Cold exposure promotes atherosclerotic plaque growth and instability via UCP1-dependent lipolysis

Uncoupling protein 1-mediated protective effects of β3-adrenergic receptor agonist on kidney fibrosis via promoting adipose tissue browning in diabetic mice

BACKGROUND

Diabetes mellitus (DM) is a global health concern. Diabetic kidney disease (DKD) is a prevalent severe complication of DM and therapy is urgently needed. Adipose tissue (AT) plays a crucial role in the energy mediation through glucolipid metabolism. Mirabegron is a specific β3-adrenergic receptor agonist, which can activate thermogenesis in adipocytes, improve energy consumption, and increase insulin sensitivity and glucose tolerance. Therefore, mirabegron may play a role in DKD pathogenesis. However, its effects and precise mechanisms remain unclear.

METHODS

A DKD mouse model based on type 2 DM (T2DM) was constructed and treated with mirabegron. Mice with AT surgically removed and mice with uncoupling protein 1 (Ucp1) knockout were used to confirm whether thermogenesis induced by mirabegron was the key process.

RESULTS

Mirabegron promoted AT browning in DKD mice. Mirabegron increased insulin sensitivity, promoted glucolipid metabolism, reduced inflammatory factor levels in kidney tissue, and improved renal function and fibrosis in DKD mice. Notably, all of these benefits disappeared in AT-removed DKD mice or in Ucp1 knockout DKD mice.

CONCLUSIONS

Mirabegron protects against kidney fibrosis in DM mice by activating AT thermogenesis via the UCP1 pathway. Thus, mirabegron may provide a promising potential option for DKD therapy.

Stroke risk associated with cold spells occurring during the warm season

BACKGROUND

Recent climate changes have resulted in a rising frequency of extreme cold events that take place during the warm season. Few studies have investigated the impact of these warm-season cold spells on cardiovascular health. Here, we aimed to investigate the potential relationship between exposure to relatively low temperature exposure during the warm season and stroke risk.

METHODS

We conducted a time-stratified case-crossover study using a validated, complete, and detailed registration of all stroke cases in the city of Augsburg, Germany, from 2006 to 2020 to assess the association between the occurrence of stroke and exposure to cold spell events during the warm season (May-October). Six cold spell definitions were created using different relative temperature thresholds (1st, 2.5th, and 5th percentiles) and durations (more than 1-2 consecutive days). Conditional logistic regression with distributed lag models was then applied to assess the accumulated effects of these warm-season cold spells on stroke risk over a lag period of 0-6 days, with adjustments for daily mean temperature.

RESULTS

Results confirmed that warm-season cold spells were significantly linked to an elevated risk of stroke with effects that could persist three days after exposure. The cumulative odds ratio (OR) estimates for the cold spells using the 2.5th percentile as air temperature threshold reached 1.29 (95% confidence interval (CI): 1.09-1.53) and 1.23 (95%CI: 1.05-1.44) for durations more than one and two days, respectively. Warm-season cold spells also had significant associations with both transient ischemic attacks and ischemic strokes. The stratified analysis showed that the elderly population (aged ≥ 65 years), females, and stroke cases characterized by minor symptoms demonstrated a significantly increased stroke risk of the effects of warm season cold spells.

CONCLUSIONS

This study presents strong evidence for an overlooked association between warm-season cold spells and an increased risk of stroke occurrence. These findings further highlight the multifaceted ways in which climate change can affect human health.

Novel predictor for metabolic syndrome: Para-aortic adipose tissue

BACKGROUND

Metabolic Syndrome (MetS) is an independent risk factor for cardiovascular disease. Perivascular fat depots not only serve as energy storage but also function as endocrine organs. Para-aortic adipose tissue (PAT), a perivascular local adipose tissue, has been suggested to play a role in obesity-mediated vascular disease, and has been associated with MetS components and measures of coronary and abdominal aortic calcification. PAT was previously described and examined using tomography and magnetic resonance imaging. This study aimed to describe the features of para-aortic adipose tissue measured echocardiographically in individuals with MetS.

METHODS

Patients were divided into two groups according to their MetS status. The hypoechoic space in front of the ascending aorta was considered a PAT on the parasternal long-axis view. Possible covariates for the regression analysis were determined using the DAGitty diagram.

RESULTS

A total of 494 patients were enrolled in this study. The PAT was significantly higher in the MetS group [9.6 (6.1/10.6) vs. 6.1 (0.9/9) mm, p < 0.001]. Logistic regression analysis revealed that PAT (OR=2,15, p = 0,003) was significantly associated with MetS. 7.55 mm of PAT has a sensitivity of 65 % and specificity of 65 % [AUC = 0.675, p < 0.001, 95 % CI (0.623-0.726)] in predicting the presence of MetS.

CONCLUSIONS

Based on the measurements obtained using this newly described modality in transthoracic echocardiography, its relationship with MetS was determined. These results can guide clinicians in diagnosing MetS.

"Unveiling the impacts of climatic cold events on the cardiovascular health in animal models"

Climate change is increasingly driving extreme weather events, leading to drastic temperature fluctuations worldwide. While overall temperatures rise, many regions are simultaneously experiencing severe cold spells that threaten the health of human populations, especially to vulnerable populations including the elderly and those with pre-existing conditions. Exposure to cold stress triggers significant physiological and biochemical disruptions. As cardiovascular diseases (CVDs) rank among the leading causes of global morbidity and mortality, the exacerbation of these conditions by cold exposure underscores critical public health challenges. The complex pathophysiological processes in cold-induced CVDs require careful analysis at an organ-system level, making animal models an ideal tool for replicating human physiological and molecular responses in a controlled environment. However, a detailed mechanism linking cold exposure and cardiovascular dysfunction remains incompletely understood, particularly in the context of animal models. Therefore, this comprehensive review aims to address and analyze from traditional rodent models to less conventional ruminants, broilers, canines, and primate animal models to understand cold stress-induced CVDs, with an extensive account of the potential molecular mechanisms and pathways such as oxidative stress, inflammation, vasomotor dysfunction, and apoptosis, along with emerging roles of cold shock proteins (CSPs), etc. We also delve into various potential therapeutic approaches and preventive measures in cold stress conditions. In conclusion, this review is the first to comprehensively address the underexplored cardiovascular complications arising from cold stress and their underlying mechanisms, particularly using animal models. Furthermore, it provides a foundation for advancing the development of more effective and targeted therapies through translational research.

Effects of Prolonged Cold Stress on Vascular Function in Guinea Pigs With Atherosclerosis

RESEARCH OBJECTIVE

This study explored the effects of long-term cold stress (CS) on aortic vascular function in guinea pigs.

RESEARCH METHODS

Hartley guinea pigs (n = 32) were divided into the following groups: atherosclerosis (AS), CS, and menthol-stimulated (M), and control (C). On days 1, 15, 30, 45, and 60, guinea pigs in the AS, CS, and M groups were intraperitoneally injected with bovine serum albumin. The C group was provided with maintenance feed and room temperature water. The AS group was provided with a high-fat diet and room temperature water. The CS group was maintained in a refrigerator at 4°C, while providing a high-fat diet and iced water. The M group was administered menthol solution, and provided with a high-fat diet and room temperature water. The modeling period lasted for 120 days. On day 121, abdominal aortic sera and aortic samples were obtained after intraperitoneal injection of sodium pentobarbital. Blood rheology tests were conducted to assess blood adhesion, biochemical tests to assess lipid levels, and enzyme-linked immunosorbent assays to detect serum nuclear factor-κB, tumor necrosis factor-α, and interleukin-1β, and endothelial nitric oxide synthase, nitric oxide, and endothelin-1 (ET-1) in aortic tissue. Hematoxylin and eosin and oil red O staining were used to examine pathologic changes in the aorta, Western blotting to detect transient receptor potential melastatin 8 and protein kinase G protein expression, quantitative polymerase chain reaction was used to measure VCAM-1 mRNA expression level.

RESEARCH FINDINGS

Prolonged exposure to CS exacerbated lipid-metabolism disorders in guinea pigs fed a high-fat diet, increased aortic vascular cell adhesion, and exacerbated vascular inflammation, leading to endothelial injury, ultimately worsening pathologic changes associated with aortic atherosclerosis.

Brown and beige adipose tissue-derived metabokine and lipokine inter-organ signalling in health and disease

Adipose tissue has an established endocrine function through the secretion of adipokines. However, a role for bioactive metabolites and lipids, termed metabokines and lipokines, is emerging in adipose tissue-mediated autocrine, paracrine and endocrine signalling and inter-organ communication. Traditionally seen as passive entities, metabolites are now recognized for their active roles in regulating cellular signalling and local and systemic metabolism. Distinct from white adipose tissue, specific endocrine functions have been attributed to thermogenic brown and beige adipose tissues. Brown and beige adipose tissues have been identified as sources of metabokines and lipokines, which influence diverse metabolic pathways, such as fatty acid β-oxidation, mitochondrial function and glucose homeostasis, across a range of tissues, including skeletal muscle, adipose tissue and heart. This review explores the intricate signalling mechanisms of brown and beige adipose tissue-derived metabokines and lipokines, emphasizing their roles in maintaining metabolic homeostasis and their potential dysregulation in metabolic diseases. Furthermore, we discuss the therapeutic potential of targeting these pathways, proposing that precise modulation of metabokine receptors and transporters could offer superior specificity and efficacy in comparison to conventional approaches, such as β-adrenergic signalling-stimulated activation of brown adipose tissue thermogenesis. Understanding the complex interactions between adipokines, metabokines and lipokines is essential for developing a systems-level approach to new interventions for metabolic disorders, underscoring the need for continued research in this rapidly evolving field.

