Dipeptidyl Peptidase 4 (DPP4) as A Novel Adipokine: Role in Metabolism and Fat Homeostasis

Soluble DPP4 promotes hepatocyte lipid accumulation via SOX2-SCD1 signaling and counteracts DPP4 inhibition

Dipeptidyl peptidase-4 (DPP4), a well-known target of antidiabetic therapy, is implicated in steatotic liver disease. However, its role in hepatic lipid metabolism, particularly the distinct functions of soluble DPP4 (sDPP4) and membrane-bound DPP4 (mbDPP4), remains unclear. Here, we identify SOX2 as a key mediator linking sDPP4 to hepatocyte lipid accumulation, uncovering a previously unreported regulatory mechanism. sDPP4 promotes free fatty acid (FFA)-induced lipid accumulation and triglyceride (TG) synthesis in hepatocytes by upregulating SOX2, a stemness-associated transcription factor. SOX2 induction increased the expression of stearoyl-coenzyme A desaturase 1 (SCD1), a key lipogenic enzyme, supporting the role of SOX2-SCD1 signaling in sDPP4-mediated hepatic steatosis. SOX2 silencing abolished these effects, confirming its requirement for sDPP4-induced lipid accumulation. Similarly, mbDPP4 overexpression increased FFA-induced lipid synthesis and SOX2 expression, while its knockdown suppressed these responses. Pharmacological inhibition of mbDPP4 activity reduced lipid accumulation and downregulated SOX2, SCD1, and fatty acid synthase expression. However, exogenous sDPP4 reversed these effects, counteracting the lipid-suppressing effect of DPP4 inhibition. In vivo, high-fat diet (HFD)-fed mice exhibited increased plasma sDPP4 levels, whereas hepatic mbDPP4 expression remained unchanged. This correlated with enhanced hepatic SOX2 expression, suggesting that elevated sDPP4 may contribute to hepatic lipid accumulation independent of mbDPP4 activity. Collectively, our findings highlight the role of sDPP4-SOX2 signaling in hepatic lipid accumulation and underscore the need to distinguish sDPP4 from mbDPP4 in steatotic liver disease. Targeting the sDPP4-SOX2 axis could be explored as a potential therapeutic approach for steatotic liver disease.

Insights into the Roles of GLP-1, DPP-4, and SGLT2 at the Crossroads of Cardiovascular, Renal, and Metabolic Pathophysiology

In recent years, new drugs for the treatment of type 2 diabetes (T2D) have been proposed, including glucagon-like peptide 1 (GLP-1) agonists or sodium-glucose cotransporter 2 (SGLT2) inhibitors and dipeptidyl peptidase-4 (DPP-4) inhibitors. Over time, some of these agents (in particular, GLP-1 agonists and SGLT2 inhibitors), which were initially developed for their glucose-lowering actions, have demonstrated significant beneficial pleiotropic effects, thus expanding their potential therapeutic applications. This review aims to discuss the mechanisms, pleiotropic effects, and therapeutic potential of GLP-1, DPP-4, and SGLT2, with a particular focus on their cardiorenal benefits beyond glycemic control.

Inhibition of DPP-4 Attenuates Endotoxemia-Induced NLRC4 Inflammasome and Inflammation in Visceral Adipose Tissue of Mice Fed a High-Fat Diet

Inflammasomes are protein complexes that trigger pro-inflammatory responses and promote many diseases, including adipose tissue dysfunction. Linagliptin (L), a DPP-4 inhibitor used for type 2 diabetes therapy, has putative anti-inflammatory effects. This work explores L effects on inflammasome regulation, inflammation, and adipose tissue dysfunction in obese mice. Male C57BL/6N mice were fed a normal chow (NC) diet, high-fat (HF) diet, or HF diet with L (HFL) for 15 weeks. Gene expression and histological examinations were performed on visceral (VAT) and subcutaneous (SAT) adipose tissue samples. Biomarkers were quantified on sera. Murine macrophages were utilized for in vitro analyses. L decreased HF-induced endotoxemia and circulating inflammatory indicators. Despite having no effect on body weight, L reduced VAT inflammation by decreasing endotoxemia-induced NLRC4 inflammasome, inflammation severity, and fat cell hypertrophy. Although SAT response differed from VAT, inflammation was slightly reduced in this tissue too. In vitro, L modulated inflammation by directly reducing the pro-inflammatory macrophage phenotype. In obesity, increased NLRC4 inflammasome expression links endotoxemia and VAT inflammation. L protected against endotoxemia, maybe by affecting gut permeability and VAT responses. The decreased polarization of macrophages toward a pro-inflammatory phenotype and the reduction in adipocyte hypertrophy are involved in the response to L.

