Objective—To determine the effects of advanced age on whole-body protein synthesis and activation of the mechanistic target of rapamycin (mTOR) signaling pathway in skeletal muscle of horses.
Animals—Six 22- to 26-year-old (aged) and six 7- to 14-year-old (mature) horses.
Procedures—Whole-body protein synthesis was measured with a 2-hour primed constant infusion of 13C sodium bicarbonate, followed by a 4-hour primed constant infusion of 1-13C phenylalanine. After the infusions, a biopsy specimen was obtained from a gluteus medius muscle and activation of protein kinase B (Akt), p70 riboprotein S6 kinase (S6K1), riboprotein S6 (rpS6), and eukaryotic initiation factor 4E binding protein 1 (4EBP1) was determined with western immunoblot analysis. For all horses, inflammatory cytokine expression in muscle and blood samples was measured with quantitative real-time PCR analysis.
Results—Advanced age had no effect on whole-body protein synthesis or the phosphorylation of Akt, rpS6, and 4EBP1; however, muscle specimens of aged horses had 42% lower phosphorylation of S6K1 than did those of mature horses. Aged and mature horses had similar inflammatory cytokine expression in muscle and blood samples.
Conclusions and Clinical Relevance—The lower S6K1 activation for aged horses, compared with that for mature horses, could be indicative of low rates of muscle protein synthesis in aged horses. However, advanced age had no effect on any other indicators of whole-body or muscle protein synthesis or on measures of systemic or muscle inflammation, which suggested that protein metabolism and subsequently requirements may not differ between healthy mature and aged horses.
Objective—To determine concentrations of cytokine mRNA in horses with exercise-induced pulmonary hemorrhage (EIPH) after racing.
Procedures—Following tracheobronchoscopy, the severity of EIPH was graded (scale of 0 to 4), and venous blood samples were collected from 10 horses in each grade. After RNA isolation and cDNA synthesis, real-time PCR assay was conducted to detect cytokinespecific mRNA for interleukin (IL)-1, IL-6, and IL-10; interferon (INF)-γ; and tumor necrosis factor (TNF)-α.
Results—Neither location nor grade of EIPH affected the expression of IL-1 and INF-γ. There was significantly greater overall expression of IL-6 mRNA at sea level, with significantly more IL-6 expressed in horses with grade 4 EIPH than in horses with grade 0, 1, or 2 EIPH. At a high altitude, no difference was detected for IL-6 expression among the various EIPH grades. There was significantly greater overall expression of TNF-α mRNA at a high altitude; however, there was no difference within the various grades of EIPH. Expression of IL-10 was significantly affected by grade of EIPH because horses with grade 3 EIPH expressed significantly more IL-10 mRNA than did horses with grade 0 or 2 EIPH; this expression was not affected by location.
Conclusions and Clinical Relevance—At sea level, increased IL-6 expression was associated with more severe EIPH, and altitude may affect gene expressions of the proinflammatory cytokine TNF-α and anti-inflammatory cytokine IL-6. Studies on protein concentrations of cytokine expression are needed. The pathophysiologic importance of these findings remains to be explained.
Objective—To evaluate systemic effects of IV infusion
of ATP-MgCl2 subsequent to infusion of a low
dose of endotoxin in horses.
Animals—12 adult horses.
Procedure—Horses were administered endotoxin
(lipopolysaccharide [LPS]) or saline (0.9% NaCl) solution,
IV, during a 30-minute period. Immediately thereafter,
horses in each group were infused IV with ATP-MgCl2 or
saline solution. Two weeks later, horses were administered
the opposite solution (LPS or saline solution), but
it was followed by the same infusion as 2 weeks previously
(ie, ATP-MgCl2 or saline solution). Cardiopulmonary
and clinicopathologic variables, cytokine activity, and
endothelin (ET) concentrations were recorded.
Results—IV infusion of ATP-MgCl2 after administration
of a low dose of endotoxin failed to attenuate the
cardiopulmonary, clinicopathologic, and cytokine alterations
that develop secondary to endotoxin exposure.
