DLK1 Regulates Whole-Body Glucose Metabolism: A Negative Feedback Regulation of the Osteocalcin-Insulin Loop

TY - JOUR

T1 - DLK1 Regulates Whole-Body Glucose Metabolism

T2 - A Negative Feedback Regulation of the Osteocalcin-Insulin Loop

AU - Abdallah, Basem M

AU - Ditzel, Nicholas

AU - Laborda, Jorge

AU - Karsenty, Gerard

AU - Kassem, Moustapha

N1 - © 2015 by the American Diabetes Association. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered.

PY - 2015/9

Y1 - 2015/9

N2 - The endocrine role of the skeleton in regulating energy metabolism is supported by a feed-forward loop between circulating osteoblast (OB)-derived undercarboxylated osteocalcin (Glu-OCN) and pancreatic b-cell insulin; in turn, insulin favors osteocalcin (OCN) bioactivity. These data suggest the existence of a negative regulation of this cross talk between OCN and insulin. Recently, we identified delta like-1 (DLK1) as an endocrine regulator of bone turnover. Because DLK1 is colocalized with insulin in pancreatic b-cells, we examined the role of DLK1 in insulin signaling in OBs and energy metabolism. We show that Glu-OCN specifically stimulates Dlk1 expression by the pancreas. Conversely, Dlk1-deficient (Dlk1-/-) mice exhibited increased circulating Glu-OCN levels and increased insulin sensitivity, whereas mice overexpressing Dlk1 in OB displayed reduced insulin secretion and sensitivity due to impaired insulin signaling in OB and lowered Glu-OCN serum levels. Furthermore, Dlk1-/- mice treated with Glu-OC experienced significantly lower blood glucose levels than Glu-OCN-treated wild-type mice. The data suggest that Glu-OCN-controlled production of DLK1 by pancreatic b-cells acts as a negative feedback mechanism to counteract the stimulatory effects of insulin on OB production of Glu-OCN, a potential mechanism preventing OCN-induced hypoglycemia.

AB - The endocrine role of the skeleton in regulating energy metabolism is supported by a feed-forward loop between circulating osteoblast (OB)-derived undercarboxylated osteocalcin (Glu-OCN) and pancreatic b-cell insulin; in turn, insulin favors osteocalcin (OCN) bioactivity. These data suggest the existence of a negative regulation of this cross talk between OCN and insulin. Recently, we identified delta like-1 (DLK1) as an endocrine regulator of bone turnover. Because DLK1 is colocalized with insulin in pancreatic b-cells, we examined the role of DLK1 in insulin signaling in OBs and energy metabolism. We show that Glu-OCN specifically stimulates Dlk1 expression by the pancreas. Conversely, Dlk1-deficient (Dlk1-/-) mice exhibited increased circulating Glu-OCN levels and increased insulin sensitivity, whereas mice overexpressing Dlk1 in OB displayed reduced insulin secretion and sensitivity due to impaired insulin signaling in OB and lowered Glu-OCN serum levels. Furthermore, Dlk1-/- mice treated with Glu-OC experienced significantly lower blood glucose levels than Glu-OCN-treated wild-type mice. The data suggest that Glu-OCN-controlled production of DLK1 by pancreatic b-cells acts as a negative feedback mechanism to counteract the stimulatory effects of insulin on OB production of Glu-OCN, a potential mechanism preventing OCN-induced hypoglycemia.

KW - Animals

KW - Feedback, Physiological

KW - Glucose

KW - Hypoglycemia

KW - Insulin

KW - Insulin Resistance

KW - Insulin-Secreting Cells

KW - Intercellular Signaling Peptides and Proteins

KW - Mice

KW - Mice, Knockout

KW - NIH 3T3 Cells

KW - Osteoblasts

KW - Osteocalcin

KW - RNA, Messenger

KW - Reverse Transcriptase Polymerase Chain Reaction

KW - Signal Transduction

U2 - 10.2337/db14-1642

DO - 10.2337/db14-1642

M3 - Journal article

C2 - 25918236

SN - 0012-1797

VL - 64

SP - 3069

EP - 3080

JO - Diabetes

JF - Diabetes

IS - 9

ER -