Plasma adiponectin concentrations in patients with chronic renal failure: relationship with metabolic risk factors and ischemic heart disease

AIMS

To compare plasma adiponectin levels between healthy controls and patients with chronic renal failure and to examine for a relationship between plasma adiponectin levels and ischemic heart disease as well as aortic distensibility which is an early marker of atherosclerosis.

METHODS

We included 89 patients with CRF (45 on and 44 not on hemodialysis) and 70 controls in a cross-sectional study. Plasma adiponectin levels were measured by radioimmunoassay. Aortic distensibility was assessed by high-resolution ultrasonography.

RESULTS

Plasma adiponectin levels were significantly almost twice as high in patients with renal failure compared to controls (9.7 +/- 1.1 vs. 5.4 +/- 0.6 microg/ml, p < 0.0001). No significant differences were found between renal patients on hemodialysis and not on hemodialysis (p = 0.71). Multivariate linear regression analysis in the renal patient group demonstrated a significant negative relationship between plasma adiponectin levels and ischemic heart disease (p = 0.02). The same analysis in the control subjects group showed a significant, negative relationship between plasma adiponectin levels and body mass index (p = 0.02) and a highly significant positive relationship with the high density lipoprotein cholesterol (p < 0.0001). In the total study population, glomerular filtration rate was the only independent predictor of plasma adiponectin concentrations. Aortic distensibility was lower in renal patients than in controls at a high level of significance (p < 0.0001). However, no significant relationship could be found between plasma adiponectin and aortic distensibility in either the controls or the renal patients.

CONCLUSIONS

Plasma adiponectin levels are almost twice as high in patients with chronic renal failure in comparison with healthy controls, but not different between renal patients on and those not on hemodialysis. In addition, low plasma adiponectin levels are strongly associated with ischemic heart disease, but not with aortic distensibility in chronic renal failure.

Differential effects of high-fat and high-carbohydrate content isoenergetic meals on plasma active ghrelin concentrations in lean and obese women

AIM

To study the effect of two different isoenergetic meals, one rich in carbohydrates and one rich in fat, on plasma active ghrelin levels in lean or obese subjects.

METHODS

Eight obese and eight lean women, strictly matched for age, were fed two isoenergetic meals of different composition, one rich in fat and one rich in carbohydrates (CHO), on separate days. Plasma active ghrelin levels were measured just before and at 1, 2 and 3 hours after meal consumption.

RESULTS

Overall, plasma active ghrelin levels were significantly lower in the obese compared to the lean women (71.7 +/- 29.7 vs. 222.2 +/- 127.2 pmol/liter respectively, p < 0.0001). Furthermore, ghrelin levels decreased significantly by 30 % from baseline values in the lean subjects in the first hour after the CHO-rich meal (mean difference +/- SD): -66.2 +/- 49.0 pmol/liter (p = 0.03), returning to near-baseline levels by 2 hours, while no significant change was observed in the obese subjects. After the fat-rich meal, active ghrelin levels did not change significantly in either group (p > 0.05).

CONCLUSIONS

A fat-rich meal does not suppress plasma active ghrelin levels in either lean or obese women. Moreover, in obese, unlike lean women, a high carbohydrate meal also fails to suppress plasma ghrelin levels, which are already quite low. This suggests that ghrelin-induced satiety mechanisms may be compromised in these subjects.

Aortic distensibility is reduced in subjects with type 2 diabetes and cardiac autonomic neuropathy

BACKGROUND

Reduced aortic distensibility predicts cardiovascular mortality in patients with type 2 diabetes and impaired glucose tolerance. Cardiac autonomic neuropathy is common in subjects with diabetes. However, the relationship between the elastic properties of the aorta and autonomic neuropathy has not been studied to date in subjects with type 2 diabetes.

MATERIALS AND METHODS

In this cross-sectional study, a total of 87 subjects with type 2 diabetes (27 with and 60 without cardiac autonomic neuropathy) as well as 60 healthy individuals, matched for age and sex with the diabetic subjects, were examined. Cardiac autonomic neuropathy was diagnosed on the basis of the battery of the classic cardiovascular autonomic function tests. Aortic distensibility was assessed by high-resolution ultrasonography.

RESULTS

Diabetic patients had reduced aortic distensibility in comparison with the control subjects: 1.81 +/- 0.58 vs. 2.53 +/- 0.34 10-6 cm2 dyn-1, respectively (P < 0.0001). In addition, diabetic individuals with cardiac autonomic neuropathy had reduced aortic distensibility as compared with patients without this complication: 1.60 +/- 0.72 vs. 1.90 +/- 0.48 10-6 cm2 dyn-1, respectively (P = 0.02). Multivariate linear regression analysis in the diabetic group, after controlling for a number of confounding factors such as age, systolic and diastolic blood pressure, duration of diabetes and presence as well as severity of cardiac autonomic neuropathy, demonstrated a significant and independent association between duration of diabetes [B = -0.02, SE(B) = 0.01, P = 0.01] and presence of cardiac autonomic neuropathy [B = -0.29, SE(B) = 0.14, P = 0.03] with aortic distensibility.

