Elevated Blood Pressure and Serum γ -Glutamyltransferase as Significant Characteristics of Smokers With Chronic Kidney Disease

BACKGROUND: Smoking is a risk factor for chronic kidney disease (CKD). However, it is speculated that only a small subset of sensitive smokers develop CKD. OBJECTIVES: We aimed to reveal the characteristics of such smokers sensitive to the renal effects of smoking with respect to cardiovascular (CV) risk factors associated with smoking and/or CKD. PATIENTS AND METHODS: Renal functions and CVD risk factors were assessed in middle-aged male workers. The patients were comprised of 336 nonsmokers, 332 smokers currently smoking up to one pack per day, and 38 who smoked more than one pack per day. CKD was determined by estimated glomerular filtration rate (eGFR) from serum creatinine and urinary albumin to creatinine ratio (ACR). The independent and interactive effects of smoking and CKD on the CVD risk factors adjusted for age, body mass index, alcohol consumption, and physical activity were statistically analyzed. RESULTS: In comparison to nonsmokers, smokers had significantly higher waist circumference, white blood cells (WBC), serum triglycerides, γ-glutamyltransferase (GGT), and C-reactive protein (CRP) and lower serum high-density lipoprotein cholesterol and uric acid. On the other hand, blood pressure (BP) and WBC tended to be higher in those showing CKD than others. Serum GGT and fasting plasma glucose were significantly higher, and insulin resistance index of homeostatic model assessment (HOMA-IR) tended to be higher in those with CKD. Serum CRP was especially high in those with moderate to severe CKD. A significant interactive effect of smoking and CKD on BP and serum GGT levels was detected, i.e. BP and GGT were not different in the subjects among nonsmokers with and without CKD, but were conspicuously high among smokers with CKD. No significant interactive effect was found on either HOMA-IR or serum CRP. CONCLUSIONS: Smokers with a higher BP and/or serum GGT may be at a higher risk of developing CKD. The associations of BP and serum GGT with CKD in smokers are not entirely mediated by increased insulin resistance or chronic inflammation caused by smoking.