Circulating Ism1 Reduces the Risk of Type 2 Diabetes but not Diabetes-Associated NAFLD

Metformin Increases Serum Isthmin-1 Levels and Lowers Low-Density Lipoprotein: Potential Implications for Lipid Metabolism in T2DM

Background and Objectives: Type 2 Diabetes Mellitus (T2DM) is a metabolic disease caused by the failure of the skeletal muscle, liver and adipose tissue to respond to insulin. Metformin is the first choice for the treatment of T2DM. Isthmin 1 (Ism1) is a newly discovered adipokine that affects all carbohydrate, lipid and protein metabolism. This study examines the changes in serum and salivary levels of Ism1 in patients using metformin, considering its potential as a follow-up marker for T2DM if present in the salivary glands. Materials and Methods: The study included 30 newly diagnosed T2DM patients and 30 non-diabetic controls. Ism1 was measured by ELISA in serum and saliva after 3 months and compared with routine biochemical parameters. Immunostaining of Ism1 was performed in salivary glands. Results: Ism1 was immunohistochemically detected in salivary glands for the first time. Serum Ism1 levels increased significantly after 3 months of metformin treatment (p = 0.028). The increase in salivary Ism1 levels did not reach statistical significance. Fasting plasma glucose (FPG) (p < 0.001), HbA1c (p < 0.001) and LDL (p = 0.015) levels decreased with metformin. There was a significant negative correlation between the increase in Ism1 levels and the decrease in LDL levels (rho = -0.362, p = 0.05). Conclusions: Despite its first detection in salivary glands, the hypothesis that Ism1 may be a surveillance marker in T2DM could not be confirmed. The negative correlation of Ism1 with LDL levels suggests that Ism1 may contribute to the ameliorative effect of metformin on serum lipids. Further studies are needed to support this conclusion.

Role of Dardarin and Isthmin-1 in the Protective Effect of Hydroxytyrosol Against Corn Syrup-Induced Liver Damage

INTRODUCTION

In this study, it was investigated whether dardarin (LRRK2) and isthmin-1 (ISM1) play a role in the protective effect of hydroxytyrosol (HT) used to prevent liver damage caused by corn syrup in rats.

METHODS

Rats were divided into four groups with six in each group: 1) control, 2) HT, 3) corn syrup, and 4) corn syrup + HT. Rats were given water containing 30% corn syrup for six weeks. At the same time, HT-containing liquid was given orally at 4 ml/kg/day, alone and together with corn syrup for six weeks. The weights of the rats were measured every week. LRRK2 and ISM1 molecules in liver tissue were evaluated by histopathological methods. Biochemical parameters were also examined with the enzyme-linked immunosorbent assay (ELISA) method.

RESULTS

It was found that weight gain was less in rats receiving HT than in those consuming corn syrup. The increase in cholesterol, triglyceride, and liver enzyme levels because of corn syrup consumption decreased with HT consumption. As a result of histopathological analysis, it was observed that the increase in LRRK2 and ISM1 levels observed in the liver tissue in the corn syrup-administered group decreased when HT was administered together with corn syrup. In addition, it was determined that the increase in sinusoidal expansion and hepatocyte necrosis observed in the liver tissue as a result of corn syrup application decreased as a result of the application of HT together with corn syrup.

CONCLUSION

The protective effect of HT against the damage caused by corn syrup in the liver has been demonstrated once again; however, LRRK2 and ISM1 are thought to contribute to this issue.

Novel secreted regulators of glucose and lipid metabolism in the development of metabolic diseases

The tight regulation of glucose and lipid metabolism is crucial for maintaining metabolic health. Dysregulation of these processes can lead to the development of metabolic diseases. Secreted factors, or hormones, play an essential role in the regulation of glucose and lipid metabolism, thus also playing an important role in the development of metabolic diseases such as type 2 diabetes and obesity. Given the important roles of secreted factors, there has been significant interest in identifying new secreted factors and new functions for existing secreted factors that control glucose and lipid metabolism. In this review, we evaluate novel secreted factors or novel functions of existing factors that regulate glucose and lipid metabolism discovered in the last decade, including secreted isoform of endoplasmic reticulum membrane complex subunit 10, vimentin, cartilage intermediate layer protein 2, isthmin-1, lipocalin-2, neuregulin-1 and neuregulin-4. We discuss their discovery, tissues of origin, mechanisms of action and sex differences, emphasising their potential to regulate metabolic processes central to diabetes. Additionally, we discuss the translational barriers, particularly the absence of identified receptors, that hamper their functional characterisation and further therapeutic development. Ultimately, the identification of new secreted factors may give insights into previously unidentified pathways of disease progression and mechanisms of glucose and lipid homeostasis.

