Tissue-specific suppression of thyroid hormone signaling in various mouse models of aging

DNA damage contributes to the process of aging, as underscored by premature aging syndromes caused by defective DNA repair. Thyroid state changes during aging, but underlying mechanisms remain elusive. Since thyroid hormone (TH) is a key regulator of metabolism, changes in TH signaling have widespread effects. Here, we reveal a significant common transcriptomic signature in livers from hypothyroid mice, DNA repair-deficient mice with severe (Csbm/m/Xpa-/-) or intermediate (Ercc1-/Δ-7) progeria and naturally aged mice. A strong induction of TH-inactivating deiodinase D3 and decrease of TH-activating D1 activities are observed in Csbm/m/Xpa-/- livers. Similar findings are noticed in Ercc1-/Δ-7, in naturally aged animals and in wild-type mice exposed to a chronic subtoxic dose of DNAdamaging agents. In contrast, TH signaling in muscle, heart and brain appears unaltered. These data show a strong suppression of TH signaling in specific peripheral organs in premature and normal aging, probably lowering metabolism, while other tissues appear to preserve metabolism. D3-mediated TH inactivation is unexpected, given its expression mainly in fetal tissues. Our studies highlight the importance of DNA damage as the underlying mechanism of changes in thyroid state. Tissue-specific regulation of deiodinase activities, ensuring diminished TH signaling, may contribute importantly to the protective metabolic response in aging

Tissue-Specific Suppression of Thyroid Hormone Signaling in Various Mouse Models of Aging

DNA damage contributes to the process of aging, as underscored by premature aging syndromes caused by defective DNA repair. Thyroid state changes during aging, but underlying mechanisms remain elusive. Since thyroid hormone (TH) is a key regulator of metabolism, changes in TH signaling have widespread effects. Here, we reveal a significant common transcriptomic signature in livers from hypothyroid mice, DNA repair-deficient mice with severe (Csbm/m/Xpa-/-) or intermediate (Ercc1-/Δ-7) progeria and naturally aged mice. A strong induction of TH-inactivating deiodinase D3 and decrease of TH-activating D1 activities are observed in Csbm/m/Xpa-/- livers. Similar findings are noticed in Ercc1-/Δ-7, in naturally aged animals and in wild-type mice exposed to a chronic subtoxic dose of DNA-damaging agents. In contrast, TH signaling in muscle, heart and brain appears unaltered. These data show a strong suppression of TH signaling in specific peripheral organs in premature and normal aging, probably lowering metabolism, while other tissues appear to preserve metabolism. D3-mediated TH inactivation is unexpected, given its expression mainly in fetal tissues. Our studies highlight the importance of DNA damage as the underlying mechanism of changes in thyroid state. Tissue-specific regulation of deiodinase activities, ensuring diminished TH signaling, may contribute importantly to the protective metabolic response in aging.status: publishe

Tissue-specific suppression of thyroid hormone signaling in various mouse models of aging

DNA damage contributes to the process of aging, as underscored by premature aging syndromes caused by defective DNA repair. Thyroid state changes during aging, but underlying mechanisms remain elusive. Since thyroid hormone (TH) is a key regulator of metabolism, changes in TH signaling have widespread effects. Here, we reveal a significant common transcriptomic signature in livers from hypothyroid mice, DNA repair-deficient mice with severe (Csbm/m/Xpa-/-) or intermediate (Ercc1-/Δ-7) progeria and naturally aged mice. A strong induction of TH-inactivating deiodinase D3 and decrease of TH-activating D1 activities are observed in Csbm/m/Xpa-/- livers. Similar findings are noticed in Ercc1-/Δ-7, in naturally aged animals and in wild-type mice exposed to a chronic subtoxic dose of DNAdamaging agents. In contrast, TH signaling in muscle, heart and brain appears unaltered. These data show a strong suppression of TH signaling in specific peripheral organs in premature and normal aging, probably lowering metabolism, while other tissues appear to preserve metabolism. D3-mediated TH inactivation is unexpected, given its expression mainly in fetal tissues. Our studies highlight the importance of DNA damage as the underlying mechanism of changes in thyroid state. Tissue-specific regulation of deiodinase activities, ensuring diminished TH signaling, may contribute importantly to the protective metabolic response in aging

Thyroid state in skeletal muscle of progeroid and naturally aged mice.

