Insulin-like growth factors and diabetes

Effects of concomitant obesity and diabetes on the aggressiveness and outcomes of differentiated thyroid cancer patients

OBJECTIVE

Obesity and diabetes are the risk factors for cancer development including differentiated thyroid cancer (DTC). Contradictory accumulated data indicates the possible negative effects of obesity and hyperglyceamia as a factor for aggressiveness of DTC. The aim of the present study is to investigate the association of high body mass index (BMI) and presence of type 2 diabetes mellitus (T2DM) on the histological aggressiveness and clinical outcomes in DTC patients followed for over 4 years in a single center.

METHODS

Consequative 526 DTC patients who had undergone total thyroidectomy and/or radioactive iodine (RAI) ablation were reviewed retrospectively. Patients were divided into groups based on their BMI: normal weight, overweight, obese and also were evalauted in 3 groups presence of diabetes, prediabetes and nomoglyceamia. Histological aggressiveness of DTC at the time of diagnosis and clinical response at the time of last clinical visit were reassessed according to the criteria suggested by ATA 2015 guideline.

RESULTS

No differences in histopathologic features, risk of recurrence, cumulative dose of RAI ablation and prevalence of 131I avid metastatic disease were demonstrated among the groups both classified according to BMI and hyperglycemia. Mean of 3.4 year follow-up also showed no differences in the clinial repsonse to therapy and percentage of nonthyroid primary cancer in DTC patients.

CONCLUSION

In this retrospective study we demonstrated that obesity and T2DM have no additive effect on DTC aggressiveness and response to therapy. DTC patients with obesity and diabetes can be treated according to present guidelines without requirement for spesific attention.

Increased kidney cancer risk in diabetes mellitus patients: a population-based cohort study in Lithuania

BACKGROUND

Diabetes is associated with increased risk of various cancers but its association with kidney cancer is unclear. The objective of this study was to evaluate the association between T2DM with or without metformin use and the risk of kidney cancer in a population-based national cohort in Lithuania.

METHODS

The cohort was composed of diabetic patients identified in the NHIF database during 2000-2012. Cancer cases were identified by record linkage with the national Cancer Registry. Standardized incidence ratios (SIRs) for kidney cancer as a ratio of observed number of cancer cases in diabetic patients to the expected number of cancer cases in the underlying general population were calculated.

RESULTS

T2DM patients (11,592) between 2000 and 2012 were identified. Overall, 598 cases of primary kidney cancer were identified versus 393.95 expected yielding an overall SIR of 1.52 (95% CI: 1.40-1.64). Significantly higher risk was found in males and females. Significantly higher risk of kidney cancer was also found in both metformin users and never-users' groups (SIRs 1.45, 95% CI: 1.33-1.60 and 1.78 95% CI: 1.50-2.12, respectively).

CONCLUSIONS

The patients with T2DM have higher risk for kidney cancer compared with the general Lithuanian population.

Lifestyle and Non-muscle Invasive Bladder Cancer Recurrence, Progression, and Mortality: Available Research and Future Directions

BACKGROUND:

A broad, comprehensive review of studies exploring associations between lifestyle factors and non-muscle invasive bladder cancer (NMIBC) outcomes is warranted to consolidate recommendations and identify gaps in research.

OBJECTIVE:

To summarize the literature on associations between lifestyle factors and clinical outcomes among patients with NMIBC.

METHODS:

PubMed was systematically queried for articles published through March 2019 regarding lifestyle factors and recurrence, progression, cancer-specific mortality, and all-cause mortality among patients with NMIBC.

RESULTS:

Notwithstanding many ambiguities, there is good-quality evidence suggesting a benefit of smoking avoidance/cessation, healthy body mass index (BMI), and type II diabetes mellitus prevention and treatment. Lactobacillus casei probiotic supplementation may reduce recurrence. There have been individual studies suggesting a benefit for uncooked broccoli and supplemental vitamin E as well as avoidance of supplemental vitamin B9, areca nut chewing, and a “Western diet” pattern high in fried foods and red meat. Additional studies do not suggest associations between NMIBC outcomes and use of fibrin clot inhibitors; insulin and other oral hypoglycemics; statins; supplemental selenium, vitamin A, vitamin C, and vitamin B6; fluid intake and intake of specific beverages (e.g., alcohol, coffee, green tea, cola); various dietary patterns (e.g., Tex-Mex, high fruit and vegetable, low-fat); and occupational and chemical exposures.

CONCLUSIONS:

Despite a myriad of publications on lifestyle factors and NMIBC, a need remains for research on unexplored associations (e.g., physical activity) and further studies that can elucidate causal effects. This would inform future implementation strategies for healthy lifestyle change in NMIBC patients.

Study on the relationship between insulin growth factor 1 and liver fibrosis in patients with chronic hepatitis C with type 2 diabetes mellitus

OBJECTIVE

To investigate the correlation between serum protein level of insulin growth factor 1 (IGF-1) and the degree of liver fibrosis in patients with chronic hepatitis C (CHC) combined with type 2 diabetes mellitus (T2DM).

METHODS

The cases are divided into four groups. Then serum levels of IFG-1, alanine aminotransferase (ALT), aspartate aminotransferase (AST), hepatitis C virus (HCV) RNA, and HCV genotypes were detected simultaneously in patients with hepatitis C, liver stiffness measurement (LSM) was measured by transient elastography, and aspartate aminotransferase platelet ratio (APRI) score was determined.

RESULTS

There was no significant difference between CHC with T2DM group and CHC group in diabetes family history (P > 0.05), but the difference between the two groups were significantly lower than that of T2DM group ( P < 0.05). The levels of fasting insulin and homeostatic model assessment of insulin resistance (HOMA-IR) in CHC group with T2DM group were significantly higher than those in the other two groups ( P < 0.05), while the IGF-1 RNA and the serum protein level in the two groups were significantly lower than those in the CHC group, and were lower than those in the control group ( P < 0.05). The level of serum IGF-1 was negatively correlated with HOMA-IR, LSM, and APRI score in CHC with T2DM group ( r = -0.71, -0.75, and -0.69; P < 0.01).

CONCLUSION

The degree of hepatic fibrosis in patients with CHC combined with T2DM was higher than that in non-T2DM patients with CHC, which was mainly related to insulin resistance (IR) induced by 1b genotype HCV infection. IR can lead to impaired synthesis of IGF-1, and the degree of damage has a corresponding relationship with hepatic fibrosis.

Impact of Glycemic Control and Metformin Use on the Recurrence and Progression of Non-Muscle Invasive Bladder Cancer in Patients with Diabetes Mellitus

The purpose of the present study was to determine the potential relationships of glycemic control and use of metformin with non-muscle invasive bladder cancer characteristics. We reviewed data from 645 patients with non-muscle invasive bladder cancer between January 2004 and May 2015. We analyzed the association of pre and post-operative glycemic control and use of metformin with clinical characteristics of bladder tumors. We also analyzed the association of glycemic control and use of metformin with recurrence-free and progression-free survivals. Diabetes mellitus patients showed decreased recurrence-free survival (hazard ratio 1.42; 95% confidence interval 1.1-1.9; P = 0.021) and progression-free survival (hazard ratio 1.79; 95% confidence interval 1.1-2.8; P = 0.013). Diabetes mellitus patients with a HbA1c ≥ 7.0% demonstrated a higher rate of progression (P = 0.026). Kaplan-Meier analysis showed that progression-free survival rate was associated with poor baseline glycemic control (P = 0.026) and post-operative glycemic control (P = 0.025). However, use of metformin had no impact on the recurrence (P = 1.00) and progression (P = 0.282). In conclusion, poor baseline and post-operative glycemic control was related with shorter progression-free survival of patients with non-muscle invasive bladder cancer. Use of metformin had no impact on the recurrence and progression. Therefore, tight glycemic control and close follow-up for bladder tumor may be beneficial in patients with poor glycemic control.

