Chronic taurine treatment ameliorates reduction in saline-induced diuresis and natriuresis

Bibliometric and Visual Analysis of Global Research on Taurine, Creatine, Carnosine, and Anserine with Metabolic Syndrome: From 1992 to 2022

Red meat and animal-sourced protein are often disparaged as risk factors for developing metabolic syndrome, while emerging research has shown the beneficial effects of dietary taurine, creatine, carnosine, and anserine which are all exclusively abundant in red meat. Thus, it is imperative to highlight the available evidence to help promote red meat as part of a well-balanced diet to optimize human health. In this study, a bibliometric analysis was conducted to investigate the current research status of dietary taurine, creatine, carnosine, and anserine with metabolic syndrome, identify research hotspots, and delineate developmental trends by utilizing the visualization software CiteSpace. A total of 1094 publications were retrieved via the Web of Science Core Collection from 1992 to 2022. There exists a gradual increase in the number of publications on this topic, but there is still much room for research papers to rise. The United States has participated in the most studies, followed by China and Japan. The University of Sao Paulo was the research institute contributing the most; Kyung Ja Chang and Sanya Roysommuti have been identified as the most prolific authors. The analysis of keywords reveals that obesity, lipid profiles, blood pressure, and glucose metabolism, as well as ergogenic aid and growth promoter have been the research hotspots. Inflammation and diabetic nephropathy will likely be frontiers of future research related to dietary taurine, creatine, carnosine, and anserine. Overall, this paper may provide insights for researchers to further delve into this field and enlist the greater community to re-evaluate the health effects of red meat.

The effects of taurine supplementation on obesity and browning of white adipose tissue in high-fat diet-fed mice

Background: In recent years, a new type of adipose tissue (beige adipose tissue) has been mentioned, unlike white adipose tissue (WAT) and brown adipose tissue (BAT). Beige cells are capable of thermogenesis like BAT. In response to various agents, beige cells can develop within WAT through a process called "browning." Therefore, the prevention of obesity and related diseases by providing WAT browning with new potential agents has been extensively studied in recent years. Taurine has many physiological functions in the body and has beneficial effects on obesity and related metabolic disorders. For this reason, we aimed to investigate whether taurine supplementation has effects on browning of WAT and attenuating obesity. Methods: Thirty-two male C57BL/6 mice were used for the study. Mice were divided into 4 groups as control, control + taurine, high fat diet (HFD) and HFD + taurine, and fed for 20 weeks. Taurine was given in drinking water (5%). Epididymal WAT samples were obtained from mice and RNA was extracted from these tissues. Expression levels of FLCN, mTOR, TFE3, PGC-1α, PGC1-1β, AMPK, S6K and UCP1 genes were measured by real-time PCR. Results: Taurine supplementation reduced HFD-induced obesity. No UCP1 expression was detected in any of the groups studied. Any of the gene expressions were not significantly different between HFD and HFD + taurine groups. Reduced PGC-1α and PGC-1β expressions were observed in both HFD and HFD + taurine groups. Conclusions: Taurine reduced the obesity in HFD fed mice, but had no effect on browning of epididymal WAT in this study.

Effect of Taurine on iNOS-Mediated DNA Damage in Drug-Induced Renal Injury

Owing to an outstanding wide antitumor spectrum and excellent anti-tumor effect cisplatin has been used in chemotherapy for malignant tumor. However, cisplatin has strong side effects such as renal injury. Taurine has been found to protect against inflammatory tissue damage in a variety of experimental models. The aim of the present study was to investigate the effect of taurine against iNOS dependent DNA damage in cisplatin-induced renal injury in rats. With the help of a rat model of drug-induced kidney damage, we have assessed the nephrotoxic effects of different doses of cisplatin in the presence and absence of taurine. Immunohistochemical methods were used to examine the distribution of arginine, iNOS, citrulline and 8-nitroguanine in renal tissue. The expression levels of citrulline, iNOS, and 8-nitroguanine immunoreactivities were found to increase as a function of the dose of cisplatin used, and to decrease in the presence of taurine. The expression level of arginine immunoreactivity was reduced as a function of the dose of cisplatin used. On the other hand, iNOS, 8-nitroguanine and citrulline immunohistochemical staining showed an intense immunoreactivity in the renal tubule of cisplatin-treated animals; and arginine immunoreactivity was localized in the renal tubule of taurine-treated animals. We also confirmed the decrease of citrulline and iNOS expression in the renal tubule after taurine administration as well as the expression level of 8-nitroguanine, a nitrative stress marker in the same animals. The present results support the concept that taurine may have a protective role in the formation of cisplatin-related DNA lesions arising through iNOS-mediated nitrative stress.

