Sex modifies the consequences of extended fructose consumption on liver health, motor function, and physiological damage in rats

Regulation of Fructose Metabolism in Nonalcoholic Fatty Liver Disease

Elevations in fructose consumption have been reported to contribute significantly to an increased incidence of obesity and metabolic diseases in industrial countries. Mechanistically, a high fructose intake leads to the dysregulation of glucose, triglyceride, and cholesterol metabolism in the liver, and causes elevations in inflammation and drives the progression of nonalcoholic fatty liver disease (NAFLD). A high fructose consumption is considered to be toxic to the body, and there are ongoing measures to develop pharmaceutical therapies targeting fructose metabolism. Although a large amount of work has summarized the effects fructose exposure within the intestine, liver, and kidney, there remains a gap in our knowledge regarding how fructose both indirectly and directly influences immune cell recruitment, activation, and function in metabolic tissues, which are essential to tissue and systemic inflammation. The most recent literature demonstrates that direct fructose exposure regulates oxidative metabolism in macrophages, leading to inflammation. The present review highlights (1) the mechanisms by which fructose metabolism impacts crosstalk between tissues, nonparenchymal cells, microbes, and immune cells; (2) the direct impact of fructose on immune cell metabolism and function; and (3) therapeutic targets of fructose metabolism to treat NAFLD. In addition, the review highlights how fructose disrupts liver tissue homeostasis and identifies new therapeutic targets for treating NAFLD and obesity.

Sex differences in systemic inflammation and immune function in diet-induced obesity rodent models: A systematic review

Understanding sex differences in immunological responses in the context of obesity is important to improve health outcomes. This systematic review aimed to investigate sex differences in systemic inflammation, immune cell phenotype, and function in diet-induced obesity (DIO) animal models. A systematic search in Medline, Embase, and CINAHL from inception to April 2023 was conducted, using a combination of the following concepts: sex, obesity, cytokines, and immune cell phenotypes/function. Forty-one publications reporting on systemic inflammation (61%), cell phenotype (44%), and/or function (7%) were included. Females had lower systemic inflammation compared with males in response to DIO intervention and a higher proportion of macrophage (M)2-like cells compared with males that had a higher proportion of M1-like in adipose tissue. Although there were no clear sex differences in immune function, high-fat DIO intervention remains an important factor in the development of immune dysfunction in both males and females, including disturbances in cytokine production, proliferation, and migration of immune cells. Yet, the mechanistic links between diet and obesity on such immune dysfunction remain unclear. Future studies should investigate the role of diet and obesity in the functionality of immune cells and employ adequate methods for a high-quality investigation of sex differences in this context.

Sucrose consumption modifies the urethrogenital reflex and histological organization of the bulbospongiosus muscle in the male rat

Disorders of the bulbospongiosus muscle (Bsm) are associated with male sexual dysfunction, such as premature ejaculation. We determined the effect of sucrose-water consumption during pregnancy-lactation and postnatal on reflex responses and morphology of Bsm fibers in adult male Wistar rat offspring. Female rats were mated and grouped into consumed tap water mothers and sucrose-water (5 %) mothers during pregnancy-lactation to obtain experimental groups. Male pups were weaned and assigned into four groups (n = 12; each group). Those from control mothers who continued drinking tap water (CM-CO group) or sucrose water (CM-SO group), and those from sucrose mothers who drank tap water (SM-CO group) or continued drinking sucrose water (SM-SO group) until adult life. In male rat offspring (n = 6 per group) was recorded the electrical activity of Bsm was recorded during penile stimulation and urethrogenital reflex (UGR). Other male rat offspring were designated for histological analysis (n = 6 per group). Sucrose consumption during prenatal stages increased the frequency of the Bsm during UGR, while pre and postnatal consumption modified muscle fiber cross-sectional area and increased the collagen content, suggesting that a combination of a diet with pre- and postnatal sucrose changes the Bsm morphophysiology possibly causing male sexual dysfunctions.

