Plasminogen activator inhibitor-1 deficiency ameliorates insulin resistance and hyperlipidemia but not bone loss in obese female mice

Dynamic Changes in Adiponectin and Resistin Drive Remission of Cardiometabolic Risk Biomarkers in Individuals with Obesity Following Bariatric Surgery

The remission of obesity-related diseases following bariatric surgery appears to result from the reorganization of metabolic and hormonal pathways involving adipokines. This study aimed to investigate the relationship between changes in body adiposity and serum adipokine levels, as well as the association between variations in adiponectin or resistin levels and cardiometabolic risk blood biomarkers before and after Roux-en-Y gastric bypass. A longitudinal and prospective study was conducted with bariatric surgery patients. Anthropometric, body composition and blood biochemical parameters were measured before and at 2 and 6 months post-surgery. The data were analyzed using ANOVA, Pearson or Spearman correlation, and simple linear regression with a significance level of p < 0.05. Among 36 mostly female patients aged 30 to 39 years, significant reductions in body weight (-26.8%), fat mass (-50%), waist circumference (-18%) and waist-to-height ratio (-22%) were observed post-surgery. Serum adiponectin levels increased (+107%), while resistin (-12.2%), TNF-α (-35%), and PAI-1 (-11.1%) decreased. Glucose, insulin, CRP, cholesterol, LDL-c, triglycerides, and vitamin D also decreased. Waist circumference variation showed a positive correlation with PAI-1 and TNF-α and a negative correlation with adiponectin. The total fat mass showed a positive correlation with PAI-1. Adiponectin variation correlated negatively with glucose, resistin, and CRP but positively with HDL-c. Resistin showed a positive correlation with insulin and CRP. In conclusion, 6 months post-bariatric surgery, reducing abdominal adiposity had a more significant impact on serum adipokine levels than total fat mass. Adiponectin increase and resistin decrease acted as endocrine mediators driving the remission of cardiometabolic risk biomarkers in individuals with obesity following Roux-en-Y gastric bypass.

Effects of elastase-induced emphysema on muscle and bone in mice

Chronic obstructive pulmonary disease (COPD) causes sarcopenia and osteoporosis. However, the mechanisms underlying muscle and bone loss as well as the interactions between muscle and bone in the COPD state remain unclear. Therefore, we herein investigated the effects of the COPD state on muscle and bone in mice intratracheally administered porcine pancreatic elastase (PPE). The intratracheal administration of PPE to mice significantly reduced trabecular bone mineral density (BMD), trabecular bone volume, trabecular number, cortical BMD and cortical area. It also significantly decreased grip strength, but did not affect muscle mass or the expression of myogenic differentiation-, protein degradation- or autophagy-related genes in the soleus and gastrocnemius muscles. Among the myokines examined, myostatin mRNA levels in the soleus muscles were significantly elevated in mice treated with PPE, and negatively related to grip strength, but not bone parameters, in mice treated with or without 2 U PPE in simple regression analyses. Grip strength positively related to bone parameters in mice treated with or without PPE. In conclusion, we showed that a PPE model of COPD in mice exerts dominant effects on bone rather than skeletal muscles. Increased myostatin expression in the soleus muscles of mice in the COPD state may negatively relate to a reduction in grip strength, but not bone loss.

The Association of Acute Phase Proteins in Stress and Inflammation-Induced T2D

Acute phase proteins (APPs), such as plasminogen activator inhibitor-1 (PAI-1), serum amyloid A (SAA), and C-reactive protein (CRP), are elevated in type-2 diabetes (T2D) and are routinely used as biomarkers for this disease. These APPs are regulated by the peripheral mediators of stress (i.e., endogenous glucocorticoids (GCs)) and inflammation (i.e., pro-inflammatory cytokines), with both implicated in the development of insulin resistance, the main risk factor for the development of T2D. In this review we propose that APPs, PAI-1, SAA, and CRP, could be the causative rather than only a correlative link between the physiological elements of risk (stress and inflammation) and the development of insulin resistance.

Systematic Review and Meta-Analysis of SERPINE1 4G/5G Insertion/Deletion Variant With Circulating Lipid Levels

Background

Recent studies have shown that the 4G/5G insertion/deletion variant of SERPINE1 (rs1799889) is closely linked to coronary artery disease (CAD). This study aims to clarify the effects of the rs1799889 variant on lipid levels and to insight into the mechanisms underlying the rs1799889 variant and CAD.

