PI:Inna Astapova, PhD
Abstract: The Role of UCP1 in Glucose Homeostasis
The worldwide increase in the epidemic of type 2 diabetes (DM2) presents a serious public health issue. Obesity or increased adiposity is thought to be a major contributor to the pathogenesis of DM2. Recent evidence suggests that converting classic white fat into beige, which is characterized by increased expression of uncoupling protein 1 (UCP1) in the process known as “browning” may have beneficial metabolic effects. In particular, it has been suggested that browning may increase energy expenditure due to the ability of UCP1 dissipate energy as heat, and therefore provide means of achieving negative energy balance and weight loss. However, whether sufficient amounts UCP1 protein are expressed in beige fat to achieve enough thermogenesis to result in weight loss is controversial. Here, based on biochemical considerations, we propose that the primary function of UCP1 in beige fat is not to produce heat, but instead to facilitate de novo lipogenesis (DNL) from glucose and that this is an important mechanism to regulate glucose homeostasis. Consistent with this, adipose tissue DNL has recently been demonstrated to regulate glucose homeostasis in humans and animals. Moreover, the PPARγ agonists, thiazolidinediones (TZDs) which exert powerful glucose-lowering and insulin-sensitizing effects, have been shown to promote adipose tissue DNL and cause browning. We propose that the beneficial effects of TZDs depend on beige fat adipose DNL facilitated by UCP1. Here, using UCP1 KO mice, we will test whether UCP1 is important for adipose tissue DNL in the setting of high-carbohydrate feeding. We will also determine whether UCP1 is required for the beneficial effects of TZDs on glucose homeostasis. These studies will provide fundamental insight into the physiology by which glucose homostasis is regulated leading to new strategies for the treatment of DM2.
PI: Alexander S. Banks, PhD
Abstract: Personalized Therapy for Type 2 Diabetes: A Novel Pharmacogenetic Approach
Personalized medicine for diabetes promises to improve both cost and efficacy of care. This approach depends both on understanding the pathogenesis of the disorder and deploying the most effective and appropriate treatments. PPARg is both a master regulator of adipocyte differentiation and also a critical mediator of adipose tissue insulin sensitivity. Obesity induced phosphorylation of PPARg via cyclin dependent kinase 5 (Cdk5) promotes insulin resistance. Both this phosphorylation event and insulin resistance can be reversed by administration of thiazolidinediones (TZDs). Cdkal1 is one of the most reproducibly identified human diabetes susceptibility genes, yet its biochemical function is unknown. It is homologous to a protein known to bind p35, the Cdk5 regulatory protein. We have found that disease-associated SNPs in Cdkal1 alter expression of Cdkal1 in human adipose tissue. We have also confirmed that Cdkal1 binds p35 and promotes protein stability and Cdk5 kinase activity. We hypothesize that Cdkal1 will promote PPARg phosphorylation and insulin resistance. Correspondingly, because the TZDs are FDA approved anti-diabetic therapeutics which effectively reverses PPARg phosphorylation, we believe that individuals harboring the disease associated alleles of Cdkal1 may specifically benefit from treatment with this class of drugs.
We propose to create mice bearing a gain-of-function allele of Cdkal1 capable of tissue specific activation. In fat-specific Cdkal1 transgenic mice, we will examine the metabolic and biochemical consequences of increasing Cdkal1 expression in adipose tissue when challenged with obesity. Interacting partners of Cdkal1 will be identified via mass spectrometry. The transcriptional consequences of increasing Cdkal1 expression in vivo will also be examined. Lastly, the metabolic response of these mice to TZDs will be examined relative to controls.
Following the research in this proposal, the function of a human diabetes associated allele will be elucidated. These results will form the basis of an R01 application.
PI: Jae Hyuang Chang, MD
Abstract: Role of proximal tubule injury in the pathogenesis of diabetic nephropathy
Diabetic nephropathy (DN) has been traditionally considered as a primary glomerular disease. We suggest that the kidney tubule plays a primary role in the development of DN, and that subsequent tubulointerstitial injury may lead to glomerular changes in diabetes.We will investigate if selective proximal tubule injury alone can accelerate diabetic kidney disease in a genetic model of type 1 diabetes (Akita mice). For these studies, we have crossed a mouse containing the tubule-specific Six2-Cre allele with a mouse transgenic for a Cre-inducible simian diphtheria toxin receptor (iDTR). Six2-Cre/iDTR mice will be bred with Akita mice to create diabetic animals which develop isolated proximal tubule damage upon administration of diphtheria toxin. The severity of the kidney disease will then be quantitated by determining the effects of targeted tubular damage on the severity of albuminuria, urinary kidney injury molecule (KIM)-1 excretion, hypertension, kidney function, renal hypertrophy, and renal histopathological abnormalities in the tubulointerstitium (interstitial fibrosis and tubular atrophy, and vascular rarefaction) and glomeruli (mesangial expansion, matrix accumulation, and basement membrane thickening) by both light microscopy and electron microscopy, as well as expression of pro-fibrotic growth factors at both the mRNA and protein levels. If the proposed studies are successful, the findings will provide the conceptual framework for the development of novel pharmacological therapies that protect the proximal tubule against injury for the treatment of diabetic kidney disease in humans.
