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Diabetologia Jul 2021Homo sapiens evolved under conditions of intermittent food availability and prolonged fasting between meals. Periods of fasting are important for recovery from...
AIMS/HYPOTHESIS
Homo sapiens evolved under conditions of intermittent food availability and prolonged fasting between meals. Periods of fasting are important for recovery from meal-induced oxidative and metabolic stress, and tissue repair. Constant high energy-density food availability in present-day society contributes to the pathogenesis of chronic diseases, including diabetes and its complications, with intermittent fasting (IF) and energy restriction shown to improve metabolic health. We have previously demonstrated that IF prevents the development of diabetic retinopathy in a mouse model of type 2 diabetes (db/db); however the mechanisms of fasting-induced health benefits and fasting-induced risks for individuals with diabetes remain largely unknown. Sirtuin 1 (SIRT1), a nutrient-sensing deacetylase, is downregulated in diabetes. In this study, the effect of SIRT1 stimulation by IF, fasting-mimicking cell culture conditions (FMC) or pharmacological treatment using SRT1720 was evaluated on systemic and retinal metabolism, systemic and retinal inflammation and vascular and bone marrow damage.
METHODS
The effects of IF were modelled in vivo using db/db mice and in vitro using bovine retinal endothelial cells or rat retinal neuroglial/precursor R28 cell line serum starved for 24 h. mRNA expression was analysed by quantitative PCR (qPCR). SIRT1 activity was measured via histone deacetylase activity assay. NR1H3 (also known as liver X receptor alpha [LXRα]) acetylation was measured via western blot analysis.
RESULTS
IF increased Sirt1 mRNA expression in mouse liver and retina when compared with non-fasted animals. IF also increased SIRT1 activity eightfold in mouse retina while FMC increased SIRT1 activity and expression in retinal endothelial cells when compared with control. Sirt1 expression was also increased twofold in neuronal retina progenitor cells (R28) after FMC treatment. Moreover, FMC led to SIRT1-mediated LXRα deacetylation and subsequent 2.4-fold increase in activity, as measured by increased mRNA expression of the genes encoding ATP-binding cassette transporter (Abca1 and Abcg1). These changes were reduced when retinal endothelial cells expressing a constitutively acetylated LXRα mutant were tested. Increased SIRT1/LXR/ABC-mediated cholesterol export resulted in decreased retinal endothelial cell cholesterol levels. Direct activation of SIRT1 by SRT1720 in db/db mice led to a twofold reduction of diabetes-induced inflammation in the retina and improved diabetes-induced visual function impairment, as measured by electroretinogram and optokinetic response. In the bone marrow, there was prevention of diabetes-induced myeloidosis and decreased inflammatory cytokine expression.
CONCLUSIONS/INTERPRETATION
Taken together, activation of SIRT1 signalling by IF or through pharmacological activation represents an effective therapeutic strategy that provides a mechanistic link between the advantageous effects associated with fasting regimens and prevention of microvascular and bone marrow dysfunction in diabetes.
Topics: Animals; Cattle; Cell Death; Cells, Cultured; Diabetes Mellitus, Experimental; Diabetic Angiopathies; Fasting; Gene Expression; Heterocyclic Compounds, 4 or More Rings; Hypoglycemic Agents; Liver X Receptors; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Rats; Retina; Retinal Neurons; Retinal Vessels; Signal Transduction; Sirtuin 1
PubMed: 33770194
DOI: 10.1007/s00125-021-05431-5 -
Journal of Neuroinflammation Apr 2022Macular subretinal fibrosis is the end-stage complication of neovascular age-related macular degeneration (nAMD). We previously developed a mouse model of two-stage...
BACKGROUND
Macular subretinal fibrosis is the end-stage complication of neovascular age-related macular degeneration (nAMD). We previously developed a mouse model of two-stage laser-induced subretinal fibrosis that mimics closely the dynamic course of macular fibrosis in nAMD patients. This study was aimed to understand the molecular mechanism of subretinal fibrosis.
METHODS
Subretinal fibrosis was induced in C57BL/6J mice using the two-stage laser-induced protocol. Twenty days later, eyes were collected and processed for RNA sequencing (RNA-seq) analysis. DESeq2 was used to determine the differentially expressed genes (DEGs). Gene Ontology (GO) and KEGG were used to analyze the enriched pathways. The expression of the selected DEGs including Mmp12 was verified by qPCR. The expression of MMP12 in subretinal fibrosis of mouse and nAMD donor eyes was examined by immunofluorescence and confocal microscopy. The expression of collagen 1, αSMA and fibronectin and cytokines in bone marrow-derived macrophages from control and subretinal fibrosis mice were examined by qPCR, immunocytochemistry and Luminex multiplex cytokine assay. The MMP12 specific inhibitor MMP408 was used to evaluate the effect of MMP12 on TGFβ-induced macrophage-to-myofibroblast transition (MMT) in vitro and its role in subretinal fibrosis in vivo.
