An update on the potential role of C-peptide in diabetes and osteoporosis

C-Peptide and BMi predict anti-hyperglycemic treatment lines in breast cancer patients treated with Alpelisib

PURPOSE

Alpelisib is a PI3K (Phosphoinositide 3-kinases) inhibitor used for breast cancer which develops hyperglycemia based on its action on glucose metabolism regulation. This study aims to identify potential risk factors predicting hyperglycemia development and the need for multiple treatments for hyperglycemia in patients receiving Alpelisib.

METHODS

Fourteen women diagnosed with metastatic hormone receptor-positive breast cancer carrying PI3K mutations who initiated treatment with Alpelisib were monitored through consultations in the Oncology and Endocrinology departments. Non-parametric ROC curves were generated to assess the need for three or more antidiabetic medications to achieve glycemic control.

RESULTS

The study population had a median age of 64 years (range:48-69) with a median body mass index (BMI) of 26.6 kg/m2 (range: 22.9-29.4). Overweight was observed in 35.7% of the participants and obesity in 21.4%. Fifty percent of the participants had prediabetes, and 85.7% developed hyperglycemia requiring pharmacological treatment, although none of them needed to discontinue treatment for this reason. Baseline C-peptide levels and BMI were associated with the number of antidiabetic drugs used (Spearman's Rho 0.553, p = 0.040; Spearman's Rho 0.581, p = 0.030, respectively). ROC curve analysis showed and area under the curve (AUC) of 0.819 for the variable risk profile (defined as baseline C-peptide >10.5 ng/ml and BMI > 27 kg/m2), whereas AUC values were 0.556 and 0.514 for HbA1c and baseline glucose, respectively, (p = 0.012).

CONCLUSION

A joint follow-up by an Oncology department and a Diabetes Unit can prevent treatment discontinuation in patients under Alpelisib therapy. Baseline BMI and plasma C-peptide levels can predict an increased need for anti-hyperglycemic treatment.

A novel antisense lncRNA, ARBAG harboring an RNA destabilizing GWAS variant for C-peptide dictates the transcript isoforms of GABRA6 in cerebellum

Human disease-associated genetic variations often map to long non-coding RNA (lncRNA) genes; however, elucidation of their functional impact is challenging. We previously identified a new genetic variant rs4454083 (A/G) residing in exon of an uncharacterized lncRNA ARBAG that strongly associates with plasma levels of C-peptide, a hormone that regulates insulin bioavailability. On the opposite strand, rs4454083 also corresponds to an intron of a cerebellum-specific GABA receptor subunit gene GABRA6 that mediates strengthening of inhibitory synapses by insulin. Here, we show that alleles of rs4454083 modulate transcript levels of the antisense gene, ARBAG, which then controls the expression of the sense gene, GABRA6. Predisposing to low C-peptide, GG (a minor allele genotype across ethnicities) stabilizes ARBAG lncRNA causing higher transcript levels in cerebellum. ARBAG lncRNA abundance leads to cleavage of GABRA6 mRNA at the complementary region, resulting in a dysfunctional GABRA6 protein that would not be recruited for synapse strengthening. Together, our findings in human cerebellar cell-line and induced Pluripotent Stem Cells (iPSCs) demonstrate biological role of a novel lncRNA in determining the ratio of mRNA isoforms of a protein-coding gene and the ability of an embedded variant in modulating lncRNA stability leading to inter-individual differences in protein expression.

The Predictive Ability of C-Peptide in Distinguishing Type 1 Diabetes From Type 2 Diabetes: A Systematic Review and Meta-Analysis

OBJECTIVE

This systematic review and meta-analysis aimed to investigate the predictive ability of plasma connecting peptide (C-peptide) levels in discriminating type 1 diabetes (T1D) from type 2 diabetes (T2D) and to inform evidence-based guidelines in diabetes classification.