Hyperactive browning and hypermetabolism: potentially dangerous element in critical illness

Brown/beige adipose tissue has attracted much attention in previous studies because it can improve metabolism and combat obesity through non-shivering thermogenesis. However, recent studies have also indicated that especially in critical illness, overactivated brown adipose tissue or extensive browning of white adipose tissue may bring damage to individuals mainly by exacerbating hypermetabolism. In this review, the phenomenon of fat browning in critical illness will be discussed, along with the potential harm, possible regulatory mechanism and corresponding clinical treatment options of the induction of fat browning. The current research on fat browning in critical illness will offer more comprehensive understanding of its biological characteristics, and inspire researchers to develop new complementary treatments for the hypermetabolic state that occurs in critically ill patients.

Mechanism of cold exposure delaying wound healing in mice

Cold temperatures have been shown to slow skin wound healing. However, the specific mechanisms underlying cold-induced impairment of wound healing remain unclear. Here, we demonstrate that small extracellular vesicles derived from cold-exposed mouse plasma (CT-sEVs) decelerate re-epithelialization, increase scar width, and weaken angiogenesis. CT-sEVs are enriched with miRNAs involved in the regulation of wound healing-related biological processes. Functional assays revealed that miR-423-3p, enriched in CT-sEVs, acts as a critical mediator in cold-induced impairment of angiogenic responses and poor wound healing by inhibiting phosphatase and poly(A) binding protein cytoplasmic 1 (PABPC1). These findings indicate that cold delays wound healing via miR-423-3p in plasma-derived sEVs through the inhibition of the ERK or AKT phosphorylation pathways. Our results enhance understanding of the molecular mechanisms by which cold exposure delays soft tissue wound healing.

Keys to the switch of fat burning: stimuli that trigger the uncoupling protein 1 (UCP1) activation in adipose tissue

As one of the main pathogenic factors of cardiovascular and cerebrovascular diseases, the incidence of metabolic diseases such as adiposity and metabolic dysfunction-associated steatotic liver disease (MASLD) is increasing annually. It is urgent and crucial to find more therapeutic targets to treat these diseases. Mainly expressed in brown adipocytes, mitochondrial uncoupling protein 1 (UCP1) is key to the thermogenesis of classical brown adipose tissue (BAT). Furthermore, white adipose tissue (WAT) is likely to express more UCP1 and subsequently acquire the ability to undergo thermogenesis under certain stimuli. Therefore, targeting and activating UCP1 to promote increased BAT thermogenesis and browning of WAT are helpful in treating metabolic diseases, such as adiposity and MASLD. In this case, the stimuli that activate UCP1 are emerging. Therefore, we summarize the thermogenic stimuli that have activated UCP1 in recent decades, among which cold exposure is one of the stimuli first discovered to activate BAT thermogenesis. As a convenient and efficient therapy with few side effects and good metabolic benefits, physical exercise can also activate the expression of UCP1 in adipose tissue. Notably, for the first time, we have summarized and demonstrated the stimuli of traditional Chinese medicines that can activate UCP1, such as acupuncture, Chinese herbal formulas, and Chinese medicinal herbs. Moreover, pharmacological agents, functional foods, food ingredients, and the gut microbiota are also commonly associated with regulating and activating UCP1. The identification and analysis of UCP1 stimuli can greatly facilitate our understanding of adipose tissue thermogenesis, including the browning of WAT. Thus, it is more conducive to further research and therapy for glucose and lipid metabolism disorders.

Cross-talks between perivascular adipose tissue and neighbors: multifaceted nature of nereids

Perivascular adipose tissue (PVAT) is a unique fat depot surrounding blood vessels and plays a vital role in the progression of vascular remodeling and dysfunction. PVAT exhibits remarkable differences in structure, phenotype, origin, and secretome across anatomical locations. The proximity of PVAT to neighboring vascular beds favors a niche for bidirectional communication between adipocytes and vascular smooth muscle cells, endothelial cells, and immune cells. In this review, we update our understanding of PVAT's regional differences and provide a comprehensive exploration of how these differences impact cross-talks between PVAT and the vascular wall. Different PVAT depots show different degrees of vasoprotective function and resilience to pathological changes such as obesity and vasculopathies, shaping multifaceted interactions between PVAT depots and adjacent vasculatures. The depot-specific resilience may lead to innovative strategies to manage cardiometabolic disorders.

The role of sirtuins and uncoupling proteins on vascular aging: The Northern Manhattan Study experience

Aging affects all organs. Arteries, in particular, are among the most affected. Vascular aging (VA) is defined as age-associated changes in function and structure of vessels. Classical VA phenotypes are carotid intima-media thickness (IMT), carotid plaque (CP), and arterial stiffness (STIFF). Individuals have different predisposition to these VA phenotypes and their associated risk of cardiovascular events. Some develop an early vascular aging (EVA), and others are protected and identified as having supernormal vascular aging (SUPERNOVA). The mechanisms leading to these phenotypes are not well understood. In the Northern Manhattan Study (NOMAS), we found genetic variants in the 7 Sirtuins (SIRT) and 5 Uncoupling Proteins (UCP) to be differently associated with risk to developing VA phenotypes. In this article, we review the results of genetic-epidemiology studies to better understand which of the single nucleotide polymorphisms (SNPs) in SIRT and UCP are responsible for both EVA and SUPERNOVA.

Seasonal variability of lesions distribution in acute ischemic stroke: A retrospective study

Seasonal variability could have an impact on the incidence and outcome of stroke. However, little is known about the correlation between seasonal variability and location of acute cerebral infarction. This study aimed to explore the relationship between onset season and the lesions distribution of acute ischemic stroke (AIS). We retrospectively analysis data from 1488 AIS patients admitted to the Second Hospital of Tianjin Medical University from 2018 to 2022. All subjects completed head magnetic resonance imaging examination (MRI) and were divided into four groups according to the onset seasons. The lesions distribution of AIS was evaluated for anterior/posterior/double circulation infarction (DCI), unilateral/bilateral infarctions, and single/multiple cerebral infarctions based on MRI. Logistic regression models were employed to assess the association of season with lesions distribution of AIS. Subgroup analysis was performed in different stroke subtypes. Of 1488 patients, 387 (26.0%) AIS occurred in spring, 425 (28.6%) in summer, 331 (22.2%) in autumn and 345 (23.2%) in winter. Multivariate logistic regression demonstrated that the winter group had 2.15 times (95% CI:1.44-3.21) risk of multiple infarctions, 2.69 times (95% CI:1.80-4.02) of bilateral infarctions and 1.54 times (95% CI:1.05-2.26) of DCI compared with summer group, respectively. Subgroup analysis showed an increased risk of multiple (p < 0.01) or bilateral infarctions (p < 0.01) in small-artery occlusion (SAO) subtype, and higher risk of bilateral infarctions (p < 0.01) or DCI (p < 0.05) in large artery atherosclerosis (LAA) subtype during winter. No significant associations of season with lesions distribution in cardioembolism subtype. Our study highlighted a prominent seasonal variability in the lesions distribution of AIS, particularly in LAA and SAO subtypes. The findings could help to formulating meteorological risk warning strategies for different subtypes.

[Activation of α7 nAChR improves white fat homeostasis and promotes beige adipogenesis and thermogenesis in obese mice]

OBJECTIVE

To investigate the effects of α7 nicotinic acetylcholine receptor (nAChR) agonist on β3-adrenoceptor agonist-induced impairment of white fat homeostasis and beige adipose formation and heat production in obese mice.

METHODS

Forty obese C57BL/6J mice were randomized into high-fat feeding group, β3-adrenoceptor agonist-treated model group, α7 nAChR agonist group, and α7 nAChR inhibitor group (n=10), with another 10 mice with normal feeding as the blank control group. White adipose tissue from the epididymis of the mice were sampled for HE staining of the adipocytes. The expression levels of TNF-α, IL-1β, IL-10 and TGF-β in the white adipose tissue were determined by ELISA, and the mRNA levels of iNOS, Arg1, UCP-1, PRDM-16 and PGC-1α were detected using RT-qPCR. Western blotting was performed to detect the expression levels of NF-κB P65, p-JAK2, p-STAT3 in the white adipose tissue.

RESULTS

Compared with those in the blank control group, the mice with high-fat feeding showed significantly increased body weight, more fat vacuoles in the white adipose tissue, increased volume of lipid droplets in the adipocytes, upregulated iNOS mRNA expression and protein expression of TNF-α and IL-1β, and lowered expression of Arg-1 mRNA and IL-10 and TGF-β proteins (P < 0.01). Treatment with α7 nAChR significantly reduced mRNA levels of PRDM-16, PGC-1α and UCP-1, lowered TNF-α and IL-1β expressions, increased IL-10 and TGF-β expressions, and reduced M1/M2 macrophage ratio in the white adipose tissues (P < 0.05 or 0.01).