Chronic intake of high dietary sucrose induces sexually dimorphic metabolic adaptations in mouse liver and adipose tissue

Almost all effective treatments for non-alcoholic fatty liver disease (NAFLD) involve reduction of adiposity, which suggests the metabolic axis between liver and adipose tissue is essential to NAFLD development. Since excessive dietary sugar intake may be an initiating factor for NAFLD, we have characterized the metabolic effects of liquid sucrose intake at concentrations relevant to typical human consumption in mice. We report that sucrose intake induces sexually dimorphic effects in liver, adipose tissue, and the microbiome; differences concordant with steatosis severity. We show that when steatosis is decoupled from impairments in insulin responsiveness, sex is a moderating factor that influences sucrose-driven lipid storage and the contribution of de novo fatty acid synthesis to the overall hepatic triglyceride pool. Our findings provide physiologic insight into how sex influences the regulation of adipose-liver crosstalk and highlight the importance of extrahepatic metabolism in the pathogenesis of diet-induced steatosis and NAFLD.

Nonalcoholic fatty liver disease shows significant sex dimorphism

Nonalcoholic fatty liver disease (NAFLD), which has been renamed metabolic dysfunction-associated fatty liver disease, is a growing global medical problem. The incidence of NAFLD and its associated end-stage liver disease is increasing each year, and many research advancements have been achieved to date. This review focuses on the current knowledge of the sex differences in NAFLD and does not elaborate on areas without differences. Studies have revealed significant sex differences in the prevalence, influencing factors, pathophysiology, complications and therapies of NAFLD. Men have a higher incidence than women. Compared with women, men exhibit increased visceral fat deposition, are more susceptible to leptin resistance, lack estrogen receptors, and tend to synthesize fatty acids into fat storage. Male patients will experience more severe hepatic fibrosis and a higher incidence of liver cancer. However, once NAFLD occurs, women show a faster progression of liver fibrosis, higher levels of liver cell damage and inflammation and are less likely to undergo liver transplantation than men. In general, men have more risk factors and more severe pathophysiological reactions than women, whereas the development of NAFLD is faster in women, and the treatments for women are more limited than those for men. Thus, whether sex differences should be considered in the individualized prevention and treatment of NAFLD in the future is worth considering.

Beyond the X Factor: Relevance of Sex Hormones in NAFLD Pathophysiology

Non-alcoholic fatty liver disease (NAFLD) is a major health issue worldwide, being frequently associated with obesity, unbalanced dietary regimens, and reduced physical activity. Despite their greater adiposity and reduced physical activity, women show a lower risk of developing NAFLD in comparison to men, likely a consequence of a sex-specific regulation of liver metabolism. In the liver, sex differences in the uptake, synthesis, oxidation, deposition, and mobilization of lipids, as well as in the regulation of inflammation, are associated with differences in NAFLD prevalence and progression between men and women. Given the major role of sex hormones in driving hepatic sexual dimorphism, this review will focus on the role of sex hormones and their signaling in the regulation of hepatic metabolism and in the molecular mechanisms triggering NAFLD development and progression.

Clinical impact of sexual dimorphism in non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH)

NAFLD/NASH is a sex-dimorphic disease, with a general higher prevalence in men. Women are at reduced risk of NAFLD compared to men in fertile age, whereas after menopause women have a comparable prevalence of NAFLD as men. Indeed, sexual category, sex hormones and gender habits interact with numerous NAFLD factors including cytokines, stress and environmental factors and alter the risk profiles and phenotypes of NAFLD. In the present review, we summarized the last findings about the influence of sex on epidemiology, pathogenesis, progression in cirrhosis, indication for liver transplantation and alternative therapies, including lifestyle modification and pharmacological strategies. We are confident that an appropriate consideration of sex, age, hormonal status and sociocultural gender differences will lead to a better understanding of sex differences in NAFLD risk, therapeutic targets and treatment responses and will aid in achieving sex-specific personalized therapies.

Dietary fructose intake is correlated with fat distribution in the Newfoundland population

OBJECTIVE

Increased dietary fructose intake is associated with elevated body weight and body mass index. Few studies are available regarding the relationship between fat distribution and dietary fructose intake. The aim of this study was to investigate the association between dietary fructose intake and fat distribution in adults in a large Newfoundland cohort.

