ABSTRACT
Our previous
work has suggested that recombinant bovine
interleukin-8 (rbIL-8)
treatment might influence
cow metabolism. Therefore, this study was conducted to initially assess the effects of systemic
administration of rbIL-8 on response to a
glucose challenge,
blood metabolites,
insulin,
growth hormone,
insulin-like growth factor-1, immune
cell populations, and inflammatory
parameters in Holstein bull calves. Calves from 30 ± 6 d of
life were individually housed and randomly allocated to 1 of 2
treatment groups rbIL-8 (rbIL-8, n = 10) and control (CTR, n = 8). Calves assigned to the rbIL-8 group received 1 s.c.
injection (d 1, 0900 h) and 6 i.v.
injections (d 1 at 1600 h, d 2 and 3 at 0900 h and 1600 h, and d 4 at 0900 h) of rbIL-8 (4 µg/kg of
body weight), whereas the CTR group received 2 mL of sterile
saline solution at each
time point. Day of enrollment was considered as d 1, and the study duration was 10 d.
Insulin concentrations and whole-body
glucose disappearance were evaluated by an i.v.
glucose tolerance test conducted at 12 h and 7 d following the last rbIL-8
injection. Rectal
temperature and
blood samples were collected on d 1, 2, 3, and 4 at -30 (before
treatment, 0830 h), 30, 60, 120, 240, and 360 min relative to
treatment, and daily at 0830 h for the
rest of the study period.
Serum was harvested, and the following
parameters were measured ß-hydroxybutyrate (BHB),
nonesterified fatty acids,
glucose,
insulin,
plasma urea nitrogen,
haptoglobin, and differential
blood count. Significant differences were considered when P ≤ 0.05 and a trend if 0.05
Serum glucose levels and glucose area under the curve (AUC) did not differ between treatment groups in response to the glucose challenge. However, calves treated with rbIL-8 had greater serum insulin concentration and insulin AUC compared with controls. Administration of rbIL-8 increased rectal temperature (rbIL-8 = 39.3 ± 0.1; CTR = 38.9 ± 0.1°C; ±standard error), BHB concentrations (rbIL-8 = 3.54 ± 0.10; CTR = 2.99 ± 0.12 mg/dL), counts of lymphocytes (rbIL-8 = 4.52 ± 0.12; CTR = 3.84 ± 0.14 × 103/µL), monocytes (rbIL-8 = 0.87 ± 0.03; CTR = 0.67 ± 0.04 × 103/µL), and granulocytes (rbIL-8 = 3.54 ± 0.22; CTR = 2.66 ± 0.24 × 103/µL). We conclude that rbIL-8 induces insulin resistance in Holstein bull calves, accompanied by systemic inflammation and altered blood metabolites and white blood cell populations.