METHODS

We conducted a holistic review and meta-analysis using PubMed, MEDLINE, EMBASE, and Scopus. The citations were screened from 1942 to 2021. The quality criteria and the preferred reporting items for systematic reviews and meta-analysis checklist were applied. The protocol was registered with the International Prospective Register of Systematic Reviews (PROSPERO) (CRD42022355088).

RESULTS

A total of 23,658 abstracts were screened and 46 full texts reviewed. Of the 46 articles screened, 12 articles were included for the meta-analysis. Included studies varied by race, age, time, and proportion of individuals. The main outcome measure in all studies was C-peptide levels. A significant association was reported between C-peptide levels and the classification and diagnosis of diabetes. Furthermore, lower concentrations and the cutoff of <0.20 nmol/L for fasting or random plasma C-peptide was indicative of T1D. In addition, this meta-analysis revealed the predictive ability of C-peptide levels in discriminating T1D from T2D. Results were consistent using both fixed- and random-effect models. The I2 value (98.8%) affirmed the variability in effect estimates was due to heterogeneity rather than sampling error among all selected studies.

CONCLUSION

Plasma C-peptide levels are highly associated and predictive of the accurate classification and diagnosis of diabetes types. A plasma C-peptide cutoff of ≤0.20 mmol/L is indicative of T1D and of ≥0.30 mmol/L in the fasting or random state is indicative of T2D.

Preventing muscle wasting: pro-insulin C-peptide prevents loss in muscle mass in streptozotocin-diabetic rats

BACKGROUND

C-peptide therapy exerts several positive actions on nerves, vasculature, smooth muscle relaxation, kidney function and bone. To date, the role of C-peptide in preventing type 1 diabetes-related muscle atrophy has not been investigated. Our aim was to evaluate if C-peptide infusion prevents muscle wasting in diabetic rats.

METHODS

Twenty-three male Wistar rats were randomly divided into three groups: normal control group, diabetic group and diabetic group plus C-peptide. Diabetes was induced by streptozotocin injection, and C-peptide was administered subcutaneously for 6 weeks. The blood samples were obtained at baseline, before streptozotocin injection and at the end of the study to assess C-peptide, ubiquitin and other laboratory parameters. We also tested the ability of C-peptide to regulate the skeletal muscle mass, the ubiquitin-proteasome system, the autophagy pathway as well as to improve muscle quality.

RESULTS

C-peptide administration reversed hyperglycaemia (P = 0.02) and hypertriglyceridaemia (P = 0.01) in diabetic plus C-peptide rats compared with diabetic control rats. The diabetic-control animals displayed a lower weight of the muscles in the lower limb considered individually than the control rats and the diabetic plus C-peptide rats (P = 0.03; P = 0.03; P = 0.04; P = 0.004, respectively). The diabetic-control rats presented a significantly higher serum concentration of ubiquitin compared with the diabetic plus C-peptide and the control animals (P = 0.02 and P = 0.01). In muscles of the lower limb, the pAmpk expression was higher in the diabetic plus C-peptide than the diabetic-control rats (in the gastrocnemius, P = 0.002; in the tibialis anterior P = 0.005). The protein expression of Atrogin-1 in gastrocnemius and tibialis was lower in the diabetic plus C-peptide than in diabetic-control rats (P = 0.02, P = 0.03). After 42 days, the cross-sectional area in the gastrocnemius of the diabetic plus C-peptide group had been reduced by 6.6% while the diabetic-control rats had a 39.5% reduction compared with the control animals (P = 0.02). The cross-sectional area of the tibialis and the extensor digitorum longus muscles was reduced, in the diabetic plus C-peptide rats, by 10% and 11%, respectively, while the diabetic-control group had a reduction of 65% and 45% compared with the control animals (both P < 0.0001). Similar results were obtained for the minimum Feret's diameter and perimeter.

CONCLUSIONS

C-peptide administration in rats could protect skeletal muscle mass from atrophy induced by type 1 diabetes mellitus. Our findings could suggest that targeting the ubiquitin-proteasome system, Ampk and muscle-specific E3 ubiquitin ligases such as Atrogin-1 and Traf6 may be an effective strategy for molecular and clinical intervention in the muscle wasting pathological process in T1DM.

