Elevated levels of leptin and insulin but not of TNF alpha are associated with hypertension in type 2 diabetic males.

Leptin and TNF alpha are thought to influence blood pressure. Therefore, the aim of our study was to investigate leptin and TNF alpha levels and their association with blood pressure, sex steroids, insulin, creatinine and lipids in type 2 diabetic patients. In 424 type 2 diabetic patients (79 hypertensive females [+Hf], 79 normotensive females [-Hf]; 133 hypertensive males [+Hm], 133 normotensive males [-Hm]) matched for sex, age and BMI serum leptin levels were measured by RIA and TNF alpha, insulin, estradiol, progesterone by ELISA as well as free testosterone by RIA. Leptin levels were comparable in +Hf and -Hf (16.5 +/- 1.0 microg/l vs 16.3 +/- 1.0 microg/l) but higher in +Hm as compared to -Hm (8.3 +/- 0.47 microg/l vs 6.5 +/- 0.34 microg/l; p<0.05). In addition, in comparison to -Hm serum levels of insulin (190 +/- 10 pmol/l vs 161 +/- 11 pmol/l; p< 0.005) and also of creatinine (118.6 +/- 3.6 micromol/l vs 101.7 +/- 2.3; p< 0.0001) were higher in +Hm. Pearson's Correlation coefficient revealed a positive correlation between levels of leptin and diastolic blood pressure (p<0.05) and also between leptin and insulin (p<0.001) in males, however, only before correction for BMI. No correlation between leptin and creatinine was found in males and females. Levels of TNF alpha were comparable in all subgroups. No correlation between levels of TNF alpha and serum leptin levels, blood pressure and insulin was found. In females TNF alpha was positively correlated with creatinine (p<0.001) and in males positively with progesterone (p<0.001). Taken together, higher serum leptin levels were found in hypertensive type 2 diabetic males as compared to normotensives, which may be related to the BMI and higher levels of insulin. These findings are accompanied by a trend to lower levels of free testosterone in hypertensive type 2 diabetic males. TNF alpha levels were comparable in female and male hypertensive and normotensive type 2 diabetic subjects.     

Plasma leptin levels are associated with coronary atherosclerosis in type 2 diabetes

Leptin signaling may promote atherothrombosis and lead to cardiovascular disease. However, whether leptin is associated with human atherosclerosis, distinct from thrombosis, is unknown. We determined the association of plasma leptin levels with coronary artery calcification (CAC), a measure of coronary atherosclerosis, in a cross-sectional study of type 2 diabetes. Leptin levels were associated with CAC after adjusting for established risk factors [odds ratio (95% confidence interval) for 5 ng/ml leptin increase: 1.31 (1.10-1.55); P = 0.002]. Leptin remained associated with CAC after further controlling for body mass index (BMI) [1.29 (1.07-1.55); P = 0.008], waist circumference [1.30 (1.09-1.57); P = 0.003], C-reactive protein (CRP) levels [1.28 (1.07-1.55); P = 0.008], and subclinical vascular disease [1.30 (1.08-1.57); P = 0.006]. Addition of BMI (P = 0.97), waist (P = 0.55), or CRP (P = 0.39) to a model with leptin failed to improve the model's explanatory power, whereas addition of leptin to a model with BMI (P = 0.029), waist (P = 0.006), or CRP (P = 0.005) improved the model significantly. Plasma leptin levels were associated with CAC in type 2 diabetes after controlling adiposity and CRP. Whether leptin signaling promotes atherosclerosis directly or represents a therapeutic target for the prevention of atherosclerotic cardiovascular disease remains to be explored.     

The development of microalbuminuria is associated with raised longitudinal adiponectin levels in female but not male adolescent patients with type 1 diabetes

AIMS/HYPOTHESIS: We determined the longitudinal relationship between adiponectin levels and the development of microalbuminuria in an inception cohort of children with type 1 diabetes. METHODS: Blood samples collected annually over a median of 9.0 (range 1.3-14.9) years were assayed for adiponectin and HbA(1c) in 55 children (36 girls) with type 1 diabetes and microalbuminuria whose age of onset of diabetes was 9.4 years (range 2.2-15.4). Samples were also assayed from normoalbuminuric children (controls) matched for age, sex and duration of diabetes. RESULTS: Overall, adiponectin levels were higher in girls than in boys, but only after 11 years of age (median [range]: 15.3 [5.8-124.4] vs 11.6 [4.1-26.5] mg/l, p < 0.001). Furthermore, adiponectin levels were higher in girls with microalbuminuria than in control girls, but this was only apparent after the onset of microalbuminuria (p = 0.001, adjusted for BMI, daily insulin dose, HbA(1c) and age). In boys, adiponectin levels did not differ between those with microalbuminuria and controls. Further sex-related discordant associations with adiponectin levels were observed; in girls, adiponectin levels were positively related to HbA(1c) levels (r = 0.2, p = 0.05) and urine albumin excretion (r = 0.3, p < 0.05) and inversely related to BMI (r = -0.2, p < 0.05). These associations were absent in boys. CONCLUSIONS/INTERPRETATION: In adolescent girls with type 1 diabetes but not in boys, adiponectin levels increase with increasing urine albumin excretion and onset of microalbuminuria. Although causal links cannot be inferred, this sexual dimorphism may reflect interactive effects of hyperglycaemia and sex steroids on risk of complications and adiponectin production.     

