An isolated polypeptide comprising the amino acid sequence: X 1 X 2 X 3 GTFTSDX 10 X 11 X 12 X 13 LX 15 X 16 X 17 X 18 AQEFX 23 X 24 X 25 LEDE-Z-tail (SEQ ID NO: 1), wherein: X 1 is Y or W; X 2 is S, G or T; X 3 is Q or H; X 10 is Y or H; X 11 is S or T; X 12 is K or R; X 13 is Y, L or W; X 15 is D or E; X 16 is S, 2-Aminoisobutyric acid (Aib), A, E, L, Q, K, or I; X 17 is K, E, S, T, or A; X 18 is A, R, S, E, L, T or Y; X 23 is T or V; X 24 is K, I, L, or Aib; X 25 is H or W; and Z-tail is absent; or is selected from the group consisting of EEPSSGAPPPS-OH (SEQ ID NO: 4); EPSSGAPPPS-OH (SEQ ID NO: 5); GAPPPS-OH (SEQ ID NO: 6); GGPSSGAPPPS-OH (SEQ ID NO: 7); GPSSGAPPPS-OH (SEQ ID NO: 8); KRNKNPPPS-OH (SEQ ID NO: 9); KRNKNPPS-OH (SEQ ID NO: 10); KRNKPPIA-OH (SEQ ID NO: 11); KRNKPPPA-OH (SEQ ID NO: 150); KRNKPPPS-OH (SEQ ID NO: 12); KSSGKPPPS-OH (SEQ ID NO: 13); PESGAPPPS-OH (SEQ ID NO: 14); PKSGAPPPS-OH (SEQ ID NO: 15); PKSKAPPPS-NH 2 (SEQ ID NO: 16); PKSKAPPPS-OH (SEQ ID NO: 17); PKSKEPPPS-NH 2 (SEQ ID NO: 18); PKSKEPPPS-OH (SEQ ID NO: 19); PKSKQPPPS-OH (SEQ ID NO: 20); PKSKSPPPS-NH 2 (SEQ ID NO: 21); PKSKSPPPS-OH (SEQ ID NO: 22); PRNKNNPPS-OH (SEQ ID NO: 23); PSKGAPPPS-OH (SEQ ID NO: 24); PSSGAPPPSE-OH (SEQ ID NO: 25); PSSGAPPPS-NH 2 (SEQ ID NO: 26); PSSGAPPPS-OH (SEQ ID NO: 27); PSSGAPPPSS-OH (SEQ ID NO: 28); PSSGEPPPS-OH (SEQ ID NO: 29); PSSGKKPPS-OH (SEQ ID NO: 30); PSSGKPPPS-NH 2 (SEQ ID NO: 31); PSSGKPPPS-OH (SEQ ID NO: 32); PSSGSPPPS-OH (SEQ ID NO: 33); PSSKAPPPS-OH (SEQ ID NO: 34); PSSKEPPPS-OH (SEQ ID NO: 35); PSSKGAPPPS-OH (SEQ ID NO: 36); PSSKQPPPS-OH (SEQ ID NO: 37); PSSKSPPPS-OH (SEQ ID NO: 38); SGAPPPS-OH (SEQ ID NO: 39); and SSGAPPPS-OH(SEQ ID NO: 40). X 1 is Y or W; X 2 is S, G or T; X 3 is Q or H; X 10 is Y or H; X 11 is S or T; X 12 is K or R; X 13 is Y, L or W; X 15 is D or E; X 16 is S, 2-Aminoisobutyric acid (Aib), A, E, L, Q, K, or I; X 17 is K, E, S, T, or A; X 18 is A, R, S, E, L, T or Y; X 23 is T or V; X 24 is K, I, L, or Aib; X 25 is H or W; and Z-tail is absent; or is selected from the group consisting of EEPSSGAPPPS-OH (SEQ ID NO: 4); EPSSGAPPPS-OH (SEQ ID NO: 5); GAPPPS-OH (SEQ ID NO: 6); GGPSSGAPPPS-OH (SEQ ID NO: 7); GPSSGAPPPS-OH (SEQ ID NO: 8); KRNKNPPPS-OH (SEQ ID NO: 9); KRNKNPPS-OH (SEQ ID NO: 10); KRNKPPIA-OH (SEQ ID NO: 11); KRNKPPPA-OH (SEQ ID NO: 150); KRNKPPPS-OH (SEQ ID NO: 12); KSSGKPPPS-OH (SEQ ID NO: 13); PESGAPPPS-OH (SEQ ID NO: 14); PKSGAPPPS-OH (SEQ ID NO: 15); PKSKAPPPS-NH 2 (SEQ ID NO: 16); PKSKAPPPS-OH (SEQ ID NO: 17); PKSKEPPPS-NH 2 (SEQ ID NO: 18); PKSKEPPPS-OH (SEQ ID NO: 19); PKSKQPPPS-OH (SEQ ID NO: 20); PKSKSPPPS-NH 2 (SEQ ID NO: 21); PKSKSPPPS-OH (SEQ ID NO: 22); PRNKNNPPS-OH (SEQ ID NO: 23); PSKGAPPPS-OH (SEQ ID NO: 24); PSSGAPPPSE-OH (SEQ ID NO: 25); PSSGAPPPS-NH 2 (SEQ ID NO: 26); PSSGAPPPS-OH (SEQ ID NO: 27); PSSGAPPPSS-OH (SEQ ID NO: 28); PSSGEPPPS-OH (SEQ ID NO: 29); PSSGKKPPS-OH (SEQ ID NO: 30); PSSGKPPPS-NH 2 (SEQ ID NO: 31); PSSGKPPPS-OH (SEQ ID NO: 32); PSSGSPPPS-OH (SEQ ID NO: 33); PSSKAPPPS-OH (SEQ ID NO: 34); PSSKEPPPS-OH (SEQ ID NO: 35); PSSKGAPPPS-OH (SEQ ID NO: 36); PSSKQPPPS-OH (SEQ ID NO: 37); PSSKSPPPS-OH (SEQ ID NO: 38); SGAPPPS-OH (SEQ ID NO: 39); and SSGAPPPS-OH(SEQ ID NO: 40).