Myeloid Deletion of α1AMPK Exacerbates Atherosclerosis in LDL Receptor Knockout (LDLRKO) Mice

The anti-atherosclerosis effect and molecular mechanism of AMPKα1 by polarizing monocytes to an M2 phenotype via cell-intrinsic lysosomal lipolysis

Regulating the differentiation of monocytes into M2 macrophages can promote the regression of Atherosclerosis (AS) plaque. However, the key molecules regulating the differentiation of monocytes to M2 are unknown. In this study, we reported that adenosine-activated protein kinase α1 (AMPKα1) plays an anti-AS role by polarizing monocytes to an M2 phenotype via promoting fatty acid oxidation (FAO). AMPKα1 enhances the decomposition of cholesterol esters by increasing lysosomal acid lipase expression to provide fatty acids for FAO. Furthermore, AMPKα1 can induce lysosomal biogenesis and enhance lipolysis by promoting the transcription factor EB (TFEB) expression and facilitating TFEB nuclear translocation. In conclusion, AMPKα1 enhances the decomposition of cholesterol esters by increasing lysosomal acid lipase expression to produce fatty acids, which may represent a mechanism to promote FAO and inflammatory monocytes differentiation towards M2 phenotype.

AMPK-mediated regulation of endogenous cholesterol synthesis does not affect atherosclerosis in a murine Pcsk9-AAV model

BACKGROUND AND AIMS

Dysregulated cholesterol metabolism is a hallmark of atherosclerotic cardiovascular diseases, yet our understanding of how endogenous cholesterol synthesis affects atherosclerosis is not clear. The energy sensor AMP-activated protein kinase (AMPK) phosphorylates and inhibits the rate-limiting enzyme in the mevalonate pathway HMG-CoA reductase (HMGCR). Recent work demonstrated that when AMPK-HMGCR signaling was compromised in an Apoe-/- model of hypercholesterolemia, atherosclerosis was exacerbated due to elevated hematopoietic stem and progenitor cell mobilization and myelopoiesis. We sought to validate the significance of the AMPK-HMGCR signaling axis in atherosclerosis using a non-germline hypercholesterolemia model with functional ApoE.

METHODS

Male and female HMGCR S871A knock-in (KI) mice and wild-type (WT) littermate controls were made atherosclerotic by intravenous injection of a gain-of-function Pcsk9D374Y-adeno-associated virus followed by high-fat and high-cholesterol atherogenic western diet feeding for 16 weeks.

RESULTS

AMPK activation suppressed endogenous cholesterol synthesis in primary bone marrow-derived macrophages from WT but not HMGCR KI mice, without changing other parameters of cholesterol regulation. Atherosclerotic plaque area was unchanged between WT and HMGCR KI mice, independent of sex. Correspondingly, there were no phenotypic differences observed in hematopoietic progenitors or differentiated immune cells in the bone marrow, blood, or spleen, and no significant changes in systemic markers of inflammation. When lethally irradiated female mice were transplanted with KI bone marrow, there was similar plaque content relative to WT.

CONCLUSIONS

Given previous work, our study demonstrates the importance of preclinical atherosclerosis model comparison and brings into question the importance of AMPK-mediated control of cholesterol synthesis in atherosclerosis.

Navigating the Maze of Kinases: CaMK-like Family Protein Kinases and Their Role in Atherosclerosis

Circulating low-density lipoprotein (LDL) levels are a major risk factor for cardiovascular diseases (CVD), and even though current treatment strategies focusing on lowering lipid levels are effective, CVD remains the primary cause of death worldwide. Atherosclerosis is the major cause of CVD and is a chronic inflammatory condition in which various cell types and protein kinases play a crucial role. However, the underlying mechanisms of atherosclerosis are not entirely understood yet. Notably, protein kinases are highly druggable targets and represent, therefore, a novel way to target atherosclerosis. In this review, the potential role of the calcium/calmodulin-dependent protein kinase-like (CaMKL) family and its role in atherosclerosis will be discussed. This family consists of 12 subfamilies, among which are the well-described and conserved liver kinase B1 (LKB1) and 5' adenosine monophosphate-activated protein kinase (AMPK) subfamilies. Interestingly, LKB1 plays a key role and is considered a master kinase within the CaMKL family. It has been shown that LKB1 signaling leads to atheroprotective effects, while, for example, members of the microtubule affinity-regulating kinase (MARK) subfamily have been described to aggravate atherosclerosis development. These observations highlight the importance of studying kinases and their signaling pathways in atherosclerosis, bringing us a step closer to unraveling the underlying mechanisms of atherosclerosis.

Myeloid AMPK signaling restricts fibrosis but is not required for metformin improvements during CDAHFD-induced NASH in mice

Metabolic programming underpins inflammation and liver macrophage activation in the setting of chronic liver disease. Here, we sought to identify the role of an important metabolic regulator, AMP-activated protein kinase (AMPK), specifically within myeloid cells during the progression of non-alcoholic steatohepatitis (NASH) and whether treatment with metformin, a firstline therapy for diabetes and activator of AMPK could stem disease progression. Male and female Prkaa1fl/fl/Prkaa2fl/fl (Flox) control and Flox-LysM-Cre+ (MacKO) mice were fed a low-fat control or a choline-deficient, amino acid defined 45% Kcal high-fat diet (CDAHFD) for 8 weeks, where metformin was introduced in the drinking water (50 or 250 mg/kg/day) for the last 4 weeks. Hepatic steatosis and fibrosis were dramatically increased in response to CDAHFD-feeding compared to low-fat control. While myeloid AMPK signaling had no effect on markers of hepatic steatosis or circulating markers, fibrosis as measured by total liver collagen was significantly elevated in livers from MacKO mice, independent of sex. Although treatment with 50 mg/kg/day metformin had no effect on any parameter, intervention with 250 mg/kg/day metformin completely ameliorated hepatic steatosis and fibrosis in both male and female mice. While the protective effect of metformin was associated with lower final body weight, and decreased expression of lipogenic and Col1a1 transcripts, it was independent of myeloid AMPK signaling. These results suggest that endogenous AMPK signaling in myeloid cells, both liver-resident and infiltrating, acts to restrict fibrogenesis during CDAHFD-induced NASH progression but is not the mechanism by which metformin improves markers of NASH.