Circulating leptin levels are not associated with cardiovascular morbidity and mortality in women with diabetes: a prospective cohort study

Aims/hypothesis Leptin, an adipocyte-secreted hormone, plays an important role in regulating neuroendocrine and immune function as well as insulin resistance and metabolism. Our objective was to examine the relationship between leptin levels and cardiovascular morbidity and overall mortality in women with type 2 diabetes. Subjects and methods This prospective cohort study included 1,194 women with a confirmed diagnosis of type 2 diabetes, who provided a blood sample at baseline in 1989–1990. Participants were followed for 12 years for the development of health outcomes including cardiovascular disease (CVD) events as well as total mortality. Results There were 218 new CVD events and 228 deaths from all causes. Cox proportional hazards analysis was used to estimate the relative risks (RRs) for each quintile level of leptin compared with the lowest quintile. Leptin levels were positively associated with several CVD risk factors including BMI and inflammatory markers, but were not independently associated with the incidence of CVD or total mortality in women with diabetes. The multivariate RRs (95% CIs) for CVD across the quintiles of leptin were 0.96 (0.61–1.53), 0.99 (0.61–1.61), 1.04 (0.63–1.71), 1.02 (0.59–1.75) (p for trend = 0.83). Conclusions/interpretation Although circulating leptin levels are associated with obesity and inflammatory markers, they are not significantly related to the risk of CVD or mortality in women with diabetes.     

Free fatty acids are associated with pulse pressure in women, but not men, with type 1 diabetes mellitus

Cardiovascular disease (CVD) is the leading cause of death in type 1 diabetes mellitus (T1D). Pulse pressure, a measure of arterial stiffness, is elevated in T1D and associated with CVD. Free fatty acids (FFAs), elevated in women and abdominal adiposity, are also elevated in T1D and CVD. We thus examined the association of fasting FFAs with pulse pressure and coronary artery calcification (CAC, a marker of coronary atherosclerotic burden) in an adult population (n = 150) of childhood-onset T1D and whether any such associations varied by abdominal adiposity and sex. Mean age and diabetes duration were 42 and 33 years, respectively, when CAC, visceral abdominal adiposity (VAT), and subcutaneous abdominal adiposity (SAT) were determined by electron beam tomography. Free fatty acids were determined by in vitro colorimetry. Pulse pressure was calculated as systolic blood pressure minus diastolic blood pressure. Free fatty acids were log transformed before analyses, and all analyses were controlled for serum albumin. Free fatty acids were associated with pulse pressure in women (r = 0.24, P = .04), but not in men (r = 0.07, P = .55). An interaction for the prediction of pulse pressure was noted between FFAs and both VAT (P = .03) and SAT (P = .008) in women, but only a marginal interaction with SAT (P = .09) and no interaction for VAT (P = .40) with FFAs were observed in men. In multivariable linear regression analysis allowing for serum albumin, age, height, heart rate, albumin excretion rate, hemoglobin A_1c, high-density lipoprotein cholesterol, hypertension medication use, FFAs, SAT, and the interaction between FFAs and SAT, the interaction between FFAs and SAT remained associated with pulse pressure in women (FFAs, P = .04; interaction term, P = .03), but not men (FFAs, P = .32; interaction term, P = .32). FFAs showed no association with log-transformed CAC. Although FFAs were not associated with CAC in either sex, they were associated with pulse pressure in women and their effect appeared to vary by abdominal adiposity, particularly SAT. This finding might help explain the loss of the sex difference in CVD in T1D.     

