Investigation of the Putative Associations Between Dairy Consumption and Incidence of Type 1 and Type 2 Diabetes

A1 and A2 milk caseins-comparative FTIR and spectroflourimetry analysis

Around 35% of the total caseins are β-caseins, which are further classified as A1 β-caseins and A2 β-caseins, based on differences in the amino acid composition of both. A2 is the wild type genetic variant of β-casein while A1 is the mutant. The present study aimed at the isolation of A1 and A2 casein from different cow milk sources and its characterization by using simple chemical techniques, viz. FTIR and spectrofluorimetry. The commercial milk sample from Bos indicus (Gir) (A2) was obtained from Bombay Panjrapole, Mumbai and two commercially available packaged cow milk samples (pasteurized, skimmed) namely from Gokul and Mother Dairy (A1) were also obtained for comparison analysis from the local market. The isolation of casein was performed by standard method and analyzed using SDS-PAGE, FTIR and spectrofluorimetry. There was evidence that the A2 milk lacked histidine and rich in aromatic amino acids like tryptophan using FTIR and spectrofluorimetry techniques.

A1 beta-casein milk protein and other environmental pre-disposing factors for type 1 diabetes

Globally type 1 diabetes incidence is increasing. It is widely accepted that the pathophysiology of type 1 diabetes is influenced by environmental factors in people with specific human leukocyte antigen haplotypes. We propose that a complex interplay between dietary triggers, permissive gut factors and potentially other influencing factors underpins disease progression. We present evidence that A1 β-casein cows’ milk protein is a primary causal trigger of type 1 diabetes in individuals with genetic risk factors. Permissive gut factors (for example, aberrant mucosal immunity), intervene by impacting the gut’s environment and the mucosal barrier. Various influencing factors (for example, breastfeeding duration, exposure to other dietary triggers and vitamin D) modify the impact of triggers and permissive gut factors on disease. The power of the dominant trigger and permissive gut factors on disease is influenced by timing, magnitude and/or duration of exposure. Within this framework, removal of a dominant dietary trigger may profoundly affect type 1 diabetes incidence. We present epidemiological, animal-based, in vitro and theoretical evidence for A1 β-casein and its β-casomorphin-7 derivative as dominant causal triggers of type 1 diabetes. The effects of ordinary milk containing A1 and A2 β-casein and milk containing only the A2 β-casein warrant comparison in prospective trials.

Investigation into the bioavailability of milk protein-derived peptides with dipeptidyl-peptidase IV inhibitory activity using Caco-2 cell monolayers

In recent years, peptides derived from a variety of dietary proteins have been reported to exhibit inhibitory activity against the dipeptidyl-peptidase IV (DPP-IV) enzyme, a target in the management of type 2 diabetes. While much attention has been given to the production and identification of peptides with DPP-IV inhibitory activity from food proteins, particularly dairy proteins, little is known on the bioavailability of these molecules. In this study, the stability and transport of five previously identified milk-derived peptides (LKPTPEGDL, LPYPY, IPIQY, IPI and WR) and a whey protein isolate (WPI) digest with DPP-IV-inhibitory activity were investigated using Caco-2 cell monolayers as a model system for human intestinal absorption. Even though a small percentage (ranging from 0.05% for LPYPY to 0.47% for WR) of the bioactive peptides added to the apical side was able to cross the monolayer intact, all five peptides investigated were susceptible to peptidase action during the transport study. Conversely, only minor changes to the WPI digest composition were observed. Determination of the DPP-IV inhibitory activity of the peptides and amino acids identified in the apical and basolateral solutions showed that most degradation products were less effective at inhibiting DPP-IV than the peptide they originated from. Findings from this research suggest that the susceptibility of food-derived DPP-IV inhibitory peptides to degradation by intestinal brush border membrane enzymes may alter their biological activity in vivo. Further research should be conducted to enhance the bioavailability of DPP-IV inhibitory peptides.

The bioactive effects of casein proteins on enteroendocrine cell health, proliferation and incretin hormone secretion

Previous studies suggest that casein exerts various anti-diabetic effects. However, it is not known which casein proteins are bioactive, nor their effects on enteroendocrine cells. This study evaluated the effects of intact whole casein, intact individual proteins (alpha, beta and kappa casein) and hydrolysates on an enteroendocrine cell line. High content analysis accurately monitored changes in cell health and intracellular glucagon-like peptide-1 (GLP-1) content. Cheese ripening duration and GLP-1 secretory responses were also considered. Beta casein significantly stimulated enteroendocrine cell proliferation and all caseins were potent GLP-1 secretagogues (except kappa casein). Interestingly the GLP-1 secretory activity was almost always lost or significantly reduced upon hydrolysis with proteolytic enzymes. Only pepsin-derived beta casein hydrolysates had significantly increased potency compared with the intact protein, but this was diminished with prolonged hydrolysis. In conclusion casein proteins are not detrimental to enteroendocrine cells, and alpha and beta casein are particularly beneficial stimulating proliferation and GLP-1 secretion.