Macrophage AMPK β1 activation by PF-06409577 reduces the inflammatory response, cholesterol synthesis, and atherosclerosis in mice

Atherosclerotic cardiovascular disease is characterized by both chronic low-grade inflammation and dyslipidemia. The AMP-activated protein kinase (AMPK) inhibits cholesterol synthesis and dampens inflammation but whether pharmacological activation reduces atherosclerosis is equivocal. In the current study, we found that the orally bioavailable and highly selective activator of AMPKβ1 complexes, PF-06409577, reduced atherosclerosis in two mouse models in a myeloid-derived AMPKβ1 dependent manner, suggesting a critical role for macrophages. In bone marrow-derived macrophages (BMDMs), PF-06409577 dose dependently activated AMPK as indicated by increased phosphorylation of downstream substrates ULK1 and acetyl-CoA carboxylase (ACC), which are important for autophagy and fatty acid oxidation/de novo lipogenesis, respectively. Treatment of BMDMs with PF-06409577 suppressed fatty acid and cholesterol synthesis and transcripts related to the inflammatory response while increasing transcripts important for autophagy through AMPKβ1. These data indicate that pharmacologically targeting macrophage AMPKβ1 may be a promising strategy for reducing atherosclerosis.

Short salsalate administration affects cell proliferation, metabolism, and inflammation in polycystic kidney disease

Metabolic reprogramming is a driver of autosomal dominant polycystic kidney disease (ADPKD) progression and a potential therapeutic intervention route. We showed before that the AMP-associated protein kinase (AMPK) activator salsalate attenuates cystic disease progression. Here, we aim to study the early, direct effects of short salsalate treatment in adult-onset conditional Pkd1 deletion mice. Cystic mice were treated with salsalate for two weeks, after which NMR metabolomics and RNA sequencing analyses were performed. Pkd1 deletion resulted in clear metabolomic dysregulation. Short salsalate treatment has small, but significant, effects, reverting acetylcarnitine and phosphocholine concentrations back to wildtype levels, and showing associations with altered purine metabolism. RNA sequencing revealed that short salsalate treatment, next to restoring energy metabolism toward wildtype levels, also affects cell proliferation and inflammation, in PKD. We show that salsalate positively affects major dysregulated processes in ADPKD: energy metabolism, cell proliferation, and inflammation, providing more insights into its working mechanisms.

AMPK integrates metabolite and kinase-based immunometabolic control in macrophages

OBJECTIVE

Previous mechanistic studies on immunometabolism have focused on metabolite-based paradigms of regulation, such as itaconate. Here, we, demonstrate integration of metabolite and kinase-based immunometabolic control by AMP kinase.

METHODS

We combined whole cell quantitative proteomics with gene knockout of AMPKα1.

RESULTS

Comparing macrophages with AMPKα1 catalytic subunit deletion with wild-type, inflammatory markers are largely unchanged in unstimulated cells, but with an LPS stimulus, AMPKα1 knockout leads to a striking M1 hyperpolarisation. Deletion of AMPKα1 also resulted in increased expression of rate-limiting enzymes involved in itaconate synthesis, metabolism of glucose, arginine, prostaglandins and cholesterol. Consistent with this, we observed functional changes in prostaglandin synthesis and arginine metabolism. Selective AMPKα1 activation also unlocks additional regulation of IL-6 and IL-12 in M1 macrophages.

CONCLUSIONS

Together, our results validate AMPK as a pivotal immunometabolic regulator in macrophages.

Loss of myeloid Tsc2 predisposes to angiotensin II-induced aortic aneurysm formation in mice

RATIONALE

Genetic studies have proved the involvement of Tuberous sclerosis complex subunit 2 (Tsc2) in aortic aneurysm. However, the exact role of macrophage Tsc2 in the vascular system remains unclear. Here, we examined the potential function of macrophage Tsc2 in the development of aortic remodeling and aortic aneurysms.

METHODS AND RESULTS

Conditional gene knockout strategy combined with histology and whole-transcriptomic analysis showed that Tsc2 deficiency in macrophages aggravated the progression of aortic aneurysms along with an upregulation of proinflammatory cytokines and matrix metallopeptidase-9 in the angiotensin II-induced mouse model. G protein-coupled receptor 68 (Gpr68), a proton-sensing receptor for detecting the extracellular acidic pH, was identified as the most up-regulated gene in Tsc2 deficient macrophages compared with control macrophages. Additionally, Tsc2 deficient macrophages displayed higher glycolysis and glycolytic inhibitor 2-deoxy-D-glucose treatment partially attenuated the level of Gpr68. We further demonstrated an Tsc2-Gpr68-CREB network in macrophages that regulates the inflammatory response, proteolytic degradation and vascular homeostasis. Gpr68 inhibition largely abrogated the progression of aortic aneurysms caused by Tsc2 deficiency in macrophages.

CONCLUSIONS

The findings reveal that Tsc2 deficiency in macrophages contributes to aortic aneurysm formation, at least in part, by upregulating Gpr68 expression, which subsequently drives proinflammatory processes and matrix metallopeptidase activation. The data also provide a novel therapeutic strategy to limit the progression of the aneurysm resulting from Tsc2 mutations.

Dnmt3b Deficiency in Myf5+-Brown Fat Precursor Cells Promotes Obesity in Female Mice

Increasing energy expenditure through activation of brown fat thermogenesis is a promising therapeutic strategy for the treatment of obesity. Epigenetic regulation has emerged as a key player in regulating brown fat development and thermogenic program. Here, we aimed to study the role of DNA methyltransferase 3b (Dnmt3b), a DNA methyltransferase involved in de novo DNA methylation, in the regulation of brown fat function and energy homeostasis. We generated a genetic model with Dnmt3b deletion in brown fat-skeletal lineage precursor cells (3bKO mice) by crossing Dnmt3b-floxed (fl/fl) mice with Myf5-Cre mice. Female 3bKO mice are prone to diet-induced obesity, which is associated with decreased energy expenditure. Dnmt3b deficiency also impairs cold-induced thermogenic program in brown fat. Surprisingly, further RNA-seq analysis reveals a profound up-regulation of myogenic markers in brown fat of 3bKO mice, suggesting a myocyte-like remodeling in brown fat. Further motif enrichment and pyrosequencing analysis suggests myocyte enhancer factor 2C (Mef2c) as a mediator for the myogenic alteration in Dnmt3b-deficient brown fat, as indicated by decreased methylation at its promoter. Our data demonstrate that brown fat Dnmt3b is a key regulator of brown fat development, energy metabolism and obesity in female mice.