Perinatal taurine exposure affects adult arterial pressure control

Taurine is an abundant, free amino acid found in mammalian cells that contributes to many physiologic functions from that of a simple cell osmolyte to a programmer of adult health and disease. Taurine's contribution extends from conception throughout life, but its most critical exposure period is during perinatal life. In adults, taurine supplementation prevents or alleviates cardiovascular disease and related complications. In contrast, low taurine consumption coincides with increased risk of cardiovascular disease, obesity and type II diabetes. This review focuses on the effects that altered perinatal taurine exposure has on long-term mechanisms that control adult arterial blood pressure and could thereby contribute to arterial hypertension through its ability to program these cardiovascular regulatory mechanisms very early in life. The modifications of these mechanisms can last a lifetime and transfer to the next generation, suggesting that epigenetic mechanisms underlie the changes. The ability of perinatal taurine exposure to influence arterial pressure control mechanisms and hypertension in adult life appears to involve the regulation of growth and development, the central and autonomic nervous system, the renin-angiotensin system, glucose-insulin interaction and changes to heart, blood vessels and kidney function.

Taurine and the renal system

Taurine participates in a number of different physiologic and biologic processes in the kidney, often reflected by urinary excretion patterns. The kidney is key to aspects of taurine body pool size and homeostasis. This review will examine the renal-taurine interactions relative to ion reabsorption; renal blood flow and renal vascular endothelial function; antioxidant properties, especially in the glomerulus; and the role of taurine in ischemia and reperfusion injury. In addition, taurine plays a role in the renal cell cycle and apoptosis, and functions as an osmolyte during the stress response. The role of the kidney in adaptation to variations in dietary taurine intake and the regulation of taurine body pool size are described. Finally, the protective function of taurine against several kidney diseases is reviewed.

Differential effects of taurine treatment and taurine deficiency on the outcome of renal ischemia reperfusion injury

Taurine possesses membrane stabilization, osmoregulatory and antioxidant properties, aspects of relevance to ischemic injury. We tested the hypothesis that body taurine status is a determinant of renal ischemic injury. Accordingly, renal function and structure were examined in control (C), taurine-treated (TT) and taurine deficient (TD) rats that were subjected to bilateral renal ischemia (60 min) followed by reperfusion (IR); sham operated rats served as controls. Baseline urine osmolality was greater in the TD group than in the control and the TT groups, an effect associated with increased renal aquaporin 2 level. The IR insult reduced urine osmolality (i.e., day-1 post insult); the TD/IR group displayed a more marked recovery in urine osmolality by day-6 post insult than the other two groups. Fluid and sodium excretions were lower in the TD/IR group, suggesting propensity to retention. Histopathological examination revealed the presence of tubular necrotic foci in the C/IR group than sham controls. While renal architecture of the TD/IR group showed features resembling sham controls, the TT/IR group showed dilated tubules, which lacked immunostaining for aquaporin 2, but not 1, suggestive of proximal tubule origin. Finally, assessment of cell proliferation and apoptosis revealed lower proliferation but higher apoptotic foci in the TT/IR group than other IR groups. Collectively, the results indicate that body taurine status is a major determinant of renal IR injury.

