GPR40 is a member of the free fatty acid G protein coupled receptor family and is activated by saturated and unsaturated carboxylic acids with carbon chain lengths greater than six. Expression analysis shows that GPR40 is specifically expressed in brain and in insulin-producing beta cells in the pancreas. Activation of GPR40 by long-chain fatty acids has been shown to amplify glucose-stimulated insulin secretion, suggesting that GPR40 may represent an important target for drugs that regulate diabetes. GPR40 has also been shown to be overexpressed in breast cancer cells, where it may regulate cell growth.