Serum leptin levels are associated with bone mass in nonobese women

Both serum leptin and bone mineral density are positively correlated with body fat, generating the hypothesis that leptin may be a systemic and/or local regulator of bone mass. We investigated 214 healthy, nonobese Australian women aged 20-91 yr. Bone mineral content, projected bone area, and body fat mass were measured by dual energy x-ray absorptiometry and fasting serum leptin levels by RIA. Associations between bone mineral content (adjusted for age, body weight, body fat mass, and bone area) and the natural logarithm of serum leptin concentrations were analyzed by multiple regression techniques. There was a significant positive association at the lateral spine, two proximal femur sites (Ward's triangle and trochanter), and whole body (partial r(2) = 0.019 to 0.036; all P < 0.05). Similar trends were observed at the femoral neck and posterior-anterior-spine. With bone mineral density the dependent variable (adjusted for age, body weight, and body fat mass), the association with the natural logarithm of leptin remained significant at the lateral spine (partial r(2) = 0.030; P = 0.011), was of borderline significance at the proximal femur sites (partial r(2) = 0.012 to 0.017; P = 0.058 to 0.120), and was not significant at the other sites. Our results demonstrate an association between serum leptin levels and bone mass consistent with the hypothesis that circulating leptin may play a role in regulating bone mass.     

Elevated serum ceruloplasmin levels are associated with albuminuria in Korean men with type 2 diabetes mellitus

The aim of this study was to examine the possible association between serum ceruloplasmin, a copper carrying protein, and albuminuria in 456 males with type 2 diabetes. Multivariate regression analysis demonstrated that elevated serum ceruloplasmin was a determinant of albuminuria independently of conventional risk factors.     

The age at diagnosis of type 1 diabetes continues to decrease in Belgian boys but not in girls: a 15-year survey

BACKGROUND: The age at clinical onset of type 1 diabetes is decreasing. Preliminary Belgian data suggested that this anticipation occurred preferentially in boys. We investigated whether this gender-specific anticipation could be confirmed over a 15-year observation period. METHODS: In Antwerp, we studied incidence trends between 1989 and 2003 in 746 type 1 diabetic patients under age 40. For 2928 antibody-positive patients diagnosed nationwide during the same period, age at diagnosis was analysed according to gender and calendar year. RESULTS: In Antwerp, the incidence of type 1 diabetes under age 15 increased significantly with time from 10.9/100 000/year in 1989-1993 to 15.8/100 000/year in 1999-2003 (p = 0.008). The rising incidence in children was largely restricted to boys under age 10 where the incidence more than doubled during the 15-year period (6.8/100 000/year in 1989-1993 vs 17.2/100 000/year in 1999-2003; p < 0.001). Such an increase was not found in girls under age 10 (p = 0.54). This selective trend toward younger age at diagnosis in boys was confirmed in the larger group of Belgian patients where the median age at diagnosis decreased in boys-but not in girls-from 20 years in 1989-1993 to 15 years in 1999-2003 (p < 0.001). CONCLUSIONS: Over a 15-year observation period, a selective anticipation of clinical onset of type 1 diabetes was found in boys but not in girls. This suggests that an environmental factor may preferentially accelerate the sub-clinical disease process in young boys.     

Insulin-resistant patients with type 2 diabetes mellitus have higher serum leptin levels independently of body fat mass

In obese people, an increase of plasma leptin levels is well-known and is seen as a consequence of the increased body fat mass. Moreover, a relationship between fasting concentrations of leptin and insulin has been described. Hyperinsulinemia is considered to be indicative of insulin resistance. We aimed at elucidating the interrelations between leptin, insulin and insulin resistance in type 2 diabetic patients. Under metabolic ward conditions, we investigated 21 moderately overweight men with type 2 diabetes. The patients had a mean age of 49.1 years, a mean body mass index (BMI) of 26.8 kg/m², and a mean diabetes duration of 82.5 months. All patients were treated with diet alone. We measured fasting leptin and insulin levels, body composition by determination of total body water, and insulin resistance by euglycemic hyperinsulinemic clamp technique. At univariate analysis, fasting leptin level significantly and positively correlated with BMI (r=0.49, p=0.02) and with fasting insulin (r=0.69, p=0.001), while it negatively correlated with the glucose disposal rate (r=−0.62, p=0.002). Furthermore, leptin was inversely correlated with HDL-cholesterol (r=−0.45, p=0.04). When excluding the influence of body fat mass or of BMI in partial correlation analysis, the correlations between leptin and insulin or insulin sensitivity remained significant. The relationship between insulin resistance (as measured directly in the clamp experiments) and leptin concentrations was also shown by subdividing the diabetic patients according to tertiles of insulin sensitivity. The highest fasting leptin levels were observed in those patients with the most expressed insulin resistance. Our data point to a functional relationship between insulin resistance and leptin concentrations in insulin-resistant type 2 diabetic men, independently of body composition. This relationship is believed to be mediated by insulin. Received: 2 August 2000 / Accepted in revised form: 20 February 2002     

