Effect of peroral chromium administration on the insulin axis and IGF system in Holstein calves.

Hrom je hemijski elemenat čija je biološka aktivnost još uvek predmet izučavanja kod domaćih životinja. Kod ljudi i laboratorijskih životinja je dokazano da hrom utiče na efekte insulina sa posledičnim uticajem na regulaciju metabolizma ugljenih hidrata, proteina i lipida, Ovaj efekat je posebno izražen kod mladih jedinki tokom perioda rasta. Osim uticaja na insulinski signalni put, postoje indicije da hrom može uticati i na IGF sistem, ali u dosadašnjim ispitivanjima, osim uticaja hroma na promene koncentracije IGF-I, uglavnom nije proučavan uticaj hroma na ostale komponente ovog sistema (IGF vezujuće proteine i receptore za IGF molekule). Cilј ove disertacije je bio da se ispita uticaj peroralnog davanja hroma (organski trovalentni hrom vezan za kvasac) na insulinsku osovinu i IGF sistem kod teladi uzrasta od mesec dana do četiri meseca. Ovaj uzrast je odabran jer je to period kada telad prelazi sa mlečne ishrane na ishranu kabastim i koncentrovanim hranivima, svojstvenu odraslim preživarima i predstavlja period metaboličkog “prestrojavanja”. Za ogled je izabrano 24 teladi holštajn-frizijske rase uzrasta mesec (32±3) dana, koja su podeljena u dve grupe. Teladi PoCr grupe (n=12) je svakodnevno, izazivanjem refleksa sisanja brizgalicom, peroralno aplikovan hrom rastvoren u mleku, dok je kontrolnoj, NCr grupi (n=12) u istom periodu aplikovano samo mleko. Tokom ogleda, od obe grupe, su uzimani uzorci mišićnog tkiva 0. i 70. dana, kao i uzorci krvi u intervalima od 10 dana, odnosno 0., 10., 20., 30., 40., 50., 60. i 70. dana, kada je vršeno i merenje telesne mase. Takođe su izvedeni intravenski testovi opterećenja glukozom (IVGTT) četiri puta u toku trajanja ogleda i to 0., 30., 50. i 70 dana ogleda. U uzorcima mišičnog tkiva određivana je zastupljenost proteina signalnog puta insulina i to: insulinskog receptora (IR), supstrata insulinskog receptora fosforilisanog na tirozinu 632 (pIRS-1 Tyr632), supstrata insulinskog receptora fosforilisanog na na serinu 307 (pIRS-1 Ser307), protein kinaze B (Akt) fosforilisane na serinu 473 (pAkt Ser473), transportnog molekula za glukozu (GLUT4) i AMP - zavisne protein kinase (AMPK)...Chromium is a chemical element whose biological activity is still subject of study in domestic animals. In humans and laboratory animals it has been proven that chromium has impact on the effects of insulin, with the consequent effect on the regulation of carbohydrate, protein, and lipid metabolism. This effect is particularly pronounced in young animals during the growth period. In addition to the effects on the insulin signal pathway, there are indications that chromium may also affect the IGF system. Nevertheless, expect the influence of chromium on changes in IGF-I concentration, previous studies did not investigate influence of chromium on other components of this system (IGF-binding proteins and receptors for IGF molecules). The objective of this study was to investigate the effect of peroral chromium (chromium enriched yeast) administration on the insulin axis and IGF system in calves at the age from one to four months. This age was chosen because it is the period when calves are switching from milk feeding to forages and concentrate, characteristic for adult ruminants and represents a period of metabolic turnover. Twenty-four Holstein-Friesian calves aged 1 month (32 ± 3 days) were chosen for the study and divided into two groups. The PoCr group (n = 12) that perorally received 0.04 mg of Cr/kg of body mass during 70 days. Chromium dissolved in milk was administered to each calf using a syringe that caused suckling reflex. The NCr group (n = 12) acted as a control group, and has received milk, by peroral application and with no added Cr during the same period. Muscle tissue samples were taken from both groups on days 0 and 70. Blood samples were taken in the intervals of 10 days, meaning on days 10, 20, 30, 40, 50, 60, and 70, when body mass was also measured. Intravenous glucose tolerance tests (IVGTT) were performed, four times during the experiment, meaning on days 0, 30, 50. and 70..