SEASONAL CHANGES OF METABOLIC PARAMETERS IN YOUNG MEN IN THE CONDITIONS OF THE EUROPEAN NORTH
Кочан Т.И.1, Есева Т.В.2, Бойко Е.Р.3
1ORCID: 0000-0002-8084-4056, кандидат биологических наук, доцент, 2ORCID: 0000-0003-3480-0762, научный сотрудник, 3ORCID: 0000-0002-8027-898X, доктор медицинских наук, профессор, Институт физиологии Коми Научного центра Уральского отделения Российской академии наук, Сыктывкар, Россия
СЕЗОННЫЕ ИЗМЕНЕНИЯ МЕТАБОЛИЧЕСКИХ ПОКАЗАТЕЛЕЙ У МОЛОДЫХ МУЖЧИН В УСЛОВИЯХ ЕВРОПЕЙСКОГО СЕВЕРА
Аннотация
Изменчивость значимых метаболических показателей человека в течение года недостаточно изучена. Понимание причин колебаний концентрации метаболитов в крови имеет большое значение для клинической практики, поскольку далеко не всегда можно сказать, какие из обнаруживаемых сдвигов в функционировании той или иной системы организма имеют адаптационный характер, а какие уже служат признаком патологии. Целью настоящего исследования было исследование сезонной динамики метаболических показателей молодых мужчин в условиях Европейского Севера России (62° с. ш.) в течение года. Субъектами исследования были двадцать здоровых призывников (средний возраст 19 ± 0,5 года), первого года службы, т.е. с небольшим периодом проживания на Севере. В крови обследуемых, взятой из вены утром натощак, измеряли концентрацию глюкозы, лактата, триглицеридов, общего холестерина, альбумина и мочевины с помощью унифицированных колориметрических методов с использованием наборов Chronolab (Швейцария). Установлено, что значение биохимических показателей крови здоровых молодых людей в течение года изменяется на 40 – 200%, выходя за рамки физиологических норм. Это указывает на метаболическую адаптацию организма к меняющимся факторам окружающей среды и должно учитываться в клинической практике.
Ключевые слова: человек, питание, обмен веществ, адаптация, север.
Kochan T.I.1, Eseva T.V.2, Bojko E.R.3
1ORCID: 0000-0002-8084-4056, PhD in Biology, Associate Professor, 2ORCID: 0000-0003-3480-0762, Researcher, 3ORCID: 0000-0002-8027-898X, Dr of Medical Sciences, Professor, Institute of Physiology of Komi of Scientific Center of the Ural branch of the Russian Academy of Sciences, Syktyvkar, Russia
SEASONAL CHANGES OF METABOLIC PARAMETERS IN YOUNG MEN IN THE CONDITIONS OF THE EUROPEAN NORTH
Abstract
Variability of significant metabolic parameters of a person during the year is not sufficiently studied. Understanding the causes of fluctuations in the concentration of metabolites in the blood is of great importance for clinical practice, because it is not always possible to say which of the observed shifts in the functioning of a particular body system are adaptive, and that already serve as a sign of pathology. The aim of this study was to study the seasonal dynamics of the metabolic parameters of young men in the European North of Russia (62° N latitude) during the year. Subjects of the study were twenty healthy conscripts (mean age 19 ± 0.5 years), the first year of service, i.е. with a small period of residence in the North. In the blood of the examinees, taken from the vein in the morning on an empty stomach, the concentration of glucose, lactate, triglycerides, total cholesterol, albumin and urea was measured using unified colorimetric methods using the Chronolab (Switzerland) kits. It is established that the value of biochemical indicators of the blood of healthy young people change by 40-200% during the year, going beyond physiological norms. This indicates metabolic adaptation of the organism to changing environmental factors and should be taken into account in clinical practice.
Keywords: man, nutrition, metabolism, adaptation, North.
Introduction
Adaptation of biological systems to changing conditions of internal or external environment is based on metabolic adaptation, that is, quantitative changes in metabolic processes in cells. At the present time, significant factual material has been collected on the changes in metabolic processes in the human body under the influence of natural factors of the North. Inhabitants of the North have revealed such deviation from the norm as hypoxia [1, P. 229], [2, P. 115], [5, P. 153], [6, P. 99] hypoglycemia [3, P. 257], [4, P. 90], [5, P. 58], hypovitaminosis [3, P. 236]. According to a number of authors [7, P. 102], [8, P. 57], [9, P. 29] oxygen consumption and indirectly calculated heat production in this parameter among residents of the North in the initial period of adaptation to cold are decreasing, indicating a decrease in energy supply due to aerobic oxidation of substances. In these conditions, in our opinion, the energy role of anaerobic glycolysis increases significantly [10, p. 757], which leads to a significant decrease in the concentration of glucose and increase lactate in the blood plasma. However, clinical diagnostics still do not take into account seasonal features of metabolism, and even small deviations from normal conditions are regarded to be a violation of human health. Therefore, the study of seasonal dynamics of biochemical indicators in blood during the annual cycle is relevant.
