Modulating the Effects of Diabetes on Osseointegration With Aminoguanidine and Doxycycline

Effect of Anti-Diabetic Medications on Dental Implants: A Scoping Review of Animal Studies and Their Relevance to Humans

Animal studies have ascertained that hyperglycemia adversely affects bone metabolism and dental implant osseointegration. However, diabetic patients show low occurrence of unfavorable hard or soft peri-implant tissue changes, differences that are possibly due to treatment with anti-diabetic medications. This scoping review aimed to systematically examine the effects of these drugs on implant outcomes and explore the predictive modality of animal studies for clinical practice according to type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). Three electronic databases (MEDLINE, EBSCOHost, and Cochrane) were searched according to the PRISMA-ScR standards for studies on diabetic animals that received titanium implants and anti-diabetic treatments. Risk assessment was performed using the SYRCLE Risk-of-Bias (RoB) tool. Twenty-one papers were included, encompassing six types of medications. Fifteen studies were on T1DM animals, and only six involved T2DM models. T1DM animals were treated with non-insulin drugs in four investigations, while insulin was utilized in 11 other studies. In T2DM experiments, five administered non-insulin drugs, and only one applied locally delivered insulin. Only insulin in T1DM studies produced a positive influence on bone-implant contact (BIC), bone mineral content, and removal torque values. Inappropriate drug selection, inadequate glycemic control, and high RoB depict a mismatch between the research focus and the translational rationale to clinical practice. There remains a knowledge gap regarding T2DM investigations due to the lack of studies. More data are needed concerning intraoral implants and the performance of osseointegrated implants in patients with a later onset of diabetes. Future research should reflect the pathophysiology and treatment of each type of diabetes to ensure clinical applicability.

Full Arch Implant-Prosthetic Rehabilitation in Patients with Type I Diabetes Mellitus: Retrospective Clinical Study with 10 Year Follow-Up

The aim of this retrospective clinical study was to evaluate and compare implant survival, marginal bone loss, and clinical and prosthetic complications in healthy patients and patients with type I diabetes undergoing full arch implant-prosthetic rehabilitation. A total of 47 patients needing total fixed rehabilitation of one or both arches were enrolled for this study. Based on the absence of any systemic diseases (Group A) or the presence of type I diabetes (Group B), the sample was divided into two groups. According to the grade of bone atrophy in the posterior region, patients received full arch rehabilitation (of one or both jaws) with 6 axial implants or, if the residual posterior bone height was insufficient, All-on-Four rehabilitation and a total 236 dental implants were placed. Follow-up visits were performed 1 week after surgery, at 3 and 6 months and then once a year for the next 10 years. No statistically significant differences between groups were recorded about implant survival rates, marginal bone loss, or clinical and prosthetic complications. However, concerning complications, post-surgical bleeding and wound infection were recorded in Group A more than in Group B. In cases of compensated diabetes compensation, implant placement could be considered a safe procedure.

Osseointegration Pharmacology: A Systematic Mapping Using Artificial Intelligence

Clinical performance of osseointegrated implants could be compromised by the medications taken by patients. The effect of a specific medication on osseointegration can be easily investigated using traditional systematic reviews. However, assessment of all known medications requires the use of evidence mapping methods. These methods allow assessment of complex questions, but they are very resource intensive when done manually. The objective of this study was to develop a machine learning algorithm to automatically map the literature assessing the effect of medications on osseointegration. Datasets of articles classified manually were used to train a machine-learning algorithm based on Support Vector Machines. The algorithm was then validated and used to screen 599,604 articles identified with an extremely sensitive search strategy. The algorithm included 281 relevant articles that described the effect of 31 different drugs on osseointegration. This approach achieved an accuracy of 95%, and compared to manual screening, it reduced the workload by 93%. The systematic mapping revealed that the treatment outcomes of osseointegrated medical devices could be influenced by drugs affecting homeostasis, inflammation, cell proliferation and bone remodeling. The effect of all known medications on the performance of osseointegrated medical devices can be assessed using evidence mappings executed with highly accurate machine learning algorithms.

