[Relationship of vitamin A and thyroid function in Arctic residents]

At the present time the prevalence of thyroid diseases keeps growing, so knowledge of the factors affecting thyroid activity is very important. Vitamin A (retinol) is a fat-soluble vitamin with a hormone-like effect that can influence both the expression of thyroidstimulating hormone in the pituitary gland and the synthesis of thyroid hormones. The aim of the research was to study vitamin A serum level and its relationship with the thyroid profile in residents of the Arctic zone of the Russian Federation, depending on gender. Material and methods. In the course of a single-center observational cross-sectional study, 304 apparently healthy residents of villages in the Arkhangelsk region (103 men and 201 women) were examined. The serum concentration of vitamin A was determined by the fluorometric method, and the content of thyroid parameters was determined by the enzyme immunoassay. The integral thyroid index (ITI) and the index of peripheral conversion of iodothyronines (IPC) were calculated. The subjects were divided into 4 groups depending on the quartile of vitamin A. The relative risk of developing subclinical hypothyroidism was calculated with a reduced concentration of vitamin A. Results. The content of vitamin A was 1.97 (1.18; 2.97) μmol/l. Retinol levels in the female population were significantly lower than in the male population (1.85 vs 2.27 μmol/l, p<0.0001). Women in group 1 compared with group 4 showed significantly higher levels of thyrotropin (2.33 vs 1.40 μIU/ml, p=0.0002) and thyroxin (109.8 vs 99.4 nmol/l, p=0.010), while the ITI values, on the contrary, were the lowest (8.12 and 13.85 c.u., p=0.0002). The relative risk calculation showed that vitamin A levels below 1.39 μmol/L increase the risk of subclinical hypothyroidism in women by 2.01 times [95% confidence interval 1.07-3.78]. Men in group 4 compared with group 1 showed a lower content of thyroxin (83.0 vs 109.2 nmol/l, p=0.009) against the background of higher IPC values (0.019 vs 0.016 c.u., p=0.046). Conclusion. In the inhabitants of the Arctic, the content of vitamin A is within the reference values, however, in 24.3% of men, its level is above the norm. In women, the concentration of retinol is significantly lower, and its level of less than 1.39 μmol/l increases the risk of developing subclinical hypothyroidism by 2.0 times. Increased values of vitamin A in the inhabitants of the North cause lower levels of thyroxine and an increase in the peripheral conversion of iodothyronines, which is more pronounced in men.

[Analysis of vitamin A and thyroid blood levels in the indigenous and local Caucasian population of the Arctic]

Previously, differences in the thyroid profile of Arctic residents were shown depending on the vitamin A blood level. However, dietary habits and metabolism peculiarities in the aboriginal and Caucasian representatives of the North population may be the cause of different retinol supply and therefore be one of the reasons for changes in their thyroid activity. The purpose of the research was to assess vitamin A and thyroid blood levels in the aboriginal and local Caucasian population representatives of the Russian Arctic territories. Material and methods. In the single-center observational cross-sectional study, apparently healthy residents of villages in the Arkhangelsk region were examined (n=281): 145 representatives of the local Caucasian population and 136 representatives of the aboriginal population, with the proportion of tundra nomadic aborigines at 34%, village aborigines at 66%. Vitamin A blood serum level was determined by the fluorometric method, and the thyroid content [thyroid stimulating hormone (TSH), thyroxine (T4), triiodothyronine (T3), free T4, free T3] was determined by enzyme immunoassay. The integral thyroid index (ITI) as well as the index of peripheral conversion of iodothyronine (IPC) total and free fractions were calculated. Results. The level of retinol in the indigenous population of the Arctic was lower than that in the local Caucasian population (1.84 [1.26; 2.56] versus 2.10 [1.70; 2.42] μmol/L, p=0.014). However, its deficiency was found only in village aborigines (20.5% of women and 11.8% of men). At the same time, they have the maximum tension of the pituitarythyroid system: lower level of free T3 and free fractions' IPC than in the nomadic and Caucasian population, and TSH levels were higher than in the Caucasian population. Increased vitamin A levels prevailed among the nomadic population: in 60.7% of men and 11% of women retinol level exceeded the norm. At the same time, they have increased metabolic activity of thyroid hormones: higher levels of free T3 and free fractions' IPC compared with sedentary aboriginal population. No pronounced features of the thyroid profile were found in local Caucasians at normal blood concentrations of vitamin A. Conclusion. The lowest retinol levels are observed in settled aborigines (especially young women) living in villages and experiencing the greatest transformation of traditional lifestyle and nutrition, which is combined with higher TSH blood levels and decreased thyroid hormone metabolism. The highest retinol levels were found in nomadic aborigines (especially young men), which increase the reserves of antioxidant defense and support high metabolism of thyroid hormones. However, the high percentage of people with excessive vitamin A blood level in this group raises concerns due to the possible negative consequences. Therefore, it is necessary to monitor fat soluble vitamin levels among Arctic aboriginal populations. Social support measures should be taken for settled residents of villages, enabling them to consume more traditional foods rich in vitamin A. The causes of excessive blood retinol in nomadic aborigines require further study and control.

