Garlic Biological Activities
Garlic-derived organosulfur compounds have been found to inhibit mediators of the inflammatory response, including cytokines, chemokines, adhesion molecules, and enzymes like cyclooxygenase (COX), lipoxygenase (LOX), and inducible nitric oxide synthase (iNOS). Nuclear factor-kappa B (NF-κB) is a transcription factor that binds DNA and induces the transcription of the COX-2 gene, other pro-inflammatory genes, as well as genes involved in cell proliferation, adhesion, survival, and differentiation. The anti-inflammatory effects of organosulfur compounds result from their ability to counteract the activation of pro-inflammatory pathways — like NF-κB-, MAPK-, and PI3K/Akt-dependent signaling pathways — by pro-inflammatory stimuli. DATS inhibited bacterial lipopolysaccharide (LPS)-induced macrophage activation by limiting LPS binding to toll-like receptor 4 (TLR4) and blocking the upregulation of TLR4 and TLR4-associated molecule MyoD88 expression. DATS also inhibited LPS-induced NF-κB-dependent expression of COX-2, iNOS, tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β). In a mouse model of inflammation, the decrease of LPS-induced paw edema by DATS was associated with reduced serum concentrations of the pro-inflammatory cytokines, TNF-α, IL-6, and monocyte chemotactic protein-1 (MCP-1).
Various chronic diseases, such as cancer and cardiovascular diseases, are related with inflammatory processes; in these conditions, different types of therapeutic and natural tools have been used to prevent them. In this context, garlic has shown to exert potent anti-inflammatory effects by decreasing the inflammatory biomarkers in end-stage renal disease and adult patients. A double-blind randomized clinical trial showed a significant reduction of inflammatory cytokines, such as interleukin 6 (IL-6), C-reactive protein (CRP), and erythrocyte sedimentation rate when standardized GE was administered at 400 mg twice a day for eight weeks in peritoneal dialysis patients. In addition, a meta-analysis revealed that garlic supplementation, including AGE, garlic powder and garlic capsule, reduced serum concentrations of tumor necrosis factor alpha (TNF-α), and CRP, but did not affect serum adiponectin and leptin in healthy adults.
Immune cells are responsible for the anti-inflammation effect; aged garlic contains various compounds that can improve immune systems by modulating cytokine production. For example, the consumption of aged garlic supplementation at a dose of 2.56 g per day for 90 days increased the activity of immune cells, such as γδ-T and natural killer (NK) cells and decreased inflammation by reducing TNF-α and IL-6 in obese adults. Interestingly, the same dose of GE boosted immune cell function, decreasing the severity of cough and flu  and increasing urinary cytokine IL-12 excretion, even if no significant effect on IL-8 and TNF-α were found. In addition, a negative correlation has been found between organosulfur compounds of AGE and obesity-induced inflammation in a randomized, double-blind, placebo-controlled clinical trial. After taking AGE supplement at a dose of 3.6 g per day for six weeks, SAC reduced obesity-induced inflammation by releasing hydrogen sulfide (H2S) via increasing its endogenous products. Moreover, garlic supplementation increased microbial richness and diversity and improved inflammation condition, in patients with uncontrolled hypertension, while no significant effects have been found after garlic consumption at 2.1 g per day for 12 weeks, on inflammation in overweight subjects and type 2 diabetes patients with high cardiovascular risk.
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