Chronic hyperglycemia as a risk factor in implant therapy

It has been estimated that by 2030, the number of patients with diabetes aged > 64 years will be > 82 million in underdeveloped countries, and > 48 million in developed countries. Chronic hyperglycemia delays wound healing by reducing the expression of growth factors in the wound fluid and re-epithelialization. Impaired wound healing in patients with diabetes has also been associated with inhibition of the production of stromal cell-derived factor-1alpha by several tissues including bone marrow, brain, heart, spleen, and gingivae. Chronic hyperglycemia interferes with the osseointegration of implants by deferring the expression of fibronectin and integrins. Results from experimental studies have shown a significantly higher bone-to-implant contact around implants placed in healthy animals compared with animals with streptozotocin-induced diabetes. Moreover, persistent hyperglycemia plays a role in abnormal differentiation of osteoclasts, thereby making bone tissue more susceptible to resorption. Furthermore, persistent hyperglycemia has also been associated with increased peri-implant soft tissue inflammation (increased peri-implant bleeding on probing and probing depth) and crestal bone loss. Clinical studies have shown that under optimal glycemic control dental implants can show success and survival rates of up to 100% in patients diagnosed with diabetes. Although patients with diabetes can undergo dental implant therapy and can exhibit implant survival similar to those in systemically healthy individuals, the contribution of glycemic control and regular oral hygiene maintenance cannot be disregarded.

Peri-implant soft tissue inflammatory parameters and crestal bone loss among waterpipe (narghile) smokers and never-smokers with and without type 2 diabetes mellitus

BACKGROUND

Peri-implant soft tissue inflammatory parameters and crestal bone loss (CBL) among waterpipe smokers (WS) with and without type 2 diabetes mellitus (T2DM) remains uninvestigated. The aim of the present study was to assess peri-implant soft tissue inflammatory parameters and CBL among WS and never smokers (NS) with and without T2DM.

METHODS

Demographic data and information regarding duration of implants in function, daily frequency of smoking, duration and treatment of T2DM, and daily toothbrushing was collected using a questionnaire. Peri-implant plaque index (PI), bleeding on probing (BOP), probing depth (PD) ≥4 mm, CBL, and hemoglobin A1c (HbA1c) levels were assessed in all individuals. Level of significance was set at 5%.

RESULTS

Seventy-nine male individuals (39 patients with T2DM [20 WS and 19 NS] and 40 systemically healthy individuals [21 WS smokers and 19 NS]) were included. The mean age was comparable among individuals in all groups. The mean HbA1c levels were significantly higher among patients with T2DM compared to controls (P < 0.01). Peri-implant PI, BOP, PD, and CBL were comparable among WS and NS with T2DM. Among patients without T2DM, PI (P < 0.05), PD ≥4 mm (P < 0.05) and mesial and distal CBL (P < 0.05) were significantly higher in WS than NS. Among individuals without T2DM, BOP was significantly higher among NS (P < 0.05) than WS. In patients with T2DM, BOP was comparable among WS and NS.

CONCLUSIONS

Peri-implant soft tissue inflammatory parameters and CBL were comparable among WS and NS with T2DM. Among individuals without T2DM, these parameters were worse among WS than NS.

Therapeutic Effects of HIF-1α on Bone Formation around Implants in Diabetic Mice Using Cell-Penetrating DNA-Binding Protein

Patients with uncontrolled diabetes are susceptible to implant failure due to impaired bone metabolism. Hypoxia-inducible factor 1α (HIF-1α), a transcription factor that is up-regulated in response to reduced oxygen during bone repair, is known to mediate angiogenesis and osteogenesis. However, its function is inhibited under hyperglycemic conditions in diabetic patients. This study thus evaluates the effects of exogenous HIF-1α on bone formation around implants by applying HIF-1α to diabetic mice and normal mice via a protein transduction domain (PTD)-mediated DNA delivery system. Implants were placed in the both femurs of diabetic and normal mice. HIF-1α and placebo gels were injected to implant sites of the right and left femurs, respectively. We found that bone-to-implant contact (BIC) and bone volume (BV) were significantly greater in the HIF-1α treated group than placebo in diabetic mice (p < 0.05). Bioinformatic analysis showed that diabetic mice had 216 differentially expressed genes (DEGs) and 21 target genes. Among the target genes, NOS2, GPNMB, CCL2, CCL5, CXCL16, and TRIM63 were found to be associated with bone formation. Based on these results, we conclude that local administration of HIF-1α via PTD may boost bone formation around the implant and induce gene expression more favorable to bone formation in diabetic mice.

