The effect of dietary fish oil on weight gain and insulin sensitivity is dependent on APOE genotype in humanized targeted replacement mice

Effects of the ApoE genotype on cognitive function in aging mice fed with a high-fat diet and the protective potential of n-3 polyunsaturated fatty acids

The ApoE4 allele is the strongest genetic determinant for Alzheimer's disease (AD), while obesity is a strong environmental risk for AD. The modulatory effect of the ApoE genotype on aging-related cognitive function in tandem with a high-fat diet (HFD) remains uncertain. This study aimed to elucidate the effects of ApoE3/ApoE4 genotypes in aged mice exposed to a HFD, and the benefits of n-3 polyunsaturated fatty acids (PUFAs) from fish oil. Remarkably, the HFD led to weight gain and lipid accumulation, more pronounced in ApoE3 mice, while ApoE4 mice experienced exacerbated cerebral insulin resistance, neuroinflammation, and oxidative stress. Critically, n-3 PUFAs modulated the cerebral insulin signaling via the IRS-1/AKT/GLUT4 pathway, mitigated microglial hyperactivity, and reduced IL-6 and MDA levels, thereby counteracting cognitive deficits. These findings highlight the contrasting impacts of ApoE genotypes on aging mice exposed to a HFD, supporting n-3 PUFAs as a strategic nutritional intervention for brain health, especially for ApoE4 carriers.

Human APOE4 Protects High-Fat and High-Sucrose Diet Fed Targeted Replacement Mice against Fatty Liver Disease Compared to APOE3

Recent genome- and exome-wide association studies suggest that the human APOE ε4 allele protects against non-alcoholic fatty liver disease (NAFLD), while ε3 promotes hepatic steatosis and steatohepatitis. The present study aimed at examining the APOE genotype-dependent development of fatty liver disease and its underlying mechanisms in a targeted replacement mouse model. Male mice expressing the human APOE3 or APOE4 protein isoforms on a C57BL/6J background and unmodified C57BL/6J mice were chronically fed a high-fat and high-sucrose diet to induce obesity. After 7 months, body weight gain was more pronounced in human APOE than endogenous APOE expressing mice with elevated plasma biomarkers suggesting aggravated metabolic dysfunction. APOE3 mice exhibited the highest liver weights and, compared to APOE4, massive hepatic steatosis. An untargeted quantitative proteome analysis of the liver identified a high number of proteins differentially abundant in APOE3 versus APOE4 mice. The majority of the higher abundant proteins in APOE3 mice could be grouped to inflammation and damage-associated response, and lipid storage, amongst others. Results of the targeted qRT-PCR and Western blot analyses contribute to the overall finding that APOE3 as opposed to APOE4 promotes hepatic steatosis, inflammatory- and damage-associated response signaling and fibrosis in the liver of obese mice. Our experimental data substantiate the observation of an increased NAFLD-risk associated with the human APOEε3 allele, while APOEε4 appears protective. The underlying mechanisms of the protection possibly involve a higher capacity of nonectopic lipid deposition in subcutaneous adipose tissue and lower hepatic pathogen recognition in the APOE4 mice.

Association between APOE Genotype with Body Composition and Cardiovascular Disease Risk Markers Is Modulated by BMI in Healthy Adults: Findings from the BODYCON Study

Body mass index (BMI) has been suggested to play an important role in the relationship between the APOLIPOPROTEIN (APO)E genotype and cardiovascular disease (CVD) risk. Using data from the BODYCON cross-sectional study (n = 360 adults) we assessed the association between body composition and CVD risk markers according to APOE genotype, with examination of the role of BMI. In this study cohort, the APOE2/E3 group had lower fasting blood lipids than APOE4 carriers and APOE3/E3 group (p ≤ 0.01). After stratifying the group according to BMI, APOE4 carriers in the normal BMI subgroup had a higher lean mass compared with the APOE3/E3 group (p = 0.02) whereas in the overweight/obese subgroup, the android to gynoid percentage fat ratio was lower in APOE4 carriers than APOE3/E3 group (p = 0.04). Fasting lipid concentrations were only different between the APOE2/E3 and other genotype groups within the normal weight BMI subgroup (p ≤ 0.04). This finding was associated with a lower dietary fibre and a higher trans-fat intake compared with APOE4 carriers, and a lower carbohydrate intake relative to the APOE3/E3 group. Our results confirm previous reports that BMI modulates the effect of APOE on CVD risk markers and suggest novel interactions on body composition, with diet a potential modulator of this relationship.

