Gestational Diabetes Is Characterized by Reduced Mitochondrial Protein Expression and Altered Calcium Signaling Proteins in Skeletal Muscle

The rising prevalence of gestational diabetes mellitus (GDM) affects up to 18% of pregnant women with immediate and long-term metabolic consequences for both mother and infant. Abnormal glucose uptake and lipid oxidation are hallmark features of GDM prompting us to use an exploratory proteomics approach to investigate the cellular mechanisms underlying differences in skeletal muscle metabolism between obese pregnant women with GDM (OGDM) and obese pregnant women with normal glucose tolerance (ONGT). Functional validation was performed in a second cohort of obese OGDM and ONGT pregnant women. Quantitative proteomic analysis in rectus abdominus skeletal muscle tissue collected at delivery revealed reduced protein content of mitochondrial complex I (C-I) subunits (NDUFS3, NDUFV2) and altered content of proteins involved in calcium homeostasis/signaling (calcineurin A, α1-syntrophin, annexin A4) in OGDM (n = 6) vs. ONGT (n = 6). Follow-up analyses showed reduced enzymatic activity of mitochondrial complexes C-I, C-III, and C-IV (−60–75%) in the OGDM (n = 8) compared with ONGT (n = 10) subjects, though no differences were observed for mitochondrial complex protein content. Upstream regulators of mitochondrial biogenesis and oxidative phosphorylation were not different between groups. However, AMPK phosphorylation was dramatically reduced by 75% in the OGDM women. These data suggest that GDM is associated with reduced skeletal muscle oxidative phosphorylation and disordered calcium homeostasis. These relationships deserve further attention as they may represent novel risk factors for development of GDM and may have implications on the effectiveness of physical activity interventions on both treatment strategies for GDM and for prevention of type 2 diabetes postpartum

Clinical characteristics of the subjects for Study 2.

<p>Data are mean ± SEM. OGTT, oral glucose tolerance test. Independent <i>t</i>-test *<i>P</i><0.05.</p><p>Clinical characteristics of the subjects for Study 2.</p

Mitochondrial respiratory chain complex proteins are not different between ONGT and OGDM women.

<p>Complex I (<i>A</i>), complex II (<i>B</i>), complex III (<i>C</i>), complex IV (<i>D</i>). Representative Western blots where calnexin is used as loading control (<i>E</i>).</p

AMPK phosphorylation is reduced in OGDM women, though regulators of mitochondrial biogenesis are not.

<p>Quantitative bar graphs of PPARα (<i>A</i>) and PGC-1α (<i>B</i>), total AMPK (<i>C</i>), and phospho-AMPK (<i>D</i>) protein content in pyramidalis muscle collected during scheduled cesarean section. Representative Western blots where calnexin is used as loading control (<i>E</i>). Data are mean ± SEM. *<i>P</i><0.05 <i>vs</i>. NGT.</p

Mitochondrial enzyme activity is reduced in skeletal muscle of OGDM women.

<p>Quantitative bar graphs of mitochondrial DNA copy number (<i>A</i>) and enzyme activity of citrate synthase (<i>B</i>) complex I (<i>C</i>), complex II (<i>D</i>), complex III (<i>E</i>), and complex IV (<i>F</i>) of the respiratory chain in pyramidalis muscle collected during scheduled cesarean section. Data are mean ± SEM. *<i>P</i><0.05 <i>vs</i>. NGT.</p

Work flow of statistical analysis of single proteins.

<p>Work flow of statistical analysis of single proteins.</p