Increased intestinal permeability precedes clinical onset of type 1 diabetes

AIMS/HYPOTHESIS

Recent observations have shown subclinical intestinal abnormalities in human type 1 diabetes. Whether these are related to the pathogenetic process or secondary to the diabetes remains to be clarified. The aim of this study was to investigate this issue by examining intestinal permeability to sugars in subjects at different stages of type 1 diabetes: preclinical, new-onset and long-term established disease.

METHODS

Eighty-one subjects with islet autoimmunity (18 preclinical, 28 new-onset and 35 long-term type 1 diabetes) and 40 healthy control subjects were investigated by a lactulose-mannitol test, consisting of oral administration of the two sugars and measurement of their urinary excretion.

RESULTS

All groups of subjects with islet autoimmunity showed an increase in intestinal permeability (p < or = 0.009 vs controls) to the disaccharide lactulose, indicative of a damaged barrier, but a similar permeability to the monosaccharide mannitol (NS vs controls), indicative of an integral surface mucosa; consequently there was an increase in the lactulose:mannitol excretion ratio (p < or = 0.025 vs controls).

CONCLUSIONS/INTERPRETATION

These findings indicate the presence of a subclinical enteropathy associated with type 1 diabetes that is already detectable before clinical onset of the disease, and suggest that the small intestine is an organ participating in the pathogenetic process of type 1 diabetes.

Islet autoantibody markers in IDDM: risk assessment strategies yielding high sensitivity

Identification of islet autoantigens offers the possibility that antibody tests other than islet cell antibodies may be used for assessing risk of insulin-dependent diabetes mellitus (IDDM). The aim of this study was to determine the combination of islet autoantibody markers that could identify most future cases of IDDM. Islet cell antibodies, antibodies to glutamic acid decarboxylase (GAD)65, 37,000/40,000 M(r) islet tryptic fragments, carboxypeptidase-H, and islet cell autoantigen (ICA)69 were measured in sera from 100 newly-diagnosed IDDM patients, 27 individuals prior to onset of IDDM, and 83 control subjects. Islet cell antibodies were detected in 88% of IDDM patients and 81% with pre-IDDM, GAD65 antibodies in 70% of IDDM patients and 89% with pre-IDDM, and antibodies to 37,000/40,000 M(r) islet tryptic fragments in 54% of IDDM patients and in 48% with pre-IDDM. The latter were found only in conjunction with islet cell antibodies and were more frequent in young onset cases. All 20 IDDM patients and the 3 pre-IDDM subjects who had islet cell antibodies without GAD65 antibodies had antibodies to 37,000/40,000 M(r) islet tryptic fragments, and all but one had disease onset before age 15 years. No sera strongly immunoprecipitated in vitro translated ICA69 or carboxypeptidase-H; 4% of patients had anti-ICA69 and 11% anti-carboxypeptidase-H levels above those of the control subjects. The findings suggest that none of the single antibody specificities are as sensitive as islet cell antibodies, but that a combination of GAD65 antibodies and antibodies to 37,000/40,000 M(r) islet tryptic fragments has the potential to identify more than 90% of future cases of IDDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Residual beta-cell function and spontaneous clinical remission in type 1 diabetes mellitus: the role of puberty

To investigate the role of puberty on spontaneous clinical remission and on secretion of residual C-peptide during the first year of type 1 diabetes mellitus, we studied 77 pre-pubertal, 39 pubertal and 41 post-pubertal type 1 diabetic patients. Spontaneous partial clinical remission (HbA1c within the normal range and insulin dose less than 0.3 U x kg(-1) body weight x day(-1) lasting for at least 10 days) decreased with duration of diabetes: months 3 vs 6 vs 12, respectively 13 vs 7 vs 4% (P<0.025). Remission was higher in post-pubertal than pubertal and prepubertal patients: month 6 respectively 20 vs 5 vs 1% (P<0.001). Secretion of C-peptide was significantly lower in pre-pubertal than the other two groups of patients. Basal and stimulated C-peptide secretion were higher in patients in clinical remission than in those who were not: basal value 0.4 (0.26-0.53) vs 0.28 (0.14-0.4) nmol/l (P<0.05); stimulated value 0.63 (0.5-0.95) vs 0.56 (0.31-0.74) nmol/l (P<0.05). Spontaneous remission is less frequent in children and adolescent patients than in adult post-pubertal patients, but different mechanisms may be involved. Low residual insulin secretion seems implicated in children meanwhile low insulin sensitivity could be more important in pubertal patients.

