Intramammary lipopolysaccharide challenge in early versus mid-lactation dairy cattle: immune, production, and metabolic responses.

Study objectives were to compare the immune response, metabolism and production following intramammary lipopolysaccharide (IMM LPS) administration in early and mid-lactation cows. Early (E-LPS; n = 11; 20 ± 4 d in milk [DIM]) and mid- (M-LPS; n = 10; 155 ± 40 DIM) lactation cows were enrolled in an experiment consisting of 2 periods (P). During P1 (5 d) cows were fed ad libitum and baseline data were collected, including liver and muscle biopsies. At the beginning of P2 (3 d) cows received 10 mL sterile saline containing 10 µg of LPS from Escherichia coli O111:B4/mL into the left rear quarter of the mammary gland, and liver and muscle biopsies were collected at 12 h post-LPS. Tissues were analyzed for metabolic flexibility, which measures substrate switching capacity from pyruvic acid to palmitic acid oxidation. Data were analyzed with the MIXED procedure in SAS 9.4. Rectal temperature was assessed hourly for the first 12 h post-LPS and every 6 h thereafter for the remainder of P2. All cows developed a febrile response following LPS, but E-LPS had a more intense fever than M-LPS cows (0.7°C at 5 h after LPS). Blood samples were collected at 0, 3, 6, 9, 12, 24, 36, 48, and 72 h post-LPS for analysis of systemic inflammation and metabolism parameters. Total serum Ca decreased after LPS (26% at 6 h nadir) but did not differ by lactation stage (LS). Circulating neutrophils decreased, then increased post-LPS in both LS, but E-LPS had exaggerated neutrophilia (56% from 12 to 48 h) compared with M-LPS. Haptoglobin increased after LPS (15-fold) but did not differ by LS. Many circulating cytokines were increased post-LPS, and IL-6, IL-10, TNF-α, MCP-1, and IP-10 were further augmented in E-LPS compared with M-LPS cows. Relative to P1, all cows had reduced milk yield (26%) and dry matter intake (DMI; 14%) on d 1 that did not differ by lactation stage (LS). Somatic cell score increased rapidly in response to LPS regardless of LS and gradually decreased from 18 h onwards. Milk component yields decreased after LPS. However, E-LPS had increased fat (11%) and tended to have increased lactose (8%) yield compared with M-LPS cows throughout P2. Circulating glucose was not affected by LPS. Nonesterified fatty acids (NEFA) decreased in E-LPS (29%) but not M-LPS cows. ß-hydroxybutyrate (BHB) slightly increased (14%) over time post-LPS regardless of LS. Insulin increased after LPS in all cows, but E-LPS had blunted hyperinsulinemia (52%) compared with M-LPS cows. Blood urea nitrogen (BUN) increased after LPS and the relative change in BUN was elevated in E-LPS cows compared with M-LPS cows (36 and 13%, respectively, from 9 to 24 h). During P1, metabolic flexibility was increased in liver and muscle in early lactating cows compared with mid-lactation cows, but 12 h post-LPS, metabolic flexibility was reduced and did not differ by LS. In conclusion, IMM LPS caused severe immune activation and E-LPS cows had a more intense inflammatory response compared with M-LPS cows, but the effects on milk synthesis was similar between LS. Some parameters of the E-LPS metabolic profile suggest continuation of metabolic adjustments associated with early lactation to support both a robust immune system and milk synthesis.

Prolonged voluntary wheel running reveals unique adaptations in mdx mice treated with microdystrophin constructs ± the nNOS-binding site.

We tested the effects of prolonged voluntary wheel running on the muscle function of mdx mice treated with one of two different microdystrophin constructs. At 7 weeks of age mdx mice were injected with a single dose of AAV9-CK8-microdystrophin with (gene therapy 1, GT1) or without (gene therapy 2, GT2) the nNOS-binding domain and were assigned to one of four gene therapy treated groups: mdxRGT1 (run, GT1), mdxGT1 (no run, GT1), or mdxRGT2 (run,GT2), mdxGT2 (no run, GT2). There were two mdx untreated groups injected with excipient: mdxR (run, no gene therapy) and mdx (no run, no gene therapy). A third no treatment group, Wildtype (WT) received no injection and did not run. mdxRGT1, mdxRGT2 and mdxR performed voluntary wheel running for 52 weeks; WT and remaining mdx groups were cage active. Robust expression of microdystrophin occurred in diaphragm, quadriceps, and heart muscles of all treated mice. Dystrophic muscle pathology was high in diaphragms of non-treated mdx and mdxR mice and improved in all treated groups. Endurance capacity was rescued by both voluntary wheel running and gene therapy alone, but their combination was most beneficial. All treated groups increased in vivo plantarflexor torque over both mdx and mdxR mice. mdx and mdxR mice displayed ∼3-fold lower diaphragm force and power compared to WT values. Treated groups demonstrated partial improvements in diaphragm force and power, with mdxRGT2 mice experiencing the greatest improvement at ∼60% of WT values. Evaluation of oxidative red quadriceps fibers revealed the greatest improvements in mitochondrial respiration in mdxRGT1 mice, reaching WT levels. Interestingly, mdxGT2 mice displayed diaphragm mitochondrial respiration values similar to WT but mdxRGT2 animals showed relative decreases compared to the no run group. Collectively, these data demonstrate that either microdystrophin construct combined with voluntary wheel running increased in vivo maximal muscle strength, power, and endurance. However, these data also highlighted important differences between the two microdystrophin constructs. GT1, with the nNOS-binding site, improved more markers of exercise-driven adaptations in metabolic enzyme activity of limb muscles, while GT2, without the nNOS-binding site, demonstrated greater protection of diaphragm strength after chronic voluntary endurance exercise but decreased mitochondrial respiration in the context of running.

