The changes in immune cells concentration during the progression of pre-diabetes to type 2 diabetes in a diet-induced pre-diabetic rat model.
Mzimela, Nomusa Christina.
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T2D has been discovered to be preceded by a long-lasting condition known as prediabetes. The primary cause of prediabetes and T2D has also been shown to be continuous consumption of unhealthy diets and living a sedentary lifestyle. Type 2 diabetic patients have been discovered to have a supressed immune system, but it is still debatable whether immune activation begins at the pre-diabetes stage or during overt T2D. According to literature, T2D is a result of elevated levels of glucose known as hyperglycaemia caused by a condition called insulin resistance. Additionally, T2D has also been shown to be characterised by increased levels of triglycerides, low density lipoproteins (LDL) and decreased levels of high-density lipoproteins (HDL). Insulin resistance then causes metabolic and signalling pathways such as oxidative stress, activation of PKC pathway, formation of advanced glycation end products (AGEs) and shunting of polyol pathway which trigger metabolic inflammation resulting in a dysregulated innate immunity. Dysregulated innate immunity in T2D patients has also been discovered to be due immune response caused by hyperglycaemia. However, it has not been discovered if immune activation occurs at the pre-diabetes stage. It has not been discovered if upregulation of inflammatory markers occurs at prediabetes stage. This study envisaged to characterise the changes that occur in immune cell concentration during the progression of pre-diabetic stage and if there is upregulation of inflammatory markers such as fibrinogen, CRP, CD40L, p-selectin, IL-6 and TNF-α during pre-diabetic stage. To accomplish this, male Sprague Dawley rats were divided into two groups. The first group was fed a high-fat high-carbohydrate diet for 20 weeks to induce pre-diabetes and the second group was fed a normal rat diet for 20 weeks. To confirm if the animals were pre-diabetic, criteria according to American Diabetes Association were used. The animals were then divided into 2 groups which is the pre-diabetic group with 6 animals and a non-diabetic control with another 6 animals. The animals were then further monitored for another 12 weeks (experimental period) while fed the same diet. Blood was collected for haemocytometer analysis on week 0,4,8 and 12 of the experimental periods after which the animals were sacrificed. Plasma was collected from centrifuged blood for ELISA (TNF- α, CRP, P-selectin, CD40 L, fibrinogen & IL-6). Adipose tissue was collected for histology. The results showed a significant decrease in blood percentage count of neutrophils and eosinophils at week 12 experimental period and these immune cells were further observed embedded in-between the adipocytes of adipose tissue. This indicated that neutrophils and eosinophils are produced due to hyperglycaemia and then recruited to the inflamed area such as adipose tissue. The blood percentage count of lymphocytes, basophils and monocytes showed a significant increase at week 12, indicating their increase in production in the bone marrow during immune response. Additionally, the results showed a significant increase in inflammatory cytokines such as TNF-α, IL-6, CRP and P-selectin. The results also showed a slight increase in inflammatory markers such as CD40L and fibrinogen. These finding indicate that there is immune activation during pre-diabetes stage due to changes in immune cells concentration and upregulation of inflammatory markers.