Genetic Variation Determines PPARγ Function and Anti-diabetic Drug Response In Vivo.

SNPs affecting disease risk often reside in non-coding genomic regions. Here, we show that SNPs are highly enriched at mouse strain-selective adipose tissue binding sites for PPARγ, a nuclear receptor for anti-diabetic drugs. Many such SNPs alter binding motifs for PPARγ or cooperating factors and functionally regulate nearby genes whose expression is strain selective and imbalanced in heterozygous F1 mice. Moreover, genetically determined binding of PPARγ accounts for mouse strain-specific transcriptional effects of TZD drugs, providing proof of concept for personalized medicine related to nuclear receptor genomic occupancy. In human fat, motif-altering SNPs cause differential PPARγ binding, provide a molecular mechanism for some expression quantitative trait loci, and are risk factors for dysmetabolic traits in genome-wide association studies. One PPARγ motif-altering SNP is associated with HDL levels and other metabolic syndrome parameters. Thus, natural genetic variation in PPARγ genomic occupancy determines individual disease risk and drug response.

Natural human genetic variation determines basal and inducible expression of PM20D1, an obesity-associated gene.

PM20D1 is a candidate thermogenic enzyme in mouse fat, with its expression cold-induced and enriched in brown versus white adipocytes. Thiazolidinedione (TZD) antidiabetic drugs, which activate the peroxisome proliferator-activated receptor-γ (PPARγ) nuclear receptor, are potent stimuli for adipocyte browning yet fail to induce Pm20d1 expression in mouse adipocytes. In contrast, PM20D1 is one of the most strongly TZD-induced transcripts in human adipocytes, although not in cells from all individuals. Two putative PPARγ binding sites exist near the gene's transcription start site (TSS) in human but not mouse adipocytes. The -4 kb upstream site falls in a segmental duplication of a nearly identical intronic region +2.5 kb downstream of the TSS, and this duplication occurred in the primate lineage and not in other mammals, like mice. PPARγ binding and gene activation occur via this upstream duplicated site, thus explaining the species difference. Furthermore, this functional upstream PPARγ site exhibits genetic variation among people, with 1 SNP allele disrupting a PPAR response element and giving less activation by PPARγ and TZDs. In addition to this upstream variant that determines PPARγ regulation of PM20D1 in adipocytes, distinct variants downstream of the TSS have strong effects on PM20D1 expression in human fat as well as other tissues. A haplotype of 7 tightly linked downstream SNP alleles is associated with very low PMD201 expression and correspondingly high DNA methylation at the TSS. These PM20D1 low-expression variants may account for human genetic associations in this region with obesity as well as neurodegenerative diseases.

Macular thickness fluctuation in neovascular age-related macular degeneration treated with anti-vascular endothelial growth factor.

OBJECTIVE: To establish whether increased variability in macular thickness in neovascular age-related macular degeneration (nAMD) patients affects visual outcomes in clinical practice DESIGN: Retrospective cohort study PARTICIPANTS: Treatment-naive nAMD patients studied over 24 months METHODS: Central subfield thickness (CST) values from optical coherence tomography were collected quarterly from baseline to 24 months, and standard deviations (SDs) were calculated. The relationship was modeled with mixed-effects regression between CST SD and 24-month change in visual acuity (VA). Linear regression modeling determined predictors of CST SD. RESULTS: A total of 422 eyes with nAMD were studied. Baseline and 24-month CST values (mean ± SD) were 331.2 ± 97.6 and 253.4 ± 53.6 µm (Δ = -77.8 ± 104.7 µm, p < 0.001), with CST SD across 24 months of 42.0 ± 32.8 µm. Baseline and 24-month VA were 58.8 ± 19.2 and 62.4 ± 20.6 Early Treatment of Diabetic Retinopathy Study letters (Δ = +3.7 ± 20.8 letters, p = 0.008). CST SD over 24 months was a statistically significant negative predictor of 24-month change in VA (-15.41 [-20.98, -9.83] letters per 100 µm, p < 0.001). Quartile analysis of 24-month VA by CST SD showed a +11.2-letter difference between the first and last quartiles (p < 0.001). Baseline CST was a predictor of 24-month CST SD (24.88 [22.69, 27.06] µm per 100 µm, p < 0.001). CONCLUSIONS: Higher macular thickness fluctuations are related to poorer visual outcomes at 24 months in patients with nAMD treated with anti-vascular endothelial growth factor injections. Macular thickness variability may be an important prognostic factor of visual outcomes in nAMD eyes.

