Maternal Intake of Either Fructose or the Artificial Sweetener Acesulfame-K Results in Differential and Sex-Specific Alterations in Markers of Skin Inflammation and Wound Healing Responsiveness in Mouse Offspring: A Pilot Study

Growing evidence has demonstrated that maternal artificial sweetener (AS) consumption may not be a beneficial alternative when compared to sugar-sweetened beverages and potentially leads to metabolic dysfunction in adult offspring. Compromised skin integrity and wound healing associated with type 2 diabetes can lead to complications such as diabetic pressure injury (PI). In this context, the skin plays an important role in the maintenance of metabolic homeostasis, yet there is limited information on the influence of sugar- or AS-sweetened beverages during pregnancy on developmental programming and offspring skin homeostasis. This study examined the impact of maternal fructose or acesulfame-k consumption on offspring wound healing. Female C57Bl/6 mice received a chow diet ad libitum with either water (CD), fructose (FR; 34.7 mM fructose), or AS (AS; 12.5 mM Acesulfame-K) throughout pregnancy and lactation. PIs were induced in offspring at 9 weeks of age (n = 6/sex/diet). PIs and healthy skin biopsies were collected for later analysis. Maternal AS intake increased skin inflammatory markers in healthy biopsies while an FR diet increased Tgfb expression, and both diets induced subtle changes in inflammatory markers post-wound inducement in a sex-specific manner. Furthermore, a maternal FR diet had a significant effect on pressure wound severity and early wound healing delay, while AS maternal diet had a sex-specific effect on the course of the healing process. This study demonstrates the need for a better understanding of developmental programming as a mediator of later-life skin integrity and wound responsiveness.

Measuring the Rate of Lipolysis in Ex vivo Murine Adipose Tissue and Primary Preadipocytes Differentiated In Vitro

Adipocytes store energy in the form of triglycerides in lipid droplets. This energy can be mobilized via lipolysis, where the fatty acid side chains are sequentially cleaved from the glycerol backbone, resulting in the release of free fatty acids and glycerol. Due to the low expression of glycerol kinase in white adipocytes, glycerol re-uptake rates are negligible, while fatty acid re-uptake is dictated by the fatty acid binding capacity of media components such as albumin. Both glycerol and fatty acid release into media can be quantified by colorimetric assays to determine the lipolytic rate. By measuring these factors at multiple time points, one can determine the linear rate of lipolysis with high confidence. Here, we provide a detailed protocol for the measurement of lipolysis in in vitro differentiated adipocytes and ex vivo adipose tissue from mice. This protocol may also be optimized for other preadipocyte cell lines or adipose tissue from other organisms; considerations and optimization parameters are discussed. This protocol is designed to be useful in determining and comparing the rate of adipocyte lipolysis between mouse models and treatments.

Adipocyte-Secreted IL-6 Sensitizes Macrophages to IL-4 Signaling

Complex bidirectional cross talk between adipocytes and adipose tissue immune cells plays an important role in regulating adipose function, inflammation, and insulin responsiveness. Adipocytes secrete the pleiotropic cytokine IL-6 in response to both inflammatory and catabolic stimuli. Previous studies have suggested that IL-6 secretion from adipocytes in obesity may promote adipose tissue inflammation. Here, we investigated catabolic stimulation of adipocyte IL-6 secretion and its impact on adipose tissue immune cells. In obesity, catecholamine resistance reduces cAMP-driven adipocyte IL-6 secretion in response to catabolic signals. By restoring adipocyte catecholamine sensitivity in obese adipocytes, amlexanox stimulates adipocyte-specific IL-6 secretion. We report that in this context, adipocyte-secreted IL-6 activates local macrophage STAT3 to promote Il4ra expression, thereby sensitizing them to IL-4 signaling and promoting an anti-inflammatory gene expression pattern. Supporting a paracrine adipocyte to macrophage mechanism, these effects could be recapitulated using adipocyte conditioned media to pretreat bone marrow-derived macrophages prior to polarization with IL-4. The effects of IL-6 signaling in adipose tissue are complex and context specific. These results suggest that cAMP-driven IL-6 secretion from adipocytes sensitizes adipose tissue macrophages to IL-4 signaling.