CONCLUSION

Activation of α7 nAchR improves white adipose tissue homeostasis impairment induced by β3 agonist, promotes transformation of M1 to M2 macrophages, reduces inflammatory response in white adipose tissue, and promote beige adipogenesis and thermogenesis in obese mice.

Spermidine activates adipose tissue thermogenesis through autophagy and fibroblast growth factor 21

Spermidine exerts protective roles in obesity, while the mechanism of spermidine in adipose tissue thermogenesis remains unclear. The present study first investigated the effect of spermidine on cold-stimulation and β3-adrenoceptor agonist-induced thermogenesis in lean and high-fat diet-induced obese mice. Next, the role of spermidine on glucose and lipid metabolism in different types of adipose tissue was determined. Here, we found that spermidine supplementation did not affect cold-stimulated thermogenesis in lean mice, while significantly promoting the activation of adipose tissue thermogenesis under cold stimulation and β3-adrenergic receptor agonist treatment in obese mice. Spermidine treatment markedly enhanced glucose and lipid metabolism in adipose tissues, and these results were associated with the activated autophagy pathway. Moreover, spermidine up-regulated fibroblast growth factor 21 (FGF21) signaling and its downstream pathway, including PI3K/AKT and AMPK pathways in vivo and in vitro. Knockdown of Fgf21 or inhibition of PI3K/AKT and AMPK pathways in brown adipocytes abolished the thermogenesis-promoting effect of spermidine, suggesting that the effect of spermidine on adipose tissue thermogenesis might be regulated by FGF21 signaling via the PI3K/AKT and AMPK pathways. The present study provides new insight into the mechanism of spermidine on obesity and its metabolic complications, thereby laying a theoretical basis for the clinical application of spermidine.

Effect of repeatedly applied cold water immersion on subclinical atherosclerosis, inflammation, fat accumulation and lipid profile parameters of volunteers

Significant acute cardiovascular, metabolic, and endocrine changes have been traced to short-lasting cold water immersion (CWI); however, the long-term impact of recurrent CWI on atherogenesis, lipid parameters, and fat distribution has not yet been studied. The goal of this study was to investigate the alleged protective effect. A total of 35 healthy volunteers were monitored for a period of 5 months during which the CWI was performed under standardized conditions (three times per week for 7-10 min, without neoprene equipment). Volunteers with measured weight or muscle mass increases of more than 5% were ineligible. An analogous control group (N = 30) was included. At the onset and completion of the study, blood samples were obtained, and clinical assessments took place. PCSK9 and hsCRP levels were measured together with other lipid-related and non-lipid-related indicators. Carotid intima-media thickness test (cIMT) and echo-tracking for the identification of arterial stiffness (PWV, AI, and β) were used to identify early vascular alterations. Hepatorenal index (HRI) calculations served to quantify liver steatosis, while changes in subcutaneous and visceral fat thickness were used to quantify fat distribution. The given protocol was successfully completed by 28 volunteers. Long-term repeated CWI resulted in a significant decline in cIMT (p = 0.0001), AI (p = 0.0002), Beta (p = 0.0001), and PWV (p = 0.0001). PCSK9 (p = 0.01) and hsCRP (p = 0.01) showed a significant decrease when compared to initial values. In comparison to the starting values, liver fat accumulation decreased by 11% on average (HRI p = 0.001). LDL, TC, TG, and VLDL levels all significantly decreased as well. We suggest that repeated CWI may have beneficial impact on lipid, non-lipid, and lipid-related indices, as well as atherogenesis and liver fat storage.

Pinuseldarone, a Clerodane-Type Diterpene from Pinus eldarica Needles and Phytochemicals as Novel Agents for Regulating Brown Adipogenesis and Thermogenesis

Phytochemical investigation of the MeOH extract of Pinus eldarica needles led to the isolation and identification of a new clerodane-type diterpene, pinuseldarone (1), along with a known flavonoid, 5,4'-dihydroxy-3,7,8-trimethoxy-6-C-methylflavone (2), through HPLC purification. The structure of the new compound 1 was elucidated using spectroscopic methods, including 1D and 2D NMR, as well as HRESIMS. Its absolute configuration was established through NOESY analysis and computational methods, including electronic circular dichroism (ECD) calculations and gauge-including atomic orbital NMR chemical shift calculations, followed by DP4+ probability analysis. The metabolic implications of the isolated compounds were assessed using a cultured brown adipocyte model derived from murine brown adipose tissue. It was observed that treatment with dihydroxy-3,7,8-trimethoxy-6-C-methylflavone (2) downregulates the adipogenic marker C/EBPδ and fatty acid transporter CD36, resulting in a significant reduction in lipid accumulation during brown adipocyte differentiation. However, pinuseldarone (1) treatment did not affect brown adipocyte differentiation. Interestingly, pretreatment with pinuseldarone (1) potentiated the pharmacological stimulation of brown adipocytes, seemingly achieved by sensitizing their response to β3-adrenoreceptor signaling. Therefore, our findings indicate that phytochemicals derived from P. eldarica needles could potentially serve as valuable compounds for adjusting the metabolic activity of brown adipose tissue, a vital component in maintaining whole-body metabolic homeostasis.

Therapeutic Potential for Beta-3 Adrenoreceptor Agonists in Peripheral Arterial Disease and Diabetic Foot Ulcers

Annually, peripheral arterial disease is estimated to cost over USD 21 billion and diabetic foot disease an estimated at USD 9-13 billion. Mirabegron is a TGA-approved beta-3 adrenoreceptor agonist, shown to be safe and effective in the treatment of overactive bladder syndrome by stimulating bladder smooth muscle relaxation. In this review, we discuss the potential use of beta-3 adrenoreceptor agonists as therapeutic agents repurposed for peripheral arterial disease and diabetic foot ulcers. The development of both conditions is underpinned by the upregulation of oxidative stress pathways and consequential inflammation and hypoxia. In oxidative stress, there is an imbalance of reactive oxygen species and nitric oxide. Endothelial nitric oxide synthase becomes uncoupled in disease states, producing superoxide and worsening oxidative stress. Agonist stimulation of the beta-3 adrenoreceptor recouples and activates endothelial nitric oxide synthase, increasing the production of nitric oxide. This reduces circulating reactive oxygen species, thus decreasing redox modification and dysregulation of cellular proteins, causing downstream smooth muscle relaxation, improved endothelial function and increased angiogenesis. These mechanisms lead to endothelial repair in peripheral arterial disease and an enhanced perfusion in hypoxic tissue, which will likely improve the healing of chronic ulcers.

Hypoxia-induced signaling in the cardiovascular system: pathogenesis and therapeutic targets

Hypoxia, characterized by reduced oxygen concentration, is a significant stressor that affects the survival of aerobic species and plays a prominent role in cardiovascular diseases. From the research history and milestone events related to hypoxia in cardiovascular development and diseases, The "hypoxia-inducible factors (HIFs) switch" can be observed from both temporal and spatial perspectives, encompassing the occurrence and progression of hypoxia (gradual decline in oxygen concentration), the acute and chronic manifestations of hypoxia, and the geographical characteristics of hypoxia (natural selection at high altitudes). Furthermore, hypoxia signaling pathways are associated with natural rhythms, such as diurnal and hibernation processes. In addition to innate factors and natural selection, it has been found that epigenetics, as a postnatal factor, profoundly influences the hypoxic response and progression within the cardiovascular system. Within this intricate process, interactions between different tissues and organs within the cardiovascular system and other systems in the context of hypoxia signaling pathways have been established. Thus, it is the time to summarize and to construct a multi-level regulatory framework of hypoxia signaling and mechanisms in cardiovascular diseases for developing more therapeutic targets and make reasonable advancements in clinical research, including FDA-approved drugs and ongoing clinical trials, to guide future clinical practice in the field of hypoxia signaling in cardiovascular diseases.

Role of lisinopril in the therapeutic management of cardiovascular disease by targeting microtubule affinity regulating kinase 4: molecular docking and molecular dynamics simulation approaches

Cardiovascular diseases (CVDs) are a major cause of premature adult death. Various factors contribute to the development of CVDs, such as atherosclerosis leading to myocardial infarction (MI), and compromised cardiac function after MI leads to chronic heart failure with systemic health complications and a high mortality rate. Microtubule detyrosination has rapidly evolved as an essential mechanism to regulate cardiomyocyte contractility. Microtubule affinity regulating kinase 4 (MARK4) regulates cardiomyocyte contractility in a way that it promotes phosphorylation of microtubule-associated protein 4, thereby facilitating the access of vasohibin 2-a tubulin carboxypeptidase-to microtubules for the detyrosination of α-tubulin. Lisinopril, a drug belonging to the class of angiotensin-converting enzyme inhibitors, is used to treat high blood pressure. This is also used to treat heart failure, which plays a vital role in improving the survival rate post-heart attack. In this study, we will evaluate the MARK4 inhibitory potential of lisinopril employing molecular docking and molecular dynamics (MD) simulation approaches. Molecular docking analysis suggested that lisinopril binds to MARK4 with a significant binding affinity forming interactions with functionally essential residues of MARK4. Additionally, MD simulation deciphered the structural dynamics and stability of the MARK4-lisinopril complex. The findings of MD studies established that minimal structural deviations are observed during simulation, affirming the stability of the MARK4-lisinopril complex. Altogether, this study demonstrates lisinopril's crucial role in the therapeutic management of CVD by targeting MARK4.Communicated by Ramaswamy H. Sarma.