Age-related changes in the parameters of carbohydrate metabolism and supply of vitamins B1, B2 in residents of two northern regions

A great deal of research was being done in studying of the age-related characteristics of carbohydrate metabolism and the provision of vitamins B1, B2 among the population of the Subarctic (SR) and Arctic (AR) regions, differing in the extreme natural and climatic-geographic living conditions. The surveyed population was divided into five age groups: 16-21, 22-35, 36-45, 46-60 and 61-74 years old. The parameters of carbohydrate metabolism (glucose, lactate, pyruvate) were determined in the blood serum, the content of thiamine (thiamin diphosphate effect) and riboflavin - in hemolysates, and the values of the lactate/pyruvate ratio (Lac/Pyr) were calculated. Statistical data processing was performed by nonparametric methods. An increase in glucose levels was found in persons of older age groups. Age-related fluctuations of metabolites of carbohydrate metabolism were manifested by a lower content of lactate and the value of the Lac/Pyr ratio in persons aged 16-21 years. Regardless of the age and region of the survey, there were revealed high lactate concentrations, Lac/Pyr values and reduced pyruvate levels, as well as low glucose levels in group aged 16-21 year in AR. For vitamins B1, B2, no pronounced age-related changes were observed, while the content of riboflavin was higher in persons of SR. Moderate hypovitaminosis of thiamin was detected in 13-20,1% and 6,1-22,7% of cases in SR and AR, pronounced - 8,3-11,6% and 4,6-23,5%, respectively, vitamin B2 deficiency was noted in 19,4-23,9% of persons in the AR and in 33,8-42,9% of persons in the AR. Vitamins in both regions at different age periods contributed to the formation of levels of indicators of carbohydrate metabolism: glucose and pyruvate in SR, lactate in AR.

[Relationships between the lipid metabolic parameters and the humoral factors of natural immunity in children and adolescents]

With age, antiatherogenic defense in North aboriginal children is regulated by the humoral mechanisms of immunity, by increasing the levels of immunoglobulins (IgG, IgA), interleukin-4, and tumor necrosis factor-a and decreasing the content of interleukin-8 and interferon-alpha in particular, by reflecting the ability of the immune system to maintain and reduce the atherogenicity of blood lipids.

[Spare capacities of endocrine and metabolic indexes in the European North inhabitants during glucose tolerance test depending on photoperiod]

The standard gluco-tolerance test was carried out in 104 healthy women, 20-30 years living in Archangelsk at different year periods (October, March, December and June). The higher spare capacities levels were determined for glucose, lactate and pyruvate against the background of lactate dehydrogenase activity, insulin, C-peptide and cortisol in October and March.

[Relationships between serum content of tocopherol, retinol, and reproductive hormones in children]

Changes in the relations between the blood levels of vitamins E, A, and the hormones of the pituitary-gonad hormones (gonadotropic, sex steroid hormones) were studied in children at different pubertal stages. It has been found that at different pubertal stages, there is a change in the correlations the nature of which is determined by the relation to the blood concentrations of vitamins E and A.

[Specificity of metabolic processes observed in the glucose tolerance test in residents of the European North]

The reserve potentialities of metabolism processes and the specificity of the functioning in the course of glucose-tolerance test made in virtually healthy residence of the European North were studied with respect to body weight. A slowed utilization of glucose, triglycerides and of free fatty acids due to an intensified insulin concentration was detected, which essentially affects, in persons with excessive weight, the nature of the mentioned changes and belongs to the risk category of diabetes mellitus and ischemic heart disease.

[Endocrine and metabolic profile features in railway stock workers]

The studies covered physiologic features of adrenal cortex, pancreatic insular apparatus and carbohydrates metabolites in apparently healthy railway stock workers, in accordance with occupation, age, length of service and season. The authors proved dependence of endocrine and serum metabolic parameters on occupational activity type, age, length of service and season.

[Impact of the use of alcoholic beverages on lipid metabolic parameters in Northern Water Basin workers]

The nature of changes in lipid metabolic parameters was studied in the sailors, river transport workers, and fishermen of the Northern Water Basin in relation to the specific features of their working conditions and the frequency of drinking alcoholic beverages. It was shown that there was imbalance in the levels of lipid parameters, which was more pronounced in sailors and river transport workers.

[Insulin level, glycemia, insulin resistance and β-cell function in relation to the lifestyle of Arctic indigenous people. Are there conditions for diabetes and which type?]

BACKGROUND

Modern studies suggest that lifestyle changes of the indigenous Arctic residents lead to the loss of the "adaptive polar type of metabolism", which is characterized by the intensification of protein metabolism, optimization of lipid metabolism, and minimization of carbohydrate metabolism at low insulin concentrations. How to survive the era of change?

