Gestational Diabetes and Weight

Introduction

What is gestational diabetes?

In a simple definition, gestational diabetes is a kind of diabetes that occurs during pregnancy. The cause of type 1 diabetes mellitus (DM) is due to the body not being able to produce enough insulin, and the cause of type 2 DM is due to the body not utilising the insulin produced efficiently (insulin insensitivity), but these causes are ruled out in gestational diabetes. While all these factors that cause other forms of diabetes might be in place, gestational diabetes develops amidst that during pregnancy in some women. In gestational diabetes, women who were previously not diagnosed with diabetes develop serious hyperglycaemia.¹ The cause is interwoven between dysfunctional pancreatic cells not producing enough insulin and insulin insensitivity to cells. Gestational diabetes can result in such complications as the risk of type 2 DM, increased risk of cardiovascular disease, maternal death or even foetal death.¹ Overweight, obesity, age and family are the most likely risk factors for gestational diabetes mellitus (GDM).

Symptoms

There are no specific symptoms of GDM as most of the symptoms are usually common during pregnancy. Some symptoms of hyperglycaemia include increased thirst, frequent urination, tiredness and dry mouth. There is also the risk of foetal death, preeclampsia, and increased birth weight that might result in delivering the baby through caesarean section.

Obesity is a risk factor for GDM

Fat tissue releases hormones promoting insulin resistance

The two major hormones released by the fat tissues are leptin and adiponectin.³

Leptin: This is a satiety hormone secreted by the adipocytes.1 They inhibit appetite-stimulating peptides and hence reduce the uptake of glucose through the regulation of GLUT-4, a glucose transporter. However, during pregnancy, leptin increases insulin resistance by affecting the sensitivity of insulin receptors. Leptin secretion also increases during pregnancy.

Adiponectin: This is another hormone secreted by the adipocytes. It has a stronger effect on insulin resistance in GDM than leptin. It does so by activating AMP-activated protein kinase within insulin-sensitive cells.

List the hormones, and briefly explain how they cause insulin resistance

Pregnancy hormones can also promote insulin resistance

In pregnancy, the body does some forms of adjustments in order to meet up with the nutritional requirements of the growing foetus.⁴ Some of these physiological changes include adaptation to the haematological, renal, cardiovascular, respiratory and metabolic systems. During early pregnancy, there is an increased insulin sensitivity, which results in increased uptake and storage of glucose to meet the nutritional needs of the foetus through the supply of essential nutrients. However, as the pregnancy progresses, there is a decrease in insulin sensitivity brought about by the surge in pregnancy hormones that leads to insulin resistance. Some of these hormones include oestrogen, progesterone, placental lactogen, leptin, cortisol and placental growth hormones. 

List the hormones, briefly explain how they cause insulin resistance

The combination of these hormones significantly increases the likelihood of developing gestational diabetes

The combination of pregnancy hormones leads to insulin resistance. This results in increased blood glucose levels and a consequent increase in the endogenous production of glucose and breakdown of fat tissues, which further leads to elevated blood glucose levels. 

Explain that they disrupt the homeostasis of insulin and glucose regulation

Can losing excess weight prevent gestational diabetes?

Being overweight/obese is the major risk factor for gestational diabetes. Exercise, diet and general lifestyle modification are recommended to reduce the risk of gestational diabetes. Diets rich in saturated fats, red meats and refined sugars are associated with the risk of GDM, while diets rich in fibres, polyunsaturated fats and micronutrients are associated with a reduced risk of GDM.^{1, 2} It is therefore important to lose some weight when planning to get pregnant through exercise and diet modifications to reduce the risk of gestational diabetes.

Recommended that people who are trying to get pregnant lose excess weight - be careful writing this paragraph, keep in mind that body weight is a sensitive topic for many

Conclusion

Beta-cells dysfunction and insulin resistance both play roles in gestational diabetes.⁵ Beta-cells are responsible for the secretion of insulin, which increases the uptake of glucose from the blood. Dysfunctional beta-cells lead to decreased production of insulin and hence elevated blood glucose during pregnancy, which might lead to some complications like cardiovascular diseases in either the mother or the child, preeclampsia, stillbirth or even increased birth weight as a result of increased glucose uptake by the foetus which invariably increases the chances of obesity in the child. Insulin insensitivity is another cause of GDM, which is mainly due to pregnancy hormones. Obesity/overweight is a major risk factor for gestational diabetes; hence, it is recommended that you lose some weight while trying to get pregnant to reduce the risk of GDM.