The mechanisms underpinning beta‐cell compensation for obesity‐associated insulin resistance and beta‐cell failure in type 2 diabetes remain poorly understood. We used a large‐scale strategy to ...determine the time‐dependent transcriptomic changes in islets of diabetes‐prone db/db and diabetes‐resistant ob/ob mice at 6 and 16 weeks of age. Differentially expressed genes were subjected to cluster, gene ontology, pathway and gene set enrichment analyses. A distinctive gene expression pattern was observed in 16 week db/db islets in comparison to the other groups with alterations in transcriptional regulators of islet cell identity, upregulation of glucose/lipid metabolism, and various stress response genes, and downregulation of specific amino acid transport and metabolism genes. In contrast, ob/ob islets displayed a coordinated downregulation of metabolic and stress response genes at 6 weeks of age, suggestive of a preemptive reconfiguration in these islets to lower the threshold of metabolic activation in response to increased insulin demand thereby preserving beta‐cell function and preventing cellular stress. In addition, amino acid transport and metabolism genes were upregulated in ob/ob islets, suggesting an important role of glutamate metabolism in beta‐cell compensation. Gene set enrichment analysis of differentially expressed genes identified the enrichment of binding motifs for transcription factors, FOXO4, NFATC1, and MAZ. siRNA‐mediated knockdown of these genes in MIN6 cells altered cell death, insulin secretion, and stress gene expression. In conclusion, these data revealed novel gene regulatory networks involved in beta‐cell compensation and failure. Preemptive metabolic reconfiguration in diabetes‐resistant islets may dampen metabolic activation and cellular stress during obesity.
Insulin secretion from pancreatic β-cells is critical for maintaining glucose homeostasis and deregulation of circulating insulin levels is associated with the development of metabolic diseases. ...While many factors have been implicated in the stimulation of insulin secretion, the mechanisms that subsequently reduce insulin secretion remain largely unexplored. Here we demonstrate that mice with β-cell specific ablation of the Y1 receptor exhibit significantly upregulated serum insulin levels associated with increased body weight and adiposity. Interestingly, when challenged with a high fat diet these β-cell specific Y1-deficient mice also develop hyperglycaemia and impaired glucose tolerance. This is most likely due to enhanced hepatic lipid synthesis, resulting in an increase of lipid accumulation in the liver. Together, our study demonstrates that Y1 receptor signaling negatively regulates insulin release, and pharmacological inhibition of Y1 receptor signalling for the treatment of non-insulin dependent diabetes should be taken into careful consideration.
Chronic high salt intake is one of the leading causes of hypertension. Salt activates the release of the key neurotransmitters in the hypothalamus such as vasopressin to increase blood pressure, and ...neuropepetide Y (NPY) has been implicated in the modulation of vasopressin levels. NPY in the hypothalamic arcuate nucleus (Arc) is best known for its control in appetite and energy homeostasis, but it is unclear whether it is also involved in the development of salt‐induced hypertension. Here, we demonstrate that wild‐type mice given 2% NaCl salt water for 8 weeks developed hypertension which was associated with marked downregulation of NPY expression in the hypothalamic Arc as demonstrated in NPY‐GFP reporter mice as well as by in situ hybridization analysis. Furthermore, salt intake activates neurons in the hypothalamic paraventricular nucleus (PVN) where mRNA expression of brain‐derived neurotrophic factor (BDNF) and vasopressin was found to be upregulated, leading to elevated serum vasopressin levels. This finding suggests an inverse correlation between the Arc NPY level and expression of vasopressin and BDNF in the PVN. Specific restoration of NPY by injecting AAV‐Cre recombinase into the Arc only of the NPY‐targeted mutant mice carrying a loxP‐flanked STOP cassette reversed effects of salt intake on vasopressin and BDNF expression, leading to a normalization of salt‐dependent blood pressure. In summary, our study uncovers an important Arc NPY‐originated neuronal circuitry that could sense and respond to peripheral electrolyte signals and thereby regulate hypertension via vasopressin and BDNF in the PVN.
Background
: Pancreatic beta cell dedifferentiation may be an important contributing factor to beta cell failure in type 2 diabetes, but the triggering stimuli are poorly understood. Macrophage ...levels are elevated in the islets of humans and mice with type 2 diabetes, but their effect on beta cell identity is not clear. Our goal was to examine the gene expression changes in islet-associated macrophages in obesity models with opposing disposition to diabetes development and to assess their potential contribution to beta cell (mal)adaptation.
Methods:
Islets were isolated from lean control, obese diabetes-prone
db/db
and obese diabetes-resistant
ob/ob
mice. Macrophages were sorted using flow cytometry. Islets were treated
ex vivo
with clodronate-containing liposomes to deplete macrophages. Gene expression was assessed by real-time RT-PCR.
