Membrane digestion and nutrient assimilation in early development.

Area of Science:

• Biochemistry
• Developmental Biology
• Gastroenterology

Background:

• Membrane digestion, involving the apical glycocalyx and brush border enzymes, plays a crucial role in nutrient absorption.
• Digestive enzyme activity and distribution change significantly during early development and the transition to adult nutrition.

Purpose of the Study:

• To investigate the regulatory mechanisms of membrane and intraluminal digestion during ontogeny.
• To explore the influence of dietary lipids and hormonal factors, such as hydrocortisone, on intestinal enzyme activity.
• To examine the role of stress in modulating brush border enzyme synthesis and activity.

Main Methods:

• Separation techniques for the apical glycocalyx to study enzyme distribution.
• Analysis of enzyme activity and distribution in the small intestine during developmental transitions.
• Investigation of dietary and hormonal effects on enzyme synthesis and membrane incorporation.
• Experimental induction of stress in animal models to observe effects on enzyme expression.

Main Results:

• Membrane digestion is dominant in early development, shifting to intraluminal digestion with adult nutrition.
• Dietary lipids are essential for maintaining enzyme activity gradients in the small intestine.
• Hydrocortisone influences enzyme synthesis and membrane integration during nutritional transition.
• Stressors were found to induce sucrase, maltases, gamma-amylase, peptidases, and alkaline phosphatase, while repressing lactase in suckling rats.

Conclusions:

• Digestive enzyme regulation is complex, involving substrate availability, dietary components, hormonal signals, and stress.
• The transition from milk to adult diet involves significant changes in digestive enzyme profiles, influenced by lipids and stress.
• Stress, mediated via the hypothalamus-adrenal axis, can significantly alter the expression of brush border enzymes during development.