Serum isthmin-1 is a potential biomarker for metabolic dysfunction associated fatty liver disease in patients with metabolic syndrome and type 2 diabetes mellitus

INTRODUCTION

Metabolic dysfunction associated fatty liver disease (MAFLD) is a prevalent condition in patients with type 2 diabetes mellitus (T2DM). Isthmin-1 (ISM1) is an adipokine that promotes glucose uptake and improves glucose tolerance and hepatic steatosis. Although ISM1 has been shown to be associated with T2DM, its role in patients with MAFLD and metabolic syndrome (MetS) remains insufficiently examined. This study aimed to investigate the relationship between serum ISM1 and MAFLD in patients with T2DM and the potential involvement of MetS in this association.

RESEARCH DESIGN AND METHODS

A total of 250 participants were divided into four groups: 60 patients with T2DM and MAFLD, 60 with newly diagnosed T2DM, 60 with MAFLD, and 70 healthy controls. Serum ISM1 levels were measured using ELISA. The distribution of ISM1 concentration in the combined data was divided into quartiles, and the Cochran-Armitage trend test was performed to estimate the significant trends across increasing quartiles.

RESULTS

Compared with the controls, patients with coexisting MAFLD, MetS, and T2DM exhibited significantly elevated serum ISM1 concentrations. Serum ISM1 levels in the overweight/obese group were also higher than those in the lean group. Serum ISM1 levels were positively correlated with body mass index (BMI), uric acid, alanine aminotransferase, aspartate aminotransferase, total cholesterol (TC), low-density lipoprotein cholesterol, fasting insulin, and homeostasis model assessment of insulin resistance and negatively associated with age and high-density lipoprotein cholesterol (HDL-C). BMI, TC, and HDL-C were independently associated with serum ISM1 concentration. The relative risks for MAFLD, T2DM, and T2DM with MAFLD increased significantly with higher ISM1 quartiles. Furthermore, a positive correlation was observed between serum ISM1 levels and the number of MetS components, with the elevated plasma levels of ISM1 escalating the risk of developing MetS to some extent.

CONCLUSIONS

The combination of ISM1 with TG and UA was identified as the best predictive factor for diagnosing MAFLD and MetS, potentially due to their contribution to aggravating the metabolic state.

Sex-specific association of circulating Isthmin-1 with isolated post-challenge hyperglycemia

Introduction

To explore the distribution of Isthmin-1 (ISM1) level and its association with isolated post-challenge hyperglycemia (IPH).

Methods

A total of 522 participants without a history of diabetes were invited to attend a standard 75g 2-h oral glucose tolerance test (OGTT), and 71 subjects were further invited for a 3-h oral minimal model test. Insulin sensitivity and β-cell function were evaluated using both HOMA and estimated from OGTT. Circulating ISM1 levels were determined by a commercially available ELISA kit.

Results

A total of 76 (14.6%) participants were diagnosed as IPH, accounting for 61.3% of the newly diagnosed diabetes. ISM1 levels were significantly higher in men than in women (1.74 ng/mL versus 0.88 ng/mL). The inverse correlation between ISM1 and β-cell function and IPH was only significant in men. After multivariate adjustment, per unit increment in ISM1 was associated with 0.68-fold (95% CI: 0.49-0.90) reduced odds ratio (OR) of IPH in men. Compared to men with the lowest ISM1 levels, the adjusted OR of IPH with the highest ISM1 levels decreased by 73% (95% CI: 0.11-0.61). Moreover, incorporation of ISM1 into the New Chinese Diabetes Risk Score (NCDRS) model yielded a substantial improvement in net reclassification improvement of 58% (95% CI: 27%-89%) and integrated discrimination improvement of 6.4% (95% CI: 2.7%-10.2%) for IPH.

Conclusions

ISM1 was significantly and independently associated with IPH, and serves as a feasible biomarker for the early identification of men with high risk of IPH.

