Transgenic Overexpression of Galectin-3 in Pancreatic β Cells Attenuates Hyperglycemia in Mice: Synergistic Antidiabetic Effect With Exogenous IL-33

Galectin-3 in metabolic disorders: mechanisms and therapeutic potential

Galectin-3 (Gal3), a β-galactoside-binding lectin, is expressed predominantly in immunological and inflammatory cells. Gal3 expression is elevated in metabolic diseases, including obesity, diabetes, and metabolic dysfunction-associated steatotic liver disease (MASLD), and plays an important role in the progression of these diseases. In this review, we summarize the structure and post-translational modifications of Gal3 and the cellular functions of Gal3 according to its subcellular localization. We focused on the pathological functions and molecular mechanisms of Gal3 in various cell types. In particular, extracellular Gal3 and intracellular Gal3 may have different physiological and pathological functions. We also discuss promising Gal3 inhibitors or antibodies that are currently in clinical trials and outstanding questions and challenges for future pursuit.

Central role of Galectin-3 at the cross-roads of cardiac inflammation and fibrosis: Implications for heart failure and transplantation

Cardiac inflammation and fibrosis are central pathogenic mechanisms leading to heart failure. Transplantation is still the treatment of choice for many patients undergoing end-stage heart failure who remain symptomatic despite optimal medical therapy. In spite of considerable progress, the molecular mechanisms linking inflammation, fibrosis and heart failure remain poorly understood. Galectin-3 (GAL3), a chimera-type member of the galectin family, has emerged as a critical mediator implicated in cardiac inflammatory, vascular and fibrotic processes through modulation of different cellular compartments including monocytes and macrophages, fibroblasts, endothelial cells and vascular smooth muscle cells via glycan-dependent or independent mechanisms. GAL3-driven circuits may hierarchically amplify cytokine production and function, immune cell activation and fibrosis cascades, influencing a wide range of cardiovascular disorders. Thus, GAL3 emerges as a potential therapeutic target to counteract aberrant inflammation and fibrosis during heart failure and a potential biomarker of heart failure and clinical outcome of heart transplantation.

Adipocyte-specific FAK deletion promotes pancreatic β-cell apoptosis via adipose inflammatory response to exacerbate diabetes mellitus

BACKGROUND

White adipose tissue (WAT) has a key role in maintaining energy balance throughout the body, and their dysfunction take part in the regulation of diabetes mellitus. However, the internal regulatory mechanisms underlying are still unknown.

METHODS AND RESULTS

We generated adipocyte-specific FAK KO (FAK-AKO) mice and investigated their phenotype. The cascade of adipocyte, macrophage in adipocyte tissues, and pancreatic β-cells were proposed in FAK-AKO mice and validated by cell line studies using 3T3-L1, Raw264.7 and Min6. The FAK-AKO mice exhibited glucose intolerance, reduced adipose tissue mass and increased apoptosis, lipolysis and inflammatory response in adipose tissue. We further demonstrate that adipocyte FAK deletion increases β cell apoptosis and inflammatory infiltrates into islets, which is potentiated if mice were treated with STZ. In the STZ-induced diabetes model, FAK AKO mice exhibit less serum insulin content and pancreatic β cell area. Moreover, serum pro-inflammatory factors increased and insulin levels decreased after glucose stimulation in FAK AKO mice. In a parallel vitro experiment, knockdown or inhibition of FAK during differentiation also increased apoptosis, lipolysis and inflammatory in 3T3-L1 adipocytes, whereas the opposite was observed upon overexpression of FAK. Moreover, coculturing LPS-treated RAW264.7 macrophages with knockdown FAK of 3T3-L1 adipocytes increased macrophage pro-inflammatory response. Furthermore, conditioned medium from above stimulated Min6 cells apoptosis (with or without STZ), whereas the opposite was observed upon overexpression of FAK. Mechanistically, FAK protein interact with TRAF6 in adipocytes and knockdown or inhibition of FAK activated TRAF6/TAK1/NF-κB signaling, which exacerbates inflammation of adipocytes themselves.

