Maternal Metabolic Syndrome Programs Mitochondrial Dysfunction via Germline Changes across Three Generations

Abstract

Maternal obesity impairs offspring health, but the responsible mechanisms are not fully established. To address this question, we fed female mice a high-fat/high-sugar diet from before conception until weaning and then followed the outcomes in the next three generations of offspring, all fed a control diet. We observed that female offspring born to obese mothers had impaired peripheral insulin signaling that was associated with mitochondrial dysfunction and altered mitochondrial dynamic and complex proteins in skeletal muscle. This mitochondrial phenotype persisted through the female germline and was passed down to the second and third generations. Our results indicate that maternal programming of metabolic disease can be passed through the female germline and that the transfer of aberrant oocyte mitochondria to subsequent generations may contribute to the increased risk for developing insulin resistance.

Figure 1. Maternal metabolic syndrome leads to glucose intolerance and altered insulin signaling in the first generation (F1) female offspring

Metabolic parameters were measured in F0-HF/HS and F0-Con mice prior to mating (A–F) and in the F1 female offspring (G–J). Body weight (A and G), body composition presented as percent fat mass (FM) and fat-free mass (FFM) (B), glucose tolerance test (C and H), and serum insulin (D and I), triglyceride (E), and cholesterol (F) were measured in mice after a 6 h fast. Western blot analysis of tyrosine phosphorylation of IRS1(tyr895) and serine phosphorylation of AKT(ser473) in F1 mixed fiber muscle (J). All data are expressed as mean ± SEM. *P < 0.05 by Student’s T-test.

Figure 2. Mitochondrial function and morphology are altered in F1-HF/HS skeletal muscles

Soleus (A–E) and lateral gastrocnemius (F–H) were isolated from eight-week old F1 mice. Representative transmission electron microscopy (TEM) images of soleus (A) and lateral gastrocnemius (F). Arrowheads depict lipid droplets, star indicates mitochondria undergoing fission, and arrows denote abnormal inner mitochondrial membrane morphology. Lipid peroxidation content measured by malondialdehyde (MDA) in soleus muscle (B). Morphological analysis of TEM images lipid content in soleus muscle (C). HADHA activity (D) and mitochondrial respiration (E) in soleus muscle. Western blot analysis of DRP1, P-DRP1(ser616), P-DRP1/DRP1 (Ratio) and OPA1 in lateral gastrocnemius (G) and electron transport chain complex content (CI = NDUFB8, CII = total complex, CIII = Core protein 2, CIV = subunit I and CV = alpha subunit) (H). All data are expressed as mean ± SEM. *P < 0.05 by Student’s T-test.

Figure 3. Mitochondrial function and morphology are altered in F1-HF/HS oocytes

Oocytes were collected from eight-week old F1 mice. Mitochondrial morphologies were analyzed from TEM images (A-C). Representative low-magnification TEM images of mitochondria for F1-Con and F1-HF/HS oocytes (A: Left). High-magnification (A: Right) images depict normal mitochondria in F1-Con (upper right panel) and abnormal mitochondria (lower right panel) in F1-HF/HS oocytes. Yellow arrowheads depict lipid droplet, yellow arrows denote abnormal inner mitochondrial membrane morphology, and red arrows indicate normal circular cristae. TEM image analysis for mitochondrial size (B) and mean roundness (C). Western blot analysis of OPA1 (D) via western blotting. Mitochondrial DNA copy number (20 single oocytes, n = 6 mice) (E). mice) ATP (F), citrate (G), and phosphocreatine (H) from 60 oocytes, n = 4 per group. All data are expressed as mean ± SEM. *P < 0.05 by Student’s T-test.

Figure 4. Altered mitochondrial morphology and dynamics and complex proteins are transferred to F3-HF/HS mice through the F2-HF/HS female germline

Lateral gastrocnemius muscle was isolated from eight-week old F2 (A–C) and F3 (D–G) offspring. Oocytes were collected from the F2 mice (D). Representative transmission electron microscopy (TEM) images of lateral gastrocnemius muscle (F2: A, F3: E). Star indicates mitochondria undergoing fission, and arrows denote abnormal inner mitochondrial membrane morphology. Western blot analysis DRP1, P-DRP1(ser616), and OPA1 in lateral gastrocnemius muscle (F2: B, F3: F) and F2-oocytes (C) and electron transport chain complex content (CI = NDUFB8, CII = total complex, CIII = Core protein 2, CIV = subunit I and CV = alpha subunit) (F2:C, F3:G). All data are expressed as mean ± SEM. *P < 0.05 by Student’s T-test.