Macrophage Infiltration In Adipose Tissue Research Articles

Dipeptidyl peptidase-4 disturbs adipocyte differentiation via the negative regulation of the glucagon-like peptide-1/adiponectin-cathepsin K axis in mice under chronic stress conditions.

Exposure to chronic psychosocial stress is a risk factor for metabolic disorders. Because dipeptidyl peptidase-4 (DPP4) and cysteinyl cathepsin K (CTSK) play important roles in human pathobiology, we investigated the role(s) of DPP4 in stress-related adipocyte differentiation, with a focus on the glucagon-like peptide-1 (GLP-1)/adiponectin-CTSK axis invivo and invitro. Plasma and inguinal adipose tissue from non-stress wild-type (DPP4+/+), DPP4-knockout (DPP4-/-) and CTSK-knockout (CTSK-/-) mice, and stressed DPP4+/+, DPP4-/-, CTSK-/-, and DPP4+/+ mice underwent stress exposure plus GLP-1 receptor agonist exenatide loading for 2 weeks and then were analyzed for stress-related biological and/or morphological alterations. On day 14 under chronic stress, stress decreased the weights of adipose tissue and resulted in harmful changes in the plasma levels of DPP4, GLP-1, CTSK, adiponectin, and tumor necrosis factor-α proteins and the adipose tissue levels of CTSK, preadipocyte factor-1, fatty acid binding protein-4, CCAAT/enhancer binding protein-α, GLP-1 receptor, peroxisome proliferator-activated receptor-γ, perilipin2, secreted frizzled-related protein-4, Wnt5α, Wnt11 and β-catenin proteins and/or mRNAs as well as macrophage infiltration in adipose tissue; these changes were rectified by DPP4 deletion. GLP-1 receptor activation and CTSK deletion mimic the adipose benefits of DPP4 deficiency. Invitro, CTSK silencing and overexpression respectively prevented and facilitated stress serum and oxidative stress-induced adipocyte differentiation accompanied with changes in the levels of pref-1, C/EBP-α, and PPAR-γ in 3T3-L1 cells. Thus, these findings indicated that increased DPP4 plays an essential role in stress-related adipocyte differentiation, possibly through a negative regulation of GLP-1/adiponectin-CTSK axis activation in mice under chronic stress conditions.

Gamma-aminobutyric acid supplementation improves olanzapine-induced insulin resistance by inhibiting macrophage infiltration in mice subcutaneous adipose tissue.

To investigate whether gamma-aminobutyric acid (GABA) supplementation improves insulin resistance during olanzapine treatment in mice and to explore the underlying mechanisms. Insulin resistance and body weight gain were induced in mice by 10 weeks of olanzapine treatment. Simultaneously, the mice were administered GABA after 4 weeks of olanzapine administration. We found that mice treated with olanzapine had lower GABA levels in serum and subcutaneous white adipose tissue (sWAT). GABA supplementation restored GABA levels and improved olanzapine-induced lipid metabolism disorders and insulin resistance. Chronic inflammation in adipose tissue is one of the main contributors to insulin resistance. We found that GABA supplementation inhibited olanzapine-induced adipose tissue macrophage infiltration and M1-like polarization, especially in sWAT. In vitro studies showed that stromal vascular cells, rather than adipocytes, were sensitive to GABA. Furthermore, the results suggested that GABA improves olanzapine-induced insulin resistance at least in part through a GABAB receptor-dependent pathway. These findings suggest that targeting GABA may be a potential therapeutic approach for olanzapine-induced metabolic disorders.

The New Challenge of Obesity - Obesity-Associated Nephropathy.

In recent years, obesity has become one of the major diseases that affect human health and consume human health resources, especially when it causes comorbidities such as hypertension, diabetes, cardiovascular disease and kidney disease. Many studies have demonstrated that obesity is associated with the development of chronic kidney disease and can exacerbate the progression of end-stage renal disease. This review described the mechanisms associated with the development of obesity-associated nephropathy and the current relevant therapeutic modalities, with the aim of finding new therapeutic targets for obesity-associated nephropathy. The mechanisms of obesity-induced renal injury include, in addition to the traditional alterations in renal hemodynamics, the involvement of various mechanisms such as macrophage infiltration in adipose tissue, alterations in adipokines (leptin and adiponectin), and ectopic deposition of lipids. At present, there is no "point-to-point" treatment for obesity-induced kidney injury. The renin-angiotensin-aldosterone system (RAAS) inhibitors, sodium-dependent glucose transporter 2 (SGLT-2) inhibitors and bariatric surgery described in this review can reduce urinary protein to varying degrees and delay the progression of kidney disease. In addition, recent studies on the therapeutic effects of intestinal flora on obesity may reduce the incidence of obesity-related kidney disease from the perspective of primary prevention. Both of these interventions have their own advantages and disadvantages, so the continuous search for the mechanism of obesity-induced related kidney disease will be extremely helpful for the future treatment of obesity-related kidney disease.

