The Interplay of Adipokines and Pancreatic Beta Cells in Metabolic Regulation and Diabetes

From lipids to glucose: Investigating the role of dyslipidemia in the risk of insulin resistance

Dyslipidemia is recognized as one of the most prevalent metabolic disorders and is frequently associated with other prevalent conditions, particularly diabetes mellitus. There appears to be a bidirectional connection between these two metabolic disorders. While considerable research has focused on how insulin resistance can lead to lipid abnormalities, the reverse relationship specifically, how dyslipidemia could assist in developing insulin resistance and diabetes mellitus has received relatively less attention. This review aims to comprehensively evaluate the mechanisms through which dyslipidemia can induce insulin resistance. Dyslipidemia is primarily classified into three main categories: hypercholesterolemia, hypertriglyceridemia, and low levels of HDL. These conditions may promote insulin resistance across multiple pathways, including the accumulation of lipid metabolites, dysfunction of pancreatic β-cells, increased reactive oxygen species, endoplasmic reticulum stress and inflammation, endothelial dysfunction, alterations in adiponectin levels, changes in bile acid composition and concentration, and dysbiosis of gut microbiota. However, further investigation is required to fully elucidate the cellular and molecular mechanisms underlying the relationship between lipid disorders and insulin resistance. Emphasizing such research could facilitate the development of therapeutic strategies targeting both conditions simultaneously.

Analysis of postprandial time trends and influencing factors of blood glucose and insulin in type 2 diabetes mellitus (T2DM) with metabolic dysfunction-associated steatotic liver disease (MASLD): a retrospective study based on propensity score matching (PSM)

BACKGROUND

Metabolic dysfunction-associated steatotic liver disease (MASLD) and type 2 diabetes mellitus (T2DM) are increasingly prevalent metabolic disorders worldwide, with a complex bidirectional relationship between them. Currently, there is a lack of research on the trajectories of blood glucose and insulin concentration over time after eating in patients with MASLD and T2DM.

METHODS

This clinical cohort included diagnosed T2DM patients in a large hospital over the past five years, was divided into an observation group (with MASLD) and a control group (without MASLD). The postprandial time trends of blood glucose and insulin concentration were analysed within two hours after eating. A strategy of backward iterative feature elimination combined with propensity score matching (PSM) was employed to screen for potential associated factors that might influence these trends.

RESULTS

In total, there were 521 in the observation group and 373 in the control group. In terms of blood glucose, the postprandial time-concentration trajectories for both groups shown a significant time main effect (F = 1145.567, P < 0.001), a significant group main effect (F = 15.340, P < 0.001), and a significant time*group interaction effect (F = 2.873, P = 0.035); After matching all the factors, the time*group interaction effect of blood glucose was not significant, but the differences from group main effect still existed. In terms of insulin, the postprandial time-concentration trajectories for both groups shown a significant time main effect (F = 309.429, P < 0.001), a significant group main effect (F = 6.319, P < 0.012), and a significant time*group interaction effect (F = 20.057, P < 0.001), but the trajectories crossed; After matching 4 factors such as Smoking, Essential Hypertension (EH), Body Mass Index (BMI), Triglyceride (TG) and Ca2+, neither the group main effect nor the time*group interaction effect on insulin was significant any more.

CONCLUSION

The postprandial trends of blood glucose and insulin concentration over time shown significant differences between T2DM patients with and without MASLD. IL-6 might be associated with the insulin resistance, while EH and Ca2+ might be related to the islet β-cell function. Smoking and TG might participate in both of the above processes. The strategy of backward iterative with PSM had demonstrated a relatively satisfactory effect in feature screening.

