Increased metabolism of infused 1‐methylxanthine by working muscle

Youd, Joanne Maree; Newman, John; Clark, Michael G.; Appleby, Geoffrey J.; Rattigan, Stephen; Tong, Alex C.Y.; Vincent, Michelle A.

doi:10.1046/j.1365-201x.1999.00572.x

Cited by 18 publications

(17 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The metabolism of 1-MX, by the capillary endothelial enzyme xanthine oxidase, has been used previously by us as an indicator of nutritive flow (27,41). Figure 3 shows the effect of insulin, 5-HT, and the combination of insulin ϩ 5-HT on 1-MX metabolism, determined at the 80-min time point, when steady-state conditions have been attained (27).…”

Section: Resultsmentioning

confidence: 99%

Nonnutritive flow impairs uptake of fatty acid by white muscles of the perfused rat hindlimb

Clerk

Smith

Rattigan

et al. 2003

American Journal of Physiology-Endocrinology and Metabolism

Self Cite

View full text Add to dashboard Cite

Triglyceride hydrolysis by the perfused rat hindlimb is enhanced with serotonin-induced nonnutritive flow (NNF) and may be due to the presence of nonnutritive route-associated connective tissue fat cells. Here, we assess whether NNF influences muscle uptake of 0.55 mM palmitate in the perfused hindlimb. Comparisons were made with insulin-mediated glucose uptake. NNF induced during 60 nM insulin infusion inhibited hindlimb oxygen uptake from 22.0 ± 0.5 to 9.7 ± 0.8 μmol · g−1 · h−1( P < 0.001), 1-methylxanthine metabolism (indicator of nutritive flow) from 5.8 ± 0.4 to 3.8 ± 0.4 nmol · min−1 · g−1( P = 0.004), glucose uptake from 29.2 ± 1.7 to 23.1 ± 1.8 μmol · g−1 · h−1( P = 0.005) and muscle 2-deoxyglucose uptake from 82.1 ± 4.6 to 41.6 ± 6.7 μmol · g−1 · h−1( P < 0.001). Palmitate uptake, unaffected by insulin alone, was inhibited by NNF in extensor digitorum longus, white gastrocnemius, and tibialis anterior muscles; average inhibition was from 13.9 ± 1.2 to 6.9 ± 1.4 μmol · g−1 · h−1( P = 0.02). Thus NNF impairs both fatty acid and glucose uptake by muscle by restricting flow to myocytes but, as shown previously, favors triglyceride hydrolysis and uptake into nearby connective tissue fat cells. The findings have implications for lipid partitioning in limb muscles between myocytes and attendant adipocytes.

show abstract

Section: Resultsmentioning

confidence: 99%

Nonnutritive flow impairs uptake of fatty acid by white muscles of the perfused rat hindlimb

Clerk

Smith

Rattigan

et al. 2003

American Journal of Physiology-Endocrinology and Metabolism

Self Cite

View full text Add to dashboard Cite

show abstract

“…Others have shown that xanthine oxidase is predominantly located in capillary endothelial cells (29), and on this basis, we conducted experiments to see whether the metabolism of infused 1-MX, targeted for the capillary endothelial cells, changed in proportion to nutritive (capillary) flow. We found that when flow was predominantly non-nutritive, metabolism of 1-MX was markedly reduced (30), and when flow was predominantly nutritive, as with exercise, metabolism was increased (31). On this basis, 1-MX metabolism was used to assess changes in capillary recruitment due to insulin under normal conditions (21), when non-nutritive flow predominated (23), and in the presence of TNF-␣ (24).…”

