Increased monocyte-derived reactive oxygen species in type 2 diabetes: role of endoplasmic reticulum stress

Immunometabolic Signatures of Circulating Monocytes in Humans With Obesity and Insulin Resistance

Obesity is associated with chronic inflammation and metabolic complications, including insulin resistance (IR). Immune cells drive inflammation through the rewiring of intracellular metabolism. However, the impact of obesity-related IR on the metabolism and functionality of circulating immune cells, like monocytes, remains poorly understood. To increase insight into the interindividual variation of immunometabolic signatures among individuals and their role in the development of IR, we assessed systemic and tissue-specific IR and circulating immune markers, and we characterized metabolic signatures and cytokine secretion of circulating monocytes from 194 individuals with a BMI ≥25 kg/m2. Monocyte metabolic signatures were defined using extracellular acidification rates (ECARs) to estimate glycolysis and oxygen consumption rates (OCRs) for oxidative metabolism. Although monocyte metabolic signatures and function based on cytokine secretion varied greatly among study participants, they were strongly associated with each other. The ECAR-to-OCR ratio, representing the balance between glycolysis and oxidative metabolism, was negatively associated with fasting insulin levels, systemic IR, and liver-specific IR. These results indicate that monocytes from individuals with IR were relatively more dependent on oxidative metabolism, whereas monocytes from more insulin-sensitive individuals were more dependent on glycolysis. Additionally, circulating CXCL11 was negatively associated with the degree of systemic IR and positively with the ECAR-to-OCR ratio in monocytes, suggesting that individuals with high IR and a monocyte metabolic dependence on oxidative metabolism also have lower levels of circulating CXCL11. Our findings suggest that monocyte metabolism is related to obesity-associated IR progression and deepen insights into the interplay between innate immune cell metabolism and IR development in humans.

ARTICLE HIGHLIGHTS

l-norleucine on high glucose-induced insulin sensitivity and mitochondrial function in skeletal muscle cells

l-norleucine, an isomer of leucine, stimulates the anabolic process of insulin. However, it is not known if and how it improves insulin sensitivity and insulin resistance. This experiment describes the generation of an insulin resistance model using high glucose-induced cells and the administration of 1.0 mmol/L l-norleucine for 48 h, to observe the effects on metabolism and gene expression in skeletal muscle cells. The results showed that l-norleucine significantly increased mitochondrial ATP content, decreased the amount of reactive oxygen species (ROS) and promoted the expression of mitochondrial generation-related genes TFAM, AMPK, PGC-1α in cells under high glucose treatment; at the same time, l-norleucine also increased glucose uptake, suggesting that l-norleucine increased insulin sensitivity and improved insulin resistance. This study suggesting that l-norleucine improves insulin resistance by ameliorating oxidative stress damage of mitochondria, improving mitochondrial function, and improving insulin sensitivity in skeletal muscle cell caused by high glucose, rather than by altering mitochondrial efficiency.

Transcriptomic analysis reveals Cilostazol's role in ameliorating cardiovascular disease: Inhibition of monocyte-to-macrophage differentiation and reduction of endothelial cell reactive oxygen species production

Background

Cardiovascular diseases (CVDs) are the leading global cause of death, with atherosclerosis as the primary cause. Chronic inflammation, endothelial dysfunction, and the role of molecules like nitric oxide and reactive oxygen species are crucial in this context. Our previous research indicated that cilostazol and ginkgo biloba extract could enhance the ability of endothelial cells to dissolve blood clots, but the effects of cilostazol on monocytes remain unexplored.

Method

This study utilized peripheral blood mononuclear cells from 10 healthy donors, treated ex vivo with cilostazol. RNA-sequencing, over-representation analysis, xCell stromal cell analysis, and Gene Set Enrichment Analysis were employed to investigate the gene expression changes and biological pathways affected by cilostazol treatment.