Comparative transcriptome and mutation analyses of the pancreatic islets of a rat model of obese type 2 diabetes identifies a frequently distributed nonsense mutation in the lipocalin 2 gene

Type 2 diabetes (T2D) is a multifactorial disease caused by insulin resistance and impaired insulin secretion from pancreatic β-cells, but the precise mechanisms remain to be elucidated. To identify primary genetic factors of T2D in a rat model, we performed comparative transcriptome and mutation analyses of the pancreatic islets between the obese Zucker fatty rat and the Zucker fatty rat-derived T2D model Zucker fatty diabetes mellitus (ZFDM) rat. Among differentially expressed genes irrespective of obesity and glucose intolerance states, we identified a nonsense mutation, c.409C > T (p.Gln137X), in the lipocalin 2 (Lcn2) gene which encodes a secreted protein called neutrophil gelatinase-associated lipocalin, a well-known biomarker for inflammation. We examined the relevance of the Lcn2 mutation with T2D in the ZFDM rat by using genome editing and genetic linkage analysis and confirmed that the Lcn2 mutation exhibits no significant association with the onset of T2D. Interestingly, we found that the Lcn2 mutation is distributed widely in rat species, such as commonly used DA and F344 strains. Our data indicate that several rat strains would serve as Lcn2 deficient models, contributing to elucidate the pathophysiological roles of Lcn2 in a wide variety of phenotypes.

Mechanisms and effects of AdipoRon, an adiponectin receptor agonist, on ovarian granulosa cells-a systematic review

Granulosa cells, crucial components of ovarian follicles, play a fundamental role in follicle development, hormone production, and overall reproductive health. These cells are integral to steroidogenesis, including the synthesis and secretion of key hormones such as estrogen and progesterone. Dysregulation of granulosa cells can lead to reproductive disorders, including polycystic ovary syndrome and infertility. This systematic review provides a comprehensive evaluation of AdipoRon, a synthetic agonist of adiponectin receptors AdipoR1 and AdipoR2, and its effects on ovarian function, with a particular focus on granulosa cells. Due to the absence of clinical trials, the review centers on preclinical studies to explore AdipoRon's potential therapeutic benefits and to suggest future research directions. A detailed literature search across databases such as PubMed, Scopus, Web of Science, Embase, and Google Scholar was conducted using terms related to AdipoRon and ovarian function. The review encompasses four preclinical studies involving various models: primary granulosa cells from rats, laying hens' granulosa cells, human luteinized granulosa cells, and chicken ovary follicles. Findings indicate that AdipoRon enhances glucose absorption in rat granulosa cells by stimulating glucose transporter 1 expression, modulates steroid hormone secretion in laying hens' granulosa cells, and affects cell proliferation and steroidogenesis in human luteinized granulosa cells. Additionally, AdipoRon, in conjunction with recombinant chicken adiponectin, influences ovarian follicular cell proliferation and steroidogenesis in chicken ovary follicles. This review highlights the need for further investigation into AdipoRon's long-term effects and its potential applications in reproductive health and therapy.

Evaluation of Soluble Tumor Necrosis Factor-Like Weak Inducer of Apoptosis, Omentin, and Tumor Necrosis Factor-α in Subjects with Periodontitis and Type 2 Diabetes Mellitus

Purpose: Periodontal disease worsens glycemic control due to the bidirectional link between periodontitis and type 2 diabetes mellitus (T2DM), involving inflammatory markers such as soluble tumor necrosis factor-like weak inducer of apoptosis (sTWEAK), tumor necrosis factor-α (TNF-α), and omentin-1. However, their combined role in T2DM with periodontitis has not been studied. This study aimed to evaluate the levels of these biomarkers in periodontitis patients with T2DM before and after nonsurgical periodontal therapy (NSPT). Materials and Methods: Sixty subjects were divided into four groups (15 each): Group I (systemically and periodontally healthy), Group II (systemically healthy with periodontitis), and Groups III and IV (periodontitis with T2DM, exhibiting good glycemic control [hemoglobin A1c (HbA1c) <7%] and poor control [HbA1c >8%]), respectively. Periodontal parameters such as plaque index, bleeding index, probing pocket depth, and clinical attachment level were assessed. Serum samples were collected at baseline and 3 months to measure sTWEAK, omentin-1, and TNF-α levels using ELISA. HbA1c levels were evaluated at baseline and 3 months. Results: TNF-α was significantly elevated in all groups compared with sTWEAK and omentin-1. However, omentin-1 levels were higher in the healthy group compared with all other groups. Periodontal parameters and biomarker levels showed significant improvement across all groups after 3 months post-NSPT. Conclusion: TNF-α and sTWEAK may serve as diagnostic markers, while omentin-1 can be a reliable prognostic marker for evaluating NSPT effects in T2DM patients with periodontitis and varying glycemic control.

