The alkaline comet assay, or single cell gel electrophoresis, is one of the most popular methods for assessing DNA damage in human population. One of the open issues concerning this assay is the identification of those factors that can explain the large inter-individual and inter-laboratory variation. International collaborative initiatives such as the hCOMET project - a COST Action launched in 2016 - represent a valuable tool to meet this challenge. The aims of hCOMET were to establish reference values for the level of DNA damage in humans, to investigate the effect of host factors, lifestyle and exposure to genotoxic agents, and to compare different sources of assay variability. A database of 19,320 subjects was generated, pooling data from 105 studies run by 44 laboratories in 26 countries between 1999 and 2019. A mixed random effect log-linear model, in parallel with a classic meta-analysis, was applied to take into account the extensive heterogeneity of data, due to descriptor, specimen and protocol variability. As a result of this analysis interquartile intervals of DNA strand breaks (which includes alkali-labile sites) were reported for tail intensity, tail length, and tail moment (comet assay descriptors). A small variation by age was reported in some datasets, suggesting higher DNA damage in oldest age-classes, while no effect could be shown for sex or smoking habit, although the lack of data on heavy smokers has still to be considered. Finally, highly significant differences in DNA damage were found for most exposures investigated in specific studies. In conclusion, these data, which confirm that DNA damage measured by the comet assay is an excellent biomarker of exposure in several conditions, may contribute to improving the quality of study design and to the standardization of results of the comet assay in human populations.

The comet assay or single cell gel electrophoresis, is the most common method used to measure strand breaks and a variety of other DNA lesions in human populations. To estimate the risk of overall mortality, mortality by cause, and cancer incidence associated to DNA damage, a cohort of 2,403 healthy individuals (25,978 person-years) screened in 16 laboratories using the comet assay between 1996 and 2016 was followed-up. Kaplan–Meier analysis indicated a worse overall survival in the medium and high tertile of DNA damage (p < 0.001). The effect of DNA damage on survival was modelled according to Cox proportional hazard regression model. The adjusted hazard ratio (HR) was 1.42 (1.06–1.90) for overall mortality, and 1.94 (1.04–3.59) for diseases of the circulatory system in subjects with the highest tertile of DNA damage. The findings of this study provide epidemiological evidence encouraging the implementation of the comet assay in preventive strategies for non-communicable diseases.

Purpose of the study. An analysis of indices of free radical oxidation and respiration of mitochondria of heart cells in a malignant process in presence of diabetes mellitus and chronic neurogenic pain in experimental animals.Materials and methods. The study included outbred female rats (n=32) and С57ВL/6 female mice (n=84). Experimental groups of rats were: intact group 1 (n=8), control group 1 (n=8) with diabetes mellitus (DM), comparison group 1 (n=8) with standard subcutaneous transplantation of Guerin’s carcinoma, main group 1 (n=8) with Guerin’s carcinoma transplanted after 1 week of persistent hyperglycemia. Experimental groups of mice were: intact group 2 (n=21), control group 2 (n=21) with a model of chronic neurogenic pain (CNP), comparison group 2 (n=21) with standard subcutaneous transplantation of melanoma (B16/F10), main group 2 (n=21) (CNP+B16/F10) with melanoma transplanted 3 weeks after the CNP model creation. Heart mitochondria were isolated by differential centrifugation. Levels of cytochrome C (ng/mg of protein), 8-hydroxy-2'-deoxyguanosine (8-OHdG) (ng/mg of protein), and malondialdehyde (MDA) (μmol/g of protein) were measured in mitochondrial samples by ELISA. Statistical analysis was performed using the Statistica 10.0 program.Results. DM in rats upregulated 8-OHdG by 6.3 times and MDA by 1.9 times (р=0.0000) and downregulated cytochrome C by 1.5 times (р=0.0053) in heart cell mitochondria, compared to intact values. DM+Guerin’s carcinoma in rats increased 8-OHdG by 14.0 times and MDA by 1.7 times (р=0.0000) and decreased cytochrome C by 1.5 times (р=0.0000), compared to intact values. CNP in mice did not affect the studied parameters in mitochondria of the heart. CNP+B16/F10 in mice increased 8-OHdG by 7.1 times and MDA by 1.6 times (р=0.0000) and decreased cytochrome C by 1.6 times (р=0.0008).Conclusions. Comorbidity (diabetes mellitus, chronic neurogenic pain) together with malignant pathology aggravates mitochondrial dysfunction of heart cells with destabilization of the respiratory chain mediated by free radical oxidation processes.