METHODS

We analyzed 2298 adults from CODING (Complex Diseases in the New found land Population: Environment and Genetics) study. Intake of dietary fructose was evaluated from the Willett food frequency questionnaire. Fat distribution was estimated by dual-energy x-ray absorptiometry. Partial correlation analysis was used to determine the correlations of dietary fructose intake with fat distribution adjusted for major confounding factors.

RESULTS

Daily dietary fructose intake was negatively associated with arm fat in postmenopausal women (r = -0.080, P < 0.05), but positively associated with arm fat in premenopausal women after adjusting for age, total calorie intake, and physical activity levels (r = 0.079, P < 0.05). Dietary fructose intake was negatively correlated with both arm fat (r = -0.131, P < 0.05) and visceral fat (r = -0.124 measured in mass, r = -0.124 measured in volume respectively; P < 0.05) in men <45 y of age, not in men ≥45 y.

CONCLUSION

This study demonstrated that dietary fructose intake is significantly correlated with arm fat in both women and men, and visceral fat in men in the Newfoundland free-living population. The correlations are sex- and menopause-status dependent.

High Fructose Diet Induces Sex-specific Modifications in Synaptic Respiration and Affective-like Behaviors in Rats

The consequences of excessive fructose intake extend beyond those of metabolic disorder to changes in emotional regulation and cognitive function. Long-term consumption of fructose, particularly common when begun in adolescence, is more likely to lead to deleterious consequences than acute consumption. These long-term consequences manifest differently in males and females, suggesting a sex-divergent mechanism by which fructose can impair physiology and neural function. The purpose of the current project was to investigate a possible sex-specific mechanism by which elevated fructose consumption drives behavioral deficits and accompanying metabolic symptoms - specifically, synaptic mitochondrial function. Male and female rats were fed a high fructose diet beginning at weaning and maintained into adulthood. Measures of physiological health across the diet consumption period indicated that females were more likely to gain weight than males while both displayed increased circulating blood glucose. As adults, females fed the high fructose diet displayed increased floating behavior in the forced swim task while males exhibited increased exploratory behavior in the open field. Synaptic respiration was altered by diet in both females and males but the effect was sex-divergent - fructose-fed females had increased synaptic respiration while males showed a decrease. When exposed to an acute energetic challenge, the pattern was reversed. Taken together, these data indicate that diet-induced alterations to neural function and physiology are sex-specific and highlight the need to consider sex as a biological variable when treating metabolic disease. Furthermore, these data suggest that synaptic mitochondrial function may contribute directly to the behavioral consequences of elevated fructose consumption.

Impact of liver-specific GLUT8 silencing on fructose-induced inflammation and omega oxidation

Excessive consumption of high-fructose diets is associated with insulin resistance, obesity, and non-alcoholic fatty liver disease (NAFLD). However, fructose differentially affects hepatic regulation of lipogenesis in males and females. Hence, additional studies are necessary in order to find strategies taking gender disparities in fructose-induced liver damage into consideration. Although the eighth member of facilitated glucose transporters (GLUT8) has been linked to fructose-induced macrosteatosis in female mice, its contribution to the inflammatory state of NAFLD remains to be elucidated. Combining pharmacological, biochemical, and proteomic approaches, we evaluated the preventive effect of targeted liver GLUT8 silencing on liver injury in a mice female fructose-induced non-alcoholic steatohepatitis female mouse model. Liver GLUT8-knockdown attenuated fructose-induced ER stress, recovered liver inflammation, and dramatically reduced fatty acid content, in part, via the omega oxidation. Therefore, this study links GLUT8 with liver inflammatory response and suggests GLUT8 as a potential target for the prevention of NAFLD.

Analysis of sex differences in dietary copper-fructose interaction-induced alterations of gut microbial activity in relation to hepatic steatosis

BACKGROUND

Inadequate copper intake and increased fructose consumption represent two important nutritional problems in the USA. Dietary copper-fructose interactions alter gut microbial activity and contribute to the development of nonalcoholic fatty liver disease (NAFLD). The aim of this study is to determine whether dietary copper-fructose interactions alter gut microbial activity in a sex-differential manner and whether sex differences in gut microbial activity are associated with sex differences in hepatic steatosis.

