Vitamin B₁₂ conjugation of peptide-YY_3-36 decreases food intake compared to native peptide-YY_3-36 upon subcutaneous administration in male rats

Challenges to peptide-based therapies include rapid clearance, ready degradation by hydrolysis/ proteolysis, and poor intestinal uptake and/or a need for blood brain barrier transport. This work evaluates the efficacy of conjugation of vitamin B₁₂ (B₁₂) on sc administered peptide tyrosine tyrosine (PYY)_3-36 function. In the current experiments, a B₁₂-PYY_3-36 conjugate was tested against native PYY_3-36, and an inactive conjugate B₁₂-PYYC36 (null control) in vitro and in vivo. In vitro experiments demonstrated similar agonism for the neuropeptide Y2 receptor by the B₁₂-PYY_3-36 conjugate (EC50 26.5nM)comparedwith nativePYY_3-36 (EC50 16.0 nM), with the null control having an EC50 of 1.8 μM. In vivo experiments were performed in young adult male Sprague Dawley rats (9 wk). Daily treatments were delivered sc in five 1-hour pulses, each pulse delivering 5-10 nmol/kg, by implanted microinfusion pumps. Increases in hindbrain Fos expression were comparable 90 minutes after B₁₂-PYY_3-36 or PYY_3-36 injection relative to saline or B₁₂-PYYC36. Food intake was reduced during a 5-day treatment for both B₁₂-PYY_3-36- (24%, P = .001) and PYY_3-36-(13%, P = .008) treated groups relative to baseline. In addition, reduction of food intake after the three dark cycle treatment pulses was more consistent with B₁₂-PYY_3-36 treatment (-26%, -29%, -27%) compared with the PYY_3-36 treatment (-3%, -21%, -16%), and B₁₂-PYY_3-36 generated a significantly longer inhibition of food intake vs PYY_3-36 treatment after the first two pulses (P=.041 and P = .036, respectively). These findings demonstrate a stronger, more consistent, and longer inhibition of food intake after the pulses of B₁₂-PYY_3-36 conjugate compared with the native PYY_3-36.