INTRODUCTION

It is well established that hyperglycemia is a major causative factor for micro-vascular disease. In addition, recent epidemiological reports have suggested that postprandial hyperglycemia is an important risk factor for cardiovascular diseases, although the pathological role of chronic hyperglycemia is still controversial. Several well-researched theories have been proposed to explain how chronic hyperglycemia or postprandial hyperglycemia causes the micro-and macro-vascular derangements. These theories include increased polyol pathway flux, increased advanced glycation end-product (AGE) formation, activation of protein kinase C (PKC) and increased oxidative stress. Among them, oxidative stress has been paid increasing attention to as a common mediator of these biochemical abnormalities. Among many possible sources for oxidative stress, recent reports including ours have shown that a PKC-dependent activation of NAD(P)H oxidase may be a major source for increased oxidative stress in vascular tissues of diabetes and insulin resistant state. In this article, we show that this mechanism may be an effective therapeutic target for preventing diabetic vascular complications.

INCREASED OXIDATIVE STRESS IN DIABETIC VASCULAR TISSUES AND ITS UNDERLYING MECHANISM

A number of in vitro and in vivo studies have demonstrated that many protein, lipid and DNA markers of oxidative stress are increased in vascular tissues from animals and patients with diabetes [1-4]. We also showed the increase in reactive oxygen species (ROS) production in diabetic animal models by in vivo electron spin resonance method that is non-invasive and more specific than above-mentioned oxidative stress markers [5]. Several mechanisms for increased oxidative stress have been postulated. In the process of mitochondrial respiration, several percentages of oxygen consumed is converted into superoxide. High glucose level was reported to increase such a mitochondrial superoxide production in vascular endothelial cells [6]. High glucose level also can increase ROS production through glucose auto-oxidation, increased non-enzymatic glycation of proteins and activation of xanthine oxidase. Among possible various sources, increasing evidence has indicated that NAD(P)H oxidase may be the most important source for ROS production in diabetic vascular tissues. We first reported that high glucose level stimulated ROS production in cultured vascular cells through a PKC-dependent activation of NAD(P)H oxidase [7]. The non-phagocytic NAD(P)H oxidase comprises of a membrane-associated cytochrome b558 composed of Nox family proteins (gp91phox, Nox1, and Nox4) and p22phox, and several cytosolic regulatory components, p47phox, p67phox and small GTP binding protein Rac 1 or Rac 2. Our in vitro evidence has been supported by accumulating evidence showing that the activity of NAD(P)H oxidase, in parallel with the increased level of its subunit proteins, is increased in vascular tissues form animal models and diabetic patients [5,8-11]. We also reported that the expression of essential subunits of Nox4 and p22phox in the kidney of diabetic animal models [12]. Activation of Rac-1 and translocation of p47phox and p67phox, both of which are mediated by PKC activation, are supposed to be the mechanism underlying high glucose level-induced NAD(P)H oxidase activation [13,14]. The superoxide production from NAD(P)H oxidase is controlled by its expression dynamics as well as by its activation. The mechanism for increased expression of NAD(P)H oxidase subunits in diabetic vascular tissues remained to be well established, since the regulatory mechanism of the expression of NAD(P)Oxidase subunits is generally not fully understood. In the knockout mouse of the PKC β isoform, the normalization of increased expression of Nox4, oxidative stress, proteinuria and tissue abnormalities in diabetic kidney was observed [15]. These findings also support the role of PKC activation in the increased expression of NAD(P)H oxidase subunits. The detailed molecular mechanism should be clarified in the further studies.

ROLE OF LOCAL RENIN-ANGIOTENSIN SYSTEM IN OXIDATIVE STRESS

Experimental and clinical trials have suggested that blockade of the renin-angiotensin system (RAS) with angiotensin 1-converting enzyme (ACE) inhibitors or angiotensin II (ATII) receptor blocker (ARB) have some protective effects on diabetic nephropathy and cardiovascular events, which appear to be independent of its antihypertensive effect. ATII was reported to mediate NAD(P)H oxidase-dependent superoxide production via PKC activation. We reported the improvement of Nox4 expression and oxidative stress in the kidney of diabetic mice by administration of ARB [16]. ACE is involved in the production of tissue ATII, but it is recently suggested that chymase has more efficient tissue ATII-forming activities than ACE in several species including human and hamsters. In addition, several reports have shown that chymase expression may be up-regulated in diabetic renal tissues [17]. We have confirmed that chymase expression increases in renal tissues, aorta and cardiac tissues of streptozotocin-induced diabetic hamster and examined the effect of chymase-specific inhibitor [18]. Oral administration of the chymase-specific inhibitors protected against elevated intra-renal ATII concentrations, Nox4 expression, oxidative stress, and renal dysfunction including proteinuria and mesangial expansion in streptozotocin-induced diabetic hamsters [18]. It also normalized oxidative stress, Nox4 expression and myocardial fibrosis in diabetic hamsters [19]. Because low-grade inflammation is known to occur in diabetic vascular tissues, including renal tissues, infiltrated inflammatory cells, such as mast cells, may be the source of the increased chymase levels. High glucose is the initiator of increased oxidative stress and inflammation, but the subsequent increases in chymase expression and local ATII production may further accelerate ROS production and inflammation, ultimately forming a vicious cycle of oxidative stress and inflammation, although this hypothesis should be evaluated in future studies.

