Metabolic syndrome and renal sodium handling in three ethnic groups living in England.
OBJECTIVE
Increased proximal renal sodium re-absorption is associated with central adiposity and insulin resistance in white men. Our study examined whether this association also exists in other ethnic groups with different prevalences of insulin resistance and associated metabolic abnormalities.


METHODS
We studied the association between fractional renal excretion of endogenous lithium (FELi) and metabolic syndrome in a population study of 1190 randomly selected men and women who where 40 to 59 years of age (426 white, 397 of African and 367 of South Asian origin). Anthropometric values, blood pressure, biochemical values, questionnaire data and timed urine collections were obtained with standardised techniques. Endogenous lithium in serum and urine was measured by absorption spectrophotometry. Metabolic markers were the homeostasis model assessment (HOMA) index, waist circumference, serum triglycerides, serum HDL cholesterol and metabolic syndrome as defined by Adult Treatment Panel III criteria.


RESULTS
In white men and women a higher rate of proximal sodium re-absorption was inversely associated with higher waist circumference, serum triglycerides and HOMA index, and with lower serum HDL cholesterol (all p< or =0.001). No associations were found in people of African or South Asian origin. The former had lower FELi than the other groups. White people with the metabolic syndrome had a lower FELi than those without (15.9% vs 19.0%; p=0.003). No difference was found in people of African or South Asian origin.


CONCLUSIONS
Increased proximal sodium re-absorption is associated with the metabolic syndrome in white men and women. This relationship is not seen in people of African or South Asian origin, despite a greater degree of insulin resistance.
Barbato
A
A
Department of Community Health Sciences, St George's Hospital Medical School, Cranmer Terrace, SW17 0RE, London, UK.
Cappuccio
F P
FP
Folkerd
E J
EJ
Strazzullo
P
P
Sampson
B
B
Cook
D G
DG
Alberti
K G M M
KG
D000328:Adult; D000349:Africa / Q000208:ethnology; D001208:Asia / Q000208:ethnology; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure; D015992:Body Mass Index; D002784:Cholesterol / Q000097:blood; D004739:England / Q000453:epidemiology; D005006:Ethnicity; D005260:Female; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology; D007668:Kidney / Q000502:physiology* / Q000503:physiopathology; D008094:Lithium / Q000493:pharmacokinetics; D008297:Male; D024821:Metabolic Syndrome / Q000453:epidemiology* / Q000378:metabolism / Q000503:physiopathology; D008875:Middle Aged; D012964:Sodium / Q000652:urine*; D014280:Triglycerides / Q000097:blood
D001786:Blood Glucose; D014280:Triglycerides; D002784:Cholesterol; D008094:Lithium; D012964:Sodium