A peptide from wheat germ abolishes the senile osteoporosis by regulating OPG/RANKL/RANK/TRAF6 signaling pathway

BACKGROUND

Oxidative stress played a key role in the development of bone brittleness and is an important pathogenic factor of senile osteoporosis. A variety of animal and plant-derived peptides have been shown to have significant anti-osteoporosis effects in vivo and in vitro.

PURPOSE

In this study, we aim to explore the possible mechanism of wheat germ peptide ADWGGPLPH on senile osteoporosis.

STUDY DESIGN

Naturally, aged rats were used as animal models of senile osteoporosis.

METHODS

Wheat germ peptide ADWGGPLPH was administered from 9-months-old to 21-months-old, and the effect of ADWGGPLPH on preventing senile osteoporosis was evaluated by measuring serum biochemical indexes, bone histomorphometry, bone biomechanics, and other indexes to elucidate the mechanism of ADWGGPLPH in delaying senile osteoporosis by detecting the expression of osteoporosis-related proteins.

RESULTS

The results showed that ADWGGPLPH could effectively reduce the level of oxidative stress and improve the microstructure and bone mineral density in senile osteoporosis rats. In addition, ADWGGPLPH could improve the proliferation and differentiation activity of osteoblasts and effectively inhibit osteoclasts' differentiation by regulating the OPG/RANKL/RANK/TRAF6 pathway.

CONCLUSION

ADWGGPLPH from wheat germ exhibited a notably effect on senile osteoporosis and has a high potential in the development of the nutrient regimen to against senile osteoporosis.

Alterations of glycaemia, insulin resistance and body mass index within the C-peptide optimal range in non-diabetic patients

The study focused on changes or cut-offs of glycaemia, insulin resistance and body mass index within the C-peptide reference range (260-1730 pmol/l). The metabolic profile of individuals in the Czech Republic without diabetes (n = 3186) was classified by whiskers and quartiles of C-peptide into four groups with the following ranges: 290-510 (n = 694), 511-710 (n = 780), 711-950 (n = 720) and 951-1560 pmol/l (n = 673). Fasting levels of glucose, insulin, HOMA IR (Homeostasis Model Assessment for Insulin Resistance) and BMI (body mass index) were compared by a relevant C-peptide range. Participants taking medication to control glycaemia were excluded. The evaluation involved correlations between C-peptides and the above parameters, F-test and t-test. Changes in glucose levels (from 5.3 to 5.6 mmol/l) between the groups were lower in comparison to insulin, which reached relatively greater changes (from 4.0 to 14.2 mIU/l). HOMA IR increased considerably with growing C-peptide concentrations (0.9, 1.5, 2.2 and 3.5) and BMI values showed a similar trend (28.3, 31.0, 33.6 and 37.4). Considerable changes were observed for insulin (5.2 mIU/l, 57.8%) and HOMA IR (1.3, 61.3%) between groups with C-peptide ranges of 711-950 and 951-1560 pmol/l. Although correlations involving C-peptide, insulin, glucose and BMI seemed to be non-significant (up to rxy = 0.25), the mean values of insulin, HOMA IR and BMI showed statistically significant changes between all groups with various C-peptide concentrations (p ≤ 0.001). Generally, most important differences appeared in glucose metabolism and body mass index between C-peptide ranges of 711-950 and 951-1560 pmol/l. Absolute and relative changes of C-peptide concentrations are possible to use for the assessment of glucose regulatory mechanism. The spectrum of investigated parameters could be a useful tool to prevent the risks linked with the alterations of glycaemia.