Role of antioxidant activity of taurine in diabetes

The unifying hypothesis of diabetes maintains that reactive oxygen species (ROS) generated in the mitochondria of glucose-treated cells promote reactions leading to the development of diabetic complications. Although the unifying hypothesis attributes the generation of oxidants solely to impaired glucose and fatty acid metabolism, diabetes is also associated with a decline in the levels of the endogenous antioxidant taurine in a number of tissues, raising the possibility that changes in taurine status might also contribute to the severity of oxidant-mediated damage. There is overwhelming evidence that taurine blocks toxicity caused by oxidative stress, but the mechanism underlying the antioxidant activity remains unclear. One established antioxidant action of taurine is the detoxification of hypochlorous acid. However, not all of the antioxidant actions of taurine are related to hypochlorous acid because they are detected in isolated cell systems lacking neutrophils. There are a few studies showing that taurine either modulates the antioxidant defenses or blocks the actions of the oxidants, but other studies oppose this interpretation. Although taurine is incapable of directly scavenging the classic ROS, such as superoxide anion, hydroxyl radical, and hydrogen peroxide, there are numerous studies suggesting that it is an effective inhibitor of ROS generation. The present review introduces a novel antioxidant hypothesis, which takes into consideration the presence of taurine-conjugated tRNAs in the mitochondria. Because tRNA conjugation is required for normal translation of mitochondrial-encoded proteins, taurine deficiency reduces the expression of these respiratory chain components. As a result, flux through the electron transport chain decreases. The dysfunctional respiratory chain accumulates electron donors, which divert electrons from the respiratory chain to oxygen, forming superoxide anion in the process. Restoration of taurine levels increases the levels of conjugated tRNA, restores respiratory chain activity, and increases the synthesis of ATP at the expense of superoxide anion production. The importance of this and other actions of taurine in diabetes is discussed.

Evaluation of Taurine as an Osmotic Agent for Peritoneal Dialysis Solution

Objective

The development of a glucose-free peritoneal dialysis (PD) solution is important because glucose has been associated with functional and morphological damage to the peritoneal membrane. The ultrafiltration (UF) and biocompatibility of new PD solutions containing taurine (PD-taurine) instead of glucose as an osmolite were tested in a rat PD model.

Methods

To determine the solution's UF ability, different concentrations of taurine in PD solutions were compared to glucose-based PD solutions (PD-glucose) by giving single intraperitoneal injections for 2, 4, and 6 hours. To examine the biocompatibility of PD-taurine, the rats were divided into 3 groups: a 3.86% PD-glucose group, a 3.5% PD-taurine group and a not dialyzed group. The rats were given 10-mL injections of PD fluids intraperitoneally 3 times daily for 7 days. A peritoneal equilibration test (PET) was performed using a 1.9% xylitol solution at the time the rats were sacrificed. Mesothelial cell monolayers were obtained from the animals and studied based on a population analysis.

Results

The net UF of PD-taurine increased in a dose-dependent manner; the 3.5% PD-taurine solution was equivalent to the 3.86% PD-glucose solution after 4 hours. The PET showed that the drainage volume and the D4/D0 ratio for xylitol after 4 hours with PD-taurine solution were significantly greater than with the PD-glucose solution ( p < 0.001 and p < 0.001 respectively). Mesothelial and fibroblast-like cell proliferation was significantly less with PD-taurine than with PD-glucose ( p < 0.01).

Conclusions

These results indicate that PD-taurine resulted in net UF equivalent to that of PD-glucose and was more biocompatible than PD-glucose with respect to the peritoneal membrane.

Vascular reactivity changes in glucose-intolerant rat

The vascular effects of glucose-intolerance were investigated using the neonatal streptozotocin-treated (nSTZ) rat model. Glucose-intolerance was initiated by administration of STZ (90 mg/kg, IP) into 2-day-old male rats. Aortic reactivity was assessed in vitro at 3 and 6 months of age. Both the 3- and 6-month-old nSTZ rats displayed higher blood glucose levels in response to a glucose challenge. At 3 months of age, aortic responsiveness to both norepinephrine and acetylcholine was not altered. However, at 6 months of age, the responses of endothelium-denuded aortas from nSTZ rats to norepinephrine and serotonin were enhanced compared to controls. Endothelium-mediated relaxation of aortas from these animals to acetylcholine was also augmented, and this effect was linked to NO release. Although norepinephrine did not elicit enhancement of aortic contraction in calcium-free medium in 6-month-old nSTZ rats, the responses to both maximum and submaximum concentrations of the agonist after readdition of calcium were greater in these tissues than in control preparations. Pretreatment of aortas with calphostin C eliminated the difference in NE-induced contraction between the control and experimental groups. Although the concentration-response curves for phorbol 12,13-dibutyrate were not different between the 2 groups, the responses of the aortas from 6-month-old nSTZ rats to a submaximum concentration of the phorbol ester were enhanced relative to controls, and this enhancement was normalized with calphostin C. Overall, the data suggest that glucose-intolerance of sufficient duration causes increases in vascular reactivity to agonists. While these findings warrant further investigations, such vascular alterations during the prediabetes stage of glucose intolerance can be a predisposing factor for the eventual development of cardiovascular complications.

