Leptin regulates glucose homeostasis during starvation, study finds
The brain accounts for less than 2% of the body's weight. However, even at rest, it consumes approximately 20% of the body's energy. Why does the brain have so large an energy budget? Although this question has not been fully understood, it is believed that the brain requires a lot of energy to fuel electrical impulses that neurons use to communicate with other neurons or other types of cells.
The brain may be the most complex and magnificent organ in the human body. It's made of over 100 billion neurons that communicate through synapses. It possesses important functions such as perception, motor control, homeostasis, arousal, sleep, learning, memory, research, and reasoning. These functions are essential for our survival. Efficient energy supply is needed for the brain to function properly. If energy supply to the brain is not enough, neurological disorders like stroke and spinal cord injury can occur.
Glucose, a type of sugar, is the major source of energy for every cell in the body. The brain depends on glucose to operate normally and gets glucose and oxygen from the blood. Starvation, a state in which the body does not get enough energy intake due to a lack of food, can change the body's energy metabolism. During periods of starvation, the body switches from burning carbohydrates to burning fat to maintain blood glucose levels stable and provide required glucose for the brain. This process has been associated with a drop in insulin -- a key hormone regulating glucose levels. Now, a study of Yale University School of Medicine has suggested that another hormone, called leptin, may also play a key role.
Described in Cell on 4 January 2018, the study (Leptin Mediates a Glucose-Fatty Acid Cycle to Maintain Glucose Homeostasis in Starvation) has demonstrated that the hormone leptin, which is secreted from fat cells and which regulates energy balance by inhibiting hunger, functions to promote a shift from carbohydrate to fat oxidation and maintain glucose homeostasis and glucose supply to the brain during starvation. The researchers made the discovery by analyzing the rate of fat and carbohydrate metabolism in rats during starvation. The study highlights the need to further explore the role of leptin in the maintenance of glucose homeostasis in starvation.
The corresponding author of this study, Prof. Gerald Shulman at Yale, has been focused on intracellular glucose and fat metabolism in humans. His research sheds light on the cellular mechanisms of insulin resistance and type 2 diabetes. Besides, his research extends understanding of the pathogenesis of some other health problems like dyslipidemia and cardiometabolic disease.
Leptin was first discovered in 1994. Since then, a lot of efforts have been made to understand its role. Leptin appears to be best known for its role in regulating energy homeostasis. Further, it also modulates body weight, metabolism, and endocrine function. Lack of leptin has been associated with health conditions like lipodystrophy, hypothalamic amenorrhea, and congenital leptin deficiency. For patients with these health conditions, a leptin replacement therapy may significantly improve their symptoms. Leptin works through leptin receptor expressed throughout the body. Problems in the expression of leptin or leptin receptor have been linked to obesity, and analysis of serum leptin levels is a useful test in patients with severe early-onset obesity.