Insulin sensitivity of the brain linked to control of weight and body fat
MedWire News: High insulin sensitivity of the brain is associated with stricter adherence to physical activity targets, as well as reduction of dietary fat and saturated fatty acids, show German researchers.
As reported in the journal Diabetologia, Otto Tschritter (University of Tübingen, Germany) and team investigated 28 individuals without diabetes who underwent an oral glucose tolerance test (OGTT) at baseline followed by a two-step hyperinsulinemic-euglycemic clamp and a saline experiment 1-2 weeks later.
The investigation was an additional arm of the Tuebingen Lifestyle Intervention Program (TULIP).
The authors measured cerebrocortical insulin sensitivity among the participants before they took part in a lifestyle intervention program, designed to promote weight loss, reduce fat and saturated fatty acid intake, and increase fiber intake. Total adipose tissue (TAT), visceral adipose tissue (VAT), and intrahepatic lipid (IHL) were measured at baseline and after 9 months and 2 years of the intervention.
The authors report that high baseline cerebral insulin sensitivity was associated with a more pronounced loss of TAT and VAT after 9 months and 2 years than was insulin resistance.
The changes in TAT (correlation coefficient = -0.59 at 9 months, -0.70 at 2 years) and VAT (correlation coefficient = -0.76 at 9 months, -0.62 at 2 years) correlated negatively with insulin-stimulated cerebrocortical theta activity at baseline.
"To our knowledge, this study is the first to show that the cerebrocortical response to insulin is relevant for future development of body fat in humans," say the authors.
IHL and change in 2-hour plasma glucose during the OGTT were not associated with cerebral insulin sensitivity measures independently of body weight change.
Evaluation of diet and activity revealed that high baseline insulin-stimulated theta activity was associated with a more pronounced decrease in fat intake, a relative increase in carbohydrate intake, and better compliance with physical activity target, compared with lower levels.
"It is most likely that both reducing food, especially fat, intake and increasing energy expenditure are mechanisms that link high insulin-sensitivity of the brain to decreases in body fat and body weight," write Tschritter and team.
The authors say this may suggest that insulin resistance in the brain elevates serum concentrations of saturated fatty acids not only by increasing visceral fat mass, but also more directly by decreasing physical activity and increasing intake of saturated fat.
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By Sally Robertson