Association between low C-peptide and low lumbar bone mineral density in postmenopausal women without diabetes

The bidirectional association of C-peptide with cardiovascular risk in nondiabetic adults and patients with newly diagnosed type 2 diabetes mellitus: a retrospective cohort study

Background

Recent literature reported the biological role of C-peptide, but this role is still controversial and unclear. The primary aim of this study was to investigate associations between C-peptide and cardiovascular biomarkers as well as events.

Methods

A total of 55636 participants who had a health examination from 2017 to 2021 were included. Of them, 6727 participants visited the hospital at least twice. Cardiovascular biomarkers like high-sensitivity C-reactive protein (hs-CRP) and high-sensitivity cardiac troponin T (hs-cTnT) were measured and their relationships with fasting C-peptide were evaluated for all participants. Cardiovascular events were obtained during the last visit and their associations with C-peptide were evaluated for those participants who visited the hospital at least twice.

Results

Among the included participants, 11.1% had a previous type 2 diabetes mellitus (T2DM). In the participants without previous T2DM, the relationships between fasting C-peptide and hs-CRP and hs-cTnT were negative if the value of fasting C-peptide was < 1.4 ng/mL and positive if the value was ≥ 1.4 ng/mL. These relationships remained significant after adjusting for hemoglobin A1c, insulin resistance index, and its interaction with C-peptide, even if the participants were stratified by glucose metabolism status or levels of insulin resistance index. Hazard ratios of cardiovascular events were first decreased and then increased with the increasing of baseline C-peptide levels, though these associations became unsignificant using the multivariate Cox regression model. Unlike the participants without previous T2DM, the associations of C-peptide with cardiovascular biomarkers and events were not significant in the patients with previous T2DM.

Conclusions

The associations of C-peptide with cardiovascular biomarkers and events were different between the participants without previous T2DM and those with previous T2DM. The effect of C-peptide on cardiovascular risk may be bidirectional, play a benefit role at a low level, and play a harmful role at a high level in the nondiabetic adults and the patients with newly diagnosed T2DM.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12933-022-01636-z.

Relation between the insulin lowering rate and changes in bone mineral density: Analysis among subtypes of type 1 diabetes mellitus

AIMS/INTRODUCTION

Bone mineral density (BMD) in patients with type 1 diabetes mellitus (T1DM) is reduced due to impaired insulin secretion. However, it is unclear whether the rate of BMD reduction is affected by T1DM subtypes. This study aimed to clarify the difference in BMD across T1DM subtypes: slowly progressive (SP), acute-onset (AO), and fulminant (F).

METHODS

This was a retrospective, single-center, cross-sectional study conducted on 98 adult T1DM patients. The main outcome included the BMD Z-score (BMD-Z) measured at the lumbar spine (LS) and femoral neck (FN).

RESULTS

The LS BMD-Z was lower in the AO than in the SP (p =0.03). No differences were observed when compared to the F. The FN BMD-Z tended to be higher in the SP than in the AO and F. Multiple regression analyses showed that the LS BMD-Z was associated with subtypes (AO vs. SP) (p =0.01), but not subtypes (F vs. SP), adjusted for sex, duration, retinopathy, and C-peptide immunoreactivity (CPR). When patients were divided into disease duration tertiles, in the first and second tertiles, the CPR levels were lower in the AO or F than in the SP. In contrast, LS and FN BMD-Z differed between the AO and SP only in the second tertiles (both p <0.01), with a similar tendency between the F and SP.

CONCLUSIONS

Among T1DM subtypes, BMD has time-dependent changes, which reveals that BMD decline follows impaired insulin secretion. These results provide novel insights into the association between the low insulin exposure duration and BMD.