HUMAN EVIDENCE FOR THE EFFECTIVENESS OF ANTIOXIDANT ON DIABETIC COMPLICATIONS

Although the involvement of oxidative stress in diabetic vascular complications has been demonstrated in vitro and in animal studies, the effectiveness of antioxidant therapy is still controversial because there have been very few human studies indicating the beneficial effects of antioxidants on diabetic vascular complications. Bilirubin has been recognized as an important endogenous antioxidant [20] and also reported to have an inhibitory effect on the activity of NAD(P)H oxidase [21]. We therefore compared the prevalence of vascular complications in patients with diabetes and Gilbert syndrome (a congenital hyperbilirubinemia) and in patients with diabetes without Gilbert syndrome [22]. The adjusted odds ratio for the association of Gilbert syndrome with retinopathy was 0.22 (P<001); with macroalbuminuria, 0.20 (P=0.01); with coronary artery disease, 0.21 (P=0.04); and with cerebrovascular disease, 0.50 (P=0.22) (Table 1). This study showed for the first time the lower prevalence of vascular complications in patients with diabetes and Gilbert syndrome, as well as reduced markers of oxidative stress and inflammation (Fig. 1). These findings strongly suggest that antioxidant therapy may be useful for preventing the development of diabetic vascular complications. Furthermore, serum bilirubin concentrations were demonstrated to be negatively associated with albuminuria in patients with type 2 diabetes [23]. Another group of Japanese investigators reported in their cross-sectional study on more than 3,000 participants, that compared to subjects with in the lowest bilirubin quartile, those with the highest bilirubin levels had a four times lower prevalence of diabetic retinopathy [24]. Interestingly, our cross-sectional study of 12,949 general persons revealed an inverse relation between serum bilirubin level and the prevalence of type 2 diabetes [25]. In a large Korean cross-sectional study on almost 94,000 subjects, high serum bilirubin was also found to be associated with the reduced risk of diabetes mellitus and diabetic nephropathy [26]. Consistent with these data, low prevalence of metabolic syndrome in subjects with phenotypic Gilbert syndrome was described in a recent large Korean study on more than12,000 participants [27]. Antioxidant therapy may be useful for inhibiting the onset of diabetes itself as well as inhibiting diabetic complications.

ANTIOXIDANT THERAPY TARGETING THE MECHANISM FOR PKC-NAD(P)H OXIDASE ACTIVATION

We have proposed an antioxidant therapy using the drugs or chemicals which target the mechanism for PKC-NAD(P)H oxidase activation for preventing diabetic vascular complications [28]. The possible mechanism underlying PKC-NAD(P)H oxidase activation and drugs or chemicals targeting its mechanism are shown in Fig. 2.

Statin

We noted the ability of statin to inhibit geranylgeranylation of small GTP binding protein Rho family including Rac. We found that pitavastatin inhibited high glucose-induced increase in ROS production in parallel with inhibition of Rac-1 activity in cultured aortic smooth muscle cells [13]. Such inhibition by pitavastatin was reversed by coincubation with mevalonic acid. In addition, we found that pitavastatin treatment prevented the increased free ROS production in diabetic rats using the above-mentioned in vivo electron spin resonance method [13]. Furthermore, we showed that pitavastatin administration improved albuminuria and histologic abnormalities such as increased renal mesangial expansion in db/db mice, along with the improvement of renal Nox4 expression and oxidative stress [29]. The results in recent our clinical trial may be in support for the effectiveness of pitavastatin treatment on albuminuria in diabetic patients [30].

ARB and chymase-specific inhibitor

In addition to the beneficial effect on vascular complications, we have shown that oral administration of ARB attenuated the increased expression of NAD(P)H oxidase in pancreatic islets together with the inhibition of oxidative stress and restored decreased insulin contents in islets of db/db mice [31]. These drugs may have a protective effect on the onset of type 2 diabetes.

Bilirubin and biliverdin

To directly examine the beneficial effect of bilirubin and biliverdin (a precursor of bilirubin), we determined whether hereditary hyperbilirubinemic Gunn rats and biliverdin-treated diabetic db/db mice were resistant to the development of renal dysfunction. Both rodent models had less albuminuria and complete protection against the progression of mesangial expansion, accompanied by the normalization of oxidative stress and Nox4 expression [32]. These results suggested that biliverdin and biliverdin may protect against diabetic nephropathy and this may lead to a novel antioxidant therapy for diabetic nephropathy. Similar beneficial effect was also found in oral administration of phycocyanin derived from Spirulina platensis, a blue-green algae, and its chromophore phycocyanobilin, which has a chemical structure similar to that of biliverdin (unpublished data).

In addition, biliverdin treatment delayed progressive worsening of glucose tolerance in db/db mice mainly via inhibition of oxidative stress-induced β-cell damage, suggesting the possible effectiveness of antioxidant therapy for preventing the onset type 2 diabetes as well as preventing diabetic complications [33].

