Serum fructosamine as a screening test for diabetes in the elderly: a pilot study

A review of glycated albumin as an intermediate glycation index for controlling diabetes

INTRODUCTION

This article reviews glycated albumin (GA) as a potential intermediate-term glycation index to fill the gap between self-monitoring of blood glucose (SMBG) and hemoglobin A1c testing in diabetes management. The introduction gives an assessment of available short-, medium-, and long-term glycemic indicators. METHODOLOGIES AND UTILITY: Methods of GA measurement are summarized, and the variance of normal and diabetic GA values are discussed. Greatest uniformity in GA measurement is generally associated with immunoassay and the newer affinity chromatography methodologies utilized by reference laboratories. Utility of GA measurement includes its value as a marker for glycation, its substantial relationship to diabetes complications such as nephropathy and coronary artery disease, and as an unambiguous indicator of glycemic control in diabetes patients undergoing hemodialysis. Studies support the utility of GA in detecting short-term changes in glycemic control, and GA testing has been strongly recommended for gestational diabetes.

RESULTS AND DISCUSSION

The results of a survey with mailings to over 3500 diabetes care professionals primarily in the United States are outlined and analyzed (margin of error: +/-6.5%, 95% confidence). Respondents strongly supported the need for a test for intermediate glycemic control as well as the utility of a rapid GA test as a monthly glycemic indicator.

CONCLUSIONS

Such a test, as yet unavailable, could increase compliance and enhance empowerment among diabetes patients. It also has the potential to reduce the number of recommended SMBG tests, which may result in significant health care cost savings.

The biochemistry of aging

Although philosophers and scientists have long been interested in the aging process, general interest in this fascinating and highly important topic was minimal before the 1960s. In recent decades, however, interest in aging has greatly accelerated, not only since the elderly form an ever-increasing percentage of the population, but because they utilize a significant proportion of the national expenditures. In addition, many people have come to the realization that one can now lead a very happy, active, and productive life well beyond the usual retirement age. Scientifically, aging is an extremely complex, multifactorial process, and numerous aging theories have been proposed; the most important of these are probably the genomic and free radical theories. Although it is abundantly clear that our genes influence aging and longevity, exactly how this takes place on a chemical level is only partially understood. For example, what kinds of genes are these, and what proteins do they control? Certainly they include, among others, those that regulate the processes of somatic maintenance and repair, such as the stress-response systems. The accelerated aging syndromes (i.e., Hutchinson-Gilford, Werner's, and Down's syndromes) are genetically controlled, and studies of them have decidedly increased our understanding of aging. In addition, C. elegans and D. melanogaster are important systems for studying aging. This is especially true for the former, in which the age-1 mutant has been shown to greatly increase the life span over the wild-type strain. This genetic mutation results in increased activities of the antioxidative enzymes, Cu-Zn superoxide dismutase and catalase. Thus, the genomic and free radical theories are closely linked. In addition, trisomy 21 (Down's syndrome) is characterized by a significantly shortened life span; it is also plagued by increased oxidative stress which results in various free radical-related disturbances. Exactly how this extra chromosome results in an increased production of reactive oxygen species is, however, only partially understood. There is considerable additional indirect evidence supporting the free radical theory of aging. Not only are several major age-associated diseases clearly affected by increased oxidative stress (atherosclerosis, cancer, etc.), but the fact that there are numerous natural protective mechanisms to prevent oxyradical-induced cellular damage speaks loudly that this theory has a key role in aging [the presence of superoxide dismutase, catalase, glutathione peroxidase, and glutathione reductase, among others; various important intrinsic (uric acid, bilirubin, -SH proteins, glutathione, etc.) and extrinsic (vitamins C, E, carotenoids, flavonoids, etc.) antioxidants; and metal chelating proteins to prevent Fenton and Haber-Weiss chemistry]. In addition, a major part of the free radical theory involves the damaging role of reactive oxygen species and various toxins on mitochondria. These lead to numerous mitochondrial DNA mutations which result in a progressive reduction in energy output, significantly below that needed in body tissues. This can result in various signs of aging, such as loss of memory, hearing, vision, and stamina. Oxidative stress also inactivates critical enzymes and other proteins. In addition to these factors, caloric restriction is the only known method that increases the life span of rodents; studies currently underway suggest that this also applies to primates, and presumably to humans. Certainly, oxidative stress plays an important role here, although other, as yet unknown, factors are also presumably involved. Exactly how the other major theories (i.e., immune, neuroendocrine, somatic mutation, error catastrophe) control aging is more difficult to define. The immune and neuroendocrine systems clearly deteriorate with age. (ABSTRACT TRUNCATED)

Clinical validity of a self-test fructosamine in outpatient diabetic management

BACKGROUND

Measurement of glycated hemoglobin and hemoglobin A1c (HbA1c) is now well established as the best means of measuring overall glucose control in managing diabetes. Other glycated serum protein assays reflecting recent glycemic control, e.g., glycated albumin and glycated protein (fructosamine), have also been validated in clinical studies. Regardless of the method, the expense and inconvenience of laboratory testing of blood samples may contribute to the well-documented underutilization of clinical glycated protein assessment. Accordingly, a rapid, inexpensive fingerstick test of fructosamine has been developed. This study cross-sectionally and prospectively assesses the clinical validity of fingerstick fructosamine versus laboratory determination.

