Underlying Kidney Diseases and Complications for COVID-19: A Review

There is mounting evidence supporting that patients with kidney diseases are particularly vulnerable to coronavirus disease-2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). The review was conducted to examine the risk and complications of COVID-19 among patients with confirmed cases of underlying kidney disease. A search of Google Scholar, PubMed and Science direct databases to August 2020 was conducted using search terms pertaining to kidney diseases, renal insufficiency, kidney injury, angiotensin receptors, hemodialysis, and kidney transplant. We briefly reviewed COVID-19 in the context of kidney diseases. A significant proportion of hospitalized patients for COVID-19 have acute kidney injury, which further deteriorates their prognosis. COVID-19 increases morbidity and mortality among people already diagnosed with kidney disorders and obesity due to multiple organ injury caused by the SARS-CoV-2. This review supports the need for clinicians to carefully manage and monitor all patients with renal disorders in order to minimize acute kidney injuries. Although some therapeutic drugs have been suggested by some studies, treatment should be administered cautiously not to worsen the condition of the kidney. Further studies are required to highlight the efficient management of patients with underlying kidney diseases, who are infected with SARS-CoV-2. With proactive systematic screening and triaging, close monitoring and prompt management of coexisting other infections, the COVID-19 disease burden among these patients could be reduced.

Resistance training enhances insulin suppression of endogenous glucose production in elderly women

An altered prenatal environment during maternal obesity predisposes offspring to insulin resistance, obesity, and their consequent comorbidities, type 2 diabetes and cardiovascular disease. Telomere shortening and frailty are additional risk factors for these conditions. The aim of this study was to evaluate the effects of resistance training on hepatic metabolism and ectopic fat accumulation. Thirty-five frail elderly women, whose mothers' body mass index (BMI) was known, participated in a 4-mo resistance training program. Endogenous glucose production (EGP) and hepatic and visceral fat glucose uptake were measured during euglycemic hyperinsulinemia with [(18)F]fluorodeoxyglucose and positron emission tomography. Ectopic fat was measured using magnetic resonance spectroscopy and imaging. We found that the training intervention reduced EGP during insulin stimulation [from 5.4 (interquartile range 3.0, 7.0) to 3.9 (-0.4, 6.1) μmol·kg body wt(-1)·min(-1), P = 0.042] in the whole study group. Importantly, the reduction was higher among those whose EGP was more insulin resistant at baseline (higher than the median) [-5.6 (7.1) vs. 0.1 (5.4) μmol·kg body wt(-1)·min(-1), P = 0.015]. Furthermore, the decrease in EGP was associated with telomere elongation (r = -0.620, P = 0.001). The resistance training intervention did not change either hepatic or visceral fat glucose uptake or the amounts of ectopic fat. Maternal obesity did not influence the studied measures. In conclusion, resistance training improves suppression of EGP in elderly women. The finding of improved insulin sensitivity of EGP with associated telomere lengthening implies that elderly women can reduce their risk for type 2 diabetes and cardiovascular disease with resistance training.

Resistance training improves skeletal muscle insulin sensitivity in elderly offspring of overweight and obese mothers

AIMS/HYPOTHESIS

Maternal obesity predisposes offspring to adulthood morbidities, including type 2 diabetes. Type 2 diabetes and insulin resistance have been associated with shortened telomere length. First, we aimed to investigate whether or not maternal obesity influences insulin sensitivity and its relationship with leucocyte telomere length (LTL) in elderly women. Second, we tested whether or not resistance exercise training improves insulin sensitivity in elderly frail women.

METHODS

Forty-six elderly women, of whom 20 were frail offspring of lean/normal weight mothers (OLM, BMI ≤26.3 kg/m2) and 17 were frail offspring of overweight/obese mothers (OOM,BMI ≥28.1 kg/m2), were studied before and after a 4 month resistance training (RT) intervention. Muscle insulin sensitivity of glucose uptake was measured using 18F-fluoro-2-deoxyglucose and positron emission tomography with computed tomography during a hyperinsulinaemic–euglycaemic clamp. Muscle mass and lipid content were measured using magnetic resonance and LTL was measured using real-time PCR.

