Correlation between IGF-2 and IGF-1 levels in type 1 diabetic Iraqi patients

BACKGROUND

Diabetes Mellitus (DM) is considered a global epidemic, causing several complications, such as cardiovascular mortality, diabetic retinopathy, diabetic nephropathy, and kidney failure, which is a profound socioeconomic challenge to public health. Lifestyle and rapid ecological shifts have changed risk factors and diabetes epidemiology [1][2]. Recent studies show that there are More than 240 million individuals with Diabetes, and this may reach 370 million people in 2030. Generally, T1D (Type 1 diabetes mellitus) is a subtype of diabetes observed in young people with an insulin disorder. T1D people account for about 5–10% of cases of total diabetes worldwide [3–5]. While research is ongoing, comprehensive screening for T1D is still evolving. T1D is believed to arise from a combination of impaired immune regulation and reduced β-cell viability or function, which results in hyperglycemia; thus, exogenous insulin replacement is necessary for treatment [6]. The (IGF axis) insulin-like growth factor axis, IGF-1 and IGF-2, has been suggested as a promising approach for addressing these deficiencies, leading to diabetic complications Risk [7][8]. Dysregulation of IGFs has been observed both prior to and following the diagnosis (clinically) of T1D, suggesting their potential as innovative biomarkers for enhancing disease prediction [9][10]. Structurally, IGF-1 and IGF-2 share significant similarities with insulin and can exert comparable metabolic effects. However, in T1D, they are incapable of compensating for the loss in insulin production [11][12].

In type 1 diabetes (T1D), the insulin-like growth factor (IGF) system is profoundly disrupted, characterized by suppressed levels of both IGF-1 and IGF-2 alongside elevated IGF-binding protein-1 (IGFBP-1). This imbalance, reflected in an altered IGF-1/IGF-2 ratio, emerges early in the disease process and persists with long-term duration. The dysregulation is influenced by factors such as pubertal status, glycemic control, and disease duration, contributing to impaired anabolic signaling, growth disturbances in children, and potential links to chronic complications. Insulin deficiency in T1D drives a disproportionate decline in IGF-1 relative to IGF-2, shifting their physiological equilibrium. Consequently, the IGF-1/IGF-2 ratio may offer a more integrated assessment of metabolic derangement than measurement of either factor alone. To capture this broader perspective, the present study evaluated the IGF-1/IGF-2 ratio as a complementary marker of IGF axis disruption in type 1 diabetes. [13][14]. IGFs are hormones predominantly proven to be produced in the liver that promote cellular proliferation through the broadly expressed IGF-1 receptor. The production of IGFs is temporally regulated, with IGF-2 playing a crucial role primarily during fetal and embryonic development, while IGF1 is essential in postnatal growth [15]. Insulin is a key regulator for hepatic IGF-1 production; in T1D, the deficiency of insulin will directly impact the liver’s ability to produce IGF-1. Also, the increasing levels of IGF-binding proteins, particularly IGFBP-1 and IGFBP-3, can bind to IGF-1, limiting its availability and biological activity [16]. Moreover, oxidative stress and chronic inflammation, which are common in T1D, will suppress IGF-1 production [17].