FAP expression in adipose tissue macrophages promotes obesity and metabolic inflammation.

Adipose tissue macrophages (ATM) are key players in the development of obesity and associated metabolic inflammation which contributes to systemic metabolic dysfunction. We here found that fibroblast activation protein α (FAP), a well-known marker of cancer-associated fibroblast, is selectively expressed in murine and human ATM among adipose tissue-infiltrating leukocytes. Macrophage FAP deficiency protects mice against diet-induced obesity and proinflammatory macrophage infiltration in obese adipose tissues, thereby alleviating hepatic steatosis and insulin resistance. Mechanistically, FAP specifically mediates monocyte chemokine protein CCL8 expression by ATM, which is further upregulated upon high-fat-diet (HFD) feeding, contributing to the recruitment of monocyte-derived proinflammatory macrophages with no effect on their classical inflammatory activation. CCL8 overexpression restores HFD-induced metabolic phenotypes in the absence of FAP. Moreover, macrophage FAP deficiency enhances energy expenditure and oxygen consumption preceding differential body weight after HFD feeding. Such enhanced energy expenditure is associated with increased levels of norepinephrine (NE) and lipolysis in white adipose tissues, likely due to decreased expression of monoamine oxidase, a NE degradation enzyme, by Fap-/- ATM. Collectively, our study identifies FAP as a previously unrecognized regulator of ATM function contributing to diet-induced obesity and metabolic inflammation and suggests FAP as a potential immunotherapeutic target against metabolic disorders.

Myeloid SENP3 deficiency protects mice from diet and age-induced obesity via regulation of YAP1 SUMOylation

Obesity is characterized by chronic low-grade inflammation, which is driven by macrophage infiltration in adipose tissue and leads to elevated cytokines such as interleukin-1β (IL-1β) in the circulation and tissues. Previous studies demonstrate that SENP3, a redox-sensitive SUMO2/3-specific protease, is strongly implicated in the development and progression of cancer and cardiovascular diseases. However, the role of SENP3 in obesity-associated inflammation remains largely unknown. To better understand the effects of SENP3 on adipose tissue macrophage (ATM) activation and function within the context of obesity, we generated mice with myeloid-specific deletion of SENP3 (Senp3flox/flox;Lyz2-Cre mice). We found that the expression of SENP3 is dramatically increased in ATMs during high-fat diet (HFD)-induced obesity in mice. Senp3flox/flox;Lyz2-Cre mice show lower body weight gain and reduced adiposity and adipocyte size after challenged with HFD and during aging. Myeloid-specific SENP3 deletion attenuates macrophage infiltration in adipose tissue and reduces serum levels of inflammatory factors during diet and age-induced obesity. Furthermore, we found that SENP3 knockout markedly inhibits cytokine release from macrophage after lipopolysaccharide and palmitic acid treatment in vitro. Mechanistically, in cultured peritoneal macrophages, SENP3 protein level is enhanced by IL-1β, in parallel with the upregulation of Yes-associated protein 1 (YAP1). Moreover, we demonstrated that SENP3 modulates de-SUMO modification of YAP1 and SENP3 deletion abolishes the upregulation of YAP1 induced by IL-1β. Most importantly, SENP3 deficiency reduces YAP1 protein level in adipose tissue during obesity. Our results highlight the important role of SENP3 in ATM inflammation and diet and age-induced obesity.