METHODS

Male and female weanling Sprague-Dawley (SD) rats were fed ad libitum with an AIN-93G purified rodent diet with defined copper content for 8 weeks. The copper content is 6 mg/kg and 1.5 mg/kg in adequate copper diet (CuA) and marginal copper diet (CuM), respectively. Animals had free access to either deionized water or deionized water containing 10% fructose (F) (w/v) as the only drink during the experiment. Body weight, calorie intake, plasma alanine aminotransferase, aspartate aminotransferase, and liver histology as well as liver triglyceride were evaluated. Fecal microbial contents were analyzed by 16S ribosomal RNA (16S rRNA) sequencing. Fecal and cecal short-chain fatty acids (SCFAs) were determined by gas chromatography-mass spectrometry (GC-MS).

RESULTS

Male and female rats exhibit similar trends of changes in the body weight gain and calorie intake in response to dietary copper and fructose, with a generally higher level in male rats. Several female rats in the CuAF group developed mild steatosis, while no obvious steatosis was observed in male rats fed with CuAF or CuMF diets. Fecal 16S rRNA sequencing analysis revealed distinct alterations of the gut microbiome in male and female rats. Linear discriminant analysis (LDA) effect size (LEfSe) identified sex-specific abundant taxa in different groups. Further, total SCFAs, as well as, butyrate were decreased in a more pronounced manner in female CuMF rats than in male rats. Of note, the decreased SCFAs are concomitant with the reduced SCFA producers, but not correlated to hepatic steatosis.

CONCLUSIONS

Our data demonstrated sex differences in the alterations of gut microbial abundance, activities, and hepatic steatosis in response to dietary copper-fructose interaction in rats. The correlation between sex differences in metabolic phenotypes and alterations of gut microbial activities remains elusive.

Role of sex and high-fat diet in metabolic and hypothalamic disturbances in the 3xTg-AD mouse model of Alzheimer's disease

Background

Hypothalamic dysfunction occurs early in the clinical course of Alzheimer’s disease (AD), likely contributing to disturbances in feeding behavior and metabolic function that are often observed years prior to the onset of cognitive symptoms. Late-life weight loss and low BMI are associated with increased risk of dementia and faster progression of disease. However, high-fat diet and metabolic disease (e.g., obesity, type 2 diabetes), particularly in mid-life, are associated with increased risk of AD, as well as exacerbated AD pathology and behavioral deficits in animal models. In the current study, we explored possible relationships between hypothalamic function, diet/metabolic status, and AD. Considering the sex bias in AD, with women representing two-thirds of AD patients, we sought to determine whether these relationships vary by sex.

Methods

WT and 3xTg-AD male and female mice were fed a control (10% fat) or high-fat (HF 60% fat) diet from ~ 3–7 months of age, then tested for metabolic and hypothalamic disturbances.

Results

On control diet, male 3xTg-AD mice displayed decreased body weight, reduced fat mass, hypoleptinemia, and mild systemic inflammation, as well as increased expression of gliosis- and inflammation-related genes in the hypothalamus (Iba1, GFAP, TNF-α, IL-1β). In contrast, female 3xTg-AD mice on control diet displayed metabolic disturbances opposite that of 3xTg-AD males (increased body and fat mass, impaired glucose tolerance). HF diet resulted in expected metabolic alterations across groups (increased body and fat mass; glucose intolerance; increased plasma insulin and leptin, decreased ghrelin; nonalcoholic fatty liver disease-related pathology). HF diet resulted in the greatest weight gain, adiposity, and glucose intolerance in 3xTg-AD females, which were associated with markedly increased hypothalamic expression of GFAP and IL-1β, as well as GFAP labeling in several hypothalamic nuclei that regulate energy balance. In contrast, HF diet increased diabetes markers and systemic inflammation preferentially in AD males but did not exacerbate hypothalamic inflammation in this group.

Conclusions

These findings provide further evidence for the roles of hypothalamic and metabolic dysfunction in AD, which in the 3xTg-AD mouse model appears to be dependent on both sex and diet.

