A Study of Selected Enzymes Related to Energy Metabolism in Saudi Autistic Children

Autism is a severe neurodevelopment disorder with degenerative actions reaching to all biological functions of the body. As it starts early in life, its symptoms might be fatal and it ranges from behavioral characteristics to mental retardation and muscle atrophy. Many autistic individuals suffer from epileptic episodes at an early age of life . The causes of autism are heterogeneous and predominantly genetically and metabolic factors. However, it is thought that it arises as a result of the interaction between genetic and environmental factors together with oxidative stress linking the two . Deficiency of purine nucleotides, impairment of energy metabolism and toxic effects are potential mechanisms for brain damage associated with autism. In this piece, certain biochemical parameters were measured in blood samples of 30 children with autism (6 females and 24 males aged (5 to 15) and the obtained data were compared with another 30 healthy-age matching control. the diagnosis of autism was made by a child neuropsychiatric based on the criteria of autistic disorder as defined in the Diagnostic and Statistical Manual of mental disorder, Fourth addition (DSM-IV). The studied biochemical parameters were measured in red blood cells or serum of autistic children compared to age-matching controls. The results show a significant alteration of most of the measured parameters. Enzymes related to energy utilization such as : Na+/K+ ATPase and Creatine kinase were measured and found to be significantly higher in autistic children when compared to their age-matched controls. Na+/ K+ ATPase was found to be (0.013±0.008 μmols Pi released/ minute/ ml plasma) in autistic children when compared to their age- matched controls (0.005±0.003 μmols Pi released/ minute/ ml plasma) while creatine kinase recorded a value of (284.27±242.477 μmols Pi released/ minute/ ml plasma) compared to a value of (164.941±94.495 μmols Pi released/ minute/ ml plasma)). Higher activity of Na+/K+ ATPase proved the depletion of ATP which could be correlated to brain damage in autistic children. On the other hand, the recorded elevated creatine kinase activity in autistic Saudi children supports the phenomenon of energy metabolism impairment which involved in many neurodegenerative diseases. Moreover elevation of this enzyme could explain muscle atrophy previously reported in certain cases of autism. This study was extended to measure ectonucleotidases (NTPdases) as enzymes catalyzing breakdown of extracellular purine nucleotides. While ATPase did not record different activity levels in autistic children, ADPase showed higher activity in autistic children compared to age-matching controls. The adenylate energy charge (AEC) as a clinically important parameter reflecting the energy status of individuals was also screened in autistic compared to control. Both autistic and control subjects recorded a more or less similar AEC values. This in turn proved that the change in the previously mentioned parameters (Na+/K+ ATPase, CK and ADPase) did not affect the amazingly stabilized energy charge that was achieved physiologically in autistic children with out being recognized as the change in the AEC varied from (0.814±0.094) in autistic children when compared to normal (0.806±0.081). The mechanism of AEC stabilization was fully discussed in relation to the significantly altered bioenergetic parameters measured in this work. Moreover, lactate as a product of utilizing glucose the most important source of energy in the body was found to be higher in autistic patients (1.398±0.819 μmols/l) than in normal ones (0.872±0.335 μmol/l). This work successfully recorded Na+/K+, CK, ADPase and lactate as biochemical markers involved in the etiology of autism in Saudi population which could be helpful in early diagnosis and intervention