Sucralose can improve glucose tolerance and upregulate expression of sweet taste receptors and glucose transporters in an obese rat model

Nutritive/non-nutritive sweeteners and high fat diet contribute to dysregulation of sweet taste receptors and metabolic derangements in oral, intestinal and central nervous tissues

OBJECTIVES

Overconsumption of non-nutritive sweeteners is associated with obesity, whereas the underlying mechanisms remain controversial. This study aimed to investigate the effects of long-term consumption of nutritive or non-nutritive sweeteners with or without high fat diet on sweet taste receptor expression in nutrient-sensing tissues and energy regulation dependent on sweet-sensing.

METHODS

50 Male Sprague-Dawley rats (140-160 g) were assigned to 10 groups (n = 5/group). All received fructose at 2.5% or 10%, sucralose at 0.01% or 0.015% or water with a normal chow diet or high fat diet for 12 weeks. Food and drink intake were monitored daily. Oral glucose tolerance test and intraperitoneal glucose tolerance test were performed at week 10 and 11 respectively. Serum was obtained for measurement of biochemical parameters. Tongue, duodenum, jejunum, ileum, colon and hypothalamus were rapidly removed to assess gene expression.

RESULTS

Long-term consumption of sweeteners impaired glucose tolerance, increased calorie intake and body weight. A significant upregulation of sweet taste receptor expression was observed in all the four intestinal segments in groups fed 0.01% sucralose or 0.015% sucralose, most strikingly in the ileum, accompanied by elevated serum glucagon-like peptide-1 levels and up-regulated expression of sodium-dependent glucose cotransporter 1 and glucose transporter 2. A significant down-regulation in the tongue and hypothalamus was observed in groups fed 10% fructose or 0.015% sucralose, with alterations in hypothalamic appetite signals. The presence of high fat diet differentially modulates sweet taste perception in nutrient-sensing tissues.

CONCLUSIONS

Long-term consumption of whether nutritive sweeteners or non-nutritive sweeteners combined with high fat diet contribute to dysregulation of sweet taste receptor expression in oral, intestinal and central nervous tissues.

Long-Term Consumption of Sucralose Induces Hepatic Insulin Resistance through an Extracellular Signal-Regulated Kinase 1/2-Dependent Pathway

Sugar substitutes have been recommended to be used for weight and glycemic control. However, numerous studies indicate that consumption of artificial sweeteners exerts adverse effects on glycemic homeostasis. Although sucralose is among the most extensively utilized sweeteners in food products, the effects and detailed mechanisms of sucralose on insulin sensitivity remain ambiguous. In this study, we found that bolus administration of sucralose by oral gavage enhanced insulin secretion to decrease plasma glucose levels in mice. In addition, mice were randomly allocated into three groups, chow diet, high-fat diet (HFD), and HFD supplemented with sucralose (HFSUC), to investigate the effects of long-term consumption of sucralose on glucose homeostasis. In contrast to the effects of sucralose with bolus administration, the supplement of sucralose augmented HFD-induced insulin resistance and glucose intolerance, determined by glucose and insulin tolerance tests. In addition, we found that administration of extracellular signal-regulated kinase (ERK)-1/2 inhibitor reversed the effects of sucralose on glucose intolerance and insulin resistance in mice. Moreover, blockade of taste receptor type 1 member 3 (T1R3) by lactisole or pretreatment of endoplasmic reticulum stress inhibitors diminished sucralose-induced insulin resistance in HepG2 cells. Taken together, sucralose augmented HFD-induced insulin resistance in mice, and interrupted insulin signals through a T1R3-ERK1/2-dependent pathway in the liver.

Sweet taste receptor subunit T1R3 regulates casein secretion and phosphorylation of STAT5 in mammary epithelial cells

During lactation, mammary epithelial cells (MECs) on the apical membrane are in contact with lactose in milk, while MECs on the basolateral membrane are in contact with glucose in blood. Both glucose and lactose are sweeteners that are sensed by a sweet taste receptor. Previously, we have shown that lactose exposure on the basolateral membrane, but not the apical membrane, inhibits casein production and phosphorylation of STAT5 in MECs. However, it remains unclear whether MECs have a sweet taste receptor. In this study, we confirmed that the sweet taste receptor subunit T1R3 existed in both the apical and basolateral membranes of MECs. Subsequently, we investigated the influence of apical and basolateral sucralose as a ligand for the sweet taste receptor using a cell culture model. In this model, upper and lower media were separated by the MEC layer with less-permeable tight junctions. The results showed in the absence of glucose, both apical and basolateral sucralose induced phosphorylation of STAT5, which is a positive transcriptional factor for milk production. In contrast, the T1R3 inhibitor basolateral lactisole reducing phosphorylated STAT5 and secreted caseins in the presence of glucose. Furthermore, exposure of the apical membrane to sucralose in the presence of glucose inhibited the phosphorylation of STAT5. Simultaneously, GLUT1 was partially translocated from the basolateral membrane to the cytoplasm in MECs. These results suggest that T1R3 functions as a sweet receptor and is closely involved in casein production in MECs.

