Cardiovascular risk factors, smoking and kidney function

Quelle signification pour le taux de cholestérol après 75 ans?

Increasing comorbidity with aging reduces the predictive power of cardiovascular risk factors. From the age of 70 onward, total cholesterol levels decrease, perhaps associated with changes in the composition of some lipoprotein fractions. In subjects older than 75 years, being in the lowest quartile of cholesterol, insulinemia or serum albumin concentrations is associated with increased mortality. Cholesterol levels below 189 mg/dL in subjects older than 75 years should be considered an early sign of unidentified comorbidity or of rapid functional decline. HDL cholesterol levels, rather than total or LDL cholesterol, were inversely associated with increased mortality from ischemic coronary disease and stroke appears to rise as HDL cholesterol levels fall, rather than total or LDL cholesterol. On the other hand, LDL concentrations below 106 mg/dL and HDL concentrations below 36 mg/dL were associated with an increased risk of death from infectious disease. Stroke incidence, in particular, ischemic stroke, is highest in subjects older than 75 years. HDL cholesterol levels above 35 mg/dL appear to have a protective effect against ischemic stroke in subjects younger than 70 years. Two interventional drug studies investigating the effects of two statins (simvastatin and pravastatin) found that in subgroups of subjects older than 75 these drugs were associated with a reduction in all-cause mortality and cardiovascular morbidity, regardless of total cholesterol levels, but had no short-term effect on cognitive function.

Effects of long-term passive smoking on the diameter of glomeruli in rats: Histopathological evaluation

BACKGROUND AND AIMS

Long-term smoking increases the risk of renal diseases and it also causes the progression of the diseases. The aim of this study was to evaluate the effects of smoking on glomeruli in healthy rats exposed to long-term passive smoking for a short period of time after birth.

METHODS

Sixty-five rats were randomly assigned into four groups. Groups 1 (18 males) and 2 (18 females) were exposed to smoke, whereas groups 3 (15 males) and 4 (14 females) were not exposed to smoke. Overall, 130 renal units were evaluated, and diameters of 10 different glomeruli were measured. The renal and bodyweights of the rats were measured.

RESULTS

The diameter of the glomeruli was 95.51 +/- 9.25 and 100.91 +/- 4.06 microm in groups 1 and 3, respectively (P < 0.05). It was 97.32 +/- 4.06 and 98.86 +/- 6.25 microm in groups 2 and 4, respectively (P > 0.05). Irrespective of the sex, the diameter of the glomeruli was 96.42 +/- 7.15 microm in smokers and 99.92 +/- 5.56 microm in non-smokers (P < 0.05). The renal weights of the male rats affected by smoke were significantly lower than that of those that were not affected by smoke (P < 0.05). Bodyweights of male rats affected by smoke were significantly lower that of those not affected (P < 0.05). There was a weak correlation between the diameter of the glomeruli and the bodyweights of male rats affected by smoke (r = 0.474, P < 0.05).

CONCLUSION

We conclude that passive smoking might have a negative affect on renal morphometry and body growth.

Intraportal nicotine infusion in rats decreases hepatic blood flow through endothelin-1 and both endothelin A and endothelin B receptors

Smoking has been demonstrated to aggravate liver injury. Nicotine, a major pharmacological component of tobacco smoke, affects a multitude of functions. Smoking and nicotine induce synthesis of endothelin (ET)-1. The effect of intraportal infusion of nicotine on hepatic circulation and an involvement of ET-1 and ET receptor in the action of nicotine were investigated in rats. Nicotine (0-100 microg/kg/h) was infused into the portal vein of urethane-anesthetized rats, and changes of hepatic blood flow were evaluated. Intraportal infusion of nicotine dose-dependently decreased hepatic blood flow and increased portal pressure without any alteration of heart rate or arterial blood pressure. This action of intraportal nicotine was completely abolished by pretreatment of ET-1 antibody. Either BQ485 (ET(A) receptor antagonist) or BQ788 (ET(B) receptor antagonist) partially reversed the effect of nicotine, and combination of BQ788 and BQ485 completely abolished it. These findings suggest that nicotine inhibits hepatic circulation through ET-1, and ET(A) and ET(B) receptor.

Effects of current smoking and smoking discontinuation on renal function and proteinuria in the general population

BACKGROUND

Smoking may adversely affect the progression of renal diseases. However, it is unknown whether smoking affects renal function in subjects without nephropathy.

METHODS

In 1998, 28,409 volunteers from the general population were examined at the Institut Régional pour la Santé (IRSA). Renal function was estimated with creatinine clearance using the Cockcroft formula. Dipstick proteinuria was assessed on an overnight urine sample by a trained technician.

RESULTS

Adjusted creatinine clearance was higher in current smokers than in former smokers and never smokers (100.6 +/- 13.6 vs. 98.8 +/- 13.9 mL/min/1.73 m2, P < 0.0001, and vs. 98.5 +/- 14.0 mL/min/1. 73 m2, P < 0.0001, respectively). This difference was predominant in men and weak in women, and was associated with the number of cigarettes smoked daily. The slope of the projected age-related decline in the creatinine clearance accelerated with age, but it was similar in current smokers, former smokers, and never smokers. Creatinine clearance was associated with a relative risk of proteinuria [for each mL/min/1.73 m2, the relative risk was 1.007 (95% CI, 1.000 to 1.015), P = 0.056, for 1+ or higher proteinuria; and 1.018 (1.004 to 1.030), P = 0.0078, for 2+ or higher proteinuria]. Current and former smokers had a marked risk of 2 or higher proteinuria [adjusted RR (95% CI), 3.26 (1.66 to 6.80), P = 0. 0009, and 2.69 (1.24 to 5.99), respectively, P = 0.013, vs. never smoking], which was independent of the daily or cumulative cigarette consumption.

CONCLUSIONS

In the general population, smokers do not exhibit lower creatinine clearance than never smokers. In fact, creatinine clearance is slightly higher in current smokers at least in men, even when normotensive and hypertensive subjects are analyzed separately, but the difference is small, especially in women. This effect seems reversible upon smoking discontinuation. Chronic smoking results in a marked risk of irreversible proteinuria that may occur despite moderate smoking.