Serum leptin levels are higher but are not independently associated with severity or mortality in the multiple organ dysfunction/systemic inflammatory response syndrome: a matched case control and a longitudinal study

OBJECTIVE: Hypercatabolism and immune dysfunction are closely associated with the development of systemic inflammatory response--multiple organ dysfunction (SIRS/MODS) in critical illness. It remains unclear however, whether leptin, an adipocyte-derived hormone whose levels are influenced by several cytokines and which regulates immune function, food-intake and energy expenditure is independently related to the development of and/or severity and mortality from SIRS/MODS. DESIGN AND PATIENTS: To assess the role of leptin in SIRS/MODS we performed a matched case control and a longitudinal study (14 days) in 35 critically ill patients with SIRS/MODS and 35 matched controls. RESULTS: Baseline leptin levels were positively associated with body mass index (BMI) and TNF-alpha (P < 0.01) in patients and with IGF-1 and IL-6 levels (P < 0.05) in controls. Furthermore, leptin levels exhibited a progressive increase from the first to the last day of the study and although baseline levels were not different, peak leptin levels as well as leptin levels on the last day of the study were significantly higher in cases than in controls (P < 0.05). TNF-alpha levels, IL-6 and cortisol levels were also higher, whereas IGF-1 levels were lower in cases (P < 0.05). To assess whether leptin levels are independently associated with SIRS/MODS we performed multivariate logistic regression analysis which revealed that leptin up-regulation in cases is mediated by elevated TNF-alpha and cortisol levels. Finally, there was no independent association between leptin and survival in this group of critically ill patients. CONCLUSION: We conclude that cytokines and cortisol upregulate leptin levels, which may contribute to the development of the hypercatabolism, wasting and immune dysfunction but leptin levels are not independently associated with severity or mortality of patients with systemic inflammatory response-multiple organ dysfunction.     

Elevated urokinase-type plasminogen activator plasma levels are associated with deterioration of liver function but not with hepatocellular carcinoma

We measured urokinase-type plasminogen activator (u-PA) plasma levels in patients with various chronic liver diseases, including hepatocellular carcinoma (HCC), also measuring these levels in healthy volunteers. Plasma u-PA levels in the group of patients with decompensated liver cirrhosis (mean modified Pugh score of 14 points) were markedly elevated and significantly higher than those in the patients with decompensated liver cirrhosis with HCC (modified Pugh score of 10 points), those with compensated liver cirrhosis with HCC, and those with compensated liver cirrhosis. Patients in all these three latter groups had moderately and significantly elevated u-PA levels compared to levels in the chronic hepatitis group and the healthy volunteers, but the levels were not significantly different from each other. There was no relationship between u-PA plasma level and the type of HCC tumor invasion or number or size of tumors. Significant correlations were found between u-PA plasma levels and the results of seven different liver function tests in three groups without associated HCC; u-PA antigen and prothrombin time (%), hepaplastin test (%), serum cholinesterase, serum albumin, serum total cholesterol, and indocyanine green clearance correlated negatively, while u-PA antigen and serum total bilirubin correlated positively. These results suggest that plasma u-PA is associated with deterioration of liver function but not with HCC invasion.     

Elevated serum CK18 levels in chronic hepatitis C patients are associated with advanced fibrosis but not steatosis

Summary. Cytokeratin‐18 (CK‐18) is a major intermediate filament protein in liver cells. The M30 fragment of CK‐18 has been identified as a useful marker of apoptosis associated with fibrosis and steatosis in nonalcoholic steatohepatitis (NASH). We sought to assess the relationship of this marker and steatosis in a cohort of adult patients with chronic hepatitis C. The study cohort included sera from 267 treatment‐naïve chronic hepatitis C (CHC) patients and 100 healthy controls with normal alanine aminotransferase (ALT). Biopsies from CHC patients were assessed for METAVIR fibrosis stage, Histology Activity Index (HAI) inflammation score and steatosis grade by expert histopathologists. The M30 fragment of CK‐18 was quantified by ELISA. Wilcoxon Rank Sum, Spearman Correlation and Linear Regression tests were performed for statistical analysis. Median CK‐18 levels were higher in CHC patients compared to controls (411 vs 196 U/L, P < 0.0001). Fibrosis stage was associated with increasing serum CK‐18 levels (P = 0.015) and CK‐18 levels were higher for F2–F4 vs F0–F1 (500 vs 344 U/L; P = 0.001). There was no association between CK‐18 and increasing steatosis grade 1, 2 or 3 (460.7 vs 416.8 vs 508.3 U/L; P = 0.35) and presence or absence of steatosis (445.3 vs 365.8 U/L; P = 0.075). Fibrosis stage was independently associated with serum M30 in a multivariable linear regression model (P = 0.03). CK‐18 levels were higher in CHC compared to healthy controls and associated with hepatic fibrosis. There was no difference in CK‐18 M30 levels between CHC patients with and without steatosis. Although apoptosis may still contribute to hepatitis C virus (HCV)‐mediated steatosis, our results suggest that serum CK‐18 will not be a clinically useful test for identifying significant steatosis in CHC.     

