Proton Pump Inhibitors and Fractures in Adults: A Critical Appraisal and Review of the Literature

Despite the large number of patients worldwide being on proton pump inhibitors (PPIs) for acid-related gastrointestinal disorders, uncertainty remains over their long-term safety. Particularly, the potential side effects of these drugs on bone health have been evaluated in the last years. The purpose of our narrative review is to gather and discuss results of clinical studies focusing on the interactions between PPIs and fracture risk. Data generated mainly from nested case-control studies and meta-analysis suggest that long-term/high-dose PPIs users are characterized by an increased risk of fragility fractures, mainly hip fractures. However, in these studies, the PPIs-induced bone impairment is often not adjusted for different confounding variables that could potentially affect bone health, and exposure to PPIs was reported using medical prescriptions without adherence evaluation. The mechanisms of the PPI-related bone damage are still unclear, but impaired micronutrients absorption, hypergastrinemia, and increased secretion of histamine may play a role. Clinicians should pay attention when prescribing PPIs to subjects with a preexistent high risk of fractures and consider antiosteoporotic drugs to manage this additive effect on the bone. However, further studies are needed to clarify PPIs action on the bone

Severe hypophosphatemic osteomalacia secondary to fanconi syndrome due to adefovir: A case report

OBJECTIVE: Generalized proximal, type 2, renal tubular acidosis, also known as Fanconi syndrome, is a generalized dysfunction of the proximal renal tubule characterized by impaired reabsorption and increased urinary loss of phosphate and other solutes, such as uric acid, glucose, amino acids, and bicarbonate. Chronic hypophosphatemia is the second most common cause of osteomalacia after vitamin D deficiency in adult patients and can have a heterogeneous presentation, ranging from mild symptoms such as muscle weakness and skeletal pain to more severe presentation, such as disabling myopathy, severe bone and joint pain, difficulty walking, and even bone fractures. METHODS: This report describes a case of severe hypophosphatemic osteomalacia with multiple fragility fractures induced by adefovir, which was worsened and confounded by a previous treatment with zoledronic acid and required prolonged intravenous potassium phosphate administration. RESULTS: We highlight the limited diagnostic value of dual X-ray absorptiometry and bone scintigraphy in this challenging diagnosis. Bone metabolism should always be assessed in patients treated with adefovir for early detection of osteomalacia due to Fanconi syndrome. CONCLUSION: Although rare, this condition may be life-threatening and mimic other bone metabolic disorders that are treated with drugs that may further impair phosphate balance

Autoantibody and T cell responses to oxidative post-translationally modified insulin neoantigenic peptides in type 1 diabetes

Aims/hypothesis: Antibodies specific to oxidative post-translational modifications (oxPTM) of insulin (oxPTM-INS) are present in most individuals with type 1 diabetes, even before the clinical onset. However, the antigenic determinants of such response are still unknown. In this study, we investigated the antibody response to oxPTM-INS neoepitope peptides (oxPTM-INSPs) and evaluated their ability to stimulate humoral and T cell responses in type 1 diabetes. We also assessed the concordance between antibody and T cell responses to the oxPTM-INS neoantigenic peptides. Methods: oxPTM-INS was generated by exposing insulin to various reactive oxidants. The insulin fragments resulting from oxPTM were fractionated by size-exclusion chromatography further to ELISA and LC-MS/MS analysis to identify the oxidised peptide neoepitopes. Immunogenic peptide candidates were produced and then modified in house or designed to incorporate in silico-oxidised amino acids during synthesis. Autoantibodies to the oxPTM-INSPs were tested by ELISA using sera from 63 participants with new-onset type 1 diabetes and 30 control participants. An additional 18 fresh blood samples from participants with recently diagnosed type 1 diabetes, five with established disease, and from 11 control participants were used to evaluate, in parallel, CD4+ and CD8+ T cell activation by oxPTM-INSPs. Results: We observed antibody and T cell responses to three out of six LC-MS/MS-identified insulin peptide candidates: A:12–21 (SLYQLENYCN, native insulin peptide 3 [Nt-INSP-3]), B:11–30 (LVEALYLVCGERGFFYTPKT, Nt-INSP-4) and B:21–30 (ERGFFYTPKT, Nt-INSP-6). For Nt-INSP-4 and Nt-INSP-6, serum antibody binding was stronger in type 1 diabetes compared with healthy control participants (p≤0.02), with oxidised forms of ERGFFYTPKT, oxPTM-INSP-6 conferring the highest antibody binding (83% binders to peptide modified in house by hydroxyl radical [●OH] and &gt;88% to in silico-oxidised peptide; p≤0.001 vs control participants). Nt-INSP-4 induced the strongest T cell stimulation in type 1 diabetes compared with control participants for both CD4+ (p&lt;0.001) and CD8+ (p=0.049). CD4+ response to oxPTM-INSP-6 was also commoner in type 1 diabetes than in control participants (66.7% vs 27.3%; p=0.039). Among individuals with type 1 diabetes, the CD4+ response to oxPTM-INSP-6 was more frequent than to Nt-INSP-6 (66.7% vs 27.8%; p=0.045). Overall, 44.4% of patients showed a concordant autoimmune response to oxPTM-INSP involving simultaneously CD4+ and CD8+ T cells and autoantibodies. Conclusions/interpretation: Our findings support the concept that oxidative stress, and neoantigenic epitopes of insulin, may be involved in the immunopathogenesis of type 1 diabetes. Graphical abstract: [Figure not available: see fulltext.].</p

