The Rhamnogalacturonan-II Dimer Decreases Intestinal Absorption and Tissue Accumulation of Lead in Rats

Abstract

The rhamnogalacturonan-II dimer (dRG-II) forms strong complexes in vitro with lead (Pb) and other selected cations. We examined the in vivo bioavailability of Pb complexed with dRG-II and the effect of unleaded dRG-II on the intestinal absorption and tissue retention of Pb in rats. Forty male Wistar rats were divided into four groups. Each group consumed a purified control diet for 3 wk or the same diet supplemented with: i) 3 mg of Pb/kg, ii) 0.5 g of leaded dRG-II/kg, or iii) 0.5 g of leaded dRG-II/kg and 4.5 g of unleaded dRG-II/kg. The leaded dRG-II provided approximately 3 mg of Pb/kg of diet. A chemical balance study was conducted during the last 5 d of the 3-wk study, and blood and organs were sampled for Pb and mineral analyses. The apparent intestinal absorptions of Pb were 62.3, 15.2, 11.8 and -0.1%, and Pb balances were 1.9, 9.6, 5.6 and -0.2 microg/d for the control and the three experimental groups, respectively. The Pb complexed with dRG-II was less available than Pb acetate, as reflected by significantly lower blood and tissue Pb levels. The addition of unleaded dRG-II decreased the intestinal absorption and the tissue retention of Pb significantly. We further found that the apparent absorption and status of magnesium, zinc and iron were unaffected by Pb treatment or dRG-II addition. We conclude that dRG-II may be useful in decreasing toxicity related to chronic Pb exposure. Human studies will be necessary however, to further evaluate the clinical utility of this beneficial effect.

The effect of modified citrus pectin on urinary excretion of toxic elements

“…The urinary excretion of the known neuro-and immunotoxins: arsenic, mercury, cadmium and lead, increased within 1-6 days of MCP treatment. The ability to rapidly detect significant changes in urinary excretion of metals with a mild treatment such as MCP is encouraging, especially given the small number of heterogeneous known as metal cation chelators Tahiri et al, 2000). Native sized pectin persists in the gut until it is completely degraded by bacterial fermentation in the colon.…”

“…Additionally, the cation chelation by rhamnogalacturonan II dimers is specific for Pb, Ba, Sr, La, Eu, Ce, Pr and Nd, whereas essential cations such as Ca, Mg, Fe, Zn and Cu are not bound Tahiri et al, 2000). Although some metals (cadmium and strontium) vary widely in their placement in the relative binding affinity series (Table 3), lead consistently exhibits the highest affinity for pectin.…”

Comparison of five in vitro digestion models to in vivo experimental results: Lead bioaccessibility in the human gastrointestinal tract

“…Site-specific risk 9 assessment studies incorporate soil ingestion with a maximal daily intake of 50 and 150 mg 10 soil d -1 for adults and children, respectively [4] . Reported human soil intake rates generally 11 range from 1 to 50 mg/d for adults and from 100 to 500 mg/d for children [5][6][7] . However, pica 12 afflicted children may show an unusual hand-to-mouth behaviour and can ingest up to 20 g 13 soil/d [6] .…”

Oral Lead Exposure Induces Dysbacteriosis in Rats

“…Despite intensive study, there is still vigorous debate about the toxic effects of lead, mainly concerning low-level exposure in the general population owing to environmental pollution by lead alone 9) and in combination with other compounds 10) . Total Pb dietary intake for an adult may vary from 20 to 150 µg per day in most countries 11,12) with a daily dose of 0.2-2 mg regarded as safe 13) . The main routes of lead entrance into the human body (food, water, dust) involve the intestinal system.…”