CONCLUSION

Adipocyte FAK deletion promotes both adipocyte apoptosis and adipose tissue inflammation. Pro-inflammatory factors released by the FAK-null adipose tissue further trigger apoptosis in pancreatic islets induced by the administration of STZ, thereby exacerbating the diabetes mellitus. This study reveals a link between FAK-mediated adipose inflammation and diabetes mellitus, a mechanism that has not been previously recognized.

Galectin-3 impairs calcium transients and β-cell function

In diabetes, macrophages and inflammation are increased in the islets, along with β-cell dysfunction. Here, we demonstrate that galectin-3 (Gal3), mainly produced and secreted by macrophages, is elevated in islets from both high-fat diet (HFD)-fed and diabetic db/db mice. Gal3 acutely reduces glucose-stimulated insulin secretion (GSIS) in β-cell lines and primary islets in mice and humans. Importantly, Gal3 binds to calcium voltage-gated channel auxiliary subunit gamma 1 (CACNG1) and inhibits calcium influx via the cytomembrane and subsequent GSIS. β-Cell CACNG1 deficiency phenocopies Gal3 treatment. Inhibition of Gal3 through either genetic or pharmacologic loss of function improves GSIS and glucose homeostasis in both HFD-fed and db/db mice. All animal findings are applicable to male mice. Here we show a role of Gal3 in pancreatic β-cell dysfunction, and Gal3 could be a therapeutic target for the treatment of type 2 diabetes.

Unraveling the role of galectin-3 in cardiac pathology and physiology

Galectin-3 (Gal-3) is a carbohydrate-binding protein with multiple functions. Gal-3 regulates cell growth, proliferation, and apoptosis by orchestrating cell-cell and cell-matrix interactions. It is implicated in the development and progression of cardiovascular disease, and its expression is increased in patients with heart failure. In atherosclerosis, Gal-3 promotes monocyte recruitment to the arterial wall boosting inflammation and atheroma. In acute myocardial infarction (AMI), the expression of Gal-3 increases in infarcted and remote zones from the beginning of AMI, and plays a critical role in macrophage infiltration, differentiation to M1 phenotype, inflammation and interstitial fibrosis through collagen synthesis. Genetic deficiency of Gal-3 delays wound healing, impairs cardiac remodeling and function after AMI. On the contrary, Gal-3 deficiency shows opposite results with improved remodeling and function in other cardiomyopathies and in hypertension. Pharmacologic inhibition with non-selective inhibitors is also protective in cardiac disease. Finally, we recently showed that Gal-3 participates in normal aging. However, genetic absence of Gal-3 in aged mice exacerbates pathological hypertrophy and increases fibrosis, as opposed to reduced fibrosis shown in cardiac disease. Despite some gaps in understanding its precise mechanisms of action, Gal-3 represents a potential therapeutic target for the treatment of cardiovascular diseases and the management of cardiac aging. In this review, we summarize the current knowledge regarding the role of Gal-3 in the pathophysiology of heart failure, atherosclerosis, hypertension, myocarditis, and ischemic heart disease. Furthermore, we describe the physiological role of Gal-3 in cardiac aging.

The Role of Galectin 3 in the Pathogenesis of Diabetes Mellitus: Focus on Β-Cell Function and Survival

Galectin 3 is a lectin expressed in many tissues with a significant biological role in physiological and pathological processes. Our review aims to sublimate the effects of galectin 3 on the β-cells function and survival. Data about the effect of galectin 3 on β- cells are scarce and contradictory. Several studies have shown that reduced activity of the galectin 3 gene reduces the risk of developing type 1 diabetes in an experimental model of diabetes in galectin 3 deficient mice. On the other side, in an experimental model of type 1 diabetes with mice with selectively enhanced expression of galectin 3 in β-cells, was shown that increased expression of this lectin has a protective role. Unlike type 1 diabetes where the autoimmune process plays a dominant role in pathogenesis, the pathogenesis of type 2 diabetes is multifactorial. One of the main factors which contribute to type 2 diabetes, the insulin resistance, is related to the concentration of soluble galectin 3. The effect of galectin 3 is very important for β-cell function. When a harmful factor acts on a β-cell, its intracellular concentration increases to preserve the function of β-cells and prevent their apoptosis, by blocking the internal path of apoptosis. However, excessive accumulation of galectin 3 inside the cell leads to its secretion, which encourages tissue inflammation. Based on all the above, galectin 3 has a double effect on β-cells.