The Effect of Acute Oral Galactose Administration on the Redox System of the Rat Small Intestine

Abstract

Galactose is a ubiquitous monosaccharide with important yet incompletely understood nutritive and physiological roles. Chronic parenteral d-galactose administration is used for modeling aging-related pathophysiological processes in rodents due to its ability to induce oxidative stress (OS). Conversely, chronic oral d-galactose administration prevents and alleviates cognitive decline in a rat model of sporadic Alzheimer’s disease, indicating that galactose may exert beneficial health effects by acting in the gut. The present aim was to explore the acute time-response of intestinal redox homeostasis following oral administration of d-galactose. Male Wistar rats were euthanized at baseline (n = 6), 30 (n = 6), 60 (n = 6), and 120 (n = 6) minutes following orogastric administration of d-galactose (200 mg/kg). The overall reductive capacity, lipid peroxidation, the concentration of low-molecular-weight thiols (LMWT) and protein sulfhydryls (SH), the activity of Mn and Cu/Zn superoxide dismutases (SOD), reduced and oxidized fractions of nicotinamide adenine dinucleotide phosphates (NADPH/NADP), and the hydrogen peroxide dissociation rate were analyzed in duodenum and ileum. Acute oral administration of d-galactose increased the activity of SODs and decreased intestinal lipid peroxidation and nucleophilic substrates (LMWT, SH, NADPH), indicating activation of peroxidative damage defense pathways. The redox system of the small intestine can acutely tolerate even high luminal concentrations of galactose (0.55 M), and oral galactose treatment is associated with a reduction rather than the increment of the intestinal OS. The ability of oral d-galactose to modulate intestinal OS should be further explored in the context of intestinal barrier maintenance, and beneficial cognitive effects associated with long-term administration of low doses of d-galactose.

The absence of gastrointestinal redox dyshomeostasis in the brain-first rat model of Parkinson’s disease induced by bilateral intrastriatal 6-hydroxydopamine

“…The presented results provide solid evidence against the existence of pronounced gastrointestinal redox dyshomeostasis in a brain-first rat model of PD induced by bilateral intrastriatal administration of 6-OHDA 12 weeks after model induction. Although the possibility that redox dyshomeostasis was present but too subtle to be estimated with a high degree of certainty using the current experimental design and methodological approach cannot be completely excluded, a substantial dropout rate and pronounced motor deficits ( administration of the 200 mg/kg D-galactose solution) [37] and in other neurotoxin-based models of brain-first-induced neurodegeneration [31,32].…”

“…Low molecular weight thiols (with glutathione (GSH) being the most abundant) and free protein sulfhydryls (SH) were quantified by measuring 5-thio-2-nitrobenzoic acid (TNB) following the reaction of 5,5T-dithio-bis(2-nitrobenzoic acid) (DTNB) with the supernatant and the pellet after precipitation of proteins with sulfosalicylic acid [31,36,37]. Briefly, 25 μL of each homogenate was incubated with 4% w/v sulfosalicylic acid in ddH 2 O for 1 h on ice in a 1:1 volumetric ratio.…”

“…The activity of superoxide dismutase (SOD) was determined indirectly by the inhibition of the 1,2,3trihydroxybenzene (THB) autoxidation [38,39] using a modified protocol [37,40]. The homogenates (3 μl for duodenum or 6 μl for ileum and colon) were placed in a 96-well plate and incubated with a 100 μl of the buffer for measuring total SOD activity (80 μL of the THB solution (60 mM THB dissolved in 1 mM HCl) added to 4000 μL of 0.05 M Tris-HCl and 1 mM Na2EDTA (pH 8.2)) or Fe/Mn-SOD activity ((80 μL of the THB solution (60 mM THB dissolved in 1 mM HCl) added to 4000 μL of 0.05 M Tris-HCl, 1 mM Na2EDTA, 2 mM KCN (pH 8.2)).…”

“…The activity of superoxide dismutase (SOD) was determined indirectly by the inhibition of the 1,2,3trihydroxybenzene (THB) autoxidation [38,39] using a modified protocol [37,40]…”

The Effect of the Sodium—Glucose Cotransporter Inhibitor on Cognition and Metabolic Parameters in a Rat Model of Sporadic Alzheimer’s Disease

“…Catalase activity. Catalase activity was estimated from H 2 O 2 dissociation rate using modified Hadwan’s procedure [ 28 ], described in detail in [ 29 ]. Briefly, tissue homogenates (15 μL HPC; 7 μL duodenum) were incubated with 150 μL of the Co(NO 3 ) 2 solution (0.1 g of Co(NO 3 ) 2 × 6 H 2 O in 5 mL ddH 2 O mixed with 0.05 g (NaPO 3 ) 6 dissolved in 5 mL ddH 2 O; added to 90 mL of NaHCO 3 solution (8.1 g in 90 mL ddH 2 O)) followed by 50 μL 10 mM H 2 O 2 in PBS to obtain baseline values.…”