Location: Obesity and Metabolism Research Unit
Project Number: 5306-51530-019-57
Start Date: Jan 01, 2012
End Date: Dec 31, 2014
Specific Aim 1--Ascertain Whether the Pro-Inflammatory Effects of MCFA-Carnitine Result in Insulin Resistance in Skeletal Muscle and Adipocyte Preparations. Muscle and adipose tissues are important sites for glucose disposal and metabolism. Activators of PRRs and downstream JNK and NF'B activation have been associated with diminution of insulin signaling. Thus, in Aim 1 we will fully characterize the impact of exogenous acylcarnitines on insulin signaling cascades and glucose uptake in muscle preparations and in 3T3-L1 adipocytes. We hypothesize that the pro-inflammatory effects of L-C14-carnitine will have functional implications to reduce insulin action. Specific Aim 2--Ascertain Whether the Pro-Inflammatory Effects of MCFA-Carnitine are Inhibited by PUFA via a GPR120-Dependent Pathway. Diets rich in '3-polyunsaturated fatty acids (PUFA) are known to dampen inflammation in vivo, and PUFAs attenuate the PRR-dependent pro-inflammatory effects of TLR activators in cell culture systems. Recently, it was reported that '3-PUFA (docosahexanoic acid, DHA) effects are largely via the GPCR GPR120 that inactivates nodes of the inflammatory cascade. Since acylcarnitines share some inflammation-associated systems with saturated FAs, in Aim 2 we will test the hypothesis that DHA will reduce acylcarnitine-induced inflammation. We further reason that such an activity, in part, will be driven by activation of the '3-PUFA receptor GPR120. Specific Aim 3--Determine if MCFA-Carnitine Specifically Activates Intracellular Endosomal TLRs (TLR7, TLR8, TLR9). Our studies using murine and human cell systems and murine TLR gene constructs have successfully excluded several cell-surface PRRs as primary targets of L-C14-carnitine in terms of activation of pro-inflammatory pathways (e.g., TLR1-TLR6, see Preliminary Results). The effects of acylcarnitine in macrophage cells appear to involve MyD88, an adaptor protein shared by several TLRs. In Aim 3 we will test the hypothesis that L-C14-carnitine exerts its inflammatory effects through one or more of the MyD88-dependent endosomal PRRs TRL7, TLR8, or TLR9.