Accelerated NaCl-induced hypertension in taurine-deficient rat: Role of renal function

Taurine modulates blood pressure and renal function. As the kidney plays a pivotal role in long-term control of arterial pressure, we tested the hypothesis that taurine-deficient rats display maladaptive renal and blood pressure responses to uninephrectomy. Control and taurine-deficient (i.e., beta-alanine-treated) rats with either one or two remaining kidneys were fed diets containing basal or high (8%) NaCl diet. Urine osmolality was greater in the taurine-deficient than controls fed a normal NaCl diet; proteinuria and blood pressure were unaffected by uninephrectomy. Following 6 weeks on an 8% NaCl diet, the uninephrectomized (UNX) animals developed significant hypertension, which was more severe in the taurine-deficient group; baroreflex function was unaffected. However, the UNX taurine-deficient rats displayed impaired ability to dispose of an acute isotonic saline volume load before a switchover to a high NaCl diet. Nonetheless, a more protracted exposure (i.e., 14 weeks) to dietary NaCl excess eliminated the blood pressure differential between the two groups; at this stage, renal excretory responses to an acute saline volume load or to atrial natriuretic peptide were similar in the two groups. Nonetheless, hypertensive taurine-deficient rats displayed greater proteinuria, although both groups excreted proteins of similar molecular weights ( approximately 15-66 kDa). Further, taurine-deficient kidney specimens displayed periarterial mononuclear cell infiltrates with strong immunoreactivity to the histiocyte marker CD68, suggestive of increased phagocytic activity. In conclusion, taurine deficiency modulates renal adaptation to combined uninephrectomy and dietary NaCl excess, resulting in an accelerated development of hypertension.

Effects of dietary salt and fat on taurine excretion in healthy and diseased rats

Taurine modulates renal and cardiovascular function. Although the kidney regulates body taurine status, the impact of renal and cardiovascular risk factors, such as dietary intake of excess NaCl and saturated fat, on renal handling of taurine is less clear. One would predict that the kidney would modulate taurine excretion during dietary NaCl excess to insure adequate osmotic homeostasis. Similarly, fat feeding would be expected to affect taurine homeostasis, as taurine is involved in bile acid conjugation and therefore fat emulsification. To examine these aspects, male rats were divided into four groups: basal fat diet (control), high fat diet (FAT), basal fat and high salt diet (SALT) and a combination of a high fat and salt diet (FATSALT). While the control, FAT and SALT groups excreted similar amounts of taurine; the SALTFAT group excreted significantly more taurine than the other 3 groups. Although all of the dietary regimens increased renal tissue content of taurine, the increases were greatest in the two SALT groups. In a subsequent study, we examined the effect of excess dietary fat on taurine handling by the hypertensive (H) and hypertensive-glucose intolerant (HGI) rat. When fed a basal fat diet, the HGI group excreted more taurine than the H group, an effect likely related to increased endogenous taurine biosynthesis, alterations in renal function or a combination of the two effects. While excess fat intake increased urinary taurine excretion in the H group, it reduced taurine excretion in the HGI group. Nonetheless, kidney taurine content was similar in the 4 groups. Taken together, the data suggest that dietary constituents and preexisting systemic disorders are important modulators of renal handling of taurine.

