Diabetes modulates differentially creatine kinase-specific activity responsiveness to estradiol-17beta and to raloxifene in rat organs

Effect of IAPP on the proteome of cultured Rin-5F cells

Background

Islet amyloid polypeptide (IAPP) or amylin deposits can be found in the islets of type 2 diabetes patients. The peptide is suggested to be involved in the etiology of the disease through formation of amyloid deposits and destruction of β islet cells, though the underlying molecular events leading from IAPP deposition to β cell death are still largely unknown.

Results

We used OFFGEL™ proteomics to study how IAPP exposure affects the proteome of rat pancreatic insulinoma Rin-5F cells. The OFFGEL™ methodology is highly effective at generating quantitative data on hundreds of proteins affected by IAPP, with its accuracy confirmed by In Cell Western and Quantitative Real Time PCR results. Combining data on individual proteins identifies pathways and protein complexes affected by IAPP. IAPP disrupts protein synthesis and degradation, and induces oxidative stress. It causes decreases in protein transport and localization. IAPP disrupts the regulation of ubiquitin-dependent protein degradation and increases catabolic processes. IAPP causes decreases in protein transport and localization, and affects the cytoskeleton, DNA repair and oxidative stress.

Conclusions

Results are consistent with a model where IAPP aggregates overwhelm the ability of a cell to degrade proteins via the ubiquitin system. Ultimately this leads to apoptosis. IAPP aggregates may be also toxic to the cell by causing oxidative stress, leading to DNA damage or by decreasing protein transport. The reversal of any of these effects, perhaps by targeting proteins which alter in response to IAPP, may be beneficial for type II diabetes.

Electronic supplementary material

The online version of this article (10.1186/s12858-018-0099-3) contains supplementary material, which is available to authorized users.

High glucose impaired estrogen receptor alpha signaling via β-catenin in osteoblastic MC3T3-E1

Diabetic Mellitus is a risk factor for osteoporosis. It has been suggested that altered estrogen or estrogen receptor α/β (ERα/β) signaling may be involved in diabetic osteoporosis. The present study is to investigate the effects of high glucose on ERα/β signaling in osteoblastic MC3T3-E1 and how the altered signaling of ERα/β affect osteoblastic bone formation. ERα/β signaling was demonstrated as ERα/β protein expression (Western Blotting) and ER transcription activity (Luciferase Reporter assays). Proliferation (WSK-1 assaying), differentiation (ALP staining) and mineralization (Alizalard Red staining) of MC3T3-E1 were examined to evaluate bone formation function. It has been found that high glucose increased ERα/β expression dose-dependently and time-dependently, but high glucose (33mM) decreased ERα transcription activity. 17β-estradiol increased the ERα/β expression dose-dependently in normal medium, but decreased the ERα/β expression dose-dependently in medium with high glucose (33mM). High glucose decreased bone formation and also decreased the osteogenic effects of 17β-estradiol (10^-8M). High glucose decreased β-catenin expression dose-dependently and time-dependently. LiCl, an inhibitor of β-catenin degradation, decreased ERα expression but increased ERα transcription activity. When compared with high glucose treatment, LiCl (5mM) increased ALP activity and calcified nodes. Besides, high glucose also decreased the protein expression PI-3K, pAKT/AKT, GSK-3β. In conclusion, the present study suggested that high glucose may impair ERα transcription activity by inhibiting β-catenin signaling in osteoblastic MC3T3-E1, leading decreased bone formation ligand-dependently or ligand-independently.

Diabetes Mellitus and Bone Regeneration: A Systematic Review and Meta-Analysis of Animal Studies

BACKGROUND

The regeneration of bone defects resulting from trauma, resection of tumors, infection, or congenital disease is a challenge, and bone grafts are utilized in a wide array of clinical settings to augment bone repair and regeneration. Diabetes mellitus (DM) is a chronic metabolic disease, which affects 8.3% of the world population, summing ∼387 million individuals. The consequences of the disease, for example, hyperglycemia, have been associated to a reduced capacity to form bone and poor bone quality, influencing bone healing. Our aim was to systematically review the literature to the effect of diabetic condition on bone regeneration in animal models, when using bone substitute materials from different origins, and perform a meta-analysis to quantitatively study the effect of DM on bone regeneration.

METHODS

An extensive search strategy was carried out through PubMed and EMBASE to identify the potential relevant studies published from database inception until July 1, 2015. Initially, the title and abstract of 1409 studies were screened, after which inclusion criteria sorted 29 studies for full-text evaluation. After using exclusion criteria, a final number of seven studies could be included in the review.

RESULTS

The seven included studies that passed our inclusion/exclusion criteria were all type 1 diabetes, comprising a total of 189 animals and 14 intrastudy comparisons. These studies presented a consistent and reduced risk of bias and showed a significant average effect size of -6.87% of bone formation for diabetes type 1 versus healthy condition [95% confidence interval: -10.55 to -3.18; I² = 87.4%; p = 0.0003].

INTERPRETATION

These findings prove that DM type 1 negatively influences bone formation compared with a healthy condition, irrespective of the bone substitute material used.

