The lactase persistence -13910C>T polymorphism shows indication of association with abdominal obesity among Portuguese children

Higher milk consumption is associated with a lower risk of diabetes mellitus: A case-control study

BACKGROUND & AIMS

Studies have determined that people with genetically defined lactase non-persistence have lower dairy intake that may lead to an increase risk of various non-communicable diseases. Furthermore, lactase non-persistence itself has been associated with insulin resistance. However, data on lactase non-persistence status and dairy intake in developing countries are sparse. We therefore aimed to define 1) the prevalence of lactase non-persistence among individuals with diabetes and non-diabetes in Thai population and 2) the links between lactase non-persistence, milk consumption, and risk of diabetes mellitus.

METHODS

We conducted a case-control study from participants of the National Health Examination Survey. DNA was isolated from the blood for LCT -13910C>T (rs4988235) polymorphism and processed using the Bio-rad c1000 touch thermal cycler and MALDI-TOF Mass Spectrometry MassARRAY Typer v4.0 (Agena Bioscience, San Diego, CA, USA) at the Center for Medical Genomics, Faculty of Medicine Ramathibodi Hospital. Cases were participants with previously diagnosed diabetes mellitus or fasting plasma glucose ≥126 mg/dL (n = 1,756) vs. the controls (n = 2,380).

RESULTS

We included 4,136 participants, 62% female, and 98.8% were > 30 years old. Homozygous CC genotype (i.e., lactase non-persistence) was noted in 98.6% and only 1.4% carried heterozygous CT. Most (76%) consumed milk <1 portion/month. Participants with either CC or CT genotype had comparable milk consumption and the risk of diabetes mellitus. Males, older adults, and lower education had a lower chance of consuming milk at least one portion per month. Besides various baseline variables, we found that higher milk consumption was associated with a lower DM risk (P = .01).

CONCLUSION

The prevalence of lactase non-persistence in Thai population is very high. A significant difference in milk consumption frequency in relation to the lactase non-persistence status was not found. However, higher milk consumption is associated with a lower risk of diabetes mellitus.

Evidence for a causal association between milk intake and cardiometabolic disease outcomes using a two-sample Mendelian Randomization analysis in up to 1,904,220 individuals

BACKGROUND

High milk intake has been associated with cardio-metabolic risk. We conducted a Mendelian Randomization (MR) study to obtain evidence for the causal relationship between milk consumption and cardio-metabolic traits using the lactase persistence (LCT-13910 C > T, rs4988235) variant as an instrumental variable.

METHODS

We tested the association of LCT genotype with milk consumption (for validation) and with cardio-metabolic traits (for a possible causal association) in a meta-analysis of the data from three large-scale population-based studies (1958 British Birth Cohort, Health and Retirement study, and UK Biobank) with up to 417,236 participants and using summary statistics from consortia meta-analyses on intermediate traits (N = 123,665-697,307) and extended to cover disease endpoints (N = 86,995-149,821).

RESULTS

In the UK Biobank, carriers of 'T' allele of LCT variant were more likely to consume milk (P = 7.02 × 10^-14). In meta-analysis including UK Biobank, the 1958BC, the HRS, and consortia-based studies, under an additive model, 'T' allele was associated with higher body mass index (BMI) (P_{meta-analysis} = 4.68 × 10^-12) and lower total cholesterol (TC) (P = 2.40 × 10^-36), low-density lipoprotein cholesterol (LDL-C) (P = 2.08 × 10^-26) and high-density lipoprotein cholesterol (HDL-C) (P = 9.40 × 10^-13). In consortia meta-analyses, 'T' allele was associated with a lower risk of coronary artery disease (OR:0.86, 95% CI:0.75-0.99) but not with type 2 diabetes (OR:1.06, 95% CI:0.97-1.16). Furthermore, the two-sample MR analysis showed a causal association between genetically instrumented milk intake and higher BMI (P = 3.60 × 10^-5) and body fat (total body fat, leg fat, arm fat and trunk fat; P < 1.37 × 10^-6) and lower LDL-C (P = 3.60 × 10^-6), TC (P = 1.90 × 10^-6) and HDL-C (P = 3.00 × 10^-5).