Exploring How Adipose Tissue, Obesity, and Gender Influence the Immune Response to Vaccines: A Comprehensive Narrative Review

Vaccines represent an essential tool for the prevention of infectious diseases. Upon administration, a complex interaction occurs between the vaccine formulation and the recipient's immune system, ultimately resulting in protection against disease. Significant variability exists in individual and population responses to vaccination, and these differences remain the focus of the ongoing research. Notably, well-documented factors, such as age, gender, and genetic predisposition, influence immune responses. In contrast, the effects of overweight and obesity have not been as thoroughly investigated. The evidence indicates that a high body mass index (BMI) constitutes a significant risk factor for infections in general, with adipose tissue playing a crucial role in modulating the immune response. Furthermore, suboptimal levels of vaccine seroconversion have been observed among individuals with obesity. This review provides a plausible examination of the immunity and protection conferred by various vaccines in individuals with an overweight status, offering a comprehensive analysis of the mechanisms to enhance vaccination efficiency.

Comparative efficacy and safety of sitagliptin or gliclazide combined with metformin in treatment-naive patients with type 2 diabetes: A single-center, prospective, randomized, controlled, noninferiority study with genetic polymorphism analysis

BACKGROUND

This study evaluates the efficacy and safety of sitagliptin versus gliclazide, combined with metformin, in treatment-naive patients with type 2 diabetes mellitus (T2DM) and glucotoxicity.

METHODS

In this single-center, randomized, controlled noninferiority trial, 129 treatment-naive patients with T2DM with glucotoxicity (fasting plasma glucose [FPG] ≥ 200 mg/dL and glycated hemoglobin ≥ 9.0%) were randomized to receive sitagliptin plus metformin (n = 66) or gliclazide plus metformin (n = 63) for 12 weeks. Sitagliptin and gliclazide were given for the first 4 weeks, followed by metformin monotherapy for 8 weeks. Efficacy end points included changes in glycemic control, body weight, and β-cell function at baseline, 4 weeks, and 12 weeks.

RESULTS

After 12 weeks, mean glycated hemoglobin reductions were 4.03% in the sitagliptin group and 4.13% in the gliclazide group, with a mean difference of -0.097 (95% confidence interval, -0.648 to 0.453), confirming noninferiority. Both groups showed significant FPG reductions at 4 weeks (P < .05). The sitagliptin group achieved faster glycemic targets, greater FPG and body weight reductions, and higher rates of FPG < 6.1 mmol/L (26.2% vs 5.7%; P = .012). No significant differences were observed in β-cell function or hypoglycemia incidence (P > .05). Genetic analysis showed specific single-nucleotide polymorphisms affected drug efficacy: dipeptidyl peptidase-4 rs2909451 TT and rs4664443 GG genotypes showed lower efficacy with sitagliptin, while GLP1R rs3765467 AG and KCNJ11 rs2285676 CC genotypes responded better to sitagliptin.

CONCLUSION

Sitagliptin combined with metformin is noninferior to gliclazide combined with metformin in treatment-naive patients with T2DM with glucotoxicity. Genetic polymorphisms significantly affect drug efficacy, highlighting the importance of personalized medicine. The sitagliptin group achieved glycemic targets more quickly and had greater weight reductions without increased adverse effects.

