Associations between serum leptin level and bone turnover in kidney transplant recipients.
OBJECTIVE
Obesity is associated with increased parathyroid hormone (PTH) in the general population and in patients with chronic kidney disease (CKD). A direct effect of adipose tissue on bone turnover through leptin production has been suggested, but such an association has not been explored in kidney transplant recipients.


METHODS
This study examined associations of serum leptin with PTH and with biomarkers of bone turnover (serum beta crosslaps [CTX, a marker of bone resorption] and osteocalcin [OC, a marker of bone formation]) in 978 kidney transplant recipients. Associations were examined in multivariable regression models. Path analyses were used to determine if the association of leptin with bone turnover is independent of PTH.


RESULTS
Higher leptin levels were associated with higher PTH and lower vitamin D levels, and adjustment for vitamin D attenuated the association between leptin and PTH. However, higher leptin was also significantly associated with lower levels of the bone turnover markers: 1 SD higher leptin was associated with 0.13 lower log-OC (-0.17, -0.08, P < 0.001) and 0.030 lower log-CTX (-0.045, -0.016, P < 0.001) after multivariable adjustments. Path analysis indicated that the association of leptin with PTH was mostly mediated through vitamin D, and that the association between leptin and bone turnover was independent of PTH and vitamin D.


CONCLUSIONS
Elevated leptin level is associated with lower bone turnover independent of its effects on serum PTH in kidney transplant recipients.
Kovesdy
Csaba P
CP
Division of Nephrology, Salem Veterans Affairs Medical Center, Salem, Virginia, USA. csaba.kovesdy@va.gov
Molnar
Miklos Z
MZ
Czira
Maria E
ME
Rudas
Anna
A
Ujszaszi
Akos
A
Rosivall
Laszlo
L
Szathmari
Miklos
M
Covic
Adrian
A
Keszei
Andras
A
Beko
Gabriella
G
Lakatos
Peter
P
Kosa
Janos
J
Mucsi
Istvan
I
D000328:Adult; D000368:Aged; D016723:Bone Remodeling; D024042:Collagen Type I / Q000097:blood; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D016030:Kidney Transplantation; D020738:Leptin / Q000097:blood*; D008297:Male; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood; D010281:Parathyroid Hormone / Q000097:blood; D010455:Peptides / Q000097:blood; D014807:Vitamin D / Q000031:analogs & derivatives / Q000097:blood
D024042:Collagen Type I; D020738:Leptin; D010281:Parathyroid Hormone; D010455:Peptides; C052929:collagen type I trimeric cross-linked peptide; D015675:Osteocalcin; D014807:Vitamin D; C104450:25-hydroxyvitamin D