Glycemic control is impaired in the evening in prediabetes through multiple diurnal rhythms.
OBJECTIVE
Recent studies suggest that circadian rhythms regulate glucose metabolism, weight loss, and even drug efficacy. Moreover, molecules targeted at the circadian clock show promise in treating metabolic disease. Therefore, this study set out to better characterize interactions among diurnal rhythms in prediabetes.


METHODS
Ten subjects with prediabetes completed oral glucose tolerance tests at 0700h and 1900h on the same day. Lipids and hormones were also measured.


RESULTS
Two-hour and three-hour glucose tolerances were worse in the evening by 40±52mg/dl (p=0.02) and 62±46mg/dl (p=0.001), respectively. These impairments were explained by lower insulin sensitivity (OGIS; 5.14±1.02 vs. 4.74±0.77mg/kg/min; p=0.03) and 2-hour AUC insulin levels (87.4±37.6 vs. 69.8±40.2mU∙hr/l; p=0.02) in the evening. Intriguingly, more insulin resistant subjects had weaker rhythms in insulin sensitivity (r=-0.66; p=0.04) but enhanced rhythms in insulin (r=-0.67; p=0.03) and cortisol (r=-0.78; p=0.008) levels. Importantly, the rhythms in cortisol primarily but also insulin sensitivity drove the declines in evening glucose tolerance (r=0.86; p=0.002).


CONCLUSIONS
Glycemic control is dramatically impaired in the evening in people with prediabetes, particularly when the cortisol rhythm is weak, but is unrelated to the rhythm in insulin levels. Therefore, food intake at dinnertime may need to be curbed in prediabetes.
Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, USA.
Tance
T
Sonnier
Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, USA.
Jennifer
J
Rood
Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, USA; Center for Stem Cell Research and Regenerative Medicine, Tulane University School of Medicine, New Orleans, LA 70112, USA; LaCell LLC, New Orleans, LA 70112, USA.
Jeffrey M
JM
Gimble
Pennington Biomedical Research Center, 6400 Perkins Road, Baton Rouge, LA 70808, USA. Electronic address: courtney.peterson@pbrc.edu.
Courtney M
CM
Peterson
D000328:Adult; D000368:Aged; D001786:Blood Glucose / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D018149:Glucose Intolerance / Q000097:blood; D005951:Glucose Tolerance Test; D006801:Humans; D007328:Insulin / Q000097:blood; D007333:Insulin Resistance; D008055:Lipids / Q000097:blood; D008297:Male; D008875:Middle Aged; D011236:Prediabetic State / Q000097:blood*; D013997:Time Factors
D001786:Blood Glucose; D007328:Insulin; D008055:Lipids
Circadian rhythms; Cortisol; Diurnal rhythm; Glucose tolerance; Oral Glucose Tolerance Test (OGTT); Prediabetes