Nutrient regulation of inflammatory signalling in obesity and vascular disease

Despite obesity and diabetes markedly increasing the risk of developing cardiovascular diseases, the molecular and cellular mechanisms that underlie this association remain poorly characterised. In the last 20 years it has become apparent that chronic, low-grade inflammation in obese adipose tissue may contribute to the risk of developing insulin resistance and type 2 diabetes. Furthermore, increased vascular pro-inflammatory signalling is a key event in the development of cardiovascular diseases. Overnutrition exacerbates pro-inflammatory signalling in vascular and adipose tissues, with several mechanisms proposed to mediate this. In this article, we review the molecular and cellular mechanisms by which nutrients are proposed to regulate pro-inflammatory signalling in adipose and vascular tissues. In addition, we examine the potential therapeutic opportunities that these mechanisms provide for suppression of inappropriate inflammation in obesity and vascular disease.

Agomelatine reduces circulating triacylglycerides and hepatic steatosis in fructose-treated rats

Agomelatine (AGO) is an antidepressant drug with agonistic activity at melatonin receptor 1 (MT1) and MT2 and with neutral antagonistic activity at serotonin receptor 5-HT2_C. Although experimental studies show that melatonin reduces hypertriglyceridemia and hepatic steatosis induced by excessive fructose intake, no studies have tested if AGO exerts similar actions. To address this issue we have treated male Wistar rats with fructose (15% in the drinking water) and/or AGO (40 mg/kg/day) for two weeks. AGO reduced body weight gain, feeding efficiency and hepatic lipid levels without affecting caloric intake in fructose-treated rats. AGO has also decreased very low-density lipoprotein (VLDL) production and circulating TAG levels after an oral load with olive oil. Accordingly, treatment with AGO reduced the hepatic expression of fatty acid synthase (Fasn), a limiting step for hepatic de novo lipogenesis (DNLG). The expression of apolipoprotein B (Apob) and microsomal triglyceride transfer protein (Mttp) in the ileum, two crucial proteins for intestinal lipoprotein production, were also downregulated by treatment with AGO. Altogether, the present data show that AGO mimics the metabolic benefits of melatonin when used in fructose-treated rats. This study also suggests that it is relevant to evaluate the potential of AGO to treat metabolic disorders in future clinical trials.

Balasubramide derivative 3C attenuates atherosclerosis in apolipoprotein E-deficient mice: role of AMPK-STAT1-STING signaling pathway

We previously reported the neuroprotective effects of (+)-balasubramide derived compound 3C, but its action on atherosclerosis in vivo remains unknown. The study was designed to investigate the potential effects of 3C on atherogenesis and explore the possible underlying mechanisms. 3C ameliorated high-fat diet-induced body weight gain, hyperlipidemia, and atherosclerotic plaque burden in apolipoprotein E-deficient (ApoE^-/-) mice after 10 weeks of treatment. 3C suppressed the expression of genes involved in triglyceride synthesis in liver. 3C prevented aortic inflammation as evidenced by reduction of adhesive molecule levels and macrophage infiltration. Mechanistic studies revealed that activation of AMP-activated protein kinase (AMPK) is central to the athero-protective effects of 3C. Increased AMPK activity by 3C resulted in suppressing interferon-γ (IFN-γ) induced activation of signal transducer and activator of transcription-1 (STAT1) and stimulator of interferon genes (STING) signaling pathways and downstream pro-inflammatory markers. Moreover, 3C inhibited ox-LDL triggered lipid accumulation and IFN-γ induced phenotypic switch toward M1 macrophage in RAW 264.7 cells. Our present data suggest that 3C prevents atherosclerosis via pleiotropic effects, including amelioration of lipid profiles, vascular inflammation and macrophage pro-inflammatory phenotype. 3C has the potential to be developed as a promising drug for atherosclerosis and related cardiovascular disease.

AMP-activated protein kinase: A remarkable contributor to preserve a healthy heart against ROS injury

Heart failure is one of the leading causes of death and disability worldwide. Left ventricle remodeling, fibrosis, and ischemia/reperfusion injury all contribute to the deterioration of cardiac function and predispose to the onset of heart failure. Adenosine monophosphate-activated protein kinase (AMPK) is the universally recognized energy sensor which responds to low ATP levels and restores cellular metabolism. AMPK activation controls numerous cellular processes and, in the heart, it plays a pivotal role in preventing onset and progression of disease. Excessive reactive oxygen species (ROS) generation, known as oxidative stress, can activate AMPK, conferring an additional role of AMPK as a redox-sensor. In this review, we discuss recent insights into the crosstalk between ROS and AMPK. We describe the molecular mechanisms by which ROS activate AMPK and how AMPK signaling can further prevent heart failure progression. Ultimately, we review the potential therapeutic approaches to target AMPK for the treatment of cardiovascular disease and prevention of heart failure.

Signal transduction in primary cilia - analyzing and manipulating GPCR and second messenger signaling

The primary cilium projects from the surface of most vertebrate cells, where it senses extracellular signals to regulate diverse cellular processes during tissue development and homeostasis. Dysfunction of primary cilia underlies the pathogenesis of severe diseases, commonly referred to as ciliopathies. Primary cilia contain a unique protein repertoire that is distinct from the cell body and the plasma membrane, enabling the spatially controlled transduction of extracellular cues. G-protein coupled receptors (GPCRs) are key in sensing environmental stimuli that are transmitted via second messenger signaling into a cellular response. Here, we will give an overview of the role of GPCR signaling in primary cilia, and how ciliary GPCR signaling can be targeted by pharmacology, chemogenetics, and optogenetics.

