both glucose and lipid uptake, converting them to energy. Activated brown fat is able to clear excess lipids and glucose from the bloodstream, making this tissue an attractive therapeutic target to treat obesity, diabetes, and many other metabolic syndromes.

Judith Simcox, an assistant professor in the biochemistry department at UW-Madison, is attempting to understand the sources of lipids circulating in our blood that fuel brown fat thermogenesis and uncover the cross-tissue communication pathways that regulate the production of these lipids. Specifically, Simcox is focusing her research on answering two major questions: how are liver-produced lipids taken up and metabolized in brown adipocytes, and how is hepatic lipid processing regulated in cold exposure?

In her research, Simcox exposed mice to an extremely cold environment and tracked the level of acylcarnitines, a type of lipid that is produced in the liver, particularly during periods without food. A sudden drop of temperature will trigger the release of stored lipids from fat cells which will be directed into the liver to be further processed. Due to this, Simcox chose to focus on the liver as the communicating organ for the adipose cells.

“Brown fat cells can be utilized to treat obesity as it can increase both glucose and lipid uptakes of the body” — Judith Simcox

According to Simcox, there are two central goals in the medical field in relation to lipids: characterizing the many lipid species circulating in the blood to use them as diagnostic markers of disease and understanding how to clear excess lipids from the body in diseases such as cardiovascular disease and fatty liver disease. Simcox’s research attempts to answer these questions by identifying circulating lipids in cold exposure and by activating brown adipose cells to increase the clearance of excess lipids.

In addition to its application in the medical field, this method also has potential in agriculture, particularly on livestock such as pigs. Simcox added that by observing the stress that temperature puts on pigs, we have the potential to find the optimal temperature for their metabolism. Because they do not have natural brown adipose tissues, pigs, especially piglets, are sensitive to cold temperatures and hypothermia, which is a major agricultural problem. To combat this issue, a “biomarker” of temperature is needed to know the optimal range of temperature for the biochemical reactions within the pigs. In order to do that, Simcox states that the understanding of all metabolic pathways is crucial, as the pathways can provide agricultural scientists much detail on the sustainment of the body temperature.

Simcox hopes that in the future she will be able to identify biochemical pathways that regulate metabolism that is altered in metabolic diseases such as fatty liver disease and by tracking lipid species to their final destinations. From the medical field to the farm field, mapping lipid pathways has enormous potential that will help eradicate the negative stigma of fat.

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