PKC β2 inhibitor

Among various isoforms, preferential activation of PKC β isoform is reported to occur in many vascular tissues in the diabetic state [34]. PKC β isoform-specific inhibitor LY33531 improves dysfunction and tissue changes in kidney and retina of the experimental diabetic animal model [35] and the results in the clinical trial are reported to be useful [36], although it does not yet reach a clinical application. The participation of the antioxidant action is presumed in part of the mechanism.

Glucagon-like peptide-1 (GLP-1) analog

Currently, the GLP-1 receptor agonist exendin-4 and the GLP-1 analog liraglutide are used to treat type 2 diabetes. The major downstream pathway of GLP-1 receptor activation is generation of the second messenger cAMP followed by activation of PKA or Epac2, and NAD(P)H oxidases have been reported to be inhibited by PKA activation in phagocytes. We therefore hypothesized that GLP-1 receptor agonists may inhibit renal NAD(P)H oxidase. In the streptozotocin-induced type 1 diabetes models, liraglutide treatment did not significantly affect plasma glucose levels or body weights, but it still normalized urinary albuminuria in diabetic rats in parallel with normalization of oxidative stress and expression of renal NAD(P)H oxidase components (Nox4, gp91phox, p22phox, p47phox), independently of a glucose-lowering effect [37]. Liraglutide inhibited NADPH-dependent superoxide production from cultured renal mesangial cells, and its inhibitory effect was reversed by the adenylate cyclase inhibitor SQ22536 and the PKA inhibitor H89, but not reversed by Epac2 inhibition. These results suggested that the effect of liraglutide on NAD(P)H oxidase was mediated by the cAMP-PKA pathway. Its clinical efficacy should be tested in human trial.

CONCLUSION

In this review, the experimental and clinical studies on the role of oxidative stress in the development of diabetic vascular complication and the molecular mechanism underlying oxidative stress are discussed. These studies strongly show that antioxidant therapy is potentially effective to protect against diabetic vascular complications and one of the therapeutic targeting mechanism is activation or up-regulation of PKC-NAD(P)H oxidase. In this article, the effectiveness of several drugs or chemicals which can inhibit this mechanism is shown. These drug or chemicals are expected to be clinically effective for preventing diabetic vascular complications, but the development of more effective drugs for clinical use is also expected.

Acknowledgements

ACKNOWLEDGMENTS

We appreciate the excellent assistance of Ms. Eri Nagashima for making this manuscript. This work was supported in part by the Special Coordination Funds for Promoting Science and Technology, Japan (SCF funding program "Innovation Center for Medical Redox Navigation").

NOTES

No potential conflict of interest relevant to this article was reported.

