Background: Alginolytic systems from marine bacteria are crucial for algal biomass conversion, yet their molecular mechanisms remain poorly understood. Results: Structural and biochemical characterization of two paralogous marine alginate lyases highlights details on complementary roles and differences with terrestrial enzymes. Conclusion: Bacterial alginolytic enzymes are specifically adapted to the unique characteristics of the natural substrate. Significance: Marine microbes evolved complex degradation systems targeting habitat-specific polysaccharides.
Diabetes Mellitus Type 2 prevalence is increasing worldwide; thus efforts to develop novel therapeutic strategies are required. Amaranthus caudatus (AC) is a pseudo-cereal with reported anti-diabetic effects that is usually consumed in food preparations in Bolivia. This study evaluated the anti-diabetic nutraceutical property of an AC hydroethanolic extract that contains mainly sugars and traces of polyphenols and amino acids (as shown by nalysis with liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR)), in type 2 diabetic Goto-Kakizaki (GK) rats and healthy Wistar (W) rats. A single oral administration of AC extract (2000 mg/kg body weight) improved glucose tolerance during Oral Glucose Tolerance Tests (OGTT) in both GK rats and in W rats. Long-term treatment (21 days) with AC (1000 mg/kg b.w.) improved the glucose tolerance evaluated by the area under the curve (AUC) of glucose levels during the OGTT, in both GK and W rats. The HbA1c levels were reduced in both GK (19.83%) and W rats (10.7%). This effect was secondary to an increase in serum insulin levels in both GK and W rats and confirmed in pancreatic islets, isolated from treated animals, where the chronic AC exposure increased the insulin production 4.1-fold in GK and 3.7-fold in W rat islets. Furthermore, the effect of AC on in vitro glucose-dependent insulin secretion (16.7 mM glucose) was concentration-dependent up to 50 mg/mL, with 8.5-fold increase in GK and 5.7-fold in W rat islets, and the insulin secretion in perifused GK and W rat islets increased 31 and nine times, respectively. The mechanism of action of AC on insulin secretion was shown to involve calcium, PKA and PKC activation, and G-protein coupled-exocytosis since the AC effect was reduced 38% by nifedipine (L-type channel inhibitor), 77% by H89 (PKA inhibitor), 79% by Calphostine-C (PKC inhibitor) and 20% by pertussis toxin (G-protein suppressor).
The hydroxy protons of κ- and κ/μ-hybrid carrageenan oligosaccharides have been studied by NMR spectroscopy in 85% H(2)O/15% acetone-d(6). Hydration and hydrogen bonding interactions in di- (κ), tetra- (κκ), hexa (κκκ), and octa- (κκκκ) κ-oligosaccharides and hexa- (κμκ), octa- (κμμκ), and deca- (κμμμκ) κ/μ-oligosaccharides have been investigated by measuring the chemical shifts, temperature coefficients, and chemical exchange of the hydroxy protons. These NMR parameters indicate that no strong and persistent intramolecular hydrogen bonds involving hydroxy protons stabilize the structure of κ-carrageenan oligosaccharides in aqueous solution. In the κ/μ-oligosaccharides, the presence of chemical exchange between OH3 of α-d-Gal-6-sulfate (D6S) and OH2 of β-d-Gal-4-sulfate (G4S) across the β-d-Gal-4-S-(1→4)-α-d-Gal-6-S linkage reveals the existence of a weak hydrogen bond interaction between the two hydroxyl groups. The smaller temperature coefficients of OH2_D6S and OH3_D6S indicate reduced hydration, interpreted as spatial proximity to the 4-sulfate group and O5 ring oxygen of the neighboring G4S residues, respectively. These first experimental results on the conformation of κ/μ-carrageenan oligosaccharides shine light on the potential role of "kinks" in the properties of the three-dimensional carrageenan gel network.
Lupinus mutabilis (LM) is a legume part of Bolivian traditional diet that has a nutraceutical property reducing blood glucose levels. The prevalence of type 2 diabetes is increasing worldwide thus; the search for novel anti-diabetic drugs is needed. Based on its traditional use, we evaluated the anti-diabetic effect of LM in the spontaneously diabetic Goto-Kakizaki (GK) rat, a model of type 2 diabetes and in Wistar (W) rats as healthy control. LM seeds hydroethanolic extract, analyzed by gas chromatography-mass spectrometry and high-performance liquid chromatography-high resolution mass spectrometry, is a complex mixture of volatile and non-volatile components. A single oral administration of LM extract (2000 mg/kg b.w.) improved glucose tolerance during the oral glucose tolerance test (OGTT) (30–120 min) in GK and W rats (p < 0.0001). The long-term treatment with LM (1000 mg/kg b.w.), for 21 days, improved the area under the curve (AUC) of glucose during OGTT at day 20, in both GK (p < 0.01) and W rats (p < 0.01). The HbA1c (GK rats, p < 0.05 and W rats, p < 0.0001) and the non-fasting glucose (GK rats, p < 0.05) were also reduced. LM increased both serum insulin levels (2.4-fold in GK rats and 2.5-fold W rats), and the glucose-induced (16.7 mM glucose) insulin release in isolated islets from treated animals (6.7-fold in GK rats, and 6.6-fold in W rats). Moreover, LM (10 mg/mL) stimulated in vitro glucose induced (16.7 mM glucose) insulin release in batch incubated GK and W rat islets (p < 0.0001). In perifused GK rat islets, insulin release in 16.7 mM glucose was increased 95.3-fold compared to untreated islets (p < 0.0001), while no significant differences were found in perifused W rat islets. The LM mechanism of action, evaluated using inhibitory compounds of the insulin secretion pathway, showed that LM-dependent insulin secretion was reduced 42% by diazoxide (p < 0.001), 70% by nifedipine (p < 0.001), 86.7% by H89 (p < 0.0001), 70.8% by calphostine-C (p < 0.0001) and 93% by pertussis toxin (p < 0.0001). A similar effect was observed in W rats islets. Our findings provide evidence that LM has an anti-diabetic effect through stimulation of insulin release. The effect is-dependent on L-type calcium channel, protein kinase A and C systems, and G protein-coupled exocytosis and is partially mediated by K-ATP channels.
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