Anna Garland's PhD Defence

In Vitro and In Vivo Investigations of Inflammatory and Morphometric Consequences in Overweight Equines

Equine obesity effects up to 70% of the domesticated population and increases the risk for

chronic inflammatory conditions. The purpose of this thesis was to investigate morphometric

changes and associated inflammatory consequences in overweight horses undergoing

weight loss. Four studies were conducted. Study #1 investigated an in vitro organ culture

model of inflammation to determine effects of inflamed and non-inflamed adipose tissue

(AT) on cartilage responses to an inflammatory challenge. Cartilage explants were cultured

for a total of 192h in either culture media or media pre-conditioned with AT, and stimulated

for 48h directly with LPS, or indirectly with AT-LPS conditioned media. Media samples were

analyzed for PGE2, NO, GAG, and RvD1. The inflamed AT elicited a greater inflammatory

response from cartilage explants than direct LPS stimulation. Study #2 characterized

morphometric changes in horses undergoing a 16-week weight gain program to determine

how individual subcutaneous AT (SAT) depots are affected by weight gain. Horses

underwent 14 measurements {body weight [BW; weight tape and bioelectrical impedance

analysis (BIA)], cresty neck score, whole body condition score (BCS), 8 individual BCS

(neck, shoulder, leg, withers, ribs, back, haunches, tailhead), and fat mass (BIA; % and

kg)}. Morphometrics showed non-uniform increases across the SAT depots and over the

16-weeks of weight gain, with the greatest increase in BCS in the tailhead depot. Study #3 

investigated morphometrics in overweight horses undergoing one of three weight loss

programs (daily exercise, feed restriction, and feed restriction plus daily exercise), or a

weight-maintenance group. During weeks 1, 5 and 10, horses underwent 14 measurements

(as described for study #2). Exercise-based programs produced greater reductions in

morphometrics than the feed restriction alone program. Study #4 investigated the

inflammatory consequences of each weight loss program to a standardized exercise test

(SET; Weeks 1, 5, 10). Blood plasma and synovial fluid were collected at -48h prior to the

SET, 1, 8, and 12h after cessation of the SET. Samples were analyzed for PGE2, NO, and

GAG. Exercise-based programs increased the inflammatory response to the SET in the

articulating joint, while feed restriction alone reduced the response.