Methods and Results

By searching PubMed and the Cochrane databases for studies published before 31 October 2021, 40 studies conducted on a total of 13,117 subjects were included for the analysis. The consistent findings for the effects of the 5G allele of rs1799889 variant on lipid metabolism were the significantly decreased triglycerides (TG) [standardized mean difference (SMD) = –0.12, 95% CI = –0.21 to 0.03, P = 0.01], total cholesterol (TC) (SMD = –0.12, 95% CI = –0.17 to 0.06, P < 0.001), and low-density lipoprotein cholesterol (LDL-C) (SMD = –0.13, 95% CI = –0.23 to 0.03, P = 0.01) levels. Intriguingly, the significant effects of the rs1799889 variant on LDL-C (SMD = –0.15, 95% CI = –0.26 to 0.05, P < 0.01) and TC (SMD = –0.17, 95% CI = –0.27 to 0.07, P < 0.01) levels were primarily observed in the Asian population. However, the significant effect of the rs1799889 variant on high-density lipoprotein cholesterol (HDL-C) (SMD = 0.26, 95% CI = 0.03–0.48, P = 0.03) levels was detected only in female subjects.

Conclusion

The rs1799889 variant of SERPINE1 is a protective genetic factor against CAD, the Asian population with the 5G allele of the rs1799889 variant may have a reduced CAD risk.

Role of peripheral myelin protein 22 in chronic exercise-induced interactions of muscle and bone in mice

Exercise is important for the prevention and treatment of sarcopenia and osteoporosis. Although the interactions between skeletal muscles and bone have recently been reported, the myokines linking muscle to bone during exercise remain unknown. We previously revealed that chronic exercise using treadmill running blunts ovariectomy-induced osteopenia in mice. We herein performed an RNA sequence analysis of the gastrocnemius and soleus muscles of male mice with or without chronic exercise to identify the myokines responsible for the effects of chronic exercise on the muscle/bone relationship. We extracted peripheral myelin protein 22 (PMP22) as a humoral factor that was putatively induced by chronic exercise in the soleus and gastrocnemius muscles of mice from the RNA sequence analysis. Chronic exercise significantly enhanced the expression of PMP22 in the gastrocnemius and soleus muscles of female mice. PMP22 suppressed macrophage-colony stimulating factor and receptor activator factor κB ligand-induced increases in the expression of osteoclast-related genes and osteoclast formation from mouse bone marrow cells. Moreover, PMP22 significantly inhibited osteoblast differentiation, alkaline phosphatase activity, and mineralization in mouse osteoblast cultures; however, the overexpression of PMP22 did not affect muscle phenotypes in mouse muscle C2C12 cells. A simple regression analysis revealed that PMP22 mRNA levels in the gastrocnemius and soleus muscles were positively related to cortical bone mineral density at the femurs of mice with or without chronic exercise. In conclusion, we identified PMP22 as a novel myokine induced by chronic exercise in mice. We first showed that PMP22 suppresses osteoclast formation and the osteoblast phenotype in vitro.

Changes in bone mass associated with obesity and weight loss in humans: Applicability of animal models

The implications of obesity and weight loss for human bone health are not well understood. Although the bone changes associated with weight loss are similar in humans and rodents, that is not the case for obesity. In humans, obesity is generally associated with increased bone mass, an outcome which is exacerbated by advanced age and menopause. In rodents, by contrast, bone mass decreases in proportion to severity and duration of obesity, and is influenced by sex, age and mechanical load. Despite these discrepancies, rodents are frequently used to model the situation in humans. In this review, we summarise the existing knowledge of the effects of obesity and weight loss on bone mass in humans and rodents, focusing on the translatability of findings from animal models. We then describe how animal models should be used to broaden the understanding of the relationship between obesity, weight loss, and skeletal health in humans. Specifically, we highlight the aspects of study design that should be considered to optimise translatability of the rodent models of obesity and weight loss. Notably, the sex, age, and nutritional status of the animals should ideally match those of interest in humans. With these caveats in mind, and depending on the research question asked, our review underscores that animal models can provide valuable information for obesity and weight-management research.

A novel PAI-1 inhibitor prevents ageing-related muscle fiber atrophy

Sarcopenia is among the most common medical problems of the aging population worldwide and a major social concern. Here, we explored the therapeutic potential of TM5484, a novel orally available PAI-1 inhibitor, to prevent sarcopenia. The sarcopenic phenotypes of the calf muscle of 12- and 6-month-old middle-aged mice were compared. Although significant decline of isometric gastrocnemius muscle force was detected in the older untreated mice, those administered TM5484 had significantly greater calf muscle force, as determined using isometric measurements by electrical stimulation. Histological analysis indicated that cross-sectional gastrocnemius muscle fibers in untreated older mice were thinner than those in younger mice; however, TM5484-treated group showed thicker fibers than younger mice. Treatment with TM5484 for 6 months enhanced Igf1, Atrogin-1, Mt-Co1, and Chrna1 mRNA expression in the mice gastrocnemius muscle, with increased serum IGF-1 concentration. TM5484 induced dose-dependent Igf1, Atrogin-1, and Chrna1 expression in C2C12 myoblastic cells, confirming cell autonomous effect. Further, the presence of plasmin for 72 h caused significantly increased Igf1 expression in C2C12 cells. These findings suggest that oral PAI-1 inhibitors represent a promising therapeutic candidate for preventing sarcopenia progression in humans.

