Free Fatty Acid Increases the Expression of NLRP3-Caspase1 in Adipose Tissue Macrophages in Obese Severe Acute Pancreatitis

Exploring lipidome mediated inflammatory pathways in acute pancreatitis using mendelian randomization

Acute pancreatitis (AP) is a severe gastrointestinal condition with an increasing incidence of hyperlipidemic etiology. The investigation employed a two-sample, bidirectional Mendelian randomization method to investigate potential causal relationship between lipidome profiles, inflammatory mediators, and AP. Exploration of genetic variants across the genome in a study population of 10,630 AP cases and 844,679 non-AP individuals revealed multiple lipidome entities significantly associated with AP risk. The study identified 23 lipid species with unidirectional causal effects on AP after accounting for heterogeneity, pleiotropy, and potential reverse causation. Additionally, five inflammatory factors (CD5, IL-13, MMP-1, STAMBP, TNFRSF9) showed significant potential causal relationship with AP. Further analysis elucidated the intricate interplay between specific lipid species and inflammatory mediators in influencing AP incidence. Notably, Sterol ester (27:1/20:4) and several phosphatidylcholine species, including PC (17:0_20:4), PC (18:0_20:4), PC (18:0_20:5), and PC (O-18:2_20:4), were negatively associated with AP risk. This protective effect was partially mediated through decreased levels of inflammatory markers, particularly STAMBP and MMP-1. The study found that these phosphatidylcholines and sterol esters significantly reduced the levels of these pro-inflammatory factors, thereby potentially mitigating AP risk. Conversely, Phosphatidylinositol (16:0_18:1) demonstrated a positive association with AP risk. This detrimental effect was partially mediated by increased levels of MMP-1 and STAMBP, suggesting a pro-inflammatory mechanism. The study provides evidence that this specific phosphatidylinositol species may exacerbate AP risk by promoting inflammatory pathways. These findings elucidate the complex interplay between lipid metabolites, inflammation, and AP pathogenesis, potentially informing novel therapeutic strategies. The study highlights the utility of Mendelian randomization in uncovering potential causal relationship in AP. It underscores the requirement for further study into the molecular mechanisms underlying lipid-mediated inflammation in AP, particularly the roles of phosphatidylcholines and sterol esters in modulating inflammatory responses. Further studies are warranted to confirm our observations in laboratory models and assess their translational value in developing AP preventive and therapeutic strategies.

Blockage of ATGL-mediated breakdown of lipid droplets in microglia alleviates neuroinflammatory and behavioural responses to lipopolysaccharides

Lipid droplets (LD) are triglyceride storing organelles that have emerged as an important component of cellular inflammatory responses. LD lipolysis via adipose triglyceride lipase (ATGL), the enzyme that catalyses the rate-limiting step of triglyceride lipolysis, regulates inflammation in peripheral immune and non-immune cells. ATGL elicits both pro- and anti-inflammatory responses in the periphery in a cell-type dependent manner. The present study determined the impact of ATGL inhibition and microglia-specific ATGL genetic loss-of-function on acute inflammatory and behavioural responses to pro-inflammatory insult. First, we evaluated the impact of lipolysis inhibition on lipopolysaccharide (LPS)-induced expression and secretion of cytokines and phagocytosis in mouse primary microglia cultures. Lipase inhibitors (ORlistat and ATGListatin) and LPS led to LD accumulation in microglia. Pan-lipase inhibition with ORlistat alleviated LPS-induced expression of IL-1β and IL-6. Specific inhibition of ATGL had a similar action on CCL2, IL-1β and IL-6 expression in both neonatal and adult microglia cultures. CCL2 and IL-6 secretion were also reduced by ATGListatin or knockdown of ATGL. ATGListatin increased phagocytosis in neonatal cultures independently from LPS treatment. Second, targeted and untargeted lipid profiling revealed that ATGListatin reduced LPS-induced generation of pro-inflammatory prostanoids and modulated ceramide species in neonatal microglia. Finally, the role of microglial ATGL in neuroinflammation was assessed using a novel microglia-specific and inducible ATGL knockout mouse model. Loss of microglial ATGL in adult male mice dampened LPS-induced expression of IL-6 and IL-1β and microglial density. LPS-induced sickness- and anxiety-like behaviours were also reduced in male mice with loss of ATGL in microglia. Together, our results demonstrate potent anti-inflammatory effects produced by pharmacological or genetic inhibition of ATGL-mediated triglyceride lipolysis and thereby propose that supressing microglial LD lipolysis has beneficial actions in acute neuroinflammatory conditions.

