Gluconeogenesis from lactate in the developing rat. Studies in vivo

Area of Science:

• Biochemistry
• Developmental Biology
• Metabolism

Background:

• Lactate serves as a crucial substrate for gluconeogenesis, the process of glucose synthesis.
• Understanding developmental changes in gluconeogenesis is vital for comprehending neonatal metabolism and energy homeostasis.

Purpose of the Study:

• To investigate the metabolic fate of lactate and its incorporation into glucose and glycogen in rats of different ages.
• To quantify and compare the rates of gluconeogenesis in suckling (2- and 10-day-old) versus weaned (30-day-old) rats.

Main Methods:

• Intraperitoneal injection of labeled lactate (l-[U-(14)C]lactate) into rats aged 2, 10, and 30 days.
• Measurement of specific radioactivity in plasma lactate and glucose, as well as in liver and muscle glycogen over time.
• Analysis of carbon-14 incorporation to determine metabolic flux and gluconeogenic rates.

Main Results:

• Plasma lactate radioactivity decreased with a half-life of 20–33 minutes across all age groups.
• Specific radioactivity of plasma glucose was significantly higher (at least fourfold) in 2- and 10-day-old rats compared to 30-day-old rats.
• (14)C incorporation into liver glycogen was minimal (<5% of plasma glucose levels).

Conclusions:

• Young suckling rats demonstrate a substantially higher rate of gluconeogenesis from lactate compared to weaned rats.
• These findings highlight significant developmental adaptations in glucose metabolism and energy production strategies during early life stages.