Obesity-induced inflammation is associated with alterations in subcellular zinc pools and premature mammary gland involution in lactating mice

Stephen R. Hennigar, Vanessa Velasquez, Shannon Kelleher

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Abstract

Background: Lactation failure is common in overweight and obesewomen; however, the precisemechanism remains unknown. Objective: We tested the hypothesis that obesity-induced inflammation in the mammary gland (MG) redistributes subcellular zinc pools to promote cell death of mammary epithelial cells (MECs) and premature involution. Methods: Female DBA/2J mice were fed a high-fat (obese; 45% kcal from fat, n = 60) or control diet (lean; 10% kcal from fat, n = 50) for 5 wk and bred. MG cytokines and macrophage infiltration were determined by reverse transcriptasepolymerase chain reaction and F4/80 staining, respectively. Zinc concentration was analyzed by atomic absorption spectroscopy, and zinc transporters and markers of endoplasmic reticulum (ER) stress, autophagy, and involution were measured by immunoblot. To confirm effects of inflammation, tumor necrosis factor-a (TNF) or vehicle was injected into adjacent MGs of lean lactating C57BL/6 mice (n = 5) and cultured MECs (HC11 cells) were treated with TNF in vitro. Results: Seventy-seven percent of obese mice failed to lactate (lean: 39%; P < 0.001). Obese mice capable of lactating had greater macrophage infiltration (obese: 135 6 40.4 macrophages/mm2; lean: 63.8 6 8.9 macrophages/mm2; P < 0.001) and elevated TNF expression (P < 0.05), concurrent with lower zrt- irt-like protein 7 abundance (P < 0.05) and higher ER zinc concentration (obese: 0.36 6 0.004 μg Zn/mg protein; lean: 0.30 6 0.02 μg Zn/mg protein; P < 0.05) compared with lean mice. Heat shock protein 5 (HSPA5) expression (P < 0.05) was suppressed in the MG of obese mice, which was consistent with HSPA5 suppression in TNF-injected MGs (P < 0.01) and MECs treated with TNF in vitro (P < 0.01). Moreover, obesity increased lysosomal activity (P < 0.05) and autophagy in the MG, which corresponded to increased zinc transporter 2 abundance and lysosomal zinc concentration compared with lean mice (obese: 0.20 6 0.02 μg Zn/mg protein; lean: 0.14 6 0.01 μg Zn/mg protein; P < 0.05). Importantly, MGs of obese mice exhibited markers of apoptosis (P = 0.05) and involution (P < 0.01), which were not observed in lean mice. Conclusions: Diet-induced obesity created a proinflammatoryMGmicroenvironment inmice, whichwas associated with zincmediated ER stress and autophagy and the activation of premature involution.

Original languageEnglish (US)
Pages (from-to)1999-2005
Number of pages7
JournalJournal of Nutrition
Volume145
Issue number9
DOIs
StatePublished - Jan 1 2015

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Obese Mice
Human Mammary Glands
Zinc
Tumor Necrosis Factor-alpha
Obesity
Inflammation
Autophagy
Macrophages
Endoplasmic Reticulum Stress
Breast
Epithelial Cells
Fats
Proteins
Diet
Inbred DBA Mouse
Inbred C57BL Mouse
Lactation
Endoplasmic Reticulum
Lactic Acid
Spectrum Analysis

