Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2011 Jan 14;6(1):e14503.
doi: 10.1371/journal.pone.0014503.

Paradoxical increase in TAG and DAG content parallel the insulin sensitizing effect of unilateral DGAT1 overexpression in rat skeletal muscle

Silvie Timmers  1 , Johan de Vogel-van den Bosch, Matthijs K C Hesselink, Denis van Beurden, Gert Schaart, Maria Joao Ferraz, Mario Losen, Pilar Martinez-Martinez, Marc H De Baets, Johannes M F G Aerts, Patrick Schrauwen
Affiliations

Paradoxical increase in TAG and DAG content parallel the insulin sensitizing effect of unilateral DGAT1 overexpression in rat skeletal muscle

Silvie Timmers et al. PLoS One. .

Abstract

Background: The involvement of muscle triacylglycerol (TAG) storage in the onset of insulin resistance is questioned and the attention has shifted towards inhibition of insulin signalling by the lipid intermediate diacylglycerol (DAG). The enzyme 1,2-acylCoA:diacylglyceroltransferase-1 (DGAT1) esterifies a fatty acyl-CoA on DAG to form TAG. Therefore, the aim of the present study was to investigate if unilateral overexpression of DGAT1 in adult rat Tibialis anterior (TA) muscle will increase conversion of the lipid intermediate DAG into TAG, thereby improving muscle insulin sensitivity.

Methodology/principal findings: The DGAT1 gene construct was injected in the left TA muscle of male rats on chow or high-fat (45% kcal) diet for three weeks, followed by application of one 800 V/cm and four 80 V/cm pulses, using the contralateral leg as sham-electroporated control. Seven days after electroporation, muscle specific insulin sensitivity was assessed with a hyperinsulinemic euglycemic clamp using 2-deoxy-[3H]glucose. Here, we provide evidence that unilateral overexpression of DGAT1 in TA muscle of male rats is associated with an increased rather than decreased DAG content. Strikingly, this increase in DAG content was accompanied by improved muscle insulin sensitivity. Interestingly, markers of muscle lipolysis and mitochondrial function were also increased in DGAT1 overexpressing muscle.

Conclusions/significance: We conclude that unilateral DGAT1 overexpression can rescue insulin sensitivity, possibly by increasing DAG and TAG turnover in skeletal muscle. In case of a proper balance between the supply and oxidation of fatty acids in skeletal muscle, the lipid intermediate DAG may not exert harmful effects on insulin signalling.

PubMed Disclaimer

Conflict of interest statement

Competing Interests: This study was funded by Top Institute Food and Nutrition. TI Food and Nutrition was formerly known as WCFS. Partners are major Dutch food companies and research organizations. A VICI (grant 918.96.618) and a VIDI (grant 917.66.359) for innovative research from the Netherlands Organization for Scientific Research (NWO) supports the work of P. Schrauwen and M. Hesselink, respectively. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Therefore, this does not alter the authors' adherence to all the PLoS ONE policies on sharing data and materials.

Figures

Figure 1
Figure 1. Electroporation of DGAT1 in TA muscle of rats on CHOW and HFD is associated with an increased partitioning of fatty acids towards IMCL.
IMCL levels after three weeks of dietary intervention, area fraction reflects the percentage of the total measured cell surface covered by lipid droplets. Data are expressed as mean ± SEM (n = 10–12). *P<0.05 CHOW-DGAT1 vs. CHOW-control, # P<0.05 HFD-DGAT1 vs. HFD-control.
Figure 2
Figure 2. Three weeks of high-fat feeding is associated with an increased TA DAG content compared to rats on CHOW.
DGAT1 overexpression leads to an increase in TA DAG content in rats on CHOW and tended to increase DAG content in rats on HFD. Data are expressed as mean ± SEM (n = 6). *P<0.05 CHOW-DGAT1 and HFD-control vs. CHOW-control.
Figure 3
Figure 3. Three weeks of high-fat feeding is not associated with an increased TA ceramide content compared to rats on CHOW.
DGAT1 overexpression does not result in an increase in TA ceramide content in rats on CHOW or HFD. Data are expressed as mean ± SEM (n = 10–12).
Figure 4
Figure 4. Three weeks of high-fat feeding compared to rats on CHOW decreased whole-body insulin sensitivity as assessed by hyperinsulinemic eulgycemic clamp.
DGAT1 overexpression in TA muscle increased muscle specific insulin sensitivity both in rats on CHOW as HFD. (A) Steady-state whole-body glucose infusion rates in rats on CHOW and HFD for three weeks. (B) 2DG uptake in TA muscle of CHOW fed rats after bolus injection of 2-deoxy-[3H]glucose under the same clamping conditions as in A. (C) 2DG uptake in TA muscle of HFD fed rats after bolus injection of 2-deoxy-[3H]glucose under the same clamping conditions as in A. Data are expressed as mean ± SEM (n = 10–12). *P<0.05 CHOW-DGAT1 and HFD-control vs. CHOW-control, # P<0.05 HFD-DGAT1 vs. HFD-control.
Figure 5
Figure 5. DGAT1 overexpression is associated with an increased mitochondrial function and biogenesis in HFD-fed rats.
(A) Western blot analysis of PGC1α (B) OXPHOS complexes and (C) UCP3 in rat TA muscle. Data are expressed as mean ± SEM (n = 10–12). # P<0.05 HFD-DGAT1 vs. HFD-control.
Figure 6
Figure 6. DGAT1 overexpression results in bigger lipid droplets in HFD-fed rats.
(A) Electron microscopy revealed an increase in lipid droplet diameter in DGAT1 overexpressing TA muscle of HFD-fed rats. (B) Western blot analysis of OXPAT in rat TA muscle. Data are expressed as mean ± SEM (n = 10–12).
Figure 7
Figure 7. The turnover of DAG and TAG is increased in the DGAT1 overexpressing TA muscle.
(A) Western blotting of ATGL, (B) CGI58 (C) and ADRP in rat TA muscle. Data are expressed as mean ± SEM (n = 10–12). # P<0.05 HFD-DGAT1 vs. HFD-control.
See this image and copyright information in PMC

References

    1. Boden G, Lebed B, Schatz M, Homko C, Lemieux S. Effects of acute changes of plasma free fatty acids on intramyocellular fat content and insulin resistance in healthy subjects. Diabetes. 2001;50:1612–1617. - PubMed
    1. Bachmann OP, Dahl DB, Brechtel K, Machann J, Haap M, et al. Effects of intravenous and dietary lipid challenge on intramyocellular lipid content and the relation with insulin sensitivity in humans. Diabetes. 2001;50:2579–2584. - PubMed
    1. Phillips DI, Caddy S, Ilic V, Fielding BA, Frayn KN, et al. Intramuscular triglyceride and muscle insulin sensitivity: evidence for a relationship in nondiabetic subjects. Metabolism. 1996;45:947–950. - PubMed
    1. Pan DA, Lillioja S, Kriketos AD, Milner MR, Baur LA, et al. Skeletal muscle triglyceride levels are inversely related to insulin action. Diabetes. 1997;46:983–988. - PubMed
    1. Perseghin G, Scifo P, De Cobelli F, Pagliato E, Battezzati A, et al. Intramyocellular triglyceride content is a determinant of in vivo insulin resistance in humans: a 1H-13C nuclear magnetic resonance spectroscopy assessment in offspring of type 2 diabetic parents. Diabetes. 1999;48:1600–1606. - PubMed

Publication types