The role of perivascular adipose tissue-secreted adipocytokines in cardiovascular disease

Perivascular adipose tissue and the vessel wall are connected through intricate bidirectional paracrine and vascular secretory signaling pathways. The secretion of inflammatory factors and oxidative products by the vessel wall in the diseased segment has the ability to influence the phenotype of perivascular adipocytes. Additionally, the secretion of adipokines by perivascular adipose tissue exacerbates the inflammatory response in the diseased vessel wall. Therefore, quantitative and qualitative studies of perivascular adipose tissue are of great value in the context of vascular inflammation and may provide a reference for the assessment of cardiovascular ischemic disease.

Kaempferol regulates the thermogenic function of adipocytes in high-fat-diet-induced obesity via the CDK6/RUNX1/UCP1 signaling pathway

Activation of adipose tissue thermogenesis is a promising strategy in the treatment of obesity and obesity-related metabolic disorders. Kaempferol (KPF) is a predominant dietary flavonoid with multiple pharmacological properties, such as anti-inflammatory and antioxidant activities. In this study, we sought to characterize the role of KPF in adipocyte thermogenesis. We demonstrated that KPF-treated mice were protected from diet-induced obesity, glucose tolerance, and insulin resistance, accompanied by markedly increased energy expenditure, ex vivo oxygen consumption of white fat, and increased expression of proteins related to adaptive thermogenesis. KPF-promoted beige cell formation is a cell-autonomous effect, since the overexpression of cyclin-dependent kinase 6 (CDK6) in preadipocytes partially reversed browning phenotypes observed in KPF-treated cells. Overall, these data implicate that KPF is involved in promoting beige cell formation by suppressing CDK6 protein expression. This study provides evidence that KPF is a promising natural product for obesity treatment by boosting energy expenditure.

Associations between high-altitude adaptation and risk of cardiovascular diseases: a bidirectional Mendelian randomization study

High-altitude adaptation (HAA) was reported to be significantly associated with reduced risks for multiple cardiovascular diseases (CVDs). However, the causality and direction of the associations are largely uncharacterized. We aimed to examine the potential causal relationships between HAA and six types of CVD, including coronary artery disease (CAD), cerebral aneurysm, ischemic stroke, peripheral artery disease, arrhythmia and atrial fibrillation. We obtained the summary data from largest available genome-wide association study of HAA and six types of CVD. Two-sample bidirectional Mendelian randomization (MR) analyses were performed to infer the causality between them. In the sensitivity analyses, MR-Egger regression analyses and MR-Pleiotropy RESidual Sum and Outlier (MR-PRESSO) global analyses were used to assess the pleiotropic effects; Cochran's Q tests were used to test the heterogeneity by inverse variance-weighted (IVW) and MR-Egger methods; and the leave-one-out analyses were used to examine whether some single nucleotide polymorphisms (SNPs) could influence the results independently. The MR main analyses showed that the genetically instrumented HAA was significantly causally associated with the reduced risks of CAD (odds ratio [OR] = 0.029; 95% confidence interval [CI] = 0.004-0.234; P = 8.64 × 10-4). In contrast, there was no statistically significant relationship between CVDs and HAA. Our findings provide evidence for the causal effects of HAA on the reduced risks of CAD. However, there is no causality of CVDs on HAA. These findings might be helpful in developing the prevention and intervention strategies for CAD.

NPRC deletion mitigated atherosclerosis by inhibiting oxidative stress, inflammation and apoptosis in ApoE knockout mice

Previous studies suggested a beneficial effect of natriuretic peptides in animal models of cardiovascular disease, but the role of natriuretic peptide receptor C (NPRC) in the pathogenesis of atherosclerosis (AS) remains unknown. This study was designed to test the hypothesis that NPRC may promote AS lesion formation and instability by enhancing oxidative stress, inflammation, and apoptosis via protein kinase A (PKA) signaling. ApoE-/- mice were fed chow or Western diet for 12 weeks and NPRC expression was significantly increased in the aortic tissues of Western diet-fed mice. Systemic NPRC knockout mice were crossed with ApoE-/- mice to generate ApoE-/-NPRC-/- mice, and NPRC deletion resulted in a significant decrease in the size and instability of aortic atherosclerotic lesions in ApoE-/-NPRC-/- versus ApoE-/- mice. In addition, endothelial cell-specific NPRC knockout attenuated atherosclerotic lesions in mice. In contrast, endothelial cell overexpression of NPRC aggravated the size and instability of atherosclerotic aortic lesions in mice. Experiments in vitro showed that NPRC knockdown in human aortic endothelial cells (HAECs) inhibited ROS production, pro-inflammatory cytokine expression and endothelial cell apoptosis, and increased eNOS expression. Furthermore, NPRC knockdown in HAECs suppressed macrophage migration, cytokine expression, and phagocytosis via its effects on endothelial cells. On the contrary, NPRC overexpression in endothelial cells resulted in opposite effects. Mechanistically, the anti-inflammation and anti-atherosclerosis effects of NPRC deletion involved activation of cAMP/PKA pathway, leading to downstream upregulated AKT1 pathway and downregulated NF-κB pathway. In conclusion, NPRC deletion reduced the size and instability of atherosclerotic lesions in ApoE-/- mice via attenuating inflammation and endothelial cell apoptosis and increasing eNOS expression by modulating cAMP/PKA-AKT1 and NF-κB pathways. Thus, targeting NPRC may provide a promising approach to the prevention and treatment of atherosclerosis.

Cold exposure protects against medial arterial calcification development via autophagy

Medial arterial calcification (MAC), a systemic vascular disease different from atherosclerosis, is associated with an increased incidence of cardiovascular events. Several studies have demonstrated that ambient temperature is one of the most important factors affecting cardiovascular events. However, there has been limited research on the effect of different ambient temperatures on MAC. In the present study, we showed that cold temperature exposure (CT) in mice slowed down the formation of vitamin D (VD)-induced vascular calcification compared with room temperature exposure (RT). To investigate the mechanism involved, we isolated plasma-derived exosomes from mice subjected to CT or RT for 30 days (CT-Exo or RT-Exo, respectively). Compared with RT-Exo, CT-Exo remarkably alleviated the calcification/senescence formation of vascular smooth muscle cells (VSMCs) and promoted autophagy by activating the phosphorylation of AMP-activated protein kinase (p-AMPK) and inhibiting phosphorylation of mammalian target of rapamycin (p-mTOR). At the same time, CT-Exo promoted autophagy in β-glycerophosphate (β-GP)-induced VSMCs. The number of autophagosomes and the expression of autophagy-related proteins ATG5 and LC3B increased, while the expression of p62 decreased. Based on a microRNA chip microarray assay and real-time polymerase chain reaction, miR-320a-3p was highly enriched in CT-Exo as well as thoracic aortic vessels in CT mice. miR-320a-3p downregulation in CT-Exo using AntagomiR-320a-3p inhibited autophagy and blunted its anti-calcification protective effect on VSMCs. Moreover, we identified that programmed cell death 4 (PDCD4) is a target of miR-320a-3p, and silencing PDCD4 increased autophagy and decreased calcification in VSMCs. Treatment with CT-Exo alleviated the formation of MAC in VD-treated mice, while these effects were partially reversed by GW4869. Furthermore, the anti-arterial calcification protective effects of CT-Exo were largely abolished by AntagomiR-320a-3p in VD-induced mice. In summary, we have highlighted that prolonged cold may be a good way to reduce the incidence of MAC. Specifically, miR-320a-3p from CT-Exo could protect against the initiation and progression of MAC via the AMPK/mTOR autophagy pathway.

"Humanizing" mouse environments: Humidity, diurnal cycles and thermoneutrality

Thermoneutral housing has been shown to promote more accurate and robust development of several pathologies in mice. Raising animal housing temperatures a few degrees may create a relatively straightforward opportunity to improve translatability of mouse models. In this commentary, we discuss the changes of physiology induced in mice housed at thermoneutrality, and review techniques for measuring systemic thermogenesis, specifically those affecting storage and mobilization of lipids in adipose depots. Environmental cues are a component of the information integrated by the brain to calculate food consumption and calorie deposition. We show that relative humidity is one of those cues, inducing a rapid sensory response that is converted to a more chronic susceptibility to obesity. Given high inter-institutional variability in the regulation of relative humidity, study reproducibility may be improved by consideration of this factor. We evaluate a "humanized" environmental cycling protocol, where mice sleep in warm temperature housing, and are cool during the wake cycle. We show that this protocol suppresses adaptation to cool exposure, with consequence for adipose-associated lipid storage. To evaluate systemic cues in mice housed at thermoneutral temperatures, we characterized the circulating lipidome, and show that sera are highly depleted in some HDL-associated phospholipids, specifically phospholipids containing the essential fatty acid, 18:2 linoleic acid, and its derivative, arachidonic acid (20:4) and related ether-phospholipids. Given the role of these fatty acids in inflammatory responses, we propose they may underlie the differences in disease progression observed at thermoneutrality.

