Severe thiamine deficiency complicated by weight loss protects against renal ischaemia-reperfusion injury in rats.

Sir,

Injury due to reperfusion after prior ischaemia (IRI) is an important cause of delayed graft function after renal transplantation [1]. Studies in dogs and rats suggest that thiamine is protective against IRI in heart and brain [2-4]. It has been argued that many organs, including kidneys are deficient in thiamine at the moment of transplantation [4]. We aimed to investigate the effect of severe tissue thiamine deficiency on ischaemia-reperfusion injury in rat kidneys.

Male inbred Lewis rats (± 270 g) (Harlan, Zeist, The Netherlands) were fed with a thiamine-deficient diet (Arie Blok, Woerden, The Netherlands). The diet only contained trace amounts of thiamine (0.16 μg/kg, equalling ∼0.04% of the thiamine content of regular chow). Control animals were orally supplemented with 400 μg thiamine/day in a 2.5% sucrose solution, whereas the thiamine-deficient animals only received the same volume of the sucrose solution. After 4 weeks, ischaemia-reperfusion procedures were performed. Anaesthesia was induced by 5% isoflurane and maintained on 3% isoflurane. The rats were placed on a homothermic table to maintain core body temperature at 37°C and the left kidney was subjected to 45 min of ischaemia, followed by reperfusion. Nephrectomy of the contralateral right kidney was performed during ischaemia of the left kidney. Kidney tissue samples were snap-frozen and stored at −80°C in 4% formalin. Plasma and red blood cells were also stored at −80°C. Tissue transketolase activity was measured according to the kinetic method of Chamberlain et al. [5]. Thiamine, thiamine monophosphate and thiamine pyrophosphate were determined by HPLC with fluorimetric detection [6]. All experimental procedures were approved by the Committee for Animal Experiments of the University of Groningen and performed according to the principles of laboratory animal care.

In the third week of the experiment, growth of the thiamine-deficient rats was significantly slower than that in the control rats (12.1 ± 6.3 g versus 21.0 ± 4.7 g, respectively, P = 0.003). In the fourth week, the thiamine-deficient rats lost weight, whereas the control rats gained weight (−9.5 ± 8.8 g versus 15.4 ± 5.2 g, respectively, P < 0.001), resulting in a significant difference in body weight before ischaemia reperfusion (326 ± 13.8 g versus 355 ± 22.8 g respectively, P = 0.006). Induction of thiamine deficiency resulted in significant decreases in renal biochemical and functional thiamine status at the moment of ischaemia reperfusion (Table 1). There was no difference in baseline plasma creatinine concentrations prior to ischaemia reperfusion between thiamine-deficient and control rats (16.7 ± 1.8 μmol/L versus 16.9 ± 2.4 μmol/L respectively, P = 0.88). At the first day after ischaemia-reperfusion, plasma creatinine concentrations were significantly lower in thiamine-deficient rats than in control rats (71.7 ± 22.2 versus 162 ± 106, respectively, P = 0.02).

Table 1

Transketolase activity and thiamine and thiamine metabolites

		Thiamine deficient
	Control (n = 11)	(n = 8)	P-value
TK activity	13.9 (2.4)	7.7 (1.5)	<0.001
TPP	81.2 (13.2)	15.7 (6.5)	<0.001
TMP	26.2 (4.9)	0.4 (0.4)	<0.001
THM	90.2 (15.2)	2.5 (0.8)	<0.001

TK activity is expressed as mU/mg protein. TPP, TMP and THM are expressed as pmol/mg protein.

In this study, we found that thiamine deficiency complicated by weight loss is protective against renal IRI rather than a factor that increases susceptibility. Interestingly, it is long known that in hearts prolonged fasting protects against IRI [7]. To the best of our knowledge our study is the first to suggest that a similar phenomenon may be present for the kidney. If future studies confirm that fasting/wasting protects against IRI in the kidney, this may lead to identification of new mechanisms and methods for priming of kidneys for prevention of IRI.

Conflict of interest statement. None declared.