REFERENCES

• 1. Baynes JW. Role of oxidative stress in development of complications in diabetes. Diabetes 1991;40:405-412. ArticlePubMed
• 2. Oberley LW. Free radicals and diabetes. Free Radic Biol Med 1988;5:113-124. ArticlePubMed
• 3. Ha H, Kim C, Son Y, Chung MH, Kim KH. DNA damage in the kidneys of diabetic rats exhibiting microalbuminuria. Free Radic Biol Med 1994;16:271-274. ArticlePubMed
• 4. Kakimoto M, Inoguchi T, Sonta T, Yu HY, Imamura M, Etoh T, Hashimoto T, Nawata H. Accumulation of 8-hydroxy-2'-deoxyguanosine and mitochondrial DNA deletion in kidney of diabetic rats. Diabetes 2002;51:1588-1595. ArticlePubMedPDF
• 5. Sonta T, Inoguchi T, Tsubouchi H, Sekiguchi N, Kobayashi K, Matsumoto S, Utsumi H, Nawata H. Evidence for contribution of vascular NAD(P)H oxidase to increased oxidative stress in animal models of diabetes and obesity. Free Radic Biol Med 2004;37:115-123. ArticlePubMed
• 6. Nishikawa T, Edelstein D, Du XL, Yamagishi S, Matsumura T, Kaneda Y, Yorek MA, Beebe D, Oates PJ, Hammes HP, Giardino I, Brownlee M. Normalizing mitochondrial superoxide production blocks three pathways of hyperglycaemic damage. Nature 2000;404:787-790. ArticlePubMedPDF
• 7. Inoguchi T, Li P, Umeda F, Yu HY, Kakimoto M, Imamura M, Aoki T, Etoh T, Hashimoto T, Naruse M, Sano H, Utsumi H, Nawata H. High glucose level and free fatty acid stimulate reactive oxygen species production through protein kinase C: dependent activation of NAD(P)H oxidase in cultured vascular cells. Diabetes 2000;49:1939-1945. ArticlePubMedPDF
• 8. Hink U, Li H, Mollnau H, Oelze M, Matheis E, Hartmann M, Skatchkov M, Thaiss F, Stahl RA, Warnholtz A, Meinertz T, Griendling K, Harrison DG, Forstermann U, Munzel T. Mechanisms underlying endothelial dysfunction in diabetes mellitus. Circ Res 2001;88:E14-E22. ArticlePubMed
• 9. Kim YK, Lee MS, Son SM, Kim IJ, Lee WS, Rhim BY, Hong KW, Kim CD. Vascular NADH oxidase is involved in impaired endothelium-dependent vasodilation in OLETF rats, a model of type 2 diabetes. Diabetes 2002;51:522-527. ArticlePubMedPDF
• 10. Guzik TJ, Mussa S, Gastaldi D, Sadowski J, Ratnatunga C, Pillai R, Channon KM. Mechanisms of increased vascular superoxide production in human diabetes mellitus: role of NAD(P)H oxidase and endothelial nitric oxide synthase. Circulation 2002;105:1656-1662. ArticlePubMed
• 11. Inoguchi T, Sonta T, Tsubouchi H, Etoh T, Kakimoto M, Sonoda N, Sato N, Sekiguchi N, Kobayashi K, Sumimoto H, Utsumi H, Nawata H. Protein kinase C-dependent increase in reactive oxygen species (ROS) production in vascular tissues of diabetes: role of vascular NAD(P)H oxidase. J Am Soc Nephrol 2003;14(8 Suppl 3):S227-S232. PubMed
• 12. Etoh T, Inoguchi T, Kakimoto M, Sonoda N, Kobayashi K, Kuroda J, Sumimoto H, Nawata H. Increased expression of NAD(P)H oxidase subunits, NOX4 and p22phox, in the kidney of streptozotocin-induced diabetic rats and its reversibity by interventive insulin treatment. Diabetologia 2003;46:1428-1437. ArticlePubMedPDF
• 13. Tsubouchi H, Inoguchi T, Sonta T, Sato N, Sekiguchi N, Kobayashi K, Sumimoto H, Utsumi H, Nawata H. Statin attenuates high glucose-induced and diabetes-induced oxidative stress in vitro and in vivo evaluated by electron spin resonance measurement. Free Radic Biol Med 2005;39:444-452. ArticlePubMed
• 14. Kitada M, Koya D, Sugimoto T, Isono M, Araki S, Kashiwagi A, Haneda M. Translocation of glomerular p47phox and p67phox by protein kinase C-beta activation is required for oxidative stress in diabetic nephropathy. Diabetes 2003;52:2603-2614. PubMed
• 15. Ohshiro Y, Ma RC, Yasuda Y, Hiraoka-Yamamoto J, Clermont AC, Isshiki K, Yagi K, Arikawa E, Kern TS, King GL. Reduction of diabetes-induced oxidative stress, fibrotic cytokine expression, and renal dysfunction in protein kinase Cbeta-null mice. Diabetes 2006;55:3112-3120. PubMed
• 16. Sonta T, Inoguchi T, Matsumoto S, Yasukawa K, Inuo M, Tsubouchi H, Sonoda N, Kobayashi K, Utsumi H, Nawata H. In vivo imaging of oxidative stress in the kidney of diabetic mice and its normalization by angiotensin II type 1 receptor blocker. Biochem Biophys Res Commun 2005;330:415-422. ArticlePubMed
• 17. Huang XR, Chen WY, Truong LD, Lan HY. Chymase is upregulated in diabetic nephropathy: implications for an alternative pathway of angiotensin II-mediated diabetic renal and vascular disease. J Am Soc Nephrol 2003;14:1738-1747. PubMed
• 18. Maeda Y, Inoguchi T, Takei R, Sawada F, Sasaki S, Fujii M, Kobayashi K, Urata H, Nishiyama A, Takayanagi R. Inhibition of chymase protects against diabetes-induced oxidative stress and renal dysfunction in hamsters. Am J Physiol Renal Physiol 2010;299:F1328-F1338. ArticlePubMed
