Dietary fructose feeding increases adipose methylglyoxal accumulation in rats in association with low expression and activity of glyoxalase-2 - PubMed (original) (raw)

Dietary fructose feeding increases adipose methylglyoxal accumulation in rats in association with low expression and activity of glyoxalase-2

Christopher Masterjohn et al. Nutrients. 2013.

Abstract

Methylglyoxal is a precursor to advanced glycation endproducts that may contribute to diabetes and its cardiovascular-related complications. Methylglyoxal is successively catabolized to D-lactate by glyoxalase-1 and glyoxalase-2. The objective of this study was to determine whether dietary fructose and green tea extract (GTE) differentially regulate methylglyoxal accumulation in liver and adipose, mediated by tissue-specific differences in the glyoxalase system. We fed six week old male Sprague-Dawley rats a low-fructose diet (10% w/w) or a high-fructose diet (60% w/w) containing no GTE or GTE at 0.5% or 1.0% for nine weeks. Fructose-fed rats had higher (P < 0.05) adipose methylglyoxal, but GTE had no effect. Plasma and hepatic methylglyoxal were unaffected by fructose and GTE. Fructose and GTE also had no effect on the expression or activity of glyoxalase-1 and glyoxalase-2 at liver or adipose. Regardless of diet, adipose glyoxalase-2 activity was 10.8-times lower (P < 0.05) than adipose glyoxalase-1 activity and 5.9-times lower than liver glyoxalase-2 activity. Adipose glyoxalase-2 activity was also inversely related to adipose methylglyoxal (r = -0.61; P < 0.05). These findings suggest that fructose-mediated adipose methylglyoxal accumulation is independent of GTE supplementation and that its preferential accumulation in adipose compared to liver is due to low constitutive expression of glyoxalase-2.

PubMed Disclaimer

Figures

Figure 1

Figure 1

Major pathways of methylglyoxal (MGO) formation and detoxification. MGO in vivo is formed primarily from two pathways [2,24]. (Upper Right) triose phosphates derived from glycolysis spontaneously dephosphorylate to form MGO. (Upper Left) Acetone derived from ketogenesis is successively converted by cytochrome P450 2E1 (CYP2E1) to acetol and then to MGO. MGO detoxification (bottom left) occurs through the glutathione (GSH)-dependent glyoxalase (GLO) pathway [2]. MGO and GSH spontaneously form a hemithioacetal adduct that is successively detoxified by GLO-1 and GLO-2 to

d

-lactate, which is then converted to pyruvate by

d

-lactate dehydrogenase.

Figure 2

Figure 2

(a) MGO concentrations in plasma. (b) MGO concentrations in liver. (c) MGO concentrations in adipose. MGO concentrations are shown from rats fed a starch-based control diet containing 50% (w/w) starch and 10% (w/w) fructose (Control), a high-fructose diet containing 60% fructose (Fructose), the fructose diet containing 0.5% green tea extract (GTE) (w/w) (Fructose + 0.5% GTE), or the fructose diet containing 1.0% GTE (Fructose + 1.0% GTE) for nine weeks (means ± SE; n = 8–9/group). Samples were acidified with PCA, derivitized with OPD, and analyzed by HPLC-UV. 1-Way ANOVA main effects are significant for adipose (P < 0.01) but not plasma or liver (_P_ > 0.05). Group means without a common superscript are different (P < 0.05).

