The plasminogen receptor Plg-RKT regulates adipose function and metabolic homeostasis

The association between fatty acids and atherosclerotic diseases: A mendelian randomization study

BACKGROUND

The current observational studies have disputed the relationship between various fatty acids and atherosclerotic diseases, and the causal relationship between the two is still unclear.

METHODS

In this study, we utilized the available genome-wide association studies (GWAS) summary data on fatty acids and atherosclerotic diseases from the IEU OpenGWAS project. After identifying the appropriate single nucleotide polymorphisms (SNPs) as instrumental variables, we employed the MR-PRESSO outlier test to remove extreme values. Subsequently, we conducted a two-sample mendelian randomization (MR) analysis and performed sensitivity analyses to ensure the reliability of the results.

RESULTS

The results of MR analysis suggest that ratio of saturated fatty acids to total fatty acids is positively correlated with the incidence rate of coronary heart disease (OR = 1.341, 95% CI = 1.016-1.769, P value = 0.038), monounsaturated fatty acid levels is negatively correlated with the incidence of stroke (OR = 0.800, 95% CI = 0.642-0.996, P value = 0.046), and docosahexaenoic acid levels is negatively correlated with the incidence of peripheral artery disease (OR = 0.747, 95% CI = 0.572-0.976, P value = 0.033). All results showed no heterogeneity or pleiotropy, but leave-one-out tests showed that the analysis results of some fatty acids were driven by a single SNP.

CONCLUSIONS

This study highlights the existence of causal relationships between fatty acids and atherosclerotic diseases at the genetic level. These findings provide valuable insights for potential prevention measures and therapeutic targets for the three atherosclerotic diseases.

Liver-derived plasminogen mediates muscle stem cell expansion during caloric restriction through the plasminogen receptor Plg-RKT

An intriguing effect of short-term caloric restriction (CR) is the expansion of certain stem cell populations, including muscle stem cells (satellite cells), which facilitate an accelerated regenerative program after injury. Here, we utilized the MetRSL274G (MetRS) transgenic mouse to identify liver-secreted plasminogen as a candidate for regulating satellite cell expansion during short-term CR. Knockdown of circulating plasminogen prevents satellite cell expansion during short-term CR. Furthermore, loss of the plasminogen receptor KT (Plg-RKT) is also sufficient to prevent CR-related satellite cell expansion, consistent with direct signaling of plasminogen through the plasminogen receptor Plg-RKT/ERK kinase to promote proliferation of satellite cells. Importantly, we are able to replicate many of these findings in human participants from the CALERIE trial. Our results demonstrate that CR enhances liver protein secretion of plasminogen, which signals directly to the muscle satellite cell through Plg-RKT to promote proliferation and subsequent muscle resilience during CR.

Investigating the association of previously identified genome-wide significant loci (rs10739076 and rs1784692) with PCOS susceptibility and its related traits in Indian women

OBJECTIVE(S)

Polycystic ovary syndrome (PCOS) is a multifactorial endocrinopathy with an enigmatic etiology. Hallmark features include irregular menstrual cycles, insulin resistance and hyperandrogenemia and affected women are prone to development of adverse reproductive and cardiometabolic outcomes like anovulatory infertility, impaired glucose tolerance, type 2 diabetes, dyslipidemia, metabolic syndrome and cardiovascular disease. Genetic underpinnings of PCOS have been investigated extensively using genome-wide association studies, which have led to the identification of several novel susceptibility loci. However, as ethnic diversity contributes to phenotypic and genetic heterogeneity, we undertook the first genetic association study to determine the association of rs10739076 of PLGRKT and rs1784692 of ZBTB16 with PCOS susceptibility and its related traits in Indian women.

STUDY DESIGN

The present case-control study comprised 497 women with PCOS diagnosed according to the Rotterdam criteria and 233 age matched healthy women as controls. All participants were characterized in terms of anthropometric, hormonal and metabolic parameters and the variants were investigated by direct sequencing. Genotypic and genotype-phenotype association of these variants with PCOS susceptibility and its related biochemical and hormonal traits was analyzed with appropriate statistical tests.

RESULTS

The genotypic and allelic frequencies of rs1784692 of ZBTB16 were significantly decreased in lean women with PCOS only, and this variant was associated with lowered insulin levels, HOMA-IR, LH:FSH ratio along with increased ApoA1 levels and QUICKI in them. Although, the PLGRKT variant, rs10739076, showed similar frequency distribution in both lean and obese groups, it was found to be associated with reduced fasting glucose in all women with PCOS.