Hepatocellular Carcinoma in Diabetic Patients - a Single Center Experience

INTRODUCTION

Hepatocellular carcinoma (HCC) represents a major health concern worldwide; identifying risk factors and associated conditions that may lead to its development are therefore of utmost importance to the medical community. An association between diabetes mellitus (DM) and development of HCC on underlying liver conditions has been previously suggested. The aim of our study is to reveal possible significant statistical correlations between the two entities, which might warrant further study of the pathophysiological mechanisms behind this association.

PATIENTS AND METHODS

We have prospectively included consecutive cirrhotic patients admitted to our medical clinic over a period of four years, between 2010 and 2014. Diagnostic was established using the EASL criteria. We have documented history of hyperglycemia and any changes of serum values in these patients, evaluating DM patients within the LC lot. From these patients we have selected all patients with imaging suggestive for HCC and established positive diagnosis on the criteria established in the latest EASL guidelines. We have used statistical tests to identify possible correlations between these pathologies.

RESULTS

We have identified 2718 consecutive patients with LC and successfully included 2556. Of these, 164 also had HCC. A total of 371 patients had DM - 54 also had HCC while 317 remained cancer-free through our study period. We found positive correlations between the presence of DM and HCC. Subgroup analysis of the HCC cohort revealed a positive association between DM and liver cirrhosis and chronic hepatitis. We did not find positive relationships between DM and overall liver conditions, splenomegaly, hepatomegaly, other significant symptoms, substance abuse and main serum values.

CONCLUSIONS

We have found several significant correlations between DM and underlying liver conditions in a HCC cohort. Our study, however, did not reveal other significant associations regarding these diseases. Further studies are required to determine the precise role this disease plays in the development and severity of liver diseases.

Insulin-like Growth Factor-1 (IGF-1): Demographic, Clinical and Laboratory Data in 120 Consecutive Adult Patients with Thalassaemia Major

INTRODUCTION

IGF-1 deficiency in TM patients in children and adolescents has been attributed to chronic anemia and hypoxia, chronic liver disease, iron overload and other associated endocrinopathies, e.g. growth hormone deficiency (GHD). Few data are available in the literature regarding adult TM patients and growth disorders. The aim of this study was to measure IGF-1 values and other clinical data in a large number of adult patients with TM to evaluate the possible relationships between them.

PATIENTS AND METHODS

A cohort of 120 adult patients with TM was studied for plasma levels of IGF-1. Plasma total IGF-1 was determined by chemiluminescent immunometric assay (CLIA) method. In eleven patients (3 females) the GH response during glucagon stimulation test (GST) was also evaluated.

RESULTS

Fifty percent of patients (33 males and 27 females) had IGF-1 levels <- 2 SDs below normative values for healthy subjects matched for age and sex. In these patients endocrine complications and elevations of aminotransferases (ALT) were more common compared to TM patients with IGF1 > -2SDs. In multivariate regression analyses, height, weight, BMI, serum ferritin, ALT, HCV serology and left ventricular ejection fraction (LVEF) were not significantly related to IGF-1, but a significant correlation was found in females between HCV-RNA positivity and IGF-1, ALT and serum ferritin. AGHD was diagnosed in 6 (4 males) out of 11 patients (54.5%) who had glucagon stimulation tests and in 5 out of 8 (62.5%) with IGF-1 <-2SD. The mean age of patients with GHD was 39.3 years (range: 25-49 years, median: 39 years) versus 35.8 years (range: 27-45 years, median: 37.5 years) in non-GHD patients. A positive correlation between GH peak after GST and IGF-1 level was found (r: 0.6409; p: < 0.05).

CONCLUSIONS

In 50% of TM patients the IGF-1 levels were 2SDs below average values for healthy individuals. IGF-1 deficiency was more common in TM patients with associated endocrine complications, and a significant correlation was found in HCV-RNA positive females among IGF-1, ALT, and serum ferritin. Further data in a larger group of patients are needed to confirm whether IGF-1 level <-2 SDs may be a potential criterion for additional studies in TM patients. This datum could avoid performing GH stimulation tests in the majority of them.

Diabetes mellitus and risk of thyroid cancer: a meta-analysis

INTRODUCTION

Diabetes mellitus (DM) is an important risk factor for endocrine cancers; however, the association with thyroid cancer is not clear. We performed a systematic review and meta-analysis to clarify the association between thyroid cancer and DM.

METHODS

We searched MEDLINE, PUBMED and EMBASE databases through July 2012, using search terms related to diabetes mellitus, cancer, and thyroid cancer. We conducted a meta-analysis of the risk of incidence of thyroid cancer from pre-existing diabetes. Of 2,123 titles initially identified, sixteen articles met our inclusion criteria. An additional article was identified from a bibliography. Totally, 14 cohort and 3 case-control studies were selected for the meta-analysis. The risks were estimated using random-effects model and sensitivity test for the studies which reported risk estimates and used different definition of DM.

RESULTS

Compared with individuals without DM, the patients with DM were at 1.34-fold higher risk for thyroid cancer (95% CI 1.11-1.63). However, there was heterogeneity in the results (p<0.0001). Sensitivity tests and studies judged to be high quality did not show heterogeneity and DM was associated with higher risk for thyroid cancer in these sub-analyses (both of RRs = 1.18, 95% CIs 1.08-1.28). DM was associated with a 1.38-fold increased risk of thyroid cancer in women (95% CI 1.13-1.67) after sensitivity test. Risk of thyroid cancer in men did not remain significant (RR 1.11, 95% CI 0.80-1.53).

CONCLUSIONS

Compared with their non-diabetic counterparts, women with pre-existing DM have an increased risk of thyroid cancer.

Type 2 diabetes: a protective factor for prostate cancer? An overview of proposed mechanisms

Diabetes mellitus and prostate cancer are 2 of the most important public health concerns, especially in the elderly population. Although diabetes has been recognized as a potent risk factor for many types of cancers, there is a large amount of evidence that shows that it has a protective role against prostate cancer. The underlying cause of this protective role is not fully understood, however, some mechanisms have been proposed in this area. In the present study we have reviewed these mechanisms and some new mechanisms are also proposed.

Association between diabetes or antidiabetic therapy and lung cancer: A meta-analysis

Aims/Introduction

Diabetes can increase the risk of cancers at several sites, but the association between diabetes and lung cancer remains unclear. We aimed to provide the quantitative estimates for the association between diabetes or antidiabetic treatment and lung cancer risk in the present meta‐analysis.

Materials and Methods

Cohort studies were identified by searching the PubMed database (January 1960 through October 2012) and manually assessing the cited references in the retrieved articles. Study‐specific relative risks (RRs) and 95% confidence intervals (CIs) were estimated using a random‐effects model. Study quality was assessed using the Newcastle–Ottawa scale.

Results

A total of 19 cohort studies were included in the present meta‐analysis. Of these, 14 studies focused on the association between diabetes and lung cancer incidence, and seven studies focused on the association between antidiabetic treatment and lung cancer incidence. Compared with non‐diabetic individuals, diabetic patients do not have an increased risk of lung cancer (RR = 1.04, 95% CI 0.87–1.24). The association between diabetes and lung cancer remained not statistically significant in subgroup analysis stratified by study characteristics, study quality, diabetes ascertainment or important confounders. A null association between insulin or biguanides therapy and lung cancer risk was found. However, the diabetic patients receiving thiazolidinedione (TZD) treatment had a 20% reduced risk of lung cancer than those without TZD treatment.

Conclusions

No association between diabetes and lung cancer risk was found. However, TZD treatment might reduce lung cancer risk in diabetic patients.

Diabetes mellitus and incidence and mortality of kidney cancer: a meta-analysis

BACKGROUND

Diabetes is associated with increased risk of a spectrum of cancers, but there are few meta-analyses on the association between diabetes and kidney cancer. We performed a meta-analysis of case-control studies and cohort studies to address the incidence and mortality of kidney cancer in diabetes.

METHODS

Studies were identified by searching PubMed database and manual assessment of the cited references in the retrieved articles. Study-specific relative risks (RRs) and 95% confidence intervals (CIs) were estimated using a random-effect model. Study quality was assessed using the Newcastle-Ottawa scale.