Palmitoleic acid on top of HFD ameliorates insulin resistance independent of diacylglycerols and alters gut microbiota in C57BL/6J mice

With the prevalence of obesity and obesity-related metabolic syndrome, such as insulin resistance in recent years, it is urgent to explore effective interventions to prevent the progression of obesity-related metabolic syndrome. Palmitoleic acid is a monounsaturated fatty acid that is available from dietary sources, mainly derived from marine products. Palmitoleic acid plays a positive role in maintaining glucose homeostasis and reducing inflammation. However, it is still unknow the mechanism of palmitoleic acid in ameliorating insulin resistance. Here, we investigated the effects of palmitoleic acid on chow diet (CD)-fed and high-fat diet (HFD)-fed mice, which were fed CD or HFD for 12 weeks before administration. We administrated mice with BSA (control), oleic acid, or palmitoleic acid for 6 weeks on top of CD or HFD feeding. We found that palmitoleic acid only improved glucose homeostasis in HFD-fed obese mice by increasing glucose clearance and reducing HOMA-IR. Further study explored that palmitoleic acid changed the composition of gut microbiota by decreasing Firmicutes population and increasing Bacteroidetes population. In colon, palmitoleic acid increased intestinal tight junction integrity and reduced inflammation. Moreover, palmitoleic acid decreased macrophage infiltration in liver and adipose tissue and increase glucose uptake in adipose tissue. Diacylglycerol (DAG) in tissue (for example, liver) is found to positively correlated with HOMA-IR. HFD enhanced the levels of DAGs in liver but not in adipose tissue in this study. Palmitoleic acid did not reverse the high DAG levels induced by HFD in liver. Therefore, in HFD-fed mice, palmitoleic acid reduced insulin resistance by an independent-manner of DAGs. It might be associated with the beneficial effects of palmitoleic acid on altering the gut microbiota composition, improving of intestinal barrier function, and downregulating the inflammation in colon, liver, and adipose tissue.

A lipid-associated macrophage lineage rewires the spatial landscape of adipose tissue in early obesity.

Adipose tissue macrophage (ATM) infiltration is associated with adipose tissue dysfunction and insulin resistance in mice and humans. Recent single-cell data highlight increased ATM heterogeneity in obesity but do not provide a spatial context for ATM phenotype dynamics. We integrated single-cell RNA-Seq, spatial transcriptomics, and imaging of murine adipose tissue in a time course study of diet-induced obesity. Overall, proinflammatory immune cells were predominant in early obesity, whereas nonresident antiinflammatory ATMs predominated in chronic obesity. A subset of these antiinflammatory ATMs were transcriptomically intermediate between monocytes and mature lipid-associated macrophages (LAMs) and were consistent with a LAM precursor (pre-LAM). Pre-LAMs were spatially associated with early obesity crown-like structures (CLSs), which indicate adipose tissue dysfunction. Spatial data showed colocalization of ligand-receptor transcripts related to lipid signaling among monocytes, pre-LAMs, and LAMs, including Apoe, Lrp1, Lpl, and App. Pre-LAM expression of these ligands in early obesity suggested signaling to LAMs in the CLS microenvironment. Our results refine understanding of ATM diversity and provide insight into the dynamics of the LAM lineage during development of metabolic disease.

Brown adipocyte mineralocorticoid receptor deficiency impairs metabolic regulation in diet-induced obese mice

Activation of brown adipose tissue (BAT) contributes to energy dissipation and metabolic health. Although mineralocorticoid receptor (MR) antagonists have been demonstrated to improve metabolism under obesity, the underlying mechanisms remain incompletely understood. We aimed to evaluate the role of BAT MR in metabolic regulation. After 8 weeks of high-fat diet (HFD) feeding, BAT MR KO (BMRKO) mice manifested significantly increased bodyweight, fat mass, serum fasting glucose, and impaired glucose homeostasis compared with littermate control (LC) mice, although insulin resistance and fasting serum insulin were not significantly changed. Metabolic cage experiments showed no change in O2 consumption, CO2 production, or energy expenditure in obese BMRKO mice. RNA sequencing analysis revealed downregulation of genes related to fatty acid metabolism in BAT of BMRKO-HFD mice compared with LC-HFD mice. Moreover, H&E and immunohistochemical staining demonstrated that BMRKO exacerbated HFD-induced macrophage infiltration and proinflammatory genes in epididymal white adipose tissue (eWAT). BMRKO-HFD mice also manifested significantly increased liver weights and hepatic lipid accumulation, an increasing trend of genes related to lipogenesis and lipid uptake, and significantly decreased genes related to lipolytic and fatty acid oxidation in the liver. Finally, the level of insulin-induced AKT phosphorylation was substantially blunted in eWAT but not liver or skeletal muscle of BMRKO-HFD mice compared with LC-HFD mice. These data suggest that BAT MR is required to maintain metabolic homeostasis, likely through its regulation of fatty acid metabolism in BAT and impacts on eWAT and liver.

