MIRMIRA LAB

12/15-lipoxygenase catalyzes the oxygenation of fatty acids to produce lipid pro-inflammatory mediators, the primary being 12-HETE. One of our initial studies showed that the deletion of 12/15-lipoxygenase in the pancreas is sufficient to protect against obesity-induced glucose intolerance, via a mechanism involving Nrf2-mediated activation of antioxidant genes (Tersey et al. MCB 2014). Additionally, we showed that an inhibitor of 12/15-lipoxygenase was able to prevent beta cell dysfunction in a mouse model of type 1 diabetes (Hernadez-Perez et al. Diabetes 2017), through reductions in oxidative stress. New studies are seeking to identify different roles of 12/15-lipoxygenase in the islets versus in the macrophage during the onset of type 1 diabetes. Deleting 12/15-lipoxygenase in the macrophage results in a loss of migration to the site of injury and protection from type 1 diabetes in the NOD mouse model (Kulkarni et al. JCI Insights 2021). Deleting 12/15-lipoxygenase solely in the β cell results in an alteration of immune cell recruitment and activation and ultimately a protection from type 1 diabetes in the NOD mouse model (Pineros, et al. Cell Reports 2022).

Additionally, we are also currently studying a newly deorphaned G protein-coupled receptor, GPR31, which has been identified as a receptor for 12-HETE. 

Chronic low-grade inflammation is a well established feature of obesity, and the macrophage is a major player in perpetuating the inflammatory phenotype that contributes to insulin resistance. The 12/15-lipoxygenase (12/15-LOX) enzyme yields bioactive inflammatory mediators and is activated by hyperglycemia and cytokine damage to promote macrophage inflammatory activity (Fig 1).  Macrophage 12/15-LOX plays a major role in obesity development.  Our projects aims to better understand the role of 12/15-LOX in macrophages during the development of obesity and insulin resistance to determine if this pathway can be targeted in humans for the treatment and prevention of metabolic disease.  

Type 1 diabetes (T1D) is a complex and heterogenous disease.  Insulin-producing β cells are the target of destruction by the immune system, and those who display autoantibodies against β cell antigens are at highest risk for developing the disease.  Development of autoantibodies is a relatively late event in the pathogenesis of the disease, and recent studies using immune-suppressive agents in these individuals delays the onset of diabetes, but does not prevent it.  This finding suggests that even earlier detection of the disease may be necessary if prevention strategies are to work as intended.  Compounding this problem is the fact that the great majority of individuals (~80%) who are diagnosed with T1D do not have a first degree relative with the disease—hence, it is hard to know who to screen.  Therefore the development of simple and rapid biomarkers for those at risk of developing T1D are needed.

The Mirmira Lab has had an ongoing effort to screen for such biomarkers by taking an approach different from the focus of the rest of the field on immunobiology.  We posit that the β cell exhibits early dysfunction from prevailing environmental stress, and the ensuing stress pathways generate aberrant proteins that break immune tolerance.  Our projects surrounding biomarker discovery involve many approaches: 

1. A focus on identifying stress pathways that are activated in β cells, and identifying how these pathways might lead to tolerance breakdown.  In particular, our recent interest is on the Integrated Stress Response (ISR) and the formation of stress granules and the release of Extracellular Vesicles (EVs).  This project involves the manipulation of the ISR using small molecules and interfering RNAs in a variety of biological systems (zebrafish, rodents, human β cell lines, and human islets), and interrogating the contents of stress granules and EVs by RNA deep sequencing and proteomics. 

2. A focus on the epigenetic state of liberated DNA and RNA species.  In collaboration with several groups around the world, we have been developing PCR based assays to identify epigenetically modified nucleic acid species that are uniquely liberated by β cells as they undergo stress or death in the early stages of T1D.  Already, we have used such assays to show that unaffected relatives of T1D subjects have evidence of β cell stress and possibly death. 

3. A focus on small and long noncoding RNAs.  We have been collaborating with investigators at Indiana University to develop a comprehensive mapping of small and long noncoding RNAs that emanate (are released extracellularly) by human β cells in response to stress.

4. Comprehensive biomarker panels.  Using publicly available data and data accumulated in experiments above, we have been working with bioinformaticians to develop machine learning algorithms to identify specific panels of biomarkers (nucleic acids, proteins, lipid species, metabolites) that reflect specific states of β cell health and stress.