Chest
Volume 125, Issue 4, April 2004, Pages 1292-1298
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Clinical Investigations
EXERCISE
Altered Exercise Gas Exchange as Related to Microalbuminuria in Type 2 Diabetic Patients

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Study objective

Microalbuminuria in diabetes mellitus is a risk factor for cardiovascular disease. We hypothesized that microalbuminuria in type 2 diabetic patients is related to impaired cardiopulmonary function during exercise, and that the severity of impairment is correlated with the degree of microalbuminuria.

Design

Twenty of each of the following categories of subjects performed symptom-limited cardiopulmonary exercise testing on a cycle ergometer: (1) type 2 diabetic patients with normoalbuminuria (daily urinary albumin excretion [UAE] < 30 mg/d); (2) type 2 diabetic patients with microalbuminuria (daily UAE, 30 to 300 mg/d); and (3) normal control subjects.

Measurements and results

Oxygen consumption (

o2) of patients with microalbuminuria was lower than that of control subjects at anaerobic threshold (AT) [p < 0.001], and was lower than both control subjects (p < 0.001) and patients with normoalbuminuria (p = 0.015) at peak exercise. There was a progressive worsening in gas exchange efficiency at the lungs, as measured by minute ventilation (
e)/carbon dioxide production (
co2) at AT or Δ
e
co2 slope, (p = 0.006 and p = 0.019, respectively) going from control subjects to patients with normoalbuminuria and then to patients with microalbuminuria. Left ventricular ejection fractions and BP were similar in patients with normoalbuminuria and microalbuminuria. More patients with microalbuminuria (n = 9) than with normoalbuminuria (n = 2) demonstrated diastolic dysfunction (p = 0.013). These 11 patients had lower peak
o2 values (p = 0.001) and higher daily UAE (p = 0.028). An inverse linear relationship was found between peak
o2 and log10 daily UAE (r = − 0.57, r2 = 0.29, p < 0.001).

Conclusions

Abnormalities reflecting reduced oxygen transport and impaired gas exchange efficiency were found during exercise, and were especially profound in patients with microalbuminuria. These changes could be secondary to pulmonary microangiopathy and myocardial interstitial changes. Increases in capillary permeability to proteins may take place in the myocardium as they do in the kidneys, and contribute to impaired myocardial distensibility and hence diastolic dysfunction.

Section snippets

Subject Recruitment

From November 2000 to June 2002, three categories of subjects were recruited from Pamela Youde Nethersole Eastern Hospital, Hong Kong: (1) type 2 diabetic patients with normoalbuminuria (defined as daily urinary albumin excretion [UAE] < 30 mg/d), (2) type 2 diabetic patients with microalbuminuria (defined as daily UAE of 30 to 300 mg/d), and (3) normal control subjects. The latter were volunteers free of diabetes mellitus, and were recruited from among the hospital staff. Subjects of both

Results

Twenty patients were recruited into each of the three groups: control, normoalbuminuria, and microalbuminuria. Their baseline characteristics are shown in Table 1. There were no statistical differences among the three groups for age, body weight, and height. The three groups also had similar resting lung function (Table 2).

Exercise testing parameters are shown in Table 3. All subjects exercised until exhaustion. All stopped exercise because of leg fatigue or generalized weakness, none because

Discussion

Our findings confirmed that cardiopulmonary abnormalities were present in type 2 diabetic patients during exercise, and the severity of some of these abnormalities were correlated with the level of microalbuminuria. Impaired exercise capacity in terms of peak

o2 or WR has been documented in both type 1 diabetes711131415 and type 2 diabetes16 to be related to longstanding disease,11 higher total glycosylated hemoglobin A1,14 higher body mass index, female sex, older age, higher resting systolic

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  • Cited by (17)

    • Cardiorespiratory capacity is associated with favourable cardiovascular risk profile in patients with Type 2 diabetes

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      Future research will determine the duration, type, intensity and frequency of regular exercise which is required to induce beneficial alterations in hemostatic markers. To our knowledge, there is only one study evaluating the influence of exercise on UAE (Lau et al., 2004). In our study we confirmed that exercise capacity was inversely associated with UAE.

    • Lactate and ventilatory thresholds in type 2 diabetic women

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      The observed LT values were 0.97 ± 0.27 l O2 min−1[27] and 13.5 ± 1.9 ml O2 kg−1 min−1[34]. These differences may be related to pathological complications, insulin [33,36] and antihypertensive use [35,36] and higher fasting glucose values (188–215 mg/dl) [27,34,35] presented by the patients of cited studies, indicating a more advanced pathological condition when compared to our volunteers. Moreover, cycle ergometer exercise was employed in most studies [27,33,35,36].

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    This work was performed at the Departments of Medicine and Nuclear Medicine, Pamela Youde Nethersole Eastern Hospital, Hong Kong, China.

    All expenses were supported by the Department of Medicine, Pamela Youde Nethersole Eastern Hospital, Hong Kong, China.

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