Tropical Weight Loss
Tropical Weight Loss
Photo: Keira Burton
Green tea significantly increased sperm concentration (P < 0.05) (Fig. 2a) and sperm vitality control (P < 0.05). The increase in sperm vitality was up to 40% and 54.8% in the 2% and 5% green tea treated groups, respectively (Fig. 2b).
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Read More »The results on the effect of green tea extract or its polyphenols (such as EGCG) on the male reproductive functions and spermatogenesis are conflicting32,33,34,35,37. Also, a high dose of green tea extract caused renal toxicity and hepatotoxic effects12,15,19. Hence, we aim to report on the overall effect of consumption of green tea ad libitum on the male reproductive system after the completion of one spermatogenic cycle in rats, as well as on the kidney and liver functions. Green tea leaves contain 30–40% polyphenols2,8. Similar to previous studies1,14, in vitro analysis of green tea in our study revealed the presence of these polyphenols and further demonstrated a concentration-dependent increase in total polyphenols, flavanol, flavonol, and soluble solids. Further analysis of the antioxidant capacity of green tea in vitro, using FRAP showed a concentration-dependent increase; however, it remained unchanged in the serum of the treated male rats. These were indicating a possible higher antioxidant property with higher concentrations of the extract. Our study however, also showed no change in the serum FRAP after drinking green tea in vivo, which supports the findings of Maxwell & Thorpe42. Contrary to our study, consumption of green tea significantly increased plasma FRAP in humans43. The possible explanation could be due to the differences in bioavailability of green tea, as bioavailability and transformation of EGCG, the predominant catechin in green tea, differs significantly between humans, mice and rats44. Low bioavailability of EGCG was also demonstrated following administration of GTP as the sole source of drinking fluid in rats, with a higher level seen in mice45. The animals consumed green tea extract (2 and 5%) ad libitum, and their average intake was comparable to the control group and corresponds to approximately 40 cups per day in an 80 kg man. The study demonstrated a progressive rise in the weekly weight of animals, with no obvious signs of clinical toxicity or behavioural changes in the rats, indicating the well-being of the animals during the treatment period. Furthermore, body weight gain of the treated rats also remained unchanged. Similar, to our study, administration of green tea (70 mg/kg/day) to rats for 63 days or 90 days did not affect body weight gain32,33. However, a transient reduction in body weight was observed at week 5 in the 5% treatment group and may be attributed to taste aversion and reduced food intake. Kao et al. however, reported that EGCG (a predominant green tea polyphenol) reduced body weight in rats37. Green tea catechins (especially EGCG) are responsible for the reduced body weight by decreasing the differentiation and proliferation of adipocytes during lipogenesis46. Also, a significant rise in weight loss was observed in humans following consumption of a high dose of green tea for 12 weeks. It may be attributed to inhibition of ghrelin secretion, which leads to increased adiponectin levels47. Although our study, however, showed a remarkable rise in kidney weight, the creatinine level remained unchanged, suggesting that green tea did not damage renal function. Another study revealed that high concentrations of green tea catechins (5%) increased the kidney weight, with no histopathologcal observation48. Also, l-theanine (a predominant free amino acid found in tea) was shown to increase kidney weight in rats, with no histological correlations49. Higher protein or amino acid intake modulates renal hemodynamic by increasing renal blood flow and elevating intraglomerular pressure that results in an increased glomerular filtration rate (GFR) as as well an increased kidney volume and weight50. The increased weight in our study may be attributed to the catechins or amino acid (l-theanine) content in green tea and was considered not to be toxicologically significant as there was no obvious histopathological changes in the kidney together with a comparable level of creatinine as the control. Besides, the weight of the liver remained unchanged, with significantly reduced levels of AST and ALT. Both of these findings suggest that consumption of green tea at least in rats had no detrimental effects, as also supported by the histological sections of the treated kidneys and liver. Our study is in corroboration with Bun et al.6, as no sign of evidence of distinctive hepatotoxicity was found in green tea treated rats, as this study showed no hepatic functional disorders based on the levels of ALT and AST in serum, as well as histological sections of the liver. The results of the current study are in line with the literature data suggesting hepatoprotective properties of green tea preparations51,52,53. Takami et al. revealed that prolonged intake (90 days) of high concentrations of green tea catechins (5%) brought about hepatotoxic effects in male rats by the increased levels of ALT and AST48, which could suggest that the use isolated or pure polyphenols could be detrimental to the functioning of these organs. Furthermore, case-reports have associated the use of concentrated green tea-based supplements with liver toxicity in humans54,55. Our study demonstrated that the level of testosterone (which plays a crucial role in spermatogenesis) remained unchanged, even though, a trend to increased values was observed with increasing concentration of green tea. Other studies showed that green tea extract and EGCG produced a substantial drop in testosterone level in Leydig cells in vitro5,56, while testosterone production in vivo studies showed a reduction35,37, increment34 or remained unchanged32 in male rats. A possible explanation for these variations could be due to the use of different forms of the plant (crude extract, or isolated compounds), modes of administration or length of treatment.