Maternal intake of fructose or artificial sweetener during pregnancy and lactation has persistent effects on metabolic and reproductive health of dams post-weaning

As rates of obesity, diabetes, and related comorbidities have increased, the consumption of artificial sweeteners (ASs) as sugar substitutes has also risen in popularity as they are perceived as a healthier alternative to sugar sweetened products. However, there is conflicting evidence regarding the impact of AS intake on metabolic and reproductive health. Glucose intolerance during pregnancy due to intake of sugar sweetened foods can result in an increased risk for the development of type 2 diabetes post-pregnancy. However, limited information exists on the impact of AS intake during pregnancy and lactation on the mother's health in later life. We hypothesised both AS and fructose would impair metabolic health post-partum (PP) following maternal consumption during pregnancy and lactation. Female C57Bl/6 mice received a standard control diet ad libitum with either water (CD), fructose (Fr; 34.7 mm intake), or AS (AS;12.5 mm Acesulfame-K) throughout pregnancy and lactation. Post-weaning, AS and Fr dams were fed the CD diet for the remainder of the experiment. Oral glucose tolerance tests were undertaken 8 weeks PP and dams were humanely killed at 9 weeks PP, with adipose tissue and ovaries collected for analysis. Experimental diets did not influence maternal bodyweight. At 8 weeks PP, increased glucose intolerance was evident in both AS and Fr dams. Adipocyte size was significantly increased in both the AS and Fr groups PP. Further, in the ovary, AS increased expression of genes associated with follicular development and ovulation. Therefore, ASs may not represent beneficial substitutes to fructose during pregnancy, with the potential to increase the risk of T2DM in later life in mothers.

Toxicity of oxidized fish oil in pregnancy - a dose response study in rats

INTRODUCTION

Fish oil (FO) supplements are consumed during pregnancy to increase dietary omega-3. However, FO is often oxidized past recommended limits. In rats, a large dose of highly oxidized FO substantially increased newborn mortality, but the effects of human-relevant doses of less oxidized oil are unknown. A dose-response study in rats was conducted to estimate the safe level of oxidation during pregnancy.

METHODOLOGY

Sprague-Dawley rat dams were mated, then individually housed and provided with a gel treatment on each day of pregnancy. Treatment groups differed only in the FO content of the gel; control (no oil), PV5, PV10, and PV40 (0.05ml of FO oxidized to a peroxide value (PV) of 5, 10, or 40meq/kg), or PV40(1ml) (1ml of PV40). A subset of dams was culled on gestational day 20 to enable sampling, and the remainder were allowed to give birth. Newborn mortality was recorded. Offspring were sampled at postnatal days 2 and 21, and dams at day 21.

RESULTS

There were no signs of unwellness during pregnancy. However, there was markedly increased neonatal mortality affecting the PV40(1ml) (12.8%) and PV40 (6.3%) groups, but not the control, PV5, or PV10 groups (1-1.4%). Dietary oxidized FO altered the expression of placental genes involved in antioxidant pathways and the production of free radicals. Conclusions Highly oxidized FO was toxic in rat pregnancy leading to a marked increase in mortality even at a human-relevant dose. We observed no toxic effects of FOs with PV≤ 10meq/kg, suggesting that this is an appropriate maximum limit.

Impact of Maternal Intake of Artificial Sweetener, Acesulfame-K, on Metabolic and Reproductive Health Outcomes in Male and Female Mouse Offspring