Carnosine Supplementation Has No Effect on Inflammatory Markers in Adults with Prediabetes and Type 2 Diabetes: A Randomised Controlled Trial

BACKGROUND/OBJECTIVES

In vitro studies suggest that carnosine reduces inflammation by upregulating anti-inflammatory mediators and downregulating pro-inflammatory cytokines. However, human clinical trials examining the effects of carnosine on inflammatory biomarkers are scant. We conducted a secondary analysis of a double-blind randomised controlled trial (RCT) to examine the effects of carnosine supplementation on inflammatory markers and adipokines in participants with prediabetes or well-controlled type 2 diabetes (T2D).

METHODS

Out of 88 participants who were recruited, 49 adults with prediabetes or well-controlled T2D (HbA1c: 6.6 ± 0.7% [mean ± SD]) who were treated with diet and/or metformin were eligible for inclusion. Participants were randomised to receive 2 g/day of carnosine or a matching placebo for 14 weeks. We measured serum concentrations of monocyte chemoattractant protein-1 (MCP-1), interleukin (IL)-6, IL-10, C-reactive protein (CRP), tumour necrosis factor-α (TNF-α), adiponectin, leptin, adipsin, serpin, and resistin levels at baseline and after 14 weeks. The trial was registered at clinicaltrials.gov (NCT02917928).

RESULTS

Forty-one participants (M = 29/F = 12) aged 53 (42.6, 59.3) years [median (IQR)] completed the trial. After 14 weeks of supplementation, changes in pro- and anti-inflammatory cytokine and adipokine levels did not differ between the carnosine and placebo groups (p > 0.05 for all). The results remained unchanged after adjustment for confounders including age, sex, and anthropometric measures (e.g., body fat percentage and visceral adipose tissue).

CONCLUSIONS

In individuals with prediabetes and well-controlled T2D, carnosine supplementation did not result in any significant changes in inflammatory markers. Larger RCTs with longer follow-up durations are needed to evaluate whether carnosine may be beneficial in individuals with poorly controlled T2D.

Oxylipins Derived from PUFAs in Cardiometabolic Diseases: Mechanism of Actions and Possible Nutritional Interactions

Oxylipins are oxidized fatty acids, both saturated and unsaturated, formed through pathways that involve singlet oxygen or dioxygen-mediated oxygenation reactions and are primarily produced by enzyme families such as cyclooxygenases, lipoxygenases, and cytochrome P450. These lipid-based complex bioactive molecules are pivotal signal mediators, acting in a hormone-like manner in the pathophysiology of numerous diseases, especially cardiometabolic diseases via modulating plenty of mechanisms. It has been reported that omega-6 and omega-3 oxylipins are important novel biomarkers of cardiometabolic diseases. Moreover, collected literature has noted that diet and dietary components, especially fatty acids, can modulate these oxygenated lipid products since they are mainly derived from dietary omega-3 and omega-6 polyunsaturated fatty acids (PUFAs) or linoleic acid and α-linolenic by elongation and desaturation pathways. This comprehensive review aims to examine their correlations to cardiometabolic diseases and how diets modulate oxylipins. Also, some aspects of developing new biomarkers and therapeutical utilization are detailed in this review.