<p>T3 concentrations (A) and activities of D2 (B) and D3 (C) in muscle of 15-day-old WT and XAA (Csbm/m/Xpa-/-) mice (n = 3/group). T4 (D) and T3 (E) concentrations and activities of D2 (F) and D3 (G) in muscle of 18-week-old WT and MAA (Ercc1-/Δ-7) mice (n = 3/group). T4 (H) and T3 (I) concentrations and activities of D2 (J) and D3 (K) in muscle of 26-, 104-, and 130-week-old WT mice (n = 3-5/group). Values represent mean ± SE per group. * P < 0.05</p

Thyroid state in brains of progeroid and naturally aged mice.

<p>Homogenates of whole brain or hemispheres were used. T4 (A) and T3 (B) concentrations in brains of 7-, 12-, 15-, and 18-day-old WT (squares) and XAA (Csbm/m/Xpa-/-) mice (n = 3/group). Activities of D2 (C) and D3 (D) brains of 7-, 12-, 15-, and 18-day-old WT and XAA (Csbm/m/Xpa-/-) mice (n = 3/group). T4 (E) and T3 (F) concentrations and D3 activity (G) in brains of 4-, and 18-week-old WT (black bars) and MAA (Ercc-/Δ-7) (white bars) mice (n = 3/group). It was not possible to measure D2 activity due to technical constraints. Values represent mean ± SE per group. * P < 0.05; ** P < 0.01; *** P < 0.001.</p

Thyroid state in serum of progeroid and naturally aged mice.

<p>Serum T4 (A) and T3 (B) concentrations in 7-, 12-, 15-, and 18-day-old WT (squares) and XAA (Csbm/m/Xpa-/-) mice (circles) (n = 3/group). Serum T4 (C) and T3 (D) concentrations in 4-, and 18-week-old WT (black bars) and MAA (Ercc1-/Δ-7) (white bars) mice (n = 3/group). Serum T4 and T3 concentrations in 26-, 104-, and 130-week-old WT male mice (n = 3-4/group) (E). Serum TSH levels in 15-day old WT and XAA (Csbm/m/Xpa-/-) mice (F) and in 26-, 104-, and 130-week-old WT male mice (G). Values represent mean ± SE per group. * P < 0.05; ** P < 0.01; *** P < 0.001; # P = 0.054.</p

Liver D1 and D3 activity in DEHP-treated WT mice.

<p>Activities of D1 (A) and D3 (B) in 10-wk-old WT animals after exposure or not to subtoxic doses of the pro-oxidant DEHP for 2, 12 and 39 weeks. Values represent mean ± SE per group (n = 5). * P < 0.05; ** P < 0.01.</p

Schematic representation of the survival response.

<p>Several types of stress (e.g. DNA damage and aging) can trigger a differential response in various tissues. This response ensures decreased TH signalling in liver and kidney, while it preserves TH signalling in brain, muscle and heart.</p

Gene expression changes in livers from progeroid and normal aging mice.

<p>Gene expression of the T3-responsive genes Dio1 and Thrsp in 18-day-old XAA (Csbm/m/Xpa-/-) (A) and 16-week-old MAA (Ercc1-/Δ-7) mice (B). * P < 0.005; # P = 0.12. Expression profiling of a set of known T3-responsive genes in 15-day-old XAA (Csbm/m/Xpa-/-) (C) and 16-week-old MAA (Ercc1-/Δ-7) mice (D) mutants compared to age-matched controls. Values represent mean ± SE * P < 0.05; ** P < 0.005; $ P < 0.1; # P = 0.12.</p

Histological examination of haematoxylin/eosin-stained thyroid glands of 15-day-old WT and XAA (Csbm/m/Xpa-/-) (A) and 16-week-old WT and MAA (Ercc1-/Δ-7) (B) mice (all magnifications 10x).

<p>The thyroid follicles (denoted by asterisk) surrounded by thyrocytes (denoted by arrow) are similar between WT and progeria models.</p