PI: Pei-Jung Lin, PhD
PI: Nicola M. McKeown, Ph.D.
Abstract: Interactions between Sugar-Sweetened Beverage Consumption and ChREBP in the Development of Insulin Resistance
Abstract: Estimating costs of multiple chronic conditions among adults with diabetes.
Most adults with diabetes have at least one co-existing chronic condition and 40% have three or more. As the number of comorbidities increases, the risks of poor patient outcomes (e.g., unnecessary hospitalizations, adverse drug events, mortality) also increase. Although previous studies have shown that the type and severity of certain conditions, not just the number of comorbidities, matter, less attention has been paid to multiple chronic comorbidities (MCCs) and how MCCs impact diabetes care. Patients with MCCs are known to require high levels of health care and account for a significant proportion of health care costs. However, the most expensive MCC clusters in diabetes have yet to be identified. Nor is it clear how the patterns vary by age. Our recent analysis of 161,174 adult patients with Type 2 diabetes found that the leading MCC combination was the presence of hypertension-hyperlipidemia-obesity and no other diagnosed comorbidities (19% of the sample), based on data from electronic health records, encounter files, and lab values supplied by U.S. providers in the 2008-2012 Humedica datasets. The top 10 mutually exclusive MCC clusters accounted for roughly 70% of diabetes patients. We also found that MCC cluster patterns exhibit substantial heterogeneity across patients and by age. For example, the most notable difference by age was a higher prevalence of obesity in the younger cohort. Unlike previous research that focused on two-way or three-way combinations between and among comorbidities, our analysis examined a large number of the most common MCC combinations for diabetes. Building on this work, the proposed project will quantify health care costs of MCCs in diabetes, identify high-cost MCC clusters, and examine opportunities to reduce costs. Because the Humedica datasets contain health care utilization data rather than costs, we will assign costs to each MCC cluster based on the health care services a patient used. We will determine the services used based on the following utilization variables: diagnostic related groups (DRGs), Current Procedural Terminology (CPT) codes, and Healthcare Common Procedure Coding System (HCPCS) codes. For each service utilized, we will assign a standardized cost of care using a Medicare-based algorithm. The proposed study will extend prior work by using considerably more-detailed and extensive information about MCCs in diabetes patients. Identifying the most expensive MCC clusters will help better target high-cost diabetes patients for disease management. In addition to improving clinical care, such information can be used to refine diabetes risk adjustment measures. The results can help guide payment reforms and improve cost prediction for diabetes patients with MCCs.
There is current debate over whether excessive intake of added sugars is linked to metabolic syndrome and type 2 diabetes mellitus. The link between these negative health outcomes and sugar-sweetened beverage (SSB) intake has been of particular interest, as SSB are significant contributors to added sugar intake in the United States. Sucrose and high fructose corn syrup (HFCS), the two major sugars in the diet, are disaccharide sugars composed of the monosaccharide sugars glucose and fructose. It has been already established that these monosaccharides increase the expression of key enzymes involved in de novo lipogenesis via the carbohydrate response element-binding protein (ChREBP). Previous work has shown that ChREBP regulates the expression of glycolytic and lipogenic gene programs in an insulin-independent manner. However, the role of genes in maintaining a balance between sugar utilization and sugar-induced metabolic disturbances in the context of high sugar intake is not well established. We hypothesize that the effect of ChREBP on glucose homeostasis and insulin sensitivity is dependent on consumption of sugar intake.
In addition, we hypothesize that polymorphisms associated with increased ChREBP activity will reduce glycemia and insulin levels when dietary sugar intake is low. In contrast, activating polymorphisms in ChREBP will increase glycemia and insulin resistance when sugar availability is high. We will use data generated from The Cohorts for Heart and Aging Research in Genomic Epidemiology (CHARGE) Consortium to examine our hypotheses. Our specific aims are to conduct a meta analysis determining whether polymorphisms in 15 single nucleotide polymorphisms (SNPs) including (1) ChREBP,
(2) genes thought to regulate ChREBP activity, or (3) polymorphisms identified as determinants of hypertriglyceridemia interact with SSB to promote insulin resistance. The results of this meta-analysis may serve as preliminary data linking gene-diet interactions to glucose/insulin metabolism and, thus, may lead to specific interventions based on reducing dietary sugar intake in genetically predisposed individuals.