Chemerin in the Spotlight: Revealing Its Multifaceted Role in Acute Myocardial Infarction

Chemerin, an adipokine known for its role in adipogenesis and inflammation, has emerged as a significant biomarker in cardiovascular diseases, including acute myocardial infarction (AMI). Recent studies have highlighted chemerin's involvement in the pathophysiological processes of coronary artery disease (CAD), where it modulates inflammatory responses, endothelial function, and vascular remodelling. Elevated levels of chemerin have been associated with adverse cardiovascular outcomes, including increased myocardial injury, left ventricular dysfunction, and heightened inflammatory states post-AMI. This manuscript aims to provide a comprehensive review of the current understanding of chemerin's role in AMI, detailing its molecular mechanisms, clinical implications, and potential as a biomarker for diagnosis and prognosis. Additionally, we explore the therapeutic prospects of targeting chemerin pathways to mitigate myocardial damage and improve clinical outcomes in AMI patients. By synthesizing the latest research findings, this review seeks to elucidate the multifaceted role of chemerin in AMI and its promise as a target for innovative therapeutic strategies.

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.

Branched-chain amino acids supplementation induces insulin resistance and pro-inflammatory macrophage polarization via INFGR1/JAK1/STAT1 signal pathway

BACKGROUND

Obesity is a global epidemic, and the low-grade chronic inflammation of adipose tissue in obese individuals can lead to insulin resistance and type 2 diabetes. Adipose tissue macrophages (ATMs) are the main source of pro-inflammatory cytokines in adipose tissue, making them an important target for therapy. While branched-chain amino acids (BCAA) have been strongly linked to obesity and type 2 diabetes in humans, the relationship between BCAA catabolism and adipose tissue inflammation is unclear. This study aims to investigate whether disrupted BCAA catabolism influences the function of adipose tissue macrophages and the secretion of pro-inflammatory cytokines in adipose tissue, and to determine the underlying mechanism. This research will help us better understand the role of BCAA catabolism in adipose tissue inflammation, obesity, and type 2 diabetes.

METHODS

In vivo, we examined whether the BCAA catabolism in ATMs was altered in high-fat diet-induced obesity mice, and if BCAA supplementation would influence obesity, glucose tolerance, insulin sensitivity, adipose tissue inflammation and ATMs polarization in mice. In vitro, we isolated ATMs from standard chow and high BCAA-fed group mice, using RNA-sequencing to investigate the potential molecular pathway regulated by BCAA accumulation. Finally, we performed targeted gene silence experiment and used immunoblotting assays to verify our findings.

RESULTS

We found that BCAA catabolic enzymes in ATMs were influenced by high-fat diet induced obesity mice, which caused the accumulation of both BCAA and its downstream BCKA. BCAA supplementation will cause obesity and insulin resistance compared to standard chow (STC) group. And high BCAA diet will induce pro-inflammatory cytokines including Interlukin-1beta (IL-1β), Tumor Necrosis Factor alpha (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) secretion in adipose tissue as well as promoting ATMs M1 polarization (pro-inflammatory phenotype). Transcriptomic analysis revealed that a high BCAA diet would activate IFNGR1/JAK1/STAT1 pathway, and IFNGR1 specific silence can abolish the effect of BCAA supplementation-induced inflammation and ATMs M1 polarization.

CONCLUSIONS

The obesity mice model reveals the catabolism of BCAA was disrupted which will cause the accumulation of BCAA, and high-level BCAA will promote ATMs M1 polarization and increase the pro-inflammatory cytokines in adipose tissue which will cause the insulin resistance in further. Therefore, reducing the circulating level of BCAA can be a therapeutic strategy in obesity and insulin resistance patients.

Novel insight into the role of A-kinase anchoring proteins (AKAPs) in ischemic stroke and therapeutic potentials

Ischemic stroke, a devastating disease associated with high mortality and disability worldwide, has emerged as an urgent public health issue. A-kinase anchoring proteins (AKAPs) are a group of signal-organizing molecules that compartmentalize and anchor a wide range of receptors and effector proteins and have a major role in stabilizing mitochondrial function and promoting neurodevelopmental development in the central nervous system (CNS). Growing evidence suggests that dysregulation of AKAPs expression and activity is closely associated with oxidative stress, ion disorder, mitochondrial dysfunction, and blood-brain barrier (BBB) impairment in ischemic stroke. However, the underlying mechanisms remain inadequately understood. This review provides a comprehensive overview of the composition and structure of A-kinase anchoring protein (AKAP) family members, emphasizing their physiological functions in the CNS. We explored in depth the molecular and cellular mechanisms of AKAP complexes in the pathological progression and risk factors of ischemic stroke, including hypertension, hyperglycemia, lipid metabolism disorders, and atrial fibrillation. Herein, we highlight the potential of AKAP complexes as a pharmacological target against ischemic stroke in the hope of inspiring translational research and innovative clinical approaches.

