Nicotinamide promotes differentiation of pancreatic endocrine progenitors from human pluripotent stem cells through poly (ADP-ribose) polymerase inhibition

Abstract

The generation of pancreatic endocrine progenitor cells is an important step in the differentiation of beta cells from human pluripotent stem cells (hPSC). This stage is marked by the expression of Nkx6.1, a transcription factor with well understood downstream targets but with unclear upstream regulators. In hPSC differentiation, Nkx6.1 is strongly induced by nicotinamide, a derivative of vitamin B3, which has three known functions within a cell. Nicotinamide inhibits two classes of enzymes known as poly-ADP-ribose polymerases (PARPs) and sirtuins. It also contributes to the cellular pool of nicotinamide adenosine deoxynucleotide (NAD+) after conversion in the nicotinamide salvage pathway. Induction of Nkx6.1 expression in pancreatic endocrine progenitors by nicotinamide was mimicked by 3 PARP inhibitors (PJ34, olaparib, NU1025). Small molecule inhibition of the nicotinamide salvage pathway reduced Nkx6.1 expression but not Pdx1 expression and caused alteration in NAD+/NADH ratio. Nkx6.1 expression was not affected by sirtuin inhibition. Metabolic profiling of differentiating pancreatic and endocrine progenitors showed that oxygen consumption increases as differentiation progresses, and that nicotinamide reduces oxygen consumption rate. Expression of Nkx6.1 and other beta cell related genes, including Ins2 and Pdx1 increased in mouse islets after exposure to nicotinamide. In summary, nicotinamide induced Nkx6.1 expression in differentiating human pancreatic endocrine progenitors through inhibition of the PARP family of enzymes. Nicotinamide administration was also associated with increased NAD+/NADH ratio, without affecting Nkx6.1 expression. Similarly, the association between nicotinamide and Nkx6.1 expression was also seen in isolated mouse islets. These observations show a link between the regulation of beta cell identity and the effectors of NAD+ metabolism, suggesting possible therapeutic targets in the field of diabetes.

Stem cells differentiation into insulin-producing cells (IPCs): recent advances and current challenges

“…Nicotinamide has historically been used to augment pancreatic β-cell differentiation and to protect islet cells from toxic insults, due to its antioxidant properties. Studies showed that cells exposure to nicotinamide is essential for robust nkx6.1 expression in hiPSC differentiation to pancreatic endocrine progenitors, acting predominantly through PARP (poly-ADPribose polymerases) inhibition [167,168]. Thowfeequ et al [169] showed that the addition of betacellulin and nicotinamide to the modified differentiation protocol sustained PDX1 expression and induced pancreatic β-cell differentiation in human ES cell line.…”

In vitro generation of transplantable insulin-producing cells from canine adipose-derived mesenchymal stem cells

“…Likewise, it has been reported that taurine, an essential amino acid, affects the pancreas development, enhances and maintains the endocrine function, and increases the size and number of the islets (El Idrissi et al, 2009). Also, NIC, a form of vitamin B, acts as a poly (ADP-ribose) polymerase inhibitor that is used to promote MSCs homing functional PE/IPCs and preserve the islet viability and function by protection of NAD + /NADH ratio (Yang et al, 2015;Woodford et al, 2020). Thus, both taurine and NIC are used during differentiation into PE/IPCs and in vitro preservation.…”