Results

The study identified specific gene sets and pathways that were enriched or reduced in response to cilostazol treatment, providing insights into its effects on monocytes and potential therapeutic applications in CVD. The analysis also revealed the potential impact of cilostazol on the stromal cell compartment, further broadening our understanding of its multifaceted role.

Conclusion

The findings offer a nuanced understanding of the advantages and mechanisms of cilostazol in CVD, uncovering novel therapeutic targets and strategies to enhance the clinical application of cilostazol and contributing to the broader implications of this therapy in cardiovascular health.

The Perfect Cup? Coffee-Derived Polyphenols and Their Roles in Mitigating Factors Affecting Type 2 Diabetes Pathogenesis

Type 2 diabetes (T2D) is a growing health concern with an estimated 462 million people having been diagnosed worldwide. T2D is characterized by chronically elevated blood glucose and insulin resistance, which culminate in a diminished function of the β-cell mass in its later stages. This can be perpetuated by and result in inflammation, excess reactive oxygen species production, obesity, and the dysregulation of multiple cellular pathways. Many naturally occurring small molecules have been investigated in terms of their roles in modulating glucose homeostasis and β-cell function. Many of these compounds can be found in commonly used sources of food and drink. Interestingly, a correlation has been observed between coffee consumption and T2D incidence. However, the specific compounds responsible for this correlation and their mechanisms are still somewhat undetermined. This paper reviews recent research findings on the effects of several polyphenols that are either found in coffee or are metabolites of compounds found in coffee (enterodiol, enterolactone, matairesinol, secoisolariciresinol, kaempferol, quercetin, and chlorogenic acid) on glucose homeostasis and health complications associated with glucose dysregulation, with a special emphasis on their potential anti-diabetic effects. The factors that affect polyphenol content in coffee are also addressed.

Bromocriptine-QR Therapy Reduces Sympathetic Tone and Ameliorates a Pro-Oxidative/Pro-Inflammatory Phenotype in Peripheral Blood Mononuclear Cells and Plasma of Type 2 Diabetes Subjects

Bromocriptine-QR is a sympatholytic dopamine D2 agonist for the treatment of type 2 diabetes that has demonstrated rapid (within 1 year) substantial reductions in adverse cardiovascular events in this population by as yet incompletely delineated mechanisms. However, a chronic state of elevated sympathetic nervous system activity and central hypodopaminergic function has been demonstrated to potentiate an immune system pro-oxidative/pro-inflammatory condition and this immune phenotype is known to contribute significantly to the advancement of cardiovascular disease (CVD). Therefore, the possibility exists that bromocriptine-QR therapy may reduce adverse cardiovascular events in type 2 diabetes subjects via attenuation of this underlying chronic pro-oxidative/pro-inflammatory state. The present study was undertaken to assess the impact of bromocriptine-QR on a wide range of immune pro-oxidative/pro-inflammatory biochemical pathways and genes known to be operative in the genesis and progression of CVD. Inflammatory peripheral blood mononuclear cell biology is both a significant contributor to cardiovascular disease and also a marker of the body’s systemic pro-inflammatory status. Therefore, this study investigated the effects of 4-month circadian-timed (within 2 h of waking in the morning) bromocriptine-QR therapy (3.2 mg/day) in type 2 diabetes subjects whose glycemia was not optimally controlled on the glucagon-like peptide 1 receptor agonist on (i) gene expression status (via qPCR) of a wide array of mononuclear cell pro-oxidative/pro-inflammatory genes known to participate in the genesis and progression of CVD (OXR1, NRF2, NQO1, SOD1, SOD2, CAT, GSR, GPX1, GPX4, GCH1, HMOX1, BiP, EIF2α, ATF4, PERK, XBP1, ATF6, CHOP, GSK3β, NFkB, TXNIP, PIN1, BECN1, TLR2, TLR4, TLR10, MAPK8, NLRP3, CCR2, GCR, L-selectin, VCAM1, ICAM1) and (ii) humoral measures of sympathetic tone (norepinephrine and normetanephrine), whole-body oxidative stress (nitrotyrosine, TBARS), and pro-inflammatory factors (IL-1β, IL-6, IL-18, MCP-1, prolactin, C-reactive protein [CRP]). Relative to pre-treatment status, 4 months of bromocriptine-QR therapy resulted in significant reductions of mRNA levels in PBMC endoplasmic reticulum stress-unfolded protein response effectors [GRP78/BiP (34%), EIF2α (32%), ATF4 (29%), XBP1 (25%), PIN1 (14%), BECN1 (23%)], oxidative stress response proteins [OXR1 (31%), NRF2 (32%), NQO1 (39%), SOD1 (52%), CAT (26%), GPX1 (33%), GPX4 (31%), GCH1 (30%), HMOX1 (40%)], mRNA levels of TLR pro-inflammatory pathway proteins [TLR2 (46%), TLR4 (20%), GSK3β (19%), NFkB (33%), TXNIP (18%), NLRP3 (32%), CCR2 (24%), GCR (28%)], mRNA levels of pro-inflammatory cellular receptor proteins CCR2 and GCR by 24% and 28%, and adhesion molecule proteins L-selectin (35%) and VCAM1 (24%). Relative to baseline, bromocriptine-QR therapy also significantly reduced plasma levels of norepinephrine and normetanephrine by 33% and 22%, respectively, plasma pro-oxidative markers nitrotyrosine and TBARS by 13% and 10%, respectively, and pro-inflammatory factors IL-18, MCP1, IL-1β, prolactin, and CRP by 21%,13%, 12%, 42%, and 45%, respectively. These findings suggest a unique role for circadian-timed bromocriptine-QR sympatholytic dopamine agonist therapy in reducing systemic low-grade sterile inflammation to thereby reduce cardiovascular disease risk.

