Changes in fat distribution influence reduction in insulin sensitivity
Decreases in whole-body insulin sensitivity that can accompany aging appear to be influenced by other age-related changes in the distribution of adipose tissue, particularly visceral abdominal fat accumulation, according to recent findings.
Conversely, muscle mitochondrial function and chronological age do not appear to be independent predictors of reduced insulin sensitivity, the researchers wrote.
Ian R. Lanza, PhD, professor of medicine at the Mayo Clinic College of Medicine, and colleagues collected data on 116 adults without diabetes from three clinical studies conducted at the Mayo Clinic between 2010 and 2015. Participants were classified as young (< 45 years; 54%), middle-aged (45-65 years; 23%) and elderly ( 65 years; 23%).
Researchers found that increasing age was associated with increasing adiposity, reduced aerobic fitness and reduced mitochondrial oxidative capacity.
Positive correlations were seen between intrahepatic lipids and other measures of adiposity, including BMI, percent fat, subcutaneous abdominal fat and visceral abdominal fat, whereas intramyocellular lipid was not significantly associated with any of these variables. Analysis of three separate multiple regression models found visceral abdominal fat (P < .0001) and intrahepatic lipids (P = .002) to be independent negative predictors of peripheral insulin sensitivity.
Positive predictors of peripheral insulin sensitivity were whole-body maximum oxygen uptake (P = .0007) and intramyocellular lipid (P = .023). Peripheral insulin sensitivity was not significantly predicted by mitochondrial capacity or efficiency.
A strong, inverse correlation was revealed between suppression of endogenous glucose production during hyperinsulinemia and percent fat and subcutaneous abdominal fat. Homeostasis model assessment of insulin resistance (HOMA-IR)–identified whole-body maximum oxygen uptake, intramyocellular lipid and age were independent predictors.
“Collectively, this work highlights the importance of adiposity, especially visceral fat, and regional distribution of fat on whole-body insulin sensitivity, and suggests that neither chronological age nor skeletal muscle mitochondrial function appear to be important independent determinants of insulin sensitivity,” the researchers wrote.