In vivo creatine kinase reaction kinetics at rest and stress in type II diabetic rat heart

The effects of type II diabetes on cardiac creatine kinase (CK) enzyme activity and/or flux are unknown. We therefore measured steady‐state phosphocreatine (PCr) and adenosine triphosphate (ATP) content and forward CK reaction kinetic parameters in Zucker Diabetic Fatty (ZDF) rat hearts, a type II diabetes research model. At baseline the PCr to ATP ratio (PCr/ATP) was significantly lower in diabetic heart when compared with matched controls (1.71 ± 0.21 vs. 2.26 ± 0.24, P < 0.01). Furthermore, the forward CK reaction rate constant (k_f) was higher in diabetic animals (0.52 ± 0.09 s⁻¹ vs. 0.35 ± 0.06 s⁻¹, P < 0.01) and CK flux calculated as a product of PCr concentration ([PCr]) and k_f was similar between two groups (4.32 ± 1.05 μmol/g/s vs. 4.94 ± 1.23 μmol/g/s, P = 0.20). Dobutamine administration resulted in similar increases in heart rate (~38%) and k_f (~0.12 s⁻¹) in both groups. No significant change in PCr and ATP content was observed with dobutamine. In summary, our data showed reduced PCr/ATP in diabetic myocardium as an indicator of cardiac energy deficit. The forward CK reaction rate constant is elevated at baseline which might reflect a compensatory mechanics to support energy flux through the CK shuttle and maintain constant ATP supply. When hearts were stimulated similar increase in k_f was observed in both groups thus it seems that CK shuttle does not limit ATP supply for the range of workload studied.

Noninvasive ³¹P MRS was used to measure PCr concentration ([PCr]) and creatine kinase (CK) reaction flux in type II diabetic rat hearts. [PCr] was reduced in diabetic myocardium as compared to controls, indicative of impairment in mitochondrial ATP production. The forward CK reaction rate constant was elevated, possibly reflecting a compensatory mechanism to support increased flux through the CK shuttle required to support cardiac work. CK reaction velocity increased in both diabetic and control hearts to maintain constant ATP content at higher work.

Estrogens and hyperglycemic modulation of mRNAs expressions involved in bone metabolism: an overshadowed association?

Human bone cell line (SaOS2) express different mRNAs involved in bone biology and physiology such as estrogen receptor α (ERα), estrogen receptor β (ERβ), vitamin D receptor (VDR), 1α, 25 hydroxy vitamin D(3) hydroxylase (1OHase) as well as 12 and 15 lipoxygenases (12LO and 15LO). These mRNAs are modulated by estrogenic compounds. Since the skeletal protective effects of estrogens are not discernible in diabetic women, we tested whether the expression of the parameters measured here and their modulations by estrogens, in SaOS2 cells grown in growth medium containing high glucose (HG; 9.0 g/L; 44 mM) compared to normal glucose (NG; 4.5 g/L; 22 mM). High Glucose (HG) significantly increased DNA synthesis and creatine kinase (CK) specific activity in SaOS2 cells. Stimulations of DNA but not of CK by E(2), by 4, 4', 4''-[4-propyl-(1H)-pyrazol-1, 3, 5- triyl] tris-phenol (PPT, ERα specific agonist), or by 2, 3-bis (4-hydroxyphenyl)-propionitrile (DPN, ERβ specific agonist), were abolished by HG. HG itself upregulated the expression of mRNA of 12LO and 15LO and upregulated to much less extent of ERβ and VDR, but had no effect on the expression of mRNA of ERα and 1OHase. The different hormonal treatments modulated the expressions of 12LO and 15LO mRNAs which was reduced in HG, whereas the induction of their products 12HETE and 15HETE was only slightly affected by HG. The exact mechanism of HG effects on bone cell responses is yet to be investigated and its relationship to human bone physiology is not yet clear.

The response of creatine kinase specific activity in rat pituitary to estrogenic compounds and vitamin d less-calcemic analogs

We examined the response of rat female pituitary at different metabolic stages to treatments with estrogenic compounds and vitamin D analogs. Immature or ovariectomized (Ovx) female rats responded by increased creatine kinase specific activity (CK) to estradiol-17β (E₂), genistein (G), daidzein (D), biochainin A (BA), quecertin (Qu), carboxy- G (cG), carboxy- BA (cBA), and raloxifene (Ral). The response was inhibited when Ral was injected together with the estrogens. CK was increased when hormones were injected daily into Ovx rats for 4 different time periods. Pretreatment with the less-calcemic vitamin D analogs JK 1624 F₂-2 (JKF) or QW 1624 F₂-2 (QW) followed by estrogenic injection resulted in increased response and sensitivity to E₂ and loss of inhibition of E₂ by Ral. CK was also increased by feeding with E₂ or licorice or its components dose- and time- dependent in immature or Ovxrats. Diabetic female rats did not respond to increased doses of E₂. In conclusion, rat female pituitary is estrogens-responsive organ, suggesting to considerits response for HRT in postmenopausal women for both beneficial and hazardous aspects.