PECULIARITIES OF METABOLISM OF TRACE ELEMENTS DEPENDENT ON THE ECOLOGY AND ARTERIAL HYPERTENSION IN NOMADIC SHEPHERDS OF CENTRAL ASIA

Irina U. Stoox, Galina V. Kashkan, Lyudmila P. Agulova, Nina G. Yuneman, Department of Arterial Hypertension, Cardiology Institute, Tomsk, 634012, Russia Department of General and Inorganic Chemistry, Polytechnic University of Tomsk, 634034, Russia

This study was designed to evaluate the role of ecological factors in genesis hypertension twice more common in the nomadic shepherds than among the settled inhabitants of Central Asia (Tuva). The concentrations of nine elements and the activity of parathyroid hormone in the serum, the concentrations of sixteen trace elements in the hair of nomadic shepherds and settled inhabitants were determined. The mineral composition of the species of drinking water, tea, meat were examined. The obtained results were considered in terms of age and sex of surveyed population and the geochemical peculiarities of the region. The results confirmed the prohypertensive role of the Mg deficiency in nomadic Tuvanese people and allowed to suppose a contribution of some trace elements to the conformation of the epidemiological peculiarities of cardiovascular pathology in Tuva.

Introduction. The arterial hypertension (AH) among the nomadic shepherds (NSh) of Tuva happens twice more often in comparison with the settled Tuvanese inhabitants (ST), and ischemic heart disease (IHD) happens among NSh seldom. It means AH is not a risk factor of IHD among NSh. [Stoox I.U.,1998]. The authors have attempted to assess a role of ecology in the origin of such epidemiologic paradox.

Methodology. NSh (n = 93) and ST (n = 103) of Tuva were surveyed during a long-term forwarding standardized researches of the epidemiology of AH and IHD. NSh have the closer connection with food chain environment. Their diet consists of meat and dairy products. Besides, they like tea boiled in a salty water with milk. The drinking water of this region is soft, as a rule. The food of ST is much more various. They eat products of other regions, in particular fruits, and also much vegetables, berries and much less meat and dairy products. The samples of drinking water (n=13), traditional tea with milk and salt (n=3), and meat of domestic animals (n=16) were analyzed. The official data about 113 sources of drinking water were used.

Arterial blood pressure (AP), the lipid spectrum of serum, the concentrations of Mg, Ca, Ca²⁺, Al, V, Mn, Fe, Cu, Pb, the activity of parathyroid hormone (PTH) in serum, and the concentrations of Mg, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mo, Ag, Cd, Sn, Ba, and Pb in hair were examined. The methods of flame photometry (serum, water), atomic-emission spectroscopy (serum, hair, tea, meat, and water), ion-selective measures (Ca²⁺), radioimmunoassay (PTH) were used. There were applied the standardized technique for all methods except the determination of the trace elements of hair and meat by the atomic-emission method with the arc source of initiation of a sample. The last technique was developed by the authors [Kashkan, etc. 1988]. This is a method of simultaneous determination of 14 trace elements in biological objects with a previous express-ashing of a sample. The accuracy of the technique was confirmed by the results of interlaboratory experiment. The statistical assesment of measurements and correlation analysis of the obtained results were carried out.

Results. The concentration of Mg (0.76±0.033 mmol/L) and the activity of PTH (42,6±2,9 pg/mL) in serum of NSh were studied to be lower than those of serum of ST (1.13±0.04 mmol/L) and (63.9±4.4 pg/mL), respectively. The differences were proved by the collation of the arranged groups of 19 persons in each in terms of sex and age. Correlation bonds among Mg, age, and AP were not revealed (Fig. 1 and 2).

There were no differences in the concentrations of Ca, Ca²⁺, Na, and K in serum between the groups but the correlation bonds of these elements were great different (Fig.1 and 2). The direct correlation of Са in the serum of NSh with systolic (SAP) and diastolic arterial pressure (DAP) were revealed. The direct correlation of Са in the serum with DAP, SAP and potassium were revealed among normotensive NSh. There were no such correlation bonds among ST but they were characterized by the contrary correlation of Ca²⁺ with SAP and the direct correlation of Na with DAP. The positive correlation of Mg and Na in serum were revealed among hypertensive ST.

