Zonulin levels in complicated pregnancy: a systematic review and meta-analysis

Does Second Trimester Maternal Serum Zonulin Level Predict Gestational Diabetes Mellitus?

Zonulin, a protein that regulates intestinal permeability, has attracted attention as a potential biomarker for GDM. Therefore, this study aims to investigate whether there are differences in zonulin levels between the GDM group and control groups, especially between those receiving different treatments (diet and insulin). Based on this idea, we included 90 patients with a gestational age between 24 and 28 weeks in our study. While GDM was not detected in 33 of these patients, as a result of OGTT, 57 patients were diagnosed with GDM and these patients were followed throughout their pregnancy. Gestational diabetes was diagnosed by an OGTT performed between 24 and 28 weeks of gestation according to American Diabetes Association (ADA) standards. During follow-up, GDM patients were divided into two groups according to whether they required insulin treatment. Plasma zonulin levels were determined using enzyme-linked immunosorbent assay (ELISA) techniques. The GDM group had significantly higher plasma zonulin levels than the control group (p < 0.005). According to our research, zonulin may be a non-invasive biomarker involved in the etiology of GDM. Large-scale research on this topic is still needed.

Changes in Oxidative Stress and Intestinal Permeability during Pregnancy in Women with Gestational Diabetes Mellitus Treated with Metformin or Insulin and Healthy Controls: A Randomized Controlled Trial

Both oxidative stress and intestinal permeability are increased in hyperglycemic situations and have been shown to be reduced by metformin in type 2 diabetes mellitus (T2DM) patients. The aim of this study was to elucidate the effect of metformin on oxidative stress and intestinal permeability in women with gestational diabetes mellitus (GDM) treated with metformin compared to those treated with insulin and healthy controls. A total of 120 women were included from August 2016 to February 2022: 41 received metformin (MET group), 38 received insulin (INS group), and 41 were healthy controls. Baseline and antenatal visits were carried out at 25.4 ± 4.8 and 36.1 ± 0.8 weeks of pregnancy, respectively. Advanced oxidation protein products (AOPPs), total antioxidant capacity (TAC), and zonulin levels were measured at every visit. Zonulin levels from baseline to prepartum visit increased significantly in both healthy controls (0.6 ± 0.9 to 1.2 ± 1.7 ng/mL, p = 0.004) and the INS group (0.4 ± 0.3 to 0.6 ± 0.5 ng/mL, p = 0.034) but did not significantly change in the MET group (0.4 ± 0.4 to 0.5 ± 0.4 ng/mL, p = 0.202). However, TAC and AOPP levels significantly increased in women with GDM, both in the INS and MET groups but not in the healthy controls. In conclusion, in our population, metformin has been shown to avoid an increase in intestinal permeability but failed to avoid an increase in oxidative stress related to hyperglycemia.

Zonulin as a Potential Therapeutic Target in Microbiota-Gut-Brain Axis Disorders: Encouraging Results and Emerging Questions

The relationship between dysbiosis and central nervous diseases has been proved in the last 10 years. Microbial alterations cause increased intestinal permeability, and the penetration of bacterial fragment and toxins induces local and systemic inflammatory processes, affecting distant organs, including the brain. Therefore, the integrity of the intestinal epithelial barrier plays a central role in the microbiota-gut-brain axis. In this review, we discuss recent findings on zonulin, an important tight junction regulator of intestinal epithelial cells, which is assumed to play a key role in maintaining of the blood-brain barrier function. In addition to focusing on the effect of microbiome on intestinal zonulin release, we also summarize potential pharmaceutical approaches to modulate zonulin-associated pathways with larazotide acetate and other zonulin receptor agonists or antagonists. The present review also addresses the emerging issues, including the use of misleading nomenclature or the unsolved questions about the exact protein sequence of zonulin.