Adipocyte Ceramides-The Nexus of Inflammation and Metabolic Disease

Adipose depots are heterogeneous tissues that store and sense fuel levels. Through the secretion of lipids, cytokines, and protein hormones (adipokines), they communicate with other organ systems, informing them of the organism's nutritional status. The adipose tissues include diverse types of adipocytes (white, beige, and brown) distinguished by the number/size of lipid droplets, mitochondrial density, and thermogenic capacity. Moreover, they include a spectrum of immune cells that modulate metabolic activity and tissue remodeling. The unique characteristics and interplay of these cells control the production of ceramides, a class of nutrient signals derived from fat and protein metabolism that modulate adipocyte function to regulate glucose and lipid metabolism. The excessive accumulation of ceramides contributes to the adipose tissue inflammation and dysfunction that underlies cardiometabolic disease. Herein we review findings on this important class of lipid species and discuss their role at the convergence point that links overnutrition/inflammation to key features of the metabolic syndrome.

Roles of Olfactomedin 1 in Muscle and Bone Alterations Induced by Gravity Change in Mice

Microgravity causes both muscle and bone loss. Although we previously revealed that gravity change influences muscle and bone through the vestibular system in mice, its detailed mechanism has not been elucidated. In this study, we investigated the roles of olfactomedin 1 (OLFM1), whose expression was upregulated during hypergravity in the soleus muscle, in mouse bone cells. Vestibular lesion significantly blunted OLFM1 expression in the soleus muscle and serum OLFM1 levels enhanced by hypergravity in mice. Moreover, a phosphatidylinositol 3-kinase inhibitor antagonized shear stress-enhanced OLFM1 expression in C2C12 myotubes. As for the effects of OLFM1 on bone cells, OLFM1 inhibited osteoclast formation from mouse bone marrow cells and mouse preosteoclastic RAW264.7 cells. Moreover, OLFM1 suppressed RANKL expression and nuclear factor-κB signaling in mouse osteoblasts. Serum OLFM1 levels were positively related to OLFM1 mRNA levels in the soleus muscle and trabecular bone mineral density of mice. In conclusion, we first showed that OLFM1 suppresses osteoclast formation and RANKL expression in mouse cells.

Adipose Tissue-Derived Stem Cell Sheet Improves Glucose Metabolism in Obese Mice

Previous studies indicate that the administration of adipose tissue-derived stem cells (ADSCs) through the venous route improves insulin resistance partly through a reduction in the proinflammatory cytokines in diabetic animals. However, the effects of ADSC sheet transplantation for the treatment of diabetes and obesity still remained unknown. In this study, we investigated the effects of ADSC sheet transplantation into the subcutaneous sites on the diabetic state of mice fed high-fat and high-sucrose diet (HF/HSD). ADSCs were isolated and propagated from subcutaneous adipose tissues of non-diabetic intact mice. We used the thermoresponsive designated cell culture dishes to fabricate ADSC cell sheets. ADSC sheet transplantation into the subcutaneous sites significantly improved glucose intolerance induced by HF/HSD in mice. ADSC-conditioned medium (CM) augmented the phosphorylation of Akt with or without insulin in mouse C2C12 myotubes and mouse 3T3-L1 adipocytes. Plasma adiponectin and tumor necrosis factor-α (TNF-α) levels were significantly increased and decreased by ADSC sheet transplantation in mice with or without HF/HSD, respectively. Moreover, ADSC sheet enhanced adiponectin expression in the subcutaneous adipose tissues in HF/HSD-fed mice, whereas it reduced TNF-α expression in the visceral adipose tissues. ADSC-CM enhanced and reduced the protein levels of adiponectin and TNF-α in 3T3-L1 adipocytes, respectively. In conclusion, we first revealed that ADSC sheet transplantation into the subcutaneous sites improves glucose intolerance in mice fed with HF/HSD. Changes of adiponectin and TNF-α production from the host adipose tissues might be involved in the effects of ADSC sheet on glucose metabolism in mice. ADSC sheet transplantation therapy may be a novel clinical application for diabetes.