Effect of curcumin on bone tissue in the diabetic rat: repair of peri-implant and critical-sized defects

This study determined the effect of curcumin on bone healing in animals with diabetes mellitus (DM). One hundred rats were divided into five groups: DM+PLAC, DM+CURC, DM+INS, DM+CURC+INS, and non-DM (CURC, curcumin; PLAC, placebo; INS, insulin). Critical calvarial defects were created and titanium implants were inserted into the tibiae. Calvarial defects were analyzed histometrically, and BMP-2, OPN, OPG, RANKL, Runx2, Osx, β-catenin, Lrp-5, and Dkk1 mRNA levels were quantified by PCR. The implants were removed for a torque evaluation, the peri-implant tissue was collected for mRNA quantification of the same bone-related markers, and the tibiae were submitted to micro-computed tomography. The DM+CURC+INS and non-DM groups exhibited greater closure of the calvaria when compared to the DM+PLAC group (P<0.05). Increased retention of implants was observed in the DM+CURC, DM+CURC+INS, and non-DM groups when compared to the DM+PLAC group (P<0.05). CURC improved bone volume and increased bone-implant contact when compared to DM+PLAC (P<0.05). In calvarial samples, CURC favourably modulated RANKL/OPG and Dkk1 and improved β-catenin levels when compared to DM+PLAC (P<0.05). In peri-implant samples, Dkk1 and RANKL/OPG were down-regulated and BMP-2 up-regulated by CURC when compared to DM+PLAC (P<0.05). CURC reverses the harmful effects of DM in bone healing, contributing to the modulation of bone-related markers.

Effect of Resveratrol on Critical-Sized Calvarial Defects of Diabetic Rats: Histometric and Gene Expression Analysis

PURPOSE

This study investigated the influence of resveratrol (RESV) on the repair of bone critical defects in calvaria of animals with induced diabetes mellitus (DM).

MATERIAL AND METHODS

One hundred rats were divided into 5 groups: induced DM + RESV administration (DM + RESV; n = 20); induced DM plus placebo solution administration (DM + PLAC; n = 20); induced DM plus insulin therapy (DM + INS; n = 20); induced DM plus administration of RES and INS (DM + RESV + INS; n = 20); and nondiabetic controls (NDM; n = 20). DM was induced by intraperitoneal injection of streptozotocin 50 mg/kg 3 days before the surgical procedures. Two critical calvarial defects were created in each animal at the start of the study (day 0). Treatments were administered from day 0 to day 30 of the experiment, when animals were euthanized. One defect was processed for histometric analysis to measure closure of the bone defect. The tissue of the other defect was analyzed for quantification of bone morphogenetic protein-2 (BMP-2), osteopontin, osteoprotegerin, receptor activator of nuclear factor-κB ligand, runt-related transcription factor-2, osterix (Osx), β-catenin, lipoprotein receptor-related protein-5, and dikkop-1 mRNA by quantitative polymerase chain reaction.

RESULTS

Histometric results showed that the DM + RESV, DM + RESV + INS, and NDM groups exhibited greater closure of the bone defects compared with the PLAC- or INS-treated groups (P < .05). Diabetic animals treated with RESV plus INS showed higher levels of BMP-2 and Osx; Osx also was positively increased in animals treated with INS alone (P < .05).

CONCLUSIONS

The use of RESV, regardless of the presence of INS, positively influenced bone repair in animals with induced DM. Further, the combination of INS plus RESV was necessary for the modulation of BMP-2 gene expression.

Role of mechanical curettage with and without adjunct antimicrobial photodynamic therapy in the treatment of peri-implant mucositis in cigarette smokers: A randomized controlled clinical trial

OBJECTIVE

The aim of the present 12-weeks follow-up randomized clinical trial was to investigate the outcome of mechanical curettage (MC) with or without adjunct antimicrobial photodynamic therapy (aPDT) in the treatment of peri-implant mucositis in cigarette smokers.

METHODS

Therapeutically, subjects with peri-implant mucositis were divided into 2 groups: (a) Group-A: MC+aPDT; and (b) Group-B: MC alone (control group). In both groups, peri-implant plaque index (PI), bleeding on probing (BOP) and probing pocket depth (PPD) were gauged at baseline and after 12-weeks follow-up. Group comparisons were performed using the Kruskall-Wallis test. P-values less than 0.05 were considered statistically significant.

RESULTS

Fifty-four male patients (28 in Group-A and 26 in Group-B) were included. The mean age of individuals in groups A and B were 50.6±0.8 and 52.2±0.5years, respectively. In groups A and B the participants were smoking 16.5±2.7 and 14.2±1.7 cigarettes daily since 25.2±6.5 and 24.6±4.3years, respectively. Periimplant PI, BOP and PPD were comparable among individuals in both groups at baseline. At 12-weeks follow-up, there was a significant reduction in PI (P<0.001) and PPD (P<0.001) among patients in groups A and B compared with their respective baseline values. At 12-weeks follow-up, PI (P<0.001) and PPD (P<0.001) were significantly higher among patients in Group-B compared with Group-A (P<0.001). BOP was comparable in both groups at baseline and at 12-weeks follow-up.

