Curcumin's role in combating obesity and neuroinflammation

A new study highlights the antioxidant and anti-inflammatory effects of curcumin, suggesting its potential as a therapeutic agent for metabolic disorders and brain health.

A recent Nutrients study explores the medicinal role of curcumin in the treatment and prevention of neuroinflammation and metabolic disorders.

Curcumin: Source, properties, and metabolism

Curcumin is extracted from the rhizome of turmeric, which is otherwise known as Curcuma longa, a plant in the Zingerberaceae family.

Curcumin is a polyphenolic compound characterized by two aromatic rings with conjugated double bonds. The chemical structure of curcumin supports its electron donor role and prevents free radical formation.

Phenolic compounds impart color to many fruits and play a vital role in facilitating seed dispersal. Polyphenols also protect plants from oxidative damage caused by sunlight and other environmental factors, in addition to preserving the organoleptic qualities of plant food products like red wine, olive oils, and wheat.

Polyphenols are mostly soluble in organic solvents like acetone and ethanol and insoluble in water. These compounds also remain stable in acidic conditions, such as the stomach, which allows curcumin to remain intact to influence metabolic processes beyond the gastrointestinal tract.

Enzymes in the intestines and liver degrade curcumin in two phases. During phase I, the double bonds in curcumin are reduced to produce metabolites like dihydrocurcumin, hexa-hydrocurcumin, tetrahydrocurcumin, and octahydrocurcumin.

During phase II, these metabolites are conjugated with glucuronic acid and sulfate. Some studies have reported that curcumin may also be metabolized by gut bacteria, particularly in the colon.

The antioxidant activity of curcumin and its metabolites

Polyphenols can counteract inflammation and oxidative stress, both of which are processes implicated in the development of chronic degenerative diseases. Certain metabolites derived from curcumin, such as tetrahydrocurcumin, exhibit anti-inflammatory and antioxidant properties.

Both in vitro and in vivo studies have highlighted the anti-inflammatory activity of curcumin. In human THP1 monocytes, curcumin doses ranging from 7.5 μM to 30 μM successfully mitigated the effects of stimulation with bacterial toxin (LPS) and INFγ (interferon γ) in a dose-dependent manner. This antioxidant activity was attributed to the blocking of toll-like receptor 4 / mitogen-activated protein kinase (TLR4/MAPK) and nuclear factor κB (NF-κB) pathways, as well as reversed M1 polarization.

Curcumin doses of 25.5 μM or less have also been shown to reduce inflammasome activation. One recent study also reported that 20 μM of curcumin may prevent inflammation-related damage caused by hypoxia.

The effects of curcumin on obesity and inflammation

A recent meta-analysis revealed that consuming 1,500 mg or more of curcumin every day for one month could significantly reduce body mass index (BMI) values and other body parameters, especially when combined with lifestyle changes. Considering its medicinal properties, various curcumin-based formulations have been devised to improve the bioavailability of this polyphenol compound, such as co-administering curcumin with piperine and nanocurcumin encapsulation.

In vitro studies have reported that curcumin influences the cellular viability rate and cell cycle regulation of preadipocytes. At high doses, curcumin promotes DNA fragmentation and enhances the apoptotic rate by activating caspases.

Low doses of curcumin reduce cell proliferation without affecting viability. Mechanistically, curcumin reduces the retinoblastoma protein (Rb) phosphorylation and delays clonal expansion and the cell cycle, thereby exerting antiadipogenic effects.

Curcumin also interferes with adenosine monophosphate (AMP)-activated kinase (AMPK) activity to block anabolism and promote lipid catabolism, both of which can support the management of obesity and metabolic syndrome. More specifically, activated AMPK reduces lipogenesis by inhibiting acetyl CoA carboxylase (ACC), prevents triglyceride synthesis by inhibiting glycerol-3-phosphate acyltransferase-1 (GPAT-1), and triggers β-oxidation of fatty acids by increasing transport with carnitine palmitoyltransferase-1 (CPT-1).

Within the brain, low doses of curcumin may prevent inflammation by inhibiting microglia polarization and reducing the expression of pro-inflammatory markers, like interleukin 1β (IL-1β) and IL-6. Curcumin also increases the activity of anti-inflammatory molecules like arginase 1 and IL-4.

Curcumin as a treatment for obesity and neurodegenerative diseases

Clinical trial results have highlighted the beneficial effects of curcumin in treating overweight patients with chronic systemic inflammation. For example, 80 mg of curcumin daily for three months led to a significant reduction in serum high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) levels in overweight/obese patients with nonalcoholic fatty liver disease (NAFLD) between 25 and 50 years of age.

In a separate study, type 2 diabetes (T2D) patients treated with 300 mg daily of curcuminoids for three months exhibited a significant reduction in insulin resistance parameters and circulating levels of free fatty acid (FFA), which are often present in high amounts in obese patients with inflammation. Obese patients with T2D and depression who were treated with 1,500 mg daily of curcuminoids for one year also reported a significant reduction in depressive symptoms.

The oral administration of curcumin affects the intestinal microbial composition, particularly the genera Bacteroides, Alistipes, Parabacteroides, and Alloprevotella, which increases short-chain fatty acid (SCFA) synthesis in the cecum and colon. Multiple studies have also reported the neuroprotective effects of curcumin through its activity throughout the gut-brain axis.

In the future, additional research is needed to confirm the translational potential of curcumin in clinical practice. Large clinical trials with heterogeneous populations should also be conducted to confirm the clinical utility of curcumin in treating patients with metabolic disorders and neurodegenerative diseases.

• Cerullo, M., Armeli, F., Mengoni, B., et al. (2025) Curcumin Modulation of the Gut–Brain Axis for Neuroinflammation and Metabolic Disorders Prevention and Treatment. Nutrients 17(9); 1430. doi:10.3390/nu17091430