Chickens from lines selected for high and low body weight show differences in fatty acid oxidation efficiency and metabolic flexibility in skeletal muscle and white adipose tissue.

OBJECTIVE: The Virginia lines of chickens have resulted from more than 55 generations of artificial selection for low (LWS) or high (HWS) juvenile body weight. We hypothesized that the relative hyperphagia and greater body weight in juvenile HWS chickens are associated with altered fatty acid oxidation efficiency and metabolic flexibility in tissues associated with energy sensing and storage, and relative cellular hypertrophy in white adipose tissue. METHODS: Hypothalamus, liver, pectoralis major, gastrocnemius, abdominal fat, clavicular fat and subcutaneous fat were collected from the juvenile (56-65 days old) LWS and HWS chickens for metabolic, gene expression and histological assays. RESULTS: The HWS chickens had reduced fatty acid oxidation efficiency in abdominal fat (P<0.0001) and reduced rates of oxidation in abdominal fat and gastrocnemius (P<0.0001) as compared with the LWS. There was reduced citrate synthase activity in white adipose tissue (P<0.0001) and greater metabolic inflexibility in skeletal muscle (P=0.006) of the HWS compared with the LWS. Greater pyruvate dehydrogenase kinase 4 (PDK4) and forkhead box O1A (FoxO1) mRNA were found in skeletal muscle and white adipose tissue of 56-day-old HWS than LWS. Expression of peroxisome proliferator-activated receptor γ (PPARγ) in all adipose tissue depots was greater (P<0.05) in LWS than in HWS chickens. The HWS chickens had larger (P<0.0001) and fewer (P<0.0001) adipocytes per unit area than the LWS. CONCLUSION: Compared with the LWS, the HWS chickens have impaired metabolic flexibility and fatty acid oxidation efficiency due to greater pyruvate dehydrogenase activity to accommodate the influx of acetyl-CoA from fatty acid oxidation in skeletal muscle and adipose tissue. These metabolic adaptations can be linked to differences in gene expression regulation, adipocyte cellularity and body composition between the lines, which may provide valuable insight into metabolic disorders in other species.

Fiber hypertrophy and increased oxidative capacity can occur simultaneously in pig glycolytic skeletal muscle.

An inverse relationship between skeletal muscle fiber cross-sectional area (CSA) and oxidative capacity suggests that muscle fibers hypertrophy at the expense of oxidative capacity. Therefore, our objective was to utilize pigs possessing mutations associated with increased oxidative capacity [AMP-activated protein kinase (AMPKγ3(R200Q))] or fiber hypertrophy [ryanodine receptor 1 (RyR1(R615C))] to determine if these events occur in parallel. Longissimus muscle was collected from wild-type (control), AMPKγ3(R200Q), RyR1(R615C), and AMPKγ3(R200Q)-RyR1(R615C) pigs. Regardless of AMPK genotype, RyR(R615C) increased fiber CSA by 35%. In contrast, AMPKγ3(R200Q) pig muscle exhibited greater citrate synthase and ß-hydroxyacyl CoA dehydrogenase activity. Isolated mitochondria from AMPKγ3(R200Q) muscle had greater maximal, ADP-stimulated oxygen consumption rate. Additionally, AMPKγ3(R200Q) muscle contained more (∼50%) of the mitochondrial proteins succinate dehydrogenase and cytochrome c oxidase and more mitochondrial DNA. Surprisingly, RyR1(R615C) increased mitochondrial proteins and DNA, but this was not associated with improved oxidative capacity, suggesting that altered energy metabolism in RyR1(R615C) muscle influences mitochondrial proliferation and protein turnover. Thus pigs that possess both AMPKγ3(R200Q) and RyR(R615C) exhibit increased muscle fiber CSA as well as greater oxidative capacity. Together, our findings support the notion that hypertrophy and enhanced oxidative capacity can occur simultaneously in skeletal muscle and suggest that the signaling mechanisms controlling these events are independently regulated.