RT Journal Article
SR Electronic
T1 Glucokinase Is a Critical Regulator of Ventromedial Hypothalamic Neuronal Glucosensing
JF Diabetes
JO Diabetes
FD American Diabetes Association
SP 412
OP 420
DO 10.2337/diabetes.55.02.06.db05-1229
VO 55
IS 2
A1 Kang, Ling
A1 Dunn-Meynell, Ambrose A.
A1 Routh, Vanessa H.
A1 Gaspers, Larry D.
A1 Nagata, Yasufumi
A1 Nishimura, Teruyuki
A1 Eiki, Junichi
A1 Zhang, Bei B.
A1 Levin, Barry E.
YR 2006
UL http://diabetes.diabetesjournals.org/content/55/2/412.abstract
AB To test the hypothesis that glucokinase is a critical regulator of neuronal glucosensing, glucokinase activity was increased, using a glucokinase activator drug, or decreased, using RNA interference combined with calcium imaging in freshly dissociated ventromedial hypothalamic nucleus (VMN) neurons or primary ventromedial hypothalamus (VMH; VMN plus arcuate nucleus) cultures. To assess the validity of our approach, we first showed that glucose-induced (0.5–2.5 mmol/l) changes in intracellular Ca2+ concentration ([Ca2+]i) oscillations, using fura-2 and changes in membrane potential (using a membrane potential–sensitive dye), were highly correlated in both glucose-excited and -inhibited neurons. Also, glucose-excited neurons increased (half-maximal effective concentration [EC50] = 0.54 mmol/l) and glucose-inhibited neurons decreased (half-maximal inhibitory concentration [IC50] = 1.12 mmol/l) [Ca2+]i oscillations to incremental changes in glucose from 0.3 to 5 mmol/l. In untreated primary VMH neuronal cultures, the expression of glucokinase mRNA and the number of demonstrable glucosensing neurons fell spontaneously by half over 12–96 h without loss of viable neurons. Transfection of neurons with small interfering glucokinase RNA did not affect survival but did reduce glucokinase mRNA by 90% in association with loss of all demonstrable glucose-excited neurons and a 99% reduction in glucose-inhibited neurons. A pharmacological glucokinase activator produced a dose-related increase in [Ca2+]i oscillations in glucose-excited neurons (EC50 = 0.98 mmol/l) and a decrease in glucose-inhibited neurons (IC50 = 0.025 μmol/l) held at 0.5 mmol/l glucose. Together, these data support a critical role for glucokinase in neuronal glucosensing.