The aim of this study was to investigate the changes of the metabolic parameters of young men in the conditions of the European North of Russia during the year.
Materials and methods
The subjects were twenty healthy male volunteers (average age 19 ± 0.5 years) serving in the European North of Russia (Syktyvkar, latitude 62° N), they daily spent 6 to10 hours outdoors every day. The young people were not residents of the subarctic region. During the survey, they were in the military service for four to six months. The study was conducted over a 12-month period. Examinations were performed during the last 10 days of each month. The subjects underwent a medical examination and were free from any diseases and disorders that could affect their participation in the study. None of the recruited individuals were obese (body mass index < 30). The participants were informed about the research objectives and provided written consent.
Blood was taken monthly from the ulnar vein of men into vacutainer tubes (Becton Dickinson BP, UK) after overnight fasting. We measured the blood concentrations of glucose, lactate, triglycerides, total cholesterol, albumin and urea by enzymatic colorimetric methods using Chronolab kits (Switzerland). The actual nutrition was studied using the questionnaire based on the Album of Foodstuff Portions and Dishes, developed by the Institute of Nutrition of the Russian Academy of Medical Sciences.
The obtained results were analyzed with Statistica 6.0 (StatSoft, Tulsa, USA). The statistical importance of seasonal changes of the studied indices was assessed by Student T-criterion (in case of normal value distribution) and by Wilcoxon nonparametric W-criterion (in case of asymmetric distribution of values). The data are presented as the mean with standard errors of the mean (SEM).
Results
Monitoring of the metabolic state in young men throughout the year revealed its dependence on seasonal environmental factors. The concentration of metabolites varied throughout the year as follows: blood glucose – 3.6-5.13 mmol/l, lactate – 1.34-2.75 mmol/l, triglycerides – 0.52-1.58 mmol/l, total cholesterol – 2.66-4.0 mmol/l, albumin – 46.2-59.4 g/l, urea – 3.42-5.7 mmol/l (Table 1).
Air temperatures were obtained from the Meteorological Office. The lowest temperature was recorded in January and the highest in August. Significant unexpected temperature changes were recorded in March (cooling by 4 °C in comparison with February) and in May (significant increase to + 27 °C in the afternoon against -2 °C in April). These temperatures undoubtedly influenced the metabolic states.
Table 1 – Dynamics of the metabolite concentrations in the blood of young men over one year
One feature of the nutrition of the subjects (Fig. 1) was the increased content of carbohydrates in the diet throughout the survey period (significantly exceeding the normal values), while the content of fats was below the normal value. A deficiency in fat content was observed in the diet of the subjects throughout the year. The daily consumption of proteins was higher than normal in autumn, winter and spring, whereas in summer, it significantly decreased, falling below the normal value in June and August. Changes in the daily energy values of the diets were in accordance with the dynamics of carbohydrate consumption.
Changes in the blood metabolite concentrations also had a seasonal nature. With a significant decrease in air temperature during November (down to -16 ... -19° C in the survey days), the concentration of triglycerides in the blood of the test subjects increased significantly (by a factor of 1.6, p<0.001), indicating an increase in lipogenesis. The concentrations of cholesterol and urea decreased by 21% (p<0.01) and 13% (p<0.01), respectively. The contents of glucose and lactate did not significantly change.
A distinctive feature of subjects’ metabolism in December, when the temperature of the air on surveyed days was -15 and -6 °C and length of daylight decreased to a minimum (5 h, 9 min), was an increase in the blood glucose concentration to a maximum value (19% increase compared to the November values, p<0.01). In addition, the cholesterol level increased by 24% (p<0.01), and conversely, a decrease of 60% of the triglyceride content was observed (p<0.01). The concentrations of lactate, albumin and urea remained at the levels observed during November.
In January, as the air temperature significantly decreased (surveyed values of -18 and -24 °C), the blood glucose concentration significantly decreased by 23% (p<0.001), apparently as a result of the increased glycolysis intensity. However, the level of lactate also decreased by 16% (p<0.05), which was evidence of its increased utilization in metabolic processes. The increase in plasma albumin was higher than normal (maximum of 58.8 g / l, 27% increase over the previous month, p<0.001), possibly due to the increase in its functional value during the transport of free fatty acids in connection with the intensification of lipolysis. The concentration of total cholesterol decreased by 14% (p<0.001), and the urea content remained at the same level as in December.
