Hyperglycemia- and hyperinsulinemia-induced insulin resistance causes alterations in cellular bioenergetics and activation of inflammatory signaling in lymphatic muscle

Abstract

Insulin resistance is a well-known risk factor for obesity,metabolic syndrome (MetSyn) and associated cardiovascular diseases, but its mechanisms are undefined in the lymphatics. Mesenteric lymphatic vessels from MetSyn or LPS-injected rats exhibited impaired intrinsic contractile activity and associated inflammatory changes. Hence, we hypothesized that insulin resistance in lymphatic muscle cells (LMCs) affects cell bioenergetics and signaling pathways that consequently alter contractility.LMCswere treatedwith different concentrations of insulin or glucose or both at various time points to determine insulin resistance. Onset of insulin resistance significantly impaired glucose uptake, mitochondrial function, oxygen consumption rates, glycolysis, lactic acid, and ATP production in LMCs. Hyperglycemia and hyperinsulinemia also impaired the PI3K/Akt while enhancing the ERK/ p38MAPK/JNK pathways in LMCs. Increased NF-kB nuclear translocation and macrophage chemoattractant protein-1 and VCAM-1 levels in insulin-resistant LMCs indicated activation of inflammatory mechanisms. In addition, increased phosphorylation ofmyosin light chain-20, a key regulator of lymphaticmuscle contraction,was observed in insulin-resistant LMCs. Therefore, our data elucidate the mechanisms of insulin resistance in LMCs and provide the first evidence that hyperglycemia and hyperinsulinemia promote insulin resistance and impair lymphatic contractile status by reducing glucose uptake, altering cellular metabolic pathways, and activating inflammatory signaling cascades.