Publikationsdatenbank

Studies on the influence of zinc on trace element status of neonatal piglets and copper concentration in kidney of weaned piglets including zinc-related genes (2019)

Art

Hochschulschrift

Autor

Zetzsche, Alina (WE 4)

Quelle

Berlin: Mensch & Buch Verlag Berlin, 2019 — VII, 83 Seiten

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/26576

Kontakt

Institut für Tierernährung

Königin-Luise-Str. 49
14195 Berlin
+49 30 838 52256
tierernaehrung@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Zinc (Zn) is a trace mineral which has to supply to man an animal via nutrition. Through its participation in approximately 6000 proteins, 300 metallo-enzymes and its uniqueness of metals in involvement of all six enzyme classes the importance for organisms is demonstrated. However, it is an ambivalent metal, considering Zn surplus and undersupply have severe consequences (see chapters 2.3 Zinc deficiency and genetic disorder in zinc metabolism and 2.4 Zinc poisoning). Thus, Zn could be the limited growth factor and consequently the sufficient concentration in piglets´ feed is indispensable. Therefore, we conducted a feeding trial of suckling piglets to investigate the effect of trace elements in mineral organ concentrations and expression of Zn-related genes (see Chapter 4: Influence of formula versus sow milk feeding on trace element status and expression of zincrelated genes in the jejunum, liver and pancreas of neonatal piglets). Randomly selected neonatal piglets were divided into two groups (n=8 per group). The control group stayed by their mothers, whereby the second group were separated from the sows after uptake of colostrum, held in acryl boxes in sets of two and received milk replacer for a trial period of 14 days. After experimental time, BW of both groups did not differ significantly to each other (approximately 5.0 kg). To determine mineral concentration of Zn, Cu, Mn and Fe, tissues of jejunum, pancreas and liver were analysed by atomic absorption spectrometry. While Zn concentration in liver tissue of formula (FO) suckled piglets was approximately threefold higher compared to sow milk group (569 mg/kg DM and 188 mg/kg DM, respectively; P<0.01), they did not differ in pancreatic and jejunal tissue. Furthermore, Cu concentration in analysed tissues were comparable between both groups. Both, Fe and Mn concentration increased significantly in liver and jejunum in FO fed group (P<0.05). Following, we determined mRNA contents by using real-time-PCR and subsequent calculated relative mRNA abundance by the use of housekeeping genes (succinate dehydrogenase subunit A, ß-microglobulin and ß-actin), mean ct and PCR efficiency. This way, relative contents of Zn transporter (ZnT1 and 2 for reducing cellular Zn and ZIP4 for increasing cellular Zn concentration), metallothionein (MT-1A, MT-2B and MT-3 as cellular storage and detoxification proteins), divalent metal ion transporter (DMT1, transporting several divalent ions across the cellular membrane) and a proinflammatory cytokine (interleukin (IL)-6), involved in Fe metabolism in liver tissue) mRNA were determined. Neither in pancreas nor in jejunum changes occur. But in liver tissue all determined MT isoforms and IL-6 increased significantly in FO group. On the contrary, ZnT1 and DMT1 were significantly higher in sow milk suckled piglets. Finally, Spearman´s correlation was executed to get a deeper insight into correlations of minerals and gene expression in liver tissue (see Table 4.5). In conclusion, accumulation of diverse minerals and increased MT expression in tissues of FO fed piglets, although fed concentration satisfied recommendation of NRC for very young, but weaned, piglets, let us propose the question, whether requirements are possibly lower as to date expected. Considering the rising number of litter size per sow and limited ability of nourish the piglets, artificial rearing systems and therefore composition of milk replacer are an instant problem. On the other hand, high dietary Zn concentration were used as antibiotic-free growth promoter in pig breeding for decades. Indeed, accumulation in different tissues and environmental pollution through excreted Zn were reported, dietary Zn up to the high of 3000 mg Zn/kg DM remains in weaning piglets´ nutrition (see chapter 2.5 Requirement and recommendation of zinc). Thus, we conducted an animal trial to examine the impact of Zn and Cu co-accumulation on mineral metabolism involved proteins in kidney tissue of weaned piglets after 14 and 28 days. Furthermore, we measured mineral concentrations of several tissues to evaluate whether prolonged pharmacological dietary Zn intake rise further on and if a regression of Zn tissue concentration occurs after 14 days of withdraw to required dietary Zn (see Chapter 5: Accumulation of copper in the kidney of pigs fed high dietary zinc is due to metallothionein expression with minor effects on genes involved in copper metabolism). Therefore, 40 weaned piglets were randomly divided into two groups (n=16 and 24, respectively) for the first two weeks and afterwards a third group was created and after further two weeks remaining 24 piglets were euthanized to take samples (n=8 per group). The tissue Zn concentration (measured by atomic absorption spectrometry) were higher in jejunum, liver, pancreas, and bone of high fed Zn group (HZn, 2100 mg Zn/kg DM) compared to normal dietary Zn group (NZn, 100 mg Zn/kg DM) after 14 and 28 experimental days, respectively. The group which switched from HZn to NZn after 14 days (CZn group) did not differ from NZn group, which indicated that Zn accumulation is reversible. Kidney tissue was the only of analysed tissues showing a Co-accumulation of Zn and Cu and a strong positive correlation to each other (R=0.67; P<0.05). Therefore, we determined relative mRNA concentration of Zn transporter (ZnT1, ZIP4), DMT1, MT-1a, MT-2b, MT-3 and genes which are involved in Cu metabolism (plasma membrane Cu transporter: Ctr1, Cu chaperons: Atox-1, CCS and ATP7A, Cu/Zn superoxide dismutase: SOD1 and a cytoplasmic binding protein ceruloplasmin: CP) in kidney tissue using real-time qPCR. Relative mRNA concentration of Cu metabolism involved proteins did not differ between time points and groups, apart from decreased Atox-1 after two weeks and increased Ctr1 over time in HZn group, respectively. Contrary, relative MT expression of all three measured iso-enzymes were higher in HZn group at both time points, compared to NZn and CZn group. Thereby, the most distinct effect was observed in MT-1a expression, followed by MT-2b and MT-3, possibly due to binding affinities or tempo of adaptation processes. To conclude, despite usually carefully regulated Zn homeostasis, counter regulation in jejunal absorption processes during excessive high dietary Zn concentration for two and four weeks did not protect against Zn accumulation in several tissues, which is an indicator for outbalanced homeostasis. Furthermore, Zn induced MT expression resulted in Cu Coaccumulation in kidney, whereby Cu metabolism involved genes did not adapt on transcription level. Indeed, all mentioned changes were reversible by a change to normal dietary Zn intake for two weeks. Nevertheless, further quantitative studies were required to determine the reason for renal co-accumulation of Zn and Cu, consequences on urinary element emission and body Cu status of piglets.