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Fructose has recently been proposed to stimulate vasopressin secretion in humans. Fructose-induced vasopressin secretion is not only postulated to result from ingestion of fructose-containing drinks but may also occur from endogenous fructose production via activation of the polyol pathway. This raises the question of whether fructose might be involved in some cases of vasopressin-induced hyponatremia, especially in situations where the cause is not fully known such as in the syndrome of inappropriate secretion of diuretic hormone (SIADH) and exercise-associated hyponatremia, which has been observed in marathon runners. Here we discuss the new science of fructose and vasopressin, and how it may play a role in some of these conditions, as well as in the complications associated with rapid treatment (such as the osmotic demyelination syndrome). Studies to test the role of fructose could provide new pathophysiologic insights as well as novel potential treatment strategies for these common conditions.

An important aspect of survival is to assure enough food, water, and oxygen. Here, we describe a recently discovered response that favors survival in times of scarcity, and it is initiated by either ingestion or production of fructose. Unlike glucose, which is a source for immediate energy needs, fructose metabolism results in an orchestrated response to encourage food and water intake, reduce resting metabolism, stimulate fat and glycogen accumulation, and induce insulin resistance as a means to reduce metabolism and preserve glucose supply for the brain. How this survival mechanism affects brain metabolism, which in a resting human amounts to 20% of the overall energy demand, is only beginning to be understood. Here, we review and extend a previous hypothesis that this survival mechanism has a major role in the development of Alzheimer’s disease and may account for many of the early features, including cerebral glucose hypometabolism, mitochondrial dysfunction, and neuroinflammation. We propose that the pathway can be engaged in multiple ways, including diets high in sugar, high glycemic carbohydrates, and salt. In summary, we propose that Alzheimer’s disease may be the consequence of a maladaptation to an evolutionary-based survival pathway and what had served to enhance survival acutely becomes injurious when engaged for extensive periods. Although more studies are needed on the role of fructose metabolism and its metabolite, uric acid, in Alzheimer’s disease, we suggest that both dietary and pharmacologic trials to reduce fructose exposure or block fructose metabolism should be performed to determine whether there is potential benefit in the prevention, management, or treatment of this disease.

In this narrative review, we present the hypothesis that key mutations in two genes, occurring 15 and 10 million years ago (MYA), were individually and then collectively adaptive for ancestral humans during periods of starvation, but are maladaptive in modern civilization (i.e., “thrifty genes”), with the consequence that these genes not only increase our risk today for obesity, but also for alcoholism. Both mutations occurred when ancestral apes were experiencing loss of fruit availability during periods of profound climate change or environmental upheaval. The silencing of uricase (urate oxidase) activity 15 MYA enhanced survival by increasing the ability for fructose present in dwindling fruit to be stored as fat, a consequence of enhanced uric acid production during fructose metabolism that stimulated lipogenesis and blocked fatty acid oxidation. Likewise, a mutation in class IV alcohol dehydrogenase ~10 MYA resulted in a remarkable 40‐fold increase in the capacity to oxidize ethanol (EtOH), which allowed our ancestors to ingest fallen, fermenting fruit. In turn, the EtOH ingested could activate aldose reductase that stimulates the conversion of glucose to fructose, while uric acid produced during EtOH metabolism could further enhance fructose production and metabolism. By aiding survival, these mutations would have allowed our ancestors to generate more fat, primarily from fructose, to survive changing habitats due to the Middle Miocene disruption and also during the late‐Miocene aridification of East Africa. Unfortunately, the enhanced ability to metabolize and utilize EtOH may now be acting to increase our risk for alcoholism, which may be yet another consequence of once‐adaptive thrifty genes. We review mutations for uricase and class IV alcohol dehydrogenase and present the hypothesis that they were adaptive for survival during periods of starvation in our past—allowing ancestral humans to generate more fat, primarily from fructose—but are maladaptive in modern civilization (i.e., “thrifty genes”), with the consequence that these genes not only increase our risk today for obesity, but also for alcoholism. Thus, alcoholism may reflect yet another contemporary and adverse consequence of once‐adaptive selection on thrifty genes.