CONCLUSION

Type 2 diabetes is associated with a significant reduction in the elastic properties of the aorta. In addition, known duration of diabetes and presence of cardiac autonomic neuropathy are the main predictors of aortic distensibility in subjects with type 2 diabetes.

Differential effects of high-fat and high-carbohydrate isoenergetic meals on cardiac autonomic nervous system activity in lean and obese women

Food ingestion can influence autonomic nervous system activity. This study compares the effects of 2 different isoenergetic meals on sympathetic nervous system (SNS) activity, assessed by heart rate variability (HRV) and plasma norepinephrine (NE) levels, in lean and obese women. Fifteen lean and 15 obese healthy women were examined on 2 occasions: after a carbohydrate (CHO)-rich and after a fat-rich test meal. Measurements of blood pressure, heart rate, resting energy expenditure, plasma glucose, lipids, insulin, leptin, and NE, as well as spectral analysis of the HRV, were performed at baseline and every 1 hour for 3 hours after meals. At baseline, obese women had higher SNS activity than lean controls (higher values of low-to-high frequency ratio [LF/HF], 1.52 +/- 0.31 v 0.78 +/- 0.13, P=.04; and plasma NE levels, 405.6 +/- 197.9 v 240.5 +/- 95.8 pg/mL, P<.0001). After the CHO-rich meal a greater increase in LF/HF and in plasma NE levels was observed in lean, compared to obese women (1.21 +/- 0.6 v 0.32 +/- 0.06, P=.04; and 102.9 +/- 35.4 v 38.7 +/- 12.3 pg/mL, P=.01, respectively), while no differences were observed after the fat-rich meal. Meal-induced thermogenesis was higher after the CHO-rich as compared to the fat-rich meal and was comparable between lean and obese women. Changes in HRV were not associated with the thermogenic response to the test meals. In conclusion, consumption of a CHO-rich meal causes greater cardiac SNS activation in lean than in obese women, while fat ingestion does not result in any appreciable change in either group. SNS activation does not appear to influence the thermic effect of the food in either lean or obese women.

Lack of Effect of Acute Repaglinide Administration on Postprandial Lipaemia in Patients with Type 2 Diabetes Mellitus

The effect of acute repaglinide administration (2 mg) on postprandial glycaemia and lipaemia has been examined in 20 subjects with type 2 diabetes mellitus. Each subject received in the morning, after a 12 to 14 h fast, a standard mixed meal (total energy 783 kcal), preceded by one tablet of 2 mg repaglinide or placebo. Chylomicrons and chylomicron-deficient plasma were prepared by ultracentrifugation. Triglyceride levels in CM fraction (CM-triglycerides) in total plasma as well as in CM-deficient plasma (non-CM-triglycerides) were determined. A significant reduction in postprandial glycaemia was observed after repaglinide administration compared to placebo ( p < 0.001). Plasma concentrations of total triglycerides, CM-triglycerides, non-CM-triglycerides, free fatty acids and the other plasma lipids measured, were not significantly different between the two phases of the study. It is concluded that, in contrast to sulphonylureas, acute repaglinide administration does not improve postprandial lipaemia in patients with type 2 diabetes.

Natural history and prognostic factors of diabetic nephropathy in type 2 diabetes

BACKGROUND

The causes and mechanisms of increased mortality of patients with diabetic nephropathy are unclear, and its natural history is poorly understood.

AIM

To evaluate risk factors for mortality in type 2 diabetic patients with nephropathy.

DESIGN

Retrospective study of clinical and biochemical parameters in diabetic nephropathic patients and controls sampled from a secondary care register.

METHODS

We studied 170 type 2 diabetic patients (from 1987 to 1995) with nephropathy (proteinuria >0.5 g/24 h) and 170 non-nephropathic patients. Follow-up was until death or December 1997. Details of demographics, clinical and treatment history were obtained from medical records.

