Leptin and amylin act in an additive manner to activate overlapping signaling pathways in peripheral tissues: in vitro and ex vivo studies in humans.
OBJECTIVE
Amylin interacts with leptin to alter metabolism. We evaluated, for the first time, amylin- and/or leptin-activated signaling pathways in human peripheral tissues (hPTs).


METHODS
Leptin and amylin signaling studies were performed in vitro in human primary adipocytes (hPAs) and human peripheral blood mononuclear cells (hPBMCs) and ex vivo in human adipose tissue (hAT) from male versus female subjects, obese versus lean subjects, and subjects with subcutaneous versus omental adipose tissue.


RESULTS
The long form of leptin receptor was expressed in human tissues and cells studied in ex vivo and in vitro, respectively. Leptin and amylin alone and in combination activate signal transducer and activator of transcription 3 (STAT3), AMP-activated protein kinase, Akt, and extracellular signal-regulated kinase signaling pathways in hAT ex vivo and hPAs and hPBMCs in vitro; all phosphorylation events were saturable at leptin and amylin concentrations of ∼50 and ∼20 ng/ml, respectively. The effects of leptin and amylin on STAT3 phosphorylation in hPAs and hPBMCs in vitro were totally abolished under endoplasmic reticulum stress and/or in the presence of a STAT3 inhibitor. Results similar to those in the in vitro studies were observed in hAT studied ex vivo.


CONCLUSIONS
Leptin and amylin activate overlapping intracellular signaling pathways in humans and have additive, but not synergistic, effects in signaling pathways studied in hPTs in vitro and ex vivo.
Moon
Hyun-Seuk
HS
Division of Endocrinology, Diabetes, and Metabolism, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, USA.
Chamberland
John P
JP
Diakopoulos
Kalliope N
KN
Fiorenza
Christina G
CG
Ziemke
Florencia
F
Schneider
Benjamin
B
Mantzoros
Christos S
CS
D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D002478:Cells, Cultured; D004347:Drug Interactions; D006801:Humans; D066298:In Vitro Techniques; D058228:Islet Amyloid Polypeptide / Q000494:pharmacology*; D020738:Leptin / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D050796:STAT3 Transcription Factor / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*
D058228:Islet Amyloid Polypeptide; D020738:Leptin; D050796:STAT3 Transcription Factor; D051057:Proto-Oncogene Proteins c-akt; D055372:AMP-Activated Protein Kinases