Does exercise training prior to ovariectomy protect against liver and adipocyte fat accumulation in rats?

Abstract

Objective To determine whether a training state protects against the metabolically deleterious effects of ovariectomy on liver and adipocyte fat accumulation in rats.

Design Female rats were randomly assigned to each group (n = 8 rats/group). The animals were first either exercise-trained (Tr) for 6 weeks or kept sedentary (Sed) before being sham-operated (Sham), ovariectomized (Ovx), or ovariectomized with 17β-estradiol supplementation (OvxE2). Following surgery, sedentary rats either remained sedentary (Sed-Sed) or undertook exercise training for 6 weeks (Sed-Tr) while exercise-trained rats either became sedentary (Tr-Sed) or resumed exercise training (Tr-Tr).

Results Body weight and energy intake along with intra-abdominal and subcutaneous fat pad weights and homeostasis model assessment of insulin resistance (HOMA-IR) were significantly (p < 0.01) increased in the Ovx group compared to the Sham and OvxE2 groups. Rats kept in a sedentary state after surgery showed the higher (p < 0.05) values for all of these variables whether they were trained or not before surgery (Sed-Sed and Tr-Sed), indicating no protective effect of a previous exercise-trained state. On the other hand, training conducted after surgery resulted in a lowering of fat mass and HOMA-IR whether rats had been trained or not before surgery (Sed-Tr and Tr-Tr), indicating the effectiveness of exercise training even initiated after surgery. These responses were independent of surgery. Interestingly, liver triacylglycerol concentrations followed a pattern of responses identical to fat mass with the exception that all of the responses were observed only in the Ovx group (p < 0.05).

Conclusion There is no protective effect of a previous exercise-training state on ovariectomy-induced liver and adipocyte fat accumulation if rats remain sedentary after ovariectomy. However, training conducted concurrently with estrogen withdrawal has protective effects, especially on liver fat accumulation, whether or not rats were previously trained.

Key words:

• HEPATIC STEATOSIS
• PLASMA LIPID PROFILE
• HOMA-IR
• ESTROGENS
• TRAINING CESSATION

Conflict of interest  Nil.

Source of funding  This work was supported by grants from the Canadian Institute of Health Research (D.P. and J.M.L., T 0602 145.02) and the Natural Sciences and Engineering Research Council of Canada (J.M.L., 7594).