Since I’m not that long in diabetes business, two new Cell papers from Collombat and Kubicek labs looked quite sensational for me. Both are the products of multi-centered collaborations, and both report regeneration of insulin-producing beta-cells in vivo with small molecules.
As I learned from introductions, reprogramming of pancreatic alpha cells (glucagon-secreting) into beta cells is a sort of a Holy Grail of regenerative medicine for diabetes treatment. Naturally, first attempts to reprogramming were performed with aid of transcription factors. But pretty soon small molecules kicked in. These were kinase inhibitors and chromatin-altering probes from Stuart Schreiber lab, resveratrol (of course!), and peptide hormone betatrophin. OK, the last one doesn’t count, and it’s not a small molecule anyway. What’s unusual about the latest Cell papers, is that they describe reprogramming by small molecules acting pretty high upstream from direct gene regulation . Both papers involve messing with GABAA receptor signaling.
Let’s start with the Kubicek lab paper, which found that common (yet Nobel-winning) malaria drug, artemisinin, can make pancreatic alpha cells to secret insulin. The authors identified artemisinin and its metabolite dehydroartemisinin from a library of 280 existing drugs . After they found that the drugs induce insulin secretion, they identified gephyrin as the most likely target. Then, via electrophysiology and a series of inhibitory tests, they linked gephyrin-mediated activity to GABAA receptor signaling. Known agonists of GABAA, however, didn’t increase insulin secretion as much as artemisinin (after 72 h treatment of cells). The drug then increased mass of beta cells islets in zebrafish, healthy and diabetic mice (while reducing basal glucose level in the last ones). Finally, it altered gene expression in human alpha cells and increased insulin secretion by the islets. Frankly, the figure 7A-C, which is supposed to convince in the last effect, raises some questions as data look cherry-picked from different donors. But authors do address that by briefly mentioning donor-to-donor variability. And it’s not surprising at n = 6 sample size.
The paper from Collombat lab branches from the screening results of the first one. Once researchers noticed that activation of GABA signaling correlates with alpha-to-beta conversion, they thought “why not injecting plain ol’ GABA into mice?” And miraculously this simple idea worked. Just look at the jaw-dropping figures 1B-D! Figure S7C,G (below) can somewhat give you the feeling, but go check out the main paper, you won’t be disappointed.
Here are the main results: daily injections of GABA at 250 μg/kg over three months convert pancreatic alpha cells into beta. But what’s even more exciting is that the new alpha cells are continuously being produced to compensate for those that were converted into beta! They even caught small fraction of cells in some transitional state, where they secret both glucagon and insulin. I particularly liked the discussion section where authors warn that before you, all excited, rush to inject diabetic patients with GABA think why there’s not enough beta cells in the first place. Yes, it is patient’s immune system that attacks her own beta cells. So before this approach makes into clinic one needs to figure out that autoimmune component of type 1 diabetes.
In a sum we have two great papers with rock-solid mouse data and some exciting preliminary results in human beta cells. Let’s see where it will end up. Regardless of the future success, isn’t it amazing how small, simple, and seemingly well-known molecules like GABA (and artemisinin for that matter) can upturn human cells identity?
 OK, authors do not strictly claim reprogramming as the identity of cells doesn’t change completely from alpha to beta, but their secretory activity is definitely flipped.
 Side note: check out this sexy acoustic liquid handler they used.