International Journal of Alzheimer's Disease

Volume 2012 (2012), Article ID 918680, 9 pages

doi:10.1155/2012/918680

Review Article

Is There Inflammatory Synergy in Type II Diabetes Mellitus and Alzheimer’s Disease?

Lih-Fen Lue,¹ Cassandra Andrade,¹ Marwan Sabbagh,² and Douglas Walker³

¹Laboratory of Neuroregeneration, Banner Sun Health Research Institute, 10515 West Santa Fe Drive, Sun City, AZ 85351, USA

²Cleo Roberts Center for Clinical Research, Banner Sun Health Research Institute, 10515 West Santa Fe Drive, Sun City, AZ 85351, USA

³Laboratory of Neuroinflammation, Banner Sun Health Research Institute, 10515 West Santa Fe Drive, Sun City, AZ 85351, USA

Received 31 January 2012; Accepted 19 April 2012

Academic Editor: Joseph El Khoury

Copyright © 2012 Lih-Fen Lue et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

Metabolic dysregulation, including abnormal glucose utilization and insulin resistance or deficiency, occurs at an early stage of AD independent of type II diabetes mellitus (T2DM). Thus, AD has been considered as type 3 diabetes. T2DM is a risk factor for AD; the coexistence of these two diseases in a society with an increasing mean age is a significant issue. Recently, research has focused on shared molecular mechanisms in these two diseases with the goal of determining whether treating T2DM can lessen the severity of AD. The progress in this field lends strong support to several mechanisms that could affect these two diseases, including insulin resistance and signaling, vascular injuries, inflammation, and the receptor for advanced glycation endproducts and their ligands. In this paper, we focus on inflammation-based mechanisms in both diseases and discuss potential synergism in these mechanisms when these two diseases coexist in the same patient.

1. Introduction

Alzheimer’s disease (AD) and type 2 diabetes mellitus (T2DM) are diseases prevalent in the elderly population. T2DM can increase the risk for developing dementia by 1.5- to 2-fold, and it is considered an important risk factor for AD [1–8]. As the prevalence rate of T2DM is the highest in the age group 65 and older (26.8% in year 2010 according to Center for Disease Controls and Prevention;  http://www.cdc.gov/diabetes/pubs/estimates07.htm), it is a serious concern how T2DM might impact the prevalence rate of AD, and how it might affect the treatment of AD patients. As the mean population age is increasing, both of these two diseases could become much more significant issues. The issue could be further compounded by the epidemic-like phenomenon of obesity that is spreading across all ages [9–11]. At the current annual increase of 0.3–0.6%, there could be 75% of adults that are overweight or obese by 2015 [11]. Obesity is a major risk factor for developing T2DM [2, 12]. Moreover, obesity in middle-age subjects is a negative modifier of T2DM [13]. It has been shown recently that insulin resistance, which is also a risk factor for AD, is associated with lower brain volume and executive function in a large, relatively healthy, middle-aged, community-based cohort [14]. A lack of comprehensive preventive and intervention strategies for these interlinked diseases could lead to a more severe crisis for the healthcare system and the health of the public [15].

There has been promising progress made in identifying links between T2DM and dementia in the last decade. Special research attention has been directed towards the mechanisms by which T2DM may affect cognitive function and pathogenesis of AD, and towards determining whether treating T2DM might be effective in reducing incidence of AD by modifying AD pathogenesis. The major mechanisms through which T2DM may influence AD include insulin resistance, impaired insulin receptor (IR), and insulin growth factor (IGF) signaling, glucose toxicity, advanced glycation endproducts (AGEs) and the receptor for advanced glycation endproducts (RAGEs), cerebrovascular injury, vascular inflammation, and others [5, 16–20]. There are a number of comprehensive reviews available on insulin resistance and growth factor signaling as molecular mechanisms linking AD and T2DM [8, 16, 17, 21]. Additional discussion focusing on whether there is a causal relationship between AD and T2DM from the studies of epidemiology, clinical trials, and imaging can be found in a review article published in the March issue of Journal of Alzheimer’s Disease [18].

The goal of this paper is to focus on a less studied topic: how inflammation-based mechanisms in T2DM might affect AD neuroinflammation and microglial activation. As T2DM and AD both have significant inflammatory components, it is important to assess whether inflammation is synergized when these two diseases coexist. As there has been little research conducted on this aspect, we will review inflammatory mechanisms with respect to each disease and discuss the possibility for these mechanisms to converge.

2. Inflammation and Diabetes

An association of inflammation with T2DM can possibly be demonstrated before clinical diagnosis. This is based on several epidemiological studies that demonstrated greater white blood cell counts or higher levels of inflammatory markers, including C-reactive protein (CRP) and interleukin-6 (IL-6) in healthy middle-aged subjects who later developed T2DM [22–24]. However, not only is chronic inflammation a risk factor for developing T2DM, but it is also an important contributor to the pathogenic mechanisms.

2.1. IL-1 and Its Receptor

The beta cells from T2DM subjects contain elevated levels of IL-1, a potent pro-inflammatory cytokine, and reduced levels of IL-1 receptor antagonist (IL-1ra) [25]. IL-1ra is a naturally produced molecule that inhibits IL-1 activity on its receptor, IL-1 receptor [26]. In vitro studies demonstrated that IL-1 increased release of insulin by pancreatic islet cells in the presence of high glucose concentration and promoted glucose oxidation [27]. Islet beta cells can be damaged by exposure to IL-1, in a dose- and time-dependent manner [28]. High glucose concentration induced IL-1 expression, but reduced expression of IL-1ra, resulting in an imbalance between IL-1 and IL-1ra, which impaired insulin secretion and cell proliferation and increased apoptosis [29]. A study in T2DM GK rats has shown that IL-1ra treatment at high dose improved glucose sensitivity, insulin processing, and suppressed inflammation and infiltration of immune cells [30]. The GK rats developed T2DM at a young age and the pancreatic tissues expressed elevated levels of IL-1, and IL-1-driven inflammatory cytokines and chemokines such as tumor necrosis factor-alpha (TNF-, monocyte chemotactic protein-1 (MCP-1), and macrophage inflammatory protein-1alpha (MIP-1), along with abnormal infiltration of macrophages and granulocytes [30]. This study supported that an imbalance between IL-1 and IL-1ra leads to pancreatic islet inflammation and release of insulin. Clinical trials using anakinra, a recombinant human IL-1ra, or inhibition of IL-1 receptor signaling has shown effectiveness in correcting beta cells dysfunction and reduced systemic inflammation in T2DM [31, 32]. In fact, IL-1ra is the only anti-inflammatory treatment approved by Food and Drug Administration for T2DM [33].