• 19. Maeda Y, Inoguchi T, Takei R, Hendarto H, Ide M, Inoue T, Kobayashi K, Urata H, Nishiyama A, Takayanagi R. Chymase inhibition prevents myocardial fibrosis through the attenuation of NOX4-associated oxidative stress in diabetic hamsters. J Diabetes Investig Epub 2012 Feb 21. DOI: http://dx.doi.org/10.1111/j.2040-1124.2012.00202.x.Article
• 20. Stocker R, Yamamoto Y, McDonagh AF, Glazer AN, Ames BN. Bilirubin is an antioxidant of possible physiological importance. Science 1987;235:1043-1046. ArticlePubMed
• 21. Lanone S, Bloc S, Foresti R, Almolki A, Taille C, Callebert J, Conti M, Goven D, Aubier M, Dureuil B, El-Benna J, Motterlini R, Boczkowski J. Bilirubin decreases nos2 expression via inhibition of NAD(P)H oxidase: implications for protection against endotoxic shock in rats. FASEB J 2005;19:1890-1892. ArticlePubMedPDF
• 22. Inoguchi T, Sasaki S, Kobayashi K, Takayanagi R, Yamada T. Relationship between Gilbert syndrome and prevalence of vascular complications in patients with diabetes. JAMA 2007;298:1398-1400. Article
• 23. Fukui M, Tanaka M, Shiraishi E, Harusato I, Hosoda H, Asano M, Hasegawa G, Nakamura N. Relationship between serum bilirubin and albuminuria in patients with type 2 diabetes. Kidney Int 2008;74:1197-1201. ArticlePubMed
• 24. Yasuda M, Kiyohara Y, Wang JJ, Arakawa S, Yonemoto K, Doi Y, Ninomiya T, Ishibashi T. High serum bilirubin levels and diabetic retinopathy: the Hisayama Study. Ophthalmology 2011;118:1423-1428. ArticlePubMed
• 25. Ohnaka K, Kono S, Inoguchi T, Yin G, Morita M, Adachi M, Kawate H, Takayanagi R. Inverse associations of serum bilirubin with high sensitivity C-reactive protein, glycated hemoglobin, and prevalence of type 2 diabetes in middle-aged and elderly Japanese men and women. Diabetes Res Clin Pract 2010;88:103-110. ArticlePubMed
• 26. Han SS, Na KY, Chae DW, Kim YS, Kim S, Chin HJ. High serum bilirubin is associated with the reduced risk of diabetes mellitus and diabetic nephropathy. Tohoku J Exp Med 2010;221:133-140. ArticlePubMed
• 27. Choi SH, Yun KE, Choi HJ. Relationships between serum total bilirubin levels and metabolic syndrome in Korean adults. Nutr Metab Cardiovasc Dis Epub 2011 Jun 22. DOI: http://dx.doi.org/10.1016/j.numecd.2011.03.001.Article
• 28. Inoguchi T, Nawata H. NAD(P)H oxidase activation: a potential target mechanism for diabetic vascular complications, progressive beta-cell dysfunction and metabolic syndrome. Curr Drug Targets 2005;6:495-501. PubMed
• 29. Fujii M, Inoguchi T, Maeda Y, Sasaki S, Sawada F, Saito R, Kobayashi K, Sumimoto H, Takayanagi R. Pitavastatin ameliorates albuminuria and renal mesangial expansion by downregulating NOX4 in db/db mice. Kidney Int 2007;72:473-480. ArticlePubMed
• 30. Kimura S, Inoguchi T, Yokomizo H, Maeda Y, Sonoda N, Takayanagi R. Randomized comparison of pitavastatin and pravastatin treatment on the reduction of urinary albumin in patients with type 2 diabetic nephropathy. Diabetes Obes Metab 2012;14:666-669. ArticlePubMed
• 31. Nakayama M, Inoguchi T, Sonta T, Maeda Y, Sasaki S, Sawada F, Tsubouchi H, Sonoda N, Kobayashi K, Sumimoto H, Nawata H. Increased expression of NAD(P)H oxidase in islets of animal models of type 2 diabetes and its improvement by an AT1 receptor antagonist. Biochem Biophys Res Commun 2005;332:927-933. ArticlePubMed
• 32. Fujii M, Inoguchi T, Sasaki S, Maeda Y, Zheng J, Kobayashi K, Takayanagi R. Bilirubin and biliverdin protect rodents against diabetic nephropathy by downregulating NAD(P)H oxidase. Kidney Int 2010;78:905-919. ArticlePubMed
• 33. Ikeda N, Inoguchi T, Sonoda N, Fujii M, Takei R, Hirata E, Yokomizo H, Zheng J, Maeda Y, Kobayashi K, Takayanagi R. Biliverdin protects against the deterioration of glucose tolerance in db/db mice. Diabetologia 2011;54:2183-2191. ArticlePubMedPDF
• 34. Inoguchi T, Battan R, Handler E, Sportsman JR, Heath W, King GL. Preferential elevation of protein kinase C isoform beta II and diacylglycerol levels in the aorta and heart of diabetic rats: differential reversibility to glycemic control by islet cell transplantation. Proc Natl Acad Sci U S A 1992;89:11059-11063. ArticlePubMedPMC
• 35. Ishii H, Jirousek MR, Koya D, Takagi C, Xia P, Clermont A, Bursell SE, Kern TS, Ballas LM, Heath WF, Stramm LE, Feener EP, King GL. Amelioration of vascular dysfunctions in diabetic rats by an oral PKC beta inhibitor. Science 1996;272:728-731. ArticlePubMed
• 36. He Z, King GL. Can protein kinase C beta-selective inhibitor, ruboxistaurin, stop vascular complications in diabetic patients? Diabetes Care 2005;28:2803-2805. PubMed
• 37. Hendarto H, Inoguchi T, Maeda Y, Ikeda N, Zheng J, Takei R, Yokomizo H, Hirata E, Sonoda N, Takayanagi R. GLP-1 analog liraglutide protects against oxidative stress and albuminuria in streptozotocin-induced diabetic rats via protein kinase A-mediated inhibition of renal NAD(P)H oxidases. Metabolism Epub 2012 May 1. DOI: http://dx.doi.org/10.1016/j.metabol.2012.03.002.Article

