Folate treatment partially reverses gestational low-protein diet-induced glucose intolerance and the magnitude of reversal is age and sex dependent

Vitamin B12 is correlated with insulin resistance and metabolism disorder markers in women with recurrent pregnancy loss

OBJECTIVES

Recurrent pregnancy loss (RPL) seriously affects women's reproductive and mental health, and the incidence has increased in recent years. Insulin resistance (IR) acts as a significant contributing factor to RPL. Studies suggest that vitamin B12, folate intake, and homocysteine are correlated with IR, but the exact nature remains controversial and requires further investigation. In this study, we aimed to assess the levels and correlations between vitamin B12-folate-homocysteine and insulin resistance in RPL patients.

STUDY DESIGN

73 control subjects and 256 RPL patients (144 RPL patients without IR and 112 RPL patients with IR) were included in this observational retrospective cross-sectional study. The differences in vitamin B12, folate, and homocysteine levels between RPL patients with and without IR were analyzed using a Student's t-test. Pearson correlations were utilized to examine the correlation between vitamin B12-folate-homocysteine and glucose and lipid metabolism parameters. Multivariable linear regressions were used to assess the independent correlation of each factor with HOMA-IR.

RESULTS

Compared to the control subjects, RPL patients exhibited lower vitamin B12 (p < 0.001) and folate (p < 0.001), and higher homocysteine (p = 0.001). RPL patients with IR described decreases in vitamin B12 (p = 0.003) and folate (p = 0.028), and increases in homocysteine (p = 0.033) as RPL patients without IR. Vitamin B12 in RPL patients was significantly negatively correlated with homocysteine (r = -0.348, p < 0.001), HOMA-IR (r = -0.214, p < 0.001), BMI (r = -0.160, p = 0.017), TG (r = -0.148, p = 0.039) and CHO (r = -0.149, p = 0.038) and positively correlated with folate (r = 0.217, p < 0.001). In multivariable linear regressions, after adjusting for age, strong correlations were observed between vitamin B12 (β = -0.197, p = 0.010), BMI (β = 0.466, p < 0.001), and HOMA-IR in RPL patients.

CONCLUSION

Vitamin B12 is significantly correlated with IR in RPL patients. Circulating vitamin B12-folate-homocysteine metabolism could be a window of the pathological process of IR, obesity, and lipid metabolism disorders in RPL patients.

Low Protein Programming Causes Increased Mitochondrial Fusion and Decreased Oxygen Consumption in the Hepatocytes of Female Rats

The liver is one of the major organs involved in the regulation of glucose and lipid homeostasis. The effectiveness of metabolic activity in hepatocytes is determined by the quality and quantity of its mitochondria. Mitochondrial function is complex, and they act via various dynamic networks, which rapidly adapt to changes in the cellular milieu. Our present study aims to investigate the effects of low protein programming on the structure and function of mitochondria in the hepatocytes of adult females. Pregnant rats were fed with a control or isocaloric low-protein diet from gestational day 4 until delivery. A normal laboratory chow was given to all dams after delivery and to pups after weaning. The rats were euthanized at 4 months of age and the livers were collected from female offspring for investigating the mitochondrial structure, mtDNA copy number, mRNA, and proteins expression of genes associated with mitochondrial function. Primary hepatocytes were isolated and used for the analysis of the mitochondrial bioenergetics profiles. The mitochondrial ultrastructure showed that the in utero low-protein diet exposure led to increased mitochondrial fusion. Accordingly, there was an increase in the mRNA and protein levels of the mitochondrial fusion gene Opa1 and mitochondrial biogenesis genes Pgc1a and Essra, but Fis1, a fission gene, was downregulated. Low protein programming also impaired the mitochondrial function of the hepatocytes with a decrease in basal respiration ATP-linked respiration and proton leak. In summary, the present study suggests that the hepatic mitochondrial dysfunction induced by an in utero low protein diet might be a potential mechanism linking glucose intolerance and insulin resistance in adult offspring.

Maternal low protein diet and fetal programming of lean type 2 diabetes

Maternal nutrition is found to be the key factor that determines fetal health in utero and metabolic health during adulthood. Metabolic diseases have been primarily attributed to impaired maternal nutrition during pregnancy, and impaired nutrition has been an immense issue across the globe. In recent years, type 2 diabetes (T2D) has reached epidemic proportion and is a severe public health problem in many countries. Although plenty of research has already been conducted to tackle T2D which is associated with obesity, little is known regarding the etiology and pathophysiology of lean T2D, a variant of T2D. Recent studies have focused on the effects of epigenetic variation on the contribution of in utero origins of lean T2D, although other mechanisms might also contribute to the pathology. Observational studies in humans and experiments in animals strongly suggest an association between maternal low protein diet and lean T2D phenotype. In addition, clear sex-specific disease prevalence was observed in different studies. Consequently, more research is essential for the understanding of the etiology and pathophysiology of lean T2D, which might help to develop better disease prevention and treatment strategies. This review examines the role of protein insufficiency in the maternal diet as the central driver of the developmental programming of lean T2D.

Prenatal Low-Protein Diet Affects Mitochondrial Structure and Function in the Skeletal Muscle of Adult Female Offspring

Gestational low-protein (LP) diet leads to glucose intolerance and insulin resistance in adult offspring. We had earlier demonstrated that LP programming affects glucose disposal in females. Mitochondrial health is crucial for normal glucose metabolism in skeletal muscle. In this study, we sought to analyze mitochondrial structure, function, and associated genes in skeletal muscles to explore the molecular mechanism of insulin resistance LP-programmed female offspring. On day four of pregnancy, rats were assigned to a control diet containing 20% protein or an isocaloric 6% protein-containing diet. Standard laboratory diet was given to the dams after delivery until the end of weaning and to pups after weaning. Gestational LP diet led to changes in mitochondrial ultrastructure in the gastrocnemius muscles, including a nine-fold increase in the presence of giant mitochondria along with unevenly formed cristae. Further, functional analysis showed that LP programming caused impaired mitochondrial functions. Although the mitochondrial copy number did not show significant changes, key genes involved in mitochondrial structure and function such as Fis1, Opa1, Mfn2, Nrf1, Nrf2, Pgc1b, Cox4b, Esrra, and Vdac were dysregulated. Our study shows that prenatal LP programming induced disruption in mitochondrial ultrastructure and function in the skeletal muscle of female offspring.