Role of Na+, K+-ATPase ion pump in osteoinduction

Porous biphasic calcium phosphate bioceramic (BCP) possesses osteoinductivity to induce the osteoblastic commitment of mesenchymal stem cells (MSCs) and ectopic bone formation. However, the underlying mechanism remains enigmatic. We performed a gene array analysis of MSCs cocultured with BCP to screen for candidate osteoinductive modulators. Na⁺, K⁺-ATPase (NKA), an ion transporter, therefore was identified as a crucial ion transporter in regulating the osteogenesis of the cells. NKA activator, a polyclonal antibody, enriched the cytomembrane abundance of NKA and lead to an enhanced osteogenic effect of BCP. As indicated in gene array analysis and suggested by co-immunoprecipitation assay, protein phosphatase 2A (PP2A) was elevated by BCP to dephosphorylate NKA and prevent its endocytosis. The inhibition of NKA by ouabain resulted in an adverse effect on osteoinductivity of BCP. We further altered NKA activity in mice implanted with BCP and found that the intensity and incidence of osteoinduction was increased by the NKA activator. We went one step further by investigating the potential of targeting NKA in osteoporotic bone regeneration. Activating NKA upregulated osteogenic gene expression and calcium deposition ability of osteoporotic osteoblasts. Furthermore, activation of NKA in mice ameliorated estrogen-deficiency induced bone loss, in terms of increased bone mass and improved bending strength. With this osteoinductive bioceramic derived ion transporter target, we demonstrate that the activation of NKA has significant potential to revolutionize the regeneration of bone. STATEMENT OF SIGNIFICANCE: In this study, we identified an important role of Na⁺, K⁺-ATPase (NKA) have played in osteoinductivity of biphasic calcium phosphate bioceramic (BCP). Furthermore, we demonstrated the therapeutic potential of targeting NKA in osteoporotic bone regeneration. Numerous gene and protein targets to treat osteoporosis were discovered every year, mainly obtained by genomic and proteomic screenings of a large population. In contrast, our study identified an unrevealed bone regenerating target from the upregulated genes induced by an osteoinductive biomaterial. The approach was cost-saving since it did not require a large sample pool. Furthermore, the target derived from this approach was proven to be anabolic. Identification of an anabolic agent holds significant value since most of the current anti-osteoporotic therapies are antiresorptive.

Bone mineral density spectrum in individuals with type 1 diabetes, latent autoimmune diabetes in adults, and type 2 diabetes

OBJECTIVE

To assess bone mineral density (BMD) and associated clinical factors in patients with type 1 diabetes (T1D), latent autoimmune diabetes in adults (LADA), and type 2 diabetes (T2D) and in non-diabetic subjects.

METHODS

Total 108 age-, sex-, disease duration-, and postmenopausal ratio-matched patients with T1D, LADA, and T2D each and 216 age-, sex-, and postmenopausal ratio-matched non-diabetic controls. Anthropometric, biochemical, and BMD data were collected and analysed.

RESULTS

BMD of total hip and lumbar spine of individuals in the LADA group was lower than those in the T2D and control groups but higher than those in the T1D group. After adjusting for body mass index (BMI), a significant difference in BMD in the lumbar spine was seen between groups. After adjustment for smoking, BMI, 25-(OH) vitamin D, calcium, haemoglobin A1c, and diabetic complication scores, BMD values of patients in LADA group were not significantly different from those of patients in T1D and T2D groups. Multiple stepwise regression analysis showed that BMD was (a) positively associated with weight and C-peptide, and negatively associated with age in patients with diabetes, (b) positively associated with C-peptide in the T1D and LADA groups. The proportion of patients with osteoporosis in the T1D, LADA, T2D, and control groups was 55.6%, 45.4%, 34.3%, and 26.9%, respectively.

CONCLUSIONS

BMD values in T1D, LADA, and T2D were in an increasing order of mention. Patients with autoimmune diabetes were more susceptible to osteoporosis. A lower C-peptide level may be responsible for decreased BMD in individuals with autoimmune diabetes.

