sirolimus and Metabolic-Diseases

The endoplasmic reticulum (ER) is the principal organelle responsible for correct protein folding, a step in protein synthesis that is critical for the functional conformation of proteins. ER stress is a primary feature of secretory cells and is involved in the pathogenesis of numerous human diseases, such as certain neurodegenerative and cardiometabolic disorders. The unfolded protein response (UPR) is a defense mechanism to attenuate ER stress and maintain the homeostasis of the organism. Two major degradation systems, including the proteasome and autophagy, are involved in this defense system. If ER stress overwhelms the capacity of the cell's defense mechanisms, apoptotic death may result. This review is focused on the various pharmacological modulators that can protect cells from damage induced by ER stress. The possible mechanisms for cytoprotection are also discussed.

Topics: Angiotensin Receptor Antagonists; Animals; Endoplasmic Reticulum Stress; Humans; Metabolic Diseases; Protease Inhibitors; Protein Kinase Inhibitors; Sirolimus; Unfolded Protein Response

The mammalian target of rapamycin (mTOR) signaling pathway is a master regulator of cell growth and metabolism. Deregulation of the mTOR pathway has been implicated in a number of human diseases such as cancer, diabetes, obesity, neurological diseases, and genetic disorders. Rapamycin, a specific inhibitor of mTOR, has been shown to be useful in the treatment of certain diseases. Here we discuss its mechanism of action and highlight recent findings regarding the effects and limitations of rapamycin monotherapy and the potential utility of combination therapy with rapamycin.

Topics: Aging; Drug Therapy, Combination; Humans; Longevity; Lung Diseases; Metabolic Diseases; Neoplasms; Nervous System Diseases; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Identifying regulatory mechanisms that influence inflammation in metabolic tissues is critical for developing novel metabolic disease treatments. Here, we investigated the role of microRNA-146a (miR-146a) during diet-induced obesity in mice. miR-146a is reduced in obese and type 2 diabetic patients and our results reveal that miR-146a-/- mice fed a high-fat diet (HFD) have exaggerated weight gain, increased adiposity, hepatosteatosis, and dysregulated blood glucose levels compared to wild-type controls. Pro-inflammatory genes and NF-κB activation increase in miR-146a-/- mice, indicating a role for this miRNA in regulating inflammatory pathways. RNA-sequencing of adipose tissue macrophages demonstrated a role for miR-146a in regulating both inflammation and cellular metabolism, including the mTOR pathway, during obesity. Further, we demonstrate that miR-146a regulates inflammation, cellular respiration and glycolysis in macrophages through a mechanism involving its direct target Traf6. Finally, we found that administration of rapamycin, an inhibitor of mTOR, was able to rescue the obesity phenotype in miR-146a-/- mice. Altogether, our study provides evidence that miR-146a represses inflammation and diet-induced obesity and regulates metabolic processes at the cellular and organismal levels, demonstrating how the combination of diet and miRNA genetics influences obesity and diabetic phenotypes.

Topics: Animals; Blood Glucose; Diet, High-Fat; Disease Models, Animal; Female; Gene Expression; Humans; Hyperglycemia; Inflammation; Insulin; Intra-Abdominal Fat; Macrophages; Male; Metabolic Diseases; Mice; Mice, Inbred C57BL; Mice, Knockout; MicroRNAs; NF-kappa B; Obesity; Proto-Oncogene Proteins c-akt; Sirolimus; TOR Serine-Threonine Kinases; Weight Gain

SHORT syndrome is a rare, recognizable syndrome resulting from heterozygous mutations in PIK3R1 encoding a regulatory subunit of phosphoinositide-3-kinase (PI3K). The condition is characterized by short stature, intrauterine growth restriction, lipoatrophy and a facial gestalt involving a triangular face, deep set eyes, low hanging columella and small chin. PIK3R1 mutations in SHORT syndrome result in reduced signaling through the PI3K-AKT-mTOR pathway. We performed whole exome sequencing for an individual with clinical features of SHORT syndrome but negative for PIK3R1 mutation and her parents. A rare de novo variant in PRKCE was identified. The gene encodes PKCε and, as such, the AKT-mTOR pathway function was assessed using phospho-specific antibodies with patient lymphoblasts and following ectopic expression of the mutant in HEK293 cells. Kinase analysis showed that the variant resulted in a partial loss-of-function. Whilst interaction with PDK1 and the mTORC2 complex component SIN1 was preserved in the mutant PKCε, it bound to SIN1 with a higher affinity than wild-type PKCε and the dynamics of mTORC2-dependent priming of mutant PKCε was altered. Further, mutant PKCε caused impaired mTORC2-dependent pAKT-S473 following rapamycin treatment. Reduced pFOXO1-S256 and pS6-S240/244 levels were also observed in the patient LCLs. To date, mutations in PIK3R1 causing impaired PI3K-dependent AKT activation are the only known cause of SHORT syndrome. We identify a SHORT syndrome child with a novel partial loss-of-function defect in PKCε. This variant causes impaired AKT activation via compromised mTORC2 complex function.

