PI3K integrates the effects of insulin and leptin on large-conductance Ca2+-activated K+ channels in neuropeptide Y neurons of the hypothalamic arcuate nucleus.
The adipocyte-derived hormone leptin and the pancreatic beta-cell-derived hormone insulin function as afferent signals to the hypothalamus in an endocrine feedback loop that regulates body adiposity. They act in hypothalamic centers to modulate the function of specific neuronal subtypes, such as neuropeptide Y (NPY) neurons, by modifying neuronal electrical activity. To investigate the intrinsic activity of these neurons and their responses to insulin and leptin, we used a combination of morphological features and immunocytochemical technique to identify the NPY neurons of hypothalamic arcuate nucleus (ARC) and record whole cell large-conductance Ca(2+)-activated potassium (BK) currents on them. We found that both of the hormones increase the peak amplitude of BK currents, shifting the steady-state activation curve to the left. The effect of both insulin and leptin can be prevented by pretreatment with inhibitors of tyrosine kinase and phosphatidylinositol 3-kinase (PI3K) but not MAPK. These data indicate that PI3K-mediated signals are the common regulators of BK channels by insulin and leptin and mediated the two hormones' identical activatory effects on ARC NPY neurons. The effect of insulin and leptin together was similar to that of insulin or leptin alone, and leptin or insulin pretreatment did not lead to insulin- or leptin-sensitizing effects, respectively. These intracellular signaling mechanisms may play key roles in regulating ARC NPY neuron activity and physiological processes such as the control of food intake and body weight, which are under the combined control of insulin and leptin.
Yang
Meng-Jie
MJ
Dept. of Pharmacology, Tongji Medical College, Huazhong Univ. of Science and Technology, Wuhan, Hubei 430030 China.
Wang
Fang
F
Wang
Jiang-Hua
JH
Wu
Wen-Ning
WN
Hu
Zhuang-Li
ZL
Cheng
Jin
J
Yu
Dan-Fang
DF
Long
Li-Hong
LH
Fu
Hui
H
Xie
Na
N
Chen
Jian-Guo
JG
D050154:Adiposity / Q000502:physiology; D000818:Animals; D001111:Arcuate Nucleus of Hypothalamus / Q000166:cytology / Q000378:metabolism; D002478:Cells, Cultured; D007150:Immunohistochemistry; D007328:Insulin / Q000378:metabolism*; D051036:Large-Conductance Calcium-Activated Potassium Channels / Q000378:metabolism*; D020738:Leptin / Q000378:metabolism*; D009474:Neurons / Q000145:classification / Q000378:metabolism*; D009478:Neuropeptide Y / Q000378:metabolism; D018408:Patch-Clamp Techniques; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015290:Second Messenger Systems / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology
D007328:Insulin; D051036:Large-Conductance Calcium-Activated Potassium Channels; D020738:Leptin; D009478:Neuropeptide Y; D019869:Phosphatidylinositol 3-Kinases