All Science Journal Classification (ASJC) codes

  • Medicine (miscellaneous)
  • Nutrition and Dietetics

Cite this

Hennigar, Stephen R. ; Velasquez, Vanessa ; Kelleher, Shannon. / Obesity-induced inflammation is associated with alterations in subcellular zinc pools and premature mammary gland involution in lactating mice. In: Journal of Nutrition. 2015 ; Vol. 145, No. 9. pp. 1999-2005.
@article{d99ecf9bf8084c3b970f7d69491b89df,
title = "Obesity-induced inflammation is associated with alterations in subcellular zinc pools and premature mammary gland involution in lactating mice",
abstract = "Background: Lactation failure is common in overweight and obesewomen; however, the precisemechanism remains unknown. Objective: We tested the hypothesis that obesity-induced inflammation in the mammary gland (MG) redistributes subcellular zinc pools to promote cell death of mammary epithelial cells (MECs) and premature involution. Methods: Female DBA/2J mice were fed a high-fat (obese; 45{\%} kcal from fat, n = 60) or control diet (lean; 10{\%} kcal from fat, n = 50) for 5 wk and bred. MG cytokines and macrophage infiltration were determined by reverse transcriptasepolymerase chain reaction and F4/80 staining, respectively. Zinc concentration was analyzed by atomic absorption spectroscopy, and zinc transporters and markers of endoplasmic reticulum (ER) stress, autophagy, and involution were measured by immunoblot. To confirm effects of inflammation, tumor necrosis factor-a (TNF) or vehicle was injected into adjacent MGs of lean lactating C57BL/6 mice (n = 5) and cultured MECs (HC11 cells) were treated with TNF in vitro. Results: Seventy-seven percent of obese mice failed to lactate (lean: 39{\%}; P < 0.001). Obese mice capable of lactating had greater macrophage infiltration (obese: 135 6 40.4 macrophages/mm2; lean: 63.8 6 8.9 macrophages/mm2; P < 0.001) and elevated TNF expression (P < 0.05), concurrent with lower zrt- irt-like protein 7 abundance (P < 0.05) and higher ER zinc concentration (obese: 0.36 6 0.004 μg Zn/mg protein; lean: 0.30 6 0.02 μg Zn/mg protein; P < 0.05) compared with lean mice. Heat shock protein 5 (HSPA5) expression (P < 0.05) was suppressed in the MG of obese mice, which was consistent with HSPA5 suppression in TNF-injected MGs (P < 0.01) and MECs treated with TNF in vitro (P < 0.01). Moreover, obesity increased lysosomal activity (P < 0.05) and autophagy in the MG, which corresponded to increased zinc transporter 2 abundance and lysosomal zinc concentration compared with lean mice (obese: 0.20 6 0.02 μg Zn/mg protein; lean: 0.14 6 0.01 μg Zn/mg protein; P < 0.05). Importantly, MGs of obese mice exhibited markers of apoptosis (P = 0.05) and involution (P < 0.01), which were not observed in lean mice. Conclusions: Diet-induced obesity created a proinflammatoryMGmicroenvironment inmice, whichwas associated with zincmediated ER stress and autophagy and the activation of premature involution.",
author = "Hennigar, {Stephen R.} and Vanessa Velasquez and Shannon Kelleher",
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Obesity-induced inflammation is associated with alterations in subcellular zinc pools and premature mammary gland involution in lactating mice. / Hennigar, Stephen R.; Velasquez, Vanessa; Kelleher, Shannon.

In: Journal of Nutrition, Vol. 145, No. 9, 01.01.2015, p. 1999-2005.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Obesity-induced inflammation is associated with alterations in subcellular zinc pools and premature mammary gland involution in lactating mice

AU - Hennigar, Stephen R.