2.2. RAGE and the Ligands

The receptor for advanced glycation endproducts (RAGE), a pattern-recognition receptor, interacts with its ligands resulting in persistent inflammatory responses at sites where the ligands concentrate. These mechanisms have been shown to play a pivotal role in propagation of vascular injuries, a major complication of diabetes [34–37]. The major RAGE ligands in diabetes are advanced glycation endproducts (AGEs), which are derivatives of lipids, proteins, and ribonucleic acids. These are modified by nonenzymatic glycosylation, followed by rearrangement, dehydration, and eventually becoming irreversible cross-linked macromolecules [38, 39]. The amount of these heterogeneous products increases with age, but is further enhanced by diabetes or hyperglycemic conditions [40–42]. Circulating neutrophils can play a role in enhancing the formation of AGE in response to inflammatory activation of the myeloperoxidase system [43]. Diabetes-associated RAGE-AGE interactions induced reactive oxygen species-mediated inflammatory responses in vascular cells (endothelial cells, smooth muscle cells, and pericytes) and mononuclear phagocytes; all of these cells are critically involved in diabetes-associated atherosclerosis, nephropathy, and retinopathy [37, 44–48].

Recent evidence also demonstrated that RAGE is involved in inflammation-based mechanisms of islet cell death. Activation of RAGE by S100B and high mobility group box 1 (HMG1) caused apoptotic death of pancreatic beta cells through an NADPH oxidase-mediated mechanism [49]. The interaction of AGE with RAGE induced apoptosis of islet beta cell and impaired the function of secreting insulin in an in vitro study [50]. Inhibition of AGE formation and blockade of RAGE-mediated chronic inflammatory mechanisms are currently considered to be therapeutic strategies for diabetes and diabetes-associated macro- and microvascular complications [51–54].

Human vascular cells express a novel splice variant of the RAGE gene that encodes for a soluble RAGE protein, named endogenous secretory RAGE (esRAGE). The esRAGE protein neutralizes the action of AGE on vascular cells, thus preventing AGE from activating cell-surface (or full-length) RAGE signaling [55]. There is another form of soluble RAGE (sRAGE) that is not generated by alternative splicing; instead, it is a product of catalytic cleavage of membrane bound full-length RAGE by enzymes such as a disintegrin and metalloprotease 10 [56–58]. There was a negative correlation between the expression levels of full-length membrane RAGE and sRAGE expression in monocytes from T2DM [59]. Enhancing sRAGE-associated protective mechanisms are also molecular targets in developing T2DM therapeutics [60].

2.3. Other Pattern-Recognition Receptors

Toll-like receptors (TLRs) are pattern-recognition receptors consisting of 12 family members in humans. They are crucial for innate immune functions. Evidence has emerged that some of the TLR members are involved in mediating inflammatory responses in metabolic disorders. TLR2 and TLR4 expressions were elevated in the cell surface of monocytes, derived from patients with metabolic syndrome, and released higher levels of IL-1, IL-6, and Il-8 following lipopolysaccharide stimulation [61, 62]. High glucose increases the expression of TLR2 and TLR4, which can be accentuated by the presence of free fatty acids [63, 64]. These effects were mediated via protein kinase C (PKC)-/PKC- by stimulation of NADPH oxidase [63]. The inflammatory responses induced by TLR2 and TLR4 are mediated through the activation of NF-B [65]. TLR4 is upregulated in pancreatic islet cells and a chemokine ligand, interferon-inducible protein (IP)-10 (or CXCL10), was identified to activate this receptor leading to islet cell death [66]. IP-10 can be induced by high glucose through TLR2 and TLR4 [67].

CD36 (oxidized low-density lipoprotein receptor, oxLDL receptor, or scavenger receptor B, MSR-B) is also a pattern recognition receptor which serves as a co-receptor for TLR2 and TLR6 heterodimers, as well as TLR4 and TLR6 heterodimers [68]. High glucose, oxLDL, free fatty acids, and low high density lipoprotein receptors (HDLs) cholesterol concentrations were shown to increase the expression of CD36 in monocytes/macrophages, resulting in vascular oxidative injury, increased leukocyte adhesion, and promoting atherogenesis [69]. Deficiency of CD36 in transgenic mice improves insulin signaling, inflammation, and atherogenesis [70, 71].

3. Diabetes and Alzheimer’s Disease Pathology

There have been several studies investigating whether T2DM worsens the hallmark pathology of AD, namely, neuritic plaques and neurofibrillary tangles. In a study involving 143 diabetic and 567 nondiabetic AD patients, no differences were observed between these two groups in A load, neuritic plaque, and neurofibrillary tangle scores [72]. In another study, the presence of diabetes has even been shown to be negatively associated with the abundance of neuritic plaques and neurofibrillary tangles [73]. In line with this finding, Nelson and colleagues observed that although AD patients with diabetes had significantly more infarcts and vascular damage, the plaque scores, as measured by Consortium to Establish a Registry for Alzheimer Disease criteria, were significantly lower [74]. Using biochemical and histological approaches, Sonnen et al. found inconsistent results between biochemical and neuropathological results [75]. Using formic acid to extract detergent-insoluble A from amyloid deposits in superior and medial temporal samples, they found that the concentrations of A42 in formic-acid extract were significantly higher in AD patients without T2DM than in AD patients with T2DM. This was regardless of neuritic plaque scores and neurofibrillary tangle distribution that did not differ between AD cases with and those without T2DM. The same study also investigated whether T2DM leads to more oxidative reactivity and neuroinflammation. The results showed that AD cases without T2DM had significantly higher levels of free-radicals as measured by -isoprostanes, whereas AD cases with T2DM had significantly greater IL-6 concentrations in cortical tissues than AD without T2DM. It is worth noting that IL-6 is one of three key acute phase proteins shown to be significantly elevated in temporal cortical samples of AD subjects [51]. Neurons in the brain of T2DM patients could be more vulnerable to the toxicity of A due to the defective insulin receptor signaling [76]. Conversely, the defect in insulin receptor signaling could lead to increased production of A and A-induced oxidative damage of the mitochondria [17]. These are among the mechanisms that increase the neuronal degeneration in association with the condition of T2DM.

