As the L4F peptide was developed to mimic apoA-I function, and this appears to be borne out by our in vitro studies, we have compared apoA-I overexpression with L4F treatment in several pathophysiological endpoints in Ldlr male mice fed the HFHSC diet. The effect of apoA-I overexpression on insulin resistance in the Ldlr DIO model has not been reported on previously, and thus an important dataset for comparison to L4F treatment. Provided chronic inflammation which is associated with obesity related insulin resistance, our in vitro findings suggest that L4F and apoA-I overexpression could potentially improve GSK1120212 glucose tolerance in an in vivo model of DIO. In our previous study apoA-I overexpression relieved some of the adipose tissue inflammation. However, in the present study L4F treatment of 100 mg/day/ mouse had no impact on adipose tissue or systemic inflammatory markers. Further, neither the overexpression of apoA-I nor treatment with L4F had an impact on glucose tolerance nor glucose stimulated insulin levels. Note that neither apoAI overexpression nor L4F treatment had an impact on weight gain or adiposity in this model, confirmed in the peptide study by body composition analysis. ApoA-I and L4F mimetics are often cited for their anti-atherosclerotic properties. This effect of apoA-I overexpression in Ldlr mice fed a high fat diet has been documented and confirmed in the present study. Yet, L4F treatment had no such effect at a dosage of 100 mg/day/ mouse. It is striking that despite the dramatic effect of L4F on 3T3L1 cells, the peptide is without influence on the measured parameters studied in vivo at 100 mg/day/mouse. One limitation of this study is that the absence of any in vivo effect of peptide treatment raises questions about the efficacy of the dose and route of administration of the peptide. We have followed protocols and dosages that have been shown in apoE and ob/ob mice to be effective. The dose we employed, is equal to the effective dose of 4.5 mg/kg/day shown by Navab and colleagues to reduce plasma SAA levels. Importantly, they have found the dose was determining rather than the concentration in the plasma. This group has further suggested that the primary function of the peptides is to attenuate the oxidized lipid and unsaturated lysophosphatidic acid concentrations in the intestine. The current study utilized the L version of the peptide injected subcutaneously as it is not stable for oral delivery while other studies have used the D version of the peptide which is stable for oral delivery. However, data suggests that neither the route of administration nor the enantiomer version of the peptide determines effectiveness. One study directly compared L4F versus D4F delivered subcutaneously in rabbits and found similar reductions in atherosclerosis. While studies suggest the site of action is primarily in the intestine, Navab and colleagues have shown D4F is similarly effective when delivered subcutaneously or orally and equivalent amounts appear in the feces. L4F delivered orally with niclosamide was equally effective in reducing SAA in apoE mice as L4F delivered subcutaneously. This suggests that the effect of 4F peptide on inflammation and atherosclerosis is independent of route of administration and the enantiomer version of the peptide, and thus does not explain the lack of effect in the current study. Given the above discussion, it is possible that either L4F does not influence obesity, inflammation, or atherosclerosis in this model or that a higher dose of peptide is required to affect these outcomes in this model. In addition, we have no information on the role of oxidized lipids in the intestine in our model. Further work is needed to address the effectiveness of 4F p.