RESULTS
RNA-seq analysis of RPE-choroid from subretinal fibrosis eyes uncovered 139 DEGs (fold change log2(fc) ≥ 0.5, FDR < 0.05), including 104 up-regulated and 35 were down-regulated genes. The top 25 enrichment GO terms were related to inflammation, blood vessels/cardiovascular development and angiogenesis. One of the most significantly upregulated genes, Mmp12, contributed to 12 of the top 25 GO terms. Higher levels of MMP12 were detected in subretinal fibrotic lesions in nAMD patients and the mouse model, including in F4/80 or Iba1 macrophages. BMDMs from subretinal fibrosis mice expressed higher levels of MMP12, collagen-1, αSMA and fibronectin. MMP408 dose-dependently suppressed TGFβ-induced MMT in BMDMs. In vivo treatment with MMP408 (5 mg/kg) significantly reduced subretinal fibrosis accompanied by reduced F4/80 macrophage infiltration.
CONCLUSIONS
MMP12 critically contributes to the development of subretinal fibrosis, partially through promoting MMT.
Topics: Animals; Fibrosis; Humans; Matrix Metalloproteinase 12; Mice; Mice, Inbred C57BL; Retina
PubMed: 35382832
DOI: 10.1186/s12974-022-02433-x -
American Journal of Human Genetics Mar 2022Recurrence risk calculations in autosomal recessive diseases are complicated when the effect of genetic variants and their population frequencies and penetrances are...
Recurrence risk calculations in autosomal recessive diseases are complicated when the effect of genetic variants and their population frequencies and penetrances are unknown. An example of this is Stargardt disease (STGD1), a frequent recessive retinal disease caused by bi-allelic pathogenic variants in ABCA4. In this cross-sectional study, 1,619 ABCA4 variants from 5,579 individuals with STGD1 were collected and categorized by (1) severity based on statistical comparisons of their frequencies in STGD1-affected individuals versus the general population, (2) their observed versus expected homozygous occurrence in STGD1-affected individuals, (3) their occurrence in combination with established mild alleles in STGD1-affected individuals, and (4) previous functional and clinical studies. We used the sum allele frequencies of these severity categories to estimate recurrence risks for offspring of STGD1-affected individuals and carriers of pathogenic ABCA4 variants. The risk for offspring of an STGD1-affected individual with the "severe|severe" genotype or a "severe|mild with complete penetrance" genotype to develop STGD1 at some moment in life was estimated at 2.8%-3.1% (1 in 36-32 individuals) and 1.6%-1.8% (1 in 62-57 individuals), respectively. The risk to develop STGD1 in childhood was estimated to be 2- to 4-fold lower: 0.68%-0.79% (1 in 148-126) and 0.34%-0.39% (1 in 296-252), respectively. In conclusion, we established personalized recurrence risk calculations for STGD1-affected individuals with different combinations of variants. We thus propose an expanded genotype-based personalized counseling to appreciate the variable recurrence risks for STGD1-affected individuals. This represents a conceptual breakthrough because risk calculations for STGD1 may be exemplary for many other inherited diseases.
Topics: ATP-Binding Cassette Transporters; Cross-Sectional Studies; Genetic Counseling; Humans; Mutation; Stargardt Disease
PubMed: 35120629
DOI: 10.1016/j.ajhg.2022.01.008 -
Molecular Therapy : the Journal of the... Sep 2022Adenine base editors (ABEs) are novel genome-editing tools, and their activity has been greatly enhanced by eight additional mutations, thus named ABE8e. However,...
Adenine base editors (ABEs) are novel genome-editing tools, and their activity has been greatly enhanced by eight additional mutations, thus named ABE8e. However, elevated catalytic activity was concomitant with frequent generation of bystander mutations. This bystander effect precludes its safe applications required in human gene therapy. To develop next-generation ABEs that are both catalytically efficient and positionally precise, we performed combinatorial engineering of NG-ABE8e. We identify a novel variant (NG-ABE9e), which harbors nine mutations. NG-ABE9e exhibits robust and precise base-editing activity in human cells, with more than 7-fold bystander editing reduction at some sites, compared with NG-ABE8e. To demonstrate its practical utility, we used NG-ABE9e to correct the frequent T17M mutation in Rhodopsin for autosomal dominant retinitis pigmentosa. It reduces bystander editing by ∼4-fold while maintaining comparable efficiency. NG-ABE9e possesses substantially higher activity than NG-ABEmax and significantly lower bystander editing than NG-ABE8e in rice. Therefore, this study provides a versatile and improved adenine base editor for genome editing.
