Biology subjects

Mamo, J.

Publications and source records attributed to Mamo, J..

4 recordsLinked to original sources

bioRxiv2022

Plasma amyloid-beta homeostasis is associated with Body Mass Index and weight-loss in people with overweight and obesity

BACKGROUNDObesity is linked to a higher incidence of Alzheimers disease (AD). Studies show that plasma amyloid-{beta} (A{beta}) dyshomeostasis, particularly low 42/40 ratio indicates a heightened risk for developing AD. However, the relationship between body mass index (BMI) and circulating plasma A{beta} has not been extensively studied. OBJECTIVEWe hypothesised that people with a high BMI have altered plasma A{beta} homeostasis compared with people with a lower BMI. We also tested whether reducing BMI by calorie-restriction could normalise plasma concentrations of A{beta}. METHODSPlasma concentrations of A{beta}40, A{beta}42 and A{beta}42/40 ratio were measured in 106 participants with BMIs classified as lean, overweight, or obese. From this cohort, twelve participants with overweight or obese BMIs entered a 12-week calorie-restriction weight loss program. We then tested whether decreasing BMI affected plasma A{beta} concentrations. RESULTSPlasma A{beta}42/40 ratio was 17.54% lower in participants with an obese BMI compared to lean participants (p<0.0001), and 11.76% lower compared to participants with an overweight BMI (p<0.0001). The weight loss regimen decreased BMI by an average of 4.02% (p=0.0005) and was associated with a 6.5% decrease in plasma A{beta}40 (p=0.0425). However, weight loss showed negligible correlations with plasma A{beta}40, A{beta}42 and A{beta}42/40 ratio. CONCLUSIONObesity is associated with aberrant plasma A{beta} homeostasis which may be associated with an increased risk for AD. Weight loss appears to lower A{beta}40, but large-scale longitudinal studies in addition to molecular studies are required to elucidate the underlying mechanisms of how obesity and weight loss influence plasma A{beta} homeostasis.

physiology↗

bioRxiv2022

A highly sensitive LC-MS/MS method for quantitative determination of 7 vitamin D metabolites in mouse brain tissue

Despite its critical role in neurodevelopment and brain function, vitamin-D (vit-D) homeostasis, metabolism and kinetics within the central nervous system remain largely undetermined. Thus, it is of critical importance to establish an accurate, highly sensitive and reproducible method to quantitate vit-D in brain tissue. Here, we present a novel liquid chromatography tandem mass spectrometry (LC-MS/MS) method and for the first time, demonstrate detection of seven major vit-D metabolites in brain tissues of C57BL/6J wild-type mice, namely: 1,25(OH)2D3, 3-epi-1,25(OH)2D3, 1,25(OH)2D2, 25(OH)D3, 25(OH)D2, 24,25(OH)2D3, and 24,25(OH)2D2. Chromatographic separation was achieved on a pentaflurophenyol column 3 mM ammonium formate with water/methanol [A] and methanol/isopropanol [B] phases. Detection was by positive-ion electrospray tandem mass spectrometry. We used calibration standards of each metabolite prepared in brain matrices to validate the detection range, precision, accuracy and recovery. Isotopically labelled analogues, 1,25(OH)2D3-d3, 25(OH)D3-C5 and 24,25(OH)2D3-d6, served as the internal standards for the closest molecular related metabolite in all measurements. The calibration range was between 1 fg/mL to 10 ng/mL with an LLOD and LLOQ of 10 fg/mL and 3 fg/mL, respectively. The intra-/inter-day precision and accuracy for measuring brain vit-D metabolites ranged between 0.12-11.53% and 0.28-9.11%, respectively. Recovery ranged between 99.06% and 106.9% for all metabolites. Collectively, the sensitivity and efficiency of our method supersedes previously reported protocols used to measure vit-D and to our knowledge, the first protocol to reveal the abundance of 25(OH)D2, 1,25(OH)D2 and 24,25(OH)2D2, in brain tissue of any species. This technique may be important in supporting the future advancement of pre-clinical research into the function of vit-D in neurophysiological, neuropsychiatric, and neurodegeneration.

physiology↗

bioRxiv2021

The effects of chronic consumption of lipid-rich and delipidated bovine dairy milk on brown adipose tissue volume in wild-type mice

Brown adipose tissue (BAT) activation is associated with increased energy expenditure by inducing non-shivering thermogenesis. Ingestion of a milk fat globule membrane (MFGM) supplement and a high calorie diet are reported gateways into BAT activation. However, little is known about the effect of MFGM and high calorie diets on BAT volume. To gain insight into this, mice were maintained on a high fat (HF) or low-fat (LF) diet in conjunction with either full-cream (FC) or skim bovine dairy milk (BDM). After being maintained on their respective diets for 13 weeks, body composition, including BAT volume, was measured using X-ray microtomography. A high calorie diet resulted in an increase in BAT volume and mice consuming a HF diet in conjunction with FC BDM had significantly greater BAT volume than all other groups. Conversely, mice consuming a HF diet in addition to skim milk had lower BAT volume compared to the HF control. The data presented suggests that consumption of a high calorie diet in conjunction with FC BDM increases BAT volume in wild-type mice. This study may provide valuable insight into future studies investigating BAT volume and BAT activity in relation to environmental factors including diet.

physiology↗

bioRxiv2020

Purification and Characterization of Aspartic Protease Produced from Aspergillus oryzae DRDFS13 under Solid-State Fermentation

Aspartic proteases (E.C.3.4.23.) are endopeptidases with molecular masses ranging between 30-45 kDa. They depend on aspartic acid residues for their catalytic activity and show maximal activity at low pH. Thus the main objective of the present study was to purify and characterize aspartic protease from locally identified fungi by solid-state fermentation. The aspartic protease in the current study was obtained from A. oryzae DRDFS13 under SSF. The crude enzyme extract was purified by size-exclusion (SEC) and ion-exchange (IEC) chromatography. The protein contents of crude enzyme and IEC fractions were determined by BCA methods while the presence of N-glycosylation was checked using Endo-H. Inhibition studies were conducted using protease inhibitors. The milk-clotting activity (MCA), protease activity (PA); molecular weight and enzyme kinetics were determined using standard methods. Optimum temperature and stability, optimum pH and stability, and the effect of cations on MCA were assessed using standard methods. The maximum MCA (477.11 U/mL) was recorded from IEC fraction A8. The highest specific activity (183.50 U/mg), purification fold (6.20) and yield (9.2%) were also obtained from the same fraction (IEC A8). The molecular weight of 40 kDa was assigned for the purified enzyme (IEC A8). However, its molecular weight was decreased to 30 KDa upon deglycosylation assay which infers that the protein is glycosylated. Incubation of the pure enzyme (IEC A8) with pepstatin A caused a 94 % inhibition on MCA. The dialyzed enzyme showed a Km and Vmax values of 17.50 mM and 1369 U, respectively. The enzyme showed maximum MCA at 60 {degrees}C and pH 5.0 with stability at pH 4.5-6.5 and temperature 35-45 {degrees}C. Most cat-ions stimulate the activity of the enzyme; moreover, the highest MCA was detected at 50 mM of MnSO4. Furthermore, the results obtained in the present study confirmed that the aspartic protease enzyme produced from A. oryzae DRDFS13 and purified in ion-exchange chromatography could be used as a substitute source of rennet enzyme for cheese production. ImportanceThe production of pure aspartic protease enzyme from local microbes which is useful to substitute shortage of calf rennet enzyme and valuable to diversify cheese production throughout the world.

microbiology↗