The combination of LPS and ATP-MgCl2 potentiated
pulmonary hypertension, leukopenia, and neutropenia
when compared with the combination of LPS and
saline solution. The combination of LPS and ATP-MgCl2
resulted in thrombocytopenia. Endothelin concentration
was increased in jugular venous and pulmonary
arterial plasma in horses receiving LPS and
ATP-MgCl2. Similar increases were not observed with
LPS and saline solution.
Conclusions and Clinical Relevance—Administration
of ATP-MgCl2 did not protect horses from systemic
effects of experimentally induced endotoxemia.
Furthermore, the use of ATP-MgCl2 during endotoxemia
may worsen the cardiopulmonary and clinicopathologic
status of affected horses. Because ATP and
other adenine nucleotides are released from cells during
shock, their potential role in the development of
hemodynamic derangements, leukocyte adherence,
and coagulopathies during endotoxemic episodes warrants
further investigation. (Am J Vet Res 2004;65:
Objective—To evaluate the effect of diets enriched with eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) on in vivo production of interleukin (IL)-1, IL-6, tumor necrosis factor (TNF)-α, prostaglandin E2 (PGE2), and platelet-activating factor (PAF) in dogs.
Animals—15 young healthy dogs.
Procedures—Dogs were randomly allocated to receive an isocaloric ration supplemented with sunflower oil (n = 5), fish oil (5), or fish oil plus vitamin E (5) for 12 weeks. At week 12, in vivo production of inflammatory mediators was evaluated in serum at multiple time points for 6 hours following stimulation with IV administration of lipopolysaccharide (LPS).
Results—Serum activity or concentration (area under the curve) of IL-1, IL-6, and PGE2 significantly increased after LPS injection in all groups but to a lesser extent in dogs receiving the fish oil diet, compared with results for dogs receiving the sunflower oil diet. Serum activity of TNF-α and PAF concentration also increased significantly after LPS injection in all groups but did not differ significantly among groups.
Conclusions and Clinical Relevance—A fish oil–enriched diet consisting of 1.75 g of EPA/kg of diet and 2.2 g of DHA/kg of diet (dry-matter basis) with an n-6:n-3 fatty acid ratio of 3.4:1 was associated with significant reductions in serum PGE2 concentrations and IL-1 and IL-6 activities. Results supported the use of EPA- and DHA-enriched diets as part of antiinflammatory treatments for dogs with chronic inflammatory diseases. Additional studies in affected dogs are warranted to further evaluate beneficial anti-inflammatory effects of EPA- and DHA-enriched diets.
Objective—To determine safety, efficacy, and
immunogenicity of an intranasal cold-adapted modified-
live equine influenza virus vaccine administered
to ponies following induction of exercise-induced
Animals—Fifteen 9- to 15-month old ponies that had
not had influenza.
Procedure—Five ponies were vaccinated after 5 days of strenuous exercise on a high-speed treadmill, 5
were vaccinated without undergoing exercise, and 5
were not vaccinated or exercised and served as controls.
Three months later, all ponies were challenged
by nebulization of homologous equine influenza virus.
Clinical and hematologic responses and viral shedding
were monitored, and serum and nasal secretions
were collected for determination of influenza-virus-specific
antibody isotype responses.
Results—Exercise caused immunosuppression, as
indicated by depression of lymphocyte proliferation in
response to pokeweed mitogen. Vaccination did not
result in adverse clinical effects, and none of the vaccinated
ponies developed clinical signs of infection following
challenge exposure. In contrast, challenge exposure
caused marked clinical signs of respiratory tract
disease in 4 control ponies. Vaccinated and control
ponies shed virus after challenge exposure. Antibody
responses to vaccination were restricted to serum
IgGa and IgGb responses in both vaccination groups.
After challenge exposure, ponies in all groups generated
serum IgGa and IgGb and nasal IgA responses.
Patterns of serum hemagglutination inhibition titers
were similar to patterns of IgGa and IgGb responses.
Conclusions and Clinical Relevance—Results suggested that administration of this MLV vaccine to
ponies with exercise-induced immunosuppression
was safe and that administration of a single dose to
ponies provided clinical protection 3 months later. (J
Am Vet Med Assoc 2001;218:900–906)
Objective—To determine whether an inflammatory challenge induces insulin resistance in horses and examine possible contributions of adipose tissue to inflammatory cytokine production.
Animals—15 adult mares.
