Administration of saccharin to neonatal mice influences body composition of adult males and reduces body weight of females

Obesogenic potentials of environmental artificial sweeteners with disturbances on both lipid metabolism and neural responses

Artificial sweeteners (ASs) entered the environments after application and emissions. Recent studies showed that some ASs had obesogenic risks. However, it remained unclear whether such risks are common and how they provoke such effects. Presently, the effects of 8 widely used ASs on lipid accumulation were measured in Caenorhabditis elegans. Potential mechanisms were explored with feeding and locomotion behavior, lipid metabolism and neural regulation. Results showed that acesulfame (ACE), aspartame (ASP), saccharin sodium (SOD), sucralose (SUC) and cyclamate (CYC) stimulated lipid accumulation at μg/L levels, showing obesogenic potentials. Behavior investigation showed that ACE, ASP, SOD, SUC and CYC biased more feeding in the energy intake aspect against the locomotion in the energy consumption one. Neotame (NEO), saccharin (SAC) and alitame (ALT) reduced the lipid accumulation without significant obesogenic potentials in the present study. However, all 8 ASs commonly disturbed enzymes (e.g., acetyl-CoA carboxylase) in lipogenesis and those (e.g., carnitine palmitoyl transferase) in lipolysis. In addition, ASs disturbed PPARγ (via expressions of nhr-49), TGF-β/DAF-7 (daf-7) and SREBP (sbp-1) pathways. Moreover, they also interfered neurotransmitters including serotonin (5-HT), dopamine (DA) and acetylcholine (ACh), with influences in Gsα (e.g., via expressions of gsα-1, ser-7), glutamate (e.g., mgl-1), and cGMP-dependent signaling pathways (e.g., egl-4). In summary, environmental ASs commonly disturbed neural regulation connecting behavior and lipid metabolism, and 5 out of 8 showed clear obesogenic potentials. ENVIRONMENTAL IMPLICATION: Artificial sweeteners (ASs) are become emerging pollutants after wide application and continuous emission. Recent studies showed that some environmental ASs had obesogenic risks. The present study employed Caenorhabditis elegans to explore the influences of 8 commonly used ASs on lipid metabolisms and also the underlying mechanisms. Five out of 8 ASs stimulated lipid accumulation at μg/L levels, and they biased energy intake against energy consumption. The other three ASs reduced the lipid accumulation. ASs commonly disturbed lipogenesis and lipolysis via PPARγ, TGF-β and SREBP pathways, and also influenced neurotransmitters with Gsα, glutamate and cGMP-dependent signaling pathways.

Non-nutritive Sweeteners: Weight Loss or Weight Gain?

The consumption of non-nutritive sweeteners (NNS) is on the rise among different populations. In parallel, the debate about their potential health benefits and risks remains inconclusive. Numerous published studies elucidate the impact of NNS on general health, weight control, and the risk of certain diseases. However, no definitive conclusions regarding the effect of chronic NNS use on weight have been reached in humans. This review summarizes current evidence related to the biological role of NNS and their subsequent effects on weight. The mechanisms of action through which NNS impact weight are discussed, including their effect on sweet taste receptors, cognition, metabolic and endocrine functions, intestinal microbiota, and adiposity. Conflicting evidence is hindering the formulation of precise recommendations, but the evidence opposing the use of NNS remains weak, and the ultimate impact on weight largely relies on several other behavioral patterns.

Effects of Nonnutritive Sweeteners on Body Composition Changes during Pubertal Growth

The effects of consuming specific types of nonnutritive sweeteners (NNSs) on adiposity changes in children have remained inconsistent. In this study, we aimed to investigate the effects of the intake of different kinds of NNSs on long-term adiposity changes during pubertal growth. Furthermore, we examined the above relationships among different sexes, pubertal stages, and levels of obesity. A total of 1893 6-15-year-old adults were recruited and followed-up every 3 months. The NNS-FFQ (Food Frequency Questionnaire) was conducted and urine samples were collected to investigate the effects of the selected sweeteners, which included acesulfame potassium, aspartame, sucralose, glycyrrhizin, steviol glycosides, and sorbitol. Multivariate linear mixed-effects models were used to examine the relationship between NNS intake and body composition. The consumption of aspartame, sucralose, glycyrrhizin, stevioside, and sorbitol was associated with decreased fat mass and increased fat-free mass. In the highest tertile group, the effects of NNS consumption on fat mass corresponded to values of -1.21 (95% CI: -2.04 to -0.38) for aspartame, -0.62 (95% CI: -1.42 to 0.19) for sucralose, -1.26 (95% CI: -2.05 to -0.47) for glycyrrhizin, -0.90 (95% CI: -2.28 to 0.48) for stevioside, and -0.87 (95% CI: -1.67 to -0.08) for sorbitol, while the effects on fat-free mass corresponded to values of 1.20 (95% CI: 0.36 to -0.38) for aspartame, 0.62 (95% CI: -0.19 to 1.43) for sucralose, 1.27 (95% CI: 0.48 to 2.06) for glycyrrhizin, 0.85 (95% CI: -0.53 to 2.23) for stevioside, and 0.87 (95% CI: 0.08 to 1.67) for sorbitol. Particularly, aspartame and sorbitol revealed a dose-responsiveness effect. The above finding was more prominent among girls than boys. Moreover, fat mass was significantly reduced in normal-weight children who consumed a moderate amount of aspartame and a large amount of glycyrrhizin and sorbitol compared with obese children. In conclusion, the NNS-specific and sex-specific effects of long-term NNS consumption revealed associations of decreasing fat mass and increasing fat-free mass for children undergoing pubertal growth.

