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Elevated circulating triglycerides (i.e., dyslipidemia) is a hallmark of insulin resistance and is generally caused by decrease in lipoprotein lipase (LPL) activity. LPL hydrolyzes triglycerides (TG) into free fatty acids in plasma for use and/or storage in tissues (i.e., adipose, skeletal muscle). Plasma apolipoproteins (Apos) C3 and C2 interact with LPL to modulate its function by activating or inhibiting LPL. Previous research shows, in the metabolic environment of insulin resistance, the concentration of ApoC3 is increased in plasma while that of ApoC2 is decreased. Thus, Apos are considered key factors in regulating plasma lipid metabolism via modulation of LPL function. The purpose of this study was to investigate the concentrations of ApoC3 and ApoC2 in plasma and along endothelial-bound LPL activity in insulin resistant and healthy/non-insulin resistant individuals. We evaluated insulin resistance (IR)/insulin sensitivity (IS) using an oral glucose tolerance test (i.e., Matsuda index calculation) in subjects between ages 19 and 45 years old. Subjects were placed in the following two groups: 1) IR, if Matsuda index 7.0 (N=11, 9 males, 2 females; BMI: 18-26 kg/m2). Subjects received an intravenous insulin infusion (0.5 mU/kg/min) for 30 minutes to resemble increased postprandial plasma insulin response. To release whole-body endothelial-bound LPL, subjects received an injection of intravenous heparin (75 UI/kg). Plasma samples were collected 10 minutes after the heparin infusion and analyzed for LPL concentration and activity, and ApoC3 and ApoC2 concentrations using ELISA. Differences between IS and IR subjects were determined using a t-test, and the P value was set at P < 0.05. Plasma LPL concentrations were not different between groups (IR = 457 ± 17 ng/ml, IS = 453 ± 27 ng/ml, P > 0.05), but plasma LPL activity was higher in the IR subjects (IR = 665 ± 113 nmol/min/ml, IS = 365 ± 59 nmol/min/ml, P = 0.02). IR subjects had higher concentrations of plasma ApoC3 (IR = 3.6 ± 0.5 mg/dl, IS = 2.7 ± 0.2 mg/dl, P=0.03) but ApoC2 was not different between groups (IR = 0.15 ± 0.03 mg/dl, IS = 0.11 ± 0.01 mg/dl, P = 0.11). The ratio of circulating LPL to circulating ApoC3 (IR = 145 ± 22, IS = 176 ± 15) or circulating ApocC2 (IR = 4104 ± 844, IS = 4391 ± 483) were not different between groups (P > 0.05). We conclude that interactions of LPL with APOC3 and ApoC2 may not be main determinants regulating differential whole-body plasma LPL activity under plasma insulin-stimulated conditions in insulin resistant humans. American Diabetes Association Grant #7-12-CT-40 This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Inflammation of adipose tissue (AT) is key for the development of insulin resistance (IR) in obesity. We previously showed that 3 months supplementation of fish oil (FO, 4g/day), a well-known anti-inflammatory agent, induced 25% improvement in glucose disposal during euglycemic-hyperinsulinemic clamp in 13 obese, insulin resistant subjects (ADA abstract Hernandez J., et al 2017). To explore the mechanism(s) linked to this improvement, we first performed a microarray analysis of subcutaneous (SC) AT samples pre and post FO supplementation. Functional analysis indicated anti-inflammatory pathways as the principal pathways to be enriched after FO supplementation. We identified APOE (1.87 Fold Change (FC) Post vs. Pre-FO, P=0.004) among the most significantly enhanced genes, as APOE was common to the top 5 enriched anti-inflammatory pathways. RT-PCR analysis confirmed the changes in expression levels of several genes in these pathways including APOE, APOC1, MS4A6E, MMP9, MMP7, DEFB132, C1QTNF7, and POPDC3, thereby validating the microarray findings. Plasma and SC AT RT-PCR analysis showed significantly decreased inflammatory markers (IL1B: -0.28 FC, P=0.04, MCP1: -0.44 FC, P=0.04, CD68: -0.36 FC P=0.01) post vs. pre-FO. Additionally, mRNA adiponectin levels increased (FC +0.45 Post vs. Pre, P=0.02), while leptin decreased (FC -.030 Post vs. Pre, P=0.02). Furthermore, ω3PUFA supplementation significantly reduced plasma FFA levels (Post-FO: 0.578+0.061mM vs. Pre-FO: 0.719 +0.055mM P Disclosure C. Rau: None. T. Li: None. J.D. Hernandez: None. M.Y. Masuda: None. X. Zhang: None. P. Wang: None. D.K. Coletta: None. E. DeFilippis: None. Funding Arizona Department of Health Services (14-00003606); Kathryn H. and Roger Penske Career Development Award