Student becomes teacher: training faster deep learning lightweight networks for automated identification of optical coherence tomography B-scans of interest using a student-teacher framework.

This work explores a student-teacher framework that leverages unlabeled images to train lightweight deep learning models with fewer parameters to perform fast automated detection of optical coherence tomography B-scans of interest. Twenty-seven lightweight models (LWMs) from four families of models were trained on expert-labeled B-scans (∼70 K) as either "abnormal" or "normal", which established a baseline performance for the models. Then the LWMs were trained from random initialization using a student-teacher framework to incorporate a large number of unlabeled B-scans (∼500 K). A pre-trained ResNet50 model served as the teacher network. The ResNet50 teacher model achieved 96.0% validation accuracy and the validation accuracy achieved by the LWMs ranged from 89.6% to 95.1%. The best performing LWMs were 2.53 to 4.13 times faster than ResNet50 (0.109s to 0.178s vs. 0.452s). All LWMs benefitted from increasing the training set by including unlabeled B-scans in the student-teacher framework, with several models achieving validation accuracy of 96.0% or higher. The three best-performing models achieved comparable sensitivity and specificity in two hold-out test sets to the teacher network. We demonstrated the effectiveness of a student-teacher framework for training fast LWMs for automated B-scan of interest detection leveraging unlabeled, routinely-available data.

Pparγ1 Facilitates ErbB2-Mammary Adenocarcinoma in Mice.

HER2, which is associated with clinically aggressive disease, is overexpressed in 15-20% of breast cancers (BC). The host immune system participates in the therapeutic response of HER2+ breast cancer. Identifying genetic programs that participate in ErbB2-induced tumors may provide the rational basis for co-extinction therapeutic approaches. Peroxisome proliferator-activated receptor γ (PPARγ), which is expressed in a variety of malignancies, governs biological functions through transcriptional programs. Herein, genetic deletion of endogenous Pparγ1 restrained mammary tumor progression, lipogenesis, and induced local mammary tumor macrophage infiltration, without affecting other tissue hematopoietic stem cell pools. Endogenous Pparγ1 induced expression of both an EphA2-Amphiregulin and an inflammatory INFγ and Cxcl5 signaling module, that was recapitulated in human breast cancer. Pparγ1 bound directly to growth promoting and proinflammatory target genes in the context of chromatin. We conclude Pparγ1 promotes ErbB2-induced tumor growth and inflammation and represents a relevant target for therapeutic coextinction. Herein, endogenous Pparγ1 promoted ErbB2-mediated mammary tumor onset and progression. PPARγ1 increased expression of an EGF-EphA2 receptor tyrosine kinase module and a cytokine/chemokine 1 transcriptional module. The induction of a pro-tumorigenic inflammatory state by Pparγ1 may provide the rationale for complementary coextinction programs in ErbB2 tumors.

Therapeutic Potential of the Ranibizumab Port Delivery System in the Treatment of AMD: Evidence to Date.

Age-related macular degeneration (AMD) is one of the leading causes of blindness in older adults worldwide. The advent of intravitreal neutralization of vascular endothelial growth factor (VEGF) has revolutionized the management of patients with neovascular AMD, but current anti-VEGF therapies carry a high threshold of patient burden. The ranibizumab port delivery system (PDS) is an implanted, refillable reservoir that continuously supplies the anti-VEGF medication ranibizumab directly into the vitreous, eliminating the need for frequent intravitreal injections. It has most recently been evaluated in the Phase II LADDER trial demonstrating the efficacy and safety of the PDS, with Phase III trials currently underway. This review presents both the promise and drawbacks of the PDS in the treatment of AMD from the current literature.

Atypical ophthalmic manifestations of disseminated intravascular coagulation in a newborn.