Effects of C-Peptide Replacement Therapy on Bone Microarchitecture Parameters in Streptozotocin-Diabetic Rats

C-peptide therapy protects against diabetic micro- and macrovascular damages and neuropatic complications. However, to date, the role of C-peptide in preventing diabetes-related bone loss has not been investigated. Our aim was to evaluate if C-peptide infusion improves bone quality in diabetic rats. Twenty-three male Wistar rats were randomly divided into three groups: normal control group; sham diabetic control group; diabetic plus C-peptide group. Diabetes was induced by streptozotocin injection and C-peptide was delivered subcutaneously for 6 weeks. We performed micro-CT and histological testing to assess several trabecular microarchitectural parameters. At the end, diabetic plus C-peptide rats had a higher serum C-peptide (p = 0.02) and calcium (p = 0.04) levels and tibia weight (p = 0.02) than the diabetic control group. The diabetic plus C-peptide group showed a higher trabecular thickness and cross-sectional thickness than the diabetic control group (p = 0.01 and p = 0.03). Both the normal control and diabetic plus C-peptide groups had more Runx-2 and PLIN1 positive cells in comparison with the diabetic control group (p = 0.045 and p = 0.034). Diabetic rats receiving C-peptide had higher quality of trabecular bone than diabetic rats not receiving this treatment. If confirmed, C-peptide could have a role in improving bone quality in diabetes.

Osteoporosis pathology in people with severe motor and intellectual disability

OBJECTIVES

We assessed the severity and pathology of osteoporosis in children and adults with severe motor and intellectual disabilities (SMID) by evaluating bone enzymes, by which we aimed to determine adequate treatment approaches for preventing fractures.

METHODS

Ninety patients (44 men, 46 women; mean age, 34.5 years) underwent bone quality assessment. Quantitative ultrasonography (QUS) was used to measure the T-score and Z-score of the calcaneus, and blood tests were used to measure bone-specific alkaline phosphatase and tartrate-resistant acid phosphatase 5b levels as bone formation and resorption markers, as well as calcium, phosphorous, and parathyroid hormone levels as routine examination.

RESULTS

Bone formation and resorption marker levels were within normal ranges in adults, although they were high during the growth period in children and adolescents and in elderly women. Patients receiving tube feeding showed a significantly lower Z-score than those without tube feeding. Tube feeding was a significant factor for the Z-score, whereas age, vitamin supplements, and anti-epileptic drugs were not.

CONCLUSIONS

The severity of osteoporosis in SMID started during the growth period and seems to be caused by a lack of an effective increase in bone mineral density. Any treatment should be started during the growth period. More study about tube feeding is needed.

Multiple Cell Signalling Pathways of Human Proinsulin C-Peptide in Vasculopathy Protection

A major hallmark of diabetes is a constant high blood glucose level (hyperglycaemia), resulting in endothelial dysfunction. Transient or prolonged hyperglycemia can cause diabetic vasculopathy, a secondary systemic damage. C-Peptide is a product of cleavage of proinsulin by a serine protease that occurs within the pancreatic β-cells, being secreted in similar amounts as insulin. The biological activity of human C-peptide is instrumental in the prevention of diabetic neuropathy, nephropathy and other vascular complications. The main feature of type 1 diabetes mellitus is the lack of insulin and of C-peptide, but the progressive β-cell loss is also observed in later stage of type 2 diabetes mellitus. C-peptide has multifaceted effects in animals and diabetic patients due to the activation of multiple cell signalling pathways, highlighting p38 mitogen-activated protein kinase and extracellular signal-regulated kinase ½, Akt, as well as endothelial nitric oxide production. Recent works highlight the role of C-peptide in the prevention and amelioration of diabetes and also in organ-specific complications. Benefits of C-peptide in microangiopathy and vasculopathy have been shown through conservation of vascular function, and also in the prevention of endothelial cell death, microvascular permeability, neointima formation, and in vascular inflammation. Improvement of microvascular blood flow by replacing a physiological amount of C-peptide, in several tissues of diabetic animals and humans, mainly in nerve tissue, myocardium, skeletal muscle, and kidney has been described. A review of the multiple cell signalling pathways of human proinsulin C-peptide in vasculopathy protection is proposed, where the approaches to move beyond the state of the art in the development of innovative and effective therapeutic options of diabetic neuropathy and nephropathy are discussed.

