Chronic inflammation and type 2 diabetes

Inflammation is the body’s protective response towards insult or injury. It is a defensive mechanism that helps to neutralise any threat to the body. Our wellbeing and survival depend upon the efficiency and carefully balanced control of inflammation in the body. If inflammation is not resolved quickly, it can develop into many chronic diseases (See my previous article on “Beware of chronic inflammation”). In this article, I will explore how chronic inflammation can lead to type 2 diabetes.

Diabetes is when your blood sugar level too high.

There are two major types of diabetes: type 1 and type 2. Type 1 diabetes is considered an auto-immune disease as it involved the body’s immune system actively attacking the pancreatic cells that produce insulin. In contrast, type 2 diabetes is regarded as a progressive condition whereby the cells in the body are gradually becoming resistant to insulin. Such an effect causes the pancreatic cells to produce more insulin and eventual losing its ability to produce enough insulin.  Insulin is the hormone that promotes the absorption of glucose from the bloodstream into cells. Blood glucose level will rise without sufficient insulin and become hyperglycaemia which can be harmful to the body.

Obesity and an unhealthy diet both increase the risk of developing type 2 diabetes.

We now know that there are many risk factors for type 2 diabetes. Development of the disease can be due to genetic factor, ethnicity, and ageing, which one cannot change. However, factors such as being overweight or obese, an unhealthy diet, insufficient physical activity and smoking are modifiable through healthy lifestyles and diet. Being overweight or obese is characterised by the deposit of fat tissues in the liver, pancreas, muscle, surrounding blood vessels, and heart. Fat accumulation increases tissues’ insulin resistance through the releasing of many signalling proteins and factors, as well as free fatty acids that promote inflammation and insulin resistance [1].

Fat cells in the body cause inflammation which make cells resistant to insulin.

When the fat is forming in the pancreas, it can also reduce the pancreatic cells’ ability to secrete insulin, causing less insulin to be produced.  Insulin is generated from the beta cells in the pancreas. The beta cells can become overstressed in insulin production, which stimulates the localised inflammation. The effect is the destruction of beta cells that further reduce insulin production, forming a vicious cycle [2].

Localised inflammation in pancreas can desctroy B cells that secrete insulin.

Chronic inflammation can also develop from the gut. An unhealthy diet can be the culprit. Excessive animal fats, processed meat, refined carbohydrates and alcohol consumption can change the bacteria composition in the digestive tract.    It is now known that the gut microbiota plays a vital role in modulating the immune system. Improper diet can cause the growth of harmful bacteria that generate circulating toxins (such as lipopolysaccharide) which trigger inflammatory responses from the innate immune cells. The harmful bacteria also cause an increase in gut permeability (or ‘leaky gut’) that allow the escape of these toxins into the blood circulation. The results is the increase in the whole body (systemic) low-grade inflammation leading to many metabolic disorders, including type 2 diabetes [3].   

The composition of gut microflora can cause inflammation in the body.

Chronic inflammation can be measured with several blood markers, and there is evidence that these markers are high in patients with type 2 diabetes. A systematic review [4] of 10 studies with 19,709 participants and 4,480 cases found that the risk of type 2 diabetes is correlated with the level of interleukin-6 in blood. A meta-analysis involving 22 studies of a total of 40,735 participants and 5,753 cases further showed that elevated c-reactive protein (CRP) levels were significantly associated with increased risk of type 2 diabetes [4].

However, such inflammation does not develop overnight. For even among young people, the sign of low-grade inflammation can be detected with the high-sensitive CRP (hs-CRP) marker. A study in Korean among 1,723 youths aged 10-18 found that elevated hs-CRP was commonly associated with high body mass index and the condition of prediabetes [5].

Eat more vegatables – they help to lower inflammation!

In summary, type 2 diabetes develops due to long-term, low-grade inflammation. Sedentary lifestyles and an unhealthy diet can lead to accumulation of fat tissues, overstressing of pancreatic cells, and changes in the gut microbiota, all of which stimulates the cascading effects of inflammation. Over time, the cells before resistance to insulin which cause elevated blood glucose. So, lower inflammation and you will reduce the risk of type 2 diabetes.

Reference

[1]        A. Gastaldelli, M. Gaggini, R.A. DeFronzo, Role of adipose tissue insulin resistance in the natural history of type 2 diabetes: Results from the San Antonio metabolism study, Diabetes. 66 (2017) 815 LP – 822. doi:10.2337/db16-1167.

[2]        W. Quan, E.-K. Jo, M.-S. Lee, Role of pancreatic β-cell death and inflammation in diabetes., Diabetes. Obes. Metab. 15 Suppl 3 (2013) 141–151. doi:10.1111/dom.12153.

[3]        P.D. Cani, M. Osto, L. Geurts, A. Everard, Involvement of gut microbiota in the development of low-grade inflammation and type 2 diabetes associated with obesity, Gut Microbes. 3 (2012) 279–288. doi:10.4161/gmic.19625.

[4]        X. Wang, W. Bao, J. Liu, Y.-Y. Ouyang, D. Wang, S. Rong, X. Xiao, Z.-L. Shan, Y. Zhang, P. Yao, L.-G. Liu, Inflammatory markers and risk of type 2 diabetes: a systematic review and  meta-analysis., Diabetes Care. 36 (2013) 166–175. doi:10.2337/dc12-0702.

[5]        S.H. Shin, Y.J. Lee, Y.A. Lee, J.H. Kim, S.Y. Lee, C.H. Shin, High-sensitivity C-reactive protein is associated with prediabetes and adiposity in Korean youth, Metab. Syndr. Relat. Disord. 18 (2020) 47–55. doi:10.1089/met.2019.0076.

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