Bacterial Infection Increases Periodontal Bone Loss in Diabetic Rats through Enhanced Apoptosis

Abstract

Periodontal disease is the most common osteolytic disease in humans and is significantly increased by diabetes mellitus. We tested the hypothesis that bacterial infection induces bone loss in diabetic animals through a mechanism that involves enhanced apoptosis. Type II diabetic rats were inoculated with Aggregatibacter actinomycetemcomitans and treated with a caspase-3 inhibitor, ZDEVD-FMK, or vehicle alone. Apoptotic cells were measured with TUNEL; osteoblasts and bone area were measured in H&E sections. New bone formation was assessed by labeling with fluorescent dyes and by osteocalcin mRNA levels. Osteoclast number, eroded bone surface, and new bone formation were measured by tartrate-resistant acid phosphatase staining. Immunohistochemistry was performed with an antibody against tumor necrosis factor-α. Bacterial infection doubled the number of tumor necrosis factor-α–expressing cells and increased apoptotic cells adjacent to bone 10-fold (P < 0.05). Treatment with caspase inhibitor blocked apoptosis, increased the number of osteoclasts, and eroded bone surface (P < 0.05); yet, inhibition of apoptosis resulted in significantly greater net bone area because of an increase in new bone formation, osteoblast numbers, and an increase in bone coupling. Thus, bacterial infection in diabetic rats stimulates periodontitis, in part through enhanced apoptosis of osteoblastic cells that reduces osseous coupling through a caspase-3–dependent mechanism. Periodontal disease is the most common osteolytic disease in humans and is significantly increased by diabetes mellitus. We tested the hypothesis that bacterial infection induces bone loss in diabetic animals through a mechanism that involves enhanced apoptosis. Type II diabetic rats were inoculated with Aggregatibacter actinomycetemcomitans and treated with a caspase-3 inhibitor, ZDEVD-FMK, or vehicle alone. Apoptotic cells were measured with TUNEL; osteoblasts and bone area were measured in H&E sections. New bone formation was assessed by labeling with fluorescent dyes and by osteocalcin mRNA levels. Osteoclast number, eroded bone surface, and new bone formation were measured by tartrate-resistant acid phosphatase staining. Immunohistochemistry was performed with an antibody against tumor necrosis factor-α. Bacterial infection doubled the number of tumor necrosis factor-α–expressing cells and increased apoptotic cells adjacent to bone 10-fold (P < 0.05). Treatment with caspase inhibitor blocked apoptosis, increased the number of osteoclasts, and eroded bone surface (P < 0.05); yet, inhibition of apoptosis resulted in significantly greater net bone area because of an increase in new bone formation, osteoblast numbers, and an increase in bone coupling. Thus, bacterial infection in diabetic rats stimulates periodontitis, in part through enhanced apoptosis of osteoblastic cells that reduces osseous coupling through a caspase-3–dependent mechanism. Diabetes is a chronic inflammatory disease characterized by hyperglycemia that affects 26 million Americans.1Gong Z. Muzumdar R.H. Pancreatic function, type 2 diabetes, and metabolism in aging.Int J Endocrinol. 2012; 2012: 320482Crossref PubMed Scopus (88) Google Scholar Diabetes has several complications, such as cardiovascular, renal, microvascular, and periodontal diseases. Periodontal disease is one of the most common forms of osteolytic bone disease and one of the most frequent complications of the diabetes.2Lamster I.B. Lalla E. Borgnakke W.S. Taylor G.W. The relationship between oral health and diabetes mellitus.J Am Dent Assoc. 2008; 139: 19S-24SAbstract Full Text Full Text PDF PubMed Scopus (282) Google Scholar Recent research suggests that the relationship between periodontitis and diabetes is reciprocal.3Lalla E. Papapanou P.N. Diabetes mellitus and periodontitis: a tale of two common interrelated diseases.Nat Rev Endocrinol. 