Metabolic Regulation and Hormonal Integration (1D) Practice Test

In a crossover study, 12 healthy adults completed two 90-minute sessions after an overnight fast. In one session they received a continuous infusion of insulin (target plasma insulin 60

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0pM) with euglycemic clamp (plasma glucose maintained at $5.0\pm0.2,\text{mM}$). In the other session they received saline. A microdialysis probe sampled interstitial fluid from vastus lateralis, and muscle biopsies were assayed for glycogen content. At 90 minutes, insulin increased whole-body glucose infusion rate required to maintain euglycemia, while plasma free fatty acids fell from $0.55$ to $0.18,\text{mM}$. Which outcome is most consistent with insulin s integrated action on skeletal muscle metabolism during the clamp?

Researchers study counterregulatory hormones during acute hypoglycemia. Participants receive an insulin infusion until plasma glucose reaches $2.8,\text{mM}$ for 20 minutes. One group receives a nonselective 

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0-adrenergic blocker; the other receives placebo. In placebo, plasma lactate rises from $1.1$ to $2.6,\text{mM}$ and heart rate increases by 18 bpm; in the blocked group, heart rate does not change and lactate rises only to $1.5,\text{mM}$. Which outcome is most consistent with 

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0-adrenergic signaling s role in metabolic regulation during hypoglycemia?