Elevated levels of mannan-binding lectin in patients with type 1 diabetes

The hepatic protein mannan-binding lectin (MBL) activates the complement system on binding to carbohydrate patterns and is involved in first-line defense against invading microorganisms. Emerging evidence indicates that in some situations MBL may cause inexpedient complement activation and tissue injury through binding to endothelial glycosylations. MBL levels are suppressed by insulin treatment in critically ill patients, and, hypothetically, hepatic portal hypoinsulinemia could lead to increased levels of MBL in patients with type 1 diabetes. We measured MBL and C-reactive protein (CRP) levels in 132 normoalbuminuric type 1 diabetic patients and 66 healthy age- and sex-matched controls. The median MBL concentration was higher in diabetic patients than in healthy controls [1290 micro g/liter (interquartile range, IQR 354-2961 micro g/liter) vs. 970 micro g/liter (IQR 277-1607 micro g/liter), P = 0.025], whereas CRP concentrations were similar among patients and controls [1.42 mg/liter (IQR 0.95-2.21) vs. 1.21 mg/l (IQR 0.74-2.13), NS]. In diabetic subjects, CRP levels correlated with poor glycemic control as indicated by hemoglobin A(1c) and daily insulin dose, which was not the case with MBL. MBL concentrations were positively correlated with urinary albumin excretion (r = 0.22; P = 0.013) and increased with increasing urinary albumin excretion tertile (P = 0.036). In conclusion, our data demonstrate that circulating MBL concentrations are significantly elevated in patients with type 1 diabetes and suggest a possible role of MBL in the pathogenesis of renovascular complications in diabetes.     

Serum adiponectin levels are inversely associated with overall and central fat distribution but are not directly regulated by acute fasting or leptin administration in humans: cross-sectional and interventional studies

Adiponectin is an adipocyte-secreted protein that circulates in high concentrations in the serum and acts to increase insulin sensitivity. Previous studies have shown that serum adiponectin is inversely associated with fat mass and insulin resistance in humans and that acute fasting decreases adipose tissue adiponectin mRNA expression in rodents. Whether acute energy deprivation, body fat distribution, or serum hormone levels are associated with circulating adiponectin in humans remains largely unknown. To identify predictors of serum adiponectin levels, we evaluated the association of adiponectin with several anthropometric, metabolic, and hormonal variables in a cross-sectional study of 121 women without a known history of diabetes. We also performed interventional studies to assess whether fasting for 48 h and/or leptin administration regulates serum adiponectin in healthy men and women. Our cross-sectional study shows that, in addition to overall obesity, central fat distribution is an independent negative predictor of serum adiponectin and suggests that adiponectin may represent a link between central obesity and insulin resistance. In addition, estradiol is negatively and independently associated with adiponectin, whereas there is no association between serum adiponectin and leptin, cortisol, or free testosterone levels. Our interventional studies demonstrate that neither fasting for 48 h, resulting in a low leptin state, nor leptin administration at physiological or pharmacological doses alters serum adiponectin levels. Further studies are needed to fully elucidate the physiology of adiponectin in humans and its role in the pathogenesis of insulin-resistant states.     

Immunoglobulin heavy chain switch region polymorphisms are not associated with type 1 diabetes

In order to ascertain whether the immunoglobulin heavy chain genes are important in the aetiology of Type 1 diabetes, we have used restriction fragment length polymorphism (RFLP) analysis of genomic DNA to study 148 Caucasoid subjects with Type 1 diabetes and 146 normal Caucasoid subjects. A DNA probe homologous to the switch regions for the IgM (S mu) and IgA1 (S alpha 1) genes when used in conjunction with the restriction endonuclease Sst I detects RFLPs at both these loci. There were no significant differences in phenotype or gene frequencies for the alleles of S mu or S alpha 1 in the patients when compared with control subjects; nor were there significant associations of S mu or S alpha 1 with HLA-DR type or gender.