• A new study suggests that the level of inflammation in people with prediabetes may predict if they progress to type 2 diabetes.
• Inflammation level was determined by measuring high-sensitivity C-reactive protein (hs-CRP).
• Participants with the highest level of hs-CRP were 1.8-fold more likely to develop type 2 diabetes and less likely to return to normal blood glucose levels than those with low hs-CRP levels.
• CRP may be a tool to indicate the likelihood of middle-aged and older adults with prediabetes developing type 2 diabetes.

The level of inflammation in middle-aged and elderly individuals with prediabetes may predict if they progress to type 2 diabetes, according to new research.

In the study, participants with the highest levels of the inflammation marker, high sensitivity C-reactive protein (hs-CRP), were more likely to progress from prediabetes to type 2 and less likely to return to normal blood glucose levels compared to participants with the lowest hs-CRP levels.

“Our study is the first to show that higher levels of inflammatory factors, represented by CRP, are associated with increased odds of progression to diabetes, and lower levels of CRP are associated with increased odds of regressing to normoglycaemia over a 4-year follow-up in middle-aged and older Chinese with prediabetes,” the researchers wrote.

The study, “High sensitivity C-reactive protein and prediabetes progression and regression in middle-aged and older adults: A prospective cohort study”, was published in Journal of Diabetes Investigation.

What is Inflammation, and how is it measured?

Inflammation is the natural response to infection, damaged cells, harmful substances and injury. The body typically activates immune cells that produce a variety of proteins, including cytokines and prostaglandins, to resolve it. Inflammation is protective if short-term but harmful when long-term or chronic because it causes silent damage throughout the body. Chronic inflammation is a significant part of prediabetes, which occurs when the body becomes insulin-resistant. Although it is a high-risk state for developing type 2 diabetes, only about 5-10% of people with prediabetes progress to type 2 diabetes.

CRP is a protein mainly produced by the liver and fat cells. Scientists use it as a marker to assess tissue damage, infection, and inflammation in patients. Most healthy adults have CRP levels lower than 0.3 mg/dL. However, CRP levels of 0.8-1.0 mg/dL or lower are also considered normal. Previous studies show that patients with high CRP levels are at a greater risk of developing prediabetes and type 2 diabetes. However, it is currently unclear whether CRP levels are associated with patients progressing from prediabetes to type 2 diabetes.

“To test whether plasma [blood] CRP can be used to identify high-risk prediabetes and then develop optional preventive strategies, we employed a large-scale national cohort, China Health and Retirement Longitudinal Study (CHARLS), to investigate the relationship between hs-CRP and prediabetes progression and regression in middle-aged and older Chinese population”, the researchers wrote. Of note, CHARLS is a longitudinal survey of people in China aged at least 45 years that is nationally representative and evaluates the social, economic and health conditions of local residents.  

Higher risk of progression to type 2 diabetes in participants with moderate and high levels of CRP

A total of 2874 adults [mean age 64 years, 44.7% male) with prediabetes participated in the study; they were followed for four years. Prediabetes was defined as fasting plasma glucose of 100 mg/dL (5.6 mmol/L) to 125 mg/dL (6.9 mmol/L) or HbA1c 5.7-6.4% (39-47 mmol/L).  Participants provided blood samples to measure fasting blood glucose, glycated haemoglobin (HbA1c) and CRP at the study’s start and follow-up. They were divided into three groups based on their CRP levels: 969 were in the low group (<0.67 mg/dL), 951 were in the middle (0.67 -1.62 mg/dL), and 954 were in the high group (>1.62 mg/dL).

After adjusting for age, sex, body mass index, high blood pressure, obesity, high cholesterol and several other health markers, middle and high CRP groups were 1.6 and 1.8-fold, more likely to progress to type 2 diabetes than the low group. They were also less likely than the low group to return to normal blood glucose levels. However, these associations were more evident in females than males, suggesting that “prediabetes may need to be closely monitored in middle-aged and older women with elevated hs-CRP”.