Prkaa1 Metabolically Regulates Monocyte/Macrophage Recruitment and Viability in Diet-Induced Murine Metabolic Disorders

Myeloid cells, including monocytes/macrophages, primarily rely on glucose and lipid metabolism to provide the energy and metabolites needed for their functions and survival. AMP-activated protein kinase (AMPK, its gene is PRKA for human, Prka for rodent) is a key metabolic sensor that regulates many metabolic pathways. We studied recruitment and viability of Prkaa1-deficient myeloid cells in mice and the phenotype of these mice in the context of cardio-metabolic diseases. We found that the deficiency of Prkaa1 in myeloid cells downregulated genes for glucose and lipid metabolism, compromised glucose and lipid metabolism of macrophages, and suppressed their recruitment to adipose, liver and arterial vessel walls. The viability of macrophages in the above tissues/organs was also decreased. These cellular alterations resulted in decreases in body weight, insulin resistance, and lipid accumulation in liver of mice fed with a high fat diet, and reduced the size of atherosclerotic lesions of mice fed with a Western diet. Our results indicate that AMPKα1/PRKAA1-regulated metabolism supports monocyte recruitment and macrophage viability, contributing to the development of diet-induced metabolic disorders including diabetes and atherosclerosis.

The SGLT2 inhibitor canagliflozin suppresses lipid synthesis and interleukin-1 beta in ApoE deficient mice

Sodium-glucose cotransporter 2 inhibitors such as canagliflozin lower blood glucose and reduce cardiovascular events in people with type 2 diabetes through mechanisms that are not fully understood. Canagliflozin has been shown to increase the activity of the AMP-activated protein kinase (AMPK), a metabolic energy sensor important for increasing fatty acid oxidation and energy expenditure and suppressing lipogenesis and inflammation, but whether AMPK activation is important for mediating some of the beneficial metabolic effects of canagliflozin has not been determined. We, therefore, evaluated the effects of canagliflozin in female ApoE-/- and ApoE-/-AMPK β1-/- mice fed a western diet. Canagliflozin increased fatty acid oxidation and energy expenditure and lowered adiposity, blood glucose and the respiratory exchange ratio independently of AMPK β1. Canagliflozin also suppressed liver lipid synthesis and the expression of ATP-citrate lyase, acetyl-CoA carboxylase and sterol response element-binding protein 1c independently of AMPK β1. Canagliflozin lowered circulating IL-1β and studies in bone marrow-derived macrophages indicated that in contrast with the metabolic adaptations, this effect required AMPK β1. Canagliflozin had no effect on the size of atherosclerotic plaques in either ApoE-/- and ApoE-/-AMPK β1-/- mice. Future studies investigating whether reductions in liver lipid synthesis and macrophage IL-1β are important for the cardioprotective effects of canagliflozin warrant further investigation.

Myeloid deletion and therapeutic activation of AMPK do not alter atherosclerosis in male or female mice

The dysregulation of myeloid-derived cell metabolism can drive atherosclerosis. AMP-activated protein kinase (AMPK) controls various aspects of macrophage dynamics and lipid homeostasis, which are important during atherogenesis. Using LysM-Cre to drive the deletion of both the α1 and α2 catalytic subunits (MacKO), we aimed to clarify the role of myeloid-specific AMPK signaling in male and female mice made acutely atherosclerotic by injection of AAV vector encoding a gain-of-function mutant PCSK9 (PCSK9-AAV) and WD feeding. After 6 weeks of WD feeding, mice received a daily injection of either the AMPK activator A-769662 or a vehicle control for an additional 6 weeks. Following this (12 weeks total), we assessed myeloid cell populations and differences between genotype or sex were not observed. Similarly, aortic sinus plaque size, lipid staining, and necrotic area did not differ in male and female MacKO mice compared with their littermate floxed controls. Moreover, therapeutic intervention with A-769662 showed no treatment effect. There were also no observable differences in the amount of circulating total cholesterol or triglyceride, and only minor differences in the levels of inflammatory cytokines between groups. Finally, CD68+ area and markers of autophagy showed no effect of either lacking AMPK signaling or AMPK activation. Our data suggest that while defined roles for each catalytic AMPK subunit have been identified, complete deletion of myeloid AMPK signaling does not significantly impact atherosclerosis. Additionally, these findings suggest that intervention with the first-generation AMPK activator A-769662 is not able to stem the progression of atherosclerosis.

Testosterone Increases the Expression and Phosphorylation of AMP Kinase α in Men With Hypogonadism and Type 2 Diabetes

CONTEXT

Adenosine 5'-monophosphate-activated protein kinase-α (AMPKα) is a mediator of exercise-induced glucose uptake in skeletal muscle.

OBJECTIVE

We evaluated whether AMPKα expression and phosphorylation are reduced in skeletal muscle and adipose tissue of patients with hypogonadotropic hypogonadism (HH), and whether testosterone replacement therapy results in restoration of the expression and phosphorylation of AMPKα.

DESIGN

This is a secondary analysis of a previously completed trial that showed an insulin-sensitizing effect of testosterone therapy in men with type 2 diabetes and HH.

SETTING

Clinical research center at university.

PATIENTS

Thirty-two men with HH and 32 eugonadal men were compared at baseline.

INTERVENTIONS

Men with HH were treated with intramuscular injections of testosterone or placebo every 2 weeks for 22 weeks. Quadriceps muscle biopsies and subcutaneous abdominal fat biopsies were obtained before and after 4-hour euglycemic hyperinsulinemic clamp, prior to and after testosterone or placebo therapy.

OUTCOME MEASURES AND RESULTS

mRNA expression of AMPKα in hypogonadal men was lower by 37% in adipose tissue and 29% in skeletal muscle, respectively, compared with levels in eugonadal men, while phosphorylated AMPKα was lower by 22% and 28%, respectively. Following testosterone replacement, the expression of AMPKα did not alter in the fasting state but increased markedly by 41% and 46% in adipose tissue and muscle, respectively, after the clamp. In contrast, phosphorylated AMPKα increased by 69% in muscle after testosterone therapy but did not change following the clamp.

CONCLUSIONS

Testosterone modulates the expression of AMPKα and phosphorylated AMPKα. These effects may contribute to the improved insulin sensitivity following testosterone therapy.