Role of irisin in androgen-deficient muscle wasting and osteopenia in mice

Androgen deficiency plays a crucial role in the pathogenesis of male osteoporosis and sarcopenia. Myokines have recently been identified as humoral factors that are involved in the interactions between muscle and bone; however, the influence of androgen deficiency on these interactions remains unclear. Therefore, we herein investigated the roles of humoral factors linking muscle to bone using orchidectomized mice with sarcopenia and osteopenia. Orchidectomy (ORX) significantly reduced muscle mass, grip strength, and trabecular bone mineral density (BMD) in mice. Among the myokines examined, ORX only significantly reduced fibronectin type III domain-containing 5 (Fndc5) mRNA levels in both the soleus and gastrocnemius muscles of mice. In simple regression analyses, Fndc5 mRNA levels in the soleus muscle positively correlated with trabecular BMD, but not cortical BMD. The administration of irisin, a product of Fndc5, significantly protected against the decrease induced in trabecular BMD, but not muscle mass, by androgen deficiency in mice. In conclusion, the present results demonstrated that androgen deficiency decreases the expression of irisin in the skeletal muscle of mice. Irisin may be involved in muscle/bone relationships negatively affected by androgen deficiency.

Dual-reporter high-throughput screen for small-molecule in vivo inhibitors of plasminogen activator inhibitor type-1 yields a clinical lead candidate

Plasminogen activator inhibitor type-1 (PAI-1) is a serine protease inhibitor (serpin) implicated in numerous pathological processes, including coronary heart disease, arterial and venous thrombosis, and chronic fibrotic diseases. These associations have made PAI-1 an attractive pharmaceutical target. However, the complexity of the serpin inhibitory mechanism, the inherent metastability of serpins, and the high-affinity association of PAI-1 with vitronectin in vivo have made it difficult to identify pharmacologically effective small-molecule inhibitors. Moreover, the majority of current small-molecule PAI-1 inhibitors are poor pharmaceutical candidates. To this end and to find leads that can be efficiently applied to in vivo settings, we developed a dual-reporter high-throughput screen (HTS) that reduced the rate of nonspecific and promiscuous hits and identified leads that inhibit human PAI-1 in the high-protein environments present in vivo Using this system, we screened >152,000 pure compounds and 27,000 natural product extracts (NPEs), reducing the apparent hit rate by almost 10-fold compared with previous screening approaches. Furthermore, screening in a high-protein environment permitted the identification of compounds that retained activity in both ex vivo plasma and in vivo Following lead identification, subsequent medicinal chemistry and structure-activity relationship (SAR) studies identified a lead clinical candidate, MDI-2268, having excellent pharmacokinetics, potent activity against vitronectin-bound PAI-1 in vivo, and efficacy in a murine model of venous thrombosis. This rigorous HTS approach eliminates promiscuous candidate leads, significantly accelerates the process of identifying PAI-1 inhibitors that can be rapidly deployed in vivo, and has enabled identification of a potent lead compound.

Antioxidant, anti-hyperlipidemia and hepatic protection of enzyme-assisted Morehella esculenta polysaccharide

The aims of this work were to investigate the antioxidant, anti-hyperlipidemia and hepatic protection of Morehella esculenta polysaccharide (MPS) from fruiting body and its enzyme-assisted MPS (EnMPS). The in vitro scavenging rates of EnMPS at 600 mg/L on superoxide, hydroxyl and 1,1‑diphenyl‑2‑pyrazole hydrazide (DPPH) radicals were 76.92 ± 2.61%, 66.74 ± 2.56% and 75.78 ± 2.4%, higher than those of MPS, respectively. Animals experiments showed that the EnMPS exhibited superior abilities of reducing hepatic lipid levels by monitoring the serum enzyme activities (ALP, ALT, ALB and AST) and serum lipid levels (CK, TC, TG, HDL-C, LDL-C and LDH), enhancing the hepatic antioxidant enzymes (FFA, SOD, CAT and T-AOC) and decreasing the lipid peroxidation (MDA and MPO). The results suggested that the EnMPS can act as a natural candidate for developing drugs to reduce blood lipids, resist oxidation and protect the liver.

A small-molecule PAI-1 inhibitor prevents bone loss by stimulating bone formation in a murine estrogen deficiency-induced osteoporosis model

Osteoporosis is a progressive bone disease caused by an imbalance between bone resorption and formation. Recently, plasminogen activator inhibitor-1 (PAI-1) was shown to play an important role in bone metabolism using PAI-1-deficient mice. In this study, we evaluated the therapeutic benefits of novel, orally available small-molecule PAI-1 inhibitor (iPAI-1) in an estrogen deficiency-induced osteoporosis model. Eight-week-old C57BL/6J female mice were divided into three groups: a sham + vehicle (Sham), ovariectomy + vehicle (OVX + v), and OVX + iPAI-1 (OVX + i) group. iPAI-1 was administered orally each day for 6 weeks starting the day after the operation. Six weeks of iPAI-1 treatment prevented OVX-induced trabecular bone loss in both the femoral bone and lumbar spine. Bone formation activity was significantly higher in the OVX + i group than in the OVX + v and Sham groups. Unexpectedly, OVX-induced osteoclastogenesis was partially, but significantly reduced. Fluorescence-activated cell sorting analyses indicated that the number of bone marrow stromal cells was higher in the OVX + i group than that in the OVX + v group. A colony-forming unit-osteoblast assay indicated enhanced mineralized nodule formation activity in bone marrow cells isolated from iPAI-1-treated animals. Bone marrow ablation analysis indicated that the remodeled trabecular bone volume was significantly higher in the iPAI-1-treated group than that in the control group. In conclusion, our results suggest PAI-1 blockade via a small-molecule inhibitor is a new therapeutic approach for the anabolic treatment of postmenopausal osteoporosis.

