Hypertrophic pancreatic islets (PI) of Goto Kakizaki (GK) diabetic rats contain a lower number of β-cells vs. non-diabetic Wistar rat PI. Remaining β-cells contain reduced mitochondrial (mt) DNA per nucleus (copy number), probably due to declining mtDNA replication machinery, decreased mt biogenesis or enhanced mitophagy. We confirmed mtDNA copy number decrease down to <30% in PI of one-year-old GK rats. Studying relations to mt nucleoids sizes, we employed 3D superresolution fluorescent photoactivable localization microscopy (FPALM) with lentivirally transduced Eos conjugate of mt single-stranded-DNA-binding protein (mtSSB) or transcription factor TFAM; or by 3D immunocytochemistry. mtSSB (binding transcription or replication nucleoids) contoured "nucleoids" which were smaller by 25% (less diameters >150 nm) in GK β-cells. Eos-TFAM-visualized nucleoids, composed of 72% localized TFAM, were smaller by 10% (immunochemically by 3%). A theoretical ~70% decrease in cell nucleoid number (spatial density) was not observed, rejecting model of single mtDNA per nucleoid. The β-cell maintenance factor Nkx6.1 mRNA and protein were declining with age (>12-fold, 10 months) and decreasing with fasting hyperglycemia in GK rats, probably predetermining the impaired mtDNA replication (copy number decrease), while spatial expansion of mtDNA kept nucleoids with only smaller sizes than those containing much higher mtDNA in non-diabetic β-cells.

• MeSH
• Insulin-Secreting Cells metabolism   pathology   MeSH
• DNA-Binding Proteins genetics   MeSH
• Diabetes Mellitus, Experimental genetics   metabolism   pathology   MeSH
• Homeodomain Proteins genetics   MeSH
• Rats MeSH
• Humans MeSH
• DNA, Mitochondrial genetics   MeSH
• Mitochondria genetics   pathology   MeSH
• Mitophagy genetics   MeSH
• Pancreas, Exocrine metabolism   MeSH
• Rats, Wistar MeSH
• DNA Replication genetics   MeSH
• Transcription Factors genetics   MeSH
• DNA Copy Number Variations genetics   MeSH
• Animals MeSH
• Check Tag
• Rats MeSH
• Humans MeSH
• Male MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• DNA-Binding Proteins MeSH
• Homeodomain Proteins MeSH
• DNA, Mitochondrial MeSH
• Nkx6-1 protein, rat MeSH Browser
• Tfam protein, rat MeSH Browser
• Transcription Factors MeSH

Mild constitutive hyperbilirubinemia is associated with a reduced risk of cardiovascular diseases, diabetes, and cancer. Since these pathologies are associated with aging, inflammation, and oxidative stress, we investigated whether hyperbilirubinemia interferes with ROS homeostasis in cell cultures and with inflammation, senescence, and mitochondrial dysfunction in aged rats. Human embryonic kidney cells and rat primary fibroblasts showed a dose-dependent decrease in the ratio of oxidized/reduced glutathione, intracellular H2O2 levels, and mitochondrial ROS production, with increasing bilirubin concentrations in the culture media. Compared to their normobilirubinemic siblings, aged hyperbilirubinemic Gunn rats showed significantly smaller amounts of visceral fat, better glucose tolerance, and decreased serum levels of proinflammatory cytokines TNFα, IL-1β, and IL-18. Simultaneously, livers from Gunn rats showed decreased expression of senescence markers and cell cycle inhibitors p21 and p16. Mitochondria from aged Gunn rats showed higher respiration and lower H2O2 production compared to controls. In conclusion, we demonstrated that mildly elevated serum bilirubin is generally associated with attenuation of oxidative stress and with better anthropometric parameters, decreased inflammatory status, increased glucose tolerance, fewer signs of cellular senescence, and enhanced mitochondrial function in aged rats.

• MeSH
• Bilirubin blood   MeSH
• Fibroblasts metabolism   pathology   MeSH
• Hyperbilirubinemia blood   pathology   MeSH
• Intracellular Space metabolism   MeSH
• Cells, Cultured MeSH
• Metabolic Diseases complications   pathology   MeSH
• Mitochondria metabolism   MeSH
• Rats, Gunn MeSH
• Reactive Oxygen Species metabolism   MeSH
• Aging pathology   MeSH
• Inflammation complications   pathology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Bilirubin MeSH
• Reactive Oxygen Species MeSH

Reduced beta cell mass in pancreatic islets (PI) of Goto-Kakizaki (GK) rats is frequently observed in this diabetic model, but knowledge on delta cells is scarce. Aiming to compare delta cell physiology/pathology of GK to Wistar rats, we found that delta cell number increased over time as did somatostatin mRNA and delta cells distribution in PI is different in GK rats. Subtle changes in 6-week-old GK rats were found. With maturation and aging of GK rats, disturbed cytoarchitecture occurred with irregular beta cells accompanied by delta cell hyperplasia and loss of pancreatic polypeptide (PPY) positivity. Unlike the constant glucose-stimulation index for insulin PI release in Wistar rats, this index declined with GK age, whereas for somatostatin it increased with age. A decrease of GK rat PPY serum levels was found. GK rat body weight decreased with increasing hyperglycemia. Somatostatin analog octreotide completely blocked insulin secretion, impaired proliferation at low autocrine insulin, and decreased PPY secretion and mitochondrial DNA in INS-1E cells. In conclusion, in GK rats PI, significant local delta cell hyperplasia and suspected paracrine effect of somatostatin diminish beta cell viability and contribute to the deterioration of beta cell mass. Altered PPY-secreting cells distribution amends another component of GK PI's pathophysiology.