Kidney disease, especially when it is associated with a reduction in estimated glomerular filtration rate, can be associated with an increase in serum urate (uric acid), suggesting that hyperuricemia in subjects with kidney disease may be a strictly secondary phenomenon. Mendelian randomization studies that evaluate genetic scores regulating serum urate also generally have not found evidence that serum urate is a causal risk factor in chronic kidney disease. Nevertheless, this is countered by a large number of epidemiologic, experimental, and clinical studies that have suggested a potentially important role for uric acid in kidney disease and cardiovascular disease. Here, we review the topic in detail. Overall, the studies strongly suggest that hyperuricemia does have an important pathogenic role that likely is driven by intracellular urate levels. An exception may be the role of extracellular uric acid in atherosclerosis and vascular calcification. One of the more striking findings on reviewing the literature is that the primary benefit of lowering serum urate in subjects with CKD is not by slowing the progression of renal disease, but rather by reducing the incidence of cardiovascular events and mortality. We recommend large-scale clinical trials to determine if there is a benefit in lowering serum urate in hyperuricemic subjects in acute and chronic kidney disease and in the reduction of cardiovascular morbidity and mortality in subjects with end-stage chronic kidney disease.

We report a case of a patient who developed dialysis-requiring acute kidney injury (AKI) after the use of canagliflozin. A 66-year-old man with type 2 diabetes who was recovering from left knee septic arthritis at a rehabilitation facility was admitted with oliguric AKI 5 days after starting treatment with canagliflozin, an inhibitor of sodium/glucose cotransporter 2 (SGLT2). The patient presented with hematuria, non–nephrotic-range proteinuria, and serum creatinine level of 6.8 (baseline, 1.1-1.3) mg/dL. There was no recent use of radiocontrast agents or exposure to other nephrotoxins. The patient subsequently required hemodialysis. Due to recent antibiotic use (ampicillin-sulbactam), acute interstitial nephritis was considered in the differential diagnosis. Kidney biopsy was performed, which showed the presence of osmotic nephropathy. The patient’s kidney function returned to baseline after 2 weeks of hemodialysis. This case provides evidence of an association of osmotic nephropathy with the use of canagliflozin and discusses potential mechanisms. We recommend kidney biopsy for cases of severe AKI associated with SGLT2 inhibitors to better understand the relationship of this complication with the use of this class of medications.

An epidemic of chronic kidney disease of unknown etiology (Mesoamerican nephropathy) has emerged in hot regions of Central America. We have demonstrated that dehydration associated with recurrent heat exposure causes chronic kidney disease in animal models. However, the independent influence of core body temperature on kidney injury has not been explored. In the present study, we tested the hypothesis that kidney injury could be accelerated by increasing body temperature independent of external temperature. Wild-type mice were exposed to heat (39.5°C, 30 min, 2 times daily) with or without the mitochondrial uncoupling agent 2,4-dinitrophenol (DNP) for 10 days. Core temperature, renal function, proteinuria, and renal histological and biochemical analyses were performed. Isolated mitochondria markers of oxidative stress were evaluated from kidney tissue. DNP increased body core temperature in response to heat by 1°C (42 vs. 41°C), which was transient. The mild increase in temperature correlated with worsening albuminuria (R= 0.715, P< 001), renal tubular injury, and interstitial infiltration of monocytes/macrophages. Tubular injury was marked in the outer medulla. This was associated with a reduction in kidney tissue ATP levels (nonheated control: 16.71 ± 1.33 nmol/mg and DNP + heat: 13.08 ± 1.12 nmol/mg, P< 0.01), reduced mitochondria, and evidence for mitochondrial oxidative stress. The results of the present study suggest that kidney injury in heat stress is markedly worsened by increasing core temperature. This is consistent with the hypothesis that clinical and subclinical heat stroke may play a role in Mesoamerican nephropathy.

Alzheimer's disease (AD) brains display A beta (Aβ) plaques, inflammatory changes and neurofibrillary tangles (NFTs). Converging evidence suggests a neuronal origin of Aβ. We performed a temporal study of intraneuronal Aβ accumulation in Down syndrome (DS) brains. Sections from temporal cortex of 70 DS cases aged 3 to 73 years were examined immunohistochemically for immunoreactivity (IR) for the Aβ N-terminal, the Aβ40 C-terminus and the Aβ42 C-terminus. N-terminal antibodies did not detect intracellular Aβ Aβ40 antibodies did not detect significant intracellular Aβ, but older cases showed Aβ40 IR in mature plaques. in contrast, Aβ42 antibodies revealed clear-cut intraneuronal IR. All Aβ42 antibodies tested showed strong intraneuronal Aβ42 IR in very young DS patients, especially in the youngest cases studied (e.g., 3 or 4 yr. old), but this IR declined as extracellular Applaques gradually accumulated and matured. No inflammatory changes were associated with intraneuronal Aβ. We also studied the temporal development of gliosis and NFT formation, revealing that in DS temporal cortex, inflammation and NFT follow A β deposition. We conclude that Aβ42 accumulates intracellulary prior to extracellular Aβ deposition in Down syndrome, and that subsequent maturation of extracellular Aβ deposits elicits inflammatory responses and precedes NFTs.

