MRL/Mpj mice are the only known strain of mouse that can regenerate cardiac lesions and completely heal ear punches without scarring. This study was undertaken to determine if MRL mice also have greater regrowth capabilities in amputated digit tips. Right paw digit tips of neonatal MRL mice were dissected, with the left front paws as uncut controls. Controls used for regrowth comparison were the DBA/2 and C57BL/6 inbred mouse strains. Consecutive x-ray images were captured of front paws at 0, 7, 14, 21, and 28 days postamputation. MRL mouse digit tips were found to distally regrow more quickly and reform nails partially and completely to a greater degree in comparison with DBA and B6 mice (p<0.05). We next undertook microarray expression analysis to identify the genes involved in digit tip regrowth. Four hundred genes out of 15,000 were significantly differentially expressed (p<0.05) in MRL, DBA, and B6 mice at day 4 in comparison with day 0 control tissue. Multiple differences between MRL, DBA, and B6 strains were found in genes that are implicated in the WNT signaling pathway and transcription. We conclude that MRL mice regrow digits distally more rapidly and partially and completely regrow nails to a greater degree than B6 and DBA strains. This enhanced regrowth is likely due to strain-specific increased expression of genes involved in growth and development.

Epidermal fatty acid‐binding protein (E‐FABP), a member of the family of FABPs, exhibits a robust expression in neurons during axonal growth in development and in nerve regeneration following nerve injury. This study examines the impact of E‐FABP expression in normal neurite extension in differentiating pheochromocytoma cell (PC12) cultures supplemented with selected long chain free fatty acids (LCFFA). We found that E‐FABP binds to a broad range of saturated and unsaturated LCFFAs, including those with potential interest for neuronal differentiation and axonal growth such as C22:6n‐3 docosahexaenoic acid (DHA), C20:5n‐3 eicosapentaenoic acid (EPA), and C20:4n‐6 arachidonic acid (ARA). PC12 cells exposed to nerve growth factor (NGFDPC12) exhibit high E‐FABP expression that is blocked by mitogen‐activated protein kinase kinase (MEK) inhibitor U0126. Nerve growth factor‐differentiated pheochromocytoma cells (NGFDPC12) antisense clones (NGFDPC12‐AS) which exhibit low E‐FABP expression have fewer/shorter neurites than cells transfected with vector only or NGFDPC12 sense cells (NGFDPC12‐S). Replenishing NGFDPC12‐AS cells with biotinylated recombinant E‐FABP (biotin‐E‐FABP) protein restores normal neurite outgrowth. Cellular localization of biotin‐E‐FABP in NGFDPC12 was detected mostly in the cytoplasm and in the nuclear region. Treatment of NGFDPC12 with DHA, EPA, or ARA further enhances neurite length but it does not trigger further induction of TrkA or MEK phosphorylation or E‐FABP mRNA observed in differentiating PC12 cells without LCFFA supplementation. Significantly, DHA and EPA neurite stimulating effects are higher in NGFDPC12‐S than in NGFDPC12‐AS cells. These findings are consistent with the scenario that neurite extension of differentiating PC12 cells, including further stimulation by DHA and EPA, requires sufficient cellular levels of E‐FABP.

Genes for the fatty acid binding protein (FABP) family encode small 14–15 kDa cytosolic proteins and can be regulated during type 2 diabetes mellitus (T2DM) and obesity. This study compared association of single nucleotide polymorphisms (SNPs) in FABP1-5 with T2DM in different ethnic groups. Associations with T2DM of SNPs in these proteins were assessed in African American (AA), non-Hispanic White (NHW), and Hispanic American (HA) individuals. A total of 650 DNA samples were genotyped; control samples were obtained from Coriell’s North American Human Variation Panel Repository (NAVP) of apparently healthy individuals and T2DM cases were taken from the American Diabetes Association GENNID Study. The rs454550 SNP of FABP5 showed a significant association with T2DM in NHW (OR: 9.03, 95% CI: 1.13–71.73, p=0.014). Our analysis also identified a new FABP5 SNP (nSNP) that showed a significant association with T2DM in NHW (OR: 0.44, 95% CI: 0.19–0.99, p=0.045) and AA (OR: 0.17, 95% CI: 0.03–0.80, p=0.016). The Ala54Thr FABP2 polymorphism was significantly associated with T2DM in HA individuals only (OR: 1.85, 95% CI: 1.05–3.27, p=0.032). All other FABP SNPs did not show association with T2DM. These findings suggest a potential distinct role of SNPs in FABP5, 2 genes in T2DM in different populations.

