The association of elevated serum lipocalin 2 levels with diabetic peripheral neuropathy in type 2 diabetes

Lipocalin-2 as a fundamental protein in type 2 diabetes and periodontitis in mice

BACKGROUND

Lipocalin-2 (LCN-2) is an osteokine that suppresses appetite, stimulates insulin secretion, regulates bone remodeling, and is induced by proinflammatory cytokines. The aim of this work was to investigate the participation of LCN-2 in periodontitis associated with type 2 diabetes (T2D) by evaluating alveolar bone loss, glycemic control, inflammation, and femur fragility.

METHODS

A murine model of periodontitis with T2D and elevated LCN-2 concentration was used. Functional LCN-2 inhibition was achieved using an anti-LCN-2 polyclonal antibody, and isotype immunoglobulin G was used as a control. The alveolar bone and femur were evaluated by micro-CT. Glucose metabolism was determined. Tumor necrosis factor (TNF-α) and receptor activator of nuclear factor kappa-B ligand (RANKL) levels in alveolar bone lysates were quantified using ELISA, and serum cytokines were quantified using flow cytometry. A three-point bending test was performed in the femur, and RANKL levels were measured in femur lysates using ELISA.

RESULTS

Functional inhibition of LCN-2 in T2D-periodontitis mice decreased alveolar bone loss in buccal and palatal surfaces and preserved the microarchitecture of the remaining bone, decreased TNF-α and RANKL in alveolar bone, reduced hyperglycemia, glucose intolerance, and insulin resistance, and increased insulin production through improving the functionality of pancreatic β cells. Furthermore, this inhibition increased serum free-glycerol levels, decreased serum interleukin (IL)-6, increased serum IL-4, and reduced femur fragility and RANKL expression in the femur.

CONCLUSIONS

LCN-2 participates in periodontitis associated with T2D. Inhibiting its function in mice with T2D and periodontitis improves pancreatic β-cell function, and glucose metabolism and decreases inflammatory cytokines and bone-RANKL levels, which results in the preservation of femoral and alveolar bone microarchitecture.

PLAIN LANGUAGE SUMMARY

In this study, we explored the role of a bone protein known as lipocalin-2 (LCN-2) in the connection between periodontitis and type 2 diabetes (T2D). Periodontitis is a destructive gum and alveolar bone disease. LCN-2 levels are increased in both T2D and periodontitis. Using a mouse model of T2D with periodontitis, we examined how blocking LCN-2 function affected various aspects of these two diseases. We found that this inhibition led to significant improvements. First, it reduced alveolar bone loss and preserved bone structure by decreasing local inflammation and bone resorption. Second, it improved glucose and lipid metabolism, leading to better blood-sugar control and decreased insulin resistance. Blocking the functions of LCN-2 also decreased systemic inflammation throughout the body and strengthened bone integrity. Overall, our results suggest that LCN-2 plays a crucial role in the periodontitis associated with T2D. By inhibiting LCN-2 function, we were able to improve pancreatic function, improve glucose metabolism, reduce inflammation, and enhance bone health. Targeting LCN-2 could be a promising strategy for the harmful effects of T2D and periodontitis.

Systemic Neutrophil Gelatinase-Associated Lipocalin Alterations in Chronic Pancreatitis: A Multicenter, Cross-Sectional Study

INTRODUCTION

Chronic pancreatitis (CP) is a progressive fibroinflammatory disorder lacking therapies and biomarkers. Neutrophil gelatinase-associated lipocalin (NGAL) is a proinflammatory cytokine elevated during inflammation that binds fatty acids (FAs) such as linoleic acid. We hypothesized that systemic NGAL could serve as a biomarker for CP and, with FAs, provide insights into inflammatory and metabolic alterations.

METHODS

NGAL was measured by immunoassay, and FA composition was measured by gas chromatography in plasma (n = 171) from a multicenter study, including controls (n = 50), acute and recurrent acute pancreatitis (AP/RAP) (n = 71), and CP (n = 50). Peripheral blood mononuclear cells (PBMCs) from controls (n = 16), AP/RAP (n = 17), and CP (n = 15) were measured by cytometry by time-of-flight.

RESULTS

Plasma NGAL was elevated in subjects with CP compared with controls (area under the curve [AUC] = 0.777) or AP/RAP (AUC = 0.754) in univariate and multivariate analyses with sex, age, body mass index, and smoking (control AUC = 0.874; AP/RAP AUC = 0.819). NGAL was elevated in CP and diabetes compared with CP without diabetes ( P < 0.001). NGAL + PBMC populations distinguished CP from controls (AUC = 0.950) or AP/RAP (AUC = 0.941). Linoleic acid was lower, whereas dihomo-γ-linolenic and adrenic acids were elevated in CP ( P < 0.05). Linoleic acid was elevated in CP with diabetes compared with CP subjects without diabetes ( P = 0.0471).

DISCUSSION

Elevated plasma NGAL and differences in NGAL + PBMCs indicate an immune response shift that may serve as biomarkers of CP. The potential interaction of FAs and NGAL levels provide insights into the metabolic pathophysiology and improve diagnostic classification of CP.

Serum and Tissue Lipocalin-2 Expression in Chronic Kidney Disease Pruritic Patients

BACKGROUND

Uremic pruritus is an irritating symptom for patients with end-stage kidney disease. Lipocalin-2 (LCN2) has relevant importance in several biological cellular processes and immunity. It is also a major player in the progression of many disorders, such as renal injury.

