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K(ATP) channel openers protect rat islets against the toxic effect of streptozotocin
1Department of Medical Sciences, Uppsala University, Sweden.
Abstract:
We examined the influence of two K(ATP) channel openers, diazoxide and an analog (NNC 55-0118), on experimental beta-cell damage induced by streptozotocin (STZ; 0.5 mmol/l). Rat pancreatic islets were exposed to diazoxide or NNC 55-0118 for 30 min and were further incubated for 30 min after the addition of STZ. The islets were then washed and cultured for 24 h. Islets exposed to STZ alone showed extensive morphological damage, reduced glucose oxidation, low insulin content, and severely impaired glucose-stimulated insulin secretion and proinsulin biosynthesis. Islets treated with STZ in the presence of the channel openers (0.03-0.30 mmol/l) showed dose-dependent preservation of the morphology and improved glucose oxidation rates, insulin content, and secretion. NNC 55-0118 was capable of fully counteracting the STZ impairment, whereas diazoxide had a less protective effect. NNC 55-0118 did not counteract STZ-induced depression of islet NAD levels when examined 2 h after STZ exposure, which suggests that the mechanism of action by NNC 55-0118 is not through an inhibition of poly(ADP-ribose) polymerase. The results illustrate that K(ATP) channel openers can protect insulin-producing cells against toxic damage, an effect that may be of use in subjects with ongoing insulitis.
Insights
K(ATP) channel openers, diazoxide and NNC 55-0118, protected pancreatic beta-cells from streptozotocin-induced damage. NNC 55-0118 demonstrated superior protective effects, preserving cell morphology and function.
Area of Science:
- Endocrinology
- Molecular Biology
- Cell Biology
Background:
- Streptozotocin (STZ) induces experimental beta-cell damage, mimicking aspects of Type 1 diabetes.
- K(ATP) channels play a crucial role in beta-cell function and survival.
Purpose of the Study:
- To investigate the protective effects of K(ATP) channel openers, diazoxide and NNC 55-0118, against STZ-induced beta-cell damage.
- To elucidate the potential therapeutic applications of these compounds in conditions involving beta-cell injury.
Main Methods:
- Rat pancreatic islets were exposed to STZ alone or in combination with varying concentrations of diazoxide or NNC 55-0118.
- Cellular morphology, glucose oxidation, insulin content, and insulin secretion were assessed after 24 hours of culture.
- NAD levels were measured to explore potential mechanisms of action.
Main Results:
- STZ exposure caused significant beta-cell damage, including impaired morphology, reduced glucose oxidation, and diminished insulin secretion.
- Co-administration of diazoxide and NNC 55-0118 dose-dependently protected beta-cells from STZ-induced damage.
- NNC 55-0118 exhibited a more potent protective effect than diazoxide, fully counteracting STZ-induced impairments.
- NNC 55-0118 did not prevent STZ-induced NAD depletion, suggesting its protective mechanism is independent of poly(ADP-ribose) polymerase inhibition.
Conclusions:
- K(ATP) channel openers, particularly NNC 55-0118, offer significant protection against STZ-induced beta-cell toxicity.
- These findings suggest a potential therapeutic strategy for protecting insulin-producing cells in inflammatory conditions like insulitis.