DPP-IV as a potential candidate in anti-obesity and obesity-related diseases treatment

Along with social development and lifestyle changes, the number of overweight and obese patients worldwide is rising annually. Obesity is a chronic metabolic disease with complex etiology. Dipeptidyl peptidase IV (DPP-IV) is a novel adipokine with significantly elevated expression in the visceral fat of obese patients. DPP-IV is a molecule that regulates metabolic homeostasis and inflammatory processes. Through its enzymatic activity, it plays a significant part in achieving hypoglycemic and weight loss effects through various pathways. DPP-IV and DPP-IV inhibitors also have pleiotropic effects in modulating obesity-related diseases by reducing obesity-related inflammation, ameliorating inflammatory bowel disease (IBD), improving hepatic steatosis and lowering cardiovascular risk, and even decreasing the risk of novel coronavirus disease-19 (COVID-19). This paper reviews the mechanisms of action based on DPP-IV targets in obesity and metabolic homeostasis, as well as their active role in the treatment of chronic diseases associated with obesity.

The Impact of Gastrointestinal Hormones on Human Adipose Tissue Function

BACKGROUND

Obesity is a global issue, the development of which depends on many interacting factors. Among these, hormones secreted in the gastrointestinal tract play an important role. The aim of this review was to assess the impact of these hormones on the functions of adipose tissue.

METHODS

The analysis was based on the latest research concerning both adipose tissue and gastrointestinal hormones.

RESULTS

It was found that these hormones can significantly affect adipose tissue, both directly and indirectly. Some hormones, when secreted in excess, can stimulate adipose tissue formation processes, while others can inhibit them. The impact of hormones depends on the location and type of adipose tissue as well as the physiological state of the body. It should also be noted that no hormone acts in isolation but in close cooperation with other factors.

CONCLUSIONS

The relationship between gastrointestinal hormones and adipose tissue, and their role in obesity, is a complex and evolving field of study. Further research is necessary, particularly into the interactions between hormones and other factors, as well as their mutual interactions.

Adipokines in the Crosstalk between Adipose Tissues and Other Organs: Implications in Cardiometabolic Diseases

Adipose tissue was previously regarded as a dormant organ for lipid storage until the identification of adiponectin and leptin in the early 1990s. This revelation unveiled the dynamic endocrine function of adipose tissue, which has expanded further. Adipose tissue has emerged in recent decades as a multifunctional organ that plays a significant role in energy metabolism and homeostasis. Currently, it is evident that adipose tissue primarily performs its function by secreting a diverse array of signaling molecules known as adipokines. Apart from their pivotal function in energy expenditure and metabolism regulation, these adipokines exert significant influence over a multitude of biological processes, including but not limited to inflammation, thermoregulation, immune response, vascular function, and insulin sensitivity. Adipokines are pivotal in regulating numerous biological processes within adipose tissue and facilitating communication between adipose tissue and various organs, including the brain, gut, pancreas, endothelial cells, liver, muscle, and more. Dysregulated adipokines have been implicated in several metabolic diseases, like obesity and diabetes, as well as cardiovascular diseases. In this article, we attempted to describe the significance of adipokines in developing metabolic and cardiovascular diseases and highlight their role in the crosstalk between adipose tissues and other tissues and organs.

Teneligliptin: A potential therapeutic approach for diabetic cardiomyopathy

In this editorial, we comment on the article by Zhang et al. Diabetes mellitus is a chronic disorder associated with several complications like cardiomyopathy, neuropathy, and retinopathy. Diabetes prevalence is increasing worldwide. Multiple diabetes medications are prescribed based on individual patients' needs. However, the exact mechanisms by which many of these drugs exert their pro-tective effects remain unclear. Zhang et al elucidates molecular mechanisms undelaying cardioprotective effect of the dipeptidyl peptidase-IV inhibitor, teneligliptin. Briefly, teneligliptin alleviates the activation of NOD-like receptor protein 3 inflammasome, a multiprotein complex that plays a pivotal role in regulating the innate immune system and inflammatory signaling. Suppression of NOD-like receptor protein 3 inflammasome activity reduces the expression of cytokines, oxygen radicals and inflammation. These findings highlight teneligliptin as an anti-diabetic cardioprotective reagent.