Cyclodextrins (CDs) are used to deliver hydrophobic molecules in aqueous environments. Methyl-β-cyclodextrin (MβCD), a member of this family of molecules, has been proposed to be a good carrier to deliver fatty acids to cells in culture. This report focuses on studying the in vitro effects of MβCD on nerve growth factor-differentiated PC12 (NGFDPC12) cells, a tissue culture model to study neuronal survival and differentiation. The main findings are: (1) NGFDPC12 cells have normal viability when exposed to 0.12% MβCD but showed a significant loss in cell viability at higher concentrations; (2) NGFDPC12 cells exposed to 0.25% MβCD exhibit nuclear condensation, blebbing and apoptotic bodies, and whole cell lysates exhibited an increase in caspase-3-like activity and high levels of Bax and Bcl-X L protein expression compared to control. Cultures treated with 0.25% MβCD also showed cleavage of normal 21-kDa Bax protein into a 18-kDa fragment. (3) Experiments using 0.12% MβCD to deliver oleic acid did not affect cell viability, in contrast NGFDPC12 cultures in which 0.25% MβCD concentration is used exhibited similar loss of cell viability as observed with 0.25% MβCD alone. Treating these cultures with caspase-3 inhibitor z-VAD-fmk did not protect the cells from MβCD toxic effects. (4) Immortalized Schwann cells (iSC) exposed to MβCD 0.12% did not show loss of cell viability while 0.25% MβCD triggered a significant toxicity but with a different dose and time course dynamic than NGFDPC12 cells. Thus, NGDPC12 or iSC cell cultures exposed to 0.12% MβCD exhibits normal viability while higher concentrations increase in cell death and apoptosis.

Epidermal fatty acid-binding protein (E-FABP/FABP5/DA11) binds and transport long-chain fatty acids in the cytoplasm and may play a protecting role during neuronal injury. We examined whether E-FABP protects nerve growth factor-differentiated PC12 cells (NGFDPC12 cells) from lipotoxic injury observed after palmitic acid (C16:0; PAM) overload. NGFDPC12 cells cultures treated with PAM/bovine serum albumin at 0.3 mM/0.15 mM show PAM-induced lipotoxicity (PAM-LTx) and apoptosis. The apoptosis was preceded by a cellular accumulation of reactive oxygen species (ROS) and higher levels of E-FABP. Antioxidants MCI-186 and N-acetyl cysteine prevented E-FABP's induction in expression by PAM-LTx, while tert-butyl hydroperoxide increased ROS and E-FABP expression. Non-metabolized methyl ester of PAM, methyl palmitic acid (mPAM), failed to increase cellular ROS, E-FABP gene expression, or trigger apoptosis. Treatment of NGFDPC12 cultures with siE-FABP showed reduced E-FABP levels correlating with higher accumulation of ROS and cell death after exposure to PAM. In contrast, increasing E-FABP cellular levels by pre-loading the cells with recombinant E-FABP diminished the PAM-induced ROS and cell death. Finally, agonists for PPARβ (GW0742) or PPARγ (GW1929) increased E-FABP expression and enhanced the resistance of NGFDPC12 cells to PAM-LTx. We conclude that E-FABP protects NGFDPC12 cells from lipotoxic injury through mechanisms that involve reduction of ROS.Epidermal fatty acid-binding protein (E-FABP) may protect nerve cells from the damaging exposure to high levels of free fatty acids (FA). We show that E-FABP can neutralize the effects of reactive oxygen species (ROS) generated by the high levels of FA in the cell and protect PC12 cells from lipotoxic injuries common in Type 2 diabetes neuropathy. Potentially, E-FABP gene up-regulation may be mediated through the NFkB pathway and future studies are needed to further evaluate this proposition.