CONCLUSION(S)

To the best of our knowledge, this is the first study to demonstrate that ZBTB16 variant showed significant association with reduced PCOS susceptibility in lean rather than obese Indian women, highlighting the impact of obesity on determining genetic predisposition to PCOS in Indian women. In contrast, PLGRKT variant did not influence PCOS risk in lean or obese women. Importantly, both variants exerted a protective effect on glucose metabolism, insulin resistance, gonadotropin and lipid levels in women with PCOS. Determination of susceptibility variants for PCOS demand population specific replication studies to ascertain best candidate loci for PCOS.

Overexpression of Plg-RKT protects against adipose dysfunction and dysregulation of glucose homeostasis in diet-induced obese mice

The plasminogen receptor, Plg-RKT, is a unique cell surface receptor that is broadly expressed in cells and tissues throughout the body. Plg-RKT localizes plasminogen on cell surfaces and promotes its activation to the broad-spectrum serine protease, plasmin. In this study, we show that overexpression of Plg-RKT protects mice from high fat diet (HFD)-induced adipose and metabolic dysfunction. During the first 10 weeks on the HFD, the body weights of mice that overexpressed Plg-RKT (Plg-RKT-OEX) were lower than those of control mice (CagRosaPlgRKT). After 10 weeks on the HFD, CagRosaPlgRKT and Plg-RKT-OEX mice had similar body weights. However, Plg-RKT-OEX mice showed a more metabolically favourable body composition phenotype. Plg-RKT-OEX mice also showed improved glucose tolerance and increased insulin sensitivity. We found that the improved metabolic functions of Plg-RKT-OEX mice were mechanistically associated with increased energy expenditure and activity, decreased proinflammatory adipose macrophages and decreased inflammation, elevated brown fat thermogenesis, and higher expression of adipose PPARγ and adiponectin. These findings suggest that Plg-RKT signalling promotes healthy adipose function via multiple mechanisms to defend against obesity-associated adverse metabolic phenotypes.

Single-cell RNA seq identifies Plg-RKT-PLG as signals inducing phenotypic transformation of scar-associated macrophage in liver fibrosis

Hepatic macrophages play a central role in liver fibrosis. Scar-associated macrophages (SAMs), a recently identified subgroup of macrophages, play an important role in this process. However, the mechanism by which SAMs transform during liver fibrosis is still unclear. In this study, we aimed to characterize SAMs and elucidate the underlying mechanism of SAM transformation. Bile duct ligation (BDL) and carbon tetrachloride (CCl₄) were used to induce mouse liver fibrosis. Non-parenchymal cells were isolated from normal/fibrotic livers and were analyzed using single cell RNA sequencing (scRNA-seq) or mass cytometry (CyTOF). The glucan-encapsulated siRNA particles (siRNA-GeRPs) was employed to perform macrophage selective gene knockdown. The results of scRNA-seq and CyTOF revealed that SAMs, which derived from bone marrow-derived macrophages (BMMs), accumulated in mouse fibrotic livers. Further analysis showed that SAMs highly expressed genes related to fibrosis, indicating the pro-fibrotic functions of SAMs. Moreover, plasminogen receptor Plg-R_KT was highly expressed by SAMs, suggesting the role of Plg-R_KT and plasminogen (PLG) in SAM transformation. In vitro, PLG-treated BMMs transformed into SAMs and expressed SAM functional genes. Knockdown of Plg-R_KT blocked the effects of PLG. In vivo, selective knockdown of Plg-R_KT in intrahepatic macrophages of BDL- and CCl₄-treated mice reduced the number of SAMs and alleviated BDL- and CCl₄-induced liver fibrosis, suggesting that Plg-R_KT-PLG played an important role in liver fibrosis by mediating SAM transformation. Our findings reveal that SAMs are crucial participants in liver fibrosis. Inhibition of SAM transformation by blocking Plg-R_KT might be a potential therapeutic target for liver fibrosis.

Updated experimental cellular models to study polycystic ovarian syndrome

Polycystic ovarian syndrome (PCOS) develops due to hormonal imbalance and hyperandrogenism. Animal models are widely used to study PCOS because they mimic essential characteristics of human PCOS; however, the pathogenesis of PCOS remains unclear. Different sources of novel drugs are currently being screened as therapeutic strategies to alleviate PCOS and its symptoms. Simplified cell line in-vitro models could be preliminarily used to screen the bioactivity of various drugs. This review describes different cell line models focusing on the PCOS condition and its complications. Therefore, the bioactivity of the drugs could be preliminarily screened in a cell line model before moving to higher animal models.