Cardiovascular risk factors in type I (insulin-dependent) diabetic patients with and without proteinuria

Diabetes mellitus en niños y adolescentes: complicaciones crónicas y enfermedades asociadas

Diabetes is one of the most common chronic diseases. Type 1, or autoimmune, diabetes accounts for more than 95 % of cases in children and adolescents. Chronic hyperglycemia per se is responsible for the development of several microvascular (retinopathy, nephropathy, neuropathy) and macrovascular complications (ischemic heart disease, cerebrovascular disease, and peripheral vascular disease). Other autoimmune diseases are also more frequent in type 1 diabetic patients. The present review aims to provide an update on some recent advances in this field to aid early detection of these complications and prevent or delay their progression through improved metabolic control.

Complications of diabetes mellitus in childhood

Complications of diabetes include retinopathy, nephropathy, neuropathy, macrovascular disease, and associated autoimmune diseases. Clinical manifestations of complications uncommonly present in childhood and adolescence. Screening during the early years can identify subclinical disease and it offers an opportunity for early intervention. The Diabetes and Complications Control Trial has provided evidence for the long-term benefits of good glycemic control in preventing and delaying the onset of microvascular complications. Complications begin to manifest during adolescence, during which time all efforts should be made to educate and support young persons in achieving optimal diabetes control.

Occurrence of sialic acids in healthy humans and different disorders

Sialic acid (SA), N-acetylated derivatives of neuraminic acid, play a central role in the biomedical functioning of humans. The normal range of total sialic acid (TSA) level in serum/plasma is 1.58-2.22 mmol L-1, the free form of SA only constituting 0.5-3 mumol L-1 and the lipid-associated (LSA) forms 10-50 mumol L-1. Notably, considerably higher amounts of free SA are found in urine than in serum/plasma (approximately 50% of the total SA). In inherited SA storage diseases such as Salla's disease, SA levels are elevated many times over, and their determination during clinical investigation is well established. Furthermore, a number of reports describe elevated SA levels in various other diseases, tentatively suggesting broader clinical utility for SA markers. Increased SA concentrations have been reported during inflammatory processes, probably resulting from increased levels of richly sialylated acute-phase glycoproteins. A connection between increased SA levels and elevated stroke and cardiovascular mortality risk has also been reported. In addition, SA levels are slightly increased in cancer, positively correlating with the degree of metastasis, as well as in alcohol abuse, diabetes, chronic renal failure and chronic glomerulonephritis. Several different mechanisms are assumed to underlie the elevated SA concentrations in these disorders. The apparent non-specificity of SA to a given disease limits the potential clinical usefulness of SA determination. In addition, some non-pathological factors, such as aging, pregnancy and smoking, may cause changes in SA concentrations. The absolute increases in SA levels are also rather small (save those in inherited SA storage disorders); this further limits the clinical potential of SA as a marker. Tentatively, SA markers might serve as adjuncts, when combined with other markers, in disease screening, disease progression follow-up, and in the monitoring of treatment response. To become clinically useful, however, the existing SA determination assays need to be considerably refined to reduce interferences, to be specific for certain SA forms, and to be more easy to use.

Diabetic nephropathy and pregnancy

Knowledge of the pathogenic mechanisms of diabetic nephropathy (by which hyperglycemia, hyperfiltration, and hypertension cause the gradual development of microproteinuria, mesangial expansion, and eventual glomerular closure) provides the basis for effective treatment. Intensified glycemic control and antihypertensive therapy that is safe for the fetus are crucial for success during pregnancy. Considered outcome measures include perinatal survival, size at birth, child development, and long-term maternal renal function.

Serum sialic acid concentration is elevated in IDDM especially in early diabetic nephropathy

OBJECTIVES

Elevated serum sialic acid concentration is a strong predictor of cardiovascular mortality in non-diabetic subjects. Because patients with insulin-dependent diabetes mellitus (IDDM) and albuminuria have a highly increased cardiovascular morbidity and mortality, we hypothesized that IDDM patients with albuminuria would have an increased concentration of serum sialic acid.

DESIGN

Cross-sectional study.

SETTING

Outpatient clinic at Steno Diabetes Centre, Gentofte, Denmark.

SUBJECTS

Twenty-six non-diabetic controls and 74 IDDM patients with normoalbuminuria (urinary albumin excretion [UAE] < 30 mg 24 h-1; n = 37), incipient nephropathy (UAE 30-300 mg 24 h-1; n = 20) and clinical nephropathy (UAE > 300 mg 24 h-1; n = 17), matched for sex, age and body mass index (BMI).