RESULTS

Mean follow-up was 5.3 years. Of the patients with nephropathy at baseline, 63 (37%) died compared with 14 (8%) non-nephropathic patients (chi(2)=53.8, p<0.0001). Age- and sex-adjusted all-cause mortality rates were 8.1 (6.4, 9.8) and 1.4 (0.5, 2.2) deaths per 100 person-years, respectively (rate ratio 5.8). Forty-four patients (57%) died from cardiovascular causes (rate ratio 5.4). Mortality was directly proportional to degree of proteinuria: 0.5-2 g/24 h, 4.6 (2.9-7.1); >2 g/24 h, 9.9 (7.3-13.5) per 100 patient-years. A 36% (5-78%) excess risk of mortality was observed for each log unit increase in proteinuria. Multivariate Cox regression analyses confirmed a five-fold excess risk for all-cause and cardiovascular mortality in patients with nephropathy compared with those without. This was independent of other risk factors including baseline age [5% (1-8%)/year], creatinine [2.5 (1.12-5.6)/10 micromol/l] and glycaemic control (HbA(1c)) [15% (1-31%) per 1% rise].

CONCLUSIONS

Proteinuria is a potentially preventable and reversible risk factor associated with high mortality in type 2 diabetic patients. Prevention of the development of overt nephropathy and improvement in diabetes control may reduce mortality in these patients.

Role of neuropathy and plasma nitric oxide in recurrent neuropathic and neuroischemic diabetic foot ulcers

Various factors are associated with foot ulceration, including delayed reporting of ulcers, poor glycemic control, and severity of neuropathy. Several studies have looked at the role of nitric oxide in wound healing. However, no studies have examined its role in the occurrence and recurrence of diabetic foot ulceration. In a cross-sectional study we examined the role of neuropathy, retinopathy, nephropathy, and plasma nitric oxide (estimated from plasma nitrite and nitrate) levels in diabetic patients with recurrent and non-recurrent neuropathic and neuroischemic foot ulcers. Patients with recurrent foot ulcers had higher vibration perception threshold values compared to patients with non-recurrent foot ulcers (47.4 +/- 5.7 volts versus 39.5 +/- 10.3 volts respectively, P < 0.05). In addition, subjects with recurrent foot ulcers had significantly higher plasma nitric oxide compared to subjects with non-recurrent foot ulcers (46.9 +/- 6.3 microm/L versus 30.2 +/- 2.4 microm/L respectively, P < 0.01). Multivariate logistic regression analysis adjusted for age, sex, hemoglobin A1c, presence of retinopathy and nephropathy, vibration perception threshold, plasma creatinine, and total nitric oxide, indicated that only vibration perception threshold was independently associated with the presence of an ulcer [odds ratio: 1.26 (1.10-1.46); P <0.001)] and the recurrence of foot ulcers [odds ratio: 1.13 (1.01-1.27); P =0.04)]. This study has shown that although plasma nitric oxide is higher in patients with recurrent neuropathic and neuroischemic foot ulcers, severity of neuropathy was the most important factor associated with the development and recurrence of foot ulcers in diabetic patients.

Peripheral neuropathy does not invariably coexist with autonomic neuropathy in diabetes mellitus

Background: Peripheral somatic and autonomic neuropathies are the most common types of diabetic polyneuropathy. Although duration and degree of hyperglycemia are considered to be risk factors for both autonomic and peripheral neuropathy, recent studies have raised the question of a different development and natural history of these neuropathies in diabetes. In addition, a few studies have investigated the relationship between chronic painful and autonomic neuropathy. The aim of this study was to investigate to what extent autonomic and peripheral neuropathy coexist, as well as whether painful neuropathy is more common in diabetic patients with autonomic neuropathy. Methods: Subjects with type 1 (n=52; mean age 31.7 years) and type 2 diabetes (n=53; mean age 54.5 years) were studied. Evaluation of peripheral neuropathy was based on clinical symptoms (neuropathic symptom score), signs (neuropathy disability score), and quantitative sensory testing (vibration perception threshold). Assessment of autonomic neuropathy was based on the battery of standardized cardiovascular autonomic function tests. Results: Prevalence rates of pure autonomic and of pure peripheral neuropathy in patients with type 1diabetes were 28.8 and 13.5%, respectively. The respective rates in patients with type 2 diabetes were 20.7% (P=0.33 vs. type 1 diabetes) and 20.7% (P=0.32). Peripheral and autonomic neuropathy coexisted in 28.8% of type 1 and in 45.3% of type 2 diabetic subjects (P=0.08). Prevalence rates of chronic painful neuropathy in subjects with type 1 diabetes, with and without autonomic neuropathy, were 16.6 and 22.7%, respectively (P=0.85) and in type 2 diabetic subjects 20 and 22.2%, respectively (P=0.58). Multivariate analysis after adjustment for age, sex, blood pressure, duration of diabetes, HBA(1c), and presence of retinopathy or microalbuminuria showed that neither the indices of peripheral nerve function (neuropathic symptom score, neuropathy disability score, vibration perception threshold) nor the presence of peripheral neuropathy or chronic painful neuropathy are associated with the presence of autonomic neuropathy in individuals with either type 1 or type 2 diabetes. Conclusions: Peripheral and autonomic neuropathies do not invariably coexist in diabetes. In addition, chronic painful neuropathy may be present irrespective of the presence of autonomic neuropathy.