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Read More »Reproductive organ weights are used as indicators of reproductive toxicity57, and a reduction of testicular weight is a sensitive parameter for interpretation of male gonadal toxicity58. In line with the observed level of testosterone and similar to a previous study33, intake of green tea in this study did not alter the weight of testosterone dependent organs (testis, epididymis, seminal vesicles and prostate gland). Also, histological sections of the testis and epididymis revealed no obvious alteration in their structures. Furthermore, sperm quality is also used as an important indicator of chemical-induced toxicity on testis59. While a study demonstrated that green tea extract did not affect sperm concentration and viability33, our present study showed that green tea significantly increased sperm concentration and sperm vitality, rather, sperm motility and velocity functions were unaffected. However, morphometric measurements in our study showed a significant reduction in the diameter and epithelial height of the seminiferous tubule. In contrast, epithelial heights of cauda epididymis increased, and that of the caput remained unchanged. Contrary to our study, green tea did not affect the diameter of the seminiferous tubule33; however, a reducing trend was observed. Reproductive toxicants are known to reduce the diameter and epithelial height of seminiferous tubule as well as impair spermatogenesis59,60,61. Our study however, demonstrated an increase in sperm viability, concentration, and epithelial heights of epidiydymis with no dinstinct distortion of the seminiferous tubules or loss of spermatogenic cells. The mechanism of action responsible for these increment is unclear and requires further investigation to understand the impact on the male reproductive functions and fertility outcome. Bioactive compounds in tea such as catechins, caffeine, and l-theanine62 are shown to possess conflicting effects on the male reproductive system. For instance, low concentrations of caffeine (mainly derived from tea leaves) stimulates lactate (the preferred metabolic substrate for developing germ cells) production (5 and 50 µM), and increases expression of glucose transporters (50 µM; GLUTs) in human Sertoli cells (hSCs)63. In another study, administration of caffeine (200 mg/kg body weight) negatively affected the male reproductive functions as demonstrated by the reduced testicular and epidydimal weight, distortion of the histo-architecture of the seminiferous tubule and loss of spermatogenic cells, sperm count, motility and viability with increase abnormal sperm64,65. In addition, maternal consumption of caffeine during gestation (26 and 45 mg/kg) and lactation (25 and 35 mg/kg) was shown to also negatively affect male reproductive function in the male offspring rats as indicated by a significant reduction in testicular weight, diameter and epithelial heights of seminiferous tubules, testosterone production and sperm quality66. EGCG was shown to have an antiproliferative effect on hSCs (5 and 50 µM), although lactate production was maintained (5 and 50 µM) with an increased consumption of glucose and pyruvate (50 µM). However, it decreased the mitochondrial membrane potential (50 µM) and conversion of pyruvate to alanine (5 and 50 µM), which ensures the regular production of lactate67. l-Theanine, on the other hand, increased hSC proliferation, glucose consumption and mitochondrial membrane potential, although lactate production remained unchanged68. Also, supplementation of sperm storage media for up to 3 days either with caffeine (71 µg/ml), EGCG (82 µg/ml) or l-theanine (19 µg/ml) had no effect on sperm viability, while the supplementation with a combination of these three compounds significantly increased sperm viability, suggesting a synergestic effect of the components of tea rather than an individual bioactive compound69. Hence, a possible explanation for the increased sperm concentration and viability in our study might be attributed to an increased lactate production by the Sertoli cells or increased GLUT protein levels and activities, although further studies are required to validate this. In order to fertilise an oocyte, capacitated spermatozoa must undergo acrosome reaction, and consists of the release of the hydrolytic enzyme in the secretory vesicle of the sperm acrosome, for the degradation of the zona pellucida of the oocyte. A premature or spontaneous acrosome reaction makes the spermatozoa incompetent to interact with the oocyte and thereby to impair its fertilisation rate70. This study revealed a significant increase in spontaneous acrosome reaction, posing a question on the ability of these spermatozoa to fertilise an oocyte. Production of F-actin during capacitation was shown to be crucial in the prevention of spontaneous acrosome reaction71. An increase in cyclic adenosine monophosphate (cAMP) results in the activation of protein kinase A (PKA) at the onset of capacitation, which indirectly