CONCLUSION

In cigarette smokers, MC with adjunct aPDT is more effective in the treatment of peri-implant mucositis compared with MC alone.

Dental Implant Sites in Healthy versus Diabetic Subjects: A Two-Year Clinical and Bacteriological Assessment

The aim of this study was to analyze by Real-Time Polymerase Chain Reaction (PCR) possible differences in periimplant microbiota of patients without significant systemic diseases versus patients affected by non-insulin-dependent diabetes mellitus (NIDDM), both treated with dental implants with the same implant-abutment system. Patients suffering from NIDDM, and those with no history of major systemic diseases, treated with dental implants at the Prosthodontics Operative Unit of “Sapienza” University of Rome in the period February 2009 - March 2010 were considered. Clinical parameters as well as microbiological profile were evaluated for each implant site at 3, 6,12, and 24 month follow-up. Crevicular fluid was collected for microbial sampling and analyzed by Real-Time PCR in order to identify the possible presence of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum and Prevotella intermedia. Eight patients suffering from NIDDM and 22 with no history of major systemic diseases were included in the present investigation, each having received one to three dental implants. All the implants had been loaded 3 months after surgery, and the average follow-up after implant placement was 26.37±3.86. Clinical parameters showed no noticeable difference between the two groups, except for the Implant Stability Quotient (ISQ) that showed significantly lower values in NIDDM patients. A slightly higher amount of the considered pathogenic bacteria were retrieved in samples collected from patients with NIDDM (7.38×105) in comparison with those of healthy subjects (6.78×105), though the differences were below statistical significance. Within the limitations of the present study, a slight correlation was empirically detected between gene expression profiles of microbial populations and history of NIDDM, which however remained below the statistical significance. Further well-designed clinical studies may be useful to conclusively clarify the impact of subgingival microflora on the increased susceptibility of diabetic patients to periimplantitis.

Effects of long-term doxycycline on bone quality and strength in diabetic male DBA/2J mice

In type 1 diabetes, diabetic bone disease (DBD) is characterized by decreased bone mineral density, a state of low bone turnover and an increased risk of fracture. Animal models of DBD demonstrate that acquired alterations in trabecular and cortical bone microarchitecture contribute to decreased bone strength in diabetes. With anti-collagenolytic and anti-inflammatory properties, tetracycline derivatives may prevent diabetes-related decreases in bone strength. To determine if doxycycline, a tetracycline class antibiotic, can prevent the development of DBD in a model of long-term diabetes, male DBA/2J mice, with or without diabetes, were treated with doxycycline-containing chow for 10 weeks (dose range, 28-92 mg/kg/day). Long-term doxycycline exposure was not deleterious to the microarchitecture or biomechanical properties of healthy bone in male DBA/2J mice. Doxycycline treatment also did not prevent or alleviate the deleterious changes in trabecular microarchitecture, cortical structure, and biomechanical properties of bone induced by chronic diabetes.

The Effect of Systemic Delivery of Aminoguanidine versus Doxycycline on the Resorptive Phase of Alveolar Bone Following modified Widman Flap in Diabetic Rats: A Histopathological and Scanning Electron Microscope (SEM) study

OBJECTIVES

Aminoguanidine (guanylhydrazinehydrochloride) is a drug that prevents many of the classical systemic complications of diabetes including diabetic osteopenia through its inhibitory activity on the accumulation of advanced glycation end -products (AGEs). The aim of the present study was to evaluate the effectiveness of aminoguanidine versus doxycycline in reducing alveolar bone resorption following mucoperiosteal flap in diabetic rats, using the conventional histopathology and scanning electron microscope (SEM).

METHODS

Twenty-seven male albino rats were used in this study. Periodontal defects were induced experimentally on lower anterior teeth. All rats were subjected to induction of diabetes, by IV injection of the pancreatic B-cells toxin alloxan monohydrate. After eight weeks following the establishment of periodontal defects in all rats, the ligation was removed and 3 rats were scarified as negative control (group 1). The remaining animals were divided into three group based on treatment applied following mucoperiosteal flap surgery. Group 2 received saline treatment only, group 3 received doxycycline periostat (1.5 mg/kg/day) for 3 weeks, and group 4 received aminoguanidine (7.3 mmol/kg) for 3 weeks. The fasting glucose level was measured weekly post operatively. After 21 days all rats were sacrificed. Three anterior parts of the mandible of each group was prepared for histopathological examination and two parts were prepared for SEM.

