Cortistatin regulates glucose-induced electrical activity and insulin secretion in mouse pancreatic beta-cells

Serum Cortistatin Level in Type 2 Diabetes Mellitus and Its Relationship with Nonalcoholic Fatty Liver Disease

Purpose

To evaluate serum cortistatin (CST) levels in type 2 diabetes mellitus (T2DM) patients with or without non-alcoholic fatty liver disease (NAFLD) and to examine the relationship between CST and NAFLD.

Methods

A total of 90 T2DM patients, which included 56 NAFLD patients (referred to as DM+NAFLD group) and 34 patients without NAFLD (DM-only group), and 83 non-diabetes individuals that included 39 NAFLD patients (NAFLD-only group) and 44 without NAFLD that acted as the normal-control group (NC group). The differences in the serum CST levels between the groups were compared, and the correlations between CST and other variables were calculated by applying both correlational analysis and multiple linear regression analysis.

Results

The mean serum CST levels were significantly lower in the DM+NAFLD and DM groups than in the NC group (P < 0.05). In addition, the CST levels were lower in the DM group relative to that in the NAFLD group (P < 0.05). However, no statistical difference was noted in the serum CST between diabetic patients with and without NAFLD (P > 0.05). Similarly, in the non-diabetic group, the serum CST level was not significantly different between individuals with and without NAFLD (P > 0.05). Furthermore, the serum CST levels were negatively associated with the levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), fasting plasma glucose (FPG), homeostasis model assessment-insulin resistance (HOMA-IR), and insulin cell function index (HOMA-β). Conversely, the serum CST levels were positively associated with high-density lipoprotein cholesterol (HDL-C). The data obtained through multiple linear regression implied that LDL-C and HOMA-β, but not HOMA-IR, were closely related to serum CST levels.

Conclusion

T2DM was related to decreased serum CST. However, serum CST was correlated with HOMA-β in T2DM patients, while HOMA-IR was not. There was no correlation between CST and NAFLD.

δ-Cells: The Neighborhood Watch in the Islet Community

Somatostatin-secreting δ-cells have aroused great attention due to their powerful roles in coordination of islet insulin and glucagon secretion and maintenance of glucose homeostasis. δ-cells exhibit neuron-like morphology with projections which enable pan-islet somatostatin paracrine regulation despite their scarcity in the islets. The expression of a range of hormone and neurotransmitter receptors allows δ-cells to integrate paracrine, endocrine, neural and nutritional inputs, and provide rapid and precise feedback modulations on glucagon and insulin secretion from α- and β-cells, respectively. Interestingly, the paracrine tone of δ-cells can be effectively modified in response to factors released by neighboring cells in this interactive communication, such as insulin, urocortin 3 and γ-aminobutyric acid from β-cells, glucagon, glutamate and glucagon-like peptide-1 from α-cells. In the setting of diabetes, defects in δ-cell function lead to suboptimal insulin and glucagon outputs and lift the glycemic set-point. The interaction of δ-cells and non-δ-cells also becomes defective in diabetes, with reduces paracrine feedback to β-cells to exacerbate hyperglycemia or enhanced inhibition of α-cells, disabling counter-regulation, to cause hypoglycemia. Thus, it is possible to restore/optimize islet function in diabetes targeting somatostatin signaling, which could open novel avenues for the development of effective diabetic treatments.

Decreased maternal serum cortistatin levels in pregnancies with gestational diabetes mellitus

Objective: To investigate serum cortistatin levels in women with gestational diabetes mellitus (GDM) and women with uncomplicated pregnancies.Material and methods: This case-control study consisted of 40 pregnancies with GDM and 41 healthy singleton pregnancies matched for maternal and gestational age. The maternal serum levels of cortistatin were measured with enzyme-linked immunosorbent assay and compared between groups.Results: Cortistatin levels were significantly lower in GDM group (48.85 ± 20.18 versus 65.84 ± 33.98 ng/ml, p = .008). There was a statistically significant difference in cortistatin levels between different treatment modalities and control group (χ²(2) = 8.828, p = .012). Pairwise comparisons showed that diet group had significantly lower CST levels than control group (p = .012). Serum cortistatin levels were negatively correlated with serum insulin and glucose levels and HOMA-IR (r = -0.358, p = .001; r = -0.303, p = .006; r = -0.444, p < .001, respectively).Conclusion: Cortistatin levels were significantly lower in GDM pregnancies and related to serum insulin and glucose levels and HOMA-IR in pregnancy. This may help to better clarify the mechanism of GDM pathogenesis.