Fig. 1 – The contents of protein, fat, carbohydrates and the energy in the daily rations of young men in the different months of the examination
Note. * p <0.05, ** p <0.01 compared to the previous month.– line of norm contentIn January, as the air temperature significantly decreased (surveyed values of -18 and -24°C), the blood glucose concentration significantly decreased by 23% (p<0.001), apparently as a result of the increased glycolysis intensity. However, the level of lactate also decreased by 16% (p<0.05), which was evidence of its increased utilization in metabolic processes. The increase in plasma albumin was higher than normal (maximum of 58.8 g / l, 27% increase over the previous month, p<0.001), possibly due to the increase in its functional value during the transport of free fatty acids in connection with the intensification of lipolysis. The concentration of total cholesterol decreased by 14% (p<0.001), and the urea content remained at the same level as in December.
In February, as the temperatures warmed (-11 and -9° C), there was a tendency towards an increase in the glucose, lactate, triglyceride, and total cholesterol levels, but the concentrations of albumin and urea significantly decreased (by 17 and 14% compared to the January indices).
An unexpected cold snap in March during the surveyed days (-15 and -13° C) caused a short-term adaptive reaction of the body. This was evidenced by a decrease in the glucose concentration below the physiological normal value of 73% (p<0.001) compared to the previous month, which indicated an increased role of glycolysis in maintaining the body's temperature homeostasis. Lactate in the blood also significantly decreased by 45% (p<0.001), but to a lesser extent compared with glucose. In parallel, the level of triglycerides decreased by 24% (p<0.05), whereas the albumin and urea concentrations increased by 21% (p<0.001) and 12% (p<0.05), respectively).
In April, with an increase in the length of daylight (15 h 20 min), significant warming was noted, but the effect of low temperatures (-1° С, -2° С) continued. Metabolic changes at this time of year included a significant increase in the concentrations of glucose, lactate and triglycerides by 24, 105 and 54% (p<0.001), respectively. The concentrations of total cholesterol and urea tended to increase, while the albumin content decreased by 4% (p<0.001), but still exceeded the physiological normal value. The maximum accumulation of lactate above the normal upper limit, which took place against the background of a normal glycemic level, indicated a higher rate of its formation compared with its use.
In May, with the loss of the effect of negative air temperatures and a sharp warming trend (up to 15° C in the morning and 27° C at noon), the concentrations of lactate, triglycerides and total cholesterol significantly decreased compared to April (by 24, 42 and 15%, respectively). The concentration of glucose did not change significantly. At the same time, the urea level increased by 20% compared to the previous month (p<0.001) to the maximum value observed, indicating extensive deamination of amino acids and possibly their active use in both the Krebs cycle and gluconeogenesis.
During polar summer, in June, with an increase in air temperature (17° C) and the maximum length of daylight (19 h 46 min), the concentrations of glucose, lactate, albumin and urea in the blood remained virtually unchanged. The triglyceride level increased by 87% (p<0.01), while the cholesterol content decreased to a minimum value, by 21% (p<0.001) compared to the May index.
In July (7° C, 11° C), metabolic changes in the subjects included a significant decrease in urea (by 29%, p<0.01) as well as triglycerides and blood lactate (by 24 and 10%, respectively). The concentrations of glucose and albumin were maintained at the levels of the previous month. The concentration of cholesterol increased by 32% (p<0.001).
With an increase in air temperature during August (to 17° C in the morning and to 23° C in the day), the concentrations of glucose, albumin and urea did not show any significant changes. However, the level of triglycerides continued to decline and was significantly lower than in June (by 30%, p<0.01). The concentration of cholesterol also decreased by 15% relative to July (p<0.01), while the lactate content in the blood increased by 48% (p<0.001).
In September, which was quite warm (6° C, 12° C), the contents of glucose and urea in the blood of young men did not undergo significant changes. At the same time, the concentrations of lactate, triglycerides and cholesterol decreased significantly by 23% (p<0.05), 25% (p<0.01), and 15% (p<0.01), respectively. However, the concentration of albumin reached its maximum value, exceeding the reference values.
Conclusion
Thus, the monitoring of blood biochemical indicators reflecting the state of carbohydrate, protein and lipid metabolism in young people who are recent inhabitants of the North allowed us to reveal that the main feature of their metabolism compared with young northerners of the same age [10, P. 757] is signs of hypoglycemia, manifested not in October and November, but in March. The characteristics of the metabolic changes in March, when the glucose level decreases together with the reduction of lactate and triglycerides concentration to the minimum values, are connected, in our opinion, with short-term adaptation of the organism of the young men to a sudden drop in temperature, which is revealed in the increased utilization of the mentioned metabolites and growing of considerable tension in the processes of energy supply of the organism. The concentration of metabolites of carbohydrate, lipid and protein metabolism in the blood of young healthy men with a small period of residence in the North varies within the same range as that of young northerners [10, P. 758], change throughout the year by a factor of 1.4 or more times, exceeding the reference values. Reason for this is the adaptation of metabolism in response to seasonal changes in environmental conditions. The established fact should be taken into account in clinical practice and requires further research taking into account the age of people, their region of residence and the impact of natural factors.
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