RESULTS

Aminoguanidine treated group (group 4) showed statistically significant increased new bone formation, higher number of osteoblasts and decrease osteoclasts number, resorptive lacunae and existing inflammatory cell infiltration as compared to positive control group (group 2) (P<0.05). Doxycycline was also effective in reducing bone loss as documental by histopathological study.

CONCLUSION

The present study showed that aminoguanidine was significantly effective in reducing alveolar bone loss and can modify the detrimental effects of diabetes in alveolar bone resorption.

Dental implant survival in diabetic patients; review and recommendations

Rising population of diabetic individuals across the world has become a big concern to the society. The persistent hyperglycemia may affect each and every tissue and consequently results in morbidity and eventually mortality in diabetic patients. A direct negative response of diabetes has been observed on oral tissues with few contradictions however, little are known about effect of diabetes on dental implant treatment and the consequent results. Many studies concerned with osteointegration and prognosis of dental implant in diabetic patients have been conducted and published since 1994. These studies have been critically reviewed to understand the impact of diabetes on the success of dental implant and the factors to improve osseointegration and consequently survival of dental implant in diabetic patients. Theoretical literatures and studies in diabetic animals substantiate high failure rate of implants but most of clinical studies indicated statistically insignificant failure of dental implants even in moderately uncontrolled diabetic patients. Success of dental implant in well and fairly controlled diabetic patients with proper treatment planning, prophylactic remedies and adequate postsurgical maintenance appears as good as normal individuals.

Soft-tissue wound healing by anti-advanced glycation end-products agents

The blocking of advanced glycation end-products (AGE) has been shown to reduce diabetic complications and control periodontitis. This study investigated the pattern of palatal wound-healing after graft harvesting under the administration of aminoguanidine (AG), an AGE inhibitor, or N-phenacylthiazolium bromide (PTB), a glycated cross-link breaker. Full-thickness palatal excisional wounds (5.0 x 1.5 mm(2)) were created in 72 Sprague-Dawley rats. The rats received daily intraperitoneal injections of normal saline (control), AG, or PTB and were euthanized after 4 to 28 days. The wound-healing pattern was assessed by histology, histochemistry for collagen matrix deposition, immunohistochemistry for AGE and the AGE receptor (RAGE), and the expression of RAGE, as well as inflammation- and recovery-associated genes. In the first 14 days following AG or PTB treatments, wound closure, re-epithelialization, and collagen matrix deposition were accelerated, whereas AGE deposition, RAGE-positive cells, and inflammation were reduced. RAGE and tumor necrosis factor-alpha were significantly down-regulated at day 7, and heme oxygenase-1 was persistently down-regulated until day 14. The levels of vascular endothelial growth factor, periostin, type I collagen, and fibronectin were all increased at day 14. In conclusion, anti-AGE agents appeared to facilitate palatal wound-healing by reducing AGE-associated inflammation and promoting the recovery process.

Rehabilitative considerations for dental implants in the diabetic patient

Diabetes is a serious illness that affects many people, and there are many new cases diagnosed every year in all populations around the world. Dental implant is one of the restorative methods to replace missing teeth. As implants are directly anchored into bones, they provide stability, a more natural appearance, and minimize the risk of bone resorption. Thus, today, there is a high demand of dental implants and it is inevitable to meet diabetics who request implant treatment. However, Diabetes mellitus patients may pose contraindications to dental implants because of microvascular complications leading to slower healing process after surgery. Studies have shown that dental implantation failure rate in diabetic patients is much higher than that in non-diabetic patients. This article reviews the effect of diabetes on the osseointegration of implants and the soft tissue healing. It presents the factors used in assessing the severity of diabetes and its complications, as well as considerations for rehabilitation planning in these patients. In addition, the role of antibiotic prophylaxis has been reviewed since its effect on wound healing in diabetics is controversial. Integration of these factors by the dentist can dictate whether, as well as what type of implant supported prosthesis should be given to the diabetic patient.

Systematic review of pre-clinical models assessing implant integration in locally compromised sites and/or systemically compromised animals

OBJECTIVE

The aim was to systematically search the dental literature for pre-clinical models assessing implant integration in locally compromised sites (part 1) and systemically compromised animals (part 2), and to evaluate the quality of reporting of included publications.