Sweet Taste Receptor T1R3 Expressed in Leydig Cells Is Closely Related to Homeostasis of the Steroid Hormone Metabolism Profile

Taste receptor type 1 subunit 3 (T1R3) is initially expressed in mammal tongue for recognition and response of sweet/umami tastants and is critical to nutrient absorption, even endocrine. In this study, down-regulation of related steroidogenic enzymes such as StAR, 3β-HSD, CYP17A1, and 17β-HSD with the decrease of T1R3 expression was found in Leydig cells treated by a T1R3 inhibitor (lactisole). The abundances of progesterone, 17a-hydroxyprogesterone, androstenedione, testosterone, and deoxycorticosterone were down-regulated by 2.3, 3.5, 1.4, 1.6, and 2.2 times, respectively, after T1R3 inhibition. In addition, opposite results were found in saccharin sodium treatment. T1R3 activation contributed to intracellular cyclic adenosine monophosphate (cAMP) accumulation (14.41 ± 0.58 vs 20.21 ± 0.65) and increased testosterone (20.31 ± 3.49 vs 50.01 ± 7.44) and steroidogenic metabolite levels. Coadministration of human chorionic gonadotropin and saccharin sodium resulted in elevating the testosterone and cAMP levels and enhancing the expression levels of steroidogenic-related factors. Similarly, intratesticular injection of lactisole and saccharin sodium further confirmed that T1R3 inhibition/activation affected the expression of related steroidogenic enzymes and the testosterone levels in mice. The above findings suggest that T1R3 plays a role in testicular steroidogenesis.

Personalized microbiome-driven effects of non-nutritive sweeteners on human glucose tolerance

Non-nutritive sweeteners (NNS) are commonly integrated into human diet and presumed to be inert; however, animal studies suggest that they may impact the microbiome and downstream glycemic responses. We causally assessed NNS impacts in humans and their microbiomes in a randomized-controlled trial encompassing 120 healthy adults, administered saccharin, sucralose, aspartame, and stevia sachets for 2 weeks in doses lower than the acceptable daily intake, compared with controls receiving sachet-contained vehicle glucose or no supplement. As groups, each administered NNS distinctly altered stool and oral microbiome and plasma metabolome, whereas saccharin and sucralose significantly impaired glycemic responses. Importantly, gnotobiotic mice conventionalized with microbiomes from multiple top and bottom responders of each of the four NNS-supplemented groups featured glycemic responses largely reflecting those noted in respective human donors, which were preempted by distinct microbial signals, as exemplified by sucralose. Collectively, human NNS consumption may induce person-specific, microbiome-dependent glycemic alterations, necessitating future assessment of clinical implications.

Consumption of non-nutritive sweeteners during pregnancy

In an effort to reduce sugar consumption to prevent diabetes mellitus and cardiovascular diseases, "sugar-free" or "no added sugar" products that substitute sugar with non-nutritive sweeteners (NNSs) (eg, Splenda, Sweet'N Low, and Stevia) have become increasingly popular. The use of these products during pregnancy has also increased, with approximately 30% of pregnant women reporting intentional NNS consumption. In clinical studies with nonpregnant participants and animal models, NNSs were shown to alter gut hormonal secretion, glucose absorption, appetite, kidney function, in vitro insulin secretion, adipogenesis, and microbiome dysbiosis of gut bacteria. In pregnant animal models, NNS consumption has been associated with altered sweet taste preference later in life and metabolic dysregulations in the offspring (eg, elevated body mass index, increased risk of obesity, microbiome dysbiosis, and abnormal liver function tests). Despite the accumulating evidence, no specific guidelines for NNS consumption are available for pregnant women. Furthermore, there are limited clinical studies on the effects of NNS consumption during pregnancy and postpartum and long-term outcomes in the offspring.

