Hypoglycemic Potential of Carica papaya in Liver Is Mediated through IRS-2/PI3K/SREBP-1c/GLUT2 Signaling in High-Fat-Diet-Induced Type-2 Diabetic Male Rats

Regardless of socioeconomic or demographic background, the prevalence of type 2 diabetes mellitus, which affects more than half a billion people worldwide, has been steadily increasing over time. The health, emotional, sociological, and economic well-being of people would suffer if this number is not successfully handled. The liver is one of the key organs accountable for sustaining metabolic balance. Elevated levels of reactive oxygen species inhibit the recruitment and activation of IRS-1, IRS-2, and PI3K-Akt downstream signaling cascade. These signaling mechanisms reduce hepatic glucose absorption and glycogenesis while increasing hepatic glucose output and glycogenolysis. In our work, an analysis of the molecular mechanism of Carica papaya in mitigating hepatic insulin resistance in vivo and in silico was carried out. The gluconeogenic enzymes, glycolytic enzymes, hepatic glycogen tissue concentration, oxidative stress markers, enzymatic antioxidants, protein expression of IRS-2, PI3K, SREBP-1C, and GLUT-2 were evaluated in the liver tissues of high-fat-diet streptozotocin-induced type 2 diabetic rats using q-RT-PCR as well as immunohistochemistry and histopathology. Upon treatment, C. papaya restored the protein and gene expression in the liver. In the docking analysis, quercetin, kaempferol, caffeic acid, and p-coumaric acid present in the extract were found to have high binding affinities against IRS-2, PI3K, SREBP-1c, and GLUT-2, which may have contributed much to the antidiabetic property of C. papaya. Thus, C. papaya was capable of restoring the altered levels in the hepatic tissues of T2DM rats, reversing hepatic insulin resistance.

Stage-specific protein regulation during somatic embryo development of Carica papaya L. 'Golden'

Somatic embryogenesis is an important biotechnological technique for large-scale propagation of elite genotypes. Identifying stage-specific compounds associated with somatic embryo development can help elucidate the ontogenesis of Carica papaya L. somatic embryos and improve tissue culture protocols. To identify the stage-specific proteins that are present during the differentiation of C. papaya somatic embryos, proteomic analyses of embryos at the globular, heart, torpedo and cotyledonary developmental stages were performed. Mass spectrometry data have been deposited in the ProteomeXchange with the dataset identifier PXD021107. Comparative proteomic analyses revealed a total of 801 proteins, with 392 classified as differentially accumulated proteins in at least one of the developmental stages. The globular-staged presented a higher number of unique proteins (16), and 7 were isoforms of 60S ribosomal proteins, suggesting high translational activity at the beginning of somatic embryogenesis. Proteins related to mitochondrial metabolism accumulated to a high degree at the early developmental stages and then decreased with increasing development, and they contributed to cell homeostasis in early somatic embryos. A progressive increase in the accumulation of vicilin, late embryogenesis abundant proteins and chloroplastic proteins that lead to somatic embryo maturation was also observed. The differential accumulation of acetylornithine deacetylase and S-adenosylmethionine synthase 2 proteins was correlated with increases in putrescine and spermidine contents, which suggests that both polyamines should be tested to determine whether they increase the conversion rates of globular- to cotyledonary-staged somatic embryos. Taken together, the results showed that somatic embryo development in C. papaya is regulated by the differential accumulation of proteins, with ribosomal and mitochondrial proteins more abundant during the early somatic embryo stages and seed maturation proteins more abundant during the late stages.