Fig. 1

Serum high sensitivity C-reactive protein (hs-CRP) levels and the amounts of urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) excretion. (A) Comparison between diabetic patients with Gilbert syndrome, GS (+), and those without it, GS (-). Due to their skewed distribution, serum hs-CRP levels (ng/mL) and the amounts of urinary 8-OHdG excretion (urinary 8-OHdG to creatinine ratio, µg/gCr) were log10 transformed before all analyses. (B) Correlation between total bilirubin levels and serum hs-CRP levels. Spearman correlation analysis: r=-0.213, P<0.0001.

Fig. 2

The mechanism underlying increased oxidative stress in diabetic vascular tissues and possible antioxidant therapies targeting its mechanism for inhibiting diabetic vascular complications. ARB, angiotensin II receptor blocker; PKC, protein kinase C; ATII, angiotensin II; GLP-1, glucagon-like peptide-1.

Table 1

Adjusted odds ratio for retinopathy, macroalbuminuria, coronary artery disease and cerebrovascular disease in diabetic patients with Gilbert syndrome compared with those without it

In stepwise logistic regression analysis, the prevalence of retinopathy was significantly associated with Gilbert syndrome (GS), duration of diabetes, HbA1c; the prevalence of macroalbumiuria was associated with GS, duration of diabetes, triglyceride; the prevalence of coronary artery disease was associated with GS, duration of diabetes, systolic blood pressure; the prevalence of cerebrovascular disease was associated with age, triglyceride, but not GS.

Odds ratio (OR) for retinopathy, macroalbuminuria, coronary artery disease and cerebrovascular disease was adjusted for significantly determinant variables, respectively.