Identification of Isthmin-1 in common carp (Cyprinus carpio L.) and the effects on glucose metabolism in vivo and in vitro

Isthmin-1 (Ism1) plays roles in glucose uptake in mammals as an adipokine. To investigate its role in the glucose metabolism of common carp (Cyprinus carpio. L), the Ism1 sequence was cloned, and its expression and distribution in tissues were detected. In addition, we prepared and purified the recombinant Ism1 protein using the E. coli expression system and assessed changes in the expression of key genes related to glucose metabolism through both in vivo injection experiments and primary hepatocyte experiments in vitro. The results revealed that the open reading frame of Ism1 was 1377 bp long, encoding 458 amino acids. Similarity analysis indicated that Ism1 exhibited a close evolutionary relationship with goldfish (Carassius auratus), sharing 98.35% amino acid similarity. Ism1 was expressed in all tissues of common carp, with the highest level observed in the heart, followed by the gill, head kidney, and hepatopancreas. Distinct patterns of Ism1 expression were identified during the oral glucose tolerance test and long-term high-carbohydrate and high-fat diet feeding experiments. In vivo studies demonstrated that the serum glucose concentration was reduced on treatment with Ism1, accompanied by a significant upregulation of mRNA levels for gk, hk, and pfk genes in hepatopancreas; conversely pepck and g6pase mRNA levels were significantly downregulated in the hepatopancreas under these conditions as well. Furthermore, our primary hepatocyte experiment confirmed that Ism1 could inhibit pepck and g6pase mRNA expression, while promoting gk, hk, and pfk mRNA expression levels. In conclusion, Ism1, in common carp, could participate in the glucose metabolism, which provides essential information for future studies on the function of Ism1.

The paracrine isthmin1 transcriptionally regulated by C/EBPβ exacerbates pulmonary vascular leakage in murine sepsis

It is known that pulmonary vascular leakage, a key pathological feature of sepsis-induced lung injury, is largely regulated by perivascular cells. However, the underlying mechanisms have not been fully uncovered. In the present study, we aimed to evaluate the role of isthmin1, a secretory protein originating from alveolar epithelium, in the pulmonary vascular leakage during sepsis and to investigate the regulatory mechanisms of isthmin1 gene transcription. We observed an elevated isthmin1 gene expression in the pulmonary tissue of septic mice induced by cecal ligation and puncture (CLP), as well as in primary murine alveolar type II epithelial cells (ATII) exposed to lipopolysaccharide (LPS). Furthermore, we confirmed that isthmin1 derived from ATII contributes to pulmonary vascular leakage during sepsis. Specifically, adenovirus-mediated isthmin1 disruption in ATII led to a significant attenuation of the increased pulmonary microvascular endothelial cell (PMVEC) hyperpermeability in a PMVEC/ATII coculture system when exposed to LPS. In addition, adeno-associated virus 9 (AAV9)-mediated knockdown of isthmin1 in the alveolar epithelium of septic mice significantly attenuated pulmonary vascular leakage. Finally, mechanistic studies unveiled that nuclear transcription factor CCAAT/enhancer binding protein (C/EBP)β participates in isthmin1 gene activation by binding directly to the cis-regulatory element of isthmin1 locus and may contribute to isthmin1 upregulation during sepsis. Collectively, the present study highlighted the impact of the paracrine protein isthmin1, derived from ATII, on the exacerbation of pulmonary vascular permeability in sepsis and revealed a new regulatory mechanism for isthmin1 gene transcription.NEW & NOTEWORTHY This article addresses the role of the alveolar epithelial-secreted protein isthmin1 on the exacerbation of pulmonary vascular permeability in sepsis and identified nuclear factor CCAAT/enhancer binding protein (C/EBP)β as a new regulator of isthmin1 gene transcription. Targeting the C/EBPβ-isthmin1 regulatory axis on the alveolar side would be of great value in the treatment of pulmonary vascular leakage and lung injury induced by sepsis.

Isthmin-1 (ISM1), a novel adipokine that reflects abdominal adipose tissue distribution in individuals with obesity

BACKGROUND

The assessment of obesity-related health risks has traditionally relied on the Body Mass Index and waist circumference, but their limitations have propelled the need for a more comprehensive approach. The differentiation between visceral (VIS) and subcutaneous (SC) fat provides a finer-grained understanding of these risks, yet practical assessment methods are lacking. We hypothesized that combining the SC-VIS fat ratio with non-invasive biomarkers could create a valuable tool for obesity-related risk assessment.