Sera from patients with IDDM and healthy individuals have antibodies to ICA69 on western blots but do not immunoprecipitate liquid phase antigen

ICA69 is a recently cloned pancreatic islet protein proposed as a potential target of autoimmunity in insulin dependent diabetes mellitus (IDDM). The aim of our study was to verify the relevance of ICA69 antibodies as markers of the disease. We measured antibodies to ICA69 in sera from newly-diagnosed IDDM patients, in age- and sex-matched normal controls, and in sera prior to the onset of IDDM (pre-IDDM). Human islet ICA69 was cloned and inserted into a bacterial expression vector and an in vitro transcription vector. Binding to affinity purified recombinant ICA69 on Western blots was found in 33/48 (68%) sera from newly-diagnosed IDDM patients and in 36/56 (64%) controls. No differences in band intensity were found between IDDM and controls. Using immunoprecipitation of 35S methionine labelled in vitro translated ICA69, none of 53 sera from newly diagnosed IDDM patients, 0 of 57 control sera and 1 of 24 pre-IDDM sera had detectable antibodies. We conclude that solid-phase assays are inappropriate for measurement of ICA69 antibodies as specific markers of IDDM and that antibodies to ICA69 are not detected by a liquid-phase immunoprecipitation assay. These data support neither a role for ICA69 as a relevant autoantigen in IDDM, nor a role for the measurement of antibodies to ICA69 in the prediction of IDDM.

Two-step islet autoantibody screening for risk assessment of type 1 diabetes in relatives

OBJECTIVE

To examine the performance of islet cell antibodies (ICAs) and antibodies to glutamate decarboxylase (GADA), IA-2 (IA-2 antibody [IA-2A]), and insulin (insulin autoantibody [IAA]), alone and in combination, in assessing type 1 diabetes risk within type 1 diabetic families to identify a practical and effective screening strategy for predicting type 1 diabetes in relatives.

RESEARCH DESIGN AND METHODS

ICA, GADA, IA-2A, and IAA were determined in 806 first-degree relatives participating in a prospective type 1 diabetes family study (median follow-up 6.17 years, range 0.6-8.3). The conferred risk of developing type 1 diabetes within 6 years was evaluated by Kaplan-Meier for each antibody marker, used alone or in combination.

RESULTS

ICAs were detected in 3%, GADA in 5.1%, IA-2A in 2.5%, and IAA in 3.7% of relatives; > or =1 antibody markers were detected in 10.7% of relatives and > or =2 were detected in 1.9% of relatives. The risk of type 1 diabetes at 6 years was 1.5% in relatives with only 1 marker and 24.8% in relatives with > or =2 markers. As a practical and effective strategy for type 1 diabetes risk assessment in relatives, this study indicates a first-step screening based on GADA and IA-2A measurement--which identified 6.5% of relatives, including all who developed the disease, with a 6-year type 1 diabetes risk of 9.0%--followed by a second step based on ICA and IAA measurement in relatives with either GADA or IA-2A, which identified a total of 1.9% of all relatives as having > or =2 markers, and a 6-year risk of 24.8%, including 6 of 7 who developed type 1 diabetes.

CONCLUSIONS

A two-step antibody screening, based first on GADA and IA-2A and then on ICA and IAA measurements in identified individuals, is likely to be a practical, sensitive, and effective strategy for predicting type 1 diabetes in first-degree relatives.

Susceptibility of black bullhead Ameiurus melas to a panel of ranavirus isolates

Ranaviruses are considered a serious threat to lower vertebrates, including fish, amphibians and reptiles. However, epidemiological data on these agents are lacking, and further investigations are needed to understand the role of carriers and to update the list of susceptible hosts. We carried out various experimental infections under controlled conditions to contribute to the current knowledge on the susceptibility of black bullhead Ameiurus melas to European catfish virus (ECV) and other ranaviruses. A panel of 7 ranavirus isolates was used to challenge duplicate groups of A. melas juveniles maintained in aquaria supplied with running dechlorinated tap water. The experiments were performed at 15 and 25 degrees C. The results confirmed the high susceptibility of A. melas to ECV infection. Furthermore, a significant mortality associated with the typical signs of systemic viral infections was observed in groups challenged with Epizootic haematopoietic necrosis virus (EHNV) at 25 degrees C, and to a lesser extent, at 15 degrees C. No significant mortality was recorded in fish challenged with European sheatfish virus (ESV), Frog virus 3 (FV3), Rana esculenta virus-like (REV-like), Bohle iridovirus (BIV) or short-finned eel virus (SERV).

