Perinatal nutrition plays a key role in organogenesis and fetal development. Excessive or insufficient consumption of a specific nutrient during pregnancy and lactation has been linked to developmental programming of various adult diseases [1
]. Developmental programming is defined as the process by which an environmental insult applied during critical periods of early life causes long-term effects on the structure or function of an organism [2
]. This notion is currently recognized as “developmental origins of health and disease” (DOHaD) [3
]. Increased consumption of saturated fat has been associated with obesity-related disorders [4
]. In this regard, perinatal high-fat (HF) diet leads to a variety of metabolic syndrome-related phenotypes in adult offspring, including hypertension [5
]. On the contrary, the DOHaD concept also affords preventive strategies to reverse programmed processes before clinical phenotype is becoming evident, by so-called reprogramming [7
Because nutritional insults in gestation create very similar outcome in adult offspring [1
], there might be some common mechanisms contributing to the pathogenesis of programmed hypertension. Emerging evidence indicates that inappropriate activation of the renin-angiotensin system (RAS) and changes in composition of the gut microbiota are involved in the pathogenesis of hypertension [8
]. Blockers of the classical angiotensin-converting enzyme (ACE)/angiotensin (Ang) II/angiotensin type 1 receptor (AT1R) axis are well-established drugs for the treatment of hypertension [13
]. As another important element of the RAS, ACE2 appears to adjust angiotensin II type 2 receptor (AT2R) and angiotensin (1–7) receptor Mas in a way that opposes the development of hypertension [13
]. Both axes of the RAS have been examined on their roles in developmental programming of hypertension [14
]. Several microbial markers have been linked to hypertension, such as an increased Firmicutes
(F/B) ratio and a decreased abundance of beneficial microbes [8
]. Additionally, gut microbiota-derived metabolites short-chain fatty acids (SCFAs), especially acetate, butyrate, and propionate, and trimethylamine N-oxide (TMAO) are involved in the development of hypertension [16
]. The gut microbiota link between the mother and offspring is continued at and after birth by microbes present during delivery as well as postnatal breast milk [19
]. Perinatal HF diet was reported to alter gut microbiota in adult offspring [20
]. These findings suggest that gut microbiota and its metabolites not only impact hypertension development but also serve as a link between mothers consuming a diet high in saturated fat and programmed hypertension in their adult offspring.
The consumption of probiotics (i.e., beneficial microbes) and prebiotics (i.e., indigestible dietary fiber that fuels the beneficial microbes) have been reported to modulate gut microbiota and treat a variety of diseases [21
]. Our previous report demonstrated that maternal microbiota-targeted therapy protected adult rat offspring against programmed hypertension induced by perinatal high-fructose consumption [22
]. However, little is known whether restoration of gut microbiome by probiotics or prebiotics could serve as a reprogramming strategy to prevent hypertension programmed by perinatal HF intake. The overall goal of this work was to use a perinatal HF diet-induced programmed hypertension model, to dissect the contributions of prebiotic inulin and probiotic Lactobacillus casei
on gut microbiota and their metabolites, RAS, and programmed hypertension in adult offspring.
Our study describes, for the first time, prebiotic inulin or probiotic Lactobacillus casei protecting male offspring against hypertension programmed by perinatal high-fat diet, and puts special focus on the analysis of gut microbiota, microbiota-derived metabolites, and the RAS. Our major results can be summarized as follows: (1) perinatal HF diet induced elevation of BP in adult male offspring, which was prevented by either prebiotic or probiotic therapy; (2) maternal prebiotic therapy decreased fecal concentrations of propionate and acetate in offspring at 3 and 16 weeks of age, respectively; (3) prebiotic or probiotic therapy caused a reduction of plasma TMAO level and TMAO-to-TMA ratio; (4) HF diet increased renal mRNA expression of Agt and Ace and protein level of AT1R, which either prebiotic or probiotic therapy prevented; (5) perinatal HF diet increased the F/B ratio, and decreases of genera Lactobacillus and Akkermansia abundance in gut microbiota of 3-week-old offspring, all of which were restored by maternal microbiota-targeted therapy; and (6) probiotic therapy restored perinatal HF-diet-induced a reduction of several Lactobacillus species as well as genus Lactobacillus at 3 and 16 weeks of age, respectively.
