In vitro palmitate treatment of myotubes from postmenopausal women leads to ceramide accumulation, inflammation and affected insulin signaling.

Julie Abildgaard,Katherine G Langley,Bente Klarlund Pedersen,Anette T Pedersen,Birgitte Lindegaard,Camilla Scheele,Darren C Henstridge,Darcy Johannsen

doi:10.1371/journal.pone.0101555

Julie Abildgaard, Katherine G Langley + Show 6 more

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https://doi.org/10.1371/journal.pone.0101555

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Journal: PloS one	Publication Date: Jul 7, 2014
Citations: 59	License type: CC BY 4.0

Affiliation: Rigshospitalet, Baker IDI Heart and Diabetes Institute

Abstract

Menopause is associated with an increased incidence of insulin resistance and metabolic diseases. In a chronic palmitate treatment model, we investigated the role of skeletal muscle fatty acid exposure in relation to the metabolic deterioration observed with menopause. Human skeletal muscle satellite cells were isolated from premenopausal (n = 6) and postmenopausal (n = 5) women. In an in vitro model, the myotubes were treated with palmitate (300 µM) for one-, two- or three days during differentiation. Effects on lipid accumulation, inflammation and insulin signaling were studied. Palmitate treatment led to a 108% (CI 95%: 50%; 267%) increase in intramyocellular ceramide in the myotubes from the postmenopausal women (post-myotubes) compared with a 26% (CI 95%: −57%; 96%) increase in myotubes from the premenopausal women (pre-myotubes), (p<0.05). Furthermore, post-myotubes had a 22% (CI 95%: 4%; 34%) increase in pJNK (p = 0.04) and a 114% (CI 95%: 50%; 177%) increase in Hsp70 protein expression (p = 0.03) after three days of palmitate treatment, compared with pre-myotubes, in which no increase in either pJNK (−12% (CI 95: −26%; 2%)) or Hsp70 (7% (CI 95: −78%; 91%)) was detected. Furthermore, post-myotubes showed a blunted insulin stimulated phosphorylation of AS160 in response to chronic palmitate treatment compared with pre-myotubes (p = 0.02). The increased intramyocellular ceramide content in the post-myotubes was associated with a significantly higher mRNA expression of Serine Palmitoyltransferase1 (SPT1) after one day of palmitate treatment (p = 0.03) in post-myotubes compared with pre-myotubes. Our findings indicate that post-myotubes are more prone to develop lipid accumulation and defective insulin signaling following chronic saturated fatty acid exposure as compared to pre-myotubes.

Highlights

At the time of menopausal transition women experience a significant increase in the incidence of metabolic diseases including metabolic syndrome [1,2], diabetes [3] and cardiovascular disease [4,5,6]
The increased intramyocellular ceramide content was primarily driven by an increase in Cer16:0, which was responsible for 61% of the total ceramide content after 3 days of palmitate treatment
All subspecies of ceramide were significantly increased by palmitate treatment, except from Cer24:1, Inflammatory and cell stress response to palmitate stimulation

Summary

Introduction

At the time of menopausal transition women experience a significant increase in the incidence of metabolic diseases including metabolic syndrome [1,2], diabetes [3] and cardiovascular disease [4,5,6]. The increased incidence of metabolic diseases during menopause is associated with changes in body composition, as postmenopausal women have decreased skeletal muscle mass [7,8,9] as well as increased visceral fat mass [9,10]. As a consequence of inadequate fat oxidation, excess adiposity often leads to ectopic fat storage of lipid metabolites including triacylglycerols (TAGs), diacylglycerols (DAGs) and ceramides in metabolic tissues such as skeletal muscle. These stored metabolites could be a contributing factor to the increasing insulin resistance observed after the menopausal transition. The roles of TAGs and DAGs in the development of insulin resistance are more controversial [18,21,22]

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