Epitalon Research Article – Part 3

This is the Epitalon Research Aticle – Part 3

Part 3 – The results

Results

Age-related body weight dynamics

Mean values of body weight for mice at different ages in the control and treated withEpithalon groups are displayed in Table 1.

The body weight of the mice in both groups increased with age, exceeding by 13 months the body weight of 3-month-old animals by 44.5% in the control group (P<0.001), and by 48.5% in the group given Epitalon (P<0.01). There were no differences in the body weight between groups at any period of observation.

Age-related dynamics of food consumption

Measurements showed that the amount of food consumed by the mice in the control (saline) group was practically stable from the age of 5 months to the age of 16 months, increasing slightly at the age of 18 months. Mice treated with Epitalon consumed more food from the 5th to the 16th months of their life than the control group (Table 2).

Age-related dynamics of estrous function in mice

The estrous function in the animals of both age groups was examined every three months, starting when the mice were three months old. The following parameters of estrous function were estimated: the length of the estrus, the relative rate of estrous cycle phases (in percent); and the relative number of short (5 days) estrous cycles. The relative number of animals with regular cycles and irregular cycles (persistent estrus and anestrus) were also calculated. Judging by the data presented in Table 3, the length of estrous cycle in the control female SHR mice increased with advancing age (P<0.05; Student’sttest).

Thus, no essential age-related alterations in the rate of estrous cycle phases were observed. However, the relative number of short estrous cycles decreased significantly with age (37.1% at the age of 3 months, 9.4% at the age of 12 months (P<0.05; Fischer’s exact test) and zero at the age of 15 months, whereas the number of long cycles rose (5.1% at the age of 6 months and 36% at the age of 15 months,P<0.05; Fischer’s exact test).

In the group of mice exposed to Epitalon the length of estrous cycles did not change with the age of the animals and decreased in comparison with the agematched controls at the age of 15 months (P<0.05). There was no significant age-related decrease in the number of short cycles, or an increase in the number of long cycles. The number of mice with regular cycles did not change significantly with age in both groups (Table 3).

Age-related dynamics of body temperature in mice

Data on body temperature alterations in the mice exposed to saline or Epitalon are presented in Table 4. The control mice and mice treated with Epitalon revealed a significant decrease in body temperature with age, both on the whole (irrespective of the estrous cycle phases) and in any of the phases. No cyclic alterations in rectal body temperature during the estrus cycle were observed in mice of the control group, but the temperature at diestrus was significantly higher than that in estrus in mice treated with Epitalon at the age of 15 months (P<0.05). It should be noted that the average body temperature in the mice treated with Epitalon was not significantly different from the control mice during the entire period of observation (Table 4).

Chromosome aberrations in mouse bone marrow cells

The incidence of chromosome aberrations in bone marrow cells of 3-month-old female SHR was 2.1 ±0.29%. At the age of 12 months this parameter increased to 8.2 ±0.41% (P<0.001; Wilcoxon–Mann–Whitney test) in the group injected with saline. In mice treated from the age of 3 months with Epitalon the incidence of chromosome aberrations at the age of 12 months was 6.8±0.21(-17.1%;P<0.05).

Survival and longevity of female SHR mice

Survival dynamics in the mice treated with either saline or DSIP are demonstrated in Table 5 and Figure 1.

The survival dynamics were in general similar in all groups up to the age of 22 months. However, thereafter, the number of survivors was much higher in Epitalon-treated groups. The last mouse in the control group died at the age of 739 days (24.3 months), whereas in the groups treated with Epitalon 12% of mice survived to this age, and the maximum life span was 830 days (27.3 months, + 12.3%). The mean life span of mice treated with Epitalon did not change as compared with controls. However, the life span in the last 10% of the mice increased for the duration of Epitalon treatment by 3.1 months (+ 13.3%,P<0.01; Student’st-test) (Table 6).

Spontaneous tumor development in female SHR mice

The total tumor incidence in the control female mice was 36%. Mammary carcinomas and leukemias developed most frequently, corresponding to the oncological characteristics of female SHR mice (Anisimov et al. 1989). The treatment with Epitalon failed to influence the total or malignant tumor incidence in comparison with that of the control group.

However, the incidence of leukemias during the treatment with Epitalon decreased 6-fold (P<0.01; Fischer’s exact test). There was no significant difference in the incidence of any other tumors between the group of mice
treated with the peptide and saline (Table 7). The treatment with Epitalon significantly shifted to right the total tumor yield curve as compared with the control group (Figure 2).

Mathematical model and estimations of survival of tumor-free and tumor-bearing mice

A mathematical analysis of the survival data of the mice from the control and melatonin-treated groups has been done separately for three different contexts:

for all animals in each group (total cases); (2) for fatal tumor-bearing mice, and (3) for fatal tumor-free mice. We composed the groups of animals without consideration of possible effects caused by dependence between these groups.

The Gompertz model shows a slowdown (by 29.0.4%) of the population aging rate (calculated as αin the Gompertz equation) and a corresponding increase in MRTD under the influence of Epitalon. The mortality rate in the group of fatal tumor-free mice treated with Epithalon was decreased by 32.5% as compared with the controls (P<0.05, Table 8).