METHODS AND RESULTS

A clinical study of 125 individuals with obesity revealed significant differences in abdominal fat distribution measured by CT-scan among genders and distinct models of obesity, including visceral, subcutaneous, and the SC/VIS ratio. Stratification based on these models highlighted various metabolic changes. The SC/VIS ratio emerged as an excellent metric to differentiate metabolic status. Gene expression analysis identified candidate biomarkers, with ISM1 showing promise. Subsequent validation demonstrated a correlation between ISM1 levels in SC and plasma, reinforcing its potential as a non-invasive biomarker for fat distribution. Serum adipokine levels also correlated with the SC/VIS ratio. The Receiver Operating Characteristic analysis revealed ISM1's efficacy in discriminating individuals with favorable metabolic profiles based on adipose tissue distribution. Correlation analysis also suggested that ISM1 was involved in glucose regulation pathways.

CONCLUSION

The study's results support the hypothesis that the SC-VIS fat ratio and its derived non-invasive biomarkers can comprehensively assess obesity-related health risks. ISM1 could predict abdominal fat partitioning and be a potential biomarker for evaluating obesity-related health risks.

Investigation of serum isthmin 1 concentration in pregnant women diagnosed with gestational diabetes mellitus; a case-control study

OBJECTIVE

Isthmin 1 (ISM1) is an adipokine that improves hyperglycemia by increasing glucose uptake in a non-insulin-dependent manner. Studies have shown that ISM is associated with the development of type 2 diabetes mellitus. Based on this, we aimed to investigate serum ISM1 concentrations of pregnant women with gestational diabetes mellitus (GDM).

METHODS

This case-control study was conducted with 80 pregnant women who applied to the Gynecology and Obstetrics Clinic of Umraniye Training and Research Hospital between April 2022 and November 2022. While 40 pregnant women diagnosed with GDM according to 75 g OGTT results formed the GDM group, 40 pregnant women with normal OGTT results formed the control group. The two groups were compared in terms of serum ISM1 concentrations.

RESULTS

Both groups were similar in terms of demographic characteristics (p > 0.05). Fasting blood glucose levels, 1st-hour and 2nd-hour blood glucose levels in 75 g OGTT, fasting insulin levels, and HOMA-IR were significantly higher in the GDM group (p > 0.05, for each). Both groups were similar in terms of maternal waist circumference, periumbilical, and epigastric subcutaneous adipose tissue thickness (p > 0.05, for each).Both groups were similar in terms of the gestational week at blood sampling for ISM1 (p = 0.253). The median maternal serum ISM1 concentration was found to be 3243.94 pg/ml in the GDM group, while it was determined as 2785.29 pg/ml in the non-GDM group (p = 0.026).ROC analysis was performed to determine the value of maternal serum ISM1 concentration in predicting GDM. AUC analysis of maternal serum ISM1 for estimation of GDM was 0.645 (p = 0.026, 95% CI = 0.523 - 0.766). The optimal threshold value for maternal serum ISM1 concentration was determined as 3124.41 pg/ml with 62.5% sensitivity and 62.5% specificity.

CONCLUSIONS

Serum ISM1 concentrations were found to be higher in pregnant women with GDM than in healthy controls. Whether or how ISM1 participates in the pathophysiology of GDM remains to be investigated.

Global prevalence of non-alcoholic fatty liver disease in type 2 diabetes mellitus: an updated systematic review and meta-analysis

INTRODUCTION

Non-alcoholic fatty liver disease (NAFLD) is the leading cause of chronic liver disease, with type 2 diabetes mellitus (T2DM) as a major predictor. Insulin resistance and chronic inflammation are key pathways in the pathogenesis of T2DM leading to NAFLD and vice versa, with the synergistic effect of NAFLD and T2DM increasing morbidity and mortality risks. This meta-analysis aims to quantify the prevalence of NAFLD and the prevalence of clinically significant and advanced fibrosis in people with T2DM.

METHODS

MEDLINE and Embase databases were searched from inception until 13 February 2023. The primary outcomes were the prevalence of NAFLD, non-alcoholic steatohepatitis (NASH) and fibrosis in people with T2DM. A generalised linear mixed model with Clopper-Pearson intervals was used for the analysis of proportions with sensitivity analysis conducted to explore heterogeneity between studies.