The vestibular system is critical for the changes in muscle and bone induced by hypergravity in mice

Gravity changes concurrently affect muscle and bone as well as induce alterations in vestibular signals. However, the role of vestibular signals in the changes in muscle and bone induced by gravity changes remains unknown. We therefore investigated the effects of vestibular lesions (VL) on the changes in muscle and bone induced by 3 g hypergravity for 4 weeks in C57BL/6J mice. Quantitative computed tomography analysis revealed that hypergravity increased muscle mass surrounding the tibia and trabecular bone mineral content, adjusting for body weight in mice. Hypergravity did not affect cortical bone and fat masses surrounding the tibia. Vestibular lesions blunted the increases in muscle and bone masses induced by hypergravity. Histological analysis showed that hypergravity elevated the cross‐sectional area of myofiber in the soleus muscle. The mRNA levels of myogenic genes such as MyoD, Myf6, and myogenin in the soleus muscle were elevated in mice exposed to hypergravity. Vestibular lesions attenuated myofiber size and the mRNA levels of myogenic differentiation markers enhanced by hypergravity in the soleus muscle. Propranolol, a β‐blocker, antagonized the changes in muscle induced by hypergravity. In conclusion, this study is the first to demonstrate that gravity changes affect muscle and bone through vestibular signals and subsequent sympathetic outflow in mice.

TM5441, a plasminogen activator inhibitor-1 inhibitor, protects against high fat diet-induced non-alcoholic fatty liver disease

Recent evidences showed that elevation of plasminogen activator inhibitor 1 (PAI-1) was responsible in mediating obesity-induced non-alcoholic fatty liver disease (NAFLD) and metabolic disorders. Here, we investigated the effect of TM5441, an oral PAI-1 inhibitor that lacks of bleeding risk, on high-fat diet (HFD)-induced NAFLD. HFD-fed C57BL/6J mice was daily treated with 20 mg/kg TM5441. To examine the preventive effect, 10-week-treatment was started along with initiation of HFD; alternatively, 4-week-treatment was started in mice with glucose intolerance in the interventional strategy. In vivo study showed that early and delayed treatment decreased hepatic steatosis. Particularly, early treatment prevented the progression of hepatic inflammation and fibrosis in HFD mice. Interestingly, both strategies abrogated hepatic insulin resistance and mitochondrial dysfunction, presented by enhanced p-Akt and p-GSK3β, reduced p-JNK signaling, along with p-AMPK and PGC-1α activation. Consistently, TM5441 treatment in the presence of either PAI-1 exposure or TNF-α stimulated-PAI-1 activity showed a restoration of mitochondrial biogenesis related genes expression on HepG2 cells. Thus, improvement of insulin sensitivity and mitochondrial function was imperative to partially explain the therapeutic effects of TM5441, a novel agent targeting HFD-induced NAFLD.

Plasminogen activator inhibitor-1 deficiency enhances subchondral osteopenia after induction of osteoarthritis in mice

BACKGROUND

Subchondral osteopenia is important for the pathophysiology of osteoarthritis (OA). Although previous studies suggest that plasminogen activator inhibitor-1 (PAI-1), an inhibitor of fibrinolysis, is related to bone metabolism, its role in OA remains unknown. We therefore investigated the roles of PAI-1 in the subchondral bone in OA model mice.

METHODS

Wild type (WT) and PAI-1-deficient (KO) mice were ovariectomized (OVX), and then destabilization of the medial meniscus (DMM) surgery was performed.

RESULTS

DMM and OVX significantly decreased the trabecular bone mineral density of the subchondral bone evaluated by quantitative computed tomography in PAI-1 KO mice. The effects of OVX and/or PAI-1 deficiency on the OARSI score for the evaluation of the progression of knee degeneration were not significant. PAI-1 deficiency significantly augmented receptor activator nuclear factor κB ligand mRNA levels enhanced by IL-1β in mouse primary osteoblasts, although it did not affect osteoblast differentiation. Moreover, PAI-1 deficiency significantly increased osteoclast formation from mouse bone marrow cells.

CONCLUSION

We showed that PAI-1 deficiency accelerates the subchondral osteopenia after induction of OA in mice. PAI-1 might suppress an enhancement of bone resorption and subsequent subchondral osteopenia after induction of OA in mice.