AMP-activated protein kinase: the current landscape for drug development

Since the discovery of AMP-activated protein kinase (AMPK) as a central regulator of energy homeostasis, many exciting insights into its structure, regulation and physiological roles have been revealed. While exercise, caloric restriction, metformin and many natural products increase AMPK activity and exert a multitude of health benefits, developing direct activators of AMPK to elicit beneficial effects has been challenging. However, in recent years, direct AMPK activators have been identified and tested in preclinical models, and a small number have entered clinical trials. Despite these advances, which disease(s) represent the best indications for therapeutic AMPK activation and the long-term safety of such approaches remain to be established.

Tectorigenin attenuates diabetic nephropathy by improving vascular endothelium dysfunction through activating AdipoR1/2 pathway

Diabetic nephropathy (DN), a kind of microvascular complication, is a primary cause of end-stage renal disease worldwide. However, therapeutic drugs for DN treatment are still in lack. The glomerular endothelium is essential to maintain selective permeability of glomerular filtration barrier and glomerular vasculature function. Growing evidences show that endothelial dysfunction or injury is the initial stage of vascular damage in DN, which can be induced by hyperglycemia, lipotoxicity, and inflammation. Therefore, to improve the function of vascular endothelium in kidney is a key point for treatment of DN. As a plant isoflavone, tectorigenin (TEC) has attracted considerable attention due to its anti-proliferative and anti-inflammatory functions. However, whether TEC could inhibit the DN development remains unknown. In this study, we examined the effects of TEC on DN development in db/db mice, a type of genetic defect diabetic mice that can spontaneously develop into severe renal dysfunction. Intriguingly, TEC treatment restored diabetes-induced glucose and lipid metabolic disorder; and improved the deterioration of renal function, particularly the renal endothelium function in db/db mice. Additionally, TEC inhibited the renal inflammation via reducing macrophages infiltration and M1 polarization. Moreover, TEC inhibited lipopolysaccharide (LPS)-induced endothelial injury and M1 polarization in vitro. Mechanistically, TEC partially restored the reduction in expression of adiponectin receptor 1/2 (AdipoR1/2), pi-LKB1, pi-AMPKα, and PPARα in vitro and in vivo. Noteworthy, these beneficial pharmacological activities mediated by TEC were significantly attenuated after AdipoR1/2 knockdown by siRNA, indicating that AdipoR1/2 plays a critical role in protection against DN. Collectively, these results suggested that TEC have a potently effect for retarding type 2 diabetes-associated DN.

Anti-Inflammatory and Antioxidant Effects of Acetyl-L-Carnitine on Atherosclerotic Rats

Background

The purpose of the present study was to evaluate the regulatory effects of acetyl-L-carnitine (ALCAR) on atherosclerosis in Wister rats and to explore its anti-atherosclerotic mechanism.

Material/Methods

We randomly divided 32 Wister rats into 4 groups: a normal diet group (control group, n=8), a normal diet+ALCAR group (ALCAR group, n=8), an atherosclerosis group (AS group, n=8), and an atherosclerosis+ALCAR group (AS+ALCAR group, n=8). The serum lipid distribution, oxidative stress, inflammatory factors and adiponectin (APN) in the blood, and heart and aortic tissues were determined using the standard assay kits, xanthine oxidase method, and ELISA, respectively. HE staining was performed to observe aortic pathology structure change, and the level of angiotensin II (AngII) in the aorta was assessed using radioimmunoassay. In addition, real-time quantitative PCR and Western blot analysis were applied to detect the expression of iNOS, IL-1β, TNF-α, and CRP in the aortic and heart tissues.

Results

Compared with the AS group, the levels of serum TC, TG, LDL, and VLDL in rats decreased significantly, while HDL level significantly increased in the AS+ALCAR group. ALCAR administration enhanced the SOD and GSH-Px activities and decreased MDA activity. APN level was significantly elevated in the AS group, but ALCAR had no significant effect on APN. Further, ALCAR reduced the expressions of inflammation factors TNF-α, IL-1β, iNOS, and CRP, and the concentration of AngII in serum, aortic, and heart tissues.

Conclusions

ALCAR can inhibit the expressions of inflammatory factors and antioxidation to suppress the development of atherosclerosis by adjusting blood lipid in the myocardium of AS rats.

α1AMPK deletion in myelomonocytic cells induces a pro-inflammatory phenotype and enhances angiotensin II-induced vascular dysfunction

Aims

Immune cell function involves energy-dependent processes including growth, proliferation, and cytokine production. Since the AMP-activated protein kinase (AMPK) is a crucial regulator of intracellular energy homeostasis, its expression and activity may also affect innate and adaptive immune cell responses. Therefore, we aimed to investigate the consequences of α1AMPK deletion in myelomonocytic cells on vascular function, inflammation, and hypertension during chronic angiotensin II (ATII) treatment.

Methods and results

We generated a mouse strain with α1AMPK deletion in lysozyme M+ myelomonocytic cells. Compared to controls, chronic ATII infusion (1 mg/kg/day for 7 days) lead to increased vascular oxidative stress and aggravated endothelial dysfunction in LysM-Cre+ x α1AMPKfl/fl mice. This was accompanied by an increased aortic infiltration of CD11b+F4/80+ macrophages and enhanced pro-inflammatory cytokine release (tumour necrosis factor-alpha, interferon-gamma, and interleukin-6). Mechanistically, we found that increased expression of C-C chemokine receptor 2 (CCR2) in α1AMPK deficient myelomonocytic cells facilitated their recruitment to the vascular wall. In addition, expression of the ATII receptor type 1a and the oxidative burst was increased in these cells, indicating an increased susceptibility towards pro-oxidant stimuli.

Conclusions

In summary, α1AMPK deletion in myelomonocytic cells aggravates vascular oxidative stress and dysfunction by enhancing their recruitment to the vascular wall and increasing their susceptibility towards pro-oxidant stimuli. Our observations suggest that metabolic control in myelomonocytic cells has profound implications for their inflammatory phenotype and may trigger the development of vascular disease.