C-peptide ameliorates high glucose-induced podocyte dysfunction through the regulation of the Notch and TGF-β signaling pathways

The podocyte is one of the main components of the glomerular filtration barrier in the kidney, and its injury may contribute to proteinuria, glomerulosclerosis and eventually kidney failure. C-peptide, a cleavage product of proinsulin, shows therapeutic potential for treating diabetic nephropathy (DN). The aim of this study was to investigate the effect of C-peptide on high glucose-induced podocyte dysfunction. In the present study, we found that the protective effects of islet transplantation were superior to simple insulin therapy for the treatment of DN in streptozotocin (STZ)-treated rats. And such superiority may due to the function of C-peptide secreted at the implanted site. Based on this background, we determined that the application of C-peptide significantly prevented high glucose-induced podocyte injury by increasing the expression of nephrin and synaptopodin. Meanwhile, C-peptide suppressed high glucose-induced epithelial-mesenchymal transition (EMT) and renal fibrosis via decreasing the expression of snail, vimentin, α-smooth muscle actin (α-SMA) and connective tissue growth factor (CTGF). Moreover, the Notch and transforming growth factor-β (TGF-β) signaling pathways were activated by high glucose, and treatment with C-peptide down-regulated the expression of the Notch signaling molecules Notch 1 and Jagged 1 and the TGF-β signaling molecule TGF-β1. These findings suggested that C-peptide might serve as a novel treatment method for DN and podocyte dysfunction.

Glycolipid toxicity induces osteogenic dysfunction via the TLR4/S100B pathway

Diabetes can cause bone metabolism disorders and osteoporosis. The occurrence of both diabetes mellitus and osteoporosis increases the disability and mortality of elderly individuals due to pathological fracture. Abnormal metabolism of nutrientsis considered to be one of the important mechanisms of diabetes mellitus-induced osteoporosis. This study preliminarily explored the roles of TLR4 (Toll-like receptor 4) and S100B in osteogenic dysfunction induced by glycolipid toxicity. In this study, a diabetic rat model and TLR4-knockdown diabetic rat model were used in vivo. MC3T3-E1 cells in a high glucose and palmitic acid environment were used as glycolipid toxicity cell models in vitro. We investigated the effects of TLR4 and S100B on osteogenesis by overexpression or inhibition of TLR4 and S100B in vitro. We found that when TLR4 or S100B was inhibited, ALP and OCN were significantly up-regulated and p-ERK was significantly down regulated in the glycolipid model. These results suggest that TLR4/S100B may play a role in reducing glycolipid toxicity by regulating ERK phosphorylation.

High Glucose Enhances the Odonto/Osteogenic Differentiation of Stem Cells from Apical Papilla via NF-KappaB Signaling Pathway

Objective

The transport and metabolism of glucose are important during mammalian development. High glucose can mediate the biological characteristics of mesenchymal stem cells (MSCs). However, the role of high glucose in the odonto/osteogenic differentiation of stem cells from apical papilla (SCAPs) is unclear.

Materials and Methods

SCAPs were isolated and identified in vitro. Then, SCAPs were cultured in normal α-MEM and high glucose α-MEM separately. MTT assay was applied to observe the proliferation of SCAPs. ALP activity, alizarin red staining, real-time RT-PCR, and western blot were used to detect the odonto/osteogenic capacity of SCAPs as well as the participation of NF-κB pathway.

Results

SCAPs in 25mmol/L glucose group expressed the maximum proteins of RUNX2 and ALP as compared with those in 5, 10, and 15 mmol/L groups. MTT assay showed that 25 mmol/L glucose suppressed the proliferation of SCAPs. ALP assay, alizarin red staining, real-time RT-PCR, and western blot showed 25 mmol/L high glucose can obviously enhance the odonto/osteogenic capacity of SCAPs. Moreover, the NF-κB pathway was activated in 25mmol/L glucose-treated SCAPs and the odonto/osteogenic differentiation was inhibited following the inhibition of NF-κB signaling pathway.

Conclusions

High glucose can enhance the odonto/osteogenic capacity of SCAPs via NF-κB pathway.

Increased frequency of impaired fasting glucose and isolated systolic hypertension in Paget's disease of bone

PURPOSE

Scanty data about glucose metabolism and hypertension have been reported in Paget's disease of bone (PDB) to be related with increased cardiovascular mortality. The aim of the present study was to evaluate glucose and blood pressure levels in PDB, looking for their association with disease severity.

