Fuel metabolism and energy stores in fasting or suckling newborn guinea pigs.
Newborn guinea-pigs delivered by Caesarean section at term were fasted for 48h at 35 degrees C and compared with suckling neonates. For the first 18h of fasting, blood glucose concentration remains at a normal level: a rapid liver glycogenolysis contributes to glucose production but indirect evidence suggests also that active gluconeogenesis from lactate, alanine and glycerol occurs at this time. Despite high liver triacylglycerol levels at birth and increased plasma free fatty acids the blood ketone body concentration remains very low which suggests that free fatty acid availability is not the only factor controlling the onset of ketogenesis at birth. After 24h of fasting, blood glucose concentration decreases whereas suckling newborns remain normoglycaemic. A mild hypoglycaemia is observed in fasting newborn which is not related to an unavailability of fat-derived substrates since mobilization of fat stores induces an increase of plasma free fatty acid levels and high blood concentration of ketone bodies. This relative hypoglycaemia is probably related to the lack of glucose and/or gluconeogenic substrate intake strengthened by an unavailability of some endogenous gluconeogenic precursors since a lack of a mobilization of protein stores characterizes this period. The maintenance of glucose homeostasis in suckling neonates reflects an active gluconeogenesis; a theoretical calculation shows an important contribution of each milk constituent including amino acids to sustain an endogenous glucose production.
D000090:Acetoacetates / Q000097:blood; D000409:Alanine / Q000097:blood; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism*; D001786:Blood Glucose / Q000032:analysis*; D004734:Energy Metabolism; D005215:Fasting; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D005943:Gluconeogenesis; D005990:Glycerol / Q000097:blood; D006168:Guinea Pigs; D007657:Ketone Bodies / Q000097:blood*; D007773:Lactates / Q000097:blood; D050356:Lipid Metabolism; D008112:Liver Glycogen / Q000032:analysis; D011506:Proteins / Q000378:metabolism; D011773:Pyruvates / Q000097:blood; D013391:Sucking Behavior
D000090:Acetoacetates; D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D007657:Ketone Bodies; D007773:Lactates; D008112:Liver Glycogen; D011506:Proteins; D011773:Pyruvates; D000409:Alanine; D005990:Glycerol