Review on the role of nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome pathway in diabetes: mechanistic insights and therapeutic implications

This review explores the pivotal role of the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome in the pathogenesis of diabetes and its complications, highlighting the therapeutic potential of various oral hypoglycemic drugs targeting this pathway. NLRP3 inflammasome activation, triggered by metabolic stressors like hyperglycemia, hyperlipidemia, and free fatty acids (FFAs), leads to the release of pro-inflammatory cytokines interleukin-1β and interleukin-18, driving insulin resistance, pancreatic β-cell dysfunction, and systemic inflammation. These processes contribute to diabetic complications such as nephropathy, neuropathy, retinopathy, and cardiovascular diseases (CVD). Here we discuss the various transcriptional, epigenetic, and gut microbiome mediated regulation of NLRP3 activation in diabetes. Different classes of oral hypoglycemic drugs modulate NLRP3 inflammasome activity through various mechanisms: sulfonylureas inhibit NLRP3 activation and reduce inflammatory cytokine levels; sodium-glucose co-transporter 2 inhibitors (SGLT2i) suppress inflammasome activity by reducing oxidative stress and modulating intracellular signaling pathways; dipeptidyl peptidase-4 inhibitors mitigate inflammasome activation, protecting against renal and vascular complications; glucagon-like peptide-1 receptor agonists attenuate NLRP3 activity, reducing inflammation and improving metabolic outcomes; alpha-glucosidase inhibitors and thiazolidinediones exhibit anti-inflammatory properties by directly inhibiting NLRP3 activation. Agents that specifically target NLRP3 and inhibit their activation have been identified recently such as MCC950, Anakinra, CY-09, and many more. Targeting the NLRP3 inflammasome, thus, presents a promising strategy for managing diabetes and its complications, with oral hypoglycemic drugs offering dual benefits of glycemic control and inflammation reduction. Further research into the specific mechanisms and long-term effects of these drugs on NLRP3 inflammasome activity is warranted.

Efficacy and safety of orlistat in male patients with overweight/obesity and hyperuricemia: results of a randomized, double-blind, placebo-controlled trial

BACKGROUND

Obesity is associated with elevated serum uric acid (SUA) levels and frequent gout flares. Losing weight can reduce the SUA level and gout flares. The effect of orlistat on SUA levels and gout flares in patients with overweight/obesity and hyperuricemia (HUA) has not been extensively studied. This study investigated the effects of orlistat on SUA levels and gout flares compared to placebo in overweight and obese patients with HUA.

METHODS

A total of 72 Chinese patients with overweight/obesity and HUA were randomly divided into a placebo group (35, 48.6%) and an orlistat group (37, 51.4%); the trial lasted 12 weeks. The primary endpoints were the relative changes in body weight, the SUA level, and gout flares in the per-protocol population.

RESULTS

Orlistat reduced the proportion of patients with gout flares (log-rank P = 0.023, hazard ratio = 0.31, 95% confidence interval 0.11-0.85). There was no significant difference in SUA level between the two groups. The average weight loss of the orlistat group was 2.85 kg, and the average weight loss of the placebo group was 0.76 kg. The weight loss in the orlistat group was significantly greater than that in the control group (P < 0.05).

CONCLUSIONS

This study is the first to demonstrate that orlistat has no significant effect on SUA levels in patients with overweight/obesity and HUA. The utility of orlistat as an adjunct therapy to prevent gout flares during weight loss in patients with HUA was emphasized.

TRIAL REGISTRATION

Clinicaltrials.gov NCT05496075.

The roles of tissue-resident macrophages in sepsis-associated organ dysfunction

Sepsis, a syndrome caused by a dysregulated host response to infection and characterized by life-threatening organ dysfunction, particularly septic shock and sepsis-associated organ dysfunction (SAOD), is a medical emergency associated with high morbidity, high mortality, and long-term sequelae. Tissue-resident macrophages (TRMs) are a subpopulation of macrophages derived primarily from yolk sac progenitors and fetal liver during embryogenesis, located primarily in non-lymphoid tissues in adulthood, capable of local self-renewal independent of hematopoiesis, and developmentally and functionally restricted to the non-lymphoid organs in which they reside. TRMs are the first line of defense against life-threatening conditions such as sepsis, tumor growth, traumatic-associated organ injury, and surgical-associated injury. In the context of sepsis, TRMs can be considered as angels or demons involved in organ injury. Our proposal is that sepsis, septic shock, and SAOD can be attenuated by modulating TRMs in different organs. This review summarizes the pathophysiological mechanisms of TRMs in different organs or tissues involved in the development and progression of sepsis.