Procedures—Lipopolysaccharide (0.045 μg/kg, IV) or saline solution was administered, and insulin sensitivity was determined by means of the hyperinsulinemic, euglycemic clamp procedure or an adipose tissue biopsy was performed. Adipose tissue samples were collected, and mature adipocytes were obtained. Mature adipocytes were stimulated with lipopolysaccharide or dedifferentiated into preadipocytes and then stimulated with lipopolysaccharide. Interleukin-1, interleukin-6, and tumor necrosis factor A expression in blood, adipose tissue, and adipocytes was quantified with a real-time, reverse transcriptase– PCR assay.
Results—Lipopolysaccharide induced a transient increase in insulin sensitivity followed by a reduction in insulin sensitivity at 24 hours. Increased cytokine expression was observed in blood and adipose tissue following administration of lipopolysaccharide, and adipocytes and preadipocytes stimulated with lipopolysaccharide stained positive for tumor necrosis factor A. Expression of interleukin-1, interleukin-6, and tumor necrosis factor A was detected in preadipocytes stimulated with lipopolysaccharide, and interleukin-6 and tumor necrosis factor A were detected in mature adipocytes stimulated with lipopolysaccharide.
Conclusions and Clinical Relevance—Results indicated that insulin resistance develops following systemic inflammation in horses and suggested that adipose tissue may contribute to this inflammatory response. Methods to regulate insulin sensitivity may improve clinical outcome in critically ill patients.
To evaluate surfactant protein D (SP-D) concentrations in serum and bronchoalveolar lavage fluid (BALF) from young healthy horses on pasture or housed in a typical barn.
20 young healthy horses.
Horses were randomly assigned to 1 of 2 groups (pasture, n = 10; barn, 10), and serum and BALF samples were collected for SP-D determination at baseline (all horses on pasture) and 2 weeks and 4 weeks after the barn group of horses was relocated from the pasture to the barn. Other evaluations included physical and tracheoscopic examinations. Findings were compared within and between groups.
Physical and tracheoscopic examinations, CBC, and serum biochemical analysis did not reveal evidence of respiratory disease, and no significant differences were present within and between groups. Serum SP-D concentrations did not significantly differ within and between groups, but BALF SP-D concentrations were significantly lower for the barn group at 2 weeks but not at 4 weeks, compared with baseline. The BALF SP-D concentration-to-BALF total protein concentration ratio was < 1.5 and did not significantly differ within and between groups.
CONCLUSIONS AND CLINICAL RELEVANCE
A mild decrease was evident in the concentration of SP-D in the BALF collected from young healthy horses after 2 weeks of exposure to a barn environment. The clinical importance of this finding remains to be determined.
To perform lipidomic analysis of surfactant and plasma from asthmatic and healthy horses.
30 horses with clinical signs of asthma and 30 age-matched control horses.
Detailed history, physical examination, CBC, and bronchoalveolar lavage fluid (BALF) cytologies were obtained. Asthmatic horses were grouped based on their BALF inflammatory profile: severe equine asthma (SEA), mild equine asthma with neutrophilic airway inflammation (MEA-N), or mild equine asthma with eosinophilic airway inflammation (MEA-E). Each asthma group was assigned its own age-matched control group. Lipidomic analysis was completed on surfactant and plasma. Surfactant protein D (SP-D) concentrations were measured in serum and BALF.
SEA surfactant was characterized by a phospholipid deficit and altered composition (increased ceramides, decreased phosphatidylglycerol, and increased cyclic phosphatidic acid [cPA]). In comparison, MEA-N surfactant only had a decrease in select phosphatidylglycerol species and increased cPA levels. The plasma lipidomic profile was significantly different in all asthma groups compared to controls. Specifically, all groups had increased plasma phytoceramide. SEA horses had increased plasma cPA and diacylglycerol whereas MEA-N horses only had increased cPA. MEA-E horses had increases in select ceramides and dihydrocermides. Only SEA horses had significantly increased serum SP-D concentrations.
The most significant surfactant alterations were present in SEA (altered phospholipid content and composition); only mild changes were observed in MEA-N horses. The plasma lipidomic profile was significantly altered in all groups of asthmatic horses and differed among groups. Data from a larger population of asthmatic horses are needed to assess implications for diagnosis, prognosis, and treatment.