When determining whether T2DM affects the types and development of amyloid plaques, a significant increase in A40-immunoreactive dense plaques, but not in cored plaques, was observed [77]. Dense plaques are considered to be at an earlier stage of maturation, and more toxic than core-only plaques (or burnt-out plaques). Using RAGE immunoreactivity as a marker for oxidatively stressed cells, the authors detected a significant increase in RAGE-immunoreactive cells in the hilus of dentate gyrus in AD cases with T2DM than in AD cases without T2DM [77]. It is intriguing how T2DM might affect the maturation of amyloid plaques. Could this be mediated through its effects on microglial activation? The authors noticed a looser association of activated microglia with dense plaques in AD subjects with T2DM when compared to AD subjects without T2DM. There could be several possible interpretations for this finding. It could suggest that there was an enhanced microglial phagocytic function in AD with T2DM, thus facilitating the removal of amyloid surrounding the amyloid core. This could also be due to the modification of microglia activation state by additional stimuli in AD with T2DM. Previous research has shown the association of primed, enlarged, or phagocytic microglia with amyloid plaques of different maturation stages [78]. When IL-1 used as a marker for microglial activation, a greater number of IL-1-immunoreactive microglia were associated with diffuse neuritic amyloid plaques, but they did not associate with nonneuritic dense core plaques [78, 79]. A more detailed analysis is necessary to elucidate whether co-existence of T2DM with AD alters the development of amyloid plaques, as well as the phenotypic and functional characteristics of microglia activation. This would require utilization of various microglial activation markers along with antibodies that can detect A40- or A42-predominant amyloid plaques, and antibodies that can detect neuritic components within the plaques. The potential effects of T2DM on microglia activation during development of AD are proposed in Figure 1.

Figure 1: Potential effects of type 2 diabetes mellitus on microglial activation in Alzheimer’s disease. Type 2 diabetes mellitus (T2DM) affects the brain with chronic impairment of insulin production and glycaemic control in the periphery. T2DM also causes macro- and microvascular diseases in which inflammation plays a pivotal role. Cerebral microvascular diseases developed from T2DM complications lead to compromised blood-brain barrier function and endothelial cell activation. Microglia can respond to vascular injury and inflammation. Microglial activation is a process of functional and morphological transformation. We propose here that they can be staged as surveillance, proinflammatory, inflammatory, phagocytic, and degenerative states; the transformation depends on the type, distance, potency, and duration of stimulation. We propose that T2DM might promote the activation of microglia through vascular inflammation and the effects on neuronal metabolic dysfunction.

4. RAGE-Mediated Inflammation in AD Brain

RAGE-mediated mechanisms play crucial roles in the pathogenesis of T2DM and associated vascular complications, but RAGE is also an important cell-signaling receptor involved in various aspects of AD. RAGE is expressed in the brain in neurons, microglia, and astrocytes [80–82]. A is a specific ligand for RAGE, which interacts with the N-terminal domain of RAGE [83]. RAGE expression was elevated in AD pathology-enriched brain regions, including hippocampus and inferior frontal cortex, when compared to cerebellum where AD pathology is limited. RAGE expression was also increased in neurons and microglia in the hippocampus [80, 82]. The interaction of A with neuronal RAGE leads to reactive oxygen species-mediated cellular stress and activation of the transcription faction NF-B, resulting in increased inflammatory gene and protein expression. For example, elevated secretion of macrophage colony-stimulating factor (M-CSF) and tumor necrosis factor alpha (TNF-) by microglia and BV-2 cells was observed [80, 84]. In experiments using cultures of postmortem human microglia and an in vitro A plaque model, A-induced directional migration of microglia was shown to be RAGE-dependent. This was shown by the inhibition of microglial migratory responses to A when RAGE was blocked by anti-RAGE (Fab′)₂ [80]. The involvement of RAGE-mediated microglial activation in exacerbation of synaptic degeneration, neuroinflammation, and A levels has been illustrated in a study that compared human amyloid precursor protein (APP) single-transgenic mice to double-transgenic mice over expressing the human RAGE gene in microglia along with mutated APP transgene [85, 86]. Enhanced IL-1 and TNF- production, increased infiltration of microglia and astrocytes in amyloid plaques, increased levels of A40 and A42, reduced acetylcholine esterase (AChE) activity, and accelerated deterioration of spatial learning/memory were observed in the double-transgenic mice when compared to single transgenic APP or RAGE mice [85]. The involvement of microglial RAGE in driving these consequences was further elucidated in the same study by using signal transduction-defective mutant RAGE [dominant negative (DN)-RAGE] to microglia. The DN-RAGE gene in APP transgenic mice prevented the loss of AChE activity, reduced plaque load, and improved spatial and memory functions [85]. These findings demonstrated that RAGE signaling in microglia played a critical role in promoting inflammatory responses that could lead to increase in A levels and synaptic dysfunction.

Increased association of AGEs, a RAGE ligand, has been observed in amyloid deposits, and in astrocytes and microglia. This correlated with increased inducible nitric oxide synthase in AD pathology-rich area [87]. The nitric oxide-mediated oxidative mechanisms can mediate the cytotoxicity of AGE [88]. Other RAGE ligands upregulated in AD brains include S100B, S100A9, S100A12, and HMG1 [89, 90]. Although S100B and S100A8 are known as inflammatory cytokines of myeloid phagocytes, their expression by human microglia can be induced by chronic exposure to A1-42 [91].

Increases in formation of AGE could also result in upregulation of macrophage scavenger receptor CD36. Elevated expression of CD36 correlated with the presence of amyloid deposits, but not the clinical diagnosis of AD. The expression of CD36 by microglia promotes adhesion to fibrillar A, increases oxidative stress and proinflammatory responses, and affects microglial uptake of A [92].

5. RAGE, Ligands, and Cytokine Cascade

One feature that makes RAGE a critical inflammatory receptor is that its expression is increased by its ligands; this creates a positive feedback mechanism that can perpetuate inflammation once it sets off [37, 46, 93, 94]. The amplification of inflammatory consequences can also be further fueled by additional cytokines. For example, in monocytic lineage cells, preexposure to AGE followed by treatment of IL-6 or TNF- can induce release of the RAGE ligands, S100A8 and S100A9 [95]. Preexposure of endothelial cells to AGE has also been shown to increase IL-6, intercellular adhesion molecule-1, vascular adhesion molecule-1, and MCP-1 upon stimulation with S100A8/A9 heterodimers [93]. These findings illustrate how RAGE and its ligands can combine with cytokine-mediated inflammation to exacerbate chronic inflammatory diseases such as AD and T2DM.