Impact of body mass on autonomic function in persons with type 2 diabetes

The aim of this study was to investigate the influence of body mass on autonomic nerve function in persons with type 2 diabetes. Towards this aim we studied two groups of diabetic persons. Group 1: n = 30 lean (mean age 57.2+/-12.5 years, body mass index (BMI) 22.5+/-1.8 kg/m2]. Group 2: n = 35 overweight and obese (age 52.3+/-10.3 years, BMI 28.8 + 3.2 kg/m2). Autonomic neuropathy (DAN) was assessed using the battery of the five classical tests. DAN was diagnosed when at least two of the five tests were abnormal. Abnormalities of the heart rate based tests were considered as indication of parasympathetic and of blood pressure changes as indication of sympathetic dysfunction. The prevalence rates of DAN were not different between group 2 and group 1 (54.2 and 53.3%, respectively, P = 0.54). The same was valid for the rates of parasympathetic and sympathetic dysfunction in the studied groups (51.4 and 53.3% (P = 0.87) in group 2 and 34.2 and 33.3% (P = 0.93) in group 1, respectively). When the values of the arithmetic expression of each single autonomic function test were compared, no significant difference could be shown between the studied groups. In addition, no significant correlation was found between BMI and indices of DAN. These data indicate that moderate increase of body mass does not affect autonomic function in persons with type 2 diabetes.

Methicillin-resistant Staphylococcus aureus: an increasing problem in a diabetic foot clinic

AIM

To study the prevalence of pathogenic organisms and the prevalence and outcome of methicillin-resistant Staphylococcus aureus (MRSA) infection in foot ulcers in diabetic patients.

METHODS

A retrospective analysis of wound swabs taken from infected foot ulcers in diabetic patients, selected from an outpatient diabetic foot clinic. Seventy-five patients (79 ulcers) with positive wound swabs were included. Size of ulcer and time to healing, in particular for MRSA-infected ulcers, were measured in all patients.

RESULTS

Gram-positive aerobic bacteria were the commonest micro-organism isolated (56.7%) followed by gram-negative aerobic bacteria and anaerobes (29.8% and 13.5%, respectively). Of the gram-positive aerobes, S. aureus was found most frequently and 40% were MRSA. MRSA was isolated more commonly in patients treated with antibiotics prior to the swab compared to those who had not received antibiotics (P = 0.01). Patients whose foot ulcers were infected by MRSA had longer healing time than patients whose ulcers were infected by methicillin-sensitive S. aureus (mean (range) 35.4 (19-64) and 17.8 (8-24) weeks, respectively, P = 0.03).

CONCLUSION

MRSA infection is common in diabetic foot ulcers and is associated with previous antibiotic treatment and prolonged time to healing. Further studies are required to assess the need for antibiotics in treating foot ulcers in diabetes and to assess the optimum therapeutic approach to this problem.

Corrected QT interval in relation to the severity of diabetic autonomic neuropathy

The aim of this study was to investigate to what extent the existence of objective signs of diabetic autonomic neuropathy affects the corrected QT interval (QTc) in diabetic subjects. A total of 105 diabetic subjects (type 1, n = 53; type 2, n = 52) as well as 40 matched (by age and sex) control subjects were studied. All subjects underwent the battery of five Ewing tests. Autonomic neuropathy was diagnosed if two of the five tests were abnormal. In addition, the result of each test was considered as normal (grade = 0), borderline (grade = 1) or abnormal (grade = 2), and on the basis of the sum of the scores we calculated a total score for autonomic neuropathy. The QTc interval was measured at rest, and a value > 440 ms was considered abnormal. The QTc interval was significantly more prolonged in diabetic persons with autonomic neuropathy than in those without neutopathy and in control subjects: 408.4 +/- 24.2 ms vs. 394.6 +/- 27.9 ms and 393.6 +/- 25.5 ms respectively (P = 0.001). Furthermore, multivariate analysis controlling for age, sex, systolic and diastolic blood pressure, body mass index (BMI), waist-hip ratio (WHR), smoking, type and duration of diabetes, type of treatment, HBA1c and total score of autonomic neuropathy eliminated the role of all these factors as potential confounders except for the total score of autonomic neuropathy, which was found to affect QTc interval independently and significantly (P = 0.012). In summary, the present study confirmed the well-known relation between autonomic neuropathy and QTc interval; in addition, it showed that QTc prolongation is associated with major degrees of autonomic neuropathy.