2011; 7: 738-748Crossref PubMed Scopus (564) Google Scholar, 4Bascones-Martinez A. Arias-Herrera S. Criado-Camara E. Bascones-Ilundain J. Bascones-Ilundain C. Periodontal disease and diabetes.Adv Exp Med Biol. 2012; 771: 76-87PubMed Google Scholar People with diabetes are more susceptible to periodontitis, and periodontitis may affect serum glucose levels and contribute to progression of diabetes.5Gurav A.N. Periodontitis and insulin resistance: casual or causal relationship?.Diabetes Metab J. 2012; 36: 404-411Crossref PubMed Scopus (45) Google Scholar Diabetes may contribute to periodontitis because of its effect on inflammation.6Otomo-Corgel J. Pucher J.J. Rethman M.P. Reynolds M.A. State of the science: chronic periodontitis and systemic health.J Evid Based Dent Pract. 2012; 12: 20-28Abstract Full Text Full Text PDF PubMed Scopus (170) Google Scholar, 7Nassar H. Kantarci A. van Dyke T.E. Diabetic periodontitis: a model for activated innate immunity and impaired resolution of inflammation.Periodontol 2000. 2007; 43: 233-244Crossref PubMed Scopus (86) Google Scholar Despite being triggered by bacterial infection, periodontal bone loss is tied to the inflammatory host response, which leads to the generation of prostaglandins and cytokines that stimulate osteoclastogenesis and periodontal bone loss.8Li Q. Valerio M.S. Kirkwood K.L. MAPK usage in periodontal disease progression.J Signal Transduct. 2012; 2012: 308943Crossref PubMed Google Scholar Several of the detrimental aspects of periodontal disease have recently been shown to be mediated by elevated levels of tumor necrosis factor-α (TNF-α).9Garlet G.P. Destructive and protective roles of cytokines in periodontitis: a re-appraisal from host defense and tissue destruction viewpoints.J Dent Res. 2010; 89: 1349-1363Crossref PubMed Scopus (464) Google Scholar, 10Graves D.T. Li J. Cochran D.L. Inflammation and uncoupling as mechanisms of periodontal bone loss.J Dent Res. 2011; 90: 143-153Crossref PubMed Scopus (204) Google Scholar TNF-α is a proinflammatory cytokine produced by leukocytes and other cell types.11Croft M. Benedict C.A. Ware C.F. Clinical targeting of the TNF and TNFR superfamilies.Nat Rev Drug Discov. 2013; 12: 147-168Crossref PubMed Scopus (315) Google Scholar Enhanced TNF-α levels have been directly linked to cellular changes in diabetic retinopathy, deficits in wound healing, and diabetes-enhanced periodontitis.12Behl Y. Krothapalli P. Desta T. Dipiazza A. Roy S. Graves D.T. Diabetes-enhanced tumor necrosis factor-{alpha} production promotes apoptosis and the loss of retinal microvascular cells in type 1 and type 2 models of diabetic retinopathy.Am J Pathol. 2008; 172: 1411-1418Abstract Full Text Full Text PDF PubMed Scopus (181) Google Scholar, 13Pacios S. Kang J. Galicia J. Gluck K. Patel H. Ovaydi-Mandel A. Petrov S. Alawi F. Graves D.T. Diabetes aggravates periodontitis by limiting repair through enhanced inflammation.FASEB J. 2012; 26: 1423-1430Crossref PubMed Scopus (113) Google Scholar, 14Kayal R.A. Siqueira M. Alblowi J. McLean J. Krothapalli N. Faibish D. Einhorn T.A. Gerstenfeld L.C. Graves D.T. TNF-alpha mediates diabetes-enhanced chondrocyte apoptosis during fracture healing and stimulates chondrocyte apoptosis through FOXO1.J Bone Miner Res. 2010; 25: 1604-1615Crossref PubMed Scopus (125) Google Scholar Some of the detrimental effects of diabetes-enhanced TNF-α levels may be because of the induction of cell death by triggering caspase activity. Caspases are a family of cysteine proteases that can act as either initiators (caspases 2, 8, and 9) or executioners (caspases 3, 6, and 7) of apoptosis.15Chowdhury I. Tharakan B. Bhat G.K. Caspases: an update.Comp Biochem Physiol B Biochem Mol Biol. 2008; 151: 10-27Crossref PubMed Scopus (300) Google Scholar Caspase-3 appears to play a central role in bacteria and lipopolysaccharide-mediated apoptosis.16Al-Mashat H.A. Kandru S. Liu R. Behl Y. Desta T. Graves D.T. Diabetes enhances mRNA levels of proapoptotic genes and caspase activity, which contribute to impaired healing.Diabetes. 