Results:
Macrophage levels were increased in islets from
db/db
mice but not in islets from
ob/ob
mice compared to controls. Macrophages from
db/db
and
ob/ob
islets displayed distinct changes in gene expression, suggesting differential shifts in functional state. Macrophages from
db/db
islets maintained pro-inflammatory gene expression, whereas macrophages from
ob/ob
islets shifted towards an anti-inflammatory gene expression pattern with elevated levels of transforming growth factor beta 1 (
Tgfb1
) and reduced interleukin 1 beta (
IL1b
). Clodronate-liposome treatment of islets depleted macrophages, as evidenced by reduced mRNA expression of
CD11b
and
F4/80
. The depletion of macrophages in
db/db
islets increased the expression of beta cell identity genes. The mRNA levels of islet-associated transcription factors (
Mafa
and
Pdx1
), glucose transporter (
Glut2
), ATP-sensitive potassium channel (
kcnj11
), incretin receptor (
Gipr
) and adaptive unfolded protein response genes (
Xbp1
,
Hspa5
,
Pdia4
and
Fkbp11
) were increased in
db/db
islets after macrophage depletion, whereas the mRNA levels of the deleterious UPR effector,
Ddit3
, were reduced. Furthermore, macrophage depletion in
db/db
islets reduced the expression of genes involved in inflammatory (
IL1b
,
Fas
and
Nfkbia
) and oxidative stress catalase (
Cat
) and heme oxygenase-1 (
Hmox1
). In contrast, depletion of macrophages in islets of
ob/ob
mice did not affect beta cell identity gene expression.
Conclusion
: These novel findings suggest that distinct alterations in islet macrophages of obese mice are critically important for the maintenance of beta cell compensation or the loss of beta cell identity in diabetes. Depleting islet macrophages could be beneficial for reducing beta cell stress and preserving beta cell identity in type 2 diabetes.
Activins are members of the TGF-β superfamily and have been linked to prostate cancer. There are four mammalian activin subunits (β
A
, β
B
, β
C
, and β
E
) that dimerize to form functional ...proteins. The role of activin-A (β
A
-β
A
) has been relatively well characterized and has been shown to generally inhibit growth in the prostate. In contrast, little is known about the biological function of the β
C
and β
E
subunits. Previous work indicated activin-C (β
C
-β
C
) to be an antagonist of activin-A. This is important because resistance to activin-A growth inhibition occurs during prostate cancer progression. This paradox is not currently well understood. Hence, we hypothesize that local expression of the activin-β
C
subunit antagonizes activin-A-dependent growth inhibition and represents a key factor contributing to acquired insensitivity to activin-A observed in prostate cancer progression. To test our hypothesis, we characterized the ventral prostate lobes of 9-month-old transgenic mice over-expressing activin-β
C
and examined the expression of activin-β
A
, activin-β
C
, and the activin intracellular signaling factor, Smad-2, in human prostate diseases. Prostate epithelial cell hyperplasia, low-grade prostatic intraepithelial neoplasia (PIN) lesions, alterations in cell proliferation, and reduced Smad-2 nuclear localization were evident in mice over-expressing activin-β
C
. Increased activin-β
A
and -β
C
subunit immunoreactive scores and decreased Smad-2 nuclear localization were also evident in human prostate cancer. This study suggests that over-expression of activin-β
C
is associated with murine and human prostate pathologies. We conclude that the activin-β
C
subunit may have therapeutic and/or diagnostic implications in human prostate disease.
Display omitted
G3139 is an antisense oligodeoxyribonucleotide (ODN) developed as a Bcl-2 down-regulating agent for the treatment of acute myelogenous leukemia (AML). However, the clinical efficacy ...of G3139 has been shown to be limited due to its rapid plasma clearance and low permeability. To enhance the effective delivery of G3139, this work prepared a novel nano gene delivery vector (aCD33-NKSN) consisting of a CD33 antigbody (aCD33), a nuclear localization signal (NLS), gene fusion peptides (KALA), and stearic acid (SA) for CD33 antigen targeting and nuclear localization. The aCD33-NKSN/G3139 nanoparticles were spherical and uniformly sized with a positive charge and sustained release. They had an excellent G3139 loading capacity and colloidal stability. The aCD33-NKSN/G3139 delivered G3139 into the nucleus of Kasumi-1 cells and aCD33-NKSN/G3139 could more effectively inhibited Bcl-2 expression and induced apoptosis in Kasumi-1 cells versus free G3139. The aCD33-NKSN/G3139 administration was more effective at inhibiting tumor growth, and significantly prolonged the survival time of mice in contrast to free G3139. The results illustrate that aCD33-NKSN/G3139 nanoparticles could improve the antitumor activity of encapsulated G3139 due to aCD33 targeting and the ability to perform nuclear localization, The results offer a promising clinical application potential for the treatment of acute myeloid leukemia.