Continuous Hypobaric Hypoxia may Promote Atherosclerosis Progression in Apolipoprotein E-deficient Mice

Background: Intermittent normobaric hypoxia can promote the progression of atherosclerotic plaques. However, the effect of continuous hypobaric hypoxia (CHH), which is a major feature of high-altitude environment, on atherosclerosis has not been investigated thoroughly. Materials and Methods: After eight weeks of high-cholesterol diet, 30 male ApoE^-/- mice were randomly divided into control and CHH groups. Mice in the CHH group lived in a hypobaric chamber with an oxygen content of 10% and air pressure of 364 mmhg (equal to 5,800 m altitude above sea level) for 4 weeks, while mice in the control group lived in normoxia condition. Then all mice were euthanized and the atherosclerotic lesion size and plaque stability in the aortic root were assessed. Intraplaque angiogenesis was characterized by immunostaining of CD31 and endomucin, which are identified as specific markers of vascular endothelial cells. Immunohistochemistry and qRT-PCR were performed to measure inflammatory cytokines. Results: Four weeks of CHH exposure promoted the growth of atherosclerotic lesions (p=0.0017) and decreased the stability of atherosclerotic plaques. In CHH group, plaque smooth muscle cells and collagen contents decreased, while plaque macrophages and lipids contents increased significantly (p<0.001). The contents of CD31 (p=0.0379) and endomucin (p=0.0196) in the plaque was higher in the CHH group and correlated with angiogenesis progression. Further, the content of monocyte chemotactic protein-1 (p=0.0376) and matrix metalloproteinase-2 was significantly higher (p=0.0212) in the CHH group. Conclusions: CHH may accelerate atherosclerosis progression in ApoE^-/- mice by promoting angiogenesis and inflammation.

Curcumin improves metabolic response and increases expression of thermogenesis-associated markers in adipose tissue of male offspring from obese dams

Maternal obesity and dietary style in the pregnancy-lactation period may result in long-term effects on the metabolic health of the offspring, thus increasing the risk of diseases, such as obesity, diabetes, and cardiovascular diseases. Curcumin is a natural polyphenolic compound that has beneficial properties on metabolism. Accordingly, this study is intended to evaluate the effects of curcumin supplementation in pregnant and lactating female mice on the anthropometric, metabolic and molecular parameters of the offspring fed a hyperglycemic diet. The study was conducted with 24 male mice randomized into three groups: i) control group (SD) originating from dams fed a standard diet; ii) hyperglycemic group (HGD) originating from dams fed a hyperglycemic diet; iii) curcumin group (CUR) originating from dams fed a hyperglycemic diet and supplemented with curcumin in the pregnancy-lactation period. All offspring groups were fed a hyperglycemic diet for 12 weeks. Anthropometricand biochemical parameters were measured, as well as the expression of thermogenesis-associated markers in the interscapular brown and inguinal white adipose tissues. The results showed less weight gain in the CUR group, with a concomitant reduction in food consumption compared to the HGD group. Biochemical parameters indicated lower levels of total cholesterol, glucose, and insulin for the CUR group, in addition to improved glucose tolerance and insulin sensitivity. The molecular evaluation indicated increased mRNA expression levels of UCP1 and PRDM16 in the brown and white adipose tissues. It is concluded that curcumin supplementation in the pregnancy-lactation period in dams with diet-induced obesity may lead to improvements in the offspring's metabolic phenotype, even if they are submitted to an obesogenic environment, possibly via thermogenesis activation.

Insulin-like growth factor 1 reduces coronary atherosclerosis in pigs with familial hypercholesterolemia

Although murine models of coronary atherosclerotic disease have been used extensively to determine mechanisms, limited new therapeutic options have emerged. Pigs with familial hypercholesterolemia (FH pigs) develop complex coronary atheromas that are almost identical to human lesions. We reported previously that insulin-like growth factor 1 (IGF-1) reduced aortic atherosclerosis and promoted features of stable plaque in a murine model. We administered human recombinant IGF-1 or saline (control) in atherosclerotic FH pigs for 6 months. IGF-1 decreased relative coronary atheroma in vivo (intravascular ultrasound) and reduced lesion cross-sectional area (postmortem histology). IGF-1 increased plaque's fibrous cap thickness, and reduced necrotic core, macrophage content, and cell apoptosis, consistent with promotion of a stable plaque phenotype. IGF-1 reduced circulating triglycerides, markers of systemic oxidative stress, and CXCL12 chemokine levels. We used spatial transcriptomics (ST) to identify global transcriptome changes in advanced plaque compartments and to obtain mechanistic insights into IGF-1 effects. ST analysis showed that IGF-1 suppressed FOS/FOSB factors and gene expression of MMP9 and CXCL14 in plaque macrophages, suggesting possible involvement of these molecules in IGF-1's effect on atherosclerosis. Thus, IGF-1 reduced coronary plaque burden and promoted features of stable plaque in a pig model, providing support for consideration of clinical trials.

Intermittent Fasting Resolves Dyslipidemia and Atherogenesis in Apolipoprotein E-Deficient Mice in a Diet-Dependent Manner, Irrespective of Sex

In humans and animal models, intermittent fasting (IF) interventions promote body weight loss, improve metabolic health, and are thought to lower cardiovascular disease risk. However, there is a paucity of reports on the relevance of such nutritional interventions in the context of dyslipidemia and atherosclerotic cardiovascular diseases. The present study assessed the metabolic and atheroprotective effects of intermittent fasting intervention (IF) in atherosclerosis-prone apolipoprotein E-deficient (Apoe-/-) mice. Groups of male and female Apoe-/- mice were fed a regular (chow) or atherogenic (high-fat, high-cholesterol, HFCD) diet for 4 months, either ad libitum or in an alternate-day fasting manner. The results show that IF intervention improved glucose and lipid metabolism independently of sex. However, IF only decreased body weight gain in males fed chow diet and differentially modulated adipose tissue parameters and liver steatosis in a diet composition-dependent manner. Finally, IF prevented spontaneous aortic atherosclerotic lesion formation in mice fed chow diet, irrespective of sex, but failed to reduce HFCD-diet-induced atherosclerosis. Overall, the current work indicates that IF interventions can efficiently improve glucose homeostasis and treat atherogenic dyslipidemia, but a degree of caution is warranted with regard to the individual sex and the composition of the dietary regimen.

Mirabegron-induced brown fat activation does not exacerbate atherosclerosis in mice with a functional hepatic ApoE-LDLR pathway

Activation of brown adipose tissue (BAT) with the β3-adrenergic receptor agonist CL316,243 protects mice from atherosclerosis development, and the presence of metabolically active BAT is associated with cardiometabolic health in humans. In contrast, exposure to cold or treatment with the clinically used β3-adrenergic receptor agonist mirabegron to activate BAT exacerbates atherosclerosis in apolipoprotein E (ApoE)- and low-density lipoprotein receptor (LDLR)-deficient mice, both lacking a functional ApoE-LDLR pathway crucial for lipoprotein remnant clearance. We, therefore, investigated the effects of mirabegron treatment on dyslipidemia and atherosclerosis development in APOE*3-Leiden.CETP mice, a humanized lipoprotein metabolism model with a functional ApoE-LDLR clearance pathway. Mirabegron activated BAT and induced white adipose tissue (WAT) browning, accompanied by selectively increased fat oxidation and attenuated fat mass gain. Mirabegron increased the uptake of fatty acids derived from triglyceride (TG)-rich lipoproteins by BAT and WAT, which was coupled to increased hepatic uptake of the generated cholesterol-enriched core remnants. Mirabegron also promoted hepatic very low-density lipoprotein (VLDL) production, likely due to an increased flux of fatty acids from WAT to the liver, and resulted in transient elevation in plasma TG levels followed by a substantial decrease in plasma TGs. These effects led to a trend toward lower plasma cholesterol levels and reduced atherosclerosis. We conclude that BAT activation by mirabegron leads to substantial metabolic benefits in APOE*3-Leiden.CETP mice, and mirabegron treatment is certainly not atherogenic. These data underscore the importance of the choice of experimental models when investigating the effect of BAT activation on lipoprotein metabolism and atherosclerosis.

Beiging of perivascular adipose tissue regulates its inflammation and vascular remodeling

Although inflammation plays critical roles in the development of atherosclerosis, its regulatory mechanisms remain incompletely understood. Perivascular adipose tissue (PVAT) has been reported to undergo inflammatory changes in response to vascular injury. Here, we show that vascular injury induces the beiging (brown adipose tissue-like phenotype change) of PVAT, which fine-tunes inflammatory response and thus vascular remodeling as a protective mechanism. In a mouse model of endovascular injury, macrophages accumulate in PVAT, causing beiging phenotype change. Inhibition of PVAT beiging by genetically silencing PRDM16, a key regulator to beiging, exacerbates inflammation and vascular remodeling following injury. Conversely, activation of PVAT beiging attenuates inflammation and pathological vascular remodeling. Single-cell RNA sequencing reveals that beige adipocytes abundantly express neuregulin 4 (Nrg4) which critically regulate alternative macrophage activation. Importantly, significant beiging is observed in the diseased aortic PVAT in patients with acute aortic dissection. Taken together, vascular injury induces the beiging of adjacent PVAT with macrophage accumulation, where NRG4 secreted from the beige PVAT facilitates alternative activation of macrophages, leading to the resolution of vascular inflammation. Our study demonstrates the pivotal roles of PVAT in vascular inflammation and remodeling and will open a new avenue for treating atherosclerosis.

