Abnormalities of renal sodium handling in the metabolic syndrome. Results of the Olivetti Heart Study.
OBJECTIVE
The mechanisms underlying high blood pressure in the framework of metabolic syndrome (MS) are not clarified: we thus analyzed the relationship of MS and its components to renal tubular sodium handling among participants of the Olivetti Heart Study, an epidemiological investigation of a representative sample of adult white male population in southern Italy.


METHODS
Proximal (FPRNa) and distal (FDRNa) fractional sodium reabsorption were estimated by the clearance of exogenous lithium in 702 participants aged 25-75 years examined in 1994-1995. Blood pressure and relevant anthropometric and biochemical variables were also measured. The diagnosis of MS was based on modified National Cholesterol Education Program (NCEP)-Adult Treatment Panel III (ATP III) criteria.


RESULTS
FPRNa, but not FDRNa, was directly associated with body mass index (BMI), waist circumference, diastolic pressure, serum triglyceride and uric acid, independently of age and of antihypertensive treatment. After adjustment for age, FPRNa, but not FDRNa, was significantly greater in individuals with MS, as compared to those without [77.6% (95% confidence interval = 76.7-80.1) versus 74.4% (73.7-75.1), P < 0.001]. A similar difference was observed after the exclusion of participants on current antihypertensive treatment (P = 0.018). In untreated individuals, a significant interaction was observed between obesity and insulin resistance as related to FPRNa (P = 0.002): the highest age-adjusted levels of FPRNa were detected in obese hypertensive and obese insulin-resistant participants.


CONCLUSIONS
In this sample of an adult male population, MS was associated with an increased rate of FPRNa. This finding is relevant to the pathophysiology of MS and possibly to the prevention of its cardiovascular and renal consequences.
Strazzullo
Pasquale
P
Department of Clinical and Experimental Medicine, Federico II Medical School, University of Naples, Italy. strazzul@unina.it
Barbato
Antonio
A
Galletti
Ferruccio
F
Barba
Gianvincenzo
G
Siani
Alfonso
A
Iacone
Roberto
R
D'Elia
Lanfranco
L
Russo
Ornella
O
Versiero
Marco
M
Farinaro
Eduardo
E
Cappuccio
Francesco P
FP
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D000886:Anthropometry; D000959:Antihypertensive Agents / Q000627:therapeutic use; D015415:Biomarkers / Q000097:blood / Q000652:urine; D001794:Blood Pressure; D015992:Body Mass Index; D016022:Case-Control Studies; D003404:Creatinine / Q000378:metabolism; D005919:Glomerular Filtration Rate; D006801:Humans; D006973:Hypertension / Q000188:drug therapy / Q000453:epidemiology / Q000378:metabolism / Q000503:physiopathology; D007333:Insulin Resistance; D007558:Italy / Q000453:epidemiology; D007686:Kidney Tubules, Distal / Q000187:drug effects / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D016014:Linear Models; D008094:Lithium / Q000378:metabolism; D008297:Male; D024821:Metabolic Syndrome / Q000175:diagnosis / Q000453:epidemiology / Q000378:metabolism* / Q000503:physiopathology; D008875:Middle Aged; D009765:Obesity / Q000453:epidemiology / Q000378:metabolism / Q000503:physiopathology; D012964:Sodium / Q000378:metabolism*; D016896:Treatment Outcome; D044465:White People
D000959:Antihypertensive Agents; D015415:Biomarkers; D008094:Lithium; D012964:Sodium; D003404:Creatinine