Milk-soluble formula increases food intake and reduces Il6 expression in elderly rat hypothalami

The malnutrition of elderly is accompanied by several metabolic dysfunctions especially the alteration of energy homeostasis regulation and the loss of insulin responsiveness. Nutritional recommendations aim to enrich food by providing high protein and energy supplements. The nutrients that were widely studied the protein composition and the quality of lipids. Despite, the numerous studies attempting to overcome malnutrition in the elderly through nutritional supplementations; it is still necessary to study the combinations between protein, lipids and vitamin D. This could be achieved in animal models for elderly malnutrition. In the present study we investigated the impact of several diet formulae on insulin responsiveness, inflammation and hypothalamic gene expression of key genes involved in energy homeostasis control. To mimic elderly malnutrition, old Wistar rats were food restricted (-50%) during 12 weeks and then re-fed during 4 weeks with different isocaloric diets: control diet (C), diet where milk soluble proteins replaced casein (MSP), a blend of dairy fat/rapeseed/DHA (MRD) as fat or a full formulae that combines milk soluble proteins and a blend of dairy fat/rapeseed/DHA (FF). All re-feeding diets contain vitamin D. We conclude that: 1) food restriction led to the up-regulation of insulin receptor in liver and adipose tissue accompanied with increased TNFα in the hypothalamus; 2) in all re-fed groups, re-feeding led to similar body weight gain during the re-fed period; 3) re-feeding with a blend of dairy fat/rapeseed/DHA and milk soluble proteins induced higher food intake on the fourth week of re-feeding associated with reduced hypothalamic IL-6 expression.