The effect of restricting energy intake on diabetes in Psammomys obesus

The aim of this paper was to determine whether restricting energy intake would reduce the elevated levels of glucose, insulin, cholesterol and triglyceride in diabetic Psammomys obesus (sand rat). Between 11 and 12 weeks of age Psammomys obesus were divided into three groups based on blood glucose and plasma insulin levels in the fed ad libitum state; group 1 was normoglycemic (4.4 ± 0.3 mM) and normoinsulinemic (0.46 ± 0.04 ng/ml), group 2 was normoglycemic (5.0 ± 0.3 mM) and hyperinsulinemic (3.58 ± 0.62 ng/ml) and group 3 was hyperglycemic (11.2 ± 1.2 mM) and hyperinsulinemic (6.23 ± 0.73 ng/ml). Energy intake was restricted to 67% of normal for 2 weeks before ad libitum feeding was resumed for a further 2 weeks. Animals in group 3 developed the most abnormalities when compared to group 1 including increased levels of food intake (16.3 ± 0.5 vs 14.2 ± 0.5 g/day, P < 0.05), body weight (192 ± 5 vs 162 ± 4 g, P < 0.05), triglycerides (1.5 ± 0.2 vs 0.96 ± 0.08 mM, P < 0.05), and cholesterol (2.8 ± 0.2 vs 2.1 ± 0.1 mM, P < 0.05). In group 3, food restriction was effective in reducing glucose levels (but not insulin) both during and following the restriction period respectively (11.2 ± 1.2 vs 4.6 ± 0.5, and 5.9 ± 1.3, mM, P < 0.05). In group 2, energy restriction had similar effects by reducing glucose levels (5.03 ± 0.26 vs 4.2 ± 0.13 and 3.99 ± 0.19, mM, baseline vs restriction and post restriction, P < 0.05) and insulin levels (3.57 ± 0.62 vs 0.96 ± 0.27 and 1.50 ± 0.39, ng/ml, baseline vs restriction and post restriction, P < 0.05). Cholesterol and triglyceride levels were also reduced in group 2 and group 3 during the restriction period (P < 0.05). In addition, glucose and insulin responses to the meal tolerance test were also reduced for group 2 and group 3 during the restriction period. In group 1, glucose, insulin and triglyceride levels were not significantly reduced during the restriction period. Furthermore, energy restriction did not significantly reduce body weight in any group suggesting that the restriction level was not excessive. These results have clearly demonstrated the effect of food restriction in reducing elevated glucose, insulin and lipid levels associated with hyperinsulinemia and NIDDM in Psammomys obesus.