METHODS

A Medline search (1966-2011) was performed, complimented by additional hand searching. The quality of reporting of the included publications was evaluated using the 20 items of the ARRIVE (Animals in Research In Vivo Experiments) guidelines.

RESULTS

One-hundred and seventy-six (part 1; mean ARRIVE score = 15.6 ± 2.4) and 104 (part 2; 16.2 ± 1.9) studies met the inclusion criteria. The overall mean score for all included studies amounted to 15.8 ± 2.2. Housing (38.3%), allocation of animals (37.9%), numbers analysed (50%) and adverse events (51.4%) of the ARRIVE guidelines were the least reported. Statistically significant differences in mean ARRIVE scores were found depending on the publication date (p < 0.05), with the highest score of 16.7 ± 1.6 for studies published within the last 2 years.

CONCLUSIONS

A large number of studies met the inclusion criteria. The ARRIVE scores revealed heterogeneity and missing information for selected items in more than 50% of the publications. The quality of reporting shifted towards better-reported pre-clinical trials within recent years.

The transmembrane transport of metformin by osteoblasts from rat mandible

Previous studies have demonstrated that metformin, one of systemic antihyperglycemic drugs, can slow bone loss caused by diabetes mellitus and has an osteogenic action on osteoblasts in vitro. It is tempting to speculate that metformin would be transported into bone tissues around dental implant by topical administration to improve the bone-implant contact in diabetic patients. In this study, the osteoblasts from rat mandible were cultured with 5.5 mM (control) or 16.5 mM d-glucose, then the uptake of metformin by osteoblasts was detected with high performance liquid chromatography (HPLC). Rat organic cation transporter (rOct) expression was characterized by immunocytochemistry, RT-PCR and Western blotting. It was found that, the uptake of metformin was saturable, Na(+)-dependent, affected by extracellular pH and inhibited by both phenformin and cimetidine (an inhibitor of Octs). rOct1 but no rOct2 was expressed extensively in osteoblasts and the protein level of rOct1 could be up-regulated by metformin. The uptake of metformin and phosphorylated-rOct1 at hyperglycaemic cell culture (16.5 mM d-glucose) significantly increased versus 5.5 mM control (p < 0.05). In conclusion, rat osteoblasts have the ability to transport the metformin intra-cellularly, the uptake of metformin by osteoblasts is a secondary active transportation mediated by rOct1 and high-glucose can improve the uptake of metformin by osteoblasts through phosphorylation of rOct1. The current results suggest that metformin could be used for dental implant topically in type 2 diabetic patients to increase the bone formation, therefore, to enhance the success rate of dental implants clinically.

The dual face of endogenous alpha-aminoketones: pro-oxidizing metabolic weapons

Amino metabolites with potential prooxidant properties, particularly alpha-aminocarbonyls, are the focus of this review. Among them we emphasize 5-aminolevulinic acid (a heme precursor formed from succinyl-CoA and glycine), aminoacetone (a threonine and glycine metabolite), and hexosamines and hexosimines, formed by Schiff condensation of hexoses with basic amino acid residues of proteins. All these metabolites were shown, in vitro, to undergo enolization and subsequent aerobic oxidation, yielding oxyradicals and highly cyto- and genotoxic alpha-oxoaldehydes. Their metabolic roles in health and disease are examined here and compared in humans and experimental animals, including rats, quail, and octopus. In the past two decades, we have concentrated on two endogenous alpha-aminoketones: (i) 5-aminolevulinic acid (ALA), accumulated in acquired (e.g., lead poisoning) and inborn (e.g., intermittent acute porphyria) porphyric disorders, and (ii) aminoacetone (AA), putatively overproduced in diabetes mellitus and cri-du-chat syndrome. ALA and AA have been implicated as contributing sources of oxyradicals and oxidative stress in these diseases. The end product of ALA oxidation, 4,5-dioxovaleric acid (DOVA), is able to alkylate DNA guanine moieties, promote protein cross-linking, and damage GABAergic receptors of rat brain synaptosome preparations. In turn, methylglyoxal (MG), the end product of AA oxidation, is also highly cytotoxic and able to release iron from ferritin and copper from ceruloplasmin, and to aggregate proteins. This review covers chemical and biochemical aspects of these alpha-aminoketones and their putative roles in the oxidative stress associated with porphyrias, tyrosinosis, diabetes, and cri-du-chat. In addition, we comment briefly on a side prooxidant behaviour of hexosamines, that are known to constitute building blocks of several glycoproteins and to be involved in Schiff base-mediated enzymatic reactions.