Figure 3

Figure 3

GLO-1 and GLO-2 activities in liver and adipose tissue. GLO-1 and GLO-2 activities are shown from rats fed a starch-based control diet containing 50% (w/w) starch and 10% (w/w) fructose (Control), a high-fructose diet containing 60% fructose (Fructose), the fructose diet containing 0.5% GTE (w/w) (Fructose + 0.5% GTE), or the fructose diet containing 1.0% GTE (Fructose + 1.0% GTE) for nine weeks (means ± SE; n = 8–9/group). Enzyme activities were measured spectrophotometrically in tissue homogenate. GLO-1 activity was determined by measuring the rate at which MGO-GSH hemithioacetal was converted to _S_-

d

-lactoylglutathione whereas GLO-2 activity was determined by measuring the disappearance of _S_-

d

/

l

-lactoylglutathione. Data were analyzed by 3-way ANOVA. Main effect of enzyme was significant (P < 0.001), but main effects of tissue and group were not (_P_ > 0.05). A significant tissue by enzyme interaction was observed (P < 0.001), but no other significant interactions were detected (_P_ > 0.05). *, significant difference between tissues for the same GLO enzyme (P < 0.01). $, significant difference between GLO enzymes within a tissue (P < 0.01).

Figure 4

Figure 4

GLO-1 and GLO-2 mRNA expression in liver and adipose tissue. GLO-1 and GLO-2 mRNA expression are shown from rats fed a starch-based control diet containing 50% (w/w) starch and 10% (w/w) fructose (Control), a high-fructose diet containing 60% fructose (Fructose), the fructose diet containing 0.5% GTE (w/w) (Fructose + 0.5% GTE), or the fructose diet containing 1.0% GTE for nine weeks (Fructose + 1.0% GTE) (means ± SE; n = 8–9/group). RNA was isolated using TRIzol and reverse transcribed by MMLV reverse transcriptase for RT-PCR analysis using the primers described in Methods and Materials. Data were normalized to GLO-1 mRNA in the control group and analyzed by 3-way ANOVA. Main effects of tissue and enzyme as well as tissue by enzyme interaction were all significant (P < 0.01). There was no effect of diet (_P_ > 0.05) or interaction between diet and tissue (P > 0.05) or group (P > 0.05). A significant 3-way diet by tissue by enzyme interaction was observed (P < 0.05), but no pairwise differences between diets were detected (_P_ > 0.05). *, significant difference between tissues for the same GLO enzyme (P < 0.01). $, significant difference between GLO enzymes for within a tissue (P < 0.01).

Figure 5

Figure 5

(a) Linear regression of MGO on hepatic GLO-1 activity. (b) Linear regression of hepatic MGO on hepatic GLO-2 activity. (c) Linear regression of adipose MGO on adipose GLO-1 activity. (d) Linear regression of adipose MGO on adipose GLO-2 activity. The relation between adipose GLO-2 and adipose MGO was significant (P < 0.0001), but the other relations were not (_P_ > 0.05).

Similar articles

Cited by

References

    1. Matsumura Y., Iwasawa A., Kobayashi T., Kamachi T., Ozawa T., Kohno M. The reactivity of alpha-oxoaldehyde with reactive oxygen species in diabetes complications. J. Clin. Biochem. Nutr. 2013;52:128–132. doi: 10.3164/jcbn.12-70. - DOI - PMC - PubMed
    1. Thornalley P.J. Glyoxalase I—Structure, function and a critical role in the enzymatic defence against glycation. Biochem. Soc. Trans. 2003;31:1343–1348. doi: 10.1042/BST0311343. - DOI - PubMed
    1. McLellan A.C., Thornalley P.J., Benn J., Sonksen P.H. Glyoxalase system in clinical diabetes mellitus and correlation with diabetic complications. Clin. Sci. (Lond.) 1994;87:21–29. - PubMed
    1. Dhar A., Desai K.M., Wu L. Alagebrium attenuates acute methylglyoxal-induced glucose intolerance in Sprague-Dawley rats. Br. J. Pharmacol. 2010;159:166–175. doi: 10.1111/j.1476-5381.2009.00469.x. - DOI - PMC - PubMed
    1. Dhar A., Dhar I., Jiang B., Desai K.M., Wu L. Chronic methylglyoxal infusion by minipump causes pancreatic beta-cell dysfunction and induces type 2 diabetes in Sprague-Dawley rats. Diabetes. 2011;60:899–908. - PMC - PubMed

Publication types

MeSH terms

Substances

LinkOut - more resources