Single-cell analysis of insulin-regulated fatty acid uptake in adipocytes.
Increased body fat correlates with the enlargement of average fat cell size and reduced adipose tissue insulin sensitivity. It is currently unclear whether adipocytes, as they accumulate more triglycerides and grow in size, gradually become less insulin sensitive or whether obesity-related factors independently cause both the enlargement of adipocyte size and reduced adipose tissue insulin sensitivity. In the first instance, large and small adipocytes in the same tissue would exhibit differences in insulin sensitivity, whereas, in the second instance, adipocyte size per se would not necessarily correlate with insulin response. To analyze the effect of adipocyte size on insulin sensitivity, we employed a new single-cell imaging assay that resolves fatty acid uptake and insulin response in single adipocytes in subcutaneous adipose tissue explants. Here, we report that subcutaneous adipocytes are heterogeneous in size and intrinsic insulin sensitivity. Whereas smaller adipocytes respond to insulin by increasing lipid uptake, adipocytes with cell diameters larger than 80-100 microm are insulin resistant. We propose that, when cell size approaches a critical boundary, adipocytes lose insulin-dependent fatty acid transport. This negative feedback mechanism may protect adipocytes from lipid overload and restrict further expansion of adipose tissue, which leads to obesity and metabolic complications.
Varlamov
Oleg
O
Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, 97006, USA.
Somwar
Romel
R
Cornea
Anda
A
Kievit
Paul
P
Grove
Kevin L
KL
Roberts
Charles T
CT
D017667:Adipocytes / Q000166:cytology / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D001786:Blood Glucose / Q000378:metabolism; D001896:Boron Compounds / Q000737:chemistry; D015331:Cohort Studies; D005227:Fatty Acids / Q000378:metabolism*; D005260:Female; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D007328:Insulin / Q000097:blood / Q000378:metabolism; D007333:Insulin Resistance / Q000502:physiology*; D008253:Macaca mulatta; D018613:Microscopy, Confocal; D050151:Subcutaneous Fat / Q000166:cytology / Q000378:metabolism*
C530974:4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-dodecanoic acid; D001786:Blood Glucose; D001896:Boron Compounds; D005227:Fatty Acids; D007328:Insulin