Perivascular adipose tissue (PVAT) has been reported to undergo inflammatory changes in response to vascular injury. Here, the authors show that vascular injury induces the beiging (brown adipose tissue-like phenotype change) of PVAT, which fine-tunes inflammatory response as a protective mechanism.

The Role and Regulatory Mechanism of Brown Adipose Tissue Activation in Diet-Induced Thermogenesis in Health and Diseases

Brown adipose tissue (BAT) has been considered a vital organ in response to non-shivering adaptive thermogenesis, which could be activated during cold exposure through the sympathetic nervous system (SNS) or under postprandial conditions contributing to diet-induced thermogenesis (DIT). Humans prefer to live within their thermal comfort or neutral zone with minimal energy expenditure created by wearing clothing, making shelters, or using an air conditioner to regulate their ambient temperature; thereby, DIT would become an important mechanism to counter-regulate energy intake and lipid accumulation. In addition, there has been a long interest in the intriguing possibility that a defect in DIT predisposes one to obesity and other metabolic diseases. Due to the recent advances in methodology to evaluate the functional activity of BAT and DIT, this updated review will focus on the role and regulatory mechanism of BAT biology in DIT in health and diseases and whether these mechanisms are applicable to humans.

Activin receptor-like kinase 7 promotes apoptosis of vascular smooth muscle cells via activating Smad2/3 signaling in diabetic atherosclerosis

Vascular smooth muscle cells (VSMCs) is a vital accelerator in the late phase of diabetic atherosclerosis, but the underlying mechanism remains unclear. The aim of our study was to investigate whether activin receptor-like kinase 7 (ALK7)-Smad2/3 pathway plays an important role in VSMC apoptosis of diabetic atherosclerosis. It was shown that ALK7 expression was obviously elevated in the aorta of ApoE−/− mice with type 2 diabetes mellitus. Inhibition of ALK7 expression significantly improved the stability of atherosclerotic plaques and reduced cell apoptosis. Further experiments showed that ALK7 knockdown stabilized atherosclerotic plaques by reducing VSMC apoptosis via activating Smad2/3. Our study uncovered the important role of ALK7-Smad2/3 signaling in VSMCs apoptosis, which might be a potential therapeutic target in diabetic atherosclerosis.

Role of thermogenic adipose tissue in lipid metabolism and atherosclerotic cardiovascular disease: lessons from studies in mice and humans

Brown adipocytes within brown adipose tissue (BAT) and beige adipocytes within white adipose tissue dissipate nutritional energy as heat. Studies in mice have shown that activation of thermogenesis in brown and beige adipocytes enhances the lipolytic processing of triglyceride-rich lipoproteins (TRLs) in plasma to supply these adipocytes with fatty acids for oxidation. This process results in formation of TRL remnants that are removed from the circulation through binding of apolipoprotein E (ApoE) on their surface to the low-density lipoprotein receptor (LDLR) on hepatocytes, followed by internalization. Concomitantly, lipolytic processing of circulating TRLs leads to generation of excess surface phospholipids that are transferred to nascent high-density lipoproteins (HDL), increasing their capacity for reverse cholesterol transport. Activation of thermogenic adipocytes thus lowers circulating triglycerides and non-HDL-cholesterol, while it increases HDL-cholesterol. The combined effect is protection from atherosclerosis development, which becomes evident in humanized mouse models with an intact ApoE-LDLR clearance pathway only, and is additive to the effects of classical lipid-lowering drugs including statins and proprotein convertase subtilisin/kexin type 9 inhibitors. A large recent study revealed that the presence of metabolically active BAT in humans is associated with lower triglycerides, higher HDL-cholesterol and lower risk of cardiovascular diseases. This narrative review aims to provide leads for further exploration of thermogenic adipose tissue as a therapeutic target. To this end, we describe the latest knowledge on the role of BAT in lipoprotein metabolism and address, for example, the discovery of the β2-adrenergic receptor as the dominant adrenergic receptor in human thermogenic adipocytes.

Upregulation of Endothelial DKK1 (Dickkopf 1) Promotes the Development of Pulmonary Hypertension Through the Sp1 (Specificity Protein 1)/SHMT2 (Serine Hydroxymethyltransferase 2) Pathway

BACKGROUND

Pulmonary hypertension (PH) is a cancer-like proliferative disease, which has no curative treatment options. The dysfunction of pulmonary artery endothelial cells plays a key role in PH. DKK1 (Dickkopf 1) is a secretory glycoprotein that exerts proproliferative effects on tumor cells. In the present study, we aimed to identify the role and underlying mechanism of DKK1 in the development of PH, which still remain unclear.

METHODS AND RESULTS

We found endothelial DKK1 expression was upregulated in serum and lung tissues obtained from patients with PH, mice with hypoxia-induced PH, and human pulmonary artery endothelial cells cultured under hypoxic conditions. Endothelium-specific DKK1-knockout (DKK1ECKO) mice significantly ameliorated hypoxia+Sugen5416 and hypoxia-induced PH. More importantly, neutralizing anti-DKK1 antibody treatment significantly attenuated established hypoxia+Sugen5416 PH. Results of proteome analysis of control and DKK1-knockdown human pulmonary artery endothelial cells identified a significantly differentially expressed protein, SHMT2 (serine hydroxymethyltransferase 2), a key metabolic enzyme in one-carbon metabolism, as a novel DKK1 target. DKK1 knockdown in human pulmonary artery endothelial cells cultured under hypoxic conditions decreased the cellular NADPH/NADP+ ratio, increased reactive oxygen species levels and the extent of mitochondrial DNA damage, and inhibited mitochondrial membrane hyperpolarization. In the context of this altered redox defense and mitochondrial disorder, DKK1 induced a proproliferative and antiapoptotic phenotype in endothelial cells. Furthermore, we confirmed that DKK1 regulated SHMT2 transcription through the AKT-Sp1 (specificity protein 1) signaling axis.

CONCLUSIONS

Our data provide robust evidence and molecular explanations for the associations between DKK1, redox defense, mitochondrial disorders, and PH and reveal a novel target for PH treatment.

An update on brown adipose tissue and obesity intervention: Function, regulation and therapeutic implications

Overweight and obesity have become a world-wide problem. However, effective intervention approaches are limited. Brown adipose tissue, which helps maintain body temperature and contributes to thermogenesis, is dependent on uncoupling protein1. Over the last decade, an in-creasing number of studies have found that activating brown adipose tissue and browning of white adipose tissue can protect against obesity and obesity-related metabolic disease. Brown adipose tissue has gradually become an appealing therapeutic target for the prevention and re-versal of obesity. However, some important issues remain unresolved. It is not certain whether increasing brown adipose tissue activity is the cause or effect of body weight loss or what the risks might be for sympathetic nervous system-dependent non-shivering thermogenesis. In this review, we comprehensively summarize approaches to activating brown adipose tissue and/or browning white adipose tissue, such as cold exposure, exercise, and small-molecule treatment. We highlight the functional mechanisms of small-molecule treatment and brown adipose tissue transplantation using batokine, sympathetic nervous system and/or gut microbiome. Finally, we discuss the causality between body weight loss induced by bariatric surgery, exercise, and brown adipose tissue activity.

Lipid Transport in Brown Adipocyte Thermogenesis

Non-shivering thermogenesis is an energy demanding process that primarily occurs in brown and beige adipose tissue. Beyond regulating body temperature, these thermogenic adipocytes regulate systemic glucose and lipid homeostasis. Historically, research on thermogenic adipocytes has focused on glycolytic metabolism due to the discovery of active brown adipose tissue in adult humans through glucose uptake imaging. The importance of lipids in non-shivering thermogenesis has more recently been appreciated. Uptake of circulating lipids into thermogenic adipocytes is necessary for body temperature regulation and whole-body lipid homeostasis. A wide array of circulating lipids contribute to thermogenic potential including free fatty acids, triglycerides, and acylcarnitines. This review will summarize the mechanisms and regulation of lipid uptake into brown adipose tissue including protein-mediated uptake, lipoprotein lipase activity, endocytosis, vesicle packaging, and lipid chaperones. We will also address existing gaps in knowledge for cold induced lipid uptake into thermogenic adipose tissue.

Mitochondrial uncoupling protein 1 antagonizes atherosclerosis by blocking NLRP3 inflammasome-dependent interleukin-1β production

Mitochondrial uncoupling protein 1 (UCP1) is the hallmark of brown adipocytes responsible for cold- and diet-induced thermogenesis. Here, we report a previously unidentified role of UCP1 in maintaining vascular health through its anti-inflammatory actions possibly in perivascular adipose tissue. UCP1 deficiency exacerbates dietary obesity-induced endothelial dysfunction, vascular inflammation, and atherogenesis in mice, which was not rectified by reconstitution of UCP1 in interscapular brown adipose tissue. Mechanistically, lack of UCP1 augments mitochondrial membrane potential and mitochondrial superoxide, leading to hyperactivation of the NLRP3-inflammasome and caspase-1–mediated maturation of interleukin-1β (IL-1β). UCP1 deficiency–evoked deterioration of vascular dysfunction and atherogenesis is reversed by IL-1β neutralization or a chemical mitochondrial uncoupler. Furthermore, UCP1 knockin pigs (which lack endogenous UCP1) are refractory to vascular inflammation and coronary atherosclerosis. Thus, UCP1 acts as a gatekeeper to prevent NLRP3 inflammasome activation and IL-1β production in the vasculature, thereby conferring a protective effect against cardiovascular diseases.

