Spirulina (dietary supplement)

Spirulina is a biomass of cyanobacteria (blue-green algae) that can be consumed by humans and animals. The three species are Arthrospira platensis, A. fusiformis, and A. maxima. Cultivated worldwide, Arthrospira is used as a dietary supplement or whole food. It is also used as a feed supplement in the aquaculture, aquarium, and poultry industries. Arthrospira The species A. maxima and A. platensis were once classified in the genus Spirulina. The common name, spirulina, refers to the dried biomass of A. platensis, which belongs to photosynthetic bacteria that cover the groups Cyanobacteria and Prochlorophyta. Scientifically, a distinction exists between spirulina and the genus Arthrospira. Species of Arthrospira have been isolated from alkaline brackish and saline waters in tropical and subtropical regions. Among the various species included in the genus Arthrospira, A. platensis is the most widely distributed and is mainly found in Africa, but also in Asia. A. maxima is believed to be found in California and Mexico. The term spirulina remains in use for historical reasons. Arthrospira species are free-floating, filamentous cyanobacteria characterized by cylindrical, multicellular trichomes in an open left-handed helix. They occur naturally in tropical and subtropical lakes with high pH and high concentrations of carbonate and bicarbonate. A. platensis occurs in Africa, Asia, and South America, whereas A. maxima is confined to Central America. Most cultivated spirulina is produced in open-channel raceway ponds, with paddle wheels used to agitate the water. Spirulina thrives at a pH around 8.5 and above and a temperature around . They are autotrophic, meaning that they are able to make their own food, and do not need a living energy or organic carbon source. A nutrient feed for growing it is: Baking soda Potassium nitrate Sea salt- Potassium phosphate Iron sulphate Spirulina was a food source for the Aztecs and other Mesoamericans until the 16th century; the harvest from Lake Texcoco in Mexico and subsequent sale as cakes were described by one of Cortés' soldiers.

The role of nicotinamide riboside metabolism in pancreatic beta cells

Angélique Satoko Cercillieux

Pancreatic beta cells play a major role in the regulation of glucose homeostasis by secreting insulin in response to elevated blood glucose levels. A gradual deterioration of functional beta cell mass and the chronic elevation of blood glucose levels are central to development of type 2 diabetes. While the etiologies of Type 2 diabetes and age-related metabolic complications are complex, they are often associated with a decline of intracellular nicotinamide adenine dinucleotide (NAD+). NAD+ levels are maintained through the balance between its synthesis from NAD+ precursors and its degradation by several families of enzymes, including the sirtuin family of protein deacetylases, the ADP-ribosyl transferase enzymes (ARTDs or PARPs) and cADP ribose hydrolases (CD38). NAD+ declines are mostly associated with increased NAD+ consumption, which can be counteracted by dietary supplementation of NAD+ precursors. However, our knowledge on how different tissues utilize and respond to different NAD+ precursors for NAD+ synthesis is still incomplete. This, in turn, limits our ability to provide therapeutic benefits in clinical settings. In this project, we aim to understand the relevance of a particular NAD+ precursor, nicotinamide riboside (NR), in beta cell physiology and its potential use to treat beta cell dysfunction. To do so, we have used mice that are deficient for nicotinamide riboside kinase 1 (NRK1), the first and rate-limiting enzyme for the transformation of NR into NAD+. We demonstrate that NRK1 whole body knockout mice exhibit impaired insulin secretion after a meal or upon glucose challenge when fed a high fat diet. However, NRK1 deficiency in beta cell was not the causality for beta cell failure as differences observed in the NRK1 whole body KO mice were not phenocopied in NRK1 beta cell specific KO mice. Aged NRK1 whole body KO mice also exhibited dysfunctional beta cells and significant loss of insulin content and beta cell mass. Furthermore, NRK1 deficiency exacerbates the decline of NAD+ bioavailability and mitochondria function with age, even promoting fibrosis in multiple tissues. Together, our data suggests that endogenous NR metabolism is critical in maintaining whole body NAD+ homeostasis and to protect against mitochondria dysfunction and stress-related cell responses in pancreatic beta cells.

EPFL2022

Milk Allergen Detection: Sensitive Label-Free Voltammetric Immunosensor Based on Electropolymerization

Sandro Carrara, Tugba Kilic, Paul Jean Philipp

We present in this work, first time in literature, a voltammetric label-free biosensor for detection of alpha lactalbumin (alpha-LB) in meal samples. Food allergy concern necessitates strict regulations in food labelling and innovative monitoring strategies for prevention of sepsis-related death. As major food allergens, dietary samples often contain whey proteins, including alpha-LB as one of the key allergenic. Available detection methods for alpha-LB are based on successive labelling steps and hence have long assay times with limited sensitivity. The new detection method presented here is based on capturing of alpha-LB via entrapped alpha-LB antibody (alpha-LB-Ab) through electropolymerization of polypyrrole (PPy) and then measuring the conductivity decrease by differential pulse voltammetry (DPV). This new label-free voltammetric biosensor for alpha-LB exhibits the best limit of detection (0.19 fg/mL) published so far in literature, with high selectivity and capability to quantify alpha-LB in real milk samples too.

2020

The role of nicotinamide riboside metabolism in pancreatic beta cells

Angélique Satoko Cercillieux

EPFL2022