Diurnal variations in peripheral insulin resistance and plasma non-esterified fatty acid concentrations: a possible link?
Level 2 - randomized trial
Randomized crossover physiological study in healthy volunteers
PubMed 10456206 · doi:10.1177/000456329903600407
What was done
Nine healthy men underwent short insulin tolerance tests at 0830 h and 2030 h to assess diurnal variations in peripheral insulin sensitivity and plasma non-esterified fatty acid (NEFA) concentrations. Arterialized plasma glucose and venous plasma NEFA levels were measured. Conditions were standardized for fasting duration, pre-test meal, and exercise.
What was found
Insulin sensitivity (KITT) was significantly higher in the morning than in the evening: (20 +/- 7) x 10(-3) mmol/L/min versus (11.6 +/- 2) x 10(-3) mmol/L/min (P < 0.05). Fasting NEFA concentrations were lower in the morning compared to the evening: 373 +/- 84 mumol/L versus 913 +/- 122 mumol/L (P < 0.01). Following insulin administration, NEFA concentrations decreased more slowly in the morning than in the evening: 149 +/- 26 mumol/L/15 min versus 491 +/- 91 mumol/L/15 min (P < 0.01).
Why it matters
This study confirms that diurnal variations in insulin sensitivity and circulating NEFA levels occur independently of acute meals or exercise, contributing to the understanding of circadian metabolic regulation.
Limits
The sample size is very small (n = 9) and includes only healthy men. The proposed causal role of elevated evening NEFA levels in driving insulin resistance is speculative and not directly established by the study design.
Cited by
- supports Humans exhibit lower insulin sensitivity later in the evening compared to earlier in the day.