Biology subjects

Delibegovic, M.

Publications and source records attributed to Delibegovic, M..

8 recordsLinked to original sources

bioRxiv2025

Myeloid cell protein tyrosine phosphatase 1B (PTP1B) drives retinal neurodegeneration in diabetic mice

Diabetic retinopathy (DR) is the leading cause of vision loss in the working age population with public health economic implications worldwide. Systemic inflammation and leukocyte activation are early events in diabetes, while microglial activation, neuroinflammation, and retinal neurodegeneration are early events in DR. Protein tyrosine phosphatase 1B (PTP1B) plays a complex role in monocyte / macrophage activation which may impact DR. We therefore investigated the role of myeloid cell-specific PTP1B using LysMcre-PTP1B fl/fl (LysM-PTP1B) mice, as well as a PTP1B inhibitor, MSI-1436, in the early stages of DR. Mice were rendered diabetic for six weeks using anomer-equilibrated streptozotocin (STZ). Retinal changes were evaluated by histology and immunohistochemistry, and systemic leukocyte activation by flow cytometry. Mitochondrial function in high glucose-challenged, cultured bone marrow-derived macrophages (BMDMs) from LysM-PTP1B and MSI-I436-treated mice was determined in vitro. Both myeloid cell-specific depletion and pharmacological inhibition of PTP1B prevent STZ-induced retinal neurodegeneration, development of acellular retinal capillaries, as well as microglial and systemic leukocyte activation without effect on development of diabetes. In vitro, inhibition of PTP1B prevented high glucose-induced mitochondrial dysfunction in BMDMs. We conclude that inhibition of PTP1B prevents DR by decreasing myeloid cell-driven inflammation and PTP1B represents a therapeutic target for prevention DR. HighlightsO_LIMyeloid cell PTP1B is required to induce retinal neurodegeneration in diabetes C_LIO_LIBoth local (microglia) and systemic (bone-marrow derived) myeloid cells are implicated C_LIO_LIInhibition of myeloid cell PTP1B prevents development of acellular retinal capillaries in diabetic mice C_LIO_LIPTP1B mediates superoxide production, decreases mitochondrial membrane potential and increases macrophages cell death in chronic conditions associated with abnormally high glucose. C_LI Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=196 SRC="FIGDIR/small/682409v1_ufig1.gif" ALT="Figure 1"> View larger version (43K): org.highwire.dtl.DTLVardef@d8f71dorg.highwire.dtl.DTLVardef@47c8bforg.highwire.dtl.DTLVardef@cc800dorg.highwire.dtl.DTLVardef@1eade18_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2024

Preclinical evaluation of tissue-selective gene therapies for congenital generalised lipodystrophy

Lipodystrophy is a rare disorder which can be life-threatening. Here individuals fail to develop or maintain appropriate adipose tissue stores. This typically causes severe metabolic complications, including hepatic steatosis and lipoatrophic diabetes. There is no cure for lipodystrophy, and treatment options remain very limited. Here we evaluate whether tissue-selective adeno-associated virus (AAV) vectors can provide a targeted form of gene therapy for lipodystrophy, using a preclinical lipodystrophic mouse model of Bscl2 deficiency. We designed AAV vectors containing the mini/aP2 or thyroxine-binding globulin promoter to selectively target adipose or liver respectively. The AAV-aP2 vectors also contained the liver-specific microRNA-122 target sequence, restricting hepatic transgene expression. Systemic delivery of AAV-aP2 vectors overexpressing human BSCL2 restored adipose tissue development and metabolic health in lipodystrophic mice without detectable expression in the liver. High doses (1x1012 GCs) of liver-selective vectors led to off target expression and adipose tissue development, whilst low doses (1x1010 GCs) expressed selectively and robustly in the liver but did not improve metabolic health. This reveals that adipose tissue-selective, but not liver directed, AAV-mediated gene therapy is sufficient to substantially recover metabolic health in generalised lipodystrophy. This provides an exciting potential new avenue for an effective, targeted, and thereby safer therapeutic intervention.

molecular biology↗

bioRxiv2024

Effects of age and dietary methionine restriction on cognitive and behavioural phenotypes in the rTg4510 model of frontotemporal dementia

Metabolic disorders such as diabetes and obesity are linked to neurodegenerative diseases, with evidence of decreased brain glucose metabolism and insulin resistance in patients with dementia. Given the rising prevalence of age-related diseases, lifestyle adjustments and nutritional interventions are gaining interest. Dietary methionine restriction (MR) is a nutritional intervention that enhances insulin sensitivity and delays ageing-associated metabolic alterations. Since the potential impact of MR on neurodegenerative diseases like dementia is not fully understood, we here examined the metabolic and behavioural phenotypes of a murine tauopathy model (rTg4510), which overexpresses human P301L mutated tau, and assessed the impact of an 8-week dietary MR. The rTg4510 mice and wild type (WT) littermates were assessed at 6 and 12 months of age. While rTg4510 mice displayed progressive behavioural and motor impairments at 6 and 12 months of age, MR led to significant benefits in the aged 12-month-old cohort, improving motor coordination and learning, short-term memory, and social recognition. These effects were accompanied by increased glycolysis in the hippocampus and higher FGF21 levels in the cortex. These benefits occurred in the absence of alterations in glucose metabolism/adiposity in this model. Overall, our results support the positive impact of MR on rTg4510 mice, suggesting this as a potential therapeutic intervention to delay and/or improve the progression in tau-related disease.