PI: Deborah Mitchell, MD
Abstract: Bone mineralization and microarchitecture in youth with type 1 diabetes
Background: Osteoporosis is a well-described but often neglected complication of type 1 diabetes (T1DM). Adults with T1DM are at very high risk for fracture, and sub-optimal bone accrual in childhood may contribute significantly to this risk. Adolescence is a critical time for bone mineral accrual, with ~50% of peak bone mass acquired during the pubertal years and >90% by age 18_ENREF_10. Since T1DM typically presents in childhood, an effect of T1DM on bone formation has the potential to cause a significant deficit in peak bone mass and thus fracture resistance. To date, the pathogenesis of T1DM-associated bone fragility remains unclear. In particular, elevated hemoglobin A1c (HgbA1c) is inconsistently associated with lower bone mineral density in the available literature. In addition, a role for insulin-like growth factor 1 (IGF1), an important anabolic factor for bone which is suppressed in the setting of T1DM, has been suggested.
Objective: The overall goal of this study is to determine whether T1DM leads to reduced bone formation and impaired bone microarchitecture during childhood, and to identify the underlying pathophysiology. I propose to prospectively study the rate of bone mineral accrual in adolescents with T1DM compared to age- and race-matched controls. I will use both dual-energy X-ray absorptiometry (DXA) and high-resolution peripheral quantitative computed tomography (HR-pQCT) which will allow me to investigate the effects of T1DM on mineralization and microarchitecture of both the cortical and trabecular skeletal compartments.
- The rate of volumetric bone mineral density (vBMD) accrual will be decreased in T1DM.
- In T1DM, inferior glycemic control will be associated with decreased bone accrual and impaired development of microarchitecture.
- Lower serum IGF1 will be associated with decreased bone accrual and microarchitecture development independent of glycemic control.
Methods: I will enroll 22 girls with T1DM ages 10-16 and 22 age- and race-matched controls. I will limit this pilot study to girls, as normal values of BMD and of microarchitectural parameters differ by sex. Thus, by limiting the study to a single sex, I will increase power to detect differences. At baseline, 6 months, and 12 months, I will measure areal BMD by DXA at the spine, hip, whole body, and distal radius as well as volumetric BMD by HR-pQCT at the distal radius and distal tibia. At each time point, I will measure serum levels of HgbA1c and IGF1 as well as other key determinants of bone and mineral metabolism.
Importance: Bone disease is a long-described but poorly understood complication of T1DM. This project aims first to accurately describe the specific changes in bone volumetric density and microarchitecture underpinning diabetic bone disease. In addition, I will prospectively assess the effect of factors including glycemic control, IGF1 levels, and mineral ion metabolism on bone mineral accrual. This study addresses critical knowledge gaps regarding the effect of T1DM on bone accrual and, by extension, on fracture risk. By identifying determinants of bone accrual in children with T1DM, we will better understand the complex pathophysiology of diabetes-associated osteoporosis. This knowledge will ultimately inform trials of interventional strategies to prevent fragility fractures in this population.
PI: Francisco J, Quintana, Ph.D.
Arrest of the diabetogenic T-cell response using IL-27-treated tolerogenic dendritic cells loaded with β-cell antigens
IL-27 controls pathogenic Th1 and Th17 responses in vivo, supporting its therapeutic use for the treatment of autoimmunity. IL-27, however, has also been reported to act directly on T cells to boost CD8+ T-cell responses, suggesting that IL-27 administration has the potential to worsen autoimmune disorders. We found that IL-27 induces tolerogenic dendritic cells (DCs) that arrest the development of autoimmune inflammation. DC vaccination has been successfully used to induce immunity against tumors and pathogens, indeed, the US Food and Drug Administration has recently approved the use of a DC vaccine for the treatment of advanced prostate cancer. Conversely, vaccination with tolerogenic DCs has been shown to induce antigen specific tolerance in humans and experimental models of autoimmunity. Based on our preliminary data we hypothesize that vaccination with tolerogenic IL-27 conditioned DCs loaded with β-cell antigens will have an ameliorating effect in NOD diabetes. Thus, in this project we propose to study the therapeutic potential of vaccination with tolerogenic DCs induced with IL-27, to exploit the anti-inflammatory activities of IL-27 while avoiding its potential pathogenic effects. Specifically, we propose to study the use of DCs pretreated with IL-27 and loaded with β-cell specific antigens (insulin or a mimotope) to control the diabetogenic T cell response. Our specific aims are:
- SPECIFIC AIM 1: WHAT IS THE EFFECT OF VACCINATION WITH IL-27 TREATED DCS CONTAINING MIMO OR INSULIN ON TREG AND THE DIABETOGENIC IMMUNE RESPONSE IN NOD MICE? We found that IL-27 treated DCs promote the differentiation of Tregs and limit pathogenic Th1 and Th17 responses, suppressing established inflammation in vivo. In this Aim we will study the effects of IL-27 treated DCs loaded with MIMO or insulin on islet-specific immunity.
