Dipeptidyl peptidase-4 activity might be a link between tumour necrosis factor alpha and insulin resistance in type 1 diabetes

Combination of vitamin D and dipeptidyl peptidase-4 inhibitors (VIDPP-4i) as an immunomodulation therapy for autoimmune diabetes

Type 1 diabetes (T1D) and latent autoimmune diabetes in adults (LADA) represent the most common types of autoimmune diabetes and are characterized by different age of onset, degrees of immune-mediated destruction of pancreatic beta cells and rates of disease progression towards insulin dependence. Several immunotherapies aimed to counteract autoimmune responses against beta cells and preserve beta-cell function are currently being investigated, particularly in T1D. Preliminary findings suggest a potential role of combination therapy with vitamin D and dipeptidyl peptidase-4 (DPP-4) inhibitors (VIDPP-4i) in preserving beta-cell function in autoimmune diabetes. This manuscript aims to provide a comprehensive overview of the immunomodulatory properties of vitamin D and DPP-4 inhibitors, as well as the rationale for investigation of their combined use as an immunomodulation therapy for autoimmune diabetes.

THE ASSOCIATION OF SUBCLINICAL INSULIN RESISTANCE WITH THYROID AUTOIMMUNITY IN EUTHYROID INDIVIDUALS

Hashimoto thyroiditis is characterized by anti-thyroid peroxidase (anti-TPO) and anti-thyroglobulin (anti-Tg) antibodies that gradually lead to thyroid cell destruction. As hypothyroidism has been associated with insulin resistance (IR), we aimed to investigate whether IR is associated with thyroid antibody presence and whether the degree of IR correlates with their concentration in euthyroid individuals. A total of 164 non-diabetic, euthyroid individuals, average age 34 years, were included in the study, divided into two groups according to Hashimoto thyroiditis and underwent 5-hour oral glucose tolerance test. The degree of IR was evaluated by the Homeostatic Model Assessment of Insulin Resistance (HOMA-IR). The Hashimoto thyroiditis group had higher HOMA-IR (p=0.003) and lower glucose levels (p=0.04). HOMA-IR correlated positively with anti-TPO (p<0.001). Linear logistic regression revealed that anti-TPO concentration increased by 18.13 (p=0.001) with each HOMA-IR unit. IR might trigger thyroid antibody production and Hashimoto thyroiditis development, which needs to be evaluated in further larger scale follow up studies.

Role of Incretin Axis in Inflammatory Bowel Disease

The inflammatory bowel diseases (IBDs), including Crohn's disease (CD) and ulcerative colitis (UC), are chronic inflammatory conditions of the gastrointestinal tract and involve a complicated reciprocity of environmental, genetic, and immunologic factors. Despite substantial advances in the foundational understanding of the immunological pathogenesis of IBD, the detailed mechanism of the pathological progression in IBD remains unknown. In addition to Th1/Th2 cells, whose role in IBD has been previously well defined, recent evidence indicates that Th17 cells and Tregs also play a crucial role in the development of IBD. Diets which contain excess sugars, salt, and fat may also be important actors in the pathogenesis of IBD, which may be the cause of high IBD incidence in western developed and industrialized countries. Up until now, the reason for the variance in prevalence of IBD between developed and developing countries has been unknown. This is partly due to the increasing popularity of western diets in developing countries, which makes the data harder to interpret. The enterocrinins glucagon-like peptides (GLPs), including GLP-1 and GLP-2, exhibit notable benefits on lipid metabolism, atherosclerosis formation, plasma glucose levels, and maintenance of gastric mucosa integrity. In addition to the regulation of nutrient metabolism, the emerging role of GLPs and their degrading enzyme dipeptidyl peptidase-4 (DPP-4) in gastrointestinal diseases has gained increasing attention. Therefore, here we review the function of the DPP-4/GLP axis in IBD.

Persons with latent autoimmune diabetes in adults express higher dipeptidyl peptidase-4 activity compared to persons with type 2 and type 1 diabetes

AIMS

We aimed to determine serum dipeptidyl peptidase-4 (DPP-4) activity in a group of persons with latent autoimmune diabetes in adults (LADA) and to compare it with persons with type 1, type 2 diabetes and healthy controls.

METHODS

DPP-4 activity measurement was performed in 67 persons (21 with type 1, 26 type 2 and 19 with LADA) and 13 healthy age and gender matched controls.

RESULTS

Persons with LADA showed highest DPP-4 activity among the study groups (32.71±3.55 vs 25.37±2.84 vs 18.57±2.54 vs 18.57±2.61U/L p<0.001). Mean glutamic acid autoantibody in persons with LADA was 164.32±86.28IU/mL. It correlated with DPP-4 activity (r=0.484, p=0.013). Furthermore, DPP-4 activity correlated with waist circumference (r=0.279, p=0.034) and glycated haemoglobin A1c (r=0.483, p<0.001), as well as with LDL cholesterol (r=0.854, p<0.001) and total daily insulin dose (r=0.397, p=0.001). In the multinomial regression analysis DPP-4 activity remained associated with both LADA (prevalence ratio 1.058 (1.012-1.287), p=0.001) and type 1 diabetes (prevalence ratio 1.506 (1.335-1.765), p<0.001) while it did not show an association with type 2 diabetes (prevalence ratio 0.942 (0.713-1.988), p=0.564).

CONCLUSIONS

Persons with LADA express higher DPP-4 activity compared to persons with both type 1 and type 2 diabetes. The possible pathophysiological role of DPP-4 in the LADA pathogenesis needs to be further evaluated.