Insulin resistance in the St. Thomas' mixed hyperlipidaemic (SMHL) rabbit, a model for familial combined hyperlipidaemia.

The St. Thomas mixed hyperlipidaemic (SMHL) rabbit exhibits an inherited hyperlipidaemia similar to that seen in familial combined hyperlipidaemia (FCHL). In this study, we investigated whether the SMHL rabbit is insulin resistant, a condition often associated with FCHL. Six young and six mature combined hyperlipidaemic SMHL rabbits, age/sex matched New Zealand White (NZW) control rabbits and six young hypercholesterolaemic Watanabe heritable hyperlipidaemic (WHHL) control rabbits were fed a 0.08% (w/w) cholesterol-enriched diet for at least 1 month prior to the start of the experiment. We performed an oral glucose tolerance test after an overnight fast by dosing the rabbits with a solution of 1 g of glucose per kg body weight. Blood was withdrawn just before and 15, 30, 45, 60 and 120 min after administration of the oral glucose dose. Plasma glucose levels were similar in SMHL, WHHL and NZW rabbits throughout the oral glucose tolerance test. Fasting glucose levels were slightly increased in WHHL rabbits but not in young and adult SMHL rabbits as compared to NZW rabbits. The area under the curve (AUC) for the insulin response was significantly increased for both young (P<0.05) and mature (P<0.05) SMHL rabbits, and in WHHL rabbits, compared with NZW rabbits. The AUC for the ratio of glucose:insulin response to the glucose dose was decreased in young and mature SMHL rabbits (P<0.05 and P<0.01, respectively) and in young WHHL rabbits (P<0.05), compared with NZW rabbits. Only WHHL rabbits showed an increased AUC for the non-esterified fatty acid response compared to NZW rabbits. Log-transformed plasma triglycerides values were significantly correlated with the log-transformed AUC for the insulin response in young SMHL rabbits (r=0.81; P<0.05) and with the AUC for the insulin response in mature SMHL rabbits (r=0.84; P<0.05). WHHL rabbits showed no significant correlation. In conclusion, SMHL rabbits are insulin resistant, the severity of which appears to increase with age. Therefore, the SMHL rabbit offers a valuable animal model in which to study the relation between hypertriglyceridaemia and insulin resistance.