Open AccessEffect of Dietary Nonstructural Carbohydrate Content on Activation of 5′‐Adenosine Monophosphate‐Activated Protein Kinase in Liver, Skeletal Muscle, and Digital Laminae of Lean and Obese Ponies
Author(s) -
Burns T.A.,
Watts M.R.,
Weber P.S.,
McCutcheon L.J.,
Geor R.J.,
Belknap J.K.
Publication year - 2014
Publication title -
journal of veterinary internal medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.356
H-Index - 103
eISSN - 1939-1676
pISSN - 0891-6640
DOI - 10.1111/jvim.12356
Subject(s) - medicine , endocrinology , ampk , skeletal muscle , hyperinsulinemia , protein kinase a , adenosine monophosphate , adenosine , biology , insulin , insulin resistance , kinase , biochemistry
Background In EMS ‐associated laminitis, laminar failure may occur in response to energy failure related to insulin resistance ( IR ) or to the effect of hyperinsulinemia on laminar tissue. 5′‐Adenosine‐monophosphate‐activated protein kinase ( AMPK ) is a marker of tissue energy deprivation, which may occur in IR . Hypothesis/Objectives To characterize tissue AMPK regulation in ponies subjected to a dietary carbohydrate ( CHO ) challenge. Animals Twenty‐two mixed‐breed ponies. Methods Immunohistochemistry and immunoblotting for total AMPK and phospho(P)‐AMPK and RT‐ qPCR for AMPK‐responsive genes were performed on laminar, liver, and skeletal muscle samples collected after a 7‐day feeding protocol in which ponies stratified on body condition score (BCS; obese or lean) were fed either a low‐CHO diet (ESC + starch, approximately 7% DM; n = 5 obese, 5 lean) or a high‐CHO diet (ESC + starch, approximately 42% DM; n = 6 obese, 6 lean). Results 5′‐Adenosine‐monophosphate‐activated protein kinase was immunolocalized to laminar keratinocytes, dermal constituents, and hepatocytes. A high‐ CHO diet resulted in significantly decreased laminar [P‐ AMPK ] in lean ponies ( P = .03), but no changes in skeletal muscle (lean, P = .33; obese, P = .43) or liver (lean, P = .84; obese, P = .13) [P‐ AMPK ]. An inverse correlation existed between [blood glucose] and laminar [P‐ AMPK ] in obese ponies on a high‐ CHO diet. Conclusions and Clinical Importance Laminar tissue exhibited a normal response to a high‐ CHO diet (decreased [P‐ AMPK ]), whereas this response was not observed in liver and skeletal muscle in both lean (skeletal muscle, P = .33; liver, P = .84) and obese (skeletal muscle, P = .43; liver, P = .13) ponies.