Role of structured individual patient education in the prevention of vascular complications in newly diagnosed type 2 diabetes: the INdividual Therapeutic Education in Newly Diagnosed type 2 diabetes (INTEND) randomized controlled trial

OBJECTIVE

Recent studies showed that a structured patient therapeutic education (PTE) may decrease both mortality and the development of diabetes complications. Nevertheless, no data are available in the literature on the impact of individual PTE on the complications in newly diagnosed type 2 diabetic patients. Aim of the present randomized controlled trial is to evaluate the impact of individual PTE on the occurrence of macrovascular complications in newly diagnosed type 2 diabetic patients when compared to usual care (UC) and group PTE.

DESIGN AND METHODS

Six hundred newly diagnosed type 2 diabetic patients will be enrolled. The patients will be randomly assigned to one of these three groups: individual PTE, group PTE and UC. A comprehensive and complete PTE will be delivered to all the patients: PTE will include eleven themes. Primary composite endpoint of the study is occurrence of vascular complications, including cardiovascular death, non fatal coronary disease, non fatal stroke, peripheral artery disease. Secondary endpoints are: foot ulcers, amputations, sexual dysfunction, quality of life, microvascular complications, bone health, intensification of diabetes and hypertension therapy.

RESULTS AND CONCLUSIONS

The present trial can give precious information on the features for the most effective PTE.

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

PURPOSE

C-peptide secretion is deficient or absent in type 1 diabetes mellitus. It is well accepted that insulin replacement therapy cannot prevent the development of long-term diabetes-related complications, which can often be disabling or even life-threatening. Several cross-sectional investigations have suggested that residual C-peptide production in patients with type 1 diabetes mellitus would help prevent a number of complications. In animal models of diabetes and in patients with type 1 diabetes mellitus, C-peptide replacement improves renal function, skin and skeletal muscle blood flow, nerve conduction, glucose utilization, and other diabetes-related complications. Recent investigations suggest a new beneficial effect of C-peptide, which to date has never been studied. It is known that osteoporosis is the most prevalent short-term complication in type 1 diabetes mellitus. This review will highlight new insights into the pathophysiology and future therapeutic modalities for osteoporosis in individuals with diabetes.

METHODS

This review provides a concise summary of old and new insights into the role of C-peptide in diabetes-related complications.

RESULTS

The data suggest that C-peptide is a bioactive peptide, acting independently of insulin, which binds to a G-protein-coupled membrane binding site in different cell types. By triggering Ca²⁺-dependent intracellular signaling pathways, both Na⁺, K⁺-ATPase and endothelial nitric oxide synthase are activated. C-peptide may act on osteoblast cells by ERK 1/2 pathway activation, modulate collagen biosynthesis and RANKL expression. Furthermore, C-peptide-deficient postmenopausal women, not affected by diabetes, have a lower bone mineral density than those with normal C-peptide levels.

CONCLUSION

Taken together these studies encourage further investigations to elucidate the role of C-peptide in preventing bone loss in type 1 diabetes mellitus and in those individuals with C-peptide deficiency and osteoporosis.

Association between low C-peptide and fragility fractures in postmenopausal women without diabetes

PURPOSE

C-peptide has been shown to exert several, previously unknown, biological effects. A recent cross-sectional study demonstrated an association between low C-peptide serum levels and low lumbar bone density of postmenopausal women not affected by diabetes. To date, very little research attention has been directed toward the association between C-peptide and osteoporotic fractures. To contribute toward filling this gap, we investigated the association between C-peptide and fractures in postmenopausal women.