Glutathione prevents high glucose-induced pancreatic fibrosis by suppressing pancreatic stellate cell activation via the ROS/TGFβ/SMAD pathway

The activation of pancreatic stellate cells (PSCs) is the key mechanism of pancreatic fibrosis, which can lead to β-cell failure. Oxidative stress is an important risk factor for PSC activation. There is no direct evidence proving if administration of glutathione can inhibit fibrosis and β-cell failure. To explore the role of glutathione in pancreatic fibrosis and β-cell failure induced by hyperglycaemia, we established a rat model of pancreatic fibrosis and β-cell failure. The model was founded through long-term oscillating glucose (LOsG) intake and the setup of a sham group and a glutathione intervention group. In vitro, rat PSCs were treated with low glucose, high glucose, or high glucose plus glutathione to explore the mechanism of high glucose-induced PSC activation and the downstream effects of glutathione. Compared with sham rats, LOsG-treated rats had higher reactive oxygen species (ROS) levels in peripheral leukocytes and pancreatic tissue while TGFβ signalling was upregulated. In addition, as the number of PSCs and pancreatic fibrosis increased, β-cell function was significantly impaired. Glutathione evidently inhibited the upregulation of TGFβ signalling and several unfavourable outcomes caused by LOsG. In vitro treatment of high glucose for 72 h resulted in higher ROS accumulation and potentiated TGFβ pathway activation in PSCs. PSCs showed myofibroblast phenotype transformation with upregulation of α-SMA expression and increased cell proliferation and migration. Treatment with either glutathione or TGFβ pathway inhibitors alleviated these changes. Together, our findings suggest that glutathione can inhibit PSC activation-induced pancreatic fibrosis via blocking ROS/TGFβ/SMAD signalling in vivo and in vitro.

Differential Modulation of 25-hydroxycholecalciferol on Innate Immunity of Broiler Breeder Hens

Simple Summary

No predominant changes between R- vs. Ad-feed intake on leukocyte defense against pathogens were observed in broiler breeder hens despite some differences in inflammatory and respiratory burst responses. Overall, supplemental 25-OH-D₃ had more pronounced effects on the innate immunity of Ad-hens. In vitro studies confirmed the differential effects of 25-OH-D₃ to rescue immune functions altered by glucose and/or palmitic acid exposure.