CONCLUSIONS

Our large-scale MR study provides genetic evidence for the association of milk consumption with higher BMI but lower serum cholesterol levels. These data suggest no need to limit milk intakes with respect to cardiovascular disease risk, with the suggested benefits requiring confirmation in further studies.

A MicroRNA Linking Human Positive Selection and Metabolic Disorders

Positive selection in Europeans at the 2q21.3 locus harboring the lactase gene has been attributed to selection for the ability of adults to digest milk to survive famine in ancient times. However, the 2q21.3 locus is also associated with obesity and type 2 diabetes in humans, raising the possibility that additional genetic elements in the locus may have contributed to evolutionary adaptation to famine by promoting energy storage, but which now confer susceptibility to metabolic diseases. We show here that the miR-128-1 microRNA, located at the center of the positively selected locus, represents a crucial metabolic regulator in mammals. Antisense targeting and genetic ablation of miR-128-1 in mouse metabolic disease models result in increased energy expenditure and amelioration of high-fat-diet-induced obesity and markedly improved glucose tolerance. A thrifty phenotype connected to miR-128-1-dependent energy storage may link ancient adaptation to famine and modern metabolic maladaptation associated with nutritional overabundance.

Gut-microbiome-related LCT genotype and 2-year changes in body composition and fat distribution: the POUNDS Lost Trial

BACKGROUND/OBJECTIVES

Gut microbiome regulates host energy metabolism and adiposity. A recent study identified a genome-wide significant variant in the lactase (LCT) gene that determines gut-microbiome abundance. We investigated whether the LCT variant influenced long-term changes in adiposity among overweight and obese individuals.

SUBJECTS/METHODS

We included 583 whites with LCT variant rs4988235 (G allele as Bifidobacterium-abundance-increasing allele) who were randomly assigned to one of four weight-loss diets varying in macronutrient contents. Two-year changes in adiposity measures were assessed according to the LCT genotype and weight-loss diets.

RESULTS

We observed a significant interaction between the LCT genotype and dietary protein intake on changes in whole body total fat mass %, trunk fat %, superficial adipose tissue mass (SAT), visceral adipose tissue mass (VAT), and total adipose tissue mass (TAT) (Pinteraction < 0.05 for all). In response to high-protein diet, carrying the G allele of LCT variant rs4988235 was associated with greater reduction of whole body total fat mass % (β [SE] -0.9 [0.43], P = 0.04), trunk fat % (-1.06 [0.58], P = 0.07), SAT (-0.89 [0.42], P = 0.04), VAT (-0.63 [0.27], P = 0.03), and TAT (-1.69 [0.76], P = 0.03). Conversely, increasing numbers of the G allele tended to be related to less reduction of these outcomes in response to low-protein diet.

CONCLUSIONS

Long-term improvement of body fat composition and distribution was significantly influenced by the Bifidobacterium-related LCT genotype and dietary protein intake. Overweight and obese individuals with the G allele of LCT variant rs4988235 may benefit improving adiposity by eating a low-calorie, high-protein diet.

The lactase -13910C>T polymorphism (rs4988235) is associated with overweight/obesity and obesity-related variables in a population sample of Portuguese young adults

BACKGROUND/OBJECTIVES

Several studies reported associations of the lactase gene (LCT) polymorphism -13910C>T (rs4988235) with obesity-related variables and obesity in adults. This study aimed to replicate previously reported associations in a population sample of Portuguese young adults.

SUBJECTS/METHODS

We genotyped 447 subjects from central and northern regions of Portugal (mean age 20.81±4.24 years) for the lactase variant -13910C>T (rs4988235), using TaqMan probes. Anthropometric variables (weight, height and body fat) were measured using standardized procedures and body mass index (BMI) (kg/m²) was calculated.