Brown Adipose Tissue Activation Is Involved in Atherosclerosis of ApoE-/- Mice Induced by Chronic Intermittent Hypoxia

Background: Obstructive sleep apnea is an atherogenesis factor of which chronic intermittent hypoxia is a prominent feature. Chronic intermittent hypoxia (CIH) exposure can sufficiently activate the sympathetic system, which acts on the β3 adrenergic receptors of brown adipose tissue (BAT). However, the activity of BAT and its function in CIH-induced atherosclerosis have not been fully elucidated.

Methods: This study involved ApoE^−/− mice which were fed with a high-fat diet for 12 weeks and grouped into control and CIH group. During the last 8 weeks, mice in the CIH group were housed in cages to deliver CIH (12 h per day, cyclic inspiratory oxygen fraction 5–20.9%, 180 s cycle). Atherosclerotic plaques were evaluated by Oil Red O, hematoxylin and eosin, Masson staining, and immunohistochemistry. Afterward, we conducted immunohistochemistry, western blotting, and qRT-PCR of uncoupling protein 1 (UCP1) to investigate the activation of BAT. The level of serum total cholesterol (TC), triglyceride, low-density lipoprotein cholesterol (LDL-c), high-density lipoprotein cholesterol (HDL-c), and free fatty acid (FFA) were measured. Finally, RNA-Sequencing was deployed to explore the differentially expressed genes (DEGs) and their enriched pathways between control and CIH groups.

Results: Chronic intermittent hypoxia exposure promoted atherosclerotic plaque area with increasing CD68, α-SMA, and collagen in plaques. BAT activation was presented during CIH exposure with UCP1 up-regulated. Serum TC, triglyceride, LDL-c, and FFA were increased accompanied by BAT activation. HDL-c was decreased. Mechanistically, 43 lipolysis and lipid metabolism-associated mRNA showed different expression profiling between the groups. Calcium, MAPK, and adrenergic signaling pathway included the most gene number among the significantly enriched pathways.

Conclusion: This study first demonstrated that BAT activation is involved in the progression of CIH-induced atherosclerosis, possibly by stimulating lipolysis.

SUR1-E1506K mutation impairs glucose tolerance and promotes vulnerable atherosclerotic plaque phenotype in hypercholesterolemic mice

BACKGROUND AND AIMS

Diabetes is a major risk factor of atherosclerosis and its complications. The loss-of-function mutation E1506K in the sulfonylurea receptor 1 (SUR1-E1506K) induces hyperinsulinemia in infancy, leading to impaired glucose tolerance and increased risk of type 2 diabetes. In this study, we investigate the effect of SUR1-E1506K mutation on atherogenesis in hypercholesterolemic LDLR-/- mice.

METHODS

SUR1-E1506K mutated mice were cross-bred with LDLR-/- mice (SUR1Δ/LDLR-/-), 6 months old mice were fed a western-diet (WD) for 6 months to induce advanced atherosclerotic plaques. At the age of 12 months, atherosclerosis and plaque morphology were analyzed and mRNA gene expression were measured from aortic sections and macrophages. Glucose metabolism was characterized before and after WD. Results were compared to age-matched LDLR-/- mice.

RESULTS

Advanced atherosclerotic plaques did not differ in size between the two strains. However, in SUR1Δ/LDLR-/- mice, plaque necrotic area was increased and smooth muscle cell number was reduced, resulting in higher plaque vulnerability index in SUR1Δ/LDLR-/- mice compared to LDLR-/- mice. SUR1Δ/LDLR-/- mice exhibited impaired glucose tolerance and elevated fasting glucose after WD. The positive staining area of IL-1β and NLRP3 inflammasome were increased in aortic sections in SUR1Δ/LDLR-/- mice compared to LDLR-/- mice, and IL-18 plasma level was elevated in SUR1Δ/LDLR-/- mice. Finally, the mRNA expression of IL-1β and IL-18 were increased in SUR1Δ/LDLR-/- bone marrow derived macrophages in comparison to LDLR-/- macrophages in response to LPS.

CONCLUSIONS

SUR1-E1506K mutation impairs glucose tolerance and increases arterial inflammation, which promotes a vulnerable atherosclerotic plaque phenotype in LDLR-/- mice.

Human Brown Adipose Tissue and Metabolic Health: Potential for Therapeutic Avenues

Obesity-associated metabolic abnormalities comprise a cluster of conditions including dyslipidemia, insulin resistance, diabetes and cardiovascular diseases that has affected more than 650 million people all over the globe. Obesity results from the accumulation of white adipose tissues mainly due to the chronic imbalance of energy intake and energy expenditure. A variety of approaches to treat or prevent obesity, including lifestyle interventions, surgical weight loss procedures and pharmacological approaches to reduce energy intake and increase energy expenditure have failed to substantially decrease the prevalence of obesity. Brown adipose tissue (BAT), the primary source of thermogenesis in infants and small mammals may represent a promising therapeutic target to treat obesity by promoting energy expenditure through non-shivering thermogenesis mediated by mitochondrial uncoupling protein 1 (UCP1). Since the confirmation of functional BAT in adult humans by several groups, approximately a decade ago, and its association with a favorable metabolic phenotype, intense interest on the significance of BAT in adult human physiology and metabolic health has emerged within the scientific community to explore its therapeutic potential for the treatment of obesity and metabolic diseases. A substantially decreased BAT activity in individuals with obesity indicates a role for BAT in the setting of human obesity. On the other hand, BAT mass and its prevalence correlate with lower body mass index (BMI), decreased age and lower glucose levels, leading to a lower incidence of cardio-metabolic diseases. The increased cold exposure in adult humans with undetectable BAT was associated with decreased body fat mass and increased insulin sensitivity. A deeper understanding of the role of BAT in human metabolic health and its interrelationship with body fat distribution and deciphering proper strategies to increase energy expenditure, by either increasing functional BAT mass or inducing white adipose browning, holds the promise for possible therapeutic avenues for the treatment of obesity and associated metabolic disorders.

Cold-induced Conversion of Connective Tissue Skeleton in Brown Adipose Tissues

Thermogenesis via fatty acid-induced uncoupled mitochondrial respiration is the primary function of brown adipose tissue (BAT). In response to changes in ambient temperatures, the weight and specific gravity of BAT change, depending on the quantity of lipid droplets stored in brown adipocytes (BA). Such conditions should result in the reconstruction of connective tissue skeletons, especially of collagen fiber networks, although the mechanisms have not been clarified. This study showed that, within 4 hr of exposing mice to a cold environment, collagen fibers in the extracellular matrix (ECM) of BAT became discontinuous, twisted, emancipated, and curtailed. Surprisingly, the structure of collagen fibers returned to normal after the mice were kept at room temperature for 19 hr, indicating that the alterations in collagen fiber structures are physiological processes association with adaptation to cold environments. These dynamic changes in connective tissue skeletons were not observed in white adipose tissues, suggesting that they are unique to BAT. Interestingly, the vascular permeability of BAT was also augmented by exposure to cold. Collectively, these findings indicate that dynamic changes in ECM collagen fibers provide high flexibility to BAT, enabling the adjustment of tissue structures and the regulation of vascular permeability, resulting in adaptation to changes in ambient temperatures.

Deficient Chaperone-Mediated Autophagy Promotes Inflammation and Atherosclerosis

Rationale: The NLRP3 inflammasome is an important driver of atherosclerosis. Our previous study shows that chaperone-mediated autophagy (CMA), one of the main lysosomal degradative process, has a regulatory role in lipid metabolism of macrophage. However, whether the NLRP3 inflammasome is regulated by CMA and the role of CMA in atherosclerosis remain unclear. Objective: To determine the role of CMA in the regulation of NLRP3 inflammasome and atherosclerosis. Methods and Results: The expression of CMA marker, lysosome associated membrane protein type 2A (LAMP-2A), was first analyzed in ApoE-/- mouse aortas and human coronary atherosclerotic plaques and a significant down-regulation of LAMP-2A in advanced atherosclerosis in both mice and human was observed. To selectively block CMA, we generated macrophage-specific conditional LAMP-2A-knockout mouse strains in C57BL/6 mice and ApoE-/- mice. Deletion of macrophage LAMP-2A accelerated atherosclerotic lesion formation in the aortic root and the whole aorta in ApoE-/- mice. Mechanistically, LAMP-2A deficiency promoted NLRP3 inflammasome activation and subsequent release of mature IL-1β in macrophages and atherosclerotic plaques. Furthermore, gain-of-function studies verified that restoration of LAMP-2A levels in LAMP-2A-deficient macrophages greatly attenuated NLRP3 inflammasome activation. Importantly, we identified the NLRP3 protein as a CMA substrate and demonstrated that LAMP-2A deficiency did not affect the NLRP3 mRNA levels but hindered degradation of the NLRP3 protein through CMA pathway. Conclusions: CMA function becomes impaired during the progression of atherosclerosis, which increases NLRP3 inflammasome activation and secretion of IL-1β, promoting vascular inflammation and atherosclerosis progression. Our study unveils a new mechanism by which NLRP3 inflammasome is regulated in macrophages and atherosclerosis, thus providing a new insight into the role of autophagy-lysosomal pathway in atherosclerosis. Pharmacological activation of CMA may provide a novel therapeutic strategy for atherosclerosis and other NLRP3 inflammasome/IL-1β-driven diseases.