Fig.1 Correlation of the concentrations of macro- and trace elements, the lipids of serum, arterial blood pressure, and age of the nomadic shepherds of Tuva

Fig.2 Correlation of the concentrations of macro- and trace elements, the lipids of serum, arterial blood pressure, and age of the settled inhabitants of Tuva

All the group: direct correlation ; reverse

Normotensive NSh and ST: direct correlation ; reverse

Hypertensive NSh and ST: direct correlation ; reverse

The concentration of Mg in the hair of NSh (99.5±8.5 mg/kg) is lower than in ST (131.7±17.9 mg/kg). The contrary correlation of Mg in the hair of NSh with SAP becomes evident.

Having collated of the concentrations of Al, V, Mn, Fe, Cu, and Pb in the serum of NSh and ST, we found out that V was lower and Pb was higher in NSh than in ST. The correlation bonds among the trace elements in the serum of NSh and also with other data of NSh (Fig.1) and ST (Fig.2) were differed considerably. The amount of correlation bonds was equal to 23 and 14 in NSh and ST, respectively. It was great of importance the existence of the direct correlation of Mn with the antisclerotic lipoproteins of high density (LHD) and the reverse correlation of Mn in serum with the triglycerides (TG) and the cholesterin (Ch) of ST.

The comparison of the trace elements in the hair of NSh and ST are shown in Table 1. It demonstrates the higher concentrations of Al, Mn, Fe, Ba in the hair of NSh in comparison with ST and the norms; the higher concentration of Cd in both groups (the prevalence of Cd among ST); the lower concentration of V, Cr, and Cu among NSh in comparison with ST though these values are within the limits of the norms in both groups.

The official data about 113 sources of drinking water were analyzed. The hardness of water from 7 to 10 mmol/L was considered as normal. The concentration of Mg equal to 10 mg/L was estimated as a low limit. Thus, 79 % of water sources contain soft water with the hardness from 0.6 to 5.8 mmol/L. The concentration of Ba changed from 0.006 to 0.015 mg/L in 17 sources that was within limits of the norm. The concentrations of V, Cr, Mn, Fe, Ni, Cu, Zn, Mo, Sn, Hg, and Pb were within the limits of the norms too. The concentration of Mg in drinking water changed from 0.54 to 2.6 mg/L and in tea - from 6.8 to 12.0 mg/L. The average concentration of Mg in meat samples was 126,77±32.1 mg/kg. This fact may be considered as the decrease in comparison with the normal data (150 – 230 mg/kg). The prevalence of V, Cr, Ba, and Mn, the decrease of Cu and Zn and the normal values of Fe, Ni, and Sn were revealed in meat.

Table 1: Concentrations of Trace Elements in Hair (mg/kg) of NSh and ST

Ele-ment	NSh			ST			Norms [ Kist, 1987] Limits M	NSh-ST Р
	n	M	m	n	M	m
Al V Cr Mn Fe Co Ni Cu Zn Mo Ag Cd Sn Ba Pb	28 34 34 34 34 34 25 34 34 34 32 16 33 34 31	50.3 0.44 0.75 10.7 64.7 1.89 0.73 13.8 93.7 0.21 0.35 3.24 0.62 19.2 2.59	5.22 0.02 0.04 1.4 7.8 0.21 0.13 1.39 7.45 0.009 0.09 0.45 0.02 1.62 0.41	25 26 23 28 26 26 21 26 26 22 26 19 19 23 26	15.5 0.94 1.75 2.39 28.0 1.28 1.23 20.1 188.4 0.28 0113 9.19 0.48 7.85 4.1	2.08 0.06 0.29 0.2 3.3 0.27 0.19 1.27 15.7 0.02 0.01 0.83 0.05 0.54 0.8	4.2-4.6; 5.5 0.0045-0.53; 0.14 0.13-3.65; 3.8 0.25-5.7; 0.8, 1.2 5-44.7; 23.7, 30 0.2-1.5; 5.97 0.6-12; 2.33, 7.5 15; 19 10.2 260; 218; 174 0.064-0.2; 9.47 0.024-3.8; 3.5 0.24-2.7; 0.26 1.0 0.55-42; 1.8; 5 3-70; 2.73; 50	<0.001 <0.05 <0.05 <0.01 <0.001 >0.05 >0.05 <0.05 <0.01 >0.05 >0.05 <0.01 >0.05 <0.01 >0.05

Footnote: Statistically significant differences are typed in bold.

