Final answer:
Glucocorticoid hormones stimulate the production of enzymes responsible for hepatic gluconeogenesis and ketone body formation during starvation, ensuring essential organs receive energy when glucose is limited.
Step-by-step explanation:
The enzymes that provide substrates for hepatic gluconeogenesis and ketone body formation during times of starvation are primarily stimulated by glucocorticoid hormones, which are secreted in response to stress such as fasting and starvation. These hormones activate certain pathways in the liver, facilitating the conversion of amino acids and other substances into glucose and ketone bodies.
Under conditions of low blood sugar, glucocorticoids stimulate the liver to synthesize enzymes necessary for gluconeogenesis. Glucocorticoids also promote the breakdown of skeletal muscle protein into amino acids, which are then transported to the liver. Here, some amino acids are used as precursors for gluconeogenesis while others that are ketogenic are converted into Acetyl-CoA, an essential substrate for ketone body synthesis.
Ketone bodies like acetoacetate and ß-hydroxybutyrate are then utilized by organs such as the brain and heart as an alternative energy source when glucose is scarce. This metabolic shift is crucial during prolonged periods of starvation to ensure energy supply to vital organs.