Visceral fat and beta cell function in non-diabetic humans.
OBJECTIVE
Preferential visceral adipose tissue (VAT) accumulation has been clearly associated with insulin resistance. In contrast, the impact of visceral obesity on beta cell function is controversial.


METHODS
In 62 non-diabetic women and men (age 24-69 years, BMI 21-39 kg/m2), we measured VAT and subcutaneous adipose tissue (SAT) fat mass by magnetic resonance imaging. We also measured insulin secretion and beta cell function by C-peptide deconvolution and physiological modelling of data from a frequently sampled, 75-g, 3-h OGTT, respectively.


RESULTS
VAT (range 0.1-3.1 kg) was strongly related to sex, age and BMI; SAT was related to sex and BMI. Controlling for sex, age, BMI and SAT by multivariate analysis, excess VAT was associated with a clinical phenotype comprising higher plasma glucose levels, BP, heart rate and serum transaminases. The corresponding metabolic phenotype consisted of insulin resistance (partial r=-0.38) and hyperinsulinaemia (partial r=0.29). The latter, however, was appropriate for the degree of insulin resistance regardless of obesity and abdominal fat distribution. Moreover, none of the model-derived parameters describing beta cell function (glucose sensitivity, rate sensitivity and potentiation) was independently associated with excess VAT.


CONCLUSIONS
In non-diabetic Caucasian adults of either sex, preferential visceral fat deposition in itself is part of an insulin-resistant phenotype. The insulin secretory response to a physiological challenge is increased to fully compensate for the insulin resistance, but the dynamics of beta cell function (glucose sensitivity, rate sensitivity and potentiation) are largely preserved.
Gastaldelli
A
A
CNR Institute of Clinical Physiology, University of Pisa School of Medicine, Pisa, Italy. amalia@ifc.cnr.it
Sironi
A M
AM
Ciociaro
D
D
Positano
V
V
Buzzigoli
E
E
Giannessi
D
D
Lombardi
M
M
Mari
A
A
Ferrannini
E
E
D000273:Adipose Tissue / Q000502:physiology*; D000328:Adult; D000886:Anthropometry; D019540:Area Under Curve; D001835:Body Weight / Q000502:physiology; D002096:C-Peptide / Q000378:metabolism; D005260:Female; D005947:Glucose / Q000494:pharmacology; D018149:Glucose Intolerance; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000502:physiology*; D008055:Lipids / Q000097:blood; D008279:Magnetic Resonance Imaging; D008297:Male; D008954:Models, Biological; D010186:Pancreatic Function Tests; D010641:Phenotype
D002096:C-Peptide; D007328:Insulin; D008055:Lipids; D005947:Glucose