Table 1.

Some of the genetic mutations implicated in human obesity.

Rare but crucial mutations
Leptin	Produced by adipose tissue, leptin reduces food intake in rats if centrally injected. Mutation on chromosome 7 found in one obese family [72].
Leptin receptor	CNS receptor for leptin, Mutation on chromosome 1 associated with three cases of human obesity [73].
Melanocortin 4 receptor	CNS receptor involved in the suppression of appetite Mutations on chromosome 18 associated with several cases of obesity [74].
Prohormone convertase 2	Converts proinsulin to insulin and C-peptide. Polymorphisms on Chromosome 20 are associated with a higher relative risk of NIDDM and obesity [75].
Mutations of probably minimal clinical impact
Uncoupling proteins	UCP 2 and 3 mapped close to 11q 13 which is linked to human obesity and hyperinsulinemia [76].
Insulin Receptor Substrate	Important in cell signalling mediating the action of insulin. Candidate gene because of putative (IRS-1) involvement in insulin resistance. Recent studies of polymorphisms in African Americans showed no link with obesity [77].
β3-adrenoreceptor	Polymorphisms of this adrenoreceptor have been associated with an increased relative risk of obesity in some studies of Asian and Caucasian populations [78].