RESULTS

The OOM group had lower thigh muscle insulin sensitivity compared with the OLM group (p=0.048) but similar whole body insulin sensitivity. RT improved whole body and skeletal muscle insulin sensitivity in the OOM group only (p=0.004 and p=0.013, respectively), and increased muscle mass in both groups (p <0 .01). In addition, in the OOM group, LTL correlated with different thigh muscle groups insulin sensitivity (ρ ≥ 0.53; p ≤ 0.05). Individuals with shorter LTL showed a higher increase in skeletal muscle insulin sensitivity after training (ρ ≥ −0.61; p ≤ 0.05).

CONCLUSIONS/INTERPRETATION

Maternal obesity and having telomere shortening were associated with insulin resistance in adult offspring. A resistance exercise training programme may reverse this disadvantage among offspring of obese mothers. Trial registration: ClinicalTrials.gov NCT01931540.

Enhanced fatty acid uptake in visceral adipose tissue is not reversed by weight loss in obese individuals with the metabolic syndrome

AIMS/HYPOTHESIS

Obesity causes an imbalance in fat mass distribution between visceral and subcutaneous adipose tissue (AT) depots. We tested the hypothesis that this relates to increased NEFA uptake between these depots in obese compared with healthy participants. Second, we hypothesised that a diet very low in energy (very low calorie diet [VLCD]) decreases fat mass in obese participants and that this is associated with the decline in NEFA uptake.

METHODS

NEFA uptake in AT depots was measured with [(18)F]-fluoro-6-thia-heptadecanoic acid ((18)F-FTHA) and positron emission tomography (PET) in 18 obese participants with the metabolic syndrome before and after a 6 week VLCD. Whole body fat oxidation was measured using indirect calorimetry and [U-(13)C]palmitate. Sixteen non-obese participants were controls.

RESULTS

Obese participants had >100% higher (p < 0.0001) NEFA uptake in the visceral and subcutaneous abdominal AT depots than controls. VLCD decreased AT mass in all regions (12% to 21%), but NEFA uptake was decreased significantly (18%; p < 0.006) only in the femoral AT. Whole body carbohydrate oxidation decreased, while fat oxidation increased.

CONCLUSIONS/INTERPRETATION

The data demonstrate that weight loss caused by VLCD does not affect abdominal fasting NEFA uptake rates. We found that visceral fat takes up more NEFAs than subcutaneous AT depots, even after weight loss.

Systemic metabolic markers and myocardial glucose uptake in type 2 diabetic and coronary artery disease patients treated for 16 weeks with rosiglitazone, a PPARγ agonist

INTRODUCTION

Treatment with rosiglitazone, a peroxisome proliferator-activated receptor-γ agonist, in type 2 diabetic mellitus (T2DM) patients is under scrutiny because it affects adversely cardiovascular outcomes. In T2DM patients, with existing coronary heart disease, short-term treatment with rosiglitazone increases myocardial glucose uptake (MGU). Serum metabolic and lipoprotein subclass changes, which may be associated with this rosiglitazone-induced improvement, are unknown.

METHODS

Patients with both T2DM and coronary heart disease were separated into placebo (n = 26) and treatment (rosiglitazone 4-8 mg; n = 25) groups. After 16 weeks of treatment, serum NMR metabolomics was used to measure circulating low-molecular-weight metabolites and lipoprotein subclasses and lipids that are associated with T2DM before and after the treatment. Significant metabolic measure changes after rosiglitazone treatment were correlated to MGU values assessed with [(18)F]fluorodeoxyglucose positron emission tomography.

RESULTS

Compared to placebo, the treatment significantly increased circulating glutamine and decreased lactate concentrations. Circulating lactate concentrations showed a significant inverse association with MGU after rosiglitazone treatment.

CONCLUSION

In T2DM patients with existing coronary heart disease, short-term rosiglitazone treatment caused minor improvements in metabolism: serum lactate and glutamine concentrations changed, reflecting improvements in insulin sensitivity, and circulating lactate concentrations inversely correlated to increases in myocardial glucose uptake.

The impact of gender and serum estradiol levels on HDL-mediated reverse cholesterol transport

OBJECTIVE

Premenopausal women have a lower incidence of cardiovascular disease compared to men of the same age. Endogenous oestrogens, especially estradiol, presumably protect against atherosclerosis by a variety of mechanisms. Reverse cholesterol transport (RCT) mechanisms also provide protection against this disease. RCT is defined as the removal of cholesterol from peripheral macrophage foam cells, via high-density lipoproteins (HDL), and cholesterol transportation to the liver for excretion. We have previously shown in a preliminary study that HDL, isolated from premenopausal women, enhanced macrophage cholesterol efflux compared to HDL derived from age-matched male subjects.