Role of follistatin in muscle and bone alterations induced by gravity change in mice

Interactions between muscle and bone have been recently noted. We reported that the vestibular system plays crucial roles in the changes in muscle and bone induced by hypergravity in mice. However, the details of the mechanisms by which gravity change affects muscle and bone through the vestibular system still remain unknown. Here, we investigated the roles of humoral factors linking muscle to bone and myostatin-related factors in the hypergravity-induced changes in muscle and bone in mice with vestibular lesions (VL). Hypergravity elevated serum and mRNA levels of follistatin, an endogenous inhibitor of myostatin, in the soleus muscle of mice. VL blunted the hypergravity-enhanced levels of follistatin in the soleus muscle of mice. Simulated microgravity decreased follistatin mRNA level in mouse myoblastic C2C12 cells. Follistatin elevated the mRNA levels of myogenic genes as well as the phosphorylation of Akt and p70S6 kinase in C2C12 cells. As for bone metabolism, follistatin antagonized the mRNA levels of osteogenic genes suppressed by activin A during the differentiation of mesenchymal cells into osteoblastic cells. Moreover, follistatin attenuated osteoclast formation enhanced by myostatin in the presence of receptor activator of nuclear factor-κB ligand in RAW 264.7 cells. Serum follistatin levels were positively related to bone mass in mouse tibia. In conclusion, the present study provides novel evidence that hypergravity affects follistatin levels in muscle through the vestibular system in mice. Follistatin may play some roles in the interactions between muscle and bone metabolism in response to gravity change.

Causal Effect of Plasminogen Activator Inhibitor Type 1 on Coronary Heart Disease

Background

Plasminogen activator inhibitor type 1 (PAI‐1) plays an essential role in the fibrinolysis system and thrombosis. Population studies have reported that blood PAI‐1 levels are associated with increased risk of coronary heart disease (CHD). However, it is unclear whether the association reflects a causal influence of PAI‐1 on CHD risk.

Methods and Results

To evaluate the association between PAI‐1 and CHD, we applied a 3‐step strategy. First, we investigated the observational association between PAI‐1 and CHD incidence using a systematic review based on a literature search for PAI‐1 and CHD studies. Second, we explored the causal association between PAI‐1 and CHD using a Mendelian randomization approach using summary statistics from large genome‐wide association studies. Finally, we explored the causal effect of PAI‐1 on cardiovascular risk factors including metabolic and subclinical atherosclerosis measures. In the systematic meta‐analysis, the highest quantile of blood PAI‐1 level was associated with higher CHD risk comparing with the lowest quantile (odds ratio=2.17; 95% CI: 1.53, 3.07) in an age‐ and sex‐adjusted model. The effect size was reduced in studies using a multivariable‐adjusted model (odds ratio=1.46; 95% CI: 1.13, 1.88). The Mendelian randomization analyses suggested a causal effect of increased PAI‐1 level on CHD risk (odds ratio=1.22 per unit increase of log‐transformed PAI‐1; 95% CI: 1.01, 1.47). In addition, we also detected a causal effect of PAI‐1 on elevating blood glucose and high‐density lipoprotein cholesterol.

Conclusions

Our study indicates a causal effect of elevated PAI‐1 level on CHD risk, which may be mediated by glucose dysfunction.

Plasminogen Activator Inhibitor-1 and Diagnosis of the Metabolic Syndrome in a West African Population

BACKGROUND

Metabolic syndrome (MetS) is diagnosed by the presence of at least 3 of the following: obesity, hypertension, hyperglycemia, hypertriglyceridemia, and low high-density lipoprotein. Individuals with MetS also typically have elevated plasma levels of the antifibrinolytic factor, plasminogen activator inhibitor-1 (PAI-1), but the relationships between PAI-1 and MetS diagnostic criteria are not clear. Understanding these relationships can elucidate the relevance of MetS to cardiovascular disease risk, because PAI-1 is associated with ischemic events and directly involved in thrombosis.

METHODS AND RESULTS

In a cross-sectional analysis of 2220 Ghanaian men and women from urban and rural locales, we found the age-standardized prevalence of MetS to be as high as 21.4% (urban women). PAI-1 level increased exponentially as the number of diagnostic criteria increased linearly (P<10-13), supporting the conclusion that MetS components have a joint effect that is stronger than their additive contributions. Body mass index, triglycerides, and fasting glucose were more strongly correlated with PAI-1 than with canonical MetS criteria, and this pattern did not change when pair-wise correlations were conditioned on all other risk factors, supporting an independent role for PAI-1 in MetS. Finally, whereas the correlations between conventional risk factors did not vary significantly by sex or across urban and rural environments, correlations with PAI-1 were generally stronger among urban participants.