METHODS

Fifty-one subjects (18 control, 33 with diabetes) participated in a cross-sectional study and 20 subjects with type 2 diabetes participated in a prospective, 6-week study with clinical intervention consisting of glipizide gits or metformin in mono- and combination therapy. Subjects had weekly laboratory determination of serum fructosamine, glycated hemoglobin, and fasting glucose; fingerstick fructosamine was obtained at each clinic visit.

RESULTS

Fingerstick fructosamine was shown to correlate highly to laboratory fructosamine (r = 0.80, p < 0.001) and glycated hemoglobin (r = 0.81, p < 0.001). In the clinical intervention study subjects, significant decreases in fasting glucose (p < 0.001), laboratory fructosamine (p < 0.001), and fingerstick fructosamine (p < 0.001) were noted compared to baseline. The subject's self-test fingerstick fructosamine mirrored laboratory testing of fructosamine in detection of changes in clinical glucose control.

CONCLUSIONS

This study demonstrates that fingerstick fructosamine correlates well to laboratory assessment of fructosamine and glycated hemoglobin. The patient self-test fructosamine provides the same clinical information as laboratory assessment.

Serum fructosamine level and the risk of hip fracture in elderly women: a case-cohort study within the study of osteoporotic fractures

PURPOSE

While a high serum fructosamine level may be an indicator of undiagnosed diabetes, a low level may be indicative of poor nutrition or frailty. As malnutrition is a risk factor for osteoporosis, low serum fructosamine levels may be associated with an increased risk of osteoporotic fracture. We examined the association between serum fructosamine levels and the risk of subsequent hip and vertebral fracture.

SUBJECTS AND METHODS

We performed a case-cohort study within the Study of Osteoporotic Fractures. Subjects were elderly, ambulatory, community-dwelling, Caucasian, women. Fructosamine levels were measured in baseline serum. Incident vertebral fractures were identified by comparing baseline spinal radiographs to those obtained an average of 3.5 years later. Hip fractures were confirmed by radiograph. We randomly selected 101 women who suffered a hip fracture, 100 women who developed a vertebral fracture, and 276 controls. We compared fructosamine levels in women with subsequent osteoporotic fractures to controls. All analyses were adjusted for age, weight, and use of estrogens.

RESULTS

Women with fructosamine levels in the lowest decile (< or = 223 micromol/L) had a three-fold increase in the risk of hip fracture (95% confidence interval 1.4-6.4), compared with all other women. Adjustment for markers of frailty, including smoking, functional status, and serum albumin levels, reduced the strength of this association. No clear association was observed between serum fructosamine level and the risk of vertebral fracture.

CONCLUSION

Low serum fructosamine levels, which likely reflect frailty or malnutrition, may be a useful clinical tool to identify women at risk for hip fracture.

Diabetes mellitus in older persons

The relative importance and mechanisms of deficient insulin secretion versus deficient action during aging are still debated. Whatever mechanisms eventually explain the emergence of impaired glucose tolerance during aging, the clinically important extrinsic modifiers of glycemic levels include diet, medications, activity, and chronic illness and stress. Although prospective studies are not available in the elderly, retrospective studies suggest that good blood glucose control reduces the likelihood and severity of stroke, cardiovascular disease, visual impairment, nephropathy, infections, and even cognitive dysfunction. Good control also seems to reduce nocturia, polyuria, and hypovolemia. Therapy of older persons begins with diet, exercise, and oral agents, failing which, insulin is employed. Since many of the newer oral agents carry less risk of hypoglycemia, achieving tighter control in the elderly has become more feasible.

Diabetes in the elderly

Diabetes affects at least 20% of the population over the age of 65. Half of these patients are unaware that they have the disease. Diabetes in middle-aged subjects is characterized by an impairment in glucose induced insulin release, increased fasting hepatic glucose output and resistance to insulin mediated glucose disposal. In contrast, diabetes in the elderly is primarily associated with insulin deficiency. The presentation of diabetes in the aged is often non-specific. The elderly have an increased frequency of complications from diabetes. They are particularly susceptible to hypoglycaemia, because of reduced awareness of hypoglycaemic warning symptoms and altered release of counterregulatory hormones. Although no data are yet available from randomized controlled trials, there is abundant epidemiological evidence to suggest that adequate control of blood glucose can be expected to reduce the risk of long-term complications. A team approach is ideal for the management of the elderly patient with diabetes. Little data is available on which to base a diet and exercise prescription for elderly patients. Gliclazide appears to be the sulphonylurea of choice in the aged because it is associated with a lower frequency of hypoglycaemic reactions. Urine glucose testing is unreliable, and capillary glucose monitoring is preferred. Fructosamine may prove to be superior to haemoglobin A1C for monitoring long-term control.