According to recent studies, levels of IGF-1 are linked with the progression of microvascular complications like retinopathy and nephropathy in T1D [18]. Overexpression of IGF-2 in patients with T1D (overexpression in beta cells in the pancreas) will impair beta cells’ function and increase susceptibility to damage, which suggests its role in the progression of T1D disease [19][20]. Studying IGF-2 in T1D levels gives better biomarkers for diagnosis, prediction, and therapeutic strategies (such as targeting IGF-binding proteins to improve metabolic outcomes) as IGF-2 has been proven to have a pivotal role in growth, development, and metabolism [21]. In the circulation, about 98% of insulin-like growth factors (IGFs) are bound to special proteins known as IGF-binding proteins (IGFBPs), which regulate the transport of IGF-1 into target cells and perform multiple functions [22]. These proteins not only transport IGFs, but also play a regulatory role in the hormonal effects of IGFs by controlling their availability to their receptors. In addition, IGFBPs produced locally within tissues act as autocrine or paracrine regulators of IGF activity [23][24]. Patients with T1D suffer from low levels of IGF-1, both in its total form and free form, along with disturbances in other components of the IGF axis [25][26]. In 1984, research was done on the impact of glycemic control on serum IGFs in DM, and it revealed that IGF-2 values were not affected by glycemic control in all subjects [27]. Insulin, IGF-1, and IGF-2 are peptides that have similar structures associated with the same receptors. These receptor-ligand associations induce intracellular signaling cascades, resulting in regulation and metabolic effects that may be linked to hypoglycemia or diabetes complications [18]. In 2020, Claire Greenhill’s study demonstrated that serum concentrations of IGF-1 and IGF-2 were significantly lower in individuals testing positive for (T1D)-predictive autoantibodies (AAb+) compared to AAb−relatives of T1D participants. Additionally, the research indicated that IGF-1 levels tended to decline as the duration of the disease progressed [28]. Recently, a study has indicated that IGF-2 can cause hypoglycemia through its interaction with both insulin and IGF receptors. Patients with IGF-2-induced hypoglycemia exhibit a fasting hypoglycemic state, characterized by decreased levels of ketones, IGF-1, endogenous insulin, and growth hormone (GH) [29][30].

Comprehension of the IGF family in T1D is important for controlling insulin treatment, reducing diabetes complications, and looking at new therapies. The future direction of IGF pathways may improve β-cell regeneration and metabolic control and contribute to better long-term management of T1D [18][31].

RESEARCH AIM

The aim of this study is to evaluate serum IGF-2 levels in adult Iraqi patients with type 1 diabetes and to examine the relationship between these levels and IGF-1.

MATERIALS AND METHODS

Study design and patients

This cross-sectional study included 160 individuals matched for age and gender (80 patients with type 1 diabetes and 80 healthy controls), age and sex matched, recruited between September and December 2024 at the National diabetes center, Mustansiriyah University. Patients were diagnosed with type 1 diabetes by endocrinology specialists based on American Diabetes Association criteria, including clinical history, the need for continuous insulin therapy, and documented presence of at least one autoantibody (GAD, IA-2, or ZnT8) and low levels of C-peptide (<0.2 nmol/L). Only patients who had been followed for at least one year and were receiving regular insulin therapy were included in the study.

Exclusion criteria: patients who have hepatic or renal dysfunction, pregnancy, recent infections, use of immunosuppressants, anti-inflammatory drugs, or those receiving corticosteroids, GH therapy, or nutritional supplements that affect IGF levels. At the same time, the healthy group is composed of those who do not have any diabetes or systemic disease.

Place and period of the research

Place of the research

National diabetes center/Mustansiriyah University.

Period of the research

From September 2024 until December 2024.

Methods

A total of eight milliliters of blood was collected using a disposable plastic needle, with the sample divided into two parts: one placed in a disposable gel tube and the remaining 2 mL transferred to an Ethylenediaminetetraacetic acid (EDTA) tube. The gel tube samples were centrifuged for 7 minutes at 3000 rpm to separate the serum for laboratory analysis. BMI (Body mass index) was calculated using the following formula: BMI = weight (kg)/height² (m²).

IGF-1 levels were measured using a DiaSorin analyzer with the Elecsys IGF-1 kit (Germany). Fasting Blood Sugar (FBS), Blood Urea (B.U), Serum Creatinine (S.C), and Lipid Profile tests were performed using the Cobas C1-11 device with respective kits (Gluc2, UREAL, CREP2, Cholesterol, Triglyceride, Low-density lipoprotein (LDL), and High-density lipoprotein (HDL) kits). Hemoglobin A1c levels were assessed using the A1C-3 Kit on the same Cobas C1-11 device. IGF-2 levels were quantified using the ELISA method with the Human IGF-2 ELISA Kit (ELK Biotechnology, USA).

Statistical analysis

This study performed statistical analyses via SPSS version 26.0 (SPSS Inc., Chicago, IL, USA). The Shapiro-Wilk test was used to assess whether the data followed a parametric (normal) or non-parametric distribution; all parameters were found to exhibit non-parametric distributions. Consequently, to analyze statistical differences between the T1D group and the control group, the Mann-Whitney U was used. The results are presented as medians, along with the minimum and maximum values. Moreover, to analyze relationships between different variables, the Spearman correlation test was also used. When the p-value was less than 0.05, the results were considered statistically significant.