neuroscience↗

bioRxiv2023

Cardiomyocyte-specific deletion of PTP1B protects against HFD-induced cardiomyopathy through direct regulation of cardiac metabolic signaling

BackgroundHeart failure is the number one cause of death worldwide and mortality is directly correlated with the high incidence of obesity and diabetes. Indeed, the epidemic phenomenon of obesity was projected to reach 50% in the US by the year 2030. However, the mechanisms linking metabolic dysfunction with heart disease are not clear. Protein Tyrosine Phosphatase 1B (PTP1B), a negative regulator of insulin signaling, is considered to be an emerging therapeutic target against the development of obesity, insulin resistance, and diabetes. Increased PTP1B levels and activity have been observed in brain, muscle and adipose tissues isolated from obese and/or diabetic animals, as well as in human obese human patients. Its role, however, and the mechanisms by which it modulates metabolic processes in the heart remain unknown. Method and ResultsWe generated cardiomyocyte (CM)-specific PTP1B knock-out (PTP1Bfl/fl::MHCCre/+) mice to investigate the cardiomyocyte-specific role of PTP1B in response to high fat diet (HFD)-induced cardiac dysfunction. While we did not observe any physiological or functional cardiac differences at baseline, in response to HFD, we found that PTP1Bfl/fl::MHCCre/+ mice were protected against development of cardiac hypertrophy, mitochondrial dysfunction, and diminished cardiac steatosis. Metabolomics data revealed that hearts with CM-specific deletion of PTP1B had increased fatty acid oxidation and NAD+ metabolism, but reduced glucose metabolism; we further validated these findings by real-time qPCR analysis. Mechanistically, we identified a novel PTP1B PKM2-AMPK axis in the heart, which acts as a molecular switch to promote fatty acid oxidation. In this regard, we identified that hearts from PTP1Bfl/fl::MHCCre/+ mice had upregulated levels of nicotinamide adenine dinucleotide (NAD+) and NAD phosphate (NADPH), leading to higher levels of nicotinamide phosphoribosyl transferase (NAMPT), the rate-limiting step of the NAD+ salvage pathway and an enzyme associated with obesity and diabetes. ConclusionsTogether, these results suggest that CM-specific deletion of PTP1B mediates a substrate switch from glucose to fatty acid metabolism, protecting hearts against development of HFD-induced cardiac hypertrophy and dysfunction through mechanisms involving a novel PTP1B/PKM2/AMPK axis that is critical for the regulation of NAMPT and NAD+ biosynthesis.

molecular biology↗

bioRxiv2023

How stra(i)nge are your controls? A comparative analysis of metabolic phenotypes in commonly used C57 substrains

In recent years, the use of insufficiently characterised control subjects has been a contributing factor to increasing irreproducibility in different areas of biomedical research including neuroscience and metabolism. There is now a growing awareness of phenotypic differences between the metabolic profiles of C57BL/6 substrains which are commonly used as control animals. We here investigated baseline metabolic characteristics such as glucose regulation, fasted serum insulin levels and hepatic insulin signalling in five different C57BL/6 sub-strains (N, J, JOla, JRcc) of both sexes, obtained from two commercial vendors Charles River Laboratories (Crl) and Envigo (Env). Our results indicated systematic and tissue-specific differences between substrains, modulated by both vendor and sex in all parameters investigated, not necessarily mediated by the presence of the Nnt mutation. Not only were there differences between 6J and 6N as expected, all three 6J sub-strains exhibited different profiles, even from the same breeder. Two distinct metabolic profiles were identified, one in which low insulin levels resulted in impaired glucose clearance (6JCrl; both sexes) and the other, where sustained elevations in fasted basal insulin levels led to glucose intolerance (male 6JRccEnv). Further, 6JRccEnv displayed sex differences in both glucose clearance and hepatic insulin signalling markers. In comparison, the two 6N substrains of either sex, irrespective of vendor, did not exhibit considerable differences, with 6NCrl animals presenting a good choice as a healthy baseline control for many types of experiments. Overall, our data emphasise the importance of selecting and characterising control subjects regarding background, sex, and supplier to ensure proper experimental outcomes in biomedical research.

physiology↗

bioRxiv2022

Fenretinide inhibits obesity and fatty liver disease but induces Smpd3 to increase serum ceramides and worsen atherosclerosis in LDLR-/- mice.

