Enhanced Pulsatile Growth Hormone Secretion and Altered Metabolic Hormones by in Vivo Hexarelin Treatment in Streptozotocin-Induced Diabetic Rats

Beta-Cell Tipe1 Orchestrates Insulin Secretion and Cell Proliferation by Promoting Gαs/cAMP Signaling via USP5

Inadequate β-cell mass and insulin secretion are essential for the development of type 2 diabetes (T2D). TNF-α-induced protein 8-like 1 (Tipe1) plays a crucial role in multiple diseases, however, a specific role in T2D pathogenesis remains largely unexplored. Herein, Tipe1 as a key regulator in T2D, contributing to the maintenance of β cell homeostasis is identified. The results show that the β-cell-specific knockout of Tipe1 (termed Ins2-Tipe1BKO) aggravated diabetic phenotypes in db/db mice or in mice with high-fat diet-induced diabetes. Notably, Tipe1 improves β cell mass and function, a process that depends on Gαs, the α subunit of the G-stimulating protein. Mechanistically, Tipe1 inhibited the K48-linked ubiquitination degradation of Gαs by recruiting the deubiquitinase USP5. Consequently, Gαs or cAMP agonists almost completely restored the dysfunction of β cells observed in Ins2-Tipe1BKO mice. The findings characterize Tipe1 as a regulator of β cell function through the Gαs/cAMP pathway, suggesting that Tipe1 may emerge as a novel target for T2D intervention.

Chitosan-Encapsulated Nano-selenium Targeting TCF7L2, PPARγ, and CAPN10 Genes in Diabetic Rats

This study investigates the antidiabetic and antioxidant potential of chitosan-encapsulated selenium nanoparticles in streptozotocin-induced diabetic model. Glibenclamide was used as a reference antidiabetic drug. Forty-eight adult male Wistar rats were used along the study and divided equally into 6 groups of (I) normal control, (II) chitosan-encapsulated selenium nanoparticles (CTS-SeNPs), (III) glibenclamide, (IV) streptozotocin (STZ), (V) STZ + CTS-SeNPs, and (VI) STZ + Glib. The animals were sacrificed on the 35th day of the experiment. Serum glucose, insulin, IGF-1, ALT, AST, CK-MB, oxidative stress, lipid profile, and inflammatory parameters were subsequently assessed. Also, the expression level of TCF7L2, CAPN10, and PPAR-γ genes were evaluated using qPCR. In addition, histopathological studies on pancreatic tissue were carried out. The results revealed that STZ induced both diabetes and oxidative stress in normal rats, manifested by the significant changes in the studied parameters and in the physical structure of pancreatic tissue. Oral administration of CTS-SeNPs or Glib results in a significant amelioration of the levels of serum fasting blood glucose, insulin, IGF-1, AST, ATL, and CK-MB as compared with STZ-induced diabetic rats. CTS-SeNPs and Glib diminished the level of lipid peroxidation, increased total antioxidant capacity level, as well as possessed strong inhibition against serum α-amylase and α-glucosidase activities. Diabetic animals received CTS-SeNPs, or Glib demonstrated a significant (p < 0.05) decrease in the expression level of TCF7L2 and CAPN10 genes with a significant increase in the expression level of PPAR-γ gene, compared to STZ group. The above findings clarify the promising antidiabetic and antioxidant effect of CTS-SeNPs, recommending its inclusion in the currently used protocols for the treatment of diabetes and in the prevention of its related complications.

Podocyte derived TNF-α mediates monocyte differentiation and contributes to glomerular injury

Diabetes shortens the life expectancy by more than a decade, and the excess mortality in diabetes is correlated with the incidence of kidney disease. Diabetic kidney disease (DKD) is the leading cause of end-stage kidney disease. Macrophage accumulation predicts the severity of kidney injury in human biopsies and experimental models of DKD. However, the mechanism underlying macrophage recruitment in diabetes glomeruli is unclear. Elevated plasma growth hormone (GH) levels in type I diabetes and acromegalic individuals impaired glomerular biology. In this study, we examined whether GH-stimulated podocytes contribute to macrophage accumulation. RNA-seq analysis revealed elevated TNF-α signaling in GH-treated human podocytes. Conditioned media from GH-treated podocytes (GH-CM) induced differentiation of monocytes to macrophages. On the other hand, neutralization of GH-CM with the TNF-α antibody diminished GH-CM's action on monocytes. The treatment of mice with GH resulted in increased macrophage recruitment, podocyte injury, and proteinuria. Furthermore, we noticed the activation of TNF-α signaling, macrophage accumulation, and fibrosis in DKD patients' kidney biopsies. Our findings suggest that podocytes could secrete TNF-α and contribute to macrophage migration, resulting in DKD-related renal inflammation. Inhibition of either GH action or TNF-α expression in podocytes could be a novel therapeutic approach for DKD treatment.

Rhythmic growth hormone secretion in physiological and pathological conditions: Lessons from rodent studies

Evolutionally conserved in all mammalians, the release of GH occurs in a rhythmic pattern, characterized by several dominant surges (pulsatile GH) with tonic low inter-pulse levels (tonic GH). Such pulsatile secretion pattern is essential for many physiological actions of GH on different tissues with defined gender dimorphism. Rhythmic release of pulsatile GH is tightly controlled by hypothalamic neurons as well as peripheral metabolic factors. Changes of GH pattern occur within a range of sophisticated physiological and pathological settings and significantly contribute to growth, ageing, survival and disease predispositions. Precise analysis of GH secretion pattern is vitally important for a comprehensive understanding of the function of GH and the components that regulate GH secretion pattern.