Excitation transfer and quenching in photosystem II, enlightened by carotenoid triplet state in leaves.

Accumulation of carotenoid (Car) triplet states was investigated by singlet-triplet annihilation, measured as chlorophyll (Chl) fluorescence quenching in sunflower and lettuce leaves. The leaves were illuminated by Xe flashes of 4 µs length at half-height and 525-565 or 410-490 nm spectral band, maximum intensity 2 mol quanta m-2 s-1, flash photon dose up to 10 µmol m-2 or 4-10 PSII excitations. Superimposed upon the non-photochemically unquenched Fmd state, fluorescence was strongly quenched near the flash maximum (minimum yield Fe), but returned to the Fmd level after 30-50 µs. The fraction of PSII containing a 3Car in equilibrium with singlet excitation was calculated as Te = (Fmd-Fe)/Fmd. Light dependence of Te was a rectangular hyperbola, whose initial slope and plateau were determined by the quantum yields of triplet formation and annihilation and by the triplet lifetime. The intrinsic lifetime was 9 µs, but it was strongly shortened by the presence of O2. The triplet yield was 0.66 without nonphotochemical quenching (NPQ) but approached zero when NP-Quenched fluorescence approached 0.2 Fmd. The results show that in the Fmd state a light-adapted charge-separated PSIIL state is formed (Sipka et al., The Plant Cell 33:1286-1302, 2021) in which Pheo-P680+ radical pair formation is hindered, and excitation is terminated in the antenna by 3Car formation. The results confirm that there is no excitonic connectivity between PSII units. In the PSIIL state each PSII is individually turned into the NPQ state, where excess excitation is quenched in the antenna without 3Car formation.

Differential effect of endogenous glucagon-like peptide-1 on prandial glucose counterregulatory response to hypoglycaemia in humans with and without bariatric surgery.

AIM: To determine the effect of endogenous glucagon-like peptide 1 (GLP-1) on prandial counterregulatory response to hypoglycaemia after gastric bypass (GB). MATERIALS AND METHODS: Glucose fluxes, and islet-cell and gut hormone responses before and after mixed-meal ingestion, were compared during a hyperinsulinaemic-hypoglycaemic (~3.2 mmol/L) clamp with and without a GLP-1 receptor (GLP-1R) antagonist exendin-(9-39) infusion in non-diabetic patients who had previously undergone GB compared to matched participants who had previously undergone sleeve gastrectomy (SG) and non-surgical controls. RESULTS: Exendin-(9-39) infusion raised prandial endogenous glucose production (EGP) response to insulin-induced hypoglycaemia in the GB group but had no consistent effect on EGP response among the SG group or non-surgical controls (p < 0.05 for interaction). The rates of systemic appearance of ingested glucose or prandial glucose utilization did not differ among the three groups or between studies with and without exendin-(9-39) infusion. Blockade of GLP-1R had no effect on insulin secretion or insulin action but enhanced prandial glucagon in all three groups. CONCLUSIONS: These results indicate that impaired post-meal glucose counterregulatory response to hypoglycaemia after GB is partly mediated by endogenous GLP-1, highlighting a novel pathogenic mechanism of GLP-1 in developing hypoglycaemia in this population.

American Society for Metabolic and Bariatric Surgery 2022 estimate of metabolic and bariatric procedures performed in the United States.

BACKGROUND: Metabolic and bariatric surgery (MBS), despite being the most effective durable treatment for obesity, remains underused as approximately 1% of all qualified patients undergo surgery. The American Society for Metabolic and Bariatric Surgery established a Numbers Taskforce to specify the annual rate of obesity treatment interventions utilization and to determine if patients in need are receiving appropriate treatment. OBJECTIVE: To provide the best estimated number of metabolic and bariatric procedures being performed in the United States in 2022. SETTING: United States. METHODS: We reviewed data from the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program and National Surgical Quality Improvement Program. In addition, data from industry and state databases were used to estimate activity at non-accredited centers. Data from 2022 were compared mainly with data from the previous 2 years. RESULTS: Compared with 2021, the total number of MBS performed in 2022 increased from approximately 262,893 to 280,000. The sleeve gastrectomy (SG) continues to be the most commonly performed procedure. The gastric bypass procedure trend remained relatively stable. The percentage of revision procedures and biliopancreatic diversion with duodenal switch procedures increased slightly. Intragastric balloon placement increased from the previous year. Endoscopic sleeve gastroplasty increased in numbers. CONCLUSIONS: There was a 6.5% increase in MBS volume from 2021 to 2022 and a 41% increase from 2020, which demonstrates a recovery from the COVID-19 pandemic. SG continues to be the most dominant MBS procedure.