APOE4 genotype exacerbates the impact of menopause on cognition and synaptic plasticity in APOE-TR mice

The impact of sex and menopausal status in Alzheimer's disease remains understudied despite increasing evidence of greater female risk, particularly in APOE4 carriers. Utilizing female APOE-TR mice maintained on a high-fat diet background we induced ovarian failure through repeated VCD injections, to mimic human menopause. At 12 months of age, recognition memory and spatial memory were assessed using object recognition, Y-maze spontaneous alternation, and Barnes maze. A VCD*genotype interaction reduced the recognition memory (P < .05), with APOE4 VCD-treated animals unable to distinguish between novel and familiar objects. APOE4 mice displayed an additional 37% and 12% reduction in Barnes (P < .01) and Y-maze (P < .01) performance, indicative of genotype-specific spatial memory impairment. Molecular analysis indicated both VCD and genotype-related deficits in synaptic plasticity with BDNF, Akt, mTOR, and ERK signaling compromised. Subsequent reductions in the transcription factors Creb1 and Atf4 were also evident. Furthermore, the VCD*genotype interaction specifically diminished Ephb2 expression, while Fos, and Cnr1 expression reduced as a consequence of APOE4 genotype. Brain DHA levels were 13% lower in VCD-treated animals independent of genotype. Consistent with this, we detected alterations in the expression of the DHA transporters Acsl6 and Fatp4. Our results indicate that the combination of ovarian failure and APOE4 leads to an exacerbation of cognitive and neurological deficits.

Ozone and Particulate Matter Exposure and Alzheimer's Disease: A Review of Human and Animal Studies

Alzheimer's disease (AD), an aging-related neurodegenerative disease, is a major cause of dementia in the elderly. Although the early-onset (familial) AD is attributed to mutations in the genes coding for amyloid-β protein precursor (AβPP) and presenilin1/presenilin 2 (PS1/PS2), the cause for the late-onset AD (LOAD), which accounts for more than 95% of AD cases, remains unclear. Aging is the greatest risk factor for LOAD, whereas the apolipo protein E4 allele (APOEɛ4) is believed to be a major genetic risk factor in acquiring LOAD, with female APOEɛ4 carriers at highest risk. Nonetheless, not all the elderly, even older female APOEɛ4 carriers, develop LOAD, suggesting that other factors, including environmental exposure, must play a role. This review summarizes recent studies that show a potential role of environmental exposure, especially ozone and particulate matter exposure, in the development of AD. Interactions between environmental exposure, genetic risk factor (APOEɛ4), and sex in AD pathophysiology are also discussed briefly. Identification of environmental risk factor(s) and elucidation of the complex interactions between genetic and environmental risk factors plus aging and female sex in the onset of AD will be a key to our understanding of the etiology and pathogenesis of AD and the development of the strategies for its prevention and treatment.

Weight gain and neuroadaptations elicited by high fat diet depend on fatty acid composition

