Metabolomic Insights into Canine Pregnancy: Understanding Mid- and Late-Gestation Changes

Metabolism during pregnancy is a dynamic and tightly regulated process designed to support rapid fetal growth and development. In dogs, this process is particularly intense due to the short gestation period and high fetal demands. Metabolomics, an advanced analytical approach that evaluates metabolites in blood serum, provides a comprehensive understanding of systemic metabolic changes during pregnancy^1,2,3. This approach enables veterinarians to gain deeper insights into physiological adaptations and their clinical implications. 

Metabolic Programming During Pregnancy 

Pregnancy induces several metabolic adaptations that allow the dam to maintain euglycemia while supporting fetal development. These include increased hepatic glucose production, reduced peripheral insulin sensitivity, and relatively stable hepatic insulin responsiveness¹. Together, these changes ensure a continuous supply of glucose to the fetuses despite increasing nutritional demands. 

Protein metabolism also undergoes significant changes, with increased protein deposition in maternal and fetal tissues, particularly during the third trimester. Additionally, hormonal factors such as leptin rise in response to increased food intake, although noticeable body weight gain may occur only in late pregnancy^1,4. 

Metabolomic Clustering: Understanding Patterns 

The study identified five distinct clusters of metabolic parameters based on their temporal patterns. Clusters 1, 2, and 3 are particularly relevant for understanding changes during mid- and late pregnancy¹. 

Cluster 1: Parameters Elevated in Mid-Pregnancy 

Mid-pregnancy is characterized by increased concentrations of total fatty acids and specific lipid fractions. These changes reflect the growing energy demands of the fetuses and the need for substrates essential for development¹. 

Polyunsaturated fatty acids (PUFAs), including omega-3 and omega-6 fatty acids, are significantly elevated during this stage. These fatty acids play a crucial role in the development of the nervous system, retina, and other vital organs. Docosahexaenoic acid (DHA), in particular, is essential for brain development and constitutes a significant proportion of brain lipids¹. 

Cholesterol levels, including free and total cholesterol, also peak during mid-pregnancy. Lipoprotein dynamics show complex patterns, with certain components such as LDL and HDL lipids reaching their highest levels during this phase before declining later. 

An important clinical marker, glycoprotein acetyls (GlycA), also peaks in mid-pregnancy, indicating increased systemic inflammatory activity associated with placentation [36]. This rise is consistent with increased acute-phase proteins observed during pregnancy. 

Phenylalanine is the only amino acid showing a marked increase during this stage. It plays a critical role in protein synthesis and neurotransmitter production, underscoring its importance in fetal development⁵. 

Cluster 2: Parameters Reduced in Mid-Pregnancy 

In contrast, certain metabolites such as oleic acid and specific lipids associated with very low-density lipoproteins (VLDL) show a decline during mid-pregnancy. These reductions may reflect shifts in lipid utilization and transport as the maternal system adapts to fetal demands¹. 

Understanding these decreases is important for clinicians, as they may represent normal physiological adaptations rather than pathological deficiencies. 

Cluster 3: Parameters Elevated in Late Pregnancy 

Late pregnancy is marked by significant metabolic shifts, particularly in glucose and lipid metabolism. Insulin resistance becomes more pronounced, leading to increased blood glucose levels^1,6. Despite this, gestational diabetes is rare in dogs, suggesting effective compensatory mechanisms. 

Triglycerides, including total, LDL, and VLDL triglycerides, peak during this stage, reflecting increased lipid mobilization to support fetal growth. These findings align with observations in human pregnancies, where lipid levels rise progressively until delivery¹. 

Clinical Interpretation and Practical Relevance 

The metabolomic changes observed during pregnancy highlight the importance of stage-specific nutritional and clinical management. Elevated fatty acids and lipids in mid-pregnancy indicate the need for adequate dietary fat intake, particularly essential fatty acids. 

In late pregnancy, increased glucose and triglyceride levels emphasize the importance of monitoring metabolic health to prevent complications. Although certain conditions such as gestational diabetes, are rare in dogs, understanding these metabolic trends can aid in early detection of abnormalities¹. 

Conclusion 

Metabolomic profiling provides valuable insights into the complex metabolic adaptations occurring during canine pregnancy. The identification of distinct clusters of metabolic changes allows veterinarians to better understand the physiological demands of each stage. By integrating this knowledge into clinical practice, veterinarians can optimize nutritional strategies, improve monitoring, and enhance reproductive outcomes. 

Reference 

1. Arlt SP, Ottka C, Lohi H, Hinderer J, Lüdeke J, Müller E, Weber C, Kohn B, Bartel A. Metabolomics during canine pregnancy and lactation. PloS one. 2023 May 10;18(5):e0284570. https://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0284570&type=printable 

2. Ottka C, Vapalahti K, Puurunen J, Vahtera L, Lohi H. A novel canine nuclear magnetic resonance spectroscopy‐based metabolomics platform: validation and sample handling. Veterinary Clinical Pathology. 2021 Sep;50(3):410-26. https://onlinelibrary.wiley.com/doi/pdf/10.1111%2Fvcp.12954 

3. Puurunen J, Ottka C, Salonen M, Niskanen JE, Lohi H. Age, breed, sex and diet influence serum metabolite profiles of 2000 pet dogs. Royal Society Open Science. 2022 Feb 1;9(2). https://royalsocietypublishing.org/rsos/article/9/2/211642/96821 

4. Troisi A, Cardinali L, Menchetti L, Speranza R, Verstegen JP, Polisca A. Serum concentrations of leptin in pregnant and non‐pregnant bitches. Reproduction in Domestic Animals. 2020 Apr;55(4):454-9. https://cris.unibo.it/bitstream/11585/801206/5/troisi2020.pdf 

5.  Connelly MA, Otvos JD, Shalaurova I, Playford MP, Mehta NN. GlycA, a novel biomarker of systemic inflammation and cardiovascular disease risk. Journal of translational medicine. 2017 Oct 27;15(1):219. https://link.springer.com/content/pdf/10.1186/s12967-017-1321-6.pdf 
6. Behrend E, Holford A, Lathan P, Rucinsky R, Schulman R. 2018 AAHA diabetes management guidelines for dogs and cats. Journal of the American Animal Hospital Association. 2018 Jan 1;54(1):1-21. https://www.drlawrenvet.com/s/diabetes-guidelines_final.pdf