The NRF2 Gene: Glutathione, Sulforaphane & Beyond

NFE2L2 is the gene that codes for the NRF2 nuclear transcription factor. Nuclear transcription factors comprise a family of genes that each control the expression of numerous target genes. NRF2 is normally ubiquinated and inactive within the cytoplasm of cells. Under conditions of cellular stress, NRF2 becomes activated and mobilizes to the nucleus, where it modulates the expression of numerous ARE genes (antioxidant response elements).

The NRF2 gene is the subject of ongoing research for inflammatory-based diseases because it controls the expression of many critical antioxidant systems. Indeed, numerous associations between polymorphisms of NFE2L2 SNP’s and inflammatory diseases have been identified. Additionally, much research has been conducted regarding natural products and supplements that are capable of increasing the expression of NRF2.

NRF2 & The Antioxidant Response Elements (ARE’s)

Upon activation through nuclear transcription, NRF2 induces the modulation of the following ARE’s:

• NQO1 – Semi quinone reductase
• UDP-glucuronosyltransferase (UGT1a1, UGT1a6) – Controls glucuronidation
• SRXN1 – Sulfiredoxin-1  Regulates sulfur oxidoreductases
• TXNRD1 – Thioredoxin Reducatase-1 regulates redox reactions
• HMOX1 – heme oxygenase-1, breaks down hemoglobin into biliverdin in the spleen
• GSTM – Glutathione transferase: Exports glutathione conjugates
• MRP’s – Multidrug resistance associated proteins – Membrane transport proteins involved in efflux mechanisms, toxin removal and bile incorporation
• GCLC – Glutamate cysteine ligase, which acts to increase glutathione synthesis
• KEAP1 – Kelch-like ECH-associated protein 1
• Inhibition of NF Kappa ß, which is another transcription factor that modulates cytokines
• The NRF2 gene also appears to control the expression of Thyroglobulin (TG)

NFE2L2 Gene Research

The SNP’s rs35652124, rs6706649, rs6721961 are located within the promoter region of the gene. Promoter region SNP’s are significant because they are the parts of the gene that influence the expression and levels of NRF2. Therefore, variations of promoter region SNP’s will have a direct effect on NRF2 expression. Hence, much research has been done on these SNP’s as its related to various diseases, biomarkers and health conditions. As can be observed below, genotype and their effects are not straightforward, nor linear. Effects of each genotype likely involve gender, racial, and disease-specific differences.

• The risk allele for the above-mentioned SNP’s are known to induce lower expression of NRF2 (R)
• The NFE2L2 SNP rs6721961, referred to as the -617 variant, the allele ‘A’ has been shown in vitro to bind less efficiently to ARE (antioxidant response element)-like sequences of the target genes (R).
• For the NFE2L2 SNP rs6721961, male carriers of the ‘A’ allele showed significantly lower levels of cholinesterase (the enzyme that breaks down choline and acetylcholine), lower blood pressure and higher levels of Iron, in a Japanese cohort. Because NRF2 modulates the expression of HMOX-1 (centrally involved in iron degradation), the A’ allele of rs6721961 may result in lower HMOX-1 expression, and higher iron levels. The study also identified that carriers of the ‘C’ allele of NFE2L2 rs35652124 featured significantly lower HDL cholesterol, but higher cholinesterase (R). It can be deduced that the ‘A’ allele of rs6721961 and ‘C’ allele of rs35652124 may result in lower transcriptional activity of NFE2L2, and thus reduced expression of NRF2.
• For female, Japanese carriers of the NFE2L2 variant rs35652124, the ‘C’ allele is associated with lower total cholesterol and lower systolic blood pressure (R).
• or the NFE2L2 variant, rs6721961, the ‘AA’ genotype is significantly associated with Type 2 Diabetes in a Chinese cohort. According to the referenced study: “Compared to individuals with the CC genotype, those with the AA genotype had lower total anti-oxidative capacity, superoxide dismutase, catalase, glutathione, glutathione peroxidase activity; and lower homeostasis model assessment of β-cell function index” (R). Paradoxically, a study of this same SNP in a Mexican cohort found that the AA genotype was protective against Type 2 Diabetes (R). Thus it may be deduced that population and racial differences may affect outcomes.
• With renal cancer, when the genotype features the ‘A’ allele of rs672961, or higher NRF2 expression, there is an association with greater metastases and poor outcomes (R)
• The risk alleles of the NRF2 promoter region haplotypes are associated with severity and respiratory failure in COPD (chronic obstructive pulmonary disease) (R)
• The risk alleles for the haplogroup of NRF2 promoter SNP’s combined with a SELENOS gene SNP is significantly associated with Hashimoto’s thyroiditis (R)
• The NRF2 gene appears to control the expression of Thyroglobulin (TG). Thyroglobulin is a large protein within the thyroid gland that functions to generate T4 and T3. The ‘T’ allele of rs6706649 is significantly associated with lower levels of Thyroglobulin. TG comprises 50% of the total protein content of the thyroid gland. TG is essential for the biosynthesis of Both T4 and T3 (R)
• The allele ‘G’ for rs6721961 has been found associated to hypertension (R)
• The allele ‘G’ for rs6721961 is significantly associated with childhood asthma, especially with poor air quality conditions (R)
• In an Indian population, the TT genotype for rs35652124 is significantly associated with Type 2 Diabetes risk, as well as complications. TT for this SNP is not the standard risk factor, but apparently is less desirable for T2D in some populations (R)