Excessive accumulation of epicardial adipose tissue promotes microvascular obstruction formation after myocardial ischemia/reperfusion through modulating macrophages polarization

BACKGROUND

Owing to its unique location and multifaceted metabolic functions, epicardial adipose tissue (EAT) is gradually emerging as a new metabolic target for coronary artery disease risk stratification. Microvascular obstruction (MVO) has been recognized as an independent risk factor for unfavorable prognosis in acute myocardial infarction patients. However, the concrete role of EAT in the pathogenesis of MVO formation in individuals with ST-segment elevation myocardial infarction (STEMI) remains unclear. The objective of the study is to evaluate the correlation between EAT accumulation and MVO formation measured by cardiac magnetic resonance (CMR) in STEMI patients and clarify the underlying mechanisms involved in this relationship.

METHODS

Firstly, we utilized CMR technique to explore the association of EAT distribution and quantity with MVO formation in patients with STEMI. Then we utilized a mouse model with EAT depletion to explore how EAT affected MVO formation under the circumstances of myocardial ischemia/reperfusion (I/R) injury. We further investigated the immunomodulatory effect of EAT on macrophages through co-culture experiments. Finally, we searched for new therapeutic strategies targeting EAT to prevent MVO formation.

RESULTS

The increase of left atrioventricular EAT mass index was independently associated with MVO formation. We also found that increased circulating levels of DPP4 and high DPP4 activity seemed to be associated with EAT increase. EAT accumulation acted as a pro-inflammatory mediator boosting the transition of macrophages towards inflammatory phenotype in myocardial I/R injury through secreting inflammatory EVs. Furthermore, our study declared the potential therapeutic effects of GLP-1 receptor agonist and GLP-1/GLP-2 receptor dual agonist for MVO prevention were at least partially ascribed to its impact on EAT modulation.

CONCLUSIONS

Our work for the first time demonstrated that excessive accumulation of EAT promoted MVO formation by promoting the polarization state of cardiac macrophages towards an inflammatory phenotype. Furthermore, this study identified a very promising therapeutic strategy, GLP-1/GLP-2 receptor dual agonist, targeting EAT for MVO prevention following myocardial I/R injury.

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 in vivo and in vitro. 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. In vitro, 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.

Increased Thyroid DPP4 Expression Is Associated With Inflammatory Process in Patients With Hashimoto Thyroiditis

CONTEXT

Dipeptidyl peptidase-4 (DPP4) is originally described as a surface protein in lymphocytes. Lymphocyte infiltration and subsequent destruction of thyroid tissue have been considered as the central pathological mechanism in Hashimoto thyroiditis (HT).

OBJECTIVE

The present study aimed to investigate DPP4 expression in peripheral blood and thyroid tissue in HT patients, and explore the role of DPP4 in the pathophysiological process of HT.

METHODS

This case-control study recruited 40 drug-naive HT patients and 81 control individuals. Peripheral blood and thyroid specimens were collected for assessing the expression and activity of DPP4. Moreover, single-cell RNA sequencing (scRNA-seq) analysis of 6 "para-tumor tissues" samples from scRNA-seq data set GSE184362 and in vitro cell experiments were also conducted.

RESULTS

The HT patients had similar DPP4 serum concentration and activity as the controls. However, the expression and activity of DPP4 was significantly increased in the thyroid of the HT group than in the control group. The scRNA-seq analysis showed that DPP4 expression was significantly increased in the HT group, and mainly expressed in T cells. Further in vitro studies showed that inhibition of lymphocyte DPP4 activity with sitagliptin downregulated the production of inflammatory factors in co-cultured thyroid cells.

CONCLUSION

DPP4 expression was significantly increased in the thyroid of the HT group compared with the control group, and was mainly localized in the lymphocytes. Inhibition of lymphocyte DPP4 activity reduced the production of inflammatory factors in co-cultured thyroid cells. Therefore, inhibition of DPP4 may have a beneficial effect by alleviating inflammatory reactions in HT patients.

