Effect of dietary carbohydrate challenge on activation of 5’-adenosine monophosphate activated protein kinase (AMPK) in liver, skeletal muscle, and digital laminae of lean and obese ponies

s / Journal of Equine Veterinary Science 33 (2013) 838–859 846 secretion, and glucose dynamics in Thoroughbred mares. Am J Vet Res 2011;72:666–74. [17] Fowden AL, Barnes RJ, Comline RS, Silver M. Pancreatic bcell function in the fetal foal and mare. J Endocrinol 1980;87: 293–301. [18] varewijck AJ, Janssen JAMJL. Insulin and its analogues and their affinities for the IGF1 receptor. Endocr Relat Cancer 2012;19: F63–75. [19] Shynlova O, Tsui P, Dorogin A, Langille BL, Lye SJ. Insulin-like growth factors and their binding proteins define specific phases of myometrial differentiation during pregnancy in the rat. Biol Reprod 2006;76:571–8. [20] Blakesley VA, Scrimgeour A, Esposito D, Le Roith D. Signaling via the insulin-like growth factor-I receptor: does it differ from insulin receptor signaling? Cytokine Growth Factor Rev 1996;7: 153–9. [21] Knott L, Tarlton JF, Craft H, Webster AJ. Effects of housing, parturition and diet change on the biochemistry and biomechanics of the support structures of the hoof of dairy heifers. Vet J 2007;174: 277–87. [22] Tarlton JF, Holah DE, Evans KM, Jones S, Pearson GR, Webster AJ. Biomechanical and histopathological changes in the support structures of bovine hooves around the time of first calving. Vet J 2002; 163:196–204. 009 Effect of dietary carbohydrate challenge on activation of 5’-adenosine monophosphate activated protein kinase (AMPK) in liver, skeletal muscle, and digital laminae of lean and obese ponies T.A. Burns , M.R. Watts , P. Weber , R.J. Geor , L.J. McCutcheon , and J.K. Belknap 1 1 College of Veterinary Medicine, The Ohio State University, Columbus, OH, 2 College of Veterinary Medicine, Michigan State University, East Lansing, MI Take-home message: Skeletal muscle and liver likely contribute to systemic IR in EMS, but laminar injury is more likely due to the local effects of hyperinsulinemia. Introduction: Hyperinsulinemia may increase the risk for laminitis associated with equine metabolic syndrome (EMS). The enzyme 5’-adenosinemonophosphate activated protein kinase (AMPK) is a potential therapeutic target, as it decreases systemic insulin resistance (IR). The AMPK agonist metformin has been used to treat EMS-affected equids; however, regulation of AMPK in equine tissue is largely uncharacterized. The purpose of this study was to characterize the localization and activation state of AMPK in liver, skeletal muscle, and laminae of ponies following high-carbohydrate (CHO) feeding. Materials and Methods: Mixed-breed ponies were assigned to one of two groups based on body condition: lean or obese. Ponies received either a low-CHO diet (n1⁄45 obese, n1⁄45 lean) or the same diet supplemented with sweet feed and oligofructose (high-CHO diet; n1⁄46 obese, n1⁄46 lean) for 7 days. Samples of laminae, middle gluteal muscle, and liver were collected following euthanasia; samples were formalin-fixed or snap frozen. Results: Immunohistochemistry was used to localize AMPK to keratinocytes and vascular elements in the laminae and to hepatocytes in the liver. Western blot for phospho(P)-AMPK demonstrated significantly decreased laminar P-AMPK with high-CHO feeding (p 1⁄4 0.01). In contrast, P-AMPK was unchanged in skeletal muscle (p 1⁄4 0.33) and tended to increase in liver (p 1⁄4 0.13) following dietary CHO challenge. Discussion: Unchanged or increased P-AMPK concentration with high-CHO feeding is consistent with tissue IR in skeletal muscle and liver. The decreased laminar P-AMPK with CHO challenge suggests that laminar tissue remains insulin-sensitive. Conclusion and Clinical Relevance: Whereas skeletal muscle and liver likely contribute to systemic IR in EMS, laminar injury is more likely due to the local effects of hyperinsulinemia, not local IR or energy failure. 010 Adipokine, chemokine, and cytokine expression profiles in adipose tissue depots of lean and overweight ponies P.S.D. Weber , K.N. Schermerhorn , L.J. McCutcheon , B. Norby , T.A. Burns , J.K. Belknap , and R.J. Geor 1 Michigan State University, East Lansing, MI, 2 The Ohio State University, Columbus, OH Take-home message: Adipose tissue of overweight ponies demonstrates a proinflammatory profile that may contribute to a systemic inflammatory state. Introduction: Accumulating evidence in humans indicates that obesity causes chronic, low-grade inflammation mediated by the production of adipokines, chemokines, and cytokines in adipose tissue (AT). The purpose of this study was to investigate if this phenomenon exists in overweight ponies. Materials and Methods: Adipose tissue was collected from 5 different depots (nuchal, tail, mesenteric, omental, and retroperitoneal) from lean (n1⁄45) and overweight (n1⁄45) mixed-breed ponies. Total RNA was extracted, synthesized into cDNA, and analyzed by RT-qPCR to quantify expression of macrophage activation marker (CD68), monocyte chemoattractant protein-1 (MCP-1), and interleukin-6 (IL-6), IL-1b, IL-8, adiponectin, and leptin. Data were analyzed using a mixed linear model and significance was set at p 0.05. Results: The expression of CD68, MCP-1, and IL-6 was significantly higher in overweight ponies compared with lean ponies. These differences were depot-independent. The expression of IL-1b and IL-8 did not differ between groups but was higher in visceral compared with subcutaneous depots. A significant interaction of body type and depot was observed for adiponectin and leptin expression. Omental adiponectin expression was significantly lower and mesenteric leptin expression was significantly higher in overweight ponies. Discussion and Conclusions: These results indicate that macrophages are present in visceral and subcutaneous AT of overweight ponies and that adipokines, chemokines, and cytokines are differentially expressed in lean and overweight ponies and/or across depots. Adipose tissue of overweight ponies demonstrates a proinflammatory profile that may contribute to a systemic inflammatory state.