Leptin metabolically licenses T cells for activation to link nutrition and immunity.

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2014-01-01

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Immune responses are highly energy-dependent processes. Activated T cells increase glucose uptake and aerobic glycolysis to survive and function. Malnutrition and starvation limit nutrients and are associated with immune deficiency and increased susceptibility to infection. Although it is clear that immunity is suppressed in times of nutrient stress, mechanisms that link systemic nutrition to T cell function are poorly understood. We show in this study that fasting leads to persistent defects in T cell activation and metabolism, as T cells from fasted animals had low glucose uptake and decreased ability to produce inflammatory cytokines, even when stimulated in nutrient-rich media. To explore the mechanism of this long-lasting T cell metabolic defect, we examined leptin, an adipokine reduced in fasting that regulates systemic metabolism and promotes effector T cell function. We show that leptin is essential for activated T cells to upregulate glucose uptake and metabolism. This effect was cell intrinsic and specific to activated effector T cells, as naive T cells and regulatory T cells did not require leptin for metabolic regulation. Importantly, either leptin addition to cultured T cells from fasted animals or leptin injections to fasting animals was sufficient to rescue both T cell metabolic and functional defects. Leptin-mediated metabolic regulation was critical, as transgenic expression of the glucose transporter Glut1 rescued cytokine production of T cells from fasted mice. Together, these data demonstrate that induction of T cell metabolism upon activation is dependent on systemic nutritional status, and leptin links adipocytes to metabolically license activated T cells in states of nutritional sufficiency.

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10.4049/jimmunol.1301158

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Saucillo, Donte C, Valerie A Gerriets, John Sheng, Jeffrey C Rathmell and Nancie J Maciver (2014). Leptin metabolically licenses T cells for activation to link nutrition and immunity. J Immunol, 192(1). pp. 136–144. 10.4049/jimmunol.1301158 Retrieved from https://hdl.handle.net/10161/10314.

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Scholars@Duke

MacIver

Nancie Jo MacIver

Adjunct Associate Professor in the Department of Pediatrics

My laboratory is broadly interested in how large changes in nutritional status (e.g. malnutrition or obesity) influence T cell immunity.  Malnutrition can lead to immunodeficiency and increased risk of infection, whereas obesity is associated with inflammation that promotes multiple diseases including autoimmunity, type 2 diabetes, and cardiovascular disease.  We have identified the adipocyte-secreted hormone leptin as a critical link between nutrition and immunity.  Leptin is secreted from adipocytes in proportion to adipocyte mass and is therefore decreased in malnutrition and increased in obesity.  We have found that leptin is a critical regulator of effector T cell glucose metabolism and thereby drives effector T cell activation.  From these initial findings, we have established further lines of investigation, as summarized here.

(1) Determining molecular mechanisms of T cell dysfunction in malnutrition – Our goal is to identify metabolic and epigenetic mechanisms by which malnutrition and decreased leptin alter T cell function leading to increased susceptibility to infection and protection against autoimmune diseases.  We study this using a mouse model of autoimmunity, experimental autoimmune encephalomyelitis (EAE).

(2) Elucidating mechanisms of T cell inflammation in obesity-induced type 2 diabetes – Our goal is to identify molecular and metabolic mechanisms by which obesity alters the Teff/Treg balance, resulting in inflammation and subsequent insulin resistance leading to type 2 diabetes.  With our collaborators from UNC Chapel Hill, we are also identifying immunometabolic changes in obese animals and humans that correlate with increased susceptibility to influenza.

(3) Determining the role of insulin and IGF-1 in regulating T cell function and metabolism – Our goal is to identify how insulin influences both T cell glucose uptake and T cell differentiation/cytokine production and determine the role of insulin signaling in T cells in the setting of obesity-associated diabetes.  We hypothesize that insulin has a direct role in T cell function through its abiltiy to alter T cell glucose metabolism, influence T cell cytokine production, and impact the pathophysiology of obesity-associated type 2 diabetes. 


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