Increased insulin sensitivity in mice lacking collectrin, a downstream target of HNF-1alpha.
Collectrin is a downstream target of the transcription factor hepatocyte nuclear factor-1alpha (HNF-1alpha), which is mutated in maturity-onset diabetes of the young subtype 3 (MODY3). Evidence from transgenic mouse models with collectrin overexpression in pancreatic islets suggests divergent roles for collectrin in influencing beta-cell mass and insulin exocytosis. To clarify the function of collectrin in the pancreas, we used a mouse line with targeted deletion of the gene. We examined pancreas morphology, glucose homeostasis by ip glucose tolerance testing (IPGTT) and insulin tolerance testing (IPITT), and pancreas function by in vivo acute-phase insulin response determination and glucose-stimulated insulin secretion from isolated islets. We find no difference in either pancreas morphology or function between wild-type and collectrin-deficient animals (Tmem27(-/y)). However, we note that by 6 months of age, Tmem27(-/y) mice exhibit increased insulin sensitivity by IPITT and decreased adiposity by dual-energy x-ray absorptiometry scanning compared with wild-type. We have previously reported that Tmem27(-/y) mice exhibit profound aminoaciduria due to failed renal recovery. We now demonstrate that Tmem27(-/y) animals also display inappropriate excretion of some short-chain acylcarnitines derived from amino acid and fatty acid oxidation. We provide further evidence for compensatory up-regulation of oxidative metabolism in Tmem27(-/y) mice, along with enhanced protein turnover associated with preserved lean mass even out to 1.5 yr of age. Our studies suggest that collectrin-deficient mice activate a number of adaptive mechanisms to defend energy homeostasis in the setting of ongoing nutrient losses.
Malakauskas
Sandra M
SM
Department of Medicine, Duke University, Durham, North Carolina 27710, USA. smalak@uab.edu
Kourany
Wissam M
WM
Zhang
Xiao Yin
XY
Lu
Danhong
D
Stevens
Robert D
RD
Koves
Timothy R
TR
Hohmeier
Hans E
HE
Muoio
Deborah M
DM
Newgard
Christopher B
CB
Le
Thu H
TH
D000210:Acute-Phase Reaction / Q000378:metabolism; D050154:Adiposity / Q000187:drug effects; D000596:Amino Acids / Q000097:blood; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D005215:Fasting / Q000097:blood; D005502:Food; D005947:Glucose / Q000494:pharmacology; D005951:Glucose Tolerance Test; D051538:Hepatocyte Nuclear Factor 1-alpha / Q000378:metabolism*; D007328:Insulin / Q000378:metabolism*; D007333:Insulin Resistance; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008562:Membrane Glycoproteins / Q000172:deficiency* / Q000378:metabolism; D051379:Mice; D010641:Phenotype; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D013851:Thinness / Q000097:blood / Q000378:metabolism; D013997:Time Factors
D000596:Amino Acids; D051538:Hepatocyte Nuclear Factor 1-alpha; D007328:Insulin; D008562:Membrane Glycoproteins; C504407:Tmem27 protein, mouse; D005947:Glucose