Evaluation of glucose dose on intravenous glucose tolerance test traits in Holstein-Friesian heifers

Abstract

Glucose metabolism in dairy and beef cattle has received considerable attention because balanced blood glucose is essential for numerous processes, such as milk production and general health. The glucose tolerance test measures the ability of an organism to regulate blood glucose levels. Glucose half-life time (GHLT) has high heritability and could serve as a potential parameter to breed for metabolic resistance. However, studies focusing on identification of an adequate glucose dose have not yet been conducted in cattle. The objective of this study was to analyze the effect of 5 different glucose doses (0.5, 1, 1.5, 2, and 3 g/kg of body weight) on intravenous glucose tolerance test (ivGTT) traits and insulin responses in nongestating heifers. A total of 150 tests were performed in 30 Holstein-Friesian heifers aged 13 to 15 mo. Blood samples were obtained every 7 min after glucose injection until min 63. Glucose traits and insulin parameters included blood serum glucose and insulin concentration at min 0 (basal concentration), min 7 to 21 (peak glucose and insulin concentration), and min 63 (last sampling) relative to glucose administration, glucose and insulin area under the curve (GAUC and IAUC), and GHLT estimated between min 14 and 42. Serum glucose and insulin concentrations were measured according to the hexokinase colorimetric method and radioimmunoassay, respectively. Generalized linear mixed model was used to test for significant differences in ivGTT traits, insulin responses, and glucose elimination rates (k) over time at different glucose doses. Maximum glucose and insulin concentrations at min 63 increased with higher glucose doses. Significantly lower GHLT were obtained at increasing glucose doses, whereas GAUC and IAUC were significantly higher at increasing doses. The k values were affected by glucose dose and by time interval. Glucose dose greatly affected most ivGTT traits, insulin responses, and glucose elimination rates. Therefore, researchers should standardize their methods to achieve repeatable results and use the same time points for GHLT calculation. Higher glucose doses (≥1.5 g/kg of body weight) triggered glucose concentrations above the glucose renal threshold during the initial 42 min, whereas the lowest glucose concentration failed to induce a maximum insulin response. Further research is necessary to determine an adequate dose inducing maximum insulin responses with minimum renal glucose losses.

Phycocyanin Improves Reproductive Ability in Obese Female Mice by Restoring Ovary and Oocyte Quality

“…GraphPad Prism 7 software was used to calculate area under the curve (AUC) values for both GTT and ITT. Glucose tolerance refers to a reduction in the body's ability to regulate blood glucose levels (González-Grajales et al, 2018), and insulin resistance refers to a reduction in the response of a peripheral target tissue to a physiological concentration of insulin (Hotamisligil et al, 1993).…”

Chronic prepartum light-dark phase shifts in cattle disrupt circadian clocks, decrease insulin sensitivity and mammary development, and are associated with lower milk yield through 60 days postpartum

“…This can be due to several factors that include the time relative to last meal, and physiological state; these baseline indices were created to measure human insulin sensitivity and adapted for cattle (Holtenius and Holtenius, 2007;De Koster et al, 2017;González-Grajales et al, 2017). There is also the concern that insulin disappearance occurs through several insulin-independent pathways including renal filtration and fetal and mammary gland uptake depending on the physiological state of the animal (González-Grajales et al, 2018;Malacco et al, 2020). Although the gold standard of measuring insulin sensitivity in dairy cows has been the use of the insulin euglycemic clamp, several studies have evaluated insulin sensitivity using IVGTT and RQUICKI alone (Pires et al, 2007;Mann et al, 2016).…”

Short communication: Effect of glucose infusion dose and stage of lactation on glucose tolerance test kinetics in lactating dairy cows

“…Glucose doses ranging from 0.10 to 3.0 g/kg of BW during IVGTT in cattle have been reported in the literature (Bigner et al, 1996;Subiyatno et al, 1996;Holtenius et al, 2003;Wheelock et al, 2010;Spears et al, 2012;González-Grajales et al, 2018). The literature suggests that an insufficient dose of glucose during an IVGTT may fail to elicit maximal pancreatic insulin release, whereas a dose that is too high may overwhelm the ability of the kidney to resorb glucose and result in excretion of glucose in urine (González-Grajales et al, 2018). Both scenarios could result in inaccurate evaluations of glucose kinetics and inaccurate estimates of insulin resistance.…”