Plasma Exosomes Aggravate Acute Pancreatitis by Promoting M1 Polarization of Adipose Tissue Macrophages in Obesity-Related Severe Acute Pancreatitis

BACKGROUND AND AIMS

Obesity may be a risk factor for severe acute pancreatitis (SAP). However, its precise mechanism is not yet fully understood.

METHODS

We fed rats with a standard laboratory diet (SLD) and a high-fat diet (HFD). SAP model rats were established by retrograde injection of sodium taurocholate. Serum non-esterified fatty acids (NEFAs), lipase (LPS), and myeloperoxidase (MPO) were measured, as were adipose IL-1, IL-6, IL-10, and TNF-α levels. HE staining was performed to determine the severity of pancreatitis. Serum exosomes were extracted from rats with obesity-related SAP, verified by transmission electron microscopy (TEM) and western blot analysis, and co-cultured with THP-1 cells. Flow cytometry was used to analyze the M1 and M2 phenotypes of macrophages in adipose tissues and THP-1 cells. Q-PCR was used to analyze the levels of IL-1, IL-6, IL-10, and TNF-α in each group of cells.

RESULTS

The body weight and serum NEFA concentrations of rats in the HFD group were significantly higher than those in the SLD group. Adipose tissue macrophages in the HFD group exhibited a higher percentage of the M1 type than those in the SLD group. The severity of pancreatitis were significantly increased in the HFD + SAP group. Pro-inflammatory macrophages and cytokines were significantly higher in the HFD + SAP group and THP-1 cells co-cultured with serum exosomes extracted from rats with obesity-related SAP.

CONCLUSIONS

Obesity might worsen the severity of pancreatitis by amplifying the immune response and activating M1 polarization in adipose tissue macrophages via serum exosomes in rats of obesity-related SAP. In our study, we isolated exosomes from the serum of mice with obesity-related SAP. After inducing THP-1 cells to become M0-typed macrophages, we co-cultured the cells with exosomes and observed that exosomes from obesity-related SAP increased the proportion of M1-typed macrophages and promoted the release of pro-inflammatory factors such as IL-1, IL-6, and TNF. Therefore, obesity might worsen the severity of pancreatitis by amplifying the immune response and activating M1 polarization in adipose tissue macrophages via serum exosomes in rats of obesity-related SAP.

Murine Chronic Pancreatitis Model Induced by Partial Ligation of the Pancreatic Duct Encapsulates the Profile of Macrophage in Human Chronic Pancreatitis

Immune responses are an integral part of the pathogenesis of pancreatitis. Studies applying the mouse model of pancreatitis induced by partial ligation of the pancreatic duct to explore the pancreatic immune microenvironment are still lacking. The aim of the present study is to explore the macrophage profile and associated regulatory mechanisms in mouse pancreatitis, as well as the correlation with human chronic pancreatitis (CP). In the present study, the mouse model of pancreatitis was induced by partial ligation of the pancreatic duct. Mice in the acute phase were sacrificed at 0, 4, 8, 16, 32, 72 h after ligation, while mice in the chronic phase were sacrificed at 7, 14, 21, 28 days after ligation. We found that the pancreatic pathological score, expression of TNF-α and IL-6 were elevated over time and peaked at 72h in the acute phase, while in the chronic phase, the degree of pancreatic fibrosis peaked at day 21 after ligation. Pancreatic M1 macrophages and pyroptotic macrophages showed a decreasing trend over time, whereas M2 macrophages gradually rose and peaked at day 21. IL-4 is involved in the development of CP and is mainly derived from pancreatic stellate cells (PSCs). The murine pancreatitis model constructed by partial ligation of the pancreatic duct, especially the CP model, can ideally simulate human CP caused by obstructive etiologies in terms of morphological alterations and immune microenvironment characteristics.