New Mediators in the Crosstalk between Different Adipose Tissues

Adipose tissue is a multifunctional organ that regulates many physiological processes such as energy homeostasis, nutrition, the regulation of insulin sensitivity, body temperature, and immune response. In this review, we highlight the relevance of the different mediators that control adipose tissue activity through a systematic review of the main players present in white and brown adipose tissues. Among them, inflammatory mediators secreted by the adipose tissue, such as classical adipokines and more recent ones, elements of the immune system infiltrated into the adipose tissue (certain cell types and interleukins), as well as the role of intestinal microbiota and derived metabolites, have been reviewed. Furthermore, anti-obesity mediators that promote the activation of beige adipose tissue, e.g., myokines, thyroid hormones, amino acids, and both long and micro RNAs, are exhaustively examined. Finally, we also analyze therapeutic strategies based on those mediators that have been described to date. In conclusion, novel regulators of obesity, such as microRNAs or microbiota, are being characterized and are promising tools to treat obesity in the future.

Contribution of amino acids in the active site of dipeptidyl peptidase 4 to the catalytic action of the enzyme

Dipeptidyl peptidase 4 (DP4)/CD26 regulates the biological function of various peptide hormones by releasing dipeptides from their N-terminus. The enzyme is a prominent target for the treatment of type-2 diabetes and various DP4 inhibitors have been developed in recent years, but their efficacy and side effects are still an issue. Many available crystal structures of the enzyme give a static picture about enzyme-ligand interactions, but the influence of amino acids in the active centre on binding and single catalysis steps can only be judged by mutagenesis studies. In order to elucidate their contribution to inhibitor binding and substrate catalysis, especially in discriminating the P1 amino acid of substrates, the amino acids R125, N710, E205 and E206 were investigated by mutagenesis studies. Our studies demonstrated, that N710 is essential for the catalysis of dipeptide substrates. We found that R125 is not important for dipeptide binding but interacts in the P1`position of the peptide backbone. In contrast to dipeptide substrates both amino acids play an essential role in the binding and arrangement of long natural substrates, particularly if lacking proline in the P1 position. Thus, it can be assumed that the amino acids R125 and N710 are important in the DP4 catalysed substrate hydrolysis by interacting with the peptide backbone of substrates up- and downstream of the cleavage site. Furthermore, we confirmed the important role of the amino acids E205 and E206. However, NP Y, displaying proline in P1 position, is still processed without the participation of E205 or E206.

Exploring the clinical utility of DPP-IV and SGLT2 inhibitors in papillary thyroid cancer: a literature review

In the realm of clinical management, Papillary Thyroid Cancer (PTC) stands out as a prevalent thyroid malignancy, characterized by significant metabolic challenges, particularly in the context of carbohydrate metabolism. Recent studies have unveiled promising applications of Dipeptidyl Peptidase-IV (DPP-IV) and Sodium-Glucose Cotransporter 2 (SGLT2) inhibitors, which are conventionally employed in the treatment of type 2 diabetes mellitus (T2DM), as potential adjuncts in anticancer therapy. DPP-IV and SGLT2 inhibitors can be imply to counteract the Warburg effect in cancer, with a specific focus on PTC, owing to their potential metabolic advantages and their influence on the tumor microenvironment, achieved by imposing restrictions on glucose accessibility. Consequently, a comprehensive review has been undertaken, involving meticulous examination of the existing body of evidence pertaining to the utilization of DPP-IV and SGLT2 inhibitors in the context of PTC. The mechanisms of action inherent to these inhibitors have been thoroughly explored, drawing upon insights derived from preclinical investigations. Furthermore, this review initiates discussions concerning the implications for future research directions and the formulation of innovative therapeutic strategies for PTC. As the intricate interplay between carbohydrate metabolism, the Warburg effect, and cancer progression garners increasing attention, attaining a comprehensive understanding of the roles played by DPP-IV and SGLT2 inhibitors in PTC management may serve as the cornerstone for novel approaches aimed at enhancing patient care and broadening the spectrum of available therapeutic modalities.