As in T2DM, there is a deficiency in the anti-inflammatory function of sRAGE in AD due to a gradual decline in the circulating levels of sRAGE [57, 96, 97]. With this protective function being compromised and with several RAGE ligands elevated, it is possible that the coexistence of AD and T2DM would result in accentuated inflammatory responses, both in the periphery and in the brain. Small molecules that can block RAGE activation or enhance the protective function of sRAGE are a strategy which may be beneficial to both AD and T2DM [98, 99].

6. Conclusion

There is strong evidence supporting inflammation as key feature in the brain of AD and in the pancreas of T2DM as summarized in Table 1. A wide range of inflammatory mediators and receptors are involved in these two diseases, although complement activation is a prominent feature in AD, but not in T2DM [100]. The presence of infiltrated lymphocytes is controversial in AD [76, 101]. Therefore, current research findings support the inflammation-based pathogenic mechanisms in both diseases. Although research investigating that T2DM may alter brain inflammation in AD is limited, there is a great possibility that T2DM could accentuate microglial activation, neuroinflammation, and vascular inflammatory/oxidative injury in AD brains through mechanisms mediated by RAGE and other pattern-recognition receptors, and the cascade of cytokine and chemokines. Figure 2 illustrates the potential of RAGE-centric mechanisms in the central and peripheral systems when both diseases coexist. As microglia play a central role in initiation and propagation of neuroinflammation, and anti-inflammation is one of the preventive and disease modifying strategies for AD, more studies will be needed to characterize the patterns of microglial activation in AD patients with T2DM and AD patients without T2DM.

Table 1: Inflammatory responses detected in the brain of Alzheimer’s disease and the pancreas of diabetes mellitus.

Disease-affected brain regions in Alzheimer’s disease patients
Pancreas in T2DM patients

Elevated inflammatory markers
Cytokines (e.g., IL-1, IL-1, IL-6, TNF-), chemokines (e.g., IL-8, MCP-1), acute phase proteins (e.g., ACT-1, Serum amyloid P), activated complement proteins (e.g., C3, C5a, C5b-9), and S100B
Cytokines (e.g., IL-1, IL-6, TNF-), chemokines (e.g., IL-8, IP-1, MCP-1, MIP-1), growth factor (G-CSF), S100B, and HMGB1

Immune cell infiltration
Rare presence of lymphocytes or macrophages
Increased macrophages, T-lymphocytes, and granulocytes

Involvement of pattern recognition receptors and major ligands
MSR-A, MSR-B, RAGE, TLR2, TLR4; amyloid beta, AGE
MSR-A, MSR-B, RAGE, TLR2, TLR4: amylin, AGE, IP-10

Figure 2: RAGE-driven inflammatory synergy in Alzheimer’s disease with type 2 diabetes mellitus. Receptor for advanced glycation endproducts- (RAGEs) mediated inflammatory responses play an important roles in pathogenesis of Alzheimer’s disease (AD) and type 2 diabetes mellitus (T2DM). In AD, A is the most prominent ligand that interacts with RAGE leading to inflammatory signaling. The interaction also leads to microglia secretion of M-CSF which can further upregulate the expression of RAGE in microglia. Other inflammatory cytokines and chemokines are also produced upon the activation of RAGE, including IL-1, IL-6, TNF-, and MCP-1. Several of these inflammatory mediators also can modulate the expression of RAGE and its ligands. A number of other ligands are also expressed at elevated levels in the AD brain including AGE, S100A8, S100A9, S100A12, S100B, and HMG1. In T2DM, advanced glycation endproducts (AGEs) are the major ligand. Interaction with RAGE, AGE induces production of other RAGE ligands and inflammatory cytokines and chemokines, which is the major mechanism for propagation of vascular inflammatory injury in T2DM-associated vascular diseases. Thus, RAGE-mediated inflammatory responses might be accentuated when these two diseases coexist in the same patient.

Abbreviations

AD: | Alzheimer’s disease
AChE: | Acetylcholine esterase
(ACT-1): | Anti-chymotrypsin-1
AGE: | Advanced glycation endproducts
APP: | Amyloid precursor protein
CRP: | C-reactive protein
DN: | dominant negative
esRAGE: | endogenous secretory receptor for advanced glycation endproducts
G-CSF: | Granulocyte-colony stimulating factor
HMG1: | High mobility group box
IGF: | Insulin growth factor
IR: | Insulin receptor
IL: | Interleukin
(IL-1ra): | Interleukin-1 receptor antagonist
IP-10: | Interferon-inducible protein-10
MCP-1: | Monocyte chemotactic protein-1
M-CSF: | Macrophage colony stimulating factor
(MIP-1): | Macrophage inflammatory protein-1
MSR: | macrophage scavenger receptor
HDL: | High density lipoprotein
(ox-LDL): | oxidized low density lipoprotein
PKD: | Protein kinase
RAGE: | Receptor for advanced glycation endproducts
sRAGE: | Soluble RAGE
TLR: | Toll-like receptor
TNF-: | Tumor necrosis factor-alpha
T2DM: | Type 2 diabetes mellitus.

Acknowledgments

The authors would like to thank Alzheimer’s Association (IIRG-09-91996) and Arizona Alzheimer’s Research Consortium for the funding.

References

S. Ahtiluoto, T. Polvikoski, M. Peltonen et al., “Diabetes, Alzheimer disease, and vascular dementia: a population-based neuropathologic study,” Neurology, vol. 75, no. 13, pp. 1195–1202, 2010.

C. C. Lee, S. G. Glickman, D. R. Dengel, M. D. Brown, and M. A. Supiano, “Abdominal adiposity assessed by dual energy x-ray absorptiometry provides a sex-independent predictor of insulin sensitivity in older adults,” Journals of Gerontology A, vol. 60, no. 7, pp. 872–877, 2005.

J. A. Luchsinger, C. Reitz, B. Patel, M. X. Tang, J. J. Manly, and R. Mayeux, “Relation of diabetes to mild cognitive impairment,” Archives of Neurology, vol. 64, no. 4, pp. 570–575, 2007.