Osteopontin-driven T-cell accumulation and function in adipose tissue and liver promoted insulin resistance and MAFLD.

This study investigated the contribution of osteopontin/secreted phosphoprotein 1 (SPP1) to T-cell regulation in initiation of obesity-driven adipose tissue (AT) inflammation and macrophage infiltration and the subsequent impact on insulin resistance (IR) and metabolic-associated fatty liver disease (MAFLD) development. SPP1 and T-cell marker expression was evaluated in AT and liver according to type 2 diabetes and MAFLD in human individualswith obesity. The role of SPP1 on T cells was evaluated in Spp1-knockout mice challenged with a high-fat diet. In humanswith obesity, elevated SPP1 expression in AT was parallel to T-cell marker expression (CD4, CD8A) and IR. Weight loss reversed AT inflammation with decreased SPP1 and CD8A expression. In liver, elevated SPP1 expression correlated with MAFLD severity and hepatic T-cell markers. In mice, although Spp1 deficiency did not impact obesity, it did improve AT IR associated with prevention of proinflammatory T-cell accumulation at the expense of regulatory T cells. Spp1 deficiency also decreased ex vivo helper T cell, subtype 1 (Th1)polarization of AT CD4+ and CD8+ T cells. In addition, Spp1 deficiency significantly reduced obesity-associated liver steatosis and inflammation. Current findings highlight a critical role of SPP1 in the initiation of obesity-driven chronic inflammation by regulating accumulation and/or polarization of T cells. Early targeting of SPP1 could be beneficial for IR and MAFLD treatment.

Antiobesity Effect of Lacticaseibacillus paracasei LM-141 on High-Fat Diet-Induced Rats through Alleviation of Inflammation and Insulin Resistance.

In this study, we set out to evaluate the antiobesity activities of our newly isolated Lacticaseibacillus paracasei LM-141 (LPLM141) using a high-fat diet (HFD)-fed rat model. Male Sprague-Dawley rats were fed with a HFD with or without low-dosage (2 × 107 CFU/day per rat) or high-dosage (2 × 109 CFU/day per rat) LPLM141 for 14 weeks. The results showed that administration of LPLM141 significantly decreased body weight gain, liver weight, adipose tissue weight, and epididymal white adipocyte size increased by HFD feeding. The abnormal serum lipid profile induced by HFD feeding was normalized by administration of LPLM141. The enhanced chronic low-grade inflammation in HFD-fed rats was reduced by LPLM141 supplementation, as reflected by decreased serum lipopolysaccharide (LPS) and monocyte chemoattractant protein-1 (MCP-1) levels, reduced macrophage infiltration in adipose tissue, and increased serum adiponectin concentration. In addition, the elevations of proinflammatory cytokine genes and suppression of PPAR-γ mRNA in adipose tissues of rats fed with a HFD were markedly reversed by LPLM141 administration. Oral administration of LPLM141 induced browning of epididymal white adipose tissue (eWAT) and activation of interscapular brown adipose tissue (iBAT) in rats fed with HFD. Consumption of LPLM141 exhibited a significant amelioration in insulin resistance, which were mechanistically caused by downregulation of the serum leptin level and upregulation of hepatic IRS-1 and p-Akt protein expressions, in HFD treated rats. LPLM141 consumption significantly decreased hepatic lipogenic gene expressions and preserved liver function stimulated by HFD treatment. Administration of LPLM141 obviously mitigated hepatic steatosis observed in HFD feeding rats. Our current findings shed light on LPLM141 supplementation that exhibited an antiobesity effect in HFD-fed rats by alleviating inflammation and insulin resistance, which further highlighted the potential of utilizing LPLM141 as a preventive/therapeutic probiotic agent for obesity.

CD40LG and GZMB were correlated with adipose tissue macrophage infiltration and involved in obstructive sleep apnea related metabolic dysregulation: Evidence from bioinformatics analysis.