Transgenerational transmission of behavioral phenotypes produced by exposure of male mice to saccharin and nicotine

The use of non-nutritive sweeteners such as saccharin is widely prevalent. Although saccharin is considered safe for human consumption, it produces behavioral changes in experimental animals. We report that saccharin’s behavioral effects are much more pervasive than currently recognized. In a mouse model, saccharin exposure produced motor impulsivity not only in the saccharin-exposed males but also in their offspring. In addition, the offspring showed locomotor hyperactivity and working memory deficit not observed in fathers. Spermatazoal DNA was hypermethylated in the saccharin-exposed fathers, especially at dopamine receptor promoter regions, suggesting that epigenetic modification of germ cell DNA may mediate transgenerational transmission of behavioral phenotypes. Dopamine’s role in hyperactivity was further highlighted by the finding that the stimulant drug methylphenidate mitigated the hyperactivity. Nicotine is another substance that is widely used. Its use via smokeless tobacco products, some of which contain saccharin, is on the rise contributing to concerns about adverse outcomes of co-exposure to saccharin and nicotine. We found that co-exposure of male mice to saccharin and nicotine produced significant behavioral impairment in their offspring. Thus, our data point to potential adverse neurobehavioral consequences of exposure to saccharin alone or saccharin and nicotine for the exposed individuals and their descendants.

A novel mouse model overexpressing Nocturnin results in decreased fat mass in male mice

Nocturnin (NOCT) belongs to the Mg²⁺ dependent Exonucleases, Endonucleases, Phosphatase (EEP) family of enzymes that exhibit various functions in vitro and in vivo. NOCT is known to function as a deadenylase, cleaving poly-A tails from mRNA (messenger RNA) transcripts. Previously, we reported a role for NOCT in regulating bone marrow stromal cell differentiation through its interactions with PPARγ. In this study, we characterized the skeletal and adipose tissue phenotype when we globally overexpressed Noct in vivo. After 12 weeks of Noct overexpression, transgenic male mice had lower fat mass compared to controls, with no significant differences in the skeleton. Based on the presence of a mitochondrial target sequence in NOCT, we determined that mouse NOCT protein localizes to the mitochondria; subsequently, we found that NOCT overexpression led to a significant increase in the preadipocytes ability to utilize oxidative phosphorylation for ATP (adenosine triphosphate) generation. In summary, the effects of NOCT on adipocytes are likely through its novel role as a mediator of mitochondrial function.

How Non-nutritive Sweeteners Influence Hormones and Health

Non-nutritive sweeteners (NNSs) elicit a multitude of endocrine effects in vitro, in animal models, and in humans. The best-characterized consequences of NNS exposure are metabolic changes, which may be mediated by activation of sweet taste receptors in oral and extraoral tissues (e.g., intestine, pancreatic β cells, and brain), and alterations of the gut microbiome. These mechanisms are likely synergistic and may differ across species and chemically distinct NNSs. However, the extent to which these hormonal effects are clinically relevant in the context of human consumption is unclear. Further investigation following prolonged exposure is required to better understand the role of NNSs in human health, with careful consideration of genetic, dietary, anthropometric, and other interindividual differences.

Lactational programming of glucose homeostasis: a window of opportunity

The window of lactation is a critical period during which nutritional and environmental exposures impact lifelong metabolic disease risk. Significant organ and tissue development, organ expansion and maturation of cellular functions occur during the lactation period, making this a vulnerable time during which transient insults can have lasting effects. This review will cover current literature on factors influencing lactational programming such as milk composition, maternal health status and environmental endocrine disruptors. The underlying mechanisms that have the potential to contribute to lactational programming of glucose homeostasis will also be addressed, as well as potential interventions to reduce offspring metabolic disease risk.

Saccharin Increases Fasting Blood Glucose but Not Liver Insulin Resistance in Comparison to a High Fructose-Fed Rat Model