Section: Discussionmentioning

confidence: 99%

Exercise Training Improves Insulin-Mediated Capillary Recruitment in Association With Glucose Uptake in Rat Hindlimb

et al. 2001

View full text Add to dashboard Cite

Exercise training is considered to be beneficial in the treatment and prevention of insulin insensitivity, and much of the effect occurs in muscle. We have recently shown that capillary recruitment by insulin in vivo is associated with and may facilitate insulin action to increase muscle glucose uptake. In the present study, we examined the effect of 14 days of voluntary exercise training on euglycemic-hyperinsulinemic clamped (10 mU ⅐ min ؊1 ⅐ kg ؊1 for 2 h), anesthetized rats. Whole-body glucose infusion rate (GIR), hindleg glucose uptake, femoral blood flow (FBF), vascular resistance, and capillary recruitment, as measured by metabolism of infused 1-methylxanthine (1-MX), were assessed. In sedentary animals, insulin caused a significant (P < 0.05) increase in FBF (1.6-fold) and capillary recruitment (1.7-fold) but a significant decrease in vascular resistance. In addition, hindleg glucose uptake was increased (4.3-fold). Exercise training increased insulin-mediated GIR (24%), hindleg glucose uptake (93%), and capillary recruitment (62%) relative to sedentary animals. Neither capillary density nor total xanthineoxidase activity in skeletal muscle were increased as a result of the training regimen used. We concluded that exercise training improves insulin-mediated increases in capillary recruitment in combination with augmented muscle glucose uptake. Increased insulin-mediated glucose uptake may in part result from the improved hemodynamic control attributable to exercise training.

show abstract

“…Values are means±SE for n=8-10 in each group. *p<0.05 difference from Sal; # p<0.05 difference from Ins Xanthine oxidase activity Metabolism of 1-MX by xanthine oxidase of the hind limb muscle vasculature, which is measured under saturating conditions of 1-MX, has been shown to reflect changes in nutritive flow [25,28]. However, because conditions are saturating, a change in the level of xanthine oxidase activity could also influence the rate of metabolism of 1-MX.…”

Section: -Mx Metabolismmentioning

confidence: 99%

Acute glucosamine-induced insulin resistance in muscle in vivo is associated with impaired capillary recruitment

et al. 2005

Self Cite

View full text Add to dashboard Cite

Aims/hypothesis: Glucose toxicity and glucosamine-induced insulin resistance have been attributed to products of glucosamine metabolism. In addition, endothelial cell nitric oxide synthase is inhibited by glucosamine. Since insulin has endothelial nitric-oxide-dependent vasodilatory effects in muscle, we hypothesise that glucosamine-induced insulin resistance in muscle in vivo is associated with impaired vascular responses including capillary recruitment. Materials and methods: Glucosamine (6.48 mg kg −1 min −1 for 3 h) was infused with or without insulin (10 mU kg −1 min −1 ) into anaesthetised rats under euglycaemic conditions. Results: Glucosamine infusion alone increased blood glucosamine (1.9±0.1 mmol/l) and glucose (5.4±0.2 to 7.7± 0.3 mmol/l) (p<0.05) but not insulin. Glucosamine induced both hepatic and muscle insulin resistance as evident from measures of glucose appearance and disposal as well as hindleg glucose uptake, which was inhibited by approx. 50% (p<0.05). Insulin-mediated increases in femoral arterial blood flow and capillary recruitment were completely blocked by glucosamine. Conclusion/interpretation: Glucosamine mediates a major impairment of insulin action in muscle vasculature associated with the insulin resistance of muscle. Further studies will be required to assess whether the impaired capillary recruitment contributes to insulin resistance.

show abstract

Increased metabolism of infused 1‐methylxanthine by working muscle

Cited by 18 publications

References 30 publications

Nonnutritive flow impairs uptake of fatty acid by white muscles of the perfused rat hindlimb

Nonnutritive flow impairs uptake of fatty acid by white muscles of the perfused rat hindlimb

Exercise Training Improves Insulin-Mediated Capillary Recruitment in Association With Glucose Uptake in Rat Hindlimb

Acute glucosamine-induced insulin resistance in muscle in vivo is associated with impaired capillary recruitment

Contact Info

Product

Resources

About