In 2019, the first cases of SARS-CoV-2 were detected in Wuhan, China, and by early 2020 the first cases were identified in the United States. SARS-CoV-2 infections increased in the US causing many states to implement stay-at-home orders and additional safety precautions to mitigate potential outbreaks. As policies changed throughout the pandemic and restrictions lifted, there was an increase in demand for COVID-19 testing which was costly, difficult to obtain, or had long turn-around times. Some academic institutions, including Boston University (BU), created an on-campus COVID-19 screening protocol as part of a plan for the safe return of students, faculty, and staff to campus with the option for in-person classes. At BU, we put together an automated high-throughput clinical testing laboratory with the capacity to run 45,000 individual tests weekly by Fall of 2020, with a purpose-built clinical testing laboratory, a multiplexed reverse transcription PCR (RT-qPCR) test, robotic instrumentation, and trained staff. There were many challenges including supply chain issues for personal protective equipment and testing materials in addition to equipment that were in high demand. The BU Clinical Testing Laboratory (CTL) was operational at the start of Fall 2020 and performed over 1 million SARS-CoV-2 PCR tests during the 2020-2021 academic year.

We substituted neutral amino acids for some positively charged residues (R42, K107, K146, R148 and K229) that line the active site of aldolase A in an effort to determine binding sites for inositol 1,4,5-trisphosphate. In addition, D33 (involved in carbon-carbon bond cleavage) was mutated. K229A and D33S aldolases showed almost no catalytic activity, but Ins(1,4,5)P3 binding was similar to that determined with the use of wild-type aldolase A. R42A, K107A, K146R and R148A had markedly decreased affinities for Ins(1,4,5)P3 binding, increased EC50 values for Fru(1,6)P2-evoked release of bound Ins(1,4,5)P3 and increased Ki values for Ins(1,4,5)P3-evoked inhibition of aldolase activity. K146Q (positive charge removal) had essentially no catalytic activity and could not bind Ins(1,4,5)P3. Computer-simulated docking of Ins(1,4,5)P3 in the aldolase A structure was consistent with electrostatic binding of Ins(1,4,5)P3 to K107, K146, R148, R42, R303 and backbone nitrogens, as has been reported for Fru(1,6)P2 binding. Results indicate that Ins(1,4,5)P3 binding occurs at the active site and is not dependent on having a catalytically active enzyme; they also suggest that there is competition between Ins(1,4,5)P3 and Fru(1,6)P2 for binding. Although Ins(1,4,5)P3 binding to aldolase involved electrostatic interactions, the aldolase A Ins(1,4,5)P3-binding domain did not show other similarities to pleckstrin homology domains or phosphotyrosine-binding domains known to bind Ins(1,4,5)P3 in other proteins.

Hereditary fructose intolerance (HFI) is a potentially fatal autosomal recessive disease of carbohydrate metabolism. HFI patients are deficient in aldolase B, the isozyme expressed in fructose‐metabolizing tissues. The eight protein coding exons, including splicing signals, of the aldolase B gene from one American HFI patient were amplified by the polymerase chain reaction (PCR). Single‐strand conformational polymorphism (SSCP) analysis and direct sequence determination were applied to the amplified fragments. The mutations in the patient's alleles were identified as a nonsense mutation (R59op) in exon 3 and a missense mutation (C134R) in exon 5. These mutations were confirmed by sequence determination of cloned PCR‐amplified exons 3 and 5 from the patient. Allele specific oligonucleotide (ASO) hybridizations of amplified exons 3 and 5 showed the Mendelian inheritance of both mutations. Site‐directed mutagenesis was used to generate an expression plasmid for the C134R mutation, and the mutant enzyme was expressed in bacteria. Assays of partially purified enzyme preparations showed that this missense mutation results in an apparently unstable enzyme that retains partial activity. This is the first evidence for a partially active aldolase B from an HFI individual with an identified mutation, and supports the hypothesis that adequate gluconeogenesis/glycolysis is maintained in HFI patients by the presence of partially active enzymes.— Brooks, C. C., Tolan, D. R. A partially active mutant aldolase B from a patient with hereditary fructose intolerance. FASEB J.8: 107‐113; 1994.

