Low blood levels of the vitamin D metabolite 25-hydroxyvitamin D [25(OH)D] have been associated with an increased risk and poorer outcomes of various cancers, including hematological malignancies. The Central Kazakhstan area has a relatively high incidence rate of leukemia. However, the relationship between vitamin D status and leukemia or other types of cancer in Kazakhstan has not yet been addressed. Therefore, in this first pilot single-center study conducted in Central Kazakhstan, we compared plasma levels of 25(OH)D and the vitamin D receptor (VDR) gene expression levels in peripheral blood mononuclear cells of patients with leukemia and demographically matching healthy volunteers. The levels of 25(OH)D in patients were found to be significantly lower (10.8 ± 7.0 ng/mL; n = 31) than in healthy subjects (21.6 ± 7.8 ng/mL; n = 34; p < 0.0001). A similar difference was observed in both younger (60 years old) participants, though there was no association between 25(OH)D concentration and age within the patient group. In female patients, 25(OH)D levels were significantly lower than in male patients (p = 0.04). No significant seasonal variations of 25(OH)D were observed in either the patient or the control group. VDR gene expression levels appeared to be similar in leukemia patients and healthy subjects, and no correlation between the cellular VDR expression and plasma 25(OH)D concentrations was observed in either group of participants. We did not observe a significant association of 25(OH)D or VDR levels and overall survival of leukemia patients. This observational study conducted for the first time in Kazakhstan supports previous findings demonstrating reduced blood 25(OH)D levels in cancer (leukemia) patients. Larger studies are required to determine whether low 25(OH)D plasma concentrations represent a risk factor for leukemia development and/or progression.

Low plasma levels of the vitamin D metabolite 25-hydroxyvitamin D [25(OH)D] and the vitamin D receptor (VDR) gene single nucleotide polymorphisms (SNPs) have been associated with the body’s susceptibility to infectious diseases, including COVID-19. In this pilot retrospective study, representatives of the Kazakh population (central Kazakhstan) were divided into groups based on the test for IgM and IgG for coronavirus infection. We compared the 25(OH)D plasma levels and concluded that the COVID-19-positive group values (25.17 ng/mL ± 16.65) were statistically lower (p = 0.0114) compared to the COVID-19-negative ones (35.58 ng/mL ± 20.67). There was no association between age, gender and 25(OH)D concentration within the groups (p > 0.05). The genotyping of rs2228570 was performed using a TaqMan Real-Time PCR assay. Allele C predominated among the COVID-19-negative participants and significantly reduced the likelihood of coronavirus infection (p < 0.0001; OR = 0.0804; 95% CI 0.02357–0.2798). There were no statistically significant differences in the frequencies of the A, G and T alleles in the studied groups (p > 0.05). The GG genotype of rs2228570 was associated with a 4.131-fold increased likelihood of COVID-19 infection (p = 0.0288; χ² = 5.364; OR = 4.131; 95% CI 1.223–13.71). Comprehensive studies are required to determine whether low 25(OH)D plasma concentrations and genetic background represent a risk factor for COVID-19 infection.

There is still no definitive confirmation regarding the association between ACE2 gene polymorphisms and COVID-19. This study was conducted to analyze the distribution of alleles and genotypes of the ACE2 gene rs2285666 and rs35803318 two polymorphisms and their possible association with COVID-19 among two ethnic groups, namely, the Kazakhs and Eastern Slavs, residing within the same geographic area in the city of Karaganda, Republic of Kazakhstan. This research was conducted for the first time in Kazakhstan. The genotyping was performed using the Amplification-Refractory Mutation System (ARMS) PCR. A substantial connection of rs2285666 with COVID-19 in the studied Kazakh and Eastern Slavs populations (p>0.05) was not observed. It has been determined that certain alleles and genotypes serve as protective markers against COVID-19. It was determined that the G allele (p = 0.0217) of rs2285666 among Kazakh men reduced the likelihood of coronavirus infection. It was concluded that the C allele and CC genotype of rs35803318 have a statistically significant association with protection against COVID-19 among only Eastern Slavs. There were no differences in the alleles and genotypes of polymorphism between males and females. Thus, the analysis of the rs2285666 and rs35803318 polymorphisms has revealed that these two variants of the ACE2 gene do not exert an influence on the risk of contracting COVID-19.

This pilot study investigated the single nucleotide polymorphisms rs731236, rs1544410, and rs7975232 of the VDR gene using real-time ARMS-PCR in a cohort of 119 individuals of Kazakh ethnic group. Participants were stratified into COVID-19-positive (p-COVID-19; n = 88) and COVID-19-negative (no-COVID-19; n = 31) groups based on the detection of SARS-CoV-2-specific IgM and IgG antibodies by ELISA. The allelic and genotypic distributions of all three SNPs conformed to Hardy–Weinberg equilibrium. No statistically significant differences in allele or genotype frequencies were observed between the groups for rs731236, rs7975232, or rs1544410 (p > 0.05), indicating that these polymorphisms do not influence susceptibility to SARS-CoV-2 infection in the studied population. A borderline association was noted for the heterozygous CT genotype of rs1544410 (p = 0.0548), suggesting a potential protective effect (OR = 0.426; 95% Cl: 0.1816 – 0.9563). Despite the limited sample size, this is the first study to examine rs731236, rs1544410, and rs7975232 in relation to SARS-CoV-2 susceptibility within the Kazakh ethnic population, and one of the few to simultaneously analyze all four alleles of rs1544410.