Adipose tissue resident eosinophils (AT-EOS) are thought to play a pivotal role in whole-body energy homeostasis. However, the precise role of, and the mechanisms underlying AT-EOS in the regulation of whole-body energy metabolism remains elusive. This is because of the limitations of rodent models which have been genetically engineered to either produce elevated whole-body eosinophils or knock-out models for this hematopoietic lineage. To determine the function of AT-EOS, we generated a transgenic mouse model overexpressing human eotaxin[AV1] 2 (hEo2), which is an eosinophil specific chemokine, under the control of a fat-specific aP2 promoter, to recruit circulating EOS exclusively into adipose (hEo2tg). Compared to wild type (WT) littermates of both genders, hEo2tg mice displayed a significant increase of AT-EOS in multiple AT depots including, perirenal and subcutaneous white adipose tissue (sWAT). However, EOS were not increased in brown adipose tissue (BAT). When fed a high-fat diet (HFD), hEo2tg mice gained less weight (males weight: 45.5 ±0.7g vs. 51 ±0.4g, P Disclosure T. Li: None. W. LeSuer: None. A. Singh: None. J.D. Hernandez: None. X. Zhang: None. D. Jelinek: None. J. Liu: None. A. Vella: Advisory Panel; Self; vTv Therapeutics. Research Support; Self; Novo Nordisk Inc. E.A. Jacobsen: None. E. DeFilippis: None. Funding National Center for Advancing Translational Sciences (KL2TR002379)

Eosinophils (EOS) have been shown to play a major role in animal adipose tissue (AT) metabolism by promoting insulin sensitivity (IS) through an increase in alternatively activated macrophages (M2). Additionally, AT EOS are known to be decreased in obese mice. Currently, translational evidence is lacking for the role of EOS in human AT metabolism and IS. We investigated whether human AT-resident EOS numbers, as in animal models, are decreased in obese subjects and correlate with their degree of insulin resistance (IR). To date, we have studied 16 lean subjects (F15/M1, age 43 +2 years old; BMI 22.5+0.4kg/m2; HOMA-IR: 0.99 +0.38) and 22 obese, IR subjects (17F/5M, age 42 +1.3 years old; BMI: 38.9 +1.0kg/m2; HOMA-IR:5.0 +1.6) undergoing elective laparoscopic surgery. During surgical procedure, subcutaneous (SC) and omental (OM) fat was harvested. Stromal vascular fraction (SVF) was isolated after collagenase digestion of the fat samples. SVF was subjected to FACS analysis using BD Biosciences FACSAria III Cell Sorter with EOS count normalized as percent of CD45+ cells. Viable EOS were isolated and cytospin preparation was stained with a Diff-Quik. EOS isolated from SC AT of lean(L) subjects were found to significantly outnumber those obtained from obese (Ob) subjects by a 2.1:1 ratio (SC L:2.34 +0.29 vs. SC Ob: 1.11 +0.21, P Disclosure J.D. Hernandez: None. T. Li: None. C. Rau: None. M.Y. Masuda: None. J.A. Madura: None. E.A. Jacobsen: None. E. DeFilippis: None. Funding Arizona Department of Health Services (14-00003606); Arizona Biomedical Research Commission; Kathryn H. and Roger Penske Career Development Award

The physiological changes observed in skeletal muscle following exercise training may be due to epigenetic modifications. Previously, we have shown increased methylation of cytosines (5.0 to 24.4%) in sorbin and SH3 domain containing 3 (SORBS3) in obesity. In another study, we showed decreased methylation (-5.6 to -24.2%) of SORBS3 following weight loss induced by bariatric surgery. The aim of this study was to determine whether an exercise training regimen alters DNA methylation of SORBS3. Skeletal muscle biopsies were obtained basally from five insulin-resistant obese (BMI: 32.3±0.8 kg/m2) participants (41.8±3.3 years) before and after 8-weeks of supervised exercise training. After training, BMI and total body weight were unchanged. Training increased peak aerobic capacity (VO2peak) from 20.2±1.9 to 24.3±2.7 mL/kg/min. We performed next generation methylation reduced representation bisulfite sequencing on DNA isolated from the vastus lateralis muscle biopsies. MethylSig analysis revealed 4 cytosines that were decreased in methylation following the exercise training (chr8.22423199: -19.3%, chr8.22423207: -14.6%; chr8.22423252: -27.5% and chr8.22423257: -12.3%, all Benjamini Hochberg q Disclosure S.E. Day: None. L. Garcia: None. R.L. Coletta: None. E. DeFilippis: None. L. Mandarino: None. D.K. Coletta: None.