Autoantibody and T cell responses to oxidative post-translationally modified insulin neoantigenic peptides in type 1 diabetes

Aims/hypothesis Antibodies specific to oxidative post-translational modifications (oxPTM) of insulin (oxPTM-INS) are present in most individuals with type 1 diabetes, even before the clinical onset. However, the antigenic determinants of such response are still unknown. In this study, we investigated the antibody response to oxPTM-INS neoepitope peptides (oxPTM-INSPs) and evaluated their ability to stimulate humoral and T cell responses in type 1 diabetes. We also assessed the concordance between antibody and T cell responses to the oxPTM-INS neoantigenic peptides. Methods oxPTM-INS was generated by exposing insulin to various reactive oxidants. The insulin fragments resulting from oxPTM were fractionated by size-exclusion chromatography further to ELISA and LC-MS/MS analysis to identify the oxidised peptide neoepitopes. Immunogenic peptide candidates were produced and then modified in house or designed to incorporate in silico-oxidised amino acids during synthesis. Autoantibodies to the oxPTM-INSPs were tested by ELISA using sera from 63 participants with new-onset type 1 diabetes and 30 control participants. An additional 18 fresh blood samples from participants with recently diagnosed type 1 diabetes, five with established disease, and from 11 control participants were used to evaluate, in parallel, CD4(+) and CD8(+) T cell activation by oxPTM-INSPs. Results We observed antibody and T cell responses to three out of six LC-MS/MS-identified insulin peptide candidates: A:12-21 (SLYQLENYCN, native insulin peptide 3 [Nt-INSP-3]), B:11-30 (LVEALYLVCGERGFFYTPKT, Nt-INSP-4) and B:21-30 (ERGFFYTPKT, Nt-INSP-6). For Nt-INSP-4 and Nt-INSP-6, serum antibody binding was stronger in type 1 diabetes compared with healthy control participants (p &amp;lt;= 0.02), with oxidised forms of ERGFFYTPKT, oxPTM-INSP-6 conferring the highest antibody binding (83% binders to peptide modified in house by hydroxyl radical [(OH)-O-?] and &amp;gt;88% to in silico-oxidised peptide; p &amp;lt;= 0.001 vs control participants). Nt-INSP-4 induced the strongest T cell stimulation in type 1 diabetes compared with control participants for both CD4(+) (p&amp;lt;0.001) and CD8(+) (p=0.049). CD4(+) response to oxPTM-INSP-6 was also commoner in type 1 diabetes than in control participants (66.7% vs 27.3%; p=0.039). Among individuals with type 1 diabetes, the CD4(+) response to oxPTM-INSP-6 was more frequent than to Nt-INSP-6 (66.7% vs 27.8%; p=0.045). Overall, 44.4% of patients showed a concordant autoimmune response to oxPTM-INSP involving simultaneously CD4(+) and CD8(+) T cells and autoantibodies. Conclusions/interpretation Our findings support the concept that oxidative stress, and neoantigenic epitopes of insulin, may be involved in the immunopathogenesis of type 1 diabetes.Funding Agencies|JDRF [1-SRA-2017-512-Q-R]; European Foundation for the Study of Diabetes Future Leaders Mentorship Programme for Clinical Diabetologists 2018; Italian Ministry of Health [GR-201812365982]; AstraZeneca; Ordine dei Medici ed Odontoiatri di Salerno (OMCeO Salerno); European Foundation for the Study of Diabetes/Novo Nordisk Programme for Diabetes Research in Europe 2020; Fondazione Italiana Sclerosi Multipla [2020/R/13]; Progetti di Rilevante Interesse Nazionale [202077EYN7]</p