FABP2 Human

What is the basic structure and function of human FABP2?

Human FABP2 is a 132 amino acid cytosolic protein with a flattened beta-barrel structure (called a beta-clam) generated by a series of antiparallel beta-strands and two alpha-helices . It functions primarily in the uptake, metabolism, and transfer of fatty acids across cellular membranes in enterocytes . FABP2 preferentially binds sixteen to twenty carbon long-chain fatty acids and facilitates their intracellular transport . The protein's mechanism involves initial binding of ligands to the outside of the molecule, which induces a conformational change resulting in "internalization" of the ligand .

How is FABP2 different from other fatty acid binding proteins?

While all FABPs are highly conserved in tertiary structure, there is only modest amino acid identity between family members. FABP2 forms a subgroup with liver/L-FABP and heart/H-FABP based on amino acid sequence . Human FABP2 shows 33% amino acid identity to human H-FABP and 24% to L-FABP . Unlike some other FABPs, FABP2 expression is largely restricted to intestinal tissue, reflecting its specialized role in dietary fatty acid absorption .

What is the evolutionary conservation of FABP2 across species?

Human FABP2 demonstrates high conservation across mammalian species, sharing 78% amino acid identity with mouse, 82% with rat, and 86% with canine FABP2 . This high degree of conservation suggests the critical functional importance of this protein throughout mammalian evolution and provides justification for the use of animal models in studying FABP2-related mechanisms.

What are the most clinically significant variants of the FABP2 gene?

The most extensively studied and clinically significant variant of FABP2 is the missense Ala54Thr variation, which results from an A for G substitution in codon 54 of exon 2 . This variant alters the structure and function of FABP2, resulting in increased fatty acid absorption in vivo . Other notable variants include:

• Silent variants in codons 71 (T for C) and 118 (A for G)

• A microsatellite in intron 2 with 7 alleles including trinucleotide repeats of 10-15 consecutive ATT sequences

• An A for G SNP in the 3′ noncoding region

How is the Ala54Thr FABP2 variant distributed across different populations?

The Thr54 allele is common across diverse populations but shows variation in frequency. Below is a representative distribution based on available data:

This variation in frequency across populations may contribute to differential susceptibility to metabolic disorders .

How do we determine FABP2 genotypes in research studies?

Methodologically, FABP2 genotyping typically involves:

• DNA extraction from blood or tissue samples

• PCR amplification of the relevant gene regions

• Restriction fragment length polymorphism (RFLP) analysis or direct sequencing

• For the Ala54Thr variant specifically, HhaI restriction enzyme digestion is commonly used as the G→A substitution at codon 54 eliminates a HhaI restriction site

For large population studies, high-throughput methods such as TaqMan assays may be employed for more efficient genotyping .

What are the recommended methods for measuring FABP2 levels in human samples?

The quantification of FABP2 in human samples typically employs enzyme-linked immunosorbent assays (ELISA). The Human FABP2 solid-phase sandwich ELISA is designed to measure the target protein bound between a matched antibody pair . This method:

• Uses a pre-coated target-specific capture antibody in microplate wells

• Adds samples, standards, or controls to bind to the immobilized antibody

• Forms a sandwich with the addition of a detector antibody

• Develops signal through substrate reaction with the enzyme-antibody-target complex

• Produces measurable signal proportional to FABP2 concentration

The assay can be used with human serum, plasma, or cell culture medium and recognizes both natural and recombinant human FABP2 .

How should recombinant FABP2 protein be handled and stored for experimental use?

Recombinant human FABP2/I-FABP protein is typically supplied as a 0.2 μm filtered solution in PBS and glycerol . Proper handling recommendations include:

• Immediate storage upon receipt at recommended temperatures (typically -20°C to -80°C)

• Use of a manual defrost freezer to avoid repeated freeze-thaw cycles

• For carrier-free versions (without BSA), special care must be taken to maintain protein stability

• When reconstituting lyophilized protein, gentle mixing rather than vortexing is recommended to prevent protein denaturation

For applications where the presence of BSA could interfere, carrier-free protein is recommended, while BSA-containing preparations are preferred for cell/tissue culture or as ELISA standards .

What are the validated techniques for measuring FABP2 binding activity?