2006; 55: 487-495Crossref PubMed Scopus (77) Google Scholar, 17Alikhani M. Alikhani Z. He H. Liu R. Popek B.I. Graves D.T. Lipopolysaccharides indirectly stimulate apoptosis and global induction of apoptotic genes in fibroblasts.J Biol Chem. 2003; 278: 52901-52908Crossref PubMed Scopus (58) Google Scholar In addition, it has been shown that TNF-α can stimulate the expression of several pro-apoptotic genes, many of which are regulated by the pro-apoptotic transcription factor, forkhead box-O1 (FOXO1).18Ponugoti B. Dong G. Graves D.T. Role of forkhead transcription factors in diabetes-induced oxidative stress.Exp Diabetes Res. 2012; 2012: 939751Crossref PubMed Scopus (151) Google Scholar The functional role of apoptosis in pathological processes can be studied with caspase inhibitors, which are small peptides that block the activity of well-defined caspases.19Callus B.A. Vaux D.L. Caspase inhibitors: viral, cellular and chemical.Cell Death Differ. 2007; 14: 73-78Crossref PubMed Scopus (156) Google Scholar These inhibitors have been used in animal models to attenuate cell death and diminish tissue damage in ischemic conditions, sepsis, and other pathological processes.20Concha N.O. Abdel-Meguid S.S. Controlling apoptosis by inhibition of caspases.Curr Med Chem. 2002; 9: 713-726Crossref PubMed Scopus (50) Google Scholar, 21Wilson S.E. Mohan R.R. Hong J. Lee J. Choi R. Liu J.J. Apoptosis in the cornea in response to epithelial injury: significance to wound healing and dry eye.Adv Exp Med Biol. 2002; 506: 821-826Crossref PubMed Scopus (2) Google Scholar Other studies using caspase inhibitors have shown that part of the detrimental effect of diabetes on healing after infection is the result of increased fibroblast or osteoblast apoptosis.16Al-Mashat H.A. Kandru S. Liu R. Behl Y. Desta T. Graves D.T. Diabetes enhances mRNA levels of proapoptotic genes and caspase activity, which contribute to impaired healing.Diabetes. 2006; 55: 487-495Crossref PubMed Scopus (77) Google Scholar, 22Siqueira M.F. Li J. Chehab L. Desta T. Chino T. Krothpali N. Behl Y. Alikhani M. Yang J. Braasch C. Graves D.T. Impaired wound healing in mouse models of diabetes is mediated by TNF-alpha dysregulation and associated with enhanced activation of forkhead box O1 (FOXO1).Diabetologia. 2010; 53: 378-388Crossref PubMed Scopus (163) Google Scholar To understand how diabetes may affect periodontal bone loss through apoptosis, we used a caspase-3/7 inhibitor in a type 2 Goto-Kakizaki (GK) diabetic rat model of periodontal disease induced by bacterial infection. The aim of this study was to determine how apoptosis of osteoblasts contributed to periodontal bone loss by its effect on bone formation in diabetic animals. GK male and female rats were purchased from Charles River Laboratories (Wilmington, MA). The GK rat naturally develops type 2 diabetes mellitus at the age of approximately 12 weeks. Rats were housed in separate cages and fed powdered food (Laboratory Rodent Meal Diet 5001; Purina Mills Feeds, St. Louis, MO). When glucose levels were >220 mg/dL, and glycated hemoglobin levels were >7.0%, they were classified as diabetic. All animal procedures were approved by the Institutional Animal Care and Use Committee. Diabetic (GK) rats received antibiotics ad libitum in their drinking water for 4 days (20 mg kanamycin and 20 mg ampicillin) and were swabbed with a 0.12% chlorhexidine gluconate rinse during the past 2 days (Procter and Gamble, Cincinnati, OH) to facilitate colonization by Aggregatibacter actinomycetemcomitans. After 3 days without and for 3 A. actinomycetemcomitans cells A. a A. actinomycetemcomitans New were by oral to diabetic (GK) and A. actinomycetemcomitans cells was in their food a for as K. D. B.A. genes of actinomycetemcomitans are for in a rat A. 2003; PubMed Scopus Google Scholar Some received or caspase-3 inhibitor 4 after the as for 4 days to A. actinomycetemcomitans K. D. B.A. genes of actinomycetemcomitans are for in a rat A. 2003; PubMed Scopus Google Scholar These animals were 1 and 2 after the of the and after A. actinomycetemcomitans Caspase-3 inhibitor, was by at 4 and rats were 1 or 2 treated with caspase inhibitor were with the of Immunohistochemistry was performed with an antibody against TNF-α The number of cells adjacent to bone was as we have S. Kang J. Galicia J. Gluck K. Patel H. Ovaydi-Mandel A. Petrov S. Alawi F. Graves D.T. Diabetes aggravates periodontitis by limiting repair through enhanced inflammation.FASEB J. 2012; 26: 1423-1430Crossref PubMed Scopus (113) Google Scholar at Apoptotic cells were by Apoptosis was measured with with an antibody to apoptotic The number of apoptotic cells was at with an using