Macrophages in inflammation, repair and regeneration

Tissue injury triggers a complex series of cellular responses, starting from inflammation activated by tissue and cell damage and proceeding to healing. By clearing cell debris, activating and resolving inflammation and promoting fibrosis, macrophages play key roles in most, if not all, phases of the response to injury. Recent studies of the mechanisms underlying the initial inflammation and later tissue regeneration and repair revealed that macrophages bridge these processes in part by supporting and activating stem/progenitor cells, clearing damaged tissue, remodeling extracellular matrix to prepare scaffolding for regeneration and promoting angiogenesis. However, macrophages also have a central role in the development of pathology induced by failed resolution (e.g. chronic inflammation) and excessive scarring. In this review, we summarize the activities of macrophages in inflammation and healing in response to acute injury in tissues with differing regenerative capacities. While macrophages lead similar processes in response to tissue injury in these tissues, their priorities and the consequences of their activities differ among tissues. Moreover, the magnitude, nature and duration of injury also greatly affect cellular responses and healing processes. In particular, continuous injury and/or failed resolution of inflammation leads to chronic ailments in which macrophage activities may become detrimental.

Rheb (Ras Homolog Enriched in Brain 1) Deficiency in Mature Macrophages Prevents Atherosclerosis by Repressing Macrophage Proliferation, Inflammation, and Lipid Uptake

Objective:

Macrophage foam cell formation is an important process in atherosclerotic plaque development. The small GTPase Rheb (Ras homolog enriched in brain 1) regulates endocytic trafficking that is critical for foam cell formation. However, it is unclear whether and how macrophage Rheb regulates atherogenesis, which are the focuses of the current study.

Approach and Results:

Immunofluorescence study confirmed the colocalization of Rheb in F4/80 and Mac-2 (galectin-3)–labeled lesional macrophages. Western blot and fluorescence-activated cell sorting analysis showed that Rheb expression was significantly increased in atherosclerotic lesions of atherosclerosis-prone (apoE −/− [apolipoprotein E deficient]) mice fed with Western diet. Increased Rheb expression was also observed in oxidized LDL (low-density lipoprotein)–treated macrophages. To investigate the in vivo role of macrophage Rheb, we established mature Rheb mKO (macrophage-specific Rheb knockout) mice by crossing the Rheb floxed mice with F4/80-cre mice. Macrophage-specific knockout of Rheb in mice reduced Western diet–induced atherosclerotic lesion by 32%, accompanied with a decrease in macrophage content in plaque. Mechanistically, loss of Rheb in macrophages repressed oxidized LDL–induced lipid uptake, inflammation, and macrophage proliferation. On the contrary, lentivirus-mediated overexpression of Rheb in macrophages increased oxidized LDL–induced lipid uptake and inflammation, and the stimulatory effect of Rheb was suppressed by the mTOR (mammalian target of rapamycin) inhibitor rapamycin or the PKA (protein kinase A) activator forskolin.

Conclusions:

Macrophage Rheb plays important role in Western diet–induced atherosclerosis by promoting macrophage proliferation, inflammation, and lipid uptake. Inhibition of expression and function of Rheb in macrophages is beneficial to prevent diet-induced atherosclerosis.

Dietary cholesterol is essential to mast cell activation and associated obesity and diabetes in mice

Mast cell (MC) deficiency in Kit^W-sh/W-sh mice and inhibition with disodium chromoglycate (DSCG) or ketotifen reduced obesity and diabetes in mice on a high-cholesterol (1.25%) Western diet. Yet, Kit-independent MC-deficient mice and mice treated with DSCG disproved MC function in obesity and diabetes when mice are fed a high-fat diet (HFD) that contains no cholesterol. This study reproduced the obesity and diabetes inhibitory activities of DSCG and ketotifen from mice on a Western diet. Yet, such inhibitory effects were diminished in mice on the HFD. DSCG and ketotifen MC inhibitory activities were recovered from mice on the HFD supplemented with the same amount of cholesterol (1.25%) as that in the Western diet. DSCG and ketotifen effectively blunted the high-cholesterol diet-induced elevations of blood histamine and adipose tissue MC degranulation. Pearson's correlation test demonstrated significant and positive correlations between plasma histamine and total cholesterol or low-density lipoprotein-cholesterol (LDL). In cultured bone marrow-derived MCs, plasma from mice following a Western diet or a cholesterol-supplemented HFD, but not those from HFD-fed mice, induced MC degranulation and the release of β-hexosaminidase, histamine, and serotonin. IgE, LDL, very low-density lipoprotein, and high-density lipoprotein also induced MC activation, which can be inhibited by DSCG and ketotifen depending on the doses and types of MC inhibitors and cholesterol, and also the MC granule molecules of interest. DSCG or ketotifen lost their activities in inhibiting LDL-induced activation of MCs from LDL receptor-deficient mice. These results indicate that dietary cholesterol critically influences the function of mouse MCs.

New insights into oxidative stress and inflammation during diabetes mellitus-accelerated atherosclerosis

Oxidative stress and inflammation interact in the development of diabetic atherosclerosis. Intracellular hyperglycemia promotes production of mitochondrial reactive oxygen species (ROS), increased formation of intracellular advanced glycation end-products, activation of protein kinase C, and increased polyol pathway flux. ROS directly increase the expression of inflammatory and adhesion factors, formation of oxidized-low density lipoprotein, and insulin resistance. They activate the ubiquitin pathway, inhibit the activation of AMP-protein kinase and adiponectin, decrease endothelial nitric oxide synthase activity, all of which accelerate atherosclerosis. Changes in the composition of the gut microbiota and changes in microRNA expression that influence the regulation of target genes that occur in diabetes interact with increased ROS and inflammation to promote atherosclerosis. This review highlights the consequences of the sustained increase of ROS production and inflammation that influence the acceleration of atherosclerosis by diabetes. The potential contributions of changes in the gut microbiota and microRNA expression are discussed.

Methods to Evaluate AMPK Regulation of Macrophage Cholesterol Homeostasis

Macrophages are a driving force in the development and progression of atherosclerosis, a chronic condition that can lead to cardiovascular disease. In this chapter we describe methods that monitor macrophage cholesterol homeostasis such as cholesterol synthesis, uptake, and efflux, all with the use of AMPK activators and potential genetic models that could help shed light on the role of this metabolic regulator in atherosclerosis and other chronic diseases.

