The effects of losartan on memory performance and leptin resistance induced by obesity and high-fat diet in adult male rats

Leptin is a hormone secreted by adipose tissue and is involved not only in the regulation of feeding and energy expenditure, but also its role in memory enhancement has been demonstrated as well. The partial transfer of leptin across the blood-brain barrier in obese individuals causes leptin resistance and prevents leptin reaching brain. On the other hand, studies have shown that angiotensin antagonists such as losartan can improve memory and learning abilities. The aim of this study was to evaluate the effects of losartan on improving memory and leptin resistance induced by high fat diet in obese rats. 40 Wistar male rats were divided in 4 groups: control (C), losartan (LOS), high-fat diet (HFD) and high-fat diet and losartan (HFD and LOS). The spatial memory performances of the rats were assessed in the Morris water maze after 2 months of treatment. Then they were weighed and serum levels of leptin and triglyceride were measured. In spite of receiving high-fat diet, no significant differences in body weight were observed in the (HFD & LOS) group. In the Morris water maze trial, the (LOS) and (HFD & LOS) groups also showed a significant reduction (P <0.05) in latency and path length. In addition, a significant decrease (P <0.05) in serum levels of leptin and no significant difference in serum levels of triglyceride was observed in the (HFD & LOS) group. Losartan can improve leptin resistance induced by obesity and high fat diet. At the same time, it modulates body weight and enhances learning and memory.