RESULTS

A total of 24 studies were included. We found that diabetes was significantly associated with increased risk of kidney cancer (RR=1.40, 95% CI=1.16 to 1.69), and the results were consistent between case-control and cohort studies. A slightly stronger positive relation was observed in women (RR=1.47, 95% CI=1.18 to 1.83) than in men (RR=1.28, 95% CI=1.10 to 1.48). Additional analyses indicated that the increased risk of kidney cancer was independent of alcohol consumption, body mass index (BMI)/obesity and smoking. However, there was no association between diabetes and mortality of kidney cancer (RR=1.12, 95% CI=0.99 to 1.20), without heterogeneity (P=0.419, I(2)=1.8%).

CONCLUSIONS

Diabetes mellitus may increase the risk of kidney cancer in both women and men.

Impact of diabetes on oncologic outcome of colorectal cancer patients: colon vs. rectal cancer

Background

To evaluate the impact of diabetes on outcomes in colorectal cancer patients and to examine whether this association varies by the location of tumor (colon vs. rectum).

Patients and methods

This study includes 4,131 stage I-III colorectal cancer patients, treated between 1995 and 2007 (12.5% diabetic, 53% colon, 47% rectal) in South Korea. Cox proportional hazards modeling was used to determine the prognostic influence of DM on survival endpoints.

Results

Colorectal cancer patients with DM had significantly worse disease-free survival (DFS) [hazard ratio (HR) 1.17, 95% confidence interval (CI): 1.00–1.37] compared with patients without DM. When considering colon and rectal cancer independently, DM was significantly associated with worse overall survival (OS) (HR: 1.46, 95% CI: 1.11–1.92), DFS (HR: 1.45, 95% CI: 1.15–1.84) and recurrence-free survival (RFS) (HR: 1.32, 95% CI: 0.98–1.76) in colon cancer patients. No association for OS, DFS or RFS was observed in rectal cancer patients. There was significant interaction of location of tumor (colon vs. rectal cancer) with DM on OS (P = 0.009) and DFS (P = 0.007).

Conclusions

This study suggests that DM negatively impacts survival outcomes of patients with colon cancer but not rectal cancer.

Diabetes mellitus and the incidence of colorectal cancer: an updated systematic review and meta-analysis

AIM

The purpose of this study was to determine whether diabetes mellitus is associated with an increased risk of colorectal cancer.

METHODS

Relevant studies were identified in MEDLINE and EMBASE (up until November 1st, 2011). Inclusion criteria were original, peer-reviewed publications, with case-control and cohort studies (for studies on diabetes mellitus and colorectal cancer). Summary relative risks with 95% confidence intervals were calculated with a random-effects model.

RESULTS

Twenty-four studies including eight case-control and 16 cohort studies, with a total of 3,659,341 participants, were included in this updated systematic review and meta-analysis, and all involved diabetes mellitus and colorectal cancer risk. Meta-analysis of the 24 included studies indicated that diabetes was associated with an increased risk of colorectal cancer, compared with no diabetes (summary RR of colorectal cancer incidence = 1.26, 95% CI = 1.20-1.31), without heterogeneity between studies (P(heterogeneity) = 0.296). Sub-group analyses found that these results were consistent between case-control and cohort studies and among studies conducted in different areas. The association between diabetes and colorectal cancer incidence did not differ significantly by sex and sub-sites. Insulin therapy was also positively associated with risk of colorectal cancer (summary RR = 1.61, 95% CI 1.18-1.35), with evidence of heterogeneity between studies (P(heterogeneity) = 0.014).

CONCLUSIONS

Our findings further support a relationship between diabetes and increased risk of colon and rectal cancer in both women and men, and insulin therapy for diabetes may increase this risk.

Evaluation of IGF-I levels and serum protein profiles of diabetic cats and dogs

In this study, we measured the insulin-like growth factor (IGF)-I levels and evaluated the serum protein profiles of diabetic, insulin-treated, and healthy cats and dogs. The total IGF-I concentrations were 33.74 ± 3.4 ng/mL for normal, 25.8 ± 4.5 ng/mL for diabetic, and 180.4 ± 31.4 ng/mL for insulin-treated cats. IGF-I concentrations were 46.4 ± 6.6 ng/mL for normal, 25.1 ± 4.1 ng/mL for diabetic, and 303.0 ± 61.3 ng/mL for insulin-treated dogs. Total serum protein profiles were analyzed by SDS-PAGE. Fourteen bands ranging from 25 to 240 kDa in size were observed for cats, and 17 bands ranging from 25 to 289 kDa were observed for dogs. The densities of the bands differed among control, diabetic, and insulin-treated animals. In conclusion, we found that serum protein profiles and IGF-I concentrations were altered in both diabetic and insulin-treated animals. When judiciously interpreted in the light of other clinical and laboratory data, the techniques used in our study provide a valuable modality for measuring the severity of diabetes mellitus in dogs and cats.

Diabetes mellitus and incidence of kidney cancer: a meta-analysis of cohort studies

AIMS/HYPOTHESIS

Diabetes is associated with increased risk of cancer at several sites, but its association with cancer of the kidney is unclear. We performed a systematic review with meta-analysis to examine the association between diabetes and incidence of kidney cancer.

METHODS

Pertinent studies were identified by searching PubMed (from January 1966 to December 2010) and reviewing the reference lists of relevant articles. We included cohort studies reporting RR estimates and 95% CI (or data to calculate them) of the association between diabetes and kidney cancer incidence. Summary RRs were calculated using a random-effects model.

RESULTS

Nine cohort studies met the inclusion criteria. Analysis of all studies showed that compared with individuals without diabetes, patients with diabetes had a statistically significant increased risk of kidney cancer (RR 1.42, 95% CI 1.06-1.91). There was heterogeneity among studies (p < 0.001 for heterogeneity). The association was stronger in women (RR 1.70, 95% CI 1.47-1.97) than in men (RR 1.26, 95% CI 1.06-1.49). When restricting the analysis to studies that had adjusted for body mass index (n = 3) or cigarette smoking (n = 3), the RRs were 1.12 (95% CI 0.99-1.27) and 1.29 (95% CI 1.05-1.58), respectively.

CONCLUSIONS/INTERPRETATION

This meta-analysis indicates a positive association between diabetes and risk of kidney cancer. Future research should attempt to establish whether this association is causal.

Is diabetes a causal agent for colorectal cancer? Pathophysiological and molecular mechanisms

The possible relationship between diabetes mellitus (DM) and colorectal cancer (CRC), concerning pathophysiological and molecular mechanisms is highlighted in this review. The most recent and complete articles and developments in this particular field were thoroughly reviewed. Common risk factors, such as obesity, sedentary lifestyle, and Western diet between DM and CRC, led to the theory that DM might be a causal agent for CRC development. Various studies have connected type 2 DM and CRC, either proximal or distal, in both sexes. Additionally, chronic insulin treatment has been linked with increased colorectal tumor risk among type 2 diabetic patients. Interestingly, elevated hemoglobin A1c has been proven to be an independent predictor of aggressive clinical behavior in CRC patients. These mechanisms include the insulin-like growth factor-hyperinsulinemia theory and the participation of oncogenic intracellular signaling pathways. Furthermore, it has been proposed that Cox-2 inhibitors might have a role in decreasing the incidence of CRC. Finally, the use of statins to reduce the risk for colon cancer in patients with diabetes has remained controversial. Diabetic patients over 50 should receive counseling regarding their elevated risk for CRC, and screening colonoscopy should be recommended before initiating insulin therapy. However, there are no current guidelines, and this strategy is not yet applicable to some countries, as the corresponding risk would not allow screening colonoscopy to be adopted. There is strong evidence to indicate that DM is a causal agent for CRC development. This conclusion provides new impetus for re-evaluating CRC screening worldwide.

