Effects of fructose-induced hypertriglyceridemia on hepatorenal toxicity of acetaminophen in rats. II. Role of enhancement of fructose metabolism and overproduction of triglyceride in the liver and kidney on hepatorenal toxicity of acetaminophen

Diabetes and hypertriglyceridemia modify the mode of acetaminophen-induced hepatotoxicity and nephrotoxicity in rats and mice

Certain disease conditions can modify drug-induced toxicities, which, in turn, may cause a medication-related health crisis. Therefore, preclinical investigations into the alterations in drug-induced toxicities using appropriate disease animal models are very important. This paper reviews the reported data related to the effects of diabetes and hypertriglyceridemia, common lifestyle-related diseases in a modern society, on acetaminophen (APAP)-induced hepatotoxicity and nephrotoxicity in rats and mice. It has generally been reported that diabetes protects rats and mice from APAP-induced hepatotoxicity and there are several reports that help to speculate on the effects of diabetes on APAP-induced nephrotoxicity. In fructose-induced hypertriglyceridemic rats, hepatotoxicity of APAP becomes apparently less severe, whereas nephrotoxicity of APAP becomes significantly more severe. The mechanisms of alteration of APAP-induced hepatorenal toxicity under diabetic and hypertriglyceridemic conditions are also discussed in this paper.

Hepatotoxicity of acetaminophen and N-acetyl-p-benzoquinone imine and enhancement by fructose

1. Although oral administration of 400 mg/kg acetaminophen (APAP) or 1.8-3.4 g/kg sucrose had no effect on serum levels of alanine aminotransferase (ALT) and sorbitol dehydrogenase (SDH), their co-administration resulted in 20-fold increases in ALT/SDH activities. APAP alone (1250 mg/kg, p.o.) caused the elevation hepatotoxicity parameters, but the levels were lower than observed with co-administration of APAP (400 mg/kg) and sucrose (2.6 or 3.4 g/kg). 2. Sucrose-associated increase in serum ALT/SDH activities was selective with APAP and not detected with carbon tetrachloride (160 mg/kg, i.p.), D-galactosamine (400 mg/kg, i.p.) or alpha-naphthyl isothiocyanate (100 mg/kg, p.o.). 3. To verify the synergistic mechanism of sucrose, a major reactive intermediate of APAP, N-acetyl-p-benzoquinone imine (NAPQI), was given via the portal vein to rat pretreated with sucrose. Clear elevation of ALT/SDH activities was detected in the co-treated group. These results, together with an allopurinol-inhibition experiment, suggest the involvement of high-dose sucrose at a step(s) occurring after the metabolic activation of APAP. 4. Co-administration of glucose or fructose as well as sucrose elevated APAP-induced hepatotoxicity parameters in rat. Fructose but not glucose elevated APAP- or NAPQI-induced LDH leakage in a primary hepatocyte system. The results suggest the primary role of fructose is on the sucrose enhancement of APAP toxicity in rat.

Enhanced nephrotoxicity of acetaminophen in fructose-induced hypertriglyceridemic rats: effect of partial hepatectomy

Fructose-induced hypertriglyceridemic rats become resistant to hepatotoxicity and susceptible to nephrotoxicity of acetaminophen (APAP). Enhanced susceptibility to APAP nephrotoxicity in fructose-pretreated rats is due, at least in part, to increased renal APAP concentration at the early phase (15 and 30 min after APAP administration). However, the mechanism of an increase in renal APAP concentration is still obscure. The present study was designed to test the hypothesis that a decrease in capacity of hepatic APAP metabolism is responsible for an increase in renal APAP concentration in fructose-pretreated rats. Non-pretreated rats and fructose-pretreated rats (25% fructose in drinking water for 3 weeks) received 70% or 90% partial hepatectomy (PH) or sham operation at 1 hr before APAP administration (600 or 750 mg/kg, i.p.). PH did not potentiate APAP nephrotoxicity and renal APAP concentration, and fructose-pretreated rats showed server renal lesions and greater renal APAP concentration than non-pretreated rats irrespective of PH. The result indicates that an increase in renal APAP concentration in the fructose-pretreated rats has no relation to an alteration in hepatic metabolic capacity of APAP.

Effects of fructose-induced hypertriglyceridemia on hepatorenal toxicity of acetaminophen in rats: role of pharmacokinetics and metabolism of acetaminophen

Fructose-induced hypertriglyceridemic rats become resistant to hepatotoxicity and susceptible to nephrotoxicity of acetaminophen (APAP), as compared with normal ones. The present study was designed to test the hypothesis that alterations in the distribution of APAP and in the intrinsic susceptibility to toxicants are responsible for the alteration in hepatorenal toxicity of APAP in fructose-induced hypertriglyceridemic rats. Following APAP-administration (750 mg/kg, i.p.), fructose-pretreated rats (25% fructose in drinking water for 5 weeks) showed nephrotoxicity of APAP more promptly and more severely than normal ones. Renal APAP-concentrations at the early phase (15 and 30 min. after APAP-administration) were significantly greater in fructose-pretreated rats than those in normal ones. Plasma and hepatic APAP concentrations in fructose-pretreated rats were greater than those in normal ones only at the later phase (plasma; 6 hr, liver; 6 and 12 hr after APAP-administration). There were no significant differences in the APAP-induced depletion of hepatic and renal glutathione and in the basal hepatic and renal cytochrome P-450 contents between these rats. Fructose-pretreated rats were also more susceptible to p-aminophenol (PAP), a nephrotoxic metabolite of APAP, than normal rats. Therefore, enhanced susceptibility to APAP-nephrotoxicity in fructose-pretreated rats may be due, at least in part, to increased renal APAP concentration and increased intrinsic susceptibility to the metabolic nephrotoxicant.