High-Fat Diet Causes Subfertility and Compromised Ovarian Function Independent of Obesity in Mice.

Excess calorie consumption, particularly of a diet high in fat, is a risk factor for both obesity and reproductive disorders. Animal model studies indicate that elevated dietary fat can influence some reproductive functions independent of obesity. In the current study we sought to determine whether a high-fat diet (HFD) impacts ovarian function, long-term fertility, and local and systemic markers of inflammation independent of obesity. Five-week-old mice were fed either low-fat diet (control group-LF-Ln) or HFD for 10 wk and were divided based on body weight into high-fat obese (HF-Ob: >25 g) and high-fat lean (HF-Ln: <22 g). Ovaries were collected to assess ovarian follicles and to determine the degree of local inflammation. Serum proinflammatory cytokines were also measured. A group of animals was followed for breeding trials for 5 mo while being exposed to LFD or HFD. We found that both 10-wk and 32-wk exposure to HFD resulted in depleted primordial follicles regardless of obesity phenotype. Macrophage counts revealed increased tissue inflammation in the ovary independent of obesity. In addition, serum proinflammatory cytokines were increased in HF-Ln and HF-Ob in comparison to LF-Ln mice. Moreover, HFD had a sustained effect on litter production rate and number of pups per litter regardless of obese phenotype. This study describes for the first time that exposure to HFD causes significant reduction in primordial follicles, compromised fertility, produced higher proinflammatory cytokine levels, and increased ovarian macrophage infiltration, independent of obesity. The negative effects of HFD on primordial follicles may be mediated by increased tissue inflammation.

Agonistic Anti-CD40 Antibody Triggers an Acute Liver Crisis With Systemic Inflammation in Humanized Sickle Cell Disease Mice.

Sickle cell disease (SCD) is an inherited hemolytic disorder, defined by a point mutation in the ß-globin gene. Stress conditions such as infection, inflammation, dehydration, and hypoxia trigger erythrocyte sickling. Sickled red blood cells (RBCs) hemolyze more rapidly, show impaired deformability, and increased adhesive properties to the endothelium. In a proinflammatory, pro-coagulative environment with preexisting endothelial dysfunction, sickled RBCs promote vascular occlusion. Hepatobiliary involvement related to the sickling process, such as an acute sickle hepatic crisis, is observed in about 10% of acute sickle cell crisis incidents. In mice, ligation of CD40 with an agonistic antibody leads to a macrophage activation in the liver, triggering a sequence of systemic inflammation, endothelial cell activation, thrombosis, and focal ischemia. We found that anti-CD40 antibody injection in sickle cell mice induces a systemic inflammatory and hemodynamic response with accelerated hemolysis, extensive vaso-occlusion, and large ischemic infarctions in the liver mimicking an acute hepatic crisis. Administration of the tumor necrosis factor-α (TNF-α) blocker, etanercept, and the heme scavenger protein, hemopexin attenuated end-organ damage. These data collectively suggest that anti-CD40 administration offers a novel acute liver crisis model in humanized sickle mice, allowing for evaluation of therapeutic proof-of-concept.

The effect of dietary nitrate supplementation on the speed-duration relationship in mice with sickle cell disease.

