Publikationsdatenbank

Intracellular magnesium concentration in healthy horses and horses with insulin dysregulation (2020)

Art

Hochschulschrift

Autor

Winter, Judith Christine (WE 17)

Quelle

Berlin: Mensch und Buch Verlag Berlin, 2020 — II, 49 Seiten

Sprache

Englisch

Verweise

URL (Volltext): https://refubium.fu-berlin.de/handle/fub188/27704

Kontakt

Pferdeklinik

Oertzenweg 19 b
14163 Berlin
+49 30 838 62299 / 62300
pferdeklinik@vetmed.fu-berlin.de

Abstract / Zusammenfassung

Magnesium metabolism is closely connected with insulin, glucose homeostasis and the diseases metabolic syndrome and diabetes mellitus in humans. Especially the free intracellular magnesium concentration [Mg2+]i is of interest in these patients, as it resembles the status in the tissue and is more reliable than the serum magnesium concentration. The equine metabolic syndrome is an important and widespread disease that shows many similarities to human diabetes mellitus. Human diabetes mellitus patients often display a magnesium deficit in the serum or at the cellular level and benefit from magnesium supplementation. Reasons for these deficits are versatile and include a low magnesium content in the diet, renal losses due to hyperglycemic glycosuria and magnesium shifts resulting in an intracellular magnesium deficit. Horses’ diets typically contain high amounts of magnesium and baseline hyperglycemia with glycosuria and urinary losses of magnesium rarely occur. A whole body magnesium deficit is therefore unlikely to develop. However, shifts from the intracellular to the extracellular compartment are reasonable and studies comparable to those in human medicine have not been performed in horses yet. To establish reference ranges in healthy horses, the free intracellular magnesium concentration was measured by mag-fura 2 spectrophotometry in blood lymphocytes in 12 non-obese horses at 9 a.m., 12 a.m. and 4 p.m. according to a protocol designed for human blood lymphocytes. Additionally, the serum magnesium concentration was measured. In all horses, the total serum magnesium concentration was within the reference range. The mean free magnesium concentration in blood lymphocytes of all horses was 0.291 ± 0.067 mmol/L with no significant difference among the time points. The reference range for the free intracellular magnesium concentration in equine lymphocytes was set at 0.16–0.42 mmol/L. The established values are slightly lower than those in healthy humans. The second part of the study included 38 obese horses with insulin dysregulation, diagnosed by a positive combined glucose insulin tolerance test (CGIT) and phenotypic signs of equine metabolic syndrome. [Mg2+]i was significantly lower in horses with EMS (P=0.015) than in healthy horses, but still within the established reference range. We further demonstrated a positive correlation between the intracellular magnesium concentration and the proxy MIRG (modified insulin-to glucose ratio). The multivariate model revealed that only MIRG was significantly associated with [Mg2+]i, whereas all other factors had no additional influence. Thus, MIRG increase by 1 represents a [Mg2+ ]i increase by 0.015 mmol/L. This means, the decreased [Mg2+ ]i in EMS horses can be partially reversed by increased secretion of insulin from pancreatic β-cells. These findings substantiate the crucial role of insulin in regulating intracellular magnesium homeostasis and its relevance in EMS. Further studies should examine the role of magnesium metabolism in horses with metabolic syndrome, especially in horses with more pronounced insulin resistance.