in a adjacent to bone and in were performed with to animals were as cells in of bone in sections. eroded and new bone formation were measured with tartrate-resistant acid phosphatase as S. Kang J. Galicia J. Gluck K. Patel H. Ovaydi-Mandel A. Petrov S. Alawi F. Graves D.T. Diabetes aggravates periodontitis by limiting repair through enhanced inflammation.FASEB J. 2012; 26: 1423-1430Crossref PubMed Scopus (113) Google Scholar Bone was measured by using St. Louis, and fluorescent staining. was by at 4 and was labeling of new bone formation was measured by in sections. The area between the two fluorescent was D.L. He Yang Liu L. of bone of B. 2012; PubMed Scopus Google Scholar Bone coupling was as the bone number of or the of eroded Bone area was measured as the area by were performed with to animals was from the of the and as S. Kang J. Galicia J. Gluck K. Patel H. Ovaydi-Mandel A. Petrov S. Alawi F. Graves D.T. Diabetes aggravates periodontitis by limiting repair through enhanced inflammation.FASEB J. 2012; 26: 1423-1430Crossref PubMed Scopus (113) Google Scholar mRNA levels of osteocalcin were assessed by using and for osteocalcin were to a The were performed with to animals with and performed with were performed using 20 of with was used to the between at a and to from with the other The significance was at < Apoptosis was measured as the number of apoptotic cells and the number of apoptotic cells I.B. Lalla E. Borgnakke W.S. Taylor G.W. The relationship between oral health and diabetes mellitus.J Am Dent Assoc. 2008; 139: 19S-24SAbstract Full Text Full Text PDF PubMed Scopus (282) Google Scholar in the periodontal adjacent to bone and the bone the number of apoptotic cells was after A. actinomycetemcomitans infection, the of apoptosis increased by approximately in cells adjacent to bone and the bone surface (P < 0.05). The increase in apoptosis with infection can be for by a increase in expression of pro-apoptotic such as in to the cells was and more doubled to at (P < 0.05). Treatment with and caspase-3 inhibitor apoptosis to levels The was shown with the number of cells and In a small effect on Bone is by bone formation in a to as Bone cellular for coupling of bone formation and Biol. 2008; PubMed Scopus Google Scholar In periodontal disease and other bone pathological conditions, bone coupling is D.T. Li J. Cochran D.L. Inflammation and uncoupling as mechanisms of periodontal bone loss.J Dent Res. 2011; 90: 143-153Crossref PubMed Scopus (204) Google Scholar We inhibition of apoptosis the number of osteoblasts after induction of periodontal disease with an increase in apoptosis (P < 0.05). periodontitis with the of antibiotics increased the number of osteoblasts by (P < 0.05). with caspase-3 inhibitor increased the number by at and at with the without or inhibitor (P < 0.05). Thus, of the increase in osteoblast be directly tied to apoptosis from with the caspase-3 bone area increased with caspase-3 inhibitor (P < periodontal bone loss is by inhibition of apoptosis in diabetic Periodontitis was induced in GK diabetic rats treated with or caspase-3 inhibitor, as in sections. Bone area was as the area by < a between the and < a with To the of caspase-3 inhibitor on new bone formation was measured with with which used the as a and that the of new bone formation increased diabetic rats were treated with caspase-3 inhibitor (P < Treatment with the in bone the of new bone formation was measured at the by expression of osteocalcin mRNA Diabetic rats osteocalcin mRNA levels at weeks. When diabetic rats were treated with inhibitor, was a increase with the (P < 0.05). new bone formation was assessed using fluorescent in and The of caspase inhibitor increased the of new bone formation by at and at with the at the (P < effect on the of bone bone formation is increased by caspase Periodontitis was induced in GK diabetic which were treated with or caspase-3 inhibitor, as in and New bone formation was measured using fluorescent in sections. The between fluorescent was used to new bone The the between bone and periodontal between periodontal and New bone formation was assessed at and < a between the and < a with the To the effect of caspase-3 inhibitor on bone the number of 6, and the eroded