Pyruvate inhibits zinc-mediated pancreatic islet cell death and diabetes.
OBJECTIVE
We have shown that zinc ion (Zn2+) in secretory granules of pancreatic beta cells could act as a paracrine death effector in streptozotocin-induced diabetes. As Zn2+ has been reported to perturb glycolysis, we studied if pyruvate could inhibit Zn(2+)-mediated islet cell death in vitro and streptozotocin-induced diabetes in vivo by normalizing intracellular energy metabolism.


METHODS
Cell death was measured by quantitative viable cell staining and Hoechst/propidium iodide staining. ATP was measured by bioluminescence determination. Pyruvate was infused through the tail vein 1 h before streptozotocin administration. Beta-cell volume was measured by point counting of the insulin-containing cells.


RESULTS
Zn2+ induced classical necrosis on MIN6N8 insulinoma cells which was associated with a rapid decline of intracellular ATP levels. Pyruvate inhibited Zn(2+)-induced necrosis of insulinoma cells and depletion of intracellular ATP by Zn2+. Pyruvate did not inhibit other types of necrosis or apoptosis. Energy substrates such as oxaloacetate, alpha-ketoglutarate and succinic acid dimethylester also attenuated Zn(2+)-induced insulinoma cell death. Methylpyruvate that does not generate NAD+ in the cytoplasm or alpha-ketoisocaproate that stimulates ATP generation exclusively in mitochondria also protected insulinoma cells from Zn(2+)-induced necrosis. Pyruvate infusion inhibited the development of diabetes by protecting beta-cell mass after streptozotocin administration.


CONCLUSIONS
These results indicate that pyruvate inhibits Zn(2+)-induced necrosis of beta cells in vitro by protecting intracellular ATP levels and also streptozotocin-induced diabetes in vivo where Zn2+ has been reported to act as a paracrine death effector.
Chang
I
I
Department of Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Cho
N
N
Koh
J-Y
JY
Lee
M-S
MS
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000952:Antigens, Polyomavirus Transforming; D000975:Antioxidants / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D002471:Cell Transformation, Neoplastic; D003921:Diabetes Mellitus, Experimental / Q000473:pathology*; D005047:Etoposide / Q000633:toxicity; D007340:Insulinoma / Q000473:pathology; D007371:Interferon-gamma / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects / Q000473:pathology*; D009243:NAD / Q000378:metabolism; D009336:Necrosis; D010190:Pancreatic Neoplasms / Q000473:pathology; D019289:Pyruvic Acid / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019311:Staurosporine / Q000494:pharmacology; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D015032:Zinc / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D000952:Antigens, Polyomavirus Transforming; D000975:Antioxidants; D014409:Tumor Necrosis Factor-alpha; D009243:NAD; D005047:Etoposide; D007371:Interferon-gamma; D019289:Pyruvic Acid; D000255:Adenosine Triphosphate; D019311:Staurosporine; D015032:Zinc