Mitochondrial dysfunction is currently acknowledged as a central
pathomechanism of most common diseases of the 21st century.
Recently, the assessment of the bioenergetic profile of human
peripheral blood cells has emerged as a novel research field with
potential applications in the development of disease biomarkers.
In particular, platelets have been successfully used for
the ex vivo analysis of mitochondrial respiratory function in
several acute and chronic pathologies. An increasing number of
studies support the idea that evaluation of the bioenergetic
function in circulating platelets may represent the peripheral
signature of mitochondrial dysfunction in metabolically active
tissues (brain, heart, liver, skeletal muscle). Accordingly,
impairment of mitochondrial respiration in peripheral platelets
might have potential clinical applicability as a diagnostic and
prognostic tool as well as a biomarker in treatment monitoring.
The aim of this minireview is to summarize current information in
the field of platelet mitochondrial dysfunction in both acute and
chronic diseases.
Mitochondria are considered central regulator of the aging process; however, majority of studies dealing with the impact of age on mitochondrial oxygen consumption focused on skeletal muscle concluding (although not uniformly) a general declining trend with advancing age. In addition, gender related differences in mitochondrial respiration have not been satisfactorily described yet. The aim of the present study was to evaluate mitochondrial oxygen consumption in various organs of aging male and female Fischer 344 rats at the ages of 6, 12 and 24 months. Mitochondrial respiration of homogenized (skeletal muscle, left and right heart ventricle, hippocampus, cerebellum, kidney cortex), gently mechanically permeabilized (liver) tissue or intact cells (platelets) was determined using high-resolution respirometry (oxygraphs O2k, Oroboros, Austria). The pattern of age-related changes differed in each tissue: in the skeletal muscle and kidney cortex of both sexes and in female heart, parameters of mitochondrial respiration significantly declined with age. Resting respiration of intact platelets displayed an increasing trend and it did not correlate with skeletal muscle respiratory states. In the heart of male rats and brain tissues of both sexes, respiratory states remained relatively stable over analyzed age categories with few exceptions of lower mitochondrial oxygen consumption at the age of 24 months. In the liver, OXPHOS capacity was higher in females than in males with either no difference between the ages of 6 and 24 months or even significant increase at the age of 24 months in the male rats. In conclusion, the results of our study indicate that the concept of general pattern of age-dependent decline in mitochondrial oxygen consumption across different organs and tissues could be misleading. Also, the statement of higher mitochondrial respiration in females seems to be conflicting, since the genderrelated differences may vary with the tissue studied, combination of substrates used and might be better detectable at younger ages than in old animals.