bone surface that activity were Osteoclast and activity increased by approximately after the infection 6, and increase with the with the with caspase inhibitor increased the number of by and eroded bone surface by (P < 0.05). To the of diabetes on bone the of new bone formation by labeling was by an of or eroded bone surface Treatment with antibiotics increase in bone coupling. Treatment with caspase-3 inhibitor significantly increased bone coupling by approximately measured to or by eroded bone surface (P < 0.05). We that diabetes significantly enhanced in the and that the diabetes-enhanced was tied to levels of apoptosis in the and tissue of diabetic S. Kang J. Galicia J. Gluck K. Patel H. Ovaydi-Mandel A. Petrov S. Alawi F. Graves D.T. Diabetes aggravates periodontitis by limiting repair through enhanced inflammation.FASEB J. 2012; 26: 1423-1430Crossref PubMed Scopus (113) Google Scholar, J. B. S. Li Y. H. Graves D.T. Aggregatibacter actinomycetemcomitans infection enhances apoptosis in through a mechanism in 2012; PubMed Scopus (45) Google Scholar In the we the role of levels of apoptosis in diabetic animals to determine its to periodontal bone of bone formation and bone to bone coupling. We a to which is to after periodontal infection was to for bone to and bone coupling after infection was D.T. D. Dyke T.E. G. The of models to to periodontal 2008; PubMed Scopus (282) Google Scholar, R. Desta T. Krothapalli N. M. Q. Graves D.T. Diabetes enhances periodontal bone loss through enhanced and bone Dent Res. 2006; PubMed Scopus Google Scholar The that apoptosis significantly the number of and periodontal cells of osteoblast numbers, which were significantly increased apoptosis was The inhibitor increased significantly the of new bone by from bone and mRNA levels of the bone the number of and their activity were increased by the caspase-3 the net effect was an increase in bone area because of enhanced bone that bacterial infection in diabetic animals during the of bone formation has a on periodontal disease through enhanced apoptosis of osteoblasts that bone or their is the to that that apoptosis significantly to periodontal bone loss in Other diabetic complications have been associated with enhanced levels of apoptosis. diabetic and diabetes-enhanced disease are significantly by apoptosis of cells and M. and cell death in diabetic 2002; PubMed Scopus Google Scholar, L. Li G. L. Y. Kang apoptosis in mouse caspase-3 activation 2002; PubMed Scopus Google Scholar The inhibition of apoptosis through caspase-3 has been linked to pathological a in study caspase-3 blocked that leads to L. M. Caspase-3 to and in 2011; PubMed Scopus Google Scholar in in with a central infection, that the caspase-3 were associated with a in of central tissue K.L. Caspase-3 activation is for in 2010; PubMed Scopus Google Scholar Diabetes leads to the of pro-apoptotic the formation of oxidative and E. Papapanou P.N. Diabetes mellitus and periodontitis: a tale of two common interrelated diseases.Nat Rev Endocrinol. 2011; 7: 738-748Crossref PubMed Scopus (564) Google Scholar, B. Dong G. Graves D.T. Role of forkhead transcription factors in diabetes-induced oxidative stress.Exp Diabetes Res. 2012; 2012: 939751Crossref PubMed Scopus (151) Google Scholar may contribute to apoptosis. In addition, expression of several genes of pro-apoptotic or expression of and is enhanced by R.A. Siqueira M. Alblowi J. McLean J. Krothapalli N. Faibish D. Einhorn T.A. Gerstenfeld L.C. Graves D.T. TNF-alpha mediates diabetes-enhanced chondrocyte apoptosis during fracture healing and stimulates chondrocyte apoptosis through FOXO1.J Bone Miner Res. 2010; 25: 1604-1615Crossref PubMed Scopus (125) Google Scholar, H.A. Kandru S. Liu R. Behl Y. Desta T. Graves D.T. Diabetes enhances mRNA levels of proapoptotic genes and caspase activity, which contribute to impaired healing.Diabetes. 