Ethics review

Based on the information in the research report, The Ethics Committee at Mustansiriyah University/National Diabetes Center reviewed the article report we submitted on 05-09-2024. The review process included assessing the research’s objectives, informed consent process, participant recruitment procedures, methodology, plans for data management, and confidentiality measures.

RESULTS

Eighty patients (diagnosed with T1D) and 80 control subjects were included in our study. The mean age = 30.15 years and SD 9.68. Among patients: 45 males (56.3%) and 35 females (43.7%). Among controls: 43 males (53.8%) and 37 females (46.3%). The gender of the patients was roughly distributed in Figure 1.

The current study investigated levels of IGF-2 in T1D patients and healthy controls. Additionally, this study further explored the variations in the concentrations of IGF-1, FBS, HbA_1c, and IGF1/IGF-2 Ratio (IGF1/2 Ratio) among different cohorts. All the studied parameters have shown significant differences between healthy controls and T1D patients (p=0.000), as in Table 1.

Moreover, the current study has measured (TG) Triglyceride, (CH) total cholesterol, (HDL) high-density lipoprotein, (LDL) low-density lipoprotein, (VLDL) very low-density lipoprotein, (B.U) Blood Urea, and (S.C) Serum Creatinine levels to all of the studied groups, and the statistics revealed that there is a difference that is significant between all the biochemical parameters (p<0.05) see Table 2.

Also, correlation studies showed a positive correlation between FBS and HbA_1c: (r=0.601, p=0.000), FBS and IGF-2: (r=0.540, p=0.000), HbA_1c and IGF-2: (r=0.740, p=0.000), IGF-1 and IGF-1/2 Ratio: (r=0.754, p=0.000). while, a negative correlation were observed between FBS and IGF-1: (r=-0.694, p=0.000), FBS and IGF-1/2 Ratio: (r=-0.604, p=0.000), HbA_1c and IGF-1: (r=-0.702, p=0.000), HbA_1c and IGF-1/2 Ratio: (r=-0.750, p=0.000), IGF-2 and IGF-1: (r=-0.648, p=0.000), IGF-2 and IGF-1/2 Ratio: (r=-0.967, p=0.000) see Table 3.

While BMI shows a positive correlation with all of the following: FBS (r=0.293, p=0.018), HbA_1c (r=0.325, p=0.008), IGF-2 (r=0.339, p=0.006). And a negative correlation with both IGF-1 (r=-0.280, p=0.024) and IGF-1/2 Ratio (r=-0.328, p=0.009), Table 3.

DISCUSSION

This study compared IGF-1 and IGF-2 levels in patients with type 1 diabetes and healthy individuals, and investigated the relationship between these parameters and glycemic indicators. The results showed that IGF-1 levels were lower and IGF-2 levels were higher in the type 1 diabetes group. IGF-1 production is largely regulated by insulin and growth hormone. Insulin deficiency, seen in type 1 diabetes, may contribute to decreased IGF-1 synthesis in the liver. Chronic hyperglycemia and metabolic stress have also been reported to suppress IGF-1 production. This appears consistent with the negative correlation between IGF-1 and HbA_1c and FBS observed in our study. Correlation analyses were conducted to examine relationships among these variables. Results revealed significant differences in all biochemical parameters between patients and controls (p<0.05), as well as notable correlations among FBS, HbA_1c, IGF-1, IGF-2, and other variables. These findings highlight key biochemical alterations in T1D, as Khan et al. studied in 2023 [32].

The observed significant differences between IGF-2 and IGF-1 values in T1D and healthy controls suggest a dysregulation of the IGF system in T1D. Growth hormone (GH) stimulates the synthesis of IGF-1 in the liver and peripheral tissues; later, IGF1 mediates GH’s anabolic and metabolic effects, including stimulation of muscle mass, bone growth, and glucose uptake via endocrine, autocrine, and paracrine pathways. IGF-1 is considered the main mediator of GH in both growth and metabolic regulation [33]. It is known to play a critical role in glucose metabolism, insulin sensitivity, and tissue repair. Reduced IGF-1 levels in T1D patients, as indicated by the negative correlations with FBS and HbA_1c, align with previous studies showing that chronic hyperglycemia and insulin deficiency suppress IGF-1 production. Since the liver is the primary organ responsible for producing IGF-1, when the liver is stressed by prolonged high glucose levels, IGF-1 production decreases, as stated by Kubo et al. [34].