Abstract

Past immunological studies in broilers focused on juveniles within the rapid pre-slaughter growth period and may not reflect adult immune responses, particularly in breeders managed with chronic feed restriction (R). The study aimed to assess innate immune cell functions in respect to R vs. ad libitum (Ad) feed intake in breeder hens with and without dietary 25-hydroxycholecalciferol (25-OH-D₃) supplementation. Ad-feed intake consistently suppressed IL-1β secretion, respiratory burst, and cell livability in peripheral heterophils and/or monocytes along the feeding trial from the age of 51 to 68 weeks. Supplemental 25-OH-D₃ repressed IL-1β secretion and respiratory burst of both cells mostly in R-hens, but promoted monocyte phagocytosis, chemotaxis, and bacterial killing activity in Ad-hens in accompany with relieved hyperglycemia, hyperlipidemia, and systemic inflammation. Overnight cultures with leukocytes from R-hens confirmed the differential effects of 25-OH-D₃ to rescue immune functions altered by glucose and/or palmitic acid exposure. Studies with specific inhibitors further manifested the operative mechanisms via glucolipotoxicity in a cell type- and function-dependent manner. The results concluded no predominant changes between R- vs. Ad-feed intake on leukocyte defense against pathogens despite some differential differences, but supplemental 25-OH-D₃ exerts more pronounced effects in Ad-hens.

The Mitochondrial Antioxidant SS-31 Modulates Oxidative Stress, Endoplasmic Reticulum Stress, and Autophagy in Type 2 Diabetes

Mitochondrial dysfunction has been shown to play a central role in the pathophysiology of type 2 diabetes (T2D), and mitochondria-targeted agents such as SS-31 are emerging as a promising strategy for its treatment. We aimed to study the effects of SS-31 on leukocytes from T2D patients by evaluating oxidative stress, endoplasmic reticulum (ER) stress and autophagy. Sixty-one T2D patients and 53 controls were included. Anthropometric and analytical measurements were performed. We also assessed reactive oxygen species (ROS) production, calcium content, the expression of ER stress markers GRP78, CHOP, P-eIF2α, and autophagy-related proteins Beclin1, LC3 II/I, and p62 in leukocytes from T2D and control subjects treated or not with SS-31. Furthermore, we have evaluated the action of SS-31 on leukocyte-endothelium interactions. T2D patients exhibited elevated ROS concentration, calcium levels and presence of ER markers (GRP78 and CHOP gene expression, and GRP78 and P-eIF2α protein expression), all of which were reduced by SS-31 treatment. SS-31 also led to a drop in BECN1 gene expression, and Beclin1 and LC3 II/I protein expression in T2D patients. In contrast, the T2D group displayed reduced p62 protein levels that were restored by SS-31. SS-20 (with non-antioxidant activity) did not change any analyzed parameter. In addition, SS-31 decreased rolling flux and leukocyte adhesion, and increased rolling velocity in T2D patients. Our findings suggest that SS-31 exerts potentially beneficial effects on leukocytes of T2D patients modulating oxidative stress and autophagy, and ameliorating ER stress.

CD4 and MHCII phenotypic variability of peripheral blood monocytes in dogs

In humans and mice, the detailed phenotypic and functional characterization of peripheral blood monocytes allows for identification of three monocyte subsets. There are also evidences of monocyte phenotypic heterogeneity in other species, including cattle, sheep, pig and horse. However, little is known about such variability in dogs. The aim of the study was to determine whether and how peripheral blood monocytes of healthy dogs differ in the presence of MHCII and CD4 and in the basal production of reactive oxygen species (ROS). Three distinct subsets of CD11b+CD14+ monocytes were found in peripheral blood samples of healthy dogs, based on the variations in the density of MHCII and CD4 surface molecules: MHCII+CD4- (Mo1), MHCII+CD4+ (Mo2) and MHCII-CD4+ (Mo3). The Mo2 and Mo3 were significantly lower in percentage than Mo1 but their basal ROS production was higher. Within the Mo2 and Mo3 subsets, the percentage of cells producing ROS was significantly higher comparing to cells lacking this activity. Canine peripheral blood monocytes vary in the expression of MHCII and CD4 and in the activity suggesting that cells within the three identified subsets carry out different functions. The higher production of ROS in non-activated cells within small subsets of Mo2 and Mo3 monocytes might indicate their immunomodulatory potential.

