High-fat diet during pregnancy promotes fetal skeletal muscle fatty acid oxidation and insulin resistance in an ovine model

Abstract

Maternal diet during pregnancy is associated with offspring metabolic risk trajectory in humans and animal models, but the prenatal origins of these effects are less clear. We examined the effects of a high-fat diet (HFD) during pregnancy on fetal skeletal muscle metabolism and metabolic risk parameters using an ovine model. White-faced ewes were fed a standardized diet containing 5% fat wt/wt (CON), or the same diet supplemented with 6% rumen-protected fats (11% total fat wt/wt; HFD) beginning 2 wk before mating until midgestation (GD75). Maternal HFD increased maternal weight gain, fetal body weight, and low-density lipoprotein levels in the uterine and umbilical circulation but had no significant effects on circulating glucose, triglycerides, or placental fatty acid transporters. Fatty acid (palmitoylcarnitine) oxidation capacity of permeabilized hindlimb muscle fibers was >50% higher in fetuses from HFD pregnancies, whereas pyruvate and maximal (mixed substrate) oxidation capacities were similar to CON. This corresponded to greater triacylglycerol content and protein expression of fatty acid transport and oxidation enzymes in fetal muscle but no significant effect on respiratory chain complexes or pyruvate dehydrogenase expression. However, serine-308 phosphorylation of insulin receptor substrate-1 was greater in fetal muscle from HFD pregnancies along with c-jun-NH₂ terminal kinase activation, consistent with prenatal inhibition of skeletal muscle insulin signaling. These results indicate that maternal high-fat feeding shifts fetal skeletal muscle metabolism toward a greater capacity for fatty acid over glucose utilization and favors prenatal development of insulin resistance, which may predispose offspring to metabolic syndrome later in life.NEW & NOTEWORTHY Maternal diet during pregnancy is associated with offspring metabolic risk trajectory in humans and animal models, but the prenatal origins of these effects are less clear. This study examined the effects of a high-fat diet during pregnancy on metabolic risk parameters using a new sheep model. Results align with findings previously reported in nonhuman primates, demonstrating changes in fetal skeletal muscle metabolism that may predispose offspring to metabolic syndrome later in life.

Keywords: fetal programming; maternal obesity; metabolic syndrome; nutrition; skeletal muscle.

Figure 1.

Placental fatty acid transporter expression. Maternal high-fat diet (HFD) had no effect on the placental (cotyledon) protein expression of fatty acid transport protein 1 (FATP1; A), FATP4 (B), or the fatty acid translocase CD36 (C) compared with control (CON). Data are means ± SE (n = 5 or 6/group) expression normalized to total sample protein by amido black (AB) staining.

Figure 2.

Fetal skeletal muscle fatty acid transporter expression. Maternal high-fat diet (HFD) led to greater fetal M. biceps femoris protein expression of fatty acid transport protein 1 (FATP1; A), FATP4 (B), fatty acid translocase/CD36 (C), and the plasmalemmal fatty acid binding protein (FABPpm; D) compared with control (CON) fetuses. Data are means ± SE (n = 5–9/group) of relative expression normalized to total sample protein by amido black (AB) staining. #P < 0.10, *P < 0.05.

Figure 3.

Fetal skeletal muscle oxidative capacities. Maternal high-fat diet (HFD) had no significant effect on the capacity of permeabilized fetal M. biceps femoris fibers to oxidize carbohydrates (pyruvate + malate; CHO) during OXPHOS (+ ADP) or LEAK states (no ADP; A) but increased capacities to oxidize fatty acids (palmitoylcarnitine + malate; FAT) during both states (B), which equates to a much greater relative capacity to oxidize fats over carbohydrates during OXPHOS (C). Maternal HFD decreased OXPHOS coupling control with both substrates (main effect of diet by ANOVA; D) but had no effect on maximal OXPHOS-linked oxidative capacity supported by a combination of CHO, FAT, and amino acid substrates (E). Data are means ± SE (n = 5–9/group) of oxygen consumption rates expressed per milligram of permeabilized muscle tissue. *P < 0.05. CHO, carbohydrate; OXPHOS, oxidative phosphorylation.

Figure 4.

Expression of oxidative metabolism enzymes in fetal skeletal muscle. Maternal high-fat diet (HFD) led to greater fetal M. biceps femoris expression of enzymes involved in the transport and oxidation of long-chain fatty acids (A) but had no effect on the expression or phosphorylation of pyruvate dehydrogenase (B), or electron transport chain complexes (C). Muscle triacylglycerol content (D) and mRNA expression of PPARγ, a transcriptional regulator of fetal muscle fatty acid metabolism (E), were also greater in HFD compared with control (CON) fetuses. Data are means ± SE (n = 5–9/group) of relative expression normalized to total sample protein by amido black (AB) staining. *P < 0.05. ACADVL, very long-chain acyl-CoA dehydrogenase; CI-V, respiratory chain complexes I-V; CPT1B, carnitine palmitoyltransferase-1β; HADHA long-chain hydroxyacyl-CoA dehydrogenase-A; (p)PDH, (phospho) pyruvate dehydrogenase; PDK1, PDH kinase-1; PGC1α, PPARγ coactivator 1-α; PPAR, peroxisome proliferator -activated receptor; TAG, triacylglycerol.

Figure 5.

Fetal muscle insulin signaling. Maternal high-fat diet (HFD) decrease protein expression of insulin receptor substrate-1 (IRS-1) but increased its phosphorylation at serine-307 (A) along with the phosphorylated (active) c-Jun NH₂-terminal kinase (JNK1/2; B). In contrast, maternal HFD had no effect on IRS-1 phosphorylation at serine-1101 (C) or protein kinase C (PKC; D). Data are means ± SE (n = 5–9/group) of relative expression normalized to total sample protein by amido black (AB) staining or ratio of phosphorylated:total enzyme expression. *P < 0.05.

Figure 6.

Fetal liver triglyceride content and enzyme expression. Maternal high-fat diet (HFD) increased fetal liver triglyceride content (A) but had no effect on protein expression of fatty acid transporter-1 (FATP1) or FATP4 (B), expression or serine-307 phosphorylation of insulin receptor substrate-1 (IRS-1; C), or the gluconeogenesis enzyme phosphoenolpyruvate carboxykinase-1 (PCK1; D). Data are means ± SE (n = 5–9/group) of relative expression normalized to total sample protein by amido black (AB) staining or ratio of phosphorylated to total enzyme expression. *P < 0.05.