On the other side, the elevated IGF-2 concentrations in T1D patients, as evidenced by the positive correlations with FBS and HbA_1c, may reflect compensatory mechanisms or altered metabolic pathways; this aligns with Crowley et al. findings that observed elevated IGF-2 levels in T1D patients and suggest IGF-2’s role in glucose regulation (as IGF-2 can function similarly to insulin, causing a reduction in blood sugar levels by binding to insulin receptors and IGF receptors) [28]. IGF-2, which is less dependent on GH regulation than IGF-1, may be upregulated in response to persistent hyperglycemia. However, this increase in IGF-2 does not appear to compensate for the reduced IGF-1 levels, as suggested by the strong negative correlation between IGF-1 and IGF-2 (r=-0.648, p=0.000). This inverse relationship underscores the complex interplay between these two growth factors in the context of metabolic dysfunction [11][35].

The strong positive correlations between FBS, HbA_1c, and IGF-2 (r=0.540–0.740, p=0.000) indicate that higher blood glucose levels are associated with higher IGF-2 concentrations. This finding supports the hypothesis that IGF-2 may be used as an indicator of chronic hyperglycemia in patients with T1D [24]. Conversely, the negative correlations between FBS, HbA_1c, and IGF-1 (r=-0.694 to -0.702, p=0.000) highlight the detrimental effects of poor glycemic control on IGF-1 synthesis. These results are consistent with prior studies, [24][36][37] demonstrating that chronic hyperglycemia impairs the GH/IGF-1 axis and leads to reduced IGF-1 bioavailability, as in Clemmons’ study (2007) [38].

In this study, statistically significant differences were observed in lipid profile parameters between patients with type 1 diabetes and a healthy control group (p < 0.05). However, contrary to the classic diabetic dyslipidemia pattern, median TG, CH, LDL, and VLDL values were found to be higher in the control group compared to the patient group. This unexpected finding can be explained by various factors such as individuals’ dietary habits, use of lipid-lowering therapy, metabolic differences, or characteristics of the sample group. Therefore, the results obtained should be interpreted cautiously and may not directly reflect the typical dyslipidemia profile specific to diabetes.

Furthermore, the higher HDL levels in the control group suggest that this group has a more balanced lipid profile. The observed differences in renal function markers (blood urea and serum creatinine) may be indicative of early metabolic or renal changes in patients with type 1 diabetes. Elevated blood urea and serum creatinine levels suggest early signs of diabetic nephropathy, which is consistent with the known microvascular complications of T1D [24].

Kubo et al. (2022) noted that increased adiposity in obese patients could be a key contributing factor to the heightened prevalence of comorbidities associated with various metabolic disorders [34]. In the present study, the positive correlations between BMI and FBS, HbA_1c, and IGF-2 (r=0.293–0.339, p<0.05) suggest that increased adiposity exacerbates hyperglycemia and alters IGF-2 levels. Obesity is a known risk factor for insulin resistance, even in T1D patients, and may contribute to the dysregulation of the IGF system [35].

Conversely, the negative correlations between BMI and IGF-1 (r=-0.280, p=0.024) and the IGF-1/2 Ratio (r=-0.328, p=0.009) further underscore the adverse effects of excess body weight on the GH/IGF-1 axis [38]. As Hoeflich and Russo noted in their study, Inhibition of IGF-1 production in the liver, resulting from obesity-related growth hormone resistance, may explain the low blood IGF-1 levels associated with increased obesity [39]. However, it remains unclear whether changes in liver IGF-binding protein (IGF-BP) production, caused by hyperinsulinemia, lead to decreased or increased IGF-1 levels, a matter of scientific debate [40].

