γ-Aminobutyric acid (GABA) and glucagon-like peptide-1 receptor agonist (GLP-1RA) improve rodent β-cell survival and function. In human β-cells, GABA exerts stimulatory effects on proliferation and anti-apoptotic effects, whereas GLP-1RA drugs have only limited effects on proliferation. We previously demonstrated that GABA and sitagliptin (Sita), a dipeptidyl peptidase-4 inhibitor which increases endogenous GLP-1 levels, mediated a synergistic β-cell protective effect in mice islets. However, it remains unclear whether this combination has similar effects on human β-cell. To address this question, we transplanted a suboptimal mass of human islets into immunodeficient NOD-scid-gamma mice with streptozotocin-induced diabetes, and then treated them with GABA, Sita, or both. The oral administration of either GABA or Sita ameliorated blood glucose levels, increased transplanted human β-cell counts and plasma human insulin levels. Importantly, the combined administration of the drugs generated significantly superior results in all these responses, as compared to the monotherapy with either one of them. The proliferation and/or regeneration, improved by the combination, were demonstrated by increased Ki67+, PDX-1+, or Nkx6.1+ β-cell numbers. Protection against apoptosis was also significantly improved by the drug combination. The expression level of α-Klotho, a protein with protective and stimulatory effects on β cells, was also augmented. Our study indicates that combined use of GABA and Sita produced greater therapeutic benefits, which are likely due to an enhancement of β-cell proliferation and a decrease in apoptosis.
Wenjuan Liu, Harry Kevin Lau, Dong Ok Son, Tianru Jin, Yehong Yang, Zhaoyun Zhang, Yiming Li, Gerald J Prud’homme, and Qinghua Wang
Amanda K Mauro, Nauman Khurshid, Danielle M Berdahl, Amanda C Ampey, Daniel Adu, Dinesh M Shah, and Derek S Boeldt
Endothelial dysfunction is a prominent feature of preeclampsia, a hypertensive disorder of pregnancy, and contributes to multiple symptoms characteristic of the syndrome. A myriad of growth factors and cytokines are dysregulated in preeclampsia as compared to normal pregnancy, however, a complete appreciation of the effect of changing concentrations of these factors on endothelial function is lacking. In this study, we evaluate the effect of a variety of growth factors and cytokines on Ca2+ signaling and monolayer integrity. We report that VEGF165, TNFα, EGF, and IL-1β either improve or inhibit Ca2+ signaling depending on dose, whereas TNFα and IL-1β reduce monolayer integrity and bFGF increases monolayer integrity. Additionally, to model the effects of combinations of growth factors and cytokines, we screened for Ca2+ signaling changes in response to 16 dose combinations of VEGF165 and TNFα together. This revealed an optimal combination capable of supporting pregnancy-adapted Ca2+ signaling, and that changes in either VEGF165 or TNFα dose would result in a shift toward suppressed function. This study shows in detail how growth factor or cytokine concentration effects endothelial cell function. Such data can be used to model how changing growth factor and cytokine levels in normal pregnancy may contribute to healthy endothelial function and in preeclampsia may promote endothelial dysfunction. The results of VEGF165 and TNFα combination treatments suggest that more complex growth factor and cytokine combination modeling may be important in order to more accurately understand the effects of circulating factors on the endothelial function.
Aarti D Rohira, David M Lonard, and Bert W O’Malley
Tissue parenchyma is the functional unit of an organ and all of the remaining cells within that organ collectively make up the tissue stroma. The stroma includes fibroblasts, endothelial cells, immune cells, and nerves. Interactions between stromal and epithelial cells are essential for tissue development and healing after injury. These interactions are governed by growth factors, inflammatory cytokines and hormone signaling cascades. The steroid receptor coactivator (SRC) family of proteins includes three transcriptional coactivators that facilitate the assembly of multi-protein complexes to induce gene expression in response to activation of many cellular transcription factor signaling cascades. They are ubiquitously expressed and are especially critical for the developmental function of steroid hormone responsive tissues. The SRCs are overexpressed in multiple cancers including breast, ovarian, prostate and endometrial cancers. In this review, we focus on the role of the SRCs in regulating the functions of stromal cell components responsible for angiogenesis, inflammation and cell differentiation.
