Metabolic Profiles in Ovine Carotid Arteries with Developmental Maturation and Long-Term Hypoxia

Abstract

Background: Long-term hypoxia (LTH) is an important stressor related to health and disease during development. At different time points from fetus to adult, we are exposed to hypoxic stress because of placental insufficiency, high-altitude residence, smoking, chronic anemia, pulmonary, and heart disorders, as well as cancers. Intrauterine hypoxia can lead to fetal growth restriction and long-term sequelae such as cognitive impairments, hypertension, cardiovascular disorders, diabetes, and schizophrenia. Similarly, prolonged hypoxic exposure during adult life can lead to acute mountain sickness, chronic fatigue, chronic headache, cognitive impairment, acute cerebral and/or pulmonary edema, and death.

Aim: LTH also can lead to alteration in metabolites such as fumarate, 2-oxoglutarate, malate, and lactate, which are linked to epigenetic regulation of gene expression. Importantly, during the intrauterine life, a fetus is under a relative hypoxic environment, as compared to newborn or adult. Thus, the changes in gene expression with development from fetus to newborn to adult may be as a consequence of underlying changes in the metabolic profile because of the hypoxic environment along with developmental maturation. To examine this possibility, we examined the metabolic profile in carotid arteries from near-term fetus, newborn, and adult sheep in both normoxic and long-term hypoxic acclimatized groups.

Results: Our results demonstrate that LTH differentially regulated glucose metabolism, mitochondrial metabolism, nicotinamide cofactor metabolism, oxidative stress and antioxidants, membrane lipid hydrolysis, and free fatty acid metabolism, each of which may play a role in genetic-epigenetic regulation.

Fig 1. A. Venn diagram of carotid artery metabolites altered with developmental maturation in comparing normoxic fetus and newborn, fetus and adult, and newborn and adult.

B. Venn diagram of metabolites altered with long-term hypoxia exposure on comparing normoxic versus hypoxic fetus, newborn, and adult carotid arteries.

Fig 2. Biochemical importance plot based on Random Forest classification of metabolic profile from normoxic and hypoxic carotid arteries from (A) Fetus (B) Newborn and (C) Adults.

The metabolites are plotted according to the increasing importance to group separation to elucidate the metabolic fingerprint for hypoxia in fetal carotid arteries as compared to normoxic counterpart. N = 8 in each group.

Fig 3. Box plots of glucose metabolism pathway comparing the six study groups In each box plots the boxes from left to right represent: normoxic and hypoxic fetus (Term); normoxic and hypoxic newborn (NB); and normoxic and hypoxic adult (Adult).

The Fig also demonstrates an overview of glucose metabolism pathway. Upward red arrow means significantly (P < 0.05) higher for the noted comparison. Downward green arrow means significantly (P < 0.05) lower for the noted comparison. Upward and downward arrows together means approach significance (0.05 < P < 0.1). N = 8 in each group.

Fig 4. Box plots of the mitochondrial metabolism pathway comparing the six study groups.

In each Fig are shown from left to right: normoxic and hypoxic fetus; normoxic and hypoxic newborn (NB); and normoxic and hypoxic adult. The Fig also demonstrates an overview of mitochondrial metabolism pathway. Upward red arrow means significantly (P < 0.05) higher for the noted comparison. Downward green arrow means significantly (P < 0.05) lower for the noted comparison. Upward and downward arrows together means approach significance (0.05 < P < 0.1). N = 8 in each group.

Fig 5. Box plots of the nicotinamide cofactor metabolism pathway comparing the six study groups.

In each diagram are shown from left to right: normoxic and hypoxic fetus; normoxic and hypoxic newborn (NB); and normoxic and hypoxic adult. The Fig also demonstrates an overview of the nicotinamide cofactor metabolism pathway. Upward red arrow means significantly (P < 0.05) higher for the noted comparison. Downward green arrow means significantly (P < 0.05) lower for the noted comparison. Upward and downward arrows together means approach significance (0.05 < P < 0.1). N = 8 in each group.

Fig 6. Box plots of the oxidative stress and antioxidants metabolism pathway comparing the six study groups.

In each diagram are shown from left to right: normoxic and hypoxic fetus; normoxic and hypoxic newborn (NB); and normoxic and hypoxic adult. The Fig also demonstrates an overview of the oxidative stress and antioxidants metabolism pathway. Upward red arrow means significantly (P < 0.05) higher for the noted comparison. Downward green arrow means significantly (P < 0.05) lower for the noted comparison. Upward and downward arrows together means approach significance (0.05 < P < 0.1). N = 8 in each group.

Fig 7. Box plots of the membrane lipid hydrolysis pathway comparing the six study groups.

In each diagram are shown from left to right: normoxic and hypoxic fetus; normoxic and hypoxic newborn (NB); and normoxic and hypoxic adult. The Fig also demonstrates an overview of the membrane lipid hydrolysis pathway Upward red arrow means significantly (P < 0.05) higher for the noted comparison. Downward green arrow means significantly (P < 0.05) lower for the noted comparison. Upward and downward arrows together means approach significance (0.05 < P < 0.1). N = 8 in each group.

Fig 8. Box plots of the free fatty acid metabolism pathway comparing the six study groups.

In each diagram are shown from left to right: normoxic and hypoxic fetus; normoxic and hypoxic newborn (NB); and normoxic and hypoxic adult. The Fig also demonstrates an overview of the free fatty acid metabolism pathway. Upward red arrow means significantly (P < 0.05) higher for the noted comparison. Downward green arrow means significantly (P < 0.05) lower for the noted comparison. Upward and downward arrows together means approach significance (0.05 < P < 0.1). N = 8 in each group.