• MeSH
• Insulin Antagonists pharmacology   MeSH
• Insulin-Secreting Cells drug effects   metabolism   pathology   MeSH
• Somatostatin-Secreting Cells drug effects   metabolism   pathology   MeSH
• Diabetes Mellitus, Type 2 blood   metabolism   pathology   MeSH
• Hyperplasia MeSH
• Immunohistochemistry MeSH
• Rats, Inbred Strains MeSH
• Insulin metabolism   MeSH
• Insulin Resistance * MeSH
• RNA, Messenger metabolism   MeSH
• Cell Line, Tumor MeSH
• Octreotide pharmacology   MeSH
• Pancreatic Polypeptide antagonists & inhibitors   genetics   metabolism   MeSH
• Rats, Wistar MeSH
• Cell Proliferation drug effects   MeSH
• Insulin Secretion MeSH
• Somatostatin antagonists & inhibitors   genetics   metabolism   MeSH
• Aging * MeSH
• Cell Survival drug effects   MeSH
• Gene Expression Regulation, Developmental MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Insulin Antagonists MeSH
• Insulin MeSH
• RNA, Messenger MeSH
• Octreotide MeSH
• Pancreatic Polypeptide MeSH
• Somatostatin MeSH

A moderate elevation of reactive oxygen species (ROS) production and a mild inhibition of mitochondrial respiratory chain have been associated with a health promotion and a lifespan extension in several animal models of aging. Here, we tested whether this phenomenon called mitohormesis could be mediated by L-lactate. The treatment with 5 mM L-lactate significantly increased H2O2 production and slightly inhibited the respiration in cultured skin fibroblasts and in isolated mitochondria. The L-lactate exposure was associated with oxidation of intracellular glutathione, phosphorylation of 5'AMP-activated protein kinase (AMPK), and induction of peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α) transcription. A replicative aging of fibroblasts (L0) with a constant (LC), or intermittent 5 mM L-lactate (LI) in media showed that the high-passage LI fibroblasts have higher respiration, lower H2O2 release, and lower secretion of L-lactate compared to L0 and LC. This protection against mitochondrial dysfunction in LI cells was associated with lower activity of mechanistic target of rapamycin complex 1 (mTORC1), less signs of cellular senescence, and increased autophagy compared to L0 and LC. In conclusion, we demonstrated that intermittent but not constant exposure to L-lactate triggers mitohormesis, prevents aging-associated mitochondrial dysfunction, and improves other markers of aging.

• MeSH
• Fibroblasts cytology   drug effects   metabolism   MeSH
• Phosphorylation drug effects   MeSH
• Glutathione metabolism   MeSH
• Liver metabolism   MeSH
• Microscopy, Confocal MeSH
• Cells, Cultured MeSH
• Lactic Acid pharmacology   MeSH
• DNA, Mitochondrial metabolism   MeSH
• Mitochondria drug effects   genetics   metabolism   MeSH
• Mice MeSH
• Oxidative Stress drug effects   MeSH
• Hydrogen Peroxide metabolism   MeSH
• Rats, Wistar MeSH
• PPAR gamma genetics   metabolism   MeSH
• Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha MeSH
• AMP-Activated Protein Kinases metabolism   MeSH
• Reactive Oxygen Species metabolism   MeSH
• Aging * MeSH
• TOR Serine-Threonine Kinases metabolism   MeSH
• Transcription Factors genetics   metabolism   MeSH
• Animals MeSH
• Check Tag
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Names of Substances
• Glutathione MeSH
• Lactic Acid MeSH
• DNA, Mitochondrial MeSH
• Hydrogen Peroxide MeSH
• PPAR gamma MeSH
• Ppargc1a protein, rat MeSH Browser
• Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha MeSH
• AMP-Activated Protein Kinases MeSH
• Reactive Oxygen Species MeSH
• TOR Serine-Threonine Kinases MeSH
• Transcription Factors MeSH

We reviewed mechanisms that determine reactive oxygen species (redox) homeostasis, redox information signaling and metabolic/regulatory function of autocrine insulin signaling in pancreatic β cells, and consequences of oxidative stress and dysregulation of redox/information signaling for their dysfunction. We emphasize the role of mitochondrion in β cell molecular physiology and pathology, including the antioxidant role of mitochondrial uncoupling protein UCP2. Since in pancreatic β cells pyruvate cannot be easily diverted towards lactate dehydrogenase for lactate formation, the respiration and oxidative phosphorylation intensity are governed by the availability of glucose, leading to a certain ATP/ADP ratio, whereas in other cell types, cell demand dictates respiration/metabolism rates. Moreover, we examine the possibility that type 2 diabetes mellitus might be considered as an inevitable result of progressive self-accelerating oxidative stress and concomitantly dysregulated information signaling in peripheral tissues as well as in pancreatic β cells. It is because the redox signaling is inherent to the insulin receptor signaling mechanism and its impairment leads to the oxidative and nitrosative stress. Also emerging concepts, admiting participation of redox signaling even in glucose sensing and insulin release in pancreatic β cells, fit in this view. For example, NADPH has been firmly established to be a modulator of glucose-stimulated insulin release.

• MeSH
• Insulin-Secreting Cells metabolism   pathology   MeSH
• Homeostasis * MeSH
• Insulin metabolism   MeSH
• Humans MeSH
• Mitochondria metabolism   MeSH
• Oxidation-Reduction MeSH
• Oxidative Stress MeSH
• Insulin Secretion MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Review MeSH
• Names of Substances
• Insulin MeSH