Diabetes and risk of incident cancer: a large population-based cohort study in Israel

Type 2 diabetes mellitus has been associated with an increased risk of a variety of cancers in observational studies, but few have reported the relationship between diabetes and cancer risk in men and women separately. The main goal of this retrospective cohort study was to evaluate the sex-specific risk of incident overall and site-specific cancer among people with DM compared with those without, who had no reported history of cancer at the start of the follow-up in January 2000. During an average of 8 years of follow-up (SD = 2.5), we documented 1,639 and 7,945 incident cases of cancer among 16,721 people with DM and 83,874 free of DM, respectively. In women, DM was associated with an adjusted hazard ratio of 1.96 (95% CI: 1.53-2.50) and 1.41 (95% CI: 1.20-1.66) for cancers of genital organs and digestive organs, respectively. A significantly reduced HR was observed for skin cancer (0.38; 95% CI: 0.22-0.66). In men with DM, there was no significant increase in overall risk of cancer. DM was related with a 47% reduction in the risk of prostate cancer. These findings suggest that the nature of the association between DM and cancer depends on sex and specific cancer site.

Diabetes mellitus and risk of prostate cancer in the health professionals follow-up study

History of diabetes may be associated with decreased prostate cancer (PCa) risk. Published studies have not always accounted for time since diabetes diagnosis or confounding and effect modification by lifestyle factors. The authors investigated the relationship between diabetes and PCa risk in men in the Health Professionals Follow-Up Study from 1986 to 2004. During that time, 4,511 new PCa cases were identified. Multivariate hazard ratios (HR) were estimated using Cox regression. The HR of PCa comparing men with vs. without diabetes was 0.83 and 95% confidence interval (CI): 0.74, 0.94. PCa risk was not reduced in the first year after diabetes diagnosis (HR: 1.30, CI: 0.97, 1.72), was lower for men diagnosed for 1-6 years (HR: 0.82, CI: 0.66, 1.02), and was even lower for men who had been diagnosed for 6-15 (HR: 0.75, CI: 0.61, 0.93) or >15 years (HR: 0.78, CI: 0.63, 0.96). Reduced PCa risk was stronger in men diagnosed before 1994 (pre-PSA era) vs. after 1994. The authors also demonstrated that obese and diabetic men had a lower HR for PCa than those who were either not obese and diabetic or obese and non-diabetic. Results are consistent with the hypothesis that diabetes is associated with reduced PCa risk. Potential biological mechanisms are discussed.

Diabetes mellitus worsens the recurrence rate after potentially curative therapy in patients with hepatocellular carcinoma associated with nonviral hepatitis

BACKGROUND AND AIM

The aim of this retrospective study was to examine the relationship between diabetes mellitus and recurrence of hepatocellular carcinoma after potentially curative therapy for hepatocellular carcinoma with nonviral hepatitis.

METHODS

We studied 40 consecutive hepatocellular carcinoma patients who were diagnosed between 1980 and 2006 with hepatocellular carcinoma associated with non-B, non-C hepatitis, and later underwent surgical resection or radiofrequency ablation.

RESULTS

Twenty-two out of the 40 patients developed hepatocellular carcinoma recurrence within a median of 3.7 years. In the 18 patients with diabetes mellitus, the cumulative rates of hepatocellular carcinoma recurrence were 22.2% at the first year, 55.6% at the second year, 61.1% at the third year, 61.1% at the fourth year, and 80.6% at the fifth year. The cumulative rates of hepatocellular carcinoma recurrence in 22 nondiabetic patients were 24.6% at the first year, 24.6% at the second year, 31.5% at the third year, 31.5% at the fourth year, and 31.5% at the fifth year. The hepatocellular carcinoma recurrence rate was significantly higher in diabetic patients than in nondiabetics (P = 0.026). The multivariate Cox proportional model identified old age and diabetes as the only significant predictors for recurrence. The hazard ratio of hepatocellular carcinoma recurrence in diabetic patients was 4.61 (P = 0.007). There was no significant difference in overall survival rate between diabetic and nondiabetic patients (P = 0.392).

CONCLUSION

Diabetes is a significant predictor of tumor recurrence after potentially curative therapy for hepatocellular carcinoma in patients with nonviral hepatitis.

Diabetic osteopathy and the IGF system in the Goto-Kakizaki rat

OBJECTIVE

Diabetes mellitus is associated with an increased risk of osteopenia, fracture and Charcot arthropathy. Abnormalities of the IGF system commonly observed in diabetes may underlie this "diabetic osteopathy" as IGF-I and its binding proteins (IGFBPs) have been shown to affect osteoblast and osteoclast activity.

DESIGN

In type-2 diabetic and control rats we analyzed IGF-I and IGFBP-1 and -4 levels in serum, and notably, also the IGF-I levels in cortical bone, ankles and vertebrae by immunoassays. Osteopathy was assessed by radiography and dual energy X-ray absorptiometry.

RESULTS

In the diabetic rats IGF-I was significantly reduced in serum and diaphyseal bone while IGFBP-1 and IGFBP-4 were increased in serum. The periosteal and endosteal diameters were increased in the diaphysis of humerus and tibia (changes similar to those in elderly humans) while bone mineral density was reduced in long bone metaphyses and vertebrae.

CONCLUSIONS

Our study demonstrates both systemic and local disturbances of the IGF-system in rats with type-2 diabetes, consistent with the observed enhanced endosteal erosion in long bone diaphyses, and osteopenia in metaphyses and vertebrae. Whether similar IGF-system changes contribute to osteopathy in patients with diabetes and if treatment of diabetes can reverse the osteopathy has yet to be explored.

Liver insulin-like growth factor 2 methylation in hepatitis C virus cirrhosis and further occurrence of hepatocellular carcinoma

AIM: To assess the predictive value of the insulin-like growth factor 2 (Igf2) methylation profile for the occurrence of Hepatocellular Carcinoma (HCC) in hepatitis C (HCV) cirrhosis.

METHODS: Patients with: (1) biopsy-proven compensated HCV cirrhosis; (2) available baseline frozen liver sample; (3) absence of detectable HCC; (4) regular screening for HCC; (5) informed consent for genetic analysis were studied. After DNA extraction from liver samples and bisulfite treatment, unbiased PCR and DHPLC analysis were performed for methylation analysis at the Igf2 locus. The predictive value of the Igf2 methylation profile for HCC was assessed by Kaplan-Meier and Cox methods.

RESULTS: Among 94 included patients, 20 developed an HCC during follow-up (6.9 ± 3.2 years). The methylation profile was hypomethylated, intermediate and hypermethylated in 13, 64 and 17 cases, respectively. In univariate analysis, two baseline parameters were associated with the occurrence of HCC: age (P = 0.01) and prothrombin (P = 0.04). The test of linear tendency between the three ordered levels of Igf2 methylation and probability of HCC occurrence was significant (Log Rank, P = 0.043; Breslow, P = 0.037; Tarone-Ware, P = 0.039).

CONCLUSION: These results suggest that hypome-thylation at the Igf2 locus in the liver could be predictive for HCC occurrence in HCV cirrhosis.

Hormonal profile of diabetic men and the potential link to prostate cancer

OBJECTIVE

Previous studies suggest men with diabetes may be at reduced risk for prostate cancer as compared to men without diabetes. To investigate potential biological mechanisms, hormonal profiles of diabetic men and non-diabetic controls were compared.

METHODS

In the Health Professionals Follow-Up Study, plasma levels of C-peptide, testosterone, sex-hormone binding globulin, insulin-like growth factor-1, and insulin-like growth factor binding protein-3 were determined in 171 diabetic men and 3,001 non-diabetic controls. Multiple linear regression analysis was conducted and least square means were calculated for hormones of interest.

RESULTS

Plasma levels of several hormones either < or =1, 1.1-6, 6.1-14.9, or > or =15 years after diagnosis with diabetes were examined. As time since diabetes diagnosis increased, plasma levels of C-peptide and IGFBP-3 significantly decreased (p for trend: C-peptide =.05, IGFBP-3 =.03). While testosterone and SHBG levels both significantly increased with increasing time since diabetes diagnosis (p for trend: testosterone =.02, SHBG =.002), the ratio of testosterone to SHBG decreased, suggesting a reduction in bioavailable testosterone. Plasma IGF-1 levels were lower in diabetics than non-diabetics, but no significant time trend was noted.