Recent data indicate that artificial sweeteners (AS) may have deleterious effects on glucose metabolism. The purpose of this study was to compare the effects of AS and the effects of a high fructose diet (HFrD) on glucose metabolism and insulin resistance (IR) in Sprague-Dawley (SD) rats. SD rats were fed either regular chow, chow with saccharin (Sac) (0.1 mg/mL) placed in their water, or HFrD for seven weeks. Glucose, insulin, and triglycerides (Tg) levels were measured upon completion. A homeostatic model assessment (HOMA)-IR index was used to determine insulin resistance. The liver was stained to detect signs of a fatty liver. Hepatic mRNA expression of glucose metabolism regulation genes, Srepb-1c (sterol regulatory element binding protein) and ChREB (α & β) (carbohydrate response element binding protein), as well as other glycolytic and lipogenic genes including glucose-6-phosphatase (G6pc), were considered IR markers. Both HFrD and Sac significantly increased fasting blood glucose levels compare to the control (140 ± 5 and 137 ± 6 vs. 118 ± 3 mg/dL, respectively, p < 0.05). However, only HFrD increased insulin secretion (0.99 ± 0.12 vs. 0.7 ± 0.1 and 0.6 ± 0.1 ug/L), Tg levels (420 ± 43 vs. 152 ± 20 and 127 ± 13 mg/dL), and the HOMA-IR index (3.4 ± 0.4 vs. 2.3 ± 0.36 and 2.13 ± 0.3) (HFrD vs. control and sac, p < 0.05). Fatty liver changes were only observed in HFrD fed rats. The expression of ChREB β, Srepb-1c, and G6pc mRNA were only significantly elevated (between 2-10 times folds, p < 0.05) in HFrD fed rats. Sac may increase fasting blood glucose but has no effect on liver insulin resistance.

Early-Life Exposure to Non-Nutritive Sweeteners and the Developmental Origins of Childhood Obesity: Global Evidence from Human and Rodent Studies

Non-nutritive sweeteners (NNS) are increasingly consumed by children and pregnant women around the world, yet their long-term health impact is unclear. Here, we review an emerging body of evidence suggesting that early-life exposure to NNS may adversely affect body composition and cardio-metabolic health. Some observational studies suggest that children consuming NNS are at increased risk for obesity-related outcomes; however, others find no association or provide evidence of confounding. Fewer studies have examined prenatal NNS exposure, with mixed results from different analytical approaches. There is a paucity of RCTs evaluating NNS in children, yielding inconsistent results that can be difficult to interpret due to study design limitations (e.g., choice of comparator, multifaceted interventions). The majority of this research has been conducted in high-income countries. Some rodent studies demonstrate adverse metabolic effects from NNS, but most have used extreme doses that are not relevant to humans, and few have distinguished prenatal from postnatal exposure. Most studies focus on synthetic NNS in beverages, with few examining plant-derived NNS or NNS in foods. Overall, there is limited and inconsistent evidence regarding the impact of early-life NNS exposure on the developmental programming of obesity and cardio-metabolic health. Further research and mechanistic studies are needed to elucidate these effects and inform dietary recommendations for expectant mothers and children worldwide.

Saccharin induced liver inflammation in mice by altering the gut microbiota and its metabolic functions

Maintaining the balance of the gut microbiota and its metabolic functions is vital for human health, however, this balance can be disrupted by various external factors including food additives. A range of food and beverages are sweetened by saccharin, which is generally considered to be safe despite controversial debates. However, recent studies indicated that saccharin perturbed the gut microbiota. Inflammation is frequently associated with disruptions of the gut microbiota. The aim of this study is to investigate the relationship between host inflammation and perturbed gut microbiome by saccharin. C57BL/6J male mice were treated with saccharin in drinking water for six months. Q-PCR was used to detect inflammatory markers in mouse liver, while 16S rRNA gene sequencing and metabolomics were used to reveal changes of the gut microbiota and its metabolomic profiles. Elevated expression of pro-inflammatory iNOS and TNF-α in liver indicated that saccharin induced inflammation in mice. The altered gut bacterial genera, enriched orthologs of pathogen-associated molecular patterns, such as LPS and bacterial toxins, in concert with increased pro-inflammatory metabolites suggested that the saccharin-induced liver inflammation could be associated with the perturbation of the gut microbiota and its metabolic functions.

Immune and metabolic responses in early and late sepsis during mild dietary zinc restriction

BACKGROUND

Mild dietary zinc (Zn) deficiency is widespread in human populations, but its influence on recovery after acute illness is poorly understood. In a mouse model of abdominal sepsis (cecal ligation puncture), systemic immune responses and liver metabolism were monitored in early (24 h) and late (5 d) phases, under control conditions and during mild dietary Zn restriction.

METHODS

Mice were fed diets adequate or marginally deficient (ZM) in Zn (30 versus 10 mg zinc/kg diet) for 4 wk, before undergoing laparotomy alone (nonseptic control) or cecal ligation puncture (septic).