METHODS

We performed an observational cross-sectional study in 54 patients with PDB and 54 age, sex and BMI-matched controls. Glucose and blood pressure levels and parameters of bone and mineral metabolism were assessed.

RESULTS

Patients with PDB showed increased glucose levels (6.3 ± 1.7 vs 5.3 ± 1.4 mmol/l, p < 0.001) and prevalence of impaired fasting glucose (14.8%, 5.3-24.3 vs 1.9%, 0-5.4, p < 0.02) as well as enhanced systolic blood pressure (145.9 ± 21.3 vs 132.9 ± 18.9 mmHg, p < 0.005), pulse pressure (69.6 ± 20.0 vs 56.0 ± 16.9 mmHg, p < 0.01) and prevalence of isolated systolic hypertension (46.3%, 33.0-59.6 vs 16.7%, 6.7-26.6, p < 0.003) in comparison to controls. Moreover, we found a positive association of (1) glucose levels with ionized calcium and bone alkaline phosphatase; (2) both systolic and pulse pressure with total and bone alkaline phosphatase (p < 0.05). By multiple linear regression analysis (R² = 0.26; p < 0.05) serum ionized calcium correlated with glucose levels (β = 0.44; p < 0.04), after adjusting for age and BMI.

CONCLUSIONS

Our study shows increased fasting glucose, systolic and pulse pressure levels as well as enhanced prevalence of impaired fasting glucose and isolated systolic hypertension in PDB, potentially accounting for increased cardiovascular mortality. Furthermore, our findings suggest high serum calcium and/or increased bone alkaline phosphatase as a link between PDB and cardio-metabolic disorders.

Development of a double-antibody sandwich ELISA for rapid detection to C-peptide in human urine

C-peptide level is recognized as an important indicator of diabetes diagnosis. A sensitive and specific double-antibody sandwich enzyme-linked immunosorbent assay for the detection of C-peptide based on double antibody sandwich method was studied in this paper. The rabbit and hen were innunized with PLL-C-peptide and BSA-C-peptide respectively to obtain specific Yolk antibody (IgY) and polyclonal antibody used to construct the sandwich ELISA for the measurement of C-peptide. The limit of detection was 0.51 μg/mL and the half maximal inhibitory concentration (IC50) was 3.26 μg/mL. The method developed in the study showed no evident cross-reactivity with other similar analogs. The detection standard curve of C-peptide exhibited a good linearity (R² = 0.9896, n = 15). 17 types of the urine of diabetes patients on c-peptide levels compared with the hospital type of diabetes information, with a conclusion of a high consistent rate. Therefore, the methods could be selectively used for rapid screening of C-peptide in human urine, and the type of diabetes has some referential significance.

Managing and maintaining bone mineral density in diabetes patients with pharmacotherapy

INTRODUCTION

The population of patients with osteoporosis and diabetes is increasing as the aging population increases. Loss of bone mineral density occurs in patients with diabetes, but is not always a priority in the practice setting. The aim of this review is to discuss clinical considerations when managing osteoporosis in patients with diabetes. Areas covered: The pathophysiology of decreased bone mineral density in patients with diabetes is discussed. Additionally, diabetic risk factors for fracture, such as hypoglycemia, the National Osteoporosis Foundation recommendations for osteoporosis, and secondary causes of osteoporosis, including disease and medication related causes, are discussed. Furthermore, recommendations for antihyperglycemic agents, thiazolidinediones, canagliflozin, insulin, metformin, and sitagliptin are discussed due to their effects on bone mineral density. Expert opinion: Even though diabetes is an important risk factor for osteoporosis, assessing bone health in diabetic patients is often overlooked. Ensuring adequate prevention and treatment strategies for osteoporosis is vitally important with our diabetic patients as the population ages. T-scores and FRAX scores likely underrepresent a diabetic patients risk for fracture, and this should be taken into consideration in treatment decisions. Future studies are needed to determine optimal pharmacologic treatment of hyperglycemia in this population.