Effect of Dietary Geranylgeraniol and Green Tea Polyphenols on Glucose Homeostasis, Bone Turnover Biomarkers, and Bone Microstructure in Obese Mice

Previously, we demonstrated that the administration of either geranylgeraniol (GGOH) or green tea polyphenols (GTP) improved bone health. This study examined the combined effects of GGOH and GTP on glucose homeostasis in addition to bone remodeling in obese mice. We hypothesized that GGOH and GTP would have an additive or synergistic effect on improving glucose homeostasis and bone remodeling possibly in part via suppression of proinflammatory cytokines. Forty-eight male C57BL/6J mice were assigned to a high-fat diet (control), HFD + 400 mg GGOH/kg diet (GG), HFD + 0.5% GTP water (TP), or HFD + GGOH + GTP (GGTP) diet for 14 weeks. Results demonstrated that GTP supplementation improved glucose tolerance in obese mice. Neither GGOH nor GTP affected pancreas insulin or bone formation procollagen type I intact N-terminal, bone volume at the lumbar vertebrae, or bone parameters at the trabecular bone and cortical bone of the femur. There was an interactive effect for serum bone resorption collagen type 1 cross-linked C-telopeptide concentrations, resulting in no-GGOH and no-GTP groups having the highest values. GGOH increased trabecular number and decreased trabecular separation at the lumbar vertebrae. GTP increased trabecular thickness at lumbar vertebrae. The GG group produced the greatest connectivity density and the lowest structure model index. Only GTP, not GGOH, decreased adipokines concentrations (resistin, leptin, monocyte chemoattractant protein-1, and interleukin-6). In an obese male mouse model, individual GGOH and GTP supplementation improved glucose homeostasis, serum CTX, and trabecular microstructure of LV-4. However, the combined GGOH and GTP supplementation compromises such osteoprotective effects on serum CTX and trabecular bone of obese mice.

The Associations between Maternal Serum Aspartame and Sucralose and Metabolic Health during Pregnancy

OBJECTIVE

We aimed to investigate the associations between maternal serum aspartame/sucralose levels and metabolic health during pregnancy.

METHODS

A nested population-based case-control study was conducted in 109 women with and without gestational diabetes mellitus (GDM). Serum aspartame and sucralose levels were assessed using an ultraperformance liquid chromatography coupled to a tandem mass spectrometry system.

RESULTS

We detected the presence of circulating aspartame and sucralose in all participants at fasting. No differences in serum aspartame or sucralose levels were observed between GDM and non-GDM groups. In the fully-adjusted linear regression models, serum aspartame levels were positively associated with insulin resistance index, total cholesterol, and LDL cholesterol. In the fully-adjusted logistic regression models, higher serum aspartame levels were positively associated with elevated HbA1c, insulin resistance, hypercholesterolemia, and hyper-LDL cholesterolemia. In the GDM group, the significant associations between higher serum aspartame levels and elevated HbA1c, insulin resistance, and hypo-HDL cholesterolemia persisted, while positive associations were found between higher serum aspartame levels and insulin resistance and hyper-LDL cholesterolemia in the non-GDM group. Serum sucralose levels were negatively associated with HbA1c.

CONCLUSIONS

The study found that maternal serum aspartame levels were positively associated with insulin resistance index, total cholesterol, and LDL cholesterol during pregnancy. This finding provides the different effects of specific NNS on metabolic health during pregnancy.

Sucralose consumption ameliorates high-fat diet-induced glucose intolerance and liver weight gain in mice

Sucralose is one of the most widely used artificial sweeteners used by the food industry to reduce the calorie density of their products. Although broadly regarded as innocuous, studies show contrasting results depending on whether the research subjects are lean or overweight. In this study, we studied the effect of sucralose consumption on glucose homeostasis in a model of obesity. Male C57BL/6J mice were fed ad libitum with control or a high-fat diet (HFD) and drank either water or sucralose (0.1 mg/mL) for 8 weeks. To characterize the ensuing metabolic changes, we evaluated weight gain, glucose and pyruvate tolerance, and physical performance. Also, we assessed markers of steatosis and mitochondrial mass and function in the liver. Our results show that sucralose reduced weight gain, glucose, and pyruvate intolerance, and prevented the decrease in physical performance of HFD-fed mice. In the liver, sucralose also had a positive effect, preventing the decrease in mitochondrial mass exerted by HFD. Altogether, our results indicate that in the context of an obesogenic diet, sucralose has a beneficial effect at the organismal and hepatic levels.

Low Doses of Sucralose Alter Fecal Microbiota in High-Fat Diet-Induced Obese Rats

Artificial sweeteners (AS) have been widely used as sugar substitutes to reduce calorie intake. However, it was reported that high doses of AS induced glucose intolerance via modulating gut microbiota. The objective of this study was to investigate the effects of lower doses of sucralose on fecal microbiota in obesity. Eight weeks after high-fat diet (HFD), the male Sprague Dawley rats were randomly divided into four groups (6 in each group) and administrated by a daily gavage of 2 ml normal saline (CON), 0.54 mM sucralose (N054), 0.78 mM sucralose (N078), and 324 mM sucrose (S324), respectively. After 4 weeks, fecal samples were obtained and analyzed by 16S ribosomal RNA gene sequencing. The richness and diversity of fecal microbiota were not changed by sucralose or sucrose. Both 0.54 mM (0.43 mg) and 0.78 mM (0.62 mg) sucralose tended to reduce the beneficial bacteria, Lactobacillaceae and Akkermansiaceae. The relative abundance of family Acidaminoccaceae and its genus Phascolarctobacteriam were increased after 0.54 mM sucralose. In functional prediction, 0.54 mM sucralose increased profiles of carbohydrate metabolism, whereas 0.78 mM sucralose enhanced those of amino acid metabolism. The lower doses of sucralose might alter the compositions of fecal microbiota. The effects of sucralose in different dosages should be considered in the future study.