METHODS

A cohort of 133 non-diabetic postmenopausal women with and without a history of fractures was evaluated in this cross-sectional investigation. Standardized interviews were performed to gather information on the patients' fracture history. All of the participants underwent a bone mineral density assessment by DXA, radiographs, and a serum C-peptide measurement.

RESULTS

Thirty-four women presented fractures. Bivariate analysis revealed an inverse correlation between C-peptide and fractures (r = -0.27, p = 0.002). A significant difference in mean C-peptide levels was also found between women with vs. without fractures (p = 0.01, adjusted for age, BMI and glucose). Logistic regression analysis showed that C-peptide levels, femoral and vertebral BMD were all negatively associated with fracture status (B = -1.097, ES = 0.401, p = 0.006, 95% CI 0.15-0.73; B = -15.6, SE = 4.17, p < 0.001, CI 0.001-0.002; B = -24.8, SE = 5.23, p < 0.001, CI 0001-0.002; respectively).

CONCLUSIONS

This study confirms an inverse association between serum C-peptide levels and a history of fractures in postmenopausal women without diabetes. These results suggest that C-peptidemay exert an effect on bone mineral density. However, further large-scale studies are needed to corroborate this finding and investigate the potential underlying mechanisms involved.

Evaluation of circulating sRAGE in osteoporosis according to BMI, adipokines and fracture risk: a pilot observational study

Background

Osteoporosis is a systemic metabolic disease based on age-dependent imbalance between the rates of bone formation and bone resorption. Recent studies on the pathogenesis of this disease identified that bone remodelling impairment, at the base of osteoporotic bone fragility, could be related to protein glycation, in association to oxidative stress. The glycation reactions lead to the generation of glycation end products (AGEs) which, in turn, accumulates into bone, where they binds to the receptor for AGE (RAGE). The aim of this study is to investigate the potential role of circulating sRAGE in osteoporosis, in particular evaluating the correlation of sRAGE with the fracture risk, in association with bone mineral density, the fracture risk marker FGF23, and lipid metabolism.

Results

Circulating level of soluble RAGE correlate with osteopenia and osteoporosis level. Serum sRAGE resulted clearly associated on the one hand to bone fragility and, on the other hand, with BMI and leptin. sRAGE is particularly informative because serum sRAGE is able to provide, as a single marker, information about both the aspects of osteoporotic disease, represented by bone fragility and lipid metabolism.

Conclusions

The measure serum level of sRAGE could have a potential diagnostic role in the monitoring of osteoporosis progression, in particular in the evaluation of fracture risk, starting from the prevention and screening stage, to the osteopenic level to osteoporosis.

Bone turnover response is linked to both acute and established metabolic changes in ultra-marathon runners

Bone and energy metabolisms regulation depends on a two-way street aimed at regulating energy utilization. Mountain ultra-marathons are highly demanding aerobic performances that deeply affect the whole body homeostasis. In this study we aimed to investigate and characterize the metabolic profile (in terms of hormones involved in energy metabolism), the inflammatory adipokines, and the bone turnover; in particular the osteocalcin-mediated response has been compared in experienced mountain ultra-marathons runners versus control subjects. Serum concentrations of specific markers of bone turnover (pro-collagen type I N-terminal propeptide, carboxylated/undercarboxylated osteocalcin), measured by enzyme-linked immunosorbent assay, and metabolic hormones (C-peptide, insulin, glucagon, glucagon-like peptide, gastric-inhibitory peptide, ghrelin, leptin, resistin, and visfatin), measured by fluorescent-based multiplex assay, were compared before and after a 65 km mountain ultra-marathons in 17 trained runners and 12 age-matched controls characterized by a low physical activity profile. After the mountain ultra-marathons, runners experienced a reduction in pro-collagen type I N-terminal propeptide, though it remained higher than in controls; while carboxylated osteocalcin remained unchanged. Among the metabolic hormones, only glucagon and leptin were different between runners and controls at rest. C-peptide and leptin decreased after the mountain ultra-marathons in runners; while glucagon, glucagon-like peptide 1, resistin, and visfatin were all increased. Uncarboxylated osteocalcin (and uncarboxylated/carboxylated osteocalcin ratio) was decreased and this highly correlated with insulin and C-peptide levels. In conditions of high energy expenditure, homeostasis is maintained at expenses of bone metabolism. Changes in the uncarboxylated osteocalcin clearly mark the global energy needs of the body.

