SUN-095 Attenuation of Inflammation by a Novel Small Molecule Prevents High Fat Diet-Induced Nonalcoholic Fatty Liver Disease

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of both metabolic and inflammatory diseases, and it has become pervasive worldwide. Inflammation, including inflammation resulting from free fatty acid (FFA) activation of toll-like receptor (TLR) signaling, has been suggested to be an essential component of the pathophysiology of both insulin resistance and NAFLD. High fat (HF) diets promote an increased uptake and storage of FFAs and triglycerides in hepatocytes, which initiates inflammation and steatosis that induces lipotoxicity and an exacerbation of inflammation. In previous studies, we have established the efficacy of phenylmethimazole, a TLR3/4 inhibitor, to prevent and reverse HF diet-induced NAFLD, inflammation, and insulin resistance. A new library of small molecule compounds, including COB-214, was generated to identify even more potent inhibitors of inflammation. The objectives of this study were to evaluate the efficacy of COB-214 to delay and/or prevent hepatic steatosis, inflammation, and insulin resistance in a HF diet-induced model of NAFLD. C57BL/6J male mice were fed a HF diet (60 % fat, 20% protein, 70% carbohydrate) and divided into 3 groups (N=8 for each group): sham injection (stress control), DMSO (vehicle control), COB-214. Each treatment was administered once daily at a dosage of 1mg/kg for 16 weeks. Histological examination of liver sections from these mice using hematoxylin and eosin (H&E) revealed less hepatic lipid accumulation in mice treated with COB-214 when compared to mice in the sham- and DMSO-treated groups. Transcription of pro-inflammatory cytokines was down-regulated in both liver and mesenteric adipose tissue isolated from COB-214-treated mice when compared to sham- and DMSO-treated mice. Treatment with COB-214 prevented HF diet-induced insulin resistance measured by a 3-hour intraperitoneal glucose tolerance test (IPGTT) and 1.5-hour intraperitoneal insulin tolerance test (IPITT). Future directions include determining the efficacy of COB-214 to reverse HF diet-induced NAFLD, inflammation, and insulin resistance. At the conclusion of this study, we hope to have established the role of a novel class of small molecule inhibitors of inflammation in the treatment and prevention of NAFLD.

Phenylmethimazole abrogates diet-induced inflammation, glucose intolerance and NAFLD

Nonalcoholic fatty liver disease (NAFLD) is the hepatic manifestation of both metabolic and inflammatory diseases and has become the leading chronic liver disease worldwide. High-fat (HF) diets promote an increased uptake and storage of free fatty acids (FFAs) and triglycerides (TGs) in hepatocytes, which initiates steatosis and induces lipotoxicity, inflammation and insulin resistance. Activation and signaling of Toll-like receptor 4 (TLR4) by FFAs induces inflammation evident in NAFLD and insulin resistance. Currently, there are no effective treatments to specifically target inflammation associated with this disease. We have established the efficacy of phenylmethimazole (C10) to prevent lipopolysaccharide and palmitate-induced TLR4 signaling. Because TLR4 is a key mediator in pro-inflammatory responses, it is a potential therapeutic target for NAFLD. Here, we show that treatment with C10 inhibits HF diet-induced inflammation in both liver and mesenteric adipose tissue measured by a decrease in mRNA levels of pro-inflammatory cytokines. Additionally, C10 treatment improves glucose tolerance and hepatic steatosis despite the development of obesity due to HF diet feeding. Administration of C10 after 16 weeks of HF diet feeding reversed glucose intolerance, hepatic inflammation, and improved hepatic steatosis. Thus, our findings establish C10 as a potential therapeutic for the treatment of NAFLD.

Diet is critical for prolonged glycemic control after short-term insulin treatment in high-fat diet-induced type 2 diabetic male mice

Background

Clinical studies suggest that short-term insulin treatment in new-onset type 2 diabetes (T2DM) can promote prolonged glycemic control. The purpose of this study was to establish an animal model to examine such a “legacy” effect of early insulin therapy (EIT) in long-term glycemic control in new-onset T2DM. The objective of the study was to investigate the role of diet following onset of diabetes in the favorable outcomes of EIT.

Methodology

As such, C57BL6/J male mice were fed a high-fat diet (HFD) for 21 weeks to induce diabetes and then received 4 weeks of daily insulin glargine or sham subcutaneous injections. Subsequently, mice were either kept on the HFD or switched to a low-fat diet (LFD) for 4 additional weeks.

Principal Findings

Mice fed a HFD gained significant fat mass and displayed increased leptin levels, increasing insulin resistance (poor HOMA-IR) and worse glucose tolerance test (GTT) performance in comparison to mice fed a LFD, as expected. Insulin-treated diabetic mice but maintained on the HFD demonstrated even greater weight gain and insulin resistance compared to sham-treated mice. However, insulin-treated mice switched to the LFD exhibited a better HOMA-IR compared to those mice left on a HFD. Further, between the insulin-treated and sham control mice, in spite of similar HOMA-IR values, the insulin-treated mice switched to a LFD following insulin therapy did demonstrate significantly better HOMA-B% values than sham control and insulin-treated HFD mice.