Michela Rossi, Giulia Battafarano, Viviana De Martino, Alfredo Scillitani, Salvatore Minisola, and Andrea Del Fattore
Bone remodelling is a complex mechanism regulated by osteoclasts and osteoblasts and perturbation of this process leads to the onset of diseases, which may be characterised by altered bone erosion or formation. In this review, we will describe some bone formation-related disorders as sclerosteosis, van Buchem disease, hypophosphatasia and Camurati–Engelmann disease. In the past decades, the research focused on these rare disorders offered the opportunity to understand important pathways regulating bone formation. Thus, the identification of the molecular defects behind the etiopathology of these diseases will open the way for new therapeutic approaches applicable also to the management of more common bone diseases including osteoporosis.
Qiaoli Cui, Yijing Liao, Yaojing Jiang, Xiaohang Huang, Weihong Tao, Quanquan Zhou, Anna Shao, Ying Zhao, Jia Li, Anran Ma, Zhihong Wang, Li Zhang, Zunyuan Yang, Yinan Liang, Minglin Wu, Zhenyan Yang, Wen Zeng, and Qinghua Wang
Glucagon-like peptide 1 (GLP-1) is an insulinotropic hormone and plays an important role in regulating glucose homeostasis. GLP-1 has a short half-life (t1/2 < 2 min) due to degrading enzyme dipeptidyl peptidase-IV and rapid kidney clearance, which limits its clinical application as a therapeutic reagent. We demonstrated recently that supaglutide, a novel GLP-1 mimetic generated by recombinant fusion protein techniques, exerted hypoglycemic and β-cell trophic effects in type 2 diabetes db/db mice. In the present study, we examined supaglutide’s therapeutic efficacy and pharmacokinetics in diabetic rhesus monkeys. We found that a single subcutaneous injection of supaglutide of tested doses transiently and significantly reduced blood glucose levels in a dose-dependent fashion in the diabetic monkeys. During a 4-week intervention period, treatment of supaglutide of weekly dosing dose-dependently decreased fasting and random blood glucose levels. This was associated with significantly declined plasma fructosamine levels. The repeated administration of supaglutide remarkably also decreased body weight in a dose-dependent fashion accompanied by decreased food intake. Intravenous glucose tolerance test results showed that supaglutide improved glucose tolerance. The intervention also showed enhanced glucose-stimulated insulin secretion and improved lipid profile in diabetic rhesus monkeys. These results reveal that supaglutide exerts beneficial effects in regulating blood glucose and lipid homeostasis in diabetic rhesus monkeys.
Guangcui Xu, Tingting Yan, Qiang Peng, Haibin Li, Weidong Wu, Xianwen Yi, and Yingzheng Zhao
Oxidative stress is proposed to be involved in nonalcoholic fatty liver disease (NAFLD). However, antioxidant therapy results in controversial outcomes. Therefore, we generated a new antioxidant/NAFLD mouse model, LiasHigh/HighLeprdb/db mice, by crossbreeding Leprdb/db mice, an obesity mouse model, with LiasHigh/High mice, generated by overexpression of lipoic acid synthase gene (Lias) and having increased endogenous antioxidant capacity, to investigate whether the new model could block the development of NAFLD. We have systemically characterized the novel model based on the main features of human NAFLD, determined the impact of enhanced endogenous antioxidant capacity on the retardation of NAFLD and elucidated the underlying mechanisms using various biological and pathological methods. We found that LiasHigh/HighLeprdb/db mice ameliorated many pathological changes of NAFLD compared with the control. In particular, LiasHigh/HighLeprdb/db mice displayed the improved liver mitochondrial function, reflecting the decline of mitochondrial microvesicular steatosis, and reduced oxidative stress, which mainly contributes to the alleviation of pathologic alterations of the NAFLD progression. Our new model shows that mitochondrial dysfunction is a major pathogenesis for liver steatosis. Overexpression of Lias gene effectively reduces oxidative stress and protects mitochondria, and consequently attenuates NAFLD/NASH.