Vitamin D and insulin resistance

Vitamin D is a steroid hormone, which in active form binds to the vitamin D receptor. Expression of the vitamin D receptor in diverse cell types (pancreatic islet cells, myocytes, hepatocytes and adipocytes) raises the suspicion that vitamin D may be involved in multiple cellular processes, including the response to insulin. Insulin resistance is a characteristic feature of type 2 DM, and its attenuation may reduce the incidence of type 2 DM and cardiovascular disease. In observational studies, low serum 25-hydroxyvitamin D (25-OHD) concentrations are associated with an increased risk of type 2 DM. It has been suggested that increasing serum 25-OHD concentrations may have beneficial effects on glucose and insulin homeostasis. However, cross-sectional and interventional studies of vitamin D supplementation provide conflicting results and demonstrate no clear beneficial effect of vitamin D on insulin resistance. These studies are complicated by inclusion of different patient cohorts, different 25-OHD assays and different doses and preparations of vitamin D. Any possible association may be confounded by alterations in PTH, 1,25-dihydroxyvitamin D or tissue vitamin D concentrations. We identified 39 studies via MEDLINE and PUBMED. We review the evidence from 10 studies (seven observational and three interventional) examining vitamin D and type 2 DM incidence, and 29 studies (one prospective observational, 12 cross-sectional and 16 interventional trials) examining vitamin D and insulin resistance. Based on this data, it is not possible to state that vitamin D supplementation has any effect on type 2 DM incidence or on insulin resistance. Data from the multiple ongoing randomized controlled trials of vitamin D supplementation due to report over the next few years should help to clarify this area.

Adaptation to Lactose in Lactase Non Persistent People: Effects on Intolerance and the Relationship between Dairy Food Consumption and Evalution of Diseases

Dairy foods contain complex nutrients which interact with the host. Yet, evolution of lactase persistence has divided the human species into those that can or cannot digest lactose in adulthood. Such a ubiquitous trait has differential effects on humanity. The literature is reviewed to explore how the divide affects lactose handling by lactase non persistent persons. There are two basic differences in digesters. Firstly, maldigesters consume less dairy foods, and secondly, excess lactose is digested by colonic microflora. Lactose intolerance in maldigesters may occur with random lactose ingestion. However, lactose intolerance without maldigestion tends to detract from gaining a clear understanding of the mechanisms of symptoms formation and leads to confusion with regards to dairy food consumption. The main consequence of intolerance is withholding dairy foods. However, regular dairy food consumption by lactase non persistent people could lead to colonic adaptation by the microbiome. This process may mimic a prebiotic effect and allows lactase non persistent people to consume more dairy foods enhancing a favorable microbiome. This process then could lead to alterations in outcome of diseases in response to dairy foods in lactose maldigesters. The evidence that lactose is a selective human prebiotic is reviewed and current links between dairy foods and some diseases are discussed within this context. Colonic adaptation has not been adequately studied, especially with modern microbiological techniques.

Influence of candidate polymorphisms on the dipeptidyl peptidase IV and μ-opioid receptor genes expression in aspect of the β-casomorphin-7 modulation functions in autism

Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with population prevalence of approximately 60-70 per 10,000. Data shows that both opioid system function enhancement and opiate administration can result in autistic-like symptoms. Cow milk opioid peptides, including β-casomorphin-7 (BCM7, Tyr-Pro-Phe-Pro-Gly-Pro-Ile), affect the μ-opioid receptor (MOR) and are subjected to degradation resulting from the proline dipeptidyl peptidase IV (DPPIV, EC 3.4.14.5) enzyme activity. The presence of MOR and DPPIV activity are crucial factors determining biological activity of BCM7 in the human body. Our study examined the effect of β-casomorphin-7 on the MOR and DPPIV genes expression according to specific point mutations in these genes. In addition, we investigated frequency of A118G SNP in the MOR gene and rs7608798 of the DPPIV (A/G) gene in healthy and autistic children. Our research indicated correlation in DPPIV gene expression under the influence of BCM7 and hydrolyzed milk between healthy and ASD-affected children with genotype GG (P<0.0001). We also observed increased MOR gene expression in healthy children with genotype AG at polymorphic site A118G under influence of BCM7 and hydrolyzed milk. The G allele frequency was 0.09 in MOR gene and 0.68 in the DPPIV gene. But our results suggest no association between presence of the alleles G and A at position rs7608798 in DPPIV gene nor alleles A and G at position A118G of the MOR and increased incidence of ASD. Our studies emphasize the compulsion for genetic analysis in correlation with genetic factors affecting development and enhancement of autism symptoms.

Associations between dairy intake and metabolic risk parameters in a healthy French-Canadian population

Observational studies support that dairy product intake is associated with a reduced risk of developing type 2 diabetes; however, several clinical studies report conflicting results on the association between dairy product consumption and metabolic parameters. The aim of this study was to determine associations between dairy product consumption and metabolic profile. Dietary data, using a validated food frequency questionnaire, and fasting blood samples were collected from 233 French Canadians. Plasma phospholipid (PL) fatty acids (FA) concentrations were determined by gas chromatography. Subjects consumed 2.5 ± 1.4 portions of dairy products daily, including 1.6 ± 1.3 portions of low-fat (LF) and 0.90 ± 0.70 portions of high-fat (HF) dairy products. Trans-palmitoleic acid level in plasma PL was related to HF dairy consumption (r = 0.15; p = 0.04). Total (r = –0.21; p = 0.001) and LF dairy (r = –0.20; p = 0.003) intakes were inversely correlated with fasting plasma glucose level. Total dairy intake was inversely associated to systolic blood pressure (r = –0.17; p = 0.008) and diastolic blood pressure (r = –0.14; p = 0.03). LF dairy intake was also inversely correlated with systolic blood pressure (r = –0.17; p = 0.009). Total dairy intake was correlated with plasma C-reactive protein (CRP) (r = 0.15; p = 0.03). No association was found between HF dairy consumption and the risk factors studied. In conclusion, dairy intake is inversely associated with glycaemia and blood pressure; yet, it may modify CRP levels. Moreover, trans-palmitoleic FA levels in plasma PL may be potentially used to assess full-fat dairy consumption.