Background: Redirecting glucose from skeletal muscle and adipose tissue, likely benefits the tumor's energy demand to support tumor growth, as cancer patients with type 2 diabetes have 30% increased mortality rates. The aim of this study was to elucidate tissue-specific contributions and molecular mechanisms underlying cancer-induced metabolic perturbations.Methods: Glucose uptake in skeletal muscle and white adipose tissue (WAT), as well as hepatic glucose production, were determined in control and Lewis lung carcinoma (LLC) tumor-bearing C57BL/6 mice using isotopic tracers. Skeletal muscle microvascular perfusion was analyzed via a real-time contrast-enhanced ultrasound technique. Finally, the role of fatty acid turnover on glycemic control was determined by treating tumor-bearing insulin-resistant mice with nicotinic acid or etomoxir.Results: LLC tumor-bearing mice displayed reduced insulin-induced blood-glucose-lowering and glucose intolerance, which was restored by etomoxir or nicotinic acid. Insulin-stimulated glucose uptake was 30-40% reduced in skeletal muscle and WAT of mice carrying large tumors. Despite compromised glucose uptake, tumor-bearing mice displayed upregulated insulin-stimulated phosphorylation of TBC1D4 Thr642 (+18%), AKT Ser474 (+65%), and AKT Thr309 (+86%) in muscle.Insulin caused a 70% increase in muscle microvascular perfusion in control mice, which was abolished in tumor-bearing mice. Additionally, tumor-bearing mice displayed increased (+45%) basal (not insulin-stimulated) hepatic glucose production.Conclusions: Cancer can result in marked perturbations on at least six metabolically essential functions; i) insulin's blood-glucose-lowering effect, ii) glucose tolerance, iii) skeletal muscle and WAT insulin-stimulated glucose uptake, iv) intramyocellular insulin signaling, v) muscle microvascular perfusion, and vi) basal hepatic glucose production in mice. The mechanism causing cancer-induced insulin resistance may relate to fatty acid metabolism..

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20Background: Redirecting glucose from skeletal muscle and adipose tissue, likely benefits the 21 tumor's energy demand to support tumor growth, as cancer patients with type 2 diabetes have 30% 22 increased mortality rates. The aim of this study was to elucidate tissue-specific contributions and 23 molecular mechanisms underlying cancer-induced metabolic perturbations. 24Methods: Glucose uptake in skeletal muscle and white adipose tissue (WAT), as well as hepatic 25 glucose production, were determined in control and Lewis lung carcinoma (LLC) tumor-bearing 26 C57BL/6 mice using isotopic tracers. Skeletal muscle microvascular perfusion was analyzed via a 27 real-time contrast-enhanced ultrasound technique. Finally, the role of fatty acid turnover on 28 glycemic control was determined by treating tumor-bearing insulin-resistant mice with nicotinic 29 acid or etomoxir. 30Results: LLC tumor-bearing mice displayed reduced insulin-induced blood-glucose-lowering and 31 glucose intolerance, which was restored by etomoxir or nicotinic acid. Insulin-stimulated glucose 32 uptake was 30-40% reduced in skeletal muscle and WAT of mice carrying large tumors. Despite 33 compromised glucose uptake, tumor-bearing mice displayed upregulated insulin-stimulated 34 phosphorylation of TBC1D4 Thr642 (+18%), AKT Ser474 (+65%), and AKT Thr309 (+86%) in muscle. 35Insulin caused a 70% increase in muscle microvascular perfusion in control mice, which was 36 abolished in tumor-bearing mice. Additionally, tumor-bearing mice displayed increased (+45%) 37 basal (not insulin-stimulated) hepatic glucose production. 38Conclusions: Cancer can result in marked perturbations on at least six metabolically essential 39 functions; i) insulin's blood-glucose-lowering effect, ii) glucose tolerance, iii) skeletal muscle and 40 WAT insulin-stimulated glucose uptake, iv) intramyocellular insulin signaling, v) muscle 41 microvascular perfusion, and vi) basal hepatic glucose production in mice. The mechanism causing 42 cancer-induced insulin resistance may relate to fatty acid metabolism. 43 3