CONCLUSION

This study of hormonal profiles of diabetic versus non-diabetic men identified changes in diabetic men that may be consistent with reduced prostate cancer risk.

Type 2 diabetes mellitus as risk factor for colorectal cancer

Colorectal cancer occurs more frequently in patients with type 2 diabetes mellitus. The hyperinsulinemia-hypothesis suggests that elevated levels of insulin and free IGF-1 promote proliferation of colon cells and lead to a survival benefit of transformed cells, ultimately resulting in colorectal cancer. In patients with type 2 diabetes mellitus, epidemiological studies show an increased risk for colorectal cancer and an even higher risk if patients are treated with sulphonylureas or insulin. Moreover, tumour progression at hyperinsulinemia is more rapid and tumour-associated mortality is increased. Colorectal cancer can be avoided by screening. Recommendations for colorectal cancer screening should employ the recent epidemiologic evidence. All patients with type 2 diabetes mellitus should be recommended to undergo colonoscopy before starting insulin therapy, and screening intervals should not exceed 5 years. For this concept, a review of the evidence is presented, and a screening algorithm for colorectal cancer in patients with type 2 diabetes mellitus is proposed.

Diabetes mellitus increases the risk of hepatocarcinogenesis in patients with alcoholic cirrhosis: A preliminary report

AIM

Diabetes mellitus (DM) has been reported to increase the risk of hepatocellular carcinogenesis in chronic liver diseases. This study aims to elucidate whether DM is an independent risk factor for the appearance of hepatocellular carcinoma (HCC) in patients with alcoholic cirrhosis.

METHODS

Forty-seven patients with alcoholic cirrhosis were retrospectively observed for a median of 6.8 years. The patients showed a history of heavy alcohol intake of 500 kg or more until the diagnosis of cirrhosis, and no patients had hepatitis B surface antigen, hepatitis B virus DNA measured by nested polymerase chain reaction, or antihepatitis C virus.

RESULTS

During the observation period, HCC developed in nine patients (19.1%). Cumulative appearance rates of HCC were 10.5%, 23.8% and 33.3% at the end of the fifth, 10th and 15th years, respectively. When they were divided into two groups according to the association of diabetes, carcinogenesis rates in patients with (n = 11) and without (n = 36) DM, cumulative carcinogenesis rates were 32.7% and 3.2% at the end of fifth year, 32.7% and 20.2% at the tenth year, and 66.3% and 20.2% at the 15th year, respectively. Crude carcinogenesis rate in the patient with DM was significantly higher than that of patients without DM (P = 0.0034). Multivariate analysis disclosed a higher age (hazard ratio 28.1, P = 0.007), and association of DM (hazard ratio 21.7, P = 0.006) significantly affected future carcinogenesis rate.

CONCLUSION

DM seemed to be an independent risk factor for hepatocarcinogenesis in the cohort study of patients with alcoholic cirrhosis.

A meta-analysis of diabetes mellitus and the risk of prostate cancer

BACKGROUND

Studies investigating the association between diabetes mellitus and prostate cancer have reported inconsistent findings. We examined this association by conducting a detailed meta-analysis of the studies published on the subject.

METHODS

MEDLINE and EMBASE databases and bibliographies of retrieved articles were searched. Studies investigating the relationship between diabetes mellitus and prostate cancer were included in the meta-analysis. Potential sources of heterogeneity between studies were explored and publication bias was evaluated. Pooled relative risk (RR) was calculated using the random-effects model. Numerous relevant subgroup analyses were also done.

RESULTS

We included 19 studies, published between 1971 and 2005, in the meta-analysis and found an inverse association between diabetes mellitus and prostate cancer [RR, 0.84, 95% confidence interval (CI), 0.76-0.93, P for heterogeneity <or= 0.01]. For cohort studies alone, the RR was 0.81 (95% CI, 0.71-0.92, P for heterogeneity <or= 0.01) and for case-control studies alone, the RR was 0.89 (95% CI, 0.72-1.11, P for heterogeneity = 0.02). The significant heterogeneity was mitigated in some of the subgroup analyses. For studies conducted before prostate-specific antigen screening was introduced as a common procedure, the RR was 0.94 (95% CI, 0.85-1.03, P for heterogeneity = 0.15), and for studies conducted after this time, the RR was 0.73 (95% CI, 0.64-0.83, P for heterogeneity = 0.10). For studies that adjusted for three or more potential confounders, the RR was 0.74 (95% CI, 0.65-0.85, P for heterogeneity = 0.06) and for studies that adjusted for less than three potential confounders, the RR was 0.93 (95% CI, 0.86-1.02, P for heterogeneity = 0.18).

CONCLUSION

This study suggests an inverse relationship between diabetes and prostate cancer. Potential biological mechanisms underlying this association, as well as possible biases, are discussed.

Role of insulin-like growth factor-1 in colon cancerogenesis: a case-control study

BACKGROUND

Our aim was to establish whether individuals who developed colon cancer have elevated blood levels of insulin-like growth factor-1 (IGF-1).

METHODS

This was a case/control study in which 52 patients with colon cancer and a corresponding control group were investigated. Data on age, weight, height, and sex of subjects were recorded and levels of IGF-1 and growth hormone, as well as insulin and C-peptide levels, were measured in the morning before eating, 90 min after breakfast and again 90 min after lunch.

RESULTS

We found significantly higher levels of IGF-1 in blood of colon cancer patients compared to the control group. No differences in the levels of growth hormone, insulin and C-peptide in blood were found between colon cancer patients and the control group. It was found that the increase of IGF-1 level was followed by a 3.15-fold increased risk for developing colon cancer. There were no differences in the levels of IGF-1 in blood in all three measurements in the group of colon cancer patients, whereas differences were found in the control group. We found differences in the levels of insulin and C-peptide in blood in all three measurements in both groups of patients. No differences were found in the levels of growth hormone in blood in all three measurements in both groups of patients.

CONCLUSIONS

The results of this study suggest a positive correlation between the increased levels of IGF-1 and colon cancer and are thus consistent with the hypothesis that the level of IGF-1 plays an important role in the development of colon cancer.

Alteration of the gene and protein levels of insulin-like growth factors in streptozotocin-induced diabetic male rats

Insulin-like growth factor (IGFs: IGF-I and IGF-II) systems have been reported to be associated with the onset of diabetic mellitus. Therefore, we investigated the effect of diabetes on regulation of the IGF system in the liver, kidneys and heart, which are important organs in the pathogenesis of diabetes. The experimental groups were subdivided into three groups: 1) controls, 2) streptozotocin (STZ)-induced untreated diabetic group, and 3) an insulin-treated group (plus diabetic rats). In the present study, starting on the second day after STZ treatment, the diabetic group exhibited hyperglycemia, polyuria, and polydipsia, which are characteristic of diabetes melittus. Serum levels of IGF-I were decreased, but those of IGF-II were increased in the diabetic group compared with the controls. The expression levels of IGF-I and IGF-II protein in the livers of the diabetic group had a similar pattern to the serum. In addition, the expression levels of liver IGF-I mRNA and IGF-II mRNA were decreased in the diabetic groups. In the heart, IGF-I levels were decreased, but IGF-II levels were increased in the untreated diabetic groups, which was consistent with the expression levels of their mRNA. However, both the IGF-I and IGF-II levels in the kidneys were increased in the untreated diabetic groups, but the mRNA levels were decreased. Insulin treatment ameliorated the changes of IGF system in the serum, liver, kidneys, and heart. In conclusion, diabetes induced alteration of the IGF system tissue-specifically, and this was blocked by insulin treatment.

