Using this systematic approach, it has been possible to cover >99% of all bariatric surgery, cross-matching our data with nation-wide registries for in-hospital care, cause of death, and permitting regular nation-wide audit. Several scientific studies have used, or are using, what seems to be the most comprehensive database in obesity surgery.

Salt-inducible kinase 2 (SIK2) is an AMP-activated protein kinase (AMPK) related kinase abundantly expressed in adipose tissue. Our aim was to identify molecular targets and functions of SIK2 in adipocytes, and to address the role of PKA-mediated phosphorylation of SIK2 on Ser358. Modulation of SIK2 in adipocytes resulted in altered phosphorylation of CREB-regulated transcription co-activator 2 (CRTC2), CRTC3 and class IIa histone deacetylase 4 (HDAC4). Furthermore, CRTC2, CRTC3, HDAC4 and protein phosphatase 2A (PP2A) interacted with SIK2, and the binding of CRTCs and PP2A to wild-type but not Ser358Ala SIK2, was reduced by cAMP elevation. Silencing of SIK2 resulted in reduced GLUT4 (also known as SLC2A4) protein levels, whereas cells treated with CRTC2 or HDAC4 siRNA displayed increased levels of GLUT4. Overexpression or pharmacological inhibition of SIK2 resulted in increased and decreased glucose uptake, respectively. We also describe a SIK2-CRTC2-HDAC4 pathway and its regulation in human adipocytes, strengthening the physiological relevance of our findings. Collectively, we demonstrate that SIK2 acts directly on CRTC2, CRTC3 and HDAC4, and that the cAMP-PKA pathway reduces the interaction of SIK2 with CRTCs and PP2A. Downstream, SIK2 increases GLUT4 levels and glucose uptake in adipocytes.

The most frequently used and effective treatment for morbid obesity is Roux-en-Y gastric bypass surgery (RYGB), which results in rapid remission of type 2 diabetes in most cases. To what extent this is accounted for by weight loss or other factors remains elusive. To gain insight into these mechanisms, we investigated the effects of RYGB on b-cell function and b-cell mass in the pig, a species highly reminiscent of the human. RYGB was performed using linear staplers during open surgery. Sham-operated pigs were used as controls. Both groups were fed a low-calorie diet for 3 weeks after surgery. Intravenous glucose tolerance tests were performed 2 weeks after surgery. Body weight in RYGB pigs and sham-operated, pair-fed control pigs developed similarly. RYGB pigs displayed improved glycemic control, which was attributed to increases in b-cell mass, islet number, and number of extraislet b-cells. Pancreatic expression of insulin and glucagon was elevated, and cells expressing the glucagon-like peptide 1 receptor were more abundant in RYGB pigs. Our data from a pig model of RYGB emphasize the key role of improved b-cell function and b-cell mass to explain the improved glucose tolerance after RYGB as food intake and body weight remained identical.Roux-en-Y gastric bypass surgery (RYGB) leads to remission of type 2 diabetes (T2D) in most patients within days after surgery (1). Importantly, this occurs long before any substantial weight loss has occurred (2). The reason for this remains a controversy, as studies have shown that the beneficial effects of RYGB on T2D are weight loss independent (e.g., [3]), while others suggest that they result from reduced food intake (4). Clinical studies have shown that RYGB has greater effect on remission of T2D than, for example, vertical sleeve gastrectomy, despite similar weight loss (5). This is in support of weight-independent factors underlying the resolution of T2D upon RYGB. One factor, accounting for the beneficial metabolic effects of RYGB, may be changes in circulating levels of gut hormones and their effects on the islets. In particular, increased levels of the incretin hormone glucagon-like peptide 1 (GLP-1) have been implicated as a factor contributing to remission of T2D (2,6). The effect of RYGB on glucose-dependent insulinotropic peptide (GIP) is less clear (6,7). Other factors, including gut microbiota (8), intestinal glucose sensing (9), and bile acids (10), may also contribute. Nevertheless, it is of great clinical importance to resolve this issue, as it will have a strong impact on how treatment for a large group of patients is devised. In fact, if a specific mechanism were to be identified, it could be used as the basis for a new treatment modality.One problem in the dissection of effects of RYGB on glucose metabolism is that studies on b-cell mass in humans are lacking, and it is extremely difficult to generalize from data in rodents (11) because of huge differences in pancreatic anatomy and physiology between the species. To circumvent these problems, we devel...

This is the first study to describe the expression and function of SIKs in human adipocytes. Our data suggest that SIKs might be protective in the development of obesity-induced insulin resistance, with implications for future treatment strategies.