Taurine protects against methotrexate-induced toxicity and inhibits leukocyte death

The efficacy of methotrexate (MTX), a widely used cytotoxic chemotherapeutic agent, is often limited by severe side effects and toxic sequelae. Regarding the mechanisms of these side effects, several hypotheses have been put forward, among which oxidative stress is noticeable. The present study was undertaken to determine whether taurine, a potent free radical scavenger, could ameliorate MTX-induced oxidative injury and modulate immune response. Following a single dose of methotrexate (20 mg/kg), either saline or taurine (50 mg/kg) was administered for 5 days. After decapitation of the rats, trunk blood was obtained and the ileum, liver, and kidney were removed to measure malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity, and collagen content, as well as histological examination. Our results showed that MTX administration increased the MDA, MPO activity, and collagen contents and decreased GSH levels in all tissues (P < 0.001), while these alterations were reversed in taurine-treated group (P < 0.05-0.01). Elevated (P < 0.001) TNF-alpha level observed following MTX treatment was depressed with taurine (P < 0.01). Oxidative burst of neutrophils stimulated by phorbol myristate acetate was reduced in saline-treated MTX group (P < 0.001), while taurine abolished this effect. Similarly, flow cytometric measurements revealed that leukocyte apoptosis and cell death were increased in MTX-treated animals, while taurine reversed these effects (P < 0.05). Reduced cellularity in bone marrow samples of MTX-treated group (P < 0.01) was reversed back to control levels in taurine-treated rats. Severe degeneration of the intestinal mucosa, liver parenchyma, glomerular, and tubular epithelium observed in saline-treated group was improved by taurine treatment. In conclusion, it appears that taurine protects against methotrexate-induced oxidant organ injury and inhibits leukocyte apoptosis and may be of therapeutic potential in alleviating the systemic side effects of chemotherapeutics.

Effects of chronic chromium picolinate treatment in uninephrectomized rat

Chromium picolinate [Cr(pic)3] is a nutritional supplement that is advocated as an adjuvant therapy for impaired glucose tolerance/type 2 diabetes because it improves glucose homeostasis. Because renal dysfunction is a major complication of type 2 diabetes, the potential impact of Cr(pic)3 on kidney function requires due consideration. This investigation takes added importance because the kidney is not only the principal route of elimination for chromium but also an organ that preferentially accumulates it. To avoid the confounding influence of chronic hyperglycemia, and its associated complications, we used the unilaterally nephrectomized (UNX) rat that shows impaired kidney function with age. We tested the hypothesis that chronic treatment of the UNX rat with Cr(pic)3 exacerbates the age-related decline in renal function. Accordingly, UNX rats were fed a diet lacking (eg, control; n=5) or containing 5 mg/kg of Cr(pic)3 (n=7) for 60 days. The treatment did not affect glucose tolerance as reflected by lack of any effect on changes in blood glucose concentration during glucose tolerance testing. Although nonfasting blood glucose concentrations were similar between the 2 groups, plasma insulin concentration was lower in the Cr(pic)3-treated group (P<.05), suggesting improved insulin sensitivity. Body weight, blood pressure, heart rate, daily food and fluid consumption, daily urinary fluid and electrolyte excretions, urine osmolality, and daily protein excretion were similar between the 2 groups before and during Cr(pic)3 treatment. Although renal excretory responses to acute administration of a 5% isotonic saline volume load were similar between the 2 groups, the Cr(pic)3-treated group displayed a more robust ability to excrete a 10% isotonic saline volume load, an effect primarily related to reduced tubular reabsorption of the filtered fluid and sodium loads. In conclusion, chronic Cr(pic)3 did not adversely affect renal function. Rather, the treatment improved the ability of the animal to dispose of an acute isotonic saline volume load, suggesting preservation of renal function in the UNX rat.