RESULTS

Frequency of genotypes was 35.8% CC (lactase nonpersistent, LNP), 48.1% CT and 16.1% TT, consistent with Hardy-Weinberg equilibrium (P=1). The frequency for the minor -13910 T allele was 0.402. Assuming a dominance model for the lactase persistence (LP) minor T-allele, linear regression models showed statistically significant associations between the LP genotype CT/TT and BMI, fat mass and weight (β=1.114, P=0.003; β=1.309, P=0.007 and β=2.67, P=0.021, respectively) after adjustment for age and sex. In concordance, logistic regression showed significant association between LP genotype CT/TT and overweight/obesity (OR=1.77; CI 1.08-2.92; P=0.023), as well as with high fat percentage ranges (OR=1.58; CI 1.01-2.46; P=0.041), when adjusting for age and sex. No significant interaction was obtained between the LCT polymorphism and physical activity for BMI (P_int=0.454) or FAT % (P_int=0.421).

CONCLUSIONS

In the Portuguese sample of young adults, the lactase -13910C>T polymorphism revealed significant associations with the obesity-related anthropometric variables BMI, fat mass and weight, and previously observed associations with the obesity risk were also confirmed.

Association of lactase persistence genotype with milk consumption, obesity and blood pressure: a Mendelian randomization study in the 1982 Pelotas (Brazil) Birth Cohort, with a systematic review and meta-analysis

Background: Milk intake has been associated with lower blood pressure (BP) in observational studies, and randomized controlled trials suggested that milk-derived tripeptides have BP-lowering effects. Milk intake has also been associated with body mass index (BMI). Nevertheless, it is unclear whether increasing milk consumption would reduce BP in the general population.

Methods: We investigated the association of milk intake with obesity and BP using genetically-defined lactase persistence (LP) based on the rs4988235 polymorphism in a Mendelian randomization design in the 1982 Pelotas (Southern Brazil) Birth Cohort. These results were combined with published reports identified through a systematic review using meta-analysis.

Results: In the 1982 Pelotas Birth Cohort, milk intake was 42 [95% confidence interval (CI): 18; 67) ml/day higher in LP individuals. In conventional observational analysis, each 1-dl/day increase in milk intake was associated with −0.26 (95% CI: −0.33; −0.19) kg/m² in BMI and −0.31 (95% CI: −0.46; −0.16) and -0.35 (95% CI: −0.46; −0.23) mmHg in systolic and diastolic BP, respectively. These results were not corroborated when analysing LP status, but confidence intervals were large. In random effects meta-analysis, LP individuals presented higher BMI [0.17 (95% CI: 0.07; 0.27) kg/m²] and higher odds of overweight-obesity [1.09 (95% CI: 1.02; 1.17)]. There were no reliable associations for BP.

Conclusions: Our study supports that LP is positively associated with obesity, suggesting that the negative association of milk intake with obesity is likely due to limitations of conventional observational studies. Our findings also do not support that increased milk intake leads to lower BP.

Evidence of impaired carbohydrate assimilation in euthyroid patients with Hashimoto's thyroiditis

BACKGROUND/OBJECTIVES

Hashimoto's thyroiditis (HT) represents a wide-spread autoimmune disease. In euthyroid patients with HT, an impaired assimilation of common carbohydrates has been observed. Our objectives were to compare the frequency of (1) fructose (FM), lactose (LM) and sorbitol malassimilation (SM), (2) gastrointestinal symptoms (GS) following carbohydrate ingestion and (3) recurrent GS relevant to the participants' daily lives.

SUBJECTS/METHODS

We conducted a prospective case-control study of 45 ambulatory patients with HT and 38 healthy volunteers, matched with regard to age, gender and area of origin. Hydrogen breath tests with fructose, lactose, sorbitol and glucose were performed, the lactose testing additionally comprising measurements of capillary blood glucose (cBG). GS during the tests and recurrent GS concerning the participants' daily lives were assessed. A food-frequency questionnaire was administered.

RESULTS

FM was diagnosed in 48.9% of patients compared with 26.3% of the control group (P=0.035). In all, 42.2% of patients with HT and 21.1% of healthy controls showed LM (P=0.04). FM and/or LM was present in 73.3% of the patients and in 42.1% of healthy controls (P=0.004). GS after the ingestion of fructose (P=0.003) or lactose (P=0.025) and recurrent GS were significantly more prevalent in the case group. The consumption of free fructose, lactose or sorbitol did not differ.

CONCLUSIONS

Carbohydrate malassimilation and gastrointestinal complaints are frequent in euthyroid patients with HT, leading to novel clinical and pathophysiological considerations and concepts.