Autoimmune responses to the beta cell autoantigen, insulin, and the INS VNTR-IDDM2 locus

Type 1 diabetes is associated with autoimmunity to insulin. Genetic susceptibility to type 1 diabetes is polygenic and includes the INS VNTR-IDDM2 locus which may regulate the expression of insulin in pancreas and thymus. In order to determine whether insulin autoimmunity could be attributed to a genetic susceptibility conferred by the INS VNTR-IDDM2 locus, peripheral blood T cell proliferation to human insulin and insulin autoantibodies (IAA) was measured in patients with new onset type 1 diabetes and control subjects. IAA were detected in 21 of 53 patients and in none of 25 control subjects, while T cell responses were low (stimulation index range 0.4-7.2) and similar in both groups. Both antibody and T cell responses were higher in younger subjects and IAA were more prevalent in patients with the HLA-DR4 allele. No relationship was observed between humoral and cellular responses to insulin. No association was found between the INS VNTR-IDDM2-susceptible allele and insulin autoimmunity. Increased T cell responses and IAA were found in patients with either the diabetes-susceptible or the diabetes-protective INS VNTR-IDDM2 locus genotypes, and increased T cell responses were also found in control subjects with either susceptible or protective INS VNTR-IDDM2 locus genotypes. This study confirms that primary T cell proliferative responses to insulin are low and detectable also in control subjects. The detection of T cell proliferation and autoantibodies to insulin in subjects with and without the protective INS VNTR-IDDM2 locus genotypes does not support the hypothesis of an allele-specific capacity for tolerance induction which could determine a susceptibility to develop autoimmunity against the insulin protein and subsequently diabetes.

Effects of hyperglycaemia on visual evoked potentials in insulin-dependent diabetic patients

Multimodality evoked potentials frequently reveal subclinical involvement of the central nervous system in patients with insulin-dependent diabetes mellitus. We devised this study to evaluate the possible effects of acute hyperglycaemia on visual evoked potential (VEP) parameters in type 1 diabetic patients. A hyperglycaemic clamp (250 mg/dl for 180 min) was performed in ten patients. Monocular pattern reversal VEPs (check size 15', contrast 50%) were recorded before, and every 30 min after the start of the clamp. Basal VEP latencies and amplitudes were normal bilaterally in nine patients. No significant changes in pattern reversal and flash VEP parameters were observed after the induction or during the clamp period. None of the neurophysiological parameters evaluated during the test was related to the duration of the disease, the basal VEP latency or amplitude or the presence of retinopathy. Our data suggest that the neurophysiological abnormalities detected in insulin-dependent diabetic patients are due to structural involvement of the central nervous pathways and not to functional damage induced by acute short-term hyperglycaemia.

Prednisone administration in recent onset type I diabetes

The aim of our study was to investigate the efficacy of prednisone to preserve pancreatic beta-cell function in patients with recent-onset Type I diabetes mellitus (IDDM). Twenty-five patients with IDDM, aged 24 +/- 6 years, entered the trial within 8 weeks of the onset of diabetes. They were allocated, according to a single blind randomized protocol, to one of the following treatments: (A) prednisone (15 mg/day), (B) indomethacin (100 mg/day), (C) placebo. All treatments lasted 8 months and all patients achieved satisfactory metabolic control with a multi-injection regimen (three injections/day) within a few weeks, and maintained it throughout the entire period of observation. Only minor side effects were observed in the prednisone-treated patients. A lower insulin requirement was observed in the prednisone group than in other patients at 12 months (0.33 +/- 0.11 vs 0.57 +/- 0.06 U/kg/day, P less than 0.05), 18 months (0.34 +/- 0.11 vs 0.64 +/- 0.06, P less than 0.05) and 24 months (0.38 +/- 0.10 vs 0.63 +/- 0.05, P less than 0.05). Endogenous insulin release, evaluated as urinary C-peptide, was higher in the prednisone group than in other patients at 3, 6, 9, 12, 18 and 24 months (P less than 0.05). ANOVA confirmed differences among the three groups. Our study indicates that prednisone administration, at low doses and for a long period of time, effectively restored endogenous insulin release in IDDM patients.