Non-alcoholic Fatty Liver Disease as a Canonical Example of Metabolic Inflammatory-Based Liver Disease Showing a Sex-Specific Prevalence: Relevance of Estrogen Signaling

There is extensive evidence supporting the interplay between metabolism and immune response, that have evolved in close relationship, sharing regulatory molecules and signaling systems, to support biological functions. Nowadays, the disruption of this interaction in the context of obesity and overnutrition underlies the increasing incidence of many inflammatory-based metabolic diseases, even in a sex-specific fashion. During evolution, the interplay between metabolism and reproduction has reached a degree of complexity particularly high in female mammals, likely to ensure reproduction only under favorable conditions. Several factors may account for differences in the incidence and progression of inflammatory-based metabolic diseases between females and males, thus contributing to age-related disease development and difference in life expectancy between the two sexes. Among these factors, estrogens, acting mainly through Estrogen Receptors (ERs), have been reported to regulate several metabolic pathways and inflammatory processes particularly in the liver, the metabolic organ showing the highest degree of sexual dimorphism. This review aims to investigate on the interaction between metabolism and inflammation in the liver, focusing on the relevance of estrogen signaling in counteracting the development and progression of non-alcoholic fatty liver disease (NAFLD), a canonical example of metabolic inflammatory-based liver disease showing a sex-specific prevalence. Understanding the role of estrogens/ERs in the regulation of hepatic metabolism and inflammation may provide the basis for the development of sex-specific therapeutic strategies for the management of such an inflammatory-based metabolic disease and its cardio-metabolic consequences.

Fructose vs glucose decreased liking/wanting and subsequent intake of high-energy foods in young women

Recent research on the health impacts of added sugar has prompted the comparison of the effects of its 2 major components: glucose and fructose. Fructose was identified as a risk factor for obesity and metabolic syndrome. However, because of the differences in metabolic responses and responsivity of reward circuitry to palatable food, it is unknown if glucose and fructose induce similar appetite-related responses in humans with varying weights. This study compared the behavioral responses to food in young women of a healthy weight (n = 31) and with excess weight (n = 28). We hypothesized that (1) the inhibitory effect of glucose (vs fructose) on food-related responses would be greater in subjects of a healthy weight than in those with overweight/obesity and (2) subjects with overweight/obesity would exhibit a stronger preference for food than subjects with a healthy weight. After an overnight fast, the subjects ingested a glucose or equienergetic fructose beverage on 2 separate days, respectively. Then, they completed liking and wanting ratings and 2 decision-making tasks followed by ad libitum food intake. The results revealed that fructose reduced both liking and wanting for food in subjects with overweight/obesity and also decreased energy intake in all subjects. Relative to the healthy-weight group, subjects with overweight/obesity preferred the immediate reward. Moreover, only in the healthy-weight group were liking and wanting scores for food positively associated with actual food consumption. Overall, fructose (vs glucose) showed an acute inhibitory effect on appetite-related responses in subjects with excess weight.

Macrophages in the pathophysiology of NAFLD: The role of sex differences

Nonalcoholic fatty liver disease (NAFLD) is a multifactorial pathological condition, which recognizes a certain sexual dimorphism. Experimental and clinical studies provided evidence for a critical role of macrophages in NAFLD development and progression. Especially, liver-resident macrophages (also known as Kupffer cells) are likely the common final pathway of several pro-steatosic signals. A huge amount of danger-associated molecular patterns recognized by Kupffer cells is provided within the liver by lipid and glucose toxicity. Other pro-inflammatory signals come from surrounding tissues into the portal vein, directly to the liver: they come from dysfunctional adipocytes, adipose tissue macrophages and gut dysbiosis. These complex crosstalks are differently represented across sexes, as sexual hormones control many of these processes. Sexual dimorphism then modulates metabolic and inflammatory cascades driving the liver from a simple steatosis to NAFLD and beyond. Here, metabolic and inflammatory mechanisms underlying NALFD pathophysiology will be updated. A special attention will be paid to describe sex-related differences that could provide insights for patient stratification and more tailored therapeutic approaches.