Melissa Chisholm November 22nd, 2016 Brown Adipose Tissue Melissa Chisholm November 22nd, 2016

What is Brown Adipose Tissue Type of fat responsible for non-shivering thermoregulation of the body Abundant in Babies ( back, spine and around the shoulders) Recently found in some adults in mostly the upper chest and neck area Brown adipose tissue (BAT), also known as brown fat, is one of two types of fat found in humans and other mammals the other type is known as white fat. Brown fat's main function is to generate body heat. Humans and mammals with higher levels of brown fat take longer to start shivering from the cold, than those with lower levels. That is why newborns do not shiver in the cold, their brown adipose tissue levels are higher than in older humans and it protects the baby from hypothermia. 5% of their body weight is approximately BAT.

Brown Adipose Tissue Has similar characteristics as muscle tissue BAT thought to be derived from the same stem cells Brown fat seems to act similarly to muscle tissue in many ways, Both skeletal muscle and brown adipose tissue cells have more mitochondria per cell than most other cell types in the body such as epithelial, skin, or white adipose tissue, and both skeletal muscle cells and brown adipose tissue participate in the regulation of body temperature.

What is the difference between brown and white adipose tissue? White Adipose Tissue or white fat. When we consume too many calories, the body stores the excess energy in the form of white fat. White fat is the type of fat that most of us try to avoid accumulating. White fat cells store energy in the form of fat droplets. White fat does help us to regulate our temperature by insulating organs, but it does little to burn calories like brown fat does. White fat is found below the skin (subcutaneous) and around the organs (visceral fat, which can be especially dangerous) and accumulates from a surplus of calories. White fat has an effect on hormone production and hunger levels, and in healthy, non-overweight humans, it can comprise up to 20 percent of body weight in men and 25 percent in women. WAT have a nucleus , a large fat droplet and few mitochondria BAT:Brown fat cells contain many mitochondria and are made of a larger number of fatty droplets, which are also smaller than those that make up white fat. The high number of mitochondria which are rich in iron and that BAT have a rich blood supply give BAT their brown color. Within brown fat’s mitochondria heat is able to be generated that helps regulate the body’s internal temperature in response to the changing environment outside.

How does brown adipose tissue work? Cold activates the sympathetic nervous system. Noradrenaline is released by the postganglionic neurons. The noradrenaline binds to G-protein-coupled receptors on the adipocytes surface. The second messenger cAMP is generated and moves into the nucleus where it binds to the promoter of the gene encoding an enzyme that converts thyroxine (T4) to triiodothyronine (T3) [Link]. T3 enters the nucleus and bind to the promoter of the gene encoding uncoupling protein1 (UCP1). UCP1 inserts into the inner membrane of the mitochondria where it allows the protons that have been pumped out into the intermembrane space by the electron transport chain to return to the matrix without having to pass through ATP synthase.

Benefits of Brown Adipose Tissue Contributes to overall caloric expenditure Utilizes glucose and free fatty acids circulating in the body Improves heart health Glucose homeostasis 1. Burns Calories Brown fat cells use more calories than other types of fat cells do, helping you to potentially shed stored body fat and maintain a healthy weight more easily. It does this to regulate our internal temperature and help us survive even in cold climates. (4) BAT contributes to overall energy expenditure and can even help you lose weight because it prevents a “positive energy balance” (eating more calories than you can burn). As you probably know, energy intake comes from food consumption, whereas the major contributors to energy expenditure are exercise and simply the energy it takes to keep you alive (basic metabolic processes). According to the American Diabetes Association, brown fat activity can also impact daily energy expenditure and prove to be an effective therapy for obesity. (5) 2. Decreases Dangerous Fat Brown fat can decrease white fat stores, which might lower your risk for chronic diseases like diabetes, heart disease, stroke and other concerns related to aging and obesity. 3. Improves Heart Health Studies show brown fat has benefits for your heart too, including naturally lowering cholesterol and triglyceride levels. It’s believed that  brown fat can fuel itself with circulating triglycerides taken up from the bloodstream (a good thing, since in excess these contribute to numerous diseases). 4. Stabilizes Blood Sugar A new discovery has been made recently by researchers at Stockholm University showing that brown fat cells are capable of altering glucose uptake, drawing sugar out of the blood to fuel muscle cells. This helps to stabilize blood sugar levels and might prevent things like fatigue, cravings, headaches and overeating. Most importantly, it can lower your risk for type 2 diabetes. (6) In fact, brown fat’s signal pathway differs from the signal pathway triggered by insulin, which means it’s possible that brown fat can be activated and especially benefit patients who already have type 2 diabetes and are not responsive to insulin’s effects.