Mouse Model Of Glucose Intolerance Research Articles

Single-cell RNA sequencing combined with single-cell proteomics identifies the metabolic adaptation of islet cell subpopulations to high-fat diet in mice.

Islets have complex heterogeneity and subpopulations. Cell surface markers representing alpha, beta and delta cell subpopulations are urgently needed for investigations to explore the compositional changes of each subpopulation in obesity progress and diabetes onset, and the adaptation mechanism of islet metabolism induced by a high-fat diet (HFD). Single-cell RNA sequencing (scRNA-seq) was applied to identify alpha, beta and delta cell subpopulation markers in an HFD-induced mouse model of glucose intolerance. Flow cytometry and immunostaining were used to sort and assess the proportion of each subpopulation. Single-cell proteomics was performed on sorted cells, and the functional status of each alpha, beta and delta cell subpopulation in glucose intolerance was deeply elucidated based on protein expression. A total of 33,999 cells were analysed by scRNA-seq and clustered into eight populations, including alpha, beta and delta cells. For alpha cells, scRNA-seq revealed that the Ace2low subpopulation had downregulated expression of genes related to alpha cell function and upregulated expression of genes associated with beta cell characteristics in comparison with the Ace2high subpopulation. The impaired function and increased fragility of ACE2low alpha cells exposure to HFD was further suggested by single-cell proteomics. As for beta cells, the CD81high subpopulation may indicate an immature signature of beta cells compared with the CD81low subpopulation, which had robust function. We also found differential expression of Slc2a2 in delta cells and a potentially stronger cellular function and metabolism in GLUT2low delta cells than GLUT2high delta cells. Moreover, an increased proportion of ACE2low alpha cells and CD81low beta cells, with a constant proportion of GLUT2low delta cells, were observed in HFD-induced glucose intolerance. We identified ACE2, CD81 and GLUT2 as surface markers to distinguish, respectively, alpha, beta and delta cell subpopulations with heterogeneous maturation and function. The changes in the proportion and functional status of islet endocrine subpopulations reflect the metabolic adaptation of islets to high-fat stress, which weakened the function of alpha cells and enhanced the function of beta and delta cells to bring about glycaemic homeostasis. Our findings provide a fundamental resource for exploring the mechanisms maintaining each islet endocrine subpopulation's fate and function in health and disease. The scRNA-seq analysis datasets from the current study are available in the Gene Expression Omnibus (GEO) repository under the accession number GSE203376.

Differential expression of glycoprotein IV on monocyte subsets following high-fat diet feeding and the impact of short-term low-dose aspirin treatment

ObjectiveTo assess the levels of glycoprotein GPIV (CD36) expression on peripheral blood monocyte subsets, in a mouse model of glucose intolerance. Moreover, to determine the effect of; low-dose aspirin (LDA) alone, LDA combined with metformin, or clopidogrel alone, on the expression of CD36 on subsets of circulating monocytes. MethodThe study consisted of two experimental phases. In experiment one, the mice (n = 14) were randomised to receive a low-fat diet (LFD) or a high-fat diet (HFD) for eight weeks. Whereas the secondary phase of the experiment, comprised of twenty-four HFD-fed mice treated with LDA alone (3 mg/kg), or in combination with metformin (150 mg/kg), or clopidogrel alone (10 mg/kg) for six weeks. The surface expression of CD36 on monocytes was measured using flow cytometry. ResultThe levels of CD36 expression on monocytes were upregulated in the HFD-fed compared to LFD-fed group (p < 0.05). In addition, HFD group showed; no significant changes in body weight (p = 0.3848), however, blood glucose (p = 0.0002) and insulin (p = 0.0360) levels were markedly increased following HFD-feeding. Interestingly, all treatments reduced the expression of CD36 on monocytes, decreased fasting blood glucose levels (p = 0.0024) and increased circulating monocyte levels (p = 0.0217) when compared to the untreated HFD group. Moreover, treatment with LDA alone increased basophils levels (p = 0.0272), while when combined with metformin showed an improved effect in enhancing eosinophil levels (p = 0.0302). ConclusionHFD-feeding increased the expression of CD36 on monocyte subsets. LDA as a monotherapy or combined with metformin was as effective as clopidogrel monotherapy, in downregulating the expression of CD36 on monocyte subsets. These treatments may be of relevance in preventing cardiovascular complications associated with impaired glucose tolerance.

M2 Macrophage Immunotherapy Abolishes Glucose Intolerance by Increasing IL-10 Expression and AKT Activation

Aim: Glucose intolerance associates with M1/M2 macrophage unbalance. We thus wanted to examine the effect of M2 macrophage administration on mouse model of glucose intolerance. Materials & methods: C57BL/6 mice fed a high-fat diet (HFD) for 12 weeks and then received thrice 20mg/kg streptozotocin (HFD-GI). Bone marrow-derived stem cells were collected from donor mice and differentiated/activated into M2 macrophages for intraperitoneal administration into HFD-GI mice. Results: M2 macrophage treatment abolished glucose intolerance independently of obesity. M2 macrophage administration increased IL-10 in visceral adipose tissue and serum, but showed no effect on serum insulin. While nitric oxide synthase-2 and arginase-1 remained unaltered, M2 macrophage treatment restored AKT phosphorylation in visceral adipose tissue. Conclusion: M2 macrophage treatment abolishes glucose intolerance by increasing IL-10 and phosphorylated AKT.

BMP4-BMPR1A Signaling in β Cells Is Required for and Augments Glucose-Stimulated Insulin Secretion

Impaired glucose-stimulated insulin secretion (GSIS) and perturbed proinsulin processing are hallmarks of beta cell dysfunction in type 2 diabetes. Signals that can preserve and/or enhance beta cell function are therefore of great therapeutic interest. Here we show that bone morphogenetic protein 4 (Bmp4) and its high-affinity receptor, Bmpr1a, are expressed in beta cells. Mice with attenuated BMPR1A signaling in beta cells show decreased expression of key genes involved in insulin gene expression, proinsulin processing, glucose sensing, secretion stimulus coupling, incretin signaling, and insulin exocytosis and develop diabetes due to impaired insulin secretion. We also show that transgenic expression of Bmp4 in beta cells enhances GSIS and glucose clearance and that systemic administration of BMP4 protein to adult mice significantly stimulates GSIS and ameliorates glucose tolerance in a mouse model of glucose intolerance. Thus, BMP4-BMPR1A signaling in beta cells plays a key role in GSIS.