Researchers from House Wellness Foods Corp, Japan, conducted a 12-week randomized, double-blind, placebo-controlled study to investigate the effect of CLE on chronic inflammation and postprandial hyperglycemia in middle-aged and elderly participants with overweight and glycemia in the normal/prediabetes range.
The resulting data indicated that serum levels of the inflammation marker high-sensitivity CRP (hsCRP) and blood sugar marker hemoglobin A1c (HbA1c) were significantly lower in the CLE group than in the placebo group. In the oral glucose tolerance test (OGTT), the post-load glucose plasma level, time to peak concentrations of glucose and insulin, and insulin sensitivity indices were also significantly improved in the CLE group.
"These results suggest that daily intake of CLE may have the potential to improve insulin resistance and postprandial hyperglycemia by reducing chronic low-grade inflammation," the researchers concluded.
Turmeric and inflammation
Inflammation, which can be acute or chronic, plays a critical role in the body’s defense mechanism. Acute inflammation removes pathogens and other harmful foreign bodies while inducing the healing process. Chronic inflammation is slow and long-term and could be mediated by immune cells, such as macrophages.
Chronic inflammation can also be induced by aging, obesity, unbalanced diet, insufficient sleep, psychological stress and physical inactivity. A prominent marker of low-grade inflammation is C-reactive protein (CRP). Marginally elevated CRP levels indicate an increased risk of diabetes, cancer and coronary heart disease.
Glucose plays an important role in maintaining physiological homeostasis in the human body. Insulin is an anabolic hormone synthesized by the pancreas, which regulates the energy supply by modifying micronutrients. An increased intake of carbohydrates and fat leads to obesity, which leads to impaired glycometabolism.
C. longa is a popular spice that contains curcumin, a lipophilic polyphenolic compound that possesses anti-inflammatory, antioxidant and anti-obesity functions. Besides curcumin, it also contains bisacurone and turmeronols A and B.
The role of CLE on inflammation and postprandial glucose metabolism
First, the researchers investigated the effect of CLE and the active components of C. longa on lipopolysaccharide-induced inflammation in RAW264.7 macrophages. They found a significant decrease in the production of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and nitric oxide with CLE, turmeronol A and bisacurone. Significant inhibition of each of these substances was also observed, except for TNF-α, with turmeronol B.
For the in vivo study, a total of 110 overweight participants (body mass index ≥ 23 and <30 kg/m2), between the age of 40 and 69 years, with normal or prediabetic glycemic index, were equally and randomly assigned to CLE or placebo groups.
Participants took two CLE or placebo capsules per day for 12 weeks. Subsequently, the impact of CLE on chronic inflammation and postprandial hyperglycemia were assessed.
Resulting data indicated that intake of CLE significantly reduced serum hsCRP and HbA1c levels. Furthermore, in the OGTT, post-load plasma glucose level, time to peak concentration of glucose and insulin, and insulin sensitivity indices were significantly improved in the CLE group.
These results suggest that CLE may improve insulin sensitivity and postprandial hyperglycemia by reducing chronic inflammation and that this reduction is due at least partly to the anti-inflammatory effects of turmeronols A and B and bisacurone.
The researchers noted that mechanistically, CLE improved postprandial hyperglycemia and insulin sensitivity by reducing chronic low-grade inflammation. Therefore, a regular intake of CLE could lower the risk of prediabetes and type 2 diabetes by improving insulin resistance and postprandial hyperglycemia. However, the called for more research to validate the efficacy of turmeronols A and B and bisacurone in humans.
Journal: Frontiers in Nutrition
“Curcuma longa extract reduces serum inflammatory markers and postprandial hyperglycemia in healthy but borderline participants with overweight and glycemia in the normal/prediabetes range: A randomized, double-blind, and placebo-controlled trial.
Authors: Ryusei Uchio et al.