CONCLUSIONS

MetS prevalence in the West African population we studied was comparable to that of the industrialized West. PAI-1 may serve as a key link between MetS, as currently defined, and the endpoints with which it is associated. Whether this association is generalizable will require follow-up.

A novel plasminogen activator inhibitor-1 inhibitor, TM5441, protects against high-fat diet-induced obesity and adipocyte injury in mice

BACKGROUND AND PURPOSE

Obesity is one of the most prevalent chronic diseases worldwide, and dysregulated adipocyte function plays an important role in obesity-associated metabolic disorder. The level of plasma plasminogen activator inhibitor-1 (PAI-1) is increased in obese subjects, and PAI-1 null mice show improved insulin sensitivity when subjected to high-fat and high-sucrose diet-induced metabolic stress, suggesting that a best-in-class PAI-1 inhibitor may become a novel therapeutic agent for obesity-associated metabolic syndrome. TM5441 is a novel orally active PAI-1 inhibitor that does not cause bleeding episodes. Hence, in the present study we examined the preventive effect of TM5441 on high-fat diet (HFD)-induced adipocyte dysfunction.

EXPERIMENTAL APPROACH

Ten-week-old C57BL/6J mice were fed a normal diet (18% of total calories from fat) or HFD (60% of total calories from fat) for 10 weeks, and TM5441 (20 mg·kg(-1) oral gavage) was administered daily with the initiation of HFD.

KEY RESULTS

TM5441 prevented HFD-induced body weight gain and systemic insulin resistance. TM5441 normalized HFD-induced dysregulated JNK and Akt phosphorylation, suggesting that it prevents the insulin resistance of adipocytes. TM5441 also attenuated the macrophage infiltration and increased expression of pro-inflammatory cytokines, such as inducible nitric oxide synthase, induced by the HFD. In addition, TM5441 prevented the HFD-induced down-regulation of genes involved in mitochondrial biogenesis and function, suggesting that it may prevent adipocyte inflammation and dysregulation by maintaining mitochondrial fitness.

CONCLUSION AND IMPLICATIONS

Our data suggest that TM5441 may become a novel therapeutic agent for obesity and obesity-related metabolic disorders.

A High-Saturated-Fat, High-Sucrose Diet Aggravates Bone Loss in Ovariectomized Female Rats

BACKGROUND

Estrogen deficiency in women and high-saturated fat, high-sucrose (HFS) diets have both been recognized as risk factors for metabolic syndrome. Studies on the combined actions of these 2 detrimental factors on the bone in females are limited.

OBJECTIVE

We sought to determine the interactive actions of estrogen deficiency and an HFS diet on bone properties and to investigate the underlying mechanisms.

METHODS

Six-month-old Sprague Dawley sham or ovariectomized (OVX) rats were pair fed the same amount of either a low-saturated-fat, low-sucrose (LFS) diet (13% fat calories; 15% sucrose calories) or an HFS diet (42% fat calories; 30% sucrose calories) for 12 wk. Blood, liver, and bone were collected for correspondent parameters measurement.

RESULTS

Ovariectomy decreased bone mineral density in the tibia head (TH) by 62% and the femoral end (FE) by 49% (P < 0.0001). The HFS diet aggravated bone loss in OVX rats by an additional 41% in the TH and 37% in the FE (P < 0.05). Bone loss in the HFS-OVX rats was accompanied by increased urinary deoxypyridinoline concentrations by 28% (P < 0.05). The HFS diet induced cathepsin K by 145% but reduced osteoprotegerin mRNA expression at the FE of the HFS-sham rats by 71% (P < 0.05). Ovariectomy significantly increased peroxisome proliferator-activated receptor γ mRNA expression by 136% and 170% at the FE of the LFS- and HFS-OVX rats, respectively (P < 0.05). The HFS diet aggravated ovariectomy-induced lipid deposition and oxidative stress (OS) in rat livers (P < 0.05). Trabecular bone mineral density at the FE was negatively correlated with rat liver malondialdehyde concentrations (R(2) = 0.39; P < 0.01).

CONCLUSIONS

The detrimental actions of the HFS diet and ovariectomy on bone properties in rats occurred mainly in cancellous bones and were characterized by a high degree of bone resorption and alterations in OS.

[Adiponectin in health and disease]

Over the past 20 years after the discovery of adiponectin, much knowledge about its effect in health and disease has been gained. Adiponectin has antidiabetic, antiatherogenic, anti-inflammatory, immunomodulatory, metabolic, vasoprotective, and antiapoptotic properties. However, an understanding stems from the given literature review that much remains to be explored. Adiponectin has not yet commonly used in clinical practice, but cardiologists, endocrinologists, pediatricians, oncologists, and physicians of many specialties are interested in its preventive and therapeutic applications.