Our findings are in line with previous reports demonstrating that consumption of HF diet by pregnant dams causes programmed hypertension and kidney damage in their adult male offspring [28
]. Although prebiotics and certain probiotic strains (e.g., Lactobacillus
) have shown beneficial effect on hypertension-related disorders [31
], to our knowledge, this is the first study to report maternal prebiotics/probiotics therapy prevented adult rat offspring from hypertension programmed by perinatal high-fat intake. In the current study, the BP-lowering effect of either probiotic or prebiotic therapy was starting from 12 weeks of age (i.e., 9 weeks after stopping probiotic or prebiotic therapy) and over time. Thus, the reduction of BP is primary through reprogramming effect rather than an acute effect. These findings support the notion that HF diet-induced early overnutrition results in hypertension in adulthood and 6-week administration of inulin or Lactobacillus casei
during pregnancy and lactation could protect the development of hypertension later in life. Although prebiotic inulin or probiotic Lactobacillus casei
showed similar BP-lowering effect in the present study, there might be a synergistic effect by combining prebiotic and probiotic therapies (i.e., synbiotics). It is also interesting to elucidate whether another modulation of gut microbiota targeted approach, fecal microbiota transplant, has beneficial effect on hypertension programmed by perinatal HF intake.
This aspect of the research suggested that the anti-hypertensive effects of probiotic and prebiotic therapies link to alterations of the gut microbiota. Gut microbiota dysbiosis in early life may have a wide range of deleterious health consequences, including an increased risk of hypertension [32
]. Although dietary fat has been suggested to be a causative factor with the gut microbiota dysbiosis in human and experimental studies [34
], little attention has been paid to explore the impact of perinatal HF intake on the offspring gut microbiota [35
]. Our results go beyond previous studies, showing that reshaping gut microbiota by maternal prebiotic or probiotic therapy could aid in overcoming hypertension programmed by HF diet-induced early overnutrition. At the phylum level, we observed that prebiotic or probiotic therapy prevented HF-induced hypertension is relevant to a reduced abundance of Firmicutes
with a proportional increase in Bacteroidetes
. The F/B ratio is associated with increased BP in several models of hypertension [7
]. Our results here showed that perinatal HF diet increased the F/B ratio at 3 weeks of age, prior to the development of hypertension. Conversely, prebiotic or probiotic therapy decreased the F/B ratio and prevented adult male offspring against the rise in BP. However, the F/B ratio was comparable among the four groups at 16 weeks of age, a stage of established hypertension. Our findings suggest that the F/B ratio might serve as a microbial marker for predicting hypertension.
According to our data, prebiotic or probiotic therapy protects adult offspring against elevated BP related to an increased abundance of phylum Verrucomicrobia
and genera Lactobacillus
. This is consistent with what has been found in previous studies reporting Akkermansia
, a genus in the phylum Verrucomicrobia
, as a beneficial gut microbe [38
]. Likewise, Lactobacillus
has been reported to be one of the beneficial probiotic bacterial strains [40
]. HF diet caused a reduction of genus Lactobacillus
, whereas probiotic Lactobacillus casei
therapy preserved the decreases of several Lactobacillus
species caused by perinatal HF consumption. Additionally, results from a previous study demonstrated that Collinsella aerofaciens
is increased in patients with coronary artery disease [41
]. However, we observed that HF diet reduced Collinsella aerofaciens
, which was reversed by prebiotic or probiotic therapy. Hence, it remains unclear whether alterations of gut microbiota act as a counterbalancing mechanism in response to perinatal HF diet or whether certain alterations of microbial populations interact directly with hypertension phenotype. Future research should further identify and confirm these microbial markers in other developmental programming models of hypertension. It has been reported that the composition of human gut microbiota changes with age [42
]. We observed not only the alterations of gut microbiota compositions were different with age, but also some microbial makers (i.e., F/B ratio) appeared at 3 weeks while disappeared at 16 weeks of age. One possible reason is programming effects of perinatal high-fat diet and maternal probiotics/prebiotics therapy might be diminished as time went by. Another possibility is that all rats consumed the same post-weaning diet.