Guidelines advising pregnant women to avoid food and beverages with high fat and sugar have led to an increase in the consumption of "diet" options sweetened by artificial sweeteners (AS). Yet, there is limited information regarding the impact of AS intake during pregnancy on the long-term risk of cardiometabolic and reproductive complications in adult offspring. This study examined the influence of maternal acesulfame-K (Ace-K) and fructose consumption on metabolic and reproductive outcomes in offspring. Pregnant C57BL/6 mice received standard chow ad-libitum with either water (CD), fructose (Fr; 20% kcal intake), or AS (AS; 12.5 mM Ace-K) throughout pregnancy and lactation (n = 8/group). Postweaning offspring were maintained on a CD diet for the remainder of the experiment. Body weight, food intake, and water intake were measured weekly. Oral glucose tolerance tests (OGTT) were undertaken at 12 weeks, and the offspring were culled at week 14. Female, but not male, AS groups exhibited decreased glucose tolerance compared to Fr. There was an increase in gonadal fat adipocyte size in male offspring from AS and Fr groups compared to CD groups. In female offspring, adipocyte size was increased in the Fr group compared to the CD group. In female, but not male offspring, there was a trend toward increase in Fasn gene expression in AS group compared to the CD group. Maternal AS and Fr also negatively impacted upon female offspring estrus cycles and induced alterations to markers associated with ovulation. In summary, exposure to Ace-k via the maternal diet leads to impaired glucose tolerance and impacts adipocyte size in a sex-specific manner as well as significantly affecting estrus cycles and related gene markers in female offspring. This has implications in terms of providing tailored dietary advice for pregnant women and highlights the potential negative influence of artificial sweetener intake in the context of intergenerational impacts.

Interleukin-1 Receptor-1 Deficiency Impairs Metabolic Function in Pregnant and Non-Pregnant Female Mice

SCOPE

Glucose intolerance during pregnancy is associated with short- and long-term maternal and offspring health consequences. In young male mice, knockout of the major pro-inflammatory mediator interleukin-1-receptor-1 (IL1R1) protects against high-fat diet (HFD)-induced glucose intolerance and metabolic dysfunction. This phenotype has not been examined during pregnancy. The hypothesis that IL1R1 depletion will protect females against HFD-induced glucose intolerance and metabolic dysfunction before, during, and post pregnancy is tested.

METHODS AND RESULTS

C57BL/6J control and IL1R1 knockout (IL1R1-/- ) mice are randomized to either a control diet (10% kcal from fat) or HFD (45% kcal from fat), and three distinct cohorts are established: nulliparous, pregnant, and postpartum females. Contrary to the authors' hypothesis, it is found that IL1R1-/- does not protect against glucose intolerance in nulliparous or pregnant females, and while control HFD animals see a resolution of glucose tolerance postpartum, IL-1R1-/- mice remain impaired. These effects are accompanied by adipocyte hypertrophy, hyperleptinemia, and increased adipose tissue inflammatory gene expression. Maternal genotype differentially affects fetal growth in male and female fetuses, demonstrating sexual dimorphism in this genotype prior to birth.

CONCLUSIONS

These findings suggest that IL1R1 signaling is important for normal metabolic functioning in females, during and outside of pregnancy.

Interleukin 1 Receptor 1 Knockout and Maternal High Fat Diet Exposure Induces Sex-Specific Effects on Adipose Tissue Adipogenic and Inflammatory Gene Expression in Adult Mouse Offspring

Background: The global incidence of obesity continues to rise, increasing the prevalence of metabolic diseases such as insulin resistance, dyslipidemia, and type 2 diabetes mellitus. Low-grade chronic inflammation, associated with the obese state, also contributes to the development of these metabolic comorbidities. Interleukin-1-receptor-1 (IL-1R1), a pro-inflammatory mediator, bridges the metabolic and inflammatory systems. In young male mice, deficiency of IL-1R1 (IL-1R1^-/-) paired with a high-fat diet (HFD) offered beneficial metabolic effects, however in female mice, the same pairing led to metabolic dysfunction. Therefore, we examined the contribution of maternal HFD in combination with IL1R1^-/- to metabolic health in adult offspring. Methods: Female C57BL/6 and IL-1R1^-/- mice were randomly assigned to a control diet (10% kcal from fat) or HFD (45% kcal from fat) 10 days prior to mating and throughout gestation and lactation. Male and female offspring were housed in same-sex pairs post-weaning and maintained on control diets until 16 weeks old. At 15 weeks, an oral glucose tolerance test (OGTT) was performed to assess glucose tolerance. Histological analysis was carried out to assess adipocyte size and gene expression of adipogenic and inflammatory markers were examined. Results: IL-1R1^-/- contributed to increased body weight in male and female adult offspring, irrespective of maternal diet. IL-1R1^-/- and maternal HFD increased adipocyte size in the gonadal fat depot of female, but not male offspring. In female offspring, there was reduced expression of genes involved in adipogenesis and lipid metabolism in response to IL1R1^-/- and maternal HFD. While there was an increase in inflammatory gene expression in response to maternal HFD, this appeared to be reversed in IL1R1^-/- female offspring. In male offspring, there was no significant impact on adipogenic or lipid metabolism pathways. There was an increase in inflammatory gene expression in IL1R1^-/- male offspring from HFD-fed mothers. Conclusion: This study suggests that IL-1R1 plays a complex and important role in the metabolic health of offspring, impacting adipogenesis, lipogenesis, and inflammation in a sex-specific manner.