MATERIALS AND METHODS

Here, we expanded this study by analysing a larger population of healthy volunteers and evaluated the capacity of HDL derived from women with high or low serum E2 concentrations, mainly representing premenopausal and postmenopausal women, respectively, or men (each group consisting of 30 subjects) to facilitate cholesterol removal from human THP-1 macrophages. HDL isolated from serum samples was incubated with [(3)H] cholesterol oleate-loaded macrophages for 16 h, after which cholesterol efflux to HDL was determined.

RESULTS

No significant differences in the efflux-promoting ability of HDL existed among the three groups. Relevant plasma factors involved in further steps of RCT, such as cholesterol ester transfer protein (CETP), phospholipid transfer protein (PLTP) and lecithin:cholesterol acyltransferase (LCAT) activities were also analysed, but no differences were observed among the study groups.

CONCLUSION

The results do not support a role for estradiol status or gender in modifying the initial step of RCT as a protective mechanism against cardiovascular disease.

Depletion of FOXP3+ regulatory T cells promotes hypercholesterolemia and atherosclerosis

Atherosclerosis is a chronic inflammatory disease promoted by hyperlipidemia. Several studies support FOXP3-positive regulatory T cells (Tregs) as inhibitors of atherosclerosis; however, the mechanism underlying this protection remains elusive. To define the role of FOXP3-expressing Tregs in atherosclerosis, we used the DEREG mouse, which expresses the diphtheria toxin (DT) receptor under control of the Treg-specific Foxp3 promoter, allowing for specific ablation of FOXP3+ Tregs. Lethally irradiated, atherosclerosis-prone, low-density lipoprotein receptor-deficient (Ldlr(-/-)) mice received DEREG bone marrow and were injected with DT to eliminate FOXP3(+) Tregs. Depletion of Tregs caused a 2.1-fold increase in atherosclerosis without a concomitant increase in vascular inflammation. These mice also exhibited a 1.7-fold increase in plasma cholesterol and an atherogenic lipoprotein profile with increased levels of VLDL. Clearance of VLDL and chylomicron remnants was hampered, leading to accumulation of cholesterol-rich particles in the circulation. Functional and protein analyses complemented by gene expression array identified reduced protein expression of sortilin-1 in liver and increased plasma enzyme activity of lipoprotein lipase, hepatic lipase, and phospholipid transfer protein as mediators of the altered lipid phenotype. These results demonstrate that FOXP3(+) Tregs inhibit atherosclerosis by modulating lipoprotein metabolism.

Human macrophage cholesterol efflux potential is enhanced by HDL-associated 17beta-estradiol fatty acyl esters

High-density lipoprotein (HDL) and 17beta-estradiol independently provide protection against atherosclerosis. Estradiol fatty acyl esters incorporate into HDL and whether this association enhances the atheroprotective properties of HDL is unclear. The study objective was to clarify the role that HDL-associated estradiol fatty acyl esters play in mediating the initial steps of reverse cholesterol transport. Cholesterol efflux potential from cholesterol loaded macrophage cells to HDL-associated estradiol ester or between HDL from premenopausal women and age-matched males and the cellular receptors involved were examined. Human THP-1 macrophages, loaded with [(3)H]cholesterol oleate, acetylated low-density lipoprotein, were pretreated with or without SR-BI inhibitors or an estrogen receptor antagonist and incubated with either HDL-associated estradiol oleate, HDL lacking estradiol oleate, or isolated HDL from females and males, and cholesterol efflux was measured. Cellular internalization and hydrolysis of HDL-associated [(3)H]estradiol ester were determined. HDL-associated estradiol oleate and premenopausal female HDL demonstrated significantly higher cholesterol efflux capacity to media than male HDL. SR-BI and estrogen receptor inhibition significantly reduced this effect. Cells internalized and subsequently hydrolyzed HDL-associated [(3)H]estradiol ester to [(3)H]estradiol and again SR-BI inhibition reduced this internalization. These results demonstrate that HDL-mediated macrophage cholesterol efflux potential is enhanced by HDL-associated estradiol esters.

