Cell Bio Bites Topic : Mitochondrial Proton Gradient and Uncoupling Protein in Brown
Fat
Mitochondrial Proton Gradient Dissipation and Uncoupling Protein in Brown Adipose Tissue Primordial Components in Neonatal and Hibernal Survival by Paula Sahyoun 20559361

For
BIO 130 Tutorial Section 116
Areen Duqoum

Mitochondrial Proton Gradient Dissipation and Uncoupling Protein in Brown Adipose Tissue Primordial Components in Neonatal and Hibernal Survival

Thermoregulation is an important aspect in survival. Often survival is dependent on an organism’s ability to retrieve energy from their brown adipose tissues (BAT)(Cannon & Nedergaard, 2004). This process is known as proton motive force. ATP is not produced, the protons take an alternative route through an uncoupling protein 1 (UCP1), in the inner membrane. UCP1 allows the protons to return to the inner membrane after they have been actively transported out of the mitochondria by the electron transport chain. Without the proton gradient, oxidative phosphorylation is uncoupled and the energy is instead released as heat. (Vidal-Puig et al, 1997) Through the dissipation of mitochondrial proton gradient, brown adipose tissue and the uncoupling protein work to ensure the survival of organism that are unable to thermoregulate themselves, such as neonatal and hibernating mammals.

The thermogenic properties of BAT are vital for infant survival in early stages of life. Newborns are extremely susceptibility to heat loss and are at high risk of hypothermia. (Boron & Boulpaep, 2011) This is due to the body’s surface to volume ratio (large skin surface in relation to the baby’s body mass). Furthermore, the newborn is vulnerable to harsh exterior environmental conditions, they have poor insolation, and are unable to use muscle contraction (shivering thermogenesis) to avoid heat loss. Infants have weak and underdevelop immune systems making additional protection necessary. (Cannon & Nedergaard, 2004) In order to counter these issues, 5% of an infant’s body weight is comprised of BAT. (Nordqvist, 2014) BAT has the unique ability to perform non-shivering thermogenesis. The process commences under cold-induced conditions. This helps the child maintain normal body temperature by dissipating energy, as the child grows older and gains the ability to thermoregulate themselves, their BAT reserves will significantly decrease. (Nordqvist, 2014) In short, without BAT, newborns would not be able to regulate their body temperature and consequently are at a higher risk for developing hypothermia.

During hibernation, mammals have to keep warm while inactive, cold induced non-shivering thermogenesis provides the mammal with enough heat to maintain vital bodily functions. Hibernation is the lethargic state certain mammals enter during the winter season. The animals keep alive by burning their fat resources (BAT). (Cannon & Nedergaard, 2004) Cold-inducing thermogenesis releases epinephrine and starts the proton motor force process, using UCP1 in uncoupling oxidation respiration in order to perform anaerobic glycolysis and release the energy as heat. (Nordqvist,