Both obesity and obstructive sleep apnea (OSA) can lead to metabolic dysregulation and systemic inflammation. Similar to obesity, increasing evidence has revealed that immune infiltration in the visceral adipose tissue (VAT) is associated with obstructive sleep apnea-related morbidity. However, the pathological changes and potential molecular mechanisms in visceral adipose tissue of obstructive sleep apnea patients need to be further studied. Herein, by bioinformatics analysis and clinical validation methods, including the immune-related differentially expressed genes (IRDEGs) analysis, protein-protein interaction network (PPI), functional enrichment analysis, a devolution algorithm (CIBERSORT), spearman's correlation analysis, polymerase chain reaction (PCR), Enzyme-linked immunosorbent assay (ELISA) and immunohistochemistry (IHC), we identified and validated 10 hub IRDEGs, the relative mRNA expression of four hub genes (CRP, CD40LG, CCL20, and GZMB), and the protein expression level of two hub genes (CD40LG and GZMB) were consistent with the bioinformatics analysis results. Immune infiltration results further revealed that obstructive sleep apnea patients contained a higher proportion of pro-inflammatory M1 macrophages and a lower proportion of M2 macrophages. Spearman's correlation analysis showed that CD40LG was positively correlated with M1 macrophages and GZMB was negatively correlated with M2 macrophages. CD40LG and GZMB might play a vital role in the visceral adipose tissue homeostasis of obstructive sleep apnea patients. Their interaction with macrophages and involved pathways not only provides new insights for understanding molecular mechanisms but also be of great significance in discovering novel small molecules or other promising candidates as immunotherapies of OSA-associated metabolic complications.

Ceruloplasmin-Deficient Mice Show Dysregulation of Lipid Metabolism in Liver and Adipose Tissue Reduced by a Protein Replacement

Ceruloplasmin is a ferroxidase that plays a role in iron homeostasis; its deficiency fosters inter alia iron accumulation in the liver, which expresses the soluble form of the protein secreted into the bloodstream. Ceruloplasmin is also secreted by the adipose tissue, but its role in adipocytes has been poorly investigated. We hypothesized that ceruloplasmin might have a role in iron/lipid interplay. We investigated iron/lipid dysmetabolism in the liver and adipose tissue of the ceruloplasmin-deficient mouse (CpKO) model of aceruloplasminemia and evaluated the effectiveness of ceruloplasmin replacement. We found that CpKO mice were overweight, showing adipose tissue accumulation, liver iron deposition and steatosis. In the adipose tissue of CpKO mice, iron homeostasis was not altered. Conversely, the levels of adiponectin and leptin adipokines behaved opposite to the wild-type. Increased macrophage infiltration was observed in adipose tissue and liver of CpKO mice, indicating tissue inflammation. The treatment of CpKO mice with ceruloplasmin limited liver iron accumulation and steatosis without normalizing the expression of iron homeostasis-related proteins. In the CpKO mice, the protein replacement limited macrophage infiltration in both adipose and hepatic tissues reduced the level of serum triglycerides, and partially recovered adipokines levels in the adipose tissue. These results underline the link between iron and lipid dysmetabolism in ceruloplasmin-deficient mice, suggesting that ceruloplasmin in adipose tissue has an anti-inflammatory role rather than a role in iron homeostasis. Furthermore, these data also indicate that ceruloplasmin replacement therapy may be effective at a systemic level.

Abstract P065: Effects of metformin on breast tissue inflammation in premenopausal women with components of metabolic syndrome