2006; 55: 487-495Crossref PubMed Scopus (77) Google Scholar The between pro-apoptotic and and of factors may be by of the forkhead such as a role in cell and apoptosis and may be a to B. Dong G. Graves D.T. Role of forkhead transcription factors in diabetes-induced oxidative stress.Exp Diabetes Res. 2012; 2012: 939751Crossref PubMed Scopus (151) Google Scholar, A. transcription factors in and 2008; PubMed Scopus Google Scholar In periodontal of the pro-apoptotic effect of infection has been linked to the host D.T. Li J. Cochran D.L. Inflammation and uncoupling as mechanisms of periodontal bone loss.J Dent Res. 2011; 90: 143-153Crossref PubMed Scopus (204) Google Scholar, J. in periodontal Biol. 2012; PubMed Scopus Google Scholar In studies have that the inhibition of TNF-α reduces apoptosis of tissue and S. Kang J. Galicia J. Gluck K. Patel H. Ovaydi-Mandel A. Petrov S. Alawi F. Graves D.T. Diabetes aggravates periodontitis by limiting repair through enhanced inflammation.FASEB J. 2012; 26: 1423-1430Crossref PubMed Scopus (113) Google Scholar, R. Desta T. Behl Y. Graves D.T. necrosis mediates diabetes-enhanced apoptosis of cells and diabetic J Pathol. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar or their such as stimulate apoptosis through a M. Alikhani Z. He H. Liu R. Popek B.I. Graves D.T. Lipopolysaccharides indirectly stimulate apoptosis and global induction of apoptotic genes in fibroblasts.J Biol Chem. 2003; 278: 52901-52908Crossref PubMed Scopus (58) Google Scholar, R. Desta T. Behl Y. Graves D.T. necrosis mediates diabetes-enhanced apoptosis of cells and diabetic J Pathol. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar We that TNF-α expression was in to bone after bacterial infection. bacterial from A. actinomycetemcomitans or other bacteria may apoptosis, this has been in in studies of periodontal Aggregatibacter actinomycetemcomitans from to Dent Res. 2010; 89: PubMed Scopus Google Scholar, D. S.E. T.A. Graves D.T. of oral bacteria with epithelial cell 2011; 26: PubMed Scopus Google Scholar We have shown that by periodontal induces apoptosis of or osteoblasts through enhanced TNF-α R. Desta T. Behl Y. Graves D.T. necrosis mediates diabetes-enhanced apoptosis of cells and diabetic J Pathol. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar, D. M. S. G. S. Desta T. A. Y. necrosis fibroblast apoptosis, and formation in response to Dent Res. PubMed Scopus Google Scholar The host response to periodontal in has been shown to stimulate apoptosis of bone cells through activation of M. M. S. Graves D.T. apoptosis in through activation of and the transcription J Physiol 2007; PubMed Scopus Google Scholar of caspase-3 cells from and oxidative apoptosis in osteoblasts from oxidative apoptosis through of caspase-3 PubMed Scopus Google Scholar that by apoptosis of cells and their is and that the cell death a role in periodontal bone loss in diabetic animals. Thus, apoptosis of osteoblasts or their is a limiting in bone coupling. In to inflammatory by caspase-3 reduces apoptosis by caspase-3 activity in N. M. E. T. T. Caspases family are in the of the of Full Text Full Text PDF PubMed Scopus Google Scholar Caspase-3 inhibitors apoptosis in N. M. E. T. T. Caspases family are in the of the of Full Text Full Text PDF PubMed Scopus Google Scholar, of caspase-3 activity in apoptotic in Full Text Full Text PDF PubMed Scopus Google Scholar These with in which the number of and their activity were increased caspase-3 is is a greater increase in bone formation that the net effect of apoptosis in diabetic animals is to bone is with other pathological in which and osteoblast apoptosis, through the caspase-3 have been shown to contribute to bone formation and bone in and inflammatory D. J. S. C. M. 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D. an role in bone fracture 2013; PubMed Scopus Google Scholar We have recently shown that diabetes-enhanced TNF-α a role in the resolution of periodontal and bone S. Kang J. Galicia J. Gluck K. Patel H. Ovaydi-Mandel A. Petrov S. Alawi F. Graves D.T. Diabetes aggravates periodontitis by limiting repair through enhanced inflammation.FASEB J. 2012; 26: 1423-1430Crossref PubMed Scopus (113) Google Scholar, Galicia J. Dong G. Alawi F. Graves D.T. expression during diabetic Dent Res. 2012; PubMed Scopus Google Scholar These with that diabetes-enhanced periodontitis is significantly by elevated levels of and apoptosis. studies may mechanisms by which diabetes leads to enhanced TNF-α which may be in bone coupling. We for in the and for in the in of research that are in the of The of PDF