RESULTS

156 studies met the inclusion criteria, and a pooled analysis of 1 832 125 patients determined that the prevalence rates of NAFLD and NASH in T2DM were 65.04% (95% CI 61.79% to 68.15%, I2=99.90%) and 31.55% (95% CI 17.12% to 50.70%, I2=97.70%), respectively. 35.54% (95% CI 19.56% to 55.56%, I2=100.00%) of individuals with T2DM with NAFLD had clinically significant fibrosis (F2-F4), while 14.95% (95% CI 11.03% to 19.95%, I2=99.00%) had advanced fibrosis (F3-F4).

CONCLUSION

This study determined a high prevalence of NAFLD, NASH and fibrosis in people with T2DM. Increased efforts are required to prevent T2DM to combat the rising burden of NAFLD.

PROSPERO REGISTRATION NUMBER

CRD42022360251.

Advances in research of biological functions of Isthmin-1

Isthmin-1 (ISM1) was initially thought to be a brain secretory factor, but with the development of technical means of research and the refinement of animal models, numerous studies have shown that this molecule is expressed in multiple tissues, suggesting that it may have multiple biological functions. As a factor that regulates growth and development, ISM1 is expressed in different animals with spatial and temporal variability and can coordinate the normal development of multiple organs. Recent studies have found that under the dependence of a non-insulin pathway, ISM1 can lower blood glucose, inhibit insulin-regulated lipid synthesis, promote protein synthesis, and affect the body's glucolipid and protein metabolism. In addition, ISM1 plays an important role in cancer development by promoting apoptosis and anti-angiogenesis, and by regulating multiple inflammatory pathways to influence the body's immune response. The purpose of this paper is to summarize relevant research results from recent years and to describe the key features of the biological functions of ISM1. We aimed to provide a theoretical basis for the study of ISM1 related diseases, and potential therapeutic strategies. The main biological functions of ISM1. Current studies on the biological functions of ISM1 focus on growth and development, metabolism, and anticancer treatment. During embryonic development, ISM1 is dynamically expressed in the zebrafish, African clawed frog, chick, mouse, and human, is associated with craniofacial malformations, abnormal heart localization, and hematopoietic dysfunction. ISM1 plays an important role in regulating glucose metabolism, lipid metabolism, and protein metabolism in the body. ISM1 affects cancer development by regulating cellular autophagy, angiogenesis, and the immune microenvironment.

Serum Isthmin-1 Was Increased in Type 2 Diabetic Patients but Not in Diabetic Sensorimotor Peripheral Neuropathy

Purpose

This study aimed to investigate the relationship between serum isthmin-1 (ISM1) and type 2 diabetes mellitus (T2DM), and the alteration of serum ISM1 level in both diabetic sensorimotor peripheral neuropathy (DSPN) and diabetic adults with obesity.

Patients and Methods

We recruited 180 participants (120 T2DM and 60 controls) in the cross-sectional study. First, we compared the serum ISM1 concentration in diabetic patients and non-diabetic controls. Secondly, according to DSPN, patients were divided into DSPN and non-DSPN groups. Last, patients were categorized as lean T2DM (15 males, 15 females), overweight T2DM (35 males, 19 females), and obese T2DM groups (23 males, 13 females) according to gender and body mass index (BMI). All participants were collected with clinical characteristics and biochemical profiles. Serum ISM1 was detected in all subjects by ELISA.

Results

Higher serum ISM1 [7.78 ng/mL (IQR: 6.33-9.06) vs 5.22 (3.86-6.04), P <0.001] was observed in diabetic patients compared to non-diabetic controls. Binary logistic regression analysis showed that serum ISM1 was a risk factor for type 2 diabetes after adjustment (OR=4.218, 95% CI: 1.843-9.653, P=0.001). Compared to the non-DSPN group, serum ISM1 level was not changed significantly in patients who suffered from DSPN. Diabetic females with obesity had lower level of serum ISM1 (7.10±1.29 ng/mL) when compared to the lean T2DM (8.42±1.36 ng/mL, P <0.05) and the overweight T2DM (8.33±1.27 ng/mL, P <0.05). However, serum ISM1 was not changed significantly in male groups or all patients together.

Conclusion

Serum ISM1 was a risk factor for type 2 diabetes, and it was associated with diabetic adults with obesity while there was sexual dimorphism. However, serum ISM1 levels were not correlated with DSPN.