Cardiorespiratory Fitness Is Related to Physical Inactivity, Metabolic Risk Factors, and Atherosclerotic Burden in Glucose-Intolerant Renal Transplant Recipients

Abstract

The mechanisms of reduced cardiorespiratory fitness (CF) in renal transplant recipients (RTR) have not been studied closely. This study evaluated the relationships between CF and specific cardiovascular risk factors (metabolic syndrome [MS], physical inactivity, myocardial ischemia, and atherosclerotic burden) in glucose-intolerant RTR. Data were recorded on 71 glucose-intolerant RTR (mean age 55 yr; 55% male; median transplant duration 5.7 yr). MS was defined using National Cholesterol Education Programme Adult Treatment Panel III criteria. Resting and exercise stress echocardiography were performed, and myocardial ischemia was identified by new or worsening wall motion abnormalities. Cardiorespiratory fitness was determined using peak oxygen uptake (VO 2 ) by expired gas analysis. Atherosclerotic burden was assessed by carotid intima-media thickness (IMT). Mean peak VO 2 was 19 ؎ 7 ml/kg per min and was significantly lower than predicted peak VO 2 (29 ؎ 6 ml/kg per min; P < 0.001). Patients with MS (63%) had reduced CF (17 ؎ 6 versus 22 ؎ 8 ml/kg per min; P ‫؍‬ 0.001) and were more likely to be physically inactive (76 versus 48%; P ‫؍‬ 0.02). CF was reduced in 14 patients with myocardial ischemia (15 ؎ 3 versus 20 ؎ 7 ml/kg per min; P ‫؍‬ 0.05). CF was positively correlated with male gender, height, and physical activity and inversely correlated with number of MS risk factors and IMT (adjusted R 2 ‫؍‬ 0.66). Carotid IMT added incremental value to clinical variables in determining VO 2 (adjusted R 2 ‫؍‬ 0.65 versus 0.63; P ‫؍‬ 0.04). Reduced CF is associated with physical inactivity, MS, and atherosclerotic burden in glucose-intolerant RTR. Further studies should address whether increasing exercise and modifying MS risk factors improve CF in RTR.

Exercise Limitation Following Transplantation

“…When data including RTx, controls, and chronic renal failure on dialysis patients were pooled, Vo 2peak was strongly correlated with thigh muscle CSA (r = 0.81) and strength (r = 0.83). This relationship is shown in Figure 1 (paralleling what is reported in liver and lung transplant recipients) and inversely correlated with fatigability (r = −0.53) (248 (11). Thus, both glucose-intolerant and glucose-tolerant RTx patients had subnormal peak aerobic exercise capability and this was more impaired in glucose intolerant patients.…”

“…In RTx that were glucose-intolerant (diabetic) or with normal glucose tolerance,Vo 2peak was only 65.1% and 80.3% of age-predicted values, respectively (11). During maximal incremental exercise, the peak systolic BP increased to 169 mmHg, and 61% of patients achieved the target HR of greater than 85% age-predicted maximum.…”

“…Furthermore, it is likely that their reported maximal exercise values are considerably below their own potential maximum pre-RTx, as athletic populations typically demonstrate much higherVo 2peak than the average population, although this obviously cannot be tested in these RTx recipients (237). Studies in RTx patients with mean ages of 40 to 50 years also demonstrated a lowVo 2peak relative to controls or predicted values (11,248,265). Petersen et al found aVo 2peak of 27.0 ml.kg −1 .min −1 in nine RTx aged 41 years (254, 317), which was 76% of the matched control group.…”

Cardiorespiratory fitness in young adults with a history of renal transplantation in childhood

“…Although the majority of Rtx participants achieved an RER (a physiological indicator of maximal effort)≥1.05, a few participants did not meet these criteria consistent with other findings in patients with CKD [39,40]. Rtx patients in general are unaccustomed to strenuous exercise, and metabolic changes as a consequence of CKD may play a role [41].…”

Physical Activity and Renal Transplantation

“…Cardiorespiratory fitness was correlated with physical activity and the lower cardiorespiratory fitness was associated with physical inactivity. Whether increasing physical activity should improve cardiorespiratory fitness in renal transplanted patients remains to be determined [12]. This relationship was explored also in renal transplanted children.…”