High-density lipoprotein-associated 17beta-estradiol fatty acyl ester uptake by Fu5AH hepatoma cells: implications of the roles of scavenger receptor class B, type I and the low-density lipoprotein receptor

17beta-estradiol (E2) fatty acyl esters naturally incorporate into high-density lipoprotein (HDL). The objective was to elucidate mechanisms involved in HDL-associated E2 cellular uptake and to determine the intracellular distribution of E2 and its fatty acyl esters (E2-FAE) after uptake. [3H]E2 or [3H] cholesterol was incubated with human serum for 24 h to allow for fatty acyl esterification. Total-HDL containing [3H]E2-FAE or [3H]cholesterol esters was isolated by sequential density ultracentrifugation and then incubated with Fu5AH rat hepatoma cells for various time points. Cellular uptake was determined by intracellular radioactivity as a percentage of total radioactivity. Chemical inhibition of scavenger receptor class B, type I and low-density lipoprotein (LDL) receptor competition assays were performed to determine cellular uptake mechanisms. Compared to HDL-[3H]cholesterol, cellular uptake of HDL-[3H]E2 occurred at an initially rapid rate. SR-BI inhibition resulted in a decrease in HDL-E2 uptake and LDL impaired this uptake in a concentration-dependent manner. Accordingly, pretreatment of cells with BLT-1 combined with LDL addition significantly attenuated HDL-E2 uptake. HDL-E2-FAE was hydrolyzed into free E2 with the maximum at 24 h. Fu5AH cells facilitate HDL-E2 uptake by at least SR-BI and LDL receptor pathways and intracellular hydrolysis of E2-FAE into free E2 ensues.

Functional LCAT deficiency in human apolipoprotein A-I transgenic, SR-BI knockout mice

Reduction of plasma LCAT activity has been observed in several conditions in which the size of HDL particles is increased; however, the mechanism of this reduction remains elusive. We investigated the plasma activity, mass, and in vivo catabolism of LCAT and its association with HDL particles in human apolipoprotein A-I transgenic, scavenger receptor class B type I knockout (hA-ITg SR-BI-/-) mice. Compared with hA-ITg mice, hA-ITg SR-BI-/- mice had a 4-fold higher total plasma cholesterol concentration, which occurred predominantly in 13-18 nm diameter HDL particles, a significant reduction in plasma esterified cholesterol-total cholesterol (EC/TC) ratio, and significantly lower plasma LCAT activity, suggesting a decrease in LCAT protein. However, LCAT protein in plasma, hepatic mRNA for LCAT, and in vivo turnover of 35S-radiolabeled LCAT were similar in both genotypes of mice. HDL from hA-ITg SR-BI-/- mice was enriched in sphingomyelin (SM), relative to phosphatidylcholine, and had less associated [35S]LCAT radiolabel and endogenous LCAT activity compared with HDL from hA-ITg mice. We conclude that the decreased EC/TC ratio in the plasma of hA-ITg SR-BI-/- mice is attributed to a reduction in LCAT reactivity with SM-enriched HDL particles.

Odorant receptors directly activate phospholipase C/inositol-1,4,5-trisphosphate coupled to calcium influx in Odora cells

Mechanisms by which odorants activate signaling pathways in addition to cAMP are hard to evaluate in heterogeneous mixtures of primary olfactory neurons. We used single cell calcium imaging to analyze the response to odorant through odorant receptor (OR) U131 in the olfactory epithelial cell line Odora (Murrell and Hunter 1999), a model system with endogenous olfactory signaling pathways. Because adenylyl cyclase levels are low, agents activating cAMP formation do not elevate calcium, thus unmasking independent signaling mediated by OR via phospholipase C (PLC), inositol-1,4,5-trisphosphate (IP(3)), and its receptor. Unexpectedly, we found that extracellular calcium is required for odor-induced calcium elevation without the release of intracellular calcium, even though the latter pathway is intact and can be stimulated by ATP. Relevant signaling components of the PLC pathway and G protein isoforms are identified by western blot in Odora cells as well as in olfactory sensory neurons (OSNs), where they are localized to the ciliary zone or cell bodies and axons of OSNs by immunohistochemistry. Biotinylation studies establish that IP(3) receptors type 2 and 3 are at the cell surface in Odora cells. Thus, individual ORs are capable of elevating calcium through pathways not directly mediated by cAMP and this may provide another avenue for odorant signaling in the olfactory system.