AIM

To evaluate LCN2 expression in chronic kidney disease (CKD) pruritic patients in serum together with immunohistochemical expression in skin samples and further correlation of their results with the studied clinicopathologic parameters.

MATERIALS AND METHODS

Serum level of LCN2 (assessed by enzyme-linked immunosorbent assay) and skin immunohistochemical expression were investigated in 25 CKD patients and 25 healthy controls. Ten patients were subjected to narrowband ultraviolet B phototherapy for 12 weeks then re-evaluated for serum and tissue LCN2 after therapy.

RESULTS

LCN2 expression was increased significantly in both the epidermis and dermal adnexa in CKD patients over controls. Also, serum LCN2 level was higher in patients than in healthy subjects and was significantly associated with itching severity, grades of CKD, urea, and creatinine serum level. Tissue and serum levels of LCN2 were significantly diminished in CKD patients following narrowband therapy along with improvement of the severity of pruritus.

CONCLUSIONS

The increased serum and tissue LCN2 expression in CKD pruritic patients and its pronounced decrease, in addition to the improvement of pruritus after treatment, suggest a major pathogenic role of LCN2 in uremic pruritus.

The mediating role of HbA1c in the association between elevated low-density lipoprotein cholesterol levels and diabetic peripheral neuropathy in patients with type 2 diabetes mellitus

BACKGROUND

Increased levels of low-density lipoprotein cholesterol (LDL-C) have been identified as one potential risk factor for diabetic peripheral neuropathy (DPN) in patients. The current study seeks to clarify the link between LDL-C, hyperglycemia, and DPN in patients with type 2 diabetes mellitus (T2DM).

METHODS

Here, a total of 120 T2DM individuals were recruited. These volunteers with T2DM were divided into 2 groups, based on the presence or absence of peripheral neuropathy. Additionally, their baseline characteristics were compared. Association among LDL-C and glycosylated hemoglobin (HbA1c) levels and DPN, particularly with respect to specific nerve conduction velocity were analyzed. To identify factors influencing DPN, regression was performed. Furthermore, mediation analysis was employed to evaluate the indirect, direct and total effects of LDL-C on specific nerve conduction velocity, with HbA1c serving as a mediator.

RESULTS

Compared to 55 patients without DPN, 65 patients with DPN demonstrated elevated levels of LDL-C and HbA1c. Both LDL-C and HbA1c have been found to be associated with reduced the motor fiber conduction velocities of Ulnar (or the Common peroneal) nerve in diabetic patients. HbA1c is one of the known risk factors for DPN in individuals with T2DM. Further mediation analysis revealed that the effect of LDL-C on the Ulnar (or the Common peroneal) nerve motor fiber conduction velocities are fully mediated by HbA1c in patients with T2DM.

CONCLUSIONS

The impact of elevated LDL-C levels upon the Ulnar (or the Common peroneal) nerve motor fiber conduction velocities in patients with T2DM was found to be entirely mediated by increased HbA1c levels.

Relationship of serum lncRNA XIST and miR-30d-5p levels with diabetic peripheral neuropathy in type 2 diabetes

OBJECTIVE

To investigate the relationship between serum long non-coding RNA (lncRNA) X inactive specific transcript (XIST) and microRNA-30d-5p (miR-30d-5p) expression levels in type 2 diabetic peripheral neuropathy (DPN).

METHODS

Clinical data of patients with only type 2 diabetes mellitus (pure T2DM group), DPN patients (DPN group) and healthy patients (control group) admitted to Inner Mongolia Forestry General Hospital from August 2019 to April 2022 were retrospectively analyzed, with 76 cases in each group. The serum lncRNA XIST and miR-30d-5p expression levels of each group were compared. The correlation between serum lncRNA XIST and miR-30d-5p in DPN patients was analyzed. The influencing factors of DPN occurrence were analyzed. Also, the diagnostic value of serum lncRNA XIST and miR-30d-5p for DPN was analyzed.

RESULTS

There were significant differences in the lncRNA XIST and miR-30d-5p expression levels among the pure T2DM group, DPN group, and control group. LncRNA XIST expression level was negatively correlated with miR-30d-5p in DPN patients (P<0.05). Triglycerides, hemoglobin A1c, miR-30d-5p were risk factors for the occurrence of DPN, and lncRNA XIST was a protective factor (P<0.05). The areas under the curve (AUC) of serum lncRNA XIST and miR-30d-5p for the diagnosis of DPN were 0.851 and 0.845, respectively, and the AUC of lncRNA XIST and miR-30d-5p combined was 0.932, with a sensitivity of 92.1%, and a specificity of 85.5%.

CONCLUSION

Both lncRNA XIST and miR-30d-5p may be involved in the development of type 2 DPN. Therefore, detecting serum levels of both may be helpful for clinical diagnosis and treatment of type 2 DPN.

The Emerging Role of Bone-Derived Hormones in Diabetes Mellitus and Diabetic Kidney Disease

Diabetic kidney disease (DKD) causes the greatest proportion of end-stage renal disease (ESRD)-related mortality and has become a high concern in patients with diabetes mellitus (DM). Bone is considered an endocrine organ, playing an emerging role in regulating glucose and energy metabolism. Accumulating research has proven that bone-derived hormones are involved in glucose metabolism and the pathogenesis of DM complications, especially DKD. Furthermore, these hormones are considered to be promising predictors and prospective treatment targets for DM and DKD. In this review, we focused on bone-derived hormones, including fibroblast growth factor 23, osteocalcin, sclerostin, and lipocalin 2, and summarized their role in regulating glucose metabolism and DKD.