Incorporation of [3-3H]Glucose and 2-[1-14C]Deoxyglucose Into Glycogen in Heart and Skeletal Muscle In Vivo: Implications for the Quantitation of Tissue Glucose Uptake

Abstract

2-deoxyglucose has been widely used to quantitate tissue glucose uptake in vivo, assuming that 2-deoxyglucose is transported and phosphorylated but not further metabolized. We examined the validity of this assumption by infusing [3-3H]glucose and 2-[1-14C]deoxyglucose in a similar primed continuous fashion to chronically catheterized, freely moving rats during normoglycemic hyperinsulinemic conditions. The rates of 2-deoxyglucose uptake were determined from the accumulation of 2-[1-14C]deoxyglucose-6-phosphate and 2-[1-14C]deoxyglucose-6-phosphate combined with the rate of the incorporation of 2-[1-14C]deoxyglucose into glycogen in rectus abdominis muscle and the heart. When the rates of glycogen synthesis during the 2-h hyperinsulinemic period from the two tracers were compared in rectus abdominis muscle, the rate of glycogen synthesis was twofold higher when measured with [3-3H]glucose (337 +/- 14 micromol x kg(-1) x min(-1)) than when measured with 2-[1-14C]deoxyglucose (166 +/- 10 micromol x kg(-1) x min(-1), P < 0.001). In the heart, the rate of glycogen synthesis was twofold higher when measured with 2-[1-14C]deoxyglucose (141 +/- 20 micromol x kg(-1) x min(-1)) than when measured with [3-3H]glucose (72 +/- 15 micromol x kg(-1) x min(-1), P < 0.001). The rate of 2-deoxyglucose uptake was 29% underestimated in rectus abdominis muscle, when counts found in glycogen were not included in glucose uptake calculations (398 +/- 25 vs. 564 +/- 25 micromol x kg(-1) x min(-1), P < 0.001). In the heart, glucose uptake was underestimated by 7% if glycogen counts were not taken into account (1,786 +/- 278 vs. 1,926 +/- 291 micromol x kg(-1) dry x min(-1), P < 0.05). The fraction of [3-3H]glucose incorporated into glycogen of total glucose metabolism (calculated from 2-deoxyglucose conversion to 2-deoxyglucose-6-phosphate and glycogen) was 0.6 (337/564) in rectus abdominis muscle and 0.037 (72/1,926) in the heart. We conclude that 2-deoxyglucose is incorporated into glycogen in the heart and in skeletal muscle in vivo under normoglycemic hyperinsulinemic conditions in the rat. Failure to consider the incorporation of 2-deoxyglucose into glycogen will underestimate the rate of tissue glucose uptake. To avoid such problems, the amount of 2-deoxyglucose incorporated into glycogen should be quantitated in subsequent studies.

Skeletal Muscle-Selective Knockout of LKB1 Increases Insulin Sensitivity, Improves Glucose Homeostasis, and Decreases TRB3

“…Blood was collected from the tail, and the glucose concentration was determined with a One Touch II glucose monitor (Lifescan). Muscle glucose uptake in vivo was determined as described previously (47). Blood samples (25 l) for the measurement of glucose and specific activities were obtained from the tail vein at 0, 20, 40, 60, 90, and 120 min.…”

A model to explore the interaction between muscle insulin resistance and beta-cell dysfunction in the development of type 2 diabetes.

“…Tissue-specific accumulation of 2-DG-6-P was determined as previously described, with minor modifications (12). Briefly, 100-500 mg tissue was homogenized in 2 ml distilled water; 1.6 ml of the homogenate was immediately transferred to 1.6 ml of 7% ice-cold perchloric acid.…”

“…Glycogen concentration. Glycogen concentration after KOH hydrolysis was measured microfluorometrically, as previously described (12). Briefly, dried tissue or glycogen precipitate was dissolved in 1N KOH (15 min, 55°C).…”

“…The dried pellet was dissolved in 100 µl of 1N KOH (55°C, 15 min), diluted with 300 µl distilled water, and buffered to pH 4.9 with 2 vol of 1:1 vol 0.25N HCl:0.15N Na-acetate, as previously described (12). A 1-ml sample was counted for [ 3 H]-radioactivity, and the remainder was measured microfluorometrically for glycogen concentration after amyloglucosidase treatment (12). The specific activity of glycogen was calculated by dividing the [ 3 H]-radioactivity by the respective glycogen concentration.…”

AMPK stimulation increases LCFA but not glucose clearance in cardiac muscle in vivo

“…After this, 500 l of supernatant were diluted to 1 ml in distilled H2O before fluor (10 ml) was added and samples were counted. Treatment with Ba(OH) 2 (35,44). Sample 3 H radioactivity was corrected for beta emissions originating from 125 I as described for plasma samples.…”