“Our study shows that low concentrations of inflammatory markers represented by CRP can effectively promote regression to normoglycaemia in middle-aged and elderly people with prediabetes, and high levels of CRP can also make prediabetic patients progress to diabetes”, the researchers wrote. “These results suggest that the level of hs-CRP may be a common indicator to verify the progression of prediabetes”, they added.

How can people with prediabetes reduce inflammation?

Inflammation is not the only factor that drives prediabetes; diet also strongly influences inflammation.¹ The Mediterranean diet, for example, has been shown to decrease the production of inflammatory proteins in many conditions, while high in trans fats and sugar have been shown to increase them.² Therefore, one way to reduce inflammation is to eat an inflammatory diet.

Such a diet prioritises:¹

• Low-glycaemic carbohydrates, especially non-starchy vegetables, fruits, whole grains and legumes. These foods provide slow energy release, stabilising blood sugar levels, and provide satiety. Fruits and vegetables are also rich in essential vitamins and minerals and antioxidant compounds that neutralise harmful free radicals contributing to inflammation. Notably, high-glycaemic carbohydrates like cakes, biscuits, sweets and ice cream can encourage the body to produce destructive free radicals and proteins that trigger chronic inflammation.
• Omega-3 fats: They are typically found in oily fish such as salmon, sardines, mackerel, catfish and anchovies.  They are also present in walnuts, flaxseeds and chia seeds. These omega-3 fats can dampen existing inflammation by encouraging the body to produce resolvins, proteins that control the activation and trafficking of immune cells into inflammation sites.
• Plant proteins: They are low in saturated fat and good sources of fibre and phytonutrients that reduce inflammation. Legumes, including beans, lentils, tofu and tempeh, are excellent plant proteins.
• Healthy fats: Nuts, seeds, olives and avocado are fantastic sources. These foods are rich in unsaturated fatty acids that support heart health.
• Tea, especially green and black tea. They are rich sources of antioxidants and polyphenols that contribute to reducing inflammation.
• Herbs and spices: Ginger and turmeric are the two herbs with the most extensive evidence supporting their impact on inflammation. Studies show that they block the action of specific inflammatory proteins.
• Limits highly processed foods: they can contain large amounts of trans and saturated fats, sugar and salt. Trans fats affect blood fat profile; they raise LDL (bad) cholesterol and triglycerides and can reduce HDL (good) cholesterol. They have also been linked to higher levels of CRP.

Eating mindfully and in smaller amounts, managing stress, and regular activity is also crucial for reducing inflammation.^1,3

The Keypoint

Inflammation is a driving force for many chronic diseases, including type 2 diabetes. This study has found that people with prediabetes and high levels of inflammation may be more likely to develop type 2 diabetes.

Eating a nutritious diet that limits processed foods and staying active are great ways to reduce inflammation and prevent type 2 diabetes. Contact your health care provider or registered nutritionist/dietitian for tailored advice.

References

1. Ricker, M.A, & Hass, W.C. (2017) Anti-inflammatory diet in clinical practice: A review. Nutrition in Clinical Practice, 32(3): 318-325. https://doi.org/10.1177/0884533617700353.
2. Zwickey, H., Horgan, A., Hanes, D., Schiffke, H., Moore, A., Wahbeh, H., Jordan, J., Ojeda, L., McMurry, M., Elmer, P., & Purnell, J. Q. (2019). Effect of the Anti-Inflammatory Diet in People with Diabetes and Pre-Diabetes: A Randomized Controlled Feeding Study. Journal of Restorative Medicine, 8(1). https://doi.org/10.14200/jrm.2019.0107.
3. Xing, H., Lu, J., Yoong, S.Q., Tan, Y.Q., Kusuyama, J., & Wu, X.V. (2022) Effect of aerobic and resistance exercise intervention on inflammaging of type 2 diabetes mellitus in middle-aged and older adults: a systematic review and meta-analysis. The Journal of Post-Acute and Long-Term Care Medicine, https://doi.org/10.1016/j.jamda.2022.01.055.