Method to screen for an activator of adipose-resident NK cells
Obesity is associated with a state of chronic low-grade inflammation and the present invention establishes that adipose-resident natural killer T (NKT) cells attenuate inflammation in adipose tissue and improves systemic glucose homeostasis in mice at different stages of obesity. Accordingly, the present invention provides methods of treating type-2 diabetes or those at risk for type-2 diabetes using activators of adipose-resident NKT cells. Such activators include particular glycolipids (e.g., a-galactosylceramide and its analogs other than sulfated analogs) and cytokines that promote M2 macrophage polarization. The invention also includes methods to screen for activators of adipose-resident NKT cells.
1. A method to screen for an activator of adipose-resident NKT cells which comprises
(a) feeding at least one mouse a high fat diet (HFD) for at least about 4 days up to about 24 weeks;
(b) administering a candidate activator to said at least one mouse;
(c) sacrificing said at least one mouse from about 4 to about 7 days after administering said activator;
(d) preparing white adipose tissue (WAT) from said at least one mouse; and
(e) detecting whether (i) said WAT contains increased expression, relative to expression in WAT from a control mouse of any one or more of IL-4, IL-13, IL-12, Arginase 1 (Arg1), chitinase 3-like 3 (Chi313), C-type lectin domain family 7, member a (Clec7a), Programmed cell death 1 ligand 2 (Pdc11g2), Resistin like alpha (Retn1a), Interleukin 1 receptor antagonist (IL-1rn), and Interleukin receptor 4 alpha (IL-4ra), (ii) M2 macrophage polarization increases in said WAT relative to that in WAT from said control mouse, (iii) whether at least one T H 2 cytokine is produced, or a combination of (i), (ii) or (iii), wherein the control mouse is fed with the HFD and is not administered with said activator, thereby determining that said candidate activator is an activator of adipose-resident NKT cells.
2. The method of claim 1 , wherein increased expression is detected by a Northern blot, by a nucleic acid hybridization technique, by RNA-Seq, by PCR, by ELISA, by immunoblotting or by immunohistochemical staining.
3. The method of claim 1 , wherein said at least one mouse is a wild-type mouse or has a genetic predisposition to obesity.
4. The method of claim 1 , wherein said at least one T H 2 cytokine is selected from the group consisting of IL-4, IL-10, IL-12 and IL-13.