Abstract
Triggers of the autoimmune response that leads to type 1 diabetes (T1D) remain poorly understood. A possibility is that parallel changes in both T cells and target cells provoke autoimmune attack. We previously documented greater Ca2+ transients in fibroblasts from T1D subjects than non-T1D after exposure to fatty acids (FA) and tumor necrosis factor α (TNFα). These data indicate that metabolic and signal transduction defects present in T1D can be elicited ex vivo in isolated cells. Changes that precede T1D, including inflammation, may activate atypical responses in people that are genetically predisposed to T1D. To identify such cellular differences in T1D, we quantified a panel of metabolic responses in fibroblasts and peripheral blood cells (PBMCs) from age-matched T1D and non-T1D subjects, as models for non-immune and immune cells, respectively. Fibroblasts from T1D subjects accumulated more lipid, had higher LC-CoA levels and converted more FA to CO2, with less mitochondrial proton leak in response to oleate alone or with TNFα, using the latter as a model of inflammation. T1D-PBMCs contained and also accumulated more lipid following FA exposure. In addition, they formed more peroxidized lipid than controls following FA exposure. We conclude that both immune and non-immune cells in T1D subjects differ from controls in terms of responses to FA and TNFα. Our results suggest a differential sensitivity to inflammatory insults and FA that may precede and contribute to T1D by priming both immune cells and their targets for autoimmune reactions.
Highlights
Type 1 Diabetes (T1D) is an autoimmune disease with a genetic predisposition that primes the immune system, mainly T cells, to destroy the insulin-producing β cells of the pancreas
Both T1D and control fibroblasts increase lipid content following fatty acids (FA) incubation (Fig 1, compare A to B and C to D), fibroblasts from T1D subjects accumulated more lipid than fibroblasts from control subjects under both control (Fig 1C vs 1A) and FA-stimulated conditions (Fig 1D vs 1B), and lipid accumulation was largely independent of plating density (Fig 1E)
Results from lipid accumulation studies in PBMCs were somewhat different: lipid levels were similar in PBMCs from control and T1D subjects in the absence of stimulation Fig 2, left panels), and only PBMCs from T1D subjects increased lipid content in response to FA (Fig 2, right panels)
Summary
Type 1 Diabetes (T1D) is an autoimmune disease with a genetic predisposition that primes the immune system, mainly T cells, to destroy the insulin-producing β cells of the pancreas. We demonstrated that T1D cells differ in cellular metabolism while resting and while responding to FA (oleate) and cytokines (TNFα) compared to cells from non-T1D subjects.
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