TISSUE-SPECIFIC REGULATION OF INSULIN-LIKE GROWTH FACTORS AND INSULIN-LIKE GROWTH FACTOR BINDING PROTEINS IN MALE DIABETIC RATS IN VIVO AND IN VITRO

1. Insulin-like growth factors (IGFs) are associated with the development of diabetes mellitus. The liver, kidney and heart have been implicated as important organs in the onset of diabetes mellitus. However, the effect of diabetes on the IGF system in these organs has not been fully described. Thus, we investigated changes in IGF-I, IGF-II and IGF binding proteins (IGFBPs) in male steptozotocin-induced diabetic rats, as well as in a high glucose-induced in vitro model. 2. Serum levels of IGF-I were decreased, but the levels of IGF-II were increased, in diabetic rats compared with controls. The expression of IGFBP-3 in the serum was markedly decreased; in contrast, the expression of IGFBP-1 and -2 was increased in diabetic rats. The expression of IGF-I, IGF-II, IGFBP-1, IGFBP-2, IGFBP-3 and IGFBP-4 in the liver of the diabetic group was similar to that in the serum of diabetic rats. 3. In heart tissue of the diabetic group, IGF-I levels were decreased, but IGF-II levels were increased. In addition, the expression of IGFBP-3, IGFBP-1 and IGFBP-2 was decreased in diabetic rats. 4. In the kidney of the diabetic group, IGF-I and IGF-II levels were increased. There was only slight expression of IGFBP-3 in the kidney and this was not altered in diabetic rats. Levels of IGFBP-1 and -2 were markedly increased in the kidney of diabetic rats. 5. Insulin treatment recovered the changes in expression of IGF-I, IGF-II and IGFBPs in the serum, liver, heart and kidney. In the liver, heart and kidney, the expression of the insulin receptor was increased in male diabetic rats. 6. In conclusion, diabetes tissue-specifically alters the IGF system in the liver, heart and kidney in rats; this effect can be recovered by insulin treatment.

Diabetes mellitus and risk of bladder cancer: a meta-analysis

AIMS/HYPOTHESIS

Epidemiological evidence indicates that individuals with diabetes mellitus have an increased risk of several cancers. We performed a systematic review with meta-analysis to evaluate the association between diabetes and risk of bladder cancer.

METHODS

Pertinent studies were identified by searching MEDLINE (from January 1966 to July 2006) and by reviewing the reference lists of retrieved articles. We included case-control and cohort studies reporting relative risk (RR) estimates with 95% CIs (or data to calculate them) of bladder cancer associated with diabetes. Studies of type 1 diabetes were not included. Summary RRs were calculated using a random-effects model.

RESULTS

A total of 16 studies (seven case-control studies, three cohort studies and six cohort studies of diabetic patients) fulfilled the inclusion criteria. Analysis of all studies showed that diabetes was associated with an increased risk of bladder cancer, compared with no diabetes (RR = 1.24, 95% CI 1.08-1.42). There was strong evidence of heterogeneity among these studies (p < 0.0001). Stratification by study design found that diabetes was associated with an increased risk of bladder cancer in case-control studies (RR = 1.37, 95% CI 1.04-1.80, p (heterogeneity) = 0.005) and cohort studies (RR = 1.43, 95% CI 1.18-1.74, p (heterogeneity) = 0.17), but not in cohort studies of diabetic patients (RR = 1.01, 95% CI 0.91-1.12, p (heterogeneity) = 0.35).

CONCLUSIONS/INTERPRETATION

Findings from this meta-analysis suggest that individuals with diabetes may have a modestly increased risk of bladder cancer.

Type 2 diabetes and hepatocellular carcinoma: A cohort study in high prevalence area of hepatitis virus infection

This study aimed to elucidate the relationship of type 2 diabetes, other known risk factors, and primary hepatocellular carcinoma (HCC) in countries with a high prevalence of hepatitis infection. We followed a prospective cohort of 54,979 subjects who participated in the Keelung Community-Based Integrated Screening program between 1999 and 2002. A total of 5,732 subjects with type 2 diabetes cases were identified at enrollment on the basis of fasting blood glucose level, and a total of 138 confirmed HCC cases were identified either through two-stage liver cancer screening or linkage with the National Cancer Registry. The independent effect of type 2 diabetes on the incidence of HCC and the interaction between type 2 diabetes and hepatitis infection or lipids profile were assessed using the Cox proportional hazards regression model. After controlling for age, sex, hepatitis B virus (HBV), hepatitis C virus (HCV), smoking, and alcohol consumption, the association between type 2 diabetes and incidence of HCC (excluding 33 prevalent cases identified at enrollment) was modified by HCV status and cholesterol level. The associations were only statistically significant (adjusted hazard ratio [HR] = 2.08 [1.03-4.18]) for being HCV negative and for having hypercholesterolemia (adjusted HR = 2.81 [1.20-6.55]). These statistically significant findings remained even excluding cases of diabetes newly diagnosed at enrollment. In conclusion, in an area with a high prevalence of hepatitis virus infection, type 2 diabetes increases the risk of developing HCC in those who are HCV negative or have a high level of total cholesterol.

Diabetes mellitus and cancer risk in a population-based case-control study among men from Montreal, Canada

Diabetics may have a higher risk of cancer, notably liver and pancreatic cancers. Evidence about other cancer types remains sparse. The authors examined potential associations between diabetes and several types of cancer in a large multicancer case-control project carried out in Montreal, Canada, in the 1980s. This report, based on 3,107 male cancer cases and 509 population controls, uses information on diabetes and several covariates collected by interview. Adjusted odds ratios (ORs) and 95% confidence intervals (CI) were estimated for the associations between diabetes and each of 12 cancer types. Risks of pancreatic and liver cancers were increased among diabetics: adjusted ORs were 2.1 (95% CI: 1.0, 4.3) for pancreatic and 3.1 (95% CI: 1.1, 8.8) for liver cancer. The increased risk of pancreatic cancer was completely restricted to those with recent onset of diabetes; this was likely a manifestation of reverse causality. Conversely, the increased risk of liver cancer was independent of the interval between diabetes and cancer diagnoses. No associations were observed with melanoma, non-Hodgkin's lymphoma, cancers of the esophagus, stomach, colon, rectum, lung, prostate, bladder and kidney. In conclusion, diabetes was associated with an increased risk of liver cancer among men, but with no other cancer type including pancreatic cancer.

Caffeic acid phenethyl ester ameliorates changes in IGFs secretion and gene expression in streptozotocin-induced diabetic rats

The protective effect of caffeic acid phenethyl ester (CAPE) against diabetes-induced alteration of IGFs protein and gene expression was investigated in serum, liver, heart, and kidney. In the present study, diabetic rats exhibited the decrease of IGF-I content in serum, liver and heart but the increase of that in kidney and CAPE blocked them. Diabetic rats also manifested the increase of IGF-II content in serum, liver, heart, and kidney and CAPE prevented them. CAPE prevented the diabetes-induced decrease of liver IGF-I mRNA and IGF-II mRNA, which is similar to pattern of IGFs mRNA in kidney. Moreover, diabetic rats exhibited the decrease of heart IGF-I mRNA but the increase of IGF-II mRNA and CAPE blocked them. In conclusion, CAPE, in part, prevented diabetes-induced alteration of IGF-I and IGF-II protein and gene expression in liver, heart, and kidney in rats.

An evaluation of the role of insulin-like growth factors (IGF) and of type-I IGF receptor signalling in hepatocarcinogenesis and in the resistance of hepatocarcinoma cells against drug-induced apoptosis

Strong evidence emphasizes the role of the insulin-like growth factor (IGF) system and of type-I IGF receptor (IGF-IR) signalling in tumourigenesis. In this connection: (i) changes in the expression pattern of components of the IGF system (autocrine/paracrine expression of IGF-I and -II, overexpression of IGF-IR, decreased expression of IGF-binding proteins (IGFBPs) and of type-II IGF receptor/cation-independent mannose-6-phosphate receptor (IGF-II/M6PR) and (ii) increased serum concentrations of proteases that cleave the IGFBPs (e.g., cathepsin D) were observed in patients with hepatocellular carcinomas (HCC), in human hepatoma cell lines and in their conditioned culture medium, as well as in rodent models of hepatocarcinogenesis. Accordingly, studies carried out with animal models do suggest that the IGF system and IGF-IR signalling may play a role in hepatocarcinogenesis and in deregulated proliferation and apoptosis of HCC cells. Finally the instrumental role of Raf/MEK/ERK, one of the signalling cascades stimulated by IGF-IR, in anthracycline-induced apoptosis of HepG2 and Huh-7 human hepatoma cell lines emphasizes that care must be taken when designing combinations of antitumoural molecules for antineoplastic treatment. This review addresses the putative roles of the IGF system in primary HCC, with a special focus on the underlying molecular mechanisms. In a second part it emphasizes the putative interference of IGF-IR signalling with chemotherapeutic drug-induced apoptosis in human hepatoma cells.

