Fatty Acid Binding Protein

Fatty acid binding proteins (FABPs) bind to fatty acids and other lipids and function as cytoplasmic lipid chaperones (1,2). They participate in the transport of fatty acids and other lipids to various cellular pathways (2). Research studies have shown that common variants of the human liver FABP gene FABP1 play a role in the development of type 2 diabetes and insulin resistance (3).

Fatty acid binding protein 3 (FABP3) is predominantly expressed in heart, skeletal muscle, brain, and mammary gland (4). FABP3 may play a role in supplying energy to the heart and other tissues (5). The release of FABP3 from the heart upon infarction is used as a serum marker for myocardial stress and cardiotoxicity (6). Additional studies suggest that FABP3 is a potential tumor suppressor in breast cancer (7).

The predominant FABP found in adipocytes is fatty acid binding protein 4 (FABP4), also called adipocyte fatty acid binding protein or aP2. FABP4 is also expressed in macrophages (8). FABP4 knockout mice fed a high-fat and high-calorie diet become obese but develop neither insulin resistance nor diabetes, suggesting that this protein might be a link between obesity and insulin resistance and diabetes (9). Mice deficient in both FABP4 and ApoE show protection against atherosclerosis compared to those deficient only in ApoE (8). Mice carrying a FABP4 genetic variant exhibit both reduced FABP4 expression and a reduced potential for developing type 2 diabetes and coronary heart disease. A related study in humans indicated a similar pattern, suggesting that FABP4 may be a potential therapeutic target in the treatment of these disorders (1).

Fatty acid binding protein 5 (FABP5) is known as the epidermal FABP, as it was originally identified in studies on psoriasis (10), where it was shown to play a role in keratinocyte differentiation (11). It has since been found to play diverse roles in other normal physiological processes as well as in disease states (12).

Fatty acid binding protein 7 (FABP7) is abundantly expressed in fetal brain and may be essential for development (13). Expression is required for the establishment of the radial glial fiber system, a system necessary for cortical layer development (14). Increased FABP7 expression is associated with reduced survival in patients with glioblastoma (15) and is also found in glial cells following nerve injury (16). Investigators have found that loss of FABP7 may be involved in breast cancer development and progression, and FABP7 expression has been shown to induce mammary differentiation and inhibit breast cancer cell growth (17,18).