Ophthalmic manifestations of disseminated intravascular coagulation (DIC) in a newborn are rare. Ocular involvement typically involves the posterior segment bilaterally and manifests as choroidal and/or retinal hemorrhages associated with fibrin thrombi in the choriocapillaris. We present the case of a newborn girl with DIC secondary to sepsis who subsequently developed nonclearing hyphema, related secondary cataract, 360° posterior synechiae, and nonclearing vitreous hemorrhage in the right eye and diffuse retinal hemorrhage in the left eye. The right fundus was not visible because of intraocular bleeding. The patient underwent cataract surgery at 39 days of life and was left aphakic. Two weeks later, she required subsequent vitrectomy because of a nonclearing vitreous hemorrhage. She developed amblyopia of the right eye and a right esotropia that required strabismus surgery. At 7 years of age, the patient's visual acuity was 20/50 in the right eye and 20/20 in the left eye.

Adipose KLF15 Controls Lipid Handling to Adapt to Nutrient Availability.

Adipose tissue stores energy in the form of triglycerides. The ability to regulate triglyceride synthesis and breakdown based on nutrient status (e.g., fed versus fasted) is critical for physiological homeostasis and dysregulation of this process can contribute to metabolic disease. Whereas much is known about hormonal control of this cycle, transcriptional regulation is not well understood. Here, we show that the transcription factor Kruppel-like factor 15 (KLF15) is critical for the control of adipocyte lipid turnover. Mice lacking Klf15 in adipose tissue (AK15KO) display decreased adiposity and are protected from diet-induced obesity. Mechanistic studies suggest that adipose KLF15 regulates key genes of triglyceride synthesis and inhibits lipolytic action, thereby promoting lipid storage in an insulin-dependent manner. Finally, AK15KO mice demonstrate accelerated lipolysis and altered systemic energetics (e.g., locomotion, ketogenesis) during fasting conditions. Our study identifies adipose KLF15 as an essential regulator of adipocyte lipid metabolism and systemic energy balance.

Targeting PPARγ in the epigenome rescues genetic metabolic defects in mice.

Obesity causes insulin resistance, and PPARγ ligands such as rosiglitazone are insulin sensitizing, yet the mechanisms remain unclear. In C57BL/6 (B6) mice, obesity induced by a high-fat diet (HFD) has major effects on visceral epididymal adipose tissue (eWAT). Here, we report that HFD-induced obesity in B6 mice also altered the activity of gene regulatory elements and genome-wide occupancy of PPARγ. Rosiglitazone treatment restored insulin sensitivity in obese B6 mice, yet, surprisingly, had little effect on gene expression in eWAT. However, in subcutaneous inguinal fat (iWAT), rosiglitazone markedly induced molecular signatures of brown fat, including the key thermogenic gene Ucp1. Obesity-resistant 129S1/SvImJ mice (129 mice) displayed iWAT browning, even in the absence of rosiglitazone. The 129 Ucp1 locus had increased PPARγ binding and gene expression that were preserved in the iWAT of B6x129 F1-intercrossed mice, with an imbalance favoring the 129-derived alleles, demonstrating a cis-acting genetic difference. Thus, B6 mice have genetically defective Ucp1 expression in iWAT. However, when Ucp1 was activated by rosiglitazone, or by iWAT browning in cold-exposed or young mice, expression of the B6 version of Ucp1 was no longer defective relative to the 129 version, indicating epigenomic rescue. These results provide a framework for understanding how environmental influences like drugs can affect the epigenome and potentially rescue genetically determined disease phenotypes.

Thiazolidinediones and the promise of insulin sensitization in type 2 diabetes.

Type 2 diabetes is caused by insulin resistance coupled with an inability to produce enough insulin to control blood glucose, and thiazolidinediones (TZDs) are the only current antidiabetic agents that function primarily by increasing insulin sensitivity. However, despite clear benefits in glycemic control, this class of drugs has recently fallen into disuse due to concerns over side effects and adverse events. Here we review the clinical data and attempt to balance the benefits and risks of TZD therapy. We also examine potential mechanisms of action for the beneficial and harmful effects of TZDs, mainly via agonism of the nuclear receptor PPARγ. Based on critical appraisal of both preclinical and clinical studies, we discuss the prospect of harnessing the insulin sensitizing effects of PPARγ for more effective, safe, and potentially personalized treatments of type 2 diabetes.