Effects of personality on metabolic control in IDDM patients

OBJECTIVE

The aim of this study was to evaluate the relationship between poor metabolic control and maladaptive personality traits (according to the Diagnostic and Statistical Manual of Mental Disorders, Third Edition-Revised) in an adult-onset insulin-dependent diabetes mellitus sample group (n = 77).

RESEARCH DESIGN AND METHODS

Metabolic control was evaluated through glycosylated hemoglobin (HbA1c). Personality traits were assessed with the Personality Diagnostic Questionnaire-Revised, a self-administered questionnaire. Residual pancreatic secretion (fasting serum C-peptide) was also evaluated.

RESULTS

Principal components analysis revealed three personality profiles: "withdrawn-suspicious" (P1), "dramatic-dependent" (P2), and "aggressive-irresponsible" (P3). Multiple linear regression analysis showed that C-peptide levels and P2 personality profiles were significant and independent predictors of HbA1c plasma levels: P2 predicted high HbA1c values and C-peptide predicted low HbA1c levels.

CONCLUSIONS

These data suggest that a P2 personality profile is a significant predictor of poor metabolic control.

HLA-antigens in Italian type 1 diabetic patients: role of DR3/DR4 antigens and breast feeding in the onset of the disease

HLA-A, B, C, DR and DQ typing was performed in 381 Italian insulin-dependent diabetic patients and in 905 normal Italian subjects. The diabetic patients had significantly higher frequencies of HLA-Cw7, B8, B18, DR3, DR4, DQw2 and DQw3 and significantly lower frequencies of HLA-B17, Bw51, DR2, DR7 and DRw11. The frequency of heterozygosity for HLA-DR3/DR4 was significantly higher in patients who developed the disease in the first 2 years of life and DR3+/DR4-, DQw2 and DQw3 alleles were higher in those aged less than 14 years at onset. The HLA-DR4 allele was associated with onset of diabetes in autumn and HLA-B18 with onset in Autumn-winter. Diabetic children who were breast fed had a later onset of insulin-dependent diabetes mellitus than those who were bottle fed but these differences were independent of HLA typing (11.8 +/- 0.72 years vs 9.23 +/- 0.42 years; mean +/- SEM). We conclude that: (1) in general, HLA distribution in Italian insulin-dependent diabetic patients reflects previous data reported in other European and North American populations; (2) HLA-DR3 and DR4 are strongly associated with insulin-dependent diabetes in Italy as well, and these alleles seem to predispose to an earlier onset of the disease; and (3) breast feeding may delay the onset of the disease.

T cell responses to type 1 diabetes related peptides sharing homologous regions

Glutamic acid decarboxylase (GAD) 65 is a major autoantigen in type 1 diabetes. Regions of homology exist between GAD65 (residues 250-273) and the Coxsackie P2-C protein (residues 28-50) and between GAD65 (residues 506-518) and proinsulin (residues 24-36), and each of these has been reported to be a diabetes-associated T cell target. The aim of this study was to determine whether the homologous regions are shared targets of T lymphocyte reactivity in individual patients with type 1 diabetes. T cell proliferation against the corresponding peptide pairs, GAD254-276 and Coxsackie P2-C32-54 and GAD506-518 and proinsulin24-36, were measured in peripheral blood mononuclear cells from 26 patients with newly diagnosed type 1 diabetes and 24 control subjects. Responses with stimulation indices higher than 3 were found against each of the antigens tested in both patients and control subjects, and no differences were observed between groups. A strong positive correlation was found between responses to the corresponding peptide pairs GAD254-276 and Coxsackie P2-C32-54 (r=0.77, P<0.0001), and between responses to the corresponding peptide pairs GAD506-518 and proinsulin24-36 (r=0.66, P<0.0001). However, a similar correlation was also observed between responses to the noncorresponding pairs Coxsackie P2-C32-54 and proinsulin24-36 (r=0.82, P<0.0001), Coxsackie P2-C32-54 and GAD506-518 (r=0.82, P<0.0001), and GAD254-276 and proinsulin24-36 (r=0.83, P<0.0001). Strikingly, increased responses to peptides were found almost exclusively in subjects with high stimulation indices against the recall antigen tetanus toxoid, further suggesting that peripheral blood T cell responses are related to a general subject hyperreactivity. These data suggest that proliferative T cell responses to peptides containing putative autoreactive epitopes of GAD65 and proinsulin are not specific for type 1 diabetes, that correlation between T cell reactivity to peptides is not restricted to those containing homologous regions, and that non-antigen-specific factors are important determinants of in vitro measurements of T cell reactivity.

