Diabetes-induced abnormalities of mitochondrial function in rat brain cortex: the effect of n-3 fatty acid diet

Diabetic encephalopathy, a proven complication of diabetes is associated with gradually developing end-organ damage in the CNS increasing the risk of stroke, cognitive dysfunction or Alzheimer's disease. This study investigated the response of rat cortical mitochondria to streptozotocin-induced diabetes and the potential for fish oil emulsion (FOE) to modulate mitochondrial function. Diabetes-induced deregulation of the respiratory chain function as a result of diminished complex I activity (CI) and cytochrome c oxidase hyperactivity was associated with attenuation of antioxidant defense of isolated cortical mitochondria, monitored by SOD activity, the thiol content, the dityrosine and protein-lipid peroxidation adduct formation. A parallel reduction in phosphorylation of the energy marker AMPK has pointed out to disrupted energy homeostasis. Dietary FOE administration partially preserved CI activity, restored AMPK phosphorylation, but was unable to attenuate oxidative stress and prevent the shift toward saturated fatty acids in the cardiolipin composition. Moreover, diabetes has induced alterations in the protein expression of the regulatory COX4 subunit of cytochrome c oxidase, in the inhibitory factor IF1 and ATP5A subunit of F₀F₁-ATP synthase, in the uncoupling protein UCP4 and supramolecular organization of the respiratory complexes. FOE administration to diabetic rats has partially reversed these alterations. This study suggests diabetes-induced dysfunction of brain cortical mitochondria and its modulation by FOE administration. The intricate diabetic milieu and the n-3 FA nutrigenomic strength, however require further investigations to be able to unequivocally evaluate neuroprotective and adverse effects of FOE supplementation on the diabetic brain function.