Pregnancy and Insulin Regulation

Placenta and Foetal Development

• The rate of transfer of nutrients across the placenta to the foetus depends on their concentration in the maternal circulation.
• The environment in which the foetus develops is controlled by maternal metabolism, which changes throughout pregnancy to ensure:
  • The foetus is supplied with the range of nutrients it requires.
  • Nutrients are supplied at the appropriate rate for each stage of development.
  • Maternal nutrient homeostasis is maintained with minimal disturbances.
  • The foetus is buffered from any major disturbances in maternal nutrient supply.

Maternal Metabolism During Pregnancy

• Maternal metabolism changes during pregnancy, with the magnitude of the effect depending on the stage of pregnancy.
• These changes are long-term adaptive responses of maternal metabolism that are hormonally mediated.
• Hormones involved include maternal insulin and foetal-placental unit hormones such as oestrogens, progesterone, and placental lactogen.

Role of Insulin

• Insulin plays a major role in controlling the changes in maternal metabolism that occur in pregnancy.
• Insulin concentration in the maternal circulation increases as pregnancy proceeds, promoting the uptake and storage of nutrients, largely as fat in maternal adipose tissue.

Role of Foetal-Placental Hormones

• Foetal-placental hormones become increasingly important as pregnancy proceeds, opposing the actions of insulin.
• These hormones have effects on maternal metabolism that are anti-insulin.

Metabolic Changes During Pregnancy

• During the first half of pregnancy, maternal nutrient homeostasis changes to increase maternal nutrient stores (especially adipose tissue) in preparation for the more rapid growth of the foetus, birth, and subsequent lactation.

Gestational Diabetes

• Gestational diabetes is a type of diabetes that develops during pregnancy in women who didn't previously have diabetes.
• It affects how cells use sugar (glucose), causing high blood sugar levels that can affect both the mother and the baby.
• The placenta produces high levels of hormones that impair insulin function, leading to elevated blood sugar levels.
• If the pancreas can't keep up with the increased demand for insulin during pregnancy, blood sugar levels rise too high, resulting in gestational diabetes.

Diagnosis and Management of Gestational Diabetes

• Gestational diabetes is usually asymptomatic, so screening is essential during pregnancy.
• Initial screening involves a glucose challenge test (GCT) between weeks 24 and 28 of pregnancy.
• If the results are higher than normal, further testing is required, including a follow-up glucose tolerance test (GTT).

Metabolic Response to Exercise

• The body needs to meet the acute oxygen and fuel demands of cardiac and skeletal muscle during exercise and ensure that the end products of metabolism are removed.
• The metabolic response to exercise ensures:
  • The increased energy demands of skeletal and cardiac muscle are met by mobilization of fuel molecules from energy stores.
  • There are minimal disturbances to homeostasis by keeping the rate of mobilization equal to the rate of utilization.
  • The glucose supply to the brain is maintained (prevent hypoglycaemia).
  • The end products of metabolism are removed as quickly as possible.

Energy Requirements of Exercise

• The energy requirements of exercise largely reflect the increased activity of skeletal and cardiac muscles.
• The energy for muscle contraction comes from the hydrolysis of ATP.
• The rate of ATP turnover in skeletal muscle increases during exercise, and the energy for muscle contraction is regenerated from ADP by various mechanisms.