INS and type 2 diabetes mellitus: These findings add to the evidence that Gremlin 1 mRNA expression might not reflect its plasma levels and support our findings that a reduction in Gremlin 1 level might not be the causative factor for improving insulin sensitivity after sleeve gastrectomy but also adds an implication to future therapeutic uses as the benefit of elevated levels of Gremlin 1 after bariatric surgery remains unexplained, complicating the prospect of systemic Gremlin 1-based antagonism in the treatment of type 2 diabetes mellitus.