Conclusion/Interpretation

Early insulin treatment in HFD-induced T2DM in C57BL6/J mice was only beneficial in animals that were switched to a LFD after insulin treatment which may explain why a similar legacy effect in humans is achieved clinically in only a portion of cases studied, emphasizing a vital role for diet adherence in diabetes control.

L-Arginine Supplementation in Type II Diabetic Rats Preserves Renal Function and Improves Insulin Sensitivity by Altering the Nitric Oxide Pathway

Rat studies demonstrated that type II diabetes mellitus (T2DM) decreases both the production and bioavailability of nitric oxide (NO). L-arginine (LA) provides the precursor for the production of NO. We hypothesized that LA dietary supplementation will preserve NO production via endothelial nitric oxide synthase (eNOS) causing renal microvascular vasodilation and increased glomerular blood flow and thus increasing glomerular filtration rate (GFR). This would impede the formation of reactive oxygen species which contributes to cell damage and death. LA supplementation preserved GFR in the treated diabetic rats compared to untreated diabetic rats. We provide evidence that this effect may be due to increased levels of eNOS and urinary cyclic guanosine monophosphate, which leads to renal microvascular vasodilation. Plasma nitrotyrosine was decreased in the LA treated rats; however, plasma nitrite levels remained unaffected as expected. Marked improvements in glucose tolerance were also observed in the LA treated diabetic rats. These results demonstrate that LA supplementation preserves NO activity and may delay the onset of insulin resistance and renal dysfunction during hyperglycemic stress. These results suggest the importance of the NO pathway in consequent renal dysfunction and in the development of insulin resistance in diabetic rats.

Toll-like receptor 3 involvement in Coxsackievirus B 4 acceleration of type 1 diabetes. (P6134)

Viruses are important in the pathogenesis of type 1 diabetes mellitus (T1DM). A pancreatrophic strain of coxsackievirus, CVB4, which is associated with the development of T1DM in humans, accelerates the development of T1DM in NOD mice. Toll-Like Receptor 3 (TLR3) is activated by viral dsRNA and is broadly expressed by NOD mice and human pancreatic beta cells, suggesting that TLR3 signaling may be important in CVB4 acceleration of T1DM. We used NOD mice deficient in TLR3 (TLR3 KO) to test the hypothesis that TLR3 signaling is important in CVB4 acceleration of T1DM in NOD mice. We report that TLR3 KO NOD mice are markedly protected from CVB4 acceleration of T1DM compared to wild type (WT) NOD mice. Similarly, we have observed that phenylmethimazole (C10), which has recently been shown to inhibit dsRNA-triggered TLR3 signaling, also delays CVB4 acceleration of T1DM in NOD mice. In preliminary experiments to investigate the mechanism by which TLR3 deficiency provides protection from T1DM in this model, we observed marked differences in T regulatory cell populations between TLR3 KO and WT NOD mice, and a significant enhancement of viral clearance in C10-treated NOD mice. These results indicate the distinct importance of TLR3 signaling in environmental (i.e. viral) induction of T1DM and that C10 could potentially protect β cells from virus-induced insulitis.

Three-dimensional graphic reconstruction of the insect exoskeleton through confocal imaging of endogenous fluorescence

The exoskeleton of the cockroach leg was imaged via confocal microscopy to generate digital graphic reconstructions of its three-dimensional structure. The cuticle is autofluorescent and can be visualized without staining, but is maximally imaged in aldehyde-fixed preparations viewed under krypton-argon laser illumination (yellow green (568 nm) excitation, commonly used in confocal microscopes). Images of the entire trochanteral segment of the leg were constructed as montages from optical sections taken as overlapping series that were coincident in the z-axis. Reconstructions of the exoskeleton from these images showed that strain sensing mechanoreceptors are located in association with buttresses and thickenings that form a consistent internal architecture in both juvenile and adult animals. Accuracy of reconstructions was gauged by embedding specimens in Spurr's resin and histologically sectioning them perpendicular to the optical plane of section (z-axis). Comparison of plastic sections with two-dimensional images generated by "resectioning" the software model showed that reconstructed exoskeleton had a high level of accuracy. Imaging of older and larger animals was limited by the sclerotization and increased thickness of the cuticle. Surface extraction algorithms were used to generate vector graphic files in CAD format for export to software used in engineering and design. Among other potential uses, these models have been studied by Finite Element Analysis to examine the distribution of mechanical strains in the exoskeleton that occur during posture and locomotion. The advantages and limitations of the techniques are discussed. These methods may be used in studying the exoskeleton and the anatomy of cuticular mechanoreceptors of other arthropods to similar advantage.