Cloning, expression, characterization, and role in autocrine cell growth of cell surface retention sequence binding protein-1

Cell surface retention sequence binding protein-1 (CRSBP-1) is a cell surface binding protein for the cell surface retention sequence (CRS) motif of the v-sis gene product (platelet-derived growth factor-BB). It has been shown to be responsible for cell surface retention of the v-sis gene product in v-sis-transformed cells (fibroblasts) and has been hypothesized to play a role in autocrine growth and transformation of these cells. Here we demonstrate that the CRSBP-1 cDNA cloned from bovine liver libraries encodes a 322-residue type I membrane protein containing a 23-residue signal peptide, a 215-residue cell surface domain, a 21-residue transmembrane domain, and a 63-residue cytoplasmic domain. CRSBP-1 expressed in transfected cells is an approximately 120-kDa disulfide-linked homodimeric glycoprotein and exhibits dual ligand (CRS-containing growth regulators (v-sis gene product and insulin-like growth factor binding protein-3, IGFBP-3) and hyaluronic acid) binding activity. CRSBP-1 overexpression (by stable transfection of cells with CRSBP-1 cDNA) enhances autocrine loop signaling, cell growth, and tumorigenicity (in mice) of v-sis-transformed cells. CRSBP-1 expression also enhances autocrine cell growth mediated by IGFBP-3 in human lung carcinoma cells (H1299 cells), which express very little, if any, endogenous CRSBP-1 and exhibits a mitogenic response to exogenous IGFBP-3, stably transfected with IGFBP-3 cDNA. However, CRSBP-1 overexpression does not affect growth of normal and transformed cells that do not produce these CRS-containing growth regulators. These results suggest that CRSBP-1 plays a role in autocrine regulation of cell growth mediated by growth regulators containing CRS.

The relationship between the circulating IGF system and the presence of retinopathy in Type 1 diabetic patients

BACKGROUND

Patients with proliferative diabetic retinopathy (PDR) have increased vitreous levels of insulin-like growth factor (IGF)-I, IGF-II and IGF binding proteins (IGFBPs). This accumulation is probably caused by increased leakiness of the blood-retina barrier and influx of circulating IGFs and IGFBPs. To date, interest has focused on the role of circulating total IGF-I in the development of PDR, and there are only sparse data on circulating levels of free IGF-I and IGFBPs.

METHODS

We compared fasting serum samples from matched groups of Type 1 diabetic patients with no retinopathy (n = 29), non-PDR (n = 13) and PDR (n = 16). We also included matched controls (n = 26). Serum was analysed for free and total IGF-I and -II, free plus dissociable IGF-I, IGFBP-1, -2 and -3, IGFBP-1-bound IGF-I as well as IGFBP-3 proteolysis.

RESULTS

When compared with controls, diabetic patients (n = 58) showed reduced (P < 0.0005) levels of free and total IGFs, free plus dissociable IGF-I and IGFBP-3, whereas levels of IGFBP-1, IGFBP-1-bound IGF-I and IGFBP-2 were elevated. IGFBP-3 proteolysis remained unaltered. When comparing diabetic patients with different degrees of retinopathy, IGFBP-2 and IGFBP-1-bound IGF-I were the only parameters that differed significantly. Patients with retinopathy (non-PDR as well as PDR) had elevated IGFBP-2 (P < 0.03) and reduced IGFBP-1-bound IGF-I (P < 0.03), when compared with patients without retinopathy. Noteworthy, both parameters correlated (0.11 < r2 < 0.14, P < 0.02) with the severity of retinopathy.

CONCLUSION

Our study gives no evidence of a direct role of circulating free IGF-I in the development of PDR, whereas IGFBP-2 and IGFBP-1-bound IGF-I showed a relationship with the degree of retinopathy. However, further investigations are needed in order to clarify the basis and clinical relevance of this finding.

Diabetic neuropathy and nerve regeneration

Diabetic neuropathy is the most common peripheral neuropathy in western countries. Although every effort has been made to clarify the pathogenic mechanism of diabetic neuropathy, thereby devising its ideal therapeutic drugs, neither convinced hypotheses nor unequivocally effective drugs have been established. In view of the pathologic basis for the treatment of diabetic neuropathy, it is important to enhance nerve regeneration as well as prevent nerve degeneration. Nerve regeneration or sprouting in diabetes may occur not only in the nerve trunk but also in the dermis and around dorsal root ganglion neurons, thereby being implicated in the generation of pain sensation. Thus, inadequate nerve regeneration unequivocally contributes to the pathophysiologic mechanism of diabetic neuropathy. In this context, the research on nerve regeneration in diabetes should be more accelerated. Indeed, nerve regenerative capacity has been shown to be decreased in diabetic patients as well as in diabetic animals. Disturbed nerve regeneration in diabetes has been ascribed at least in part to all or some of decreased levels of neurotrophic factors, decreased expression of their receptors, altered cellular signal pathways and/or abnormal expression of cell adhesion molecules, although the mechanisms of their changes remain almost unclear. In addition to their steady-state changes in diabetes, nerve injury induces injury-specific changes in individual neurotrophic factors, their receptors and their intracellular signal pathways, which are closely linked with altered neuronal function, varying from neuronal survival and neurite extension/nerve regeneration to apoptosis. Although it is essential to clarify those changes for understanding the mechanism of disturbed nerve regeneration in diabetes, very few data are now available. Rationally accepted replacement therapy with neurotrophic factors has not provided any success in treating diabetic neuropathy. Aside from adverse effects of those factors, more rigorous consideration for their delivery system may be needed for any possible success. Although conventional therapeutic drugs like aldose reductase (AR) inhibitors and vasodilators have been shown to enhance nerve regeneration, their efficacy should be strictly evaluated with respect to nerve regenerative capacity. For this purpose, especially clinically, skin biopsy, by which cutaneous nerve pathology including nerve regeneration can be morphometrically evaluated, might be a safe and useful examination.

Evaluation of total IGF-I assay methods using samples from Type I and Type II diabetic patients

Measurements of circulating insulin-like growth factor-I (IGF-I) levels are an important part of many studies on growth and development. Circulating IGF-I levels are growth hormone (GH) dependent and are also impacted by age, gender, nutritional status and disease. Moreover, IGF-I is the main pharmacodynamic marker of GH activity. The majority of circulating IGF-I is associated with high affinity insulin-like growth factor-binding proteins (IGFBPs), making accurate and precise measurements of total IGF-I concentrations in biological matrices technically challenging. Many total IGF-I assay methods combine an immunoassay with a sample preparation method aimed at removing IGFBPs. However, not all sample preparation methods efficiently remove all IGFBPs or BP fragments (BPFs), and there is currently no reference method for IGF-I measurement against which these IGF-I assays can be calibrated. We have evaluated a number of IGF-I immunoassays and sample preparation methods using plasma samples from normal donors and from donors with Type I and Type II diabetes mellitus. In order to eliminate the variability between assays due to differences in assay standardization, we used the same preparation of highly pure, fully characterized IGF-I as the standard for all assays. We found that the data produced by many of the IGF-I assay methods showed good agreement when IGF-I levels in samples from normal individuals were measured. However, we found that these agreements were quite poor when IGF-I levels in samples from diabetics were measured. This was true of methods that claimed to physically separate IGFBPs from IGF-I either by acid/ethanol extraction or by acid chromatography. Several methods have recently been developed that physically separate IGF-I from IGFBPs followed by a chemical displacer to displace any residual BPs or BPFs from IGF-I. We found that the data generated by these displacement methods showed good agreement when assaying samples from diabetic as well as normal donors. There is considerable discussion in the literature as to whether individuals with diabetes have normal circulating levels of IGF-I. Many of the published studies are based on assays that may not accurately measure IGF-I levels due to problems with assay standardization and/or with assay methodology. Displacement methods may enable us to more accurately measure IGF-I levels in diabetes.