A. Ott, R. P. Stolk, F. van Harskamp, H. A. Pols, A. Hofman, and M. M. Breteler, “Diabetes mellitus and the risk of dementia: the Rotterdam study,” Neurology, vol. 53, no. 9, pp. 1937–1942, 1999.

G. Razay, A. Vreugdenhil, and G. Wilcock, “The metabolic syndrome and Alzheimer disease,” Archives of Neurology, vol. 64, no. 1, pp. 93–96, 2007.

E. M. Schrijvers, J. C. Witteman, E. J. Sijbrands, A. Hofman, P. J. Koudstaal, and M. M. B. Breteler, “Insulin metabolism and the risk of Alzheimer disease: the Rotterdam study,” Neurology, vol. 75, no. 22, pp. 1982–1987, 2010.

R. Stewart and D. Liolitsa, “Type 2 diabetes mellitus, cognitive impairment and dementia,” Diabetic Medicine, vol. 16, no. 2, pp. 93–112, 1999.

M. W. Strachan, R. M. Reynolds, R. E. Marioni, and J. F. Price, “Cognitive function, dementia and type 2 diabetes mellitus in the elderly,” Nature Reviews Endocrinology, vol. 7, no. 2, pp. 108–114, 2011.

M. L. Baskin, J. Ard, F. Franklin, and D. B. Allison, “Prevalence of obesity in the United States,” Obesity Reviews, vol. 6, no. 1, pp. 5–7, 2005.

E. S. Ford, C. Li, G. Zhao, and J. Tsai, “Trends in obesity and abdominal obesity among adults in the United States from 1999-2008,” International Journal of Obesity, vol. 35, no. 5, pp. 736–743, 2011.

Y. Wang and M. A. Beydoun, “The obesity epidemic in the United States—gender, age, socioeconomic, racial/ethnic, and geographic characteristics: a systematic review and meta-regression analysis,” Epidemiologic Reviews, vol. 29, no. 1, pp. 6–28, 2007.

W. T. Cefalu, Z. Q. Wang, S. Werbel et al., “Contribution of visceral fat mass to the insulin resistance of aging,” Metabolism, vol. 44, no. 7, pp. 954–959, 1995.

H. Bruehl, O. T. Wolf, V. Sweat, A. Tirsi, S. Richardson, and A. Convit, “Modifiers of cognitive function and brain structure in middle-aged and elderly individuals with type 2 diabetes mellitus,” Brain Research, vol. 1280, no. C, pp. 186–194, 2009.

Z. S. Tan, A. S. Beiser, C. S. Fox et al., “Association of metabolic dysregulation with volumetric brain magnetic resonance imaging and cognitive markers of subclinical brain aging in middle-aged adults: the framingham offspring study,” Diabetes Care, vol. 34, no. 8, pp. 1766–1770, 2011.

J. G. Ryan, “Cost and policy implications from the increasing prevalence of obesity and diabetes mellitus,” Gender Medicine, vol. 6, supplement 1, pp. 86–108, 2009.

B. Cholerton, L. D. Baker, and S. Craft, “Insulin resistance and pathological brain ageing,” Diabetic Medicine, vol. 28, no. 12, pp. 1463–1475, 2011.

S. M. de la Monte, “Contributions of brain insulin resistance and deficiency in amyloid-related neurodegeneration in Alzheimer's diseas,” Drugs, vol. 72, no. 1, pp. 49–66, 2012.

J. A. Luchsinger, “Type 2 diabetes andcognitive impairment: linking mechanisms,” Journal of Alzheimer's Disease. In press

P. A. Maher and D. R. Schubert, “Metabolic links between diabetes and Alzheimer's disease,” Expert Review of Neurotherapeutics, vol. 9, no. 5, pp. 617–630, 2009.

Å. Sjöholm and T. Nyström, “Inflammation and the etiology of type 2 diabetes,” Diabetes/Metabolism Research and Reviews, vol. 22, no. 1, pp. 4–10, 2006.

D. Bosco, A. Fava, M. Plastino, T. Montalcini, and A. Pujia, “Possible implications of insulin resistance and glucose metabolism in Alzheimer's disease pathogenesis,” Journal of Cellular and Molecular Medicine, vol. 15, no. 9, pp. 1807–1821, 2011.

A. D. Pradhan, J. E. Manson, N. Rifai, J. E. Buring, and P. M. Ridker, “C-reactive protein, interleukin 6, and risk of developing type 2 diabetes mellitus,” JAMA, vol. 286, no. 3, pp. 327–334, 2001.

B. Thorand, H. Löwel, A. Schneider et al., “C-reactive protein as a predictor for incident diabetes mellitus among middle-aged men: results from the MONICA Augsburg Cohort study, 1984–1998,” Archives of Internal Medicine, vol. 163, no. 1, pp. 93–99, 2003.

B. Vozarova, C. Weyer, R. S. Lindsay, R. E. Pratley, C. Bogardus, and P. A. Tataranni, “High white blood cell count is associated with a worsening of insulin sensitivity and predicts the development of type 2 diabetes,” Diabetes, vol. 51, no. 2, pp. 455–461, 2002.

M. Böni-Schnetzler, J. Thorne, G. Parnaud et al., “Increased interleukin (IL)-1β messenger ribonucleic acid expression in β-cells of individuals with type 2 diabetes and regulation of IL-1β in human islets by glucose and autostimulation,” Journal of Clinical Endocrinology and Metabolism, vol. 93, no. 10, pp. 4065–4074, 2008.

W. P. Arend, “Interleukin-1 receptor antagonist: discovery, structure and properties,” Cytokine and Growth Factor Reviews, vol. 2, no. 4, pp. 193–205, 1990.

D. L. Eizirik and S. Sandler, “Human interleukin-1β induced stimulation of insulin release from rat pancreatic islets is accompanied by an increase in mitochondrial oxidative events,” Diabetologia, vol. 32, no. 11, pp. 769–773, 1989.

J. P. Palmer, S. Helqvist, G. A. Spinas et al., “Interaction of β-cell activity and IL-1 concentration and exposure time in isolated rat islets of langerhans,” Diabetes, vol. 38, no. 10, pp. 1211–1216, 1989.

C. A. Dinarello, “A clinical perspective of IL-1β as the gatekeeper of inflammation,” European Journal of Immunology, vol. 41, no. 5, pp. 1203–1217, 2011.

