In vitro and in vivo effect of parathyroid hormone analogue (1-14) containing -amino-iso-butyric acid residue (Aib)1,3.
Firstly, parathyroid hormone (1-14) [PTH (1-14)] analogue containing various -amino-iso-butyric acid residue (Aib) was synthesized by exchanging the 1st and 3rd Ala residues of alpha carbon of PTH (1-14). This analogue revealed to have the quite tight and stable -helical structure using the nuclear magnetic resonance (NMR) analysis. The biological activities of these analogues were examined using a cAMP- generating assay in LLC-PK1 cell lines stably transfected with the wild- type human PTH1 receptor. Only the PTH analogue substituted with methyl moiety without acetylation showed significant cAMP generating action with 15.0 +/- 3.414 of EC50. Then, we used an ovariectomized rat model system to compare the in vivo effects of parathyroid hormone analogue with that of PTH (1-84). Daily subcutaneous administration of the unacetylated Aib1,3PTH (1-14) for 5 weeks in 30 nM/kg subcutaneously with positive control group receiving PTH (1-84) with 8 nM/ kg were performed. However, there was no significant change in spinal or femoral bone mineral density assessed by dual x-ray absorptiometry (DXA) in the Aib1,3PTH (1-14) group where definite increase of these parameters shown in the PTH (1-84) group (p < 0.001). Assessment of bone strength was evaluated with no significant differences among all groups. It was quite disappointing to see the actual discrepancies between the result of significant pharmacokinetic potency and the in vivo clinical effect of the Aib1,3PTH (1-14). However, there are several limitations to mention, such as the short duration of treatment, matter of dosage, and insufficient effect of tight -helical structures with absence of C-terminus. In conclusion, our findings suggest that unacetylated Aib1,3PTH (1-14) did not exhibit any anabolic effects at the bones of ovariectomized rats.
Rhee
Yumie
Y
Department of Internal Medicine, College of Medicine, Yonsei University, #134 Shinchon-dong, Seodaemun-gu, Seoul 120-752, Korea.
Lee
Weontae
W
Lee
Eun Jin
EJ
Ma
Suhyun
S
Park
So Young
SY
Lim
Sung-Kil
SK
D000409:Alanine / Q000737:chemistry; D000595:Amino Acid Sequence; D000621:Aminoisobutyric Acids / Q000378:metabolism*; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D001842:Bone and Bones / Q000378:metabolism; D002460:Cell Line; D000242:Cyclic AMP / Q000378:metabolism; D003720:Densitometry; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D018374:LLC-PK1 Cells; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015233:Models, Statistical; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D010281:Parathyroid Hormone / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism*; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D051381:Rats; D013052:Spectrometry, X-Ray Emission; D013314:Stress, Mechanical; D013329:Structure-Activity Relationship; D013997:Time Factors; D014162:Transfection
D000621:Aminoisobutyric Acids; C470125:PTH protein, human; D010281:Parathyroid Hormone; D010455:Peptides; C100049:2-aminoisobutyric acid; D000242:Cyclic AMP; D000409:Alanine