Proinsulin C-peptide modulates the expression of ERK1/2, type I collagen and RANKL in human osteoblast-like cells (Saos-2)

A lower bone mass accompanied by a higher bone fragility with increased risk of fracture are observed in individuals with type 1 diabetes mellitus. Low C-peptide levels are associated with low lumbar mineral density in postmenopausal woman. In this work, we investigated the role of C-peptide on the osteoblast cell biology in vitro. We examined intracellular pathways and we found that C peptide activates ERK1/2 in human osteoblast-like cells (Saos-2). We also observed that proinsulin C-peptide prevents a reduction of type I collagen expression and decreases, in combination with insulin, receptor activator of nuclear factor-κB (RANKL) levels. In this work we show for the first time that Cpeptide activates a specific intracellular pathway in osteoblasts and it modulates the expression of protein involved in bone remodeling. Our results suggest that both C-peptide may have a role in bone metabolism. Further studies are needing to fully clarify its role.

Dietary Patterns and Fractures Risk in the Elderly

PURPOSE

Although the role of dietary factors in the prevention of bone loss and fractures has been investigated in many studies, few studies have examined the association between dietary patterns and total body bone density. Our aim was to determine the relations between dietary patterns and whole-body bone mineral density (WB-BMD) and the association between dietary patterns, fractures, and multiple fractures in the elderly.

METHODS

This cross-sectional study included 177 individuals aged ≥65 years. A dual X-ray absorptiometry scan was performed to measure BMD. Dietary patterns were ascertained by a combination of dietary intake assessment and principal components analysis.

RESULTS

Only three dietary patterns correlated with whole-body bone density. The multivariate-adjusted mean bone density across tertiles of these dietary patterns showed that the highest tertile of both the patterns 1 and 2 had a significantly higher bone density than the lowest tertile (pattern 1: 1.021 ± 0.01 and 1.070 ± 0.01 g/cm² for T1 and T3, respectively; p = 0.043; pattern 2: 1.023 ± 0.01, and 1.081 ± 0.01 g/cm² for T1 and T3, respectively; p = 0.003). We also find significant gender difference in these results. The highest adherence to the dietary pattern 5 was associated with decreased odds of having fractures (OR = 0.20, p = 0.009), and adherence to the pattern 1 was negatively associated with multiple fractures.

CONCLUSION

A high adherence to the dietary pattern 1 (high intake of grains, fish and olive oil) was associated with a high BMD and a low number of fractures. The highest adherence to the dietary pattern 5 (legumes and wine) was associated with decreased odds of having fractures. Our finding would suggest a potential bone-preserving properties of specific dietary patterns in the elderly.

Bone Microarchitecture in Type 1 Diabetes: It Is Complicated

Patients with type 1 diabetes (T1DM) experience a disproportionate number of fractures for their bone mineral density (BMD). Differences in bone microarchitecture from those without the disease are thought to be responsible. However, the literature is inconclusive. New studies of the microarchitecture using three-dimensional imaging have the advantage of providing in vivo estimates of "bone quality," rather than examining areal BMD alone. There are drawbacks in that most studies have been done on those with less than a 30-year duration of T1DM, and the techniques used to measure vary as do the sites assessed. In addition to the rise in these imaging techniques, very recent literature presents evidence of an intimate relationship between skeletal health and vascular complications in T1DM. The following review provides an overview of the available studies of the bone microarchitecture in T1DM with a discussion of the burgeoning field of complications and skeletal health.