Topics: Adenine; CRISPR-Cas Systems; Gene Editing; Humans; Mutation
PubMed: 35821638
DOI: 10.1016/j.ymthe.2022.07.010 -
JAMA Ophthalmology Jun 2020Rhegmatogenous retinal detachment is a potentially sight-threatening condition. The role of myopia or intraocular pressure (IOP) in retinal detachment remains unclear. (Observational Study)
Observational Study
IMPORTANCE
Rhegmatogenous retinal detachment is a potentially sight-threatening condition. The role of myopia or intraocular pressure (IOP) in retinal detachment remains unclear.
OBJECTIVE
To determine if myopia or IOP is associated with retinal detachment risk using genetic data.
DESIGN, SETTING, AND PARTICIPANTS
Observational analyses and 2-sample mendelian randomization were used to evaluate the associations between myopia, IOP, and retinal detachment risk in European descent participants from the UK Biobank (UKBB) cohort (n = 405 692). For retinal detachment, a genome-wide association study on 4257 cases and 39 181 controls in the UKBB was conducted. Genetic variants associated with mean spherical equivalent (MSE) refractive error (n = 95 827) and IOP (n = 101 939) were derived using independent participants from the retinal detachment genome-wide association study. Recruitment to the UKBB occurred between 2006 and 2010, and data analysis occurred from February 2019 to March 2020.
MAIN OUTCOMES AND MEASURES
The odds ratio (OR) of retinal detachment caused by per-unit increases in MSE refractive error (in diopters [D]) and IOP (in mm Hg).
RESULTS
Of the 405 692 participants in the UKBB cohort, the mean (SD) age was 56.87 (7.96) years, the mean (SD) MSE was -0.31 (2.65) D, the mean (SD) corneal-compensated IOP was 16.05 (3.49) mm Hg, and 4253 participants (1.0%) had retinal detachment. Genetic analyses of the 4257 cases and 39 181 controls identified 2 novel retinal detachment genes: COL22A1 (lead single-nucleotide variant rs11992725; P = 4.8 × 10-10) and FAT3 (lead single-nucleotide variant rs10765568; P = 1.2 × 10-15). Genetically assessed MSE refractive error was negatively associated with retinal detachment (per-unit [D] increase in MSE refractive error: OR, 0.72; 95% CI, 0.69-0.76; P = 3.8 × 10-44). For each 6-D decrease in MSE refractive error (representing the move of refractive error from emmetropia to high myopia), retinal detachment risk increased 7.2-fold (95% CI, 5.19-9.27). For per-unit (mm Hg) genetically assessed increase in IOP, the risk of retinal detachment increased by 8% (OR, 1.08; 95% CI, 1.03-1.14; P = .001).
CONCLUSIONS AND RELEVANCE
This study provides genetic support for the assertion that myopia and IOP are associated with the risk of retinal detachment and that myopia prevention efforts may help prevent retinal detachment.
Topics: Biological Specimen Banks; Female; Genome-Wide Association Study; Humans; Intraocular Pressure; Male; Mendelian Randomization Analysis; Middle Aged; Myopia; Retinal Detachment; Risk Factors; United Kingdom; Visual Acuity
PubMed: 32352494
DOI: 10.1001/jamaophthalmol.2020.1231 -
Proceedings of the National Academy of... May 2023Age-related macular degeneration, Stargardt disease, and their mouse model are characterized by accelerated accumulation of the pigment lipofuscin, derived from...
Age-related macular degeneration, Stargardt disease, and their mouse model are characterized by accelerated accumulation of the pigment lipofuscin, derived from photoreceptor disc turnover in the retinal pigment epithelium (RPE); lipofuscin accumulation and retinal degeneration both occur earlier in albino mice. Intravitreal injection of superoxide (O) generators reverses lipofuscin accumulation and rescues retinal pathology, but neither the target nor mechanism is known. Here we show that RPE contains thin multi-lamellar membranes (TLMs) resembling photoreceptor discs, which associate with melanolipofuscin granules in pigmented mice but in albinos are 10-fold more abundant and reside in vacuoles. Genetically over-expressing tyrosinase in albinos generates melanosomes and decreases TLM-related lipofuscin. Intravitreal injection of generators of O or nitric oxide (NO) decreases TLM-related lipofuscin in melanolipofuscin granules of pigmented mice by ~50% in 2 d, but not in albinos. Prompted by evidence that O plus NO creates a dioxetane on melanin that excites its electrons to a high-energy state (termed "chemiexcitation"), we show that exciting electrons directly using a synthetic dioxetane reverses TLM-related lipofuscin even in albinos; quenching the excited-electron energy blocks this reversal. Melanin chemiexcitation assists in safe photoreceptor disc turnover.