Immunomodulatory activity of dipeptidyl peptidase-4 inhibitors in immune-related diseases

Dipeptidyl peptidase-4 (DPP-4), also known as CD26, is a 110-kDa cell surface glycoprotein with enzymatic and signal transducing activity. DPP-4/CD26 is expressed by various cells, including CD4+ and CD8+ T cells, B cells, dendritic cells, macrophages, and NK cells. DPP-4 inhibitors (DPP-4i) were introduced to clinics in 2006 as new oral antihyperglycemic drugs approved for type 2 diabetes mellitus treatment. In addition to glucose-lowering effects, emerging data, from clinical studies and their animal models, suggest that DPP-4i could display anti-inflammatory and immunomodulatory effects as well, but the molecular and immunological mechanisms of these actions are insufficiently investigated. This review focuses on the modulatory activity of DPP-4i in the immune system and the possible application of DPP-4i in other immune-related diseases in patients with or without diabetes.

Dipeptidyl Peptidase 4 Stimulation Induces Adipogenesis-Related Gene Expression of Adipose Stromal Cells

Adipogenesis has emerged as a new therapeutic target for regulating metabolism and achieving anti-inflammatory and anti-atherosclerotic effects via the release of adiponectin. However, at present, the effects and mechanism of action of dipeptidyl peptidase 4 (DPP4) stimulation on adiponectin production and adipogenesis have not been clarified. Here, we investigated the effects of DPP4 stimulation with monocyte chemoattractant protein-1 (MCP-1) on platelet-derived growth factor receptor alpha (PDGFRα) expression in adipose tissue and blood adiponectin levels. Stromal vascular fractions (SVFs) purified from human subcutaneous adipose tissue and inguinal adipose tissue of obese and diabetic (Leprdb/db) mice were treated with 50 ng of MCP-1 and plasma from control (Lepr+/+) mice supplemented with 10 ng or 50 ng of MCP-1. Treatment of SVFs from human subcutaneous adipose tissues with 50 ng of MCP-1 significantly increased AdipoQ, DPP4, peroxisome proliferator-activated receptor gamma (PPARγ), fatty-acid-binding protein (FABP4), and SERBF1 mRNA expression. MCP-1-supplemented plasma increased adiponectin, CCAAT-Enhancer-binding protein alpha (C/EBPα), DPP4, IL-33, and PDGFRα mRNA expression and adiponectin and DPP4 protein expression, while decreasing the expression of IL-10 mRNA in SVFs compared with the levels in the plasma treatment group. MCP-1-supplemented plasma was shown to increase PPARγ, PPARγ2, adiponectin, DPP4, and FABP4 and decrease IL-10 mRNA expression in PDGFRα cells from adipose tissue. Meanwhile, MCP-1-supplemented plasma increased MCP-1, PDGFRα, TNFα, adiponectin, and IL-1β and decreased IL-10 and FOXP3 mRNA expression in DPP4 cells. Moreover, the injection of MCP-1-supplemented plasma into adipose tissue increased the proportion of DPP4+ cells among PDGFRα+ cells from adipose tissue and plasma adiponectin levels of Leprdb/db mice compared with the levels in the plasma injection group. Our results demonstrate that DPP4+ cells are important adipose progenitor cells. Stimulation of DPP4 with MCP-1 increases adipogenesis-related gene expression and the population of DPP4+ cells among PDGFRα+ cells in SVFs and blood adiponectin levels. DPP4 stimulation could be a novel therapy to increase local adipogenesis and systemic adiponectin levels.