J. A. Ehses, G. Lacraz, M. H. Giroix et al., “IL-1 antagonism reduces hyperglycemia and tissue inflammation in the type 2 diabetic GK rat,” Proceedings of the National Academy of Sciences of the United States of America, vol. 106, no. 33, pp. 13998–14003, 2009.

C. A. Dinarello and R. C. Thompson, “Blocking IL-1: interleukin 1 receptor antagonist in vivo and in vitro,” Immunology Today, vol. 12, no. 11, pp. 404–410, 1991.

C. M. Larsen, M. Faulenbach, A. Vaag et al., “Interleukin-1-receptor antagonist in type 2 diabetes mellitus,” The New England Journal of Medicine, vol. 356, no. 15, pp. 1517–1526, 2007.

M. S. H. Akash, Q. Shen, K. Rehman, and S. Chen, “Interleukin-1 receptor antagonist: a new therapy for type 2 diabetes mellitus,” Journal of Pharmaceutical Sciences, vol. 101, supplement 5, pp. 1647–1658, 2012.

O. Hori, S. D. Yan, S. Ogawa et al., “The receptor for advanced glycation end-products has a central role in mediating the effects of advanced glycation end-products on the development of vascular disease in diabetes mellitus,” Nephrology Dialysis Transplantation, vol. 11, supplement 5, pp. 13–16, 1996.

A. M. Schmidt, S. D. Yan, S. F. Yan, and D. M. Stern, “The biology of the receptor for advanced glycation end products and its ligands,” Biochimica et Biophysica Acta, vol. 1498, no. 2-3, pp. 99–111, 2000.

M. Sensi, F. Pricci, D. Andreani, and U. Di Mario, “Advanced nonenzymatic glycation endproducts (age): their relevance to aging and the pathogenesis of late diabetic complications,” Diabetes Research, vol. 16, no. 1, pp. 1–9, 1991.

S. Yamagishi, “Role of advanced glycation end products (AGEs) and receptor for AGEs (RAGE) in vascular damage in diabetes,” Experimental Gerontology, vol. 46, no. 4, pp. 217–224, 2011.

P. Chellan and R. H. Nagaraj, “Protein crosslinking by the Maillard reaction: dicarbonyl-derived imidazolium crosslinks in aging and diabetes,” Archives of Biochemistry and Biophysics, vol. 368, no. 1, pp. 98–104, 1999.

S. R. Thorpe and J. W. Baynes, “Role of the maillard reaction in diabetes mellitus and diseases of aging,” Drugs and Aging, vol. 9, no. 2, pp. 69–77, 1996.

E. B. Frye, T. P. Degenhardt, S. R. Thorpe, and J. W. Baynes, “Role of the Maillard reaction in aging of tissue proteins: advanced glycation end product-dependent increase in imidazolium cross-links in human lens proteins,” Journal of Biological Chemistry, vol. 273, no. 30, pp. 18714–18719, 1998.

M. Sensi, F. Pricci, G. Pugliese et al., “Enhanced nonenzymatic glycation of eye lens proteins in experimental diabetes mellitus: an approach for the study of protein alterations as mediators of normal aging phenomena,” Archives of Gerontology and Geriatrics, vol. 15, supplement 1, pp. 333–337, 1992.

P. Ulrich and A. Cerami, “Protein glycation, diabetes, and aging,” Recent Progress in Hormone Research, vol. 56, pp. 1–21, 2001.

M. M. Anderson, J. R. Requena, J. R. Crowley, S. R. Thorpe, and J. W. Heinecke, “The myeloperoxidase system of human phagocytes generates Nepsilon-(carboxymethyl)lysine on proteins: a mechanism for producing advanced glycation end products at sites of inflammation,” Journal of Clinical Investigation, vol. 104, no. 1, pp. 103–113, 1999.

G. R. Barile, S. I. Pachydaki, S. R. Tari et al., “The RAGE axis in early diabetic retinopathy,” Investigative Ophthalmology and Visual Science, vol. 46, no. 8, pp. 2916–2924, 2005.

S. Sakurai, H. Yonekura, Y. Yamamoto et al., “The AGE-RAGE system and diabetic nephropathy,” Journal of the American Society of Nephrology, vol. 14, supplement 3, no. 8, pp. S259–S263, 2003.

A. M. Schmidt, M. Hofmann, A. Taguchi, S. D. Yan, and D. M. Stern, “RAGE: a multiligand receptor contributing to the cellular response in diabetic vasculopathy and inflammation,” Seminars in Thrombosis and Hemostasis, vol. 26, no. 5, pp. 485–493, 2000.

M. T. Win, Y. Yamamoto, S. Munesue et al., “Regulation of RAGE for attenuating progression of diabetic vascular complications,” Experimental Diabetes Research, vol. 2012, Article ID 894605, 8 pages, 2012.

S. Yamagishi, M. Takeuchi, Y. Inagaki, K. Nakamura, and T. Imaizumi, “Role of advanced glycation end products (AGEs) and their receptor (RAGE) in the pathogenesis of diabetic microangiopathy,” International Journal of Clinical Pharmacology Research, vol. 23, no. 4, pp. 129–134, 2003.

B. W. Lee, H. Y. Chae, S. J. Kwon, S. Y. Park, J. Ihm, and S. H. Ihm, “RAGE ligands induce apoptotic cell death of pancreatic β-cells via oxidative stress,” International Journal of Molecular Medicine, vol. 26, no. 6, pp. 813–818, 2010.

Y. Zhu, T. Shu, Y. Lin et al., “Inhibition of the receptor for advanced glycation endproducts (RAGE) protects pancreatic β-cells,” Biochemical and Biophysical Research Communications, vol. 404, no. 1, pp. 159–165, 2011.

K. P. Chandra, A. Shiwalkar, J. Kotecha et al., “Phase I clinical studies of the advanced glycation end-product (AGE)-breaker TRC4186: safety, tolerability and pharmacokinetics in healthy subjects,” Clinical Drug Investigation, vol. 29, no. 9, pp. 559–575, 2009.

G. Li, J. Tang, Y. Du, C. Lee, and T. S. Kern, “Beneficial effects of a novel RAGE inhibitor on early diabetic retinopathy and tactile allodynia,” Molecular Vision, vol. 17, pp. 3156–3165, 2011.

J. Peyroux and M. Sternberg, “Advanced glycation endproducts (AGEs): pharmacological inhibition indiabetes,” Pathologie Biologie, vol. 54, no. 7, pp. 405–419, 2006.