Historically, FABP2 binding activity has been measured by fluorescence titration using synthetic ligands such as cis-parinaric acid . In this technique:

• Increasing concentrations of ligand are added to a fixed concentration of FABP2

• The fluorescence intensity changes as the ligand binds to the protein

• Binding affinity is calculated from the resulting titration curve

• Competitive binding assays using fluorescently labeled fatty acids

• Isothermal titration calorimetry (ITC)

• Surface plasmon resonance (SPR)

What is the evidence for FABP2's role in insulin resistance?

Research has established associations between FABP2 variants, particularly the Ala54Thr polymorphism, and insulin resistance. Key findings include:

• The Thr54 variant shows increased binding affinity for long-chain fatty acids compared to the Ala54 variant

• This increased binding leads to enhanced fatty acid absorption and altered lipid metabolism

• Studies have demonstrated associations between the Thr54 allele and insulin resistance after accounting for the independent effects of body composition and habitual physical activity levels on insulin sensitivity

Importantly, the relationship between FABP2 variants and insulin resistance appears to be modulated by environmental factors, particularly diet composition. Some studies demonstrate that the association between Ala54Thr FABP2 and insulin sensitivity is only observed when individuals are consuming a high-fat diet .

How does FABP2 interact with dietary factors in metabolic disease development?

FABP2-dietary interactions are complex and significant for understanding metabolic disease mechanisms:

• The Thr54 variant has been shown to have unusual metabolic effects depending on diet composition

• High-fat diets may unmask or exacerbate the metabolic effects of the Thr54 variant

• Some evidence suggests that dietary fatty acid composition (saturated vs. unsaturated) may differentially affect FABP2 function based on genotype

• These interactions highlight the importance of gene-environment considerations in metabolic disease research

This gene-diet interaction provides a mechanistic explanation for the variable results observed across different studies investigating FABP2 variants and metabolic outcomes.

What methodological approaches are recommended when studying FABP2 in relation to type 2 diabetes?

When investigating FABP2's relationship to type 2 diabetes, researchers should consider:

• Accounting for the independent and substantial effects of body composition, habitual physical activity levels, and diet on insulin resistance

• Incorporating measurements of both fasting and dynamic indices of glucose metabolism (OGTT or clamp studies)

• Including analysis of gene-environment interactions, particularly dietary composition

• Stratifying analyses by ethnicity given the population variation in allele frequencies

• Employing longitudinal study designs when possible to establish temporal relationships

Failure to account for these factors may explain the inconsistent results observed in many previous studies of FABP2 and diabetes risk.

How can researchers effectively study gene-environment interactions involving FABP2?

To properly investigate FABP2 gene-environment interactions, researchers should:

• Collect detailed phenotypic data including body composition (preferably using DXA or other precise methods)

• Quantify habitual physical activity using validated instruments or objective measures

• Assess dietary intake with detailed food frequency questionnaires or food records with particular attention to fat intake

• Consider crossover design studies where participants are exposed to different dietary conditions

• Employ statistical methods specifically designed to detect interaction effects, such as regression models with interaction terms

• Ensure adequate sample sizes to power interaction analyses

Recent studies highlight that the effects of FABP2 variants may only become apparent when appropriate environmental contexts are considered in the analysis.

What are the current approaches for targeting FABP2 in therapeutic research?

Current approaches for targeting FABP2 in therapeutic research include:

• Development of small molecule inhibitors that can modulate FABP2 binding affinity or selectivity

• Dietary interventions tailored to FABP2 genotype, particularly modifying dietary fat composition

• Investigation of FABP2 as a biomarker for intestinal damage or metabolic disease progression

• Exploration of the potential for RNA interference or gene editing approaches to modify FABP2 expression in specific tissues

These approaches represent potential personalized medicine strategies for addressing metabolic disorders associated with FABP2 variants.

What are the recommended experimental models for studying FABP2 function?

Researchers have several options for experimental models when studying FABP2 function:

• Cell culture models:

  • Caco-2 cells (human intestinal epithelial cell line)

  • Primary intestinal epithelial cells

• Animal models:

  • FABP2 knockout mice

  • Transgenic models expressing human FABP2 variants

  • Diet-induced obesity models combined with FABP2 genotyping

• Human studies:

  • Intervention studies stratified by FABP2 genotype

  • Ex vivo studies using intestinal biopsy samples

  • Population studies with detailed phenotyping

The choice of model should be guided by the specific research question, with consideration of the high degree of sequence conservation (78-86%) between human FABP2 and its rodent orthologs .