Identification of effective micrornas in the evaluation of genotype-phenotype relationship in nonketotic hyperglycinemia patients

Nonketotic hyperglycinemia (NKH), glycine encephalopathy is an autosomal recessive (OR) amino acid metabolism disorder. Glycine accumulates in the body due to the defect in the glycine-cleavage enzyme complex. Diagnosis; determined by an increase in cerebrospinal fluid (CSF) and plasma glycine levels. The CSF/plasma glycine ratio in NKH is usually 0.08-0.25 µmol/L. The increase in CSF glycine level is an important indicator for NKH, but the most reliable diagnostic method in NKH is genetic analysis. The first findings in NKH usually occur at birth or in the first weeks. There is no suitable treatment method yet to change the prognosis of NKH, current treatments are aimed at preventing and removing glycine accumulation in the body. Elevated glycine can also be seen in propionic acidemia called ketotic hyperglycinemia, methylmalonic acidemia and beta ketothiolase enzyme deficiency. In these patients, high glycine levels are accompanied by severe acidosis and ketosis. This condition is called ketotic hyperglycinemia. Ketosis is the stimulus for early intervention in ketotic hyperglycinemia. It has been reported in the literature that NKH is seen approximately twice as frequently as ketotic hyperglycinemia. These conditions, which increase glycine in CSF, also cause a high CSF/plasma glycine ratio. This situation states that the CSF/plasma glycine ratio is not an adequate criterion for diagnosis in NKH and highlights the importance of the existence of a more specific diagnostic method for NKH. The biochemical pathology resulting from changes in any of the four proteins in the glycine-cleavage enzyme that causes NKH is well understood, but there is no genotype-phenotype relationship yet in the literature. MicroRNAs (miRNA) are small non-coding RNAs that function as transcriptional and post-transcriptional regulators of gene expression. Due to their regulatory role, they can provide new perspectives in terms of diagnosis and treatment of diseases. Identifying disease-associated miRNAs and their respective targets provides new molecular perspectives on disease, enabling the design of new therapeutic strategies. miRNAs are found in stable form in body fluids, making them suitable for routine clinical processing and analysis, and are used as novel disease biomarkers and for evaluation of treatment response. Early diagnosis is very important in hereditary metabolic diseases such as NKH, which lead to accumulation of toxic substances as a result of metabolic block. Therefore, it is necessary to develop alternative methods for early diagnosis of inherited metabolic diseases. We think that miRNAs can be used as a more specific and faster biomarker for early diagnosis of inherited metabolic diseases such as NKH. The use of circulating miRNAs as biomarkers; It is thought that it will be useful to detect the early stages of a disease, prevent, cure or slow the disease, distinguish pathologies, predict the prognosis and monitor the response to treatment. Although many inherited metabolic disease miRNA studies have been carried out in the literature, there is no previous study examining the relationship of NKH miRNA. In this project study, we aim to investigate the role of miRNAs in NKH using our previous knowledge about NKH disease and miRNAs. The aim of the study was to compare the expression of miRNAs in NKH between the patient and control group. In the study, large-scale miRNA profiling will be performed by comparing the miRNAs isolated from the blood, urine and CSF fluids of the control group consisting of NKH patients and healthy individuals. miRNAs will be analyzed and confirmed by qRT-PCR analysis by selecting miRNAs whose expression differs significantly between the control and patient group according to the results obtained. Finally, the effect of candidate miRNA on phenotype in NKH will be examined. Our study will be the first to examine the NKH miRNA relationship.