Figure & Data

References

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  Archives of Pharmacal Research.2019; 42(3): 252.     CrossRef
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  So Jin Lee, Hun Ju Lee, Hyun jeong Oh, Taehwa Go, Dae Ryong Kang, Jang Young Kim, Ji Hye Huh
  Scientific Reports.2018;[Epub]     CrossRef
• Role of peroxisome proliferator–activated receptor-gamma activation on visfatin, advanced glycation end products, and renal oxidative stress in obesity-induced type 2 diabetes mellitus
  A Tabassum, T Mahboob
  Human & Experimental Toxicology.2018; 37(11): 1187.     CrossRef
• Coffee consumption and reduced risk of developing type 2 diabetes: a systematic review with meta-analysis
  Mattias Carlström, Susanna C Larsson
  Nutrition Reviews.2018; 76(6): 395.     CrossRef
• Liraglutide ameliorates early renal injury by the activation of renal FoxO1 in a type 2 diabetic kidney disease rat model
  Pin Chen, Xiaozhi Shi, Xiangjin Xu, Yiyang Lin, Zhulin Shao, Rongdan Wu, Lihong Huang
  Diabetes Research and Clinical Practice.2018; 137: 173.     CrossRef
• Antioxidant effects of vitamins in type 2 diabetes: a meta-analysis of randomized controlled trials
  Maria E. Balbi, Fernanda S. Tonin, Antonio M. Mendes, Helena H. Borba, Astrid Wiens, Fernando Fernandez-Llimos, Roberto Pontarolo
  Diabetology & Metabolic Syndrome.2018;[Epub]     CrossRef
• Gilbert syndrome in patients with type 1 diabetes-Prevalence, glycemic control, and microalbuminuria
  Sigal Singer, Nurit Pilpel, Orit Pinhas-Hamiel
  Pediatric Diabetes.2017; 18(8): 803.     CrossRef
• Low serum bilirubin level predicts the development of chronic kidney disease in patients with type 2 diabetes mellitus
  Kang Hee Ahn, Sang Soo Kim, Won Jin Kim, Jong Ho Kim, Yun Jeong Nam, Su Bin Park, Yun Kyung Jeon, Bo Hyun Kim, In Joo Kim, Yong Ki Kim
  The Korean Journal of Internal Medicine.2017; 32(5): 875.     CrossRef
• Tiron ameliorates high glucose‐induced cardiac myocyte apoptosis by PKCδ‐dependent inhibition of osteopontin
  Ping Jiang, Deling Zhang, Hong Qiu, Xianqi Yi, Yemin Zhang, Yingkang Cao, Bo Zhao, Zhongyuan Xia, Changhua Wang
  Clinical and Experimental Pharmacology and Physiology.2017; 44(7): 760.     CrossRef
• Protective effects of 6-Gingerol on vascular endothelial cell injury induced by high glucose via activation of PI3K-AKT-eNOS pathway in human umbilical vein endothelial cells
  Dan Liu, Mengqing Wu, Yi Lu, Tao Xian, Yupeng Wang, Bowei Huang, Guohua Zeng, Qiren Huang
  Biomedicine & Pharmacotherapy.2017; 93: 788.     CrossRef
• Adenosine signaling in diabetes mellitus and associated cardiovascular and renal complications
  Maria Peleli, Mattias Carlstrom
  Molecular Aspects of Medicine.2017; 55: 62.     CrossRef
• Diabetes and increased lipid peroxidation are associated with systemic inflammation even in well-controlled patients
  Alliny de Souza Bastos, Dana T. Graves, Ana Paula de Melo Loureiro, Carlos Rossa Júnior, Sâmia Cruz Tfaile Corbi, Fausto Frizzera, Raquel Mantuaneli Scarel-Caminaga, Niels Olsen Câmara, Oelisoa M. Andriankaja, Meire I. Hiyane, Silvana Regina Perez Orrico
  Journal of Diabetes and its Complications.2016; 30(8): 1593.     CrossRef
• Agkistrodon acutus-purified protein C activator protects human umbilical vein endothelial cells against H2O2-induced apoptosis
  Shu Li, Yun Hong, Xin Jin, Xianwei Li, Entao Sun, Genbao Zhang, Linming Lu, Liuwang Nie
  Pharmaceutical Biology.2016; 54(12): 3285.     CrossRef
• The impact of mast cells on cardiovascular diseases
  Eva Kritikou, Johan Kuiper, Petri T. Kovanen, Ilze Bot
  European Journal of Pharmacology.2016; 778: 103.     CrossRef
• Comparison of acarbose and metformin therapy in newly diagnosed type 2 diabetic patients with overweight and/or obesity
  Weiping Sun, Chunping Zeng, Lizhen Liao, Juan Chen, Ying Wang
  Current Medical Research and Opinion.2016; 32(8): 1389.     CrossRef
• Mechanisms for the cardiovascular effects of glucagon-like peptide-1
  H. Poudyal
  Acta Physiologica.2016; 216(3): 277.     CrossRef
• Integrated scientific data bases review on asulacrine and associated toxicity
  Attia Afzal, Muhammad Sarfraz, Zimei Wu, Guangji Wang, Jianguo Sun
  Critical Reviews in Oncology/Hematology.2016; 104: 78.     CrossRef
• Impact of Diabetes and Defective Thyroid Ontogenesis on Audition
  Luciene da Cruz Fernandes
  Journal of Diabetes, Metabolic Disorders & Control.2016;[Epub]     CrossRef
• Serum Total Bilirubin Levels Provide Additive Risk Information over the Framingham Risk Score for Identifying Asymptomatic Diabetic Patients at Higher Risk for Coronary Artery Stenosis
  Jaechan Leem, Eun Hee Koh, Jung Eun Jang, Chang-Yun Woo, Jin Sun Oh, Min Jung Lee, Joon-Won Kang, Tae-Hwan Lim, Chang Hee Jung, Woo Je Lee, Joong-Yeol Park, Ki-Up Lee
  Diabetes & Metabolism Journal.2015; 39(5): 414.     CrossRef
• Clinical implications of carotid artery intima media thickness assessment on cardiovascular risk stratification in hyperlipidemic Korean adults with diabetes: the ALTO study
  Eun-Gyoung Hong, Jung Hun Ohn, Seong Jin Lee, Hyuk Sang Kwon, Sin Gon Kim, Dong Jun Kim, Dong Sun Kim
  BMC Cardiovascular Disorders.2015;[Epub]     CrossRef
• Undiagnosed diabetes is prevalent in younger adults and associated with a higher risk cardiometabolic profile compared to diagnosed diabetes
  Yong-ho Lee, Ehrin J. Armstrong, Gyuri Kim, Jaewon Oh, Seok-Min Kang, Byung-Wan Lee, Chul Woo Ahn, Bong Soo Cha, Hyun Chul Lee, Christos S. Mantzoros, Eun Seok Kang