α₂-Antiplasmin is involved in bone loss induced by ovariectomy in mice

The mechanism of postmenopausal osteoporosis is not fully understood. α2-Antiplasmin (α2-AP) is the primary inhibitor of plasmin in the fibrinolytic system, but is known to have activities beyond fibrinolysis. However, its role in bone metabolism and the pathogenesis of osteoporosis remains unknown. In the current study, we therefore examined the effects of α2-AP deficiency on ovariectomy (OVX)-induced bone loss by using wild-type and α2-AP-deficient mice. Quantitative computed tomography analysis revealed that α2-AP deficiency blunted OVX-induced trabecular bone loss in mice. Moreover, α2-AP deficiency significantly blunted serum levels of bone-specific alkaline phosphatase, cross-linked C-telopeptide of type I collagen, and interleukin (IL)-1β elevated by OVX. α2-AP treatment elevated the levels of IL-1β and tumor necrosis factor (TNF)-α mRNA in RAW 264.7 cells, although it suppressed osteoclast formation induced by receptor activator of nuclear factor-κB ligand. α2-AP treatment activated ERK1/2 and p38 MAP kinase pathways in RAW 264.7 cells, and these MAP kinase inhibitors antagonized the levels of IL-1β mRNA elevated by α2-AP. The data demonstrate that α2-AP is linked to bone loss due to OVX, through a mechanism that depends in part on the production of IL-1β and TNF-α in monocytes.

Serpine1 Mediates Porphyromonas gingivalis Induced Insulin Secretion in the Pancreatic Beta Cell Line MIN6

Periodontitis is an inflammatory disease resulting in destruction of gingiva and alveolar bone caused by an exuberant host immunological response to periodontal pathogens. Results from a number of epidemiological studies indicate a close association between diabetes and periodontitis. Results from cross-sectional studies indicate that subjects with periodontitis have a higher odds ratio of developing insulin resistance (IR). However, the mechanisms by which periodontitis influences the development of diabetes are not known. Results from our previous studies using an animal model of periodontitis suggest that periodontitis accelerates the onset of hyperinsulinemia and IR. In addition, LPS from a periodontal pathogen, Porphyromonas gingivalis (Pg), stimulates Serpine1 expression in the pancreatic beta cell line MIN6. Based on these observations, we hypothesized that a periodontal pathogen induces hyperinsulinemia and Serpine1 may be involved in this process. To test this hypothesis, we co-incubated Pg with the pancreatic beta cell line MIN6 and measured the effect on insulin secretion by MIN6 cells. We further determined the involvement of Serpine1 in insulin secretion by downregulating Serpine1 expression. Our results indicated that Pg stimulated insulin secretion by approximately 3.0 fold under normoglycemic conditions. In a hyperglycemic state, Pg increased insulin secretion by 1.5 fold. Pg significantly upregulated expression of the Serpine1 gene and this was associated with increased secretion of insulin by MIN6 cells. However, cells with downregulated Serpine1 expression were resistant to Pg stimulated insulin secretion under normoglycemic conditions. We conclude that the periodontal pathogen, Pg, induced insulin secretion by MIN6 cells and this induction was, in part, Serpine1 dependent. Thus, Serpine1 may play a pivotal role in insulin secretion during the accelerated development of hyperinsulinemia and the resulting IR in the setting of periodontitis.

Role of plasminogen activator inhibitor-1 in glucocorticoid-induced diabetes and osteopenia in mice

Long-term use of glucocorticoids (GCs) causes numerous adverse effects, including glucose/lipid abnormalities, osteoporosis, and muscle wasting. The pathogenic mechanism, however, is not completely understood. In this study, we used plasminogen activator inhibitor-1 (PAI-1)-deficient mice to explore the role of PAI-1 in GC-induced glucose/lipid abnormalities, osteoporosis, and muscle wasting. Corticosterone markedly increased the levels of circulating PAI-1 and the PAI-1 mRNA level in the white adipose tissue of wild-type mice. PAI-1 deficiency significantly reduced insulin resistance and glucose intolerance but not hyperlipidemia induced by GC. An in vitro experiment revealed that active PAI-1 treatment inhibits insulin-induced phosphorylation of Akt and glucose uptake in HepG2 hepatocytes. However, this was not observed in 3T3-L1 adipocytes and C2C12 myotubes, indicating that PAI-1 suppressed insulin signaling in hepatocytes. PAI-1 deficiency attenuated the GC-induced bone loss presumably via inhibition of apoptosis of osteoblasts. Moreover, the PAI-1 deficiency also protected from GC-induced muscle loss. In conclusion, the current study indicated that PAI-1 is involved in GC-induced glucose metabolism abnormality, osteopenia, and muscle wasting in mice. PAI-1 may be a novel therapeutic target to mitigate the adverse effects of GC.