Abstract Background: Obesity, with increasing worldwide prevalence, is associated with increased breast cancer burden. The association is attributed to multiple metabolic disturbances including chronic inflammation due to dysfunctional adipose tissue. Features of local breast adipose tissue inflammation such as macrophage infiltration and an enriched pro-inflammatory gene signature were recently reported in mouse models of obesity and in women with high adiposity or metabolic disorders. Strategies that can reduce obesity-induced chronic inflammation may lead to reduction of breast cancer risk. Metformin, a widely used anti-diabetic drug, exerts favorable effects on multiple metabolic disturbances. This study aims to evaluate the clinical effects of metformin on breast tissue inflammation. Methods: Macrophage infiltration and polarization were determined in breast core needle biopsies collected at baseline and 6 months after agent intervention from a Phase II randomized, double-blind, placebo-controlled trial of metformin in premenopausal women with components of metabolic syndrome. Macrophage infiltration was assessed using a pan macrophage marker (CD68) by immunohistochemistry (IHC). M1 and M2 macrophages were assessed using CD40 and CD206 surface markers, respectively, by IHC. The primary endpoint is the change in macrophage density in breast adipose tissue. Secondary endpoints include the change in macrophage density in breast stroma and epithelium tissues, the proportion of M1 (pro-inflammatory) and M2 (anti-inflammatory) macrophages in breast adipose, stroma, and epithelium tissues. Results: Baseline biopsies from 76 participants (40 in the metformin arm and 36 in the placebo arm) were available for CD68 analysis. The baseline CD68 density was 22.48 ± 3.25, 67.26 ± 9.68, 418.81± 71.02 (mean±SE) per mm2 in breast adipose, stroma, and epithelium tissues, respectively. Biopsies from 71 participants (34 in the metformin arm and 37 in the placebo arm) were available for CD68 analysis at 6 months. Comparing to placebo, metformin intervention led to a significant reduction in CD68 density in breast adipose tissue (p = 0.01) but did not change the CD68 density in breast epithelium and stroma tissues. Conclusion: Metformin intervention resulted in favorable changes in macrophage infiltration in breast adipose tissue in premenopausal women with component of metabolic syndrome. Studies are ongoing to evaluate the effects of metformin on macrophage polarization. Citation Format: Liane E. Pinto, Sara Centuori, Jose Guillen-Rodriguez, Denise J. Roe, Edgar Tapia, Pavani Chalasani, H-H. Sherry Chow. Effects of metformin on breast tissue inflammation in premenopausal women with components of metabolic syndrome. [abstract]. In: Proceedings of the AACR Special Conference: Precision Prevention, Early Detection, and Interception of Cancer; 2022 Nov 17-19; Austin, TX. Philadelphia (PA): AACR; Can Prev Res 2023;16(1 Suppl): Abstract nr P065.

Genetic ablation of diabetes-associated gene Ccdc92 reduces obesity and insulin resistance in mice

Multiple genome-wide association studies (GWAS) have identified specific genetic variants in the coiled-coil domain containing 92 (CCDC92) locus that is associated with obesity and type 2 diabetes in humans. However, the biological function of CCDC92 in obesity and insulin resistance remains to be explored. Utilizing wild-type (WT) and Ccdc92 whole-body knockout (KO) mice, we found that Ccdc92 KO reduced obesity and increased insulin sensitivity under high-fat diet (HFD) conditions. Ccdc92 KO inhibited macrophage infiltration and fibrosis in white adipose tissue (WAT), suggesting Ccdc92 ablation protects against adipose tissue dysfunction. Ccdc92 deletion also increased energy expenditure and further attenuated hepatic steatosis in mice on an HFD. Ccdc92 KO significantly inhibited the inflammatory response and suppressed the NLR Family Pyrin Domain Containing 3 (NLRP3) inflammasome in WAT. Altogether, we demonstrated the critical role of CCDC92 in metabolism, constituting a potential target for treating obesity and insulin resistance.

Dynamics of adipose tissue macrophage populations after gastric bypass surgery.

This case-control study aimed to analyze the dynamics of macrophage infiltration in subcutaneous adipose tissue following bariatric surgery or conservative treatment of obesity and to clarify whether these features predict the weight loss outcome after the surgery. Subcutaneous tissue samples taken before and 12 months after laparoscopic Roux-en-Y gastric bypass surgery (n=39) or conservative (n=43) treatment for obesity were analyzed. Fat cell size was determined, and with CD68 immunohistochemistry, crown-like structures (CLS) were counted and single macrophages were quantitated. A major decline in CLS density from 4.1 (SD 3.5) to 1.1 (SD 0.8) per 1000 fat cells (p < 0.000) was found, regardless of the degree of weight loss after the surgery. Surgery had no effect on the fraction of infiltrating single-cell macrophages in subcutaneous adipose tissue. The abundance of these macrophage populations before the intervention did not predict the degree of postsurgery weight loss or suboptimal response to the surgery. The effect of gastric bypass on adipose tissue inflammatory status associates closely with CLS density even in subjects with suboptimal weight loss. The study suggests that factors related to bypass surgery other than weight loss modify the inflammatory response in adipose tissue.

Obesity and diabetes - are they always together?