RESULTS

Among nonseptic mice, the ZM state was not associated with differences in inflammation or metabolic responses. Among septic mice, mortality did not differ between the zinc adequate and ZM groups. In the early phase, the ZM state amplified increases in plasma interleukin (IL) 6, tumor necrosis factor alpha, and IL-10, while dampening the interferon gamma response. In the late phase, subtle but significant ZM-associated increases were observed in plasma IL-5 and interferon gamma levels and hepatic protein synthesis, the latter of which appeared to be mammalian target of rapamycin independent and was associated with increased hepatic tumor necrosis factor alpha messenger RNA content.

CONCLUSIONS

Without increasing mortality, the ZM state is associated with a more disordered acute systemic inflammatory response and persistence or enhancement of acute phase responses within the liver parenchyma.

Lipodystrophy and severe metabolic dysfunction in mice with adipose tissue-specific insulin receptor ablation

OBJECTIVE

Insulin signaling plays pivotal roles in the development and metabolism of many tissues and cell types. A previous study demonstrated that ablation of insulin receptor (IR) with aP2-Cre markedly reduced adipose tissues mass and protected mice from obesity. However, multiple studies have demonstrated widespread non-adipocyte recombination of floxed alleles in aP2-Cre mice. These findings underscore the need to re-evaluate the role of IR in adipocyte and systemic metabolism with a more adipose tissue-specific Cre mouse line.

METHODS

We generated and phenotyped a new adipose tissue-specific IR mouse model using the adipose tissue-specific Adipoq-Cre line.

RESULTS

Here we show that the Adipoq-Cre-mediated IR KO in mice leads to lipodystrophy and metabolic dysfunction, which is in stark contrast to the previous study. In contrast to white adipocytes, absence of insulin signaling does not affect development of marrow and brown adipocytes, but instead is required for lipid accumulation particularly for the marrow adipocytes. Lipodystrophic IR KO mice have profound insulin resistance, hyperglycemia, organomegaly, and impaired adipokine secretion.

CONCLUSIONS

Our results demonstrate differential roles for insulin signaling for white, brown, and marrow adipocyte development and metabolic regulation.

Metabolic phenotype and adipose and liver features in a high-fat Western diet-induced mouse model of obesity-linked NAFLD

nonalcoholic fatty liver disease (NAFLD), an obesity and insulin resistance associated clinical condition - ranges from simple steatosis to nonalcoholic steatohepatitis. To model the human condition, a high-fat Western diet that includes liquid sugar consumption has been used in mice. Even though liver pathophysiology has been well characterized in the model, little is known about the metabolic phenotype (e.g., energy expenditure, activity, or food intake). Furthermore, whether the consumption of liquid sugar exacerbates the development of glucose intolerance, insulin resistance, and adipose tissue dysfunction in the model is currently in question. In our study, a high-fat Western diet (HFWD) with liquid sugar [fructose and sucrose (F/S)] induced acute hyperphagia above that observed in HFWD-fed mice, yet without changes in energy expenditure. Liquid sugar (F/S) exacerbated HFWD-induced glucose intolerance and insulin resistance and impaired the storage capacity of epididymal white adipose tissue (eWAT). Hepatic TG, plasma alanine aminotransferase, and normalized liver weight were significantly increased only in HFWD+F/S-fed mice. HFWD+F/S also resulted in increased hepatic fibrosis and elevated collagen 1a2, collagen 3a1, and TGFβ gene expression. Furthermore, HWFD+F/S-fed mice developed more profound eWAT inflammation characterized by adipocyte hypertrophy, macrophage infiltration, a dramatic increase in crown-like structures, and upregulated proinflammatory gene expression. An early hypoxia response in the eWAT led to reduced vascularization and increased fibrosis gene expression in the HFWD+F/S-fed mice. Our results demonstrate that sugary water consumption induces acute hyperphagia, limits adipose tissue expansion, and exacerbates glucose intolerance and insulin resistance, which are associated with NAFLD progression.

Exposure to non-nutritive sweeteners during pregnancy and lactation: Impact in programming of metabolic diseases in the progeny later in life

The nutritional environment during embryonic, fetal and neonatal development plays a crucial role in the offspring's risk of developing diseases later in life. Although non-nutritive sweeteners (NNS) provide sweet taste without contributing to energy intake, animal studies showed that long-term consumption of NSS, particularly aspartame, starting during the perigestational period may predispose the offspring to develop obesity and metabolic syndrome later in life. In this paper, we review the impact of NNS exposure during the perigestational period on the long-term disease risk of the offspring, with a particular focus on metabolic diseases. Some mechanisms underlying NNS adverse metabolic effects have been proposed, such as an increase in intestinal glucose absorption, alterations in intestinal microbiota, induction of oxidative stress and a dysregulation of appetite and reward responses. The data reviewed herein suggest that NNS consumption by pregnant and lactating women should be looked with particular caution and requires further research.