The results of this study indicate that it is generally in line with previous research that has addressed the role of both IGF-1 and IGF-2 in diabetes. Studies have shown that lower IGF-1 levels are associated with poor blood sugar control, as well as an increased risk of diabetes complications such as nerve, kidney, or eye damage. Similarly, high levels of IGF-2 have been reported in cases of metabolic stress, such as obesity and diabetes, but the exact role of this hormone in these cases remains unclear. That is, despite the observation of its elevation, its direct effect or how it participates in the development of the disease still needs to be further researched and clarified [41][42]. IGF-2 expression may be influenced by nutritional status and insulin levels, and as seen in T1D, the body may increase IGF-2 production as a compensatory mechanism to try to compensate for impaired insulin signaling and decreased IGF-1 activity, yet it is insufficient in restoring normal glycemic control [16][43]. The inverse relationship between IGF-1 and IGF-2 observed in this study adds to the growing body of evidence suggesting a dynamic balance between these two growth factors. Also, in diabetic nephropathy, the weak renal clearance of IGF-2 will lead to its accumulation in circulation [44].

Due to its potential risks, some IGF therapies have shown an improvement in glycemic control and insulin sensitivity in animal models, but not in humans (it may lead to hypoglycemia or promote tumor growth spatially for IGF-2 therapies) [18][45]. The administration of IGF-1 to healthy people led to a decrease in blood glucose concentrations; however, its effect was equivalent to almost a tenth of the strength of the insulin effect. Recent evidence confirms that IGF-1 administration improves carbohydrate balance and insulin sensitivity. On the other hand, IGF-2 is less studied therapeutically; its modulation has not been explored clinically [46][47].

Unlike IGF-1, IGF-2’s role in T1D is not well established yet. IGF-2 may affect beta-cells and influence their susceptibility to damage, leading to dysfunction of these cells. Also, it may influence autoimmunity and inflammatory signaling [33][48]. Although the current study does not claim IGF-2 as a standalone diagnostic marker, the observed alterations in IGF-2 levels in T1D patients highlight its potential use as a prognostic indicator, and its measurement may help in future monitoring of therapeutic response, but it will need further validation.

Although this study provides important data on IGF axis disorders in T1D patients, there are a number of determinants that should be taken into account. The first of these determinants is the small size of the sample, which may affect the generalization power of the extracted results. In addition, some potential confusing factors, such as dietary pattern, physical activity level, and co-drugs, which may directly or indirectly affect IGF levels, have not been taken into account. In order to enhance the reliability of the results, it is recommended that future studies with a longitudinal design involving a larger number of participants take these variables into account.

CONCLUSION

This study reveals significant dysregulation of the IGF system in T1D patients, characterized by reduced IGF-1 and elevated IGF-2 levels, which correlate strongly with poor glycemic control (FBS and HbA_1c). These alterations are accompanied by systemic metabolic disturbances, including dyslipidemia, early signs of renal dysfunction, and associations with BMI. The inverse levels between IGF-1 and IGF-2 in T1D reflect pathological adaptations to chronic insulin deficiency. The findings underscore the potential of IGF-1 and IGF-2 as biomarkers of disease progression and highlight the need for further research into their therapeutic implications in T1D patients.

OTHER INFORMATION

The source of financing. No external funding was received for this work from any governmental, commercial, or non-profit organizations. The study was conducted using internal resources and the authors’ own input.

Conflicts of interest. We identify the importance of publishing research findings that contribute to scientific knowledge in diabetes mellitus. However, they affirm their commitment to conducting this study with integrity and transparency, regardless of the potential impact on their academic careers.

The authors confirm that they have disclosed these potential conflicts of interest to the journal editorial team. They are committed to conducting this research with the highest scientific rigor and integrity standards.

Participation of Authors. Emad Mahmoud Eltayef — significant contribution to the study design, data collection, analysis, and interpretation; writing and reviewing the manuscript; Karam Gharb — significant contribution to data analysis, interpretation, and manuscript preparation; Lujain A. Ghannawi — contribution to data collection, analysis, and manuscript writing; Safaa Ehssan Atta — significant contribution to the study design, data collection, analysis, and interpretation; writing and reviewing the manuscript; Isam Noori Salman — significant contribution to the study design, data collection, analysis, and interpretation; writing the manuscript. All authors reviewed and approved the final version of the manuscript and collectively agreed to take full responsibility for all aspects of the work, ensuring the accuracy and integrity of the content and addressing any concerns that may arise.

Acknowledgements. We thank all the diabetic patients who participated in this research and made this work possible. This study was supported by the Mustansiriyah University/National Diabetes Center.