Lipocalin-2: a role in hepatic gluconeogenesis via AMP-activated protein kinase (AMPK)

Energy homeostasis in the bone

The bone serves as an energy reservoir and actively engages in whole-body energy metabolism. Numerous studies have determined fuel requirements and bioenergetic properties of bone under physiological conditions as well as the dysregulation of energy metabolism associated with bone metabolic diseases. Here, we review the main sources of energy in bone cells and their regulation, as well as the endocrine role of the bone in systemic energy homeostasis. Moreover, we discuss metabolic changes that occur as a result of osteoporosis. Exploration in this area will contribute to an enhanced comprehension of bone energy metabolism, presenting novel possibilities to address metabolic diseases.

Research Progress on Lipocalin-2 in Diabetic Encephalopathy

Diabetic encephalopathy is a central nervous complication of diabetes mellitus which is characterized by cognitive impairment and structural and neurochemical abnormalities, which is easily neglected. Lipocalin-2 (LCN2) is a 25 kDa transporter in the lipocalin family that can transport small molecules, including fatty acids, iron, steroids, and lipopolysaccharides in the circulation. Recently, LCN2 has been found to be a significant regulator of insulin resistance and glucose homeostasis. Numerous studies have shown that LCN2 is connected to central nervous system abnormalities, including neuroinflammation and neurodegeneration, while the latest researches have found that LCN2 is closely related to the development of diabetic encephalopathy. Nevertheless, its precise role in the pathogenesis of diabetic encephalopathy remains to be determined. In this paper, we review recent evidence on the role of LCN2 in diabetic encephalopathy from multiple perspectives in order to decipher the impact of LCN2 in both the aetiology and treatment of diabetic encephalopathy.

Antimicrobial Peptide LCN2 Inhibited Uropathogenic Escherichia coli Infection in Bladder Cells in a High-Glucose Environment through JAK/STAT Signaling Pathway

JAK/STAT plays a key role in regulating uropathogenic Escherichia coli (UPEC) infection in urothelial cells, probably via antimicrobial peptide (AMP) production, in diabetic patients with urinary tract infections. Whether multiple pathways regulate AMPs, especially lipid-carrying protein-2 (LCN2), to achieve a vital effect is unknown. We investigated the effects of an LCN2 pretreatment on the regulation of the JAK/STAT pathway in a high-glucose environment using a bladder cell model with GFP-UPEC and phycoerythrin-labeled TLR-4, STAT1, and STAT3. Pretreatment with 5 or 25 μg/mL LCN2 for 24 h dose-dependently suppressed UPEC infections in bladder cells. TLR-4, STAT1, and STAT3 expression were dose-dependently downregulated after LCN2 pretreatment. The LCN2-mediated alleviation of UPEC infection in a high-glucose environment downregulated TLR-4 and the JAK/STAT transduction pathway and decreased the UPEC-induced secretion of exogenous inflammatory interleukin (IL)-6 and IL-8. Our study provides evidence that LCN2 can alleviate UPEC infection in bladder epithelial cells by decreasing JAK/STAT pathway activation in a high-glucose environment. LCN2 dose-dependently inhibits UPEC infection via TLR-4 expression and JAK/STAT pathway modulation. These findings may provide a rationale for targeting LCN2/TLR-4/JAK/STAT regulation in bacterial cystitis treatment. Further studies should explore specific mechanisms by which the LCN2, TLR-4, and JAK/STAT pathways participate in UPEC-induced inflammation to facilitate the development of effective therapies for cystitis.

Multiomics Analysis Revealed the Molecular Mechanism of miRNAs in Fluoride-Induced Hepatic Glucose and Lipid Metabolism Disorders

Fluoride-induced liver injury seriously endangers human and animal health and animal food safety, but the underlying mechanism remains unclear. This study aims to explore the mechanism of miRNAs in fluoride-induced hepatic glycolipid metabolism disorders. C57 male mice were used to establish the fluorosis model (22.62 mg/L F^-, 12 weeks). The results indicated that fluoride increased fluoride levels, impaired the structure and function, and disrupted the glycolipid metabolism in the liver. Furthermore, the sequencing results showed that fluoride exposure resulted in the differential expression of 35 miRNAs and 480 mRNAs, of which 23 miRNAs were related to glycolipid metabolism. miRNA-mRNA network analyses and RT-PCR revealed that miRNAs mediated fluoride-induced disturbances in the hepatic glycolipid metabolism. Its possible mechanism was to regulate the insulin pathway, PPAR pathway, and FOXO pathway, which in turn affected the bile secretion, the metabolic processes of glucose, the decomposition of lipids, and the synthesis of unsaturated fatty acids in the liver. This study provides a theoretical basis for miRNAs as diagnostic indicators and target drugs for the treatment of fluoride-induced liver injury.

Association Of Blood Lipocalin-2 Levels with Gestational Diabetes Mellitus: A Systematic Review and Meta-Analysis

Lipocalin-2 (LCN2) is becoming recognized as a pleiotropic mediator of metabolic disorders. However, the relationship between LCN2 and gestational diabetes mellitus (GDM) is not well understood. We performed a systematic review and meta-analysis to explore it. A systematic search of Cochrane Library, PubMed, Embase, Scopus, Web of Science, Chinese National Knowledge Infrastructure, and Wan-fang Database was done for relevant articles published up to September 29, 2021. Standardized mean difference (SMD) with 95% confidence intervals (CI) was calculated to explore the association of LCN2 levels with GDM using Revman 5.3 and Stata 15.1. Fifteen case-control studies were included in this meta-analysis. The patients with GDM had significantly higher levels of blood LCN2 than parturients with normal glucose tolerance (SMD=3.41, 95% CI=2.24 to 4.58). Meta-regression and subgroup analysis were conducted to investigate the source of heterogeneity. Likely sources of heterogeneity were age and testing methods. This study found that GDM showed higher blood LCN2 levels than controls. However, caution is warranted on the interpretation of these findings. Standardized LCN2 measurement methods and longitudinal studies are required to disentangle and better understand the relationships observed.

Regulatory Effects of Functional Soluble Dietary Fiber from Saccharina japonica Byproduct on the Liver of Obese Mice with Type 2 Diabetes Mellitus

Though the relationship between dietary fiber and physical health has been investigated widely, the use of dietary fiber from marine plants has been investigated relatively rarely. The Saccharina japonica byproducts after the production of algin contain a large amount of insoluble polysaccharide, which will cause a waste of resources if ignored. Soluble dietary fiber (SDF)prepared from waste byproducts of Saccharina japonica by alkaline hydrolysis method for the first time had a wrinkled microscopic surface and low crystallinity, which not only significantly reduced liver index, serum levels of aspartate aminotransferase (AST) and alanine amiotransferase (ALT), and liver fat accumulation damage to the livers of obese diabetic mice, but also activated the PI3K/AKT signaling pathway to increase liver glycogen synthesis and glycolysis. By LC-MS/MS employing a Nexera UPLC tandem QE high-resolution mass spectrometer, the 6 potential biomarker metabolites were screened, namely glycerophosphocholine (GPC), phosphocholine (PCho), pantothenic acid, glutathione (GSH), oxidized glutathione (GSSG), and betaine; several pathways of these metabolites were associated with lipid metabolism, glycogen metabolism, and amino acid metabolism in the liver were observed. This study further provided a detailed insight into the mechanisms of SDF from Saccharina japonica byproducts in regulating the livers of obese mice with type 2 diabetes and laid a reliable foundation for the further development and utilization of Saccharina japonica.

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.