Pancreatic Mitochondrial Complex I Exhibit Aberrant Hyperactivity in Diabetes, by Ayzia Gholston

This study focusses on the dangerous effects of diabetes mellitus that is caused by impairment of glucose metabolism. The bodys homeostasis seeks to maintain blood glucose level at a very slim range of between 3.9 to 4.5 mmol/L. The normal random blood glucose should not exceed 5.5 mmol/L for non-diabetic persons. Blood glucose functions to provide electrons that are stored in NADH and FADH2 used in the mitochondrial electron transport chain. Therefore, when the blood glucose levels are high, the electrons provided are in surplus resulting in a redox imbalance.

NAD is a fundamental molecule in the metabolism and redox signaling. In diabetes, the balance between NADH and NAD can be severely perturbed. NADH may overproduce due to the influx of hyperglycemia, and this may cause an activation of the polyol pathway. When this happen, NAD may be depleted by over-activation of the polyol ADP ribose polymerase. Lactase dehydrogenase is known to regenerate NAD, it converts glycolysis generated pyruvate to lactate, and the level of lactate dehydrogenase is three which is very low. So excess NADH would overload or overwhelm complex one that is a major site in the mitochondrial for NAD recycling.

NADH/NAD redox imbalance is known to induce cellular oxidative stress, this is recognized as the major mechanism by which high levels of blood glucose (hyperglycemia) causes three cell failure. It remains unknown how pancreatic mitochondrial complex I handle NADH/NAD overload or NADH/NAD redox imbalance and any potential consequences of this working with diabetes. The study then showed that pancreatic mitochondrial complex I exhibited up-regulation or hyperactivity in type I streptozotocin (STZ) diabetic mice and rats, in type II diabetic rats and mice and cultured three cells.

Further studies with streptozotocin (STZ) induced diabetes in rats showed that complex I hyperactivity can be diminished by metformin.

Streptozotocin and metformin hydrochloride were two of the drugs used in the study. Animals were also used, but the procedures used on the animals were approved by the institutional care and use committee of the University of North Texas Health Science Center, and the use of the animals was by NIH guidelines for the care and use of laboratory animals. Freshly prepared STZ was injected into rats that had fasted overnight to avoid altering the blood glucose levels. The dosage was 50mg/kg, and it was done daily for five days. The tail-pricking method was used to determine the blood glucose levels. Any rat that had a blood sugar level of above 300mg/dl was considered diabetic. To confirm the experiment, control rats were used that were injected with 1ml citrate buffer only instead of STZ.

INS-1 cell cultures were then purchased whereas B cell mitochondria were obtained from the pancreatic tissues of both the control and diabetic rats. Gradient centrifugation method was used to prepare pancreatic mitochondria. On the other hand, enzyme activity assays were determined by non-gradient BN-PAGE where potassium phosphate was used as a buffer. Other methods used included a measuring kit that was purchased from BioVision that determined the NAD/NADH ratio. Data presentation and analysis was done using a couple of ways. First, a digital scanner was used to document the Gel images and statistical analysis done using GraphPad.

The research findings ascertained that NAD/NADH redox balance is significantly affected in many diabetic tissues that have excess NADH. The diabetic pancreas also exhibited a lesser NAD/NADH ration as compared to the non-diabetic controls.