Glucocorticoid/Adiponectin Axis Mediates Full Activation of Cold-Induced Beige Fat Thermogenesis

Glucocorticoids (GCs), a class of corticosteroids produced by the adrenal cortex in response to stress, exert obesity-promoting effects. Although adaptive thermogenesis has been considered an effective approach to counteract obesity, whether GCs play a role in regulating cold stress-induced thermogenesis remains incompletely understood. Here, we show that the circulating levels of stress hormone corticosterone (GC in rodents) were significantly elevated, whereas the levels of adiponectin, an adipokine that was linked to cold-induced adaptive thermogenesis, were decreased 48 h post cold exposure. The administration of a glucocorticoid hydrocortisone downregulated adiponectin protein and mRNA levels in both WAT and white adipocytes, and upregulated thermogenic gene expression in inguinal fat. In contrast, mifepristone, a glucocorticoid receptor antagonist, enhanced adiponectin expression and suppressed energy expenditure in vivo. Mechanistically, hydrocortisone suppressed adiponectin expression by antagonizing PPARγ in differentiated 3T3-L1 adipocytes. Ultimately, adiponectin deficiency restored mifepristone-decreased oxygen consumption and suppressed the expression of thermogenic genes in inguinal fat. Taken together, our study reveals that the GCs/adiponectin axis is a key regulator of beige fat thermogenesis in response to acute cold stress.

An atherosclerotic plaque-targeted single-chain antibody for MR/NIR-II imaging of atherosclerosis and anti-atherosclerosis therapy

Background

Oxidation-specific epitopes (OSEs) are rich in atherosclerotic plaques. Innate and adaptive immune responses to OSEs play an important role in atherosclerosis. The purpose of this study was to develop novel human single-chain variable fragment (scFv) antibody specific to OSEs to image and inhibit atherosclerosis.

Results

Here, we screened a novel scFv antibody, named as ASA6, from phage-displayed human scFv library. ASA6 can bind to oxidized LDL (Ox-LDL) and atherosclerotic plaques. Meanwhile, ASA6 can also inhibit the uptake of Ox-LDL into macrophage to reduce macrophage apoptosis. The atherosclerotic lesion area of ApoE^−/− mice administrated with ASA6 antibody was significantly reduced. Transcriptome analysis reveals the anti-atherosclerosis effect of ASA6 is related to the regulation of fatty acid metabolism and inhibition of M1 macrophage polarization. Moreover, we conjugated ASA6 antibody to NaNdF₄@NaGdF₄ nanoparticles for noninvasive imaging of atherosclerotic plaques by magnetic resonance (MR) and near-infrared window II (NIR-II) imaging.

Conclusions

Together, these data demonstrate the potential of ASA6 antibody in targeted therapy and noninvasive imaging for atherosclerosis.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-021-01047-4.

Prolonged Treatment with Grains of Paradise (Aframomum melegueta) Extract Recruits Adaptive Thermogenesis and Reduces Body Fat in Humans with Low Brown Fat Activity

Increasing adaptive thermogenesis through the activation of brown adipose tissue (BAT) is a promising practical strategy for preventing obesity and related disorders. Ingestion of a single dose of 40 mg of an extract of Grains of Paradise (GP), a ginger family species, reportedly triggers BAT thermogenesis in individuals with high but not in those with low BAT activity. We hypothesized that prolonged treatment with GP might revive BAT in individuals who have lost active BAT. In the present study, we recruited 9 healthy young male volunteers with reduced BAT that was assessed by fluorodeoxyglucose positron emission tomography and computed tomography (FDG-PET/CT) following 2-h cold exposure at 19ºC. The subjects ingested GP extract (40 mg/d) or placebo every day for 5 wk. Before and after the treatment with either GP or placebo, their body composition and BAT-dependent cold-induced thermogenesis (CIT)-a non-invasive index of BAT-were measured in a single-blinded, randomized, placebo-controlled cross-over design. Their whole-body resting energy expenditure at a thermoneutral condition remained unchanged following GP treatment. However, CIT after treatment was significantly higher in GP-treated individuals than in placebo-treated individuals. Body weight and fat-free mass did not change significantly following GP or placebo treatment. Notably, body fat percentage slightly but significantly decreased after GP treatment but not after placebo treatment. These results suggest that repeated ingestion of GP elevates adaptive thermogenesis through the re-activation of BAT, thereby reducing body fat in individuals with low BAT activity.

Alterations in mitochondrial biogenesis and respiratory activity, inflammation of the senescence-associated secretory phenotype, and lipolysis in the perirenal fat and liver of rats following lifelong exercise and detraining

The primary aims of this study were to determine the effects of lifelong exercise and detraining on age-related alterations in mitochondrial function, inflammation associated with senescence-associated secretory phenotype (SASP), and lipolysis in the perirenal fat and liver of rats. Female Sprague-Dawley rats were randomly assigned to four groups: young control (n = 12), old control (n = 12), detraining (n = 12), and lifelong exercise (n = 12). We then investigated mitochondrial function, SASP-associated inflammation, and lipolysis in the perirenal fat and liver using qRT-PCR and western blotting to assess the expression of AKT, hypoxia-inducible factor 1α (HIF-1α), nuclear factor-kappa B (NF-κB), c-jun kinase (JNK), and p38 mitogen-activated protein kinase (p38MAPK). In the tissues of both the perirenal fat and liver, lifelong exercise significantly improved mitochondrial function, SASP-associated inflammation, and lipolysis. Meanwhile, pathways associated with inflammatory regulation were inhibited, predominantly via the activation of phosphorylated-AKT (p-AKT) and suppression of HIF-1α in both tissues, and via JNK in the perirenal fat and p38MAPK in the liver. Furthermore, detraining activated NF-κB expression in both tissues and induced the upregulation of serum high-sensitivity C-reactive protein (hsCRP) levels. Collectively, lifelong exercise was found to exert beneficial effects by ameliorating age-related alterations in mitochondrial function, SASP-associated inflammation, and lipolysis in perirenal fat and liver tissues, potentially inhibiting inflammation via the JNK and p38 MAPK pathways, respectively, as well as the HIF-1α and AKT pathways in both tissues. In contrast, detraining induced high levels of circulating hsCRP by activating the NF-κB signaling pathway in both tissues.

Microtubule affinity regulating kinase 4: A promising target in the pathogenesis of atherosclerosis

Microtubule affinity regulating kinase 4 (MARK4), an important member of the serine/threonine kinase family, regulates the phosphorylation of microtubule-associated proteins and thus modulates microtubule dynamics. In human atherosclerotic lesions, the expression of MARK4 is significantly increased. Recently, accumulating evidence suggests that MARK4 exerts a proatherogenic effect via regulation of lipid metabolism (cholesterol, fatty acid, and triglyceride), inflammation, cell cycle progression and proliferation, insulin signaling, and glucose homeostasis, white adipocyte browning, and oxidative stress. In this review, we summarize the latest findings regarding the role of MARK4 in the pathogenesis of atherosclerosis to provide a rationale for future investigation and therapeutic intervention.

Browning of White Adipocytes in Fat Grafts Associated With Higher Level of Necrosis and Type 2 Macrophage Recruitment

BACKGROUND

Induced browning adipocytes were assumed less viable and more prone to necrosis for their hypermetabolic property. A previous study showed that browning of adipocytes was more evident in fat grafts with necrosis in humans.

OBJECTIVES

The authors aimed to estimate whether fat transfer-induced browning biogenesis was associated with necrosis and its potential inflammation mechanisms in murine models.

METHODS

Human subcutaneous adipose from thigh or abdomen of 5 patients via liposuction was injected in 100 µL or 500 µL (n = 20 per group) into the dorsal flank of 6- to 8-week-old female nude mice fed with normal chow diet and harvested after 2, 4, 8, and 12 weeks. Control groups did not receive any grafting procedures (sham operation), where lipoaspirates were analyzed immediately after harvest. Histology and electronic microscopy, immunological analyses of browning markers, necrosis marker, and type I/II macrophages markers in mice were performed.

RESULTS

Histology and electronic microscopy showed browning adipocytes in fat grafts with a higher level of necrosis (0.435 ± 0.017 pg/mL for cleaved caspase-3, **P < 0.01), IL-6 (749.0 ± 134.1 pg/mL,***P < 0.001) and infiltration of type 2 macrophage profiles in mice (twofold increase, *P < 0.05).

CONCLUSIONS

Browning of adipocytes induced by fat transfer in mice is in parallel with post-grafting necrotic levels associated with elevated interleukin-6 and activated type 2 macrophage profiles, which promote browning development.