Diabetes mellitus and malignant tumors are among the most common and complex diseases. Epidemiological studies have shown a strong relationship between these pathologies. The causality of this relationship has not yet been unambiguously established, but a number of probable biological mechanisms have been proposed to explain it through the effects of hyperglycemia, hyperinsulinemia on the process of oncogenesis. An important role in this is played by the axis of insulin-like growth factors, their receptors and binding proteins (IGF / IGFR / IGFBP). The review provides data on the structural elements of the insulin / IGF / IGFR / IGFBP signaling axis and their internal relationships in diabetes mellitus and in the development of malignant tumors. Significant changes in the axis that occur during the formation of the diabetic environment prepare the background, which, under certain conditions, can lead to the stimulation or inhibition of tumor development. The considered signaling system, playing a significant role in the physiology of normal cells, often functions as a decisive factor in the survival of tumor cells, providing fine context-dependent regulation of many cellular processes associated with oncogenesis. However, despite many years of in-depth studies of the pathogenesis of diabetes mellitus and malignant tumors, the molecular mechanisms of the relationship between these pathologies are still largely unclear, and the internal heterogeneity of pathologies complicates research and interpretation of the results, leaving many questions.

Aim. Our aim has been to develop an experimental model of the tumor growth against the background of hypothyroidism in rats of both genders in order to study possible influence made by hypothyroidism on progression of malignant tumors of various histological types. Materials and methods. In our studies we have used 100 outbred albino rats of both genders, with an individual body mass of 150-180 g. The female rats (n=30) and the male rats (n=30) have received Mercazolil at a day dosage of 2,5 mg/100g of the body weight for 30 days. After hypothyroidism in the treated rodents had been confirmed, one group of them (15 females and 15 males) were subcutaneously inoculated with the Guerin’s carcinoma cells, and another group (covering other 15 females and other 15 males) has been undergone to transplantation of the Sarcoma 45 cells. The reference group has included the rats of both genders with subcutaneously inoculated the Guerin’s carcinoma cells (n=10 females and n=10 males) and Sarcoma 45 cells (n=10 females and n=10 males), but without reproduction of the hypothyroidism model. Upon expiration of one month, within the 3 day period, we have estimated with a radioisotope analysis (RIA) standard assay kits (Immunotech, Czekh Republic) the levels of the thyroid hormones in blood of the tested animals as follows: Triiodothyronine (T3) (pM/L), total Thyroxine (T4) (pM/L) and Thyroid-Stimulating Hormon (TSH) (μU/mL). The obtained data have been processed with Statistica 10.0. Results. Upon the treatment with Mercazolil, we have found in the females a decrease by a factor of 7,3 in the total level of Thyroxine and an increase by a factor 1,6 in the TSH level (p<0,05), while in the males we have recorded a reduction by a factor of 2 in the total level of Thyroxine and an increase by a factor of 1,5 in the TSH level (p<0,05). In this case, the average sizes of the tumors in the female rats with Guerin’s carcinoma and hypothyroidism have been found smaller than those found in the reference group as given below: upon expiration of 4 days they are 1,3 times smaller (p<0,05), upon expiration of 7 and 10 days the volumes have been found 1,4 times smaller (p<0,05); upon expiration of 14 days the volumes have been recorded to be 1,5 times less (p<0,05); upon expiration of 18 days they have been reported to be 1,3 times less (p<0,05), and upon expiration of 21 days they have been estimated to be 1,4 times less (p<0,05). As to the males with Guerin’s carcinoma and hypothyroidism, the average sizes of their tumors as against the reference group data have been recorded to be smaller as follows: upon expiration of 4 days they are found 13,3 times less; upon expiration of 7 days they have been recorded to be 7,5 times smaller; upon expiration of 10 days the volumes have been estimated to be 1,9 times less (p<0,05), and upon expiration of 14 days they have been found to be 2,6 times less. The survival rate in the female rats in the main test has been recorded to be 1,6 times higher (p<0,05) against the data in the reference group, while the survival rate in the males has not shown any significant differences therein. In the female rates with S 45 growing against the background of hypothyroidism the average sizes of the tumors have been found to be less than those identified in the reference group as follows: after 4 days, the sizes have been recorded to be 1,4 times less (p<0,05); after 7 and 10 days they have been recorded to be 1,6 and 3,2 times smaller, respectively (p<0,05); after 14 days they have been found to be 3,9 times less, and after 18 days they have been recorded to be 4,8 times less. In the males at tumor growth week stage 1, the tumor sizes have increased 3,1 times as against 4 days of the tumor growth; upon expiration of 10 days the sizes have been found to be 7,1 times greater as compared with the previous period; upon expiration of 2 weeks they have increased 1,5 times (p<0,05); upon expiration of 18 and 21 days the tumor sizes have been recorded to be greater by a factor of 2,3 and by a factor of 1,6, respectively (p<0,05). The life spans in the female rodents in the main test group has been reported to be longer by a factor of 1,8 (p<0,05) than it has been the case with the reference group, and the average life span in the males has reached 21 days. Conclusion. We have revealed that in the female rates diagnosed with hypothyroidism the sizes of the subcutaneous tumor nodes of Guerin’s carcinoma and S 45 show slower progression as against that recorded in the reference group, and the life span recorded in the above rodents has been found as significantly longer, while in the male rats with hypothyroidism we have observed an irregular, slower, progression of the tumor nodes of Guerin’s carcinoma and S 45 within the period of 14 days, but subsequently we have detected the same progression rate as it is the case with the reference group data.