Postabsorptive muscle protein metabolism in type 1 diabetic patients after pancreas transplantation

Insulin was shown to induce protein anabolism in vivo mainly by inhibiting proteolysis. Heterotopic pancreas transplantation in type 1 diabetes mellitus is characterized by peripheral hyperinsulinemia due to systemic rather than portal insulin delivery. Therefore, we studied the postabsorptive muscle protein metabolism in type 1 diabetic patients with or without pancreas transplantation. The forearm balance technique was performed in 9 type 1 diabetic patients on exogenous insulin treatment, in 4 type 1 diabetic patients following successful pancreas transplantation and in 6 healthy volunteers. Labelled leucine and phenylalanine were infused to quantify whole-body and muscle protein synthesis, respectively. In the postabsorptive state, whole-body protein synthesis (leucine kinetics) was similar in pancreas-transplanted patients and controls. In contrast, muscle protein synthesis tended to be less negative in pancreas-transplanted patients with respect to type 1 diabetic patients and healthy volunteers. The present data suggest that recipients with peripheral insulin delivery and chronic hyperinsulinemia are characterized by a preferential stimulation of protein synthesis in muscle rather than in the splanchnic district. When insulin was infused acutely, while maintaining euglycemia, the whole-body and muscle protein synthesis rates were approximately halved in type 1 diabetic patients with and without pancreas transplantation. We conclude that pancreas transplantation is able to normalize basal and insulin-stimulated protein metabolism. Chronic hyperinsulinemia counteract steroid-induced protein degradation by means of a mild, but persistent stimulation of muscle protein synthesis.

Personality traits and metabolic control: a study in insulin-dependent diabetes mellitus patients

BACKGROUND

In the present study the authors evaluated the relationship between personality traits (according to DSM-III-R) and poor metabolic control in an adult onset insulin-dependent diabetes mellitus sample (n = 77).

METHODS

Personality traits were assessed with the Personality Diagnostic Questionnaire--Revised. Metabolic control was evaluated through glycosilated hemoglobin (HbA1c): poor metabolic control was defined as HbA1c > or = 9% (normal values < 6.0%).

RESULTS

Principal Component Analysis revealed three personality profiles: 'Cluster A/C Mixed', 'Cluster B Dependent' and 'Cluster B Aggressive'. Oneway ANCOVA, using sex as covariate, revealed a significant association (p = 0.01) only between poor metabolic control and Cluster B Dependent profile. No correlation was found between HbA1c and the other profiles.

CONCLUSION

These data suggest that a specific personality profile is associated with poor metabolic control.

Worse impact of second wave COVID-19 pandemic in adults but not in children with inflammatory bowel disease: an Italian single tertiary center experience

OBJECTIVE

From September 2020, a second wave of COVID-19 pandemic started. We aimed at exploring the impact of SARS-CoV-2 infection in IBD patients during the two waves.

PATIENTS AND METHODS

All IBD patients with a confirmed diagnosis of SARS-CoV-2 infection were enrolled. They were sorted into two groups (those infected before September 2020, and those from September 2020 to January 2021) and compared by demographic and clinical data.

RESULTS

Twenty-five patients (out of about 600 with a follow-up visit) were infected with SARS-CoV-2 (4.1%). Sixteen were male and the mean age was 46.5 ± 14.3 years (range 24-74). Six were smokers and 11 had comorbidities; 2 were on steroids and 17 on immunosuppressants or biologics. Three patients (12%) needed hospitalization and other three patients were treated with azithromycin, steroids and LMWH, all of them during the second wave. No patient died or developed any sequelae. Two subjects were infected during the first wave (0.3 vs. 3.83, p<0.0001). Non-significant differences were found between the two groups.