Expression of several muscle-specific genes was monitored during chicken muscle development and myoblast differentiation in primary cultures. The individual patterns of expression for many muscle-specific genes are well documented in ovoand in other model systems of muscle development. However, comparison of aldolase A to other muscle-specific genes in one system has not been reported. Both sarcomeric and cytosolic genes important for the adult muscle fiber were examined in order to elucidate their timing of expression and its relationship to cell fusion. Steady-state mRNA expression was measured using RNase protection assays with cRNA probes generated from cDNA clones for muscle creatine kinase, fast skeletal troponin-T, embryonic myosin heavy chain, and aldolase A. Nonmuscle genes expressed largely in the embryo, aldolase C and β-actin, were used as controls. The expression of all six genes revealed differences in temporal expression patterns between limb and axial muscle. The temporal expression patterns of all six genes were also monitored in primary myoblast cultures relative to myoblast fusion. In both axial and limb myoblast cultures most of the muscle-specific genes were expressed prior to fusion. During the differentiation of myoblasts to myotubes there was a biphasic pattern in the expression of the muscle-specific genes. The appearance of measurable mRNA was detected by 16 hr in culture, prior to appreciable fusion of the cells. During further differentiation the expression increased gradually and then more rapidly at 96 hr, once fusion was complete. Meanwhile, the nonmuscle embryonic gene expression declined only slightly. For one gene, aldolase A, expression was delayed relative to the other muscle-specific genes, both in the appearance of measurable mRNA and in the later rapid increase in mRNA.

The glycolytic enzyme aldolase is concentrated in a domain around stress fibers in living Swiss 3T3 cells, but the mechanism by which aldolase is localized has not been revealed. We have recently identified a molecular binding site for F-actin on aldolase, and we hypothesized that this specific binding interaction, rather than a nonspecific mechanism, is responsible for localizing aldolasein vivo.In this report, we have used fluorescent analog cytochemistry of a site-directed mutant of aldolase to demonstrate that actin-binding activity localizes this molecule along stress fibers in quiescent cells and behind active ruffles in the leading edge of motile cells. The specific cytoskeletal association of aldolase could play a structural role in cytoplasm, and it may contribute to metabolic regulation, metabolic compartmentation, and/or cell motility. Functional duality may be a widespread feature among cytosolic enzymes.

Aldolase (E.C. 4.1.2.13), a homotetrameric protein encoded by the ALDOA gene, converts fructose-1,6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. Three isozymes are encoded by distinct genes. The sole aldolase present in red blood cells and skeletal muscle is the A isozyme. We report here the case of a girl of Sicilian descent with aldolase A deficiency. Clinical manifestations included transfusion-dependent anemia until splenectomy at age 3 and increasing muscle weakness, with death at age 4 associated with rhabdomyolysis and hyperkalemia. Sequence analysis of the ALDOA coding regions revealed 2 novel heterozygous ALDOA mutations in conserved regions of the protein. The paternal allele encoded a nonsense mutation, Arg303X, in the enzyme-active site. The maternal allele encoded a missense mutation, Cys338Tyr, predicted to cause enzyme instability. This is the most severely affected patient reported to date and only the second with both rhabdomyolysis and hemolysis.

Aldolase (E.C. 4.1.2.13), a homotetrameric protein encoded by the ALDOAgene, converts fructose-1,6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde-3-phosphate. Three isozymes are encoded by distinct genes. The sole aldolase present in red blood cells and skeletal muscle is the A isozyme. We report here the case of a girl of Sicilian descent with aldolase A deficiency. Clinical manifestations included transfusion-dependent anemia until splenectomy at age 3 and increasing muscle weakness, with death at age 4 associated with rhabdomyolysis and hyperkalemia. Sequence analysis of the ALDOAcoding regions revealed 2 novel heterozygous ALDOAmutations in conserved regions of the protein. The paternal allele encoded a nonsense mutation, Arg303X, in the enzyme-active site. The maternal allele encoded a missense mutation, Cys338Tyr, predicted to cause enzyme instability. This is the most severely affected patient reported to date and only the second with both rhabdomyolysis and hemolysis.

A 26 amino acid peptide has successfully been purified viarecombinant expression as an intein fusion protein accompanied by cleavage without the need for any exogenous proteases or cofactors, thus offering a practical, inexpensive approach to produce isotopically labelled peptides.

A 26 amino acid peptide has successfully been purified via recombinant expression as an intein fusion protein accompanied by cleavage without the need for any exogenous proteases or cofactors, thus offering a practical, inexpensive approach to produce isotopically labelled peptides.