Sickle cell disease (SCD) causes exercise intolerance likely due to impaired skeletal muscle function and low nitric oxide (NO) bioavailability. Dietary nitrate improves hemodynamic and metabolic control during exercise in humans and animals. The purpose of this investigation was to assess the impact of nitrate supplementation on exercise capacity as measured by the running speed to exercise duration relationship [critical speed (CS)]in mice with SCD. We tested the hypothesis that nitrate supplementation via beetroot juice (BR) would attenuate the exercise intolerance observed in mice with SCD. Ten wild-type (WT) and 18 Berkley sickle-cell mice (BERK) received water (WT: n = 10, BERK: n = 10) or nitrate-rich BR (BERK+BR: n = 8, nitrate dose 1 mmol/kg/day) for 5 days. Following the supplementation period, all mice performed 3-5 constant-speed treadmill tests that resulted in exhaustion within 1.5 to 20 min. Time to exhaustion vs. treadmill speed was fit to a hyperbolic model to determine CS. CS was significantly lower in BERK vs. WT and BERK+BR with no significant difference between WT and BERK+BR (WT: 36.6 ± 1.6, BERK: 23.8 ± 1.5, BERK+BR: 31.1 ± 2.1 m/min, P < 0.05). Exercise tolerance, measured via CS, was significantly lower in BERK mice relative to WT. However, BERK mice receiving 5 days of nitrate supplementation exhibited no difference in exercise tolerance when compared with WT. These results support the potential utility of a dietary nitrate intervention to improve functionality in SCD patients.NEW & NOTEWORTHY Sickle cell disease compromises muscle O2 delivery resulting in exercise intolerance. Dietary nitrate supplementation increases skeletal muscle blood flow during exercise and may improve exercise capacity in a mouse model of sickle cell disease. We investigated the effects of dietary nitrate supplementation on exercise tolerance in a mouse model of sickle cell disease using the treadmill speed-duration relationship (critical speed). Mice with sickle cell disease provided with a dietary nitrate supplement had a critical speed not significantly different from healthy wild-type mice.

High-fat diet exposure, regardless of induction of obesity, is associated with altered expression of genes critical to normal ovulatory function.

We evaluated the impact of high-fat diet (HFD) on ovarian gene expression. Female 5-week-old C57BL/6J mice were fed a 60% HFD or standard chow for 10 weeks. HFD-fed mice were then separated into obese (HF-Ob) and lean (HF-Ln) based on body weight. HFD exposure led to impairment of the estrous cycle, changes in hormones affecting reproduction, and decreased primordial follicles regardless of the development of obesity. RNA-sequencing of whole ovaries identified multiple genes with altered expression after HFD, with 25 genes displaying decreased expression in both HF-Ln and HF-Ob mice compared to the chow-fed controls (q < 0.05). Several of these 25 genes are involved in normal ovarian functions, including ovulation (Edn2, Tnfaip6, Errfi1, Prkg2, and Nfil3), luteinization (Edn2), and luteolysis (Nr4a1). Taken together, elevated dietary fat intake, regardless of obesity, is associated with impaired estrous cycle, depletion of the ovarian reserve, and altered expression of genes critical to normal ovulatory function.

Fat-1 Transgene Is Associated With Improved Reproductive Outcomes.

High intake of ω-3 polyunsaturated fatty acids (PUFAs) has been associated with a variety of health benefits. However, the role of ω-3 PUFAs in female reproductive function is unclear, with studies showing both positive and negative effects. The type of diet that ω-3 fatty acids are consumed with, for example, a balanced diet vs a high-fat diet (HFD), may influence how ω-3 fatty acids affect female reproductive function. To address the role of ω-3 PUFAs in female reproduction, we used the fat-1 mouse both with and without HFD exposure. Fat-1 mice constitutively express the fat-1 transgene, allowing the conversion of ω-6 to ω-3 fatty acids to yield an optimal tissue ratio of ω-6 to ω-3 fatty acids (∼1:1). In our study, at 15 weeks of age, fat-1 mice had elevated primordial follicles compared with wild-type controls with both standard chow and HFD feeding. Higher serum levels of the ω-3 docosahexaenoic acid (DHA), docosapentaenoic acid (DPA), and eicosapentaenoic acid (EPA) were positively associated with primordial follicle numbers, whereas the ratio of the ω-6 arachidonic acid to EPA + DPA + DHA had the opposite effect. Furthermore, fat-1 mice had increased pregnancy rates and shorter time to pregnancy when fed an HFD compared with wild-type mice. In conclusion, our novel preclinical model suggests that high tissue levels of long-chain ω-3 PUFAs are associated with an improved ovarian reserve and improved reproductive outcomes. Further studies are needed to evaluate ω-3 PUFAs as a potential intervention strategy in women with diminished ovarian reserve.