Glutathione prevents chronic oscillating glucose intake-induced β-cell dedifferentiation and failure

Modern lifestyles have altered diet and metabolic homeostasis, with increased sugar intake, glycemic index, and prediabetes. A strong positive correlation between sugar consumption and diabetic incidence is revealed, but the underlying mechanisms remain obscure. Here we show that oral intake of long-term oscillating glucose (LOsG) (4 times/day) for 38 days, which produces physiological glycemic variability in rats, can lead to β-cells gaining metabolic memory in reactive oxygen species (ROS) stress. This stress leads to suppression of forkhead box O1 (FoxO1) signaling and subsequent upregulation of thioredoxin interacting protein, inhibition of insulin and SOD-2 expression, re-expression of Neurog3, and β-cell dedifferentiation and functional failure. LOsG-treated animals develop prediabetes exhibiting hypoinsulinemia and glucose intolerance. Dynamic and timely administration of antioxidant glutathione prevents LOsG/ROS-induced β-cell failure and prediabetes. We propose that ROS stress is the initial step in LOsG-inducing prediabetes. Manipulating glutathione-related pathways may offer novel options for preventing the occurrence and development of diabetes.

Reactive oxygen species (ROS) in macrophage activation and function in diabetes

In a diabetic milieu high levels of reactive oxygen species (ROS) are induced. This contributes to the vascular complications of diabetes. Recent studies have shown that ROS formation is exacerbated in diabetic monocytes and macrophages due to a glycolytic metabolic shift. Macrophages are important players in the progression of diabetes and promote inflammation through the release of pro-inflammatory cytokines and proteases. Because ROS is an important mediator for the activation of pro-inflammatory signaling pathways, obesity and hyperglycemia-induced ROS production may favor induction of M1-like pro-inflammatory macrophages during diabetes onset and progression. ROS induces MAPK, STAT1, STAT6 and NFκB signaling, and interferes with macrophage differentiation via epigenetic (re)programming. Therefore, a comprehensive understanding of the impact of ROS on macrophage phenotype and function is needed in order to improve treatment of diabetes and its vascular complications. In the current comprehensive review, we dissect the role of ROS in macrophage polarization, and analyze how ROS production links metabolism and inflammation in diabetes and its complications. Finally, we discuss the contribution of ROS to the crosstalk between macrophages and endothelial cells in diabetic complications.

IL-8 analogue CXCL8 (3-72) K11R/G31P, modulates LPS-induced inflammation via AKT1-NF-kβ and ERK1/2-AP-1 pathways in THP-1 monocytes

IL-8 is elevated during inflammation, and it initiates cascade of down-stream reactions. Its antagonist, CXCL8 (3-72) K11R/G31P (G31P), represses inflammatory reactions via competitive binding to CXC chemokine family, preferentially G protein-couple receptors (GPCRs) CXCR1/2. This study reports the effect of G31P on the transcription profile of lipopolysaccharide (LPS) induced inflammation in THP-1 monocytes ex-vivo. LPS (1 µg/ml) induced elevation of IL-8 was significantly reduced by G31P (20 µg/ml and 30 µg/ml), with relatively increased inhibition of CXCR2 than CXCR1. Transcription of IL-1β, IL-6, and TNF-α were significantly inhibited, while IL-10 remained relatively unchanged. G31P treatment also had repressing effect on the inflammatory associated enzymes COX-2, MMP-2, and MMP-9. Significant restriction of c-Fos, and NF-kβ mRNA expression was observed, while that of c-Jun was marginally elevated. Conversely, SP-1 mRNA expression was seen to increase appreciably by G31P treatment. While the translation of pAKT, pERK1/2, and p65- NF-kβ were down-regulated by the G31P following THP-1 cells stimulation with LPS, reactive oxygen species (ROS) expression was on the positive trajectory. Collectively, the IL-8 analogue, G31P, modulates the inflammatory profile of LPS induced inflammation in THP-1 monocytes via AKT1-NF-kβ and ERK1/2-AP-1 pathways.