CONCLUSIONS

A higher number of IBD patients were infected during the second wave. No patient developed a severe form of pneumonia, even those treated with immunosuppressants or biologics. No risk factor for hospitalization was found.

HLA-DQ screening for risk assessment of insulin dependent diabetes in northern Italy

Genetic markers may be used to improve the prediction of insulin-dependent diabetes mellitus (type 1) in individuals with islet autoantibodies. In order to develop a risk assessment strategy for the Lombardy region of northern Italy based on genetic and immunological markers, we analyzed HLA DQA1 and DQB1 alleles in 60 type 1 probands and their first-degree relatives and 65 unrelated control subjects from the same area using polymerase chain reaction (PCR) and oligonucleotide probes. The major risk haplotypes were DQA1 *0501-DQB1*0201 (39.1% of diabetic vs. 8.9% of non-diabetic haplotypes) and DQA1 *0301-DQB1*0302(20% of diabetic vs 7.1% of non-diabetic haplotypes). Stratified analysis showed DQA1*0102-DQB1*0502 also to be associated with type 1 susceptibility when found together with DQA1*0501-DQB1*0201 or DQA1*0301-DQB1*0302. One type 1 patient had the type 1-protective DQA1*0102-DQB1*0602 haplotype. Overall, 88% of patients and 20% of unrelated control subjects had either DQA1*0501-DQB1*0201 or DQA1*0301-DQB1*0302 in the absence of DQA1*0102-DQB1*0602. These data suggest that typing for markers identifying these three haplotypes in the Lombardy population will achieve a sensitivity of almost 90% and exclude 80% of children from subsequent islet autoantibody testing.

Cellular and humoral immunity against cow's milk proteins in type 1 diabetes

Cow's milk beta-casein has been proposed as a candidate trigger of autoimmunity associated with type 1 diabetes. In this study, cellular and humoral immunity against beta-casein was compared to that against other major cow's milk proteins in patients with recent onset type 1 diabetes and control subjects. T cell responses were found against alpha-casein, beta-casein, beta-lactoglobulin and bovine serum albumin in both patients with type 1 diabetes (stimulation index: 0.2-22.8, n=23) and control subjects (stimulation index: 0.1-18.2, n=22), with no significant differences between groups. Twelve (52%) patients and nine (41%) control subjects had stimulation indices >3 to at least one protein, including 9 (39%) patients and 4 (18%) control subjects against beta-casein, all but one of these also having elevated responses to alpha-casein. The highest responses (stimulation index >9) were against alpha- and beta-casein in some patients and control subjects who had the HLA DR3 allele. Antibody levels against alpha-casein, beta-casein and beta-lactoglobulin were low in both patients (n=59) and control subjects (n=52). Nevertheless, significantly higher IgG binding to both alpha-casein in ELISA (P=0.02) and beta-casein using ELISA (P=0.02) and RIA (P=0.04) was observed in patients aged <15 years compared to control subjects of similar age. No relationship was found between cellular and humoral immunity against individual antigens. These data show that immune responses to cow's milk are not limited to patients with diabetes and not solely against beta-casein.

13C-octanoic acid breath test for measuring gastric emptying of solids

Non invasive evaluation of gastric emptying is generally performed by scintigraphy which is, however, difficult to perform and not suitable to children and childbearing women. A new method based on stable isotope breath testing analysis has been introduced in clinical practice: the 13C-octanoic acid breath test. In this paper, an overview of the current knowledge on this technique is given with special emphasis on the principle of the test, the mathematics used to analyse the results, and the physiological, pathological, and pharmacological aspects of gastric emptying studied with this new method.