Fenretinide is a synthetic retinoid that can prevent obesity and improve insulin sensitivity in mice by directly altering retinol/retinoic acid homeostasis and inhibiting excess ceramide biosynthesis. We determined the effects of Fenretinide on LDLR-/- mice fed high-fat/high-cholesterol diet +/- Fenretinide, a model of atherosclerosis and non-alcoholic fatty liver disease (NAFLD). Fenretinide prevented obesity, improved insulin sensitivity and completely inhibited hepatic triglyceride accumulation, ballooning and steatosis. Moreover, Fenretinide decreased the expression of hepatic genes driving NAFLD, inflammation and fibrosis e.g. Hsd17b13, Cd68 and Col1a1. The mechanisms of Fenretinides beneficial effects in association with decreased adiposity were mediated by inhibition of ceramide synthesis, via hepatic DES1 protein, leading to increased dihydroceramide precursors. However, Fenretinide treatment in LDLR-/- mice enhanced circulating triglycerides and worsened aortic plaque formation. Interestingly, Fenretinide led to a 4-fold increase in hepatic sphingomyelinase Smpd3 expression, via a retinoic acid-mediated mechanism and a further increase in circulating ceramide levels, linking induction of ceramide generation via sphingomyelin hydrolysis to a novel mechanism of increased atherosclerosis. Thus, despite beneficial metabolic effects, Fenretinide treatment may under certain circumstances enhance the development of atherosclerosis. However, targeting both DES1 and Smpd3 may be a novel, more potent therapeutic approach for the treatment of metabolic syndrome.

physiology↗

bioRxiv2021

An ancient polymorphic regulatory region within the BDNF gene associated with obesity modulates anxiety-like behaviour in mice and humans.

Obesity and anxiety are morbidities notable for their increased impact on society during the recent COVID-19 pandemic. Understanding the mechanisms governing susceptibility to these conditions will increase quality of life and our resilience to future pandemics. In the current study we explored the function of a highly conserved regulatory region (BE5.1) within the BDNF gene that harbours a polymorphism strongly associated with obesity (rs10767664; p=4.69x10-26). Analysis in primary cells suggested that the major T-allele of BE5.1 was an enhancer whereas the obesity associated A-allele was not. However, CRISPR/CAS9 deletion of BE5.1 from the mouse genome (BE5.1KO) produced no significant effect on the expression of BDNF transcripts in the hypothalamus, no change in weight gain after 28 days and only a marginally significant increase in food intake. Nevertheless, transcripts were significantly increased in the amygdala of female mice and elevated zero maze and marble burying tests demonstrated a significant increase in anxiety-like behaviour that could be reversed by diazepam. Consistent with these observations, human GWAS cohort analysis demonstrated a significant association between rs10767664 and anxiousness in human populations. Intriguingly, interrogation of the human GTEx eQTL database demonstrated no effect on BDNF mRNA levels associated with rs10767664 but a highly significant effect on BDNF-antisense (BDNF-AS) gene expression and splicing suggesting a possible mechanism. We discuss our findings within the context of the known function and regulation of BDNF in obesity and anxiety whilst exploring the validity of interrogating GWAS data using comparative genomics and functional analysis using CRISPR genome editing in mice.

genetics↗

bioRxiv2019

CRISPR disruption and UK Biobank analysis of a highly conserved polymorphic enhancer suggests its role in anxiety and male alcohol intake.

Excessive alcohol intake is associated with 5.9% of global deaths. However, this figure is especially acute in men such that 7.6% of deaths can be attributed to alcohol intake. Previous studies identified a significant interaction between genotypes of the galanin (GAL) gene with anxiety and alcohol abuse in different male populations but were unable to define a mechanism. To address these issues the current study analysed the human UK Biobank cohort and identified a significant interaction (n=115,865; p=0.0007) between allelic variation (GG or CA genotypes) in the highly conserved human GAL5.1 enhancer, alcohol intake (AUDIT questionnaire scores) and anxiety in men that was consistent with these previous studies. Critically, disruption of GAL5.1 in mice using CRISPR genome editing significantly reduced GAL expression in the amygdala and hypothalamus whilst producing a corresponding reduction in ethanol intake in KO mice. Intriguingly, we also found evidence of reduced anxiety-like behaviour in male GAL5.1KO animals mirroring that seen in humans. Using bioinformatic analysis and co-transfection studies we further identified the EGR1 transcription factor, that is co expressed with GAL in amygdala and hypothalamus, as being important in the protein kinase C (PKC) supported activity of the GG genotype of GAL5.1 but less so in the CA genotype. Our unique study uses a novel combination of human association analysis, CRISPR genome editing in mice, animal behavioural analysis and cell culture studies to identify a highly conserved regulatory mechanism linking anxiety and alcohol intake that might contribute to increased susceptibility to anxiety and alcohol abuse in men.

genetics↗