Skeletal muscle and hepatic insulin signaling is maintained in heat-stressed lactating Holstein cows

Abstract

Multiparous cows (n=12; parity=2; 136±8 d in milk, 560±32kg of body weight) housed in climate-controlled chambers were fed a total mixed ration (TMR) consisting primarily of alfalfa hay and steam-flaked corn. During the first experimental period (P1), all 12 cows were housed in thermoneutral conditions (18°C, 20% humidity) with ad libitum intake for 9 d. During the second experimental period (P2), half of the cows were fed for ad libitum intake and subjected to heat-stress conditions [WFHS, n=6; cyclical temperature 31.1 to 38.9°C, 20% humidity: minimum temperature humidity index (THI)=73, maximum THI=80.5], and half of the cows were pair-fed to match the intake of WFHS cows in thermal neutral conditions (TNPF, n=6) for 9 d. Rectal temperature and respiration rate were measured thrice daily at 0430, 1200, and 1630 h. To evaluate muscle and liver insulin responsiveness, biopsies were obtained immediately before and after an insulin tolerance test on the last day of each period. Insulin receptor (IR), insulin receptor substrate 1 (IRS-1), AKT/protein kinase B (AKT), and phosphorylated AKT (p-AKT) were measured by Western blot analyses for both tissues. During P2, WFHS increased rectal temperature and respiration rate by 1.48°C and 2.4-fold, respectively. Heat stress reduced dry matter intake by 8kg/d and, by design, TNPF cows had similar intake reductions. Milk yield was decreased similarly (30%) in WFHS and TNPF cows, and both groups entered into a similar (-4.5 Mcal/d) calculated negative energy balance during P2. Insulin infusion caused a less rapid glucose disposal in P2 compared with P1, but glucose clearance did not differ between environments in P2. In liver, insulin increased p-AKT protein content in each period. Phosphorylation ratio of AKT increased 120% in each period after insulin infusion. In skeletal muscle, protein abundance of the IR, IRS, and AKT remained stable between periods and environment. Insulin increased skeletal muscle p-AKT in each period, but the phosphorylation ratio (abundance of phosphorylated protein:abundance of total protein) of AKT was decreased in P2 for TNPF animals, but not during WFHS. These results indicate that mild systemic insulin resistance during HS may be related to reduced nutrient intake but skeletal muscle and liver insulin signaling remains unchanged.

Impacts of chronic and increasing lipopolysaccharide exposure on production and reproductive parameters in lactating Holstein dairy cows

“…In brief, a 2 to 3 cm incision was made between the tailhead and the tuber ischia and adipose tissue was collected. For skeletal muscle collection, an incision (~5 cm) was made in the skin of the hind limb overlying semitendinosus muscle, and a sterile biopsy punch (8 mm, Miltex Inc., York, PA) was used for collecting a tissue core as previously described (Xie et al, 2016). Following collection, adipose and muscle biopsy sites were sutured, cleaned with 70% isopropanol, and disinfected with an aerosol bandage (AluShield, Neogen Corp., Lexington, KY).…”

Reproductive and lactational responses of multiparous dairy cattle to short-term postpartum chromium supplementation during the summer months

“…Likewise, blood glucose concentrations in the current experiment did not differ between treatment groups ( Table 1 ). Previous work from our laboratory and others suggests that insulin-stimulated glucose uptake is already maximized in heat-stressed dairy cattle ( Rhoads et al, 2009 ; Xie et al, 2016 ; Stewart et al, 2022 ). Consequently, it is likely that Cr is unable to further increase glucose uptake under these conditions.…”

Comparison of production-related responses to hyperinsulinemia and hypoglycemia induced by clamp procedures or heat stress of lactating dairy cattle

“…Fortunately, there is no reason to believe that the increase in rectal temperature was caused by an immune response. The insulin used in this study is commonly administered intravenously to cattle with no adverse effects (Butler et al, 2003;Piantoni et al, 2013;McCracken et al, 2015;Xie et al, 2016), and the infusate was prepared under sterile conditions using pharmaceutical-grade materials. Furthermore, endotoxin levels are measured by the insulin supplier as part of their quality control assessment and were found to be negligible (0.1 endotoxin units/mg).…”

“…Despite the variation in response observed during the HHC, mean baseline blood glucose concentrations decreased as expected when cows were subjected to high ambient temperatures. Blood glucose concentrations typically decline during heat stress, and this response has been observed in dairy cattle (Rhoads et al, 2009;Wheelock et al, 2010;Xie et al, 2016) as well as other species (Lee and Scott, 1916;Mahjoubi et al, 2014;Victoria Sanz Fernandez et al, 2015). Although it is logical to assume that the decline in circulating glucose concentrations during heat stress is a consequence of reduced feed intake, the accompanying collection of metabolic changes suggest that glucose is being preferentially used by extramammary tissues during heat stress (reviewed in Baumgard and Rhoads, 2013).…”