159. Sustained Weight Loss and Altered Lipid Taste Sensitivity Induced by Modulation of Salivary PYY and Excendin-4 in Mice

Abstract

Peptide tyrosine-tyrosine (PYY), known to induce satiation when present in plasma, has recently been described to modulate body weight (BW) and food intake (FI) of diet induced obese (DIO) mice when included in saliva. Similarly, glucagon-like peptide 1 (GLP-1), a GI peptide present in both plasma and saliva, also modulates BW and FI. The purpose of this project was to study the anorexigenic effect of sustained elevation of PYY and Excendin-4 (Ex-4, a GLP-1R agonist) in saliva of mice. Using recombinant Adeno-associated virus serotype 8 (rAAV8) we performed gene transfer of GFP (control), PYY, Ex-4, and PYY-Ex-4 dual vectors to the submandibular salivary glands of C57BL/6 mice fed a high fat diet. We observed a significant (p < 0.05) decrease in BW of mice treated with either Ex-4, or PYY-Ex-4 dual vectors when compared to controls. Notably, mice treated with PYY-Ex-4 dual vector displayed a significant decrease in BW as early as 1-week post vector administration while Ex-4 mice alone did not demonstrate a significant loss until 8 weeks post-injection. PYY mice, while demonstrating a decreasing trend in BW gain with respect to GFP mice, did not show a significant difference in BW during the 12-week experiment. To determine whether the anorexigenic effect of salivary PYY and Ex-4 is modulated through taste perception, we utilized a Davis Rig gustometer to generate brief access taste response curves for a panel of tastants for all groups of treated mice. Notably, the Ex-4 as well as the PYY-Ex-4 dual group displayed a significant increase in sensitivity to intralipid stimulus, suggesting that this taste modality plays a role in BW modulation. This observed weight loss and altered taste perception in PYY and Ex4 treated mice while significant, is complicated by the unintended transduction of hepatocytes. Unintended transduction of the liver may allow for the elevated levels of PYY and Ex4 in the bloodstream in addition to saliva. In order to observe the saliva-specific effect of dual PYY Ex4 vector administration, we have developed viral constructs containing miR122 target sequences, a liver specific micro RNA (miRNA), and miR206, a skeletal muscle specific miRNA, target sequences in the 3’ UTR of each construct. These micro RNA target sequences will suppress vector expression in off target tissues such as the skeletal muscle and liver. Additionally, all viral constructs were packaged into AAV5 instead of AAV8 which has the same transduction efficiency of salivary glands but decreased transduction of the murine liver. Using these miRNA constructs, we have observed no detectable expression of GFP in the murine liver.