Emerging evidence supports that gut microbiota-derived metabolites such as SCFAs and TMAO are involved in BP regulation [12
]. We observed that maternal inulin therapy decreases fecal propionate and acetate level at 3 and 16 weeks of age, respectively. Propionate and acetate have been reported to induce vasodilatation via mediating SCFA receptor [12
]. Accordingly, decreased propionate or acetate level is presumed to induce rather than reduce BP. Whether SCFAs play a beneficial or harmful role in the development of hypertension programmed by perinatal HF diet remains to be clarified.
Recent evidence reveals microbiota-derived metabolites TMAO and TMA related to cardiovascular disease [16
], with not always consistent results [43
]. Given that dietary factors are associated with plasma concentrations of TMA [16
] and that TMAO level is controlled by its synthesis and metabolism, simultaneously measures of the TMAO-to-TMA ratio and the DMA-to-TMAO ratio were expected to reflect a cumulative state of TMAO. In the current study, perinatal HF diet caused the increases of TMA levels in adult offspring. Additionally, maternal probiotic or prebiotic therapy caused a lower TMAO-to-TMA ratio but a higher DMA-to-TMAO ratio than those in the HF group. These findings suggested the beneficial effects of prebiotic or probiotic treatment on HF-induced programmed hypertension are due to, at least in part, the prevention of TMAO accumulation. Consequently, more studies are required to simultaneous determinations of TMAO-related metabolites and ratios for their utility in predicting hypertension in other developmental models.
Furthermore, another possible beneficial effect of prebiotic and probiotic therapies is attributed to mediation of the RAS. In line with previous studies showing that high-fat intake activates the RAS [22
], our results demonstrated that HF diet increased renal mRNA expression of Agt
. Currently, there are two counterbalancing axes of the RAS: the classical ACE–Ang II–AT1R axis that promotes vasoconstriction and the non-classical ACE2–angiotensin (1–7)–MAS axis responsible for vasodilatation [13
]. Our results cast a new light on the beneficial effects of prebiotic or probiotic therapy on HF-induced programmed hypertension is related to inhibition of the classical axis (i.e., Ace
and AT1R expression) and activation of ACE2 in the non-classical axis. Since the presence of ACE-inhibitory peptides with anti-hypertensive effects have been reported during prebiotics and probiotic bacteria supplementation [45
], the possibility of mediation of the RAS via prebiotic and probiotic therapies warrants further investigation.
This study has some limitations that have to be pointed out. First, we analyzed gut microbiota in offspring only at 3 and 16 weeks of age. The long-term effects of maternal prebiotic or probiotic therapy on offspring gut microbiota deserve further evaluation. Second, we did not analyze other organs responsible for BP regulation. The BP-lowering effect of probiotic or prebiotic might be related to other organs, such as the heart, brain, and vasculature. Another limitation is that we did not conduct the control group treated with prebiotic or prebiotic. The reason is due to that probiotics/prebiotics used in healthy people have only minor adverse effect, if any [40
]. Moreover, we mainly focus on hypertension in this study. In addition to hypertension, maternal HF diet has been linked to a variety of metabolic syndrome-related phenotypes in adult offspring. Accordingly, whether maternal gut microbiota-targeted therapy may have beneficial effects on other HF-induced adverse metabolic diseases deserve further clarification. Probiotics and prebiotics have been shown to promote the release of the gut hormone glucagon-like peptide 1 (GLP1) [46
], resulting in reduced food intake, improved glucose tolerance, and promoted weight loss in obese people [48
]. Given that we did not record food consumption by mothers in the current study, effects of prebiotic or probiotic therapy on BP later in life could be due to reduced food intake of dams, which might be independent of gut microbiota. Last, the small number of animals included might not reveal a true effect.