Overconsumption of food is a major health concern in the western world. Palatable food has been shown to alter the activity of neural circuits, and obesity has been linked to alterations in the connectivity between the hypothalamus and cortical regions involved in decision-making and reward processing, putatively modulating the incentive value of food. Outlining neurophysiological adaptations induced by dietary intake of high fat diets (HFD) is thus valuable to establish how the diet by itself may promote overeating. To this end, C57BL/6 mice were fed HFD rich in either saturated fatty acids (HFD-S) or polyunsaturated fatty acids (HFD-P), or a low-fat control diet (LFD) for four weeks. Food and energy intake were monitored and ex vivo electrophysiology was employed to assess neuroadaptations in lateral hypothalamus (LH) and corticostriatal circuits, previously associated with food intake. In addition, the effects of dietary saturated and polyunsaturated fatty acids on the gene expression of NMDA, AMPA and GABA_A receptor subunits in the hypothalamus were investigated. Our data shows that mice fed HFD-P had increased daily food and energy intake compared with mice fed HFD-S or LFD. However, this increase in energy intake had no obesogenic effects. Electrophysiological recordings demonstrated that HFD-P had a selective effect on glutamatergic neurotransmission in the LH, which was concomitant with a change in mRNA expression of AMPA receptor subtypes Gria1, Gria3 and Gria4, with no effect on the mRNA expression of NMDA receptor subtypes or GABA_A receptor subtypes. Furthermore, while synaptic output from corticostriatal subregions was not significantly modulated by diet, synaptic plasticity in the form of long-term depression (LTD) was impaired in the dorsomedial striatum of mice fed HFD-S. In conclusion, this study suggests that the composition of fatty acids in the diet not only affects weight gain, but may also modulate neuronal function and plasticity in brain regions involved in food intake.

Common Variants in Lipid Metabolism-Related Genes Associate with Fat Mass Changes in Response to Dietary Monounsaturated Fatty Acids in Adults with Abdominal Obesity

BACKGROUND

Different fatty acids (FAs) can vary in their obesogenic effect, and genetic makeup can contribute to fat deposition in response to dietary FA composition. However, the antiobesogenic effects of the interactions between dietary MUFAs and genetics have scarcely been tested in intervention studies.

OBJECTIVE

We evaluated the overall (primary outcome) and genetically modulated (secondary outcome) response in body weight and fat mass to different levels of MUFA consumption.

METHODS

In the Canola Oil Multicenter Intervention Trial II, a randomized, crossover, isocaloric, controlled-feeding multicenter trial, 44 men and 71 women with a mean age of 44 y and an increased waist circumference (men ∼108 cm and women ∼102 cm) consumed each of 3 oils for 6 wk, separated by four 12-wk washout periods. Oils included 2 high-MUFA oils-conventional canola and high-oleic canola (<7% SFAs, >65% MUFAs)-and 1 low-MUFA/high-SFA oil blend (40.2% SFAs, 22.0% MUFAs). Body fat was measured using DXA. Five candidate single-nucleotide polymorphisms (SNPs) were genotyped using qualitative PCR. Data were analyzed using a repeated measures mixed model.

RESULTS

No significant differences were observed in adiposity measures following the consumption of either high-MUFA diet compared with the low-MUFA/high-SFA treatment. However, when stratified by genotype, 3 SNPs within lipoprotein lipase (LPL), adiponectin, and apoE genes influenced, separately, fat mass changes in response to treatment (n = 101). Mainly, the LPL rs13702-CC genotype was associated with lower visceral fat (high-MUFA: -216.2 ± 58.6 g; low-MUFA: 17.2 ± 81.1 g; P = 0.017) and android fat mass (high-MUFA: -267.3 ± 76.4 g; low-MUFA: -21.7 ± 102.2 g; P = 0.037) following average consumption of the 2 high-MUFA diets.

CONCLUSIONS

Common variants in LPL, adiponectin, and apoE genes modulated body fat mass response to dietary MUFAs in an isocaloric diet in adults with abdominal obesity. These findings might eventually help in developing personalized dietary recommendations for weight control. The trial was registered at clinicaltrials.gov as NCT02029833 (https://www.clinicaltrials.gov/ct2/show/NCT02029833?cond=NCT02029833&rank=1).

Egg oil from Portunus trituberculatus alleviates insulin resistance through activation of insulin signaling in mice

Marine bioactive lipids have been utilized to overcome insulin resistance. However, oil from swimming crab has never been studied. Here, we analyzed the constituents of egg oil from Portunus trituberculatus (Pt-egg oil) and investigated its protective effects against insulin resistance in mice on a high-fat diet. The results showed that Pt-egg oil contained 52.05% phospholipids, 8.61% free fatty acids (especially eicosapentaenoic acid and docosahexaenoic acid), 32.38% triglyceride, 4.79% total cholesterol, and ditissimus astaxanthin. Animal experiments showed that Pt-egg oil significantly mitigated insulin resistance and was associated with reductions in blood glucose, insulin, glucose tolerance, insulin tolerance, serum lipids, and hepatic glycogen. Pt-egg oil activated the phosphatidylinositol 3-hydroxy kinase (PI3K)/protein kinase B (Akt)/glucose transporter 4 pathway in skeletal muscle both at the transcriptional level and at the translational level. Pt-egg oil also promoted hepatic glycogen synthesis through activation of the PI3K/Akt/glycogen synthase kinase-3 beta pathway. These indicate that Pt-egg oil can be used as an alternative to marine bioactive lipids to improve insulin resistance.