MAIN OUTCOME MEASURES

Serum sialic acid concentration, concurrent fasting blood glucose, glycated haemoglobin (HbA1c), serum creatinine, plasma fibrinogen and erythrocyte sedimentation rate.

RESULTS

Normoalbuminuric patients had a higher serum sialic acid concentration (mmol L-1) than non-diabetic controls (1.83 +/- 0.24 vs. 1.67 +/- 0.26; P < 0.02). Serum sialic acid concentration was further increased in patients with incipient nephropathy (2.02 +/- 0.37; P < 0.03) and in patients with clinical nephropathy (2.13 +/- 0.33; P < 0.002) compared with normoalbuminuric IDDM patients. Serum sialic acid correlated strongly with plasma fibrinogen (r = 0.78; P < 0.0001) and erythrocyte sedimentation rate (r = 0.62; P < 0.0001). In a multiple regression analysis including UAE, retinopathy status, fasting blood glucose, HbA1c, mean blood pressure, serum creatinine, age, BMI, duration and smoking. UAE and fasting blood glucose were the independent variables which correlated significantly with serum sialic acid concentration (P < 0.0001 and P < 0.05, respectively).

CONCLUSION

Serum sialic acid is elevated in IDDM especially in albuminuric patients. Whether elevated serum sialic acid is predictive for early diabetic nephropathy and cardiovascular disease in IDDM has to be shown in the future.

Plasma beta-thromboglobulin and platelet factor 4 are not increased in insulin-dependent diabetic patients with microalbuminuria

To evaluate the possibility that platelet dysfunctions contribute to the cardiovascular risk of microalbuminuric insulin-dependent diabetic (IDD) patients, we have measured beta-thromboglobulin (BTG) and platelet factor 4 (PF4) in 74 IDD patients with different degrees of albuminuria (8 macro-, 36 micro- and 30 normoalbuminuric) and in 30 non-diabetic control subjects. BTG values (20.4 +/- 1.5 SEM in normo-, 22.2 +/- 1.2 in micro-, 101.1 +/- 2.9 in macroalbuminuric patients and 21.8 +/- 1.1 IU/ml in control subjects) were significantly higher (P < 0.001) in the macroalbuminuric patients, but similar among the other groups. These results suggest that platelet hyperactivation is not present in the microalbuminuric stage of diabetic nephropathy, only in overt nephropathy.

Microalbuminuria: pathogenesis, prognosis and management

The development in recent years of sensitive assays specific for albumin has facilitated extensive investigation of the pathophysiology and clinical significance of microalbuminuria. It is now clear that the appearance of microalbuminuria represents a crucial event in the natural histories of diabetes mellitus and essential hypertension. It reflects the presence of generalized vascular damage and is strongly predictive of subsequent renal failure, cardiovascular morbidity, and death. Therapeutic interventions, including strict diabetic and blood-pressure control, can reduce microalbuminuria and improve the overall prognosis. The detection and treatment of microalbuminuria in these high-risk groups should now form an integral part of their management. Large-scale screening programmes are also recommended for insulin-dependent diabetics.

Exercise options for persons with diabetic complications

Exercise is a cornerstone in the management of diabetes, yet many persons with diabetes fail to participate in basic physical activity due to secondary diabetic complications. This inactivity can lead to disuse syndrome--a deterioration of functional capacity. Disuse syndrome, coupled with diabetes, can produce significant physiological problems and further disability. This review provides the health educator with information about the pathology and role of exercise for persons with diabetic complications. Examples of exercise to minimize disuse syndrome are given for individuals with peripheral vascular disease, retinopathy, neuropathies, and nephropathy.

Albuminuria reflects widespread vascular damage. The Steno hypothesis

Albuminuria in Type 1 (insulin-dependent) diabetes is not only an indication of renal disease, but a new, independent risk-marker of proliferative retinopathy and macroangiopathy. The coincidence of generalised vascular dysfunction and albuminuria, advanced mesangial expansion, proliferative retinopathy, and severe macroangiopathy suggests a common cause of albuminuria and the severe renal and extrarenal complications associated with it. Enzymes involved in the metabolism of anionic components of the extracellular matrix (e.g. heparan sulphate proteoglycan) vulnerable to hyperglycaemia, seem to constitute the primary cause of albuminuria and the associated complications. Genetic polymorphism of such enzymes is possibly the main reason for variation in susceptibility.