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.

Strengthening the Evidence for a Causal Link between Type 2 Diabetes Mellitus and Pancreatic Cancer: Insights from Two-Sample and Multivariable Mendelian Randomization

This two-sample Mendelian randomization (MR) study was conducted to investigate the causal associations between type 2 diabetes mellitus (T2DM) and the risk of pancreatic cancer (PaCa), as this causal relationship remains inconclusive in existing MR studies. The selection of instrumental variables for T2DM was based on two genome-wide association study (GWAS) meta-analyses from European cohorts. Summary-level data for PaCa were extracted from the FinnGen and UK Biobank databases. Inverse variance weighted (IVW) and four other robust methods were employed in our MR analysis. Various sensitivity analyses and multivariable MR approaches were also performed to enhance the robustness of our findings. In the IVW and Mendelian Randomization Pleiotropy RESidual Sum and Outlier (MR-PRESSO) analyses, the odds ratios (ORs) for each 1-unit increase in genetically predicted log odds of T2DM were approximately 1.13 for PaCa. The sensitivity tests and multivariable MR supported the causal link between T2DM and PaCa without pleiotropic effects. Therefore, our analyses suggest a causal relationship between T2DM and PaCa, shedding light on the potential pathophysiological mechanisms of T2DM's impact on PaCa. This finding underscores the importance of T2DM prevention as a strategy to reduce the risk of PaCa.

Quercetin modulates expression of serum exosomal long noncoding RNA NEAT1 to regulate the miR-129-5p/BDNF axis and attenuate cognitive impairment in diabetic mice

AIMS

Cognitive impairment poses a considerable health challenge in the context of type 2 diabetes mellitus (T2DM), emphasizing the need for effective interventions. This study delves into the therapeutic efficacy of quercetin, a natural flavonoid, in mitigating cognitive impairment induced by T2DM in murine models.

MATERIALS AND METHODS

Serum exosome samples were obtained from both T2DM-related and healthy mice for transcriptome sequencing, enabling the identification of differentially expressed mRNAs and long noncoding RNAs (lncRNAs). Subsequent experiments were conducted to ascertain the binding affinity between mmu-miR-129-5p, NEAT1 and BDNF. The structural characteristics and dimensions of isolated exosomes were scrutinized, and the expression levels of exosome-associated proteins were quantified. Primary mouse hippocampal neurons were cultured for in vitro validation, assessing the expression of pertinent genes as well as neuronal vitality, proliferation, and apoptosis capabilities. For in vivo validation, a T2DM mouse model was established, and quercetin treatment was administered. Changes in various parameters, cognitive ability, and the expression of insulin-related proteins, along with pivotal signaling pathways, were monitored.

KEY FINDINGS

Analysis of serum exosomes from T2DM mice revealed dysregulation of NEAT1, mmu-miR-129-5p, and BDNF. In vitro investigations demonstrated that NEAT1 upregulated BDNF expression by inhibiting mmu-miR-129-5p. Overexpression of mmu-miR-129-5p or silencing NEAT1 resulted in the downregulation of insulin-related protein expression, enhanced apoptosis, and suppressed neuronal proliferation. In vivo studies validated that quercetin treatment significantly ameliorated T2DM-related cognitive impairment in mice.

SIGNIFICANCE

These findings suggest that quercetin holds promise in inhibiting hippocampal neuron apoptosis and improving T2DM-related cognitive impairment by modulating the NEAT1/miR-129-5p/BDNF pathway within serum exosomes.