Dose-dependent effects of fish oil on cardio-metabolic biomarkers in healthy middle-aged and elderly Chinese people: a double-blind randomized controlled trial

n-3PUFA consumption has been widely accepted as a nutritional strategy for the secondary prevention of cardiovascular events in patients at high risk of cardiovascular disease (CVD), but little is known about the dose-response relationship between dietary n-3PUFA and serum biomarkers associated with cardiovascular health in the general population. The present study involved a 12-week double-blind, randomized controlled trial to explore the effects of fish oil with different doses (0.31, 0.62 and 1.24 g d-1 of EPA and DHA) on serum fatty acids and cardio-metabolic biomarkers including adiponectin, inflammatory markers, lipid profiles and fasting glucose in healthy middle-aged and elderly Chinese people. 240 volunteers met our inclusion criteria. A total of 39 subjects dropped out and 201 finally completed the intervention. No significant differences in baseline characteristics and daily intakes of dietary nutrients were detected among all groups. After a 12-week intervention, fish oil dose-dependently enhanced serum EPA, DHA, n-3PUFA and adiponectin (except for 0.31 g d-1), but decreased serum n-6/n-3PUFA, TG and fasting glucose. Changes in the above indicators from the baseline to week 12 in fish oil groups significantly differed from those in the control. Meanwhile, all the doses of EPA and DHA led to decreases in serum CRP; only 1.24 g d-1 led to an increase in HDL-C with a concurrent decrease in TC/HDL-C even though these changes were not significantly different among all groups. All the findings suggested that fish oil dose-dependently regulated serum PUFA and cardio-metabolic biomarkers including adiponectin, CRP, lipid profiles and fasting glucose in healthy middle-aged and elderly Chinese people who consumed insufficient dietary n-3PUFA, and the most desirable changes were observed for 1.24 g d-1.

Comparative Proteomic Analysis of Two Differently Extracted Coptis chinensis in the Treatment of Type 2 Diabetic Rats

Coptis chinensis (CC) is widely used to treat diabetes in traditional Chinese medicine due to its significant hypoglycemic and hypolipidemic effects. It was reported that CC powders are more effective than CC decoctions. In this study, a rat model of type 2 diabetes was established and treated with supercritical-extracted CC and gastric juice extracted CC, respectively. Body weight, fasting plasma insulin, insulin resistance index, and lipid profiles were measured along with oral glucose tolerance tests (OGTTs). In addition, the levels of plasma proteins were compared between type 2 diabetic rats and CC-treated rats using an iTRAQ-based quantitative proteomic analysis. The results showed that the plasma levels of triglyceride (TC), total cholesterol (TG), and low-density lipoprotein (LDL) in rats of both CC-treated groups were significantly decreased. In addition, the proteomic analysis identified 929 proteins, while 15 proteins were selected from these 929 proteins based on their expression levels and bioinformatic results. Among these 15 proteins, 9 proteins (IGF-1, Igfbp4, Igfbp-6, Igfals, C2, C4, Cfi, Prdx-2, and Prdx-3) were upregulated in the two CC-treated groups, while 6 proteins (Pla2g7, Pcyox1, ApoC-1, ApoC-3, ApoB-100, and ApoE) were downregulated. The functions of these proteins are associated with glucose metabolism, insulin action, immunity, inflammation, lipid metabolism, oxidation, and antioxidation. The two differently extracted CC did not show significant differences in terms of their treatment efficacy. This research expanded our understanding on the therapeutic effects and mechanisms of CC in the treatment of type 2 diabetes.