ISSN 1470-3947 (print) | ISSN 1479-6848 (online)

Endocrine Abstracts (2008) 16 OC1.8

Differential sensitivity of men and women to anorexigenic and memory improving effects of intranasal insulin

Christian Benedict1, Werner Kern3, Bernd Schultes2, Jan Born1, Hendrik Lehnert3 & Manfred Hallschmid1

1Department of Neuroendocrinology, University of Lübeck, Lübeck, Germany; 2Interdisciplinary Obesity Center East-Switzerland, Kantonsspital St Gallen, St Gallen, Switzerland; 3Internal Medicine I, University of Lübeck, Lübeck, Germany.

Background: Central nervous insulin is critically involved in the regulation of body weight and memory processing. Long-term administration of intranasal insulin reduces body weight in men but not in women while improving hippocampus-dependent memory processing in both genders. Here, acute effects of intranasal insulin on food intake and memory functions were studied in men and women.

Methods: Thirty-two healthy, normal-weight subjects (14 men, 18 women) were intranasally administered 160 IU regular human insulin or vehicle before performing a hippocampus-dependent 2-D-object location task, a working memory task (digit span) and a hippocampus-independent mirror tracing task. Subsequently, food intake from an ad libitum breakfast buffet was measured.

Findings: Insulin treatment decreased food intake in men but not in women (difference to placebo condition, men: −192.57±78.48 kcal, P<0.03; women: 18.54±42.89 kcal, P>0.67). In contrast, hippocampus-dependent memory and working memory were improved in women (P<0.03, P<0.05, respectively) whereas men did not benefit from acute insulin treatment (P>0.17, P>0.20). Performance on the hippocampus-independent mirror tracing task was not affected by insulin in both sexes.

Interpretation: In accordance with animal data, our results indicate that men are more sensitive than women to the acute anorexigenic effect of central nervous insulin signaling whereas insulin’s beneficial effect on hippocampus-dependent memory functions are more pronounced in women. Our findings provide first support for the notion of a fundamental gender difference in central nervous insulin signaling that pertains to the regulation of energy homeostasis and memory functions.

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