NRF2 Promotion Therapies: Sulforaphane

NRF2 promotion therapies have been the subject of much scientific research. The most notable research has consistently established that isothiocyanate compounds from cruciferous vegetables (most notably broccoli sprouts) are potent inducers of Sulforaphane. Once the G.I. tract converts isothiocyanates into sulforaphane, there is the potential for induction of NRF2 activation. It should be pointed out that enzymatic conversion of isothiocyanates into sulforaphane is required. The enzyme myrosinase has been identified as significant, and likely essential for this conversion to take place. Myrosinase is found in the raw and unprocessed broccoli and broccoli sprout, as well as in horseradish and wasabi root (and other isothiocyanate foods). Heating destroys myrosinase. It may be deduced that in the absence of adequate myrosinase, less sulforaphane will be produced in the gut. Myrosinase is also marketed as an enzyme in various sulforaphane-producing supplements.

The way sulforaphane actually works is by the inhibition of glutathione in the liver. Isothiocyanate compounds such as sulforaphane derived from cruciferous vegetables act as hormetic-modifiers on the Nrf2 system. Through sulforaphane’s inhibition of glutathione, the activities of KEAP1 and Cullin-3 ubiquination are inhibited. This temporary stress response induces the translocation of NRF2 to the nucleus, where it acts as a transcription factor.

In addition to effects on the liver, sulforaphane is known to cross the blood brain barrier and is proposed as being neuroprotective R.

Other Notable Activators of NRF2

There are dozens of natural interventions that have experimentally raised levels of NRF2. Some of the most notable include:

• Acute, stressful exercise activates NRF2 in the heart R
• Alpha Lipoic acid – Research is less robust than sulforaphane, but nontheless lipoic acid has been shown to induce NRF2 in rats (R). In rats, lipoic acid prevents steatosis (fatty liver) via NRF2 activation (R)
• Ketogenic Diet – Research in rats has found continuous ketogenic feeding increases levels of NRF2 as well as NRF2 target genes, NQO1 and GCLC (R)
• Curcumin has been shown to increase NRF2 activation in lymphocytes in Type 2 diabetic patients R

Should I Be Concerned About Sulforaphane If I Have Hashimoto’s or Hypothyroidism?

The question pertains to the clinical use of broccoli sprouts, or other isothiocyanate-containing foods, supplements of beverages. The concern that some people have is that if one has hypothyroidism or Hashimoto’s thyroiditis, one should be cautious about including cruciferous vegetable products because of the potential goitrogenic effects. A 12-week randomized controlled trial was conducted to establish if there is any need for concern. The study found that broccoli sprout beverage had no effect on TSH, Free T4 or Thyroglobulin levels, and did not affect autoimmune antibodies. The authors concluded: “Long-term ingestion of a sulforaphane-rich broccoli sprout beverage is safe for the thyroid gland” (R).

NRF2 Gene Status & The Metabolic Healing Nutrigenomics Report

The Metabolic Healing Nutrigenomics report allows healthcare practitioners as well as consumers to analyze their raw data files from 23andme and AncestryDNA. Our report includes analysis of NFE2L2 (the NRF2 gene).