- SPECIFIC AIM 2: WHAT IS THE EFFECT OF TOLEROGENIC DCS INDUCED WITH IL-27 ON SPONTANEOUS NOD DIABETES? We have obtained positive results with the administration of IL-27 treated DCs on established relapsing-remitting EAE, 30 days after disease induction. We will test whether the administration of tolerogenic DCs arrests spontaneous NOD diabetes, and to study the value of islet-specific antibodies as biomarkers to monitor response to treatment.
In summary, the studies proposed in this project investigate the role of IL-27 signaling in DCs in the regulation of islet-specific immunity, and its potential exploitation as a therapeutic approach for T1D.
PI: Kristy Townsend, PhD
Abstract: Mechanisms of fatty acid sensing and uptake by brown adipocytes
Obesity is currently a global pandemic, associated with high rates of metabolic co-morbidities such as type 2 diabetes mellitus and cardiovascular disease. Obesity results from an energy imbalance when energy intake exceeds energy expenditure and excess calories are stored in white adipose tissue. Given the relative lack of success with most obesity treatment options, there is a pressing need to better understand the physiological regulation of energy balance as well as the pathophysiology of obesity in order to identify new targets for the development of novel treatments. Brown adipose tissue (BAT), or the energy-expending thermogenic adipose tissue of the body, is a promising target in this respect. Increasing BAT mass or activity would likely combat obesity and reverse the development of co-morbidities. The development and functional properties of BAT are starting to be understood, but many questions remain unanswered. In order for BAT to undergo such high levels of energy expenditure, it requires a readily available fuel source, which includes fatty acids either stored in its multilocular lipid droplets taken up as fatty acids released from white adipose tissue lipolysis. It is currently unclear exactly how BAT regulates its fatty acid fuel supply, including the sensing, uptake and oxidation of these fats. Mouse models lacking the fatty acid transporters CD36 or FATP1 are unable to undergo theremogenesis and do not survive cold exposure, further underscoring the importance of fatty acids for BAT function. Our work has demonstrated that treatment with the bone morphogenetic protein 7 (BMP7) is able to increase fatty acid uptake and oxidation in brown adipocytes, resulting in greater rates of mitochondrial respiration. Furthermore, we have demonstrated that this situation of increased fatty acid uptake and utilization is also associated with an increase of the fatty acid sensor GPR120. Nothing is known about how fatty acid sensing, and specifically GPR120, affects BAT function. We seek to determine how GPR120, which has recently been associated with human obesity, affects fatty acid sensing and uptake by CD36 and FATP1 to affect mitochondrial activity and energy expenditure in brown adipocytes. A better understanding of the mechanisms underlying fuel utilization by BAT will provide novel opportunities for treating obesity.
PI: Heidi Yeh, MD
Abstract: Targeting pathways of inflammation in islet allotransplantation post kidney transplantation using AAT
Isolated pancreatic islet transplantation holds potential as a minimally invasive approach to replenish the beta cell mass in type I diabetes. Recent data indicate that implementation of post Edmonton anti-rejection and anti-inflammation drug regimens resulted in markedly improved results of islet transplantation with long-term insulin independence approaching or equaling the rate in whole organ pancreas transplants at the five-year time point. Despite this success, a number of obstacles still impede achieving the full potential of islet transplantation, including: 1) the frequent need for infusions from more than one donor to achieve insulin independence, 2) early loss of a significant portion of transplanted islet mass, 3) gradual attrition of islet mass over time, and 4) the cost of the procedure. The current proposal seeks to evaluate a novel strategy to minimize early loss of islets and thus improve islet engraftment by administering the anti-inflammatory, immunomodulatory agent ?-1 antitrypsin (AAT; Aralast). AAT is a clinically available agent that is used to treat A1AT deficiency and which has demonstrated remarkable promise in both mouse studies and preclinical large animal experiments as a means to increase engraftment and promote long-term graft survival. We hypothesize that AAT induced increases in initial engrafted mass will enhance the rate single donor cure rates and reduce chronic attrition of islet mass prolonging insulin independence and improving the overall efficiency of the procedure. To test this thesis, we will conduct pilot studies in 3 patients receiving islet allotransplants post kidney transplants and assess engrafted islet mass. The results will be compared to already transplanted patients who have received islet transplants using a similar immunosuppressive and islet isolation protocol. The immunological impact of AAT administration will also be monitored.