Developmental programming of aging of isolated pancreatic islet glucose-stimulated insulin secretion in female offspring of mothers fed low-protein diets in pregnancy and/or lactation

Protein restriction during lactation causes transgenerational metabolic dysfunction in adult rat offspring

Introduction

Protein restriction during lactation can induce metabolic dysfunctions and has a huge impact on the offspring's phenotype later in its life. We tested whether the effects of a maternal low-protein diet (LP) in rats can be transmitted to the F2 generation and increase their vulnerability to dietary insults in adulthood.

Methods

Female Wistar rats (F0) were fed either a low-protein diet (LP; 4% protein) during the first 2 weeks of lactation or a normal-protein diet (NP; 23% protein). The female offspring (F1 generation) were maintained on a standard diet throughout the experiment. Once adulthood was reached, female F1 offspring from both groups (i.e., NP-F1 and LP-F1) were bred to proven males, outside the experiment, to produce the F2 generation. Male F2 offspring from both groups (NP-F2 and LP-F2 groups) received a standard diet until 60 days old, at which point they received either a normal fat (NF; 4.5% fat) or a high fat diet (HF; 35% fat) for 30 days.

Results

At 90 days old, LPNF-F2 offspring had increased lipogenesis and fasting insulinemia compared to NPNF-F2, without alteration in insulin sensitivity. HF diet caused increased gluconeogenesis and displayed glucose intolerance in LPHF-F2 offspring compared to LPNF-F2 offspring. Additionally, the HF diet led to damage to lipid metabolism (such as steatosis grade 3), higher body weight, fat pad stores, and hepatic lipid content.

Discussion

We concluded that an F0 maternal protein restricted diet during lactation can induce a transgenerational effect on glucose and liver metabolism in the F2 generation, making the offspring's liver more vulnerable to nutritional injury later in life.

Rodent studies of developmental programming and ageing mechanisms: Special issue: In utero and early life programming of ageing and disease

Compelling evidence exists indicating that developmental programming influences ageing. Programming alters life-course phenotype in multiple organs, predisposing to diseases such as diabetes, obesity and cardiovascular disease that shorten lifespan. This review describes studies in rodents, the most commonly studied species, addressing interactions of programming challenges with ageing. We first consider ageing and programming of insulin function that has been clearly shown to decrease with age. It is important to evaluate ageing in pancreatic islets isolated from other systems. Studies discussed show premature pancreatic islet ageing resulting from both maternal under- and overnutrition. New ways to determine programming of adipose tissue and effects on fat storage are explored. Oxidative stress is a major factor that regulates ageing in tissues. Oxidative stress is discussed in relation to reproductive and cardiovascular ageing. Premature ageing is associated with both low and high glucocorticoid function. Both over and undernutrition have offspring sex-specific programming effects on life-course glucocorticoid concentrations. Evidence is provided that maternal age at conception affects offspring endocrine and metabolism ageing. Finally, the importance of matching foetal nutrition and energy availability with composition and energy content in the post-weaning diet is demonstrated. This mismatch can lead to a greatly shortened lifespan. General principles are discussed throughout. For example, sexual dimorphism of age-related outcomes can be marked. Accelerated ageing occurs early in life. Improving knowledge on programming ageing interactions will improve health span as well as lifespan. Finally, there are considerable similarities in outcomes programmed by maternal undernutrition and overnutrition.

The nonhuman primate hypothalamo-pituitary-adrenal axis is an orchestrator of programming-aging interactions: role of nutrition

Developmental programming alters life-course multi-organ function and significantly affects life-course health. Recently, interest has developed in how programming may influence the rate of aging. This review describes interactions of nutrition and programming-aging interactions in hypothalamo-pituitary-adrenal (HPA) development and function from fetal development to old age. A full picture of these interactions requires data on levels of HPA activity relating to the hypothalamic, adrenal cortical, circulating blood, and peripheral cortisol metabolism. Data are provided from studies on our baboon, nonhuman primate model both across the normal life course and in offspring of maternal baboons who were moderately undernourished by a global 30% diet reduction during pregnancy and lactation. Sex differences in offspring outcomes in response to similar challenges are described. The data clearly show programming of increased HPA axis activity by moderate maternal undernutrition. Increased postnatal circulating cortisol concentrations are related to accelerated aging of the brain and cardiovascular systems. Future studies should address peripheral cortisol production and the influence of aging advantage in females. These data support the view that the HPA is an orchestrator of interactions of programming-aging mechanisms.