Lucie E Bourne, Caroline PD Wheeler-Jones, and Isabel R Orriss
Biomineralisation, the deposition of mineral onto a matrix, can be both a physiological and pathological process. Bone formation involves the secretion of an extracellular matrix (ECM) by osteoblasts and subsequent mineralisation of that matrix. It is regulated by a number of local and systemic factors and is necessary for maintenance of normal bone health. Conversely, mineralisation (or calcification) of soft tissues, including the vasculature, is detrimental to that tissue, leading to diseases such as arterial medial calcification (AMC). The mechanisms underlying AMC development are not fully defined, though it is thought that vascular smooth muscle cells (VSMCs) drive this complex, cell-mediated process. Similarly, AMC is regulated by a variety of enzymes and molecules, many of which have already been implicated in the regulation of bone mineralisation. This review will provide an overview of the similar, and sometimes opposing effects of these signalling molecules on the regulation of bone mineralisation and AMC.
Meghan F Hogan, Daryl J Hackney, Alfred C Aplin, Thomas O Mundinger, Megan J Larmore, Joseph J Castillo, Nathalie Esser, Sakeneh Zraika, and Rebecca L Hull
Islet endothelial cells produce paracrine factors important for islet beta-cell function and survival. Under conditions of type 2 diabetes, islet endothelial cells exhibit a dysfunctional phenotype including increased expression of genes involved in cellular adhesion and inflammation. We sought to determine whether treatment of hyperglycemia with the sodium glucose co-transporter 2 inhibitor empagliflozin, either alone or in combination with metformin, would improve markers of endothelial cell function in islets, assessed ex vivo, and if such an improvement is associated with improved insulin secretion in a mouse model of diabetes in vivo. For these studies, db/db diabetic mice and non-diabetic littermate controls were treated for 6 weeks with empagliflozin or metformin, either alone or in combination. For each treatment group, expression of genes indicative of islet endothelial dysfunction was quantified. Islet endothelial and beta-cell area was assessed by morphometry of immunochemically stained pancreas sections. Measurements of plasma glucose and insulin secretion during an intravenous glucose tolerance test were performed on vehicle and drug treated diabetic animals. We found that expression of endothelial dysfunction marker genes is markedly increased in diabetic mice. Treatment with either empagliflozin or metformin lowered expression of the dysfunction marker genes ex vivo, which correlated with improved glycemic control, and increased insulin release in vivo. Empagliflozin treatment was more effective than metformin alone, with a combination of the two drugs demonstrating the greatest effects. Improving islet endothelial function through strategies such as empagliflozin/metformin treatment may provide an effective approach for improving insulin release in human type 2 diabetes.
Michael E Symonds, Mark Pope, Ian Bloor, James Law, Reham Alagal, and Helen Budge
Adipose tissue is usually laid down in small amounts in the foetus and is characterised as possessing small amounts of the brown adipose tissue-specific mitochondrial uncoupling protein (UCP)1. In adults, a primary factor determining the abundance and function of UCP1 is ambient temperature. Cold exposure causes activation and the rapid generation of heat through the free flow of protons across the mitochondria with no requirement to convert ADP to ATP. In rodents, housing at an ambient temperature below thermoneutrality promotes the appearance of beige like adipocytes. These arise as discrete regions of UCP1 containing cells in white fat depots. There is increasing evidence to show that to gain credible translational results on brown and beige fat function in rodent models that they should be housed at thermoneutrality. This not only reflects the type of environment in which humans spend a majority of their time, but is in accord with the rise of global temperature caused by industrialisation and the uncontrolled burning of fossil fuels. There is now good evidence in adult humans, that stimulating brown fat can improve glucose homeostasis which can be achieved either by nutritional or pharmacological interventions. The challenge, therefore, is to establish credible developmental models in animals maintained at thermoneutrality which will elucidate the true impact of nutrition. The primary focus should fall specifically on the components of breast milk and how these modulate long term effects on brown or beige fat development and function.