Protective Effects of Taurine against Nicotine-Induced Oxidative Damage of Rat Urinary Bladder and Kidney

Several studies demonstrate that taurine treatment prevents tissue damage in various models of inflammation. Experiments have shown that chronic nicotine administration caused oxidant damage in various organs by increasing lipid peroxidation products and decreasing the activity of endogenous antioxidants. The aim of this study was to investigate the effects of taurine treatment on nicotine-induced oxidative changes in rat urinary bladder and kidney and to explore the possible mechanisms of action. Male Wistar albino rats were injected with nicotine hydrogen bitartrate (0.6 mg/kg i.p.) or saline for 21 days. Taurine was administered (50 mg/kg i.p.) alone or along with nicotine injections. At the end of the treatment period bladder tissue was used for in vitro contractility studies, or stored along with kidney tissue for the measurement of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen content. Tissue samples were also examined histologically. Serum samples were stored for the measurement of MDA, GSH, blood urea nitrogen, creatinine and lactate dehydrogenase activity. Chronic nicotine treatment decreased the contractile activity of the bladder strips to carbachol and increased lipid peroxidation, MPO levels and tissue collagen content of the bladder and kidney samples. Taurine supplementation to nicotine-treated animals reversed the contractile dysfunction of the bladder strips. It also preserved the renal functions, restored the endogenous GSH levels and decreased high lipid peroxidation and MPO activities in both urinary bladder and kidney tissues. These data suggest that taurine supplementation effectively counteracts the deleterious effect of chronic nicotine administration on bladder and kidney functions and attenuates oxidative damage possibly by its antioxidant effects.

Taurine depletion alters vascular reactivity in rats

We recently showed that chronic taurine supplementation is associated with attenuation of contractile responses of rat aorta to norepinephrine and potassium chloride. However, the potential involvement of endogenous taurine in modulation of vascular reactivity is not known. Therefore, we examined the effect of β-alanine-induced taurine depletion on the in vitro reactivity of rat aorta to selected vasoactive agents. The data indicate that both norepinephrine- and potassium-chloride-induced maximum contractile responses of endothelium-denuded aortae were enhanced in taurine-depleted rats compared with control animals. However, taurine depletion did not affect tissue sensitivity to either norepinephrine or potassium chloride. By contrast, sensitivity of the endothelium-denuded aortae to sodium nitroprusside was attenuated by taurine depletion. Similarly, taurine deficiency reduced the relaxant responses of endothelium-intact aortic rings elicited by submaximal concentrations of acetylcholine, and this effect was associated with decreased nitric oxide production. Taken together, the data suggest that taurine depletion augments contractility but attenuates relaxation of vascular smooth muscle in a nonspecific manner. Impairment of endothelium-dependent responses, which is at least in part associated with reduced nitric oxide generation, may contribute to the attenuation of the vasorelaxant responses. These vascular alterations could be of potential consequence in pathological conditions associated with taurine deficiency.Key words: rat aorta, β-alanine, taurine depletion, vascular reactivity.

Renoprotective effects of chronic candesartan treatment in uninephrectomized rat

The authors recently observed an age-dependent reduction in the diuretic and natriuretic responses to plasma volume expansion in uninephrectomized control and glucose-intolerant rats. To determine the involvement of angiotensin II AT receptors in this phenomenon, the authors tested the hypothesis that chronic candesartan treatment preserves renal excretory function in the uninephrectomized rat. Control and glucose-intolerant rats underwent right nephrectomy at 4 weeks of age. Two weeks later, the animals in each group were further subdivided and maintained on tap water containing either candesartan cilexetil (10 mg. kg(-1). day(-1) ) or vehicle. Renal excretory responses to acute extracellular fluid volume expansion (5% of body weight over 30 min) were determined in the 9-month-old conscious animal. Candesartan treatment markedly reduced the mean arterial pressure of controls and glucose-intolerant rats. Nonetheless, the baseline rates of fluid and electrolyte excretion, as well as the saline volume-induced diuretic, natriuretic, and kaliuretic responses, were greater in the candesartan-treated rats than in their vehicle-treated counterparts. The augmented baseline rates of fluid and sodium excretion in candesartan-treated rats were caused by a reduction in tubular reabsorption activity and an increase in glomerular filtration rate. However, the candesartan-mediated enhancement in saline volume-induced diuresis and natriuresis was caused by a reduction in tubular reabsorption activity. In addition to improving renal function, candesartan treatment reduced proteinuria in both groups. In conclusion, chronic blockade of the angiotensin II receptors exerts hypotensive and renoprotective effects in the aging uninephrectomized rat.