Inhibition of SARS-CoV-2 infection by Porphyromonas gingivalis and the oral microbiome

The COVID-19 pandemic persists despite the availability of vaccines, and it is therefore crucial to develop new therapeutic and preventive approaches. In this study, we investigated the potential role of the oral microbiome in SARS-CoV-2 infection. Using an in vitro SARS-CoV-2 pseudovirus infection assay, we found a potent inhibitory effect exerted by Porphyromonas gingivalis on SARS-CoV-2 infection mediated by known P. gingivalis compounds such as phosphoglycerol dihydroceramide (PGDHC) and gingipains as well as by unknown bacterial factors. We found that the gingipain-mediated inhibition of infection is likely due to cytotoxicity, while PGDHC inhibited virus infection by an unknown mechanism. Unidentified factors present in P. gingivalis supernatant inhibited SARS-CoV-2 likely via the fusion step of the virus life cycle. We addressed the role of other oral bacteria and found certain periodontal pathogens capable of inhibiting SARS-CoV-2 pseudovirus infection by inducing cytotoxicity on target cells. In the human oral cavity, we observed the modulatory activity of oral microbial communities varied among individuals in that some saliva-based cultures were capable of inhibiting while others were enhancing infection. These findings contribute to our understanding of the complex relationship between the oral microbiome and viral infections, offering potential avenues for innovative therapeutic strategies in combating COVID-19.

Inhibition of SARS-CoV-2 infection by Porphyromonas gingivalis and the oral microbiome

The COVID-19 pandemic persists despite the availability of vaccines, and it is, therefore, crucial to develop new therapeutic and preventive approaches. In this study, we investigated the potential role of oral microbiome in SARS-CoV-2 infection. Using an in vitro SARS-CoV-2 pseudovirus infection assay, we found a potent inhibitory effect exerted by Porphyromonas gingivalis on SARS-CoV-2 infection mediated by known P. gingivalis compounds such as phosphoglycerol dihydroceramide (PGDHC) and gingipains as well as by unknown bacterial factors. We found that the gingipain-mediated inhibition of infection is likely due to cytotoxicity, whereas PGDHC inhibited virus infection by an unknown mechanism. Unidentified factors present in P. gingivalis supernatant inhibited SARS-CoV-2 likely via the fusion step of the virus life cycle. We addressed the role of other oral bacteria and found certain periodontal pathogens capable of inhibiting SARS-CoV-2 pseudovirus infection by inducing cytotoxicity on target cells. In the human oral cavity, we observed that the modulatory activity of oral microbial communities varied among individuals, in that some saliva-based cultures were capable of inhibiting while others were enhancing infection. These findings contribute to our understanding of the complex relationship between the oral microbiome and viral infections, offering potential avenues for innovative therapeutic strategies in combating COVID-19.

IMPORTANCE

The oral microbiome is important in health and disease, and in this study, we addressed the potential role of the oral microbiome in COVID-19 infection. Our in vitro studies suggest that certain bacteria of the oral microbiome such as P. gingivalis produce compounds that could potentially inhibit SARS-CoV-2 infection. These findings elucidating the interactions between the oral microbiome and SARS-CoV-2 infection will be important in our understanding of COVID-19 pathogenesis and the development of innovative therapeutic and preventive strategies against COVID-19 infection.

Metabolic, genetic and immunological features of relatives of type 1 diabetes patients with elevated insulin resistance

PURPOSE

Insulin resistance plays a pivotal role in the preclinical stages of type 1 diabetes (T1D).

OBJECTIVE

This study aims at exploring the genetic, metabolic, and immunological features associated with insulin resistance among individuals at risk of developing T1D.

METHODS

We retrospectively selected relatives of individuals with T1D from participants in the TrialNet Pathway to Prevention study. They were categorized into two groups: high-H (n = 27) and low-H (n = 30), based on the upper and lower quartiles of insulin resistance assessed using the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR). Genetic predisposition was determined using the T1D Genetic Risk Score 1 (GRS1). Additionally, glucose control was evaluated through an oral glucose tolerance test and levels of metabolic hormones and inflammatory cytokines were measured in the serum. Flow cytometry analysis was employed to assess frequency and phenotype of islet-specific CD8 T cells.

RESULTS

While GRS1 were similar between the low-H and high-H groups, high-H individuals displayed a distinct metabolic profile, characterized by compensatory hyperinsulinemia, even while maintaining normoglycemia. Circulating cytokine levels were similar between the two groups. However, immune profiling revealed a central memory and activated profile of GAD65-specific CD8 T cells, along with an increased frequency of insulin-specific CD8 T cells in high-H individuals. The enrichment in insulin-specific CD8 T cells was independent of body mass.

CONCLUSION

These findings highlight the intricate interplay between insulin resistance, genetic factors, and immune activation in the context of T1D susceptibility, indicating potential connections between insulin resistance and immune responses specific to islet cells.