  American Heart Journal.2015; 170(4): 760.     CrossRef
• Common polymorphisms in antioxidant genes are associated with diabetic nephropathy in Type 2 diabetes patients
  Jasna Klen, Katja Goričar, Andrej Janež, Vita Dolžan
  Personalized Medicine.2015; 12(3): 187.     CrossRef
• Increased endogenous serotonin level in diabetic conditions may lead to cardiac valvulopathy via reactive oxygen species regulation
  Tahir Ali, Hina Waheed, Farhat Shaheen, Madiha Mahmud, Qamar Javed, Iram Murtaza
  Biologia.2015; 70(2): 273.     CrossRef
• Antioxidant Effects of Statins in the Management of Cardiometabolic Disorders
  Soo Lim, Philip Barter
  Journal of Atherosclerosis and Thrombosis.2014; 21(10): 997.     CrossRef
• Evidence-Based Practice Use of Incretin-Based Therapy in the Natural History of Diabetes
  Stanley Schwartz
  Postgraduate Medicine.2014; 126(3): 66.     CrossRef
• Low serum bilirubin concentration is a novel risk factor for the development of albuminuria in patients with type 2 diabetes
  Hiroshi Okada, Michiaki Fukui, Muhei Tanaka, Shinobu Matsumoto, Kanae Kobayashi, Hiroya Iwase, Kiichiro Tomiyasu, Koji Nakano, Goji Hasegawa, Naoto Nakamura
  Metabolism.2014; 63(3): 409.     CrossRef
• Serum total bilirubin levels and prevalence of diabetic retinopathy in a Chinese population (中国人群血清总胆红素水平与糖尿病视网膜病变相关性的研究)
  Syeda Sadia Najam, Jichao Sun, Jie Zhang, Min Xu, Jieli Lu, Kan Sun, Mian Li, Tiange Wang, Yufang Bi, Guang Ning
  Journal of Diabetes.2014; 6(3): 221.     CrossRef
• Roles of oxidative stress, adiponectin, and nuclear hormone receptors in obesity-associated insulin resistance and cardiovascular risk
  Morihiro Matsuda, Iichiro Shimomura
  Hormone Molecular Biology and Clinical Investigation.2014;[Epub]     CrossRef
• Unilateral injection of Aβ25–35 in the hippocampus reduces the number of dendritic spines in hyperglycemic rats
  Zayda Lazcano, Oscar Solis, María Elena Bringas, Daniel Limón, Alfonso Diaz, Blanca Espinosa, Isabel García‐Peláez, Gonzalo Flores, Jorge Guevara
  Synapse.2014; 68(12): 585.     CrossRef
• Role of angiotensin-converting enzyme 2 (ACE2) in diabetic cardiovascular complications
  Vaibhav B. Patel, Nirmal Parajuli, Gavin Y. Oudit
  Clinical Science.2014; 126(7): 471.     CrossRef
• Pathogenesis of Chronic Hyperglycemia: From Reductive Stress to Oxidative Stress
  Liang-Jun Yan
  Journal of Diabetes Research.2014; 2014: 1.     CrossRef
• Daily intake of vitamin D‐ or calcium‐vitamin D‐fortified Persian yogurt drink (doogh) attenuates diabetes‐induced oxidative stress: evidence for antioxidative properties of vitamin D
  B. Nikooyeh, T. R. Neyestani, N. Tayebinejad, H. Alavi‐Majd, N. Shariatzadeh, A. Kalayi, M. Zahedirad, S. Heravifard, S. Salekzamani
  Journal of Human Nutrition and Dietetics.2014; 27(s2): 276.     CrossRef
• Roles of adiponectin and oxidative stress in obesity-associated metabolic and cardiovascular diseases
  Morihiro Matsuda, Iichiro Shimomura
  Reviews in Endocrine and Metabolic Disorders.2014; 15(1): 1.     CrossRef
• PKCδ-dependent Activation of the Ubiquitin Proteasome System is Responsible for High Glucose-induced Human Breast Cancer MCF-7 Cell Proliferation, Migration and Invasion
  Shan Zhu, Feng Yao, Wen-Huan Li, Jin-Nan Wan, Yi-Min Zhang, Zhao Tang, Shahzad Khan, Chang-Hua Wang, Sheng-Rong Sun
  Asian Pacific Journal of Cancer Prevention.2013; 14(10): 5687.     CrossRef
• Increased oxidative stress in obesity: Implications for metabolic syndrome, diabetes, hypertension, dyslipidemia, atherosclerosis, and cancer
  Morihiro Matsuda, Iichiro Shimomura
  Obesity Research & Clinical Practice.2013; 7(5): e330.     CrossRef
• Hydrogen Sulfide Suppresses High Glucose–Induced Expression of Intercellular Adhesion Molecule-1 in Endothelial Cells
  Qingbo Guan, Xiaolei Wang, Ling Gao, Jicui Chen, Yuantao Liu, Chunxiao Yu, Nan Zhang, Xu Zhang, Jiajun Zhao
  Journal of Cardiovascular Pharmacology.2013; 62(3): 278.     CrossRef
• Clinical Marker of Platelet Hyperreactivity in Diabetes Mellitus
  Jin Hwa Kim, Hak Yeon Bae, Sang Yong Kim
  Diabetes & Metabolism Journal.2013; 37(6): 423.     CrossRef
• Glucose initially inhibits and later stimulates blood ROS generation
  Thomas Stief
  Journal of Diabetes Mellitus.2013; 03(01): 15.     CrossRef
• Oxidative Stress in Cardiovascular Diseases and Obesity: Role of p66Shc and Protein Kinase C
  Elena De Marchi, Federica Baldassari, Angela Bononi, Mariusz R. Wieckowski, Paolo Pinton
  Oxidative Medicine and Cellular Longevity.2013; 2013: 1.     CrossRef
• Toxicological and pharmacological concerns on oxidative stress and related diseases
  Soodabeh Saeidnia, Mohammad Abdollahi
  Toxicology and Applied Pharmacology.2013; 273(3): 442.     CrossRef
• Comparison of antioxidant, α-glucosidase inhibition and anti-inflammatory activities of the leaf and root extracts ofSmilax chinaL.
  Kyoung Kon Kim, Yun Hwan Kang, Dae Jung Kim, Tae Woo Kim, Myeon Choe
  Journal of Nutrition and Health.2013; 46(4): 315.     CrossRef
• Correlation between blood glucose fluctuations and activation of oxidative stress in type 1 diabetic children during the acute metabolic disturbance period
  Di WU, Chun-xiu GONG, Xi MENG, Qiu-lan YANG
  Chinese Medical Journal.2013; 126(21): 4019.     CrossRef
• Oxidative stress and its complications in human health
  Guniz M. Koksal
  Advances in Bioscience and Biotechnology.2012; 03(08): 1113.     CrossRef