controls the phosphorylation of protein tyrosine, hyperactivated motility and actin polymerisation72. Further to this, calmodulin kinase II (CAMKII) and phospholipase D (PLD) were shown to be major pathways responsible for the polymerisation of actin71. Tsirulnikov et al. further showed that PKA protects the sperm from undergoing spontaneous acrosome reaction by inducing actin polymerisation via PLD and CAMKII73. The possible explanation for the increased spontaneous acrosome reaction as seen in this study could be due to inhibition of PKA, actin polymerisation or CAMKII and PLD pathways, which needs to be further interrogated. Isotani et al. rather reported that acrosin-disrupted spermatozoa equally pierced the zona pellucida as the wild-type spermatozoa, rather, a delayed dispersal rate of cumulus oophorus cells caused a decrease in the number of fertilised oocyte and litter size74. Hence, the effect of green tea or its polyphenolic compounds on fertility rate must be further investigated to understand better the implication of spontaneous acrosome reaction observed in this study. In comparison to the findings of this study, a previous study showed that black tea increased sperm vitality, motility, the epithelial height of the cauda epididymis, kidney weight, as well as spontaneous acrosome reaction while decreasing the activities of AST and ALT and diameter and epithelial height of the seminiferous tubule75, however, an increased creatinine activity was observed. Another study demonstrated the aphrodisiac property of black tea, accompanied by an increase in testosterone production in rats76. White tea, which is known to have a higher level of antioxidants compared to green, oolong and black teas14, stimulated lactate production in Sertoli cells, which provides nutritional support to the developing germ cells77, as well as increased rat sperm viability1. White tea was also shown to improve prediabetes-induced reproductive dysfunction through increment in glucose transporters 2 and 3 (GLUT 2 and GLUT 3) protein levels and phosphofructokinase 1 (PFK1) activity, sperm motility, with restoration of testicular lactate content and sperm viability78. In another study, white tea improved testiscular antioxidant potential and sperm concentration, and restored sperm quality (motility, morphology and viability) in prediabetic male rats79. These are suggestive of possible effects of the antioxidants in these plants on various aspects of male reproductive functions.
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Read More »Most of the beneficial effects of green tea are attributed to the antioxidant and free-radical scavenging properties, its polyphenols and flavonols80. Our study showed that the levels of CAT, GSH, MDA, SOD were unaffected by green tea in the liver, kidney and testes of the treated rats, which indicates the safety of the plant and suggests that a balance between the scavenging activity of the antioxidant and generation of ROS is not compromised, thereby preventing oxidative stress under the tested conditions. Another study showed that testicular CAT and GSH remained unchanged while a significant increase in SOD was noted33. Green tea extract was shown to protect testicular tissue against oxidative damage by increasing its antioxidant defence mechanism as demonstrated by the increased SOD and GSH activities with a resultant decrease in lipid peroxidation81. Antioxidant therapy is used to eliminate, take up or reduce the formation of ROS. Antioxidant supplements are categorised based on their activities as a preventive antioxidant (e.g. lactoferrin), which prevents the formation of reactive oxygen species (ROS), and scavenging antioxidants (e.g. vitamins C and E), which removes already present ROS82. The antioxidants are also classified as enzymatic (natural) oxidants (includes glutathione reductase, catalase, superoxide dismutase) and non-enzymatic oxidants, (includes vitamins B, C and E, carotenoid, carnitine, cysteine), which are derived from fruits and vegetables83. For instance, intake of a low amount of vitamin C was associated with increased oxidative stress84, while high levels of antioxidant (supraphysiological level) resulted in reductive stress, which is as destructive to cells as oxidative stress. For instance, administration of high concentrations of ascorbate was shown to have similar effects by causing oxidative stress85. A balance must be attained in the use of medicinal plants with an antioxidant in order to prevent oxidative or reductive stress. This study demonstrates that continuous and prolonged intake of aqueous extract of green tea improved sperm parameters, specifically sperm concentration and vitality, and appears to be safe in the rats. However, subtle structural changes observed in the reduced diameter and epithelial heights of the seminiferous tubule and increased spontaneous acrosome reaction needs further investigation to understand the implications on fertility outcomes.
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