Type 2 diabetes increases oocyte mtDNA mutations which are eliminated in the offspring by bottleneck effect

BACKGROUND

Diabetes induces many complications including reduced fertility and low oocyte quality, but whether it causes increased mtDNA mutations is unknown.

METHODS

We generated a T2D mouse model by using high-fat-diet (HFD) and Streptozotocin (STZ) injection. We examined mtDNA mutations in oocytes of diabetic mice by high-throughput sequencing techniques.

RESULTS

T2D mice showed glucose intolerance, insulin resistance, low fecundity compared to the control group. T2D oocytes showed increased mtDNA mutation sites and mutation numbers compared to the control counterparts. mtDNA mutation examination in F1 mice showed that the mitochondrial bottleneck could eliminate mtDNA mutations.

CONCLUSIONS

T2D mice have increased mtDNA mutation sites and mtDNA mutation numbers in oocytes compared to the counterparts, while these adverse effects can be eliminated by the bottleneck effect in their offspring. This is the first study using a small number of oocytes to examine mtDNA mutations in diabetic mothers and offspring.

Alterations in lipid metabolism due to a protein-restricted diet in rats during gestation and/or lactation

Perinatal malnutrition affects not only fetal and neonatal growth, but also the health of offspring in adulthood, as suggested by the concept of metabolic programming. The impact of maternal protein malnutrition on the metabolism of offspring is demonstrated with the current data. One group of pregnant/lactating female rats was fed with an isocaloric diet having normal protein content. Three other groups were provided 50% of this protein level during pregnancy and/or lactation. The growth and metabolic state of the offspring was monitored. The expression of genes regulating lipid metabolism was determined, including SREBP-1c and SIRT-1 in liver and retroperitoneal adipose tissue. Blood cholesterol and triglycerides were higher in the adult offspring (at 110 days of age) fed a protein-restricted diet than in the adult offspring fed a normal diet. Protein restriction likely leads to inadequate detection of glucose levels, as suggested by the reduced expression of the gene for GCK, the sensor of glucose in the liver. The effects of a protein-restricted diet were highly dependent on the window in which this limitation occurred. There was a more adverse effect when the rats underwent protein restriction during gestation than lactation, leading to lower body weight and alterations in lipid metabolism in adult offspring.

Maternal protein restriction during gestation impairs female offspring pancreas development in the rat

A maternal low-protein (LP) diet programs fetal pancreatic islet β-cell development and function and predisposes offspring to metabolic dysfunction later in life. We hypothesized that maternal protein restriction during pregnancy differentially alters β- and α-cell populations in offspring by modifying islet ontogeny and function throughout life. We aimed to investigate the effect of an LP maternal diet on pancreatic islet morphology and cellular composition in female offspring on postnatal days (PNDs) 7, 14, 21, 36, and 110. Mothers were divided into 2 groups: during pregnancy, the control group (C) was fed a diet containing 20% casein, and the LP group was fed an isocaloric diet with 10% casein. Offspring pancreases were obtained at each PND and then processed. β and α cells were detected by immunohistochemistry, and cellular area and islet size were quantified. Islet cytoarchitecture and total area were similar in C and LP offspring at all ages studied. At the early ages (PNDs 7-21), the proportion of β cells was lower in LP than C offspring. The proportion of α cells was lower in LP than C offspring on PND 14 and higher on PND 21. The β/α-cell ratio was lower in LP compared with C offspring on PNDs 7 and 21 and higher on PND 36 (being similar on PNDs 14 and 110). We concluded that maternal protein restriction during pregnancy modifies offspring islet cell ontogeny by altering the proportions of islet sizes and by reducing the number of β cells postnatally, which may impact pancreatic function in adult life.

The Role of Maternal Dietary Proteins in Development of Metabolic Syndrome in Offspring

The prevalence of metabolic syndrome and obesity has been increasing. Pre-natal environment has been suggested as a factor influencing the risk of metabolic syndrome in adulthood. Both observational and experimental studies showed that maternal diet is a major modifier of the development of regulatory systems in the offspring in utero and post-natally. Both protein content and source in maternal diet influence pre- and early post-natal development. High and low protein dams’ diets have detrimental effect on body weight, blood pressure191 and metabolic and intake regulatory systems in the offspring. Moreover, the role of the source of protein in a nutritionally adequate maternal diet in programming of food intake regulatory system, body weight, glucose metabolism and blood pressure in offspring is studied. However, underlying mechanisms are still elusive. The purpose of this review is to examine the current literature related to the role of proteins in maternal diets in development of characteristics of the metabolic syndrome in offspring.