Serum and CSF soluble CD26 and CD30 concentrations in healthy pediatric surgical outpatients

Low levels of soluble DPP4 among Saudis may have constituted a risk factor for MERS endemicity

Most of the cases of Middle East respiratory syndrome coronavirus (MERS-CoV) were reported in Saudi Arabia. Dipeptidyl peptidase-4 (DPP4) was identified as the receptor for the virus. The level of soluble DPP4 (sDPP4) was found to be reduced in MERS-CoV infected patients while high levels of sDPP4 were suggested to be protective against MERS-CoV in animal models. We investigated whether the Saudi population has lower levels of sDPP4 which makes them more susceptible to MERS-CoV infection and, therefore, could explain the larger number of cases from the country. Blood samples were collected from 219 Saudi blood donors and 200 blood donors from other ethnic groups. The plasma level of sDPP4 was measured by ELISA and the following SNPs in the DPP4 gene; rs35128070, rs1861978, rs79700168, and rs17574, were genotyped by TaqMan SNP genotyping assay. The average level of plasma sDDP4 was significantly lower in Saudis than other Arabs and non-Arabs (P value 0.0003 and 0.012, respectively). The genotypes AG of rs35128070 and GT of rs1861978 were significantly associated with lower sDPP4 among Saudis (P value 0.002 for each). While both genotypes AA and AG of rs79700168 and rs17574 were associated with significantly lower average sDPP4 level in Saudis compared to other ethnic groups (P value 0.031 and 0.032, and 0.027 and 0.014, respectively). Herein, we report that the Saudi population has lower levels of plasma sDPP4 than other ethnic groups, which is associated with genetic variants in the DPP4 gene. This may have contributed to increase the susceptibility of the Saudi population to MERS-CoV infection and could be a factor in the long-lasting persistence of the virus in the country.

CD26 and Asthma: a Comprehensive Review

Asthma is a heterogeneous and chronic inflammatory family of disorders of the airways with increasing prevalence that results in recurrent and reversible bronchial obstruction and expiratory airflow limitation. These diseases arise from the interaction between environmental and genetic factors, which collaborate to cause increased susceptibility and severity. Many asthma susceptibility genes are linked to the immune system or encode enzymes like metalloproteases (e.g., ADAM-33) or serine proteases. The S9 family of serine proteases (prolyl oligopeptidases) is capable to process peptide bonds adjacent to proline, a kind of cleavage-resistant peptide bonds present in many growth factors, chemokines or cytokines that are important for asthma. Curiously, two serine proteases within the S9 family encoded by genes located on chromosome 2 appear to have a role in asthma: CD26/dipeptidyl peptidase 4 (DPP4) and DPP10. The aim of this review is to summarize the current knowledge about CD26 and to provide a structured overview of the numerous functions and implications that this versatile enzyme could have in this disease, especially after the detection of some secondary effects (e.g., viral nasopharyngitis) in type II diabetes mellitus patients (a subset with a certain risk of developing obesity-related asthma) upon CD26 inhibitory therapy.

High DPP-4 Concentrations in Adolescents Are Associated With Low Intact GLP-1

CONTEXT

Dipeptidyl peptidase 4 (DPP-4) metabolizes glucagon-like peptide-1 (GLP-1), and increased DPP4 levels are associated with obesity and visceral adiposity in adults.

OBJECTIVE

Investigating DPP-4 levels in adolescents and their association with (1) circulating intact GLP-1 levels and glucose tolerance; (2) body mass index (BMI); and (3) visceral, subcutaneous, and liver fat compartments.

DESIGN

Cross-sectional study, July 2012 to April 2015.

SETTING

Pediatric obesity clinic, Uppsala University Hospital.

PATIENTS AND PARTICIPANTS

Children and adolescents with obesity (n = 59) and lean controls (n = 21) aged 8 to 18 years.

MAIN OUTCOME MEASURES

BMI SD score, fasting plasma concentrations of DPP-4, total and intact GLP-1, fasting and oral glucose tolerance test (OGTT) concentrations of glucose, and visceral adipose tissue (VAT) and subcutaneous adipose tissue volumes and liver fat fraction.

RESULTS

Plasma DPP-4 levels decreased with age in both obese (41 ng/mL per year) and lean subjects (48 ng/mL per year). Plasma DPP-4 levels were higher in males in both the obesity and lean groups. With adjustments for age and sex, plasma DPP-4 level was negatively associated with intact GLP-1 at fasting (β = -12.3; 95% CI: -22.9, -1.8) and during OGTT (β = -12.1; 95% CI: -22.5, -1.7). No associations were found between DPP-4 and plasma glucose levels measured at fasting or after a 2-hour OGTT. Plasma DPP-4 level was 19% higher in obese subjects. Among adipose tissue compartments, the strongest association was with VAT (β = 0.05; 95% CI: -0.02, 0.12).

CONCLUSIONS

In adolescents, high plasma DPP-4 concentrations were associated with low proportions of intact GLP-1, high BMI, young age, and male sex. The observed associations are compatible with increased metabolism of GLP-1 in childhood obesity.

Cut to the chase: a review of CD26/dipeptidyl peptidase-4's (DPP4) entanglement in the immune system

CD26/DPP4 (dipeptidyl peptidase 4/DP4/DPPIV) is a surface T cell activation antigen and has been shown to have DPP4 enzymatic activity, cleaving-off amino-terminal dipeptides with either L-proline or L-alanine at the penultimate position. It plays a major role in glucose metabolism by N-terminal truncation and inactivation of the incretins glucagon-like peptide-1 (GLP) and gastric inhibitory protein (GIP). In 2006, DPP4 inhibitors have been introduced to clinics and have been demonstrated to efficiently enhance the endogenous insulin secretion via prolongation of the half-life of GLP-1 and GIP in patients. However, a large number of studies demonstrate clearly that CD26/DPP4 also plays an integral role in the immune system, particularly in T cell activation. Therefore, inhibition of DPP4 might represent a double-edged sword. Apart from the metabolic benefit, the associated immunological effects of long term DPP4 inhibition on regulatory processes such as T cell homeostasis, maturation and activation are not understood fully at this stage. The current data point to an important role for CD26/DPP4 in maintaining lymphocyte composition and function, T cell activation and co-stimulation, memory T cell generation and thymic emigration patterns during immune-senescence. In rodents, critical immune changes occur at baseline levels as well as after in-vitro and in-vivo challenge. In patients receiving DPP4 inhibitors, evidence of immunological side effects also became apparent. The scope of this review is to recapitulate the role of CD26/DPP4 in the immune system regarding its pharmacological inhibition and T cell-dependent immune regulation.