Endoplasmic Reticulum Stress Mediates Methamphetamine-Induced Blood-Brain Barrier Damage

Methamphetamine (METH) abuse causes serious health problems worldwide, and long-term use of METH disrupts the blood-brain barrier (BBB). Herein, we explored the potential mechanism of endoplasmic reticulum (ER) stress in METH-induced BBB endothelial cell damage in vitro and the therapeutic potential of endoplasmic reticulum stress inhibitors for METH-induced BBB disruption in C57BL/6J mice. Exposure of immortalized BMVEC (bEnd.3) cells to METH significantly decreased cell viability, induced apoptosis, and diminished the tightness of cell monolayers. METH activated ER stress sensor proteins, including PERK, ATF6, and IRE1, and upregulated the pro-apoptotic protein CHOP. The ER stress inhibitors significantly blocked the upregulation of CHOP. Knockdown of CHOP protected bEnd.3 cells from METH-induced cytotoxicity. Furthermore, METH elevated the production of reactive oxygen species (ROS) and induced the dysfunction of mitochondrial characterized by a Bcl2/Bax ratio decrease, mitochondrial membrane potential collapse, and cytochrome c. ER stress release was partially reversed by ROS inhibition, and cytochrome c release was partially blocked by knockdown of CHOP. Finally, PBA significantly attenuated METH-induced sodium fluorescein (NaFluo) and Evans Blue leakage, as well as tight junction protein loss, in C57BL/6J mice. These data suggest that BBB endothelial cell damage was caused by METH-induced endoplasmic reticulum stress, which further induced mitochondrial dysfunction, and that PBA was an effective treatment for METH-induced BBB disruption.

No effect of ascorbate on cutaneous vasodilation and sweating in older men and those with type 2 diabetes exercising in the heat

Aging and chronic disease such as type 2 diabetes (T2D) are associated with impairments in the body's ability to dissipate heat. To reduce the risk of heat-related injuries in these heat vulnerable individuals, it is necessary to identify interventions that can attenuate this impairment. We evaluated the hypothesis that intradermal administration of ascorbate improves cutaneous vasodilation and sweating in older adults via nitric oxide synthase (NOS)-dependent mechanisms during exercise in the heat and whether these improvements, if any, are greater in individuals with T2D. Older males with (n = 12, 61 ± 9 years) and without (n = 12, 64 ± 7 years) T2D performed two 30-min bouts of cycling at a fixed rate of metabolic heat production of 500 W (~70% peak oxygen uptake) in the heat (35°C); each followed by a 20- and 40-min recovery, respectively. Cutaneous vascular conductance (CVC) and sweat rate were measured at four intradermal microdialysis sites treated with either (1) lactated Ringer (Control), (2) 10 mmol/L ascorbate (an antioxidant), (3) 10 mmol/L L-NAME (non-selective NOS inhibitor), or (4) a combination of ascorbate + L-NAME. In both groups, ascorbate did not modulate CVC or sweating during exercise relative to Control (all P > 0.05). In comparison to Control, L-NAME alone or combined with ascorbate attenuated CVC during exercise (all P ≤ 0.05) but had no influence on sweating (all P > 0.05). We show that in both healthy and T2D older adults, intradermal administration of ascorbate does not improve cutaneous vasodilation and sweating during exercise in the heat. However, NOS plays an important role in mediating cutaneous vasodilation.