The Leptin Hormone

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The leptin hormone is a peptide that is responsible for the management of body weight. This specific hormone sends signals to the brain with information about the amount of fat stores in the body, and can prevent food intake or increase the expenditure of energy by interacting with the hypothalamus. (Strosberg and Issad 1999) Studies done on mice with naturally occurring mutations concluded that mice with a loss of function mutation to the leptin protein became obese because there were no signals being sent to the brain to inhibit food intake. When leptin was given to the mice that exhibited this mutation their excessive eating stopped, and they were able to return to a healthy weight. Subsequently, loss of function mutations of the leptin …show more content…
These signals are sent at intervals during the day, which usually correspond to meal times and include information about the body’s glucose, insulin and fatty acid levels. These signals help the brain to make decisions about the regulation of food intake and energy expenditure. Mice who have a mutation of the leptin protein (ob/ob) are consequentially severely obese. Mice who have a mutation of the leptin receptor (db/db) also show severe obesity, as well as hyperglycemia, which is an excess of glucose in the bloodstream. When the ob gene was transferred to the db/db mice, the mice remained obese, as well as when the db gene was transferred to the ob/ob mice. Only when cross-circulation experiments (a process of anatomically joining two individuals) were conducted on the mice, did the effects on obesity change. The ob/ob mice stopped eating as much and lost weight, while the db/db mice continued to eat the same amount and stayed at the same weight. These experiments concluded that ob/ob mice fail to send signals, but can respond to them if they are present, while db/db mice send the signals but lack the ability to respond. (Campfield et al. …show more content…
These experiments concluded that the amount of body fat you have is proportional to the amount of leptin in the body. Further research has experimented on increasing and decreasing leptin concentrations in rodents. When leptin was at a high concentration the rodents decreased food intake and lowered body fat, while decreasing leptin concentration increased food intake and body fat. (Isreal and Chua 2009) Although mutations of the ob gene in mice resulted in severe obesity, no mutations were found on the ob gene of obese humans until very recently. The genes of two relatives of Pakistani origin who had very low levels of leptin were sequenced and it was found that they both had a deletion of a guanine, which resulted in a nonsense mutation. As well the sequencing of an obese Turkish patient showed a missense mutation at the same codon that is mutated in the ob/ob mice. (Strosberg and Issad
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