In Vitro Palmitate Treatment of Myotubes from Postmenopausal Women Leads to Ceramide Accumulation, Inflammation and Affected Insulin Signaling

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.

Fenofibrate improves high-fat diet-induced and palmitate-induced endoplasmic reticulum stress and inflammation in skeletal muscle

“…Our study also showed that FA pretreatment could significantly decrease the mRNA expression of NFκB (Fig. 5A), similar to the results of Abildgaard et al [28].…”

“…Abildgaard et al [28] proved that palmitate-treated myotubes showed increased phosphorylation of JNK. Our results also showed that PA treatment could upregulate the phosphorylation of JNK, which positively correlated with the severity of IR (p-JNK/JNK).…”

Reduced Fat Oxidation During Exercise in Post-Menopausal Overweight-Obese Women with Higher Lipid Accumulation Product Index

“…In vitro studies revealed that the accumulation of lipid intermediates in peripheral tissues, mainly muscle tissue, leads to low fat oxidation and altered fatty acid metabolism through increased inflammatory pathway [30]. In this way, an in vitro study with myotubes from postmenopausal women treated with fatty acid leads to ceramide accumulation and inflammation, reducing insulin signaling [31]. Here, we believed that the higher CRP levels identified in MUO postmenopausal women in our study may contribute to low fat oxidation rate during exercise.…”

Metabolic control and sex: A focus on inflammatory‐linked mediators

“…Women have greater insulin‐stimulated leg glucose uptake than matched men despite having higher intramyocellular triacylglycerol content (Hoeg et al, ), whereas increasing lipid levels through lipid infusion results in less insulin resistance of skeletal muscle glucose uptake in women than men (Hoeg et al, ). Interestingly, skeletal muscle cells from premenopausal women (high‐oestrogen environment) showed a lower stress response after prolonged in vitro fatty acid (palmitate) treatment compared with skeletal muscle cells from postmenopausal women (low‐oestrogen environment; Abildgaard et al, ). Although Torres et al () recently showed that oestrogen has a direct impact on the mitochondrial membrane viscosity and improves bioenergetic function of the mitochondrion, suggesting that the sex‐mediated differences in lipid tolerability could be partly mediated by oestrogen.…”