Effect of AMPK signal pathway on pathogenesis of abdominal aortic aneurysms

Background and aims

Determine the effect of AMPK activation and inhibition on the development of AAA (abdominal aortic aneurysm).

Methods

AAA was induced in ApoE^−/− mice by Ang II (Angiotensin II)-infusion. AICAR (5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside) was used as AMPK activator and Compound C was used as AMPK inhibitor. We further investigate the effect of metformin, a widely used anti-diabetic drug which could activate AMPK signal pathway, on the pathogenesis of aneurysm.

Results

Phospho-AMPK level was significantly decreased in AAA tissue compared with control aortas. AICAR significantly reduced the incidence, severity and mortality of aneurysm in the Ang II-infusion model. AICAR also alleviated macrophage infiltration and neovascularity in Ang II infusion model at day 28. The expression of pro-inflammatory factors, angiogenic factors and the activity of MMPs were also alleviated by AICAR during AAA induction. On the other hand, Compound C treatment did not exert obvious protective effect. AMPK activation may inhibit the activation of nuclear factor-κB (NF-κB) and signal transducer and activator of transcription-3 (STAT-3) during AAA induction. Administration of metformin also activated AMPK signal pathway and retarded AAA progression in Ang II infusion model.

Conclusions

Activation of AMPK signaling pathway may inhibit the Ang II-induced AAA in mice. Metformin may be a promising approach to the treatment of AAA.

Pharmacological inhibition of protein tyrosine phosphatase 1B protects against atherosclerotic plaque formation in the LDLR-/- mouse model of atherosclerosis

Cardiovascular disease (CVD) is the most prevalent cause of mortality among patients with type 1 or type 2 diabetes, due to accelerated atherosclerosis. Recent evidence suggests a strong link between atherosclerosis and insulin resistance, due to impaired insulin receptor (IR) signalling. Here, we demonstrate that inhibiting the activity of protein tyrosine phosphatase 1B (PTP1B), the major negative regulator of the IR prevents and reverses atherosclerotic plaque formation in an LDLR^−/− mouse model of atherosclerosis. Acute (single dose) or chronic PTP1B inhibitor (trodusquemine) treatment of LDLR^−/− mice decreased weight gain and adiposity, improved glucose homeostasis and attenuated atherosclerotic plaque formation. This was accompanied by a reduction in both, circulating total cholesterol and triglycerides, a decrease in aortic monocyte chemoattractant protein-1 (MCP-1) expression levels and hyperphosphorylation of aortic Akt/PKB and AMPKα. Our findings are the first to demonstrate that PTP1B inhibitors could be used in prevention and reversal of atherosclerosis development and reduction in CVD risk.

AMPK as a Therapeutic Target for Treating Metabolic Diseases

The AMP-activated protein kinase (AMPK) is a central regulator of multiple metabolic pathways and may have therapeutic importance for treating obesity, insulin resistance, type 2 diabetes (T2D), non-alcoholic fatty liver disease (NAFLD), and cardiovascular disease (CVD). Given the ubiquitous expression of AMPK, it has been a challenge to evaluate which tissue types may be most beneficially poised for mediating the positive metabolic effects of AMPK-centered treatments. In this review we evaluate the metabolic phenotypes of transgenic mouse models in which AMPK expression and function have been manipulated, and the impact this has on controlling lipid metabolism, glucose homeostasis, and inflammation. This information may be useful for guiding the development of AMPK-targeted therapeutics to treat chronic metabolic diseases.

Myeloid protein tyrosine phosphatase 1B (PTP1B) deficiency protects against atherosclerotic plaque formation in the ApoE-/- mouse model of atherosclerosis with alterations in IL10/AMPKα pathway

Objective

Cardiovascular disease (CVD) is the most prevalent cause of mortality among patients with Type 1 or Type 2 diabetes, due to accelerated atherosclerosis. Recent evidence suggests a strong link between atherosclerosis and insulin resistance due to impaired insulin receptor (IR) signaling. Moreover, inflammatory cells, in particular macrophages, play a key role in pathogenesis of atherosclerosis and insulin resistance in humans. We hypothesized that inhibiting the activity of protein tyrosine phosphatase 1B (PTP1B), the major negative regulator of the IR, specifically in macrophages, would have beneficial anti-inflammatory effects and lead to protection against atherosclerosis and CVD.

Methods

We generated novel macrophage-specific PTP1B knockout mice on atherogenic background (ApoE^−/−/LysM-PTP1B). Mice were fed standard or pro-atherogenic diet, and body weight, adiposity (echoMRI), glucose homeostasis, atherosclerotic plaque development, and molecular, biochemical and targeted lipidomic eicosanoid analyses were performed.

Results

Myeloid-PTP1B knockout mice on atherogenic background (ApoE^−/−/LysM-PTP1B) exhibited a striking improvement in glucose homeostasis, decreased circulating lipids and decreased atherosclerotic plaque lesions, in the absence of body weight/adiposity differences. This was associated with enhanced phosphorylation of aortic Akt, AMPKα and increased secretion of circulating anti-inflammatory cytokine interleukin-10 (IL-10) and prostaglandin E2 (PGE₂), without measurable alterations in IR phosphorylation, suggesting a direct beneficial effect of myeloid-PTP1B targeting.

Conclusions

Here we demonstrate that inhibiting the activity of PTP1B specifically in myeloid lineage cells protects against atherosclerotic plaque formation, under atherogenic conditions, in an ApoE^−/− mouse model of atherosclerosis. Our findings suggest for the first time that macrophage PTP1B targeting could be a therapeutic target for atherosclerosis treatment and reduction of CVD risk.

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PTP1B inhibition as therapy for atherosclerosis/cardiovascular disease is proposed.

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Myeloid-PTP1B mice on ApoE^−/− background (ApoE^−/−/LysM-PTP1B) were generated.

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ApoE^−/−/LysM-PTP1B had improved glucose homeostasis with no body weight differences.

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ApoE^−/−/LysM-PTP1B had lower lipids and protection against atherosclerotic plaques.

