Exercise fights off diabetes in nonobese Asians
Poor aerobic fitness leads to high ectopic fat deposits which, in turn, lowers insulin sensitivity and increases insulin secretion in healthy, nonobese Asians, according to a Singapore study.
“[O]ur findings suggest that interventions and public health policies to promote participation in exercise for improving aerobic fitness and body composition may be useful to protect against metabolic abnormalities involved in the pathogenesis of type 2 diabetes in nonobese Asians,” said researchers.
Researchers cross-sectionally measured insulin sensitivity, insulin secretion rate (ISR), percent body fat, visceral adipose tissue, cardiorespiratory fitness and physical activity engagement in 60 healthy, nonobese Asians (mean age 41.8±13.4 years). Mean body mass index (BMI) was 21.9±1.7 kg/m2, while median sitting time per week was 6.5 hours. [Eur J Clin Invest 2019;doi:10.1111/eci.13079]
There was a significant but inverse correlation between insulin sensitivity and various indices of total body adiposity and ectopic fat deposition, such as BMI (r, –0.492; p<0.001), percent body fat (r, –0.460; p<0.001), abdominal visceral fat tissue (VAT) volume (r, –0.623; p<0.001) and intrahepatic triglyceride (IHTG; r, –0.601; p<0.001).
Similarly, indices of ectopic fat deposits correlated significantly with the cumulative postprandial ISR, calculated as the area under the curve (AUC) >180 minutes after ingestion of a mixed meal (percent body fat: r, 0.303; p=0.018; VAT: r, 0.409; p=0.01; IHTG: r, 0.333; p=0.002).
Moreover, intramyocellar lipid (IMCL) content was associated negatively with insulin sensitivity (r, 0.239; p=0.066) and positively with insulin secretion (r, 0.241; p=0.064), both with borderline significance.
In terms of cardiorespiratory fitness, maximal oxygen uptake showed significant inverse correlations with percent body fat (r, –0.743; p<0.001), VAT (r, –0.476; p<0.001) and IHTG (r, –0.467; p<0.001), but not with IMCL (r, –0.155; p=0.240).
In comparison, maximal oxygen uptake was significantly and positively associated with insulin sensitivity (r, 0.658; p<0.001) and negatively with ISR (r, –0.420; p<0.001).
These findings were further confirmed in multiple stepwise linear regression analyses, where BMI, maximal oxygen uptake and IHTG were identified as among the significant and independent predictors of insulin sensitivity. On the other hand, VAT and maximal oxygen uptake were among the important determinants of ISR.
“Clearly … our results indicate that excess fat deposition in the intra-abdominal area and the liver are strongly associated with metabolic dysfunction in nonobese Asians,” manifesting as impaired peripheral insulin sensitivity and greater insulin secretion in the pancreas, said researchers.
“Interestingly, we did not detect any associations between IMCL and measures of metabolic function,” a relationship that has previously been shown significant in nonobese Caucasian populations, they noted. However, that the present cohort is Asian in composition may account for this difference. [Diabetologia 1999;42:113-116; Diabetes 2014;63:1093-1102]
“[P]oor cardiorespiratory fitness, likely due to insufficient participation in vigorous physical activity, is strongly associated with ectopic fat deposition and metabolic dysfunction,” researchers said, highlighting the need for measures and interventions that will promote vigorous physical activity even among nonobese individuals.