S. Rahbar, “Novel inhibitors of glycation and AGE formation,” Cell Biochemistry and Biophysics, vol. 48, no. 2-3, pp. 147–157, 2007.

H. Yonekura, Y. Yamamoto, S. Sakurai et al., “Novel splice variants of the receptor for advanced glycation end-products expressed in human vascular endothelial cells and pericytes, and their putative roles in diabetes-induced vascular injury,” Biochemical Journal, vol. 370, no. 3, pp. 1097–1109, 2003.

A. Galichet, M. Weibel, and C. W. Heizmann, “Calcium-regulated intramembrane proteolysis of the RAGE receptor,” Biochemical and Biophysical Research Communications, vol. 370, no. 1, pp. 1–5, 2008.

A. Raucci, S. Cugusi, A. Antonelli et al., “A soluble form of the receptor for advanced glycation endproducts (RAGE) is produced by proteolytic cleavage of the membrane-bound form by the sheddase a disintegrin and metalloprotease 10 (ADAM10),” The FASEB Journal, vol. 22, no. 10, pp. 3716–3727, 2008.

L. Zhang, M. Bukulin, E. Kojro et al., “Receptor for advanced glycation end products is subjected to protein ectodomain shedding by metalloproteinases,” Journal of Biological Chemistry, vol. 283, no. 51, pp. 35507–35516, 2008.

X. H. Tam, S. W. Shiu, L. Leng, R. Bucala, D. J. Betteridge, and K. C. Tan, “Enhanced expression of receptor for advanced glycation end-products is associated with low circulating soluble isoforms of the receptor in Type 2 diabetes,” Clinical Science, vol. 120, no. 2, pp. 81–89, 2011.

S. F. Yan, R. Ramasamy, and A. M. Schmidt, “Soluble RAGE: therapy and biomarker in unraveling the RAGE axis in chronic disease and aging,” Biochemical Pharmacology, vol. 79, no. 10, pp. 1379–1386, 2010.

M. R. Dasu, S. Devaraj, S. Park, and I. Jialal, “Increased toll-like receptor (TLR) activation and TLR ligands in recently diagnosed type 2 diabetic subjects,” Diabetes Care, vol. 33, no. 4, pp. 861–868, 2010.

I. Jialal, B. A. Huet, H. Kaur, A. Chien, and S. Devaraj, “Increased toll-like receptor activity in patients with metabolic syndrome,” Diabetes Care, vol. 35, no. 4, pp. 900–904, 2012.

M. R. Dasu, S. Devaraj, L. Zhao, D. H. Hwang, and I. Jialal, “High glucose induces toll-like receptor expression in human monocytes mechanism of activation,” Diabetes, vol. 57, no. 11, pp. 3090–3098, 2008.

M. R. Dasu and I. Jialal, “Free fatty acids in the presence of high glucose amplify monocyte inflammation via toll-like receptors,” American Journal of Physiology, vol. 300, no. 1, pp. E145–E154, 2011.

G. M. Barton and R. Medzhitov, “Toll-like receptor signaling pathways,” Science, vol. 300, no. 5625, pp. 1524–1525, 2003.

F. T. Schulthess, F. Paroni, N. S. Sauter et al., “CXCL10 Impairs β cell function and viability in diabetes through TLR4 signaling,” Cell Metabolism, vol. 9, no. 2, pp. 125–139, 2009.

S. Devaraj and I. Jialal, “Increased secretion of IP-10 from monocytes under hyperglycemia is via the TLR2 and TLR4 pathway,” Cytokine, vol. 47, no. 1, pp. 6–10, 2009.

C. R. Stewart, L. M. Stuart, K. Wilkinson et al., “CD36 ligands promote sterile inflammation through assembly of a Toll-like receptor 4 and 6 heterodimer,” Nature Immunology, vol. 11, no. 2, pp. 155–161, 2010.

S. Gautam and M. Banerjee, “The macrophage Ox-LDL receptor, CD36 and its association with type II diabetes mellitus,” Molecular Genetics and Metabolism, vol. 102, no. 4, pp. 389–398, 2011.

D. J. Kennedy and S. R. Kashyap, “Pathogenic role of scavenger receptor CD36, metabolic syndrome and diabetes,” Metabolic Syndrome and Related Disorders, vol. 9, no. 4, pp. 239–245, 2011.

D. J. Kennedy, S. Kuchibhotla, K. M. Westfall, R. L. Silverstein, R. E. Morton, and M. Febbraio, “A CD36-dependent pathway enhances macrophage and adipose tissue inflammation and impairs insulin signalling,” Cardiovascular Research, vol. 89, no. 3, pp. 604–613, 2011.

I. Alafuzoff, L. Aho, S. Helisalmi, A. Mannermaa, and H. Soininen, “β-amyloid deposition in brains of subjects with diabetes,” Neuropathology and Applied Neurobiology, vol. 35, no. 1, pp. 60–68, 2009.

M. S. Beeri, J. M. Silverman, K. L. Davis et al., “Type 2 diabetes is negatively associated with Alzheimer's disease neuropathology,” Journals of Gerontology A, vol. 60, no. 4, pp. 471–475, 2005.

P. T. Nelson, C. D. Smith, E. A. Abner et al., “Human cerebral neuropathology of Type 2 diabetes mellitus,” Biochimica et Biophysica Acta - Molecular Basis of Disease, vol. 1792, no. 5, pp. 454–469, 2009.

J. A. Sonnen, E. B. Larson, K. Brickell et al., “Different patterns of cerebral injury in dementia with or without diabetes,” Archives of Neurology, vol. 66, no. 3, pp. 315–322, 2009.

P. Picone, D. Giacomazza, V. Vetri et al., “Insulin-activated Akt rescues Aβ oxidative stress-induced cell death by orchestrating molecular trafficking,” Aging Cell, vol. 10, pp. 832–843, 2011.

T. Valente, A. Gella, X. Fernàndez-Busquets, M. Unzeta, and N. Durany, “Immunohistochemical analysis of human brain suggests pathological synergism of Alzheimer's disease and diabetes mellitus,” Neurobiology of Disease, vol. 37, no. 1, pp. 67–76, 2010.