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Protection was via a PGE₂/IL-10/AMPKα mechanism.

Effect of a single bout of aerobic exercise on high-fat meal-induced inflammation

BACKGROUND AND AIMS

Chronic low-grade inflammation is involved in the development of metabolic disorders including atherosclerosis, type 2 diabetes (T2D) and metabolic syndrome. Aerobic exercise has been shown to be anti-inflammatory and attenuate postprandial blood lipids, however, the effect of exercise on postprandial inflammation remains unclear. The aim of this study was to determine the protective effect of a single bout of aerobic exercise against postprandial lipemia and peripheral blood mononuclear cell (PBMC) inflammation and to evaluate associations with changes in the energy-sensing enzyme, AMP-activated protein kinase (AMPK).

MATERIALS AND METHODS

Healthy male subjects (n=12, age=23±2, %Fat=19±2) reported to the laboratory following an overnight fast (12-14h) on two separate occasions for consumption of a high-fat meal (HFM). Participants completed an acute bout of aerobic exercise the afternoon prior to one of the HFM visits.

RESULTS AND CONCLUSION

Results indicate that the single bout of moderate aerobic exercise increased AMPK signaling in PBMCs, as shown by increased phosphorylated acetyl-CoA carboxylase (p-ACC). This may be due to decreases in the AMPK inhibitory kinases PKD and GSK3β. Additionally, prior moderate intensity exercise decreased postprandial lipemia (PPL) and some mediators of the inflammatory pathway, such as p-NF-κB. These findings that acute aerobic exercise improves AMPK and NF-κB signaling in human PBMCs contribute support to the anti-inflammatory roles of exercise.

AMP-Activated Protein Kinase: An Ubiquitous Signaling Pathway With Key Roles in the Cardiovascular System

The AMP-activated protein kinase (AMPK) is a key regulator of cellular and whole-body energy homeostasis, which acts to restore energy homoeostasis whenever cellular energy charge is depleted. Over the last 2 decades, it has become apparent that AMPK regulates several other cellular functions and has specific roles in cardiovascular tissues, acting to regulate cardiac metabolism and contractile function, as well as promoting anticontractile, anti-inflammatory, and antiatherogenic actions in blood vessels. In this review, we discuss the role of AMPK in the cardiovascular system, including the molecular basis of mutations in AMPK that alter cardiac physiology and the proposed mechanisms by which AMPK regulates vascular function under physiological and pathophysiological conditions.

AMP-activated protein kinase α1 promotes atherogenesis by increasing monocyte-to-macrophage differentiation

Monocyte-to-macrophage differentiation, which can be initiated by physiological or atherogenic factors, is a pivotal process in atherogenesis, a disorder in which monocytes adhere to endothelial cells and subsequently migrate into the subendothelial spaces, where they differentiate into macrophages and macrophage-derived foam cells and cause atherosclerotic lesions. However, the monocyte-differentiation signaling pathways that are activated by atherogenic factors are poorly defined. Here we report that the AMP-activated protein kinase α1 (AMPKα1) in monocytes promotes atherosclerosis by increasing monocyte differentiation and survival. Exposure of monocytes to oxidized low-density lipoprotein, 7-ketocholesterol, phorbol 12-myristate 13-acetate, or macrophage colony-stimulated factor (M-CSF) significantly activated AMPK and promoted monocyte-to-macrophage differentiation. M-CSF-activated AMPK is via M-CSF receptor-dependent reactive oxygen species production. Consistently, genetic deletion of AMPKα1 or pharmacological inhibition of AMPK blunted monocyte-to-macrophage differentiation and promoted monocyte/macrophage apoptosis. Compared with apolipoprotein E knock-out (ApoE^-/-) mice, which show impaired clearing of plasma lipoproteins and spontaneously develop atherosclerosis, ApoE^-/-/AMPKα1^-/- mice showed reduced sizes of atherosclerotic lesions and lesser numbers of macrophages in the lesions. Furthermore, aortic lesions were decreased in ApoE^-/- mice transplanted with ApoE^-/-/AMPKα1^-/- bone marrow and in myeloid-specific AMPKα1-deficient ApoE^-/- mice. Finally, rapamycin treatment, which abolished delayed monocyte differentiation in ApoE^-/-/AMPKα1^-/- mice, lost its atherosclerosis-lowering effects in these mice. Mechanistically, we found that AMPKα1 regulates FoxO3-dependent expression of both LC3 and ULK1, which are two important autophagy-related markers. Rapamycin treatment increased FoxO3 activity as well as LC3 and ULK1 expressions in macrophages from AMPKα1^-/- mice. Our results reveal that AMPKα1 deficiency impairs autophagy-mediated monocyte differentiation and decreases monocyte/macrophage survival, which attenuates atherosclerosis in ApoE^-/- mice in vivo.

Broccoli-Derived Nanoparticle Inhibits Mouse Colitis by Activating Dendritic Cell AMP-Activated Protein Kinase

The intestinal immune system is continuously exposed to massive amounts of nanoparticles derived from food. Whether nanoparticles from plants we eat daily have a role in maintaining intestinal immune homeostasis is poorly defined. Here, we present evidence supporting our hypothesis that edible nanoparticles regulate intestinal immune homeostasis by targeting dendritic cells (DCs). Using three mouse colitis models, our data show that orally given nanoparticles isolated from broccoli extracts protect mice against colitis. Broccoli-derived nanoparticle (BDN)-mediated activation of adenosine monophosphate-activated protein kinase (AMPK) in DCs plays a role in not only prevention of DC activation but also induction of tolerant DCs. Adoptively transferring DCs pre-pulsed with total BDN lipids, but not sulforaphane (SFN)-depleted BDN lipids, prevented DSS-induced colitis in C57BL/6 (B6) mice, supporting the role of BDN SFN in the induction of DC tolerance. Adoptively transferring AMPK^+/+, but not AMPK^-/-, DCs pre-pulsed with SFN prevented DSS-induced colitis in B6 mice, further supporting the DC AMPK role in SFN-mediated prevention of DSS-induced colitis. This finding could open new preventive or therapeutic avenues to address intestinal-related inflammatory diseases via activating AMPK.