Dipeptidyl peptidase 4 inhibitor reduces tumor-associated macrophages and enhances anti-PD-L1-mediated tumor suppression in non-small cell lung cancer

PURPOSE

The efficacy of immune checkpoint inhibitors such as programmed cell death ligand 1 (PD-L1) antibodies in non-small cell lung cancer (NSCLC) is limited, and combined use with other therapies is recommended. Dipeptidyl peptidase 4 (DPP4) inhibitors, a class of small molecule inhibitors, are highly effective for treating type 2 diabetes. Emerging evidence implicates DPP4 inhibitors as immunomodulators that modify aspects of innate and adaptive immunity. We evaluated the combination of a DPP4 inhibitor (anagliptin) and PD-L1 blockade in an NSCLC mouse model.

METHODS

The effect of the combination of anti-PD-L1 and anagliptin was evaluated in subcutaneous mouse models of NSCLC. Tumor-infiltrating immune cells were analyzed by flow cytometry. Bone marrow-derived monocytes of C57BL/6 mice were isolated in vitro to examine the underlying mechanism of anagliptin on the differentiation and polarization of macrophage.

RESULTS

Anagliptin dramatically improved the efficacy of PD-L1 antibody monotherapy by inhibiting macrophage formation and M2 polarization in the tumor microenvironment. Mechanistically, anagliptin suppressed the production of reactive oxygen species in bone marrow monocytes by inhibiting NOX1 and NOX2 expression induced by macrophage colony-stimulating factor, reduced late ERK signaling pathway activation, and inhibited monocyte-macrophage differentiation. However, the inhibitory effect was reactivated by lipopolysaccharide and interferon-gamma interacting with corresponding receptors during M1 macrophage polarization, but not M2.

CONCLUSIONS

Anagliptin can enhance PD-L1 blockade efficacy in NSCLC by inhibiting macrophage differentiation and M2 macrophage polarization, and combination therapy may be a promising strategy for treating PD-L1 blockade therapy-resistant patients with NSCLC.

Glucagon-like peptide-1 and glucagon-like peptide-2 regulation during human liver regeneration

Accumulating evidence suggests that metabolic demands of the regenerating liver are met via lipid metabolism and critical regulators of this process. As such, glucagon-like peptide-1 (GLP-1) and glucagon-like peptide-2 (GLP-2) critically affect hepatic regeneration in rodent models. The present study aimed to evaluate potential alterations and dynamics of circulating GLP-1 and GLP-2 in patients undergoing liver resections, focusing on post-hepatectomy liver failure (PHLF). GLP-1, GLP-2, Interleukin-6 (IL-6) and parameters of lipid metabolism were determined perioperatively in fasting plasma of 46 patients, who underwent liver resection. GLP-1 and GLP-2 demonstrated a rapid and consistently inverse time course during hepatic regeneration with a significant decrease of GLP-1 and increase of GLP-2 on POD1. Importantly, these postoperative dynamics were significantly more pronounced when PHLF occurred. Of note, the extent of resection or development of complications were not associated with these alterations. IL-6 mirrored the time course of GLP-2. Assessing the main degradation protein dipeptidyl peptidase 4 (DPP4) no significant association with either GLP-1 or -2 could be found. Additionally, in PHLF distinct postoperative declines in plasma lipid parameters were present and correlated with GLP-2 dynamics. Our data suggest dynamic inverse regulation of GLP-1 and GLP-2 during liver regeneration, rather caused by an increase in expression/release than by changes in degradation capacity and might be associated with inflammatory responses. Their close association with circulating markers of lipid metabolism and insufficient hepatic regeneration after liver surgery suggest a critical involvement during these processes in humans.

The Role of Adipokines in Inflammatory Mechanisms of Obesity

Adipokines are currently widely studied cellular signaling proteins produced by adipose tissue and involved in various processes, including inflammation; energy and appetite modulation; lipid and glucose metabolism; insulin sensitivity; endothelial cell functioning; angiogenesis; the regulation of blood pressure; and hemostasis. The current review attempted to highlight the key functions of adipokines in the inflammatory mechanisms of obesity, its complications, and its associated diseases. An extensive search for materials on the role of adipokines in the pathogenesis of obesity was conducted online using the PubMed and Scopus databases until October 2022.