Topics: Adaptor Proteins, Signal Transducing; Adolescent; Dwarfism; Female; Growth Disorders; HEK293 Cells; Humans; Hypercalcemia; Mechanistic Target of Rapamycin Complex 2; Metabolic Diseases; Mutation; Nephrocalcinosis; Phosphatidylinositol 3-Kinases; Phosphorylation; Protein Kinase C-epsilon; Proto-Oncogene Proteins c-akt; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Apolipoprotein E ɛ4 allele is a common susceptibility gene for late-onset Alzheimer's disease. Brain vascular and metabolic deficits can occur in cognitively normal apolipoprotein E ɛ4 carriers decades before the onset of Alzheimer's disease. The goal of this study was to determine whether early intervention using rapamycin could restore neurovascular and neurometabolic functions, and thus impede pathological progression of Alzheimer's disease-like symptoms in pre-symptomatic Apolipoprotein E ɛ4 transgenic mice. Using in vivo, multimodal neuroimaging, we found that apolipoprotein E ɛ4 mice treated with rapamycin had restored cerebral blood flow, blood-brain barrier integrity and glucose metabolism, compared to age- and gender-matched wild-type controls. The preserved vasculature and metabolism were associated with amelioration of incipient learning deficits. We also found that rapamycin restored the levels of the proinflammatory cyclophilin A in vasculature, which may contribute to the preservation of cerebrovascular function in the apolipoprotein E ɛ4 transgenics. Our results show that rapamycin improves functional outcomes in this mouse model and may have potential as an effective intervention to block progression of vascular, metabolic and early cognitive deficits in human Apolipoprotein E ɛ4 carriers. As rapamycin is FDA-approved and neuroimaging is readily used in humans, the results of the present study may provide the basis for future Alzheimer's disease intervention studies in human subjects.

Topics: Alzheimer Disease; Animals; Apolipoprotein E4; Blood-Brain Barrier; Cerebrovascular Circulation; Glucose Metabolism Disorders; Learning Disabilities; Metabolic Diseases; Mice; Mice, Transgenic; Neuroimaging; Secondary Prevention; Sirolimus; Vascular Diseases

Topics: Aging; Animals; Antifungal Agents; Cell Proliferation; Disease; Drug Administration Schedule; Geriatrics; Humans; Immunosuppressive Agents; Intracellular Signaling Peptides and Proteins; Longevity; Metabolic Diseases; Neoplasms; Primary Prevention; Protein Serine-Threonine Kinases; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

The p70 S6 ribosomal protein kinase 1 (S6K) is a substrate and effector of the mammalian target of rapamycin (mTOR). The mTOR/S6K pathway is implicated in cancer and metabolic disorders. To study the molecular regulation of S6K and identify specific inhibitors, availability of active recombinant S6K and robust enzyme assays are critically needed. To date, however, expression of active recombinant S6K has not been feasible as S6K activation requires a cascade of phosphorylation events. We have compared several engineered S6K enzymes. Expression of the Flag-S6KDeltaCT(T389E) in HEK293 cells resulted in a highly active S6K that was constitutively phosphorylated on T229 in the activation-loop (T-loop). The active enzyme was readily purified in large scale by anti-Flag affinity chromatography achieving a high purity. We developed a high capacity homogeneous time-resolved fluorescence resonance energy transfer. Lance assay for measurement of substrate phosphorylation and analysis of kinetic parameters. The Michaelis constant (Km) values of S6K for ATP and the Biotin-S6 substrate peptide were determined to be 21.4+/-0.29 and 0.9+/-0.48 microM, respectively. The Lance assay was further validated with a diverse panel of literature inhibitors, in which the PKC inhibitors staurosporine, Ro-318220, and the PKA inhibitor Balanol potently inhibited S6K. Dose-response and inhibition mechanism by these inhibitors were also studied. Our data provide a new simplified strategy to achieve rapid production of active S6K and demonstrate utility of the Lance assay for S6K enzyme screen in searching for specific inhibitors.

Topics: Antibiotics, Antineoplastic; Cell Line; Dose-Response Relationship, Drug; Enzyme Inhibitors; Fluorescence Resonance Energy Transfer; Humans; Metabolic Diseases; Neoplasms; Phosphorylation; Protein Kinases; Protein Processing, Post-Translational; Recombinant Proteins; Ribosomal Protein S6 Kinases, 70-kDa; Signal Transduction; Sirolimus; TOR Serine-Threonine Kinases

Kidney transplant recipients require careful follow-up in both the early (< 6 months) and late posttransplant periods. Monitoring should focus on graft function and the most common complications of immunosuppression therapy. Infections, especially CMV infection, require particular attention in the first few months after transplantation, when immunosuppression is most intense. In both the early and the late posttransplant periods, an emphasis should be placed on intensive management of CVD risk factors (e.g., hypertension, hyperlipidemia, cigarette smoking). Screening for malignancies known to occur with a high incidence after transplantation is also important. With the improved short-term survival rates brought about by new, potent immunosuppressive agents, emphasis has now shifted to the prevention and treatment of posttransplant complications in kidney transplant recipients. A heightened awareness of these complications, along with a cooperative effort between primary care physicians and transplant programs, offers the best hope for further improvement in outcomes after kidney transplantation.

Topics: Cardiovascular Diseases; Cyclosporine; Cytomegalovirus Infections; Glucocorticoids; Humans; Immunosuppressive Agents; Kidney Transplantation; Metabolic Diseases; Monitoring, Physiologic; Neoplasms; Risk Assessment; Sirolimus; Tacrolimus; Transplantation, Homologous