Translational regulation of renal proximal tubular epithelial cell transforming growth factor-beta1 generation by insulin

We have previously demonstrated that the proximal tubular cell may contribute to the pathogenesis of renal interstitial fibrosis in diabetes. Transforming growth factor (TGF)-beta1 is one of a group of pro-fibrotic cytokines and growth factors, which have been associated with the development of interstitial fibrosis. The aim of the current study was to examine the effect of insulin on the generation of TGF-beta1 by proximal tubular cells. HK-2 cells were grown to confluence in the absence of insulin, and serum deprived for 48 hours before all experimental manipulations. Addition of insulin (5 microg/ml) to the culture medium led to a time-dependent increase in TGF-beta1 concentration in the cell culture supernatant, and increased incorporation of radiolabeled amino acids into TGF-beta1 suggestive of de novo TGF-beta1 protein synthesis. Addition of insulin did not alter TGF-beta1 mRNA expression as assessed by reverse transcriptase-polymerase chain reaction or Northern analysis. Insulin-induced increase in TGF-beta1 concentration was not abrogated by actinomycin D, however, stimulation by insulin, in the presence of cycloheximide led to a dose-dependent decrease in TGF-beta1 production. Addition of insulin had no effect on TGF-beta1 mRNA stability as assessed by actinomycin D chase, but led to increased binding of a cytoplasmic protein to a putative stem loop structure in the 5'-UTR of TGF-beta1 mRNA, previously implicated in the posttranscriptional control of TGF-beta1 synthesis. To address the functional significance of insulin-induced alteration in TGF-beta1 synthesis, we examined its effect on matrix turnover. Insulin stimulated type IV collagen gene expression and an increase in the concentrations of the type IV collagen laid down in the extracellular matrix. This increase in type IV collagen was abrogated when cells were stimulated by insulin in the presence of an anti-TGF-beta1-blocking antibody. In conclusion the data demonstrate that insulin may directly alter the production of TGF-beta1 by renal proximal tubular cells by a posttranscriptional mechanism, and that this may have implications for the increase in extracellular matrix that accompanies diabetic nephropathy.

Insulin, insulin-like growth factors and colon cancer: a review of the evidence

Insulin and insulin-like growth factor (IGF) axes are major determinants of proliferation and apoptosis and thus may influence carcinogenesis. In various animal models, modulation of insulin and IGF-1 levels through various means, including direct infusion, energy excess or restriction, genetically induced obesity, dietary quality including fatty acid and sucrose content, inhibition of normal insulin secretion and pharmacologic inhibition of IGF-1, influences colonic carcinogenesis. Human evidence also associates high levels of insulin and IGF-1 with increased risk of colon cancer. Clinical conditions associated with high levels of insulin (noninsulin-dependent diabetes mellitus and hypertriglyceridemia) and IGF-1 (acromegaly) are related to increased risk of colon cancer, and increased circulating concentrations of insulin and IGF-1 are related to a higher risk of colonic neoplasia. Determinants and markers of hyperinsulinemia (physical inactivity, high body mass index, central adiposity) and high IGF-1 levels (tall stature) are also related to higher risk. Many studies indicate that dietary patterns that stimulate insulin resistance or secretion, including high consumption of sucrose, various sources of starch, a high glycemic index and high saturated fatty acid intake, are associated with a higher risk of colon cancer. Although additional environmental and genetic factors affect colon cancer, the incidence of this malignancy was invariably low before the technological advances that rendered sedentary lifestyles and obesity common, and increased availability of highly processed carbohydrates and saturated fatty acids. Efforts to counter these patterns are likely to have the most potential to reduce colon cancer incidence, as well as cardiovascular disease and diabetes mellitus.

Insulin-like growth factor (IGF)-binding protein-6 inhibits IGF-II-induced but not basal proliferation and adhesion of LIM 1215 colon cancer cells

IGF-II is an autocrine growth factor for many colon cancer cells. This study aimed to determine the role of IGF-II in proliferation and adhesion of LIM 1215 colon cancer cells. RT-PCR demonstrated expression of IGF-I and IGF-II mRNA. Addition of IGF-I or -II increased monolayer proliferation in a dose-dependent manner. Although addition of IGFBP-6 had no effect on basal proliferation, coincubation of IGFBP-6 decreased IGF-II but not IGF-I-induced proliferation. Colony formation in agar was increased by IGF-II, an effect inhibited by coincubation with IGFBP-6. IGFBP-6 alone significantly decreased colony formation. Preincubation of cells with IGF-II increased adhesion to type IV collagen, fibronectin and laminin. IGFBP-6 had no effect on basal cell adhesion but completely inhibited the effects of IGF-II. LIM 1215 colon cancer cells are therefore IGF-responsive but IGF-II is not a major autocrine factor for these cells in monolayer, suggesting heterogeneity between colon carcinoma cell lines with respect to the role of the IGF system.

IGF-I mRNA and signaling in the diabetic retina

IGF-I promotes the survival of multiple cell types by activating the IGF-I receptor (IGF-IR), which signals downstream to a serine/threonine kinase termed Akt. Because in diabetes vascular and neural cells of the retina undergo accelerated apoptosis, we examined IGF-I synthesis and signaling in the human and rat diabetic retina. In retinas obtained postmortem from six donors aged 64 +/- 8 years with a diabetes duration of 7 +/- 5 years, IGF-I mRNA levels were threefold lower than in the retinas of six age-matched nondiabetic donors (P = 0.005). In the retinas of rats with 2 months' duration of streptozotocin-induced diabetes, IGF-I mRNA levels were similar to those of control rats, but after 5 months of diabetes they failed to increase to the levels recorded in age-matched controls (P < 0.02). Retinal IGF-I expression was not altered by hypophysectomy, proving to be growth-hormone independent. IGF-IR levels were modestly increased in the human diabetic retinas (P = 0.02 vs. nondiabetic retinas) and were unchanged in the diabetic rats. Phosphorylation of the IGF-IR could be measured only in the rat retina, and was not decreased in the diabetic rats (94 +/- 18% of control values). In the same diabetic rats, phosphorylation of Akt was 123 +/- 21% of control values. There was not yet evidence of increased apoptosis of retinal microvascular cells after 5 months of streptozotocin-induced diabetes. Hence, in the retina of diabetic rats, as in the retina of diabetic human donors, IGF-I mRNA levels are substantially lower than in age-matched nondiabetic controls, whereas IGF-IR activation and signaling are not affected, at least for some time. This finding suggests that in the diabetic retina, the activation of the IGF-IR is modulated by influences that compensate for, or are compensated by, decreased IGF-I synthesis.

Effects of experimental diabetes on renal IGF/IGFBP system during neonatal period in the rat

Changes in the renal synthesis and concentration of insulin-like growth factors (IGFs) and their serum-binding proteins (IGFBPs) reported in insulin-deficient diabetes mellitus may be implicated in the alterations of the kidney function and morphology accompanying this disease. Most research on this subject has been carried out in adult animals, as well as in peripubertal rats, when the regulation of the IGF system is fully dependent on serum growth hormone (GH). However, relevant differences in the regulatory pathways of IGFs between adult and neonatal periods have been described. To examine the response of the IGF/IGFBP system of neonatal kidney to diabetes, renal IGF-I and -II and IGFBP-1, -2, and -3 concentration and mRNA expression were determined in streptozotocin-induced diabetic rat neonates. Diabetic neonates exhibited a kidney weight-to-body weight ratio higher than that of control rats, together with decreased IGF-I and increased IGF-II renal concentration. Because kidney mRNA expression of both IGFs decreased, the elevated renal IGF-II might result from increased uptake from circulation. Insulin treatment recovered the altered IGFs to control values, indicating the insulin-dependent regulation of IGFs in the neonatal kidney. Elevated levels of the IGFBP-1 and -2 in the kidney of diabetic neonates did not result from changes in their kidney mRNA transcript expression, suggesting also a possible uptake from circulation.