AU - Velasquez, Vanessa

AU - Kelleher, Shannon

PY - 2015/1/1

Y1 - 2015/1/1

N2 - Background: Lactation failure is common in overweight and obesewomen; however, the precisemechanism remains unknown. Objective: We tested the hypothesis that obesity-induced inflammation in the mammary gland (MG) redistributes subcellular zinc pools to promote cell death of mammary epithelial cells (MECs) and premature involution. Methods: Female DBA/2J mice were fed a high-fat (obese; 45% kcal from fat, n = 60) or control diet (lean; 10% kcal from fat, n = 50) for 5 wk and bred. MG cytokines and macrophage infiltration were determined by reverse transcriptasepolymerase chain reaction and F4/80 staining, respectively. Zinc concentration was analyzed by atomic absorption spectroscopy, and zinc transporters and markers of endoplasmic reticulum (ER) stress, autophagy, and involution were measured by immunoblot. To confirm effects of inflammation, tumor necrosis factor-a (TNF) or vehicle was injected into adjacent MGs of lean lactating C57BL/6 mice (n = 5) and cultured MECs (HC11 cells) were treated with TNF in vitro. Results: Seventy-seven percent of obese mice failed to lactate (lean: 39%; P < 0.001). Obese mice capable of lactating had greater macrophage infiltration (obese: 135 6 40.4 macrophages/mm2; lean: 63.8 6 8.9 macrophages/mm2; P < 0.001) and elevated TNF expression (P < 0.05), concurrent with lower zrt- irt-like protein 7 abundance (P < 0.05) and higher ER zinc concentration (obese: 0.36 6 0.004 μg Zn/mg protein; lean: 0.30 6 0.02 μg Zn/mg protein; P < 0.05) compared with lean mice. Heat shock protein 5 (HSPA5) expression (P < 0.05) was suppressed in the MG of obese mice, which was consistent with HSPA5 suppression in TNF-injected MGs (P < 0.01) and MECs treated with TNF in vitro (P < 0.01). Moreover, obesity increased lysosomal activity (P < 0.05) and autophagy in the MG, which corresponded to increased zinc transporter 2 abundance and lysosomal zinc concentration compared with lean mice (obese: 0.20 6 0.02 μg Zn/mg protein; lean: 0.14 6 0.01 μg Zn/mg protein; P < 0.05). Importantly, MGs of obese mice exhibited markers of apoptosis (P = 0.05) and involution (P < 0.01), which were not observed in lean mice. Conclusions: Diet-induced obesity created a proinflammatoryMGmicroenvironment inmice, whichwas associated with zincmediated ER stress and autophagy and the activation of premature involution.

AB - Background: Lactation failure is common in overweight and obesewomen; however, the precisemechanism remains unknown. Objective: We tested the hypothesis that obesity-induced inflammation in the mammary gland (MG) redistributes subcellular zinc pools to promote cell death of mammary epithelial cells (MECs) and premature involution. Methods: Female DBA/2J mice were fed a high-fat (obese; 45% kcal from fat, n = 60) or control diet (lean; 10% kcal from fat, n = 50) for 5 wk and bred. MG cytokines and macrophage infiltration were determined by reverse transcriptasepolymerase chain reaction and F4/80 staining, respectively. Zinc concentration was analyzed by atomic absorption spectroscopy, and zinc transporters and markers of endoplasmic reticulum (ER) stress, autophagy, and involution were measured by immunoblot. To confirm effects of inflammation, tumor necrosis factor-a (TNF) or vehicle was injected into adjacent MGs of lean lactating C57BL/6 mice (n = 5) and cultured MECs (HC11 cells) were treated with TNF in vitro. Results: Seventy-seven percent of obese mice failed to lactate (lean: 39%; P < 0.001). Obese mice capable of lactating had greater macrophage infiltration (obese: 135 6 40.4 macrophages/mm2; lean: 63.8 6 8.9 macrophages/mm2; P < 0.001) and elevated TNF expression (P < 0.05), concurrent with lower zrt- irt-like protein 7 abundance (P < 0.05) and higher ER zinc concentration (obese: 0.36 6 0.004 μg Zn/mg protein; lean: 0.30 6 0.02 μg Zn/mg protein; P < 0.05) compared with lean mice. Heat shock protein 5 (HSPA5) expression (P < 0.05) was suppressed in the MG of obese mice, which was consistent with HSPA5 suppression in TNF-injected MGs (P < 0.01) and MECs treated with TNF in vitro (P < 0.01). Moreover, obesity increased lysosomal activity (P < 0.05) and autophagy in the MG, which corresponded to increased zinc transporter 2 abundance and lysosomal zinc concentration compared with lean mice (obese: 0.20 6 0.02 μg Zn/mg protein; lean: 0.14 6 0.01 μg Zn/mg protein; P < 0.05). Importantly, MGs of obese mice exhibited markers of apoptosis (P = 0.05) and involution (P < 0.01), which were not observed in lean mice. Conclusions: Diet-induced obesity created a proinflammatoryMGmicroenvironment inmice, whichwas associated with zincmediated ER stress and autophagy and the activation of premature involution.

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