Topics: Mice; Animals; Melanins; Lipofuscin; Macular Degeneration; Retina; Retinal Pigment Epithelium; ATP-Binding Cassette Transporters
PubMed: 37155898
DOI: 10.1073/pnas.2216935120 -
The American Journal of Geriatric... Aug 2023To evaluate the correlation between cognitive signatures and the risk of diabetic vascular complications and mortality, based on a multicountry prospective study.
OBJECTIVE
To evaluate the correlation between cognitive signatures and the risk of diabetic vascular complications and mortality, based on a multicountry prospective study.
METHODS
The participants comprised 27,773 diabetics from the UK Biobank (UKB) and 1307 diabetics from the Guangzhou Diabetic Eye Study (GDES) cohort. The exposures were brain volume and cognitive screening tests for UKB participants, whilst the global cognitive score (GCS) measuring orientation to time and attention, episodic memory, and visuospatial abilities were determined for GDES participants. The outcomes for the UKB group were mortality, as well as macrovascular (myocardial infarction [MI] and stroke), microvascular (end-stage renal disease [ESRD], and diabetic retinopathy [DR]) events. The outcomes for the GDES group were retinal and renal microvascular damage.
RESULTS
In the UKB group, a 1-SD reduction in brain gray matter volume was associated with 34%-77% higher risks of incident MI, ESRD, and DR. The presence of impaired memory was associated with 18%-73% higher risk of mortality and ESRD; impaired reaction was associated with 1.2-1.7-fold higher risks of mortality, stroke, ESRD, and DR. In the GDES group, the lowest GCS tertile exhibited 1.4-2.2-fold higher risk of developing referable DR and a twofold faster decline in renal function and retinal capillary density compared with the highest tertile. Restricting data analysis to individuals aged less than 65 years produced consistent results.
CONCLUSION
Cognitive decline significantly elevates the risk of diabetic vascular complications and is correlated with retinal and renal microcirculation damage. Cognitive screening tests are strongly recommended as routine tools for management of diabetes.
Topics: Humans; Cohort Studies; Prospective Studies; Diabetic Retinopathy; Diabetic Angiopathies; Cognition; Kidney Failure, Chronic; Stroke; Brain; Risk Factors; Diabetes Mellitus, Type 2
PubMed: 37230837
DOI: 10.1016/j.jagp.2023.04.010 -
Scientific Reports Jun 2023Alzheimer disease (AD) is the most prevalent cause of dementia in the elderly. Although impaired cognition and memory are the most prominent features of AD,...
Alzheimer disease (AD) is the most prevalent cause of dementia in the elderly. Although impaired cognition and memory are the most prominent features of AD, abnormalities in visual functions often precede them, and are increasingly being used as diagnostic and prognostic markers for the disease. Retina contains the highest concentration of the essential fatty acid docosahexaenoic acid (DHA) in the body, and its deficiency is associated with several retinal diseases including diabetic retinopathy and age related macular degeneration. In this study, we tested the hypothesis that enriching retinal DHA through a novel dietary approach could ameliorate symptoms of retinopathy in 5XFAD mice, a widely employed model of AD. The results show that 5XFAD mice have significantly lower retinal DHA compared to their wild type littermates, and feeding the lysophosphatidylcholine (LPC) form of DHA and eicosapentaenoic acid (EPA) rapidly normalizes the DHA levels, and increases retinal EPA by several-fold. On the other hand, feeding similar amounts of DHA and EPA in the form of triacylglycerol had only modest effects on retinal DHA and EPA. Electroretinography measurements after 2 months of feeding the experimental diets showed a significant improvement in a-wave and b-wave functions by the LPC-diet, whereas the TAG-diet had only a modest benefit. Retinal amyloid β levels were decreased by about 50% by the LPC-DHA/EPA diet, and by about 17% with the TAG-DHA/EPA diet. These results show that enriching retinal DHA and EPA through dietary LPC could potentially improve visual abnormalities associated with AD.
Topics: Mice; Animals; Docosahexaenoic Acids; Eicosapentaenoic Acid; Lysophosphatidylcholines; Alzheimer Disease; Amyloid beta-Peptides; Retina; Retinal Diseases; Diet
PubMed: 37280266
DOI: 10.1038/s41598-023-36268-0