Analyzing human knockouts to validate GPR151 as a therapeutic target for reduction of body mass index

Abstract

Novel drug targets for sustained reduction in body mass index (BMI) are needed to curb the epidemic of obesity, which affects 650 million individuals worldwide and is a causal driver of cardiovascular and metabolic disease and mortality. Previous studies reported that the Arg95Ter nonsense variant of GPR151, an orphan G protein-coupled receptor, is associated with reduced BMI and reduced risk of Type 2 Diabetes (T2D). Here, we further investigate GPR151 with the Pakistan Genome Resource (PGR), which is one of the largest exome biobanks of human homozygous loss-of-function carriers (knockouts) in the world. Among PGR participants, we identify eleven GPR151 putative loss-of-function (plof) variants, three of which are present at homozygosity (Arg95Ter, Tyr99Ter, and Phe175LeufsTer7), with a cumulative allele frequency of 2.2%. We confirm these alleles in vitro as loss-of-function. We test if GPR151 plof is associated with BMI, T2D, or other metabolic traits and find that GPR151 deficiency in complete human knockouts is not associated with clinically significant differences in these traits. Relative to Gpr151+/+ mice, Gpr151-/- animals exhibit no difference in body weight on normal chow and higher body weight on a high-fat diet. Together, our findings indicate that GPR151 antagonism is not a compelling therapeutic approach to treatment of obesity.

Fig 1. GPR151 variant proteins are not stably expressed.

Western blot expression of HEK293 cells transfected with pcDNA3.1 plasmids encoding GPR151 variants with N-terminal HA-tag. The expected molecular weight of wild-type (WT) GPR151 is 47 kilodaltons (kDa). Na⁺/K⁺ ATPase is shown as a loading control.

Fig 2. Gpr151^-/- mice do not express Gpr151 mRNA.

(A and B) Sections of mouse brain containing the medial habenula (MHb) and lateral habenula (LHb) from Gpr151^+/+ and Gpr151^-/- mice, respectively, stained with a riboprobe for Gpr151. (C and D) Sections of mouse intestine containing the ileum and jejunum from Gpr151^+/+ and Gpr151^-/- mice, respectively, stained with a riboprobe for Gpr151. Black arrows indicate cells containing Gpr151 mRNA. Inset shows higher magnification of boxed region.

Fig 3. Male Gpr151^-/- mice gain weight on high-fat diet (HFD).

(A) Body weights of male Gpr151^+/+ and Gpr151^-/- mice on a standard chow diet (chow) and high-fat diet (HFD). Data are presented as ± standard error of the mean (SEM). * p < 0.05, ** p < 0.01, *** p < 0.001, **** p < 0.0001, repeated measures, two-way ANOVA followed by post-hoc analysis using Sidak’s multiple comparisons test. (B) Cumulative food intake in kcal (kilocalories) of male Gpr151^+/+ and Gpr151^-/- mice on a standard chow diet and high-fat diet. Data are presented as ± SEM. (C) Body weights of female Gpr151^+/+ and Gpr151^-/- mice on a standard chow diet and high-fat diet. Data are presented as ± SEM.