Alzheimer’s disease (AD) is the most prevalent form of dementia, accounting for 60-70% of all dementias. AD is often under-diagnosed and recognized only at a later, more advanced stage, and this ...delay in diagnosis has been suggested as a contributing factor in the numerous unsuccessful AD treatment trials. Although there is no known cure for AD, early diagnosis is important for disease management and care. A hallmark of AD is the deposition of amyloid-β (Aβ)-containing senile neuritic plaques and neurofibrillary tangles composed of hyperphosporylated tau in the brain. However, current in vivo methods to quantify Aβ in the brain are invasive, requiring radioactive tracers and positron emission tomography. Towards development of alternative methods to assess AD progression, we focus on the retinal manifestation of AD pathology. The retina is an extension of the central nervous system uniquely accessible to light-based, non-invasive ophthalmic imaging. However, earlier studies in human retina indicate that the literature is divided on the presence of Aβ in the AD retina. To help resolve this disparity, this study assessed retinal tissues from neuropathologically confirmed AD cases to determine the regional distribution of Aβ in retinal wholemounts and to inform on future retinal image studies targeting Aβ. Concurrent post-mortem brain tissues were also collected. Neuropathological cortical assessments including neuritic plaque (NP) scores and cerebral amyloid angiopathy (CAA) were correlated with retinal Aβ using immunohistochemistry, confocal microscopy, and quantitative image analysis. Aβ load was compared between AD and control (non-AD) eyes. Our results indicate that levels of intracellular and extracellular Aβ retinal deposits were significantly higher in AD than controls. Mid-peripheral Aβ levels were greater than central retina in both AD and control eyes. In AD retina, higher intracellular Aβ was associated with lower NP score, while higher extracellular Aβ was associated with higher CAA score. Our data support the feasibility of using the retinal tissue to assess ocular Aβ as a surrogate measure of Aβ in the brain of individuals with AD. Specifically, mid-peripheral retina possesses more Aβ deposition than central retina, and thus may be the optimal location for future in vivo ocular imaging.
The work described in this paper is the development of a buckling model based on the classical energy method of flange area material using a one-dimensional beam geometry assumption to predict flange ...wrinkling in hot deep drawing aluminium alloys with macro-textured blankholder surfaces. A series of deep drawing experiments utilising different macro-textured tool surfaces were performed to investigate the effects of process parameters and texture features on flange wrinkling. The results have shown that wrinkling occurs when the hollow dimension of radially grooved textures reached a certain magnitude dependent on process conditions. A dislocation-driven based continuum damage mechanism (CDM) material model for aluminium alloys at elevated temperatures was used to model the viscoplastic behaviour during deformation. The newly developed buckling model was validated by comparison with experimental results. The predicted results showed that the resistance to wrinkling increases with increasing forming temperature and decreasing forming speed, depending on the particular viscoplastic characteristics of the work-piece. The effects of texture ratio and draw ratio on wrinkling were found to be more significant than the effects of the temperature and strain rate. The buckling model developed in this paper can be used to model the flange wrinkling phenomena, as well as the non-isothermal feature in the hot stamping condition using the macro-textured tool surfaces.
•A flange buckling model for hot forming AA6082 with textured tools were developed.•The non-isothermal feature of hot stamping process was modelled.•Hot deep drawing were performed to validate the developed buckling model.•Effects of process parameters and tool textures on wrinkling were analysed.
The in-die quenching is a key stage in the hot stamping volume production chain which determines the post-formed strength of lightweight alloy components, tool life, and hot stamping productivity. In ...this paper, the performance of in-die quenching, reflected by the quenching efficiency (the time of work-piece held within stamping dies) and die surface temperature during the simulated hot stamping process of AA6082, was experimentally and analytically investigated. A range of in-die quenching experiments were performed for different initial work-piece and die temperatures, quenching pressures, work-piece thickness, and die clearances, under hot stamping conditions. In addition, a one-dimensional (1D) closed-form heat transfer model was used to calculate the die surface temperature evolution that is difficult to obtain during practical manufacture situations. The results have shown that the in-die quenching efficiency can be significantly increased by decreasing the initial work-piece and die temperatures. Die clearances are required to be designed precisely to obtain sufficiently high quenching rates and satisfying post-formed strength for hot-stamped panel components. This study systematically considered an extensive variety of influencing factors on the in-die quenching performance, which can provide practical guides for stamping tool designers and manufacture systems for hot-stamping volume production.
PDF