Obesity and type 2 diabetes mellitus (DM 2) are two interrelated metabolic diseases widespread throughout the developed world. However, up to 30% of individuals with a long history of obesity do not have a carbohydrate metabolism disorder. This article presents the results of a multi-year study of adipose tissue biology in obese individuals with DM 2 compared with individuals with the same history of obesity without DM 2. Comparative analysis of hormonal, cellular, and genetic factors in two groups of patients showed that DM 2 occurs in individuals with abnormal proliferation and adipogenic differentiation of mesenchymal stem cells (MSCs) of adipose tissue. It leads to adipocyte hypertrophy and inflammatory infiltration of adipose tissue macrophages, resulting in increased insulin resistance and diabetogenic effects. These disorders are due to abnormal expression of genes responsible for the proliferation and adipogenic differentiation of MSCs. The study of the possible reversibility of abnormal changes in adipose tissue MSCs in obese patients after significant weight loss and DM 2 remission appears to be a promising research direction. The ability to control adipose tissue progenitor cells may represent a new target for treating and preventing metabolic disorders in obesity.

Acetylation of PPARγ in macrophages promotes visceral fat degeneration in obesity.

Obesity is characterized by chronic, low-grade inflammation, which is driven by macrophage infiltration of adipose tissue. PPARγ is well established to have an anti-inflammatory function in macrophages, but the mechanism that regulates its function in these cells remains to be fully elucidated. PPARγ undergoes post-translational modifications (PTMs), including acetylation, to mediate ligand responses, including on metabolic functions. Here, we report that PPARγ acetylation in macrophages promotes their infiltration into adipose tissue, exacerbating metabolic dysregulation. We generated a mouse line that expresses a macrophage-specific, constitutive acetylation-mimetic form of PPARγ (K293Qflox/flox:LysM-cre, mK293Q) to dissect the role of PPARγ acetylation in macrophages. Upon high-fat diet feeding to stimulate macrophage infiltration into adipose tissue, we assessed the overall metabolic profile and tissue-specific phenotype of the mutant mice, including responses to the PPARγ agonist Rosiglitazone. Macrophage-specific PPARγ K293Q expression promotes proinflammatory macrophage infiltration and fibrosis in epididymal white adipose tissue, but not in subcutaneous or brown adipose tissue, leading to decreased energy expenditure, insulin sensitivity, glucose tolerance, and adipose tissue function. Furthermore, mK293Q mice are resistant to Rosiglitazone-induced improvements in adipose tissue remodeling. Our study reveals that acetylation is a new layer of PPARγ regulation in macrophage activation, and highlights the importance and potential therapeutic implications of such PTMs in regulating metabolism.

RF04 | PSUN313 A Natural Antibody Against Oxidized Phospholipids Improves Glucose Metabolism in Aging Mice

Abstract Oxidative stress-induced lipid peroxidation generates oxidized phospholipids (OxPL), such as oxidized phosphatidylcholine, that are pro-inflammatory moieties present on oxidized low density lipoproteins and apoptotic cells. OxPL have been implicated in the pathogenesis of cardiovascular, neurological, autoimmune, liver, and lung diseases. It has been shown earlier that OxPL decrease bone formation. Natural antibodies (NAb) produced by B-1 lymphocytes, bind OxPL and prevent their inflammatory activity. The NAb E06 blocks oxidized phosphatidylcholine, and transgenic expression of a single chain (scFv) form of the antigen-binding domain of E06 IgM (E06-scFv) prevents many age-associated diseases, such as atherosclerosis, non-alcoholic steatohepatitis and age-related bone loss. OxPL are also implicated in the pathogenesis of the metabolic syndrome and diabetes by either causing insulin resistance, increasing macrophage infiltration and inflammation in white adipose tissue, decreasing insulin gene expression, and/or causing death of pancreatic beta cells through induction of oxidative stress and amyloid protein misfolding. Consistent with this evidence, NAb produced by B-1b lymphocytes are protective against obesity associated inflammation, glucose intolerance, and insulin resistance. In the work reported here, we have investigated the impact of oxidized phosphatidylcholine on glucose metabolism and age–related glucose intolerance. To this end, we aged chow-fed female and male C57BL/6 E06-scFv transgenic mice (and their WT littermates) up to 22 and 24 months. Both male and female E06-scFv transgenic mice accumulated less fat mass than WT littermates during aging, as determined by sequential body composition measurements by DXA. Intraperitoneal glucose tolerance test, performed at 10 and at 15 months of age, showed that glucose tolerance was greater in both male and female E06-ScFv transgenic mice than WT littermates and did not differ from the glucose tolerance of young mice. Insulin sensitivity, measured by insulin tolerance test, was increased in 4- and 10-month-old old transgenic females and in 15-month-old transgenic males. There was no difference in food consumption calculated over 5 days or the production of glucose after pyruvate infusion, indicating similar liver gluconeogenesis in both strains. Physical activity or energy expenditure, measured by indirect calorimetry in 11-month-old females, was indistinguishable between transgenic and WT mice. However, E06-scFv transgenic mice exhibited a significant increase in the respiratory exchange ratio, indicating that utilization of glucose was the main metabolic source under basal conditions. Collectively, these results show that blocking oxidized phosphatidylcholine improves age–related glucose intolerance in mice fed a normal diet; hence, OxPL are major culprits of the aging-associated glucose intolerance. Therefore, targeting OxPL with a neutralizing antibody represents a novel therapeutic intervention that may simultaneously ameliorate several age-associated diseases, including the metabolic syndrome and diabetes. Presentation: Saturday, June 11, 2022 1:42 p.m. - 1:47 p.m., Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.