Consumption of the Artificial Sweetener Acesulfame Potassium throughout Pregnancy Induces Glucose Intolerance and Adipose Tissue Dysfunction in Mice

BACKGROUND

Sugar-sweetened beverage consumption is associated with metabolic dysfunction. Artificially sweetened beverages (ASBs) are often promoted as an alternative. However, evidence for the safety of ASB consumption during pregnancy is lacking.

OBJECTIVES

The effects of sugar-sweetened beverage and ASB consumption during pregnancy in mice were examined, and we hypothesized that both sugar-sweetened beverages and ASBs would impair maternal metabolic function.

METHODS

Pregnant female C57BL/6J mice received control drinking water (CD), high-fructose corn syrup (Fr; 20% kcal intake; 335 mM), or the artificial sweetener acesulfame potassium (AS; 12.5 mM) in their drinking water, from gestational day (GD) 0.5 (n = 8/group). Body weights and food and water intakes were assessed every second day, an oral-glucose-tolerance test (OGTT) was performed at GD 16.5, and mice were culled at GD 18.5. RT-PCR was carried out on adipose tissue, liver, and gut. Adipose tissue morphology was assessed using histological methods. In a separate cohort of animals, pregnancy length was assessed. Repeated-measures ANOVA was performed for the OGTT and weight gain data. All other data were analyzed by 1-way ANOVA.

RESULTS

Fr and AS significantly impaired glucose tolerance, as demonstrated by OGTT (21% and 24% increase in AUC, respectively; P = 0.0006). Fr and AS reduced expression of insulin receptor (39.5% and 33% reduction, respectively; P = 0.02) and peroxisome proliferator-activated receptor γ (45.2% and 47%, respectively; P = 0.039), whereas Fr alone reduced expression of protein kinase B (36.9% reduction; P = 0.048) and resulted in an increase in adipocyte size and leptin concentrations (40% increase; P = 0.03). AS, but not Fr, reduced male fetal weight (16.5% reduction; P = 0.04) and female fetal fasting blood glucose concentration at cull (20% reduction; P = 0.02) compared with CD. AS significantly reduced the length of pregnancy compared with the CD and Fr groups (1.25 d shorter; P = 0.02).

CONCLUSIONS

Fr and AS consumption were associated with maternal metabolic dysfunction in mice. AS was also associated with reduced fetal growth and fetal hypoglycemia. Therefore, ASBs may not be a beneficial alternative to sugar-sweetened beverages during pregnancy.

Preclinical Models of Altered Early Life Nutrition and Development of Reproductive Disorders in Female Offspring

Early epidemiology studies in humans have and continue to offer valuable insight into the Developmental Origins of Health and Disease (DOHaD) hypothesis, which emphasises the importance of early-life nutritional and environmental changes on the increased risk of metabolic and reproductive disease in later life. Human studies are limited and constrained by a range of factors which do not apply to preclinical research. Animal models therefore offer a unique opportunity to fully investigate the mechanisms associated with developmental programming, helping to elucidate the developmental processes which influence reproductive diseases, and highlight potential biomarkers which can be translated back to the human condition. This review covers the use and limitations of a number of animal models frequently utilised in developmental programming investigations, with an emphasis on dietary manipulations which can lead to reproductive dysfunction in offspring.