AIM

To assess insulinemia, glycemia, β-cell secretory activity, and insulin sensitivity in Arctic indigenous people in relation to their lifestyle.

MATERIALS AND METHODS

A cross-sectional study of a population of indigenous Arctic residents (Nenets, Komi) aged from 22 to 60 years was conducted. Insulin levels were studied in blood serum using ELISA, and glucose levels using the spectrophotometric method. Insulin resistance (HOMA-IR) and β-cell function (HOMA1-%β) indices were calculated.

RESULTS

397 people were examined; 89 (22%) of them were nomadic people (NP) and 44 (49%) were male. Another 308 (78%) were sedentary people (SP), and 69 (22%) were male. The insulin level was significantly lower in NP (6.0 [3.5-11.8] µU/ml) compared to SP (8.3 [4.6-13.1] µU/ml), p=0.006. There was no difference in glycemia (4.6 [4.2-5.0] in NP and 4.6 [4.1-5.2] in SP) between lifestyles.The HOMA-IR was significantly lower in NP (1.3 [0.7-2.4]) than in SP (1.8 [0.95-2.8]), p=0.013. IR-HOMA >2 units was 1.8 times more frequent in the SP than in NP, with adjusted for sex, age, and BMI OR=0.56; 95% CI: 0.33-0.96, p=0.034. The median HOMA1-%β was 128 [67-241] % in NP and 144 [93-236]% in SP with no significant differences between groups. The proportion of individuals with HOMA1-%β <48.9 was 17% in NP versus 5% in SP, p<0.001. The adjusted odds of having HOMA1-%β <48.9 in NP are 3.5 times higher than in SP; 95% CI: 1.56-7.92, p=0.002. Fifty-six cases of glycemia ≥5.6 mmol/l were identified: 13.5% in NP and 14.3% in SP. The ratio IR-HOMA >2/ HOMA1-%β <48.9/BMI was 1.8 units/45%/25.2 kg/m2 in NP and 3.0 units/88%/29.6 kg/m2 in SP.

CONCLUSION

Maintaining a nomadic lifestyle helps keep lower insulin concentrations; at the same time, glycemic levels in the groups were similar. In the NP group, there was a high proportion of individuals with low β-cell secretory activity, predominantly men; in the SP group, more individuals were insulin-resistant. Analysis of cases of glycemia ≥5.6 mmol/l confirmed, that hyperglycemia in a nomadic lifestyle was associated with β-cell hypofunction and the absence of obesity; on the contrary, in a sedentary lifestyle, it was associated with increased insulin resistance and obesity.

[Correlation of parameters of carbohydrate metabolism and saturated fatty acids in blood serum in elderly people.]

The study involved 106 elderly people of the Arctic aged 61-74 years, 42 of them were residents of the Subarctic region (SR) and 64 residents of the Arctic region (AR). Using gas-liquid chromatography there was determined the serum content of saturated fatty acids (SFA): short-chain (SCFA), medium-chain (MCFA) and long-chain (LCFA); and the levels of carbohydrate metabolism parameters were determined by spectrophotometric methods. Correlation analysis showed that elderly people of SR had no significant interrelationships between the contents of SCFA, MCFA and LCFA, since all the correlation dependences were weak (r=0,2-0,29, p=0,08-0,786), against AR with a lower occurrence of high values of glucose (Glu), lactate (Lac) and low pyruvate (Pyr). In AR, with the highest occurrence of high and low values of GIu, the greatest number of its interrelations was noted with LCFA (palmitic, margarine, stearic, behenic, tricosanoic), then with MCFA (myristic, pentadecanoic) and SCFA (pelargonic), low values of Pyr with MCFA (lauric, myristic, ∑MCFA) and SCFA (decanoic), and a slight decrease in the occurrence of high levels of Lac and Lac/Pyr with LCFA (palmitic, margarine, stearic, tricosanoic), MCFA (lauric, tridecanoic) and SCFA (caproic, capric).

[The role of fatty acids, water-soluble vitamins, calcium, phosphorus in maintaining carbohydrate metabolism in youth population of two different climatic geographic regions]

The sampling of youth population aged 16-21 years was examined in the northern (the Arkhangelskaia oblast) and the southern (the Southern Osetia) regions. The indicators of carbohydrate and lipid metabolism, provision of organism with calcium, phosphorus, thiamine, riboflavin were established. In the southern region decreasing of level of glucose, calcium and increasing of lactate, pyruvate, fatty acids were detected under decreased provision of organism with thiamine. The application of correlation analysis confirmed dependence of parameters of carbohydrate metabolism in individuals of the northern region from level of calcium and thiamine and in examined in both regions from riboflavin. At that, in the northern region fatty acids contributed maximally into alteration of level of glucose, pyruvate and values of ratio lactate/pyruvate. In the southern region saturated and polyunsaturated acids impacted on decreasing of activity of anaerobic processes.