Metabolic Syndrome Ameliorated by 4-Methylesculetin by Reducing Hepatic Lipid Accumulation

Obesity is a chronic metabolic disease caused by an imbalance between energy intake and expenditure during a long period and is characterized by adipose tissue disfunction and hepatic steatosis. The aim of this study was to investigate the effect of 4-methylesculetin (4-ME), a coumarin derivative, upon adipose microenvironment and hepatic steatosis in mice induced by a high-fat diet (HFD), and to explore potential mechanisms of its beneficial effect on metabolic disorders. HFD-fed mice displayed visceral obesity, insulin resistance, and hepatic lipid accumulation, which was remarkably ameliorated by 4-ME treatment. Meanwhile, 4-ME ameliorated adipocyte hypertrophy, macrophage infiltration, hypoxia, and fibrosis in epididymal adipose tissue, thus improving the adipose tissue microenvironment. Furthermore, 4-ME reversed the increase in CD36, PPAR-γ, SREBP-1, and FASN, and the decrease in CPT-1A, PPAR-α, and Nrf2 translocation into the nucleus in livers of HFD mice and in FFA-incubated hepatocytes. Moreover, the beneficial effects of 4-ME upon lipid deposition and the expression of proteins related to lipid metabolism in FFA-induced LO2 cells were abolished by ML385, a specific Nrf2 inhibitor, indicating that Nrf2 is necessary for 4-ME to reduce hepatic lipid deposition. These findings suggested that 4-ME might be a potential lead compound candidate for preventing obesity and MAFLD.

Adipocyte size, adipose tissue fibrosis, macrophage infiltration and disease risk are different in younger and older individuals with childhood versus adulthood onset obesity.

The timing of obesity onset and age have been shown to affect the risk of obesity-related comorbidities, although the impact of each of these factors on markers of adipose tissue function remains unclear. The aim of this study was to determine whether differences in regional adipose tissue characteristics vary with age and age of obesity onset, and whether these differences are associated with the markers of cardiometabolic health. Adipose tissue samples were obtained from 80 female bariatric surgery candidates who were classified by age of obesity onset and age into 4 groups: (1) younger adults (<40 y) with childhood-onset obesity (<18 y) (Child-Young); (2) younger adults with adulthood-onset obesity (>18 y) (Adult-Young); (3) older adults (>55 y) with childhood-onset obesity (Child-Old); and (4) older adults with adulthood-onset obesity (Adult-Old). Adipocyte diameter, adipose tissue fibrosis, and macrophage infiltration were determined in subcutaneous (SAT) and visceral adipose tissue (VAT). Clinical parameters were obtained from participants' medical records. Visceral adipocyte size in the Child-Young group was the smallest of all the groups. Age affected visceral infiltration of M1-like cells with greater percent of M1-like cells in the Adult-Old and Child-Old groups. Though not significant, a stepwise increase in M2-like macrophages in VAT was observed with Adult-Young having the smallest followed by Adult-Old, Child-Young, and Child-Old having the greatest percent of M2-like macrophages. Pericellular fibrosis accumulation in SAT and VAT varied with both age and onset, particularly in the Child-Old group, which had the lowest fibrosis levels. Markers of cardiometabolic health (fasting glucose, glycated hemoglobin, total, HDL- and LDL-cholesterol and triglyceride concentrations) were positively and well-associated with adipose tissue characteristics of the Child-Old group but not of the Adult-Young group. Older adults with childhood-onset obesity, who had the greatest duration of obesity exposure, were particularly vulnerable to the cardiometabolic effects associated with perturbations in adipose tissue characteristics. These results suggest that age and age of obesity onset may have independent and cumulative effects on obesity pathology.