Pancreatic beta cells from db/db mice show cell-specific [Ca2+]i and NADH responses to glucose but not to alpha-ketoisocaproic acid.
OBJECTIVE
We recently showed that timing and magnitude of the glucose-induced cytoplasmic calcium [Ca2+]i response are reproducible and specific for the individual beta cell. We now wanted to identify which step(s) of stimulus-secretion coupling determine the cell specificity of the [Ca2+]i response and whether cell specificity is lost in beta-cells from diabetic animals. Besides glucose, we studied the effects of glyceraldehyde, a glycolytic intermediate, and alpha-ketoisocaproic acid (KIC), a mitochondrial substrate.


METHODS
Early [Ca2+]i changes were studied stimulations in fura-2-labeled dispersed beta cells from lean, ob/ob, and db/db mice. Lag time and peak height were compared during 2 consecutive stimulations with the same stimulator. Nicotinamide adenine dinucleotide (NADH) responses to glucose and KIC were studied as a measure of metabolic flux.


RESULTS
Both glyceraldehyde and KIC induced cell-specific temporal responses in lean mouse beta cells with a correlation between lag times for [Ca2+]i rise during the first and second stimulation. Beta cells from ob/ob and db/db mice showed cell-specific temporal [Ca2+]i responses to glucose and glyceraldehyde but not to KIC. Glucose induced cell-specific NADH responses in all 3 models, but KIC did so only in lean mouse [beta] cells.


CONCLUSIONS
A cell-specific response may be induced at several steps of beta-cell stimulus-secretion coupling. Mitochondrial metabolism generates a cell-specific response in normal beta cells but not in db/db and ob/ob mouse beta cells.
Gustavsson
Natalia
N
Department of Integrative Medical Biology, Section for Histology and Cell Biology, Umeå University, Umeå, Sweden. natalia.gustavsson@histocel.umu.se
Larsson-Nyrén
Gerd
G
Lindström
Per
P
D000818:Animals; D001835:Body Weight; D002118:Calcium / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D005947:Glucose / Q000494:pharmacology*; D006019:Glycolysis / Q000502:physiology; D066298:In Vitro Techniques; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D007651:Keto Acids / Q000494:pharmacology*; D051379:Mice; D008820:Mice, Obese; D008928:Mitochondria / Q000378:metabolism; D009243:NAD / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D007651:Keto Acids; D009243:NAD; C013082:alpha-ketoisocaproic acid; D005947:Glucose; D002118:Calcium