W. S. Griffin, J. G. Sheng, G. W. Roberts, and R. E. Mrak, “Interleukin-1 expression in different plaque types in Alzheimer's disease: significance in plaque evolution,” Journal of Neuropathology and Experimental Neurology, vol. 54, no. 2, pp. 276–281, 1995.

J. G. Sheng, R. E. Mrak, and W. S. Griffin, “Microglial interleukin-1α expression in brain regions in Alzheimer's disease: correlation with neuritic plaque distribution,” Neuropathology and Applied Neurobiology, vol. 21, no. 4, pp. 290–301, 1995.

L. F. Lue, D. G. Walker, L. Brachova et al., “Involvement of microglial receptor for advanced glycation endproducts (RAGE)in Alzheimer's disease: identification of a cellular activation mechanism,” Experimental Neurology, vol. 171, no. 1, pp. 29–45, 2001.

N. Sasaki, S. Toki, H. Chowei et al., “Immunohistochemical distribution of the receptor for advanced glycation end products in neurons and astrocytes in Alzheimer's disease,” Brain Research, vol. 888, no. 2, pp. 256–262, 2001.

S. D. Yan, X. Chen, J. Fu et al., “RAGE and amyloid-β peptide neurotoxicity in Alzheimer's disease,” Nature, vol. 382, no. 6593, pp. 685–691, 1996.

M. O. Chaney, W. B. Stine, T. A. Kokjohn et al., “RAGE and amyloid β interactions: atomic force microscopy and molecular modeling,” Biochimica et Biophysica Acta, vol. 1741, no. 1-2, pp. 199–205, 2005.

S. D. Yan, H. Zhu, A. Zhu et al., “Receptor-dependent cell stress and amyloid accumulation in systemic amyloidosis,” Nature Medicine, vol. 6, no. 6, pp. 643–651, 2000.

F. Fang, L. F. Lue, S. Yan et al., “RAGE-dependent signaling in microglia contributes to neuroinflammation, Aβ accumulation, and impaired learning/memory in a mouse model of Alzheimer's disease,” FASEB Journal, vol. 24, no. 4, pp. 1043–1055, 2010.

N. Origlia, C. Bonadonna, A. Rosellini et al., “Microglial receptor for advanced glycation end product-dependent signal pathway drives β-amyloid-induced synaptic depression and long-term depression impairment in entorhinal cortex,” Journal of Neuroscience, vol. 30, no. 34, pp. 11414–11425, 2010.

A. Wong, H. J. Lüth, W. Deuther-Conrad et al., “Advanced glycation endproducts co-localize with inducible nitric oxide synthase in Alzheimer's disease,” Brain Research, vol. 920, no. 1-2, pp. 32–40, 2001.

C. Loske, A. Neumann, A. M. Cunningham et al., “Cytotoxicity of advanced glycation endproducts is mediated by oxidative stress,” Journal of Neural Transmission, vol. 105, no. 8-9, pp. 1005–1015, 1998.

C. E. Shepherd, J. Goyette, V. Utter et al., “Inflammatory S100A9 and S100A12 proteins in Alzheimer's disease,” Neurobiology of Aging, vol. 27, no. 11, pp. 1554–1563, 2006.

K. Takata, Y. Kitamura, D. Tsuchiya, T. Kawasaki, T. Taniguchi, and S. Shimohama, “High mobility group box protein-1 inhibits microglial Aβ clearance and enhances Aβ neurotoxicity,” Journal of Neuroscience Research, vol. 78, no. 6, pp. 880–891, 2004.

D. G. Walker, J. Link, L.-F. Lue, J. E. Dalsing-Hernandez, and B. E. Boyes, “Gene expression changes by amyloid β peptide-stimulated human postmortem brain microglia identify activation of multiple inflammatory processes,” Journal of Leukocyte Biology, vol. 79, no. 3, pp. 596–610, 2006.

I. S. Coraci, J. Husemann, J. W. Berman et al., “CD36, a class B scavenger receptor, is expressed on microglia in Alzheimer's disease brains and can mediate production of reactive oxygen species in response to β-amyloid fibrils,” American Journal of Pathology, vol. 160, no. 1, pp. 101–112, 2002.

P. Ehlermann, K. Eggers, A. Bierhaus et al., “Increased proinflammatory endothelial response to S100A8/A9 after preactivation through advanced glycation end products,” Cardiovascular Diabetology, vol. 5, article 6, 2006.

S. F. Yan, R. Ramasamy, and A. M. Schmidt, “Receptor for AGE (RAGE) and its ligands-cast into leading roles in diabetes and the inflammatory response,” Journal of Molecular Medicine, vol. 87, no. 3, pp. 235–247, 2009.

K. Eggers, K. Sikora, M. Lorenz et al., “RAGE-dependent regulation of calcium-binding proteins S100A8 and S100A9 in human THP-1,” Experimental and Clinical Endocrinology and Diabetes, vol. 119, no. 6, pp. 353–357, 2011.

R. Ghidoni, L. Benussi, M. Glionna et al., “Decreased plasma levels of soluble receptor for advanced glycation end products in mild cognitive impairment,” Journal of Neural Transmission, vol. 115, no. 7, pp. 1047–1050, 2008.

L. F. Lue, Y. M. Kuo, T. Beach, and D. G. Walker, “Microglia activation and anti-inflammatory regulation in alzheimer's disease,” Molecular Neurobiology, vol. 41, no. 2-3, pp. 115–128, 2010.

M. N. Sabbagh, A. Agro, J. Bell, P. S. Aisen, E. Schweizer, and D. Galasko, “PF-04494700, an oral inhibitor of receptor for advanced glycation end products (RAGE), in Alzheimer disease,” Alzheimer Disease & Associated Disorders, vol. 25, pp. 206–212, 2010.

L. Zhang, R. Postina, and Y. Wang, “Ectodomain shedding of the receptor for advanced glycation end products: a novel therapeutic target for Alzheimer's disease,” Cellular and Molecular Life Sciences, vol. 66, no. 24, pp. 3923–3935, 2009.

M. V. Kolev, M. M. Ruseva, C. L. Harris, B. P. Morgan, and R. M. Donev, “Implication of complement system and its regulators in alzheimer's disease,” Current Neuropharmacology, vol. 7, no. 1, pp. 1–8, 2009.

T. Town, J. Tan, R. A. Flavell, and M. Mullan, “T-cells in Alzheimer's disease,” NeuroMolecular Medicine, vol. 7, no. 3, pp. 255–264, 2005.