Discussion. The prohypertensive role of magnesium deficiency in a human body is known [Morris A.D., Connel J.M. 1994]. We think that the decrease of Mg in serum and hair is the direct symptom of Mg deficiency in the organisms of NSh. Besides, our researches have showed decreasing the activity of PTH in serum that can also be considered as a marker of magnesium deficiency. [Lucas P.A., Woodhead J.S., 1985].

Ba and Mg are antagonists [Bachx P.H., etc 1991], therefore, being careful, we regard the increase of concentration of Ва in the hair of NSh also as a marker of Mg deficiency. On the other hand Ba can penetrate to the organism of a person from the eaten meat of domestic animals enriched by Ba. Taken together these results allow to think of combination of strengthened penetration of Ва in the organisms of NSh with its delay there caused by the Mg deficiency. The large frequency of arcus senilis among NSh in the age of till 50 years was an additional evidence of high concentration of Ba in their organisms. We observed this symptom even at the people more young than 30 years. The dependence between the high concentration of Ba and arterial hypertension is known. The demonstrated results and their interpretation have a good agreement with the higher activity of arterioles as a result of Ba influence when Mg is deficiency. In addition to the stated arguments, there is a direct evidence of the prohypertensive influence of Mg deficiency among NSh, namely, the reverse correlation of Mg in their hair with SAP.

It is difficult enough to interpret the registered decrease of the V, Cr, and Cu concentrations in the hair of NSh, and also some other deviations because the limits of norms are often very wide or imprecise and can not correspond to the studied region. In this connection, it seems to be logical to recommend the determination of the regional norms of trace elements in the biosubstrata of a human body. The comparisons of deviations in mineral composition of the serum, the hair of NSh and ST, the consumed meat, the soil, and the water of the given region, shown in Table 2, allowed to suppose the relation between epidemiological peculiarities of cardiovascular pathology in Tuva and its geochemical features.

Table 2: Comparisons of Deviations in Mineral Composition of Biological Objects with Geochemical Features (soil and water) of Tuva

Ele-ment	NSh		ST		Meat	Geochemical Features
	Serum	Hair	Serum	Hair
Mg V Cr Mn Fe Cu Zn Ba Pb	L = ? = = = ? ? H	L = = H H L L H =	= H ? = = = ? ? =	= H H = = = = = =	L ? H H = L L H =	L H H H = H ? = =

Footnote: = - no deviations; ? – unknown; H–increased concentration; L- decreased concentration

Conclusion. Thus, the high frequency of arterial hypertension among nomadic shepherds of Tuva can be explained by the ecologically reasoned Mg deficiency and the prevalence of Ba in their organisms. The environmental influence on the settled Tuvanese inhabitants is less on account of the less connection of ST with food chain environment.

The low frequency of ischemic heart disease among NSh can be supposedly linked with ecologically reasoned influence of Mn on their organisms. We proceeded from the assumption that we revealed the higher concentration of Mn in the hair of NSh and meat of domestic animals, and the correlation of the concentration of Mn with lipids. Besides, there are literature data about the antisclerotic role of Mn and its high concentration in the soil of Tuva.

In conclusion, it may be said that the mineral composition of hair can be a good indicator of a human health and an assistant to make a choice of differentiated preventive measures for any region with epidemiological peculiarities.

References:

Stoox I.U. (1998), Ecological Factors of Risk of Arterial Hypertension. Tomsk, Russia.

Kashkan G.V. , Kuleshov V.I., Baranova O.V. (1988), J Analyt. Chem. № 7, pp.1190-1194.

Кist А.Л., (1987), Phenomenology of Biogeochemistry and Bioinorganic Chemistry. Russia

Morris A.D., Connel J.M. (1994) , Am. J. Med.Sci. (307/2 Suppl.): pp. 47-52.

Lucas P.A., Woodhead J.S., (1985), In: Health D, Mark S.G.: Moscow, Publisher, pp.116-138

Bachx P.H., O’Rourke B., Marban E., (1991), Am. J. Hypertension. № 4: pp. 416-421.