The effect of hyperglycemia on in vivo adipose tissue metabolism was studied with microdialysis in seven lean patients with insulin-dependent diabetes mellitus (IDDM) receiving a constant infusion of insulin (36 pmol·m−2 · min−1). Glucose was infused in a randomized fashion to maintain either a lower glucose level (6.6 ± 0.3 mM, mean ± SE) or hyperglycemia (11.8 ± 0.8 mM) for 3 h. For insulin concentrations of 84 ± 12 and 96 ± 12 pM, hyperglycemia (11.8 ± 0.8 mM) did not alter the plasma glycerol or lactate levels significantly but resulted in a significant (P < 0.0001) increase in plasma free fatty acid levels (0.49 ± 0.13 vs. 0.32 ± 0.08 mM). Plasma catecholamine levels were unchanged during hyperglycemia. Interstitial glycerol concentrations, measured in abdominal subcutaneous adipose tissue as an index of lipolysis, were not significantly influenced by hyperglycemia when compared with concentrations at the lower glucose level (92 ± 30 vs. 106 ± 18 µM). Moreover, hyperglycemia did not change abdominal adipose interstitial lactate levels significantly (1,248 ± 174 vs. 1,351 ± 159 microM during euglycemia). It may be concluded that hyperglycemia has no independent antilipolytic effect in IDDM subjects. Furthermore, in these patients, hyperglycemia gives no further lactate production in the subcutaneous adipose tissue in the presence of low physiological insulin levels.

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